Anti-Inflammatory Effect of the Proteasome Inhibitor Bortezomib on Endotoxin-Induced Uveitis in Rats

Abstract

We evaluated the anti-inflammatory effect of bortezomib (Velcade), a proteasome inhibitor, on endotoxin-induced uveitis (EIU) in rats and lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. EIU was induced by footpad injection of LPS into Lewis rats. MG-132 (10 mg/kg), or high-dose (0.2 mg/kg) or low-dose (0.05 mg/kg) bortezomib was given 30 minutes before LPS injection in each treatment group. The rats were sacrificed 24 hours later to observe the inflammatory response in tissues. The expression levels of fractalkine, MCP-1, ICAM-1, and iNOS were evaluated by PCR and Western blot analysis. Immunohistochemical (IHC) studies were used to demonstrate the expression of pro-inflammatory mediators and nuclear factor-kappa B (NF-κB) p65 in the iris and ciliary body. The DNA-binding activity of NF-κB was evaluated using an electrophoretic mobility shift assay (EMSA). An in vitro study using RAW 264.7 cells was performed to verify the results. Pretreatment with high-dose bortezomib significantly attenuated the inflammatory response of EIU. Reduced expression of inflammatory mediators always was observed in the high-dose bortezomib and MG-132 groups, but invariably was not noted in the low-dose bortezomib group. Decreased DNA-binding activity of NF-κB was noted in those rats pretreated with high-dose bortezomib or MG-132. In vitro study demonstrated the dose-dependent anti-inflammatory effects of bortezomib in LPS-stimulated RAW cells, consistent with the results obtained in vivo. Bortezomib inhibits EIU, probably by inhibiting the activation of NF-κB, which in turn, down-regulates the expression of the associated inflammatory genes. Proteasome inhibition may be a potential treatment strategy for uveitis.