Endocrine Abstracts

Inappropriately high secretion of aldosterone can lead to hypertension and its various cardiovascular consequences. We previously showed that microRNA (miRNA) plays a significant role in the regulation of aldosterone biosynthesis. In this study we measured miRNA levels in H295R cells, the most commonly-used human adrenocortical cell line, and investigated how these change in response to the stimulation of aldosterone biosynthesis.

H295R cells (n=3 per group) were stimulated with either 100 nM angiotensin II (AngII), 10 mM dibutyryl cyclic AMP (dbcAMP, to simulate ACTH effects) or 20 mM potassium chloride (KCl) for 24 h. Each treatment significantly increased aldosterone synthase (CYP11B2) mRNA relative to basal unstimulated cells. Microarray analysis also revealed significant and consistent changes in the quantities of specific miRNAs relative to basal levels: 20 miRNAs were differentially expressed in the AngII-treated cells, 68 in the dbcAMP-treated cells and 66 in the KCl-treated cells. Expression of 6 miRNAs was consistently altered across all three treatments, with the majority localising to one of two miRNA clusters located on either chromosome 13 or the X chromosome. Bioinformatic analysis with Ingenuity Pathway Analysis (IPA) software was used to predict mRNA targets for these six differentially-expressed miRNAs, but no direct effects on steroidogenic enzymes were identified. However, effects on various cholesterol-related genes, such as LDLR and ABCA1, were predicted. In conclusion, we have shown that consistent changes in miRNA profile result from various aldosterone-stimulating treatments in vitro. This includes a reduction in clustered miRNAs predicted to affect genes regulating cell cholesterol levels. This suggests a mechanism by which steroid biosynthesis could be affected and complements our results from aldosterone-producing adenoma (APA) tissue, which had consistent differences in miRNA profile relative to normal adrenal tissue. We now intend to investigate the impact of these miRNAs on cholesterol-related genes and corticosteroid biosynthesis.

Disclosure: Ministry of Education, Malaysia.