Apoptosis in Anthracycline Cardiomyopathy

Natural Products for Preventing and Managing Anthracycline-Induced Cardiotoxicity: A Comprehensive Review

Doxorubicin (DOX) is an anthracycline anticancer agent that is highly effective in the treatment of solid tumors. Given the multiplicity of mechanisms involved in doxorubicin-induced cardiotoxicity, it is difficult to identify a precise molecular target for toxicity. The findings of a literature review suggest that natural products may offer cardioprotective benefits against doxorubicin-induced cardiotoxicity, both in vitro and in vivo. However, further confirmatory studies are required to substantiate this claim. It is of the utmost importance to direct greater attention towards the intricate signaling networks that are of paramount importance for the survival and dysfunction of cardiomyocytes. Notwithstanding encouraging progress made in preclinical studies of natural products for the prevention of DOX-induced cardiotoxicity, these have not yet been translated for clinical use. One of the most significant obstacles hindering the development of cardioprotective adjuvants based on natural products is the lack of adequate bioavailability in humans. This review presents an overview of current knowledge on doxorubicin DOX-induced cardiotoxicity, with a focus on the potential benefits of natural compounds and herbal preparations in preventing this adverse effect. As literature search engines, the browsers in the Scopus, PubMed, Web of Science databases and the ClinicalTrials.gov register were used.

Anthracycline-Induced Cardiomyopathy in Cancer Survivors: Management and Long-Term Implications

Recent advancements in personalized treatments, such as anthracycline chemotherapy, coupled with timely diagnoses, have contributed to a decrease in cancer-specific mortality rates and an improvement in cancer prognosis. Anthracyclines, a potent class of antibiotics, are extensively used as anticancer medications to treat a broad spectrum of tumors. Despite these advancements, a considerable number of cancer survivors face increased risks of treatment complications, particularly the cardiotoxic effects of chemotherapeutic drugs like anthracyclines. These effects can range from subclinical manifestations to severe consequences such as irreversible heart failure and death, highlighting the need for effective management of chemotherapy side effects for improved cancer care outcomes. Given the lack of specific treatments, early detection of subclinical cardiac events post-anthracycline therapy and the implementation of preventive strategies are vital. An interdisciplinary approach involving cardiovascular teams is crucial for the prevention and efficient management of anthracycline-induced cardiotoxicity. Various factors, such as age, gender, duration of treatment, and comorbidities, should be considered significant risk factors for developing chemotherapy-related cardiotoxicity. Tools such as electrocardiography, echocardiography, nuclear imaging, magnetic resonance imaging, histopathologic evaluations, and serum biomarkers should be appropriately used for the early detection of anthracycline-related cardiotoxicity. Furthermore, understanding the underlying biological mechanisms is key to developing preventive measures and personalized treatment strategies to mitigate anthracycline-induced cardiotoxicity. Exploring specific cardiotoxic mechanisms and identifying genetic variations can offer fresh perspectives on innovative, personalized treatments. This chapter aims to discuss cardiomyopathy following anthracycline therapy, with a focus on molecular mechanisms, preventive strategies, and emerging treatments.

ROCK1 deficiency preserves caveolar compartmentalization of signaling molecules and cell membrane integrity

In this study, we investigated the roles of ROCK1 in regulating structural and functional features of caveolae located at the cell membrane of cardiomyocytes, adipocytes, and mouse embryonic fibroblasts (MEFs) as well as related physiopathological effects. Caveolae are small bulb-shaped cell membrane invaginations, and their roles have been associated with disease conditions. One of the unique features of caveolae is that they are physically linked to the actin cytoskeleton that is well known to be regulated by RhoA/ROCKs pathway. In cardiomyocytes, we observed that ROCK1 deficiency is coincident with an increased caveolar density, clusters, and caveolar proteins including caveolin-1 and -3. In the mouse cardiomyopathy model with transgenic overexpressing Gαq in myocardium, we demonstrated the reduced caveolar density at cell membrane and reduced caveolar protein contents. Interestingly, coexisting ROCK1 deficiency in cardiomyocytes can rescue these defects and preserve caveolar compartmentalization of β-adrenergic signaling molecules including β1-adrenergic receptor and type V/VI adenylyl cyclase. In cardiomyocytes and adipocytes, we detected that ROCK1 deficiency increased insulin signaling with increased insulin receptor activation in caveolae. In MEFs, we identified that ROCK1 deficiency increased caveolar and total levels of caveolin-1 and cell membrane repair ability after mechanical or chemical disruptions. Together, these results demonstrate that ROCK1 can regulate caveolae plasticity and multiple functions including compartmentalization of signaling molecules and cell membrane repair following membrane disruption by mechanical force and oxidative damage. These findings provide possible molecular insights into the beneficial effects of ROCK1 deletion/inhibition in cardiomyocytes, adipocytes, and MEFs under certain diseased conditions.

Role of Sodium-Glucose Co-Transporter-2 Inhibitor During Anthracycline Use: An Updated Review

The coalescence of anthracycline-induced cardiotoxicity and the evolving role of sodium-glucose co-transporter-2 (SGLT-2) inhibitors in oncology and cardiology has prompted a comprehensive review of their mechanisms, clinical implications, and future directions. Anthracyclines, potent chemotherapeutic agents, have been integral in cancer treatment, yet their potential for cardiac harm necessitates careful monitoring and management. We explore the multifactorial nature of anthracycline-induced cardiotoxicity, encompassing diverse patient populations, cumulative doses, and interplay with other treatments. While advancements in imaging and biomarker assessments aid in early detection, the lack of standardized criteria poses challenges. The emergent role of SGLT-2 inhibitors, initially developed for diabetes management, presents a novel avenue for cardioprotection. Beyond glycemic control, these inhibitors exhibit pleiotropic effects, including enhanced diuresis, anti-inflammatory actions, and modulation of energy sources. Consequently, SGLT-2 inhibitors are being investigated for their potential to mitigate cardiotoxic effects, promising an innovative approach in cardio-oncology. Despite these advancements, limitations in data interpretation and patient-specific considerations persist. The future of anthracycline-induced cardiotoxicity research lies in predictive biomarkers, precision medicine, multidisciplinary collaboration, and tailored treatment regimens. By navigating these challenges and harnessing emerging strategies, we aim to optimize cancer treatment efficacy while safeguarding cardiovascular health, ultimately paving the way for a new era of personalized and comprehensive oncologic care.

Anthracycline-induced cardiotoxicity: mechanisms, monitoring, and prevention

Anthracyclines are the most fundamental and important treatment of several cancers especially for lymphoma and breast cancer. However, their use is limited by a dose-dependent cardiotoxicity which may emerge early at the initiation of anthracycline administration or several years after termination of the therapy. A full comprehending of the mechanisms of anthracycline-induced cardiotoxicity, which has not been achieved and is currently under the efforts, is critical to the advance of developing effective methods to protect against the cardiotoxicity, as well as to early detect and treat it. Therefore, we review the recent progress of the mechanism underlying anthracycline-induced cardiotoxicity, as well as approaches to monitor and prevent this issue.

