Metallothionein prevents cardiac pathological changes in diabetes by modulating nitration and inactivation of cardiac ATP synthase

Diabetic cardiomyopathy - Zinc preventive and therapeutic potentials by its anti-oxidative stress and sensitizing insulin signaling pathways

Oxidative stress and insulin resistance are two key mechanisms for the development of diabetic cardiomyopathy (DCM, cardiac remodeling and dysfunction). In this review, we discussed how zinc and metallothionein (MT) protect the heart from type 1 or type 2 diabetes (T1D or T2D) through its anti-oxidative function and insulin-mediated PI3K/Akt signaling activation. Both T1D and T2D-induced DCM, shown by cardiac structural remodeling and dysfunction, in wild-type mice, but not in cardiomyocyte-specific overexpressing MT mice. In contrast, mice with global MT gene deletion were more susceptible to the development of DCM. When we used zinc to treat mice with either T1D or T2D, cardiac remodeling and dysfunction were significantly prevented along with increased cardiac MT expression. To support the role of zinc homeostasis in insulin signaling pathways, treatment of diabetic mice with zinc showed the preservation of phosphorylation levels of insulin-mediated glucose metabolism-related Akt2 and GSK-3β and even rescued cardiac pathogenesis induced by global deletion of Akt2 gene in a MT-dependent manner. These results suggest the protection by zinc from DCM is through both the induction of MT and sensitization of insulin signaling. Combined our own and other works, this review comprehensively summarized the roles of zinc homeostasis in the development and progression of DCM and its therapeutic implications. At the end, we provided pre-clinical and clinical evidence for the preventive and therapeutic potential of zinc supplementation through its anti-oxidative stress and sensitizing insulin signaling actions. Understanding the intricate connections between zinc and DCM provides insights for the future interventional approaches.

Polysaccharides from apple pomace exhibit anti-fatigue activity through increasing glycogen content

The polysaccharides were isolated from apple pomace by hot-water extraction, and their anti-fatigue activity was evaluated in C2C12 muscle myoblasts and male Kunming mice. The purified polysaccharides from apple pomace (PAP) have a molecular weight of 1.74 × 105 Da and were composed of mannose, rhamnose, glucose, galactose and arabinose. In C2C12 myoblasts, PAP showed no cytotoxicity in the concentrations of 0-300 μg/ml. PAP treatment increased the glycogen content, while the ATP content was not affected in C2C12 myoblasts. Further investigation found that the activity and gene expression of glycogen synthase, rather than glycogen phosphorylase, were upregulated by PAP treatment. The studies in vivo showed that PAP treatment did not affect the food intake and weight again in mice. Importantly, PAP prolonged the exhaustive swimming time, increased hepatic and skeletal muscle glycogen levels, and effectively inhibited the accumulation of blood lactic and blood urea nitrogen in mice. Taken together, the results suggested that PAP exhibit anti-fatigue activity in vitro and in vivo through increasing glycogen content.

Comparative transcriptome analysis reveals that ATP synthases regulate Fusarium oxysporum virulence by modulating sugar transporter gene expressions in tobacco

Fusarium oxysporum is a main causative agent of tobacco root rot, severely affecting tobacco growth. Here, 200 F. oxysporum strains were isolated and examined for their virulence toward tobacco plants. These strains were divided into disease class 1-3 (weak virulence), 4-6 (moderate virulence), and 7-9 (strong virulence). To understand the virulence mechanism of F. oxysporum, a comparative transcriptome study was performed using weak, moderate, and strong virulence-inducing strains. The results showed that expression levels of 1,678 tobacco genes were positively correlated with virulence levels, while expression levels of 3,558 genes were negatively associated with virulence levels. Interestingly, the expression levels of ATP synthase genes were positively correlated with F. oxysporum virulence. To verify whether ATP synthase gene expression is associated with F. oxysporum virulence, 5 strains each of strong, moderate, and weak virulence-inducing strains were tested using qRT-PCR. The results confirmed that ATP synthase gene expression is positively correlated with virulence levels. Knock-out mutants of ATP synthase genes resulted in a relatively weak virulence compared to wild-type as well as the inhibition of F. oxysporum-mediated suppression of NtSUC4, NtSTP12, NtHEX6, and NtSWEET, suggesting that ATP synthase activity is also associated with the virulence. Taken together, our analyses show that ATP synthases are key genes for the regulation of F. oxysporum virulence and provide important information for understanding the virulence mechanism of F. oxysporum in tobacco root rot.

