Cardiac troponin T as an indicator of reduced left ventricular contractility in experimental anthracycline-induced cardiomyopathy

Cardiac miRNA expression during the development of chronic anthracycline-induced cardiomyopathy using an experimental rabbit model

Background: Anthracycline cardiotoxicity is a well-known complication of cancer treatment, and miRNAs have emerged as a key driver in the pathogenesis of cardiovascular diseases. This study aimed to investigate the expression of miRNAs in the myocardium in early and late stages of chronic anthracycline induced cardiotoxicity to determine whether this expression is associated with the severity of cardiac damage. Method: Cardiotoxicity was induced in rabbits via daunorubicin administration (daunorubicin, 3 mg/kg/week; for five and 10 weeks), while the control group received saline solution. Myocardial miRNA expression was first screened using TaqMan Advanced miRNA microfluidic card assays, after which 32 miRNAs were selected for targeted analysis using qRT-PCR. Results: The first subclinical signs of cardiotoxicity (significant increase in plasma cardiac troponin T) were observed after 5 weeks of daunorubicin treatment. At this time point, 10 miRNAs (including members of the miRNA-34 and 21 families) showed significant upregulation relative to the control group, with the most intense change observed for miRNA-1298-5p (29-fold change, p < 0.01). After 10 weeks of daunorubicin treatment, when a further rise in cTnT was accompanied by significant left ventricle systolic dysfunction, only miR-504-5p was significantly (p < 0.01) downregulated, whereas 10 miRNAs were significantly upregulated relative to the control group; at this time-point, the most intense change was observed for miR-34a-5p (76-fold change). Strong correlations were found between the expression of multiple miRNAs (including miR-34 and mir-21 family and miR-1298-5p) and quantitative indices of toxic damage in both the early and late phases of cardiotoxicity development. Furthermore, plasma levels of miR-34a-5p were strongly correlated with the myocardial expression of this miRNA. Conclusion: To the best of our knowledge, this is the first study that describes alterations in miRNA expression in the myocardium during the transition from subclinical, ANT-induced cardiotoxicity to an overt cardiotoxic phenotype; we also revealed how these changes in miRNA expression are strongly correlated with quantitative markers of cardiotoxicity.

Preparation and Evaluation of Animal Models of Cardiotoxicity in Antineoplastic Therapy

The continuous development of antineoplastic therapy has significantly reduced the mortality of patients with malignant tumors, but its induced cardiotoxicity has become the primary cause of long-term death in patients with malignant tumors. However, the pathogenesis of cardiotoxicity of antineoplastic therapy is currently unknown, and practical means of prevention and treatment are lacking in clinical practice. Therefore, how to effectively prevent and treat cardiotoxicity while treating tumors is a major challenge. Animal models are important tools for studying cardiotoxicity in antitumor therapy and are of great importance in elucidating pathophysiological mechanisms and developing and evaluating modality drugs. In this paper, we summarize the existing animal models in antitumor therapeutic cardiotoxicity studies and evaluate the models by observing the macroscopic signs, echocardiography, and pathological morphology of the animals, aiming to provide a reference for subsequent experimental development and clinical application.

Role of Biomarkers in Prediction of Cardiotoxicity During Cancer Treatment

Purpose of review

As cancer survivor rates improve with early screening and modern treatment options, cardiotoxicity is becoming an increasing problem. It is imperative for physicians to recognize adverse events early so that appropriate measures can be taken before advanced and permanent cardiac dysfunction ensues. In this review, we will evaluate the literature surrounding current cardiac biomarkers in the detection of cardiotoxicity during cancer treatment as well as discuss the role of emerging novel biomarkers.

Recent findings

Troponin and brain natriuretic peptides show promise in the detection of subclinical cardiotoxicity during cancer treatment. In addition to identifying late complications among cancer survivors, they have the potential to predict patients who are at risk of developing cardiotoxicity prior to the initiation of cancer therapy. However, there are also conflicting data due to varying study design.

