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ABSTRACT: Brown Norway rats (BN, BN/NHsdMcwi) are profoundly resistant to developing acute kidney injury (AKI) following ischemia reperfusion. To help define the genetic basis for this resistance, we used consomic rats, in which individual chromosomes from BN rats were placed into the genetic background of Dahl SS rats (SS, SS/JrHsdMcwi) to determine which chromosomes contain alleles contributing to protection from AKI. The parental strains had dramatically different sensitivity to ischemia reperfusion with plasma creatinine levels following 45 min of ischemia and 24 h reperfusion of 4.1 and 1.3 mg/dl in SS and BN, respectively. No consomic strain showed protection similar to the parental BN strain. Nine consomic strains (SS-7(BN), SS-X(BN), SS-8(BN), SS-4(BN), SS-15(BN), SS-3(BN), SS-10(BN), SS-6(BN), and SS-5(BN)) showed partial protection (plasma creatinine about 2.5-3.0 mg/dl), suggesting that multiple alleles contribute to the severity of AKI. In silico analysis was performed using disease ontology database terms and renal function quantitative trait loci from the Rat Genome Database on the BN chromosomes giving partial protection from AKI. This tactic identified at least 36 candidate genes, with several previously linked to the pathophysiology of AKI. Thus, natural variants of these alleles or yet-to-be identified alleles on these chromosomes provide protection against AKI. These alleles may be potential modulators of AKI in susceptible patient populations.Kidney International advance online publication, 12 December 2012; doi:10.1038/ki.2012.391.
Kidney International 12/2012; · 6.61 Impact Factor
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ABSTRACT: While it is known that the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to ischemic injury in the heart and brain, its role in kidney injury is unclear. Here we determined the effects on ischemia-reperfusion injury of the 20-HETE analogues, 20-hydroxyeicosa-5(Z), 14(Z)-dienoic acid (5,14-20-HEDE), and N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-20-HEDGE), and of the inhibitor of 20-HETE synthesis N-hydroxy-N-(4-butyl-2 methylphenyl) formamidine (HET0016). Using Sprague-Dawley rats we found that while treatment with the inhibitor exacerbated renal injury, infusion of both 5,14-20-HEDE and 5,14-20-HEDGE significantly attenuated injury when compared to vehicle or inhibitor-treated rats. Medullary blood flow, measured by laser-Doppler flowmetry, decreased to half of the baseline one hour after reperfusion in the control rats, but 5,14-20-HEDGE completely prevented this. Treatment of control animals with 5,14-20-HEDGE increased urine output and sodium excretion without altering their mean arterial pressure or glomerular filtration rate. Our results suggest that 20-HETE analogues protect the kidney from ischemia-reperfusion injury by inhibiting renal tubular sodium transport and preventing the post-ischemic fall in medullary blood flow. Analogues of 20-HETE may be useful in the treatment of acute ischemic kidney injury.
Kidney International 01/2009; 75(5):511-7. · 6.61 Impact Factor
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ABSTRACT: Oxidant-mediated apoptosis has been implicated in renal injury due to ischemia reperfusion (IR); however, the apoptotic signaling pathways following IR have been incompletely defined. The purpose of this study was to examine the role of oxidants on cell death in a model of in vitro simulated IR injury in renal proximal tubular epithelial cells by analyzing the effects of a cell-permeable superoxide dismutase mimetic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTmPyP). Renal proximal tubular epithelial cells were ATP depleted for 2, 4, or 6 h, followed by 2 h of recovery. We found that MnTmPyP was effective in attenuating cytotoxicity (P<0.001) and decreasing steady-state oxidant levels (P<0.001) and apoptotic cell death (P<0.001) following ATP depletion-recovery. MnTmPyP treatment prevented the early cytosolic release of cytochrome c and increased Bcl-2 protein levels following short durations of ATP depletion-recovery. After longer periods of ATP depletion-recovery, we observed a significant increase in TNF-alpha protein levels (P<0.001) and caspase-8 activation (P<0.001), both of which were decreased (P<0.001) by treatment with MnTmPyP. Our results suggest that oxidant mediated apoptosis via the mitochondrial pathway during the early phase of ATP depletion and by activation of the receptor-mediated apoptotic pathway following longer durations of injury.
