Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytosolic phospholipase A(2)alpha (cPLA(2)alpha; type IVA), an essential initiator of stimulus-dependent arachidonic acid (AA) metabolism, underwent caspase-mediated cleavage at Asp(522) during apoptosis. Although the resultant catalytically inactive N-terminal fragment, cPLA(2)(1-522), was inessential for cell growth and the apoptotic process, it was constitutively associated with cellular membranes and attenuated both the A23187-elicited immediate and the interleukin-1-dependent delayed phases of AA release by several phospholipase A(2)s (PLA(2)s) involved in eicosanoid generation, without affecting spontaneous AA release by PLA(2)s implicated in phospholipid remodeling. Confocal microscopic analysis revealed that cPLA(2)(1-522) was distributed in the nucleus. Pharmacological and transfection studies revealed that Ca(2+)-independent PLA(2) (iPLA(2); type VI), a phospholipid remodeling PLA(2), contributes to the cell death-associated increase in fatty acid release. iPLA(2) was cleaved at Asp(183) by caspase-3 to a truncated enzyme lacking most of the first ankyrin repeat, and this cleavage resulted in increased iPLA(2) functions. iPLA(2) had a significant influence on cell growth or death, according to cell type. Collectively, the caspase-truncated form of cPLA(2)alpha behaves like a naturally occurring dominant-negative molecule for stimulus-induced AA release, rendering apoptotic cells no longer able to produce lipid mediators, whereas the caspase-truncated form of iPLA(2) accelerates phospholipid turnover that may lead to apoptotic membranous changes.
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PMID:Distinct roles of two intracellular phospholipase A2s in fatty acid release in the cell death pathway. Proteolytic fragment of type IVA cytosolic phospholipase A2alpha inhibits stimulus-induced arachidonate release, whereas that of type VI Ca2+-independent phospholipase A2 augments spontaneous fatty acid release. 1074 87

Methylazoximethanol (MAM) acetate-induced cell death in the external granule cell layer of the developing cerebellum affects clusters of cells with morphological features of apoptosis. This is accompanied by selective induction of active caspase-3 expression and increased c-Jun/AP-1 (N) immunoreactivity in dying cells, as revealed with immunohistochemistry. Since the antibody to cJun/AP-1 (N) cross-reacts with epitopes emerging after caspase-mediated proteolysis during apoptosis, these results indicate that MAM-induced cell death is associated with active caspase-3 expression and function in dying cells. In order to investigate the involvement of tissue-type plasminogen activator (tPA), which has been implicated in certain forms of neuronal cell death, MAM-induced cell death has been examined in tPA-/- and tPA+/+ mice. No differences in the number of dying cells, as seen with haematoxylin and eosin staining and in situ end-labelling of fragmented nuclear DNA-processed sections, were seen between tPA-/- and tPA+/+ mice. These results indicate that tPA is not involved in MAM-induced cell death in the developing brain.
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PMID:Methylazoximethanol acetate-induced cell death in the granule cell layer of the developing mouse cerebellum is associated with caspase-3 activation, but does not depend on the tissue-type plasminogen activator. 1116 42

Quinacrine (QU), a phospholipase-A2 (PLA-2) inhibitor has been used clinically as a chemotherapeutic adjuvant. To understand the mechanisms leading to its chemotherapeutic effect, we have investigated QU-induced apoptotic signaling pathways in human cervical squamous carcinoma HeLa cells. In this study, we found that QU induced cytochrome c-dependent apoptotic signaling. The release of pro-apoptotic cytochrome c was QU concentration- and time-dependent, and preceded activation of caspase-9 and -3. Flow cytometric FACScan analysis using fluorescence intensities of DiOC6 demonstrated that QU-induced cytochrome c release was independent of mitochondrial permeability transition (MPT), since the concentrations of QU that induced cytochrome c release did not alter mitochondrial membrane potential (delta pai(m)). Moreover, kinetic analysis of caspase activities showed that cytochrome c release led to the activation of caspase-9 and downstream death effector, caspase-3. Caspase-3 inhibitor (Ac-DEVD-CHO) partially blocked QU-induced apoptosis, suggesting the importance of caspase-3 in this apoptotic signaling mechanism. Supplementation with arachidonic acid (AA) sustained caspase-3 activation induced by QU. Using inhibitors against cellular arachidonate metabolism of lipooxygenase (Nordihydroxyguaiaretic Acid, NDGA) and cyclooxygenase (5,8,11,14-Eicosatetraynoic Acid, ETYA) demonstrated that QU-induced apoptotic signaling may be dependent on its role as a PLA-2 inhibitor. Interestingly, NDGA attenuated QU-induced cytochrome c release, caspase activity as well as apoptotic cell death. The blockade of cytochrome c release by NDGA was much more effective than that attained with cyclosporin A (CsA), a MPT inhibitor. ETYA was not effective in blocking cytochrome c release, except under very high concentrations. Caspase inhibitor z-VAD blocked the release of cytochrome c suggesting that this signaling event is caspase dependent, and caspase-8 activation may be upstream of the mitochondrial events. In summary, we report that QU induced cytochrome c-dependent apoptotic signaling cascade, which may be dependent on its role as a PLA-2 inhibitor. This apoptotic mechanism induced by QU may contribute to its known chemotherapeutic effects.
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PMID:Quinacrine induces cytochrome c-dependent apoptotic signaling in human cervical carcinoma cells. 1133 32

