Therapeutic effects of the total lignans from Vitex negundo seeds on collagen-induced arthritis in rats

The seeds of Vitex negundo, with rich lignans metabolites, have been widely used as a traditional Chinese medicine and Ayurvedic herbal medicine for the treatment of rheumatism and joint inflammation. The total lignans of Vitex negundo seeds (TOV) were suggested to play an important role in the treatment of arthritis. The aim of the study was designed to investigate the anti-arthritic effects of TOV on collagen-induced arthritis (CIA) in rats as well as its possible mechanisms. TOV was prepared by combined macroporous resin and polyamide column chromatography, and constituents of TOV were analyzed by HPLC. CIA model in rats was established by immunization with chicken type II collagen and then the rats were intragastrically administrated with TOV for 30 days. Rat arthritis was evaluated by measurements of hind paw edema, arthritis index score, weight growth and indices of thymus and spleen, and by histological examination. Levels of serum MMP-2, MMP-3, MMP-9, IL-1β, IL-6, IL-8, IL-10, IL-17A and TNF-α were also examined. In addition, the expression of COX-2, iNOS and IκB, p–IκB in synovial tissues was evaluated by western blotting. The analgesic and anti-inflammatory effects of TOV were also evaluated in acetic acid-induced writhing and xylene-induced ear edema in mice, respectively. In addition, acute toxicity test was employed to preliminarily assess the safety of TOV. TOV significantly inhibited the paw edema and decreased the arthritis index, with no influence on the body weight and the indices of thymus and spleen of CIA rats. Meanwhile, TOV dose-dependently reduced the infiltration of inflammatory cells, synovial hyperplasia and attenuated cartilage damage. Additionally, the serum levels of IL-1β, IL-6, IL-8, IL-17A, TNF-α, MMP-3 and MMP-9 were markedly decreased, while the level of serum IL-10 was increased in TOV-treated rats. The significant reduction of the expression of COX-2, iNOS and p-IκB and the notable increase of IκB in synovial tissues were also observed in TOV-treated animals. TOV also significantly inhibited acetic acid-induced writhing and decreased xylene-induced ear edema in mice. Finally, the maximal tolerable dose (MTD) of TOV was determined to be 16.0 g/kg. These results suggest that TOV has significant anti-arthritic effects on collagen-induced arthritis in rats, which may be attributed to the inhibition of the levels of IL-1β, IL-6, IL-8, IL-17A, TNF-α, MMP-3 and MMP-9, and the increase of IL-10 in serum as well as down-regulation of the protein expression of COX-2 and iNOS in synovial tissues via suppressing the phosphorylation and degradation of IκB. Due to its high efficacy and safety, TOV can be regarded as a promising drug candidate for rheumatoid arthritis treatment.