Doxorubicin cardiomyopathy is associated with a decrease in calcium release channel of the sarcoplasmic reticulum in a chronic rabbit model

Long noncoding RNA RMRP ameliorates doxorubicin-induced apoptosis by interacting with PFN1 in a P53-Dependent manner

Doxorubicin (DOX) often causes acute or chronic cardiotoxicity during its application. LncRNA RMRP has been reported to be associated with several biological processes, such as cartilage-hair hypoplasia, but the relationship between RMRP and DOX-induced cardiotoxicity and chronic heart failure remains obscure. To test this hypothesis, GSE124401 and GSE149870 were processed for bioinformatics, and differentially expressed RMRP was then verified in the peripheral blood of 21 patients with heart failure compared with 7 controls. For in vitro validation, we used AC16 and HEK-293T cells. qPCR was used to detect the mRNA expression levels. The degree of apoptosis was detected by Western blot and TUNEL staining. Furthermore, the interaction between RMRP and PFN1 mRNA was verified by dual-luciferase reporter assays. In bioinformatics, RMRP showed significant downregulation, which was verified in clinical samples (p < 0.001) and DOX-treated AC16 models (p < 0.0001). Next, overexpression of RMRP could significantly alleviate DOX-induced apoptosis, and a potential downstream molecule of RMRP, PFN1, was also negatively associated with this change. RESCUE experiments further confirmed that PFN1 could be regulated by RMRP at both the RNA and protein levels, serving as a downstream mediator of RMRP's cardioprotective effects. This interaction was then confirmed to be a direct combination (p < 0.0001). Finally, we found that overexpression of RMRP could inhibit the expression of p53 and its phosphorylation level by suppressing PFN1. In summary, RMRP could exert cardioprotective effects via the PFN1/p53 axis, holding great promise for serving as a therapeutic target and potential biomarker.

Potential role of the apelin-APJ pathway in sex-related differential cardiotoxicity induced by doxorubicin in mice

Preclinical and clinical findings suggest sexual dimorphism in cardiotoxicity induced by a chemotherapeutic drug, doxorubicin (DOX). However, molecular alterations leading to sex-related differential vulnerability of heart to DOX toxicity are not fully explored. In the present study, RNA sequencing in hearts of B6C3F₁ mice indicated more differentially expressed genes in males than females (224 vs. 19; ≥1.5-fold, False Discovery Rate [FDR] < 0.05) at 1 week after receiving 24 mg/kg total cumulative DOX dose that induced cardiac lesions only in males. Pathway analysis further revealed probable inactivation of cardiac apelin fibroblast signaling pathway (p = 0.00004) only in DOX-treated male mice that showed ≥1.25-fold downregulation in the transcript and protein levels of the apelin receptor, APJ. In hearts of DOX-treated females, the transcript levels of apelin (1.24-fold) and APJ (1.47-fold) were significantly (p < 0.05) increased compared to saline-treated controls. Sex-related differential DOX effect was also observed on molecular targets downstream of the apelin-APJ pathway in cardiac fibroblasts and cardiomyocytes. In cardiac fibroblasts, upregulation of Tgf-β2, Ctgf, Sphk1, Serpine1, and Timp1 (fibrosis; FDR < 0.05) in DOX-treated males and upregulation of only Tgf-β2 and Timp1 (p < 0.05) in females suggested a greater DOX toxicity in hearts of males than females. Additionally, Ryr2 and Serca2 (calcium handling; FDR < 0.05) were downregulated in conjunction with 1.35-fold upregulation of Casp12 (sarcoplasmic reticulum-mediated apoptosis; FDR < 0.05) in DOX-treated male mice. Drug effect on the transcript level of these genes was less severe in female hearts. Collectively, these data suggest a likely role of the apelin-APJ axis in sex-related differential DOX-induced cardiotoxicity in our mouse model.

Doxorubicin-induced delayed-onset subclinical cardiotoxicity in mice

Subclinical cardiotoxicity at low total cumulative doxorubicin (DOX) doses can manifest into cardiomyopathy in long-term cancer survivors. However, the underlying mechanisms are poorly understood. In male B6C3F₁ mice, assessment of cardiac function by echocardiography was performed at 1, 4, 10, 17, and 24 weeks after exposure to 6, 9, 12, and 24 mg/kg total cumulative DOX doses or saline (SAL) to monitor development of delayed-onset cardiotoxicity. The 6- or 9-mg/kg total cumulative doses resulted in a significant time-dependent decline in systolic function (left ventricular ejection fraction (LVEF) and fractional shortening (FS)) during the 24-week recovery although there was not a significant alteration in % LVEF or % FS at any specific time point during the recovery. A significant decline in systolic function was elicited by the cardiotoxic cumulative DOX dose (24 mg/kg) during the 4- to 24-week period after treatment compared to SAL-treated counterparts. At 24 weeks after DOX treatment, a significant dose-related decrease in the expression of genes and proteins involved in sarcoplasmic reticulum (SR) calcium homeostasis (Ryr2 and Serca2) was associated with a dose-related increase in the transcript level of Casp12 (SR-specific apoptosis) in hearts. These mice also showed enhanced apoptotic activity in hearts indicated by a significant dose-related elevation in the number of apoptotic cardiomyocytes compared to SAL-treated counterparts. These findings collectively suggest that a steady decline in SR calcium handling and apoptosis might be involved in the development of subclinical cardiotoxicity that can evolve into irreversible cardiomyopathy later in life.

Noncoding RNAs in doxorubicin-induced cardiotoxicity and their potential as biomarkers and therapeutic targets

Anthracyclines, such as doxorubicin (DOX), are well known for their high efficacy in treating multiple cancers, but their clinical usage is limited due to their potential to induce fatal cardiotoxicity. Such detrimental effects significantly impact the overall physical condition or even induce the morbidity and mortality of cancer survivors. Therefore, it is extremely important to understand the mechanisms of DOX-induced cardiotoxicity to develop methods for the early detection of cytotoxicity and therapeutic applications. Studies have shown that many molecular events are involved in DOX-induced cardiotoxicity. However, the precise mechanisms are still not completely understood. Recently, noncoding RNAs (ncRNAs) have been extensively studied in a diverse range of regulatory roles in cellular physiological and pathological processes. With respect to their roles in DOX-induced cardiotoxicity, microRNAs (miRNAs) are the most widely studied, and studies have focused on the regulatory roles of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), which have been shown to have significant functions in the cardiovascular system. Recent discoveries on the roles of ncRNAs in DOX-induced cardiotoxicity have prompted extensive interest in exploring candidate ncRNAs for utilization as potential therapeutic targets and/or diagnostic biomarkers. This review presents the frontier studies on the roles of ncRNAs in DOX-induced cardiotoxicity, addresses the possibility and prospects of using ncRNAs as diagnostic biomarkers or therapeutic targets, and discusses the possible reasons for related discrepancies and limitations of their use.

