Suppression of doxorubicin cardiotoxicity by overexpression of catalase in the heart of transgenic mice

Longitudinal Changes in Multiple Biomarkers Are Associated with Cardiotoxicity in Breast Cancer Patients Treated with Doxorubicin, Taxanes, and Trastuzumab

BACKGROUND

Biomarkers may play an important role in identifying patients at risk for cancer therapy cardiotoxicity. Our objectives were to define the patterns of change in biomarkers with cancer therapy and their associations with cardiotoxicity.

METHODS

In a multicenter cohort of 78 breast cancer patients undergoing doxorubicin and trastuzumab therapy, 8 biomarkers were evaluated at baseline and every 3 months over a maximum follow-up of 15 months. These biomarkers, hypothesized to be mechanistically relevant to cardiotoxicity, included high-sensitivity cardiac troponin I (hs-cTnI), high-sensitivity C-reactive protein (hsCRP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), growth differentiation factor 15 (GDF-15), myeloperoxidase (MPO), placental growth factor (PlGF), soluble fms-like tyrosine kinase receptor-1 (sFlt-1), and galectin 3 (gal-3). We determined if biomarker increases were associated with cardiotoxicity at the same visit and the subsequent visit over the entire course of therapy. Cardiotoxicity was defined by the Cardiac Review and Evaluation Criteria; alternative definitions were also considered.

RESULTS

Across the entire cohort, all biomarkers except NT-proBNP and gal-3 demonstrated increases by 3 months; these increases persisted for GDF-15, PlGF, and hs-cTnI at 15 months. Increases in MPO, PlGF, and GDF-15 were associated with cardiotoxicity at the same visit [MPO hazard ratio 1.38 (95% CI 1.10-1.71), P = 0.02; PlGF 3.78 (1.30-11.0), P = 0.047; GDF-15 1.71 (1.15-2.55), P = 0.01] and the subsequent visit. MPO was robust to alternative outcome definitions.

CONCLUSIONS

Increases in MPO are associated with cardiotoxicity over the entire course of doxorubicin and trastuzumab therapy. Assessment with PlGF and GDF-15 may also be of value. These findings motivate validation studies in additional cohorts.

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

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

A splice variant of the human ion channel TRPM2 modulates neuroblastoma tumor growth through hypoxia-inducible factor (HIF)-1/2α

The calcium-permeable ion channel TRPM2 is highly expressed in a number of cancers. In neuroblastoma, full-length TRPM2 (TRPM2-L) protected cells from moderate oxidative stress through increased levels of forkhead box transcription factor 3a (FOXO3a) and superoxide dismutase 2. Cells expressing the dominant negative short isoform (TRPM2-S) had reduced FOXO3a and superoxide dismutase 2 levels, reduced calcium influx in response to oxidative stress, and enhanced reactive oxygen species, leading to decreased cell viability. Here, in xenografts generated with SH-SY5Y neuroblastoma cells stably expressing TRPM2 isoforms, growth of tumors expressing TRPM2-S was significantly reduced compared with tumors expressing TRPM2-L. Expression of hypoxia-inducible factor (HIF)-1/2α was significantly reduced in TRPM2-S-expressing tumor cells as was expression of target proteins regulated by HIF-1/2α including those involved in glycolysis (lactate dehydrogenase A and enolase 2), oxidant stress (FOXO3a), angiogenesis (VEGF), mitophagy and mitochondrial function (BNIP3 and NDUFA4L2), and mitochondrial electron transport chain activity (cytochrome oxidase 4.1/4.2 in complex IV). The reduction in HIF-1/2α was mediated through both significantly reduced HIF-1/2α mRNA levels and increased levels of von Hippel-Lindau E3 ligase in TRPM2-S-expressing cells. Inhibition of TRPM2-L by pretreatment with clotrimazole or expression of TRPM2-S significantly increased sensitivity of cells to doxorubicin. Reduced survival of TRPM2-S-expressing cells after doxorubicin treatment was rescued by gain of HIF-1 or -2α function. These data suggest that TRPM2 activity is important for tumor growth and for cell viability and survival following doxorubicin treatment and that interference with TRPM2-L function may be a novel approach to reduce tumor growth through modulation of HIF-1/2α, mitochondrial function, and mitophagy.

Heart failure and mitochondrial dysfunction: the role of mitochondrial fission/fusion abnormalities and new therapeutic strategies

The treatment of heart failure (HF) has evolved during the past 30 years with the recognition of neurohormonal activation and the effectiveness of its inhibition in improving the quality of life and survival. Over the past 20 years, there has been a revolution in the investigation of the mitochondrion with the development of new techniques and the finding that mitochondria are connected in networks and undergo constant division (fission) and fusion, even in cardiac myocytes. This has led to new molecular and cellular discoveries in HF, which offer the potential for the development of new molecular-based therapies. Reactive oxygen species are an important cause of mitochondrial and cellular injury in HF, but there are other abnormalities, such as depressed mitochondrial fusion, that may eventually become the targets of at least episodic treatment. The overall need for mitochondrial fission/fusion balance may preclude sustained change in either fission or fusion. In this review, we will discuss the current HF therapy and its impact on the mitochondria. In addition, we will review some of the new drug targets under development. There is potential for effective, novel therapies for HF to arise from new molecular understanding.

Antioxidant catalase rescues against high fat diet-induced cardiac dysfunction via an IKKβ-AMPK-dependent regulation of autophagy

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a variety of biological processes including obesity. However, the precise mechanism of action behind obesity-induced changes in autophagy still remains elusive. This study was designed to examine the role of the antioxidant catalase in high fat diet-induced changes in cardiac geometry and function as well as the underlying mechanism of action involved with a focus on autophagy. Wild-type (WT) and transgenic mice with cardiac overexpression of catalase were fed low or high fat diet for 20 weeks prior to assessment of myocardial geometry and function. High fat diet intake triggered obesity, hyperinsulinemia, and hypertriglyceridemia, the effects of which were unaffected by catalase transgene. Myocardial geometry and function were compromised with fat diet intake as manifested by cardiac hypertrophy, enlarged left ventricular end systolic and diastolic diameters, fractional shortening, cardiomyocyte contractile capacity and intracellular Ca²⁺ mishandling, the effects of which were ameliorated by catalase. High fat diet intake promoted reactive oxygen species production and suppressed autophagy in the heart, the effects of which were attenuated by catalase. High fat diet intake dampened phosphorylation of inhibitor kappa B kinase β(IKKβ), AMP-activated protein kinase (AMPK) and tuberous sclerosis 2 (TSC2) while promoting phosphorylation of mTOR, the effects of which were ablated by catalase. In vitro study revealed that palmitic acid compromised cardiomyocyte autophagy and contractile function in a manner reminiscent of fat diet intake, the effect of which was significantly alleviated by inhibition of IKKβ, activation of AMPK and induction of autophagy. Taken together, our data revealed that the antioxidant catalase counteracts against high fat diet-induced cardiac geometric and functional anomalies possibly via an IKKβ-AMPK-dependent restoration of myocardial autophagy. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Chemotherapy-enhanced inflammation may lead to the failure of therapy and metastasis

The lack of therapy and the failure of existing therapy has been a challenge for clinicians in treating various cancers. Doxorubicin, 5-fluorouracil, cisplatin, and paclitaxel are the first-line therapy in various cancers; however, toxicity, resistance, and treatment failure limit their clinical use. Their status leads us to discover and investigate more targeted therapy with more efficacy. In this article, we dissect literature from the patient perspective, the tumor biology perspective, therapy-induced metastasis, and cell data generated in the laboratory.