A systematic review of the protective effects of silymarin/silibinin against doxorubicin-induced cardiotoxicity

PURPOSE

Although doxorubicin chemotherapy is commonly applied for treating different malignant tumors, cardiotoxicity induced by this chemotherapeutic agent restricts its clinical use. The use of silymarin/silibinin may mitigate the doxorubicin-induced cardiac adverse effects. For this aim, the potential cardioprotective effects of silymarin/silibinin against the doxorubicin-induced cardiotoxicity were systematically reviewed.

METHODS

In this study, we performed a systematic search in accordance with PRISMA guideline for identifying all relevant studies on "the role of silymarin/silibinin against doxorubicin-induced cardiotoxicity" in different electronic databases up to June 2022. Sixty-one articles were obtained and screened based on the predefined inclusion and exclusion criteria. Thirteen eligible papers were finally included in this review.

RESULTS

According to the echocardiographic and electrocardiographic findings, the doxorubicin-treated groups presented a significant reduction in ejection fraction, tissue Doppler peak mitral annulus systolic velocity, and fractional shortening as well as bradycardia, prolongation of QT and QRS interval. However, these echocardiographic abnormalities were obviously improved in the silymarin plus doxorubicin groups. As well, the doxorubicin administration led to induce histopathological and biochemical changes in the cardiac cells/tissue; in contrast, the silymarin/silibinin co-administration could mitigate these induced alterations (for most of the cases).

CONCLUSION

According to the findings, it was found that the co-administration of silymarin/silibinin alleviates the doxorubicin-induced cardiac adverse effects. Silymarin/silibinin exerts its cardioprotective effects via antioxidant, anti-inflammatory, anti-apoptotic activities, and other mechanisms.

Cell death regulation in myocardial toxicity induced by antineoplastic drugs

Homeostatic regulation of cardiomyocytes plays a critical role in maintaining normal physiological activity of cardiac tissue. Severe cardiotoxicity can lead to heart disease, including but not limited to arrhythmias, myocardial infarction and cardiac hypertrophy. In recent years, significant progress has been made in developing new therapies for cancer that have dramatically changed the treatment of several malignancies and continue to improve patient survival, but can also lead to serious cardiac adverse effects. Mitochondria are key organelles that maintain homeostasis in myocardial tissue and have been extensively involved in various cardiovascular disease episodes, including ischemic cardiomyopathy, heart failure and stroke. Several studies support that mitochondrial targeting is a major determinant of the cardiotoxic effects triggered by chemotherapeutic agents increasingly used in solid and hematologic tumors. This antineoplastic therapy-induced mitochondrial toxicity is due to different mechanisms, usually altering the mitochondrial respiratory chain, energy production and mitochondrial kinetics, or inducing mitochondrial oxidative/nitrosative stress, ultimately leading to cell death. This review focuses on recent advances in forms of cardiac cell death and related mechanisms of antineoplastic drug-induced cardiotoxicity, including autophagy, ferroptosis, apoptosis, pyroptosis, and necroptosis, explores and evaluates key proteins involved in cardiac cell death signaling, and presents recent advances in cardioprotective strategies for this disease. It aims to provide theoretical basis and targets for the prevention and treatment of pharmacological cardiotoxicity in clinical settings.

Molecular Mechanisms of Ferroptosis and Relevance to Cardiovascular Disease

Ferroptosis has recently been demonstrated to be a novel regulated non-apoptotic cell death characterized by iron-dependence and the accumulation of lipid peroxidation that results in membrane damage. Excessive iron induces ferroptosis by promoting the generation of both soluble and lipid ROS via an iron-dependent Fenton reaction and lipoxygenase (LOX) enzyme activity. Cytosolic glutathione peroxidase 4 (cGPX4) pairing with ferroptosis suppressor protein 1 (FSP1) and mitochondrial glutathione peroxidase 4 (mGPX4) pairing with dihydroorotate dehydrogenase (DHODH) serve as two separate defense systems to detoxify lipid peroxidation in the cytoplasmic as well as the mitochondrial membrane, thereby defending against ferroptosis in cells under normal conditions. However, disruption of these defense systems may cause ferroptosis. Emerging evidence has revealed that ferroptosis plays an essential role in the development of diverse cardiovascular diseases (CVDs), such as hemochromatosis-associated cardiomyopathy, doxorubicin-induced cardiotoxicity, ischemia/reperfusion (I/R) injury, heart failure (HF), atherosclerosis, and COVID-19–related arrhythmias. Iron chelators, antioxidants, ferroptosis inhibitors, and genetic manipulations may alleviate the aforementioned CVDs by blocking ferroptosis pathways. In conclusion, ferroptosis plays a critical role in the pathogenesis of various CVDs and suppression of cardiac ferroptosis is expected to become a potential therapeutic option. Here, we provide a comprehensive review on the molecular mechanisms involved in ferroptosis and its implications in cardiovascular disease.

Saponins and their derivatives: Potential candidates to alleviate anthracycline-induced cardiotoxicity and multidrug resistance

Anthracyclines (ANTs) continue to play an irreplaceable role in oncology treatment. However, the clinical application of ANTs has been limited. In the first place, ANTs can cause dose-dependent cardiotoxicity such as arrhythmia, cardiomyopathy, and congestive heart failure. In the second place, the development of multidrug resistance (MDR) leads to their chemotherapeutic failure. Oncology cardiologists are urgently searching for agents that can both protect the heart and reverse MDR without compromising the antitumor effects of ANTs. Based on in vivo and in vitro data, we found that natural compounds, including saponins, may be active agents for other both natural and chemical compounds in the inhibition of anthracycline-induced cardiotoxicity (AIC) and the reversal of MDR. In this review, we summarize the work of previous researchers, describe the mechanisms of AIC and MDR, and focus on revealing the pharmacological effects and potential molecular targets of saponins and their derivatives in the inhibition of AIC and the reversal of MDR, aiming to encourage future research and clinical trials.

Exploring Moderators of the Effect of High vs. Low-to-Moderate Intensity Exercise on Cardiorespiratory Fitness During Breast Cancer Treatment – Analyses of a Subsample From the Phys-Can RCT

Introduction

The results from the physical training and cancer randomized controlled trial (Phys-Can RCT) indicate that high intensity (HI) strength and endurance training during (neo-)adjuvant cancer treatment is more beneficial for cardiorespiratory fitness (CRF, measured as peak oxygen uptake [VO2peak]) than low-to-moderate intensity (LMI) exercise. Adherence to the exercise intervention and demographic or clinical characteristics of patients with breast cancer undergoing adjuvant treatment may moderate the exercise intervention effect on VO2peak. In this study, the objective was to investigate whether baseline values of VO2peak, body mass index (BMI), time spent in moderate- to vigorous-intensity physical activity (MVPA), physical fatigue, age, chemotherapy treatment, and the adherence to the endurance training moderated the effect of HI vs. LMI exercise on VO2peak.