A short review: Doxorubicin and its effect on cardiac proteins

Doxorubicin (DOX) is a boon for cancer-suffering patients. However, the undesirable effect on health on vital organs, especially the heart, is a limiting factor, resulting in an increased number of patients with cardiac dysfunction. The present review focuses on the contractile machinery and associated factors, which get affected due to DOX toxicity in chemo-patients for which they are kept under life-long investigation for cardiac function. DOX-induced oxidative stress disrupts the integrity of cardiac contractile muscle proteins that alter the rhythmic mechanism and oxygen consumption rate of the heart. DOX is an oxidant and it is further discussed that oxidative stress prompts the damage of contractile components and associated factors, which include Ca²⁺ load through Ca²⁺ ATPase, SERCA, ryanodine receptor-2, phospholamban, and calsequestrin, which ultimately results in left ventricular ejection and dilation. Based on data and evidence, the associated proteins can be considered as clinical markers to develop medications for patients. Even with the advancement of various diagnosing tools and modified drugs to mitigate DOX-induced cardiotoxicity, the risk could not be surmounted with survivors of cancer.

Acylated Ghrelin Protects the Hearts of Rats from Doxorubicin-Induced Fas/FasL Apoptosis by Stimulating SERCA2a Mediated by Activation of PKA and Akt

This study investigated if the cardioprotective effect of acylated ghrelin (AG) against doxorubicin (DOX)-induced cardiac toxicity in rats involves inhibition of Fas/FasL-mediated cell death. It also investigated if such an effect is mediated by restoring Ca⁺² homeostasis from the aspect of stimulation of SERCA2a receptors. Adult male Wistar rats were divided into 4 groups (20 rats/each) as control, control + AG, DOX, and DOX + AG. AG was co-administered to all rats consecutively for 35 days. In addition, isolated cardiomyocytes were cultured and treated with AG in the presence or absence of DOX with or without pre-incubation with [D-Lys3]-GHRP-6 (a AG receptor antagonist), VIII (]an Akt inhibitor), or KT-5720 (a PKA inhibitor). AG increased LVSP, dp/dt_max, and dp/dt_min in both control and DOX-treated animals and improved cardiac ultrastructural changes in DOX-treated rats. It also inhibited ROS in control rats and lowered LVEDP, intracellular levels of ROS and Ca²⁺, and activity of calcineurin in LVs of DOX-treated rats. Concomitantly, it inhibited LV NFAT-4 nuclear translocation and downregulated their protein levels of Fas and FasL. Mechanistically, in control or DOX-treated hearts or cells, AG upregulated the levels of SERCA2a and increased the activities of PKA and Akt, leading to increase phosphorylation of phospholamban at Ser¹⁶ and Thr¹⁷. All these effects were abolished by D-Lys3-GHRP-6, VIII, or KT-5720 and were independent of food intake or GH/IGF-1. In conclusion, AG cardioprotection against DOX involves inhibition of extrinsic cell death and restoring normal Ca⁺² homeostasis.

Modulation of Nrf2 by quercetin in doxorubicin-treated rats

Doxorubicin (DOXO), a potent and widely used chemotherapeutic agent, causes irreversible heart failure by increasing oxidative stress, which limits its clinical utility. Nuclear factor erythroid-derived 2 -like 2 (Nrf2) is a prominent central regulator of cellular impenetrable to oxidants. The purpose of the study is to assess the ameliorative outcome of quercetin in cardiomyopathic rats induced by doxorubicin. Cardiomyopathy was produced in rats by single intraperitoneal weekly with DOXO (2 mg/kg) for 4 weeks. The rats were divided into five groups: (I) control group; (II) DOXO (2 mg/kg, i.p.) group; (III-V) DOXO + quercetin (10 mg/kg, 25 mg/kg and 50 mg/kg, orally), and were treated for 7 weeks. At the end of the treatment duration, cardiac function and biochemical parameters were assessed. Quercetin (10 mg/kg, 25 mg/kg and 50 mg/kg, orally) treatment reduced the raised blood pressure (BP) and left ventricular dysfunction. Withal, it prevented the rise in CKMB and LDH, suggesting the effect of quercetin in the maintaining the integrity of the cell membrane Besides, it also prevented the alteration in electrolyte levels, the activity of ATPase, and antioxidant status. Quercetin increased Nrf2 mRNA expression and reduced histological abnormalities compared to the DOXO control group. In conclusion, quercetin protected against DOXO- induced cardiomyopathy, by increasing expression of NRF2, and thereby increasing antioxidant defense and restoring biochemical and histological abnormalities.

Carbonyl Reductase 1 Plays a Significant Role in Converting Doxorubicin to Cardiotoxic Doxorubicinol in Mouse Liver, but the Majority of the Doxorubicinol-Forming Activity Remains Unidentified

Doxorubicin is a widely used cancer therapeutic, but its effectiveness is limited by cardiotoxic side effects. Evidence suggests cardiotoxicity is due not to doxorubicin, but rather its metabolite, doxorubicinol. Identification of the enzymes responsible for doxorubicinol formation is important in developing strategies to prevent cardiotoxicity. In this study, the contributions of three murine candidate enzymes to doxorubicinol formation were evaluated: carbonyl reductase (Cbr) 1, Cbr3, and thioredoxin reductase 1 (Tr1). Analyses with purified proteins revealed that all three enzymes catalyzed doxorubicin-dependent NADPH oxidation, but only Cbr1 and Cbr3 catalyzed doxorubicinol formation. Doxorubicin-dependent NADPH oxidation by Tr1 was likely due to redox cycling. Subcellular fractionation results showed that doxorubicin-dependent redox cycling activity was primarily microsomal, whereas doxorubicinol-forming activity was exclusively cytosolic, as were all three enzymes. An immunoclearing approach was used to assess the contributions of the three enzymes to doxorubicinol formation in the complex milieu of the cytosol. Immunoclearing Cbr1 eliminated 25% of the total doxorubicinol-forming activity in cytosol, but immunoclearing Cbr3 had no effect, even in Tr1 null livers that overexpressed Cbr3. The immunoclearing results constituted strong evidence that Cbr1 contributed to doxorubicinol formation in mouse liver but that enzymes other than Cbr1 also played a role, a conclusion supported by ammonium sulfate fractionation results, which showed that doxorubicinol-forming activity was found in fractions that contained little Cbr1. In conclusion, the results show that Cbr1 accounts for 25% of the doxorubicinol-forming activity in mouse liver cytosol but that the majority of the doxorubicinol-forming activity remains unidentified. SIGNIFICANCE STATEMENT: Earlier studies suggested carbonyl reductase (Cbr) 1 plays a dominant role in converting chemotherapeutic doxorubicin to cardiotoxic doxorubicinol, but a new immunoclearing approach described herein shows that Cbr1 accounts for only 25% of the doxorubicinol-forming activity in mouse liver cytosol, that two other candidate enzymes-Cbr3 and thioredoxin reductase 1-play no role, and that the majority of the activity remains unidentified. Thus, targeting Cbr1 is necessary but not sufficient to eliminate doxorubicinol-associated cardiotoxicity; identification of the additional doxorubicinol-forming activity is an important next challenge.

