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Z. Zhou, R. P. Barrett, S. McClellan, L. D. Hazlett; Fas-Fas Ligand Interaction Promotes Apoptosis and Down-Regulates Inflammation in P. aeruginosa Infected Cornea. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2395.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study was to test the role of the Fas pathway in the resistance response of BALB/c mice following P. aeruginosa infection by contrasting the response of CPt.C3-Faslgld/J (FasL-/-) vs. wild type BALB/c (wt) mice.
To initiate infection, cornea were scarified and P. aeruginosa delivered topically. At various times postinfection (p.i.), slit lamp examination, clinical score, bacterial plate counts, myeloperoxidase (MPO), nitrite, TUNEL, RT-PCR and ELISA assays were performed. In addition, in vitro studies tested peritoneal macrophage (Mϕ) elicited from the two mouse groups after stimulation with lipopolysaccharide (LPS) followed by RT-PCR and ELISA assays.
FasL-/- vs. wt mice exhibited worsened corneal disease at 3 and 5 days p.i., as well as significantly elevated viable bacterial counts and PMN number at both 1 and 3 days p.i. Intense TUNEL staining for apoptotic cells was seen in wt mice at 1 day p.i., but was delayed in FasL-/- mice until 3 days p.i. The early apoptotic pattern correlated with elevated mRNA levels for caspases 3, 8, 9 and BAX in wt vs. FasL-/- mouse cornea at 1 day p.i. Furthermore, mRNA expression levels for TNF-, TNF- receptor, MIP-2, IFN-γ and inducible nitric oxide synthase (iNOS) were significantly elevated in the infected cornea of FasL-/- vs. wt mice and ELISA assay selectively confirmed the mRNA difference at the protein level for MIP-2 expression. In addition, FasL-/- mice also showed increased nitrite levels (Griess reaction) in the infected cornea. In vitro, LPS stimulated Mϕ from FasL-/- mice expressed significantly less caspase 3, and more MIP-2 and TNF- when compared to cells from wt mice, consistent with the in vivo data.
These data provide evidence that Fas-FasL interaction in the cornea modulates the immune response and improves disease outcome through promotion of earlier apoptosis of inflammatory cells and down-regulation of local inflammatory cytokines/chemokines and nitric oxide (nitrite) after P. aeruginosa infection.
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