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)

Mature mouse oligodendrocytes (OLs) are susceptible to death in demyelinating diseases such as multiple sclerosis and in brain injury following neurotrauma, ischemia, or stroke. To understand mechanisms leading to death of mature OLs and develop strategies for protection, we utilized cultures of mature mouse OLs to investigate the role of caspases and calpains in OL cell death mediated by different mechanisms. The agents used were (i) staurosporine, which induces apoptotic death via inhibition of protein kinases; (ii) kainate, which activates non-NMDA glutamate receptors; (iii) thapsigargin, which releases intracellular calcium stores; and (iv) SNAP, which releases active NO species and causes necrotic cell death. Inhibitors blocking primary effector caspases (including caspase 3), the FAS (death receptor)-mediated initiator caspases (including caspase 8), and stress-induced caspases (including caspase 9), were tested for their protective effects. Inhibition of caspases 3, 8, and 9 each robustly protected OLs following insult with staurosporine, thapsigargin, or kainate when added at optimal times. The time of addition of the inhibitors for maximal protection varied with the agent, from 1 h of preincubation before addition of staurosporine to 6 h after addition of kainate. Much less protection was seen for the NO generator SNAP under any condition. The role of calcium in OL death in each model was investigated by chelating extracellular Ca++ with EGTA, and by inhibiting the Ca++-activated calpain proteases. Calcium chelation did not protect against staurosporine, but decreased OL death initiated by kainate, thapsigargin, or NO. The calpain inhibitors PD150606 and calpain inhibitor I protected from cell death initiated by staurosporine, kainate, and thapsigargin, but not from cell death initiated by the NO donor SNAP.
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PMID:Protection of mature oligodendrocytes by inhibitors of caspases and calpains. 1258 72

The physiological role of the uracil nucleotide-preferring P2Y(6) and P2Y(4) receptors is still unclear, although they are widely distributed in various tissues. In an effort to identify their biological functions, we found that activation by UDP of the rat P2Y(6) receptor expressed in 1321N1 human astrocytes significantly reduced cell death induced by tumor necrosis factor alpha (TNF alpha). This effect of UDP was not observed in non-transfected 1321N1 cells. Activation of the human P2Y(4) receptor expressed in 1321N1 cells by UTP did not elicit this protective effect, although both receptors were coupled to phospholipase C. The activation of P2Y(6) receptors prevented the activation of both caspase-3 and caspase-8 resulting from TNF alpha exposure. Even a brief (10-min) incubation with UDP protected the cells against TNF alpha-induced apoptosis. Interestingly, UDP did not protect the P2Y(6)-1321N1 cells from death induced by other methods, i.e. oxidative stress induced by hydrogen peroxide and chemical ischemia. Therefore, it is suggested that P2Y(6) receptors interact rapidly with the TNF alpha-related intracellular signals to prevent apoptotic cell death. This is the first study to describe the cellular protective role of P2Y(6) nucleotide receptor activation.
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PMID:Tumor necrosis factor alpha-induced apoptosis in astrocytes is prevented by the activation of P2Y6, but not P2Y4 nucleotide receptors. 1262 23

Focal ischemia by middle cerebral artery occlusion (MCAO) results in necrosis at the infarct core and activation of complex signal pathways for cell death and cell survival in the penumbra. Recent studies have shown activation of the extrinsic and intrinsic pathways of caspase-mediated cell death, as well as activation of the caspase-independent signaling pathway of apoptosis in several paradigms of focal cerebral ischemia by transient MCAO to adult rats and mice. The extrinsic pathway (cell-death receptor pathway) is initiated by activation of the Fas receptor after binding to the Fas ligand (Fas-L); increased Fas and Fas-L expression has been shown following focal ischemia. Moreover, focal ischemia is greatly reduced in mice expressing mutated (nonfunctional) Fas. Increased expression of caspase-1, -3, -8, and -9, and of cleaved caspase-8, has been observed in the penumbra. Activation of the intrinsic (mitochondrial) pathway following focal ischemia is triggered by Bax translocation to and competition with Bcl-2 and other members of the Bcl-2 family in the mitochondria membrane that is followed by cytochrome c release to the cytosol. Bcl-2 over-expression reduces infarct size. Cytochrome c binds to Apaf-1 and dATP and recruits and cleaves pro-caspase-9 in the apoptosome. Both caspase-8 and caspase-9 activate caspase-3, among other caspases, which in turn cleave several crucial substrates, including the DNA-repairing enzyme poly(ADP-ribose) polymerase (PARP), into fragments of 89 and 28 kDa. Inhibition of caspase-3 reduces the infarct size, further supporting caspase-3 activation following transient MCAO. In addition, caspase-8 cleaves Bid, the truncated form of which has the capacity to translocate to the mitochondria and induce cytochrome c release. The volume of brain infarct is greatly reduced in Bid-deficient mice, thus indicating activation of the mitochondrial pathway by cell-death receptors following focal ischemia. Recent studies have shown the mitochondrial release of other factors; Smac/DIABLO (Smac: second mitochondrial activator of caspases: DIABLO: direct IAP binding protein with low pI) binds to and neutralizes the effects of the X-linked inhibitor of apoptosis (XIAP). Finally, apoptosis-inducing factor (AIF) translocates to the mitochondria and the nucleus following focal ischemia and produces peripheral chromatin condensation and large-scale DNA strands, thus leading to the caspase-independent cell death pathway of apoptosis. Delineation of the pro-apoptotic and pro-survival signals in the penumbra may not only increase understanding of the process but also help to rationalize strategies geared to reducing brain damage targeted at the periphery of the infarct core.
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PMID:Signaling of cell death and cell survival following focal cerebral ischemia: life and death struggle in the penumbra. 1272 25

