Aging and estrogen-dependent HDAC2 regulation: implications in cardiac injury

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Project Summary The risk of cardiovascular disease (CVD) increases in females with aging and falling estrogen (E2) levels during menopause, yet the beneficial effects of postmenopausal hormone-replacement therapy (HRT) on reducing the risk remain controversial. Estrogen mediates its protective effects by inducing its receptor ERα binding to E2-target genes. Dysregulation of epigenetic enzymes like histone deacetylases (HDACs) are implicated in pathological aging and class I HDAC2 functions as a positive regulator of cardiac hypertrophy (CH) in response to stress. The long-term research goal is to contribute toward the development of clinically useful mechanism-based interventions to treating or preventing CVD in postmenopausal aging females. The overall objective for this R03 application is to establish proof of concept of age dependent E2/ERα signaling regulating HDAC2 expression in heart under physiological and pathophysiological conditions. The central hypothesis is that endogenous E2/ERα signaling is cardioprotective through the inhibition of HDAC2 expression in premenopausal females. The rationale underlying this project is that proof of concept of age- dependent E2/ERα-mediated repression of HDAC2 expression and cardio protection will enable subsequent definitive R01 studies aimed at designing strategies to treat or prevent heart diseases in aging females. The central hypothesis will be examined with 2 Specific Aims: 1) Identify age-dependent effects of E2/ER alpha on cardiac HDAC2 expression. Under this aim a) cultured human CM (HCM) isolated from normal male, pre and postmenopausal female ventricular heart tissue will be utilized to establish transcriptional repression of HDAC2 gene via actions of E2/ERα and (b) young and old female and male mice heart tissues will be utilized to determine age- and sex-dependent regulation of cardiac ERs and HDAC2 gene expression and activity by novel Droplet Digital PCR (ddPCR), molecular and biochemical techniques. 2) Determine the functional consequences of ovariectomy and E2 on cardiac function and regulation of HDAC2 expression/activity. In this aim, effects of E2 on HDAC2 repression will be studied in drug–induced CH in ovariectomized (young and aged) female mice by utilizing echocardiography, systolic blood pressure measurements, ELISA, histology, and gene expression studies. The research proposed in this application is innovative in the applicant's opinion, because it utilizes new ddPCR technique and studies a novel regulatory mechanism of E2/ERα-mediated HDAC2 repression at the transcription level in heart. This will lead to define new E2/ERα transcriptional target and its functional role in the heart of young and aging females. The proposed research is significant because it is expected to provide strong scientific justification for the continued research and development of combinatorial drug with E2 for aging females.