Promoting Mitochondrial Biogenesis Protects against Doxorubicin-Induced Cardiomyocyte Injury

Although anthracyclines such as doxorubicin (DOX) are highly effective chemotherapeutic agents and widely used for various malignancies, they are known to cause dose-related and life-threatening cardiotoxicity. This well-recognized and unpredictable complication of anthracycline therapy may be either permanent and/or reversible, leading to heart failure in many patients while severely impacting quality of life. The pathophysiology has not been fully elucidated but DOX's activation of cell death pathways and inhibition of mitochondrial biogenesis have been implicated in disease pathogenesis. In recent clinical trials, the β-blocker carvedilol and the angiotensin converting enzyme inhibitor (ACEi) enalapril have been shown to modestly mitigate cardiovascular events, but the mechanisms remain poorly understood. While prior studies have shown either carvedilol or enalapril might promote mitochondrial biogenesis, we reasoned whether such roles might prevent anthracycline-induced mitochondrial dysfunction. To test this hypothesis, we investigated rat myoblastic cells (H9c2 cells) and human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), which were treated either with DOX or pretreated with carvedilol or enalapril followed by DOX. Mitochondrial respiration was examined using Seahorse assay to evaluate mitochondrial function whereas mitochondrial content was determined via qPCR and flow cytometry. Western blotting and qPCR were also performed to evaluate expression of targets involved in mitochondrial dynamics (fission/fusion) and biogenesis. DOX treatment alone resulted in decreased oxygen consumption rates (OCR) when compared with control. In contrast, carvedilol pretreatment prevented DOX-induced suppression of mitochondrial function for both H9c2 cells and human iPSC-CMs. One-way ANOVA analysis indicated a significant improvement in maximal OCR with carvedilol pretreatment compared with DOX-treatment in human iPSC-CMs. We found that DOX treatment expectedly reduced percentage of live cells overall and one-way ANOVA analysis indicated significant increase in mitochondrial densities. The apparent increased mitochondrial densities in the DOX-treated group may have resulted from increased fission as opposed to biogenesis. To evaluate this possible association with mitochondrial biogenesis, western blotting and qPCR were also performed to assess for expression of targets involved in mitochondrial dynamics (fission/fusion). Our ongoing studies are evaluating alternative methods to manipulate mitochondrial content as a therapeutic maneuver. Ongoing studies are seeking to refine the combinatorial roles for regulating mitochondrial dynamics as a major contributor for cardioprotection against anthracycline-induced cardiotoxicity. © FASEB.