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Li Y, Liu H, Peng W, Song Z. Nicorandil improves clinical outcomes in patients with stable angina pectoris requiring PCI: a systematic review and meta-analysis of 14 randomized trials. Expert Rev Clin Pharmacol 2018; 11:855-865. [PMID: 30079778 DOI: 10.1080/17512433.2018.1508342] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Yiliang Li
- Department of Neurology, The Third Xiangya Hospital, Central South University, Changsha, China
- Clinical Medicine, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Hai Liu
- Third Department of Cardiac Surgery, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Wei Peng
- Department of Cardiology, The Central Hospital of Loudi Affiliated to the University of South China, Loudi, China
| | - Zhi Song
- Department of Neurology, The Third Xiangya Hospital, Central South University, Changsha, China
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Mitochondria-Targeted Antioxidants: Future Perspectives in Kidney Ischemia Reperfusion Injury. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2016; 2016:2950503. [PMID: 27313826 PMCID: PMC4894993 DOI: 10.1155/2016/2950503] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/28/2016] [Indexed: 02/03/2023]
Abstract
Kidney ischemia/reperfusion injury emerges in various clinical settings as a great problem complicating the course and outcome. Ischemia/reperfusion injury is still an unsolved puzzle with a great diversity of investigational approaches, putting the focus on oxidative stress and mitochondria. Mitochondria are both sources and targets of ROS. They participate in initiation and progression of kidney ischemia/reperfusion injury linking oxidative stress, inflammation, and cell death. The dependence of kidney proximal tubule cells on oxidative mitochondrial metabolism makes them particularly prone to harmful effects of mitochondrial damage. The administration of antioxidants has been used as a way to prevent and treat kidney ischemia/reperfusion injury for a long time. Recently a new method based on mitochondria-targeted antioxidants has become the focus of interest. Here we review the current status of results achieved in numerous studies investigating these novel compounds in ischemia/reperfusion injury which specifically target mitochondria such as MitoQ, Szeto-Schiller (SS) peptides (Bendavia), SkQ1 and SkQR1, and superoxide dismutase mimics. Based on the favorable results obtained in the studies that have examined myocardial ischemia/reperfusion injury, ongoing clinical trials investigate the efficacy of some novel therapeutics in preventing myocardial infarct. This also implies future strategies in preventing kidney ischemia/reperfusion injury.
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Mackenzie RWA, Watt P. A Molecular and Whole Body Insight of the Mechanisms Surrounding Glucose Disposal and Insulin Resistance with Hypoxic Treatment in Skeletal Muscle. J Diabetes Res 2016; 2016:6934937. [PMID: 27274997 PMCID: PMC4871980 DOI: 10.1155/2016/6934937] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 04/04/2016] [Accepted: 04/12/2016] [Indexed: 12/22/2022] Open
Abstract
Although the mechanisms are largely unidentified, the chronic or intermittent hypoxic patterns occurring with respiratory diseases, such as chronic pulmonary disease or obstructive sleep apnea (OSA) and obesity, are commonly associated with glucose intolerance. Indeed, hypoxia has been widely implicated in the development of insulin resistance either via the direct action on insulin receptor substrate (IRS) and protein kinase B (PKB/Akt) or indirectly through adipose tissue expansion and systemic inflammation. Yet hypoxia is also known to encourage glucose transport using insulin-dependent mechanisms, largely reliant on the metabolic master switch, 5' AMP-activated protein kinase (AMPK). In addition, hypoxic exposure has been shown to improve glucose control in type 2 diabetics. The literature surrounding hypoxia-induced changes to glycemic control appears to be confusing and conflicting. How is it that the same stress can seemingly cause insulin resistance while increasing glucose uptake? There is little doubt that acute hypoxia increases glucose metabolism in skeletal muscle and does so using the same pathway as muscle contraction. The purpose of this review paper is to provide an insight into the mechanisms underpinning the observed effects and to open up discussions around the conflicting data surrounding hypoxia and glucose control.
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Affiliation(s)
- R. W. A. Mackenzie
- Department of Life Science, Whitelands College, University of Roehampton, Holybourne Avenue, London SW15 4DJ, UK
- *R. W. A. Mackenzie:
| | - P. Watt
- University of Brighton, Hillbrow, Denton Road, Eastbourne BN20 7SP, UK
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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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Gao G, Wang W, Tadagavadi RK, Briley NE, Love MI, Miller BA, Reeves WB. TRPM2 mediates ischemic kidney injury and oxidant stress through RAC1. J Clin Invest 2014; 124:4989-5001. [PMID: 25295536 DOI: 10.1172/jci76042] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 09/04/2014] [Indexed: 02/06/2023] Open
Abstract
Ischemia is a leading cause of acute kidney injury. Kidney ischemia is associated with loss of cellular ion homeostasis; however, the pathways that underlie ion homeostasis dysfunction are poorly understood. Here, we evaluated the nonselective cation channel transient receptor potential melastatin 2 (TRPM2) in a murine model of kidney ischemia/reperfusion (I/R) injury. TRPM2-deficient mice were resistant to ischemic injury, as reflected by improved kidney function, reduced histologic damage, suppression of proapoptotic pathways, and reduced inflammation. Moreover, pharmacologic TRPM2 inhibition was also protective against I/R injury. TRPM2 was localized mainly in kidney proximal tubule epithelial cells, and studies in chimeric mice indicated that the effects of TRPM2 are due to expression in parenchymal cells rather than hematopoietic cells. TRPM2-deficient mice had less oxidative stress and lower levels of NADPH oxidase activity after ischemia. While RAC1 is a component of the NADPH oxidase complex, its relation to TRPM2 and kidney ischemic injury is unknown. Following kidney ischemia, TRPM2 promoted RAC1 activation, with active RAC1 physically interacting with TRPM2 and increasing TRPM2 expression at the cell membrane. Finally, inhibition of RAC1 reduced oxidant stress and ischemic injury in vivo. These results demonstrate that TRPM2-dependent RAC1 activation increases oxidant stress and suggest that therapeutic approaches targeting TRPM2 and/or RAC1 may be effective in reducing ischemic kidney injury.
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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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Zhang Z, Tang QY, Alaimo JT, Davies AG, Bettinger JC, Logothetis DE. SLO-2 isoforms with unique Ca(2+) - and voltage-dependence characteristics confer sensitivity to hypoxia in C. elegans. Channels (Austin) 2013; 7:194-205. [PMID: 23590941 DOI: 10.4161/chan.24492] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Slo channels are large conductance K (+) channels that display marked differences in their gating by intracellular ions. Among them, the Slo1 and C. elegans SLO-2 channels are gated by calcium (Ca ( 2+) ), while mammalian Slo2 channels are activated by both sodium (Na (+) ) and chloride (Cl (-) ). Here, we report that SLO-2 channels, SLO-2a and a novel N-terminal variant isoform, SLO-2b, are activated by Ca ( 2+) and voltage, but in contrast to previous reports they do not exhibit Cl (-) sensitivity. Most importantly, SLO-2 provides a unique case in the Slo family for sensing Ca ( 2+) with the high-affinity Ca ( 2+) regulatory site in the RCK1 but not the RCK2 domain, formed through interactions with residues E319 and E487 (that correspond to D362 and E535 of Slo1, respectively). The SLO-2 RCK2 domain lacks the Ca ( 2+) bowl structure and shows minimal Ca ( 2+) dependence. In addition, in contrast to SLO-1, SLO-2 loss-of-function mutants confer resistance to hypoxia in C. elegans. Thus, the C. elegans SLO-2 channels possess unique biophysical and functional properties.
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Affiliation(s)
- Zhe Zhang
- Department of Physiology and Biophysics, Virginia Commonwealth University, Medical College of Virginia Campus, Richmond, VA, USA.
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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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Sauriyal DS, Jaggi AS, Singh N, Muthuraman A. Investigating the role of endogenous opioids and KATP channels in glycerol-induced acute renal failure. Fundam Clin Pharmacol 2011; 26:347-55. [PMID: 21392099 DOI: 10.1111/j.1472-8206.2011.00936.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The present study was designed to investigate the possible role of endogenous opioids and K(ATP) channels in glycerol-induced acute renal failure (ARF) in rats. The rats were subjected to rhabdomyolytic ARF by single intramuscular injection of hypertonic glycerol (50% v/v; 8 mL/kg), and the animals were sacrificed after 24 h of glycerol injection. The plasma creatinine, blood urea nitrogen, creatinine clearance, and histopathological studies were performed to assess the degree of renal injury. Naltrexone (2.5, 5.0 and 10.0 mg/kg s.c.), glibenclamide (5.0 and 10.0 mg/kg i.p.), and minoxidil (25 and 50 mg/kg) were employed to explore the role of endogenous opioids and K(ATP) channels in rhabdomyolysis-induced ARF. Pretreatment with naltrexone and glibenclamide attenuated hypertonic glycerol-induced renal dysfunction in a dose-dependent manner, suggesting the role of endogenous opioids and K(ATP) channels in the pathogenesis of myoglobuniric renal failure. However, the simultaneous pretreatment with naltrexone (10 mg/kg s.c.) and glibenclamide (10 mg/kg i.p.) did not enhance the reno-protective effects of individual drugs, suggesting that release of endogenous opioids and opening of K(ATP) channels constitute a single pathway in acute renal injury triggered by hypertonic glycerol-induced rhabdomyolysis. Furthermore, administration of minoxidil abolished the attenuating effects of naltrexone in glycerol-induced renal failure, suggesting that opening of K(ATP) channels is downstream to opioid receptor activation. It is concluded that hypertonic glycerol-induced rhabdomyolysis may involve release of endogenous opioids that in turn modulate K(ATP) channels to contribute in the pathogenesis of ARF.
