High-glucose-increased expression and activation of NADPH oxidase in human vascular smooth muscle cells is mediated by 4-hydroxynonenal-activated PPARα and PPARβ/δ

High glucose induces vascular smooth muscle cell (SMC) dysfunction by generating oxidative stress attributable, in part, to the up-regulated NADPH oxidases (Nox). We have attempted to elucidate the high-glucose-generated molecular signals that mediate this effect and hypothesize that products of high-glucose-induced lipid peroxidation regulate Nox by activating peroxisome proliferator-activated receptors (PPARs). Human aortic SMCs were exposed to glucose (5.5-25 mM) or 4-hydroxynonenal (1-25 μM, 4-HNE). Lucigenin assay, real-time polymerase chain reaction, western blot, and promoter analyses were employed to investigate Nox. We found that high glucose generated an increase in Nox activity and expression. It also promoted oxidative stress that consequently induced lipid peroxidation, which resulted in the production of 4-HNE. Pharmacological inhibition of Nox activity significantly reduced the formation of high-glucose-induced 4-HNE. Exposure of SMCs to non-cytotoxic concentrations (1-10 μM) of 4-HNE alone mimicked the effect of high glucose incubation, whereas scavenging of 4-HNE by N-acetyl L-cysteine completely abolished both the effects of high glucose and 4-HNE. The latter exerted its effect by activating PPARα and PPARβ/δ, but not PPARγ, as assessed pharmacologically by the inhibitory effect of selective antagonists and following the silencing of the expression of these receptors. These new data indicate that 4-HNE, generated following Nox activation, functions as an endogenous activator of PPARα and PPARβ/δ. The newly discovered "lipid peroxidation products-PPARs-Nox axis" represents a novel mechanism of Nox regulation and an additional therapeutic target for oxidative stress in diabetes.

The role of reactive oxygen species in microvascular remodeling

The microcirculation is a portion of the vascular circulatory system that consists of resistance arteries, arterioles, capillaries and venules. It is the place where gases and nutrients are exchanged between blood and tissues. In addition the microcirculation is the major contributor to blood flow resistance and consequently to regulation of blood pressure. Therefore, structural remodeling of this section of the vascular tree has profound implications on cardiovascular pathophysiology. This review is focused on the role that reactive oxygen species (ROS) play on changing the structural characteristics of vessels within the microcirculation. Particular attention is given to the resistance arteries and the functional pathways that are affected by ROS in these vessels and subsequently induce vascular remodeling. The primary sources of ROS in the microcirculation are identified and the effects of ROS on other microcirculatory remodeling phenomena such as rarefaction and collateralization are briefly reviewed.

Can Tea Consumption be a Safe and Effective Therapy Against Diabetes Mellitus-Induced Neurodegeneration?

Diabetes mellitus (DM) is a metabolic disease that is rapidly increasing and has become a major public health problem. Type 2 DM (T2DM) is the most common type, accounting for up to 90-95% of the new diagnosed DM cases. The brain is very susceptible to glucose fluctuations and hyperglycemia-induced oxidative stress (OS). It is well known that DM and the risk of developing neurodegenerative diseases are associated. Tea, Camellia sinensis L., is one of the most consumed beverages. It contains several phytochemicals, such as polyphenols, methylxanthines (mainly caffeine) and L-theanine that are often reported to be responsible for tea's health benefits, including in brain. Tea phytochemicals have been reported to be responsible for tea's significant antidiabetic and neuroprotective properties and antioxidant potential. Epidemiological studies have shown that regular consumption of tea has positive effects on DM-caused complications and protects the brain against oxidative damage, contributing to an improvement of the cognitive function. Among the several reported benefits of tea consumption, those related with neurodegenerative diseases are of great interest. Herein, we discuss the potential beneficial effects of tea consumption and tea phytochemicals on DM and how their action can counteract the severe brain damage induced by this disease.

Aldosterone activates transcription factor Nrf2 in kidney cells both in vitro and in vivo

AIMS

An increased kidney cancer risk was found in hypertensive patients, who frequently exhibit hyperaldosteronism, known to contribute to kidney injury, with oxidative stress playing an important role. The capacity of kidney cells to up-regulate transcription factor nuclear factor-erythroid-2-related factor 2 (Nrf2), a key regulator of the cellular antioxidative defense, as a prevention of aldosterone-induced oxidative damage was investigated both in vitro and in vivo.

RESULTS

Aldosterone activated Nrf2 and increased the expression of enzymes involved in glutathione (GSH) synthesis and detoxification. This activation depended on the mineralocorticoid receptor (MR) and oxidative stress. In vitro, Nrf2 activation, GSH amounts, and target gene levels decreased after 24 h, while oxidant levels remained high. Nrf2 activation could not protect cells against oxidative DNA damage, as aldosterone-induced double-strand breaks and 7,8-dihydro-8-oxo-guanine (8-oxodG) lesions steadily rose. The Nrf2 activator sulforaphane enhanced the Nrf2 response both in vitro and in vivo, thereby preventing aldosterone-induced DNA damage. In vivo, Nrf2 activation further had beneficial effects on the aldosterone-caused blood pressure increase and loss of kidney function.

INNOVATION

This is the first study showing the activation of Nrf2 by aldosterone. Moreover, the results identify sulforaphane as a substance that is capable of preventing aldosterone-induced damage both in vivo and in vitro.

CONCLUSION

Aldosterone-induced Nrf2 adaptive response cannot neutralize oxidative actions of chronically increased aldosterone, which, therefore could be causally involved in the increased cancer incidence of hypertensive individuals. Enhancing the cellular antioxidative defense with sulforaphane might exhibit beneficial effects.

Reactive oxygen species adversely impacts bone marrow microenvironment in diabetes

Significance: Patients with diabetes mellitus suffer an excess of cardiovascular complications and recover worse from them as compared with their nondiabetic peers. It is well known that microangiopathy is the cause of renal damage, blindness, and heart attacks in patients with diabetes. This review highlights molecular deficits in stem cells and a supporting microenvironment, which can be traced back to oxidative stress and ultimately reduce stem cells therapeutic potential in diabetic patients.

RECENT ADVANCES

New research has shown that increased oxidative stress contributes to inducing microangiopathy in bone marrow (BM), the tissue contained inside the bones and the main source of stem cells. These precious cells not only replace old blood cells but also exert an important reparative function after acute injuries and heart attacks.

CRITICAL ISSUES

The starvation of BM as a consequence of microangiopathy can lead to a less efficient healing in diabetic patients with ischemic complications. Furthermore, stem cells from a patient's BM are the most used in regenerative medicine trials to mend hearts damaged by heart attacks.

