Disruption of nitric oxide synthase 3 protects against the cardiac injury, dysfunction, and mortality induced by doxorubicin

Recent progress in doxorubicin-induced cardiotoxicity and protective potential of natural products

BACKGROUND

As an anthracycline antibiotic, doxorubicin (DOX) is one of the most potent and widely used chemotherapeutic agents for various types of solid tumors. Unfortunately, clinical application of this drug results in severe side effects of cardiotoxicity.

PURPOSE

We aim to review the research focused on elimination or reduction of DOX cardiotoxicity without affecting its anticancer efficacy by natural products.

METHODS

This study is based on pertinent papers that were retrieved by a selective search using relevant keywords in PubMed and ScienceDirect. The literature mainly focusing on natural products and herb extracts with therapeutic efficacies against experimental models both in vitro and in vivo was identified.

RESULTS

Current evidence revealed that multiple molecules and signaling pathways, such as oxidative stress, iron metabolism, and inflammation, are associated with DOX-induced cardiotoxicity. Based on these knowledge, various strategies were proposed, and thousands of compounds were screened. A number of natural products and herb extracts demonstrated potency in limiting DOX cardiotoxicity toward cultured cells and experimental animal models.

CONCLUSIONS

Though a panel of natural products and herb extracts demonstrate protective effects on DOX-induced cardiotoxicity in cells and animal models, their therapeutic potentials for clinical needs further investigation.

Oxidative Stress and Cellular Response to Doxorubicin: A Common Factor in the Complex Milieu of Anthracycline Cardiotoxicity

The production of reactive species is a core of the redox cycling profile of anthracyclines. However, these molecular characteristics can be viewed as a double-edged sword acting not only on neoplastic cells but also on multiple cellular targets throughout the body. This phenomenon translates into anthracycline cardiotoxicity that is a serious problem in the growing population of paediatric and adult cancer survivors. Therefore, better understanding of cellular processes that operate within but also go beyond cardiomyocytes is a necessary step to develop more effective tools for the prevention and treatment of progressive and often severe cardiomyopathy experienced by otherwise successfully treated oncologic patients. In this review, we focus on oxidative stress-triggered cellular events such as DNA damage, senescence, and cell death implicated in anthracycline cardiovascular toxicity. The involvement of progenitor cells of cardiac and extracardiac origin as well as different cardiac cell types is discussed, pointing to molecular signals that impact on cell longevity and functional competence.

Activation of miR-34a-5p/Sirt1/p66shc pathway contributes to doxorubicin-induced cardiotoxicity

The molecular mechanisms underlying anthracyclines-induced cardiotoxicity have not been well elucidated. MiRNAs were revealed dysregulated in the myocardium and plasma of rats received Dox treatment. MicroRNA-34a-5p (miR-34a-5p) was verified increased in the myocardium and plasma of Dox-treated rats, but was reversed in rats received Dox plus DEX treatments. Human miR-34a-5p was also observed increased in the plasma of patients with diffuse large B-cell lymphoma after 9- and 16-week epirubicin therapy. Up-regulation of miR-34a-5p was observed in Dox-induced rat cardiomyocyte H9c2 cells. MiR-34a-5p could augment Bax expression, but inhibited Bcl-2 expression, along with the increases of the activated caspase-3 and mitochondrial potentials in H9C2 cells. MiR-34a-5p was verified to modulate Sirt1 expression post-transcriptionally. In parallel to Sirt1 siRNA, miR-34a-5p could enhance p66shc expression, accompanied by increases of Bax and the activated caspase-3 and a decrease of Bcl-2 in H9c2 cells. Moreover, enforced expression of Sirt1 alleviated Dox-induced apoptosis of H9c2 cells, with suppressing levels of p66shc, Bax, the activated caspase-3 and miR-34a-5p, and enhancing Bcl-2 expression. Therefore, miR-34a-5p enhances cardiomyocyte apoptosis by targeting Sirt1, activation of miR-34a-5p/Sirt1/p66shc pathway contributes to Dox-induced cardiotoxicity, and blockage of this pathway represents a potential cardioprotective effect against anthracyclines.

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.

Folic acid reduces doxorubicin-induced cardiomyopathy by modulating endothelial nitric oxide synthase

The use of doxorubicin (DOXO) as a chemotherapeutic drug has been hampered by cardiotoxicity leading to cardiomyopathy and heart failure. Folic acid (FA) is a modulator of endothelial nitric oxide (NO) synthase (eNOS), which in turn is an important player in diseases associated with NO insufficiency or NOS dysregulation, such as pressure overload and myocardial infarction. However, the role of FA in DOXO‐induced cardiomyopathy is poorly understood. The aim of this study was to test the hypothesis that FA prevents DOXO‐induced cardiomyopathy by modulating eNOS and mitochondrial structure and function. Male C57BL/6 mice were randomized to a single dose of DOXO (20 mg/kg intraperitoneal) or sham. FA supplementation (10 mg/day per oral) was started 7 days before DOXO injection and continued thereafter. DOXO resulted in 70% mortality after 10 days, with the surviving mice demonstrating a 30% reduction in stroke volume compared with sham groups. Pre‐treatment with FA reduced mortality to 45% and improved stroke volume (both P < 0.05 versus DOXO). These effects of FA were underlain by blunting of DOXO‐induced cardiomyocyte atrophy, apoptosis, interstitial fibrosis and impairment of mitochondrial function. Mechanistically, pre‐treatment with FA prevented DOXO‐induced increases in superoxide anion production by reducing the eNOS monomer:dimer ratio and eNOS S‐glutathionylation, and attenuated DOXO‐induced decreases in superoxide dismutase, eNOS phosphorylation and NO production. Enhancing eNOS function by restoring its coupling and subsequently reducing oxidative stress with FA may be a novel therapeutic approach to attenuate DOXO‐induced cardiomyopathy.

Effects of ranolazine in a model of doxorubicin-induced left ventricle diastolic dysfunction

BACKGROUND AND PURPOSE

Doxorubicin is a highly effective anticancer drug, but its clinical application is hampered by cardiotoxicity. Asymptomatic diastolic dysfunction can be the earliest manifestation of doxorubicin cardiotoxicity. Therefore, a search for therapeutic intervention that can interfere with early manifestations and possibly prevent later development of cardiotoxicity is warranted. Increased doxorubicin-dependent ROS may explain, in part, Ca²⁺ and Na⁺ overload that contributes to diastolic dysfunction and development of heart failure. Therefore, we tested whether the administration of ranolazine, a selective blocker of late Na⁺ current, immediately after completing doxorubicin therapy, could affect diastolic dysfunction and interfere with the progression of functional decline.

EXPERIMENTAL APPROACH

Fischer 344 rats received a cumulative dose of doxorubicin of 15 mg·kg^-1 over a period of 2 weeks. After the assessment of diastolic dysfunction, the animals were treated with ranolazine (80 mg·kg^-1 , daily) for the following 4 weeks.

