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)

In a model of cerebral hypoxia-ischemia in the immature rat, widespread brain injury is produced in the ipsilateral hemisphere, whereas the contralateral hemisphere is left undamaged. Previously, we found that calpains were equally translocated to cellular membranes (a prerequisite for protease activation) in the ipsilateral and contralateral hemispheres. However, activation, as judged by degradation of fodrin, occurred only in the ipsilateral hemisphere. In this study we demonstrate that calpastatin, the specific, endogenous inhibitor protein to calpain, is up-regulated in response to hypoxia and may be responsible for the halted calpain activation in the contralateral hemisphere. Concomitantly, extensive degradation of calpastatin occurred in the ipsilateral hemisphere, as demonstrated by the appearance of a membrane-bound 50-kDa calpastatin breakdown product. The calpastatin breakdown product accumulated in the synaptosomal fraction, displaying a peak 24 h post-insult, but was not detectable in the cytosolic fraction. The degradation of calpastatin was blocked by administration of CX295, a calpain inhibitor, indicating that calpastatin acts as a suicide substrate to calpain during hypoxia-ischemia. In summary, calpastatin was up-regulated in areas that remain undamaged and degraded in areas where excessive activation of calpains and infarction occurs.
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PMID:Calpastatin is up-regulated in response to hypoxia and is a suicide substrate to calpain after neonatal cerebral hypoxia-ischemia. 1031 18

We investigated the distribution of protein kinase C (PKC) isoforms in the subcellular fractions (P1, 1,000-g pellet; P2, 10,000-g pellet; P3, 100,000-g pellet; S, 100,000-g supernatant) of rat forebrain after ischemia or reperfusion by immunoblotting. PKC-delta and -epsilon isoforms were predominant in the P2 (synaptosome-rich) fraction, whereas PKC-alpha, -beta, -gamma, -epsilon, and -zeta isoforms were rich in the S (cytosolic) fraction. With time of ischemia (5-30 min), PKC-alpha, -beta, and -gamma translocated to the P2 and P3 fractions, whereas reperfusion for 60 min after 30 min of ischemia reduced PKC-beta activity greatly and PKC-alpha and -gamma activities to a lesser extent. There was no redistribution of PKC-delta, -epsilon, and -zeta after ischemia or reperfusion. A calpain inhibitor, acetylleucylleucylnorleucinal, inhibited the down-regulation of PKC-beta, through intravenous injection. The PKC translocation to the P2 fraction was accompanied by their dephosphorylation, transition of PKC-alpha from dimer to trimer, and the decrease in activity. These data show that PKC-alpha, -beta, and -gamma isoforms translocate chiefly to the synaptosome in ischemic brain in association with the dephosphorylation, multimeric change, and inactivation, followed by the proteolysis of PKC-beta by calpain after postischemic reperfusion.
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PMID:Translocation and down-regulation of protein kinase C-alpha, -beta, and -gamma isoforms during ischemia-reperfusion in rat brain. 1034 67

Glutamate is believed to be an excitatory amino acid neurotransmitter in the retina. Enzymes for glutamate metabolism, such as glutamate dehydrogenase, ornithine aminotransferase, glutaminase, and aspartate aminotransferase (AAT), exist mainly in the mitochondria. The abnormal increase of intracellular calcium ions in ischemic retinal cells may cause an influx of calcium ions into the mitochondria, subsequently affecting various mitochondrial enzyme activities through the activity of mitochondrial calpain. As AAT has the highest level of activity among enzymes involved in glutamate metabolism, we investigated the change of AAT activity in ischemic and hypoxic rat retinas and the protection against such activity by calpain inhibitors. We used normal RCS (rdy+/rdy+) rats. For the in vivo studies, we clamped the optic nerve of anesthetized rats to induce ischemia. In the in vitro studies, the eye cups were incubated with Locke's solution saturated with 95% N2/5% CO2. The activity of cytosolic AAT (cAAT) was about 20% of total activity, whereas mitochondrial AAT (mAAT) was about 75% in rat retina. Ninety minutes of ischemia or hypoxia caused a 20% decrease in mAAT activity, whereas cAAT activity remained unchanged. To examine the contribution of intracellular calcium ions to the degradation of mAAT, we used Ca2+-free Locke's solution containing 1 mM EGTA, ryanodine (Ca2+ channel blocker), and thapsigargin (Ca2+-ATPase inhibitor). In the present study, thapsigargin in Ca2+-free Locke's solution, but not ryanodine in this solution, was found to prevent AAT degradation. AAT degradation was also prevented by calpain inhibitors (Ca2+-dependent protease inhibitor) such as calpeptin at 1 nM, 10 nM, 0.1 microM, 1 microM and 10 microM, and by calpain inhibitor peptide, but not by other protease inhibitors (10 microM leupeptin, pepstatin, chymostatin). Additionally, we determined the subcellular localization of calpain activity and examined the change of calpain activity in ischemic rat retinas. Our results suggest that decreased activity of mAAT in ischemic and hypoxic rat retinas might be evoked by the degradation by calpain-catalyzed proteolysis in mitochondria.
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PMID:Possible mechanism for the decrease of mitochondrial aspartate aminotransferase activity in ischemic and hypoxic rat retinas. 1039 49

