Doxorubicin-induced cardiomyocyte apoptosis: Role of mitofusin 2

BackgroundDoxorubicin (DOX) is an anti-tumor agent that is widely used in clinical setting for cancer treatment. The application of the DOX, however, is limited by its cardiac toxicity which can induce heart failure through an undefined mechanism. Mitofusin 2 (Mfn2) is a mitochondrial GTPase fusion protein that is located on the outer membrane of mitochondria (OMM). The Mfn2 plays an important role in mitochondrial fusion and fission. The aim of this study is to identify the role of the Mfn2 in DOX-induced cardiomyocyte apoptosis.MethodsCultured neonatal rat cardiomyocytes were used in this study. Mfn2 expression in cardiomyocytes was determined after the cardiomyocytes were challenged with DOX. Cardiomyocyte mitochondrial fission, mitochondrial reactive oxygen species (ROS) production was assessed with mitochondrial fragmentation and MitoSOX fluorescence probe, respectively. Cardiomyocyte apoptosis was determined with caspase3 activity and TUNEL staining.ResultsChallenging of the cardiomyocytes with DOX resulted in increasing in cardiomyocyte oxidative stress and apoptosis. In addition, levels of Mfn2 in cardiomyocytes were decreased after the cells were challenged with DOX which was associated with increased mitochondrial fission (fragmentation) and mitochondrial ROS production. An increase in cardiomyocyte levels of Mfn2 attenuated the DOX-induced increase in mitochondrial fission and prevented cardiomyocyte mitochondrial ROS production. An increase in cardiomyocyte levels of Mfn2 or pretreatment of cardiomyocytes with an anti-oxidant, Mito-tempo, also prevented the DOX-induced cardiomyocyte apoptosis.ConclusionOur results indicate that DOX results in a decreased cardiomyocyte Mfn2 expression which promotes mitochondrial fission and ROS production further leads to cardiomyocyte apoptosis.     

Attenuation of doxorubicin-induced contractile and mitochondrial dysfunction in mouse heart by cellular glutathione peroxidase

The cardiac toxicity of doxorubicin (DOX), a potent anticancer anthracycline antibiotic, is believed to be mediated through the generation of reactive oxygen species (ROS) in cardiomyocytes. This study aims to determine the function of cellular glutathione peroxidase (Gpx1), which is located in both mitochondria and cytosol, in defense against DOX-induced cardiomyopathy using a line of transgenic mice with cardiac overexpression of Gpx1. The Gpx1-overexpressing hearts were markedly more resistant than nontransgenic hearts to DOX-induced acute functional derangements, including impaired contractility and diastolic properties, decreased coronary flow rate, and reduced heart rate. In addition, DOX treatment impairs mitochondrial function of nontransgenic hearts as evident in a decreased rate of NAD-linked State 3 respiration, presumably a result of inactivation of complex I activity. This is associated with increases in the rates of NAD- and FAD-linked State 4 respiration and declines in P/O ratio, suggesting that the electron transfer and oxidative phosphorylation are uncoupled in these mitochondrial samples. These functional deficits of mitochondria could be largely prevented by Gpx1 overexpression. Taken together, these studies provide new evidence to further support the role of ROS, particularly H(2)O(2) and/or fatty acid hydroperoxides, in causing contractile and mitochondrial dysfunction in mouse hearts acutely exposed to DOX.     

Manipulation of Cardiac Phosphatidylinositol 3-Kinase (PI3K)/Akt Signaling by Apoptosis Regulator through Modulating IAP Expression (ARIA) Regulates Cardiomyocyte Death during Doxorubicin-induced Cardiomyopathy