Summary

Although biomarkers are an attractive option in the detection of cardiotoxicity among cancer patients, current recommendations surrounding its role are based on expert consensus opinion. Further research with appropriately designed prospective trials is required to guide optimal clinical practice.

In vivo and in vitro assessment of the role of glutathione antioxidant system in anthracycline-induced cardiotoxicity

The clinical usefulness of anthracycline antineoplastic drugs is limited by their cardiotoxicity. Its mechanisms have not been fully understood, although the induction of oxidative stress is widely believed to play the principal role. Glutathione is the dominant cellular antioxidant, while glutathione peroxidase (GPx) together with glutathione reductase (GR) constitutes the major enzymatic system protecting the cardiac cells from oxidative damage. Therefore, this study aimed to assess their roles in anthracycline cardiotoxicity. Ten-week intravenous administration of daunorubicin (DAU, 3 mg/kg weekly) to rabbits induced heart failure, which was evident from decreased left ventricular ejection fraction and release of cardiac troponins to circulation. However, no significant changes in either total or oxidized glutathione contents or GR activity were detected in left ventricular tissue of DAU-treated rabbits when compared with control animals. GPx activity in the cardiac tissue significantly increased. In H9c2 rat cardiac cells, 24-h DAU exposure (0.1-10 μM) induced significant dose-dependent toxicity. Cellular content of reduced glutathione was insignificantly decreased, oxidized glutathione and GR activity were unaffected, and GPx activity was significantly increased. Neither buthionine sulfoximine (BSO, glutathione biosynthesis inhibitor) nor 2-oxo-4-thiazolidine-carboxylic acid (OTC, glutathione biosynthetic precursor) had significant effects on DAU cytotoxicity. This contrasted with model oxidative injury induced by hydrogen peroxide, which cytotoxicity was increased by BSO and decreased by OTC. In conclusion, our results suggest that the dysfunction of glutathione antioxidant system does not play a causative role in anthracycline cardiotoxicity.

Cardiac troponin is the most effective translational safety biomarker for myocardial injury in cardiotoxicity

There is an overwhelming weight of evidence that certifies cardiac troponin (cTn) as the preferred, defacto, translational, safety biomarker for myocardial injury in cardiotoxicity. As well as being the gold standard for cardiac injury in man, it has been widely used for clinical assessment and monitoring of cardiac toxicity in humans being treated for cancer. Furthermore, several dozen preclinical published studies have directly confirmed its effectiveness in laboratory animals for assessment of cardiotoxicity. It is gradually being reverse translated from human into animal use as a safety biomarker. Its use is especially merited whenever there is any safety signal indicating potential cardiotoxicity and its required inclusion as a routine biomarker in preclinical safety studies seems on the horizon. There are some considerations that are unique to use of cTn assays in animals. Lack of awareness of these has, historically, significantly inhibited the introduction of cTn as a safety biomarker in preclinical toxicology. Firstly, cross-species reactivity is usually but not always high. Secondly, there is a background of cardiac injury that needs to be controlled for, including spontaneous cardiomyopathy in Sprague Dawley rats, and inappropriate blood collection methods. Also, there are faster kinetics of clearance in rats than for humans. Also, coincident muscle injury is frequent with cardiotoxicity and requires a skeletal muscle biomarker. Because cTn assays were developed for detection of gross cardiac necrosis, such as occurs with myocardial infarct, the more sensitive assays should be used for preclinical studies. However, analytic sensitivity is higher for standard preclinical studies than for clinical diagnostic testing because of use of concurrent controls and use of batch analysis that eliminates interassay variability. No other biomarker of myocardial injury comes close to cTn in effectiveness, including CK-MB, LDH-1 and 2, myoglobin, and FABP3. In addition to the use of cTn for monitoring active myocardial degeneration, there is growing evidence that measurements of brain natriuretic peptide (BNP) may be effective for monitoring drug-induced left ventricular dysfunction.

