Abstract 110: Anesthetic Preconditioning and Mitochondrial Slo K + Channel Activity Require Slo2.1

Abstract

Introduction: Volatile anesthetic preconditioning (APC) protects the heart from ischemia-reperfusion (IR) injury. APC elicits evolutionarily-conserved protective signaling pathways that converge at the mitochondrial level, where the Slo family of K + channels is thought to mediate protection through an unknown mechanism. Recent work in C. elegans has focused attention on the Slo2 gene product as a transducer of APC effects on hypoxic survival. In mammals, Slo2 has diverged into two paralogs, Slo 2.1 (KCNT2; Slick) and Slo2.2 (KCNT1; Slack). These genes code for Na + -activated K + channels and are highly expressed in brain, but their function in cardiomyocytes and/or mitochondria is unknown. Methods: The contribution of Slo channels to cardiac physiology was characterized using knockout mice, including Slo1 and two novel Slo2.x alleles. APC was assessed through ex-vivo cardiac IR injury. Isolated mitochondrial K + channel activity was assessed using a Tl + flux assay, and by patch-clamp of cardiac mitoplasts. Electron microscopy was used to assess mitochondrial morphology in primary cardiomyocytes and Seahorse extracellular flux analysis used to assess bioenergetics. Results: The Slo2.x ( double KO ) and the Slo2.1 single KO mice could not be protected from cardiac IR injury by APC. Physiologic approaches demonstrated that Slo2.1 is present in mitochondria and Slo2.1 -dependent mitochondrial K + transport can be triggered directly by volatile anesthetics. Cardiomyocytes from Slo2.x dKO mice exhibited profound metabolic remodeling and electron microscopy revealed that Slo2.1 knockouts had enlarged circular mitochondria. In contrast, Slo1 KO mice responded normally to APC and exhibited wild type mitochondrial physiology. Conclusion: Slo2.1 activation protects against cardiac IR, and is required for APC. Slo2.1 also contributes to mitochondrial metabolic homeostasis. As a molecular target for APC, identification of Slo2.1 may facilitate development of targeted therapeutic molecules that can protect the heart and minimize the side effects of volatile anesthetics.