Biphasic ocular inflammatory response to endotoxin-induced uveitis in the mouse

Objective: To examine the kinetics and mechanisms of endotoxin-induced uvei tis in the mouse. Methods: C3H/HeN mice were injected subcutaneously with 0.3 mg of Salmonell a typhimurium lipopolysaccharide (LPS) in 0.1 mt of phosphate-buffered sali ne solution or phosphate-buffered saline solution alone in 3 separate exper iments; mice were killed after 1, 3, 5, and 7 days. In 2 other separate exp eriments, mice were killed 1, 3, 6, and 24 hours after LPS injection. All e yes were collected for histological examination, immunohistochemical analys es, aqueous protein level determination, and reverse transcriptase-polymera se chain reaction for ocular interleukin (IL)1 alpha, IL-6, tumor necrosis factor or, and granulocyte-macrophage colony-stimulating factor messenger R NA (mRNA). Enzyme-linked immunosorbent assay was used to measure tumor necr osis factor or and IL-6 levels in aqueous and serum samples. Results: Results were consistent for all experiments. Numbers of ocular inf lammatory cells and levels of aqueous protein peaked 1 and 5 days after LPS injection. Control mice did not develop inflammation. Serum and aqueous IL -6 and ocular IL-6 mRNA levels peaked at 1 day and subsided at 3 days. Howe ver, ocular IL-1 alpha, tumor necrosis factor or, and granulocyte-macrophag e colony-stimulating factor mRNA appeared, peaked, and sub-sided at 3, 5, a nd 7 days, respectively. Predominant infiltrating cells were neutrophils at 1 day and macrophages at 5 days. Although no ocular inflammatory cells wer e detected before 24 hours after LPS injection, tumor necrosis factor or mR NA was noticed at 1 hour, peaked at 3 hours, and disappeared at 6 hours and granulocyte-macrophage colony-stimulating factor mRNA was spotted only at 3 hours after LPS injection. Conclusions: The ocular inflammatory response to C3H/ HeN mouse endotoxin-i nduced uveitis is biphasic for 7 days. The first wave appears at day 1 and subsides by day 3. A second, higher peak appears at day 5. The 2 inflammato ry waves are related to the kinetics of the different cytokines released in the eye. This is in contrast to the rat monophasic endotoxin-induced uveit is model, which has only one peak of intense inflammation associated with c ytokine release. Clinical Relevance: A biphasic inflammatory response associated with cytoki ne release lasting several days is observed in C3H/HeN mice with endotoxin- induced uveitis. Because human anterior uveitis has a tendency to be recurr ent in nature, this might be a better experimental model.