Saposhnikovia divaricata (SD), called "Fangfeng" in China, is commonly used in clinical compound prescription for treatment of rheumatoid arthritis (RA), but its actions on RA have not been clarified. The present study aims to determine the anti-inflammatory activity of SD chromone extract (SCE), the major bioactive component of SD, on collagen-induced arthritis (CIA) rats, and elucidate its underlying mechanisms with regards to its molecular basis of action on human fibroblast-like synoviocytes derived from RA patients (HFLS-RA).
CIA model on rats was constructed by injection of bovine type II collagen. Rats were pre-treated with different dosages of SCE from 3 days before till 35 days after model building. The progression of CIA was evaluated by macroscopic scoring, X-ray observation and hematoxylin and eosin (HE) staining of paws. HFLS-RA were pre-treated with different concentrations of SCE prior to stimulation with 10 ng/ml of tumor necrosis factor (TNF) α. By radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA), levels of interleukin (IL)-1β, IL-6, TNFα and prostaglandin E2 (PGE2) were quantified respectively. Nuclear factor (NF-κB) p65 expression and DNA-binding activity were tested by immunohistochemisty and electrophoretic mobility shift assay (EMSA) respectively. Phosphorylation of extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 MAPKs were examined by immunohistochemisty staining and western blot analysis.
Histological examination and radiological observation demonstrated that SCE significantly reduced the inflammatory responses in the joints of CIA rats. SCE inhibited the production of TNFα, IL-1β, and IL-6 in the joint tissues and sera. The level of PGE2 in sera was also decreased by SCE. Moreover, SCE treatment in vivo was able to reduce protein level of NF-κB, the transcriptional factor closely related to the inflammatory process, in articular synovium and cartilage of CIA rats. In addition, SCE inhibited p-ERK, p-JNK and p-p38 expression, which were considered to be involved in the phosphorylation of transcription factor NF-κB and the transcription of pro-inflammatory factors. Further, SCE inhibited NF-κB DNA binding activity and attenuated the phosphorylation of ERK, JNK and p38 MAPKs, in a concentration-dependent manner in cultured HFLS-RA.
These results highlight the anti-arthritic potential of SCE, and provide further evidence of the involvement of the NF-κB and MARKs inhibition in the effects of SCE.