Humid heat exposure induced oxidative stress and apoptosis in cardiomyocytes through the angiotensin II signaling pathway

Exposure to humid heat stress leads to the initiation of serious physiological dysfunction that may result in heat-related diseases, including heat stroke, heat cramp, heat exhaustion, and even death. Increasing evidences have shown that the humid heat stress-induced dysfunction of the cardiovascular system was accompanied with severe cardiomyocyte injury; however, the precise mechanism of heat stress-induced injury of cardiomyocyte remains unknown. In the present study, we hypothesized that humid heat stress promoted oxidative stress through the activation of angiotensin II (Ang II) in cardiomyocytes. To test our hypothesis, we established mouse models of humid heat stress. Using the animal models, we found that Ang II levels in serum were significantly up-regulated and that the Ang II receptor AT1 was increased in cardiomyocytes. The antioxidant ability in plasma and heart tissues which was detected by the ferric reducing/antioxidant power assay was also decreased with the increased ROS production under humid heat stress, as was the expression of antioxidant genes (SOD2, HO-1, GPx). Furthermore, we demonstrated that the Ang II receptor antagonist, valsartan, effectively relieved oxidative stress, blocked Ang II signaling pathway and suppressed cardiomyocyte apoptosis induced by humid heat stress. In addition, overexpression of antioxidant genes reversed cardiomyocyte apoptosis induced by Ang II. Overall, these results implied that humid heat stress increased oxidative stress and caused apoptosis of cardiomyocytes through the Ang II signaling pathway. Thus, targeting the Ang II signaling pathway may provide a promising approach for the prevention and treatment of cardiovascular diseases caused by humid heat stress.

Nongenomic effects of estrogen mediate the dose-related myocardial oxidative stress and dysfunction caused by acute ethanol in female rats

Acute ethanol lowers blood pressure (BP) and cardiac output in proestrus and after chronic estrogen (E2) replacement in ovariectomized (OVX) female rats. However, whether rapid nongenomic effects of estrogen mediate these hemodynamic effects of ethanol remains unanswered. To test this hypothesis, we investigated the effect of ethanol (0.5 or 1.5 g/kg iv) on left ventricular (LV) function and oxidative markers in OVX rats pretreated 30 min earlier with 1 μg/kg E2 (OVXE2) or vehicle (OVX) and in proestrus sham-operated (SO) rats. In SO rats, ethanol caused significant and dose-related reductions in BP, rate of rise in LV pressure (LV dP/dtmax), and LV developed pressure (LVDP). These effects of ethanol disappeared in OVX rats and were restored in OVXE2 rats, suggesting rapid estrogen receptor signaling mediates the detrimental effects of ethanol on LV function. Ex vivo studies revealed that the estrogen-dependent myocardial dysfunction caused by ethanol was coupled with higher LV 1) generation of reactive oxygen species (ROS), 2) expression of malondialdehyde and 4-hydroxynonenal protein adducts, 3) phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinases (ERK1/2), and 4) catalase activity. ERK1/2 inhibition by PD-98059 (1 mg/kg iv) abrogated the myocardial dysfunction, hypotension, and the elevation in myocardial ROS generation caused by ethanol. We conclude that rapid estrogen receptor signaling is implicated in cellular events that lead to the generation of aldehyde protein adducts and Akt/ERK1/2 phosphorylation, which ultimately mediate the estrogen-dependent LV oxidative stress and dysfunction caused by ethanol in female rats.

Cytosolic H2O2 mediates hypertrophy, apoptosis, and decreased SERCA activity in mice with chronic hemodynamic overload

Oxidative stress in the myocardium plays an important role in the pathophysiology of hemodynamic overload. The mechanism by which reactive oxygen species (ROS) in the cardiac myocyte mediate myocardial failure in hemodynamic overload is not known. Accordingly, our goals were to test whether myocyte-specific overexpression of peroxisomal catalase (pCAT) that localizes in the sarcoplasm protects mice from hemodynamic overload-induced failure and prevents oxidation and inhibition of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), an important sarcoplasmic protein. Chronic hemodynamic overload was caused by ascending aortic constriction (AAC) for 12 wk in mice with myocyte-specific transgenic expression of pCAT. AAC caused left ventricular hypertrophy and failure associated with a generalized increase in myocardial oxidative stress and specific oxidative modifications of SERCA at cysteine 674 and tyrosine 294/5. pCAT overexpression ameliorated myocardial hypertrophy and apoptosis, decreased pathological remodeling, and prevented the progression to heart failure. Likewise, pCAT prevented oxidative modifications of SERCA and increased SERCA activity without changing SERCA expression. Thus cardiac myocyte-restricted expression of pCAT effectively ameliorated the structural and functional consequences of chronic hemodynamic overload and increased SERCA activity via a post-translational mechanism, most likely by decreasing inhibitory oxidative modifications. In pressure overload-induced heart failure cardiac myocyte cytosolic ROS play a pivotal role in mediating key pathophysiologic events including hypertrophy, apoptosis, and decreased SERCA activity.

The effects of dietary restriction on oxidative stress in rodents

Oxidative stress is observed during aging and in numerous age-related diseases. Dietary restriction (DR) is a regimen that protects against disease and extends life span in multiple species. However, it is unknown how DR mediates its protective effects. One prominent and consistent effect of DR in a number of systems is the ability to reduce oxidative stress and damage. The purpose of this review is to comprehensively examine the hypothesis that dietary restriction reduces oxidative stress in rodents by decreasing reactive oxygen species (ROS) production and increasing antioxidant enzyme activity, leading to an overall reduction of oxidative damage to macromolecules. The literature reveals that the effects of DR on oxidative stress are complex and likely influenced by a variety of factors, including sex, species, tissue examined, types of ROS and antioxidant enzymes examined, and duration of DR. Here we present a comprehensive review of the existing literature on the effect of DR on mitochondrial ROS generation, antioxidant enzymes, and oxidative damage. In a majority of studies, dietary restriction had little effect on mitochondrial ROS production or antioxidant activity. On the other hand, DR decreased oxidative damage in the majority of cases. Although the effects of DR on endogenous antioxidants are mixed, we find that glutathione levels are the most likely antioxidant to be increased by dietary restriction, which supports the emerging redox-stress hypothesis of aging.