PI3K/Akt signaling plays an important role in the regulation of cardiomyocyte death machinery, which can cause stress-induced cardiac dysfunction. Here, we report that apoptosis regulator through modulating IAP expression (ARIA), a recently identified transmembrane protein, regulates the cardiac PI3K/Akt signaling and thus modifies the progression of doxorubicin (DOX)-induced cardiomyopathy. ARIA is highly expressed in the mouse heart relative to other tissues, and it is also expressed in isolated rat cardiomyocytes. The stable expression of ARIA in H9c2 cardiac muscle cells increased the levels of membrane-associated PTEN and subsequently reduced the PI3K/Akt signaling and the downstream phosphorylation of Bad, a proapoptotic BH3-only protein. When challenged with DOX, ARIA-expressing H9c2 cells exhibited enhanced apoptosis, which was reversed by the siRNA-mediated silencing of Bad. ARIA-deficient mice exhibited normal heart morphology and function. However, DOX-induced cardiac dysfunction was significantly ameliorated in conjunction with reduced cardiomyocyte death and cardiac fibrosis in ARIA-deficient mice. Phosphorylation of Akt and Bad was substantially enhanced in the heart of ARIA-deficient mice even after treatment with DOX. Moreover, repressing the PI3K by cardiomyocyte-specific expression of dominant-negative PI3K (p110α) abolished the cardioprotective effects of ARIA deletion. Notably, targeted activation of ARIA in cardiomyocytes but not in endothelial cells reduced the cardiac PI3K/Akt signaling and exacerbated the DOX-induced cardiac dysfunction. These studies, therefore, revealed a previously undescribed mode of manipulating cardiac PI3K/Akt signaling by ARIA, thus identifying ARIA as an attractive new target for the prevention of stress-induced myocardial dysfunction.     

硫化氢通过调控SIRT1抑制阿霉素诱导的H9c2细胞损伤

目的探讨硫化氢（H₂S）对阿霉素（DOX）诱导的H9c2细胞损伤的影响及其作用机制。 方法H₂S对DOX心肌毒性保护作用的实验分组为：对照组（Control组）,5?μmol/?L DOX处理组（A组）,5?μmol/L DOX和400?μmol/L NaHS共同处理组（B组）,400?μmol/L NaHS单独处理组（C组）,5?μmol/L DOX、400?μmol/L NaHS和15?μmol/L Sirtinol共同处理组（D组）,15?μmol/L Sirtinol单独处理组（E组）。SIRT1是否参与H₂S抗DOX心肌毒性作用机制的实验分组为：对照组（Control组）,5?μmol/L DOX处理组（F组）,5?μmol/L DOX和400?μmol/L NaHS共同处理组（G组）,5?μmol/L DOX、400?μmol/L NaHS和15?μmol/L Sirtinol共同处理组（H组）,15?μmol/L Sirtinol单独处理组（I组）。使用MTT法检测细胞活力;Elisa法检测细胞MDA以及SOD水平;DCFH-?DA荧光探针法检测ROS水平;采用Western Blot法检测SIRT1蛋白表达。使用单因素方差分析法进行统计学分析。 结果NaHS预处理可抑制DOX导致的H9c2细胞活力下降：Control组,A组、B组、C组细胞活力分别为100﹪、（54.58±1.58）﹪、（85.05±4.31）﹪、（100.22±4.46）﹪ （F = 134.9,P < 0.001）。NaHS预处理可减弱DOX引起的H9c2细胞ROS、MDA水平的增加以及SOD水平的降低：Control组的ROS、MDA和SOD水平分别是100﹪、（34.18±1.56） μmol/g、（53.69±1.44） U/?mg;A组的ROS、MDA和SOD水平分别是（174.90±12.65）﹪、（72.65±2.66） μmol/g、（31.80±2.05） U/?mg;B组的ROS、MDA和SOD水平分别是（126.08±6.25）﹪、（44.59±1.92） μmol/g、（48.06±1.56） U/mg;C组的ROS、MDA和SOD水平分别是（91.86±1.66）﹪、（32.93±1.56）?μmol/?g、（55.93±1.58）?U/?mg （F?= 83.26,P < 0.001;F = 271.4,P < 0.001;F = 127.0,P < 0.001）。F组（6、12、24?h）H9c2细胞SIRT1蛋白表达水平分别是（0.45±0.03）、（0.27±0.02）、（0.25±0.03）,较Control组（1.00±0.00）降低（F = 611.1,P < 0.001）。本研究还发现,NaHS预处理H9c2细胞能阻止DOX引起的SIRT1蛋白表达下调：Control组、F组、G组、H组的SIRT1蛋白表达水平分别是（1.00±0.00）、（0.31±0.03）、（0.60±0.04）、（1.09±0.09）（F = 123.4,P?2S对DOX诱导的H9c2细胞活力降低的抑制作用：Control组,F组、G组、H组、I组细胞活力分别为100﹪、（54.58±1.58）﹪、（85.37±3.62）﹪、（71.11±2.11）﹪、（97.53±1.45）﹪ （F = 238.2,P < 0.001）。Sirtinol预处理可明显逆转H₂S对DOX导致的H9c2细胞ROS和MDA含量增加及SOD水平降低的抑制作用：Control组的ROS、MDA和SOD水平分别是100﹪、（35.84±2.22）μmol/?g、（53.03±3.16） U/mg;F组的ROS、MDA和SOD水平分别是（184.6±11.33）﹪、（74.78±5.30）μmol/g、（29.26±0.85）U/mg;G组的ROS、MDA和SOD水平分别是（126.5±7.57）﹪、（41.95±3.43）μmol/g、（52.61±2.26）U/mg;H组的ROS、MDA和SOD水平分别是（174.7±5.50）﹪、（67.69±1.52） μmol/g、（35.33±1.95） U/mg,I组的ROS、MDA和SOD水平分别是（98.03±2.86）﹪、（37.66±2.49）μmol/g、51.14 U/mg（F = 112.0,P < 0.001;F = 93.73,P < 0.001;F = 84.92,P < 0.001）。 结论H₂S通过调控SIRT1抑制DOX诱导的H9c2细胞损伤。     

