Modern diagnostic strategies for early recognition of cancer therapeutics-related cardiac dysfunction involve cardiac troponins measurement. Still, the role of other markers of cardiotoxicity is still unclear. The present study was designed to investigate dynamics of response of human cardiomyocytes derived from induced pluripotent stem cells (hiPCS-CMs) to doxorubicin with the special emphasis on their morphological changes in relation to expression and organization of troponins. The hiPCS-CMs were treated with doxorubicin concentrations (1 and 0.3 µM) for 48 h and followed for next up to 6 days. Exposure of hiPCS-CMs to 1 µM doxorubicininduced suppression of both cardiac troponin T (cTnT) and cardiac troponin I (cTnI) gene expression. Conversely, lower 0.3 µM doxorubicin concentration produced no significant changes in the expression of aforementioned genes. However, the intracellular topography, arrangement, and abundance of cardiac troponin proteins markedly changed after both doxorubicin concentrations. In particular, at 48 h of treatment, both cTnT and cTnI bundles started to reorganize, with some of them forming compacted shapes extending outwards and protruding outside the cells. At later intervals (72 h and onwards), the whole troponin network collapsed and became highly disorganized following, to some degree, overall changes in the cellular shape. Moreover, membrane permeability of cardiomyocytes was increased, and intracellular mitochondrial network rearranged and hypofunctional. Together, our results demonstrate complex effects of clinically relevant doxorubicin concentrations on hiPCS-CM cells including changes in cTnT and cTnI, but also in other cellular compartments contributing to the overall cytotoxicity of this class of cytostatics.

• Keywords
• cardiotoxicity, doxorubicin, hiPCS-CMs, mitochondria, morphology, troponins,
• MeSH
• Cell Line MeSH
• Doxorubicin pharmacology   toxicity   MeSH
• Induced Pluripotent Stem Cells cytology   drug effects   MeSH
• Myocytes, Cardiac cytology   drug effects   metabolism   MeSH
• Cardiotoxicity MeSH
• Humans MeSH
• Antineoplastic Agents pharmacology   toxicity   MeSH
• Troponin metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Doxorubicin MeSH
• Antineoplastic Agents MeSH
• Troponin MeSH

Catecholamines may undergo iron-promoted oxidation resulting in formation of reactive intermediates (aminochromes) capable of redox cycling and reactive oxygen species (ROS) formation. Both of them induce oxidative stress resulting in cellular damage and death. Iron chelation has been recently shown as a suitable tool of cardioprotection with considerable potential to protect cardiac cells against catecholamine-induced cardiotoxicity. However, prolonged exposure of cells to classical chelators may interfere with physiological iron homeostasis. Prochelators represent a more advanced approach to decrease oxidative injury by forming a chelating agent only under the disease-specific conditions associated with oxidative stress. Novel prochelator (lacking any iron chelating properties) BHAPI [(E)-Ń-(1-(2-((4-(4,4,5,5-tetramethyl-1,2,3-dioxoborolan-2-yl)benzyl)oxy)phenyl)ethylidene) isonicotinohydrazide] is converted by ROS to active chelator HAPI with strong iron binding capacity that efficiently inhibits iron-catalyzed hydroxyl radical generation. Our results confirmed redox activity of oxidation products of catecholamines isoprenaline and epinephrine, that were able to activate BHAPI to HAPI that chelates iron ions inside H9c2 cardiomyoblasts. Both HAPI and BHAPI were able to efficiently protect the cells against intracellular ROS formation, depletion of reduced glutathione and toxicity induced by catecholamines and their oxidation products. Hence, both HAPI and BHAPI have shown considerable potential to protect cardiac cells by both inhibition of deleterious catecholamine oxidation to reactive intermediates and prevention of ROS-mediated cardiotoxicity.

