| Backgrounds and Objectives: Rheumatoid arthritis(RA) is a class of common autoimmune disease with very high rate of morbidity and disability due to different causes, which is characterized by chronic, progressive and erosive arthritis, and its pathogenesis is mainly inflammatory cell infiltration, synovial proliferation and bone destruction. Although the present clinical treatment of RA has been greatly improved, but there is still a need for the identification of new pathways in order to further increase efficacy, particularly in patients in whom the disease dose not respond to current therapies. Cannabinoid receptor 2(CB2) is expressed mainly in the peripheral immune system and is becoming a hot research topic in many disease areas in recent years because of its significant anti-inflammatory effect, such as allergic contact dermatitis, multiple sclerosis and others. And because it has no side effects of the central nervous system after activating, CB2 agonist has become the focus of attention in the research. The purpose of this study is to explore whether CB2 can be a new target for the treatment of RA, and analyze the possible mechanism of CB2 selective agonist HU-308 on the treatment of RA bone destruction through the Wnt pathway.Methods: 40 DBA/1 male mice were randomly divided into 4 groups: normal sham group, CIA model group receiving normal saline, low dose of HU-308 treatment group(1mg/kg), high dose of HU-308 treatment group(10mg/kg). Arthritis of mice was induced by injecting bovine II collagen to DBA/1 mice. Sham group of mice were not treated, and given conventional feeding. Vehicle group of mice were given intraperitoneal injection of normal saline 0.1ml/kg/d. The hind paw thickness and arthritic index of mice were observed and measured. Histological changes and Micro-CT examination were to evaluate the features of the arthritis. The number of osteoclast was determined by using Tartrate-resistant acid-phosphatase(TRAP) staining. The levels of ?-catenin, Dickkopf-1(Dkk1), Sclerostin(Scl), RANKL and OPG were detected by immunohistochemical staining technique.Results: In CIA mice, according to the results of the semi-quantitative analysis, 10 mg/kg dose of HU-308 treatment can effectively reduce the degree of joint swelling, and also delay the occurrence and development of arthritis. The results of HE staining showed that 10 mg/kg dose of HU-308 could effectively reduce the proliferation of synovial tissue and the invasion of inflammatory cells in the joint cavity. The results of Safranin O staining showed that compared with the Vehicle group, the cartilage cells were significantly increased and the cartilage layer structure was significantly increased in the H-HU-308 treatment group. The results of TRAP staining showed that there were a large number of osteoclasts in the Vehicle group, and the number of osteoclasts in the H-HU-308 treatment group was significantly decreased. The results of Micro-CT imaging analysis showed that 10 mg/kg dose of HU-308 could significantly reduce the damage of articular cartilage and bone in CIA mice, but it cannot be observed obvious therapeutic effect of 1mg/kg dose HU-308 treatment. The results of immunohistochemical staining showed that the expression of Dickkopf-1 and Sclerostin in Vehicle group was significantly increased and the expression was significantly decreased after Selective CB2 agonist treatment. But the expression of ?-catenin in the treatment group was significantly higher than those in the vehicle group. The expression intensity of RANKL in H-HU-308 group was significantly more decreased than in the vehicle group, but the expression of OPG is higher than in the vehicle group.Conclusions: By activating Wnt/β-catenin pathway, HU-308 reduces the expression of Dkk1 and Scl, and is able to regulate the balance of RANKL/OPG, inhibiting the destruction of cartilage and bone tissue. CB2 is expected to become a new target for treatment of bone destruction in RA. |
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