CJK 06. Annexin 5 stimulates testosterone release from the primary cultured rat leydig cells

To study the effect of annexin 5 on testosterone secretion from primary rat Leydig cells and the underlying mechanism.

Isolated rat Leydig cells were treated with annex in 5, while siRNA transfection on annexin 5. Testosterone production was detected by chemiluminescence assay, and related enzymes including steroidogenic acute regulatory (StAR) protein, P450scc, 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) and 17α-hydroxylase for testosterone synthesis were examined by RT-PCR and western blotting.

Annexin 5 significantly stimulated testosterone secretion from rat Leydig cells in dose- and time-dependent manners (P<0.05). The protein level in annexin 5 after siRNA transfection was significantly decreased. The level of testosterone was significantly decreased at 24 h after siRNA1 transfection.The mRNA expression of StAR, P450scc, 3β-HSD and 17β-HSD but 17α-hydroxylase was significantly stimulated by annexin 5. Protein expression of P450scc, 3β-HSD and 17β-HSD was also induced by annexin 5. And protein expression of P450scc, 3β-HSD and 17β-HSD significantly decreased after siRNA1 transfection.The significant activation of ERK1/2 signaling was observed at 5, 10, and 30 min after annexin 5 treatment. After pretreatment of Leydig cells with the ERK inhibitor PD98059 (50 μmol/L) for 20 min, the effect of annexin 5 on promoting testosterone secretion and increasing the expression of P450scc, 3β-HSD and 17β- HSD were completely reversed (p <0.05).

Annexin 5 was firstly found to regulate testosterone secretion in rat Leydig cells and the mRNA and protein expression of P450scc, 3β-HSD and 17β-HSD. The mechanism was related to ERK1/2 signaling that mediates the expression of P450scc, 3β-HSD and 17β-HSD and influences the effect of annexin 5 in Leydig cells.