• Keywords
• BHAPI, Cardiotoxicity, Catecholamines, HAPI, Iron chelation, Prochelator,
• MeSH
• Epinephrine antagonists & inhibitors   toxicity   MeSH
• Biocatalysis MeSH
• Cell Line MeSH
• Iron Chelating Agents pharmacology   MeSH
• Glutathione metabolism   MeSH
• Hydroxyl Radical metabolism   MeSH
• Isoproterenol antagonists & inhibitors   toxicity   MeSH
• Cardiotonic Agents pharmacology   MeSH
• Catecholamines antagonists & inhibitors   toxicity   MeSH
• Rats MeSH
• Boronic Acids pharmacology   MeSH
• Humans MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Oxidative Stress drug effects   MeSH
• Prodrugs pharmacology   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Semicarbazones pharmacology   MeSH
• Boron Compounds pharmacology   MeSH
• Iron chemistry   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Epinephrine MeSH
• Iron Chelating Agents MeSH
• Glutathione MeSH
• Hydroxyl Radical MeSH
• Isoproterenol MeSH
• Cardiotonic Agents MeSH
• Catecholamines MeSH
• Boronic Acids MeSH
• N'-(1-(2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyloxy)phenyl)ethylidene)isonicotinohydrazide MeSH Browser
• Prodrugs MeSH
• Reactive Oxygen Species MeSH
• Semicarbazones MeSH
• Boron Compounds MeSH
• Iron MeSH

Anthracyclines (such as doxorubicin or daunorubicin) are among the most effective anticancer drugs, but their usefulness is hampered by the risk of irreversible cardiotoxicity. Dexrazoxane (ICRF-187) is the only clinically approved cardioprotective agent against anthracycline cardiotoxicity. Its activity has traditionally been attributed to the iron-chelating effects of its metabolite with subsequent protection from oxidative stress. However, dexrazoxane is also a catalytic inhibitor of topoisomerase II (TOP2). Therefore, we examined whether dexrazoxane and two other TOP2 catalytic inhibitors, namely sobuzoxane (MST-16) and merbarone, protect cardiomyocytes from anthracycline toxicity and assessed their effects on anthracycline antineoplastic efficacy. Dexrazoxane and two other TOP2 inhibitors protected isolated neonatal rat cardiomyocytes against toxicity induced by both doxorubicin and daunorubicin. However, none of the TOP2 inhibitors significantly protected cardiomyocytes in a model of hydrogen peroxide-induced oxidative injury. In contrast, the catalytic inhibitors did not compromise the antiproliferative effects of the anthracyclines in the HL-60 leukemic cell line; instead, synergistic interactions were mostly observed. Additionally, anthracycline-induced caspase activation was differentially modulated by the TOP2 inhibitors in cardiac and cancer cells. Whereas dexrazoxane was upon hydrolysis able to significantly chelate intracellular labile iron ions, no such effect was noted for either sobuzoxane or merbarone. In conclusion, our data indicate that dexrazoxane may protect cardiomyocytes via its catalytic TOP2 inhibitory activity rather than iron-chelation activity. The differential expression and/or regulation of TOP2 isoforms in cardiac and cancer cells by catalytic inhibitors may be responsible for the selective modulation of anthracycline action observed.

• MeSH
• Anthracyclines pharmacology   MeSH
• Biocatalysis drug effects   MeSH
• Cell Cycle drug effects   MeSH
• Daunorubicin pharmacology   MeSH
• Dexrazoxane pharmacology   MeSH
• DNA Topoisomerases, Type II metabolism   MeSH
• Doxorubicin pharmacology   MeSH
• Glutathione metabolism   MeSH
• Glutathione Disulfide metabolism   MeSH
• HL-60 Cells MeSH
• Topoisomerase II Inhibitors pharmacology   MeSH
• Myocytes, Cardiac cytology   drug effects   metabolism   MeSH
• Caspases metabolism   MeSH
• Rats MeSH
• Cells, Cultured MeSH
• Drug Interactions MeSH
• Humans MeSH
• Animals, Newborn MeSH
• Piperazines pharmacology   MeSH
• Rats, Wistar MeSH
• Cell Proliferation drug effects   MeSH
• Flow Cytometry MeSH
• Thiobarbiturates pharmacology   MeSH
• Cell Survival drug effects   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anthracyclines MeSH
• Daunorubicin MeSH
• Dexrazoxane MeSH
• DNA Topoisomerases, Type II MeSH
• Doxorubicin MeSH
• Glutathione MeSH
• Glutathione Disulfide MeSH
• Topoisomerase II Inhibitors MeSH
• Caspases MeSH
• merbarone MeSH Browser
• Piperazines MeSH
• sobuzoxane MeSH Browser
• Thiobarbiturates MeSH