脓毒症时树突状细胞内质网应激与自噬在TIPE2介导免疫障碍中的作用及其信号机制

Tumor necrosis factor-α-induced protein-8 like-2 (TIPE2) has been identified as a novel negative regulator gene for controlling inflammation, and it is critically involved in the pathogenesis of both inflammatory response and tumor in mice and humans. In our recent study, we found that TIPE2 was closely related to cellular immune dysfunction after acute insults. However, fundamental questions regarding the mechanisms underlying the negative regulation of TIPE2 on dendritic cells (DCs) remain unresolved. The current study was conducted to investigate the potential role of TIPE2 in regulating the response of endoplasmic reticulum stress (ERS) and autophagy/ER-phagy in DCs, and explore the molecular mechanisms concerning the immune dysfunction of DCs regulated by TIPE2 in the setting of septic challenge. Using cell or mice model of TIPE2-knockdown or TIPE2-overexpression, interventions with tunicamycin (TM, to induce pharmaceutical ERS) or salubrinal (Sal, to relieve the ERS response and protect cells from ER-related apoptosis) as well as regulators towards the key molecules in the signaling pathway of ERS and autophagy/ER-phagy, including GRP78/p53, IRE1α/JNK, and FAM134B/Atg40, would be used both in vitro and in vivo experiments to evaluate the possible influence of TIPE2 on immune function of DCs together with underlying signal transduction. Our findings might help to clarify the potential role and significance of ERS and autophagy/ER-phagy reaction in immunomodulation of DCs mediated by TIPE2, thus shed a light to the development of novel therapeutic strategies for improving the host immune response and the clinical outcome of patients with sepsis and subsequent multiple organ dysfunction syndrome.

既往资料多关注肿瘤坏死因子-α诱导蛋白-8样分子2(TIPE2)的肿瘤及炎症调节作用，我们新近研究发现TIPE2与细胞免疫功能紊乱密切相关，它可抑制树突状细胞(DC)成熟分化，但其负向调控机制缺乏了解。本项目拟探讨TIPE2对脓毒症时DC中内质网应激(ERS)、自噬/ER-phagy反应的影响及其与机体免疫功能障碍的内在联系；采用TIPE2基因敲除/过表达小鼠模型，通过衣霉素诱导ERS反应、Salubrinal缓解ERS反应以及对ERS、自噬/ER-phagy信号转导中重要调控分子GRP78/p53、IRE1α/JNK及FAM134B/Atg40表达等进行干预，并结合临床试验深入分析TIPE2介导DC细胞ERS和自噬反应的关键信号通路及其免疫调节效应。该项目从新的角度进一步认识TIPE2介导DC免疫反应的重要作用与信号机制，为探索脓毒症及多器官损害的免疫调理策略开辟新途径。

脓毒症状态下TNF-α诱导蛋白-8样分子2(TIPE2)与机体免疫功能障碍密切相关，但其负向调控机制缺乏了解。本项目探讨TIPE2对脓毒症时树突状细胞(DC)内质网应激(ERS)、自噬/内质网自噬(ER-phagy)反应的影响及其在免疫应答失调中的作用，解析TIPE2介导DC细胞ERS和自噬反应的关键信号通路与调节途径。主要结果如下：(1)沉默TIPE2基因表达后DC成熟分化增强，并促进T细胞增殖活性，过表达TIPE2则抑制DC免疫调节效应。脓毒症TIPE2 KO组促凋亡蛋白表达显著增强、凋亡率增加，同时GRP78、p-JNK和p-IRE1α表达上调、ER形态异常，而TIPE2 KI组DC凋亡显著减弱。IRE1α抑制剂预处理TIPE2 KO组DC凋亡率、p-JNK水平下降，动物生存率显著改善。提示TIPE2参与DC细胞ERS反应过程，通过负向调节IRE1α活化影响DC免疫应答状态。(2) TIPE2 KI动物给予自噬诱导剂后DC介导T细胞增殖反应有效改善，TIPE2 KO组给予自噬抑制剂则下调DC免疫效应。TAK1或JNK抑制剂处理后DC自噬水平受抑，提示脓毒症状态下TIPE2对DC自噬活性具有抑制作用，与其下调TAK1/JNK信号有关。(3)发现ER-phagy 受体FAM134B通过C1qb依赖方式参与脓毒症DC反应。FAM134B KO时DC功能障碍、ER-phagy活性减弱，TIPE2 KO小鼠DC中ER-phagy增强，p-PERK和ATF4表达上调。表明TIPE2通过下调PERK-eIF2α-ATF4通路抑制FAM134B表达及ER-phagy活性，是脓毒症时TIPE2调控FAM134B介导ER-phagy的重要机制。上述结果从新的视角深化对TIPE2介导DC免疫反应的重要意义和分子机制的认识，为探索脓毒症免疫调理策略提供新思路、开辟新途径。