Testosterone Induction of Cyclooxygenase 2 (COX2) Expression and Prostaglandin F2 alpha (PGF2 alpha) Production in Hamster Leydig Cells

FRUNGIERI MB; MATZKIN ME; GONZALEZ-CALVAR SI; MAYERHOFER A; CALANDRA RS

Giessen, Alemania

Workshop; 5th International Workshop of Molecular Andrology; 2009

Justus-Liebig-Universität Gießen

We have previously observed expression of cyclooxygenase 2 (COX2), the key enzyme in the biosynthesis of prostaglandins (PGs), in reproductively active Syrian hamster Leydig cells, and reported an inhibitory role of PGF2 alpha on hamster testicular steroidogenesis (Frungieri et al, Endocrinology 147: 4476, 2006). In this study, we further investigated COX2 expression in hamster Leydig cells during sexual development and the photoperiodic gonadal regression. By immunohistochemistry and Western blot, COX2 is mostly expressed in pubertal and reproductively active adult hamsters with high circulating levels of LH and androgens. Thus, we studied the role of these hormones in the regulation/maintenance of testicular COX2/PGF2 alpha. In active hamster Leydig cells purified using a discontinuous Percoll density gradient, LH and testosterone induced COX2 expression (by RT-PCR and Western blot) and PGF2alpha production (by immunoassay), and their actions were abolished by the antiandrogen bicalutamide (Bi). These results indicate that LH does not exert a direct effect in PGs synthesis. Testosterone also stimulated phosphorylation of the extracellular signal-regulated kinase isoforms 1/2 (erk 1/2) within minutes (1-3 min) and hours (2-3 h), but the testosterone metabolite dihydrotestosterone (DHT) had no effect on COX2 and erk 1/2. Because Bi and U0126, an inhibitor of the mitogen-activated protein kinase kinase (MEK) abolished testosterone actions on erk 1/2 and COX2, our studies indicate that testosterone directly induces COX2/PGF2alpha in hamster Leydig cells via androgen receptors and a non-classical mechanism that involves erk 1/2 activation. Since PGF2alpha inhibits testosterone production, it might imply the existence of a regulatory loop that is setting a brake on steroidogenesis. Thus, the androgen environment might be crucial for the regulation of testicular PG production at least during sexual development and photoperiodic variations in hamsters.