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Boder P, Mary S, Mark PB, Leiper J, Dominiczak AF, Padmanabhan S, Rampoldi L, Delles C. Mechanistic interactions of uromodulin with the thick ascending limb: perspectives in physiology and hypertension. J Hypertens 2021; 39:1490-1504. [PMID: 34187999 PMCID: PMC7611110 DOI: 10.1097/hjh.0000000000002861] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Hypertension is a significant risk factor for cardiovascular disease and mortality worldwide. The kidney is a major regulator of blood pressure and electrolyte homeostasis, with monogenic disorders indicating a link between abnormal ion transport and salt-sensitive hypertension. However, the association between salt and hypertension remains controversial. Thus, there is continued interest in deciphering the molecular mechanisms behind these processes. Uromodulin (UMOD) is the most abundant protein in the normal urine and is primarily synthesized by the thick ascending limb epithelial cells of the kidney. Genome-wide association studies have linked common UMOD variants with kidney function, susceptibility to chronic kidney disease and hypertension independent of renal excretory function. This review will discuss and provide predictions on the role of the UMOD protein in renal ion transport and hypertension based on current observational, biochemical, genetic, pharmacological and clinical evidence.
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Affiliation(s)
- Philipp Boder
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sheon Mary
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Patrick B. Mark
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - James Leiper
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anna F. Dominiczak
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Sandosh Padmanabhan
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Luca Rampoldi
- Molecular Genetics of Renal Disorders Unit, Division of Genetics and Cell Biology, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Christian Delles
- BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom
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Gonzalez-Vicente A, Saez F, Monzon CM, Asirwatham J, Garvin JL. Thick Ascending Limb Sodium Transport in the Pathogenesis of Hypertension. Physiol Rev 2019; 99:235-309. [PMID: 30354966 DOI: 10.1152/physrev.00055.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The thick ascending limb plays a key role in maintaining water and electrolyte balance. The importance of this segment in regulating blood pressure is evidenced by the effect of loop diuretics or local genetic defects on this parameter. Hormones and factors produced by thick ascending limbs have both autocrine and paracrine effects, which can extend prohypertensive signaling to other structures of the nephron. In this review, we discuss the role of the thick ascending limb in the development of hypertension, not as a sole participant, but one that works within the rich biological context of the renal medulla. We first provide an overview of the basic physiology of the segment and the anatomical considerations necessary to understand its relationship with other renal structures. We explore the physiopathological changes in thick ascending limbs occurring in both genetic and induced animal models of hypertension. We then discuss the racial differences and genetic defects that affect blood pressure in humans through changes in thick ascending limb transport rates. Throughout the text, we scrutinize methodologies and discuss the limitations of research techniques that, when overlooked, can lead investigators to make erroneous conclusions. Thus, in addition to advancing an understanding of the basic mechanisms of physiology, the ultimate goal of this work is to understand our research tools, to make better use of them, and to contextualize research data. Future advances in renal hypertension research will require not only collection of new experimental data, but also integration of our current knowledge.
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Affiliation(s)
| | - Fara Saez
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Casandra M Monzon
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jessica Asirwatham
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University , Cleveland, Ohio
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3
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Zhang G, Gui S, Wang W, Meng D, Meng Q, Luan H, Zhao R, Zhang J, Sui H. Acute stimulatory effect of tumor necrosis factor on the basolateral 50 pS K channels in the thick ascending limb of the rat kidney. Mol Med Rep 2018; 18:4733-4738. [PMID: 30221721 DOI: 10.3892/mmr.2018.9475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 08/13/2018] [Indexed: 11/05/2022] Open
Abstract
The aim of the present study was to investigate the acute effect and mechanism of tumor necrosis factor (TNF) on basolateral 50 pS K channels in the thick ascending limb (TAL) of the rat kidney. The TAL tubules were isolated from the rat kidney, and the activity of the 50 pS K channels was recorded using the patch‑clamp technique. The results indicated that the application of TNF (10 nM) significantly activated the 50 pS K channels and the TNF effect was concentration‑dependent. Inhibition of protein kinase A, phospholipase A2 and protein tyrosine kinase using pathway inhibitors (H89, AACOCF3 and Herbimycin A, respectively) did not abolish the stimulatory effect of TNF, indicating that none of these pathways mediated the TNF effect. By contrast, the phenylarsine oxide inhibitor against protein tyrosine phosphatase (PTP) decreased the activity of the 50 pS K channels and blocked the stimulatory effect of TNF on these channels. Furthermore, western blot analysis demonstrated that the application of TNF (10 nM) in the TAL increased the phosphorylation of PTP, an indication of PTP activity stimulation. Thus, it was concluded that the acute application of TNF may stimulate the basolateral 50 pS K channel in the TAL and the stimulatory effect of TNF may be mediated by the PTP‑dependent pathway.