FUTURE DIRECTIONS

A deeper understanding of redox signaling in BM stem cells will lead to new modalities for preserving local and systemic homeostasis and to more effective treatments of diabetic cardiovascular complications.

Oxidative stress: implications for the development of diabetic retinopathy and antioxidant therapeutic perspectives

In recent decades, localized tissue oxidative stress has been implicated as a key component in the development of diabetic retinopathy (DR). Increasing evidence shows that oxidative stress caused by diabetes-induced metabolic abnormalities is the most common mechanism associated with the pathogenesis of DR for both type 1 and type 2 diabetes. Increase in intracellular reactive oxygen species (ROS) concentrations results in the activation of several mechanisms involved in the pathogenesis of DR. In particular, damage or dysfunction caused by oxidative stress still persists even after glycemia has been normalized. Despite considerable evidence showing the beneficial effects of antioxidants in preventing the development of retinopathy, results from large-scale clinical trials on classic antioxidants are somewhat ambiguous. Scavenging reactive radicals may not be the most ideal antioxidant strategy in DR. Advances in understanding the function of ROS in the development of DR can lead to the development of new therapeutic strategies based on the mechanisms of ROS generation and scavenging. Increasing amounts of data have demonstrated the promising prospect of antioxidant therapy and its beneficial effects in vision protection. Therefore, new strategies that utilize antioxidants as additive therapy should be implemented in the treatment of DR.

Carbonylated plasma proteins as potential biomarkers of obesity induced type 2 diabetes mellitus

Protein carbonylation is a common nonenzymatic oxidative post-translational modification, which is often considered as biomarker of oxidative stress. Recent evidence links protein carbonylation also to obesity and type 2 diabetes mellitus (T2DM), though the protein targets of carbonylation in human plasma have not been identified. In this study, we profiled carbonylated proteins in plasma samples obtained from lean individuals and obese patients with or without T2DM. The plasma samples were digested with trypsin, carbonyl groups were derivatized with O-(biotinylcarbazoylmethyl)hydroxylamine, enriched by avidin affinity chromatography, and analyzed by RPC-MS/MS. Signals of potentially modified peptides were targeted in a second LC-MS/MS analysis to retrieve the peptide sequence and the modified residues. A total of 158 unique carbonylated proteins were identified, of which 52 were detected in plasma samples of all three groups. Interestingly, 36 carbonylated proteins were detected only in obese patients with T2DM, whereas 18 were detected in both nondiabetic groups. The carbonylated proteins originated mostly from liver, plasma, platelet, and endothelium. Functionally, they were mainly involved in cell adhesion, signaling, angiogenesis, and cytoskeletal remodeling. Among the identified carbonylated proteins were several candidates, such as VEGFR-2, MMP-1, argin, MKK4, and compliment C5, already connected before to diabetes, obesity and metabolic diseases.

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.

Resveratrol protects vascular smooth muscle cells against high glucose-induced oxidative stress and cell proliferation in vitro

Background

Resveratrol exhibits beneficial effects against numerous degenerative diseases at different stages of pathogenesis. This study investigated potential mechanisms and resveratrol effects on high glucose (HG)-induced oxidative stress (30 mM d-glucose, 30 min) and cell proliferation (30 mM d-glucose, 24 h) in vascular smooth muscle cells (VSMCs).

Material/Methods

Intracellular reactive oxygen species (ROS) generation was detected by 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Total antioxidant capacity (TAC), malonyldialdehyde (MDA), glutathione (GSH), and superoxide dismutase (SOD) were measured to evaluate oxidative stress. VSMC proliferation was measured by CCK-8 assays and through propidium iodide-based cell cycle analysis. Expression of NAD(P)H oxidase, proliferation proteins, and cell signalling were assessed by immunoblot analysis.

Results

Co-treatment of primary cultures of VSMCs with 1–100 μM resveratrol decreased HG-induced ROS overproduction (P<0.05). Resveratrol also abolished HG-induced phosphorylation of oxidase subunit p47 phox and reduced HG-induced cyclin D1, cyclin E, and PCNA expression in a concentration-dependent manner. Furthermore, resveratrol (10 μM) attenuated HG-induced phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK), ERK 1/2, and JNK1/2 without affecting total levels. HG stimulation enhanced downstream IκB-α phosphorylation and NF-κB activity, and resveratrol repressed these effects.

Conclusions

Resveratrol inhibits HG-induced oxidative stress and VSMC proliferation by suppressing ROS generation, NADPH oxidase, Akt phosphorylation, p38 MAPK/JNK/ERK phosphorylation, and IκB-α and NF-κB activities.

Luteolin protects HUVECs from TNF-α-induced oxidative stress and inflammation via its effects on the Nox4/ROS-NF-κB and MAPK pathways

AIM

Inflammation and oxidative stress are now recognized to be two important contributing factors to the development of atherosclerosis(AS). NADPH oxidase-4 (Nox4)-derived reactive oxygen species(ROS), NF-κB and MAPK play crucial roles in these processes. Luteolin, a flavone rich in many plants, can interrupt the molecular expression and inhibit the progression of inflammation and oxidative stress. The present study was designed to test whether luteolin inhibits TNF-α-induced inflammation and oxidative stress in human umbilical vein endothelial cells(HUVECs) and identify some of the mechanisms underlying these effects.

METHODS

HUVECs were treated with luteolin in the presence/absence of TNF-α. The mechanism of luteolin against TNF-α-induced cell injury was evaluated using Western blotting, real-time RT-PCR and flow cytometry analyses.

RESULTS

Luteolin suppressed the TNF-α-activated ROS generation, as well as the Nox4, p22phox, and ICAM-1 and VCAM-1 expression. Luteolin also enhanced the Bcl-2 and reduced caspase-3, -9 expression in the TNF-α-treated HUVECs. Finally, luteolin inhibited the TNF-α-induced transcriptional activity of NF-κB and p38 in addition to ERK1/2 phosphorylation. The inhibitors and siRNA of Nox4 and NF-κB not only reduced ROS generation, p38, ERK1/2 phosphorylation and the ICAM-1 and VCAM-1 expression, but also enhanced Bcl-2 expression. The inhibitor of p38 had the same effect on the expression of ICAM-1, VCAM-1 and Bcl-2, while the inhibitor of ERK1/2 increased the Bcl-2 expression rather than reducing the ICAM-1 and VCAM-1 expression.

