Thrombopoietin protects against in vitro and in vivo cardiotoxicity induced by doxorubicin

Bicontinuous cubic liquid crystalline nanoparticles for oral delivery of Doxorubicin: implications on bioavailability, therapeutic efficacy, and cardiotoxicity

PURPOSE

The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin.

METHODS

Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process variables and lyophilized. Structural elucidation of the reconstituted formulation was performed using HR-TEM and SAXS analysis. The developed formulation was subjected to exhaustive cell culture experiments for delivery potential (Caco-2 cells) and efficacy (MCF-7 cells). Finally, in vivo pharmacokinetics, pharmacodynamic studies in DMBA induced breast cancer model and cardiotoxicity were also evaluated.

RESULTS

The reconstituted formulation exhibited Pn3m type cubic structure, evident by SAXS and posed stability in simulated gastrointestinal fluids and at accelerated stability conditions for 6 months. Dox-LCNPs revealed significantly higher cell cytotoxicity (16.23-fold) against MCF-7 cell lines as compared to free drug owing to its preferential localization in the vicinity of nucleus. Furthermore, Caco-2 cell experiments revealed formation of reversible "virtual pathways" in the cell membrane for Dox-LCNPs and hence posed significantly higher relative oral bioavailability (17.74-fold). Subsequently, Single dose of Dox-LCNPs (per oral) led to significant reduction in % tumor burden (~42%) as compared that of ~31% observed in case of Adriamycin® (i.v.) when evaluated in DMBA induced breast cancer model. Moreover, Dox induced cardiotoxicity was also found to be significantly lower in case of Dox-LCNPs as compared to clinical formulations (Adriamycin® and Lipodox®).

CONCLUSION

Incorporation of Dox in the novel LCNPs demonstrated improved antitumor efficacy and safety profile and can be a viable option for oral chemotherapy.

Protective effect of ocotillol against doxorubicin‑induced acute and chronic cardiac injury

Doxorubicin (Dox) has been clinically observed to exert marked anticancer activity. However, it is severely restricted by its associated dose‑dependent cardiotoxicity, which may be attenuated by decreasing the cumulative dosage via combining with a non‑toxic 'sensitizer'. We previously reported that ocotillol is capable of enhancing the antitumor activity of Dox; however, the effects of ocotillol on its cardiotoxicity remain unclear. In the current study, the effects of ocotillol on the toxicity of Dox were investigated, particularly its role in cardiotoxicity. In the acute injury model, pre‑administration of ocotillol prolonged the survival time. In the chronic animal model, pre‑administration of ocotillol decreased the elevated levels of plasma creatine kinase (CK) and CK‑MB, as well as attenuated the pathological changes that occurred. Pre‑treatment with ocotillol ameliorated the decreased glutathione level and reduced the cumulated malondialdehyde in the heart tissue. In addition, pre‑treatment with ocotillol restored the lowered white blood cell count. The results indicate that Dox co‑treatment with ocotillol may effectively alleviate its associated toxic injury, particularly cardiotoxicity. Thus, co‑administration of Dox with ocotillol may be a potential therapeutic strategy.

Human resistin in chemotherapy-induced heart failure in humanized male mice and in women treated for breast cancer

Resistin is a circulating mediator of insulin resistance mainly expressed in human monocytes and responsive to inflammatory stimuli. Recent clinical studies have connected elevated resistin levels with the development and severity of heart failure. To further our understanding of the role of human resistin in heart failure, we studied a humanized mouse model lacking murine resistin but transgenic for the human Retn gene (Hum-Retn mice), which exhibits basal and inflammation-stimulated resistin levels similar to humans. Specifically, we explored whether resistin underlies acute anthracycline-induced cardiotoxicity. Remarkably, doxorubicin (25mg/kg ip) led to a 4-fold induction of serum resistin levels in Hum-Retn mice. Moreover, doxorubicin-induced cardiotoxicity was greater in the Hum-Retn mice than in littermate controls not expressing human resistin (Retn(-/-)). Hum-Retn mice showed increased cardiac mRNA levels of inflammatory and cell adhesion genes compared with Retn(-/-) mice. Macrophages, but not cardiomyocytes, from Hum-Retn mice treated with doxorubicin in vitro showed dramatic induction of hRetn (human resistin) mRNA and protein expression. We also examined resistin levels in anthracycline-treated breast cancer patients with and without cardiotoxicity. Intriguingly, serum resistin levels in women undergoing anthracycline-containing chemotherapy increased significantly at 3 months and remained elevated at 6 months in those with subsequent cardiotoxicity. Further, elevation in resistin correlated with decline in ejection fraction in these women. These results suggest that elevated resistin is a biomarker of anthracycline-induced cardiotoxicity and may contribute in the development of heart failure via its direct effects on macrophages. These results further implicate resistin as a link between inflammation, metabolism, and heart disease.

Ethanolic extract of Boswellia ovalifoliolata bark and leaf attenuates doxorubicin-induced cardiotoxicity in mice

The aim of the study was to investigate the potential protective effect of ethanolic extract of Boswellia ovalifoliolata (BO) bark and leaf against doxorubicin (DOX)-induced cardiotoxicity in mice. Ethanolic extracts of BO bark (400 mg/kg) and leaves (250 mg/kg) were given orally to mice for 9 consecutive days and DOX (15 mg/kg; i.p.) was administered on the seventh day. Extract protected against DOX-induced ECG changes. It significantly inhibited DOX-provoked glutathione depletion and accumulation of malondialdehyde. The decrease in antioxidant enzyme activities of catalase, superoxide dismutase, glutathione peroxidase in cardiac tissue were significantly (p<0.05) mitigated after treatment with BO bark and leaf extracts. Pretreatment with BO significantly (p<0.05) restored the levels of DOX-induced rise of SGPT, SGOT, serum lactate dehydrogenase and creatine kinase-MB levels. These findings suggest that ethanolic extract of BO has protective effects against DOX-induced cardiotoxicity.

Higenamine Combined with [6]-Gingerol Suppresses Doxorubicin-Triggered Oxidative Stress and Apoptosis in Cardiomyocytes via Upregulation of PI3K/Akt Pathway

Sini decoction is a well-known formula of traditional Chinese medicine, which has been used to treat cardiovascular disease for many years. Previously, we demonstrated that Sini decoction prevented doxorubicin-induced heart failure in vivo. However, its active components are still unclear. Thus, we investigated the active components of Sini decoction and their cardioprotective mechanisms in the in vitro neonatal rat cardiomyocytes and H9c2 cell line models of doxorubicin-induced cytotoxicity. Our results demonstrated that treatment with higenamine or [6]-gingerol increased viability of doxorubicine-injured cardiomyocytes. Moreover, combined use of higenamine and [6]-gingerol exerted more profound protective effects than either drug as a single agent, with effects similar to those of dexrazoxane, a clinically approved cardiac protective agent. In addition, we found that treatment with doxorubicin reduced SOD activity, increased ROS generation, enhanced MDA formation, induced release of LDH, and triggered the intrinsic mitochondria-dependent apoptotic pathway in cardiomyocytes, which was inhibited by cotreatment of higenamine and [6]-gingerol. Most importantly, the cytoprotection of higenamine plus [6]-gingerol could be abrogated by LY294002, a PI3K inhibitor. In conclusion, combination of higenamine and [6]-gingerol exerts cardioprotective effect against doxorubicin-induced cardiotoxicity through activating the PI3K/Akt signaling pathway. Higenamine and [6]-gingerol may be the active components of Sini decoction.

Evaluation of Short-Term Use of N-Acetylcysteine as a Strategy for Prevention of Anthracycline-Induced Cardiomyopathy: EPOCH Trial - A Prospective Randomized Study

Background and Objectives

We investigate to determine whether N-acetylcysteine (NAC) can prevent anthracycline-induced cardiotoxicity.

