MicroRNA-210 suppresses glucocorticoid receptor expression in response to hypoxia in fetal rat cardiomyocytes

Hypoxia is a common intrauterine stressor, often resulting in intrauterine growth restriction and increased risk for cardiovascular disease later in life. The aim of this work was to test the hypothesis that microRNA-210 (miR-210) mediates the detrimental suppression of glucocorticoid receptor (GR) in response to hypoxia in fetal rat cardiomyocytes. Cardiomyocytes isolated from gestational day 21 Sprague Dawley fetal rats showed increased miR-210 levels and reduced GR abundance after exposure to ex vivo hypoxia (1% O2). In regard to mechanisms, the different contributions of hypoxia response elements (HREs) motifs in the regulation of miR-210 promoter activity and the miR-210-mediated repression of GR expression were determined in rat embryonic heart-derived myogenic cell line H9c2. Moreover, using a cell culturebased model of hypoxia-reoxygenation injury, we assessed the cytotoxic effects of GR suppression under hypoxic conditions. The results showed that hypoxia induced HIF-1a-dependent miR-210 production, as well as miR-210-mediated GR suppression, in cardiomyocytes. Furthermore, inhibition or knockdown of GR exacerbated cell death in response to hypoxia-reoxygenation injury. Altogether, the present study demonstrates that the HIF-1a-dependent miR-210-mediated suppression of GR in fetal rat cardiomyocytes increases cell death in response to hypoxia, providing novel evidence for a possible mechanistic link between fetal hypoxia and programming of ischemic-sensitive phenotype in the developing heart.