Dexrazoxane. A review of its use as a cardioprotective agent in patients receiving anthracycline-based chemotherapy

Evolution of Theories on Doxorubicin-Induced Late Cardiotoxicity-Role of Topoisomerase

Doxorubicin (DOX) has been widely used as a cytotoxic chemotherapeutic. However, DOX has a number of side effects, such as myelotoxicity or gonadotoxicity, the most dangerous of which is cardiotoxicity. Cardiotoxicity can manifest as cardiac arrhythmias, myocarditis, and pericarditis; life-threatening late cardiotoxicity can result in heart failure months or years after the completion of chemotherapy. The development of late cardiomyopathy is not yet fully understood. The most important question is how DOX reprograms the cardiomyocyte, after which DOX is excreted from the body, initially without symptoms. However, clinically overt cardiomyopathy develops over the following months and years. Since the 1980s, DOX-induced disorders in cardiomyocytes have been thought to be related to oxidative stress and dependent on the Fe/reactive oxygen species (ROS) mechanism. That line of evidence was supported by dexrazoxane (DEX) protection, the only Food and Drug Administration (FDA)-approved drug for preventing DOX-induced cardiomyopathy, which complexes iron. Thus, the hypothesis related to Fe/ROS provides a plausible explanation for the induction of the development of late cardiomyopathy via DOX. However, in subsequent studies, DEX was used to identify another important mechanism in DOX-induced cardiomyopathy that is related to topoisomerase 2β (Top2β). Does the Top2β hypothesis explain the mechanisms of the development of DOX-dependent late heart failure? Several of these mechanisms have been identified to date, proving the involvement of Top2β in the regulation of the redox balance, including oxidative stress. Thus, the development of late cardiomyopathy can be explained based on mechanisms related to Top2β. In this review, we highlight free radical theory, iron imbalance, calcium overload, and finally, a theory based on Top2β.

Alkaloidal Extracts from Avicennia africana P. Beauv. (Avicenniaceae) Leaf: An Antiplasmodial, Antioxidant, and Erythrocyte Viable

Background

The emergence of drug-resistant parasites impedes disease management and eradication efforts. Hence, a reinvigorated attempt to search for potent lead compounds in the mangroves is imperative.

Aim

This study evaluates in vitro antiplasmodial activity, antioxidant properties, and cytotoxicity of A. africana leaf alkaloidal extracts.

Methods

The A. africana leaves were macerated with 70% ethanol to obtain a total crude extract. Dichloromethane and chloroform-isopropanol (3 : 1, v/v) were used to extract the crude alkaloids and quaternary alkaloids from the total crude. The antiplasmodial activities of the alkaloidal extracts were performed against 3D7 P. falciparum chloroquine-sensitive clone via the SYBR Green I fluorescence assay with artesunate serving as the reference drug. The alkaloidal extracts were further evaluated for antioxidant properties via the total antioxidant capacity (TAC), the total glutathione concentration (GSH), the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, and the ferric-reducing antioxidant power (FRAP) methods. The cytotoxic activity of the alkaloidal extracts was tested on erythrocytes using a 3-(4,5-dimethylthiazol-2-yl)-5-diphenyltetrazolium bromide-MTT assay with little modification. The phytocompounds in the alkaloidal extracts were identified via gas chromatography-mass spectrometry (GC-MS) techniques.

Results

The total crude extract showed good antiplasmodial activity (IC50 = 11.890 µg/mL). The crude and quaternary alkaloidal extracts demonstrated promising antiplasmodial effects with IC50 values of 6.217 and 6.285 µg/mL, respectively. The total crude and alkaloidal extracts showed good antioxidant properties with negligible cytotoxicity on erythrocytes with good selectivity indices. The GC-MS spectral analysis of crude alkaloidal extracts gave indole and isoquinoline alkaloids and several other compounds. Dexrazoxane was found to be the main compound predicted, with an 86% peak area in the quaternary alkaloidal extract.

Conclusion

The crude and quaternary alkaloidal extracts exhibited antiplasmodial activities and ability to inhibit oxidative stress with negligible toxicity on erythrocytes. This may be good characteristics to avoid oxidative stress related to Plasmodium infection in the treatment of malaria.

Breast Cancer and the Cardiovascular Disease: A Narrative Review

Breast cancer is the most common malignancy affecting females worldwide and is also among the top causes of all cancer-related deaths. Cardiovascular disease (CVD) is known to have the highest rate of mortality in women. There are several risk factors for both CVD and breast cancer that overlap, such as diet, smoking, and obesity, and also the current breast cancer treatment has a significant detrimental effect on cardiovascular health in general. Patients with exposure to potentially cardiotoxic treatments, including anthracyclines, trastuzumab, and radiation therapy, are more likely to develop CVD than non-cancer controls. Early detection and treatment may reduce the risk of the development of cardiac morbidity and mortality and would increase the number of breast cancer survivors. This article provides a comprehensive overview of breast cancer, identifies shared risk factors among breast cancer and CVD, and the cardiotoxic effects of therapy. It also reviews possible prevention and treatment of CVD in breast cancer patients and reviews literature about chemoprevention of cardiac disease in the setting of breast cancer treatment.

Dimethyl Fumarate Ameliorates Doxorubicin-Induced Cardiotoxicity By Activating the Nrf2 Pathway

Doxorubicin (DOX) is limited in clinical application because of its cardiotoxicity. Oxidative stress and apoptosis are crucial in DOX-induced cardiac injury. Dimethyl fumarate (DMF) is an FDA-approved oral drug with powerful effects to reduce oxidative stress and apoptosis through the Nrf2 pathway. This study was aimed to determine whether DMF can protect against DOX-induced cardiac injury. We used both neonatal rat cardiomyocytes (NRCMs) in vitro and DOX-induced cardiac toxicity in vivo to explore the effects of DMF. The results showed that DMF significantly improved cell viability and morphology in NRCMs. In addition, DMF alleviated DOX-induced cardiac injury in rats, as evidenced by decreased CK-MB, LDH levels, improved survival rates, cardiac function, and pathological changes. Moreover, DMF significantly inhibited cardiac oxidative stress by reducing MDA levels and increasing GSH, SOD, and GSH-px levels. And DMF also inhibited DOX-induced cardiac apoptosis by modulating Bax, Bcl-2 and cleaved caspase-3 expression. Moreover, DMF exerted its protective effects against DOX by promoting Nrf2 nuclear translocation, which activated its downstream antioxidant gene Hmox1. Silencing of Nrf2 attenuated the protective effects of DMF in NRCMs as manifested by increased intracellular oxidative stress, elevated apoptosis levels, and decreased cell viability. In addition, DMF showed no protective effects on the viability of DOX-treated tumor cells, which suggested that DMF does not interfere with the antitumor effect of DOX in vitro. In conclusion, our data confirmed that DMF alleviated DOX-induced cardiotoxicity by regulating oxidative stress and apoptosis through the Nrf2 pathway. DMF may serve as a new candidate to alleviate DOX-related cardiotoxicity in the future.

