Differential roles of nitric oxide synthase isozymes in cardiotoxicity and mortality following chronic doxorubicin treatment in mice

Bradykinin receptor participates in doxorubicin-induced cardiotoxicity by modulating iNOS signal pathway

Doxorubicin (DOX), an effective and broad-spectrum anthracycline antibiotic, is widely used in the treatment of numerous malignancies. However, dose-dependent cardiotoxicity limits the clinical application of DOX, and the molecular mechanisms are still unknown. In this study, we used the BK receptor B1/B2 double-knockout (B1B2 -/- ) mice to observe the role of BK receptor in cardiotoxicity induced by DOX and the underlying mechanisms. DOX induced myocardial injury with increased serum levels of AST, CK, and LDH, upregulated tissue expression of bradykinin B1/B2 receptor, FABP4 and iNOS, and downregulated expression of eNOS. However, these altered releases of myocardial enzyme and the expression level of iNOS were significantly prevented in the B1B2-/- mice. We concluded that the activation of both B1 and B2 receptors of BK were involved in the DOX-induced acute myocardial injury, possibly mediated through iNOS signaling pathways.

Molecular mechanisms of endothelial remodeling under doxorubicin treatment

Doxorubicin (DOX) is an effective antineoplastic agent used to treat various types of cancers. However, its use is limited by the development of cardiotoxicity, which may result in heart failure. The exact mechanisms underlying DOX-induced cardiotoxicity are not fully understood, but recent studies have shown that endothelial-mesenchymal transition (EndMT) and endothelial damage play a crucial role in this process. EndMT is a biological process in which endothelial cells lose their characteristics and transform into mesenchymal cells, which have a fibroblast-like phenotype. This process has been shown to contribute to tissue fibrosis and remodeling in various diseases, including cancer and cardiovascular diseases. DOX-induced cardiotoxicity has been demonstrated to increase the expression of EndMT markers, suggesting that EndMT may play a critical role in the development of this condition. Furthermore, DOX-induced cardiotoxicity has been shown to cause endothelial damage, leading to the disruption of the endothelial barrier function and increased vascular permeability. This can result in the leakage of plasma proteins, leading to tissue edema and inflammation. Moreover, DOX can impair the production of nitric oxide, endothelin-1, neuregulin, thrombomodulin, thromboxane B2 etc. by endothelial cells, leading to vasoconstriction, thrombosis and further impairing cardiac function. In this regard, this review is devoted to the generalization and structuring of information about the known molecular mechanisms of endothelial remodeling under the action of DOX.

Anticancer Effects of Tacrolimus on Induced Hepatocellular Carcinoma in Mice

BACKGROUND

Tacrolimus is a calcineurin inhibitor widely used for immunological disorders. However, there is a significant controversy regarding its effect on the liver. The present study was conducted to evaluate the anticancer effects of tacrolimus on an induced murine hepatocellular carcinoma (HCC) model and its possible hepatotoxicity at standard therapeutic doses.

METHODS

Fifty-four male mice were divided into five groups: a control healthy group, control HCC group, tacrolimus-treated group, doxorubicin (DOXO)-treated group, and combined tacrolimus- and DOXO-treated group. The activity of liver enzymes, including alkaline phosphatase, gamma-glutamyl transferase, lactate dehydrogenase, alanine transaminase, and aspartate transaminase, was determined. Serum vascular endothelial growth factor (VEGF) was measured using an enzyme-linked immunosorbent assay. A quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to measure the expression of proliferating cell nuclear antigen (PCNA), Bax, and p53 mRNA. Immunohistochemical staining for cyclin D1 and VEGF was performed.

RESULTS

Mice that received combined treatment with tacrolimus and DOXO exhibited the best improvement in all parameters when compared with the groups that received DOXO or tacrolimus alone (p < 0.001).

