Extracellular superoxide dismutase regulates cardiac function and fibrosis

Use of Electron Paramagnetic Resonance (EPR) to Evaluate Redox Status in a Preclinical Model of Acute Lung Injury

PURPOSE

Patients with hyper- vs. hypo-inflammatory subphenotypes of acute respiratory distress syndrome (ARDS) exhibit different clinical outcomes. Inflammation increases the production of reactive oxygen species (ROS) and increased ROS contributes to the severity of illness. Our long-term goal is to develop electron paramagnetic resonance (EPR) imaging of lungs in vivo to precisely measure superoxide production in ARDS in real time. As a first step, this requires the development of in vivo EPR methods for quantifying superoxide generation in the lung during injury, and testing if such superoxide measurements can differentiate between susceptible and protected mouse strains.

PROCEDURES

In WT mice, mice lacking total body extracellular superoxide dismutase (EC-SOD) (KO), or mice overexpressing lung EC-SOD (Tg), lung injury was induced with intraperitoneal (IP) lipopolysaccharide (LPS) (10 mg/kg). At 24 h after LPS treatment, mice were injected with the cyclic hydroxylamines 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine hydrochloride (CPH) or 4-acetoxymethoxycarbonyl-1-hydroxy-2,2,5,5-tetramethylpyrrolidine-3-carboxylic acid (DCP-AM-H) probes to detect, respectively, cellular and mitochondrial ROS - specifically superoxide. Several probe delivery strategies were tested. Lung tissue was collected up to one hour after probe administration and assayed by EPR.

RESULTS

As measured by X-band EPR, cellular and mitochondrial superoxide increased in the lungs of LPS-treated mice compared to control. Lung cellular superoxide was increased in EC-SOD KO mice and decreased in EC-SOD Tg mice compared to WT. We also validated an intratracheal (IT) delivery method, which enhanced the lung signal for both spin probes compared to IP administration.

CONCLUSIONS

We have developed protocols for delivering EPR spin probes in vivo, allowing detection of cellular and mitochondrial superoxide in lung injury by EPR. Superoxide measurements by EPR could differentiate mice with and without lung injury, as well as mouse strains with different disease susceptibilities. We expect these protocols to capture real-time superoxide production and enable evaluation of lung EPR imaging as a potential clinical tool for subphenotyping ARDS patients based on redox status.

Impact of high Spirulina diet, extruded or supplemented with enzymes, on blood cells, systemic metabolites, and hepatic lipid and mineral profiles of broiler chickens

The impact of 15% dietary inclusion of Spirulina (Arthrospira platensis) in broiler chickens was explored, focusing on blood cellular components, systemic metabolites and hepatic lipid and mineral composition. From days 14 to 35 of age, 120 broiler chickens were divided and allocated into four dietary treatments: a standard corn and soybean meal-based diet (control), a 15% Spirulina diet, a 15% extruded Spirulina diet, and a 15% Spirulina diet super-dosed with an enzyme blend (0.20% porcine pancreatin plus 0.01% lysozyme). The haematological analysis revealed no significant deviations (p > 0.05) in blood cell counts across treatments, suggesting that high Spirulina inclusion maintains haematological balance. The systemic metabolic assessment indicated an enhanced antioxidant capacity in birds on Spirulina diets (p < 0.001), pointing toward a potential reduction in oxidative stress. However, the study noted a detrimental impact on growth performance metrics, such as final body weight and feed conversion ratio (both p < 0.001), in the Spirulina-fed treatments, with the super-dosed enzyme blend supplementation failing to alleviate these effects but with extrusion mitigating them. Regarding hepatic composition, birds on extruded Spirulina and enzyme-supplemented diets showed a notable increase in n-3 fatty acids (EPA, DPA, DHA) (p < 0.001), leading to an improved n-6/n-3 PUFA ratio (p < 0.001). Despite this positive shift, a reduction in total hepatic lipids (p = 0.003) was observed without a significant change in cholesterol levels. Our findings underscore the need for further exploration into the optimal inclusion levels, processing methods and potential enzymatic enhancements of Spirulina in broiler diets. Ultimately, this research aims to strike a balance between promoting health benefits and maintaining optimal growth performance in poultry nutrition.

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

Redox imbalance in patients with heart failure and ICD/CRT-D intervention. Can it be an underappreciated and overlooked arrhythmogenic factor? A first preliminary clinical study

Introduction: Redox imbalance and oxidative stress are involved in the pathogenesis of arrhythmias. They also play a significant role in pathogenesis of heart failure (HF). In patients with HFand implanted cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D), the direct current shocks may be responsible for additional redox disturbances and additionally increase arrhythmia risk. However, the precise role of oxidative stress in potentially fatal arrhythmias and shock induction remains unclear. Methods: 36 patients with diagnosed HF and implanted ICD/CRT-D were included in this study. Patients were qualified to the study group in case of registered ventricular arrhythmia and adequate ICD/CRT-D intervention. The control group consisted of patients without arrhythmia with elective replacement indicator (ERI) status. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) in erythrocyte (RBC), SOD, GPx activity and reactive oxygen/nitrogen species (ROS/RNS) concentration in plasma were determined. The values were correlated with glucose, TSH, uric acid, Mg and ion concentrations. Results: In the perishock period, we found a significant decrease in RBC and extracellular (EC) SOD and RBC CAT activity (p = 0.0110, p = 0.0055 and p = 0.0002, respectively). EC GPx activity was also lower (p = 0.0313). In all patients, a decrease in the concentration of all forms of glutathione was observed compared to the ERI group. Important association between ROS/RNS and GSH, Mg, TSH and uric acid was shown. A relationship between the activity of GSH and antioxidant enzymes was found. Furthermore, an association between oxidative stress and ionic imbalance has also been demonstrated. The patients had an unchanged de Haan antioxidant ratio and glutathione redox potential. Conclusion: Here we show significant redox disturbances in patients with HF and ICD/CRT-D interventions. Oxidative stress may be an additional risk factor for the development of arrhythmia in patients with HF. The detailed role of oxidative stress in ventricular arrhythmias requires further research already undertaken by our team.

