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Pulgar VM, Cruz-Diaz N, Westwood BM, Chappell MC. Angiotensinogen uptake and stimulation of oxidative stress in human pigment retinal epithelial cells. Peptides 2022; 152:170770. [PMID: 35183655 DOI: 10.1016/j.peptides.2022.170770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 02/12/2022] [Accepted: 02/16/2022] [Indexed: 12/27/2022]
Abstract
We previously reported that isolated proximal tubules (PT) internalize the precursor protein angiotensinogen and that the 125Iodine-labeled protein accumulated in the nuclear and mitochondrial fractions of the PT cells; however, whether internalization of angiotensinogen occurs in non-renal epithelial cells is unknown. Therefore, the present study assessed the cellular uptake of 125I-angiotensinogen in human retinal pigment ARPE-19 epithelial cells, a widely utilized cell model for the assessment of retinal injury, inflammation and oxidative stress. ARPE-19 cells, maintained in serum-free media to remove extracellular sources of bovine serum angiotensinogen and renin, were incubated with 125Iodine-angiotensinogen at 37 °C and revealed the time-dependent uptake of angiotensinogen over 24 h. In contrast, incubation with labelled Ang II, Ang-(1-7) or Ang I revealed minimal cellular uptake. Subcellular fractionation following a 4-hour uptake of 125I-angiotensinogen revealed that the majority of the labeled protein localized to the nuclear fraction with lower accumulation in the mitochondrial and cytosolic fractions. Finally, we show that addition of angiotensinogen (2 nM) to the ARPE-19 cells increased oxidative stress as assessed by DCF fluorescence that was blocked by pretreatment of the cells with either the NADPH oxidase 1/4 inhibitor GKT137831, apocynin or atorvastatin, but not the AT1 receptor antagonist losartan. In contrast, treatment of the cells with Angiotensin II at an equivalent dose to angiotensinogen failed to stimulate oxidative stress. We conclude that human retinal pigment cells internalize angiotensinogen to elicit an increase in oxidative stress through a pathway that appears distinct from the Ang II-AT1 receptor axis.
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Affiliation(s)
- Victor M Pulgar
- Department of Pharmaceutical Sciences, Campbell University, Buies-Creek, NC, United States; Hypertension & Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, NC,United States
| | - Nildris Cruz-Diaz
- Hypertension & Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, NC,United States
| | - Brian M Westwood
- Hypertension & Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, NC,United States
| | - Mark C Chappell
- Hypertension & Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, NC,United States.
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Wilson BA, Cruz-Diaz N, Su Y, Rose JC, Gwathmey TM, Chappell MC. Angiotensinogen import in isolated proximal tubules: evidence for mitochondrial trafficking and uptake. Am J Physiol Renal Physiol 2016; 312:F879-F886. [PMID: 27903492 PMCID: PMC5451555 DOI: 10.1152/ajprenal.00246.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 11/11/2016] [Accepted: 11/23/2016] [Indexed: 12/15/2022] Open
Abstract
The renal proximal tubules are a key functional component of the kidney and express the angiotensin precursor angiotensinogen; however, it is unclear the extent that tubular angiotensinogen reflects local synthesis or internalization. Therefore, the current study established the extent to which angiotensinogen is internalized by proximal tubules and the intracellular distribution. Proximal tubules were isolated from the kidney cortex of male sheep by enzymatic digestion and a discontinuous Percoll gradient. Tubules were incubated with radiolabeled 125I-angiotensinogen for 2 h at 37°C in serum/phenol-free DMEM/F12 media. Approximately 10% of exogenous 125I-angiotensinogen was internalized by sheep tubules. Subcellular fractionation revealed that 21 ± 4% of the internalized 125I-angiotensinogen associated with the mitochondrial fraction with additional labeling evident in the nucleus (60 ± 7%), endoplasmic reticulum (4 ± 0.5%), and cytosol (15 ± 4%; n = 4). Subsequent studies determined whether mitochondria directly internalized 125I-angiotensinogen using isolated mitochondria from renal cortex and human HK-2 proximal tubule cells. Sheep cortical and HK-2 mitochondria internalized 125I-angiotensinogen at a comparable rate of (33 ± 9 vs. 21 ± 10 pmol·min-1·mg protein-1; n = 3). Lastly, unlabeled angiotensinogen (100 nM) competed for 125I-angiotensinogen uptake to a greater extent than human albumin in HK-2 mitochondria (60 ± 2 vs. 16 ± 13%; P < 0.05, n = 3). Collectively, our data demonstrate angiotensinogen import and subsequent trafficking to the mitochondria in proximal tubules. We conclude that this pathway may constitute a source of the angiotensinogen precursor for the mitochondrial expression of angiotensin peptides.
