Antioxidants protect against reactive oxygen species associated with adriamycin-treated cardiomyocytes

Didymin Inhibits Proliferation and Induces Apoptosis in Gastric Cancer Cells by Modulating the PI3K/Akt Pathway

Gastric cancer (GC) is a malignant tumor with high morbidity and mortality rates worldwide. This study aimed to investigate the effects and mechanisms of action of didymin, a dietary flavonoid glycoside, on GC treatment. Human GC cell lines Hs-746T and AGS were used to assess the effects of didymin on cell viability, cell proliferation, and cell cycle. The results showed that didymin decreased the proliferative capacity of GC cells and blocked cell cycle. Didymin decreased wound healing, invasion, and migration capacities of GC cells. Mitochondrial reactive oxygen species (ROS) levels and mitochondrial membrane potentials were reduced in cells treated with didymin. Network pharmacology analysis revealed that the therapeutic effects of didymin on AGS cells were related to the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. In vivo mouse xenograft studies confirmed that didymin treatment decreased tumor cell proliferation, cell cycle protein levels, and Akt phosphorylation. The present study demonstrated that didymin regulates mitochondrial function and the PI3K/Akt pathway to inhibit cell proliferation and induce apoptosis in GC cells in vitro and in vivo. Therefore, didymin is a promising drug for the treatment of GC.

Role of Oxidative Stress Signaling, Nrf2, on Survival and Stemness of Human Adipose-Derived Stem Cells Exposed to X-rays, Protons and Carbon Ions

Some cancers have a poor prognosis and often lead to local recurrence because they are resistant to available treatments, e.g., glioblastoma. Attempts have been made to increase the sensitivity of resistant tumors by targeting pathways involved in the resistance and combining it, for example, with radiotherapy (RT). We have previously reported that treating glioblastoma stem cells with an Nrf2 inhibitor increases their radiosensitivity. Unfortunately, the application of drugs can also affect normal cells. In the present study, we aim to investigate the role of the Nrf2 pathway in the survival and differentiation of normal human adipose-derived stem cells (ADSCs) exposed to radiation. We treated ADSCs with an Nrf2 inhibitor and then exposed them to X-rays, protons or carbon ions. All three radiation qualities are used to treat cancer. The survival and differentiation abilities of the surviving ADSCs were studied. We found that the enhancing effect of Nrf2 inhibition on cell survival levels was radiation-quality-dependent (X-rays > proton > carbon ions). Furthermore, our results indicate that Nrf2 inhibition reduces stem cell differentiation by 35% and 28% for adipogenesis and osteogenesis, respectively, using all applied radiation qualities. Interestingly, the results show that the cells that survive proton and carbon ion irradiations have an increased ability, compared with X-rays, to differentiate into osteogenesis and adipogenesis lineages. Therefore, we can conclude that the use of carbon ions or protons can affect the stemness of irradiated ADSCs at lower levels than X-rays and is thus more beneficial for long-time cancer survivors, such as pediatric patients.

Reactive oxygen species in cancer: Current findings and future directions

Reactive oxygen species (ROS), a class of highly bioactive molecules, have been widely studied in various types of cancers. ROS are considered to be normal byproducts of numerous cellular processes. Typically, cancer cells exhibit higher basal levels of ROS compared with normal cells as a result of an imbalance between oxidants and antioxidants. ROS have a dual role in cell metabolism: At low to moderate levels, ROS act as signal transducers to activate cell proliferation, migration, invasion, and angiogenesis. In contrast, high levels of ROS cause damage to proteins, nucleic acids, lipids, membranes, and organelles, leading to cell death. Extensive studies have revealed that anticancer therapies that manipulate ROS levels, including immunotherapies, show promising in vitro as well as in vivo results. In this review, we summarize molecular mechanisms and oncogenic functions that modulate ROS levels and are useful for the development of cancer therapeutic strategies. This review also provides insights into the future development of effective agents that regulate the redox system for cancer treatment.

Effects of Calorie Restriction and Voluntary Exercise on Doxorubicin-Induced Cardiotoxicity

Introduction: Doxorubicin (DOX) is a widely used chemotherapeutic agent with known cardiotoxic properties, while calorie restriction (CR) and exercise have well-documented cardioprotective effects. No studies have investigated the effects of CR alone or the combined effects of CR and exercise on DOX cardiotoxicity. Methods: Rats were divided into 4 groups based on their food intake (ad libitum or CR) and activity (sedentary or voluntary wheel running [WR]). After completing a 16-week treatment, animals received either DOX (15 mg/kg) or saline (SAL) and cardiac function was measured 5 days after treatment. Chromatography was used to quantify left ventricular DOX accumulation. Results: Left ventricular developed pressure (LVDP), end systolic pressure (ESP), and left ventricular maximal rate of pressure development (dP/dt_max) were significantly higher in the CR + DOX group when compared with DOX. Fractional shortening, LVDP, ESP, dP/dt_max, and dP/dt_min were significantly higher in the CR + WR + DOX group compared with the DOX group. In addition, the CR + WR + DOX group showed significantly higher LVDP and ESP compared with the WR + DOX group. DOX accumulation in the heart was 5-fold lower (P < .05) in the CR + WR + DOX group compared with the DOX group. Conclusion: This is the first study to demonstrate that CR can reduce cardiac DOX accumulation, and confirms the protective role of CR against DOX-induced cardiac dysfunction. Our data also show that combining a known cardioprotective intervention, exercise training, with CR results in additive benefits in the protection against DOX cardiotoxicity.

Trolox prevents high glucose-induced apoptosis in rat myocardial H9c2 cells by regulating GLUT-4 and antioxidant defense mechanism

Redox imbalance due to hyperglycemia is a causative factor for an increased generation of reactive oxygen species (ROS) that leads to mitochondrial dysfunction and the release of cytochrome-c. The aim of the present study is to elucidate the functional role of oxidative stress (OS) in the induction of apoptosis in H9c2 cells in the hyperglycemic state through glucose transporter-4 (GLUT-4) regulation and antioxidant status. H9c2 cells were incubated with 15, 24, and 33 mM glucose for 24, 48, and 72 hr to induce hyperglycemic stress. Hyperglycemic episodes have significantly influenced GLUT-4 mRNA regulation, depleted glutathione (GSH) and its associated enzymes, reduced cellular antioxidant enzymes (AOEs), caused nuclear condensation, and induced apoptosis by activating caspase-9 and 3 and annexin V binding in a concentration and duration-dependent manner. Trolox pretreatment significantly enhanced the GLUT-4 mRNA and antioxidant defense mechanism, suppressed nuclear condensation, and prevented cytochrome-c release, thereby reducing mitochondrial-dependent apoptosis. The present study shows that the toxic effect of high glucose is significantly regulated and that OS induction can be prevented through a water-soluble vitamin E analog "Trolox" treatment.

Antioxidant Therapeutic Strategies for Cardiovascular Conditions Associated with Oxidative Stress

Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability to scavenge these ROS by endogenous antioxidant systems, where ROS overwhelms the antioxidant capacity. Excessive presence of ROS results in irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Oxidative stress plays a crucial role in the pathogenesis of cardiovascular diseases related to hypoxia, cardiotoxicity and ischemia-reperfusion. Here, we describe the participation of OS in the pathophysiology of cardiovascular conditions such as myocardial infarction, anthracycline cardiotoxicity and congenital heart disease. This review focuses on the different clinical events where redox factors and OS are related to cardiovascular pathophysiology, giving to support for novel pharmacological therapies such as omega 3 fatty acids, non-selective betablockers and microRNAs.