Transcriptomic profiling reveals p53 as a key regulator of doxorubicin-induced cardiotoxicity

Doxorubicin is an important anticancer drug in the clinic. Unfortunately, it causes cumulative and dose-dependent cardiotoxic side effects. As the population of cancer survivors who have been exposed to treatment continues to grow, there is increased interest in assessing the long-term cardiac effects of doxorubicin and understanding the underlying mechanisms at play. In this study, we investigated doxorubicin-induced transcriptomic changes using RNA-sequencing (RNAseq) and a cellular model comprised of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Analyses of predicted upstream regulators identified the p53 protein as a key regulator of transcriptomic changes induced by doxorubicin. Clustering and pathway analyses showed that increased death receptor (DR) expression and enrichment of the extrinsic apoptotic pathway are significantly associated with doxorubicin-induced cardiotoxicity. Increased expression of p53 and DRs were confirmed via immunoblotting. Our data pinpoints increased DR expression as an early transcriptomic indicator of cardiotoxicity, suggesting that DR expression might function as a predictive biomarker for cardiac damage.

Ferulic acid ameliorates doxorubicin-induced cardiac toxicity in rats

Ferulic acid (FA) is a phenolic compound with potent antioxidant activity. The objective of the study was to study the protective effects of FA on doxorubicin (Dox)-induced myocardial toxicity in rats. Wistar rats received vehicle (control) or Dox (20 mg/kg, i.p.) or telmisartan (Tel; 10 mg/kg, p.o.) or ferulic acid (20 mg/kg and 40 mg/kg, p.o.) for 7 days followed by treatment with Dox (20) on the fifth day of treatment, except the control group. On day 8, electrocardiographic parameters were recorded followed by blood withdrawal and then the animals were sacrificed for histopathology. Administration of Dox showed prolonged RR, QTc interval, and QRS complex. The levels of serum CK-MB, LDH, IL-1β, and IL-6 were significantly increased (p < 0.01). Similarly, levels of Ca⁺², Mg⁺² ATPase, and Ca⁺² ATPase and expression of ANP and BNP were significantly higher as compared to the control. In the FA-treated group, ECG was normal. The serum levels of CK-MB, LDH, IL-1β, and IL-6 were not elevated. Heart tissue Ca⁺², Mg⁺² ATPase, and Ca⁺² ATPase did not show a statistical difference compared to the control group. The FA treatment attenuated the expression of ANP and BNP. FA (20 and 40) augmented myocardial GSH and Na⁺/K⁺ ATPase. Histopathology of the heart confirmed the cardioprotective effect of FA.

Progression of excitation-contraction coupling defects in doxorubicin cardiotoxicity

Cardiac failure is a common complication in cancer survivors treated with anthracyclines. Here we followed up cardiac function and excitation-contraction (EC) coupling in an in vivo doxorubicin (Dox) treated mice model (iv, total dose of 10 mg/Kg divided once every three days). Cardiac function was evaluated by echocardiography at 2, 6 and 15 weeks after the last injection. While normal at 2 and 6 weeks, ejection fraction was significantly reduced at 15 weeks. In order to evaluate the underlying mechanisms, we measured [Ca²⁺]_i transients by confocal microscopy and action potentials (AP) by patch-clamp technique in cardiomyocytes isolated at these times. Three phases were observed: 1/depression and slowing of the [Ca²⁺]_i transients at 2 weeks after treatment, with occurrence of proarrhythmogenic Ca²⁺ waves, 2/compensatory state at 6 weeks, and 3/depression on [Ca²⁺]_i transients and cell contraction at 15 weeks, concomitant with in-vivo defects. These [Ca²⁺]_i transient alterations were observed without cellular hypertrophy or AP prolongation and mirrored the sarcoplasmic reticulum (SR) Ca²⁺ load variations. At the molecular level, this was associated with a decrease in the sarcoplasmic reticulum Ca²⁺ ATPase (SERCA2a) expression and enhanced RyR2 phosphorylation at the protein kinase A (PKA, pS2808) site (2 and 15 weeks). RyR2 phosphorylation at the Ca²⁺/calmodulin dependent protein kinase II (CaMKII, pS2814) site was enhanced only at 2 weeks, coinciding with the higher incidence of proarrhythmogenic Ca²⁺ waves. Our study highlighted, for the first time, the progression of Dox treatment-induced alterations in Ca²⁺ handling and identified key components of the underlying Dox cardiotoxicity. These findings should be helpful to understand the early-, intermediate-, and late- cardiotoxicity already recorded in clinic in order to prevent or treat at the subclinical level.

A Doxorubicin-induced Cardiomyopathy Model in Adult Zebrafish

The genetically accessible adult zebrafish (Danio rerio) has been increasingly used as a vertebrate model for understanding human diseases such as cardiomyopathy. Because of its convenience and amenability to high throughput genetic manipulations, the generation of acquired cardiomyopathy models, such as the doxorubicin-induced cardiomyopathy (DIC) model in adult zebrafish, is opening the doors to new research avenues, including discovering cardiomyopathy modifiers via forward genetic screening. Different from the embryonic zebrafish DIC model, both initial acute and later chronic phases of cardiomyopathy can be determined in the adult zebrafish DIC model, enabling the study of stage-dependent signaling mechanisms and therapeutic strategies. However, variable results can be obtained with the current model, even in the hands of experienced investigators. To facilitate future implementation of the DIC model, we present a detailed protocol on how to generate this DIC model in adult zebrafish and describe two alternative ways of intraperitoneal (IP) injection. We further discuss options on how to reduce variations to obtain reliable results and provide suggestions on how to appropriately interpret the results.

Mechanism of doxorubicin cardiotoxicity evaluated by integrating multiple molecular effects into a biophysical model

BACKGROUND AND PURPOSE

Doxorubicin (DOX) is an effective cancer therapeutic agent but causes therapy-limiting cardiotoxicity. The effects of DOX and its metabolite doxorubicinol (DOXL) on individual channels have been well characterized in isolation. However, it is unknown how the action and interaction of affected channels combine to generate the phenotypic cardiotoxic outcome. We sought to develop an in silico model that links drug effects on channels to action potential duration (APD) and intracellular Ca²⁺ concentration in order to address this gap in knowledge.

EXPERIMENTAL APPROACH

We first propose two methods to obtain, from published values, consensus drug effects on the currents of individual channels, transporters and pumps. Separately, we obtained equivalent values for APD and Ca²⁺ concentration (the readouts used as surrogates for cardiotoxicity). Once derived, the consensus effects on the currents were incorporated into established biophysical models of the cardiac myocyte and were refined adjusting the sarcoplasmic reticulum Ca²⁺ leak current (I_Leak ) until the consensus effects on APD and Ca²⁺ dynamics were replicated. Using factorial analysis, we then quantified the relative contribution of each channel to DOX and DOXL cardiotoxicity.

KEY RESULTS

The factorial analysis identified the rapid delayed rectifying K⁺ current, the L-type Ca²⁺ current and the sarcoplasmic reticulum I_Leak as the targets primarily responsible for the cardiotoxic effects on APD and Ca²⁺ dynamics.

CONCLUSIONS AND IMPLICATIONS

This study provides insight into the mechanisms of DOX-induced cardiotoxicity and a framework for the development of future diagnostic and therapeutic strategies.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

The paradox of the first cycle of chemotherapy-transient improvement of contractility and diastolic function after the first cycle of anthracycline-based chemotherapy: a prospective clinical trial

Aims

Breast cancer is the most common cancer among women, and anthracyclines are the most commonly administered drugs for these patients. Cardiotoxicity is one of the complications, which limits the success of this therapy. Very few studies have evaluated anthracycline toxicities within the first few hours after the first infusion, and the majority of published studies were performed in animal models. The present study aimed to evaluate changes in echocardiographic parameters in women with breast cancer 24 hours after receiving the first dose of an anthracycline.

