抑制HK2调控同种异体反应性T细胞有氧糖酵解，诱导移植免疫耐受及机制研究

When activated by an foreign antigen,T cell undergoes dramatic changes in their energetic metabolism pathway, by switching from oxidative phosphorylation to aerobic glycolysis. Previous studies suggest aerobic glycolysis is critical in the regulation of proliferation, differentiation and function of activated T cells. Effector T cells engage in aerobic glycolysis to achieve their differentiation and functional characteristics, whereas regulatory T cells use oxidative phosphorylation fulfill their differentiation and function. Hexokinase2(HK2）is one of the key enzymes in regulating glycolysis. We previously found that HK2 exhibited much more higher expression in non-specific activated T cells than in naive T cells, and HK2 specific inhibitor exerted proliferation inhibition effect in activated T cells and decrease Th17/Treg ratio.We propose that down-regulating metabolic reprograming of activated effctor T cells during an allo-immune response by targeting HK2 may effectively inhibit their proliferation and differentiation, while promote production of regulatory T cells, and may finally achieve long term allo-graft survival.

T细胞受抗原激活后，能量代谢途径发生明显改变：氧化磷酸化转为有氧糖酵解。研究表明，有氧糖酵解途径对激活T细胞的增殖、分化及功能发挥均有重要影响；效应T细胞依靠有氧糖酵解实现其分化过程并发挥功能，而调节性T细胞却采用氧化磷酸化来发挥其功能。己糖激酶2(HK2)是介导有氧糖酵解途径的关键酶，抑制HK2的表达可明显抑制细胞的有氧糖酵解。课题组前期研究发现：激活T细胞HK2表达比静息态明显升高，应用HK2特异性抑制剂阻断糖酵解可明显抑制T细胞增殖，并可降低体外诱导Th17/Treg的比例。我们推断，抑制HK2可削弱效应T细胞的有氧糖酵解，有效抑制器官移植同种反应性效应T细胞的增殖、分化及功能，促进调节性T细胞的产生，从而实现移植物的长期存活乃至诱导免疫耐受。我们从效应T细胞能量代谢和免疫功能的关系出发，对HK2这一潜在的新型免疫抑制靶点在器官移植免疫中的重要作用及相关机制进行初步探索。

T细胞能量代谢可能与免疫调节密切相关。本研究主要探究了有氧糖酵解关键酶Hexokinase 2对同种异体T细胞增殖、活化和分化的调控。在我们的研究中，我们发现3-BrPA（HK2的抑制剂）能抑制同种异体反应性T细胞的增殖和活化，并上调PD-1的表达。成熟树突状细胞与T细胞共培养体系中NF-κB通路被激活，而3-BrPA加入后NF-κB通路被抑制。在共培养体系中加入PD-1抑制剂可部分逆转同种异体反应性T细胞的增殖，提示HK2抑制剂可能是通过NF-κB通路以及上调PD-1的表达等抑制同种异体反应性T细胞的增殖，活化。同时，混合培养体系中3-BrPA组的T细胞向Treg细胞分化。在小鼠心脏移植模型中，与对照组相比，3-BrPA组同种异体反应性T细胞（CD3+CD44+CD62L-)比例减少，Treg细胞比例增加，生存率增加，3-BrPA能使Treg比例增加，这与细胞实验的结果相符，这也可能是HK2抑制剂促进移植耐受的主要机制之一。