title: 4-HPR-mediated leukemia cell cytotoxicity is triggered by ceramide-induced mitochondrial oxidative stress and is regulated downstream by Bcl-2.
abstract: We have previously reported that, in leukemia cells, the cytotoxicity of the anticancer agent N-(4-hydroxyphenyl)retinamide (4-HPR) is mediated by mitochondria-derived reactive oxygen species (ROS) and cardiolipin peroxidation. Here, we have analyzed at greater depth the 4-HPR-triggered molecular events, demonstrating that 4-HPR induces an early (15 min) increase in ceramide levels by sphingomyelin hydrolysis and later (from 1 h) by de novo synthesis. Using specific inhibitors of both pathways, we demonstrate that ceramide accumulation is responsible for early ROS generation, which act as apoptotic signalling intermediates leading to conformational activation of Bak and Bax, loss of mitochondrial membrane potential (DeltaPsim), mitochondrial membrane permeabilization (MMP) and cell death. Enforced expression of Bcl-2 has no effect on 4-HPR-induced oxidative stress, but notably prevents mitochondrial alterations and apoptosis, indicating that Bcl-2 functions by regulating events downstream of ROS generation. In conclusion, our study delineates for the fist time the sequence and timing of the principal events induced by 4-HPR in leukemia cells and points to the potential use of modulators of ceramide metabolism as enhancers in 4-HPR-based therapies.
authors: Department of Cell Biology and Histology, Faculty of Medicine and Dentistry, University of the Basque Country, Barrio Sarriena s/n, Leioa, Bizkaia, Spain.
authors: Maria-Celia
authors: MC
authors: Morales
authors: Gorka
authors: G
authors: Pérez-Yarza
authors: Naiara N
authors: NN
authors: Rementería
authors: María-Dolores
authors: MD
authors: Boyano
authors: Aintzane
authors: A
authors: Apraiz
authors: Antonio
authors: A
authors: Gómez-Muñoz
authors: Encarna
authors: E
authors: Pérez-Andrés
authors: Aintzane
authors: A
authors: Asumendi
mesh_terms: D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002518:Ceramides / Q000494:pharmacology*; D017313:Fenretinide / Q000494:pharmacology*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007945:Leukemia, Lymphoid / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D019814:Myristic Acid / Q000378:metabolism; D018384:Oxidative Stress; D010710:Phosphates / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D016588:Anticarcinogenic Agents; C494826:BAX protein, human; D002518:Ceramides; D010710:Phosphates; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D013109:Sphingomyelins; D051028:bcl-2-Associated X Protein; D019814:Myristic Acid; D017313:Fenretinide