Expression of interleukin-6 in the cornea in response to infection with different strains of Pseudomonas aeruginosa

Strains of Pseudomonas aeruginosa causing keratitis can be either cytotoxic (6206) or invasive (6294), while a strain (Paer1) causing contact lens-ind uced acute red eye has been shown to be neither. In situ hybridization was used to examine the location and identity of cells expressing interleukin-6 (IL-6) mRNA in the murine cornea and changes in expression in response to infection with different strains of P. aerginosa. The number of IL-6-positi ve cells was determined by image analysis, IL-6 protein levels were measure d by an enzyme-linked immunosorbent assay. BALB/c mice were challenged by u se of the wounded-cornea model with P. aeruginosa 6294, 6206, or Paer1 (2 x 10(6) CFU), At time intervals up to 24 h, postchallenge corneal tissue was probed for IL-6 mRNA IL-6 mRNA expression was rapidly elevated in the epit helium in response to strains 6294 and 6206, At the conclusion of the exper iments, infiltrating inflammatory cells also stained positively for IL-6 mR NA, In contrast, corneas challenged with strain Paer1 showed significant up regulation of IL-6 mRNA only at 4 h postchallenge. Three distinct patterns of IL-6 mRNA expression in the mouse cornea occur in response to these thre e ocular isolates of P, aeruginosa, The data obtained for mRNA expression i n the cornea for all three strains of P, aeruginosa correlated well with IL -6 protein analysis of whole-eye homogenates. Differences in the cytokine r esponses to these strains correlate with differences in the pathology assoc iated with each strain and may offer an opportunity to develop strategies f or the improved management of ocular inflammation.