Adriamycin, 14-hydroxydaunomycin, a new antitumor antibiotic from S. peucetius var. caesius. Reprinted from Biotechnology and Bioengineering, Vol. XI, Issue 6, Pages 1101-1110 (1969)

Doxorubicin conjugates: a practical approach for its cardiotoxicity alleviation

INTRODUCTION

Doxorubicin (DOX) emerges as a cornerstone in the arsenal of potent chemotherapeutic agents. Yet, the clinical deployment of DOX is tarnished by its proclivity to induce severe cardiotoxic effects, culminating in heart failure and other consequential morbidities. In response, a panoply of strategies has undergone rigorous exploration over recent decades, all aimed at attenuating DOX's cardiotoxic impact. The advent of encapsulating DOX within lipidic or polymeric nanocarriers has yielded a dual triumph, augmenting DOX's therapeutic efficacy while mitigating its deleterious side effects.

AREAS COVERED

Recent strides have spotlighted the emergence of DOX conjugates as particularly auspicious avenues for ameliorating DOX-induced cardiotoxicity. These conjugates entail the fusion of DOX through physical or chemical bonds with diminutive natural or synthetic moieties, polymers, biomolecules, and nanoparticles. This spectrum encompasses interventions that impinge upon DOX's cardiotoxic mechanism, modulate cellular uptake and localization, confer antioxidative properties, or refine cellular targeting.

EXPERT OPINION

The endorsement of DOX conjugates as a compelling stratagem to mitigate DOX-induced cardiotoxicity resounds from this exegesis, amplifying safety margins and the therapeutic profile of this venerated chemotherapeutic agent. Within this ambit, DOX conjugates stand as a beacon of promise in the perpetual pursuit of refining chemotherapy-induced cardiac compromise.

MAR4 Streptomyces: A Unique Resource for Natural Product Discovery

Marine-derived Streptomyces have long been recognized as a source of novel, pharmaceutically relevant natural products. Among these bacteria, the MAR4 clade within the genus Streptomyces has been identified as metabolically rich, yielding over 93 different compounds to date. MAR4 strains are particularly noteworthy for the production of halogenated hybrid isoprenoid natural products, a relatively rare class of bacterial metabolites that possess a wide range of biological activities. MAR4 genomes are enriched in vanadium haloperoxidase and prenyltransferase genes, thus accounting for the production of these compounds. Functional characterization of the enzymes encoded in MAR4 genomes has advanced our understanding of halogenated, hybrid isoprenoid biosynthesis. Despite the exceptional biosynthetic capabilities of MAR4 bacteria, the large body of research they have stimulated has yet to be compiled. Here we review 35 years of natural product research on MAR4 strains and update the molecular diversity of this unique group of bacteria.

Insights into the involvement of long non-coding RNAs in doxorubicin resistance of cancer

Doxorubicin is one of the most classical chemotherapeutic drugs for the treatment of cancer. However, resistance to the cytotoxic effects of doxorubicin in tumor cells remains a major obstacle. Aberrant expression of long non-coding RNAs (lncRNAs) has been associated with tumorigenesis and development via regulation of chromatin remodeling, transcription, and post-transcriptional processing. Emerging studies have also revealed that dysregulation of lncRNAs mediates the development of drug resistance through multiple molecules and pathways. In this review, we focus on the role and mechanism of lncRNAs in the progress of doxorubicin resistance in various cancers, which mainly include cellular drug transport, cell cycle disorder, anti-apoptosis, epithelial-mesenchymal transition, cancer stem cells, autophagy, tumor microenvironment, metabolic reprogramming and signaling pathways. This review is aimed to provide potential therapeutic targets for future cancer therapy, especially for the reversal of chemoresistance.

The potential of facultative predatory Actinomycetota spp. and prospects in agricultural sustainability

Actinomycetota in the phylum of bacteria has been explored extensively as a source of antibiotics and secondary metabolites. In addition to acting as plant growth-promoting agents, they also possess the potential to control various plant pathogens; however, there are limited studies that report the facultative predatory ability of Actinomycetota spp. Furthermore, the mechanisms that underline predation are poorly understood. We assessed the diversity of strategies employed by predatory bacteria to attack and subsequently induce the cell lysing of their prey. We revisited the diversity and abundance of secondary metabolite molecules linked to the different predation strategies by bacteria species. We analyzed the pros and cons of the distinctive predation mechanisms and explored their potential for the development of new biocontrol agents. The facultative predatory behaviors diverge from group attack "wolfpack," cell-to-cell proximity "epibiotic," periplasmic penetration, and endobiotic invasion to degrade host-cellular content. The epibiotic represents the dominant facultative mode of predation, irrespective of the habitat origins. The wolfpack is the second-used approach among the Actinomycetota harboring predatory traits. The secondary molecules as chemical weapons engaged in the respective attacks were reviewed. We finally explored the use of predatory Actinomycetota as a new cost-effective and sustainable biocontrol agent against plant pathogens.

Congo Red as a Supramolecular Carrier System for Doxorubicin: An Approach to Understanding the Mechanism of Action

The uptake and distribution of doxorubicin in the MCF7 line of breast-cancer cells were monitored by Raman measurements. It was demonstrated that bioavailability of doxorubicin can be significantly enhanced by applying Congo red. To understand the mechanism of doxorubicin delivery by Congo red supramolecular carriers, additional monolayer measurements and molecular dynamics simulations on model membranes were undertaken. Acting as molecular scissors, Congo red particles cut doxorubicin aggregates and incorporated them into small-sized Congo red clusters. The mixed doxorubicin/Congo red clusters were adsorbed to the hydrophilic part of the model membrane. Such behavior promoted transfer through the membrane.

Discovery of Proteins Responsible for Resistance to Three Chemotherapy Drugs in Breast Cancer Cells Using Proteomics and Bioinformatics Analysis

Chemoresistance is a daunting obstacle to the effective treatment of breast cancer patients receiving chemotherapy. Although the mechanism of chemotherapy drug resistance has been explored broadly, the precise mechanism at the proteome level remains unclear. Especially, comparative studies between widely used anticancer drugs in breast cancer are very limited. In this study, we employed proteomics and bioinformatics approaches on chemoresistant breast cancer cell lines to understand the underlying resistance mechanisms that resulted from doxorubicin (DR), paclitaxel (PR), and tamoxifen (TAR). In total, 10,385 proteins were identified and quantified from three TMT 6-plex and one TMT 10-plex experiments. Bioinformatics analysis showed that Notch signaling, immune response, and protein re-localization processes were uniquely associated with DR, PR, and TAR resistance, respectively. In addition, proteomic signatures related to drug resistance were identified as potential targets of many FDA-approved drugs. Furthermore, we identified potential prognostic proteins with significant effects on overall survival. Representatively, PLXNB2 expression was associated with a highly significant increase in risk, and downregulation of ACOX3 was correlated with a worse overall survival rate. Consequently, our study provides new insights into the proteomic aspects of the distinct mechanisms underlying chemoresistance in breast cancer.

miR-488-3p Protects Cardiomyocytes against Doxorubicin-Induced Cardiotoxicity by Inhibiting CyclinG1

Objective

To investigate the protective effects and regulatory mechanism of miR-488-3p on doxorubicin-induced cardiotoxicity.

