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 necros is factor-alpha TNF(alpha) on lactate dehydrogenase A (LDH A), a key enzyme involved in lactate production. To this end, use was made of a primary cul ture system of porcine testicular Sertoli cells. TNF alpha stimulated LDH A messenger RNA (mRNA) expression in a dose (ED50 = 2.5 ng/ml; 0.1 nM TNF al pha-dependent manner. This stimulatory effect was time dependent, with an e ffect detected after 6 h of TNF alpha treatment and maximal after 48 h of e xposition (5-fold; P < 0.001). The direct effect of TNF alpha 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. Inhib itors of protein synthesis (cycloheximide), gene transcription (actinomycin D and dichlorobenzimidazole riboside), tyrosine kinase (genistein), and pr otein kinase C (bisindolylmaleimide) abrogated completely (actinomycin D, d ichlorobenzimidazole riboside, cycloheximide, and genistein) or partially ( bisindolylmaleimide) TNF alpha-induced LDH A mRNA expression. These observa tions suggest that the stimulatory effect of TNF alpha on LDH A mRNA expres sion requires protein synthesis and may involve a protein tyrosine kinase a nd protein kinase C. In addition, we report that LDH A mRNA levels were inc reased in Sertoli cells treated with FSH. However, although the cytokine en hances 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 meta bolic cooperation between Sertoli and postmeiotic germ cells in the seminif erous tubules.