Abstract
Purpose: :
Conjunctival epithelial cells serve as a first line of defense against pathogens presented to the innate immune system. The inflammatory response to Gram-negative bacteria is initiated by Toll-like receptor 4 (TLR4). The purpose of our study was to investigate whether a TLR4 ligand induces production of inflammatory cytokines in human conjunctival epithelial cells (HCECs) through nuclear factor kappa-B (NF-ΚB).
Methods: :
HCECs were stimulated with various concentrations of lipopolysaccharide (LPS). HCECs were evaluated for TLR4 expression by reverse transcriptase polymerase chain reaction (RT-PCR) and flow cytometric analysis. The innate immune response was quantified by measuring expression of the inflammatory cytokines IL-6 and IL-8. Functional NF-ΚB activation was examined using a luciferase reporter assay.
Results: :
Expression of TLR4-specific mRNA as well as its corresponding protein was observed both intracellularly and on the cell surface of HCECs. Incubation of HCECs with LPS led to activation of the NF-ΚB transcription factor and secretion of IL-6 and IL-8 in a dose dependent manner. Blockade of TLR4 and TRAF6 activity abolished induction of the inflammatory response to LPS in HCECs. LPS did not induce the expression of TLR4 in HCECs.
Conclusions: :
Our results demonstrated that surface expression of TLR4 in human conjunctival epithelial cells was able to elicit a TLR4-mediated innate immune response and contribute to an inflammatory environment on the ocular surface.
Keywords: conjunctiva • inflammation • immunomodulation/immunoregulation