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Query: UMLS:C0920646 (renal ischemia)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Renal levels of glutathione are markedly decreased during periods of renal ischemia due to catabolism to cysteine. We previously demonstrated that cysteine accumulates in the tissue as the thiol during ischemia, and resumption of blood flow causes a transient elevation of cysteine levels in the renal venous effluent and return of tissue cysteine levels to control values. In this study, the oxidation state of renal venous cyst(e)ine was determined. Although cysteine accumulated as the reduced thiol during ischemia, cysteine released into the renal vein upon blood reflow was found to be almost entirely in the disulfide form. To distinguish between oxidation of arterial cysteine and renal cysteine formed from ischemia-induced reduced glutathione (GSH) catabolism, a labeling procedure was developed to label kidney GSH with 35S without significant labeling of arterial plasma cyst(e)ine. With this procedure, the source of oxidized cysteine that appeared in the renal venous plasma after ischemia was identified as resulting from renal GSH catabolism. The data indicate that a rapid oxidative process occurs during the initial period of blood reflow to the postischemic kidney. After 35 min of ischemia, 3 mumol cysteine/g dry wt were released from the kidney and oxidized. Cysteine oxidation is also expected to generate oxygen-centered free radicals. Pretreatment of animals with deferoxamine, a iron chelator, was without effect on the relative amount of venous cysteine in the oxidized form, arguing against a role for free iron in this oxidative process.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cysteine oxidation by the postischemic rat kidney. 159 Apr 23

To determine whether iron participates in free radical-mediated postischemic renal injury and lipid peroxidation, we examined the effects of removal of endogenous iron or provision of exogenous iron following renal ischemia, as well as the effects of renal ischemia and reperfusion on renal venous and urinary "free" iron. Rats underwent 60 minutes of renal ischemia and were studied after either 24 hours (inulin clearance) or 15 minutes (renal malondialdehyde content) of reperfusion. Infusion of the iron chelator deferoxamine (200 mg/kg/hr) during the first 60 minutes of reperfusion resulted in a marked improvement in renal function (inulin clearance: 879 +/- 154 vs. 314 +/- 74 microliter/min; P less than 0.025) and a reduction in lipid peroxidation (renal malondialdehyde: 0.449 +/- 0.06 vs. 0.698 +/- 0.08 mmol/mg prot; P less than 0.05) compared to control animals. Infusion of 50 mg/kg/hr deferoxamine also protected renal function after ischemia (inulin clearance: 624 +/- 116 vs. 285 +/- 90 microliter/min; P less than 0.05) and resulted in less histologic injury. Iron-saturated deferoxamine had no protective effect. Conversely, infusion of the iron complex EDTA-FeCl3 during reperfusion exacerbated postischemic renal dysfunction and lipid peroxidation. Following renal ischemia there was no detectable increase in "free" iron in arterial or renal venous plasma. However, urinary "free" iron increased 10- to 20-fold following reperfusion. Iron chelators which underwent filtration and gained access to this free iron in the urine (free deferoxamine or inulin-conjugated deferoxamine) provided protection, whereas a chelator confined to the vascular space (dextran-conjugated deferoxamine) did not.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of iron in postischemic renal injury in the rat. 314 49

In ischemic acute renal failure oxygen free radicals may mediate injury. In addition, iron appears to play a critical role in hydroxyl radical formation and lipid peroxidation during reperfusion of ischemic kidneys. To determine whether iron may play a similar role in pigment (heme protein)-induced acute renal failure, we studied the effects of the iron chelator deferoxamine in two experimental models of pigment-induced acute renal failure, intramuscular glycerol injection and intravenous hemoglobin infusion without and with concurrent ischemia in the rat. Intramuscular injection of 50% glycerol (5 ml/kg) caused inulin clearance to fall to 0.13 +/- 0.03 (SE) ml/min (normal value, 1.0-1.2 ml/min). Continuous infusion of deferoxamine beginning at the time of glycerol injection significantly attenuated this renal dysfunction. Deferoxamine-treated animals had an inulin clearance of 0.37 +/- 0.06 ml/min (P less than 0.01). Glycerol injection was also associated with significant lipid peroxidation, measured as renal malondialdehyde content. Deferoxamine-treated glycerol-injected rats had renal malondialdehyde content not significantly different from control animals. In another model of heme pigment-induced renal injury, hemoglobin was infused to produce hemoglobinuria. Inulin clearance 1 h after hemoglobin infusion was significantly reduced to 0.84 +/- 0.5 ml/min (P less than 0.025). Infusion of deferoxamine after hemoglobin prevented the hemoglobin-induced decrease in inulin clearance. Thirty minutes of renal ischemia followed by infusion of hemoglobin resulted in more severe renal dysfunction with inulin clearance of 0.54 +/- 0.08 ml/min. Deferoxamine infused at the time of reperfusion attenuated the fall in glomerular filtration rate after ischemia and hemoglobin infusion:inulin clearance 1.04 +/- 0.07 (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hemoglobin- and myoglobin-induced acute renal failure in rats: role of iron in nephrotoxicity. 341 10

