Rac1 signalling mediates doxorubicin-induced cardiotoxicity through both reactive oxygen species-dependent and -independent pathways

Misoprostol ameliorates doxorubicin induced cardiac damage by decreasing oxidative stress and apoptosis in rats

We investigated the potential cardioprotective effects of misoprostol (MP) on doxorubicin (DOX) induced cardiac damage using histologic and biochemical assessment of rat heart. We used 21 male rats divided randomly into three groups: group 1, control; group 2, DOX; group 3, DOX + MP. The control group was given 0.5 ml 0.9% NaCl intraperitoneally (i.p.) and 1 ml 0.9% NaCl orally for 6 days. DOX was administered as a single dose of 20 mg/kg i.p. on day 3. MP was administered orally for 6 days. We found that treatment with MP decreased significantly serum cardiac troponin-I, brain natriuretic peptide levels, and lactate dehydrogenase, aspartate aminotransferase, alanine transaminase and creatine kinase isoenzyme-MB activities. DOX increased the malondialdehyde level and decreased the catalase, superoxide dismutase activities and glutathione levels; MP prevented these alterations. MP also decreased NADPH oxidase-4 and caspase-3 levels. In the DOX + MP group, oxidative stress was decreased, antioxidant activity was increased and histopathological changes were decreased compared to the DOX group. Cardiac damage caused by DOX was attenuated by MP treatment owing to the antioxidative and anti-apoptotic effects of MP. MP may be useful for reducing the severity of DOX induced damage.

Prevalence of Major Cardiac Events of Anthracycline-Induced Cardiotoxicity in Southwestern Iran: Different Response Patterns to Cumulative Dose

Background:

Anthracyclines are widely used chemotherapeutic agents in several cancers. Since its use, survival improved significantly among cancer patients and has been reported to be up to 80%. However, anthracyclines possess several cardiac, renal and hematological toxicities which limit their use in practice. Cardiotoxicity is still the most important and dose-limiting side effect of anthracycline treatment. Here we aimed to investigate the frequency of anthracyclineinduced cardiomyopathy in pediatric malignancies in Khuzestan Province, Iran.

Methods:

A total of 112 patients were enrolled in the present study. Patients were allocated to the case or control group based on receiving anthracycline. Echocardiographic examinations were performed by a cardiologist. Electrocardiograms were also recorded.

Results:

We showed that cancer patients who underwent anthracycline treatment showed cardiomyopathy as defined by lower LVEF (Left Ventricular Ejection Fraction) among patients (p = 0.041). Abnormal LVEF was reported with a frequency of about 9.5% in patients (p = 0.026). However, LVFS (Left Ventricular Fraction Shortening), QRS voltage and QT interval did not differ significantly between treatment and control groups. Our data analysis revealed that this difference is mainly related to high cumulative dose since high cumulative dose of anthracycline (>300 mg/m2) leads to lower LVEF and LVFS and higher QRS voltage in comparison with lower cumulative dose (<300 mg/m2) and control group; but there was no significant difference between low dose and control group. Different age groups and type of malignancy including hematological and solid tumors did not show any significant differences for echocardiographic and electrocardiograms parameters.

Conclusion:

In our study, lower LVEF among patients who received anthracyclines were mainly related to a high cumulative dose of anthracyclines, which emphasizes the effect of cumulative dose for cardiotoxic effects. Larger studies are needed to investigate possible other risk factors for cardiotoxicity.

Cardamonin protects against doxorubicin-induced cardiotoxicity in mice by restraining oxidative stress and inflammation associated with Nrf2 signaling

The clinical application of doxorubicin (DOX) for cancer treatment is limited due to its cardiotoxicity. However, the basic pathophysiological molecular mechanisms underlying DOX-induced cardiomyopathy have not yet been completely clarified, and the disease-specific therapeutic strategies are lacking. The aim of the present study was to investigate the potential cardioprotective effect of cardamonin (CAR), a flavone found in Alpinia plant, on DOX-induced cardiotoxicity in a mouse model. At first, in DOX-treated mouse cardiomyocytes, CAR showed significantly cytoprotective effects through elevating nuclear factor erythroid-2 related factor 2 (Nrf2) signaling, and reducing the degradation of Nrf2. This process then improved the anti-oxidant system, as evidenced by the up-regulated expression levels of haem oxygenase-1 (HO1), NAD(P)H:quinone oxidoreductase 1 (NQO1), glutamate-cysteine ligase modifier subunit (GCLM), superoxide dismutase (SOD), glutathione (GSH) and catalase (CAT). In contrast, DOX-induced increases in malondialdehyde (MDA) and reactive oxygen species (ROS) were highly inhibited by CAR treatments. Additionally, DOX-induced apoptosis and inflammatory response in cardiomyocytes were diminished by CAR through reducing the Caspase-3 and nuclear factor-κB (NF-κB) signaling pathways, respectively. Then, in the DOX-induced animal model with cardiotoxicity, we confirmed that through improving Nrf2 signaling, CAR markedly suppressed oxidative stress, apoptosis and inflammatory response in hearts of mice, improving cardiac function eventually. Together, our findings demonstrated that CAR activated Nrf2-related cytoprotective system, and protected the heart from oxidative damage, apoptosis and inflammatory injury, suggesting that CAR might be a potential therapeutic strategy in the prevention of DOX-associated myocardiopathy.

Cell adhesion to collagen promotes leukemia resistance to doxorubicin by reducing DNA damage through the inhibition of Rac1 activation

Chemoresistance is a major hurdle in anti-cancer therapy. Growing evidence indicates that integrin-mediated cell adhesion to extracellular matrix plays a major role in chemoresistance. However, the underlying mechanisms are not fully understood. We have previously shown that the collagen-binding integrin α2β1 promoted doxorubicin resistance in acute T cell lymphoblastic leukemia (T-ALL). In this study, we found that acute myeloid leukemia (AML) cell lines also express α2β1 integrin and collagen promoted their chemoresistance as well. Furthermore, we found that high levels of α2 integrin correlate with worse overall survival in AML. Our results showed that doxorubicin-induced apoptosis in leukemic cells is associated with activation of Ras-related C3 botulinum toxin substrate 1 (Rac1) and that collagen inhibited this pathway. The protective effect of collagen is associated with the inhibition of Rac1-induced DNA damage as evaluated by the comet assay and the phosphorylated levels of histone H2AX (γ-H2AX). Together these results show that by inhibiting pro-apoptotic Rac1, α2β1 integrin can be a major pathway protecting leukemic cells from genotoxic agents and may thus represent an important therapeutic target in anti-cancer treatment.

Bnip3 mediates doxorubicin-induced cardiomyocyte pyroptosis via caspase-3/GSDME

AIMS

This study was aimed to investigate the role of GSDME-mediated pyroptosis in cardiac injury induced by Doxorubicin (DOX), and to evaluate the role of BH3-only protein Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) in regulation of DOX-induced pyroptosis.

MAIN METHODS

HL-1 cardiomyocytes and C57BL/6J mice were treated by DOX to establish DOX-induced cardiotoxicity in vitro and in vivo models, respectively. Cell transfection was applied to regulate the expression of caspase-3, GSDME and Bnip3. Western blot was used for measuring expression of protein level. LDH-cytotoxicity assay was used to detect the LDH release. The Flow cytometry analysis was used to detect the cell death. Echocardiography was used to determine the cardiac function. HE staining was used for observing pathological feature of heart tissues.