Methods

The C57BL/6 mice and primary cardiomyocytes were used to construct doxorubicin-induced cardiomyocyte injury models in vivo and in vitro. The levels of miR-488-3p and its downstream target genes were analyzed by quantitative real-time PCR. Mouse cardiac function, cell survival, cellular injury-related proteins, and the apoptosis level of cardiomyocytes were analyzed by echocardiography, MTT analysis, Western blotting, and DNA laddering separately.

Results

Cardiomyocyte injury caused by a variety of stimuli can lead to the reduction of miR-488-3p level, especially when stimulated with doxorubicin. Doxorubicin led to significant decrease in cardiac function, cell autophagic flux blockage, and apoptosis in vivo and in vitro. The expression of miR-488-3p's target gene, CyclinG1, increased remarkably in the doxorubicin-treated neonatal mouse cardiomyocytes. Overexpression of miR-488-3p inhibited CyclinG1 expression, increased cardiomyocyte viability, and attenuated doxorubicin-induced cardiomyocyte autophagic flux blockage and apoptosis.

Conclusions

miR-488-3p is one of the important protective miRNAs in doxorubicin-induced cardiotoxicity by inhibiting the expression of CyclinG1, which provides insight into the possible clinical application of miR-488-3p/CyclinG1 as therapeutic targets in doxorubicin-induced cardiovascular diseases.

Innovative approaches for treatment of osteosarcoma

Osteosarcoma (OS) is the most common primary malignant bone tumor, which usually occurs in children and adolescents. It is generally a high-grade malignancy presenting with extreme metastases to the lungs or other bones. The etiology of the disease is multifaceted and still remains obscure. A combination of surgery and chemotherapy has played a major role in the treatment of OS over the past three decades, and consequently, the overall survival rates for the disease have remained unchanged. Therefore, there is an urgent need to employ new comprehensive analyses and technologies to develop significantly more informative classification systems, with the aim of developing more effective and less toxic therapies for OS patients. This review discusses the existing knowledge of OS therapy and potential methods to develop novel therapeutic agents for the disease.

Icariin Protects H9c2 Rat Cardiomyoblasts from Doxorubicin-Induced Cardiotoxicity: Role of Caveolin-1 Upregulation and Enhanced Autophagic Response

Doxorubicin (Doxo) is a widely used antineoplastic drug which often induces cardiomyopathy, leading to congestive heart failure through the intramyocardial production of reactive oxygen species (ROS). Icariin (Ica) is a flavonoid isolated from Epimedii Herba (Berberidaceae). Some reports on the pharmacological activity of Ica explained its antioxidant and cardioprotective effects. The aim of our study was to assess the protective activities of Ica against Doxo-detrimental effects on rat heart-tissue derived embryonic cardiac myoblasts (H9c2 cells) and to identify, at least in part, the molecular mechanisms involved. Our results showed that pretreatment of H9c2 cells with 1 μM and 5 μM of Ica, prior to Doxo exposure, resulted in an improvement in cell viability, a reduction in ROS generation, the prevention of mitochondrial dysfunction and mPTP opening. Furthermore, for the first time, we identified one feasible molecular mechanism through which Ica could exerts its cardioprotective effects. Indeed, our data showed a significant reduction in Caveolin-1(Cav-1) expression levels and a specific inhibitory effect on phosphodiesterase 5 (PDE5a) activity, improving mitochondrial function compared to Doxo-treated cells. Besides, Ica significantly prevented apoptotic cell death and downregulated the main pro-autophagic marker Beclin-1 and LC3 lipidation rate, restoring physiological levels of activation of the protective autophagic process. These results suggest that Ica might have beneficial cardioprotective effects in attenuating cardiotoxicity in patients requiring anthracycline chemotherapy through the inhibition of oxidative stress and, in particular, through the modulation of Cav-1 expression levels and the involvement of PDE5a activity, thereby leading to cardiac cell survival.

Phosphocreatine attenuates doxorubicin-induced cardiotoxicity by inhibiting oxidative stress and activating TAK1 to promote myocardial survival in vivo and in vitro

Myocardial apoptosis and necroptosis are the major etiological factor during doxorubicin (DOX) induced cardiotoxicity, and one of the important reasons that limit the drug's clinical application. Up to date, its mechanism has not been fully elucidated. The protective role of phosphocreatine (PCr) in heart surgery and medical cardiology has been observed in numerous clinical trials. This study aimed to evaluate cardioprotective actions of PCr against DOX-induced cardiotoxicity and investigate the underlying mechanism involving in transforming growth factor β-activated kinase 1 (TAK1) mediated myocardial survive signaling pathway. Male Sprague-Dawleyrats were intraperitoneally (ip) injected with normal saline (NS) or DOX (2 mg/kg) alone or DOX with PCr (200 mg/kg) used as animal model. The data showed that DOX significantly impaired cardiac function and structure, induced oxidative stress, myocardial apoptosis and necroptosis, and dramatically down-regulated the expression level of TAK1, while the intervention of PCr obviously attenuated cardiac dysfunction, oxidative stress, myocardial apoptosis and necroptosis, especially alleviated the decrease of TAK1 expression. In vitro analysis, after H9c2 cells were pretreated with or without PCr (0.5 mM) or N-Acetyl-L-cysteine (NAC, 0.5 mM) or 5Z-7-oxozeaenol (5z-7-Ox, 1 μM) for 1 h, subsequently treated with DOX (1 μM) for 24 h. The results revealed that inhibition of TAK1 further deteriorated apoptotic and necroptotic cell death induced by DOX in H9c2 cells, but didn't affect oxidative stress. While the pretreatment of PCr or NAC enhanced antioxidant activity to reduce oxidative stress, significantly alleviated apoptotic and necroptotic cell death induced by DOX in H9c2 cells. Consistent with the results in vivo, PCr or NAC significantly inhibited the decrease of TAK1 expression induced by DOX. In conclusion, oxidative stress induced by DOX inhibits the expression of TAK1, and leads to myocardial apoptotic and necroptotic death, while the intervention of PCr increases antioxidant activity to alleviate oxidative stress, which in turn activates TAK1 signaling pathway to promote myocardial survival, and finally attenuate DOX-induced cardiotoxicity.

