Granulocyte colony-stimulating factor improves left ventricular function of doxorubicin-induced cardiomyopathy

Zymosan A Improved Doxorubicin-Induced Ventricular Remodeling by Evoking Heightened Cardiac Inflammatory Responses and Healing in Mice

Background Doxorubicin-induced myocardial injury is reflected by the presence of vacuolization in both clinical and animal models. The lack of scar tissue to replace the vacuolizated cardiomyocytes indicates that insufficient cardiac inflammation and healing occurred following doxorubicin injection. Whether improved macrophage activity by zymosan A (zymosan) ameliorates doxorubicin-induced ventricular remodeling in mice is unknown. Methods and Results Mice were intravenously injected with vehicle or doxorubicin (5 mg/kg per week, 4 weeks), and cardiac structure and function were assessed by echocardiography. Two distinct macrophage subsets in hearts following doxorubicin injection were measured at different time points by flow cytometry. Moreover, cardiomyocyte vacuolization, capillary density, collagen content, and ventricular tensile strength were assessed. The therapeutic effect of zymosan (3 mg/kg, single injection) on doxorubicin-induced changes in the aforementioned parameters was determined. At the cellular level, the polarization of monocytes to proinflammatory or reparative macrophages were measured, with or without doxorubicin (0.25 and 0.5 μmol/L). Doxorubicin led to less proinflammatory and reparative macrophage infiltration in the heart in the early phase, with decreased cardiac capillary density and collagen III in the chronic phase. In cell culture, doxorubicin (0.5 μmol/L) repressed macrophage transition toward both proinflammatory and reparative subset. Zymosan enhanced both proinflammatory and reparative macrophage infiltration in doxorubicin-injected hearts, evoking a heightened acute inflammatory response. Zymosan alleviated doxorubicin-induced cardiomyocyte vacuolization in the chronic phase, in parallel with enhanced collagen content, capillary density, and ventricular tensile strength. Conclusions Zymosan improved cardiac healing and ameliorated doxorubicin-induced ventricular remodeling and dysfunction by activating macrophages at an optimal time.

Granulocyte-colony stimulating factor ameliorates di-ethylhexyl phthalate-induced cardiac muscle injury via stem cells recruitment, Desmin protein regulation, antifibrotic and antiapoptotic mechanisms

Phthalates are common plasticizers present in medical-grade plastics and other everyday products. Di-ethylhexyl phthalate (DEHP) has been noted as a causative risk factor for the initiation and augmentation of cardiovascular functional disorders. G-CSF is a glycoprotein found in numerous tissues throughout the body and is currently applied in clinical practice and has been tested in congestive heart failure. We aimed to examine in depth the effect of DEHP on the histological and biochemical structure of the cardiac muscle in adult male albino rats and the mechanisms underlying the possible ameliorative effect of G-CSF. Forty-eight adult male albino rats were divided into control group, DEHP group, DEHP+ G-CSF group and DEHP-recovery group. We measured serum levels of aspartate aminotransferase (AST), creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase (LDH). Left ventricular sections were processed for light and electron microscope examination, and immunohistochemical staining of Desmin, activated Caspase-3 and CD34. DEHP significantly increased enzyme levels, markedly distorted the normal architecture of cardiac muscle fibers, downregulated Desmin protein levels and enhanced fibrosis, and apoptosis. G-CSF treatment significantly decreased the enzyme levels compared to DEHP group. It enhanced CD34 positive stem cells recruitment to injured cardiac muscle, therefore improved the ultrastructural features of most cardiac muscle fibers via anti-fibrotic and anti-apoptotic effects in addition to increased Desmin protein expression levels. The recovery group showed partial improvement due to persistent DEHP effect. In conclusion, administration of G-CSF effectively corrected the histopathological, immunohistochemical and biochemical alterations in the cardiac muscle after DEHP administration by stem cells recruitment, Desmin protein regulation, antifibrotic and antiapoptotic mechanisms.

Cardiotoxicity of Anticancer Drugs: Molecular Mechanisms and Strategies for Cardioprotection

Chemotherapy and targeted therapies have significantly improved the prognosis of oncology patients. However, these antineoplastic treatments may also induce adverse cardiovascular effects, which may lead to acute or delayed onset of cardiac dysfunction. These common cardiovascular complications, commonly referred to as cardiotoxicity, not only may require the modification, suspension, or withdrawal of life-saving antineoplastic therapies, with the risk of reducing their efficacy, but can also strongly impact the quality of life and overall survival, regardless of the oncological prognosis. The onset of cardiotoxicity may depend on the class, dose, route, and duration of administration of anticancer drugs, as well as on individual risk factors. Importantly, the cardiotoxic side effects may be reversible, if cardiac function is restored upon discontinuation of the therapy, or irreversible, characterized by injury and loss of cardiac muscle cells. Subclinical myocardial dysfunction induced by anticancer therapies may also subsequently evolve in symptomatic congestive heart failure. Hence, there is an urgent need for cardioprotective therapies to reduce the clinical and subclinical cardiotoxicity onset and progression and to limit the acute or chronic manifestation of cardiac damages. In this review, we summarize the knowledge regarding the cellular and molecular mechanisms contributing to the onset of cardiotoxicity associated with common classes of chemotherapy and targeted therapy drugs. Furthermore, we describe and discuss current and potential strategies to cope with the cardiotoxic side effects as well as cardioprotective preventive approaches that may be useful to flank anticancer therapies.