Striatal enriched phosphatase (STEP) is a family of protein tyrosine phosphatases enriched within the CNS. A member of this family, STEP61, is a membrane-associated protein located in postsynaptic densities of striatal neurons. In this study, we demonstrate that STEP61, is cleaved into smaller isoforms. To clarify the mechanism of cleavage, STEP61 was transiently expressed in NT2/D1 neuronal precursor cells. Exposure of transfected cells to the calcium ionophore, A23187, or to thapsigargin resulted in the rapid cleavage of STEP61. Pretreatment with the calpain inhibitor, calpeptin, or EGTA prevented proteolysis. One of the cleavage products has a relative molecular mass of 33 kDa (STEP33). A protein with the identical mobility is detected following calpain treatment of STEP61 fusion protein or postsynaptic densities purified from rat striatum. Exposure of primary neuronal cultures to glutamate also led to a significant increase in the concentration of a low molecular weight form of STEP. Taken together, these results suggest that in response to a rapid influx of calcium, STEP61, is proteolytically cleaved by calpain, leading to the release of a smaller isoform. This model may explain the rapid appearance of STEP33 in response to transient hypoxia-ischemia in the brain as cells attempt to counter the increase in tyrosine phosphorylation levels following neuronal insults.
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PMID:Calcium-dependent cleavage of striatal enriched tyrosine phosphatase (STEP). 1053 58

Acute renal failure was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow and urinary osmolality were measured to test the effectiveness of drugs. Renal function in untreated acute renal failure rats markedly decreased at 24 h after reperfusion. The administration of PSI, N-benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal, a proteasome inhibitor, at a dose of 1 mg/kg before the occlusion abolished the decreases in the renal function of acute renal failure rats. Calpeptin (1 mg/kg), a calpain inhibitor, attenuated the deterioration of renal function to the same extent as 0.1 mg/kg PSI, but no significant difference was observed between the untreated and calpeptin-treated acute renal failure groups. Histopathological examination of the kidney of untreated acute renal failure rats revealed severe lesions, such as tubular necrosis, proteinaceous casts in tubuli and medullary congestion, all of which were significantly suppressed by PSI (1 mg/kg) treatment. In contrast, calpeptin, at the same dose, was ineffective against the development of renal lesions. These results suggest that proteasome participates in the pathogenesis of ischemic acute renal failure. Thus, proteasome may be a potential target for the identification of agents that may be useful in the treatment of diseases whose etiology is dependent on ischemia/reperfusion.
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PMID:Proteasome participates in the pathogenesis of ischemic acute renal failure in rats. 1061 18

Calpains are ubiquitous Ca(2+)-activated neutral proteases that have been implicated in ischemic and traumatic CNS injury. Ischemia and trauma of central white matter are dependent on Ca2+ accumulation, and calpain overactivation likely plays a significant role in the pathogenesis. Adult rat optic nerves, representative central white matter tracts, were studied in an in vitro anoxic model. Functional recovery following 60 min of anoxia and reoxygenation was measured electrophysiologically. Calpain activation was assessed using western blots with antibodies against calpain-cleaved spectrin breakdown products. Sixty minutes of in vitro anoxia increased the amount of spectrin breakdown approximately 20-fold over control, with a further increase after reoxygenation to >70 times control, almost as much as 2 h of continuous anoxia. Blocking voltage-gated Na+ channels with tetrodotoxin or removing bath Ca2+ was highly neuroprotective electrophysiologically and resulted in a marked reduction of spectrin degradation. The membrane-permeable calpain inhibitors MDL 28,170 and calpain inhibitor-I (10-100 microM) were effective at reducing spectrin breakdown in anoxic and reoxygenated optic nerves, but no electrophysiological improvement was observed. We conclude that calpain activation is an important step in anoxic white matter injury, but inhibition of this Ca(2+)-dependent process in isolation does not improve functional outcome, probably because other deleterious Ca(2+)-activated pathways proceed unchecked.
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PMID:Calpain inhibitors confer biochemical, but not electrophysiological, protection against anoxia in rat optic nerves. 1080 Sep 55