Xanthine oxidase (XO) activity and hydroxyl radical (.OH) formation are widely proposed mediators of renal reperfusion injury, potentially altering the severity of, and recovery from, postischemic acute renal failure. The goal of this study was to ascertain whether combination XO inhibitor (oxypurinol) and .OH scavenger (Na benzoate) therapy, given at the time of renal ischemia, alters the extent of: (1) tubular necrosis and filtration failure; (2) DNA fragmentation/apoptosis (assessed in situ by terminal deoxynucleotidyl transferase reactivity); (3) early tubular regenerative responses (proliferating cell nuclear antigen expression; (3H)thymidine incorporation); and (4) the rate and/or degree of functional and morphologic repair. The effects of XO inhibition, .OH scavengers, and "catalytic" iron (FeSO4) on human proximal tubular cell proliferation in vitro were also assessed with a newly established cell line (HK-2). Male Sprague-Dawley rats were subjected to 35 min of bilateral renal arterial occlusion with or without oxypurinol/benzoate therapy. These agents did not alter the extent of tubular necrosis or filtration failure, proliferating cell nuclear antigen expression or thymidine incorporation, or the rate/extent of renal functional/morphologic repair. DNA fragmentation did not precede tubular necrosis, and it was unaffected by antioxidant therapy. By 5 days postischemia, both treatment groups demonstrated regenerating epithelial fronds that protruded into the lumina. These structures contained terminal deoxynucleotidyl transferase-reactive, but morphologically intact, cells, suggesting the presence of apoptosis. Oxypurinol and .OH scavengers (benzoate; dimethylthiourea) suppressed in vitro tubular cell proliferation; conversely, catalytic Fe had a growth-stimulatory effect. These results suggest that: (1) XO inhibition/.OH scavenger therapy has no discernible net effect on postischemic acute renal failure; (2) DNA fragmentation does not precede tubular necrosis, suggesting that it is not a primary mediator of ischemic cell death; and (3) antioxidants can be antiproliferative for human tubular cells, possibly mitigating their potential beneficial effects.
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PMID:An evaluation of antioxidant effects on recovery from postischemic acute renal failure. 791 60

Because chronic iron overload can cause organ injury in hemochromatosis and because iron participates in injury during renal ischemia-reperfusion, the effect of mild subacute renal iron loading on the susceptibility to ischemic acute renal failure was evaluated. Male Sprague-Dawley rats were injected with iron nitrilotriacetate (1 mg iron/kg BW i.p. daily) for 5 days. Controls were instead injected with nitrilotriacetate. Seventy-two hours later animals were subjected to 40-min renal artery ischemia. Iron loading produced a 28% increase in kidney iron content without any change in baseline renal function (plasma creatinine) or histology. Ischemic renal injury was far more severe in iron-loaded animals. Plasma creatinine 24 and 48 h after ischemia was significantly higher in iron-loaded rats (3.3 and 3.4 vs. 2.2 and 0.8 mg/dL) and GFR was significantly lower in iron-loaded rats (0.30 vs. 0.78 mL/min). In addition, iron-loaded rats showed a dramatically greater extent of damage by histologic evaluation using a semiquantitative scoring method. Therefore, a small increase in renal iron content greatly increased renal injury after an ischemic insult. These findings may be relevant to human renal disease because there is accumulating evidence of renal iron accumulation in a variety of proteinuric and chronic renal diseases.
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PMID:Iron loading enhances susceptibility to renal ischemia in rats. 793 55

