Increased plasma endothelin-1 and cardiac nitric oxide during doxorubicin-induced cardiomyopathy

The major limiting factor in long-term administration of doxorubicin is the development of cumulative dose-dependent cardiomyopathy and congestive heart failure. Although several mechanisms have been suggested to explain the exact cause of doxorubicin-induced cardiomyopathy, the role of the vascular endothelium-derived vasoactive mediators in the pathophysiology of this toxic effect is still unknown. Accordingly, the present study has been initiated to investigate whether the changes in plasma level of endothelin-1 and nitric oxide along with cardiac nitric oxide are associated with the development of doxorubicin-induced cardiomyopathy. Doxorubicin was injected with a single dose of 5 mg/kg and every other day with a dose of 5 mg/kg, intraperitoneally, to have four cumulative doses of, 10, 15, 20 and 25 mg/kg in five separate groups of male rats. An additional group receiving a single dose of 20 mg/kg and one receiving normal saline were also included in the study. Twenty-four hr after the last dose, the animals were sacrificed and the plasma levels of endothelin-1 and nitric oxide in addition to cardiac nitric oxide were determined. The results show that doxorubicin caused a statistically significant increase of 85%, 76% and 97% in plasma endothelin-1 at a cumulative dose levels of 10, 15 and 20 mg/kg, respectively. However, the level of plasma nitric oxide remained unchanged. Furthermore, doxorubicin treatment resulted in a significant dose-dependent increase in serum lactate dehydrogenase and creatine phosphokinase. In contrast, the increase in nitric oxide production in cardiac tissue by doxorubicin was not dose-dependent with the maximum increase (81%) at a cumulative dose of 10 mg/kg. It is worth mentioning that plasma endothelin-1 and cardiac nitric oxide were significantly increased at 24 hr after the single dose of 20 mg/kg doxorubicin. The increase of plasma endothelin-1 and cardiac nitric oxide with the cardiomyopathy enzymatic indices, may point to the conclusion that both endothelin-1 and cardiac nitric oxide are increased during the development of doxorubicin-induced cardiomyopathy.     

Effect of lycopene on doxorubicin-induced cardiotoxicity: an echocardiographic, histological and morphometrical assessment

Doxorubicin is an excellent chemotherapeutic agent utilized for several types of cancer but the irreversible doxorubicin-induced cardiac damage is the major limitation for its use. Oxidative stress seems to be associated with some phase of the toxicity mechanism process. To determine if lycopene protects against doxorubicin-induced cardiotoxicity, male Wistar rats were randomly assigned either to control, lycopene, doxorubicin or doxorubicin + lycopene groups. They received corn oil (control, doxorubicin) or lycopene (5 mg/kg body weight a day) (lycopene, doxorubicin + lycopene) by gavage for a 7-week period. They also received saline (control, lycopene) or doxorubicin (4 mg/kg) (doxorubicin, doxorubin + lycopene) intraperitoneally by week 3, 4, 5 and 6. Animals underwent echocardiogram and were killed for tissue analyses by week 7. Mean lycopene levels (nmol/kg) in liver were higher in the doxorubicin + lycopene group (5822.59) than in the lycopene group (2496.73), but no differences in lycopene were found in heart or plasma of these two groups. Lycopene did not prevent left ventricular systolic dysfunction induced by doxorubicin. However, morphologic examination revealed that doxorubicin-induced myocyte damage was significantly suppressed in rats treated with lycopene. Doxorubicin treatment was followed by increase of myocardium interstitial collagen volume fraction. Our results show that: (i) doxorubicin-induced cardiotoxicity was confirmed by echocardiogram and morphological evaluations; (ii) lycopene absorption was confirmed by its levels in heart, liver and plasma; (iii) lycopene supplementation provided myocyte protection without preventing interstitial collagen accumulation increase; (iv) doxorubicin-induced cardiac dysfunction was not prevented by lycopene supplementation; and (v) lycopene depletion was not observed in plasma and tissues from animals treated with doxorubicin.     