Proteomic Network Analysis of Bronchoalveolar Lavage Fluid in Ex-Smokers to Discover Implicated Protein Targets and Novel Drug Treatments for Chronic Obstructive Pulmonary Disease

Bronchoalveolar lavage of the epithelial lining fluid (BALF) can sample the profound changes in the airway lumen milieu prevalent in chronic obstructive pulmonary disease (COPD). We compared the BALF proteome of ex-smokers with moderate COPD who are not in exacerbation status to non-smoking healthy control subjects and applied proteome-scale translational bioinformatics approaches to identify potential therapeutic protein targets and drugs that modulate these proteins for the treatment of COPD. Proteomic profiles of BALF were obtained from (1) never-smoker control subjects with normal lung function (n = 10) or (2) individuals with stable moderate (GOLD stage 2, FEV1 50−80% predicted, FEV1/FVC < 0.70) COPD who were ex-smokers for at least 1 year (n = 10). After identifying potential crucial hub proteins, drug−proteome interaction signatures were ranked by the computational analysis of novel drug opportunities (CANDO) platform for multiscale therapeutic discovery to identify potentially repurposable drugs. Subsequently, a literature-based knowledge graph was utilized to rank combinations of drugs that most likely ameliorate inflammatory processes. Proteomic network analysis demonstrated that 233 of the >1800 proteins identified in the BALF were significantly differentially expressed in COPD versus control. Functional annotation of the differentially expressed proteins was used to detail canonical pathways containing the differential expressed proteins. Topological network analysis demonstrated that four putative proteins act as central node proteins in COPD. The drugs with the most similar interaction signatures to approved COPD drugs were extracted with the CANDO platform. The drugs identified using CANDO were subsequently analyzed using a knowledge-based technique to determine an optimal two-drug combination that had the most appropriate effect on the central node proteins. Network analysis of the BALF proteome identified critical targets that have critical roles in modulating COPD pathogenesis, for which we identified several drugs that could be repurposed to treat COPD using a multiscale shotgun drug discovery approach.

Cardiac Toxicity From Adjuvant Targeting Treatment for Breast Cancer Post-Surgery

Breast cancer is one of the most prevalent types of cancers worldwide, especially for females. Surgery is the preferred treatment for breast cancer, and various postoperative adjuvant therapies can be reasonably used according to different pathological characteristics, especially traditional radiotherapy, chemotherapy, and endocrine therapy. In recent years, targeting agent therapy has also become one of the selective breast cancer treatment strategies, including anti-HER-2 drugs, CDK4/6 inhibitor, poly ADP-ribose polymerase inhibitor, PI3K/AKT/mTOR pathway inhibitor, ER targeting drugs, and aromatase inhibitor. Because of the different pathologic mechanisms of these adjuvant therapies, each of the strategies may cause cardiotoxicity in clinic. The cardiac adverse events of traditional endocrine therapy, radiotherapy, and chemotherapy for breast cancer have been widely detected in clinic; however, the targeting therapy agents have been paid more attention with the extension of application. This review will summarize the cardiac toxicity of various adjuvant therapies for breast cancer, especially for targeting drug therapy.

Dexrazoxane Alleviated Doxorubicin-Induced Nephropathy in Rats

INTRODUCTION

Doxorubicin (DOX), an anthracycline antitumor agent, has been widely used against various solid tumors and hematological malignancies. However, the clinical application of DOX is restricted by its multiple organ toxicity including nephrotoxicity. This study investigated the protective effects and mechanisms of dexrazoxane (DZR) against DOX-induced nephropathy in rats.

METHODS

Male Sprague Dawley rats received 2.5 mg/kg DOX once a week for 5 consecutive weeks. 24-h urinary protein and renal function injury biomarkers were determined to evaluate the renal function. Histopathological changes and glomerulosclerosis were examined by hematoxylin and eosin and periodic acid-Schiff staining. The change of renal ultrastructure in the DOX-induced rats was observed by the electron microscopy. The renal apoptosis was detected by TUNEL staining and measured the protein expression of Caspase-3, Bcl-2, and Bax. Renal interstitial fibrosis was determined by Masson staining and immunohistochemistry examination. The levels of vimentin, alpha-smooth muscle actin (α-SMA), and transforming growth factor β (TGF-β) in kidney tissue were detected by Western blot.

RESULTS

DZR pretreatment markedly raised the survival rate and improved the renal dysfunction in DOX-treated rats. DZR ameliorated DOX-induced histopathological lesion of glomerular and tubular and apoptosis. DZR restored the oxidant/antioxidant balance via regulating the levels of MDA, SOD, and TAC. DZR reduced DOX-induced collagen IV deposition and renal interstitial fibrosis and downregulated the fibrosis-related protein expressions of vimentin, α-SMA, and TGF-β1.

CONCLUSION

Our results suggest DZR exerted its protective effects against DOX-induced nephropathy through inhibition of lipid peroxidation, apoptosis, and fibrosis.

Pediatric Chemotherapy Drugs Associated With Cardiotoxicity

Pediatric cancers are a common cause of childhood morbidity. As a result, chemotherapeutic regimens have been designed to target childhood cancers. These medications are necessary to treat pediatric cancers, however, oncology management options are accompanied by multiple negative and potentially fatal adverse effects. Although anthracyclines are the most commonly used chemotherapeutic agents associated with cardiotoxicity, we also explore other chemotherapeutic drugs used in children that can potentially affect the heart. Genetic variations resulting in single nucleotide polymorphism (SNP) have the propensity to modify the cardiotoxic effects of the chemotherapy drugs. The clinical presentation of the cardiac effects can vary from arrhythmias and heart failure to completely asymptomatic. A range of imaging studies and laboratory investigations can protect the heart from severe outcomes. The physiology of the heart and the effect of drugs in children vary vividly from adults; therefore, it is crucial to study the cardiotoxic effect of chemotherapy drugs in the pediatric population. This review highlights the potential contributing factors for cardiotoxicity in the pediatric population and discusses the identification and management options.

Interim Analysis of the Phase II Study: Noninferiority Study of Doxorubicin with Upfront Dexrazoxane plus Olaratumab for Advanced or Metastatic Soft-Tissue Sarcoma

PURPOSE

To report the interim analysis of the phase II single-arm noninferiority trial, testing the upfront use of dexrazoxane with doxorubicin on progression-free survival (PFS) and cardiac function in soft-tissue sarcoma (STS).

PATIENTS AND METHODS

Patients with metastatic or unresectable STS who were candidates for first-line treatment with doxorubicin were deemed eligible. An interim analysis was initiated after 33 of 65 patients were enrolled. Using the historical control of 4.6 months PFS for doxorubicin in the front-line setting, we tested whether the addition of dexrazoxane affected the efficacy of doxorubicin in STS. The study was powered so that a decrease of PFS to 3.7 months would be considered noninferior. Secondary aims included cardiac-related mortality, incidence of heart failure/cardiomyopathy, and expansion of cardiac monitoring parameters including three-dimensional echocardiography. Patients were allowed to continue on doxorubicin beyond 600 mg/m2 if they were deriving benefit and were not demonstrating evidence of symptomatic cardiac dysfunction.

RESULTS

At interim analysis, upfront use of dexrazoxane with doxorubicin demonstrated a PFS of 8.4 months (95% confidence interval: 5.1-11.2 months). Only 3 patients were removed from study for cardiotoxicity, all on > 600 mg/m2 doxorubicin. No patients required cardiac hospitalization or had new, persistent cardiac dysfunction with left ventricular ejection fraction remaining below 50%. The median administered doxorubicin dose was 450 mg/m2 (interquartile range, 300-750 mg/m2).

CONCLUSIONS

At interim analysis, dexrazoxane did not reduce PFS in patients with STS treated with doxorubicin. Involvement of cardio-oncologists is beneficial for the monitoring and safe use of high-dose anthracyclines in STS.See related commentary by Benjamin and Minotti, p. 3809.