Free Radical Biology and Medicine 02/2008; 44(4):518-26. · 5.42 Impact Factor
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ABSTRACT: Oxidative stress is important in the pathogenesis of renal ischemia-reperfusion (IR) injury; however whether imbalances in reactive oxygen production and disposal account for susceptibility to injury is unclear. The purpose of this study was to compare necrosis, apoptosis, and oxidative stress in IR-resistant Brown Norway rats vs. IR-susceptible Sprague-Dawley (SD) rats in an in vivo model of renal IR injury. As superoxide (O (2) (.-) ) interacts with nitric oxide (NO) to form peroxynitrite, inducible NO synthase (iNOS) and nitrotyrosine were also examined. Renal IR was induced in SD and BN rats by bilateral clamping of renal arteries for 45 min followed by reperfusion for 24 h (SD 24 and BN 24, respectively). BN rats were resistant to renal IR injury as evidenced by lower plasma creatinine and decreased acute tubular necrosis. TUNEL staining analysis demonstrated significantly decreased apoptosis in the BN rats vs. SD rats after IR. Following IR, O (2) (.-) levels were also significantly lower in renal tissue of BN rats vs. SD rats (P < 0.05) in conjunction with a preservation of the O (2) (.-) dismutating protein, CuZn superoxide dismutase (CuZn SOD) (P < 0.05). This was accompanied by an overall decrease in 4-hydroxynonenal adducts in the BN but not SD rats after IR. BN rats also displayed lower iNOS expression (P < 0.05) resulting in lower tissue NO levels and decreased nitrotyrosine formation (P < 0.01) following IR. Collectively these results show that the resistance of the BN rat to renal IR injury is associated with a favorable balance of oxidant production vs. oxidant removal.
Molecular and Cellular Biochemistry 10/2007; 304(1-2):1-11. · 2.06 Impact Factor
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ABSTRACT: An in vivo model of intrinsic resistance to ischemia could be invaluable to define how specific pathways to injury or putative protectors from injury affect the severity of acute renal failure (ARF). The purpose of this study was to determine whether separate rat strains had differential sensitivity to renal ischemia, characterize the extent of protection, and begin to define differences in gene expression that might impact on the severity of ARF.
The sensitivity to 45 minutes of renal ischemia in Sprague-Dawley rat (SD) was compared with 2 lines of Brown-Norway rats (BN/Mcw, BN/Hsd). Constitutive and inducible stress protein expression was compared between strains.
At 24 hours' reperfusion, SD rats had higher creatinine (3.4 mg/dL), elevated Na and water excretion, and proximal tubule necrosis. Both strains of BN rats were resistant to loss of renal function (Scr = 0.9 mg/dL at 24 hours' reflow) and had preserved renal morphology. BN rats had no redistribution of Na,K-ATPase into detergent-soluble cortical extracts found early (15 minutes) after ischemia in SD rats. Hsc73 expression did not differ between strains and was not induced by ischemia. Compared with SD, induction of Hsp25 and 72 by renal ischemia was blunted in both BN strains. Constitutive Hsp25 was higher in both BN-Mcw and BN-Hsd compared with SD rat kidney. Constitutive Hsp72 was significantly higher only in BN-Mcw kidneys. Immunohistochemistry showed baseline Hsp72 and 25 expression was increased in proximal tubules of BN-Mcw versus SD.
BN rat kidney is resistant to ischemic injury and provides a new model for studying cytoprotective mechanisms. Initial study of strain-specific gene expression suggests particular stress proteins are among the potential mechanisms contributing to protection against ARF.
