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Kashlan OB, Wang XP, Sheng S, Kleyman TR. Epithelial Na + Channels Function as Extracellular Sensors. Compr Physiol 2024; 14:1-41. [PMID: 39109974 PMCID: PMC11309579 DOI: 10.1002/cphy.c230015] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
The epithelial Na + channel (ENaC) resides on the apical surfaces of specific epithelia in vertebrates and plays a critical role in extracellular fluid homeostasis. Evidence that ENaC senses the external environment emerged well before the molecular identity of the channel was reported three decades ago. This article discusses progress toward elucidating the mechanisms through which specific external factors regulate ENaC function, highlighting insights gained from structural studies of ENaC and related family members. It also reviews our understanding of the role of ENaC regulation by the extracellular environment in physiology and disease. After familiarizing the reader with the channel's physiological roles and structure, we describe the central role protein allostery plays in ENaC's sensitivity to the external environment. We then discuss each of the extracellular factors that directly regulate the channel: proteases, cations and anions, shear stress, and other regulators specific to particular extracellular compartments. For each regulator, we discuss the initial observations that led to discovery, studies investigating molecular mechanism, and the physiological and pathophysiological implications of regulation. © 2024 American Physiological Society. Compr Physiol 14:5407-5447, 2024.
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Affiliation(s)
- Ossama B. Kashlan
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Computational and Systems Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
| | - Xue-Ping Wang
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaohu Sheng
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thomas R. Kleyman
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh,
Pittsburgh, Pennsylvania
- Department of Pharmacology and Chemical Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
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2
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Zhang J, Yuan HK, Chen S, Zhang ZR. Detrimental or beneficial: Role of endothelial ENaC in vascular function. J Cell Physiol 2021; 237:29-48. [PMID: 34279047 DOI: 10.1002/jcp.30505] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 06/29/2021] [Accepted: 07/01/2021] [Indexed: 12/19/2022]
Abstract
In the past, it was believed that the expression of the epithelial sodium channel (ENaC) was restricted to epithelial tissues, such as the distal nephron, airway, sweat glands, and colon, where it is critical for sodium homeostasis. Over the past two decades, this paradigm has shifted due to the finding that ENaC is also expressed in various nonepithelial tissues, notably in vascular endothelial cells. In this review, the recent findings of the expression, regulation, and function of the endothelial ENaC (EnNaC) are discussed. The expression of EnNaC subunits is reported in a variety of endothelial cell lines and vasculatures, but this is controversial across different species and vessels and is not a universal finding in all vascular beds. The expression density of EnNaC is very faint compared to ENaC in the epithelium. To date, little is known about the regulatory mechanism of EnNaC. Through it can be regulated by aldosterone, the detailed downstream signaling remains elusive. EnNaC responds to increased extracellular sodium with the feedforward activation mechanism, which is quite different from the Na+ self-inhibition mechanism of ENaC. Functionally, EnNaC was shown to be a determinant of cellular mechanics and vascular tone as it can sense shear stress, and its activation or insertion into plasma membrane causes endothelial stiffness and reduced nitric oxide production. However, in some blood vessels, EnNaC is essential for maintaining the integrity of endothelial barrier function. In this context, we discuss the possible reasons for the distinct role of EnNaC in vasculatures.
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Affiliation(s)
- Jun Zhang
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Hui-Kai Yuan
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuo Chen
- Department of Biopharmaceutical Sciences, School of Pharmacy, Harbin Medical University (Daqing), Daqing, China
| | - Zhi-Ren Zhang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang Key Laboratory for Metabolic Disorder & Cancer Related Cardiovascular Diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
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3
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Wang QS, Liang C, Jiang S, Zhu D, Sun Y, Niu N, Yang X, Yang YC, Dong BH, Yao J, Yu CJ, Lou J, Tang LL, Wu MM, Zhang ZR, Ma HP. NaHS or Lovastatin Attenuates Cyclosporine A-Induced Hypertension in Rats by Inhibiting Epithelial Sodium Channels. Front Pharmacol 2021; 12:665111. [PMID: 34122084 PMCID: PMC8187945 DOI: 10.3389/fphar.2021.665111] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 04/19/2021] [Indexed: 12/01/2022] Open
Abstract
The use of cyclosporine A (CsA) in transplant recipients is limited due to its side effects of causing severe hypertension. We have previously shown that CsA increases the activity of the epithelial sodium channel (ENaC) in cultured distal nephron cells. However, it remains unknown whether ENaC mediates CsA-induced hypertension and how we could prevent hypertension. Our data show that the open probability of ENaC in principal cells of split-open cortical collecting ducts was significantly increased after treatment of rats with CsA; the increase was attenuated by lovastatin. Moreover, CsA also elevated the levels of intracellular cholesterol (Cho), intracellular reactive oxygen species (ROS) via activation of NADPH oxidase p47phox, serum- and glucocorticoid-induced kinase isoform 1 (Sgk1), and phosphorylated neural precursor cell-expressed developmentally downregulated protein 4-2 (p-Nedd4-2) in the kidney cortex. Lovastatin also abolished CsA-induced elevation of α-, ß-, and γ-ENaC expressions. CsA elevated systolic blood pressure in rats; the elevation was completely reversed by lovastatin (an inhibitor of cholesterol synthesis), NaHS (a donor of H2S which ameliorated CsA-induced elevation of reactive oxygen species), or amiloride (a potent ENaC blocker). These results suggest that CsA elevates blood pressure by increasing ENaC activity via a signaling cascade associated with elevation of intracellular ROS, activation of Sgk1, and inactivation of Nedd4-2 in an intracellular cholesterol-dependent manner. Our data also show that NaHS ameliorates CsA-induced hypertension by inhibition of oxidative stress.
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Affiliation(s)
- Qiu-Shi Wang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
| | - Chen Liang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Shuai Jiang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Di Zhu
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Yu Sun
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Na Niu
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Xu Yang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Yan-Chao Yang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Bi-Han Dong
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Jie Yao
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Chang-Jiang Yu
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Jie Lou
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Liang-Liang Tang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Ming-Ming Wu
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Zhi-Ren Zhang
- Departments of Pharmacy and Cardiology, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Heilongjiang key laboratory for Metabolic disorder & cancer related cardiovascular diseases, NHC Key Laboratory of Cell Transplantation, Harbin Medical University & Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, United States
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Mraheil MA, Toque HA, La Pietra L, Hamacher J, Phanthok T, Verin A, Gonzales J, Su Y, Fulton D, Eaton DC, Chakraborty T, Lucas R. Dual Role of Hydrogen Peroxide as an Oxidant in Pneumococcal Pneumonia. Antioxid Redox Signal 2021; 34:962-978. [PMID: 32283950 PMCID: PMC8035917 DOI: 10.1089/ars.2019.7964] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Significance:Streptococcus pneumoniae (Spn), a facultative anaerobic Gram-positive human pathogen with increasing rates of penicillin and macrolide resistance, is a major cause of lower respiratory tract infections worldwide. Pneumococci are a primary agent of severe pneumonia in children younger than 5 years and of community-acquired pneumonia in adults. A major defense mechanism toward Spn is the generation of reactive oxygen species, including hydrogen peroxide (H2O2), during the oxidative burst of neutrophils and macrophages. Paradoxically, Spn produces high endogenous levels of H2O2 as a strategy to promote colonization. Recent Advances: Pneumococci, which express neither catalase nor common regulators of peroxide stress resistance, have developed unique mechanisms to protect themselves from H2O2. Spn generates high levels of H2O2 as a strategy to promote colonization. Production of H2O2 moreover constitutes an important virulence phenotype and its cellular activities overlap and complement those of other virulence factors, such as pneumolysin, in modulating host immune responses and promoting organ injury. Critical Issues: This review examines the dual role of H2O2 in pneumococcal pneumonia, from the viewpoint of both the pathogen (defense mechanisms, lytic activity toward competing pathogens, and virulence) and the resulting host-response (inflammasome activation, endoplasmic reticulum stress, and damage to the alveolar-capillary barrier in the lungs). Future Directions: An understanding of the complexity of H2O2-mediated host-pathogen interactions is necessary to develop novel strategies that target these processes to enhance lung function during severe pneumonia.
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Affiliation(s)
- Mobarak Abu Mraheil
- Institute for Medical Microbiology, Justus-Liebig University, Giessen, Germany
| | - Haroldo A Toque
- Vascular Biology Center and Medical College of Georgia at Augusta University, Augusta, Georgia, USA.,Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Luigi La Pietra
- Institute for Medical Microbiology, Justus-Liebig University, Giessen, Germany
| | - Juerg Hamacher
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland.,Internal Medicine V-Pneumology, Allergology, Respiratory and Environmental Medicine, Faculty of Medicine, Saarland University, Saarbrücken, Germany
| | - Tenzing Phanthok
- Department of Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Alexander Verin
- Vascular Biology Center and Medical College of Georgia at Augusta University, Augusta, Georgia, USA.,Department of Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Joyce Gonzales
- Department of Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Yunchao Su
- Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - David Fulton
- Vascular Biology Center and Medical College of Georgia at Augusta University, Augusta, Georgia, USA.,Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
| | - Douglas C Eaton
- Department of Medicine, Emory School of Medicine, Atlanta, Georgia, USA
| | - Trinad Chakraborty
- Institute for Medical Microbiology, Justus-Liebig University, Giessen, Germany
| | - Rudolf Lucas
- Vascular Biology Center and Medical College of Georgia at Augusta University, Augusta, Georgia, USA.,Department of Pharmacology and Toxicology, Medical College of Georgia at Augusta University, Augusta, Georgia, USA.,Department of Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia, USA
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5
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Zheleznova NN, Kumar V, Kurth T, Cowley AW. Hydrogen peroxide (H 2O 2) mediated activation of mTORC2 increases intracellular Na + concentration in the renal medullary thick ascending limb of Henle. Sci Rep 2021; 11:7300. [PMID: 33790341 PMCID: PMC8012714 DOI: 10.1038/s41598-021-86678-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 03/05/2021] [Indexed: 11/22/2022] Open
Abstract
Hydrogen peroxide (H2O2) production in the renal outer medulla is an important determinant of renal medullary blood flow and blood pressure (BP) salt-sensitivity in Dahl salt-sensitive (SS) rats. The mechanisms and pathways responsible for these actions are poorly understood. Recently, we have discovered that the mTOR complex 2 (mTORC2) plays a critical role in BP salt-sensitivity of SS rats by regulating Na+ homeostasis. PP242, an inhibitor of mTORC1/2 pathways exhibits potent natriuretic actions and completely prevented salt-induced hypertension in SS rats. In the present study, we have found that chronic infusion of H2O2 into the single remaining kidney of Sprague Dawley (SD) rats (3 days) stimulated the functional marker (pAKTSer473/AKT) of mTORC2 activity measured by Western Blot analysis. No changes in mTORC1 activity in OM were observed as determined by pS6Ser235/236/S6. Using fluorescent microscopy and the Na+ sensitive dye Sodium Green, we have shown that H2O2 (100 µM added in the bath) increased intracellular sodium concentration ([Na+]i) in renal medullary thick ascending limbs (mTALs) isolated from SD rats. These responses were almost completely abolished by pretreatment of mTAL with 10 µM PP242, indicating that mTORC1/2 pathways were involved in the H2O2 induced increase of [Na+]i. mTAL cell volume remained unchanged (± 1%) by H2O2 as determined by 3D reconstruction confocal laser scanning microscopy techniques. Consistent with the microscopy data, Western Blot analysis of proteins obtained from freshly isolated mTAL treated with 100 µM H2O2 exhibited increased activity/phosphorylation of AKT (pAKTSer473/AKT) that was inhibited by PP242. This was associated with increased protein activity of the apical membrane cotransporter Na+-K+-2Cl- (NKCC2) and the Na/H exchanger (NHE-3). Na+-K+-ATPase activity was increased as reflected an increase in the ratio of pNa+-K+-ATPaseSer16 to total Na+-K+-ATPase. Overall, the results indicate that H2O2 mediated activation of mTORC2 plays a key role in transducing the observed increases of cytosolic [Na+]i despite associated increases of basolateral pump activity.
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Affiliation(s)
- Nadezhda N Zheleznova
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI, 53226, USA.
| | - Vikash Kumar
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI, 53226, USA
| | - Theresa Kurth
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI, 53226, USA
| | - Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI, 53226, USA.
