Relationship between Doxorubicin-Induced Ecg Changes and Myocardial Alterations in Rats

2-Methoxyestradiol ameliorates doxorubicin-induced cardiotoxicity by regulating the expression of GLUT4 and CPT-1B in female rats

The clinical usage of doxorubicin (DOX) is hampered due to cardiomyopathy. Studies reveal that estrogen (E2) modulates DOX-induced cardiotoxicity. Yet, the exact mechanism is unclear. The objective of the current study is to evaluate the influence of E2 and more specifically its metabolite 2-methoxyestradiol (2ME) on cardiac remodeling and the reprogramming of cardiac metabolism in rats subjected to DOX cardiotoxicity. Seventy-two female rats were divided into groups. Cardiotoxicity was induced by administering DOX (2.5 mg/kg three times weekly for 2 weeks). In some groups, the effect of endogenous E2 was abolished by ovariectomy (OVX) or by using the estrogen receptor (ER) blocker Fulvestrant (FULV). The effect of administering exogenous E2 or 2ME in the OVX group was studied. Furthermore, the influence of entacapone (COMT inhibitor) on induced cardiotoxicity was investigated. The evaluated cardiac parameters included ECG, histopathology, cardiac-related enzymes (creatine kinase isoenzyme-MB (CK-MB) and lactate dehydrogenase (LDH)), and lipid profile markers (total cholesterol (TC), triglyceride (TG), and high-density lipoprotein (HDL)). The expression levels of key metabolic enzymes (glucose transporter-4 (GLUT4) and carnitine palmitoyltransferase-1B (CPT-1B)) were assessed. Our results displayed that co-treatment of E2 and/or 2ME with DOX significantly reduced DOX-induced cardiomyopathy and enhanced the metabolism of the heart through the maintenance of GLUT4 and CPT-1B enzymes. On the other hand, co-treatment of DOX with OVX, entacapone, or FULV increased the toxic effect of DOX by further reducing these important metabolic enzymes. E2 and 2ME abrogate DOX-induced cardiomyopathy partly through modulation of GLUT 4 and CPT-1B enzymes.

Effect of Theobroma cacao L. on the Efficacy and Toxicity of Doxorubicin in Mice Bearing Ehrlich Ascites Carcinoma

Background and objective: Doxorubicin is a widely used chemotherapeutic agent that causes oxidative stress leading to cardiotoxicity, hepatotoxicity, and nephrotoxicity. In contrast, Theobroma cacao L. has been recorded as an anticancer agent and found to be protective against multiple chemical-induced organ injuries, including heart, liver, and kidney injuries. The present study investigated the possible role of extracts from T. cacao beans for organ-protective effects in doxorubicin-induced toxicity in mice bearing Ehrlich ascites carcinoma (EAC). Methodology: After survival analysis in rodents, cocoa bean extract (COE) was investigated for its efficacy against EAC-induced carcinoma and its organ-protective effect against doxorubicin-treated mice with EAC-induced carcinoma. Results: Significant reductions in EAC and doxorubicin-induced alterations were observed in mice administered the COE, either alone or in combination with doxorubicin. Furthermore, COE treatment significantly increased the mouse survival time, life span percentage, and antioxidant defense system. It also significantly improved cardiac, hepatic, and renal function biomarkers and markers for oxidative stress, and it also reduced doxorubicin-induced histopathological changes. Conclusion: COE acted against doxorubicin-induced organ toxicity; potent antioxidant and anticancer activities were also reflected by the COE itself. The COE may therefore serve as an adjuvant nutraceutical in cancer chemotherapy.

Regulation of Transplanted Cell Homing by FGF1 and PDGFB after Doxorubicin Myocardial Injury

