title: Mitochondrial membrane permeabilization and superoxide production during apoptosis. A single-cell analysis.
abstract: The temporal relationship between mitochondrial membrane permeabilization and reactive oxygen species production during apoptosis remains unknown. We analyzed the rate of superoxide production of human breast carcinoma cells expressing a cytochrome c-green fluorescent protein (cyt-c-GFP) fusion protein at the single-cell level during apoptosis. In cells treated with the proapoptotic agents staurosporine (3 microm) or tumor necrosis factor-alpha (100 ng/ml), the release of cyt-c-GFP was individually set for each cell, and the majority of the fusion protein was released in less than 10 min. Prior to the release of the fusion protein, cells demonstrated a constant rate of superoxide production determined with the probe hydroethidine. After the release was completed, the superoxide concentration increased rapidly to a level more than 3-fold above baseline. Treatment with the broad spectrum caspase inhibitor z-Val-Ala-Asp(O-methyl)-fluoromethylketone (z-VAD-fmk; 200 microm) did not alter the kinetics of the cyt-c-GFP release but significantly reduced superoxide concentration after the release of cyt-c-GFP. Interestingly, treatment with z-VAD-fmk also reduced the increase in superoxide concentration in response to menadione in the absence of mitochondrial cyt-c-GFP release. Mitochondrial depolarization with the protonophore carbonyl cyanide p-trifluoromethoxy-phenylhydrazone per se did not trigger cyt-c-GFP release or an increase in superoxide production. Our data suggest that mitochondria increase their superoxide production during apoptosis directly after the quantitative release of soluble intermembrane proteins and demonstrate novel antioxidative effects of the commonly used caspase inhibitor z-VAD-fmk.
authors.affiliation: Interdisciplinary Center for Clinical Research (IZKF), Westphalian Wilhelms-University, D-48149 Münster, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Düssmann
authors.forename: Donat
authors.initials: D
authors.lastname: Kögel
authors.forename: Markus
authors.initials: M
authors.lastname: Rehm
authors.forename: Jochen H M
authors.initials: JH
authors.lastname: Prehn
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001943:Breast Neoplasms; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D010539:Permeability; D010617:Phenanthridines / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013367:Submitochondrial Particles / Q000187:drug effects / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D024483:Vitamin K 3 / Q000494:pharmacology
chemical_list: D008164:Luminescent Proteins; D010617:Phenanthridines; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D049452:Green Fluorescent Proteins; C058428:hydroethidine; D024483:Vitamin K 3; D003513:Cycloheximide