Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.4.2.30 (PARP)
13,611 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In cerebral ischemia, the disappointment related to anti-glutamate strategies in clinical trials has led to examine new targets for the treatment of stroke. In vitro studies demonstrated that overactivation of glutamate receptors leads to nitric oxide (NO) production that contributes to the excitotoxic neuronal death. The role of NO was then studied in in vivo models of cerebral ischemia. In the early phase after ischemia, NO is produced by the constitutive endothelial and neuronal isoforms of NO-synthase (NOS 3 and NOS 1) while in the later phase, the inducible NOS (NOS 2) is responsible for the delayed production of NO. NOS 3 appears beneficial via vasodilatation and inhibition of leukocyte adhesion and platelet aggregation. By contrast NOS 1 and NOS 2 were demonstrated deleterious in cerebral ischemia. This was shown by three distinct strategies: selective inhibitors, mutant mice deficient in NOS 1 or NOS 2, and antisenses directed to one of these isoforms. Moreover it is now thought that NO-induced neuronal death is mainly mediated through the formation of peroxynitrite anions resulting from the reaction between NO and superoxyde anion. Peroxynitrites indeed damage lipids, proteins and nucleic acids. DNA strand breaks in turn activate poly(ADP-ribose) polymerase (PARP). Overactivation of this enzyme in pathological conditions such as cerebral ischemia seems deleterious by depleting ATP stores. Thus inhibition of the NO-peroxynitrites-PARP pathway may lead to neuroprotective therapeutics in stroke.
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PMID:[NO synthases: new pharmacological targets in cerebrovascular accident?]. 1266 62

We investigated the effect of 3-aminobenzamide (3-AB), an inhibitor of the nuclear enzyme poly(ADP-ribose) polymerase (PARP), against early ischemia/reperfusion (IR) injury in heart transplantation. In our experimental model, rat heart subjected to heterotopic transplantation, low temperature global ischemia (2 h) was followed by an in vivo reperfusion (60 min). In these conditions, and in the absence of 3-AB treatment, clear signs of oxidative stress, such as lipid peroxidation, increase in protein carbonyls and DNA strand breaks, were evident; PARP was markedly activated in concomitance with a significant NAD+ and ATP depletion. The results of microscopic observations (nuclear clearings, plasma membrane discontinuity), and the observed rise in the serum levels of heart damage markers, suggested the development of necrotic processes while, conversely, no typical sign of apoptosis was evident. Compared to the effects observed in untreated IR heart, the administration of 3-AB (10 mg/kg to the donor and to the recipient animal), but not that of its inactive analogue 3-aminobenzoic acid, significantly modified the above parameters: the levels of oxidative stress markers were significantly reduced; PARP activation was markedly inhibited and this matched a significant rise in NAD+ and ATP levels. PARP inhibition also caused a reduced release of the cardiospecific damage markers and attenuated morphological cardiomyocyte alterations, save that, in this condition, we noted the appearance of typical apoptotic markers: activation of caspase-3, oligonucleosomal DNA fragmentation, ISEL positive nuclei. Possible mechanisms for these effects are discussed, in any case the present results indicate that PARP inhibition has an overall beneficial effect against myocardial reperfusion injury, mainly due to prevention of energy depletion. In this context, the signs of apoptosis observed under 3-AB treatment might be ascribed to the maintenance of sufficient intracellular energy levels. These latter allow irreversible damages triggered during the ischemic phase to proceed towards apoptosis instead of towards necrosis, as it appears to happen when the energetic pools are depleted by high PARP activity.
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PMID:Beneficial effects of poly (ADP-ribose) polymerase inhibition against the reperfusion injury in heart transplantation. 1268 29

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

Oxidative stress plays a pivotal role in ischemic-reperfusion cell injury. Oxygen-derived free radicals trigger DNA strand damage, which is responsible for the activation of poly(ADP-ribose) polymerase (PARP). Recent studies have shown that peroxynitrite is the primary mediator of DNA damage and, hence, PARP activation after ischemia. PARP activation depletes NAD and ATP pools, ultimately resulting in necrotic cell death by loss of energy stores. Our study shows that PARP is upregulated as early as 15 min after 1 h of transient focal cerebral ischemia and remains for 8 h. We also examined the role of superoxide in PARP induction using copper/zinc-superoxide dismutase transgenic mice. Immunohistochemical and Western blotting data showed that there was no increased induction in PARP expression in these mice, suggesting that one of the mechanisms by which ischemic injury is attenuated in these mice might be by the inhibition of PARP induction. Furthermore, double staining of ischemic tissue with a PARP antibody and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) indicated that most cells that are positive for TUNEL do not stain for the PARP antibody, confirming recent reports that PARP activation is involved in necrotic cell death rather than apoptosis during ischemic-reperfusion injury.
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PMID:Role of superoxide in poly(ADP-ribose) polymerase upregulation after transient cerebral ischemia. 1275 3