KEY FINDINGS

Our results showed that GSDME-mediated pyroptosis was involved in DOX-induced cardiotoxicity in vivo. We showed that HL-1 cardiomyocytes exposed to DOX exhibited morphological features of pyroptosis in vitro. We also showed that DOX induced activation of caspase-3 and eventually triggered GSDME-dependent pyroptosis, which was reduced by the silence or inhibitor of caspase-3. We further showed that knockdown of GSDME inhibited DOX-induced cardiomyocyte pyroptosis in vitro. Finally, DOX increased the expression of Bnip3, whereas silencing of Bnip3 blunted cardiomyocyte pyroptosis induced by DOX, which was regulated through caspase-3 activation and GSDME cleavage.

SIGNIFICANCE

Our findings revealed a novel pathway that cardiomyocyte pyroptosis is regulated through Bnip3-caspase-3-GSDME pathway following DOX treatment, suggesting that Bnip3-dependent pyroptosis may offer a novel therapeutic strategy to reduce cardiotoxicity induced by DOX.

Effects of steroidal saponins extract from Ophiopogon japonicus root ameliorates doxorubicin-induced chronic heart failure by inhibiting oxidative stress and inflammatory response

CONTEXT

Ophiopogonis Radix, the root of Ophiopogon japonicus (Thunb.) Ker-Gawl (Liliaceae), is a Traditional Chinese Medicine, which has been investigated to possess effective treatment of cardiovascular diseases.

OBJECTIVE

This study evaluates the cardioprotective effects of steroidal saponins extract from Ophiopogon japonicus (SOJ) root against doxorubicin-induced chronic heart failure (CHF) through the amelioration of oxidative stress and inflammation.

MATERIALS AND METHODS

A Sprague-Dawley rat model of CHF was established by intraperitoneally injected with DOX. All rats were randomly divided into four groups: Control group, CHF group, CHF + SOJ (100 mg/kg) treatment group, SOJ (100 mg/kg) treatment group (n = 8/group). After six weeks administration, biometric and echocardiography were measured. The levels of biochemical parameters were measured using commercial kits.

RESULTS

The values of LVESP, +dP/dtmax, -dP/dtmax, EF and FS increased to 116.20 ± 1.68 mmHg, 2978.71 ± 168.26 mmHg/s, 3452.61 ± 286.09 mmHg/s, 68.26 ± 5.28% and 31.97 ± 3.79%, respectively; the values of LVEDP, LVESD and LVEDD decreased to 8.85 ± 0.84 mmHg, 8.39 ± 0.45 mm and 12.36 ± 0.87 mm in CHF + SOJ group. In addition, the levels of IL-6, TNF-α and IL-1β decreased to 154.41 ± 7.72 pg/mg protein, 110.02 ± 6.96 pg/mg protein and 39.39 ± 5.27 pg/mg protein, respectively; the relative activity of p38 MAPK decreased to 2.60 ± 0.40 in CHF + SOJ group. Furthermore, the activities of SOD, CAT and GSH-Px increased to 268.77 ± 6.20 U/mg protein, 13.68 ± 0.68 U/mg protein and 316.90 ± 8.08 µmol/mg protein, and the content of MDA decreased to 4.03 ± 0.43 nmol/mg protein in CHF + SOJ group.

CONCLUSIONS

SOJ exerts the cardioprotective effect against DOX-induced CHF through suppressing inflammatory and oxidative stress. These results provide evidence that SOJ might be an effective treatment for CHF.

Nicotinamide riboside promotes autolysosome clearance in preventing doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is widely used as a first-line chemotherapeutic drug for various malignancies. However, DOX causes severe cardiotoxicity, which limits its clinical uses. Oxidative stress is one of major contributors to DOX-induced cardiotoxicity. While autophagic flux serves as an important defense mechanism against oxidative stress in cardiomyocytes, recent studies have demonstrated that DOX induces the blockage of autophagic flux, which contributes to DOX cardiotoxicity. The present study investigated whether nicotinamide riboside (NR), a precursor of nicotinamide adenine dinucleotide (NAD)⁺, prevents DOX cardiotoxicity by improving autophagic flux. We report that administration of NR elevated NAD⁺ levels, and reduced cardiac injury and myocardial dysfunction in DOX-injected mice. These protective effects of NR were recapitulated in cultured cardiomyocytes upon DOX treatment. Mechanistically, NR prevented the blockage of autophagic flux, accumulation of autolysosomes, and oxidative stress in DOX-treated cardiomyocytes, the effects of which were associated with restoration of lysosomal acidification. Furthermore, inhibition of lysosomal acidification or SIRT1 abrogated these protective effects of NR during DOX-induced cardiotoxicity. Collectively, our study shows that NR enhances autolysosome clearance via the NAD⁺/SIRT1 signaling, thereby preventing DOX-triggered cardiotoxicity.

Role of oxidative stress in cardiotoxicity of antineoplastic drugs

Tumors and heart disease are two of the leading causes of human death. With the development of anti-cancer therapy, the survival rate of cancer patients has been significantly improved. But at the same time, the incidence of cardiovascular adverse events caused by cancer treatment has also been considerably increased, such as arrhythmia, left ventricular (LV) systolic and diastolic dysfunction, and even heart failure (HF), etc., which seriously affects the quality of life of cancer patients. More importantly, the occurrence of adverse events may lead to the adjustment or the cessation of anti-cancer treatment, which affects the survival rate of patients. Understanding the mechanism of cardiotoxicity (CTX) induced by antineoplastic drugs is the basis of adequate protection of the heart without impairing the efficacy of antineoplastic therapy. Based on current research, a large amount of evidence has shown that oxidative stress (OS) plays an essential role in CTX induced by antineoplastic drugs and participates in its toxic reaction directly and indirectly. Here, we will review the mechanism of action of OS in cardiac toxicity of antineoplastic drugs, to provide new ideas for researchers, and provide further guidance for clinical prevention and treatment of cardiac toxicity of anti-tumor drugs in the future.

Inhibition of the cardiac myocyte mineralocorticoid receptor ameliorates doxorubicin-induced cardiotoxicity

Aim

Anthracyclines such as doxorubicin are widely used in cancer therapy but their use is limited by cardiotoxicity. Up to date there is no established strategy for the prevention of anthracyclin-induced heart failure. In this study, we evaluated the role of the cardiac myocyte mineralocorticoid receptor (MR) during doxorubicin-induced cardiotoxicity.

Methods and results

A single high-dose or repetitive low-dose doxorubicin administration lead to markedly reduced left ventricular function in mice. Treatment with the MR antagonist eplerenone prevented doxorubicin-induced left ventricular dysfunction. In order to identify the cell types and molecular mechanisms involved in this beneficial effect we used a mouse model with cell type-specific MR deletion in cardiac myocytes. Cardiac myocyte MR deletion largely reproduced the effect of pharmacological MR inhibition on doxorubicin-induced cardiotoxicity. RNAseq from isolated cardiac myocytes revealed a repressive effect of doxorubicin on gene expression which was prevented by MR deletion.

Conclusions

We show here that (i) eplerenone prevents doxorubicin-induced left ventricular dysfunction in mice, and (ii) this beneficial effect is related to inhibition of MR in cardiac myocytes. Together with present clinical trial data our findings suggest that MR antagonism may be appropriate for the prevention of doxorubicin-induced cardiotoxicity.

