Anthracyclines remain the cornerstone of treatment in many malignancies but these agents have a cumulative dose relationship with cardiotoxicity. Development of cardiomyopathy and congestive heart failure induced by anthracyclines are typically dose-dependent, irreversible, and cumulative. Although past studies of cardiotoxicity have focused on anthracyclines, more recently interest has turned to anticancer drugs that target many proteins kinases, such as tyrosine kinases. An attractive model to explain the mechanism of this cardiotoxicity could be myocyte loss through cell death pathways. Inhibition of mitochondrial transition permeability is a valuable tool to prevent doxorubicin-induced cardiotoxicity. In response to anthracycline treatment, activation of several protein kinases, neuregulin/ErbB2 signaling, and transcriptional factors modify mitochondrial functions that determine cell death or survival through the modulation of mitochondrial membrane permeability. Cellular response to anthracyclines is also modulated by a myriad of transcriptional factors that influence cell fate. Several novel targeted chemotherapeutic agents have been associated with a small but worrying risk of left ventricular dysfunction. Agents such as trastuzumab and tyrosine kinase inhibitors can lead to cardiotoxicity that is fundamentally different from that caused by anthracyclines, whereas biological effects converge to the mitochondria as a critical target.
The anthracycline antibiotic doxorubicin (DOX) is a potent cancer chemotherapeutic agent that exerts both acute and chronic cardiotoxicity. Here we show that in adult mouse cardiomyocytes, DOX activates (i) the pro-apoptotic p53, (ii) p38MAPK and JNK, (iii) Bax translocation, (iv) cytochrome c release, and (v) caspase 3. Further, it (vi) inhibits expression of anti-apoptotic Akt, Bcl-2 and Bcl-xL, and (vii) induces internucleosomal degradation and cell death. WNT1-Inducible Signaling Pathway Protein-1 (WISP1), a CCN family member and a matricellular protein, inhibits DOX-mediated cardiomyocyte death. WISP1 inhibits DOX-induced p53 activation, p38 MAPK and JNK phosphorylation, Bax translocation to mitochondria, and cytochrome c release into cytoplasm. Additionally, WISP1 reverses DOX-induced suppression of Bcl-2 and Bcl-xL expression and Akt inhibition. The pro-survival effects of WISP1 were recapitulated by the forced expression of mutant p53, wild-type Bcl-2, wild-type Bcl-xL, or constitutively active Akt prior to DOX treatment. WISP1 also induces the pro-survival factor Survivin via PI3K/Akt signaling. Overexpression of wild-type, but not mutant Survivin, blunts DOX cytotoxicity. Further, WISP1 stimulates PI3K-Akt-dependent GSK3β phosphorylation and β-catenin nuclear translocation. Importantly, WISP1 induces its own expression. Together, these results provide important insights into the cytoprotective effects of WISP1 in cardiomyocytes, and suggest a potential therapeutic role for WISP1 in DOX-induced cardiotoxicity.
CCN; WISP; doxorubicin; cardiomyocytes; growth factors; cardiotoxicity
Doxorubicin (DOX) is a widely used antitumor drug, but its application is limited due to its cardiotoxic side effects. Hsp20 has been recently shown to protect cardiomyocytes against apoptosis, induced by ischemia/reperfusion injury or by prolonged β-agonist stimulation. However, it is not clear whether Hsp20 would exert similar protective effects against DOX-induced cardiac injury. Actually, DOX-treatment was associated with down-regulation of Hsp20 in the heart. To elucidate the role of Hsp20 in DOX-triggered cardiac toxicity, Hsp20 was first overexpressed ex vivo by adenovirus-mediated gene delivery. Increased Hsp20 levels conferred higher resistance to DOX-induced cell death, compared to GFP-control. Furthermore, cardiac-specific overexpression of Hsp20 in vivo significantly ameliorated acute DOX-triggered cardiomyocyte apoptosis and animal mortality. Hsp20-transgenic mice also showed improved cardiac function and prolonged survival after chronic administration of DOX. The mechanisms underlying these beneficial effects were associated with preserved Akt phosphorylation/activity and attenuation of DOX-induced oxidative stress. Co-immunoprecipitation studies revealed an interaction between Hsp20 and phosphorylated Akt. Accordingly, BAD phosphorylation was preserved and cleaved caspase-3 was decreased in DOX-treated Hsp20-TG hearts, consistent with the Hsp20's anti-apoptotic effects. Parallel ex vivo experiments showed that either infection with a dominant-negative Akt adenovirus or pre-incubation of cardiomyocytes with the PI3-kinase inhibitors significantly attenuated the protective effects of Hsp20. Taken together, our findings indicate that overexpression of Hsp20 inhibits DOX-triggered cardiac injury, and these beneficial effects appear to be dependent on Akt activation. Thus, Hsp20 may constitute a new therapeutic target in ameliorating the cardiotoxic effects of DOX-treatment in cancer patients.
