Doxorubicin induces protein ubiquitination and inhibits proteasome activity during cardiotoxicity

Comprehensive ubiquitome analysis reveals persistent mitochondrial remodeling disruptions from doxorubicin-induced cardiotoxicity in aged CD-1 male mice

Doxorubicin (DOX)-associated cardiotoxicity is characterized by long-term manifestations, whose mechanisms remain incompletely understood, and is exacerbated by various risk factors, with age being a prominent contributor. The objective of this study was to assess the enduring cardiac molecular impacts of DOX in old CD-1 male mice, focusing on ubiquitinated proteins. At 19 months of age, DOX group received a cumulative dose of 9.0 mg/kg of DOX, while control animals got saline solution. Animals were sacrificed 2 months after the administration. DOX induced heart structural changes and increased proteolytic activity. Additionally, increased protein ubiquitination was observed in DOX group, despite the decreased content of the E3 ubiquitin-protein ligase Atrogin-1. A search of poly-ubiquitinated proteins, enriched by tandem ubiquitin-binding entities (TUBEs), showed increased poly-ubiquitination of proteins associated with sarcomere organization and mitochondrial metabolism processes by DOX. Increased mitochondrial density inferred by higher citrate synthase activity was found in DOX group. Moreover, decreased biogenesis and auto(mito)phagy occurred in DOX animals, proven by decreased peroxisome proliferator-activated receptor γ coactivator 1 α, Beclin1 and microtubule-associated protein light chain 3 content. These findings indicate a reduction in mitochondrial biogenesis and accumulation of dysfunctional mitochondria in the aged heart, along with elevated levels of poly-ubiquitinated proteins after DOX treatment. Thus, the disruption of mitochondrial remodeling and impaired protein ubiquitination emerge as enduring consequences of DOX-induced cardiotoxicity, persisting for even 2 months after DOX exposure. This underscores the long-lasting impact of DOX, with significant effects continuing beyond the period of administration, which advocates for longer clinical surveillance.

Doxorubicin or Epirubicin Versus Liposomal Doxorubicin Therapy-Differences in Cardiotoxicity

Doxorubicin (DOX) is an important drug used in the treatment of many malignancies. Unfortunately DOX causes various side effects, with cardiotoxicity being the most characteristic. Risk factors for DOX induced cardiotoxicity (DIC) include cumulative dose of DOX, preexisting cardiovascular diseases, dyslipidemia, diabetes, smoking, along with the use of other cardiotoxic agents. Development of DIC is associated with many pathological phenomena - increased oxidative stress, as well as upregulation of ferroptosis, apoptosis, necrosis, and autophagy. In DIC expression of many microRNAs is also deregulated. In order to avoid cardiotoxicity and still use DOX effectively DOX derivatives such as epirubicin were synthesized. Nowadays a new liposomal form of DOX (L-DOX) appeared as an alternative to conventional treatment with greatly reduced cardiotoxicity. L-DOX can be divided into two groups of substances - pegylated (PLD) with increased solubility and stability, and non-pegylated (NLPD). Many metaanalyses, clinical along with preclinical studies have shown L-DOX treatment is associated with a smaller decrease of left ventricular ejection fraction (LVEF) and other heart functions, but efficacy of this treatment is comparable to the use of convenctional DOX.

Concomitant Administration of Dantrolene is Sufficient to Protect Against Doxorubicin-Induced Cardiomyopathy

Background

Doxorubicin (DOX), a commonly used anticancer agent, can result in cardiac dysfunction, presenting a significant clinical challenge. DOX has been shown to induces Ca2+ leakage via the ryanodine receptor 2 (RYR2) of the sarcoplasmic reticulum, increasing Ca2+ levels in the cytoplasm.

Objectives

This study investigated whether stabilizing RYR2 could suppress DOX-induced cardiomyopathy (DIC) and identified the optimal duration of dantrolene treatment as a pharmacological method.

Methods

We investigated the effects of RYR2 stabilization on DOX cardiotoxicity using in vivo and in vitro experiments.

Results

DOX administration caused calmodulin dissociation, marked Ca2+ leakage from RYR2, and increased oxidative stress in isolated cardiomyocytes. Stabilizing the RYR2 tetramer-either pharmacologically with dantrolene or genetically via RYR2 V3599K mutation, which enhances calmodulin binding affinity-suppressed these effects. In DIC mice models, DOX impaired cardiac function, increased fibrosis and TUNEL-positive cells, reduced GRP78, and elevated lipid peroxide levels, leading to endoplasmic reticulum stress and ferroptosis. Both continuous dantrolene treatment and RYR2 V3599K mutation improved cardiac function. Interestingly, dantrolene administration provided myocardial protection even when terminated 7 days after DOX.

Conclusions

Short-term concomitant use of dantrolene offers a promising and clinically feasible strategy to prevent DIC. Given dantrolene's established clinical safety as a treatment for malignant hyperthermia, these findings suggest potential for repositioning dantrolene in DIC prevention.

Anthracycline-induced cardiotoxicity: An overview from cellular structural perspective

Anthracyclines are broad-spectrum anticancer drugs, but their clinical use is limited due to their severe cardiotoxicity. Anthracycline-induced cardiotoxicity (AIC) remains a significant cause of heart disease-related mortality in many cancer survivors. The underlying mechanisms of AIC have been explored over the past few decades. Reactive oxygen species and drug-induced inhibition of topoisomerase II beta are well-studied mechanisms, with mitochondria being a prominently investigated organelle. Emerging mechanisms such as ferroptosis, Ca2+ overload, autophagy and inflammation mediators have been implicated in recent years. In this review, our goal is to summarize and update the roles of various mechanisms in AIC, focusing on different cellular levels and further explore promising therapeutic approaches targeting these organelles or pathways.