The aim of this study was to investigate the role of secondary free radicals and calpain, a calcium-activated cysteine protease, in the development of reperfusion injury in the heart. The time course of radical generation was assessed directly by Electron Paramagnetic Resonance (EPR) and spin trapping with N-ter butyl-alpha-phenylnitrone (PBN), in isolated perfused rat heart subjected to 30 minutes of global ischemia and 30 minutes of reperfusion. The effect of leupeptin, a calpain inhibitor, was assessed on postischemic dysfunction. The antioxidant properties of leupeptin were also investigated by using allophycocyanin, a fluorescent protein sensitive to oxidative stress generated by the H2O2 + Cu++ system. Moreover, we measured the capacities of leupeptin to scavenge hydroxyl (.OH) and superoxide (O2-.) radicals using EPR technique. Our results show that myocardial reperfusion is associated with an increase of alkyl, alkoxyl free radicals release; the administration of catalase 5.10(5) UI/L significantly reduces this release, but didn't improve the postischemic contractile function of the heart. In our study leupeptin 50 microM possess, in vitro, antioxidant properties and scavenging abilities against .OH and O2-., in return leupeptin does not influence the cardiac functions during reperfusion period. In conclusion, our results confirm that myocardial reperfusion induces an important production of secondary free radicals associated with contractile dysfunction. The role of calpain in myocardial ischemia-reperfusion injury remains to be clarified 1) by assessing the activities of calpain and calpastain, its main endogenous inhibitor, during these periods, 2) by measuring the ability of leupeptin in inhibiting the calpain dependent proteolysis.
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PMID:[Demonstration of secondary free radicals and the role of calpain in functional changes associated with the myocardial ischemia-reperfusion sequence]. 1098 32

Testicular torsion requires emergent release of the twisted spermatic cord. Ischemia/reperfusion (I/R) plays an important role in its pathogenesis, and recent data suggest that germ cells undergo apoptosis during I/R. In a model of torsion/detorsion (i.e., I/R) of the rat testis, involvement of calpain and caspase in necrotic and apoptotic cell death was examined. After 1 h of ischemia followed by 0, 0.5, 1, 6, or 24 h of reperfusion, the germ cells positively stained with in situ TUNEL, and DNA fragmentation, activation of caspase-3, and proteolysis of caspase substrates increased with time of reperfusion, demonstrating apoptosis. In addition, m-calpain activation and proteolysis of alpha-fodrin were increased during reperfusion, and its activation is thought to be involved in the necrosis. A calpain inhibitor, acety-leucyl-leucyl-norleucinal, inhibited the phenomena associated with apoptosis and necrosis induced by I/R, although a caspase inhibitor, Z-Val-Ala-Asp-fluoromethlyketone, only inhibited apoptotic changes. The inhibition of calpain but not caspase ameliorated the injury after 60 days of reperfusion following 1 h of ischemia. The calpain inhibitor injected just before reperfusion effectively suppressed alpha-fodrin proteolysis, suggesting its usefulness in the treatment of testicular torsion.
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PMID:Inhibition of calpain but not caspase protects the testis against injury after experimental testicular torsion of rat. 1105 63

The objectives of this study were (1) to assess the role of a proteasome-dependent proteolytic pathway in the pathogenesis of acute renal failure (ARF) induced by ischemia-reperfusion, and (2) to determine the involvement of this proteolytic pathway in the enhanced production of renal endothelin-1 (ET-1) in this model of ARF. ARF was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow, urinary osmolality and fractional excretion of sodium were measured to test the effectiveness of drugs used. Renal function in untreated ARF rats markedly decreased at 24 h after reperfusion. In addition, a marked increase in renal ET-1 content was evident in the ARF rats, compared to the sham-operated rats. Intraperitoneal injection of a proteasome inhibitor (PSI), N-benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal, at a dose of 1 mg/kg, 1 h before the clamping, significantly attenuated the renal function impairment in the ischemic ARF rats, and the effect was accompanied by a decrease in renal ET-1 content. On the other hand, a calpain inhibitor, calpeptin, had little effect at the same dose. These results suggest that a proteasome-dependent proteolytic pathway is involved in the enhanced production of ET-1 in the kidney and the consequent renal functional damage in ischemic ARF.
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PMID:Proteasome inhibition attenuates renal endothelin-1 production and the development of ischemic acute renal failure in rats. 1107 83

The relative contributions of apoptosis and necrosis in brain injury have been a matter of much debate. Caspase-3 has been identified as a key protease in the execution of apoptosis, whereas calpains have mainly been implicated in excitotoxic neuronal injury. In a model of unilateral hypoxia-ischemia in 7-day-old rats, caspase-3-like activity increased 16-fold 24 h postinsult, coinciding with cleavage of the caspase-3 proenzyme and endogenous caspase-3 substrates. This activation was significantly decreased by pharmacological calpain inhibition, using CX295, a calpain inhibitor that did not inhibit purified caspase-3 in vitro. Activation of caspase-3 by m-calpain, but not mu-calpain, was facilitated in a dose-dependent manner in vitro by incubating cytosolic fractions, containing caspase-3 proform, with calpains. This facilitation required the presence of some active caspase-3 and could be abolished by including the specific calpain inhibitor calpastatin. This indicates that initial cleavage of caspase-3 by m-calpain, producing a 29-kDa fragment, facilitates the subsequent cleavage into active forms. This is the first report to our knowledge suggesting a direct link between the early, excitotoxic, calcium-mediated activation of calpain after cerebral hypoxia-ischemia and the subsequent activation of caspase-3, thus representing a tentative pathway of "pathological apoptosis."
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PMID:Synergistic activation of caspase-3 by m-calpain after neonatal hypoxia-ischemia: a mechanism of "pathological apoptosis"? 1112 42


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