apoptosis; cardiomyopathy; doxorubicin; heat-shock protein; Akt
Activation of ε protein kinase C (εPKC) protects hearts from ischemic injury. However, some of the mechanism(s) of εPKC mediated cardioprotection are still unclear. Identification of εPKC targets may aid to elucidate εPKC–mediated cardioprotective mechanisms. Previous studies, using a combination of εPKC transgenic mice and difference in gel electrophoresis (DIGE), identified a number of proteins involved in glucose metabolism, whose expression was modified by εPKC. These studies, were accompanied by metabolomic analysis, and suggested that increased glucose oxidation may be responsible for the cardioprotective effect of εPKC. However, whether these εPKC-mediated alterations were due to differences in protein expression or phosphorylation was not determined.
Methods and Results
Here, we used an εPKC-specific activator peptide, ψεRACK, in combination with phosphoproteomics to identify εPKC targets, and identified proteins whose phosphorylation was altered by selective activation of εPKC most of the identified proteins were mitochondrial proteins and analysis of the mitochondrial phosphoproteome, led to the identification of 55 spots, corresponding to 37 individual proteins, which were exclusively phosphorylated, in the presence of ψεRACK. The majority of the proteins identified were proteins involved in glucose and lipid metabolism, components of the respiratory chain as well as mitochondrial heat shock proteins.
In summary the protective effect of εPKC during ischemia involves phosphorylation of several mitochondrial proteins involved in glucose, lipid metabolism and oxidative phosphorylation. Regulation of these metabolic pathways by εPKC phosphorylation may lead to εPKC-mediated cardioprotection induced by ψεRACK.
εPKC; ischemia; phosphorylation; mitochondria
Cardioprotection, such as preconditioning and postconditioning, have been shown to result in a significant reduction in cell death. Many of the signaling pathways activated by cardioprotection have been elucidated, but there is still a lack of understanding of the mechanisms by which these signaling pathways reduce cell death. Mitochondria have been reported to be an important player in many types of apoptotic and necrotic cell death. If mitochondria play an important role in cell death, then it seems reasonable to consider that cardioprotective mechanisms might act, at least in part, by opposing mitochondrial cell death pathways. One of the major mechanisms of cell death in ischemia-reperfusion is suggested to be the opening of a large conductance pore in the inner mitochondrial membrane, known as the mitochondrial permeability transition pore. Inhibition of this mitochondrial pore appears to be one of the major mechanisms by which cardioprotection reduces cell death. Cardioprotection activates a number of signaling pathways that reduce the level of triggers (reactive oxygen species and calcium) or enhances inhibitors of the mitochondrial permeability transition pore at the start of reperfusion.
Doxorubicin (DOX) is considered as one of the best antineoplastic agents. However, its clinical use is restricted by its associated cardiotoxicity, which is mediated by the production of reactive oxygen species. In this study, 20(S)-ginsenoside Rh2 (Rh2) was explored whether it had protective effects against DOX-induced cardiotoxicity. In vitro study on H9C2 cell line, as well as in vivo investigation in one mouse and one rat model of DOX-induced cardiomyopathy, was carried out. The results showed that pretreatment with Rh2 significantly increased the viability of DOX-injured H9C2 cells. In the mouse model, Rh2 could suppress the DOX-induced release of the cardiac enzymes into serum and improved the occurred pathological changes through ameliorating the decreased antioxidant biomolecules and the cumulated lipid peroxidation malondialdehyde in heart tissues. In the rat model, Rh2 could attenuate the change of ECG resulting from DOX administration. Furthermore, Rh2 enhanced the antitumor activity of DOX in A549 cells. Our findings thus demonstrated that Rh2 pretreatment could effectively alleviate heart injury induced by DOX, and Rh2 might act as a novel protective agent in the clinical usefulness of DOX.
