Abstract 10213: Acute Protein Kinase C Beta Inhibition Preserves Coronary Endothelial Function After Cardioplegic Hypoxia/Reoxygenation

Abstract

Introduction: Cardioplegic ischemia and reperfusion (CP-I/R) or CP-hypoxia and reoxygenation (CP-H/R) are associated with protein kinase C (PKC) overexpression/activation and coronary endothelial dysfunction. Hypothesis: This study aimed to determine whether acute inhibition of PKC could protect against CP-H/R-induced coronary endothelial dysfunction. Methods: Isolated small coronary arteries from mice (n = 6/group, male and female) were subjected to hyperkalemic, cardioplegic hypoxia (1 hour) and reoxygenation (1 hour) with Krebs buffer. The vessels undergoing CP-H/R were divided into 2 groups: those treated with the selective PKCβ inhibitor Ruboxistaurin (RBX, 50 nM, CP-H/R + RBX group) 5 minutes before and during CP-H/R, and those that received no treatment. Sham control vessels were continuously perfused with oxygenated Krebs buffer without CP-H/R and drug treatment. Vascular reactivity was measured by vessel myography. At the end of 1-hour re-oxygenation, all vessels were pretreated with endothelin-1; then, responses to the endothelium-dependent, NO-mediated vasodilator adenosine-diphosphate (ADP) and the endothelium-dependent/SK channel activator NS309 were examined. Results: CP-H/R caused a significant decrease in the coronary relaxation response to the endothelium-dependent, NO-mediated vasodilator ADP (10 - 4 M, * P =0.006) and the SK channel activator NS309 (10 -5 M, * P =0.0001) as compared with the Sham control group. Treatment with the selective PKCβ inhibitor RBX significantly increased the recovery of coronary relaxation responses to ADP ( # P = 0.031) and NS309 ( # P =0.004) compared with the untreated CP-H/R group (Figure). Conclusion: Acute inhibition of PKCβ significantly improved the recovery of coronary endothelial function after a period of CP-H/R injury in the mouse coronary microvasculature, suggesting that acute PKCβ inhibition may be a novel approach for protecting coronary endothelial function during CP-H/R.