CONCLUSION

The combination of DOXO and tacrolimus was more effective in the management of HCC compared with either agent alone. This improvement was detected by the reduction of liver enzymes and the improvement of the histopathological picture. The involved mechanisms included significant apoptosis induction demonstrated by upregulation of bax along with a reduction in angiogenesis demonstrated by downregulation of VEGF. This was accompanied by inhibition of cell cycle progression mediated by upregulated p53 and downregulated PCNA and cyclin D1.

Protective effect of curcumin nanoparticles against cardiotoxicity induced by doxorubicin in rat

The present study designed to investigate the protective effect of curcumin nanoparticles (CUR-NPs) on the cardiotoxicity induced by doxorubicin. Rats were divided into four groups; control, rats treated daily with CUR-NPs (50 mg/kg) for 14 days, rats treated with an acute dose of doxorubicin (20 mg/kg) and rats treated daily with CUR-NPs for 14 days injected with doxorubicin on the 10th day. After electrocardiogram (ECG) recording from rats at different groups, rat decapitation was carried out and the heart of each rat was excised out to measure the oxidative stress parameters; lipid peroxidation (MDA), nitric oxide (NO) and reduced glutathione (GSH) and the activities of Na,K,ATPase and acetylcholinesterase (AchE). In addition, the levels of dopamine (DA), norepinephrine (NE) and serotonin (5-HT) were determined in the cardiac tissues. Lactate dehydrogenase (LDH) activity was measured in the serum. The ECG recordings indicated that daily pretreatment with CUR- NPs has prevented the tachycardia (i.e. increase in heart rate) and ameliorated the changes in ST wave and QRS complex induced by doxorubicin. In addition, CUR-NPs prevented doxorubicin induced significant increase in MDA, NO, DA, AchE and LDH and doxorubicin induced significant decrease in GSH, NE, 5-HT and Na,K,ATPase. According to the present findings, it could be concluded that CUR-NPs have a protective effect against cardiotoxicity induced by doxorubicin. This may shed more light on the importance of CUR-NPs pretreatment before the application of doxorubicin therapy.

Ursolic acid prevents doxorubicin-induced cardiac toxicity in mice through eNOS activation and inhibition of eNOS uncoupling

In addition to the known antitumour effects of ursolic acid (UA), increasing evidence indicates that this molecule plays a role in cardiac protection. In this study, the effects of ursolic acid on the heart in mice treated with doxorubicin (DOX) were assessed. The results showed that ursolic acid improved left ventrical fractional shortening (LVFS) and left ventrical ejection fraction (LVEF) of the heart, increased nitrogen oxide (NO) levels, inhibited reactive oxygen species (ROS) production and decreased cardiac apoptosis in mice treated with doxorubicin. Mechanistically, ursolic acid increased AKT and endothelial nitric-oxide synthase (eNOS) phosphorylation levels, and enhanced eNOS expression, while inhibiting doxorubicin induced eNOS uncoupling through NADPH oxidase 4 (NOX4) down-regulation. These effects of ursolic acid resulted in heart protection from doxorubicin-induced injury. Therefore, ursolic acid may be considered a potential therapeutic agent for doxorubicin-associated cardiac toxicity in clinical practice.

Pristimerin protects against doxorubicin-induced cardiotoxicity and fibrosis through modulation of Nrf2 and MAPK/NF-kB signaling pathways

Background/purpose

Pristimerin (Pris) is triterpenoid compound with many biological effects. Until now, nothing is known about its effect on doxorubicin (DOX)-induced cardiotoxicity. Hence, this study investigated the impact of Pris on DOX-induced cardiotoxic effects.

Materials and methods

Rats were treated with Pris 1 week before and 2 weeks contaminant with repeated DOX injection. Afterwards, electrocardiography (ECG), biochemical, histopathological, PCR, and Western blot assessments were performed.