Muscle Strength, Body Composition, and Physical Activity in Women Receiving Chemotherapy for Breast Cancer

There is evidence to suggest that treatment of breast cancer with chemotherapy can induce metabolic changes in skeletal muscle. Women undergoing treatment for breast cancer with certain chemotherapeutic agents can experience declines in lean body mass and muscle strength and a subsequent increase in body weight. These alterations not only can lead to declines in physical function but also predispose women to weight-related chronic illness. Excess body weight may also play a role in the development or recurrence of breast cancer. There is evidence that physical exercise may improve body composition and enhance muscular endurance, flexibility, and quality of life (QOL) in women with breast cancer. While studies of aerobic, resistance, and combinations of aerobic and resistance exercise for women with breast cancer have been conducted, most studies employed supervised aerobic exercise sessions. Few studies have examined the role of resistance exercise or the combination of resistance and aerobic exercise in maintaining or increasing muscle strength while preserving lean body mass in this population. The relatively small sample sizes and short duration of physical activity interventions in previous studies make it difficult to detect dose responses to exercise training. Physical activity interventions with larger sample sizes and of longer duration are necessary to achieve long-term health outcomes. Physical activity interventions that include the older or more obese women with breast cancer are also needed, as this population may be most at risk of functional decline and the development of chronic illness. Interventions appropriate for women treated for breast cancer who have comorbid disease are also needed. Newer, more intense chemotherapy regimens may induce a differential effect on muscle strength and body composition. However, the role of physical activity during dose-dense chemotherapy protocols has not been established.

Ameliorative effect of naringin against doxorubicin-induced acute cardiac toxicity in rats

CONTEXT

Doxorubicin (Dox) is one of the most active chemotherapeutic agents used to treat various types of cancers. Its clinical utility is compromised due to fatal cardiac toxicity characterized by an irreversible cardiomyopathy.

OBJECTIVE

This study evaluates the cardioprotective potential of naringin (NR) against Dox-induced acute cardiac toxicity in rats.

MATERIALS AND METHODS

Male Wistar rats were randomly divided into five groups. NR (50 and 100 mg/kg) was administered intraperitoneally (i.p.) daily from 0 to 14 d. Doxorubicin (15 mg/kg, i.p.) was given as a single dose on the 10th day. On the 14th day, all animals were sacrificed and oxidative stress parameters that include malondialdehyde (MDA), glutathione (GSH) level, superoxide dismutase (SOD), catalase (CAT) activities, and all mitochondrial complexes (I-IV) activities were evaluated along with histopathological studies of the heart.

RESULTS

Doxorubicin-induced cardiotoxicity was confirmed by increased (p < 0.05) MDA, decreased (p < 0.05) GSH levels, SOD, and CAT activities, mitochondrial complexes (I-IV) activities in the heart tissue. NR (100 mg/kg) showed cardioprotection as evident from significant decreased MDA (p < 0.001) level, raised (p < 0.001) GSH level, SOD and CAT activities and increased mitochondrial complexes I (p < 0.01), II (p < 0.001), III (p < 0.001), and IV (p < 0.05) activities. Further, Dox-induced cardiotoxicity was confirmed by histopathological studies. These obtained results indicated the protective role of NR against Dox-induced cardiac toxicity in rats.

CONCLUSION

NR can be used in combination with Dox due to its high cardioprotective effect against Dox-induced cardiomyopathy.

A multi-parameter in vitro screen in human stem cell-derived cardiomyocytes identifies ponatinib-induced structural and functional cardiac toxicity

Ponatinib, a multi-targeted TKI and potent pan-ABL inhibitor, approved for the treatment of Ph + ALL and CML, was temporarily withdrawn from the U.S. market due to severe vascular adverse events. Cardiac-specific toxicities including myocardial infarction, severe congestive heart failure, and cardiac arrhythmias have also been shown with ponatinib. Targeted oncology agents such as ponatinib have transformed cancer treatment but often induce toxicity due to inhibition of survival pathways shared by both cancer and cardiac cells. These toxicities are often missed by the standard preclinical toxicity assessment methods, which include human Ether-à-go-go-related gene (hERG) and animal toxicity testing. In this study, we show that a multiparameter in vitro toxicity screening approach using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) accurately predicted the cardiac toxicity potential of ponatinib. This in vitro model evaluated ponatinib's effect on the overall cell health, mitochondrial stress, and function of hiPSC-CM and also provided mechanistic insight into the signaling pathways and cellular structures altered with treatment. We show here that ponatinib rapidly inhibits prosurvival signaling pathways, induces structural cardiac toxicity (as shown by actin cytoskeleton damage, mitochondrial stress, cell death, and troponin secretion), and disrupts cardiac cell beating. Most of these effects occurred at doses between 10× and 50× ponatinib's Cmax, a dose range shown to be relevant for accurate prediction of in vivo toxicity. Together these studies show that a comprehensive in vitro screening tool in a more relevant human cardiac cell model can improve the detection of cardiac toxicity with targeted oncology agents such as ponatinib.

The tell-tale heart: molecular and cellular responses to childhood anthracycline exposure

Since the modern era of cancer chemotherapy that began in the mid-1940s, survival rates for children afflicted with cancer have steadily improved from 10% to current rates that approach 80% (60). Unfortunately, many long-term survivors of pediatric cancer develop chemotherapy-related health effects; 25% are afflicted with a severe or life-threatening medical condition, with cardiovascular disease being a primary risk (96). Childhood cancer survivors have markedly elevated incidences of stroke, congestive heart failure (CHF), coronary artery disease, and valvular disease (96). Their cardiac mortality is 8.2 times higher than expected (93). Anthracyclines are a key component of most curative chemotherapeutic regimens used in pediatric cancer, and approximately half of all childhood cancer patients are exposed to them (78). Numerous epidemiologic and observational studies have linked childhood anthracycline exposure to an increased risk of developing cardiomyopathy and CHF, often decades after treatment. The acute toxic effects of anthracyclines on cardiomyocytes are well described; however, myocardial tissue is comprised of additional resident cell types, and events occurring in the cardiomyocyte do not fully explain the pathological processes leading to late cardiomyopathy and CHF. This review will summarize the current literature regarding the cellular and molecular responses to anthracyclines, with an important emphasis on nonmyocyte cardiac cell types as well as those that mediate the myocardial injury response.

Aldo-keto reductase 7A5 (AKR7A5) attenuates oxidative stress and reactive aldehyde toxicity in V79-4 cells

Aldo-keto reductase (AKR) enzymes are critical in the detoxification of endogenous and exogenous aldehydes. In previous studies, we have shown that AKR7A5 enzyme is catalytically active towards aldehydes arising from lipid peroxidation (LPO) and that it can significantly protect against 4-hydroxynonenal-induced apoptosis, suggesting a protective role against the consequences of oxidative stress. The aim of this study was to elucidate the cytoprotective effect of AKR7A5 against oxidative stress using a transgenic mammalian cell line expressing AKR7A5. Results show that expression of AKR7A5 in V79-4 cells provides significant protection against the cytotoxicity of H2O2 and menadione, with its expression altering the IC50 of H2O2 from 1.1 to 2.3 mM and the IC50 of menadione from 8.6 to 9.6 μM, thus providing direct evidence for its anti-oxidant activity. Cells expressing AKR7A5 were also found to be more resistant to several LPO-derived aldehydes--trans-2-nonenal, hexanal and methylglyoxal. In addition the ability of AKR7A5 to enable the cells to cope with ROS accumulation and glutathione depletion was assessed. V79-4 cells overexpressing AKR7A5 were able to lower cellular ROS levels following treatment with H2O2 and menadione. AKR7A5 was also able to maintain cellular glutathione homeostasis in the presence of H2O2 and menadione. These findings indicate the importance of AKR7A5 in protecting cells from the damaging effects of oxidative stress, and that this cytoprotective function is carried out through multiple pathways.