Prevention of doxorubicin-induced acute cardiotoxicity by an experimental antioxidant compound

Doxorubicin is a widely used anticancer agent, but its application is restricted by its cardiotoxic side effects. The current theory of its cardiotoxicity is based on free radical formation. The compound H-2545, having a 3-carboxamido-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole moiety, was reported to exhibit antioxidant properties and accumulate in cell membranes, scavenging free radicals at the site of formation. Therefore, we hypothesized that H-2545 could reduce the doxorubicin-induced acute deterioration of cardiac function. Langendorff-perfused rat hearts were treated with doxorubicin and/or H-2545, its metabolite H-2954, or dihydrolipoamide. High-energy phosphate levels, contractile function, lipid peroxidation, protein oxidation, and Akt phosphorylation were investigated. We also determined whether the antioxidants influenced doxorubicin toxicity on malignant cells. During perfusion with doxorubicin, the energetic and functional parameters of the myocardium were improved by adding H-2545. H-2545 significantly diminished doxorubicin-induced lipid and protein damage. On H-2545 treatment, the doxorubicin-triggered Akt phosphorylation was markedly reduced, whereas dihydrolipoamide had such an effect only at higher concentrations. H-2545 did not alter the anticancer effect of doxorubicin on malignant cell lines. We propose that the coadministration of the antioxidant H-2545 attenuates doxorubicin-induced acute cardiotoxicity without interfering with its anticancer effects. Prevention of the acute adverse effects of doxorubicin on myocardium may hinder the later development of cardiomyopathy.     

Protective effect of saponins from Panax notoginseng against doxorubicin-induced cardiotoxicity in mice

The dried rhizome of Panax notoginseng is a traditional Chinese herb extensively used for treatment of cardiovascular diseases and other ailments. Panax notoginseng saponins (PNS) are known as the major pharmacologically active constituents. The purpose of this study was to investigate the cardioprotective effects of PNS against doxorubicin-induced cardiotoxicity and its possible influence on the anti-tumor activity of doxorubicin. Five groups of ICR mice were treated with saline (control group), doxorubicin alone (20 mg/kg I. P.), PNS alone, doxorubicin pretreated with PNS (100 mg/kg I. G. for 5 consecutive days) or amifostine (single dose of 200 mg/kg I. V., used as positive control). After 72 h of doxorubicin treatment, cardiac function, serum levels of lactate dehydrogenase (LDH), creatine kinase (CK) and creatine kinase isoenzyme (CK-MB) and activities of antioxidant enzymes in heart tissue were measured. Pretreatment with PNS significantly protected the mice from DOX-induced cardiotoxicity as evidenced from improved ventricular contractile function, lower levels of serum LDH, CK and CK-MB, minimal morphological changes in hearts, and normalization of myocardial superoxide dismutase, glutathione peroxidase and catalase activities. Additionally, IN VITRO cytotoxic studies demonstrated that PNS did not compromise the inhibitory effect of doxorubicin on the proliferation of cancer cells. These results imply the potentially clinical application of PNS to overcome the negative side effects of doxorubicin.     

Screening of antioxidants from medicinal plants for cardioprotective effect against doxorubicin toxicity

Doxorubicin is an important and effective anticancer drug widely used for the treatment of various types of cancer but its clinical use is limited by dose-dependent cardiotoxicity. Elevated tissue levels of cellular superoxide anion/oxidative stress are a mechanism by which doxorubicin-induced cardiotoxicity. Selected medicinal plant extracts were tested for their antioxidant capacity and cardioprotective effect against doxorubicin-induced cardiotoxicity. The cardiac myoblasts H9c2 were incubated with the antioxidants ascorbic acid, trolox, N-acetylcysteine or selected medicinal plant extracts including; 1) ethanolic extracts from Curcuma longa L-EtOH Phyllanthus emblica L-EtOH, and Piper rostratum Roxb-EtOH; and 2) water extracts from Curcuma longa L-H2O and Morus alba L-H2O. The cardioprotective effects of these extracts were evaluated by crystal violet cytotoxicity assay. IC50s of doxorubicin were compared in the presence or absence of ascorbic acids, trolox, N-acetylcysteine or plant extracts. Morus alba L-H2O showed the highest antioxidant properties evaluated by ferric reducing/antioxidant power assay. Ascorbic acid and N-acetylcysteine had modest effects on the protection of doxorubicin-induced cytotoxicity while trolox showed insignificant protective effect. All plant extracts protected cardiac toxicity at different degrees except that Curcuma longa L-EtOH had no protective effect. Phyllanthus emblica-EtOH (100 microg/ml) showed the highest cardioprotective effect (approximately 12-fold doxorubicin IC50 increase). The data demonstrate that antioxidants from natural sources may be useful in the protection of cardiotoxicity in patients who receive doxorubicin.     

