Bz-423 superoxide signals B cell apoptosis via Mcl-1, Bak, and Bax

• Published in: Biochemical pharmacology 2009-10, Vol.78 (8), p.966-973
• Main Authors: Blatt, Neal B., Boitano, Anthony E., Lyssiotis, Costas A., Opipari, Anthony W., Glick, Gary D.
• Format: Article
• Language: English
• Subjects: Apoptosis; Apoptosis - physiology; Avidin - metabolism; B-Lymphocytes - metabolism; Bak; Bax; bcl-2 Homologous Antagonist-Killer Protein - metabolism; bcl-2-Associated X Protein - metabolism; Benzodiazepine; Benzodiazepines - pharmacology; Biological and medical sciences; Biotinylation; Cell Death - drug effects; Cell Line, Tumor; Cell Survival - drug effects; Coloring Agents - metabolism; Electroporation; Fluoresceins - metabolism; Fluorescent Antibody Technique, Indirect; Humans; Mcl-1; Medical sciences; Membrane Potentials - drug effects; Myeloid Cell Leukemia Sequence 1 Protein; Pharmacology. Drug treatments; Propidium - metabolism; Proto-Oncogene Proteins c-bcl-2 - metabolism; RNA, Small Interfering - metabolism; Signal Transduction - drug effects; Superoxide; Superoxides - metabolism
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2009.05.025

Bz-423 is a pro-apoptotic 1,4-benzodiazepine with therapeutic properties in murine models of lupus demonstrating selectivity for autoreactive lymphocytes. Bz-423 modulates the F 1F 0-ATPase, inducing the formation of superoxide within the mitochondrial respiratory chain, which then functions as a second messenger initiating apoptosis. In order to understand some of the features that contribute to the increased sensitivity of lymphocytes, we report the signaling pathway engaged by Bz-423 in a Burkitt lymphoma cell line (Ramos). Following the generation of superoxide, Bz-423-induced apoptosis requires the activation of Bax and Bak to induce mitochondrial outer membrane permeabilization and cytochrome c release. Knockdown of the BH3-only proteins Bad, Bim, Bik, and Puma inhibits Bz-423 apoptosis, suggesting that these proteins serve as upstream sensors of the oxidant stress induced by Bz-423. Treatment with Bz-423 results in superoxide-dependent Mcl-1 degradation, implicating this protein as the link between Bz-423-induced superoxide and Bax and Bak activation. In contrast to fibroblasts, B cell death induced by Bz-423 is independent of c-Jun N-terminal kinase. These results demonstrate that superoxide generated from the mitochondrial respiratory chain as a consequence of a respiratory transition can signal a specific apoptotic response that differs across cell types.