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Affiliation(s)
- Bryan A Wilson
- Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and
| | - Nildris Cruz-Diaz
- Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and
| | - Yixin Su
- Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - James C Rose
- Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - TanYa M Gwathmey
- Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and
| | - Mark C Chappell
- Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and
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A possible mechanism for the progression of chronic renal disease and congestive heart failure. ACTA ACUST UNITED AC 2014; 9:54-63. [PMID: 25539896 DOI: 10.1016/j.jash.2014.09.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 09/11/2014] [Accepted: 09/13/2014] [Indexed: 12/15/2022]
Abstract
Chronic neurologic diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as various forms of chronic renal disease and systolic congestive heart failure, are among the most common progressive degenerative disorders encountered in medicine. Each disease follows a nearly relentless course, albeit at varying rates, driven by progressive cell dysfunction and drop-out. The neurologic diseases are characterized by the progressive spread of disease-causing proteins (prion-like proteins) from cell to cell. Recent evidence indicates that cell autonomous renin angiotensin systems operate in heart and kidney, and it is known that functional intracrine proteins can also spread between cells. This then suggests that certain progressive degenerative cardiovascular disorders such as forms of chronic renal insufficiency and systolic congestive heart failure result from dysfunctional renin angiotensin system intracrine action spreading in kidney or myocardium.
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Alzayadneh EM, Chappell MC. Nuclear expression of renin-angiotensin system components in NRK-52E renal epithelial cells. J Renin Angiotensin Aldosterone Syst 2014; 16:1135-48. [PMID: 24961503 DOI: 10.1177/1470320313515039] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
INTRODUCTION Isolated nuclei of sheep proximal tubules express angiotensin (Ang) receptors as well as angiotensinogen (AGT) and renin. The present study characterized the NRK-52E tubular epithelial cell line for the intracellular expression of renin-angiotensin system (RAS) components. METHODS RAS components were visualized by immunofluorescent staining in intact cells and protein expression in isolated nuclei. RESULTS An antibody to the angiotensin I (Ang I) sequence of AGT (AI-AGT) revealed only cytosolic staining, while an antibody to an internal sequence of AGT (Int-AGT) revealed primarily nuclear staining. Immunoblots of nuclear and cytosolic fractions confirmed the differential cell staining of AGT. Immunostaining for renin was present on nuclei of intact cells. Nuclear renin activity averaged 0.77±0.05 nmol/mg protein/h that was reduced by aliskiren (0.13±0.01 nmol/mg/h, n=3, p<0.01); trypsin activation increased activity three-fold. Peptide staining localized angiotensin II (Ang II) and Ang-(1-7) to the nucleus and peptide content averaged 59±2 and 57±22 fmol/mg (n=4), respectively. Peptide metabolism in isolated nuclei revealed the processing of Ang I to Ang-(1-7) by thimet oligopeptidase. CONCLUSION We conclude that the NRK-52E cells express an intracellular RAS localized to the nucleus and may be an appropriate cell model to elucidate the functional relevance of this system.