SIRT3 deacetylates and activates OPA1 to regulate mitochondrial dynamics during stress

Mitochondrial morphology is regulated by the balance between two counteracting mitochondrial processes of fusion and fission. There is significant evidence suggesting a stringent association between morphology and bioenergetics of mitochondria. Morphological alterations in mitochondria are linked to several pathological disorders, including cardiovascular diseases. The consequences of stress-induced acetylation of mitochondrial proteins on the organelle morphology remain largely unexplored. Here we report that OPA1, a mitochondrial fusion protein, was hyperacetylated in hearts under pathological stress and this posttranslational modification reduced the GTPase activity of the protein. The mitochondrial deacetylase SIRT3 was capable of deacetylating OPA1 and elevating its GTPase activity. Mass spectrometry and mutagenesis analyses indicated that in SIRT3-deficient cells OPA1 was acetylated at lysine 926 and 931 residues. Overexpression of a deacetylation-mimetic version of OPA1 recovered the mitochondrial functions of OPA1-null cells, thus demonstrating the functional significance of K926/931 acetylation in regulating OPA1 activity. Moreover, SIRT3-dependent activation of OPA1 contributed to the preservation of mitochondrial networking and protection of cardiomyocytes from doxorubicin-mediated cell death. In summary, these data indicated that SIRT3 promotes mitochondrial function not only by regulating activity of metabolic enzymes, as previously reported, but also by regulating mitochondrial dynamics by targeting OPA1.

Protective effect of saffron extract against doxorubicin cardiotoxicity in isolated rabbit heart

CONTEXT

Anticancer treatments such as anthracyclines are effective; however, they induce cardiotoxicity by releasing radical oxygen species (ROS). Saffron (Crocus sativus; Iridaceae) is a widely used spice with antioxidant properties and numerous health benefits that may provide cardioprotection.

OBJECTIVE

To assess the effect of saffron against acute myocardium damage by anthracyclines compared with electrolysis as a free radical generating system.

MATERIALS AND METHODS

According to the Langendorff method, we used the model of an isolated rabbit heart perfused in retrograde. In one set of experiments, ROS was generated by electrolysis of the perfused heart solution (3 mA for 30 min) in the presence and absence of saffron extracts at the optimal dose (10 μg/ml). In another set, we perfused the heart with anthracycline, i.e. 30 μM doxorubicin (Doxo) in the presence and absence of 10 μg/ml saffron extracts. We evaluated cardiodynamics, as well as biochemical and pathological parameters, to emphasize the effectiveness of the treatment with saffron extract using the optimal dose of catalase (150 IU) as a positive control.

RESULTS

ROS generated, respectively, by electrolysis and by Doxo significantly (p < 0.05) affects cardiovascular function; it decreased ventricular pressure (45.02 and 40.41%), heart rate (36.31 and 22.39%) and coronary flow (50.98 and 36.67%). Increased lipid peroxidation of the myocardium was also observed (118.22 and 56.58%), while superoxide dismutase activity decreased (48.33 and 38.70%). The myocardial architecture was altered and the intercellular spaces increased.

CONCLUSION

Saffron perfused during electrolysis helps trap ROS and significantly improves myocardial function; however, saffron was less effective against Doxo, thus suggesting that mechanisms other than oxidative stress underlie Doxo cardiotoxicity.

Early increases in multiple biomarkers predict subsequent cardiotoxicity in patients with breast cancer treated with doxorubicin, taxanes, and trastuzumab

OBJECTIVES

The aim of this study was to determine if individual or multiple biomarkers are associated with cardiotoxicity in patients with breast cancer undergoing cancer therapy.

BACKGROUND

Current methods to identify patients at risk for cardiotoxicity from cancer therapy are inadequate.

METHODS

We measured 8 biomarkers in a multicenter cohort of 78 patients with breast cancer undergoing doxorubicin and trastuzumab therapy: ultrasensitive troponin I (TnI), high-sensitivity C-reactive protein (CRP), N-terminal pro-B-type natriuretic peptide (NT-proBNP), growth differentiation factor (GDF)-15, myeloperoxidase (MPO), placental growth factor (PlGF), soluble fms-like tyrosine kinase receptor (sFlt)-1, and galectin (gal)-3. Cardiotoxicity, defined by the Cardiac Review and Evaluation Committee criteria, was assessed every 3 months for up to 15 months. Hazard ratios (HRs) of cardiotoxicity risk were assessed for each biomarker at baseline, at visit 2 (3 months), and as a function of the difference between visit 2 and baseline. Joint models were assessed for the most promising biomarkers.

RESULTS

TnI, CRP, GDF-15, MPO, PlGF, and sFlt-1 levels increased from baseline to visit 2 (p < 0.05). A greater risk of cardiotoxicity was associated with interval changes in TnI (HR: 1.38 per SD; 95% confidence interval: 1.05 to 1.81; p = 0.02) and MPO (HR: 1.34 per SD; 95% confidence interval: 1.00 to 1.80; p = 0.048) and in models combining both markers (p = 0.007 and p = 0.03, respectively). The risk of cardiotoxicity was 46.5% in patients with the largest changes in both markers (ΔTnI >121.8 μg/l; ΔMPO >422.6 pmol/l).

CONCLUSIONS

Early increases in TnI and MPO levels offer additive information about the risk of cardiotoxicity in patients undergoing doxorubicin and trastuzumab therapy. Independent validation of these findings is necessary before application to clinical practice.

Protective effect of mitochondrial ferritin on cytosolic iron dysregulation induced by doxorubicin in HeLa cells

Doxorubicin (DOX) is an anticancer drug with cardiotoxic side effects mostly caused by iron homeostasis dysregulation. Mitochondria are involved in iron trafficking and mitochondrial ferritin (FtMt) was shown to provide protection against cellular iron imbalance. Therefore, we hypothesized that FtMt overexpression could limit DOX effects on iron homeostasis. Heart's homogenates of DOX-treated C57BL/6 mice were analyzed for cytosolic and mitochondrial iron-related proteins' expression and activity, revealing high cytosolic ferritin and ferritin-bound iron, low transferrin-receptor 1 and a strong hepcidin upregulation. Mitochondrial iron-related proteins (aconitase, succinate-dehydrogenase, frataxin) seemed, however, unaffected, although a partial inactivation of superoxide dismutase 2 was detected. Importantly, the ectopic expression of FtMt in human HeLa cells partially reverted DOX-induced iron imbalance. Our results, while confirming DOX effects on iron homeostasis, demonstrate that DOX affects more cytosolic than mitochondrial iron metabolism both in murine hearts and human HeLa cells and that FtMt overexpression is able to prevent most of these effects in HeLa cells.

Hydrogen peroxide-mediated SERCA cysteine 674 oxidation contributes to impaired cardiac myocyte relaxation in senescent mouse heart

Background

A hallmark of aging of the cardiac myocyte is impaired sarcoplasmic reticulum (SR) calcium uptake and relaxation due to decreased SR calcium ATPase (SERCA) activity. We tested the hypothesis that H₂O₂‐mediated oxidation of SERCA contributes to impaired myocyte relaxation in aging.

Methods and Results

Young (5‐month‐old) and senescent (21‐month‐old) FVB wild‐type (WT) or transgenic mice with myocyte‐specific overexpression of catalase were studied. In senescent mice, myocyte‐specific overexpression of catalase (1) prevented oxidative modification of SERCA as evidenced by sulfonation at Cys674, (2) preserved SERCA activity, (3) corrected impaired calcium handling and relaxation in isolated cardiac myocytes, and (4) prevented impaired left ventricular relaxation and diastolic dysfunction. Nitroxyl, which activates SERCA via S‐glutathiolation at Cys674, failed to activate SERCA in freshly isolated ventricular myocytes from senescent mice. Finally, in adult rat ventricular myocytes in primary culture, adenoviral overexpression of SERCA in which Cys674 is mutated to serine partially preserved SERCA activity during exposure to H₂O₂.

