TUMOR-NECROSIS-FACTOR-ALPHA ALTERS BOVINE LUTEAL CELL SYNTHETIC CAPACITY AND VIABILITY

Tumor necrosis factor-alpha (TNF-alpha) is a macrophage-derived cytokine that is also reportedly produced by granulosal cells and is localized in luteal cells. The present study employed serum-free culture of midcycle bovine luteal cells to investigate the effects of TNF-alpha, alone and with other cytokines, on luteal function. TNF-alpha (1-1000 ng/ml) produced a dose-dependent increase in prostaglandin (PG)F2-alpha and -keto-PGF1-alpha synthesis on all days of culture, but had no effect on basal progesterone (P4) production. TNF-alpha, in combination with other known stimulators of luteal PG synthesis, interleukin-1-beta (2.5 ng/ml) or interferon-gamma (IFN-gamma, 100 U/ml), had synergistic effects on PGF2-alpha production (> 50-fold above control, P < 0.05) whereas interferon-alpha (1000 U/ml) significantly suppressed TNF-alpha-stimulated PGF2-alpha production. By day 7 of culture, TNF-alpha inhibited LH-stimulated P4 production (P < 0.05). Luteal cell numbers were significantly reduced by IFN-gamma but not by TNF-alpha alone. However, the combination of TNF-alpha + IFN-gamma was extremely cytotoxic (only 20% of cells maintained as compared to control). Finally, TNF-alpha (100 ng/ml) enhanced the expression of Class I major histocompatibility complex antigens on cultured bovine luteal cells but did not alter IFN-gamma induction of Class II major histocompatibility complex antigens. In light of these findings, it appears that TNF-alpha, in conjunction with other cytokines, is a modulator of luteal cell function in vitro. The stimulation of PG synthesis, as well as cytotoxic effects of TNF-alpha, may suggest a role in luteolysis.