Redox cycling of anthracyclines by cardiac mitochondria. I. Anthracycline radical formation by NADH dehydrogenase

Early metabolomics changes in heart and plasma during chronic doxorubicin treatment in B6C3F1 mice

The present study aimed to identify molecular markers of early stages of cardiotoxicity induced by a potent chemotherapeutic agent, doxorubicin (DOX). Male B6C3F1 mice were dosed with 3 mg kg(-1) DOX or saline via tail vein weekly for 2, 3, 4, 6 or 8 weeks (cumulative DOX doses of 6, 9, 12, 18 or 24 mg kg(-1) , respectively) and euthanized a week after the last dose. Mass spectrometry-based and nuclear magnetic resonance spectrometry-based metabolic profiling were employed to identify initial biomarkers of cardiotoxicity before myocardial injury and cardiac pathology, which were not noted until after the 18 and 24 mg kg(-1) cumulative doses, respectively. After a cumulative dose of 6 mg kg(-1) , 18 amino acids and four biogenic amines (acetylornithine, kynurenine, putrescine and serotonin) were significantly increased in cardiac tissue; 16 amino acids and two biogenic amines (acetylornithine and hydroxyproline) were significantly altered in plasma. In addition, 16 acylcarnitines were significantly increased in plasma and five were significantly decreased in cardiac tissue compared to saline-treated controls. Plasma lactate and succinate, involved in the Krebs cycle, were significantly altered after a cumulative dose of 6 mg kg(-1) . A few metabolites remained altered at higher cumulative DOX doses, which could partly indicate a transition from injury processes at 2 weeks to repair processes with additional injury happening concurrently before myocardial injury at 8 weeks. These altered metabolic profiles in mouse heart and plasma during the initial stages of injury progression due to DOX treatment may suggest these metabolites as candidate early biomarkers of cardiotoxicity. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Doxorubicin induced heart failure: Phenotype and molecular mechanisms

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

Sirt3 protects mitochondrial DNA damage and blocks the development of doxorubicin-induced cardiomyopathy in mice

Doxorubicin (Doxo) is a chemotherapeutic drug widely used to treat variety of cancers. One of the most serious side effects of Doxo is its dose-dependent and delayed toxicity to the heart. Doxo is known to induce cardiac mitochondrial damage. Recently, the mitochondrial sirtuin SIRT3 has been shown to protect mitochondria from oxidative stress. Here we show that overexpression of SIRT3 protects the heart from toxicity of Doxo by preventing the drug-induced mitochondrial DNA (mtDNA) damage. Doxo treatment caused depletion of Sirt3 levels both in primary cultures of cardiomyocytes and in mouse hearts, which led to massive acetylation of mitochondrial proteins. Doxo-induced toxicity to cardiomyocytes was associated with increased reactive oxygen species (ROS) production, mitochondrial fragmentation, and cell death. Overexpression of SIRT3 helped to attenuate Doxo-induced ROS levels and cardiomyocyte death. Sirt3 knockout (Sirt3.KO) mice could not endure the full dose of Doxo treatment, developed exacerbated cardiac hypertrophy, and died during the course of treatment, whereas Sirt3 transgenic (Sirt3.tg) mice were protected against Doxo-induced cardiotoxicity. Along with Sirt3, we also observed a concomitant decrease in levels of oxoguanine-DNA glycosylase-1 (OGG1), a major DNA glycosylase that hydrolyzes oxidized-guanine (8-oxo-dG) to guanine. Depletion of OGG1 levels was associated with increased mtDNA damage. Sirt3.KO mice and Doxo-treated mice showed increased 8-oxo-dG adducts in DNA and corresponding increase in mtDNA damage, whereas, 8-oxo-dG adducts and mtDNA damage were markedly reduced in Sirt3 overexpressing transgenic mice hearts. These results thus demonstrated that Sirt3 activation protects the heart from Doxo-induced cardiotoxicity by maintaining OGG1 levels and protecting mitochondria from DNA damage.

Early transcriptional changes in cardiac mitochondria during chronic doxorubicin exposure and mitigation by dexrazoxane in mice

Identification of early biomarkers of cardiotoxicity could help initiate means to ameliorate the cardiotoxic actions of clinically useful drugs such as doxorubicin (DOX). Since DOX has been shown to target mitochondria, transcriptional levels of mitochondria-related genes were evaluated to identify early candidate biomarkers in hearts of male B6C3F1 mice given a weekly intravenous dose of 3mg/kg DOX or saline (SAL) for 2, 3, 4, 6, or 8 weeks (6, 9, 12, 18, or 24 mg/kg cumulative DOX doses, respectively). Also, a group of mice was pretreated (intraperitoneally) with the cardio-protectant, dexrazoxane (DXZ; 60 mg/kg) 30 min before each weekly dose of DOX or SAL. At necropsy a week after the last dose, increased plasma concentrations of cardiac troponin T (cTnT) were detected at 18 and 24 mg/kg cumulative DOX doses, whereas myocardial alterations were observed only at the 24 mg/kg dose. Of 1019 genes interrogated, 185, 109, 140, 184, and 451 genes were differentially expressed at 6, 9, 12, 18, and 24 mg/kg cumulative DOX doses, respectively, compared to concurrent SAL-treated controls. Of these, expression of 61 genes associated with energy metabolism and apoptosis was significantly altered before and after occurrence of myocardial injury, suggesting these as early genomics markers of cardiotoxicity. Much of these DOX-induced transcriptional changes were attenuated by pretreatment of mice with DXZ. Also, DXZ treatment significantly reduced plasma cTnT concentration and completely ameliorated cardiac alterations induced by 24 mg/kg cumulative DOX. This information on early transcriptional changes during DOX treatment may be useful in designing cardioprotective strategies targeting mitochondria.

A PGC-1α-Mediated Transcriptional Network Maintains Mitochondrial Redox and Bioenergetic Homeostasis against Doxorubicin-Induced Toxicity in Human Cardiomyocytes: Implementation of TT21C

Chemical toxicity testing is fast moving in a direction that relies increasingly on cell-basedin vitroassays anchored on toxicity pathways according to the toxicity testing in the 21st century vision. Identifying points of departure (POD) via these assays and revealing their mechanistic underpinnings via computational modeling of the relevant pathways are critical and challenging steps. Here we used doxorubicin (DOX) as a prototype chemical to study mitochondrial toxicity in human AC16 cells. Mitochondrial toxicity has been linked to cardiovascular risk of DOX, which has limited its clinical use as an antitumor drug. Ourin vitrostudy revealed a well-defined POD concentration of DOX below which adaptive induction of proliferator-activated receptor-γ coactivator-1α (PGC-1α) -mediated mitochondrial genes, including NRF-1, MnSOD, UCP2, and COX1, concurred with negligible changes in mitochondrial superoxide and cytotoxicity. At higher DOX concentrations adversity became significant with elevated superoxide and suppressed ATP levels. A computational model was formulated to simulate the PGC-1α-mediated transcriptional network comprising multiple negative feedback loops that underlie redox and bioenergetics homeostasis in the mitochondrion. The model recapitulated the transition phase from adaptive to adverse responses, supporting the notion that saturated induction of PGC-1α-mediated gene network underpins POD. The model further predicts (follow-up experiments verified) that silencing PGC-1α compromises the adaptive function of the transcriptional network, leading to disruption of mitochondria and cytotoxicity at lower DOX concentrations. In summary, our study demonstrates that combining pathway-focusedin vitroassays and computational simulation of relevant biochemical network is synergistic for understanding dose-response behaviors in the low-dose region and identifying POD.