Conclusion

Oxidative modification of SERCA at Cys674 contributes to decreased SERCA activity and impaired myocyte relaxation in the senescent heart. Strategies to decrease oxidant levels and/or protect target proteins such as SERCA may be of value to preserve diastolic function in the aging heart.

Phosphodiesterase-5 inhibitor tadalafil attenuates oxidative stress and protects against myocardial ischemia/reperfusion injury in type 2 diabetic mice

Diabetic patients exhibit increased risk for the development of cardiovascular diseases primarily because of impaired nitric oxide (NO) bioavailability. The phosphodiesterase-5 (PDE-5) inhibitor sildenafil restores NO signaling and protects against ischemia/reperfusion (I/R) injury. In this study, we determined the effect of the long-acting PDE-5 inhibitor tadalafil on diabetes-associated complications and its role in attenuating oxidative stress after I/R injury in type 2 diabetic db/db mice. Adult male db/db mice (n=40/group) were randomized to receive dimethyl sulfoxide (10% DMSO, 0.2ml, ip) or tadalafil (1mg/kg in 10% DMSO, ip) for 28 days. After 28 days treatment, the hearts were isolated and subjected to 30min global ischemia followed by 60min reperfusion in the Langendorff mode. Infarct size was measured using computer morphometry of tetrazolium-stained sections. Cardiomyocytes were isolated from a subset of hearts and subjected to 40min simulated ischemia followed by 1h of reoxygenation (SI/RO). Dichlorodihydrofluorescein diacetate and JC-1 staining was used to measure reactive oxygen species (ROS) generation and mitochondrial membrane potential (Δψm), respectively. Another subset of hearts was used for the estimation of lipid peroxidation, glutathione, and the expression of myocardial pRac1, Rac1, gp91(phox), p47(phox), and p67(phox) by Western blot. Tadalafil treatment improved the metabolic status and reduced infarct size compared to the untreated db/db mice (21.2±1.8% vs 45.8±2.8%; p<0.01). The db/db mice showed enhanced oxidative stress in cardiomyocytes as indicated by a significant increase in ROS production. Cardiac NAD(P)H oxidase activity, lipid peroxidation, and oxidized glutathione were also increased in db/db mice compared to nondiabetic control animals. Tadalafil treatment in db/db mice suppressed oxidative stress, attenuated myocardial expression of pRac1 and gp91(phox), and also preserved the loss of Δψm in cardiomyocytes after SI/RO. In conclusion, these results demonstrate that chronic treatment with tadalafil attenuates oxidative stress and improves mitochondrial integrity while providing powerful cardioprotective effects in type 2 diabetes.

Higenamine Combined with [6]-Gingerol Suppresses Doxorubicin-Triggered Oxidative Stress and Apoptosis in Cardiomyocytes via Upregulation of PI3K/Akt Pathway

Sini decoction is a well-known formula of traditional Chinese medicine, which has been used to treat cardiovascular disease for many years. Previously, we demonstrated that Sini decoction prevented doxorubicin-induced heart failure in vivo. However, its active components are still unclear. Thus, we investigated the active components of Sini decoction and their cardioprotective mechanisms in the in vitro neonatal rat cardiomyocytes and H9c2 cell line models of doxorubicin-induced cytotoxicity. Our results demonstrated that treatment with higenamine or [6]-gingerol increased viability of doxorubicine-injured cardiomyocytes. Moreover, combined use of higenamine and [6]-gingerol exerted more profound protective effects than either drug as a single agent, with effects similar to those of dexrazoxane, a clinically approved cardiac protective agent. In addition, we found that treatment with doxorubicin reduced SOD activity, increased ROS generation, enhanced MDA formation, induced release of LDH, and triggered the intrinsic mitochondria-dependent apoptotic pathway in cardiomyocytes, which was inhibited by cotreatment of higenamine and [6]-gingerol. Most importantly, the cytoprotection of higenamine plus [6]-gingerol could be abrogated by LY294002, a PI3K inhibitor. In conclusion, combination of higenamine and [6]-gingerol exerts cardioprotective effect against doxorubicin-induced cardiotoxicity through activating the PI3K/Akt signaling pathway. Higenamine and [6]-gingerol may be the active components of Sini decoction.

NADPH oxidases in heart failure: poachers or gamekeepers?

SIGNIFICANCE

Oxidative stress is involved in the pathogenesis of heart failure but clinical antioxidant trials have been unsuccessful. This may be because effects of reactive oxygen species (ROS) depend upon their source, location, and concentration. Nicotinamide adenine dinucleotide phosphate oxidase (Nox) proteins generate ROS in a highly regulated fashion and modulate several components of the heart failure phenotype.

RECENT ADVANCES

Two Nox isoforms, Nox2 and Nox4, are expressed in the heart. Studies using gene-modified mice deficient in Nox2 activity indicate that Nox2 activation contributes to angiotensin II-induced cardiomyocyte hypertrophy, atrial fibrillation, and the development of interstitial fibrosis but may also positively modulate physiological excitation-contraction coupling. Nox2 contributes to myocyte death under stress situations and plays important roles in postmyocardial infarction remodeling, in part by modulating matrix metalloprotease activity. In contrast to Nox2, Nox4 is constitutively active at a low level and induces protective effects in the heart under chronic stress, for example, by maintaining myocardial capillary density. However, high levels of Nox4 could have detrimental effects.

CRITICAL ISSUES

The effects of Nox proteins during the development of heart failure likely depend upon the isoform, activation level, and cellular distribution, and may include beneficial as well as detrimental effects. More needs to be learnt about the precise regulation of abundance and biochemical activity of these proteins in the heart as well as the downstream signaling pathways that they regulate.

FUTURE DIRECTIONS

The development of specific approaches to target individual Nox isoforms and/or specific cell types may be important for the achievement of therapeutic efficacy in heart failure.

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.

Soybean β-conglycinin induces inflammation and oxidation and causes dysfunction of intestinal digestion and absorption in fish

β-Conglycinin has been identified as one of the major feed allergens. However, studies of β-conglycinin on fish are scarce. This study investigated the effects of β-conglycinin on the growth, digestive and absorptive ability, inflammatory response, oxidative status and gene expression of juvenile Jian carp (Cyprinus carpio var. Jian) in vivo and their enterocytes in vitro. The results indicated that the specific growth rate (SGR), feed intake, and feed efficiency were reduced by β-conglycinin. In addition, activities of trypsin, chymotrypsin, lipase, creatine kinase, Na(+),K(+)-ATPase and alkaline phosphatase in the intestine showed similar tendencies. The protein content of the hepatopancreas and intestines, and the weight and length of the intestines were all reduced by β-conglycinin. β-Conglycinin increased lipid and protein oxidation in the detected tissues and cells. However, β-conglycinin decreased superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR) activities and glutathione (GSH) content in the intestine and enterocytes. Similar antioxidant activity in the hepatopancreas was observed, except for GST. The expression of target of rapamycin (TOR) gene was reduced by β-conglycinin. Furthermore, mRNA levels of interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) genes were increased by β-conglycinin. However, β-conglycinin increased CuZnSOD, MnSOD, CAT, and GPx1b gene expression. In conclusion, this study indicates that β-conglycinin induces inflammation and oxidation, and causes dysfunction of intestinal digestion and absorption in fish, and finally reduces fish growth. The results of this study provide some information to the mechanism of β-conglycinin-induced negative effects.