Role of Enzymic Antioxidants in Mediating Oxidative Stress and Contrasting Wound Healing Capabilities in Oral Mucosal/Skin Fibroblasts and Tissues

Unlike skin, oral mucosal wounds are characterized by rapid healing and minimal scarring, attributable to the "enhanced" healing properties of oral mucosal fibroblasts (OMFs). As oxidative stress is increasingly implicated in regulating wound healing outcomes, this study compared oxidative stress biomarker and enzymic antioxidant profiles between patient-matched oral mucosal/skin tissues and OMFs/skin fibroblasts (SFs) to determine whether superior oral mucosal antioxidant capabilities and reduced oxidative stress contributed to these preferential healing properties. Oral mucosa and skin exhibited similar patterns of oxidative protein damage and lipid peroxidation, localized within the lamina propria/dermis and oral/skin epithelia, respectively. SOD1, SOD2, SOD3 and catalase were primarily localized within epithelial tissues overall. However, SOD3 was also widespread within the lamina propria localized to OMFs, vasculature and the extracellular matrix. OMFs were further identified as being more resistant to reactive oxygen species (ROS) generation and oxidative DNA/protein damage than SFs. Despite histological evaluation suggesting that oral mucosa possessed higher SOD3 expression, this was not fully substantiated for all OMFs examined due to inter-patient donor variability. Such findings suggest that enzymic antioxidants have limited roles in mediating privileged wound healing responses in OMFs, implying that other non-enzymic antioxidants could be involved in protecting OMFs from oxidative stress overall.

GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis in doxorubicin-induced heart failure through inhibition of NADPH oxidase-derived oxidative stress

Doxorubicin (DOX), which is widely used for the treatment of cancer, induces cardiomyopathy associated with NADPH oxidase-derived reactive oxygen species. GSK2795039 is a novel small molecular NADPH oxidase 2 (Nox2) inhibitor. In this study, we investigated whether GSK2795039 prevents receptor-interacting protein kinase 1 (RIP1)-RIP3-mixed lineage kinase domain-like protein (MLKL)-mediated cardiomyocyte necroptosis in DOX-induced heart failure through NADPH oxidase inhibition. Eight-week old mice were randomly divided into 4 groups: control, GSK2795039, DOX and DOX plus GSK2795039. H9C2 cardiomyocytes were treated with DOX and GSK2795039. In DOX-treated mice, the survival rate was reduced, left ventricular (LV) end-systolic dimension was increased and LV fractional shortening was decreased, and these alterations were attenuated by the GSK2795039 treatment. GSK2795039 inhibited not only myocardial NADPH oxidase subunit gp91phox (Nox2) protein, but also p22phox, p47phox and p67phox proteins and prevented oxidative stress 8-hydroxy-2'-deoxyguanosine levels in DOX-treated mice. RIP3 protein and phosphorylated RIP1 (p-RIP1), p-RIP3 and p-MLKL proteins, reflective of their respective kinase activities, markers of necroptosis, were markedly increased in DOX-treated mice, and the increases were prevented by GSK2795039. GSK2795039 prevented the increases in serum lactate dehydrogenase and myocardial fibrosis in DOX-treated mice. Similarly, in DOX-treated cardiomyocytes, GSK2795039 improved cell viability, attenuated apoptosis and necrosis and prevented the increases in p-RIP1, p-RIP3 and p-MLKL expression. In conclusion, GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis through inhibition of NADPH oxidase-derived oxidative stress, leading to the improvement of myocardial remodeling and function in DOX-induced heart failure. These findings suggest that GSK2795039 may have implications for the treatment of DOX-induced cardiomyopathy.

The Molecular Mechanisms of Defective Copper Metabolism in Diabetic Cardiomyopathy

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, connective tissue crosslinking, and antioxidant defense. Copper level has been proved to be closely related to the morbidity and mortality of cardiovascular diseases such as atherosclerosis, heart failure, and diabetic cardiomyopathy (DCM). Copper deficiency can induce cardiac hypertrophy and aggravate cardiomyopathy, while copper excess can mediate various types of cell death, such as autophagy, apoptosis, cuproptosis, pyroptosis, and cardiac hypertrophy and fibrosis. Both copper excess and copper deficiency lead to redox imbalance, activate inflammatory response, and aggravate diabetic cardiomyopathy. This defective copper metabolism suggests a specific metabolic pattern of copper in diabetes and a specific role in the pathogenesis and progression of DCM. This review is aimed at providing a timely summary of the effects of defective copper homeostasis on DCM and discussing potential underlying molecular mechanisms.

An Emerging Role of Defective Copper Metabolism in Heart Disease

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, iron mobilization, connective tissue crosslinking, antioxidant defense, melanin synthesis, blood clotting, and neuron peptide maturation. Increasing lines of evidence obtained from studies of cell culture, animals, and human genetics have demonstrated that dysregulation of copper metabolism causes heart disease, which is the leading cause of mortality in the US. Defects of copper homeostasis caused by perturbed regulation of copper chaperones or copper transporters or by copper deficiency resulted in various types of heart disease, including cardiac hypertrophy, heart failure, ischemic heart disease, and diabetes mellitus cardiomyopathy. This review aims to provide a timely summary of the effects of defective copper homeostasis on heart disease and discuss potential underlying molecular mechanisms.

Gallic acid protects against isoproterenol-induced cardiotoxicity in rats

BACKGROUND

Gallic acid (GA) is a polyphenolic agent with interesting pharmacological impacts on the cardiovascular system.

OBJECTIVE

The present study purposed to study the protective effects of GA at 25 and 50 mg/kg against isoproterenol (ISO)-induced cardiac damage in ischemia/reperfusion (I/R) in rats.

METHODS

Male Wistar rats were randomly assigned into six groups: Control, Control treated with GA at 25 mg/kg (GA25), Control treated with GA at 50 mg/kg (GA50), Hypertrophic rats induced by ISO (ISO), Hypertrophic rats treated with GA at 25 mg/kg (ISO+GA25), and Hypertrophic rats treated with GA at 50 mg/kg (ISO+GA50). Heart isolation was performed to induce a cardiac I/R injury model. Cardiac hemodynamic parameters were recorded. Serum Lactate Dehydrogenase (LDH) and Creatine Kinase-MB (CK-MB) and cardiac Superoxide dismutases (SOD) levels were evaluated. The gene expression of Sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a) was assessed.

RESULTS

We found that GA at 50 mg/kg was significantly increased cardiac function at post I/R period in ISO-induced hypertrophic hearts. Moreover, it suppressed cardiac hypertrophy, the serum LDH and CK-MB levels in ISO injected rats. Administration of GA at 50 mg/kg was significantly increased SOD level and SERCA2a gene expression in the hypertrophic hearts.

CONCLUSION

GA at 50 mg/kg could improve cardiac performance possibly by increasing antioxidant defense enzymes, reducing cell damage, and enhancing SERCA2a gene expression in hypertrophic heart induced by ISO in I/R injury conditions.

