Modification of cardiac disease by transgenically altered histone deacetylase 6

Histone deacetylase 6 (HDAC6) is known to deacetylate amino acid lysine in alpha-tubulin. However, the functional role of HDAC6 in the progression of cardiac disease remains uncertain. The functional role of HDAC6 in the hearts was examined using transgenic (TG) mice expressing either human wild-type HDAC6, deacetylase inactive HDAC6 (HDAC6^{H216A, H611A}), and human HDAC6 replaced all serine or threonine residues with aspartic acid at N-terminal 1- 43 amino acids (HDAC6^NT-allD) specifically in the hearts. Overexpression of wild-type HDAC6 significantly reduced acetylated tubulin levels, and overexpression of HDAC6^{H216A, H611A} significantly increased it in the mouse hearts. Detectable acetylated tubulin disappeared in HDAC6^NT-allD TG mouse hearts. Neither histological alteration nor alteration of cardiac function was observed in the HDAC6 TG mouse hearts. To analyze the role of HDAC6 and acetylated tubulin in disease conditions, we examined HDAC6 in isoprenaline-induced hypertrophy or pressure-overload hypertrophy (TAC). No obvious alteration in the heart weight/body weight ratio or gene expressions of hypertrophic markers between NTG and HDAC6^NT-allD mice was observed following treatment with isoprenaline. In contrast, a marked reduction in the shortening fraction and dilated chamber dilatation was detected in the HDAC6^NT-allD TG mouse hearts 2 weeks after TAC. A sustained low level of acetylated tubulin and acetylated cortactin was observed in the TAC HDAC6^NT-allD TG mouse hearts. Cardiac HDAC6 activity that can regulate acetylated levels of tubulin and cortactin may be critical factors involved in cardiac disease such as pressure-overload hypertrophy.