Abstract：
Asthma is characterized by aberrant airway smooth muscle (ASM) proliferation, which increases the thickness of the ASM layer within the airway wall and exacerbates airway obstruction during asthma attacks. The mechanisms that drive ASM proliferation in asthma are not entirely elucidated. Ten-eleven translocation methylcytosine dioxygenase (TET) is an enzyme that participates in the regulation of DNA methylation by catalyzing the hydroxylation of 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC). The generation of 5-hmC disinhibits the gene silencing effect of 5-mC. In this study, TET1 activity and protein were enhanced in asthmatic human ASM cell cultures. Moreover, the level of 5-hmC was higher in asthmatic ASM cells as compared to nonasthmatic ASM cells. Knockdown (KD) of TET1, but not TET2, reduced the level of 5-hmC in asthmatic cells. Because the cytoskeletal protein nestin controls cell proliferation by modulating mechanistic target of rapamycin (mTOR), we evaluated the effects of TET1 KD on this pathway. TET1 KD reduced nestin expression in ASM cells. Moreover, TET1 inhibition alleviated the platelet-derived growth factor (PDGF)-induced phosphorylation of p70S6K, 4E-BP, S6, and Akt. TET1 inhibition also attenuated the proliferation of ASM cells. Taken together, these results suggest that TET1 drives ASM proliferation via the nestin-mTOR axis.
摘要：
哮喘的特征是异常的气道平滑肌（ASM）增殖，这增加了气道壁内ASM层的厚度，并在哮喘发作期间加剧了气道阻塞。哮喘中驱动ASM增殖的机制尚未完全阐明。10-11易位甲基胞嘧啶双加氧酶（TET）是一种通过催化5-甲基胞嘧啶（5-mC）羟化为5-羟甲基胞嘧啶（5-hmC）参与DNA甲基化调节的酶。5-hmC的产生解除了5-mC的基因沉默效应。在这项研究中,在哮喘人类ASM细胞培养物中，TET1活性和蛋白质得到增强。此外，5-hmC在哮喘ASM细胞中的水平高于非哮喘ASM细胞。TET1而不是TET2的敲低（KD）降低了哮喘细胞中5-hmC的水平。因为细胞骨架蛋白巢蛋白通过调节雷帕霉素的机制靶标（mTOR）来控制细胞增殖，我们评估了TET1KD对该通路的影响.TET1KD降低ASM细胞中巢蛋白的表达。此外，TET1抑制减轻了血小板衍生生长因子（PDGF）诱导的p70S6K磷酸化，4E-BP,S6和Akt.TET1抑制也减弱了ASM细胞的增殖。一起来看,这些结果表明TET1通过nestin-mTOR轴驱动ASM增殖.
