Antioxidant defense against anthracycline cardiotoxicity by metallothionein

Metallothionein isoforms as double agents - Their roles in carcinogenesis, cancer progression and chemoresistance

Metallothioneins (MTs) are small cysteine-rich intracellular proteins with four major isoforms identified in mammals, designated MT-1 through MT-4. The best known biological functions of MTs are their ability to bind and sequester metal ions as well as their active role in redox homeostasis. Despite these protective roles, numerous studies have demonstrated that changes in MT expression could be associated with the process of carcinogenesis and participation in cell differentiation, proliferation, migration, and angiogenesis. Hence, MTs have the role of double agents, i.e., working with and against cancer. In view of their rich biochemical properties, it is not surprising that MTs participate in the emergence of chemoresistance in tumor cells. Many studies have demonstrated that MT overexpression is involved in the acquisition of resistance to anticancer drugs including cisplatin, anthracyclines, tyrosine kinase inhibitors and mitomycin. The evidence is gradually increasing for a cellular switch in MT functions, showing that they indeed have two faces: protector and saboteur. Initially, MTs display anti-oncogenic and protective roles; however, once the oncogenic process was launched, MTs are utilized by cancer cells for progression, survival, and contribution to chemoresistance. The duality of MTs can serve as a potential prognostic/diagnostic biomarker and can therefore pave the way towards the development of new cancer treatment strategies. Herein, we review and discuss MTs as tumor disease markers and describe their role in chemoresistance to distinct anticancer drugs.

Use of integrated imaging and serum biomarker profiles to identify subclinical dysfunction in pediatric cancer patients treated with anthracyclines

BACKGROUND

Anthracycline induced cardiomyopathy is a major cause of mortality and morbidity among pediatric cancer survivors. It has been postulated that oxidative stress induction and inflammation may play a role in the pathogenesis of this process. Accordingly, the present study performed an assessment of biomarker profiles and functional imaging parameters focused upon potential early determinants of anthracycline induced cardiomyopathy.

METHODS

Patients (10-22 years) were prospectively enrolled between January 2013 and November 2014. Thirteen subjects completed the study and underwent serial cardiac magnetic resonance imaging and plasma biomarker profiling performed 24-48 h after the first anthracycline dose and at set dose intervals. In addition, we collected plasma samples from 62 healthy controls to examine normal plasma biomarker profiles.

RESULTS

Left ventricular ejection fraction (LVEF) decreased from 64.3 ± 6.2 at the first visit to 57.5 ± 3.3 (p = 0.004) 1 year after chemotherapy. A decline in longitudinal strain magnitude occurred at lower cumulative doses. A differential inflammatory/matrix signature emerged in anthracycline induced cardiomyopathy patients compared to normal including increased interleukin-8 and MMP levels. With longer periods of anthracycline dosing, MMP-7, a marker of macrophage proteolytic activation, increased by 165 ± 54% whereas interleukin-10 an anti-inflammatory marker decreased by 75 ± 13% (both p < 0.05). MMP7 correlated with time dependent changes in EF.

CONCLUSIONS

Asymptomatic pediatric patients exposed to anthracycline therapy develop abnormal strain parameters at lower cumulative doses when compared to changes in EF. A differential biomarker signature containing both inflammatory and matrix domains occur early in anthracycline treatment. Dynamic changes in these domains occur with increased anthracycline doses and progression to anthracycline induced cardiomyopathy. These findings provide potential prognostic and mechanistic insights into the natural history of anthracycline induced cardiomyopathy.

TRIAL REGISTRATION NUMBER

NCT03211520 Date of Registration February 13, 2017, retrospectively registered.

Transcriptional patterns of reverse remodeling with left ventricular assist devices: a consistent signature

INTRODUCTION

Left ventricular assist device (LVAD) therapy has revolutionized the treatment of patients with advanced heart failure. Although originally intended for bridge-to-transplantation and destination therapy indications, a small subset of patients supported with LVADs exhibit complete myocardial recovery leading to device explanation. However, genetic and molecular determinants of partial and/or complete myocardial recovery remain largely unknown. Areas covered: We summarize current knowledge on alterations in heart failure transcriptome in response to LVAD support, as well as discuss common gene signatures potentially responsible for the reverse remodeling phenotype in the failing human heart. Expert commentary: Reverse remodeling after LVAD is likely a continuum between fully and partially recovered myocardium. Multicenter cardiac tissue repositories linked with detailed phenotype information may facilitate identification of genetic signals responsible for myocardial recovery in LVAD supported patients in the foreseeable future.