Cardiolipin nanodisks confer protection against doxorubicin-induced mitochondrial dysfunction

Doxorubicin (DOX) is an aqueous soluble anthracycline therapeutic widely used in cancer treatment. Although DOX anti-cancer activity is dose-dependent, increased dosage enhances the risk of cardiotoxicity. Despite intensive investigation, the molecular basis of this undesirable side effect has yet to be established. In addition to serving as a DNA intercalation agent, DOX is known to bind to the signature mitochondrial phospholipid, cardiolipin (CL). Consistent with this, DOX associates with aqueous soluble nanoparticles, termed nanodisks (ND), comprised solely of CL and an apolipoprotein scaffold. Fluorescence microscopy analysis revealed that DOX uptake, and targeting to the nucleus of cultured hepatocarcinoma (HepG2) or breast cancer (MCF7) cells, was unaffected by its association with CL-ND. Subsequent studies revealed that free DOX and DOX-CL-ND were equivalent in terms of growth inhibition activity in both cell lines. By contrast, in studies with H9C2 cardiomyocytes, DOX-CL-ND induced a lesser concentration-dependent decline in cell viability than free DOX. Whereas incubation of H9C2 cardiomyocytes with free DOX caused a steep decline in maximal oxygen consumption rate, DOX-CL-ND treated cells were largely unaffected. The data indicate that association of DOX with CL-ND does not diminish its cancer cell growth inhibition activity yet confers protection to cardiomyocytes from DOX-induced effects on aerobic respiration. This study illustrates that interaction with CL plays a role in DOX-induced mitochondrial dysfunction and suggests CL-ND provide a tool for investigating the mechanistic basis of DOX-induced cardiotoxicity.     

Resveratrol protects cardiomyocytes from oxidative stress through SIRT1 and mitochondrial biogenesis signaling pathways

Reactive oxygen species (ROS) is generated by oxidative stress and plays an important role in various cardiac pathologies. The SIRT1 signaling pathway and mitochondrial biogenesis play essential roles in mediating the production of ROS. SIRT1 activated by resveratrol protects cardiomyocytes from oxidative stress, but the exact mechanisms by which SIRT1 prevents oxidative stress, and its relationship with mitochondrial biogenesis, remain unclear. In this study, it was observed that after stimulation with 50 μM H₂O₂ for 6 h, H9C2 cells produced excessive ROS and downregulated SIRT1. The mitochondrial protein NDUFA13 was also downregulated by ROS mediated by SIRT1. Resveratrol induced the expression of SIRT1 and mitochondrial genes NDUFA1, NDUFA2, NDUFA13 and Mn-SOD. However, the production of these genes was reversed by SIRT1 inhibitor nicotinamide. These results suggest that resveratrol inhibits ROS generation in cardiomyocytes via SIRT1 and mitochondrial biogenesis signaling pathways.     