Cardiomyocyte Atrophy, an Underestimated Contributor in Doxorubicin-Induced Cardiotoxicity

Left ventricular (LV) mass loss is prevalent in doxorubicin (DOX)-induced cardiotoxicity and is responsible for the progressive decline of cardiac function. Comparing with the well-studied role of cell death, the part of cardiomyocyte atrophy (CMA) playing in the LV mass loss is underestimated and the knowledge of the underlying mechanism is still limited. In this review, we summarized the recent advances in the DOX-induced CMA. We found that the CMA caused by DOX is associated with the upregulation of FOXOs and “atrogenes,” the activation of transient receptor potential canonical 3-NADPH oxidase 2 (TRPC3-Nox2) axis, and the suppression of IGF-1-PI3K signaling pathway. The imbalance of anabolic and catabolic process may be the common final pathway of these mechanisms. At last, we provided some strategies that have been demonstrated to alleviate the DOX-induced CMA in animal models.

Granulocyte Colony-Stimulating Factor Does Not Influence Clostridium Perfringens α-Toxin-Induced Myonecrosis in Mice

Clostridium perfringens type A causes gas gangrene characterized by myonecrosis and development of an effective therapy for treating affected patients is of clinical importance. It was recently reported that the expression of granulocyte colony-stimulating factor (G-CSF) is greatly up-regulated by C. perfringens infection. However, the role of G-CSF in C. perfringens-mediated myonecrosis is still unclear. Here, we assessed the destructive changes in C. perfringens-infected skeletal muscles and tested whether inhibition of G-CSF receptor (G-CSFR) signaling or administration of recombinant G-CSF affects the tissue injury. Severe edema, contraction of muscle fiber diameter, and increased plasma creatine kinase activity were observed in mice intramuscularly injected with C. perfringens type A, and the destructive changes were α-toxin-dependent, indicating that infection induces the destruction of skeletal muscle in an α-toxin-dependent manner. G-CSF plays important roles in the protection of tissue against damage and in the regeneration of injured tissue. However, administration of a neutralizing antibody against G-CSFR had no profound impact on the destructive changes to skeletal muscle. Moreover, administration of recombinant human G-CSF, filgrastim, imparted no inhibitory effect against the destructive changes caused by C. perfringens. Together, these results indicate that G-CSF is not beneficial for treating C. perfringens α-toxin-mediated myonecrosis, but highlight the importance of revealing the mechanism by which C. perfringens negates the protective effects of G-CSF in skeletal muscle.

Advantages of prophylactic versus conventionally scheduled heart failure therapy in an experimental model of doxorubicin-induced cardiomyopathy

BACKGROUND

Chemotherapy-induced left ventricular dysfunction represents a major clinical problem, which is often only recognised at an advanced stage, when supportive therapy is ineffective. Although an early heart failure treatment could positively influence the health status and clinical outcome, there is still no evidence of routine prophylactic cardioprotection for the majority of patients without previous cardiovascular history awaiting potentially cardiotoxic chemotherapy. In this study, we set out to investigate whether a prophylactic cardioprotective therapy relative to a conventionally scheduled heart failure treatment is more effective in preventing cardiotoxicity in a rodent model of doxorubicin (DOX)-induced cardiomyopathy.

METHODS

Male Wistar rats (n = 7-11 per group) were divided into 4 subgroups, namely negative controls receiving intravenous saline (CON), positive controls receiving intravenous DOX (6 cycles; D-CON), and DOX-treated animals receiving either prophylactic (PRE, started 1 week before DOX) or conventionally applied (POST, started 1 month after DOX) combined heart failure therapy of oral bisoprolol, perindopril and eplerenone. Blood pressure, heart rate, body weight and echocardiographic parameters were monitored in vivo, whereas myocardial fibrosis, capillarisation, ultrastructure, myofilament function, apoptosis, oxidative stress and mitochondrial biogenesis were studied in vitro.

RESULTS

The survival rate in the PRE group was significantly improved compared to D-CON (p = 0.0207). DOX increased the heart rate of the animals (p = 0.0193), while the blood pressure (p ≤ 0.0105) and heart rate (p = 0.0029) were significantly reduced in the PRE group compared to D-CON and POST. The ejection fraction remained preserved in the PRE group compared to D-CON or POST (p ≤ 0.0237), while none of the treatments could prevent the DOX-induced increase in the isovolumetric relaxation time. DOX decreased the rate of the actin-myosin cross-bridge cycle, irrespective of any treatment applied (p ≤ 0.0433). The myocardium of the D-CON and POST animals displayed pronounced ultrastructural damage, which was not apparent in the PRE group (p ≤ 0.033). While the DOX-induced apoptotic activity could be reduced in both the PRE and POST groups (p ≤ 0.0433), no treatment was able to prevent fibrotic remodelling or the disturbed mitochondrial biogenesis.

CONCLUSION

For attenuating DOX-induced adverse myocardial effects, prophylactic cardioprotection has many advantages compared to a late-applied treatment.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

An Alpha-1A Adrenergic Receptor Agonist Prevents Acute Doxorubicin Cardiomyopathy in Male Mice

Alpha-1 adrenergic receptors mediate adaptive effects in the heart and cardiac myocytes, and a myocyte survival pathway involving the alpha-1A receptor subtype and ERK activation exists in vitro. However, data in vivo are limited. Here we tested A61603 (N-[5-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-5,6,7,8-tetrahydronaphthalen-1-yl]methanesulfonamide), a selective imidazoline agonist for the alpha-1A. A61603 was the most potent alpha-1-agonist in activating ERK in neonatal rat ventricular myocytes. A61603 activated ERK in adult mouse ventricular myocytes and protected the cells from death caused by the anthracycline doxorubicin. A low dose of A61603 (10 ng/kg/d) activated ERK in the mouse heart in vivo, but did not change blood pressure. In male mice, concurrent subcutaneous A61603 infusion at 10 ng/kg/d for 7 days after a single intraperitoneal dose of doxorubicin (25 mg/kg) increased survival, improved cardiac function, heart rate, and cardiac output by echocardiography, and reduced cardiac cell necrosis and apoptosis and myocardial fibrosis. All protective effects were lost in alpha-1A-knockout mice. In female mice, doxorubicin at doses higher than in males (35-40 mg/kg) caused less cardiac toxicity than in males. We conclude that the alpha-1A-selective agonist A61603, via the alpha-1A adrenergic receptor, prevents doxorubicin cardiomyopathy in male mice, supporting the theory that alpha-1A adrenergic receptor agonists have potential as novel heart failure therapies.

