Division of Rheumatology, Department of Internal Medicine, The Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-ku, Tokyo, 105-8461, Japan.
Department of Orthopaedic Surgery, The Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-ku, Tokyo, 105-8461, Japan.
Sci Rep. 2023 May 9;13(1):7528. doi: 10.1038/s41598-023-34469-1.
Peptidylarginine deiminase 4 (PAD4) contributes to the production of citrullinated proteins as autoantigens for anti-citrullinated protein antibodies (ACPAs) in rheumatoid arthritis (RA). PAD4 can also self-deiminate via autocitrullination. However, the role of this process in RA pathogenesis has not been elucidated. This study aimed to clarify PAD4 function before and after autocitrullination and identify citrullinated PAD4 in the synovial fluid of patients with RA. The autocitrullination of recombinant human PAD4 (rhPAD4) was catalyzed in vitro and determined using anti-modified citrulline immunoblotting. Monocyte chemotaxis was evaluated using Boyden chambers, and citrullinated rhPAD4's ability to induce arthritis was assessed in a C57BL/6J mouse model. Citrullinated PAD4 levels were measured in the synovial fluid of patients with RA and osteoarthritis using a novel enzyme-linked immunosorbent assay. Chemotactic findings showed that citrullinated rhPAD4 recruited monocytes in vitro, whereas unmodified rhPAD4 did not. Compared to unmodified rhPAD4, citrullinated rhPAD4 induced greater inflammation in mouse joints through monocyte migration. More citrullinated PAD4 was found in the synovial fluid of patients with RA than in those with osteoarthritis. Citrullinated PAD4 was even detected in ACPA-negative patients with RA. The autocitrullination of PAD4 amplified inflammatory arthritis through monocyte recruitment, suggesting an ACPA-independent role of PAD4 in RA pathogenesis.
肽基精氨酸脱亚氨酶 4（PAD4）有助于产生瓜氨酸化蛋白，作为类风湿关节炎（RA）中抗瓜氨酸化蛋白抗体（ACPA）的自身抗原。PAD4 也可以通过自身瓜氨酸化进行自我脱亚氨化。然而，这一过程在 RA 发病机制中的作用尚未阐明。本研究旨在阐明自身瓜氨酸化前后 PAD4 的功能，并鉴定 RA 患者滑液中的瓜氨酸化 PAD4。在体外催化重组人 PAD4（rhPAD4）的自身瓜氨酸化，并使用抗修饰瓜氨酸免疫印迹法进行测定。使用 Boyden 室评估单核细胞趋化性，并在 C57BL/6J 小鼠模型中评估瓜氨酸化 rhPAD4 诱导关节炎的能力。使用新的酶联免疫吸附试验测量 RA 和骨关节炎患者滑液中的瓜氨酸化 PAD4 水平。趋化性研究结果表明，瓜氨酸化 rhPAD4 可在体外募集单核细胞，而未修饰的 rhPAD4 则不能。与未修饰的 rhPAD4 相比，瓜氨酸化 rhPAD4 通过单核细胞迁移诱导小鼠关节产生更大的炎症。在 RA 患者的滑液中发现了更多的瓜氨酸化 PAD4，而在骨关节炎患者中则较少。甚至在 ACPA 阴性的 RA 患者中也检测到了瓜氨酸化 PAD4。PAD4 的自身瓜氨酸化通过单核细胞募集放大炎症性关节炎，表明 PAD4 在 RA 发病机制中具有 ACPA 非依赖性作用。
