Roles of oxidative stress and Akt signaling in doxorubicin cardiotoxicity

Nanotechnology for the theranostic opportunity of breast cancer lung metastasis: recent advancements and future challenges

Lung metastasis of breast cancer is rapidly becoming a thorny problem in the treatment of patients with breast cancer and an obstacle to long-term survival. The main challenges of treatment are the absence of therapeutic targets and drug resistance, which promotes the development of nanotechnology in the diagnosis and treatment process. Taking advantage of the controllability and targeting of nanotechnology, drug-targeted delivery, controlled sustained release, multi-drug combination, improved drug efficacy, and reduced side effects can be realized in the process of the diagnosis and treatment of metastatic breast cancer (MBC). Several nanotechnology-based theranostic strategies have been investigated in breast cancer lung metastases (BCLM): targeted drug delivery, imaging analysis, immunotherapy, gene therapy, and multi-modality combined therapy, and some clinical applications are in the research phase. In this review, we present current nanotechnology-based diagnosis and treatment approaches for patients of incurable breast cancer with lung metastases, and we hope to be able to summarize more effective and promising nano-drug diagnosis and treatment systems that aim to improve the survival of patients with advanced MBC. We describe nanoplatform-based experimental studies and clinical trials targeting the tumor and the tumor microenvironment (TME) for BCLM to obtain more targeted treatment and in the future treatment steps for patients to provide a pioneering strategy.

Echinacoside ameliorates doxorubicin‑induced cardiac injury by regulating GPX4 inhibition‑induced ferroptosis

Echinacoside (ECH) is a compound derived from the natural herbs Cistanche and Echinacea, which has considerable protective effects on heart failure (HF). HF is characterized by myocardial damage and abnormal ferroptosis. Glutathione peroxidase 4 (GPX4) is an important regulator of ferroptosis, which plays a role in ferroptosis-related diseases. Despite this, the therapeutic mechanisms of ECH against HF remain unknown. Therefore, the aim of the present study was to investigate the cardioprotective effect and underlying mechanisms of ECH in the treatment of doxorubicin (DOX)-induced chronic HF (CHF). Cell proliferation was assessed using a CCK-8 assay. Furthermore, cardiac cell injury and oxidative stress were determined by measuring the lactate dehydrogenase (LDH), malondialdehyde (MDA), and glutathione (GSH) levels. The levels of Fe2+ and lipid reactive oxygen species (ROS), and expression of the biomarkers of ferroptosis, including GPX4 and prostaglandin-endoperoxide synthase 2 (PTGS2), were measured to examine cardiomyocyte ferroptosis. Additionally, RNA interference was used to silence Gpx4. In vitro and in vivo, ECH considerably reduced the MDA and LDH levels and increased the GSH level, thereby attenuating DOX-induced cardiac injury and oxidative stress. Meanwhile, ECH treatment decreased the lipid ROS levels and PTGS2 expression while increasing GPX4 expression, thereby alleviating DOX-induced cardiomyocyte ferroptosis. Moreover, knockdown of Gpx4 inhibited the protective effects of ECH on DOX-induced accumulation of lipid ROS in cardiomyocytes. These findings indicate that ECH can reduce DOX-induced cardiac injury by inhibiting ferroptosis via GPX4, highlighting its value as a potentially valuable therapeutic target in the management of CHF.

Intermediate Molecular Phenotypes to Identify Genetic Markers of Anthracycline-Induced Cardiotoxicity Risk

Cardiotoxicity due to anthracyclines (CDA) affects cancer patients, but we cannot predict who may suffer from this complication. CDA is a complex trait with a polygenic component that is mainly unidentified. We propose that levels of intermediate molecular phenotypes (IMPs) in the myocardium associated with histopathological damage could explain CDA susceptibility, so variants of genes encoding these IMPs could identify patients susceptible to this complication. Thus, a genetically heterogeneous cohort of mice (n = 165) generated by backcrossing were treated with doxorubicin and docetaxel. We quantified heart fibrosis using an Ariol slide scanner and intramyocardial levels of IMPs using multiplex bead arrays and QPCR. We identified quantitative trait loci linked to IMPs (ipQTLs) and cdaQTLs via linkage analysis. In three cancer patient cohorts, CDA was quantified using echocardiography or Cardiac Magnetic Resonance. CDA behaves as a complex trait in the mouse cohort. IMP levels in the myocardium were associated with CDA. ipQTLs integrated into genetic models with cdaQTLs account for more CDA phenotypic variation than that explained by cda-QTLs alone. Allelic forms of genes encoding IMPs associated with CDA in mice, including AKT1, MAPK14, MAPK8, STAT3, CAS3, and TP53, are genetic determinants of CDA in patients. Two genetic risk scores for pediatric patients (n = 71) and women with breast cancer (n = 420) were generated using machine-learning Least Absolute Shrinkage and Selection Operator (LASSO) regression. Thus, IMPs associated with heart damage identify genetic markers of CDA risk, thereby allowing more personalized patient management.