Inflammation leads through PGE/EP3 signaling to HDAC5/MEF2-dependent transcription in cardiac myocytes

The myocyte enhancer factor 2 (MEF2) regulates transcription in cardiac myocytes and adverse remodeling of adult hearts. Activators of G protein-coupled receptors (GPCRs) have been reported to activate MEF2, but a comprehensive analysis of GPCR activators that regulate MEF2 has to our knowledge not been performed. Here, we tested several GPCR agonists regarding their ability to activate a MEF2 reporter in neonatal rat ventricular myocytes. The inflammatory mediator prostaglandin E₂ (PGE₂) strongly activated MEF2. Using pharmacological and protein-based inhibitors, we demonstrated that PGE₂ regulates MEF2 via the EP₃ receptor, the βγ subunit of G_i/o protein and two concomitantly activated downstream pathways. The first consists of Tiam1, Rac1, and its effector p21-activated kinase 2, the second of protein kinase D. Both pathways converge on and inactivate histone deacetylase 5 (HDAC5) and thereby de-repress MEF2. In vivo, endotoxemia in MEF2-reporter mice induced upregulation of PGE₂ and MEF2 activation. Our findings provide an unexpected new link between inflammation and cardiac remodeling by de-repression of MEF2 through HDAC5 inactivation, which has potential implications for new strategies to treat inflammatory cardiomyopathies.

Distinct contribution of Rac1 expression in cardiomyocytes to anthracycline-induced cardiac injury

Cardiotoxicity is the dose limiting adverse effect of anthracycline-based anticancer therapy. Inhibitor studies point to Rac1 as therapeutic target to prevent anthracycline-induced cardiotoxicity. Yet, supporting genetic evidence is still missing and the pathophysiological relevance of different cardiac cell types is unclear. Here, we employed a tamoxifen-inducible cardiomyocyte-specific rac1 knock-out mouse model (Rac1^{flox/flox/MHC-MerCreMer}) to investigate the impact of Rac1 expression in cardiomyocytes on cardiac injury following doxorubicin treatment. Distinctive stress responses resulting from doxorubicin treatment were observed, including upregulation of systemic markers of inflammation (IL-6, IL-1α, MCP-1), cardiac damage (ANP, BNP), DNA damage (i.e. DNA double-strand breaks (DSB)), DNA damage response (DDR) and cell death. Measuring the acute doxorubicin response, the serum level of MCP-1 was elevated, cardiac mRNA expression of Hsp70 was reduced and cardiac DDR was specifically enhanced in Rac1 deficient mice. The frequency of apoptotic heart cells remained unaffected by Rac1. Employing a subactue model, the number of doxorubicin-induced DSB was significantly reduced if Rac1 is absent. Yet, the doxorubicin-triggered increase in serum ANP and BNP levels remained unaffected by Rac1. Overall, knock-out of rac1 in cardiomyocytes confers partial protection against doxorubicin-induced cardiac injury. Hence, the data provide first genetic evidence supporting the view that pharmacological targeting of Rac1 is useful to widen the therapeutic window of anthracycline-based anticancer therapy by alleviating acute/subacute cardiomyocyte damage. Furthermore, considering published data obtained from the use of pharmacological Rac1 inhibitors, the results of our study indicate that Rac1-regulated functions of cardiac cell types others than cardiomyocytes additionally influence the adverse outcomes of anthracycline treatment on the heart.

Ischaemic Preconditioning Protects Cardiomyocytes from Anthracycline-Induced Toxicity via the PI3K Pathway

PURPOSE

Anthracyclines cause chronic irreversible cardiac failure, but the mechanism remains poorly understood. Emerging data indicate that cardiac damage begins early, suggesting protective modalities delivered in the acute stage may confer prolonged benefit. Ischaemic preconditioning (IPC) activates the pro-survival reperfusion injury salvage kinase (RISK) pathway which involves PI3-kinase and MAPK/ERK1/2.

METHODS

We investigated whether simulated IPC (sIPC), in the form of a sublethal exposure to a hypoxic buffer simulating ischaemic conditions followed by reoxygenation, protects primary adult rat cardiomyocytes against anthracycline-induced injury. PI3-kinase and MAPK/ERK1/2 were inhibited using LY294002, and PD98059. The role of reactive oxygen species (ROS), mitochondrial membrane potential (Δψm) and mitochondrial permeability transition pore (mPTP) were also investigated in doxorubicin-treated cells. We further examined whether sIPC protected HeLa cancer cells from doxorubicin-induced death.

RESULTS

sIPC protected cardiomyocytes against doxorubicin-induced death (35.4 ± 1.7% doxorubicin vs 14.7 ± 1.5% doxorubicin + sIPC; p < 0.01). This protection was abrogated by the PI3-kinase inhibitor, LY294002, but not the MAPK/ERK1/2 inhibitor, PD98059. A ROS scavenger failed to rescue cardiomyocytes from doxorubicin toxicity, and no significant influence on Δψm or mPTP opening was identified after subjecting cells to a doxorubicin insult. Importantly, sIPC did not protect HeLa cancer cells from doxorubicin-induced death.

CONCLUSION

sIPC is able to protect cardiomyocytes against anthracycline injury via a pathway involving PI3-kinase. This mechanism appears to be independent of ROS, changes to Δψm, and mPTP. Further investigation of the mechanism of sIPC-induced protection against anthracycline-injury is warranted.

Sulforaphane protection against the development of doxorubicin-induced chronic heart failure is associated with Nrf2 Upregulation

BACKGROUND

Doxorubicin (DOX) is an anthracycline antitumor drug. However, its clinical use is limited by dose-dependent cardiotoxicity and even progresses to chronic heart failure (CHF).

OBJECTIVE

This study aims to investigate whether the Nrf2 activator, sulforaphane (SFN), can prevent DOX-induced CHF.

METHODS

Male Sprague-Dawley rats which received treatment for 6 weeks were divided into four groups (n=30 per group): control, SFN, DOX and DOX plus SFN group.

RESULTS

Results revealed that DOX induced progressive cardiac damage as indicated by increased cardiac injury markers, cardiac inflammation, fibrosis and oxidative stress. SFN significantly prevented DOX-induced progressive cardiac dysfunction between 2-6 weeks and prevented DOX-induced cardiac function deterioration. Furthermore, it significantly decreased ejection fraction and increased the expression of brain natriuretic peptide. SFN also almost completely prevented DOX-induced cardiac oxidative stress, inflammation and fibrosis. SFN upregulated NF-E2-related factor 2 (Nrf2) expression and transcription activity, which was reflected by the increased mRNA expression of Nrf2 and its downstream genes. Furthermore, in cultured H9c2 cardiomyocytes, the protective effect of SFN against DOX-induced fibrotic and inflammatory responses was abolished by Nrf2 silencing.

CONCLUSION

We arrived at the conclusion that DOX-induced CHF can be prevented by SFN through the upregulation of Nrf2 expression and transcriptional function.