Subjects and Methods

A total of 103 patients were enrolled in this prospective randomized open label controlled trial. They are patients first diagnosed with breast cancer or lymphoma, who require chemotherapy, including anthracycline like adriamycine or epirubicine. Patients were randomized to the NAC group {n=50; 1200 mg orally every 8 hours starting before and ending after the intravenous infusion of anthracycline in all chemotherapy cycles (3-6)} or the control group (n=53). Primary outcome was the decrease in left ventricular ejection fraction (LVEF) absolutely ≥10% from the baseline and concomitantly <50% at 6-month. Composite of all-cause death, heart failure and readmission were compared.

Results

The primary outcome was not significantly different in the NAC and control groups {3/47 (6.4%) vs. 1/52 (1.9%), p=0.343}. The mean LVEF significantly decreased in both the NAC (from 64.5 to 60.8%, p=0.001) and control groups (from 64.1 to 61.3%, p<0.001) after the completion of whole chemotherapy. The mean LVEF change did not differ between the two groups (-3.64% in NAC vs. -2.78% in control group, p=0.502). Left ventricular (LV) end systolic dimension increased with higher trend in NAC by 3.08±4.56 mm as compared with 1.47±1.83 mm in the control group (p=0.064). LV end diastolic dimension did not change in each group and change does not differ in both. Peak E, A and E/A ratio change and cardiac enzymes were comparable in two groups. Cumulative 12-month event rate was 6% and 3.8% in the NAC group and the control group, respectively, with no difference (p=0.672).

Conclusion

We cannot prove that NAC prevents anthracycline-induced cardiomyopathy.

Over-expression of calpastatin aggravates cardiotoxicity induced by doxorubicin

AIMS

Doxorubicin causes damage to the heart, which may present as cardiomyopathy. However, the mechanisms by which doxorubicin induces cardiotoxicity remain not fully understood and no effective prevention for doxorubicin cardiomyopathy is available. Calpains, a family of calcium-dependent thiol-proteases, have been implicated in cardiovascular diseases. Their activities are tightly controlled by calpastatin. This study employed transgenic mice over-expressing calpastatin to investigate the role of calpain in doxorubicin-induced cardiotoxicity.

METHODS AND RESULTS

Doxorubicin treatment decreased calpain activities in cultured neonatal mouse cardiomyocytes and in vivo mouse hearts, which correlated with down-regulation of calpain-1 and calpain-2 proteins. Over-expression of calpastatin or incubation with pharmacological calpain inhibitors enhanced apoptosis in neonatal and adult cardiomyocytes induced by doxorubicin. In contrast, over-expression of calpain-2 but not calpain-1 attenuated doxorubicin-induced apoptosis in cardiomyocytes. The pro-apoptotic effects of calpain inhibition were associated with down-regulation of protein kinase B (AKT) protein and mRNA expression, and a concomitant reduction in glycogen synthase kinase-3beta (GSK-3β) phosphorylation (Ser9) in doxorubicin-treated cardiomyocytes. Blocking AKT further increased doxorubicin-induced cardiac injuries, suggesting the effects of calpain inhibition may be mediated by inactivating the AKT signalling. In an in vivo model of doxorubicin-induced cardiotoxicity, over-expression of calpastatin exacerbated myocardial dysfunction as assessed by echocardiography and haemodynamic measurement in transgenic mice 5 days after doxorubicin injection. The 5-day mortality was higher in transgenic mice (29.16%) compared with their wild-type littermates (8%) after doxorubicin treatment.

CONCLUSION

Over-expression of calpastatin enhances doxorubicin-induced cardiac injuries through calpain inhibition and thus, calpains may protect cardiomyocytes against doxorubicin-induced cardiotoxicity.

Cardioprotective Effects of 20(S)-Ginsenoside Rh2 against Doxorubicin-Induced Cardiotoxicity In Vitro and In Vivo

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.

Protective effect of guggulsterone against cardiomyocyte injury induced by doxorubicin in vitro

BACKGROUND

Doxorubicin (DOX) is an effective antineoplastic drug; however, clinical use of DOX is limited by its dose-dependent cardiotoxicity. It is well known that reactive oxygen species (ROS) play a vital role in the pathological process of DOX-induced cardiotoxicity. For this study, we evaluated the protective effects of guggulsterone (GS), a steroid obtained from myrrh, to determine its preliminary mechanisms in defending against DOX-induced cytotoxicity in H9C2 cells.

METHODS

In this study, we used a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) release measurements, and Hoechst 33258 staining to evaluate the protective effect of GS against DOX-induced cytotoxicity in H9C2 cells. In addition, we observed the immunofluorescence of intracellular ROS and measured lipid peroxidation, caspase-3 activity, and apoptosis-related proteins by using Western blotting.

RESULTS

The MTT assay and LDH release showed that treatment using GS (1-30 μM) did not cause cytotoxicity. Furthermore, GS inhibited DOX (1 μM)-induced cytotoxicity in a concentration-dependent manner. Hoechst 33258 staining showed that GS significantly reduced DOX-induced apoptosis and cell death. Using GS at a dose of 10-30 μM significantly reduced intracellular ROS and the formation of MDA in the supernatant of DOX-treated H9C2 cells and suppressed caspase-3 activity to reference levels. In immunoblot analysis, pretreatment using GS significantly reversed DOX-induced decrease of PARP, caspase-3 and bcl-2, and increase of bax, cytochrome C release, cleaved-PARP and cleaved-caspase-3. In addition, the properties of DOX-induced cancer cell (DLD-1 cells) death did not interfere when combined GS and DOX.

CONCLUSION

These data provide considerable evidence that GS could serve as a novel cardioprotective agent against DOX-induced cardiotoxicity.

Thrombopoietin improved ventricular function and regulated remodeling genes in a rat model of myocardial infarction

BACKGROUND

Thrombopoietin (TPO) protects against heart damages by doxorubicin-induced cardiomyopathy in animal models. We aimed to investigate the therapeutic efficacy of TPO for treatment of myocardial infarction (MI) in a rat model and explored the mechanisms in terms of the genome-wide transcriptional profile, TPO downstream protein signals, and bone marrow endothelial progenitor cells (EPCs).

METHODS

Sprague-Dawley rats were divided into 3 groups: Sham-operated, MI (permanent ligation of the left coronary artery) and MI+TPO. Three doses of TPO were administered weekly for 2 weeks, and outcomes were assessed at 4 or 8 weeks post-injury.

RESULTS AND CONCLUSIONS

TPO treatment significantly improved left ventricular function, hemodynamic parameters, myocardium morphology, neovascularization and infarct size. MI damage upregulated a large cohort of gene expressions in the infarct border zone, including those functioned in cytoskeleton organization, vascular and matrix remodeling, muscle development, cell cycling and ion transport. TPO treatment significantly reversed these modulations. While phosphorylation of janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3) and protein kinase B (AKT) was modified in MI animals, TPO treatment regulated phosphorylation of STAT3 and extracellular signal-regulated kinases (ERK), and bone morphogenetic protein 1 (BMP1) protein level. TPO also increased EPC colonies in the bone marrow of MI animals. Our data showed that TPO alleviated damages of heart tissues from MI insults, possibly mediated by multi-factorial mechanisms including suppression of over-reacted ventricular remodeling, regulation of TPO downstream signals and mobilization of endothelial progenitor cells. TPO could be developed for treatment of cardiac damages.