Plasminogen activator inhibitor-1 (PAI-1) plays an important role in the processes of peripheral tissue remodeling and fibrinolysis through the regulation of plasminogen activation. We found that cultured human astrocytes efficiently released PAI-1, and that both mRNA expression and protein release of PAI-1 were suppressed by pretreatment of the cells with daunorubicin. To examine the role of PAI-1 in the nervous system, neuronally differentiated PC-12 cells (PC-12 neurons) were maintained in a PAI-1-deficient culture medium derived from daunorubicin-pretreated astrocytes. The deficiency of PAI-1 in the medium caused a significant reduction in Bcl-2 and Bcl-XL mRNAs and an increase in Bcl-XS and Bax mRNAs in PC-12 neurons at 3 h. The changes in balance between mRNA expressions of the anti- and pro-apoptotic Bcl-2 family proteins caused caspase-3 activation following the release of cytochrome c from mitochondria. Apoptotic morphological change and DNA fragmentation were also observed in the neuronal cells at 24 h. Addition of exogenous PAI-1 protein to the inhibitor-deficient medium blocked the apoptotic changes in PC-12 neurons. However, addition of PAI-1 antibodies to control medium caused similar apoptotic changes in PC-12 neurons. During the apoptotic processes, plasminogen activator (PA) activity in the PAI-1-deficient medium was as low as the control level. The present data suggest that PAI-1 has physiological functions other than its role as PA inhibitor for the survival of neurons.
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PMID:Deficient release of plasminogen activator inhibitor-1 from astrocytes triggers apoptosis in neuronal cells. 1145 96

Cell signaling commanding death or survival in human epileptic hippocampus is difficult to trace because of the long interval between the beginning of symptoms and the sampling of damaged cerebral tissue for neuropathological examination. Intraperitoneal injection of the glutamate analogue kainic acid (KA) is a useful tool to analyze the effects of seizures and the excitotoxic damage in the rodent hippocampus. KA acts on NMDA and KA receptors, whereas it has little impact on AMPA receptors. Neurons of the hilus and CA3 neurons are primary targets of KA, although parvalbumin containing GABAergic neurons are less vulnerable than glutamatergic neurons. Immediate responses to KA are hsp 70 mRNA induction and HSP 70/72 protein expression, as well as c fos and c jun mRNA, and c Fos and c Jun protein expression in the hippocampus. Yet increased c Fos and c Jun expression is not a predictor of cell death or cell survival. In contrast, the tissular plasminogen activator (tPA) and the membrane Fas/Fas L signaling pathway probably have a role in facilitating cell death following KA injection. The involvement of other pathways remains controversial. Increased expression of the pro apoptotic Bax together with decreased Bcl 2 suggests Bax mediated apoptosis. Activation of the mitochondrial pathway includes leakage of citochrome c to the cytosol and activation of the caspase cascade leading to apoptosis. However, other studies have emphasized the limited expression of caspase 3, the main executioner of apoptosis, and the relevance of necrosis as the main form of cell death following KA excitotoxicity. Phosphorylation dependent activation of several kinases, including MAPK, p 38 and JNK/SAPK, and their substrates has been found in KA treated animals. Decreased CREBp expression is associated with cell death whereas increased ATF 2P and Elk 1P are associated with cell survival. Trophic factors probably do not play a significant role during the early stages of hippocanmpal damage but they are important in the remodeling of the granukle cells and the sprouting of mossy fibers to the molecular layer of the dentate gyrus. This abnormal regeneration, in turn, facilitates seizure recruitment and the chronic maintenance of convulsions.
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PMID:[Cell signaling in the epileptic hippocampus]. 1204 Apr 99