Materials and Methods

We used data collected from a subsample from the Phys-Can RCT; women who were diagnosed with breast cancer and had a valid baseline and post-intervention VO2peak test were included (n = 255). The exercise interventions from the RCT included strength and endurance training at either LMI, which was continuous endurance training at 40–50% of heart rate reserve (HRR), or at HI, which was interval training at 80–90% of HRR, with similar exercise volume in the two groups. Linear regression analyses were used to investigate moderating effects using a significance level of p < 0.10. Statistically significant interactions were examined further using the Johnson–Neyman (J-N) technique and regions of significance (for continuous variables) or box plots with adjusted means of post-intervention VO2peak (for binary variables).

Results

Age, as a continuous variable, and adherence, dichotomized into < or > 58% based on median, moderated the effect of HI vs. LMI on CRF (B = −0.08, 95% CI [−0.16, 0.01], pinteraction = 0.06, and B = 1.63, 95% CI [−0.12, 3.38], pinteraction = 0.07, respectively). The J-N technique and regions of significance indicated that the intervention effect (HI vs. LMI) was positive and statistically significant in participants aged 61 years or older. Baseline measurement of CRF, MVPA, BMI, physical fatigue, and chemotherapy treatment did not significantly moderate the intervention effect on CRF.

Conclusion

Women with breast cancer who are older and who have higher adherence to the exercise regimen may have larger effects of HI exercise during (neo-)adjuvant cancer treatment on CRF.

Beyond hypertension: Diastolic dysfunction associated with cancer treatment in the era of cardio-oncology

Cancer patients are at an increased risk of cardiovascular events. Both old-generation cytostatics/cytotoxics and new-generation "targeted" drugs can in fact damage cardiomyocytes, endothelial cells of veins and arteries, specialized cells of the conduction system, pericardium, and valves. A new discipline, cardio-oncology, has therefore developed with the aim of protecting cancer patients from cardiovascular events, while also providing them with the best possible oncologic treatment. Anthracyclines have long been known to elicit cardiotoxicity that, depending on treatment- or patient-related factors, may progress with a variable velocity toward cardiomyopathy and systolic heart failure. However, early compromise of diastolic function may precede systolic dysfunction, and a progression of early diastolic dysfunction to diastolic rather than systolic heart failure has been documented in long-term cancer survivors. This chapter first describes general notions about hypertension in the cancer patient and then moves on reviewing the pathophysiology and clinical trajectories of diastolic dysfunction, and the molecular mechanisms of anthracycline-induced diastolic dysfunction. Diastolic dysfunction can in fact be caused and/or aggravated by hypertension. Pharmacologic foundations and therapeutic opportunities to prevent or treat diastolic dysfunction before it progresses toward heart failure are also reviewed, with a special emphasis on the mechanisms of action of drugs that raised hopes to treat diastolic dysfunction in the general population (sacubitril/valsartan, guanylyl cyclase activators, phosphodiesterase inhibitors, ranolazine, inhibitors of type-2 sodium-glucose-inked transporter). Cardio-oncologists will be confronted with the risk:benefit ratio of using these drugs in the cancer patient.

microRNAs signatures as potential biomarkers of structural cardiotoxicity in human-induced pluripotent stem-cell derived cardiomyocytes

Identification of early biomarkers of heart injury and drug-induced cardiotoxicity is important to eliminate harmful drug candidates early in preclinical development and to prevent severe drug effects. The main objective of this study was to investigate the expression of microRNAs (miRNAs) in human-induced pluripotent stem cell cardiomyocytes (hiPSC-CM) in response to a broad range of cardiotoxic drugs. Next generation sequencing was applied to hiPSC-CM treated for 72 h with 40 drugs falling into the categories of functional (i.e., ion channel blockers), structural (changes in cardiomyocytes structure), and general (causing both functional and structural) cardiotoxicants as well as non-cardiotoxic drugs. The largest changes in miRNAs expression were observed after treatments with structural or general cardiotoxicants. The number of deregulated miRNAs was the highest for idarubicin, mitoxantrone, and bortezomib treatments. RT-qPCR validation confirmed upregulation of several miRNAs across multiple treatments at therapeutically relevant concentrations: hsa-miR-187-3p, hsa-miR-146b-5p, hsa-miR-182-5p (anthracyclines); hsa-miR-365a-5p, hsa-miR-185-3p, hsa-miR-184, hsa-miR-182-5p (kinase inhibitors); hsa-miR-182-5p, hsa-miR-126-3p and hsa-miR-96-5p (common some anthracyclines, kinase inhibitors and bortezomib). Further investigations showed that an upregulation of hsa-miR-187-3p and hsa-miR-182-5p could serve as a potential biomarker of structural cardiotoxicity and/or an additional endpoint to characterize cardiac injury in vitro.

8-Oxoguanine DNA Glycosylase (OGG1) Deficiency Exacerbates Doxorubicin-Induced Cardiac Dysfunction

Doxorubicin is an anthracycline widely used for the treatment of various cancers; however, the drug has a common deleterious side effect, namely a dose-dependent cardiotoxicity. Doxorubicin treatment increases the generation of reactive oxygen species, which leads to oxidative stress in the cardiac cells and ultimately DNA damage and cell death. The most common DNA lesion produced by oxidative stress is 7,8-dihydro-8-oxoguanine (8-oxoguanine), and the enzyme responsible for its repair is the 8-oxoguanine DNA glycosylase (OGG1), a base excision repair enzyme. Here, we show that the OGG1 deficiency has no major effect on cardiac function at baseline or with pressure overload; however, we found an exacerbation of cardiac dysfunction as well as a higher mortality in Ogg1 knockout mice treated with doxorubicin. Our transcriptomic analysis also showed a more extensive dysregulation of genes in the hearts of Ogg1 knockout mice with an enrichment of genes involved in inflammation. These results demonstrate that OGG1 attenuates doxorubicin-induced cardiotoxicity and thus plays a role in modulating drug-induced cardiomyopathy.

