Abstract 14409: TRPA1 Channels Are a Source of Calcium-driven Cellular Mechano-arrhythmogenicity

Abstract

Introduction: Pathologic changes in myocardial mechanics and hemodynamic load result in arrhythmias via mechanically-induced changes in electrophysiology or intracellular Ca 2+ (‘mechano-arrhythmogenicity’). While molecular mechanisms driving mechano-arrhythmogenicity are poorly defined, they are associated with disease-related alterations in voltage-Ca 2+ dynamics. Objective: Define mechanisms of mechano-arrhythmogenicity during alterations in voltage-Ca 2+ dynamics in rabbit ventricular myocytes. Methods: Rabbit (♀, NZW) LV myocytes were transiently stretched (8-16% change in sarcomere length, 100ms) during diastole or late repolarisation in control or during K ATP channel activation (pinacidil). Drugs were used to buffer Ca 2+ (BAPTA), stabilise RyR (dantrolene), non-selectively block stretch-activated channels (streptomycin), or specifically block (HC-030031) or activate (AITC) mechano-sensitive TRPA1 channels. Voltage-Ca 2+ dynamics were simultaneously monitored with fluorescent dyes (di-4-ANBDQPQ, Fluo-5F) and a single camera-optical splitter system and diastolic Ca 2+ was measured using Fura Red. Results: Pinacidil caused greater shortening of the AP than Ca 2+ transient (-144±17 vs -74±11ms; n =24 cells, N =7 rabbits; p <0.001) with no change in cell stiffness or contractility. Stretch during pinacidil application caused arrhythmias in both diastole and late repolarisation (8 and 10% of stretches; n =46, N =5), which voltage-Ca 2+ imaging revealed were Ca 2+ -driven. Arrhythmias were reduced with BAPTA (3 and 0% of stretches; p <0.05), streptomycin (4 and 2%; p <0.05), and HC-030031(2 and 1%; p <0.01), while dantrolene had no effect ( n =40, N =5 for each). Stretch in diastole during AITC application also caused arrhythmias (15%; p <0.001), which were blocked by HC-030031 (4%; p <0.001) or BAPTA (3%; p <0.001; n =40, N =5 each). Both AITC and pinacidil caused an increase in diastolic Ca 2+ (112±29 and 78±29% of control; p<0.05), which was reduced by HC-030031 with AITC (26±24%; p <0.05), but not with pinacidil ( n =25, N =5 each). Conclusions: TRPA1 activation increases mechano-arrhythmogenicity via a Ca 2+ -driven mechanism and may represent a novel anti-arrhythmic target in pathologies involving altered cardiac mechanics.