Gp130-mediated STAT3 activation by S-propargyl-cysteine, an endogenous hydrogen sulfide initiator, prevents doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) could trigger a large amount of apoptotic cells in the myocardium, which leads to dilated cardiomyopathy and heart failure. S-propargyl-cysteine (SPRC), a producing agent of endogenous hydrogen sulfide (H2S), possesses cardioprotective efficacy. However, the specific effect and mechanism of SPRC in Dox-induced cardiotoxicity remain elusive. Given gp130 with its main downstream signaling molecule, signal transducer and activator of transcription 3 (STAT3), is involved in cardiac myocyte survival and growth; the present study was performed to elucidate whether SPRC counteracts Dox-induced cardiotoxicity, and if so, whether the gp130/STAT3 pathway is involved in this cardioprotective activity. SPRC stimulated the activation of STAT3 via gp130-mediated transduction tunnel in vitro and in vivo. In Dox-stimulated cardiotoxicity, SPRC enhanced cell viability, restored expression of gp130/STAT3-regulated downstream genes, inhibited apoptosis and oxidative stress, and antagonized mitochondrial dysfunction and intracellular Ca(2+) overload. Intriguingly, blockade of gp130/STAT3 signaling abrogated all these beneficial capacities of SPRC. Our findings present the first piece of evidence for the therapeutic properties of SPRC in alleviating Dox cardiotoxicity, which could be attributed to the activation of gp130-mediated STAT3 signaling. This will offer a novel molecular basis and therapeutic strategy of H2S donor for the treatment of heart failure.

Protection against doxorubicin-induced myocardial dysfunction in mice by cardiac-specific expression of carboxyl terminus of hsp70-interacting protein

Carboxyl terminus of Hsp70-interacting protein (CHIP) is a critical ubiquitin ligase/cochaperone to reduce cardiac oxidative stress, inflammation, cardiomyocyte apoptosis and autophage etc. However, it is unclear whether overexpression of CHIP in the heart would exert protective effects against DOX-induced cardiomyopathy. Cardiac-specific CHIP transgenic (CHIP-TG) mice and the wild-type (WT) littermates were treated with DOX or saline. DOX-induced cardiac atrophy, dysfunction, inflammation, oxidative stress and cardiomyocyte apoptosis were significantly attenuated in CHIP-TG mice. CHIP-TG mice also showed higher survival rate than that of WT mice (40% versus 10%) after 10-day administration of DOX. In contrast, knockdown of CHIP by siRNA in vitro further enhanced DOX-induced cardiotoxic effects. Global gene microarray assay revealed that after DOX-treatment, differentially expressed genes between WT and CHIP-TG mice were mainly involved in apoptosis, atrophy, immune/inflammation and oxidative stress. Mechanistically, CHIP directly promotes ubiquitin-mediated degradation of p53 and SHP-1, which results in activation of ERK1/2 and STAT3 pathways thereby ameliorating DOX-induced cardiac toxicity.

Local injection of granulocyte-colony stimulating factor accelerates wound healing in a rat excisional wound model

A systemic treatment of granulocyte-colony stimulating factor (G-CSF) is known to improve healings of damaged tissues. However, recent studies suggested local actions of G-CSF on the healing processes of damaged tissues. We investigated the treatment effect of locally injected G-CSF and compared to that of systemically injected G-CSF in a rat model. A wound was created on the rat dorsum and treated either by local injection or by systemic injection of G-CSF. Wound healing rate, deposition of collagen, and gene expression were evaluated. G-CSF receptor (G-CSFR) protein was detected by Western blotting. The wound healing rate in the local injection group was significantly higher than that in the systemic injection group at days 9 and 15; it was also significantly higher than that in the control group at days 3, 9, and 15. The expression of G-CSFR protein in wound tissues was higher than in normal skin tissues. The local injection of G-CSF is more effective than systemic injection of G-CSF in promoting wound healing, which may implicate the local action of G-CSF treatment in wound healing processes.

Granulocyte-colony stimulating factor reduces cardiomyocyte apoptosis and ameliorates diastolic dysfunction in Otsuka Long-Evans Tokushima Fatty rats

BACKGROUND

In recent studies, granulocyte-colony stimulating factor (G-CSF) was shown to improve cardiac function in myocardial infarction and non-ischemic cardiomyopathies. The mechanisms of these beneficial effects of G-CSF in diabetic cardiomyopathy are not yet fully understood. Therefore, we investigated the mechanisms of action of G-CSF on diabetic cardiomyopathy in a rat model of type 2 diabetes.

METHODS

Seventeen-week-old OLETF (Otsuka Long Evans Tokushima Fatty) diabetic rats and LETO (Long Evans Tokushima Otuska) rats were randomized to treatment with 5 days of G-CSF (100 μg/kg/day) or with saline. Cardiac function was evaluated by serial echocardiography performed before and 4 weeks after treatment. We measured expression of the G-CSF receptor (GCSFR) and Bcl-2, as well as the extent of apoptosis in the myocardium.

RESULTS

G-CSF treatment significantly improved cardiac diastolic function in the serial echocardiography assessments. Expression of G-CSFR was down-regulated in the diabetic myocardium (0.03 ± 0.12 % vs. 1 ± 0.15 %, p < 0.05), and its expression was stimulated by G-CSF treatment (0.03 ± 0.12 % vs. 0.42 ± 0.06 %, p < 0.05). In addition, G-CSF treatment increased the expression of Bcl-2 in the diabetic myocardium (0.69 ± 0.06 % vs. 0.26 ± 0.11 %, p < 0.05), consistent with the reduced cardiomyocyte apoptosis (9.38 ± 0.67 % vs. 17.28 ± 2.16 %, p < 0.05).