Therapeutic potential of targeting oxidative stress in diabetic cardiomyopathy

Even in the absence of coronary artery disease and hypertension, diabetes mellitus (DM) may increase the risk for heart failure development. This risk evolves from functional and structural alterations induced by diabetes in the heart, a cardiac entity termed diabetic cardiomyopathy (DbCM). Oxidative stress, defined as the imbalance of reactive oxygen species (ROS) has been increasingly proposed to contribute to the development of DbCM. There are several sources of ROS production including the mitochondria, NAD(P)H oxidase, xanthine oxidase, and uncoupled nitric oxide synthase. Overproduction of ROS in DbCM is thought to be counterbalanced by elevated antioxidant defense enzymes such as catalase and superoxide dismutase. Excess ROS in the cardiomyocyte results in further ROS production, mitochondrial DNA damage, lipid peroxidation, post-translational modifications of proteins and ultimately cell death and cardiac dysfunction. Furthermore, ROS modulates transcription factors responsible for expression of antioxidant enzymes. Lastly, evidence exists that several pharmacological agents may convey cardiovascular benefit by antioxidant mechanisms. As such, increasing our understanding of the pathways that lead to increased ROS production and impaired antioxidant defense may enable the development of therapeutic strategies against the progression of DbCM. Herein, we review the current knowledge about causes and consequences of ROS in DbCM, as well as the therapeutic potential and strategies of targeting oxidative stress in the diabetic heart.

Speckle-tracking echocardiography combined with imaging mass spectrometry assesses region-dependent alterations

Left ventricular (LV) contraction is characterized by shortening and thickening of longitudinal and circumferential fibres. To date, it is poorly understood how LV deformation is altered in the pathogenesis of streptozotocin (STZ)-induced type 1 diabetes mellitus-associated diabetic cardiomyopathy and how this is associated with changes in cardiac structural composition. To gain further insights in these LV alterations, eight-week-old C57BL6/j mice were intraperitoneally injected with 50 mg/kg body weight STZ during 5 consecutive days. Six, 9, and 12 weeks (w) post injections, echocardiographic analysis was performed using a Vevo 3100 device coupled to a 30-MHz linear-frequency transducer. Speckle-tracking echocardiography (STE) demonstrated impaired global longitudinal peak strain (GLS) in STZ versus control mice at all time points. 9w STZ animals displayed an impaired global circumferential peak strain (GCS) versus 6w and 12w STZ mice. They further exhibited decreased myocardial deformation behaviour of the anterior and posterior base versus controls, which was paralleled with an elevated collagen I/III protein ratio. Additionally, hypothesis-free proteome analysis by imaging mass spectrometry (IMS) identified regional- and time-dependent changes of proteins affecting sarcomere mechanics between STZ and control mice. In conclusion, STZ-induced diabetic cardiomyopathy changes global cardiac deformation associated with alterations in cardiac sarcomere proteins.

Metallothionein Protects the Heart Against Myocardial Infarction via the mTORC2/FoxO3a/Bim Pathway