KEY RESULTS

While diastolic and systolic function progressively deteriorated in doxorubicin-treated animals, treatment with ranolazine relieved diastolic dysfunction and prevented worsening of systolic function, decreasing mortality. Ranolazine lowered myocardial NADPH oxidase 2 expression and oxidative/nitrative stress. Expression of the Na⁺ /Ca²⁺ exchanger 1 and Na_v 1.5 channels was reduced and of the sarcoplasmic/endoplasmic reticulum Ca²⁺ -ATPase 2 protein was increased. In addition, ranolazine lowered doxorubicin-induced hyper-phosphorylation and oxidation of Ca²⁺ /calmodulin-dependent protein kinase II, and decreased myocardial fibrosis.

CONCLUSIONS AND IMPLICATIONS

Ranolazine, by the increased Na⁺ influx, induced by doxorubicin, altered cardiac Ca²⁺ and Na⁺ handling and attenuated diastolic dysfunction induced by doxorubicin, thus preventing the progression of cardiomyopathy.

LINKED ARTICLES

This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Foxo3a inhibits mitochondrial fission and protects against doxorubicin-induced cardiotoxicity by suppressing MIEF2

Doxorubicin (DOX) as a chemotherapeutic drug is widely used to treat a variety of human tumors. However, a major factor limiting its clinical use is its cardiotoxicity. The molecular components and detailed mechanisms regulating DOX-induced cardiotoxicity remain largely unidentified. Here we report that Foxo3a is downregulated in the cardiomyocyte and mouse heart in response to DOX treatment. Foxo3a attenuates DOX-induced mitochondrial fission and apoptosis in cardiomyocytes. Cardiac specific Foxo3a transgenic mice show reduced mitochondrial fission, apoptosis and cardiotoxicity upon DOX administration. Furthermore, Foxo3a directly targets mitochondrial dynamics protein of 49kDa (MIEF2) and suppresses its expression at transcriptional level. Knockdown of MIEF2 reduces DOX-induced mitochondrial fission and apoptosis in cardiomyocytes and in vivo. Also, knockdown of MIEF2 protects heart from DOX-induced cardiotoxicity. Our study identifies a novel pathway composed of Foxo3a and MIEF2 that mediates DOX cardiotoxicity. This discovery provides a promising therapeutic strategy for the treatment of cancer therapy and cardioprotection.

Decreased Soluble Guanylate Cyclase Contributes to Cardiac Dysfunction Induced by Chronic Doxorubicin Treatment in Mice

AIMS

The use of doxorubicin, a potent chemotherapeutic agent, is limited by cardiotoxicity. We tested the hypothesis that decreased soluble guanylate cyclase (sGC) enzyme activity contributes to the development of doxorubicin-induced cardiotoxicity.

RESULTS

Doxorubicin administration (20 mg/kg, intraperitoneally [IP]) reduced cardiac sGC activity in wild-type (WT) mice. To investigate whether decreased sGC activity contributes to doxorubicin-induced cardiotoxicity, we studied mice with cardiomyocyte-specific deficiency of the sGC α1-subunit (mice with cardiomyocyte-specific deletion of exon 6 of the sGCα1 allele [sGCα1^-/-CM]). After 12 weeks of doxorubicin administration (2 mg/kg/week IP), left ventricular (LV) systolic dysfunction was greater in sGCα1^-/-CM than WT mice. To further assess whether reduced sGC activity plays a pathogenic role in doxorubicin-induced cardiotoxicity, we studied a mouse model in which decreased cardiac sGC activity was induced by cardiomyocyte-specific expression of a dominant negative sGCα1 mutant (DNsGCα1) upon doxycycline removal (Tet-off). After 8 weeks of doxorubicin administration, DNsGCα1^tg/+, but not WT, mice displayed LV systolic dysfunction and dilatation. The difference in cardiac function and remodeling between DNsGCα1^tg/+ and WT mice was even more pronounced after 12 weeks of treatment. Further impairment of cardiac function was attenuated when DNsGCα1 gene expression was inhibited (beginning at 8 weeks of doxorubicin treatment) by administering doxycycline. Furthermore, doxorubicin-associated reactive oxygen species generation was higher in sGCα1-deficient than WT hearts. Innovation and Conclusion: These data demonstrate that a reduction in cardiac sGC activity worsens doxorubicin-induced cardiotoxicity in mice and identify sGC as a potential therapeutic target. Various pharmacological sGC agonists are in clinical development or use and may represent a promising approach to limit doxorubicin-associated cardiotoxicity. Antioxid. Redox Signal. 26, 153-164.

Effects of doxorubicin on cardiac muscle subsarcolemmal and intermyofibrillar mitochondria

Doxorubicin (DOX) is a highly effective chemotherapeutic used in the treatment of a broad spectrum of malignancies. However, clinical use of DOX is highly limited by cumulative and irreversible cardiomyopathy that occurs following DOX treatment. The pathogenesis of DOX-induced cardiac muscle dysfunction is complex. However, it has been proposed that the etiology of this myopathy is related to mitochondrial dysfunction, as a result of the dose-dependent increase in the mitochondrial accumulation of DOX. In this regard, cardiac muscle possesses two morphologically distinct populations of mitochondria. Subsarcolemmal (SS) mitochondria are localized just below the sarcolemma, whereas intermyofibrillar (IMF) mitochondria are found between myofibrils. Mitochondria in both regions exhibit subtle differences in biochemical properties, giving rise to differences in respiration, lipid composition, enzyme activities and protein synthesis rates. Based on the heterogeneity of SS and IMF mitochondria, we hypothesized that acute DOX administration would have distinct effects on each cardiac mitochondrial subfraction. Therefore, we isolated SS and IMF mitochondria from the hearts of female Sprague-Dawley rats 48h after administration of DOX. Our results demonstrate that while SS mitochondria appear to accumulate greater amounts of DOX, IMF mitochondria demonstrate a greater apoptotic and autophagic response to DOX exposure. Thus, the divergent protein composition and function of the SS and IMF cardiac mitochondria result in differential responses to DOX, with IMF mitochondria appearing more susceptible to damage after DOX treatment.

Pathways of cardiac toxicity: comparison between chemotherapeutic drugs doxorubicin and mitoxantrone

Anthracyclines, e.g., doxorubicin (DOX), and anthracenediones, e.g., mitoxantrone (MTX), are drugs used in the chemotherapy of several cancer types, including solid and non-solid malignancies such as breast cancer, leukemia, lymphomas, and sarcomas. Although they are effective in tumor therapy, treatment with these two drugs may lead to side effects such as arrhythmia and heart failure. At the same clinically equivalent dose, MTX causes slightly reduced cardiotoxicity compared with DOX. These drugs interact with iron to generate reactive oxygen species (ROS), target topoisomerase 2 (Top2), and impair mitochondria. These are some of the mechanisms through which these drugs induce late cardiomyopathy. In this review, we compare the cardiotoxicities of these two chemotherapeutic drugs, DOX and MTX. As described here, even though they share similarities in their modes of toxicant action, DOX and MTX seem to differ in a key aspect. DOX is a more redox-interfering drug, while MTX induces energy imbalance. In addition, DOX toxicity can be explained by underlying mechanisms that include targeting of Top2 beta, mitochondrial impairment, and increases in ROS generation. These modes of action have not yet been demonstrated for MTX, and this knowledge gap needs to be filled.

