Th17细胞介导的炎症免疫对2型糖尿病大鼠胰岛β细胞功能的研究

The previous three decades have witnessed a dramatic increase in the prevalence of type 2 diabetes in developing countries, especially in China. Dysfunction of islet beta cell is considered as the key factor in the development of type 2 diabetes. However, the related mechanism still remains unclear. Recently, the viewpoint of type 2 diabetes as an immune disease has been widely concerned. The latest research found that Th17 cells play a prominent role in the pathogenesis of insulitis in type 1 diabetes. Our research group has long been dedicated in the mechanism of dysfunction of islet beta cell in type 2 diabetes. Preliminary studies revealed that the level of IL-17 secreted by Th17 cells was significantly elevated in type 2 diabetic rats, which also can be seen an important inflammatory factor in bodies. Thus, we assumed that immune-inflammation signal triggered by Th17 might play a decision role in the phenotypic changes of beta cell in type 2 diabetes. To prove the hypothesis, the present study intends to build up the animal and cell models of immune-inflammation crosstalk in type 2 diabetes by which we could observe the immune signal triggered by Th17 in the development of beta cell disorder and its possible regulatory mechanism. On this basis, we then plan to directionally block this immune signal by specific neutralizing antibody and observe its influence on the gene expression of inflammatory cytokines and signaling pathways in vivo and in vitro. Through these studies, we seek to illustrate that immune signal triggered by Th17 plays an important role in the dysfunction of islet beta cell in type 2 diabetes model. And we intend to explore new therapies to eliminate the morbidity of diabetes mellitus in the background of generally improved nutrition level.

2型糖尿病在包括我国在内的广大发展中国家呈急剧蔓延趋势。胰岛β细胞功能障碍是2型糖尿病发生发展关键，但机制未明。近年，2型糖尿病免疫学观点备受关注。新近研究发现，新型Th17细胞介导的炎症免疫对1型糖尿病免疫性胰岛炎的发生起着决定性作用。本课题组长期致力于2型糖尿病胰岛功能损伤发生机制的研究。前期研究揭示，2型糖尿病大鼠血浆Th17免疫信号分子IL-17水平显著升高。我们假设：2型糖尿病大鼠Th17细胞炎症免疫通路过度活化，导致胰岛β细胞表型变化，终至功能障碍。为证明假设，本项目拟通过体内及体外实验，观察2型糖尿病大鼠Th17炎症免疫通路及胰岛细胞功能表型变化；继而通过抗IL-17抗体特异性阻断此免疫信号，观察炎性因子表达和重要信号通路磷酸化水平的变化，及对2型糖尿病的治疗效果。藉此明确Th17介导的炎症免疫在2型糖尿病胰岛细胞功能损伤中的作用及机制，为糖尿病的防治开辟新的干预靶点和途径。

2型糖尿病在广大发展中国家呈急剧蔓延趋势。胰岛β细胞功能障碍是2型糖尿病发生发展的关键环节，但机制未明。近年来，2型糖尿病免疫学观点备受关注，2型糖尿病被认为有类似于1型糖尿病的免疫学发生机制，是以多种免疫细胞和炎症因子为主要表型特征的慢性代谢性炎症疾病。新近发现，新型免疫细胞Th17及其特异性细胞因子IL-17对糖尿病免疫性胰岛炎的发生起着决定性作用。本研究通过体内外实验，探讨Th17细胞及相关细胞因子IL-17介导的炎症免疫在2型糖尿病胰岛β细胞功能障碍中的作用，阐明Th17细胞及其细胞因子IL-17对胰岛β细胞的免疫调控机制。研究结果表明：⑴自发性2型糖尿病大鼠血清炎症水平明显提高，血清中多种炎性细胞因子含量较高，尤其是Th17特异性细胞因子IL-17（IL-17A）的水平明显升高，明确了2型糖尿病大鼠由IL-17介导的特异性免疫炎症状态。⑵基因表达分析显示，细胞因子IL-17及其受体IL-17RA特异性高表达于2型糖尿病大鼠胰岛，而其它的IL-17细胞因子家族成员没有变化。⑶进一步研究发现，IL-17可以影响JAK-STAT信号通路分子的基因表达，同时诱导胰岛分泌标志性炎性细胞因子IL-6，扩大炎症信号。⑷给予JAK-STAT信号通路特异性抑制剂后，IL-17本底表达无改变，但是能抑制炎性因子IL-6的水平，进一步证实IL-17可通过调控JAK-STAT信号通路介导IL-6的表达及分泌。⑸IL-17在功能表型上可以抑制胰岛β细胞的活性、诱导细胞凋亡，而JAK-STAT抑制剂加入后则逆转了此作用，并表现为剂量依赖性。⑹免疫细胞-胰岛组织共培养实验发现，IL-17中和抗体干预可抑制Th17/IL-17共培养体系胰岛IL-6的分泌水平，进一步从细胞和组织水平论证了阻断Th17/IL-17炎症免疫信号能抑制糖尿病的胰岛代谢性炎症。总之，本研究聚焦于2型糖尿病代谢性炎症的免疫学特征，以动物实验和细胞实验相互佐证，明确了Th17/IL-17炎症免疫途径在2型糖尿病胰岛β细胞功能障碍发生发展中的作用，揭示出Th17/IL-17通过JAK-STAT信号通路调控胰岛代谢性炎症反应，为2型糖尿病的发病机制研究及临床干预策略提供了崭新的思路。