Intermediate molecular phenotypes to identify genetic markers of anthracycline-induced cardiotoxicity risk

Cardiotoxicity due to anthracyclines (CDA) affects cancer patients, but we cannot predict who may suffer from this complication. CDA is a complex disease whose polygenic component is mainly unidentified. We propose that levels of intermediate molecular phenotypes in the myocardium associated with histopathological damage could explain CDA susceptibility; so that variants of genes encoding these intermediate molecular phenotypes could identify patients susceptible to this complication. A genetically heterogeneous cohort of mice generated by backcrossing (N = 165) was treated with doxorubicin and docetaxel. Cardiac histopathological damage was measured by fibrosis and cardiomyocyte size by an Ariol slide scanner. We determine intramyocardial levels of intermediate molecular phenotypes of CDA associated with histopathological damage and quantitative trait loci (ipQTLs) linked to them. These ipQTLs seem to contribute to the missing heritability of CDA because they improve the heritability explained by QTL directly linked to CDA (cda-QTLs) through genetic models. Genes encoding these molecular subphenotypes were evaluated as genetic markers of CDA in three cancer patient cohorts (N = 517) whose cardiac damage was quantified by echocardiography or Cardiac Magnetic Resonance. Many SNPs associated with CDA were found using genetic models. LASSO multivariate regression identified two risk score models, one for pediatric cancer patients and the other for women with breast cancer. Molecular intermediate phenotypes associated with heart damage can identify genetic markers of CDA risk, thereby allowing a more personalized patient management. A similar strategy could be applied to identify genetic markers of other complex trait diseases.

Doxorubicin-Conjugated Zinc Oxide Nanoparticles, Biogenically Synthesised Using a Fungus Aspergillus niger, Exhibit High Therapeutic Efficacy against Lung Cancer Cells

This study reports the therapeutic effectiveness of doxorubicin-conjugated zinc oxide nanoparticles against lung cancer cell line. The zinc oxide nanoparticles (ZnONPs) were first synthesised using a fungus, isolated from air with an extraordinary capability to survive in very high concentrations of zinc salt. Molecular analysis based on 18S rRNA gene sequencing led to its identification as Aspergillus niger with the NCBI accession no. OL636020. The fungus was found to produce ZnONPs via the reduction of zinc ions from zinc sulphate. The ZnONPs were characterised by various biophysical techniques. ZnONPs were further bioconjugated with the anti-cancer drug doxorubicin (DOX), which was further confirmed by different physical techniques. Furthermore, we examined the cytotoxic efficacy of Doxorubicin-bioconjugated-ZnONPs (DOX-ZnONPs) against lung cancer A549 cells in comparison to ZnONPs and DOX alone. The cytotoxicity caused due to ZnONPs, DOX and DOX-ZnONPs in lung cancer A549 cells was assessed by MTT assay. DOX-ZnONPs strongly inhibited the proliferation of A549 with IC50 value of 0.34 μg/mL, which is lower than IC50 of DOX alone (0.56 μg/mL). Moreover, DOX-ZnONPs treated cells also showed increased nuclear condensation, enhanced ROS generation in cytosol and reduced mitochondrial membrane potential. To investigate the induction of apoptosis, caspase-3 activity was measured in all the treated groups. Conclusively, results of our study have established that DOX-ZnONPs have strong therapeutic efficacy to inhibit the growth of lung cancer cells in comparison to DOX alone. Our study also offers substantial evidence for the biogenically synthesised zinc oxide nanoparticle as a promising candidate for a drug delivery system.

Anthracycline-induced cardiomyopathy: cellular and molecular mechanisms

Despite the known risk of cardiotoxicity, anthracyclines are widely prescribed chemotherapeutic agents. They are broadly characterized as being a robust effector of cellular apoptosis in rapidly proliferating cells through its actions in the nucleus and formation of reactive oxygen species (ROS). And, despite the early use of dexrazoxane, no effective treatment strategy has emerged to prevent the development of cardiomyopathy, despite decades of study, suggesting that much more insight into the underlying mechanism of the development of cardiomyopathy is needed. In this review, we detail the specific intracellular activities of anthracyclines, from the cell membrane to the sarcoplasmic reticulum, and highlight potential therapeutic windows that represent the forefront of research into the underlying causes of anthracycline-induced cardiomyopathy.