Kidney International 07/2004; 65(6):2201-11. · 6.61 Impact Factor
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ABSTRACT: Treatment of acute renal failure (ARF) would be enhanced by identification of factors that accelerate renal recovery from injury. Parathyroid hormone-related protein (PTHrP) and hepatocyte growth factor (HGF) have been shown to stimulate proliferation in proximal nephron-derived cells. For studying the pathophysiologic roles and therapeutic potential of these two factors in ARF, transgenic mice overexpressing PTHrP or HGF in the proximal tubule under the direction of the gamma-glutamyl transpeptidase-I promoter were developed. These mice display (1) abundant expression of the respective transgenes in the kidney; (2) similar PTH type I receptor and HGF receptor (c-met) expression levels in the proximal tubule compared with control littermates; and (3) normal renal morphology, function, and tubule cell proliferation under basal conditions. However, in contrast to control mice, when acute ischemic renal injury was induced, renal function rapidly and dramatically recovered in HGF-overexpressing mice. In addition, 48 h after ischemia, HGF-overexpressing transgenic mice displayed a fourfold increase in tubule cell proliferation and a threefold decrease in apoptotic tubule cell death compared with control mice. In contrast, PTHrP-overexpressing mice responded to either ischemic or folic acid-induced renal damage similarly to control mice. These studies demonstrate that overexpression of PTHrP in the proximal nephron of mice does not seem to provide protection against acute renal injury. In marked contrast, HGF overexpression results in dramatic protection from ischemia-induced ARF, without inducing any apparent alteration in the physiology of the kidney under normal conditions. These studies suggest that HGF, when targeted specifically to the proximal tubule, may have therapeutic potential in providing protection against ischemia-induced renal failure.
Journal of the American Society of Nephrology 02/2004; 15(1):112-25. · 9.66 Impact Factor
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ABSTRACT: The purpose of the study was to determine whether Hsp27 interacts with actin and could protect against selected manifestations of injury from energy depletion in renal epithelia. LLC-PK1 cells were stably transfected to overexpress human Hsp27 tagged with green fluorescence protein (GFP). Transfected expression of the labeled Hsp27 did not reduce endogenous Hsp25 levels in the cells compared with either nontransfected cells or cells transfected with GFP alone used as the transfectant control (G). By fluorescence energy transfer (FRET) between GFP-tagged Hsp27 and rhodamine phalloidin-decorated actin, minimal interaction was found in uninjured control cells. In ATP-depleted cells, Hsp27 was associated closely with F-actin at lateral cell boundaries and with aggregated actin within the cell body. Less Hsp27 interaction with actin was found during recovery; but when adjusted for total phalloidin fluorescence, FRET between Hsp27 and F-actin did not change between 2-h ATP depletion and 4-h recovery. Where Hsp27 association with actin persisted during recovery, it was principally with the residual aggregates of actin in the cell body. Detachment of Na,K-ATPase from the cytoskeleton at 2-h ATP depletion was significantly less in Hsp27 cells compared with transfectant control G cells but not at 4-h ATP depletion. Detachment of ezrin from the cytoskeleton during ATP depletion was nearly complete and was not prevented in the Hsp27 cells. Protection of the Hsp27 cells was not attributable to preservation of cellular ATP levels. Hsp27 appears to have specific actions in renal epithelia subjected to energy depletion, including interacting with actin to preserve architecture in specific intracellular domains.
