Microbial compounds induce the expression of pro-inflammatory cytokines, chemokines and human β-defensin-2 in vaginal epithelial cells

Vaginal epithelium has a powerful innate immune system that protects the female reproductive organs from bacterial and fungal infections. In the present study, we aimed to explore whether the Toll-like receptor (TLR) signaling pathway and the induction of pro-inflammatory cytokines and antimicrobial peptides could contribute to the protection against pathogenic microorganisms in vaginal epithelia, using an immortalized vaginal epithelial cell line PK E6/E7 as a model. We found that TLR2 and TLR4 receptors are expressed in vivo in the vaginal epithelia and in vitro in PK E6/E7 vaginal epithelial cell line. The Gram-negative cell wall compound lipopolysaccharide (LPS), the Gram-positive compound peptidoglycan (PGN), heat-killed Candida albicans and zymosan significantly (P < 0.05) induced the expression of pro-inflammatory cytokines and chemokines such as TNF-α and IL-8/CXCL8 in vaginal epithelial cells. Furthermore, the expression and production of human β-defensin-2 (hBD2), an antimicrobial peptide with chemotactic functions, was also up-regulated in PK E6/E7 cells after treatment with LPS, PGN or C. albicans. Treatment of vaginal epithelial cells with microbial compounds induced the activation and nuclear translocation of NF-κB transcription factor, a key element of innate and adaptive immune responses. In our work, we provide evidence that microbial compounds induce the production of pro-inflammatory cytokines, chemokines and antimicrobial peptides in vaginal epithelial cells. In vivo, vaginal epithelial cell-derived inflammatory mediators and antimicrobial peptides may play important roles in vaginal immune responses and in the elimination of pathogens from the female reproductive tract.