Results

Pris effectively alleviated DOX-induced deleterious cardiac damage. It inhibited DOX-induced ECG abnormities as well as DOX-induced elevation of serum indices of cardiotoxicity. The histopathological cardiac lesions and fibrosis were remarkably improved in Pris-treated animals. Pris reduced hydroxyproline content and attenuated the mRNA and protein expression of the pro-fibrogenic genes. The antioxidant activity of Pris was prominent through the amelioration of oxidative stress parameters and enhancement of antioxidants. Furthermore, Pris enhanced the activation of nuclear factor-erythroid 2 related factor 2 (Nrf2) signaling pathway as it increased the mRNA and protein expression of Nrf2 and Nrf2-dependent antioxidant genes (GCL, NQO1, HO-1). Additionally, the anti-inflammatory effect of Pris was obvious through the inhibition of mitogen activated protein kinase (MAPK)/nuclear factor kappa-B (NF-kB) signaling and subsequent inhibition of inflammatory mediators.

Conclusion

This study provides evidence of the cardioprotective activity of Pris which is related to the modulation of Nrf2 and MAPK/NF-kB signaling pathways.

Aldose reductase inhibitor, fidarestat prevents doxorubicin-induced endothelial cell death and dysfunction

Despite doxorubicin (Dox) being one of the most widely used chemotherapy agents for breast, blood and lung cancers, its use in colon cancer is limited due to increased drug resistance and severe cardiotoxic side effects that increase mortality associated with its use at high doses. Therefore, better adjuvant therapies are warranted to improve the chemotherapeutic efficacy and to decrease cardiotoxicity. We have recently shown that aldose reductase inhibitor, fidarestat, increases the Dox-induced colon cancer cell death and reduces cardiomyopathy. However, the efficacy of fidarestat in the prevention of Dox-induced endothelial dysfunction, a pathological event critical to cardiovascular complications, is not known. Here, we have examined the effect of fidarestat on Dox-induced endothelial cell toxicity and dysfunction in vitro and in vivo. Incubation of human umbilical vein endothelial cells (HUVECs) with Dox significantly increased the endothelial cell death, and pre-treatment of fidarestat prevented it. Further, fidarestat prevented the Dox-induced oxidative stress, formation of reactive oxygen species (ROS) and activation of Caspase-3 in HUVECs. Fidarestat also prevented Dox-induced monocyte adhesion to HUVECs and expression of ICAM-1 and VCAM-1. Fidarestat pre-treatment to HUVECs restored the Dox-induced decrease in the Nitric Oxide (NO)-levels and eNOS expression. Treatment of HUVECs with Dox caused a significant increase in the activation of NF-κB and expression of various inflammatory cytokines and chemokines which were prevented by fidarestat pre-treatment. Most importantly, fidarestat prevented the Dox-induced mouse cardiac cell hypertrophy and expression of eNOS, iNOS, and 3-Nitrotyrosine in the aorta tissues. Further, fidarestat blunted the Dox-induced expression of various inflammatory cytokines and chemokines in vivo. Thus, our results suggest that by preventing Dox-induced endothelial cytotoxicity and dysfunction, AR inhibitors could avert cardiotoxicity associated with anthracycline chemotherapy.

Rat Model of Cardiotoxic Drug-Induced Cardiomyopathy

Cardiotoxicity from cancer drugs remains a clinical problem. To find reliable markers of cardiotoxicity, animal models were proposed and potential new diagnostic markers have been actively investigated using these models. Here we describe our protocols, using male Sprague-Dawley rats, for inducing cardiomyopathy by single injection of high-dose doxorubicin (5-10 mg/kg) or multiple injections (2-4 times) of low-dose doxorubicin (2.5 mg/kg) with combined single injection of trastuzumab (10 mg/kg). The cardiotoxicity is evaluated by imaging modalities (echocardiography and nuclear imaging), serum troponin levels, and histopathological analyses.

