title: Arsenic trioxide-induced apoptosis is independent of stress-responsive signaling pathways but sensitive to inhibition of inducible nitric oxide synthase in HepG2 cells.
abstract: Arsenic trioxide (As(2)O(3)) has been found to be remarkably effective in the treatment of patients with acute promyelocytic leukemia (APL). Although evidences for the proapoptotic activity of As(2)O(3) have been suggested in leukemic and other solid cancer cells, the nature of intracellular mechanisms is far from clear. In the present study, we investigated As(2)O(3) affect on the stress-responsive signaling pathways and pretreatment with antioxidants using HepG2 cells. When treated with micromolar concentrations of As(2)O(3), HepG2 cells became highly apoptotic paralleled with activation of caspase-3 and members of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase (ERK) and c-jun NH(2)-terminal kinase (JNK) but not p38 MAP kinase. However, inhibition of each kinase activity failed to inhibit apoptosis by As(2)O(3). Addition of n-acetyl cysteine (NAC) or diphenyleneiodonium (DPI) effectively protected cells from apoptosis and significantly lowered As(2)O(3)-induced activation of caspase-3. However, neither NAC nor DPI was able to effect ERK or JNK activation induced by As(2)O(3). Guanidinoethyldisulfide dihydrochloride (GED) and 2-ethyl-2-thiopseudourea (ETU), known inhibitors of the inducible nitric oxide synthase (iNOS), also suppressed the apoptotic activity of As(2)O(3). These results suggest that As2O3 induces caspase-mediated apoptosis involving a mechanism generating oxidative stress. However, activation of some stress-responsive signaling pathways by As(2)O(3) may not be the major determinant in the course of apoptotic processes.
authors.affiliation: Department of Medicine, College of Medicine and Cheju National University, Ara-1, Jeju 690-756, Korea.
authors.forename: Shin-Hae
authors.initials: SH
authors.lastname: Kang
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Song
authors.forename: Hee-Kyoung
authors.initials: HK
authors.lastname: Kang
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Kang
authors.forename: Se-Jae
authors.initials: SJ
authors.lastname: Kim
authors.forename: Hyun-Wook
authors.initials: HW
authors.lastname: Kang
authors.forename: Young-Ki
authors.initials: YK
authors.lastname: Lee
authors.forename: Deok-Bae
authors.initials: DB
authors.lastname: Park
mesh_terms: D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D018384:Oxidative Stress / Q000187:drug effects; D010087:Oxides / Q000008:administration & dosage / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000975:Antioxidants; D001152:Arsenicals; D004791:Enzyme Inhibitors; D010087:Oxides; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D000077237:Arsenic Trioxide