Abstract 4138062: Pharmacological inhibition of HDAC6 improves post-infarction cardiac function by limiting mitochondrial fission in type 2 diabetic mice

Introduction: Histone deacetylase (HDAC) 6 functions to remove acetyl groups from lysine residues on histone and non-histone proteins. We showed that the augmented activity of HDAC6 in diabetic mice undergoing myocardial ischemia/reperfusion injury (MIRI) was associated with mitochondrial damage. However, it remains unclear how the inhibition of HDAC6 activity affects post-MIRI cardiac remodeling and function in type 2 diabetes. Hypothesis: HDAC6 inhibition suppresses adverse cardiac remodeling and improves mitochondrial dynamics and cardiac function after MIRI in type 2 diabetic mice. Methods: Type 2 diabetic db/db, db/+, and C57BL/6 mice underwent coronary artery occlusion for 20 min followed by reperfusion. Tubastatin A, a selective inhibitor of HDAC6, was injected intraperitoneally 60 min before coronary artery occlusion and once daily after surgery. Mouse hearts were evaluated with echocardiography 28 days after surgery. Myocardium was imaged using electron microscopy, and the expression of mitochondrial dynamin-related protein 1 (DRP1) and fission 1 was measured by Western blotting analysis. H9c2 cardiomyocytes were subjected to hypoxia for 3 hours followed by normoxia for 24 hours in the presence of 5.5- or 25.0-mM D-dextrose and tubastatin A or vehicle. Results: There were no significant differences in the activity of HDAC6, left ventricular diameters and fractional shortening, mitochondrial density volume and surface area, and the ratios of DRP1/GAPDH and fission 1/GAPDH between the db/+ and C57BL/6 groups. Compared to both db/+ and C57BL/6 groups, HDAC6 activity was lower, left ventricular diameters at both end diastole and end systole were longer, fractional shortening and mitochondrial surface area were smaller, and the expression of DRP1 and fission 1 was increased in the db/db group 28 days after MIRI. Interestingly, 10 mg/kg Tubastatin A significantly mitigated these effects of MIRI in db/db mice. Hypoxia/reoxygenation in the presence of 25.0-mM D-dextrose augmented HDAC6 activity and increased the expression of DRP1 and FIS1, which were blocked by Tubastatin A. Conclusions: Tubastatin A prevents post-MIRI cardiac remodeling and improves cardiac function by limiting mitochondrial fission in type 2 diabetic mice.