There is no effective treatment for the total recovery of myocardial injury caused by an anticancer drug, doxorubicin (Dox). In this study, using a Dox-induced cardiac injury model, we compared the cardioprotective effects of ventricular cells harvested from 11.5-day old embryonic mice (E11.5) with those from E14.5 embryos. Our results indicate that tail-vein-infused E11.5 ventricular cells are more efficient at homing into the injured adult myocardium, and are more angiogenic, than E14.5 ventricular cells. In addition, E11.5 cells were shown to mitigate the cardiomyopathic effects of Dox. In vitro, E11.5 ventricular cells were more migratory than E14.5 cells, and RT-qPCR analysis revealed that they express significantly higher levels of cytokine receptors Fgfr1, Fgfr2, Pdgfra, Pdgfrb and Kit. Remarkably, mRNA levels for Fgf1, Fgf2, Pdgfa and Pdgfb were also found to be elevated in the Dox-injured adult heart, as were the FGF1 and PDGFB protein levels. Addition of exogenous FGF1 or PDGFB was able to enhance E11.5 ventricular cell migration in vitro, and, whereas their neutralizing antibodies decreased cell migration. These results indicate that therapies raising the levels of FGF1 and PDGFB receptors in donor cells and or corresponding ligands in an injured heart could improve the efficacy of cell-based interventions for myocardial repair.

Modulatory effect of metformin on cardiotoxicity induced by doxorubicin via the MAPK and AMPK pathways

AIMS

Doxorubicin (DOX) is an effective anthracycline anticancer drug. However, the clinical usage of it is limited due to its severe cardiotoxicity side effects. Metformin (Met) is a kind of first-line antihyperglycemic drug which has a potential protective effect on the heart，it is often used for oral treatment of type 2 diabetes. In this study, we explored whether Met could attenuate cardiotoxicity induced by DOX.

MATERIALS AND METHODS

For the sake of exploring the Met protective effect and mechanism, we established the DOX-induced cardiotoxicity models both in H9C2 cells incubated with 5 μM DOX in vitro and Sprague-Dawley rats treated with 20 mg/kg cumulative dose of DOX.

KEY FINDINGS

Met is able to inhibit growth inhibition and apoptosis of H9C2 cells induced by DOX. The heart indexes of rats were examined to evaluate the Met cardiotoxicity protection. Met improved the abnormal indexes, serum markers of cardiac heart injury, echocardiography, electrocardiogram, cardiac pathology, cardiomyocyte apoptosis, and oxidative stress markers induced by DOX. Furthermore, in vivo and in vitro studies demonstrated that Met protected against DOX-induced increasing cleaved caspase-3 and Bax. Met also prevented the downregulation of Bcl-2, activated the AMPK pathway, and inhibited the MAPK pathway.

SIGNIFICANCE

Met showed protective effects on DOX-induced cardiotoxicity by reducing oxidative stress and apoptosis, as well as regulating AMPK and MAPK signaling pathways.

The Rat Model in the Comparative Evaluation of Anthracyclines Cardiotoxicity

In the present investigation, the cardiotoxic effects of three anthracycline analogs (doxorubicin, 4′-epi-doxorubicin and 4′-deoxy-doxorubicin) were compared. For this purpose, 9.0 mg/kg of doxorubicin, divided into three closely spaced sub-doses, were injected intravenously in rats. The two derivatives were administered according to the same time schedule and their doses were chosen on the basis of the clinically adopted ratio, doxorubicin : 4′-epidoxorubicin : 4′-deoxy-doxorubicin = 1:1: 0.5. The degree of cardiomyopathy induced by the three anthracyclines was evaluated by ECG changes and morphological alterations. Doxorubicin was found to produce a significant degree of cardiotoxicity, thus confirming the validity of the experimental model adopted. Both 4′-substituted derivatives proved to be less cardiotoxic than the parent compound, although not completely devoid of this side effect.

Doxorubicin induced heart failure: Phenotype and molecular mechanisms

Long term survival of childhood cancers is now more than 70%. Anthracyclines, including doxorubicin, are some of the most efficacious anticancer drugs available. However, its use as a chemotherapeutic agent is severely hindered by its dose-limiting toxicities. Most notably observed is cardiotoxicity, but other organ systems are also degraded by doxorubicin use. Despite the years of its use and the amount of information written about this drug, an understanding of its cellular mechanisms is not fully appreciated. The mechanisms by which doxorubicin induces cytotoxicity in target cancer cells have given insight about how the drug damages cardiomyocytes. The major mechanisms of doxorubicin actions are thought to be as an oxidant generator and as an inhibitor of topoisomerase 2. However, other signaling pathways are also invoked with significant consequences for the cardiomyocyte. Further the interaction between oxidant generation and topoisomerase function has only recently been appreciated and the consequences of this interaction are still not fully understood. The unfortunate consequences of doxorubicin within cardiomyocytes have promoted the search for new drugs and methods that can prevent or reverse the damage caused to the heart after treatment in cancer patients. Alternative protocols have lessened the impact on newly diagnosed cancer patients. However the years of doxorubicin use have generated a need for monitoring the onset of cardiotoxicity as well as understanding its potential long-term consequences. Although a fairly clear understanding of the short-term pathologic mechanisms of doxorubicin actions has been achieved, the long-term mechanisms of doxorubicin induced heart failure remain to be carefully delineated.