Cardioprotective effects of inorganic nitrate/nitrite in chronic anthracycline cardiotoxicity: Comparison with dexrazoxane

Dexrazoxane (DEX) is a clinically available cardioprotectant that reduces the toxicity induced by anthracycline (ANT) anticancer drugs; however, DEX is seldom used and its action is poorly understood. Inorganic nitrate/nitrite has shown promising results in myocardial ischemia-reperfusion injury and recently in acute high-dose ANT cardiotoxicity. However, the utility of this approach for overcoming clinically more relevant chronic forms of cardiotoxicity remains elusive. Hence, in this study, the protective potential of inorganic nitrate and nitrite against chronic ANT cardiotoxicity was investigated, and the results were compared to those using DEX. Chronic cardiotoxicity was induced in rabbits with daunorubicin (DAU). Sodium nitrate (1g/L) was administered daily in drinking water, while sodium nitrite (0.15 or 5mg/kg) or DEX (60mg/kg) was administered parenterally before each DAU dose. Although oral nitrate induced a marked increase in plasma NOx, it showed no improvement in DAU-induced mortality, myocardial damage or heart failure. Instead, the higher nitrite dose reduced the incidence of end-stage cardiotoxicity, prevented related premature deaths and significantly ameliorated several molecular and cellular perturbations induced by DAU, particularly those concerning mitochondria. The latter result was also confirmed in vitro. Nevertheless, inorganic nitrite failed to prevent DAU-induced cardiac dysfunction and molecular remodeling in vivo and failed to overcome the cytotoxicity of DAU to cardiomyocytes in vitro. In contrast, DEX completely prevented all of the investigated molecular, cellular and functional perturbations that were induced by DAU. Our data suggest that the difference in cardioprotective efficacy between DEX and inorganic nitrite may be related to their different abilities to address a recently proposed upstream target for ANT in the heart - topoisomerase IIβ.

Protective effects of madecassoside against Doxorubicin induced nephrotoxicity in vivo and in vitro

Madecassoside (MA), a triterpenoid saponin isolated from C. asitica, exerts various pharmacological activity including antioxidative and antinflammatory. Doxorubicin (DOX), a common chemotherapeutic drug, has been reported to induce numerous toxic side effects including renal-toxicity. We hypothesized that MA administration may decrease renal-toxicity caused by DOX. In this study, we investigated this hypothesis by introducing MA and DOX into the culture of Human Proximal Tubule Cells HK-2 and mice model. Our in vivo study demonstrated that MA (12 mg/kg), treatment for two weeks attenuated DOX-induced renal injury via protecting renal function, recovering antioxidant enzyme activity, inhibiting Bax, p-ERK1/2, NF-κB p65, iNOS expression and increasing Bcl-2 expression. Similar findings were obtained in our in vitro studies with treatment of DOX and/or MA. Further studies with application of iNOS inhibitor and ERK1/2 kinase inhibitor indicated that the inhibitory effects of MA on DOX-induced apoptosis and inflammation might be mediated by the suppression of the activation of cleaved caspase-3, ERK1/2 pathways, NF-κB p65 and NO production. These results suggest that MA is a promising protective agent for DOX-induced renal toxicity and can be a potential candidate to protect against renal toxicity in DOX-treated cancer patients.

Effects of Chronic Endurance Exercise on Doxorubicin-Induced Thymic Damage

The use of prior exercise training has shown promise in minimizing doxorubicin (DOX)-induced physical impairments. The purpose of this study was to compare changes in thymus mass, thymocyte (T-cell) number, and tissue peroxidation following chronic endurance exercise and DOX treatment in the rat. The thymus mass, number of viable T-cells, and levels of malondialdehyde and 4-hydroxyalkenals (MDA+4-HAE) were compared 3 days post-injection between rats assigned to the following treatment conditions: (a) 10 weeks of endurance training, followed by a saline injection 24 hours after the last training session (TM+SAL); (b) treadmill training as above, followed by a single, bolus 10-mg/kg injection of DOX (TM+10); (c) treadmill training with 12.5 mg/kg of DOX (TM+12.5); (d) sedentary (without exercise) and a saline injection (SED+SAL); (e) sedentary with 10 mg/kg of DOX (SED+10); and (f) sedentary with 12.5 mg/kg (SED+12.5). Thymic mass and T-cell numbers significantly decreased following DOX injections. TM rats exhibited significantly less lipid peroxidation compared with paired-dose SED groups. TM+10 did not significantly differ from SED+SAL in thymic levels of lipid peroxidation. We conclude that chronic endurance exercise decreases levels of lipid peroxidation in the thymus seen with acute DOX treatment.

Emerging delivery systems to reduce doxorubicin cardiotoxicity and improve therapeutic index: focus on liposomes

Anthracyclines are powerful anticancer agents and among the most important tools in the chemotherapy armamentarium of medical oncologists. They are approved for use in the treatment of a broad variety of solid and hematologic neoplasms. However, the usefulness of these agents, particularly doxorubicin, the most widely used anthracycline, is limited by considerable toxicity, especially damage to the cardiac muscle, which is cumulative and mostly irreversible, restricting extended use of this drug. In the last 30 years, extensive research with a variety of drug-delivery systems has attempted to overcome this limitation, with clinical success mostly confined to liposome formulations. Liposomal doxorubicin, and particularly pegylated liposomal doxorubicin, has shown significant pharmacologic advantages and an added clinical value over doxorubicin. Here, we review the mechanisms of action and toxicity of doxorubicin, and ways to reduce toxicity, with a focus on liposome-based drug-delivery systems.

Ameliorative effect of naringin against doxorubicin-induced acute cardiac toxicity in rats

CONTEXT

Doxorubicin (Dox) is one of the most active chemotherapeutic agents used to treat various types of cancers. Its clinical utility is compromised due to fatal cardiac toxicity characterized by an irreversible cardiomyopathy.

OBJECTIVE

This study evaluates the cardioprotective potential of naringin (NR) against Dox-induced acute cardiac toxicity in rats.

MATERIALS AND METHODS

Male Wistar rats were randomly divided into five groups. NR (50 and 100 mg/kg) was administered intraperitoneally (i.p.) daily from 0 to 14 d. Doxorubicin (15 mg/kg, i.p.) was given as a single dose on the 10th day. On the 14th day, all animals were sacrificed and oxidative stress parameters that include malondialdehyde (MDA), glutathione (GSH) level, superoxide dismutase (SOD), catalase (CAT) activities, and all mitochondrial complexes (I-IV) activities were evaluated along with histopathological studies of the heart.

RESULTS

Doxorubicin-induced cardiotoxicity was confirmed by increased (p < 0.05) MDA, decreased (p < 0.05) GSH levels, SOD, and CAT activities, mitochondrial complexes (I-IV) activities in the heart tissue. NR (100 mg/kg) showed cardioprotection as evident from significant decreased MDA (p < 0.001) level, raised (p < 0.001) GSH level, SOD and CAT activities and increased mitochondrial complexes I (p < 0.01), II (p < 0.001), III (p < 0.001), and IV (p < 0.05) activities. Further, Dox-induced cardiotoxicity was confirmed by histopathological studies. These obtained results indicated the protective role of NR against Dox-induced cardiac toxicity in rats.

CONCLUSION

NR can be used in combination with Dox due to its high cardioprotective effect against Dox-induced cardiomyopathy.

Left Ventricular Aneurysm Presenting as a Late Complication of Childhood Chemotherapy

Cardiotoxicity is a well known adverse effect of chemotherapy. Multiple cardiac injuries have been reported including cardiomyopathy, pericarditis, myocarditis, angina, arrhythmias, and myocardial infarction. A left ventricular aneurysm due to chemotherapy is a rare and a dangerous complication which is particularly challenging in diagnosis requiring a high index of suspicion and periodic imaging. We present a case of a young Caucasian male with a past medical history of Acute Lymphocytic Leukemia status after chemotherapy during his childhood diagnosed with left ventricular aneurysm several years later.