Type IIB DNA topoisomerase is downregulated by trastuzumab and doxorubicin to synergize cardiotoxicity

Despite heightened risk of cardiotoxicity associated with combination therapy of anthracyclines and trastuzumab in HER2-positive breast cancer patients, little research effort has been invested in exploring the molecular mechanisms of cardiotoxicity induced by this combination therapy. In this study, we demonstrate that trastuzumab downregulates both gene and protein expressions of type IIB DNA topoisomerase/DNA topoisomerase IIB (TOP2B), a major intracellular target mediating doxorubicin-induced cardiotoxicity, in human primary cardiomyocytes. This in turn induces DNA damage activity and DNA double strand breaks, which is indicated by the enhanced phosphorylation of H2AX (γH2AX) and ataxia telangiectasia and Rad3-related protein (ATR pS428) in trastuzumab-treated cardiomyocytes. Furthermore, concurrent or sequential treatment of doxorubicin and trastuzumab significantly increases the downregulation of the protein levels of TOP2B, enhances apoptosis and cell growth inhibition, and promotes production of reactive oxidative and nitrative species in human cardiomyocytes as compared to either trastuzumab or doxorubicin treatment, indicating augmentation of cardiotoxicity in combination therapy. Additionally, our data reveal that doxorubicin treatment increases the levels of ErbB2/HER2 expression in human cardiomyocytes as compared with that in cells not treated with doxorubicin, leading to the enhanced activity downstream of HER2 signaling. Consequently, this may render the cardiomyocytes to become addicted to HER2 signaling for survival under stressed conditions. Enhanced HER2 protein expression leaves cardiomyocytes more sensitive to trastuzumab treatment after doxorubicin exposure. This study provides molecular basis for significantly increased cardiotoxicity in cancer patients who are treated with anthracyclines and trastuzumab-based combination regimens.

Histamine 2 receptor antagonism elicits protection against doxorubicin-induced cardiotoxicity in rodent model

Doxorubicin (DOX), an anthracycline-based antibiotic, is regularly used in the management of carcinomas, and haematological malignancies have been downplayed in chemotherapy because of its ability to induce dilated cardiomyopathy (DCM). Dexrazoxane is approved to combat the cardiotoxicity, but limited by its adverse effects. Redox imbalance and reactive oxygen species generation plays major role in DOX-induced cardiotoxicity. Histamine, known to mediate various cardiovascular effects, but nevertheless the role of histamine or its receptors in DOX-induced DCM is remained obscure. Hence, this study is aimed to examine the effect of Famotidine (FAM), a H2 receptor antagonist on DOX-induced DCM in Wistar rats. Myocardial antioxidant status, stress and apoptosis markers, myocardial morphology and function were evaluated as the end points. Treatment with FAM has alleviated DOX doxorubicin-induced cardiotoxicity by reducing oxidative and nitrosative stress evident from lipid peroxidation and total nitrate-to-nitrite ratio, and enhanced the activity of super oxide dismutase. Cardiac stress markers like LDH and Na⁺-K⁺ATPase activities as well as CK-MB and Cardiac troponin levels were reduced by FAM treatment. It also normalised the myocardial function as assessed by 2D echocardiography and myocardial index. Treatment imparted anti-apoptotic effect as evident from decrease in myocardial caspase 3 and 9 activity and cleaved PARP expression. Effect of FAM is found to be comparable to the standard ACE inhibitor Captopril (CAP). The results from this study collectively suggest H2 receptor antagonism as a novel therapeutic strategy to impart biochemical, structural and functional improvement indicating its cardio-protective activity.

Rac1-mediated cardiac damage causes diastolic dysfunction in a mouse model of subacute doxorubicin-induced cardiotoxicity

The anticancer efficacy of anthracyclines is limited by congestive heart failure. Clinically established markers of early onset of cardiotoxicity following anthracycline treatment and preventive measures are missing. Although statins are reported to alleviate anthracycline-induced cardiotoxicity in vivo, the molecular mechanisms involved remain elusive. In vitro data point to Rac1 as major target of the cytoprotective statin effects. Here we investigated whether specific inhibition of Rac1 by NSC23766 is as effective as lovastatin in preventing subacute cardiotoxicity following doxorubicin treatment. C57BL/6 mice were treated over 3 weeks with multiple low doses of doxorubicin (6 × 3 mg/kg BW, i.p.) and the level of DNA damage, apoptosis and regenerative proliferation as well as pro-inflammatory, pro-fibrotic and oxidative stress responses were investigated. Moreover, heart function was monitored by echocardiography. Doxorubicin induced subacute cardiotoxicity which was reflected on the level of residual DNA damage, frequency of apoptotic and mitotic cells as well as elevated mRNA expression of markers of heart failure, remodeling and mitochondrial biogenesis. These molecular markers of cardiotoxicity were mitigated to a similar extent by co-treatment with either lovastatin (10 mg/kg BW, p.o.) or NSC23766 (5 mg/kg BW, i.p.) three times a week. Moreover, doxorubicin caused diastolic dysfunction as reflected by increased E-wave acceleration time (EAT), which again was prevented by pharmacological inhibition of Rac1. Inhibition of Rac1 signaling is of major relevance for the cardioprotective effects of lovastatin in the context of anthracycline-induced cardiotoxicity. Moreover, EAT is a useful marker of subacute cardiotoxicity caused by persisting harmful effects of doxorubicin.

The epigenetic landscape related to reactive oxygen species formation in the cardiovascular system

Cardiovascular diseases are among the leading causes of death worldwide. Reactive oxygen species (ROS) can act as damaging molecules but also represent central hubs in cellular signalling networks. Increasing evidence indicates that ROS play an important role in the pathogenesis of cardiovascular diseases, although the underlying mechanisms and consequences of pathophysiologically elevated ROS in the cardiovascular system are still not completely resolved. More recently, alterations of the epigenetic landscape, which can affect DNA methylation, post-translational histone modifications, ATP-dependent alterations to chromatin and non-coding RNA transcripts, have been considered to be of increasing importance in the pathogenesis of cardiovascular diseases. While it has long been accepted that epigenetic changes are imprinted during development or even inherited and are not changed after reaching the lineage-specific expression profile, it becomes more and more clear that epigenetic modifications are highly dynamic. Thus, they might provide an important link between the actions of ROS and cardiovascular diseases. This review will provide an overview of the role of ROS in modulating the epigenetic landscape in the context of the cardiovascular system.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Pleiotropic Effects of Statins on the Cardiovascular System

The statins have been used for 30 years to prevent coronary artery disease and stroke. Their primary mechanism of action is the lowering of serum cholesterol through inhibiting hepatic cholesterol biosynthesis thereby upregulating the hepatic low-density lipoprotein (LDL) receptors and increasing the clearance of LDL-cholesterol. Statins may exert cardiovascular protective effects that are independent of LDL-cholesterol lowering called pleiotropic effects. Because statins inhibit the production of isoprenoid intermediates in the cholesterol biosynthetic pathway, the post-translational prenylation of small GTP-binding proteins such as Rho and Rac, and their downstream effectors such as Rho kinase and nicotinamide adenine dinucleotide phosphate oxidases are also inhibited. In cell culture and animal studies, these effects alter the expression of endothelial nitric oxide synthase, the stability of atherosclerotic plaques, the production of proinflammatory cytokines and reactive oxygen species, the reactivity of platelets, and the development of cardiac hypertrophy and fibrosis. The relative contributions of statin pleiotropy to clinical outcomes, however, remain a matter of debate and are hard to quantify because the degree of isoprenoid inhibition by statins correlates to some extent with the amount of LDL-cholesterol reduction. This review examines some of the currently proposed molecular mechanisms for statin pleiotropy and discusses whether they could have any clinical relevance in cardiovascular disease.