Involvement of thrombopoietin in acinar cell necrosis in L-arginine-induced acute pancreatitis in mice

Thrombopoietin (TPO) plays an important role in injuries of different tissues. However, the role of TPO in acute pancreatitis (AP) is not yet known. The aim of the study was to determine the involvement of TPO in AP. Serum TPO was assayed in necrotizing pancreatitis induced by L-arginine in mice. Recombinant TPO and anti-TPO antibody were given to mice with necrotizing pancreatitis. Amylase, lipase, lactate dehydrogenase, myeloperoxidase activity and pancreatic water content were assayed in serum and tissue samples. Pancreas and lung tissue samples were also collected for histological evaluation. Immunohistochemistry of amylase α and PCNA were applied for the study of acinar regeneration and TUNEL assay for the detection of apoptosis in the pancreas. Increased levels of serum TPO were found in necrotizing pancreatitis. After TPO administration, more severe acinar necrosis was found and blockade of TPO reduced the acinar necrosis in this AP model. Acinar regeneration and apoptosis in the pancreas were affected by TPO and antibody treatment in necrotizing pancreatitis. The severity of pancreatitis-associated lung injury was worsened after TPO treatment, but attenuated after Anti-TPO antibody treatment. In conclusion, serum TPO is up-regulated in the necrotizing pancreatitis induced by L-arginine in mice and may be a risk factor for the pancreatic acinar necrosis in AP. As a pro-necrotic factor, blockade of TPO can attenuate the acinar necrosis in AP and may be a possible therapeutic intervention for AP.

Baicalein protects against doxorubicin-induced cardiotoxicity by attenuation of mitochondrial oxidant injury and JNK activation

The cardiotoxicity of doxorubicin limits its clinical use in the treatment of a variety of malignancies. Previous studies suggest that doxorubicin-associated cardiotoxicity is mediated by reactive oxygen species (ROS)-induced apoptosis. We therefore investigated if baicalein, a natural antioxidant component of Scutellaria baicalensis, could attenuate ROS generation and cell death induced by doxorubicin. Using an established chick cardiomyocyte model, doxorubicin (10 µM) increased cell death in a concentration- and time-dependent manner. ROS generation was increased in a dose-response fashion and associated with loss of mitochondrial membrane potential. Doxorubicin also augmented DNA fragmentation and increased the phosphorylation of ROS-sensitive pro-apoptotic kinase c-Jun N-terminal kinase (JNK). Adjunct treatment of baicalein (25 µM) and doxorubicin for 24 h significantly reduced both ROS generation (587 ± 89 a.u. vs. 932 a.u. ± 121 a.u., P < 0.01) and cell death (30.6 ± 5.1% vs. 46.8 ± 8.3%, P < 0.01). The dissipated mitochondrial potential and increased DNA fragmentation were also ameliorated. Along with the reduction of ROS and apoptosis, baicalein attenuated phosphorylation of JNK induced by doxorubicin (1.7 ± 0.3 vs. 3.0 ± 0.4-fold, P < 0.05). Co-treatment of cardiomyocytes with doxorubicin and JNK inhibitor SP600125 (10 µM; 24 h) reduced JNK phosphorylation and enhanced cell survival, suggesting that the baicalein protection against doxorubicin cardiotoxicity was mediated by JNK activation. Importantly, concurrent baicalein treatment did not interfere with the anti-proliferative effects of doxorubicin in human breast cancer MCF-7 cells. In conclusion, baicalein adjunct treatment confers anti-apoptotic protection against doxorubicin-induced cardiotoxicity without compromising its anti-cancer efficacy.

Thrombopoietin as biomarker and mediator of cardiovascular damage in critical diseases

Thrombopoietin (TPO) is a humoral growth factor originally identified for its ability to stimulate the proliferation and differentiation of megakaryocytes. In addition to its actions on thrombopoiesis, TPO directly modulates the homeostatic potential of mature platelets by influencing their response to several stimuli. In particular, TPO does not induce platelet aggregation per se but is able to enhance platelet aggregation in response to different agonists (“priming effect”). Our research group was actively involved, in the last years, in characterizing the effects of TPO in several human critical diseases. In particular, we found that TPO enhances platelet activation and monocyte-platelet interaction in patients with unstable angina, chronic cigarette smokers, and patients with burn injury and burn injury complicated with sepsis. Moreover, we showed that TPO negatively modulates myocardial contractility by stimulating its receptor c-Mpl on cardiomyocytes and the subsequent production of NO, and it mediates the cardiodepressant activity exerted in vitro by serum of septic shock patients by cooperating with TNF-α and IL-1β. This paper will summarize the most recent results obtained by our research group on the pathogenic role of elevated TPO levels in these diseases and discuss them together with other recently published important studies on this topic.

Mitochondria death/survival signaling pathways in cardiotoxicity induced by anthracyclines and anticancer-targeted therapies

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.

Chemotherapy-induced cardiotoxicity in women

Chemotherapy-induced cardiotoxicity (CIC) is a major complication found with some life-saving medications used to treat breast and other cancers. Cardiotoxicity may present immediately during treatment or years later. These patients need education, screening, preventive measures, prompt interventions, and proper follow-up. This article focuses on CIC in patients who have breast cancer, but the process of evaluation and treatment design applies to all types of cancer and organ toxicities. Comprehensive pretreatment history, examination, and testing are needed for proper diagnosis and staging. CIC and other toxicities need to be considered in drug selection, treatment sequencing, testing, and appropriate follow-up.

Histone deacetylase inhibitors augment doxorubicin-induced DNA damage in cardiomyocytes

Histone deacetylase inhibitors have emerged as a new class of anticancer therapeutics with suberoylanilide hydroxamic acid (Vorinostat) and depsipeptide (Romidepsin) already being approved for clinical use. Numerous studies have identified that histone deacetylase inhibitors will be most effective in the clinic when used in combination with conventional cancer therapies such as ionizing radiation and chemotherapeutic agents. One promising combination, particularly for hematologic malignancies, involves the use of histone deacetylase inhibitors with the anthracycline, doxorubicin. However, we previously identified that trichostatin A can potentiate doxorubicin-induced hypertrophy, the dose-limiting side-effect of the anthracycline, in cardiac myocytes. Here we have the extended the earlier studies and evaluated the effects of combinations of the histone deacetylase inhibitors, trichostatin A, valproic acid and sodium butyrate on doxorubicin-induced DNA double-strand breaks in cardiomyocytes. Using γH2AX as a molecular marker for the DNA lesions, we identified that all of the broad-spectrum histone deacetylase inhibitors tested augment doxorubicin-induced DNA damage. Furthermore, it is evident from the fluorescence photomicrographs of stained nuclei that the histone deacetylase inhibitors also augment doxorubicin-induced hypertrophy. These observations highlight the importance of investigating potential side-effects, in relevant model systems, which may be associated with emerging combination therapies for cancer.

Role of hypoxia-inducible factors in the dexrazoxane-mediated protection of cardiomyocytes from doxorubicin-induced toxicity

BACKGROUND AND PURPOSE

Iron aggravates the cardiotoxicity of doxorubicin, a widely used anticancer anthracycline, and the iron chelator dexrazoxane is the only agent protecting against doxorubicin cardiotoxicity; however, the mechanisms underlying the role of iron in doxorubicin-mediated cardiotoxicity and the protective role of dexrazoxane remain to be established. As iron is required for the degradation of hypoxia-inducible factors (HIF), which control the expression of antiapoptotic and protective genes, we tested the hypothesis that dexrazoxane-dependent HIF activation may mediate the cardioprotective effect of dexrazoxane.

EXPERIMENTAL APPROACH

Cell death, protein levels (by immunoblotting) and HIF-mediated transcription (using reporter constructs) were evaluated in the rat H9c2 cardiomyocyte cell line exposed to low doses of doxorubicin with or without dexrazoxane pretreatment. HIF levels were genetically manipulated by transfecting dominant-negative mutants or short hairpin RNA.

KEY RESULTS

Treatment with dexrazoxane induced HIF-1α and HIF-2α protein levels and transactivation capacity in H9c2 cells. It also prevented the induction of cell death and apoptosis by exposure of H9c2 cells to clinically relevant concentrations of doxorubicin. Suppression of HIF activity strongly reduced the protective effect of dexrazoxane. Conversely, HIF-1α overexpression protected against doxorubicin-mediated cell death and apoptosis also in cells not exposed to the chelator. Exposure to dexrazoxane increased the expression of the HIF-regulated, antiapoptotic proteins survivin, Mcl1 and haem oxygenase.