Nauclea orientalis (L.) Bark Extract Protects Rat Cardiomyocytes from Doxorubicin-Induced Oxidative Stress, Inflammation, Apoptosis, and DNA Fragmentation

The therapeutic efficacy of anthracycline antibiotic, doxorubicin (Dox), is hampered due to the dose-dependent cardiotoxicity. The objective of the study was to explore the counteraction of aqueous bark extract of Nauclea orientalis in Dox-induced cardiotoxicity in Wistar rats. The acute and subchronic toxicity study performed with 2.0 g/kg of the plant extract revealed biochemical and haematological parameters to be within the physiological range, and no histological alterations were observed in any organs isolated. Screening of plant extract for the protection of the myocardium from Dox-induced oxidative stress, inflammation, and apoptosis was performed on five groups of rats: control, plant extract control, Dox control (distilled water (D.H₂O) 2 weeks + on the 11^th day single injection of Dox, 18 mg/kg), plant + Dox (2.0 g/kg plant extract 2 weeks + on the 11^th day Dox, 18 mg/kg), and positive control, dexrazoxane. A significant increase in cardiac biomarkers and lipid peroxidation (p < 0.001) and a significant decrease in antioxidant parameters (p < 0.001) were observed in the Dox control group. All these parameters were reversed significantly (p < 0.05) in the plant-pretreated group. The histopathological assessment of myocardial damage provided supportive evidence for the biochemical results obtained. Inflammatory markers, myeloperoxidase, expression of TNFα and caspase-3, and DNA fragmentation (TUNEL positive nuclei) were significantly elevated (p < 0.05), and expression of Bcl-2 was significantly decreased (p < 0.05) in the Dox control; however, all these parameters were significantly reversed in the plant extract-treated group. In conclusion, the aqueous bark extract of Nauclea orientalis (2.0 g/kg) has the ability to attenuate the Dox-induced oxidative stress, inflammation, apoptosis, and DNA fragmentation in Wistar rats.

Cardiac inflammation and fibrosis following chemo/radiation therapy: mechanisms and therapeutic agents

The incidence of cardiovascular disorders is one of the most concerns among people who underwent cancer therapy. The heart side effects of cancer therapy may occur during treatment to some years after the end of treatment. Some epidemiological studies confirm that heart diseases are one of the most common reasons for mortality among patients that were received treatment for cancer. Experimental studies and also clinical investigations indicate that inflammatory changes such as pericarditis, myocarditis, and also fibrosis are key mechanisms of cardiac diseases following chemotherapy/radiotherapy. It seems that chronic oxidative stress, massive cell death, and chronic overproduction of pro-inflammatory and pro-fibrosis cytokines are the key mechanisms of cardiovascular diseases following cancer therapy. Furthermore, infiltration of inflammatory cells and upregulation of some enzymes such as NADPH Oxidases are a hallmark of heart diseases after cancer therapy. In the current review, we aim to explain how radiation or chemotherapy can induce inflammatory and fibrosis-related diseases in the heart. We will explain the cellular and molecular mechanisms of cardiac inflammation and fibrosis following chemo/radiation therapy, and then review some adjuvants to reduce the risk of inflammation and fibrosis in the heart.

The molecular mosaic of regulated cell death in the cardiovascular system

Cell death is now understood to be a highly regulated process that contributes to normal development and tissue homeostasis, alongside its role in the etiology of various pathological conditions. Through detailed molecular analysis, we have come to know that all cells do not always die in the same way, and that there are at least 7 processes involved, including: apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, and autophagy-mediated cell death. These processes act as pieces in the mosaic of cardiomyocyte cell death, which come together depending on context and stimulus. This review details each individual process, as well as highlights how they come together to produce various cardiac pathologies. By knowing how the pieces go together we can aim towards the development of efficacious therapeutics, which will enable us to prevent cardiomyocyte loss in the face of stress, both reducing mortality and improving quality of life.

Regulated cell death pathways in doxorubicin-induced cardiotoxicity

Doxorubicin is a chemotherapeutic drug used for the treatment of various malignancies; however, patients can experience cardiotoxic effects and this has limited the use of this potent drug. The mechanisms by which doxorubicin kills cardiomyocytes has been elusive and despite extensive research the exact mechanisms remain unknown. This review focuses on recent advances in our understanding of doxorubicin induced regulated cardiomyocyte death pathways including autophagy, ferroptosis, necroptosis, pyroptosis and apoptosis. Understanding the mechanisms by which doxorubicin leads to cardiomyocyte death may help identify novel therapeutic agents and lead to more targeted approaches to cardiotoxicity testing.

Biomimetic microsystems for cardiovascular studies

Traditional tissue culture platforms have been around for several decades and have enabled key findings in the cardiovascular field. However, these platforms failed to recreate the mechanical and dynamic features found within the body. Organs-on-chips (OOCs) are cellularized microfluidic-based devices that can mimic the basic structure, function, and responses of organs. These systems have been successfully utilized in disease, development, and drug studies. OOCs are designed to recapitulate the mechanical, electrical, chemical, and structural features of the in vivo microenvironment. Here, we review cardiovascular-themed OOC studies, design considerations, and techniques used to generate these cellularized devices. Furthermore, we will highlight the advantages of OOC models over traditional cell culture vessels, discuss implementation challenges, and provide perspectives on the state of the field.

Cardioprotective effects of exercise training on doxorubicin-induced cardiomyopathy: a systematic review with meta-analysis of preclinical studies

Doxorubicin (DOX)-induced cardiotoxicity in chemotherapy is a major treatment drawback. Clinical trials on the cardioprotective effects of exercise in cancer patients have not yet been published. Thus, we conducted a systematic review and meta-analysis of preclinical studies for to assess the efficacy of exercise training on DOX-induced cardiomyopathy. We included studies with animal models of DOX-induced cardiomyopathy and exercise training from PubMed, Web of Sciences and Scopus databases. The outcome was the mean difference (MD) in fractional shortening (FS, %) assessed by echocardiography between sedentary and trained DOX-treated animals. Trained DOX-treated animals improved 7.40% (95% CI 5.75-9.05, p < 0.001) in FS vs. sedentary animals. Subgroup analyses revealed a superior effect of exercise training execution prior to DOX exposure (MD = 8.20, 95% CI 6.27-10.13, p = 0.010). The assessment of cardiac function up to 10 days after DOX exposure and completion of exercise protocol was also associated with superior effect size in FS (MD = 7.89, 95% CI 6.11-9.67, p = 0.020) vs. an echocardiography after over 4 weeks. Modality and duration of exercise, gender and cumulative DOX dose did were not individually associated with changes on FS. Exercise training is a cardioprotective approach in rodent models of DOX-induced cardiomyopathy. Exercise prior to DOX exposure exerts greater effect sizes on FS preservation.

Consideration of Sex as a Biological Variable in the Development of Doxorubicin Myotoxicity and the Efficacy of Exercise as a Therapeutic Intervention

Doxorubicin (DOX) is an anthracycline antibiotic used to treat a wide variety of hematological and solid tumor cancers. While DOX is highly effective at reducing tumor burden, its clinical use is limited by the development of adverse effects to both cardiac and skeletal muscle. The detrimental effects of DOX to muscle tissue are associated with the increased incidence of heart failure, dyspnea, exercise intolerance, and reduced quality of life, which have been reported in both patients actively receiving chemotherapy and cancer survivors. A variety of factors elevate the probability of DOX-related morbidity in patients; however, the role of sex as a biological variable to calculate patient risk remains unclear. Uncertainty regarding sexual dimorphism in the presentation of DOX myotoxicity stems from inadequate study design to address this issue. Currently, the majority of clinical data on DOX myotoxicity come from studies where the ratio of males to females is unbalanced, one sex is omitted, and/or the patient cohort include a broad age range. Furthermore, lack of consensus on standard outcome measures, difficulties in long-term evaluation of patient outcomes, and other confounding factors (i.e., cancer type, drug combinations, adjuvant therapies, etc.) preclude a definitive answer as to whether differences exist in the incidence of DOX myotoxicity between sexes. This review summarizes the current clinical and preclinical literature relevant to sex differences in the incidence and severity of DOX myotoxicity, the proposed mechanisms for DOX sexual dimorphism, and the potential for exercise training to serve as an effective therapeutic countermeasure to preserve muscle strength and function in males and females.

