Abstract 11926: Selective Inhibition of Rho Kinase 2 Limits No Re-Flow in Rat Hearts Following Ischemia/Reperfusion

Abstract

Introduction: Myocardial infarction causes several types of injury to the myocardium including lethal cell injury and ‘no-reflow’ (NRF) /microvascular obstruction (MVO). Nonselective Rho Kinase (ROCK1/2) inhibitors such as Fasudil, ameliorate myocardial ischemia/reperfusion (I/R) injury but cause unwanted hypotension. Selective ROCK2 inhibitors (e.g.: KD025) are safe in clinical trials without causing haemodynamic compromise, however they have not been investigated in myocardial I/R. ROCK inhibitors prevent vascular smooth muscle cell (VSMC) contraction; such VSMC contraction/coronary spasm being features of ‘no-reflow’ (NRF) and microvascular obstruction (MVO). At present, there are limited therapies to improve ischemic MVO outcomes, and prognosis is poor. Hypothesis: Using a rat model, we hypothesised that, i) ROCK2 mRNA is expressed in myocardium and coronary vasculature and ii) The selective ROCK2 inhibitor KD025, would reduce infarct size (IS%) and NRF% (MVO) following I/R. Methods: RNA scope in-situ hybridisation was performed with a fluorescent, multiplex assay for ROCK1/2 & VSMC mRNA in myocardium and coronary vasculature. Male SD rats underwent in-vivo myocardial infarction with 30min ischemia, 180min reperfusion. 15min prior to reperfusion, the ROCK inhibitors Fasudil and KD025 or vehicle (DMSO) were administered i.p. For IS%, myocardium was stained with TTC, and regions not perfused with 1.5% Thioflavin S (NRF%), were visualised under UV light. Results: RNAscope confirmed the presence of ROCK2 mRNA within myocardium and VSMC of coronary arteries. Fasudil ( 10mg/kg ) vs control significantly reduced regional IS% ( 30.3 ± 4.4 vs 52.9 ± 3.8 , p=0.02, n=15 ) and area of NRF% ( 12.4 ± 2.8 vs 28.6 ± 2.2 , p=0.001, n=15 ). However, there was significant hypotension;- Mean BP (mmHg) (72±3.9) vs control (84±2.3, p=0.007 ). KD025 ( 100mg/kg) did not reduce IS%, but significantly reduced the area of NRF% vs control ( 18.4 ± 2.8 vs 28.6 ± 2.2, p=0.02, n=14 ) without hypotensive effect. Conclusions: Our results suggest that ROCK2 may be a prospective target in the management of coronary circulation reperfusion injury and ischemic MVO.