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.

The second member of transient receptor potential-melastatin channel family protects hearts from ischemia-reperfusion injury

The second member of the transient receptor potential-melastatin channel family (TRPM2) is expressed in the heart and vasculature. TRPM2 channels were expressed in the sarcolemma and transverse tubules of adult left ventricular (LV) myocytes. Cardiac TRPM2 channels were functional since activation with H2O2 resulted in Ca(2+) influx that was dependent on extracellular Ca(2+), was significantly higher in wild-type (WT) myocytes compared with TRPM2 knockout (KO) myocytes, and inhibited by clotrimazole in WT myocytes. At rest, there were no differences in LV mass, heart rate, fractional shortening, and +dP/dt between WT and KO hearts. At 2-3 days after ischemia-reperfusion (I/R), despite similar areas at risk and infarct sizes, KO hearts had lower fractional shortening and +dP/dt compared with WT hearts. Compared with WT I/R myocytes, expression of the Na(+)/Ca(2+) exchanger (NCX1) and NCX1 current were increased, expression of the α1-subunit of Na(+)-K(+)-ATPase and Na(+) pump current were decreased, and action potential duration was prolonged in KO I/R myocytes. Post-I/R, intracellular Ca(2+) concentration transients and contraction amplitudes were equally depressed in WT and KO myocytes. After 2 h of hypoxia followed by 30 min of reoxygenation, levels of ROS were significantly higher in KO compared with WT LV myocytes. Compared with WT I/R hearts, oxygen radical scavenging enzymes (SODs) and their upstream regulators (forkhead box transcription factors and hypoxia-inducible factor) were lower, whereas NADPH oxidase was higher, in KO I/R hearts. We conclude that TRPM2 channels protected hearts from I/R injury by decreasing generation and enhancing scavenging of ROS, thereby reducing I/R-induced oxidative stress.

Oxidative activation of Ca(2+)/calmodulin-activated kinase II mediates ER stress-induced cardiac dysfunction and apoptosis

Endoplasmic reticulum (ER) stress elicits oxidative stress and intracellular Ca(2+) derangement via activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). This study was designed to examine the role of CaMKII in ER stress-induced cardiac dysfunction and apoptosis as well as the effect of antioxidant catalase. Wild-type FVB and transgenic mice with cardiac-specific overexpression of catalase were challenged with the ER stress inducer tunicamycin (3 mg/kg ip for 48 h). Presence of ER stress was verified using the ER stress protein markers immunoglobulin binding protein (BiP) and C/EBP homologous protein (CHOP), the effect of which was unaffected by catalase overexpression. Echocardiographic assessment revealed that tunicamycin elicited cardiac remodeling (enlarged end-systolic diameter without affecting diastolic and ventricular wall thickness), depressed fractional shortening, ejection fraction, and cardiomyocyte contractile capacity, intracellular Ca(2+) mishandling, accumulation of reactive oxygen species (superoxide production and NADPH oxidase p47phox level), CaMKII oxidation, and apoptosis (evidenced by Bax, Bcl-2/Bax ratio, and TUNEL staining), the effects of which were obliterated by catalase. Interestingly, tunicamycin-induced cardiomyocyte mechanical anomalies and cell death were ablated by the CaMKII inhibitor KN93, in a manner reminiscent of catalase. These data favored a permissive role of oxidative stress and CaMKII activation in ER stress-induced cardiac dysfunction and cell death. Our data further revealed the therapeutic potential of antioxidant or CaMKII inhibition in cardiac pathological conditions associated with ER stress. This research shows for the first time that contractile dysfunction caused by ER stress is a result of the oxidative activation of the CaMKII pathway.

Dexrazoxane for the prevention of cardiac toxicity and treatment of extravasation injury from the anthracycline antibiotics

The cumulative cardiac toxicity of the anthracycline antibiotics and their propensity to produce severe tissue injury following extravasation from a peripheral vein during intravenous administration remain significant problems in clinical oncologic practice. Understanding of the free radical metabolism of these drugs and their interactions with iron proteins led to the development of dexrazoxane, an analogue of EDTA with intrinsic antineoplastic activity as well as strong iron binding properties, as both a prospective cardioprotective therapy for patients receiving anthracyclines and as an effective treatment for anthracycline extravasations. In this review, the molecular mechanisms by which the anthracyclines generate reactive oxygen species and interact with intracellular iron are examined to understand the cardioprotective mechanism of action of dexrazoxane and its ability to protect the subcutaneous tissues from anthracycline-induced tissue necrosis.

Cardiac-specific catalase overexpression rescues anthrax lethal toxin-induced cardiac contractile dysfunction: role of oxidative stress and autophagy

BACKGROUND

Lethal and edema toxins secreted by Bacillus anthracis during anthrax infection were found to incite serious cardiovascular complications. However, the underlying mechanisms in anthrax lethal toxin-induced cardiac anomalies remain unknown. This study was designed to evaluate the impact of antioxidant enzyme catalase in anthrax lethal toxin-induced cardiomyocyte contractile dysfunction.

METHODS

Wild type (WT) and cardiac-specific catalase overexpression mice were challenged with lethal toxin (2 μg/g, intraperotineally (i.p.)). Cardiomyocyte contractile and intracellular Ca(2+) properties were assessed 18 h later using an IonOptix edge-detection system. Proteasome function was assessed using chymotrypsin-like and caspase-like activities. GFP-LC3 puncta and Western blot analysis were used to evaluate autophagy and protein ubiquitination.

RESULTS

Lethal toxin exposure suppressed cardiomyocyte contractile function (suppressed peak shortening, maximal velocity of shortening/re-lengthening, prolonged duration of shortening/re-lengthening, and impaired intracellular Ca(2+) handling), the effects of which were alleviated by catalase. In addition, lethal toxin triggered autophagy, mitochondrial and ubiquitin-proteasome defects, the effects of which were mitigated by catalase. Pretreatment of cardiomyocytes from catalase mice with the autophagy inducer rapamycin significantly attenuated or ablated catalase-offered protection against lethal toxin-induced cardiomyocyte dysfunction. On the other hand, the autophagy inhibitor 3-MA ablated or significantly attenuated lethal toxin-induced cardiomyocyte contractile anomalies.

CONCLUSIONS

Our results suggest that catalase is protective against anthrax lethal toxin-induced cardiomyocyte contractile and intracellular Ca(2+) anomalies, possibly through regulation of autophagy and mitochondrial function.

