Cameron, B. A. | Search bioRxiv

bioRxiv2021

Mechano-arrhythmogenicity is enhanced during late repolarisation in ischemia and driven by a TRPA1-, calcium-, and reactive oxygen species-dependent mechanism

BackgroundCardiac dyskinesis in regional ischemia results in arrhythmias through mechanically-induced changes in electrophysiology ( mechano-arrhythmogenicity) that involve ischemic alterations in voltage-calcium (Ca2+) dynamics, creating a vulnerable period (VP) in late repolarisation. ObjectiveTo determine cellular mechanisms of mechano-arrhythmogenicity in ischemia and define the importance of the VP. Methods and ResultsVoltage-Ca2+ dynamics were simultaneously monitored in rabbit ventricular myocytes by dual-fluorescence imaging to assess the VP in control and simulated ischemia (SI). The VP was longer in SI than in control (146{+/-}7 vs 54{+/-}8ms; p<0.0001) and was reduced by blocking KATP channels with glibenclamide (109{+/-}6ms; p<0.0001). Cells were rapidly stretched (10-18% increase in sarcomere length over 110-170ms) with carbon fibres during diastole or the VP. Mechano-arrhythmogenicity, associated with stretch and release in the VP, was greater in SI than control (7 vs 1% of stretches induced arrhythmias; p<0.005) but was similar in diastole. Arrhythmias during the VP were more complex than in diastole (100 vs 69% had sustained activity; p<0.05). In the VP, incidence was reduced with glibenclamide (2%; p<0.05), by chelating intracellular Ca2+ (BAPTA; 2%; p<0.05), blocking mechano-sensitive TRPA1 (HC-030031; 1%; p<0.005), or by scavenging (NAC; 1%; p<0.005) or blocking reactive oxygen species (ROS) production (DPI; 2%; p<0.05). Ratiometric Ca2+ imaging revealed that SI increased diastolic Ca2{+/-} (+9{+/-}1%, p<0.0001), which was not prevented by HC-030031 or NAC. ConclusionIn ischemia, mechano-arrhythmogenicity is enhanced specifically during the VP and is mediated by ROS, TRPA1, and Ca2+.

physiology↗

bioRxiv2020

TRPA1 channels are a source of calcium-driven cardiac mechano-arrhythmogenicity

SUMMARY PARAGRAPHMaintenance of cardiac function involves a regulatory loop in which electrical excitation causes the heart to contract through excitation-contraction coupling (ECC),1 and the mechanical state of the heart directly affects its electrical activity through mechano-electric coupling (MEC).2 However, in pathological states such as acute ischaemia that alter early or late electro-mechanical coordination (i.e., disturbances in ECC or repolarisation-relaxation coupling, RRC), MEC may contribute to the initiation and / or sustenance of arrhythmias (mechano-arrhythmogenesis).3 The molecular identity of specific factor(s) underlying mechano-arrhythmogenesis in acute ischaemia, however, remain undefined.4 By rapid stretch of rabbit single left ventricular cardiomyocytes, we show that upon ATP-sensitive potassium channel-induced alterations of RRC, overall vulnerability to mechano-arrhythmogenesis is increased, with mechano-sensitive5-11 transient receptor potential kinase ankyrin 1 (TRPA1) channels12 acting as the molecular driver through a Ca2+-mediated mechanism. Specifically, TRPA1 activation drives stretch-induced excitation and creates a substrate for self-sustained arrhythmias, which are maintained by increased cytosolic free Ca2+ concentration ([Ca2+]i) and spontaneous [Ca2+]i oscillations. This TRPA1-dependent mechano-arrhythmogenesis involves microtubules, and can be prevented by block of TRPA1 or buffering of [Ca2+]i. Thus, in cardiac pathologies with disturbed RRC dynamics and / or augmented TRPA1 activity, TRPA1 may represent an anti-arrhythmic target with untapped therapeutic potential.13-17

physiology↗