Inhibitory effects of pyrrolidine dithiocarbamate on endotoxin-induced uveitis in Lewis rats

PURPOSE. To determine the effect of pyrrolidine dithiocarbamate (PDTC), an antioxidant nuclear factor (NF)-kappaB inhibitor, on the ocular inflammation induced by lipopolysaccharide (LPS). METHODS. Endotoxin-induced uveitis (EIU) was produced by a footpad injection of 200 mug LPS in male Lewis rats. PDTC (200 mg/kg) was injected intraperitoneally 30 minutes before the LPS administration. The number of infiltrating cells and protein concentration in the aqueous humor (AqH) was determined from the AqH collected at 24 hours. Immunohistochemical staining with a monoclonal antibody against activated NF-kappaB was performed to evaluate the effect of PDTC on NF-kappaB activation. Interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha mRNA expression in the iris-ciliary body (ICB) was determined by RNase protection assay (RPA). The levels of these cytokines and nitric oxide (NO) production were also determined. RESULTS. The number of cells in the AqH was 1100 +/- 254 cells/muL in rats injected with LPS and 90 +/- 43 cells/muL in rats pretreated with PDTC (P < 0.001). The concentration of proteins was significantly, lower in the AqH of rats pretreated with PDTC than in those without PDTC. The number of activated NF-kappaB-positive cells in the ICB was reduced by the PDTC treatment. The ICB at 6 hours after LPS injection exhibited increased expression of IL-1beta, IL-6, and TNF-alpha mRNAs, which was decreased after PDTC pretreatment. PDTC also significantly diminished the levels of these cytokines and nitrite-nitrate in the AqH. CONCLUSIONS. These results suggest that PDTC reduces ocular inflammation in eyes with EIU by downregulating proinflammatory cytokine expression and by inhibiting the NF-kappaB-dependent signaling pathway.