CONCLUSIONS AND IMPLICATIONS

Our results showing HIF-dependent prevention of doxorubicin toxicity in dexrazoxane-treated H9c2 cardiomyocytes suggest that HIF activation may be a mechanism contributing to the protective effect of dexrazoxane against anthracycline cardiotoxicity.

Flavaglines alleviate doxorubicin cardiotoxicity: implication of Hsp27

Background

Despite its effectiveness in the treatment of various cancers, the use of doxorubicin is limited by a potentially fatal cardiomyopathy. Prevention of this cardiotoxicity remains a critical issue in clinical oncology. We hypothesized that flavaglines, a family of natural compounds that display potent neuroprotective effects, may also alleviate doxorubicin-induced cardiotoxicity.

Methodology/Principal Findings

Our in vitro data established that a pretreatment with flavaglines significantly increased viability of doxorubicin-injured H9c2 cardiomyocytes as demonstrated by annexin V, TUNEL and active caspase-3 assays. We demonstrated also that phosphorylation of the small heat shock protein Hsp27 is involved in the mechanism by which flavaglines display their cardioprotective effect. Furthermore, knocking-down Hsp27 in H9c2 cardiomyocytes completely reversed this cardioprotection. Administration of our lead compound (FL3) to mice attenuated cardiomyocyte apoptosis and cardiac fibrosis, as reflected by a 50% decrease of mortality.

Conclusions/Significance

These results suggest a prophylactic potential of flavaglines to prevent doxorubicin-induced cardiac toxicity.

Activation of AMP-activated protein kinase contributes to doxorubicin-induced cell death and apoptosis in cultured myocardial H9c2 cells

Despite its potent antitumor effect, clinical use of Doxorubicin is limited because of serious side effects including myocardial toxicity. Understanding the cellular mechanism involved in this process in a better manner is beneficial for optimizing Doxorubicin treatment. In the current study, the authors focus on the AMP-activated protein kinase (AMPK) in the said process. In this study, the authors discovered for the first time that Doxorubicin induces AMPK activation in cultured rat embryonic ventricular myocardial H9c2 cells. Reactive oxygen species (ROS)-dependent LKB1 activation serves as the upstream signal for AMPK activation by Doxorubicin. Evidence in support of the activation of AMPK contributing to Doxorubicin-induced H9c2 cell death/apoptosis--probably by modulating multiple downstream signal targets, including regulating JNK, p53, and inhibiting mTORC1--is provided in this article.

Haploinsufficiency of target of rapamycin attenuates cardiomyopathies in adult zebrafish

RATIONALE

Although a cardioprotective function of target of rapamycin (TOR) signaling inhibition has been suggested by pharmacological studies using rapamycin, genetic evidences are still lacking. We explored adult zebrafish as a novel vertebrate model for dissecting signaling pathways in cardiomyopathy.

OBJECTIVE

We generated the second adult zebrafish cardiomyopathy model induced by doxorubicin. By genetically analyzing both the doxorubicin and our previous established anemia-induced cardiomyopathy models, we decipher the functions of TOR signaling in cardiomyopathies of different etiology.

METHODS AND RESULTS

Along the progression of both cardiomyopathy models, we detected dynamic TOR activity at different stages of pathogenesis as well as distinct effects of TOR signaling inhibition. Nevertheless, cardiac enlargement in both models can be effectively attenuated by inhibition of TOR signaling through short-term rapamycin treatment. To assess the long-term effects of TOR reduction, we used a zebrafish target of rapamycin (ztor) mutant identified from an insertional mutagenesis screen. We show that TOR haploinsufficiency in the ztor heterozygous fish improved cardiac function, prevented pathological remodeling events, and ultimately reduced mortality in both adult fish models of cardiomyopathy. Mechanistically, these cardioprotective effects are conveyed by the antihypertrophy, antiapoptosis, and proautophagy function of TOR signaling inhibition.

CONCLUSIONS

Our results prove adult zebrafish as a conserved novel vertebrate model for human cardiomyopathies. Moreover, we provide the first genetic evidence to demonstrate a long-term cardioprotective effect of TOR signaling inhibition on at least 2 cardiomyopathies of distinct etiology, despite dynamic TOR activities during their pathogenesis.

Oxidative stress markers may not be early markers of doxorubicin-induced cardiotoxicity in rabbits

This study was performed to determine whether oxidative stress markers may be early markers of doxorubicin-induced cardiotoxicity. Forty-four male rabbits were randomly divided into four doxorubicin groups and one control group (8 rabbits). The control group received saline, and rabbits in the doxorubicin groups received 2 mg/kg doxorubicin weekly for 1 (group 1, 8 rabbits), 2 (group 2, 8 rabbits), 4 (group 3, 9 rabbits) or 8 (group 4, 11 rabbits) weeks. Echocardiography was performed to measure left ventricular ejection fraction, fractional shortening and the E/A ratio. Cardiotoxicity scores were determined by light microscopy using Billingham's method and by electron microscopy. Serum glutathione peroxidase (GPx) and superoxide dismutase (SOD) concentrations were quantified by a rabbit-specific enzyme-linked immunosorbent assay (ELISA). The Billingham cardiomyopathy scores for the rabbits in groups 3 or 4 were significantly higher (p<0.05) compared to the scores for the control group or groups 1 and 2. Myocardial injury was demonstrable by electron microscopy in groups 2, 3 and 4 (p<0.05). Serum GPx concentrations decreased only in group 4 compared to the control group (p<0.05). No changes were measured in serum SOD concentration. The results indicate that oxidative stress markers may not be early markers of doxorubicin-induced cardiotoxicity.

Trichostatin A accentuates doxorubicin-induced hypertrophy in cardiac myocytes

Histone deacetylase inhibitors represent a new class of anticancer therapeutics and the expectation is that they will be most effective when used in combination with conventional cancer therapies, such as the anthracycline, doxorubicin. The dose-limiting side effect of doxorubicin is severe cardiotoxicity and evaluation of the effects of combinations of the anthracycline with histone deacetylase inhibitors in relevant models is important. We used a well-established in vitro model of doxorubicin-induced hypertrophy to examine the effects of the prototypical histone deacetylase inhibitor, Trichostatin A. Our findings indicate that doxorubicin modulates the expression of the hypertrophy-associated genes, ventricular myosin light chain-2, the alpha isoform of myosin heavy chain and atrial natriuretic peptide, an effect which is augmented by Trichostatin A. Furthermore, we show that Trichostatin A amplifies doxorubicin-induced DNA double strand breaks, as assessed by γH2AX formation. More generally, our findings highlight the importance of investigating potential side effects that may be associated with emerging combination therapies for cancer.

Beneficial effects of carbon monoxide-releasing molecule-2 (CORM-2) on acute doxorubicin cardiotoxicity in mice: role of oxidative stress and apoptosis

Doxorubicin (DXR) has been used in variety of human malignancies for decades. Despite its efficacy in cancer, clinical usage is limited because of its cardiotoxicity, which has been associated with oxidative stress and apoptosis. Carbon monoxide-releasing molecules (CORMs) have been shown to reduce the oxidative damage and apoptosis. The present study investigated the effects of CORM-2, a fast CO-releaser, against DXR-induced cardiotoxicity in mice using biochemical, histopathological and gene expression approaches. CORM-2 (3, 10 and 30 mg/kg/day) was administered intraperitoneally (i.p.) for 10 days and terminated the study on day 11. DXR (20 mg/kg, i.p.) was injected before 72 h of termination. Mice treated with DXR showed cardiotoxicity as evidenced by elevation of serum creatine kinase (CK) and lactate dehydrogenase (LDH), tissue malondialdehyde (MDA), caspase-3 and decrease the level of total antioxidant status (TAS) in heart tissues. Pre- and post-treatment with CORM-2 (30 mg/kg, i.p.) elicited significant improvement in CK, LDH, MDA, caspase-3 and TAS levels. Histopathological studies showed that cardiac damage with DXR has been reversed with CORM-2+DXR treatment. There was dramatic decrease in hematological count in DXR-treated mice, which has been improved with CORM-2. Furthermore, there was also elevation of mRNA expression of heme oxygenase-1, hypoxia inducible factor-1 alpha, vascular endothelial growth factor and decrease in inducible-nitric oxide synthase expression upon treatment with CORM-2 that might be linked to cardioprotection. These data suggest that CORM-2 treatment provides cardioprotection against acute doxorubicin-induced cardiotoxicity in mice and this effect may be attributed to CORM-2-mediated antioxidant and anti-apoptotic properties.