CONCLUSIONS

Luteolin attenuates TNF-α-induced oxidative stress and inflammation via its effects on the Nox4/ROS-NF-κB and MAPK pathways. These results suggest that luteolin may provide a beneficial effect in treating vascular diseases associated with oxidative stress and inflammation.

Nitric oxide, oxidative stress, and p66Shc interplay in diabetic endothelial dysfunction

Increased oxidative stress and reduced nitric oxide (NO) bioavailability play a causal role in endothelial cell dysfunction occurring in the vasculature of diabetic patients. In this review, we summarized the molecular mechanisms underpinning diabetic endothelial and vascular dysfunction. In particular, we focused our attention on the complex interplay existing among NO, reactive oxygen species (ROS), and one crucial regulator of intracellular ROS production, p66Shc protein.

AGEs breaking and antioxidant treatment improves endothelium-dependent dilation without effect on flow-mediated remodeling of resistance arteries in old Zucker diabetic rats

BACKGROUND

A chronic increase in blood flow in resistance arteries is associated with increased lumen diameter (outward remodeling) and improved endothelium (NO)-mediated relaxation. Flow-mediated remodeling of resistance arteries is essential for revascularization in ischemic diseases. Nevertheless, it is impaired in 12 to 24-month old rats and in young Zucker Diabetic Fatty (ZDF) rats due to advanced glycation end products (AGEs) and oxidative stress. As type 2 diabetes occurs preferentially in older subjects we investigated flow-mediated remodeling and the effect of the AGEs breaker ALT-711 associated or not to the antioxidant TEMPOL in one-year old lean (LZ) and ZDF rats.

METHODS

Mesenteric resistance arteries were exposed to high (HF) or normal blood flow (NF) in vivo. They were collected after 2 weeks for in vitro analysis.

RESULTS

In LZ rats, diameter expansion did not occur despite a significant increase in blood flow in HF arteries. Nevertheless, endothelium-mediated relaxation was higher in HF than in NF arteries. ALT-711, alone or in combination with TEMPOL, restored outward remodeling in HF arteries in association with AGEs reduction. TEMPOL alone had no effect. ALT-711, TEMPOL or the combination of the 2 drugs did not significantly affect endothelium-mediated relaxation in HF and NF arteries.In ZDF rats, diameter did not increase despite the increase in blood flow and endothelium-mediated relaxation was further decreased in HF arteries in association with AGEs accumulation and excessive oxidative stress. In both NF and HF arteries, endothelium-mediated relaxation was lower in ZDF than in LZ rats. ALT-711, TEMPOL or their combination did not improve remodeling (diameter equivalent in HF and NF arteries). In parallel, they did not reduce AGEs level and did not improve MMPs activity. Nevertheless, ALT-711 and TEMPOL partly improved endothelium-mediated relaxation through a reduction of oxidative stress and the association of ALT-711 and TEMPOL fully restored relaxation to the level found in LZ rats.

CONCLUSIONS

ALT-711 did not improve outward remodeling in mature ZDF rats but it reduced oxidative stress and consequently improved endothelium-dependent relaxation. In mature LZ rats, ALT-711 improved outward remodeling and reduced AGEs level. Consequently, AGEs breaking is differently useful in ageing whether it is associated with diabetes or not.

N-Acetylcysteine prevents congenital heart defects induced by pregestational diabetes

BACKGROUND

Pregestational diabetes is a major risk factor of congenital heart defects (CHDs). Glutathione is depleted and reactive oxygen species (ROS) production is elevated in diabetes. In the present study, we aimed to examine whether treatment with N-acetylcysteine (NAC), which increases glutathione synthesis and inhibits ROS production, prevents CHDs induced by pregestational diabetes.

METHODS

Female mice were treated with streptozotocin (STZ) to induce pregestational diabetes prior to breeding with normal males to produce offspring. Some diabetic mice were treated with N-acetylcysteine (NAC) in drinking water from E0.5 to the end of gestation or harvesting of the embryos. CHDs were identified by histology. ROS levels, cell proliferation and gene expression in the fetal heart were analyzed.

RESULTS

Our data show that pregestational diabetes resulted in CHDs in 58% of the offspring, including ventricular septal defect (VSD), atrial septal defect (ASD), atrioventricular septal defects (AVSD), transposition of great arteries (TGA), double outlet right ventricle (DORV) and tetralogy of Fallot (TOF). Treatment with NAC in drinking water in pregestational diabetic mice completely eliminated the incidence of AVSD, TGA, TOF and significantly diminished the incidence of ASD and VSD. Furthermore, pregestational diabetes increased ROS, impaired cell proliferation, and altered Gata4, Gata5 and Vegf-a expression in the fetal heart of diabetic offspring, which were all prevented by NAC treatment.

CONCLUSIONS

Treatment with NAC increases GSH levels, decreases ROS levels in the fetal heart and prevents the development of CHDs in the offspring of pregestational diabetes. Our study suggests that NAC may have therapeutic potential in the prevention of CHDs induced by pregestational diabetes.

The role of antioxidants and other agents in alleviating hyperglycemia mediated oxidative stress and injury in liver

Several antioxidants and agents having similar antioxidant effects are known to exert beneficial effects in ameliorating the injurious effects of hyperglycemia on liver in different diabetic in vitro and in vivo models. The review deals with some of the agents which have been shown to exert protective effects on liver against hyperglycemic insult and the various mechanisms involved. The different classes of agents which protect the diabetic liver or decrease the severity of hyperglycemia mediated injury include flavonoids, catechins, and other polyphenolic compounds, curcumin and its derivatives, certain vitamins, hormones and drugs, trace elements, prototypical antioxidants and amino acids. Some of the pronounced changes mediated by the antioxidants in liver exposed to hyperglycemia include decreased oxidative stress, and alterations in carbohydrate and lipid metabolism. Other mechanisms through which the agents ameliorate hyperglycemia mediated liver injury include decrease in oxidative DNA and protein damage, restoration of mitochondrial structural and functional integrity, decrease in inflammation and improved insulin signaling. Thus, antioxidants may prove to be an important mode of defense in maintaining normal hepatic functions in diabetes.