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Affiliation(s)
- Ebaa M Alzayadneh
- The Hypertension & Vascular Research Center, Wake Forest University Health Sciences, USA
| | - Mark C Chappell
- The Hypertension & Vascular Research Center, Wake Forest University Health Sciences, USA
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Abstract
The renin-angiotensin system (RAS) constitutes one of the most important hormonal systems in the physiological regulation of blood pressure through renal and nonrenal mechanisms. Indeed, dysregulation of the RAS is considered a major factor in the development of cardiovascular pathologies, including kidney injury, and blockade of this system by the inhibition of angiotensin converting enzyme (ACE) or blockade of the angiotensin type 1 receptor (AT1R) by selective antagonists constitutes an effective therapeutic regimen. It is now apparent with the identification of multiple components of the RAS within the kidney and other tissues that the system is actually composed of different angiotensin peptides with diverse biological actions mediated by distinct receptor subtypes. The classic RAS can be defined as the ACE-Ang II-AT1R axis that promotes vasoconstriction, water intake, sodium retention, and other mechanisms to maintain blood pressure, as well as increase oxidative stress, fibrosis, cellular growth, and inflammation in pathological conditions. In contrast, the nonclassical RAS composed primarily of the AngII/Ang III-AT2R pathway and the ACE2-Ang-(1-7)-AT7R axis generally opposes the actions of a stimulated Ang II-AT1R axis through an increase in nitric oxide and prostaglandins and mediates vasodilation, natriuresis, diuresis, and reduced oxidative stress. Moreover, increasing evidence suggests that these non-classical RAS components contribute to the therapeutic blockade of the classical system to reduce blood pressure and attenuate various indices of renal injury, as well as contribute to normal renal function.
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Affiliation(s)
- Mark C Chappell
- The Hypertension & Vascular Disease Center, Department of Physiology & Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA.
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Navar LG, Satou R, Gonzalez-Villalobos RA. The increasing complexity of the intratubular Renin-Angiotensin system. J Am Soc Nephrol 2012; 23:1130-2. [PMID: 22677556 DOI: 10.1681/asn.2012050493] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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Weyer K, Glerup S. Placental Regulation of Peptide Hormone and Growth Factor Activity by proMBP1. Biol Reprod 2011; 84:1077-86. [DOI: 10.1095/biolreprod.110.090209] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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Uptake and metabolism of the novel peptide angiotensin-(1-12) by neonatal cardiac myocytes. PLoS One 2011; 6:e15759. [PMID: 21249217 PMCID: PMC3018413 DOI: 10.1371/journal.pone.0015759] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 11/22/2010] [Indexed: 11/19/2022] Open
Abstract
Background Angiotensin-(1–12) [Ang-(1–12)] functions as an endogenous substrate for the productions of Ang II and Ang-(1–7) by a non-renin dependent mechanism. This study evaluated whether Ang-(1–12) is incorporated by neonatal cardiac myocytes and the enzymatic pathways of 125I-Ang-(1–12) metabolism in the cardiac myocyte medium from WKY and SHR rats. Methodology/Principal Findings The degradation of 125I-Ang-(1–12) (1 nmol/L) in the cultured medium of these cardiac myocytes was evaluated in the presence and absence of inhibitors for angiotensin converting enzymes 1 and 2, neprilysin and chymase. In both strains uptake of 125I-Ang-(1–12) by myocytes occurred in a time-dependent fashion. Uptake of intact Ang-(1–12) was significantly greater in cardiac myocytes of SHR as compared to WKY. In the absence of renin angiotensin system (RAS) enzymes inhibitors the hydrolysis of labeled Ang-(1–12) and the subsequent generation of smaller Ang peptides from Ang-(1–12) was significantly greater in SHR compared to WKY controls. 125I-Ang-(1–12) degradation into smaller Ang peptides fragments was significantly inhibited (90% in WKY and 71% in SHR) in the presence of all RAS enzymes inhibitors. Further analysis of peptide fractions generated through the incubation of Ang-(1–12) in the myocyte medium demonstrated a predominant hydrolytic effect of angiotensin converting enzyme and neprilysin in WKY and an additional role for chymase in SHR. Conclusions/Significance These studies demonstrate that neonatal myocytes sequester angiotensin-(1–12) and revealed the enzymes involved in the conversion of the dodecapeptide substrate to biologically active angiotensin peptides.