microRNAs and Acute Myeloid Leukemia Chemoresistance: A Mechanistic Overview

Up until the early 2000s, a functional role for microRNAs (miRNAs) was yet to be elucidated. With the advent of increasingly high-throughput and precise RNA-sequencing techniques within the last two decades, it has become well established that miRNAs can regulate almost all cellular processes through their ability to post-transcriptionally regulate a majority of protein-coding genes and countless other non-coding genes. In cancer, miRNAs have been demonstrated to play critical roles by modifying or controlling all major hallmarks including cell division, self-renewal, invasion, and DNA damage among others. Before the introduction of anthracyclines and cytarabine in the 1960s, acute myeloid leukemia (AML) was considered a fatal disease. In decades since, prognosis has improved substantially; however, long-term survival with AML remains poor. Resistance to chemotherapy, whether it is present at diagnosis or induced during treatment is a major therapeutic challenge in the treatment of this disease. Certain mechanisms such as DNA damage response and drug targeting, cell cycling, cell death, and drug trafficking pathways have been shown to be further dysregulated in treatment resistant cancers. miRNAs playing key roles in the emergence of these drug resistance phenotypes have recently emerged and replacement or inhibition of these miRNAs may be a viable treatment option. Herein, we describe the roles miRNAs can play in drug resistant AML and we describe miRNA-transcript interactions found within other cancer states which may be present within drug resistant AML. We describe the mechanisms of action of these miRNAs and how they can contribute to a poor overall survival and outcome as well. With the precision of miRNA mimic- or antagomir-based therapies, miRNAs provide an avenue for exquisite targeting in the therapy of drug resistant cancers.

Cardiac spheroids as promising in vitro models to study the human heart microenvironment

Three-dimensional in vitro cell systems are a promising alternative to animals to study cardiac biology and disease. We have generated three-dimensional in vitro models of the human heart ("cardiac spheroids", CSs) by co-culturing human primary or iPSC-derived cardiomyocytes, endothelial cells and fibroblasts at ratios approximating those present in vivo. The cellular organisation, extracellular matrix and microvascular network mimic human heart tissue. These spheroids have been employed to investigate the dose-limiting cardiotoxicity of the common anti-cancer drug doxorubicin. Viability/cytotoxicity assays indicate dose-dependent cytotoxic effects, which are inhibited by the nitric oxide synthase (NOS) inhibitor L-NIO, and genetic inhibition of endothelial NOS, implicating peroxynitrous acid as a key damaging agent. These data indicate that CSs mimic important features of human heart morphology, biochemistry and pharmacology in vitro, offering a promising alternative to animals and standard cell cultures with regard to mechanistic insights and prediction of toxic effects in human heart tissue.

Arginine-Nitric Oxide Metabolites and Cardiac Dysfunction in Patients With Breast Cancer

BACKGROUND

Oxidative/nitrosative stress and endothelial dysfunction are hypothesized to be central to cancer therapeutics-related cardiac dysfunction (CTRCD). However, the relationship between circulating arginine-nitric oxide (NO) metabolites and CTRCD remains unstudied.

OBJECTIVES

This study sought to examine the relationship between arginine-NO metabolites and CTRCD in a prospective cohort of 170 breast cancer patients treated with doxorubicin with or without trastuzumab.

METHODS

Plasma levels of arginine, citrulline, ornithine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and N-monomethylarginine (MMA) were quantified at baseline, 1 month, and 2 months after doxorubicin initiation. Determinants of baseline biomarker levels were identified using multivariable linear regression, and Cox regression defined the association between baseline levels and 1- or 2-month biomarker changes and CTRCD rate in 139 participants with quantitated echocardiograms at all time points.

RESULTS

Age, hypertension, body mass index, and African-American race were independently associated with ≥1 of baseline citrulline, ADMA, SDMA, and MMA levels. Decreases in arginine and citrulline and increases in ADMA were observed at 1 and 2 months (all p < 0.05). Overall, 32 participants experienced CTRCD over a maximum follow-up of 5.4 years. Hazard ratios for ADMA and MMA at 2 months were 3.33 (95% confidence interval [CI]: 1.12 to 9.96) and 2.70 (95% CI: 1.35 to 5.41), respectively, and 0.78 (95% CI: 0.64 to 0.97) for arginine at 1 month.

