Effects of adriamycin on respiratory chain activities in mitochondria from rat liver, rat heart and bovine heart. Evidence for a preferential inhibition of complex III and IV

Cardiotoxicity of Anticancer Drugs: Molecular Mechanisms, Clinical Management and Innovative Treatment

With the continuous refinement of therapeutic measures, the survival rate of tumor patients has been improving year by year, while cardiovascular complications related to cancer therapy have become increasingly prominent. Exploring the mechanism and prevention strategy of cancer therapy-related cardiovascular toxicity (CTR-CVT) remains one of the research hotspots in the field of Cardio-Oncology in recent years. Cardiotoxicity of anticancer drugs involves heart failure, myocarditis, hypertension, arrhythmias and vascular toxicity, mechanistically related to vascular endothelial dysfunction, ferroptosis, mitochondrial dysfunction and oxidative stress. To address the cardiotoxicity induced by different anticancer drugs, various therapeutic measures have been put in place, such as reducing the accumulation of anticancer drugs, shifting to drugs with less cardiotoxicity, using cardioprotective drugs, and early detection. Due to the very limited treatments available to ameliorate anticancer drugs-induced cardiotoxicity, a few innovations are being shifted from animal studies to human studies. Examples include mitochondrial transplantation. Mitochondrial transplantation has been proven to be effective in in vivo and in vitro experiments. Several recent studies have demonstrated that intercellular mitochondrial transfer can ameliorate doxorubicin(DOX)-induced cardiotoxicity, laying the foundation for innovative therapies in anticancer drugs-induced cardiotoxicity. In this review, we will discuss the current status of anticancer drugs-induced cardiotoxicity in terms of the pathogenesis and treatment, with a focus on mitochondrial transplantation, and we hope that this review will bring some inspiration to you.

A Hypothesis Concerning the role of PPAR family on Cardiac Energetics in Adriamycin-Induced Cardiomyopathy

Adriamycin is an effective anti-neoplastic drug against a variety of cancer types. However, the drug causes adverse side-effects in a number of organ systems. Cardiomyopathy is one of the life-threatening side-effects of Adriamycin. In the current work, we have derived the possible involvement of PPAR family members in the development of Adriamycin-induced cardiomyopathy. Dysregulation of PPAR family by Adriamycin causes impairment in the transport and β-oxidation of fatty acids, the key substrate for ATP synthesis in heart. Evidences suggest that dysregulation of PPAR family results in alters the recruitment of glucose transporters. Furthermore, Hemeoxygenase-1 is a crucial enzyme regulating the iron homeostasis in the heart whose expression is regulated by PPAR family. Inverse relationship exists between the expression levels of PPARγ and hemeoxygenase-1. Adriamycin upregulates the expression of hemeoxygenase-1 which in turn disrupts the iron homeostasis in cardiomyocytes. Our molecular docking results show that Adriamycin has high affinity for iron binding sites of hemeoxygenase-1, thereby hindering formation of iron-sulfur complex. Lack of iron-sulfur complex impairs the electron transport chain. In addition, succinate dehydrogenase subunit A is downregulated by Adriamycin. The lack of this subunit uncouples Krebs cycle from ETC. Further lack of this subunit causes increases the concentration of succinate which further alters the mitochondrial membrane potential. Overall, in the present work we hypothesize that alteration in the expression of PPAR family members is one of the major causes of metabolic chaos and oxidative stress caused by Adriamycin during the development of cardiomyopathy.

PET imaging of mitochondrial function in acute doxorubicin-induced cardiotoxicity: a proof-of-principle study

Mitochondrial dysfunction plays a key role in doxorubicin-induced cardiotoxicity (DIC). In this proof-of-principle study, we investigated whether PET mapping of cardiac membrane potential, an indicator of mitochondrial function, could detect an acute cardiotoxic effect of doxorubicin (DOX) in a large animal model. Eight Yucatan pigs were imaged dynamically with [¹⁸F](4-Fluorophenyl)triphenylphosphonium ([¹⁸F]FTPP⁺) PET/CT. Our experimental protocol included a control saline infusion into the left anterior descending coronary artery (LAD) followed by a DOX test infusion of either 1 mg/kg or 2 mg/kg during PET. We measured the change in total cardiac membrane potential (ΔΨ_T), a proxy for the mitochondrial membrane potential, ΔΨ_m, after the saline and DOX infusions. We observed a partial depolarization of the mitochondria following the DOX infusions, which occurred only in myocardial areas distal to the intracoronary catheter, thereby demonstrating a direct association between the exposure of the mitochondria to DOX and a change in ΔΨ_T. Furthermore, doubling the DOX dose caused a more severe depolarization of myocardium in the LAD territory distal to the infusion catheter. In conclusion, [¹⁸F]FTPP⁺ PET-based ΔΨ_T mapping can measure partial depolarization of myocardial mitochondria following intracoronary DOX infusion in a large animal model.

Mitochondrial-Targeted Therapy for Doxorubicin-Induced Cardiotoxicity

Anthracyclines, such as doxorubicin, are effective chemotherapeutic agents for the treatment of cancer, but their clinical use is associated with severe and potentially life-threatening cardiotoxicity. Despite decades of research, treatment options remain limited. The mitochondria is commonly considered to be the main target of doxorubicin and mitochondrial dysfunction is the hallmark of doxorubicin-induced cardiotoxicity. Here, we review the pathogenic mechanisms of doxorubicin-induced cardiotoxicity and present an update on cardioprotective strategies for this disorder. Specifically, we focus on strategies that can protect the mitochondria and cover different therapeutic modalities encompassing small molecules, post-transcriptional regulators, and mitochondrial transfer. We also discuss the shortcomings of existing models of doxorubicin-induced cardiotoxicity and explore advances in the use of human pluripotent stem cell derived cardiomyocytes as a platform to facilitate the identification of novel treatments against this disorder.

Toxic Mechanisms of the Heart: A Review*

Toxic injury is one of the many ways by which the functional integrity of the heart may become compromised. Any of the subcellular elements may be the target of toxic injury, including all of the various membranes and organelles. Understanding the mechanisms underlying cardiotoxicity may lead to treatment of the toxicity or to its prevention. Doxorubicin and its analogs are very important cancer chemotherapeutic agents that can cause cardiotoxicity. Other agents which are cardiotoxic and which have profound public health implications include the alkaloid emetine in ipecac syrup, cocaine, and ethyl alcohol. The most important cardiotoxic mechanisms proposed for doxorubicin include oxidative stress with its resultant damage to myocardial elements, changes in calcium homeostasis, decreased ability to produce ATP, and systemic release of cardiotoxic humoral mediators from tissue mast cells. Each of the first 3 mechanisms can lead to each of the other 2, and the causal relationships between all of these mechanisms are not clear. New evidence suggests that doxorubicinol, one of the metabolites of doxorubicin may be the moiety responsible for cardiotoxicity. Several other potential mechanisms also have been proposed for doxorubicin. Emetine in ipecac syrup is the first aid treatment of choice for many acute toxic oral ingestions and the alkaloid, itself, is used to treat amebiasis. Cardiotoxicity occurs following chronic exposure, such as occurs therapeutically in amebiasis and with ipecac abuse by bulemics. A number of mechanisms are proposed for emetine cardiotoxicity, but the current mechanistic literature is quite scarce. Cocaine abuse recently has caught the public interest, in particular because of the drug-related sudden deaths of certain athletes. Cocaine can cause hypertension, arrhythmias, and reduced coronary blood flow, each of which can contribute to its lethality. However, it may be possible that cocaine sudden death episodes are more related to hyperthermia and convulsive seizures, rather than to cardiovascular toxicity. Chronic alcohol use leads to dilated cardiomyopathy and failure as part of the general physical degeneration that occurs with alcoholism. Several mechanisms are proposed for the cardiomyopathy, but only 2 things seem clear. The cardiotoxicity is due to an intrinsic effect of alcohol, rather than to malnutrition or co-toxicity, and abstinence is the only effective treatment for the cardiomyopathy. Recent articles indicate that very moderate use of alcohol may be beneficial and protect against cardiovascular-related morbidity. One explanation for these findings seems to be that the non-drinking groups, against whom the moderate drinking comparisons were made, were enriched in former drinkers with significant alcohol-related cardiovascular pathology.

