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.     

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.     

Mechanisms underlying the protective effect of eugenol in rats with acute doxorubicin cardiotoxicity

The protective effect of eugenol and its possible mechanisms were investigated in rats with acute doxorubicin cardiotoxicity. Cardiac toxicity was induced by a single intraperitoneal injection of doxorubicin (20 mg/kg). Eugenol treatment (5 mg/kg/day, orally) was started 2 days before doxorubicin administration and continued for five consecutive days. Eugenol significantly reduced the elevated serum creatine kinase and lactate dehydrogenase levels, and restored the electrocardiographic disturbances resulted from doxorubicin administration. Also, eugenol reversed doxorubicin-induced deficits in the antioxidant defense mechanisms, decreased lipid peroxidation and attenuated the elevations in cytosolic Ca²⁺ and nitric oxide levels in cardiac tissue. In addition, doxorubicin-induced cardiac tissue damage observed by histopathological examination was markedly ameliorated with eugenol. Immunohistochemical analysis revealed that eugenol prevented the doxorubicin-induced activation of caspase-3 in cardiomyocytes. The cardioprotective effect afforded by eugenol was not significantly inhibited by prior administration of capsazepine, the transient potential vanilloid receptor-1 antagonist. It was concluded that eugenol, through its antioxidant activity and its ability to reduce cardiac Ca²⁺ accumulation and nitric oxide levels, is a potential candidate to protect against acute doxorubicin cardiotoxicity, a major and dose-limiting clinical problem.     

Organic anion-transporting polypeptides contribute to the hepatic uptake of berberine

Abstract

1.?The purpose of this study was to investigate the mechanism of hepatic uptake of berberine. Berberine accumulation in hepatocytes was found to be highly dependent on active uptake, which could not be explained by liver organic cation transporter (OCT) alone.

2.?Our studies indicated that berberine uptake was significantly suppressed by rifampicin, cyclosporine A and glycyrrhizic acid, which act as specific inhibitors of different Oatp isoforms (Oatp1a1, Oatp1a4 and Oatp1b2) in rat hepatocytes. The combination of OCT and OATP inhibitors further reduced berberine accumulation in both rat and human hepatocytes. The uptake of berberine could be increased in human HEK293-OATP1B3 but not in OATP1B1-transfected HEK 293 cells.

3.?Rifampicin could reduce the berberine liver extraction ratio (ER) and double its concentration in the effluent in isolated rat livers. Further in vivo study indicated that berberine plasma exposure could be significantly increased by co-administration of the OATP inhibitor rifampicin or the substrate rosuvastatin.

4.?In conclusion, this study demonstrated that both OCT and OATP contribute to the accumulation of berberine in the liver. OATPs may have important roles in berberine liver disposition and potential clinically relevant drug--drug interactions.     

基于药动学及代谢物组学研究多柔比星在大鼠体内的心脏毒性

目的 测定多柔比星大剂量给药后原型药物及代谢产物的药动学特征及组织分布,以明确代谢产物在多柔比星急性心脏毒性中的作用。方法 测定多柔比星血清及心脏组织源性代谢物的变化特点,寻找与心脏毒性发生相关的代谢生物标志物及心脏毒性的潜在机制。利用LC-MS/MS测定多柔比星及多柔比星醇的浓度,利用GC-MS进行血清及心脏组织的代谢物组学分析。结果 多柔比星大鼠体内单剂量给药后,在心脏组织呈现高分布,且高剂量（10 mg·kg^-1）时分布显著增加。多柔比星醇的代谢转换率很低,且在心脏组织中的分布较低。代谢物组学研究结果表明,小分子能量物质酮体及脂肪酸为血清样本中的主要差异性物质。心脏组织中主要差异性物质为脂肪酸和甘油单酯。结论 多柔比星单剂量给药后,其在心脏中分布较高,且高剂量时特异性分布增加。多柔比星醇在血清及心脏组织中的浓度较低,推测其在急性毒性中的作用有限。多柔比星单剂量给药会引起心脏组织内的以脂质代谢为主的能量代谢异常,能量代谢对多柔比星相关的急性心肌毒性具有重要作用。     

Cardioprotective effects of rosuvastatin and carvedilol on delayed cardiotoxicity of doxorubicin in rats

Context: Doxorubicin is widely used anti-neoplastic drug but has serious cardiotoxicity. Long-term cardioprotective effects of statin and carvedilol against delayed cardiotoxicity of doxorubicin was not well elucidated.

