In vitro regulation of rat Sertoli cell transferrin expression by tumor necrosis factor alpha and retinoic acid

In the present study, we examined the in vitro regulation of 20-day-old rat Sertoli cell transferrin expression by tumor necrosis factor alpha (TNFalpha), a paracrine factor produced by germ cells. Addition of TNFalpha to highly purified cultured Sertoli cells resulted in a dose and time-dependent enhancement in the levels of transferrin mRNA (Northern-blot) and protein (RadioImmunoAssay) with an ED50 of 120 pM. Co-treatment of Sertoli cells with the optimal dose of retinoic acid (RA, a potent inducer of transferrin) and TNFalpha induced a stimulation of transferrin that was significantly higher than the FIRT combination, a well known mixture of transferrin activators. Actinomycin D inhibited the effects of TNFalpha and of RA, suggesting that ongoing RNA synthesis was required to enhance transferrin. We next demonstrated that RA and TNFalpha exerted additive effects on transferrin expression as assessed by dose-response and kinetics studies. Moreover pre-treatment with RA, while greatly increasing the amount of transferrin produced, did not modify Sertoli cell responsiveness to TNFalpha. Together these results show that TNFalpha and RA are likely to act independently, additively and at least at the transcriptional level to increase transferrin expression.