Sex-specific regulation of cardiac microRNAs targeting mitochondrial proteins in pressure overload.

BACKGROUND: Maladaptive remodeling in pressure overload (PO)-induced left ventricular hypertrophy (LVH) may lead to heart failure. Major sex differences have been reported in this process. The steroid hormone 17ß-estradiol, along with its receptors ERα and ERß, is thought to be crucial for sex differences and is expected to be protective, but this may not hold true for males. Increasing evidence demonstrates a major role for microRNAs (miRNAs) in PO-induced LVH. However, little is known about the effects of biological sex and ERß on cardiac miRNA regulation and downstream mitochondrial targets. We aimed at the analysis of proteins involved in mitochondrial metabolism testing the hypothesis that they are the target of sex-specific miRNA regulation. METHODS: We employed the transverse aortic constriction model in mice and assessed the levels of five mitochondrial proteins, i.e., Auh, Crat, Decr1, Hadha, and Ndufs4. RESULTS: We found a significant decrease of the mitochondrial proteins primarily in the male overloaded heart compared with the corresponding control group. Following computational analysis to identify miRNAs putatively targeting these proteins, our in vitro experiments employing miRNA mimics demonstrated the presence of functional target sites for miRNAs in the 3'-untranslated region of the messenger RNAs coding for these proteins. Next, we assessed the levels of the functionally validated miRNAs under PO and found that their expression was induced only in the male overloaded heart. In contrast, there was no significant effect on miRNA expression in male mice with deficient ERß. CONCLUSION: We put forward that the male-specific induction of miRNAs and corresponding downregulation of downstream protein targets involved in mitochondrial metabolism may contribute to sex-specific remodeling in PO-induced LVH.

Sex- and estrogen-dependent regulation of a miRNA network in the healthy and hypertrophied heart.

BACKGROUND: In pressure overload, profibrotic gene expression and cardiac fibrosis are more pronounced in males than in females. Sex-specific and estrogen-dependent regulation of microRNAs (miRNAs), such as miR-21, may be a potential mechanism leading to sex differences in fibrosis. OBJECTIVES: To analyze the influence of sex, estrogen, and estrogen receptor beta (ERß) on the expression of miR-21 and to identify additional miRNAs potentially involved in sex-specific pressure overload-induced cardiac remodeling. METHODS: The sex-specific regulation of fibrosis-related miRNAs was analyzed in male and female wild type and ERß-deficient mice after transverse aortic constriction (TAC), in rat fibroblasts, and in a cardiomyocyte-like cell line. RESULTS: We report the sex-specific expression of functionally-related miR-21, -24, -27a, -27b, 106a, -106b and the regulation of their expression by estrogen in a sex-specific manner. These effects were abolished in ERß-deficient mice. We demonstrate the presence of common functional target sites for these miRNAs on three repressors of the mitogen-activated protein kinase signaling pathway, i.e. Rasa1, Rasa2 and Spry1, which may all lead to cardiac fibrosis. As expected, transfection with miRNA mimics targeting these repressors induced ERK1/2 phosphorylation. CONCLUSIONS: Estrogen regulates a network of miRNAs in a sex-specific manner via ERß. Our data suggest that the sex-specific expression of these miRNAs may be related to sex differences in fibrosis after pressure overload.