title: Oxidative degradation of cardiotoxic anticancer anthracyclines to phthalic acids. Novel function or ferrylmyoglobin.
abstract: We show that the pseudoperoxidase activity of ferrylmyoglobin (MbIV) promotes oxidative degradation of doxorubicin (DOX), an anticancer anthracycline known to induce severe cardiotoxicity. MbIV, formed in vitro by reacting horse heart MbIII with H2O2, caused disappearance of the spectrum of DOX at 477 nm and appearance of UV-absorbing chromophores that indicated opening and degradation of its tetracyclic ring. Electron spray ionization mass spectrometry analyses of DOX/MbIV ultrafiltrates showed that DOX degradation resulted in formation of 3-methoxyphthalic acid, the product of oxidative modifications of its methoxy-substituted ring D. Other methoxy-substituted anthracyclines similarly released 3-methoxyphthalic acid after oxidation by MbIV, whereas demethoxy analogs released simple phthalic acid. Kinetic and stoichiometric analyses of reactions between DOX and MbIII/H2O2 or hemin/H2O2 showed that the porphyrin radical of MbIV-compound I and the iron-oxo moiety of MbIV-compound II were sequentially involved in oxidizing DOX; however, oxidation by compound I formed more 3-methoxyphthalic acid than oxidation by compound II. Sizeable amounts of 3-methoxyphthalic acid were formed in the heart of mice treated with DOX, in human myocardial biopsies exposed to DOX in vitro, and in human cardiac cytosol that oxidized DOX after activation of its endogenous myoglobin by H2O2. Importantly, H9c2 cardiomyocytes were damaged by low concentrations of DOX but could tolerate concentrations of 3-methoxyphthalic acid higher than those measured in murine or human myocardium. These results unravel a novel function for MbIV in the oxidative degradation of anthracyclines to phthalic acids and suggest that this may serve a salvage pathway against cardiotoxicity.
authors.affiliation: Department of Chemistry, Menarini Ricerche, 00040 Pomezia, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Cartoni
authors.forename: Pierantonio
authors.initials: P
authors.lastname: Menna
authors.forename: Emanuela
authors.initials: E
authors.lastname: Salvatorelli
authors.forename: Daniela
authors.initials: D
authors.lastname: Braghiroli
authors.forename: Rossella
authors.initials: R
authors.lastname: Giampietro
authors.forename: Fabio
authors.initials: F
authors.lastname: Animati
authors.forename: Andrea
authors.initials: A
authors.lastname: Urbani
authors.forename: Piero
authors.initials: P
authors.lastname: Del Boccio
authors.forename: Giorgio
authors.initials: G
authors.lastname: Minotti
mesh_terms: D000818:Animals; D018943:Anthracyclines / Q000737:chemistry*; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004317:Doxorubicin / Q000737:chemistry / Q000378:metabolism; D006736:Horses; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D008297:Male; D008786:Metmyoglobin / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D008956:Models, Chemical; D009206:Myocardium / Q000378:metabolism; D009211:Myoglobin / Q000737:chemistry / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D010795:Phthalic Acids / Q000737:chemistry* / Q000494:pharmacology; D011166:Porphyrins / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: C483040:3-methoxyphthalic acid; D018943:Anthracyclines; D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D009211:Myoglobin; D010795:Phthalic Acids; D011166:Porphyrins; C028048:ferrylmyoglobin; D008786:Metmyoglobin; D004317:Doxorubicin; D006861:Hydrogen Peroxide; D007501:Iron; D010100:Oxygen