7-deacetyl-gedunin suppresses proliferation of Human rheumatoid arthritis synovial fibroblast through activation of Nrf2/ARE signaling

Rheumatoid arthritis (RA) is an chronic autoimmune disease and characterized by high incidence. However, there is no effective therapies for RA. Therefore, it is urgent to discover new drugs for RA treatment. Nuclear factor erythroid 2 (NF-E2)-related factor (Nrf2) can effectively protect against arthritic inflammatory diseases through diverse stages, such as regulating redox balance, detoxification, metabolism and inflammation. Dimethyl fumarate (DMF), targets the Nrf2 pathway, was approved by FDA for the clinical treatment of multiple sclerosis (MS), which is another autoimmune disease. The latest report shown that DMF ameliorates complete Freund's adjuvant-induced arthritis in rats through activation of the Nrf2/HO-1 signaling pathway. Hence, Nrf2 serves as an important target for inflammation interference and oxidative stress of macrophages and RASFs in RA; therefore, it can be adopted as an effective therapeutic approach in the future. Rheumatoid arthritis synovial fibroblasts (RASFs) play crucial roles in the RA pathogenesis. Our results revealed that 7-deacetyl-gedunin (7-d-GDN), derived from fruits of Toona sinensis (A. Juss.) Roem, significantly inhibited RASFs proliferation in dose- and time- dependent manners and inhibited cell viability in MH7A cells, which is a kind of immortal cell line from joints of patients with RA. Additionally, 7-d-GDN remarkably down-regulated MMP-1/3/9/13 in RASFs, IL-6 and IL-33 in MH7A cells. Besides, 7-d-GDN sharply inhibited reactive oxygen species (ROS) in RASFs. Further mechanistic study demonstrated that 7-d-GDN induced heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase quinone 1(NQO1), which all participated in suppressing of oxidative stress. Additionally, 7-d-GDN increased sequestosome 1 (SQSTM1, p62), causing down-regulating Kelch-like ECH-associated protein 1 (Keap1), which resulting in NF-E2-related factor 2 (Nrf2) cytoplasm accumulation and subsequently translocation into nucleus. Collectively, 7-d-GDN exerts the anti-inflammatory effect through regulating anti-oxidative enzymes via p62/ Nrf2/ARE signaling. All suggest that the potential of 7-d-GDN in suppression of inflammation, especially antagonizing RA severity. Our works support for drugs discovery in RA treatment.