TUMOR-NECROSIS-FACTOR-ALPHA ANTAGONIZES FOLLICLE-STIMULATING-HORMONE ACTION IN CULTURED SERTOLI CELLS

In the present study, we have tested the effect of tumor necrosis fact or-alpha (TNFalpha) on FSH action in cultured purified Sertoli cells i solated from immature porcine testes. FSH action was evaluated through three different parameters (aromatase activity, lactate production, a nd alpha-inhibin production). TNFalpha was shown to reduce (about 40-6 0% decrease) FSH-stimulated but not basal aromatase activity (evaluate d through the conversion of testosterone into estradiol) in a dose- an d time-dependent manner. The maximal and half-maximal (IC50) effects w ere observed with 6 ng/ml (3.5 x 10(-10) M) and 0.6 ng/ml (3.5 x 10(-1 1) M), respectively, after a long-term (72 h) treatment. TNFalpha (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 th e antigonadotropin action of the cytokine is probably exerted at a ste p located beyond cAMP formation. The inhibitory effect of TNFalpha was not limited to the action of FSH on aromatase activity but also exten ded to the gonadotropin action on lactate and inhibin-alpha chain prod uction in Sertoli cells. As for FSH-induced aromatase activity, TNFalp ha reduced FSH-stimulated lactate accumulation with an IC50 of 0.6 ng/ ml, after a long-term (72 h) treatment. Again, the cytokine reduced la ctate production stimulated by 8-bromo-cAMP, suggesting that TNFalpha antagonistic action against FSH is exerted at post-cAMP levels. Finall y, TNFalpha exerted a more pronounced inhibitory effect (>90% inhibiti on) on alpha-inhibin than on inhibin heterodimer production. These inh ibitory effects of TNFalpha on the gonadotropin action are probably ex erted directly on Sertoli cells, since TNFalpha high affinity binding sites (dissociation constant approximately 5.3 x 10(-10) M) are presen t in primary cultures of purified porcine Sertoli cells. Altogether, t he present findings show that TNFalpha antagonizes FSH action on Serto li cell functions such as aromatase activity and lactate and alpha-inh ibin production. Such an inhibitory effect is probably exerted at a bi ochemical step(s) located beyond cAMP generation.