Doxorubicin-Induced Cardiac Toxicity Is Mediated by Lowering of Peroxisome Proliferator-Activated Receptor δ Expression in Rats

The present study investigates the changes of peroxisome proliferator-activated receptors δ (PPARδ) expression and troponin phosphorylation in heart of rats which were treated with doxorubicin (DOX). Wistar rats which were treated with DOX according to a previous method. The protein levels of PPARδ and troponin phosphorylation were measured using Western blot. The PPARδ expression in heart was markedly reduced in DOX-treated rats showing a marked decrease in cardiac dP/dT and cardiac output. Also, cardiac troponin phosphorylation was lowered in DOX-treated rats. Meanwhile, combined treatment with the agonist of PPARδ (GW0742) reversed the decrease of cardiac dP/dT and cardiac output in DOX-treated rats. Then, primary cultured cardiomyocytes from neonatal rats were used to measure the changes of calcium concentration in cells. In addition to both decrease of PPARδ expression and troponin phosphorylation in neonatal cardiomyocytes by DOX, a marked decrease of calcium concentration was also observed. Our results suggest the mediation of cardiac PPARδ in DOX-induced cardiotoxicity in rats. Thus, activation of PPARδ may restore the expression of p-TnI and the cardiac performance in DOX-induced cardio toxicity in rats.

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.

Lecithinized copper,zinc-superoxide dismutase as a protector against doxorubicin-induced cardiotoxicity in mice

Production of superoxide radicals from doxorubicin is widely accepted to be the cause of the cardiotoxicity induced by this antitumor agent. Pretreatment with superoxide dismutase could improve the therapeutic application. Aim of the present study was to determine whether lecithinized superoxide dismutase (PC-SOD) can serve as a cardioprotective drug during doxorubicin treatment. The protective potential of PC-SOD on doxorubicin-induced cardiotoxicity was investigated in BALB/c mice. The possible influence of PC-SOD on the antitumor activity of doxorubicin was investigated in vitro as well as in vivo. Mice were treated intravenously with doxorubicin (4 mg x kg(-1)) or doxorubicin and PC-SOD (5000, 20000 or 80000 U x kg(-1)) weekly x 6 and appropriate controls were included. Cardiotoxicity was monitored for 8 weeks by ECG measurement. The influence of PC-SOD on the antitumor activity of doxorubicin was evaluated in three human malignant cell lines. Nude mice bearing OVCAR-3 human ovarian cancer xenografts were treated intravenously with doxorubicin (8 mg x kg(-1)) alone or preceded by PC-SOD 20000 or 80000 U x kg(-1) weekly x 2 and appropriate controls were included. PC-SOD prevented doxorubicin-induced cardiotoxicity already at 5000 U x kg(-1) whereas 20000 and 80000 U x kg(-1) were equally protective. No toxicity was observed in mice treated with PC-SOD. PC-SOD did not interfere with the antiproliferative effects of doxorubicin in vitro. In vivo, PC-SOD had no negative effect on the inhibition of xenograft growth induced by doxorubicin. It can be concluded that PC-SOD protects the heart, but not the tumor against doxorubicin. These data suggest that PC-SOD may be a suitable cardioprotector during doxorubicin treatment.