Cardiomyocytes are post-mitotic, long-lived cells until disruptions to pro-survival factors occur after myocardial ischemia. To gain an understanding of the factors involved with ischemic injury, we examined expression changes in pro-survival and opposing pro-apoptotic signals at early and chronic periods of ischemia using an in vivo murine model. Alterations of pro-survival proteins such as the inhibitor of apoptosis protein on chromosome X (xIAP) and the apoptotic repressor protein (ARC) have not been evaluated in a murine model of cardiac ischemia. Early ischemia (1 day) resulted in a 50% reduction in ARC protein levels relative to sham-operated left ventricles, without significant changes in the expression of xIAP or other pro-survival factors. In contrast, a deficiency of xIAP expression was found in cardiac infarcts starting after 1 week, concomitant with significant evidence of apoptotic cell death and an up-regulation of pro-apoptotic signals including Bax, tumor necrosis factor-a, and caspase-8 activation. Chronic ischemia (after 2 weeks) was associated with elevated levels of other pro-survival factors such as Bcl-xL and the phosphorylated form of Akt, as part of the adaptive remodeling of the myocardium. Altogether, these findings suggest that strategies to increase IAP expression may promote myocyte survival after chronic ischemia.
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PMID:Ischemia elicits a coordinated expression of pro-survival proteins in mouse myocardium. 1280 54

Cardiomyocyte apoptosis by Fas ligand (FasL)/Fas signaling is associated with various pathophysiological conditions, such as ischemia/reperfusion injury and congestive heart failure. In this study, we tested the hypothesis that shedding of membrane FasL is a mechanism for downregulating FasL/Fas signaling and both membrane and soluble FasL are involved in cardiomyocyte hypoxia/reoxygenation (H/R) injury. We also examined the relative importance of mitochondrial damage and direct cleavage of the executioner caspases by activated initiator caspase 8 in the propagation of FasL/Fas signaling activated by either recombinant membrane FasL or H/R. We demonstrated that in neonatal rat cardiomyocytes maintained under normal culture conditions, recombinant human soluble FasL increased caspase 3 activation by twofold but did not reduce cell viability. In contrast, infection with a recombinant adenoviral vector expressing the non-cleavable human FasL (Ad2/nchFasL) resulted in cardiomyocyte death that was attenuated by soluble FasL. H/R increased the mRNA levels of both FasL and Fas and activated caspases 8, 9 and 3, indicating the activation of FasL/Fas signaling. Z-IETD.fmk and Z-LEHD.fmk, selective inhibitors for caspases 8 and 9, respectively, abolished caspase 3 activation induced by Ad2/nchFasL or H/R. Z-IETD.fmk also significantly reduced Ad2/nchFasL- or H/R-induced cardiomyocyte death. H/R potentiated membrane FasL-induced cell death. These results suggest that shedding of membrane FasL downregulates FasL/Fas signaling in cardiomyocytes and both membrane and soluble FasL contribute to H/R injury. Activation of FasL/Fas signaling by either recombinant membrane FasL under normal culture conditions or H/R causes cardiomyocyte death mainly through the mitochondrial damage/caspase 9 activation pathway.
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PMID:Differential effects of membrane and soluble Fas ligand on cardiomyocytes: role in ischemia/reperfusion injury. 1281 72