Chemotherapy-Induced Cardiotoxicity: Overview of the Roles of Oxidative Stress

Chemotherapy-induced cardiotoxicity is a serious complication that poses a serious threat to life and limits the clinical use of various chemotherapeutic agents, particularly the anthracyclines. Understanding molecular mechanisms of chemotherapy-induced cardiotoxicity is a key to effective preventive strategies and improved chemotherapy regimen. Although no reliable and effective preventive treatment has become available, numerous evidence demonstrates that chemotherapy-induced cardiotoxicity involves the generation of reactive oxygen species (ROS). This review provides an overview of the roles of oxidative stress in chemotherapy-induced cardiotoxicity using doxorubicin, which is one of the most effective chemotherapeutic agents against a wide range of cancers, as an example. Current understanding in the molecular mechanisms of ROS-mediated cardiotoxicity will be explored and discussed, with emphasis on cardiomyocyte apoptosis leading to cardiomyopathy. The review will conclude with perspectives on model development needed to facilitate further progress and understanding on chemotherapy-induced cardiotoxicity.

Drug-induced mitochondrial dysfunction and cardiotoxicity

Mitochondria has an essential role in myocardial tissue homeostasis; thus deterioration in mitochondrial function eventually leads to cardiomyocyte and endothelial cell death and consequent cardiovascular dysfunction. Several chemical compounds and drugs have been known to directly or indirectly modulate cardiac mitochondrial function, which can account both for the toxicological and pharmacological properties of these substances. In many cases, toxicity problems appear only in the presence of additional cardiovascular disease conditions or develop months/years following the exposure, making the diagnosis difficult. Cardiotoxic agents affecting mitochondria include several widely used anticancer drugs [anthracyclines (Doxorubicin/Adriamycin), cisplatin, trastuzumab (Herceptin), arsenic trioxide (Trisenox), mitoxantrone (Novantrone), imatinib (Gleevec), bevacizumab (Avastin), sunitinib (Sutent), and sorafenib (Nevaxar)], antiviral compound azidothymidine (AZT, Zidovudine) and several oral antidiabetics [e.g., rosiglitazone (Avandia)]. Illicit drugs such as alcohol, cocaine, methamphetamine, ecstasy, and synthetic cannabinoids (spice, K2) may also induce mitochondria-related cardiotoxicity. Mitochondrial toxicity develops due to various mechanisms involving interference with the mitochondrial respiratory chain (e.g., uncoupling) or inhibition of the important mitochondrial enzymes (oxidative phosphorylation, Szent-Györgyi-Krebs cycle, mitochondrial DNA replication, ADP/ATP translocator). The final phase of mitochondrial dysfunction induces loss of mitochondrial membrane potential and an increase in mitochondrial oxidative/nitrative stress, eventually culminating into cell death. This review aims to discuss the mechanisms of mitochondrion-mediated cardiotoxicity of commonly used drugs and some potential cardioprotective strategies to prevent these toxicities.

ErbB2 overexpression upregulates antioxidant enzymes, reduces basal levels of reactive oxygen species, and protects against doxorubicin cardiotoxicity

Levels of the HER2/ErbB2 protein in the heart are upregulated in some women during breast cancer therapy, and these women are at high risk for developing heart dysfunction after sequential treatment with anti-ErbB2/trastuzumab or doxorubicin. Doxorubicin is known to increase oxidative stress in the heart, and thus we considered the possibility that ErbB2 protein influences the status of cardiac antioxidant defenses in cardiomyocytes. In this study, we measured reactive oxygen species (ROS) in cardiac mitochondria and whole hearts from mice with cardiac-specific overexpression of ErbB2 (ErbB2(tg)) and found that, compared with control mice, high levels of ErbB2 in myocardium result in lower levels of ROS in mitochondria (P = 0.0075) and whole hearts (P = 0.0381). Neonatal cardiomyocytes isolated from ErbB2(tg) hearts have lower ROS levels and less cellular death (P < 0.0001) following doxorubicin treatment. Analyzing antioxidant enzyme levels and activities, we found that ErbB2(tg) hearts have increased levels of glutathione peroxidase 1 (GPx1) protein (P < 0.0001) and GPx activity (P = 0.0031) in addition to increased levels of two known GPx activators, c-Abl (P = 0.0284) and Arg (P < 0.0001). Interestingly, although mitochondrial ROS emission is reduced in the ErbB2(tg) hearts, oxygen consumption rates and complex I activity are similar to control littermates. Compared with these in vivo studies, H9c2 cells transfected with ErbB2 showed less cellular toxicity and produced less ROS (P < 0.0001) after doxorubicin treatment but upregulated GR activity (P = 0.0237) instead of GPx. Our study shows that ErbB2-dependent signaling contributes to antioxidant defenses and suggests a novel mechanism by which anticancer therapies involving ErbB2 antagonists can harm myocardial structure and function.

Cyclovirobuxine D Attenuates Doxorubicin-Induced Cardiomyopathy by Suppression of Oxidative Damage and Mitochondrial Biogenesis Impairment

The clinical application of doxorubicin (DOX) is compromised by its cardiac toxic effect. Cyclovirobuxine D (CVB-D) is a steroid alkaloid extracted from a traditional Chinese medicine, Buxus microphylla. Our results showed that CVB-D pretreatment markedly attenuated DOX-induced cardiac contractile dysfunction and histological alterations. By using TUNEL assay and western blot analysis, we found that CVB-D pretreatment reduced DOX-induced apoptosis of myocardial cells and mitochondrial cytochrome c release to cytosol. CVB-D pretreatment ameliorated DOX-induced cardiac oxidative damage including lipid peroxidation and protein carbonylation and a decrease in the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG). Moreover, CVB-D was found to prevent DOX-induced mitochondrial biogenesis impairment as evidenced by preservation of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and nuclear respiratory factor 1 (NRF1), as well as mitochondrial DNA copy number. These findings demonstrate that CVB-D protects against DOX-induced cardiomyopathy, at least in part, by suppression of oxidative damage and mitochondrial biogenesis impairment.

Myocardial MiR-30 downregulation triggered by doxorubicin drives alterations in β-adrenergic signaling and enhances apoptosis

The use of anthracyclines such as doxorubicin (DOX) has improved outcome in cancer patients, yet associated risks of cardiomyopathy have limited their clinical application. DOX-associated cardiotoxicity is frequently irreversible and typically progresses to heart failure (HF) but our understanding of molecular mechanisms underlying this and essential for development of cardioprotective strategies remains largely obscure. As microRNAs (miRNAs) have been shown to play potent regulatory roles in both cardiovascular disease and cancer, we investigated miRNA changes in DOX-induced HF and the alteration of cellular processes downstream. Myocardial miRNA profiling was performed after DOX-induced injury, either via acute application to isolated cardiomyocytes or via chronic exposure in vivo, and compared with miRNA profiles from remodeled hearts following myocardial infarction. The miR-30 family was downregulated in all three models. We describe here that miR-30 act regulating the β-adrenergic pathway, where preferential β1- and β2-adrenoceptor (β1AR and β2AR) direct inhibition is combined with Giα-2 targeting for fine-tuning. Importantly, we show that miR-30 also target the pro-apoptotic gene BNIP3L/NIX. In aggregate, we demonstrate that high miR-30 levels are protective against DOX toxicity and correlate this in turn with lower reactive oxygen species generation. In addition, we identify GATA-6 as a mediator of DOX-associated reductions in miR-30 expression. In conclusion, we describe that DOX causes acute and sustained miR-30 downregulation in cardiomyocytes via GATA-6. miR-30 overexpression protects cardiac cells from DOX-induced apoptosis, and its maintenance represents a potential cardioprotective and anti-tumorigenic strategy for anthracyclines.