CONCLUSIONS

In breast cancer patients undergoing doxorubicin therapy, early alterations in arginine-NO metabolite levels occurred, and early biomarker changes were associated with a greater CTRCD rate. Our findings highlight the potential mechanistic and translational relevance of this pathway to CTRCD.

Developing a rat model of dilated cardiomyopathy with improved survival

To compare the continuous infusion and intermittent bolus injection administration protocols of doxorubicin (Dox) under the same cumulative dose (12 mg/kg), and establish a rat dilated cardiomyopathy model with improved survival, a total of 150 Sprague-Dawley (SD) rats were divided into three groups: a control group, administered with normal saline; a Dox 1 group, administration twice a week at 1 mg/kg; a Dox 2, administration once a week at 2 mg/kg. Mortality rates in the Dox 1 and Dox 2 groups were 22% and 48%, respectively (P<0.05). As shown by echocardiography, both Dox groups exhibited significant chamber dilatation and reduced cardiac function (all P<0.05 vs. control). Plasma brain natriuretic peptide and C-reactive protein concentrations were significantly increased (P<0.05) with both Dox regimens. The concentrations of Caspase-3 in myocardial tissues of rats significantly increased in both doxorubicin regimens. Myocardial metabolism imaging by histology and ¹⁸F-fluoro-deoxyglucose-positron emission tomography (¹⁸FDG-PET) both revealed decreased myocardial viability and necrosis, and even interstitial fibrosis, in left ventricles (LVs) in both Dox groups. Serum creatinine and aspartate aminotransferase concentrations were significantly higher in the Dox 2 model than in the Dox 1 model. Doxorubicin given at both regimens induced dilated cardiomyopathy, while its administration at lower doses with more frequent infusions reduced the mortality rate.

Testosterone Antagonizes Doxorubicin-Induced Senescence of Cardiomyocytes

Background

Chronic cardiotoxicity is less common in male than in female patients receiving doxorubicin and other anthracyclines at puberty and adolescence. We hypothesized that this sex difference might be secondary to distinct activities of sex hormones on cardiomyocyte senescence, which is thought to be central to the development of long‐term anthracycline cardiomyopathy.

Methods and Results

H9c2 cells and neonatal mouse cardiomyocytes were exposed to doxorubicin with or without prior incubation with testosterone or 17β‐estradiol, the main androgen and estrogen, respectively. Testosterone, but not 17β‐estradiol, counteracted doxorubicin‐elicited senescence. Downregulation of telomere binding factor 2, which has been pinpointed previously as being pivotal to doxorubicin‐induced senescence, was also prevented by testosterone, as were p53 phosphorylation and accumulation. Pretreatment with the androgen receptor antagonist flutamide, the phosphatidylinositol 3 kinase inhibitor LY294002, and the nitric oxide synthase inhibitor L‐NG‐nitroarginine methyl ester abrogated the reduction in senescence and the normalization of telomere binding factor 2 levels attained by testosterone. Consistently, testosterone enhanced the phosphorylation of AKT and nitric oxide synthase 3. In H9c2 cells, doxorubicin‐stimulated senescence was still observed up to 21 days after treatment and increased further when cells were rechallenged with doxorubicin 14 days after the first exposure to mimic the schedule of anthracycline‐containing chemotherapy. Remarkably, these effects were also inhibited by testosterone.

Conclusions

Testosterone protects cardiomyocytes against senescence caused by doxorubicin at least in part by modulating telomere binding factor 2 via a pathway involving the androgen receptor, phosphatidylinositol 3 kinase, AKT, and nitric oxide synthase 3. This is a potential mechanism by which pubescent and adolescent boys are less prone to chronic anthracycline cardiotoxicity than girls.

The role of nitric oxide in Doxorubicin-induced cardiotoxicity: experimental study

Objective: We evaluated the myocardial damage in rats treated with doxorubicin (DOX) alone and in combination with nitric oxide synthase (NOS) inhibitors.

