Ye Qing, Pang Shu, Zhang Wenjing, Guo Xiaotong, Wang Jianli, Zhang Yongtao, Liu Yang, Wu Xiao, Jiang Fan
From the School of Basic Medicine, Shandong University, Jinan, Shandong Province, China (Q.Y., S.P., W.Z., X.G., J.W., Y.L., F.J.); Key Laboratory of Cardiovascular Remodeling and Function Research & The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Qilu Hospital of Shandong University, Jinan, Shandong, China (X.W.); and Department of Cardiology, Qing Dao Central Hospital, Qing Dao, Shandong Province, China (Y.Z.).
Arterioscler Thromb Vasc Biol. 2017 Mar;37(3):476-484. doi: 10.1161/ATVBAHA.116.308401. Epub 2017 Jan 5.
RNA polymerase I (Pol I)-dependent rRNA synthesis is a determinant factor in ribosome biogenesis and thus cell proliferation. The importance of dysregulated Pol I activity in cardiovascular disease, however, has not been recognized. Here, we tested the hypothesis that specific inhibition of Pol I might prevent arterial injury-induced neointimal hyperplasia.
CX-5461 is a novel selective Pol I inhibitor. Using this tool, we demonstrated that local inhibition of Pol I blocked balloon injury-induced neointima formation in rat carotid arteries in vivo. Neointimal development was associated with augmented rDNA transcriptional activity as evidenced by the increased phosphorylation of upstream binding factor-1. The beneficial effect of CX-5461 was mainly mediated by inducing G2/M cell cycle arrest of proliferating smooth muscle cells without obvious apoptosis. CX-5461 did not induce p53 stabilization but increased p53 phosphorylation and acetylation and activated the ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related (ATR) pathway. Inhibition of ATR, but not of ataxia telangiectasia mutated, abolished the cytostatic effect of CX-5461 and p53 phosphorylation. In addition, inhibition of p53 or knockdown of the p53 target GADD45 mimicked the effect of ATR inhibition. In vivo experiments showed that the levels of phospho-p53 and acetyl-p53, and activity of the ataxia telangiectasia mutated/ATR pathway were all augmented in CX-5461-treated vessels.
Pol I can be therapeutically targeted to inhibit the growth of neointima, supporting that Pol I is a novel biological target for preventing arterial restenosis. Mechanistically, Pol I inhibition elicited G2/M cell cycle arrest in smooth muscle cells via activation of the ATR-p53 axis.
RNA聚合酶I（Pol I）依赖性rRNA合成是核糖体生物合成及细胞增殖的决定性因素。然而，Pol I活性失调在心血管疾病中的重要性尚未得到认识。在此，我们检验了以下假说：特异性抑制Pol I可能预防动脉损伤诱导的内膜增生。
CX-5461是一种新型选择性Pol I抑制剂。利用该工具，我们证明在体内局部抑制Pol I可阻断大鼠颈动脉球囊损伤诱导的内膜形成。内膜发育与rDNA转录活性增强相关，上游结合因子-1磷酸化增加证明了这一点。CX-5461的有益作用主要通过诱导增殖平滑肌细胞的G2/M期细胞周期阻滞而介导，无明显凋亡。CX-5461未诱导p53稳定，但增加了p53磷酸化和乙酰化，并激活了共济失调毛细血管扩张症突变/共济失调毛细血管扩张症和Rad3相关（ATR）途径。抑制ATR而非共济失调毛细血管扩张症突变可消除CX-5461的细胞生长抑制作用和p53磷酸化。此外，抑制p53或敲低p53靶标GADD45可模拟ATR抑制的效果。体内实验表明，在CX-5461处理的血管中，磷酸化p53和乙酰化p53水平以及共济失调毛细血管扩张症突变/ATR途径的活性均增强。
Pol I可作为治疗靶点以抑制内膜生长，支持Pol I是预防动脉再狭窄的新型生物学靶点。机制上，抑制Pol I通过激活ATR-p53轴引发平滑肌细胞的G2/M期细胞周期阻滞。