Autophagy upregulation promotes survival and attenuates doxorubicin-induced cardiotoxicity

This study evaluated whether the manipulation of autophagy could attenuate the cardiotoxic effects of doxorubicin (DXR) in vitro as well as in a tumour-bearing mouse model of acute doxorubicin-induced cardiotoxicity. We examined the effect of an increase or inhibition of autophagy in combination with DXR on apoptosis, reactive oxygen species (ROS) production and mitochondrial function. H9C2 rat cardiac myoblasts were pre-treated with bafilomycin A1 (autophagy inhibitor, 10 nM) or rapamycin (autophagy inducer, 50 μM) followed by DXR treatment (3 μM). The augmentation of autophagy with rapamycin in the presence of DXR substantially ameliorated the detrimental effects induced by DXR. This combination treatment demonstrated improved cell viability, decreased apoptosis and ROS production and enhanced mitochondrial function. To corroborate these findings, GFP-LC3 mice were inoculated with a mouse breast cancer cell line (EO771). Following the appearance of tumours, animals were either treated with one injection of rapamycin (4 mg/kg) followed by two injections of DXR (10 mg/kg). Mice were then sacrificed and their hearts rapidly excised and utilized for biochemical and histological analyses. The combination treatment, rather than the combinants alone, conferred a cardioprotective effect. These hearts expressed down-regulation of the pro-apoptotic protein caspase-3 and cardiomyocyte cross-sectional area was preserved. These results strongly indicate that the co-treatment strategy with rapamycin can attenuate the cardiotoxic effects of DXR in a tumour-bearing mouse model.

RETRACTED: Cardiac-specific overexpression of catalase attenuates lipopolysaccharide-induced myocardial contractile dysfunction: Role of autophagy

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. After an institutional investigation into the work of Dr. Jun Ren, University of Wyoming subsequently conducted an examination of other selected publications of Dr. Ren's under the direction of the HHS Office of Research Integrity. Based on the findings of this examination, the University of Wyoming recommended this article be retracted due to concerns regarding data irregularities inconsistent with published conclusions. Specifically, University of Wyoming found evidence of data irregularities and image reuse in Figure 2 that significantly affect the results and conclusions reported in the manuscript.

Effect of short-term treatment with levosimendan on oxidative stress in renal tissues of rats

The aim of this study is to evaluate the influences of short-term treatment with levosimendan (chemical formula: C14H12N6O) on oxidative stress and some trace element levels in renal tissues of healthy rats. A total of 20 male Wistar-albino rats were randomly divided into two groups, each consisting of 10 rats. Animals in the first group were not treated with levosimendan and served as control. Animals in the second group were injected intraperitoneally with 12 µg/kg levosimendan and served as levosimendan group. Animals in both the groups were killed 3 days after the treatment, and their kidneys were harvested for the determination of tissue oxidant/antioxidant statues and trace element levels in renal tissues. The tissue malondialdehyde level was significantly (p < 0.001) lower in levosimendan group than in controls. The protective enzyme activities such as superoxide dismutase, catalase, and glutathione peroxidase and antioxidant glutathione level were significantly (p < 0.001) higher in levosimendan group than in controls. It was concluded that levosimendan reduced oxidative stress by avoiding lipid peroxidation and production of reactive oxygen species, and overactivating and/or increasing the protective antioxidant enzyme levels in renal tissues of rats. It is supposed that this experimental study provides beneficial data for clinicians in the management of renal tissue damage related to obstruction and/or ischemia.

Short-term levosimendan treatment protects rat testes against oxidative stress

The objective of this study was to evaluate the effect of short-term levosimendan exposure on oxidant/antioxidant status and trace element levels in the testes of rats under physiological conditions. Twenty male Wistar albino rats were randomly divided into two groups of 10 animals each. Group 1 was not exposed to levosimendan and served as control. Levosimendan (12 µg/kg) diluted in 10 mL 0.9% NaCl was administered intraperitoneally to group 2. Animals of both groups were sacrificed after 3 days and their testes were harvested for the determination of changes in tissue oxidant/antioxidant status and trace element levels. Tissue malondialdehyde (MDA) was significantly lower in the levosimendan group (P < 0.001) than in the untreated control group and superoxide dismutase and glutathione peroxidase (GSH-Px) levels were significantly higher in the levosimendan group (P < 0.001). Carbonic anhydrase, catalase and GSH levels were not significantly different from controls. Mg and Zn levels of testes were significantly higher (P < 0.001) and Co, Pb, Cd, Mn, and Cu were significantly lower (P < 0.001) in group 2 compared to group 1. Fe levels were similar for the two groups (P = 0.94). These results suggest that 3-day exposure to levosimendan induced a significant decrease in tissue MDA level, which is a lipid peroxidation product and an indicator of oxidative stress, and a significant increase in the activity of an important number of the enzymes that protect against oxidative stress in rat testes.

Effect of levosimendan injection on oxidative stress of rat myocardium

This experiment was designed to investigate the effect of levosimendan injection on lipid peroxidation product malondialdehyde (MDA) and antioxidant glutathione (GSH) levels, and activities of antioxidant enzymes in myocardium of rats. Twenty male Wistar-albino rats were divided randomly into 2 study groups, each consisting of 10 rats. The animals in the first group were not treated with drug and served as control. It was found that the MDA and GSH levels decreased in levosimendan injected group. Superoxide dismutase, glutathione peroxidase, catalase and carbonic anhydrase enzyme activities were lower in levosimendan injected group than controls. It was concluded that lower tissue free radical level caused by levosimendan injection led to a lower antioxidant enzymes synthesis in the body and a decrease in the antioxidant enzyme activity and free radical scavenger level in myocardium of rat.

Inhibition of AMP-activated protein kinase α (AMPKα) by doxorubicin accentuates genotoxic stress and cell death in mouse embryonic fibroblasts and cardiomyocytes: role of p53 and SIRT1

Doxorubicin, an anthracycline antibiotic, is widely used in cancer treatment. Doxorubicin produces genotoxic stress and p53 activation in both carcinoma and non-carcinoma cells. Although its side effects in non-carcinoma cells, especially in heart tissue, are well known, the molecular targets of doxorubicin are poorly characterized. Here, we report that doxorubicin inhibits AMP-activated protein kinase (AMPK) resulting in SIRT1 dysfunction and p53 accumulation. Spontaneously immortalized mouse embryonic fibroblasts (MEFs) or H9C2 cardiomyocyte were exposed to doxorubicin at different doses and durations. Cell death and p53, SIRT1, and AMPK levels were examined by Western blot. In MEFs, doxorubicin inhibited AMPK activation, increased cell death, and induced robust p53 accumulation. Genetic deletion of AMPKα1 reduced NAD(+) levels and SIRT1 activity and significantly increased the levels of p53 and cell death. Pre-activation of AMPK by 5-aminoimidazole-4-carboxamide ribonucleoside or transfection with an adenovirus encoding a constitutively active AMPK (AMPK-CA) markedly reduced the effects of doxorubicin in MEFs from Ampkα1 knock-out mice. Conversely, pre-inhibition of Ampk further sensitized MEFs to doxorubicin-induced cell death. Genetic knockdown of p53 protected both wild-type and Ampkα1(-/-) MEFs from doxorubicin-induced cell death. p53 accumulation in Ampkα1(-/-) MEFs was reversed by SIRT1 activation by resveratrol. Taken together, these data suggest that AMPK inhibition by doxorubicin causes p53 accumulation and SIRT1 dysfunction in MEFs and further suggest that pharmacological activation of AMPK might alleviate the side effects of doxorubicin.