PKC-δ isozyme gene silencing restores vascular function in diabetic rat

Abstract Background: Endothelium and K+ channel functionality in smooth muscle cells (SMCs) regulates vascular function and is exposed to damage in diabetes. The regulatory enzyme protein kinase C (PKC) is known to play a key role in vascular tone regulation in health and disease. In this study, we evaluated the effect of PKC-δ gene silencing using small interfering RNAs (siRNAs) on endothelial dysfunction and acquired potassium channelopathy in vascular SMCs in diabetes. Methods: The experimental design comprised diabetes induction by streptozotocin (65 mg/kg) in rats, RNA interference, isolated aortic ring contractile recordings, whole-cell patch-clamp technique, measurements of reactive oxygen species (ROS), and real-time polymerase chain reaction technique. Animals were killed by cervical dislocation following ketamine (45 mg/kg, i.p.) and xylazine (10 mg/kg, i.p.) anesthesia administration on the third month of diabetes and on the seventh day after intravenous injection of siRNAs. Results: The aortas of diabetic rats demonstrated depressed endothelium-dependent relaxation and integral SMCs outward K+ currents as compared with those of controls. On the seventh day, PKC-δ gene silencing effectively restored K+ currents and increased the amplitude of vascular relaxation up to control levels. An increased level of PKC-δ mRNA in diabetic aortas appeared to be reduced after targeted PKC-δ gene silencing. Similarly, the level of ROS production that was increased in diabetes came back to control values after siRNAs administration. Conclusions: The silencing of PKC-δ gene expression using siRNAs led to restoration of vasodilator potential in rats with diabetes mellitus. It is likely that the siRNA technique can be a good therapeutic tool to normalize vascular function in diabetes.

A role for diallyl trisulfide in mitochondrial antioxidative stress contributes to its protective effects against vascular endothelial impairment

Persistent hyperglycemia increases a systemic oxidative stress, causing the onset of vascular endothelial dysfunction and atherosclerosis. Diallyl trisulfide (DAT), a natural organosulfur compound in garlic, has been reported to have actions of dilating blood vessels and antibacteria, etc. In this study, models of obese diabetic rat in vivo and high glucose concentration (HG)-induced endothelial cell injury in vitro were used to investigate the protective effects of DAT on vascular endothelial injury and its underlying mechanisms. In the in vivo model, the obese diabetic rats were injected venously with DAT (5.0 mg kg(-1)d(-1)) and Vitamin E (1.0 mg kg(-1)d(-1)) respectively, once daily for 7 consecutive days. In the in vitro model, HG-injured HUVEC were treated with or without DAT (25 µmol L(-1), 50 µmol L(-1), 100 µmol L(-1)) or Vitamin E (25 µmol L(-1)) respectively for 24h. The extents of vascular endothelial injury and protective effects of DAT were evaluated. The results both in vivo and in vitro displayed that DAT-treatment significantly attenuated the endothelial cell impairments. Besides, DAT-treatment markedly decreased the levels of malondialdehyde (MDA) and reactive oxygen species, whereas elevated the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in mitochondrium. Moreover, DAT-treatment considerably improved mitochondrial respiration function. Taken together, our results suggest that DAT protects vascular endothelium from HG or hyperglycemia induced-injury by reducing mitochondrial oxidative stress. The findings provide a novel insight for DAT to potentially treat the oxidative stress diseases, i.e., atherosclerosis, diabetes, and neurodegenerative diseases.

Respiratory Viral Infections and Subversion of Cellular Antioxidant Defenses

Reactive oxygen species (ROS) formation is part of normal cellular aerobic metabolism, due to respiration and oxidation of nutrients in order to generate energy. Low levels of ROS are involved in cellular signaling and are well controlled by the cellular antioxidant defense system. Elevated levels of ROS generation due to pollutants, toxins and radiation exposure, as well as infections, are associated with oxidative stress causing cellular damage. Several respiratory viruses, including respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and influenza, induce increased ROS formation, both intracellularly and as a result of increased inflammatory cell recruitment at the site of infection. They also reduce antioxidant enzyme (AOE) levels and/or activity, leading to unbalanced oxidative-antioxidant status and subsequent oxidative cell damage. Expression of several AOE is controlled by the activation of the nuclear transcription factor NF-E2-related factor 2 (Nrf2), through binding to the antioxidant responsive element (ARE) present in the AOE gene promoters. While exposure to several pro-oxidant stimuli usually leads to Nrf2 activation and upregulation of AOE expression, respiratory viral infections are associated with inhibition of AOE expression/activity, which in the case of RSV and hMPV is associated with reduced Nrf2 nuclear localization, decreased cellular levels and reduced ARE-dependent gene transcription. Therefore, administration of antioxidant mimetics or Nrf2 inducers represents potential viable therapeutic approaches to viral-induced diseases, such as respiratory infections and other infections associated with decreased cellular antioxidant capacity.

Natural compounds as modulators of NADPH oxidases

Reactive oxygen species (ROS) are cellular signals generated ubiquitously by all mammalian cells, but their relative unbalance triggers also diseases through intracellular damage to DNA, RNA, proteins, and lipids. NADPH oxidases (NOX) are the only known enzyme family with the sole function to produce ROS. The NOX physiological functions concern host defence, cellular signaling, regulation of gene expression, and cell differentiation. On the other hand, increased NOX activity contributes to a wide range of pathological processes, including cardiovascular diseases, neurodegeneration, organ failure, and cancer. Therefore targeting these enzymatic ROS sources by natural compounds, without affecting the physiological redox state, may be an important tool. This review summarizes the current state of knowledge of the role of NOX enzymes in physiology and pathology and provides an overview of the currently available NADPH oxidase inhibitors derived from natural extracts such as polyphenols.

Beneficial Effect of 7-O-Galloyl-D-sedoheptulose, a Polyphenol Isolated from Corni Fructus, against Diabetes-Induced Alterations in Kidney and Adipose Tissue of Type 2 Diabetic db/db Mice

Traditional medicines are being focused on as possible treatments for diabetes and its complications because of their negligible toxic and/or side effects. In line with this, our group has reported that Corni Fructus, a traditional medicine considered exhibiting beneficial effects on liver and kidney functions, possessed an antidiabetic effect via ameliorating glucose-mediated metabolic disorders. To add to these findings, we screened the iridoid glycoside fraction containing morroniside and loganin, and low molecular weight polyphenol fraction containing 7-O-galloyl-d-sedoheptulose (GS) from Corni Fructus. To our knowledge, GS is a compound only detected in Corni Fructus, and its biological activity has been poorly understood until now. For these reasons, we examined whether GS has an ameliorative effect on diabetic changes using type 2 diabetic db/db mice. Our findings suggest that GS has a beneficial effect on the pathological state of the serum, kidney, and adipose tissue related to diabetic damage.