Iron-dependent free radical reactions and renal ischemia are believed to be critical mediators of myohemoglobinuric acute renal failure. Thus, this study assessed whether catalytic iron exacerbates O2 deprivation-induced proximal tubular injury, thereby providing an insight into this form of renal failure. Isolated rat proximal tubular segments (PTS) were subjected to either hypoxia/reoxygenation (H/R: 27:15 min), "chemical anoxia" (antimycin A; 7.5 microM x 45 min), or continuous oxygenated incubation +/- ferrous (Fe2+) or ferric (Fe3+) iron addition. Cell injury (% lactic dehydrogenase [LDH] release), lipid peroxidation (malondialdehyde, [MDA]), and ATP depletion were assessed. Under oxygenated conditions, Fe2+ and Fe3+ each raised MDA (approximately 7-10x) and decreased ATP (approximately 25%). Fe2+, but not Fe3+, caused LDH release (31 +/- 2%). During hypoxia, Fe2+ and Fe3+ worsened ATP depletion; however, each decreased LDH release (approximately 31 to approximately 22%; P < 0.01). Fe(2+)-mediated protection was negated during reoxygenation because Fe2+ exerted its intrinsic cytotoxic effect (LDH release: Fe2+ alone, 31 +/- 2%; H/R 36 +/- 2%; H/R + Fe2+, 41 +/- 2%). However, Fe(3+)-mediated protection persisted throughout reoxygenation because it induced no direct cytotoxicity (H/R, 39 +/- 2%; H/R + Fe3+, 25 +/- 2%; P < 0.002). Fe3+ also decreased antimycin toxicity (41 +/- 4 vs. 25 +/- 3%; P < 0.001) despite inducing marked lipid peroxidation and without affecting ATP. These results indicate that catalytic iron can mitigate, rather than exacerbate, O2 deprivation/reoxygenation PTS injury.
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PMID:Inorganic iron effects on in vitro hypoxic proximal renal tubular cell injury. 843 70

Reactive oxygen species (ROS) have been implicated in the pathophysiology of renal ischemia/reperfusion injury. Endothelin-1 (ET-1) is generated in abundance in renal ischemia/reperfusion with resultant decreases in renal blood flow and glomerular filtration rate. To determine if ROS regulate ET-1 production, the effect of ROS donors or scavengers on ET-1 protein and mRNA levels in cultured human mesangial cells was examined. Incubation with xanthine/xanthine oxidase, glucose oxidase, or H2O2 caused a dose-dependent rise in ET-1 release. Similarly, xanthine/xanthine oxidase or H2O2 augmented ET-1 mRNA levels. In contrast, the ROS scavengers dimethylthiourea (DMTU), dimethylpyrroline N-oxide, or pyrrolidine dithiocarbamate reduced basal ET-1 release, while DMTU lowered ET-1 mRNA levels. Deferoxamine, an iron chelator, also decreased basal ET-1 release. Superoxide dismutase potentiated the ET-1 stimulatory effect of xanthine/xanthine oxidase, while catalase abrogated the effect of xanthine/xanthine oxidase and H2O2. The effects of ROS were unrelated to changes in nitric oxide production or cytotoxicity. These data indicate that exogenously or endogenously-derived ROS can increase ET-1 production by human mesangial cells. While superoxide anion reduces ET-1 levels, H2O2 leads to enhanced production of the peptide. ROS stimulation of mesangial cell ET-1 production may contribute to impaired glomerular hemodynamics in the setting of renal ischemia/reperfusion injury.
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PMID:Effect of reactive oxygen species on endothelin-1 production by human mesangial cells. 877 Sep 66

In mammals the rate-limiting step in heme catabolism is the heme oxygenase (HO) system. Two isozymes, HO-1 and HO-2, oxidatively cleave the substrate to form biliverdin, and the potential cellular messenger, CO; the chelated iron is released as the result of the tetrapyrrole ring opening. Biliverdin is subsequently reduced to bilirubin, an antioxidant, by biliverdin reductase. The aim of the present study was to investigate the involvement of HO-1, a heat shock/stress protein, in protection offered by the spin trap agent, N-tert-butyl-alpha-phenyl-nitrone (PBN), against kidney ischemia/reperfusion injury. For this, HO-1 expression and assessment of the parameters associated with tissue-oxidative injury were compared in the presence or absence of PBN pretreatment of rats (100 mg/kg i.p., 30 min) before the onset of 30-min ischemia. Twenty-four hours after reperfusion, Northern blot analysis showed an unprecedented approximately 37-fold increase in 1.8-kb HO-1 mRNA in PBN pretreated rat kidney; HO-2 mRNA levels did not increase. At 48 h, the levels of HO-1 mRNA remained nearly 14-fold higher than the control value. In the absence of PBN, the levels measured approximately 5- and 2-fold higher than control values at the 24- and 48-h intervals, respectively. PBN pretreatment also resulted in a most impressive increase in the levels of HO-1 protein as judged by Western blot analysis and measurement of enzyme activity at the 24-h time point. As detected by immunohistochemical analysis, PBN pretreatment caused an increase in HO-1 and biliverdin reductase-immunoreactive proteins in the cortex and in the outer stripe of the outer medulla. In the absence of PBN pretreatment, there was an intense immunostaining for HO-1 in the medullary rays, which corresponded with iron and lipid peroxidation staining of the region; these observations were not made with PBN-pretreated kidneys. Collectively, the findings are consistent with the likelihood that suprainduction of HO-1 gene expression protects the kidney from free radical-mediated injury by increasing the capacity to produce the potent cellular antioxidant bilirubin. We also suggest spin trap-mediated protection against ischemia/reperfusion injury is likely due to a sustained elevation of HO-1 gene expression by formation of stable radicals.
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PMID:Spin trap (N-t-butyl-alpha-phenylnitrone)-mediated suprainduction of heme oxygenase-1 in kidney ischemia/reperfusion model: role of the oxygenase in protection against oxidative injury. 1052 16

