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S.A. McClellan, X. Huang, L.D. Hazlett; IFN–: A Critical Regulator of Nitric Oxide Mediated Bacterial Killing in P. aeruginosa Keratitis. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4943.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Since IFN–γ may regulate levels of nitric oxide (NO), required for bacterial killing and the resistance response of BALB/c mice, the role of IFN–γ in regulating production of NO after corneal infection with Pseudomonas aeruginosa was examined using wildtype (wt) BALB/c vs. IFN–γ knockout (–/–) mice that endogenously lack the cytokine. Methods: Semi–quantitative RT–PCR was used to determine levels of mRNA for IFN–γ in resistant (cornea heals) wt BALB/c vs. IFN–γ –/– (susceptible, cornea perforates) mice at days 0, 1, 3, 5, and 7 p.i. NO levels were quantitiated in IFN–γ –/– and wt BALB/c mice at 3 and 5 days p.i. by detection of nitrite using the Griess reaction. Protein levels in cornea were analyzed at 5 days p.i. in IFN–γ –/–and wt BALB/c mice for cytokines/chemokines, including IL–1ß, IL–6, IL–10 and MIP–1α (CCL3) using a conventional ELISA assay. Results: Expression of IFN–γ mRNA levels was detectable only in the wt BALB/c mouse cornea at 1, 3, 5, and 7 days p.i., with peak expression levels seen at 5 days p.i. Corneal nitrite levels, as measured by the Griess reaction, were significantly higher in IFN–γ –/– vs. wt BALB/c mice at both 3 and 5 days p.i. Corneas from IFN–γ –/– mice also contained significantly more IL–1ß (2 fold) and MIP–1α (10 fold) protein than corneas of wt mice, but there was no difference in protein expression levels for IL–6 or IL–10 between the two groups. Conclusions: IFN–γ is critical for regulation of corneal NO production. Endogenous lack of IFN–γ leads to upregulation of the pro–inflammatory cytokine IL–1ß (and TNF–α) that are capable of inducing nitric oxide synthase (iNOS) transcription that contributes to higher and sustained NO production and corneal perforation.
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