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Affiliation(s)
- Guoyan Zhang
- Department of Urology, First Affiliated Hospital, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Shiliang Gui
- Department of Urology, First Affiliated Hospital, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Weiqun Wang
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Dexin Meng
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Qingmin Meng
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Haiyan Luan
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Rixin Zhao
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Jiatian Zhang
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
| | - Hongyu Sui
- Department of Physiology, Basic Medical College, Jiamusi University, Jiamusi, Heilongjiang 154007, P.R. China
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Monzon CM, Occhipinti R, Pignataro OP, Garvin JL. Nitric oxide reduces paracellular resistance in rat thick ascending limbs by increasing Na + and Cl - permeabilities. Am J Physiol Renal Physiol 2017; 312:F1035-F1043. [PMID: 28274930 DOI: 10.1152/ajprenal.00671.2016] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/22/2017] [Accepted: 02/24/2017] [Indexed: 01/04/2023] Open
Abstract
About 50% of the Na+ reabsorbed in thick ascending limbs traverses the paracellular pathway. Nitric oxide (NO) reduces the permselectivity of this pathway via cGMP, but its effects on absolute Na+ ([Formula: see text]) and Cl- ([Formula: see text]) permeabilities are unknown. To address this, we measured the effect of l-arginine (0.5 mmol/l; NO synthase substrate) and cGMP (0.5 mmol/l) on [Formula: see text] and [Formula: see text] calculated from the transepithelial resistance (Rt) and [Formula: see text]/[Formula: see text] in medullary thick ascending limbs. Rt was 7,722 ± 1,554 ohm·cm in the control period and 6,318 ± 1,757 ohm·cm after l-arginine treatment (P < 0.05). [Formula: see text]/[Formula: see text] was 2.0 ± 0.2 in the control period and 1.7 ± 0.1 after l-arginine (P < 0.04). Calculated [Formula: see text] and [Formula: see text] were 3.52 ± 0.2 and 1.81 ± 0.10 × 10-5 cm/s, respectively, in the control period. After l-arginine they were 6.65 ± 0.69 (P < 0.0001 vs. control) and 3.97 ± 0.44 (P < 0.0001) × 10-5 cm/s, respectively. NOS inhibition with Nω-nitro-l-arginine methyl ester (5 mmol/l) prevented l-arginine's effect on Rt Next we tested the effect of cGMP. Rt in the control period was 7,592 ± 1,470 and 4,796 ± 847 ohm·cm after dibutyryl-cGMP (0.5 mmol/l; db-cGMP) treatment (P < 0.04). [Formula: see text]/[Formula: see text] was 1.8 ± 0.1 in the control period and 1.6 ± 0.1 after db-cGMP (P < 0.03). [Formula: see text] and [Formula: see text] were 4.58 ± 0.80 and 2.66 ± 0.57 × 10-5 cm/s, respectively, for the control period and 9.48 ± 1.63 (P < 0.007) and 6.01 ± 1.05 (P < 0.005) × 10-5 cm/s, respectively, after db-cGMP. We modeled NO's effect on luminal Na+ concentration along the thick ascending limb. We found that NO's effect on the paracellular pathway reduces net Na+ reabsorption and that the magnitude of this effect is similar to that due to NO's inhibition of transcellular transport.
