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  • Title: TLR4 is required for host resistance in Pseudomonas aeruginosa keratitis.
    Author: Huang X, Du W, McClellan SA, Barrett RP, Hazlett LD.
    Journal: Invest Ophthalmol Vis Sci; 2006 Nov; 47(11):4910-6. PubMed ID: 17065506.
    Abstract:
    PURPOSE: To determine the role of Toll-like receptor 4 (TLR4) in Pseudomonas aeruginosa (P. aeruginosa) keratitis in resistant (cornea-healing) BALB/c mice. METHODS: Corneal TLR4 mRNA levels were tested by real-time PCR in BALB/c mice before and after infection. Clinical score, slit lamp, histopathology, bacterial counts, and polymorphonuclear neutrophil (PMN) quantitation were performed in the infected cornea of TLR4-deficient (TLR4(lps-d)) and wild-type BALB/c mice. mRNA for IL-1beta, MIP-2, IFN-gamma, IL-18, inducible nitric oxide synthase (iNOS), and beta-defensin-2 levels were measured by real-time PCR. Protein levels for IL-1beta, MIP-2, and IFN-gamma were tested by ELISA. RESULTS: In resistant BALB/c mice, TLR4 mRNA expression was significantly upregulated in the cornea after P. aeruginosa infection. In contrast, TLR4-deficient mice were susceptible to infection with P. aeruginosa and showed increased corneal opacity, PMN infiltration, bacterial counts, and perforated infected corneas. After infection, TLR4-deficient mice also showed increased mRNA expression of proinflammatory cytokines (IL-1beta and MIP-2) and type-1-associated cytokines (IFN-gamma and IL-18) when compared with wild-type BALB/c mice. ELISA analyses showed that IL-1beta, MIP-2, and IFN-gamma protein levels also were significantly upregulated in the cornea of TLR4-deficient versus wild-type mice. In contrast, levels of iNOs and beta-defensin-2 were significantly decreased in TLR4-deficient compared with wild-type mice. CONCLUSIONS: TLR4 is critical in host resistance to P. aeruginosa, as its deficiency results in increased PMN infiltration and proinflammatory cytokine production, decreased iNOs and beta-defensin-2 production, impaired bacterial killing, and a susceptible phenotype.
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