Potential role of endoplasmic reticulum stress in doxorubicin-induced cardiotoxicity-an update

As a chemotherapy agent, doxorubicin is used to combat cancer. However, cardiotoxicity has limited its use. The existing strategies fail to eliminate doxorubicin-induced cardiotoxicity, and an in-depth exploration of its pathogenesis is in urgent need to address the issue. Endoplasmic reticulum stress (ERS) occurs when Endoplasmic Reticulum (ER) dysfunction results in the accumulation of unfolded or misfolded proteins. Adaptive ERS helps regulate protein synthesis to maintain cellular homeostasis, while prolonged ERS stimulation may induce cell apoptosis, leading to dysfunction and damage to tissue and organs. Numerous studies on doxorubicin-induced cardiotoxicity strongly link excessive activation of the ERS to mechanisms including oxidative stress, calcium imbalance, autophagy, ubiquitination, and apoptosis. The researchers also found several clinical drugs, chemical compounds, phytochemicals, and miRNAs inhibited doxorubicin-induced cardiotoxicity by targeting ERS. The present review aims to outline the interactions between ERS and other mechanisms in doxorubicin-induced cardiotoxicity and summarize ERS's role in this type of cardiotoxicity. Additionally, the review enumerates several clinical drugs, phytochemicals, chemical compounds, and miRNAs targeting ERS for considering therapeutic regimens that address doxorubicin-induced cardiotoxicity.

Mechanisms of Cardiovascular Toxicities Induced by Cancer Therapies and Promising Biomarkers for Their Prediction: A Scoping Review

AIM

With the advancement of anti-cancer medicine, cardiovascular toxicities due to cancer therapies are common in oncology patients, resulting in increased mortality and economic burden. Cardiovascular toxicities caused by cancer therapies include different severities of cardiomyopathy, arrhythmia, myocardial ischaemia, hypertension, and thrombosis, which may lead to left ventricular dysfunction and heart failure. This scoping review aimed to summarise the mechanisms of cardiovascular toxicities following various anti-cancer treatments and potential predictive biomarkers for early detection.

METHODS

PubMed, Cochrane, Embase, Web of Science, Scopus, and CINAHL databases were searched for original studies written in English related to the mechanisms of cardiovascular toxicity induced by anti-cancer therapies, including chemotherapy, targeted therapy, immunotherapy, radiation therapy, and relevant biomarkers. The search and title/abstract screening were conducted independently by two reviewers, and the final analysed full texts achieved the consensus of the two reviewers.

RESULTS

A total of 240 studies were identified based on their titles and abstracts. In total, 107 full-text articles were included in the analysis. Cardiomyocyte and endothelial cell apoptosis caused by oxidative stress injury, activation of cell apoptosis, blocking of normal cardiovascular protection signalling pathways, overactivation of immune cells, and myocardial remodelling were the main mechanisms. Promising biomarkers for anti-cancer therapies related to cardiovascular toxicity included placental growth factor, microRNAs, galectin-3, and myeloperoxidase for the early detection of cardiovascular toxicity.

CONCLUSION

Understanding the mechanisms of cardiovascular toxicity following various anti-cancer treatments could provide implications for future personalised treatment methods to protect cardiovascular function. Furthermore, specific early sensitive and stable biomarkers of cardiovascular system damage need to be identified to predict reversible damage to the cardiovascular system and improve the effects of anti-cancer agents.

Hydrogen sulfide alleviates mitochondrial damage and ferroptosis by regulating OPA3-NFS1 axis in doxorubicin-induced cardiotoxicity

Ferroptosis is a major cause of cardiotoxicity induced by doxorubicin (DOX). Previous studies have shown that hydrogen sulfide (H₂S) inhibits ferroptosis in cardiomyocytes and myoblasts, but the underlying mechanism has not been fully elucidated. In this study, we investigated the role of H₂S in protecting against DOX-induced cardiotoxicity both in vivo and in vitro, and elucidated the potential mechanisms involved. We found that DOX downregulated the expression of glutathione peroxidase 4 (GPX4) and NFS1, and upregulated the expression of acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) expression level, resulting in increased lipid peroxidation and ferroptosis. Additionally, DOX inhibited MFN2 expression and increased DRP1 and FIS1 expression, leading to abnormal mitochondrial structure and function. In contrast, exogenous H₂S inhibited DOX-induced ferroptosis by restoring GPX4 and NFS1 expression, and reducing lipid peroxidation in H9C2 cells. This effect was similar to that of the ferroptosis antagonist ferrostatin-1 (Fer-1) in protecting against DOX-induced cardiotoxicity. We further demonstrated that the protective effect of H₂S was mediated by the key mitochondrial membrane protein optic atrophy 3 (OPA3), which was downregulated by DOX and restored by exogenous H₂S. Overexpression of OPA3 alleviated DOX-induced mitochondrial dysfunction and ferroptosis both in vivo and in vitro. Mechanistically, NFS1 has an inhibitory effect on ferroptosis, and NFS1 deficiency increases the susceptibility of cardiomyocytes to ferroptosis. OPA3 is involved in the regulation of ferroptosis by interacting with NFS1. Post-translationally, DOX promoted OPA3 ubiquitination, while exogenous H₂S antagonized OPA3 ubiquitination by promoting OPA3 s-sulfhydration. In summary, our findings suggested that H₂S protects against DOX-induced cardiotoxicity by inhibiting ferroptosis via targeting the OPA3-NFS1 axis. This provides a potential therapeutic strategy for the treatment of DOX-induced cardiotoxicity.

