Tumor necrosis factor-alpha antagonizes follicle-stimulating hormone action in cultured Sertoli cells

Abstract

In the present study, we have tested the effect of tumor necrosis factor-alpha (TNF alpha) on FSH action in cultured purified Sertoli cells isolated from immature porcine testes. FSH action was evaluated through three different parameters (aromatase activity, lactate production, and alpha-inhibin production). TNF alpha was shown to reduce (about 40-60% decrease) FSH-stimulated but not basal aromatase activity (evaluated through the conversion of testosterone into estradiol) in a dose- and time-dependent manner. The maximal and half-maximal (IC50) effects were observed with 6 ng/ml (3.5 x 10(-10) M) and 0.6 ng/ml (3.5 x 10(-11) M), respectively, after a long-term (72 h) treatment. TNF alpha (20 ng/ml) also inhibited Sertoli cell aromatase activity when stimulated with 8-bromo-cAMP (0.01-3 mM, 72 h) instead of FSH, suggesting that the antigonadotropin action of the cytokine is probably exerted at a step located beyond cAMP formation. The inhibitory effect of TNF alpha was not limited to the action of FSH on aromatase activity but also extended to the gonadotropin action on lactate and inhibin-alpha chain production in Sertoli cells. As for FSH-induced aromatase activity, TNF alpha reduced FSH-stimulated lactate accumulation with an IC50 of 0.6 ng/ml, after a long-term (72 h) treatment. Again, the cytokine reduced lactate production stimulated by 8-bromo-cAMP, suggesting that TNF alpha antagonistic action against FSH is exerted at post-cAMP levels. Finally, TNF alpha exerted a more pronounced inhibitory effect (> 90% inhibition) on alpha-inhibin than on inhibin heterodimer production. These inhibitory effects of TNF alpha on the gonadotropin action are probably exerted directly on Sertoli cells, since TNF alpha high affinity binding sites (dissociation constant approximately 5.3 x 10(-10) M) are present in primary cultures of purified porcine Sertoli cells. Altogether, the present findings show that TNF alpha antagonizes FSH action on Sertoli cell functions such as aromatase activity and lactate and alpha-inhibin production. Such an inhibitory effect is probably exerted at a biochemical step(s) located beyond cAMP generation.