Endotoxin–Induced Uveitis in Fat–1 Transgenic Mice

Abstract

Purpose: : Omega–3 polyunsaturated fatty acids (n–3 PUFA) are reported to possess anti–inflammatory properties in certain organs such as heart, lung, bowel, joint, and skin, but their effect on the eye is unknown. To investigate the possible role of endogenous PUFA in ocular inflammation, we studied endotoxin–induced uveitis (EIU) in the fat–1 mouse, a transgenic mouse with a C–elegans encoded gene that results in an altered lipid profile with high endogenous n–3 PUFA.

Methods: : Fat–1 transgenic (n = 35) and wild–type control mice (n = 26) were maintained on an identical diet that was high in n–6 PUFA with a significantly low n–3 PUFA content. EIU was induced by a single intraperitoneal injection of 200 µg of Salmonella typhimurium lipopolysaccharide (LPS) in 0.1 ml PBS. Control groups received a 0. 1 ml PBS injection. All mice were euthanized 24 hours after injection. Routine ocular histopathology was performed. Expression of cytokine and chemokine level in the eyes was analyzed by quantitative real–time PCR for IL–6, TNF–α, MCP–1, RANTES, IL–1α, IFN–γ and IP–10/ CXCL10. Lipid profiles in serum and muscle were measured by gas chromatography.

Results: : The Experiment was repeated three times and had reproducible results. The lipid analysis demonstrated that the fat–1 mice showed a significantly lower ratio of n–6: n–3 PUFA (5.76) and were significantly higher in n–3 PUFA (6.80%) than the wild–type mice (n–6: n–3 PUFA ratio 49.35, n–3 PUFA 1.07%, respectively). Serum n–6: n–3 PUFA ratios decreased in EIU. The fat–1 mice had a much lower mortality (3.70%) as compared to the wild–type mice (28.98%) after LPS injection. The EIU score was somewhat lower in the fat–1 mice (9.38±2.82, mean± SE) compared to the wild–type mice (15.77±3.18). The CXCL10 expressions of eyes in the fat–1 mice (83.28–folds) were markedly increased as compared to the wild–type mice (17.20–folds); IP–10 and IFN–γ transcripts of fat–1 mouse lungs (149.90–fold, 5.30–fold) and spleens (59.57–fold, 1.45–fold) were also higher as compared to the transcript expression of CXCL10 and IFN–γ of the wild–type mice lung (20.52–fold and 1.13–fold respectively) and spleen (27.58–fold and 0.84–fold, respectively).

Conclusions: : These data suggest that the higher level of endogenous n–3 PUFA protects against LPS endtoxin shock. CXCL10, a T–cell chemokine may downregulate EIU in fat–1 mice.

Keywords: cytokines/chemokines • inflammation • uveitis-clinical/animal model