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Affiliation(s)
- Casandra M Monzon
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio; .,Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires, Buenos Aires, Argentina; and
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
| | - Omar P Pignataro
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires, Buenos Aires, Argentina; and.,Laboratorio de Endocrinología Molecular y Transducción de Señales, Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires, Argentina
| | - Jeffrey L Garvin
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio
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5
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Boersma PM, Haarsma LD, Schotanus MP, Ubels JL. TNF-R1 and FADD mediate UVB-Induced activation of K + channels in corneal epithelial cells. Exp Eye Res 2017; 154:1-9. [PMID: 27818316 PMCID: PMC5679195 DOI: 10.1016/j.exer.2016.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 10/24/2016] [Accepted: 11/02/2016] [Indexed: 11/25/2022]
Abstract
The goal of this study was to elucidate the role of Fas, TNF-R1, FADD and cytochrome c in UVB-induced K+ channel activation, an early step in UVB-induced apoptosis, in human corneal limbal epithelial (HCLE) cells. HCLE cells were treated with Fas, TNF-R1 or FADD siRNA and exposed to 80 or 150 mJ/cm2 UVB. K+ channel activation and loss of intracellular K+ were measured using whole-cell patch-clamp recording and ion chromatography, respectively. Cytochrome c was measured with an ELISA kit. Cells in which Fas was knocked down exhibited identical UVB-induced K+ channel activation and loss of intracellular K+ to control cells. Cells in which TNF-R1 or FADD were knocked down demonstrated reduced K+ channel activation and decreased loss of intracellular K+ following UVB, relative to control cells. Application of TNF-α, the natural ligand of TNF-R1, to HCLE cells induced K+ channel activation and loss of intracellular K+. Cytochrome c was translocated to the cytosol by 2 h after exposure to 150 mJ/cm2 UVB. However, there was no release by 10 min post-UVB. The data suggest that UVB activates TNF-R1, which in turn may activate K+ channels via FADD. This conclusion is supported by the observation that TNF-α also causes loss of intracellular K+. This signaling pathway appears to be integral to UVB-induced K+ efflux, since knockdown of TNF-R1 or FADD inhibits the UVB-induced K+ efflux. The lack of rapid cytochrome c translocation indicates cytochrome c does not play a role in UVB-induced K+ channel activation.
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Affiliation(s)
- Peter M Boersma
- Department of Biology, Calvin College, 3201 Burton St. SE, Grand Rapids, MI 49546, USA; Department of Physics and Astronomy, Calvin College, 3201 Burton St. SE, Grand Rapids, MI 49546, USA
| | - Loren D Haarsma
- Department of Physics and Astronomy, Calvin College, 3201 Burton St. SE, Grand Rapids, MI 49546, USA
| | - Mark P Schotanus
- Department of Biology, Calvin College, 3201 Burton St. SE, Grand Rapids, MI 49546, USA
| | - John L Ubels
- Department of Biology, Calvin College, 3201 Burton St. SE, Grand Rapids, MI 49546, USA.
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6
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Proinflammatory Cytokines and Potassium Channels in the Kidney. Mediators Inflamm 2015; 2015:362768. [PMID: 26508816 PMCID: PMC4609835 DOI: 10.1155/2015/362768] [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: 07/24/2015] [Accepted: 09/09/2015] [Indexed: 01/08/2023] Open
Abstract
Proinflammatory cytokines affect several cell functions via receptor-mediated processes. In the kidney, functions of transporters and ion channels along the nephron are also affected by some cytokines. Among these, alteration of activity of potassium ion (K(+)) channels induces changes in transepithelial transport of solutes and water in the kidney, since K(+) channels in tubule cells are indispensable for formation of membrane potential which serves as a driving force for the transepithelial transport. Altered K(+) channel activity may be involved in renal cell dysfunction during inflammation. Although little information was available regarding the effects of proinflammatory cytokines on renal K(+) channels, reports have emerged during the last decade. In human proximal tubule cells, interferon-γ showed a time-dependent biphasic effect on a 40 pS K(+) channel, that is, delayed suppression and acute stimulation, and interleukin-1β acutely suppressed the channel activity. Transforming growth factor-β1 activated KCa3.1 K(+) channel in immortalized human proximal tubule cells, which would be involved in the pathogenesis of renal fibrosis. This review discusses the effects of proinflammatory cytokines on renal K(+) channels and the causal relationship between the cytokine-induced changes in K(+) channel activity and renal dysfunction.