Aims: Cardiac-specific overexpression of metallothionein (MT) has been shown to be beneficial in ischemic heart disease, but the detailed mechanisms through which MT protects against myocardial infarction (MI) remain unknown. This study assessed the involvement of the mTORC2/FoxO3a/Bim pathway in the cardioprotective effects of MT. Results: MI was induced in wild-type (FVB) mice and in cardiac-specific MT-overexpressing transgenic (MT-TG) mice by ligation of the left anterior descending (LAD) coronary artery. Cardiac function was better; infarct size and cardiomyocyte apoptosis were lower in MT-TG mice than in FVB mice after MI. Moreover, MT-TG mice exhibited better phenotypes after LAD ligation than FVB mice treated with Mn(III)tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP; a reactive oxygen species [ROS] scavenger) and cardiac-specific catalase-overexpressing transgenic (CAT-TG) mice, which showed the same ROS levels as MT-TG mice after MI. Activation of mechanistic target of rapamycin complex 2 (mTORC2) was essential for the cardioprotective effects of MT against MI. In addition, MT attenuated the downregulation of phospho-FoxO3a after MI, inhibiting the expression of the apoptosis-associated gene Bim, located downstream of FoxO3a, and reducing the level of apoptosis after MI. To mimic ischemic-injured FVB and MT-TG mice in vitro, H9c2 and MT-overexpressing H9c2 (H9c2MT7) cardiomyocytes were subjected to oxygen and glucose deprivation, with the results being consistent with those obtained in vivo. Innovation and Conclusion: The cardioprotective effects of MT against MI are not entirely dependent upon its ability to eliminate ROS. Rather, MT overexpression mostly protects against MI through the mTORC2-FoxO3a-Bim pathway.

Implications of impaired zinc homeostasis in diabetic cardiomyopathy and nephropathy

Impaired zinc homeostasis is observed in diabetes mellitus (DM2) and its complications. Zinc has a specific role in pancreatic β-cells via insulin synthesis, storage, and secretion. Intracellular zinc homeostasis is tightly controlled by zinc transporters (ZnT and Zip families) and metallothioneins (MT) which modulate the uptake, storage, and distribution of zinc. Several investigations in animal models demonstrate the protective role of MT in DM2 and its cardiovascular or renal complications, while a copious literature shows that a common polymorphism (R325W) in ZnT8, which affects the protein's zinc transport activity, is associated with increased DM2 risk. Emerging studies highlight a role of other zinc transporters in β-cell function, suggesting that targeting them could make a possible contribution in managing the hyperglycemia in diabetic patients. This article summarizes the current findings concerning the role of zinc homeostasis in DM2 pathogenesis and development of diabetic cardiomyopathy and nephropathy and suggests novel therapeutic targets. © 2017 BioFactors, 43(6):770-784, 2017.

Effects of Chronic and Acute Zinc Supplementation on Myocardial Ischemia-Reperfusion Injury in Rats

The present study aims to explore the effects of chronic and acute zinc sulfate supplementation on myocardial ischemia-reperfusion injury in rats. The study registered 50 adult male rats which were divided into five groups in equal numbers as follows: group 1, normal control; group 2, sham; group 3, myocardial ischemia reperfusion (My/IR): the group which was fed on a normal diet and in which myocardial I/R was induced; group 4, myocardial ischemia reperfusion + chronic zinc: (5 mg/kg i.p. zinc sulfate for 15 days); and group 5, myocardial ischemia reperfusion + acute zinc: the group which was administered 15 mg/kg i.p. zinc sulfate an hour before the operation and in which myocardial I/R was induced. The collected blood and cardiac tissue samples were analyzed using spectrophotometric method to determine levels of MDA, as an indicator of tissue injury, and GSH, as an indicator of antioxidant activity. The highest plasma and heart tissue MDA levels were measured in group 3 (p < 0.05). Group 5 had lower MDA values than group 3, while group 4 had significantly lower MDA values than groups 3 and 5 (p < 0.05). The highest erythrocyte GSH values were found in group 4 (p < 0.05). Erythrocyte GSH values in group 5 were higher than those in group 3 (p < 0.05). The highest GSH values in heart tissue were measured in group 4 (p < 0.05). The results of the study reveal that the antioxidant activity inhibited by elevated oxidative stress in heart ischemia reperfusion in rats is restored partially by acute zinc administration and markedly by chronic zinc supplementation.

