Histone Deacetylase Inhibition Reduces Pulmonary Vein Arrhythmogenesis through Calcium Regulation

- We studied the electrical effects of HDAC inhibitors on PV cardiomyocytes and AF inducibility in vivo.
- MPT0E014 (a pan HDAC inhibitor) reduced PV (but not SAN) cardiomyocytes spontaneous activity and AF inducibility.
- MPT0E014 changed PV arrhythmogenesis through class I HDAC inhibition.
- MPT0E014 decreased Ca2 + sparks and Ca2 + transients with reduced RyR2 and NCX protein expression.
- HDAC inhibition plays a critical role in PV arrhythmogenesis, which contributes to AF genesis.

Pulmonary veins (PVs) play a critical role in the pathophysiology of atrial fibrillation (AF). Histone deacetylases (HDACs) are vital to calcium homeostasis and AF genesis. However, the electrophysiological effects of HDAC inhibition were unclear. This study evaluated whether HDAC inhibition can regulate PV electrical activity through calcium modulation.Whole-cell patch-clamp, confocal microscopic with fluorescence, and Western blot were used to evaluate electrophysiological characteristics and Ca2 + dynamics in isolated rabbit PV cardiomyocytes with and without MPT0E014 (a pan HDAC inhibitor), MS-275 (HDAC1 and 3 inhibitor), and MC-1568 (HDAC4 and 6 inhibitor) for 5 ~ 8 h. Atrial electrical activity and induced-AF (rapid atrial pacing and acetylcholine infusion) were measured in rabbits with and without MPT0E014 (10 mg/kg treated for 5 hours) in vivo.MPT0E014 (1 μM)-treated PV cardiomyocytes (n = 12) had slower beating rates (2.1 ± 0.2 vs. 2.8 ± 0.1 Hz, p < 0.05) than control PV cardiomyocytes. However, control (n = 11) and MPT0E014 (1 μM)-treated (n = 12) SAN cardiomyocytes had similar beating rates (3.2 ± 0.2 vs. 2.9 ± 0.3 Hz). MS-275-treated PV cardiomyocytes (n = 12, 2.3 ± 0.2 Hz), but not MC-1568-treated PV cardiomyocytes (n = 14, 3.1 ± 0.3 Hz) had slower beating rates than control PV cardiomocytes. MPT0E014-treated PV cardiomyocytes (n = 14) had a lower frequency (2.4 ± 0.6 vs. 0.3 ± 0.1 spark/mm/s, p < 0.05) of Ca2 + sparks than control PV (n = 17) cardiomyocytes. As compared to control, MPT0E014-treated PV cardiomyocytes had reduced Ca2 + transient amplitudes, sodium-calcium exchanger currents, and ryanodine receptor expressions. Moreover, MPT0E014-treated rabbits had less AF and shorter AF duration than control rabbits.In conclusions, HDAC inhibition reduced PV arrhythmogenesis and AF inducibility with modulation on calcium homeostasis.