Angiotensin II-induced production of mitochondrial reactive oxygen species: potential mechanisms and relevance for cardiovascular disease

SIGNIFICANCE

The role of reactive oxygen species (ROS) in angiotensin II (AngII) induced endothelial dysfunction, cardiovascular and renal remodeling, inflammation, and fibrosis has been well documented. The molecular mechanisms of AngII pathophysiological activity involve the stimulation of NADPH oxidases, which produce superoxide and hydrogen peroxide. AngII also increases the production of mitochondrial ROS, while the inhibition of AngII improves mitochondrial function; however, the specific molecular mechanisms of the stimulation of mitochondrial ROS is not clear.

RECENT ADVANCES

Interestingly, the overexpression of mitochondrial thioredoxin 2 or mitochondrial superoxide dismutase attenuates AngII-induced hypertension, which demonstrates the importance of mitochondrial ROS in AngII-mediated cardiovascular diseases.

CRITICAL ISSUES

Although mitochondrial ROS plays an important role in normal physiological cell signaling, AngII, high glucose, high fat, or hypoxia may cause the overproduction of mitochondrial ROS, leading to the feed-forward redox stimulation of NADPH oxidases. This vicious cycle may contribute to the development of pathological conditions and facilitate organ damage in hypertension, atherosclerosis, and diabetes.

FUTURE DIRECTIONS

The development of antioxidant strategies specifically targeting mitochondria could be therapeutically beneficial in these disease conditions.

Manganese neurotoxicity and the role of reactive oxygen species

Manganese (Mn) is an essential dietary nutrient, but an excess or accumulation can be toxic. Disease states, such as manganism, are associated with overexposure or accumulation of Mn and are due to the production of reactive oxygen species, free radicals, and toxic metabolites; alteration of mitochondrial function and ATP production; and depletion of cellular antioxidant defense mechanisms. This review focuses on all of the preceding mechanisms and the scientific studies that support them as well as providing an overview of the absorption, distribution, and excretion of Mn and the stability and transport of Mn compounds in the body.

SFAs do not impair endothelial function and arterial stiffness

BACKGROUND

It is uncertain whether saturated fatty acids (SFAs) impair endothelial function and contribute to arterial stiffening.

OBJECTIVE

We tested the effects of replacing SFAs with monounsaturated fatty acids (MUFAs) or carbohydrates on endothelial function and arterial stiffness.

DESIGN

With the use of a parallel-designed randomized controlled trial in 121 insulin-resistant men and women, we measured vascular function after 1 mo of consumption of a high-SFA (HS) diet and after 24 wk after random assignment to the HS diet or diets that contained <10% SFAs and were high in either MUFAs or carbohydrates. The primary outcome was a change in flow-mediated dilation (FMD), and secondary outcomes were changes in carotid to femoral pulse wave velocity (PWV) and plasma 8-isoprostane F2α-III concentrations.

RESULTS

For 112 participants with data available for analysis on the specified outcomes, no significant differences were shown. FMD with the HS reference diet was 6.7 ± 2.2%, and changes (95% CIs) after 6 mo of intervention were +0.3 (-0.4, 1.1), -0.2 (-0.8, 0.5), and -0.1 (-0.6, 0.7) with HS, high-MUFA (HM), and high-carbohydrate (HC) diets, respectively. After consumption of the HS reference diet, the geometric mean (±SD) PWV was 7.67 ± 1.62 m/s, and mean percentages of changes (95% CIs) were -1.0 (-6.2, 4.3) with the HS diet, 2.7 (-1.4, 6.9) with the HM diet, and -1.0 (-5.5, 3.4) with the HC diet. With the HS reference diet, the geometric mean (±SD) plasma 8-isoprostane F2α-III concentration was 176 ± 85 pmol/L, and mean percentage of changes (95% CIs) were 1 (-12, 14) with the HS diet, 6 (-5, 16) with the HM diet, and 4 (-7, 16) with the HC diet.

CONCLUSION

The replacement of SFAs with MUFAs or carbohydrates in healthy subjects does not affect vascular function. This trial was registered at Current Controlled Trials (http://www.controlled-trials.com/ISRCTN) as ISRCTN 29111298.

Current status of NADPH oxidase research in cardiovascular pharmacology

The implications of reactive oxygen species in cardiovascular disease have been known for some decades. Rationally, therapeutic antioxidant strategies combating oxidative stress have been developed, but the results of clinical trials have not been as good as expected. Therefore, to move forward in the design of new therapeutic strategies for cardiovascular disease based on prevention of production of reactive oxygen species, steps must be taken on two fronts, ie, comprehension of reduction-oxidation signaling pathways and the pathophysiologic roles of reactive oxygen species, and development of new, less toxic, and more selective nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors, to clarify both the role of each NADPH oxidase isoform and their utility in clinical practice. In this review, we analyze the value of NADPH oxidase as a therapeutic target for cardiovascular disease and the old and new pharmacologic agents or strategies to prevent NADPH oxidase activity. Some inhibitors and different direct or indirect approaches are available. Regarding direct NADPH oxidase inhibition, the specificity of NADPH oxidase is the focus of current investigations, whereas the chemical structure-activity relationship studies of known inhibitors have provided pharmacophore models with which to search for new molecules. From a general point of view, small-molecule inhibitors are preferred because of their hydrosolubility and oral bioavailability. However, other possibilities are not closed, with peptide inhibitors or monoclonal antibodies against NADPH oxidase isoforms continuing to be under investigation as well as the ongoing search for naturally occurring compounds. Likewise, some different approaches include inhibition of assembly of the NADPH oxidase complex, subcellular translocation, post-transductional modifications, calcium entry/release, electron transfer, and genetic expression. High-throughput screens for any of these activities could provide new inhibitors. All this knowledge and the research presently underway will likely result in development of new drugs for inhibition of NADPH oxidase and application of therapeutic approaches based on their action, for the treatment of cardiovascular disease in the next few years.