Anthracycline-Induced Cardiomyopathy in Adults

Anthracyclines are one of the most commonly used antineoplastic agent classes, and a core part of the treatment in breast cancers, hematological malignancies, and sarcomas. Their benefit is decreased by their well-recognized cardiotoxicity. The purpose of this review is to outline the presentation, mechanisms, diagnosis, and treatment of anthracyclines-induced cardiotoxicity. Symptomatic heart failure occurs in 2% to 5% of patients treated with anthrayclines and may be higher in older patients or patients with cardiovascular risk factors. The mechanisms involved in anthracycline-induced cardiotoxicity involve myocyte loss by apoptosis in the presence of a limited regenerative capacity. Once symptomatic, anthracycline-induced cardiotoxicity is associated with markedly decreased survival. Left ventricular ejection fraction (LVEF), mostly determined using echocardiography, is used to monitor patients treated with anthracyclines. As more than 1/3 of patients treated with anthracyclines do not recover their baseline LVEF once it is decreased, more sensitive echocardiographic indices of LV function such as myocardial deformation or biomarkers have been studied in patients monitoring. Cardioprotective treatments such as angiotensin-converting enzyme inhibitors, beta-blockers, iron chelators, statins, and metformin are also the topic of research efforts.

Ataxia telangiectasia mutated in cardiac fibroblasts regulates doxorubicin-induced cardiotoxicity

AIMS

Doxorubicin (Dox) is a potent anticancer agent that is widely used in the treatment of a variety of cancers, but its usage is limited by cumulative dose-dependent cardiotoxicity mainly due to oxidative damage. Ataxia telangiectasia mutated (ATM) kinase is thought to play a role in mediating the actions of oxidative stress. Here, we show that ATM in cardiac fibroblasts is essential for Dox-induced cardiotoxicity.

METHODS AND RESULTS

ATM knockout mice showed attenuated Dox-induced cardiotoxic effects (e.g. cardiac dysfunction, apoptosis, and mortality). As ATM was expressed and activated predominantly in cardiac fibroblasts, fibroblast-specific Atm-deleted mice (Atm(fl/fl);Postn-Cre) were generated to address cell type-specific effects, which showed that the fibroblast is the key lineage mediating Dox-induced cardiotoxicity through ATM. Mechanistically, ATM activated the Fas ligand, which subsequently regulated apoptosis in cardiomyocytes at later stages. Therapeutically, a potent and selective inhibitor of ATM, KU55933, when administered systemically was able to prevent Dox-induced cardiotoxicity.

CONCLUSION

ATM-regulated effects within cardiac fibroblasts are pivotal in Dox-induced cardiotoxicity, and antagonism of ATM and its functions may have potential therapeutic implications.

New signal transduction paradigms in anthracycline-induced cardiotoxicity

Anthracyclines, such as doxorubicin, are the most potent and widely used chemotherapeutic agents for the treatment of a variety of human cancers, including solid tumors and hematological malignancies. However, their clinical use is hampered by severe cardiotoxic side effects and cancer therapy-related heart disease has become a leading cause of morbidity and mortality among cancer survivors. The identification of therapeutic strategies limiting anthracycline cardiotoxicity with preserved antitumor efficacy thus represents the current challenge of cardio-oncologists. Anthracycline cardiotoxicity has been originally ascribed to the ability of this class of drugs to disrupt iron metabolism and generate excess of reactive oxygen species (ROS). However, small clinical trials with iron chelators and anti-oxidants failed to provide any benefit and suggested that doxorubicin cardiotoxicity is not solely due to redox cycling. New emerging explanations include anthracycline-dependent regulation of major signaling pathways controlling DNA damage response, cardiomyocyte survival, cardiac inflammation, energetic stress and gene expression modulation. This review will summarize recent studies unraveling the complex web of mechanisms of doxorubicin-mediated cardiotoxicity, and identifying new druggable players for the prevention of heart disease in cancer patients. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

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.

Ginsenoside Rg3 antagonizes adriamycin-induced cardiotoxicity by improving endothelial dysfunction from oxidative stress via upregulating the Nrf2-ARE pathway through the activation of akt

BACKGROUND

Adriamycin (ADM) is an antineoplastic agent that is effective against a wide range of cancers, but cardiac toxicity limits its clinical application. Ginsenoside Rg3 (Rg3), an anti-cancer active ingredient of Panax ginseng, was reported to have anti-oxidative, anti-apoptotic, and cardioprotective properties.

PURPOSE

The current study aimed to investigate the possible protective effect of Rg3 against ADM-induced cardiotoxicity.

STUDY DESIGN

The activity of Rg3 to improve endothelial dysfunction was processed both in vivo and in vitro.

METHODS

We investigated the cardioprotective effect of Rg3 on ADM treated rats by echocardiography. The endothelial dysfunction was assessed using an aortic ring assay. Cardiac microvascular endothelial cells were cultured to investigate the effects of Rg3 on ADM-treated cells.

RESULTS

Results showed that Rg3 could ameliorate the decrease in the ejection fraction and fractional shortening that was induced by ADM, and improve the left ventricular outflow. The aortic ring assay showed that Rg3 could partially recover the abnormal vascular function. In vitro studies showed that Rg3 could promote cell viability to attenuate ADM induced oxidative damage and apoptosis. This counteraction was achieved partially via activation of the Nrf2-ARE pathway through the activation of Akt.

CONCLUSION

These findings elucidated the potential of Rg3 as a promising reagent for treating ADM-induced cardiotoxicity in clinic.

The utility of cardiac biomarkers and echocardiography for the early detection of bevacizumab- and sunitinib-mediated cardiotoxicity

The recent introduction of novel anticancer therapies, including bevacizumab (BVZ) and sunitinib (SNT), is associated with an increased risk of cardiotoxicity. However, early identification of left ventricular (LV) systolic dysfunction may facilitate dose modification and avoid the development of advanced heart failure. Using a murine model of BVZ- and SNT-mediated cardiotoxicity, we investigated whether cardiac biomarkers and/or tissue velocity imaging (TVI) using echocardiography can detect early changes in cardiac function, before a decrease in LV ejection fraction is identified. A total of 75 wild-type C57Bl/6 male mice were treated with either 0.9% saline, BVZ, or SNT. Serial monitoring of blood pressure, high-sensitivity troponin I, and echocardiographic indexes were performed over a 14-day study period, after which the mice were euthanized for histological and biochemical analyses. Mice treated with either BVZ or SNT developed systemic hypertension as early as day 7, which increased by day 14. Cardiac biomarkers, specifically high-sensitivity troponin I, were not predictive of early LV systolic dysfunction. Although conventional LV ejection fraction values decreased at day 13 in mice treated with either BVZ or SNT, TVI confirmed early LV systolic dysfunction at day 8. Histological and biochemical analysis demonstrated loss of cellular integrity, increased oxidative stress, and increased cardiac apoptosis in mice treated with BVZ or SNT therapy at day 14. In a murine model of BVZ- or SNT-mediated cardiomyopathy, noninvasive assessment by TVI detected early LV systolic dysfunction before alterations in conventional echocardiographic indexes.

