Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the impact of perfusate buffer composition on the relative degree of protection afforded by Na+/H+ exchanger (NHE) inhibition during ischemia as opposed to during reperfusion. Isolated rat hearts were perfused with bicarbonate- or HEPES-buffered medium. There was infusion of HOE 694 immediately before ischemia, during initial reperfusion, or during both of these periods. With bicarbonate-buffered medium, HOE 694 improved the post-ischemic recovery of left ventricular developed pressure (LVDP) when given before ischemia and before ischemia plus during reperfusion. In the presence of HEPES-buffered medium, however, HOE 694 significantly improved recovery of LVDP in all protocols. HOE 694 also provided an almost complete recovery of LVDP (88 +/- 9% vs 30 +/- 7% in controls) when given before ischemia plus during reperfusion. In conclusion, our results suggest that the influence of NHE activity during reperfusion on the extent of functional recovery is modulated significantly by perfusate buffer composition.
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PMID:[Effects of Na(+)-HCO3- symport on ischemia/reperfusion injury; Na+/H+ exchanger inhibitor and buffer composition]. 1467 18

We investigated the effects of nitric oxide (NO) on hepatocellular killing after simulated ischemia/reperfusion and characterized signaling factors triggering cytoprotection by NO. Cultured rat hepatocytes were incubated in anoxic Krebs-Ringer-HEPES buffer at pH 6.2 for 4 hours and reoxygenated at pH 7.4 for 2 hours. During reoxygenation, some hepatocytes were exposed to combinations of NO donors (S-nitroso-N-acetylpenicillamine [SNAP] and others), a cGMP analogue (8-bromoguanosine-3,5-cGMP [8-Br-cGMP]), and a cGMP-dependent protein kinase inhibitor (KT5823). Cell viability was determined by way of propidium iodide fluorometry. Inner membrane permeabilization and mitochondrial depolarization were monitored by confocal microscopy. SNAP, but not oxidized SNAP, increased cGMP during reperfusion and decreased cell killing. Other NO donors and 8-Br-cGMP also prevented cell killing. Both guanylyl cyclase and cGMP-dependent kinase inhibition blocked the cytoprotection of NO. However, 5-hydroxydecanoate and diazoxide- mitochondrial K(ATP) channel modulators-did not affect NO-dependent cytoprotection or reperfusion injury. During reoxygenation, confocal microscopy showed mitochondrial repolarization, followed by depolarization, inner membrane permeabilization, and cell death. In the presence of either SNAP or 8-Br-cGMP, mitochondrial repolarization was sustained after reperfusion preventing inner membrane permeabilization and cell death. In isolated rat liver mitochondria, a cGMP analogue in the presence of a cytosolic extract and adenosine triphosphate blocked the Ca(2+)-induced mitochondrial permeability transition (MPT), an effect that was reversed by KT5823. In conclusion, NO prevents MPT-dependent necrotic killing of ischemic hepatocytes after reperfusion through a guanylyl cyclase and cGMP-dependent kinase signaling pathway, events that may represent the target of NO cytoprotection in preconditioning.
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PMID:Nitric oxide protects rat hepatocytes against reperfusion injury mediated by the mitochondrial permeability transition. 1518 94

The Na(+)/H(+) exchanger (NHE) and/or the Na(+)/HCO(3)(-) cotransporter (NBC) were blocked during ischemia in isolated rat hearts. Intracellular Na(+) concentration ([Na(+)](i)), intracellular pH (pH(i)), and energy-related phosphates were measured by using simultaneous (23)Na and (31)P NMR spectroscopy. Hearts were subjected to 30 min of global ischemia and 30 min of reperfusion. Cariporide (3 microM) or HCO(3)(-)-free HEPES buffer was used, respectively, to block NHE, NBC, or both. End-ischemic [Na(+)](i) was 320 +/- 18% of baseline in HCO(3)(-)-perfused, untreated hearts, 184 +/- 6% of baseline when NHE was blocked, 253 +/- 19% of baseline when NBC was blocked, and 154 +/- 6% of baseline when both NHE and NBC were blocked. End-ischemic pH(i) was 6.09 +/- 0.06 in HCO(3)(-)-perfused, untreated hearts, 5.85 +/- 0.02 when NHE was blocked, 5.81 +/- 0.05 when NBC was blocked, and 5.70 +/- 0.01 when both NHE and NBC were blocked. NHE blockade was cardioprotective, but NBC blockade and combined blockade were not, the latter likely due to a reduction in coronary flow, because omission of HCO(3)(-) under conditions of NHE blockade severely impaired coronary flow. Combined blockade of NHE and NBC conserved intracellular H(+) load during reperfusion and led to massive Na(+) influx when blockades were lifted. Without blockade, both NHE and NBC mediate acid-equivalent efflux in exchange for Na(+) influx during ischemia, NHE much more than NBC. Blockade of either one does not affect the other.
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PMID:Relative contributions of Na+/H+ exchange and Na+/HCO3- cotransport to ischemic Nai+ overload in isolated rat hearts. 1531 98