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6
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Pavlov TS, Palygin O, Isaeva E, Levchenko V, Khedr S, Blass G, Ilatovskaya DV, Cowley AW, Staruschenko A. NOX4-dependent regulation of ENaC in hypertension and diabetic kidney disease. FASEB J 2020; 34:13396-13408. [PMID: 32799394 DOI: 10.1096/fj.202000966rr] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 07/17/2020] [Accepted: 07/20/2020] [Indexed: 12/11/2022]
Abstract
NADPH oxidase 4 (NOX4) is the most abundant NOX isoform in the kidney; however, its importance for renal function has only recently emerged. The NOX4-dependent pathway regulates many factors essential for proper sodium handling in the distal nephron. However, the functional significance of this pathway in the control of sodium reabsorption during the initiation of chronic kidney disease is not established. The goal of this study was to test Nox4-dependent ENaC regulation in two models: SS hypertension and STZ-induced type 1 diabetes. First, we showed that genetic ablation of Nox4 in Dahl salt-sensitive (SS) rat attenuated a high-salt (HS)-induced increase in epithelial Na+ channel (ENaC) activity in the cortical collecting duct. We also found that H2 O2 upregulated ENaC activity, and H2 O2 production was reduced in both the renal cortex and medulla in SSNox4-/- rats fed an HS diet. Second, in the streptozotocin model of hyperglycemia-induced renal injury ENaC activity in hyperglycemic animals was elevated in SS but not SSNox4-/- rats. NaCl cotransporter (NCC) expression was increased compared to healthy controls, while expression values between SS and SSNox4-/- groups were similar. These data emphasize a critical contribution of the NOX4-mediated pathway in maladaptive upregulation of ENaC-mediated sodium reabsorption in the distal nephron in the conditions of HS- and hyperglycemia-induced kidney injury.
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Affiliation(s)
- Tengis S Pavlov
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Division of Hypertension and Vascular Research, Henry Ford Health System, Detroit, MI, USA
| | - Oleg Palygin
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Elena Isaeva
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Sherif Khedr
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Department of Physiology, Faculty of Medicine, Ain Shams University, Cairo, Egypt
| | - Gregory Blass
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Allen W Cowley
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA.,Clement J. Zablocki VA Medical Center, Milwaukee, WI, USA
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7
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Sowers JR, Habibi J, Aroor AR, Yang Y, Lastra G, Hill MA, Whaley-Connell A, Jaisser F, Jia G. Epithelial sodium channels in endothelial cells mediate diet-induced endothelium stiffness and impaired vascular relaxation in obese female mice. Metabolism 2019; 99:57-66. [PMID: 31302199 PMCID: PMC6901094 DOI: 10.1016/j.metabol.2019.153946] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 07/10/2019] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Mineralocorticoid receptor activation of the epithelial sodium channel in endothelial cells (ECs) (EnNaC) is accompanied by aldosterone induced endothelial stiffening and impaired nitric oxide (NO)-mediated arterial relaxation. Recent data support enhanced activity of the alpha subunit of EnNaC (αEnNaC) mediates this aldosterone induced endothelial stiffening and associated endothelial NO synthase (eNOS) activation. There is mounting evidence that diet induced obesity diminishes expression and activation of AMP-activated protein kinase α (AMPKα), sirtuin 1 (Sirt1), which would be expected to lead to impaired downstream eNOS activation. Thereby, we posited that enhanced EnNaC activation contributes to diet induced obesity related increases in stiffness of the endothelium and diminished NO mediated vascular relaxation by increasing oxidative stress and related inhibition of AMPKα, Sirt1, and associated eNOS inactivation. MATERIALS/METHODS Sixteen to twenty week-old αEnNaC knockout (αEnNaC-/-) and wild type littermate (EnNaC+/+) female mice were fed a mouse chow or an obesogenic western diet (WD) containing excess fat (46%) and fructose (17.5%) for 16 weeks. Sodium currents of ECs, endothelial stiffness and NO mediated aortic relaxation were examined along with indices of aortic oxidative stress, vascular remodeling and fibrosis. RESULTS Enhanced EnNaC activation-mediated WD-induced increases in sodium currents in isolated lung ECs, increased endothelial stiffness and impaired aortic endothelium-dependent relaxation to acetylcholine (10-9-10-4 mol/L). These abnormalities occurred in conjunction with WD-mediated aortic tissue oxidative stress, inflammation, and decreased activation of AMPKα, Sirt1, and downstream eNOS were substantially mitigated in αEnNaC-/- mice. Importantly, αEnNaC-/- prevented WD induced increases in endothelial stiffness and related impairment of endothelium-dependent relaxation as well as aortic fibrosis and remodeling. However, EnNaC signaling was not involved in diet-induced abnormal expression of adipokines and CYP11b2 in abdominal aortic perivascular adipose tissue. CONCLUSION These data suggest that endothelial specific EnNaC activation mediates WD-induced endothelial stiffness, impaired eNOS activation, aortic fibrosis and remodeling through increased aortic oxidative stress and increased inflammation related to a reduction of AMPKα and Sirt 1 mediated eNOS phosphorylation/activation and NO production.
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Affiliation(s)
- James R Sowers
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA; Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO 65212, USA
| | - Javad Habibi
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA
| | - Annayya R Aroor
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA
| | - Yan Yang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA
| | - Guido Lastra
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA
| | - Michael A Hill
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA; Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, Columbia, MO 65212, USA
| | - Adam Whaley-Connell
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Department of Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA
| | - Frederic Jaisser
- INSERM, UMRS 1138, Cordeliers Research Center, Sorbonne University, USPC, Université Paris Descartes, Université Paris Diderot, F-75006 Paris, France
| | - Guanghong Jia
- Diabetes and Cardiovascular Center, University of Missouri School of Medicine, Columbia, MO 65212, USA; Research Service, Harry S Truman Memorial Veterans Hospital, 800 Hospital Dr, Columbia, MO 65201, USA; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65212, USA; Department of Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA.
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8
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Wu M, Liang C, Yu X, Song B, Yue Q, Zhai Y, Linck V, Cai Y, Niu N, Yang X, Zhang B, Wang Q, Zou L, Zhang S, Thai TL, Ma J, Sutliff RL, Zhang Z, Ma H. Lovastatin attenuates hypertension induced by renal tubule-specific knockout of ATP-binding cassette transporter A1, by inhibiting epithelial sodium channels. Br J Pharmacol 2019; 176:3695-3711. [PMID: 31222723 PMCID: PMC6715779 DOI: 10.1111/bph.14775] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Revised: 05/12/2019] [Accepted: 06/08/2019] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND AND PURPOSE We have shown that cholesterol is synthesized in the principal cells of renal cortical collecting ducts (CCD) and stimulates the epithelial sodium channels (ENaC). Here we have determined whether lovastatin, a cholesterol synthesis inhibitor, can antagonize the hypertension induced by activated ENaC, following deletion of the cholesterol transporter (ATP-binding cassette transporter A1; ABCA1). EXPERIMENTAL APPROACH We selectively deleted ABCA1 in the principal cells of mouse CCD and used the cell-attached patch-clamp technique to record ENaC activity. Western blot and immunofluorescence staining were used to evaluate protein expression levels. Systolic BP was measured with the tail-cuff method. KEY RESULTS Specific deletion of ABCA1 elevated BP and ENaC single-channel activity in the principal cells of CCD in mice. These effects were antagonized by lovastatin. ABCA1 deletion elevated intracellular cholesterol levels, which was accompanied by elevated ROS, increased expression of serum/glucocorticoid regulated kinase 1 (Sgk1), phosphorylated neural precursor cell-expressed developmentally down-regulated protein 4-2 (Nedd4-2) and furin, along with shorten the primary cilium, and reduced ATP levels in urine. CONCLUSIONS AND IMPLICATIONS These data suggest that specific deletion of ABCA1 in principal cells increases BP by stimulating ENaC channels via a cholesterol-dependent pathway which induces several secondary responses associated with oxidative stress, activated Sgk1/Nedd4-2, increased furin expression, and reduced cilium-mediated release of ATP. As ABCA1 can be blocked by cyclosporine A, these results suggest further investigation of the possible use of statins to treat CsA-induced hypertension.
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Affiliation(s)
- Ming‐Ming Wu
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Chen Liang
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Xiao‐Di Yu
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Bin‐Lin Song
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Qiang Yue
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Yu‐Jia Zhai
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Valerie Linck
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Yong‐Xu Cai
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Na Niu
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Xu Yang
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Bao‐Long Zhang
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Qiu‐Shi Wang
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - Li Zou
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Shuai Zhang
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Tiffany L. Thai
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
| | - Jing Ma
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of MedicineAtlanta Veterans Affairs Medical CenterDecaturGeorgia
| | - Roy L. Sutliff
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of MedicineAtlanta Veterans Affairs Medical CenterDecaturGeorgia
| | - Zhi‐Ren Zhang
- Departments of Cardiology and Clinic Pharmacy, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and TreatmentHarbin Medical University Cancer HospitalHarbinChina
| | - He‐Ping Ma
- Department of PhysiologyEmory University School of MedicineAtlantaGeorgia
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9
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Gonzalez-Vicente A, Hong N, Garvin JL. Effects of reactive oxygen species on renal tubular transport. Am J Physiol Renal Physiol 2019; 317:F444-F455. [PMID: 31215804 DOI: 10.1152/ajprenal.00604.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Reactive oxygen species (ROS) play a critical role in regulating nephron transport both via transcellular and paracellular pathways under physiological and pathological circumstances. Here, we review the progress made in the past ~10 yr in understanding how ROS regulate solute and water transport in individual nephron segments. Our knowledge in this field is still rudimentary, with basic information lacking. This is most obvious when looking at the reported disparate effects of superoxide ([Formula: see text]) and H2O2 on proximal nephron transport, where there are no easy explanations as to how to reconcile the data. Similarly, we know almost nothing about the regulation of transport in thin descending and ascending limbs, information that is likely critical to understanding the urine concentrating mechanism. In the thick ascending limb, there is general agreement that ROS enhance transcellular reabsorption of NaCl, but we know very little about their effects on the paracellular pathway and therefore Ca2+ and Mg2+ transport. In the distal convoluted tubule, precious little is known. In the collecting duct, there is general agreement that ROS stimulate the epithelial Na+ channel.
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Affiliation(s)
- Agustin Gonzalez-Vicente
- Department of Inflammation and Immunity, Cleveland Clinic, Lerner Research Institute, Cleveland, Ohio
| | - Nancy Hong
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University Cleveland, Ohio
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University Cleveland, Ohio
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10
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Mies F, Virreira M, Goolaerts A, Djerbib S, Beauwens R, Shlyonsky V, Boom A. DUOX1-mediated hydrogen peroxide release regulates sodium transport in H441 bronchiolar epithelial cells. Acta Physiol (Oxf) 2019; 225:e13166. [PMID: 30052308 DOI: 10.1111/apha.13166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 11/26/2022]
Abstract
AIM Dexamethasone has been shown to induce the formation of epithelial domes by bronchiolar H441 cells. It stimulates the expression of both amiloride inhibitable epithelial sodium channels (ENaC) and dual oxidase-1 (DUOX1). We therefore ask the question whether DUOX1 expression and production of submillimolar amounts of H2 O2 is instrumental for the sodium channel upregulation observed in H441 cells. METHODS In vitro cell culture, nystatin-perforated whole-cell patch-clamp technique, immunocytochemistry and RT-PCR methods have been used. RESULTS Cells forming epithelial domes induced by dexamethasone (0.1 μmol L-1 , 24 hours) and by 5-aza-2'-deoxytidine (1 μmol L-1 , 48 hours) expressed more DUOX1 protein compared with other cells in the monolayer. Dome formation could be inhibited by exogenous catalase in a concentration-dependent manner and by the NADPH oxidase inhibitor diphenyliodonium, which suggested the involvement of H2 O2 . While single application of 0.2 mmol L-1 H2 O2 induced transient dome formation, lower doses were ineffective and higher doses disrupted the cell monolayer. Hydrogen peroxide (0.1 mmol L-1 ) activated acutely amiloride-sensitive whole-cell currents from 3.91 ± 0.79 pA pF-1 to 4.76 ± 0.98 pA pF-1 in dome-forming cells and had no effect in cells outside of domes. ENaC but not DUOX1 transcription was potentiated by catalase in the presence of dexamethasone, which suggested negative feedback of H2 O2 on ENaC gene expression. CONCLUSION Our observations suggest that tonic production of H2 O2 by DUOX1 participates in maintaining the level of vectorial sodium transport by lung epithelial cells. Moreover, the system appears to be well tuned as it would allow H2 O2 -dependent innate immunity without inducing airway/alveolar sodium and fluid hyperabsorption.
