Chang Yan, Han Ping, Wang Yueye, Jia Chengyan, Zhang Bingjie, Zhao Yingjie, Li Susu, Li Siyu, Wang Xinwei, Yang Xuezhi, Wei Wei
Key Laboratory of Anti-Inflammatory and Immune Medicine, Anhui Collaborative Innovation Center of Anti-inflammatory and Immune Medicine, Institute of Clinical Pharmacology, Anhui Medical University, Ministry of Education, Hefei, Anhui Province, China.
Br J Pharmacol. 2022 Jun;179(12):3024-3042. doi: 10.1111/bph.15787. Epub 2022 Mar 21.
Abnormal kynurenine (Kyn) metabolism has been closely linked to the pathogenesis of rheumatoid arthritis (RA). The aims of this study were to investigate the role of tryptophan 2,3-dioxygenase 2 (TDO2), a rate-limiting enzyme that converts tryptophan (Trp) to Kyn, in regulating fibroblast-like synoviocyte (FLS)-mediated synovial inflammation in autoimmune arthritis.
The expression of TDO2 was determined by immunohistochemistry, confocal laser scanning fluorescence microscopy, imaging flow cytometry and Western blot. TDO2 activity was tested by HPLC and colorimetric assay. TDO2 siRNA and TDO2 inhibitor 680C91 were used to inhibit TDO2 in AA-FLS function in vitro. A rat model of adjuvant-induced arthritis (AA) was used to evaluate the in vivo effect of allopurinol (Allo), a TDO2 inhibitor.
TDO2 expression was strongly increased in synovial tissue and FLS of RA and AA. Immune cells were found to express high amount of TDO2 proteins at the peak stage of AA. Pharmacological inhibition or knockdown of TDO2 in AA-FLS resulted in a reduced proliferation, secretion, migration and invasion. Kyn restored the inhibitory effect of TDO2 inhibition on activation of AA-FLS. Allo treatment ameliorated the arthritis severity and decreased the activity of TDO2.
Our results suggest that elevated TDO2 expression may contribute to synovial inflammation and joint destruction during arthritis. Therefore, targeting TDO2 activity and the Kyn pathway of Trp degradation may represent a potential therapeutic strategy in RA.
犬尿氨酸（Kyn）代谢异常与类风湿关节炎（RA）的发病机制密切相关。本研究旨在探讨色氨酸2,3-双加氧酶2（TDO2），一种将色氨酸（Trp）转化为Kyn的限速酶，在调节自身免疫性关节炎中由成纤维细胞样滑膜细胞（FLS）介导的滑膜炎症中的作用。
通过免疫组织化学、共聚焦激光扫描荧光显微镜、成像流式细胞术和蛋白质印迹法测定TDO2的表达。通过高效液相色谱法和比色法检测TDO2活性。使用TDO2小干扰RNA（siRNA）和TDO2抑制剂680C91在体外抑制AA-FLS功能中的TDO2。采用佐剂性关节炎（AA）大鼠模型评估TDO2抑制剂别嘌呤醇（Allo）的体内作用。
RA和AA的滑膜组织及FLS中TDO2表达显著增加。发现在AA的高峰期免疫细胞表达大量TDO2蛋白。对AA-FLS中TDO2进行药理抑制或敲低导致增殖、分泌、迁移和侵袭减少。Kyn恢复了TDO2抑制对AA-FLS激活的抑制作用。Allo治疗改善了关节炎严重程度并降低了TDO2活性。
我们的结果表明，TDO2表达升高可能在关节炎期间导致滑膜炎症和关节破坏。因此，靶向TDO2活性和Trp降解的Kyn途径可能是RA的一种潜在治疗策略。