Baicalein Protects Cardiomyocytes Against Mitochondrial Oxidant Injury Associated with JNK Inhibition and Mitochondrial Akt Activation

Baicalein, a flavonoid derived from Scutellaria baicalensis Georgi, possesses cardioprotection against oxidant injury by scavenging reactive oxygen species (ROS). Few studies investigate whether baicalein protection is mediated by attenuating mitochondrial ROS and modulating the prosurvival and proapoptotic signaling. Primary cultured chick cardiomyocytes were used to study the role of baicalein in mitochondrial superoxide [Formula: see text] generation and signaling of Akt and JNK. Cells were exposed to H 2 O 2 for 2 h and baicalein was given 2 h prior to and during 2 h of H 2 O 2 exposure. Cell viability was assessed by propidium iodide and DNA fragmentation. H 2 O 2 (500 μM) significantly induced 45.3 ± 6.2% of cell death compared to the control (p < 0.001) and resulted in DNA laddering. Baicalein (10, 25 or 50 μM) dose-dependently reduced the cell death to 38.7 ± 5.6% (p = 0.226); 31.2 ± 3.9% (p < 0.01); 30.3 ± 5.3% (p < 0.01), respectively. It also attenuated DNA laddering. Further, baicalein decreased intracellular ROS and mitochondrial [Formula: see text] generation that was confirmed by superoxide dismutase PEG-SOD and mitochondria electron transport chain complex III inhibitor stigmatellin. In addition, baicalein increased Akt phosphorylation and decreased JNK phosphorylation in H 2 O 2-exposed cells. Moreover, baicalein augmented mitochondrial phosphorylation of Akt Thr308 and GSK3β Ser9, and prevented mitochondrial cytochrome c release assessed by cellular fractionation. Our results suggest that baicalein cardioprotection may involve an attenuation of mitochondrial [Formula: see text] and an increase in mitochondrial phosphorylation of Akt and GSK3β while decreasing JNK activation.

Protective effect of saffron extract against doxorubicin cardiotoxicity in isolated rabbit heart

CONTEXT

Anticancer treatments such as anthracyclines are effective; however, they induce cardiotoxicity by releasing radical oxygen species (ROS). Saffron (Crocus sativus; Iridaceae) is a widely used spice with antioxidant properties and numerous health benefits that may provide cardioprotection.

OBJECTIVE

To assess the effect of saffron against acute myocardium damage by anthracyclines compared with electrolysis as a free radical generating system.

MATERIALS AND METHODS

According to the Langendorff method, we used the model of an isolated rabbit heart perfused in retrograde. In one set of experiments, ROS was generated by electrolysis of the perfused heart solution (3 mA for 30 min) in the presence and absence of saffron extracts at the optimal dose (10 μg/ml). In another set, we perfused the heart with anthracycline, i.e. 30 μM doxorubicin (Doxo) in the presence and absence of 10 μg/ml saffron extracts. We evaluated cardiodynamics, as well as biochemical and pathological parameters, to emphasize the effectiveness of the treatment with saffron extract using the optimal dose of catalase (150 IU) as a positive control.

RESULTS

ROS generated, respectively, by electrolysis and by Doxo significantly (p < 0.05) affects cardiovascular function; it decreased ventricular pressure (45.02 and 40.41%), heart rate (36.31 and 22.39%) and coronary flow (50.98 and 36.67%). Increased lipid peroxidation of the myocardium was also observed (118.22 and 56.58%), while superoxide dismutase activity decreased (48.33 and 38.70%). The myocardial architecture was altered and the intercellular spaces increased.

CONCLUSION

Saffron perfused during electrolysis helps trap ROS and significantly improves myocardial function; however, saffron was less effective against Doxo, thus suggesting that mechanisms other than oxidative stress underlie Doxo cardiotoxicity.

Doxorubicin-antioxidant co-drugs

Doxorubicin-antioxidant multitarget compounds 6 and 7 were obtained by combining doxorubicin (DOX) with caffeic and ferulic acids through an ester linkage at C-14. The products were studied in in vitro models of cardiomyocytes and breast cancer cells, characterized by different degrees of resistance to DOX, due to different expressions of ATP binding cassette (ABC) transporters. Compound 7 was found to be less toxic than DOX in cardiomyocytes and to display the same possibly higher toxicity against the resistant breast cancer cells. This result shows that appropriate DOX-antioxidant co-drugs can limit the onset of cardiac damage, a significant side-effect of DOX, without impairing the antitumor activity of the parent antibiotic.

Imaging of early modification in cardiomyopathy: the doxorubicin-induced model

Doxorubicin chemotherapy is effective and widely used to treat acute lymphoblastic leukemia. However, its effectiveness is hampered by a wide spectrum of dose-dependent cardiotoxicity including both morphological and functional changes, affecting primarily the myocardium. Non-invasive imaging techniques are used for the diagnosis and monitoring of these cardiotoxic effects. The purpose of this review is to summarize and compare the most common imaging techniques used in early detection and therapeutic monitoring of doxorubicin-induced cardiotoxicity and the suggested mechanisms of such side effects. Imaging techniques using echocardiography including conventional 2D and 3D echocardiography along with MRI sequences including Tagging, Cine, and quantitative MRI in detecting early myocardial damage are also reviewed. As there is a multitude of reported indices and imaging methods to assess particular functional alterations, we limit this review to the most relevant techniques based on their clinical application and their potential to early detection of doxorubicin-induced cardiotoxic effects.

Protective role of atorvastatin against doxorubicin-induced cardiotoxicity and testicular toxicity in mice

Doxorubicin (DOX), a potent chemotherapeutic agent, is widely used for the treatment of various malignancies. However, its clinical uses are limited due to its dose-dependent adverse effects particularly cardiac and testicular toxicities. DOX-induced toxicity is mainly due to the induction of oxidative stress. Atorvastatin (ATV), a 3-hydroxy 3-methyl glutaryl coenzyme A reductase inhibitor, with lipid-lowering activity, acts as an antioxidant at lower doses. It possesses pleiotropic effects independent of cholesterol-lowering property usually shown at lower doses, which include antioxidant and anti-inflammatory activities. The present study was aimed to investigate the possible protection exerted by atorvastatin against oxidative stress and DNA damage induced by DOX in the heart and testes of mice. The protective role of ATV in the heart and testes of DOX-treated mice was evident from the amelioration of oxidative stress, DNA and cellular damage. The present study clearly indicates that ATV offers a significant protection against DOX-induced oxidative stress and DNA damage in the heart and testes of mice.

