Honokiol induces autophagic cell death in malignant glioma through reactive oxygen species-mediated regulation of the p53/PI3K/Akt/mTOR signaling pathway

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Abstract

Honokiol, an active constituent extracted from the bark of Magnolia officinalis, possesses anticancer effects. Apoptosis is classified as type I programmed cell death, while autophagy is type II programmed cell death. We previously proved that honokiol induces cell cycle arrest and apoptosis of U87 MG glioma cells. Subsequently in this study, we evaluated the effect of honokiol on autophagy of glioma cells and examined the molecular mechanisms. Administration of honokiol to mice with an intracranial glioma increased expressions of cleaved caspase 3 and light chain 3 (LC3)-II. Exposure of U87 MG cells to honokiol also induced autophagy in concentration- and time-dependent manners. Results from the addition of 3-methyladenine, an autophagy inhibitor, and rapamycin, an autophagy inducer confirmed that honokiol-induced autophagy contributed to cell death. Honokiol decreased protein levels of PI3K, phosphorylated (p)-Akt, and p-mammalian target of rapamycin (mTOR) in vitro and in vivo. Pretreatment with a p53 inhibitor or transfection with p53 small interfering (si)RNA suppressed honokiol-induced autophagy by reversing downregulation of p-Akt and p-mTOR expressions. In addition, honokiol caused generation of reactive oxygen species (ROS), which was suppressed by the antioxidant, vitamin C. Vitamin C also inhibited honokiol-induced autophagic and apoptotic cell death. Concurrently, honokiol-induced alterations in levels of p-p53, p53, p-Akt, and p-mTOR were attenuated following vitamin C administration. Taken together, our data indicated that honokiol induced ROS-mediated autophagic cell death through regulating the p53/PI3K/Akt/mTOR signaling pathway.

Original languageEnglish
Pages (from-to)59-69
Number of pages11
JournalToxicology and Applied Pharmacology
Volume304
DOIs
Publication statusPublished - Aug 1 2016

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Autophagy
Cell death
Sirolimus
Phosphatidylinositol 3-Kinases
Glioma
Reactive Oxygen Species
Ascorbic Acid
Apoptosis
honokiol
Magnolia
Cell Cycle Checkpoints
Caspase 3
Small Interfering RNA
Transfection
Cell Death
Down-Regulation
Antioxidants
Cells

Keywords

  • Journal Article

Cite this

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title = "Honokiol induces autophagic cell death in malignant glioma through reactive oxygen species-mediated regulation of the p53/PI3K/Akt/mTOR signaling pathway",
abstract = "Honokiol, an active constituent extracted from the bark of Magnolia officinalis, possesses anticancer effects. Apoptosis is classified as type I programmed cell death, while autophagy is type II programmed cell death. We previously proved that honokiol induces cell cycle arrest and apoptosis of U87 MG glioma cells. Subsequently in this study, we evaluated the effect of honokiol on autophagy of glioma cells and examined the molecular mechanisms. Administration of honokiol to mice with an intracranial glioma increased expressions of cleaved caspase 3 and light chain 3 (LC3)-II. Exposure of U87 MG cells to honokiol also induced autophagy in concentration- and time-dependent manners. Results from the addition of 3-methyladenine, an autophagy inhibitor, and rapamycin, an autophagy inducer confirmed that honokiol-induced autophagy contributed to cell death. Honokiol decreased protein levels of PI3K, phosphorylated (p)-Akt, and p-mammalian target of rapamycin (mTOR) in vitro and in vivo. Pretreatment with a p53 inhibitor or transfection with p53 small interfering (si)RNA suppressed honokiol-induced autophagy by reversing downregulation of p-Akt and p-mTOR expressions. In addition, honokiol caused generation of reactive oxygen species (ROS), which was suppressed by the antioxidant, vitamin C. Vitamin C also inhibited honokiol-induced autophagic and apoptotic cell death. Concurrently, honokiol-induced alterations in levels of p-p53, p53, p-Akt, and p-mTOR were attenuated following vitamin C administration. Taken together, our data indicated that honokiol induced ROS-mediated autophagic cell death through regulating the p53/PI3K/Akt/mTOR signaling pathway.",
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author = "Chien-Ju Lin and Ta-Liang Chen and Yuan-Yun Tseng and Gong-Jhe Wu and Ming-Hui Hsieh and Yung-Wei Lin and Ruei-Ming Chen",
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T1 - Honokiol induces autophagic cell death in malignant glioma through reactive oxygen species-mediated regulation of the p53/PI3K/Akt/mTOR signaling pathway