Resveratrol attenuates doxorubicin-induced cardiomyocyte apoptosis in mice through SIRT1-mediated deacetylation of p53

AIMS

Doxorubicin (DOX) is an anthracycline drug with a wide spectrum of clinical antineoplastic activity, but increased apoptosis has been implicated in its cardiotoxicity. Resveratrol (RES) was shown to harbour major health benefits in diseases associated with oxidative stress. In this study, we aimed to determine the effect of RES on DOX-induced myocardial apoptosis in mice.

METHODS AND RESULTS

Male Balb/c mice were randomized to one of the following four treatments: saline, RES, DOX, or RES plus DOX (10 mice in each group). DOX treatment markedly depressed cardiac function, decreased the heart weight, the body weight, and the ratio of heart weight to body weight, but inversely increased the level of protein carbonyl, malondialdehyde, and serum lactate dehydrogenase, and induced mitochondrial cytochrome c release and cardiomyocyte apoptosis. However, these effects of DOX were ameliorated by its combination with RES. Further studies with a co-immunoprecipitation assay revealed an interaction between p53 and Sirtuin 1 (SIRT1). It was found by western blot and electrophoretic mobility shift assay that DOX treatment increased p53 protein acetylation and cytochrome c release from mitochondria, activated p53 binding at the Bax promoter, and up-regulated Bax expression, but supplementation with RES could weaken all these effects.

CONCLUSION

The protective effect of RES against DOX-induced cardiomyocyte apoptosis is associated with the up-regulation of SIRT1-mediated p53 deacetylation.

A novel role of thrombopoietin as a physiological modulator of coronary flow

Thrombopoietin (TPO) is known for its ability to stimulate platelet production. However, little is currently known whether TPO plays a physiological function in the heart. The potential vasodilatory role of TPO was tested on the isolated rat heart. The expression of TPO receptor (c-mpl) and the TPO-dependent eNOS phosphorylation (P(Ser1179)) were studied on Cardiac-derived normal Human Micro Vascular Endothelial Cells (HMVEC-C) by Western blot analysis. While TPO (10-200 pg/mL) did not modify coronary flow (CF) under basal conditions, it reduced the coronary constriction caused by endothelin-1 (ET-1; 10nM) in a dose-dependent manner. This effect was blocked by both Wortmannin (100 nM) and L-NAME (100 nM); on HMVEC-C, TPO induced eNOS phosphorylation through a Wortmannin sensitive mechanism. Taken together, our data suggest a potential role of TPO as a physiological regulator of CF. By acting on specific receptors present on endothelial cells, TPO may induce PI3K/Akt-dependent eNOS phosphorylation and NO release.

Cardioprotective effect of dexrazoxane in a rat model of myocardial infarction: anti-apoptosis and promoting angiogenesis

OBJECTIVES

Dexrazoxane (DZR) is a clinically approved agent for preventive treatment of doxorubicin-induced cardiotoxicity. The objective of this study was to investigate the cardioprotective effects of DZR in a rat model of myocardial infarction (MI).

METHODS

Sprague-Dawley rats were randomly divided into four groups: MI (n = 16), MI + DZR (n = 16), SHAM-operated (n = 14) and DZR-only (n = 9). MI animals were subjected to left anterior descending coronary artery ligation. DZR was administered as a single dose at 125 mg/kg intraperitoneally. Four weeks after treatment, cardiac function by echocardiography, infarct size, capillary density in the infarct border zone, bone marrow-derived endothelial progenitor cells (EPCs), and cardiac expression of Bax were measured.

RESULTS

Our results demonstrated that MI animals had compromised heart parameters. DZR treatment in MI animals resulted in reduction in infarct size (P = 0.013) and improved cardiac functions in terms of fractional shortening (P = 0.004) and ejection fraction (P = 0.004). The capillary density (P = 0.008) and bone marrow-derived EPCs (P < 0.05) were higher in the MI + DZR group than those in the untreated MI group. Bax expression was down-regulated in heart tissues of MI + DZR animals (P = 0.043).

CONCLUSIONS

Our study demonstrated that DZR exerted a cardioprotective effect in the rat model of MI, and the mechanism might be associated with anti-apoptosis and increased neovascularization.

Platelet-derived growth factor enhances platelet recovery in a murine model of radiation-induced thrombocytopenia and reduces apoptosis in megakaryocytes via its receptors and the PI3-k/Akt pathway

BACKGROUND

Platelet-derived growth factor is involved in the regulation of hematopoiesis. Imatinib mesylate, a platelet-derived growth factor receptor inhibitor, induces thrombocytopenia in a significant proportion of patients with chronic myeloid leukemia. Although our previous studies showed that platelet-derived growth factor enhances megakaryocytopoiesis in vitro, the in vivo effect of platelet-derived growth factor in a model of radiation-induced thrombocytopenia has not been reported.

DESIGN AND METHODS

In this study, we investigated the effect of platelet-derived growth factor on hematopoietic stem/progenitor cells and platelet production using an irradiated-mouse model. We also explored the potential molecular mechanisms of platelet-derived growth factor on thrombopoiesis in M-07e cells.

RESULTS

Platelet-derived growth factor, like thrombopoietin, significantly promoted the recovery of platelets and the formation of bone marrow colony-forming unit-megakaryocyte in irradiated mice. Histology confirmed the protective effect of platelet-derived growth factor, as shown by an increased number of hematopoietic stem/progenitor cells and a reduction of apoptosis. In a megakaryocytic apoptotic model, platelet-derived growth factor had a similar anti-apoptotic effect as thrombopoietin on megakaryocytes. We also demonstrated that platelet-derived growth factor activated the PI3-k/Akt signaling pathway, while addition of imatinib mesylate reduced p-Akt expression.

CONCLUSIONS

Our findings show that platelet-derived growth factor enhances platelet recovery in mice with radiation-induced thrombocytopenia. This radioprotective effect is likely to be mediated via platelet-derived growth factor receptors with subsequent activation of the PI3-k/Akt pathway. We also provide a possible explanation that blockage of platelet-derived growth factor receptors may reduce thrombopoiesis and play a role in imatinib mesylate-induced thrombocytopenia.

Acute doxorubicin cardiotoxicity is associated with miR-146a-induced inhibition of the neuregulin-ErbB pathway

Aims

A significant increase in congestive heart failure (CHF) was reported when the anti-ErbB2 antibody trastuzumab was used in combination with the chemotherapy drug doxorubicin (Dox). The aim of the present study was to investigate the role(s) of miRNAs in acute Dox-induced cardiotoxicity.

Methods and results

Neuregulin-1-ErbB signalling is essential for maintaining adult cardiac function. We found a significant reduction in ErbB4 expression in the hearts of mice after Dox treatment. Because the proteasome pathway was only partially involved in the reduction of ErbB4 expression, we examined the involvement of microRNAs (miRs) in the reduction of ErbB4 expression. miR-146a was shown to be up-regulated by Dox in neonatal rat cardiac myocytes. Using a luciferase reporter assay and overexpression of miR-146a, we confirmed that miR-146a targets the ErbB4 3′UTR. After Dox treatment, overexpression of miR-146a, as well as that of siRNA against ErbB4, induced cell death in cardiomyocytes. Re-expression of ErbB4 in miR-146a-overexpressing cardiomyocytes ameliorated Dox-induced cell death. To examine the loss of miR-146a function, we constructed ‘decoy’ genes that had tandem complementary sequences for miR-146a in the 3′UTR of a luciferase gene. When miR-146a ‘decoy’ genes were introduced into cardiomyocytes, ErbB4 expression was up-regulated and Dox-induced cell death was reduced.