Dark Side of Cancer Therapy: Cancer Treatment-Induced Cardiopulmonary Inflammation, Fibrosis, and Immune Modulation

Advancements in cancer therapy increased the cancer free survival rates and reduced the malignant related deaths. Therapeutic options for patients with thoracic cancers include surgical intervention and the application of chemotherapy with ionizing radiation. Despite these advances, cancer therapy-related cardiopulmonary dysfunction (CTRCPD) is one of the most undesirable side effects of cancer therapy and leads to limitations to cancer treatment. Chemoradiation therapy or immunotherapy promote acute and chronic cardiopulmonary damage by inducing reactive oxygen species, DNA damage, inflammation, fibrosis, deregulation of cellular immunity, cardiopulmonary failure, and non-malignant related deaths among cancer-free patients who received cancer therapy. CTRCPD is a complex entity with multiple factors involved in this pathogenesis. Although the mechanisms of cancer therapy-induced toxicities are multifactorial, damage to the cardiac and pulmonary tissue as well as subsequent fibrosis and organ failure seem to be the underlying events. The available biomarkers and treatment options are not sufficient and efficient to detect cancer therapy-induced early asymptomatic cell fate cardiopulmonary toxicity. Therefore, application of cutting-edge multi-omics technology, such us whole-exome sequencing, DNA methylation, whole-genome sequencing, metabolomics, protein mass spectrometry and single cell transcriptomics, and 10 X spatial genomics, are warranted to identify early and late toxicity, inflammation-induced carcinogenesis response biomarkers, and cancer relapse response biomarkers. In this review, we summarize the current state of knowledge on cancer therapy-induced cardiopulmonary complications and our current understanding of the pathological and molecular consequences of cancer therapy-induced cardiopulmonary fibrosis, inflammation, immune suppression, and tumor recurrence, and possible treatment options for cancer therapy-induced cardiopulmonary toxicity.

Serum superoxide dismutase activity: a sensitive, convenient, and economical indicator associated with the prevalence of chronic type 2 diabetic complications, especially in men

To investigate the relationship between serum superoxide dismutase (SOD) activity and the presence of chronic complications in patients with type 2 diabetes mellitus (T2DM). We conducted a retrospective cross-sectional study in patients with T2DM. They were assigned to three groups (Q1, Q2, and Q3) by SOD levels in both sexes. Clinical characteristics, cardiovascular disease, diabetic retinopathy, nephropathy, and peripheral neuropathy were compared. The relationship between the SOD and the prevalence of chronic complications was analyzed by binary logistic regression. Statistical analysis was performed in SPSS 26.0 (SPSS Inc., Chicago, IL). A total of 645 T2DM patients (401 men and 244 women) with complete data for SOD and medical records of complications were included. In men, patients in the Q1 group (lowest serum SOD activity) had the highest prevalence of diabetes with atherosclerosis (AS) (p<.001), DN (p=.029), and DPN (p=.001). In comparison, only DN was found to have the highest prevalence in the Q1 group in women (p=.010). In the multivariate analysis, patients in the Q1 group had a 3.0-, 1.6-, 1.9-, and 2.4-fold risk for the prevalence of AS, DR, DN, and DPN, respectively, compared with the Q3 group. In women, a 7.0-fold risk for the prevalence of DN in the Q1 group was found compared with the Q3 group. After adjusting for the age, duration of T2DM, body mass index, pulse pressure, alanine transaminase, clearance of creatinine, triglyceride, glycosylated hemoglobin, and fasting C-peptide in the models, the differences found in both men and women persisted. SOD activity is related to cardiovascular and microvascular diseases in men and the prevalence of diabetic nephropathy in women in T2DM.

SOD3 deficiency induces liver fibrosis by promoting hepatic stellate cell activation and epithelial-mesenchymal transition

Hepatic stellate cell (HSC) activation plays an important role in the pathogenesis of liver fibrosis, and epithelial-mesenchymal transition (EMT) is suggested to potentially promote HSC activation. Superoxide dismutase 3 (SOD3) is an extracellular antioxidant defense against oxidative damage. Here, we found downregulation of SOD3 in a mouse model of liver fibrosis induced by carbon tetrachloride (CCl4 ). SOD3 deficiency induced spontaneous liver injury and fibrosis with increased collagen deposition, and further aggravated CCl4 -induced liver injury in mice. Depletion of SOD3 enhanced HSC activation marked by increased α-smooth muscle actin and subsequent collagen synthesis primarily collagen type I in vivo, and promoted transforming growth factor-β1 (TGF-β1)-induced HSC activation in vitro. SOD3 deficiency accelerated EMT process in the liver and TGF-β1-induced EMT of AML12 hepatocytes, as evidenced by loss of E-cadherin and gain of N-cadherin and vimentin. Notably, SOD3 expression and its pro-fibrogenic effect were positively associated with sirtuin 1 (SIRT1) expression. SOD3 deficiency inhibited adenosine monophosphate-activated protein kinase (AMPK) signaling to downregulate SIRT1 expression and thus involving in liver fibrosis. Enforced expression of SIRT1 inhibited SOD3 deficiency-induced HSC activation and EMT, whereas depletion of SIRT1 counteracted the inhibitory effect of SOD3 in vitro. These findings demonstrate that SOD3 deficiency contributes to liver fibrogenesis by promoting HSC activation and EMT process, and suggest a possibility that SOD3 may function through modulating SIRT1 via the AMPK pathway in liver fibrosis.

Effect of cellular and ECM aging on human iPSC-derived cardiomyocyte performance, maturity and senescence

Cardiovascular diseases are the leading cause of death worldwide and their occurrence is highly associated with age. However, lack of knowledge in cardiac tissue aging is a major roadblock in devising novel therapies. Here, we studied the effects of cell and cardiac extracellular matrix (ECM) aging on the induced pluripotent stem cell (iPSC)-derived cardiomyocyte cell state, function, as well as response to myocardial infarction (MI)-mimicking stress conditions in vitro. Within 3-weeks, young ECM promoted proliferation and drug responsiveness in young cells, and induced cell cycle re-entry, and protection against stress in the aged cells. Adult ECM improved cardiac function, while aged ECM accelerated the aging phenotype, and impaired cardiac function and stress defense machinery of the cells. In summary, we have gained a comprehensive understanding of cardiac aging and highlighted the importance of cell-ECM interactions. This study is the first to investigate the individual effects of cellular and environmental aging and identify the biochemical changes that occur upon cardiac aging.