Anthracycline Chemotherapy and Cardiotoxicity

Anthracycline chemotherapy maintains a prominent role in treating many forms of cancer. Cardiotoxic side effects limit their dosing and improved cancer outcomes expose the cancer survivor to increased cardiovascular morbidity and mortality. The basic mechanisms of cardiotoxicity may involve direct pathways for reactive oxygen species generation and topoisomerase 2 as well as other indirect pathways. Cardioprotective treatments are few and those that have been examined include renin angiotensin system blockade, beta blockers, or the iron chelator dexrazoxane. New treatments exploiting the ErbB or other novel pro-survival pathways, such as conditioning, are on the cardioprotection horizon. Even in the forthcoming era of targeted cancer therapies, the substantial proportion of today's anthracycline-treated cancer patients may become tomorrow's cardiac patient.

Statins in anthracycline-induced cardiotoxicity: Rac and Rho, and the heartbreakers

Cancer patients receiving anthracycline-based chemotherapy are at risk to develop life-threatening chronic cardiotoxicity with the pathophysiological mechanism of action not fully understood. Besides the most common hypothesis that anthracycline-induced congestive heart failure (CHF) is mainly caused by generation of reactive oxygen species, recent data point to a critical role of topoisomerase II beta (TOP2B), which is a primary target of anthracycline poisoning, in the pathophysiology of CHF. As the use of the only clinically approved cardioprotectant dexrazoxane has been limited by the FDA in 2011, there is an urgent need for alternative cardioprotective measures. Statins are anti-inflammatory and anti-oxidative drugs that are clinically well established for the prevention of cardiovascular diseases. They exhibit pleiotropic beneficial properties beyond cholesterol-lowering effects that most likely rest on the indirect inhibition of small Ras homologous (Rho) GTPases. The Rho GTPase Rac1 has been shown to be a major factor in the regulation of the pro-oxidative NADPH oxidase as well as in the regulation of type II topoisomerase. Both are discussed to play an important role in the pathophysiology of anthracycline-induced CHF. Therefore, off-label use of statins or novel Rac1 inhibitors might represent a promising pharmacological approach to gain control over chronic cardiotoxicity by interfering with key mechanisms of anthracycline-induced cardiomyocyte cell death.

Salvianolic acid B protects against doxorubicin induced cardiac dysfunction via inhibition of ER stress mediated cardiomyocyte apoptosis

Salvia miltiorrhiza Bunge is a well-known medicinal plant in China. Salvianolic acid B (Sal B) is the most abundant bioactive compound extracted from the root of S. miltiorrhiza. The present study investigates the effect of Sal B on cardiac function and cardiomyocyte apoptosis in doxorubicin (DOX)-treated mice. After pretreatment with Sal B (2 mg kg-1 iv) for 7 d, male BALB/c mice were injected with a single dose of DOX (20 mg kg-1 ip). The cardioprotective effect of Sal B was observed on the 7th day after DOX treatment. DOX caused retarded body growth, apoptotic damage, and Bcl-2 expression disturbance. In contrast, Sal B pretreatment (2 mg kg-1 iv before DOX administration) attenuated the DOX induced apoptotic damage in heart tissues. Further study indicated that Sal B protected against DOX induced cardiotoxicity, at least, partially, by inhibiting endoplasmic reticulum stress, and by being involved in the PI3K/Akt pathway. These findings clarified the potential of Sal B as a promising reagent for treating DOX induced cardiotoxicity.

Ascorbate attenuates pulmonary emphysema by inhibiting tobacco smoke and Rtp801-triggered lung protein modification and proteolysis

Cigarette smoking causes emphysema, a fatal disease involving extensive structural and functional damage of the lung. Using a guinea pig model and human lung cells, we show that oxidant(s) present in tobacco smoke not only cause direct oxidative damage of lung proteins, contributing to the major share of lung injury, but also activate Rtp801, a key proinflammatory cellular factor involved in tobacco smoke-induced lung damage. Rtp801 triggers nuclear factor κB and consequent inducible NOS (iNOS)-mediated overproduction of NO, which in combination with excess superoxide produced during Rtp801 activation, contribute to increased oxido-nitrosative stress and lung protein nitration. However, lung-specific inhibition of iNOS with a iNOS-specific inhibitor, N6-(1-iminoethyl)-L-lysine, dihydrochloride (L-NIL) solely restricts lung protein nitration but fails to prevent or reverse the major tobacco smoke-induced oxidative lung injury. In comparison, the dietary antioxidant, ascorbate or vitamin C, can substantially prevent such damage by inhibiting both tobacco smoke-induced lung protein oxidation as well as activation of pulmonary Rtp801 and consequent iNOS/NO-induced nitration of lung proteins, that otherwise lead to increased proteolysis of such oxidized or nitrated proteins by endogenous lung proteases, resulting in emphysematous lung damage. Vitamin C also restricts the up-regulation of matrix-metalloproteinase-9, the major lung protease involved in the proteolysis of such modified lung proteins during tobacco smoke-induced emphysema. Overall, our findings implicate tobacco-smoke oxidant(s) as the primary etiopathogenic factor behind both the noncellular and cellular damage mechanisms governing emphysematous lung injury and demonstrate the potential of vitamin C to accomplish holistic prevention of such damage.

The ubiquitin E3 ligase TRAF6 exacerbates pathological cardiac hypertrophy via TAK1-dependent signalling

Tumour necrosis factor receptor-associated factor 6 (TRAF6) is a ubiquitin E3 ligase that regulates important biological processes. However, the role of TRAF6 in cardiac hypertrophy remains unknown. Here, we show that TRAF6 levels are increased in human and murine hypertrophied hearts, which is regulated by reactive oxygen species (ROS) production. Cardiac-specific Traf6 overexpression exacerbates cardiac hypertrophy in response to pressure overload or angiotensin II (Ang II) challenge, whereas Traf6 deficiency causes an alleviated hypertrophic phenotype in mice. Mechanistically, we show that ROS, generated during hypertrophic progression, triggers TRAF6 auto-ubiquitination that facilitates recruitment of TAB2 and its binding to transforming growth factor beta-activated kinase 1 (TAK1), which, in turn, enables the direct TRAF6-TAK1 interaction and promotes TAK1 ubiquitination. The binding of TRAF6 to TAK1 and the induction of TAK1 ubiquitination and activation are indispensable for TRAF6-regulated cardiac remodelling. Taken together, we define TRAF6 as an essential molecular switch leading to cardiac hypertrophy in a TAK1-dependent manner.

Role of NOX2 in mediating doxorubicin-induced senescence in human endothelial progenitor cells

Senescence exerts a great impact on both biological and functional properties of circulating endothelial progenitor cells (EPCs), especially in cardiovascular diseases where the physiological process of aging is accelerated upon clinical administration of certain drugs such as doxorubicin. EPC impairment contributes to doxorubicin-induced cardiotoxicity. Doxorubicin accelerates EPC aging, although mechanisms underlying this phenomenon remain to be fully clarified. Here we investigated if Nox2 activity is able to modulate the premature senescence induced in vitro by doxorubicin in human EPCs. Results showed that in conditioned media obtained from late EPC cultures, the levels of interleukin-6, isoprostanes and nitric oxide bioavailability were increased and reduced respectively after 3h of doxorubicin treatment. These derangements returned to physiological levels when cells were co-treated with apocynin or gp91ds-tat (antioxidant and specific Nox2 inhibitors, respectively). Accordingly, Nox2 activity resulted to be activated by doxorubicin. Importantly, we found that Nox2 inhibition reduced doxorubicin-induced EPC senescence, as indicated by a lower percentage of β-gal positive EPCs. In conclusion, Nox2 activity efficiently contributes to the mechanism of oxidative stress-induced increase in premature aging conferred by doxorubicin. The importance of modulation of Nox2 in human EPCs could reveal a useful tool to restore EPC physiological function and properties.

