Androgen induction of testicular cyclooxygenase-2 expression

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

Belo Horizonte, Brasil

Simposio; International Symposium on Animal Biology of Reproduction; 2006

Congreso Brasileiro de Reproducao Animal

INTRODUCTION: Prostaglandins (PGs) are derived from arachidonic acid by the action of the cyclooxygenase (COX) isoenzymes COX1 and COX2. COX2–female deficient mice are infertile. In contrast, male fertility is not affected in COX2 mutant mice from knockout 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 COX2 is not detected in normal human testes, it is expressed in testicular biopsies of men with impaired spermatogenesis and male infertility (2). Moreover, COX/PGs are upregulated in testicular cancer (3) and aging (4), affect steroid hormone production and induce testicular fibrosis (2,5). Recently, we screened testes from species ranging from mice to monkeys in order to find an animal model for further investigating testicular COX2/PGs. We only found COX2 expression in Leydig cells of the reproductively active seasonal breeder Syrian hamster (5). Thus, the active adult hamster is a readily available model to study the regulation of testicular COX2 expression and PGs production. MATERIALS AND METHODS: Testes from prepubertal to adult Syrian hamsters (Mesocricetus auratus) were used to investigate COX2 and androgen receptor expression by immunohistochemistry. Leydig cells were purified from reproductively active adult hamsters and incubated in the presence or absence of: 100 mIU/ml hCG, 1 mM testosterone, 10 mM bicalutamide (Casodex). After incubations, cells were used for RT-PCR, whereas media were used for determination of PGF2a concentration by immunoassay. Statistical analyses were performed using ANOVA followed by Student-Newman-Keuls test for multiple comparisons. Mean + SEM. RESULTS AND DISCUSSION:Peripubertal (36d old), pubertal (45-60d old) and adult (90d old) active seasonal breeder hamsters that present high circulating levels of LH and androgens, showed expression of COX2 in Leydig cells (Fig. 1A). In contrast, prepubertal animals (12–18d old) and regressed adult hamsters exposed to a short-day photoperiod (6h light, 18h dark) with low serum concentrations of LH and androgens, did not express COX2 in testes. The influence of LH and testosterone on testicular COX2 expression and PGs synthesis was evaluated by RT-PCR and immunoassay. In Leydig cells isolated from active Syrian hamsters, hCG/LH and testosterone significantly induced COX2 expression and PGF2a production (Fig. 1B,C). Both, testosterone and LH stimulatory effects on COX2 expression were abolished by the pure antiandrogen bicalutamide, suggesting that LH does not exert a direct action on PGs synthesis. Moreover, androgen receptors were identified by immunohistochemistry in Sertoli cells, myoid cells as well as in Leydig cells from prepubertal to adult Syrian hamsters. Our results demonstrate that testosterone induces COX2 expression in Leydig cells. Thus, androgen environment might be crucial for the regulation of testicular PGs production at least in hamsters. Whether our results can be extended to nonseasonal reproductive species including man remains to be clarified.