We evaluated the effects of nutrient enriched medium and hemoglobin based oxygen carrier (HBOC) upon myocardial functional recovery after 15 minutes of warm ischemia in an isovolumic Langendorff rat heart model. Hearts (n = 8/group) were perfused at constant pressure (90 mm Hg) with Krebs-Henseleit buffer or HEPES modified cell culture medium (M199) in the absence and presence of HBOC. Hearts received 15 minutes of normothermic no flow ischemia followed by 60 minutes reperfusion. Hemodynamics, coronary flow, and tissue water content were measured, and microscopic evidence of injury including TUNEL assay was assessed. Preischemic left ventricular performance (left ventricular developed pressure and maximum rate of positive and negative change in systolic pressure) and coronary flow were similar among groups. At 60 minutes of reperfusion, M199 alone provided more stable and complete left ventricular systolic and diastolic functional recovery than any other perfusate. Coronary flow rates reflected left ventricular function observed under each perfusate condition. TUNEL assay showed arterial endothelial cell death in some hearts perfused with HBOC. Tissue water content did not reflect functional recovery. The combination of M199 and HBOC was associated with poor recovery and elevated perfusate methemoglobin. In this system, postischemic dysfunction is prevented by components in M199. Added HBOC does not improve functional recovery and negates the salutary effects of M199, possibly by augmenting methemoglobin formation.
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PMID:Effects of nutrient and hemoglobin enriched cell free perfusates upon ex vivo isolated rat heart preparation. 1596 61

Chloride (Cl-) efflux induces depolarization and contraction of vascular smooth muscle cells. In the basilar arteries from the New Zealand white rabbits, the role of Cl- flux in serotonin-induced contraction was demonstrated by (i) inhibition of Na+-K+-2Cl- co-transporter (NKCC1) to decreased Cl- influx with bumetanide; (ii) a disabled Cl-/HCO3- exchanger with bicarbonate free HEPES solution; (iii) blockade of Cl- channels using 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and indanyloxyacetic acid 94, R-(+)-methylindazone (R-(+)-IAA-94); and (iv) substitution of extracellular Cl- with methanesulfonate acid (113 mmol/L; Cl-, 10 mmol/L). In addition, the expression of NKCC1 in brain tissues after neonatal hypoxia-ischemia was examined at mRNA and protein levels using RT-PCR and Western blotting techniques. NKCC1 mRNA and protein expressions were increased at 24 and 48 h and returned to normal levels at 72 h after hypoxia insult when compared with the control littermates. In conclusion, Cl- efflux regulates cerebral circulation and the up-regulation of NKCC1 after neonatal hypoxia-ischemia may contribute to brain injury.
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PMID:Role of Cl- in cerebral vascular tone and expression of Na+-K+-2Cl- co-transporter after neonatal hypoxia-ischemia. 1633 78