CONCLUSIONS

Our results suggest that G-CSF might have a cardioprotective effect in diabetic cardiomyopathy through up-regulation of G-CSFR, attenuation of apoptosis by up-regulation of Bcl-2 expression, and glucose-lowering effect. Our findings support the therapeutic potential of G-CSF in diabetic cardiomyopathy.

G-CSF does not influence C2C12 myogenesis despite receptor expression in healthy and dystrophic skeletal muscle

Granulocyte-colony stimulating factor (G-CSF) increases recovery of rodent skeletal muscles after injury, and increases muscle function in rodent models of neuromuscular disease. However, the mechanisms by which G-CSF mediates these effects are poorly understood. G-CSF acts by binding to the membrane spanning G-CSFR and activating multiple intracellular signaling pathways. Expression of the G-CSFR within the haematopoietic system is well known, but more recently it has been demonstrated to be expressed in other tissues. However, comprehensive characterization of G-CSFR expression in healthy and diseased skeletal muscle, imperative before implementing G-CSF as a therapeutic agent for skeletal muscle conditions, has been lacking. Here we show that the G-CSFR is expressed in proliferating C2C12 myoblasts, differentiated C2C12 myotubes, human primary skeletal muscle cell cultures and in mouse and human skeletal muscle. In mdx mice, a model of human Duchenne muscular dystrophy (DMD), G-CSF mRNA and protein was down-regulated in limb and diaphragm muscle, but circulating G-CSF ligand levels were elevated. G-CSFR mRNA in the muscles of mdx mice was up-regulated however steady-state levels of the protein were down-regulated. We show that G-CSF does not influence C₂C₁₂ myoblast proliferation, differentiation or phosphorylation of Akt, STAT3, and Erk1/2. Media change alone was sufficient to elicit increases in Akt, STAT3, and Erk1/2 phosphorylation in C₂C₁₂ muscle cells and suggest previous observations showing a G-CSF increase in phosphoprotein signaling be viewed with caution. These results suggest that the actions of G-CSF may require the interaction with other cytokines and growth factors in vivo, however these data provides preliminary evidence supporting the investigation of G-CSF for the management of muscular dystrophy.

Prooxidant mechanisms in iron overload cardiomyopathy

Iron overload cardiomyopathy (IOC), defined as the presence of systolic or diastolic cardiac dysfunction secondary to increased deposition of iron, is emerging as an important cause of heart failure due to the increased incidence of this disorder seen in thalassemic patients and in patients of primary hemochromatosis. At present, although palliative treatment by regular iron chelation was recommended; whereas IOC is still the major cause for mortality in patient with chronic heart failure induced by iron-overloading. Because iron is a prooxidant and the associated mechanism seen in iron-overload heart is still unclear; therefore, we intend to delineate the multiple signaling pathways involved in IOC. These pathways may include organelles such as calcium channels, mitochondria; paracrine effects from both macrophages and fibroblast, and novel mediators such as thromboxane A2 and adiponectin; with increased oxidative stress and inflammation found commonly in these signaling pathways. With further understanding on these complex and inter-related molecular mechanisms, we can propose potential therapeutic strategies to ameliorate the cardiac toxicity induced by iron-overloading.

Granulocyte colony-stimulating factor partially repairs the damage provoked by Trypanosoma cruzi in murine myocardium

BACKGROUND

The hallmark of Trypanosoma cruzi infection is cardiomyopathy that leads to end-stage heart failure. We investigated whether G-CSF, known to induce heart tissue repair by bone marrow stem cell mobilization, ameliorates T. cruzi-induced myocarditis.

METHODS AND RESULTS

T. cruzi-infected C3H/He mice were treated with G-CSF and monitored for parasite burden, BMSC mobilization, cytokine profile and cardiac remodeling. G-CSF increased the expression of CXCR4, CD34, and c-Kit, indicating mobilization and migration of BMSC, some of which differentiated to cardiomyocytes as evidenced by increased levels of GATA4(+)/MEF2C(+) cells and desmin expression in chagasic hearts. G-CSF enhanced a mixed cytokine response (IL-10+TGF-β>IFN-γ+TNF-α>IL-4) associated with increased heart inflammation and no beneficial effect on parasite control. Further, G-CSF controlled T. cruzi-induced extracellular-matrix alterations of collagens (Col I and Col llI), hydroxyproline, and glycosaminoglycan contents and promoted compensatory cardiac remodeling; however, these responses were not sufficient to control T. cruzi-induced cardiomyocyte atrophy. Benznidazole treatment prior to G-CSF resulted in the control of parasitism and parasite-induced inflammation, and subsequently, G-CSF was effective in executing the tissue repair, as evidenced by extracellular-matrix homeostasis and normalization of cardiomyocyte size in chagasic hearts.

CONCLUSIONS

G-CSF treatment after T. cruzi infection enhanced migration and homing of BMSC, some of which differentiated to cardiomyocytes. Yet, G-CSF promoted a mixed (Treg>Th1>Th2) immune response that contributed to persistent inflammation and limited improvement in cardiac homeostasis. Combinatorial therapy (BZ → G-CSF) was beneficial in arresting inflammatory processes and tissue damage in chagasic hearts.

Granulocyte colony-stimulating factor improves early remodeling in isoproterenol-induced cardiac injury in rats

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) has been used in some animal models and humans with well-established cardiovascular diseases. However, its effects in the initial stage of progressive non-ischemic heart failure are unknown.

