Prostaglandin F_2α amplifies tumor necrosis factor-α promoter activity by the FP_B prostanoid receptor

This study examines the regulation of tumor necrosis factor-α (TNF-α) promoter activity by prostaglandin F_2α (PGF _2α) in HEK cells stably expressing either the FP_A or FP_B prostanoid receptors. Cells were transiently transfected with a luciferase reporter plasmid under the control of a TNF-α promoter and luciferase activity was measured. In the absence of PGF_2α basal TNF-α reporter gene activity is elevated in FP_B cells as compared with FP_A cells. This elevated basal activity is blocked by pretreatment with a Rho inhibitor, but not by pretreatment with an inhibitor of protein kinase C (PKC). TNF-α reporter activity in FP_B cells is stimulated by PGF_2α and this is decreased by pretreatment with a chelator of intracellular calcium or by a gap junction inhibitor. In FP _B cells pretreatment with a Rho inhibitor combined with either a calcium chelator or a gap junction inhibitor decreases both basal and PGF _2α stimulated TNF-α reporter activity. Interestingly post-treatment of FP_B cells with an inhibitor of PKC decreased PGF_2α stimulated TNF-α reporter gene activity even though pretreatment did not. It, therefore, appears that PGF_2α stimulated TNF-α reporter activity in FP_B cells is amplified by a Rho-dependent mechanism involving calcium, gap junctions, and PKC. These findings may help in understanding the function of the FP_B isoform in the corpus luteum.