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Affiliation(s)
- Dharmraj Singh Sauriyal
- Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala 147002, Punjab, India
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Nilakantan V, Liang H, Mortensen J, Taylor E, Johnson CP. Variable effects of the mitoK(ATP) channel modulators diazoxide and 5-HD in ATP-depleted renal epithelial cells. Mol Cell Biochem 2009; 335:211-22. [PMID: 19784759 DOI: 10.1007/s11010-009-0271-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Accepted: 09/16/2009] [Indexed: 11/26/2022]
Abstract
The role of mitochondrial K(ATP) (mitoK(ATP)) channels in renal ischemia-reperfusion injury is controversial with studies showing both protective and deleterious effects. In this study, we compared the effects of the putative mitoK(ATP) opener, diazoxide, and the mitoK(ATP) blocker, 5-hydroxydecanoate (5-HD) on cytotoxicity and apoptosis in tubular epithelial cells derived from rat (NRK-52E) and pig (LLC-PK1) following in vitro ischemic injury. Following ATP depletion-recovery, there was a significant increase in cytotoxicity in both NRK cells and LLC-PK1 cells although NRK cells were more sensitive to the injury. Diazoxide treatment attenuated cytotoxicity in both cell types and 5-HD treatment-increased cytotoxicity in the sensitive NRK cells in a superoxide-dependant manner. The protective effect of diazoxide was also reversed in the presence of 5-HD in ATP-depleted NRK cells. The ATP depletion-mediated increase in superoxide was enhanced by both diazoxide and 5-HD with the effect being more pronounced in the cells undergoing 5-HD treatment. Further, ATP depletion-induced activation of caspase-3 was decreased by diazoxide in NRK cells. In order to determine the signaling pathways involved in apoptosis, we examined the activation of Erk and JNK in ATP-depleted NRK cells. Diazoxide-activated Erk in ATP-depleted cells, but did not have any effect on JNK activation. In contrast, 5-HD did not impact Erk levels but increased JNK activation even under controlled conditions. Further, the use of a JNK inhibitor with 5-HD reversed the deleterious effects of 5-HD. This study demonstrates that in cells that are sensitive to ATP depletion-recovery, mitoK(ATP) channels protect against ATP depletion-mediated cytotoxicity and apoptosis through Erk- and JNK-dependant mechanisms.
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Affiliation(s)
- Vani Nilakantan
- Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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Nakamura K, Komagiri Y, Kojo T, Kubokawa M. Delayed and acute effects of interferon-gamma on activity of an inwardly rectifying K+ channel in cultured human proximal tubule cells. Am J Physiol Renal Physiol 2008; 296:F46-53. [PMID: 18945831 DOI: 10.1152/ajprenal.00127.2008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The activity of an inwardly rectifying K(+) channel in cultured human renal proximal tubule cells (RPTECs) is stimulated and inhibited by nitric oxide (NO) at low and high concentrations, respectively. In this study, we investigated the effects of IFN-gamma, one of the cytokines which affect the expression of inducible NO synthase (iNOS), on intracellular NO and channel activity of RPTECs, using RT-PCR, NO imaging, and the cell-attached mode of the patch-clamp technique. Prolonged incubation (24 h) of cells with IFN-gamma (20 ng/ml) enhanced iNOS mRNA expression and NO production. In these cells, a NOS inhibitor, N(omega)-nitro-l-arginine methyl ester (l-NAME; 100 microM), elevated channel activity, suggesting that NO production was so high as to suppress the channel. This indicated that IFN-gamma would chronically suppress channel activity by enhancing NO production. Acute effects of IFN-gamma was also examined in control cells. Simple addition of IFN-gamma (20 ng/ml) to the bath acutely stimulated channel activity, which was abolished by inhibitors of IFN-gamma receptor-associated Janus-activated kinase [P6 (1 microM) and AG490 (10 microM)]. However, l-NAME did not block the acute effect of IFN-gamma. Indeed, IFN-gamma did not acutely affect NO production. Moreover, the acute effect was not blocked by inhibition of PKA, PKG, and phosphatidylinositol 3-kinase (PI3K). We conclude that IFN-gamma exerted a delayed suppressive effect on K(+) channel activity by enhancing iNOS expression and an acute stimulatory effect, which was independent of either NO pathways or phosphorylation processes mediated by PKA, PKG, and PI3K in RPTECs.
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Affiliation(s)
- Kazuyoshi Nakamura
- Dept. of Physiology, Iwate Medical Univ. School of Medicine, 19-1 Uchimaru, Morioka, 020-8505 Japan
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Sun Z, Zhang X, Ito K, Li Y, Montgomery RA, Tachibana S, Williams GM. Amelioration of oxidative mitochondrial DNA damage and deletion after renal ischemic injury by the KATP channel opener diazoxide. Am J Physiol Renal Physiol 2007; 294:F491-8. [PMID: 18160622 DOI: 10.1152/ajprenal.00263.2007] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Renal ischemia was induced in the rat by constriction of the renal artery for 45 min, and the ability of the ATP-sensitive K(+) (K(ATP)) channel opener diazoxide (DZ) to ameliorate renal ischemia-reperfusion (I/R) injury was evaluated. In this model, blood urea nitrogen and creatinine were elevated 2 days after I/R injury but returned closer to normal levels by 7 days after reperfusion. Histological staining for reactive oxygen species (ROS) was clearly positive and oxidized DNA, detected by the presence of the stable adduct 8-hydroxy-2'-deoxyguanosine, was clearly present in the cytoplasm of tubular cells after 1 h of reperfusion and declined 7 days after reperfusion. This finding was confirmed by ELISA, which detected 8-hydroxy-2'-deoxyguanosine in the mitochondrial fraction of kidney homogenates. Despite evidence of improved function measured by blood urea nitrogen and creatinine 7 days after reperfusion, the early changes in tubules were alarming. Mitochondrial DNA showed the common deletion, and the number of TdT-mediated dUTP nick-end label-positive tubular cells increased. Activation of caspase-3 continued, and abnormal levels of ROS were found in the mitochondrial fraction of cellular homogenates. Treatment with DZ before ischemia reduced or prevented the acute and subacute deleterious effects associated with renal I/R injury. We conclude that excess production of ROS by mitochondria on reperfusion is a major upstream event in renal reperfusion injury and that DZ functioned by preventing ROS accumulation in the mitochondria after I/R injury, thereby reducing oxidative stress as measured by the presence of oxidized mitochondrial DNA and features of apoptosis.
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Affiliation(s)
- Zhaoli Sun
- Department of Surgery, Johns Hopkins University School of Medicine, 720 Rutland Ave., Ross 749, Baltimore, MD 21205, USA.
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Garcia MA, Meca R, Leite D, Boim MA. Effect of Renal Ischemia/Reperfusion on Gene Expression of a pH-Sensitive K + Channel. ACTA ACUST UNITED AC 2007; 106:p1-7. [PMID: 17406122 DOI: 10.1159/000101486] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Accepted: 02/03/2007] [Indexed: 11/19/2022]
Abstract
BACKGROUND Sodium reabsorption depends on the Na/K/ATPase activity coupled to basolateral K+ recycling through K+ channels. ATP depletion reduces pump activity and increases K+ leak resulting in transport dysfunction. Kir4.1 is a pH-sensitive K+ channel expressed in the basolateral membrane of distal tubules. In this study, we evaluated whether Kir4.1 is also expressed in proximal tubules (PTs) and whether renal ischemia alters Kir4.1 mRNA expression levels. METHODS The presence of Kir4.1 mRNA was evaluated in PTs microdissected from collagenase-treated rat kidneys. Kir4.1 expression levels were estimated in the renal cortex by multiplex RT-PCR after 30 or 60 min of renal ischemia followed by 1, 24, 48 or 72 h of reperfusion. RESULTS The PCR product obtained from isolated tubules was sequenced and showed approximately 98% homology with rat Kir4.1 cDNA. Ischemia/reperfusion for 30 min induced a time-dependent reduction in Kir4.1 mRNA expression in parallel with plasma creatinine, however recovery was delayed after 60 min of ischemia, remaining reduced after 72 h of reperfusion when plasma creatinine was already normalized. CONCLUSION Kir4.1 mRNA expression was decreased by renal ischemia. The ischemia-induced cellular K+ loss may be minimized by Kir4.1 downregulation and may contribute to the mechanism by which cellular acidification induces cell protection against ATP depletion.
