PGF2α modulates the output of chemokines and pro-inflammatory cytokines in myometrial cells from term pregnant women through divergent signaling pathways

Prostaglandin F-2 alpha (PGF(2 alpha)) plays a critical role in the initiation and process of parturition. Since human labor has been described as an inflammatory event, we investigated the role of PGF(2 alpha) in the inflammatory process using cultured human uterine smooth muscle cells (HUSMCs) isolated from term pregnant women as a model. Using a multiplex assay, HUSMCs treated with PGF(2 alpha) changed their output of a number of cytokines and chemokines, with a distinct response pattern that differed between HUSMCs isolated from the upper and lower segment region of the uterus. Confirmatory enzyme-linked immunosorbent assays (ELISAs) showed that PGF(2 alpha) stimulated increased output of interleukin (IL) 1 beta, IL6, IL8 (CXCL8) and monocyte chemotactic protein-1 (MCP1, also known as chemokine (c-c motif) ligand 2, CCL2) by HUSMCs isolated from both upper and lower uterine segments. In contrast, PGF(2 alpha) inhibited tumor necrosis factor alpha (TNF alpha) release by HUMSCs from the lower uterine segment while the output of TNF alpha was undetectable in the upper segment. Small interfering (si) RNA mediated knockdown of the PGF(2 alpha) receptor prevented the changes in cytokine and chemokine output by the HUSMCs. Since the PGF(2 alpha) receptor (PTGFR) couples via the Gq protein and subsequently activates the phospholipase C (PLC) and protein kinase C (PKC) signaling pathways, we examined the role of these pathways in PGF(2 alpha) modulation of the cytokines. Inhibition of PLC and PKC reversed the effects of PGF(2 alpha). PGF(2 alpha) activated multiple signaling pathways including extracellular signal-regulated kinases (ERK) 1/2, phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), P38, calcineurin/nuclear factor of activated T-cells (NFAT) and NF-kappa B signaling. Inhibition of ERK reversed PGF(2 alpha)-induced IL1 beta, IL6 and CCL2 output, while inhibition of PI3K blocked the effect of PGF(2 alpha) on IL6, CXCL8 and CCL2 output and inhibition of NF-kB reversed PGF(2 alpha)-induced IL1b and CCL2 output. NFAT was involved in PGF(2 alpha) modulation of CCL2 and TNF alpha output. In conclusion, our results support a role of PGF(2 alpha) in creating an inflammatory environment during the late stage of human pregnancy.