Two novel anticancer compounds with minimum cardiotoxic property

BACKGROUND

Although two novel synthesized compounds with tri-aryl structures; 3-(4-chlorophenyl)-5-(4-fluorophenyl)-4-phenyl-4,5-dihydro-1,2,4-oxadiazole (A) and 3,5-bis-(4-chlorophenyl)-4-phenyl-4,5-dihydro-1,2,4-oxadiazole (B) have been previously demonstrated to possess remarkable anti-breast cancer activity, their cardiotoxicity remains a major concern due to their mechanism of action. To address this concern, we assessed the ability of these compounds to cause toxicity towards H9c2 cardiomyocytes as an in vitro model of cardiotoxicity.

METHODS

Cytotoxic activity of both compounds was explored in vitro on H9c2 cells using MTT assay. Annexin V/PI method, intracellular ROS determination and mitochondrial membrane potential assay were applied to elucidate the mechanism of action of the cell death.

RESULTS

MTT assay revealed a concentration- and time-dependent cardiotoxicity. Findings of apoptosis by double staining with annexin V and propidium iodide divulged no cell death including apoptosis and necrosis at the concentration that were effective to inhibit cancer cells proliferation (10 μM) at 24 and 48 h. Furthermore, flow cytometric measurement of membrane potential and ROS determination using DCFH-DA verified the safe concentration of the compounds against H9c2 cells with no cardiotoxic effect. However, the higher concentration of the compounds could induce cell death through ROS-mediated mitochondrial dysfunction.

CONCLUSIONS

Altogether, the results represented two novel chemical molecules possessing anti-breast cancer activity with minimum cardiac side effect.

Peptidomics Analysis Reveals Peptide PDCryab1 Inhibits Doxorubicin-Induced Cardiotoxicity

Doxorubicin (DOX) is limited due to dose-dependent cardiotoxicity. Peptidomics is an emerging field of proteomics that has attracted much attention because it can be used to study the composition and content of endogenous peptides in various organisms. Endogenous peptides participate in various biological processes and are important sources of candidates for drug development. To explore peptide changes related to DOX-induced cardiotoxicity and to find peptides with cardioprotective function, we compared the expression profiles of peptides in the hearts of DOX-treated and control mice by mass spectrometry. The results showed that 236 differential peptides were identified upon DOX treatment, of which 22 were upregulated and 214 were downregulated. Next, we predicted that 31 peptides may have cardioprotective function by conducting bioinformatics analysis on the domains of each precursor protein, the predicted score of peptide biological activity, and the correlation of each peptide with cardiac events. Finally, we verified that a peptide (SPFYLRPPSF) from Cryab can inhibit cardiomyocyte apoptosis, reduce the production of reactive oxygen species, improve cardiac function, and ameliorate myocardial fibrosis in vitro and vivo. In conclusion, our results showed that the expression profiles of peptides in cardiac tissue change significantly upon DOX treatment and that these differentially expressed peptides have potential cardioprotective functions. Our study suggests a new direction for the treatment of DOX-induced cardiotoxicity.

Drug Development and the Use of Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Disease Modeling and Drug Toxicity Screening

: Over the years, numerous groups have employed human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) as a superb human-compatible model for investigating the function and dysfunction of cardiomyocytes, drug screening and toxicity, disease modeling and for the development of novel drugs for heart diseases. In this review, we discuss the broad use of iPSC-CMs for drug development and disease modeling, in two related themes. In the first theme-drug development, adverse drug reactions, mechanisms of cardiotoxicity and the need for efficient drug screening protocols-we discuss the critical need to screen old and new drugs, the process of drug development, marketing and Adverse Drug reactions (ADRs), drug-induced cardiotoxicity, safety screening during drug development, drug development and patient-specific effect and different mechanisms of ADRs. In the second theme-using iPSC-CMs for disease modeling and developing novel drugs for heart diseases-we discuss the rationale for using iPSC-CMs and modeling acquired and inherited heart diseases with iPSC-CMs.

Clerodendrum volubile Ethanol Leaf Extract: A Potential Antidote to Doxorubicin-Induced Cardiotoxicity in Rats

Doxorubicin is widely applied in hematological and solid tumor treatment but limited by its off-target cardiotoxicity. Thus, cardioprotective potential and mechanism(s) of CVE in DOX-induced cardiotoxicity were investigated using cardiac and oxidative stress markers and histopathological endpoints. 50–400 mg/kg/day CVE in 5% DMSO in distilled water were investigated in Wistar rats intraperitoneally injected with 2.5 mg/kg DOX on alternate days for 14 days, using serum troponin I and LDH, complete lipid profile, cardiac tissue oxidative stress marker assays, and histopathological examination of DOX-treated cardiac tissue. Preliminary qualitative and quantitative assays of CVE's secondary metabolites were also conducted. Phytochemical analyses revealed the presence of flavonoids (34.79 ± 0.37 mg/100 mg dry extract), alkaloids (36.73 ± 0.27 mg/100 mg dry extract), reducing sugars (07.78 ± 0.09 mg/100 mg dry extract), and cardiac glycosides (24.55 ± 0.12 mg/100 mg dry extract). 50–400 mg/kg/day CVE significantly attenuated increases in the serum LDH and troponin I levels. Similarly, the CVE dose unrelatedly decreased serum TG and VLDL-c levels without significant alterations in the serum TC, HDL-c, and LDL-c levels. Also, CVE profoundly attenuated alterations in the cardiac tissue oxidative stress markers' activities while improving DOX-associated cardiac histological lesions that were possibly mediated via free radical scavenging and/or antioxidant mechanisms. Overall, CVE may play a significant therapeutic role in the management of DOX-induced cardiotoxicity in humans.

