Iris pigment epithelial cells express a functional lipopolysaccharide receptor complex.
OBJECTIVE
Ocular pigment epithelial cells are hypothesized to play a role in the pathogenesis of acute anterior uveitis (AAU), where LPS activation of Toll-like receptors (TLRs) may serve as a trigger. In this study, the expression of LPS receptors in iris pigment epithelium (IPE) was determined.


METHODS
RT-PCR, flow cytometry, Western blot, and immunohistochemistry were used to investigate the expression of the LPS receptor complex (TLR4, MD-2, and CD14) in primary human IPE. Cytokine secretion by LPS-treated IPE was measured by multiplex bead array and ELISA. The role of CD14 in modulating the LPS response was investigated by addition of soluble CD14 and by antibody neutralization studies. In vivo expression of CD14 was examined by immunohistochemistry and Western blot analysis.


RESULTS
IPE expressed TLR4, MD-2, and CD14 in vitro and secreted a panel of proinflammatory cytokines (IL-6, CXCL8, CXCL10, CCL2, CCL4, and CCL5) when stimulated with LPS. CXCL8 secretion by LPS-treated IPE was dependent on CD14 and TLR4. CD14 was detected in CD68+ cells in the iris by immunohistochemistry and in normal aqueous by Western blot analysis.


CONCLUSIONS
IPE cells express a functional LPS receptor complex and are capable of promoting ocular inflammation through secretion of an array of proinflammatory mediators. CD14 was identified as a key molecule that modulated the LPS response in IPE.
Chui
Jeanie J Y
JJ
Department of Pathology, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia. jeanie.chui@gmail.com
Li
Monique W M
MW
Di Girolamo
Nick
N
Chang
John H
JH
McCluskey
Peter J
PJ
Wakefield
Denis
D
D001082:Aqueous Humor / Q000378:metabolism; D015153:Blotting, Western; D018929:Cell Culture Techniques; D017931:DNA Primers; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007498:Iris / Q000166:cytology / Q000378:metabolism*; D018950:Lipopolysaccharide Receptors / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000378:metabolism; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D055213:Retinal Pigment Epithelium / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D014602:Uvea / Q000378:metabolism
D017931:DNA Primers; C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4