N-3 polyunsaturated fatty acids decrease levels of doxorubicin-induced reactive oxygen species in cardiomyocytes -- involvement of uncoupling protein UCP2

Background

Use of the chemotherapeutic drug doxorubicin (DOX) is associated with serious cardiotoxicity, as it increases levels of reactive oxygen species (ROS). N-3 polyunsaturated fatty acid dietary supplements can be of benefit to patients undergoing cancer therapy. The aims of this study were to determine whether DOX-induced cardiotoxicity is related to mitochondrial uncoupling proteins and whether eicosapentaenoic acid (EPA, C20:5 n-3) or docosahexaenoic acid (DHA, C22:6 n-3) affects DOX-induced cardiomyocyte toxicity.

Results

Treatment of H9C2 cells with DOX resulted in decreased cell viability and UCP2 expression. Treatment with 100 μM EPA or 50 μM DHA for 24 h resulted in a maximal mitochondria concentration of these fatty acids and increased UCP2 expression. Pretreatment with 100 μM EPA or 50 μM DHA prevented the DOX-induced decrease in UCP2 mRNA and protein levels, but these effects were not seen with EPA or DHA and DOX cotreatment. In addition, the DOX-induced increase in ROS production and subsequent mitochondrial membrane potential change (∆ψ) were significantly attenuated by pretreatment with EPA or DHA.

Conclusion

EPA or DHA pre-treatment inhibits the DOX-induced decrease in UCP2 expression, increase in ROS production, and subsequent mitochondrial membrane potential change that contribute to the cardiotoxicity of DOX.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-014-0101-3) contains supplementary material, which is available to authorized users.     

Hydrogen sulfide protects H9c2 cells against doxorubicin-induced cardiotoxicity through inhibition of endoplasmic reticulum stress

The roles of hydrogen sulfide (H(2)S) and endoplasmic reticulum (ER) stress in doxorubicin (DOX)-induced cardiotoxicity are still unclear. This study aimed to dissect the hypothesis that H(2)S could protect H9c2 cells against DOX-induced cardiotoxicity by inhibiting ER stress. Our results showed that exposure of H9c2 cells to DOX significantly inhibited the expression and activity of cystathionine-γ-lyase (CSE), a synthetase of H(2)S, accompanied by the decreased cell viability and the increased reactive oxygen species (ROS) accumulation. In addition, exposure of cells to H(2)O(2) (an exogenous ROS) mimicked the inhibitory effect of DOX on the expression and activity of CSE. Pretreatment with N-acetyl-L: -cysteine (NAC) (a ROS scavenger) attenuated intracellular ROS accumulation, cytotoxicity, and the inhibition of expression and activity of CSE induced by DOX. Notably, the ER stress-related proteins, including glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were obviously upregulated in DOX-treated H9c2 cells. Pretreatment with sodium hydrosulfide (NaHS, a H(2)S donor) before DOX exposure markedly suppressed DOX-induced overexpressions of GRP78 and CHOP, cytotoxicity and oxidative stress. In conclusion, we have demonstrated that ROS-mediated inhibition of CSE is involved in DOX-induced cytotoxicity in H9c2 cells, and that exogenous H(2)S can confer protection against DOX-induced cardiotoxicity partly through inhibition of ER stress.     