Acylated Ghrelin Protects the Hearts of Rats from Doxorubicin-Induced Fas/FasL Apoptosis by Stimulating SERCA2a Mediated by Activation of PKA and Akt

This study investigated if the cardioprotective effect of acylated ghrelin (AG) against doxorubicin (DOX)-induced cardiac toxicity in rats involves inhibition of Fas/FasL-mediated cell death. It also investigated if such an effect is mediated by restoring Ca⁺² homeostasis from the aspect of stimulation of SERCA2a receptors. Adult male Wistar rats were divided into 4 groups (20 rats/each) as control, control + AG, DOX, and DOX + AG. AG was co-administered to all rats consecutively for 35 days. In addition, isolated cardiomyocytes were cultured and treated with AG in the presence or absence of DOX with or without pre-incubation with [D-Lys3]-GHRP-6 (a AG receptor antagonist), VIII (]an Akt inhibitor), or KT-5720 (a PKA inhibitor). AG increased LVSP, dp/dt_max, and dp/dt_min in both control and DOX-treated animals and improved cardiac ultrastructural changes in DOX-treated rats. It also inhibited ROS in control rats and lowered LVEDP, intracellular levels of ROS and Ca²⁺, and activity of calcineurin in LVs of DOX-treated rats. Concomitantly, it inhibited LV NFAT-4 nuclear translocation and downregulated their protein levels of Fas and FasL. Mechanistically, in control or DOX-treated hearts or cells, AG upregulated the levels of SERCA2a and increased the activities of PKA and Akt, leading to increase phosphorylation of phospholamban at Ser¹⁶ and Thr¹⁷. All these effects were abolished by D-Lys3-GHRP-6, VIII, or KT-5720 and were independent of food intake or GH/IGF-1. In conclusion, AG cardioprotection against DOX involves inhibition of extrinsic cell death and restoring normal Ca⁺² homeostasis.

Mitochondria-dependent ferroptosis plays a pivotal role in doxorubicin cardiotoxicity

Doxorubicin (DOX), a chemotherapeutic agent, induces a cardiotoxicity referred to as doxorubicin-induced cardiomyopathy (DIC). This cardiotoxicity often limits chemotherapy for malignancies and is associated with poor prognosis. However, the molecular mechanism underlying this cardiotoxicity is yet to be fully elucidated. Here, we show that DOX downregulated glutathione peroxidase 4 (GPx4) and induced excessive lipid peroxidation through DOX-Fe2+ complex in mitochondria, leading to mitochondria-dependent ferroptosis; we also show that mitochondria-dependent ferroptosis is a major cause of DOX cardiotoxicity. In DIC mice, the left ventricular ejection fraction was significantly impaired, and fibrosis and TUNEL+ cells were induced at day 14. Additionally, GPx4, an endogenous regulator of ferroptosis, was downregulated, accompanied by the accumulation of lipid peroxides, especially in mitochondria. These cardiac impairments were ameliorated in GPx4 Tg mice and exacerbated in GPx4 heterodeletion mice. In cultured cardiomyocytes, GPx4 overexpression or iron chelation targeting Fe2+ in mitochondria prevented DOX-induced ferroptosis, demonstrating that DOX triggered ferroptosis in mitochondria. Furthermore, concomitant inhibition of ferroptosis and apoptosis with ferrostatin-1 and zVAD-FMK fully prevented DOX-induced cardiomyocyte death. Our findings suggest that mitochondria-dependent ferroptosis plays a key role in progression of DIC and that ferroptosis is the major form of regulated cell death in DOX cardiotoxicity.

Doxorubicin-induces NFAT/Fas/FasL cardiac apoptosis in rats through activation of calcineurin and P38 MAPK and inhibition of mTOR signalling pathways

This study investigated the role of NFAT/Fas/FasL axis in cardiomyocyte apoptosis following doxorubicin (DOX) treatment in rats and evaluated the involvement and regulation of all NFAT members in cardiac apoptosis. Forty adult male Wistar rats were divided equally into control or DOX-treated groups (15 mg/kg over 2 weeks). Cardiomyocytes were cultured and pre-incubated with various inhibitors and activators (10 μmol/L) prior to DOX exposure (1 μmol/L). In the left ventricles and cultured cells, DOX increased cytoplasmic protein levels of cytochrome C, Bax and increased the activities of caspase-8, caspase3, ERK1/2, JNK, and P38 mitogen-activated protein kinases (MAPKs), reducing levels of Bcl-2 and the activity of mTOR, and inducing cell death. In addition, DOX enhanced mRNA and protein levels of Fas and FasL. Furthermore, the nuclear and cytoplasmic levels of NFAT1 and nuclear accumulation of NFAT2-4were increased with DOX treatment. The inhibition of calcineurin with FK506 significantly inhibited the nuclear levels of NFAT2 and NFAT4 and the inhibition of P38 MAPK with SB203580 inhibited the nuclear and cytoplasmic accumulation of NFAT1. However, the activation of mTOR by IGF-1 significantly lowered NFAT3. In conclusion, NFAT/Fas/FasL-induced cell death in cardiac myocytes of DOX-treated rats is regulated, at least, by the activation of calcineurin and P38 MAPK and inhibition of mTOR.

Regulation of cell death in the cardiovascular system

The adult heart is a post-mitotic terminally differentiated organ; therefore, beyond development, cardiomyocyte cell death is maladaptive. Heart disease is the leading cause of death in the world and aberrant cardiomyocyte cell death is the underlying problem for most cardiovascular-related diseases and fatalities. In this chapter, we will discuss the different cell death mechanisms that engage during normal cardiac development, aging, and disease states. The most abundant loss of cardiomyocytes occurs during a myocardial infarction, when the blood supply to the heart is obstructed, and the affected myocardium succumbs to cell death. Originally, this form of cell death was considered to be unregulated; however, research from the last half a century clearly demonstrates that this form of cell death is multifaceted and employees various degrees of regulation. We will explore all of the cell death pathways that have been implicated in this disease state and the potential interplay between them. Beyond myocardial infarction, we also explore the role and mechanisms of cardiomyocyte cell death in heart failure, myocarditis, and chemotherapeutic-induced cardiotoxicity. Inhibition of cardiomyocyte cell death has extensive therapeutic potential that will increase the longevity and health of the human heart.

Disruption of ROCK1 gene restores autophagic flux and mitigates doxorubicin-induced cardiotoxicity

Doxorubicin is among the essential medicines with a wide antitumor spectrum, but its clinical application is limited by its cardiotoxicity. We recently discovered that ROCK1 is a key molecule in mediating cardiac remodeling in response to various stresses. To determine the roles of ROCK1 in doxorubicin cardiotoxicity, we gave three doses of doxorubicin injections to wild type (WT) and ROCK1^−/− mice with one week intervals between treatments, the cumulative dose being 24 mg/kg. ROCK1^−/− mice exhibited preserved cardiac function, reduced apoptosis, autophagy and fibrosis compared to the WT mice. To further determine the cellular mechanisms, we have examined the role of ROCK1 in cardiomyocytes using cardiomyocyte-specific knockout mice, MHC-Cre/ROCK1^fl/fl, which partially reproduced the cardioprotective characteristics of ROCK1^−/− mice, indicating that ROCK1 in both cardiomyocytes and non-cardiomyocytes mediates doxorubicin cardiotoxicity. To elucidate the molecular mechanisms, a detailed time course study after a single doxorubicin injection at 10 mg/kg was performed in ROCK1^−/− and MHC-Cre/ROCK1^fl/fl mice. The molecular analysis revealed that both ROCK1^−/− and MHC-Cre/ROCK1^fl/fl hearts exhibited significant reduction of doxorubicin-induced early responses including increased apoptotic (Bax) and autophagic (p62/SQSTM1 and LC3-II) markers, associated with reduced Beclin 1 phosphorylation on Thr119, supporting reduced Beclin 1-mediated autophagy initiation due to increased association of Beclin 1 with Bcl 2 or Bcl-XL in these hearts compared to the WT or ROCK1^fl/fl mice. These results support that ROCK1 deficiency is cardioprotective against doxorubicin-induced cardiotoxicity at least in part through reducing Beclin 1-mediated autophagy initiation in cardiomyocytes and restoring autophagic flux to ameliorate doxorubicin cardiotoxicity.

