Peroxidase- and Nitrite-Dependent Metabolism of the Anthracycline Anticancer Agents Daunorubicin and Doxorubicin

Abstract

Oxidation of the anticancer anthracyclines doxorubicin (DXR) and daunorubicin (DNR) by lactoperoxidase(LPO)/H(2)O(2) and horseradish peroxidase(HRP)/H(2)O(2) systems in the presence and absence of nitrite (NO(2)(-)) has been investigated using spectrophotometric and EPR techniques. We report that LPO/H(2)O(2)/NO(2)(-) causes rapid and irreversible loss of anthracyclines' absorption bands, suggesting oxidative degradation of their chromophores. Both the initial rate and the extent of oxidation are dependent on both NO(2)(-) concentration and pH. The initial rate decreases when the pH is changed from 7 to 5, and the reaction virtually stops at pH 5. Oxidation of a model hydroquinone compound, 2,5-di-tert-butylhydroquinone, by LPO/H(2)O(2) is also dependent on NO(2)(-); however, in contrast to DNR and DXR, this oxidation is most efficient at pH 5, indicating that LPO/H(2)O(2)/NO(2)(-) is capable of efficiently oxidizing simple hydroquinones even in the neutral form. Oxidation of anthracyclines by HRP/H(2)O(2)/NO(2)(-) is substantially less efficient relative to that by LPO/H(2)O(2)/NO(2)(-) at either pH 5 or pH 7, most likely due to the lower rate of NO(2)(-) metabolism by HRP/H(2)O(2). EPR measurements show that interaction of anthracyclines and 2,5-di-tert-butylhydroquinone with LPO/H(2)O(2)/NO(2)(-) generates the corresponding semiquinone radicals presumably via one-electron oxidation of their hydroquinone moieties. The possible role of the (*)NO(2) radical, a putative LPO metabolite of NO(2)(-), in oxidation of these compounds is discussed. Because in vivo the anthracyclines may co-localize with peroxidases, H(2)O(2), and NO(2)(-) in tissues, their oxidation via the proposed mechanism is likely. These observations reveal a novel, peroxidase- and nitrite-dependent mechanism for the oxidative transformation of the anticancer anthracyclines, which may be pertinent to their biological activities in vivo.

Doxorubicin inhibits oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by a lactoperoxidase/H2O2 system by reacting with ABTS-derived radical

“…6C (spectrum a) attributed to DOX(QH • ). The signal peak-to-peak line width of 1.83 gauss and g = 2.0058 are close to those reported previously for that radical [5,[9][10][11]. When the concentration of ABTS was increased 2-or 3-fold, the signal from DOX(QH • ) was absent and the signal from ABTS •+ was observed instead.…”

“…5 shows typical spectra observed during oxidation of DOX by LPO/H 2 O 2 /ABTS. These spectral changes are similar to those observed during exposure of anthracyclines to enzymatic or photochemical oxidizing systems [5,7,[9][10][11]26]. The rate of DOX oxidation increased as the concentration of ABTS increased (Fig.…”

“…In the presence of nitrite, acetaminophen or salicylic acid lactoperoxidase (LPO) and myeloperoxidase (MPO) also oxidize the drugs [9][10][11]. It has also been demonstrated that DOX inhibits cardiac lipid conjugated dienes and lipid hydroperoxide formation in blood plasma from the coronary sinus and femoral artery of cancer patients [12].…”

The electrochemistry of quinizarin revealed through its mediated reduction of oxygen

“…1B). Biologically this reaction is known to occur both directly via oxidation through a peroxidase (30) or alternatively indirectly via the oxidized products of the enzymes (31,32). Further it has been proposed that the oxidative degradation pathway of the anthracycline species may provide a possible route by which cardiac protection may be attained (8).…”

The Effect of Spatially Inhomogeneous Electromagnetic Field and Local Inductive Hyperthermia on Nonlinear Dynamics of the Growth for Transplanted Animal Tumors

“…The mechanisms of DOXO-induced cytotoxicity have been extensively studied and have been shown to include free radical formation and absorption of DOXO into the double helix of DNA resulting in topoisomerase II-mediated DNA damage . DOXO also causes depolarization of the membrane lipid bilayer in different cancer cell lines (Reszka et al, 2001). Current forms of DOXO are higly toxic to the patient and can cause systematic comlications, most notably cardiotoxicity.…”