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)

Rats were subjected to transient global ischemia (four vessel occlusion) and time-related changes in the selectively vulnerable hippocampal field CA1 were characterized. The assessment included ex vivo field responses to afferent stimulation, silver staining, calpain-induced spectrin breakdown, chromatolysis, and cell death, beginning at 6 h post-ischemia and continuing until total disintegration of the pyramidal cells occurred several days later. The earliest change observed was a modest increase in the slope and amplitude of field CA1 potentials (at 6 h). The hyperresponsiveness was most apparent at higher stimulation currents and persisted unchanged at 16 h post-ischemia. Three effects became detectable within 24 h, post-ischemia: (a) an increase in concentrations of calpain-mediated, spectrin breakdown products; (b) enhanced silver staining in the deep pyramidal neurons of the field CA1 with lesser, though still apparent, staining of stratum radiatum, and (c) a decrease in amplitude and slope of field CA1 responses to afferent stimulation. Both the concentration of spectrin breakdown products and the intensity of silver staining progressively increased to a maximum at four days post ischemia, while the amplitude and slope of the field responses dropped to a very low level between 24 and 48 h. Disturbances of Nissl staining were finally evident at 48 h, with nearly complete disappearance of staining at five days post-ischemia. This study provides the first demonstration of a close and early temporal relationship between calpain proteolysis, subcellular damage to the pyramidal cells and their loss of function following global ischemia, prior to their eventual death.
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PMID:Temporal ordering of pathogenic events following transient global ischemia. 959

A membrane cytoskeletal protein, fodrin, is a substrate for a Ca2+-dependent protease, calpain. It remains unknown whether mu-calpain or m-calpain is involved in the proteolysis of either alpha- or beta-fodrin and in what subcellular localization during ischemia and reperfusion of the brain. To address these issues, we examined the distribution of fodrin and calpain and the activities of calpain and calpastatin (endogenous calpain inhibitor) in the same subcellular fractions. Rat forebrain was subjected to ischemia by a combination of occlusion of both carotid arteries and systemic hypotension, whereas reperfusion was induced by releasing the occlusion. Immunoblotting, activity measurement, and casein zymography did not detect the presence of mu-calpain or a significant change of m-calpain level after ischemia or reperfusion. However, casein zymography revealed a unique Ca2+-dependent protease that was eluted with both 0.18 and 0.40 M NaCl from a DEAE-cellulose column. Alpha- and beta-fodrins and m-calpain were found to be rich in the synaptosomal, nuclear, and cytosolic subfractions by immunoblotting analysis. Reperfusion (60 min) following ischemia (30 min) induced selective proteolysis of alpha-fodrin, which was inhibited by a calpain inhibitor, acetylleucylleucylnorleucinal (400 microM, 1 ml, i.v.). The mu-calpain-specific fragment of beta-fodrin was not generated during ischemia-reperfusion, supporting the possibility of the involvement of m-calpain rather than mu-calpain in the alpha-fodrin proteolysis.
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PMID:Postischemic reperfusion induces alpha-fodrin proteolysis by m-calpain in the synaptosome and nucleus in rat brain. 960 18

The newly-developed calpain inhibitor, MDL 28170 penetrates the blood-brain barrier and inhibits brain cysteine protease activity after systemic administration. This experiment was initiated to determine if the calpain inhibitor, MDL 28170 could, by these actions, reduce neuronal damage in an animal model of global cerebral ischemia in the gerbil. The calpain inhibitor, MDL 28170 (50 mg/kg), was initiated at 0.5 and 3 h of recirculation following 5min of global ischemia. Animals subjected to ischemia but without treatment or with vehicle treatment served as controls. Evaluation by light microscopy was carried out on paraffin-embedded brain sections of gerbils which were sacrificed 7 days post-operatively. The results show that the calpain inhibitor, MDL 28170, protects against cortical neuronal damage even if the treatment is delayed until 3 h after reperfusion. However, the neuroprotective effect of this agent is less pronounced in the hippocampal CA1 sector. The results suggest that calpain-mediated proteolysis plays an important role in neuronal death due to ischemia. However, additional mechanisms by which an increased intracellular calcium concentration leads to neuronal death may exist.
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PMID:Postischemic treatment with calpain inhibitor MDL 28170 ameliorates brain damage in a gerbil model of global ischemia. 963 99

Calpains, Ca(2+)-dependent neutral proteinases (microM and mM Ca(2+)-sensitive), and their endogenous inhibitor calpastatin were examined in rat brain. Specific activity of m-calpain exceeded almost 10 times that of mu-calpain, and the both isoforms of calpain together with calpastatin were mainly located in the soluble fraction of homogenate. Acute postdecapitative ischemia of 15 min duration resulted in a gradual, time-dependent decrease of total mu-calpain activity (to 60% of control values) and in the moderate elevation of calpastatin activity (by 28%). The decrease of total mu-calpain activity coincided with its remarkable increase (above 300% of control values) in particulate fraction. In the case of m-calpain, the only observed effect of ischemia was its redistribution and, as a consequence, the elevation of activity in particulate fraction. The accumulation of breakdown products, resulting from calpain-catalyzed proteolysis of fodrin (as revealed by Western blotting) indicated activation of calpain under ischemia. The findings suggest that this rapid activation involves partial enzyme translocation toward membranes, and is followed (at least in acute phase) by mu-calpain downregulation and increased calpastatin activity.
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PMID:Dual response of calpain to rat brain postdecapitative ischemia. 964 72