Possible involvement of downregulation of the apelin-APJ system in doxorubicin-induced cardiotoxicity

Apelin peptide is an endogenous ligand of APJ (a putative receptor protein related to the angiotensin II type 1 receptor), which is a member of a G protein-coupled receptor superfamily with seven transmembrane domains. Recent findings have suggested that the apelin-APJ system plays a potential role in cardiac contraction and cardioprotection. In the present study, we show that the apelin-APJ system is disrupted in doxorubicin (Dox)-induced cardiotoxicity. We found downregulation of apelin and APJ mRNA expression in C57Bl/6J mouse hearts on days 1 and 5 after Dox administration (20 mg/kg ip). Plasma apelin levels and cardiac APJ protein expression were significantly decreased on day 5 after Dox injection. Cardiac apelin contents were reduced on day 1 but increased to basal levels on day 5 after Dox injection. We also examined the effects of APJ gene deletion on Dox-induced cardiotoxicity. Compared with wild-type mice, APJ knockout mice showed a significant depression in cardiac contractility on day 5 after Dox (15 mg/kg ip) treatment followed by a decrease in 14-day survival rates. Moreover, Dox-induced myocardial damage, cardiac protein carbonylation, and autophagic dysfunction were accelerated in APJ knockout mice. Rat cardiac H9c2 cells showed Dox-induced decreases in viability, which were prevented by APJ overexpression and the combination with apelin treatment. These results suggest that the suppression of APJ expression after Dox administration can exacerbate Dox-induced cardiotoxicity, which may be responsible for depressed protective function of the endogenous apelin-APJ system. Modulation of the apelin-APJ system may hold promise for the treatment of Dox-induced cardiotoxicity.

Increased mitochondrial emission of reactive oxygen species and calpain activation are required for doxorubicin-induced cardiac and skeletal muscle myopathy

Although doxorubicin (DOX) is a highly effective anti-tumour agent used to treat a variety of cancers, DOX administration is associated with significant side effects, including myopathy of both cardiac and skeletal muscles. The mechanisms responsible for DOX-mediated myopathy remain a topic of debate. We tested the hypothesis that both increased mitochondrial reactive oxygen species (ROS) emission and activation of the cysteine protease calpain are required for DOX-induced myopathy in rat cardiac and skeletal muscle. Cause and effect was determined by administering a novel mitochondrial-targeted anti-oxidant to prevent DOX-induced increases in mitochondrial ROS emission, whereas a highly-selective pharmacological inhibitor was exploited to inhibit calpain activity. Our findings reveal that mitochondria are a major site of DOX-mediated ROS production in both cardiac and skeletal muscle fibres and the prevention of DOX-induced increases in mitochondrial ROS emission protects against fibre atrophy and contractile dysfunction in both cardiac and skeletal muscles. Furthermore, our results indicate that DOX-induced increases in mitochondrial ROS emission are required to activate calpain in heart and skeletal muscles and, importantly, calpain activation is a major contributor to DOX-induced myopathy. Taken together, these findings show that increased mitochondrial ROS production and calpain activation are significant contributors to the development of DOX-induced myopathy in both cardiac and skeletal muscle fibres.

Phase I and pharmacokinetic study of the novel anthracycline derivative 5-imino-13-deoxydoxorubicin (GPX-150) in patients with advanced solid tumors

PURPOSE

5-imino-13-deoxydoxorubicin (DIDOX; GPX-150) is a doxorubicin analog modified in two locations to prevent formation of cardiotoxic metabolites and reactive oxygen species. Preclinical studies have demonstrated anti-cancer activity without cardiotoxicity. A phase I study was performed in order to determine the maximum-tolerated dose (MTD) of GPX-150 in patients with metastatic solid tumors.

METHODS

GPX-150 was administered as an intravenous infusion every 21 days for up to 8 cycles. An accelerated dose escalation was used for the first three treatment groups. The dosing groups were (A) 14 mg/m(2), (B) 28 mg/m(2), (C), 56 mg/m(2), (D) 84 mg/m(2), (E) 112 mg/m(2), (F) 150 mg/m(2), (G) 200 mg/m(2), and (H) 265 mg/m(2). Pharmacokinetic samples were drawn during the first 72 h of cycle 1.

RESULTS

The MTD was considered to be reached at the highest dosing level of 265 mg/m(2) since dose reduction was required in 5 of 6 patients for neutropenia. The most frequent adverse events were neutropenia, anemia, fatigue, and nausea. No patients experienced cardiotoxicity while on the study. The best overall response was stable disease in four (20 %) patients. Pharmacokinetic analysis revealed an AUC of 8.0 (±2.6) μg · h/mL, a clearance of 607 (±210) mL/min/m(2) and a t1/2β of 13.8 (±4.6) hours.

CONCLUSIONS

GPX-150 administered every 21 days has an acceptable side effect profile and no cardiotoxicity was observed. Further investigation is needed to determine the efficacy of GPX-150 in anthracycline-sensitive malignancies.

The role of TNF-α, Fas/Fas ligand system and NT-proBNP in the early detection of asymptomatic left ventricular dysfunction in cancer patients treated with anthracyclines

Background

Anthracycline-induced cardiotoxicity typically presents as congestive heart failure (CHF). As immuno-inflammatory activation and apoptosis are important mechanisms in the process of heart failure, the use of biomarkers that could detect cardiovascular toxicity before the clinical presentation is of great importance. We studied whether sTNF-a, sTNF-RI, sTNF-RII, Fas/FasLigand system and NT-proBNP associate with early cardiac dysfunction in patients receiving cardiotoxic drugs.

Methods

Two groups of breast cancer patients—group A with metastatic disease under chemotherapy with epirubicin and group B with no residual disease under a less cardiotoxic regimen—as well as healthy women were included in this prosprective study. NT-proBNP, sTNF-a, sTNF-RI, sTNF-RII, sFas, sFas-Ligand and left ventricular ejection fraction (LVEF) were determined in all patients before and after the completion of chemotherapy.

Results

In Group A, an increase in sFas levels (p < 0.001), a decrease in the sFasL levels (p = 0.010), an NT-proBNP increase (p < 0.001) and a significant reduction of LVEF (p < 0.001) was recorded post-chemotherapy. The decrease in LVEF correlated significantly with the increase in sFas, the decrease in sFasL and the rise in NT-proBNP levels. In Group B, TNF-RI levels were higher (p = 0.024) and mean sFas-L levels lower (p = 0.021) post chemotherapy with no LVEF drop. Two of group A (7.6%) patients developed symptomatic CHF 12 and 14 months respectively after the end of chemotherapy.

Conclusion

SFas, sFas-L and NT-proBNP correlate with reductions in LVEF and could be used as sensitive biochemical indices for the detection of asymptomatic left ventricular dysfunction in cancer patients under cardiotoxic chemotherapy.

