Cardioprotective Agent Dexrazoxane Research Articles

Cardioprotective effect of Robinin ameliorates Endoplasmic Reticulum Stress and Apoptosis in H9c2 cells.

Robinin is one of the glycosyloxyflavones that has been less explored for its therapeutic application, especially in the field of CVD. Herein, we explored the cardioprotective efficacy of Robinin by using H2O2 and Doxorubicin (DOX) - treated H9c2 cells as an in vitro model. H2O2 and DOX treatment resulted in severe cellular damage to the cardiomyocytes, which was followed by apoptosis. Apoptosis and nuclear morphology were analysed through Hoechst 33342 and AO/EB staining. qPCR was employed to detect the expression of apoptosis as well as ERS-related markers. Reactive oxygen species (ROS) generation was observed using DCFH-DA staining and FACS analysis. Signaling pathways involved were analysed using Western blot. Robinin pre-treatment considerably decreased the apoptotic rate by boosting the endogenous anti-oxidative activity and lowering the activity of Malonaldehyde and Lactate dehydrogenase enzyme. Robinin also inhibited the generation of ROS. Robinin reduced the expression of ERS-associated genes and proteins, thereby decreasing apoptosis-related proteins. Upon comparing the cardioprotective effect of Robinin with a known cardioprotective agent Dexrazoxane (DEX) it was revealed that DEX has more cardioprotective effect against DOX than H2O2-induced stress, while Robinin showed a significant protective effect against both H2O2 and DOX induced stress.

Substrate oxidation during exercise in childhood acute lymphoblastic leukemia survivors

Children with acute lymphoblastic leukemia (ALL) are at high risk of developing long-term cardiometabolic complications during their survivorship. Maximal fat oxidation (MFO) is a marker during exercise of cardiometabolic health, and is associated with metabolic risk factors. Our aim was to characterize the carbohydrate and fat oxidation during exercise in childhood ALL survivors. Indirect calorimetry was measured in 250 childhood ALL survivors to quantify substrate oxidation rates during a cardiopulmonary exercise test. A best-fit third-order polynomial curve was computed for fat oxidation rate (mg/min) against exercise intensity (O2peak) and was used to determine the MFO and the peak fat oxidation (Fatmax). The crossover point was also identified. Differences between prognostic risk groups were assessed (ie, standard risk [SR], high risk with and without cardio-protective agent dexrazoxane [HR + DEX and HR]). MFO, Fatmax and crossover point were not different between the groups (p = .078; p = .765; p = .726). Fatmax and crossover point were achieved at low exercise intensities. A higher MFO was achieved by men in the SR group (287.8 ± 111.2 mg/min) compared to those in HR + DEX (239.8 ± 97.0 mg/min) and HR groups (229.3 ± 98.9 mg/min) (p = .04). Childhood ALL survivors have low fat oxidation during exercise and oxidize carbohydrates at low exercise intensities, independently of the cumulative doses of doxorubicin they received. These findings alert clinicians on the long-term impact of cancer treatments on childhood ALL survivors’ substrate oxidation.

Primary prevention of chronic anthracycline cardiotoxicity with ACE inhibitor is temporarily effective in rabbits, but benefits wane in post-treatment follow-up.

Angiotensin-converting enzyme inhibitors (ACEis) have been used to treat anthracycline (ANT)-induced cardiac dysfunction, and they appear beneficial for secondary prevention in high-risk patients. However, it remains unclear whether they truly prevent ANT-induced cardiac damage and provide long-lasting cardioprotection. The present study aimed to examine the cardioprotective effects of perindopril on chronic ANT cardiotoxicity in a rabbit model previously validated with the cardioprotective agent dexrazoxane (DEX) with focus on post-treatment follow-up (FU). Chronic cardiotoxicity was induced by daunorubicin (DAU; 3 mg/kg/week for 10 weeks). Perindopril (0.05 mg/kg/day) was administered before and throughout chronic DAU treatment. After the completion of treatment, significant benefits were observed in perindopril co-treated animals, particularly full prevention of DAU-induced mortality and prevention or significant reductions in cardiac dysfunction, plasma cardiac troponin T (cTnT) levels, morphological damage, and most of the myocardial molecular alterations. However, these benefits significantly waned during 3 weeks of drug-free FU, which was not salvageable by administering a higher perindopril dose. In the longer (10-week) FU period, further worsening of left ventricular function and morphological damage occurred together with heart failure (HF)-related mortality. Continued perindopril treatment in the FU period did not reverse this trend but prevented HF-related mortality and reduced the severity of the progression of cardiac damage. These findings contrasted with the robust long-lasting protection observed previously for DEX in the same model. Hence, in the present study, perindopril provided only temporary control of ANT cardiotoxicity development, which may be associated with the lack of effects on ANT-induced and topoisomerase II β (TOP2B)-dependent DNA damage responses in the heart.

