LIGHT-LTβR/HVEM通路在1型糖尿病Tfh细胞分化中的作用机制

Type 1 diabetes is an autoimmune disease, and there isn't an effective treatment strategy for patients with T1D. Identifying the molecular mechanisms involved in the regulation in the type of immune response that underlies autoimmune tissue destruction is a critical step in designing appropriate immunomodulatory strategies. The spontaneous autoimmune diabetic NOD mice are used widely as the animal models in the study about T1D. In the previous studies, we established LIGHT -/- NOD mice successfully. It was found that, compared with the wild type NOD mice, the percentage of diabetes-free mice and CD4 +Treg cells was significantly increased, but B cells numbers and function were obviously down-regulated in the LIGHT -/- NOD mice. According to the literatures, CD4+ Treg cells control antigen-specific expansion of Tfh cell number via the coreceptor CTLA-4, and B cells are essential for Tfh cells differentiation. Moreover, Tfh cells play a critical role during the pathogenesis of Type 1 diabetes. We therefore hypothesized that LIGHT pathway mediates T1D development via the potentiating of Tfh cells differentiation. In the present studies, we will define the role of LIGHT pathway in the Tfh cells differentiation by collecting T1D patient samples and experiments in NOD mice, and then further explore the molecular and cellular mechanisms involved in LIGHT pathway regulation in Tfh cells formation by using the LIGHT-/- NOD mice and DO11RIP-mOVA mice -a transgenic mouse model of diabetes. Anticipative results will help us further unravel the precise pathogenesis of T1D, which may ultimately suggest novel treatment strategies for clinical disease.

1型糖尿病（Type 1 Diabetes，T1D）是一种自身免疫性疾病，目前临床没有有效的治愈方法。NOD小鼠是研究T1D最常见的动物模型，在前期研究中我们成功构建LIGHT-/-NOD小鼠的基础上，我们首次发现LIGHT基因缺失显著衰减NOD小鼠T1D的发生。进一步的研究表明，与WT NOD小鼠相比，LIGHT-/-NOD小鼠CD4+ Treg细胞的百分率显著上调，但B细胞频率及功能却明显下调。Tfh细胞是导致T1D病理发生的关键细胞类型，且其形成与CD4+ Treg细胞和B细胞密切相关。据此推测：LIGHT通路可能通过调节自身反应性T细胞向Tfh细胞的分化来介导T1D的发生。本课题拟通过体内外实验，明确LIGHT通路在T1D Tfh细胞形成中的作用；探讨其促Tfh细胞分化的作用机制。预期结果不但有助于T1D的免疫调控机制的阐明，并且可为T1D免疫干预策略的发展提供重要的实验依据。

Ⅰ型糖尿病（Type 1 Diabetes，T1D）是一种自身免疫性疾病，目前临床没有有效的治愈方法。非肥胖糖尿病（non-obese diabetic，NOD）小鼠是研究T1D最常见的动物模型，在此模型中我们发现LIGHT及其受体在NOD小鼠病程发展中表达升高；LIGHT基因缺失显著衰减NOD小鼠T1D的发生，表现为显著降低的血糖水平，小鼠死亡率，IAA和胰岛炎症以及提高的胰岛β细胞的功能。进一步的研究发现，LIGHT基因缺失后NOD小鼠脾脏中主要的造血细胞群不受影响；NOD小鼠胰腺淋巴结总T细胞和CD8+T细胞百分率减少，而B细胞百分率增多；NOD小鼠胰腺淋巴结中效应/记忆T细胞（CD44hiCD62Llow）的百分率降低；减少的效应/记忆T细胞可能与胰脏组织趋化因子表达下降有关。由激活T细胞分泌的IFN-γ与胰岛β细胞凋亡密切有关。为进一步探讨LIGHT是否会致敏IFNγ-诱导的β细胞凋亡以及潜在的机制，我们使用了小鼠β细胞系MIN6和小鼠原代胰岛细胞作为模型，研究发现LIGHT和IFN-γ协同降低MIN6和原代胰岛细胞的活性；而且细胞活力下降是由于提高的细胞凋亡所致。此外，除了显著增加细胞色素c的释放和NF-κB激活外,LIGHT和IFN-γ结合导致MIN6细胞中抗凋亡蛋白Bcl-2和Bcl-xL表达明显下降，而促凋亡蛋白Bak和Bax表达增加。相应地，在NOD小鼠中，LIGHT缺陷导致减少的NF-κB激活，BAK表达和外周胰岛炎。抑制NF-κB激活逆转Bcl-xL的下调和Bax的上调，并导致显著增加的细胞活力。以上结果表明LIGHT结合IFN-γ通过NF-κB/Bcl2依赖的线粒体途径诱导胰岛β细胞凋亡，这可能是LIGHT缺陷NOD小鼠T1D发病率显著下降的潜在原因。已有结果不但有助于T1D的免疫调控机制的阐明，并且可为T1D免疫干预策略的发展提供重要的实验依据。