METHODS

Wistar rats (260-300 g) were divided into three groups: control (without any intervention), ISO (150 mg/kg isoproterenol hydrochloride sc, once a day for two consecutive days), and ISO-GCSF (50 μg/kg/d G-CSF for 7 days beginning 24 h after the last administration of ISO). Echocardiography was performed at baseline and after 30 days of follow-up. Subsequently, animals were anesthetized for hemodynamic analysis. The left ventricle was removed for analysis of interstitial collagen deposition and cardiomyocyte hypertrophy.

RESULTS

Isoproterenol led to left ventricular dilation (control, 7.7 ± 0.14 mm; ISO, 8.7 ± 0.16 mm; ISO-GCSF 7.8 ± 0.09 mm; p < 0.05), myocardial fibrosis (control, 2.0 ± 0.18%; ISO, 9.1 ± 0.81%; ISO-GCSF 5.9 ± 0.58%; p < 0.05) and cardiomyocyte hypertrophy (control, 303 ± 10 μm(2); ISO, 356 ± 18 μm(2); ISO-GCSF 338 ± 11 μm(2); p < 0.05). However, G-CSF partially prevented collagen deposition and left ventricular enlargement, with a slight effect on hypertrophy. Characterizing a compensated stage of disease, hemodynamic analysis did not change.

CONCLUSION

G-CSF administered for 7 days was effective in preventing the onset of ventricular remodeling induced by high-dose isoproterenol with decreased collagen deposition and chamber preservation.

Effect of selective and non-selective cyclooxygenase inhibitors on doxorubicin-induced cardiotoxicity and nephrotoxicity in rats

CONTEXT

Doxorubicin (DX) is a highly effective chemotherapeutic agent used widely in the treatment of solid tumors; however, its optimal use was associated with cardiotoxicity and nephrotoxicity. The exact mechanism of DX-induced cardiotoxicity and nephrotoxicity is not fully explored. Induction of cyclooxygenase-2 (COX-2) activity in either cardiac or renal tissue by DX has been previously reported, indicating a possible role of COX-2 in DX-induced tissue injury. However, the nature of this role in either tissue injury is an issue of controversy.

OBJECTIVE

This study was the first that simultaneously evaluated the effects of a selective COX-2 inhibitor, nimesulide, and a non-selective COX-inhibitor, indomethacin, on DX-induced cardiotoxicity and nephrotoxicity in male Wistar rats.

MATERIALS AND METHODS

Rats were allocated into four groups. Control group, DX group (received 15 mg/kg, ip), DX + nimesulide (10 mg/kg/day, po) group, and DX + indomethacin (2 mg/kg/day, po) group. Nimesulide and indomethacin were started at the same day of DX injection and continued for 5 days.

RESULTS

The results of the present study showed that inhibition of COX-2 either by selective or non-selective COX-2 inhibitor ameliorated DX-induced cardiotoxicity but aggravated DX-induced nephrotoxicity in rats, as evidenced biochemically and histopathologically.

DISCUSSION AND CONCLUSION

Our study indicates that production of COX-2 is organ specific; consequently, the differential effect of COX-inhibitors should be considered in DX-treated patients. However, a wide scale experiment is needed for further confirmation and testing other members of COX-inhibitors (e.g. celecoxib and diclofenac).

Increased expression of integrin-linked kinase improves cardiac function and decreases mortality in dilated cardiomyopathy model of rats

Aims

Integrin-linked kinase (ILK) is a multifunctional kinase linking the extracellular matrix to intracellular signaling pathways, whose activation in the heart gives rise to a number of functional consequences. The aim of this study is to demonstrate the therapeutic and survival benefit of cardiac ILK overexpression in a rat model of dilated cardiomyopathy.

Methods and Results

The dilated cardiomyopathy model was generated in rats by intraperitoneal administration of six equal doses of doxorubicin over a 2 week period. Five weeks after the first injection, echocardiographic analysis demonstrated impaired cardiac function and, at that point, recombinant adenoviral vector harboring ILK cDNA or vehicle was injected into the myocardium, and the rats re-studied 4 weeks later. Compared with vehicle injection, ILK treatment ameliorated inflammatory cell infiltration and cardiomyocyte degeneration, as well as left ventricular dilation and dysfunction. ILK treatment was also associated with a reduction in apoptosis and an increase in proliferation of cardiomyocytes, as well as decreased oxidative stress and autophagic vacuole accumulation. Importantly, mortality was lower in rats following ILK treatment than in those following vehicle injection. In cultured neonatal rat cardiomyocytes, we also found that ILK overexpression protected against doxorubicin-induced apoptosis, giving rise to an increase in their proliferation.

Conclusions

These data demonstrate for the first time that ILK gene therapy improves cardiac function and survival in a model of dilated cardiomyopathy, and this may be mediated through suppression of inflammation, prevention of ventricular remodeling, inhibition of cardiomyocyte apoptosis and autophagy, and stimulation of cardiomyocyte proliferation.

G-CSF therapy reduces myocardial repolarization reserve in the presence of increased arteriogenesis, angiogenesis and connexin 43 expression in an experimental model of pacing-induced heart failure