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Affiliation(s)
- M A Garcia
- Disciplina de Nefrologia, Universidade Federal de São Paulo, São Paulo, Brasil
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Zager RA, Johnson AC, Lund S, Hanson SY, Abrass CK. Levosimendan protects against experimental endotoxemic acute renal failure. Am J Physiol Renal Physiol 2006; 290:F1453-62. [PMID: 16418300 DOI: 10.1152/ajprenal.00485.2005] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Endotoxemia induces a hemodynamic form of acute renal failure (ARF; renal vasoconstriction +/- reduced glomerular ultrafiltration coefficient, K(f); minimal/no histological damage). We tested whether levosimendan (LS), an ATP-sensitive K+ (K(ATP)) channel opener with cardiac ionotropic and possible anti-inflammatory properties, might have utility in combating this form of ARF. CD-1 mice were injected with LPS +/- LS. LS effects on LPS-induced systemic inflammation (plasma TNF-alpha/MCP-1; cardiorenal mRNAs), plasma NO levels, and azotemia were assessed. Because K(ATP) channel opening has been reported to mediate hypoxic tubular injury, possible adverse LS effects on ischemic ARF and ATP depletion injury were sought. Effects of diazoxide (another K(ATP) channel agonist) and glibenclamide (a channel antagonist) on hypoxic tubular injury also were assessed. Finally, the ability of LS to alter rat mesangial cell (MC) contraction in response to ANG II (elevated in sepsis) was tested. LS conferred almost complete protection against LPS-induced ARF, without any apparent reduction in the LPS-induced inflammatory response. Neither LS nor diazoxide altered ATP depletion-mediated tubule injury (in vivo or in vitro). Conversely, glibenclamide induced a marked and direct cytotoxic effect. LS completely blocked ANG II-induced MC contraction, an action likely to increase K(f). We concluded that 1) LS can confer marked protection against LPS-induced ARF; 2) this likely stems from vasoactive properties, rather than reductions in LPS-induced inflammation; and 3) K(ATP) channel agonists (but not antagonists) appear to be devoid of toxic proximal tubular cell effects. This suggests that LS, and other K(ATP) channel agonists, have a margin of safety if employed in situations (sepsis syndrome, heart failure) in which severe renal vasoconstriction might lead to ischemic ARF.
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Affiliation(s)
- Richard A Zager
- Department of Medicine, University of Washington, Seattle, USA.
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15
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Abstract
PURPOSE OF REVIEW A variety of K+ channels have been identified with the patch-clamp technique and molecular cloning in the kidney. However, it is still a challenging task to determine the location and function of the cloned K+ channels in the corresponding nephron segment. The aim of the present review is to update the recent developments regarding the location and function of the cloned K+ channels in the native tubule. Also, the review describes the new regulatory mechanism of renal outer-medullary K (ROMK) channels and the role of Ca(2+)-activated maxi K+ channels in flow-dependent K+ secretion. RECENT FINDINGS Several types of voltage-gated K+ (Kv) channel, such as KCNQ1, KCNA10 and Kv1.3, are highly expressed at the apical membrane of proximal tubules and distal tubules. They may participate in stabilizing the cell membrane potential. Moreover, studies performed in ROMK-knockout mice have shown that the apical 70 pS K+ channel is absent in the thick ascending limb in these mice, suggesting that the ROMK channel is also involved in forming the apical 70 pS K+ channel in the thick ascending limb. Three important kinases, protein tyrosine kinase, serum- and glucocorticoid-inducible kinase and with-no-lysine kinase, have been suggested to regulate the ROMK channel density in the cortical collecting duct. Low K+ intake increases protein tyrosine kinase expression and tyrosine phosphorylation of ROMK channels. Coexpression of with-no-lysine kinase with the ROMK channel decreases K+ current whereas serum- and glucocorticoid-inducible kinase 1 stimulates the ROMK current in oocytes in the presence of Na/H exchanger regulatory factor 2. The Ca-activated maxi K+ channel has been shown to be activated by an increase in flow rate in the rabbit cortical collecting duct. SUMMARY The voltage-gated K+ channels are expressed in a variety of nephron segments and play a role in stabilization of cell membrane potential. With-no-lysine kinase and serum- and glucocorticoid-inducible kinase 1 have been shown to regulate ROMK1 channels. Protein tyrosine kinase mediates the effect of K+ intake on K+ secretion by stimulation of tyrosine phosphorylation of ROMK1 channels. The Ca-activated maxi K+ channel plays a role in flow-dependent K+ secretion in the distal nephron.
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Affiliation(s)
- WenHui Wang
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA.
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Velic A, Gabriëls G, Hirsch JR, Schröter R, Edemir B, Paasche S, Schlatter E. Acute rejection after rat renal transplantation leads to downregulation of NA+ and water channels in the collecting duct. Am J Transplant 2005; 5:1276-85. [PMID: 15888031 DOI: 10.1111/j.1600-6143.2005.00890.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Renal transplantation is associated with alterations of tubular functions and of the renin-angiotensin-aldosterone system. The underlying cellular and molecular mechanisms are unclear. We used an allogeneic rat renal transplantation model of acute rejection with and without immunosuppression by cyclosporine A (CsA) and a syngeneic model as control. Uninephrectomized Lewis or Lewis-Brown-Norway (LBN) rats received a kidney from LBN-rats. Renal transporters and receptors were analyzed by immunohistochemistry, semiquantitative RT-PCR and Western-blot analysis. Intracellular Na(+) was analyzed microfluorimetrically in isolated cortical collecting ducts. mRNA expression and function of the epithelial Na(+)-channel (ENaC) and mRNA and protein expression of the water-channel AQP2 were downregulated in transplanted kidneys undergoing rejection. Expression of the serum- and glucocorticoid-kinase (Sgk1) was decreased and that of the ubiquitin-protein ligase Nedd4-2 was increased. These changes were absent under CsA-therapy and in syngeneic model. Expression and function of the Na(+)-K(+)-ATPase, expression of the secretory K(+)-channel and of the mineralocorticoid receptor remained unchanged. Reduced ENaC function is likely due to decreased Sgk1- and increased Nedd4-2 mRNA expression leading to reduced ENaC expression in the membrane. These acute downregulations of ENaC and AQP2 may be triggered to reduce energy consumption in the distal nephron to protect the kidney immediately after transplantation.
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Affiliation(s)
- Ana Velic
- Universitätsklinikum Münster, Medizinische Klinik und Poliklinik D, Experimentelle Nephrologie, Münster, Germany
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17
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Pompermayer K, Souza DG, Lara GG, Silveira KD, Cassali GD, Andrade AA, Bonjardim CA, Passaglio KT, Assreuy J, Cunha FQ, Vieira MAR, Teixeira MM. The ATP-sensitive potassium channel blocker glibenclamide prevents renal ischemia/reperfusion injury in rats. Kidney Int 2005; 67:1785-96. [PMID: 15840025 DOI: 10.1111/j.1523-1755.2005.00276.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Renal ischemia/reperfusion (I/R) is a complex neutrophil-mediated syndrome. Adenosine-triphosphate (ATP)-sensitive potassium (K(ATP)) channels are involved in neutrophil migration in vivo. In the present study, we have investigated the effects of glibenclamide, a K(ATP) channel blocker, in renal I/R injury in rats. METHODS The left kidney of the rats was excised through a flank incision and ischemia was performed in the contralateral kidney by total interruption of renal artery flow for 45 minutes. Renal perfusion was reestablished, and the kidney and lungs were removed for analysis of vascular permeability, neutrophil accumulation, and content of cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-10] 4 and 24 hours later. Renal function was assessed by measuring creatinine, Na(+), and K(+) levels in the plasma and by determination of creatinine clearance. Drugs were administered subcutaneously after the onset of ischemia. RESULTS Reperfusion of the ischemic kidney induced local (kidney) and remote (lung) inflammatory injury and marked renal dysfunction. Glibenclamide (20 mg/kg) significantly inhibited the reperfusion-associated increase in vascular permeability, neutrophil accumulation, increase in TNF-alpha levels and nuclear factor-kappaB (NF-kappaB) translocation. These inhibitory effects were noticed in the kidney and lungs. Moreover, glibenclamide markedly ameliorated the renal dysfunction at 4 and 24 hours. CONCLUSION Treatment with glibenclamide is associated with inhibition of neutrophil recruitment and amelioration of renal dysfunction following renal I/R. Glibenclamide may have a therapeutic role in the treatment of renal I/R injury, such as after renal transplantation.