Cannabidiol Protects against Doxorubicin-Induced Cardiomyopathy by Modulating Mitochondrial Function and Biogenesis

Doxorubicin (DOX) is a widely used, potent chemotherapeutic agent; however, its clinical application is limited because of its dose-dependent cardiotoxicity. DOX's cardiotoxicity involves increased oxidative/nitrative stress, impaired mitochondrial function in cardiomyocytes/endothelial cells and cell death. Cannabidiol (CBD) is a nonpsychotropic constituent of marijuana, which is well tolerated in humans, with antioxidant, antiinflammatory and recently discovered antitumor properties. We aimed to explore the effects of CBD in a well-established mouse model of DOX-induced cardiomyopathy. DOX-induced cardiomyopathy was characterized by increased myocardial injury (elevated serum creatine kinase and lactate dehydrogenase levels), myocardial oxidative and nitrative stress (decreased total glutathione content and glutathione peroxidase 1 activity, increased lipid peroxidation, 3-nitrotyrosine formation and expression of inducible nitric oxide synthase mRNA), myocardial cell death (apoptotic and poly[ADP]-ribose polymerase 1 [PARP]-dependent) and cardiac dysfunction (decline in ejection fraction and left ventricular fractional shortening). DOX also impaired myocardial mitochondrial biogenesis (decreased mitochondrial copy number, mRNA expression of peroxisome proliferator-activated receptor γ coactivator 1-alpha, peroxisome proliferator-activated receptor alpha, estrogen-related receptor alpha), reduced mitochondrial function (attenuated complex I and II activities) and decreased myocardial expression of uncoupling protein 2 and 3 and medium-chain acyl-CoA dehydrogenase mRNA. Treatment with CBD markedly improved DOX-induced cardiac dysfunction, oxidative/nitrative stress and cell death. CBD also enhanced the DOX-induced impaired cardiac mitochondrial function and biogenesis. These data suggest that CBD may represent a novel cardioprotective strategy against DOX-induced cardiotoxicity, and the above-described effects on mitochondrial function and biogenesis may contribute to its beneficial properties described in numerous other models of tissue injury.

Physical exercise prior and during treatment reduces sub-chronic doxorubicin-induced mitochondrial toxicity and oxidative stress

Doxorubicin (DOX) is an anti-cancer agent whose clinical usage results in a cumulative and dose-dependent cardiotoxicity. We have previously shown that exercise performed prior to DOX treatment reduces the resulting cardiac(mito) toxicity. We sought to determine the effects on cardiac mitochondrial toxicity of two distinct chronic exercise models (endurance treadmill training-TM and voluntary free-wheel activity-FW) when used prior and during DOX treatment. Male-young Sprague-Dawley rats were divided into six groups (n=6 per group): SAL+SED (saline sedentary), SAL+TM (12-weeks TM), SAL+FW (12-weeks FW), DOX+SED (7-weeks of chronic DOX treatment 2mg/kg per week), DOX+TM and DOX+FW. DOX administration started 5weeks after the beginning of the exercise protocol. Heart mitochondrial ultrastructural alterations, mitochondrial function (oxygen consumption and membrane potential), semi-quantification of oxidative phosphorylation (OXPHOS) proteins and their in-gel activity, as well as proteins involved in mitochondrial oxidative stress (SIRT3, p66shc and UCP2), biogenesis (PGC1α and TFAM), acetylation and markers for oxidative damage (carbonyl groups, MDA,SH, aconitase, Mn-SOD activity) were evaluated. DOX treatment resulted in ultrastructural and functional alterations and decreased OXPHOS. Moreover, DOX decreased complex I activity and content, mitochondrial biogenesis (TFAM), increased acetylation and oxidative stress. TM and FW prevented DOX-induced alteration in OXPHOS, the increase in oxidative stress, the decrease in complex V activity and in complex I activity and content. DOX-induced decreases in TFAM and SIRT3 content were prevented by TM only. Both chronic models of physical exercise performed before and during the course of sub-chronic DOX treatment translated into an improved mitochondrial bioenergetic fitness, which may result in part from the prevention of mitochondrial oxidative stress and damage.

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.

Stem cell therapy and breast cancer treatment: review of stem cell research and potential therapeutic impact against cardiotoxicities due to breast cancer treatment

A new problem has emerged with the ever-increasing number of breast cancer survivors. While early screening and advances in treatment have allowed these patients to overcome their cancer, these treatments often have adverse cardiovascular side effects that can produce abnormal cardiovascular function. Chemotherapeutic and radiation therapy have both been linked to cardiotoxicity; these therapeutics can cause a loss of cardiac muscle and deterioration of vascular structure that can eventually lead to heart failure (HF). This cardiomyocyte toxicity can leave the breast cancer survivor with a probable diagnosis of dilated or restrictive cardiomyopathy (DCM or RCM). While current HF standard of care can alleviate symptoms, other than heart transplantation, there is no therapy that replaces cardiac myocytes that are killed during cancer therapies. There is a need to develop novel therapeutics that can either prevent or reverse the cardiac injury caused by cancer therapeutics. These new therapeutics should promote the regeneration of lost or deteriorating myocardium. Over the last several decades, the therapeutic potential of cell-based therapy has been investigated for HF patients. In this review, we discuss the progress of pre-clinical and clinical stem cell research for the diseased heart and discuss the possibility of utilizing these novel therapies to combat cardiotoxicity observed in breast cancer survivors.

Mitochondrial catastrophe during doxorubicin-induced cardiotoxicity: a review of the protective role of melatonin

Anthracyclines, such as doxorubicin, are among the most valuable treatments for various cancers, but their clinical use is limited due to detrimental side effects such as cardiotoxicity. Doxorubicin-induced cardiotoxicity is emerging as a critical issue among cancer survivors and is an area of much significance to the field of cardio-oncology. Abnormalities in mitochondrial functions such as defects in the respiratory chain, decreased adenosine triphosphate production, mitochondrial DNA damage, modulation of mitochondrial sirtuin activity and free radical formation have all been suggested as the primary causative factors in the pathogenesis of doxorubicin-induced cardiotoxicity. Melatonin is a potent antioxidant, is nontoxic, and has been shown to influence mitochondrial homeostasis and function. Although a number of studies support the mitochondrial protective role of melatonin, the exact mechanisms by which melatonin confers mitochondrial protection in the context of doxorubicin-induced cardiotoxicity remain to be elucidated. This review focuses on the role of melatonin on doxorubicin-induced bioenergetic failure, free radical generation, and cell death. A further aim is to highlight other mitochondrial parameters such as mitophagy, autophagy, mitochondrial fission and fusion, and mitochondrial sirtuin activity, which lack evidence to support the role of melatonin in the context of cardiotoxicity.

Inhibition of iPLA2 β and of stretch-activated channels by doxorubicin alters dystrophic muscle function

BACKGROUND AND PURPOSE

Chronic elevation in intracellular Ca(2+) concentration participates in death of skeletal muscle from mdx mice, a model for Duchenne muscular dystrophy (DMD). Candidate pathways mediating this Ca(2+) overload involve store-operated channels (SOCs) and stretch-activated channels (SACs), which are modulated by the Ca(2+) -independent form of PL A2 (iPLA2 ). We investigated the effect of doxorubicin (Dox), a chemotherapeutic agent reported to inhibit iPLA2 in other systems, on the activity of this enzyme and on the consequences on Ca(2+) handling and muscle function in mdx mice.

EXPERIMENTAL APPROACH

Effects of Dox on iPLA2 activity, reactive oxygen species production and on Ca(2+) influx were investigated in C2C12 and mdx myotubes. The mechanism of Dox-mediated iPLA2 inhibition was evaluated using purified 6x histidine-tagged enzyme. Aequorin technology was used to assess Ca(2+) concentrations underneath the plasma membrane. Isolated muscles were exposed to fatigue protocols and eccentric contractions to evaluate the effects of Dox on muscle function.

KEY RESULTS

Dox at 1-30 μM inhibited iPLA2 activity in cells and in the purified enzyme. Dox also inhibited SAC- but not SOC-mediated Ca(2+) influx in myotubes. Stimulated elevations of Ca(2+) concentrations below the plasmalemma were also blocked. Exposure of excised muscle to Dox was not deleterious to force production and promoted recovery from eccentric contractions.