Cathepsin A contributes to left ventricular remodeling by degrading extracellular superoxide dismutase in mice

In the heart, the serine carboxypeptidase cathepsin A (CatA) is distributed between lysosomes and the extracellular matrix (ECM). CatA-mediated degradation of extracellular peptides may contribute to ECM remodeling and left ventricular (LV) dysfunction. Here, we aimed to evaluate the effects of CatA overexpression on LV remodeling. A proteomic analysis of the secretome of adult mouse cardiac fibroblasts upon digestion by CatA identified the extracellular antioxidant enzyme superoxide dismutase (EC-SOD) as a novel substrate of CatA, which decreased EC-SOD abundance 5-fold. In vitro, both cardiomyocytes and cardiac fibroblasts expressed and secreted CatA protein, and only cardiac fibroblasts expressed and secreted EC-SOD protein. Cardiomyocyte-specific CatA overexpression and increased CatA activity in the LV of transgenic mice (CatA-TG) reduced EC-SOD protein levels by 43%. Loss of EC-SOD-mediated antioxidative activity resulted in significant accumulation of superoxide radicals (WT, 4.54 μmol/mg tissue/min; CatA-TG, 8.62 μmol/mg tissue/min), increased inflammation, myocyte hypertrophy (WT, 19.8 μm; CatA-TG, 21.9 μm), cellular apoptosis, and elevated mRNA expression of hypertrophy-related and profibrotic marker genes, without affecting intracellular detoxifying proteins. In CatA-TG mice, LV interstitial fibrosis formation was enhanced by 19%, and the type I/type III collagen ratio was shifted toward higher abundance of collagen I fibers. Cardiac remodeling in CatA-TG was accompanied by an increased LV weight/body weight ratio and LV end diastolic volume (WT, 50.8 μl; CatA-TG, 61.9 μl). In conclusion, CatA-mediated EC-SOD reduction in the heart contributes to increased oxidative stress, myocyte hypertrophy, ECM remodeling, and inflammation, implicating CatA as a potential therapeutic target to prevent ventricular remodeling.

Human Neonatal Thymus Mesenchymal Stem/Stromal Cells and Chronic Right Ventricle Pressure Overload

Right ventricle (RV) failure secondary to pressure overload is associated with a loss of myocardial capillary density and an increase in oxidative stress. We have previously found that human neonatal thymus mesenchymal stem cells (ntMSCs) promote neovascularization, but the ability of ntMSCs to express the antioxidant extracellular superoxide dismutase (SOD3) is unknown. We hypothesized that ntMSCs express and secrete SOD3 as well as improve survival in the setting of chronic pressure overload. To evaluate this hypothesis, we compared SOD3 expression in ntMSCs to donor-matched bone-derived MSCs and evaluated the effect of ntMSCs in a rat RV pressure overload model induced by pulmonary artery banding (PAB). The primary outcome was survival, and secondary measures were an echocardiographic assessment of RV size and function as well as histological studies of the RV. We found that ntMSCs expressed SOD3 to a greater degree as compared to bone-derived MSCs. In the PAB model, all ntMSC-treated animals survived to the study endpoint whereas control animals had significantly decreased survival. Treatment animals had significantly less RV fibrosis and increased RV capillary density as compared to controls. We conclude that human ntMSCs demonstrate a therapeutic effect in a model of chronic RV pressure overload, which may in part be due to their antioxidative, antifibrotic, and proangiogenic effects. Given their readily available source, human ntMSCs may be a candidate cell therapy for individuals with congenital heart disease and a pressure-overloaded RV.

Improvements in SOD mimic AEOL-10150, a potent broad-spectrum antioxidant

AEOL-10150 is a broad-spectrum metalloporphyrin superoxidase dismutase (SOD) mimic specifically designed to neutralize reactive oxygen and nitrogen species. Research has shown that AEOL-10150 is a potent medical countermeasure against national security threats including sulfur mustard (SM), nerve agent exposure and radiation pneumonitis following a radiological/nuclear incident sufficient to cause acute radiation syndrome (ARS). AEOL-10150 performed well in animal safety studies, and two completed phase 1 safety studies in patients demonstrated that the drug was safe and well tolerated, indicating that AEOL-10150 has potential as a new catalytic antioxidant drug. In this article, we review improvements in AEOL-10150 in preclinical pharmacodynamic studies, especially regarding anti-SM, chlorine gas and radiation exposure studies.

Extracellular superoxide dismutase (SOD3) regulates oxidative stress at the vitreoretinal interface

Oxidative stress is a pathogenic feature in vitreoretinal disease. However, the ability of the inner retina to manage metabolic waste and oxidative stress is unknown. Proteomic analysis of antioxidants in the human vitreous, the extracellular matrix opposing the inner retina, identified superoxide dismutase-3 (SOD3) that localized to a unique matrix structure in the vitreous base and cortex. To determine the role of SOD3, Sod3^-/- mice underwent histological and clinical phenotyping. Although the eyes were structurally normal, at the vitreoretinal interface Sod3^-/- mice demonstrated higher levels of 3-nitrotyrosine, a key marker of oxidative stress. Pattern electroretinography also showed physiological signaling abnormalities within the inner retina. Vitreous biopsies and epiretinal membranes collected from patients with diabetic vitreoretinopathy (DVR) and a mouse model of DVR showed significantly higher levels of nitrates and/or 3-nitrotyrosine oxidative stress biomarkers suggestive of SOD3 dysfunction. This study analyzes the molecular pathways that regulate oxidative stress in human vitreous substructures. The absence or dysregulation of the SOD3 antioxidant at the vitreous base and cortex results in increased oxidative stress and tissue damage to the inner retina, which may underlie DVR pathogenesis and other vitreoretinal diseases.

Up-regulation of NOX1/NADPH oxidase following drug-induced myocardial injury promotes cardiac dysfunction and fibrosis

Cardiac fibrosis is a common feature in failing heart and therapeutic strategy to halt the progression of fibrosis is highly needed. We here report on NOX1, a non-phagocytic isoform of superoxide-producing NADPH oxidase, which promotes cardiac fibrosis in a drug-induced myocardial injury model. A single-dose administration of doxorubicin (DOX) elicited cardiac dysfunction accompanied by increased production of reactive oxygen species and marked elevation of NOX1 mRNA in the heart. In mice deficient in Nox1 (Nox1^-/Y), cardiac functions were well retained and overall survival was significantly improved. However, increased level of serum creatine kinase was equivalent to that of wild-type mice (Nox1^+/Y). At 4 days after DOX treatment, severe cardiac fibrosis accompanied by increased hydroxyproline content and activation of matrix metalloproteinase-9 was demonstrated in Nox1^+/Y, but it was significantly attenuated in Nox1^-/Y. When H9c2 cardiomyocytes were exposed to their homogenate, a dose-dependent increase in NOX1 mRNA was observed. Up-regulation of NOX1 mRNA in H9c2 co-incubated with their homogenate was abolished in the presence of TAK242, a TLR4 inhibitor. When isolated cardiac fibroblasts were exposed to H9c2 homogenates, increased proliferation and up-regulation of collagen 3a1 mRNA were demonstrated. These changes were significantly attenuated in cardiac fibroblasts exposed to homogenates from H9c2 harboring disrupted Nox1. These findings suggest that up-regulation of NOX1 following cellular damage promotes cardiac dysfunction and fibrosis by aggravating the pro-fibrotic response of cardiac fibroblasts. Modulation of the NOX1/NADPH oxidase signaling pathway may be a novel therapeutic strategy for preventing heart failure after myocardial injury.

