Activation of Histone Deacetylase-6 (HDAC6) Induces Contractile Dysfunction through Derailment of α-Tubulin Proteostasis in Experimental and Human Atrial Fibrillation
Background—Atrial Fibrillation (AF) is characterized by structural remodeling, contractile dysfunction and AF progression. HDACs influence acetylation of both histones and cytosolic proteins, thereby mediating epigenetic regulation and influencing cell proteostasis. As the exact function of HDACs in AF is unknown, we investigated their role in experimental and clinical AF models.
Methods and Results—Tachypacing of HL-1 atrial cardiomyocytes and Drosophila pupae hearts significantly impaired contractile function (amplitude of Ca2+ transients (CaT) and heart wall contractions). This dysfunction was prevented by inhibition of HDAC6 (tubacin) and sirtuins (nicotinamide). Tachypacing induced specific activation of HDAC6, resulting in α-tubulin deacetylation, depolymerization and degradation by calpain. Tachypacing-induced contractile dysfunction was completely rescued by dominant negative HDAC6 mutants with loss of deacetylase activity in the second catalytic domain, which bears α-tubulin deacetylase activity (TDAC). Further, in vivo treatment with the HDAC6 inhibitor tubastatin A protected atrial tachypaced dogs from electrical remodeling (APD shortening, L-type Ca2+ current reduction, AF promotion) and cellular Ca2+-handling/contractile dysfunction (loss of CaT amplitude, sarcomere contractility). Finally, atrial tissue from patients with AF also showed a significant increase in HDAC6 activity and reduction in the expression of both acetylated and total α-tubulin.
Conclusions—AF induces remodeling and loss of contractile function, at least in part through HDAC6 activation and subsequent derailment of α-tubulin proteostasis and disruption of the cardiomyocyte microtubule structure. In vivo inhibition of HDAC6 protects against AF-related atrial remodeling, disclosing the potential of HDAC6 as a therapeutic target in clinical AF.
- Received August 2, 2013.
- Revision received October 2, 2013.
- Accepted October 10, 2013.