AU - Lin, Chien-Ju

AU - Chen, Ta-Liang

AU - Tseng, Yuan-Yun

AU - Wu, Gong-Jhe

AU - Hsieh, Ming-Hui

AU - Lin, Yung-Wei

AU - Chen, Ruei-Ming

N1 - Copyright © 2016 Elsevier Inc. All rights reserved.

PY - 2016/8/1

Y1 - 2016/8/1

N2 - Honokiol, an active constituent extracted from the bark of Magnolia officinalis, possesses anticancer effects. Apoptosis is classified as type I programmed cell death, while autophagy is type II programmed cell death. We previously proved that honokiol induces cell cycle arrest and apoptosis of U87 MG glioma cells. Subsequently in this study, we evaluated the effect of honokiol on autophagy of glioma cells and examined the molecular mechanisms. Administration of honokiol to mice with an intracranial glioma increased expressions of cleaved caspase 3 and light chain 3 (LC3)-II. Exposure of U87 MG cells to honokiol also induced autophagy in concentration- and time-dependent manners. Results from the addition of 3-methyladenine, an autophagy inhibitor, and rapamycin, an autophagy inducer confirmed that honokiol-induced autophagy contributed to cell death. Honokiol decreased protein levels of PI3K, phosphorylated (p)-Akt, and p-mammalian target of rapamycin (mTOR) in vitro and in vivo. Pretreatment with a p53 inhibitor or transfection with p53 small interfering (si)RNA suppressed honokiol-induced autophagy by reversing downregulation of p-Akt and p-mTOR expressions. In addition, honokiol caused generation of reactive oxygen species (ROS), which was suppressed by the antioxidant, vitamin C. Vitamin C also inhibited honokiol-induced autophagic and apoptotic cell death. Concurrently, honokiol-induced alterations in levels of p-p53, p53, p-Akt, and p-mTOR were attenuated following vitamin C administration. Taken together, our data indicated that honokiol induced ROS-mediated autophagic cell death through regulating the p53/PI3K/Akt/mTOR signaling pathway.

AB - Honokiol, an active constituent extracted from the bark of Magnolia officinalis, possesses anticancer effects. Apoptosis is classified as type I programmed cell death, while autophagy is type II programmed cell death. We previously proved that honokiol induces cell cycle arrest and apoptosis of U87 MG glioma cells. Subsequently in this study, we evaluated the effect of honokiol on autophagy of glioma cells and examined the molecular mechanisms. Administration of honokiol to mice with an intracranial glioma increased expressions of cleaved caspase 3 and light chain 3 (LC3)-II. Exposure of U87 MG cells to honokiol also induced autophagy in concentration- and time-dependent manners. Results from the addition of 3-methyladenine, an autophagy inhibitor, and rapamycin, an autophagy inducer confirmed that honokiol-induced autophagy contributed to cell death. Honokiol decreased protein levels of PI3K, phosphorylated (p)-Akt, and p-mammalian target of rapamycin (mTOR) in vitro and in vivo. Pretreatment with a p53 inhibitor or transfection with p53 small interfering (si)RNA suppressed honokiol-induced autophagy by reversing downregulation of p-Akt and p-mTOR expressions. In addition, honokiol caused generation of reactive oxygen species (ROS), which was suppressed by the antioxidant, vitamin C. Vitamin C also inhibited honokiol-induced autophagic and apoptotic cell death. Concurrently, honokiol-induced alterations in levels of p-p53, p53, p-Akt, and p-mTOR were attenuated following vitamin C administration. Taken together, our data indicated that honokiol induced ROS-mediated autophagic cell death through regulating the p53/PI3K/Akt/mTOR signaling pathway.

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