A yeast phenomic model for the influence of Warburg metabolism on genetic buffering of doxorubicin

BACKGROUND

The influence of the Warburg phenomenon on chemotherapy response is unknown. Saccharomyces cerevisiae mimics the Warburg effect, repressing respiration in the presence of adequate glucose. Yeast phenomic experiments were conducted to assess potential influences of Warburg metabolism on gene-drug interaction underlying the cellular response to doxorubicin. Homologous genes from yeast phenomic and cancer pharmacogenomics data were analyzed to infer evolutionary conservation of gene-drug interaction and predict therapeutic relevance.

METHODS

Cell proliferation phenotypes (CPPs) of the yeast gene knockout/knockdown library were measured by quantitative high-throughput cell array phenotyping (Q-HTCP), treating with escalating doxorubicin concentrations under conditions of respiratory or glycolytic metabolism. Doxorubicin-gene interaction was quantified by departure of CPPs observed for the doxorubicin-treated mutant strain from that expected based on an interaction model. Recursive expectation-maximization clustering (REMc) and Gene Ontology (GO)-based analyses of interactions identified functional biological modules that differentially buffer or promote doxorubicin cytotoxicity with respect to Warburg metabolism. Yeast phenomic and cancer pharmacogenomics data were integrated to predict differential gene expression causally influencing doxorubicin anti-tumor efficacy.

RESULTS

Yeast compromised for genes functioning in chromatin organization, and several other cellular processes are more resistant to doxorubicin under glycolytic conditions. Thus, the Warburg transition appears to alleviate requirements for cellular functions that buffer doxorubicin cytotoxicity in a respiratory context. We analyzed human homologs of yeast genes exhibiting gene-doxorubicin interaction in cancer pharmacogenomics data to predict causality for differential gene expression associated with doxorubicin cytotoxicity in cancer cells. This analysis suggested conserved cellular responses to doxorubicin due to influences of homologous recombination, sphingolipid homeostasis, telomere tethering at nuclear periphery, actin cortical patch localization, and other gene functions.

CONCLUSIONS

Warburg status alters the genetic network required for yeast to buffer doxorubicin toxicity. Integration of yeast phenomic and cancer pharmacogenomics data suggests evolutionary conservation of gene-drug interaction networks and provides a new experimental approach to model their influence on chemotherapy response. Thus, yeast phenomic models could aid the development of precision oncology algorithms to predict efficacious cytotoxic drugs for cancer, based on genetic and metabolic profiles of individual tumors.

Doxorubicin-Induced Cardiomyopathy in Children

Doxorubicin-induced cardiotoxicity in childhood cancer survivors is a growing problem. The population of patients at risk for cardiovascular disease is steadily increasing, as five-year survival rates for all types of childhood cancers continue to improve. Doxorubicin affects the developing heart differently from the adult heart and in a subset of exposed patients, childhood exposure leads to late, irreversible cardiomyopathy. Notably, the prevalence of late-onset toxicity is increasing in parallel with improved survival. By the year 2020, it is estimated that there will be 500,000 childhood cancer survivors and over 50,000 of them will suffer from doxorubicin-induced cardiotoxicity. The majority of the research to-date, concentrated on childhood cancer survivors, has focused mostly on clinical outcomes through well-designed epidemiological and retrospective cohort studies. Preclinical studies have elucidated many of the cellular mechanisms that elicit acute toxicity in cardiomyocytes. However, more research is needed in the areas of early- and late-onset cardiotoxicity and more importantly improving the scientific understanding of how other cells present in the cardiac milieu are impacted by doxorubicin exposure. The overall goal of this review is to succinctly summarize the major clinical and preclinical studies focused on doxorubicin-induced cardiotoxicity. As the prevalence of patients affected by doxorubicin exposure continues to increase, it is imperative that the major gaps in existing research are identified and subsequently utilized to develop appropriate research priorities for the coming years. Well-designed preclinical research models will enhance our understanding of the pathophysiology of doxorubicin-induced cardiotoxicity and directly lead to better diagnosis, treatment, and prevention. © 2019 American Physiological Society. Compr Physiol 9:905-931, 2019.

Simple discrimination of sub-cycling cells by propidium iodide flow cytometric assay in Jurkat cell samples with extensive DNA fragmentation

Human leukemia Jurkat T cells were analyzed for apoptosis and cell cycle by flow cytometry, using the Annexin V/propidium iodide (PI) standard assay, and a simple PI staining in Triton X-100/digitonin-enriched PI/RNase buffer, respectively. Cells treated with doxorubicin or menadione displayed a very strong correlation between the apoptotic cell fraction measured by the Annexin V/PI assay, and the weight of a secondary cell population that emerged on the forward scatter (FS)/PI plot, as well as on the side scatter (SS)/PI and FL1/PI plots generated from parallel cell cycle recordings. In both cases, the Pearson correlation coefficients were >0.99. In cell cycle determinations, PI fluorescence was detected on FL3 (620/30 nm), and control samples exhibited the expected linear dependence of FL3 on FL1 (525/40 nm) signals. However, increasing doses of doxorubicin or menadione generated a growing subpopulation of cells displaying a definite right-shift on the FS/FL3, SS/FL3 and FL1/FL3 plots, as well as decreased PI fluorescence, indicative of ongoing fragmentation and loss of nuclear DNA. By gating on these events, the resulting fraction of presumably sub-cycling cells (i.e. cells with cleaved DNA, counting sub-G0/G1, sub-S and sub-G2/M cells altogether) was closely similar to the apoptotic rate assessed by Annexin V/PI labeling. Taken together, these findings suggest a possible way to recognize the entire population of cells undergoing apoptotic DNA cleavage and simultaneously determine the cell cycle distribution of non-apoptotic cells in PI-labeled cell samples with various degrees of DNA fragmentation, using a simple and reproducible multiparametric analysis of flow cytometric recordings.

Role of cardiolipin in stability of integral membrane proteins

Cardiolipin (CL) is a unique phospholipid with a dimeric structure having four acyl chains and two phosphate groups found almost exclusively in certain membranes of bacteria and of mitochondria of eukaryotes. CL interacts with numerous proteins and has been implicated in function and stabilization of several integral membrane proteins (IMPs). While both functional and stabilization roles of CL in IMPs has been generally acknowledged, there are, in fact, only limited number of quantitative analysis that support this function of CL. This is likely caused by relatively complex determination of parameters characterizing stability of IMPs and particularly intricate assessment of role of specific phospholipids such as CL in IMPs stability. This review aims to summarize quantitative findings regarding stabilization role of CL in IMPs reported up to now.