Mitochondria are central players in the pathophysiology of ischemia-reperfusion. Activation of plasma membrane G-coupled receptors or the Na, K-ATPase trigger cytosolic signaling pathways that result in cardioprotection. Our working hypothesis is that the occupied receptors migrate to caveolae, where signaling enzymes are scaffolded into signalosomes that bud off the plasma membrane and migrate to mitochondria. The signalosome-mitochondria interaction then initiates intramitochondrial signaling by opening the mitochondrial ATP-sensitive K+ channel (mitoKATP). MitoKATP opening causes an increase in ROS production, which activates mitochondrial protein kinase C epsilon (PKCε), which inhibits the mitochondrial permeability transition (MPT), thus decreasing cell death. We review the experimental findings that bear on these hypotheses and other modes of protection involving mitochondria.
mitochondrial KATP channel; protein kinase C; reactive oxygen species; permeability transition; signaling pathways
We searched for a drug capable of sensitization of sarcoma cells to doxorubicin (DOX). We report that the dual PI3K/mTOR inhibitor PI103 enhances the efficacy of DOX in several sarcoma cell lines and interacts with DOX in the induction of apoptosis. PI103 decreased the expression of MDR1 and MRP1, which resulted in DOX accumulation. However, the enhancement of DOX-induced apoptosis was unrelated to DOX accumulation. Neither did it involve inhibition of mTOR. Instead, the combination treatment of DOX plus PI103 activated Bax, the mitochondrial apoptosis pathway, and caspase 3. Caspase 3 activation was also observed in xenografts of sarcoma cells in nude mice upon combination of DOX with the specific PI3K inhibitor GDC-0941. Although the increase in apoptosis did not further impact on tumor growth when compared to the efficient growth inhibition by GDC-0941 alone, these findings suggest that inhibition of PI3K may improve DOX-induced proapoptotic effects in sarcoma. Taken together with similar recent studies of neuroblastoma- and glioblastoma-derived cells, PI3K inhibition seems to be a more general option to sensitize tumor cells to anthracyclines.
Doxorubicin (DOX) is one of the most widely used and successful antitumor drugs, but its cumulative and dose-dependent cardiac toxicity has been the major concern of oncologists in cancer therapeutic practice for decades. With the increasing population of cancer survivals, there is a growing need to develop preventive strategies and effective therapies against DOX-induced cardiotoxicity, in particular, the late onset cardiomyopathy. Although intensive investigations on the DOX-induced cardiotoxicity have been continued for decades, the underlying mechanisms responsible for DOX-induced cardiotoxicity have not been completely elucidated. A rapidly expanding body of evidence supports that cardiomyocyte death by apoptosis and necrosis is a primary mechanism of DOX-induced cardiomyopathy and other types of cell death, such as autophagy and senescence/aging, may participate in this process. In this review, we will focus on the current understanding of molecular mechanisms underlying DOX-induced cardiomyocyte death, including the major primary mechanism of excess production of reactive oxygen species (ROS) and other recently discovered ROS-independent mechanisms. Different sensitivity to DOX-induced cell death signals between adult and young cardiomyocytes will also be discussed.
cardiomyocyte; doxorubicin; apoptosis; necrosis; autophagy
Previous studies have suggested that increased levels of endocannabinoids in various cardiovascular disorders (e.g. different forms of shock, cardiomyopathies, atherosclerosis) through the activation of CB1 cannabinoid receptors may promote cardiovascular dysfunction and tissue injury. We have investigated the role of the main endocannabinoid anandamide metabolizing enzyme (fatty acid amide hydrolase; FAAH) in the myocardial injury induced by an important chemotherapeutic drug doxorubicin (DOX; known for its cardiotoxicity mediated by increased reactive oxygen and nitrogen species generation) using well-established acute and chronic cardiomyopathy models in mice. The DOX-induced myocardial oxidative/nitrative stress (increased 4-hydroxynonenal(HNE), protein carbonyl, nitrotyrosine levels, decreased glutathione content) correlated with multiple cell death markers, which were enhanced in FAAH knockout mice exhibiting significantly increased DOX-induced mortality and cardiac dysfunction compared to their wild types. The effects of DOX in FAAH knockouts were attenuated by CB1 receptor antagonists. Furthermore, anandamide induced enhanced cell death in human cardiomyocytes pretreated by FAAH inhibitor, and enhanced sensitivity to ROS generation in inflammatory cells of FAAH knockouts. These results suggest that in pathological conditions associated with acute oxidative/nitrative stress FAAH plays a key role in controlling the tissue injury, which is, at least in part, mediated by the activation of CB1 receptors by endocannabinoids.