Rodent models of focal and global ischemia were used to examine caspase activation. Several readouts were employed on identical tissue to provide correlative measurement of caspase induction, activation and enzymatic activity. In a rat focal ischemia model, caspase-3 enzymatic activity, as recorded by DEVD-AMC cleavage, peaked in penumbral cortex at 6-12 h following ischemia, correlating with increases in caspase 3-cleaved substrates of PARP and alpha-spectrin and subsequent disappearance of caspase-3 zymogen. Although induction of caspases 8 and 2 proteins was detectable as early as 6 h following ischemia, examination of the same tissues for caspase 8 or 2 enzymatic activities did not show significant modulation up to 12 h after ischemic insult. Caspase 9 induction was evident only after 24 h postischemia and did not correlate with elevated LDHD-AMC cleavage. Following global ischemia in gerbils, levels of caspase-3 enzyme activity peaked at 12 h in hippocampal tissue extracts. Cleaved caspase-3 signal was prominent in NeuN-positive layers in the CA1 region 6-12 h following ischemia. Interestingly, strong caspase-3 immunoreactivity was also detected in the subgranular zone of the dentate gyrus, a known region of ischemia-induced neurogenesis. Caspase-3 activation may be responsible for the loss of these cells, thereby hindering the endogenous recovery process.
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PMID:Temporal assessment of caspase activation in experimental models of focal and global ischemia. 1291 50

Nitric oxide (NO*) at low concentrations is cytoprotective for endothelial cells; however, elevated concentrations of NO* (> or =1 micromol/liter), as may be achieved during inflammatory states, can induce apoptosis and cell death. Hypoxia is associated with tissue inflammation and ischemia and, therefore, may modulate the effects of NO* on endothelial function. To examine the influence of hypoxia on NO*-mediated apoptosis, we exposed bovine aortic endothelial cells (BAEC) to (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate (diethylenetriamine NONOate, DETA-NO) (1 mmol/liter) under normoxic or hypoxic conditions (pO2 = 35 mm of Hg) and measured the indices of apoptotic cell death. BAEC treated with DETA-NO under normoxic conditions demonstrated increased levels of histone-associated DNA fragments, which was confirmed by terminal dUTP nick-end labeling assay, and hypoxic conditions augmented this response. To determine whether mitochondrial dysfunction was one mechanism by which NO* initiated apoptosis under hypoxic conditions, we evaluated mitochondrial membrane potential in (Psim). Exposure to DETA-NO resulted in a decrease in Psim and concomitant release of cytochrome c and caspase-9 activation, which were enhanced by hypoxia. By utilizing Rho0 BAEC (Rho0-EC), which lack functional mitochondria, we demonstrated that dissipation of Psim was associated with increased reactive oxygen species generation and peroxynitrite formation. Moreover, in Rho0-EC we identified activation of caspase-8 as part of the mitochondrial-independent pathway of apoptosis. To establish that peroxynitrite mediated mitochondrial damage and apoptosis, we treated BAEC and Rho0-EC with the peroxynitrite scavenger uric acid and found that the indices of apoptosis were decreased significantly. These findings confirm that high flux of NO* under hypoxic conditions promotes cell death via mitochondrial damage and mitochondrial-independent mechanisms by peroxynitrite.
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PMID:Hypoxia potentiates nitric oxide-mediated apoptosis in endothelial cells via peroxynitrite-induced activation of mitochondria-dependent and -independent pathways. 1459 20

Necrosis and apoptosis differentially contribute to myocardial injury. Determination of the contribution of these processes in ischemia-reperfusion injury would allow for the preservation of myocardial tissue. Necrosis and apoptosis were investigated in Langendorff-perfused rabbit hearts (n = 47) subjected to 0 (Control group), 5 (GI-5), 10 (GI-10), 15 (GI-15), 20 (GI-20), 25 (GI-25), and 30 min (GI-30) of global ischemia (GI) and 120 min of reperfusion. Myocardial injury was determined by triphenyltetrazolium chloride (TTC) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), bax, bcl2, poly(ADP)ribose polymerase (PARP) cleavage, caspase-3, -8, and -9 cleavage and activity, Fas ligand (FasL), and Fas-activated death domain (FADD). The contribution of apoptosis was determined separately (n = 42) using irreversible caspase-3, -8, and -9 inhibitors. Left ventricular peak developed pressure (LVPDP) and systolic shortening (SS) were significantly decreased and infarct size and TUNEL-positive cells were significantly increased (P < 0.05 vs. Control group) at GI-20, GI-25, and GI-30. Proapoptotic bax, PARP cleavage, and caspase-3 and -9 cleavage and activity were apparent at GI-5 to GI-30. Fas, FADD, and caspase-8 cleavage and activity were unaltered. Irreversible inhibition of caspase-3 and -9 activity significantly decreased (P < 0.05) infarct size at GI-25 and GI-30 but had no effect on LVPDP or SS. Myocardial injury results from a significant increase in both necrosis and apoptosis (P < 0.05 vs. Control group) evident by TUNEL, TTC staining, and caspase activity at GI-20. Intrinsic proapoptotic activation is evident early during ischemia but does not significantly contribute to infarct size before GI-25. The contribution of necrosis to infarct size at GI-20, GI-25, and GI-30 is significantly greater than that of apoptosis. Apoptosis is significantly decreased by caspase inhibition during early reperfusion, but this protection does not improve immediate postischemic functional recovery.
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PMID:Differential contribution of necrosis and apoptosis in myocardial ischemia-reperfusion injury. 1471 9

