Mitogen-Activated Protein Kinase Proteins Regulate LPS-Stimulated Release of Pro-inflammatory Cytokines and Prostaglandins from Human Gestational Tissues

The role of pro-inflammatory cytokines and prostaglandins in human labour is well established. Many of the mRNAs stabilised by the MAPK pathway encode inflammatory mediators, suggesting that this kinase pathway plays a major role in the regulation of inflammation. The aim of this study was to determine if the MAPK pathway regulates the inflammatory response in human gestational tissues. Placenta and fetal membranes (n = 5) obtained from pregnant women undergoing Caesarean section before the onset of labour were exposed to LPS, and co-incubated in the absence or presence of 12.5, 25 and 50 μM U0126 (ERK 1/2 inhibitor), SB202190 (p38 MAPK inhibitor) and SP600125 (JNK inhibitor). After 18 h incubation, tissues were collected and ERK 1/2, p38 MAPK, and JNK total and phosphorylated protein expression was assessed by ELISA and/or Western blotting. The incubation medium was collected and TNF-α, IL-1β, IL-6, IL-8, PGE2 and PGF2α release was quantified by ELISA. Treatment of placenta and fetal membranes with LPS activated all three MAPK proteins. Co-incubation with U0126, SP600125 and SB202190 significantly suppressed LPS-stimulated activation of ERK 1/2, JNK, and p38 MAPK, respectively. All cytokine and prostaglandin release was significantly suppressed by all concentrations of U0126. LPS-stimulated IL-6, TNF-α, PGE2 and PGF2α release was significantly suppressed by treatment with all concentrations of SB202190, whereas ILS-stimulated IL-1β release was only significantly inhibited in the presence of 50 μM SB202190 and there was no effect of SB202190 on LPS-stimulated IL-8 release. SP600125 significantly repressed LPS-stimulated release of IL-1β and TNF-α at all concentrations, whereas LPS-stimulated IL-6, PGE2 and PGF2α release were inhibited at 25 and 50 μM. In conclusion, the MAPK inhibitors used in this study demonstrated differential activity against a range of sequelae commonly associated with inflammation, supporting the therapeutic potential of MAPK inhibitors in pregnancy complications associated with an aberrant inflammatory response.