We tested the hypothesis that oxidized low-density lipoprotein (oxLDL), administered in sublethal doses to the culture medium of immortalized rat brain endothelial cells (ECs, GP8.39), acts as a prooxidant signal to stimulate peroxidation processes and membrane phospholipid hydrolysis. ECs were grown at confluence in a medium with or without native LDL (nLDL) or oxLDL (1.5 mg/dish; up to 350-450 nmol hydroperoxides/mg protein) for two temporally distinct phases (short incubation period up to 1 h, or long incubation period spanning 24 h). Peroxidation parameters (conjugated dienes, MDA, hydroperoxides and LDH release) and arachidonic acid (AA) release were determined. Cell lysates and subcellular fractions were assayed for cPLA(2) while the cytotoxic effect and apoptosis were monitored by morphological changes, trypan blue dye exclusion, MTT reduction test, caspase-3 activity, COMET and laser confocal fluorescence microscopy (LCFM) analyses. Effects of alpha-tocopherol and 85-kDa PLA(2) inhibitor (AACOCF(3)), alone or in combination, were also tested. Immunoblot analysis of cPLA(2) was carried out on cell fraction proteins. After incubation for 1 or 24 h, oxLDL (100-200 microM hydroperoxides), but not nLDL, markedly increased lipid peroxidation, cPLA(2) activity and AA release in a dose-dependent manner. AACOCF(3) and antioxidant alpha-tocopherol (1 mM) strongly inhibited the prooxidant-stimulated AA release. Long-term exposure (24 h) to oxLDL (100 microM) had no effect on the cPLA(2) protein content as tested by Western immunoblot analysis, while showing a sharp cytotoxic effect on the cells. Caspase-3 activity and LCFM analysis indicated that oxLDL (100/200 microM) were able to trigger an apoptotic process. The results suggest that (i) ECs may be the target of extensive oxidative damage caused by oxLDL; (ii) activation of cPLA(2) mediates liberation of AA; (iii) cPLA(2) expression was not stimulated by long-term exposure to oxLDL; (iv) oxidized specific constituents of oxLDL, acting as regulatory signals, increase the ability of ECs to degrade membrane phospholipids, end products of which are linked to the development of atherosclerotic lesions.
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PMID:Cytosolic phospholipase A2 mediates arachidonoyl phospholipid hydrolysis in immortalized rat brain endothelial cells stimulated by oxidized LDL. 1245 11

It has been demonstrated recently that rabbit renal proximal tubule cells (RPTC) express a novel Ca(2+)-independent phospholipase A(2) (iPLA(2)) whose activity localizes to the endoplasmic reticulum (ER-iPLA(2)) and is similar to group VIB PLA(2). In this study, the expression of group VIB PLA(2) was examined and the role of ER-iPLA(2) in cisplatin-induced apoptosis was determined. Cisplatin induced both time- and concentration-dependent RPTC apoptosis as determined by p53 nuclear localization, annexin V staining, caspase 3 activity, and chromatin condensation. Inhibition of ER-iPLA(2) with bromoenol lactone (5 microM) reduced cisplatin-induced annexin V binding 40%, chromatin condensation 55%, and caspase 3 activity 42%, but had no effect on p53 nuclear localization. Treatment of RPTC with the protein kinase C stimulator phorbol 12-myristate 13-acetate increased the activity of ER-iPLA(2) 2-fold and increased cisplatin-induced RPTC apoptosis. These studies demonstrate that group VIB PLA(2) is expressed in RPTC and suggest that RPTC ER-iPLA(2) is the rabbit homolog of group VIB PLA(2). These data also demonstrate that ER-iPLA(2) acts downstream of p53 and upstream of caspase 3 to mediate cisplatin-induced RPTC apoptosis. Finally, ER-iPLA(2) seems to be regulated by protein kinase C.
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PMID:Role of an endoplasmic reticulum Ca2+-independent phospholipase A2 in cisplatin-induced renal cell apoptosis. 1463 37