Mitochondrial Membrane Potential and Nuclear and Gene Expression Changes During Human Disc Cell Apoptosis: In Vitro and In Vivo Annulus Findings

STUDY DESIGN

A study using cultured human annulus cells and human annular tissue.

OBJECTIVE

To further explore and define mitochondrial mechanisms related to disc cell apoptosis in vitro and in vivo.

SUMMARY OF BACKGROUND DATA

Mitochondrial-dependent intrinsic signaling pathways are a well-recognized component of apoptosis (programmed cell death). Disc cell apoptosis is important because it is a major mechanism by which cell numbers decrease during disc degeneration. Our objective was to further explore and define mitochondrial mechanisms related to disc cell apoptosis.

METHODS

High-content screening techniques were used to study nuclear morphology and mitochondrial membrane potentials in cultured annulus cells. Gene expression in annulus tissue was studied with microarray analysis.

RESULTS

Cultured cells showed significantly increased nuclear size (an indicator of apoptosis) with increasing Thompson grade (P < 0.00001 by analysis of variance). A significant negative correlation for mitochondrial potential (which results from the difference in electrical potential generated by the electrochemical gradient across the inner membrane of the mitochondrion) versus Thompson grade was identified in cultured human annulus cells in control conditions (r = 0.356, P < 0.0001). When exposed to the K ionophore valinomycin at sublethal levels to induce apoptosis, a significant reduction in mitochondrial potential was identified versus nontreated cells. Gene expression patterns in more degenerated Thompson grade III, IV, and V discs versus healthier grade I and II discs showed significant upregulation of a number of genes with well-recognized apoptosis roles in mitochondrial potential decline (ITM2B, beta-2-microglobulin, and cathepsin B, DAP, GAS1, and PDCD5) and TNF-α associations (cathepsin B, RAC1, and PPT1).

CONCLUSION

Data presented here show the in vivo expression of apoptosis-related genes associated with the loss of mitochondrial membrane integrity and decreased mitochondrial membrane potential with increasing Thompson scores. These data, which mimic our novel, direct cell-based in vitro findings, stress the importance of mitochondrial changes related to apoptosis and TNF-α during human disc degeneration.

LEVEL OF EVIDENCE

N/A.

Schisandrin B prevents doxorubicin induced cardiac dysfunction by modulation of DNA damage, oxidative stress and inflammation through inhibition of MAPK/p53 signaling

Doxorubicin (Dox) is a highly effective antineoplastic drug. However, Dox-induced apoptosis in cardiomyocytes leads to irreversible degenerative cardiomyopathy, which limits Dox clinical application. Schisandrin B (Sch B), a dibenzocyclooctadiene derivative isolated from the fruit of Schisandra chinensis, has been shown to protect against oxidative damage in liver, heart and brain tissues in rodents. In current study, we investigated possible protective effects of Sch B against Dox-induced cardiomyopathy in mice. Mice received a single injection of Dox (20 mg/kg IP). Five days after Dox administration, left ventricular (LV) performance was significantly depressed and was improved by Sch B treatment. Sch B prevented the Dox-induced increase in lipid peroxidation, nitrotyrosine formation, and metalloproteinase activation in the heart. In addition, the increased expression of phospho-p38 MAPK and phospho-MAPK activated mitogen kinase 2 levels by Dox were significantly suppressed by Sch B treatment. Sch B also attenuated Dox-induced higher expression of LV proinflammatory cytokines, cardiomyocyte DNA damage, myocardial apoptosis, caspase-3 positive cells and phopho-p53 levels in mice. Moreover, LV expression of NADPH oxidase subunits and reactive oxygen species were significantly less in Sch B treatment mice after Dox injection. These findings suggest that Sch B attenuates Dox-induced cardiotoxicity via antioxidative and anti-inflammatory effects.

Role of Drug Metabolism in the Cytotoxicity and Clinical Efficacy of Anthracyclines

Many clinical studies involving anti-tumor agents neglect to consider how these agents are metabolized within the host and whether the creation of specific metabolites alters drug therapeutic properties or toxic side effects. However, this is not the case for the anthracycline class of chemotherapy drugs. This review describes the various enzymes involved in the one electron (semi-quinone) or two electron (hydroxylation) reduction of anthracyclines, or in their reductive deglycosidation into deoxyaglycones. The effects of these reductions on drug antitumor efficacy and toxic side effects are also discussed. Current evidence suggests that the one electron reduction of anthracyclines augments both their tumor toxicity and their toxicity towards the host, in particular their cardiotoxicity. In contrast, the two electron reduction (hydroxylation) of anthracyclines strongly reduces their ability to kill tumor cells, while augmenting cardiotoxicity through their accumulation within cardiomyocytes and their direct effects on excitation/contraction coupling within the myocytes. The reductive deglycosidation of anthracyclines appears to inactivate the drug and only occurs under rare, anaerobic conditions. This knowledge has resulted in the identification of important new approaches to improve the therapeutic index of anthracyclines, in particular by inhibiting their cardiotoxicity. The true utility of these approaches in the management of cancer patients undergoing anthracycline-based chemotherapy remains unclear, although one such agent (the iron chelator dexrazoxane) has recently been approved for clinical use.

Ophiopogonin D attenuates doxorubicin-induced autophagic cell death by relieving mitochondrial damage in vitro and in vivo

It has been reported that ophiopogonin D (OP-D), a steroidal glycoside and an active component extracted from Ophiopogon japonicas, promotes antioxidative protection of the cardiovascular system. However, it is unknown whether OP-D exerts protective effects against doxorubicin (DOX)-induced autophagic cardiomyocyte injury. Here, we demonstrate that DOX induced excessive autophagy through the generation of reactive oxygen species (ROS) in H9c2 cells and in mouse hearts, which was indicated by a significant increase in the number of autophagic vacuoles, LC3-II/LC3-I ratio, and upregulation of the expression of GFP-LC3. Pretreatment with OP-D partially attenuated the above phenomena, similar to the effects of treatment with 3-methyladenine. In addition, OP-D treatment significantly relieved the disruption of the mitochondrial membrane potential by antioxidative effects through downregulating the expression of both phosphorylated c-Jun N-terminal kinase and extracellular signal-regulated kinase. The ability of OP-D to reduce the generation of ROS due to mitochondrial damage and, consequently, to inhibit autophagic activity partially accounts for its protective effects in the hearts against DOX-induced toxicity.

Overexpression of mitofilin in the mouse heart promotes cardiac hypertrophy in response to hypertrophic stimuli

AIMS

Mitofilin was originally described as a heart muscle protein because of its abundance in the heart tissue; however, its function in the heart is still to be elucidated. Thus, this study aims at investigating the role of mitofilin in the heart in response to hypertrophic stimuli.

RESULTS

In this study, a significant increase in mitofilin expression was observed in the hearts of patients with hypertrophic cardiomyopathy. Transgenic (TG) mice with cardiomyocyte-specific overexpression of mitofilin were generated, and cardiac hypertrophy was introduced by transverse aortic constriction (TAC) or chronic infusion of isoproterenol (ISO). In TG mice overexpressing mitofilin, the level of cardiac hypertrophy was significantly greater than that in wild-type (WT) mice after TAC and ISO stimulation. A detailed analysis showed that compared with WT mice, the level of reactive oxygen species was increased after TAC and ISO induction and mitochondrial oxidative phosphorylation (OXPHOS) activity in the TG hearts was lower. These alterations may contribute to the aggravated cardiac hypertrophy observed in response to TAC and ISO stimulation.