Loss of multidrug resistance-associated protein 1 potentiates chronic doxorubicin-induced cardiac dysfunction in mice

Doxorubicin (DOX), an effective cancer chemotherapeutic agent, induces dose-dependent cardiotoxicity, in part due to its ability to cause oxidative stress. We investigated the role of multidrug resistance-associated protein 1 (Mrp1/Abcc1) in DOX-induced cardiotoxicity in C57BL wild-type (WT) mice and their Mrp1 null (Mrp1(-/-)) littermates. Male mice were administered intraperitoneal DOX (3 or 2 mg/kg body weight) or saline twice a week for 3 weeks and examined 2 weeks after the last dose (protocol A total dose: 18 mg/kg) or for 5 weeks, and mice were examined 48 hours and 2 weeks after the last dose (protocol B total dose: 20 mg/kg). Chronic DOX induced body weight loss and hemotoxicity, adverse effects significantly exacerbated in Mrp1(-/-) versus WT mice. In the heart, significantly higher basal levels of glutathione (1.41-fold ± 0.27-fold) and glutathione disulfide (1.35-fold ± 0.16-fold) were detected in Mrp1(-/-) versus WT mice, and there were comparable decreases in the glutathione/glutathione disulfide ratio in WT and Mrp1(-/-) mice after DOX administration. Surprisingly, DOX induced comparable increases in 4-hydroxynonenal glutathione conjugate concentration in hearts from WT and Mrp1(-/-) mice. However, more DOX-induced apoptosis was detected in Mrp1(-/-) versus WT hearts (P < 0.05) (protocol A), and cardiac function, assessed by measurement of fractional shortening and ejection fraction with echocardiography, was significantly decreased by DOX in Mrp1(-/-) versus WT mice (P < 0.05; 95% confidence intervals of 20.0%-24.3% versus 23.7%-29.5% for fractional shortening, and 41.5%-48.4% versus 47.7%-56.7% for ejection fraction; protocol B). Together, these data indicate that Mrp1 protects the mouse heart against chronic DOX-induced cardiotoxicity.

Cardioprotection against doxorubicin by metallothionein Is associated with preservation of mitochondrial biogenesis involving PGC-1α pathway

Metallothionein (MT) has been shown to inhibit cardiac oxidative stress and protect against the cardiotoxicity induced by doxorubicin (DOX), a potent and widely used chemotherapeutic agent. However, the mechanism of MT׳s protective action against DOX still remains obscure. Mitochondrial biogenesis impairment has been implicated to play an important role in the etiology and progression of DOX-induced cardiotoxicity. Increasing evidence indicates an intimate link between MT-mediated cardioprotection and mitochondrial biogenesis. This study was aimed to explore the possible contribution of mitochondrial biogenesis in MT׳s cardioprotective action against DOX. Adult male MT-I/II-null (MT(-/-)) and wild-type (MT(+/+)) mice were given a single dose of DOX intraperitoneally. Our results revealed that MT deficiency significantly sensitized mice to DOX-induced cardiac dysfunction, ultrastructural alterations, and mortality. DOX disrupted cardiac mitochondrial biogenesis indicated by mitochondrial DNA copy number and decreased mitochondrial number, and these effects were greater in MT(-/-) mice. Basal MT effectively protected against DOX-induced inhibition on the peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), a key regulator of mitochondrial biogenesis, and its downstream factors including mitochondrial transcription factor A. Moreover, MT was found to preserve the protein expression of manganese superoxide dismutase, a transcriptional target of PGC-1α. in vitro study showed that MT absence augmented DOX-induced increase of mitochondrial superoxide production in primary cultured cardiomyocytes. These findings suggest that MT׳s cardioprotection against DOX is mediated, at least in part, by preservation of mitochondrial biogenesis involving PGC-1α pathway.