Autophagy upregulation promotes survival and attenuates doxorubicin-induced cardiotoxicity

This study evaluated whether the manipulation of autophagy could attenuate the cardiotoxic effects of doxorubicin (DXR) in vitro as well as in a tumour-bearing mouse model of acute doxorubicin-induced cardiotoxicity. We examined the effect of an increase or inhibition of autophagy in combination with DXR on apoptosis, reactive oxygen species (ROS) production and mitochondrial function. H9C2 rat cardiac myoblasts were pre-treated with bafilomycin A1 (autophagy inhibitor, 10 nM) or rapamycin (autophagy inducer, 50 μM) followed by DXR treatment (3 μM). The augmentation of autophagy with rapamycin in the presence of DXR substantially ameliorated the detrimental effects induced by DXR. This combination treatment demonstrated improved cell viability, decreased apoptosis and ROS production and enhanced mitochondrial function. To corroborate these findings, GFP-LC3 mice were inoculated with a mouse breast cancer cell line (EO771). Following the appearance of tumours, animals were either treated with one injection of rapamycin (4 mg/kg) followed by two injections of DXR (10 mg/kg). Mice were then sacrificed and their hearts rapidly excised and utilized for biochemical and histological analyses. The combination treatment, rather than the combinants alone, conferred a cardioprotective effect. These hearts expressed down-regulation of the pro-apoptotic protein caspase-3 and cardiomyocyte cross-sectional area was preserved. These results strongly indicate that the co-treatment strategy with rapamycin can attenuate the cardiotoxic effects of DXR in a tumour-bearing mouse model.

Topoisomerase 2 alpha: a real predictor of anthracycline efficacy?

Anthracyclines are frequently used in the adjuvant setting for breast cancer treatment since it is considered that anthracycline-based chemotherapy treatment benefits breast cancer patients. Nonetheless, these drugs are associated with severe side effects and predictive factors, for sensitivity to anthracyclines, are warranted in clinical practice. Topoisomerase 2 alpha (TOP2A) is considered to be the molecular target of these drugs. The potential predictive value of TOP2A amplification and overexpression has been extensively studied in breast cancer patients treated with anthracyclines. However, results are not conclusive. In this paper, we review some of the published studies addressing the predictive value of TOP2A as well as the cellular functions of this enzyme and its status in breast cancer tissue.

Glutathione S-transferase P1 c.313A > G polymorphism could be useful in the prediction of doxorubicin response in breast cancer patients

BACKGROUND

Identification of predicting factors for anthracyclines-based chemotherapy remains a clinical challenge. Glutathione S-transferase (GSTs) enzymes detoxify chemotherapy drugs and their metabolites. Several polymorphisms in GST genes result in reduced or no activity of the enzymes. Specifically, GSTM1 and GSTT1 genes are polymorphically deleted, the polymorphism GSTP1 c.313A>G (rs1695) determines the amino acid substitution Ile105Val, where the Val-containing enzyme has reduced activity. Also, GSTA1*B allele has reduced levels of GSTA1 enzyme. Several polymorphisms in GSTs have been associated with differences in survival for cancer patients treated with chemotherapy.

PATIENTS AND METHODS

We genotyped a total of five polymorphisms in GSTM1, GSTT1, GSTP1 and GSTA1 genes in 159 patients with locally advanced breast cancer, treated with single-agent doxorubicin or docetaxel (Taxotere). Gene expression microarrays were performed in 67 breast tumor samples. We correlate this data with treatment outcome.

RESULTS

In multivariate analysis, patients homozygous GG for GSTP1 c.313A>G SNP had a lower risk of chemoresistance when treated with doxorubicin (odds ratio 0.106; confidence interval 0.012-0.898; P=0.040). No association was found in the docetaxel arm. Also, we found that GSTP1 expression varied significantly among breast cancer molecular subtypes.

CONCLUSIONS

GSTP1 may constitute another tool contributing to individualized anthracycline-based therapy.

Chemotherapy-induced weakness and fatigue in skeletal muscle: the role of oxidative stress

SIGNIFICANCE

Fatigue is one of the most common symptoms of cancer and its treatment, manifested in the clinic through weakness and exercise intolerance. These side effects not only compromise patient's quality of life (QOL), but also diminish physical activity, resulting in limited treatment and increased morbidity.

RECENT ADVANCES

Oxidative stress, mediated by cancer or chemotherapeutic agents, is an underlying mechanism of the drug-induced toxicity. Nontargeted tissues, such as striated muscle, are severely affected by oxidative stress during chemotherapy, leading to toxicity and dysfunction.

CRITICAL ISSUES

These findings highlight the importance of investigating clinically applicable interventions to alleviate the debilitating side effects. This article discusses the clinically available chemotherapy drugs that cause fatigue and oxidative stress in cancer patients, with an in-depth focus on the anthracycline doxorubicin. Doxorubicin, an effective anticancer drug, is a primary example of how chemotherapeutic agents disrupt striated muscle function through oxidative stress.

FUTURE DIRECTIONS

Further research investigating antioxidants could provide relief for cancer patients from debilitating muscle weakness, leading to improved quality of life.

Human aldo-keto reductase AKR7A2 protects against the cytotoxicity and mutagenicity of reactive aldehydes and lowers intracellular reactive oxygen species in hamster V79-4 cells

Aldo-keto reductase (AKR) enzymes are critical for the detoxication of endogenous and exogenous aldehydes. Previous studies have shown that the AKR7A2 enzyme is catalytically active toward aldehydes arising from lipid peroxidation, suggesting a potential role against the consequences of oxidative stress, and representing an important detoxication route in mammalian cells. The aim of this study was to determine the ability of AKR7A2 to protect cells against aldehyde cytotoxicity and genotoxicity and elucidate its potential role in providing resistance to oxidative stress. A transgenic mammalian cell model was developed in which AKR7A2 was overexpressed in V79-4 cells and used to evaluate the ability of AKR7A2 to provide resistance against toxic aldehydes. Results show that AKR7A2 provides increased resistance to the cytotoxicity of 4-hydroxynonenal (HNE) and modest resistance to the cytotoxicity of trans, trans-muconaldehyde (MUC) and methyglyoxal, but provided no protection against crotonaldehyde and acrolein. Cells expressing AKR7A2 were also found to be less susceptible to DNA damage, showing a decrease in mutation rate cause by 4-HNE compared to control cells. Furthermore, the role of the AKR7A2 enzyme on the cellular capability to cope with oxidative stress was assessed. V79 cells expressing AKR7A2 were more resistant to the redox-cycler menadione and were able to lower menadione-induced ROS levels in both a time and dose dependent manner. In addition, AKR7A2 was able to maintain intracellular GSH levels in the presence of menadione. Together these findings indicate that AKR7A2 is involved in cellular detoxication pathways and may play a defensive role against oxidative stress in vivo.

Blockade of Caspase-2 Activity Inhibits Ischemia/Reperfusion-Induced Mitochondrial Reactive Oxygen Burst and Cell Death in Cardiomyocytes

We previously showed that initiator caspases-2 and −8 are prominently activated in ischemia/reperfusion (I/R)-induced injury in cardiomyocytes, but while blockade of caspase-2 activity enhanced cell survival, blockade of caspase-8 activity did not protect cardiomyocytes. Because apoptotic death in these cells is characterized by a burst of reactive oxygen species (ROS) at reperfusion and their survival by inhibition of this burst, we examined the effects of blocking caspase-2 and caspase-8 activities on ROS production. Caspase-2 inhibition blocked the reperfusion-induced ROS burst, while inhibition of caspase-8 did not. We also examined effects of caspase inhibition on mitochondrial membrane potential (ΔΨm) and mitochondrial function and found that blocking caspase-2, but not caspase-8, allowed recovery of ΔΨm and mitochondrial functionality. Furthermore, knockdown of caspase-2 by small-interfering (si)RNA confirmed caspase-2 participation in cytochrome c release, which correlates with loss of ΔΨm and cell death in these cardiomyocytes.

