基于OPA1介导线粒体动力学的PPARα促进肝再生的分子事件与作用机制

The liver has a remarkable ability to regenerate following various injury or 70% partial hepatectomy (PHx). Currently, the molecular mechanisms of liver regeneration is not completely understood. Thus, it is necessary to develop more effective new target to elucidate the mechanisms of liver regeneration. Mitochondria are highly dynamic organelles that constantly undergo fission and fusion processes that closely related to their function. Disruption of mitochondrial dynamics has been demonstrated in hepatic injury induced by various causes, which could eventually result in cell injury and death..Recently, we found that the key regulators related to mitochondrial dynamics changed significantly during liver regeneration after PHx in mice. RT-qPCR and western blot analysis showed that hepatic expression of optic atrophy 1 (OPA1) which modulates mitochondrial inner fusion was down-regulated at early stages after PHx, then up-regulated at later times. Perixisome proliferation-activated receptor alpha (PPARα) plays an important role in the progression of liver regeneration. After PHx in mice, PPARα activation promoted the hepatocyte proliferation and liver regeneration. Western blot analysis showed that PPARα activation significantly down-regulated expression of OPA1 protein. Taken together, we hypothesize that OPA1-mediated mitochondrial dynamics may play an important role in the PPARα-induced liver regeneration and the mechanisms need to be further elucidated..Here, for the first time, we will assess that PPARα promotes liver regeneration via the regulation of OPA1-mediated mitochondrial dynamics and elucidate its molecular role in the regulation of OPA1 axis and the mitochondrial dynamics. In this study, PHx mouse model will be used to investigate the changes of mitochondrial dynamics (fission-fusion) during liver regeneration, and confirm the important role of OPA1-mediated mitochondrial dynamics in the progression of liver regeneration. Furthermore, primary mouse hepatocytes will be used to explore whether PPARα-induced liver regeneration is related to OPA1-mediated mitochondrial dynamics. Opa1 knock-out mice will be used to confirm that PPARα induces liver regeneration via regulating OPA1 pathway. Finally, the studies will provide a new insight into the importance of OPA1 axis and regulation of mitochondrial dynamics in PPARα-induced liver regeneration, and suggest mitochondrial dynamics might be a novel potential target for the study of liver regeneration mechanisms.

肝脏再生能力是各种肝损伤或肝手术后修复与预后的关键，目前肝再生的分子机制尚不完全清楚。线粒体动力学与各种病因引起的肝细胞损伤密切相关。我们前期研究发现，部分肝切除小鼠肝再生过程中，线粒体动力学关键调控基因OPA1显著变化。PPARα与肝再生密切相关，PPARα激活显著促进肝细胞增殖与肝再生，且PPARα激活促进线粒体融合蛋白OPA1显著下调。基于此，我们提出PPARα调控OPA1通路影响线粒体动态变化从而促进肝再生的科学假设。项目拟深入研究肝再生过程中线粒体分裂-融合动态变化，全面表征肝再生进程中的线粒体动力学；同时在细胞水平证实PPARα对线粒体动力学的影响及对OPA1的调控；最后采用Opa1基因敲除小鼠，证实PPARα通过OPA1通路发挥促进肝脏再生作用，从而获得PPARα通过调控OPA1介导线粒体动力学而促进肝再生的可靠证据，为PPARα促进肝再生作用的研究提供新思路。

肝脏再生能力是各种肝损伤或肝手术后修复与预后的关键，目前肝再生的分子机制尚不完全清楚。线粒体动力学与各种病因引起的肝细胞损伤密切相关。我们前期研究发现，部分肝切除小鼠肝再生过程中，线粒体动力学关键调控基因OPA1显著变化。PPARα与肝再生密切相关，PPARα激活显著促进肝细胞增殖与肝再生，且PPARα激活促进线粒体融合蛋白OPA1显著下调。基于此，我们提出PPARα调控OPA1通路影响线粒体动态变化从而促进肝再生的科学假设。项目拟深入研究肝再生过程中线粒体分裂-融合动态变化，证实PPARα通过OPA1通路发挥促进肝脏再生作用，从而获得PPARα通过调控OPA1介导线粒体动力学而促进肝再生的可靠证据，为PPARα促进肝再生作用的研究提供新思路。研究结果表明，PPARα激活抑制线粒体介导的细胞死亡，改善线粒体功能异常。此外，PPARα激活能逆转肝切除后OPA1表达的上调，同时下调DRP1的表达。综上所述，课题阐明了PPARα改善部分肝切除后线粒体功能异常及其介导的细胞死亡，调控线粒体动力学相关蛋白，逆转OPA1表达进而促进肝脏再生。