Acute Inhibition Of Mitochondrial Reactive Oxidative Species Improves Endothelial Sk Channel Function Following Cardioplegic Hypoxia/Reperfusion And Diabetes

Introduction: Cardioplegic-ischemia/reperfusion (CP-I/R) and diabetes mellitus (DM) are correlated with coronary endothelial dysfunction and inactivated small conductance calcium-activated-potassium (SK) channels. Increased reactive oxidative species (ROS), such as mitochondrial ROS (mROS) may contribute to oxidative injury. Thus, we hypothesized that inhibition of mROS may protect coronary SK channels and endothelial function against CP-I/R-induced injury. Objective: A cardioplegic hypoxia and reoxygenation (CP-H/R) model consisting of coronary endothelial cells and small coronary arteries with or without DM were employed for examining whether MT could protect against coronary endothelial and SK channel dysfunction. Methods: Small coronary arteries (<150μm) and endothelial cells (MHECs) were dissected from the mouse heart with non-diabetes (ND) and DM (n=6/group). The microvessels or MHECs were subjected to hypoxia with cardioplegia and re-oxygenated. The microvessels or MHECs were treated with or without MT (10 -5 M) 5-minutes before and during CP-hypoxia. Microvascular vasodilation function was assessed in vitro by administration of vasoconstrictor, then ADP or NS309,respectively. K + currents of MHECs were measured by whole-cell patch clamp. The levels of endothelial mROS was measured by MitoSox TM . Results: CP-H/R significantly attenuated endothelial SK channels activity and the coronary relaxation responses to ADP and NS309 in the ND and DM groups. Treatment with MT enhanced coronary relaxation responses to ADP or NS309 ( p <0.05, Fig 1. A, B), and similar findings were seen in endothelial SK channel currents in both ND and DM MHECs ( p <0.05, Fig 1. C-F). In addition, treating MHECs with MT reduced CP-H/R-induced mROS in ND and DM groups. Conclusions: Administration of MT improves endothelial SK channels activity which may contribute to its enhancement of endothelium-dependent vasorelaxation following CP-H/R.