The role of sirtuins in mitochondrial function and doxorubicin-induced cardiac dysfunction

Anthracycline chemotherapeutics such as doxorubicin continue to be important treatments for many cancers. Through improved screening and therapy, more patients are surviving and living longer after the diagnosis of their cancer. However, anthracyclines are associated with both short- and long-term cardiotoxic effects. Doxorubicin-induced mitochondrial dysfunction is a central mechanism in the cardiotoxic effects of doxorubicin that contributes to impaired cardiac energy levels, increased reactive oxygen species production, cardiomyocyte apoptosis and the decline in cardiac function. Sirtuins are protein deacetylases that are activated by low energy levels and stimulate energy production through their activation of transcription factors and enzymatic regulators of cardiac energy metabolism. In addition, sirtuins activate oxidative stress resistance pathways. SIRT1 and SIRT3 are expressed at high levels in the cardiomyocyte. This review examines the function of sirtuins in the regulation of cardiac mitochondrial function, with a focus on their role in heart failure and an emphasis on their effects on doxorubicin-induced cardiotoxicity. We discuss the potential for sirtuin activation in combination with anthracycline chemotherapy in order to mitigate its cardiotoxic side-effects without reducing the antineoplastic activity of anthracyclines.

Chemotherapy alters cisatracurium induced neuromuscular blockade characteristics: A prospective cohort study

STUDY OBJECTIVE

To compare the characteristics of NMDR induced muscle paralysis in breast cancer patients with and without a history of recent chemotherapy with cyclophosphamide, doxorubicin and 5-fluorouracil (CAF) regimen.

DESIGN

This is a non-randomized prospective cohort study.

SETTING

Operating room of a university-affiliated teaching hospital.

PATIENTS

Out of a total of 50 patients who had undergone mastectomy, 22 patients were allocated to the "Chemo group" and 28 patients to the "Non-Chemo group", based on a valid history of recent chemotherapy.

INTERVENTION

After induction of anesthesia with thiopental and cisatracurium, neuromuscular monitoring was started for all patients.

MEASUREMENTS

Initially the time to 100% single-twitch (ST) suppression was measured. Then, the time for the appearance of the first response to post-tetanic count (PTC) stimulation, Train-of-Four (TOF) stimulation, and TOF_50% were measured consequently.

MAIN RESULTS

Time to get ST_zero was significantly longer in the Chemo group than in the Non-chemo group. Time for the appearance of the first response of PTC and TOF and TOF_50% was significantly shorter in the Chemo group than the other group. The mean duration of intense block was 27.66 minutes in the Chemo group versus 42.47 minutes in the Non-chemo group.

CONCLUSION

This research demonstrated that in patients having undergone chemotherapy, the effect of NDMRs starts with a longer lag time and finishes earlier too. Thus, these patients are ready for intubation after a longer time. Moreover, we have to repeat cisatracurium injections after shorter intervals to maintain the desired level of blockade.

A Biophysical Systems Approach to Identifying the Pathways of Acute and Chronic Doxorubicin Mitochondrial Cardiotoxicity

The clinical use of the anthracycline doxorubicin is limited by its cardiotoxicity which is associated with mitochondrial dysfunction. Redox cycling, mitochondrial DNA damage and electron transport chain inhibition have been identified as potential mechanisms of toxicity. However, the relative roles of each of these proposed mechanisms are still not fully understood. The purpose of this study is to identify which of these pathways independently or in combination are responsible for doxorubicin toxicity. A state of the art mathematical model of the mitochondria including the citric acid cycle, electron transport chain and ROS production and scavenging systems was extended by incorporating a novel representation for mitochondrial DNA damage and repair. In silico experiments were performed to quantify the contributions of each of the toxicity mechanisms to mitochondrial dysfunction during the acute and chronic stages of toxicity. Simulations predict that redox cycling has a minor role in doxorubicin cardiotoxicity. Electron transport chain inhibition is the main pathway for acute toxicity for supratherapeutic doses, being lethal at mitochondrial concentrations higher than 200μM. Direct mitochondrial DNA damage is the principal pathway of chronic cardiotoxicity for therapeutic doses, leading to a progressive and irreversible long term mitochondrial dysfunction.

Regulation of autophagy by mitochondrial phospholipids in health and diseases

Autophagy is an evolutionarily conserved mechanism that maintains nutrient homeostasis by degrading protein aggregates and damaged organelles. Autophagy is reduced in aging, which is implicated in the pathogenesis of aging-related diseases, including cancers, obesity, type 2 diabetes, cardiovascular diseases, and neurodegenerative diseases. Mitochondria-derived phospholipids cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol are critical throughout the autophagic process, from initiation and phagophore formation to elongation and fusion with endolysosomal vesicles. Cardiolipin is also required for mitochondrial fusion and fission, an important step in isolating dysfunctional mitochondria for mitophagy. Furthermore, genetic screen in yeast has identified a surprising role for cardiolipin in regulating lysosomal function. Phosphatidylethanolamine plays a pivotal role in supporting the autophagic process, including autophagosome elongation as part of lipidated Atg8/LC3. An emerging role for phosphatidylglycerol in AMPK and mTORC1 signaling as well as mitochondrial fission may provide the first glimpse into the function of phosphatidylglycerol apart from being a precursor for cardiolipin. This review examines the effects of manipulating phospholipids on autophagy and mitophagy in health and diseases, as well as current limitations in the field. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.

Cardiac cytochrome c and cardiolipin depletion during anthracycline-induced chronic depression of mitochondrial function

AIMS

It is still unclear why anthracycline treatment results in a cardiac-specific myopathy. We investigated whether selective doxorubicin (DOX) cardiotoxicity involving mitochondrial degeneration is explained by different respiratory complexes reserves between tissues by comparing and contrasting treatment effects in heart vs liver and kidney. Alternatively, we have also explored if the degeneration is due to alterations of mitochondrial thresholds to incompatible states.

METHODS AND RESULTS

Heart, liver and kidney mitochondria were isolated from male Wistar rats weekly injected with DOX during 7weeks. Global flux and isolated step curves were obtained for Complex I, III, IV, as well as for the adenine nucleotide translocator. We show treatment-related alterations in global flux curve for Complex III in all analyzed tissues and in Complex IV activity curve solely in heart. However, all mitochondrial threshold curves remained unchanged after treatment in the analyzed tissues. No treatment-related differences were detected on transcript or protein analysis of selected respiratory complexes subunits. However, a specific loss of cytochrome c and cardiolipin was measured in heart, but not in other organs, mitochondria from DOX-treated animals.

CONCLUSIONS

Contrary to our hypothesis, impaired mitochondrial respiration could not be explained by intrinsic differences in respiratory complexes reserves among tissues or, by alterations in mitochondrial thresholds after treatment. Instead, we propose that loss of cytochrome c and cardiolipin are responsible for the depressed mitochondrial respiration observed after chronic DOX treatment. Moreover, cardiac cytochrome c and cardiolipin depletion decreases metabolic network buffering, hindering cardiac ability to respond to increased workload, accelerating cardiac aging.

Aloin: a natural antitumor anthraquinone glycoside with iron chelating and non-atherogenic activities

CONTEXT

The antitumor activity of aloin, the active anthraquinone of Aloe juice, against different murine and human tumors has been reported.

OBJECTIVE

In the present study, the impact of repeated aloin treatment at its maximum tolerated dose on serum levels of lipid profile, some elements, iron status and kidney function, compared with doxorubicin (a cardiotoxic anthracycline and inhibitor of erythropoiesis), was assessed.

MATERIALS AND METHODS

Rats were treated with a single dose of doxorubicin (30 mg/kg body weight, intraperitoneal) or aloin (50 mg/kg body weight, intramuscular) twice weekly over 2 weeks.