Grape seed proanthocyanidins ameliorate Doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) is one of the most widely used and successful chemotherapeutic antitumor drugs. Its clinical application is highly limited due to its cumulative dose-related cardiotoxicity. Proposed mechanisms include the generation of reactive oxygen species (ROS)-mediated oxidative stress. Therefore, reducing oxidative stress should be protective against Dox-induced cardiotoxicity. To determine whether antioxidant, grape seed proanthocyanidin extract (GSPE) attenuates Dox-induced ROS generation and protects cardiomyocytes from Dox-induced oxidant injury, cultured primary cardiomyocytes were treated with doxorubicin (Dox, 10 microM) alone or GSPE (50 microg/ml) with Dox (10 microM) for 24 hours. Dox increased intracellular ROS production as measured by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, induced significant cell death as assessed by propidium iodide, and declined the redox ratio of reduced glutathione (GSH)/oxidized glutathione (GSSG) and disrupted mitochondrial membrane potential as determined by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethlbenzimidazole-carbocyanide iodine (JC-1). Analysis of agarose gel electrophoresis revealed Dox-induced nuclear DNA damage with the ladder like fragmentation. GSPE treatment suppressed those alterations. Electron Spin Resonance (ESR) spectroscopy data also showed that GSPE strongly scavenged hydroxyl radical, superoxide and DPPH radicals. Together, these findings indicate that GSPE in combination with Dox has protective effect against Dox-induced toxicity in cardiomyocytes, which may be in part attributed to its antioxidative activity. Importantly, flow cytometric analysis demonstrated that co-treatment of Dox and GSPE did not decrease the proliferation-inhibitory effect of Dox in MCF-7 human breast carcinoma cells. Thus, GSPE may be a promising adjuvant to prevent cardiotoxicity without interfering with antineoplastic activity during chemotherapeutic treatment with Dox.

Therapeutic hypothermia cardioprotection via Akt- and nitric oxide-mediated attenuation of mitochondrial oxidants

Therapeutic hypothermia (TH) is a promising cardioprotective treatment for cardiac arrest and acute myocardial infarction, but its cytoprotective mechanisms remain unknown. In this study, we developed a murine cardiomyocyte model of ischemia-reperfusion injury to better determine the mechanisms of TH cardioprotection. We hypothesized that TH manipulates Akt, a survival kinase that mediates mitochondrial protection by modulating reactive oxygen species (ROS) and nitric oxide (NO) generation. Cardiomyocytes, isolated from 1- to 2-day-old C57BL6/J mice, were exposed to 90 min simulated ischemia and 3 h reperfusion. For TH, cells were cooled to 32 degrees C during the last 20 min of ischemia and the first hour of reperfusion. Cell viability was evaluated by propidium iodide and lactate dehydrogenase release. ROS production was measured by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate and mitochondrial membrane potential (DeltaPsim) by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazoly-carbocyanine iodide (JC-1). Phospho (p)-Akt (Thr308), p-Akt (Ser473), and phosphorylated heat shock protein 27 (p-HSP27) (Ser82) were analyzed by Western blot analysis. TH attenuated reperfusion ROS generation, increased NO, maintained DeltaPsim, and decreased cell death [19.3 + or - 3.3% (n = 11) vs. 44.7 + or - 2.7% (n = 10), P < 0.001]. TH also increased p-Akt during ischemia before reperfusion. TH protection and attenuation of ROS were blocked by the inhibition of Akt and NO synthase but not by a cGMP inhibitor. HSP27, a regulator of Akt, also exhibited increased phosphorylation (Ser82) during ischemia with TH. We conclude that TH cardioprotection is mediated by enhanced Akt/HSP27 phosphorylation and enhanced NO generation, resulting in the attenuation of ROS generation and the maintenance of DeltaPsim following ischemia-reperfusion.

Alterations in brain antioxidant enzymes and redox proteomic identification of oxidized brain proteins induced by the anti-cancer drug adriamycin: implications for oxidative stress-mediated chemobrain

Adriamycin (ADR) is a chemotherapeutic for the treatment of solid tumors. This quinone-containing anthracycline is well known to produce large amounts of reactive oxygen species (ROS) in vivo. A common complaint of patients undergoing long-term treatment with ADR is somnolence, often referred to as "chemobrain." While ADR itself does not cross the blood brain barrier (BBB), we recently showed that ADR administration causes a peripheral increase in tumor necrosis factor alpha (TNF-alpha), which migrates across the BBB and leads to inflammation and oxidative stress in brain, most likely contributing to the observed decline in cognition. In the current study, we measured levels of the antioxidant glutathione (GSH) in brains of mice injected intraparitoneally (i.p.) with ADR, as well as the levels and activities of several enzymes involved in brain GSH metabolism. We observed significantly decreased GSH levels, as well as altered GSH/GSSG ratio in brains of ADR treated mice relative to saline-treated controls. Also observed in brains of ADR treated mice were increased levels of glutathione peroxidase (GPx), glutathione-S-transferase (GST), and glutathione reductase (GR). We also observed increased activity of GPx, but a significant reduction in GST and GR activity in mice brain, 72 h post i.p. injection of ADR (20 mg/kg body weight). Furthermore, we used redox proteomics to identify specific proteins that are oxidized and/or have differential levels in mice brains as a result of a single i.p. injection of ADR. Visinin like protein 1 (VLP1), peptidyl prolyl isomerase 1 (Pin1), and syntaxin 1 (SYNT1) showed differential levels in ADR treated mice relative to saline-treated controls. Triose phosphate isomerase (TPI), enolase, and peroxiredoxin 1 (PRX-1) showed significantly increased specific carbonylation in ADR treated mice brain. These results further support the notion ADR induces oxidative stress in brain despite not crossing the BBB, and that antioxidant intervention may prevent ADR-induced cognitive dysfunction.

Anandamide Preserves Cardiac Function and Geometry in an Acute Doxorubicin Cardiotoxicity Rat Model

We investigated the use of the endocannabinoid anandamide as a means of cardioprotection against doxorubicin-induced cardiac dysfunction. Male rats received doxorubicin with or without anandamide pretreatment. Cardiac function was assessed in vivo using transthoracic echocardiography and ex vivo using the isolated working heart 5 days posttreatment. Doxorubicin administration without anandamide pretreatment resulted in a decline in fractional shortening (P < .05) and left ventricular wall thickness when compared to controls (P < .05). Ex vivo cardiac function analysis revealed a reduction in left ventricular developed pressure in hearts from animals receiving doxorubicin without anandamide pretreatment when compared to controls (P < .05). Left ventricles from animals receiving anandamide pretreatment before doxorubicin administration did not exhibit depressed fractional shortening, ventricular wall thickness, or developed pressure when compared to controls (P > .05). These results suggest that a potential therapy for doxorubicin-induced cardiotoxicity involves targeting the endogenous cannabinoid system.