We investigated the role of pH, reactive oxygen species (ROS), Ca2+, and the mitochondrial permeability transition (MPT) in pH-dependent ischemia-reperfusion injury to adult rat myocytes. Myocytes were incubated in anoxic Krebs-Ringer-HEPES buffer at pH 6.2 for 3 h to simulate ischemia. To simulate reperfusion, myocytes were reoxygenated at pH 6.2 or 7.4 for 2 h. Some myocytes were treated with MPT blockers (cyclosporin A and N-methyl-4-isoleucine cyclosporin) and antioxidants (desferal, diphenylphenylene diamine, and 2-mercaptopropionyl glycine). Mitochondrial membrane potential, inner membrane permeabilization, and ROS formation were imaged with tetramethylrhodamine methyl ester, calcein, and chloromethyldichlorofluorescein diacetate, respectively. For Ca2+ imaging, myocytes were coloaded with rhod-2 and fluo-4 to evaluate mitochondrial and cytosolic Ca2+, respectively. After 10 min of reperfusion at pH 7.4, calcein redistributed across the mitochondrial inner membrane, an event preceded by mitochondrial ROS formation and accompanied by hypercontracture, mitochondrial depolarization, and then cell death. Acidotic reperfusion, antioxidants, and MPT blockers each prevented the MPT, depolarization, hypercontraction, and cell killing. Antioxidants, but neither MPT blockers nor acidotic reperfusion, inhibited ROS formation after reperfusion. Furthermore, anoxic reperfusion at pH 7.4 prevented cell death. Both mitochondrial and cytosolic Ca2+ increased during ischemia but recovered in the first minutes of reperfusion. Mitochondrial and cytosolic Ca2+ overloading again occurred late after reperfusion. This late Ca2+ overloading was blocked by MPT inhibition. Intramitochondrial Ca2+ chelation by cold loading/warm incubation of BAPTA did not prevent cell death after reperfusion. In conclusion, mitochondrial ROS, together with normalization of pH, promote MPT onset and subsequent myocyte death after reperfusion. In contrast, Ca2+ overloading appears to be the consequence of bioenergetic failure after the MPT and is not a factor promoting MPT onset.
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PMID:Reactive oxygen species, but not Ca2+ overloading, trigger pH- and mitochondrial permeability transition-dependent death of adult rat myocytes after ischemia-reperfusion. 1639 72

Acid-sensing ion channels (ASICs), activated by lowering extracellular pH (pH(o)), play an important role in normal synaptic transmission in brain and in the pathology of brain ischemia. Like pH(o), intracellular pH (pH(i)) changes dramatically in both physiological and pathological conditions. Although it is known that a drop in pH(o) activates the ASICs, it is not clear whether alterations of pH(i) have an effect on these channels. Here we demonstrate that the overall activities of ASICs, including channel activation, inactivation, and recovery from desensitization, are tightly regulated by pH(i). In cultured mouse cortical neurons, bath perfusion of the intracellular alkalizing agent quinine increased the amplitude of the ASIC current by approximately 50%. In contrast, intracellular acidification by withdrawal of NH(4)Cl or perfusion of propionate inhibited the current. Increasing pH buffering capacity in the pipette solution with 40 mm HEPES attenuated the effects of quinine and NH(4)Cl. The effects of intracellular alkalizing/acidifying agents were mimicked by using intracellular solutions with pH directly buffered at high/low values. Increasing pH(i) induced a shift in H(+) dose-response curve toward less acidic pH but a shift in the steady state inactivation curve toward more acidic pH. In addition, alkalizing pH(i) induced an increase in the recovery rate of ASICs from desensitization. Consistent with its effect on the ASIC current, changing pH(i) has a significant influence on the acid-induced increase of intracellular Ca(2+), membrane depolarization, and acidosis-mediated neuronal injury. Our findings suggest that changes in pH(i) may play an important role in determining the overall function of ASICs in both physiological and pathological conditions.
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PMID:Modulation of acid-sensing ion channel currents, acid-induced increase of intracellular Ca2+, and acidosis-mediated neuronal injury by intracellular pH. 1688 60

Ischemia-reperfusion (I/R) injury causes skeletal muscle infarction and ischemic preconditioning (IPC) augments ischemic tolerance in animal models. To date, this has not been demonstrated in human skeletal muscle. This study aimed to develop an in vitro model to investigate the efficacy of simulated IPC in human skeletal muscle. Human skeletal muscle strips were equilibrated in oxygenated Krebs-Henseleit-HEPES buffer (37 degrees C). Aerobic and reperfusion phases were simulated by normoxic incubation and reoxygenation, respectively. Ischemia was simulated by hypoxic incubation. Energy store, cell viability, and cellular injury were assessed using ATP, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT), and lactate dehydrogenase (LDH) assays, respectively. Morphological integrity was assessed using electron microscopy. Studies were designed to test stability of the preparation (n = 5-11) under normoxic incubation over 24 h; the effect of 1, 2, 3, 4, or 6 h hypoxia followed by 2 h of reoxygenation; and the protective effect of hypoxic preconditioning (HPC; 5 min of hypoxia/5 min of reoxygenation) before 3 h of hypoxia/2 h of reoxygenation. Over 24 h of normoxic incubation, muscle strips remained physiologically intact as assessed by MTT, ATP, and LDH assays. After 3 h of hypoxia/2 h of reoxygenation, MTT reduction levels declined to 50.1 +/- 5.5% (P < 0.05). MTT reduction levels in HPC (82.3 +/- 10.8%) and normoxic control (81.3 +/- 10.2%) groups were similar and higher (P < 0.05) than the 3 h of hypoxia/2 h of reoxygenation group (45.2 +/- 5.8%). Ultrastructural morphology was preserved in normoxic and HPC groups but not in the hypoxia/reoxygenation group. This is the first study to characterize a stable in vitro model of human skeletal muscle and to demonstrate a protective effect of HPC in human skeletal muscle against hypoxia/reoxygenation-induced injury.
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PMID:Development of an in vitro model for study of the efficacy of ischemic preconditioning in human skeletal muscle against ischemia-reperfusion injury. 1704 28

