SAT267 BMP4, GDF11 And TGFβ2 Repress Adrenal Cell Cortisol Production By Blocking CYP17A1 And CYP11B1 Expression

Disclosure: E.C. Fischbach: None. A. Lopez: None. M. Ullenbruch: None. J. Rege: None. W.E. Rainey: None. Introduction: The adrenal cortex is responsible for the biosynthesis of multiple steroid hormones that regulate electrolyte and carbohydrate balance. Cortisol, the principal glucocorticoid in humans, is primarily produced in the middle zone of the cortex known as the zona fasciculata (ZF). The enzymes responsible for cortisol biosynthesis include cytochrome P450c17 (17α-hydroxylase), encoded by CYP17A1 and cytochrome P450c11 (11β-hydroxylase), encoded by CYP11B1. Several paracrine/autocrine regulators, including members of the transforming growth factor beta (TGFβ) superfamily, have been implicated in controlling adrenocortical cell homeostasis and steroid hormone production. Previously, we reported a bone morphogenetic protein 4 (BMP4) expression gradient in the adrenal cortex with higher levels in the zona glomerulosa (ZG) and outer ZF compared to the zona reticularis (ZR). In this study, we sought to compare adrenal expression of members of the TGFβ family including BMP4, growth differentiation factor 11 (GDF11), and transforming growth factor beta 2 (TGFβ2), and determine their effect on adrenal cell cortisol biosynthesis. Methods: Growth factor mRNA levels were studied using microarray analysis of laser captured ZG, ZF and ZR from human adrenals. The adrenal cell line, HAC15 was used to determine the effects of the TGFβ family members alone and in combination. Output measures included cell cortisol production and mRNA levels of steroidogenic enzymes using ELISA and quantitative RT-PCR, respectively. Results: Microarray analysis indicated higher mRNA levels of BMP4, GDF11 and TGFβ2 in the ZG compared with the ZF and ZR regions of the adrenal. Treatment of HAC15 cells with either BMP4 (50 ng/mL), GDF11 (50 ng/mL) or TGFβ2 (10 ng/mL) significantly inhibited cortisol production, as well as CYP11B1 and CYP17A1 mRNA levels. The inhibition was observed under basal and forskolin-stimulated conditions. Furthermore, the inhibitory effects on cortisol production and enzyme expression were additive when factors were added together. Summary: Overall, our findings suggest that the human adrenal has a gradient of multiple members of the TGFβ family. The additive action of these growth factors on adrenal cell differentiation may explain, in part, the inability of the ZG to produce cortisol and its low expression of CYP11B1 and CYP17A1. Presentation: Saturday, June 17, 2023