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Affiliation(s)
- Kenia Pompermayer
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas-Universidade Federal de Minas Gerais, Brazil
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18
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Hebert SC, Desir G, Giebisch G, Wang W. Molecular diversity and regulation of renal potassium channels. Physiol Rev 2005; 85:319-71. [PMID: 15618483 PMCID: PMC2838721 DOI: 10.1152/physrev.00051.2003] [Citation(s) in RCA: 236] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
K(+) channels are widely distributed in both plant and animal cells where they serve many distinct functions. K(+) channels set the membrane potential, generate electrical signals in excitable cells, and regulate cell volume and cell movement. In renal tubule epithelial cells, K(+) channels are not only involved in basic functions such as the generation of the cell-negative potential and the control of cell volume, but also play a uniquely important role in K(+) secretion. Moreover, K(+) channels participate in the regulation of vascular tone in the glomerular circulation, and they are involved in the mechanisms mediating tubuloglomerular feedback. Significant progress has been made in defining the properties of renal K(+) channels, including their location within tubule cells, their biophysical properties, regulation, and molecular structure. Such progress has been made possible by the application of single-channel analysis and the successful cloning of K(+) channels of renal origin.
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Affiliation(s)
- Steven C Hebert
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520-8026, USA.
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19
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Nakamura K, Hirano J, Kubokawa M. Regulation of an inwardly rectifying K+ channel by nitric oxide in cultured human proximal tubule cells. Am J Physiol Renal Physiol 2004; 287:F411-7. [PMID: 15140759 DOI: 10.1152/ajprenal.00014.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the effects of nitric oxide (NO) on activity of the inwardly rectifying K(+) channel in cultured human proximal tubule cells, using the cell-attached mode of the patch-clamp technique. An inhibitor of NO synthases, N(omega)-nitro-L-arginine methyl ester (L-NAME; 100 microM), reduced channel activity, which was restored by an NO donor, sodium nitroprusside (SNP; 10 microM) or 8-bromo-cGMP (8-BrcGMP; 100 microM). However, SNP failed to activate the channel in the presence of an inhibitor of soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 microM). Similarly, the SNP effect was abolished by a protein kinase G (PKG)-specific inhibitor, KT-5823 (1 microM), but not by a protein kinase A-specific inhibitor, KT-5720 (500 nM). Another NO donor, S-nitroso-N-acetyl-D,L-penicillamine (10 microM), mimicked the SNP-induced channel activation. In contrast to the stimulatory effect of SNP at a low dose (10 microM), a higher dose of SNP (1 mM) reduced channel activity, which was not restored by 8-BrcGMP. Recordings of membrane potential with the slow whole cell configuration demonstrated that l-NAME (100 microM) and the high dose of SNP (1 mM) depolarized the cell by 10.1 +/- 2.6 and 9.2 +/- 1.0 mV, respectively, whereas the low dose of SNP (10 microM) hyperpolarized it by 7.1 +/- 0.7 mV. These results suggested that the endogenous NO would contribute to the maintenance of basal activity of this K(+) channel and hence the potential formation via a cGMP/PKG-dependent mechanism, whereas a high dose of NO impaired channel activity independent of cGMP/PKG-mediated processes.
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Affiliation(s)
- Kazuyoshi Nakamura
- Department of Physiology II, Iwate Medical University School of Medicine, Morioka, 020-8505 Japan
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20
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Rahgozar M, Willgoss DA, Gobé GC, Endre ZH. ATP-dependent K+ channels in renal ischemia reperfusion injury. Ren Fail 2004; 25:885-96. [PMID: 14669848 DOI: 10.1081/jdi-120026024] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
ATP-dependent K+ channels (KATP) account for most of the recycling of K+ which enters the proximal tubules cell via Na, K-ATPase. In the mitochondrial membrane, opening of these channels preserves mitochondrial viability and matrix volume during ischemia. We examined KATP channel modulation in renal ischemia-reperfusion injury (IRI), using an isolated perfused rat kidney (IPRK) model, in control, IRI, IRI+200 microM diazoxide (a KATP opener), IRI + 10 microM glibenclamide (a KATP blocker) and IRI + 200 microM diazoxide + 10 microM glibenclamide groups. IRI was induced by 2 periods of warm ischemia, followed by 45 min of reperfusion. IRI significantly decreased glomerular filtration rate (GFR) and increased fractional excretion of sodium (FENa) (p < 0.01). Neither diazoxide nor glibenclamide had an effect on control kidney function other than an increase in renal vascular resistance produced by glibenclamide. Pretreatment with 200 microM diazoxide reduced the postischemic increase in FENa (p < 0.05). Adding 10 microM glibenclamide inhibited the diazoxide effect on postischemic FENa (p < 0.01). Histology showed that kidneys pretreated with glibenclamide demonstrated an increase in injury in the thick ascending limb of outer medulla (p < 0.05). Glibenclamide significantly decreased post ischemic renal vascular resistance (p < 0.05), but had no significant effect on other renal function parameters. Our results suggest that sodium reabsorption is improved by KATP activation and blockade of KATP channels during IRI has an injury enhancing effect on renal epithelial function and histology. This may be mediated through KATP modulation in cell and/or mitochondrial inner membrane.
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Affiliation(s)
- Majid Rahgozar
- Department of Medicine, Central Clinical Division, School of Medicine, University of Queensland, Brisbane, Australia
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21
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Ivorra A, Gómez R, Noguera N, Villa R, Sola A, Palacios L, Hotter G, Aguiló J. Minimally invasive silicon probe for electrical impedance measurements in small animals. Biosens Bioelectron 2003; 19:391-9. [PMID: 14615098 DOI: 10.1016/s0956-5663(03)00204-5] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
It is commonly accepted that electrical impedance provides relevant information about the physiological condition of living tissues. Currently, impedance measurements are performed with relatively large electrodes not suitable for studies in small animals due to their poor spatial resolution and to the damage that they cause to the tissue. A minimally invasive needle shaped probe for electrical impedance measurements of living tissues is presented in this paper. This micro-probe consists of four square platinum electrodes (300 microm x 300 microm) on a silicon substrate (9 mm x 0.6 mm x 0.5 mm) and has been fabricated by using standard Si microelectronic techniques. The electrodes are not equally spaced in order to optimise the signal strength and the spatial resolution. Characterisation data obtained indicate that these probes provide high spatial resolution (measurement radius <4 mm) with a useful wide frequency band going from 100 Hz to 100 kHz. A series of in vivo experiments in rat kidneys subjected to ischemia was performed to demonstrate the feasibility of the probes and the measurement system. The impedance modulus and phase were measured at 1 kHz since this frequency is sufficiently low to permit the study of the extracellular medium. The extracellular pH and K+ were also simultaneously measured by using commercial miniaturised Ion Selective Electrodes. The induced ischemia period (45 min) resulted in significant changes of all measured parameters (Delta/Z/ approximately 65%; DeltapH approximately 0.8; DeltaK+ approximately 30 mM).
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Affiliation(s)
- A Ivorra
- Centro Nacional de Microelectónica (IMB-CSIC), Campus UAB, E-08193 Bellaterra, Barcelona, Spain
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Wei Y, Babilonia E, Pedraza PL, Ferreri NR, Wang WH. Acute application of TNF stimulates apical 70-pS K+ channels in the thick ascending limb of rat kidney. Am J Physiol Renal Physiol 2003; 285:F491-7. [PMID: 12890664 DOI: 10.1152/ajprenal.00104.2003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
TNF has been shown to be synthesized by the medullary thick ascending limb (mTAL) (21). In the present study, we used the patch-clamp technique to study the acute effect of TNF on the apical 70-pS K+ channel in the mTAL. Addition of TNF (10 nM) significantly stimulated activity of the 70-pS K+ channel and increased NPo [a product of channel open probability (Po) and channel number (N)] from 0.20 to 0.97. The stimulatory effect of TNF was observed only in cell-attached patches but not in excised patches. Moreover, addition of TNF had no effect on the ROMK-like small-conductance K+ channels in the TAL. The dose-response curve of the TNF effect yielded a Km value of 1 nM, a concentration that increased channel activity to 50% maximal stimulatory effect of TNF. The concentrations required for reaching the plateau of the TNF effect were between 5 and 10 nM. The stimulatory effect of TNF on the 70-pS K+ channel was observed in the presence of N(omega)-nitro-L-arginine methyl ester. This indicated that the effect of TNF was not mediated by a nitric oxide-dependent pathway. Also, inhibition of PKA did not affect the stimulatory effect of TNF. In contrast, inhibition of protein tyrosine kinase not only increased activity of the 70-pS K+ channel but also abolished the effect of TNF. Moreover, inhibition of protein tyrosine phosphatase (PTP) blocked the stimulatory effect of TNF on the 70-pS K+ channel. The notion that the TNF effect results from stimulation of PTP activity is supported by PTP activity assay in which treatment of mTAL cells with TNF significantly increased the activity of PTP. We conclude that TNF stimulates the 70-pS K+ channel via stimulation of PTP in the mTAL.