C1qTNF-related protein-6 protects against doxorubicin-induced cardiac injury

The clinical use of doxorubicin (DOX) is limited by its toxic effect. However, there is no specific drug that can prevent DOX-related cardiac injury. C1qTNF-related protein-6 (CTRP6) is a newly identified adiponectin paralog with many protective functions on metabolism and cardiovascular diseases. However, little is known about the effect of CTRP6 on DOX-induced cardiac injury. The present study aimed to investigate whether CTRP6 could protect against DOX-related cardiotoxicity. To induce acute cardiotoxicity, the mice were intraperitoneally injected with a single dose of DOX (15 mg/kg). Cardiomyocyte-specific CTRP6 overexpression was achieved using an adenoassociated virus system at 4 weeks before DOX injection. The data in our study demonstrated that CTRP6 messenger RNA and protein expression were decreased in DOX-treated hearts. CTRP6 attenuated cardiac atrophy induced by DOX injection and inhibited cardiac apoptosis and improved cardiac function in vivo. CTRP6 also promoted the activation of protein kinase B (AKT/PKB) signaling pathway in DOX-treated mice. CTRP6 prevented cardiomyocytes from DOX-induced apoptosis and activated the AKT pathway in vitro. CTRP6 lost its protection against DOX-induced cardiac injury in mice with AKT inhibition. In conclusion, CTRP6 protected the heart from DOX-cardiotoxicity and improves cardiac function via activation of the AKT signaling pathway.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

Molecular mechanisms of cardiotoxicity of gefitinib in vivo and in vitro rat cardiomyocyte: Role of apoptosis and oxidative stress

Gefitinib (GEF) is a multi-targeted tyrosine kinase inhibitor with anti-cancer properties, yet few cases of cardiotoxicity has been reported as a significant side effect associated with GEF treatment. The main purpose of this study was to investigate the potential cardiotoxic effect of GEF and the possible mechanisms involved using in vivo and in vitro rat cardiomyocyte model. Treatment of rat cardiomyocyte H9c2 cell line with GEF (0, 1, 5, and 10μM) caused cardiomyocyte death and upregulation of hypertrophic gene markers, such as brain natriuretic peptides (BNP) and Beta-myosin heavy chain (β-MHC) in a concentration-dependent manner at the mRNA and protein levels associated with an increase in the percentage of hypertrophied cardiac cells. Mechanistically, GEF treatment caused proportional and concentration-dependent increases in the mRNA and protein expression levels of apoptotic markers caspase-3 and p53 which was accompanied with marked increases in the percentage of H9c2 cells underwent apoptosis/necrosis as compared to control. In addition, oxidative stress marker (heme oxygenase-1, HO-1) and the formation of reactive oxygen species were increased in response to GEF treatment. At the in vivo level, treatment of Wistar albino rats for 21days with GEF (20 and 30mg/kg) significantly increased the cardiac enzymes (CK, CKmb, and LDH) levels associated with histopathological changes indicative of cardiotoxicity. Similarly, in vivo GEF treatment increased the mRNA and protein levels of BNP and β-MHC whereas inhibited the antihypertrophoic gene (α-MHC) associated with increased the percentage of hypertrophied cells. Furthermore, the mRNA and protein expression levels of caspase-3, p53, and HO-1 genes and the percentage of apoptotic cells were significantly increased by GEF treatment, which was more pronounced at the 30mg/kg dose. In conclusion, GEF induces cardiotoxicity and cardiac hypertrophy in vivo and in vitro rat model through cardiac apoptotic cell death and oxidative stress pathways.

Anthracycline-Induced Cardiomyopathy in Adults

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

Cardioprotective effects of sitagliptin against doxorubicin-induced cardiotoxicity in rats

There is a large body of evidence suggesting that inhibitors of dipeptidyl peptidase-4, such as sitagliptin, may exhibit beneficial effects against different inflammatory disorders. This investigation was conducted to elucidate the potential ability of sitagliptin to counteract the injurious effects of doxorubicin in cardiac tissue. Male Wistar rats were pretreated with sitagliptin for 10 days then treated with a single dose of doxorubicin (20 mg/kg, i.p). Electrocardiography, biochemical estimation of serum and tissue markers, and histo- and immunopathological examinations were done. Results have shown that supplementation with sitagliptin resulted in significant improvement of cardiac function with contaminant decrease in serum markers of doxorubicin-induced cardiotoxicity. These results were supported by the histopathological results. Furthermore, a marked protection against oxidative stress was evident through reduction of lipid peroxidation and prevention of reduced glutathione content depletion and superoxide dismutase activity reduction in cardiac tissue of rats pretreated with sitagliptin in combination with doxorubicin. Moreover, sitagliptin ameliorated the activation of nuclear factor kappa-B and the release of inflammatory cytokines, tumour necrosis factor-alpha and nitric oxide. Finally, sitagliptin attenuated doxorubicin-induced increase in the expression of pro-apoptotic protein Bax and in the apoptotic marker, caspase-3. Collectively, these data indicate that sitagliptin pretreatment could alleviate doxorubicin-induced cardiotoxicity via reducing oxidative damage and its subsequent inflammation and apoptosis.