R-COMP versus R-CHOP as first-line therapy for diffuse large B-cell lymphoma in patients ≥60 years: Results of a randomized phase 2 study from the Spanish GELTAMO group

The use of non-pegylated liposomal doxorubicin (Myocet^® ) in diffuse large B-cell lymphoma (DLBCL) has been investigated in retrospective and single-arm prospective studies. This was a prospective phase 2 trial of DLBCL patients ≥60 years old with left ventricular ejection fraction (LVEF) ≥55% randomized to standard R-CHOP or investigational R-COMP (with Myocet^® instead of conventional doxorubicin). The primary end point was to evaluate the differences in subclinical cardiotoxicity, defined as decrease in LVEF to <55% at the end of treatment. Secondary objectives were efficacy, safety, and variations of troponin and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and LVEF along follow-up. Ninety patients were included, 45 in each group. No differences were observed in the percentage of patients with LVEF <55% at end of treatment (11% in R-CHOP arm vs. 7% in R-COMP arm, p = 0.697) or at 4 months (10% vs. 6%, respectively, p = 0.667) and 12 months (8% vs. 7%, respectively, p = 1). However, a higher percentage of R-CHOP compared with R-COMP patients showed increased troponin levels in cycle 6 (100% vs. 63%, p = 0.001) and at 1 month after treatment (88% vs. 56%, respectively, p = 0.015). Cardiovascular adverse events were seen in five R-CHOP patients (nine episodes, four grade ≥3) and in four R-COMP patients (five episodes, all grade 1-2). No significant differences in efficacy were observed. In conclusion, R-COMP is a feasible immunochemotherapy schedule for DLBCL patients ≥60 years, with similar efficacy to R-CHOP. However, the use of non-pegylated doxorubicin instead of conventional doxorubicin was not associated with less early cardiotoxicity, although some reduced cardiac safety signals were observed. Trial registration: ClinicalTrials.gov Identifier: NCT02012088.

Troponins in Experimental Studies

The aim of our study was to compare the diagnostic performance of cardiac troponin T (cTnT) and cardiac troponin I (cTnI) in three groups of rabbits: 1) control (saline 1 ml/kg i.v.); 2) daunorubicin (3 mg/kg i.v.); 3) daunorubicin (3 mg/kg i.v.) + dexrazoxane (60 mg/kg i.p.). The drugs were given once a week, 10 administrations. The concentration of cTnT was measured using Elecsys Troponin T STAT Immunoassay (Roche). The concentration of cTnI was measured using AxSYM Troponin I (Abbott). The linear regression model was applied to see if there is a dependence between cTnT and cTnI. The coefficient of determination (R2 = 0.79) was acceptable only in the control group. In the remaining cases (i.e. in the daunorubicin group and in the daunorubicin + dexrazoxane treated group) R2 was too small (0.53, and 0.06). We may conclude that in rabbits after repeated administration of cardiotoxic or cardioprotective drugs meaningful dependence between cTnT and cTnI was not found. The choice of the most suitable cardiomarker in laboratory animals deserves further studies.

Multitissue analysis of exercise and metformin on doxorubicin-induced iron dysregulation

Doxorubicin (DOX) is an effective chemotherapeutic treatment with lasting side effects in heart and skeletal muscle. DOX is known to bind with iron, contributing to oxidative damage resulting in cardiac and skeletal muscle toxicity. However, major cellular changes to iron regulation in response to DOX are poorly understood in liver, heart, and skeletal muscle. Additionally, two cotreatments, exercise (EX) and metformin (MET), were studied for their effectiveness in reducing DOX toxicity by ameliorating iron dysregulation and preventing oxidative stress. The purposes of this study were to 1) characterize the DOX-induced changes of the major iron regulation pathway in liver, heart, and skeletal muscle and 2) to determine whether EX and MET exert their benefits by minimizing DOX-induced iron dysregulation. Mice were assigned to receive saline or DOX (15 mg/kg) treatments, paired with either EX (5 days) or MET (500 mg/kg), and were euthanized 3 days after DOX treatment. Results suggest that the cellular response to DOX is protective against oxidative stress by reducing iron availability. DOX increased iron storage capacity through elevated ferritin levels in liver, heart, and skeletal muscle. DOX reduced iron transport capacity through reduced transferrin receptor levels in heart and skeletal muscle. EX and MET cotreatments had protective effects in the liver through reduced transferrin receptor levels. At 3 days after DOX, oxidative stress was mild, as shown by normal glutathione and lipid peroxidation levels. Together these results suggest that the cellular response to reduce iron availability in response to DOX treatment is sufficient to match oxidative stress.

Pharmacokinetics of the Cardioprotective Drug Dexrazoxane and Its Active Metabolite ADR-925 with Focus on Cardiomyocytes and the Heart

Dexrazoxane (DEX), the only cardioprotectant approved against anthracycline cardiotoxicity, has been traditionally deemed to be a prodrug of the iron-chelating metabolite ADR-925. However, pharmacokinetic profile of both agents, particularly with respect to the cells and tissues essential for its action (cardiomyocytes/myocardium), remains poorly understood. The aim of this study is to characterize the conversion and disposition of DEX to ADR-925 in vitro (primary cardiomyocytes) and in vivo (rabbits) under conditions where DEX is clearly cardioprotective against anthracycline cardiotoxicity. Our results show that DEX is hydrolyzed to ADR-925 in cell media independently of the presence of cardiomyocytes or their lysate. Furthermore, ADR-925 directly penetrates into the cells with contribution of active transport, and detectable concentrations occur earlier than after DEX incubation. In rabbits, ADR-925 was detected rapidly in plasma after DEX administration to form sustained concentrations thereafter. ADR-925 was not markedly retained in the myocardium, and its relative exposure was 5.7-fold lower than for DEX. Unlike liver tissue, myocardium homogenates did not accelerate the conversion of DEX to ADR-925 in vitro, suggesting that myocardial concentrations in vivo may originate from its distribution from the central compartment. The pharmacokinetic parameters for both DEX and ADR-925 were determined by both noncompartmental analyses and population pharmacokinetics (including joint parent-metabolite model). Importantly, all determined parameters were closer to human than to rodent data. The present results open venues for the direct assessment of the cardioprotective effects of ADR-925 in vitro and in vivo to establish whether DEX is a drug or prodrug.

Extracellular Vesicles Released by Cardiomyocytes in a Doxorubicin-Induced Cardiac Injury Mouse Model Contain Protein Biomarkers of Early Cardiac Injury

Purpose: Cardiac injury is a major cause of death in cancer survivors, and biomarkers for it are detectable only after tissue injury has occurred. Extracellular vesicles (EV) remove toxic biomolecules from tissues and can be detected in the blood. Here, we evaluate the potential of using circulating EVs as early diagnostic markers for long-term cardiac injury.Experimental Design: Using a mouse model of doxorubicin (DOX)-induced cardiac injury, we quantified serum EVs, analyzed proteomes, measured oxidized protein levels in serum EVs released after DOX treatment, and investigated the alteration of EV content.Results: Treatment with DOX caused a significant increase in circulating EVs (DOX_EV) compared with saline-treated controls. DOX_EVs exhibited a higher level of 4-hydroxynonenal adducted proteins, a lipid peroxidation product linked to DOX-induced cardiotoxicity. Proteomic profiling of DOX_EVs revealed the distinctive presence of brain/heart, muscle, and liver isoforms of glycogen phosphorylase (GP), and their origins were verified to be heart, skeletal muscle, and liver, respectively. The presence of brain/heart GP (PYGB) in DOX_EVs correlated with a reduction of PYGB in heart, but not brain tissues. Manganese superoxide dismutase (MnSOD) overexpression, as well as pretreatment with cardioprotective agents and MnSOD mimetics, resulted in a reduction of EV-associated PYGB in mice treated with DOX. Kinetic studies indicated that EVs containing PYGB were released prior to the rise of cardiac troponin in the blood after DOX treatment, suggesting that PYGB is an early indicator of cardiac injury.Conclusions: EVs containing PYGB are an early and sensitive biomarker of cardiac injury. Clin Cancer Res; 24(7); 1644-53. ©2017 AACRSee related commentary by Zhu and Gius, p. 1516.