Earlier in vitro studies demonstrated the remarkable potency of the lazaroid compounds to prevent oxidant-induced early cell injury. However, the ability of lazaroid compounds to limit oxidative injury in vivo(including renal ischemia-reperfusion) has been less certain, and the early clinical trials using lazaroids to limit CNS injury or organ injury in the setting of transplantation have not been promising. Lazaroid compounds are potent inhibitors of lipid peroxidation, and their inability to influence other key injury processes, particularly during the late stages of cell injury, might partly explain the limited clinical efficacy. To test this, renal tubular (LLC-PK1) cells were incubated with 250 micromH(2)O(2)for 135 min, in the presence or absence of 2-methyl aminochroman (2-MAC, U-83836E), a lazaroid with potent ability to inhibit lipid peroxidation, or desferrioxamine, (DFO) an iron chelator with broader antioxidant efficacy. Cell injury, lipid peroxidation, DNA damage and ATP depletion were measured in the early (immediately after H(2)O(2)incubation) and late (24 h after H(2)O(2)incubation) stages of cell injury. In the early stage, 2-MAC suppressed H(2)O(2)-induced lipid peroxidation and LDH release, but not the DNA damage, ATP depletion or loss of cell replication. In contrast, DFO suppressed all of the measurements. In the late stages, despite continued suppression of lipid peroxidation, only DFO maintained significant cytoprotection against H(2)O(2), and this was accompanied by reduced DNA damage, higher ATP levels and preservation of cell proliferation. Thus, the inability of the lazaroid compound 2-MAC to sustain cytoprotection in the later stages of cell injury might provide at least a partial explanation for the inefficiency of lazaroids to limit tissue injury in clinical and certain in vivo settings.
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PMID:Lazaroid compounds prevent early but not late stages of oxidant-induced cell injury: potential explanation for the lack of efficacy of lazaroids in clinical trials. 1120 66

Anemia is found in about one-third of all cases of congestive heart failure (CHF). The most likely common cause is chronic kidney insufficiency (CKI), which is present in about half of all CHF cases. The CKI is likely to be due to the renal vasoconstriction that often accompanies CHF and can cause long-standing renal ischemia. This reduces the amount of erythropoietin (EPO) produced in the kidney and leads to anemia. However, anemia can occur in CHF without CKI and is likely to be due to excessive cytokine production (for example, tumor necrosis factor-alfa (TNF-alfa) and interleukin-6 (IL-6)), which is common in CHF and can cause reduced EPO secretion, interference with EPO activity in the bone marrow and reduced iron supply to the bone marrow. The anemia itself can worsen cardiac function, both because it causes cardiac stress through tachycardia and increased stroke volume, and because it can cause a reduced renal blood flow and fluid retention, adding further stress to the heart. Long-standing anemia of any cause can cause left ventricular hypertrophy (LVH), which can lead to cardiac cell death through apoptosis and worsen the CHF. Therefore, a vicious circle is set up wherein CHF causes anemia, and the anemia causes more CHF and both damage the kidneys worsening the anemia and the CHF further. We have termed this vicious circle the cardio renal anemia (CRA) syndrome. Patients with CHF who are anemic are often resistant to all CHF medications resulting in being hospitalized repeatedly. Many studies also demonstrate that these patients die more rapidly than their non-anemic counterparts do. In addition, they have a more rapid deterioration in their renal function and can end up on dialysis. There is now evidence from both uncontrolled and controlled studies that early correction of the CHF anemia with subcutaneous EPO and intravenous (i.v.) iron improves shortness of breath and fatigue, cardiac function, renal function and exercise capability, dramatically reducing the need for hospitalization. For these reasons, it is not surprising that quality of life has also been shown to improve. As both CHF and end-stage renal disease (ESRD) are rapidly increasing, the possibility that these twin conditions can be improved by the adequate treatment of anemia offers new hope for slowing the progression of both conditions.
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PMID:The role of anemia in the progression of congestive heart failure. Is there a place for erythropoietin and intravenous iron? 1559 47


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