Protective effect of Sheng-Mai Yin, a traditional Chinese preparation, against doxorubicin-induced cardiac toxicity in rats

Background

Sheng-Mai Yin (SMY), a modern Chinese formula based on Traditional Chinese Medicine theory, has been used to treat cardiovascular diseases in Eastern Asia. Our study focuses on the cardioprotection of SMY against doxorubicin (DOX)-induced cardiac toxicity in vivo.

Methods

Rats were injected with DOX (2.5 mg/kg) in six injections over a 2-week period. SMY was administrated intragastrically at the dose of 8.35, 16.7 and 33.4 g/kg, or 16.7 g/kg only twice a day concurrently with DOX for the 2-weeks. A series of assays were performed to detect the effects of SMY on: (i) heart weight index (HWI) and left ventricular mass index (LVMI); (ii) cardiac function; (iii) heart tissue morphology; (iv) the contents of carboxy terminal propeptide of procollagen typeI (PICP), amino terminal propeptide of procollagen type III (PШNP), transforming growth factor-β1 (TGF-β1), B-type natriuretic peptide (BNP), monocyte chemoattractant protein-1 (MCP-1), interferon gamma (INF-γ) and interleukin 6 (IL-6) by ELISA; (v) the mRNA levels of TGF-β1 and toll-like receptor-2 (TLR2); and (vi) protein level of TGF-β1.

Results

Rats treated with SMY displayed the reductions of BNP and CK-MB increased by DOX in a dose-dependent manner. Moderate dose of SMY exhibited the correction for the increased HWI, LVMI, and the injured cardiac function, as well as the collagen accumulation. In addition, cardioprotection of SMY against DOX-induced cardiac toxicity was demonstrated by the reduction of myocardial fibrosis, characterized by the suppression of PICP, PШNP and TGF-β1, as well as the anti-inflammation and the regulation for cardiac immune microenvironment, characterized by the inhibition of TLR2, MCP-1, INF-γ and IL-6.

Conclusions

SMY may protect heart function through the restriction of myocardial fibrosis induced by DOX, which suggests the potentially therapeutic effect of SMY on DOX-induced cardiomyopathy.

Saffron extracts alleviate cardiomyocytes injury induced by doxorubicin and ischemia-reperfusion in vitro

Doxorubicin (DOX), a highly active chemotherapeutic drug, faces limitations in clinical application due to severe cardiotoxic effects (mainly through increased oxidative stress). Therefore, its effect is exacerbated in subjects with ischemic heart disease. We have recently reported that saffron extract (SAF), a natural compound mainly consisting of safranal and corcins, exerts a protective effect against DOX oxidative cytotoxicity in isolated rabbit hearts. Here, we aimed to investigate whether SAF exerts cardioprotection against combined ischemia-reperfusion (I/R) and DOX toxicity in H9c2 cardiomyocytes. H9c2 were subjected to simulated I/R, with or without DOX treatment at reperfusion, in the presence or absence of SAF prior to ischemia or at reperfusion. We evaluated the effects of these treatments by MTT, LDH and western blot analysis. Apoptosis was assessed by Hoechst 33258 staining, tetramethyl rhodamine methyl ester fluorescence and caspase activity. The results showed that I/R and DOX significantly decreased cardiomyocytes viability, inhibited reperfusion injury salvage kinase cardioprotective pathway, reduced contractile proteins (α-Actinine, Troponine C and MLC), increased caspase-3 expression and induced loss of mitochondrial membrane potential. These effects were remarkably inhibited by treatment with SAF (10 μg/mL) at reperfusion. SAF activated AKT/P70S6K and ERK1/2, restored contractile proteins expression, inhibited mitochondrial permeability transition pore and decreased caspase-3 activity. In conclusion, our findings indicate that SAF treatment exerted cardioprotection against I/R and DOX toxicity by reducing oxidative stress (LDH assay). Thereby, SAF offers a potential novel antioxidant therapeutic strategy to counteract I/R and DOX cardiotoxicity, paving the way for future clinical trials.

