代谢中间产物ɑ-KG通过SCARA5受体影响巨噬细胞炎症反应参与脓毒症调节的机制研究

Sepsis, characterized by life-threatening organ dysfunction, is caused by the out of control inflammatory response due to infection or stress, along with changes of cell energy metabolism and there is a close connection between them. α-KG, one of the intermediate product of TCA cycle, is the cofactor of a variety of enzymes related to epigenetic regulation. It could regulate the inflammatory response and is thought to be the important bridge between energy metabolism and inflammation. We have found that the content of α-KG changed in the serum of patients with sepsis. It could inhibit the inflammatory response of macrophages and induce the expression of SCARA5. SCARA5 is an important pattern recognition receptor of macrophages and plays an important role in the anti-inflammatory reactions. Our hypothesis is α-KG inhibit the inflammatory response and ameliorate the endotoxin tolerance in the early and late stage of sepsis, by inducing SCARA5 through epigenetic regulation and reprogramming of energy metabolism in macrophages. The project will use SoNAR，a new genetic fluorescent probe model, detecting metabolism changes in mice macrophages dynamically, and use LysMCre TET2f/f mice demonstrating α-KG regulate the expression of SCARA5 by DNA demethylation. Our study will clarify the mechanism of α-KG regulating macrophage inflammatory response in sepsis and provide new molecular targets for sepsis treatment and research strategy.

脓毒症是感染或应激引起的免疫应答失控所致的危及生命的器官功能障碍，并伴随着细胞能量代谢异常，二者之间存在密切的联系。α-KG作为TCA循环的中间产物之一，是多种表观遗传调控酶类的辅助因子，并能参与调节炎症反应，被认为是能量代谢和炎症调控之间重要的桥梁。我们前期发现α-KG在脓毒症患者血清中有动态变化，给予α-KG可以抑制巨噬细胞炎症反应，并能诱导SCARA5表达上调。SCARA5是巨噬细胞表面的一类重要模式识别受体，在抗炎反应过程中发挥重要作用。我们推测α-KG通过表观遗传调控SCARA5表达并影响巨噬细胞能量代谢的重编程，调节脓毒症进程。本项目将利用利用新型探针模型SoNAR小鼠监测脓毒症巨噬细胞的能量代谢改变，利用LysMCre TET2f/f小鼠解析α-KG通过DNA甲基化调控SCARA5表达，阐明α-KG对脓毒症巨噬细胞炎症反应的调节机制，为脓毒症治疗提供新的分子靶点和研究思路。

脓毒症是感染或应激引起的免疫应答失控反应，并伴随着巨噬细胞能量代谢异常，二者之间存在密切的联系。α-KG作为TCA循环的中间产物之一，能参与调节炎症反应，被认为是能量代谢和炎症调控之间重要的桥梁。SCARA5是巨噬细胞表面的一类重要模式识别受体，在抗炎反应过程中发挥重要作用。申请人前期研究结果发现α-KG在脓毒症患者血清中有动态变化，给予α-KG可以抑制巨噬细胞炎症反应，并能诱导SCARA5表达上调。这些结果初步表明α-KG除了调控能量代谢影响炎症反应外，也可能通过SCARA5受体影响炎症反应进程，参与脓毒症调节。.本项目在前期工作基础上，首先验证了α-KG对巨噬细胞炎症反应和脓毒症组织损伤的影响，发现α-KG能显著降低巨噬细胞和脓毒症小鼠血清中炎症因子的表达和分泌，改善组织的损伤情况。其次，证明了α-KG是通过SCARA5发挥对脓毒症的调节作用，利用慢病毒敲低SCARA5表达后α-KG抑制炎症因子和改善组织损伤的作用会减弱，说明除了影响能量代谢方式抑制炎症外，α-KG还可以通过SCARA5发挥炎症抑制作用改善脓毒症小鼠中的组织损伤情况。最后，我们阐述了α-KG调控SCARA5表达的机制，发现α-KG通过上调m6A去甲基化酶ALKBH5和FTO的表达，降低巨噬细胞的m6A甲基化水平；而抑制ALKBH5和FTO表达后，α-KG无法上调SCARA5表达。.因此，通过本研究，我们明确了除了影响能量代谢方式外，α-KG 还可以通过SCARA5发挥炎症抑制作用，改善脓毒症时的组织损伤；证明了α-KG能够影响m6A去甲基化酶ALKBH5和FTO调控SCARA5的表达。本项目研究结果阐述了能量代谢与炎症调节之间的关系及其分子调控机制，可以为脓毒症的治疗提供新的靶点，为探索新的治疗方案提供实验依据，具有重要的科学意义和潜在的临床应用价值。