Telemetrically monitored arrhythmogenic effects of doxorubicin in a dog model of heart failure

A model of chronic heart failure has been induced in dogs by repeated intracoronary infusion of doxorubicin, which is an antineoplastic medication that has dose-limiting cardiotoxic side effects. Although many of the dogs receiving doxorubicin develop typical signs of dilated cardiomypathy over 4-6 weeks, some of them suddenly die before completing the four weekly infusions of the drug. The present study was undertaken to determine whether such sudden death may be caused by the development of fatal arrhythmias during doxorubicin treatment. This was assessed by telemetrically monitoring the EKG of seven dogs, which received intracoronary infusion of 1 mg/kg doxorubicin given in four divided weekly doses. The recordings were obtained for 8-10 h on alternate days up to 4 weeks. Echo-cardiographic recordings were obtained once a week. The acute effects with each infusion of doxorubicin included a significant increase in heart rate, and no significant change in QRS complex. The cumulative prolonged effects of doxorubicin included slight reduction in QRS amplitude and duration, and marked arrhythmic changes. Four out of seven dogs showed a spectrum of arrhythmic events such as single or groups of premature ventricular complexes (PVCs), bigeminy, ventricular tachycardia (VTAC), ventricular fibrillations (VFIB), and asystole. All dogs did not show each of the events listed above and the same dog did not show all the events all the time. One of these four dogs developed VFIB for 25 min and then asystole leading to sudden death. These studies conclusively showed that fatal arrhythmias develop in some of the dogs receiving doxorubicin treatment accounting for the sporadic incidence of sudden death. Prophylactic treatment with antiarrhythmic agents may prevent such adverse events.

Cardioprotective effects of zofenopril, a new angiotensin-converting enzyme inhibitor, on doxorubicin-induced cardiotoxicity in the rat

We have studied the effect of zofenopril, a new angiotensin-converting enzyme inhibitor in preventing cardiac injury induced by chronic doxorubicin treatment in rats. Cardiac function was assessed by measuring changes in electrocardiogram (ECG) tracings, haemodynamics and cardiac responses in vivo to isoprenaline, 4 weeks after suspension of doxorubicin treatment, in vehicle-treated rats and in animals receiving zofenopril (15 mg/kg/os/day) alone, doxorubicin (1.5 mg/kg i.v. once a week for 5 weeks) or zofenopril+doxorubicin treatment. Doxorubicin induced a significant lengthening of the QalphaT interval, which was completely prevented by zofenopril treatment. The cardiac positive inotropic effect induced by i.v. isoprenaline was selectively depressed by doxorubicin (no changes in chronotropic responses) and this adverse effect of doxorubicin was also prevented in zofenopril+doxorubicin pretreated rats. Doxorubicin induced a significant increase in relative heart weight, which was likewise prevented in zofenopril+doxorubicin treated rats. In separate experiments, zofenopril did not interfere with the antitumor activity of doxorubicin (inhibition of tumor growth in nude mice xenografted with A2780 human tumor line). In conclusion, the oral administration of zofenopril is able to significantly ameliorate, up to 4 weeks after the end of doxorubicin administration, doxorubicin-induced cardiotoxicity without affecting the antitumor activity of this anthracycline.

Progressive cardiac dysfunction in adriamycin-induced cardiomyopathy rats

Cardiotoxicity is a limiting factor in the treatment of cancer with adriamycin. We administered adriamycin by a method which minimizes the risk of peritonitis in an adriamycin-induced cardiomyopathy rat model. Sixty male Wistar rats were given 1 mg/kg of adriamycin intraperitoneally 15 times over a 3-week period (total dose, 15 mg/kg) to induce the cardiomyopathy model. Fifteen control rats received 10 ml/kg body wt. saline 15 times over 3 weeks. The animals were observed for 12 weeks and assessed for mortality, and cardiac volume and function was analyzed by echocardiography at 4, 8, and 12 weeks. In rats treated with adriamycin, the cumulative mortality was 35.8% while in the controls, none of the rats died. Left ventricular diameter of the systole (LVDs) was significantly increased at 4 weeks (4.5 vs. 3.3 mm; P<0.001). Left ventricular diameter of the diastole (LVDd) was significantly increased at 12 weeks (7.9 vs. 7.0 mm; P<0.01) and the % fractional shortening (FS) was significantly decreased at 8 weeks (33.4% vs. 50.0%; P<0.01) in the adriamycin-treated rats. This administration method appears to be useful for investigating the cardiac effect of adriamycin while avoiding the influence of peritonitis typically caused by an intraperitoneal injection of higher single doses of adriamycin.

