Objective: The study aims to investigate and discuss the therapeutic effect and the mechanism of topical resveratrol (Res) on rats with uveitis. Methods: In this experimental study, 36 Wistar male rats were randomly divided into six equal groups as follow: control group, model group, 0.25% Res group, 0.5% Res
group, 1% Res group, and 0.1% dexamethasone (Dex) group. The endotoxin lipopolysaccharide (LPS) was dissolved in normal sterile saline (1 mg/ml) and subcutaneously injected (200 μg LPS) into the hind feet of rats to induce uveitis in the model group and in the four treatment groups. Rats from the control group were injected with the equal volume of the normal sterile saline solution. For the 4 treatment groups, 10 μl of Res (0.25, 0.5, or 1%) or Dex (0.1%) solutions were applied topically as drops to both eyes, every 2 hours, 6 times before LPS injection and continued every 2 hours, 6 times after injection. Rats of the control and model groups received the same amount of saline. During the observation phase, the inflammation of the anterior segment was observed, and the clinical scores were evaluated 24 h after LPS injection. Anterior segment photography was performed 24 h after LPS injection. The levels of TNF-α and IL-6 in the aqueous
humor were determined 24 h after LPS injection. At the end of experiment, the rats were sacrificed and the eyeballs were fixed for histopathological examination. The nuclear translocation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-κB) p65 in the iris ciliary body (ICB) were stained by immunohistochemistry. Data analysis was performed using one-way ANOVA and the Mann-Whitney U test. Results: In the model group, iris vasodilatation was observed 4 h after LPS injection, and the inflammatory reaction gradually increased. After 24 h, massive exudation was present in the anterior chamber, and fibrous exudation was present in the pupil area and anterior capsule of the lens. 1% Res group reacted much smaller than the model group. The composite clinical score of the model group was 4.3±1.2,which was significantly greater than for the 1% Res group, 2.0±0.6 (P<0.05). The TNF-α and IL-6 levels in the aqueous humor of the 1% Res group were significantly lower than for the model group (P<0.05).Consistent with these data, the histopathological damage of the ocular tissue treated with 1% Res was less severe than that of model group (P<0.05). Lastly, the expression of p38 MAPK and NF-κB p65 levels in the 1% Res group were lower than in the model group (P<0.05). Conclusions: The topical administration of 1% Res suppressed ocular inflammation due to LPS injection in endotoxin induced uveitis (EIU) rats and decreased the levels of inflammatory cytokines associated with the inhibition of MAPK and NF-κB signaling pathway.