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Affiliation(s)
- Yuan Wei
- Dept. of Pharmacology, New York Medical College, Valhalla, NY 10595, USA
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23
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Bonventre JV, Weinberg JM. Recent advances in the pathophysiology of ischemic acute renal failure. J Am Soc Nephrol 2003; 14:2199-210. [PMID: 12874476 DOI: 10.1097/01.asn.0000079785.13922.f6] [Citation(s) in RCA: 546] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Affiliation(s)
- Joseph V Bonventre
- Renal Division, Brigham and Women's Hospital, and Department of Medicine, Harvard Medical School, and the Harvard--MIT, Division of Health Sciences and Technology, Charlestown, Massachusetts, USA.
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24
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Abstract
Programmed cell death or apoptosis is broadly responsible for the normal homeostatic removal of cells and has been increasingly implicated in mediating pathological cell loss in many disease states. As the molecular mechanisms of apoptosis have been extensively investigated a critical role for ionic homeostasis in apoptosis has been recently endorsed. In contrast to the ionic mechanism of necrosis that involves Ca(2+) influx and intracellular Ca(2+) accumulation, compelling evidence now indicates that excessive K(+) efflux and intracellular K(+) depletion are key early steps in apoptosis. Physiological concentration of intracellular K(+) acts as a repressor of apoptotic effectors. A huge loss of cellular K(+), likely a common event in apoptosis of many cell types, may serve as a disaster signal allowing the execution of the suicide program by activating key events in the apoptotic cascade including caspase cleavage, cytochrome c release, and endonuclease activation. The pro-apoptotic disruption of K(+) homeostasis can be mediated by over-activated K(+) channels or ionotropic glutamate receptor channels, and most likely, accompanied by reduced K(+) uptake due to dysfunction of Na(+), K(+)-ATPase. Recent studies indicate that, in addition to the K(+) channels in the plasma membrane, mitochondrial K(+) channels and K(+) homeostasis also play important roles in apoptosis. Investigations on the K(+) regulation of apoptosis have provided a more comprehensive understanding of the apoptotic mechanism and may afford novel therapeutic strategies for apoptosis-related diseases.
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Affiliation(s)
- Shan Ping Yu
- Department of Pharmaceutical Sciences, School of Pharmacy, Medical University of South Carolina, 280 Calhoun Street, PO Box 250140, Charleston, SC 29425, USA.
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25
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Chang DJ, Lim CS, Lee SH, Kaang BK. Hydrogen peroxide modulates K+ ion currents in cultured Aplysia sensory neurons. Brain Res 2003; 970:159-68. [PMID: 12706257 DOI: 10.1016/s0006-8993(03)02316-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hydrogen peroxide (H(2)O(2)) causes oxidative stress and is considered a mediator of cell death in various organisms. Our previous studies showed that prolonged (>6 h) treatment of Aplysia sensory neurons with 1 mM H(2)O(2) produced hyperpolarization of the resting membrane potential, followed by apoptotic morphological changes. In this study, we examined the effect of H(2)O(2) on the membrane conductance of Aplysia sensory neurons. Hyperpolarization was induced by 10 mM H(2)O(2) within 1 h, and this was attributed to increased membrane conductance. In addition, treatment with 10 mM H(2)O(2) for 3 min produced immediate depolarization, which was due to decreased membrane conductance. The H(2)O(2)-induced hyperpolarization and depolarization were completely blocked by dithiothreitol, a disulfide-reducing agent. The later increase of membrane conductance induced by H(2)O(2) was completely blocked by 100 mM TEA, a K(+) channel blocker, suggesting that H(2)O(2)-induced hyperpolarization is due to the activation of K(+) conductance. However, the inhibition of K(+) efflux by TEA did not protect against H(2)O(2)-induced cell death in cultured Aplysia sensory neurons, which indicates that the signal pathway leading to H(2)O(2)-induced cell death is more complicated than expected.
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Affiliation(s)
- Deok-Jin Chang
- National Research Laboratory of Neurobiology, Institute of Molecular Biology and Genetics, School of Biological Sciences, College of Natural Sciences, Seoul National University, San 56-1 Silim-dong Kwanak-gu, South Korea
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26
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Sola A, Palacios L, López-Martí J, Ivorra A, Noguera N, Gómez R, Villa R, Aguiló J, Hotter G. Multiparametric monitoring of ischemia-reperfusion in rat kidney: effect of ischemic preconditioning. Transplantation 2003; 75:744-9. [PMID: 12660495 DOI: 10.1097/01.tp.0000054683.72223.2d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Microelectrode technology is a promising tool for monitoring kidney ischemia and the changes induced by its therapeutic management. Ischemic preconditioning, that is, brief ischemic periods before sustained ischemia, has been shown to protect several organs, including the kidney, from ischemia-reperfusion injury. We tested whether the effect of preconditioning could be appraised by real-time measurement of parameters representative of tissue hypoxia. METHODS In a sample of pentobarbital-anesthetized and mechanically ventilated rats, we studied the effect of renal ischemic preconditioning (10-min ischemia and 10-min reflow interval) on subsequent ischemia-reperfusion (45 min and 60 min). Renal tissue electrical impedance, extracellular pH, and potassium concentration [K+] were measured continuously by implanted microelectrodes. RESULTS Ischemia induced an early, rapid rise in extracellular potassium and impedance module, followed by a phase of slower increase, whereas pH decreased rapidly, reaching a plateau. Preconditioning treatment did not cause significant changes in interstitial pH and [K+] but increased ischemic tissue impedance. During reperfusion, the three variables recovered progressively; however, after a decline, electrical impedance showed a clear postischemic increase. This rise was suppressed by preconditioning. CONCLUSIONS Real-time measurement of any of the three parameters showed capability for early detection of ischemia. In contrast with findings in myocardial tissue, preconditioning in the kidney did not increase potassium cell loss during ischemia or improve ischemic acidosis or tissue impedance. Electrical impedance increased for a second time during reperfusion, indicating the presence of a postischemic cellular edema; concealing this episode was the most noticeable effect of the preconditioning treatment.
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Affiliation(s)
- A Sola
- Department of Medical Bioanalysis, Instituto de Investigaciones Biomédicas, IIBB-CSIC, IDIBAPS. Barcelona, Spain
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27
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Lepsy CS, Guttendorf RJ, Kugler AR, Smith DE. Effects of organic anion, organic cation, and dipeptide transport inhibitors on cefdinir in the isolated perfused rat kidney. Antimicrob Agents Chemother 2003; 47:689-96. [PMID: 12543679 PMCID: PMC151749 DOI: 10.1128/aac.47.2.689-696.2003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cefdinir (Omnicef; Abbott Laboratories) is a cephalosporin antibiotic primarily eliminated by the kidney. Nonlinear renal elimination of cefdinir has been previously reported. Cefdinir renal transport mechanisms were studied in the erythrocyte-free isolated perfused rat kidney. Studies were performed with drug-free perfusate and perfusate containing cefdinir alone to establish the baseline physiology and investigate cefdinir renal elimination characteristics. To investigate cefdinir renal transport mechanisms, inhibition studies were conducted by coperfusing cefdinir with inhibitors of the renal organic anion (probenecid), organic cation (tetraethylammonium), or dipeptide (glycylsarcosine) transport system. Cefdinir concentrations in biological samples were determined using reversed-phase high-performance liquid chromatography. Differences between treatments and controls were evaluated using analysis of variance and Dunnett's test. The excretion ratio (ER; the renal clearance corrected for the fraction unbound and glomerular filtration rate) for cefdinir was 5.94, a value indicating net renal tubular secretion. Anionic, cationic, and dipeptide transport inhibitors all significantly affected the cefdinir ER. With probenecid, the ER was reduced to 0.59, clearly demonstrating a significant reabsorptive component to cefdinir renal disposition. This finding was confirmed by glycylsarcosine studies, in which the ER was elevated to 7.95, indicating that reabsorption was mediated, at least in part, by the dipeptide transporter system. The effects of the organic cation tetraethylammonium, in which the ER was elevated to 7.53, were likely secondary in nature. The anionic secretory pathway was found to be the predominant mechanism for cefdinir renal excretion.
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Kribben A, Feldkamp T, Horbelt M, Lange B, Pietruck F, Herget-Rosenthal S, Heemann U, Philipp T. ATP protects, by way of receptor-mediated mechanisms, against hypoxia-induced injury in renal proximal tubules. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2003; 141:67-73. [PMID: 12518170 DOI: 10.1067/mlc.2003.7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We examined the effect of ATP on hypoxia-induced injury in freshly isolated rat renal proximal tubules and compared it with the effects of stable ATP analogues and ATP degradation products. Extracellular ATP significantly reduced hypoxia-induced structural cell damage (lactate dehydrogenase release). P(2)-receptor agonistic ATP analogues, including 2'-methylthio-ATP (2-Me-S-ATP), were also protective. In contrast, the P(1)-agonistic degradation products AMP and adenosine were not protective. Hypoxia-induced functional cell damage (loss of cellular potassium) was not changed by ATP or 2-Me-S-ATP. We therefore conclude that the protective property of ATP is not based on an effect of the degradation products or on a direct effect on cellular energy metabolism. The data indicate that the protective effect of ATP is mediated by P(2) receptors.
