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)

Excessive activation of poly(ADP-ribose) polymerase 1 (PARP1) leads to NAD(+) depletion and cell death during ischemia and other conditions that generate extensive DNA damage. When activated by DNA strand breaks, PARP1 uses NAD(+) as substrate to form ADP-ribose polymers on specific acceptor proteins. These polymers are in turn rapidly degraded by poly(ADP-ribose) glycohydrolase (PARG), a ubiquitously expressed exo- and endoglycohydrolase. In this study, we examined the role of PARG in the PARP1-mediated cell death pathway. Mouse neuron and astrocyte cultures were exposed to hydrogen peroxide, N-methyl-d-aspartate (NMDA), or the DNA alkylating agent, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Cell death in each condition was markedly reduced by the PARP1 inhibitor benzamide and equally reduced by the PARG inhibitors gallotannin and nobotanin B. The PARP1 inhibitor benzamide and the PARG inhibitor gallotannin both prevented the NAD(+) depletion that otherwise results from PARP1 activation by MNNG or H(2)O(2). However, these agents had opposite effects on protein poly(ADP-ribosyl)ation. Immunostaining for poly(ADP-ribose) on Western blots and neuron cultures showed benzamide to decrease and gallotannin to increase poly(ADP-ribose) accumulation during MNNG exposure. These results suggest that PARG inhibitors do not inhibit PARP1 directly, but instead prevent PARP1-mediated cell death by slowing the turnover of poly(ADP-ribose) and thus slowing NAD(+) consumption. PARG appears to be a necessary component of the PARP-mediated cell death pathway, and PARG inhibitors may have promise as neuroprotective agents.
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PMID:Poly(ADP-ribose) glycohydrolase mediates oxidative and excitotoxic neuronal death. 1159 40

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

The enzyme poly(ADP-ribose) glycohydrolase (PARG) catalyzes the hydrolysis of glycosidic bonds of ADP-ribose polymers, producing monomeric ADP-ribose units. Thus, in conjunction with poly(ADP-ribose) polymerase (PARP), PARG activity regulates the extent of in vivo poly(ADP-ribosyl)ation. Small molecule inhibitors of PARP and PARG have shown considerable promise in cellular models of ischemia-reperfusion injury and oxidative neuronal cell death. However, currently available PARG inhibitors are not ideal due to cell permeability, size, and/or toxicity concerns; therefore, new small molecule inhibitors of this important enzyme are sorely needed. Existing methodologies for in vitro assessment of PARG enzymatic activity do not lend themselves to high-throughput screening applications, as they typically use a radiolabeled substrate and determine product quantities through TLC analysis. This article describes a method whereby the ADP-ribose product of the PARG-catalyzed reaction is converted into a fluorescent dye. This highly sensitive and reproducible method is demonstrated by identifying two known PARG inhibitors in a 384-well plate assay and by subsequently determining IC(50) values for these compounds. Thus, this high-throughput, nonradioactive PARG assay should find widespread use in experiments directed toward identification of novel PARG inhibitors.
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PMID:A nonradiometric, high-throughput assay for poly(ADP-ribose) glycohydrolase (PARG): application to inhibitor identification and evaluation. 1545 Aug

Poly (ADP-ribosyl)ation, an early post-translational modification in response to DNA damage, is catalyzed by poly (ADP-ribose) polymerase (PARP-1) and catabolized by poly(ADP-ribose) glycohydrolase (PARG). The aim of this study was to investigate the role of PARG on the modulation of the inflammatory response caused by splanchnic ischemia and reperfusion. SAO shock in rats and wild-type (WT) mice was associated with a significant neutrophil infiltration in the ileum and production of tumor necrosis factor-alpha (TNF-alpha). Reperfused ileum tissue sections from SAO-shocked WT mice and rats showed positive staining for P-selectin and ICAM-1 localized mainly in the vascular endothelial cells. Genetic disruption of the PARG gene in mice or pharmacological inhibition of PARG by PARG inhibitors significantly improved the histological status of the reperfused tissues associated with reduced expression of P-selectin and ICAM-1, neutrophil infiltration into the reperfused intestine, and TNF-alpha production. These results suggest that PARG activity modulates the inflammatory response in ischemia/reperfusion and participates in end (target) organ damage under these conditions.
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PMID:PARG activity mediates intestinal injury induced by splanchnic artery occlusion and reperfusion. 1579 Oct 6

