In vitro effects of zearalenone metabolites on cell proliferation and steroidogenesis with bovine granulosa cells

Zearalenone (ZEA), an oestrogenic fusariotoxin common contaminant of feedstuffs, is rapidly metabolized in rumen into α-Zearalenol (α-ZEA) and to a lower amount β-Zearalenol (β-ZEA). The purpose of this study is to evaluate the in vitro effects of α-ZEA and β-ZEA on cell proliferation and steroidogenesis by using bovine granulosa cells (GC). Ovaries were collected from a nearby slaughterhouse and small granulosa cells (SMGC) were obtained by aspirating ovarian follicles (1-5 mm). Cells were cultured for 2 days in 10% fetal bovine serum-containing medium followed by 2 days in serumfree medium containing control or mycotoxin treatments. Cell numbers were determined using a Coulter counter while concentrations of progesterone (P4) and estradiol (E2) in cell culture medium were determined using radioimmunoassay. α-ZEA and β-ZEA were tested at 0.31 μM and at 0.31, 3.1, 31 μM, respectively. A co-exposure to α-ZEA and β-ZEA at 0.31 μM each was also carried out. All experiments were performed with and without IGF1. Cell proliferation was inhibited in presence of IGF1 at 3.1 and 31 μM of β-ZEA while without IGF1 only at 31 μM of β-ZEA was inhibitory. A synergic inhibitory effect on cell proliferation and E2 production was demonstrated after co-exposure to α-ZEA and β-ZEA only in cells treated with IGF1. Without IGF1, E2 production was strongly stimulated at 31 μM compared to the control whereas in presence of IGF1 E2 release was inhibited (by 40%) by β-ZEA at 3.1 μM. P4 production was stimulated after exposure to β-ZEA at the highest dose tested (31 μM) in presence and absence of IGF1. Further studies are in progress to better understand the mechanism of action of ZEA and its metabolites on GC.