Ataxia telangiectasia mutated in cardiac fibroblasts regulates doxorubicin-induced cardiotoxicity

AIMS

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

METHODS AND RESULTS

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

CONCLUSION

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

Paeoniflorin inhibits doxorubicin-induced cardiomyocyte apoptosis by downregulating microRNA-1 expression

Doxorubicin (DOX) is an effective anthracycline anti-tumor antibiotic. Because of its cardiotoxicity, the clinical application of DOX is limited. Paeoniflorin (PEF), a monoterpene glucoside extracted from the dry root of Paeonia, is reported to exert multiple beneficial effects on the cardiovascular system. The present study was designed to explore the protective effect of PEF against DOX-induced cardiomyocyte apoptosis and the underlying mechanism. In cultured H9c2 cells, PEF (100 µmol/l) was added for 2 h prior to exposure to DOX (5 µmol/l) for 24 h. Cell viability, creatine kinase activity, cardiomyocyte apoptosis, intracellular reactive oxygen species (ROS) levels, and the expression of microRNA-1 (miR-1) and B-cell lymphoma 2 (Bcl-2) were measured following treatment with PEF and/or DOX. The results showed that treatment with DOX notably induced cardiomyocyte apoptosis, concomitantly with enhanced ROS generation, upregulated miR-1 expression and downregulated Bcl-2 expression. These effects of DOX were significantly inhibited by pretreatment of the cells with PEF. These results suggest that the inhibitory effect of PEF on DOX-induced cardiomyocyte apoptosis may be associated with downregulation of miR-1 expression via a reduction in ROS generation.

HSP25 down-regulation enhanced p53 acetylation by dissociation of SIRT1 from p53 in doxorubicin-induced H9c2 cell apoptosis

Heat shock proteins (HSPs) play important roles in cellular stress resistance. Previous reports had already suggested that HSP27 played multiple roles in preventing doxorubicin-induced cardiotoxicity. Although HSP25 might have biological functions similar to its human homolog HSP27, the mechanism of HSP25 is still unclear in doxorubicin-induced cardiomyocyte apoptosis. To investigate HSP25 biological function on doxorubicin-induced apoptosis, flow cytometry was employed to analyze cell apoptosis in over-expressing HSP25 H9c2 cells in presence of doxorubicin. Unexpectedly, the H9c2 cells of over-expressing HSP25 have no protective effect on doxorubicin-induced apoptosis. Moreover, no detectable interactions were detected by coimmunoprecipitation between HSP25 and cytochrome c, and HSP25 over-expression failed in preventing cytochrome c release induced by doxorubicin. However, down-regulation of endogenous HSP25 by a specific small hairpin RNA aggravates apoptosis in H9c2 cells. Subsequent studies found that HSP25, but not HSP90, HSP70, and HSP20, interacted with SIRT1. Knockdown of HSP25 decreased the interaction between SIRT1 and p53, leading to increased p53 acetylation on K379, up-regulated pro-apoptotic Bax protein expression, induced cytochrome c release, and triggered caspase-3 and caspase-9 activation. These findings indicated a novel mechanism by which HSP25 regulated p53 acetylation through dissociation of SIRT1 from p53 in doxorubicin-induced H9c2 cell apoptosis.

Concepts in cardio-oncology: definitions, mechanisms, diagnosis and treatment strategies of cancer therapy-induced cardiotoxicity

There has been considerable improvement in cancer survival rates, primarily through improved preventive strategies and novel anticancer drugs. Cancer is now becoming a chronic illness and as such both short and long-term cardiotoxic effects of cancer therapy are becoming more apparent. This has led to the emergence of a new multidisciplinary specialty known as cardio-oncology, with the purpose of identifying patients who are at a higher risk for developing cardiotoxicity so that appropriate surveillance, treatment and follow-up strategies may be instituted early. The mechanisms of cardiotoxicity caused by commonly used anticancer agents are reviewed, along with the latest advances in diagnostic and preventative strategies, with the overall objective of allowing cancer patients to continue both lifesaving and palliative treatments for their malignancy.

Oxidative stress does not play a primary role in the toxicity induced with clinical doses of doxorubicin in myocardial H9c2 cells

The implication of oxidative stress as primary mechanism inducing doxorubicin (DOX) cardiotoxicity is still questionable as many in vitro studies implied supra-clinical drug doses or unreliable methodologies for reactive oxygen species (ROS) detection. The aim of this study was to clarify whether oxidative stress is involved in compliance with the conditions of clinical use of DOX, and using reliable tools for ROS detection. We examined the cytotoxic mechanisms of 2 μM DOX 1 day after the beginning of the treatment in differentiated H9c2 rat embryonic cardiac cells. Cells were exposed for 2 or 24 h with DOX to mimic a single chronic dosage or to favor accumulation, respectively. We found that apoptosis was prevalent in cells exposed for a short period with DOX: cells showed typical hallmarks as loss of anchorage ability, mitochondrial hyperpolarization followed by the collapse of mitochondrial activity, and nuclear condensation. Increasing the exposure period favored a shift to necrosis as the cells preferentially exhibited early DNA impairment and nuclear swelling. In either case, measuring the fluorescence lifetime of 1-pyrenebutyric acid or the intensities of dihydroethidium or amplex red showed a consistent pattern in ROS production which was a slight increased level far from representative of an oxidative stress. Moreover, pre-treatment with dexrazoxane provided a cytoprotective effect although it failed to detoxify ROS. Our data support that oxidative stress is unlikely to be the primary mechanism of DOX cardiac toxicity in vitro.

New signal transduction paradigms in anthracycline-induced cardiotoxicity

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

Activation of the Constitutive Androstane Receptor Increases the Therapeutic Index of CHOP in Lymphoma Treatment

The constitutive androstane receptor (CAR and NR1i3) is a key regulator of CYP2B6, the enzyme predominantly responsible for the biotransformation of cyclophosphamide (CPA) to its pharmacologically active metabolite, 4-hydroxycyclophosphamide (4-OH-CPA). Previous studies from our laboratory illustrated that CAR activation increases the formation of 4-OH-CPA; however, CPA is rarely used clinically outside of combination therapies. Here, we hypothesize that including a selective human CAR activator with the CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) regimen can improve the efficacy without exacerbating off-target toxicity of this regimen in non-Hodgkin lymphoma treatment. In this study, we have developed a novel multiorgan coculture system containing human primary hepatocytes for hepatic metabolism, lymphoma cells as a model target for CHOP, and cardiomyocytes as a major site of off-target toxicity associated with this regimen. We found that a selective human CAR activator, CITCO (6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime), altered expression of key drug-metabolizing enzymes and transporters in human hepatocytes, which positively affects the metabolic profile of CHOP. Coadministration of CITCO and CHOP in the coculture model led to significantly enhanced cytotoxicity in lymphoma cells but not in cardiomyocytes. Moreover, the beneficial effects of CITCO were abrogated when CAR knockout HepaRG cells were used in the coculture model. Importantly, synergistic anticancer effects were observed between CITCO and CHOP, in that inclusion of CITCO alongside the CHOP regimen offers comparable antineoplastic activity toward lymphoma cells at significantly reduced drug concentrations, and the decreased CHOP load attenuates cardiotoxicity. Overall, these findings provide a potentially promising novel strategy for facilitating CHOP-based chemotherapy.

