title: Pharmacologic inhibitors of extracellular signal-regulated kinase (ERKs) and c-Jun NH(2)-terminal kinase (JNK) decrease glutathione content and sensitize human promonocytic leukemia cells to arsenic trioxide-induced apoptosis.
abstract: Treatment with 1-4 microM As(2)O(3) slightly induced apoptosis in U-937 human promonocitic leukemia cells. This effect was potentiated by co-treatment with MEK/ERK (PD98059, U0126) and JNK (SP600125, AS601245) inhibitors, but not with p38 (SB203580, SB220025) inhibitors. However, no potentiation was obtained using lonidamine, doxorubicin, or cisplatin instead of As(2)O(3). Apoptosis potentiation by mitogen-activated protein kinase (MAPK) inhibitors involved both the intrinsic and extrinsic executionary pathways, as demonstrated by Bax activation and cytochrome c release from mitochondria, and by caspase-8 activation and Bid cleavage, respectively; and the activation of both pathways was prevented by Bcl-2 over-expression. Treatment with MEK/ERK and JNK inhibitors, but not with p38 inhibitors, caused intracellular glutathione (GSH) depletion, which was differentially regulated. Thus, while it was prevented by N-acetyl-L-cysteine (NAC) in the case of U0126, it behaved as a NAC-insensitive process, regulated at the level of DL-buthionine-(S,R)-sulfoximine (BSO)-sensitive enzyme activity, in the case of SP600125. The MEK/ERK inhibitor also potentiated apoptosis and decreased GSH content in As(2)O(3)-treated NB4 human acute promyelocytic leukemia (APL) cells, but none of these effects were produced by the JNK inhibitor. MEK/ERK and JNK inhibitors did not apparently affect As(2)O(3) transport activity, as measured by intracellular arsenic accumulation. SP600126 greatly induced reactive oxygen species (ROS) accumulation, while BSO and U0126 had little or null effects. These results, which indicate that glutathione is a target of MAP kinases in myeloid leukemia cells, might be exploited to improve the antitumor properties of As(2)O(3), and provide a rationale for the use of kinase inhibitors as therapeutic agents.
authors.affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040-Madrid, Spain.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Ramos
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernandez
authors.forename: Donna
authors.initials: D
authors.lastname: Amrán
authors.forename: Diego
authors.initials: D
authors.lastname: Esteban
authors.forename: Elena
authors.initials: E
authors.lastname: de Blas
authors.forename: María A
authors.initials: MA
authors.lastname: Palacios
authors.forename: Patricio
authors.initials: P
authors.lastname: Aller
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007938:Leukemia; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism*; D010087:Oxides / Q000494:pharmacology*; D010545:Peroxides / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D004791:Enzyme Inhibitors; D010087:Oxides; D010545:Peroxides; D017382:Reactive Oxygen Species; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D005978:Glutathione; D000077237:Arsenic Trioxide