Preclinical assessment of anthracycline cardiotoxicity in laboratory animals: predictiveness and pitfalls

Doxorubicin concentrations in bone tumour-relevant tissues after bolus and continuous infusion: a randomized porcine microdialysis study

PURPOSE

Doxorubicin is a widely used chemotherapeutic drug that can be administered intravenously as both a bolus infusion and a continuous infusion. The latter is believed to lower the risk of cardiotoxicity, which is a critical long-term complication of doxorubicin treatment. The local tissue concentrations of doxorubicin will be reflected in both treatment efficacy and toxicity, but very limited information is available. The aim of this study was to measure the concentration of doxorubicin after continuous and bolus infusion in tissue compartments around a typical location of a bone tumour.

METHODS

Sixteen pigs (female, Danish Landrace, mean weight 77 kg) were randomized into two groups of eight. Both groups received an intravenous infusion of 150 mg doxorubicin; Group 1 received a bolus infusion (10-15 min) and Group 2 received a continuous infusion (6 h). Before infusion, microdialysis catheters were placed intravenously and in four bone tumour-relevant tissue compartments (cancellous bone, subcutaneous tissue, synovial fluid of the knee joint and muscle tissue). Sampling was done (n = 15) over 24 h, and venous blood samples were collected as a reference.

RESULTS

Area under the concentration-time curve (AUC0-24 h) for plasma (total concentration) was significantly different between the two groups, while peak drug concentration (Cmax) was significantly higher in two compartments (plasma and synovial fluid of the knee joint) in Group 1 compared to Group 2. Overall, the unbound tissue concentrations were extremely low with values below 0.20 µg/mL.

CONCLUSION

The pharmacokinetic profile for doxorubicin in the investigated tissues is very similar when comparing bolus and 6 h continuous infusion.

Novel PLGA-based nanoformulation decreases doxorubicin-induced cardiotoxicity

Nanotechnology has the potential to provide formulations of antitumor agents with increased selectivity towards cancer tissue thereby decreasing systemic toxicity. This in vivo study evaluated the potential of novel nanoformulation based on poly(lactic-co-glycolic acid) (PLGA) to reduce the cardiotoxic potential of doxorubicin (DOX). In vivo toxicity of PLGADOX was compared with clinically approved non-PEGylated, liposomal nanoformulation of DOX (LipoDOX) and conventional DOX form (ConvDOX). The study was performed using Wistar Han rats of both sexes that were treated intravenously for 28 days with 5 doses of tested substances at intervals of 5 days. Histopathological analyses of heart tissues showed the presence of myofiber necrosis, degeneration processes, myocytolysis, and hemorrhage after treatment with ConvDOX, whereas only myofiber degeneration and hemorrhage were present after the treatment with nanoformulations. All DOX formulations caused an increase in the troponin T with the greatest increase caused by convDOX. qPCR analyses revealed an increase in the expression of inflammatory markers IL-6 and IL-8 after ConvDOX and an increase in IL-8 expression after lipoDOX treatments. The mass spectra imaging (MSI) of heart tissue indicates numerous metabolic and lipidomic changes caused by ConvDOX, while less severe cardiac damages were found after treatment with nanoformulations. In the case of LipoDOX, autophagy and apoptosis were still detectable, whereas PLGADOX induced only detectable mitochondrial toxicity. Cardiotoxic effects were frequently sex-related with the greater risk of cardiotoxicity observed mostly in male rats.

Novel metallo-β-lactamases inhibitors restore the susceptibility of carbapenems to New Delhi metallo-lactamase-1 (NDM-1)-harbouring bacteria

BACKGROUND AND PURPOSE

The production of metallo-β-lactamases is a major mechanisms adopted by bacterial pathogens to resist carbapenems. Repurposing approved drugs to restore the efficacy of carbapenems represents an efficient and cost-effective approach to fight infections caused by carbapenem resistant pathogens.

EXPERIMENTAL APPROACH

The nitrocefin hydrolysis assay was employed to screen potential New Delhi metallo-lactamase-1 (NDM-1) inhibitors from a commercially available U.S. Food and Drug Administration (FDA) approved drug library. The mechanism of inhibition was clarified by metal restoration, inductively coupled plasma mass spectrometry (ICP-MS) and molecular dynamics simulation. The in vitro synergistic antibacterial effect of the identified inhibitors with meropenem was determined by the checkerboard minimum inhibitory concentration (MIC) assay, time-dependent killing assay and combined disc test. Three mouse infection models were used to further evaluate the in vivo therapeutic efficacy of combined therapy.

KEY RESULTS

Twelve FDA-approved compounds were initially screened to inhibit the ability of NDM-1 to hydrolyse nitrocefin. Among these compounds, dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid were demonstrated to inhibit all tested metallo-β-lactamases and showed an in vitro synergistic bactericidal effect with meropenem against metallo-β-lactamases-producing bacteria. Dexrazoxane, embelin and candesartan cilexetil are metal ion chelating agents, while the inhibition of NDM-1 by nordihydroguaiaretic acid involves its direct binding to the active region of NDM-1. Furthermore, these four drugs dramatically rescued the treatment efficacy of meropenem in three infection models.

CONCLUSIONS AND IMPLICATIONS

Our observations indicated that dexrazoxane, embelin, candesartan cilexetil and nordihydroguaiaretic acid are promising carbapenem adjuvants against metallo-β-lactamases-positive carbapenem resistant bacterial pathogens.

Reduction of Doxorubicin-Induced Cardiotoxicity by Co-Administration of Smart Liposomal Doxorubicin and Free Quercetin: In Vitro and In Vivo Studies

Doxorubicin is one of the most effective chemotherapeutic agents; however, it has various side effects, such as cardiotoxicity. Therefore, novel methods are needed to reduce its adverse effects. Quercetin is a natural flavonoid with many biological activities. Liposomes are lipid-based carriers widely used in medicine for drug delivery. In this study, liposomal doxorubicin with favorable characteristics was designed and synthesized by the thin-film method, and its physicochemical properties were investigated by different laboratory techniques. Then, the impact of the carrier, empty liposomes, free doxorubicin, liposomal doxorubicin, and quercetin were analyzed in animal models. To evaluate the interventions, measurements of cardiac enzymes, oxidative stress and antioxidant markers, and protein expression were performed, as well as histopathological studies. Additionally, cytotoxicity assay and cellular uptake were carried out on H9c2 cells. The mean size of the designed liposomes was 98.8 nm, and the encapsulation efficiency (EE%) was about 85%. The designed liposomes were anionic and pH-sensitive and had a controlled release pattern with excellent stability. Co-administration of liposomal doxorubicin with free quercetin to rats led to decreased weight loss, creatine kinase (CK-MB), lactate dehydrogenase (LDH), and malondialdehyde (MDA), while it increased the activity of glutathione peroxidase, catalase, and superoxide dismutase enzymes in their left ventricles. Additionally, it changed the expression of NOX1, Rac1, Rac1-GTP, SIRT3, and Bcl-2 proteins, and caused tissue injury and cell cytotoxicity. Our data showed that interventions can increase antioxidant capacity, reduce oxidative stress and apoptosis in heart tissue, and lead to fewer complications. Overall, the use of liposomal doxorubicin alone or the co-administration of free doxorubicin with free quercetin showed promising results.