Conclusion

These findings suggested that the up-regulation of miR-146a after Dox treatment is involved in acute Dox-induced cardiotoxicity by targeting ErbB4. Inhibition of both ErbB2 and ErbB4 signalling may be one of the reasons why those patients who receive concurrent therapy with Dox and trastuzumab suffer from CHF.

Thrombopoietin modulates cardiac contractility in vitro and contributes to myocardial depressing activity of septic shock serum

Thrombopoietin (TPO) is a humoral growth factor that has been shown to increase platelet activation in response to several agonists. Patients with sepsis have increased circulating TPO levels, which may enhance platelet activation, potentially participating to the pathogenesis of multi-organ failure. Aim of this study was to investigate whether TPO affects myocardial contractility and participates to depress cardiac function during sepsis. We showed the expression of the TPO receptor c-Mpl on myocardial cells and tissue by RT-PCR, immunofluorescence and western blotting. We then evaluated the effect of TPO on the contractile function of rat papillary muscle and isolated heart. TPO did not change myocardial contractility in basal conditions, but, when followed by epinephrine (EPI) stimulation, it blunted the enhancement of contractile force induced by EPI both in papillary muscle and isolated heart. An inhibitor of TPO prevented TPO effect on cardiac inotropy. Treatment of papillary muscle with pharmacological inhibitors of phosphatidylinositol 3-kinase, NO synthase, and guanilyl cyclase abolished TPO effect, indicating NO as the final mediator. We finally studied the role of TPO in the negative inotropic effect exerted by human septic shock (HSS) serum and TPO cooperation with TNF-alpha and IL-1beta. Pre-treatment with the TPO inhibitor prevented the decrease in contractile force induced by HSS serum. Moreover, TPO significantly amplified the negative inotropic effect induced by TNF-alpha and IL-1beta in papillary muscle. In conclusion, TPO negatively modulates cardiac inotropy in vitro and contributes to the myocardial depressing activity of septic shock serum.

Attenuation of Doxorubicin-induced cardiomyopathy by endothelin-converting enzyme-1 ablation through prevention of mitochondrial biogenesis impairment

Doxorubicin is an effective antineoplastic drug; however, its clinical benefit is limited by its cardiotoxicity. The inhibition of mitochondrial biogenesis is responsible for the pathogenesis of doxorubicin-induced cardiomyopathy. Endothelin-1 is a vasoconstrictive peptide produced from big endothelin-1 by endothelin-converting enzyme-1 (ECE-1) and a multifunctional peptide. Although plasma endothelin-1 levels are elevated in patients treated with doxorubicin, the effect of ECE-1 inhibition on doxorubicin-induced cardiomyopathy is not understood. Cardiomyopathy was induced by a single IP injection of doxorubicin (15 mg/kg). Five days after treatment, cardiac function, histological change, and mitochondrial biogenesis were assessed. Echocardiography revealed that cardiac systolic function was significantly deteriorated in doxorubicin-treated wild-type (ECE-1(+/+)) mice compared with ECE-1 heterozygous knockout (ECE-1(+/-)) mice. In histological analysis, cardiomyocyte size in ECE-1(+/-) mice was larger, and cardiomyocyte damage was less. In ECE-1(+/+) mice, tissue adenosine triphosphate content and mitochondrial superoxide dismutase were decreased, and reactive oxygen species generation was increased compared with ECE-1(+/-) mice. Cardiac mitochondrial deoxyribonucleic acid copy number and expressions of key regulators for mitochondrial biogenesis were decreased in ECE-1(+/+) mice. Cardiac cGMP content and serum atrial natriuretic peptide concentration were increased in ECE-1(+/-) mice. In conclusion, the inhibition of ECE-1 attenuated doxorubicin-induced cardiomyopathy by inhibiting the impairment of cardiac mitochondrial biogenesis. This was mainly induced by decreased endothelin-1 levels and an enhanced atrial natriuretic peptide-cGMP pathway. Thus, the inhibition of ECE-1 may be a new therapeutic strategy for doxorubicin-induced cardiomyopathy.

Thrombopoietin limits IL-6 release but fails to attenuate liver injury in two hepatic stress models

OBJECTIVE

Various pleiotropic substances have been suggested as candidates that directly reduce the severity of liver injury after hepatic ischemia/reperfusion (I/R) and upon acute liver failure (ALF). Herein, we studied whether thrombopoietin (TPO), the main regulator of megakaryopoiesis and thrombopoiesis, showed hepatoprotective effects and might mediate an antiapoptotic function in liver tissue under stress.

METHODS/RESULTS

In livers with ALF or undergoing warm hepatic I/R, injury was quantified by intravital fluorescence microscopy, chemical, and immunohistochemical analysis as well as western immunoblot. Induction of both ALF and I/R injury led to hepatocellular expression of c-mpl, the receptor of TPO. Exogenous application of recombinant TPO in a low (12.5 microg/kg) as well as a high (75 microg/kg) dose, however, did not ameliorate postischemic perfusion and leukocyte endothelial cell interaction, but slightly aggravated transaminase release upon I/R. Similarly, TPO was unable to dampen hepatic microcirculatory deteriorations after the induction of ALF, but caused an increase of leukocyte accumulation and transaminase activity when applied in high dose. Low dose of TPO did not influence the amount of hepatocellular apoptosis, whereas high-dose TPO slightly diminished the activation of caspase 3. Interestingly, exogenous TPO application completely reversed the stress-induced increase of plasma IL-6 levels, suggesting a negative feedback of TPO on IL-6 release.

CONCLUSION

Although the existence of the TPO-receptor on target liver cells TPO plays only a minor role in mediating hepatocyte apoptosis and does not provide protection against hepatic injury, contrasting the efficacy of the related hematopoietic growth factor erythropoietin.

Doxorubicin-induced platelet cytotoxicity: a new contributory factor for doxorubicin-mediated thrombocytopenia

BACKGROUND

Doxorubicin (DOX) is a widely used anticancer drug for solid tumors and hematologic malignancy, but its active use is hampered by serious adverse effects, including thrombocytopenia. Although bone marrow toxicity of DOX has been suggested to be the sole mechanism underlying the reduced platelet counts, the direct effects of DOX on platelets have never been examined.

OBJECTIVE

Here, we investigated the DOX-induced platelet cytotoxicity and its underlying mechanism in an effort to elucidate the contribution of platelet cytotoxicity to DOX-induced thrombocytopenia.

RESULTS

In freshly isolated human platelets, DOX induced platelet cytotoxicity in a time-dependent and concentration-dependent manner. Reactive oxygen species (ROS) generation, decreased glutathione levels and subsequent protein thiol depletion were shown to underlie the DOX-induced platelet cytotoxicity. Conspicuously, DOX-treated platelets displayed apoptotic features such as caspase-3 activation, reduced mitochondrial transmembrane potential, and phosphatidylserine exposure. Decreased glutathiolation of procaspase-3 was shown to be a link between protein thiol depletion and caspase-3 activation. It is of note that DOX-mediated platelet cytotoxicity was significantly enhanced by shear stress, a common complicating factor in cancer patients. These in vitro results were further confirmed by an in vivo animal model, where administration of DOX induced a platelet count decrease, ROS generation, caspase-3 activation, protein thiol depletion, and damaged platelet integrity.

CONCLUSION

We demonstrated that DOX can directly induce platelet cytotoxicity through ROS generation, decreased glutathione levels, and protein thiol depletion. We believe that this study provides important evidence for the role of DOX-induced platelet cytotoxicity in the development of thrombocytopenia in DOX-treated patients.

