Protective effects of PJ34, a novel, potent inhibitor of poly(ADP-ribose) polymerase (PARP) in in vitro and in vivo models of stroke

Focal cerebral ischemia activates the nuclear protein poly(ADP-ribose) poly merase (PARP) by single DNA strand breaks which leads to energy depletion a nd cell necrosis. Deletion or inhibition of PARR protects against ischemic brain injury. Here we examined the neuroprotective effect of PJ34, a novel potent inhibitor of PARP in vitro and in vivo. Serum-free primary neuronal cultures derived from rat cortex (E15-17) and kept in culture for 10 days w ere exposed to oxygen glucose deprivation (OGD) in vitro. Neuronal injury w as quantified by LDH release after 24 h. Pretreatment with 30-1000 nM PJ34 significantly protected from OGD-induced cell injury in a dose-dependent ma nner. For in vivo experiments SV/129 mice were treated with PJ34 (50 mug) b y intraperitoneal injection 2 h before 1 h middle cerebral artery occlusion (MCAo) and again 6 h later. Twenty-three h after reperfusion ischemic inju ry was significantly decreased compared to vehicle-treated controls (infarc t volume reduction of 40%, p<0.05). Similarly, in a rat model of MCAo (2 h occlusion followed by up to 22 h reperfusion), PJ34 administration (10 mg/k g i.v.) significantly reduced infarct size, and the effect of the drug was maintained even if it was given as late as 10 min prior to reperfusion time . PJ34 significantly protected in a 4 h, but not in a 24 h permanent occlus ion model. In conclusion, PJ34, a novel, potent inhibitor of PARP exerts ma ssive neuroprotective agents, with a significant therapeutic window of oppo rtunity. The present work strengthens the concept that pharmacological PARP inhibition may be a suitable approach for the treatment of acute stroke in man.