Effects of Tumor Necrosis Factor α and Interferon γ on the Viability and mRNA Expression of TNF Receptor Type I in Endothelial Cells from the Bovine Corpus Luteum

The corpus luteum (CL) is mainly composed of luteal steroidogenic cells (LSCs) and luteal endothelial cells (LECs). Cell death of LSCs and LECs is essential for structural luteolysis. Therefore, it is important to understand the mechanisms regulating cell death in both types of luteal cells. We previously reported that a treatment combining tumor necrosis factor alpha (TNF) and interferon gamma (IFNG) induced cell death in LSCs and that LECs express TNF receptor type I (TNFRI). To investigate the mechanism of cell death in LECs, in the present study we determined the effects of the same cytokines on cell viability and TNFRI mRNA expression in cultured LECs. To induce cell death in LECs, LECs were treated with TNF or IFNG (0, 0.05, 0.5, 1.0, 2.5 nM) and a combination of TNF (0.5 riM) and IFNG (0.5 nM) for 24 h. The viability of LECs was reduced by a single treatment with TNF or IFNG dose-dependently (P<0.05). Cell viability was further decreased by treatment with a combination of TNF and IFNG (P<0.05). Cells with DNA fragmentation (TUNEL-positive cells) were observed after the treatment with TNF and IFNG. Semi-quantitative RT-PCR analysis revealed that treatment with IFNG alone or in combination with TNF increased the expression of TNFRI mRNA compared with the control (P<0.05). In summary, TNF and IFNG increased cell death in cultured bovine LECs. The upregulation of TNFRI mRNA expression by IFNG suggests that TNF and IFNG synergistically affect the death of LECs resulting in acute luteolysis.