Catalase ameliorates diabetes-induced cardiac injury through reduced p65/RelA- mediated transcription of BECN1

Catalase is an antioxidative enzyme that converts hydrogen peroxide (H₂ O₂ ) produced by superoxide dismutase from highly reactive superoxide (O₂^- ) to water and oxygen molecules. Although recent findings demonstrate that catalase, autophagy and the nuclear factor κB (NF-κB) signalling pathway are centrally involved in diabetic cardiomyopathy (DCM), the interplay between the three has not been fully characterized. Thus, the mechanism responsible for catalase-mediated protection against heart injury in diabetic mice was investigated in this study, as well as the role of NF-κB-p65 in the regulation of autophagic flux was investigated in this study. Western blot analysis revealed that catalase inhibited NF-κB activity and decreased LC3-II (microtubule-associated protein 1 light chain 3) and beclin-1 (Atg6) expression. Furthermore, up-regulation of autophagy was detrimental for cardiac function in diabetic mice. Catalase overexpression reduced the level of NF-κB subunit in the nucleus, where it initiates autophagy through activation of the key autophagy gene BECN1. To evaluate the role of the NF-κB pathway in diabetes-induced autophagy, Bay11-7082, an NF-κB inhibitor, was injected into diabetic mice, which suppressed NF-κB and attenuated diabetes-induced autophagy and myocardial apoptosis. In agreement with the in vivo results, Bay11-7082 also inhibited high-glucose-induced activation of NF-κB and the up-regulation of LC3-II and beclin-1 expression in H9c2 cells. In addition, high-glucose-induced activation of autophagic flux and apoptosis were largely attenuated by p65 siRNA, suggesting that catalase ameliorates diabetes-induced autophagy, at least in part by increasing the activity of the NF-κB pathway and p65-mediated transcription of BECN1.

Annexin A2 functions downstream of c‑Jun N‑terminal kinase to promote skin fibroblast cell migration

Delayed healing of skin wounds is one of the outcomes of diabetes mellitus (DM), a condition that affects a significant number of patients worldwide. However, the underlying mechanisms remain unknown. In order to examine proteome alterations in DM, a rat model of type 1 diabetes was developed using streptozotocin injections. The proteomic responses of normal and DM rat skin were analyzed by two‑dimensional electrophoresis, and differentially expressed proteins were identified using a liquid chromatography/mass spectrometry system. DM induced 36 and repressed 41 differentially expressed proteins, respectively. Altered proteins were involved in a number of biological processes, including RNA and protein metabolism, the tricarboxylic acid cycle, glycolysis, cytoskeleton regulation, hydrogen detoxification and calcium‑mediated signal transduction. In addition, overexpression of annexin A2, one of the signaling proteins altered by DM, accelerated the rate of human skin fibroblast cell migration. Application of SP600125, an inhibitor of a key regulator of cell migration c‑Jun N‑terminal kinase (JNK), inhibited the migration of normal cells. By contrast, SP600125 treatment did not inhibit the migration of annexin A2‑overexpressed cells, indicating that annexin A2 may function downstream of JNK. In conclusion, the results of the present study reveal the potential proteomic responses to DM in skin tissues, and demonstrate a positive functional role of annexin A2 in fibroblast cell migration.

Diabetic Microvascular Disease and Pulmonary Fibrosis: The Contribution of Platelets and Systemic Inflammation

Diabetes is strongly associated with systemic inflammation and oxidative stress, but its effect on pulmonary vascular disease and lung function has often been disregarded. Several studies identified restrictive lung disease and fibrotic changes in diabetic patients and in animal models of diabetes. While microvascular dysfunction is a well-known complication of diabetes, the mechanisms leading to diabetes-induced lung injury have largely been disregarded. We described the potential involvement of diabetes-induced platelet-endothelial interactions in perpetuating vascular inflammation and oxidative injury leading to fibrotic changes in the lung. Changes in nitric oxide synthase (NOS) activation and decreased NO bioavailability in the diabetic lung increase platelet activation and vascular injury and may account for platelet hyperreactivity reported in diabetic patients. Additionally, the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway has been reported to mediate pancreatic islet damage, and is implicated in the onset of diabetes, inflammation and vascular injury. Many growth factors and diabetes-induced agonists act via the JAK/STAT pathway. Other studies reported the contribution of the JAK/STAT pathway to the regulation of the pulmonary fibrotic process but the role of this pathway in the development of diabetic lung fibrosis has not been considered. These observations may open new therapeutic perspectives for modulating multiple pathways to mitigate diabetes onset or its pulmonary consequences.

