Effect of apocynin on NADPH oxidase-mediated oxidative stress-LOX-1-eNOS pathway in human endothelial cells exposed to high glucose

The role of oxidative stress in diabetes mellitus-induced vascular endothelial dysfunction

Diabetes mellitus is a metabolic disease characterized by long-term hyperglycaemia, which leads to microangiopathy and macroangiopathy and ultimately increases the mortality of diabetic patients. Endothelial dysfunction, which has been recognized as a key factor in the pathogenesis of diabetic microangiopathy and macroangiopathy, is characterized by a reduction in NO bioavailability. Oxidative stress, which is the main pathogenic factor in diabetes, is one of the major triggers of endothelial dysfunction through the reduction in NO. In this review, we summarize the four sources of ROS in the diabetic vasculature and the underlying molecular mechanisms by which the pathogenic factors hyperglycaemia, hyperlipidaemia, adipokines and insulin resistance induce oxidative stress in endothelial cells in the context of diabetes. In addition, we discuss oxidative stress-targeted interventions, including hypoglycaemic drugs, antioxidants and lifestyle interventions, and their effects on diabetes-induced endothelial dysfunction. In summary, our review provides comprehensive insight into the roles of oxidative stress in diabetes-induced endothelial dysfunction.

Elicitation of Inhibitory Effects for AGE-Induced Oxidative Stress in Rotator Cuff-Derived Cells by Apocynin

Advanced glycation end-products (AGEs) play a critical supportive role during musculoskeletal disorders via glycosylation and oxidative stress. Though apocynin, identified as a potent and selective inhibitor of NADPH oxidase, has been reported to be involved in pathogen-induced reactive oxygen species (ROS), its role in age-related rotator cuff degeneration has not been well clarified. Therefore, this study aims to evaluate the in vitro effects of apocynin on human rotator cuff-derived cells. Twelve patients with rotator cuff tears (RCTs) participated in the study. Supraspinatus tendons from patients with RCTs were collected and cultured. After the preparation of RC-derived cells, they were divided into four groups (control group, control + apocynin group, AGEs group, AGEs + apocynin group), and gene marker expression, cell viability, and intracellular ROS production were evaluated. The gene expression of NOX, IL-6, and the receptor for AGEs (RAGE) was significantly decreased by apocynin. We also examined the effect of apocynin in vitro. The results showed that ROS induction and increasing apoptotic cells after treatment of AGEs were significantly decreased, and cell viability increased considerably. These results suggest that apocynin can effectively reduce AGE-induced oxidative stress by inhibiting NOX activation. Thus, apocynin is a potential prodrug in preventing degenerative changes of the rotor cuff.

Dihydromyricetin protects against high glucose-induced endothelial dysfunction: Role of HIF-1α/ROR2/NF-κB

OBJECTIVES

Dihydromyricetin (DHM), a natural flavonoid isolated from vine tea with anti-inflammatory activity was evaluated for its ability to prevent vascular endothelial dysfunction caused by hyperglycaemia.

METHODS

Vasoconstrictor (phenylephrine-PE) and vasodilator (acetylcholine-ACh) responses were monitored for female rat aorta rings maintained in a bioassay organ bath for 3 h at 37 °C in either low (LG: 10 mM) or high (HG: 40 mM, to mimic hyperglycaemia) glucose-Krebs buffer in the absence or presence of 50 µM DHM. Tissues recovered from the organ bath at 3 h were fixed and analyzed for morphological changes and their expression of eNOS, iNOS, HIF-1α, GLUT1, ROR2 tyrosine kinase, NF-κB, TNF-α, Bax, Bcl2, caspase-3, and forindices of increased oxidative stress.

KEY FINDINGS

HG-incubated tissues showed increased PE-stimulated contractile response and decreased ACh-mediated endothelial vasodilation. DHM prevented both of these changes. Besides, HG incubation increased the immunoreactivity to iNOS, HIF-1α, GLUT1, ROR2, NF-κB, TNF-α, Bax, and active caspase-3, and decreased the expression of eNOS and Bcl2. Hyperglycaemia-like conditions also increased the indices of oxidative/nitrosative stress. These HG-induced changes, which were accompanied by an increase in tissue adventitial thickness and inflammatory cell infiltration, were all prevented by DHM.

