Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0920646 (renal ischemia)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal ischemia results in both a profound fall in cellular ATP and a rapid induction of the 70 kD heat-shock protein family, HSP-70. The present studies examined the relationship between cellular ATP and induction of the stress response in renal cortex. Cellular ATP, continuously monitored by in vivo 31P-NMR spectroscopy, was reduced and maintained at specific, stable levels in renal cortex by partial aortic occlusion for 45 min. Activation of heat-shock transcription factor (HSF) was detected by gel retardation assay and transcription was confirmed by Northern analysis. Activation of HSF was not present, and HSP-70 mRNA induction did not occur when ATP levels were maintained above 60% preocclusion (control) levels. Reduction in cortical ATP levels to 35-50% preocclusion values resulted in HSF activation and low-level expression of inducible HSP-70 mRNA. Cellular ATP of 20-25% control values resulted in a greater level of HSF activation and subsequent HSP-70 mRNA elaboration. HSF was activated at the end of 15 min of total occlusion. The studies indicate that a 50% reduction in cellular ATP in the renal cortex must occur before the stress response is detectable, that reduction of ATP below 25% control levels produces a more vigorous response, and that reperfusion is not required for initiation of a heat-shock response in the kidney. Cellular ATP, or the metabolic consequences associated with ATP depletion, may be a threshold factor for initiation of a stress response in the kidney.
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PMID:Activation of heat-shock transcription factor by graded reductions in renal ATP, in vivo, in the rat. 792 28

Rats within the early maintenance phase of post-ischemic acute renal failure (ARF) can resist additional ischemic insults. This study assessed whether this protection exists directly at the tubular cell level, and if so, whether it is a consequence of prior cell injury (for example, due to heat-shock protein synthesis; HSP), or if it arises in response to reductions in functional renal mass and/or the uremic environment. Rats were subjected to either 15 or 35 minutes of unilateral or bilateral renal ischemia, and after 15 minutes to 24 hours of reflow, proximal tubular segments (PTS) were isolated for study. Their viability following oxygenation and hypoxic/reoxygenation injury (H/R) was tested (LDH release). The influence of uremia/reduced renal mass was determined by studying PTS extracted 24 hours after 1 1/2 nephrectomy, and by determining whether PTS exposure to a "uremic milieu" (urine addition) blocks H/R damage. HSP effects were gauged by correlating renal cortical HSP-70 expression with degrees of in vitro protection, and by ascertaining whether in vivo hyperthermia (42 degrees C; 15 min) mitigates subsequent PTS H/R damage. Results were compared with those obtained from normal PTS. The in vivo experimental protocols did not substantially alter PTS isolation or their viability during oxygenation. Fifteen minutes of ischemia induced neither azotemia nor PTS cytoprotection. In contrast, 35 minutes of ischemia conferred marked protection against subsequent H/R, but only when azotemia was permitted to develop (protection seen after 24 hr, but not at 4 hr of reflow; protection abrogated by retention of 1 normal kidney). Renal failure in the absence of tubular necrosis (1 1/2 uninephrectomy) protected PTS from H/R damage.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Post-ischemic acute renal failure protects proximal tubules from O2 deprivation injury, possibly by inducing uremia. 793 24

Stressful stimuli such as heat, oxidative stress, heavy metals, and tissue trauma induce the expression of a family of proteins commonly referred to as stress proteins or heat shock proteins. The functions of these proteins are varied but include glycolysis, antioxidant defense, and several postulated "chaperone" functions involving the folding, unfolding, and translocation of other proteins. Heme oxygenase, the enzyme that catalyzes the degradation of heme to biliverdin, is also heat inducible and is, therefore, a heat shock protein. In the kidney, ischemia has been observed by several investigators to induce expression of the more commonly studied heat shock proteins HSP 70 and HSP 72. In addition, exposure of the kidney to myoglobin after glycerol injection induced heme oxygenase. The purpose of this study was to determine whether heme oxygenase is expressed as a stress protein after renal ischemia. Renal ischemia was induced in rats after right nephrectomy by clamping the renal artery for 40 minutes. Gene expression was evaluated after 60 minutes to 96 hours of postischemic reperfusion. There was essentially no expression of heme oxygenase at any of the time points evaluated. The absence of heme oxygenase expression was in striking contrast to the prompt and dramatic expression of HSP 70. This finding is consistent with the concept that all "stress proteins" are not equivalent and that, although there is considerable overlap between heat-sensitive gene promoters and oxidant stress-sensitive gene promoters, there is specificity for the type of stimulus that is able to activate any given stress protein gene.
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PMID:Heme oxygenase is not expressed as a stress protein after renal ischemia. 840 10