RESULTS

Acute doxorubicin treatment elevated serum levels of triacylglycerols (59.90%), total cholesterol (42.29%), cholesteryl esters (54.75%), low density lipoprotein-cholesterol (230.16%), very low density lipoprotein-cholesterol (56.42%), urea (287.53%), and creatinine (85.38%), whereas serum high density lipoprotein-cholesterol, sodium, and calcium levels were reduced (44.61, 9.61, and 9.76%, respectively), as compared with controls. In contrast, aloin treatment showed insignificant changes in all the aforementioned parameters. Both doxorubicin and aloin induced erythropoiesis impairment demonstrated by a reduction in blood hemoglobin concentration. While aloin treatment elevated serum iron level (30.28%), doxorubicin treatment reduced serum levels of iron (51.47%) and percent transferrin saturation (55.21%), and in contrast, increased serum total iron binding capacity (34.85%). The chelating affinities of iron-aloin and -doxorubicin complexes, which contain bidentate iron-binding moieties, have been shown in the infrared spectra.

DISCUSSION AND CONCLUSION

The non-cardiotoxic effect of aloin treatment was due to its non-atherogenic and iron-chelating activities, which might also contribute in part to its anti-proliferative activity.

Mitochondrial catastrophe during doxorubicin-induced cardiotoxicity: a review of the protective role of melatonin

Anthracyclines, such as doxorubicin, are among the most valuable treatments for various cancers, but their clinical use is limited due to detrimental side effects such as cardiotoxicity. Doxorubicin-induced cardiotoxicity is emerging as a critical issue among cancer survivors and is an area of much significance to the field of cardio-oncology. Abnormalities in mitochondrial functions such as defects in the respiratory chain, decreased adenosine triphosphate production, mitochondrial DNA damage, modulation of mitochondrial sirtuin activity and free radical formation have all been suggested as the primary causative factors in the pathogenesis of doxorubicin-induced cardiotoxicity. Melatonin is a potent antioxidant, is nontoxic, and has been shown to influence mitochondrial homeostasis and function. Although a number of studies support the mitochondrial protective role of melatonin, the exact mechanisms by which melatonin confers mitochondrial protection in the context of doxorubicin-induced cardiotoxicity remain to be elucidated. This review focuses on the role of melatonin on doxorubicin-induced bioenergetic failure, free radical generation, and cell death. A further aim is to highlight other mitochondrial parameters such as mitophagy, autophagy, mitochondrial fission and fusion, and mitochondrial sirtuin activity, which lack evidence to support the role of melatonin in the context of cardiotoxicity.

Redox proteomic identification of HNE-bound mitochondrial proteins in cardiac tissues reveals a systemic effect on energy metabolism after doxorubicin treatment

Doxorubicin (DOX), one of the most effective anticancer drugs, is known to generate progressive cardiac damage, which is due, in part, to DOX-induced reactive oxygen species (ROS). The elevated ROS often induce oxidative protein modifications that result in alteration of protein functions. This study demonstrates that the level of proteins adducted by 4-hydroxy-2-nonenal (HNE), a lipid peroxidation product, is significantly increased in mouse heart mitochondria after DOX treatment. A redox proteomics method involving two-dimensional electrophoresis followed by mass spectrometry and investigation of protein databases identified several HNE-modified mitochondrial proteins, which were verified by HNE-specific immunoprecipitation in cardiac mitochondria from the DOX-treated mice. The majority of the identified proteins are related to mitochondrial energy metabolism. These include proteins in the citric acid cycle and electron transport chain. The enzymatic activities of the HNE-adducted proteins were significantly reduced in DOX-treated mice. Consistent with the decline in the function of the HNE-adducted proteins, the respiratory function of cardiac mitochondria as determined by oxygen consumption rate was also significantly reduced after DOX treatment. Treatment with Mn(III) meso-tetrakis(N-n-butoxyethylpyridinium-2-yl)porphyrin, an SOD mimic, averted the doxorubicin-induced mitochondrial dysfunctions as well as the HNE-protein adductions. Together, the results demonstrate that free radical-mediated alteration of energy metabolism is an important mechanism mediating DOX-induced cardiac injury, suggesting that metabolic intervention may represent a novel approach to preventing cardiac injury after chemotherapy.

Mitochondrial topoisomerase I (top1mt) is a novel limiting factor of doxorubicin cardiotoxicity

PURPOSE

Doxorubicin is one of the most effective chemotherapeutic agents. However, up to 30% of the patients treated with doxorubicin suffer from congestive heart failure. The mechanism of doxorubicin cardiotoxicity is likely multifactorial and most importantly, the genetic factors predisposing to doxorubicin cardiotoxicity are unknown. On the basis of the fact that mtDNA lesions and mitochondrial dysfunctions have been found in human hearts exposed to doxorubicin and that mitochondrial topoisomerase 1 (Top1mt) specifically controls mtDNA homeostasis, we hypothesized that Top1mt knockout (KO) mice might exhibit hypersensitivity to doxorubicin.

EXPERIMENTAL DESIGN

Wild-type (WT) and KO Top1mt mice were treated once a week with 4 mg/kg doxorubicin for 8 weeks. Heart tissues were analyzed one week after the last treatment.

RESULTS

Genetic inactivation of Top1mt in mice accentuates mtDNA copy number loss and mtDNA damage in heart tissue following doxorubicin treatment. Top1mt KO mice also fail to maintain respiratory chain protein production and mitochondrial cristae ultrastructure organization. These mitochondrial defects result in decreased O2 consumption, increased reactive oxygen species production, and enhanced heart muscle damage in animals treated with doxorubicin. Accordingly, Top1mt KO mice die within 45 days after the last doxorubicin injection, whereas the WT mice survive.

CONCLUSIONS

Our results provide evidence that Top1mt, which is conserved across vertebrates, is critical for cardiac tolerance to doxorubicin and adaptive response to doxorubicin cardiotoxicity. They also suggest the potential of Top1mt single-nucleotide polymorphisms testing to investigate patient susceptibility to doxorubicin-induced cardiotoxicity.

Mitochondrial membrane lipid remodeling in pathophysiology: a new target for diet and therapeutic interventions

Mitochondria are arbiters in the fragile balance between cell life and death. These organelles present an intricate membrane system, with a peculiar lipid composition and displaying transverse as well as lateral asymmetry. Some lipids are synthesized inside mitochondria, while others have to be imported or acquired in the form of precursors. Here, we review different processes, including external interventions (e.g., diet) and a range of biological events (apoptosis, disease and aging), which may result in alterations of mitochondrial membrane lipid content. Cardiolipin, the mitochondria lipid trademark, whose biosynthetic pathway is highly regulated, will deserve special attention in this review. The modulation of mitochondrial membrane lipid composition, especially by diet, as a therapeutic strategy for the treatment of some pathologies will be also addressed.

Doxorubicin increases oxidative metabolism in HL-1 cardiomyocytes as shown by 13C metabolic flux analysis

Doxorubicin (DXR), an anticancer drug, is limited in its use due to severe cardiotoxic effects. These effects are partly caused by disturbed myocardial energy metabolism. We analyzed the effects of therapeutically relevant but nontoxic DXR concentrations for their effects on metabolic fluxes, cell respiration, and intracellular ATP. (13)C isotope labeling studies using [U-(13)C(6)]glucose, [1,2-(13)C(2)]glucose, and [U-(13)C(5)]glutamine were carried out on HL-1 cardiomyocytes exposed to 0.01 and 0.02 μM DXR and compared with the untreated control. Metabolic fluxes were calculated by integrating production and uptake rates of extracellular metabolites (glucose, lactate, pyruvate, and amino acids) as well as (13)C-labeling in secreted lactate derived from the respective (13)C-labeled substrates into a metabolic network model. The investigated DXR concentrations (0.01 and 0.02 μM) had no effect on cell viability and beating of the HL-1 cardiomyocytes. Glycolytic fluxes were significantly reduced in treated cells at tested DXR concentrations. Oxidative metabolism was significantly increased (higher glucose oxidation, oxidative decarboxylation, TCA cycle rates, and respiration) suggesting a more efficient use of glucose carbon. These changes were accompanied by decrease of intracellular ATP. We conclude that DXR in nanomolar range significantly changes central carbon metabolism in HL-1 cardiomyocytes, which results in a higher coupling of glycolysis and TCA cycle. The myocytes probably try to compensate for decreased intracellular ATP, which in turn may be the result of a loss of NADH electrons via either formation of reactive oxygen species or electron shunting.