CONCLUSIONS AND IMPLICATIONS

Dox showed efficacy against targets known to play a role in the pathology of DMD, namely iPLA2 and SAC. The potent SAC inhibitory effect of Dox is a novel finding that can explain partly the cardiomyopathy seen in chronic anthracycline treatment.

Cardiovascular effects of Phaleria macrocarpa extracts combined with mainstay FAC regimen for breast cancer

DLBS1425 is a bioactive compound extracted from Phaleria macrocarpa, with anti-proliferative, anti-inflammatory and anti-angiogenic properties against cancer cells. The present study was aimed to assess cardiotoxicity of DLBS1425, compared to the mainstay regimen for breast cancer, 5-fluorouracil:doxorubicin:cyclophosphamide (FAC, given at 500/50/500 mg/m(2)). Treatment with FAC regimen at standard dose resulted in very severe toxicity, so mice had no chance to survive for more than 7 days following initial drug treatment. Furthermore, histological examination on the heart revealed severe muscular damage when mice were given the FAC regimen alone (severe toxicity). FAC as chemotherapeutic regimen exerted high toxicity profile to the cardiovascular cells in this experiment. Meanwhile, treatment with DLBS1425 alone up to a dose equivalent to as high as 300 mg three times daily in human had no hazardous consequences on the heart, hematological feature, as well as general safety. In the cardiovascular cells, DLBS1425 in the presence of FAC regimen (one-eight of the initial dose) gave protection to the cardiac muscle cells as well as other hematological features. Taken together, results of the present study suggest that DLBS1425 is safe when used as adjuvant therapy for breast cancer and may be even protective against cardiac cellular damage produced by chemotherapeutic regimen.

Redox proteomic identification of HNE-bound mitochondrial proteins in cardiac tissues reveals a systemic effect on energy metabolism after doxorubicin treatment

Doxorubicin (DOX), one of the most effective anticancer drugs, is known to generate progressive cardiac damage, which is due, in part, to DOX-induced reactive oxygen species (ROS). The elevated ROS often induce oxidative protein modifications that result in alteration of protein functions. This study demonstrates that the level of proteins adducted by 4-hydroxy-2-nonenal (HNE), a lipid peroxidation product, is significantly increased in mouse heart mitochondria after DOX treatment. A redox proteomics method involving two-dimensional electrophoresis followed by mass spectrometry and investigation of protein databases identified several HNE-modified mitochondrial proteins, which were verified by HNE-specific immunoprecipitation in cardiac mitochondria from the DOX-treated mice. The majority of the identified proteins are related to mitochondrial energy metabolism. These include proteins in the citric acid cycle and electron transport chain. The enzymatic activities of the HNE-adducted proteins were significantly reduced in DOX-treated mice. Consistent with the decline in the function of the HNE-adducted proteins, the respiratory function of cardiac mitochondria as determined by oxygen consumption rate was also significantly reduced after DOX treatment. Treatment with Mn(III) meso-tetrakis(N-n-butoxyethylpyridinium-2-yl)porphyrin, an SOD mimic, averted the doxorubicin-induced mitochondrial dysfunctions as well as the HNE-protein adductions. Together, the results demonstrate that free radical-mediated alteration of energy metabolism is an important mechanism mediating DOX-induced cardiac injury, suggesting that metabolic intervention may represent a novel approach to preventing cardiac injury after chemotherapy.

Effects of short-term endurance exercise training on acute doxorubicin-induced FoxO transcription in cardiac and skeletal muscle

Doxorubicin (DOX) is a potent antitumor agent used in cancer treatment. Unfortunately, DOX can induce myopathy in both cardiac and skeletal muscle, which limits its clinical use. Importantly, exercise training has been shown to protect against DOX-mediated cardiac and skeletal muscle myopathy. However, the mechanisms responsible for this exercise-induced muscle protection remain elusive. These experiments tested the hypothesis that short-term exercise training protects against acute DOX-induced muscle toxicity, in part, due to decreased forkhead-box O (FoxO) transcription of atrophy genes. Rats (n = 6 per group) were assigned to sedentary or endurance exercise-trained groups and paired with either placebo or DOX treatment. Gene expression and protein abundance were measured in both cardiac and skeletal muscles to determine the impact of DOX and exercise on FoxO gene targets. Our data demonstrate that DOX administration amplified FoxO1 and FoxO3 mRNA expression and increased transcription of FoxO target genes [i.e., atrogin-1/muscle atrophy F-box (MaFbx), muscle ring finger-1 (MuRF-1), and BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3)] in heart and soleus muscles. Importantly, exercise training protected against DOX-induced increases of FoxO1 and MuRF-1 in cardiac muscle and also prevented the rise of FoxO3, MuRF-1, and BNIP3 in soleus muscle. Furthermore, our results indicate that exercise increased peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α) in both the heart and soleus muscles. This is important because increased PGC-1α expression is known to suppress FoxO activity resulting in reduced expression of FoxO target genes. Together, these results are consistent with the hypothesis that exercise training protects against DOX-induced myopathy in both heart (FoxO1 and MuRF-1) and skeletal muscles (FoxO3, MuRF-1, and BNIP3).

Protective effect of Mutellina purpurea polyphenolic compounds in doxorubicin-induced toxicity in H9c2 cardiomyocytes

The delayed cardiomyopathy caused by doxorubicin - an chemotherapeutic drug with broad spectrum of anticancer activity - is mainly triggered by oxidative stress. The aim of this study was to assess an effect of Mutellina purpurea methanolic extract fraction and other antioxidants of plant origin: rutin, quercetin and chlorogenic acid (all 1 mg% w/v) on oxidative stress and morphological changes induced by doxorubicin in cardiomyocytes H9c2. Mitochondrial oxidative stress in cardiomyocytes induced by 1 µM doxorubicin was evidenced by MitoTracker and RedoxSensor Red CC-1 dyes. Moreover, cardiomyocytes morphological changes and cell viability were evaluated. The tested fraction slightly reduced mitochondrial ROS fluorescence, similar to quercetin. Chlorogenic acid revealed concentration dependent prooxidative and antioxidative properties in the applied H9c2 model. The evaluation of the protective effect of tested compounds on doxorubicin-induced cytotoxicity was based on the examination of induced oxidative stress and morphology changes. The protective effect was described in the following order: rutin > chlorogenic acid (0.5 µM) > LH8 and quercetin. According to the MTT test, rutin seems to be the most promising compound that should be tested in a future studies.

Administration of chromium(III) and manganese(II) as a potential protective approach against daunorubicin-induced cardiotoxicity: in vitro and in vivo experimental evidence

Daunorubicin (DNR) is a widely used antitumor drug, but its application is limited because of its cardiotoxic side effects. The present study was designed to investigate the interaction between DNR and cardiac myosin (CM) in the presence of chromium(III) (Cr(3+)) and manganese(II) (Mn(2+)) using fluorescence spectrometry under simulative physiological conditions with the aim of exploring the influence of metal ion on DNR-CM complex and finding out an aggressive approach to abrogate of DNR-induced cardiotoxicity. In detail, the quenching and binding constant of ternary system, including metal ion, DNR, and CM, were measured and compared with the DNR-CM. The data from in vitro experiments indicate that the presence of Cr(3+) or Mn(2+) distinctly decreased the binding force between DNR and CM, and alleviated the cardiac toxicity caused by DNR. In addition, the variations in mice body weight and myocardial enzyme level were examined by in vivo experiments. Animals receiving Cr(3+) or Mn(2+) supplementation of DNR showed preservation of the normal pattern of the heart, especially 2.0 mg Cr(3+)/kg body wt or 50.0 mg Mn(2+)/kg body wt exhibited an obviously protective effect accompanied with body weight raise when compared with the mice treated with DNR alone, decreased the ratio of heart to body weight (BW) and the ratio of left ventricular mass to BW to the normal levels, and inhibited the leak of myocardial enzyme caused by DNR. As a result, this study suggests that pretreatment of lower dose of Cr(3+) (2 mg/kg wt) and moderate dose of Mn(2+) (50 mg/kg wt) might be useful and play an important role in ameliorating the cardiotoxicity of DNR treatment in cancer patients.