Materials and Methods and Results

The present study included 75 chemotherapy-naive female patients without heart failure, who were diagnosed with breast cancer and were scheduled to undergo anthracycline-based chemotherapy (epirubicin and doxorubicin). During their visits to the Heart Center, the patients underwent detail echocardiographic examination, including assessment of systolic and diastolic function and longitudinal strain. There were no differences in baseline echocardiographic parameters between patients with and those without cardiotoxicity. Cardiotoxicity was observed during follow-up in 14 patients (18.7%). Improvements in left ventricular ejection fraction and global longitudinal strain were observed at 24 hours after administration of the cytotoxic agent in the subgroup of patients without further cardiotoxicity. The changes were transient and the assessment of left ventricular ejection fraction after completion of chemotherapy revealed similar values to those before the treatment.

Conclusions

The findings of our study suggest that transient improvement in contractility and systolic and diastolic function might occur 24 hours after anthracycline administration, especially in patients who do not develop cardiotoxicity.

Anthracycline-Induced Cardiomyopathy in Adults

Anthracyclines are one of the most commonly used antineoplastic agent classes, and a core part of the treatment in breast cancers, hematological malignancies, and sarcomas. Their benefit is decreased by their well-recognized cardiotoxicity. The purpose of this review is to outline the presentation, mechanisms, diagnosis, and treatment of anthracyclines-induced cardiotoxicity. Symptomatic heart failure occurs in 2% to 5% of patients treated with anthrayclines and may be higher in older patients or patients with cardiovascular risk factors. The mechanisms involved in anthracycline-induced cardiotoxicity involve myocyte loss by apoptosis in the presence of a limited regenerative capacity. Once symptomatic, anthracycline-induced cardiotoxicity is associated with markedly decreased survival. Left ventricular ejection fraction (LVEF), mostly determined using echocardiography, is used to monitor patients treated with anthracyclines. As more than 1/3 of patients treated with anthracyclines do not recover their baseline LVEF once it is decreased, more sensitive echocardiographic indices of LV function such as myocardial deformation or biomarkers have been studied in patients monitoring. Cardioprotective treatments such as angiotensin-converting enzyme inhibitors, beta-blockers, iron chelators, statins, and metformin are also the topic of research efforts.

Effect of Remote Ischaemic Conditioning in Oncology Patients Undergoing Chemotherapy: Rationale and Design of the ERIC-ONC Study--A Single-Center, Blinded, Randomized Controlled Trial

Cancer survival continues to improve, and thus cardiovascular consequences of chemotherapy are increasingly important determinants of long‐term morbidity and mortality. Conventional strategies to protect the heart from chemotherapy have important hemodynamic or myelosuppressive side effects. Remote ischemic conditioning (RIC) using intermittent limb ischemia‐reperfusion reduces myocardial injury in the setting of percutaneous coronary intervention. Anthracycline cardiotoxicity and ischemia‐reperfusion injury share common biochemical pathways in cardiomyocytes. The potential for RIC as a novel treatment to reduce subclinical myocyte injury in chemotherapy has never been explored and will be investigated in the Effect of Remote Ischaemic Conditioning in Oncology (ERIC‐ONC) trial (clinicaltrials.gov NCT 02471885). The ERIC‐ONC trial is a single‐center, blinded, randomized, sham‐controlled study. We aim to recruit 128 adult oncology patients undergoing anthracycline‐based chemotherapy treatment, randomized in a 1:1 ratio into 2 groups: (1) sham procedure or (2) RIC, comprising 4, 5‐minute cycles of upper arm blood pressure cuff inflations and deflations, immediately before each cycle of chemotherapy. The primary outcome measure, defining cardiac injury, will be high‐sensitivity troponin‐T over 6 cycles of chemotherapy and 12 months follow‐up. Secondary outcome measures will include clinical, electrical, structural, and biochemical endpoints comprising major adverse cardiovascular clinical events, incidence of cardiac arrhythmia over 14 days at cycle 5/6, echocardiographic ventricular function, N‐terminal pro‐brain natriuretic peptide levels at 3 months follow‐up, and changes in mitochondrial DNA, micro‐RNA, and proteomics after chemotherapy. The ERIC‐ONC trial will determine the efficacy of RIC as a novel, noninvasive, nonpharmacological, low‐cost cardioprotectant in cancer patients undergoing anthracycline‐based chemotherapy.

Identification of genomic biomarkers for anthracycline-induced cardiotoxicity in human iPSC-derived cardiomyocytes: an in vitro repeated exposure toxicity approach for safety assessment

The currently available techniques for the safety evaluation of candidate drugs are usually cost-intensive and time-consuming and are often insufficient to predict human relevant cardiotoxicity. The purpose of this study was to develop an in vitro repeated exposure toxicity methodology allowing the identification of predictive genomics biomarkers of functional relevance for drug-induced cardiotoxicity in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The hiPSC-CMs were incubated with 156 nM doxorubicin, which is a well-characterized cardiotoxicant, for 2 or 6 days followed by washout of the test compound and further incubation in compound-free culture medium until day 14 after the onset of exposure. An xCELLigence Real-Time Cell Analyser was used to monitor doxorubicin-induced cytotoxicity while also monitoring functional alterations of cardiomyocytes by counting of the beating frequency of cardiomyocytes. Unlike single exposure, repeated doxorubicin exposure resulted in long-term arrhythmic beating in hiPSC-CMs accompanied by significant cytotoxicity. Global gene expression changes were studied using microarrays and bioinformatics tools. Analysis of the transcriptomic data revealed early expression signatures of genes involved in formation of sarcomeric structures, regulation of ion homeostasis and induction of apoptosis. Eighty-four significantly deregulated genes related to cardiac functions, stress and apoptosis were validated using real-time PCR. The expression of the 84 genes was further studied by real-time PCR in hiPSC-CMs incubated with daunorubicin and mitoxantrone, further anthracycline family members that are also known to induce cardiotoxicity. A panel of 35 genes was deregulated by all three anthracycline family members and can therefore be expected to predict the cardiotoxicity of compounds acting by similar mechanisms as doxorubicin, daunorubicin or mitoxantrone. The identified gene panel can be applied in the safety assessment of novel drug candidates as well as available therapeutics to identify compounds that may cause cardiotoxicity.

Chemotherapy-Induced Cardiotoxicity: Overview of the Roles of Oxidative Stress

Chemotherapy-induced cardiotoxicity is a serious complication that poses a serious threat to life and limits the clinical use of various chemotherapeutic agents, particularly the anthracyclines. Understanding molecular mechanisms of chemotherapy-induced cardiotoxicity is a key to effective preventive strategies and improved chemotherapy regimen. Although no reliable and effective preventive treatment has become available, numerous evidence demonstrates that chemotherapy-induced cardiotoxicity involves the generation of reactive oxygen species (ROS). This review provides an overview of the roles of oxidative stress in chemotherapy-induced cardiotoxicity using doxorubicin, which is one of the most effective chemotherapeutic agents against a wide range of cancers, as an example. Current understanding in the molecular mechanisms of ROS-mediated cardiotoxicity will be explored and discussed, with emphasis on cardiomyocyte apoptosis leading to cardiomyopathy. The review will conclude with perspectives on model development needed to facilitate further progress and understanding on chemotherapy-induced cardiotoxicity.