Zinc deficiency exacerbates while zinc supplement attenuates cardiac hypertrophy in high-fat diet-induced obese mice through modulating p38 MAPK-dependent signaling

Childhood obesity often leads to cardiovascular diseases, such as obesity-related cardiac hypertrophy (ORCH), in adulthood, due to chronic cardiac inflammation. Zinc is structurally and functionally essential for many transcription factors; however, its role in ORCH and underlying mechanism(s) remain unclear and were explored here in mice with obesity induced with high-fat diet (HFD). Four week old mice were fed on either HFD (60%kcal fat) or normal diet (ND, 10% kcal fat) for 3 or 6 months, respectively. Either diet contained one of three different zinc quantities: deficiency (ZD, 10mg zinc per 4057kcal), normal (ZN, 30mg zinc per 4057kcal) or supplement (ZS, 90mg zinc per 4057kcal). HFD induced a time-dependent obesity and ORCH, which was accompanied by increased cardiac inflammation and p38 MAPK activation. These effects were worsened by ZD in HFD/ZD mice and attenuated by ZS in HFD/ZS group, respectively. Also, administration of a p38 MAPK specific inhibitor in HFD mice for 3 months did not affect HFD-induced obesity, but completely abolished HFD-induced, and zinc deficiency-worsened, ORCH and cardiac inflammation. In vitro exposure of adult cardiomyocytes to palmitate induced cell hypertrophy accompanied by increased p38 MAPK activation, which was heightened by zinc depletion with its chelator TPEN. Inhibition of p38 MAPK with its specific siRNA also prevented the effects of palmitate on cardiomyocytes. These findings demonstrate that ZS alleviates but ZD heightens cardiac hypertrophy in HFD-induced obese mice through suppressing p38 MAPK-dependent cardiac inflammatory and hypertrophic pathways.

Zinc delays the progression of obesity-related glomerulopathy in mice via down-regulating P38 MAPK-mediated inflammation

OBJECTIVE

Obesity, particularly child obesity, is one of the most common public health problems in the world and raises the risk of end-stage renal disease. Zinc (Zn) is essential for multiple organs in terms of normal structure and function; however, effects of Zn deficiency or supplementation among young individuals with obesity have not been well studied.

METHODS

Weaned mice were fed high-fat diets (HFD) with varied contents of Zn (Zn deficient, adequate, and supplemented) for 3 or 6 months. This study examined associations between renal pathogenesis and dietary Zn levels, specifically assessing inflammatory pathways by utilizing P38 MAPK inhibitor SB203580.

RESULTS

HFD feeding induced typical syndromes of obesity-related renal disorders, which worsened by Zn marginal deficiency. The progression of obesity-related renal disorders was delayed by Zn supplementation. HFD induced renal inflammation, reflected by increased P38 MAPK phosphorylation along with increases of inflammatory cytokines MCP-1, IL-1β, IL-6, and TNF-α. P38 MAPK inhibition prevented renal pathological changes in mice fed with HFD and HFD/Zn deficiency.

CONCLUSIONS

P38 MAPK mediated the renal inflammatory responses, which played a central role in the pathogenesis of HFD-induced renal disorders. Zn could delay the progression of obesity-related kidney disease by down-regulating P38 MAPK-mediated inflammation.

Oral treatment with a zinc complex of acetylsalicylic acid prevents diabetic cardiomyopathy in a rat model of type-2 diabetes: activation of the Akt pathway

BACKGROUND

Type-2 diabetics have an increased risk of cardiomyopathy, and heart failure is a major cause of death among these patients. Growing evidence indicates that proinflammatory cytokines may induce the development of insulin resistance, and that anti-inflammatory medications may reverse this process. We investigated the effects of the oral administration of zinc and acetylsalicylic acid, in the form of bis(aspirinato)zinc(II)-complex Zn(ASA)2, on different aspects of cardiac damage in Zucker diabetic fatty (ZDF) rats, an experimental model of type-2 diabetic cardiomyopathy.