Hypoxia promotes 786-O cells invasiveness and resistance to sorafenib via HIF-2α/COX-2

Accumulating evidences indicated that hypoxia-induced factors and COX-2 play a important role in tumorigenesis in various human cancer. Yet, the relationship between HIFs and COX-2 in human renal cancer remains unclear. The present study was to examine the role of HIFs and COX-2 in the invasiveness and the resistance to target agent in renal cancer cell line (786-O). In 786-O cells, hypoxia induced the increase in the protein expression of HIF1 and HIF2. We also demonstrate that hypoxia up-regulated the protein expression of COX-2 and Snail, but down-regulation of E-cadherin expression in 786-O cells promoted the invasiveness of 786-O cells and enhanced the resistance of 786-O cells to sorafenib. siRNA target to HIF1α, HIF2α and NS398, a selective inhibitor of COX-2, were used in this study. Only siRNA-HIF2α significantly suppressed the protein expression of HIF2 and COX-2, then decreased the invasive ability and resistance of 786-O cells to sorafenib under hypoxia. NS398 attenuated the increase in invasive cells number and the IC50 value of sorafenib induced by hypoxia. In conclusion, our results demonstrated that hypoxia promoted the invasiveness and resistance of 786-O cells to sorafenib via HIF2 and COX-2 and induced the activation of Snail/E-cadherin, suggesting that a signalling mechanism involving HIF2/COX2 modulates invasiveness and resistance to sorafenib in 786-O cells under hypoxia.

Notch-1 mediated cardiac protection following embryonic and induced pluripotent stem cell transplantation in doxorubicin-induced heart failure

Doxorubicin (DOX), an effective chemotherapeutic drug used in the treatment of various cancers, is limited in its clinical applications due to cardiotoxicity. Recent studies suggest that transplanted adult stem cells inhibit DOX-induced cardiotoxicity. However, the effects of transplanted embryonic stem (ES) and induced pluripotent stem (iPS) cells are completely unknown in DOX-induced left ventricular dysfunction following myocardial infarction (MI). In brief, C57BL/6 mice were divided into five groups: Sham, DOX-MI, DOX-MI+cell culture (CC) media, DOX-MI+ES cells, and DOX-MI+iPS cells. Mice were injected with cumulative dose of 12 mg/kg of DOX and 2 weeks later, MI was induced by coronary artery ligation. Following ligation, 5×10⁴ ES or iPS cells were delivered into the peri-infarct region. At day 14 post-MI, echocardiography was performed, mice were sacrificed, and hearts were harvested for further analyses. Our data reveal apoptosis was significantly inhibited in ES and iPS cell transplanted hearts compared with respective controls (DOX-MI+ES: 0.48±0.06% and DOX-MI+iPS: 0.33±0.05% vs. DOX-MI: 1.04±0.07% and DOX-MI+CC: 0.96±0.21%; p<0.05). Furthermore, a significant increase in levels of Notch-1 (p<0.05), Hes1 (p<0.05), and pAkt (p<0.05) were observed whereas a decrease in the levels of PTEN (p<0.05), a negative regulator of Akt, was evident following stem cell transplantation. Moreover, hearts transplanted with stem cells demonstrated decreased vascular and interstitial fibrosis (p<0.05) as well as MMP-9 expression (p<0.01) compared with controls. Additionally, heart function was significantly improved (p<0.05) in both cell-transplanted groups. In conclusion, our data show that transplantation of ES and iPS cells blunt DOX-induced adverse cardiac remodeling, which is associated with improved cardiac function, and these effects are mediated by the Notch pathway.

The role of Nrf2-mediated pathway in cardiac remodeling and heart failure

Heart failure (HF) is frequently the consequence of sustained, abnormal neurohormonal, and mechanical stress and remains a leading cause of death worldwide. The key pathophysiological process leading to HF is cardiac remodeling, a term referring to maladaptation to cardiac stress at the molecular, cellular, tissue, and organ levels. HF and many of the conditions that predispose one to HF are associated with oxidative stress. Increased generation of reactive oxygen species (ROS) in the heart can directly lead to increased necrosis and apoptosis of cardiomyocytes which subsequently induce cardiac remodeling and dysfunction. Nuclear factor-erythroid-2- (NF-E2-) related factor 2 (Nrf2) is a transcription factor that controls the basal and inducible expression of a battery of antioxidant genes and other cytoprotective phase II detoxifying enzymes that are ubiquitously expressed in the cardiovascular system. Emerging evidence has revealed that Nrf2 and its target genes are critical regulators of cardiovascular homeostasis via the suppression of oxidative stress, which is the key player in the development and progression of HF. The purpose of this review is to summarize evidence that activation of Nrf2 enhances endogenous antioxidant defenses and counteracts oxidative stress-associated cardiac remodeling and HF.

The decrease of NAD(P)H:quinone oxidoreductase 1 activity and increase of ROS production by NADPH oxidases are early biomarkers in doxorubicin cardiotoxicity

CONTEXT

Doxorubicin cardiotoxicity displays a complex and multifactorial progression.

OBJECTIVE

Identify early biochemical mechanisms leading to a sustained imbalance of cellular bioenergetics.

METHODS

Measurements of the temporal evolution of selected biochemical markers after treatment of rats with doxorubicin (20 mg/kg body weight).