Stimulating basal mitochondrial respiration decreases doxorubicin apoptotic signaling in H9c2 cardiomyoblasts

Doxorubicin (DOX) is currently used in cancer chemotherapy, however, its use often results in adverse effects highlighted by the development of cardiomyopathy and ultimately heart failure. Interestingly, DOX cardiotoxicity is decreased by resveratrol or by physical activity, suggesting that increased mitochondrial activity may be protective. Conversely, recent studies showed that troglitazone, a PPARγ agonist, increases the cytotoxicity of DOX against breast cancer cells by up-regulating mitochondrial biogenesis. The hypothesis for the current investigation was that DOX cytotoxicity in H9c2 cardiomyoblasts is decreased when mitochondrial capacity is increased. We focused on several end-points for DOX cytotoxicity, including loss of cell mass, apoptotic signaling and alterations of autophagic-related proteins. Our results show that a galactose-based, modified cell culture medium increased H9c2 basal mitochondrial respiration, protein content, and mtDNA copy number without increasing maximal or spare respiratory capacity. H9c2 cardiomyoblasts cultured in the galactose-modified media showed lower DOX-induced activation of the apoptotic pathway, measured by decreased caspase-3 and -9 activation, and lower p53 expression, although ultimately loss of cells was not prevented. Treatment with the PPARγ agonist troglitazone had no effect on DOX toxicity in this cardiac cell line, which agrees with the fact that troglitazone did not increase mitochondrial DNA content or capacity at the concentrations and duration of exposure used in this investigation. Our results show that mitochondrial remodeling caused by stimulating basal rates of oxidative phosphorylation decreased DOX-induced apoptotic signaling and increased DOX-induced autophagy in H9c2 cardiomyoblasts. The differential effect on cytotoxicity in cardiac versus breast cancer cell lines suggests a possible overall improvement in the clinical efficacy for doxorubicin in treating cancer.

Chemotherapy-Induced Cardiotoxicity: Pathophysiology and Prevention

Along with the remarkable progress registered in oncological treatment that led to increased survival of cancer patients, treatment-related comorbidities have also become an issue for these long-term survivors. Of particular interest is the development of cardiotoxic events, which, even when asymptomatic, not only have a negative impact on the patient`s cardiac prognosis, but also considerably restrict therapeutic opportunities. The pathophysiology of cytostatic-induced cardiotoxicity implies a series of complex and intricate mechanisms, whose understanding enables the development of preventive and therapeutic strategies. Securing cardiac function is an ongoing challenge for the pharmaceutical industry and the physicians who have to deal currently with these adverse reactions. This review focuses on the main mechanism of cardiac toxicity induced by anticancer drugs and especially on the current strategies applied for preventing and minimizing the cardiac side effects.

Comparative normal/failing rat myocardium cell membrane chromatographic analysis system for screening specific components that counteract doxorubicin-induced heart failure from Acontium carmichaeli

Cell membrane chromatography (CMC) derived from pathological tissues is ideal for screening specific components acting on specific diseases from complex medicines owing to the maximum simulation of in vivo drug-receptor interactions. However, there are no pathological tissue-derived CMC models that have ever been developed, as well as no visualized affinity comparison of potential active components between normal and pathological CMC columns. In this study, a novel comparative normal/failing rat myocardium CMC analysis system based on online column selection and comprehensive two-dimensional (2D) chromatography/monolithic column/time-of-flight mass spectrometry was developed for parallel comparison of the chromatographic behaviors on both normal and pathological CMC columns, as well as rapid screening of the specific therapeutic agents that counteract doxorubicin (DOX)-induced heart failure from Acontium carmichaeli (Fuzi). In total, 16 potential active alkaloid components with similar structures in Fuzi were retained on both normal and failing myocardium CMC models. Most of them had obvious decreases of affinities on failing myocardium CMC compared with normal CMC model except for four components, talatizamine (TALA), 14-acetyl-TALA, hetisine, and 14-benzoylneoline. One compound TALA with the highest affinity was isolated for further in vitro pharmacodynamic validation and target identification to validate the screen results. Voltage-dependent K⁺ channel was confirmed as a binding target of TALA and 14-acetyl-TALA with high affinities. The online high throughput comparative CMC analysis method is suitable for screening specific active components from herbal medicines by increasing the specificity of screened results and can also be applied to other biological chromatography models.

Rodent models of heart failure: an updated review

Heart failure (HF) is one of the major health and economic burdens worldwide, and its prevalence is continuously increasing. The study of HF requires reliable animal models to study the chronic changes and pharmacologic interventions in myocardial structure and function and to follow its progression toward HF. Indeed, during the past 40 years, basic and translational scientists have used small animal models to understand the pathophysiology of HF and find more efficient ways of preventing and managing patients suffering from congestive HF (CHF). Each species and each animal model has advantages and disadvantages, and the choice of one model over another should take them into account for a good experimental design. The aim of this review is to describe and highlight the advantages and drawbacks of some commonly used HF rodents models, including both non-genetically and genetically engineered models, with a specific subchapter concerning diastolic HF models.

Imaging of early modification in cardiomyopathy: the doxorubicin-induced model

Doxorubicin chemotherapy is effective and widely used to treat acute lymphoblastic leukemia. However, its effectiveness is hampered by a wide spectrum of dose-dependent cardiotoxicity including both morphological and functional changes, affecting primarily the myocardium. Non-invasive imaging techniques are used for the diagnosis and monitoring of these cardiotoxic effects. The purpose of this review is to summarize and compare the most common imaging techniques used in early detection and therapeutic monitoring of doxorubicin-induced cardiotoxicity and the suggested mechanisms of such side effects. Imaging techniques using echocardiography including conventional 2D and 3D echocardiography along with MRI sequences including Tagging, Cine, and quantitative MRI in detecting early myocardial damage are also reviewed. As there is a multitude of reported indices and imaging methods to assess particular functional alterations, we limit this review to the most relevant techniques based on their clinical application and their potential to early detection of doxorubicin-induced cardiotoxic effects.

Cardiotoxicity of anticancer treatments: what the cardiologist needs to know

Cardiotoxicity of anticancer treatments has become an increasingly important clinical problem faced by cardiologists. Left ventricular systolic dysfunction and heart failure generate the most concern, but clinical features and prognosis vary considerably depending on the causative agent. Anthracycline-related cardiomyopathy differs fundamentally from effects associated with newer targeted agents, such as trastuzumab. Other forms of cardiovascular disease that occur as a result of cancer treatment include hypertension, thromboembolic disease, pericardial disease, arrhythmia, and myocardial ischemia. The approach to cardiovascular disease in patients with cancer is often different from that in the general population, not only because of distinct underlying mechanisms and clinical features of their heart disease, but also because of the potential ongoing need for additional cancer treatment as well as the altered duration of anticipated survival. In an effort to maximize both quality of life and survival, cardiologists and oncologists should collaborate with the aim of balancing the risks of cardiotoxicity with the benefits of oncologic therapy.