Superior renoprotective effects of the combination of breviscapine with enalapril and its mechanism in diabetic rats

Breviscapine is a flavonoid extracted from a Chinese herb Erigeron breviscapus, previously it was shown that treatment with breviscapine attenuated renal injury in the diabetic rats. The purpose of this study was to investigate whether breviscapine combined with enalapril (an ACE inhibitor) have superior renoprotective effects against diabetic nephropathy. Rats were randomly separated into five groups: control, diabetes, diabetes treated with enalapril, diabetes treated with breviscapine, or diabetes treated with combined enalapril with breviscapine. Twenty-four hours urinary AER and the levels of 3-NT in renal tissue and MDA in renal tissue and urine as well as activities and expression of PKC in renal tissue were determined, and renal tissue morphology were observed by light microscopy after 8 weeks. Expression of TGFβ1 protein was performed by immunohistochemistry method. Increased AER and kidney pathologic injury were attenuated by treatment with either enalapril or breviscapine and further reduced by the combination of the two. Elevated 3-NT in renal tissue and MDA levels in renal tissue and urine were reduced by enalapril or breviscapine and, more effectively, by combined enalapril with breviscapine. PKC activities and expression were higher in renal tissue in diabetic rats than those of the control group, which were reduced by both monotherapies, and further abrogated by combination therapy in both cases. Overexpression of TGFβ1 protein observed in the glomeruli and tubulointerstitium of diabetic rats was attenuated by enalapril or breviscapine to a similar lever and further reduced by the combination of the two. The combination of enalapril and breviscapine confers superiority over monotherapies on renoprotection, which mechanism may be at least partly correlated with synergetic suppression on increased oxidative stress and PKC activities as well as overexpression of TGFβ1 in renal tissue.

Angiotensin receptor-mediated oxidative stress is associated with impaired cardiac redox signaling and mitochondrial function in insulin-resistant rats

Activation of angiotensin receptor type 1 (AT1) contributes to NADPH oxidase (Nox)-derived oxidative stress during metabolic syndrome. However, the specific role of AT1 in modulating redox signaling, mitochondrial function, and oxidative stress in the heart remains more elusive. To test the hypothesis that AT1 activation increases oxidative stress while impairing redox signaling and mitochondrial function in the heart during diet-induced insulin resistance in obese animals, Otsuka Long Evans Tokushima Fatty (OLETF) rats (n = 8/group) were treated with the AT1 blocker (ARB) olmesartan for 6 wk. Cardiac Nox2 protein expression increased 40% in OLETF compared with age-matched, lean, strain-control Long Evans Tokushima Otsuka (LETO) rats, while mRNA and protein expression of the H₂O₂-producing Nox4 increased 40-100%. ARB treatment prevented the increase in Nox2 without altering Nox4. ARB treatment also normalized the increased levels of protein and lipid oxidation (nitrotyrosine, 4-hydroxynonenal) and increased the redox-sensitive transcription factor Nrf2 by 30% and the activity of antioxidant enzymes (SOD, catalase, GPx) by 50-70%. Citrate synthase (CS) and succinate dehydrogenase (SDH) activities decreased 60-70%, whereas cardiac succinate levels decreased 35% in OLETF compared with LETO, suggesting that mitochondrial function in the heart is impaired during obesity-induced insulin resistance. ARB treatment normalized CS and SDH activities, as well as succinate levels, while increasing AMPK and normalizing Akt, suggesting that AT1 activation also impairs cellular metabolism in the diabetic heart. These data suggest that the cardiovascular complications associated with metabolic syndrome may result from AT1 receptor-mediated Nox2 activation leading to impaired redox signaling, mitochondrial activity, and dysregulation of cellular metabolism in the heart.

Diabetes alters activation and repression of pro- and anti-inflammatory signaling pathways in the vasculature

A central mechanism driving vascular disease in diabetes is immune cell-mediated inflammation. In diabetes, enhanced oxidation and glycation of macromolecules, such as lipoproteins, insults the endothelium, and activates both innate and adaptive arms of the immune system by generating new antigens for presentation to adaptive immune cells. Chronic inflammation of the endothelium in diabetes leads to continuous infiltration and accumulation of leukocytes at sites of endothelial cell injury. We will describe the central role of the macrophage as a source of signaling molecules and damaging by-products which activate infiltrating lymphocytes in the tissue and contribute to the pro-oxidant and pro-inflammatory microenvironment. An important aspect to be considered is the diabetes-associated defects in the immune system, such as fewer or dysfunctional athero-protective leukocyte subsets in the diabetic lesion compared to non-diabetic lesions. This review will discuss the key pro-inflammatory signaling pathways responsible for leukocyte recruitment and activation in the injured vessel, with particular focus on pro- and anti-inflammatory pathways aberrantly activated or repressed in diabetes. We aim to describe the interaction between advanced glycation end products and their principle receptor RAGE, angiotensin II, and the Ang II type 1 receptor, in addition to reactive oxygen species (ROS) production by NADPH-oxidase enzymes that are relevant to vascular and immune cell function in the context of diabetic vasculopathy. Furthermore, we will touch on recent advances in epigenetic medicine that have revealed high glucose-mediated changes in the transcription of genes with known pro-inflammatory downstream targets. Finally, novel anti-atherosclerosis strategies that target the vascular immune interface will be explored; such as vaccination against modified low-density lipoprotein and pharmacological inhibition of ROS-producing enzymes.

Protective effects of andrographolide analogue AL-1 on ROS-induced RIN-mβ cell death by inducing ROS generation

Oxidative stress is considered to be a major factor contributing to pathogenesis and progression of many diseases. A novel andrographolide-lipoic acid conjugate (AL-1) could protect pancreatic β-cells from reactive oxygen species (ROS)-induced oxidative injury. However, its protective mechanism is still unclear. In this work, we used proteomics to identify AL-1-regulated proteins in β-cells and found that 13 of the 71 proteins regulated by AL-1 were closely associated with antioxidation. These differential proteins were mainly involved in the ERK1/2 and AKT1 signaling pathways. Functional investigation demonstrated that AL-1 exerted its protective effects on H₂O₂-induced cell death of β-cells by generating NADPH oxidase-dependent ROS to activate ERK1/2 and AKT1 signaling pathways. As a consequence, the expressions of antioxidant proteins including Trx1, Prx1 and Prx5, and anti-apoptotic proteins including PDCD6IP, prohibitin, galectin-1 and HSP were upregulated. AL-1 probably worked as a “vaccinum” to activate the cellular antioxidant system by inducing the generation of low concentration ROS which then reciprocally protected β-cells from oxidative damage caused by high-level ROS from H₂O₂. To the best of our knowledge, this is the first comprehensive proteomic analysis illustrating a novel molecular mechanism for the protective effects of antioxidants on β-cells from H₂O₂-induced cell death.

