* denote differences among treatments (P<0.05). denote differences among treatments (P<0.05). N = 3 cultured cell lines per group. Supplemental Figure 4. Effect of TBT exposure on mRNA expression in pre-luteinized and luteinized ATR-101 ovine primary theca cells. mRNA expression (mean SEM) of nuclear receptors in primary ovine pre-luteinized (A) and luteinized (B) ovine primary theca cells exposed to 1 ng/ml TBT (T1; or vehicle (C; control group; expression (mean SEM) in pre-luteinized ovine primary theca cells. Asterisks denote differences among treatments (P<0.05). N=3 cultured cell lines per group. U: UVI3003 (M). T: TBT. NIHMS1527483-supplement-1.pdf (725K) GUID:?42B65A96-CD58-43A2-84CE-14CE68C62307 Abstract Tributyltin (TBT), an organotin chemical used as a catalyst and biocide, can stimulate cholesterol efflux in non-steroidogenic cells. Since cholesterol is the first limiting step for sex hormone production, we hypothesized that TBT disrupts intracellular cholesterol transport and impairs steroidogenesis in ovarian theca cells. We investigated TBTs effect on cholesterol trafficking, luteinization, and steroidogenesis in theca cells of five species (human, sheep, cow, pig, and mice). Primary theca cells were exposed to an environmentally relevant dose of TBT (1 or 10 ng/ml) and/or retinoid X receptor (RXR) antagonist. The expression of in sheep theca cells was knocked down by using shRNA. Steroidogenic enzymes, cholesterol transport factors, and nuclear receptors were measured by RT-qPCR and western blotting, and intracellular cholesterol, progesterone, and testosterone secretion by ELISA. In ovine cells, TBT upregulated mRNA in theca cells. TBT also reduced intracellular cholesterol and upregulated ABCA1 protein expression but did not alter testosterone ATR-101 or progesterone production. RXR antagonist and knockdown demonstrates that TBTs effect is partially through RXR. TBTs effect on and expression was recapitulated in all five species. TBT, at an environmentally relevant dose, stimulates theca cell cholesterol extracellular efflux via the RXR pathway, triggers a compensatory upregulation of that regulates cholesterol transfer ATR-101 into the mitochondria and for cholesterol synthesis. Similar results were obtained in all five species evaluated (human, sheep, cow, pig, and mice) and are supportive of TBTs conserved mechanism of action across mammalian species. (Romani et al. 2013; Romani et al. 2014) and (Li et ATR-101 al. 2012; Melzer et al. 2011). TBTs steroidogenic effects have been reported in Leydig cells and testis (Kanimozhi et al. 2018; Kariyazono et al. 2015; Mitra et al. 2014; Nakajima et al. 2005). However, TBTs effect on ovarian steroidogenic cells has been restricted to granulosa cells. TBT Rabbit polyclonal to Complement C4 beta chain reduces estradiol synthesis in human granulosa-like tumor cells and is association with aromatase activity inhibition in bovine granulosa cells (Saitoh et al. 2001; Schoenfelder et al. 2003). However, whether TBT can affect theca cells steroidogenic function remains unknown. Cholesterol is the precursor for steroid hormone biosynthesis. In theca cells, cholesterol trafficking plays a role in progesterone synthesis. Internalized into the cytoplasm through the LDL receptor, cholesterol is transported into the endoplasmic reticulum and the mitochondrion to synthesize pregnenolone, the first intermediate of steroid hormone synthesis. Intracellular cholesterol is regulated by the cholesterol efflux regulatory protein ATP binding cassette subfamily A member 1 (ABCA1). TBT upregulates ABCA1 expression and cholesterol efflux in macrophage cells (Cui et al. 2011). TBT also upregulates ABCA1 expression in bone marrow multipotent mesenchymal stromal cells (Baker et al. 2015), which can be blocked by an RXR antagonist in a dose dependent manner (Baker et al. 2015). However, whether TBT exposure, at an.