IMBICE   05372
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA CELULAR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Cyclooxygenase-2 (COX2) and prostaglandin F2 Alpha (PGF2 alpha) in Syrian hamster Leydig cells: Inhibitory role on LH/hCG-stimulated testosterone production
Autor/es:
FRUNGIERI MB, GONZÁLEZ-CALVAR SI, ALBRECHT M, MAYERHOFER A, CALANDRA RS
Lugar:
Bad Aibling, Alemania
Reunión:
Workshop; 14th European Testis Workshop; 2006
Institución organizadora:
European Testis Workshop
Resumen:
BACKGROUND Prostaglandins (PGs) are derived from arachidonic acid by action of the cyclooxygenase (COX) isoenzymes COX-1 and COX-2. The development of mice deficient in COX-1 and/or COX-2 has shown that COX-2–null female mice are infertile. In contrast, male fertility is not affected in COX-1 or COX-2 mutant mice from knock-out experiments (1) suggesting that PGs may be not important for the functioning of the testis. This early general view is being challenged by recent observations. We have reported that whereas COX-2 is not detected in normal human testes, it is expressed in testicular biopsies of men with impaired spermatogenesis and male infertility (2). Moreover, COX is up-regulated in testicular cancer (3), COX-2 expression is induced in Brown-Norway rat Leydig cells during aging (4), and several reports describe actions of COX and PGs on steroid hormones production. Thus, testicular COX and PGs may be of relevance in male fertility disorders.   MATERIALS AND METHODS Testis from several species including Rhesus monkeys, pigs, Wistar and Sprague-Dawley rats, BALBc mice, and Syrian hamsters (Mesocricetus auratus) were used to investigate the expression of COX-2 by RT-PCR and immunohistochemistry. Hamster Leydig cells were purified and incubated in the presence or absence of several chemicals: 100 mIU/ml hCG, 100 pM to 1 mM PGD2, PGE2 or PGF2a. After incubations, cells were used for Western blotting and RT-PCR, whereas media were frozen at -20°C until concentrations of testosterone were determined by RIA. Moreover, testicular content of PGF2a in hamsters was measured by  immunoassay. Statistical analyses were performed using ANOVA followed by Student-Newman-Keuls test for multiple comparisons. Mean + SEM.   RESULTS i) COX was not seen in testes of young adult monkeys, pigs, rats or mice. In contrast, COX-2 (but not COX-1) was found in Leydig cells of pubertal and adult active seasonal breeder Syrian hamster (Fig. 1).   ii) COX-2 expression indicates PGs synthesis. Thus, testicular PGF2a concentration (fmol/g tissue: 217.14 + 31.49, n= 5) and content (fmol/testis: 390.85 + 56.68, n= 5) in active hamsters, as well as PGF2a production from isolated hamster Leydig cells (fmol/million Leydig cells: 102.69 + 5.01, n= 4-5) were measured by immunoassay. iii) When the effect of various PGs on testosterone production was investigated, PGF2a stood out because it significantly reduced, in a dose-dependent manner, hCG-stimulated testosterone release from isolated hamster Leydig cells. This mechanism involves a decreased expression of Steroidogenic Acute Regulatory (StAR) and 17b-hydroxysteroid dehydrogenase (17b-HSD) (Fig. 2).   iv) PGF2a receptors (FP) were localized in active hamster Leydig cells as well as in pathological testicular biopsies of infertile men. (Fig. 3).   CONCLUSIONS This study provides novel evidence for testicular COX-2 expression and the subsequent local production of PGF2a in the adult active seasonal breeder Syrian hamster. Our results indicate that PGF2a, probably acting by FP receptors located in Leydig cells and through a mechanism involving down-regulation of StAR and 17b-HSD expression, leads to the inhibition of LH/hCG-stimulated testosterone production. Thus, the testicular PGF2a system working in concert with the primary effect of gonadotropins on the hypothalamic-pituitary axis represents a local inhibitory control system of steroidogenesis in Syrian hamsters. Besides this novel aspect, we also found FP receptors in human pathological biopsies, i.e. samples in which we had previously described the existence of testicular COX-2 expression. Therefore, whether our findings for the Syrian hamster can be extrapolated to states of male infertility remains to be clarified. It also remains to be tested whether COX-2 and its signaling mechanism may be targets for new therapeutic approaches