The regulatory mechanisms of myogenin expression in doxorubicin-treated rat cardiomyocytes

Doxorubicin, an anthracycline antibiotic, has been used as an anti-neoplastic drug for almost 60 years. However, the mechanism(s) by which anthracyclines cause irreversible myocardial injury remains unclear. In order to delineate possible molecular signals involved in the myocardial toxicity, we assessed candidate genes using mRNA expression profiling in the doxorubicin-treated rat cardiomyocyte H9c2 cell line. In the study, it was confirmed that myogenin, an important transcriptional factor for muscle terminal differentiation, was significantly reduced by doxorubicin in a dose-dependent manner using both RT-PCR and western blot analyses. Also, it was identified that the doxorubicin-reduced myogenin gene level could not be rescued by most cardio-protectants. Furthermore, it was demonstrated how the signaling of the decreased myogenin expression by doxorubicin was altered at the transcriptional, post-transcriptional and translational levels. Based on these findings, a working model was proposed for relieving doxorubicin-associated myocardial toxicity by down-regulating miR-328 expression and increasing voltage-gated calcium channel β1 expression, which is a repressor of myogenin gene regulation. In summary, this study provides several lines of evidence indicating that myogenin is the target for doxorubicin-induced cardio-toxicity and a novel therapeutic strategy for doxorubicin clinical applications based on the regulatory mechanisms of myogenin expression.

All-trans retinoic acid protects against doxorubicin-induced cardiotoxicity by activating the ERK2 signalling pathway

BACKGROUND AND PURPOSE

Doxorubicin is a powerful antineoplastic agent for treating a wide range of cancers. However, doxorubicin cardiotoxicity of the heart has largely limited its clinical use. All-trans retinoic acid (ATRA) plays an important role in many cardiac biological processes, but its protective effects on doxorubicin-induced cardiotoxicity remain unknown. Here, we studied the effect of ATRA on doxorubicin cardiotoxicity and the underlying mechanisms.

EXPERIMENTAL APPROACHES

Cellular viability assays, Western blotting and mitochondrial respiration analyses were employed to evaluate the cellular response to ATRA in H9c2 cells and primary cardiomyocytes. Quantitative PCR and gene knockdown were performed to investigate the underlying molecular mechanisms of ATRA's effects on doxorubicin cardiotoxicity.

KEY RESULTS

ATRA significantly inhibited doxorubicin-induced apoptosis in H9c2 cells and primary cardiomyocytes. ATRA was more effective against doxorubicin cardiotoxicity than resveratrol and dexrazoxane. ATRA also suppressed reactive oxygen species generation and restored expression levels of mRNA and proteins in the phase II detoxifying enzyme system: nuclear factor-E2-related factor 2, manganese superoxide dismutase, haem oxygenase-1, and mitochondrial function (mitochondrial membrane integrity, mitochondrial DNA copy numbers and mitochondrial respiration capacity, biogenesis and dynamics). Both a ERK1/2 inhibitor (U0126) and ERK2 siRNA, but not ERK1 siRNA, abolished the protective effect of ATRA against doxorubicin-induced toxicity in H9c2 cells. Remarkably, ATRA did not compromise the anticancer efficacy of doxorubicin in gastric carcinoma cells.

CONCLUSIONS AND IMPLICATIONS

ATRA protected cardiomyocytes against doxorubicin-induced toxicity, by activating the ERK2 pathway, without compromising its anticancer efficacy. Therefore, ATRA is a promising candidate as a cardioprotective agent against doxorubicin cardiotoxicity.

Cardiac protective effects of dexrazoxane on animal cardiotoxicity model induced by anthracycline combined with trastuzumab is associated with upregulation of calpain-2

Cardiotoxicity is a well-recognized side effect induced by chemotherapeutic drugs such as anthracycline and trastuzumab through different mechanisms. Currently, accumulating evidence supports that dexrazoxane (DZR) can minimize the risk of cardiotoxicity. In this study, we investigated whether dexrzoxane could reduce cardiotoxicity in the treatment of anthracycline combined with trastuzumab. We randomly divided 90 experimental F344 rats into control group, chemotherapeutics and trastuzumab (doxorubicin [DOX] + herceptin [Her]) group, and chemotherapeutics, trastuzumab, and DZR (DOX + Her + DZR) group. Animal status and body weight, cardiac function, serum cardiac markers, cardiomyocyte apoptosis of the rats, and expression level of calpain-2 were evaluated. Left ventricular ejection fraction (LVEF) and fractional shortening (FS) of the left ventricle were observed. The serum levels of malondialdehyde (MDA) and cardiac troponin I (cTnI) and cardiomyocyte apoptosis were detected by enzyme linked immunosorbent assay and TdT-mediated dUTP nick end labeling assays. The mRNA and protein level of calpain-2 were measured by reverse transcriptase polymerase chain reaction and Western blot. We observed that the LVEF and FS of the left ventricle were significantly higher in the DOX + Her + DZR group than that in the DOX + Her group (P < 0.05). The serum levels of MDA and cTnI between DOX + Her group and DOX + Her + DZR group were significantly different. In addition, cardiomyocyte apoptosis in the DOX + Her + DZR group was significantly less severe than that in the DOX + Her group (P < 0.05). After DZR treatment, the calpain-2 mRNA and protein levels in the DOX + Her + DZR group were significantly higher than the DOX + Her group (P < 0.05). Our results suggest that DZR can effectively reduce the cardiotoxicity of combinatorial treatment of trastuzumab and anthracycline partly through upregulating calpain-2.

Activity of dexrazoxane and amifostine against late cardiotoxicity induced by the combination of doxorubicin and cyclophosphamide in vivo

Cardiotoxicity is one of the main limiting side effects of doxorubicin and cyclophosphamide (DC) treatment, and this study was organized to identify cardioprotective activity of amifostine and dexrazoxane against DC combination. BalbC/NIH mice underwent DC treatment (DC group), were pre-treated with amifostine (ADC group) or dexrazoxane (IDC group) and were killed at 1.5 and 3 months after treatments when the grade of myocardial damage was analysed by light microscopy using the Billingham scoring method. DC treatment induced severe myocardial damage with one lethal event before evaluation at 3 months. Main characteristics of DC cardiotoxicity were polymorphic myocyte degeneration and alterations in blood vessels followed by ecchymoses, haemorrhage and thromboses. Polymorphism was also found in the IDC and ADC groups, but its morphological patterns were different. In animals subject to IDC treatment, the blood vessels were better preserved than in the ADC group, whereas thrombosis was not seen in either of these two groups. Quantitatively, grade of myocardial injury in the ADC and IDC groups was significantly higher compared with the non-treated group at both times of estimation and significantly lower compared with the DC group at 1.5 months. At 3 months, significance against DC treatment was lost in the ADC group, while preserved in the IDC-treated animals. Also, there was significant progression in the ADC group comparing scores between 1.5 and 3 months. These results revealed that the cardiotoxicity of DC combination displays specific morphological hallmark and evolution in time, different to those described after doxorubicin single treatment. Neither amifostine nor dexrazoxane prevented development of cardiomyopathy induced by DC treatment.