Cardioprotection (delaying of irreversible damage in hypoxia or prevention of doxorubicin [DOX] toxicity) is achieved by increasing the energy supply, or decreasing the energy demand in the cell and may be regulated through adenosine (ADO) receptor (AR) signalling. The aim of this study was to define of the protective role of ADO A1R and A3R against these two different kinds of stress conditions via direct action on isolated cardiomyocytes. Effects of A1 and A3 adenosine receptors were assessed by comparing morphological-functional tolerance, cellular energy state and contribution of the mitochondrial KATP channels during development of hypoxia and DOX cytotoxicity.
The primary cardiac myocyte cultures were treated in a hypoxic chamber of N2 (100%) in glucose-free media. A second group of cells were treated on day 4 in culture with 0.5 to 5 μM DOX for 18 h and then incubated in drug-free growth medium for an additional 24 h or 72 h. The hypoxic and cytotoxic damage was characterized by morphological and biochemical evaluations.
The A1R and A3R selective agonists (CCPA and Cl-IB-MECA, respectively) significantly decreased damage to cardiac myocytes under hypoxic conditions. Activation of both A1R and A3R together (100 nM) was more efficient in protection against hypoxia than by each one alone. The A3R agonist Cl-IB-MECA (100 nM) shows cardioprotective activity to the DOX-treated cells; however, the A1R agonist CCPA (10 nM to 10 μM) was not effective in protection against DOX toxicity.
Activation of both the ADO receptors (A1R and A3R) leads to positive beneficial effects in cultured cardiomyocytes in 90 min hypoxia, but only A3R activation renders positive response against slowly developed DOX toxicity. Hence, the cascade of events involved in cardioprotection appears to be distinct for A1 and A3 receptor signalling.
Adenosine receptors; Cardiomyocytes; Cardioprotection; Doxorubicin; Hypoxia
Visfatin is an adipocytokine capable of mimicking the glucose-lowering effects of insulin and activating the pro-survival kinases phosphatidylinositol-3-OH kinase (PI3K)-protein kinase B (Akt) and mitogen-activated protein kinase kinase 1 and 2 (MEK1/2)-extracellular signal-regulated kinase 1 and 2 (Erk 1/2). Experimental studies have demonstrated that the activation of these kinases confers cardioprotection through the inhibition of the mitochondrial permeability transition pore (mPTP). Whether visfatin is capable of exerting direct cardioprotective effects through these mechanisms is unknown and is the subject of the current study. Anaesthetized C57BL/6 male mice were subjected to in situ 30 min. of regional myocardial ischaemia and 120 min. of reperfusion. The administration of an intravenous bolus of visfatin (5 × 10−6μmol) at the time of myocardial reperfusion reduced the myocardial infarct size from 46.1 ± 4.1% in control hearts to 27.3 ± 4.0% (n≥ 6/group, P < 0.05), an effect that was blocked by the PI3K inhibitor, wortmannin, and the MEK1/2 inhibitor, U0126 (48.8 ± 5.5% and 45.9 ± 8.4%, respectively, versus 27.3 ± 4.0% with visfatin; n≥ 6/group, P < 0.05). In murine ventricular cardiomyocytes subjected to 30 min. of hypoxia followed by 30 min. of reoxygenation, visfatin (100 ng/ml), administered at the time of reoxygenation, reduced the cell death from 65.2 ± 4.6% in control to 49.2 ± 3.7%(n > 200 cells/group, P < 0.05), an effect that was abrogated by wortmannin and U0126 (68.1 ± 5.2% and 59.7 ± 6.2%, respectively; n > 200 cells/group, P > 0.05). Finally, the treatment of murine ventricular cardiomyocytes with visfatin (100 ng/ml) delayed the opening of the mPTP induced by oxidative stress from 81.2 ± 4 sec. in control to 120 ± 7 sec. (n > 20 cells/group, P < 0.05) in a PI3K- and MEK1/2-dependent manner. We report that the adipocytokine, visfatin, is capable of reducing myocardial injury when administered at the time of myocardial reperfusion in both the in situ murine heart and the isolated murine cardiomyocytes. The mechanism appears to involve the PI3K and MEK1/2 pathways and the mPTP.