The 72-kDa heat stress protein (HSP-72) is an inducible cytoprotectant protein. Although transient renal ischemia in vivo induces HSP-72, it is not known whether prior heat stress protects renal epithelial cells from injury mediated by ATP depletion. To evaluate this hypothesis, opossum kidney (OK) cells were exposed to sodium cyanide and 2-deoxy-D-glucose in the absence of medium glucose, a maneuver that reduced cell ATP content to < 10% of the control value within 10 min and decreased cell survival. One day after 2 h of ATP depletion, OK cells previously exposed to heat stress (to induce accumulation of HSP-72) exhibited marked improvement in survival (a > 4-fold increase in total DNA), less uptake of vital dye, and less release of lactate dehydrogenase (LDH) than cells subjected to ATP depletion alone (23.0 +/- 1.6 vs. 34.1 +/- 1.2% of total LDH, respectively). Enhanced clonogenicity post-heat stress was completely prevented by cycloheximide and positively correlated with the steady-state content of HSP-72. In the recovery period after ATP depletion, cell ATP content, maximum mitochondrial ATP production rate, and total LDH activity were all significantly higher in cells with abundant HSP-72. Although the protective effects associated with heat stress are likely to be multifactoral, preserved cell metabolism and higher ATP content could enhance cellular repair processes after ATP depletion.
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PMID:Prior heat stress enhances survival of renal epithelial cells after ATP depletion. 876 25

The small heat-shock proteins appear to have a regulatory role in actin dynamics. Since cytoskeletal disruption is integral to ischemic renal injury, we evaluated expression and intracellular distribution of heat-shock protein 25 (HSP-25) in rat renal cortex after 45 min of renal ischemia. HSP-25 was constitutively expressed and induced by ischemia with peak levels reached by 6 h reflow. Ischemia caused a shift of HSP-25 from the detergent-soluble into the insoluble cytoskeletal fraction. By 2 h reflow, the majority of HSP-25 had redistributed into the soluble fraction. HSP-25 was predominantly localized in a subapical distribution in control proximal tubules, a pattern intermediate between deoxyribonuclease (DNase)-reactive and filamentous actin. After ischemia, HSP-25 dispersed through the cytoplasm with small punctate accumulations similar to DNase-reactive actin. During later reflow, all three proteins were found in coarse intracytoplasmic accumulations; however, HSP-25 and DNase-reactive actin were in separate accumulations. HSP-25 and microfilamentous actin staining returned to the subapical domain. Thus the temporal and spatial patterns of HSP-25 induction and distribution suggest specific interactions between HSP-25 and actin during the early postischemic reorganization of the cytoskeleton. HSP-25 may have additional roles distinct from actin dynamics later in the course of postischemic recovery.
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PMID:Heat-shock protein 25 induction and redistribution during actin reorganization after renal ischemia. 945 42