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Affiliation(s)
- Andreas Kribben
- Department of Nephrology and Hypertension, University Hospital Essen, Germany.
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29
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Moran JH, Mitchell LA, Grant DF. Linoleic acid prevents chloride influx and cellular lysis in rabbit renal proximal tubules exposed to mitochondrial toxicants. Toxicol Appl Pharmacol 2001; 176:153-61. [PMID: 11714247 DOI: 10.1006/taap.2001.9270] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Despite many studies elucidating the mechanisms of necrotic cell death, the role of fatty acids released during necrosis remains to be determined. The goals of this study were to determine whether linoleic acid could protect rabbit renal proximal tubules (RPT) from necrotic cell death associated with mitochondrial dysfunction and oxidative injury and to determine the mechanisms involved. Exposure to antimycin A (10 microM) for 1 h or hypoxia (perfusion with 95% N(2)/5% CO(2)) for 1 or 2 h induced approximately 70% cellular lysis, as measured by lactate dehyrogenase release, versus 10% in controls. Preincubation with linoleic acid (100 microM) fully protected RPT from cellular lysis. RPT were also protected from lysis if linoleic acid was added 15 min after the addition of antimycin A. Measurements of free intracellular Ca(2+) concentrations showed that linoleic acid did not prevent the rise in intracellular Ca(2+) associated with a 30-min exposure to antimycin A. However, the influx of extracellular (36)Cl(-) following a 30-min exposure to antimycin A was ameliorated in the presence of linoleic acid. Linoleic acid did not prevent cellular lysis after exposure to hypoxia/reoxygenation (1 h/1 h) or t-butyl hydroperoxide (500 microM, 3 h). These data suggest that linoleic acid protects RPT during the late phase of cell death associated with inhibition of the electron transport chain but not oxidative injury. Several other fatty acids also protected RPT from lysis, and structure-activity relationship studies suggest that a free carboxyl terminus and at least one double bond are required for this action.
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Affiliation(s)
- J H Moran
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
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30
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Wei Y, Lu M, Wang WH. Ca2+ mediates the effect of inhibition of Na+-K+-ATPase on the basolateral K+ channels in the rat CCD. Am J Physiol Cell Physiol 2001; 280:C920-8. [PMID: 11245609 DOI: 10.1152/ajpcell.2001.280.4.c920] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We investigated the effect of inhibiting Na+-K+-ATPase on the basolateral 18-pS K+ channel in the cortical collecting duct (CCD) of the rat kidney. Inhibiting Na+-K+-ATPase with strophanthidin decreased the activity of the 18-pS K+ channel and increased the intracellular Ca2+ to 420 nM. Removal of extracellular Ca2+ abolished the effect of strophanthidin. When intracellular Ca2+ was raised with 5 microM ionomycin or A-23187 to 300, 400, and 500 nM, the activity of the 18-pS K+ channel in cell-attached patches fell by 40, 85, and 96%, respectively. To explore the mechanism of Ca2+-induced inhibition, the effect of 400 nM Ca2+ on channel activity was studied in the presence of calphostin C, an inhibitor of protein kinase C, or KN-93 and KN-62, inhibitors of calmodulin-dependent kinase II. Addition of calphostin C or KN-93 or KN-62 failed to block the inhibitory effect of high concentrations of Ca2+ . This suggested that the inhibitory effect of high concentrations of Ca2+ was not mediated by protein kinase C or calmodulin-dependent kinase II pathways. To examine the possibility that the inhibitory effect of high concentrations of Ca2+ was mediated by the interaction of nitric oxide with superoxide, we investigated the effect of 400 nM Ca2+ on channel activity in the presence of 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron) or N(omega)-nitro-L-arginine methyl ester. Pretreatment of the tubules with 4,5-dihydroxy-1,3-benzenedisulfonic acid or N(omega)-nitro-L-arginine methyl ester completely abolished the inhibitory effect of 400 nM Ca2+ on channel activity. Moreover, application of 4,5-dihydroxy-1,3-benzenedisulfonic acid reversed the inhibitory effect of strophanthidin. We conclude that the effect of inhibiting Na+-K+-ATPase is mediated by intracellular Ca2+ and the inhibitory effect of high concentrations of Ca2+ is the result of interaction of nitric oxide with superoxide.
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Affiliation(s)
- Y Wei
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595, USA
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31
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Giebisch G, Wang W. Renal tubule potassium channels: function, regulation and structure. ACTA PHYSIOLOGICA SCANDINAVICA 2000; 170:153-73. [PMID: 11114953 DOI: 10.1046/j.1365-201x.2000.00770.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- G Giebisch
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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Engbersen R, Moons MM, Wouterse AC, Dijkman HB, Kramers C, Smits P, Russel FGM. Sulphonylurea drugs reduce hypoxic damage in the isolated perfused rat kidney. Br J Pharmacol 2000; 130:1678-84. [PMID: 10928974 PMCID: PMC1572226 DOI: 10.1038/sj.bjp.0703469] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Sulphonylurea drugs have been shown to protect against hypoxic damage in isolated proximal tubules of the kidney. In the present study we investigated whether these drugs can protect against hypoxic damage in a whole kidney preparation. Tolbutamide (200 microM) and glibenclamide (10 microM) were applied to the isolated perfused rat kidney prior to changing the gassing from oxygen to nitrogen for 30 min. Hypoxic perfusions resulted in an increased fractional excretion of glucose (FE % glucose 14.3+/-1.5 for hypoxic perfusions vs 4.9+/-1.6 for normoxic perfusions, mean +/- s.e. mean, P<0.05), which could be completely restored by 200 microM tolbutamide (5.7+/-0.4 for tolbutamide vs 14.3+/-1.5 for untreated hypoxic kidneys, P<0.01). Furthermore, tolbutamide reduced the total amount of LDH excreted in the urine (220+/-100 mU for tolbutamide vs. 1220+/-160 mU for untreated hypoxic kidneys, P<0.01). Comparable results were obtained with glibenclamide (10 microM). In agreement with the effect on functional parameters, ultrastructural analysis of proximal tubules showed increased brush border preservation in tolbutamide treated kidneys compared to untreated hypoxic kidneys. We conclude that glibenclamide and tolbutamide are both able to reduce hypoxic damage to proximal tubules in the isolated perfused rat kidney when applied in the appropriate concentrations.
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Affiliation(s)
- Richard Engbersen
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Miek M Moons
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Alfons C Wouterse
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Henry B Dijkman
- Department of Pathology, University Medical Centre Nijmegen, The Netherlands
| | - Cees Kramers
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Paul Smits
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Frans G M Russel
- Department of Pharmacology and Toxicology 233, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
- Author for correspondence:
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Lu M, MacGregor GG, Wang W, Giebisch G. Extracellular ATP inhibits the small-conductance K channel on the apical membrane of the cortical collecting duct from mouse kidney. J Gen Physiol 2000; 116:299-310. [PMID: 10919872 PMCID: PMC2229488 DOI: 10.1085/jgp.116.2.299] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have used the patch-clamp technique to study the effects of changing extracellular ATP concentration on the activity of the small-conductance potassium channel (SK) on the apical membrane of the mouse cortical collecting duct. In cell-attached patches, the channel conductance and kinetics were similar to its rat homologue. Addition of ATP to the bathing solution of split-open single cortical collecting ducts inhibited SK activity. The inhibition of the channel by ATP was reversible, concentration dependent (K(i) = 64 microM), and could be completely prevented by pretreatment with suramin, a specific purinergic receptor (P(2)) blocker. Ranking of the inhibitory potency of several nucleotides showed strong inhibition by ATP, UTP, and ATP-gamma-S, whereas alpha, beta-Me ATP, and 2-Mes ATP failed to affect channel activity. This nucleotide sensitivity is consistent with P(2)Y(2) purinergic receptors mediating the inhibition of SK by ATP. Single channel analysis further demonstrated that the inhibitory effects of ATP could be elicited through activation of apical receptors. Moreover, the observation that fluoride mimicked the inhibitory action of ATP suggests the activation of G proteins during purinergic receptor stimulation. Channel inhibition by ATP was not affected by blocking phospholipase C and protein kinase C. However, whereas cAMP prevented channel blocking by ATP, blocking protein kinase A failed to abolish the inhibitory effects of ATP. The reduction of K channel activity by ATP could be prevented by okadaic acid, an inhibitor of protein phosphatases, and KT5823, an agent that blocks protein kinase G. Moreover, the effect of ATP was mimicked by cGMP and blocked by L-NAME (N(G)-nitro-l-arginine methyl ester). We conclude that the inhibitory effect of ATP on the apical K channel is mediated by stimulation of P(2)Y(2) receptors and results from increasing dephosphorylation by enhancing PKG-sensitive phosphatase activity.
