TUMOR-NECROSIS-FACTOR-ALPHA REGULATES PLASMINOGEN-ACTIVATOR INHIBITOR-1 IN RAT TESTICULAR PERITUBULAR CELLS

We examined the regulation by tumor necrosis factor-alpha (TNF alpha) of plasminogen activator inhibitor-1 (PAI-1) in cultured peritubular c ells recovered from 20-day-old rat testes. We demonstrated that TNF al pha in a nanomolar dose range stimulated PAI-1 messenger RNA (mRNA; No rthern blots) as well as immunoreactive (Western blots) and bioactive (Stachrom) PAI-1 protein. Induction of PAI-I mRNA started 4 h after th e addition of TNF alpha (2.5-fold increase) and peaked (7-fold increas e) after 24 h of treatment. Actinomycin D and cycloheximide inhibited the effects of TNF alpha on PAI-1 mRNA, suggesting that ongoing RNA an d protein syntheses were required. The combined actions of transformin g growth factor-alpha (TGF alpha), a potent inducer of PAI-1, and TNF alpha on PAI-1 were less than additive, suggesting the activation of s ome common pathway. TNF alpha action on PAI-1, like that of TGF alpha demonstrated previously, was masked by a preexposure to phorbol myrist ate acetate (a stimulator of protein kinase C) and strongly reduced by staurosporine (an inhibitor of the protein kinase C). Furthermore, us ing genistein, to inhibit tyrosine kinase activity, we not only blocke d the action of TGF alpha on PAI-1 [initiated upon binding to the tyro sine kinase epidermal growth factor/TGF alpha receptor (EGFR)], but al so markedly reduced that of TNF alpha. Finally, TNF alpha, at a dose r ange that stimulated PAI-1, enhanced EGFR mRNA levels and EGF binding. Together, the present findings suggest that some of the biological ef fects of TNF alpha on PAI-1 might be secondary to de novo synthesis of EGFR. Because TNF alpha probably originates from testicular macrophag es, such a regulation of PAI-1 by TNF alpha may occur in the context o f physiological interactions between the testis and the immune system.