Synthesis, Characterization and Biological Evaluation of Metal Adamantyl 2-Pyridylhydrazone Complexes

Four new complexes derived from adamantly containing hydrazone (APH) ligand with Cu(II) (1), Co(II) (2), Ni(II) (3) and Zn(II) (4), have been synthesized and characterized using different physicochemical methods. The structure of the ligand APH and its copper complex 1 have been established by single-crystal X-ray diffraction direct methods, which reveal that complex 1 has distorted square-pyramidal geometry. Complexes 1–4 are screened against seven human cancer cell lines namely, breast cancer cell lines (MCF7, T47D, MDA-MB-231), prostate cancer cell lines (PC3, DU145) and the colorectal cancer cell line Coco-2, for their antiproliferative activities. Complex 1 has shown a promising anticancer activity compared to the other ones. The structural and spectroscopic analysis of APH and its complexes are confirmed by DFT calculations.

Circulating MicroRNAs as Potential Predictors of Anthracycline-Induced Troponin Elevation in Breast Cancer Patients: Diverging Effects of Doxorubicin and Epirubicin

Anthracyclines are anti-neoplastic drugs presenting cardiotoxicity as a side effect. Cardiac troponins (cTn) and echocardiography are currently used to assess cardiac damage and dysfunction, but early biomarkers identifying patients in need of preventive treatments remain a partially met need. Circulating microRNAs (miRNAs) represent good candidates, so we investigated their possible roles as predictors of troponin elevation upon anthracycline treatment. Eighty-eight female breast cancer patients administered with doxorubicin (DOX) or epirubicin (EPI) were divided into four groups basing on drug type and cTn positive (cTn+) or negative (cTn−) levels: DOX cTn−, DOX cTn+, EPI cTn− and EPI cTn+. Blood was collected at baseline, during treatment, and at follow-up. We identified plasma miRNAs of interest by OpenArray screening and single assay validation. Our results showed miR-122-5p, miR-499a-5p and miR-885-5p dysregulation in DOX patients at T0, identifying a signature separating, with good accuracy, DOX cTn− from DOX cTn+. No miRNAs showed differential expression in EPI subjects. Conversely, an anthracycline-mediated modulation (regardless of cTn) was observed for miR-34a-5p, -122-5p and -885-5p. Our study indicates specific circulating miRNAs as possible prediction markers for cardiac troponin perturbation upon anthracycline treatment. Indeed, our findings hint at the possible future use of plasma miRNAs to predict the cardiac responsiveness of patients to different anticancer agents.

Cardioprotection in cancer therapy: novel insights with anthracyclines

Anthracyclines are a class of antineoplastic agents that remain critical to modern-day cancer treatment. However, their propensity to cause cardiotoxic effects limits their use and can cause increased morbidity and mortality among patients with cancer. Currently available methods to minimize the impact of anthracycline cardiotoxicity have not been widely successful. While it is largely accepted that the generation of oxygen radicals contributes to the development of anthracycline cardiotoxicity, the exact mechanisms of cardiomyocyte injury remain unclear. In this review, we discuss the current state of basic and translational research on the cardiotoxic mechanisms of anthracyclines that have led to the discovery of new therapeutic targets. Pending validation in patient populations, these recent advances have the potential to be translated into clinical approaches that will minimize anthracycline cardiotoxicity and improve outcomes in cancer survivors.

Review on the Role of Epigenetic Modifications in Doxorubicin-Induced Cardiotoxicity

Use of anthracyclines such as doxorubicin (DOX), for the treatment of cancer, is known to induce cardiotoxicity, begetting numerous evaluations of this adverse effect. This review emphasizes the mechanism of how consideration of DOX-induced cardiotoxicity is important for the development of cardioprotective agents. As DOX is involved in mitochondrial dysfunction, enzymes involved in epigenetic modifications that use mitochondrial metabolite as substrate are most likely to be affected. Therefore, this review article focuses on the fact that epigenetic modifications, namely, DNA methylation, histone modifications, and noncoding RNA expression, contribute to DOX-associated cardiotoxicity. Early interventions needed for patients undergoing chemotherapy, to treat or prevent heart failure, would, overall, improve the survival, and quality of life of cancer patients. These epigenetic modifications can either be used as molecular markers for cancer prognosis or represent molecular targets to attenuate DOX-induced cardiotoxicity in cancer patients.

New molecular and biochemical insights of doxorubicin-induced hepatotoxicity

Chemotherapeutic antibiotic doxorubicin belongs to the anthracycline class, slaughters not only the cancer cells but also non-cancerous cells even in the non-targeted organs thereby resulting in the toxicity. The liver is primarily involved in the process of detoxification and this mini-review we focused mainly to investigate the molecular mechanisms heading hepatotoxicity caused due to doxorubicin administration. The alterations in the doxorubicin treated liver tissue include vacuolation of hepatocytes, degeneration of hepatocyte cords, bile duct hyperplasia and focal necrosis. About the literature conducted, hepatotoxicity caused by doxorubicin has been explained by estimating the levels of liver serum biomarkers, ROS production, antioxidant enzymes, lipid peroxidation, and mitochondrial dysfunction. The liver serum biomarkers such as ALT and AST, elated levels of free radicals inducing oxidative stress characterized by a surge in Nrf-2, FOXO-1 and HO-1 genes and diminution of anti-oxidant activity characterized by a decline in SOD, GPx, and CAT genes. The augmented levels of SGOT, SGPT, LDH, creatine kinase, direct and total bilirubin levels also reveal the toxicity in the hepatic tissue due to doxorubicin treatment. The molecular insight of hepatotoxicity is mainly due to the production of ROS, ameliorated oxidative stress and inflammation, deteriorated mitochondrial production and functioning, and enhanced apoptosis. Certain substances such as extracts from medicinal plants, natural products, and chemical substances have been shown to produce an alleviating effect against the doxorubicin-induced hepatotoxicity are also discussed.

