title: In Vivo Role of TLR2 and MyD88 Signaling in Eliciting Innate Immune Responses in Staphylococcal Endophthalmitis.
abstract: OBJECTIVE
  The purpose of this study was to investigate the protective mechanisms evoked by TLR2 and MyD88 signaling in bacterial endophthalmitis in vivo.
  
  
  METHODS
  Endophthalmitis was induced in wild-type (WT), TLR2(-/-), MyD88(-/-), and Cnlp(-/-) mice by intravitreal injections of a laboratory strain (RN6390) and two endophthalmitis isolates of Staphylococcus aureus. Disease progression was monitored by assessing corneal and vitreous haze, bacterial burden, and retinal tissue damage. Levels of inflammatory cytokines/chemokines were determined using quantitative RT-PCR (qRT-PCR) and ELISA. Flow cytometry was used to assess neutrophil infiltration. Cathelicidin-related antimicrobial peptide (CRAMP) expression was determined by immunostaining and dot blot.
  
  
  RESULTS
  Eyes infected with either laboratory or clinical isolates exhibited higher levels of inflammatory mediators at the early stages of infection (≤24 hours) in WT mice than in TLR2(-/-) or MyD88(-/-) mice. However, their levels surpassed that of WT mice at the later stages of infection (>48 hours), coinciding with increased bacterial burden and retinal damage. Both TLR2(-/-) and MyD88(-/-) retinas produced reduced levels of CRAMP, and its deficiency (Cnlp(-/-)) rendered the mice susceptible to increased bacterial burden and retinal tissue damage as early as 1 day post infection. Analyses of inflammatory mediators and neutrophil levels in WT versus Cnlp(-/-) mice showed a trend similar to that observed in TLR2 and MyD88 KO mice. Furthermore, we observed that even a 10-fold lower infective dose of S. aureus was sufficient to cause endophthalmitis in TLR2(-/-) and MyD88(-/-) mice.
  
  
  CONCLUSIONS
  TLR2 and MyD88 signaling plays an important role in protecting the retina from staphylococcal endophthalmitis by production of the antimicrobial peptide CRAMP.
authors: Department of Ophthalmology/Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States Department of Biological Sciences, Oakland University, Rochester, Michigan, United States.
authors: Deepa
authors: D
authors: Talreja
authors: Department of Ophthalmology/Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States Department of Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States.
authors: Pawan Kumar
authors: PK
authors: Singh
authors: Department of Ophthalmology/Kresge Eye Institute, Wayne State University, Detroit, Michigan, United States.
authors: Ashok
authors: A
authors: Kumar
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D009877:Endophthalmitis / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D007113:Immunity, Innate / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics*; D012160:Retina / Q000276:immunology / Q000473:pathology; D015398:Signal Transduction / Q000235:genetics*; D013203:Staphylococcal Infections / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D051195:Toll-Like Receptor 2 / Q000235:genetics*
chemical_list: D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D018925:Chemokines; D016207:Cytokines; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2
keywords: CRAMP; MyD88; Staphylococcus aureus; TLR2; endophthalmitis; inflammation; retinal damage