A Comprehensive Review of Dilated Cardiomyopathy in Pre-clinical Animal Models in Addition to Herbal Treatment Options and Multi-modality Imaging Strategies

Dilated cardiomyopathy (DCM) is distinguished by ventricular chamber expansion, systolic dysfunction, and normal left ventricular (LV) wall thickness, and is mainly caused due to genetic or environmental factors; however, its aetiology is undetermined in the majority of patients. The focus of this work is on pathogenesis, small animal models, as well as the herbal medicinal approach, and the most recent advances in imaging modalities for patients with dilated cardiomyopathy. Several small animal models have been proposed over the last few years to mimic various pathomechanisms that contribute to dilated cardiomyopathy. Surgical procedures, gene mutations, and drug therapies are all characteristic features of these models. The pros and cons, including heart failure stimulation of extensively established small animal models for dilated cardiomyopathy, are illustrated, as these models tend to procure key insights and contribute to the development of innovative treatment techniques for patients. Traditional medicinal plants used as treatment in these models are also discussed, along with contemporary developments in herbal therapies. In the last few decades, accurate diagnosis, proper recognition of the underlying disease, specific risk stratification, and forecasting of clinical outcome, have indeed improved the health of DCM patients. Cardiac magnetic resonance (CMR) is the bullion criterion for assessing ventricular volume and ejection fraction in a reliable and consistent direction. Other technologies, like strain analysis and 3D echocardiography, have enhanced this technique's predictive and therapeutic potential. Nuclear imaging potentially helps doctors pinpoint the causative factors of left ventricular dysfunction, as with cardiac sarcoidosis and amyloidosis.

Cardiotoxicity of Chemical Substances: An Emerging Hazard Class

(1) Background: Human health risks and hazards from chemical substances are well regulated internationally. However, cardiotoxicity, is not defined as a stand-alone hazard and therefore there are no defined criteria for the classification of substances as cardiotoxic. Identifying and regulating substances that cause cardiovascular adverse effects would undoubtedly strengthen the national health systems. (2) Methods: To overcome the aforementioned gap, a roadmap is proposed for identifying regulatory criteria from animal studies and endorse legislation in order to classify substances as cardiotoxic. The roadmap consists of: (i) the identification of the appropriate animal species and strains; (ii) the identification of the lines of scientific evidence (e.g., histopathological, biochemical and echocardiographic indices etc.) from animal studies with relevance to humans; (iii) the statistical analysis and meta-analysis for each line of scientific evidence after exposure to well-established cardiotoxicants to humans (e.g., anthracyclines) in order to identify threshold values or range of normal and/ or altered values due to exposure; (iv) validation of the above described lines of evidence in animals exposed to other alleged cardiotoxic substances (e.g., anabolic androgen steroids (AAS) and pesticides); (v) establishment of mechanisms of action based on information of either known or alleged cardiotoxicants; and (vi) introduction of novel indices and in silico methods. (3) Results: Preliminary results in rats indicate a clear distinction from normal values to values measured in rats exposed to anthracyclines regarding left ventricle (LV) fractional shortening (FS) and LV ejection fraction (EF). A distinctive pattern is similarly observed for Creatine Kinase-Myocardial Band isoenzyme (CK-MB) and cardiac tissue glutathione (GSH). These findings are encouraging and indicate that there is room for targeted research to this end, and that these specific indices and biochemical markers should be further investigated in order to be developed to regulatory criteria. (4) Conclusions: Further research should be conducted by both the scientific and regulatory community that aims to clearly define the cardiotoxicity hazard caused by chemicals and develop a full set of scientific criteria.

Human iPSC-Cardiomyocytes as an Experimental Model to Study Epigenetic Modifiers of Electrophysiology

The epigenetic landscape and the responses to pharmacological epigenetic regulators in each human are unique. Classes of epigenetic writers and erasers, such as histone acetyltransferases, HATs, and histone deacetylases, HDACs, control DNA acetylation/deacetylation and chromatin accessibility, thus exerting transcriptional control in a tissue- and person-specific manner. Rapid development of novel pharmacological agents in clinical testing-HDAC inhibitors (HDACi)-targets these master regulators as common means of therapeutic intervention in cancer and immune diseases. The action of these epigenetic modulators is much less explored for cardiac tissue, yet all new drugs need to be tested for cardiotoxicity. To advance our understanding of chromatin regulation in the heart, and specifically how modulation of DNA acetylation state may affect functional electrophysiological responses, human-induced pluripotent stem-cell-derived cardiomyocyte (hiPSC-CM) technology can be leveraged as a scalable, high-throughput platform with ability to provide patient-specific insights. This review covers relevant background on the known roles of HATs and HDACs in the heart, the current state of HDACi development, applications, and any adverse cardiac events; it also summarizes relevant differential gene expression data for the adult human heart vs. hiPSC-CMs along with initial transcriptional and functional results from using this new experimental platform to yield insights on epigenetic control of the heart. We focus on the multitude of methodologies and workflows needed to quantify responses to HDACis in hiPSC-CMs. This overview can help highlight the power and the limitations of hiPSC-CMs as a scalable experimental model in capturing epigenetic responses relevant to the human heart.

Anthraquinones as Inhibitors of SOS RAS-GEF Activity

Recent breakthroughs have reignited interest in RAS GEFs as direct therapeutic targets. To search for new inhibitors of SOS GEF activity, a repository of known/approved compounds (NIH-NACTS) and a library of new marine compounds (Biomar Microbial Technologies) were screened by means of in vitro RAS-GEF assays using purified, bacterially expressed SOS and RAS constructs. Interestingly, all inhibitors identified in our screenings (two per library) shared related chemical structures belonging to the anthraquinone family of compounds. All our anthraquinone SOS inhibitors were active against the three canonical RAS isoforms when tested in our SOS GEF assays, inhibited RAS activation in mouse embryonic fibroblasts, and were also able to inhibit the growth of different cancer cell lines harboring WT or mutant RAS genes. In contrast to the commercially available anthraquinone inhibitors, our new marine anthraquinone inhibitors did not show in vivo cardiotoxicity, thus providing a lead for future discovery of stronger, clinically useful anthraquinone SOS GEF blockers.