Protective effects of dimethyl itaconate in mice acute cardiotoxicity induced by doxorubicin

Doxorubicin (DOX) is an antitumor drug widely used in hematological tumors and various solid tumors. However, the cardiotoxicity elicited by DOX severely limits its clinical treatment. Dimethyl itaconate (DI), a common form of itaconate, is found many potential targets for prevent heart injury. Here we employed wild type and Nrf2 knockout mice and induced a cardiotoxicity model by administration of DOX to clarify the effects of DI. After treatment with DI, we found that it could effectively alleviate the cardiotoxicity by analyzing morphology, LDH levels and heart weight/body weight ratio changes. Meanwhile we demonstrated that RIP3, a key protein of necrosis, was significantly decreased in DI treated group. Further we observed that treatment with DI could suppress oxidative stress by altering Nrf2/HO-1. Compared with vehicle group, DI could increase the tissue SOD and GSH, and reduce MDA levels, then DHE staining revealed that the level of ROS in DI group reduced by half. Finally, transmission electron microscope (TEM) data showed that treatment with DI obviously decreased the mitochondrial damage. While Nrf2 was ablated in mice, the protective effects of DI were vanished and SOD, GSH, MDA became unchanged related to vehicle group. This report provides the evidence for the protective effects of DI treatment in cardiotoxicity induced by DOX. On mechanisms, DI could reduce the oxidative stress by altering Nrf2/HO-1 pathway and prevent mitochondrial from damage. Taken together, these findings of this paper will afford the new therapeutic targets in DOX related cardiotoxicity.

Development of 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and their salts as potent cytotoxic agents and topoisomerase I/IIα inhibitors

A novel series of 35 angularly fused pentacyclic 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridines and 13H-benzo[f]chromeno[4,3-b][1,7]naphthyridin-5-ium chlorides were designed and synthesized. Their cytotoxic activities were investigated against six human cancer cell lines (NCIH23, HCT15, NUGC-3, ACHN, PC-3, and MDA-MB-231). Among all screened compounds; 28, 30, 34, 35, 46, 48, 52, and 53 compounds exhibited potent cytotoxic activities against all tested human cancer cell lines. Further, these potent lead cytotoxic agents were evaluated against human Topoisomerase I and IIα inhibition. Among them, the compound 48 exhibited dual Topoisomerase I and IIα inhibition especially at 20 μM concentrations the compound 48 exhibited 1.25 times more potent Topoisomerase IIα inhibitory activity (38.3%) than the reference drug etoposide (30.6%). The compound 52 also exhibited excellent (88.4%) topoisomerase I inhibition than the reference drug camptothecin (66.7%) at 100 μM concentrations. Molecular docking studies of the compounds 48 and 52 with topo I discovered that they both intercalated into the DNA single-strand cleavage site where the compound 48 have van der Waals interactions with residues Arg364, Pro431, and Asn722 whilst the compound 52 have with Arg364, Thr718, and Asn722 residues. Both the compounds 48 and 52 have π-π stacking interactions with the stacked DNA bases. The docking studies of the compound 48 with topo IIα explored that it was bound to the topo IIα DNA cleavage site where etoposide was situated. The benzo[f]chromeno[4,3-b][1,7]naphthyridine ring of the compound 48 was stacked between the DNA bases of the cleavage site with π-π stacking interactions and there were no hydrogen bond interactions with topo IIα.

Sulbactam-enhanced cytotoxicity of doxorubicin in breast cancer cells

BACKGROUND

Multidrug resistance (MDR) is a major obstacle in breast cancer treatment. The predominant mechanism underlying MDR is an increase in the activity of adenosine triphosphate (ATP)-dependent drug efflux transporters. Sulbactam, a β-lactamase inhibitor, is generally combined with β-lactam antibiotics for treating bacterial infections. However, sulbactam alone can be used to treat Acinetobacter baumannii infections because it inhibits the expression of ATP-binding cassette (ABC) transporter proteins. This is the first study to report the effects of sulbactam on mammalian cells.

METHODS

We used the breast cancer cell lines as a model system to determine whether sulbactam affects cancer cells. The cell viabilities in the present of doxorubicin with or without sulbactam were measured by MTT assay. Protein identities and the changes in protein expression levels in the cells after sulbactam and doxorubicin treatment were determined using LC-MS/MS. Real-time reverse transcription polymerase chain reaction (real-time RT-PCR) was used to analyze the change in mRNA expression levels of ABC transporters after treatment of doxorubicin with or without sulbactam. The efflux of doxorubicin was measures by the doxorubicin efflux assay.

RESULTS

MTT assay revealed that sulbactam enhanced the cytotoxicity of doxorubicin in breast cancer cells. The results of proteomics showed that ABC transporter proteins and proteins associated with the process of transcription and initiation of translation were reduced. The mRNA expression levels of ABC transporters were also decreased when treated with doxorubicin and sulbactam. The doxorubicin efflux assay showed that sulbactam treatment inhibited doxorubicin efflux.

CONCLUSIONS

The combination of sulbactam and doxorubicin enhances the cytotoxicity of doxorubicin in the breast cancer cells by inhibiting the expression of ABC transporter proteins and proteins associated with the process of transcription and initiation of translation, and blocking the efflux of doxorubicin. Co-treatment of doxorubicin and sulbactam can be used in breast cancer treatment to decrease the prescribed dose of doxorubicin to avoid the adverse effects of doxorubicin.

Activity of CoII-Quinalizarin: A Novel Analogue of Anthracycline-Based Anticancer Agents Targets Human DNA Topoisomerase, Whereas Quinalizarin Itself Acts via Formation of Semiquinone on Acute Lymphoblastic Leukemia MOLT-4 and HCT 116 Cells

Quinalizarin (THAQ), a hydroxy-9,10-anthraquinone analogue of the family of anthracycline anticancer drugs and an inhibitor of protein kinase, was observed for its anticancer activity. Because apart from showing anticancer activity, anthracyclines and their analogues also show cardiotoxic side effects, believed to be addressed through metal complex formation; an effort was made to realize this by preparing a Co^II complex of THAQ. The aim of this study was to find out if complex formation leads to a decrease in the generation of intermediates that are responsible for toxic side effects. However, because this also meant that efficacy on cancer cells would be compromised, studies were undertaken on two cancer cell lines, namely, acute lymphoblastic leukemia (ALL) MOLT-4 and HCT116 cells. The complex decreases the flow of electrons from NADH to molecular oxygen (O₂) in the presence of NADH dehydrogenase forming less semiquinone than THAQ. It showed increased affinity toward DNA with binding constant values remaining constant over the physiological pH range unlike THAQ (for which decrease in binding constant values with increase in pH was observed). The complex is probably a human DNA topoisomerase I and human DNA topoisomerase II poison acting by stabilizing the covalent topoisomerase-cleaved DNA adduct, a phenomenon not observed for THAQ. Activity of the compounds on cancer cells suggests that THAQ was more effective on ALL MOLT-4 cells, whereas the complex performed better on HCT116 cells. Results suggest that the formation of semiquinone probably dominates the action because of THAQ, whereas the performance of the complex is attributed to increased DNA binding, inhibition of topoisomerase, and so forth. Inspite of a decrease in the generation of superoxide by the complex, it did not hamper efficacy on either cell line, probably compensated by improved DNA binding and inhibition of topoisomerase enzymes which are positive attributes of complex formation. A decrease in superoxide formation suggests that the complex could be less cardiotoxic, thus increasing its therapeutic index.

