HDAC9下调转录因子Osterix延缓肾衰后血管钙化的机制研究

Vascular calcification is a significant risk factor of cardiovascular disease in patients with chronic renal failure. Histone deacetylases have critical roles in cardiovascular disease, however their roles in vascular calcification remains to be fully elucidated. Our data has demonstrated that HDAC9 expression was significantly down-regulated during the process of high phosphate induced in vitro VSMC calcification. Further studies showed that HDAC9 knockdown significantly enhanced high phosphate induced calcium deposition in VSMCs, suggesting an inhibitory effect of HDAC9 on vascular calcification. Interestingly, HDAC9 knockdown increased the protein expression of transcription factor Osterix，however its mRNA levels remained unchanged. HDAC9 may therefore regulates Osterix via post-translational modification. We hypothesized that HDAC9 inhibits vascular calcification via up-regulating Osterix expression in a post-translational modification manner. In this project, we will investigate whether: 1, high phosphate down-regulates HDAC9 via PiT-1, Erk1/2 and Akt signaling pathways; 2, HDAC9 post-translationally modifies the transcription factor Osterix, such as its acetylation, protein stability and transcriptional activity; 3, Osterix mediates the inhibitory effect of HDAC9 on vascular calcification; 4, HDAC9 inhibits vascular calcification in vivo by using vascular smooth muscle cell conditional knockout mice fed with high phosphate and adenine. This project will reveal the inhibitory effect of HDAC9 on vascular calcification and its underlying mechanisms. It may provide novel therapeutic targets for vascular calcification in chronic renal failure.

血管钙化是慢性肾衰患者心血管疾病高发的重要危险因素。组蛋白去乙酰化酶(HDAC)与心血管疾病密切相关，但在血管钙化中的作用和机制尚不清楚。我们预实验发现，HDAC9在高磷诱导血管平滑肌细胞钙化过程中显著下调。沉默HDAC9，血管平滑肌细胞钙化加快，血管钙化促进基因Osterix mRNA水平无显著变化，但蛋白水平显著上升。我们推测HDAC9可能去乙酰化修饰Osterix抑制其蛋白稳定性,延缓血管钙化。本项目拟研究：1、钠磷协同转运子PiT-1、Erk1/2和Akt信号通路在高磷下调HDAC9中的作用；2、HDAC9对Osterix的乙酰化水平及蛋白稳定性的影响；3、Osterix在HDAC9抑制血管钙化过程中的作用；4、在HDAC9血管平滑肌细胞条件性敲除小鼠上，研究HDAC9对慢性肾衰血管钙化的抑制作用。本项目将揭示HDAC9延缓血管钙化的作用与机制，为防治血管钙化提供新的药物靶点。

血管钙化是慢性肾病患者最常见的心血管并发症，显著增加慢性肾病患者心血管疾病的发病率和死亡率。新近全基因组关联分析发现位于组蛋白去乙酰化酶HDAC9的多个遗传变异位点与心血管疾病密切相关，提示HDAC9可能是一个心血管疾病的重要调控因子。然而，HDAC9是否参与慢性肾病患者血管钙化及其具体分子机制尚不清楚。本项目研究发现：HDAC9的表达量在高磷诱导的血管平滑肌细胞钙化和高剂量Vitamin D3诱导的小鼠血管钙化过程中显著下降。高磷刺激显著抑制血管平滑肌细胞中Akt信号通路，且Akt通路抑制剂显著下调血管平滑肌细胞中HDAC9的表达。敲低或过表达HDAC9显著增加或抑制高磷诱导的血管平滑肌细胞钙化。进一步实验发现，成骨样转分化关键转录因子Osterix介导了HDAC9对血管钙化的抑制作用。本研究首次证实HDAC9是一个新的血管钙化抑制因子，并且初步揭示了其通过调控Osterix的表达抑制血管钙化的分子机制，从而为防治血管钙化提供了一个潜在的干预靶点。

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