SP1转录调控Beclin1促VSMC自噬在胸主动脉夹层发生中的作用及机制研究

Mounting evidences supports the notion that thoracic aortic dissection (TAD) is the result of biomechanical weakening of the aortic media. Previous studies showed that vascular smooth muscle cells (VSMC) phenotypic transition from the contractile to the synthetic type might result in instability of the aortic media, which are responsible for the occurrence of TAD. Accumulating evidences suggests that autophagy is activated in VSMC in vascular diseases and that it is important for VSMC phenotype switching.In a recent work we demonstrated that SP1 is overexpressed in the aortic VSMC of TAD, and that its overexpression can induce VSMC phenotypic transition and upregulate the expression of autophagy related gene Beclin1. These data suggest that SP1/Beclin1 overexpression in aortic VSMC contribute to the development of TAD. However, the mechanisms that underlie transcriptional modulation of Beclin1 by SP1 trigger VSMC autophagy in TAD still need further investigation.In this project, we propose to evaluate the role of transcriptional modulation of Beclin1 by SP1 in the VSMC phenotypic transition by multiple approaches including bioinformatic analysis, luciferase reporter assay, RNA interference, ChIP, ChIP-chip, and clinical investigation. Conceivably, elucidation of the molecular pathways involved in the regulation of the VSMC phenotypic transition in TAD by SP1/Beclin1 will provide important clues for the development and evaluation of novel therapies against TAD.

研究已表明，血管平滑肌细胞(VSMC)功能异常所造成的管壁薄弱是胸主动脉夹层(TAD)发生发展的病理基础，其中以VSMC的表型转换最为突出。因此，研究其调控机制并籍此探寻有效的TAD治疗靶点已成为该领域的探索热点。现有研究证实，自噬参与调控VSMC的表型转化，且与众多心血管疾病的发生密切相关。我们前期研究发现，转录因子SP1在TAD中膜组织中的表达水平显著上调，并伴随VSMC自噬增强；细胞学实验显示SP1高表达可以促进VSMC自噬基因Beclin1的表达及其表型转换，但相关分子机制仍有待于明确。为此，本研究拟采用染色质免疫共沉淀-芯片检测结合生物信息学分析的方法明确SP1转录上调Beclin1表达及其对VSMC表型转化的调控作用以及与TAD发病的关系；在此基础上我们还将通过临床病理检测及统计分析等对SP1/Beclin1表达与体内VSMC自噬、表型转化及TAD发生发展的相关性作进一步验证。

血管平滑肌细胞（VSMC）功能异常与胸主动脉夹层（TAD）发生发展密切相关。我们前期研究发现，转录因子SP1在TAD中膜组织中表达显著上调，并伴随VSMC自噬增强，但对于SP1是如何调控VSMC自噬而参与TAD的发生过程未见文献报道。本项目主要研究内容：1）SP1上调动脉VSMC中Beclin1表达促进细胞自噬的机制研究；2）SP1通过上调Beclin1促动脉VSMC表型转化的作用研究；3） SP1/Beclin1促动脉VSMC表型转化在TAD发生过程中的作用研究；以及4）SP1/Beclin1表达与TAD临床病理因素的相关性研究。主要研究结果：1）首次成功构建大鼠的胸主动脉夹层模型，而且该建模方法的成功率几乎为100%，成模时间仅需4周，该模型的构建方式目前未见文献报道，其为进一步对TAD的发生机制研究奠定基础。2）首次发现在TAD动脉VSMC中，自噬相关基因Beclin1的表达明显上调及VSMC自噬增强，该研究结果目前国内外均未见文献报道，其为TAD的发生机制研究开辟了新的方向。3）首次报道SP1/Beclin1在TAD组织中表达状况，并明确SP1通过与Beclin1启动子区域（序列1299-1309，cctccgcctcc）位点的结合转录调控Beclin1的表达，从而促进VSMC自噬的发生，该研究结果目前也均未见国内外文献报道。以上研究初步揭示了SP1可以通过上调Beclin1促VSMC自噬进而调控VSMC的表型转化而参与TAD发生，但其中也发现SP1参与TAD发生还有可能存在其它的信号通路。