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EN
Adenosine-5'triphosphate (ATP) is stored and co-released with various neurotransmitters but it may also act as a fast excitatory neurotransmitter trough the activation of purinoreceptor(s).In this study the effcet of ATP on phospholipase C (PLC) degrading labelled PtdIns(4,5)P2 and PtdIns in brain cortex slices, brain homogente and subcellular fractions was investigated.It was found the ATP added into brain slices activated significantly and specifically PtdIns(4,5)P2 degradation and this process was inhibited by theophylline.Moreover, ATP maintained a higher level of inositol(1,4,5,)P3 radioactivity in total water-soluble inositol metabolites.However, ATP added directly for the assay of PLC into brain homogenate of subcellular fractions inhibits phosphoinositide degradation in a eceptor-independend manner and suppresses conversion of Ins(1,4,5)P3 into Ins(1,4)P2.Our results indicate that ATP acting extracellularly through a purinergic receptor(s) activates PtdIns(4,5)P2 degradation and release of Ins(1,4,5)P3.ATP acting directly on PLC inhibits in a receptor-independent manner phosphoinositide degradation, and protect against liberation of lipid-derived second messengers.
EN
Poly(ADP-ribose) polymerase-1 (PARP-1; EC 2.4.2.30), also termed as poly(ADP-ribose) synthetase, is a key enzyme in the recognition and repair of damaged DNA. Several conditions (e.g., ischemia-reperfusion or chemical-induced injury) have been shown to overactivate PARP-1, causing neurodegeneration and necrotic or apoptotic cell death from NAD+ and ATP depletion. In contrast, inhibitors of PARP-1 have been shown to have a neuroprotective effect by ameliorating this response. The purpose of this study was to determine the effects of three routinely used organic solvents (ethanol, methanol, and dimethyl sulfoxide (DMSO)) on the activity of purified PARP-1. A dose-response was examined with each of these solvents. A 112% and 82% increase in PARP-1 activity was observed with 15% ethanol and 20% methanol, respectively. In contrast, a near 20% decrease in the activity was observed with 4% DMSO. Kinetic analysis revealed that the maximal velocity remained unchanged with increasing concentrations of DMSO up to 20%, indicating that DMSO is a competitive inhibitor of PARP-1. Thus, PARP-1 inhibition by DMSO depends on NAD+ concentration and in some pathological processes might be significant even at low DMSO concentrations. Our findings suggest that the interpretation of data from dose-response studies obtained when using common organic solvents may be dramatically skewed, either exaggerating the inherent toxicity of the compound or masking its potential for damage.
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