Analysis of Models of Doxorubicin-Induced Cardiomyopathy in Rats and Mice. A Modern View From the Perspective of the Pathophysiologist and the Clinician

Today the pharmacological possibilities of treating cancer are expanding and as a result, life expectancy is increasing against the background of chemotherapy and supportive treatment. In the conditions of successful antitumor treatment, complications associated with its toxic effect on healthy tissues and organs began to come to the fore. Anthracycline cardiomyopathy was the first serious cardiovascular complication to draw the attention of oncologists and cardiologists around the world. Anthracycline drugs such as doxorubicin, epirubicin, idarubicin are still widely used in oncological practice to treat a wide range of solid and hematological malignancies. Doxorubicin-induced cardiomyopathy is closely associated with an increase in oxidative stress, as evidenced by reactive oxygen species (ROS) nduced damage such as lipid peroxidation, and decreased levels of antioxidants. Myofibrillar destruction and dysregulation of intracellular calcium are also important mechanisms, usually associated with doxorubicin-induced cardiotoxicity. Despite the abundance of data on various mechanisms involved in the implementation of doxorubicin-induced cardiotoxicity, a final understanding of the mechanism of the development of doxorubicin cardiomyopathy has not yet been formed. It poses the most significant challenges to the development of new methods of prevention and treatment, as well as to the unambiguous choice of a specific treatment regimen using the existing pharmacological tools. In order to resolve these issues new models that could reflect the development of the chemotherapy drugs effects are needed. In this review we have summarized and analyzed information on the main existing models of doxorubicin cardiomyopathy using small laboratory animals. In addition, this paper discusses further areas of research devoted to the development and validation of new improved models of doxorubicin cardiomyopathy suitable both for studying the mechanisms of its implementation and for the preclinical drugs effectiveness assessment.

Common mechanistic pathways in cancer and heart failure. A scientific roadmap on behalf of the Translational Research Committee of the Heart Failure Association (HFA) of the European Society of Cardiology (ESC)

The co-occurrence of cancer and heart failure (HF) represents a significant clinical drawback as each disease interferes with the treatment of the other. In addition to shared risk factors, a growing body of experimental and clinical evidence reveals numerous commonalities in the biology underlying both pathologies. Inflammation emerges as a common hallmark for both diseases as it contributes to the initiation and progression of both HF and cancer. Under stress, malignant and cardiac cells change their metabolic preferences to survive, which makes these metabolic derangements a great basis to develop intersection strategies and therapies to combat both diseases. Furthermore, genetic predisposition and clonal haematopoiesis are common drivers for both conditions and they hold great clinical relevance in the context of personalized medicine. Additionally, altered angiogenesis is a common hallmark for failing hearts and tumours and represents a promising substrate to target in both diseases. Cardiac cells and malignant cells interact with their surrounding environment called stroma. This interaction mediates the progression of the two pathologies and understanding the structure and function of each stromal component may pave the way for innovative therapeutic strategies and improved outcomes in patients. The interdisciplinary collaboration between cardiologists and oncologists is essential to establish unified guidelines. To this aim, pre-clinical models that mimic the human situation, where both pathologies coexist, are needed to understand all the aspects of the bidirectional relationship between cancer and HF. Finally, adequately powered clinical studies, including patients from all ages, and men and women, with proper adjudication of both cancer and cardiovascular endpoints, are essential to accurately study these two pathologies at the same time.

Safety Considerations of Cancer Nanomedicine-A Key Step toward Translation

The rate of translational effort of nanomedicine requires strategic planning of nanosafety research in order to enable clinical trials and safe use of nanomedicine in patients. Herein, the experiences that have emerged based on the safety data of classic liposomal formulations in the space of oncology are discussed, along with a description of the new challenges that need to be addressed according to the rapid expansion of nanomedicine platform beyond liposomes. It is valuable to consider the combined use of predictive toxicological assessment supported by deliberate investigation on aspects such as absorption, distribution, metabolism, and excretion (ADME) and toxicokinetic profiles, the risk that may be introduced during nanomanufacture, unique nanomaterials properties, and nonobvious nanosafety endpoints, for example. These efforts will allow the generation of investigational new drug-enabling safety data that can be incorporated into a rational infrastructure for regulatory decision-making. Since the safety assessment relates to nanomaterials, the investigation should cover the important physicochemical properties of the material that may lead to hazards when the nanomedicine product is utilized in humans.

What is considered cardiotoxicity of anthracyclines in animal studies

Anthracyclines are commonly used anticancer drugs with well-known and extensively studied cardiotoxic effects in humans. In the clinical setting guidelines for assessing cardiotoxicity are well-established with important therapeutic implications. Cardiotoxicity in terms of impairment of cardiac function is largely diagnosed by echocardiography and based on objective metrics of cardiac function. Until this day, cardiotoxicity is not an endpoint in the current general toxicology and safety pharmacology preclinical studies, although other classes of drugs apart from anthracyclines, along with everyday chemicals have been shown to manifest cardiotoxic properties. Also, in the relevant literature there are not well-established objective criteria or reference values in order to uniformly characterize cardiotoxic adverse effects in animal models. This in depth review focuses on the evaluation of two important echocardiographic indices, namely ejection fraction and fractional shortening, in the literature concerning anthracycline administration to rats as the reference laboratory animal model. The analysis of the gathered data gives promising results and solid prospects for both, defining anthracycline cardiotoxicity objective values and delineating the guidelines for assessing cardiotoxicity as a separate hazard class in animal preclinical studies for regulatory purposes.

Evaluation of cardiac dysfunction in adult zebrafish using high frequency echocardiography

AIMS

Recently, the zebrafish has gained attention as an innovative experimental model to decipher molecular and cellular mechanisms involved in cardiovascular development and diseases. Nevertheless, the use of zebrafish models has been challenged because the transparency of these fish, which allows for accurate cardiac evaluation, disappears in adulthood. In this study, the epicardial outline method was performed to investigate the feasibility of echocardiography in assessing cardiac function in pathological adult zebrafish.

MATERIALS AND METHODS

We attempted to estimate heart failure in adult zebrafish treated with three distinct regulators of cardiac function: phenylhydrazine hydrochloride (PHZ), doxorubicin (DOX), and ethanol. B-mode and Doppler images were evaluated at frequencies of up to 50 MHz and 40 MHz, respectively. The correlation between alterations in cardiac function, haemoglobin concentration, and myocardial histopathology were assessed.

KEY FINDINGS

Cardiac output (CO) in PHZ-treated zebrafish was significantly higher than that in control zebrafish (151 ± 67 vs. 84 ± 37 μl/min, P = 0.004), whereas ejection fraction (EF) was lower (36.3 ± 10.9 vs. 50.9 ± 8.7%, P < 0.001), indicating typical high output heart failure derived from anaemia. Additionally, ventricular dysfunction in DOX-treated zebrafish was characterised by low CO (57 ± 38 μl/min) and EF (28.8 ± 10.4%), accompanied by an enlarged ventricle in diastole and systole, representing low output heart failure. For ethanol-treated zebrafish, EF was markedly reduced (39.6 ± 7.2%) indicating a dilated heart, while CO remained unchanged (90 ± 40 μl/min).

SIGNIFICANCE

The epicardial outline method is an effective way of using echocardiography to assess cardiac dysfunction in pathological adult zebrafish, unlocking a major bottleneck in this research field with limited cardiac functional assays.