visfatin; ischaemia; reperfusion; cardioprotection
The clinical use of doxorubicin (DOX), a potent antineoplastic agent, is limited by its serious side-effects, which include acute and chronic cumulative dose-related cardiotoxicity. Berberine (BER), a botanical alkaloid, has been reported to possess cardioprotective and antitumor effects. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-tetrazolium bromide (MTT) assay was used to detect the cell viability of A549, HeLa and HepG2 cells after each cell line was treated with DOX, BER or a combination of DOX and BER for 24 h. Apoptosis was evaluated by acridine orange staining. The results showed that BER and DOX exhibited dose-dependent inhibitory effects on A549 and HeLa cells which were likely mediated by inducing apoptosis. The same result was found in the combination group. Isobologram illustration and combination index (CI) analyses revealed that the combination of DOX and BER generates synergistic effects in A549 (CI=0.61) and HeLa (CI=0.73) cells. These findings indicate that BER sensitizes cells to the anticancer effects of DOX.
berberine; doxorubicin; synergistic effect; A549; HeLa
Cardioprotective signaling mediates anti-apoptotic actions through multiple mechanisms including maintenance of mitochondrial integrity. Pim-1 kinase is an essential downstream effector of AKT-mediated cardioprotection but the mechanistic basis for maintenance of mitochondrial integrity by Pim-1 remains unexplored. This study details anti-apoptotic actions responsible for enhanced cell survival in cardiomyocytes with elevated Pim-1 activity.
The purpose of this study is to demonstrate that the cardioprotective kinase Pim-1 acts to inhibit cell death by preserving mitochondrial integrity in cardiomyocytes.
Methods and Results
A combination of biochemical, molecular, and microscopic analyses demonstrate beneficial effects of Pim-1 upon mitochondrial integrity. Pim-1 protein level increases in the mitochondrial fraction with a corresponding decrease in the cytosolic fraction of myocardial lysates from hearts subjected to 30 minutes of ischemia followed by 30 minutes of reperfusion. Cardiac-specific overexpression of Pim-1 results in higher levels of anti-apoptotic Bcl-XL and Bcl-2 compared to samples from normal hearts. In response to oxidative stress challenge Pim-1 preserves the inner mitochondrial membrane potential (ΔΨm). Ultrastructure of the mitochondria is maintained by Pim-1 activity, which prevents swelling induced by calcium overload. Finally, mitochondria isolated from hearts created with cardiac-specific overexpression of Pim-1 show inhibition of cytochrome c release triggered by a truncated form of pro-apoptotic Bid.
Cardioprotective action of Pim-1 kinase includes preservation of mitochondrial integrity during cardiomyopathic challenge conditions, thereby raising the potential for Pim-1 kinase activation as a therapeutic interventional approach to inhibit cell death by antagonizing pro-apoptotic Bcl-2 family members that regulate the intrinsic apoptotic pathway.
Pim-1; mitochondria; cardiomyocyte; apoptosis
Doxorubicin (Dox) is a very potent anti-cancer agent but its usage is limited by its dose-dependent irreversible cardiotoxicity. Despite intensive research efforts, the mechanism of Dox cardiotoxicity remains to be poorly understood and consequently the means available for clinicians to prevent or effectively manage Dox cardiotoxicity are very limited. Recent studies have excitingly revealed that a therapeutic dose of Dox can activate ubiquitin-proteasome system (UPS) mediated proteolysis in cardiomyocytes and that the UPS-mediated degradation of a number of pivotal cardiac transcription factors and/or survival factors is enhanced by Dox treatment. These suggest that the Dox induced UPS activation may represent a new mechanism underlying Dox cardiotoxicity. Notably, recent experimental studies suggest that proteasome activation promotes cardiac remodeling during hypertension. This review surveys the current literature on the impact of Dox on the UPS and the potential mechanisms by which UPS activation may compromise the heart during Dox therapy.