Fat And Carbohydrate Oxidation During Cardiopulmonary Exercise Test In Childhood Acute Lymphoblastic Leukemia Survivors

PURPOSE: Analyses of indirect calorimetry during cardiopulmonary exercise tests (CPET) have the potential to bring new evidence about the metabolic health of childhood acute lymphoblastic leukemia (ALL) survivors. To propose a better knowledge of survivors’ metabolic health, we aimed to compare their carbohydrate and fat oxidation during a CPET. Moreover, we explored the long-term effects of doxorubicin and dexrazoxane on survivors’ metabolic health. METHODS: A total of 250 childhood ALL survivors were categorized into three groups depending on their prognostic risk (i.e., standard risk (SR), high risk with and without cardio-protective agent dexrazoxane (HR + DEX and HR)). They underwent a CPET on ergocycle to assess their oxygen consumption and their carbon dioxide production. Carbohydrate and fat oxidation rates were determined using the Peronnet and Massicotte’s equation. For each childhood ALL survivor, we produced a third-degree polynomial equation in order to obtain the best-fit curve for fat and carbohydrate oxidation rate (mg/min) against exercise intensity (%VO2peak). We also used them to compare carbohydrate and fat oxidation over a range of exercise intensities and to determine the maximal fat oxidation (MFO) rate and the peak fat oxidation (Fatmax) rate. MFO and Fatmax comparisons were made using one-way ANOVA. Multiple linear regression analysis was used to quantify each variable’s influence on the MFO and the Fatmax. RESULTS: We observed that MFO parameter was not different between the groups (p = 0.078) (SR = 273.7 ± 99.5 mg·min-1; HR + DEX = 247.3 ± 93.2 mg·min-1; and HR = 239.2 ± 86.0 mg·min-1). There was no difference between the groups for the Fatmax parameter (p = 0.865) (SR = 35.1 ± 7.4%; HR + DEX = 34.6 ± 7.5%; and HR = 35.7 ± 8.1%) and 14% of the variability was explained by the maximum oxygen uptake, sex and obesity. CONCLUSIONS: This study shows that although childhood ALL survivors have a reduced fat oxidation rates, that does not depend on the prognostic risk group. However, we observed a trend that suggests that the reduction of fat oxidation is doxorubicin dose-dependent and that the dexrazoxane treatment has the potential to limit these effects. Our study highlights that survivors’ metabolic health and substrate oxidation are compromised during a maximal cardiopulmonary exercise test.

A QSAR study that compares the ability of bisdioxopiperazine analogs of the doxorubicin cardioprotective agent dexrazoxane (ICRF-187) to protect myocytes with DNA topoisomerase II inhibition

The cardiotoxicity caused by doxorubicin and extravasation injury caused by anthracyclines is reduced by the clinically approved bisdioxopiperazine drug dexrazoxane. Dexrazoxane is a rings-closed analog of EDTA and is hydrolyzed in vivo to a form that strongly binds iron. Its protective effects were originally thought to be due to the ability of its metabolite to remove iron from the iron-doxorubicin complex, thereby preventing oxygen radical damage to cellular components. More recently it has been suggested that dexrazoxane may exert its protective effects by inhibiting topoisomerase IIβ in the heart and inducing a reduction in its protein levels through induction of proteasomal degradation. The ability of dexrazoxane, other bisdioxopiperazines, and mitindomide to protect against doxorubicin-induced damage was determined in primary neonatal rat myocytes. This QSAR study showed that the protection that a series of bisdioxopiperazine analogs of dexrazoxane and the bisimide mitindomide offered against doxorubicin-induced myocyte damage was highly correlated with the ability of these compounds to catalytically inhibit the decatenation activity of topoisomerase II. The structural features of the dexrazoxane analogs that contribute to the binding and inhibition of topoisomerase II have been identified. These results suggest that the inhibition of topoisomerase II in myocytes by dexrazoxane is central to its role in its activity as an anthracycline cardioprotective agent. Additionally, sequence identity analysis of the amino acids surrounding the dexrazoxane binding site showed extremely high identity, not only between both invertebrate topoisomerase II isoforms, but also with yeast topoisomerase II as well.