RESULTS

Doxorubicin treatment increased lipid oxidation, catalase activity and production of H₂O₂ by Nox-NADPH oxidases, and down-regulated

NAD(P)H

quinone oxidoreductase-1 prior eliciting changes in reduced glutathione, protein carbonyls and protein nitrotyrosines. Alterations of mitochondrial and myofibrillar bioenergetics biomarkers were detected only after this oxidative imbalance was established.

CONCLUSIONS

NAD(P)H

quinone oxidoreductase-1 activity and increase of hydrogen peroxide production by NADPH oxidases are early biomarkers in doxorubicin cardiotoxicity.

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

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

The pathological roles of environmental and redox stresses in cardiovascular diseases

Oxidative stress and inflammation are implicated in cardiovascular diseases such as atherosclerosis, reperfusion injury, hypertension, and heart failure. High levels of oxidative stress resulting from increased cardiac generation of reactive oxygen species (ROS) is thought to contribute to contractile and endothelial dysfunction, apoptosis and necrosis of myocytes, and extracellular matrix remodeling in the heart. ROS activate several transcription factors known as redox-regulated transcription factors, and these transcription factors play important roles in the pathophysiology of cardiovascular diseases. This review focuses on the pathological roles of environmental and redox stresses in cardiovascular diseases, especially severe cardiac dysfunction and the transition from compensated hypertrophy to heart failure. The aryl hydrocarbon receptor (AHR) and NF-E2 p45-related factor (Nrf2) are transcription factors involved in the regulation of drug-metabolizing enzymes. AHR has been studied as a receptor for environmental contaminants and as a mediator of chemical toxicity. However, other roles for AHR in cardiac and vascular development have recently been described. Moreover, Nrf2 protects against oxidative stress by increasing the transcription of genes, including those for several antioxidant enzymes. The roles of these transcription factors, AHR and Nrf2 in angiogenesis are also discussed in this review.

Chronic cardiotoxicity of doxorubicin involves activation of myocardial and circulating matrix metalloproteinases in rats

AIM

To investigate the role of matrix metalloproteinases (MMPs) in the responses of rats to a prolonged doxorubicin (DOX) treatment.

METHODS

Male Wistar rats were used. DOX was administered by intraperitoneal injections of seven doses (cumulative dose was 15 mg/kg). Control animals were treated with saline. Tissue or plasma samples were collected at four and eight weeks after the application of the last dose. Protein levels were determined by immunoblot assay, and MMP activities were measured by gelatin zymography. Superoxide content was analyzed using a lucigenin chemiluminescence assay and superoxide dismutase (SOD) activities with a SOD assay kit. Qualitative structural alterations of the heart were characterized by transmission electron microscopy.

RESULTS

Systolic blood pressure was higher in DOX-treated rats as compared with the control rats at 8 weeks after treatment. In contrast, there were no differences in the heart rate between the control and DOX-treated rats. DOX treatment caused marked heterogeneous subcellular alterations of cardiomyocytes and structural disorganizations of the cardiac extracellular space. The effects of DOX were linked to a stimulation of plasma MMP-2 and MMP-9 activities that had already increased by 4 weeks after the end of the treatment. In the left ventricle, however, DOX only led to increased MMP-2 activation at 8 weeks after the end of treatment. These changes in tissue MMP-2 were connected with stimulation of Akt kinase activation, inhibition of SOD, an increase in superoxide levels, induction of iNOS protein expression and caspase-3 activation.

CONCLUSION

Our results show that MMPs are involved in the chronic cardiotoxicity of DOX in rats. The data also suggest that reactive oxygen species (superoxide), NO production (iNOS) and the Akt kinase pathway can modulate MMP-2 activities in rat hearts influenced by DOX.

Berberine sensitizes mutliple human cancer cells to the anticancer effects of doxorubicin in vitro

The clinical use of doxorubicin (DOX), a potent antineoplastic agent, is limited by its serious side-effects, which include acute and chronic cumulative dose-related cardiotoxicity. Berberine (BER), a botanical alkaloid, has been reported to possess cardioprotective and antitumor effects. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-tetrazolium bromide (MTT) assay was used to detect the cell viability of A549, HeLa and HepG2 cells after each cell line was treated with DOX, BER or a combination of DOX and BER for 24 h. Apoptosis was evaluated by acridine orange staining. The results showed that BER and DOX exhibited dose-dependent inhibitory effects on A549 and HeLa cells which were likely mediated by inducing apoptosis. The same result was found in the combination group. Isobologram illustration and combination index (CI) analyses revealed that the combination of DOX and BER generates synergistic effects in A549 (CI=0.61) and HeLa (CI=0.73) cells. These findings indicate that BER sensitizes cells to the anticancer effects of DOX.