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Gwathmey TM, Westwood BM, Pirro NT, Tang L, Rose JC, Diz DI, Chappell MC. Nuclear angiotensin-(1-7) receptor is functionally coupled to the formation of nitric oxide. Am J Physiol Renal Physiol 2010; 299:F983-90. [PMID: 20810609 DOI: 10.1152/ajprenal.00371.2010] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The kidney is an important target for the actions of the renin-angiotensin system (RAS) and this tissue contains a complete local RAS that expresses the bioactive peptides angiotensin II (ANG II) and Ang-(1-7). We find both angiotensin type 1 (AT(1)R) and type 2 (AT(2)R) receptors expressed on renal nuclei that stimulate reactive oxygen species and nitric oxide (NO), respectively. Since Ang-(1-7) also exhibits actions within the kidney and the Ang-(1-7)/Mas receptor protein contains a nuclear localization sequence, we determined the expression of Ang-(1-7) receptors in nuclei isolated from the kidneys of young adult sheep. Binding studies with (125)I-[Sar(1)Thr(8)]-ANG II revealed sites sensitive to the Ang-(1-7) antagonist [d-Ala(7)]-Ang-(1-7) (DALA, A779), as well as to AT(2) and AT(1) antagonists. Incubation of Ang-(1-7) [10(-15) to 10(-9) M] with isolated cortical nuclei elicited a dose-dependent increase in the fluorescence of the NO indicator [4-amino-5-methylamino-2',7']-difluorofluorescein diacetate. The NO response to Ang-(1-7) was abolished by the NO inhibitor N-nitro-l-arginine methyl ester and DALA, but not the AT(1) antagonist losartan or the AT(2) blocker PD123319. Immunofluorescent studies utilizing the Ang-(1-7)/Mas receptor antibody revealed immunolabeling of the proximal tubules but not staining within the glomerulus in cortical sections of the sheep kidney. In the nuclear fraction of isolated proximal tubules, immunoblots revealed the precursor angiotensinogen and renin, as well as functional activity for ACE, ACE2, and neprilysin. We conclude that renal nuclei express Ang-(1-7)/Mas receptors that are functionally linked to NO formation. The marked sensitivity of the intracellular NO response to Ang-(1-7) implicates a functional role of the Ang-(1-7) axis within the nucleus. Moreover, evidence for the precursor and enzymatic components of the RAS within the nuclear compartment of the proximal tubules provides a potential pathway for the intracellular generation of Ang-(1-7).
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Affiliation(s)
- Tanya M Gwathmey
- Wake Forest Univ. Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157-1032, USA
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Re RN, Cook JL. Mechanisms of Disease: intracrine physiology in the cardiovascular system. ACTA ACUST UNITED AC 2007; 4:549-57. [PMID: 17893683 DOI: 10.1038/ncpcardio0985] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 06/14/2007] [Indexed: 01/24/2023]
Abstract
The field of intracrine physiology attempts to codify the biological actions of intracrines--extracellular signaling proteins or peptides that also operate in the intracellular space, either because they are retained in their cells of synthesis or because they have been internalized by a target cell. Intracrines are structurally diverse; hormones, growth factors, DNA-binding proteins and enzymes can all display intracrine functionality. Here, we review the role of intracrines in the heart and vasculature, including the intracrine actions of renin-angiotensin-system components in cardiac pathology, dynorphin B in cardiac development, and a variety of factors in pathologic and therapeutic angiogenesis. We argue that principles of intracrine physiology can inform our understanding of important pathologic processes such as left ventricular hypertrophy, diabetic cardiomyopathy and arrythmogenesis, and can aid the development of more-effective therapeutic interventions in cardiovascular disease.
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Affiliation(s)
- Richard N Re
- Research Division, Ochsner Clinic Foundation, 1514 Jefferson Highway, New Orleans, LA 70121, USA.
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