CONCLUSION

Our data demonstrate an anti-inflammatory protective action of DHM to preserve vascular function in the setting of hyperglycaemia.

Effects of polystyrene nanoplastics on endothelium senescence and its underlying mechanism

Global plastic use has increased rapidly, and environmental pollution associated with nanoplastics (NPs) has been a growing concern recently. However, the impact and biological mechanism of NPs on the cardiovascular system are not well characterized. This study aimed to assess the possibility that NPs exposure promotes premature endothelial cell (EC) senescence in porcine coronary artery ECs and, if so, to elucidate the underlying mechanism. Treatment of ECs with NPs promoted the acquisition of senescence markers, senescence-associated β-galactosidase activity, and p53, p21, and p16 protein expression, resulting in the inhibition of proliferation. In addition, NPs impaired endothelium-dependent vasorelaxation associated with decreased endothelial nitric oxide synthase (eNOS) expression. NPs enhanced reactive oxygen species formation in ECs, and increased oxidative stress levels were associated with the induction of NADPH oxidases expression, followed by the subsequent downregulation of Sirt1 expression. The characteristics of EC senescence and dysfunction caused by NPs are prevented by an antioxidant (N-acetylcysteine), an NADPH oxidase inhibitor (apocynin), and a Sirt1 activator (resveratrol). These findings indicate that NPs induced premature EC senescence, at least in part, through the redox-sensitive eNOS/Sirt1 signaling pathway. This study suggested the effects and underlying mechanism of NPs on the cardiovascular system, which may provide pharmacological targets to prevent NPs-associated cardiovascular diseases.

Anti-oxidative and anti-hyperglycemic properties of Agastache foeniculum essential oil and oily fraction in hyperglycemia-stimulated and lipopolysaccharide-stimulated macrophage cells: In vitro and in silico studies

ETHNOPHARMACOLOGICAL RELEVANCE

Hyperglycemia (HG) and lipopolysaccharide (LPS) often promote superoxide accumulation, which may increase oxidative stress. Reducing superoxide production in hyperglycemia and the inflammatory condition is an emerging way to reduce protein and lipid oxidation and diabetes complication.

AIM OF STUDY

To examine the effect of Agastache foeniculum essential oil (AFEO) and oil fraction (AFoil) on HG- and LPS-stimulated oxidative stress, the pathogenicity of AFEO and AFoil on oxidative stress was assessed.

METHODS

The stimulatory effects of AFEO and AFoil on the activity and expression of NADH oxide (NOX), catalase (CAT), superoxide dismutase (SOD), and the expression of nuclear respiratory factor 2 (NRF2) and nuclear factor-kappa B (NF-kB) in the stimulated macrophage cell line, J774.A1, was studied. The interaction patterns of AFEO and AFoil components with NOX, SOD, CAT, NRF2, and NF-kB proteins were also deduced using molecular docking.

RESULTS

Estragole was the main ingredient in AFEO (97%). Linolenic acid (32.10%), estragole (16.22%), palmitic acid (12.62%), linoleic acid (12.04%), and oleic acid (8.73%) were the major chemical components of the AFoil. NOX activation was stimulated in macrophage cells by HG and LPS. At 20 μg/mL, AFEO and AFoil decreased NOX activity while increased SOD and CAT activities in stimulated macrophages. AFoil with estragole and omega-3 fatty acids was better than AFEO with estragole in anti-hyperglycemic and anti-oxidative activity. According to molecular docking research, estragole, linoleic acid, and linolenic acid bind to different hydrophobic pockets of NOX, SOD, CAT, NFR2, and NF-kB using hydrogen bonds, van der Waals bonds, pi-alkyl, and pi-anion interactions, with different binding energies.

CONCLUSION

AFEO and AFoil showed antioxidant and anti-diabetic activity. The mechanisms in lowering oxidative stress markers depended on down-regulating superoxide-producing enzymes and up-regulating superoxide-removing enzymes at gene and protein levels. The AFoil emulsion can be used to reduce the detrimental impacts of hyperglycemia and oxidative stress.