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7
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Nakamura K, Komagiri Y, Kubokawa M. Interleukin-1β suppresses activity of an inwardly rectifying K+ channel in human renal proximal tubule cells. J Physiol Sci 2013; 63:377-87. [PMID: 23797607 PMCID: PMC10717820 DOI: 10.1007/s12576-013-0275-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 06/10/2013] [Indexed: 12/12/2022]
Abstract
We investigated the effect of interleukin-1β (IL-1β) on activity of an inwardly rectifying K+ channel in cultured human proximal tubule cells (RPTECs), using the patch-clamp technique and Fura-2 Ca2+ imaging. IL-1β (15 pg/ml) acutely reduced K+ channel activity in cell-attached patches. This effect was blocked by the IL-1 receptor antagonist (20 ng/ml), an inhibitor of phospholipase C, neomycin (300 μM), and an inhibitor of protein kinase C (PKC), GF109203X (500 nM). The Fura-2 Ca2+ imaging revealed that IL-1β increased intracellular Ca2+ concentration even after removal of extracellular Ca2+, which was blocked by an inhibitor of inositol 1,4,5-trisphosphate receptors, 2-aminoethoxydiphenyl borate (2-APB, 1 μM). Moreover, IL-1β suppressed channel activity in the presence of 2-APB without extracellular Ca2+. These results suggest that IL-1β suppresses K+ channel activity in RPTECs through binding to its specific receptor and activation of the PKC pathway even though intracellular Ca2+ does not increase.
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Affiliation(s)
- Kazuyoshi Nakamura
- Department of Physiology, Iwate Medical University School of Medicine, 2-1-1 Nishitokuta, Yahaba, 028-3694 Japan
| | - You Komagiri
- Department of Physiology, Iwate Medical University School of Medicine, 2-1-1 Nishitokuta, Yahaba, 028-3694 Japan
| | - Manabu Kubokawa
- Department of Physiology, Iwate Medical University School of Medicine, 2-1-1 Nishitokuta, Yahaba, 028-3694 Japan
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8
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Gonzalez-Vicente A, Garvin JL. Angiotensin II-induced hypertension increases plasma membrane Na pump activity by enhancing Na entry in rat thick ascending limbs. Am J Physiol Renal Physiol 2013; 305:F1306-14. [PMID: 23986517 DOI: 10.1152/ajprenal.00064.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Thick ascending limbs (TAL) reabsorb 30% of the filtered NaCl load. Na enters the cells via apical Na-K-2Cl cotransporters and Na/H exchangers and exits via basolateral Na pumps. Chronic angiotensin II (ANG II) infusion increases net TAL Na transport and Na apical entry; however, little is known about its effects on the basolateral Na pump. We hypothesized that in rat TALs Na pump activity is enhanced by ANG II-infusion, a model of ANG II-induced hypertension. Rats were infused with 200 ng·kg(-1)·min(-1) ANG II or vehicle for 7 days, and TAL suspensions were obtained. We studied plasma membrane Na pump activity by measuring changes in 1) intracellular Na (Nai) induced by ouabain; and 2) ouabain-sensitive oxygen consumption (QO2). We found that the ouabain-sensitive rise in Nai in TALs from ANG II-infused rats was 12.8 ± 0.4 arbitrary fluorescent units (AFU)·mg(-1)·min(-1) compared with only 9.9 ± 1.1 AFU·mg(-1)·min(-1) in controls (P < 0.024). Ouabain-sensitive oxygen consumption was 17 ± 5% (P < 0.043) greater in tubules from ANG II-treated than vehicle rats. ANG II infusion did not alter total Na pump expression, the number of Na pumps in the plasma membrane, or the affinity for Na. When furosemide (1.1 mg·kg(-1)·day(-1)) was coinfused with ANG II, no increase in plasma membrane Na pump activity was observed. We concluded that in ANG II-induced hypertension Na pump activity is increased in the plasma membrane of TALs and that this increase is caused by the chronically enhanced Na entry occurring in this model.
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Affiliation(s)
- Agustin Gonzalez-Vicente
- Dept. of Physiology and Biophysics, Case Western Reserve Univ. School of Medicine, 10900 Euclid Ave, MS 4970, Robbins-E-526, Cleveland, OH 44106-4970.