β2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways

β-adrenergic receptors (β-ARs) modulate cardiotoxicity/cardioprotection through crosstalk with multiple signaling pathways. We have previously shown that β2-ARs are cardioprotective during exposure to oxidative stress induced by doxorubicin (DOX). DOX cardiotoxicity is mediated in part through a Ca(2+)-dependent opening of the mitochondrial permeability transition (MPT), however the signals linking a cell surface receptor like the β2-AR to regulators of mitochondrial function are not clear. The objective of this study was to assess mechanisms of crosstalk between β2-ARs and mitochondrial cell death pathways. DOX administered to WT mice resulted in no acute mortality, however 85% of β2-/- mice died within 30 min. Several pro- and anti-survival pathways were altered. The pro-survival kinase, εPKC, was decreased by 64% in β2-/- after DOX vs WT (p<0.01); the εPKC activator ψεRACK partially rescued these mice (47% reduction in mortality). Activity of the pro-survival kinase Akt decreased by 76% in β2-/- after DOX vs WT (p<0.01). The α1-antagonist prazosin restored Akt activity to normal and also partially reversed the mortality (45%). Deletion of the β2-AR increased rate of Ca(2+) release by 75% and peak [Ca(2+)](i) by 20% respectively in isolated cardiomyocytes; the Ca(2+) channel blocker verapamil also partially rescued the β2-/- (26%). Mitochondrial architecture was disrupted and complex I and II activities decreased by 40.9% and 34.6% respectively after DOX only in β2-/-. The MPT blocker cyclosporine reduced DOX mortality by 41% and prazosin plus cyclosporine acted synergistically to decrease mortality by 85%. β2-ARs activate pro-survival kinases and attenuate mitochondrial dysfunction during oxidative stress; absence of β2-ARs enhances cardiotoxicity via negative regulation of survival kinases and enhancement of intracellular Ca(2+), thus predisposing the mitochondria to opening of the MPT.

Recent advances in protection against doxorubicin-induced toxicity

Anthracycline antibiotics are among the most effective and commonly used anticancer drugs. Unfortunately, their clinical use is restricted by dose-dependent toxicity. Doxorubicin is an anthracycline antibiotic and cytotoxic (antineoplastic) agent. It is commonly used against ovarian, breast, lung, uterine and cervical cancers, Hodgkin's disease, soft tissue and primary bone sarcomas, as well against in several other cancer types. It has been shown that free radicals are involved in doxorubicin-induced toxicity. Doxorubicin causes the generation of free radicals and the induction of oxidative stress, associated with cellular injury. This review illustrates recent applications of different natural products, drugs, drug delivery systems, and approaches for protection against doxorubicin-induced toxicity (2006-present).

PIKKing on PKB: regulation of PKB activity by phosphorylation

Ser/Thr protein kinase PKB/Akt is a key regulator of a wide range of cellular processes including growth, proliferation and survival. PKB is clearly a crucial signaling molecule and extensive research efforts aim to understand its regulation and action. Recent studies of the regulation of PKB activity by hydrophobic motif phosphorylation have yielded several exciting findings about members of the PI3-kinase-like family of kinases (PIKKs) acting as PKB regulators. Mammalian target of rapamycin complex 2 (mTORC2) and DNA-dependent protein kinase (DNA-PK) can both phosphorylate Ser473 and activate PKB. This present review concerns PKB regulation by mTORC2 and DNA-PK in a stimulus-dependent and context-dependent manner and the possible implications of this for PKB activity, substrate specificity and therapeutic intervention.

Pretreatment with statin attenuates the cardiotoxicity of Doxorubicin in mice

Cardiotoxicity, which may result from intense cardiac oxidative stress and inflammation, is the main limiting factor of the anticancer therapy using doxorubicin. Because statins might exert beneficial pleiotropic cardiovascular effects, among other things, by anti-inflammatory and antioxidative mechanisms, we investigated whether or not fluvastatin pretreatment can attenuate doxorubicin-induced cardiotoxicity. Five days after a single injection of doxorubicin (20 mg/kg; i.p.), left ventricular (LV) function was measured in fluvastatin-treated (DoxStatin; 100 mg/kg/day, p.o.) and saline-treated (doxorubicin) mice (n = 8 per group) by a micro conductance catheter. Untreated mice served as controls (placebo; n = 8 per group). After measurement of cardiac function, LV tissues were analyzed by molecular biological and immunohistologic methods. Injection resulted in significantly impaired LV function (LV pressure, -29%; dp/dtmax, -45%; cardiac output, -68%; P < 0.05) when compared with placebo. This was associated with a significant increase in cardiac oxidative stress, inflammation and apoptotic mechanisms, as indicated by significant increased cardiac lipid peroxidation activity, protein expression of nitrotyrosine, tumor necrosis factor alpha and Bax (P < 0.05). In contrast, DoxStatin mice showed improved LV function (LV pressure, +24%; dp/dtmax, +87%; cardiac output, +87%; P < 0.05) when compared with untreated doxorubicin mice. This was associated with reduced cardiac expression of nitrotyrosine, enhanced expression of the mitochondrial located antioxidative SOD 2, attenuated mitochondrial apoptotic pathways, and reduced cardiac inflammatory response. Statin pretreatment attenuates doxorubicin-induced cardiotoxicity via antioxidative and anti-inflammatory effects.