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 H2O2, 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 H2O2. In this study, we hypothesize that Gpx1 plays a pivotal role in the clearance of H2O2 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.
doxorubicin; glutathione peroxidase deficiency; mitochondrial function; cardiac function; apoptosis; protein nitration
Doxorubicin is a widely used chemotherapy drug, but its application is associated with cardiotoxicity. Free radical generation and mitochondrial dysfunction are thought to contribute to doxorubicin-induced cardiac failure. Angiotensin-converting enzyme (ACE) inhibitors are commonly used as cardioprotective agents and have recently been shown in clinical studies to be efficacious in the prevention of anthracycline induced heart failure. Here we evaluated a mechanism for these protective effects by testing the ability of the ACE inhibitor enalapril to preserve mitochondrial function in a model of chronic doxorubicin treatment in rats.
Sprague Dawley rats were divided into three groups and followed for a total of 10 weeks: a) control-untreated, b) Doxorubicin treated (Dox), and c) Doxorubicin + Enalapril treated (DE). Doxorubicin was administered via intraperitoneal injection at weekly intervals from week 2 through week 7. Enalapril was administered in the drinking water of the DE group for the study duration.
Doxorubicin treatment produced a significant loss in left ventricular contractility (P< 0.05), decrease in mitochondrial function via impairment of state-3 respiration, decrease in the cytosolic fraction of ATP, and up-regulation of free radical production. Enalapril significantly attenuated the decrease in percent fractional shortening (P< 0.05) and prevented the doxorubicin-associated reduction in respiratory efficiency and cytosolic ATP content (P< 0.05). Importantly, enalapril also abolished the robust doxorubicin-induced increase in free radical formation.
Administration of enalapril attenuates doxorubicin-induced cardiac dysfunction via preservation of mitochondrial respiratory efficiency and reduction in doxorubicin-associated free radical generation.
doxorubicin; mitochondria; cardiotoxicity; ACE inhibitor; free radicals
Overexpression of the adenine nucleotide translocase (ANT) has been shown to be cytotoxic in several cell types. Although ANT was originally proposed to be a critical component of the mitochondrial permeability transition (MPT) pore, recent data have suggested that this may not be the case. We therefore hypothesized that the cytotoxic actions of ANT are through an alternative mechanism, independent of the MPT pore. Infection of cultured neonatal cardiomyocytes with an ANT1-encoding adenovirus induced a gene dosage-dependent increase in cell death. However, ANT1 overexpression failed to induce MPT, and neither pharmacological nor genetic inhibition of the MPT pore was able to prevent ANT1-induced cell death. These data suggested that ANT1-induced death progressed through an MPT pore-independent pathway. Somewhat surprisingly, we observed that protein levels of Bax, a pro-apoptotic Bcl protein, were consistently elevated in ANT1-infected cardiomyocytes. Membranes isolated from ANT1-infected myocytes exhibited significantly increased amounts of membrane-inserted Bax, and immunocytochemistry revealed increased Bax activation in ANT1-infected myocytes. Co-expression with the Bax antagonist Bcl2 was able to greatly reduce the degree of ANT1-induced cell death. Furthermore, Bax/Bak-deficient fibroblasts were resistant to the cytotoxic effects of ANT1 overexpression. Interestingly, ANT1 overexpression was also associated with enhanced production of reactive oxygen species (ROS), and the antioxidant MnTBAP was able to significantly attenuate both the ANT1-induced upregulation of Bax and cell death. Taken together, these data indicate that ANT mediates cell death, not through the MPT pore, but rather via a ROS-dependent upregulation and activation of Bax.
cardiomyocytes; mitochondrial permeability transition; cell death; Bax; reactive oxygen species
β-adrenergic receptor blockers have demonstrated significant survival benefit and have become standard therapy for adults with dilated cardiomyopathy, although their efficacy in pediatric patients is still unproven. Recent data suggests that the two major cardiac β-adrenergic receptor subtypes (β1 and β2) couple differentially to intracellular signaling pathways regulating contractility and remodeling. This has led some to suggest that the β1 receptor is the “cardiotoxic subtype” whereas the β2 receptor is “cardioprotective.” Given this paradigm, there could be situations where subtype selective β-blockade or even subtype selective β-stimulation might be beneficial. However, since most of these studies have been performed in isolated cardiomyocytes, their application to clinical practice is unclear. To better understand the roles of β1- vs. β2-receptors in the pathogenesis of clinical cardiomyopathy, we and others have taken advantage of several well-characterized murine models of cardiovascular disease. These studies demonstrate that β-receptor regulation of the balance between cardioprotection and cardiotoxicity is even more complex than previously appreciated: the role of each β-receptor subtype may vary depending on the specific cardiac stressor involved (e.g. ischemia, pressure overload, genetic mutation, cardiotoxin). Furthermore, the remodeling effects of β-receptor signaling have a temporal component, depending on whether a cardiac stress is acute vs. chronic.
