Toll‐like receptor (TLR) expression and TLR‐mediated cytokine/chemokine production by human uterine epithelial cells

TLDR

The study aimed to determine which toll‑like receptors (TLRs) are expressed by the human uterine epithelial cell line ECC‑1 and whether activating these receptors alters cytokine or chemokine secretion. ECC‑1 cells express TLR1–9 (except TLR10) and, upon stimulation of TLR2, TLR4 and TLR5, secrete IL‑8, MCP‑1 and IL‑6 in a dose‑dependent manner, while TLR3, TLR7 and TLR9 agonists have no effect, indicating that uterine epithelial cells serve as innate immune sentinels by selectively inducing inflammatory mediators through specific TLR pathways.

Abstract

The objective of this study was to examine the expression of toll-like receptors (TLRs) by the uterine epithelial cell line ECC-1 and to determine if stimulation of the expressed TLRs induces changes in cytokine and/or chemokine secretion. The expression of TLR1 to TLR9 by ECC-1 cells was demonstrated by reverse transcription polymerase chain reaction, with only TLR10 not being expressed. Stimulation of ECC-1 cells using agonists to TLR2, TLR4 and TLR5 induced the expression of the chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1), as well as the pro-inflammatory cytokine IL-6, and occurred in a dose-dependent manner. In response to zymosan and flagellin, pathogen-associated molecular patterns (PAMP) that are recognized by TLR2 and TLR5 respectively, ECC-1 cells secreted significantly more IL-8, MCP-1 and IL-6 than in response to other TLR agonists. In contrast, agonists to TLR3, TLR7, and TLR9 had no effect on the secretion of the 13 cytokines or chemokines analysed. These results indicate that uterine epithelial cells are important sentinels of the innate immune system. Further it indicates that all but one of the known TLRs are expressed by ECC-1 cells and that stimulation through specific TLRs mediates changes in the expression of key chemokines and pro-inflammatory cytokines that aid in the defence of the uterus against potential pathogens.