Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0917798 (cerebral ischemia)
 17,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the CNS, where Ca(2+) overload has been established as a mechanism contributing to neuronal damage associated with excitotoxicity, stroke and ischemia, there is interest in understanding the role of calpain inhibition in rescuing neurons from death. In these settings, the activation of large stores of latent calpain may rapidly lead to the demise of the neuron within hours. The activity of calpain is strictly regulated by calcium concentrations and interactions with calpastatin (endogenous calpain inhibitor). The interaction between calpains and calpastatin is calcium dependent, and little is known about the regulation of the neuronal calpain-calpastatin system in vivo. It has been postulated that calpastatin can be modulated by nerve growth factors (NGFs). We have demonstrated in vitro as well as in vivo a neuroprotective effect of the beta(2)-adrenoceptor agonist clenbuterol (CLN) mediated through an increased NGF expression. In this study we attempt to find out whether CLN is capable (1) of modulating proteolysis regulated by the calpain-calpastatin system and (2) of attenuating DNA-fragmentation induced by cerebral ischemia. Rats received CLN daily for 1 week, were then subjected to ischemia and finally perfused at different times post-ischemia. The proteolytic activity of calpain was measured by the immunolocalisation of calpastatin and spectrin-breakdown products (SBP). The time course of apoptosis was assessed by terminal dUTP nick end-labeling (TUNEL)-staining. CLN reduced CA1-hippocampal cell damage by 23%, attenuated DNA-laddering and decreased proteolysis of spectrin by enhancing calpastatin activity. These results provide evidence that CLN is a potent neuroprotective substance, which through the enhancement of calpastatin synthesis attenuates the apoptotic machinery and modulates proteolysis.
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PMID:beta2-Adrenergic receptor responsiveness of the calpain-calpastatin system and attenuation of neuronal death in rat hippocampus after transient global ischemia. 1463 Mar 41

Microsphere embolism (ME)-induced cerebral ischemia can elicit various pathological events leading to neuronal death. Western blotting and immunohistochemical studies revealed that expression of calpastatin, an endogenous calpain inhibitor, decreased after ME induction. Calpain activation after ME was apparently due to, in part, a decrease in calpastatin in a late phase of neuronal injury. The time course of that decrease also paralleled caspase-3 activation. In vitro studies demonstrated that calpastatin was degraded by caspase-3 in a Ca(2+)/calmodulin (CaM)-dependent manner. Because CaM binds directly to calpastatin, we asked whether a novel CaM antagonist, 3-[2-[4-(3-chloro-2-methylphenylmethyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydro-chloride 3.5 hydrate (DY-9760e), inhibits caspase-3-induced calpastatin degradation during ME-induced neuronal damage. We also tested the effect of DY-9760e on degradation of fodrin, a calpain substrate. Consistent with our hypothesis, DY-9760e (25 or 50 mg/kg i.p.) treatment inhibited degradation of calpastatin and fodrin in a dose-dependent manner. Because DY-9760e showed powerful neuroprotective activity with concomitant inhibition of calpastatin degradation, cross-talk between calpain and caspase-3 through calpastatin possibly accounts for ME-induced neuronal injury. Taken together, both inhibition of caspase-3-induced calpastatin degradation and calpain-induced fodrin breakdown by DY-9760e in part mediate its neuroprotective action.
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PMID:3-[2-[4-(3-Chloro-2-methylphenylmethyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydro-chloride 3.5 hydrate (DY-9760e) is neuroprotective in rat microsphere embolism: role of the cross-talk between calpain and caspase-3 through calpastatin. 1646 55

Calpains represent a superfamily of Ca2+-activated cysteine-proteases, which are important mediators of apoptosis and necrosis. In the brain, m-calpain and micro-calpain, the two ubiquitous calpain-isoforms, are strongly activated in neurones after an excitotoxic Ca2+ influx occurring, for example, during cerebral ischemia. Because oestrogen and its receptors (ERalpha/ERbeta) can exert neuroprotective activity, we investigated their influence on expression of calpains and their endogenous inhibitor, calpastatin. We found that ectopic expression of ERalpha in human neuroblastoma SK-N-MC cells led to a ligand-independent constitutive down-regulation of m-calpain accompanied by an up-regulation of micro-calpain expression. Up-regulation of micro-calpain was reversed in the presence of oestrogen, which, in turn, could be blocked by co-treatment with the oestrogen-receptor antagonist ICI 182,780. Expression of calpastatin was not altered, either in the absence or in the presence of oestrogen. Additional studies revealed that ERalpha-expressing cells exhibited decreased calpain enzymatic activity and increased survival when cells were exposed to the Ca2+ ionophore, ionomycin. Since all investigated effects could be observed exclusively in the presence of ERalpha, but not ERbeta, and since the effects are reduced when ERalpha and ERbeta are co-expressed, our data suggest a novel ER subtype-specific neuroprotective action by repressing calpain expression and calpain activity under conditions of a massive Ca2+ influx.
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PMID:Oestrogen receptor subtype-specific repression of calpain expression and calpain enzymatic activity in neuronal cells--implications for neuroprotection against Ca-mediated excitotoxicity. 1652 85