In vitro and in vivo examination of cardiac troponins as biochemical markers of drug-induced cardiotoxicity

Cardiac troponin T (cTnT) and troponin I (cTnI) are becoming acknowledged as useful biochemical markers of drug-induced cardiotoxicity. In this study we examined the release kinetics of cTnT and cTnI using an in vitro model of isolated rat neonatal ventricular cardiomyocytes (NVCM, 72h treatment with 0.1-3microM of daunorubicin) and compared it with data from a rabbit model of chronic anthracycline-induced cardiomyopathy in vivo (3mg/kg of daunorubicin weekly, 10 weeks). In cell-culture media, the cTnI and cTnT concentrations were concentration- and time-dependently increasing in response to daunorubicin exposure and were negatively exponentially related to cardiomyocyte viability. With 3microM daunorubicin, the relative increase of AUC of cTnT and cTnI was 2.4- and 5.3-fold higher than the increase of LDH activity, respectively. In rabbits, the daunorubicin-induced cardiomyopathy was associated with progressive increase of both cTnT and cTnI. Although the correlation between cTnT and cTnI cumulative release (AUCs) was found (R=0.81; P<0.01) and both cardiac troponins corresponded well with the echocardiographically-assessed systolic dysfunction (R=0.83 and 0.81 for cTnT and cTnI, respectively; P<0.001), the first significant increase in cTnI levels was observed earlier (at a cumulative daunorubicin dose of 200mg/m(2)) than with cTnT (350mg/m(2)). In conclusion, our study has confirmed cTnT and cTnI as very sensitive and specific markers of anthracycline-induced cardiotoxicity. The troponins can become not only the bridge between the clinical and experimental studies of drug-induced cardiotoxicity but also the linkage between the preclinical experiments in vitro and in vivo.

Troponin as a marker of myocardiac damage in drug-induced cardiotoxicity

Cardiac troponins T and I (cTnT and cTnI) are becoming the serum biomarkers of choice for monitoring potential drug-induced myocardial injury in both clinical and preclinical studies. The utility of cardiac troponins has been mainly demonstrated following the administration of antineoplastic drugs and beta-sympathomimetics, although the routine use of these markers in the monitoring in patients who received anthracyclines therapy is far from settled. Unlike the previous markers, which suffered from numerous shortages, the main advantages of cardiac troponins are their high specificity and sensitivity, wide diagnostic window and the possibility to use commercially available assays in clinical settings as well as in a broad range of laboratory animals. Nevertheless, in spite of vigorous research in this area, a number of questions are still unanswered and these are discussed in this review. The main problems seem to be the lack of standardisation of variety of troponin immunoassays, the assessment of suitable cutoff for drug-induced cardiotoxicity and determination of critical diagnostic window related to the optimal timing of sample collection, which may be drug-dependent.

Study of daunorubicin cardiotoxicity prevention with pyridoxal isonicotinoyl hydrazone in rabbits

Risk of cardiotoxicity is the most serious drawback of the clinical usefulness of anthracycline antineoplastic antibiotics, which however, remain among the most powerful and widely employed anticancer drugs. In this study we have used daunorubicin-induced cardiomyopathy in rabbits as a model to investigate possible cardioprotective effects of pyridoxal isonicotinoyl hydrazone (PIH)-a principal representative of a novel group of aroylhydrazone iron chelators. Three groups of animals were used: a control group (n=11; i.v. saline), daunorubicin-treated animals (n=11; 3mg/kg, i.v.), and animals pretreated with PIH (n=9, 25 mg/kg, i.p.) 60 min before daunorubicin administration. All substances were administered once weekly for 10 weeks. Repeated administration of daunorubicin caused premature death in four animals and induced conspicuous histopathological changes in the myocardium, progressive and significant impairment of systolic heart function (a decrease in left ventricular dP/dt(max), ejection fraction, an increase in the pre-ejection period/left ventricular ejection time index), and a gradual increase in cardiac troponin T plasma concentrations. On the contrary, all the PIH-treated animals have survived all daunorubicin applications. Furthermore, in this group, the daunorubicin-induced cardiac changes were in most functional, biochemical as well as morphological parameters less pronounced than in the group receiving daunorubicin alone. Hence, PIH and other aroylhydrazones merit further investigation as potentially protective agents against anthracycline-induced cardiotoxicity.