Cardiomyopathy; adrenergic receptor; cell signaling; β-blocker; heart failure
The anthracycline doxorubicin (DOX) is an effective chemotherapeutic agent used to treat pediatric cancers, but is associated with cardiotoxicity which can manifest many years after the initial exposure. To date, very little is known about the mechanism of this late onset cardiotoxicity.
Methods and Results
To understand this problem, we developed a pediatric model of late onset DOX-induced cardiotoxicity, where juvenile mice were exposed to DOX, using a cumulative dose that did not induce acute cardiotoxicity. These mice developed normally and had no obvious cardiac abnormalities as adults. However, evaluation of the vasculature revealed that juvenile DOX exposure impaired vascular development resulting in abnormal vascular architecture in the hearts with less branching and decreased capillary density. Both physiological and pathological stress induced late onset cardiotoxicity in the adult DOX mice. Moreover, adult mice subjected to myocardial infarction (MI) developed rapid heart failure which correlated with a failure to increase capillary density in the injured area. Progenitor cells participate in regeneration and blood vessel formation after an MI, but DOX mice had fewer progenitor cells in the infarct border zone. Interestingly, DOX treatment reduced proliferation and differentiation of the progenitor cells into cells of cardiac lineages.
Our data suggest that anthracycline treatment impairs vascular development as well as progenitor cell function in the young heart, resulting in an adult heart that is more susceptible to stress.
anthracyclines; heart failure; vascularization; cardiac progenitor cells
Doxorubicin (DOX) is widely used in combination cocktails for treatment of childhood hematological cancers and solid tumors. A major factor limiting DOX usage is DOX-induced cardiotoxicity. However, it is not known whether protectants like dexrazoxane (DXR) and amifostine (AMF) can prevent DOX-mediated bone damage. The present study investigated whether administration of AMF alone or in combination with DXR would prevent any DOX-mediated bone damage. Male rat pups were treated with DOX, DXR, AMF, and their combinations. On neonate day 38, the bone mineral density (BMD), bone mineral content (BMC) and the micro-architecture of the lumbar vertebrae were analyzed. We have shown that when male rats are treated with DOX, DXR, DOX+DXR, AMF, DOX+AMF or DOX+DXR+AMF, there is a decrease in lumbar vertebral BMD (p<0.05). Furthermore, the relative bone volume (BV/TV) was decreased by DXR, DOX+DXR, and DOX+AMF treatments. Interestingly, DOX+AMF significantly increased BV/TV when compared to DXR treatment (p<0.04). The trabecular number (Tb.N) decreased with DXR and DOX+DXR and increased with DOX+AMF treatments. This information will be useful in designing better cancer combination therapies that do not lead to vertebrae deterioration.
Doxorubicin (DOX) is a broad spectrum antineoplastic drug widely used in the treatment of several hematogenous and solid human malignancies. Despite its excellent clinical efficacy as a chemotherapeutic agent, its therapeutic usage has been restricted due to its cardiotoxicity. Phosphodiesterase-5 (PDE-5) inhibitors or erectile dysfunction drugs including sildenafil, have been shown to have powerful cardioprotective effect against injuries under a variety of experimental situations including ischemia/reperfusion injury, myocardial infarction and DOX-induced cardiomyopathy. We studied the effect of – tadalafil, a long acting PDE-5 inhibitor in preventing damage in the heart with DOX treatment. Our results showed that tadalafil improved left ventricular function and survival by attenuating DOX-induced apoptosis and cardiac oxidative stress without interfering with the anti-tumor efficacy of DOX in both in vitro and in vivo tumor models. Herein, we present an overview of our study, and consider the potential mechanisms by which tadalafil, at therapeutically relevant concentrations mediate beneficial cardioprotective effects in DOX cardiotoxicity. Based on our current and previously published studies, we propose that the class of PDE-5 inhibitors can represent a novel approach which can be exploited for achieving therapeutic benefit in the treatment of DOX-induced cardiotoxicity in patients.
