Protective Effects Of(4-(1,2,4-oxadiazol-5-yl)phenyl)-2-aminoacetamide Derivatives To Adjuvant-induced Arthritis Rats By Regulating The NF-κB Signaling Pathway

Rheumatoid arthritis（RA）is a systemic autoimmune-related disease with chronic inflammation of the synovial membrane,mainly manifested as aggressive joint inflammation of the small joints of the hands and feet,mostly accumulating to extra-articular solid organs and accompanied by positive serum rheumatoid factor,the symptoms are usually joint morning stiffness,swelling,pain and dysfunction,and in severe cases,it will lead to hands and feet joint deformity and loss of function.At present,there is no specific drug for the clinical treatment of rheumatoid arthritis,most immunosuppressants can only delay the development of the disease and reduce the disability rate,and require prolonged use of drugs to play a role in relieving symptoms,but the prolonged use of drugs will bring many adverse reactions to patients,weakening patient compliance with medication,ultimately leading to poor treatment outcomes.Therefore,there is an urgent need to develop specific therapeutic drugs to address the pathogenesis of rheumatoid arthritis.The current academic view generally believes that as an autoimmune disease,the main pathogenesis of rheumatoid arthritis is very complex,involving a series of immune responses,including macrophages,chemokines,cytokines（TNF-αand IL-1β）and endogenous NO and other factors involved in the degradation of joint cartilage and bone,causing cartilage and joint destruction,and eventually leading to joint swelling,rigidity and deformity.During the development of rheumatoid arthritis,large amounts of NO,IL-1βand TNF-αare released by immune cells（e.g.macrophages）and participate in the inflammatory response,leading to bone and cartilage damage.NO,an important immunomodulatory factor,is significantly elevated in both serum and synovial fluid of patients with rheumatoid arthritis.Importantly,significantly elevated serum NO,IL-1βand TNF-αlevels in patients with rheumatoid arthritis can be used as important indicators of rheumatoid arthritis activity.Among them,TNF-αand IL-1βare closely related to the disease progression of rheumatoid arthritis.TNF-αcan be used as one of the sensitive indicators of rheumatoid arthritis activity,while IL-1βresponds to the degree of inflammatory activity to a certain extent.Notably,NO,IL-1βand TNF-αare able to regulate the nuclear factorκB（NF-κB）signaling pathway,which is further involved in the inflammatory response of rheumatoid arthritis.Based on this,targeting the above inflammation-related immune cells as well as signaling pathways could be potential therapeutic targets for rheumatoid arthritis.Therefore,finding compounds that can target and inhibit these pro-inflammatory factors and related signaling pathways will play a crucial role in the treatment of rheumatoid arthritis.Thus,in the present study we analyzed the effect of（4-（1,2,4-oxadiazol-5-yl）phenyl）-2-aminoacetamide derivatives on rheumatoid arthritis.First,we evaluated the effect of（4-（1,2,4-oxadiazol-5-yl）phenyl）-2-aminoacetamide derivatives on the production of relevant inflammatory factors in LPS-stimulated RAW264.7 cells,and the results showed that this series of compounds had good anti-inflammatory activity in vitro.Among them,compound f15 was the most prominent one,which significantly inhibited the production of relevant inflammatory factors in LPS-stimulated RAW264.7 cells with IC₅₀values of 1.05±0.25μM,3.83±0.19μM and 7.03±0.24μM for NO,IL-1βand TNF-α,respectively.Further mechanistic studies showed that f15 could significantly inhibit the activation of NF-кB signaling pathway.Furthermore,in-vivo experiment showed that f15 significantly reduced secondary foot swelling and arthritis index in adjuvant-induced arthritic rats and inhibited serum TNF-αand IL-1βproduction.The results of histopathological analysis showed that f15 significantly attenuated the inflammatory cell infiltration and synovial proliferation in adjuvant-induced arthritic rats.Therefore,based on the above results,compound f15 could be considered to have the potential to be developed as a therapeutic agent for arthritis,which is important for the subsequent development of therapeutic agents for rheumatoid arthritis.