High fat diet-fed obese rats are highly sensitive to doxorubicin-induced cardiotoxicity

Often, chemotherapy by doxorubicin (Adriamycin^®) is limited due to life threatening cardiotoxicity in patients during and posttherapy. Recently, we have shown that moderate diet restriction remarkably protects against doxorubicin-induced cardiotoxicity. This cardioprotection is accompanied by decreased cardiac oxidative stress and triglycerides and increased cardiac fatty-acid oxidation, ATP synthesis, and upregulated JAK/STAT3 pathway. In the current study, we investigated whether a physiological intervention by feeding 40% high fat diet (HFD), which induces obesity in male Sprague-Dawley rats (250-275 g), sensitizes to doxorubicin-induced cardiotoxicity. A LD₁₀ dose (8 mg doxorubicin/kg, ip) administered on day 43 of the HFD feeding regimen led to higher cardiotoxicity, cardiac dysfunction, lipid peroxidation, and 80% mortality in the obese (OB) rats in the absence of any significant renal or hepatic toxicity. Doxorubicin toxicokinetics studies revealed no change in accumulation of doxorubicin and doxorubicinol (toxic metabolite) in the normal diet-fed (ND) and OB hearts. Mechanistic studies revealed that OB rats are sensitized due to: (1) higher oxyradical stress leading to upregulation of uncoupling proteins 2 and 3, (2) downregulation of cardiac peroxisome proliferators activated receptor-α, (3) decreased plasma adiponectin levels, (4) decreased cardiac fatty-acid oxidation (666.9 ± 14.0 nmol/min/g heart in ND versus 400.2 ± 11.8 nmol/min/g heart in OB), (5) decreased mitochondrial AMP-α2 protein kinase, and (6) 86% drop in cardiac ATP levels accompanied by decreased ATP/ADP ratio after doxorubicin administration. Decreased cardiac erythropoietin and increased SOCS3 further downregulated the cardioprotective JAK/STAT3 pathway. In conclusion, HFD-induced obese rats are highly sensitized to doxorubicin-induced cardiotoxicity by substantially downregulating cardiac mitochondrial ATP generation, increasing oxidative stress and downregulating the JAK/STAT3 pathway.     

Inhibition of doxorubicin chronic toxicity in catalase-overexpressing transgenic mouse hearts.

Catalase is an important antioxidant enzyme, which has been shown to provide cardiac protection from acute toxicity induced by doxorubicin, a most effective anticancer agent. Because cumulative dose-dependent chronic cardiomyopathy due to a long-term administration of doxorubicin is a significant clinical problem, the present study was undertaken to test the hypothesis that catalase also provides protection against doxorubicin chronic cardiotoxicity. Transgenic mice containing cardiac catalase activities of 15-, 60-, or 100-fold higher than normal and nontransgenic controls were treated with doxorubicin in a cumulative dose of 45 mg/kg in five equal iv injections (9 mg/kg every other week) over a period of 10 weeks. On the second day after the last injection, the mice were sacrificed for analysis of cardiotoxicity. As compared to nontransgenic controls, doxorubicin-reduced body weight gain was significantly inhibited in the transgenic mice. There were 15% mortality in nontransgenic mice, but no mortality was observed in transgenic mice during the course of treatment. Light microscopic examination revealed that doxorubicin-induced myocardial morphological changes were markedly suppressed in the transgenic mice in an activity-dependent fashion. Under electron microscopy, extensive sarcoplasmic vacuolization and severe disruption of mitochondrial fine structure were observed in nontransgenic cardiomyocytes, but all markedly suppressed in the transgenic mice. The results indicate that catalase elevation in the heart prevents doxorubicin chronic cardiomyopathy.     

Increased Plasma Endothelin‐1 and Cardiac Nitric Oxide during Doxorubicin‐Induced Cardiomyopathy