CONCLUSION

Over-expression of mitofilin promotes cardiac hypertrophy under pathological conditions both in vivo and in vitro.

INNOVATION

Mitofilin, a mitochondria protein, is shown to be related to cardiac hypertrophy for the first time, which enhances our understanding of the role of mitochondria in cardiac hypertrophy.

Metformin protects cardiomyocyte from doxorubicin induced cytotoxicity through an AMP-activated protein kinase dependent signaling pathway: an in vitro study

Doxorubicin (Dox) is one of the most widely used antitumor drugs, but its cumulative cardiotoxicity have been major concerns in cancer therapeutic practice for decades. Recent studies established that metformin (Met), an oral anti-diabetic drug, provides protective effects in Dox-induced cardiotoxicity. Met has been shown to increase fatty acid oxidation, an effect mediated by AMP activated protein kinase (AMPK). Here we delineate the intracellular signaling factors involved in Met mediated protection against Dox-induced cardiotoxicity in the H9c2 cardiomyoblast cell line. Treatment with low dose Met (0.1 mM) increased cell viabilities and Ki-67 expressions while decreasing LDH leakages, ROS generations and [Ca2+]i. The protective effect was reversed by a co-treatment with compound-C, an AMPK specific inhibitor, or by an over expression of a dominant-negative AMPKα cDNA. Inhibition of PKA with H89 or a suppression of Src kinase by a small hairpin siRNA also abrogated the protective effect of the low dose Met. Whereas, with a higher dose of Met (1.0 mM), the protective effects were abolished regardless of the enhanced AMPK, PKA/CREB1 and Src kinase activity. In high dose Met treated cells, expression of platelet-derived growth factor receptor (PDGFR) was significantly suppressed. Furthermore, the protective effect of low dose Met was totally reversed by co-treatment with AG1296, a PDGFR specific antagonist. These data provide in vitro evidence supporting a signaling cascade by which low dose Met exerts protective effects against Dox via sequential involvement of AMPK, PKA/CREB1, Src and PDGFR. Whereas high dose Met reverses the effect by suppressing PDGFR expression.

Inactivation of the cardiomyocyte glucagon-like peptide-1 receptor (GLP-1R) unmasks cardiomyocyte-independent GLP-1R-mediated cardioprotection

GLP-1R agonists improve outcomes in ischemic heart disease. Here we studied GLP-1R-dependent adaptive and cardioprotective responses to ventricular injury. Glp1r^−/− hearts exhibited chamber-specific differences in gene expression, but normal mortality and left ventricular (LV) remodeling after myocardial infarction (MI) or experimental doxorubicin-induced cardiomyopathy. Selective disruption of the cardiomyocyte GLP-1R in Glp1r^CM−/− mice produced no differences in survival or LV remodeling following LAD coronary artery occlusion. Unexpectedly, the GLP-1R agonist liraglutide still produced robust cardioprotection and increased survival in Glp1r^CM−/− mice following LAD coronary artery occlusion. Although liraglutide increased heart rate (HR) in Glp1r^CM−/− mice, basal HR was significantly lower in Glp1r^CM−/− mice. Hence, endogenous cardiomyocyte GLP-1R activity is not required for adaptive responses to ischemic or cardiomyopathic injury, and is dispensable for GLP-1R agonist-induced cardioprotection or enhanced chronotropic activity. However the cardiomyocyte GLP-1R is essential for the control of HR in mice.

Therapeutic use of H2O2-responsive anti-oxidant polymer nanoparticles for doxorubicin-induced cardiomyopathy

Doxorubicin (DOX) is a commonly used anti-neoplastic agent but its clinical use is limited due to serious hepatic and cardiac side effects. DOX-induced toxicity is mainly associated with overproduction of reactive species oxygen (ROS) such as hydrogen peroxide (H2O2). We have recently developed H2O2-responsive anti-oxidant polymer, polyoxalate containing vanillyl alcohol (PVAX), which is designed to rapidly scavenge H2O2 and release vanillyl alcohol with anti-oxidant, anti-inflammatory and anti-apoptotic properties. In this study, we report that PVAX nanoparticles are novel therapeutic agents for treating DOX-induced cardiac and hepatic toxicity. Intraperitoneal injection of PVAX nanoparticles (4 mg/kg/day) resulted in significant inhibition in apoptosis in liver and heart of DOX-treated mice by suppressing the activation of poly (ADP ribose) polymerase 1 (PARP-1) and caspase-3. PVAX treatment also prevented DOX-induced cardiac dysfunction. Furthermore, survival rate (vehicle = 35% vs. PVAX = 75%; p < 0.05) was significantly improved in a PVAX nanoparticles-treated group compared with vehicle treated groups. Taken together, we anticipate that PVAX nanoparticles could be a highly specific and potent treatment modality in DOX-induced cardiac and hepatic toxicity.

Geranylgeranylacetone blocks doxorubicin-induced cardiac toxicity and reduces cancer cell growth and invasion through RHO pathway inhibition

Doxorubicin is a widely used chemotherapy for solid tumors and hematologic malignancies, but its use is limited due to cardiotoxicity. Geranylgeranylacetone (GGA), an antiulcer agent used in Japan for 30 years, has no significant adverse effects, and unexpectedly reduces ovarian cancer progression in mice. Because GGA reduces oxidative stress in brain and heart, we hypothesized that GGA would prevent oxidative stress of doxorubicin cardiac toxicity and improve doxorubicin's chemotherapeutic effects. Nude mice implanted with MDA-MB-231 breast cancer cells were studied after chronic treatment with doxorubicin, doxorubicin/GGA, GGA, or saline. Transthoracic echocardiography was used to monitor systolic heart function and xenografts evaluated. Mice were euthanized and cardiac tissue evaluated for reactive oxygen species generation, TUNEL assay, and RHO/ROCK pathway analysis. Tumor metastases were evaluated in lung sections. In vitro studies using Boyden chambers were performed to evaluate GGA effects on RHO pathway activator lysophosphatidic acid (LPA)-induced motility and invasion. We found that GGA reduced doxorubicin cardiac toxicity, preserved cardiac function, prevented TUNEL-positive cardiac cell death, and reduced doxorubicin-induced oxidant production in a nitric oxide synthase-dependent and independent manner. GGA also reduced heart doxorubicin-induced ROCK1 cleavage. Remarkably, in xenograft-implanted mice, combined GGA/doxorubicin treatment decreased tumor growth more effectively than doxorubicin treatment alone. As evidence of antitumor effect, GGA inhibited LPA-induced motility and invasion by MDA-MB-231 cells. These anti-invasive effects of GGA were suppressed by geranylgeraniol suggesting GGA inhibits RHO pathway through blocking geranylation. Thus, GGA protects the heart from doxorubicin chemotherapy-induced injury and improves anticancer efficacy of doxorubicin in breast cancer.

