Functional link between bone morphogenetic proteins and insulin-like peptide 3 signaling in modulating ovarian androgen production

Abstract

Bone morphogenetic proteins (BMPs) are firmly implicated as intraovarian regulators of follicle development and steroidogenesis. Here we report a microarray analysis showing that treatment of cultured bovine theca cells (TC) with BMP6 significantly (>twofold; P < 0.01) up-or down-regulated expression of 445 genes. Insulin-like peptide 3 (INSL3) was the most heavily down-regulated gene (−43-fold) with cytochrome P450, subfamily XVII (CYP17A1) and other key steroidogenic transcripts including steroidogenic acute regulatory protein (STAR), cytochrome P450 family 11, subfamily A1 (CYP11A1) and 3 beta-hydroxysteroid dehydrogenase type 1 (HSD3B1) also downregulated. BMP6 also reduced expression of nuclear receptor subfamily 5A1 (NR5A1) known to target the promoter regions of the aforementioned genes. Real-time PCR confirmed these findings and also revealed a marked reduction in expression of INSL3 receptor, relaxin/insulin-like family peptide receptor 2 (RXFP2). Secretion of INSL3 protein and androstenedione were also suppressed suggesting a functional link between BMP and INSL3 pathways in controlling androgen synthesis. RNAi-mediated knockdown of INSL3 reduced INSL3 mRNA (75%) and protein (94%) level and elicited a 77% reduction in CYP17A1 mRNA and 83% reduction in androstenedione secretion. Knockdown of RXFP2 also reduced CYP17A1 expression (81%) and androstenedione secretion (88%). Conversely, treatment with exogenous (human) INSL3 increased androstenedione secretion ∼twofold. The CYP17A1 inhibitor abiraterone abolished androgen secretion and reduced expression of both INSL3 and RXFP2. Collectively, these findings indicate a positive autoregulatory role for INSL3 signaling in maintaining thecal androgen production, and visa versa. Moreover, BMP6-induced suppression of thecal androgen synthesis may be mediated, at least in part, by reduced INSL3-RXFP2 signaling.growth factor | ovary | reproduction

Ovarian-like differentiation in eutopic and ectopic endometrioses with aberrant FSH receptor, INSL3 and GATA4/6 expression

“…The ovarian hormone INSL3 plays an important role in maintaining androgen production by ovarian theca cells by inducing CYP17 steroidogenic enzyme [16] and modulates both LH and FSH actions [16], [17]. INSL3 is regulated by LH in ovarian theca cells [18].…”

“…INSL3 is a circulating peptide hormone of the relaxin-insulin family involved in tumor cell growth, differentiation, invasion and neovascularization [33]. INSL3 induces CYP17 expression in the ovary, maintaining androgen production [16]. The highest levels of INSL3 transcripts were found in group C endometriosis also aberrantly expressing the LHR, together with the strongest induction of the complete steroidogenic cascade, involving CYP17 and CYP11.…”

Novel markers of gonadectomy-induced adrenocortical neoplasia in the mouse and ferret

“…Additionally, INSL3 is constitutively secreted by adult Leydig cells and serves as a serum biomarker of this cell type (Anand-Ivell et al, 2009), although the function of INSL3 in the adult testis remains unclear (Ivell et al, 2013). Insl3 is also expressed in the ovary, particularly in theca interna cells of the maturing follicle (Satchell et al, 2013), where it induces androgen production (Glister et al, 2013). It is conceivable that serum levels of INSL3 could be a biomarker of post-GDX adrenocortical neoplasms, and future experiments will explore this possibility.…”

International Union of Basic and Clinical Pharmacology. XCV. Recent Advances in the Understanding of the Pharmacology and Biological Roles of Relaxin Family Peptide Receptors 1–4, the Receptors for Relaxin Family Peptides

“…INSL3 has a critical role in testis descent, and INSL3 knockout mice are cryptorchid and infertile (Nef and Parada, 1999;Zimmermann et al, 1999). It plays an important role in gubernaculum development, which is involved in the first stage of testis descent, and also appears to have a role in the maintenance of ovarian function (Spanel-Borowski et al, 2001;Kawamura et al, 2004;Glister et al, 2013).…”

“…As INSL3 is a product of the thecal cells of ovarian follicles, plasma INSL3 levels have been investigated and shown to be elevated in polycystic ovary syndrome, a common female endocrine disorder characterized by excessive production of androgens from ovarian follicles (Gambineri et al, 2007;Szydlarska et al, 2012;Anand-Ivell et al, 2013). Importantly, a recent study in cows demonstrated that INSL3 has a positive autoregulatory role in maintaining thecal androgen production that is essential for normal ovarian follicle development (Glister et al, 2013).…”