Myo-inositol prevents copper-induced oxidative damage and changes in antioxidant capacity in various organs and the enterocytes of juvenile Jian carp (Cyprinus carpio var. Jian)

Although oxidative stress has been demonstrated to be involved in copper (Cu)-induced toxicity, information regarding the effect of antioxidants on Cu toxicity is still scarce. This study assessed the possible protective effects of myo-inositol (MI) against subsequent Cu exposure in juvenile Jian carp (Cyprinus carpio var. Jian) in vivo and in their enterocytes in vitro. First, oxidative stress was established by exposing fish to different concentrations of Cu (0-7.2 mg Cu/L water) for 4 days. Next, the protective effects of MI (administered as a dietary supplement for 60 days) against subsequent Cu exposure (0.6 mg Cu/L water for 4 days) were studied in fish. The third trial determined the effects of Cu exposure (0-6.0 mg Cu/L of medium for 24h) on enterocytes in vitro. Finally, enterocytes were pre-incubated with graded levels of MI (0-75 mg MI/L of medium) for 72 h and exposed to 6.0 mg Cu/L of medium for 24h. The results indicated that ≥ 0.6 mg Cu/L water could induce oxidative stress in fish (P<0.05). Cu exposure significantly induced increases in lipid peroxidation and protein oxidation in the gill, hepatopancreas and intestine in fish. However, these oxidative effects were prevented by MI pre-supplementation. MI also prevented the toxic effects of Cu on anti-superoxide anion (ASA), anti-hydroxyl radical (AHR), superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR) activities and glutathione (GSH) content in these organs. In vitro, enterocytes exposed to Cu displayed a dose-dependent injury. Moreover, cell viability, protein retention (PR), alkaline phosphatase, total-SOD (T-SOD) and Cu/ZnSOD activities were all depressed by Cu (P<0.05). Interestingly, the final experiment showed that MI pre-supplementation could block the toxic effects of Cu on the antioxidant system, and thus protect enterocytes from Cu-induced oxidative damage. All of these results indicated that the induction of key antioxidant defenses by MI pre-supplementation, including SOD, CAT, GPx, GST and GSH, may play an important role in the protection of fish against oxidative stress.

p21(WAF1/Cip1/Sdi1) knockout mice respond to doxorubicin with reduced cardiotoxicity

Doxorubicin (Dox) is an antineoplastic agent that can cause cardiomyopathy in humans and experimental animals. As an inducer of reactive oxygen species and a DNA damaging agent, Dox causes elevated expression of p21(WAF1/Cip1/Sdi1) (p21) gene. Elevated levels of p21 mRNA and p21 protein have been detected in the myocardium of mice following Dox treatment. With chronic treatment of Dox, wild type (WT) animals develop cardiomyopathy evidenced by elongated nuclei, mitochondrial swelling, myofilamental disarray, reduced cardiac output, reduced ejection fraction, reduced left ventricular contractility, and elevated expression of ANF gene. In contrast, p21 knockout (p21KO) mice did not show significant changes in the same parameters in response to Dox treatment. In an effort to understand the mechanism of the resistance against Dox induced cardiomyopathy, we measured levels of antioxidant enzymes and found that p21KO mice did not contain elevated basal or inducible levels of glutathione peroxidase and catalase. Measurements of 6 circulating cytokines indicated elevation of IL-6, IL-12, IFNγ and TNFα in Dox treated WT mice but not p21KO mice. Dox induced elevation of IL-6 mRNA was detected in the myocardium of WT mice but not p21KO mice. While the mechanism of the resistance against Dox induced cardiomyopathy remains unclear, lack of inflammatory response may contribute to the observed cardiac protection in p21KO mice.

High glucose concentration affects the oxidant-antioxidant balance in cultured mouse podocytes

Hyperglycemia is well-recognized and has long-term complications in diabetes mellitus and diabetic nephropathy. In podocytes, the main component of the glomerular barrier, overproduction of reactive oxygen species (ROS) in the presence of high glucose induces dysfunction and increases excretion of albumin in urine. This suggests an impaired antioxidant defense system has a role in the pathogenesis of diabetic nephropathy. We studied expression of NAD(P)H oxidase subunits by Western blotting and immunofluorescence and the activities of the oxidant enzyme, NAD(P)H, and antioxidant enzymes, superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT), in mouse podocytes cultured in a high glucose concentration (30  mM). We found long-term (3 and 5 days) exposure of mouse podocytes to high glucose concentrations caused oxidative stress, as evidenced by increased expression of Nox4 and activities of NAD(P)H oxidase (Δ 182%) and SOD (Δ 39%) and decreased activities of GPx (Δ -40%) and CAT (Δ -35%). These biochemical changes were accompanied by a rise in intracellular ROS production and accumulation of hydrogen peroxide in extracellular space. The role of Nox4 in ROS generation was confirmed with Nox4 siRNA. In conclusion, high glucose concentration affects the oxidant-antioxidant balance in mouse podocytes, resulting in enhanced generation of superoxide anions and its attenuated metabolism. These observations suggest free radicals may play an important role in the pathogenesis of diabetic nephropathy.

Overexpression of Nrdp1 in the heart exacerbates doxorubicin-induced cardiac dysfunction in mice

Background

Cardiac cell death and generation of oxidative stress contribute to doxorubicin (DOX)-induced cardiac dysfunction. E3 ligase Nrdp1 plays a critical role in the regulation of cell apoptosis, inflammation and production of reactive oxygen species (ROS), which may contribute to heart failure. However, the role of Nrdp1 in DOX-induced cardiac injury remains to be determined.

Methods and Results

We examined the effect of Nrdp1 overexpression with DOX treatment in rat neonatal cardiomyocytes and mouse heart tissue. Cardiomyocytes were infected with adenovirus containing GFP (Ad-GFP), Nrdp1 wild-type (Ad-Nrdp1) or the dominant-negative form of Nrdp1 (Ad-Dn-Nrdp1), then treated with DOX for 24 hr. DOX treatment increased cell death and apoptosis, with Ad-Nrdp1 infection enhancing these actions but Ad-Dn-Nrdp1 infection attenuating these effects. Furthermore, 5 days after a single injection of DOX (20 mg/kg, intraperitoneally), Nrdp1 transgenic mice (TG) showed decreased cardiac function and increased apoptosis, autophagy and oxidative stress as compared with wild-type (WT) mice (P<0.01). Survival rate was significantly lower in Nrdp1 TG mice than in WT mice 10 days after DOX injection (P<0.01).

Conclusions/Significance

These results were associated with decreased activation of Akt, extracellular signal-regulated kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) signaling pathways. Nrdp1 may be a key mediator in the development of cardiac dysfunction after DOX treatment and associated with inhibition of Akt, ERK1/2 and STAT3. Nrdp1 may be a new therapeutic target in protecting against the cardiotoxic effects of DOX.

Anthracycline cardiotoxicity

INTRODUCTION

Anthracyclines are widely prescribed anticancer agents that cause a dose-related cardiotoxicity, often aggravated by nonanthracycline chemotherapeutics or new generation targeted drugs. Anthracycline cardiotoxicity may occur anytime in the life of cancer survivors. Understanding the molecular mechanisms and clinical correlates of cardiotoxicity is necessary to improve the therapeutic index of anthracyclines or to identify active, but less cardiotoxic analogs.