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Affiliation(s)
- Frédérique Mies
- Laboratory of Physiology and Pharmacology; Université libre de Bruxelles; Brussels Belgium
| | - Myrna Virreira
- Laboratory of Cell and Molecular Physiology; Université libre de Bruxelles; Brussels Belgium
| | - Arnaud Goolaerts
- Laboratory of Physiology and Pharmacology; Université libre de Bruxelles; Brussels Belgium
| | - Sami Djerbib
- Laboratory of Cell and Molecular Physiology; Université libre de Bruxelles; Brussels Belgium
| | - Renaud Beauwens
- Laboratory of Cell and Molecular Physiology; Université libre de Bruxelles; Brussels Belgium
| | - Vadim Shlyonsky
- Laboratory of Physiology and Pharmacology; Université libre de Bruxelles; Brussels Belgium
| | - Alain Boom
- Laboratory of Cell and Molecular Physiology; Université libre de Bruxelles; Brussels Belgium
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11
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Palmitate Stimulates the Epithelial Sodium Channel by Elevating Intracellular Calcium, Reactive Oxygen Species, and Phosphoinositide 3-Kinase Activity. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:7560610. [PMID: 30622672 PMCID: PMC6304918 DOI: 10.1155/2018/7560610] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 07/22/2018] [Accepted: 08/30/2018] [Indexed: 01/28/2023]
Abstract
Previous studies indicate that the epithelial sodium channel (ENaC) in the kidney is upregulated in diabetes mellitus. Here, we show that ENaC single-channel activity in distal nephron cells was significantly increased by palmitate, a free fatty acid which is elevated in diabetes mellitus. We also show that palmitate increased intracellular Ca2+ and that after chelating intracellular Ca2+ with BAPTA-AM, palmitate failed to affect ENaC activity. Treatment of the cells with 2-aminoethoxydiphenyl borate (2-APB, an inhibitor of IP3 receptors) abolished the elevation of both intracellular Ca2+ and ENaC activity. Treatment of the cells with apocynin (an NADPH oxidase inhibitor), dithiothreitol/NaHS (reducing agents), or LY294002 (a phosphoinositide 3-kinase (PI3K) inhibitor) prevented palmitate-induced ENaC activity, whereas thimerosal (an oxidizing agent) mimicked the effects of palmitate on ENaC activity. However, these treatments did not alter the levels of intracellular Ca2+, indicating that elevation of reactive oxygen species (ROS) and activation of PI3K are downstream of the signaling cascade. Since we have shown that ROS stimulate ENaC by activating PI3K, these data together suggest that palmitate first elevates intracellular Ca2+, then activates an NADPH oxidase to elevate intracellular ROS and PI3K activity, and finally increases ENaC activity via the activated PI3K.
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12
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Nordzieke DE, Medraño-Fernandez I. The Plasma Membrane: A Platform for Intra- and Intercellular Redox Signaling. Antioxidants (Basel) 2018; 7:antiox7110168. [PMID: 30463362 PMCID: PMC6262572 DOI: 10.3390/antiox7110168] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 11/15/2018] [Accepted: 11/17/2018] [Indexed: 02/06/2023] Open
Abstract
Membranes are of outmost importance to allow for specific signal transduction due to their ability to localize, amplify, and direct signals. However, due to the double-edged nature of reactive oxygen species (ROS)—toxic at high concentrations but essential signal molecules—subcellular localization of ROS-producing systems to the plasma membrane has been traditionally regarded as a protective strategy to defend cells from unwanted side-effects. Nevertheless, specialized regions, such as lipid rafts and caveolae, house and regulate the activated/inhibited states of important ROS-producing systems and concentrate redox targets, demonstrating that plasma membrane functions may go beyond acting as a securing lipid barrier. This is nicely evinced by nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases (NOX), enzymes whose primary function is to generate ROS and which have been shown to reside in specific lipid compartments. In addition, membrane-inserted bidirectional H2O2-transporters modulate their conductance precisely during the passage of the molecules through the lipid bilayer, ensuring time-scaled delivery of the signal. This review aims to summarize current evidence supporting the role of the plasma membrane as an organizing center that serves as a platform for redox signal transmission, particularly NOX-driven, providing specificity at the same time that limits undesirable oxidative damage in case of malfunction. As an example of malfunction, we explore several pathological situations in which an inflammatory component is present, such as inflammatory bowel disease and neurodegenerative disorders, to illustrate how dysregulation of plasma-membrane-localized redox signaling impacts normal cell physiology.
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Affiliation(s)
- Daniela E Nordzieke
- Institute of Microbiology and Genetics, Department of Genetics of Eukaryotic Microorganisms, Georg August University Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany.
| | - Iria Medraño-Fernandez
- Protein Transport and Secretion Unit, Division of Genetics and Cell Biology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ospedale San Raffaele, Università Vita-Salute San Raffaele, 20132 Milan, Italy.
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13
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Lee E, Lee HS. Peroxidase expression is decreased by palmitate in cultured podocytes but increased in podocytes of advanced diabetic nephropathy. J Cell Physiol 2018; 233:9060-9069. [PMID: 30132841 PMCID: PMC6686159 DOI: 10.1002/jcp.26875] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 05/23/2018] [Indexed: 01/10/2023]
Abstract
High levels of serum free fatty acids (FFAs) are associated with lipotoxicity and type 2 diabetes. Palmitic acid (PA) is the predominant circulating saturated FFA. PA induces mitochondrial superoxide and hydrogen peroxide (H2O
2) generation in cultured podocytes. To elucidate the role of PA in antioxidant defense systems in diabetic nephropathy (DN), cultured podocytes were exposed to 250 μM PA for 1–24 hr, and protein expressions of catalase, peroxiredoxins (Prxs), and glutathione peroxidase (GPx) were examined by western blot analysis. PA induced an early transient increase in the Prx1, Prx2, and GPx1 levels in podocytes, but not catalase. Long‐term exposure of PA to podocytes significantly decreased the protein levels of Prx1, Prx2, GPx1, and catalase. Coincubation of PA‐treated cells with oleic acid, however, restored the expression of these proteins. In advanced human diabetic glomeruli, H2O2 generation was elevated as shown by increased fluorescence of dichlorofluorescein. Strong immunostaining for Prx1, Prx2, GPx1, and catalase was observed in the podocytes of advanced human DN, wherein transforming growth factor‐β1 staining was also positive. These results suggest that podocytes are susceptible to PA‐induced oxidative damage with impaired peroxidase activity and that peroxidases have futile antioxidant effects in the podocytes in the late stages of DN. Given this, PA‐induced podocyte injury via inadequate peroxidase response to H2O2 appears to play an important role in the pathogenesis of DN.
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Affiliation(s)
- Eugene Lee
- Renal Pathology Lab, Hankook Kidney and Diabetes Institute, Seoul, Korea
| | - Hyun Soon Lee
- Renal Pathology Lab, Hankook Kidney and Diabetes Institute, Seoul, Korea
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14
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Youssef P, Chami B, Lim J, Middleton T, Sutherland GT, Witting PK. Evidence supporting oxidative stress in a moderately affected area of the brain in Alzheimer's disease. Sci Rep 2018; 8:11553. [PMID: 30068908 PMCID: PMC6070512 DOI: 10.1038/s41598-018-29770-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Accepted: 07/18/2018] [Indexed: 01/15/2023] Open
Abstract
The pathogenesis of Alzheimer's disease (AD) remains to be elucidated. Oxidative damage and excessive beta-amyloid oligomers are components of disease progression but it is unclear how these factors are temporally related. At post mortem, the superior temporal gyrus (STG) of AD cases contains plaques, but displays few tangles and only moderate neuronal loss. The STG at post mortem may represent a brain region that is in the early stages of AD or alternately a region resistant to AD pathogenesis. We evaluated expression profiles and activity of endogenous anti-oxidants, oxidative damage and caspase activity in the STG of apolipoprotein ε4-matched human AD cases and controls. Total superoxide dismutase (SOD) activity was increased, whereas total glutathione peroxidase (GPX), catalase (CAT) and peroxiredoxin (Prx) activities, were decreased in the AD-STG, suggesting that hydrogen peroxide accumulates in this brain region. Transcripts of the transcription factor NFE2L2 and inducible HMOX1, were also increased in the AD-STG, and this corresponded to increased Nuclear factor erythroid 2-related factor (NRF-2) and total heme-oxygenase (HO) activity. The protein oxidation marker 4-hydroxynonenal (4-HNE), remained unchanged in the AD-STG. Similarly, caspase activity was unaltered, suggesting that subtle redox imbalances in early to moderate stages of AD do not impact STG viability.
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Affiliation(s)
- Priscilla Youssef
- Redox Biology Group, Discipline of Pathology, University of Sydney, Sydney, NSW, 2006, Australia
| | - Belal Chami
- Redox Biology Group, Discipline of Pathology, University of Sydney, Sydney, NSW, 2006, Australia
| | - Julia Lim
- Neuropathology Group, Discipline of Pathology, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Terry Middleton
- Neuropathology Group, Discipline of Pathology, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Greg T Sutherland
- Neuropathology Group, Discipline of Pathology, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Paul K Witting
- Redox Biology Group, Discipline of Pathology, University of Sydney, Sydney, NSW, 2006, Australia.
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15
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Blobner BM, Wang XP, Kashlan OB. Conserved cysteines in the finger domain of the epithelial Na + channel α and γ subunits are proximal to the dynamic finger-thumb domain interface. J Biol Chem 2018; 293:4928-4939. [PMID: 29425099 DOI: 10.1074/jbc.m117.819367] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 01/26/2018] [Indexed: 11/06/2022] Open
Abstract
The epithelial Na+ channel (ENaC) is a member of the ENaC/degenerin family of ion channels. In the structure of a related family member, the "thumb" domain's base interacts with the pore, and its tip interacts with the divergent "finger" domain. Between the base and tip, the thumb domain is characterized by a conserved five-rung disulfide ladder holding together two anti-parallel α helices. The ENaC α and γ subunits' finger domains harbor autoinhibitory tracts that can be proteolytically liberated to activate the channel and also host an ENaC-specific pair of cysteines. Using a crosslinking approach, we show that one of the finger domain cysteines in the α subunit (αCys-263) and both of the finger domain cysteines in the γ subunit (γCys-213 and γCys-220) lie near the dynamic finger-thumb domain interface. Our data suggest that the αCys-256/αCys-263 pair is not disulfide-bonded. In contrast, we found that the γCys-213/γCys-220 pair is disulfide-bonded. Our data also suggest that the γ subunit lacks the terminal rung in the thumb domain disulfide ladder, suggesting asymmetry between the subunits. We also observed functional asymmetry between the α and γ subunit finger-thumb domain interfaces; crosslinks bridging the α subunit finger-thumb interface only inhibited ENaC currents, whereas crosslinks bridging the γ subunit finger-thumb interface activated or inhibited currents dependent on the length of the crosslinker. Our data suggest that reactive cysteines lie at the dynamic finger-thumb interfaces of the α and γ subunits and may play a yet undefined role in channel regulation.
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Affiliation(s)
- Brandon M Blobner
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261
| | - Xue-Ping Wang
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261
| | - Ossama B Kashlan
- Departments of Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania 15261; Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261.
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16
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Zou L, Linck V, Zhai YJ, Galarza-Paez L, Li L, Yue Q, Al-Khalili O, Bao HF, Ma HP, Thai TL, Jiao J, Eaton DC. Knockout of mitochondrial voltage-dependent anion channel type 3 increases reactive oxygen species (ROS) levels and alters renal sodium transport. J Biol Chem 2017; 293:1666-1675. [PMID: 29180450 DOI: 10.1074/jbc.m117.798645] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/27/2017] [Indexed: 11/06/2022] Open
Abstract
It has been suggested that voltage-dependent anion channels (VDACs) control the release of superoxide from mitochondria. We have previously shown that reactive oxygen species (ROS) such as superoxide (O2̇̄) and hydrogen peroxide (H2O2) stimulate epithelial sodium channels (ENaCs) in sodium-transporting epithelial tissue, including cortical collecting duct (CCD) principal cells. Therefore, we hypothesized that VDACs could regulate ENaC by modulating cytosolic ROS levels. Herein, we find that VDAC3-knockout(KO) mice can maintain normal salt and water balance on low-salt and high-salt diets. However, on a high-salt diet for 2 weeks, VDAC3-KO mice had significantly higher systolic blood pressure than wildtype mice. Consistent with this observation, after a high-salt diet for 2 weeks, ENaC activity in VDAC3-KO mice was significantly higher than wildtype mice. EM analysis disclosed a significant morphological change of mitochondria in the CCD cells of VDAC3-KO mice compared with wildtype mice, which may have been caused by mitochondrial superoxide overload. Of note, compared with wildtype animals, ROS levels in VDAC3-KO animals fed a normal or high-salt diet were consistently and significantly increased in renal tubules. Both the ROS scavenger 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine (TEMPOL) and the mitochondrial ROS scavenger (2-(2,2,6,6-tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (mito-TEMPO) could reverse the effect of high-salt on ENaC activity and systolic blood pressure in the VDAC3-KO mice. Mito-TEMPO partially correct the morphological changes in VDAC3-KO mice. Our results suggest that knocking out mitochondrial VDAC3 increases ROS, alters renal sodium transport, and leads to hypertension.