Journal of the American Society of Nephrology 02/2003; 14(1):98-106. · 9.66 Impact Factor
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ABSTRACT: Renal ischemia is the result of a complex series of events, including decreases in oxygen supply (hypoxia) and the availability of cellular energy (ATP depletion). In this study, the functional activation of two stress-responsive transcription factors, i.e., heat shock factor-1 (HSF-1) and hypoxia-inducible factor-1 (HIF-1), in the kidney was assessed. When rats were subjected to 45 min of renal ischemia, electrophoretic mobility shift assays of kidney nuclear extracts revealed rapid activation of both HIF-1 and HSF. Western blot analyses further demonstrated that this activation resulted in increased expression of the HSF and HIF-1 target genes heat shock protein-72 and heme oxygenase-1, respectively. Whether hypoxia or ATP depletion alone could produce similar activation patterns in vitro was then investigated. Renal epithelial LLC-PK(1) cells were subjected to either ATP depletion (0.1 microM antimycin A and glucose deprivation) or hypoxia (1% O(2)). After ATP depletion, HSF was rapidly activated (within 30 min), whereas HIF-1 was unaffected. In contrast, hypoxia led to the activation of HIF-1 but not HSF. Hypoxic activation of HIF-1 was observed within 30 min and persisted for 4 h, whereas no HSF activation was detected even with prolonged periods of hypoxia. HIF-1 was transcriptionally active in LLC-PK(1) cells, as demonstrated by luciferase reporter gene assays using the vascular endothelial growth factor promoter or a synthetic promoter construct containing three hypoxia-inducible elements. Interestingly, intracellular ATP levels were not affected by hypoxia but were significantly reduced by ATP depletion. These findings suggest that HIF-1 is activated specifically by decreased O(2) concentrations and not by reduced ATP levels alone. In contrast, HSF is activated primarily by metabolic stresses associated with ATP depletion and not by isolated O(2) deprivation. In vivo, the two transcription factors are simultaneously activated during renal ischemia, which might account for observed differences between in vivo and in vitro epithelial cell injury and repair. Selective modulation of either pathway might therefore be of potential interest for modification of the response of the kidney to ischemia, as well as the processes involved in recovery from ischemia.
Journal of the American Society of Nephrology 09/2002; 13(8):2094-101. · 9.66 Impact Factor
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ABSTRACT: Recent studies have suggested that heat shock proteins (HSPs) are involved in the restoration of the cytoskeletal anchorage of Na,K-ATPase after renal ischemia. To determine their role in ischemic conditioning, we investigated whether cytoskeletal Na,K-ATPase was stabilized during repeat ischemia concurrent with 25-kD and 70-kD HSPs induction. Anesthetized rats either underwent single unilateral renal ischemia or were conditioned with bilateral renal ischemia and, after 18 h of reflow, were then subjected to repeat unilateral renal ischemia. Renal cortex was harvested, and effects of single versus repeat ischemia were compared by Triton X-100 extraction, by immunohistochemistry, and by an in vitro assay of Na,K-ATPase association with isolated cytoskeletal fractions. In contrast to single ischemia, repeat ischemia did not result in increased Triton X-100 extractability of Na,K-ATPase. Levels of 25-kD and 70-kD HSPs were significantly induced by ischemic conditioning and redistributed into the cytoskeletal fraction after single and repeat ischemia. Immunohistochemistry also showed significant disruption of Na,K-ATPase within proximal tubules only after a single episode of ischemia, whereas repeat ischemia did not alter the pattern of restored Na,K-ATPase localization in conditioned renal cortex. The preserved association of Na,K-ATPase with the cytoskeletal fraction of conditioned renal cortex was effectively abolished in vitro by addition of antibodies against 25-kD or 70-kD HSP. These results suggest that 25-kD and 70-kD HSPs induced by ischemic conditioning stabilize the cytoskeletal anchorage of Na,K-ATPase during repeat renal ischemia.
Pediatric Research 07/2002; 51(6):722-7. · 2.70 Impact Factor
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ABSTRACT: Pneumothorax is an infrequently reported complication of systemic lupus erythematosus (SLE) and carries with it a grave prognosis. We report a patient with SLE and nephritis who developed pneumothorax that responded to aggressive and prolonged therapy. Surgical management with prolonged evacuation, judicious immunosuppression, and aggressive diagnosis and treatment of infection can improve the outcome for these patients.
Pediatric Nephrology 05/2002; 17(4):261-3. · 2.52 Impact Factor