Objective: To evaluate long-term cardioprotective effects of co-administered rosuvastatin and carvedilol against chronic doxorubicin-induced cardiomyopathy (DIC) in rats.

Methods: Sixty-one rats were assigned to six groups: group I, control; group II, doxorubicin only (1.25 mg/kg, bi-daily, I.P.); group III, doxorubicin + rosuvastatin (2 mg/kg/day, P.O.); group IV, doxorubicin + rosuvastatin(10 mg/kg/day, P.O.); group V, doxorubicin + carvedilol (5 mg/kg/day, P.O.); group VI, doxorubicin + carvedilol (10 mg/kg/day, P.O.). Drugs were administered for 4 weeks (by week 4) and rats were observed without drugs for 4 weeks (by week 8).

Results: After 4 weeks discontinuation of drugs (week 8), group III showed higher +dP/dt (p = 0.058), lower ?dP/dt (p = 0.009), lower left ventricular (LV) tissue malondialdehyde (MDA; p = 0.022), and less LV fibrosis (p = 0.011) than group II. Group IV showed similar results to group III. However, in group V and VI, carvedilol failed to reduce LV dysfunction, elevation of troponin or myocardial fibrosis, although group V showed lower LV tissue MDA (p = 0.004) than group II.

Discussion and conclusions: Myocardial injury and LV systolic/diastolic dysfunction at week 8 was alleviated by co-administered rosuvastatin, but not by carvedilol. It is unclear whether the cardioprotective effect of rosuvastatin is attributed to a suppression of oxidative stress induced by doxorubicin, because carvedilol did not exhibit a cardioprotective effect despite its antioxidant effects.     

Effects of doxorubicinol on excitation--contraction coupling in guinea pig ventricular myocytes.

The cardiotoxicity of the anticancer drug doxorubicin may be related to its main metabolite doxorubicinol. In this study, the acute effects of doxorubicinol on excitation-contraction coupling in isolated guinea pig ventricular myocytes were investigated and compared with doxorubicin using the whole-cell patch-clamp-, fura-2 fluorescence- and cell-edge tracking techniques. Both drugs were applied intracellularly by diffusion from the patch electrode for 15--20 min. Doxorubicin (100 microM) prolonged the action potential duration (APD) by 31% and enhanced cell shortening by 26%. Contrary to doxorubicin, doxorubicinol (10 microM) shortened APD by 25% and decreased cell shortening by 31%. APD shortening by doxorubicinol was due to an increase of the delayed rectifier K(+) current. Neither the inward rectifier K(+) current nor the L-type Ca(2+) current was influenced by doxorubicinol. The decline in cell shortening induced by doxorubicinol was not exclusively due to APD shortening because doxorubicinol reduced the peak Ca(2+) transient by 23% in cells clamped with an action potential of constant duration. Despite opposite effects on APD and contractility, both doxorubicin and doxorubicinol produced a considerable delay in the activation and inactivation of contraction and Ca(2+) transient, compatible with an impaired function of the sarcoplasmic reticulum. It is suggested that doxorubicinol-induced APD shortening may amplify the detrimental effects of both doxorubicin and doxorubicinol on sarcoplasmic reticulum Ca(2+) load and hence on contractile function. The accumulation of doxorubicinol in the cardiac myocytes may play an important role in the time-dependent development of doxorubicin-induced ventricular dysfunction.     