Poly(ADP-ribose) is synthesized from nicotinamide adenine dinucleotide (NAD(+)) by poly(ADP-ribose) polymerase (PARP) and degraded by poly(ADP-ribose) glycohydrolase (PARG). Overactivation of the poly(ADP-ribose) pathway increases nicotinamide and decreases cellular NAD(+)/ATP, which leads to cell death. Blocking poly(ADP-ribose) metabolism by inactivating PARP has been shown to reduce ischemia injury. We investigated whether disrupting the poly(ADP-ribose) cycle by PARG inhibition could achieve similar protection. We demonstrate that either pre- or post-ischemia treatment with 40 mg/kg of N-bis-(3-phenyl-propyl)9-oxo-fluorene-2,7-diamide, a novel PARG inhibitor, significantly reduces brain infarct volumes by 40-53% in a rat model of focal cerebral ischemia. Our result provides the first evidence that PARG inhibitors can ameliorate ischemic brain damage in vivo, in support of PARG as a new therapeutic target for treating ischemia injury.
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PMID:Post-treatment with a novel PARG inhibitor reduces infarct in cerebral ischemia in the rat. 1283 3

Poly(ADP-ribose) polymerase-1 (PARP-1) is an abundant nuclear enzyme that is activated primarily by DNA damage. Upon activation, the enzyme hydrolyzes NAD(+) to nicotinamide and transfers ADP ribose units to a variety of nuclear proteins, including histones and PARP-1 itself. This process is important in facilitating DNA repair. However, excessive activation of PARP-1 can lead to significant decrements in NAD(+), and ATP depletion, and cell death (suicide hypothesis). In response to cellular damage by oxygen radicals or excitotoxicity, a rapid and strong activation of PARP-1 occurs in neurons. Excessive PARP-1 activation is implicated in a variety of insults, including cerebral and cardiac ischemia, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism, traumatic spinal cord injury, and streptozotocin-induced diabetes. The use of PARP inhibitors has, therefore, been proposed as a protective therapy in decreasing excitotoxic neuronal cell death, as well as ischemic and other tissue damage. Excitotoxic brain lesions initially result in the primary destruction of brain parenchyma and subsequently in secondary damage of neighboring neurons hours after the insult. This secondary damage of initially surviving neurons accounts for most of the volume of the infarcted area and the loss of brain function after a stroke. One major component of secondary neuronal damage is the migration of macrophages and microglial cells toward the sites of injury, where they produce large quantities of toxic cytokines and oxygen radicals. Recent evidence indicates that this microglial migration is strongly controlled in living brain tissue by expression of the integrin CD11a, which is regulated in turn by PARP-1, proposing that PARP-1 downregulation may, therefore, be a promising strategy in protecting neurons from this secondary damage, as well. Studies demonstrating an important role for PARP-1 in the regulation of gene transcription have further increased the intricacy of poly(ADP-ribosyl)ation in the control of cell homeostasis and challenge the notion that energy collapse is the sole mechanism by which poly(ADP-ribose) formation contributes to cell death. The hypothesis that PARPs might regulate cell fate as essential modulators of death and survival transcriptional programs is discussed with relation to nuclear factor kappaB and p53.
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PMID:Poly(ADP-Ribose) polymerase-1 in acute neuronal death and inflammation: a strategy for neuroprotection. 1285 16

