Induction of cyclooxygenase (COX)-2 in human vaginal epithelial cells in response to TLR ligands and TNF-α

Abstract

Problem: Mucosal inflammation caused by infections of the female lower genital tract is considered to be an important cofactor for HIV transmission. We hypothesize that COX-2, a key inflammation-related enzyme, is involved in these responses and is upregulated by microbial ligands and pro-inflammatory cytokines.

Method of study: Human vaginal epithelial cells (VK-2/E6E7) and ectocervical biopsy tissues were stimulated with TLR ligands and the cytokine TNF-α, used as surrogates of vaginal infections, and assessed for COX-2 expression and activity by microarray, real-time RT-PCR, immunoblotting, immunohistochemistry, and ELISA.

Results: TLR agonists and TNF-α induce transcriptional and translational expression of COX-2 in vaginal cells. TLR ligands, MALP2, Pam3CSK4, LTA, and imiquimod induced high epithelial COX-2 expression, while zymosan and poly dI:dC induced very low enzyme expression. Induced mRNA and protein expression correlated with increased COX-2 activity, which led to increased levels of PGE(2) in the cell culture supernatant. These cell-based findings were confirmed in primary cervicovaginal tissue explants.

Conclusion: Induction of COX-2 expression and activity and the consequent increased levels of prostaglandins are common inflammatory pathways in human cervicovaginal epithelial cells and tissues in response to diverse TLR ligands and pro-inflammatory cytokines. These findings are relevant to the understanding of genital mucosal inflammation, its potential treatment, and its possible relationship with increased tissue susceptibility to HIV-1 infection.