Doxorubicin Exposure Causes Subacute Cardiac Atrophy Dependent on the Striated Muscle-Specific Ubiquitin Ligase MuRF1

Background Anthracycline chemotherapeutics, such as doxorubicin, are used widely in the treatment of numerous malignancies. The primary dose-limiting adverse effect of anthracyclines is cardiotoxicity that often presents as heart failure due to dilated cardiomyopathy years after anthracycline exposure. Recent data from animal studies indicate that anthracyclines cause cardiac atrophy. The timing of onset and underlying mechanisms are not well defined, and the relevance of these findings to human disease is unclear. Methods and Results Wild-type mice were sacrificed 1 week after intraperitoneal administration of doxorubicin (1-25 mg/kg), revealing a dose-dependent decrease in cardiac mass ( R2=0.64; P<0.0001) and a significant decrease in cardiomyocyte cross-sectional area (336±29 versus 188±14 µm2; P<0.0001). Myocardial tissue analysis identified a dose-dependent upregulation of the ubiquitin ligase, MuRF1 (muscle ring finger-1; R2=0.91; P=0.003) and a molecular profile of muscle atrophy. To investigate the determinants of doxorubicin-induced cardiac atrophy, we administered doxorubicin 20 mg/kg to mice lacking MuRF1 (MuRF1-/-) and wild-type littermates. MuRF1-/- mice were protected from cardiac atrophy and exhibited no reduction in contractile function. To explore the clinical relevance of these findings, we analyzed cardiac magnetic resonance imaging data from 70 patients in the DETECT-1 cohort and found that anthracycline exposure was associated with decreased cardiac mass evident within 1 month and persisting to 6 months after initiation. Conclusions Doxorubicin causes a subacute decrease in cardiac mass in both mice and humans. In mice, doxorubicin-induced cardiac atrophy is dependent on MuRF1. These findings suggest that therapies directed at preventing or reversing cardiac atrophy might preserve the cardiac function of cancer patients receiving anthracyclines.

Role of microRNAs in doxorubicin-induced cardiotoxicity: an overview of preclinical models and cancer patients

Cardiotoxicity is a well-known side effect of doxorubicin (DOX), but the mechanisms leading to this phenomenon are still not completely clear. Prediction of drug-induced dysfunction onset is difficult and is still largely based on detection of cardiac troponin (cTn), a circulating marker of heart damage. In the last years, several investigations focused on the possible involvement of microRNAs (miRNAs) in DOX-induced toxicity in vitro, with contrasting results. Recently, several groups employed animal models to mimic patient’s condition, investigate the biological pathways perturbed by DOX, and identify diagnostic markers of cardiotoxicity. We reviewed the results from several studies investigating cardiac miRNAs expression in rodent models of DOX-treatment. We also discussed the data from two publications indicating the possible use of circulating miRNA as biomarkers of DOX-induced cardiotoxicity. Unfortunately, limited information was derived from these studies, as selection methods of candidate-miRNAs and heterogeneity in cardiotoxicity assessment greatly hampered the novelty and robustness of the findings. Nevertheless, at least one circulating miRNA, miR-1, showed a good potential as early biomarker of drug-mediated cardiac dysfunction onset. The use of animal models to investigate DOX-induced cardiotoxicity surely helps narrowing the gap between basic research and clinical practice. Despite this, several issues, including selection of relevant miRNAs and less-than-optimal assessment of cardiotoxicity, greatly limited the results obtained so far. Nonetheless, the association of patients-based studies with the use of preclinical models may be the key to address the many unanswered questions regarding the pathophysiology and early detection of cardiotoxicity.

Toxicological study of doxorubicin-loaded PLGA nanoparticles for the treatment of glioblastoma

Doxorubicin loaded in poloxamer 188-coated PLGA nanoparticles (Dox-NP + P188) was shown to produce a high antitumor effect against the experimental orthotopic 101.8 glioblastoma in rats upon intravenous administration. The objective of the present study was to evaluate the acute and chronic toxicity of this nanoformulation. The parent drug was used as a reference formulation. Acute toxicity of doxorubicin-loaded nanoparticles in mice and rats was similar to that of free doxorubicin. The chronic toxicity study was conducted in Chinchilla rabbits; the treatment regimen consisted of 30 daily intravenous injections using two dosage levels: 0.22 mg/kg/day and 0.15 mg/kg/day. The study included assessment of the body weight, hematological parameters, blood biochemical parameters, urinalysis, and pathomorphological evaluation of the internal organs. The results of the study demonstrated that the hematological, cardiac, and testicular toxicity of doxorubicin could be reduced by binding the drug to PLGA nanoparticles. Coating of PLGA nanoparticles with poloxamer 188 contributed to the reduction of cardiotoxicity. Functional and morphological abnormalities caused by the nanoparticulate doxorubicin were dose-dependent and reversible. Altogether these results provide evidence that the PLGA-based nanoformulation not only might enable the broadening of the spectrum of doxorubicin activity but also an improvement of its safety profile.

Using Zebrafish for Investigating the Molecular Mechanisms of Drug-Induced Cardiotoxicity

Over the last decade, the zebrafish (Danio rerio) has emerged as a model organism for cardiovascular research. Zebrafish have several advantages over mammalian models. For instance, the experimental cost of using zebrafish is comparatively low; the embryos are transparent, develop externally, and have high fecundity making them suitable for large-scale genetic screening. More recently, zebrafish embryos have been used for the screening of a variety of toxic agents, particularly for cardiotoxicity testing. Zebrafish has been shown to exhibit physiological responses that are similar to mammals after exposure to medicinal drugs including xenobiotics, hormones, cancer drugs, and also environmental pollutants, including pesticides and heavy metals. In this review, we provided a summary for recent studies that have used zebrafish to investigate the molecular mechanisms of drug-induced cardiotoxicity. More specifically, we focused on the techniques that were exploited by us and others for cardiovascular toxicity assessment and described several microscopic imaging and analysis protocols that are being used for the estimation of a variety of cardiac hemodynamic parameters.

Comparable efficacy and less toxicity of pegylated liposomal doxorubicin versus epirubicin for neoadjuvant chemotherapy of breast cancer: a case-control study

Background

Pegylated liposomal doxorubicin (PLD) and epirubicin are both superior variants of doxorubicin and are commonly applied as basic chemotherapeutics in breast cancer. However, the direct comparison of their efficacy and side effects has not been adequately reported. This study aimed to compare the efficacy and toxicity of PLD and epirubicin as neoadjuvant chemotherapy for invasive breast cancer.

Patients and methods

Women (n = 43) with invasive breast cancer who received neoadjuvant chemotherapy with the regimens containing PLD (PLD group) were analyzed and 1:2 matched with those (n = 86) who received regimens containing epirubicin (epirubicin group) according to clinical TNM staging and taxane combination.

Results

The PLD group achieved similar clinical response rate in neoadjuvant chemotherapy compared to the epirubicin group (76.7% vs 75.6%). The PLD group had a lower rate of grade 3 & 4 neutropenia (30.2% vs 60.5%), vomiting (7.0% vs 28.0%), and grade 3 & 4 alopecia (9.3% vs 43.0%), yet a higher rate of mouth ulceration (46.5% vs 11.7%). For the cardiac toxicity, the PLD group had a significantly lower rate of ventricular premature beat compared with the epirubicin group (7.0% vs 20.9%, p = 0.043), and cardiac ultrasonography monitoring showed non-significantly less PLD group patients’ left ventricular ejection fraction decline more than 10% compared with the epirubicin group (4.7% vs 8.1%, p = 0.463).