Senescence marker protein 30 has a cardio-protective role in doxorubicin-induced cardiac dysfunction

BACKGROUND

Senescence marker protein 30 (SMP30), which was originally identified as an aging marker protein, is assumed to act as a novel anti-aging factor in the liver, lungs and brain. We hypothesized that SMP30 has cardio-protective function due to its anti-aging and anti-oxidant effects on doxorubicin (DOX)-induced cardiac dysfunction.

METHODS AND RESULTS

SMP30 knockout (SMP30 KO) mice, SMP30 transgenic (SMP30 TG) mice with cardiac-specific overexpression of SMP30 gene and wild-type (WT) littermate mice at 12-14 weeks of age were given intra-peritoneal injection of DOX (20 mg/kg) or saline. Five days after DOX injection, echocardiography revealed that left ventricular ejection fraction was more severely reduced in the DOX-treated SMP30 KO mice than in the DOX-treated WT mice, but was preserved in the DOX-treated SMP30 TG mice. Generation of reactive oxygen species and oxidative DNA damage in the myocardium were greater in the DOX-treated SMP30 KO mice than in the DOX-treated WT mice, but much less in the SMP30 TG mice. The numbers of deoxynucleotidyltransferase-mediated dUTP nick end-labeling positive nuclei in the myocardium, apoptotic signaling pathways such as caspase-3 activity, Bax/Bcl-2 ratio and phosphorylation activity of c-Jun N-terminal kinase were increased in SMP30 KO mice and decreased in SMP30 TG mice compared with WT mice after DOX injection.

CONCLUSIONS

SMP30 has a cardio-protective role by anti-oxidative and anti-apoptotic effects in DOX-induced cardiotoxicity, and can be a new therapeutic target to prevent DOX-induced heart failure.

Macrophage migration inhibitory factor deficiency augments doxorubicin-induced cardiomyopathy

Background

Recent evidence has depicted a role of macrophage migration inhibitory factor (MIF) in cardiac homeostasis under pathological conditions. This study was designed to evaluate the role of MIF in doxorubicin‐induced cardiomyopathy and the underlying mechanism involved with a focus on autophagy.

Methods and Results

Wild‐type (WT) and MIF knockout (MIF^−/−) mice were given saline or doxorubicin (20 mg/kg cumulative, i.p.). A cohort of WT and MIF^−/− mice was given rapamycin (6 mg/kg, i.p.) with or without bafilomycin A1 (BafA1, 3 μmol/kg per day, i.p.) for 1 week prior to doxorubicin challenge. To consolidate a role for MIF in the maintenance of cardiac homeostasis following doxorubicin challenge, recombinant mouse MIF (rmMIF) was given to MIF^−/− mice challenged with or without doxorubicin. Echocardiographic, cardiomyocyte function, and intracellular Ca²⁺ handling were evaluated. Autophagy and apoptosis were examined. Mitochondrial morphology and function were examined using transmission electron microscopy, JC‐1 staining, MitoSOX Red fluorescence, and mitochondrial respiration complex assay. DHE staining was used to evaluate reactive oxygen species (ROS) generation. MIF knockout exacerbated doxorubicin‐induced mortality and cardiomyopathy (compromised fractional shortening, cardiomyocyte and mitochondrial function, apoptosis, and ROS generation). These detrimental effects of doxorubicin were accompanied by defective autophagolysosome formation, the effect of which was exacerbated by MIF knockout. Rapamycin pretreatment rescued doxorubicin‐induced cardiomyopathy in WT and MIF^−/− mice. Blocking autophagolysosome formation using BafA1 negated the cardioprotective effect of rapamycin and rmMIF.

Conclusions

Our data suggest that MIF serves as an indispensable cardioprotective factor against doxorubicin‐induced cardiomyopathy with an underlying mechanism through facilitating autophagolysosome formation.

Inauhzin sensitizes p53-dependent cytotoxicity and tumor suppression of chemotherapeutic agents

Toxicity and chemoresistance are two major issues to hamper the success of current standard tumor chemotherapy. Combined therapy of agents with different mechanisms of action is a feasible and effective means to minimize the side effects and avoid the resistance to chemotherapeutic drugs while improving the antitumor effects. As the most essential tumor suppressor, p53 or its pathway has been an attractive target to develop a new type of molecule-targeting anticancer therapy. Recently, we identified a small molecule, Inauhzin (INZ), which can specifically activate p53 by inducing its deacetylation. In this study, we tested if combination with INZ could sensitize tumor cells to the current chemotherapeutic drugs, cisplatin (CIS) and doxorubicin (DOX). We found that compared with any single treatment, combination of lower doses of INZ and CIS or DOX significantly promoted apoptosis and cell growth inhibition in human non-small lung cancer and colon cancer cell lines in a p53-dependent fashion. This cooperative effect between INZ and CIS on tumor suppression was also confirmed in a xenograft tumor model. Therefore, this study suggests that specifically targeting the p53 pathway could enhance the sensitivity of cancer cells to chemotherapeutic agents and markedly reduce the doses of the chemotherapy, possibly decreasing its adverse side effects.

Congenital absence of nitric oxide synthase 3 potentiates cardiac dysfunction and reduces survival in doxorubicin- and trastuzumab-mediated cardiomyopathy

BACKGROUND

Doxorubicin (DOX) and trastuzumab (TRZ) are highly effective chemotherapeutic agents in the breast cancer setting, limited by their cardiotoxic side effects. Among the potential mechanisms for this drug-induced cardiomyopathy, increased production of oxidative stress (OS) through a nitric oxide synthase 3 (NOS3)-dependent pathway has gained recent attention. The objective of the study was to determine the role of NOS3 and OS in a clinically relevant female murine model of DOX- and TRZ-induced heart failure.

METHODS

A total of 120 female mice (60 wild-type [WT] and 60 NOS3 knockout [NOS3(-/-)]) were treated with either 0.9% saline, DOX, TRZ, or DOX with TRZ (DOX+TRZ). Serial echocardiography was performed for a total of 10 days, after which the mice were euthanized for histological and biochemical analyses.

RESULTS

In WT female mice receiving DOX+TRZ, left ventricular ejection fraction (LVEF) decreased from 75 ± 3% at baseline to 46 ± 2% at day 10 (P < 0.05). In the NOS3(-/-) group, LVEF decreased from 72 ± 3% at baseline to 35 ± 2% at day 10 (P < 0.05). LVEF was significantly lower in NOS3(-/-) female mice receiving DOX+TRZ than WT mice at day 10 (P < 0.05). Compared with WT, NOS3(-/-) female mice also demonstrated increased mortality after treatment with DOX+TRZ, corroborating the echocardiographic findings. Histological analysis demonstrated increased myofibrillar degradation and loss of cell integrity in NOS3(-/-) female mice treated with DOX+TRZ. There was increased generation of oxidized phosphatidylcholine, a marker of OS, in NOS3(-/-) female mice receiving DOX+TRZ compared with control mice.

CONCLUSIONS

Congenital absence of NOS3 potentiates the cardiotoxic side effects of DOX+TRZ in an acute female murine model of chemotherapy-induced cardiomyopathy.