Effects of Doxorubicin and Fenofibrate on the activities of NADH oxidase and citrate synthase in mice

Doxorubicin (Dox) has widely been used as an anticancer drug, but its use is limited by serious toxicity to the heart, kidney and liver. Mitochondrial dysfunction is one of the potential mechanisms of toxicity but not fully understood. Fenofibrate, one of the peroxisome proliferator-activated receptor-alpha (PPARα) ligands, is involved in lipid metabolism which takes place primarily in the mitochondria, so mitochondrial function may be affected by fenofibrate. Therefore, we investigated the effects of DOX and fenofibrate on activities of both mitochondrial citrate synthase and NADH oxidase, which are marker enzymes in the tricarboxylic acid (TCA) cycle and a measure of the complex I-III-IV activity in electron transport chain, respectively. Dox (15 mg/kg) and/or fenofibrate (100 mg/kg/day) were administered to mice for 3 or 14 days, and the activities of citrate synthase and NADH oxidase were measured. Our study showed that Dox significantly inhibits the activity of citrate synthase while fenofibrate induces the activity. Similar to citrate synthase, NADH oxidase activity was also induced by fenofibrate except in spleen but inhibited by Dox except in the heart and liver. Furthermore, fenofibrate not only protects citrate synthase activity from Dox-induced toxicity in the ventricle but also significantly rescues NADH oxidase activity in the kidney. These results reveal the actions of fenofibrate and Dox on the mitochondria, and the underlying mechanism may be related to the toxicity of Dox, which has clinical implications in the side effects of Dox treatment by modulation of mitochondrial function.

Proteomic analysis of anti-tumor effects of 11-dehydrosinulariolide on CAL-27 cells

The anti-tumor effects of 11-dehydrosinulariolide, an active ingredient isolated from soft coral Sinularia leptoclados, on CAL-27 cells were investigated in this study. In the MTT assay for cell proliferation, increasing concentrations of 11-dehydrosinulariolide decreased CAL-27 cell viability. When a concentration of 1.5 μg/mL of 11-dehydrosinulariolide was applied, the CAL-27 cells viability was reduced to a level of 70% of the control sample. The wound healing function decreased as the concentration of 11-dehydrosinulariolide increased. The results in this study indicated that treatment with 11-dehydrosinulariolide for 6 h significantly induced both early and late apoptosis of CAL-27 cells, observed by flow cytometric measurement and microscopic fluorescent observation. A comparative proteomic analysis was conducted to investigate the effects of 11-dehydrosinulariolide on CAL-27 cells at the molecular level by comparison between the protein profiling (revealed on a 2-DE map) of CAL-27 cells treated with 11-dehydrosinulariolide and that of CAL-27 cells without the treatment. A total of 28 differential proteins (12 up-regulated and 16 down-regulated) in CAL-27 cells treated with 11-dehydrosinulariolide have been identified by LC-MS/MS analysis. Some of the differential proteins are associated with cell proliferation, apoptosis, protein synthesis, protein folding, and energy metabolism. The results of this study provided clues for the investigation of biochemical mechanisms of the anti-tumor effects of 11-dehydrosinulariolide on CAL-27 cells and could be valuable information for drug development and progression monitoring of oral squamous cell carcinoma (OSCC).

Changes in mitochondrial redox state, membrane potential and calcium precede mitochondrial dysfunction in doxorubicin-induced cell death

Mitochondria play central roles in cell life as a source of energy and in cell death by inducing apoptosis. Many important functions of mitochondria change in cancer, and these organelles can be a target of chemotherapy. The widely used anticancer drug doxorubicin (DOX) causes cell death, inhibition of cell cycle/proliferation and mitochondrial impairment. However, the mechanism of such impairment is not completely understood. In our study we used confocal and two-photon fluorescence imaging together with enzymatic and respirometric analysis to study short- and long-term effects of doxorubicin on mitochondria in various human carcinoma cells. We show that short-term (<30 min) effects include i) rapid changes in mitochondrial redox potentials towards a more oxidized state (flavoproteins and NADH), ii) mitochondrial depolarization, iii) elevated matrix calcium levels, and iv) mitochondrial ROS production, demonstrating a complex pattern of mitochondrial alterations. Significant inhibition of mitochondrial endogenous and uncoupled respiration, ATP depletion and changes in the activities of marker enzymes were observed after 48 h of DOX treatment (long-term effects) associated with cell cycle arrest and death.

Doxorubicin in vivo rapidly alters expression and translation of myocardial electron transport chain genes, leads to ATP loss and caspase 3 activation

Background

Doxorubicin is one of the most effective anti-cancer drugs but its use is limited by cumulative cardiotoxicity that restricts lifetime dose. Redox damage is one of the most accepted mechanisms of toxicity, but not fully substantiated. Moreover doxorubicin is not an efficient redox cycling compound due to its low redox potential. Here we used genomic and chemical systems approaches in vivo to investigate the mechanisms of doxorubicin cardiotoxicity, and specifically test the hypothesis of redox cycling mediated cardiotoxicity.

Methodology/Principal Findings

Mice were treated with an acute dose of either doxorubicin (DOX) (15 mg/kg) or 2,3-dimethoxy-1,4-naphthoquinone (DMNQ) (25 mg/kg). DMNQ is a more efficient redox cycling agent than DOX but unlike DOX has limited ability to inhibit gene transcription and DNA replication. This allowed specific testing of the redox hypothesis for cardiotoxicity. An acute dose was used to avoid pathophysiological effects in the genomic analysis. However similar data were obtained with a chronic model, but are not specifically presented. All data are deposited in the Gene Expression Omnibus (GEO). Pathway and biochemical analysis of cardiac global gene transcription and mRNA translation data derived at time points from 5 min after an acute exposure in vivo showed a pronounced effect on electron transport chain activity. This led to loss of ATP, increased AMPK expression, mitochondrial genome amplification and activation of caspase 3. No data gathered with either compound indicated general redox damage, though site specific redox damage in mitochondria cannot be entirely discounted.

Conclusions/Significance

These data indicate the major mechanism of doxorubicin cardiotoxicity is via damage or inhibition of the electron transport chain and not general redox stress. There is a rapid response at transcriptional and translational level of many of the genes coding for proteins of the electron transport chain complexes. Still though ATP loss occurs with activation caspase 3 and these events probably account for the heart damage.

Uncoupling protein downregulation in doxorubicin-induced heart failure improves mitochondrial coupling but increases reactive oxygen species generation

PURPOSE

Doxorubicin-based chemotherapy is limited by the development of dose-dependent left ventricular dysfunction and congestive heart failure caused by reactive oxygen species (ROS). Uncoupling proteins (UCP) can inhibit mitochondrial ROS production as well as decrease myocyte damage from exogenous ROS. Prior studies have shown that cardiac UCP2 and UCP3 mRNA expression is decreased with acute doxorubicin treatment. However, the expression of UCP protein in hearts with doxorubicin cardiotoxicity and the resultant changes in mitochondrial function and oxidant stress have not been determined.