Conclusion

In neoadjuvant chemotherapy for invasive breast cancer, PLD provides potentially similar efficacy and relatively less toxicity compared to epirubicin.

Experimental Models of Cardiovascular Diseases: Overview

Cardiovascular disease is one of the most common causes of deaths in clinics. Experimental models of cardiovascular diseases are essential to understand disease mechanism, to provide accurate diagnoses, and to develop new therapies. Large numbers of experimental models have been proposed and replicated by many laboratories in the past. Models with significant advantages are chosen and became more popular. Particularly, feasibility, reproducibility, and human disease resemblance are the common key factors for frequently used cardiovascular disease models. In this chapter, we provide a brief overview of these experimental models used for in vitro, in vivo, and in silico studies of cardiovascular diseases.

Morphine enhances doxorubicin-induced cardiotoxicity in the rat

Interventions to reduce the cardiotoxicity of doxorubicin are clinically relevant. Pharmacological preconditioning mimicking ischemic preconditioning has been demonstrated with morphine and represents an acceptable clinical intervention. The purpose of this study was to examine if pretreatment in vivo with morphine could reduce doxorubicin-induced cardiotoxicity ex vivo in a rat model. Wistar rats were divided into six groups and pretreated with an intraperitoneal (i.p.) injection of 3 or 10 mg/kg morphine, 1 mg/kg naloxone and saline, 1 mg/kg naloxone and 3 mg/kg morphine or saline, 60 min before excision of the heart. Biochemical indices such as troponin T (TnT) and hydrogen peroxide (H₂O₂) in effluate were measured together with physiological parameters in Langendorff hearts before and after doxorubicin infusion (2 mg/mL 0.05 mL/min for 45 min). Myocardial content of doxorubicin was measured at the end of infusion. Pretreatment with morphine, irrespective of dosage, produced a significant loss in left ventricular-developed pressure and an increase of TnT and H₂O₂ in effluate before doxorubicin infusion (p < 0.05). Morphine also produced a significant increase in left ventricular end-diastolic pressure and an increase of TnT and H₂O₂ in effluate (p < 0.05) at the end of doxorubicin infusion. Naloxone, a non-selective opioid receptor antagonist, abolished the effects of morphine both before and after doxorubicin infusion. Morphine, irrespective of dosage, increased myocardial content of doxorubicin compared to pretreatment with saline (p < 0.05). Pretreatment with morphine is associated with a cardiodepressive effect and enhances cardiotoxicity of doxorubicin measured by increased myocardial accumulation of doxorubicin and physiological and biochemical indices. The negative effects observed in our rat model are abolished by naloxone.

Safety Pharmacology of Anticancer Agents

The safety pharmacology testing for anticancer agents has historically differed for small molecule pharmaceutical drugs versus large-molecule biopharmaceuticals. For pharmaceutical drugs, dedicated safety pharmacology studies have been conducted according to the ICH M3 (R2), ICH 7A, and ICH S7B guidance documents. For biopharmaceuticals, safety pharmacology endpoints have been incorporated into the repeated-dose toxicology studies according to ICHS6 (R1). However, the introduction of the ICH S9 guidance document for the nonclinical evaluation for anticancer pharmaceuticals has allowed for a streamlined approach for both types of molecules to facilitate access of new potential therapeutics to cancer patients and to reduce the number of animal studies. Examples of the testing strategies that have previously been employed for some representative anticancer agents are provided, and their predictivity to adverse events noted in the clinic is discussed.

Diazoxide protects against doxorubicin-induced cardiotoxicity in the rat

AIM

Chemotherapy with doxorubicin is limited by cardiotoxicity. Free radical generation and mitochondrial dysfunction are thought to contribute to doxorubicin-induced cardiac failure. In this study we wanted to investigate if opening of mitochondrial KATP-channels by diazoxide is protective against doxorubicin cardiotoxicity, and if 5-hydroxydecanoate (5-HD), a selective mitochondrial KATP-channel antagonist, abolished any protection by this intervention.

METHODS

Wistar rats were divided into 7 groups (n = 6) and followed for 10 days with 5 intervention groups including the following treatments: (1) Diazoxide and doxorubicin, (2) diazoxide and 5-hydroxydecanoate (5-HD), (3) 5-HD and doxorubicin, (4) diazoxide and saline and (5) 5-HD and saline. On day 1, 3, 5 and 7 the animals received intraperitoneal (i.p.) injections with 10 mg/kg diazoxide and/or 40 mg/kg 5-HD, 30 minutes before i.p. injections with 3.0 mg/kg doxorubicin. One control group received only saline injections and the other control group received saline 30 minutes prior to 3.0 mg/kg doxorubicin. On day 10 the hearts were excised and Langendorff-perfused. Cardiac function was assessed by an intraventricular balloon and biochemical effects by release of hydrogen peroxide (H2O2) and troponin-T (TnT) in effluate from the isolated hearts, and by myocardial content of doxorubicin.

RESULTS

Doxorubicin treatment produced a significant loss in left ventricular developed pressure (LVDP) (p < 0.05) and an increase in both H2O2 and TnT release in effluate (p < 0.05). Diazoxide significantly attenuated the decrease in LVDP (p < 0.05) and abolished the increased release of H2O2 and TnT (p < 0.05). 5-HD abolished the effects of pretreatment with diazoxide, and these effects were not associated with reduced myocardial accumulation of doxorubicin.

CONCLUSIONS

Pretreatment with diazoxide attenuates doxorubicin-induced cardiac dysfunction in the rat, measured by physiological indices and TnT and H2O2 in effluate from isolated hearts. The effect could be mediated by opening of mitochondrial KATP-channels, reduced doxorubicin-associated free radical generation and decreased cardiomyocyte damage. Diazoxide represents a promising protective intervention against doxorubicin-induced acute cardiotoxicity.

Cardiotoxicity evaluation of anthracyclines in zebrafish (Danio rerio)

Drug-induced cardiotoxicity is a leading factor for drug withdrawals, and limits drug efficacy and clinical use. Therefore, new alternative animal models and methods for drug safety evaluation have been given great attention. Anthracyclines (ANTs) are widely prescribed anticancer agents that have a cumulative dose relationship with cardiotoxicity. We performed experiments to study the toxicity of ANTs in early developing zebrafish embryos, especially their effects on the heart. LC50 values for daunorubicin, pirarubicin, doxorubicin (DOX), epirubicin and DOX-liposome at 72 h post-fertilization were 122.7 μM, 111.9 μM, 31.2 μM, 108.3 μM and 55.8 μM, respectively. At the same time, zebrafish embryos were exposed to ANTs in three exposure stages and induced incomplete looping of the heart tube, pericardia edema and bradycardia in a dose-dependent manner, eventually leading to death. DOX caused the greatest heart defects in the treatment stages and its liposome reduced the effects on the heart, while daunorubicin produced the least toxicity. Genes and proteins related to heart development were also identified to be sensitive to ANT exposure and downregulated by ANTs. It revealed ANTs could disturb the heart formation and development. ANTs induced cardiotoxicity in zebrafish has similar effects in mammalian models, indicating that zebrafish may have a potential value for assessment of drug-induced developmental cardiotoxicity.