Taurine deficiency and doxorubicin: interaction with the cardiac sarcolemmal calcium pump

An anticancer drug, doxorubicin, and a naturally occurring beta-amino acid, taurine, exert opposing actions on myocardial calcium content and lipid peroxidation. Thus, we tested the hypothesis that the two agents may interact to modify cardiac calcium metabolism and indices of lipid peroxidation. Cardiac taurine levels were reduced by half in rats given tap water containing a beta-amino transport inhibitor, beta-alanine. Taurine deficiency was associated with an increased susceptibility of the heart to doxorubicin-mediated calcium accumulation, a phenomenon commonly associated with doxorubicin cardiotoxicity. Taurine deficiency also predisposed the heart to enhanced formation of malondialdehyde caused by doxorubicin administration. While increases in malondialdehyde levels are often associated with lipid peroxidation, the failure of doxorubicin to cause changes in oxidized glutathione content makes peroxidative mechanisms a less likely explanation for the potentiation of doxorubicin-mediated myocardial calcium accumulation in taurine-deficient rats. A more likely possibility is the interaction between taurine deficiency and doxorubicin to inhibit the sarcolemmal calcium pump. The data also suggest that the interaction between doxorubicin and taurine deficiency does not involve alterations in the pharmacokinetics of doxorubicin or the cardiotoxic metabolite, doxorubicinol. It is concluded that reduction in sarcolemmal calcium pump activity by taurine deficiency may contribute to myocardial calcium accumulation in hearts whose calcium homeostasis has been compromised by doxorubicin.     

Folic acid ameliorates celecoxib cardiotoxicity in a doxorubicin heart failure rat model

Context: The cardiotoxic effect of selective cyclo-oxygenase-2 inhibitors is well known. While rofecoxib and valdecoxib have been withdrawn, celecoxib remains on the market. Folic acid, a naturally occurring vitamin, has been shown to reduce myocardial ischemia and post-reperfusion injury in rats.

Objective: This study examined the cardiac effects of celecoxib and folic acid on doxorubicin-induced cardiomyopathy in rats.

Materials and methods: Cardiomyopathy was induced in male Wistar rats with six intraperitoneal injections of 2.5?mg/kg doxorubicin over a period of two weeks. The effect of 28?days of celecoxib (100?mg/kg/day) and its combination with folic acid (10?mg/kg/day) was studied on doxorubicin-induced cardiomyopathy according to serum lactate dehydrogenase (LDH), creatine kinase (CK-MB), troponin-T (Tn-T), tumor necrosis factor alpha (TNF-α), cardiac thiobarbituric acid reactive substance (TBARS), and glutathione (GSH) levels as well as systolic blood pressure (SBP), heart rate (HR) and ultrastructural studies.

Results: Celecoxib cardiotoxicity was manifested by significant increases in the LDH, Tn-T, TNF-α, CK-MB, SBP, HR (p?p?p?Discussion and conclusion: Folic acid protects against the cardiotoxic effects of celecoxib, which are aggravated in the presence of doxorubicin. Folic acid may act as a useful adjunct in patients who are taking celecoxib.     

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.     

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.     

Overexpressed SIRT6 ameliorates doxorubicin-induced cardiotoxicity and potentiates the therapeutic efficacy through metabolic remodeling

Since the utilization of anthracyclines in cancer therapy, severe cardiotoxicity has become a major obstacle. The major challenge in treating cancer patients with anthracyclines is minimizing cardiotoxicity without compromising antitumor efficacy. Herein, histone deacetylase SIRT6 expression was reduced in plasma of patients treated with anthracyclines-based chemotherapy regimens. Furthermore,overexpression of SIRT6 alleviated doxorubicin-induced cytotoxicity in cardiomyocytes, and potentiated c...     

Cardioprotective effect of grape-seed proanthocyanidins on doxorubicin-induced cardiac toxicity in rats

Context: Doxorubicin (Dox) is an anthracycline antibiotic used as anticancer agent. However, its use is limited due to its cardiotoxicity which is mainly attributed to accumulation of reactive oxygen species.

Objective: This study was conducted to assess whether the antioxidant, proanthocyanidins (Pro) can ameliorate Dox-induced cardiotoxicity in rats.