The pattern of 72-kDa heat-shock protein (HSP-72) induction after renal ischemia suggests a role in restoring cell structure. HSP-72 activity in the repair and release from denatured and aggregated proteins requires ATP. Protein aggregates were purified from normal and ischemic rat renal cortex. The addition of ATP to cortical homogenates reduced HSP-72, Na(+)-K(+)-ATPase, and actin in aggregates subsequently isolated, suggesting that their interaction is ATP dependent. Altering ATP hydrolysis in the purified aggregates, however, had different effects. ATP released HSP-72 during reflow and preserved Na(+)-K(+)-ATPase association with aggregates at 2 h but had no effect in controls or at 6 h reflow and caused no change in actin. These results indicate that HSP-72 complexes with aggregated cellular proteins in an ATP-dependent manner and suggests that enhancing HSP-72 function after ischemic renal injury assists refolding and stabilization of Na(+)-K(+)-ATPase or aggregated elements of the cytoskeleton, allowing reassembly into a more organized state.
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PMID:ATP releases HSP-72 from protein aggregates after renal ischemia. 948 21

Because of the continuing shortage of donor organs, 'marginal kidneys' are increasingly being used. The purpose of our experiments was to characterize the extent of lipid peroxidation after ischemia-reperfusion (IR) injury in rat kidney, to analyze the expressional regulation of the heat-shock response and now to discuss the clinical application of these results. After ischemia, xanthine oxidase (XO) is thought to be the main oxygen radical-generating system and malondialdehyde (MDA) is considered to be a marker of LPO. In young rats (10 weeks) a unilateral warm ischemia of 40 and 60 min duration with subsequent reperfusion up to 1 h was conducted. Beside the 'footprints' of oxidative stress, the cytosolic antioxidative capacity, expressed as superoxide anion (SOA) scavenging capacity, was investigated. There was only a moderate and transient increase of renal MDA 5 and 10 min after the onset of reoxygenation (133.57/70.67 and 97.84/91.57 vs. 49.47 nmol/g wet weight (ww) in preischemic controls). ATP breakdown (to 83/65 from 2,947 nmol/g ww) with consecutive accumulation of hypoxanthine (up to 1,105 nmol/g ww) at the end of the ischemic period and the subsequent rapid decline of hypoxanthine by XO during reperfusion were used for an assessment of the SOA-generating capacity of these kidneys. Only 1/25-1/50 of the kidney cytosol was able to scavenge the whole amount of SOA generated by the total XO activity of rat kidney. Thus, it could be analytically and stoichiometrically shown that after IR there is only a moderate oxidative stress in kidneys of young rats; this is due to their high SOA-scavenging capacity compared to their SOA-generating ability. We investigated the time course of HSP70-1 and -2 mRNA expression and its relation to cellular ATP levels in renal cortex after different periods of unilateral warm renal ischemia (10-60 min) and reperfusion (up to 60 min) in 10-week-old male Wistar rats, since IR is known to cause induction of both genes. Immediately after ischemia there was a significant induction of both HSP70i genes. While HSP70-1 expression constantly increased (up to 4-fold) during reperfusion, even to a higher extent with prolongation of ischemia, HSP70-2 mRNA - generally being expressed on a far lower level than HSP70-1 mRNA - was strongly induced (3-fold) during reperfusion only after brief periods (10 min) of ischemia. Cellular ATP levels rapidly dropped down to 5% with ischemia and the pattern of recovery during reperfusion significantly depended on the duration of the ischemic period thus showing a good relation to the heat-shock (protein) gene expression. We conclude that the HSP70-2 is the more sensitive gene with a lower threshold activation by mild injury, while the HSP70-1 gene mediates the big response of HSP induction after severe injury. Thus, the measurement of the cytosolic antioxidative capacity and the differential expression of HSP70-1 and -2 mRNA could be promising clinical tools to assess the donor viability.
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PMID:Lipid peroxidation and the expressional regulation of the heat-shock response during ischemia-reperfusion of rat kidney. 1096 99

Renal ischemia not only causes injury but also induces repair mechanisms, such as the cellular induction of the 72-kilodalton heat shock protein HSP-72. The aim of this study was to determine whether HSP-72 is excreted in urine after ischemic renal injury. The first urine of six pediatric allograft recipients was examined for proteinuria and urinary HSP-72 excretion. Sprague-Dawley rats were treated with renal ischemia or hyperthermia and renal cortex and urinary HSP-72 levels were determined. HSP-72 was excreted in the first urine of renal allografts. In rats, renal HSP-72 was induced both by renal ischemia or hyperthermia. However, only renal ischemia resulted in urinary excretion of HSP-72. Urinary excretion of HSP-72 indicates an increased renal stress response and loss of tubular cell integrity after clinical and experimental renal ischemia.
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PMID:Urinary heat shock protein-72 excretion in clinical and experimental renal ischemia. 1257 95

