Basic/Translational Science -> Cell Physiology, Pharmacology, and Signaling D-AB20 - New Mechanistic Insights on Arrhythmia Initiation and Perpetuation (ID 40) Abstract

D-AB20-01 - Cellular Mechano-arrhythmogenicity Is Enhanced By Activation Of TRPA1 Channels Via A Calcium-mediated Mechanism (ID 782)

Disclosure
 B.A. Cameron: Nothing relevant to disclose.

Abstract

Background: Despite the lethality of ventricular arrhythmias, effective drug therapies are limited, in part due to off-target effects. As disease-associated changes in tissue mechanics are pro-arrhythmic, stretch-induced effects on voltage or Ca2+ may represent novel anti-arrhythmic targets with benign secondary effects.
Objective: Determine cellular mechanisms of mechano-arrhythmogenicity during pathologic alterations of voltage-Ca2+ dynamics.
Methods: Isolated LV myocytes from rabbit (female, NZW) were paced at 1 Hz and superfused with physiologic or pinacidil-containing solution to cause KATP-channel activation. Cells were rapidly stretched (20-40 µm, 100 ms) during diastole or late repolarization using carbon fibers. Pharmacology was used to buffer Ca2+ (1 µM BAPTA), stabilize ryanodine receptors (1 µM dantrolene), block stretch-activated channels (50 µM streptomycin), or block (10 µM HC-030031) or activate (10 µM AITC) stretch-sensitive TRPA1 channels. Voltage-Ca2+ was simultaneously monitored using di-4-ANBDQPQ (20 µM) and Fluo-5F (5 µM) with a single EMCCD camera-optical splitter system. Diastolic Ca2+ was measured using Fura Red (5 µM).
Results: Pinacidil caused a greater shortening of the cellular action potential than Ca2+ transient (-144±17 vs -74±11 ms; n=24 cells, N=7 rabbits; p<0.001). Stretch of these cells caused arrhythmias (ectopy and sustained activity) in both diastole and late repolarization (8 and 10% of stretches; n=46, N=5), which voltage-Ca2+ imaging demonstrated were Ca2+-driven. Arrhythmias were reduced in both diastole and late repolarization with BAPTA (3 and 0%; p<0.05), streptomycin (4 and 2%; p<0.05), and HC-030031(2 and 1%; p<0.01), while dantrolene had no effect (5 and 6%; n=40, N=5 for each). AITC alone increased stretch-induced arrhythmias in diastole (15%; n=40; N=5; p<0.001), which was blocked by HC-030031 (4%; n=40, N=5; p<0.001). Pinacidil or AITC caused an increase in diastolic Ca2+ (78±29 and 112±29%; n=25, N=5 each).
Conclusion: Activation of TRPA1 enhances cellular mechano-arrhythmogenicity via a Ca2+-mediated mechanism, which is independent of stretch timing. TRPA1 may represent a novel anti-arrhythmic target in pathologies involving altered mechanics and Ca2+ dynamics.
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