Catalytic organometallic anticancer complexes

Organometallic complexes offer chemistry that is not accessible to purely organic molecules and, hence, potentially new mechanisms of drug action. We show here that the presence of both an iodido ligand and a sigma-donor/pi-acceptor phenylazopyridine ligand confers remarkable inertness toward ligand substitution on the half-sandwich "piano-stool" ruthenium arene complexes [(eta(6)-arene)Ru(azpy)I](+) (where arene = p-cymene or biphenyl, and azpy = N,N-dimethylphenyl- or hydroxyphenyl-azopyridine) in aqueous solution. Surprisingly, despite this inertness, these complexes are highly cytotoxic to human ovarian A2780 and human lung A549 cancer cells. Fluorescence-trapping experiments in A549 cells suggest that the cytotoxicity arises from an increase in reactive oxygen species. Redox activity of these azopyridine Ru(II) complexes was confirmed by electrochemical measurements. The first one-electron reduction step (half-wave potential -0.2 to -0.4 V) is assignable to reduction of the azo group of the ligand. In contrast, the unbound azopyridine ligands are not readily reduced. Intriguingly the ruthenium complex acted as a catalyst in reactions with the tripeptide glutathione (gamma-L-Glu-L-Cys-Gly), a strong reducing agent present in cells at millimolar concentrations; millimolar amounts of glutathione were oxidized to glutathione disulfide in the presence of micromolar ruthenium concentrations. A redox cycle involving glutathione attack on the azo bond of coordinated azopyridine is proposed. Such ligand-based redox reactions provide new concepts for the design of catalytic drugs.

Identification of p32 as a novel substrate for ATM in heart

Chemotherapeutic agents to induce DNA damage have been limited to use due to severe side effects of cardiotoxicity. ATM (Ataxia-telangiectasia mutated) is an essential protein kinase in triggering DNA damage responses. However, it is unclear how the ATM-mediated DNA damage responses are involved in the cardiac cell damage. To elucidate these functions in heart, we searched for specific substrates of ATM from mouse heart homogenate. Combining an in vitro phosphorylation following anion-exchange chromatography with purification by reverse-phase high-performance liquid chromatography (HPLC), we successfully identified p32, an ASF/SF2-associated protein, as a novel substrate for ATM. An in vitro kinase assay using recombinant p32 revealed that ATM directly phosphorylated p32. Furthermore, we determined Ser 148 of p32 as an ATM phosphorylation site. Since p32 is known to regulate mRNA splicing and transcription, p32 phosphorylation by ATM might be a new transcriptional regulatory pathway for specific DNA damage responses in heart.

Glutathione elevation by γ-glutamyl cysteine ethyl ester as a potential therapeutic strategy for preventing oxidative stress in brain mediated by in vivo administration of adriamycin: Implication for chemobrain

Oxidative stress in heart and brain by the cancer chemotherapeutic drug adriamycin (ADR), used for treating solid tumors, is well established. Long-term treatment with ADR in breast cancer patients has led to symptoms of cardiomyopathy. Less well recognized, but increasingly well documented, is cognitive dysfunction. After chemotherapy, free radical-mediated oxidative stress has been reported in both heart and brain. We recently showed a significant increase in protein oxidation and lipid peroxidation in brain isolated from mice injected intraperitonially (i.p) with ADR. Systemic administration of ADR also induces tumor necrosis factor-alpha (TNF-alpha), which leads to production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in brain. Circulating TNF also causes mitochondrial dysfunction, leading to apoptotic pathways in brain. Inducible nitric oxide synthase also plays a role in ADR-induced TNF-mediated neurotoxicity. In addition, we previously showed a significant decrease in glutathione (GSH) levels in brain isolated from ADR injected mice, along with increased expression of multidrug-resistant protein-1 (MRP-1), glutathione-S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR). There was a significant decrease in activity of brain GST. The present study was designed to test the hypothesis that, by elevating brain levels of GSH, the brain would be protected against oxidative stress in ADR-injected mice. gamma-Glutamyl cysteine ethyl ester (GCEE), a precursor of glutathione, injected i.p. (150 mg/ kg body weight) 4 hr prior ADR injection (20 mg/kg body weight) led to significantly decreased protein oxidation and lipid peroxidation in subsequently isolated mice brain compared with brain isolated from ADR-injected mice without GCEE. The GSH levels were restored to the level of brain isolated from saline-injected mice. Furthermore, the enzyme activity of GST was increased in brain isolated from ADR-injected mice previously injected with GCEE compared with the brain isolated from ADR-injected mice previously injected with saline. These results are discussed with regard to potential pharmacological prevention of brain cognitive dysfunction in patients receiving ADR chemotherapy.

Acetylsalicylic acid exhibits anticlastogenic effects on cultured human lymphocytes exposed to doxorubicin

Acetylsalicylic acid (ASA) is a non-steroidal anti-inflammatory drug (NSAID) with many pharmacological properties, such as anti-inflammatory, antipyretic and analgesic. Many studies have suggested the possible efficiency of ASA and other NSAIDs in preventing cancer. ASA could also have antimutagenic and antioxidant properties. The aim of this study was to investigate the possible clastogenic and anticlastogenic effects of different concentrations of ASA on doxorubicin-induced chromosomal aberrations in human lymphocytes. Human blood samples were obtained from six healthy, non-smoking volunteers; and the chromosomal aberration assay was carried out using conventional techniques. The parameters analyzed were mitotic index, total number of chromosomal aberrations and percentage of aberrant metaphases. The concentrations of ASA (25, 50 or 100 microg/mL) tested in combination with DXR (0.2 microg/mL) were established on the basis of the results of the mitotic index. The treatment with ASA alone was neither cytotoxic nor clastogenic (p>0.01). In lymphocyte cultures treated with different combinations of ASA and DXR, a significant decrease in the total number of chromosome aberrations was observed compared with DXR alone (p<0.01). This protective effect of ASA on DXR-induced chromosomal damage was obtained for all combinations, and it was most evident when ASA was at 25.0 microg/mL. In our experiments, ASA may have acted as an antioxidant and inhibited the chromosomal damage induced by the free radicals generated by DXR. The identification of compounds that could counteract the free radicals produced by doxorubicin could be of possible benefits against the potential harmful effects of anthracyclines. The results of this study show that there is a relevant need for more investigations in order to elucidate the mechanisms underlying the anticlastogenic effect of ASA.

Oxidative stress and toxicity induced by the nucleoside reverse transcriptase inhibitor (NRTI)--2',3'-dideoxycytidine (ddC): relevance to HIV-dementia

Human immunodeficiency virus dementia (HIVD) is the most common form of dementia occurring among young adults. In HIVD, neuronal cell loss occurs in the absence of neuronal infection. With the advent of highly active anti-retroviral therapy (HAART), the incidence of HIVD has drastically reduced, though prevalence of milder forms of HIVD continues to rise. Though these agents have been used successfully in suppressing viral production, they have also been associated with a number of side effects. Here we examine the possible role of NRTIs, in particular 2',3'-dideoxycytidine (ddC), in the neuropathology of HIVD. Synaptosomes and isolated mitochondria treated and incubated for 6 h with CSF-achievable concentrations of ddC, i.e., 6-11 ng/ml, were found to show a significant increase in oxidative stress with 40 nM ddC as measured by protein carbonyls and 3-nitrotyrosine (3NT), effects that were not observed in the more tolerable NRTI, 3TC. Protection against protein oxidation induced by ddC was observed when brain mitochondria were isolated from gerbils 1 h after injection i.p. with the brain accessible antioxidant and glutathione mimetic, tricyclodecan-9-yl-xanthogenate (D609). In addition, there is a significant reduction in the levels of anti-apoptotic protein Bcl-2 and a significant increase in cytochrome c release and also a significant increase in the expression of pro-apoptotic protein caspase-3 after mitochondria were treated with 40 nM ddC. The results reported here show that ddC at 40 nM can induce oxidative stress, cause the release of cytochrome c, and in addition, reduce the levels of anti-apoptotic proteins, increase the levels of pro-apoptotic proteins, thereby increasing the possibility for induction of apoptosis. These findings are consistent with the notion of a possible role of the NRTIs, and in particular, ddC, in the mechanisms involved in HIVD.

