Zhao Di, Guo Min, Liu Bing, Lin Qinghai, Xie Tingting, Zhang Qianqian, Jia Xiaoxia, Shu Qiang, Liang Xiaohong, Gao Lifen, Ma Chunhong
Department of Immunology, Key Laboratory for Experimental Teratology of Ministry of Education, Shandong Provincial Key Laboratory of Infection and Immunology, Shandong University School of Basic Medicine, Jinan, Shandong, P. R. China.
Department of Clinical Laboratory, Qilu Hospital of Shandong University, Jinan, Shandong, P.R. China.
J Leukoc Biol. 2017 Dec;102(6):1313-1322. doi: 10.1189/jlb.3HI0117-005RR. Epub 2017 Jul 28.
T cell Ig and mucin domain-containing molecule 3 (Tim-3) has been found to play important roles in autoimmune diseases, but whether Tim-3-mediated engulfment of apoptotic cells is involved in systemic lupus erythematosus (SLE) remains to be elucidated. In this study, we verified the role of human Tim-3 (hTim-3) as the receptor of phosphatidylserine (PS) in human embryonic kidney (HEK)293 cells, which initiated the engulfment of apoptotic cells. Both IgV and the mucin domain of Tim-3 were crucial in the phagocytosis of apoptotic cells, and there existed the key cytoplasmic domain for signal transduction. Alanine at 111, locating around the FG-CC' loop of hTim-3, was necessary for its engulfment of apoptotic cells. In accordance, Tim-3 on CD14 cells negatively correlated with the percentage of peripheral apoptotic cells in control subjects. However, although Tim-3 was significantly increased on CD14 cells in SLE patients, peripheral apoptotic cells remained much higher than those in control subjects. Tim-3 on CD14 cells showed positive correlation with percentage of apoptotic cells and level of dsDNA, indicating the involvement of Tim-3 in SLE. Accordingly, soluble Tim-3 (sTim-3) was significantly increased in plasma of SLE patients, which might contribute to higher expression of a disintegrin and metalloproteinase (ADAM)-10. Pretreatment with both plasma from SLE patients and recombinant sTim-3 greatly inhibited hTim-3-initiated phagocytosis of apoptotic cells. Furthermore, anti-Tim-3 antibody depletion of plasma from SLE patients reversed the decreased phagocytosis of apoptotic cells. Collectively, our data suggest that sTim-3 might play inhibitory roles in impaired Tim-3-mediated clearance of apoptotic cells in SLE.
含T细胞免疫球蛋白和粘蛋白结构域分子3（Tim-3）已被发现在自身免疫性疾病中发挥重要作用，但Tim-3介导的凋亡细胞吞噬是否参与系统性红斑狼疮（SLE）仍有待阐明。在本研究中，我们验证了人Tim-3（hTim-3）作为磷脂酰丝氨酸（PS）受体在人胚肾（HEK）293细胞中的作用，该作用启动了凋亡细胞的吞噬。Tim-3的IgV和粘蛋白结构域在凋亡细胞的吞噬作用中都至关重要，并且存在信号转导的关键胞质结构域。位于hTim-3的FG-CC'环周围的111位丙氨酸对于其吞噬凋亡细胞是必需的。相应地，对照组受试者中CD14细胞上的Tim-3与外周凋亡细胞百分比呈负相关。然而，尽管SLE患者CD14细胞上的Tim-3显著增加，但其外周凋亡细胞仍远高于对照组受试者。CD14细胞上的Tim-3与凋亡细胞百分比和双链DNA水平呈正相关，表明Tim-3参与了SLE。因此，SLE患者血浆中可溶性Tim-3（sTim-3）显著增加，这可能导致解整合素和金属蛋白酶（ADAM）-10表达升高。用SLE患者血浆和重组sTim-3预处理均极大地抑制了hTim-3启动的凋亡细胞吞噬作用。此外，用抗Tim-3抗体清除SLE患者血浆可逆转凋亡细胞吞噬作用的降低。总体而言，我们的数据表明sTim-3可能在SLE中Tim-3介导的凋亡细胞清除受损中发挥抑制作用。