Doxorubicin-induced death in tumour cells and cardiomyocytes: is autophagy the key to improving future clinical outcomes?

Objectives

Doxorubicin, a commonly used frontline chemotherapeutic agent for cancer, is not without side-effects. The original thinking that the drug causes necrosis in tumours has largely given way to its link with apoptosis over the past two decades.

Key findings

More recently, major biomarkers such as AMPK, p53 and Bcl-2 have been identified as important to apoptosis induction by doxorubicin. It is Bcl-2 and its interaction with Beclin-1 that has refocussed research attention on doxorubicin, albeit this time for its ability to induce autophagy. Autophagy can be either anticancerous or procancerous however, so it is critical that the reasons for which cancer cells undergo this type of cell biological event be clearly identified for future exploitation.

Summary

Taking a step back from treating patients with large doses of doxorubicin, which causes toxicity to the heart amongst other organs, and further research with this drug's molecular signalling in not only neoplastic but normal cells, may indeed redefine the way doxorubicin is used clinically and potentially lead to better neoplastic disease management.

Complications of chemotherapy, a basic science update

Anthracyclines, discovered 50 years ago, are antibiotics widely used as antineoplastic agents and are among the most successful anticancer therapies ever developed to treat a wide range of cancers, including hematological malignancies, soft tissue sarcomas and solid tumors. However, some anthracyclines, including doxorubicin, exhibit major signs of cardiotoxicity that may ultimately lead to heart failure (HF). Despite intensive research on doxorubicine-induced cardiotoxicity, the underlying mechanisms responsible for doxorubicin-induced cardiotoxicity have not been fully elucidated yet. Published literature so far has focused mostly on mitochondria dysfunction with consequent oxidative stress, Ca(2+) overload, and cardiomyocyte death as doxorubicin side effects, leading to heart dysfunction. This review focuses on the current understanding of the molecular mechanisms underlying doxorubicin-induced cardiomyocyte death (i.e.: cardiomyocyte death, mitochondria metabolism and bioenergetic alteration), but we will also point to new directions of possible mechanisms, suggesting potent prior or concomitant alterations of specific signaling pathways with molecular actors directly targeted by the anticancer drugs itself (i.e. calcium homeostasis or cAMP signaling cascade). The mechanisms of anticancer cardiac toxicity may be more complex than just mitochondria dysfunction. Partnership of both basic and clinical research is needed to promote new strategies in diagnosis, therapies with concomitant cardioprotection in order to achieve cancer treatment with acceptable cardiotoxicity along life span.

An engineered bivalent neuregulin protects against doxorubicin-induced cardiotoxicity with reduced proneoplastic potential

BACKGROUND

Doxorubicin (DOXO) is an effective anthracycline chemotherapeutic, but its use is limited by cumulative dose-dependent cardiotoxicity. Neuregulin-1β is an ErbB receptor family ligand that is effective against DOXO-induced cardiomyopathy in experimental models but is also proneoplastic. We previously showed that an engineered bivalent neuregulin-1β (NN) has reduced proneoplastic potential in comparison with the epidermal growth factor-like domain of neuregulin-1β (NRG), an effect mediated by receptor biasing toward ErbB3 homotypic interactions uncommonly formed by native neuregulin-1β. Here, we hypothesized that a newly formulated, covalent NN would be cardioprotective with reduced proneoplastic effects in comparison with NRG.

METHODS AND RESULTS

NN was expressed as a maltose-binding protein fusion in Escherichia coli. As established previously, NN stimulated antineoplastic or cytostatic signaling and phenotype in cancer cells, whereas NRG stimulated proneoplastic signaling and phenotype. In neonatal rat cardiomyocytes, NN and NRG induced similar downstream signaling. NN, like NRG, attenuated the double-stranded DNA breaks associated with DOXO exposure in neonatal rat cardiomyocytes and human cardiomyocytes derived from induced pluripotent stem cells. NN treatment significantly attenuated DOXO-induced decrease in fractional shortening as measured by blinded echocardiography in mice in a chronic cardiomyopathy model (57.7±0.6% versus 50.9±2.6%, P=0.004), whereas native NRG had no significant effect (49.4±3.7% versus 50.9±2.6%, P=0.813).

CONCLUSIONS

NN is a cardioprotective agent that promotes cardiomyocyte survival and improves cardiac function in DOXO-induced cardiotoxicity. Given the reduced proneoplastic potential of NN versus NRG, NN has translational potential for cardioprotection in patients with cancer receiving anthracyclines.

Anthracycline cardiotoxicity: prevalence, pathogenesis and treatment

Anthracyclines, such as doxorubicin and idarubicin, remain an important class of chemotherapeutic agents. Unfortunately, their efficacy in treating cancer is limited by a cumulative dose-dependent cardiotoxicity, which can cause irreversible heart failure. In this review, we discuss the pathogenesis and incidence of anthracycline-induced cardiotoxicity as well as methods to detect, prevent and treat the condition.

Myocardial extracellular volume by cardiac magnetic resonance imaging in patients treated with anthracycline-based chemotherapy

We aimed to determine whether the myocardial extracellular volume (ECV), measured using T1 measurements obtained during cardiac magnetic resonance imaging were increased in patients treated with anthracyclines. We performed cardiac magnetic resonance imaging and echocardiography and measured the ECV in 42 patients treated with anthracyclines. The data from the cardiac magnetic resonance study were compared to those from healthy volunteers. The anthracycline-treated cohort consisted of 21 men and 21 women with a mean age of 55 ± 17 years, who presented a median of 84 months after chemotherapy with a cumulative anthracycline exposure of 282 ± 65 mg/m(2) and a mean left ventricular ejection fraction of 52 ± 12%. The ECV was elevated in the anthracycline-treated patients compared to the age- and gender-matched controls (0.36 ± 0.03 vs 0.28 ± 0.02, p <0.001). A positive association was found between the ECV and left atrial volume (ECV vs indexed left atrial volume, r = 0.65, p <0.001), and negative association was found between the ECV and diastolic function (E' lateral, r = -0.64, p <0.001). In conclusion, the myocardial ECV is elevated in patients with previous anthracycline treatment and is associated with the diastolic function and increased atrial volumes.

G-protein inactivator RGS6 mediates myocardial cell apoptosis and cardiomyopathy caused by doxorubicin

Clinical use of the widely used chemotherapeutic agent doxorubicin is limited by life-threatening cardiotoxicity. The mechanisms underlying doxorubicin-induced cardiomyopathy and heart failure remain unclear but are thought to involve p53-mediated myocardial cell apoptosis. The tripartite G-protein inactivating protein RGS6 has been implicated in reactive oxygen species (ROS) generation, ATM/p53 activation, and apoptosis in doxorubicin-treated cells. Thus, we hypothesized that RGS6, the expression of which is enriched in cardiac tissue, might also be responsible for the pathologic effects of doxorubicin treatment in heart. In this study, we show that RGS6 expression is induced strongly by doxorubicin in the ventricles of mice and isolated ventricular myocytes via a posttranscriptional mechanism. While doxorubicin-treated wild-type (WT) mice manifested severe left ventricular dysfunction, loss of heart and body mass, along with decreased survival 5 days after doxorubicin administration, mice lacking RGS6 were completely protected against these pathogenic responses. Activation of ATM/p53 apoptosis signaling by doxorubicin in ventricles of WT mice was also absent in their RGS6(-/-) counterparts. Doxorubicin-induced ROS generation was dramatically impaired in both the ventricles and ventricular myocytes isolated from RGS6(-/-) mice, and the apoptotic response to doxorubicin in ventricular myocytes required RGS6-dependent ROS production. These results identify RGS6 as an essential mediator of the pathogenic responses to doxorubicin in heart, and they argue that RGS6 inhibition offers a rational means to circumvent doxorubicin cardiotoxicity in human patients with cancer.