Pathophysiology and diagnosis of cancer drug induced cardiomyopathy

The clinical manifestations of anti-cancer drug associated cardiac side effects are diverse and can range from acutely induced cardiac arrhythmias to Q-T interval prolongation, changes in coronary vasomotion with consecutive myocardial ischemia, myocarditis, pericarditis, severe contractile dysfunction, and potentially fatal heart failure. The pathophysiology of these adverse effects is similarly heterogeneous and the identification of potential mechanisms is frequently difficult since the majority of cancer patients is not only treated with a multitude of cancer drugs but might also be exposed to potentially cardiotoxic radiation therapy. Some of the targets inhibited by new anti-cancer drugs also appear to be important for the maintenance of cellular homeostasis of normal tissue, in particular during exposure to cytotoxic chemotherapy. If acute chemotherapy-induced myocardial damage is only moderate, the process of myocardial remodeling can lead to progressive myocardial dysfunction over years and eventually induce myocardial dysfunction and heart failure. The tools for diagnosing anti-cancer drug associated cardiotoxicity and monitoring patients during chemotherapy include invasive and noninvasive techniques as well as laboratory investigations and are mostly only validated for anthracycline-induced cardiotoxicity and more recently for trastuzumab-associated cardiac dysfunction.

Doxorubicin as an antioxidant: maintenance of myocardial levels of lycopene under doxorubicin treatment

The mechanism of doxorubicin-induced cardiotoxicity remains controversial. Wistar rats (n=96) were randomly assigned to a control (C), lycopene (L), doxorubicin (D), or doxorubicin+lycopene (DL) group. The L and DL groups received lycopene (5 mg/kg body wt/day by gavage) for 7 weeks. The D and DL groups received doxorubicin (4 mg/kg body wt intraperitoneally) at 3, 4, 5, and 6 weeks and were killed at 7 weeks for analyses. Myocardial tissue lycopene levels and total antioxidant performance (TAP) were analyzed by HPLC and fluorometry, respectively. Lycopene metabolism was determined by incubating (2)H(10)-lycopene with intestinal mucosa postmitochondrial fraction and lipoxygenase and analyzed with HPLC and APCI mass spectroscopy. Myocardial tissue lycopene levels in DL and L were similar. TAP adjusted for tissue protein were higher in myocardium of D than those of C (P=0.002). Lycopene metabolism study identified a lower oxidative cleavage of lycopene in D as compared to those of C. Our results showed that lycopene was not depleted in myocardium of lycopene-supplemented rats treated with doxorubicin and that higher antioxidant capacity in myocardium and less oxidative cleavage of lycopene in intestinal mucosa of doxorubicin-treated rats suggest an antioxidant role of doxorubicin rather than acting as a prooxidant.

Doxorubicin-Induced MAPK Activation in Hepatocyte Cultures Is Independent of Oxidant Damage

Doxorubicin (DOX) is a potent anticancer drug, whose clinical use is limited on account of its toxicity. DOX cytotoxic effects have been associated with reactive oxygen species (ROS) generated during drug metabolism. ROS induce signaling cascades leading to changes in the phosphorylation status of target proteins, which are keys for cell survival or apoptosis. The mitogen-activated protein kinase (MAPK) cascades are routes activated in response to oxidative stress. In this work, the effects of DOX on cytotoxicity, indicators of oxidative stress (malondialdehyde -MDA- and GSH), and the phosphorylation status of extracellular signal-regulated kinases (ERKs), c-Jun N-terminal kinases (JNKs), and p38 kinases were analyzed in primary cultures of rat hepatocytes. DOX (1-50 microM) did not modify lactate dehydrogenase (LDH) release into the medium, the levels of MDA (determined by high-performance liquid chromatography [HPLC]) or the intracellular GSH during the incubation time up to 6 h. GSH levels from mitochondria extracted by Percoll gradient from cultured hepatocytes were not modified by DOX, thus excluding its depletion or any impaired mitochondrial uptake. Characterization of proteins by Western blot analysis revealed that DOX increased phosphorylation of p38 kinases and JNK1 and JNK2 in a dose- and time-dependent manner. DOX also increased ERK2 phosphorylation at latter time points. In conclusion, DOX triggers activation of ERK, JNK, and p38 kinases in primary cultures of rat hepatocytes independently of oxidant damage.

Effects of angiotensin II receptor blocker (candesartan) in daunorubicin-induced cardiomyopathic rats

BACKGROUND

Daunorubicin is an anthracycline anti-tumor agent; anthracycline chemotherapy in cancer can cause severe cardiomyopathy leading to a frequently fatal congestive heart failure; the first-line treatment is diuretics and digoxin. Recently, angiotensin-converting enzyme inhibitors have been shown to be effective in the treatment of such toxicity. The purpose of this study was to investigate the effects of angiotensin II type-1 receptor antagonist (candesartan) in a rat model of daunorubicin-induced cardiomyopathy.

METHODS

Rats were treated with a cumulative dose of 9 mg/kg body weight daunorubicin (i.v.). 28 days later, after the development of cardiomyopathy, animals were randomly assigned to candesartan-treated (5 mg/kg/day, p.o.) or vehicle-treated groups; age-matched normal rats were used as the control group. Candesartan treatment was continued for 28 days. Hemodynamic and echocardiographic parameters were measured, cardiac protein and mRNA were analyzed, and histopathological analyses of myocardial fibrosis, cell size and apoptosis were conducted.

RESULTS

Following cardiomyopathy, left ventricular end diastolic pressure and left ventricular systolic dimension were significantly elevated; while % fractional shortening and Doppler E/A ratio were significantly reduced. Cardiomyopathic hearts showed significant increases in % fibrosis, % apoptosis, and myocyte diameter/body weight ratio; candesartan treatment reversed these changes. Fas-L protein overexpression in myopathic hearts was significantly suppressed by treatment with candesartan. Moreover, SERCA2 mRNA and protein expression were both down-regulated in myopathic hearts and restored to normal by candesartan treatment, significantly.

CONCLUSIONS

Our findings suggest that candesartan treatment significantly improved the left ventricular function and reversed the myocardial pathological changes investigated in this model of daunorubicin-induced cardiomyopathy; suggesting its potentials in limiting daunorubicin cardiotoxicity.