The Role of Topoisomerase IIβ in the Mechanisms of Action of the Doxorubicin Cardioprotective Agent Dexrazoxane.

Dexrazoxane is clinically used to reduce doxorubicin cardiotoxicity and anthracycline-induced extravasation injury. Dexrazoxane is a strong catalytic inhibitor of topoisomerase II. It can also undergo metabolism to form an iron-binding analog of EDTA. Dexrazoxane was originally thought to act by reducing iron-dependent doxorubicin-based oxidative stress. However, a competing hypothesis posits that dexrazoxane may be protective through its ability to inhibit and reduce topoisomerase IIβ protein levels in the heart. A primary neonatal rat myocyte model was used to study the mechanism by which dexrazoxane protects against doxorubicin-induced myocyte damage. This study characterized the kinetics of the rapid and nearly complete dexrazoxane-induced loss of topoisomerase IIβ protein from neonatal rat cardiac myocytes. Immunofluorescent staining of attached myocytes for topoisomerase IIβ revealed that most of the topoisomerase IIβ was localized to the nucleus, although it was also present in the cytoplasm. Dexrazoxane treatment resulted in an almost complete reduction of topoisomerase IIβ in the nucleus and a lesser reduction in the cytoplasm. The recovery of topoisomerase IIβ levels after a pulse topoisomerase IIβ inhibitory concentration of dexrazoxane occurred slowly, with partial recovery only occurring after 24h. The ability of dexrazoxane to reduce doxorubicin-induced damage to myocytes was greatest when topoisomerase IIβ levels were at their lowest.

Rutin Protects against Pirarubicin‐Induced Cardiotoxicity through TGF‐β1‐p38 MAPK Signaling Pathway

We investigated the potential protective effect of rutinum (RUT) against pirarubicin- (THP-) induced cardiotoxicity. THP was used to induce toxicity in rat H9c2 cardiomyoblasts. Positive control cells were pretreated with a cardioprotective agent dexrazoxane (DZR) prior to treatment with THP. Some of the cells were preincubated with RUT and a p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, both individually and in combination, prior to THP exposure. At a dose range of 30–70 μM, RUT significantly prevented THP-induced reduction in cell viability; the best cardioprotective effect was observed at a dose of 50 μM. Administration of RUT and SB203580, both individually as well as in combination, suppressed the elevation of intracellular ROS, inhibited cell apoptosis, and reversed the THP-induced upregulation of TGF-β1, p-p38 MAPK, cleaved Caspase-9, Caspase-7, and Caspase-3. A synergistic effect was observed on coadministration of RUT and SB203580. RUT protected against THP-induced cardiotoxicity by inhibition of ROS generation and suppression of cell apoptosis. The cardioprotective effect of RUT appears to be associated with the modulation of the TGF-β1-p38 MAPK signaling pathway.

Abstract 3060: Molecular mechanisms of the cardiotoxicity of the proteasomal-targeted anticancer drugs bortezomib and carfilzomib

Abstract Bortezomib and carfilzomib are anticancer drugs that target the proteasomal system. Case reports indicate that the use of these drugs can result in cardiotoxicity. These drugs may also be used in combination with doxorubicin, which is itself cardiotoxic. Thus, in order to determine the mechanism of this cardiotoxicity studies were undertaken using a neonatal rat myocyte primary cell model. Using LDH release as a measure of damage in the myocyte model we showed that even brief exposure (6 h) to submicromolar concentrations of bortezomib resulted in significant myocyte damage. Carfilzomib was slightly less toxic and displayed myocyte damage in the low micromolar concentration range. Utilizing a fluorogenic substrate both bortezomib and carfilzomib inhibited the chymotrypsin-like proteasomal activity of myocyte lysate in the submicromolar concentration range. The inhibition kinetics were consistent with formation of an essentially irreversible covalent complex at the active site. Bortezomib irreversibly inhibited proteasomal activity about four-fold faster than carfilzomib. Thus, the reduced toxicity of carfilzomib may be due to its slower inhibition kinetics. A brief pre-exposure (6 h) of myocytes to low non-toxic nanomolar concentrations of bortezomib greatly increased doxorubicin-mediated damage. The doxorubicin cardioprotective agent dexrazoxane partially protected the myocytes from doxorubicin treatment and from bortezomib plus doxorubicin treatment under these conditions. However, at slightly toxic bortezomib concentrations dexrazoxane offered little protection against bortezomib plus doxorubicin treatment. Bortezomib, at least over short times, did not induce oxidative damage in myocytes as measured with a fluorogenic DCF assay. Likewise, a 6 h bortezomib treatment did not affect the mitochondrial membrane potential of myocytes as measured in a JC-1 ratiometric assay. In conclusion both bortezomib and carfilzomib are potently toxic to myocytes at submicromolar concentrations, likely through their ability to irreversibly inhibit myocyte proteasomal activity. Support: CIHR; a Canada Research Chair in Drug Development. Citation Format: Brian B. Hasinoff, Xing Wu, Daywin Patel. Molecular mechanisms of the cardiotoxicity of the proteasomal-targeted anticancer drugs bortezomib and carfilzomib. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3060.