Comparison of doxorubicin- and MEN 10755-induced long-term progressive cardiotoxicity in the rat

The delayed functional cardiotoxic effects of repeated treatment with the new disaccharide anthracycline MEN 10755 and doxorubicin (1.5 mg/kg, i.v., once a week for 5 consecutive weeks) were investigated in the rat. Changes were assessed (2 days and 4 and 13 weeks after the last treatment) in ECG morphology, hemodynamics, in vivo left ventricular contractile responses to beta-adrenergic stimulation, and histopathology of both atria and ventricles. Doxorubicin induced significant and progressive prolongation of the QalphaT interval starting 2 days after suspension of treatment. At 4 and 13 weeks after the last treatment, the ECG showed a further progressive and significant impairment. MEN 10755 induced alterations similar in nature but of lesser severity compared with doxorubicin. In addition, MEN 10755-induced prolongation of the QalphaT interval was not progressive, being similar at 4 and 13 weeks after the last treatment. Although the hemodynamics were only slightly affected by both anthracyclines, a nearly complete ablation of isoprenaline-induced enhancement of ventricular function was observed 4 and 13 weeks after the last treatment with doxorubicin, whereas only mild, if any, reduction was detected in rats receiving MEN 10755. Histopathologic investigations indicated that both anthracyclines produced qualitatively similar alterations in ventricular myocytes. However, only with doxorubicin did these changes show a progression with a further significant worsening at 13 weeks as compared with 4 weeks after the last treatment. In addition, atrial lesions were evident in doxorubicin-treated rats, but not in rats receiving MEN 10755. In conclusion, an equimyelotoxic regimen of MEN 10755 produced, as compared with doxorubicin, lesser ECG alterations, smaller impairment of the ventricular response to adrenergic stimulation, and less severe myocyte lesions. Unlike doxorubicin, the histologic and functional cardiotoxic effects induced by MEN 10755 were not progressive. Further investigations are warranted to define the pharmacodynamic and/or pharmacokinetic mechanism(s) underlying the different cardiotoxic profile exhibited by the two anthracyclines.

Adriamycin-induced changes of creatine kinase activity in vivo and in cardiomyocyte culture

Adriamycin (ADM) is an anthracycline anti-neoplastic agent, whose clinical effectiveness is limited by severe side effects, including cardiotoxicity. The toxic effects of ADM are likely to be the consequence of the generation of free radicals. This study demonstrates that ADM induces significant changes in the activity of the oxidative sensitive enzyme creatine kinase (CK) in the heart in vivo and in a cardiomyocyte culture model. The changes observed are likely to reflect the ability of ADM to damage the plasma membrane of cardiac cells and to induce the direct inactivation of CK. The role for ADM-derived free radicals is one of the possible mechanisms for the CK inactivation observed during the ADM treatment.

Adriamycin induces protein oxidation in erythrocyte membranes

Adriamycin is an anthracycline antineoplastic agent whose clinical effectiveness is limited by severe side effects, including cardiotoxicity. A current hypothesis for adriamycin cardiotoxicity involves free radical oxidative stress. To investigate this hypothesis in a model system, we applied the technique of immunochemical detection of protein carbonyls, known to be increased in oxidized proteins, to study the effect of adriamycin on rat erythrocyte membranes. Erythrocytes obtained from adriamycin-treated rats demonstrated an increase of carbonyl formation in their membrane proteins. Yet, in separate experiments when adriamycin was incubated with rat erythrocyte ghosts, there was no significant increase of membrane protein carbonyls detected. In contrast, isolated erythrocytes incubated with an adriamycin-Fe3+ complex exhibited a robust carbonyl incorporation into their membrane proteins in a time-dependent manner. The level of carbonyl formation was dependent upon the concentration of Fe3+ known to form the adriamycin-Fe3+ complex. When the time course between protein carbonyl formation and lipid peroxidation was compared, protein carbonyl detection occurred earlier than lipid peroxidation as assayed by thiobarbituric acid reactive substances formation. These results are consistent with the notion that oxidative modification of membrane proteins may contribute to the development of the acute adriamycin-mediated toxicity.