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

A transient, sublethal ischemic interval confers resistance to a subsequent, otherwise lethal ischemic insult, in a process termed ischemic preconditioning. Poly(ADP-ribose) polymerase-1 (PARP-1) normally functions in DNA repair, but extensive PARP-1 activation is a major cause of ischemic cell death. Because PARP-1 can be cleaved and inactivated by caspases, we investigated the possibility that caspase cleavage of PARP-1 could contribute to ischemic preconditioning. Murine cortical cultures were treated with glucose deprivation combined with 0.5 mm 2-deoxyglucose and 5 mm azide ("chemical ischemia") to model the reversible energy failure that occurs during transient ischemia in vivo. Cortical cultures preconditioned with 15 min of chemical ischemia showed increased resistance to subsequent, longer periods of chemical ischemia. These cultures were also more resistant to the PARP-1 activating agent, N-methyl-N'-nitro-N-nitrosoguanidine, suggesting reduced capacity for PARP-1 activation after preconditioning. Immunostaining for the 89 kDa PARP-1 cleavage fragment and for poly(ADP-ribose) formation confirmed that PARP-1 was cleaved and PARP-1 activity was attenuated in the preconditioned neurons. Preconditioning also produced an increase in activated caspase-3 peptide and an increase in caspase-3 activity in the cortical cultures. A cause-effect relationship between caspase activation, PARP-1 cleavage, and ischemic preconditioning was supported by studies using the caspase inhibitor Ac-Asp-Glu-Val-Asp-aldehyde (DEVD-CHO). Cultures treated with DEVD-CHO after preconditioning showed reduced PARP-1 cleavage and reduced resistance to subsequent ischemia. These findings suggest a novel interaction between the caspase- and PARP-1-mediated cell death pathways in which sublethal caspase activation leads to PARP-1 cleavage, thereby increasing resistance to subsequent ischemic stress.
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PMID:Ischemic preconditioning by caspase cleavage of poly(ADP-ribose) polymerase-1. 1295 57

1. Caspases play a critical role in apoptosis, and are considered to be key targets for the design of cytoprotective drugs. As part of our antiapoptotic drug-discovery effort, we have synthesized and characterized Z-VD-fmk, MX1013, as a potent, irreversible dipeptide caspase inhibitor. 2. MX1013 inhibits caspases 1, 3, 6, 7, 8, and 9, with IC50 values ranging from 5 to 20 nm. MX1013 is selective for caspases, and is a poor inhibitor of noncaspase proteases, such as cathepsin B, calpain I, or Factor Xa (IC50 values >10 microm). 3. In several cell culture models of apoptosis, including caspase 3 processing, PARP cleavage, and DNA fragmentation, MX1013 is more active than tetrapeptide- and tripeptide-based caspase inhibitors, and blocked apoptosis at concentrations as low as 0.5 microm. 4. MX1013 is more aqueous soluble than tripeptide-based caspase inhibitors such as Z-VAD-fmk. 5. At a dose of 1 mg kg-1 i.v., MX1013 prevented liver damage and the lethality caused by Fas death receptor activation in the anti-Fas mouse-liver apoptosis model, a widely used model of liver failure. 6. At a dose of 20 mg kg-1 (i.v. bolus) followed by i.v. infusion for 6 or 12 h, MX1013 reduced cortical damage by approximately 50% in a model of brain ischemia/reperfusion injury. 7. At a dose of 20 mg kg-1 (i.v. bolus) followed by i.v. infusion for 12 h, MX1013 reduced heart damage by approximately 50% in a model of acute myocardial infarction. 8. Based on these studies, we conclude that MX1013, a dipeptide pan-caspase inhibitor, has a good combination of in vitro and in vivo properties. It has the ability to protect cells from a variety of apoptotic insults, and is systemically active in three animal models of apoptosis, including brain ischemia.
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PMID:MX1013, a dipeptide caspase inhibitor with potent in vivo antiapoptotic activity. 1297 77

An excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme able to catalyze the transfer of ADP-ribose from NAD to acceptor proteins, is involved in the progression of neuronal damage after brain insult. Potent and selective PARP-1 inhibitors have neuroprotective properties in experimental models of brain ischemia. As a follow up of our previous structure-activity relationship study and in search for novel potent PARP-1 inhibitors, a series of 4H-thieno[2,3-c]-isoquinolin-5-one derivatives was designed and synthesized. Tested for their ability to inhibit PARP-1, these novel derivatives showed high inhibitory potency. The unsubstituted derivative TIQ was selected for further characterization and found to be endowed with strong neuroprotective properties in models of cerebral ischemia.
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PMID:Towards new neuroprotective agents: design and synthesis of 4H-thieno[2,3-c] isoquinolin-5-one derivatives as potent PARP-1 inhibitors. 1367 79


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