Molecular Mechanisms of the Cardiotoxicity of the Proteasomal-Targeted Drugs Bortezomib and Carfilzomib.

Bortezomib and carfilzomib are anticancer drugs that target the proteasome. However, these agents have been shown to exhibit some specific cardiac toxicities by as yet unknown mechanisms. Bortezomib and carfilzomib are also being used clinically in combination with doxorubicin, which is also cardiotoxic. A primary neonatal rat myocyte model was used to study these cardiotoxic mechanisms. Exposure to submicromolar concentrations of bortezomib and carfilzomib resulted in significant myocyte damage and induced apoptosis. Both bortezomib and carfilzomib inhibited the chymotrypsin-like proteasomal activity of myocyte lysate in the low nanomolar concentration range and exhibited time-dependent inhibition kinetics. The high sensitivity of myocytes, which were determined to contain high specific levels of chymotrypsin-like proteasomal activity, to the damaging effects of bortezomib and carfilzomib was likely due to the inhibition of proteasomal-dependent ongoing sarcomeric protein turnover. A brief preexposure of myocytes to non-toxic nanomolar concentrations of bortezomib or carfilzomib greatly increased doxorubicin-mediated damage, which suggests that the combination of doxorubicin with either bortezomib or carfilzomib may produce more than additive cardiotoxicity. The doxorubicin cardioprotective agent dexrazoxane partially protected myocytes from doxorubicin plus bortezomib or carfilzomib treatment, in spite of the fact that bortezomib and carfilzomib inhibited the dexrazoxane-induced decreases in topoisomerase IIβ protein levels in myocytes. These latter results suggest that the doxorubicin cardioprotective effects of dexrazoxane and the doxorubicin-mediated cardiotoxicity were not exclusively due to targeting of topoisomerase IIβ.

Abstract 935: Lapatinib and other tyrosine kinase inhibitors greatly potentiate doxorubicin-induced damage to cardiac myocytes

Abstract Lapatinib (Tykerb) is dual tyrosine kinase inhibitor targeting the HER2 (ERBB2) and EGFR (ERBB1, HER1) pathways. Lapatinib has been shown in a clinical trial to produce low levels of cardiotoxicity that is reversible. Using a neonatal rat cardiac myocyte model we have investigated the ability of lapatinib alone, and in combination with doxorubicin, to damage myocytes. Lapatinib alone at pharmacological concentrations only slightly induced myocyte damage. However, doxorubicin-induced myocyte damage was greatly potentiated by the addition of low nanomolar lapatinib concentrations. Because trastuzumab also targets ERBB2 receptors, the lapatinib/doxorubicin combination also provides a good model to probe the mechanism of the increased cardiotoxicity caused by the concurrent use of trastuzumab and doxorubicin. Lapatinib treatment alone had little or no effect on myocyte mitochondrial membrane potential, on oxidation of intracellular DCF (dichlorofluorescein), on intracellular ATP levels, or on caspase 3/7 induction. While the doxorubicin cardioprotective agent dexrazoxane was able to greatly reduce doxorubicin-induced myocyte damage, it could only partially reduce the increase in myocyte damage produced by the lapatinib/doxorubicin treatment. Lapatinib alone had little effect on the phosphorylation status of ACC (acetyl-coenzyme A carboxylase) and AKT. Lapatinib alone decreased phosphorylated ERK (MAPK), which may have, in part, contributed to the increased doxorubicin-mediated myocyte damage. As measured by flow cytometry lapatinib-treated myocytes demonstrated an increased accumulation of doxorubicin. As lapatinib is a strong inhibitor of several ATP-dependent ABC-type efflux transporters, this likely occurred because lapatinib blocked doxorubicin efflux, thereby increasing intracellular doxorubicin concentrations. These results suggest that the clinical use of concurrent doxorubicin and lapatinib should be approached with care due to the possibility of lapatinib increasing doxorubicin cardiotoxicity. Several other kinase inhibitors (imatinib, dasatinib, sorafenib, sunitinib, gefitinib, pazopanib, nilotinib, erlotinib, vandetanib and canertinib) were also examined for their ability to potentiate doxorubicin-induced myocyte damage and induce an increase in intracellular doxorubicin levels. Support: CIHR and a Canada Research Chair in Drug Development to BBH. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 935. doi:1538-7445.AM2012-935

