Abstract
Calcium flux into and out of the sarco(endo)plasmic reticulum is vitally important to cardiac function because the cycle of calcium entry and exit controls contraction and relaxation. Putative estrogen and androgen consensus binding sites near to a CpG island are present in the cardiac calsequestrin 2 (CSQ2) promoter. Cardiomyocytes express sex hormone receptors and respond to sex hormones. We hypothesized that sex hormones control CSQ2 expression in cardiomyocytes and so affect cardiac structure/function. Echocardiographic analysis of male and female C57bl6n mice identified thinner walled and lighter hearts in females and significant concentric remodeling after long-term gonadectomy. CSQ2 and sodium-calcium exchanger-1 (NCX1) expression was significantly increased in female compared with male hearts and decreased postovariectomy. NCX1, but not CSQ2, expression was increased postcastration. CSQ2 expression was reduced when H9c2 cells were cultured in hormone-deficient media; increased when estrogen receptor-α (ERα), estrogen receptor-β (ERβ), or androgen agonists were added; and increased in hearts from ERβ-deficient mice. CSQ2 expression was reduced in mice fed a diet low in the methyl donor folic acid and in cells treated with 5-azadeoxycytidine suggesting an involvement of DNA methylation. DNA methylation in CpG in the CSQ2 CpG island was significantly different in males and females and was additionally changed postgonadectomy. Expression of DNA methyltransferases 1, 3a, and 3b was unchanged. These studies strongly link sex hormone-directed changes in CSQ2 expression to DNA methylation with changed expression correlated with altered left ventricular structure and function.