Therapeutic inhibition of mitochondrial reactive oxygen species with mito-TEMPO reduces diabetic cardiomyopathy

AIMS

The mitochondria are important sources of reactive oxygen species (ROS) in the heart. Mitochondrial ROS production has been implicated in the pathogenesis of diabetic cardiomyopathy, suggesting that therapeutic strategies specifically targeting mitochondrial ROS may have benefit in this disease. We investigated the therapeutic effects of mitochondria-targeted antioxidant mito-TEMPO on diabetic cardiomyopathy.

METHODS

The mitochondria-targeted antioxidant mito-TEMPO was administrated after diabetes onset in a mouse model of streptozotocin-induced type-1 diabetes and type-2 diabetic db/db mice. Cardiac adverse changes were analyzed and myocardial function assessed. Cultured adult cardiomyocytes were stimulated with high glucose, and mitochondrial superoxide generation and cell death were measured.

RESULTS

Incubation with high glucose increased mitochondria superoxide generation in cultured cardiomyocytes, which was prevented by mito-TEMPO. Co-incubation with mito-TEMPO abrogated high glucose-induced cell death. Mitochondrial ROS generation, and intracellular oxidative stress levels were induced in both type-1 and type-2 diabetic mouse hearts. Daily injection of mito-TEMPO for 30 days inhibited mitochondrial ROS generation, prevented intracellular oxidative stress levels, decreased apoptosis and reduced myocardial hypertrophy in diabetic hearts, leading to improvement of myocardial function in both type-1 and type-2 diabetic mice. Incubation with mito-TEMPO or inhibition of Nox2-containing NADPH oxidase prevented oxidative stress levels and cell death in high glucose-stimulated cardiomyocytes. Mechanistic study revealed that the protective effects of mito-TEMPO were associated with down-regulation of ERK1/2 phosphorylation.

CONCLUSIONS

Therapeutic inhibition of mitochondrial ROS by mito-TEMPO reduced adverse cardiac changes and mitigated myocardial dysfunction in diabetic mice. Thus, mitochondria-targeted antioxidants may be an effective therapy for diabetic cardiac complications.

Doxorubicin Redox Biology: Redox Cycling, Topoisomerase Inhibition, and Oxidative Stress

Doxorubicin (also called Adriamycin) is effective in treating a wide range of human cancers and currently considered as one of the most important drugs in cancer chemotherapeutics. The clinical use of doxorubicin is, however, associated with dosage-dependent cardiotoxicity and development of heart failure, which diminish the therapeutic index of this widely used anticancer drug. This article first surveys key research findings on doxorubicin redox biology that may impact its cardiotoxicity as well as anticancer activity. It then discusses emerging concepts, especially the topoisomerase IIb-p53-mitochondrion axis that may lead to the development of mechanistically based novel strategies to protect against cardiotoxicity and enhance the effectiveness of doxorubicin therapy.

Mitochondrial Calpain-1 Disrupts ATP Synthase and Induces Superoxide Generation in Type 1 Diabetic Hearts: A Novel Mechanism Contributing to Diabetic Cardiomyopathy

Calpain plays a critical role in cardiomyopathic changes in type 1 diabetes (T1D). This study investigated how calpain regulates mitochondrial reactive oxygen species (ROS) generation in the development of diabetic cardiomyopathy. T1D was induced in transgenic mice overexpressing calpastatin, in mice with cardiomyocyte-specific capn4 deletion, or in their wild-type littermates by injection of streptozotocin. Calpain-1 protein and activity in mitochondria were elevated in diabetic mouse hearts. The increased mitochondrial calpain-1 was associated with an increase in mitochondrial ROS generation and oxidative damage and a reduction in ATP synthase-α (ATP5A1) protein and ATP synthase activity. Genetic inhibition of calpain or upregulation of ATP5A1 increased ATP5A1 and ATP synthase activity, prevented mitochondrial ROS generation and oxidative damage, and reduced cardiomyopathic changes in diabetic mice. High glucose concentration induced ATP synthase disruption, mitochondrial superoxide generation, and cell death in cardiomyocytes, all of which were prevented by overexpression of mitochondria-targeted calpastatin or ATP5A1. Moreover, upregulation of calpain-1 specifically in mitochondria induced the cleavage of ATP5A1, superoxide generation, and apoptosis in cardiomyocytes. In summary, calpain-1 accumulation in mitochondria disrupts ATP synthase and induces ROS generation, which promotes diabetic cardiomyopathy. These findings suggest a novel mechanism for and may have significant implications in diabetic cardiac complications.

Breast Cancer Survivorship and Cardiovascular Disease: Emerging Approaches in Cardio-Oncology

OPINION STATEMENT

Cardiovascular disease (CVD) and breast cancer cause substantial morbidity and mortality in women and are major public health concerns in the USA. While aggressive screening and targeted, advanced treatment for breast cancer have had a measurable impact on breast cancer survival, treatment is not without significant cardiotoxic effects. Anthracycline-based chemotherapy can lead to left ventricular dysfunction and failure, as well as a decline in exercise tolerance and cardio-pulmonary reserve despite preserved ejection fraction. Trastuzumab, a newer monoclonal antibody targeting the Her2 receptor used in the treatment of Her2+ cancer, is also linked to left ventricular dysfunction, although the long-term cardiac effects are presently unclear. Radiation treatment particularly for left-sided breast cancer has been associated with increased rates of ischemic heart disease. As women have increasing survival and cure rates from early breast cancer, long-term consequences on the heart that are secondary to therapy are a major concern. These need to be identified, treated, and avoided when possible. Further research and clear surveillance guidelines are needed to aid the practicing clinician in CVD prevention in breast cancer survivors.

Rho GTPases: Novel Players in the Regulation of the DNA Damage Response?

The Ras-related C3 botulinum toxin substrate 1 (Rac1) belongs to the family of Ras-homologous small GTPases. It is well characterized as a membrane-bound signal transducing molecule that is involved in the regulation of cell motility and adhesion as well as cell cycle progression, mitosis, cell death and gene expression. Rac1 also adjusts cellular responses to genotoxic stress by regulating the activity of stress kinases, including c-Jun-N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38 kinases as well as related transcription factors. Apart from being found on the inner side of the outer cell membrane and in the cytosol, Rac1 has also been detected inside the nucleus. Different lines of evidence indicate that genotoxin-induced DNA damage is able to activate nuclear Rac1. The exact mechanisms involved and the biological consequences, however, are unclear. The data available so far indicate that Rac1 might integrate DNA damage independent and DNA damage dependent cellular stress responses following genotoxin treatment, thereby coordinating mechanisms of the DNA damage response (DDR) that are related to DNA repair, survival and cell death.

