调控mTOR/AMPK通路及细胞代谢途径增强iNKT细胞负向调节功能

Invariant natural killer T (iNKT) cells are a distinct subset of T cells that recognize lipid antigens presented by CD1d. After activation, iNKT cells rapidly produce copious amounts of cytokines, helping to shape the innate and adaptive immune responses. α-galactosylceramide (α-GalCer), a potent agonist of iNKT cells, has been tested as a potential therapeutic agent against autoimmune diseases. However, the effect of activated iNKT cells in vivo is unpredictable, as conflicting outcomes, like anti-inflammatory and proinflammatory responses, have been reported. Recent studies reveal the critical roles of mTOR/AMPK signaling pathway and cellular metabolic reprogramming in regulating T cell function and fate. Our preliminary data indicated that the mitochondrial metabolism was closely related with the regulatory effect of iNKT cells. In this exploratory proposal, we hypothesize that the iNKT cells function is intimately linked to their mTOR/AMPK signaling pathway and related metabolic reprogramming; metabolic switch to mitochondrial fatty acid oxidation through modulating mTOR/AMPK signaling pathway will improve regulatory capacity of iNKT cells. To testify our hypothesis, we propose to examine: 1) mTOR/AMPK pathway and metabolic reprogramming in iNKT cells upon α-GalCer stimulation under physiological or pathological status. 2) The effect of metabolic reprogramming on the regulatory capacity of iNKT cells through manipulating iNKT cellular metabolism by targeting mTOR/AMPK signaling pathway. 3) The protection potential of expanded iNKT cells in EAE mouse. Collectively, these studies will greatly expand our knowledge of iNKT cell metabolic profiles and their role in specifying iNKT cell function. Findings from these experiments may help fine tuning iNKT cell based therapeutic strategies, and thus providing a new method for harnessing iNKT cell therapeutic benefits in autoimmune diseases.

iNKT细胞可被α-GalCer特异性活化，其负向调节效应在抗自身免疫病中具有应用优势，然而iNKT细胞还可介导促炎效应，在病理微环境下，其双向效应难以控制，成为iNKT细胞在抗自身免疫病应用的难题。mTOR/AMPK通路可感应微环境能量需求并调控细胞代谢途径，我们前期研究发现iNKT细胞代谢途径改变与其功能相关，线粒体代谢增强的iNKT细胞具有更强的负向调节功能。据此，本研究提出假说：不同病理微环境可通过mTOR/AMPK通路影响iNKT细胞线粒体代谢，从而造成其促炎或负向调节效应的不确定性。因此，本项目拟研究：①在不同病理微环境中，iNKT细胞代谢途径转换与mTOR/AMPK通路的相关性，及其对细胞功能的调控作用；②干预mTOR/AMPK通路、促进细胞线粒体代谢，诱导调节性iNKT细胞；③探讨调节性iNKT细胞抗自身免疫病效应。从细胞代谢角度探索iNKT细胞功能调控的机制和干预策略。

NKT细胞具有促炎与抑炎的双向免疫调控作用，包括TCR组成相对恒定的I型NKT细胞（iNKT细胞）与TCR组成多样的II型NKT细胞，其在不同病理条件下功能调控机制不明确。本项目首先明确I型NKT细胞代谢特征及靶向线粒体抗氧化剂体外干预效应；并收集病例、建立动物模型，研究NKT细胞在自身免疫性疾病、感染性疾病与肿瘤中的数量功能变化及体内干预策略。结果显示：NKT细胞在自身免疫性肝炎中具有直接促炎效应，并且可促进其它免疫细胞活化与炎性细胞因子分泌，导致局部mTORC1/AMPK通路异常活化，促进疾病的进展与迁延。I型NKT细胞具有显著抗瘤与抗病毒效应，但是在肿瘤与慢性乙肝 感染患者体内，I型NKT细胞数量显著减少并且功能缺陷。IL-2可部分修复患者来源I型NKT细胞扩增缺陷，而IL-2与IL-15联合应用可修复其抗瘤与抗病毒细胞因子的分泌能力。代谢分析提示NKT细胞具有线粒体较小及耐受线粒体氧压力能力较弱从而易于功能失调的特点。在自身免疫病动物模型中应用抗氧化剂及靶向线粒体抗氧化剂，能够有效缓解NKT细胞依赖性自身免疫性肝炎的发生与发展，该效应与逆转局部mTORC1/AMPK信号通路异常有关。另外，抗氧化剂还可促进NKT细胞依赖性的抗瘤效应，提示活性氧压力与肿瘤微环境NKT细胞的功能失调密切相关，靶向线粒体的抗氧化剂具有较好促进NKT细胞抗瘤效用的作用。综合，本项目解析了NKT细胞对活性氧在自身免疫性肝炎、病毒感染与肿瘤等多种疾病状态下数量与功能改变及相关调控机制，并从细胞因子补充及线粒体活性氧调控这两个角度建立基于NKT细胞免疫调控的干预策略，为临床研究与应用奠定基础。