METHODS

Nondiabetic control (ZL) and ZDF rats were treated orally with vehicle or Zn(ASA)2 for 24 days. At the age of 29-30 weeks, the electrical activities, left-ventricular functional parameters and left-ventricular wall thicknesses were assessed. Nitrotyrosine immunohistochemistry, TUNEL-assay, and hematoxylin-eosin staining were performed. The protein expression of the insulin-receptor and PI3K/AKT pathway were quantified by Western blot.

RESULTS

Zn(ASA)2-treatment significantly decreased plasma glucose concentration in ZDF rats (39.0 ± 3.6 vs 49.4 ± 2.8 mM, P < 0.05) while serum insulin-levels were similar among the groups. Data from cardiac catheterization showed that Zn(ASA)2 normalized the increased left-ventricular diastolic stiffness (end-diastolic pressure-volume relationship: 0.064 ± 0.008 vs 0.084 ± 0.014 mmHg/µl; end-diastolic pressure: 6.5 ± 0.6 vs 7.9 ± 0.7 mmHg, P < 0.05). Furthermore, ECG-recordings revealed a restoration of prolonged QT-intervals (63 ± 3 vs 83 ± 4 ms, P < 0.05) with Zn(ASA)2. Left-ventricular wall thickness, assessed by echocardiography, did not differ among the groups. However histological examination revealed an increase in the cardiomyocytes' transverse cross-section area in ZDF compared to the ZL rats, which was significantly decreased after Zn(ASA)2-treatment. Additionally, a significant fibrotic remodeling was observed in the diabetic rats compared to ZL rats, and Zn(ASA)2-administered ZDF rats showed a similar collagen content as ZL animals. In diabetic hearts Zn(ASA)2 significantly decreased DNA-fragmentation, and nitro-oxidative stress, and up-regulated myocardial phosphorylated-AKT/AKT protein expression. Zn(ASA)2 reduced cardiomyocyte death in a cellular model of oxidative stress. Zn(ASA)2 had no effects on altered myocardial CD36, GLUT-4, and PI3K protein expression.

CONCLUSIONS

We demonstrated that treatment of type-2 diabetic rats with Zn(ASA)2 reduced plasma glucose-levels and prevented diabetic cardiomyopathy. The increased myocardial AKT activation could, in part, help to explain the cardioprotective effects of Zn(ASA)2. The oral administration of Zn(ASA)2 may have therapeutic potential, aiming to prevent/treat cardiac complications in type-2 diabetic patients.

The apoptotic effect and the plausible mechanism of microwave radiation on rat myocardial cells

Microwaves may exert adverse biological effects on the cardiovascular system at the integrated system and cellular levels. However, the mechanism underlying such effects remains poorly understood. Here, we report a previously uncharacterized mechanism through which microwaves damage myocardial cells. Rats were treated with 2450 MHz microwave radiation at 50, 100, 150, or 200 mW/cm(2) for 6 min. Microwave treatment significantly enhanced the levels of various enzymes in serum. In addition, it increased the malondialdehyde content while decreasing the levels of antioxidative stress enzymes, activities of enzyme complexes I-IV, and ATP in myocardial tissues. Notably, irradiated myocardial cells exhibited structural damage and underwent apoptosis. Furthermore, Western blot analysis revealed significant changes in expression levels of proteins involved in oxidative stress regulation and apoptotic signaling pathways, indicating that microwave irradiation could induce myocardial cell apoptosis by interfering with oxidative stress and cardiac energy metabolism. Our findings provide useful insights into the mechanism of microwave-induced damage to the cardiovascular system.

