Keratocan and Lumican Regulate Neutrophil Infiltration and Corneal Clarity in Lipopolysaccharide-induced Keratitis by Direct Interaction with CXCL1 (original) (raw)

Keratocan and lumican are keratan-sulfate proteoglycans (KSPG), which have a critical role in maintaining corneal clarity. To determine whether these KSPGs have a role in corneal inflammation, we examined Kera ؊/؊ and Lum ؊/؊ mice in a model of lipopolysaccharide (LPS)-induced keratitis in which wild-type mice develop increased corneal thickness and haze due to neutrophil infiltration to the corneal stroma. Corneal thickness increases caused by LPS mice were significantly lower in Kera ؊/؊ and Lum ؊/؊ than wild-type mice. Further, LPS-injected Lum ؊/؊ mice had elevated corneal haze levels compared with that of Kera ؊/؊ and wild-type. At 24 h post-injection, total enhanced green fluorescent protein-positive bone marrow-derived inflammatory cells in chimeric mice was significantly lower in Kera ؊/؊ mice and Lum ؊/؊ mice compared with wildtype mice. Neutrophil infiltration was inhibited in Kera ؊/؊ and Lum ؊/؊ mice at 6 and 24 h post-stimulation, with Lum ؊/؊ corneas having the most profound defect in neutrophil migration. Reconstitution of keratocan and lumican expression in corneas of Kera ؊/؊ and Lum ؊/؊ mice using adeno-keratocan and adeno-lumican viral vectors, respectively, resulted in normal neutrophil infiltration in response to LPS. Immunoprecipitation/Western blot analysis showed that lumican and keratocan core proteins bind the CXC chemokine KC during a corneal inflammatory response, indicating that corneal KSPGs mediate neutrophil recruitment to the cornea by regulating chemokine gradient formation. Together, these data support a significant role for lumican and keratocan in a corneal inflammatory response with respect to edema, corneal clarity, and cellular infiltration.