Materials and Methods: Twenty-four male Sprague Dawley rats (12 weeks old, weighing 262±18 g) were randomly assigned into 4 groups (n=6). Group I was the control group. In Group II, rats were treated with intraperitoneal (ip) injections of 3 mg/kg DOX once a week for 5 weeks. In Group III, rats received weekly ip injections of 30 mg/kg L-NAME (nonspecific NOS inhibitor) 30 min before DOX injections for 5 weeks. In Group IV, rats received weekly ip injections of 3 mg/kg L-NIL (inducible NOS inhibitor) 30 min before DOX injections for 5 weeks. Rats were weighed 2 times a week. At the end of 6 weeks, hearts were excised and then fixed for light and electron microscopy evaluation and tissue lipid peroxidation (malondialdehyde). Blood samples were also obtained for measuring plasma lipid peroxidation.

Results: Weight loss was observed in Group II, Group III, and Group IV. Weight loss was statistically significant in the DOX group. Findings of myocardial damage were significantly higher in animals treated with DOX only than in the control group. Histopathological findings of cardiotoxicity in rats treated with DOX in combination with L-NAME and L-NIL were not significantly different compared with the control group. The level of plasma malondialdehyde in the DOX group (9.3±3.4 µmol/L) was higher than those of all other groups.

Conclusion: Our results showed that DOX cardiotoxicity was significantly decreased when DOX was given with NO synthase inhibitors.

HBOC vasoactivity: interplay between nitric oxide scavenging and capacity to generate bioactive nitric oxide species

SIGNIFICANCE

Despite many advances in blood substitute research, the development of materials that are effective in maintaining blood volume and oxygen delivery remains a priority for emergency care and trauma. Clinical trials on hemoglobin (Hb)-based oxygen carriers (HBOCs) have not provided information on the mechanism of toxicity, although all commercial formulations have safety concerns. Specifically, it is important to reconcile the different hypotheses of Hb toxicity, such as nitric oxide (NO) depletion and oxidative reactions, to provide a coherent molecular basis for designing a safe HBOC.

RECENT ADVANCES

HBOCs with different sizes often exhibit differences in the degree of HBOC-induced vasoactivity. This has been attributed to differences in the degree of NO scavenging and in the extent of Hb extravasation. Additionally, it is appears that Hb can undergo reactions that compensate for NO scavenging by generating bioactive forms of NO.

CRITICAL ISSUES

Engineering modifications to enhance bioactive NO production can result in diminished oxygen delivery by virtue of increased oxygen affinity. This strategy can prevent the HBOC from fulfilling the intended goal on preserving oxygenation; however, the NO production effects will increase perfusion and oxygen transport.

FUTURE DIRECTIONS

Hb modifications influence NO scavenging and the capacity of certain HBOCs to compensate for NO scavenging through nitrite-mediated reactions that generate bioactive NO. Based on the current understanding of these NO-related factors, possible synthetic strategies are presented that address how HBOC formulations can be prepared that: (i) effectively deliver oxygen, (ii) maintain tissue perfusion, and (iii) limit/reverse underlying inflammation within the vasculature.

Oxidative stress, redox signaling, and metal chelation in anthracycline cardiotoxicity and pharmacological cardioprotection

SIGNIFICANCE

Anthracyclines (doxorubicin, daunorubicin, or epirubicin) rank among the most effective anticancer drugs, but their clinical usefulness is hampered by the risk of cardiotoxicity. The most feared are the chronic forms of cardiotoxicity, characterized by irreversible cardiac damage and congestive heart failure. Although the pathogenesis of anthracycline cardiotoxicity seems to be complex, the pivotal role has been traditionally attributed to the iron-mediated formation of reactive oxygen species (ROS). In clinics, the bisdioxopiperazine agent dexrazoxane (ICRF-187) reduces the risk of anthracycline cardiotoxicity without a significant effect on response to chemotherapy. The prevailing concept describes dexrazoxane as a prodrug undergoing bioactivation to an iron-chelating agent ADR-925, which may inhibit anthracycline-induced ROS formation and oxidative damage to cardiomyocytes.

