In Vivo and In Vitro Anti-Arthritic Effects of Cardenolide-Rich and Caffeoylquinic Acid-Rich Fractions of Periploca forrestii

Periploca forrestii Schltr. (P. forrestii) is a species used in Traditional Chinese Medicine (TCM) known as "Miao medicine", and has a long history of use in the treatment of rheumatism, rheumatoid arthritis (RA), and joint pain. The present study aimed to evaluate the anti-arthritis effects of the cardenolide-rich and caffeoylquinic acid-rich fractions (CDLFs and CQAFs) of P. forrestii in collagen-induced arthritic (CIA) rats, and defined the mechanisms of therapeutic action in MH7A cells treated with TNF-α. Serum rheumatoid factor (RF), TNF-α, IL-6, IL-1β, PGE₂, NO, SOD, and MDA were determined by ELISA or other commercially assay kits. Histopathological changes in ankle joint tissues were examined. The mRNA expressions of IL-1β, IL-6, COX-2, and iNOS in MH7A cells were measured by qRT-PCR assays. In addition, the expressions of iNOS, COX-2, and p65 proteins, and the phosphorylation of IκBα, p38, ERK1/2, and JNK proteins in MH7A cells were analyzed by Western blot. The results showed that CDLF and CQAF could suppress the paw swelling in CIA rats at different doses (125 mg/kg, 250 mg/kg, and 500 mg/kg). Histopathological examination suggests that the CDLF and CQAF significantly relieved the damage of the structure of the ankle joint in CIA rats. In addition, serum RF, TNF-α, IL-6, IL-1β, PGE₂, NO, and MDA were decreased, along with increased activity of serum SOD. Furthermore, CDLF and CQAF downregulated the expressions of IL-1β, IL-6, COX-2, iNOS, and p65, and inhibited the phosphorylation of IκBα, p38, ERK1/2, and JNK in MH7A cells treated with TNF-α. These findings demonstrated that both CDLF and CQAF exhibited anti-arthritic activity, which might be associated with their inhibitory effects on the NF-κB and MAPK signaling pathways.