HMGB1作为固有预警素参与1型糖尿病自身免疫反应的调控和机制研究

Although innate immunity has long been realized to be implicated in the pathogenesis of type 1 diabetes (T1D), the underlying mechanisms, however, largely remained elusive. We now obtained strong evidence supporting a role for HMGB1, an innate alarmin, in T1D development. HMGB1 is a highly conserved chromosome protein adapted by the innate immune system during evolutionary process. Because of genetic defect, NOD mice, the animal model for human T1D, show accumulation of apoptotic beta cells during neonate beta mass remodeling process, which then leads to beta cells undergoing necrosis and subsequent passive release of HMGB1 into the islet milieu. Extracellular HMGB1 is found to potently stimulate the activation of dendritic cells (DCs) and secretion of inflammatory cytokines including HMGB1. We therefore hypothesize that extracellular HMGB1 is implicated in the initiation and progression of autoimmune responses against beta cell self antigens during the course of T1D development. We will first employ an HMGB1 neutralizing antibody and recombinant HMGB1 to determine the role of HMGB1 in T1D initiation and progression. The cellular and molecular mechanisms underlying HMGB1 regulation of T1D development will be next investigated. We will also evaluate whether HMGB1 can be served as an innate therapeutic target to inhibit autoimmune initiation and progression during the course of T1D development, to prevent beta cell destruction by recurrent autoimmunity after islet transplantation, and to reverse T1D in newly diabetes onset subjects. Completion of these studies would not only produce pivotal information for better understanding of the pathetiology for T1D, but also have great potential to develop effective innate immune response based therapeutic strategies for prevention and treatment of type 1 diabetes.

胰岛β细胞被侵润的免疫细胞破坏，致使其分泌的胰岛素不足，是典型的1型糖尿病（T1D）病理特征，但其病理机制尚有待厘清。申报者所在课题组发现，人类T1D易感个体或NOD小鼠在新生期会经历β-Mass重塑，呈现β细胞生理性凋亡。易感个体由于吞噬细胞功能缺陷，致使凋亡细胞未被及时清除而发生继发性坏死而被动释放大量HMGB1，诱导免疫细胞侵润。申报者前期研究还发现，HMGB1可促进DC细胞的成熟，而DC细胞的状态是调控免疫反应发生方向的关键。本研究拟在前期工作基础上，以NOD小鼠为模型，从固有免疫的角度解析HMGB1对T1D自身免疫发生发展的调控作用；在细胞及分子水平探究HMGB1调控T1D自身免疫的分子机制；以新生糖尿病和胰岛移植小鼠为研究对象，研判HMGB1作为预警素对逆转或治疗T1D的可行性，为解析T1D发病机制提供新的理论依据，为临床开发以固有免疫为基础的治疗策略奠定实验基础。

我们的前期研究发现，高迁移率蛋白B1 (HMGB1) 通过调节树突状细胞，效应性T细胞和调节性T细胞 （Tregs）在一型糖尿病中发挥重要作用，但其作用的机制尚未完全解释。因此在本项目中，我们以NOD小鼠为模型，解析阻断HMGB1对一型糖尿病的防治效应及其机制。我们发现，中和 β-Mass 重塑时期被动释放的HMGB1不仅会抑制自身免疫的进展，还能够延迟一型糖尿病的发生。我们还发现，糖尿病小鼠于胰岛移植术后给予HMGB1中和抗体，可显著延长移植物的成活时间。此外，阻断HMGB1可有效逆转NOD小鼠新生糖尿病。进一步的研究揭示，用HMGB1体外刺激Treg，可通过PI3K-Akt-mTOR信号通路诱导STAT1的活化，活化的STAT1促进T-bet的转录而导致Treg不稳定，成为Th1样的Treg。这一结果，在小鼠体内实验中也得到了验证。与此同时，我们用ELISA检测了一型糖尿病患者血清中的HMGB1，发现其含量明显高于健康人群。这些研究结果显示，HMGB1在促进一型糖尿病的发生发展中起着重要作用。阻断HMGB1不仅可以延缓发病，还在疾病早期具有重要的治疗意义，其机制是阻断HMGB1有利于促进机体免疫调节功能，尤其是提升Treg的抑制功能及其稳定性。