The anticancer agent doxorubicin disrupts mitochondrial energy metabolism and redox balance in skeletal muscle

The combined loss of muscle strength and constant fatigue are disabling symptoms for cancer patients undergoing chemotherapy. Doxorubicin, a standard chemotherapy drug used in the clinic, causes skeletal muscle dysfunction and premature fatigue along with an increase in reactive oxygen species (ROS). As mitochondria represent a primary source of oxidant generation in muscle, we hypothesized that doxorubicin could negatively affect mitochondria by inhibiting respiratory capacity, leading to an increase in H2O2-emitting potential. Here we demonstrate a biphasic response of skeletal muscle mitochondria to a single doxorubicin injection (20mg/kg). Initially at 2h doxorubicin inhibits both complex I- and II-supported respiration and increases H2O2 emission, both of which are partially restored after 24h. The relationship between oxygen consumption and membrane potential (ΔΨ) is shifted to the right at 24h, indicating elevated reducing pressure within the electron transport system (ETS). Respiratory capacity is further decreased at a later time point (72 h) along with H2O2-emitting potential and an increased sensitivity to mitochondrial permeability transition pore (mPTP) opening. These novel findings suggest a role for skeletal muscle mitochondria as a potential underlying cause of doxorubicin-induced muscle dysfunction.

Protective effect of a direct renin inhibitor in acute murine model of cardiotoxicity and nephrotoxicity

This study aimed to investigate the possible protective effects of aliskiren against doxorubicin (DXR)-induced cardiorenal injury and to identify the mechanisms involved. Intraperitoneal administration of DXR (15 mg/kg, body weight, as a single dose) caused significant induction in the levels of angiotensin I, caspase-3, lactate dehydrogenase (LDH), lipid peroxidation malondialdehyde (MDA), urea, and creatinine. Concomitant decline in the levels of albumin and total protein in plasma, reduction in reduced glutathione (GSH), and antiperoxidative enzyme superoxide dismutase (SOD) levels followed by ultrastructural alterations in the myocardial and renal tissues were also observed. Oral administration of aliskiren (100 mg/kg, for a period of 14 days) significantly prevented all these DXR-induced adverse effects and maintained the rats near to normal status. However, telmisartan (10 mg/kg) pretreatment has shown slight protection in DXR-induced renal injury as evidenced by broadening of podocyte foot process and narrowing of slit pore diameter. The results of aliskiren were compared with telmisartan which was used as reference in this study. These results suggested that aliskiren has protective effects against acute model of DXR-induced cardiotoxicity and nephrotoxicity, implying that plasma renin activity plays a role in DXR-induced cardio-renal injury.

Attenuation of doxorubicin-induced cardiotoxicity by mdivi-1: a mitochondrial division/mitophagy inhibitor

Doxorubicin is one of the most effective anti-cancer agents. However, its use is associated with adverse cardiac effects, including cardiomyopathy and progressive heart failure. Given the multiple beneficial effects of the mitochondrial division inhibitor (mdivi-1) in a variety of pathological conditions including heart failure and ischaemia and reperfusion injury, we investigated the effects of mdivi-1 on doxorubicin-induced cardiac dysfunction in naïve and stressed conditions using Langendorff perfused heart models and a model of oxidative stress was used to assess the effects of drug treatments on the mitochondrial depolarisation and hypercontracture of cardiac myocytes. Western blot analysis was used to measure the levels of p-Akt and p-Erk 1/2 and flow cytometry analysis was used to measure the levels p-Drp1 and p-p53 upon drug treatment. The HL60 leukaemia cell line was used to evaluate the effects of pharmacological inhibition of mitochondrial division on the cytotoxicity of doxorubicin in a cancer cell line. Doxorubicin caused a significant impairment of cardiac function and increased the infarct size to risk ratio in both naïve conditions and during ischaemia/reperfusion injury. Interestingly, co-treatment of doxorubicin with mdivi-1 attenuated these detrimental effects of doxorubicin. Doxorubicin also caused a reduction in the time taken to depolarisation and hypercontracture of cardiac myocytes, which were reversed with mdivi-1. Finally, doxorubicin caused a significant elevation in the levels of signalling proteins p-Akt, p-Erk 1/2, p-Drp1 and p-p53. Co-incubation of mdivi-1 with doxorubicin did not reduce the cytotoxicity of doxorubicin against HL-60 cells. These data suggest that the inhibition of mitochondrial fission protects the heart against doxorubicin-induced cardiac injury and identify mitochondrial fission as a new therapeutic target in ameliorating doxorubicin-induced cardiotoxicity without affecting its anti-cancer properties.

Mitochondrial translocator protein (TSPO) ligands prevent doxorubicin-induced mechanical dysfunction and cell death in isolated cardiomyocytes

Contractile dysfunction and subsequent development of cardiomyopathies are well known limiting factors in the treatment of cancer with doxorubicin and have been linked to mitochondrial dysfunction. Here, using adult isolated paced cardiomyocytes, we have demonstrated that ligands of translocator protein (TSPO) 4'-chlorodiazepam and TRO40303 prevented the doxorubicin-induced alterations in contractility and improved cardiomyocyte viability. This cardioprotective effect was closely associated with both a potent reduction in reactive oxygen species production and inhibition of mitochondrial permeability transition pore opening. Thus, preventive administration of TSPO ligands may represent a novel pharmacological strategy to protect the heart during doxorubicin treatment.

An update on oxidative stress-mediated organ pathophysiology

Exposure to environmental pollutants and drugs can result in pathophysiological situations in the body. Research in this area is essential as the knowledge on cellular survival and death would help in designing effective therapeutic strategies that are needed for the maintenance of the normal physiological functions of the body. In this regard, naturally occurring bio-molecules can be considered as potential therapeutic targets as they are normally available in commonly consumed foodstuffs and are thought to have minimum side effects. This review article describes the detailed mechanisms of oxidative stress-mediated organ pathophysiology and the ultimate fate of the cells either to survive or to undergo necrotic or apoptotic death. The mechanisms underlying the beneficial role of a number of naturally occurring bioactive molecules in oxidative stress-mediated organ pathophysiology have also been included in the review. The review provides useful information about the recent progress in understanding the mechanism(s) of various types of organ pathophysiology, the complex cross-talk between these pathways, as well as their modulation in stressed conditions. Additionally, it suggests possible therapeutic applications of a number of naturally occurring bioactive molecules in conditions involving oxidative stress.

Development of a tumor-specific photoactivatable doxorubicin prodrug

This is a retrospective highlight on the publication by Ibsen and coworkers: Localized In Vivo Activation of a Photoactivatable Doxorubicin Prodrug in Deep Tumor Tissue, which appeared in a preceding issue of Photochem. Photobiol. (2013, 89:698-708). The authors describe the synthesis and properties of a novel doxorubicin (DOX) prodrug, DOX-PCB, which contains a photocleavable linker group. Systemic administration of the prodrug to a tumor-bearing animal followed by LED/fiber optic 365 nm light delivery allowed active DOX to be released site specifically in the tumor area. This elegant and timely study provides compelling evidence that photocleavable DOX-PCB can eliminate many of the toxic side effects of DOX that have plagued clinical use of this highly effective antitumor drug for many years.