A short-time model to study relevant indices of cardiotoxicity of doxorubicin in the rat

AIM

Short-time models (STM) to study the cardiotoxicity (acute or chronic) of doxorubicin in rats are of interest to assess protective interventions and pathways. STM promotes more ethical animal treatment with less stress, and at a lower cost compared to established long-time models (LTM). We wanted to investigate if an STM of 9 d yields the same information regarding cardiotoxicity as an LTM of 9 weeks.

METHODS

Male Wistar rats received identical drug administration protocols in STM and LTM. The two intervention groups (n = 6) received intraperitoneal (i.p.) injections of 2 mg/kg doxorubicin every day for five consecutive days, with a total cumulative dose of 10 mg/kg. The two control groups (n = 6), received an equivalent volume of saline injected every day for five consecutive days. Hearts from STM and LTM were excised and Langendorff-perfused after 9 d or 9 weeks, respectively, after the first drug injection. Cardiotoxicity was assessed in paced Langendorff hearts by a release of hydrogenperoxide (H2O2) and troponin T (TnT) in effluent, by myocardial accumulation of doxorubicin and its metabolite doxorubicinol, and by physiological parameters recorded during pressure, or volume-regulated perfusion.

RESULTS

In STM, hearts exposed to doxorubicin demonstrated a 15% reduction in left ventricular developed pressure (LVDP) irrespective of flow mode, and a 13% increase in aortic pressure (AoP), during volume-regulated perfusion, an index of coronary resistance, compared to controls. Left ventricular end-diastolic pressure (LVEDP) was increased by 72% during pressure-regulated perfusion and 100% during volume-regulated perfusion in STM. In LTM, hearts exposed to doxorubicin demonstrated a 40% reduction in LVDP during pressure-regulated perfusion and a 20% reduction during volume-regulated perfusion. LVEDP was 70% higher in doxorubicin-treated hearts during pressure-regulated perfusion and 80% higher during volume-regulated perfusion. In addition, aortic pressure was increased by 30% during volume-regulated perfusion. In both STM and LTM, hearts exposed to doxorubicin demonstrated a higher H2O2 and TnT release, compared to respective controls. The difference was most pronounced in STM. Myocardial content of doxorubicin was detectable in both STM and LTM. However, doxorubicinol was only detectable in STM.

CONCLUSION

STM is comparable to LTM to study relevant indices of cardiotoxicity of doxorubicin in rat hearts. Biochemical differences are more pronounced in STM, while contractile differences are more pronounced in LTM. STM could be a preferred model for preliminary studies of protective interventions.

Iron chelators with topoisomerase-inhibitory activity and their anticancer applications

SIGNIFICANCE

Iron and topoisomerases are abundant and essential cellular components. Iron is required for several key processes such as DNA synthesis, mitochondrial electron transport, synthesis of heme, and as a co-factor for many redox enzymes. Topoisomerases serve as critical enzymes that resolve topological problems during DNA synthesis, transcription, and repair. Neoplastic cells have higher uptake and utilization of iron, as well as elevated levels of topoisomerase family members. Separately, the chelation of iron and the cytotoxic inhibition of topoisomerase have yielded potent anticancer agents.

RECENT ADVANCES

The chemotherapeutic drugs doxorubicin and dexrazoxane both chelate iron and target topoisomerase 2 alpha (top2α). Newer chelators such as di-2-pyridylketone-4,4,-dimethyl-3-thiosemicarbazone and thiosemicarbazone -24 have recently been identified as top2α inhibitors. The growing list of agents that appear to chelate iron and inhibit topoisomerases prompts the question of whether and how these two distinct mechanisms might interplay for a cytotoxic chemotherapeutic outcome.

CRITICAL ISSUES

While iron chelation and topoisomerase inhibition each represent mechanistically advantageous anticancer therapeutic strategies, dual targeting agents present an attractive multi-modal opportunity for enhanced anticancer tumor killing and overcoming drug resistance. The commonalities and caveats of dual inhibition are presented in this review.

FUTURE DIRECTIONS

Gaps in knowledge, relevant biomarkers, and strategies for future in vivo studies with dual inhibitors are discussed.

Gestational doxorubicin alters fetal thyroid-brain axis

Administration of chemotherapy during pregnancy may represent a big risk factor for the developing brain, therefore we studied whether the transplacental transport of doxorubicin (DOX) may affect the development of neuroendocrine system. DOX (25 mg/kg; 3 times interaperitoneally/week) was given to pregnant rats during whole gestation period. The disturbances in neuroendocrine functions were investigated at gestation day (GD) 15 and 20 by following the maternal and fetal thyroid hormone levels, fetal nucleotides (ATP, ADP, AMP) levels and adenosine triphosphatase (Na(+), K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase) activities in two brain regions, cerebrum and cerebellum. In control group, the levels of maternal and fetal serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and fetal serum growth hormone (GH) increased from days 15 to 20, whereas in the DOX group, a decrease in maternal and fetal T4, T3 and increase in TSH levels (hypothyroid status) were observed. Also, the levels of fetal GH decreased continuously from GD 15 to 20 with respect to control group. In cerebrum and cerebellum, the levels of fetal nucleotides and the activities of fetal ATPases in control group followed a synchronized course of development. The fetal hypothyroidism due to maternal administration of DOX decreased the levels of nucleotides, ATPases activities, and total adenylate, instead, the adenylate energy charge showed a trend to an increase in both brain regions at all ages tested. These alterations were dose- and age-dependent and this, in turn, may impair the nerve transmission. Finally, DOX may act as neuroendocrine disruptor causing hypothyroidism and fetal brain energetic dysfunction.

Evaluation of miR-122 and other biomarkers in distinct acute liver injury in rats

The detection of drug-induced hepatotoxicity remains an important safety issue in drug development. A liver-specific microRNA species, microRNA-122 (miR-122), has recently shown potential for predicting liver injury in addition to the standard hepatic injury biomarkers. The objective of this study was to measure miR-122 together with several other liver markers in distinct settings of acute liver toxicity in rats to determine the value of miR-122 as a biomarker for liver injury in this species. Rats were exposed to 3 well-established liver toxicants (acetaminophen, allyl alcohol, and α-naphthyl isothiocyanate), a liver-enzyme inducer (phenobarbital), or a cardiotoxicant (doxorubicin). There was a clear increase in plasma miR-122 following administration of acetaminophen, allyl alcohol, and α-naphthyl isothiocyanate. The response of miR-122 paralleled that of other markers and was consistent with liver injury as indicated by histopathological evaluation. Furthermore, the changes in miR-122 were detected earlier than standard liver injury markers and exhibited a wide dynamic range. In contrast, miR-122 responses to phenobarbital and doxorubicin were low. Based on these findings, miR-122 shows significant promise and may provide added value for assessing liver toxicity in drug development.

