Anti-inflammatory effect of lycopene on endotoxin-induced uveitis in rats

Purpose: We evaluated the efficacy of lycopene, a dietary carotenoid and potent antioxidant, against ocular inflammation and oxidative stress in an experimental uveitis model. Methods: Endotoxin-induced uveitis (EIU) was induced in Sprague-Dawley rats by a single subcutaneous injection of 200 mu g lipopolysaccharide (LPS). Induction of EIU was preceded by daily intraperitoneal injection of 10 mg/kg lycopene for three consecutive days (Lycopene + LPS group) or equivolume vehicle (Vehicle + LPS group). A positive control group received 1 mg/kg dexamethasone pretreatment (DEX + LPS), and a negative control group received daily vehicle injection but no LPS (Vehicle Control). Twenty-four hours after LPS or final vehicle administration, eyes were enucleated, and aqueous humor was collected for measurement of the number of infiltrating cells, total protein concentration, and levels of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and oxidative stress markers. Inflammatory response severity was compared among groups clinically and histopathologically. Results: Infiltrating cell number, total protein concentration, and NO, TNF-alpha, and IL-6 levels were significantly elevated in the aqueous humor of Vehicle + LPS group rats compared to Vehicle Controls. Compared to the Vehicle + LPS group, lycopene pretreatment significantly reduced aqueous humor concentrations of oxidative stress markers, NO (0.29 +/- 0.1 mu M vs. 0.19 +/- 0.1 mu M, p=0.003), TNF-alpha (71.0 +/- 22.3 ng/ml vs. 50.1 +/- 2.1 ng/ml, p=0.043), and IL-6 (121.6 +/- 3.0 pg/ml vs. 111.1 +/- 5.6 pg/ml, p=0.008). Inflammatory score was also reduced (2.0 +/- 0.0 vs. 0.4 +/- 0.5, p=0.001). Lycopene reduced the infiltrating cell count and protein concentration, but differences did not reach significance. Most lycopene effects were equivalent to dexamethasone. Conclusions: Lycopene may aid in the clinical management of uveitis by suppressing inflammation and oxidative stress.