A large volume of experimental data supports the presence of apoptosis in failing hearts. Apoptosis in many types of cells results from exposure to cytotoxic cytokines or damaging agents. Cytotoxic cytokines such as tumor necrosis factor (TNF)-alpha or Fas ligand (FasL) bind to their receptors to activate caspase-8, while damaging agents can cause mitochondrial release of cytochrome c, which can initiate activation of caspase-9. Caspase-8 or -9 can activate a cascade of caspases. The p53 protein is often required for damaging agent-induced apoptosis. An imbalance of proapoptotic factors versus prosurvival factors in the bcl-2 family precedes the activation of caspases. Given these typical changes of apoptosis found in many cell types, the apoptotic pathway in cardiomyocytes is somewhat unconventional since in vivo experimental data reveal that apoptosis does not appear to be controlled by TNF-alpha, FasL, p53 or decrease of bcl-2. In vitro and in vivo studies suggest the importance of mitochondria and activation of caspases in cell death occurring in failing hearts. Oxidants, excessive nitric oxide, angiotensin II and catecholamines have been shown to trigger apoptotic death of cardiomyocytes. Eliminating these inducers reduces apoptosis and reverses the loss of contractile function in many cases, indicating the feasibility of the pharmacological application of antioxidants, nitric oxide synthetase inhibitors, ACE inhibitors, angiotensin II receptor antagonists and adrenergic receptor antagonists. Most inducers of apoptosis initiate a cascade of signaling events, including activation of the p38 mitogen-activated protein kinase. Small molecule inhibitors of p38 have been shown to be capable of preventing apoptosis and loss of contractile function associated with ischemia and reperfusion. Although further experimental work is needed, several studies have already indicated the beneficial effect of caspase inhibitors against cell loss and features of heart failure in vitro and in vivo. These studies indicate the importance of inhibiting apoptosis in therapeutic interventions against heart failure.
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PMID:Apoptosis and heart failure: mechanisms and therapeutic implications. 1472 98

We recently demonstrated that reperfusion rapidly induces the mitochondrial pathway of apoptosis in chick cardiomyocytes after 1 h of simulated ischemia. Here we tested whether ischemia-reperfusion (I/R)-induced apoptosis could be initiated by caspase-dependent cytochrome c release in this model of cardiomyocyte injury. Fluorometric assays of caspase activity showed little, if any, activation of caspases above baseline levels induced by 1 h of ischemia alone. However, these assays revealed rapid activation of caspase-2, yielding a 2.95 +/- 0.52-fold increase (over ischemia only) within the 1st h of reperfusion, whereas activities of caspases-3, -8, and -9 increased only slightly from their baseline levels. The rapid and prominent activation of caspase-2 suggested that it could be an important initiator caspase in this model, and using specific caspase inhibitors given only at the point of reperfusion, we tested this hypothesis. The caspase-2 inhibitor benzyloxycarbonyl-Val-Asp(Ome)-Val-Ala-Asp(Ome)-CH(2)F was the only caspase inhibitor that significantly inhibited cytochrome c release from mitochondria. This inhibitor also completely blocked activation of caspases-3, -8, and -9. The caspase-3/7 inhibitor transiently and only partially blocked caspase-2 activity and was less effective in blocking the activities of caspases-8 and -9. The caspase-8 inhibitor failed to significantly block caspase-2 or -3, and the caspase-9 inhibitor blocked only caspase-9. Furthermore, the caspase-2 inhibitor protected against I/R-induced cell death, but the caspase-8 inhibitor failed to do so. These data suggest that active caspase-2 initiates cytochrome c release after reperfusion and that it is critical for the I/R-induced apoptosis in this model.
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PMID:Caspase-dependent cytochrome c release and cell death in chick cardiomyocytes after simulated ischemia-reperfusion. 1497 33


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