TGF-β1 Regulation of Estrogen Production in Mature Rat Leydig Cells

BACKGROUND: Besides androgens, estrogens produced in Leydig cells are also crucial for mammalian germ cell differentiation. Transforming growth factor-β1 (TGF-β1) is now known to have multiple effects on regulation of Leydig cell function. The objective of the present study is to determine whether TGF-β1 regulates estradiol (E(2)) synthesis in adult rat Leydig cells and then to assess the impact of TGF-β1 on Cx43-based gap junctional intercellular communication (GJIC) between Leydig cells. METHODOLOGY/PRINCIPAL FINDINGS: Primary cultured Leydig cells were incubated in the presence of recombinant TGF-β1 and the production of E(2) as well as testosterone (T) were measured by RIA. The activity of P450arom was addressed by the tritiated water release assay and the expression of Cyp19 gene was evaluated by Western blotting and real time RT-PCR. The expression of Cx43 and GJIC were investigated with immunofluorescence and fluorescence recovery after photo-bleaching (FRAP), respectively. Results from this study show that TGF-β1 down-regulates the level of E(2) secretion and the activity of P450arom in a dose-dependent manner in adult Leydig cells. In addition, the expression of Cx43 and GJIC was closely related to the regulation of E(2) and TGF-β1, and E(2) treatment in turn restored the inhibition of TGF-β1 on GJIC. CONCLUSIONS: Our results indicate, for the first time in adult rat Leydig cells, that TGF-β1 suppresses P450arom activity, as well as the expression of the Cyp19 gene, and that depression of E(2) secretion leads to down-regulation of Cx43-based GJIC between Leydig cells.