Spironolactone Attenuates Doxorubicin-induced Cardiotoxicity in Rats

INTRODUCTION

In this study, we examined whether spironolactone (SP) could inhibit doxorubicin (DOX)-induced cardiotoxicity in the rat heart.

METHODS

Rats were randomized into four groups (n = 6): (1) the control group; (2) the SP group; (3) the DOX group; and (4) the SP + DOX group. The rats were evaluated for electrocardiography and cardiac function. The cardiac collagen, cardiomyocyte apoptosis, and the remodeling-related proteins were determined.

RESULTS

Rats treated with DOX showed prolongation of QTc and decreased left ventricular ejection fraction (EF) and fractional shortening (FS) (P < 0.05) showed left ventricular end-diastolic dimensions (LVEDD) and left ventricular end-systolic dimensions (LVESD) were significantly increased (P < 0.05). SP prevented these pathophysiological alterations (P < 0.05). In DOX-treated group, cardiac fibrosis, apoptotic cell number, and cardiac collagen volume fraction were higher than control group (P < 0.05); these effects were prevented by cotreatment of SP (P < 0.05). Moreover, the expressions of TGF-β1 and phosphorylated-Smad3 were increased after DOX treatment (P < 0.05) and significantly reduced by coadministration of SP (P < 0.05).

CONCLUSIONS

This study show that SP may have a protective effect on DOX-induced cardiotoxicity.

Loss of Mrp1 Potentiates Doxorubicin-Induced Cytotoxicity in Neonatal Mouse Cardiomyocytes and Cardiac Fibroblasts

Doxorubicin (DOX) induces dose-dependent cardiotoxicity in part due to its ability to induce oxidative stress. We showed that loss of multidrug resistance-associated protein 1 (Abcc1/Mrp1) potentiates DOX-induced cardiac dysfunction in mice in vivo Here, we characterized DOX toxicity in cultured cardiomyocytes (CM) and cardiac fibroblasts (CF) derived from C57BL wild type (WT) and Mrp1 null (Mrp1-/-) neonatal mice. CM accumulated more intracellular DOX relative to CF but this accumulation did not differ between genotypes. Following DOX (0.3-4 μM), Mrp1-/- CM, and CF, especially CM, showed a greater decrease in viability and increased apoptosis and DNA damage, demonstrated by higher caspase 3 cleavage, poly (ADP-ribose) polymerase 1 (PARP) cleavage and phosphorylated histone H2AX (γH2AX) levels versus WT cells. Saline- and DOX-treated Mrp1-/- cells had significantly higher intracellular GSH and GSSG compared with WT cells (P < .05), but the redox potential (Eh) of the GSH/GSSG pool did not differ between genotypes in CM and CF, indicating that Mrp1-/- cells maintain this major redox couple. DOX increased expression of the rate-limiting GSH synthesis enzyme glutamate-cysteine ligase catalytic (GCLc) and regulatory subunits (GCLm) to a significantly greater extent in Mrp1-/- versus WT cells, suggesting adaptive responses to oxidative stress in Mrp1-/- cells that were inadequate to afford protection. Expression of extracellular superoxide dismutase (ECSOD/SOD3) was lower (P < .05) in Mrp1-/- versus WT CM treated with saline (62% ± 8% of WT) or DOX (43% ± 12% of WT). Thus, Mrp1 protects CM in particular and CF against DOX-induced toxicity, potentially by regulating extracellular redox states.

Anthracycline-dependent cardiotoxicity and extracellular matrix remodeling

The mechanisms of anthracycline-dependent cardiotoxicity have been studied widely, with the suggested principal mechanism of anthracycline damage being the generation of reactive oxygen species by iron-anthracycline complexes, leading to lipid peroxidation and membrane damage. An increasing number of researchers studying cardiovascular events associated with anthracycline-based chemotherapy are addressing cardiac extracellular matrix (ECM) remodeling. The heart is an efficient muscular pump, with the cardiomyocytes and intramural coronary vasculature of the heart tethered in an ECM consisting of a network of fibrillar, structural proteins, mostly collagens. Increasing evidence suggests that the ECM plays a complex and diverse role in the processes initiated by anthracycline-class drugs that lead to cardiac damage. This review discusses adverse myocardial remodeling induced by anthracyclines and focuses on their mechanisms of action.

Correlations between polymorphisms of extracellular superoxide dismutase, aldehyde dehydrogenase-2 genes, as well as drinking behavior and pancreatic cancer

OBJECTIVE

To investigate the correlation between drinking behavior combined with polymorphisms of extracellular superoxide dismutase (EC-SOD) and aldehyde dehydrogenase-2 (ALDH2) genes and pancreatic cancer.

METHODS

The genetic polymorphisms of EC-SOD and ALDH2 were analyzed by polymerase chain reaction restriction fragment length polymorphism in the peripheral blood leukocytes obtained from 680 pancreatic cancer cases and 680 non-cancer controls. Subsequently the frequency of genotype was compared between the pancreatic cancer patients and the healthy controls.The relationship of drinking with pancreatic cancer was analyzed.

RESULTS

The frequencies of EC-SOD (C/G) and ALDH2 variant genotypes were 37.35% and 68.82% respectively in the pancreatic cancer cases, and were significantly higher than those in the healthy controls (21.03% and 44.56%, all P<0.01). People who carried EC-SOD (C/G) (OR=2.24, 95% CI= 1.81-4.03, P<0.01) or ALDH2 variant genotypes (OR=2.75, 95% CI=1.92-4.47, P<0.01) had a high risk to develop pancreatic cancer. Those who carried EC-SOD (C/G) genotype combined with ALDH2 variant genotype had a high risk for pancreatic cancer (29.56% vs. 6.76%, OR=7.69, 95% CI=3.58-10.51, P<0.01). The drinking rate of the pancreatic cancer group (64.12%) was significantly higher than that of the control group (40.15%; OR=2.66, 95% CI=1.30-4.42, P<0.01). An interaction between drinking and EC-SOD (C/G)/ALDH2 variant genotypes increased the risk of occurrence of pancreatic cancer (OR=25.00, 95% CI= 11.87-35.64, P<0.01).

CONCLUSION

EC-SOD (C/G), ALDH2 variant genotypes and drinking might be the risk factors of pancreatic cancer.

