Bile acids regulate SF-1 to alter cholesterol balance in adrenocortical cells via S1PR2

Abstract

Glucocorticoid synthesis typically occurs in adrenal cortex and is influenced by cholesterol balance, since cholesterol is the sole precursor of steroids. Bile acids as the signaling molecules, have been shown to promote steroidogenesis in steroidogenic cells. However, whether bile acids directly regulate cholesterol balance remains elusive. In this study, we prepared cholestatic mouse models and cultured human adrenocortical cells (H295R) treated with taurochenodeoxycholic acid (TCDCA) to determine transcription levels of cholesterol metabolism associated genes and cholesterol concentrations in adrenocortical cells. Results showed that common bile duct ligation (CBDL) and chenodeoxycholic acid (CDCA) feeding elevated the mRNA levels of Abca1, Cyp51, Hmgcr, Srb1, and Mc2r in adrenals of mice. Meanwhile, the concentrations of total cholesterol and cholesteryl ester in adrenals of CBDL and CDCA-fed mice were dramatically lowered. The total and phosphorylation levels of HSL in adrenal glands of CBDL mice were also enhanced. Similarly, TCDCA treatment in H295R cells decreased intracellular concentrations of total cholesterol and cholesteryl ester and increased transcription levels of SRB1, MC2R, and HSL as well. Inhibition of bile acids’ receptor sphingosine 1‐phosphate receptor 2 (S1PR2), extracellular signal‐regulated kinase (ERK) phosphorylation, and steroidogenic factor 1 (SF-1) respectively successfully abolished effect of TCDCA on H295R cells. SF-1s was found to be phosphorylated at Thr75 in TCDCA-treated H295R cells. While a mild increase of intracellular cAMP concentration was detected upon TCDCA treatment, inhibition of PKA activity with Rp-Isomer in H295R cells failed to decrease the expression of SF-1 and its target genes. Our findings suggest that conjugated bile acids affect cholesterol balance through regulation of SF-1 in adrenocortical cells so as to provide an adequate cholesterol supply for glucocorticoid synthesis, which improves and enriches our understanding of the mechanism whereby bile acids regulate cholesterol balance to affect adrenal function.