title: Amplification loop cascade for increasing caspase activity induced by docetaxel.
abstract: The hierarchy of events accompanying induction of apoptosis by the microtubule inhibitor docetaxel was investigated in HL-60 human leukemia cells. Treatment of HL-60 cells with docetaxel resulted in the production of reactive oxygen species (ROS), activation of caspase-3 (-like) protease, c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activation, bcl-2 phosphorylation and apoptosis. Docetaxel elicited ROS production from NADPH oxidase as demonstrated by specific oxidase inhibitor diphenylene iodonium (DPI). ROS mediated the caspase-3 activation and apoptosis in HL-60 cells. The caspase inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) effectively inhibited JNK/SAPK activation, bcl-2 phosphorylation and partially attenuated the ROS production induced by docetaxel. Docetaxel-induced bcl-2 phosphorylation was completely blocked by expression of dominant negative JNK or the JNK/SAPK inhibitor SP600125. Overexpression of bcl-2 partially prevented docetaxel-mediated ROS production and subsequent caspase-3 activation, thereby inhibiting apoptotic cell death. It is thus conferred that such sequent events as ROS production, caspase activation, JNK/SAPK activation, bcl-2 phosphorylation and the further generation of ROS should be parts of an amplification loop to increase caspase activity, thereby facilitating the apoptotic cell death process.
authors.affiliation: Department of Pharmaceutical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, Peoples' Republic of China.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Cao
authors.forename: Bin
authors.initials: B
authors.lastname: Qiao
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Ge
authors.forename: Yingjin
authors.initials: Y
authors.lastname: Yuan
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol; D000077143:Docetaxel; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008954:Models, Biological; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D043823:Taxoids / Q000494:pharmacology*; D014162:Transfection
chemical_list: D061945:Caspase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D043823:Taxoids; D000077143:Docetaxel; D048031:JNK Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases