Abstract 3576: Selective Inhibition Of Rho-kinase Type 2 In Ischemic Stroke

Abstract

Background and aims: Rho/Rho-associated protein kinase (ROCK) pathway plays a pivotal role in the pathogenesis of vascular diseases including stroke. Indeed, ROCK inhibitors improve cerebral blood flow in ischemic brain, and are neuroprotective in a variety of experimental ischemia models. Evidence suggests that ROCK type 2 (ROCK2) is more relevant in acute stroke treatment. We tested the neuroprotective efficacy and safety of a novel selective small-molecule ROCK2 inhibitor, SLx-2119, in ischemic stroke, and characterized the dose-response and therapeutic window. Methods and results: All experiments were conducted by a blinded investigator. Mice were anesthetized with isoflurane (2.5% induction, 1.2% maintenance, in 70% N2O/30% O2), and subjected to 1h transient middle cerebral artery occlusion (MCAO) using an intraluminal filament inserted via the external carotid artery. Regional CBF was monitored using a laser Doppler probed placed over the core MCA territory. Neurological deficits were assessed before sacrifice at 48h, using five-point grading. Indirect infarct volumes were calculated using 1mm-thick TTC-stained coronal sections. SLx-2119 (50-300 mg/kg) or vehicle was administered via orogastric gavage (in 0.4% methylcellulose) every 12h until 48h after reperfusion. When started 24h before MCAO (pre-ischemic treatment), SLx-2119 produced a dose-dependent decrease in infarct volume (37% decrease at 200 mg/kg and 26% decrease at 100 mg/kg) compared to vehicle treated group. Post-ischemic treatment with SLx-2119 (200 mg/kg) remained efficacious when initiated 1h (34% decrease in infarct volume) or 3h (21% decrease in infarct volume), but not 6h after MCAO, suggesting a therapeutic window between 3-6h after stroke onset in mice. SLx-2119 also improved neurological deficits, but did not alter CBF reduction in the ischemic core, systemic arterial pressure, pH or blood gas values, or mortality. Conclusions: These data suggest that selective ROCK2 inhibition improves tissue and neurological outcome in acute stroke, with an efficacy comparable to that previously reported for non-selective ROCK inhibitors. Unlike non-selective ROCK inhibitors, ROCK2 inhibition does not precipitate hypotension, an important dose-limiting side effect in acute stroke.