RECENT ADVANCES

A considerable body of evidence points to mitochondria as the key targets for anthracycline cardiotoxicity, and therefore it could be also crucial for effective cardioprotection. Numerous antioxidants and several iron chelators have been tested in vitro and in vivo with variable outcomes. None of these compounds have matched or even surpassed the effectiveness of dexrazoxane in chronic anthracycline cardiotoxicity settings, despite being stronger chelators and/or antioxidants.

CRITICAL ISSUES

The interpretation of many findings is complicated by the heterogeneity of experimental models and frequent employment of acute high-dose treatments with limited translatability to clinical practice.

FUTURE DIRECTIONS

Dexrazoxane may be the key to the enigma of anthracycline cardiotoxicity, and therefore it warrants further investigation, including the search for alternative/complementary modes of cardioprotective action beyond simple iron chelation.

Dietary inorganic nitrate alleviates doxorubicin cardiotoxicity: mechanisms and implications

Doxorubicin (DOX) is one of the most powerful and widely prescribed chemotherapeutic agents to treat divergent human cancers. However, the clinical use of DOX is restricted due to its severe cardiotoxic side-effects. There has been ongoing search for cardioprotectants against DOX toxicity. Inorganic nitrate has emerged as a bioactive compound that can be reduced into nitrite and nitric oxide in vivo and in turn plays a therapeutic role in diseases associated with nitric oxide insufficiency or dysregulation. In this review, we describe a novel concept of using dietary supplementation of inorganic nitrate to reduce DOX-induced cardiac cellular damage and dysfunction, based on our recent promising studies in a mouse model of DOX cardiotoxicity. Our data show that chronic oral ingestion of sodium nitrate, at a dose equivalent to ~400% of the Acceptable Daily Intake of the World Health Organization, alleviated DOX-induced left ventricular dysfunction and mitochondrial respiratory chain damage. Such cardioprotective effects were associated with reduction of cardiomyocyte necrosis/apoptosis, tissue lipid peroxidation, and mitochondrial H(2)O(2) generation following DOX treatment. Furthermore, proteomic studies revealed enhanced cardiac expression of mitochondrial antioxidant enzyme - peroxiredoxin 5 in the nitrate-treated animals. These studies suggest that inorganic nitrate could be an inexpensive therapeutic agent for long-term oral administration in preventing DOX-induced cardiac toxicity and myopathy during the prolonged pathological process. Future clinical trials in the cancer patients undergoing DOX chemotherapy are warranted to translate these experimental findings into an effective new therapy in preventing the DOX-induced cardiomyopathy.

Chronic cardiotoxicity of doxorubicin involves activation of myocardial and circulating matrix metalloproteinases in rats

AIM

To investigate the role of matrix metalloproteinases (MMPs) in the responses of rats to a prolonged doxorubicin (DOX) treatment.

METHODS

Male Wistar rats were used. DOX was administered by intraperitoneal injections of seven doses (cumulative dose was 15 mg/kg). Control animals were treated with saline. Tissue or plasma samples were collected at four and eight weeks after the application of the last dose. Protein levels were determined by immunoblot assay, and MMP activities were measured by gelatin zymography. Superoxide content was analyzed using a lucigenin chemiluminescence assay and superoxide dismutase (SOD) activities with a SOD assay kit. Qualitative structural alterations of the heart were characterized by transmission electron microscopy.

RESULTS

Systolic blood pressure was higher in DOX-treated rats as compared with the control rats at 8 weeks after treatment. In contrast, there were no differences in the heart rate between the control and DOX-treated rats. DOX treatment caused marked heterogeneous subcellular alterations of cardiomyocytes and structural disorganizations of the cardiac extracellular space. The effects of DOX were linked to a stimulation of plasma MMP-2 and MMP-9 activities that had already increased by 4 weeks after the end of the treatment. In the left ventricle, however, DOX only led to increased MMP-2 activation at 8 weeks after the end of treatment. These changes in tissue MMP-2 were connected with stimulation of Akt kinase activation, inhibition of SOD, an increase in superoxide levels, induction of iNOS protein expression and caspase-3 activation.

