Journal Article

Critical role of oxidative stress and sustained JNK activation in aloe-emodin-mediated apoptotic cell death in human hepatoma cells

Guo Dong Lu, Han-Ming Shen, Maxey C.M. Chung and Choon Nam Ong

in Carcinogenesis

Volume 28, issue 9, pages 1937-1945
Published in print September 2007 | ISSN: 0143-3334
Published online August 2007 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgm143
Critical role of oxidative stress and sustained JNK activation in aloe-emodin-mediated apoptotic cell death in human hepatoma cells

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Aloe-emodin (AE), one of the main bioactive anthraquinones of Rheum palmatum, possesses potent antitumor properties. Our previous proteomic study revealed that AE-induced apoptosis was associated with oxidative stress and oxidation of many redox-sensitive proteins. In this study, we aimed to further dissect the cell death-signaling pathways in AE-induced apoptosis. AE was found to cause redox imbalance and deplete the intracellular-reduced glutathione (GSH). Manipulation of the intracellular GSH with buthionine-L-sulfoximine (a GSH synthesis inhibitor) sensitized, and with glutathione monomethyl ester (a GSH donor) protected the AE-induced apoptosis, respectively. More importantly, AE treatment led to evident and sustained activation of c-Jun N-terminal kinase (JNK), an important stress-responsive mitogen-activated protein kinase (MAPK). Over-expression of antioxidant gene sod1 significantly reduced AE-induced JNK activation and cell death, suggesting that oxidative stress-mediated JNK is the effector molecule in AE-induced apoptosis. Such a notion was clearly supported by subsequent studies in which JNK activation was inhibited by JNK inhibitor, JNK small interfering RNA knockdown or over-expression of dominant-negative JNK. In addition, we provided evidence demonstrating the critical role of apoptosis signal-regulating kinase 1, a well-established MAPK kinase kinase, in AE-induced JNK activation and apoptotic cell death. Finally, we showed that dissociation of inactive JNK–Glutathione S-transferase pi (GST-pi) complex was also involved in JNK activation through GST-pi oxidation. Taken together, these results suggest that AE-induced apoptotic cell death is mediated via oxidative stress and sustained JNK activation.

Journal Article.  5500 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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