The volatile oil of Nardostachyos Radix et Rhizoma inhibits the oxidative stress-induced cell injury via reactive oxygen species scavenging and Akt activation in H9c2 cardiomyocyte

ETHNOPHARMACOLOGICAL RELEVANCE

Nardostachyos Radix et Rhizoma (NRR; the root and rhizome of Nardostachys jatamansi DC.) is a well-known medicinal herb widely used in Chinese, Uyghur and Ayurvedic medicines for the treatment of cardiovascular disorders. The oxidative stress-induced cardiomyocyte loss is the major pathogenesis of heart disorders. Here, the total volatile oil of NRR was isolated, and its function in preventing the cell death of cardiomyocyte was demonstrated.

MATERIALS AND METHODS

The cyto-protective effect of volatile oil of NRR against tBHP-induced H9c2 cardiomyocyte injury was measured by MTT assay. A promoter-report construct (pARE-Luc) containing four repeats of antioxidant response element (ARE) was applied to study the transcriptional activation of ARE. The amounts of phase ΙΙ antioxidant enzymes were analyzed by quantitative real-time polymer chain reaction (qPCR) upon the volatile oil treatment at 30 μg/mL for 24 h. The activation of Akt pathway was analyzed by western blot.

RESULTS

In cultured H9c2 cardiomyocytes, application of NRR volatile oil exhibited strong potency in preventing tBHP-induced cell death and accumulation of intracellular reactive oxygen species (ROS) in a concentration-dependent manner. In addition, the application of NRR volatile oil in cultures stimulated the gene expressions of self-defense antioxidant enzymes, which was mediated by the transcriptional activation of antioxidant response element (ARE). The induced genes were glutathione S-transferase, NAD(P)H quinone oxidoreductase, glutamate-cysteine ligase catalytic and modulatory subunits. In addition, the volatile oil of NRR activated the phosphorylation of Akt in cultured H9c2 cells. The treatment of LY294002, an Akt inhibitor, significantly inhibited the volatile oil-mediated ARE transcriptional activity, as well as the cell protective effect of NRR oil.

CONCLUSION

These results demonstrated that NRR volatile oil prevented the oxidative stress-induced cell death in H9c2 cells by (i) reducing intracellular ROS production, (ii) inducing antioxidant enzymes and (iii) activating Akt phosphorylation.

Diurnal-and sex-related difference of metallothionein expression in mice

BACKGROUND

Metallothionein (MT) is a small, cysteine-rich, metal-binding protein that plays an important role in protecting against toxicity of heavy metal and chemicals. This study was aimed to define diurnal and sex variation of MT in mice.

METHODS

Adult mice were maintained in light- and temperature-controlled facilities for 2 weeks with light on at 8:00 and light off at 20:00. The blood, liver, and kidneys were collected every 4 h during the 24 h period. Total RNA was isolated, purified, and subjected to real-time RT-PCR analysis and MT protein was determined by western blot and the Cd/hemoglobin assay.

RESULTS

The diurnal variations in mRNA levels of MT-1 and MT-2in liver were dramatic, up to a 40-foldpeak/trough ratio. MT mRNA levels in kidneys and blood also showed diurnal variation, up to 5-fold peak/trough ratio. The diurnal variation of MT mRNAs resembled the clock gene albumin site D-binding protein (Dbp), and was anti-phase to the clock gene Brain and Muscle ARNT-like Protein 1 (Bmal1) in liver and kidneys. The peaks of MT mRNA levels were higher in females than in males. Hepatic MT protein followed a similar pattern, with about a 3-fold difference.

CONCLUSION

MT mRNA levels and protein showed diurnal- and sex-variation in liver, kidney, and blood of mice, which could impact the body defense against toxic stimuli.

Mammalian metallothioneins: properties and functions

Metallothioneins (MT) are a family of ubiquitous proteins, whose role is still discussed in numerous papers, but their affinity to some metal ions is undisputable. These cysteine-rich proteins are connected with antioxidant activity and protective effects on biomolecules against free radicals, especially reactive oxygen species. In this review, the connection between zinc(II) ions, reactive oxygen species, heavy metal ions and metallothioneins is demonstrated with respect to effect of these proteins on cell proliferation and a possible negative role in resistance to heavy metal-based and non-heavy metal-based drugs.

