3-4-dihydro-5-(4-(1-piperidinyl)butoxy)-1(2h)-isoquinolinone and Hypoxia

Poly(ADP-ribose) polymerase-1 (PARP-1) is a nuclear protein that once activated by genotoxic agents, modulates its own activity and that of several other nuclear proteins. The absence or pharmacological inhibition of this protein has been proven to be beneficial in the treatment of different diseases involving a hypoxic situation. We previously reported that PARP-1 modulates the hypoxia-inducible factor-1 (HIF-1) response in vitro, but this effect has not yet been demonstrated in vivo. The brain is especially susceptible to hypoxic injury, and the present study demonstrates that PARP-1 plays a major role in the post-hypoxic response of HIF-1alpha in the cerebral cortex. Immediate post-hypoxic HIF-1alpha accumulation was higher in the presence of PARP-1, and this differential response was mediated by nitric oxide and to a lesser extent, reactive oxygen species. PARP-1 was also found to induce a more rapid but less sustained HIF-1 transcriptional activity by up-regulating the factor inhibiting HIF. The implication of PARP-1 in these results was further demonstrated by pharmacologically inhibiting PARP in wild-type mice. In conclusion, our data suggest that PARP-1 has an important regulatory role in the in vivo response of brain HIF-1 to hypoxia/reoxygenation.

Topics: Analysis of Variance; Animals; Antipyrine; Brain; Disease Models, Animal; Edaravone; Enzyme Inhibitors; Excitatory Amino Acid Transporter 2; Free Radical Scavengers; Gene Expression Regulation; Hypoxia; Hypoxia-Inducible Factor 1; Isoquinolines; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nitric Oxide; Oxidative Stress; Oxygen; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; RNA, Messenger; Thiobarbituric Acid Reactive Substances

Group I metabotropic glutamate (mGlu) receptors (i.e. mGlu1 and mGlu5) coupled to phospholipase C have been widely investigated for their possible role in excitotoxic and post-ischemic neuronal death. Recently, phospholipase C has been shown to directly stimulate the activity of poly(ADP-ribose) polymerase (PARP), a nuclear enzyme involved in DNA repair that has been proposed to play a key role in necrotic cell death. In this study, we investigated whether the stimulation of group I mGlu receptors leads to an increase in PARP activity, as detected by flow cytometry, immunodot blot and immunocytochemistry, both in baby hamster kidney cells transfected with mGlu1a or mGlu5a receptors and in cultured cortical cells. Our results show that the group I mGlu receptor agonist DHPG elicited a significant increase in PARP activity that was completely abolished by the administration of the mGlu1 antagonist 3-MATIDA and partially prevented, in cortical neurons, by the mGlu5 antagonist MPEP. To evaluate whether this pathway is involved in post-ischemic neuronal death, we used a sublethal model of oxygen-glucose deprivation in mixed cortical cell cultures. DHPG exacerbated neuronal death, and this effect was significantly prevented by the application of the PARP inhibitor DPQ. This novel pathway may contribute to the effects of mGlu1 receptors in the mechanisms leading to post-ischemic neuronal death.

Topics: Animals; Animals, Newborn; Blotting, Western; Cells, Cultured; Cerebral Cortex; Cricetinae; Drug Interactions; Enzyme Activation; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Fluorescent Antibody Technique; Gene Expression Regulation, Enzymologic; Glial Fibrillary Acidic Protein; Glucose; Hydrogen Peroxide; Hypoxia; Isoquinolines; Methoxyhydroxyphenylglycol; Mice; Neuroglia; Neurons; Piperidines; Poly(ADP-ribose) Polymerases; Pyridines; Receptors, Metabotropic Glutamate; Thiophenes; Time Factors; Transfection