Zearalenone inhibits testosterone biosynthesis in mouse Leydig cells via the crosstalk of estrogen receptor signaling and orphan nuclear receptor Nur77 expression

Zearalenone (ZEA) directly inhibits testosterone biosynthesis in Leydig cells, although the mechanisms involved remains unclear. Various experiments were performed to elucidate the molecular pathway of ZEA-mediated androgen inhibition. Leydig cells were isolated from 6 week-old male ICR mice and subjected to ZEA pre-treatment. The levels of testosterone and a series of influncing factors were measured. The results showed that ZEA caused a concentration- and time-dependent inhibition of testosterone stimulated both by hCG and cAMP (P < 0.05). Exposure to ZEA did not affect the LHR binding activity nor the protein expression (P > 0.05). However, ZEA exposure significantly elevated the cellular cAMP levels (P < 0.05) in low concentrations (5 μg/ml) or for long time periods (24 h), significantly reduce the mitochondrial membrane potential (P < 0.05). The expression of P450scc, 17β-HSD, and P450c17 at the mRNA level were significantly decreased (P < 0.05). The steroidogenic acute regulatory (StAR) and 3β-HSD expression was significantly increased (P < 0.05). Furthermore, the ERα protein expression was not affected by ZEA, but Nur77 expression was significantly inhibited (P < 0.05). These observations imply that ZEA activity interferes with testosterone biosynthesis in mouse Leydig cells via the crosstalk of estrogen receptor signaling and Nur77 expression.