Differential metal content and gene expression in rat left ventricular hypertrophy due to hypertension and hyperactivity

The spontaneously hypertensive rat (SHR) has been studied extensively as a model of left ventricular hypertrophy (LVH) and associated cardiac dysfunction due to hypertension (HT). The SHR also possesses a hyperactive trait (HA). Crossbreeding SHR with Wistar-Kyoto (WKY) control rats, which are nonHT and nonHA, followed by selected inbreeding produced two additional homozygous strains: WKHT and WKHA, in which the traits of HT and HA, respectively, are expressed separately. WKHT, WKHA and SHR all display LVH, but only the SHR exhibits cardiac dysfunction. We hypothesized that cardiac dysfunction in the SHR is uniquely characterized by calcium overload. We measured total cardiac Ca, Cu, Fe, K, Mg and Zn in the four strains. We found elevated Ca and depressed Cu, Mg and Zn with HT, but not unique to SHR. We surmise that HT promotes aberrant regulation of cardiac Ca(2+), Cu(2+), Mg(2+) and Zn(2+), which does not necessarily result in cardiac dysfunction. Interestingly, Cu was elevated in HA strains compared to nonHA counterparts. We then analyzed gene expression as mRNA of Cu-containing proteins, most notably mitochondrial-Cox, Dbh, Lox, Loxl1, Loxl2, Sod1 and Tyr. The gene expression profiles of Lox, Loxl1, Loxl2 and Sod1 were found especially high in the WKHA, which if reflective of protein content could account for the high Cu content in the WKHA. The mRNA of other genes, notably Mb, Fxyd1, Maoa and Maob were also examined. We found that Maoa gene expression and monoamine oxidase-A (MAO-A) protein content were low in the SHR compared to the other strains. The finding that MAO-A protein is low in the SHR and normal in the WKHT and WKHA strains is most consistent with the idea that MAO-A protects against the development of cardiac dysfunction in LVH but not against LVH in these rats.

Protective effect of resveratrol against doxorubicin-induced cardiac toxicity and fibrosis in male experimental rats

The possible effectiveness of resveratrol, a polyphenol present in different plants comprising berries, grapes and peanuts, on the prevention of doxorubicin-induced cardiac toxicity and fibrosis was investigated. Forty adult male Wistar albino rats were divided into four groups. Group I received normal saline, group II gavaged with resveratrol (20 mg/kg, daily for 4 weeks), group III received doxorubicin (2.5 mg/kg i.p. in six injections for 2 weeks; accumulative dose of 15 mg/kg), and group IV received doxorubicin + resveratrol (starting resveratrol intake 2 weeks before doxorubicin administration). Resveratrol significantly alleviated the increase in left ventricular lipid peroxidation, hydroxyproline, and tumor necrosis factor alpha levels as well as serum creatine kinase-myocardial band (CK-MB) activity and prevented the decrease in body and heart weights in doxorubicin-treated group. However, a marked protection against reduced glutathione content depletion and superoxide dismutase activity reduction was observed in the left ventricles of rats pretreated with resveratrol in combination with doxorubicin. Resveratrol also ameliorated the up-regulation of left ventricular caspase-3 and transforming growth factor-beta1 gene expression as well as left ventricular histopathological changes including necrosis and fibrosis induced by doxorubicin. Collectively, our results suggest that resveratrol provides a significant protection against doxorubicin-induced cardiotoxicity and fibrosis in rats. Therefore, it may be used as a promising cardioprotective agent in patients treated with doxorubicin due to malignant diseases. So, further clinical trials are required to confirm these findings.

[Correlation between drinking behavior and polymorphisms of extracellular superoxide dismutase, aldehyde dehydrogenase 2 genes, and oral squamous cell carcinoma]

OBJECTIVE

To investigate the correlation between drinking behavior and polymorphism combination of extracellular superoxide dismutase (EC-SOD) and aldehyde dehydrogenase 2 (ALDH2) genes and oral squamous cell carcinoma.

METHODS

The genetic polymorphisms of EC-SOD and ALDH2 were analyzed by polymorphism-polymerase chain reaction technique in peripheral blood leukocytes of 750 oral squamous cell carcinoma cases and 750 non-cancer controls.

RESULTS

The frequencies of EC-SOD (C/G) and ALDH2 variant genotypes were 38.27% and 69.47% in oral squamous cell carcinoma cases and 21.07% and 44.40% in healthy controls, respectively. Statistical tests showed significant difference in the frequencies between the two groups (P < 0.01). The risk of oral squamous cell carcinoma with EC-SOD (C/G) was significantly higher than that of controls (OR = 2.32). Individuals carrying ALDH2 variant genotypes had high risk of oral squamous cell carcinoma (OR = 2.85). Combined analysis of the polymorphisms showed that percentages of EC-SOD (C/G)/ALDH2 variant genotypes in oral squamous cell carcinoma and control groups were 30.67% and 6.80%, respectively (P < 0.01). Individuals carrying EC-SOD (C/G)/ALDH2 variant genotypes had high risk of oral squamous cell carcinoma (OR = 8.13). The drinking rate of the case group was significantly higher than that in the control group (OR = 2.70). Statistical analysis suggested an interaction between drinking and EC-SOD (C/G) and ALDH2 variant genotypes, which increase risk of oral squamous cell carcinoma (OR = 25.00).

CONCLUSION

EC-SOD (C/G) and ALDH2 variant genotypes and drinking are the risk factors in oral squamous cell carcinoma, which could carry out a coordinated attack of oral squamous cell carcinoma.

Extracellular superoxide dismutase ameliorates skeletal muscle abnormalities, cachexia, and exercise intolerance in mice with congestive heart failure

BACKGROUND

Congestive heart failure (CHF) is a leading cause of morbidity and mortality, and oxidative stress has been implicated in the pathogenesis of cachexia (muscle wasting) and the hallmark symptom, exercise intolerance. We have previously shown that a nitric oxide-dependent antioxidant defense renders oxidative skeletal muscle resistant to catabolic wasting. Here, we aimed to identify and determine the functional role of nitric oxide-inducible antioxidant enzyme(s) in protection against cardiac cachexia and exercise intolerance in CHF.

METHODS AND RESULTS

We demonstrated that systemic administration of endogenous nitric oxide donor S-nitrosoglutathione in mice blocked the reduction of extracellular superoxide dismutase (EcSOD) protein expression, as well as the induction of MAFbx/Atrogin-1 mRNA expression and muscle atrophy induced by glucocorticoid. We further showed that endogenous EcSOD, expressed primarily by type IId/x and IIa myofibers and enriched at endothelial cells, is induced by exercise training. Muscle-specific overexpression of EcSOD by somatic gene transfer or transgenesis (muscle creatine kinase [MCK]-EcSOD) in mice significantly attenuated muscle atrophy. Importantly, when crossbred into a mouse genetic model of CHF (α-myosin heavy chain-calsequestrin), MCK-EcSOD transgenic mice had significant attenuation of cachexia with preserved whole body muscle strength and endurance capacity in the absence of reduced HF. Enhanced EcSOD expression significantly ameliorated CHF-induced oxidative stress, MAFbx/Atrogin-1 mRNA expression, loss of mitochondria, and vascular rarefaction in skeletal muscle.

CONCLUSIONS

EcSOD plays an important antioxidant defense function in skeletal muscle against cardiac cachexia and exercise intolerance in CHF.