Global brain ischemia and reperfusion result in the degradation of the eukaryotic initiation factor (eIF) 4G, which plays a critical role in the attachment of the mRNA to the ribosome. Because eIF-4G is a substrate of calpain, these studies were undertaken to examine whether calpain I activation during global brain ischemia contributes to the degradation of eIF-4G in vivo. Immunoblots with antibodies against calpain I and eIF-4G were prepared from rat brain postmitochondrial supernatant incubated at 37 degrees C with and without the addition of calcium and the calpain inhibitors calpastatin or MDL-28,170. Addition of calcium alone resulted in calpain I activation (as measured by autolysis of the 80-kDa subunit) and degradation of eIF-4G; this effect was blocked by either 1 micromol/L calpastatin or 10 micromol/L MDL-28,170. In rabbits subjected to 20 minutes of cardiac arrest, immunoblots of brain postmitochondrial supernatants showed that the percentage of autolyzed calpain I increased from 1.9% +/- 1.1% to 15.8% +/- 5.0% and that this was accompanied by a 68% loss of eIF-4G. MDL-28,170 pretreatment (30 mg/kg) decreased ischemia-induced calpain I autolysis 40% and almost completely blocked eIF-4G degradation. We conclude that calpain I degrades eIF-4G during global brain ischemia.
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PMID:Calpain mediates eukaryotic initiation factor 4G degradation during global brain ischemia. 970 48

Much attention has been paid to proteinases derived from not only neurons but also microglia in relation to neuronal death. There is accumulating evidence that intra- and extracellular proteinases in these cells are part of the basic machinery of neuronal death pathways. Some members of the ced-3/interleukin-1 beta converting enzyme (ICE) (caspase) family of cysteine proteinases have been thought to play a major role in apoptosis of not only non-neuronal cells but also neurons. Calpain has also been demonstrated to be a mediator of the neurodegenerative response. Recent studies have shown that excitotoxic and ischemic neuronal injury could be attenuated by inhibitors of caspases and calpain. Several recent studies have suggested the involvement of endosomal/lysosomal proteinases, including cathepsins B, D and E, in neuronal death induced by excitotoxins and ischemia. Furthermore, it has been reported that the extracellular tissue-type plasminogen activator/plasmin proteolytic cascade is involved in excitotoxic injury of the hippocampal neurons. In addition to such neuronal proteinases, microglial proteinases are believed to be important for the modification of neuronal functions positively or negatively. Cathepsins E and S derived from microglia have been suggested to contribute to neuronal survival through degradation and removal of beta-amyloid, damaged neurons and cellular debris. On the other hand, 6-hydroxydopamine-induced microglial cell death was inhibited by inhibitors of aspartic proteinases and caspases, suggesting the involvement of cathepsins E and D and caspases in microglial cell death. Therefore, identification of which proteinases play a causative role in neuronal death execution and clarification of the regulators and substrates for such proteinases is very important for understanding the molecular basis of the neuronal death pathways and to develop novel neuroprotective agents.
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PMID:[Involvement of proteinases produced by both neurons and microglia in neuronal lesion and death pathways]. 978 98

Excessive mu-calpain activation has been linked to several cellular pathologies including excitotoxicity and ischemia. In erythrocytes and other non-central nervous system (CNS) cells, calpain activation is thought to occur following a Ca2+-induced translocation of inactive cytosolic enzyme to membranes and subsequent autolysis. In the present report, we show that transiently exposing primary rat cortical neurons to lethal (50 microM) N-methyl-D-aspartic acid (NMDA) caused protracted calpain activation, measured as increased spectrin hydrolysis, but this was independent of translocation or autolysis of the protease. An anti-mu-calpain antibody showed that calpain was largely membrane associated in cortical neurons, and, consequently, neither translocation nor autolysis of the protease was observed following ionomycin or lethal NMDA treatment. By contrast, in rat erythrocytes, calpain was largely cytosolic and underwent rapid translocation and autolysis in response to ionomycin. Calpain-mediated spectrin hydrolysis was specifically coupled to Ca2+ entry through the NMDA receptor because nonspecific Ca2+ influx via ionomycin or KCl-mediated depolarization failed to activate the enzyme. Thus, calpain appears selectively linked to glutamate receptors in cortical neurons and regulated by mechanisms distinct from that occurring in many non-CNS cells. The data suggest that intracellular signals coupled to the NMDA receptor are responsible for activating calpain already associated with cellular membranes in cortical cells.
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PMID:Selective coupling of mu-calpain activation with the NMDA receptor is independent of translocation and autolysis in primary cortical neurons. 978 81

