Dexrazoxane prevents doxorubicin-induced long-term cardiotoxicity and protects myocardial mitochondria from genetic and functional lesions in rats

Background and purpose: Doxorubicin causes a chronic cardiomyopathy in which reactive oxygen species ( ROS) accumulate over time and are associated with genetic and functional lesions of mitochondria. Dexrazoxane is a cardioprotective iron chelator that interferes with ROS production. We aim to analyze the effects of dexrazoxane on mitochondria in the prevention of doxorubicin-induced chronic myocardial lesions. Experimental approach: Wistar rats ( 11 weeks of age) were injected with intravenous doxorubicin ( 0.8 mg kg(-1) weekly for 7 weeks) with or without simultaneous dexrazoxane ( 8 mg kg-1). Animals were killed at 48 weeks. Cardiomyopathy was scored clinically and histologically and cardiac mitochondria were analyzed. Key results: Compared to control rats receiving saline, rats treated with doxorubicin alone developed a clinical, macroscopic, histological and ultrastructural cardiomyopathy with low cytochrome c-oxidase (COX) activity (26% of controls). The expression of the mtDNA-encoded COX II subunit was reduced (64% of controls). Myocardia exhibited a high production of ROS (malondialdehyde 338% and superoxide 787% of controls). Mitochondria were depleted of mitochondrial DNA (mtDNA copy number 46% of controls) and contained elevated levels of mtDNA deletions. Dexrazoxane co-administration prevented all these effects of doxorubicin on mitochondria, except that hearts co-exposed to doxorubicin and dexrazoxane had a slightly lower mtDNA content (81% of controls) and mtDNA deletions at low frequency. Conclusions and Implications: Dexrazoxane prevented doxorubicin induced late-onset cardiomyopathy and also protected the cardiac mitochondria from acquired ultrastructural, genetic and functional damage.