Abstract: The major limiting factor in long‐term administration of doxorubicin is the development of cumulative dose‐dependent cardiomyopathy and congestive heart failure. Although several mechanisms have been suggested to explain the exact cause of doxorubicin‐induced cardiomyopathy, the role of the vascular endothelium‐derived vasoactive mediators in the pathophysiology of this toxic effect is still unknown. Accordingly, the present study has been initiated to investigate whether the changes in plasma level of endothelin‐1 and nitric oxide along with cardiac nitric oxide are associated with the development of doxorubicin‐induced cardiomyopathy. Doxorubicin was injected with a single dose of 5 mg/kg and every other day with a dose of 5 mg/kg, intraperitoneally, to have four cumulative doses of, 10, 15, 20 and 25 mg/kg in five separate groups of male rats. An additional group receiving a single dose of 20 mg/kg and one receiving normal saline were also included in the study. Twenty‐four hr after the last dose, the animals were sacrificed and the plasma levels of endothelin‐1 and nitric oxide in addition to cardiac nitric oxide were determined. The results show that doxorubicin caused a statistically significant increase of 85%, 76% and 97% in plasma endothelin‐1 at a cumulative dose levels of 10, 15 and 20 mg/kg, respectively. However, the level of plasma nitric oxide remained unchanged. Furthermore, doxorubicin treatment resulted in a significant dose‐dependent increase in serum lactate dehydrogenase and creatine phosphokinase. In contrast, the increase in nitric oxide production in cardiac tissue by doxorubicin was not dose‐dependent with the maximum increase (81%) at a cumulative dose of 10 mg/kg. It is worth mentioning that plasma endothelin‐1 and cardiac nitric oxide were significantly increased at 24 hr after the single dose of 20 mg/kg doxorubicin. The increase of plasma endothelin‐1 and cardiac nitric oxide with the cardiomyopathy enzymatic indices, may point to the conclusion that both endothelin‐1 and cardiac nitric oxide are increased during the development of doxorubicin‐induced cardiomyopathy.     

Protective effect of thymoquinone against doxorubicin-induced cardiotoxicity in rats: a possible mechanism of protection.

Administration of thymoquinone (10 mg kg(-1)day(-1), p.o.) with drinking water starting 5 days before a single injection of doxorubicin (15 mg kg(-1)i.p.) and continuing during the experimental period ameliorated the doxorubicin-induced cardiotoxicity in rats. This protection was evidenced from the significant reduction in serum enzymes: lactate dehydrogenase elevated level, 24 h and creatine phosphokinase elevated levels, 24 h and 48 h after doxorubicin administration. The cardiotoxicity of doxorubicin has been suggested to result from the generation of superoxide free-radical. The protective action of thymoquinone was examined against superoxide anion radical either generated photochemically, biochemically or derived from calcium ionophore (A23187) stimulated polymorphonuclear leukocytes. The results indicate that thymoquinone is a potent superoxide radical scavenger, scavenging power being as effective as superoxide dismutase against superoxide. In addition thymoquinone has an inhibitory effect on lipid peroxidation induced by Fe(3+)/ascorbate using rat heart homogenate. The superoxide scavenging and anti-lipid peroxidation may explain, in part, the protective effect of thymoquinone against doxorubicin-induced cardiotoxicity. 2000 Academic Press@p$hr Copyright 2000 Academic Press.     

Asclepias Fruticosa

Context: Ficus racemosa Linn. (Moraceae) bark is a rich source of phenolic compounds having diverse biological properties including antioxidant activity. The present study evaluated the cardioprotective activity of sequential acetone extract of Ficus racemosa bark against doxorubicin-induced cardiotoxicity in rats.

Materials and methods: The extract was standardized by high-performance liquid chromatography (HPLC) and subjected to acute toxicological evaluation in mice. Cardiotoxicity was induced by administration of doxorubicin (10?mg kg^?1 i.v.) to the extract pretreated rats (250 and 500?mg kg^?1) and compared with that of Arjuna, a standard cardiotonic. Biochemical parameters included CK-MB, LDH, AST, ALT, troponin I, thiobarbituric acid reactive substances (TBARS), and glutathione.

Results: The HPLC fingerprinting of the extract indicated the presence of bergenin (0.89%) and bergapten (0.07%). In an acute toxicity study, the extract at a dose of 2?g kg^?1 did not cause any adverse changes and no mortality was observed. Administration of doxorubicin significantly increased (p?≤?0.05) serum levels of creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and alanine aminotransferase, which were decreased to an extent of 68, 63, 41, and 65%, respectively, in extract pretreated group (500?mg kg^?1). Troponin I was undetected in control group, while it was found in serum of all the experimental groups. The extract pretreatment significantly decreased (p?≤?0.05) TBARS and increased glutathione levels in serum and cardiac tissue. These observations were further substantiated by the histopathological studies.

Conclusion: The acetone extract of F. racemosa bark possesses potential cardioprotective activity against doxorubicin-induced cardiotoxicity in rats by scavenging free radicals generated by the administration of the drug.     

