Hormonal Regulation of MicroRNA Expression in Steroid Producing Cells of the Ovary, Testis and Adrenal Gland

BACKGROUND Given the emerging roles of miRNAs as potential posttranscriptional/posttranslational regulators of the steroidogenic process in adrenocortical and gonadal cells, we sought to determine miRNA profiles in rat adrenals from animals treated with vehicle, ACTH, 17α-E2 or dexamethasone. Key observations were also confirmed using hormone (Bt2cAMP)-treated mouse Leydig tumor cells, MLTC-1, and primary rat ovarian granulosa cells. METHODOLOGY RNA was extracted from rat adrenal glands and miRNA profiles were established using microarray and confirmed with qRT-PCR. The expression of some of the hormone-sensitive miRNAs was quantified in MLTC-1 and granulosa cells after stimulation with Bt2cAMP. Targets of hormonally altered miRNAs were explored by qRT-PCR and Western blotting in adrenals and granulosa cells. RESULTS Adrenals from ACTH, 17α-E2 and dexamethasone treated rats exhibited miRNA profiles distinct from control animals. ACTH up-regulated the expression of miRNA-212, miRNA-182, miRNA-183, miRNA-132, and miRNA-96 and down-regulated the levels of miRNA-466b, miRNA-214, miRNA-503, and miRNA-27a. The levels of miR-212, miRNA-183, miRNA-182, miRNA-132, miRNA-370, miRNA-377, and miRNA-96 were up-regulated, whereas miR-125b, miRNA-200b, miR-122, miRNA-466b, miR-138, miRNA-214, miRNA-503 and miRNA27a were down-regulated in response to 17α-E2 treatment. Dexamethasone treatment decreased miRNA-200b, miR-122, miR-19a, miRNA-466b and miRNA27a levels, but increased miRNA-183 levels. Several adrenal miRNAs are subject to regulation by more than one hormone. Significant cAMP-induced changes in certain miRNAs were also noted in MLTC-1 and granulosa cells. Some of the hormone-induced miRNAs in steroidogenic cells were predicted to target proteins involved in lipid metabolism/steroidogenesis. We also obtained evidence that miR-132 and miRNA-214 inhibit the expression of SREBP-1c and LDLR, respectively. CONCLUSION Our results demonstrate that expression of a number of miRNAs in steroidogenic cells of the testis, ovary and adrenal glands is subject to hormonal regulation and that miRNAs and their regulation by specific hormones are likely to play a key role in posttranscriptional/posttranslational regulation of steroidogenesis.