Interleukin-10 Mitigates Doxorubicin-Induced Endoplasmic Reticulum Stress as Well as Cardiomyopathy

The use of doxorubicin (Dox) in cancer patients carries the risk of cardiotoxicity via an increase in oxidative stress, mitochondrial dysfunction, and disturbed endoplasmic reticulum (ER) homeostasis in cardiomyocytes. The present study explores which of the ER transmembrane sensors is involved in Dox-induced apoptosis and whether interleukin-10 (IL-10) has any mitigating effect. There was a time-related increase in apoptosis in cardiomyocytes exposed to 5.43 µg/mL Dox for 0 to 48 h. Dox treatment for 24 h significantly upregulated glucose-regulated proteins 78 and 94, protein disulfide isomerase, cleavage of activating transcription factor 6α, and X-box binding protein 1. These Dox-induced changes in ER stress proteins as well as apoptosis were blunted by IL-10 (10 ng/mL). In Dox-exposed cardiomyocytes, IL-10 also promoted expression of protein kinase-like endoplasmic reticulum kinase and inositol-requiring kinase 1α, which helped in maintaining ER homeostasis. Additionally, under Dox-treatment, IL-10 downregulated caspase-12 activation as well as phosphorylation of c-JUN NH2-terminal kinase, thereby promoting cardiomyocyte survival. IL-10 was able to reduce the overexpression of mitochondrial apoptotic proteins caspase-3 as well as Bax, which were upregulated upon Dox treatment. Thus, a reduction in Dox-induced ER stress as well as apoptosis through IL-10 may provide a significant benefit in improving cardiac function.

Clarifying the pharmacological mechanisms of action of Shenfu Decoction on cardiovascular diseases using a network pharmacology approach

Since the molecular mechanisms underlying in the pathogenesis of cardiovascular diseases (CVD) are extremely complex and have not yet been elucidated in detail, CVD remain the leading cause of death worldwide. Traditional Chinese medicine involves the treatment of disease from an overall perspective, and its therapeutic effects on CVD have been demonstrated. However, the mechanisms contributing to the multiscale treatment of cardiovascular diseases at the systematic level remain unclear. Network pharmacology methods and a gene chip data analysis were integrated and applied in the present study, which was conducted to investigate the potential target genes and related pathways of Shenfu Decoction (SFD) for the treatment of myocardial injury. The gene chip analysis was initially performed, followed by network pharmacology to identify differentially expressed genes (DEG) and a functional enrichment analysis. Protein-protein networks were constructed and a module analysis was conducted. A network analysis was used to identify the target genes of SFD. Regarding the results obtained, 1134 DEG were identified using the STRING website. The module analysis revealed that nine hub genes exhibited ubiquitin-protein ligase activity. Therefore, SFD significantly alters the expression of ubiquitination-related genes and, thus, plays an important therapeutic role in the treatment of heart failure. In conclusion, hub genes may provide a more detailed understanding of the molecular mechanisms of action of as well as candidate targets for SFD therapy.

Transduction catalysis: Doxorubicin amplifies rAAV-mediated gene expression in the cortex of higher-order vertebrates

Rapid and efficient gene transduction via recombinant adeno-associated viruses (rAAVs) is highly desirable across many basic and clinical research domains. Here, we report that vector co-infusion with doxorubicin, a clinical anti-cancer drug, markedly enhanced rAAV-mediated transgene expression in the cerebral cortex across mammalian species (cat, mouse, and macaque), acting throughout the time period examined and detectable at just three days after transfection. This enhancement showed serotype generality, being common to all rAAV serotypes tested (2, 8, 9, and PHP.eB) and was observed both locally and at remote locations consistent with doxorubicin undergoing retrograde axonal transport. All these effects were observed at doses matching human blood plasma levels in clinical therapy and lacked detectable cytotoxicity as assessed by cell morphology, activity, apoptosis, and behavioral testing. Altogether, this study identifies an effective means to improve the capability and scope of in vivo rAAV applications, amplifying cell transduction at doxorubicin concentrations paralleling medical practice.

Possible Susceptibility Genes for Intervention against Chemotherapy-Induced Cardiotoxicity

Recent therapeutic advances have significantly improved the short- and long-term survival rates in patients with heart disease and cancer. Survival in cancer patients may, however, be accompanied by disadvantages, namely, increased rates of cardiovascular events. Chemotherapy-related cardiac dysfunction is an important side effect of anticancer therapy. While advances in cancer treatment have increased patient survival, treatments are associated with cardiovascular complications, including heart failure (HF), arrhythmias, cardiac ischemia, valve disease, pericarditis, and fibrosis of the pericardium and myocardium. The molecular mechanisms of cardiotoxicity caused by cancer treatment have not yet been elucidated, and they may be both varied and complex. By identifying the functional genetic variations responsible for this toxicity, we may be able to improve our understanding of the potential mechanisms and pathways of treatment, paving the way for the development of new therapies to target these toxicities. Data from studies on genetic defects and pharmacological interventions have suggested that many molecules, primarily those regulating oxidative stress, inflammation, autophagy, apoptosis, and metabolism, contribute to the pathogenesis of cardiotoxicity induced by cancer treatment. Here, we review the progress of genetic research in illuminating the molecular mechanisms of cancer treatment-mediated cardiotoxicity and provide insights for the research and development of new therapies to treat or even prevent cardiotoxicity in patients undergoing cancer treatment. The current evidence is not clear about the role of pharmacogenomic screening of susceptible genes. Further studies need to done in chemotherapy-induced cardiotoxicity.

Tetrazolium reduction assays under-report cell death provoked by clinically relevant concentrations of proteasome inhibitors

High throughput cell viability screening assays often capitalize on the ability of active enzymes or molecules within viable cells to catalyze a quantifiable chemical reaction. The tetrazolium reduction (MTT) assay relies on oxidoreductases to reduce tetrazolium into purple formazan crystals that are solubilized so absorbance reflects viability, while other assays use cellular ATP to catalyze a luminescence-emitting reaction. It is therefore important to know how accurately these assays report cellular responses, as cytotoxic anti-cancer agents promote cell death via a variety of signaling pathways, some of which may alter how these assays work. In this study, we compared the magnitude of cytotoxicity to different cell types provoked by currently used anti-cancer agents, using three different cell viability assays. We found the three assays were consistent in reporting the viability of cells treated with chemotherapy drugs or the BH3 mimetic navitoclax, but the MTT assay underreported the killing capacity of proteasome inhibitors. Additionally, the MTT assay failed to confirm the induction of caspase-mediated cell death by bortezomib at physiologically relevant concentrations, thereby mischaracterizing the mode of cell death. While the cell viability assays used allow for the rapid identification of novel cytotoxic compounds, our study emphasizes the importance for these screening assays to be complemented with a direct measure of cell death or another independent measure of cell viability. We caution researchers against using MTT assays for monitoring cytotoxicity induced by proteasome inhibitors.