An ethanolic extract of Lindera obtusiloba stems, YJP-14, improves endothelial dysfunction, metabolic parameters and physical performance in diabetic db/db mice

Lindera obtusiloba is a medicinal herb traditionally used in Asia for improvement of blood circulation, treatment of inflammation, and prevention of liver damage. A previous study has shown that an ethanolic extract of Lindera obtusiloba stems (LOE) has vasoprotective and antihypertensive effects. The possibility that Lindera obtusiloba improves endothelial function and metabolic parameters in type 2 diabetes mellitus (T2DM) remains to be examined. Therefore, the aim of the present study was to determine the potential of LOE to prevent the development of an endothelial dysfunction, and improve metabolic parameters including hyperglycemia, albuminuria and physical exercise capacity in db/db mice, an experimental model of T2DM. The effect of LOE (100 mg/kg/day by gavage for 8 weeks) on these parameters was compared to that of an oral antidiabetic drug, pioglitazone (30 mg/kg/day by gavage). Reduced blood glucose level, body weight and albumin-creatinine ratio were observed in the group receiving LOE compared to the control db/db group. The LOE treatment improved endothelium-dependent relaxations, abolished endothelium-dependent contractions to acetylcholine in the aorta, and normalized the increased vascular oxidative stress and expression of NADPH oxidase, cyclooxygenases, angiotensin II, angiotensin type 1 receptors and peroxynitrite and the decreased expression of endothelial NO synthase in db/db mice. The angiotensin-converting enzyme (ACE) activity was reduced in the LOE group compared to that in the control db/db group. LOE also inhibited the activity of purified ACE, COX-1 and COX-2 in a dose-dependent manner. In addition, LOE improved physical exercise capacity. Thus, the present findings indicate that LOE has a beneficial effect on the vascular system in db/db mice by improving endothelium-dependent relaxations and vascular oxidative stress most likely by normalizing the angiotensin system, and also on metabolic parameters, and these effects are associated with an enhanced physical exercise capacity.

Resveratrol protects vascular endothelial cells from high glucose-induced apoptosis through inhibition of NADPH oxidase activation-driven oxidative stress

INTRODUCTION

Hyperglycemia-induced oxidative stress has been implicated in diabetic vascular complications in which NADPH oxidase is a major source of reactive oxygen species (ROS) generation. Resveratrol is a naturally occurring polyphenol, which has vasoprotective effects in diabetic animal models and inhibits high glucose (HG)-induced oxidative stress in endothelial cells.

AIMS

We aimed to examine whether HG-induced NADPH oxidase activation and ROS production contribute to glucotoxicity to endothelial cells and the effect of resveratrol on glucotoxicity.

RESULTS

Using a murine brain microvascular endothelial cell line bEnd3, we found that NADPH oxidase inhibitor (apocynin) and resveratrol both inhibited HG-induced endothelial cell apoptosis. HG-induced elevation of NADPH oxidase activity and production of ROS were inhibited by apocynin, suggesting that HG induces endothelial cell apoptosis through NADPH oxidase-mediated ROS production. Mechanistic studies revealed that HG upregulated NADPH oxidase subunit Nox1 but not Nox2, Nox4, and p22(phox) expression through NF-κB activation, which resulted in elevation of NADPH oxidase activity and consequent ROS production. Resveratrol prevented HG-induced endothelial cell apoptosis through inhibiting HG-induced NF-κB activation, NADPH oxidase activity elevation, and ROS production.

CONCLUSIONS

HG induces endothelial cell apoptosis through NF-κB/NADPH oxidase/ROS pathway, which was inhibited by resveratrol. Our findings provide new potential therapeutic targets against brain vascular complications of diabetes.

Oxidative status interactome map: towards novel approaches in experiment planning, data analysis, diagnostics and therapy

Experimental evidence suggests an immense variety of processes associated with and aimed at producing reactive oxygen and/or nitrogen species. Clinical studies implicate an enormous range of pathologies associated with reactive oxygen/nitrogen species metabolism deregulation, particularly oxidative stress. Recent advances in biochemistry, proteomics and molecular biology/biophysics of cells suggest oxidative stress to be an endpoint of complex dysregulation events of conjugated pathways consolidated under the term, proposed here, "oxidative status". The oxidative status concept, in order to allow for novel diagnostic and therapeutic approaches, requires elaboration of a new logic system comprehending all the features, versatility and complexity of cellular pro- and antioxidative components of different nature. We have developed a curated and regularly updated interactive interactome map of human cellular-level oxidative status allowing for systematization of the related most up-to-date experimental data. A total of more than 600 papers were selected for the initial creation of the map. The map comprises more than 300 individual factors with respective interactions, all subdivided hierarchically for logical analysis purposes. The pilot application of the interactome map suggested several points for further development of oxidative status-based technologies.

Metabolic hypertension: concept and practice

Hypertension is a serious public health problem worldwide. More than 60% of the risk factors for hypertension are associated with metabolic disturbances. Metabolic abnormalities increase the risk for hypertension and cause high blood pressure. Improving metabolic disturbances is beneficial for hypertension treatment. Due to the importance of metabolic abnormalities in the pathogenesis of hypertension, we propose a concept of metabolic hypertension. In this review, we discuss and review the clinical types, pathogenesis, risk evaluation and management of metabolic hypertension. Elucidation of the mechanism of metabolic hypertension should facilitate the design of novel pharmacotherapeutics and dedicated antihypertensive manipulations.

Dihydroquercetin (DHQ) induced HO-1 and NQO1 expression against oxidative stress through the Nrf2-dependent antioxidant pathway

Dihydroquercetin (DHQ) is a well-known antioxidant agent. In the present investigation, we reported for the first time that DHQ stimulates the expression of phase II detoxifying enzymes through the Nrf2-dependent signaling pathway. The IC50 values of DHQ for reduction of 2,2-diphenyl-1-picrylhydrazol (DPPH), reducing power assay, lipid peroxidation assay, and xanthine oxidase inhibition were 5.96, 4.31, 2.03, and 13.24 μM, respectively. DHQ possessed considerable protective activity from oxidative DNA damage. A luciferase reporter assay also demonstrated that DHQ-activated signaling resulted in the increased transcriptional activity of Nrf2 through binding to the ARE (antioxidant response element) enhancer sequence. Furthermore, Western blotting and luciferase assay revealed DHQ activated ERK1/2, Akt, and JNK signaling pathways, subsequently leading to Nrf2 nuclear translocation. DHQ upregulated the Nrf2-related antioxidant genes heme oxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase-1 (NQO1), and glutamate-cysteine ligase modifier subunits. Inhibition of Nrf2 by siRNA reduced DHQ-induced upregulation of these antioxidant genes.

