Amiodarone induces cytochrome c release and apoptosis through an iodine-independent mechanism.
Amiodarone (AMD) is one of the most effective antiarrhythmic drugs available. However, its use is often limited by side-effects, mainly hypo- or hyperthyroidism. As AMD displays direct toxic effect on different cell types, we investigated the cytotoxic effect of AMD and its main metabolite, desethylamiodarone (DEA), in thyroid (TAD-2) and nonthyroid (HeLa) cell lines. Both AMD and DEA displayed a dose-dependent toxicity in TAD-2 and HeLa cells, although DEA was more effective. Both TAD-2 and HeLa cells underwent apoptosis, as evidenced by plasma membrane phosphatidylserine exposure and DNA fragmentation. Inhibition of protein synthesis with cycloheximide and inhibition of endogenous peroxidase activity with propylthiouracil did not affect this AMD- and DEA-induced apoptosis in TAD-2 cells. Western blot analysis did not display variations in the expression of p53, Bcl-2, Bcl-XL, and Bax proteins during the treatment with AMD and DEA. Generation of reactive oxygen species, investigated by flow cytometry with dichlorofluorescein diacetate, did not show the production of free radicals during drug treatment. Furthermore, Western blot analysis of cytosolic and mitochondrial fractions prepared from AMD-treated cells demonstrated that AMD induces the release of cytochrome c into the cytosol from the mitochondria. These data indicate that AMD induces cytochrome c release from mitochondria, triggering apoptosis through an iodine-independent mechanism, and that this process is not mediated by modulation of p53, Bcl-2, Bcl-XL, or Bax protein expression and does not involve the generation of free radicals.
Di Matola
T
T
Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università Federico II, Naples, Italy.
D'Ascoli
F
F
Fenzi
G
G
Rossi
G
G
Martino
E
E
Bogazzi
F
F
Vitale
M
M
D000638:Amiodarone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D017304:Annexin A5 / Q000032:analysis; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors; D007700:Kinetics; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D011441:Propylthiouracil / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D013961:Thyroid Gland / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D017304:Annexin A5; D000889:Anti-Arrhythmia Agents; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D003574:Cytochrome c Group; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D011441:Propylthiouracil; D003513:Cycloheximide; D007453:Iodide Peroxidase; C036116:desethylamiodarone; D000638:Amiodarone