METHODS

Heart failure was induced in Sprague-Dawley rats with intraperitoneal injections of doxorubicin (2 mg/kg t.i.w., total dose: 18 mg/kg). Mitochondria were isolated from mice receiving doxorubicin or saline injections for determination of UCP2 and UCP3 expression. In addition, mitochondrial respiration, ATP synthesis and ROS production were determined.

RESULTS

Doxorubicin-induced heart failure was associated with significant decreases in UCP2 and UCP3 protein expression compared with nonfailing hearts (P < 0.05). While the rates of state 3 and state 4 respiration and ATP synthesis were lower in mitochondria isolated from failing hearts, the respiratory control ratio was 15% higher (P < 0.05), and the ratio of ATP production to oxygen consumption was 25% higher (P < 0.05) in mitochondria from failing hearts, indicating greater coupling between citric acid cycle flux and mitochondrial ATP synthesis. However, the decrease in UCP expression was associated with 50% greater mitochondrial ROS generation (P < 0.05).

CONCLUSIONS

Downregulation of myocardial UCP2 and UCP3 in the setting of doxorubicin-induced heart failure is associated with improved efficiency of ATP synthesis, which might compensate for abnormal energy metabolism. However, this beneficial effect is counterbalanced by greater oxidant stress.

Effects of the antimalarial drug primaquine on the dynamic structure of lipid model membranes

Primaquine (PQ) is a potent therapeutic agent used in the treatment of malaria and its mechanism of action still lacks a more detailed understanding at a molecular level. In this context, we used differential scanning calorimetry (DSC), pressure perturbation calorimetry (PPC), and electron spin resonance (ESR) to investigate the effects of PQ on the lipid phase transition, acyl chain dynamics, and on volumetric properties of lipid model membranes. DSC thermograms revealed that PQ stabilizes the fluid phase of the lipid model membranes and interacts mainly with the lipid headgroups. This result was revealed by the great effect on the pretransition of phosphatidylcholines and the destabilization of the inverted hexagonal phase of a phosphatidylethanolamine bilayer. Spin probes located at different positions along the lipid chain were used to monitor different membrane regions. ESR results indicated that PQ is effective in changing the acyl chain ordering and dynamics of the whole chain of dimyristoylphosphatidylcholine (DMPC) phospholipid in the rippled gel phase. The combined ESR and PPC results revealed that the slight DMPC volume changes at the main phase transition induced by the presence of PQ is probably due to a less dense lipid gel phase. At physiological pH, the cationic amphiphilic PQ strongly interacts with the lipid headgroup region of the bilayers, causing considerable disorganization in the hydrophobic core. These results shed light on the molecular mechanism of primaquine-lipid interaction, which may be useful in the understanding of the complex mechanism of action and/or the adverse effects of this antimalarial drug.

Targeting of cancer energy metabolism

The main purpose of this review is to update and analyze the effect of several antineoplastic drugs (adriamycin, apoptodilin, casiopeinas, cisplatin, clotrimazole, cyclophosphamide, ditercalinium, NSAIDs, tamoxifen, taxol, 6-mercaptopurine, and alpha-tocopheryl succinate) and energy metabolism inhibitors (2-DOG, gossypol, delocalized lipophilic cations, and uncouplers) on tumor development and progression. The possibility that these antineoplastic drugs currently used in in vitro cancer models, in chemo-therapy, or under study in phase I to III clinical trials induce tumor cellular death by altering also metabolite concentration (i.e., ATP), enzyme activities, and/or energy metabolism fluxes is assessed. It is proposed that the use of energy metabolic therapy, as an alternative or complementary strategy, might be a promising novel approach in the treatment of cancer.

An improved method for separating cardiolipin by HPLC

Herein we report an improved method to separate cardiolipin (Ptd(2)Gro) from tissue total lipid extracts using a biphasic solvent system combined with high performance liquid chromatography. This method uses a normal phase silica column and two mobile phases: mobile phase A that was n-hexane:2-propanol (3:2 by vol) and mobile phase B that was n-hexane:2-propanol:water (56.7:37.8:5.5 by vol). The initial solvent conditions were 95% A and 5% B, with a flow rate of 1.5 mL/min. The samples were from non-derivatized aliquots of liver, heart, or brain lipid extracts. The peak corresponding to Ptd(2)Gro appeared at 31 min, was well defined and did not overlap with neighboring peaks. The adjacent peak corresponded to ethanolamine glycerophospholipids and the remaining phospholipids were eluted in a single peak. The identity of the phospholipids separated by this method was verified by thin layer chromatography (TLC) and fatty acid analysis, which confirmed that the Ptd(2)Gro was well resolved from other phospholipids. This method is useful to separate and quantify Ptd(2)Gro from small tissue samples thereby avoiding the variability associated with TLC methods.

4-HPR-mediated leukemia cell cytotoxicity is triggered by ceramide-induced mitochondrial oxidative stress and is regulated downstream by Bcl-2

We have previously reported that, in leukemia cells, the cytotoxicity of the anticancer agent N-(4-hydroxyphenyl)retinamide (4-HPR) is mediated by mitochondria-derived reactive oxygen species (ROS) and cardiolipin peroxidation. Here, we have analyzed at greater depth the 4-HPR-triggered molecular events, demonstrating that 4-HPR induces an early (15 min) increase in ceramide levels by sphingomyelin hydrolysis and later (from 1 h) by de novo synthesis. Using specific inhibitors of both pathways, we demonstrate that ceramide accumulation is responsible for early ROS generation, which act as apoptotic signalling intermediates leading to conformational activation of Bak and Bax, loss of mitochondrial membrane potential (DeltaPsim), mitochondrial membrane permeabilization (MMP) and cell death. Enforced expression of Bcl-2 has no effect on 4-HPR-induced oxidative stress, but notably prevents mitochondrial alterations and apoptosis, indicating that Bcl-2 functions by regulating events downstream of ROS generation. In conclusion, our study delineates for the fist time the sequence and timing of the principal events induced by 4-HPR in leukemia cells and points to the potential use of modulators of ceramide metabolism as enhancers in 4-HPR-based therapies.

Role of mtDNA lesions in anthracycline cardiotoxicity

Doxorubicin (adriamycin) is an effective drug in the treatment of many malignancies. Its prolonged use is, however, limited by an irreversible, dose-dependent and progressive cardiomyopathy, which may become evident even years after completion of therapy. Data from rats and humans show that oxidative phosphorylation is impaired rapidly after acute doxorubicin-exposure. Such respiratory chain dysfunction is known to enhance the production of reactive oxygen species and may lead to quantitative and qualitative injury of mitochondrial DNA (mtDNA) and its encoded respiratory chain subunits. MtDNA depletion, mtDNA mutations and respiratory defects then accumulate with time also in the absence of continued anthracycline exposure. Chronic cardiotoxicity then manifests, when the bioenergetic capacity of the organelles is severely impaired. The mitochondrial damage in late-onset doxorubicin cardiomyopathy is heart specific and not found in skeletal muscle. DOXO-EMCH, a 6-maleimidocaproyl hydrazone derivative of doxorubicin has evolved from the search for less cardiotoxic anthracyclines. At equieffective antitumor doses, DOXO-EMCH has a substantially lower heart toxicity than free doxorubicin.

New insights into doxorubicin-induced cardiotoxicity: the critical role of cellular energetics

Cardiotoxic side-effects represent a serious complication of anticancer therapy with anthracyclines, in particular with doxorubicin (DXR) being the leading drug of the group. Different hypotheses, accentuating various mechanisms and/or targets, have been proposed to explain DXR-induced cardiotoxicity. This review focuses on the myocardial energetic network as a target of DXR toxic action in heart and highlights the recent advances in understanding its role in development of the DXR related cardiac dysfunction. We present a survey of DXR-induced defects in different steps of cardiac energy metabolism, including reduction of oxidative capacity of mitochondria, changes in the profile of energy substrate utilization, disturbance of energy transfer between sites of energy production and consumption, as well as defects in energy signaling. Considering the wide spectrum and diversity of the changes reported, we attempt to integrate these facts into a common framework and to discuss important functional and temporal relationships between DXR-induced events and the possible underlying molecular mechanisms.