Mitochondrial oxidative metabolism and uncoupling proteins in the failing heart

Despite significant progress in cardiovascular medicine, myocardial ischemia and infarction, progressing eventually to the final end point heart failure (HF), remain the leading cause of morbidity and mortality in the USA. HF is a complex syndrome that results from any structural or functional impairment in ventricular filling or blood ejection. Ultimately, the heart's inability to supply the body's tissues with enough blood may lead to death. Mechanistically, the hallmarks of the failing heart include abnormal energy metabolism, increased production of reactive oxygen species (ROS) and defects in excitation-contraction coupling. HF is a highly dynamic pathological process, and observed alterations in cardiac metabolism and function depend on the disease progression. In the early stages, cardiac remodeling characterized by normal or slightly increased fatty acid (FA) oxidation plays a compensatory, cardioprotective role. However, upon progression of HF, FA oxidation and mitochondrial oxidative activity are decreased, resulting in a significant drop in cardiac ATP levels. In HF, as a compensatory response to decreased oxidative metabolism, glucose uptake and glycolysis are upregulated, but this upregulation is not sufficient to compensate for a drop in ATP production. Elevated mitochondrial ROS generation and ROS-mediated damage, when they overwhelm the cellular antioxidant defense system, induce heart injury and contribute to the progression of HF. Mitochondrial uncoupling proteins (UCPs), which promote proton leak across the inner mitochondrial membrane, have emerged as essential regulators of mitochondrial membrane potential, respiratory activity and ROS generation. Although the physiological role of UCP2 and UCP3, expressed in the heart, has not been clearly established, increasing evidence suggests that these proteins by promoting mild uncoupling could reduce mitochondrial ROS generation and cardiomyocyte apoptosis and ameliorate thereby myocardial function. Further investigation on the alterations in cardiac UCP activity and regulation will advance our understanding of their physiological roles in the healthy and diseased heart and also may facilitate the development of novel and more efficient therapies.

Cardiac-specific overexpression of catalase prevents diabetes-induced pathological changes by inhibiting NF-κB signaling activation in the heart

Catalase is an antioxidant enzyme that specifically catabolizes hydrogen peroxide (H2O2). Overexpression of catalase via a heart-specific promoter (CAT-TG) was reported to reduce diabetes-induced accumulation of reactive oxygen species (ROS) and further prevent diabetes-induced pathological abnormalities, including cardiac structural derangement and left ventricular abnormity in mice. However, the mechanism by which catalase overexpression protects heart function remains unclear. This study found that activation of a ROS-dependent NF-κB signaling pathway was downregulated in hearts of diabetic mice overexpressing catalase. In addition, catalase overexpression inhibited the significant increase in nitration levels of key enzymes involved in energy metabolism, including α-oxoglutarate dehydrogenase E1 component (α-KGD) and ATP synthase α and β subunits (ATP-α and ATP-β). To assess the effects of the NF-κB pathway activation on heart function, Bay11-7082, an inhibitor of the NF-κB signaling pathway, was injected into diabetic mice, protecting mice against the development of cardiac damage and increased nitrative modifications of key enzymes involved in energy metabolism. In conclusion, these findings demonstrated that catalase protects mouse hearts against diabetic cardiomyopathy, partially by suppressing NF-κB-dependent inflammatory responses and associated protein nitration.

Drug-induced mitochondrial dysfunction and cardiotoxicity

Mitochondria has an essential role in myocardial tissue homeostasis; thus deterioration in mitochondrial function eventually leads to cardiomyocyte and endothelial cell death and consequent cardiovascular dysfunction. Several chemical compounds and drugs have been known to directly or indirectly modulate cardiac mitochondrial function, which can account both for the toxicological and pharmacological properties of these substances. In many cases, toxicity problems appear only in the presence of additional cardiovascular disease conditions or develop months/years following the exposure, making the diagnosis difficult. Cardiotoxic agents affecting mitochondria include several widely used anticancer drugs [anthracyclines (Doxorubicin/Adriamycin), cisplatin, trastuzumab (Herceptin), arsenic trioxide (Trisenox), mitoxantrone (Novantrone), imatinib (Gleevec), bevacizumab (Avastin), sunitinib (Sutent), and sorafenib (Nevaxar)], antiviral compound azidothymidine (AZT, Zidovudine) and several oral antidiabetics [e.g., rosiglitazone (Avandia)]. Illicit drugs such as alcohol, cocaine, methamphetamine, ecstasy, and synthetic cannabinoids (spice, K2) may also induce mitochondria-related cardiotoxicity. Mitochondrial toxicity develops due to various mechanisms involving interference with the mitochondrial respiratory chain (e.g., uncoupling) or inhibition of the important mitochondrial enzymes (oxidative phosphorylation, Szent-Györgyi-Krebs cycle, mitochondrial DNA replication, ADP/ATP translocator). The final phase of mitochondrial dysfunction induces loss of mitochondrial membrane potential and an increase in mitochondrial oxidative/nitrative stress, eventually culminating into cell death. This review aims to discuss the mechanisms of mitochondrion-mediated cardiotoxicity of commonly used drugs and some potential cardioprotective strategies to prevent these toxicities.