Poly(ADP-ribosyl)ation is regulated by the synthesizing enzyme poly(ADP-ribose) polymerase-1 (PARP-1) and the degrading enzyme poly(ADP-ribose) glycohydrolase (PARG). Homeostasis of poly(ADP-ribosyl)ation has been proposed to be an important regulator for pathogenesis in multi-cellular organisms. Although the role of PARP-1 in tissue damage, inflammation and ischemia has been extensively studied, the function of PARG in various cellular processes is largely unknown. Recent studies using chemical inhibitors of PARG and genetically engineered Drosophila and mouse models that carry a disrupted PARG gene have started to shed new light on the biological function of PARG in vivo. These animal models and cells isolated from them will be useful for further validation of PARG as a potential pharmaceutical target to intervene the pathogenesis induced by acute tissue injury, ischemia and inflammation.
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PMID:Role of poly(ADP-ribose) glycohydrolase (PARG) in shock, ischemia and reperfusion. 1591 38

Excessive activation of the nuclear enzyme, poly(ADP-ribose) polymerase-1 (PARP-1) plays a prominent role in various of models of cellular injury. Here, we identify poly(ADP-ribose) (PAR) polymer, a product of PARP-1 activity, as a previously uncharacterized cell death signal. PAR polymer is directly toxic to neurons, and degradation of PAR polymer by poly(ADP-ribose) glycohydrolase (PARG) or phosphodiesterase 1 prevents PAR polymer-induced cell death. PARP-1-dependent, NMDA excitotoxicity of cortical neurons is reduced by neutralizing antibodies to PAR and by overexpression of PARG. Neuronal cultures with reduced levels of PARG are more sensitive to NMDA excitotoxicity than WT cultures. Transgenic mice overexpressing PARG have significantly reduced infarct volumes after focal ischemia. Conversely, mice with reduced levels of PARG have significantly increased infarct volumes after focal ischemia compared with WT littermate controls. These results reveal PAR polymer as a signaling molecule that induces cell death and suggests that interference with PAR polymer signaling may offer innovative therapeutic approaches for the treatment of cellular injury.
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PMID:Poly(ADP-ribose) (PAR) polymer is a death signal. 1711 82

Cumulative evidence has indicated a critical role of poly(ADP-ribose) polymerase-1 activation in ischemic brain damage. Poly(ADP-ribose) glycohydrolase (PARG) is a key enzyme in poly(ADP-ribose) catabolism. Our previous studies showed that PARG inhibitors, gallotannin (GT) and nobotanin B, can profoundly decrease oxidative cell death in vitro. Here, we tested the hypothesis that intranasal delivery of GT can decrease ischemic brain damage by inhibiting PARG. Intranasal delivery of 25 mg / kg GT within 5 hours after a 2-hour focal brain ischemia markedly decreased the infarct formation and neurological deficits of rats. The GT administration also increased poly(ADP-ribose) in the ischemic brains, suggesting that GT acts as a PARG inhibitor in vivo. Furthermore, the GT treatment abolished nuclear translocation of apoptosis-inducing factor (AIF) in the ischemic brains, suggesting that prevention of AIF translocation may contribute to the protective effects of GT. In contrast, intravenous injection of GT, at 2 hours after ischemic onset, did not reduce ischemic brain damage. Collectively, our findings suggest that PARG inhibition can significantly decrease ischemic brain injury, possibly by blocking AIF translocation. This study also highlights distinct merits of intranasal drug delivery for treating CNS diseases.
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PMID:Intranasal administration of a PARG inhibitor profoundly decreases ischemic brain injury. 1756 25