Differences in doxorubicin-induced apoptotic signaling in adult and immature cardiomyocytes

A proposed mechanism for the cardiotoxicity of doxorubicin (DOX) involves apoptosis in cardiomyocytes. In the study described here, we investigated the molecular basis for the differences in DOX-induced toxicity in adult rat cardiomyocytes (ARCM), neonatal rat cardiomyocytes (NRCM), and rat embryonic H9c2 cardiomyoblasts. Activation of caspase-9 and -3 was considerably lower in DOX-treated ARCM as compared with NRCM and H9c2 cardiomyoblasts. Addition of cytochrome c caused the activation of caspase-9 and -3 in permeabilized NRCM and H9c2 cardiomyoblasts but not in permeabilized ARCM. Expression of proapoptotic proteins, apoptotic protease activating factor-1 (Apaf1), and procaspase-9 was significantly lower, and abundance of antiapoptotic X-linked inhibitor of apoptosis protein (XIAP) was higher in ARCM, as compared with immature cardiac cells. Despite the abundance of XIAP in ARCM, its role in the inhibition of apoptosome function was dismissed, as second mitochondria-derived activator of caspases (Smac)-N7 peptide, had no effect on caspase activation in response to cytochrome c in these cells. Adenoviral expression of Apaf1 exacerbated the activation of caspase-9 and -3 in DOX-treated NRCM, but did not increase their activities in DOX-treated ARCM. This finding points to a major difference in the apoptotic signaling between immature and adult cardiomyocytes. The mitochondrial apoptotic pathway is limited in ARCM treated with DOX.     

Berberine Inhibits Doxorubicin-Triggered Cardiomyocyte Apoptosis via Attenuating Mitochondrial Dysfunction and Increasing Bcl-2 Expression

Cardiomyocyte apoptosis is an important event in doxorubicin (DOX)-induced cardiac injury. The aim of the present study was to investigate the protection of berberine (Ber) against DOX- triggered cardiomyocyte apoptosis in neonatal rat cardiomyocytes and rats. In neonatal rat cardiomyocytes, Ber attenuated DOX-induced cellular injury and apoptosis in a dose-dependent manner. However, Ber has no significant effect on viability of MCF-7 breast cancer cells treated with DOX. Ber reduced caspase-3 and caspase-9, but not caspase-8 activity in DOX-treated cardiomyocytes. Furthermore, Ber decreased adenosine monophosphate-activated protein kinase α (AMPKα) and p53 phosphorylation at 2 h, cytosolic cytochrome c and mitochondrial Bax levels and increased Bcl-2 level at 6 h in DOX-stimulated cardiomyocytes. Pretreatment with compound C, an AMPK inhibitor, also suppressed p53 phosphorylation and apoptosis in DOX-treated cardiomyocytes. DOX stimulation for 30 min led to a loss of mitochondrial membrane potential and a rise in the AMP/ATP ratio. Ber markedly reduced DOX-induced mitochondrial membrane potential loss and an increase in the AMP/ATP ratio at 1 h and 2 h post DOX exposure. In in vivo experiments, Ber significantly improved survival, increased stroke volume and attenuated myocardial injury in DOX-challenged rats. TUNEL and Western blot assays showed that Ber not only decreased myocardial apoptosis, caspase-3 activation, AMPKα and p53 phosphorylation, but also increased Bcl-2 expression in myocardium of rats exposed to DOX for 84 h. These findings indicate that Ber attenuates DOX-induced cardiomyocyte apoptosis via protecting mitochondria, inhibiting an increase in the AMP/ATP ratio and AMPKα phosphorylation as well as elevating Bcl-2 expression, which offer a novel mechanism responsible for protection of Ber against DOX-induced cardiomyopathy.     

Differences in doxorubicin-induced apoptotic signaling in adult and immature cardiomyocytes

A proposed mechanism for the cardiotoxicity of doxorubicin (DOX) involves apoptosis in cardiomyocytes. In the study described here, we investigated the molecular basis for the differences in DOX-induced toxicity in adult rat cardiomyocytes (ARCM), neonatal rat cardiomyocytes (NRCM), and rat embryonic H9c2 cardiomyoblasts. Activation of caspase-9 and -3 was considerably lower in DOX-treated ARCM as compared with NRCM and H9c2 cardiomyoblasts. Addition of cytochrome c caused the activation of caspase-9 and -3 in permeabilized NRCM and H9c2 cardiomyoblasts but not in permeabilized ARCM. Expression of proapoptotic proteins, apoptotic protease activating factor-1 (Apaf1), and procaspase-9 was significantly lower, and abundance of antiapoptotic X-linked inhibitor of apoptosis protein (XIAP) was higher in ARCM, as compared with immature cardiac cells. Despite the abundance of XIAP in ARCM, its role in the inhibition of apoptosome function was dismissed, as second mitochondria-derived activator of caspases (Smac)-N7 peptide, had no effect on caspase activation in response to cytochrome c in these cells. Adenoviral expression of Apaf1 exacerbated the activation of caspase-9 and -3 in DOX-treated NRCM, but did not increase their activities in DOX-treated ARCM. This finding points to a major difference in the apoptotic signaling between immature and adult cardiomyocytes. The mitochondrial apoptotic pathway is limited in ARCM treated with DOX.     

