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

Abstract

To examine the kinetics and mechanisms of endotoxin-induced uveitis in the mouse. C3H/HeN mice were injected subcutaneously with 0.3 mg of Salmonella typhimurium lipopolysaccharide (LPS) in 0.1 mL of phosphate-buffered saline solution or phosphate-buffered saline solution alone in 3 separate experiments; mice were killed after 1, 3, 5, and 7 days. In 2 other separate experiments, mice were killed 1, 3, 6, and 24 hours after LPS injection. All eyes were collected for histological examination, immunohistochemical analyses, aqueous protein level determination, and reverse transcriptase-polymerase chain reaction for ocular interleukin (IL)1alpha, IL-6, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor messenger RNA (mRNA). Enzyme-linked immunosorbent assay was used to measure tumor necrosis factor alpha and IL-6 levels in aqueous and serum samples. Results were consistent for all experiments. Numbers of ocular inflammatory 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. However, ocular IL-1alpha, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor mRNA appeared, peaked, and subsided at 3, 5, and 7 days, respectively. Predominant infiltrating cells were neutrophils at 1 day and macrophages at 5 days. Although no ocular inflammatory cells were detected before 24 hours after LPS injection, tumor necrosis factor alpha mRNA 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. The ocular inflammatory response to C3H/ HeN mouse endotoxin-induced 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 inflammatory waves are related to the kinetics of the different cytokines released in the eye. This is in contrast to the rat monophasic endotoxin-induced uveitis model, which has only one peak of intense inflammation associated with cytokine release. A biphasic inflammatory response associated with cytokine release lasting several days is observed in C3H/HeN mice with endotoxin-induced uveitis. Because human anterior uveitis has a tendency to be recurrent in nature, this might be a better experimental model.