In this study, we investigated the involvement of reactive oxygen species (ROS) and calcium in staurosporine (STS)-induced apoptosis in cultured retinal neurons, under conditions of maintained membrane integrity. The antioxidants idebenone (IDB), glutathione-ethylester (GSH/EE), trolox, and Mn(III)tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP) significantly reduced STS-induced caspase-3-like activity and intracellular ROS generation. Endogenous sources of ROS production were investigated by testing the effect of the following inhibitors: 7-nitroindazole (7-NI), a specific inhibitor of the neuronal isoform of nitric oxide synthase (nNOS); arachidonyl trifluoromethyl ketone (AACOCF(3)), a phospholipase A(2) (PLA(2)) inhibitor; allopurinol, a xanthine oxidase inhibitor; and the mitochondrial inhibitors rotenone and oligomycin. All these compounds decreased caspase-3-like activity and ROS generation, showing that both mitochondrial and cytosolic sources of ROS are implicated in this mechanism. STS induced a significant increase in intracellular calcium concentration ([Ca(2+)](i)), which was partially prevented in the presence of IDB and GSH/EE, indicating its dependence on ROS generation. These two antioxidants and the inhibitors allopurinol and 7-NI also reduced the number of TdT-mediated dUTP nick-end labeling-positive cells. Thus, endogenous ROS generation and the rise in intracellular calcium are important inter-players in STS-triggered apoptosis. Furthermore, the antioxidants may help to prolong retinal cell survival upon apoptotic cell death.
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PMID:Cytosolic and mitochondrial ROS in staurosporine-induced retinal cell apoptosis. 1464 98

The effects of i.p. melatonin (4 + 4 mg/kg, after induction of ischemia and at reperfusion onset) administered either alone or in combination with the thrombolytic tissue-plasminogen activator (t-PA, 10 mg/kg), on cerebral laser Doppler flow (LDF) and ischemic injury were studied after 30 min of middle cerebral artery (MCA) thread occlusion in male C57BL/6 mice. Thread occlusions resulted in reproducible focal ischemias, followed by hyperperfusion reactions immediately after thread withdrawal, as revealed by LDF measurements. Compared with animals receiving normal saline (peak LDF after reperfusion: 172.0 +/- 24.2%), postischemic LDF was significantly attenuated in animals treated with melatonin (105.1 +/- 6.7%, P < 0.05). Delivery of t-PA (132.8 +/- 22.3%) or t-PA plus melatonin (164.7 +/- 36.7%), on the contrary, did not influence postischemic LDF recordings. Twenty-four hours after reperfusion, melatonin treated mice had significantly increased neuronal survival and decreased disseminate cell injury in the ischemia-vulnerable striatum, as investigated by cresyl violet and terminal transferase biotinylated-dUTP nick end labeling stainings. The protective effects were associated with inhibition of caspase-3 activity. Melatonin administration also increased neuronal survival after 30 min MCA occlusion in animals treated with t-PA, although t-PA itself already decreased the degree of injury in a significant manner. Our data demonstrate that melatonin reduces disseminated neuronal injury in the striatum after mild focal ischemia. Brain protection is independent of hemodynamic changes and involves inhibition of caspase-3.
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PMID:Melatonin reduces disseminate neuronal death after mild focal ischemia in mice via inhibition of caspase-3 and is suitable as an add-on treatment to tissue-plasminogen activator. 1500 7

Recombinant tissue-plasminogen activator (t-PA) increases brain injury after focal ischemias leading to overt tissue infarcts. The question arose, whether t-PA may also be detrimental after mild ischemias. To clarify this issue, we submitted mice to 30 min intraluminal thread occlusions and administered normal saline or t-PA (10 mg/kg, i.v.) after reperfusion onset. Thread occlusions resulted in reproducible ischemias, followed by hyperperfusion reactions immediately after thread withdrawal. Post-ischemic LDF did not differ between saline- and t-PA-treated animals. In contrast to earlier studies, where t-PA exacerbated injury, t-PA treatment did not increase, but attenuated disseminate neuronal death in the striatum, as shown by cresyl violet, TUNEL and activated caspase-3 staining 1 and 3 days after the ischemic event (p < 0.05). Our data argue against major detrimental actions of t-PA after mild focal ischemia.
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PMID:Intravenously administered recombinant tissue-plasminogen activator attenuates neuronal injury after mild focal cerebral ischemia in mice. 1509 76


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