Doxorubicin-induced thiol-dependent alteration of cardiac mitochondrial permeability transition and respiration

Doxorubicin (DOX) is a highly effective treatment for several forms of cancer. However, clinical experience shows that DOX induces a cumulative and dose-dependent cardiomyopathy that has been ascribed to redox-cycling of the drug on the mitochondrial respiratory chain generating free radicals and oxidative stress in the process. Mitochondrial dysfunction including induction of the mitochondrial permeability transition (MPT) and inhibition of mitochondrial respiration have been implicated as major determinants in the pathogenesis of DOX cardiotoxicity. The present work was aimed at investigating whether the inhibition of mitochondrial respiration occurs secondarily to MPT induction in heart mitochondria isolated from DOX-treated rats and whether one or both consequences of DOX treatment are related with oxidation of protein thiol residues. DOX-induced oxidative stress was associated with the accumulation of products of lipid peroxidation and the depletion of alpha-tocopherol in cardiac mitochondrial membranes. No changes in mitochondrial coenzyme Q9 and Q10 concentrations were detected in hearts of DOX-treated rats. Cardiac mitochondria from DOX-treated rats were more susceptible to diamide-dependent induction of the MPT. Although DOX treatment did not affect state 4 respiration, state 3 respiration was decreased in heart mitochondria isolated from DOX-treated rats, which was reversed in part by adding either cyclosporin A or dithiothreitol, but not Trolox. The results suggest that in DOX-treated rats, (i) induction of the MPT is at least in part responsible for decreased mitochondrial respiration, (ii) heart mitochondria are more susceptible to diamide induced-MPT, (iii) thiol-dependent alteration of mitochondrial respiration is partially reversible ex vivo with dithiothreitol. Collectively, these data are consistent with the thesis that thiol-dependent alteration of MPT and respiration is an important factor in DOX-induced mitochondrial dysfunction.     

Alterations in mitochondrial dynamics with age‐related Sirtuin1/Sirtuin3 deficiency impair cardiomyocyte contractility

Sirtuin1 (SIRT1) and Sirtuin3 (SIRT3) protects cardiac function against ischemia/reperfusion (I/R) injury. Mitochondria are critical in response to myocardial I/R injury as disturbance of mitochondrial dynamics contributes to cardiac dysfunction. It is hypothesized that SIRT1 and SIRT3 are critical components to maintaining mitochondria homeostasis especially mitochondrial dynamics to exert cardioprotective actions under I/R stress. The results demonstrated that deficiency of SIRT1 and SIRT3 in aged (24–26 months) mice hearts led to the exacerbated cardiac dysfunction in terms of cardiac systolic dysfunction, cardiomyocytes contractile defection, and abnormal cardiomyocyte calcium flux during I/R stress. Moreover, the deletion of SIRT1 or SIRT3 in young (4–6 months) mice hearts impair cardiomyocyte contractility and shows aging‐like cardiac dysfunction upon I/R stress, indicating the crucial role of SIRT1 and SIRT3 in protecting myocardial contractility from I/R injury. The biochemical and seahorse analysis showed that the deficiency of SIRT1/SIRT3 leads to the inactivation of AMPK and alterations in mitochondrial oxidative phosphorylation (OXPHOS) that causes impaired mitochondrial respiration in response to I/R stress. Furthermore, the remodeling of the mitochondria network goes together with hypoxic stress, and mitochondria undergo the processes of fusion with the increasing elongated branches during hypoxia. The transmission electron microscope data showed that cardiac SIRT1/SIRT3 deficiency in aging alters mitochondrial morphology characterized by the impairment of mitochondria fusion under I/R stress. Thus, the age‐related deficiency of SIRT1/SIRT3 in the heart affects mitochondrial dynamics and respiration function that resulting in the impaired contractile function of cardiomyocytes in response to I/R.     