Doxorubicin; Cardiomyopathy; Phosphodiesterase inhibitors; PKG; cGMP; ROS
Although death receptors and chemotherapeutic drugs activate distinct apoptosis signaling cascades, crosstalk between the extrinsic and intrinsic apoptosis pathway has been recognized as an important amplification mechanism. Best known in this regard is the amplification of the Fas (CD95) signal in hepatocytes via caspase 8-mediated cleavage of Bid and activation of the mitochondrial apoptosis pathway. Recent evidence, however, indicates that activation of other BH3-only proteins may also be critical for the crosstalk between death receptors and mitochondrial triggers. In this study, we show that TNF-related apoptosis-inducing ligand (TRAIL) and chemotherapeutic drugs synergistically induce apoptosis in various transformed and untransformed liver-derived cell lines, as well as in primary human hepatocytes. Both, preincubation with TRAIL as well as chemotherapeutic drugs could sensitize cells for apoptosis induction by the other respective trigger. TRAIL induced a strong and long lasting activation of Jun kinase, and activation of the BH3-only protein Bim. Consequently, synergistic induction of apoptosis by TRAIL and chemotherapeutic drugs was dependent on Jun kinase activity, and expression of Bim and Bid. These findings confirm a previously defined role of TRAIL and Bim in the regulation of hepatocyte apoptosis, and demonstrate that the TRAIL–Jun kinase–Bim axis is a major and important apoptosis amplification pathway in primary hepatocytes and liver tumor cells.
death receptor; mitochondria; TRAIL; liver tumors; Bcl-2 homologs; Jun kinase; hepatocytes
Doxorubicin (DOX) is one of the most potent antitumor agents available; however, its clinical use is limited because of the risk of severe cardiotoxicity. Though numerous studies have ascribed DOX cardiomyopathy to specific cellular pathways, the precise mechanism remains obscure. Sini decoction (SND) is a well-known formula of Traditional Chinese Medicine (TCM) and is considered as efficient agents against DOX-induced cardiomyopathy. However, its action mechanisms are not well known due to its complex components.
A tissue-targeted metabonomic method using gas chromatography–mass spectrometry was developed to characterize the metabolic profile of DOX-induced cardiomyopathy in mice. With Elastic Net for classification and selection of biomarkers, twenty-four metabolites corresponding to DOX-induced cardiomyopathy were screened out, primarily involving glycolysis, lipid metabolism, citrate cycle, and some amino acids metabolism. With these altered metabolic pathways as possible drug targets, we systematically analyzed the protective effect of TCM SND, which showed that SND administration could provide satisfactory effect on DOX-induced cardiomyopathy through partially regulating the perturbed metabolic pathways.
The results of the present study not only gave rise to a systematic view of the development of DOX-induced cardiomyopathy but also provided the theoretical basis to prevent or modify expected damage.
Cardiomyocyte death is now recognized as a critical factor in the development of heart disease. Mitochondria are not only responsible for energy production to ensure that cardiac output meets the body’s energy demands, but they serve as critical integrators of cell survival signals. Numerous stressors are known to induce cell death by necrosis and/or apoptosis mediated through mitochondrial dysregulation. Anti- and pro-apoptotic Bcl-2 family proteins regulate apoptosis by controlling mitochondrial outer membrane permeability, whereas opening of the mitochondrial permeability transition pore (PT-pore) induces large amplitude permeability of the inner membrane and consequent rupture of the outer membrane. Akt is one of the best described survival kinases activated by receptor ligands and its activation preserves mitochondrial integrity and protects cardiomyocytes against necrotic and apoptotic death. The mechanisms responsible for Akt-mediated mitochondrial protection have not been fully elucidated. There is, however, accumulating evidence that multiple Akt target molecules, recruited through both transcriptional and post-transcriptional mechanisms, directly impinge upon and protect mitochondria. In this review we discuss mechanisms by which Akt activation can effect changes at the mitochondria that protect cardiomyocytes and attenuate pathophysiological responses of the heart.
Akt; Mitochondria; Heart; Hexokinase-II