The clinical importance of the cardiotoxicity of anthracyclines requires the availability of preclinical models able to predict the cardiotoxicity of novel anthracycline analogs in reference to doxorubicin or of cardioprotectors aimed at circumventing the deleterious effects of these drugs. The reference model has been defined long ago and has proven its validity. Weanling rabbits given weekly injections of doxorubicin for 4 months developed a cardiomyopathy, which can be assessed from a clinical and pathological point of view. Models in other animals such as rats or mice were similarly implemented, also with long-term exposures to the drug, resulting in cardiac failure and severe pathological alterations, which could be graded for comparison. Starting from the evidence that the damage caused by anthracyclines on cardiomyocytes was immediate after each injection and that the functional efficiency of the myocardium should be affected long before the morphological alterations become detectable, we developed a short-term model studying the cardiac performances of isolated perfused hearts of rats that had been treated within 12 days by repetitive administrations of the molecule(s) to be tested. This model provided the data expected from clinical experience: epirubicin appeared less cardiotoxic than doxorubicin; liposomal formulations appeared less cardiotoxic than free drug formulations; dexrazoxane strongly protected against doxorubicin cardiotoxicity. We were then able to show that paclitaxel could potentialize doxorubicin cardiotoxicity, but that docetaxel did not so; or that a high dose of dexrazoxane brought significantly higher protection than a conventional dose. Based upon these contributions, we can encourage the use of the short-term model of isolated perfused rat heart to screen the preclinical cardiotoxicity of anthracycline molecules, formulations and combinations.
"For example, the delay between anthracycline administration and the occurrence of clinical symptoms is generally 1–2 years in adults but may extend to much longer periods in children3. In experimental animal models, some side effects of DOX treatment can take weeks or months to occur4. The cardiotoxic effects of DOX often result in a cardiomyopathy that is similar to dilated cardiomyopathy. "
[Show abstract][Hide abstract] ABSTRACT: To investigate the role of matrix metalloproteinases (MMPs) in the responses of rats to a prolonged doxorubicin (DOX) treatment.
Male Wistar rats were used. DOX was administered by intraperitoneal injections of seven doses (cumulative dose was 15 mg/kg). Control animals were treated with saline. Tissue or plasma samples were collected at four and eight weeks after the application of the last dose. Protein levels were determined by immunoblot assay, and MMP activities were measured by gelatin zymography. Superoxide content was analyzed using a lucigenin chemiluminescence assay and superoxide dismutase (SOD) activities with a SOD assay kit. Qualitative structural alterations of the heart were characterized by transmission electron microscopy.
Systolic blood pressure was higher in DOX-treated rats as compared with the control rats at 8 weeks after treatment. In contrast, there were no differences in the heart rate between the control and DOX-treated rats. DOX treatment caused marked heterogeneous subcellular alterations of cardiomyocytes and structural disorganizations of the cardiac extracellular space. The effects of DOX were linked to a stimulation of plasma MMP-2 and MMP-9 activities that had already increased by 4 weeks after the end of the treatment. In the left ventricle, however, DOX only led to increased MMP-2 activation at 8 weeks after the end of treatment. These changes in tissue MMP-2 were connected with stimulation of Akt kinase activation, inhibition of SOD, an increase in superoxide levels, induction of iNOS protein expression and caspase-3 activation.
Our results show that MMPs are involved in the chronic cardiotoxicity of DOX in rats. The data also suggest that reactive oxygen species (superoxide), NO production (iNOS) and the Akt kinase pathway can modulate MMP-2 activities in rat hearts influenced by DOX.
"Furthermore therapy related cardiotoxicity has become more apparent as chemotherapy becomes more successful in lengthening patient survival . DOX cardiotoxicity is reproduced in several species including mice, indicating a non-species specific mechanism of toxicity . "
[Show abstract][Hide abstract] ABSTRACT: Doxorubicin is one of the most effective anti-cancer drugs but its use is limited by cumulative cardiotoxicity that restricts lifetime dose. Redox damage is one of the most accepted mechanisms of toxicity, but not fully substantiated. Moreover doxorubicin is not an efficient redox cycling compound due to its low redox potential. Here we used genomic and chemical systems approaches in vivo to investigate the mechanisms of doxorubicin cardiotoxicity, and specifically test the hypothesis of redox cycling mediated cardiotoxicity.
Mice were treated with an acute dose of either doxorubicin (DOX) (15 mg/kg) or 2,3-dimethoxy-1,4-naphthoquinone (DMNQ) (25 mg/kg). DMNQ is a more efficient redox cycling agent than DOX but unlike DOX has limited ability to inhibit gene transcription and DNA replication. This allowed specific testing of the redox hypothesis for cardiotoxicity. An acute dose was used to avoid pathophysiological effects in the genomic analysis. However similar data were obtained with a chronic model, but are not specifically presented. All data are deposited in the Gene Expression Omnibus (GEO). Pathway and biochemical analysis of cardiac global gene transcription and mRNA translation data derived at time points from 5 min after an acute exposure in vivo showed a pronounced effect on electron transport chain activity. This led to loss of ATP, increased AMPK expression, mitochondrial genome amplification and activation of caspase 3. No data gathered with either compound indicated general redox damage, though site specific redox damage in mitochondria cannot be entirely discounted.
These data indicate the major mechanism of doxorubicin cardiotoxicity is via damage or inhibition of the electron transport chain and not general redox stress. There is a rapid response at transcriptional and translational level of many of the genes coding for proteins of the electron transport chain complexes. Still though ATP loss occurs with activation caspase 3 and these events probably account for the heart damage.
PLoS ONE 09/2010; 5(9):e12733. DOI:10.1371/journal.pone.0012733 · 3.23 Impact Factor
"It is therefore hypothesized that treatment with antioxidants may play an important role in preventing myocardial damage. The mouse model of acute DOX toxicity is a simple and readily available small animal model particularly suitable for screening studies for different cardioprotective interventions[10,11]. In the recent years, there has been an increased research interest to develop cardioprotective and other pharmacological therapies from natural sources like animals and plants of marine origin. "
[Show abstract][Hide abstract] ABSTRACT: Treatment of cancer patients with anthracycline antibiotic doxorubicin (DOX) may be complicated by development of acute and chronic congestive heart failure (CHF), malignant arrhythmias and death. The aim of this study was to test whether an aqueous low molecular weight (LMW) extract from cod muscle decreases acute mortality in the mouse model of acute CHF caused by DOX.
A LMW fraction (<500 Da) of the aqueous phase of cod light muscle (AOX) was used for treatment of male BALB/c mice (approximately 25 g, n = 70). The animals were divided into four groups, DOX + AOX (n = 20), DOX + saline (NaCl) (n = 30), NaCl + AOX (n = 10) and NaCl only (n = 10). Echocardiography was performed in the separate subgroups (DOX treated n = 6 and controls n = 6) to verify the presence and the grade of acute CHF. The cod extract was delivered by subcutaneously implanted osmotic minipumps over the period of 2 weeks. High-dose injection of DOX was administered to randomly selected animals. The animals received single intraperitoneal injection of DOX (25 mg/kg) and were followed over two weeks for mortality.
Mortality rate was 68% lower (p < 0.05) in the mice treated with the extract. The analyses of cod extract have shown strong antioxidative effect in vitro.
The aqueous LMW cod muscles extract decreases mortality in the mouse model of DOX induced acute CHF. This effect may be mediated by cardioprotection through antioxidative mechanisms.
Journal of Experimental & Clinical Cancer Research 01/2009; 27(1):81. DOI:10.1186/1756-9966-27-81 · 4.43 Impact Factor
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