Cardiac myocyte-specific transgenic ecSOD targets mitochondria to protect against Ca(2+) induced permeability transition

ecSOD function has prototypically been associated with the extracellular space due to its secretion and localization to the extracellular matrix. A myocyte-specific ecSOD transgenic mouse has shown that it can also be localized to the myocyte intracellular compartment and is capable of attenuating Reactive oxygen species (ROS) formation and increasing NO bioavailability after ischemia reperfusion. Here, the subcellular localization of transgenic ecSOD was further defined by subcellular fractionation, immunofluorescent confocal microscopy, and Western analysis. Its impact on mitochondrial function was assessed by mitochondrial permeability transition (MPT). ecSOD was found to exist in cytosolic and nuclear fractions in addition to membrane. Colocalization of ecSOD with myocardial mitochondria was further demonstrated by confocal microscopy and subcellular fractionation of mitochondria and Western analysis. Isolated ventricular myocytes from cardiac-specific transgenic ecSOD mice were protected from hypoxia reoxygenation injury. Increased ecSOD colocalization to myocardial mitochondria in ecSOD Tg hearts limited MPT in response to Ca(2+) challenge. These results demonstrate that ecSOD is not restricted to the extracellular space and can alter MPT response to Ca(2+) suggesting mitochondrial localization of ecSOD can affect key mitochondrial functions such as MPT which are integral to cell survival.

Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD)

Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.

Impact of exercise training on redox signaling in cardiovascular diseases

Reactive oxygen and nitrogen species regulate a wide array of signaling pathways that governs cardiovascular physiology. However, oxidant stress resulting from disrupted redox signaling has an adverse impact on the pathogenesis and progression of cardiovascular diseases. In this review, we address how redox signaling and oxidant stress affect the pathophysiology of cardiovascular diseases such as ischemia-reperfusion injury, hypertension and heart failure. We also summarize the benefits of exercise training in tackling the hyperactivation of cellular oxidases and mitochondrial dysfunction seen in cardiovascular diseases.

Cardiomyocyte-restricted overexpression of extracellular superoxide dismutase increases nitric oxide bioavailability and reduces infarct size after ischemia/reperfusion

Increased levels of extracellular superoxide dismutase (ecSOD) induced by preconditioning or gene therapy protect the heart from ischemia/reperfusion injury. To elucidate the mechanism responsible for this action, we studied the effects of increased superoxide scavenging on nitric oxide (NO) bioavailability in a cardiac myocyte-specific ecSOD transgenic (Tg) mouse. Results indicated that ecSOD overexpression increased cardiac myocyte-specific ecSOD activity 27.5-fold. Transgenic ecSOD was localized to the sarcolemma and, notably, the cytoplasm of cardiac myocytes. Ischemia/reperfusion injury was attenuated in ecSOD Tg hearts, in which infarct size was decreased and LV functional recovery was improved. Using the ROS spin trap, DMPO, electron paramagnetic resonance (EPR) spectroscopy demonstrated a significant decrease in ROS in Tg hearts during the first 20 min of reperfusion. This decrease in ROS was accompanied by an increase in NO production determined by EPR using the NO spin trap, Fe-MGD. Attenuated ROS in ecSOD Tg myocytes was also supported by decreased production of peroxynitrite (ONOO⁻). Increased NO bioavailability was confirmed by attenuated guanylate cyclase-dependent (p-VASP) signaling. In conclusion, attenuation of ROS levels by cardiac-specific ecSOD overexpression increases NO bioavailability in response to ischemia/reperfusion and protects against reperfusion injury. These findings are the first to demonstrate increased NO bioavailability with attenuation of ROS by direct measurement of these reactive species (EPR, reactive fluorescent dyes) with cardiac-specific ecSOD expression. This is also the first indication that the predominantly extracellular SOD isoform is capable of cytosolic localization that affects myocardial intracellular signal transduction and function.

Excess protein O-GlcNAcylation and the progression of diabetic cardiomyopathy

We examined the role that enzymatic protein O-GlcNAcylation plays in the development of diabetic cardiomyopathy in a mouse model of Type 2 diabetes mellitus (DM2). Mice injected with low-dose streptozotocin and fed a high-fat diet developed mild hyperglycemia and obesity consistent with DM2. Studies were performed from 1 to 6 mo after initiating the DM2 protocol. After 1 mo, DM2 mice showed increased body weight, impaired fasting blood glucose, and hyperinsulinemia. Echocardiographic evaluation revealed left ventricular diastolic dysfunction by 2 mo and O-GlcNAcylation of several cardiac proteins and of nuclear transcription factor Sp1. By 4 mo, systolic dysfunction was observed and sarcoplasmic reticulum Ca(2+) ATPase expression decreased by 50%. Fibrosis was not observed at any timepoint in DM2 mice. Levels of the rate-limiting enzyme of the hexosamine biosynthetic pathway, glutamine:fructose-6-phosphate amidotransferase (GFAT) were increased as early as 2 mo. Fatty acids, which are elevated in DM2 mice, can possibly be linked to excessive protein O-GlcNAcylation levels, as cultured cardiac myocytes in normal glucose treated with oleic acid showed increased O-GlcNAcylation and GFAT levels. These data indicate that the early onset of diastolic dysfunction followed by the loss of systolic function, in the absence of cardiac hypertrophy or fibrosis, is associated with increased cardiac protein O-GlcNAcylation and increased O-GlcNAcylation levels of key calcium-handling proteins. A link between excessive protein O-GlcNAcylation and cardiac dysfunction is further supported by results showing that reducing O-GlcNAcylation by O-GlcNAcase overexpression improved cardiac function in the diabetic mouse. In addition, fatty acids play a role in stimulating excess O-GlcNAcylation. The nature and time course of changes observed in cardiac function suggest that protein O-GlcNAcylation plays a mechanistic role in the triggering of diabetic cardiomyopathy in DM2.

Effects of MnDPDP and ICRF-187 on Doxorubicin-Induced Cardiotoxicity and Anticancer Activity

Oxidative stress participates in doxorubicin (Dx)-induced cardiotoxicity. The metal complex MnDPDP and its metabolite MnPLED possess SOD-mimetic activity, DPDP and PLED have, in addition, high affinity for iron. Mice were injected intravenously with MnDPDP, DPDP, or dexrazoxane (ICRF-187). Thirty minutes later, mice were killed, the left atria were hung in organ baths and electrically stimulated, saline or Dx was added, and the contractility was measured for 60 minutes. In parallel experiments, 10 µM MnDPDP or MnPLED was added directly into the organ bath. The effect of MnDPDP on antitumor activity of Dx against two human tumor xenografts (MX-1 and A2780) was investigated. The in vitro cytotoxic activity was studied by co-incubating A2780 cells with MnDPDP, DPDP, and/or Dx. Dx caused a marked reduction in contractile force. In vivo treatment with MnDPDP and ICRF-187 attenuated the negative effect of Dx. When added directly into the bath, MnDPDP did not protect, whereas MnPLED attenuated the Dx effect by approximately 50%. MnDPDP or ICRF-187 did not interfere negatively with the anti-tumor activity of Dx, either in vivo or in vitro. Micromolar concentrations of DPDP but not MnDPDP displayed an in vitro cytotoxic activity against A2780 cells. The present results show that MnDPDP, after being metabolized to MnPLED, protects against acute Dx cardiotoxicity. Both in vivo and in vitro experiments show that cardioprotection takes place without interfering negatively with the anticancer activity of Dx. Furthermore, the results suggest that the previously described cytotoxic in vivo activity of MnDPDP is an inherent property of DPDP.