Inhibition of CACNA1H attenuates doxorubicin-induced acute cardiotoxicity by affecting endoplasmic reticulum stress

BACKGROUND

Doxorubicin (DOX) is an anticancer drug that has been widely used in the clinic. However, recently its application has been limited due to the cardiotoxic effects it has caused. Severe cardiotoxicity of DOX causes cardiac hypertrophy that may lead to heart failure. It has previously been demonstrated that CACNA1H is re-expressed in hypertrophic cardiomyocytes. In this study, we aimed to investigate the role of CACNA1H in DOX-induced acute cardiotoxicity, and to investigate its possible underlying mechanisms of action involved.

METHODS

Firstly, DOX-induced cardiac injury and changes in the expression of CACNA1H were evaluated. We explored the role of endoplasmic reticulum (ER) stress and apoptosis in mice that underwent DOX-induced cardiac injury. Next, to explore the role of CACNA1H in this process, we evaluated the changes in DOX-induced cardiac injury and ER stress after treatment with the CACNA1H specific inhibitor ABT-639. Next, we used ER stress inhibitor UR906 to verify the role of ER stress in DOX induced cardiotoxicity in H9C2 cells.

RESULTS

DOX-treatment caused acute heart injury, leading to a decrease in cardiac function in mice, an increase in apoptosis of cardiac myocytes, and a significant increase in the expression level of CACNA1H in heart tissue. Next, mice were treated with CACNA1H inhibitor ABT-639 and we demonstrated that it partly protects myocardial function and reduces myocardial cell apoptosis. In addition, our data indicated that CACNA1H may play a role in alleviating DOX-induced cardiotoxicity by reducing the severity of ER stress because the use of ABT-639 significantly changed ER stress-related proteins, including p-PERK, PERK, CHOP, GRP78, ATF6, and ATF4. Furthermore, we found that the use of ER stress inhibitor UR906 in H9C2 cells significantly alleviated the increased expression of ER stress related proteins and apoptosis related proteins caused by DOX, and meanwhile reduced the degree of intracellular oxidative stress and intracellular calcium ion concentration.

CONCLUSION

CACNA1H inhibitors significantly alleviated DOX-induced cardiotoxicity and apoptosis induced by ER stress.

Early myocardial changes induced by doxorubicin in the nonfailing dilated ventricle

Several studies have demonstrated that administration of doxorubicin (DOXO) results in cardiotoxicity, which eventually progresses to dilated cardiomyopathy. The present work aimed to evaluate the early myocardial changes of DOXO-induced cardiotoxicity. Male New Zealand White rabbits were injected intravenously with DOXO twice weekly for 8 wk [DOXO-induced heart failure (DOXO-HF)] or with an equivolumetric dose of saline (control). Echocardiographic evaluation was performed, and myocardial samples were collected to evaluate myocardial cellular and molecular modifications. The DOXO-HF group presented cardiac hypertrophy and higher left ventricular cavity diameters, showing a dilated phenotype but preserved ejection fraction. Concerning cardiomyocyte function, the DOXO-HF group presented a trend toward increased active tension without significant differences in passive tension. The myocardial GSSG-to-GSH ratio and interstitial fibrosis were increased and Bax-to- Bcl-2 ratio presented a trend toward an increase, suggesting the activation of apoptosis signaling pathways. The macromolecule titin shifted toward the more compliant isoform (N2BA), whereas the stiffer one (N2B) was shown to be hypophosphorylated. Differential protein analysis from the aggregate-enriched fraction through gel liquid chromatography-tandem mass spectrometry revealed an increase in the histidine-rich glycoprotein fragment in DOXO-HF animals. This work describes novel and early myocardial effects of DOXO-induced cardiotoxicity. Thus, tracking these changes appears to be of extreme relevance for the early detection of cardiac damage (as soon as ventricular dilation becomes evident) before irreversible cardiac function deterioration occurs (reduced ejection fraction). Moreover, it allows for the adjustment of the therapeutic approach and thus the prevention of cardiomyopathy progression.

NEW & NOTEWORTHY Identification of early myocardial effects of doxorubicin in the heart is essential to hinder the development of cardiac complications and adjust the therapeutic approach. This study describes doxorubicin-induced cellular and molecular modifications before the onset of dilated cardiomyopathy. Myocardial samples from doxorubicin-treated rabbits showed a tendency for higher cardiomyocyte active tension, titin isoform shift from N2B to N2BA, hypophosphorylation of N2B, increased apoptotic genes, left ventricular interstitial fibrosis, and increased aggregation of histidine-rich glycoprotein.

Autophagy and mitophagy in the context of doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) is a cytotoxic drug widely incorporated in various chemotherapy protocols. Severe side effects such as cardiotoxicity, however, limit Dox application. Mechanisms by which Dox promotes cardiac damage and cardiomyocyte cell death have been investigated extensively, but a definitive picture has yet to emerge. Autophagy, regarded generally as a protective mechanism that maintains cell viability by recycling unwanted and damaged cellular constituents, is nevertheless subject to dysregulation having detrimental effects for the cell. Autophagic cell death has been described, and has been proposed to contribute to Dox-cardiotoxicity. Additionally, mitophagy, autophagic removal of damaged mitochondria, is affected by Dox in a manner contributing to toxicity. Here we will review Dox-induced cardiotoxicity and cell death in the broad context of the autophagy and mitophagy processes.

