CTRP9在血管钙化中的作用及机制研究-Sp1的介导作用

Vascular calcification is a common pathologic condition that occurs in atherosclerosis, diabetes mellitus, and end-stage renal disease, and it may contribute to increased cardiovascular-related morality. This may be the result of an increase in arterial stiffness, pulse wave velocity, and systolic blood pressure, ultimately leading to reduced coronary perfusion and ventricular hypertrophy. Vascular calcification is classified as two forms: intimal calcification and medial calcification. Medial arterial calcification is associated with aging, advanced chronic kidney disease (CKD), and diabetes mellitus (DM). Adipokines, predominantly secreted by adipose tissue, are a series of factors controlling energy metabolism, inflammation, and cardiovascular function. Accumulating evidence has suggested that adipokines are involved in the regulation of vascular calcification. However, the precise roles of adipokines in vascular calcification regulation and the underlying mechanisms still require further investigation. C1q/TNF-related protein-9 (CTRP9) is a newly identified adipokine, which is ubiquitously expressed in adipose, kidney, heart, vessels and skeletal tissue. CTRP9 lowers serum insulin and glucose levels in obese (ob/ob) mice, whereas serum CTRP9 concentrations have been consistently and positively associated with arterial stiffness. A recent study shows that upregulation of CTRP9 during hypertrophic heart disease facilitates maladaptive cardiac remodeling and left ventricular dysfunction. Because CTRP9 promotes proliferation of VSMCs and CTRPs members play an important role in accelerating proliferation and differentiation of osteoblast, chondrogenic precursors and chondrocytes, we hypothesized that CTRP9 might be involved in the regulation of vascular calcification. Accumulating evidence showed that man adipokines regulated down-stream target mediated by Sp1, which plays an important regulatory role in apoptosis, fibrosis, inflammation, and other pathologic disorders. We hypothesized that CTRP9 might regulate vascular calcification mediated by Sp1.In this study, we plan to investigate the effects of CTRP9 on vascular calcification in rat and primary cultured VSMCs. The results of this study can not only improve our understanding of the mechanism of vascular calcification, but also provide new ideas and theoretical basis for clinical prevention and treatment of vascular calcification.

临床上糖尿病、终末期肾病患者血管钙化非常普遍。血管钙化的存在使血管僵硬度增加、脉压增大，造成冠脉灌注减少、心室肥厚，最终增加心血管疾病病死率，目前并没有有效的预防、治疗办法。研究证实转录因子Sp1能够直接促进BMP2转录加速平滑肌细胞表型转化，Sp1的翻译后修饰能明显影响Sp1的转录激活活性及稳定性。因此，我们推测除Sp1表达水平外，其翻译后修饰亦参与调控血管钙化，为靶向抑制Sp1促钙化作用提供了可能。此外脂肪因子参与了血管钙化进程，脂肪因子CTRP9能够促进Sp1磷酸化，同时CTRPs蛋白家族成员具有促进软骨细胞前体、成骨细胞增殖分化的作用。我们推测下调CTRP9能够通过靶向调控Sp1翻译后修饰抑制血管钙化。

血管钙化是动脉粥样硬化、衰老、慢性肾病和糖尿病的常见并发症，是心血管高发病率和高死亡率的重要原因。CTRP9与脂联素结构相似，参与调控多种心血管与代谢疾病。自噬在维持细胞稳态与应激反应中十分关键。在高磷刺激下,VSMC自噬水平显著提高,而自噬可以拮抗高磷诱导的VSMC钙化。自噬过程受到精密调控, mTOR是自噬的上游抑制因子,参与调控血管钙化过程。本研究证实，CTRP9通过自噬依赖mTOR通路调控血管钙化。人参皂苷是中药人参、西洋参等的重要成分，在多种心血管疾病及肾脏损伤中发挥保护作用。Wnt/β-catenin途径是成骨与血管钙化过程中的重要信号通路。PPAR-y属于核受体超家族成员,PPAR-γ与Wnt/β-catenin通路的互相拮抗作用在成骨与钙化过程中至为关键。本研究结果表明 ,Rb1可通过激活PPAR-γ抑制Wnt/β-catenin通路从而保护血管钙化。Sp1是一个广泛参与生命活动调控的转录因子，并在调控血管钙化中发挥重要作用。本课题组前期研究表明，Sp1可以调控BMP2来发挥促血管钙化作用。去乙酰化突变可以抑制转录因子与下游基因启动子结合，从而下调下游基因的表达。本研究确定了Sp1去乙酰化突变可以下调Sp1与BMP2启动子结合，从而改善血管钙化。本研究为血管钙化的临床防治提供的重要治疗靶点。