Amelioration of collagen-induced arthritis by Salix nigra bark extract via suppression of pro-inflammatory cytokines and oxidative stress.

Our study goals to investigate the anti-arthritic potential of Salix nigra bark methanol extract (SNME) against both inflammation and oxidative stress in the collagen-induced arthritis (CIA) rat model. Results showed that SNME exhibited maximum scavenging activity against superoxide, hypochlorous acid and hydrogen peroxide radicals along with the suppression of lipid peroxidation. Female wistar rats were immunized with porcine type II collagen and treated with SNME (100 mg/kg body weight) for 15 days starting on day 20. SNME significantly inhibited the paw swelling and arthritic score; exhibited maximum CIA inhibition of 93.7% by the end of the experimental period. Administration of SNME to arthritic rats significantly improved the histological findings in joints as evident by reduced infiltration of polymorphonuclear cells and smooth synovial lining. Roentgenograms of tibiotarsal joints of both SNME and indomethacin-treated rats showed protection against osteophyte formation, soft tissue swelling and bone resorption. Furthermore, levels of inflammatory mediators (nitric oxide, TNF-α, IL-1β, IL-6) measured in both plasma and joint exudates were significantly reduced by SNME treatment. Increased oxidative stress observed in the arthritic animals was also found to be significantly restored in SNME- treated rats. Taken together, our studies clearly indicate the potential of S. nigra as an anti-arthritic agent.