Renal ischemia-reperfusion (IR) injury is a major clinical problem without effective therapy. We recently reported that volatile anesthetics protect against renal IR injury, in part, via their anti-inflammatory properties. In this study, we demonstrate the anti-inflammatory and antinecrotic effects of sevoflurane in cultured kidney proximal tubule cells and probed the mechanisms of sevoflurane-induced renal cellular protection. To mimic inflammation, human kidney proximal tubule (HK-2) cells were treated with tumor necrosis factor-alpha (TNF-alpha; 25 ng/ml) in the presence or absence of sevoflurane. In addition, we studied the effects of sevoflurane pretreatment on hydrogen peroxide (H2O2)-induced necrotic cell death in HK-2 or porcine proximal tubule (LLC-PK1) cells. We demonstrate that sevoflurane suppressed proinflammatory effects of TNF-alpha evidenced by attenuated upregulation of proinflammatory cytokine mRNA (TNF-alpha, MCP-1) and ICAM-1 protein and reduced nuclear translocation of the proinflammatory transcription factors NF-kappaB and AP-1. Sevoflurane reduced necrotic cell death induced with H2O2 in HK-2 cells as well as in LLC-PK1 cells. Sevoflurane treatment resulted in phosphorylation of prosurvival kinases, ERK and Akt, and increased de novo HSP-70 protein synthesis without affecting the synthesis of HSP-27 or HSP-32. We conclude that sevoflurane has direct anti-inflammatory and antinecrotic effects in vitro in a renal cell type particularly sensitive to injury following IR injury. These mechanisms may, in part, account for volatile anesthetics' protective effects against renal IR injury.
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PMID:Anti-inflammatory and antinecrotic effects of the volatile anesthetic sevoflurane in kidney proximal tubule cells. 1647 75

Acute kidney injury evokes renal tubular cholesterol synthesis. However, the factors during acute kidney injury that regulate HMG CoA reductase (HMGCR) activity, the rate-limiting step in cholesterol synthesis, have not been defined. To investigate these factors, mice were subjected to 30 minutes of either unilateral renal ischemia or sham surgery. After 3 days, bilateral nephrectomy was performed and cortical tissue extracts were prepared. The recruitment of RNA polymerase II (Pol II), transcription factors (SREBP-1, SREBP-2, NF-kappaB, c-Fos, and c-Jun), and heat shock proteins (HSP-70 and heme oxygenase-1) to the HMGCR promoter and transcription region (start/end exons) were assessed by Matrix ChIP assay. HMGCR mRNA, protein, and cholesterol levels were determined. Finally, histone modifications at HMGCR were assessed. Ischemia/reperfusion (I/R) induced marked cholesterol loading, which corresponded with elevated Pol II recruitment to HMGCR and increased expression levels of both HMGCR protein and mRNA. I/R also induced the binding of multiple transcription factors (SREBP-1, SREBP-2, c-Fos, c-Jun, NF-kappaB) and heat shock proteins to the HMGCR promoter and transcription regions. Significant histone modifications (increased H3K4m3, H3K19Ac, and H2A.Z variant) at these loci were also observed but were not identified at either the 5' and 3' HMGCR flanking regions (+/-5000 bps) or at negative control genes (beta-actin and beta-globin). In conclusion, I/R activates the HMGCR gene via multiple stress-activated transcriptional and epigenetic pathways, contributing to renal cholesterol loading.
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PMID:Renal ischemia-induced cholesterol loading: transcription factor recruitment and chromatin remodeling along the HMG CoA reductase gene. 1909 62


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