Doxorubicin-conjugated dexamethasone induced MCF-7 apoptosis without entering the nucleus and able to overcome MDR-1-induced resistance

Background

Doxorubicin (DOX) is the most widely used chemotherapeutic agent that has multimodal cytotoxicity. The main cytotoxic actions of DOX occur in the nucleus. The emergence of drug-resistant cancer cells that have the ability to actively efflux DOX out of the nucleus, and the cytoplasm has led to the search for a more effective derivative of this drug.

Materials and methods

We created a new derivative of DOX that was derived via simple conjugation of the 3' amino group of DOX to the dexamethasone molecule.

Results

Despite having a lower cytotoxic activity in MCF-7 cells, the conjugated product, DexDOX, exerted its actions in a manner that was different to that of DOX. DexDOX rapidly induced MCF-7 cell apoptosis without entering the nucleus. Further analysis showed that Dex-DOX increased cytosolic oxidative stress and did not interfere with the cell cycle. In addition, the conjugated product retained its cytotoxicity in multidrug resistance-1-overexpressing MCF-7 cells that had an approximately 16-fold higher resistance to DOX.

Conclusion

We have synthesized a new derivative of DOX, which has the ability to overcome multidrug resistance-1-induced resistance. This molecule may have potential as a future chemotherapeutic agent.

Diethyl Blechnic, a Novel Natural Product Isolated from Salvia miltiorrhiza Bunge, Inhibits Doxorubicin-Induced Apoptosis by Inhibiting ROS and Activating JNK1/2

Doxorubicin (DOX) is a widely used antineoplastic agent in clinics. However, its clinical application is largely limited by its cardiotoxicity. Diethyl blechnic (DB) is a novel compound isolated from Salvia miltiorrhiza Bunge. Here, we study the effect of DB on DOX-induced cardiotoxicity and its underlying mechanisms. Cellular viability was tested by 3-[-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and protein level was evaluated by Western blotting. 5,5’,6,6’-tetrachloro-1,1’,3,3’-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining was performed to determine the mitochondrial membrane potential (MMP). Hoechst 33342 staining and TUNEL staining was performed to test the apoptosis. Reactive oxygen species (ROS) generation was investigated by using flow cytometry. DB significantly inhibited DOX-induced apoptosis in H9c2 cells and primary cultured cardiomyocytes. Moreover, DB decreased cell apoptotic morphological changes and reversed the mitochondrial membrane potential induced by DOX. Meanwhile, pre-treatment with DB increased the expression levels of B-cell lymphoma 2 (Bcl-2), B-cell lymphoma-extra-large (Bcl-xl), and survivin and reduced the expression levels of Bcl-2-associated X protein (Bax), p-p53, cytochrome c (cyt c), and cleaved-caspase 3, 7, 8, 9 in the protein levels in DOX-treated H9c2 cells. Furthermore, DB suppressed ROS generation. The DB-mediated protective effects were accompanied by increased c-Jun N-terminal kinase1/2 (JNK1/2) expression. In addition, SP600125, the inhibitor of JNK1/2, abolished the protective effect of DB. We concluded that DB protected cardiomyocytes against DOX-induced cytotoxicity by inhibiting ROS and activating the JNK1/2 pathway. Therefore, DB is a promising candidate as a cardioprotective agent against DOX-induced cardiotoxicity.

Transmembrane TNF-alpha promotes chemoresistance in breast cancer cells

Chemoresistance remains a major obstacle to successful treatment of breast cancer. Although soluble tumor necrosis factor-α (sTNF-α) has been implicated in mediating drug-resistance in human cancers, whether transmembrane tumor necrosis factor-α (tmTNF-α) plays a role in chemoresistance remains unclear. Here we found that over 50% of studied patients expressed tmTNF-α at high levels in breast cancer tissues and tmTNF-α expression positively correlated with resistance to anthracycline chemotherapy. Alteration of tmTNF-α expression changed the sensitivity of primary human breast cancer cells and breast cancer cell lines to doxorubicin (DOX). Overexpression of N-terminal fragment (NTF) of tmTNF-α, a mutant form with intact intracellular domain of tmTNF-α to transmit reverse signals, induced DOX-resistance. Mechanistically, the tmTNF-α/NTF-ERK-GST-π axis and tmTNF-α/NTF-NF-κB-mediated anti-apoptotic functions were required for tmTNF-α-induced DOX-resistance. In a xenograft mouse model, the combination of tmTNF-α suppression with chemotherapy significantly enhanced the efficacy of DOX. Our data indicate that tmTNF-α mediates DOX-resistance through reverse signaling and targeting tmTNF-α may be beneficial for the treatment of DOX-resistant breast cancer.

Recent progress in doxorubicin-induced cardiotoxicity and protective potential of natural products

BACKGROUND

As an anthracycline antibiotic, doxorubicin (DOX) is one of the most potent and widely used chemotherapeutic agents for various types of solid tumors. Unfortunately, clinical application of this drug results in severe side effects of cardiotoxicity.

PURPOSE

We aim to review the research focused on elimination or reduction of DOX cardiotoxicity without affecting its anticancer efficacy by natural products.

METHODS

This study is based on pertinent papers that were retrieved by a selective search using relevant keywords in PubMed and ScienceDirect. The literature mainly focusing on natural products and herb extracts with therapeutic efficacies against experimental models both in vitro and in vivo was identified.

RESULTS

Current evidence revealed that multiple molecules and signaling pathways, such as oxidative stress, iron metabolism, and inflammation, are associated with DOX-induced cardiotoxicity. Based on these knowledge, various strategies were proposed, and thousands of compounds were screened. A number of natural products and herb extracts demonstrated potency in limiting DOX cardiotoxicity toward cultured cells and experimental animal models.

CONCLUSIONS

Though a panel of natural products and herb extracts demonstrate protective effects on DOX-induced cardiotoxicity in cells and animal models, their therapeutic potentials for clinical needs further investigation.