Physical and chemical stability of reconstituted and diluted dexrazoxane infusion solutions

BACKGROUND AND PURPOSE

Dexrazoxane is used clinically to prevent anthracycline-associated cardiotoxicity. Hydrolysis of dexrazoxane prior to reaching the cardiac membranes severely hampers its mode of action; therefore, degradation during the preparation and administration of intravenous dexrazoxane admixtures demands special attention. Moreover, the ongoing national shortage of one dexrazoxane formulation in the United States has forced pharmacies to dispense other commercially available dexrazoxane products. However, the manufacturers' limited stability data restrict the flexibility of dexrazoxane usage in clinical practice. The aims of this study are to determine the physical and chemical stability of reconstituted and diluted solutions of two commercially available dexrazoxane formulations.

METHODS

The stability of two dexrazoxane products, brand and generic name, in reconstituted and intravenous solutions stored at room temperature without light protection in polyvinyl chloride bags was determined. The concentrations of dexrazoxane were measured at predetermined time points up to 24 h using a validated reversed phase high-performance liquid chromatography with ultraviolet detection assay.

RESULTS

Brand (B-) and generic (G-) dexrazoxane products, reconstituted in either sterile water or 0.167 M sodium lactate (final concentration of 10 mg/mL), were found stable for at least to 8 h. Infusion solutions of B-dexrazoxane, prepared according to each manufacturer's directions, were stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. Infusion solutions of G-dexrazoxane, prepared in either 5% dextrose or 0.9% sodium chloride following the manufacturer's guidelines, were also stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. All tested solutions were found physically stable up to 24 h at room temperature.

CONCLUSION

The stability of dexrazoxane infusion solutions reported herein permits advance preparation of dexrazoxane intravenous admixtures, facilitating pharmacy workflow and clinical operations. However, due to the potential risks of fluid overload when these intravenous solutions are administered to patients, caution is advised to ensure patient safety.

Cardioprotective effect of early dexrazoxane use in anthracycline treated pediatric patients

Anthracyclines play a major role in chemotherapeutic regimens for a variety of pediatric cancers, but produce undesirable dose-related cardiotoxicity. Dexrazoxane reduces early myocardial injury during anthracycline treatment, but data remain insufficient to fully understand its cardioprotective effectiveness in treating pediatric cancers and additional research is necessary to find efficient methods of dexrazoxane administration. Therefore, we retrospectively evaluated the cardioprotective effect of dexrazoxane against anthracyclines in 258 pediatric cancer patients who had received any anthracyclines from January 1997 to May 2005 at a tertiary teaching hospital in Korea. The results of this study suggest that the early use of dexrazoxane protects against the development of cardiotoxicity during anthracycline treatment in pediatric cancer patients. Further studies involving larger pediatric cancer patients are needed to evaluate the cardioprotective effect of dexrazoxane at higher cumulative doses of anthracyclines and on late-onset cardiotoxicity in long-term survivors.

Involvement of ferritin heavy chain in the preventive effect of metformin against doxorubicin-induced cardiotoxicity

Doxorubicin is a wide-spectrum chemotherapeutic agent, although a cumulative dose may cause cardiac damage and lead to heart failure. Doxorubicin cardiotoxicity is dependent on the intracellular iron pool and manifests itself by increasing oxidative stress. Our group has recently shown the ability of metformin, an oral antidiabetic with cardiovascular benefits, to protect cardiomyocytes from doxorubicin-induced damage. This work aimed to study whether metformin is able to modulate the expression of ferritin, the major intracellular iron storage protein, in cardiomyocytes and whether it is involved in their protection. The addition of metformin to adult mouse cardiomyocytes (HL-1 cell line) induced both gene and protein expression of the ferritin heavy chain (FHC) in a time-dependent manner. The silencing of FHC expression with siRNAs inhibited the ability of metformin to protect cardiomyocytes from doxorubicin-induced damage, in terms of the percentage of cell viability, the levels of reactive oxygen species, and the activity of antioxidant enzymes (catalase, glutathione peroxidase, and superoxide dismutase). In addition, metformin induced the activation of NF-κB in HL-1 cells, whereas preincubation with SN50, an inhibitor of NF-κB, blocked the upregulation of the FHC and the protective effect mediated by metformin. Taken together, these results provide new knowledge on the protective actions of metformin against doxorubicin-induced cardiotoxicity by identifying FHC and NF-κB as the major mediators of this beneficial effect.

Oxidative stress, redox signaling, and metal chelation in anthracycline cardiotoxicity and pharmacological cardioprotection

SIGNIFICANCE

Anthracyclines (doxorubicin, daunorubicin, or epirubicin) rank among the most effective anticancer drugs, but their clinical usefulness is hampered by the risk of cardiotoxicity. The most feared are the chronic forms of cardiotoxicity, characterized by irreversible cardiac damage and congestive heart failure. Although the pathogenesis of anthracycline cardiotoxicity seems to be complex, the pivotal role has been traditionally attributed to the iron-mediated formation of reactive oxygen species (ROS). In clinics, the bisdioxopiperazine agent dexrazoxane (ICRF-187) reduces the risk of anthracycline cardiotoxicity without a significant effect on response to chemotherapy. The prevailing concept describes dexrazoxane as a prodrug undergoing bioactivation to an iron-chelating agent ADR-925, which may inhibit anthracycline-induced ROS formation and oxidative damage to cardiomyocytes.

RECENT ADVANCES

A considerable body of evidence points to mitochondria as the key targets for anthracycline cardiotoxicity, and therefore it could be also crucial for effective cardioprotection. Numerous antioxidants and several iron chelators have been tested in vitro and in vivo with variable outcomes. None of these compounds have matched or even surpassed the effectiveness of dexrazoxane in chronic anthracycline cardiotoxicity settings, despite being stronger chelators and/or antioxidants.

CRITICAL ISSUES

The interpretation of many findings is complicated by the heterogeneity of experimental models and frequent employment of acute high-dose treatments with limited translatability to clinical practice.

FUTURE DIRECTIONS

Dexrazoxane may be the key to the enigma of anthracycline cardiotoxicity, and therefore it warrants further investigation, including the search for alternative/complementary modes of cardioprotective action beyond simple iron chelation.

Cardiovascular outcomes in women with advanced breast cancer exposed to chemotherapy

PURPOSE

To quantify incidence of cardiovascular outcomes in patients with advanced breast cancer receiving cardiotoxic and non-cardiotoxic chemotherapy.

METHODS

This study identified all women at a Midwestern health system with initial diagnosis of American Joint Commission on Cancer Stage III/IV breast cancer (1995-2003) and random sample of 50 women initially diagnosed with Stage I/II who progressed to Stage III/IV. The rate of new cardiovascular outcomes (heart failure, dysrhythmia, and ischemia events) for cardiotoxic (anthracycline or trastuzumab) and non-cardiotoxic agents was calculated.