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Affiliation(s)
- Li Zou
- From the Department of Nephrology, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, China.,the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Valerie Linck
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Yu-Jia Zhai
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Laura Galarza-Paez
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Linda Li
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Qiang Yue
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Otor Al-Khalili
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Hui-Fang Bao
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - He-Ping Ma
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Tiffany L Thai
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
| | - Jundong Jiao
- From the Department of Nephrology, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, China, .,the Institute of Nephrology, Harbin Medical University, Harbin, China
| | - Douglas C Eaton
- the Department of Physiology and the Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia 30322, and
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17
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Martinez-Lemus LA, Aroor AR, Ramirez-Perez FI, Jia G, Habibi J, DeMarco VG, Barron B, Whaley-Connell A, Nistala R, Sowers JR. Amiloride Improves Endothelial Function and Reduces Vascular Stiffness in Female Mice Fed a Western Diet. Front Physiol 2017; 8:456. [PMID: 28713285 PMCID: PMC5492307 DOI: 10.3389/fphys.2017.00456] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/15/2017] [Indexed: 01/25/2023] Open
Abstract
Obese premenopausal women lose their sex related cardiovascular disease protection and develop greater arterial stiffening than age matched men. In female mice, we have shown that consumption of a Western diet (WD), high in fat and refined sugars, is associated with endothelial dysfunction and vascular stiffening, which occur via activation of mineralocorticoid receptors and associated increases in epithelial Na+ channel (ENaC) activity on endothelial cells (EnNaC). Herein our aim was to determine the effect that reducing EnNaC activity with a very-low-dose of amiloride would have on decreasing endothelial and arterial stiffness in young female mice consuming a WD. To this end, we fed female mice either a WD or control diet and treated them with or without a very-low-dose of the ENaC-inhibitor amiloride (1 mg/kg/day) in the drinking water for 20 weeks beginning at 4 weeks of age. Mice consuming a WD were heavier and had greater percent body fat, proteinuria, and aortic stiffness as assessed by pulse-wave velocity than those fed control diet. Treatment with amiloride did not affect body weight, body composition, blood pressure, urinary sodium excretion, or insulin sensitivity, but significantly reduced the development of endothelial and aortic stiffness, aortic fibrosis, aortic oxidative stress, and mesenteric resistance artery EnNaC abundance and proteinuria in WD-fed mice. Amiloride also improved endothelial-dependent vasodilatory responses in the resistance arteries of WD-fed mice. These results indicate that a very-low-dose of amiloride, not affecting blood pressure, is sufficient to improve endothelial function and reduce aortic stiffness in female mice fed a WD, and suggest that EnNaC-inhibition may be sufficient to ameliorate the pathological vascular stiffening effects of WD-induced obesity in females.
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Affiliation(s)
- Luis A Martinez-Lemus
- Dalton Cardiovascular Research Center, University of MissouriColumbia, MO, United States.,Department of Biological Engineering, University of MissouriColumbia, MO, United States.,Department of Medical Pharmacology and Physiology, University of MissouriColumbia, MO, United States.,Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States
| | - Annayya R Aroor
- Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
| | - Francisco I Ramirez-Perez
- Dalton Cardiovascular Research Center, University of MissouriColumbia, MO, United States.,Department of Biological Engineering, University of MissouriColumbia, MO, United States
| | - Guanghong Jia
- Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
| | - Javad Habibi
- Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
| | - Vincent G DeMarco
- Department of Medical Pharmacology and Physiology, University of MissouriColumbia, MO, United States.,Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
| | - Brady Barron
- Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
| | - Adam Whaley-Connell
- Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States.,Division of Nephrology and Hypertension, University of MissouriColumbia, MO, United States
| | - Ravi Nistala
- Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States.,Division of Nephrology and Hypertension, University of MissouriColumbia, MO, United States
| | - James R Sowers
- Dalton Cardiovascular Research Center, University of MissouriColumbia, MO, United States.,Research Service, Harry S. Truman Memorial Veterans' HospitalColumbia, MO, United States.,Diabetes and Cardiovascular Research Center, University of MissouriColumbia, MO, United States
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18
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Liang C, Wang QS, Yang X, Niu N, Hu QQ, Zhang BL, Wu MM, Yu CJ, Chen X, Song BL, Zhang ZR, Ma HP. Oxidized low-density lipoprotein stimulates epithelial sodium channels in endothelial cells of mouse thoracic aorta. Br J Pharmacol 2017; 175:1318-1328. [PMID: 28480509 DOI: 10.1111/bph.13853] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/14/2017] [Accepted: 05/03/2017] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The epithelial sodium channel (ENaC) is expressed in endothelial cells and acts as a negative modulator of vasodilatation. Oxidized LDL (ox-LDL) is a key pathological factor in endothelial dysfunction. In the present study we examined the role of ENaC in ox-LDL-induced endothelial dysfunction and its associated signal transduction pathway. EXPERIMENTAL APPROACH Patch clamp techniques combined with pharmacological approaches were used to examine ENaC activity in the endothelial cells of a split-open mouse thoracic aorta. Western blot analysis was used to determine ENaC expression in the aorta. The aorta relaxation was measured using a wire myograph assay. KEY RESULTS Ox-LDL, but not LDL, significantly increased ENaC activity in the endothelial cells attached to split-open thoracic aortas, and the increase was inhibited by a lectin-like ox-LDL receptor-1 (LOX-1) antagonist (κ-carrageenan), an NADPH oxidase inhibitor (apocynin), and a scavenger of ROS (TEMPOL). Sodium nitroprusside, an NO donor, diminished the ox-LDL-mediated activation of ENaC, and this effect was abolished by inhibiting soluble guanylate cyclase (sGC) and PKG. Ox-LDL reduced the endothelium-dependent vasodilatation of the aorta pectoralis induced by ACh, and this reduction was partially restored by blocking ENaC. CONCLUSION AND IMPLICATIONS Ox-LDL stimulates ENaC in endothelial cells through LOX-1 receptor-mediated activation of NADPH oxidase and accumulation of intracellular ROS. Since the stimulation of ENaC can be reversed by elevating NO, we suggest that both inhibition of ENaC and an elevation of NO may protect the endothelium from ox-LDL-induced dysfunction. LINKED ARTICLES This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.
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Affiliation(s)
- Chen Liang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Qiu-Shi Wang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Xu Yang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Na Niu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Qing-Qing Hu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Bao-Long Zhang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Ming-Ming Wu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Chang-Jiang Yu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Xiao Chen
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Bin-Lin Song
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - Zhi-Ren Zhang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P. R. China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA
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Wang ZR, Liu HB, Sun YY, Hu QQ, Li YX, Zheng WW, Yu CJ, Li XY, Wu MM, Song BL, Mu JJ, Yuan ZY, Zhang ZR, Ma HP. Dietary salt blunts vasodilation by stimulating epithelial sodium channels in endothelial cells from salt-sensitive Dahl rats. Br J Pharmacol 2017; 175:1305-1317. [PMID: 28409833 DOI: 10.1111/bph.13817] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 03/26/2017] [Accepted: 04/04/2017] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND AND PURPOSE Our recent studies show that the reduced activity of epithelial sodium channels (ENaC) in endothelial cells accounts for the adaptation of vasculature to salt in Sprague-Dawley rats. The present study examines a hypothesis that enhanced ENaC activity mediates the loss of vasorelaxation in Dahl salt-sensitive (SS) rats. EXPERIMENTAL APPROACH We used the cell-attached patch-clamp technique to record ENaC activity in split-open mesenteric arteries. Western blot and immunofluorescence staining were used to evaluate the levels of aldosterone, ENaC, eNOS and NO. Blood pressure was measured with the tail-cuff method and the artery relaxation was measured with the wire myograph assay. KEY RESULTS High-salt (HS) diet significantly increased plasma aldosterone and ENaC activity in the endothelial cells of Dahl SS rats. The endothelium-dependent artery relaxation was blunted by HS challenge in these rats. Amiloride, a potent blocker of ENaC, increased both phosphorylated eNOS and NO and therefore prevented the HS-induced loss of vasorelaxation. As, in SS rats, endogenous aldosterone was already elevated by HS challenge, exogenous aldosterone did not further elevate ENaC activity in the rats fed with HS. Eplerenone, a mineralocorticoid receptor antagonist, attenuated the effects of HS on both ENaC activity and artery relaxation. CONCLUSIONS AND IMPLICATIONS These data suggest that HS diet blunts artery relaxation and causes hypertension via a pathway associated with aldosterone-dependent activation of ENaC in endothelial cells. This pathway provides one of the mechanisms by which HS causes hypertension in Dahl SS rats. LINKED ARTICLES This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.
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Affiliation(s)
- Zi-Rui Wang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Hui-Bin Liu
- Department of Clinical Pharmacy, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Harbin, China
| | - Ying-Ying Sun
- State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Qing-Qing Hu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Yu-Xia Li
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Wei-Wan Zheng
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Chang-Jiang Yu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Xin-Yuan Li
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Ming-Ming Wu
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Bin-Lin Song
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Jian-Jun Mu
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical College of Xi'an Jiaotong University, Key Laboratory of Molecular Cardiology, Xi'an, China
| | - Zu-Yi Yuan
- Department of Cardiovascular Medicine, First Affiliated Hospital of Medical College of Xi'an Jiaotong University, Key Laboratory of Molecular Cardiology, Xi'an, China
| | - Zhi-Ren Zhang
- Departments of Cardiology and Clinical Pharmacy, Harbin Medical University Cancer Hospital, Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China.,Department of Clinical Pharmacy, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Harbin, China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA
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Pavlov TS, Staruschenko A. Involvement of ENaC in the development of salt-sensitive hypertension. Am J Physiol Renal Physiol 2016; 313:F135-F140. [PMID: 28003189 DOI: 10.1152/ajprenal.00427.2016] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 12/20/2016] [Accepted: 12/20/2016] [Indexed: 02/07/2023] Open
Abstract
Salt-sensitive hypertension is associated with renal and vascular dysfunctions, which lead to impaired fluid excretion, increased cardiac output, and total peripheral resistance. It is commonly accepted that increased renal sodium handling and plasma volume expansion are necessary factors for the development of salt-induced hypertension. The epithelial sodium channel (ENaC) is a trimeric ion channel expressed in the distal nephron that plays a critical role in the regulation of sodium reabsorption in both normal and pathological conditions. In this mini-review, we summarize recent studies investigating the role of ENaC in the development of salt-sensitive hypertension. On the basis of experimental data obtained from the Dahl salt-sensitive rats, we and others have demonstrated that abnormal ENaC activation in response to a dietary NaCl load contributes to the development of high blood pressure in this model. The role of different humoral factors, such as the components of the renin-angiotensin-aldosterone system, members of the epidermal growth factors family, arginine vasopressin, and oxidative stress mediating the effects of dietary salt on ENaC are discussed in this review to highlight future research directions and to determine potential molecular targets for drug development.
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Affiliation(s)
- Tengis S Pavlov
- Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit, Michigan; and
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Ferreira F, Luxardi G, Reid B, Zhao M. Early bioelectric activities mediate redox-modulated regeneration. Development 2016; 143:4582-4594. [PMID: 27827821 DOI: 10.1242/dev.142034] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Accepted: 10/21/2016] [Indexed: 12/26/2022]
Abstract
Reactive oxygen species (ROS) and electric currents modulate regeneration; however, the interplay between biochemical and biophysical signals during regeneration remains poorly understood. We investigate the interactions between redox and bioelectric activities during tail regeneration in Xenopus laevis tadpoles. We show that inhibition of NADPH oxidase-mediated production of ROS, or scavenging or blocking their diffusion into cells, impairs regeneration and consistently regulates the dynamics of membrane potential, transepithelial potential (TEP) and electric current densities (JI) during regeneration. Depletion of ROS mimics the altered TEP and JI observed in the non-regenerative refractory period. Short-term application of hydrogen peroxide (H2O2) rescues (from depleted ROS) and induces (from the refractory period) regeneration, TEP increase and JI reversal. H2O2 is therefore necessary for and sufficient to induce regeneration and to regulate TEP and JI Epistasis assays show that voltage-gated Na+ channels act downstream of H2O2 to modulate regeneration. Altogether, these results suggest a novel mechanism for regeneration via redox-bioelectric orchestration.
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Affiliation(s)
- Fernando Ferreira
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, CA 95817, USA .,Departamento de Biologia, Centro de Biologia Molecular e Ambiental (CBMA), Universidade do Minho, Braga 4710, Portugal
| | - Guillaume Luxardi
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, CA 95817, USA
| | - Brian Reid
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, CA 95817, USA
| | - Min Zhao
- Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, CA 95817, USA .,Department of Ophthalmology, Institute for Regenerative Cures, University of California, Davis, CA 95817, USA
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The Epithelial Sodium Channel and the Processes of Wound Healing. BIOMED RESEARCH INTERNATIONAL 2016; 2016:5675047. [PMID: 27493961 PMCID: PMC4963570 DOI: 10.1155/2016/5675047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/15/2016] [Indexed: 12/19/2022]
Abstract
The epithelial sodium channel (ENaC) mediates passive sodium transport across the apical membranes of sodium absorbing epithelia, like the distal nephron, the intestine, and the lung airways. Additionally, the channel has been involved in the transduction of mechanical stimuli, such as hydrostatic pressure, membrane stretch, and shear stress from fluid flow. Thus, in vascular endothelium, it participates in the control of the vascular tone via its activity both as a sodium channel and as a shear stress transducer. Rather recently, ENaC has been shown to participate in the processes of wound healing, a role that may also involve its activities as sodium transporter and as mechanotransducer. Its presence as the sole channel mediating sodium transport in many tissues and the diversity of its functions probably underlie the complexity of its regulation. This brief review describes some aspects of ENaC regulation, comments on evidence about ENaC participation in wound healing, and suggests possible regulatory mechanisms involved in this participation.
