title: Inflammatory Response to Lipopolysaccharide on the Ocular Surface in a Murine Dry Eye Model.
abstract: Toll-like receptor 4 (TLR4) alerts cells to the presence of bacteria by initiating an inflammatory response. We hypothesize that disruption of the ocular surface barrier in dry eye enhances TLR4 signaling. This study determined whether dry eye enhances expression of inflammatory mediators in response to topically applied TLR4 ligand.
  
  
  
  A single dose of lipopolysaccharide (LPS) or vehicle (endotoxin-free water) was applied to the cornea of nonstressed (NS) mice or mice subjected to 5 days of desiccating stress (DS). After 4 hours, corneal epithelium and conjunctiva were extracted to analyze expression of inflammatory mediators via PCR. Protein expression was confirmed by immunobead assay and immunostaining.
  
  
  
  Topically applied LPS increased expression of inflammatory mediators IL-1β, CXCL10, IL-12a, and IFN-γ in the conjunctiva, and IL-1β and CXCL10 in the cornea of NS mice compared to that in untreated controls. LPS in DS mice produced 3-fold increased expression of IL-1β in cornea and 2-fold increased expression in IL-12a in conjunctiva compared to that in LPS-treated control mice.
  
  
  
  LPS increased expression of inflammatory cytokines on the ocular surface. This expression was further increased in dry eye, which suggests that epithelial barrier disruption enhances exposure of LPS to TLR4+ cells and that the inflammatory response to endotoxin-producing commensal or pathogenic bacteria may be more severe in dry eye disease.
authors.affiliation: Ocular Surface Center Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Ken T
authors.initials: KT
authors.lastname: Simmons
authors.affiliation: Ocular Surface Center Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States 2Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.
authors.forename: Yangyan
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: Ocular Surface Center Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Pflugfelder
authors.affiliation: Ocular Surface Center Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Cintia S
authors.initials: CS
authors.lastname: de Paiva
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003228:Conjunctiva / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D003315:Cornea / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004195:Disease Models, Animal; D015352:Dry Eye Syndromes / Q000139:chemically induced / Q000175:diagnosis / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D012313:RNA / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D016207:Cytokines; D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D012313:RNA