In the myocardium, the Na(+)/H(+) exchanger isoform-1 (NHE1) activity is detrimental during ischemia-reperfusion (I/R) injury, causing increased intracellular Na(+) (Na(i)(+)) accumulation that results in subsequent Ca(2+) overload. We tested the hypothesis that increased expression of NHE1 would accentuate myocardial I/R injury. Transgenic mice were created that increased the Na(+)/H(+) exchanger activity specifically in the myocardium. Intact hearts from transgenic mice at 10-15 wk of age showed no change in heart performance, resting intracellular pH (pH(i)) or phosphocreatine/ATP levels. Transgenic and wild-type (WT) hearts were subjected to 20 min of ischemia followed by 40 min of reperfusion. Surprisingly, the percent recovery of rate-pressure product (%RPP) after I/R improved in NHE1-overexpressing hearts (64 +/- 5% vs. 41 +/- 5% in WT; P < 0.05). In addition, NMR spectroscopy revealed that NHE1 overexpressor hearts contained higher ATP during early reperfusion (levels P < 0.05), and there was no difference in Na(+) accumulation during I/R between transgenic and WT hearts. HOE642 (cariporide), an NHE1 inhibitor, equivalently protected both WT and NHE1-overexpressing hearts. When hearts were perfused with bicarbonate-free HEPES buffer to eliminate the contribution of HCO(3)(-) transporters to pH(i) regulation, there was no difference in contractile recovery after reperfusion between controls and transgenics, but NHE1-overexpressing hearts showed a greater decrease in ATP during ischemia. These results indicate that the basal activity of NHE1 is not rate limiting in causing damage during I/R, therefore, increasing the level of NHE1 does not enhance injury and can have some small protective effects.
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PMID:Overexpression of the Na+/H+ exchanger and ischemia-reperfusion injury in the myocardium. 1720 1

The Na(+)/H(+) exchanger (NHE-1) plays a key role in pH(i) recovery from acidosis and is regulated by pH(i) and the ERK1/2-dependent phosphorylation pathway. Since acidosis increases the activity of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in cardiac muscle, we examined whether CaMKII activates the exchanger by using pharmacological tools and highly specific genetic approaches. Adult rat cardiomyocytes, loaded with the pH(i) indicator SNARF-1/AM were subjected to different protocols of intracellular acidosis. The rate of pH(i) recovery from the acid load (dpH(i)/dt)-an index of NHE-1 activity in HEPES buffer or in NaHCO(3) buffer in the presence of inhibition of anion transporters-was significantly decreased by the CaMKII inhibitors KN-93 or AIP. pH(i) recovery from acidosis was faster in CaMKII-overexpressing myocytes than in overexpressing beta-galactosidase myocytes (dpH(i)/dt: 0.195+/-0.04 vs. 0.045+/-0.010 min(-)(1), respectively, n=8) and slower in myocytes from transgenic mice with chronic cardiac CaMKII inhibition (AC3-I) than in controls (AC3-C). Inhibition of CaMKII and/or ERK1/2 indicated that stimulation of NHE-1 by CaMKII was independent of and additive to the ERK1/2 cascade. In vitro studies with fusion proteins containing wild-type or mutated (Ser/Ala) versions of the C-terminal domain of NHE-1 indicate that CaMKII phosphorylates NHE-1 at residues other than the canonical phosphorylation sites for the kinase (Ser648, Ser703, and Ser796). These results provide new mechanistic insights and unequivocally demonstrate a role of the already multifunctional CaMKII on the regulation of the NHE-1 activity. They also prove clinically important in multiple disorders which, like ischemia/reperfusion injury or hypertrophy, are associated with increased NHE-1 and CaMKII.
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PMID:Ca(2+)/calmodulin-dependent protein kinase II contributes to intracellular pH recovery from acidosis via Na(+)/H(+) exchanger activation. 2002 27


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