Impact of genistein on the gut microbiome of humanized mice and its role in breast tumor inhibition

Since dietary polyphenols can have beneficial effects in prevention and treatment of cancer, we tested the hypothesis that breast cancer patients’ intestinal microbiota is modulated by genistein (GE), an isoflavone found in soy, and that microbial alterations may offset the side effects brought about by chemotherapy. We demonstrated successful humanization of germ-free mice by transplanting fecal samples from breast cancer patients before and after chemotherapy. Mice were then grouped based on chemotherapy status and GE or control diet. We did not find any significant differences between pre-chemotherapy and post-chemotherapy bacterial composition and abundances. Germ-free mice on a GE diet showed differences in microbial composition as compared to mice on control diet. Four weeks after introduction of the customized GE diet, there was distinct clustering of GE-fed mice as compared to the control-fed group. In the gut microbiome of GE-treated humanized mice, there was an increase in abundance of genera Lactococcus and Eubacterium. Phylum Verrucomicrobia showed statistically significant (p = 0.02) differences in abundances between the GE-fed and control-fed groups. There was an increase in bacteria belonging to family Lachnospiraceae and Ruminococcaceae in GE-fed mice. Marked changes were observed in GE catabolism in mice humanized with fecal material from two of three patients’ post-chemotherapy with complete disappearance of 4-ethylphenol and 2-(4-hydroxyphenol) propionic acid conjugates. The post-tumor samples did not show any distinct clustering of the gut microbiota between the two diet groups. There was an increase in latency of about 25% for tumor growth of the humanized mice that were on a GE diet as compared to humanized mice on a control diet. The average tumor size for the GE group was significantly decreased compared to the non-GE group. Collectively, our results suggest that the intestinal microbiota becomes altered with a GE diet before induction of tumor. Our findings indicate that GE modulates the microbiome in humanized mice that may contribute to its effects on increasing the latency of breast tumor and reducing tumor growth.

Altered mitochondrial epigenetics associated with subchronic doxorubicin cardiotoxicity

Doxorubicin (DOX), a potent and broad-spectrum antineoplastic agent, causes an irreversible, cumulative and dose-dependent cardiomyopathy that ultimately leads to congestive heart failure. The mechanisms responsible for DOX cardiotoxicity remain poorly understood, but seem to involve mitochondrial dysfunction on several levels. Epigenetics may explain a portion of this effect. Since mitochondrial dysfunction may affect the epigenetic landscape, we hypothesize that this cardiac toxicity may result from epigenetic changes related to disruption of mitochondrial function. To test this hypothesis, eight-week-old male Wistar rats (n=6/group) were administered 7 weekly injections with DOX (2mgkg^-1) or saline, and sacrificed two weeks after the last injection. We assessed gene expression patterns by qPCR, global DNA methylation by ELISA, and proteome lysine acetylation status by Western blot in cardiac tissue from saline and DOX-treated rats. We show for the first time that DOX treatment decreases global DNA methylation in heart but not in liver. These differences were accompanied by alterations in mRNA expression of multiple functional gene groups. DOX disrupted cardiac mitochondrial biogenesis, as demonstrated by decreased mtDNA levels and altered transcript levels for multiple mitochondrial genes encoded by both nuclear and mitochondrial genomes. Transcription of genes involved in lipid metabolism and epigenetic modulation were also affected. Western blotting analyses indicated a differential protein acetylation pattern in cardiac mitochondrial fractions of DOX-treated rats compared to controls. Additionally, DOX treatment increased the activity of histone deacetylases. These results suggest an interplay between mitochondrial dysfunction and epigenetic alterations, which may be a primary determinant of DOX-induced cardiotoxicity.

A Droplet Microfluidics Based Platform for Mining Metagenomic Libraries for Natural Compounds

Historically, microbes from the environment have been a reliable source for novel bio-active compounds. Cloning and expression of metagenomic DNA in heterologous strains of bacteria has broadened the range of potential compounds accessible. However, such metagenomic libraries have been under-exploited for applications in mammalian cells because of a lack of integrated methods. We present an innovative platform to systematically mine natural resources for pro-apoptotic compounds that relies on the combination of bacterial delivery and droplet microfluidics. Using the violacein operon from C. violaceum as a model, we demonstrate that E. coli modified to be invasive can serve as an efficient delivery vehicle of natural compounds. This approach permits the seamless screening of metagenomic libraries with mammalian cell assays and alleviates the need for laborious extraction of natural compounds. In addition, we leverage the unique properties of droplet microfluidics to amplify bacterial clones and perform clonal screening at high-throughput in place of one-compound-per-well assays in multi-well format. We also use droplet microfluidics to establish a cell aggregate strategy that overcomes the issue of background apoptosis. Altogether, this work forms the foundation of a versatile platform to efficiently mine the metagenome for compounds with therapeutic potential.

Inhibition of Carbonyl Reductase 1 Safely Improves the Efficacy of Doxorubicin in Breast Cancer Treatment

AIMS

Doxorubicin (DOX) is a chemotherapeutic drug that is used to treat many cancers, but its use is limited by cardiotoxic side effect. Carbonyl reductase 1 (CBR1) is an NADPH-dependent oxidoreductase that reduces DOX to doxorubicinol (DOXOL), a less potent derivative that is responsible for DOX cardiotoxicity. Thus, we aimed to demonstrate that inhibition of CBR1 enhances the chemotherapeutic efficacy of DOX and attenuates cardiotoxicity.

RESULTS

Pharmacological or genetic inhibition of CBR1 improved the anticancer effects of DOX in preclinical models of breast cancer. RNA interference or chemical inhibition of CBR1 improved the anticancer effect of DOX in breast cancer. Moreover, CBR1 overexpression enabled breast cancer cells to obtain chemotherapeutic resistance to DOX treatment. Intriguingly, inhibition of CBR1 decreased DOX-induced cardiotoxicity in animal model. Innovation and Conclusions: Inhibition of CBR1 increases chemotherapeutic efficacy of DOX and reduces cardiotoxicity by blocking DOX reduction to DOXOL. Therefore, we offer preclinical proof-of-concept for a combination strategy to safely leverage the efficacy of doxorubicin by blunting its cardiotoxic effects that limit use of this cytotoxic agent used widely in the oncology clinic. Antioxid. Redox Signal. 26, 70-83.

iPSC-MSCs with High Intrinsic MIRO1 and Sensitivity to TNF-α Yield Efficacious Mitochondrial Transfer to Rescue Anthracycline-Induced Cardiomyopathy

Mesenchymal stem cells (MSCs) can donate mitochondria and rescue anthracycline-induced cardiomyocyte (CM) damage, although the underlying mechanisms remain elusive. We determined that the superior efficiency of mitochondrial transfer by human induced-pluripotent-stem-cell-derived MSCs (iPSC-MSCs) compared with bone marrow-derived MSCs (BM-MSCs) is due to high expression of intrinsic Rho GTPase 1 (MIRO1). Further, due to a higher level of TNFαIP2 expression, iPSC-MSCs are more responsive to tumor necrosis factor alpha (TNF-α)-induced tunneling nanotube (TNT) formation for mitochondrial transfer to CMs, which is regulated via the TNF-α/NF-κB/TNFαIP2 signaling pathway. Inhibition of TNFαIP2 or MIRO1 in iPSC-MSCs reduced the efficiency of mitochondrial transfer and decreased CMs protection. Compared with BM-MSCs, transplantation of iPSC-MSCs into a mouse model of anthracycline-induced cardiomyopathy resulted in more human mitochondrial retention and bioenergetic preservation in heart tissue. Efficacious transfer of mitochondria from iPSC-MSCs to CMs, due to higher MIRO1 expression and responsiveness to TNF-α-induced nanotube formation, effectively attenuates anthracycline-induced CM damage.