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9
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Maillé E, Trinh NTN, Privé A, Bilodeau C, Bissonnette É, Grandvaux N, Brochiero E. Regulation of normal and cystic fibrosis airway epithelial repair processes by TNF-α after injury. Am J Physiol Lung Cell Mol Physiol 2011; 301:L945-55. [DOI: 10.1152/ajplung.00149.2011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic infection and inflammation have been associated with progressive airway epithelial damage in patients with cystic fibrosis (CF). However, the effect of inflammatory products on the repair capacity of respiratory epithelia is unclear. Our objective was to study the regulation of repair mechanisms by tumor necrosis factor-α (TNF-α), a major component of inflammation in CF, in a model of mechanical wounding, in two bronchial cell lines, non-CF NuLi and CF CuFi. We observed that TNF-α enhanced the NuLi and CuFi repair rates. Chronic exposure (24–48 h) to TNF-α augmented this stimulation as well as the migration rate during repair. The cellular mechanisms involved in this stimulation were then evaluated. First, we discerned that TNF-α induced metalloproteinase-9 release, epidermal growth factor (EGF) shedding, and subsequent EGF receptor transactivation. Second, TNF-α-induced stimulation of the NuLi and CuFi wound-closure rates was prevented by GM6001 (metalloproteinase inhibitor), EGF antibody (to titrate secreted EGF), and EGF receptor tyrosine kinase inhibitors. Furthermore, we recently reported a relationship between the EGF response and K+channel function, both controlling bronchial repair. We now show that TNF-α enhances KvLQT1 and KATPcurrents, while their inhibition abolishes TNF-α-induced repair stimulation. These results indicate that the effect of TNF-α is mediated, at least in part, through EGF receptor transactivation and K+channel stimulation. In contrast, cell proliferation during repair was slowed by TNF-α, suggesting that TNF-α could exert contrasting actions on repair mechanisms of CF airway epithelia. Finally, the stimulatory effect of TNF-α on airway wound repair was confirmed on primary airway epithelial cells, from non-CF and CF patients.
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Affiliation(s)
- Emilie Maillé
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
- Département de médecine and
| | - Nguyen Thu Ngan Trinh
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
- Département de médecine and
| | - Anik Privé
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
| | - Claudia Bilodeau
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
| | - Élyse Bissonnette
- Institut Universitaire de cardiologie et de pneumologie de Québec, Département de médecine, Université Laval, Québec, Québec, Canada
| | - Nathalie Grandvaux
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
- Département de Biochimie, Université de Montréal, Montréal; and
| | - Emmanuelle Brochiero
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM)—Hôtel-Dieu, Montréal
- Département de médecine and
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Nakamura K, Komagiri Y, Kubokawa M. Effects of cytokines on potassium channels in renal tubular epithelia. Clin Exp Nephrol 2011; 16:55-60. [PMID: 22042037 DOI: 10.1007/s10157-011-0490-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2010] [Accepted: 01/03/2011] [Indexed: 12/11/2022]
Abstract
Renal tubular potassium (K(+)) channels play important roles in the formation of cell-negative potential, K(+) recycling, K(+) secretion, and cell volume regulation. In addition to these physiological roles, it was reported that changes in the activity of renal tubular K(+) channels were involved in exacerbation of renal cell injury during ischemia and endotoxemia. Because ischemia and endotoxemia stimulate production of cytokines in immune cells and renal tubular cells, it is possible that cytokines would affect K(+) channel activity. Although the regulatory mechanisms of renal tubular K(+) channels have extensively been studied, little information is available about the effects of cytokines on these K(+) channels. The first report was that tumor necrosis factor acutely stimulated the single channel activity of the 70 pS K(+) channel in the rat thick ascending limb through activation of tyrosine phosphatase. Recently, it was also reported that interferon-γ (IFN-γ) and interleukin-1β (IL-1β) modulated the activity of the 40 pS K(+) channel in cultured human proximal tubule cells. IFN-γ exhibited a delayed suppression and an acute stimulation of K(+) channel activity, whereas IL-1β acutely suppressed the channel activity. Furthermore, these cytokines suppressed gene expression of the renal outer medullary potassium channel. The renal tubular K(+) channels are functionally coupled to the coexisting transporters. Therefore, the effects of cytokines on renal tubular transporter activity should also be taken into account, when interpreting their effects on K(+) channel activity.
