CB2受体在RA炎症性关节破坏中的作用及机制

Rheumatoid arthritis (RA) is an autoimmune joint disease associated with chronic inflammation of the synovium that causes profound damage of joints. This process induces synovitis, synovial hyperplasia with neovascularization, stiffness, and pain. The final results are the destruction of articular cartilage and the erosion of bone in the joints, with some patients suffering permanent disability. Although the pathomechanism is still unclear, a number of data suggest that inflammation, synovial hyperplasia, cartilage degradation and bone destruction play significant role in RA disease. The endocannabinoid system has two receptors, which are members of the superfamily of seven transmembrane G-coupled receptors, and play an important role in the regulation of cell proliferation, differentiation, function, and death. The two specific CB receptors have been identified as CB receptors-1 (CB1) and CB receptors-2 (CB2). CB1 is predominantly expressed in brain and peripheral neurons and is responsible for the psychotropic action of cannabinoids. Whereas CB2 is absent in brain but is mainly expressed in immune cells, osteoclast and macrophage. However, the role of CB2 in the regulation of RA is still unknown. We have demonstrated that level of CB2 is elevated in RA derived fibroblast like synoviocytes (FLS). Meanwhile, cannabinoid receptor stimulation of FLS reduced the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt kinase, which were significantly increased by tumor necrosis factor-α (TNF-α) stimulation. In addition, we also demonstrated that activation of CB2 by JWH133, a CB2 selective agonist, effectively reduced the receptor activator of NF-κB ligand (RANKL) and TNF-α induced differentiation of RAW264.7 cells into tartrate-resistant acid phosphatase-positive osteoclastic cells. Accordingly, we hypothesize that the synovial hyperplasia and joint structure destruction in RA process were blocked by the functional expression of CB2 in FLS and osteoclasts. This may provide a new explanation for RA disease. In the current study, we decided to investigate the important role of CB2 in synovial hyperplasia and joint destruction of RA process. Furthermore, we also investigate the role of CB2 in FLS cell proliferation and apoptosis. In order to clarify the mechanism of CB2 in joint structure damage, we investigate the effects of CB2 in the regulation of osteoclast differentiation stimulated with RANKL and TNF-α. Meanwhile, we also investigate the mechanism of CB2 play in the intreaction between FLS and OC in RA microenvironment. In additioin, we performed a detailed analysis of how CB2 affects synovial hyperplasia and cartilage and bone destruction in mice with collagen-induced arthritis. The purpose of this study was to clarify the role of CB2 play on inflammatory responses and joint destruction in RA, and provide a promising therapeutic target for treating or preventing the signs of rheumatoid arthritis.

类风湿性关节炎（RA）可导致关节肿胀、畸形，致残率高。RA确切机制尚未阐明，多认为与自身免疫引起的炎性浸润、滑膜增生和关节破坏有关。大麻素Ⅱ型受体（CB2）是G蛋白偶联受体，在细胞增殖、分化及凋亡等多种应激事件中起重要作用。申请者预研结果证实CB2在RA成纤维样滑膜细胞（FLS）有功能性表达，且CB2能调控RA微环境中破骨细胞（OC）活化。据此，我们推测CB2在RA疾病进程中起重要作用，活化CB2能抑制RA炎症性关节破坏。为验证该假说，本项目将探讨以下内容：（1）明确CB2在RA患者样本中的表达、分布特点及其与关节破坏的相关性；（2）明确靶向干预CB2对CIA小鼠炎症性关节破坏的作用；（3）探讨CB2对FLS增殖、凋亡以及OC活化的影响及机制；（4）采用条件培养基实验观察CB2对FLS和OC相互作用的影响。本课题将从新的视觉阐明RA发生的机制，并为RA的防治提供新靶点。

类风湿关节炎（RA）是一种典型的系统性自身免疫性疾病，其特征是滑膜炎症，而滑膜炎症又导致软骨和骨破坏，破骨细胞是导致RA关节破坏的主要原因，在RA骨侵蚀过程中发挥关键性的作用；大麻素受体2（CB2）对炎症和骨溶解有重要的调节作用；因此，CB2可能是治疗RA的合适靶点。我们的研究结果发现： CB2激活减轻CIA小鼠疾病严重程度和关节破坏；CB2激动剂 JWH-133通过调控巨噬细胞从M1向M2表型再极化，抑制炎症反应；JWH133抑制CIA小鼠破骨细胞的生成；JWH-133通过调控NF-κB信号通路抑制RANKL诱导的破骨细胞活化；CB2抑制RA患者成纤维滑膜细胞（FLS）的增殖与功能。上述结果首次表明，CB2通过抑制破骨细胞的生成和调节炎症反应来抑制病理骨破坏，JWH133具有抗炎症和抗破骨细胞生成的双重作用。CB2有可能成为RA治疗的潜在靶点。

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