Neuroprotective effects of a novel water-soluble poly(ADP-ribose) polymerase-1 inhibitor, MP-124, in in vitro and in vivo models of cerebral ischemia

Cerebral ischemia induces excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), leading to neuronal cell death and the development of post-ischemic dysfunction. Blockade of PARP-related signals during cerebral ischemia has become a focus of interest as a new therapeutic approach for acute stroke treatment. The purpose of the present study was to examine the pharmacological profiles of MP-124, a novel water-soluble PARP-1 inhibitor, and its neuroprotective effects on ischemic injury in vitro and in vivo. MP-124 demonstrated competitive inhibition of the PARP-1 activity of human recombinant PARP-1 enzyme (Ki = 16.5 nmol/L). In P388D1 cells, MP-124 inhibited the LDH leakage induced by H2O2 in a concentration-dependent manner. (IC50 = 20.8 nmol/L). In rat primary cortical neurons, MP-124 also inhibited the NAD depletion and polymerized ADP-ribose formation induced by H2O2 exposure. Moreover, we investigated the neuroprotective effects of MP-124 in rat permanent and transient stroke models. In the rat permanent middle cerebral artery occlusion (MCAO) model, MP-124 was administered intravenously for 24 h from 5 min after the onset of MCAO. MP-124 (1, 3 and 10 mg/kg/h) significantly inhibited the cerebral infarction in a dose-dependent manner (18, 42 and 48%). In rat transient MCAO model, MP-124 was administered intravenously from 30 min after the onset of MCAO. MP-124 (3 and 10 mg/kg/h) significantly reduced the infarct volume (53% and 50%). The present findings suggest that MP-124 acts as a potent neuroprotective agent in focal ischemia and its actions can be attributed to a reduction in NAD depletion and PAR formation.

Research highlights
► MP-124, a novel water-soluble PARP-1 inhibitor, competitively inhibited PARP-1 activity.
► MP-124 exhibited a neuroprotective effect in rat primary cortical neurons.
► MP-124 inhibited the cerebral infarction in rat permanent and transient stroke models.