Effect of humic acid during concurrent chronic waterborne exposure of rainbow trout (Oncorhynchus mykiss) to copper, cadmium and zinc

The effects of commercial dissolved organic carbon (DOC) in moderating accumulation, biochemical responses and toxicity of a waterborne mixture of copper (Cu), cadmium (Cd) and zinc (Zn) were investigated during a chronic exposure. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to a ternary metals mixture containing (nominal concentrations in μg/l): Cu 30, Cd 15, and Zn 150 in hard water (260 mg/l as CaCO(3)) with and without addition of 5 mg/l DOC as Aldrich humic acid (HA) for 28 days. Mortality, growth, metals accumulation, ionoregulatory impairment, and oxidative stress response were measured. While growth was unaffected, 19% mortality occurred during the first week of the exposure in fish exposed to the metals mixture without added HA. The early mortality was associated with transitory whole-body sodium (Na) loss and inhibition of branchial Na(+), K(+)-ATPase activity. Although these ionoregulatory responses mechanistically suggested that Cu was the more potent toxicant than either Cd or Zn, they were not correlated uniquely with elevated tissue Cu concentrations. The effects of HA on accumulation were metal-specific and depended on the organ examined and exposure duration. Specifically, Zn accumulation occurred only in the gill early in the exposure and HA reversed it, while protection against accumulation was absent or complete for Cu and absent or partial for Cd, dependent on tissue and exposure duration. The computed ambient free metal ion activities could explain the Cd but not the Cu and Zn accumulation indicating the involvement of physiological regulatory mechanisms in defining accumulation of essential metals. Surprisingly, the metals mixture (with and without added HA) reduced the concentrations of malondialdehyde (MDA) in gill suggesting induction of reductive rather than oxidative stress. Overall these data indicate that the free metal ion activity alone is not universally a good predictor of metals mixture accumulation and chronic effects nor does consideration of the mechanisms of toxicity unambiguously identify the more potently toxic metal in a mixture.

Knockdown of metallothionein 1 and 2 does not affect atrophy or oxidant activity in a novel in vitro model

Skeletal muscle atrophy is a significant health problem that results in decreased muscle size and function and has been associated with increases in oxidative stress. The molecular mechanisms that regulate muscle atrophy, however, are largely unknown. The metallothioneins (MT), a family of genes with antioxidant properties, have been found to be consistently upregulated during muscle atrophy, although their function during muscle atrophy is unknown. Therefore, we hypothesized that MT knockdown would result in greater oxidative stress and an enhanced atrophy response in C(2)C(12) myotubes subjected to serum reduction (SR), a novel atrophy-inducing stimulus. Forty-eight hours before SR, myotubes were transfected with small interfering RNA (siRNA) sequences designed to decrease MT expression. Muscle atrophy and oxidative stress were then measured at baseline and for 72 h following SR. Muscle atrophy was quantified by immunocytochemistry and myotube diameter measurements. Oxidative stress was measured using the fluorescent probe 5-(and-6)-carboxy-2',7'-dichlorodihydrofluorescein. SR resulted in a significant increase in oxidative stress and a decrease in myotube size and protein content. However, there were no differences observed in the extent of muscle atrophy or oxidant activity following MT knockdown. We therefore conclude that the novel SR model results in a strong atrophy response and an increase in oxidant activity in cultured myotubes and that knockdown of MT does not affect that response.

Mitochondrial dysfunction and reduced prostaglandin synthesis in skeletal muscle of Group VIB Ca2+-independent phospholipase A2gamma-deficient mice

Group VIB Ca(2+)-independent phospholipase A(2)γ (iPLA(2)γ) is a membrane-bound iPLA(2) enzyme with unique features, such as the utilization of distinct translation initiation sites and the presence of mitochondrial and peroxisomal localization signals. Here we investigated the physiological functions of iPLA(2)γ by disrupting its gene in mice. iPLA(2)γ-knockout (KO) mice were born with an expected Mendelian ratio and appeared normal and healthy at the age of one month but began to show growth retardation from the age of two months as well as kyphosis and significant muscle weakness at the age of four months. Electron microscopy revealed swelling and reduced numbers of mitochondria and atrophy of myofilaments in iPLA(2)γ-KO skeletal muscles. Increased lipid peroxidation and the induction of several oxidative stress-related genes were also found in the iPLA(2)γ-KO muscles. These results provide evidence that impairment of iPLA(2)γ causes mitochondrial dysfunction and increased oxidative stress, leading to the loss of skeletal muscle structure and function. We further found that the compositions of cardiolipin and other phospholipid subclasses were altered and that the levels of myoprotective prostanoids were reduced in iPLA(2)γ-KO skeletal muscle. Thus, in addition to maintenance of homeostasis of the mitochondrial membrane, iPLA(2)γ may contribute to modulation of lipid mediator production in vivo.