Abstract C211: Dexrazoxane for the targeted prevention of anthracycline-induced cardiotoxicity (ACT) in the age of predictive biomarkers and pharmacogenomics.

Abstract Anthracycline-induced cardiotoxicity (ACT) is a life-threatening adverse drug reaction limiting anthracycline use and causing substantial morbidity and mortality. Clinical risk factors combined with specific biomarkers and predictive genetic risk profiling now offer novel avenues for high-risk patients who may benefit from preventive use of the cardioprotective agent dexrazoxane. The recent identifications of high sensitivity troponin assays and genetic variants associated with ACT (Herman et al; Lipshultz et al; Wojnowski et al.; Visscher et al.) accurately predict ACT before the myocardial damage has been done. In view of the published safety profile of dexrazoxane in long-term pediatric and adult prospective randomized trials (Lipshultz et al 2010/11; Cochrane reviews 2011) anthracycline-induced cardiotoxicity prevention with dexrazoxane should now be initiated with the first dose of doxorubicin or its analogues given rather than after the irreversible myocardial damage has already been done at the widely accepted cumulative dose of doxorubicin. A biomarker driven ‘targeted’ use of dexrazoxane in preselected high risk ACT-prone patients may lead to safer treatment options for the cost-effective anthracycline-containing chemotherapy schedules in children and adult cancer patietns with or without compromised hearts. This new preventive strategy should now be tested in randomised prospective clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C211.

Abstract 3576: Lapatinib in combination with doxorubicin is highly damaging to cardiac myocytes

Abstract Lapatinib (Tykerb) is dual tyrosine kinase inhibitor targeting the HER2 (ERBB2) and EGFR (ERBB1, HER1) pathways. It is used to treat ER+/EGFR+/HER2+ breast cancer patients and patients who have HER2-positive advanced breast cancer that has progressed after previous treatment with other chemotherapeutic agents. Lapatinib, which was initially rated as having no cardiotoxicity, has recently been shown in a clinical trial to produce low levels of cardiotoxicity that is reversible. Using a neonatal rat cardiac myocyte model we have investigated the ability of lapatinib alone and in combination with doxorubicin to damage myocytes. Lapatinib alone at pharmacological concentrations did not significantly cause myocyte damage. However, doxorubicin-induced myocyte damage was greatly increased by the addition of low nanomolar lapatinib concentrations. Previous clinical studies have shown that the combination of trastuzumab (Herceptin) and doxorubicin was highly cardiotoxic. Because trastuzumab also targets HER2 receptors, the lapatinib/doxorubicin combination provides a good model to probe the mechanism of this cardiotoxicity using a rat myocyte model. Lapatinib treatment alone had little or no effect on myocyte mitochondrial membrane potential, on oxidation of intracellular DCF (dichlorofluorescein), on intracellular ATP levels or on caspase 3/7 induction. The doxorubicin cardioprotective agent dexrazoxane was able to greatly reduce doxorubicin-induced myocyte damage. However, dexrazoxane was not able to reduce the increase in myocyte damage produced by adding lapatinib to the doxorubicin treatment. The effect of lapatinib on the change in phosphorylation of ACC (acetyl-coenzyme A carboxylase), which is a measure of a change in cellular energy status, was also determined. Doxorubicin-induced growth inhibitory effects on K562 cells, which contain very low levels of ERBB1/2 protein, were not affected by the addition of lapatinib. This result suggests that inhibition of ERBB1/2 is required for the synergistic toxic effects seen with doxorubicin in myocytes. In conclusion these results suggest that combination therapy employing doxorubicin and lapatinib may produce increased cardiotoxicity. Support: CIHR and a Canada Research Chair in Drug Development to BBH. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3576. doi:10.1158/1538-7445.AM2011-3576

Mechanisms of Myocyte Cytotoxicity Induced by the Multikinase Inhibitor Sorafenib