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Affiliation(s)
- Ming Lu
- Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Gordon G. MacGregor
- Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
| | - Wenhui Wang
- Department of Pharmacology, New York Medical College, Valhalla, New York 10595
| | - Gerhard Giebisch
- Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520
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Ashman N, Yaqoob M. Metabolic acidosis, hypokalaemia and acute renal failure with a normal urine output. Nephrol Dial Transplant 2000; 15:1083-5. [PMID: 10862656 DOI: 10.1093/ndt/15.7.1083] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- N Ashman
- Department of Renal Medicine and Transplantation, Royal London Hospital, Whitechapel, London, UK
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Sgard F, Faure C, Drieu la Rochelle C, Graham D, O'Connor SE, Janiak P, Besnard F. Regulation of ATP-sensitive potassium channel mRNA expression in rat kidney following ischemic injury. Biochem Biophys Res Commun 2000; 269:618-22. [PMID: 10708603 DOI: 10.1006/bbrc.2000.2342] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ATP-sensitive potassium (K(ATP)) channels are involved in the regulation of potassium homeostasis in kidneys. In the event of renal ischemia, they are thought to contribute to the important intracellular potassium loss observed in proximal tubules and thus to hypoxic injury. We have analyzed the transcriptional regulation of K(ATP) genes in rat kidney following transient renal ischemia. We observed that mRNA expression level was down-regulated for Kir1.1 and Kir4.1 potassium channels between 24 and 120 h after ischemia. In contrast, a strong increase in mRNA expression was observed for Kir6.1 shortly (2-6 h) after ischemia. Thus, renal ischemia followed by reperfusion provokes differential regulation of K(ATP) channel gene expression.
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Affiliation(s)
- F Sgard
- Department of Molecular and Functional Genomics, Sanofi-Synthélabo, 10 Rue des Carrières, Rueil Malmaison, 92500, France
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36
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Meng X, Reeves WB. Effects of chloride channel inhibitors on H(2)O(2)-induced renal epithelial cell injury. Am J Physiol Renal Physiol 2000; 278:F83-90. [PMID: 10644658 DOI: 10.1152/ajprenal.2000.278.1.f83] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxidative stress contributes to renal epithelial cell injury in certain settings. Chloride influx has also been proposed as an important component of acute renal epithelial cell injury. The present studies examined the role of Cl(-) in H(2)O(2)-induced injury to LLC-PK(1) renal epithelial cells. Exposure of LLC-PK(1) cells to 1 mM H(2)O(2) resulted in the following: depletion of intracellular ATP content; DNA damage; lipid peroxidation; and a loss of membrane integrity to both small molecules, e.g., trypan blue, and macromolecules, e.g., lactate dehydrogenase (LDH), and cell death. Substitution of Cl(-) by isethionate or the inclusion of certain Cl(-) channel blockers, e.g., diphenylamine-2-carboxylate (DPC), 5-nitro-2-(3-phenylpropylamino). benzoate (NPPB), and niflumic acid, prevented the H(2)O(2)-induced loss of membrane integrity to LDH. In addition, the H(2)O(2)-induced loss of membrane integrity was prevented by raising the osmolality of the extracellular solutions, by depletion of cell ATP, and by inhibitors of volume-sensitive Cl(-) channels. However, these maneuvers did not prevent the H(2)O(2)-induced permeability to small molecules or H(2)O(2)-induced ATP depletion, DNA damage, lipid peroxidation, or cell death. These results support the view that volume-sensitive Cl(-) channels play a role in the progressive loss of cell membrane integrity during injury.
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Affiliation(s)
- X Meng
- Division of Nephrology, University of Arkansas for Medical Sciences and John L. McClellan Memorial Veterans Hospital, Little Rock, Arkansas 72205, USA
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37
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Filipovic DM, Meng X, Reeves WB. Inhibition of PARP prevents oxidant-induced necrosis but not apoptosis in LLC-PK1 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:F428-36. [PMID: 10484526 DOI: 10.1152/ajprenal.1999.277.3.f428] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oxidant-induced cell injury has been implicated in the pathogenesis of several forms of acute renal failure. The present studies examined whether activation of poly(ADP-ribose)polymerase (PARP) by oxidant-induced DNA damage contributes to oxidant injury of renal epithelial cells. H2O2 exposure resulted in an increase in PARP activity and decreases in cell ATP and NAD content. These changes were significantly inhibited by 10 mM 3-aminobenzamide (3-ABA), a PARP inhibitor. In contrast, H2O2-induced DNA damage was not prevented by 3-ABA. Exposure of LLC-PK(1) cells to 1 mM H2O2 for 2 h induced necrotic cell death as measured by increased lactate dehydrogenase (LDH) release. 3-ABA completely prevented the H2O2-induced LDH release. Live/dead fluorescent staining confirmed the protection by 3-ABA. These results are consistent with the view that oxidant-induced DNA damage activates PARP and that the subsequent ATP and NAD depletion contribute to necrotic cell death. Of note, although protected from necrosis, cells treated with H2O2 and 3-ABA underwent apoptosis as evidenced by DNA fragmentation and bis-benzimide staining. In conclusion, activation of PARP contributes to oxidant-induced ATP depletion and necrosis in LLC-PK1 cells. However, PARP inhibition may target cells toward an apoptotic form of cell death.
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Affiliation(s)
- D M Filipovic
- Division of Nephrology, University of Arkansas for Medical Sciences and J. L. McClellan Memorial Veterans Affairs Hospital, Little Rock, Arkansas 72205, USA
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38
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Lu M, Wang WH. Reaction of nitric oxide with superoxide inhibits basolateral K+ channels in the rat CCD. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:C309-16. [PMID: 9688863 DOI: 10.1152/ajpcell.1998.275.1.c309] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We previously demonstrated that nitric oxide (NO) stimulates the basolateral small-conductance K+ channel (SK) via a cGMP-dependent pathway [M. Lu and W. H. Wang. Am. J. Physiol. 270 (Cell Physiol. 39): C1336-C1342, 1996]. Because NO at high concentration has been shown to react with superoxide (O-2) to form peroxynitrite (OONO-) [W. A. Pryor and G. L. Squadrito. Am. J. Physiol. 268 (Lung Cell. Mol. Physiol. 12): L699-L722, 1995 and M. S. Wolin. Microcirculation 3: 1-17, 1996], we extended our study to examine, using patch-clamp technique, the effect of high concentrations of NO on SK in cortical collecting duct (CCD) of rat kidney. Addition of NO donors [100-200 microM S-nitroso-N-acetyl-penicillamine (SNAP) or sodium nitroprusside (SNP)] reduced channel activity, defined as the product of channel number and open probability, to 15 and 25% of the control value, respectively. The inhibitory effect of NO was completely abolished in the presence of 10 mM Tiron, an intracellular scavenger of O-2. NO donors, 10 microM SNAP or SNP, which stimulate channel activity under control conditions, can also inhibit SK in the presence of an O-2 donor, pyrogallol, or in the presence of an inhibitor of superoxide dismutase, diethyldithiocarbamic acid. The inhibitory effect of NO is still observed in the presence of exogenous cGMP, suggesting that the NO-induced inhibition is not the result of decreased cGMP production. We conclude that the inhibitory effect of NO on channel activity results from an interaction between NO and O-2.
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Affiliation(s)
- M Lu
- Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA
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39
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Portilla D. Carnitine palmitoyl-transferase enzyme inhibition protects proximal tubules during hypoxia. Kidney Int 1997; 52:429-37. [PMID: 9263998 DOI: 10.1038/ki.1997.349] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The role of inhibition of the CPT enzymes responsible for accumulation of long chain acylcarnitines (LCAC) during hypoxia in the proximal tubule has not been previously examined. We have characterized CPT enzyme activities in mitochondrial fractions of rabbit proximal tubules. Malonyl CoA-sensitive CPT I activity (1.1 +/- 0.3 nmol/min/mg protein), and detergent-solubilized, malonyl CoA-insensitive CPT II activity (2.3 +/- 0.4 nmol/min/mg protein) were readily detected in proximal tubule mitochondrial fractions. Subjecting rabbit proximal tubules to various periods of hypoxia did not significantly change mitochondrial CPT I or CPT II activities. Thirty minutes of hypoxia resulted in an increase in lysophospholipid mass from 440 +/- 105 to 720 +/- 93 pmol/mg protein, N = 5, LCAC mass from 79 +/- 11 to 618 +/- 34 pmol/mg protein, N = 5, and lactate dehydrogenase (LDH) release from 9 +/- 1% to 46 +/- 3%, N = 8. Pretreatment of proximal tubules with two different CPT inhibitors, glybenclamide (Glyb) 400 microM and oxfenicine (Oxfe) 1 mM, resulted in reduction in the magnitude of hypoxia-induced lysophospholipid formation 490 +/- 160 (Glyb), 342 +/- 150 pmol/mg protein (Oxfe), N = 4, hypoxia-induced LCAC formation 295 +/- 27 (Glyb), 128 +/- 16 pmol/mg protein (Oxfe). N = 5, and LDH release 25 +/- 1% (Glyb) and 19 +/- 2% (Oxfe), N = 8. The protective effect of CPT inhibition was also associated with increased production of lactate suggesting the modulation of a substrate-mediated metabolic switch. Immunoblots demonstrated that hypoxia caused a time dependent hydrolysis of fodrin-alpha subunit and that CPT inhibition protected against hypoxia-induced fodrin proteolysis. These data suggest a unifying hypothesis that links phospholipase A2 (PLA2) activation, and hypoxia-mediated fodrin proteolysis to the proximal tubule mitochondrial CPT system. I propose that CPT inhibition may represent a novel mechanism to ameliorate proximal tubule cell death during hypoxia.