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Affiliation(s)
- Kazuyoshi Nakamura
- Department of Physiology, Iwate Medical University School of Medicine, 2-1-1 Nishitokuta, Yahaba, 028-3694, Japan
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11
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Abstract
One of the functional roles of the corneal epithelial layer is to protect the cornea, lens and other underlying ocular structures from damages caused by environmental insults. It is important for corneal epithelial cells to maintain this function by undergoing continuous renewal through a dynamic process of wound healing. Previous studies in corneal epithelial cells have provided substantial evidence showing that environmental insults, such as ultraviolet (UV) irradiation and other biohazards, can induce stress-related cellular responses resulting in apoptosis and thus interrupt the dynamic process of wound healing. We found that UV irradiation-induced apoptotic effects in corneal epithelial cells are started by the hyperactivation of K+ channels in the cell membrane resulting in a fast loss of intracellular K+ ions. Recent studies provide further evidence indicating that these complex responses in corneal epithelial cells are resulted from the activation of stress-related signaling pathways mediated by K+ channel activity. The effect of UV irradiation on corneal epithelial cell fate shares common signaling mechanisms involving the activation of intracellular responses that are often activated by the stimulation of various cytokines. One piece of evidence for making this distinction is that at early times UV irradiation activates a Kv3.4 channel in corneal epithelial cells to elicit activation of c-Jun N-terminal kinase cascades and p53 activation leading to cell cycle arrest and apoptosis. The hypothetic model is that UV-induced potassium channel hyperactivity as an early event initiates fast cell shrinkages due to the loss of intracellular potassium, resulting in the activation of scaffolding protein kinases and cytoskeleton reorganizations. This review article presents important control mechanisms that determine Kv channel activity-mediated cellular responses in corneal epithelial cells, involving activation of stress-induced signaling pathways, arrests of cell cycle progression and/or induction of apoptosis.
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Affiliation(s)
- Luo Lu
- Department of Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California Los Angeles, Harbor-UCLA Medical Center, CA 90502, USA.
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12
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Wang L, Reinach P, Lu L. TNF-alpha promotes cell survival through stimulation of K+ channel and NFkappaB activity in corneal epithelial cells. Exp Cell Res 2005; 311:39-48. [PMID: 16216243 PMCID: PMC1920499 DOI: 10.1016/j.yexcr.2005.08.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Revised: 08/18/2005] [Accepted: 08/18/2005] [Indexed: 01/08/2023]
Abstract
Tumor necrosis factor (TNF-alpha) in various cell types induces either cell death or mitogenesis through different signaling pathways. In the present study, we determined in human corneal epithelial cells how TNF-alpha also promotes cell survival. Human corneal epithelial (HCE) cells were cultured in DMEM/F-12 medium containing 10% FBS. TNF-alpha stimulation induced activation of a voltage-gated K+ channel detected by measuring single channel activity using patch clamp techniques. The effect of TNF-alpha on downstream events included NFkappaB nuclear translocation and increases in DNA binding activities, but did not elicit ERK, JNK, or p38 limb signaling activation. TNF-alpha induced increases in p21 expression resulting in partial cell cycle attenuation in the G1 phase. Cell cycle progression was also mapped by flow cytometer analysis. Blockade of TNF-alpha-induced K+ channel activity effectively prevented NFkappaB nuclear translocation and binding to DNA, diminishing the cell-survival protective effect of TNF-alpha. In conclusion, TNF-alpha promotes survival of HCE cells through sequential stimulation of K+ channel and NFkappaB activities. This response to TNF-alpha is dependent on stimulating K+ channel activity because following suppression of K+ channel activity TNF-alpha failed to activate NFkappaB nuclear translocation and binding to nuclear DNA.
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Affiliation(s)
- Ling Wang
- Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, 1124 W. Carson Street, C-2, Torrance, CA 90502, USA
| | - Peter Reinach
- Department of Biological Sciences, SUNY College of Optometry, New York, NY 10010, USA
| | - Luo Lu
- Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, 1124 W. Carson Street, C-2, Torrance, CA 90502, USA
- * Corresponding author. Fax: +1 310 222 3781. E-mail address: (L. Lu)
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