Dehydroepiandrosterone and Its CYP7B1 Metabolite 7α-Hydroxydehydroepiandrosterone Regulates 11β-Hydroxysteroid Dehydrogenase 1 Directions in Rat Leydig Cells

Background: The purpose of this study was to investigate cytochrome P450-7B1 (CYP7B1) in the human and rat testes to regulate 11 beta-hydroxysteroid dehydrogenase 1 (11 beta-HSD1) activity. We hypothesized that dehydroepiandrosterone (DHEA) and its product 7 alpha-hydroxydehydroepiandrosterone (7 alpha OHD) after catalysis of CYP7B1 played a critical role in driving the direction of 11 beta-HSD1, because 7 alpha OHD is an alternative substrate for 11 beta-HSD1. Methods: We examined the influence of DHEA and 7 alpha OHD on 11 beta-HSD1 activities in both intact Leydig cells and microsomes using radioactive substrates and identified the location of CYP7B1 in Leydig cells using immunohistochemical staining, Western blot, and qPCR. Results: We found that DHEA stimulated 11 beta-HSD1 oxidase activity in intact cells (EC50 = 0.97 +/- 0.11 mu M) and inhibited its reductase activity (IC50 = 1.04 +/- 0.06 mu M). In microsomes, DHEA was a competitive inhibitor of the reductase activity. The 11 beta-HSD1 oxidase activity in intact cells was inhibited by 7 alpha OHD (IC50 = 1.18 +/- 0.12 mu M), and the reductase activity was enhanced (EC50 = 0.7 +/- 0.04 mu M). 7 alpha OHD was a competitive inhibitor of 11 beta-HSD1 oxidase. CYP7B1 was present in rat Leydig cells, as shown by immunohistochemistry, Western blotting, and qPCR analysis. Conclusion: Our results are consistent with a conclusion that DHEA in the circulation driving 11 beta-HSD1 toward an oxidase in Leydig cells mainly through inhibiting the reductase of the enzyme, while 7 alpha OHD (CYP7B1 catalytic product of DHEA) drives the enzyme toward the opposite direction.