Toll-like receptor 4 and CD14 expression in human ciliary body and TLR-4 in human iris endothelial cells

• Published in: Experimental eye research Vol. 79; no. 2; pp. 203 - 208
• Main Authors: Brito, Beatriz E., Zamora, David O., Bonnah, Robert A., Pan, Yuzhen, Planck, Stephen R., Rosenbaum, James T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-08-2004
• Subjects: Adult; Antibodies, Monoclonal - immunology; CD14; Cells, Cultured; ciliary body; Ciliary Body - metabolism; Cytokines - biosynthesis; endothelial cells; Endothelial Cells - metabolism; Gene Expression Regulation; human; Humans; iris; Iris - metabolism; Lipopolysaccharide Receptors - metabolism; Lipopolysaccharides; Membrane Glycoproteins - genetics; Membrane Glycoproteins - immunology; Membrane Glycoproteins - metabolism; Middle Aged; Receptors, Cell Surface - genetics; Receptors, Cell Surface - immunology; Receptors, Cell Surface - metabolism; RNA, Messenger - genetics; Toll-Like Receptor 4; Toll-Like Receptors; toll-like receptor-4; endothelial cells; iris; CD14; ciliary body; human
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2004.03.012

We investigated the expression of the functional endotoxin receptor proteins Toll-like receptor-4 and CD14 in human eyes. Toll-like receptor-4 and CD14 proteins were detected by immunohistochemical analysis of sections of whole human eyes embedded in paraffin with monoclonal antibodies against human toll-like receptor-4 (HTA-125), human CD14 (RPA-M1), or as a control, an irrelevant mouse IgG1k (MOPC-21). Incubation of explants with a neutralizing anti-toll-like receptor-4 monoclonal antibody was used to determine if lipopolysaccharide stimulation of tumor necrosis factor or interleukin-6 secretion was dependent on Toll-like receptor-4 activity. Reverse transcription-polymerase chain reaction was used to detect mRNAs for toll-like receptor-4, tumor necrosis factor-α, interleukin-1β, interleukin-6 and interleukin-8, 3
hr after stimulation of cultured iris microvascular endothelial cells. By immunohistochemistry, human ciliary body non-pigmented epithelial cells showed strong expression of the endotoxin receptor proteins, toll-like receptor-4 and CD14. Toll-like receptor-4 antibodies significantly inhibited lipopolysaccharide-stimulated tumor necrosis factor secretion by the ciliary body. Toll-like receptor-4 mRNA was constitutively expressed in iris endothelial cells and slightly down-regulated by endotoxin. mRNA levels for tumor necrosis factor-α, interleukin-1β, interleukin-6 and interleukin-8 were all increased by endotoxin treatment. This is the first report that shows intraocular (ciliary body and iris) expression of toll-like receptor-4, other than in cornea. Our results show that the ciliary body also expresses CD14, which is anatomically colocalized with toll-like receptor-4. This suggests a potential interaction between both molecules during endotoxin activation of ciliary body cells. The juxtaposition of toll-like receptor-4 and CD14 in the anterior uveal tract helps to explain the sensitivity of the iris/ciliary body to bacterial endotoxin as seen in the standard animal model of endotoxin-induced uveitis.