G-CSF (granulocyte colony-stimulating factor) treatment has been shown to cause beneficial effects including a reduction of inducible arrhythmias in rodent models of ischemic cardiomyopathy. The aim of the present study was to test whether these effects do also apply to pacing-induced non-ischemic heart failure. In 24 female rabbits, heart failure was induced by rapid ventricular pacing. 24 rabbits were sham operated. The paced rabbits developed a significant decrease of ejection fraction. 11 heart failure rabbits (CHF) and 11 sham-operated (S) rabbits served as controls, whereas 13 sham (S-G-CSF) and 13 heart failure rabbits (CHF-G-CSF) were treated with 10 μg/kg G-CSF s.c. over 17 ± 4 days. G-CSF treatment caused a ~25% increased arterial and capillary density and a ~60% increased connexin 43 expression in failing hearts. In isolated, Langendorff-perfused rabbit hearts eight monophasic action potential recordings showed prolongation of repolarization in CHF as compared with controls in the presence of the QT prolonging agent erythromycin (+33 ± 12 ms; p < 0.01). Moreover, a significant increase in dispersion of repolarization contributed to a significantly higher rate of ventricular tachyarrhythmias in CHF. G-CSF-pre-treated hearts showed a further increase in prolongation of repolarization as compared with S and CHF. The further increase in dispersion of repolarization [S-G-CSF: +23 ± 9 ms (spatial), +13 ± 7 ms (temporal); CHF-G-CSF: +38 ± 14 ms (spatial), +10 ± 4 ms (temporal); p < 0.05 as compared with S and CHF], increased the incidence of ventricular tachyarrhythmias. In summary, chronic G-CSF treatment has moderate beneficial effects on parameters potentially related to hemodynamic function in the non-ischemic rabbit CHF model. However, a significant reduction of repolarization reserve might seriously challenge its suitability as a therapeutic agent for chronic CHF therapy.

Hematopoietic cytokines for cardiac repair: mobilization of bone marrow cells and beyond

Hematopoietic cytokines, traditionally known to influence cellular proliferation, differentiation, maturation, and lineage commitment in the bone marrow, include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, stem cell factor, Flt-3 ligand, and erythropoietin among others. Emerging evidence suggests that these cytokines also exert multifarious biological effects on diverse nonhematopoietic organs and tissues. Although the precise mechanisms remain unclear, numerous studies in animal models of myocardial infarction (MI) and heart failure indicate that hematopoietic cytokines confer potent cardiovascular benefits, possibly through mobilization and subsequent homing of bone marrow-derived cells into the infarcted heart with consequent induction of myocardial repair involving multifarious mechanisms. In addition, these cytokines are also known to exert direct cytoprotective effects. However, results from small-scale clinical trials of G-CSF therapy as a single agent after acute MI have been discordant and largely disappointing. It is likely that cardiac repair following cytokine therapy depends on a number of known and unknown variables, and further experimental and clinical studies are certainly warranted to accurately determine the true therapeutic potential of such therapy. In this review, we discuss the biological features of several key hematopoietic cytokines and present the basic and clinical evidence pertaining to cardiac repair with hematopoietic cytokine therapy.

Cardiomyocyte specific ablation of p53 is not sufficient to block doxorubicin induced cardiac fibrosis and associated cytoskeletal changes

Doxorubicin (Dox) is an anthracycline used to effectively treat several forms of cancer. Unfortunately, the use of Dox is limited due to its association with cardiovascular complications which are manifested as acute and chronic cardiotoxicity. The pathophysiological mechanism of Dox induced cardiotoxicity appears to involve increased expression of the tumor suppressor protein p53 in cardiomyocytes, followed by cellular apoptosis. It is not known whether downregulation of p53 expression in cardiomyocytes would result in decreased rates of myocardial fibrosis which occurs in response to cardiomyocyte loss. Further, it is not known whether Dox can induce perivascular necrosis and associated fibrosis in the heart. In this study we measured the effects of acute Dox treatment on myocardial and perivascular apoptosis and fibrosis in a conditional knockout (CKO) mouse model system which harbours inactive p53 alleles specifically in cardiomyocytes. CKO mice treated with a single dose of Dox (20 mg/kg), did not display lower levels of myocardial apoptosis or reactive oxygen and nitrogen species (ROS/RNS) compared to control mice with intact p53 alleles. Interestingly, CKO mice also displayed higher levels of interstitial and perivascular fibrosis compared to controls 3 or 7 days after Dox treatment. Additionally, the decrease in levels of the microtubule protein α-tubulin, which occurs in response to Dox treatment, was not prevented in CKO mice. Overall, these results indicate that selective loss of p53 in cardiomyocytes is not sufficient to prevent Dox induced myocardial ROS/RNS generation, apoptosis, interstitial fibrosis and perivascular fibrosis. Further, these results support a role for p53 independent apoptotic pathways leading to Dox induced myocardial damage and highlight the importance of vascular lesions in Dox induced cardiotoxicity.

Stromal Cell-Derived Factor-1 Retention and Cardioprotection for Ischemic Myocardium

Background—

Stromal cell-derived factor-1 (SDF-1) is a chemoattractant of stem/progenitor cells, and several studies have shown that SDF-1 may improve ventricular function after infarction. SDF-1 is cleaved by proteases including matrix metalloproteinase-2 (MMP-2) and CD26/dipeptidylpeptidase-4 (DPP-4), which are activated in injured tissues.

Methods and Results—

We investigated the biodistribution and functional roles of SDF-1 in experimental ischemia/reperfusion injury in rats. Radiolabeled SDF-1 given by intracoronary injection was selectively concentrated in ischemic myocardium. The enhanced uptake of SDF-1 in ischemic myocardium was not mediated by its receptor, CXCR4. Mass spectrometry and Western analyses showed that SDF-1 was cleaved by DPP-4 in plasma and myocardium, whereas a bioengineered MMP-2/DPP-4–resistant form of SDF-1, SSDF-1(S4V), was highly stable. A single dose of SSDF-1(S4V) exhibited greater potency for cardioprotection than wild-type SDF-1. SSDF-1(S4V) improved cardiac function in rats even after a 3-hour ischemic period.

Conclusions—

These results show that a single dose of protease-resistant SSDF-1(S4V) after myocardial infarction leads to dramatic improvement in angiogenesis and ventricular function even 3 hours after the onset of ischemia, revealing a simple, clinically feasible approach to prevention of heart failure.