Peroxisomes contribute to oxidative stress in neurons during doxorubicin-based chemotherapy

Doxorubicin, a commonly used anti-neoplastic agent, causes severe neurotoxicity. Doxorubicin promotes thinning of the brain cortex and accelerates brain aging, leading to cognitive impairment. Oxidative stress induced by doxorubicin contributes to cellular damage. In addition to mitochondria, peroxisomes also generate reactive oxygen species (ROS) and promote cell senescence. Here, we investigated if doxorubicin affects peroxisomal homeostasis in neurons. We demonstrate that the number of peroxisomes is increased in doxorubicin-treated neurons and in the brains of mice which underwent doxorubicin-based chemotherapy. Pexophagy, the specific autophagy of peroxisomes, is downregulated in neurons, and peroxisomes produce more ROS. 2-hydroxypropyl-β-cyclodextrin (HPβCD), an activator of the transcription factor TFEB, which regulates expression of genes involved in autophagy and lysosome function, mitigates damage of pexophagy and decreases ROS production induced by doxorubicin. We conclude that peroxisome-associated oxidative stress induced by doxorubicin may contribute to neurotoxicity, cognitive dysfunction, and accelerated brain aging in cancer patients and survivors. Peroxisomes might be a valuable new target for mitigating neuronal damage caused by chemotherapy drugs and for slowing down brain aging in general.

TFEB ameliorates the impairment of the autophagy-lysosome pathway in neurons induced by doxorubicin

Doxorubicin, a commonly used chemotherapy agent, induces severe cardio- and neurotoxicity. Molecular mechanisms of cardiotoxicity have been extensively studied, but mechanisms by which doxorubicin exhibits its neurotoxic properties remain unclear. Here, we show that doxorubicin impairs neuronal autophagy, leading to the accumulation of an autophagy substrate p62. Neurons treated with doxorubicin contained autophagosomes, damaged mitochondria, and lipid droplets. The brains from mice treated with pegylated liposomal doxorubicin exhibited autophagosomes, often with mitochondria, lipofuscin, and lipid droplets. Interestingly, lysosomes were less acidic in doxorubicin-treated neurons. Overexpression of the transcription factor EB (TFEB), which controls the autophagy-lysosome axis, increased survival of doxorubicin-treated neurons. 2-Hydroxypropyl-β-cyclodextrin (HPβCD), an activator of TFEB, also promoted neuronal survival, decreased the levels of p62, and lowered the pH in lysosomes. Taken together, substantial changes induced by doxorubicin contribute to neurotoxicity, cognitive disturbances in cancer patients and survivors, and accelerated brain aging. The TFEB pathway might be a new approach for mitigating damage of neuronal autophagy caused by doxorubicin.

Signalling mechanisms underlying doxorubicin and Nox2 NADPH oxidase-induced cardiomyopathy: involvement of mitofusin-2

BACKGROUND AND PURPOSE

The anthracycline doxorubicin (DOX), although successful as a first-line cancer treatment, induces cardiotoxicity linked with increased production of myocardial ROS, with Nox2 NADPH oxidase-derived superoxide reported to play a key role. The aim of this study was to identify novel mechanisms underlying development of cardiac remodelling/dysfunction further to DOX-stimulated Nox2 activation.

EXPERIMENTAL APPROACH

Nox2-/- and wild-type (WT) littermate mice were administered DOX (12 mg·kg-1 over 3 weeks) prior to study at 4 weeks. Detailed mechanisms were investigated in murine HL-1 cardiomyocytes, employing a robust model of oxidative stress, gene silencing and pharmacological tools.

KEY RESULTS

DOX-induced cardiac dysfunction, cardiomyocyte remodelling, superoxide production and apoptosis in WT mice were attenuated in Nox2-/- mice. Transcriptional analysis of left ventricular tissue identified 152 differentially regulated genes (using adjusted P < 0.1) in DOX-treated Nox2-/- versus WT mice, and network analysis highlighted 'Cell death and survival' as the biological function most significant to the dataset. The mitochondrial membrane protein, mitofusin-2 (Mfn2), appeared as a strong candidate, with increased expression (1.5-fold), confirmed by qPCR (1.3-fold), matching clear published evidence of promotion of cardiomyocyte cell death. In HL-1 cardiomyocytes, targeted siRNA knockdown of Nox2 decreased Mfn2 protein expression, but not vice versa. While inhibition of Nox2 activity along with DOX treatment attenuated its apoptotic and cytotoxic effects, reduced apoptosis after Mfn2 silencing reflected a sustained cytotoxic response and reduced cell viability.

CONCLUSIONS AND IMPLICATIONS

DOX-induced and Nox2-mediated up-regulation of Mfn2, rather than contributing to cardiomyocyte dysfunction through apoptotic pathways, appears to promote a protective mechanism.

LINKED ARTICLES

This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Extracellular Vesicles Released by Cardiomyocytes in a Doxorubicin-Induced Cardiac Injury Mouse Model Contain Protein Biomarkers of Early Cardiac Injury