C-(2-chloroquinoline-3-yl)-N-phenyl nitrone: new synthetic antioxidant inhibits proliferation and induces apoptosis of breast carcinoma MCF-7 cells

In this work, a new quinoline nitrone derivative, C-(2-chloroquinoline-3-yl)-N-phenyl nitrone (CQPN) was successfully prepared and proved by spectral analysis. The antioxidant activity of CQPN against various radicals was investigated and its anti-cancer properties against different human tumor cell lines including the solid tumor cell lines hepatocarcinoma (Hep-G2) and breast carcinoma (MCF-7); the hematopoietic tumor cell line lymphoblastic leukemia (1301) was also explored. CQPN activities were compared to that of the known nitrone C-phenyl-N-tert-butyl nitrone (PBN). Our results showed that although PBN was the stronger antioxidant than CQPN, the latter was an effective scavenger of different non-physiological (1,1-diphenyl-2-picrylhyrazyl) and physiological (peroxyl and hydroxyl) radicals. Both of CQPN and PBN possess a significant inhibitory property against LPS-stimulated NO production in macrophage. CQPN and PBN treatment resulted in a growth inhibition in Hep-G2 cells (IC50 31.42 microM and 18.6 microM, respectively). Unlike PBN, CQPN strongly inhibited the growth of MCF-7 cells (IC50 14.01 microM) in a dose-dependent manner. On contrary, CQPN and PBN exhibited a proliferative stimulatory activity of the immune cells including macrophages and lymphocytes. Exploring the cytotoxic effect of CQPN against MCF-7 cells indicated that CQPN led to a major time-dependent disturbance in the cell-cycle phases including progressive arrest in both S- and G2/M-phases. This disturbance was found to be associated with a kinetic induction of apoptosis. The novel nitrone derivative CQPN is a strong antioxidant, though less than PBN, and it may be an effective anti-proliferative compound against breast carcinoma.

Free radical mediated oxidative stress and toxic side effects in brain induced by the anti cancer drug adriamycin: insight into chemobrain

Adriamycin (ADR) is a chemotherapeutic agent useful in treating various cancers. ADR is a quinone-containing anthracycline chemotherapeutic and is known to produce reactive oxygen species (ROS) in heart. Application of this drug can have serious side effects in various tissues, including brain, apart from the known cardiotoxic side effects, which limit the successful use of this drug in treatment of cancer. Neurons treated with ADR demonstrate significant protein oxidation and lipid peroxidation. Patients under treatment with this drug often complain of forgetfulness, lack of concentration, dizziness (collectively called somnolence or sometimes called chemobrain). In this study, we tested the hypothesis that ADR induces oxidative stress in brain. Accordingly, we examined the in vivo levels of brain protein oxidation and lipid peroxidation induced by i.p. injection of ADR. We also measured levels of the multidrug resistance-associated protein (MRP1) in brain isolated from ADR- or saline-injected mice. MRP1 mediates ATP-dependent export of cytotoxic organic anions, glutathione S-conjugates and sulphates. The current results demonstrated a significant increase in levels of protein oxidation and lipid peroxidation and increased expression of MRP1 in brain isolated from mice, 72 h post i.p injection of ADR. These results are discussed with reference to potential use of this redox cycling chemotheraputic agent in the treatement of cancer and its chemobrain side effect in brain.

Transcriptional analysis of doxorubicin-induced cardiotoxicity

Doxorubicin is an effective chemotherapeutic agent against a broad range of tumors. However, a threshold dose of doxorubicin causes an unacceptably high incidence of heart failure and limits its clinical utility. We have established two models of doxorubicin cardiotoxicity in mice: 1) in an acute model, mice are treated with 15 mg/kg of doxorubicin once; and 2) in a chronic model, they receive 3 mg/kg weekly for 12 wk. Using echocardiography, we have monitored left ventricular function during treatment in the chronic model and seen the expected development of dilated cardiomyopathy. Treated mice showed histological abnormalities similar to those seen in patients with doxorubicin cardiomyopathy. To investigate transcriptional regulation in these models, we used a muscle-specific cDNA microarray. We have identified genes that respond to doxorubicin exposure in both models and confirmed these results using real-time PCR. In the acute model, a set of genes is regulated early and rapidly returns to baseline levels, consistent with the half-life of doxorubicin. In the chronic model, which mimics the clinical situation much more closely, we identified dysregulated genes that implicate specific mechanisms of cardiac toxicity. These include STARS, a hypertrophy-responsive gene; SNF1-kinase, a potential modulator of ATP levels; and AXUD1, a downstream target of the proapoptotic regulator AXIN1.

C-Phycocyanin Ameliorates Doxorubicin-Induced Oxidative Stress and Apoptosis in Adult Rat Cardiomyocytes

Doxorubicin (DOX), a potent antineoplastic agent, poses limitations for its therapeutic use due to the associated risk of developing cardiomyopathy and congestive heart failure. The cardiotoxicity of doxorubicin is associated with oxidative stress and apoptosis. We have recently shown that Spirulina, a blue-green alga with potent antioxidant properties, offered significant protection against doxorubicin-induced cardiotoxicity in mice. The aim of the present study was to establish the possible protective role of C-phycocyanin, one of the active ingredients of Spirulina, against doxorubicin-induced oxidative stress and apoptosis. The study was carried out using cardiomyocytes isolated from adult rat hearts. Doxorubicin significantly enhanced the formation of reactive oxygen species (ROS) in cells as measured by the 2',7'-dichlorodihydrofluorescein diacetate and dihydroethidium fluorescence. The doxorubicin-induced reactive oxygen species formation was significantly attenuated in cells pretreated with C-phycocyanin. It was further observed that the doxorubicin-induced DNA fragmentation and apoptosis, as assayed by TUNEL assay and flow cytometry coupled with BrdU-FITC/propidium iodide staining, were markedly attenuated by C-phycocyanin. C-phycocyanin also significantly attenuated the doxorubicin-induced increase in the expression of Bax protein, release of cytochrome c, and increase in the activity of caspase-3 in cells. In summary, C-phycocyanin ameliorated doxorubicin-induced oxidative stress and apoptosis in cardiomyocytes. This study further supports the crucial role of the antioxidant nature of C-phycocyanin in its cardioprotection against doxorubicin-induced oxidative stress and apoptosis.

Doxorubicin increases intracellular hydrogen peroxide in PC3 prostate cancer cells

We studied the effect of doxorubicin on the production of hydrogen peroxide by PC3 human prostate cancer cells, using a sensitive assay based on aminotriazole-mediated inhibition of catalase. PC3 cells exposed to increasing concentrations of doxorubicin had an increase in intracellular hydrogen peroxide that was concentration-dependent up to 1 microM doxorubicin. The apparent hydrogen peroxide concentration in the PC3 cells was 13 +/- 4 pM under basal steady-state conditions and increased to 51 +/- 13 pM after exposure to 1 microM doxorubicin for 30 min. The level of hydrogen peroxide in the medium as measured by Amplex Red did not increase as a result of doxorubicin treatment. PC3 cells overexpressing catalase were no more resistant to doxorubicin cytotoxicity as compared to non-transduced wild-type cells; therefore, the exact role of hydrogen peroxide in anthracycline cytotoxicity remains unproven. This study demonstrates that a specific oxidative event associated with the exposure of PC3 human prostate cancer cells to anthracyclines results in an increase in intracellular hydrogen peroxide.

