Acute toxicity of doxorubicin on isolated perfused heart: response of kinases regulating energy supply

1 Institute of Cell Biology, Swiss Federal Institute of Technology, 2 Institute of Pharmacology and Toxicology, University of Zürich, and 3 Institute of Anesthesiology, University Hospital of Zürich, Zürich, Switzerland Submitted 14 October 2004 ; accepted in final form 5 March 2005 Doxorubicin (DXR) is a widely used and efficient anticancer drug. However, its application is limited by the risk of severe cardiotoxicity. Impairment of cardiac high-energy phosphate homeostasis is an important manifestation of both acute and chronic DXR cardiotoxic action. Using the Langendorff model of the perfused rat heart, we characterized the acute effects of 1-h perfusion with 2 or 20 µM DXR on two key kinases in cardiac energy metabolism, creatine kinase (CK) and AMP-activated protein kinase (AMPK), and related them to functional responses of the perfused heart and structural integrity of the contractile apparatus as well as drug accumulation in cardiomyocytes. DXR-induced changes in CK were dependent on the isoenzyme, with a shift in protein levels of cytosolic isoenzymes from muscle-type CK to brain-type CK, and a destabilization of octamers of the mitochondrial isoenzyme (sarcometric mitochondiral CK) accompanied by drug accumulation in mitochondria. Interestingly, DXR rapidly reduced the protein level and phosphorylation of AMPK as well as phosphorylation of its target, acetyl-CoA-carboxylase. AMPK was strongly affected already at 2 µM DXR, even before substantial cardiac dysfunction occurred. Impairment of CK isoenzymes was mostly moderate but became significant at 20 µM DXR. Only at 2 µM DXR did upregulation of brain-type CK compensate for inactivation of other isoenzymes. These results suggest that an impairment of kinase systems regulating cellular energy homeostasis is involved in the development of DXR cardiotoxicity. creatine kinase; adenosine 5'-monophosphate-activated protein kinase; anthracyclines; cardiac energetics; cardiotoxicity Address for reprint requests and other correspondence: U. Schlattner, Institute of Cell Biology, Swiss Federal Institute of Technology, Hönggerberg HPM F23, CH-8093 Zürich, Switzerland (E-mail: schlattn{at}cell.biol.ethz.ch )