Protective effects of 'Khamira Abresham Hakim Arshad Wala', a unani formulation against doxorubicin-induced cardiotoxicity and nephrotoxicity

Doxorubicin is one of the most active cytotoxic agents in current use. The clinical usefulness of the doxorubicin has been precluded by its marked cardiotoxicity. The aim of the present study was to investigate the effect of Khamira Abresham Hakim Arshadwala, a well known unani cardiac tonic formulation, pre-treatment on doxorubicin-induced cardiotoxicity, and nephrotoxicity in rats. Twenty-four Wistar albino rats, divided into four groups, were used. Khamira Abresham Hakim Arshadwala was administered daily, for 7 days, and a single dose of doxorubicin (10 mg/kg, i.v.) on day 5. After 48 h of doxorubicin injection, animals were sacrificed. Lactate dehydrogenase (LDH), aspartate transaminase (AST), blood urea nitrogen (BUN), and creatinine were estimated in the serum. Heart specimens were used for biochemical estimations of lipid peroxides (MDA), reduced glutathione (GSH), catalase, and for microscopic examination of histopathological changes. Doxorubicin showed cardiotoxicity and nephrotoxicity, as evidenced by elevated activities of AST, LDH, BUN, creatinine, and MDA, depletion in GSH level, and catalase activity. Histopathological studies showed disruption of cardiac tissues in doxorubicin groups. Khamira Abresham Hakim Arshadwala pre-treatment showed a protective effect against the enzymatic changes in serum as well as cardiac and kidney tissue damage, significantly. The present findings suggest that Khamira Abresham Hakim Arshadwala significantly (p < 0.01) improved the state of markers for cardiac and kidney damage investigated in this model of doxorubicin-induced experimental cardiotoxicity and nephrotoxicity; indicating its potential in limiting doxorubicin toxicity.     

Mechanisms mediating the cardioprotective effect of carvedilol in cadmium induced cardiotoxicity. Role of eNOS and HO1/Nrf2 pathway

Cadmium (Cd) is a highly toxic heavy metal with several harmful effects including cardiotoxicity. For the first time, we aimed to evaluate the possible cardioprotective effect of carvedilol (CAR) in Cd induced cardiotoxicity and study the mechanisms involved in such protection including endothelial nitric oxide synthase (eNOS) and HO1/Nrf2 pathway. CAR (1,10 mg/kg/d) was administered orally for 4 weeks with Cd induced cardiac injury (3 mg/kg/d) orally for 4 weeks. We measured cardiac enzymes, mean arterial pressure changes, heme oxygenase-1 (HO1) and total antioxidant capacity (TAC). Moreover; cardiac tissue malondialdehyde (MDA), tumor necrosis factor alpha (TNFα), western blotting of caspase3 and eNOS levels and histopathology were evaluated. Immunoexpression of eNOS in cardiac tissue, gene expression changes of HO1, and nuclear factor erythroid 2-related factor 2 (Nrf2) using real time polymerase chain reactions (rtPCR) were detected. Our results showed that CAR could significantly decrease Cd induced cardiotoxicity.     

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.     

Angelica sinensis: a novel adjunct to prevent doxorubicin-induced chronic cardiotoxicity

Doxorubicin is an anthracycline antibiotic agent used in the treatment of a variety of solid and haematopoietic tumours, but its use is limited by formation of metabolites that induce acute and chronic cardiac toxicities. Angelica sinensis has been widely used to treat cardiovascular and cerebrovascular diseases in China. In the present study, we used an in vivo mouse model to explore whether A. sinensis could protect against doxorubicin-induced chronic cardiotoxicity. Male ICR mice were treated with distilled water or water extraction of A. sinensis (15 g/kg, orally) daily for 4 weeks, followed by saline or doxorubicin (15 mg/kg, intravenously) treatments weekly. Cardiotoxicity was assessed by electrocardiograph, antioxidant activity in cardiac tissues, serum levels of creatine kinase, aspartate aminotransferase (AST) and histopathological change in cardiac tissues. A cumulative dose of doxorubicin (60 mg/kg) caused animal death and myocardial injury characterized by increased QT interval and decreased heart rate in electrocardiograph, decrease of heart antioxidant activity, increase of serum AST, as well as myocardial lesions. Pre-treatment with A. sinensis significantly reduced mortality and improved heart performance of the doxorubicin-treated mice as evidenced from normalization of antioxidative activity and serum AST, preventing loss of myofibrils as well as improving arrhythmias and conduction abnormalities. Furthermore, the in vitro cytotoxic study showed that A. sinensis did not compromise the antitumour activity of doxorubicin. These results suggested that A. sinensis elicited a typical cardioprotective effect on doxorubicin-related oxidative stress, and could be a novel adjunct in the combination with doxorubicin chemotherapy.     