Poly (ADP-robose) glycohydrolase (PARG) is a catabolic enzyme that cleaves ADP-ribose polymers synthesized by members of the poly (ADP-ribose) polymerase (PARP) family of enzymes. The growing evidence supports the importance of a tight control of poly (ADP-ribose) metabolism by the two major enzymes, PARP-1 and PARG. Recent studies have advanced the understanding of PARPs' and PARG's functions in various cellular and physiological processes. In the last 10 years, homeostasis of poly (ADP-ribosyl)ation has been a target of pharmaceutical interventions for various pathologies. Although the polymer synthesizing enzyme PARP-1 has been well studied, the function of PARG remains largely unknown. However, a great effort has been made in recent years to delineate biological functions of PARG and to explore the therapeutical potentials of PARG inhibition in pathophysiological conditions such as inflammation, ischemia, stroke, and cancer chemotherapy.
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PMID:Poly (ADP-ribose) glycohydrolase (PARG) and its therapeutic potential. 1927 51

The biological roles of poly(ADP-ribose) polymers (PAR) and poly(ADP-ribosyl)ation of proteins in the central nervous system are diverse. The homeostasis of PAR orchestrated by poly(ADP-ribose) polymerase-1 (PARP-1) and poly(ADP-ribose) glycohydrolase (PARG) is crucial for cell physiology and pathology. Both enzymes are ubiquitously distributed in neurons and glia; however, they are segregated at the subcellular level. PARP-1 serves as a "nick sensor" for single- or double-stranded breaks in DNA and is involved in long and short patch base-excision repair, while PARG breaks down PAR. The stimulation of PARP-1 and PAR formation can activate proinflammatory transcription factors, including nuclear factor kappa B. However, hyperactivation of PARP-1 can result in depletion of NAD/ATP, and in PAR-dependent mitochondrial pore formation leading to release of apoptosis inducing factor and cell death. The role of PAR as a death signaling molecule in brain ischemia-reperfusion and inflammation as well as the effect of gender and aging is presented in this review. Modulating the PAR level through pharmacological or genetic intervention on PARP-1/PARG activity and gene expression should be a valuable way for neuroprotective strategy.
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PMID:Poly(ADP-ribose) metabolism in brain and its role in ischemia pathology. 2041 56

Poly(ADP-ribosyl)ation refers to the covalent attachment of ADP-ribose to protein, generating branched, long chains of ADP-ribose moieties, known as poly(ADP-ribose) (PAR). Poly(ADP-ribose) polymerase 1 (PARP1) is the main polymerase and acceptor of PAR in response to DNA damage. Excessive intracellular PAR accumulation due to PARP1 activation leads cell death in a pathway known as parthanatos. PAR degradation is mainly controlled by poly(ADP-ribose) glycohydrolase (PARG) and ADP-ribose-acceptor hydrolase 3 (ARH3). Our previous results demonstrated that ARH3 confers protection against hydrogen peroxide (H2O2) exposure, by lowering cytosolic and nuclear PAR levels and preventing apoptosis-inducing factor (AIF) nuclear translocation. We identified a family with an ARH3 gene mutation that resulted in a truncated, inactive protein. The 8-year-old proband exhibited a progressive neurodegeneration phenotype. In addition, parthanatos was observed in neurons of the patient's deceased sibling, and an older sibling exhibited a mild behavioral phenotype. Consistent with the previous findings, the patient's fibroblasts and ARH3-deficient mice were more sensitive, respectively, to H2O2 stress and cerebral ischemia/reperfusion-induced PAR accumulation and cell death. Further, PARP1 inhibition alleviated cell death and injury resulting from oxidative stress and ischemia/reperfusion. PARP1 inhibitors may attenuate the progression of neurodegeneration in affected patients with ARH3 deficiency.
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PMID:PARP1 inhibition alleviates injury in ARH3-deficient mice and human cells. 3083 Aug 64


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