Excitatory amino acids may promote microtubular proteolysis observed in ischemic neuronal degeneration by calcium-mediated activation of calpain, a neutral protease. We tested this hypothesis in an animal model of focal cerebral ischemia without reperfusion. Spontaneously hypertensive rats were treated with 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)quinoxaline (NBQX), a competitive antagonist of the neuronal receptor for alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), or cis-4-[phosphono-methyl]-2-piperidine carboxylic acid (CGS 19755), a competitive antagonist of the N-methyl-d-aspartate (NMDA) receptor. After treatment, all animals were subjected to permanent occlusion of the middle cerebral artery for 6 or 24 h. Infarct volumes measured in animals pretreated with CGS 19755 after 24 h of ischemia were significantly smaller than those quantified in ischemic controls. Rats pretreated with NBQX showed partial amelioration of cytoskeletal injury with preserved immunolabeling of microtubule-associated protein 2 (MAP 2) at 6 and 24 h and reduced accumulation of calpain-cleaved spectrin byproducts only at 6 h. Prevention of cytoskeletal damage was more effective after pretreatment with CGS 19755, as shown by retention of MAP 2 immunolabeling and significant restriction of calpain activity at both 6 and 24 h. Preserved immunolabeling of tau protein was observed at 6 and 24 h only in animals pretreated with CGS 19755. Western analysis performed on ischemic cortex taken from controls or rats pretreated with either NBQX or CGS 19755 suggested that loss of tau protein immunoreactivity was caused by dephosphorylation, rather than proteolysis. These results demonstrate a crucial link between excitotoxic neurotransmission, microtubular proteolysis, and neuronal degeneration in focal cerebral ischemia.
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PMID:Glutamate receptor antagonists inhibit calpain-mediated cytoskeletal proteolysis in focal cerebral ischemia. 981 16

There has been growing evidence that the breakdown of cytoskeletal proteins is an important biochemical change leading to ischemic neuronal death. In the present study, we investigated species differences in the susceptibility of fodrin to calpain activation induced by cerebral ischemia in gerbils, rats, and mice. In vivo fodrin proteolysis and degradation of microtubule-associated protein 2 after complete ischemia occurred more rapidly in the hippocampus and cerebral cortex of the gerbil brain than in the corresponding area of the rat and mouse brain. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 injected intraperitoneally before ischemia did not diminish fodrin degradation in the gerbil hippocampus. In vivo fodrin proteolysis was inhibited at 33 degrees C and enhanced at 41 degrees C compared with proteolysis at 37 degrees C during ischemia. However, in vitro fodrin proteolysis after addition of Ca2+ into the crude membrane fraction did not show any differences among three species. Although it is highly unlikely that the difference in the sensitivity of NMDA receptor or the sensitivity of calpain activation to calcium was the crucial determinant of susceptibility of fodrin degradation in the gerbil brain, the present study clearly demonstrated that fodrin in the gerbil brain was more susceptible to calpain activation induced by ischemia than that in the rat and mouse brains. Enhanced proteolysis may be one of the reasons neurons in the gerbil brain are highly vulnerable to ischemia.
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PMID:Species differences in fodrin proteolysis in the ischemic brain. 1008 86

Transient forebrain ischemia induces activation of calpain and proteolysis of a neuronal cytoskeleton, fodrin, in gerbil hippocampus. This phenomenon precedes delayed neuronal death in hippocampal CA1 neurons. We examined effects of a calpain inhibitor on delayed neuronal death after transient forebrain ischemia. In gerbils, a selective calpain inhibitor entrapped in liposome was given transvenously and 30 min later, 5-min forebrain ischemia was produced by occlusion of both common carotid arteries. On day 7, CA1 neuronal damage was examined in the hippocampal slices stained with cresyl violet. Calpain-induced proteolysis of fodrin was also examined by immunohistochemistry and immunoblot. Additionally, to assure entrapment of the inhibitor by CA1 neurons, the inhibitor-liposome complex was labeled with FITC and given to gerbils. Fluorescence in the hippocampal slices was examined by confocal laser scanning microscope. Selective CA1 neuronal damage induced by forebrain ischemia was prevented by administration of the inhibitor in a dose-dependent manner. Calpain-induced proteolysis of fodrin was also extinguished by the calpain inhibitor in a dose-dependent manner. Bright fluorescence of the FITC-labeled inhibitor was observed in the CA1 neurons. The data show an important role of calpain in the development of the ischemic delayed neuronal death. Calpain seems to produce neuronal damage by degrading neuronal cytoskeleton. Our data also show a palliative effect of the calpain inhibitor on the neurotoxic damage, which offers a new and potent treatment of transient forebrain cerebral ischemia.
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PMID:Calpain inhibitor entrapped in liposome rescues ischemic neuronal damage. 1008 55


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