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.

Tanshinone IIA sodium sulfonate protects against cardiotoxicity induced by doxorubicin in vitro and in vivo

Although doxorubicin (DXR) is an effective antineoplastic agent; the serious cardiotoxicity mediated by the production of reactive oxygen species has remained a considerable clinical problem. Our hypothesis is that tanshinone IIA sodium sulfonate (TSNIIA-SS), which holds significant affects on cardioprotection in clinic, protects against DXR-induced cardiotoxicity. In vitro investigation on H9c2 cell line, as well as in vivo study in animal model of DXR-induced chronic cardiomyopathy were performed. TSNIIA-SS significantly increased cell viability and ameliorated apoptosis of DXR-injured H9c2 cells using CCK-8 assay and Hoechst 33342 stain respectively. Furthermore, the cardio-protective effects of TSNIIA-SS were confirmed with decreasing ST-interval and QRS interval by electrocardiography (ECG); improving appearance of myocardium with haematoxylin and eosin (H&E) stain; increasing myocardial tensile strength using tension to rupture (TTR) assay and decreasing fibrosis through picric-sirius red staining comparing with those receiving DXR alone. These data have provided the considerable evidences that TSNIIA-SS is a protective agent against DXR-induced cardiac injury.

Herba leonurine attenuates doxorubicin-induced apoptosis in H9c2 cardiac muscle cells

Doxorubicin (DOX) is a highly effective antineoplastic drug. However, DOX-induced apoptosis in cardiomyocytes leads to irreversible degenerative cardiomyopathy and heart failure, which limits DOX clinical application. Leonurine is a special alkaloid for Herba leonuri, a traditional herb with cardioprotective effects. In current study, we investigated possible protective effects of Leonurine against DOX-induced cardiomyopathy in H9c2 cells. DOX-injured H9c2 cell model was made by application of 2 microM DOX. Leonurine was added to cells 2 h before DOX treatment. Pre-treated with Leonurine could attenuate DOX-induced apoptotic death of H9c2 cell, reduce MDA formation and intracellular Ca2+ overload. Leonurine also attenuated DOX-induced high expression of Bax, increased Bcl-2 expression in both protein and mRNA level. Myocardial mitochondrion is the target organelle of DOX-induced toxicity in cardiomyocytes. Leonurine moderated the dissipation of mitochondrial membrane potential (DeltaPsim) caused by DOX treatment. Our results indicated that Leonurine attenuated DOX-induced apoptosis in H9c2 cell by increasing anti-oxidant, anti-apoptotic ability and protecting mitochondrial function.

Role of superoxide, nitric oxide, and peroxynitrite in doxorubicin-induced cell death in vivo and in vitro

Doxorubicin (DOX) is a potent available antitumor agent; however, its clinical use is limited because of its cardiotoxicity. Cell death is a key component in DOX-induced cardiotoxicity, but its mechanisms are elusive. Here, we explore the role of superoxide, nitric oxide (NO), and peroxynitrite in DOX-induced cell death using both in vivo and in vitro models of cardiotoxicity. Western blot analysis, real-time PCR, immunohistochemistry, flow cytometry, fluorescent microscopy, and biochemical assays were used to determine the markers of apoptosis/necrosis and sources of NO and superoxide and their production. Left ventricular function was measured by a pressure-volume system. We demonstrated increases in myocardial apoptosis (caspase-3 cleavage/activity, cytochrome c release, and TUNEL), inducible NO synthase (iNOS) expression, mitochondrial superoxide generation, 3-nitrotyrosine (NT) formation, matrix metalloproteinase (MMP)-2/MMP-9 gene expression, poly(ADP-ribose) polymerase activation [without major changes in NAD(P)H oxidase isoform 1, NAD(P)H oxidase isoform 2, p22(phox), p40(phox), p47(phox), p67(phox), xanthine oxidase, endothelial NOS, and neuronal NOS expression] and decreases in myocardial contractility, catalase, and glutathione peroxidase activities 5 days after DOX treatment to mice. All these effects of DOX were markedly attenuated by peroxynitrite scavengers. Doxorubicin dose dependently increased mitochondrial superoxide and NT generation and apoptosis/necrosis in cardiac-derived H9c2 cells. DOX- or peroxynitrite-induced apoptosis/necrosis positively correlated with intracellular NT formation and could be abolished by peroxynitrite scavengers. DOX-induced cell death and NT formation were also attenuated by selective iNOS inhibitors or in iNOS knockout mice. Various NO donors when coadministered with DOX but not alone dramatically enhanced DOX-induced cell death with concomitant increased NT formation. DOX-induced cell death was also attenuated by cell-permeable SOD but not by cell-permeable catalase, the xanthine oxidase inhibitor allopurinol, or the NADPH oxidase inhibitors apocynine or diphenylene iodonium. Thus, peroxynitrite is a major trigger of DOX-induced cell death both in vivo and in vivo, and the modulation of the pathways leading to its generation or its effective neutralization can be of significant therapeutic benefit.

Granulocyte colony-stimulating factor protects cardiac mitochondria in the early phase of cardiac injury

Although granulocyte colony-stimulating factor (G-CSF) reportedly plays a cardioprotective role in several models of cardiac injury, clinical use of this drug in cardiac patients has been controversial. Here, we tested, in vivo and in vitro, the effect of G-CSF on cardiac mitochondria, which play a key role in determining cardiac cellular fate and function. Mild stimulation of C57/BL6 mice with doxorubicin (Dox) did not induce cardiac apoptosis or fibrosis but did induce damage to mitochondrial organization of the myocardium as observed through an electron microscope. Cardiac catheterization and echocardiography revealed that Dox did not alter cardiac systolic function or left ventricular size but did reduce diastolic function, an early sign of cardiac damage. Treatment with G-CSF attenuated significantly the damage to mitochondrial organization and rescued diastolic function. In an in vitro model for rat neonatal cardiomyocytes, a subapoptotic dose of Dox induced severe mitochondrial damage, including marked swelling of the cardiac mitochondria and/or decreased mitochondrial membrane potential. These mitochondrial changes were completely blocked by pretreatment with G-CSF. In addition, G-CSF dramatically improved ATP generation, which rescued Dox-impaired mitochondrial electron transport and oxygen consumption mainly through complex IV. These findings clearly indicate that G-CSF protects cardiac mitochondria, which are key organelles in the determination of cardiac cellular fate, in the early phase of cardiac injury.

Cardiomyocyte death in doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is one of the most widely used and successful antitumor drugs, but its cumulative and dose-dependent cardiac toxicity has been a major concern of oncologists in cancer therapeutic practice for decades. With the increasing population of cancer survivors, there is a growing need to develop preventive strategies and effective therapies against DOX-induced cardiotoxicity, in particular late-onset cardiomyopathy. Although intensive investigations on DOX-induced cardiotoxicity have continued for decades, the underlying mechanisms responsible for DOX-induced cardiotoxicity have not been completely elucidated. A rapidly expanding body of evidence supports the notion that cardiomyocyte death by apoptosis and necrosis is a primary mechanism of DOX-induced cardiomyopathy and that other types of cell death, such as autophagy and senescence/aging, may participate in this process. This review focuses on the current understanding of the 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. The different sensitivities to DOX-induced cell death signals between adult and young cardiomyocytes will also be discussed.

Acute doxorubicin cardiotoxicity is associated with p53-induced inhibition of the mammalian target of rapamycin pathway

BACKGROUND

Doxorubicin is used to treat childhood and adult cancer. Doxorubicin treatment is associated with both acute and chronic cardiotoxicity. The cardiotoxic effects of doxorubicin are cumulative, which limits its chemotherapeutic dose. Free radical generation and p53-dependent apoptosis are thought to contribute to doxorubicin-induced cardiotoxicity.

