Abstract 4129974: Increased Expression of Histone Deacetylases-2 and -6 in Left Ventricular Myocardium of Dogs with Chronic Heart Failure

Background: Histone deacetylases (HDACs) -2 and -6 are localized in the nucleus and cytoplasm of cells and have been implicated in the development of left ventricular (LV) hypertrophy, cardiac interstitial fibrosis, inflammation and worsening of LV systolic and diastolic function thus contributing to progressive worsening of heart failure (HF) with reduced ejection fraction (HFrEF) as well as HF with preserved ejection fraction (HFpEF). There is considerable interest in the application of small molecules that inhibit the activity of HDAC proteins in HF in the hope of fostering clinical benefit. Purpose: In the present study we examined the expression of HDAC-2 and -6 in LV tissue from normal (NL) dogs and dogs with chronic HF (LVEF <35%) produced by multiple sequential intracoronary microembolizations. Methods: Studies were performed in LV tissue from 7 NL dogs and 7 HF dogs. HDAC-2 and -6 protein levels were determined by Western blotting in the lysate of homogenate and 9000g supernatant (cytosolic) fractions prepared from powder of approximately 200 mg frozen LV tissue. After determining the protein by Lowry method, approximately 30 μg homogenate and 15 μg supernatant for HDAC-2 and 8 μg protein for both homogenate and supernatant for HDAC-6 were separated on 4%-20% SDS-PAGE and transferred on PVDF membrane. Band intensities were quantified in densitometric units (du). All data were normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Results: HDAC-2 proteins levels normalized to GAPDH were higher in the cytosol (0.59 ± 0.10 vs. 0.17 ± 0.04, p<0.05 vs. NL) and homogenate (0.75 ± 0.12 vs. 0.55 ± 0.10, not statistically significant) of LV tissue of dogs with HF compared to NL dogs. HDAC-6 protein levels were higher in the homogenate (2.54 ± 0.36 vs. 0.57 ± 0.19, p<0.05 vs. NL) and the cytosol (0.96 ± 0.15 vs. 0.78 ± 0.13, not statistically significant) of LV tissue of dogs with HF compared to NL dogs. Conclusions: These findings indicate upregulation of protein levels of HDAC-2 and -6 isoforms in LV myocardium of dogs with chronic HF. These abnormalities are likely to contribute to worsening HF. Selective inhibition of HDAC-2 and -6 represents a potential therapeutic approach for the treatment of both HFrEF and HFpEF.