Granulocyte-CSF induced inflammation-associated cardiac thrombosis in iron loading mouse heart and can be attenuated by statin therapy

Background

Granulocyte colony-stimulating factor (G-CSF), a hematopoietic cytokine, was recently used to treat patients of acute myocardial infarction with beneficial effect. However, controversy exists as some patients developed re-stenosis and worsened condition post G-CSF delivery. This study presents a new disease model to study G-CSF induced cardiac thrombosis and delineate its possible mechanism. We used iron loading to mimic condition of chronic cardiac dysfunction and apply G-CSF to mice to test our hypothesis.

Methods and Results

Eleven out of fifteen iron and G-CSF treated mice (I+G) showed thrombi formation in the left ventricular chamber with impaired cardiac function. Histological analysis revealed endothelial fibrosis, increased macrophage infiltration and tissue factor expression in the I+G mice hearts. Simvastatin treatment to I+G mice attenuated their cardiac apoptosis, iron deposition, and abrogated thrombus formation by attenuating systemic inflammation and leukocytosis, which was likely due to the activation of pAKT activation. However, thrombosis in I+G mice could not be suppressed by platelet receptor inhibitor, tirofiban.

Conclusions

Our disease model demonstrated that G-CSF induces cardiac thrombosis through an inflammation-thrombosis interaction and this can be attenuated via statin therapy. Present study provides a mechanism and potential therapy for G-CSF induced cardiac thrombosis.

Long-acting phosphodiesterase-5 inhibitor tadalafil attenuates doxorubicin-induced cardiomyopathy without interfering with chemotherapeutic effect

Doxorubicin (DOX) is one of the most effective anticancer drugs. However, its cardiotoxicity remains a clinical concern that severely restricts its therapeutic usage. We designed this study to investigate whether tadalafil, a long-acting phosphodiesterase-5 (PDE-5) inhibitor, protects against DOX-induced cardiotoxicity. We also sought to delineate the cellular and molecular mechanisms underlying tadalafil-induced cardioprotection. Male CF-1 outbred mice were randomized into three groups (n = 15-24/group) to receive either saline (0.2 ml i.p.), DOX (15 mg/kg, given by a single intraperitoneal injection), or tadalafil (4 mg/kg p.o. daily for 9 days) plus DOX. Left ventricular function was subsequently assessed by transthoracic echocardiography and Millar conductance catheter. Cardiac contractile function was impaired by DOX, and it was significantly improved by cotreatment with tadalafil. Tadalafil attenuated DOX-induced apoptosis and depletion of prosurvival proteins, including Bcl-2 and GATA-4, in myocardium. Cardiac oxidative stress was attenuated and antioxidant capacity was enhanced by tadalafil possibly via up-regulation of mitochondrial superoxide dismutase (MnSOD). Moreover, the tadalafil-treated group demonstrated increased cardiac cGMP level and protein kinase G (PKG) activity. Tadalafil did not interfere with the efficacy of DOX in killing human osteosarcoma cells in vitro or its antitumor effect in vivo in tumor xenograft model. We conclude that tadalafil improved left ventricular function and prevented cardiomyocyte apoptosis in DOX-induced cardiomyopathy through mechanisms involving up-regulation of cGMP, PKG activity, and MnSOD level without interfering with the chemotherapeutic benefits of DOX.

Combined therapy with cardioprotective cytokine administration and antiapoptotic gene transfer in postinfarction heart failure

We hypothesized that therapy, composed of antiapoptotic soluble Fas (sFas) gene transfer, combined with administration of the cardioprotective cytokine granulocyte colony-stimulating factor (G-CSF), would markedly mitigate cardiac remodeling and dysfunction following myocardial infarction (MI). On the 3rd day after MI induced by ligating the left coronary artery in mice, four different treatments were initiated: saline injection (Group C, n = 26); G-CSF administration (Group G, n = 27); adenoviral transfer of sFas gene (Group F, n = 26); and the latter two together (Group G+F, n = 26). Four weeks post-MI, Group G+F showed better survival than Group C (96 vs. 65%, P < 0.05) and the best cardiac function among the four groups. In Group G, the infarct scar was smaller and less fibrotic, whereas in Group F the scar was thicker, without a reduction in area, and contained abundant myofibroblasts and vascular cells; Group G+F showed both phenotypes. G-CSF exerted a beneficial effect on infarct tissue dynamics through antifibrotic and proliferative effects on granulation tissue; however, it also exerts an adverse proapoptotic effect that leads to thinning of the infarct scar. sFas appeared to offset the latter drawback. In vitro study using cultured myofibroblasts derived from the infarct tissue revealed that G-CSF increased proliferating activity of those cells accompanying activation of Akt and signal transducer and activator of transcription 3, while accelerating Fas-mediated apoptosis with increasing Bax-to-Bcl-2 ratio. The results suggest that combined use of G-CSF administration and sFas gene therapy is a potentially powerful tool against post-MI heart failure.

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.

Procyanidins produce significant attenuation of doxorubicin-induced cardiotoxicity via suppression of oxidative stress

Doxorubicin is widely prescribed in the chemotherapy of haematological malignancies and solid tumours. The major side effect of doxorubicin is oxidative injury-related cardiotoxicity, which has dramatically hindered its usage. Procyanidins from grape seeds are potent free radical scavengers that have been shown to protect against anthracycline-induced cardiotoxicity. In the present study, we tested whether procyanidins would prevent the doxorubicin-induced cardiotoxicity in rats. Rats were intraperitoneally treated with doxorubicin at a cumulative dose of 15 mg/kg with and without pre-administration of procyanidins. Our data showed that doxorubicin led to cardiac function deterioration, myocardial injury and increased oxidative stress in cardiac tissues. The cardiac function deterioration by doxorubicin included increased QT-interval and ST-interval in electrocardiograph (ECG) and decreased left ventricular developed pressure. Doxorubicin-induced myocardial injury was shown by the increased creatine kinase, alanine aminotransferase and aspartate aminotransferase in serum as well as in myocardial lesions. Pretreatment with procyanidin (150 mg/kg daily) effectively hindered the adverse effects of doxorubicin, such as myocardial injury and impaired heart function. Procyanidin pretreatment attenuated cytoplasmic vacuolization, increased left ventricular developed pressure and improved the ECG. The cardioprotective effect of procyanidin corresponded to the decrease of lipid peroxidation and the increase of cardiac antioxidant potency in doxorubicin-treated rats that were also given procyanidin. An in vitro cytotoxic study showed that procyanidins did not attenuate the antineoplastic activity of doxorubicin to A549 adenocarcinoma cells. All the above lines of evidence suggest that procyanidins protect cardiomyocytes from doxorubicin-induced cardiotoxicity via suppression of oxidative stress.

