A role for IL-17 in induction of an inflammation at the fetomaternal interface in preterm labour

Chorioamnionitis (CAM) is a major cause of preterm delivery. Inflammatory cytokines and chemokines play important roles in the pathogenesis of preterm delivery. Interleukin (IL)-17 is a key cytokine which induces inflammation and is critical to host defense. In this study, we examined the role of IL-17 in the pathogenesis of preterm delivery. The levels of cytokines including IL-17, IL-8 and tumor necrosis factor (TNF) alpha were measured by ELISA in amniotic fluid from 154 cases of preterm labor. Flow cytometry and immunohistochemical staining were performed to determine the distribution of IL-17-producing cells. IL-8 secretion was evaluated in primary cultured human amniotic mesenchymal (HAM) cells and human amniotic epithelial (HAE) cells stimulated with IL-17, TNFalpha or IL-1beta. We also studied the signaling pathway of IL-17 and TNFalpha in HAM cells. Levels of inflammatory cytokines in amniotic fluid were higher in preterm delivery cases than in term delivery cases. Furthermore, IL-8, IL-17 and TNFalpha levels were significantly higher in the preterm cases with CAM stage II or III than those without CAM. Flow cytometry and immunohistochemical staining revealed that CD3(+)CD4(+) T cells were the main source of IL-17 in the chorioamniotic membrane. Interestingly, TNFalpha-induced IL-8 secretion was enhanced by IL-17 in a dose-dependent manner in HAM cells. The IKK inhibitor BMS-345541 and mitogen-activated protein kinase (MAPK) inhibitors p38, JNK and p42/44 (ERK1/2 pathway) reduced IL-8 secretion by IL-17-stimulated and TNFalpha-stimulated HAM cells. These results indicate that IL-17, produced by T cells, promotes inflammation at the fetomaternal interface in preterm delivery.