Differential Modulation of Porcine Theca, Granulosa, and Luteal Cell Steroidogenesis in Vitro by Tumor Necrosis Factor

Abstract

The role of tumor necrosis factor α (TNFα) in ovarian function was investigated using in vitro culture of theca and granulosa cells isolated from gilt follicles (4–6 mm) and small (SLC) and large (LLC) luteal cells from mid-cycle corpora lutea. TNFα did not affect basal accumulation of progesterone (P) by theca cells after 72 h of culture. However, TNFα (0.1–100 ng/ml) caused a marked dose-dependent noncytotoxic inhibition (p < 0.05) of LH or LH+insulin (I)-stimulated P accumulation by theca cells after 72 h. Maximal inhibitions averaged 87 ± 6% at 5 ng/ml TNFα for LH-stimulated P and 69 ± 4% at 50 ng/ml TNFα for LH + I-stimulated P. The inhibitory effect of TNFα, evident by 24 h after culture, progressively increased on Days 2 and 3 of culture. The effect of TNFα on theca cells was mediated by cAMP generation as evidenced by TNFα inhibition of LH-induced cAMP accumulation and P accumulation in response to LH and forskolin but not dibutyryl cAMP. Consistent was this, TNFα had no effect on increased P accumulation by theca cells in the presence of 22-hydroxycholesterol or pregnenolone alone, but inhibited further increases in P accumulation stimulated by LH plus sterol substrates. Unlike that in theca cells, FSH-induced P accumulation in granulosa cell cultures was slightly enhanced (p < 0.05) by low doses of TNFα (0.1, 0.5, and 1.0 ng/ml) after 72 h, while higher doses (5–50 ng/ml) did not alter P accumulation. Furthermore, in experiments with luteal cells, TNFα had no effect on P accumulation in cultures of SLC or LLC after 36 h. The effect of TNFα on porcine theca cells may indicate a role in preventing premature follicular luteinization; together with previous evidence, this suggests a complex and possibly evolving physiological role for TNFα during follicular development.