Purpose: Cardiac injury is a major cause of death in cancer survivors, and biomarkers for it are detectable only after tissue injury has occurred. Extracellular vesicles (EV) remove toxic biomolecules from tissues and can be detected in the blood. Here, we evaluate the potential of using circulating EVs as early diagnostic markers for long-term cardiac injury.Experimental Design: Using a mouse model of doxorubicin (DOX)-induced cardiac injury, we quantified serum EVs, analyzed proteomes, measured oxidized protein levels in serum EVs released after DOX treatment, and investigated the alteration of EV content.Results: Treatment with DOX caused a significant increase in circulating EVs (DOX_EV) compared with saline-treated controls. DOX_EVs exhibited a higher level of 4-hydroxynonenal adducted proteins, a lipid peroxidation product linked to DOX-induced cardiotoxicity. Proteomic profiling of DOX_EVs revealed the distinctive presence of brain/heart, muscle, and liver isoforms of glycogen phosphorylase (GP), and their origins were verified to be heart, skeletal muscle, and liver, respectively. The presence of brain/heart GP (PYGB) in DOX_EVs correlated with a reduction of PYGB in heart, but not brain tissues. Manganese superoxide dismutase (MnSOD) overexpression, as well as pretreatment with cardioprotective agents and MnSOD mimetics, resulted in a reduction of EV-associated PYGB in mice treated with DOX. Kinetic studies indicated that EVs containing PYGB were released prior to the rise of cardiac troponin in the blood after DOX treatment, suggesting that PYGB is an early indicator of cardiac injury.Conclusions: EVs containing PYGB are an early and sensitive biomarker of cardiac injury. Clin Cancer Res; 24(7); 1644-53. ©2017 AACRSee related commentary by Zhu and Gius, p. 1516.

Chemotherapy-Induced Tissue Injury: An Insight into the Role of Extracellular Vesicles-Mediated Oxidative Stress Responses

The short- and long-term side effects of chemotherapy limit the maximum therapeutic dose and impair quality of life of survivors. Injury to normal tissues, especially chemotherapy-induced cardiomyopathy, is an unintended outcome that presents devastating health impacts. Approximately half of the drugs approved by the Food and Drug Administration for cancer treatment are associated with the generation of reactive oxygen species, and Doxorubicin (Dox) is one of them. Dox undergoes redox cycling by involving its quinone structure in the production of superoxide free radicals, which are thought to be instrumental to the role it plays in cardiomyopathy. Dox-induced protein oxidation changes protein function, translocation, and aggregation that are toxic to cells. To maintain cellular homeostasis, oxidized proteins can be degraded intracellularly by ubiquitin-proteasome pathway or by autophagy, depending on the redox status of the cell. Alternatively, the cell can remove oxidized proteins by releasing extracellular vesicles (EVs), which can be transferred to neighboring or distant cells, thereby instigating an intercellular oxidative stress response. In this article, we discuss the role of EVs in oxidative stress response, the potential of EVs as sensitive biomarkers of oxidative stress, and the role of superoxide dismutase in attenuating EV-associated oxidative stress response resulting from chemotherapy.

Salvianolic acid B attenuates doxorubicin-induced ER stress by inhibiting TRPC3 and TRPC6 mediated Ca2+ overload in rat cardiomyocytes

Doxorubicin (DOX)-induced cardiotoxicity is a clinically complex syndrome that leads to significant pain to cancer survivors. Endoplasmic reticulum (ER) stress has been suggested to be an important contributor to myocardium dysfunction during this phenomenon. Our previous study proved that Salvianolic acid B (Sal B) protected against doxorubicin induced cardiac dysfunction by inhibiting ER stress and cardiomyocyte apoptosis. However, the underlying molecular mechanism is not yet clearly. In this study, we investigated the protective effect and mechanisms of Sal B againest DOX-induced cardiac injury and ER stress in vivo and in vitro. After pretreatment with Sal B (0.25, 0.5, 1mg/kg i.v.) for 7 days, male SD rats were intraperitoneally injected with a single dose of DOX (3mg/kg) every 2 days for three injections. The cardioprotective effect of Sal B was observed 2 weeks after the first administration. Adult rat ventricular myocytes were isolated and treated with Sal B (20μg/ml) for 6h and then exposed in DOX (1μm) for 4h. The cardiomyocyte contractility and the level of intracellular Ca²⁺ were determined. Sal B ameliorated DOX-induced apoptosis damage in heart tissues. In vitro studies showed that DOX induced adult rat ventricular myocytes contractile dysfunction and intracellular Ca²⁺ handling derangement, disrupted mitochondrial membrane potential, raised the level of ER stress related proteins. However, Sal B pretreatment suppressed all of these adverse effects of DOX. The effects of Sal B were closely related to the inhibition of transient receptor potential canonical (TRPC) channels, as characterized by inhibiting the expression of TRPC 3 and TRPC6. These results indicate that Sal B protects against DOX-induced cardiac apoptosis and ER stress via TRPC3 and TRPC6 inhibition.

Cardiac Atrophy and Heart Failure In Cancer

Functional changes in the heart in patients with cancer can be a result of both the disease itself and various cancer therapies, and limiting cardiac damage has become an increasingly important issue as survival rates in patients with cancer have improved. Processes involved in cancer-induced cardiac atrophy may include cardiomyocyte atrophy and apoptosis, decreased protein synthesis, increased autophagy and proteolysis via the ubiquitin-proteosome system. Further to direct effects of malignancy on the heart, several chemotherapeutic agents are known to affect the myocardium, in particular the anthracyclines. The aim of this report is to review the effects of cancer and cancer treatment on the heart and what is known about the underlying mechanisms. Furthermore, clinical strategies to limit and treat cancer-associated cardiac atrophy are discussed, emphasising the benefit of a multidisciplinary approach by cardiologists and oncologists to optimise models of care to improve outcomes for patients with cancer.

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.

