Department of Animal Science, Michigan State University, 474 S. Shaw Lane, Room 1230F, East Lansing, MI, 48824, USA.
Sparrow Hospital, Lansing, MI, USA.
Arch Toxicol. 2019 Jun;93(6):1665-1677. doi: 10.1007/s00204-019-02449-y. Epub 2019 Apr 21.
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 TBT's 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 RXRα in sheep theca cells was knocked down 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. TBT upregulated StAR and ABCA1 in ovine cells, and SREBF1 mRNA in theca cells. TBT also reduced intracellular cholesterol and upregulated ABCA1 protein expression but did not alter testosterone or progesterone production. RXR antagonist and RXRα knockdown demonstrates that TBT's effect is partially through RXR. TBT's effect on ABCA1 and StAR 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 StAR that regulates cholesterol transfer into the mitochondria and SREBF1 for de novo cholesterol synthesis. Similar results were obtained in all five species evaluated (human, sheep, cow, pig, and mice) and are supportive of TBT's conserved mechanism of action across mammalian species.
三丁基锡(TBT)是一种用作催化剂和杀生剂的有机锡化学物质,可刺激非甾体生成细胞中的胆固醇外排。由于胆固醇是性激素产生的第一个限速步骤,我们假设 TBT 会破坏细胞内胆固醇转运并损害卵巢膜细胞中的类固醇生成。我们研究了 TBT 对五种物种(人、绵羊、牛、猪和小鼠)的膜细胞胆固醇转运、黄素化和类固醇生成的影响。将原代膜细胞暴露于环境相关剂量的 TBT(1 或 10ng/ml)和/或视黄醇 X 受体(RXR)拮抗剂中。使用 shRNA 敲低绵羊膜细胞中的 RXRα 表达。通过 RT-qPCR 和 Western blot 测量类固醇生成酶、胆固醇转运因子和核受体,通过 ELISA 测量细胞内胆固醇、孕酮和睾酮分泌。TBT 上调了绵羊细胞中的 StAR 和 ABCA1,以及膜细胞中的 SREBF1 mRNA。TBT 还降低了细胞内胆固醇并上调了 ABCA1 蛋白表达,但没有改变睾酮或孕酮的产生。RXR 拮抗剂和 RXRα 敲低表明,TBT 的作用部分通过 RXR。TBT 对 ABCA1 和 StAR 表达的影响在所有五种物种中均得到了重现。在环境相关剂量下,TBT 通过 RXR 途径刺激膜细胞胆固醇细胞外流出,触发 StAR 的代偿性上调,调节胆固醇向线粒体的转移和 SREBF1 用于从头胆固醇合成。在评估的所有五个物种(人、绵羊、牛、猪和小鼠)中均获得了类似的结果,支持 TBT 在哺乳动物物种中具有保守的作用机制。