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23
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Hydrogen Peroxide and Sodium Transport in the Lung and Kidney. BIOMED RESEARCH INTERNATIONAL 2016; 2016:9512807. [PMID: 27073804 PMCID: PMC4814630 DOI: 10.1155/2016/9512807] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/04/2016] [Accepted: 03/08/2016] [Indexed: 02/07/2023]
Abstract
Renal and lung epithelial cells are exposed to some significant concentrations of H2O2. In urine it may reach 100 μM, while in the epithelial lining fluid in the lung it is estimated to be in micromolar to tens-micromolar range. Hydrogen peroxide has a stimulatory action on the epithelial sodium channel (ENaC) single-channel activity. It also increases stability of the channel at the membrane and slows down the transcription of the ENaC subunits. The expression and the activity of the channel may be inhibited in some other, likely higher, oxidative states of the cell. This review discusses the role and the origin of H2O2 in the lung and kidney. Concentration-dependent effects of hydrogen peroxide on ENaC and the mechanisms of its action have been summarized. This review also describes outlooks for future investigations linking oxidative stress, epithelial sodium transport, and lung and kidney function.
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Liu HB, Zhang J, Sun YY, Li XY, Jiang S, Liu MY, Shi J, Song BL, Zhao D, Ma HP, Zhang ZR. Dietary salt regulates epithelial sodium channels in rat endothelial cells: adaptation of vasculature to salt. Br J Pharmacol 2015; 172:5634-46. [PMID: 25953733 DOI: 10.1111/bph.13185] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 04/03/2015] [Accepted: 04/26/2015] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE The epithelial sodium channel (ENaC) is expressed in vascular endothelial cells and is a negative modulator of vasodilation. However, the role of endothelial ENaCs in salt-sensitive hypertension remains unclear. Here, we have investigated how endothelial ENaCs in Sprague-Dawley (SD) rats respond to high-salt (HS) challenge. EXPERIMENTAL APPROACH BP and plasma aldosterone levels were measured. We used patch-clamp technique to record ENaC activity in split-open mesenteric arteries (MAs). Western blot and Griess assay were used to detect expression of α-ENaCs, eNOS and NO. Vasorelaxation in second-order MAs was measured with wire myograph assays. KEY RESULTS Functional ENaCs were observed in endothelial cells and their activity was significantly decreased after 1 week of HS diet. After 3 weeks of HS diet, ENaC expression was also reduced. When either ENaC activity or expression was reduced, endothelium-dependent relaxation (EDR) of MAs, in response to ACh, was enhanced. This enhancement of EDR was mimicked by amiloride, a blocker of ENaCs. By contrast, HS diet significantly increased contractility of MAs, accompanied by decreased eNOS activity and NO levels. However, ACh-induced release of NO was much higher in MAs isolated from HS rats than those from NS rats. CONCLUSIONS AND IMPLICATIONS HS intake increased the BP of SD rats, but simultaneously enhanced EDR by reducing ENaC activity and expression due to feedback inhibition. Therefore, ENaCs may play an important role in endothelial cells allowing the vasculature to adapt to HS conditions.
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Affiliation(s)
- Hui-Bin Liu
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Jun Zhang
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Ying-Ying Sun
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Xin-Yuan Li
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Shuai Jiang
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Ming-Yu Liu
- Department of Pharmacology, Harbin Medical University, Harbin, China
| | - Jing Shi
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Bin-Lin Song
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - Dan Zhao
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA
| | - Zhi-Ren Zhang
- Departments of Clinical Pharmacy and Cardiology, Institute of Clinical Pharmacy, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, China
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Hydrogen Sulfide Prevents Advanced Glycation End-Products Induced Activation of the Epithelial Sodium Channel. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:976848. [PMID: 26078825 PMCID: PMC4442307 DOI: 10.1155/2015/976848] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 12/26/2014] [Indexed: 12/27/2022]
Abstract
Advanced glycation end-products (AGEs) are complex and heterogeneous compounds implicated in diabetes. Sodium reabsorption through the epithelial sodium channel (ENaC) at the distal nephron plays an important role in diabetic hypertension. Here, we report that H2S antagonizes AGEs-induced ENaC activation in A6 cells. ENaC open probability (PO) in A6 cells was significantly increased by exogenous AGEs and that this AGEs-induced ENaC activity was abolished by NaHS (a donor of H2S) and TEMPOL. Incubating A6 cells with the catalase inhibitor 3-aminotriazole (3-AT) mimicked the effects of AGEs on ENaC activity, but did not induce any additive effect. We found that the expression levels of catalase were significantly reduced by AGEs and both AGEs and 3-AT facilitated ROS uptake in A6 cells, which were significantly inhibited by NaHS. The specific PTEN and PI3K inhibitors, BPV(pic) and LY294002, influence ENaC activity in AGEs-pretreated A6 cells. Moreover, after removal of AGEs from AGEs-pretreated A6 cells for 72 hours, ENaC PO remained at a high level, suggesting that an AGEs-related “metabolic memory” may be involved in sodium homeostasis. Our data, for the first time, show that H2S prevents AGEs-induced ENaC activation by targeting the ROS/PI3K/PTEN pathway.
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Downs CA, Kreiner L, Zhao XM, Trac P, Johnson NM, Hansen JM, Brown LA, Helms MN. Oxidized glutathione (GSSG) inhibits epithelial sodium channel activity in primary alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2015; 308:L943-52. [PMID: 25713321 PMCID: PMC4888545 DOI: 10.1152/ajplung.00213.2014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 02/15/2015] [Indexed: 11/22/2022] Open
Abstract
Amiloride-sensitive epithelial Na(+) channels (ENaC) regulate fluid balance in the alveoli and are regulated by oxidative stress. Since glutathione (GSH) is the predominant antioxidant in the lungs, we proposed that changes in glutathione redox potential (Eh) would alter cell signaling and have an effect on ENaC open probability (Po). In the present study, we used single channel patch-clamp recordings to examine the effect of oxidative stress, via direct application of glutathione disulfide (GSSG), on ENaC activity. We found a linear decrease in ENaC activity as the GSH/GSSG Eh became less negative (n = 21; P < 0.05). Treatment of 400 μM GSSG to the cell bath significantly decreased ENaC Po from 0.39 ± 0.06 to 0.13 ± 0.05 (n = 8; P < 0.05). Likewise, back-filling recording electrodes with 400 μM GSSG reduced ENaC Po from 0.32 ± 0.08 to 0.17 ± 0.05 (n = 10; P < 0.05), thus implicating GSSG as an important regulatory factor. Biochemical assays indicated that oxidizing potentials promote S-glutathionylation of ENaC and irreversible oxidation of cysteine residues with N-ethylmaleimide blocked the effects of GSSG on ENaC Po. Additionally, real-time imaging studies showed that GSSG impairs alveolar fluid clearance in vivo as opposed to GSH, which did not impair clearance. Taken together, these data show that glutathione Eh is an important determinant of alveolar fluid clearance in vivo.
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Affiliation(s)
- Charles A Downs
- Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, Georgia
| | - Lisa Kreiner
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia
| | - Xing-Ming Zhao
- Department of Computer Science, School of Electronics and Information Engineering, Tongji University, Shanghai, China
| | - Phi Trac
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia
| | - Nicholle M Johnson
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia
| | - Jason M Hansen
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia; Center for Cystic Fibrosis and Airways Disease Research at Children's Healthcare of Atlanta Hospital, Atlanta, Georgia; and
| | - Lou Ann Brown
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia; Center for Cystic Fibrosis and Airways Disease Research at Children's Healthcare of Atlanta Hospital, Atlanta, Georgia; and
| | - My N Helms
- Department Pediatrics, School of Medicine, Emory University, Atlanta, Georgia; Center for Cystic Fibrosis and Airways Disease Research at Children's Healthcare of Atlanta Hospital, Atlanta, Georgia; and
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Aminotriazole alleviates acetaminophen poisoning via downregulating P450 2E1 and suppressing inflammation. PLoS One 2015; 10:e0122781. [PMID: 25884831 PMCID: PMC4401561 DOI: 10.1371/journal.pone.0122781] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 02/14/2015] [Indexed: 12/13/2022] Open
Abstract
Aminotriazole (ATZ) is commonly used as a catalase (CAT) inhibitor. We previously found ATZ attenuated oxidative liver injury, but the underlying mechanisms remain unknown. Acetaminophen (APAP) overdose frequently induces life-threatening oxidative hepatitis. In the present study, the potential hepatoprotective effects of ATZ on oxidative liver injury and the underlying mechanisms were further investigated in a mouse model with APAP poisoning. The experimental data indicated that pretreatment with ATZ dose- and time-dependently suppressed the elevation of plasma aminotransferases in APAP exposed mice, these effects were accompanied with alleviated histological abnormality and improved survival rate of APAP-challenged mice. In mice exposed to APAP, ATZ pretreatment decreased the CAT activities, hydrogen peroxide (H2O2) levels, malondialdehyde (MDA) contents, myeloperoxidase (MPO) levels in liver and reduced TNF-α levels in plasma. Pretreatment with ATZ also downregulated APAP-induced cytochrome P450 2E1 (CYP2E1) expression and JNK phosphorylation. In addition, posttreatment with ATZ after APAP challenge decreased the levels of plasma aminotransferases and increased the survival rate of experimental animals. Posttreatment with ATZ had no effects on CYP2E1 expression or JNK phosphorylation, but it significantly decreased the levels of plasma TNF-α. Our data indicated that the LD50 of ATZ in mice was 5367.4 mg/kg body weight, which is much higher than the therapeutic dose of ATZ in the present study. These data suggested that ATZ might be effective and safe in protect mice against APAP-induced hepatotoxicity, the beneficial effects might resulted from downregulation of CYP2E1 and inhibiton of inflammation.
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Lu XY, Liu BC, Wang LH, Yang LL, Bao Q, Zhai YJ, Alli AA, Thai TL, Eaton DC, Wang WZ, Ma HP. Acute ethanol induces apoptosis by stimulating TRPC6 via elevation of superoxide in oxygenated podocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:965-74. [PMID: 25601712 DOI: 10.1016/j.bbamcr.2015.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 01/07/2015] [Accepted: 01/09/2015] [Indexed: 01/06/2023]
Abstract
Our recent studies indicate that hydrogen peroxide (H2O2) only at high concentrations can cause oxidative stress in renal epithelial cells and induce apoptosis of podocytes. Consistently, the present study shows that H2O2, even at 1 mM, failed to induce intracellular oxidative stress and apoptosis of the podocytes due to efficient activity of catalase, an enzyme which degrades H2O2 to produce water and oxygen (O2). However, H2O2 acted as a source of O2 to allow acute ethanol to induce superoxide production and cause apoptosis of the podocytes. In contrast, acute ethanol alone did not elevate intracellular superoxide, even though it stimulates expression and translocation of p47phox to the plasma membrane. Inhibition of catalase abolished not only O2 production from H2O2 degradation, but also NOX2-dependent superoxide production in the podocytes challenged by both H2O2 and acute ethanol. In parallel, acute ethanol in the presence of H2O2, but neither ethanol nor H2O2 alone, stimulated transient receptor potential canonical 6 (TRPC6) channels and caused TRPC6-dependent elevation of intracellular Ca2+. These data suggest that exogenous H2O2 does not induce oxidative stress due to rapid degradation to produce O2 in the podocytes, but the oxygenated podocytes become sensitive to acute ethanol challenge and undergo apoptosis via a TRPC6-dependent elevation of intracellular Ca2+. Since cultured podocytes are considered in hypoxic conditions, H2O2 may be used as a source of O2 to establish an ischemia-reperfusion model in some type of cultured cells in which H2O2 does not directly induce intracellular oxidative stress.
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Affiliation(s)
- Xiao-Yu Lu
- Department of Neurology, the Second Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China; Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Bing-Chen Liu
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States; Department of Radiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China; Department of Cardiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
| | - Li-Hua Wang
- Department of Neurology, the Second Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
| | - Li-Li Yang
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States; Department of Radiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China; Department of Cardiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
| | - Qing Bao
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Yu-Jia Zhai
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States; Department of Radiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China; Department of Cardiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
| | - Abdel A Alli
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Tiffany L Thai
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Douglas C Eaton
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Wei-Zhi Wang
- Department of Neurology, the Second Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
| | - He-Ping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, United States.