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

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

Cytotoxin-induced NADPH oxides activation: roles in regulation of cell death

Numerous studies have shown that a variety of cytotoxic agents can activate the NADPH oxidase system and induce redox-dependent regulation of cellular functions. Cytotoxin-induced NADPH oxidase activation may either exert cytoprotective actions (e.g., survival, proliferation, and stress tolerance) or cause cell death. Here we summarize the experimental evidence showing the context-dependent dichotomous effects of NADPH oxidase on cell fate under cytotoxic stress conditions and the potential redox signaling mechanisms underlying this phenomenon. Clearly, it is difficult to create a unified paradigm on the toxicological implications of NADPH oxidase activation in response to cytotoxic stimuli. We suggest that interventional strategies targeting the NADPH oxidase system to prevent the adverse impacts of cytotoxins need to be contemplated in a stimuli- and cell type-specific manner.

Chronic heart damage following doxorubicin treatment is alleviated by lovastatin

The anticancer efficacy of anthracyclines is limited by cumulative dose-dependent early and delayed cardiotoxicity resulting in congestive heart failure. Mechanisms responsible for anthracycline-induced heart damage are controversially discussed and effective preventive measures are preferable. Here, we analyzed the influence of the lipid lowering drug lovastatin on anthracycline-induced late cardiotoxicity three month after treatment of C57BL/6 mice with five low doses of doxorubicin (5×3mg/kg BW; i.p.). Doxorubicin increased the cardiac mRNA levels of BNP, IL-6 and CTGF, while the expression of ANP remained unchanged. Lovastatin counteracted these persisting cardiac stress responses evoked by the anthracycline. Doxorubicin-induced fibrotic alterations were neither detected by histochemical collagen staining of heart sections nor by analysis of the mRNA expression of collagens. Extensive qRT-PCR-array based analyses revealed a large increase in the mRNA level of heat shock protein Hspa1b in doxorubicin-treated mice, which was mitigated by lovastatin co-treatment. Electron microscopy together with qPCR-based analysis of mitochondrial DNA content indicate that lovastatin attenuates doxorubicin-stimulated hyperproliferation of mitochondria. This was not paralleled by increased expression of oxidative stress responsive genes or senescence-associated proteins. Echocardiographic analyses disclosed that lovastatin protects from the doxorubicin-induced decrease in the left ventricular posterior wall diameter (LVPWD), while constrictions in fractional shortening (FS) and ejection fraction (EF) evoked by doxorubicin were not amended by the statin. Taken together, the data suggest beneficial effects of lovastatin against doxorubicin-induced delayed cardiotoxicity. Clinical studies are preferable to scrutinize the usefulness of statins for the prevention of anthracycline-induced late cardiotoxicity.

Neuregulin-1/erbB activities with focus on the susceptibility of the heart to anthracyclines

Neuregulin-1 (NRG1) signaling through the tyrosine kinase receptors erbB2 and erbB4 is required for cardiac morphogenesis, and it plays an essential role in maintaining the myocardial architecture during adulthood. The tyrosine kinase receptor erbB2 was first linked to the amplification and overexpression of erbb2 gene in a subtype of breast tumor cells, which is indicative of highly proliferative cells and likely a poor prognosis following conventional chemotherapy. The development of targeted therapies to block the survival of erbB2-positive cancer cells revealed that impaired NRG1 signaling through erbB2/erbB4 heterodimers combined with anthracycline chemotherapy may lead to dilated cardiomyopathy in a subpopulation of treated patients. The ventricular-specific deletion of either erbb2 or erbb4 manifested dilated cardiomyopathy, which is aggravated by the administration of doxorubicin. Based on the exacerbated toxicity displayed by the combined treatment, it is expected that the relevant pathways would be affected in a synergistic manner. This review examines the NRG1 activities that were monitored in different model systems, focusing on the emerging pathways and molecular targets, which may aid in understanding the acquired dilated cardiomyopathy that occurs under the conditions of NRG1-deficient signaling.

Inhibition of calpain reduces oxidative stress and attenuates endothelial dysfunction in diabetes

Aims

The present study was to investigate the role of calpain in reactive oxygen species (ROS) production in endothelial cells and endothelium-dependent vascular dysfunction under experimental conditions of diabetes.

Methods and results

Exposure to high glucose activated calpain, induced apoptosis and reduced nitric oxide (NO) production without changing eNOS protein expression, its phosphorylation and dimers formation in primary human umbilical vein endothelial cells (HUVECs). These effects of high glucose correlated with intracellular ROS production and mitochondrial superoxide generation. Selectively scavenging mitochondrial superoxide increased NO production in high glucose-stimulated HUVECs. Inhibition of calpain using over-expression of calpastatin or pharmacological calpain inhibitor prevented high glucose-induced ROS production, mitochondrial superoxide generation and apoptosis, which were concurrent with an elevation of NO production in HUVECs. In mouse models of streptozotocin-induced type-1 diabetes and OVE26 type-1 diabetic mice, calpain activation correlated with an increase in ROS production and peroxynitrite formation in aortas. Transgenic over-expression of calpastatin reduced ROS production and peroxynitrite formation in diabetic mice. In parallel, diabetes-induced reduction of endothelium-dependent relaxation in aortic ring was reversed by over-expression of calpastatin in mouse models of diabetes. However, the protective effect of calpastatin on endothelium-dependent relaxation was abrogated by eNOS deletion in diabetic mice.

Conclusions

This study suggests that calpain may play a role in vascular endothelial cell ROS production and endothelium-dependent dysfunction in diabetes. Thus, calpain may be an important therapeutic target to overcome diabetes-induced vascular dysfunction.

Synergistic apoptotic effect of Doxil ® and aminolevulinic acid-based photodynamic therapy on human breast adenocarcinoma cells

BACKGROUND

5-Aminolevulinic acid (ALA) is a natural heme precursor metabolized into protoporphyrin IX (PpIX). PpIX preferentially accumulates in tumor cells resulting in the formation of singlet oxygen upon exposure to visible light. Doxil(®), an active agent against breast and ovarian cancer, is a nano-formulation of doxorubicin. This study aimed to investigate in vitro synergistic cytotoxic effect of low doses of combined chemotherapy and ALA/PDT to human breast adenocarcinoma cells (MCF-7) compared to high doses of each individual therapy.

METHODS

MCF-7 cells were pretreated with Doxil(®) (48 h) followed by ALA/PDT (4h). The cell viability was evaluated by trypan blue assay and PpIX production was measured spectrofluorometrically. Alkaline phosphatase was determined as a marker for cellular differentiation. Apoptosis and necrosis were evaluated by fluorescence stains. The apoptosis cell death pathways were investigated: detection of mitochondrial membrane potential (ΔΨm) and percent of DNA fragmentation, malondialdehyde, histone deacetylase (HDAC) activity, caspase-3 and death receptors (DR4 and DR5). Vascular endothelial growth factor (VEGF) was determined by ELISA, as an angiogenic mediator.

RESULTS

There was a higher reduction in cell viability in Doxil(®)+ALA/PDT-treated cells compared with their individual effect. The combined therapy showed enhanced apoptosis with a significant increase in the loss of ΔΨm, DNA fragmentation %, caspase-3, DR4, DR5 and lipid peroxides and inhibited HDAC. Pretreatment with Doxil(®) resulted in a twofold increase in the intracellular PpIX, by increasing the PDT killing of MCF-7 cells.

CONCLUSION

The combined therapy using 50% of IC50 of ALA/PDT and Doxil(®) possessed a synergistic apoptotic effect on MCF-7 cells compared to 100% of IC50 of each therapy through enhancing both intrinsic and extrinsic apoptotic pathways, thus may minimize side effects of Doxil(®) and ALA.