The regulation of NLRP3 inflammasome expression during the development of cardiac contractile dysfunction in chronic kidney disease

Chronic inflammation plays a crucial role in the long-term complications in patients with chronic kidney disease (CKD). This study aimed to assess the role of NLR pyrin domain-containing protein (NLRP3) inflammasome in cardiac contractile dysfunctions in CKD. The cardiac contractile function was evaluated and the expression of NLRP3 inflammasome and related cytokines in the heart was assessed in a murine sham-operated and 5/6 nephrectomy CKD model in vivo. In vitro, H9c2 cells were treated with uremic toxin indoxyl sulfate (IS), with or without NLRP3 inflammasome inhibition, which was achieved by using small interfering RNA (siRNA)-mediated knockdown of the NLRP3 gene. Moreover, the activation of nuclear factor κB (NF-κB) signaling and apoptosis marker levels were assessed in the IS-treated H9c2 cells. The results demonstrated that CKD can lead to the development of cardiac contractile dysfunction in vivo associated with the upregulation of NLRP3 inflammasome, IL-1β, IL-18, and contribute to the myocardial apoptosis. In vitro experiments showed the upregulation of inflammasome, IL-1β, and IL-18 levels, and cell apoptosis in the IS-treated H9c2 cells through the activation of NF-κB signaling pathway. The transfection of cells with si-NLRP3 was shown to alleviate IL-1β, IL-18, and cell apoptosis. Moreover, decreased cell viability induced by IS was shown to be attenuated by IL-1β or IL-18-neutralizing antibody. In summary, CKD can result in the development of cardiac contractile dysfunction associated with the upregulation of NLRP3 inflammasome/IL-1β/IL-18 axis induced by the uremic toxins.

Puerarin attenuates the daunorubicin-induced apoptosis of H9c2 cells by activating the PI3K/Akt signaling pathway via the inhibition of Ca2+ influx

Puerarin extracted from Radix Puerariae is well known for its pharmacological effects, including antioxidant, anti‑inflammatory, neuroprotective and cardioprotective properties. In this study, we aimed to investigate the effects of puerarin on the daunorubicin (DNR)-induced apoptosis of H9c2 cells and to elucidate the potential mechanisms involved. MTT assay and flow cytometry were performed to evaluate cell cytotoxicity and apoptosis, respectively. Western blot analysis was used to assess changes in the expression levels of proteins, including caspase-3, Akt and phosphorylated Akt (p-Akt). Ratiometric imaging of intracellular calcium (Ca2+) using cells loaded with Fura-2 was also carried out. Our results revealed that puerarin pre-treatment protected the H9c2 cells against DNR-induced cytotoxicity by inhibiting cell apoptosis, which was also confirmed by the decrease in the expression of cleaved caspase-3. Additionally, p-Akt activation was associated with the suppressive effects of puerarin. Following pre-treatment with puerarin, the extracellular Ca2+ influx was restrained and this resulted in a reduction in the intracellular Ca2+ levels; these effects were abrogated by LY294002 [an inhibitor of phosphatidylinositol 3-kinase (PI3K)]. The inhibition of Ca2+ influx suggested that the PI3K/Akt signaling pathway participated in the suppressive effects of puerarin against H9c2 cell apoptosis. Taken togher, our findings demonstrate that puerarin attenuates the DNR-induced apoptosis of H9c2 cells by activating the PI3K/Akt signaling pathway via the inhibition of Ca2+ influx, suggesting that puerarin may be a potential cardioprotective agent for use in the clinical treatment of cardiomyopathy triggered by DNR.

Cardiac spheroids as promising in vitro models to study the human heart microenvironment

Three-dimensional in vitro cell systems are a promising alternative to animals to study cardiac biology and disease. We have generated three-dimensional in vitro models of the human heart ("cardiac spheroids", CSs) by co-culturing human primary or iPSC-derived cardiomyocytes, endothelial cells and fibroblasts at ratios approximating those present in vivo. The cellular organisation, extracellular matrix and microvascular network mimic human heart tissue. These spheroids have been employed to investigate the dose-limiting cardiotoxicity of the common anti-cancer drug doxorubicin. Viability/cytotoxicity assays indicate dose-dependent cytotoxic effects, which are inhibited by the nitric oxide synthase (NOS) inhibitor L-NIO, and genetic inhibition of endothelial NOS, implicating peroxynitrous acid as a key damaging agent. These data indicate that CSs mimic important features of human heart morphology, biochemistry and pharmacology in vitro, offering a promising alternative to animals and standard cell cultures with regard to mechanistic insights and prediction of toxic effects in human heart tissue.

Microarray and Co-expression Network Analysis of Genes Associated with Acute Doxorubicin Cardiomyopathy in Mice

Clinical use of doxorubicin (DOX) in cancer therapy is limited by its dose-dependent cardiotoxicity. But molecular mechanisms underlying this phenomenon have not been well defined. This study was to investigate the effect of DOX on the changes of global genomics in hearts. Acute cardiotoxicity was induced by giving C57BL/6J mice a single intraperitoneal injection of DOX (15 mg/kg). Cardiac function and apoptosis were monitored using echocardiography and TUNEL assay at days 1, 3 and 5. Myocardial glucose and ATP levels were measured. Microarray assays were used to screen gene expression profiles in the hearts at day 5, and the results were confirmed with qPCR analysis. DOX administration caused decreased cardiac function, increased cardiomyocyte apoptosis and decreased glucose and ATP levels. Microarrays showed 747 up-regulated genes and 438 down-regulated genes involved in seven main functional categories. Among them, metabolic pathway was the most affected by DOX. Several key genes, including 2,3-bisphosphoglycerate mutase (Bpgm), hexokinase 2, pyruvate dehydrogenase kinase, isoenzyme 4 and fructose-2,6-bisphosphate 2-phosphatase, are closely related to glucose metabolism. Gene co-expression networks suggested the core role of Bpgm in DOX cardiomyopathy. These results obtained in mice were further confirmed in cultured cardiomyocytes. In conclusion, genes involved in glucose metabolism, especially Bpgm, may play a central role in the pathogenesis of DOX-induced cardiotoxicity.

