Fig. 9

Diagram illustrating the involvement of IL-33/ST2 axis in inflammatory reactions in human amnion fibroblasts. The inflammatory mediators pertinent to parturition such as LPS, IL-1β and SAA1 stimulate the expression of IL-33 expression and secretion via activation of NF-κB. In turn, via binding to ST2 receptor, IL-33 activates JNK, ERK1/2 and p38 by phosphorylation, which subsequently leads to the activation of NF-κB through phosphorylation of its subunit p65 resulting in increased expression of inflammatory factors including IL-1β, IL-6 as well as COX-2, the rate-limiting enzyme in PGE2 synthesis. The increased production of PGE2 and pro-inflammatory cytokines participate in fetal membrane activation, uterine contraction and cervical ripening at parturition