Alterations in myocardial energy metabolism induced by the anti-cancer drug doxorubicin

Doxorubicin and other anthracyclines are among the most potent chemotherapeutic drugs for the treatment of acute leukaemia, lymphomas and different types of solid tumours such as breast, liver and lung cancers. Their clinical use is, however, limited by the risk of severe cardiotoxicity, which can lead to irreversible congestive heart failure. There is increasing evidence that essential components of myocardial energy metabolism are among the highly sensitive and early targets of doxorubicin-induced damage. Here we review doxorubicin-induced detrimental changes in cardiac energetics, with an emphasis on the emerging importance of defects in energy-transferring and -signalling systems, like creatine kinase and AMP-activated protein kinase.

Acute toxicity of doxorubicin on isolated perfused heart: response of kinases regulating energy supply

Doxorubicin (DXR) is a widely used and efficient anticancer drug. However, its application is limited by the risk of severe cardiotoxicity. Impairment of cardiac high-energy phosphate homeostasis is an important manifestation of both acute and chronic DXR cardiotoxic action. Using the Langendorff model of the perfused rat heart, we characterized the acute effects of 1-h perfusion with 2 or 20 microM DXR on two key kinases in cardiac energy metabolism, creatine kinase (CK) and AMP-activated protein kinase (AMPK), and related them to functional responses of the perfused heart and structural integrity of the contractile apparatus as well as drug accumulation in cardiomyocytes. DXR-induced changes in CK were dependent on the isoenzyme, with a shift in protein levels of cytosolic isoenzymes from muscle-type CK to brain-type CK, and a destabilization of octamers of the mitochondrial isoenzyme (sarcometric mitochondrial CK) accompanied by drug accumulation in mitochondria. Interestingly, DXR rapidly reduced the protein level and phosphorylation of AMPK as well as phosphorylation of its target, acetyl-CoA-carboxylase. AMPK was strongly affected already at 2 microM DXR, even before substantial cardiac dysfunction occurred. Impairment of CK isoenzymes was mostly moderate but became significant at 20 microM DXR. Only at 2 microM DXR did upregulation of brain-type CK compensate for inactivation of other isoenzymes. These results suggest that an impairment of kinase systems regulating cellular energy homeostasis is involved in the development of DXR cardiotoxicity.

Ubiquinol cytochrome c reductase (UQCRFS1) gene amplification in primary breast cancer core biopsy samples

OBJECTIVES

The ubiquinol cytochrome c reductase UQCRFS1 is a key subunit of the cytochrome bc1 complex (complex III) of the mitochondrial respiratory chain. The purpose of this study is to evaluate the significance of the ubiquinol cytochrome c reductase UQCRFS1 gene amplification in primary breast cancers.

METHODS

Samples were obtained from image-guided core needle biopsies (CNB) in 40 patients with nontreated breast cancers. To examine UQCRFS1 gene amplification, we employed fluorescent in situ hybridization using BACs RP11-46I12 that harbors UQCRFS1 gene, RP11-110J19 that overlaps to RP11-46I12, and CA125 as a control gene. The amplification data were evaluated blindly of histopathological factors.

RESULTS

Amplification of UQCRFS1 gene was found in 5 of 39 specimens (12.8%). The specimens with amplified UQCRFS1 gene were associated with high grade of cancer cells (P = 0.005).

CONCLUSIONS

These results suggest that the UQCRFS1 gene appears to be involved in development of more aggressive phenotype of breast cancer.

Doxorubicin-induced cardiac mitochondrionopathy

Doxorubicin (Adriamycin) is a potent and broad-spectrum antineoplastic agent prescribed for the treatment of a variety of cancers, including both solid tumours and leukaemias. Unfortunately, despite its broad effectiveness, long-term therapy with doxorubicin is associated with a high incidence of a cumulative and irreversible dilated cardiomyopathy. Numerous mechanisms have been proposed to account for this toxicity. Although there is general consensus that doxorubicin undergoes redox cycling to generate free radicals that are responsible for mediating the various cytopathologies associated with drug exposure, the source and subcellular targets continue to be debated. This short review provides a synopsis of the evidence implicating cardiac mitochondria as key intracellular targets, both as sites of generation of highly reactive free radical intermediates as well as targets for the interference with cell calcium regulation and bioenergetic failure that are hallmarks of doxorubicin-induced cardiac failure.

Deregulation of gene expression in fetal oocytes exposed to doxorubicin

Doxorubicin is an effective anticancer drug but its use is limited due to its adverse side effects such as infertility and cardiomyopathy. Some possible mechanisms of the action of doxorubicin have been postulated, but the initial gene deregulation response has not been investigated. Fetal life stages are critical periods in mammalian oogenesis. This study analyzes gene expression alterations in mouse fetal oocytes exposed in vitro to this anticancer agent. cDNA libraries were generated from isolated fetal oocytes and differential screenings performed with cDNAs from in vitro doxorubicin-treated and -untreated oocytes. Differentially expressed genes were assessed by real-time RT-PCR to quantify the extent of their transcriptional control in doxorubicin-exposed oocytes. The results show that doxorubicin alters the expression of genes involved in the mitochondrial respiratory chain, intracellular transport and cell differentiation. Finally, the up-regulation of a differentially expressed gene (metaxin) mediated by its promoter was evaluated in a functional assay. When treated with doxorubicin, somatic cells transfected with a genetic construct including the promoter of metaxin and a reporter gene showed increases in expression similar to those observed in fetal oocytes. This demonstrates the direct effect of agent on the regulation of a specific gene.

Cardiolipin and apoptosis

Cardiolipin (CL) is recognized to be an essential phospholipid in eukaryotic energy metabolism so that physiological and pathological perturbations in its synthetic and catabolic pathways play key roles in maintaining mitochondrial structure and function, and ultimately cell survival. This review describes potential regulatory mechanisms in CL synthesis and the effects of de-acylation pathways on steady state levels of CL and its interaction with cytochrome c. The latter interaction is significant in the initiation of programmed cell death. Physiological factors that modify CL acylation include ageing, dietary influences and ischemia/reperfusion where the terminal events may be either necrosis or apoptosis. In various pathologies, phospholipase activity increases in response to production of peroxidized CL. The cell may use lysosomal or mitochondrial pathways for CL degradation. However, the manner by which CL and cytochrome c leave the mitochondria is not well understood. The lipid (CL)-bound form of cytochrome c is thought to initiate apoptosis via a lipid transfer step involving mitochondrially targeted Bid. A direct relationship between CL loss and cytochrome c release from the mitochondria has been identified as an initial step in the pathway to apoptosis. An absolute requirement for CL in the function of crucial mitochondrial proteins, e.g., cytochrome oxidase and the adenine nucleotide translocase, are likely additional factors impacting apoptosis and cellular energy homeostasis. This is reflected in the occurrence of both oncotic and apoptotic events in ischemia and reperfusion injury. Other potential clinical manifestations of perturbations of CL synthesis are discussed with particular emphasis on Barth Syndrome where a primary defect can be attributed to CL metabolism and is associated with dilated cardiomyopathy. Finally, the model of fatty acid induced apoptosis is used as a paradigm to our understanding of the temporal relationship between decreased mitochondrial CL, release of cytochrome c, and initiation of apoptosis.

