title: Arsenic trioxide-induced apoptosis in U937 cells involve generation of reactive oxygen species and inhibition of Akt.
abstract: Arsenic trioxide has recently been shown to inhibit growth and induce apoptosis in acute promyelocytic leukemia (APL), but little is known about the molecular mechanisms mediating these effects. In the present study, we determined the molecular pathways that lead to apoptosis after treatment of cells with arsenic trioxide. Arsenic trioxide treatment of U937 cells leads to apoptosis, which is accompanied by activation of caspase 3 (as measured by decreased levels of the 32 kDa inactive form and increased proteolytic cleavage of PLC-gamma1). The broad-range caspase inhibitor z-VAD-fmk inhibits this induction of apoptosis, supporting a direct link between caspase activation and arsenic trioxide induction of apoptosis. This activation of apoptosis is accompanied by release of cytochrome c, down-regulation of cIAP1, and inactivation of Akt. Bcl-2 overexpression attenuates arsenic trioxide-induced apoptosis in U937 cells by inhibition of caspase 3 activity, but not inhibition of Akt. In addition, arsenic trioxide-induced apoptosis was caused by the generation of reactive oxygen species, which was prevented by antioxidant NAC (N-acetyl-cysteine). Co-treatment with NAC markedly prevented dephosphorylation of Akt, activation of caspase 3, and down-regulation of cIAP1. These data indicate that arsenic trioxide can cause cell damage by inactivating the Akt-related cell survival pathway and generating the reactive oxygen species, providing a new mechanism for arsenic trioxide-induced apoptosis.
authors.affiliation: Department of Immunology, School of Medicine, Keimyung University, 194 Dong San-Dong Jung-Gu, Taegu 700-712, South Korea.
authors.forename: Yun-Jung
authors.initials: YJ
authors.lastname: Choi
authors.forename: Jong-Wook
authors.initials: JW
authors.lastname: Park
authors.forename: Seong-Il
authors.initials: SI
authors.lastname: Suh
authors.forename: Kyo Cheol
authors.initials: KC
authors.lastname: Mun
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Bae
authors.forename: Dae-Kyu
authors.initials: DK
authors.lastname: Song
authors.forename: Sang-Pyo
authors.initials: SP
authors.lastname: Kim
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D010087:Oxides / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020298:U937 Cells
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D001152:Arsenicals; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D010087:Oxides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000077237:Arsenic Trioxide; D000111:Acetylcysteine