Dissecting the Mechanisms of Doxorubicin and Oxidative Stress-Induced Cytotoxicity: The Involvement of Actin Cytoskeleton and ROCK1

We have recently reported that ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has superior anti-apoptotic and pro-survival effects than antioxidants against doxorubicin, a chemotherapeutic drug. Although oxidative stress is the most widely accepted mechanism, our studies suggest that ROCK1-dependent actin cytoskeleton remodeling plays a more important role in mediating doxorubicin cytotoxicity on MEFs. To further explore the contributions of ROCK1-dependent actin cytoskeleton remodeling in response to stress, this study investigates the mechanistic differences between the cytotoxic effects of doxorubicin versus hydrogen peroxide (H2O2), with a focus on cytoskeleton alterations, apoptosis and necrosis induction. We found that both types of stress induce caspase activation but with different temporal patterns and magnitudes in MEFs: H2O2 induces the maximal levels (2 to 4-fold) of activation of caspases 3, 8, and 9 within 4 h, while doxorubicin induces much higher maximal levels (15 to 25-fold) of caspases activation at later time points (16-24 h). In addition, necrosis induced by H2O2 reaches maximal levels within 4 h while doxorubicin-induced necrosis largely occurs at 16-24 h secondary to apoptosis. Moreover, both types of stress induce actin cytoskeleton remodeling but with different characteristics: H2O2 induces disruption of stress fibers associated with cytosolic translocation of phosphorylated myosin light chain (p-MLC) from stress fibers, while doxorubicin induces cortical F-actin formation associated with cortical translocation of p-MLC from central stress fibers. Furthermore, N-acetylcysteine (an antioxidant) is a potent suppressor for H2O2-induced cytotoxic effects including caspase activation, necrosis, and cell detachment, but shows a much reduced inhibition on doxorubicin-induced changes. On the other hand, ROCK1 deficiency is a more potent suppressor for the cytotoxic effects induced by doxorubicin than by H2O2. These results support the notion that doxorubicin induces caspase activation, necrosis, and actin cytoskeleton alterations largely through ROCK1-dependent and oxidative stress-independent pathways.

ROCK1 deficiency enhances protective effects of antioxidants against apoptosis and cell detachment

We have recently reported that the homologous Rho kinases, ROCK1 and ROCK2, play different roles in regulating stress-induced stress fiber disassembly and cell detachment, and the ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has remarkable anti-apoptotic, anti-detachment and pro-survival effects against doxorubicin, a chemotherapeutic drug. This study investigated the roles of ROCK isoforms in doxorubicin-induced reactive oxygen species (ROS) generation which is believed to be the major mechanism underlying its cytotoxicity to normal cells, and especially to cardiomyocytes. Different antioxidants have been shown to provide a protective role reported in numerous experimental studies, but clinical trials of antioxidant therapy showed insufficient benefit against the cardiac side effect. We found that both ROCK1-/- and ROCK2-/- MEFs exhibited reduced ROS production in response to doxorubicin treatment. Interestingly, only ROCK1 deficiency, but not ROCK2 deficiency, significantly enhanced the protective effects of antioxidants against doxorubicin-induced cytotoxicity. First, ROCK1 deficiency and N-acetylcysteine (an anti-oxidant) treatment synergistically reduced ROS levels, caspase activation and cell detachment. In addition, the reduction of ROS generation in ROCK1-/- MEFs in response to doxorubicin treatment was in part through inhibiting NADPH oxidase activity. Furthermore, ROCK1 deficiency enhanced the inhibitory effects of diphenyleneiodonium (an inhibitor of NADPH oxidase) on ROS generation and caspase 3 activation induced by doxorubicin. Finally, ROCK1 deficiency had greater protective effects than antioxidant treatment, especially on reducing actin cytoskeleton remodeling. ROCK1 deficiency not only reduced actomyosin contraction but also preserved central stress fiber stability, whereas antioxidant treatment only reduced actomyosin contraction without preserving central stress fibers. These results reveal a novel strategy to enhance the protective effect of antioxidant therapy by targeting the ROCK1 pathway to stabilize the actin cytoskeleton and boost the inhibitory effects on ROS production, apoptosis and cell detachment.

αB-crystallin regulates oxidative stress-induced apoptosis in cardiac H9c2 cells via the PI3K/AKT pathway

The present study was carried out to observe the protective effects of αB-crystallin protein on hydrogen peroxide (H2O2)-induced injury in rat myocardial cells (H9c2) and to investigate the mechanisms of these protective effects at the cellular level, which could provide the experimental basis for future applications of αB-crystallin in the treatment of cardiovascular disease. Western blotting was used to measure the expression of αB-crystallin in cultured H9c2 cells in vitro. A αB-crystallin recombinant expression vector, pcDNA3.1-Cryab, was constructed to transfect H9c2 cells for the establishment of cells that stably expressed αB-crystallin. A tetrazolium-based colorimetric assay (MTT test) was used to measure changes in the viability of the H9c2 cells at 1, 2, 3 and 4 h after induced by 150 μM H2O2 to establish a model of H2O2 injury to cells. H2O2 was applied to H9c2 cells that were stably transfected with αB-crystallin, and the effect of αB-crystallin overexpression on the viability of myocardial cells subjected to H2O2-induced injury was measured by the MTT assay. The effect of αB-crystallin overexpression on the H2O2-induced injury of H9c2 cells was also analyzed by flow cytometry. The mitochondrial components and cytoplasmic components of H9c2 cells were separated, and western blotting was used to measure the effect of αB-crystallin overexpression on the release of cytochrome c from the mitochondria. Western blotting was also used to measure the effect of αB-crystallin overexpression on the expression of the anti-apoptosis protein Bcl-2 and components of the phosphatidylinositol 3-OH kinase (PI3K)/AKT pathway. The αB-crystallin recombinant expression vector pcDNA3.1-Cryab successfully transfected H9c2 cells, and H9c2 cells that were stably transfected with αB-crystallin were established after G418 selection. The measurements carried out by western blotting showed that αB-crystallin proteins are expressed in normal H9c2 cells, but the proteins' expression was much higher in pcDNA3.1-Cryab transfected cells (P < 0.01). The MTT assays showed that 4 h of H2O2 treatment induced significant injury in H9c2 cells (P < 0.01), but αB-crystallin overexpression can effectively antagonize the H2O2-induced injury to H9c2 cells (P < 0.05). The results of flow cytometry analysis showed that αB-crystallin overexpression can significantly reduce apoptosis in H2O2-injured H9c2 cells (P < 0.05). The results of western blotting showed that αB-crystallin overexpression in myocardial cells can reduce the H2O2-induced release of cytochrome c from the mitochondria (P < 0.05), antagonize the H2O2-induced downregulation of Bcl-2 (P < 0.05) and magnify the decrease in phosphorylated AKT levels induced by H2O2 injury (P < 0.05). The overexpression of αB-crystallin has a protective effect on H2O2-injured H9c2 cells, and αB-crystallin can play a protective role by reducing apoptosis, reducing the release of cytochrome c from the mitochondria and antagonizing the downregulation of Bcl-2 expression. The protective effects of αB-crystallin may be related to the PI3K/AKT pathway.