Magnetic resonance histology of age-related nephropathy in the Sprague Dawley rat

Magnetic resonance histology (MRH) has become a valuable tool in evaluating drug-induced toxicity in preclinical models. However, its application in renal injury has been limited. This study tested the hypothesis that MRH could detect image-based biomarkers of chronic disease, inflammation, or age-related degeneration in the kidney, laying the foundation for more extensive use in evaluating drug toxicity. We examined the entire intact kidney in a spontaneous model of chronic progressive nephropathy. Kidneys from male Sprague Dawley rats were imaged at 8 weeks (n = 4) and 52 weeks (n =4) on a 9.4 T system dedicated to MR microscopy. Several potential contrast mechanisms were explored to optimize the scanning protocols. Full coverage of the entire kidney was achieved with isotropic spatial resolution at 31 microns (voxel volume = 30 pL) using a gradient recalled echo sequence. Isotropic spatial resolution of 15 microns (voxel volume < 4 pL) was achieved in a biopsy core specimen. Qualitative age-related structural changes, such as renal cortical microvasculature, tubular dilation, interstitial fibrosis, and glomerular architecture, were apparent. The nondestructive 3D images allowed measurement of quantitative differences of kidney volume, pelvis volume, main vessel volume, glomerular size, as well as thickness of the cortex, outer medulla, and inner medulla.

The clinically active PARP inhibitor AG014699 ameliorates cardiotoxicity but does not enhance the efficacy of doxorubicin, despite improving tumor perfusion and radiation response in mice

AG014699 was the first inhibitor of the DNA repair enzyme PARP-1 to enter clinical trial in cancer patients. In addition to enhancing the cytotoxic effect of DNA-damaging chemotherapies, we have previously shown that AG014699 is vasoactive, thereby having the potential to improve drug biodistribution. The effectiveness of the clinical agent doxorubicin is confounded both by poor tumor penetration and cardiotoxicity elicited via PARP hyperactivation. In this study, we analyzed the impact of AG014699 on doxorubicin tolerance and response in breast (MDA-MB-231) and colorectal (SW620, LoVo) tumor models in vitro and in vivo. As anticipated, AG014699 did not potentiate the response to doxorubicin in vitro. In vivo, AG014699 did not influence the pharmacokinetics of doxorubicin; however, it did ameliorate cardiotoxicity. Both toxicity and extent of amelioration were more pronounced in male than in female mice. AG014699 improved vessel perfusion in both MDA-MB-231 and SW620 tumors; however, this neither led to improved tumor-accumulation of doxorubicin nor enhanced therapeutic response. In contrast, when combined with radiotherapy, AG014699 significantly enhanced response both in vitro and in vivo. Real-time assessment of tumor vessel function and companion histologic studies indicate that doxorubicin causes a profound antivascular effect that counters the positive effect of AG014699 on perfusion. These data indicate that although AG014699 can enhance response to some chemotherapeutic drugs via improved delivery, this does not apply to doxorubicin. PARP inhibitors may still be of use to counter doxorubicin toxicity, and if the gender effect translates from rodents to humans, this would have greater effect in males.

Haploinsufficiency of target of rapamycin attenuates cardiomyopathies in adult zebrafish

RATIONALE

Although a cardioprotective function of target of rapamycin (TOR) signaling inhibition has been suggested by pharmacological studies using rapamycin, genetic evidences are still lacking. We explored adult zebrafish as a novel vertebrate model for dissecting signaling pathways in cardiomyopathy.

OBJECTIVE

We generated the second adult zebrafish cardiomyopathy model induced by doxorubicin. By genetically analyzing both the doxorubicin and our previous established anemia-induced cardiomyopathy models, we decipher the functions of TOR signaling in cardiomyopathies of different etiology.

METHODS AND RESULTS

Along the progression of both cardiomyopathy models, we detected dynamic TOR activity at different stages of pathogenesis as well as distinct effects of TOR signaling inhibition. Nevertheless, cardiac enlargement in both models can be effectively attenuated by inhibition of TOR signaling through short-term rapamycin treatment. To assess the long-term effects of TOR reduction, we used a zebrafish target of rapamycin (ztor) mutant identified from an insertional mutagenesis screen. We show that TOR haploinsufficiency in the ztor heterozygous fish improved cardiac function, prevented pathological remodeling events, and ultimately reduced mortality in both adult fish models of cardiomyopathy. Mechanistically, these cardioprotective effects are conveyed by the antihypertrophy, antiapoptosis, and proautophagy function of TOR signaling inhibition.

CONCLUSIONS

Our results prove adult zebrafish as a conserved novel vertebrate model for human cardiomyopathies. Moreover, we provide the first genetic evidence to demonstrate a long-term cardioprotective effect of TOR signaling inhibition on at least 2 cardiomyopathies of distinct etiology, despite dynamic TOR activities during their pathogenesis.

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.

Successful drug development despite adverse preclinical findings part 1: processes to address issues and most important findings

Unexpected adverse preclinical findings (APFs) are not infrequently encountered during drug development. Such APFs can be functional disturbances such as QT prolongation, morphological toxicity or carcinogenicity. The latter is of particular concern in conjunction with equivocal genotoxicity results. The toxicologic pathologist plays an important role in recognizing these effects, in helping to characterize them, to evaluate their risk for man, and in proposing measures to mitigate the risk particularly in early clinical trials. A careful scientific evaluation is crucial while termination of the development of a potentially useful drug must be avoided. This first part of the review discusses processes to address unexpected APFs and provides an overview over typical APFs in particular classes of drugs. If the mode of action (MoA) by which a drug candidate produces an APF is known, this supports evaluation of its relevance for humans. Tailor-made mechanistic studies, when needed, must be planned carefully to test one or several hypotheses regarding the potential MoA and to provide further data for risk evaluation. Safety considerations are based on exposure at no-observed-adverse-effect levels (NOAEL) of the most sensitive and relevant animal species and guide dose escalation in clinical trials. The availability of early markers of toxicity for monitoring of humans adds further safety to clinical studies. Risk evaluation is concluded by a weight of evidence analysis (WoE) with an array of parameters including drug use, medical need and alternatives on the market. In the second part of this review relevant examples of APFs will be discussed in more detail.

Myocardial stunning following combined modality combretastatin-based chemotherapy: two case reports and review of the literature

Myocardial stunning, known as stress cardiomyopathy, broken-heart syndrome, transient left ventricular apical ballooning, and Takotsubo cardiomyopathy, has been reported after many extracardiac stressors, but not following chemotherapy. We report 2 cases with characteristic electrocardiographic and echocardiographic features following combined modality therapy with combretastatin, a vascular-disrupting agent being studied for treatment of anaplastic thyroid cancer. In 1 patient, an ECG performed per protocol 18 hours after drug initiation showed deep, symmetric T-wave inversions in limb leads I and aVL and precordial leads V(2) through V(6). Echocardiography showed mildly reduced overall left ventricular systolic function with akinesis of the entire apex. The patient had mild elevations of troponin I. Coronary angiography revealed no epicardial coronary artery disease. The electrocardiographic and echocardiographic abnormalities resolved after several weeks. The patient remains stable from a cardiovascular standpoint and has not had a recurrence during follow-up. An electrocardiogram performed per protocol in a second patient showed deep, symmetric T-wave inversions throughout the precordial leads and a prolonged QT interval. Echocardiography showed mildly reduced left ventricular function with hypokinesis of the apical-septal wall. Acute coronary syndrome was ruled out, and both the electrocardiographic and echocardiographic changes resolved at follow-up. Although the patient remained pain-free without recurrence of anginal symptoms during long-term follow-up, the patient developed progressive malignancy and died.

