Tumor necrosis factor-alpha stimulates lactate dehydrogenase A expression in porcine cultured sertoli cells: mechanisms of action.

In the present study, we investigated the regulatory action of tumor necrosis factor-alpha (TNFalpha) on lactate dehydrogenase A (LDH A), a key enzyme involved in lactate production. To this end, use was made of a primary culture system of porcine testicular Sertoli cells. TNFalpha stimulated LDH A messenger RNA (mRNA) expression in a dose (ED50 = 2.5 ng/ml; 0.1 nM TNFalpha)-dependent manner. This stimulatory effect was time dependent, with an effect detected after 6 h of TNFalpha treatment and maximal after 48 h of exposition (5-fold; P<0.001). The direct effect of TNFalpha on LDH A mRNA could not be accounted for by an increase in mRNA stability (half-life = 9 h), but was probably due to an increase in LDH A gene transcription. Inhibitors of protein synthesis (cycloheximide), gene transcription (actinomycin D and dichlorobenzimidazole riboside), tyrosine kinase (genistein), and protein kinase C (bisindolylmaleimide) abrogated completely (actinomycin D, dichlorobenzimidazole riboside, cycloheximide, and genistein) or partially (bisindolylmaleimide) TNFalpha-induced LDH A mRNA expression. These observations suggest that the stimulatory effect of TNFalpha on LDH A mRNA expression requires protein synthesis and may involve a protein tyrosine kinase and protein kinase C. In addition, we report that LDH A mRNA levels were increased in Sertoli cells treated with FSH. However, although the cytokine enhances LDH A mRNA levels through increased gene transcription, the hormone exerts its stimulatory action through an increase in LDH A mRNA stability. The regulatory actions of the cytokine and the hormone on LDH A mRNA levels and therefore on lactate production may operate in the context of the metabolic cooperation between Sertoli and postmeiotic germ cells in the seminiferous tubules.