Hydrogen sulfide attenuates doxorubicin-induced cardiotoxicity by inhibition of the p38 MAPK pathway in H9c2 cells

We previously demonstrated the protective effect of hydrogen sulfide (H2S) against doxorubicin (DOX)-induced cardiotoxicity through inhibition of endoplasmic reticulum stress. The aim of the present study was to explore the role of p38 mitogen-activated protein kinase (MAPK) in DOX-induced cardiotoxicity and ascertain whether exogenous H2S protects DOX-induced injury by inhibiting p38 MAPK in cardiomyoblasts (H9c2). We observed that exposure of H9c2 cells to 5 µM DOX not only markedly induced injuries, including cytotoxicity, apoptosis, overproduction of reactive oxygen species (ROS) and dissipation of mitochondrial membrane potential (MMP), but also enhanced the expression level of phosphorylated (p)-p38 MAPK. The DOX-induced increase in expression of p-p38 MAPK was significantly attenuated by pretreatment of H9c2 cells with either 400 µM sodium hydrogen sulfide (NaHS) (a donor of H2S) or 1,000 µM N-acetyl-L-cysteine (NAC, an ROS scavenger) prior to exposure to DOX. Pretreatment with either 400 µM NaHS or 3 µM SB203580, a selective inhibitor of p38 MAPK, ameliorated DOX-induced cardiomyocyte injuries, as evidenced by an increase in cell viability, and decreases in the number of apoptotic cells, ROS generation as well as dissipation of MMP. In conclusion, the findings of the present study demonstrated that the activation of p38 MAPK contributes to DOX-induced injuries, including cytotoxicity, apoptosis, mitochondrial damage and oxidative stress in H9c2 cells. We also provide novel evidence that exogenous H2S protects H9c2 cells against DOX-induced cardiotoxicity by inhibition of the p38 MAPK pathway.

Carvedilol reduces the severity of atherosclerosis in apolipoprotein E-deficient mice via reducing superoxide production

It has been shown that oxidative stress may play an important role in the development of atherosclerosis, and carvedilol has the capacity of reducing oxidative stress. Accordingly, we assessed the hypothesis that carvedilol may reduce the severity of atherosclerosis in apolipoprotein E (apoE)-deficient mice in addition to its hemodynamic effects. Atherosclerosis was induced in apoE-deficient mice fed a high-fat diet containing 0.3% cholesterol. Mice were orally treated with propranolol (30 mg/kg/day), metoprolol (75 mg/kg/day) and carvedilol (10 mg/kg/day) over eight weeks (each group n = 7-9). Fatty streak plaque developed in apoE-deficient mice, and was suppressed in mice treated with all three drugs. The accumulation of macrophages and expression of CD4(+) and CD8(+) cells in the lesions were decreased by the treatment of the drugs, of which carvedilol was the most effective. In addition, carvedilol reduced superoxide production in aortic walls detected by ethidium staining. There were no significant changes in blood pressure among the study groups. The heart rates in the treated groups were decreased by 4%-12% compared with the control group, with carvedilol yielding the highest suppression of heart rate. The β-blocker treatment did not significantly modify the serum lipid profiles. Carvedilol may suppress atherosclerosis via reducing superoxide production, in addition to the hemodynamic modifications in this animal model.

Protective effect of guggulsterone against cardiomyocyte injury induced by doxorubicin in vitro

BACKGROUND

Doxorubicin (DOX) is an effective antineoplastic drug; however, clinical use of DOX is limited by its dose-dependent cardiotoxicity. It is well known that reactive oxygen species (ROS) play a vital role in the pathological process of DOX-induced cardiotoxicity. For this study, we evaluated the protective effects of guggulsterone (GS), a steroid obtained from myrrh, to determine its preliminary mechanisms in defending against DOX-induced cytotoxicity in H9C2 cells.

METHODS

In this study, we used a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) release measurements, and Hoechst 33258 staining to evaluate the protective effect of GS against DOX-induced cytotoxicity in H9C2 cells. In addition, we observed the immunofluorescence of intracellular ROS and measured lipid peroxidation, caspase-3 activity, and apoptosis-related proteins by using Western blotting.

RESULTS

The MTT assay and LDH release showed that treatment using GS (1-30 μM) did not cause cytotoxicity. Furthermore, GS inhibited DOX (1 μM)-induced cytotoxicity in a concentration-dependent manner. Hoechst 33258 staining showed that GS significantly reduced DOX-induced apoptosis and cell death. Using GS at a dose of 10-30 μM significantly reduced intracellular ROS and the formation of MDA in the supernatant of DOX-treated H9C2 cells and suppressed caspase-3 activity to reference levels. In immunoblot analysis, pretreatment using GS significantly reversed DOX-induced decrease of PARP, caspase-3 and bcl-2, and increase of bax, cytochrome C release, cleaved-PARP and cleaved-caspase-3. In addition, the properties of DOX-induced cancer cell (DLD-1 cells) death did not interfere when combined GS and DOX.

CONCLUSION

These data provide considerable evidence that GS could serve as a novel cardioprotective agent against DOX-induced cardiotoxicity.

Immunoglobulin treatment ameliorates myocardial injury in experimental autoimmune myocarditis associated with suppression of reactive oxygen species

AIMS

We tested the hypothesis that immunoglobulin ameliorated experimental autoimmune myocarditis (EAM) in mice attributing to the suppression of reactive oxygen species (ROS)-mediated myocardial injury.

METHODS

We intraperitoneally administered intact type of human immunoglobulin (Ig) or F(ab')2 fragments of human immunoglobulin, 1g/kg/day daily for 3 weeks, to male BALB/c mice with heart failure due to EAM.

RESULTS

The results showed that intact type of Ig, but not F(ab')2 type, reduced the severity of myocarditis by comparing the heart weight/body weight and lung weight/body weight ratios, pericardial effusion score, macroscopic and microscopic scores. Tissue superoxide production was marked in untreated mice with EAM, which was suppressed by the treatment of immunoglobulins. The cytotoxic activities of lymphocytes in mice with EAM treated with Ig were reduced compared with untreated controls. The shift from Th1 toward Th2 cytokine balance was demonstrated by the treatment of immunoglobulins both in vitro and in vivo.

CONCLUSION

ROS may be involved in the development of myocarditis. Intact Ig ameliorates myocardial damage in mice with myocarditis associated with suppression of ROS and cytotoxic activity of lymphocytes.