Enhanced toxicity and ROS generation by doxorubicin in primary cultures of cardiomyocytes from neonatal metallothionein-I/II null mice

The clinical use of doxorubicin (Dox), a potent anticancer drug, is limited by its concurrent dose-dependent cardiotoxicity. We previously found that metallothionein-I/II (MT-I/II) null mice are more vulnerable to Dox-induced cardiomyopathy, but it is unknown whether depletion of MT would sensitize cardiomyocytes to Dox toxicity in vitro since the protective effect of MT still remains controversial. In the present study, a primary culture system of cardiomyocytes from neonatal MT-I/II null (MT(-/-)) and corresponding wild type (MT(+/+)) mice was established to unequivocally determine the effect of MT deficiency on Dox-induced toxicity. MT concentrations in the MT(-/-) cardiomyocytes were about 2.5-fold lower than those in MT(+/+) cardiomyocytes. MT(-/-) cardiomyocytes were more sensitive to Dox-induced cytotoxicity than MT(+/+) cardiomyocytes as measured by morphological alterations, lactate dehydrogenase leakage, cell viability, and apoptosis. Dox time- and concentration-dependently increased reactive oxygen species (ROS) formation in MT(+/+) cardiomyocytes, and this effect was exaggerated in MT(-/-) cardiomyocytes. Antioxidant N-acetylcysteine (NAC) and glutathione (GSH) significantly rescued MT(+/+) but not MT(-/-)cardiomyocytes from Dox-induced cell death and ROS generation. These findings suggest that basal MT provide protection against Dox-induced toxicity in cardiomyocytes, particularly highlight the important role of MT as a cellular antioxidant on scavenging ROS.

Role of heat shock factor-1 activation in the doxorubicin-induced heart failure in mice

Treating cancer patients with chemotherapeutics, such as doxorubicin (Dox), cause dilated cardiomyopathy and congestive heart failure because of oxidative stress. On the other hand, heat shock factor-1 (HSF-1), a transcription factor for heat shock proteins (Hsps), is also known to be activated in response to oxidative stress. However, the possible role of HSF-1 activation and the resultant Hsp25 in chemotherapeutic-induced heart failure has not been investigated. Using HSF-1 wild-type (HSF-1(+/+)) and knock-out (HSF-1(-/-)) mice, we tested the hypothesis that activation of HSF-1 plays a role in the development of Dox-induced heart failure. Higher levels of Hsp25 and its phosphorylated forms were found in the failing hearts of Dox-treated HSF-1(+/+) mice. More than twofold increase in Hsp25 mRNA level was found in Dox-treated hearts. Proteomic analysis showed that there is accumulation and aggregation of Hsp25 in Dox-treated failing hearts. Additionally, Hsp25 was found to coimmunoprecipitate with p53 and vice versa. Further studies indicated that the Dox-induced higher levels of Hsp25 transactivated p53 leading to higher levels of the pro-apoptotic protein Bax, but other p53-related proteins remained unaltered. Moreover, HSF-1(-/-) mice showed significantly reduced Dox-induced heart failure and higher survival rate, and there was no change in Bax upon treating with Dox in HSF-1(-/-) mice. From these results we propose a novel mechanism for Dox-induced heart failure: increased expression of Hsp25 because of oxidant-induced activation of HSF-1 transactivates p53 to increase Bax levels, which leads to heart failure.

Cruciferous Dithiolethione-Mediated Coordinated Induction of Total Cellular and Mitochondrial Antioxidants and Phase 2 Enzymes in Human Primary Cardiomyocytes: Cytoprotection Against Oxidative/Electrophilic Stress and Doxorubicin Toxicity