ROS production and their influence on the cellular antioxidative system in human erythrocytes incubated with daunorubicin and glutaraldehyde

This study examined the effects of daunorubicin and glutaraldehyde on some parameters of erythrocytes. The aim of the article was to present the results of research aiming to identify the level of glutaraldehyde at which the hemoglobin oxidation, externalization of phosphatidylserine and the changes in the viability (hemolysis) of erythrocytes are not statistically significant and therefore this level of glutaraldehyde can be used for the drug carriers' preparation. Glutaraldehyde was used as a crosslinking agent to enhance the uptake of the drug within red blood cells and to prevent its leakage from the cells. Fluorescence microscopy, flow cytometry and fluorimetric measurements confirmed higher levels of the drug in glutaraldehyde-treated human erythrocytes. Unfortunately, substantial damage to the red blood cells was also noted. DNR increased oxidative processes in the cell, which in turn led to an increase in the reactive oxygen species (ROS) level. When the red blood cells were also treated with glutaraldehyde, ROS production was significantly higher. We also observed loss of both the reduced and the total glutathione. Moreover the decreased activity of glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) was also observed. As hemoglobin, the erythrocytes' main component plays an essential role in the erythrocytes, the level of its oxidized form (metHb) in the erythrocytes and the phosphatidylserine exposure on the erythrocyte surface were also investigated. When higher concentrations of glutaraldehyde (0.0025-0.005%) were used for the uptake of DNR the elevated level of metHb was observed. Only at 0.0005% the level of oxidized form of Hb was within the physiological level and at that level the increase in the exposure of phosphatidylserine at the cell surface was not observed to be statistically significant. Moreover the percent of released hemoglobin was less than 1%. Based on these results it was concluded that glutaraldehyde can be used as a cross-linker between the drug (DNR) and the erythrocytes only at low concentration of about 0.0005%.

Imaging of early modification in cardiomyopathy: the doxorubicin-induced model

Doxorubicin chemotherapy is effective and widely used to treat acute lymphoblastic leukemia. However, its effectiveness is hampered by a wide spectrum of dose-dependent cardiotoxicity including both morphological and functional changes, affecting primarily the myocardium. Non-invasive imaging techniques are used for the diagnosis and monitoring of these cardiotoxic effects. The purpose of this review is to summarize and compare the most common imaging techniques used in early detection and therapeutic monitoring of doxorubicin-induced cardiotoxicity and the suggested mechanisms of such side effects. Imaging techniques using echocardiography including conventional 2D and 3D echocardiography along with MRI sequences including Tagging, Cine, and quantitative MRI in detecting early myocardial damage are also reviewed. As there is a multitude of reported indices and imaging methods to assess particular functional alterations, we limit this review to the most relevant techniques based on their clinical application and their potential to early detection of doxorubicin-induced cardiotoxic effects.

Mitochondria as a target of environmental toxicants

Enormous strides have recently been made in our understanding of the biology and pathobiology of mitochondria. Many diseases have been identified as caused by mitochondrial dysfunction, and many pharmaceuticals have been identified as previously unrecognized mitochondrial toxicants. A much smaller but growing literature indicates that mitochondria are also targeted by environmental pollutants. We briefly review the importance of mitochondrial function and maintenance for health based on the genetics of mitochondrial diseases and the toxicities resulting from pharmaceutical exposure. We then discuss how the principles of mitochondrial vulnerability illustrated by those fields might apply to environmental contaminants, with particular attention to factors that may modulate vulnerability including genetic differences, epigenetic interactions, tissue characteristics, and developmental stage. Finally, we review the literature related to environmental mitochondrial toxicants, with a particular focus on those toxicants that target mitochondrial DNA. We conclude that the fields of environmental toxicology and environmental health should focus more strongly on mitochondria.

Sesamol prevents doxorubicin-induced oxidative damage and toxicity on H9c2 cardiomyoblasts

Objectives

Exposure to toxicants like doxorubicin (Dox) damages cellular components by generating reactive oxygen species (ROS). This can be attenuated using free radical scavengers and/or antioxidants.

Methods

Dox-exposed cardiac myoblasts (H9c2 cells) were treated with sesamol (12.5, 25 and 50 μm), a natural phenolic compound. Intracellular ROS inhibition, cell viability and analysis of antioxidant and biochemical markers such as superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase, reduced/oxidized glutathione, lipid peroxidation and protein carbonyl content were performed. The effect of sesamol treatment on the cytotoxic and genotoxic parameters was studied by monitoring the signalling proteins involved in the apoptotic pathway.

Key findings

Dox triggered cellular and genetic damage by increasing levels of intracellular ROS, thereby decreasing cell viability and increasing apoptosis. Sesamol reversed the cytotoxic and genotoxic effects of Dox. In addition, sesamol attenuated the pro-apoptotic proteins and improved the anti-apoptotic status. Sesamol pre-treatment also alleviated the disturbed antioxidant milieu by preventing ROS production and improving endogenous enzyme levels.

Conclusions

Among the different doses tested, 50 μm of sesamol showed maximum protection against Dox-induced oxidative damage. This reflects the significance of sesamol in ameliorating the deleterious effects associated with cancer chemotherapy.

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.

NAD(P)H:quinone oxidoreductase 1 is induced by progesterone in cardiomyocytes

NAD(P)H: quinone oxidoreductase 1 (NQO1) is a ubiquitous flavoenzyme that catalyzes two-electron reduction of various quinones by utilizing NAD(P)H as an electron donor. Our previous study found that progesterone (PG) can protect cardiomyocytes from apoptosis induced by doxorubicin (Dox). Microarray analyses of genes induced by PG had led to the discovery of induction of NQO1 mRNA. We report here that PG induces NQO1 protein and its activity in a dose-dependent manner. Whereas NQO1 is well known as a target gene of Nrf2 transcription factor due to the presence of antioxidant response element (ARE) in the promoter, PG did not activate the ARE, suggesting Nrf2-independent induction of NQO1. To address the role of NQO1 induction in PG-induced cytoprotection, we tested the effect of NQO1 inducer β-naphthoflavone and inhibitor dicoumarol. Induction of NQO1 by β-naphthoflavone decreased Dox-induced apoptosis and potentiated the protective effect of PG as measured by caspase-3 activity. PG-induced NQO1 activity was inhibited with dicoumarol, which did not affect PG-induced cytoprotection. Dicoumarol treatment alone potentiated Dox-induced caspase-3 activity. These data suggest that while NQO1 plays a role in PG-induced cytoprotection, there are additional components contributing to PG-induced cytoprotection.

Piperlongumine induces inhibition of the ubiquitin-proteasome system in cancer cells

Piperlongumine, a natural product from the plant Piperlongum, has demonstrated selective cytotoxicity to tumor cells and to show anti-tumor activity in animal models [1]. Cytotoxicity of piperlongumine has been attributed to increase in reactive oxygen species (ROS) in cancer cells. We here report that piperlongumine is an inhibitor of the ubiquitin-proteasome system (UPS). Exposure of tumor cells to piperlongumine resulted in accumulation of a reporter substrate known to be rapidly degraded by the proteasome, and of accumulation of ubiquitin conjugated proteins. However, no inhibition of 20S proteolytic activity or 19S deubiquitinating activity was observed at concentrations inducing cytotoxicity. Consistent with previous reports, piperlongumine induced strong ROS activation which correlated closely with UPS inhibition and cytotoxicity. Proteasomal blocking could not be mimicked by agents that induce oxidative stress. Our results suggest that the anti-cancer activity of piperlongumine involves inhibition of the UPS at a pre-proteasomal step, prior to deubiquitination of malfolded protein substrates at the proteasome, and that the previously reported induction of ROS is a consequence of this inhibition.