The activation of the [Ca(2+)]-dependent cysteine protease calpain plays an important role in ischemic injury. Here, the levels of two calpain-specific substrates, p35 protein and eukaryotic initiation factor 4G (eIF4G), as well as its physiological regulator calpastatin, were investigated in a rat model of transient global cerebral ischemia with or without ischemic tolerance (IT). Extracts of the cerebral cortex, whole hippocampus and hippocampal subregions after 30 min of ischemia and different reperfusion times (30 min and 4 h) were used. In rats without IT, the p35 levels slightly decreased after ischemia or reperfusion, whereas the levels of p25 (the truncated form of p35) were much higher than those in sham control rats after ischemia and remained elevated during reperfusion. The eIF4G levels deeply diminished after reperfusion and the decrease was significantly greater in CA1 and the rest of the hippocampus than in the cortex. By contrast, the calpastatin levels did not significantly decrease during ischemia or early reperfusion, but were upregulated after 4 h of reperfusion in the cortex. Although IT did not promote significant changes in p35 and p25 levels, it induced a slight increase in calpastatin and eIF4G levels in the hippocampal subregions after 4 h of reperfusion.
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PMID:Calpain-induced proteolysis after transient global cerebral ischemia and ischemic tolerance in a rat model. 1708 94

Loss of mitochondrial membrane integrity and release of apoptogenic factors are a key step in the signaling cascade leading to neuronal cell death in various neurological disorders, including ischemic injury. Emerging evidence has suggested that the intramitochondrial protein apoptosis-inducing factor (AIF) translocates to the nucleus and promotes caspase-independent cell death induced by glutamate toxicity, oxidative stress, hypoxia, or ischemia. However, the mechanism by which AIF is released from mitochondria after neuronal injury is not fully understood. In this study, we identified calpain I as a direct activator of AIF release in neuronal cultures challenged with oxygen-glucose deprivation and in the rat model of transient global ischemia. Normally residing in both neuronal cytosol and mitochondrial intermembrane space, calpain I was found to be activated in neurons after ischemia and to cleave intramitochondrial AIF near its N terminus. The truncation of AIF by calpain activity appeared to be essential for its translocation from mitochondria to the nucleus, because neuronal transfection of the mutant AIF resistant to calpain cleavage was not released after oxygen-glucose deprivation. Adeno-associated virus-mediated overexpression of calpastatin, a specific calpain-inhibitory protein, or small interfering RNA-mediated knockdown of calpain I expression in neurons prevented ischemia-induced AIF translocation. Moreover, overexpression of calpastatin or knockdown of AIF expression conferred neuroprotection against cell death in neuronal cultures and in hippocampal CA1 neurons after transient global ischemia. Together, these results define calpain I-dependent AIF release as a novel signaling pathway that mediates neuronal cell death after cerebral ischemia.
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PMID:Critical role of calpain I in mitochondrial release of apoptosis-inducing factor in ischemic neuronal injury. 1772 42

GABA is the major inhibitory neurotransmitter in the CNS and changes in GABAergic neurotransmission affect the overall activity of neuronal networks. The uptake of GABA into synaptic vesicles is mediated by the vesicular GABA transporter (VGAT), and changes in the expression of the transporter directly regulate neurotransmitter release. In this work we investigated the changes in VGAT protein levels during ischemia and in excitotoxic conditions, which may affect the demise process. We found that VGAT is cleaved by calpains following excitotoxic stimulation of hippocampal neurons with glutamate, giving rise to a stable truncated cleavage product (tVGAT). VGAT cleavage was also observed after transient middle cerebral artery occlusion in mice, a cerebral ischemia model, and following intrahippocampal injection of kainate, but no effect was observed in transgenic mice overexpressing calpastatin, a calpain inhibitor. Incubation of isolated cerebrocortical synaptic vesicles with recombinant calpain also induced the cleavage of VGAT and formation of stable tVGAT. Immunoblot experiments using antibodies targeting different regions of VGAT and N-terminal sequencing analysis showed that calpain cleaves the transporter in the N-terminal region, at amino acids 52 and 60. Immunocytochemistry of GABAergic striatal neurons expressing GFP fusion proteins with the full-length VGAT or tVGAT showed that cleavage of the transporter induces a loss of synaptic delivery, leading to a homogeneous distribution of the protein along neurites. Our results show that excitotoxicity downregulates full-length VGAT, with a concomitant generation of tVGAT, which is likely to affect GABAergic neurotransmission and may influence cell death during ischemia.
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PMID:Cleavage of the vesicular GABA transporter under excitotoxic conditions is followed by accumulation of the truncated transporter in nonsynaptic sites. 2143 Jan 62

Persistent protein synthesis inhibition (PSI) is a robust predictor of eventual neuronal death following cerebral ischemia. We thus tested the hypothesis that persistent PSI inhibition and neuronal death are causally linked. Neuronal viability strongly correlated with both protein synthesis and levels of eukaryotic (translation) initiation factor 4G1 (eIF4G1). We determined that in vitro ischemia activated calpain, which degraded eIF4G1. Overexpression of the calpain inhibitor calpastatin or eIF4G1 resulted in increased protein synthesis and increased neuronal viability compared with controls. The neuroprotective effect of eIF4G1 overexpression was due to restoration of cap-dependent protein synthesis, as well as protein synthesis-independent mechanisms, as inhibition of protein synthesis with cycloheximide did not completely prevent the protective effect of eIF4G1 overexpression. In contrast, shRNA-mediated silencing of eIF4G1 exacerbated ischemia-induced neuronal injury, suggesting eIF4G1 is necessary for maintenance of neuronal viability. Finally, calpain inhibition following global ischemia in vivo blocked decreases in eIF4G1, facilitated protein synthesis, and increased neuronal viability in ischemia-vulnerable hippocampal CA1 neurons. Collectively, these data demonstrate that calpain-mediated degradation of a translation initiation factor, eIF4G1, is a cause of both persistent PSI and neuronal death.
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PMID:Ischemia-induced calpain activation causes eukaryotic (translation) initiation factor 4G1 (eIF4GI) degradation, protein synthesis inhibition, and neuronal death. 2200 12