Materials and methods: Male Sprague–Dawely rats were divided into four groups. Group I was control. Group II received Pro (70?mg/kg, orally) once daily for 10 days. Group III received doxorubicin 15?mg/kg i.p. as a single dose on the 7th day and Group IV animals were treated with Pro once daily for 10 days and Dox on the 7th day. The parameters of study were serum biomarkers, cardiac tissue antioxidant status, ECG, and effect on aconitine-induced cardiotoxicity.

Results: Cardiac toxicity of doxorubicin was manifested as a significant increase in heart rate, elevation of the ST segment, prolongation of the QT interval and an increase in T wave amplitude. In addition, Dox enhanced aconitine-induced cardiotoxicity by a significant decrease in the aconitine dose producing ventricular tachycardia (VT). Administration of Pro significantly suppressed Dox-induced ECG changes and normalized the aconitine dose producing VT. The toxicity of Dox was also confirmed biochemically by significant elevation of serum CK-MB and LDH activities as well as myocardial MDA and GSH contents and decrease in serum catalase and myocardial SOD activities. Administration of Pro significantly suppressed these biochemical changes.

Discussion and conclusion: These results suggest that proanthocyanidins might be a potential cardioprotective agent against Dox-induced cardiotoxicity due to its antioxidant properties.     

Preclinical evaluation of the cardiotoxicity of taxane-anthracycline combinations using the model of isolated perfused rat heart

Paclitaxel strongly potentiates the cardiotoxicity of doxorubicin in the clinical setting. In this study, we aimed (1) to determine whether this potentiation could be reproduced in an ex vivo model and, if so, (2) to select drugs and protocols that did not cause this potentiation. The effect of paclitaxel and docetaxel on the cardiotoxicity induced by doxorubicin and epirubicin was studied using the model of isolated perfused rat heart. Cardiac performances were evaluated after several combination protocols administered every 2 days over a period of 12 days, and anthracycline concentrations in the heart and liver were determined on Day 12. When administered simultaneously, paclitaxel strongly potentiated the cardiotoxicity of doxorubicin ex vivo, and this effect was not due to Cremophor EL, the solvent used in the formulation of paclitaxel. The potentiation of anthracycline cardiotoxicity could be avoided by the replacement of doxorubicin by epirubicin, and/or of paclitaxel by docetaxel. Cardiotoxic potentiation was also avoided by the introduction of a 24-h lag time between the repetitive injections of doxorubicin and docetaxel. The concentration of doxorubicin and its cardiotoxic metabolite, doxorubicinol, in the heart and liver was not significantly altered by the taxanes, but that of epirubicin was increased twofold both in the heart and the liver. These results show that the potentiation of doxorubicin-induced cardiotoxicity by paclitaxel can be reproduced with an ex vivo model, and that it is not related to an increase in tissue concentration of the drug or active metabolite. Our model, therefore, may be useful for the selection of anthracycline-containing protocols with no increased risk of cardiotoxicity for the patients.     

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

Abstract

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.     

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.     

Nicorandil ameliorates mitochondrial dysfunction in doxorubicin-induced heart failure in rats: Possible mechanism of cardioprotection

Despite of its known cardiotoxicity, doxorubicin is still a highly effective anti-neoplastic agent in the treatment of several cancers. In the present study, the cardioprotective effect of nicorandil was investigated on hemodynamic alterations and mitochondrial dysfunction induced by cumulative administration of doxorubicin in rats. Doxorubicin was injected i.p. over 2 weeks to obtain a cumulative dose of 18 mg/kg. Nicorandil (3 mg/kg/day) was given orally with or without doxorubicin treatment. Heart rate and aortic blood flow were recorded 24 h after receiving the last dose of doxorubicin. Rats were then sacrificed and hearts were rapidly excised for estimation of caspase-3 activity, phosphocreatine and adenine nucleotides contents in addition to cytochrome c, Bcl2, Bax and caspase 3 expression. Moreover, mitochondrial oxidative phosphorylation capacity, creatine kinase activity and oxidative stress markers were measured together with the examination of DNA fragmentation and ultrastructural changes. Nicorandil was effective in alleviating the decrement of heart rate and aortic blood flow and the state of mitochondrial oxidative stress induced by doxorubicin cardiotoxicity. Nicorandil also preserved phosphocreatine and adenine nucleotides contents by restoring mitochondrial oxidative phosphorylation capacity and creatine kinase activity. Moreover, nicorandil provided a significant cardioprotection via inhibition of apoptotic signaling pathway, DNA fragmentation and mitochondrial ultrastructural changes. Interestingly, nicorandil did not interfere with cytotoxic effect of doxorubicin against the growth of solid Ehrlich carcinoma. In conclusion, nicorandil was effective against the development of doxorubicin-induced heart failure in rats as indicated by improvement of hemodynamic perturbations, mitochondrial dysfunction and ultrastructural changes without affecting its antitumor activity.     