Inactivation of Anthracyclines by Cellular Peroxidase

The anticancer anthracyclines, doxorubicin and daunorubicin, are highly cytotoxic to both cancer and normal cells. In this work, we have investigated the capacity of cellular myeloperoxidase to inactivate these agents. We show that incubation of human leukemia HL-60 cells with the anthracyclines in the presence of hydrogen peroxide and nitrite causes irreversible oxidation of the drugs, suggesting an extensive modification of their chromophores. Methimazole, 4-aminobenzoic acid hydrazide, or azide inhibits the reaction, suggesting that it is mediated by the cellular myeloperoxidase, an enzyme naturally present in large amounts in HL-60 cells. In contrast to the intact drugs, the oxidatively transformed anthracyclines were substantially less cytotoxic for HL-60 (assayed by apoptosis) and PC3 prostate cancer cells and H9c2 rat cardiac myoblasts in vitro (assayed by clonogenic survival), indicating that the oxidative metabolism of these agents leads to their inactivation. Using tandem mass spectrometry, we identified two specific metabolic products of the anthracycline degradation, 3-methoxyphthalic acid and 3-methoxysalicylic acid. These two metabolic products were obtained as authentic compounds and were nontoxic to HL-60 leukemic cells and cardiac myocytes. These findings may have important implications for the cellular pharmacology of anthracyclines and for clinical oncology.

Screening of antioxidants from medicinal plants for cardioprotective effect against doxorubicin toxicity

Doxorubicin is an important and effective anticancer drug widely used for the treatment of various types of cancer but its clinical use is limited by dose-dependent cardiotoxicity. Elevated tissue levels of cellular superoxide anion/oxidative stress are a mechanism by which doxorubicin-induced cardiotoxicity. Selected medicinal plant extracts were tested for their antioxidant capacity and cardioprotective effect against doxorubicin-induced cardiotoxicity. The cardiac myoblasts H9c2 were incubated with the antioxidants ascorbic acid, trolox, N-acetylcysteine or selected medicinal plant extracts including; 1) ethanolic extracts from Curcuma longa L-EtOH Phyllanthus emblica L-EtOH, and Piper rostratum Roxb-EtOH; and 2) water extracts from Curcuma longa L-H2O and Morus alba L-H2O. The cardioprotective effects of these extracts were evaluated by crystal violet cytotoxicity assay. IC50s of doxorubicin were compared in the presence or absence of ascorbic acids, trolox, N-acetylcysteine or plant extracts. Morus alba L-H2O showed the highest antioxidant properties evaluated by ferric reducing/antioxidant power assay. Ascorbic acid and N-acetylcysteine had modest effects on the protection of doxorubicin-induced cytotoxicity while trolox showed insignificant protective effect. All plant extracts protected cardiac toxicity at different degrees except that Curcuma longa L-EtOH had no protective effect. Phyllanthus emblica-EtOH (100 microg/ml) showed the highest cardioprotective effect (approximately 12-fold doxorubicin IC50 increase). The data demonstrate that antioxidants from natural sources may be useful in the protection of cardiotoxicity in patients who receive doxorubicin.

Induction of caspase-independent apoptosis in H9c2 cardiomyocytes by adriamycin treatment

The cardiotoxicity of adriamycin limits its clinical use as a powerful drug for solid tumors and malignant hematological disease. Although the precise mechanism by which it causes cardiac damage is not yet known, it has been suggested that apoptosis is the principal process in adriamycin-induced cardiomyopathy, which involves DNA fragmentation, cytochrome C release, and caspase activation. However, there has been no direct evidence for the critical involvement of caspase-3 in adriamycin-induced apoptosis. To determine the requirements for the activation of caspase-3 in adriamycin-treated cardiac cells, the effect of a caspase inhibitor on the survival of and apoptotic changes in H9c2 cells was examined. Exposure of H9c2 cells to adriamycin resulted in a time- and dose-dependent cell death, and the cleavage of pro-caspase-3 and of the nuclear protein poly (ADP'ribose) polymerase (PARP). However, neither the reduction of cell viability nor the characteristic morphological changes induced by adriamycin were prevented by pretreatment with the general caspase inhibitor z-VAD.FMK. In contrast, caspase inhibition effectively blocked the apoptosis induced by H202 in H9c2 cells, as determined by an MTT assay or microscopy. We also observed that p53 expression was increased by adriamycin, and this increase was not affected by the inhibition of caspase activity, suggesting a role for p53 in adriamycin-induced caspase-independent apoptosis in cardiac toxicity.

Carvedilol-mediated antioxidant protection against doxorubicin-induced cardiac mitochondrial toxicity

The cardiotoxicity associated with doxorubicin (DOX) therapy limits the total cumulative dose and therapeutic success of active anticancer chemotherapy. Cardiac mitochondria are implicated as primary targets for DOX toxicity, which is believed to be mediated by the generation of highly reactive free radical species of oxygen from complex I of the mitochondrial electron transport chain. The objective of this study was to determine if the protection demonstrated by carvedilol (CV), a beta-adrenergic receptor antagonist with strong antioxidant properties, against DOX-induced mitochondrial-mediated cardiomyopathy [Toxicol. Appl. Pharmacol. 185 (2002) 218] is attributable to its antioxidant properties or its beta-adrenergic receptor antagonism. Our results confirm that DOX induces oxidative stress, mitochondrial dysfunction, and histopathological lesions in the cardiac tissue, all of which are inhibited by carvedilol. In contrast, atenolol (AT), a beta-adrenergic receptor antagonist lacking antioxidant properties, preserved phosphate energy charge but failed to protect against any of the indexes of DOX-induced oxidative mitochondrial toxicity. We therefore conclude that the cardioprotective effects of carvedilol against DOX-induced mitochondrial cardiotoxicity are due to its inherent antioxidant activity and not to its beta-adrenergic receptor antagonism.

Glutathione S-transferase overexpression protects against anthracycline-induced H9C2 cell death

Anthracyclines (AC) are antitumor antibiotics with significant activity against solid and hematologic malignancies. One problem preventing more widespread use has been the development of cardiac toxicity. Experimental evidence supports oxidant stress as an important trigger and/or mediator of AC-induced cardiotoxicity (ACT). Therefore, reducing oxidant stress should be protective against ACT. To determine whether antioxidant protein overexpression can reduce ACT, we developed a cell culture model system using the H9C2 cardiac cell line exhibiting controlled overexpression of the α4-isoform of glutathione- S-transferase (GST). Treatment with the AC doxorubicin (DOX) produced both oncosis, manifested by an increase in the number of cells staining positive for Trypan blue, and apoptosis, indicated by the presence of positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. In both cases, the loss of cell viability was preceded by an AC-induced increase in fluorescence with carboxy-2′,7′-dichlorofluorescein diacetate, demonstrating the presence of high levels of reactive oxygen species (ROS). The DOX-induced increase in ROS was reduced to control levels by maximal GST overexpression. Coincident with this elimination of oxidative stress, there was a reduction in both Trypan blue and TUNEL-positive cells, indicating that GST overexpression reduced both ROS and cell death in this model system. We conclude that GST overexpression may be an important part of a protective strategy against ACT and that this model system will aid in defining steps in the pathway(s) leading to AC-induced cell death that can be therapeutically manipulated.