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.

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.

Effect of a long-term treatment with a low-dose granulocyte colony-stimulating factor on post-infarction process in the heart

Although beneficial effects of granulocyte colony-stimulating factor (G-CSF) have been demonstrated on post-myocardia infarction (MI) process, the mechanisms and feasibility are not fully agreed yet. We investigated effects of a long-term treatment with a low-dose G-CSF started 1 day after the onset of MI, on post-infarction process. One day after being made MI by left coronary ligation, mice were given G-CSF (10 μg/kg/day) for 4 weeks. The G-CSF treatment resulted in a significant mitigation of cardiac remodelling and dysfunction. In the G-CSF-treated hearts, the infarcted scar was smaller with less fibrosis and abundant vessels while in the non-infarcted area, hypertrophic cardiomyocytes with attenuated degenerative changes and reduced fibrosis were apparent. These effects were accompanied by activation of signal transducer and activator of transcription 3 (STAT3) and Akt and also by up-regulation of GATA-4, myosin heavy chain and matrix metalloproteinases-2 and -9. Apoptosis of cardiomyocytes appeared insignificant at any stages. Parthenolide, a STAT3 inhibitor, completely abolished the beneficial effects of G-CSF on cardiac function and remodelling with loss of effect on both anti-cardiomyocyte degeneration and anti-fibrosis. In contrast, wortmannin, an Akt inhibitor, did not affect G-CSF-induced benefis despite cancelling vessel increase. In conclusion, treatment with G-CSF at a small dose but for a long duration beneficially affects the post-infarction process possibly through STAT3-mediated anti-cardiomyocyte degeneration and anti-fibrosis, but not through anti-cardiomyocyte apoptosis or Akt-mediated angio-genesis. The findings may also imply a more feasible way of G-CSF administration in the clinical settings.

Tanshinone IIA protects neonatal rat cardiomyocytes from adriamycin-induced apoptosis

Tanshinone IIA (TSN) is a monomer extracted from the Chinese herb Danshen. In this study, we examined the effect of Tanshinone IIA on adriamycin (ADR)-induced apoptosis in neonatal rat cardiomyocytes and underlying molecular mechanisms. Primary cultured cardiomyocytes were treated with 1 micromol/L of adriamycin for 24 h with or without pretreatment with Tanshinone IIA (0.5-2 micromol/L) for 2 h. 3-(4,5-dimethyl thiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Hoechst staining, and flow cytometry measurement were used to assess cell viability and apoptosis. Fluorescent probes 2',7'-dichlorofluorescein diacetate and dihydroethidium were used to detect the production of reactive oxygen species. Western blotting was used to evaluate the expression of Bcl-2 and Bax proteins. Adriamycin significantly induced apoptosis in cardiomyocytes. Tanshinone IIA (0.5-2 micromol/L) ameliorated apoptosis induced by adriamycin in a dose-dependent manner. Tanshinone IIA (2 micromol/L) markedly attenuated adriamycin-induced reactive oxygen species production. Western blotting revealed that Tanshinone IIA prevented the adriamycin-mediated reduction of the ratio of Bcl-2/Bax. In conclusion, Tanshinone IIA significantly inhibits adriamycin-induced cardiomyocyte apoptosis in a dose-dependent manner, and this effect is at least partly caused by its antioxidant properties.

Treatment with an adenoviral vector encoding hepatocyte growth factor mitigates established cardiac dysfunction in doxorubicin-induced cardiomyopathy

Hepatocyte growth factor (HGF) reportedly exerts beneficial effects on the heart following myocardial infarction and during nonischemic cardiomyopathy, but the precise mechanisms underlying the latter have not been well elucidated. We generated nonischemic cardiomyopathy in mice by injecting them with doxorubicin (15 mg/kg ip). Two weeks later, when cardiac dysfunction was apparent, an adenoviral vector encoding human HGF gene (Ad.CAG-HGF, 1x10(11) particles/mouse) was injected into the hindlimb muscles; LacZ gene served as the control. Left ventricular dilatation and dysfunction normally seen 4 wk after doxorubicin administration were significantly mitigated in HGF-treated mice, as were the associated cardiomyocyte atrophy/degeneration and myocardial fibrosis. Myocardial expression of GATA-4 and a sarcomeric protein, myosin heavy chain, was downregulated by doxorubicin, but the expression of both was restored by HGF treatment. The protective effect of HGF against doxorubicin-induced cardiomyocyte atrophy was confirmed in an in vitro experiment, which also showed that neither cardiomyocyte apoptosis nor proliferation plays significant roles in the present model. Upregulation of c-Met/HGF receptor was noted in HGF-treated hearts. Among the mediators downstream of c-Met, the activation of extracellular signal-regulated kinase (ERK) was reduced by doxorubicin, but the activity was restored by HGF. Levels of transforming growth factor-beta1 and cyclooxygenase-2 did not differ between the groups. Our findings suggest the HGF gene delivery exerts therapeutic antiatrophic/degenerative and antifibrotic effects on myocardium in cases of established cardiac dysfunction caused by doxorubicin. These beneficial effects appear to be related to HGF-induced ERK activation and upregulation of c-Met, GATA-4, and sarcomeric proteins.