title: TLR-mediated induction of pro-allergic cytokine IL-33 in ocular mucosal epithelium.
abstract: Interleukin (IL) 33 has been recently identified as a ligand to the ST2 receptor that mediates Th2-dominant allergic inflammation. The purpose of this study was to explore the role of toll-like receptor (TLR)-mediated innate immunity in IL-33 induction by mucosal epithelium. Human corneal tissues and cultured primary human corneal epithelial cells (HCECs) were treated with a variety of viral or bacterial components without or with different inhibitors to evaluate the IL-33 regulation and signaling pathways. The level of mRNA expression was determined by reverse transcription and real time PCR, and protein was measured by ELISA, immunostaining and Western blotting. IL-33 mRNA and protein were largely induced by various microbial components, mainly by polyI:C and flagellin, the ligands to TLR3 and TLR5, respectively in human corneal epithelium ex vivo and in vitro cultures. Pro-IL-33 protein was normally restricted inside cells, and could be secreted outside when activated by ATP. The PolyI:C induced IL-33 production was blocked by TLR3 antibody or TRIF Inhibitory peptide, while flagellin stimulated IL-33 was blocked by TLR5 antibody or MyD88 Inhibitory peptide. Interestingly, IκB-α inhibitor (BAY11-7082) or NF-κB inhibitor (quinazoline) blocked NF-κB p65 protein nuclear translocation, and suppressed IL-33 production induced by PolyI:C and flagellin. These findings demonstrate that IL-33, an epithelium-derived pro-allergic cytokine, is induced by microbial ligands through TLR-mediated innate signaling pathways, suggesting a possible role of mucosal epithelium in Th2-dominant allergic inflammation.
authors.affiliation: Ocular Surface Center, Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Lili
authors.initials: L
authors.lastname: Zhang
authors.forename: Rong
authors.initials: R
authors.lastname: Lu
authors.forename: Guiqiu
authors.initials: G
authors.lastname: Zhao
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Pflugfelder
authors.forename: De-Quan
authors.initials: DQ
authors.lastname: Li
mesh_terms: D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D004075:Diglycerides / Q000276:immunology / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000276:immunology / Q000378:metabolism*; D005408:Flagellin / Q000276:immunology / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism; D007113:Immunity, Innate; D000067596:Interleukin-33; D007378:Interleukins / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D009842:Oligopeptides / Q000276:immunology / Q000494:pharmacology; D011070:Poly I-C / Q000276:immunology / Q000494:pharmacology; D061251:Primary Cell Culture; D011804:Quinolines / Q000494:pharmacology; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000819:agonists / Q000378:metabolism*
chemical_list: C557465:1-(2-methylpropyl)-1H-imidazo(4,5-c)quinolin 4-amine; D004075:Diglycerides; C460864:FSL-1 lipoprotein, synthetic; C506536:IL33 protein, human; D000067596:Interleukin-33; D007378:Interleukins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009842:Oligopeptides; D011804:Quinolines; D051193:Toll-Like Receptors; D005408:Flagellin; D051550:I-kappa B Kinase; D011070:Poly I-C