Susceptibility to cartap-induced lethal effect and diaphragmatic injury via ocular exposure in rabbits

Cartap is extensively used to control agricultural pests. Pertinent literatures have indicated that it causes no eye irritation [D.E. Ray, Insecticides derived from plants and other organisms, in: W.J. Hayes, E.R. Laws (Eds.), Handbook of Insecticide Toxicology, Classes of Insecticides, vol. 2, Academic Press, New York, 1991, p. 611; C. Tomlin, Cartap, in: C. Tomlin (Ed.), The Insecticide Manual, 12th ed., British Crop Protection Council, Surrey, UK, 2000, p. 144]; however, the instillation of a little cartap through the eye has caused death in rabbits. The aim of this study was to determine the ocular toxicity of cartap in New Zealand White rabbits. Cartap was directly instilled into the low conjunctival sac of eyes, at doses of 0, 5, 7.5, 10 and 12.5 mg/kg body weight. The changes in the enzymes and isoenzymes of creatine kinase (CK), lactate dehydrogenase (LD), as well as pathological changes in the muscles of the heart, thigh and diaphragm were determined in the cartap-treated rabbits. Moreover, the neuromuscular effect of cartap was examined using the isolated rabbit phrenic-nerve diaphragm model. The results indicated that rabbits developed severe signs and they died within 20 min of ocular instillation. The ocular LD50 of cartap was 8.1 mg/kg body weight. Treatment with cartap increased the activities of CK and LD enzymes and their isoenzymes, CK-1, CK-2, and CK-3 in serum, and CK-3 and LD-5 in the diaphragm. Microscopically, hypercontraction bands and the rupture of myofibers of the diaphragm were observed in dead rabbits. Cartap did not affect nerve-evoked twitch but induced irreversible contracture and twitch depression on the isolated rabbit's diaphragm. These results indicate that the rabbit is susceptible to cartap toxicity; the effect of cartap caused contracture and damage to the diaphragm might play a pivotal role in respiratory paralysis and death of rabbits during intoxication.

Esmolol is antiarrhythmic in doxorubicin-induced arrhythmia in cultured cardiomyocytes - determination by novel rapid cardiomyocyte assay

Cardiac toxicity is an uncommon but potentially serious complication of cancer therapy, especially with anthracyclines. One of the most effective anticancer drugs is doxorubicin, but its value is limited by the risk of developing cardiomyopathy and ventricular arrhythmia. When applied to a network of periodically contracting cardiomyocytes in culture, doxorubicin induces rhythm disturbances. Using a novel rapid assay based on non-invasive ion-conductance microscopy we show that the beta-antagonist esmolol can restore rhythm in doxorubicin-treated cultures of cardiomyocytes. Moreover, esmolol pre-treatment can protect the culture from doxorubicin-induced arrhythmia.

Anthracycline cardiotoxicity in transgenic mice overexpressing SR Ca2+-ATPase

Chronic anthracycline administration results in a time- and dose-dependent cardiomyopathy. The Ca-ATPase of the sarcoplasmic reticulum, SERCA2, has been implicated as a principal target for anthracycline-induced cardiotoxicity. This hypothesis predicts that improved SERCA2 function would provide protection from cardiotoxic effects of anthracycline administration. Doxorubicin was administered (1.7 mg/kg three times weekly; cumulative dose of 20 mg/kg) to 10 transgenic mice that overexpressed SERCA2 and to 10 isogenic littermates. Survival was monitored for 60 days and histologic comparisons were made of cardiac tissue. Survival in the transgenic mice was worse (1/10 60-day survivors) compared to isogenic control mice (7/10 60-day survivors). There was a greater degree of histologic damage exhibited in hearts from transgenic mice compared to isogenic controls when all available hearts were examined. These data do not support a role of SERCA2 in ameliorating anthracycline cardiotoxicity.

Effects of docosahexaenoic acid on [Ca(2+)](i) increase induced by doxorubicin in ventricular rat cardiomyocytes

The clinical use of doxorubicin (DXR) is limited by cardiotoxicity partially due to interference with intracellular Ca(2+) homeostasis and involving the activation of the sarcoplasmic reticulum (SR) Ca(2+) release channels. It is known that docosahexaenoic acid (DHA) is able to potentiate the sensitivity of cancer cells to DXR. The aim of our study was to further evaluate the effects of DHA on [Ca(2+)](i) overload induced by DXR in adult rat ventricular cardiomyocytes in order to verify if DHA interferes with DXR-induced cardiotoxicity too. [Ca(2+)](i) was measured by microfluorimetry. Our data demonstrated that 100 microM DXR induced a statistically significant [Ca(2+)](i)-increase in cardiomyocytes perfused with CaCl(2) Krebs solution (from 135.7 +/- 15 nM to 560.2 +/- 49 nM, n = 9, p < 0.01) and with Ca(2+)-free Krebs solution (from 89.3 +/- 15 nM to 551.1 +/- 35 nM, n = 9, p < 0.01). Treatment with 10 microM DHA for 20 min significantly suppressed DXR [Ca(2+)](i)- increase in cells perfused with CaCl(2) Krebs solution (142.3 +/- 12 nM, n = 9, p < 0.01) and in Ca(2+)-free procedures (100.4 +/- 12 nM, n = 9, p < 0.01). Caffeine 10 mM significantly increased [Ca(2+)](i) in cardiomyocytes perfused with CaCl(2) Krebs solution (from 135.7 +/- 15 nM to 979.2 +/- 17.8 nM, n = 9, p < 0.01) and with Ca(2+)-free Krebs solution (from 89.3 +/- 15 nM to 891.1 +/- 30 nM, n = 9, p < 0.01). Treatment with 10 microM DHA for 20 min suppressed caffeine [Ca(2+)](i)-increase in cardiomyocytes perfused with CaCl(2) Krebs solution (174.2 +/- 28 nM, n = 9, p < 0.01) and in Ca(2+)-free procedures (161.9 +/- 34 nM, n = 9, p < 0.01). In conclusion, our results suggest that DHA is able to prevent acute modifications of calcium homeostasis induced by DXR probably interfering with SR Ca(2+) release channels.

Doxorubicin and C-13 deoxydoxorubicin effects on ryanodine receptor gene expression

Chronic anthracycline administration to rabbits causes impairment of cardiac contractility and decreased gene expression of the calcium-induced calcium release channel of sarcoplasmic reticulum (SR), the ryanodine receptor (RYR2). The C-13 hydroxy metabolite (doxorubicinol), formed in the heart, has been hypothesized to contribute to anthracycline cardiotoxicity. C-13 deoxydoxorubicin is an analog unable to form the C-13 hydroxy metabolite. Therefore, doxorubicin, C-13 deoxydoxorubicin, or saline was administered to rabbits (1 mg/kg iv twice weekly for 8 weeks). Left ventricular fractional shortening (LVFS) was decreased by chronic treatment with doxorubicin (28 +/- 2%; P < 0.05), but not C-13 deoxydoxorubicin (33 +/- 2%) compared to age-matched pair-fed controls. Doxorubicin, but not C-13 deoxydoxorubicin, caused a significant reduction (P < 0.02) in the ratio of RYR2/Ca-Mg ATPase (SERCA2) mRNA levels (0.57 +/- 0.1 vs 1.22 +/- 0.2, respectively) in the left ventricle. This suggests that doxorubicinol may contribute to the downregulation of cardiac RYR2 expression in chronic doxorubicin cardiotoxicity.