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.     

Cardioprotective effect of whole fruit extract of pomegranate on doxorubicin-induced toxicity in rat

Context: Cardioprotective effects of various plants are generally attributed to their antioxidant activity. The whole fruit extract of pomegranate (WFEP), Punica granatum L. (Punicaceae), has a potent antioxidant activity.

Objective: To investigate cardioprotective effect of WFEP against doxorubicin (Dox)-induced cardiotoxicity in rats.

Materials and methods: Male Wistar rats were divided randomly into three groups of eight rats each: control (water, 5?mL/kg); Dox (10?mg/kg i.v.) and WFEP (100?mg/kg). Dox was administered in Dox and WFEP groups. After anesthetizing the animals on the last day, electrocardiogram was recorded and blood was analyzed for creatine kinase-MB isoenzyme (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) activities. Determinations of superoxide dismutase (SOD), reduced glutathione (GSH), lipid peroxidation (LPO) and histopathology of the heart tissues were carried out.

Results: The WFEP group showed decreased QT and increase in heart rate (p?<?0.05) compared to the Dox group. Significant decrease in CK-MB (p?<?0.01), LDH (p?<?0.05) and no such significant decrease in AST were observed as compared to the Dox group. There was significant increase in the level of GSH (p?<?0.05), whereas inhibition of LPO and increase in SOD concentration was not significant in the WFEP group compared to the Dox group. Histopathological study of the WFEP-treated group showed slight protection against myocardial toxicity induced by Dox.

Conclusion: Results indicate that WFEP has cardioprotective effect against Dox-induced cardiotoxicity in rats.     

Cardioprotective effect of methanolic extract of Ixora coccinea Linn. leaves on doxorubicin-induced cardiac toxicity in rats

Objectives:

To investigate the effect of methanolic extract of Ixora coccinea Linn. (MEIC) leaves against doxorubicin-induced cardiac toxicity in rats.

Material and Methods:

Albino Wistar rats were pretreated with the methanolic extract of Ixora coccinea Linn. leaves (200 and 400 mg/kg, orally) for 1 week followed with the simultaneous treatment with doxorubicin (cumulative dose of 15 mg/kg in six divided doses for 2 weeks) along with the extracts for the next 14 days. On the 22^nd day hemodynamic parameters such as blood pressure and ECG were recorded. Biochemical study including biomarkers like creatine kinase – MB (CK – MB), lactate dehydrogenase (LDH), SGOT and SGPT, tissue antioxidant markers viz. catalase (CAT), superoxide dismutase (SOD) and extent of lipid peroxidation viz. malondialdehyde (MDA) was estimated. Histopathology of heart was also done to assess the cardioprotective effect.

Results:

Pretreatment with MEIC significantly reduced (P<0.01) the ST segment elevation and also maintained the BP (P<0.01) close to normal. The MEIC significantly reduced the elevated level of biomarkers like CK - MB, LDH, SGOT, SGPT (P<0.01) near to normal, the MEIC also increased the tissue antioxidant markers viz. CAT, SOD and decreased the level of MDA (P<0.01) in cardiac tissue by dose-dependant manner. The histopathology of heart also further confirmed the cardioprotection provided by the methanolic extract of Ixora coccinea Linn. leaves.

Conclusion:

The results suggest a cardioprotective effect of Ixora coccinea Linn. leaves due to its antioxidant properties.KEY WORDS: Antioxidant, blood pressure, cardiotoxicity, electrocardiography, Ixora coccinea Linn.