title: T-2 toxin regulates steroid hormone secretion of rat ovarian granulosa cells through cAMP-PKA pathway.
abstract: T-2 toxin is a secondary metabolite produced by Fusarium genus and is a common contaminant in food and feedstuffs of cereal origin. In porcine granulosa cells(GC), T-2 toxin has been shown to inhibit the steroidogenesis; however, the mechanism has not been well understood. Gonadotropin-stimulated steroidogenesis is regulated by the cAMP-PKA pathway. In this study, we investigated potential mechanisms for T-2 toxin-induced reproductive toxicity focusing on the critical steps of the cAMP-PKA pathway affected by T-2 toxin. We first analyzed the effects of T-2 toxin on progesterone and estrogen production in rat granulosa cells. For this purpose the granulosa cells were cultured for 48 h in 10% fetal bovine serum-containing medium followed by 24h in serum-free medium containing FSH (10 ng/ml) and androstenedione (3 ng/ml), both are required for normal steroidogenesis. Treatment of these cells with T-2 toxin dose-dependently inhibited the growth of cells and the steroid hormone production. Cellular cyclic AMP levels were dose-dependently inhibited by T-2 toxin (0, 1, 10 and 100 nM, 24 h). Furthermore, we found that although the induction of progesterone by 8-Br-cAMP (a FSH mimetic) and 22R-HC (substrate for progesterone) could both be inhibited by T-2 toxin treatment, the T-2-imposed inhibitory effects could be reversed by increasing doses of 22R-HC, while increasing 8-Br-cAMP had no effects, suggesting that T2 toxin targeted at distinct mechanisms. cAMP-stimulated steroidogenic acute regulatory protein (StAR) is a rate limiting protein in progesterone synthesis. Exposure to T2 toxin caused significant suppression of StAR expression as determined by Western blotting and semi-quantitative RT-PCR suggesting StAR is a sensitive target for T-2 toxin. Taken together, our results strongly suggest that T2 toxin inhibits steroidogenesis by suppressing cAMP-PKA pathway and StAR is a target for T-2-toxin. The antisteroidogenesis effects were observable at low T-2 dose (1 ng/ml) suggesting T-2 toxin has an endocrine disruptive effect.
authors.affiliation: College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan 410128, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.affiliation: College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan 410128, PR China.
authors.forename: Di
authors.initials: D
authors.lastname: Tu
authors.affiliation: College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan 410128, PR China.
authors.forename: Li-Yun
authors.initials: LY
authors.lastname: Yuan
authors.affiliation: College of Veterinary Medicine, Hunan Agricultural University, Changsha, Hunan 410128, PR China. Electronic address: yibinzhen@163.com.
authors.forename: Jin-e
authors.initials: JE
authors.lastname: Yi
authors.affiliation: Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843, USA. Electronic address: ytian@cvm.tamu.edu.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Tian
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004785:Environmental Pollutants / Q000494:pharmacology; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006107:Granulosa Cells / Q000187:drug effects* / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism*; D051381:Rats; D011920:Rats, Inbred WF; D015398:Signal Transduction / Q000187:drug effects; D013605:T-2 Toxin / Q000494:pharmacology*
chemical_list: D004785:Environmental Pollutants; D015124:8-Bromo Cyclic Adenosine Monophosphate; D011374:Progesterone; D004958:Estradiol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D013605:T-2 Toxin
keywords: Granulosa cells; Steroid production; T-2 Toxin; cAMP-PKA pathway