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Ivonnet P, Salathe M, Conner GE. Hydrogen peroxide stimulation of CFTR reveals an Epac-mediated, soluble AC-dependent cAMP amplification pathway common to GPCR signalling. Br J Pharmacol 2014; 172:173-84. [PMID: 25220136 DOI: 10.1111/bph.12934] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 08/27/2014] [Accepted: 09/03/2014] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE H2 O2 is widely understood to regulate intracellular signalling. In airway epithelia, H2 O2 stimulates anion secretion primarily by activating an autocrine PGE2 signalling pathway via EP4 and EP1 receptors to initiate cytic fibrosis transmembrane regulator (CFTR)-mediated Cl(-) secretion. This study investigated signalling downstream of the receptors activated by H2 O2 . EXPERIMENTAL APPROACH Anion secretion by differentiated bronchial epithelial cells was measured in Ussing chambers during stimulation with H2 O2 , an EP4 receptor agonist or β2 -adrenoceptor agonist in the presence and absence of inhibitors of ACs and downstream effectors. Intracellular calcium ([Ca(2+) ]I ) changes were followed by microscopy using fura-2-loaded cells and PKA activation followed by FRET microscopy. KEY RESULTS Transmembrane adenylyl cyclase (tmAC) and soluble AC (sAC) were both necessary for H2 O2 and EP4 receptor-mediated CFTR activation in bronchial epithelia. H2 O2 and EP4 receptor agonist stimulated tmAC to increase exchange protein activated by cAMP (Epac) activity that drives PLC activation to raise [Ca(2+) ]i via Ca(2+) store release (and not entry). Increased [Ca(2+) ]i led to sAC activation and further increases in CFTR activity. Stimulation of sAC did not depend on changes in [HCO3 (-) ]. Ca(2+) -activated apical KCa 1.1 channels and cAMP-activated basolateral KV 7.1 channels contributed to H2 O2 -stimulated anion currents. A similar Epac-mediated pathway was seen following β2 -adrenoceptor or forskolin stimulation. CONCLUSIONS AND IMPLICATIONS H2 O2 initiated a complex signalling cascade that used direct stimulation of tmACs by Gαs followed by Epac-mediated Ca(2+) crosstalk to activate sAC. The Epac-mediated Ca(2+) signal constituted a positive feedback loop that amplified CFTR anion secretion following stimulation of tmAC by a variety of stimuli.
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Affiliation(s)
- P Ivonnet
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, University of Miami, Miami, Florida, USA
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Liu BC, Yang LL, Lu XY, Song X, Li XC, Chen G, Li Y, Yao X, Humphrey DR, Eaton DC, Shen BZ, Ma HP. Lovastatin-Induced Phosphatidylinositol-4-Phosphate 5-Kinase Diffusion from Microvilli Stimulates ROMK Channels. J Am Soc Nephrol 2014; 26:1576-87. [PMID: 25349201 DOI: 10.1681/asn.2013121326] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 08/25/2014] [Indexed: 12/13/2022] Open
Abstract
We recently showed that lovastatin attenuates cyclosporin A (CsA)-induced damage of cortical collecting duct (CCD) principal cells by reducing intracellular cholesterol. Previous studies showed that, in cell expression models or artificial membranes, exogenous cholesterol directly inhibits inward rectifier potassium channels, including Kir1.1 (Kcnj1; the gene locus for renal outer medullary K(+) [ROMK1] channels). Therefore, we hypothesized that lovastatin might stimulate ROMK1 by reducing cholesterol in CCD cells. Western blots showed that mpkCCDc14 cells express ROMK1 channels with molecular masses that approximate the molecular masses of ROMK1 in renal tubules detected before and after treatment with DTT. Confocal microscopy showed that ROMK1 channels were not in the microvilli, where cholesterol-rich lipid rafts are located, but rather, the planar regions of the apical membrane of mpkCCDc14 cells. Furthermore, phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2], an activator of ROMK channels, was detected mainly in the microvilli under resting conditions along with the kinase responsible for PI(4,5)P2 synthesis, phosphatidylinositol-4-phosphate 5-kinase, type I γ [PI(4)P5K I γ], which may explain the low basal open probability and increased sensitivity to tetraethylammonium observed here for this channel. Notably, lovastatin induced PI(4)P5K I γ diffusion into planar regions and elevated PI(4,5)P2 and ROMK1 open probability in these regions through a cholesterol-associated mechanism. However, exogenous cholesterol alone did not induce these effects. These results suggest that lovastatin stimulates ROMK1 channels, at least in part, by inducing PI(4,5)P2 synthesis in planar regions of the renal CCD cell apical membrane, suggesting that lovastatin could reduce cyclosporin-induced nephropathy and associated hyperkalemia.
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Affiliation(s)
- Bing-Chen Liu
- Departments of Radiology and Cardiology, Fourth Hospital of Harbin Medical University, Harbin, Heilongjiang, China; Department of Physiology and
| | - Li-Li Yang
- Departments of Radiology and Department of Physiology and Molecular Imaging Center, Harbin Medical University, Harbin, Heilongjiang, China; and
| | - Xiao-Yu Lu
- Departments of Radiology and Cardiology, Fourth Hospital of Harbin Medical University, Harbin, Heilongjiang, China; Department of Physiology and
| | - Xiang Song
- Cardiology, Fourth Hospital of Harbin Medical University, Harbin, Heilongjiang, China; Department of Physiology and
| | | | | | - Yichao Li
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Xincheng Yao
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | | | - Douglas C Eaton
- Department of Physiology and Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia
| | - Bao-Zhong Shen
- Departments of Radiology and Molecular Imaging Center, Harbin Medical University, Harbin, Heilongjiang, China; and
| | - He-Ping Ma
- Department of Physiology and Center for Cell and Molecular Signaling, Emory University School of Medicine, Atlanta, Georgia
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Jia M, Jing Y, Ai Q, Jiang R, Wan J, Lin L, Zhou D, Che Q, Li L, Tang L, Shen Y, Zhang L. Potential role of catalase in mice with lipopolysaccharide/D-galactosamine-induced fulminant liver injury. Hepatol Res 2014; 44:1151-8. [PMID: 23941578 DOI: 10.1111/hepr.12220] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 08/06/2013] [Accepted: 08/07/2013] [Indexed: 12/13/2022]
Abstract
AIM Lipopolysaccharide (LPS)-induced liver injury in D-galactosamine (D-Gal)-sensitized mice is a well-established animal model widely used in exploring the pathogenesis of fulminant hepatitis. Increasing evidence has indicated that reactive oxygen species (ROS)-induced oxidative injury may be involved in LPS/D-Gal-induced hepatitis. Catalase (CAT) is a major antioxidant enzyme while aminotriazole (ATZ) is commonly used as a CAT inhibitor. In the present study, the effects of ATZ on LPS/D-Gal-induced liver injury were investigated. METHODS Fuliminant liver injury was induced by intraperitoneal injection of LPS combined with D-Gal, ATZ was administrated 0.5 h prior to LPS/D-Gal challenge. The degree of liver injury, the level of hepatic oxidative stress, the grade of hepatic apoptosis and the survival of experimental animals were determined. RESULTS Our experimental data showed that treatment with ATZ significantly enhanced LPS/D-Gal-induced elevation of serum aspartate transaminase (AST) and alanine transaminase (ALT), exacerbated the hepatic histopathological abnormality and decreased the survival rate of experimental animals. ATZ inhibited the activity of CAT, increased the content of H2 O2 and the levels of malondialdehyde (MDA) in liver tissues. In addition, treatment with ATZ also enhanced LPS/D-Gal-induced hepatic apoptosis as evidenced by increased caspases activities in liver tissues and increased number of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells in liver sections. CONCLUSION These findings suggested that CAT might be involved in the progression of LPS/D-Gal-induced fulminant liver injury.
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Affiliation(s)
- Mengying Jia
- Department of Pathophysiology, Chongqing Medical University, Chongqing, China
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Pavlov TS, Levchenko V, Staruschenko A. Role of Rho GDP dissociation inhibitor α in control of epithelial sodium channel (ENaC)-mediated sodium reabsorption. J Biol Chem 2014; 289:28651-9. [PMID: 25164814 DOI: 10.1074/jbc.m114.558262] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The epithelial sodium channel (ENaC) is expressed in the aldosterone-sensitive distal nephron where it performs sodium reabsorption from the lumen. We have recently shown that ENaC activity contributes to the development of salt-induced hypertension as a result of deficiency of EGF level. Previous studies revealed that Rho GDP-dissociation inhibitor α (RhoGDIα) is involved in the control of salt-sensitive hypertension and renal injury via Rac1, which is one of the small GTPases activating ENaC. Here we investigated the intracellular mechanism mediating the involvement of the RhoGDIα/Rac1 axis in the control of ENaC and the effect of EGF on ENaC in this pathway. We demonstrated that RhoGDIα is highly expressed in the cortical collecting ducts of mice and rats, and its expression is down-regulated in Dahl salt-sensitive rats fed a high salt diet. Knockdown of RhoGDIα in cultured cortical collecting duct principal cells increased ENaC subunits expression and ENaC-mediated sodium reabsorption. Furthermore, RhoGDIα deficiency causes enhanced response to EGF treatment. Patch clamp analysis reveals that RhoGDIα significantly decreases ENaC current density and prevents its up-regulation by RhoA and Rac1. Inhibition of Rho kinase with Y27632 had no effects on ENaC response to EGF either in control or RhoGDIα knocked down cells. However, EGF treatment increased levels of active Rac1, which was further enhanced in RhoGDIα-deficient cells. We conclude that changes in the RhoGDIα-dependent pathway have a permissive role in the Rac1-mediated enhancement of ENaC activity observed in salt-induced hypertension.
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Affiliation(s)
- Tengis S Pavlov
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Vladislav Levchenko
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Alexander Staruschenko
- From the Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
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Thai TL, Yu L, Eaton DC, Duke BJ, Al-Khalili O, Lam HYC, Ma H, Bao HF. Basolateral P2X₄channels stimulate ENaC activity in Xenopus cortical collecting duct A6 cells. Am J Physiol Renal Physiol 2014; 307:F806-13. [PMID: 25100278 DOI: 10.1152/ajprenal.00350.2013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The polarized nature of epithelial cells allows for different responses to luminal or serosal stimuli. In kidney tubules, ATP is produced luminally in response to changes in luminal flow. Luminal increases in ATP have been previously shown to inhibit the renal epithelial Na⁺ channel (ENaC). On the other hand, ATP is increased basolaterally in renal epithelia in response to aldosterone. We tested the hypothesis that basolateral ATP can stimulate ENaC function through activation of the P2X₄receptor/channel. Using single channel cell-attached patch-clamp techniques, we demonstrated the existence of a basolaterally expressed channel stimulated by the P2X₄agonist 2-methylthio-ATP (meSATP) in Xenopus A6 cells, a renal collecting duct principal cell line. This channel had a similar reversal potential and conductance to that of P2X₄channels. Cell surface biotinylation of the basolateral side of these cells confirmed the basolateral presence of the P2X4 receptor. Basolateral addition of meSATP enhanced the activity of ENaC in single channel patch-clamp experiments, an effect that was absent in cells transfected with a dominant negative P2X₄receptor construct, indicating that activation of P2X₄channels stimulates ENaC activity in these cells. The effect of meSATP on ENaC activity was reduced after chelation of basolateral Ca²⁺ with EGTA or inhibition of phosphatidylinositol 3-kinase with LY-294002. Overall, our results show that ENaC is stimulated by P2X₄receptor activation and that the stimulation is dependent on increases in intracellular Ca²⁺ and phosphatidylinositol 3-kinase activation.
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Affiliation(s)
- Tiffany L Thai
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Ling Yu
- College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing, China
| | - Douglas C Eaton
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Billie Jean Duke
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Otor Al-Khalili
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Ho Yin Colin Lam
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Heping Ma
- Department of Physiology, Emory University, Atlanta, Georgia; and
| | - Hui-Fang Bao
- Department of Physiology, Emory University, Atlanta, Georgia; and
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Hydrogen peroxide induces vasorelaxation by enhancing 4-aminopyridine-sensitive Kv currents through S-glutathionylation. Pflugers Arch 2014; 467:285-97. [PMID: 24756196 PMCID: PMC4293500 DOI: 10.1007/s00424-014-1513-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 01/04/2014] [Accepted: 04/02/2014] [Indexed: 12/04/2022]
Abstract
Hydrogen peroxide (H2O2) is an endothelium-derived hyperpolarizing factor. Since opposing vasoactive effects have been reported for H2O2 depending on the vascular bed and experimental conditions, this study was performed to assess whether H2O2 acts as a vasodilator in the rat mesenteric artery and, if so, to determine the underlying mechanisms. H2O2 elicited concentration-dependent relaxation in mesenteric arteries precontracted with norepinephrine. The vasodilatory effect of H2O2 was reversed by treatment with dithiothreitol. H2O2-elicited vasodilation was significantly reduced by blocking 4-aminopyridine (4-AP)-sensitive Kv channels, but it was resistant to blockers of big-conductance Ca2+-activated K+ channels and inward rectifier K+ channels. A patch-clamp study in mesenteric arterial smooth muscle cells (MASMCs) showed that H2O2 increased Kv currents in a concentration-dependent manner. H2O2 speeded up Kv channel activation and shifted steady state activation to hyperpolarizing potentials. Similar channel activation was seen with oxidized glutathione (GSSG). The H2O2-mediated channel activation was prevented by glutathione reductase. Consistent with S-glutathionylation, streptavidin pull-down assays with biotinylated glutathione ethyl ester showed incorporation of glutathione (GSH) in the Kv channel proteins in the presence of H2O2. Interestingly, conditions of increased oxidative stress within MASMCs impaired the capacity of H2O2 to stimulate Kv channels. Not only was the H2O2 stimulatory effect much weaker, but the inhibitory effect of H2O2 was unmasked. These data suggest that H2O2 activates 4-AP-sensitive Kv channels, possibly through S-glutathionylation, which elicits smooth muscle relaxation in rat mesenteric arteries. Furthermore, our results support the idea that the basal redox status of MASMCs determines the response of Kv currents to H2O2.