Influence of selenium deficiency on the acute cardiotoxicity of adriamycin in rats

The influence of selenium (Se) deficiency on the acute cardiotoxicity induced by the anticancer drug adriamycin (ADR) has been studied in rats by electrocardiography. Two categories were formed by feeding groups of rats a Se-supplemented and a Se-deficient diet. The supplemented animals were taken as normals. The two categories were treated with iv injections of saline solution containing ADR at doses of 0, 7.5, and 15 mg/kg body wt. The cardiac Se concentration and glutathione peroxidase (GSH-Px) activity in the Se-deficient groups were < 2% lower than in the normals. The normal groups showed significant widening of the SaT and QaT durations when given 15 mg/kg ADR. The Se-deficient groups exhibited a dose-dependent widening of the SaT and QaT duration at 7.5 and 15 mg/kg and narrowing of the PQ duration at 15 mg/kg ADR. No heart rate or QRS duration changes were detected in both categories. Our results suggest that an imbalance of the antioxidant system is associated with Se deficiency and that Se plays a role in preventing the cardiac functional disorder attributable to oxygen free radical formation induced by ADR.

Cardiotoxicity induced by doxorubicin in vivo: protective activity of the spin trap alpha-phenyl-tert-butyl nitrone

The role of free radical generation in the development of the acute cardiotoxicity induced by doxorubicin (DXR) in the rat and the protective activity of anti-radical drugs were investigated in in vivo experiments by evaluating the body weight curve, ECG, contractile performance and coronary flow up to 10 days after DXR. A lipophilic spin trap (alpha-phenyl-tert-butyl nitrone, PBN) was continuously administered at a dose of 0.65 mg/kg every hour for 2 weeks by an intraperitoneal osmotic pump. DXR was administered i.v. at a dose of 9 mg/kg 3 days after beginning the PBN infusion. DXR impaired ECG and body weight gain after 3 days (partly reversible at later times), while contractility and coronary flow were significantly impaired throughout the experimental time. PBN was shown to prevent the DXR-induced alterations of contractility and coronary flow, while ECG was non-significantly improved. The body weight curve was not affected. Since the dose of PBN used does not produce pharmacological effects, the protective activity in rats receiving DXR indicates that free radicals may play a causal role in the acute cardiotoxicity in vivo. The use of suitable spin traps and administration schedules seems to be an interesting approach for the prevention of radical-dependent pathologies.

Effect of flunarizine on the delayed cardiotoxicity of doxorubicin in rats

The calcium antagonist flunarizine (FLN) was tested for its ability to prevent doxorubicin (DXR)-induced cardiotoxicity in the rat. A cumulative dose of 9.0 mg/kg of DXR was administered i.v. over a period of 1 week. FLN (10 mg/kg/day i.p., 6 days/week) was administered according to two different time schedules, covering respectively the first and last 4 weeks after the beginning of DXR treatment. The two schedules were adopted to assess whether early and/or delayed DXR-induced cardiotoxic effects were affected by FLN. The development of cardiac toxicity was monitored by ECG recordings. The animals were sacrificed 8 weeks after the beginning of DXR treatment. The contractile performance of isolated atria and the morphological pattern of left ventricular fragments were subsequently evaluated. The early administration schedule of FLN was shown to be ineffective in preventing DXR-induced cardiotoxicity and in some cases was actually found to potentiate the effects of DXR. In contrast, the histological evaluation of ventricular preparations from rats treated with DXR and FLN according to the delayed time schedule showed a significant improvement with respect to hearts from animals treated with DXR alone. An inhibition of the delayed calcium overload occurring after DXR administration has been proposed as a possible mechanism for this protective action.

Prevention of doxorubicin-induced cardiomyopathy by reduced glutathione

The aim of the present investigation was to evaluate the potential cardioprotective effect of reduced glutathione (GSH) against the delayed cardiomyopathy induced by doxorubicin (DXR) in a well-documented rat model. DXR was administered i.v. at a weekly dose of 3 mg/kg for a total of 4 doses; 250 or 500 mg/kg of GSH was given i.v. 10 min before and 2 h after each DXR injection, resulting in a total weekly dose of 500 or 1000 mg/kg, respectively. The development of cardiotoxicity was monitored in vivo by means of electrocardiography (QaT duration), and was evaluated by measuring the contractile performance of isolated atria and by light and electron microscopy of left ventricular samples excised 5 weeks after the last DXR administration. DXR was found to impair body weight gain and to produce an irreversible and time-dependent prolongation of QaT, a decrease in myocardial contractility of isolated atria and typical morphologic alterations, including myocyte vacuolization and myofibrillar loss. Pretreatment with GSH at a dose of 500 mg/kg x 2, but not at 250 mg/kg x 2, partially prevented the impairment of body weight gain, QaT prolongation in ECG and the decrease in myocardial contractility of isolated atria induced by DXR. Alterations of the morphologic pattern were also significantly reduced in animals receiving the higher dose of GSH. Determinations of the cardiac non-protein sulfhydryl group content showed that GSH, at doses higher than or equal to 500 mg/kg, significantly increased this parameter, irrespective of the presence of DXR. In conclusion, the present data indirectly support the hypothesis that oxidative damage is involved in DXR cardiotoxicity and indicate that maintenance of the reduced thiol pool could be an important issue in myocardial protection.

