Doxorubicinol (dxol) is the major metabolite formed in the hearts of
cancer patients being treated with the widely used chemotherapeutic agent,
doxorubicin (dox). The well-documented
cardiomyopathy associated with dox treatment has been studied in vitro and ex vivo providing evidence that the C-13 hydroxy metabolite, dxol, might play a key role in the development of dox-induced
cardiotoxicity. In this report, we have developed transgenic mice with heart-specific expression of human
carbonyl reductase (HCBR), an
enzyme that metabolizes dox to dxol. Dox was rapidly converted to dxol in the hearts of the transgenic expressers, which led to advanced development of both acute and chronic
cardiotoxicity. Acute
cardiotoxicity was evident by a 60% increase in serum
creatine kinase activity and a 5-fold increase in cardiac damage measured by electron microscopy. Myofibril degeneration was the major damage observed in acute dox toxicity. Electrocardiograph telemetry, survival data, and electron microscopy were monitored during chronic dox-induced
cardiotoxicity. HCBR expressers developed
cardiotoxicity 6-7 weeks before the nonexpressers. The HCBR expressers survived for 5 weeks compared with 12 weeks for the controls. Electrocardiograph profiles and necropsies showed the cause of death to be the development of
cardiomyopathies leading to
congestive heart failure. Levels of dxol were four times higher in the HCBR expresser hearts than in the nonexpressers. Electron microscopy data showed swelling and major structural damage of the mitochondria in the HCBR expressers. These data demonstrate that the C-13 hydroxy metabolite of dox advances the development of dox-induced
cardiotoxicity in an in vivo system and suggest that heart
carbonyl reductase activity may contribute to dox-induced
cardiotoxicity in humans.