METHODS AND RESULTS

Adult transgenic (MHC-CB7) mice expressing cardiomyocyte-restricted dominant-interfering p53 and their nontransgenic littermates were treated with doxorubicin (20 mg/kg cumulative dose). Nontransgenic mice exhibited reduced left ventricular systolic function (predoxorubicin fractional shortening [FS] 61+/-2%, postdoxorubicin FS 45+/-2%, mean+/-SEM, P<0.008), reduced cardiac mass, and high levels of cardiomyocyte apoptosis 7 days after the initiation of doxorubicin treatment. In contrast, doxorubicin-treated MHC-CB7 mice exhibited normal left ventricular systolic function (predoxorubicin FS 63+/-2%, postdoxorubicin FS 60+/-2%, P>0.008), normal cardiac mass, and low levels of cardiomyocyte apoptosis. Western blot analyses indicated that mTOR (mammalian target of rapamycin) signaling was inhibited in doxorubicin-treated nontransgenic mice but not in doxorubicin-treated MHC-CB7 mice. Accordingly, transgenic mice with cardiomyocyte-restricted, constitutively active mTOR expression (MHC-mTORca) were studied. Left ventricular systolic function (predoxorubicin FS 64+/-2%, postdoxorubicin FS 60+/-3%, P>0.008) and cardiac mass were normal in doxorubicin-treated MHC-mTORca mice, despite levels of cardiomyocyte apoptosis similar to those seen in doxorubicin-treated nontransgenic mice.

CONCLUSIONS

These data suggest that doxorubicin treatment induces acute cardiac dysfunction and reduces cardiac mass via p53-dependent inhibition of mTOR signaling and that loss of myocardial mass, and not cardiomyocyte apoptosis, is the major contributor to acute doxorubicin cardiotoxicity.

Chemotherapy-induced cardiotoxicity in women

Chemotherapy-induced cardiotoxicity (CIC) is a major complication found with some life-saving medications used to treat breast and other cancers. Cardiotoxicity may present immediately during treatment or years later. These patients need education, screening, preventive measures, prompt interventions, and proper follow-up. This article focuses on CIC in patients who have breast cancer, but the process of evaluation and treatment design applies to all types of cancer and organ toxicities. Comprehensive pretreatment history, examination, and testing are needed for proper diagnosis and staging. CIC and other toxicities need to be considered in drug selection, treatment sequencing, testing, and appropriate follow-up.

A mouse model for juvenile doxorubicin-induced cardiac dysfunction

Doxorubicin (DOX) is a potent antitumor agent. DOX can also induce cardiotoxicity, and high cumulative doses are associated with recalcitrant heart failure. Children are particularly sensitive to DOX-induced heart failure. The ability to genetically modify mice makes them an ideal experimental system to study the molecular basis of DOX-induced cardiotoxicity. However, most mouse DOX studies rely on acute drug administration in adult animals, which typically are analyzed within 1 wk. Here, we describe a juvenile mouse model of chronic DOX-induced cardiac dysfunction. DOX treatment was initiated at 2 wk of age and continued for a period of 5 wk (25 mg/kg cumulative dose). This resulted in a decline in cardiac systolic function, which was accompanied by marked atrophy of the heart, low levels of cardiomyocyte apoptosis, and decreased growth velocity. Other animals were allowed to recover for 13 wk after the final DOX injection. Cardiac systolic function improved during this recovery period but remained depressed compared with the saline injected controls, despite the reversal of cardiac atrophy. Interestingly, increased levels of cardiomyocyte apoptosis and concomitant myocardial fibrosis were observed after DOX withdrawal. These data suggest that different mechanisms contribute to cardiac dysfunction during the treatment and recovery phases.

Hexane/ethanol extract of Glycyrrhiza uralensis licorice suppresses doxorubicin-induced apoptosis in H9c2 rat cardiac myoblasts

Doxorubicin (DOX) is an anthracycline antibiotic, and has been recognized as one of the most effective anti-neoplastic agents in cancer chemotherapy. However, its usefulness is limited by its profound cardiotoxicity. Licorice is one of the most frequently prescribed agents in traditional herbal medicine, and is also employed as a natural sweetening additive. In traditional Chinese medicine, licorice root is added to a variety of herbal preparations to detoxify the effects of the other herbs in the preparation. In the present study, we explored the possibility that Glycyrrhiza uralensis licorice may alleviate DOX-induced cardiotoxicity. The hexane/ethanol extract of Glycyrrhiza uralensis (HEGU), which lacks glycyrrhizin, was prepared because glycyrrhizin intake has previously been reported to induce hypertension. In an effort to determine whether HEGU ameliorates DOX-induced cytotoxicity in H9c2 rat cardiac myoblasts, the cells were pretreated with 0-15 mg/L HEGU, then treated with doxorubicin. The pretreatment of cells with HEGU resulted in a significant mitigation of DOX-induced reductions in cell numbers (34 +/- 7%) and increases in apoptosis (53 +/- 1%). The Western blot analysis of cell lysates showed that HEGU suppressed DOX-induced increases in the levels of p53, phospho-p53 (Ser 15), and Bax. In addition, HEGU induced an increase in the levels of Bcl-xL, regardless of DOX-treatment. HEGU inhibited the DOX-induced cleavage of caspases 9, 3, and 7, as well as DOX-induced poly(ADP-ribose) polymerase cleavage. Furthermore, HEGU caused reductions in the viable cell numbers of HT-29 human colon cancer cells (IC50 = 10.7 +/- 0.3 mg/L), MDA-MB-231 human breast cancer cells (IC50 = 7.5 +/- 0.1 mg/L), and DU145 human prostate cancer cells (IC50 = 4.7 +/- 0.5 mg/L). HEGU augmented DOX-induced reductions in the viability of DU145 cells (15 +/- 1%). These results indicate that HEGU may potentially be an effective agent for the alleviation of DOX-induced cardiotoxicity.

Reactive oxygen species-independent apoptosis in doxorubicin-treated H9c2 cardiomyocytes: role for heme oxygenase-1 down-modulation

Increased oxidative stress and apoptosis have been implicated in the cardiotoxicity that limits the clinical use of doxorubicin (DOX) as an anti-tumoral drug, but the mechanism of DOX-mediated apoptosis remains unclear. We examined the interplay between oxidative stress and cell death in cardiac-derived H9c2 myocytes exposed to DOX doses in the range of the plasma levels found in patients undergoing chemotherapy. A low DOX concentration (0.25 microM) induced apoptosis, whereas the cells treated with the high dose of 2 microM also showed necrosis. The production of reactive oxygen species (ROS) and induction of oxidative stress markers was increased in the cells treated with 2 microM DOX but not in those treated with the low dose. Surprisingly, heme oxygenase (HO-1) expression was down-modulated in the cells exposed to 0.25 microM DOX, and its Bach 1 transcriptional repressor was induced. In line with the role of HO-1 as an anti-apoptotic protein, inhibiting HO-1 activity with SnPPIX was sufficient to induce apoptosis and increased DOX-mediated apoptosis, whereas hemin-induced HO-1 activation prevented DOX-mediated apoptotic cell death. In brief, our findings do not support the hypothesis that oxidative stress plays a role in the apoptotic cell death occurring in cardiomyocytes exposed to low concentrations of DOX, but suggest that DOX may facilitate the apoptosis of cardiomyocytes by inhibiting the anti-apoptotic HO-1.

Preclinical assessment of cardiac toxicity

The exact prediction of the clinical behavior of drugs represents one of the most difficult duties in preclinical drug development. The use of cell-based assay systems underpins the development of many drug candidates, but owing to the artificial character of many of these systems, cell response and physiological behavior seem to be mutually exclusive. Embryonic stem cell-derived cells represent a system that may address the disconnect between the behavior of cultured cells and cells in situ. While undifferentiated ES cells allow standardization, expansion and genetic manipulation, the differentiated cells provide a reflection of the normal physiological image of their primary counterpart. We compare common models to detect cardiac toxicity with an assay system comprising in vitro differentiated pure cardiomyocytes.