Effect of amrinone on anthracycline-induced lethal and cardiac toxicity in mice and rats

The protective role of amrinone against toxicity of anthracyclines was examined in both mice and rats. These two anthracyclines were selected since they are characterized by different patterns of toxicity. In contrast to doxorubicin, the 4'-deoxy derivative did not cause delayed mortality. The results of this investigation indicate that amrinone is an effective protective agent against acute lethal events induced by both anthracyclines. However, the inotropic agent did not reduce the delayed mortality produced by doxorubicin. This parallels the apparent lack of prevention of doxorubicin-induced myocardial toxicity in CD rats, as determined by ECG changes and by morphologic alterations following multiple drug administrations. The administration of amrinone did not interfere with the antitumor activity of 4'-deoxy-doxorubicin against C-26 colon tumor.

Effect of ICRF-187 pretreatment against doxorubicin-induced delayed cardiotoxicity in the rat

Doxorubicin (DXR), administered iv in rats at the weekly dose of 3 mg/kg for 5 weeks, significantly impaired body weight gain and induced irreversible ECG alterations, mainly consisting of a progressive prolongation of ST and QT intervals. Five weeks after the last DXR administration, the contractile performance of atria isolated from treated animals was significantly reduced. At the same time, relevant morphologic lesions, consisting of myocyte vacuolization and myofibrillar loss, were also present in the myocardium of the same rats. The study showed that ICRF-187, administered ip at a dose of 125 mg/kg, significantly prevented body weight loss. QT and ST prolongation, and the decreased contractile force induced by DXR. In addition, ICRF-187 caused a significant reduction in incidence and severity of myocardial lesions. The cardioprotective effect of ICRF-187 is not mediated by a modification in DXR pharmacokinetics in heart, since the drug was actually found to increase DXR uptake in myocardial cells.

Effect of glutathione and N-acetylcysteine on in vitro and in vivo cardiac toxicity of doxorubicin

The effects of two sulfhydryl compounds, glutathione (GSH) and N-acetylcysteine (NAC), on the cardiotoxicity of doxorubicin (DXR) were tested on in vitro and in vivo models. DXR was administered to rats as 4 weekly i.v. doses of 3 mg/kg. GSH (1.5 mmoles/kg), given i.v. 10 min before and 1 hr after DXR, was found to prevent the development of the delayed cardiotoxic effects of DXR, as assessed by electrocardiographic and mechanical parameters, as well as by histological examination of left ventricular preparations. In contrast, equimolar oral doses of NAC (1 hr before and 2 hrs after DXR) were found to be ineffective. Both GSH and NAC prevented the negative inotropic effect produced by DXR on isolated rat atria. A good correlation exists between the cardioprotective effects of the two agents and their ability to enhance the non-protein sulfhydryl group content of the myocardium. Differences observed in vivo between GSH and NAC might be accounted for by pharmacokinetic factors.

Cardiotoxic effects and the influence on the beta-adrenoceptor function of doxorubicin (Adriamycin) in the rat

The possible relationship between the effect of the anthracycline-cytostatic doxorubicin (Dox) on the cardiac beta-adrenoceptor function in vitro and the development of delayed cardiotoxicity in vivo has been investigated in the rat. Dox (10(-5)-10(-4) M) blocked the chronotropic effect of isoprenaline on isolated atria in a competitive manner. Treatment with a single dose of Dox 5 mg/kg intravenously caused marked ECG changes manifested by progressive prologations of the Q alpha T and S alpha T-intervals, which amounted to 37% and 58% respectivity 5 weeks after the medication. At this time no beta-blocking action was detectable when tested on the isolated atria in the same rats. The results indicate that the delayed cardiotoxicity induced by Dox is not mediated by an interference with the cardiac beta-adrenoceptor function.