Ceramide in apoptosis signaling: relationship with oxidative stress

Ceramide is one of the major sphingosine-based lipid second messengers that is generated in response to various extracellular agents. However, while widespread attention has focused on ceramide as a second messenger involved in the induction of apoptosis, important issues with regard to the mechanisms of ceramide formation and mode of action remain to be addressed. Several lines of evidence suggest that ceramide and oxidative stress are intimately related in cell death induction. This review focuses on the putative relationships between oxidative stress and sphingolipid metabolism in the apoptotic process and discusses the potential mechanisms that connect and regulate the two phenomena.

Doxorubicin-induced persistent oxidative stress to cardiac myocytes

We recently reported a cardioselective and cumulative oxidation of cardiac mitochondrial DNA (mtDNA) following subchronic administration of doxorubicin to rats. The mtDNA adducts persist for up to 5 weeks after cessation of doxorubicin treatment. Since the evidence suggests that this persistence of mtDNA adducts cannot be attributed to a lack of repair and replication, we investigated whether it might reflect a long-lasting stimulation of free radical-mediated adduct formation. Male Sprague-Dawley rats received weekly s.c. injections of either doxorubicin (2 mg/kg) or an equivalent volume of saline. Cardiac myocytes isolated from rats following 6 weekly injections of doxorubicin expressed a much higher rate of reactive oxygen species (ROS) formation compared to saline controls. This higher rate of ROS formation persisted for 5 weeks following the last injection. Associated with this was a persistent depression of GSH in heart tissue, while protein-thiol content was not markedly altered. These data suggest that the accumulation and persistence of oxidized mtDNA may be due, not to the stability of the adducts, but to some as yet undefined toxic lesion that causes long-lasting stimulation of ROS generation by doxorubicin. This persistent generation of ROS may contribute to the cumulative and irreversible cardiotoxicity observed clinically with the drug.

Acute doxorubicin (adriamycin) dosage does not reduce cardiac protein synthesis in vivo, but decreases diaminopeptidase I and proline endopeptidase activities

Anthracycline antibiotics are effective anticancer agents but their use is limited due to unwanted adverse side effects. The toxic effects of doxorubicin (adriamycin) include the development of defined cardiac lesions leading to cardiomyopathy in some patients. This has been reported to be due to reductions in cardiac protein synthesis. However, virtually all of these previous studies have failed to consider the specific radioactivity of the precursor pool in their measurements or have carried out their studies in vitro. To further resolve the above we measured fractional rates of cardiac protein synthesis using the "flooding dose" method in rats treated with adriamycin (5 mg/kg body wt). Controls were identically treated and injected with saline. At 2.5 or 24 h after adriamycin injection, rates of protein synthesis were measured with a flooding dose of l-[4-(3)H]phenylalanine. Measurements included free (S(i)) and protein-bound (S(b)) phenylalanine-specific radioactivities, the protein synthetic capacity (RNA/protein ratio; C(s)), the fractional rates of protein synthesis calculated from the ratio S(b)/S(i), and the protein synthetic efficiency calculated from the ratio k(s)/C(s). Complementary analyses included assays of lysosomal (cathepsins B, D, H, and L and diaminopeptidases I and II) and cytoplasmic proteases (alanyl aminopeptidase, arginyl aminopeptidase, leucyl aminopeptidase, diaminopeptidase IV, tripeptidyl aminopeptidase, and proline endopeptidase). These enzymes constitute the most active proteases in this tissue and represent an index of protein degradation capacity in cardiac muscle. The results showed that in 2.5-h dosed rats, adriamycin had no effect on S(i), S(b), C(s), k(s), or k(RNA) (P > 0.05, not significant (NS) in all instances). In 2.5-h dosed rats, levels of diaminopeptidase I activity were reduced (P < 0.05), whereas the activities of other proteases were not significantly altered (NS in all instances). In 24-h dosed rats, adriamycin reduced cardiac S(b) (P < 0.001), which would normally be interpreted as a reduction in protein synthesis. However, S(i) was also decreased in 24-h adriamycin-injected rats (P < 0.025%). C(s) was not changed (NS). Consequently, the calculated k(s) and k(RNA) values were not significantly affected in 24-h adriamycin-dosed rats (NS). There were also significant reductions in proline endopeptidase activities in rats exposed for 24 h to adriamycin. The activities of other proteases were not significantly affected at this time point (NS in all instances). In conclusion, adriamycin reduces amino acid labeling of cardiac proteins, an effect that is a consequence of altered free phenylalanine-specific radioactivities. There was some evidence of limited altered intracellular proteolysis.

Differences in the intracellular distribution of acid-sensitive doxorubicin-protein conjugates in comparison to free and liposomal formulated doxorubicin as shown by confocal microscopy

PURPOSE

To investigate differences in the cellular uptake and intracellular distribution of protein-bound doxorubicin in comparison to free doxorubicin and a liposomal formulation (CAELYX) METHODS: LXFL 529 lung carcinoma cells were incubated with an acid-sensitive transferrin and albumin conjugate of doxorubicin, a stable albumin doxorubicin conjugate, and free and liposomal doxorubicin for up to 24 h. The uptake of doxorubicin was detected with confocal laser scanning microscopy (CLSM). To investigate the intracellular localization of the anticancer drug, lysosomes, Golgi apparatus, and mitochondria were also stained by various organelle-specific fluorescent markers. In vitro efficacy of the doxorubicin derivatives was examined with the BrdU incorporation assay.

RESULTS

The acid-sensitive albumin and transferrin doxorubicin conjugates showed enhanced cytotoxicity in comparison to liposomal doxorubicin, whereas the stable albumin-doxorubicin conjugate showed only marginal activity. Of all compounds tested, doxorubicin showed the highest cytotoxicity. CLSM studies with specific markers for lysosomes, mitochondria, and the Golgi apparatus demonstrated that protein-bound doxorubicin or liberated doxorubicin was accumulated in the mitochondria and Golgi compartments, but not in the lysosomes after 24 h. Free doxorubicin showed a time-dependent intracellular shift from the nucleus to the mitochondria and Golgi apparatus. Fluorescence resulting from incubation with CAELYX was primarily detected in the nucleus.

CONCLUSIONS

Our results indicate that other organelles in addition to the cell nucleus are important sites of accumulation and interaction for protein-bound doxorubicin or intracellularly released doxorubicin as well as for free doxorubicin.

Effect of Adriamycin on the boundary lipid structure of cytochrome c oxidase: pico-second time-resolved fluorescence depolarization studies

The fluorescence dynamics of the dye 3,3'-diethyloxadicarbocyanine iodide (DODCI) was used to probe the microenvironment of cytochrome c oxidase (CcO) and cardiolipin. The dye was partitioned between an aqueous and a hydrophobic phase. The 'bound' and 'free' populations of DODCI could be separated by analysis of the time-resolved fluorescence decay of the dye. The anisotropy decay of the DODCI bound to CcO showed a unique 'dip and rise' shape that was analyzed by a combination of rotational correlation times with time-dependent weight factors for each lifetime component. Rotational dynamics studies revealed the existence of a restricted motion of the dye bound at the enzyme surface. Adriamycin, an anticancer, albeit cardiotoxic drug, was previously proposed to affect the surface structure of CcO, most likely by causing a disorder to the surface lipid arrangement. A drastic change in the rotational correlation time of the dye bound to the enzyme surface was observed, which suggested a depletion of cardiolipin layer due to complexation with the drug. The effect of Adriamycin on cardiolipin was drastic, leading to its phase separation. The present study suggests that the effect of Adriamycin on CcO is primarily a segregation of the cardiolipins.