Advanced glycation end products acutely impair ca(2+) signaling in bovine aortic endothelial cells

Post-translational modification of proteins in diabetes, including formation of advanced glycation end products (AGEs) are believed to contribute to vascular dysfunction and disease. Impaired function of the endothelium is an early indicator of vascular dysfunction in diabetes and as many endothelial cell processes are dependent upon intracellular [Ca²⁺] and Ca²⁺ signaling, the aim of this study was to examine the acute effects of AGEs on Ca²⁺ signaling in bovine aortic endothelial cells (BAEC). Ca²⁺ signaling was studied using the fluorescent indicator dye Fura-2-AM. AGEs were generated by incubating bovine serum albumin with 0–250 mM glucose or glucose-6-phosphate for 0–120 days at 37°C. Under all conditions, the main AGE species generated was carboxymethyl lysine (CML) as assayed using both gas-liquid chromatograph-mass spectroscopy and high-performance liquid chromatography. In Ca²⁺-replete solution, exposure of BAEC to AGEs for 5 min caused an elevation in basal [Ca²⁺] and attenuated the increase in intracellular [Ca²⁺] caused by ATP (100 μM). In the absence of extracellular Ca²⁺, exposure of BAEC to AGEs for 5 min caused an elevation in basal [Ca²⁺] and attenuated subsequent intracellular Ca²⁺ release caused by ATP, thapsigargin (0.1 μM), and ionomycin (3 μM), but AGEs did not affect extracellular Ca²⁺ entry induced by the re-addition of Ca²⁺ to the bathing solution in the presence of any of these agents. The anti-oxidant α-lipoic acid (2 μM) and NAD(P)H oxidase inhibitors apocynin (500 μM) and diphenyleneiodonium (1 μM) abolished these effects of AGEs on BAECs, as did the IP₃ receptor antagonist xestospongin C (1 μM). In summary, AGEs caused an acute depletion of Ca²⁺ from the intracellular store in BAECs, such that the Ca²⁺ signal stimulated by the subsequent application other agents acting upon this store is reduced. The mechanism may involve generation of reactive oxygen species from NAD(P)H oxidase and possible activation of the IP₃ receptor.

Roles of melatonin in fetal programming in compromised pregnancies

Compromised pregnancies such as those associated with gestational diabetes mellitus, intrauterine growth retardation, preeclampsia, maternal undernutrition, and maternal stress may negatively affect fetal development. Such pregnancies may induce oxidative stress to the fetus and alter fetal development through the epigenetic process that may affect development at a later stage. Melatonin is an oxidant scavenger that reverses oxidative stress during the prenatal period. Moreover, the role of melatonin in epigenetic modifications in the field of developmental programming has been studied extensively. Here, we describe the physiological function of melatonin in pregnancy and discuss the roles of melatonin in fetal programming in compromised pregnancies, focusing on its involvement in redox and epigenetic mechanisms.

Anti-inflammatory and cardioprotective effects of tadalafil in diabetic mice

Background

Insulin resistance impairs nitric oxide (NO) bioavailability and obesity promotes a state of chronic inflammation and damages the vascular endothelium. Phosphodiesterase-5 inhibitors restore NO signaling and may reduce circulating inflammatory markers, and improve metabolic parameters through a number of mechanisms. We hypothesized that daily administration of the PDE-5 inhibitor, tadalafil (TAD) will attenuate inflammation, improve fasting plasma glucose and triglyceride levels, body weight, and reduce infarct size after ischemia/reperfusion injury in obese, diabetic mice.

Methods

Twenty leptin receptor null (db/db) mice underwent treatment with TAD (1 mg/Kg) or 10% DMSO for 28 days. Body weight and fasting plasma glucose levels were determined weekly. Upon completion, hearts were isolated and subjected to 30 min global ischemia followed by 60 min reperfusion in a Langendorff model. Plasma samples were taken for cytokine analysis and fasting triglyceride levels. Infarct size was measured using computer morphometry of tetrazolium stained sections. Additionally, ventricular cardiomyocytes were isolated and subjected to 40 min of simulated ischemia and reoxygenation. Necrosis was determined using trypan blue exclusion and LDH release assay and apoptosis was assessed by TUNEL assay after 1 h or 18 h of reoxygenation, respectively.

Results

Treatment with TAD caused a reduction in infarct size in the diabetic heart (23.2±1.5 vs. 47.8±3.7%, p<0.01, n = 6/group), reduced fasting glucose levels (292±31.8 vs. 511±19.3 mg/dL, p<0.001) and fasting triglycerides (43.3±21 vs. 129.7±29 mg/dL, p<0.05) as compared to DMSO, however body weight was not significantly reduced. Circulating tumor necrosis factor-α and interleukin-1β were reduced after treatment compared to control (257±16.51 vs. 402.3±17.26 and 150.8±12.55 vs. 264±31.85 pg/mL, respectively; P<0.001) Isolated cardiomyocytes from TAD-treated mice showed reduced apoptosis and necrosis.

Conclusion

We have provided the first evidence that TAD therapy ameliorates circulating inflammatory cytokines and chemokines in a diabetic animal model while improving fasting glucose levels and reducing infarct size following ischemia-reperfusion injury in the heart.

A self-propelling cycle mediated by reactive oxide species and nitric oxide exists in LPS-activated microglia

It has been widely accepted that microglia, the innate immune cells in the brain, can be chronically activated in response to neuron death, fuelling a self-renewing cycle of microglial activation followed by further neuron damage (reactive microgliosis), which has been considered as the main reason responsible for the progressive nature of neurodegenerative diseases. In the present study, it was found that LPS (lipopolysaccharide) significantly induced the activation of N9 microglia, and the increase of NO level induced by pretreatment of LPS could last after the removal of LPS. The culture medium of activated microglia significantly decreased the viability of rat primary cortical neuron. These results can be blocked by the antioxidant N-acetylcysteine (NAC) and nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase inhibitor diphenyleneiodonium sulfate (DPI), suggesting that intracellular reactive oxide species (iROS) released from the activated microglial cells may continue to further activate microglia. Next, it was shown that the iROS level increased rapidly after the LPS treatment in microglia cells followed by the NO production through the regulation of iNOS (inducible nitric oxide synthase) expression. The increase of iROS could be reversed by gp91phox (the critical and catalytic subunit of NADPH oxidase) siRNA. Moreover, NO released from sodium nitroprusside (SNP) was able to increase the iROS production of N9 microglia by regulating of the activity and the expression of NADPH oxidase. In conclusion, our research suggests for the first time that there may exist a self-propelling cycle in microglial cells possibly mediated by iROS and NO when they become activated by LPS. It may be responsible partially for the ongoing microglial activation and the progressive nature of neurodegenerative diseases.