Contradistinction between doxorubicin and epirubicin: in-vivo metabolism, pharmacokinetics and toxicodynamics after single- and multiple-dosing in rats

There is compelling in-vitro evidence that the evaluation of doxorubicin or epirubicin pharmacokinetics based solely on plasma concentration may not fully elucidate the differences between the two drugs. Both compounds bind to erythrocytes and their different binding to haemoglobin may influence their disposition in the body. The purpose of the present study was to compare the pharmacokinetics and metabolism of doxorubicin and epirubicin based on the plasma concentration, amount associated with blood cells and simultaneous monitoring of biliary and urinary elimination of unchanged drug and metabolites after single- and multiple-dose injections. The level of sarcoplasmic reticulum Ca2+ATPase in the heart was also measured as a biomarker of cardiotoxicity. Male Sprague-Dawley rats were treated in a parallel design with doxorubicin or epirubicin on a multiple-dosing basis (4 mg kg(-1) per week) or as a single dose injection (20 mg kg(-1)). Blood, urine and bile samples were collected periodically after each dose in the multiple-dosing regimen and the single dose injection, and at the end of each experiment the hearts were removed. The concentrations of each drug in plasma, blood cells, bile and urine samples were determined, and by simultaneous curve-fitting of plasma and bile data according to compartmental analysis, the pharmacokinetic parameters and constants were estimated. The concentration of drug associated with blood cells was analysed according to non-compartmental analysis. The bile and urine samples provided the in-vivo metabolic data. The level of Ca2+ATPase in the heart, determined by Western blotting, was used as the toxicodynamic parameterto correlate with the kinetic data. Multiple-dosing regimens reduced the total plasma clearance and increased the area under the plasma concentration-time curve of both drugs. Also, the area under the curve of doxorubicin associated with blood cells increased with the weekly doses, and the related mean residence time (MRT) and apparent volume of distribution (Vdss) were steadily reduced. In contrast to doxorubicin, the MRT and Vdss of epirubicin increased significantly. Metabolic data indicated significant differences in the level of alcohol and aglycones metabolites. Doxorubicinol and doxorubicin aglycones were significantly greater than epirubicinol and epirubicin aglycone, whereas epirubicinol aglycone was greater than doxorubicinol aglycone. The area under the blood cells concentration-time curve correlated linearly with the changes in Ca2+ATPase net intensity. The results of this study demonstrate the importance of the kinetics of epirubicin and doxorubicin associated with blood cells. Linear correlation between the reduction of net intensity of the biomarker with the area under the curve of doxorubicin associated with blood cells confirms that the differences between the two compounds are related to their interaction with blood cells. This observation together with the observed differences in metabolism may underline a significant role for blood cells in distribution and metabolism of doxorubicin and epirubicin.

Chronic adriamycin treatment impairs myocardial interstitial neuronal release of norepinephrine and epinephrine

Although chronic adriamycin (doxorubicin) treatment is known to induce cardiomyopathic heart failure with sympathetic neurohumoral activation in a dose-dependent manner, its effect on local neuronal catecholamine release at the cardiac sympathetic nerve terminals remains to be clearly determined. Using a cardiac microdialysis technique, we measured dialysate norepinephrine (NE) and epinephrine (Epi) concentrations as indices of myocardial interstitial NE and Epi levels. respectively, in rabbits with chronic adriamycin treatment (ADR) (4 mg/kg/week, 6 weeks, n = 8) and in control rabbits (CNT) (n = 6). Exocytotic release was evoked by the local administration of KCl (100 mM) through the dialysis probe. Basal levels of NE and Epi did not differ between the ADR and CNT groups (NE, 11.6 +/- 6.6 vs. 20.4 +/- 17.2 pg/ml; Epi, 4.0 +/- 0.1 vs. 4.6 +/- 1.7 pg/ml: mean +/- SD). The exocytotic release was suppressed in the ADR compared with the CNT group (NE, 191.4 +/- 144.7 vs. 760.5 +/- 337.8 pg/ml; p < 0.05: Epi, 4.2 +/- 0.4 vs. 20.8 +/- 9.9 pg/ml; p < 0.05). We conclude that chronic adriamycin treatment impairs the neuronal exocytotic release of catecholamine at the cardiac sympathetic nerve terminals.

Doxorubicin and mechanical performance of cardiac trabeculae after acute and chronic treatment: a review

Doxorubicin, a very potent and often used anti-cancer drug, has a wide spectrum of biological activity. Classic studies have demonstrated that doxorubicin and other members of the anthracycline family intercalate with DNA and partially uncoil the double-stranded helix. Doxorubicin has a high affinity for cell nuclei: as much as 60% of the total intracellular amount of doxorubicin is found in the nucleus. Once binding to DNA occurs, several consequences may ensue. The binding of anthracyclines to DNA inhibits DNA polymerase and nucleic acid synthesis. In addition, anthracyclines are known to stabilize the otherwise cleavable complex between DNA and homodimeric topoisomerase II enzyme subunits, resulting in the formation of protein-linked DNA double strand breaks. In tumor cells, these anthracycline-induced perturbations are believed to result in a final common pathway of endonucleolytic DNA fragmentation known as apoptosis. Because proliferation is an important determinant of tumor growth, interference with the genome is regarded as the primary cause of the anti-tumor action of doxorubicin. Intercalation with DNA may not be important in the cardiotoxicity associated with doxorubicin therapy (see next section), because cardiac cell proliferation in humans stops after 2 months of age. This review is focussed on the effects of doxorubicin on mechanical performance in skinned cardiac trabeculae after acute and chronic administration of doxorubicin. We look especially at the mechanical performance and the molecular changes observed and related to mechanical performance.

Daunorubicin cardiotoxicity: evidence for the importance of the quinone moiety in a free-radical-independent mechanism

Anthracyclines, such as daunorubicin (Daun), and other quinone-containing compounds can stimulate the formation of toxic free radicals. The present study tests the hypothesis that the quinone moiety of Daun, by increasing free-radical production, disrupts sarcoplasmic reticulum (SR) function and thereby inhibits myocardial contractility in vitro. We compared Daun with its quinone-deficient analogue, 5-iminodaunorubicin (5-ID), using experimental interventions to produce various contractile states that depend on SR function. At concentrations of Daun or 5-ID that did not alter contractility (dF/dt) of steady-state contractions (1 Hz) in electrically paced atria isolated from adult rabbits, only Daun significantly attenuated the positive inotropic effects on dF/dt of increased rest intervals (PRP; post-rest potentiation) or increased stimulation frequencies. Attenuation was to 98+/-6% at 1 Hz, and 73+/-8 and 67+/-8% for 30 and 60 sec PRP, respectively, and 73+/-3 and 63 +/-3% at 2 and 3 Hz, respectively, for 88 microM Daun (P<0.05, vs pre-drug baseline values, mean +/- SEM). These effects of Daun were similar to those of caffeine (2 mM), an agent well known to deplete cardiac SR calcium. We also examined the effect of Daun in isolated neonatal rabbit atria, which lack mature, functional SR; Daun did not alter the force-frequency relationship or PRP contractions. Additional studies in Ca(2+)-loaded SR microsomes indicated that both Daun and 5-ID opened Ca(2+) release channels, with Daun being 20-fold more potent than 5-ID in this respect. Neither anthracycline, however, induced free-radical formation in SR preparations (assayed via nicking of supercoiled DNA) prior to stimulating Ca(2+) release. Thus, our results indicate that Daun impairs myocardial contractility in vitro by selectively interfering with SR function; the quinone moiety of Daun appears to mediate this cardiotoxic effect, acting through a mechanism that does not involve free radicals.