The use of the anticancer multikinase inhibitor sorafenib is associated with cardiac ischemia or infarction and an increase in hypertension. We investigated various mechanisms that might be responsible for its cardiotoxicity in a neonatal rat myocyte model. As measured by lactate dehydrogenase release, sorafenib treatment of myocytes caused dose-dependent damage at therapeutically relevant concentrations. It had been hypothesized that inhibition of RAF1 and BRAF kinases may be responsible for sorafenib induced cardiotoxicity. However, because sorafenib treatment did not inhibit phosphorylation of ERK (extracellular signal-regulated kinase), it was concluded that sorafenib did not exert its damaging effects through RAF inhibition of the RAF/MEK/ERK kinase cascade. The clinically approved doxorubicin cardioprotective agent dexrazoxane did not protect myocytes from damage. At lower sorafenib concentrations, at least, these results are consistent with sorafenib not being able to induce significant oxidative damage. In conclusion, given the extreme lack of kinase selectivity that sorafenib exhibits, it is likely that inhibition of kinases other than RAF, or combinations of kinases, contributes to the cardiotoxic effects of sorafenib.

Sublethal Doses of an Anti-erbB2 Antibody Leads to Death by Apoptosis in Cardiomyocytes Sensitized by Low Prosenescent Doses of Epirubicin: The Protective Role of Dexrazoxane

The cardiotoxic synergism resulting from the sequential treatment with anthracyclines and trastuzumab has been attributed to the trastuzumab-induced loss of the erbB2-related functions that serve as a salvage pathway against the damaging effects of anthracyclines. Cellular senescence is a novel mechanism of cardiotoxicity induced by subapoptotic doses of anthracyclines. After having identified prosenescent and proapoptotic doses of epirubicin and rat MAb c-erbB2/Her-2/neu Ab-9 clone B10 (B10), an anti-erbB2 monoclonal antibody, we investigated the effects of the sequential treatment with prosenescent doses of both drugs on H9c2 cells and neonatal rat cardiomyocytes pretreated with or without the cardioprotective agent dexrazoxane. Cells were analyzed by senescence-associated beta-galactosidase, single-stranded DNA, annexin/propidium double staining, F-actin, and mitochondrial transmembrane potential. ErbB2 expression levels, AKT activation, and the effects of the inhibition of nicotinamide adenine dinucleotide phosphate oxidase [NAD(P)H oxidase] and phosphoinositide-3-OH kinase (PI3K) were also assessed. Data demonstrate that 1) the toxic effects of epirubicin mainly occur through NAD(P)H oxidase activation; 2) the erbB2 overexpression induced by epirubicin is a redox-sensitive mechanism largely dependent on NAD(P)H oxidase; 3) the loss of erbB2-related functions caused by B10 determines marginal cellular changes in untreated cells, but causes massive death by apoptosis in cells previously exposed to a prosenescent dose of epirubicin, 4) dexrazoxane promotes survival pathways, as demonstrated by the activation of Akt and the PI3K-dependent erbB2 overexpression; and 5) it also prevents epirubicin-induced senescence and renders epirubicin-treated cells more resistant to treatment with B10. Data underline the importance of NAD(P)H oxidase in epirubicin-induced cardiotoxicity and shed new light on the protective mechanisms of dexrazoxane.

The iron chelator Dp44mT does not protect myocytes against doxorubicin

The iron chelating agent Dp44mT (di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone) and the clinically approved cardioprotective agent dexrazoxane (ICRF-187) were compared for their ability to protect neonatal rat cardiac myocytes from doxorubicin-induced damage. Doxorubicin is thought to induce oxidative stress on the heart muscle through iron-mediated oxygen radical damage. While dexrazoxane was able to protect myocytes from doxorubicin-induced lactate dehydrogenase release, in contrast Dp44mT synergistically increased doxorubicin-induced damage. This occurred in spite of the fact that Dp44mT quickly and efficiently removed iron(III) from its complex with doxorubicin and that Dp44mT also rapidly entered myocytes and displaced iron from a fluorescence-quenched trapped intracellular iron-calcein complex. Electron paramagnetic resonance spin trapping was used to show that iron complexes of Dp44mT were not able to generate hydroxyl radicals, suggesting that its cytotoxicity was not due to reactive oxygen species formation. In conclusion Dp44mT is unlikely to be useful as an anthracycline cardioprotective agent.

