OBJECTIVETo investigate whether the dried root of Phellodendron amurense Ruprecht (Phellodendri cortex; PC) extract improves arthritic symptoms through anti-inflammatory and immune-modulatory effects in collagen-induced arthritis in mice.

METHODSRheumatoid arthritis (RA) was induced in male DBA/1 mice by immunization with type II collagen (ColII). CIA mice were divided into 5 groups (n=10 per a group) with normal, CIA control, PC extract (50 mg/kg and 100 mg/kg)-treated, and meloxicam (50 mg/kg)-treated as the reference drug. The PC extract or meloxicam were administered orally in CIA mice once a day for 14 days after arthritis induction. Arthritic score, levels of anti-ColII IgGantibody, prostaglandin E(PGE), tumor necrosis factor (TNF)-α, and interleukin (IL)-17 in the sera of CIA mice were measured. Histopathological changes in the ankle joints of CIA mice were also analyzed by staining with hematoxylin and eosin (H and E), safranin-O and immunohistochemistry using anti-TNF-α and anti-IL-17 antibodies.

RESULTSThe arthritic score was increased in CIA mice in a time-dependent manner, as were the serum levels of anti-ColII IgGantibody, PGE, TNF-α, and IL-17. However, the oral administration of PC extract at 50 and 100 mg/kg in CIA mice significantly decreased the arthritic scores, and the serum levels of anti-ColII IgG, PGE, TNF-α, and IL-17 compared with those in the CIA group (P<0.05 or P<0.01). Furthermore, histopathological improvement of the joint architecture in CIA mice was observed after administration of PC extract. PC extract also significantly inhibited the expression of TNF-α and IL-17 in the joints of CIA mice by suppressing the expression of their mRNA and proteins.

CONCLUSIONPC extract may improve the pathological progression of RA through the inhibition of joint destruction by synovial inflammation and immune-stimulation, therefore, it would be a potential anti-arthritic agent in RA.