Taurine suppresses doxorubicin-triggered oxidative stress and cardiac apoptosis in rat via up-regulation of PI3-K/Akt and inhibition of p53, p38-JNK

The objective of the present study was to investigate the signaling mechanisms involved in the beneficial role of taurine against doxorubicin-induced cardiac oxidative stress. Male rats were administered doxorubicin. Hearts were collected 3 weeks after the last dose of doxorubicin and were analyzed. Doxorubicin administration retarded the growth of the body and the heart and caused injury in the cardiac tissue because of increased oxidative stress. Similar experiments with doxorubicin showed reduced cell viability, increased ROS generation, intracellular Ca²⁺ and DNA fragmentation, disrupted mitochondrial membrane potential and apoptotic cell death in primary cultured neonatal rat cardiomyocytes. Signal transduction studies showed that doxorubicin increased p53, JNK, p38 and NFκB phosphorylation; decreased the levels of phospho ERK and Akt; disturbed the Bcl-2 family protein balance; activated caspase 12, caspase 9 and caspase 3; and induced cleavage of the PARP protein. However, taurine treatment or cardiomyocyte incubation with taurine suppressed all of the adverse effects of doxorubicin. Studies with several inhibitors, including PS-1145 (an IKK inhibitor), SP600125 (a JNK inhibitor), SB203580 (a p38 inhibitor) and LY294002 (a PI3-K/Akt inhibitor), demonstrated that the mechanism of taurine-induced cardio protection involves activation of specific survival signals and PI3-K/Akt as well as the inhibition of p53, JNK, p38 and NFκB. These novel findings suggest that taurine might have clinical implications for the prevention of doxorubicin-induced cardiac oxidative stress.     

Mechanism of protection of moderately diet restricted rats against doxorubicin-induced acute cardiotoxicity

Clinical use of doxorubicin (Adriamycin), an antitumor agent, is limited by its oxyradical-mediated cardiotoxicity. We tested the hypothesis that moderate diet restriction protects against doxorubicin-induced cardiotoxicity by decreasing oxidative stress and inducing cardioprotective mechanisms. Male Sprague-Dawley rats (250-275 g) were maintained on diet restriction [35% less food than ad libitum]. Cardiotoxicity was estimated by measuring biomarkers of cardiotoxicity, cardiac function, lipid peroxidation, and histopathology. A LD(100) dose of doxorubicin (12 mg/kg, ip) administered on day 43 led to 100% mortality in ad libitum rats between 7 and 13 days due to higher cardiotoxicity and cardiac dysfunction, whereas all the diet restricted rats exhibited normal cardiac function and survived. Toxicokinetic analysis revealed equal accumulation of doxorubicin and doxorubicinol (toxic metabolite) in the ad libitum and diet restricted hearts. Mechanistic studies revealed that diet restricted rats were protected due to (1) lower oxyradical stress from increased cardiac antioxidants leading to downregulation of uncoupling proteins 2 and 3, (2) induction of cardiac peroxisome proliferators activated receptor-alpha and plasma adiponectin increased cardiac fatty acid oxidation (666.9+/-14.0 nmol/min/g heart in ad libitum versus 1035.6+/-32.3 nmol/min/g heart in diet restriction) and mitochondrial AMPalpha2 protein kinase. The changes led to 51% higher cardiac ATP levels (17.7+/-2.1 micromol/g heart in ad libitum versus 26.7+/-1.9 micromol/g heart in diet restriction), higher ATP/ADP ratio, and (3) increased cardiac erythropoietin and decreased suppressor of cytokine signaling 3, which upregulates cardioprotective JAK/STAT3 pathway. These findings collectively show that moderate diet restriction renders resiliency against doxorubicin cardiotoxicity by lowering oxidative stress, enhancing ATP synthesis, and inducing the JAK/STAT3 pathway.     