Use of cardiac markers to assess the toxic effects of anthracyclines given to children with cancer: A systematic review

Aim To evaluate the effectiveness of cardiac markers to quantify anthracycline-induced cardiotoxicity in children with cancer. Methods Systematic review using a priori methods. Results Seven studies, all with methodological limitations, were identified. One RCT suggests that cardiac troponin can be used to assess the effectiveness of the cardio-protective agent dexrazoxane. Cohort studies suggest that atrial natriuretic peptide and brain (B-type) natriuretic peptide are elevated in some subgroups of patients compared with healthy children; NT-pro-BNP levels are significantly elevated in children with cardiac dysfunction compared with those without; serum lipid peroxide is higher in children who have received doxorubicin compared with children not receiving doxorubicin; there are no differences in carnitine levels between children treated with doxorubicin and a healthy control group. Conclusions The limited evidence makes conclusions difficult. Research is needed to fill this important evidence gap and link short-term changes in cardiac markers to longer-term cardiac damage.

Cardioprotection against the toxic effects of anthracyclines given to children with cancer: a systematic review

To evaluate the technologies used to reduce anthracycline-induced cardiotoxicity in children. Also to evaluate cardiac markers to quantify cardiotoxicity, and identify cost-effectiveness studies and future research priorities. Eight electronic databases were searched from inception to January 2006. Bibliographies of related papers were assessed for relevant studies and experts contacted to identify additional published references. A systematic review of the evidence was undertaken using a priori methods. Four randomised controlled trials (RCTs) met the inclusion criteria of the review, each considering a different cardioprotective intervention; all trials included children with acute lymphoblastic leukaemia, and one also included children with non-Hodgkin's lymphoma. However, all had methodological limitations. No cost-effectiveness studies were identified. One RCT and six cohort studies on the use of cardiac markers met the inclusion criteria of the review, but also had methodological limitations. Of the two RCTs that considered continuous infusion versus bolus (rapid) infusion, one found that continuous infusion of doxorubicin did not offer any cardioprotection over bolus; the other suggested that continuous infusion of daunorubicin had less cardiotoxicity than bolus. Two studies considered cardioprotective agents, one concluded that dexrazoxane prevents or reduces cardiac injury without compromising the antileukaemic efficacy of doxorubicin and the other reported a protective effect of coenzyme Q10 on cardiac function during anthracycline therapy. One RCT suggested that cardiac troponin T can be used to assess the effectiveness of the cardioprotective agent dexrazoxane. Two cohort studies considering atrial natriuretic peptide and two considering brain (B-type) natriuretic peptide suggested that these chemicals are elevated in some subgroups of children treated with anthracyclines for cancer. N-terminal B-type natriuretic peptide levels were significantly elevated in children treated with anthracyclines who had cardiac dysfunction. One cohort study found that serum lipid peroxide was higher in younger children treated with doxorubicin than correspondingly aged children not receiving doxorubicin. No differences in carnitine levels were found in children treated with doxorubicin and a group of healthy children in one cohort study. It is difficult to draw conclusions about the effectiveness of technologies for reducing or preventing cardiotoxicity and about the use of cardiac markers in children as the evidence is limited in quantity and quality. The lack of standardisation for monitoring and reporting cardiac performance is problematic. Not all studies report effectiveness in terms of cardiac outcomes and event-free survival with supporting statistical analyses. Studies are mostly small and of short duration, making generalisation difficult. Increasing numbers of survivors of childhood cancer treated with anthracyclines will experience cardiac damage and require long-term surveillance and management. This will have an impact on cardiac services and costs. Diverse medical problems and other late sequelae that affect cardiac outcome will have an impact on other specialist services. Mechanisms to reduce or prevent cardiotoxicity from anthracycline therapy and cardiac markers to improve monitoring could alter the extent of this impact on service provision. RCTs of the different methods for reducing or preventing cardiotoxicity in children treated with anthracyclines for cancer with long-term follow-up are needed to determine whether the technologies influence the development of cardiac damage. Cost-effectiveness research is also required.

Myocardial content of selected elements in experimental anthracycline-induced cardiomyopathy in rabbits