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Phosphoinositide 3-kinase pathway mediates early aldosterone action on morphology and epithelial sodium channel in mammalian renal epithelia. J Membr Biol 2014; 247:461-8. [PMID: 24723072 DOI: 10.1007/s00232-014-9647-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 02/25/2014] [Indexed: 11/27/2022]
Abstract
Involvement of phosphoinositide 3-kinases (PI3Ks) in early aldosterone action on epithelial sodium channel (ENaC) in mammalian renal epithelia was investigated by hopping probe ion conductance microscopy combined with patch-clamping in this study. Aldosterone treatment enlarged the cell volume and elevated the apical membrane of renal mpkCCDc14 epithelia, which resulted in enhancing the open probability of ENaC. Inhibition of PI3K pathway by LY294002 obviously suppressed these aldosterone-induced changes in both cell morphology and ENaC activity. These results indicated the important role of PI3K pathway in early aldosterone action and the close relationship between cell morphology and ENaC activity in mammalian renal epithelia.
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Ward JBJ, Keely SJ, Keely SJ. Oxygen in the regulation of intestinal epithelial transport. J Physiol 2014; 592:2473-89. [PMID: 24710059 DOI: 10.1113/jphysiol.2013.270249] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The transport of fluid, nutrients and electrolytes to and from the intestinal lumen is a primary function of epithelial cells. Normally, the intestine absorbs approximately 9 l of fluid and 1 kg of nutrients daily, driven by epithelial transport processes that consume large amounts of cellular energy and O2. The epithelium exists at the interface of the richly vascularised mucosa, and the anoxic luminal environment and this steep O2 gradient play a key role in determining the expression pattern of proteins involved in fluid, nutrient and electrolyte transport. However, the dynamic nature of the splanchnic circulation necessitates that the epithelium can evoke co-ordinated responses to fluctuations in O2 availability, which occur either as a part of the normal digestive process or as a consequence of several pathophysiological conditions. While it is known that hypoxia-responsive signals, such as reactive oxygen species, AMP-activated kinase, hypoxia-inducible factors, and prolyl hydroxylases are all important in regulating epithelial responses to altered O2 supply, our understanding of the molecular mechanisms involved is still limited. Here, we aim to review the current literature regarding the role that O2 plays in regulating intestinal transport processes and to highlight areas of research that still need to be addressed.
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Affiliation(s)
- Joseph B J Ward
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Simon J Keely
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Newcastle NSW, Australia
| | - Stephen J Keely
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland
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Kim MJ, Johnson WA. ROS-mediated activation of Drosophila larval nociceptor neurons by UVC irradiation. BMC Neurosci 2014; 15:14. [PMID: 24433322 PMCID: PMC3898224 DOI: 10.1186/1471-2202-15-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 01/09/2014] [Indexed: 11/24/2022] Open
Abstract
Background The complex Drosophila larval peripheral nervous system, capable of monitoring sensory input from the external environment, includes a family of multiple dendritic (md) neurons with extensive dendritic arbors tiling the inner surface of the larval body wall. The class IV multiple dendritic (mdIV) neurons are the most complex with dendritic nerve endings forming direct intimate contacts with epithelial cells of the larval body wall. Functioning as polymodal mechanonociceptors with the ability to respond to both noxious mechanical stimulation and noxious heat, the mdIV neurons are also activated by nanomolar levels of the endogenous reactive oxygen species (ROS), H2O2. Although often associated with tissue damage related to oxidative stress, endogenous ROS have also been shown to function as signaling molecules at lower concentrations. The overall role of ROS in sensory signaling is poorly understood but the acutely sensitive response of mdIV neurons to ROS-mediated activation is consistent with a routine role in the regulation of mdIV neuronal activity. Larvae respond to short wavelength ultraviolet (UVC) light with an immediate and visual system-independent writhing and twisting of the body previously described as a nociceptive response. Molecular and cellular mechanisms mediating this response and potential relationships with ROS generation are not well understood. We have used the UVC-induced writhing response as a model for investigation of the proposed link between endogenous ROS production and mdIV neuron function in the larval body wall. Results Transgenic inactivation of mdIV neurons caused a strong suppression of UVC-induced writhing behavior consistent with a key role for the mdIV neurons as mediators of the behavioral response. Direct imaging of ROS-activated fluorescence showed that UVC irradiation caused a significant increase in endogenous ROS levels in the larval body wall and transgenic overexpression of antioxidant enzymes strongly suppressed the UVC-induced writhing response. Direct electrophysiological recordings demonstrated that UVC irradiation also increased neuronal activity of the mdIV neurons. Conclusions Results obtained using UVC irradiation to induce ROS generation provide evidence that UVC-induced writhing behavior is mediated by endogenous production of ROS capable of activating mdIV mechanonociceptors in the larval body wall.
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Affiliation(s)
| | - Wayne A Johnson
- Department of Molecular Physiology and Biophysics, University of Iowa, Roy J, and Lucille A, Carver College of Medicine, Iowa City, IA 52242, USA.
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Kim MJ, Ainsley JA, Carder JW, Johnson WA. Hyperoxia-triggered aversion behavior in Drosophila foraging larvae is mediated by sensory detection of hydrogen peroxide. J Neurogenet 2013; 27:151-62. [PMID: 23927496 DOI: 10.3109/01677063.2013.804920] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Reactive oxygen species (ROS) in excess have been implicated in numerous chronic illnesses, including asthma, diabetes, aging, cardiovascular disease, and neurodegenerative illness. However, at lower concentrations, ROS can also serve essential routine functions as part of cellular signal transduction pathways. As products of atmospheric oxygen, ROS-mediated signals can function to coordinate external environmental conditions with growth and development. A central challenge has been a mechanistic distinction between the toxic effects of oxidative stress and endogenous ROS functions occurring at much lower concentrations. Drosophila larval aerotactic behavioral assays revealed strong developmentally regulated aversion to mild hyperoxia mediated by H2O2-dependent activation of class IV multidendritic (mdIV) sensory neurons expressing the Degenerin/epithelial Na(+) channel subunit, Pickpocket1 (PPK1). Electrophysiological recordings in foraging-stage larvae (78-84 h after egg laying [AEL]) demonstrated PPK1-dependent activation of mdIV neurons by nanomolar levels of H2O2 well below levels normally associated with oxidative stress. Acute sensitivity was reduced > 100-fold during the larval developmental transition to wandering stage (> 96 h AEL), corresponding to a loss of hyperoxia aversion behavior during the same period. Degradation of endogenous H2O2 by transgenic overexpression of catalase in larval epidermis caused a suppression of hyperoxia aversion behavior. Conversely, disruption of endogenous catalase activity using a UAS-CatRNAi transposon resulted in an enhanced hyperoxia-aversive response. These results demonstrate an essential role for low-level endogenous H2O2 as an environment-derived signal coordinating developmental behavioral transitions.
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Affiliation(s)
- Myung Jun Kim
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, University of Iowa , Iowa City, Iowa , USA
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Trac D, Liu B, Pao AC, Thomas SV, Park M, Downs CA, Ma HP, Helms MN. Fulvene-5 inhibition of Nadph oxidases attenuates activation of epithelial sodium channels in A6 distal nephron cells. Am J Physiol Renal Physiol 2013; 305:F995-F1005. [PMID: 23863470 DOI: 10.1152/ajprenal.00098.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nadph oxidase 4 is an important cellular source of reactive oxygen species (ROS) generation in the kidney. Novel antioxidant drugs, such as Nox4 inhibitor compounds, are being developed. There is, however, very little experimental evidence for the biological role and regulation of Nadph oxidase isoforms in the kidney. Herein, we show that Fulvene-5 is an effective inhibitor of Nox-generated ROS and report the role of Nox isoforms in activating epithelial sodium channels (ENaC) in A6 distal nephron cells via oxidant signaling and cell stretch activation. Using single-channel patch-clamp analysis, we report that Fulvene-5 blocked the increase in ENaC activity that is typically observed with H2O2 treatment of A6 cells: average ENaC NPo values decreased from a baseline level of 1.04 ± 0.18 (means ± SE) to 0.25 ± 0.08 following Fulvene-5 treatment. H2O2 treatment failed to increase ENaC activity in the presence of Fulvene-5. Moreover, Fulvene-5 treatment of A6 cells blocked the osmotic cell stretch response of A6 cells, indicating that stretch activation of Nox-derived ROS plays an important role in ENaC regulation. Together, these findings indicate that Fulvene-5, and perhaps other classes of antioxidant inhibitors, may represent a novel class of compounds useful for the treatment of pathological disorders stemming from inappropriate ion channel activity, such as hypertension.
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Affiliation(s)
- David Trac
- Dept. of Pediatrics, 2015 Uppergate Dr., Atlanta, GA 30322.
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Abstract
Angiotensin II (Ang II) is the principal effector of the renin-angiotensin-aldosterone system (RAAS). It initiates myriad processes in multiple organs integrated to increase circulating volume and elevate systemic blood pressure. In the kidney, Ang II stimulates renal tubular water and salt reabsorption causing antinatriuresis and antidiuresis. Activation of the RAAS is known to enhance activity of the epithelial Na(+) channel (ENaC) in the aldosterone-sensitive distal nephron. In addition to its well described stimulatory actions on aldosterone secretion, Ang II is also capable of directly increasing ENaC activity. In this brief review, we discuss recent findings about non-classical Ang II actions on ENaC and speculate about its relevance for renal sodium handling.
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Zhang J, Chen S, Liu H, Zhang B, Zhao Y, Ma K, Zhao D, Wang Q, Ma H, Zhang Z. Hydrogen sulfide prevents hydrogen peroxide-induced activation of epithelial sodium channel through a PTEN/PI(3,4,5)P3 dependent pathway. PLoS One 2013; 8:e64304. [PMID: 23741314 PMCID: PMC3669336 DOI: 10.1371/journal.pone.0064304] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/12/2013] [Indexed: 01/12/2023] Open
Abstract
Sodium reabsorption through the epithelial sodium channel (ENaC) at the distal segment of the kidney plays an important role in salt-sensitive hypertension. We reported previously that hydrogen peroxide (H2O2) stimulates ENaC in A6 distal nephron cells via elevation of phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) in the apical membrane. Here we report that H2S can antagonize H2O2-induced activation of ENaC in A6 cells. Our cell-attached patch-clamp data show that ENaC open probability (PO) was significantly increased by exogenous H2O2, which is consistent with our previous finding. The aberrant activation of ENaC induced by exogenous H2O2 was completely abolished by H2S (0.1 mM NaHS). Pre-treatment of A6 cells with H2S slightly decreased ENaC PO; however, in these cells H2O2 failed to elevate ENaC PO. Confocal microscopy data show that application of exogenous H2O2 to A6 cells significantly increased intracellular reactive oxygen species (ROS) level and induced accumulation of PI(3,4,5)P3 in the apical compartment of the cell membrane. These effects of exogenous H2O2 on intracellular ROS levels and on apical PI(3,4,5)P3 levels were almost completely abolished by treatment of A6 cells with H2S. In addition, H2S significantly inhibited H2O2-induced oxidative inactivation of the tumor suppressor phosphatase and tensin homolog (PTEN) which is a negative regulator of PI(3,4,5)P3. Moreover, BPV(pic), a specific inhibitor of PTEN, elevated PI(3,4,5)P3 and ENaC activity in a manner similar to that of H2O2 in A6 cells. Our data show, for the first time, that H2S prevents H2O2-induced activation of ENaC through a PTEN-PI(3,4,5)P3 dependent pathway.
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Affiliation(s)
- Jianing Zhang
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Shuo Chen
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Huibin Liu
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Bingkun Zhang
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Ying Zhao
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Ke Ma
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Dan Zhao
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Qiushi Wang
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
| | - Heping Ma
- Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail: (ZZ); (HM)
| | - Zhiren Zhang
- Departments of Clinical Pharmacy and Cardiology, the 2nd Affiliated Hospital, Harbin Medical University, Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism and Treatment, Harbin, P.R. China
- * E-mail: (ZZ); (HM)
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42
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Liu BC, Song X, Lu XY, Fang CZ, Wei SP, Alli AA, Eaton DC, Shen BZ, Li XQ, Ma HP. Lovastatin attenuates effects of cyclosporine A on tight junctions and apoptosis in cultured cortical collecting duct principal cells. Am J Physiol Renal Physiol 2013; 305:F304-13. [PMID: 23720343 DOI: 10.1152/ajprenal.00074.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We used mouse cortical collecting duct principal cells (mpkCCDc14 cell line) as a model to determine whether statins reduce the harmful effects of cyclosporine A (CsA) on the distal nephron. The data showed that treatment of cells with CsA increased transepithelial resistance and that the effect of CsA was abolished by lovastatin. Scanning ion conductance microscopy showed that CsA significantly increased the height of cellular protrusions near tight junctions. In contrast, lovastatin eliminated the protrusions and even caused a modest depression between cells. Western blot analysis and confocal microscopy showed that lovastatin also abolished CsA-induced elevation of both zonula occludens-1 and cholesterol in tight junctions. In contrast, a high concentration of CsA induced apoptosis, which was also attenuated by lovastatin, elevated intracellular ROS via activation of NADPH oxidase, and increased the expression of p47phox. Sustained treatment of cells with lovastatin also induced significant apoptosis, which was attenuated by CsA, but did not elevate intracellular ROS. These results indicate that both CsA and lovastatin are harmful to principal cells of the distal tubule, but via ROS-dependent and ROS-independent apoptotic pathways, respectively, and that they counteract probably via mobilization of cellular cholesterol levels.
