Effect of Macrophage Migration Inhibitory Factor on Corneal Sensitivity after Laser In Situ Keratomileusis in Rabbit

PURPOSE: To investigate the effect of macrophage migration inhibitory factor (MIF) on corneal sensitivity after laser in situ keratomileusis (LASIK) surgery. METHODS: New Zealand white rabbits were used in this study. A hinged corneal flap (160-microm thick) was created with a microkeratome, and -3.0 diopter excimer laser ablation was performed. Expressions of MIF mRNA in the corneal epithelial cells and surrounding inflammatory cells were analyzed using reverse transcription polymerase chain reaction at 48 hours after LASIK. After LASIK surgery, the rabbits were topically given either 1) a balanced salt solution (BSS), 2) MIF (100 ng/mL) alone, or 3) a combination of nerve growth factor (NGF, 100 ug/mL), neurotrophine-3 (NT-3, 100 ng/mL), interleukin-6 (IL-6, 5 ng/mL), and leukemia inhibitory factor (LIF, 5 ng/mL) four times a day for three days. Preoperative and postoperative corneal sensitivity at two weeks and at 10 weeks were assessed using the Cochet-Bonnet esthesiometer. RESULTS: Expression of MIF mRNA was 2.5-fold upregulated in the corneal epithelium and 1.5-fold upregulated in the surrounding inflammatory cells as compared with the control eyes. Preoperative baseline corneal sensitivity was 40.56 +/- 2.36 mm. At two weeks after LASIK, corneal sensitivity was 9.17 +/- 5.57 mm in the BSS treated group, 21.92 +/- 2.44 mm in the MIF treated group, and 22.42 +/- 1.59 mm in the neuronal growth factors-treated group (MIF vs. BSS, p < 0.0001; neuronal growth factors vs. BSS, p < 0.0001; MIF vs. neuronal growth factors, p = 0.815). At 10 weeks after LASIK, corneal sensitivity was 15.00 +/- 9.65, 35.00 +/- 5.48, and 29.58 +/- 4.31 mm respectively (MIF vs. BSS, p = 0.0001; neuronal growth factors vs. BSS, p = 0.002; MIF vs. neuronal growth factors, p = 0.192). Treatment with MIF alone could achieve as much of an effect on recovery of corneal sensation as treatment with combination of NGF, NT-3, IL-6, and LIF. CONCLUSIONS: Topically administered MIF plays a significant role in the early recovery of corneal sensitivity after LASIK in the experimental animal model.

Expression of IRFs and iNOS in the Mouse Cornea with Pseudomonas Aeruginosa Keratitis

PURPOSE: To investigate the expression of IRF-1, IRF-7 and iNOS in the mice model of Pseudomonas aeruginosa keratitis. The enzymatic activity of iNOS and its expression were also investigated. METHODS: With western blot analysis, the protein expression of IRF-1, IRF-7 (at 24 hours), and iNOS (at 12 hours and 24 hours) were evaluated in the mouse model of P. aeruginosa keratitis. iNOS enzymatic activity was determined with a scintillation counter. IRF-1 and IRF-7 expression were localized with immunofluorescent labeling. The wounded control group was given the same corneal wound without bacterial inoculation, and the fellow eyes served as normal controls. RESULTS: Expression of IRF-1, IRF-7 and iNOS was highly upregulated in corneas with P. aeruginosa keratitis compared to normal or wounded corneas. iNOS enzymatic activity also was higher in infected than normal corneas. In wounded corneas, NOS2 expression and activity slightly increased at 12 hours after the infection. Intense IRF-1 immunopositivity was seen in the epithelial layer of infected corneas. Some corneal stromal cells and endothelial cells showed moderate positive labeling in infected corneas. IRF-7 showed intense labeling in the epithelial layer and endothelial cells of normal as well as infected corneas. Increased IRF-7 labeling was observed in epithelial cells in the ulcerated region of infected corneas. CONCLUSIONS: These results suggest that IRF-1, IRF-7 and iNOS may play a regulatory role in the immune responses and wound healing process in P. aeruginosa keratitis.