Investigate Pathogenic Mechanism of TXNDC5 in Rheumatoid Arthritis

Hypoxia stimulates synovial hypoperfusion in rheumatoid arthritis (RA). TXNDC5 stimulates cellular proliferation in hypoxic conditions. We previously detected increased TXNDC5 expression in synovial tissues and blood from RA patients and demonstrated that the gene encoding TXNDC5 increased RA risk. The present study investigated the pathogenic roles of TXNDC5 in RA. Transgenic mice that over-expressed TXNDC5 (TXNDC5-Tg) were generated using C57BL/6J mice and treated with bovine collagen II to induce arthritis (CIA). Synovial fibroblasts from RA patients (RASFs) were cultured and incubated with TXNDC5-siRNA or CoCl2, a chemical that induces hypoxia. CIA was observed in 80% of the TXNDC5-Tg, but only 20% of the wild-type mice (WT) developed CIA. The clinical arthritis scores reached 5 in the TXNDC5-Tg, but this index only reached 2 in the control mice. CIA TXNDC5-Tg exhibited clear pannus proliferation and bone erosion in joint tissues. A significant increase in CD4 T cells was observed in the thymus and spleen of TXNDC5-Tg during CIA. Serum levels of anti-collagen II IgG, IgG1 and IgG2a antibodies were significantly elevated in the mice. Increased cell proliferation, cell migration and TXNDC5 expression were observed in RASFs following incubation with 1 µM CoCl2. However, this effect was diminished when TXNDC5 expression was inhibited with 100 nM siRNA. TNF-alpha, IL-1α, IL-1β and IL-17 levels were significantly increased in the blood of TXNDC5-Tg mice, but the levels of these cytokines declined in the supernatant of RASFs that were treated with TXNDC5 siRNA. The expression of adiponectin, a cytokine-like mediator, decreased significantly in RASFs following TXNDC5 siRNA treatment. These results suggest that TXNDC5-over-expressing mice were susceptible to CIA. This study also suggests that hypoxia induced TXCNDC5 expression, which contributed to adiponectin expression, cytokine production and the cellular proliferation and migration of fibroblasts in RA.

缺氧可促进类风湿关节炎（RA）患者的滑膜低灌注。硫氧还蛋白结构域5（TXNDC5）可在缺氧环境中促进细胞增殖。本团队前期已在类风湿关节炎患者的滑膜组织与血液中检测到TXNDC5表达上调，并证实编码TXNDC5的基因会增加类风湿关节炎的患病风险。本研究探讨了TXNDC5在类风湿关节炎中的致病作用。本研究以C57BL/6J小鼠为背景，构建了过表达TXNDC5的转基因小鼠（TXNDC5-Tg），并通过注射牛Ⅱ型胶原诱导其发生胶原诱导性关节炎（CIA）。同时，体外培养类风湿关节炎患者滑膜成纤维细胞（RASFs），分别用TXNDC5小干扰RNA（TXNDC5-siRNA）或氯化钴（CoCl2，一种可诱导缺氧的化学试剂）对其进行孵育处理。结果显示，80%的TXNDC5-Tg小鼠发生了胶原诱导性关节炎，而野生型（WT）小鼠的造模成功率仅为20%；TXNDC5-Tg小鼠的临床关节炎评分可达5分，对照组小鼠仅为2分。发生CIA的TXNDC5-Tg小鼠关节组织可见明显的血管翳增生与骨侵蚀。在CIA造模过程中，TXNDC5-Tg小鼠的胸腺与脾脏中CD4阳性T细胞水平显著升高；小鼠血清中的抗Ⅱ型胶原IgG、IgG1及IgG2a抗体水平亦显著上调。用1μM氯化钴孵育RASFs后，可观察到细胞增殖、细胞迁移能力增强，且TXNDC5表达水平升高；而当用100nM siRNA抑制TXNDC5表达后，上述效应被显著削弱。TXNDC5-Tg小鼠血液中的肿瘤坏死因子-α（TNF-α）、白细胞介素-1α（IL-1α）、白细胞介素-1β（IL-1β）及白细胞介素-17（IL-17）水平显著升高；但在经TXNDC5 siRNA处理的RASFs细胞上清液中，上述细胞因子的水平则出现下降。经TXNDC5 siRNA处理后，RASFs中脂联素（一种细胞因子样介质）的表达水平显著降低。上述结果表明，过表达TXNDC5的小鼠易患胶原诱导性关节炎。本研究同时提示，缺氧可诱导TXNDC5表达，进而通过影响脂联素表达、细胞因子产生以及成纤维细胞的增殖与迁移，参与类风湿关节炎的病理进程。