Doxorubicin disruption of creatine transport in cardiomyocytes is prevented by PP1A/PP2 inhibition

Abstract

Doxorubicin (DOX) is commonly used to treat leukemia, lymphomas, and solid tumors such as soft-tissue sarcomas or breast cancer. A major side effect of DOX's administration is dose-dependent cardiotoxicity. DOX's effects on cardiac energy metabolism are emerging as key elements mediating this toxicity. DOX alters high-energy phosphate metabolism in cardiac myocytes by reducing the activity and shifting creatine kinase isoform distribution, and diminishing the content of phosphocreatine. Cardiomyocytes lack creatine (Cr) biosynthesis capability and rely on a specialized transporter protein (CrT) to supply the cell with Cr. Incubation of rat neonatal cardiac myocytes or HL-1 cells expressing the human CrT with 50– 100 nM DOX, for periods as short as 4 hrs, significantly and irreversibly decreased Cr transport. Kinetic analysis revealed a decrease in Vmax, not mirrored by a change in CrT protein content. Pretreatment with calyculin, a PP1a/PP2 inhibitor, abrogates the DOX induced Cr transport decrease. These DOX concentrations were not cytotoxic to the cells, and are below peak plasma concentrations (as high as 5 μM) and within the steady-state plasma concentrations (25–250 nM) recorded for DOX chemotherapy. Cr transport may represent a site for early therapeutic intervention to preserve Cr and PCr levels in the myocardium and mitigate DOX cardiotoxicity in cancer chemotherapy.