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Functional mitochondrial transfer of iPSC-MSCs attenuates Dox-induced cardiomyopathy

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High intrinsic Miro1 in iPSC-MSCs contributes to efficacious mitochondrial transfer

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iPSC-MSCs are highly responsive to TNF-α-induced tunneling nanotube formation

The anti-cancerous drug doxorubicin decreases the c-di-GMP content in Pseudomonas aeruginosa but promotes biofilm formation

Current antibiotic treatments are insufficient in eradicating bacterial biofilms, which represent the primary cause of chronic bacterial infections. Thus, there is an urgent need for new strategies to eradicate biofilm infections. The second messenger c-di-GMP is a positive regulator of biofilm formation in many clinically relevant bacteria. It is hypothesized that drugs lowering the intracellular level of c-di-GMP will force biofilm bacteria into a more treatable planktonic lifestyle. To identify compounds capable of lowering c-di-GMP levels in Pseudomonas aeruginosa, we screened 5000 compounds for their potential c-di-GMP-lowering effect using a recently developed c-di-GMP biosensor strain. Our screen identified the anti-cancerous drug doxorubicin as a potent c-di-GMP inhibitor. In addition, the drug decreased the transcription of many biofilm-related genes. However, despite its effect on the c-di-GMP content in P. aeruginosa, doxorubicin was unable to inhibit biofilm formation or disperse established biofilms. On the contrary, the drug was found to promote P. aeruginosa biofilm formation, possibly through release of extracellular DNA from a subpopulation of killed bacteria. Our findings emphasize that lowering of the c-di-GMP content in bacteria might not be sufficient to mediate biofilm inhibition or dispersal.

Nilotinib reverses ABCB1/P-glycoprotein-mediated multidrug resistance but increases cardiotoxicity of doxorubicin in a MDR xenograft model

The BCR-Abl tyrosine kinase inhibitor (TKI), nilotinib, was developed to surmount resistance or intolerance to imatinib in patients with Philadelphia-positive chronic myelogenous leukemia. Recent studies have shown that nilotinib induces potent sensitization to anticancer agents by blocking the functions of ABCB1/P-glycoprotein (P-gp) in multidrug resistance (MDR). However, changes in P-gp expression or function affect the cardiac disposition and prolong the presence of both doxorubicin (DOX) and doxorubicinol (DOXol) in cardiac tissue, thus, enhancing the risk of cardiotoxicity. In this study, we used a MDR xenograft model to evaluate the antitumor activity, tissue distribution and cardiotoxicity of DOX when co-administered with nilotinib. This information will provide more insight into the pharmacological role of nilotinib in MDR reversal and the risk of DOX cardiotoxicity. Our results showed that nilotinib significantly enhanced DOX cytotoxicity and increased intracellular rhodamine 123 accumulation in MG63/DOX cells in vitro and strongly enhanced DOX inhibition of growth of P-gp-overexpressing MG63/DOX cell xenografts in nude mice. Additionally, nilotinib significantly increased DOX and DOXol accumulation in serum, heart, liver and tumor tissues. Importantly, nilotinib induced a disproportionate increase in DOXol in cardiac tissue. In the co-administration group, CBR1 and AKR1A1 protein levels were significantly increased in cardiac tissue, with more severe necrosis and vacuole formation. These results indicate that nilotinib reverses P-gp- mediated MDR by blocking the efflux function and potentiates DOX-induced cardiotoxicity. These findings represent a guide for the design of future clinical trials and studies of pharmacokinetic interactions and may be useful in guiding the use of nilotinib in combination therapy of cancer in clinical practice.

Towards99mTc-based imaging agents with effective doxorubicin mimetics: a molecular and cellular study

^99mTc and Re conjugates of Doxorubicin accumulate in the nucleus, bind tightly to DNA and retain hTopoII inhibition.

A comprehensive review of glycosylated bacterial natural products

A systematic analysis of all naturally-occurring glycosylated bacterial secondary metabolites reported in the scientific literature up through early 2013 is presented. This comprehensive analysis of 15 940 bacterial natural products revealed 3426 glycosides containing 344 distinct appended carbohydrates and highlights a range of unique opportunities for future biosynthetic study and glycodiversification efforts.

Nuclear Targeting with an Auger Electron Emitter Potentiates the Action of a Widely Used Antineoplastic Drug

We present the combination of the clinically well-proven chemotherapeutic agent, Doxorubicin, and (99m)Tc, an Auger and internal conversion electron emitter, into a dual-action agent for therapy. Chemical conjugation of Doxorubicin to (99m)Tc afforded a construct which autonomously ferries a radioactive payload into the cell nucleus. At this site, damage is exerted by dose deposition from Auger radiation. The (99m)Tc-conjugate exhibited a dose-dependent inhibition of survival in a selected panel of cancer cells and an in vivo study in healthy mice evidenced a biodistribution which is comparable to that of the parent drug. The homologous Rhenium conjugate was found to effectively bind to DNA, inhibited human Topoisomerase II, and exhibited cytotoxicity in vitro. The collective in vitro and in vivo data demonstrate that the presented metallo-conjugates closely mimic native Doxorubicin.

A phase I study of pegylated liposomal doxorubicin and temsirolimus in patients with refractory solid malignancies

This study aimed to determine the maximum-tolerated dose and dose-limiting toxicities of pegylated liposomal doxorubicin (PLD) in combination with temsirolimus (T) in patients with refractory solid tumors. Using a standard “3+3” dose escalation design, 23 patients were enrolled in three dosing cohorts in this phase I study. The starting dose level was PLD at 30 mg/m² every 4 weeks and T at 20 mg weekly. Pharmacokinetics (PK) of doxorubicin were evaluated for patients in the expansion cohort. The most common treatment-related adverse events of all grades were mucositis/stomatitis (69.6 %), anorexia (52.2 %), thrombocytopenia (52.2 %), and fatigue (47.8 %). The recommended doses of this combination for phase II studies are 25 mg/m² PLD and 25 mg T. PK analyses suggested increased exposure of doxorubicin in this combination regimen compared to doxorubicin administered as a single agent, possibly due to PK drug interactions. Out of 18 patients evaluable for a treatment response, two had partial responses (PR) (breast cancer and hepatocellular carcinoma) and six had stable disease (SD). Two patients remained on treatment for more than 1 year. The combination of PLD and T is tolerable, and the treatment resulted in clinical benefit. The combination regimen should be further explored in appropriate tumor types.

