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

Abstract

SUMMARYThe 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.

Estradiol selectively regulates innate immune function by polarized human uterine epithelial cells in culture

“…6 We also observed that under a variety of stimuli including TLR agonists (LPS, poly (I:C)) and IL-1β, epithelial cell secretion of cytokines, chemokines, and antimicrobials is enhanced. 5,38,39,41 Recognizing that the functions of E 2 in the FRT are multifaceted, we hypothesized that the E 2 would regulate UEC immune function in a way that would allow them to act as sentinels in the FRT by protecting against potential pathogens while simultaneously providing an environment for successful fertilization, implantation, and pregnancy. To the best of our knowledge, the results presented represent the first comprehensive study that systematically examines the seemingly opposite inductive and suppressive activities of E 2 on epithelial cells from the upper FRT.…”

“…5,39 To determine if E 2 regulates the secretion of the cytokines, we evaluated the effect of E 2 on macrophage migration inhibitory factor (MIF) secretion by primary UECs. Cells were incubated with or without E 2 in the basolateral compartment for 24 h after which TLR agonists LPS (1 µg ml − 1 ) or poly (I:C) (25 µg ml − 1 ) were added to the apical compartment for another 24 h. The total time for E 2 treatment was 48 h. The CM from apical and basolateral chambers were removed and MIF was measured by enzyme-linked immuno sorbent assay (ELISA).…”

“…5 In addition to constitutive production of cytokines and chemokines (interleukin (IL)-8, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor (TNF)-α, and macrophage inflammatory protein-1β (MIP-1β), 6 epithelial cells from the upper FRT (uterus and Fallopian tubes) as well as FRT epithelial cell lines respond to PAMPs by enhanced production/secretion of these factors. 5,7 For example, the TLR3 agonist poly (I:C) elicits the secretion of a spectrum of proinflammatory cytokines and chemokines including TNF-α, IL-6, GM-CSF, and G-CSF, as well as the chemokines IL-8, monocyte chemotactic protein-1 (MCP-1), and MIP-1β that attract and activate immune cells in the FRT. 5,7 ECC-1 cells, which are derived from UECs, respond to the TLR agonists zymosan and flagellin (TLR2 and −5, respectively) by secreting increased levels of IL-8, MCP-1, and IL-6.…”

“…5,7 For example, the TLR3 agonist poly (I:C) elicits the secretion of a spectrum of proinflammatory cytokines and chemokines including TNF-α, IL-6, GM-CSF, and G-CSF, as well as the chemokines IL-8, monocyte chemotactic protein-1 (MCP-1), and MIP-1β that attract and activate immune cells in the FRT. 5,7 ECC-1 cells, which are derived from UECs, respond to the TLR agonists zymosan and flagellin (TLR2 and −5, respectively) by secreting increased levels of IL-8, MCP-1, and IL-6. In recent studies, we have also demonstrated that lipopolysaccharide (LPS) (TLR4) and Pam 3 Cys (TLR2) treatments increase the secretion of MCP-1 and IL-8 by UECs in culture.…”

Increased expression of Toll-like receptor 3 in intrahepatic biliary epithelial cells at sites of ductular reaction in diseased livers

“…TLR3 is localized to endosomes and/or the cell surface in epithelial cells, while RIG-I/MDA5 resides in the cytoplasm [3][4][5]. TLR3-expressing epithelial cells are widely distributed throughout the body, with prominent expression in intestinal, cervical, uterine, endometrial, bronchial, and corneal epithelial cells, the central nervous system, and epidermal keratinocytes [6][7][8][9][10][11][12][13][14][15][16]. The function of TLR3 has been intensively studied in some of these epithelial cells; bronchial epithelial cells recognize dsRNA by cell-surface TLR3 and induce cellular responses, including the secretion of type 1 interferon (IFN) via the Toll-IL-1R homology domain-containing adaptor molecule 1 (TICAM-1)-interferon regulatory factor 3 (IRF3) signaling pathway [11,12].…”