The mycotoxin metabolite deepoxy- deoxynivalenol increases apoptosis and decreases steroidogenesis in bovine ovarian theca cells

Abstract

The mycotoxin deoxynivalenol (DON) has been shown to inhibit ovarian granulosa cell function in cattle in vitro, but it is not known whether DON or its metabolite deepoxy-DON (DOM-1) affects theca cell function. The objectives of this study were to determine the effects of DON and of DOM-1 on theca cell steroidogenesis and apoptosis, and to determine the main pathways through which they act. Bovine theca cells were cultured in a nonluteinizing serum-free culture system, and challenged with DON or DOM-1 for 4 days to measure steroidogenesis and apoptosis, for 1-8 h to measure immediate-early genes, and for 5-60 min to measure phosphorylation of intracellular signaling proteins. Addition of DON decreased progesterone secretion at doses as low as 0.5 ng/ml but had no effect on testosterone secretion. Addition of DOM-1 inhibited progesterone and testosterone secretion at 0.5 ng/ml. Treatment of cells with 1 ng/ml DOM-1 increased the proportion of apoptotic cells, whereas DON had no effect. Addition of DON or DOM-1 stimulated phosphorylation of EIF2AK2, MAPK3/1, and AKT. However, DON inhibited and DOM-1 stimulated MAPK14 phosphorylation. DON increased the levels of mRNA encoding early-immediate genes EGR1, EGR3, and FOS, whereas DOM-1 was without effect. DOM-1 but not DON increased abundance of mRNA of the endoplasmic reticulum (ER) stress-related proteins, PRKRA and ATF4. We conclude that DOM-1 has a major impact on theca function in cattle, and possibly induces theca cell apoptosis through ER stress.

Keywords: apoptosis; follicle; ovary; ruminants; theca cells; toxicology.