线粒体去乙酰化酶SIRT3对血管重构的影响及机制

Vascular remodeling is the main pathological process of cardiovascular disease, and its mechanism has not been fully elucidated. We found that glycolysis activity of vascular smooth muscle cells (VSMC) increased and mitochondrial oxidative function decreased during vascular remodeling, suggesting that metabolic mode transition of VSMC may be an important initiating factor for phenotypic transition. Mitochondrial deacetylase SIRT3 plays a key role in maintaining the balance of cell metabolism and is involved in the occurrence of vascular remodeling. However, whether SIRT3 affects vascular remodeling by regulating the metabolic mode transition of VSMC remains unclear. In this project, we intend to construct VSMC-specific SIRT3 knockout mice to determine whether the decreased expression of SIRT3 in VSMC is an important cause of vascular remodeling. We hypothesized that remodeling-promoting factors could increase the glycolysis activity of VSMC by inhibiting SIRT3, activate the HIF-1a/KLF4 pathway to induce phenotype transition of VSMC, and activation of SIRT3 by honokiol could inhibit glycolysis by promoting oxidative phosphorylation activity of mitochondria. This project explains the molecular mechanism of VSMC phenotypic transition and vascular remodeling from a metabolic point of view, and provides theoretical basis and possible intervention targets for fundamentally preventing and treating vascular remodeling-related diseases.

血管重塑是心血管疾病的主要病理过程，其机制尚未完全阐明。我们发现血管重塑过程中血管平滑肌细胞（VSMC）糖酵解活性增加，线粒体氧化功能下降，提示VSMC代谢模式转换可能是其表型转化的重要始动因素。线粒体去乙酰化酶SIRT3在维持细胞代谢平衡中起到关键作用，并参与血管重塑的发生，但SIRT3是否通过调控VSMC代谢模式转换影响血管重塑还不清楚。在本项目中，我们拟通过构建VSMC特异性SIRT3敲除鼠，确定SIRT3在VSMC中的表达下降是否是血管重塑的重要原因。我们假设促重构因素通过抑制SIRT3造成VSMC糖酵解活性增加，激活HIF-1a/KLF4通路造成VSMC表型转化，和厚朴酚激活SIRT3能够通过促进线粒体氧化磷酸化活性，抑制糖酵解发生，从而抑制血管重构。本项目从代谢角度解释VSMC表型转化和血管重构的分子机制，为从根本上防治血管重塑相关疾病提供了理论依据和可能干预靶点。

血管平滑肌细胞（VSMC）的表型转换是血管重塑性疾病的主要病理过程，线粒体氧化磷酸化（OXPHOS）活性的下降促进了血管重塑。SIRT3是定位于线粒体的重要去乙酰化酶，维持线粒体OXPHOS活性、抑制自由基生成，并参与高血压的发生。本项目的研究目的在于明确SIRT3的表达和活性降低是否是血管重塑的关键环节。首先，我们在血管紧张素II（AngII）诱导的腹主动脉瘤（AAA）模型和颈动脉结扎诱导的血管新生内膜形成的小鼠模型中均发现，SIRT3在VSMC中表达下降。进而，我们构建了VSMC特异性SIRT3敲除鼠与他莫昔芬诱导型VSMC特异性SIRT3过表达小鼠，并对WT小鼠进行了SIRT3激活剂Honokiol的干预。我们发现，VSMC特异性的SIRT3敲除明显加重了AngII所诱导的AAA的发生概率及严重程度，以及颈动脉结扎诱导的血管新生内膜的形成。而药物诱导的VSMC中SIRT3的过表达以及SIRT3活性的增加则起着相反的作用，抑制了两种血管重塑的发生。细胞水平，血清刺激引起的VSMC表型转化伴随着SIRT3表达的降低，而过表达SIRT3或者Honokiol干预则能够抑制PDGF-BB所诱导的表型转换。Honokiol抑制了增殖的VSMC中糖酵解活性的增高，并恢复了线粒体OXPHOS水平。机制上，SIRT3的抑制造成了代谢中间产物乙酰辅酶A（Ac-CoA）的积累，伴随着表型转化重要转录因子KLF4表达的增加，其启动子上的组蛋白3赖氨酸27位点的乙酰化（H3K27ac）水平明显增加。用si-RNA敲低介导Ac-CoA从核内转运到细胞质的关键分子柠檬酸-ATP裂解酶(ACLY)能明显抑制VSMC中KLF4的表达。本项目确定了VSMC线粒体活性在血管重塑中具有重要作用，线粒体代谢调节因子SIRT3能够通过维持代谢中间产物Ac-CoA含量抑制VSMC表型转换。