TUMOR-NECROSIS-FACTOR-ALPHA ATTENUATION OF LUTEINIZING HORMONE-STIMULATED ANDROSTENEDIONE PRODUCTION BY OVARIAN THECA-INTERSTITIAL CELLS - INHIBITION AT LOCI WITHIN THE ADENOSINE 3',5'-MONOPHOSPHATE-DEPENDENT SIGNALING PATHWAY

Tumor necrosis factor-alpha (TNF) blocks LH-stimulated androstenedione production by immature rat theca-interstitial cells (TIC) in vitro. T he mechanism for TNF inhibition of LH-induced androstenedione is unkno wn and was investigated. LH stimulation of androstenedione synthesis i n TIC is mediated via a cAMP-dependent signaling pathway. LH-stimulate d cAMP in TIC-conditioned medium was reduced in a biphasic manner by T NF at 1 and 48 h, but not at 4 and 24 h. To determine whether inhibiti on of cAMP resulted from TNF interference of LH binding, TIC were give n TNF for 24 and 48 h, and LH binding was determined. TNF inhibited LH binding at 24 and 48 h. Scatchard analysis revealed a TNF-induced dec rease in LH receptor number without altered affinity. TIC were given T NF and cAMP analogs [N6-benzoyl-cA P, 8-thiomethyl-cAMP, 8-(6-aminohex yl)amino-cAMP, and N-2'-O-(Bu)2cAMP], which selectively activate cAMP- dependent protein kinase (PKA) type I and/or PKA type II, respectively . At 48 and 96 b, TNF blocked androstenedione production stimulated by all combinations of cAMP analogs; however, androstenedione synthesis recovered by 48 h after removal of TNF. Peak PKA activity in TIC was o bserved at 30 min in the presence of LH or cAMP analogs. LH- or cAMP a nalog-directed PKA activity was inhibited after concomitant exposure t o TNF; however, a 24-h pretreatment with TNF did not affect cAMP analo g-stimulated PKA activity. The results indicate that in the modulation of steroidogenesis, TNF acts at multiple sites in the PKA pathway. Fi rst, TNF suppresses LH-stimulated cAMP production by TIC. Secondly, in hibition of cAMP may result from TNF attenuation of LH binding, and th irdly, TNF inhibits PKA activity of TIC and, thus, attenuates androste nedione production.