Doxorubicin impairs cardiomyocyte viability by suppressing transcription factor EB expression and disrupting autophagy

Doxorubicin (DOX) is an effective anti-cancer agent. However, DOX treatment increases patient susceptibility to dilated cardiomyopathy. DOX predisposes cardiomyocytes to insult by suppressing mitochondrial energy metabolism, altering calcium flux, and disrupting proteolysis and proteostasis. Prior studies have assessed the role of macroautophagy in DOX cardiotoxicity; however, limited studies have examined whether DOX mediates cardiac injury through dysfunctions in inter- and/or intra-lysosomal signaling events. Lysosomal signaling and function is governed by transcription factor EB (TFEB). In the present study, we hypothesized that DOX caused myocyte injury by impairing lysosomal function and signaling through negative regulation of TFEB. Indeed, we found that DOX repressed cellular TFEB expression, which was associated with impaired cathepsin proteolytic activity across in vivo, ex vivo, and in vitro models of DOX cardiotoxicity. Furthermore, we observed that loss of TFEB was associated with reduction in macroautophagy protein expression, inhibition of autophagic flux, impairments in lysosomal cathepsin B activity, and activation of cell death. Restoration and/or activation of TFEB in DOX-treated cardiomyocytes prevented DOX-induced suppression of cathepsin B activity, reduced DOX-mediated reactive oxygen species (ROS) overproduction, attenuated activation of caspase-3, and improved cellular viability. Collectively, loss of TFEB inhibits lysosomal autophagy, rendering cardiomyocytes susceptible to DOX-induced proteotoxicity and injury. Our data reveal a novel mechanism wherein DOX primes cardiomyocytes for cell death by depleting cellular TFEB.

Bcl-2 confers survival in cisplatin treated cervical cancer cells: circumventing cisplatin dose-dependent toxicity and resistance

Background

Cisplatin is the main chemotherapeutic drug for the treatment of cervical cancers, however resistance to cisplatin is increasingly common and therefore has limited the efficacy and use of this drug in the clinic. Dose-dependent toxicity poses an additional challenge since patients suffer long-term and often permanent side-effects after treatment. Bcl-2 up-regulation has been implicated in the resistance to cisplatin in a variety of cancer cell lines, however its role in cervical cancer is confounding.

Methods

A low, non-cytotoxic concentration of cisplatin was used in the treatment of HeLa and CaSki cells. Bcl-2 expression was determined through Western blotting and immunocytochemistry before and after treatment with cisplatin. To assess the reliance of the cervical cancer cells on Bcl-2 in the presence of cisplatin, Bcl-2 knock-down was achieved through RNA interference, where after apoptosis was assessed through PARP cleavage (Western blotting), Caspase activity (Caspase-Glo^©) and PI inclusion analysis (Flow cytometry). Finally, pre-malignant and malignant cervical tissue was analysed for the presence of Bcl-2 through Western blotting and immunofluorescence.

Results

Cervical cancer cells upregulate Bcl-2 when treated with a non-cytotoxic concentration of cisplatin, which when silenced, effectively enhanced cisplatin sensitivity, and therefore significantly induced apoptosis. Analysis of the expression profile of Bcl-2 in cervical tissue revealed its up-regulation in cervical carcinoma, which agrees with results obtained from the in vitro data.

Conclusions

Our data strongly suggest that utilising a lower dose of cisplatin is feasible when combined with Bcl-2 silencing as an adjuvant treatment, thereby improving both the dose-dependent toxicity, as well as cervical cancer resistance.

Acute Treatment of Resveratrol Alleviates Doxorubicin-Induced Myotoxicity in Aged Skeletal Muscle Through SIRT1-Dependent Mechanisms

Study of the exacerbating effects of chemotherapeutics, such as doxorubicin, on the impairment of insulin metabolic signaling in aged skeletal muscle is very limited. Here, we tested the hypothesis that activation of sirtuin 1 deacetylase activity by resveratrol would prevent the disruption of insulin signaling and augmentation of catabolic markers induced by doxorubicin in aged skeletal muscle. Two- and 10-month-old senescence-accelerated mice (prone 8) were randomized to receive saline, doxorubicin, doxorubicin and resveratrol, or a combination of doxorubicin, resveratrol, and sirtinol or EX527. Doxorubicin reduced the sirtuin 1 activity without affecting the phosphorylation levels of IRS1(Ser307), mTOR(Ser2481), Akt(Thr308/Ser473), membranous glucose transporter 4, protein abundance of PDK4, and enzymatic activity of pyruvate dehydrogenase in aged muscles. Intriguingly, resveratrol attenuated the doxorubicin-induced elevations of apoptotic and catabolic markers measured as Bax, caspase 3 activity, apoptotic DNA fragmentation, MuRF-1, ubiquitinated proteins, and proteasomal activity in aged muscles, whereas these beneficial effects were abolished on inhibition of sirtuin 1 by sirtinol or EX527. Markers of insulin signaling were not affected by doxorubicin or resveratrol in the senescent skeletal muscle. Nevertheless, the antiapoptotic and anticatabolic effects of resveratrol in aged skeletal muscle treated with doxorubicin were mediated in a sirtuin 1-dependent signaling manner.

The role of frataxin in doxorubicin-mediated cardiac hypertrophy

Doxorubicin (DOX) is a highly effective anti-neoplastic agent; however, its cumulative dosing schedules are clinically limited by the development of cardiotoxicity. Previous studies have attributed the cause of DOX-mediated cardiotoxicity to mitochondrial iron accumulation and the ensuing reactive oxygen species (ROS) formation. The present study investigates the role of frataxin (FXN), a mitochondrial iron-sulfur biogenesis protein, and its role in development of DOX-mediated mitochondrial dysfunction. Athymic mice treated with DOX (5 mg/kg, 1 dose/wk with treatments, followed by 2-wk recovery) displayed left ventricular hypertrophy, as observed by impaired cardiac hemodynamic performance parameters. Furthermore, we also observed significant reduction in FXN expression in DOX-treated animals and H9C2 cardiomyoblast cell lines, resulting in increased mitochondrial iron accumulation and the ensuing ROS formation. This observation was paralleled in DOX-treated H9C2 cells by a significant reduction in the mitochondrial bioenergetics, as observed by the reduction of myocardial energy regulation. Surprisingly, similar results were observed in our FXN knockdown stable cell lines constructed by lentiviral technology using short hairpin RNA. To better understand the cardioprotective role of FXN against DOX, we constructed FXN overexpressing cardiomyoblasts, which displayed cardioprotection against mitochondrial iron accumulation, ROS formation, and reduction of mitochondrial bioenergetics. Lastly, our FXN overexpressing cardiomyoblasts were protected from DOX-mediated cardiac hypertrophy. Together, our findings reveal novel insights into the development of DOX-mediated cardiomyopathy.

