Caffeine induces apoptosis by enhancement of autophagy via PI3K/Akt/mTOR/p70S6K inhibition
Caffeine induces apoptosis by enhancement of autophagy via PI3K/Akt/mTOR/p70S6K inhibition
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DOI：
10.4161/auto.7.2.14074
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发表时间：
2011-02-01
期刊：
影响因子：
13.3
通讯作者：
Hattori, Nobutaka
中科院分区：
文献类型：
--
作者：
Saiki, Shinji;Sasazawa, Yukiko;Hattori, Nobutaka
咖啡因是最常见的神经活性化合物之一。所有已知的咖啡因诱导的细胞凋亡机制都是通过细胞周期调节或p53诱导起作用的。目前尚不清楚咖啡因诱导的细胞凋亡是否与其他细胞死亡机制（如自噬）相关。在此，我们表明，咖啡因增加微管相关蛋白1轻链3-II的水平和自噬体的数量，通过使用蛋白质印迹，电子显微镜和免疫细胞化学技术。咖啡因可显著降低磷酸化p70核糖体蛋白S6激酶（Thr 389）、S6核糖体蛋白（Ser 235/236）、4 E-BP 1（Thr 37/46）和Akt（Ser 473）。相反，ERK 1/2（Thr 202/204）被咖啡因增加，表明Akt/mTOR/p70 S6 K通路的抑制和ERK 1/2通路的激活。虽然胰岛素处理磷酸化Akt（Ser 473）并导致自噬抑制，但胰岛素处理的效果被咖啡因添加完全消除。咖啡因诱导的自噬不能被U 0126抑制ERK 1/2完全阻断。咖啡因以剂量依赖性方式诱导线粒体膜电位降低和细胞凋亡，通过3-甲基腺嘌呤或atg 7 siRNA敲低抑制自噬进一步减弱。此外，与野生型相比，用咖啡因处理的自噬缺陷小鼠胚胎成纤维细胞中早期凋亡细胞（膜联蛋白V阳性，碘化丙啶阴性）的数量减少。这些结果支持了先前关于咖啡因在人类肿瘤治疗中的使用的研究，并表明了在细胞凋亡调节中的潜在新靶点。
Caffeine is one of the most frequently ingested neuroactive compounds. All known mechanisms of apoptosis induced by caffeine act through cell cycle modulation or p53 induction. It is currently unknown whether caffeine-induced apoptosis is associated with other cell death mechanisms, such as autophagy. Herein we show that caffeine increases both the levels of microtubule-associated protein 1 light chain 3-II and the number of autophagosomes, through the use of western blotting, electron microscopy and Immunocytochemistry techniques. Phosphorylated p70 ribosomal protein S6 kinase (Thr389), S6 ribosomal protein (Ser235/236), 4E-BP1 (Thr37/46) and Akt (Ser473) were significantly decreased by caffeine. In contrast, ERK1/2 (Thr202/204) was increased by caffeine, suggesting an inhibition of the Akt/mTOR/p70S6K pathway and activation of the ERK1/2 pathway. Although insulin treatment phosphorylated Akt (Ser473) and led to autophagy suppression the effect of insulin treatnment was completely abolished by caffeine addition. Caffeine-induced autophagy was not completely blocked by inhibition ERK1/2 by U0126. Caffeine induced reduction of mitochondrial membrane potentials and apoptosis in a dose-dependent manner, which was further attenuated by the inhibition of autophagy with 3-methyladenine or atg7 siRNA knockdown. Furthermore, there was a reduced number of early apoptotic cells (annexin V positive, propidium iodide negative) among autophagy-deficient mouse embryonic fibroblasts treated with caffeine than in their wild-type counterparts. These results support previous studies on the use of caffeine in the treatment of human tumors and indicate a potential new target in the regulation of apoptosis.