Evaluation of the JT and corrected JT intervals as a new ECG method for monitoring doxorubicin cardiotoxicity in the dog

A comparison was made of the sensitivity of ECG, ultrastructural heart pathology, and plasma enzymes CK-MB and α-HBDH as methods to assess doxorubicin cardiotoxicity in adult beagle dogs given doxorubicin 30 mg/m² i.v. once a week for three times. A progressive increase in JT and QT intervals, in corrected JT (JTc) and QT (QTc) intervals as well as a reduction in both T wave amplitude and RR duration, were observed in doxorubicin-treated dogs; the electrocardiogram (ECG) abnormalities were associated with doxorubicin-induced ultrastructural changes in cardiac tissue, consisting of dilation of the sarcoplasmic reticulum, multiform, flasklike invaginations of T-tubules containing electrondense material, and interruption of the junctional sarcoplasmic reticulum, which became more severe as the observation period progressed. On the contrary, doxorubicin treatment was associated with transient changes in plasma CK-MB and α-HBDH, which were unrelated to the severity of chronic cardiotoxicity. Overall results suggest that the monitoring of the ECG parameters related to the repolarization of the cardiac muscle, and particularly JT and JTc, might be regarded as a noninvasive method for the study of doxorubicin cardiotoxicity in the dog.     

Beneficial effects of carbon monoxide-releasing molecule-2 (CORM-2) on acute doxorubicin cardiotoxicity in mice: role of oxidative stress and apoptosis

Doxorubicin (DXR) has been used in variety of human malignancies for decades. Despite its efficacy in cancer, clinical usage is limited because of its cardiotoxicity, which has been associated with oxidative stress and apoptosis. Carbon monoxide-releasing molecules (CORMs) have been shown to reduce the oxidative damage and apoptosis. The present study investigated the effects of CORM-2, a fast CO-releaser, against DXR-induced cardiotoxicity in mice using biochemical, histopathological and gene expression approaches. CORM-2 (3, 10 and 30 mg/kg/day) was administered intraperitoneally (i.p.) for 10 days and terminated the study on day 11. DXR (20 mg/kg, i.p.) was injected before 72 h of termination. Mice treated with DXR showed cardiotoxicity as evidenced by elevation of serum creatine kinase (CK) and lactate dehydrogenase (LDH), tissue malondialdehyde (MDA), caspase-3 and decrease the level of total antioxidant status (TAS) in heart tissues. Pre- and post-treatment with CORM-2 (30 mg/kg, i.p.) elicited significant improvement in CK, LDH, MDA, caspase-3 and TAS levels. Histopathological studies showed that cardiac damage with DXR has been reversed with CORM-2 + DXR treatment. There was dramatic decrease in hematological count in DXR-treated mice, which has been improved with CORM-2. Furthermore, there was also elevation of mRNA expression of heme oxygenase-1, hypoxia inducible factor-1 alpha, vascular endothelial growth factor and decrease in inducible-nitric oxide synthase expression upon treatment with CORM-2 that might be linked to cardioprotection. These data suggest that CORM-2 treatment provides cardioprotection against acute doxorubicin-induced cardiotoxicity in mice and this effect may be attributed to CORM-2-mediated antioxidant and anti-apoptotic properties.     

Cardiotoxicity of Doxorubicin: Effects of Drugs Inhibiting the Release of Vasoactive Substances

Abstract: The therapeutic usefulness of doxorubicin, an antineoplastic drug, is limited by its cardiotoxicity whose mechanism is as yet unknown. Several hypotheses have been postulated including also the release of vasoactive substances, so the aim of the present investigations was to study the relationship between the release of vasoactive substances and the development of doxorubicin-induced cardiotoxicity. The effects of the following drugs on doxorubicin-induced (cumulative dose of 20 mg/kg intraperitoneally) cardiotoxicity in rats have been evaluated: verapamil (1 and 10 mg/kg orally), that inhibits the slow channel influx of calcium and catecholamine release, acetylsalicylic acid (50 and 100 mg/kg orally), that inhibits the prostaglandin biosynthesis and release, and cromolyn sodium (cromolyn; I and 10 mg/kg orally), that inhibits the secretion of histamine. Our results showed that verapamil reduced and delayed doxorubicin-induced mortality, and limited doxorubicin-induced body weight decrease and ECG changes. Acetylsalicylic acid and cromolyn did not protect against doxorubicin-induced cardiotoxicity. These findings suggest that the release of vasoactive substances does not play a prevalent role in the development of doxorubicin-induced cardiotoxicity. The protective effect of verapamil is probably due to the inhibition of doxorubicin-induced intracellular calcium overload.