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Affiliation(s)
- Bing-Chen Liu
- Department of Cardiology, The Fourth Affiliated Hospital, Harbin Medical University, Harbin, Heilongjiang, People's Republic of China
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43
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Staruschenko A, Palygin O, Ilatovskaya DV, Pavlov TS. Epidermal growth factors in the kidney and relationship to hypertension. Am J Physiol Renal Physiol 2013; 305:F12-20. [PMID: 23637204 DOI: 10.1152/ajprenal.00112.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Members of the epidermal growth factor (EGF)-family bind to ErbB (EGFR)-family receptors that play an important role in the regulation of various fundamental cell processes in many organs including the kidney. In this field, most of the research efforts are focused on the role of EGF-ErbB axis in cancer biology. However, many studies indicate that abnormal ErbB-mediated signaling pathways are critical in the development of renal and cardiovascular pathologies. The kidney is a major site of the EGF-family ligands synthesis, and it has been shown to express all four members of the ErbB receptor family. The study of kidney disease regulation by ErbB receptor ligands has expanded considerably in recent years. In vitro and in vivo studies have provided direct evidence of the role of ErbB signaling in the kidney. Recent advances in the understanding of how the proteins in the EGF-family regulate sodium transport and development of hypertension are specifically discussed here. Collectively, these results suggest that EGF-ErbB signaling pathways could be major determinants in the progress of renal lesions, including its effects on the regulation of sodium reabsorption in collecting ducts.
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Affiliation(s)
- Alexander Staruschenko
- Department of Physiology, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA.
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44
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Liu BC, Song X, Lu XY, Li DT, Eaton DC, Shen BZ, Li XQ, Ma HP. High glucose induces podocyte apoptosis by stimulating TRPC6 via elevation of reactive oxygen species. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1434-42. [PMID: 23499875 DOI: 10.1016/j.bbamcr.2013.02.031] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 02/25/2013] [Accepted: 02/26/2013] [Indexed: 12/20/2022]
Abstract
Podocyte number is significantly reduced in diabetic patients and animal models, but the mechanism remains unclear. In the present study, we found that high glucose induced apoptosis in control podocytes which express transient receptor potential canonical 6 (TRPC6) channels, but not in TRPC6 knockdown podocytes in which TRPC6 was knocked down by TRPC6 silencing short hairpin RNA (shRNA). This effect was reproduced by treatment of podocytes with the reactive oxygen species (ROS), hydrogen peroxide (H2O2). Single-channel data from cell-attached, patch-clamp experiments showed that both high glucose and H2O2 activated the TRPC6 channel in control podocytes, but not in TRPC6 knockdown podocytes. Confocal microscopy showed that high glucose elevated ROS in podocytes and that H2O2 reduced the membrane potential of podocytes and elevated intracellular Ca(2+) via activation of TRPC6. Since intracellular Ca(2+) overload induces apoptosis, H2O2-induced apoptosis may result from TRPC6-mediated elevation of intracellular Ca(2+). These data together suggest that high glucose induces apoptosis in podocytes by stimulating TRPC6 via elevation of ROS.
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Affiliation(s)
- Bing-Chen Liu
- Department of Cardiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin, People's Republic of China
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45
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Downs CA, Trac DQ, Kreiner LH, Eaton AF, Johnson NM, Brown LA, Helms MN. Ethanol alters alveolar fluid balance via Nadph oxidase (NOX) signaling to epithelial sodium channels (ENaC) in the lung. PLoS One 2013; 8:e54750. [PMID: 23382956 PMCID: PMC3558518 DOI: 10.1371/journal.pone.0054750] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 12/14/2012] [Indexed: 02/02/2023] Open
Abstract
Chronic alcohol consumption is associated with increased incidence of ICU-related morbidity and mortality, primarily from acute respiratory distress syndrome (ARDS). However, the mechanisms involved are unknown. One explanation is that alcohol regulates epithelial sodium channels (ENaC) via oxidant signaling to promote a pro- injury environment. We used small rodent models to mimic acute and chronic alcohol consumption and tested the hypothesis that ethanol (EtOH) would affect lung fluid clearance by up-regulating ENaC activity in the lung. Fluorescence labeling of rat lung slices and in vivo mouse lung revealed an increase in ROS production in response to acute EtOH exposure. Using western blots and fluorescein-5-maleimide labeling, we conclude that EtOH exposure modifies cysteines of α-ENaC while data from single channel patch clamp analysis confirm that 0.16% EtOH increased ENaC activity in rat alveolar cells. In vivo lung fluid clearance demonstrated a latent increase in fluid clearance in mice receiving EtOH diet. Ethanol mice given a tracheal instillation of LPS demonstrated early lung fluid clearance compared to caloric control mice and C57Bl/6 mice. Standard biochemical techniques reveal that chronic EtOH consumption resulted in greater protein expression of the catalytic gp91phox subunit and the obligate Rac1 protein. Collectively these data suggest that chronic EtOH consumption may lead to altered regulation of ENaC, contributing to a ‘pro-injury’ environment in the alcohol lung.
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Affiliation(s)
- Charles A Downs
- Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, Georgia, USA.
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46
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Bao HF, Song JZ, Duke BJ, Ma HP, Denson DD, Eaton DC. Ethanol stimulates epithelial sodium channels by elevating reactive oxygen species. Am J Physiol Cell Physiol 2012; 303:C1129-38. [PMID: 22895258 PMCID: PMC3530770 DOI: 10.1152/ajpcell.00139.2012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 08/08/2012] [Indexed: 11/22/2022]
Abstract
Alcohol affects total body sodium balance, but the molecular mechanism of its effect remains unclear. We used single-channel methods to examine how ethanol affects epithelial sodium channels (ENaC) in A6 distal nephron cells. The data showed that ethanol significantly increased both ENaC open probability (P(o)) and the number of active ENaC in patches (N). 1-Propanol and 1-butanol also increased ENaC activity, but iso-alcohols did not. The effects of ethanol were mimicked by acetaldehyde, the first metabolic product of ethanol, but not by acetone, the metabolic product of 2-propanol. Besides increasing open probability and apparent density of active channels, confocal microscopy and surface biotinylation showed that ethanol significantly increased α-ENaC protein in the apical membrane. The effects of ethanol on ENaC P(o) and N were abolished by a superoxide scavenger, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (TEMPOL) and blocked by the phosphatidylinositol 3-kinase inhibitor LY294002. Consistent with an effect of ethanol-induced reactive oxygen species (ROS) on ENaC, primary alcohols and acetaldehyde elevated intracellular ROS, but secondary alcohols did not. Taken together with our previous finding that ROS stimulate ENaC, the current results suggest that ethanol stimulates ENaC by elevating intracellular ROS probably via its metabolic product acetaldehyde.
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Affiliation(s)
- Hui-Fang Bao
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, USA
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47
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Ilatovskaya DV, Pavlov TS, Levchenko V, Staruschenko A. ROS production as a common mechanism of ENaC regulation by EGF, insulin, and IGF-1. Am J Physiol Cell Physiol 2012; 304:C102-11. [PMID: 23135700 DOI: 10.1152/ajpcell.00231.2012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The epithelial Na(+) channel (ENaC) is a key transporter participating in the fine tuning of Na(+) reabsorption in the nephron. ENaC activity is acutely upregulated by epidermal growth factor (EGF), insulin, and insulin-like growth factor-1 (IGF-1). It was also proposed that reactive oxygen species (ROS) have a stimulatory effect on ENaC. Here we studied whether effects of EGF, insulin, and IGF-1 correlate with ROS production in the mouse cortical collecting duct (mpkCCD(c14)) cells. Western blotting confirmed the expression of the NADPH oxidase complex subunits in these cells. Treatment of mpkCCD(c14) cells with EGF, insulin, or IGF-1 evoked an increase in ROS production as measured by CM-H(2)DCF-DA fluorescence. ROS production caused by a xanthine-xanthine oxidase reaction also resulted in a significant elevation in short-circuit current through the mpkCCD(c14) monolayer. Transepithelial current measurements showed an acute increase of amiloride-sensitive current through the mpkCCD(c14) monolayer in response to EGF, insulin, or IGF-1. Pretreatment with the nonselective NADPH oxidase activity inhibitor apocynin blunted both ROS production and increase in ENaC-mediated current in response to these drugs. To further test whether NADPH oxidase subunits are involved in the effect of EGF, we used a stable M-1 cell line with a knockdown of Rac1, which is one of the key subunits of the NADPH oxidase complex, and measured amiloride-sensitive currents in response to EGF. In contrast to control cells, EGF had no effect in Rac1 knockdown cells. We hypothesize that EGF, insulin, and IGF-1 have a common stimulatory effect on ENaC mediated by ROS production.
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Affiliation(s)
- Daria V Ilatovskaya
- Medical College of Wisconsin, Dept. of Physiology, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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48
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Armogida M, Nisticò R, Mercuri NB. Therapeutic potential of targeting hydrogen peroxide metabolism in the treatment of brain ischaemia. Br J Pharmacol 2012; 166:1211-24. [PMID: 22352897 DOI: 10.1111/j.1476-5381.2012.01912.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
For many years after its discovery, hydrogen peroxide (H₂O₂) was viewed as a toxic molecule to human tissues; however, in light of recent findings, it is being recognized as an ubiquitous endogenous molecule of life as its biological role has been better elucidated. Indeed, increasing evidence suggests that H₂O₂ may act as a second messenger with a pro-survival role in several physiological processes. In addition, our group has recently demonstrated neuroprotective effects of H₂O₂ on in vitro and in vivo ischaemic models through a catalase (CAT) enzyme-mediated mechanism. Therefore, the present review summarizes experimental data supporting a neuroprotective potential of H₂O₂ in ischaemic stroke that has been principally achieved by means of pharmacological and genetic strategies that modify either the activity or the expression of the superoxide dismutase (SOD), glutathione peroxidase (GPx) and CAT enzymes, which are key regulators of H₂O₂ metabolism. It also critically discusses a translational impact concerning the role played by H₂O₂ in ischaemic stroke. Based on these data, we hope that further research will be done in order to better understand the mechanisms underlying H₂O₂ functions and to promote successful H₂O₂ signalling based therapy in ischaemic stroke.
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Affiliation(s)
- Marta Armogida
- Laboratory of Experimental Neurology, Fondazione Santa Lucia IRCCS, Rome, Italy
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49
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Snyder PM. Intoxicated Na(+) channels. Focus on "ethanol stimulates epithelial sodium channels by elevating reactive oxygen species". Am J Physiol Cell Physiol 2012; 303:C1125-6. [PMID: 22992679 DOI: 10.1152/ajpcell.00301.2012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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50
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Deng X, Wu K, Wan J, Li L, Jiang R, Jia M, Jing Y, Zhang L. Aminotriazole attenuated carbon tetrachloride-induced oxidative liver injury in mice. Food Chem Toxicol 2012; 50:3073-8. [PMID: 22687551 DOI: 10.1016/j.fct.2012.05.052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 05/18/2012] [Accepted: 05/30/2012] [Indexed: 01/26/2023]
Abstract
Carbon tetrachloride (CCl(4)) has been used extensively to study xenobiotic-induced oxidative liver injury. Catalase (CAT) is a major antioxidant enzyme while aminotriazole (ATZ) is commonly used as a CAT inhibitor. In the present study, the effects of ATZ on CCl(4)-induced liver injury were investigated. Our experimental data showed that pretreatment with ATZ significantly decreased CCl(4)-induced elevation of serum aspartate transaminase (AST) and alanine transaminase (ALT) and improved hepatic histopathological abnormality. ATZ dose-dependently inhibited the activity of CAT, but it reduced the content of H(2)O(2) and the levels of malondialdehyde (MDA) in liver tissues. ATZ decreased plasma level of pro-inflammatory cytokines (TNF-α and IL-6) and reduced hepatic levels of myeloperoxidase (MPO). In addition, posttreatment with ATZ also decreased the level of ALT and AST. These data indicated that ATZ effectively alleviated CCl(4)-induced oxidative liver damage. These findings suggested that ATZ might have potential value in preventing oxidative liver injury.
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Affiliation(s)
- Xinyu Deng
- Department of Pathophysiology, Chongqing Medical University, Chongqing, China
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