Alterations in cardiac structure and function in a murine model of chronic alcohol consumption

Male, wild-type, FVB strain mice were fed a nutritionally complete liquid diet supplemented with 4% ethanol v/v over a time course of 1, 2, 4, 8, 12, and 14 weeks. Controls were offered an isocaloric liquid equivalent and pair fed with their ethanol counterparts. Changes in cardiac physiology were assessed at respective time points via echocardiography. Additionally, the use of histological techniques, mRNA analysis, apoptosis determination, and immunohistochemistry were employed to determine the functional and structural changes on the heart. Echocardiograph analysis revealed a compensatory phase that occurred early in the time course (1-8 weeks) and decompensation reverting toward heart failure at weeks 12 and 14. Throughout the study, an increase in cardiomyocyte hypertrophy, cardiac fibrosis, apoptosis, TGF-β, and the presence of α-SMA-positive cells were determined. A compensatory period in mice treated with ethanol occurred early followed by a transition to a dilated phenotype over time. A number of factors may be involved in this process including the activation of myofibroblasts and their fibrotic activities that is correlated with the presence of transforming growth factor beta.

Role of superoxide-nitric oxide interactions in the accelerated age-related loss of muscle mass in mice lacking Cu,Zn superoxide dismutase

Mice lacking Cu,Zn superoxide dismutase (SOD1) show accelerated, age-related loss of muscle mass. Lack of SOD1 may lead to increased superoxide, reduced nitric oxide (NO), and increased peroxynitrite, each of which could initiate muscle fiber loss. Single muscle fibers from flexor digitorum brevis of wild-type (WT) and Sod1^−/− mice were loaded with NO-sensitive (4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate, DAF-FM) and superoxide-sensitive (dihydroethidium, DHE) probes. Gastrocnemius muscles were analyzed for SOD enzymes, nitric oxide synthases (NOS), and 3-nitrotyrosine (3-NT) content. A lack of SOD1 did not increase superoxide availability at rest because no increase in ethidium or 2-hydroxyethidium (2-HE) formation from DHE was seen in fibers from Sod1^−/− mice compared with those from WT mice. Fibers from Sod1^−/− mice had decreased NO availability (decreased DAF-FM fluorescence), increased 3-NT in muscle proteins indicating increased peroxynitrite formation and increased content of peroxiredoxin V (a peroxynitrite reductase), compared with WT mice. Muscle fibers from Sod1^−/− mice showed substantially reduced generation of superoxide in response to contractions compared with fibers from WT mice. Inhibition of NOS did not affect DHE oxidation in fibers from WT or Sod1^−/− mice at rest or during contractions, but transgenic mice overexpressing nNOS showed increased DAF-FM fluorescence and reduced DHE oxidation in resting muscle fibers. It is concluded that formation of peroxynitrite in muscle fibers is a major effect of lack of SOD1 in Sod1^−/− mice and may contribute to fiber loss in this model, and that NO regulates superoxide availability and peroxynitrite formation in muscle.

Extracellular superoxide dismutase protects cardiovascular syndecan-1 from oxidative shedding

The extracellular matrix is a complex system that regulates cell function within a tissue. The antioxidant enzyme extracellular superoxide dismutase (EC-SOD) is bound to the matrix, and previous studies show that a lack of EC-SOD results in increased cardiac injury, fibrosis, and loss of cardiac function. This study tests the hypothesis that EC-SOD protects against cardiac fibrosis mechanistically by limiting oxidative stress and oxidant-induced shedding of syndecan-1 in the extracellular matrix. Wild-type and EC-SOD null mice were treated with a single dose of doxorubicin, 15 mg/kg, and evaluated on day 15. Serum and left-ventricle tissue were collected for biochemical assays, including Western blot, mRNA expression, and immunohistochemical staining for syndecan-1. The loss of EC-SOD and doxorubicin-induced oxidative injury led to increases in shed syndecan-1 in the serum, which originates from the endothelium of the vasculature. The shed syndecan-1 ectodomain induces proliferation of primary mouse cardiac fibroblasts. This study suggests that one mechanism by which EC-SOD protects the heart against cardiac fibrosis is the prevention of oxidative shedding of cardiovascular syndecan-1 and its subsequent induction of fibroblast proliferation. This study provides potential new targets for understanding and altering fibrosis progression in the heart.

Effects of interleukin-18 on cardiac fibroblast function and gene expression

Fibroblasts are the primary cell type responsible for synthesis and remodeling of the extracellular matrix in the heart. A number of factors including growth factors, hormones and mechanical forces have been identified that modulate the production of extracellular matrix by cardiac fibroblasts. Inflammatory mediators including pro-inflammatory cytokines and chemokines also impact fibrosis of the heart. Recent studies have illustrated that interleukin-18 promotes a pro-fibrotic response in cardiac fibroblasts; however the effects of this cytokine on other aspects of fibroblast function have not been examined. While fibroblasts have long been known for their role in production and remodeling of the extracellular matrix, other functions of these cells are only now beginning to be appreciated. We hypothesize that exposure to interleukin-18 will stimulate other aspects of fibroblast behavior important in myocardial remodeling including proliferation, migration and collagen reorganization. Fibroblasts were isolated from adult male rat hearts and bioassays performed to determine the effects of interleukin-18 on fibroblast function. Treatment of fibroblasts with interleukin-18 (1-100ng/ml) resulted in increased production of extracellular matrix components and remodeling or contraction of three-dimensional collagen scaffolds by these cells. Furthermore, exposure to interleukin-18 stimulated fibroblast migration and proliferation. Treatment of heart fibroblasts with interleukin-18 resulted in the rapid activation of the c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase (PI3-kinase) pathways. Studies with pharmacological inhibitors illustrated that activation of these pathways is critical to interleukin-18 mediated alterations in fibroblast function. These studies illustrate that interleukin-18 plays a role in modulation of cardiac fibroblast function and may be an important component of the inflammation-fibrosis cascade during pathological myocardial remodeling.