AMP-activated protein kinase α2 and E2F1 transcription factor mediate doxorubicin-induced cytotoxicity by forming a positive signal loop in mouse embryonic fibroblasts and non-carcinoma cells

Doxorubicin is one of the most widely used anti-cancer drugs, but its clinical application is compromised by severe adverse effects in different organs including cardiotoxicity. In the present study we explored mechanisms of doxorubicin-induced cytotoxicity by revealing a novel role for the AMP-activated protein kinase α2 (AMPKα2) in mouse embryonic fibroblasts (MEFs). Doxorubicin robustly induced the expression of AMPKα2 in MEFs but slightly reduced AMPKα1 expression. Our data support the previous notion that AMPKα1 harbors survival properties under doxorubicin treatment. In contrast, analyses of Ampkα2(-/-) MEFs, gene knockdown of AMPKα2 by shRNA, and inhibition of AMPKα2 activity with an AMPK inhibitor indicated that AMPKα2 functions as a pro-apoptotic molecule under doxorubicin treatment. Doxorubicin induced AMPKα2 at the transcription level via E2F1, a transcription factor that regulates apoptosis in response to DNA damage. E2F1 directly transactivated the Ampkα2 gene promoter. In turn, AMPKα2 significantly contributed to stabilization and activation of E2F1 by doxorubicin, forming a positive signal amplification loop. AMPKα2 directly interacted with and phosphorylated E2F1. This signal loop was also detected in H9c2, C2C12, and ECV (human epithelial cells) cells as well as mouse liver under doxorubicin treatment. Resveratrol, which has been suggested to attenuate doxorubicin-induced cytotoxicity, significantly blocked induction of AMPKα2 and E2F1 by doxorubicin, leading to protection of these cells. This signal loop appears to be non-carcinoma-specific because AMPKα2 was not induced by doxorubicin in five different tested cancer cell lines. These results suggest that AMPKα2 may serve as a novel target for alleviating the cytotoxicity of doxorubicin.

Chronic doxorubicin cardiotoxicity modulates cardiac cytochrome P450-mediated arachidonic acid metabolism in rats

Doxorubicin [(DOX) Adriamycin] is an effective anticancer agent whose major limiting side effect is cardiotoxicity. This cardiotoxicity is predicted only by the cumulative dose of DOX where the clinical situation involves chronic drug administration. Therefore, we investigate the effect of chronic DOX cardiotoxicity on expression of the cardiac cytochrome P450 (P450) enzymes and arachidonic acid (AA) metabolism in male Sprague-Dawley (SD) rats. The chronic toxicity was induced by multiple intraperitoneal injections for a cumulative dose of 15 mg/kg divided into six injections within 2 weeks. After 14 days of the last injection, the heart, liver, and kidney were harvested, and the expression of different genes was determined by real-time polymerase chain reaction. In addition, microsomal protein from the heart was prepared and incubated with AA. Thereafter, different AA metabolites were analyzed by liquid chromatography-electrospray ionization-mass spectrometry. The chronic DOX cardiotoxicity significantly induced gene expression of hypertrophic markers, apoptotic markers, CYP2E1, CYP4A3, CYP4F1, CYP4F5, and soluble epoxide hydrolase (sEH) enzyme, which was accompanied by an increase in the activity of P450 ω-hydroxylases and sEH. In addition, both the sEH inhibitor, trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid, and the ω-hydroxylase inhibitor, N-hydroxy-N'-(4-butyl-2-methylphenyl)-formamidine (HET0016), significantly prevented the DOX-mediated induction of the hypertrophic markers in the cardiac-derived H9c2 cells, which further confirms the role of these enzymes in DOX cardiotoxicity. Furthermore, gene expression of P450 and sEH was altered in an organ-specific manner. As a result, the chronic DOX administration leads to an imbalance between P450-mediated cardiotoxic and cardioprotective pathways. Therefore, P450 ω-hydroxylases and sEH might be considered as novel targets to prevent and/or treat DOX cardiotoxicity.

Drug-induced mitochondrial dysfunction in cardiac and skeletal muscle injury

BACKGROUND

The list of clinically relevant molecules that affect skeletal and cardiac muscle mitochondria is gradually increasing, which strongly suggest that mitochondrial toxicity should be an important end point during the design and testing of novel pharmaceuticals.

OBJECTIVE

The present review intends to describe mechanisms by which clinically relevant drugs are known to alter mitochondrial function in cardiac and skeletal muscle, which is suggested to be involved in the toxicity associated with those drugs.

METHODS

Literature databases were searched in order to identify clinically relevant drugs with associated mitochondrial muscle toxicity.

CONCLUSION

Mitochondrial function is important in the context of muscle survival, hence, the requirement to identify novel mitochondrial targets and develop new therapies to counteract chemical-induced degeneration of mitochondrial function and muscle performance.

Activation of clinically used anthracyclines by the formaldehyde-releasing prodrug pivaloyloxymethyl butyrate

The anthracycline group of compounds is extensively used in current cancer chemotherapy regimens and is classified as topoisomerase II inhibitor. However, previous work has shown that doxorubicin can be activated to form DNA adducts in the presence of formaldehyde-releasing prodrugs and that this leads to apoptosis independently of topoisomerase II-mediated damage. To determine which anthracyclines would be useful in combination with formaldehyde-releasing prodrugs, a series of clinically relevant anthracyclines (doxorubicin, daunorubicin, idarubicin, and epirubicin) were examined for their capacity to form DNA adducts in MCF7 and MCF7/Dx (P-glycoprotein overexpressing) cells in the presence of the formaldehyde-releasing drug pivaloyloxymethyl butyrate (AN-9). All anthracyclines, with the exception of epirubicin, efficiently yielded adducts in both sensitive and resistant cell lines, and levels of adducts were similar in mitochondrial and nuclear genomes. Idarubicin was the most active compound in both sensitive and resistant cell lines, whereas adducts formed by doxorubicin and daunorubicin were consistently lower in the resistant compared with sensitive cells. The adducts formed by doxorubicin, daunorubicin, and idarubicin showed the same DNA sequence specificity in sensitive and resistant cells as assessed by lambda-exonuclease-based sequencing of alpha-satellite DNA extracted from drug-treated cells. Growth inhibition assays were used to show that doxorubicin, daunorubicin, and idarubicin were all synergistic in combination with AN-9, whereas the combination of epirubicin with AN-9 was additive. Although apoptosis assays indicated a greater than additive effect for epirubicin/AN-9 combinations, this effect was much more pronounced for doxorubicin/AN-9 combinations.