白介素35对脓毒症中效应T细胞自噬的影响及调节机制

Sepsis is essentially an immunological dissonance provoked by acute insults such as fulminant infection, severe trauma, and extensive burns. In the stage of immune paralysis, inhibitory or regulatory components of immune cells eventually dominate the direction of immune response and the production of inhibitory cytokines is enhanced. As an inhibitory cytokine, interleukin 35 (IL-35) is crucial for the functional state of regulatory T cells, however, its significance and potential mechanism underlying immunological dissonance during sepsis remains unclear. The objective of the present project was to investigate the expression and pathophysiological significance of IL-35 in T-cell immunity during sepsis, with the focus on the regulation of autophagy in effector T cell mediated immune response of IL-35. Meanwhile, it would be further illustrated that through STAT1-MDM2-p53 signal transduction pathway, IL-35 might execute negative effects on cytosolic high mobility group box-1 protein (HMGB1) translocation and HMGB1-Beclin 1 interaction, thereby inhibiting the autophagy of effector T cells. In addition, the potential role of HMGB1 and p53 was clarified in the process that IL-35 interfered with autophagy. Finally, autophagy would be served as a novel therapeutic target to modulate the host immune response mediated by IL-35. This study might shed a fresh light on the immunological effect of IL-35 and its regulatory mechanism, which could contribute to developing a new therapeutic way in the treatment of immune dysfunction in the setting of sepsis.

新近的研究提示，脓毒症的发生与机体免疫功能紊乱密切相关，其中调节性免疫细胞亚群占据优势并分泌抑制性细胞因子。白介素35对调节性T细胞发挥免疫抑制效应至关重要，但在脓毒症免疫功能紊乱中的作用、意义及其调节机制尚未明确。本课题拟探讨脓毒症状态下白介素35的表达规律及其对T细胞免疫功能的影响，并从分析效应T细胞自噬的角度探索其免疫效应机制；进一步揭示IL-35通过STAT1—MDM2—p53信号转导通路影响高迁移率族蛋白B1(HMGB1)迁移、干扰HMGB1—Beclin 1相互作用进而抑制自噬的分子机制；在此基础上，明确HMGB1及p53在IL-35影响效应T细胞自噬过程中的关键作用；最后，以自噬作为干预靶点，探索防治脓毒症中白介素35介导T细胞免疫功能障碍的有效策略。本研究从崭新角度深化对白介素35调控机体免疫反应过程的认识，将为脓毒症免疫功能紊乱的防治开辟新途径。

抑制性细胞因子白介素35（IL-35）是白介素12家族成员，主要由调节性T细胞等分泌。免疫抑制或免疫麻痹对于脓毒症的发生及发展至关重要，与预后不良关系密切。本项目研究发现IL-35在脓毒症免疫功能障碍中崭新的作用机制，即抑制CD4+ 效应性T细胞自噬。脓毒症实验动物模型（盲肠结扎穿孔，CLP）中，机体IL-35表达显著上调，提示IL-35在脓毒症的病理生理发展过程中发挥重要作用。重组IL-35（rIL-35）抑制脓毒症CD4+ 效应性T细胞增殖，诱导Th2异常分化并缩短实验动物生存时间，其机制在于IL-35对效应性T细胞自噬的抑制。脓毒症中，自噬对于效应性T细胞增殖及分化，甚至实验动物整体生存表现出保护作用。IL-35对效应性T细胞自噬的抑制，不是发生在自噬流即自噬体和溶酶体的融合阶段，而是在自噬起始阶段。高迁移率族蛋白B1（HMGB1）介导IL-35对效应性T细胞自噬的抑制作用。活化效应性T细胞中，HMGB1自细胞核迁移至细胞质而诱导自噬；应用EX527促进HMGB1迁移诱导自噬，而以SRT1720抑制HMGB1迁移则抑制自噬。rIL-35减少细胞核及细胞质HMGB1的表达，同时抑制细胞核HMGB1向细胞质的迁移。这是IL-35抑制效应性T细胞自噬进而发挥免疫抑制作用的重要机制。因此，促进HMGB1向细胞质迁移可以部分缓解IL-35的免疫抑制效应，而抑制HMGB1迁移则可能加重IL-35介导的免疫功能障碍。综上，本课题研究证实，脓毒症中IL-35通过抑制HMGB1依赖性自噬而介导CD4+ 效应性T细胞免疫功能障碍。由此，可以通过多层次纠正脓毒症中IL-35介导的免疫功能障碍，主要包括：1、对IL-35亚基的拮抗；2、对自噬的调控；3、对HMGB1迁移的干预。本课题研究为纠正脓毒症免疫功能障碍提供崭新的调控思路和靶点，是重要的实验依据和理论参考。