RESULTS

Of 315 patients, 90.5% (n = 285) received systemic cancer therapy; 67.7% (n = 193) received cardiotoxic drugs. Older patients were less likely to receive cardiotoxic agents (86.4%, ≤59 years vs. 31.9%, 70+ years). Adjusting for age, race, stage, surgery/radiation, estrogen receptor/progesterone receptor status, and diagnosis year, rate of new cardiac events was higher in patients exposed to cardiotoxic drugs compared with those exposed to non-cardiotoxic drugs (adjusted hazard ratio = 2.5, 95%CI = 0.9-7.2). Patients with cardiac event history (relative risk = 3.2, 95%CI = 2.0-5.1) and those with heart failure history (relative risk = 5.9, 95%CI = 2.4-14.6) were more likely to receive non-cardiotoxic treatment. Heart failure events occurred steadily over time; after 3 years of follow-up, 16% exposed to cardiotoxic drugs experienced an event, and 8% of those exposed to non-cardiotoxic drugs experienced an event.

CONCLUSIONS

Patients with cardiac comorbidity are less likely to receive cardiotoxic agents. Use of cardiotoxic agents is common; treatment is related to patient and tumor characteristics and is associated with substantial risk of cardiotoxicity that persists during patients' remaining lifespan.

Cardio-oncology in targeting the HER receptor family: the puzzle of different cardiotoxicities of HER2 inhibitors

The HER family of tyrosine kinase receptors includes several members that are clinically important targets in cancer therapies, in particular HER1 (the EGF receptor) and HER2, other members include HER3 and HER4. Trastuzumab, a humanized monoclonal antibody and lapatinib, a tyrosine kinase inhibitor, are drugs that target HER2, which is highly expressed in 20-30% of breast cancers. Trastuzumab is recommended as an adjuvant therapy for lymph node positive, HER2-positive breast cancers, or node-negative cancer with high-risk of recurrence, as well as in stage IV cancers. One serious side effect of trastuzumab is cardiomyocyte dysfunction, resulting in reduced heart contractile efficiency. The incidence of collateral effects on the heart with trastuzumab therapy increases in people with cardiovascular risk factors, heart disease and when combined with other chemotherapeutics. When cardiotoxicity was observed with trastuzumab, several studies have addressed potential cardiac damage of trastuzumab itself and lapatinib. The differences in cardiovascular effects of these two compounds are somewhat unexpected and suggest distinct mechanisms of action, which have clear implications in clinical application and prevention of cardiotoxicity in cardio-oncological approaches.

Apoptosis in Anthracycline Cardiomyopathy

Apoptosis is a tightly regulated physiologic process of programmed cell death that occurs in both normal and pathologic tissues. Numerous in vitro or in vivo studies have indicated that cardiomyocyte death through apoptosis and necrosis is a primary contributor to the progression of anthracycline-induced cardiomyopathy. There are now several pieces of evidence to suggest that activation of intrinsic and extrinsic apoptotic pathways contribute to anthracycline-induced apoptosis in the heart. Novel strategies were developed to address a wide variety of cardiotoxic mechanisms and apoptotic pathways by which anthracycline influences cardiac structure and function. Anthracycline-induced apoptosis provides a very valid representation of cardiotoxicity in the heart, an argument which has implications for the most appropriate animal models of damaged heart plus diverse pharmacological effects. In this review we describe various aspects of the current understanding of apoptotic cell death triggered by anthracycline. Differences in the sensitivity to anthracycline-induced apoptosis between young and adult hearts are also discussed.

General oxidative stress during doxorubicin-induced cardiotoxicity in rats: absence of cardioprotection and low antioxidant efficiency of alpha-lipoic acid

To evaluate the effects of alpha-lipoic acid (AL) in a model of doxorubicin (DOX)-induced cardiotoxicity, male Wistar rats were treated with DOX (1 mg/kg/d; 10 d) in combination or not with AL (50 mg/kg/d; 15 d). Plasma oxidative stress was determined by hydroperoxides (ROOH) and the ascorbyl radical/ascorbate ratio. One and two months later, the functional parameters of the hearts were determined in vivo by catheterization and cardiac oxidative stress was assessed by malonedialdehyde (MDA) and O₂*⁻ (dihydroethidium fluorescence) content in tissue. After two months, body weight was higher in the DOX-AL group than in DOX (+16%), but this was due to ascites. Histological liver alterations were observed in both the DOX and DOX-AL groups. Plasma ROOH concentrations decreased after 10 days of AL treatment, but were greater in both the DOX and DOX-AL groups. After two months, a decrease in the cardiac contractility index (-27% and -29%, respectively) and cardiac hypertrophy were observed in DOX and DOX-AL. These dysfunctions were associated with 1) a reduction in plasma ascorbate levels and an increase in the ascorbyl/ascorbate ratio and 2) an increase MDA and O₂*⁻ content in cardiac tissue. In conclusion, a cumulative dose of 10 mg/kg doxorubicin induced functional alterations in the heart associated with plasma and cardiac oxidative stress. The co-administration of the antioxidant compound AL had no beneficial effects in this situation.

Mechanisms of anthracycline cardiac injury: can we identify strategies for cardioprotection?

Anthracycline antibiotics have saved the lives of many cancer victims in the 50 plus years since their discovery. A major limitation of their use is the dose-limiting cardiotoxicity. Efforts focusing on understanding the biochemical basis for anthracycline cardiac effects have provided several strategies currently in clinical use: limit dose exposure, encapsulate anthracyclines in liposomes to reduce myocardial uptake, administer concurrently with the iron chelator dexrazoxane to reduce free iron-catalyzed reactive oxygen species formation; and modify anthracycline structure in an effort to reduce myocardial toxicity. Despite these efforts, anthracycline-induced heart failure continues to occur with consequences for both morbidity and mortality. Our inability to predict and prevent anthracycline cardiotoxicity is, in part, due to the fact that the molecular and cellular mechanisms remain controversial and incompletely understood. Studies examining the effects of anthracyclines in cardiac myocytes in vitro and small animals in vivo have demonstrated several forms of cardiac injury, and it remains unclear how these translate to the clinical setting. Given the clinical evidence that myocyte death occurs after anthracycline exposure in the form of elevations in serum troponin, myocyte cell death seems to be a probable mechanism for anthracycline-induced cardiac injury. Other mechanisms of myocyte injury include the development of cellular "sarcopenia" characterized by disruption of normal sarcomere structure. Anthracyclines suppress expression of several cardiac transcription factors, and this may play a role in the development of myocyte death as well as sarcopenia. Degradation of the giant myofilament protein titin may represent an important proximal step that leads to accelerated myofilament degradation. An interesting interaction has been noted clinically between anthracyclines and newer cancer therapies that target the erbB2 receptor tyrosine kinase. There is now evidence that erbB2 signaling in response to the ligand neuregulin regulates anthracycline uptake into cells via the multidrug-resistance protein. Therefore, up-regulation of cardiac neuregulin signaling may be one strategy to limit myocardial anthracycline injury. Moreover, assessing an individual's risk for anthracycline injury may be improved by having some measure of endogenous activity of this and other myocardial protective signals.

Dexrazoxane protects the heart from acute doxorubicin-induced QT prolongation: a key role for I(Ks)

INTRODUCTION

Doxorubicin, an anthracycline widely used in the treatment of a broad range of tumours, causes acute QT prolongation. Dexrazoxane has been shown to prevent the QT prolongation induced by another anthracycline, epirubicin, but has not yet been reported to prevent that induced by doxorubicin. Thus, the present study was designed to test whether the acute QT effects induced by doxorubicin could be blocked by dexrazoxane and to explore the mechanism. Results were compared with those obtained with a reference human ether-a-go-go (hERG) channel blocker, moxifloxacin.