Cardiotoxicity represents the main drawback of clinical usefulness of anthracycline antineoplastic drugs. In this study, a content of selected elements (Ca, Mg, K, Se, Fe) in the post-mortem removed samples of the myocardial tissue was studied in three groups of rabbits: 1) control group (i.v. saline; n = 10); 2) daunorubicin-receiving animals (DAU; 3 mg/kg, i.v; n = 11); 3) animals receiving cardioprotective iron-chelating agent dexrazoxane (DEX; 60 mg/kg, i.p.; n = 5) prior to DAU. Drugs were administered once weekly for 10 weeks. 5-7 days after the last administration, cardiac left ventricular contractility (dP/dtmax) was significantly decreased in DAU-treated animals (745 +/- 69 versus 1245 +/- 86 kPa/s in the control group; P < 0.05), while in the DEX + DAU group it was insignificantly increased (1411 +/- 77 kPa/s). Of the myocardial elements' content studied, a significant increase in total Ca against control (16.2 +/- 2.4 versus 10.6 +/- 0.9 microg/g of dry tissue; P < 0.05) was determined in the DAU-group, which was accompanied with significant decreases in Mg and K. In the heart tissue of DEX-pretreated animals, no significant changes of elements' content were found as compared to controls, while the Ca content was in these animals significantly lower than in the DAU group (9.1 +/- 0.4 versus 16.2 +/- 2.4 microg/g; P < 0.05). Hence, in this study we show that systolic heart failure induced by chronic DAU administration is primarily accompanied by persistent calcium overload of cardiac tissue and the protective action of DEX is associated with the restoration of normal myocardial Ca content.

METABOLISM OF THE CARDIOPROTECTIVE DRUG DEXRAZOXANE AND ONE OF ITS METABOLITES BY ISOLATED RAT MYOCYTES, HEPATOCYTES, AND BLOOD

The metabolism of the antioxidant cardioprotective agent dexrazoxane (ICRF-187) and one of its one-ring open metabolites to its active metal ion binding form N,N'-[(1S)-1-methyl-1,2-ethanediyl-]bis[(N-(2-amino-2-oxoethyl)]glycine (ADR-925) has been investigated in neonatal rat myocyte and adult rat hepatocyte suspensions, and in human and rat blood and plasma with a view to characterizing their hydrolysis-activation. Dexrazoxane is clinically used to reduce the iron-based oxygen free radical-mediated cardiotoxicity of the anticancer drug doxorubicin. Dexrazoxane may act through its hydrolysis product ADR-925 by removing iron from the iron-doxorubicin complex, or binding free iron, thus preventing oxygen radical formation. Our results indicate that dexrazoxane underwent partial uptake and/or hydrolysis by myocytes. A one-ring open metabolite of dexrazoxane underwent nearly complete dihydroorotase-catalyzed metabolism in a myocyte suspension. Hepatocytes that contain both dihydropyrimidinase and dihydroorotase completely hydrolyzed dexrazoxane to ADR-925 and released it into the extracellular medium. Thus, in hepatocytes, the two liver enzymes acted in concert, and sequentially, on dexrazoxane, first to produce the two ring-opened metabolites, and then to produce the metabolite ADR-925. We also showed that the hydrolysis of one of these metabolites was promoted by Ca2+ and Mg2+ in plasma, and thus, further metabolism of these intermediates likely occurs in the plasma after they are released from the liver and kidney. In conclusion, these studies provide a nearly complete description of the metabolism of dexrazoxane by myocytes and hepatocytes to its presumably active form, ADR-925.

The antitumor anthracyclines doxorubicin and daunorubicin do not inhibit cell growth through the formation of iron-mediated reactive oxygen species

The use of the anthracycline anticancer drugs doxorubicin and daunorubicin is limited by what is thought to be an iron-based oxygen radical-derived dose-dependent cardiotoxicity. The anthracyclines are also DNA topoisomerase (Topo) II poisons. It is not known if iron-mediated formation of reactive oxygen species (ROS) by the anthracyclines or their Topo II inhibitory effects are responsible for their cell growth-inhibitory effects. Experiments to test these two alternatives were carried out using a CHO-derived cell line (DZR) that was highly resistant to dexrazoxane through a Thr48IIe mutation in Topo IIalpha. The clinically used cardioprotective agent dexrazoxane likely exerts its cardioprotective effects through the chelating ability of its hydrolysis product ADR-925, an analog of EDTA. Dexrazoxane is also a cell growth inhibitor that acts through its ability to inhibit the catalytic activity of Topo II. Thus, the DZR cell line allowed us to examine the cell growth-inhibitory effects of doxorubicin and daunorubicin in the presence of dexrazoxane without the confounding effect of dexrazoxane inhibiting cell growth. The growth-inhibitory effects of neither doxorubicin nor daunorubicin were affected by pretreating DZR cells with dexrazoxane. In contrast, under similar conditions, dexrazoxane strongly protected rat cardiac myocytes from doxorubicin-induced lactate dehydrogenase release. In conclusion, the anthracyclines do not inhibit the growth of DZR cells through the generation of iron-mediated formation of ROS.