3 H-1,2-dithiole-3-thione (D3T), a cruciferous organosulfur compound, induces cytoprotective enzymes in animal cardiovascular cells. However, it remains unknown if D3T also upregulates antioxidants and phase 2 enzymes in human cardiomyocytes, and protects against cell injury induced by oxidative/electrophilic species as well as doxorubicin. In this study, we found that D3T (10–50 μM) potently induced a series of antioxidants and phase 2 enzymes in primary cultured human cardiomyocytes, including superoxide dismutase (SOD), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx) glutathione S-transferase (GST), NAD(P)H:quinone oxidoreductase 1 (NQO1), aldose reductase (AR), and heme oxygenase (HO). D3T treatment also caused elevation of SOD, GSH, GR, GPx and GST in the isolated mitochondria. We also observed a time-dependent induction by D3T of mRNA expression for Cu,ZnSOD, MnSOD, γ-glutamylcysteine ligase, GR, GSTA1, GSTM1, NQO1, AR, and HO-1. Pretreatment with D3T conferred concentration-dependent protection against cell injury induced by xanthine oxidase (XO)/xanthine, H2O2, 3-morpholinosydnonimine, 4-hydroxy-2-nonenal, and doxorubicin. Pretreatment with D3T also reduced the formation of intracellular reactive oxygen species by XO/xanthine, H2O2, and doxorubicin. In conclusion, this study demonstrated that D3T potently upregulated many antioxidants and phase 2 enzymes in human cardiomyocytes, which was accompanied by increased resistance to oxidative/electrophilic stress and doxorubicin toxicity.

Metallothionein Toxicology: Metal Ion Trafficking and Cellular Protection

The literature is replete with reports about the involvement of metallothionein in host defense against injurious chemical, biological, and physical agents. Yet, metallothionein's functional roles are still being debated. This review addresses the issues that have left the physiological significance of metallothionein in doubt and moves on to assess the MT's importance in cell toxicology. It is evident that the protein is broadly involved in protecting cells from injury due to toxic metal ions, oxidants, and electrophiles. Attention is focused on MT's structural and chemical properties that confer this widespread role in cell protection. Particular emphasis is placed on the implications of finding that metal ion unsaturated metallothionein is commonly present in many cells and tissues and the question, how does selectivity of reaction with metallothionein take place in the cellular environment that includes large numbers of competing metal binding sites and high concentrations of protein and glutathione sulfhydryl groups?

Metallothionein induction reduces caspase-3 activity and TNFalpha levels with preservation of cognitive function and intact hippocampal neurons in carmustine-treated rats

Hippocampal integrity is essential for cognitive functions. On the other hand, induction of metallothionein (MT) by ZnSO(4) and its role in neuroprotection has been documented. The present study aimed to explore the effect of MT induction on carmustine (BCNU)-induced hippocampal cognitive dysfunction in rats. A total of 60 male Wistar albino rats were randomly divided into four groups (15/group): The control group injected with single doses of normal saline (i.c.v) followed 24 h later by BCNU solvent (i.v). The second group administered ZnSO(4) (0.1 micromol/10 microl normal saline, i.c.v, once) then BCNU solvent (i.v) after 24 h. Third group received BCNU (20 mg/kg, i.v, once) 24 h after injection with normal saline (i.c.v). Fourth group received a single dose of ZnSO(4) (0.1 micromol/10 microl normal saline, i.c.v) then BCNU (20 mg/kg, i.v, once) after 24 h. The obtained data revealed that BCNU administration resulted in deterioration of learning and short-term memory (STM), as measured by using radial arm water maze, accompanied with decreased hippocampal glutathione reductase (GR) activity and reduced glutathione (GSH) content. Also, BCNU administration increased serum tumor necrosis factor-alpha (TNFalpha), hippocampal MT and malondialdehyde (MDA) contents as well as caspase-3 activity in addition to histological alterations. ZnSO(4) pretreatment counteracted BCNU-induced inhibition of GR and depletion of GSH and resulted in significant reduction in the levels of MDA and TNFalpha as well as the activity of caspase-3. The histological features were improved in hippocampus of rats treated with ZnSO(4) + BCNU compared to only BCNU-treated animals. In conclusion, MT induction halts BCNU-induced hippocampal toxicity as it prevented GR inhibition and GSH depletion and counteracted the increased levels of TNFalpha, MDA and caspase-3 activity with subsequent preservation of cognition.

Anthracycline cardiotoxicity: from bench to bedside

Anthracyclines remain among the most widely prescribed and effective anticancer agents. Unfortunately, life-threatening cardiotoxicity continues to compromise their usefulness. Despite more than four decades of investigation, the pathogenic mechanisms responsible for anthracycline cardiotoxicity have not been completely elucidated. In addition, new drugs and combination therapies often exacerbate the toxicity. The First International Workshop on Anthracycline Cardiotoxicity, held in fall 2006, in Como, Italy, focused on the state-of-the-art knowledge and discussed the research needed to address the cardiotoxicity of these drugs. Here, we incorporate these discussions into the framework of a broader review of preclinical and clinical issues.