ACE inhibition and protection from doxorubicin-induced cardiotoxicity in the rat

The angiotensin converting enzyme inhibitor zofenopril has been shown to possess cardioprotective effects toward myocardial damage induced by chronic doxorubicin treatment in the rat. In the present study we have investigated the relationship between cardioprotection exerted by 2 angiotensin converting enzyme inhibitors (zofenopril and lisinopril) and degree of inhibition of cardiac versus serum angiotensin converting enzyme. Both zofenopril and lisinopril produced a dose-dependent inhibition of serum and cardiac angiotensin converting enzyme in rats (0.1, 1 or 10 mg/kg/day in the diet for 1 week). However, zofenopril at 0.1 mg/kg/day showed a significantly (P < 0.05) greater inhibition of angiotensin converting enzyme in the myocardium than in the serum (delta about 20%). Using dose levels (0.1 mg/kg/day and 10 mg/kg/day) which inhibits partially (about 50%) or almost totally (about 80%) serum angiotensin converting enzyme, we evaluated the effects of zofenopril and lisinopril in preventing cardiac alterations (QalphaT prolongation) induced by chronic treatment with doxorubicin (1.5 mg/kg q7dx5 i.v.). Zofenopril, at a dose level (0.1 mg/kg/ day) that did not affect haemodynamics and only partially inhibits serum angiotensin converting enzyme activity, almost totally prevent the QalphaT lengthening induced by doxorubicin, whereas lisinopril was ineffective at this dose level. At the higher dose level (10 mg/kg/day), both angiotensin converting enzyme inhibitors totally prevented the electrocardiographic alteration induced by chronic doxorubicin administration. Cardioprotection exerted by zofenopril at a dose level that partially inhibits serum angiotensin converting enzyme without affecting haemodynamics, suggests that inhibition of cardiac angiotensin converting enzyme and additional cardioprotective mechanism(s) may have a role in its ability to prevent myocardial damages in the rat subjected to chronic anthracycline treatment.

Prominent cardioprotective effects of third generation beta blocker nebivolol against anthracycline-induced cardiotoxicity using the model of isolated perfused rat heart

Nebivolol is a cardioselective beta-blocker (BB) currently used for the treatment of hypertension. It has mild vasodilating properties attributed to its interaction with the L-arginine/nitric oxide pathway, a property not shared by other BBs. Carvedilol is a nonselective ss-adrenergic receptor antagonist that also blocks alpha1-adrenergic receptors and is a potent antioxidant. Anthracyclines (ANTs), daunorubicin and doxorubicin, are commonly used in the treatment of several tumours, but their cardiac toxicity prevents their use at maximum myelotoxic doses, representing an important problem. In this study, we have evaluated the role of these BBs administered in combination with ANTs (daunorubicin and doxorubicin) on a reduction in cardiac toxicity. The combination of BB and ANTs has reduced the release of GSSG and GSH; in particular, co-treatment with nebivolol to ANTs has shown a significant reduction. The total integrated creatine kinase and troponin T activities were improved by BB and ANTs co-treatment. A significant reduction of their release was observed when hearts were treated with nebivolol. Cardiac tissue activity of gluthatione reductase was not significant and similar among experimental groups. In contrast, gluthatione peroxidise, Mn-superoxide dismutase and nitrite/nitrate release were increased after co-treatment with nebivolol. Finally, three parameters have been used to evaluate the cardiac toxicity of ANTs: the left ventricular pressure developed under a constant perfusion pressure (LVDP), the rate of variation of this parameter during systole (contractility) (LV/dt)max and during diastole (relaxation) (LV(dP/dt)min. Combination with BB has shown a reduction in cardiac toxicity; in particular, nebivolol has exerted the most significant cardioprotective effect.

Use of traditional end points and gene dysregulation to understand mechanisms of toxicity: toxicogenomics in mechanistic toxicology

Microarray technologies can be used to generate massive amounts of gene expression information as an initial step to decipher the molecular mechanisms of toxicologic changes. Identifying genes whose expression is associated with specific toxic end points is an initial step in predicting, characterizing, and understanding toxicity. Analysis of gene function and the chronology of gene expression changes represent additional methods to generate hypotheses of the mechanisms of toxicity. Follow-up experiments are typically required to confirm or refute hypotheses derived from toxicogenomic data. Understanding the mechanism of toxicity for a compound is a critical step in forming a rational plan for developing counterscreens for toxicity and for increasing productivity of research and development while decreasing the risk of late-stage failure in pharmaceutical development.

Combined NT-pro-BNP and CW-Doppler ultrasound cardiac output monitoring (USCOM) in epirubicin and liposomal doxorubicin therapy

BACKGROUND

Chemotherapy with epirubicin is approved in women with breast cancer and is associated with a certain degree of cardiotoxicity.

HYPOTHESIS

Epirubicin changes stroke volume, cardiac output and systemic vascular resistance, while liposomal doxorubicin does not.

METHODS

75 patients with HER-2-positive metastatic breast cancer were continuously measured with CW-Doppler ultrasound for stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) before, during and after drug infusion in combination with NT-pro-BNP before and 10 min after drug infusion.

RESULTS

Epirubicin infusion increased stroke volume significantly in low-level NT-pro-BNP (62+/-23 ml vs. 74+/-29 ml, p=0.004) and high-level NT-pro-BNP (48+/-5 ml vs. 64+/-20 ml, p=0.131), while liposomal doxorubicin infusion increased stroke volume significantly in low-level NT-pro-BNP (54+/-16 ml vs. 67+/-22 ml, p=0.001) and high-level NT-pro-BNP (65+/-22 ml vs. 82+/-27 ml, p=0.001). Cardiac output was significantly increased in epirubicin (p=0.004) by 20% (NT-pro-BNP<125 pg/ml) and not significantly 38% (NT-pro-BNP>125 pg/ml; p=0.144), while in liposomal doxorubicin cardiac output was significantly increased by 23% (NT-pro-BNP<125 pg/ml; p=0.023) and 33% (NT-pro-BNP>125 pg/ml; p=0.001). In liposomal doxorubicin cardiac index was significantly increased by 26% (NT-pro-BNP<125 pg/ml; p=0.021) and 33% (NT-pro-BNP>125 pg/ml; p=0.0001). SVR was significantly reduced during and after epirubicin therapy.

CONCLUSION

Using the CW-Doppler USCOM a different hemodynamic response to epirubicin vs. liposomal doxorubicin is evident. Epirubicin leads to a significant upregulation of stroke volume and cardiac output, which is even more pronounced in the high-level NT-pro-BNP group, while liposomal doxorubicin does not change immediate hemodynamics. No deterioration of cardiac function using the real-time CW-Doppler ultrasound USCOM or an increase in NT-pro-BNP levels was evident during epirubicin or liposomal doxorubicin therapy.