METHODS

The effects of moxifloxacin (100 microM) and doxorubicin (30 microM), with or without dexrazoxane (from 3 to 30 microM), have been evaluated on the QTc interval in guinea-pig isolated hearts and on I(Kr) (rapid component of the delayed rectifier current) and I(Ks) (slow component of the delayed rectifier current) currents stably expressed in human embryonic kidney 293 cells.

RESULTS

Moxifloxacin (100 microM), a potent hERG blocker, prolonged QTc by 22%, and this effect was not prevented by dexrazoxane. Doxorubicin (30 microM) also prolonged QTc by 13%, did not significantly block hERG channels and specifically inhibited I(Ks) (IC(50): 4.78 microM). Dexrazoxane significantly reduced the doxorubicin-induced QTc prolongation and prevented doxorubicin-induced inhibition of I(Ks).

CONCLUSION AND IMPLICATIONS

Doxorubicin acutely prolonged the QT interval in guinea-pig heart by selective I(Ks) blockade. This effect was prevented by dexrazoxane. This result is important because it illustrates the danger of neglecting I(Ks) in favour of hERG screening alone, for early preclinical testing for possible induction of torsade de pointes.

Anthracycline-induced cardiotoxicity: overview of studies examining the roles of oxidative stress and free cellular iron

The risk of cardiotoxicity is the most serious drawback to the clinical usefulness of anthracycline antineoplastic antibiotics, which include doxorubicin (adriamycin), daunorubicin or epirubicin. Nevertheless, these compounds remain among the most widely used anticancer drugs. The molecular pathogenesis of anthracycline cardiotoxicity remains highly controversial, although the oxidative stress-based hypothesis involving intramyocardial production of reactive oxygen species (ROS) has gained the widest acceptance. Anthracyclines may promote the formation of ROS through redox cycling of their aglycones as well as their anthracycline-iron complexes. This proposed mechanism has become particularly popular in light of the high cardioprotective efficacy of dexrazoxane (ICRF-187). The mechanism of action of this drug has been attributed to its hydrolytic transformation into the iron-chelating metabolite ADR-925, which may act by displacing iron from anthracycline-iron complexes or by chelating free or loosely bound cellular iron, thus preventing site-specific iron-catalyzed ROS damage. However, during the last decade, calls for the critical reassessment of this "ROS and iron" hypothesis have emerged. Numerous antioxidants, although efficient in cellular or acute animal experiments, have failed to alleviate anthracycline cardiotoxicity in clinically relevant chronic animal models or clinical trials. In addition, studies with chelators that are stronger and more selective for iron than ADR-925 have also yielded negative or, at best, mixed outcomes. Hence, several lines of evidence suggest that mechanisms other than the traditionally emphasized "ROS and iron" hypothesis are involved in anthracycline-induced cardiotoxicity and that these alternative mechanisms may be better bases for designing approaches to achieve efficient and safe cardioprotection.

The Role of Supportive Therapy in the Era of Modern Adjuvant Treatment - Current and Future Tools

Recent advances in adjuvant treatment of breast cancer have improved progression-free and overall survival. Optimal management of treatment-induced side effects has therefore gained further importance. This review cannot provide a comprehensive overview of treatment-related toxicity and its management, but focuses on important new developments in the field of supportive therapy. Erythropoietins, while highly effective in treating chemotherapy-induced anaemia, may have detrimental effects on outcome, and should only be used with the aim to reduce the number of whole blood transfusions. Granulocyte colony-stimulating factors were a prerequisite for development of dose-dense regimens, and are also necessary in many anthracycline/taxane combination regimens. A potential tumour-stimulating effect was not proven in solid cancers. For side effects of conventional chemotherapy, such as mucositis, nausea, or diarrhoea, regularly updated guidelines may improve symptom control. Overall, modern supportive treatment tools will further reduce treatment-related mortality and help increase quality of life.

Cardiac lesions induced by testosterone: protective effects of dexrazoxane and trimetazidine

Further to our previous observation of post-mortem cardiac lesions after sudden death in several athletes with a history of anabolic steroid abuse, this study was intended to reproduce these lesions in rabbits administered testosterone oenanthate, a prototypic anabolic steroid abused by athletes, and to provide evidence for the protective effects of trimetazidine and dexrazoxane that are used as antianginal and cardioprotective drugs, respectively. Groups of six rabbits each were administered saline, testosterone, or a combination of testosterone and either trimetazidine or dexrazoxane for 3 months. Histologic cardiac lesions including necrosis, misshapen cell nuclei, interstitial and endocardial fibrosis, lymphocytic infiltrates, and vascular dystrophies were observed in testosterone-treated rabbits. In contrast, no significant lesions were observed in the animals treated with testosterone combined with either trimetazidine or dexrazoxane. This is the first study providing evidence for testosterone cardiotoxicity following sub-chronic exposure in laboratory animals. In addition, these results suggest the protective role of trimetazidine and dexrazoxane.

Utility of dexrazoxane for the reduction of anthracycline-induced cardiotoxicity

Dexrazoxane is a derivative of the powerful metal-chelating agent ethyl enediamine tetra acetic acid. Its cardioprotective effect is thought to be due to its ability to chelate iron and reduce the number of metal ions complexed with anthracycline and, consequently, decrease the formation of superoxide radicals. Preclinical studies have confirmed that dexrazoxane has significant activity as a cardioprotective agent against anthracycline-induced cardiotoxicity. Dexrazoxane is well-tolerated, with myelosuppression being the dose-limiting toxicity in Phase I trials. The cardioprotective utility of dexrazoxane has been further illustrated in a number of randomized trials. In addition no significant difference in survival has been observed between the dexrazoxane and control arms of these trials but, in one, a significantly lower response rate was observed in the dexrazoxane compared to placebo arm. Further trials are required to evaluate the efficacy of dexrazoxane in hematological malignancies as well as the adjuvant treatment of breast cancer. Its use in the paediatric setting and in the management of elderly patients with cardiac comorbidity also requires investigation. Recently, interest has focused on the use of dexrazoxane as an antidote for anthracycline extravasation. In addition the general cytoprotective activity of this drug requires further assessment, as well as selectivity in this context.

Anthracycline cardiotoxicity in childhood

Over the last 40 years, a significant advance has been made in the treatment of childhood and adult cancers. However, the increase of the survival rate points out medium- and long-term adverse effects that constitute a serious limitation for the quality of life in adults survived from a childhood cancer. Cardiovascular disease is an important cause of morbidity and mortality in adults treated with chemo- and radiotherapy for childhood cancers. Although some antitumor treatments are potentially cardiotoxic, anthracycline therapy and radiotherapy are mostly responsible for long-term cardiac damage. Anthracycline toxicity is generally limited to the myocardium, while radiation can cause injury to all components of the heart. The purpose of this review is to discuss the mechanisms of action of anthracyclines, their cardiotoxicity, the feasibility of screening, and the prevention of cardiac damage after treatment in childhood.

