Toll-like receptor 2 expression on human conjunctival epithelial cells: a pathway for Staphylococcus aureus involvement in chronic ocular proinflammatory responses.
BACKGROUND
Staphylococcus aureus colonization is common in atopic keratoconjunctivitis, potentially activating epithelial cells via toll-like receptor 2 (TLR-2) and the receptor for platelet-activating factor (PAFR).


OBJECTIVE
To examine human conjunctival epithelial cells for the expression of TLR-2 in vitro and in vivo and to evaluate the role of TLR-2 in S aureus-mediated activation of these cells.


METHODS
Conjunctival epithelial cells isolated from cadaveric tissues were stimulated with interferon gamma (IFN-gamma) or a commercial S aureus cell wall extract (Staphylococcus aureus-CWE) (with or without anti-TLR-2 blocking antibody or PAFR antagonist) and were analyzed for tumor necrosis factor alpha (TNF-alpha) and interleukin 8 (IL-8) release; surface expression of TLR-2, intercellular adhesion molecule-1, HLA, and CD14; and TLR-2 messenger RNA expression. Ocular surface cells collected via impression cytology were examined for TLR-2 expression via flow cytometry.


RESULTS
Expression of TLR-2 was up-regulated on conjunctival epithelial cells by IFN-gamma and Staphylococcus aureus-CWE. Expression of TLR-2 messenger RNA was increased by IFN-gamma. Staphylococcus aureus-CWE up-regulated intercellular adhesion molecule 1, HLA, and CD14 expression and increased TNF-alpha and IL-8 release in a dose-dependent manner. Anti-TLR-2 significantly inhibited TNF-alpha release, whereas PAFR antagonist significantly inhibited IL-8 release. Toll-like receptor 2 was expressed on conjunctival epithelial cells from 4 of 5 patients with atopic keratoconjunctivitis, 3 of 5 with seasonal allergies, and 0 of 3 without allergies.


CONCLUSIONS
Conjunctival epithelial cells express TLR-2 and may play an active role in the chronic ocular inflammatory response to S aureus through pathways that involve TLR-2 and PAFR.
Cook
Ellen B
EB
Department of Medicine, School of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53792, USA. ebc@medicine.wisc.edu
Stahl
James L
JL
Esnault
Stéphane
S
Barney
Neal P
NP
Graziano
Frank M
FM
D000293:Adolescent; D000328:Adult; D015152:Blotting, Northern; D003228:Conjunctiva / Q000276:immunology* / Q000382:microbiology; D003231:Conjunctivitis / Q000276:immunology / Q000382:microbiology*; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology; D005260:Female; D006684:HLA-DR Antigens / Q000276:immunology; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology; D016209:Interleukin-8 / Q000276:immunology; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D008875:Middle Aged; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D013203:Staphylococcal Infections / Q000276:immunology* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000276:immunology*; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology
D006684:HLA-DR Antigens; D016209:Interleukin-8; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D007371:Interferon-gamma