Division of Respiratory Diseases, Department of Internal Medicine, Jikei University School of Medicine, Tokyo 105-8461, Japan;
J Immunol. 2014 Feb 1;192(3):958-68. doi: 10.4049/jimmunol.1302341. Epub 2013 Dec 23.
Cigarette smoke (CS)-induced cellular senescence has been implicated in the pathogenesis of chronic obstructive pulmonary disease, and SIRT6, a histone deacetylase, antagonizes this senescence, presumably through the attenuation of insulin-like growth factor (IGF)-Akt signaling. Autophagy controls cellular senescence by eliminating damaged cellular components and is negatively regulated by IGF-Akt signaling through the mammalian target of rapamycin (mTOR). SIRT1, a representative sirtuin family, has been demonstrated to activate autophagy, but a role for SIRT6 in autophagy activation has not been shown. Therefore, we sought to investigate the regulatory role for SIRT6 in autophagy activation during CS-induced cellular senescence. SIRT6 expression levels were modulated by cDNA and small interfering RNA transfection in human bronchial epithelial cells (HBECs). Senescence-associated β-galactosidase staining and Western blotting of p21 were performed to evaluate senescence. We demonstrated that SIRT6 expression levels were decreased in lung homogenates from chronic obstructive pulmonary disease patients, and SIRT6 expression levels correlated significantly with the percentage of forced expiratory volume in 1 s/forced vital capacity. CS extract (CSE) suppressed SIRT6 expression in HBECs. CSE-induced HBEC senescence was inhibited by SIRT6 overexpression, whereas SIRT6 knockdown and mutant SIRT6 (H133Y) without histone deacetylase activity enhanced HBEC senescence. SIRT6 overexpression induced autophagy via attenuation of IGF-Akt-mTOR signaling. Conversely, SIRT6 knockdown and overexpression of a mutant SIRT6 (H133Y) inhibited autophagy. Autophagy inhibition by knockdown of ATG5 and LC3B attenuated the antisenescent effect of SIRT6 overexpression. These results suggest that SIRT6 is involved in CSE-induced HBEC senescence via autophagy regulation, which can be attributed to attenuation of IGF-Akt-mTOR signaling.
香烟烟雾(CS)诱导的细胞衰老与慢性阻塞性肺疾病的发病机制有关,组蛋白去乙酰化酶 SIRT6 拮抗这种衰老,可能是通过减弱胰岛素样生长因子(IGF)-Akt 信号传导。自噬通过消除受损的细胞成分来控制细胞衰老,并且通过雷帕霉素(mTOR)的哺乳动物靶标(mTOR)负调控 IGF-Akt 信号。代表性的 Sirtuin 家族 SIRT1 已被证明可以激活自噬,但是 SIRT6 在自噬激活中的作用尚未显示。因此,我们试图研究 SIRT6 在 CS 诱导的细胞衰老过程中对自噬激活的调节作用。通过 cDNA 和小干扰 RNA 转染在人支气管上皮细胞(HBEC)中调节 SIRT6 的表达水平。进行衰老相关β-半乳糖苷酶染色和 p21 的 Western 印迹以评估衰老。我们证明,慢性阻塞性肺疾病患者的肺匀浆中 SIRT6 的表达水平降低,并且 SIRT6 的表达水平与 1 秒用力呼气量/用力肺活量的百分比呈显著相关。CS 提取物(CSE)抑制 HBEC 中的 SIRT6 表达。 SIRT6 过表达抑制 CSE 诱导的 HBEC 衰老,而 SIRT6 敲低和缺乏组蛋白去乙酰化酶活性的突变体 SIRT6(H133Y)增强 HBEC 衰老。 SIRT6 过表达通过减弱 IGF-Akt-mTOR 信号传导诱导自噬。相反,SIRT6 敲低和突变 SIRT6(H133Y)的过表达抑制自噬。通过敲低 ATG5 和 LC3B 抑制自噬会减弱 SIRT6 过表达的抗衰老作用。这些结果表明,SIRT6 通过自噬调节参与 CSE 诱导的 HBEC 衰老,这归因于 IGF-Akt-mTOR 信号的减弱。
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