Resveratrol prevents doxorubicin-induced cardiotoxicity in H9c2 cells through the inhibition of endoplasmic reticulum stress and the activation of the Sirt1 pathway

Treatment with doxorubicin (DOX) is one of the major causes of chemotherapy-induced cardiotoxicity and is therefore, the principal limiting factor in the effectiveness of chemotherapy for cancer patients. DOX‑induced heart failure is thought to result from endoplasmic reticulum (ER) stress and cardiomyocyte apoptosis. Resveratrol (RV), a polyphenol antioxidant found in red wine, has been shown to play a cardioprotective role. The aim of the present study was to examine the effects of RV on DOX‑induced cardiotoxicity in H9c2 cells. We hypothesized that RV would protect H9c2 cells against DOX‑induced ER stress and subsequent cell death through the activation of the Sirt1 pathway. Our results demonstrated that the decrease observed in the viability of the H9c2 cells following exposure to DOX was accompanied by a significant increase in the expression of the ER stress‑related proteins, glucose‑regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). However, we found that RV downregulated the expression of ER stress marker protein in the presence of DOX and restored the viability of the H9c2 cells. Exposure to RV or DOX alone only slightly increased the protein expression of Sirt1, whereas a significant increase in Sirt1 protein levels was observed in the cells treated with both RV and DOX. The Sirt1 inhibitor, nicotinamide (NIC), partially neutralized the effects of RV on the expression of Sirt1 in the DOX‑treated cells and completely abolished the effects of RV on the expression of GRP78 and CHOP. The findings of our study suggest that RV protects H9c2 cells against DOX‑induced ER stress through ER stabilization, and more specifically through the activation of the Sirt1 pathway, thereby leading to cardiac cell survival.

Resveratrol protects against doxorubicin-induced cardiotoxicity in aged hearts through the SIRT1-USP7 axis

KEY POINTS

Doxorubicin induced functional deteriorations and elevations of USP7-related apoptotic/catabolic signalling in the senescent heart Resveratrol protects against doxorubicin-induced alterations through the restoration of SIRT1 deacetylase activity

ABSTRACT

A compromised cardiac function is often seen in elderly cancer patients receiving doxorubicin therapy. The present study tested the hypothesis that acute intervention with resveratrol, a natural anti-oxidant found in grapes and red wine, reduces the cardiotoxicity of doxorubicin through restoration of sirtuin 1 (SIRT1) deacetylase activity, and attenuation of the catabolic/apoptotic pathways orchestrated by USP7, a p53 deubiquitinating protein, using young (aged 2 months) and old (aged 10 months) senescence-accelerated mice prone 8 (SAMP8). Animals were randomised to receive saline, doxorubicin, and doxorubicin in combination with resveratrol, in the presence or absence of SIRT1 inhibitors, sirtinol or EX527. Resveratrol alone, but not in combination with either of the SIRT1 inhibitors, suppressed the doxorubicin-induced impairment of cardiac systolic function in aged animals. Doxorubicin reduced SIRT1 deacetylase activity, and elevated proteasomal activity and USP7; it also increased the protein level of p300 and ubiquitinated proteins in hearts from aged SAMP8. These doxorubicin-induced alterations were prevented by resveratrol, whereas the protective action of resveratrol was antagonised by sirtinol and EX527. In young SAMP8 hearts, resveratrol attenuated the doxorubicin-induced increases in acetylation of Foxo1 and transactivation of MuRF-1, whereas these mitigations were not found after treatment with SIRT1 inhibitors. However, the protein contents of acetylated Foxo1 and MuRF-1 were not affected by any of the drugs studied in aged SAMP8 hearts. Resveratrol also ameliorated the augmentation of pro-apoptotic markers including p53, Bax, caspase 3 activity and apoptotic DNA fragmentation induced by doxorubicin in hearts from aged animals, whereas these reductions were diminished by combined treatment with SIRT1 inhibitors. These data demonstrate that resveratrol ameliorates doxorubicin-induced cardiotoxicity in aged hearts through the restoration of SIRT1 activity to attenuate USP7-related catabolic/pro-apoptotic signalling.

Nrf2 deficiency exaggerates doxorubicin-induced cardiotoxicity and cardiac dysfunction

The anticancer therapy of doxorubicin (Dox) has been limited by its acute and chronic cardiotoxicity. In addition to a causative role of oxidative stress, autophagy appears to play an important role in the regulation of Dox-induced cardiotoxicity. However, the underlying mechanisms remain unclear. Accordingly, we explored a role of nuclear factor erythroid-2 related factor 2 (Nrf2) in Dox-induced cardiomyopathy with a focus on myocardial oxidative stress and autophagic activity. In wild type (WT) mice, a single intraperitoneal injection of 25 mg/kg Dox rapidly induced cardiomyocyte necrosis and cardiac dysfunction, which were associated with oxidative stress, impaired autophagy, and accumulated polyubiquitinated protein aggregates. However, these Dox-induced adverse effects were exaggerated in Nrf2 knockout (Nrf2(-/-)) mice. In cultured cardiomyocytes, overexpression of Nrf2 increased the steady levels of LC3-II, ameliorated Dox-induced impairment of autophagic flux and accumulation of ubiquitinated protein aggregates, and suppressed Dox-induced cytotoxicity, whereas knockdown of Nrf2 exerted opposite effects. Moreover, the exaggerated adverse effects in Dox-intoxicated Nrf2 depleted cardiomyocytes were dramatically attenuated by forced activation of autophagy via overexpression of autophagy related gene 5 (Atg5). Thus, these results suggest that Nrf2 is likely an endogenous suppressor of Dox-induced cardiotoxicity by controlling both oxidative stress and autophagy in the heart.