The Metabolites of the Cardioprotective Drug Dexrazoxane Do Not Protect Myocytes from Doxorubicin-Induced Cytotoxicity

Abstract

The clinically approved cardioprotective agent dexrazoxane (ICRF-187) and two of its hydrolyzed metabolites (a one-ring open form of dexrazoxane and ADR-925) were examined for their ability to protect neonatal rat cardiac myocytes from doxorubicin-induced damage. Dexrazoxane may protect against doxorubicin-induced damage to myocytes through its strongly metal-chelating hydrolysis product ADR-925, which could act by displacing iron bound to doxorubicin or chelating free or loosely bound iron, thus preventing site-specific iron-based oxygen radical damage. The results of this study showed that whereas dexrazoxane was able to protect myocytes from doxorubicin-induced lactate dehydrogenase release, neither of the metabolites displayed any protective ability. Dexrazoxane also reduced apoptosis in doxorubicin-treated myocytes. The ability of dexrazoxane and its three metabolites to displace iron from a fluorescence-quenched trapped intracellular iron-calcein complex was also determined to see whether the metabolites were taken up by myocytes. Although ADR-925 was taken up in the absence of calcium in the medium, in the presence of calcium, its uptake was greatly slowed, presumably because it formed a complex with calcium. Both of the one-ring open metabolites were taken up by myocytes and displaced iron from its complex with calcein. These results suggest either that the anionic metabolites do not have the same access to iron pools in critical cellular compartments, that their uptake is slowed in the presence of calcium, or, less likely, that dexrazoxane protects by some other mechanism.Dexrazoxane (ICRF-187; Zinecard; Fig. 1) is clinically used to reduce doxorubicin-induced cardiotoxicity (Hasinoff, 1998;Hasinoff et al., 1998). There is now considerable evidence to indicate that this toxicity may be due to iron-dependent oxygen free radical formation (Meyers, 1998) on the relatively unprotected cardiac muscle. Dexrazoxane likely acts by diffusing into the cell and hydrolyzing (Hasinoff, 1994a(Hasinoff, ,b, 1998Hasinoff et al., 1998) to its ring-opened metal ionbinding form, ADR-925 (Fig. 1), which has a structure similar to that of EDTA. ADR-925 may then either remove iron from the iron-doxorubicin complex (Buss and Hasinoff, 1993) (Huang et al., 1982;Diop et al., 2000). Thus, dexrazoxane, which is easily permeable to cells (Dawson, 1975), can be considered a neutral prodrug analog of EDTA.We previously showed in isolated hepatocytes (Hasinoff et al., 1994), in a rat model , and in humans (Schroeder et al., 2003) that dexrazoxane was rapidly metabolized to the one-ring open compounds B and C, and ADR-925 (Fig. 1). This metabolism may be due, in part, to the ability of dihydropyrimidinase, which is present in the liver and kidney, but not the heart, to enzymatically hydrolyze dexrazoxane to B and C, but not to ADR-925 (Hasinoff et al., 1998). We also recently showed that dihydroorotase, which is present in all three of these organs, enzymatically hydrolyzes B and C to ADR-925 but does not act on dexrazoxane...

The Dihydroorotase Inhibitor 5-Aminoorotic Acid Inhibits the Metabolism in the Rat of the Cardioprotective Drug Dexrazoxane and Its One-Ring Open Metabolites

“…However, the fact that ADR-925 is found in the heart (which does not contain DHPase) (Hamajima et al, 1996) either when treated with dexrazoxane or the B/C mixture suggests that B and C formed in the liver are taken up by the heart and metabolized there. In support of this conclusion we showed that isolated neonatal rat myocytes were able to take up B, C, and ADR-925 and displace iron from an intracellular fluorescence-quenched iron-calcein complex (Hasinoff et al, 2003b).…”

Deferiprone protects the isolated atria from cardiotoxicity induced by doxorubicin

“…Neither deferoxamine nor its complex with Fe 3+ could scavenge superoxide radicals or reveal cytoprotective activity [11] . ICL670A was found to not protect cardiac myocytes against DOX [7] . The antioxidant property of deferiprone would be in part due to its direct superoxide radical scavenging [11] and iron-chelating activity [5] .…”

“…This DOX-Fe 3+ complex can reduce oxygen to hydroxyl radical and other reactive oxygen species (ROS) [5] , which initiate severe damage to cardiac tissues. Efforts have been made to prevent the DOX cardiotoxicity with a number of antioxidants and iron chelators such as melatonin [6] and ICL670A (deferasirox) [7] . So far there is only one agent, dexrazoxane (Zinecard), approved by the Food and Drug Administration (FDA) to prevent cardiomyopathy induced by DOX.…”

A Mouse Model for Studying the Interaction of Bisdioxopiperazines with Topoisomerase IIα in Vivo

“…ICRF-187 is approved with the indication of reducing anthracycline-induced cardiomyopathy [dexrazoxane (Cardioxane, Zinecard)]. It is believed that the iron chelating activity of its ring-opened hydrolysis product, ADR-925, is responsible for its cardioprotective effect through the removal of iron from its highly toxic complexes with anthracyclines (Hasinoff et al, 2003b), in turn protecting the cardiac myocytes against mitochondrial damage caused by redox-cycling of the anthracycline-iron complex (Hasinoff et al, 2003a). However, an effect through topoisomerase II inhibition has never been excluded.…”