Cannabidiol Protects against Doxorubicin-Induced Cardiomyopathy by Modulating Mitochondrial Function and Biogenesis

Doxorubicin (DOX) is a widely used, potent chemotherapeutic agent; however, its clinical application is limited because of its dose-dependent cardiotoxicity. DOX’s cardiotoxicity involves increased oxidative/nitrative stress, impaired mitochondrial function in cardiomyocytes/endothelial cells and cell death. Cannabidiol (CBD) is a nonpsychotropic constituent of marijuana, which is well tolerated in humans, with antioxidant, antiinflammatory and recently discovered antitumor properties. We aimed to explore the effects of CBD in a well-established mouse model of DOX-induced cardiomyopathy. DOX-induced cardiomyopathy was characterized by increased myocardial injury (elevated serum creatine kinase and lactate dehydrogenase levels), myocardial oxidative and nitrative stress (decreased total glutathione content and glutathione peroxidase 1 activity, increased lipid peroxidation, 3-nitrotyrosine formation and expression of inducible nitric oxide synthase mRNA), myocardial cell death (apoptotic and poly[ADP]-ribose polymerase 1 [PARP]-dependent) and cardiac dysfunction (decline in ejection fraction and left ventricular fractional shortening). DOX also impaired myocardial mitochondrial biogenesis (decreased mitochondrial copy number, mRNA expression of peroxisome proliferator-activated receptor γ coactivator 1-alpha, peroxisome proliferator-activated receptor alpha, estrogen-related receptor alpha), reduced mitochondrial function (attenuated complex I and II activities) and decreased myocardial expression of uncoupling protein 2 and 3 and medium-chain acyl-CoA dehydrogenase mRNA. Treatment with CBD markedly improved DOX-induced cardiac dysfunction, oxidative/nitrative stress and cell death. CBD also enhanced the DOX-induced impaired cardiac mitochondrial function and biogenesis. These data suggest that CBD may represent a novel cardioprotective strategy against DOX-induced cardiotoxicity, and the above-described effects on mitochondrial function and biogenesis may contribute to its beneficial properties described in numerous other models of tissue injury.     

Glutathione peroxidase 1-deficient mice are more susceptible to doxorubicin-induced cardiotoxicity

Doxorubicin (DOX)-induced cardiotoxicity is thought to be mediated by the generation of superoxide anion radicals (superoxide) from redox cycling of DOX in cardiomyocyte mitochondria. Reduction of superoxide generates H(2)O(2), which diffuses throughout the cell and potentially contributes to oxidant-mediated cardiac injury. The mitochondrial and cytosolic glutathione peroxidase 1 (Gpx1) primarily functions to eradicate H(2)O(2). In this study, we hypothesize that Gpx1 plays a pivotal role in the clearance of H(2)O(2) generated by DOX. To test this hypothesis, we compared DOX-induced cardiac dysfunction, mitochondrial injury, protein nitration, and apoptosis in Gpx1-deficient and wild type mouse hearts. The Gpx1-deficient hearts showed increased susceptibility to DOX-induced acute functional derangements than wild type hearts, including impaired contractility and diastolic properties, decreased coronary flow rate, and reduced heart rate. In addition, DOX treatment impaired the mitochondrial function of Gpx1-deficient hearts. Specifically, Gpx1-deficient hearts treated with DOX demonstrated an increased rate of NAD-linked state 4 respiration and a decline in the P/O ratio relative to wild type hearts, suggesting that DOX uncouples the electron transfer chain and oxidative phosphorylation in Gpx1-deficient hearts. Finally, apoptosis and protein nitration were significantly increased in Gpx1-deficient mouse hearts compared to wild type hearts. These studies suggest that Gpx1 plays significant roles in protecting DOX-induced mitochondrial impairment and cardiac dysfunction in the acute phase.     