AREAS COVERED

The authors review the pharmacokinetic, pharmacodynamic and biochemical mechanisms of anthracycline cardiotoxicity and correlate them to clinical phenotypes of cardiac dysfunction. Attention is paid to bioactivation mechanisms that converted anthracyclines to reactive oxygen species (ROS) or long-lived secondary alcohol metabolites. Preclinical aspects and clinical implications of the "oxidative stress" or "secondary alcohol metabolite" hypotheses are discussed on the basis of literature that cuts across bench and evidence-based medicine. Interactions of anthracyclines with comorbidities or unfavorable lifestyle choices were identified as important cofactors of the lifetime risk of cardiotoxicity and as possible targets of preventative strategies.

EXPERT OPINION

Anthracycline cardiotoxicity is a multifactorial process that needs to be incorporated in a translational framework, where individual genetic background, comorbidities, lifestyles and other drugs play an equally important role. Fears for cardiotoxicity should not discourage from using anthracyclines in many oncologic settings. Cardioprotective strategies are available and should be used more pragmatically in routine clinical practice.

Cardiotoxicity of anticancer treatments: what the cardiologist needs to know

Cardiotoxicity of anticancer treatments has become an increasingly important clinical problem faced by cardiologists. Left ventricular systolic dysfunction and heart failure generate the most concern, but clinical features and prognosis vary considerably depending on the causative agent. Anthracycline-related cardiomyopathy differs fundamentally from effects associated with newer targeted agents, such as trastuzumab. Other forms of cardiovascular disease that occur as a result of cancer treatment include hypertension, thromboembolic disease, pericardial disease, arrhythmia, and myocardial ischemia. The approach to cardiovascular disease in patients with cancer is often different from that in the general population, not only because of distinct underlying mechanisms and clinical features of their heart disease, but also because of the potential ongoing need for additional cancer treatment as well as the altered duration of anticipated survival. In an effort to maximize both quality of life and survival, cardiologists and oncologists should collaborate with the aim of balancing the risks of cardiotoxicity with the benefits of oncologic therapy.

Systolic dysfunction in cardiac-specific ligand-inducible MerCreMer transgenic mice

The Cre-loxP system is a useful tool to study the physiological effects of gene knockout in the heart. One limitation with using this system in the heart is the toxic effect of chronic expression of the Cre recombinase. To circumvent this limitation, a widely used inducible cardiac-specific model, Myh6-MerCreMer (Cre), using tamoxifen (TAM) to activate Cre has been developed. The current study examined cardiac function in Cre-positive C57B/J6 mice exposed to one, three, or five daily doses of a 40 mg/kg TAM to induce Cre activity specifically in the heart. Echocardiography demonstrated no statistically significant differences in systolic function (SF) at baseline as assessed by fractional shortening. In mice exposed to five injections, a significant fall in all determinants of SF was observed 6 days after TAM was initiated. However, SF returned to baseline levels 10 days after TAM initiation although the hearts exhibited significant hypertrophy. Heart weight-to-tibia length ratios were 73 ± 3, 78.5 ± 6, and 87.6 ± 9 mg/cm for one, three, and five TAM injections, respectively. TAM had no effect on cardiac function or hypertrophy in Cre-negative mice. Cre-positive mice receiving five TAM injections had significant reductions in cardiac mitochondrial ATP and significant reductions in the expression of proteins important for the regulation of cardiac oxidative phosphorylation including peroxisome proliferator-activated receptor-γ coactivator-1α and pyruvate dehydrogenase kinase-4. Thus inducible cardiac-specific activation of Cre recombinase caused a transient decline in SF that was dependent on the number of TAM doses and associated with significant hypertrophy and alterations in mitochondrial ATP and important proteins involved in the regulation of cardiac oxidative phosphorylation.

Caloric restriction mimetic 2-deoxyglucose antagonizes doxorubicin-induced cardiomyocyte death by multiple mechanisms

Caloric restriction (CR) is a dietary intervention known to enhance cardiovascular health. The glucose analog 2-deoxy-D-glucose (2-DG) mimics CR effects in several animal models. However, whether 2-DG is beneficial to the heart remains obscure. Here, we tested the ability of 2-DG to reduce cardiomyocyte death triggered by doxorubicin (DOX, 1 μm), an antitumor drug that can cause heart failure. Treatment of neonatal rat cardiomyocytes with 0.5 mm 2-DG dramatically suppressed DOX cytotoxicity as indicated by a decreased number of cells that stained positive for propidium iodide and reduced apoptotic markers. 2-DG decreased intracellular ATP levels by 17.9%, but it prevented DOX-induced severe depletion of ATP, which may contribute to 2-DG-mediated cytoprotection. Also, 2-DG increased the activity of AMP-activated protein kinase (AMPK). Blocking AMPK signaling with compound C or small interfering RNA-mediated knockdown of the catalytic subunit markedly attenuated the protective effects of 2-DG. Conversely, AMPK activation by pharmacological or genetic approach reduced DOX cardiotoxicity but did not produce additive effects when used together with 2-DG. In addition, 2-DG induced autophagy, a cellular degradation pathway whose activation could be either protective or detrimental depending on the context. Paradoxically, despite its ability to activate autophagy, 2-DG prevented DOX-induced detrimental autophagy. Together, these results suggest that the CR mimetic 2-DG can antagonize DOX-induced cardiomyocyte death, which is mediated through multiple mechanisms, including the preservation of ATP content, the activation of AMPK, and the inhibition of autophagy.

Mitochondrial oxidative stress mediates angiotensin II-induced cardiac hypertrophy and Galphaq overexpression-induced heart failure

RATIONALE

Mitochondrial dysfunction has been implicated in several cardiovascular diseases; however, the roles of mitochondrial oxidative stress and DNA damage in hypertensive cardiomyopathy are not well understood.

OBJECTIVE

We evaluated the contribution of mitochondrial reactive oxygen species (ROS) to cardiac hypertrophy and failure by using genetic mouse models overexpressing catalase targeted to mitochondria and to peroxisomes.

METHODS AND RESULTS

Angiotensin II increases mitochondrial ROS in cardiomyocytes, concomitant with increased mitochondrial protein carbonyls, mitochondrial DNA deletions, increased autophagy and signaling for mitochondrial biogenesis in hearts of angiotensin II-treated mice. The causal role of mitochondrial ROS in angiotensin II-induced cardiomyopathy is shown by the observation that mice that overexpress catalase targeted to mitochondria, but not mice that overexpress wild-type peroxisomal catalase, are resistant to cardiac hypertrophy, fibrosis and mitochondrial damage induced by angiotensin II, as well as heart failure induced by overexpression of Gαq. Furthermore, primary damage to mitochondrial DNA, induced by zidovudine administration or homozygous mutation of mitochondrial polymerase γ, is also shown to contribute directly to the development of cardiac hypertrophy, fibrosis and failure.

CONCLUSIONS

These data indicate the critical role of mitochondrial ROS in cardiac hypertrophy and failure and support the potential use of mitochondrial-targeted antioxidants for prevention and treatment of hypertensive cardiomyopathy.