Spotlights on immunological effects of reactive nitrogen species: When inflammation says nitric oxide

Over the last decades, nitric oxide (NO) has been definitively recognised as one of the key players involved in immunity and inflammation. NO generation was originally described in activated macrophages, which still represent the prototype of NO-producing cells. Notwithstanding, additional cell subsets belonging to both innate and adaptive immunity have been documented to sustain NO propagation by means of the enzymatic activity of different nitric oxide synthase isoforms. Furthermore, due to its chemical characteristics, NO could rapidly react with other free radicals to generate different reactive nitrogen species (RNS), which have been intriguingly associated with many pathological conditions. Nonetheless, the plethora of NO/RNS-mediated effects still remains extremely puzzling. The aim of this manuscript is to dig into the broad literature on the topic to provide intriguing insights on NO-mediated circuits within immune system. We analysed NO and RNS immunological clues arising from their biochemical properties, immunomodulatory activities and finally dealing with their impact on different pathological scenarios with far prompting intriguing perspectives for their pharmacological targeting.

Diabetic cardiomyopathy and its mechanisms: Role of oxidative stress and damage

Diabetic cardiomyopathy as an important threat to health occurs with or without coexistence of vascular diseases. The exact mechanisms underlying the disease remain incompletely clear. Although several pathological mechanisms responsible for diabetic cardiomyopathy have been proposed, oxidative stress is widely considered as one of the major causes for the pathogenesis of the disease. Hyperglycemia-, hyperlipidemia-, hypertension- and inflammation-induced oxidative stress are major risk factors for the development of microvascular pathogenesis in the diabetic myocardium, which results in abnormal gene expression, altered signal transduction and the activation of pathways leading to programmed myocardial cell deaths. In the present article, we aim to provide an extensive review of the role of oxidative stress and anti-oxidants in diabetic cardiomyopathy based on our own works and literature information available.

Interplay of oxidative, nitrosative/nitrative stress, inflammation, cell death and autophagy in diabetic cardiomyopathy

Diabetes is a recognized risk factor for cardiovascular diseases and heart failure. Diabetic cardiovascular dysfunction also underscores the development of diabetic retinopathy, nephropathy and neuropathy. Despite the broad availability of antidiabetic therapy, glycemic control still remains a major challenge in the management of diabetic patients. Hyperglycemia triggers formation of advanced glycosylation end products (AGEs), activates protein kinase C, enhances polyol pathway, glucose autoxidation, which coupled with elevated levels of free fatty acids, and leptin have been implicated in increased generation of superoxide anion by mitochondria, NADPH oxidases and xanthine oxidoreductase in diabetic vasculature and myocardium. Superoxide anion interacts with nitric oxide forming the potent toxin peroxynitrite via diffusion limited reaction, which in concert with other oxidants triggers activation of stress kinases, endoplasmic reticulum stress, mitochondrial and poly(ADP-ribose) polymerase 1-dependent cell death, dysregulates autophagy/mitophagy, inactivates key proteins involved in myocardial calcium handling/contractility and antioxidant defense, activates matrix metalloproteinases and redox-dependent pro-inflammatory transcription factors (e.g. nuclear factor kappaB) promoting inflammation, AGEs formation, eventually culminating in myocardial dysfunction, remodeling and heart failure. Understanding the complex interplay of oxidative/nitrosative stress with pro-inflammatory, metabolic and cell death pathways is critical to devise novel targeted therapies for diabetic cardiomyopathy, which will be overviewed in this brief synopsis. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.