CONCLUSION

Our results show that MMPs are involved in the chronic cardiotoxicity of DOX in rats. The data also suggest that reactive oxygen species (superoxide), NO production (iNOS) and the Akt kinase pathway can modulate MMP-2 activities in rat hearts influenced by DOX.

Efficacy of melatonin, mercaptoethylguanidine and 1400W in doxorubicin- and trastuzumab-induced cardiotoxicity

Doxorubicin (DOX) and Trastuzumab (TRAST) are effective agents for the treatment of many neoplastic diseases. Cardiotoxicity is a major side effect of these drugs and limit their use. In this study, the possible protective effects of melatonin (MEL), mercaptoethylguanidine (MEG), or N-(3-(aminomethyl) benzyl) acetamidine (1400W) against the cardiotoxicity of DOX and TRAST were tested. Male Sprague-Dawley rats received an injection of DOX (20 mg/kg) alone or in combination with TRAST (10 mg/kg) to induce cardiotoxicity; daily treatments with MEL (10 mg/kg × 2), MEG (10 mg/kg × 2), or 1400W (10 mg/kg × 2) were begun 36 hr before and continued for 72 hr after DOX and TRAST administration. Oxidant/antioxidant indices of the cardiac tissue, namely, malondialdehyde, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), as well as serum levels of creatine phosphokinase (CK-MB) were measured. Additionally, the injury scores were evaluated histopathologically. Malondialdehyde levels were significantly higher, while SOD and GSH-Px activities were significantly reduced in rats with DOX- or DOX+TRAST-induced cardiotoxicity compared to normal values. All three treatment agents significantly reversed oxidative stress markers. Serum CK-MB levels were significantly increased after treatment with DOX and DOX+TRAST; these changes were also reversed by each of the treatments and resulted in near normal levels. Both the DOX- and DOX+TRAST-treated rats presented similar histopathologic injuries; in the animals treated with the protective agents, histologic protection of the cardiac tissue was apparent. These results suggested that MEL, MEG, as well as 1400 W are effective in preventing DOX- or DOX+TRAST-induced cardiotoxicity.

Atorvastatin prevents mesenchymal stem cells from hypoxia and serum-free injury through activating AMP-activated protein kinase

BACKGROUND

Mesenchymal stem cells (MSCs) are the optimal candidate of treating myocardial infarction; however, the lower survival ratio of implanted cell discourages the advantages of this treatment. Recent studies have displayed statins, which exert pleiotropic effects on the cardiovascular system partially through the increase in endothelial nitric oxide synthase (eNOS) activity, could increase the livability of cells under hypoxia and serum-free (H/SF) conditions. AMP-activated protein kinase (AMPK) is the essential part in keeping the balance of energy production and metabolism in various tissues, which is the dominant factor modulating the programmed cell death. Therefore, we hypothesized that atorvastatin could protect MSCs from H/SF injury through AMPK-eNOS pathway.

METHODS AND RESULTS

Stained with Annexin V/propidine iodine (PI), we found atorvastatin (0.001 μM-10 μM) reduced apoptosis of porcine bone marrow-derived MSCs cultured in H/SF condition; however, this effect was obstructed by compound C, an inhibitor of AMPK. This trend was similar as what bax protein, a pro-apoptosis protein, showed analyzed by Western blotting; whereas the bcl-2 protein, an anti-apoptosis protein, increased in atorvastatin treated cells. Meanwhile, MSCs treated with atorvastatin increased phosphorylation of AMPK and eNOS. The uptrend was partially inhibited by compound C.

CONCLUSIONS

Atorvastatin can activate AMPK and the phosphorylation of AMPK results in eNOS activated, which provides a novel explanation for the multi-effect of statins on cardiovascular system.