Protective effects of Danshen (Salvia miltiorrhiza) on adriamycin-induced cardiac and hepatic toxicity in rats

The present study was carried out to investigate the protective effects of Danshen (DS, Salvia miltiorrhiza) on adriamycin (ADR)-induced cardiac and hepatic toxicity. Wistar rats were divided into six groups: control group, 10 animals received saline (i.p.); 15 animals received ADR (3 mg/kg, i.p.) three times weekly, for 2 weeks; 10 animals each received DS(1) (20 mg/kg, oral) and DS(2) (100 mg/kg, oral) for 30 days; 15 animals each received DS(1) + ADR and DS(2) + ADR. The ADR-induced cardiac and hepatic toxicity and protective action of DS were determined and quantitated with the use of hemodynamic measurements, biochemical analyses of serum, synthesis rates of DNA, RNA and protein, myocardial antioxidants, lipid peroxidation and histopathological procedure. Liver function was damaged. Nucleic acid as well as protein synthesis was inhibited, while lipid peroxidation was increased. Myocardial glutathione peroxidase (GSHPx) activity and superoxide dismutase activities (SOD) were decreased and histopathology revealed myocardial lesions indicative of ADR-induced cardiac and hepatic toxicity. In contrast, administration of DS before and concurrent with ADR significantly attenuated these effects. In conclusion, DS is potentially protective against ADR-induced cardiac and hepatic toxicity.

Effects of dexrazoxane and amifostine on evolution of Doxorubicin cardiomyopathy in vivo

Doxorubicin is one of the most active drugs in oncology, with cardiotoxicity as a serious side effect of its application. The aim of this study was to investigate dexrazoxane and amifostine impact on the evolution of myocardial changes induced by doxorubicin. BalbC female mice were treated with doxorubicin only (10 mg/kg, single intravenous push), or with dexrazoxane (200 mg/kg, intraperitoneal [ip]) or amifostine (200 mg/kg, ip) 60 mins or 30 mins prior to treatment with doxorubicin, respectively. Blood sampling for determination of conventional serum-marker activity was performed 48 hrs later. The grade of histopathology changes was evaluated by light microscopy 1.5 and 3 months after treatments using the Billingham scoring method. Control groups consisted of nontreated mice. After doxorubicin-only treatment, the grade of heart tissue damage was found to increase in the period between 1.5 and 3 months. A similar but less intense progression was also detected in amifostine-pretreated animals, with significant difference among median Billingham scores between the two time points. The pretreatment with dexrazoxane suspended expansion of tissue lesions in time. Changes in serum enzyme activity revealed two correlations: the greater reduction in alpha-hydroxybutyrate dehydrogenase (alpha-HBDH) leakage is associated with a lower percentage of damaged tissue, and the creatine kinase to alpha-HBDH percent of difference ratio being greater than one is correlated with limited spreading of pathological lesions. Our results indicate that the development of doxorubicin-induced heart failure is based on a slow and persistent expansion of pathological process even long after the completion of the treatment. Dexrazoxane has proved to be successful and superior over amifostine against such an evolution of doxorubicin cardiomyopathy.

Potentiation of Doxorubicin cardiotoxicity by iron loading in a rodent model

OBJECTIVES

The role of iron toward doxorubicin (DOX) cardiotoxicity was studied using a rodent model of dietary carbonyl iron loading.

BACKGROUND

Doxorubicin, a commonly used anticancer drug, is known to cause serious and potentially life-threatening cardiotoxicity. Doxorubicin cardiotoxicity is thought to be mediated through free-radical injury.

METHODS

Male Sprague Dawley rats fed iron-rich chow (n = 8) and regular chow (n = 8) were treated with DOX or saline (4 animals in each arm). Cardiotoxicity was assessed using mortality, weight changes, Tc-99m annexin-V imaging, histopathology, and immunohistochemistry.

RESULTS

Animals fed iron-rich chow showed significantly higher DOX cardiotoxicity as evidenced by greater weight loss (107 +/- 14 g vs. 55 +/- 10 g weight loss, p < 0.05), higher annexin uptake (0.14 +/- 0.01% vs. 0.08 +/- 0.01% injected dose/g of myocardium, p < 0.05), more severe myocyte injury on electron microscopy, and significantly higher cleaved caspase-3 staining compared with regular chow fed rats given DOX. Feeding iron-rich chow alone did not result in any cardiotoxicity.

CONCLUSIONS

Dietary iron loading resulted in a substantially increased DOX cardiotoxicity in rats. Body iron stores as well as its bioavailability in tissue may be important independent predictors of susceptibility to DOX cardiotoxicity in man. Further clinical studies are warranted.

Molecular and cellular mechanisms of anthracycline cardiotoxicity

The molecular and cellular mechanisms that cause cumulative dose-dependent anthracycline-cardiotoxicity remain controversial and incompletely understood. Studies examining the effects of anthracyclines in cardiac myocytes inA vitro have demonstrated several forms of cellular injury. Cell death in response to anthracyclines can be observed by one of several mechanisms including apoptosis and necrosis. Cell death by apoptosis can be inhibited by dexrazoxane, the iron chelator that is known to prevent clinical development of heart failure at high cumulative anthracycline exposure. Together with clinical evidence for myocyte death after anthracycline exposure, in the form of elevations in serum troponin, make myocyte cell death a probable mechanism for anthracycline-induced cardiac injury. Other mechanisms of myocyte injury include the development of cellular \'sarcopenia\' characterized by disruption of normal sarcomere structure. Anthracyclines suppress expression of several cardiac transcription factors, and this may play a role in the development of myocyte death as well as sarcopenia. Degradation of the giant myofilament protein titin may represent an important proximal step that leads to accelerated myofilament degradation. Titin is an entropic spring element in the sarcomere that regulates length-dependent calcium sensitivity. Thus titin degradation may lead to impaired diastolic as well as systolic dysfunction, as well as potentiate the effect of suppression of transcription of sarcomere proteins. An interesting interaction has been noted clinically between anthracyclines and newer cancer therapies that target the erbB2 receptor tyrosine kinase. Studies of erbB2 function in viro suggest that signaling through erbB2 by the growth factor neuregulin may regulate cardiac myocyte sarcomere turnover, as well as myocyte-myocyte/myocyte-matrix force coupling. A combination of further in vitro studies, with more careful monitoring of cardiac function after exposure to these cancer therapies, may help to understand to what extent these mechanisms are at work during clinical exposure of the heart to these important pharmaceuticals.

Novel antioxidants in anthracycline cardiotoxicity

It has been suggested nitroxides and their amine precursors prevent incidence of damage caused by superoxide and hydroxyl radicals formed during the oxidative metabolism of doxorubicin (DOX) and daunorubicin (DAU). Both doxorubicin and daunorubicin have been associated with cardiac toxicity in both adults and children. The authors herein suggest that cardioprotective molecules modified by nitroxides and their secondary amine precursors can prevent or diminish the anthracycline-induced cardiomyopathy by accumulating in cardiomiocytes.

Cardiac Toxicity Related to Cancer Treatment

Cardiac toxicity is a dose-limiting toxicity that may occur during cancer treatment or several years after therapy ends. Cardiac toxicity may be caused by chemotherapy, biotherapy, and radiation therapy and may result in cardiomyopathy, congestive heart failure, dysrhythmias, and myocardial ischemia. The risk for developing cardiac toxicity varies based on type of treatment, patient age, presence of preexisting or concurrent heart disease, and concomitant treatment. Patients at high risk require careful evaluation and monitoring during and in the years following therapy to detect cardiac changes. Fortunately, cardioprotective agents and newer radiation therapy techniques decrease the risk for treatment-related cardiac toxicity. Oncology nurses can become more informed in the assessment of cardiac toxicity and can arm themselves with knowledge about early identification of symptoms as well as specific agents and treatments that increase risk for cardiac toxicity.