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Affiliation(s)
- D Portilla
- Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, USA
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40
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Abstract
These studies examined the pathways and consequences of chloride uptake into proximal tubule cells during in vitro hypoxia. The chloride channel blocker diphenylamine-2-carboxylate (DPC) markedly reduced the degree of hypoxia-induced membrane damage as measured by the release of lactate dehydrogenase (LDH). DPC reduced the release of LDH from hypoxic tubules from 38 +/- 2.7% to 16 +/- 1.7% after 30 minutes of hypoxia (P < 0.001, N = 16) and also reduced 36Cl- uptake by hypoxic tubules. The reduction in LDH release was not associated with better preservation of cell ATP content or with protection against hypoxia-induced DNA damage. Other Cl- channel blockers, such as niflumic acid, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) and 2-[(2-cyclopentyl-6,7-dichloro-2,3-dihyrdo-2-methyl-1-oxo-1H-in den-5-yl)oxy] acetic acid (IAA-94) provided even greater protection than DPC and were as effective as 2 mM glycine. The Cl- channel blockers appear to act late in the course of hypoxic injury since DNA damage, an early manifestation of injury, is not prevented by the blockers and since addition of the Cl- channel blocker after the hypoxic injury has begun reduces further membrane damage. These results support the conclusion that transport through Cl- channels contributes to hypoxic cell injury in proximal tubular cells.
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Affiliation(s)
- W B Reeves
- Division of Nephrology, University of Arkansas for Medical Sciences, Little Rock, USA
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41
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Filipovic DM, Reeves WB. Hydrogen peroxide activates glibenclamide-sensitive K+ channels in LLC-PK1 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 272:C737-43. [PMID: 9124318 DOI: 10.1152/ajpcell.1997.272.2.c737] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oxidant-induced damage has been implicated in the pathogenesis of several forms of cellular injury. The present study employed patch-clamp methods to determine if oxidant stress leads to activation of plasma membrane K+ channels in the renal epithelial LLC-PK1 cell line. Exposure of cells to H2O2 (0.1 to 5 mM) induced a rapid (within 5-10 min), dose-dependent membrane hyperpolarization. Perforated patch whole cell voltage-clamp studies were performed to determine the ion selectivity of the currents underlying this H2O2-induced cellular hyperpolarization. H2O2 (5 mM) produced a sixfold increase in the whole cell conductance. The reversal potential of the H2O2-induced current was consistent with a K+-selective conductance. This current was blocked almost completely by 5 mM barium and 500 microM glibenclamide but only partially by 15 mM tetraethylammonium. Exposure of LLC-PK1 cells to 5 mM H2O2 reduced cell ATP content by 70%. To evaluate more directly the role of ATP depletion in the activation of K+ channels, conventional whole cell patch-clamp studies were performed. Inclusion of ATP in the pipette solution prevented H2O2-induced activation of the K+ conductance. These findings indicate that H2O2 activates an ATP-sensitive, Ca2+-independent K+ conductance in LLC-PK1 cells.
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Affiliation(s)
- D M Filipovic
- Department of Internal Medicine, University of Arkansas for Medical Sciences and the John L. McClellan Veterans Affairs Hospital, Little Rock 72205, USA
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42
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Abstract
The activity of potassium (K+) channels is intimately linked to several important transport functions in renal tubules. We review recent progress concerning the properties, site along the nephron, and physiological regulation of native K+ channels, and compare their characteristics with those of recently cloned K+ channels. We do not fully cover work on K+ channels in amphibian tubules, cell cultures, and single tubule cells and do not review K+ channels in mesangial cells.
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Affiliation(s)
- W Wang
- Department of Pharmacology, New York Medical College, Valhalla 10595, USA
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43
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Quast U. ATP-sensitive K+ channels in the kidney. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1996; 354:213-25. [PMID: 8878050 DOI: 10.1007/bf00171051] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
ATP-sensitive K+ channels (KATP channels) form a link between the metabolic state of the cell and the permeability of the cell membrane for K+ which, in turn, is a major determinant of cell membrane potential. KATP channels are found in many different cell types. Their regulation by ATP and other nucleotides and their modulation by other cellular factors such as pH and kinase activity varies widely and is fine-tuned for the function that these channels have to fulfill. In most excitable tissues they are closed and open when cell metabolism is impaired; thereby the cell is clamped in the resting state which saves ATP and helps to preserve the structural integrity of the cell. There are, however, notable exceptions from this rule; in pancreatic beta-cells, certain neurons and some vascular beds, these channels are open during the normal functioning of the cell. In the renal tubular system, KATP channels are found in the proximal tubule, the thick ascending limb of Henle's loop and the cortical collecting duct. Under physiological conditions, these channels have a high open probability and play an important role in the reabsorption of electrolytes and solutes as well as in K+ homeostasis. The physiological role of their nucleotide sensitivity is not entirely clear; one consequence is the coupling of channel activity to the activity of the Na-K-ATPase (pump-leak coupling), resulting in coordinated vectorial transport. In ischemia, however, the reduced ATP/ADP ratio would increase the open probability of the KATP channels independently from pump activity; this is particularly dangerous in the proximal tubule, where 60 to 70% of the glomerular ultrafiltrate is reabsorbed. The pharmacology of KATP channels is well developed including the sulphonylureas as standard blockers and the structurally heterogeneous family of channel openers. Blockers and openers, exemplified by glibenclamide and levcromakalim, show a wide spectrum of affinities towards the different types of KATP channels. Recent cloning efforts have solved the mystery about the structure of the channel: the KATP channels in the pancreatic beta-cell and in the principal cell of the renal cortical collecting duct are heteromultimers, composed of an inwardly rectifying K+ channel and sulphonylurea binding subunit(s) with unknown stoichiometry. The proteins making up the KATP channel in these two cell types are different (though homologous), explaining the physiological and pharmacological differences between these channel subtypes.
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Affiliation(s)
- U Quast
- Pharmakologisches Institut, Universität, Medizinische Fakultät, Tübingen, Germany
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44
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Doctor RB, Bacallao R, Mandel LJ. Chapter 18 Role of the Cytoskeleton in Membrane Alterations in Ischemic or Anoxic Renal Epithelia. CURRENT TOPICS IN MEMBRANES 1996. [DOI: 10.1016/s0070-2161(08)60398-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Peters SM, Tijsen MJ, Bindels RJ, van Os CH, Wetzels JF. Protection against hypoxic injury of rat proximal tubules by felodipine via a calcium-independent mechanism. Pflugers Arch 1995; 431:20-7. [PMID: 8584414 DOI: 10.1007/bf00374373] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Most evidence for a key role of calcium entry in hypoxia-induced renal damage stems from studies with calcium channel blockers. In proximal tubules, a primary site of renal ischaemic injury, only phenyl-alkylamines, especially verapamil, have been studied. In the present study the effect of the dihydropyridine felodipine on hypoxic injury in isolated rat proximal tubules was investigated. To discriminate between the block of calcium entry and other effects, the enantiomers and a non-calcium blocking derivative of felodipine (H186/86) were included. Cell membrane injury was assessed by measuring the release of lactate dehydrogenase (LDH). At high concentrations (100 microM) felodipine, H186/86 and the two enantiomers all protected rat proximal tubules against hypoxia-induced injury to the same extent. Absence of extracellular calcium did not offer protection, but rather enhanced hypoxic injury. All dihydropyridines used increased the intracellular potassium concentration during normoxia. Felodipine attenuated the hypoxia-induced loss of cellular potassium. We have tried to mimic the effects of felodipine by using potassium channel blockers. The potassium channel blockers quinidine and glibenclamide afforded some protection against hypoxic injury, although their effects on cellular potassium were equivocal. We conclude that the dihydropyridine calcium channel blocker felodipine protects rat proximal tubules against hypoxic injury via a calcium-independent mechanism. We propose that high levels of intracellular potassium and attenuation of potassium loss during hypoxia are important in this protection.
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Affiliation(s)
- S M Peters
- Department of Nephrology, University Hospital Nijmegen, Nijmegen, The Netherlands
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