Nuclear factor E2-related factor 2-dependent myocardiac cytoprotection against oxidative and electrophilic stress

Nuclear factor E2-related factor 2 (Nrf2) is a critical regulator of cytoprotective gene expression. However, the role of this transcription factor in myocardiac cytoprotection against oxidative and electrophilic stress remains unknown. This study was undertaken to investigate if Nrf2 signaling could control the constitutive and inducible expression of antioxidants and phase 2 enzymes in primary cardiomyocytes as well as the susceptibility of these cells to oxidative and electrophilic injury. The basal expression of a series of antioxidants and phase 2 enzymes was significantly lower in cardiomyocytes from Nrf2(-/-) mice than those from wild-type littermates. Incubation of wild-type cardiomyocytes with 3H-1,2-dithiole-3-thione (D3T) led to significant induction of various antioxidants and phase 2 enzymes, including catalase, glutathione, glutathione peroxidase (GPx), glutathione reductase, glutathione S-transferase, NAD(P)H:quinone oxidoreductase 1, and heme oxygenase-1. The inducibility of the above cellular defenses except GPx by D3T was abolished in Nrf2(-/-) cardiomyocytes. As compared to wild-type cells, Nrf2(-/-) cardiomyocytes were much more susceptible to cell injury induced by H(2)O(2), peroxynitrite, and 4-hydroxy-2-nonenal. Treatment of wild-type cardiomyocytes with D3T, which upregulated the cellular defenses, resulted in increased resistance to the above oxidant- and electrophile-induced cell injury, whereas D3T treatment of Nrf2(-/-) cardiomyocytes provided no cytoprotection. This study demonstrates that Nrf2 is an important factor in controlling both constitutive and inducible expression of a wide spectrum of antioxidants and phase 2 enzymes in cardiomyocytes and is responsible for protecting these cells against oxidative and electrophilic stress. These findings also implicate Nrf2 as an important signaling molecule for myocardiac cytoprotection.

Comparative analysis of microarray data identifies common responses to caloric restriction among mouse tissues

Caloric restriction has been extensively investigated as an intervention that both extends lifespan and delays age-related disease in mammals. In mice, much interest has centered on evaluating gene expression changes induced by caloric restriction (CR) in particular tissue types, but the overall systemic effect of CR among multiple tissues has been examined less extensively. This study presents a comparative analysis of microarray datasets that have collectively examined the effects of CR in 10 different tissue types (liver, heart, muscle, hypothalamus, hippocampus, white adipose tissue, colon, kidney, lung and cochlea). Using novel methods for comparative analysis of microarray data, detailed comparisons of the effects of CR among tissues are provided, and 28 genes for which expression response to CR is most shared among tissues are identified. These genes characterize common responses to CR, which consist of both activation and inhibition of stress-response pathways. With respect to liver tissue, transcriptional effects of CR exhibited surprisingly little overlap with those of aging, and a variable degree of overlap with the potential CR-mimetic drug resveratrol. These analyses shed light on the systemic transcriptional activity associated with CR diets, and also illustrate new approaches for comparative analysis of microarray datasets in the context of aging biology.

The anthracyclines: when good things go bad

In the era of targeted therapy the anthracyclines, which were discovered almost half-century ago, may appear to be too old to be good. While it is certainly true that the prototypic anthracyclines have been around for many years, there are robust clinical facts to confute that their time is over. These drugs continue to play an undisputed role in the treatment of many forms of cancer, including hematological malignancies and solid tumors. Unfortunately, however, their main side-effect remains: a life-threatening cardiotoxicity which became apparent at the beginning of anthracyclines' clinical use. In addition to this long-standing problem, we are now discovering that new combination therapies often cause a higher than expected incidence of cardiotoxicity, as if the newly designed drugs make the heart more vulnerable to the old one. Altogether, however, an overwhelming amount of clinical evidence suggests that anthracyclines are too good to be old. Yet, they would look much better if they caused less harm to the heart when administered as either single agents or in combination with otherwise promising new drugs.