Binhai Cong1, Xiaoyan Zhu, Buqing Cao, Jian Xiao, Zhinong Wang, Xin Ni. 1. Department of Physiology and The Key Laboratory of Molecular Neurobiology of Ministry of Education, Second Military Medical University, Shanghai 200433, PR China.
Abstract
BACKGROUND: The mechanism underlying estrogen cardioprotection remains largely unknown. Urocortin (UCN), a member of corticotropin-releasing hormone (CRH) family, is one of endogenous cardioprotective factors. The goal of present study is to investigate whether estrogens regulate UCN and its receptor CRH receptor type 2 (CRHR2) in female rat heart. METHODS: 17β-estradiol (E2) was subcutaneously administrated to ovariectomized (OVX) rats for eight weeks. UCN was administrated before simulated myocardial ischemia/reperfusion (I/R). Cell damage was assessed by measurement of infarct size, activity of serum creatine kinase (CK) and lactate dehydrogenase (LDH) and percentage of TUNEL staining in myocardium. The mRNA and protein levels of UCN and CRHR2 were determined in sham operated and OVX rats with or without E2 replacement. DNA methylation frequency of CRHR2 gene promoter was determined by bisulfite-sequencing. RESULTS: UCN administration reduced infarct size, LDH and CK level and percentage of TUNEL staining upon I/R injury. The cardioprotective effects of UCN were abrogated in OVX rats and E2 replacement restored UCN-induced cardioprotection.CRHR2 mRNA and protein expression were down-regulated more than 40% in OVX rats, both of which were restored by E2 replacement. UCN mRNA and protein levels were not affected by ovariectomy and E2 replacement. Hypermethylation in CRHR2 promoter was found in OVX rats, and two of the methylated CpG sites were seated at cis-acting elements. Hypermethylation induced by OVX could also be ameliorated by E2 replacement. CONCLUSION: Estrogens maintain CRHR2 expression in myocardium, which may through an epigenetic mechanism, and enhance UCN-induced cardioprotective effects against I/R injury.
BACKGROUND: The mechanism underlying estrogen cardioprotection remains largely unknown. Urocortin (UCN), a member of corticotropin-releasing hormone (CRH) family, is one of endogenous cardioprotective factors. The goal of present study is to investigate whether estrogens regulate UCN and its receptor CRH receptor type 2 (CRHR2) in female rat heart. METHODS: 17β-estradiol (E2) was subcutaneously administrated to ovariectomized (OVX) rats for eight weeks. UCN was administrated before simulated myocardial ischemia/reperfusion (I/R). Cell damage was assessed by measurement of infarct size, activity of serum creatine kinase (CK) and lactate dehydrogenase (LDH) and percentage of TUNEL staining in myocardium. The mRNA and protein levels of UCN and CRHR2 were determined in sham operated and OVXrats with or without E2 replacement. DNA methylation frequency of CRHR2 gene promoter was determined by bisulfite-sequencing. RESULTS:UCN administration reduced infarct size, LDH and CK level and percentage of TUNEL staining upon I/R injury. The cardioprotective effects of UCN were abrogated in OVXrats and E2 replacement restored UCN-induced cardioprotection.CRHR2 mRNA and protein expression were down-regulated more than 40% in OVXrats, both of which were restored by E2 replacement. UCN mRNA and protein levels were not affected by ovariectomy and E2 replacement. Hypermethylation in CRHR2 promoter was found in OVXrats, and two of the methylated CpG sites were seated at cis-acting elements. Hypermethylation induced by OVX could also be ameliorated by E2 replacement. CONCLUSION: Estrogens maintain CRHR2 expression in myocardium, which may through an epigenetic mechanism, and enhance UCN-induced cardioprotective effects against I/R injury.