Defective one- or two-electron reduction of the anticancer anthracycline epirubicin in human heart. Relative importance of vesicular sequestration and impaired efficiency of electron addition.
One-electron quinone reduction and two-electron carbonyl reduction convert the anticancer anthracycline doxorubicin to reactive oxygen species (ROS) or a secondary alcohol metabolite that contributes to inducing a severe form of cardiotoxicity. The closely related analogue epirubicin induces less cardiotoxicity, but the determinants of its different behavior have not been elucidated. We developed a translational model of the human heart and characterized whether epirubicin exhibited a defective conversion to ROS and secondary alcohol metabolites. Small myocardial samples from cardiac surgery patients were reconstituted in plasma that contained clinically relevant concentrations of doxorubicin or epirubicin. In this model only doxorubicin formed ROS, as detected by fluorescent probes or aconitase inactivation. Experiments with cell-free systems and confocal laser scanning microscopy studies of H9c2 cardiomyocytes suggested that epirubicin could not form ROS because of its protonation-dependent sequestration in cytoplasmic acidic organelles and the consequent limited localization to mitochondrial one-electron quinone reductases. Accordingly, blocking the protonation-sequestration mechanism with the vacuolar H+-ATPase inhibitor bafilomycin A1 relocalized epirubicin to mitochondria and increased its conversion to ROS in human myocardial samples. Epirubicin also formed approximately 60% less alcohol metabolites than doxorubicin, but this was caused primarily by its higher Km and lower Vmax values for two-electron carbonyl reduction by aldo/keto-reductases of human cardiac cytosol. Thus, vesicular sequestration and impaired efficiency of electron addition have separate roles in determining a defective bioactivation of epirubicin to ROS or secondary alcohol metabolites in the human heart. These results uncover the molecular determinants of the reduced cardiotoxicity of epirubicin and serve mechanism-based guidelines to improving antitumor therapies.
Salvatorelli
Emanuela
E
Center of Excellence on Aging, G. d'Annunzio University School of Medicine, 66013 Chieti, Italy.
Guarnieri
Simone
S
Menna
Pierantonio
P
Liberi
Giovanni
G
Calafiore
Antonio M
AM
Mariggiò
Maria A
MA
Mordente
Alvaro
A
Gianni
Luca
L
Minotti
Giorgio
G
D000154:Aconitate Hydratase / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry; D000368:Aged; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D019540:Area Under Curve; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004583:Electrons; D015251:Epirubicin / Q000737:chemistry / Q000494:pharmacology*; D005260:Female; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D020128:Inhibitory Concentration 50; D007700:Kinetics; D018942:Macrolides / Q000737:chemistry; D008297:Male; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D008956:Models, Chemical; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D014176:Protein Biosynthesis; D011522:Protons; D017382:Reactive Oxygen Species; D013997:Time Factors
D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D005456:Fluorescent Dyes; D018942:Macrolides; D011522:Protons; D017382:Reactive Oxygen Species; D015251:Epirubicin; C040929:bafilomycin A1; D006861:Hydrogen Peroxide; D000251:Adenosine Triphosphatases; D000154:Aconitate Hydratase; D010100:Oxygen