Calorie restriction reduces oxidative stress by SIRT3-mediated SOD2 activation

A major cause of aging and numerous diseases is thought to be cumulative oxidative stress, resulting from the production of reactive oxygen species (ROS) during respiration. Calorie restriction (CR), the most robust intervention to extend life span and ameliorate various diseases in mammals, reduces oxidative stress and damage. However, the underlying mechanism is unknown. Here, we show that the protective effects of CR on oxidative stress and damage are diminished in mice lacking SIRT3, a mitochondrial deacetylase. SIRT3 reduces cellular ROS levels dependent on superoxide dismutase 2 (SOD2), a major mitochondrial antioxidant enzyme. SIRT3 deacetylates two critical lysine residues on SOD2 and promotes its antioxidative activity. Importantly, the ability of SOD2 to reduce cellular ROS and promote oxidative stress resistance is greatly enhanced by SIRT3. Our studies identify a defense program that CR provokes to reduce oxidative stress and suggest approaches to combat aging and oxidative stress-related diseases.     

Dietary inorganic nitrate alleviates doxorubicin cardiotoxicity: mechanisms and implications

Doxorubicin (DOX) is one of the most powerful and widely prescribed chemotherapeutic agents to treat divergent human cancers. However, the clinical use of DOX is restricted due to its severe cardiotoxic side-effects. There has been ongoing search for cardioprotectants against DOX toxicity. Inorganic nitrate has emerged as a bioactive compound that can be reduced into nitrite and nitric oxide in vivo and in turn plays a therapeutic role in diseases associated with nitric oxide insufficiency or dysregulation. In this review, we describe a novel concept of using dietary supplementation of inorganic nitrate to reduce DOX-induced cardiac cellular damage and dysfunction, based on our recent promising studies in a mouse model of DOX cardiotoxicity. Our data show that chronic oral ingestion of sodium nitrate, at a dose equivalent to ~400% of the Acceptable Daily Intake of the World Health Organization, alleviated DOX-induced left ventricular dysfunction and mitochondrial respiratory chain damage. Such cardioprotective effects were associated with reduction of cardiomyocyte necrosis/apoptosis, tissue lipid peroxidation, and mitochondrial H(2)O(2) generation following DOX treatment. Furthermore, proteomic studies revealed enhanced cardiac expression of mitochondrial antioxidant enzyme - peroxiredoxin 5 in the nitrate-treated animals. These studies suggest that inorganic nitrate could be an inexpensive therapeutic agent for long-term oral administration in preventing DOX-induced cardiac toxicity and myopathy during the prolonged pathological process. Future clinical trials in the cancer patients undergoing DOX chemotherapy are warranted to translate these experimental findings into an effective new therapy in preventing the DOX-induced cardiomyopathy.     

Resveratrol prevents doxorubicin cardiotoxicity through mitochondrial stabilization and the Sirt1 pathway

Doxorubicin (DOX) is one of the most effective chemotherapeutic drugs; however, its incidence of cardiotoxicity compromises its therapeutic index. DOX-induced heart failure is thought to be caused by reduction/oxidation cycling of DOX to generate oxidative stress and cardiomyocyte cell death. Resveratrol (RV), a stilbene found in red wine, has been reported to play a cardioprotective role in diseases associated with oxidative stress. The objective of this study was to test the ability of RV to protect against DOX-induced cardiomyocyte death. We hypothesized that RV protects cardiomyocytes from DOX-induced oxidative stress and subsequent cell death through changes in mitochondrial function. DOX induced a rapid increase in reactive oxygen species (ROS) production in cardiac cell mitochondria, which was inhibited by pretreatment with RV, most likely owing to an increase in MnSOD activity. This effect of RV caused additional polarization of the mitochondria in the absence and presence of DOX to increase mitochondrial function. RV pretreatment also prevented DOX-induced cardiomyocyte death. The protective ability of RV against DOX was abolished when Sirt1 was inhibited by nicotinamide. Our data suggest that RV protects against DOX-induced oxidative stress through changes in mitochondrial function, specifically the Sirt1 pathway leading to cardiac cell survival.