Heat shock protein 20 interacting with phosphorylated Akt reduces doxorubicin-triggered oxidative stress and cardiotoxicity

Doxorubicin (DOX) is a widely used antitumor drug, but its application is limited because of its cardiotoxic side effects. Heat shock protein (Hsp)20 has been recently shown to protect cardiomyocytes against apoptosis, induced by ischemia/reperfusion injury or by prolonged beta-agonist stimulation. However, it is not clear whether Hsp20 would exert similar protective effects against DOX-induced cardiac injury. Actually, DOX treatment was associated with downregulation of Hsp20 in the heart. To elucidate the role of Hsp20 in DOX-triggered cardiac toxicity, Hsp20 was first overexpressed ex vivo by adenovirus-mediated gene delivery. Increased Hsp20 levels conferred higher resistance to DOX-induced cell death, compared to green fluorescent protein control. Furthermore, cardiac-specific overexpression of Hsp20 in vivo significantly ameliorated acute DOX-triggered cardiomyocyte apoptosis and animal mortality. Hsp20 transgenic mice also showed improved cardiac function and prolonged survival after chronic administration of DOX. The mechanisms underlying these beneficial effects were associated with preserved Akt phosphorylation/activity and attenuation of DOX-induced oxidative stress. Coimmunoprecipitation studies revealed an interaction between Hsp20 and phosphorylated Akt. Accordingly, BAD phosphorylation was preserved, and cleaved caspase-3 was decreased in DOX-treated Hsp20 transgenic hearts, consistent with the antiapoptotic effects of Hsp20. Parallel ex vivo experiments showed that either infection with a dominant-negative Akt adenovirus or preincubation of cardiomyocytes with the phosphatidylinositol 3-kinase inhibitors significantly attenuated the protective effects of Hsp20. Taken together, our findings indicate that overexpression of Hsp20 inhibits DOX-triggered cardiac injury, and these beneficial effects appear to be dependent on Akt activation. Thus, Hsp20 may constitute a new therapeutic target in ameliorating the cardiotoxic effects of DOX treatment in cancer patients.

PKBalpha/Akt1 acts downstream of DNA-PK in the DNA double-strand break response and promotes survival

Protein kinase B (PKB/Akt) is a well-established regulator of several essential cellular processes. Here, we report a route by which activated PKB promotes survival in response to DNA insults in vivo. PKB activation following DNA damage requires 3-phosphoinositide-dependent kinase 1 (PDK1) and DNA-dependent protein kinase (DNA-PK). Active PKB localizes in the nucleus of gamma-irradiated cells adjacent to DNA double-strand breaks, where it colocalizes and interacts with DNA-PK. Levels of active PKB inversely correlate with DNA damage-induced apoptosis. A significant portion of p53- and DNA damage-regulated genes are misregulated in cells lacking PKBalpha. PKBalpha knockout mice show impaired DNA damage-dependent induction of p21 and increased tissue apoptosis after single-dose whole-body irradiation. Our findings place PKB downstream of DNA-PK in the DNA damage response signaling cascade, where it provides a prosurvival signal, in particular by affecting transcriptional p21 regulation. Furthermore, this function is apparently restricted to the PKBalpha isoform.

Toxicological evaluation of thiol-reactive compounds identified using a la assay to detect reactive molecules by nuclear magnetic resonance

We have recently reported on the development of a La assay to detect reactive molecules by nuclear magnetic resonance (ALARM NMR) to detect reactive false positive hits from high-throughput screening, in which we observed a surprisingly large number of compounds that can oxidize or form covalent adducts with protein thiols groups. In the vast majority of these cases, the covalent interactions are largely nonspecific (e.g., affect many protein targets) and therefore unsuitable for drug development. However, certain thiol-reactive species do appear to inhibit the target of interest in a specific manner. The question then arises as to the potential toxicology risks of developing a drug that can react with protein thiol groups. Here, we report on the evaluation of a large set of ALARM-reactive and -nonreactive compounds against a panel of additional proteins (aldehyde dehydrogenase, superoxide dismutase, and three cytochrome P450 enzymes). It was observed that ALARM-reactive compounds have significantly increased risks of interacting with one or more of these enzymes in vitro. Thus, ALARM NMR seems to be a sensitive tool to rapidly identify compounds with an enhanced risk of producing side effects in humans, including alcohol intolerance, the formation of reactive oxygen species, and drug-drug interactions. In conjunction with other toxicology assays, ALARM NMR should be a valuable tool for prioritizing compounds for lead optimization and animal testing.