S1PR2负向调控肝细胞自噬流对脓毒症肝功能障碍的影响和机制研究

Our previous study has found that sphingosine-1 phosphate receptor 2 (S1PR2) deficiency can obviously elevate the survival rate of septic mice, affirming the important role of S1PR2 in the pathogenesis of sepsis. Subsequently, our preliminary experiment found that S1PR2 deficiency could promote hepatocyte autophagy flux, and inhibit the phosphorylation level of mTOR which has a keeper role in negative regulation of autophagy, suggesting the effect of S1PR2 on the negative regulation of mTORC1-dependent hepatocyte autophagy flux. Recent studies have shown that prevention of hepatocyte autophagy flux induces hepatocyte injury, and which is the important factor for resulting in septic liver dysfunction. Whether S1PR2 involved in the pathogenesis of septic liver dysfunction via negative regulation of hepatocyte autophagy flux is remain unclear. This project will apply S1PR2 knockout mice and establish hepatocyte-specific S1PR2 overexpressed mice, from the systemic, cellular, organelle and molecular levels, to clarify the roles of S1PR2 in hepatocyte injury through negative regulation of hepatocyte autophagy and their roles in septic liver dysfunction, and subsequent to explore the signal pathway how S1PR2 mediated Gi protein suppress mTORC1-dependent hepatocyte autophagy. Our study will provide novel intervention targets for clinical prevention of septic liver dysfunction.

申请者前期研究发现S1PR2功能缺失可以显著提高脓毒症小鼠存活率，证实S1PR2在脓毒症发生发展中的重要作用。随后我们预实验又发现S1PR2功能缺失能够促进肝细胞自噬流，并且抑制具有自噬门控负调节作用的mTOR的磷酸化水平，提示S1PR2对mTORC1依赖的肝细胞自噬流的负向调控作用。近年研究发现肝细胞自噬流受阻引起的肝细胞损伤，是导致脓毒症肝功能障碍的重要因素。S1PR2是否调控肝细胞自噬流参与脓毒症肝功能障碍的发生发展，亟待研究证实。本项目拟运用S1PR2-/-小鼠和构建肝细胞特异性S1PR2过表达小鼠，从整体、细胞、亚细胞器和分子多个层面，明确S1PR2通过负向调控肝细胞自噬加剧肝细胞损伤的作用，及其对脓毒症肝功能障碍的影响；并深入探究S1PR2介导Gi蛋白抑制mTORC1依赖的肝细胞自噬的分子机制，为脓毒症肝功能障碍防治提供新策略。

肝脏是脓毒症多器官功能障碍中的重要靶器官，脓毒症引起的肝功能障碍是预测患者死亡的独立危险因素。然而，脓毒症肝功能障碍发病机制尚未完全阐明，更缺乏特异性的防治手段。近年研究发现肝细胞自噬流受阻引起的肝细胞损伤，是导致脓毒症肝功能障碍的重要因素。因此，探索肝细胞自噬的上游调控机制并进行干预，有望成为脓毒症肝功能障碍治疗的有效方法。本项目通过化学诱导、小干扰RNA和基因敲除模式动物模型等技术手段，从整体动物到细胞和分子水平，系统研究了S1PR2通过AKT-mTORC1信号通路对肝细胞自噬的负性调控作用，并证实S1PR2功能缺失能够缓解肝细胞损伤、肝脏合成代谢和线粒体功能障碍，从而提高脓毒症小鼠的生存率。综上所述，本项目以S1PR2负向调控肝细胞自噬为切入点，为脓毒症肝功能障碍的防治提供了新的理论依据和治疗靶点。