Native and Oxidized Low-Density Lipoproteins Increase the Expression of the LDL Receptor and the LOX-1 Receptor, Respectively, in Arterial Endothelial Cells

Atherosclerotic artery disease is the major cause of death and an immense burden on healthcare systems worldwide. The formation of atherosclerotic plaques is promoted by high levels of low-density lipoproteins (LDL) in the blood, especially in the oxidized form. Circulating LDL is taken up by conventional and non-classical endothelial cell receptors and deposited in the vessel wall. The exact mechanism of LDL interaction with vascular endothelial cells is not fully understood. Moreover, it appears to depend on the type and location of the vessel affected and the receptor involved. Here, we analyze how native LDL (nLDL) and oxidized LDL (oxLDL) modulate the expression of their receptors-classical LDLR and alternative LOX-1-in endothelial cells derived from human umbilical artery (HUAECs), used as an example of a medium-sized vessel, which is typically affected by atherosclerosis. Exposure of HUAECs to nLDL resulted in moderate nLDL uptake and gradual increase in LDLR, but not LOX-1, expression over 24 h. Conversely, exposure of HUAECs to oxLDL, led to significant accumulation of oxLDL and rapid induction of LOX-1, but not LDLR, within 7 h. These activation processes were associated with phosphorylation of protein kinases ERK1/2 and p38, followed by activation of the transcription factor AP-1 and its binding to the promoters of the respective receptor genes. Both nLDL-induced LDLR mRNA expression and oxLDL-induced LOX-1 mRNA expression were abolished by blocking ERK1/2, p-38 or AP-1. In addition, oxLDL, but not nLDL, was capable of inducing LOX-1 through the NF-κB-controlled pathway. These observations indicate that in arterial endothelial cells nLDL and oxLDL signal mainly via LDLR and LOX-1 receptors, respectively, and engage ERK1/2 and p38 kinases, and AP-1, as well as NF-κB transcription factors to exert feed-forward regulation and increase the expression of these receptors, which may perpetuate endothelial dysfunction in atherosclerosis.

Arterial Platelet Adhesion in Atherosclerosis-Prone Arteries of Obese, Insulin-Resistant Nonhuman Primates

Background

Platelet–endothelial interactions are thought to contribute to early atherogenesis. These interactions are potentiated by oxidative stress. We used in vivo molecular imaging to test the hypothesis that platelet–endothelial interactions occur at early stages of plaque development in obese, insulin‐resistant nonhuman primates, and are suppressed by NADPH‐oxidase‐2 inhibition.

Methods and Results

Six adult rhesus macaques fed a Western‐style diet for a median of 4.0 years were studied at baseline and after 8 weeks of therapy with the NADPH‐oxidase‐2‐inhibitor apocynin (50 mg/kg per day). Six lean control animals were also studied. Measurements included intravenous glucose tolerance test, body composition by dual‐energy X‐ray absorptiometry, carotid intimal medial thickness, carotid artery contrast ultrasound molecular imaging for platelet GPIbα (glycoprotein‐ Ibα) and vascular cell adhesion molecule‐1, and blood oxidative markers on mass spectrometry. Compared with lean controls, animals on a Western‐style diet were obese (median body mass: 16.0 versus 8.7 kg, P=0.003; median truncal fat: 49% versus 20%, P=0.002), were insulin resistant (4‐fold higher insulin–glucose area under the curve on intravenous glucose tolerance test, P=0.002), had 40% larger carotid intimal medial thickness (P=0.004), and exhibited oxidative signatures on proteomics. In obese but not lean animals, signal enhancement on molecular imaging was significantly elevated for GPIbα and vascular cell adhesion molecule‐1. The signal correlated modestly with intimal medial thickness but not with the degree of insulin resistance. Apocynin significantly (P<0.01) reduced median signal for GPIbα by >80% and vascular cell adhesion molecule‐1 signal by 75%, but did not affect intimal medial thickness, body mass, or intravenous glucose tolerance test results.

Conclusion

In nonhuman primates, diet‐induced obesity and insulin resistance leads to platelet–endothelial adhesion at early atherosclerotic lesion sites, which is associated with the expression of pro‐inflammatory adhesion molecules. These responses appear to be mediated, in part, through oxidative pathways.

Can Metformin Exert as an Active Drug on Endothelial Dysfunction in Diabetic Subjects?

Cardiovascular mortality is a major cause of death among in type 2 diabetes (T2DM). Endothelial dysfunction (ED) is a well-known important risk factor for the development of diabetes cardiovascular complications. Therefore, the prevention of diabetic macroangiopathies by preserving endothelial function represents a major therapeutic concern for all National Health Systems. Several complex mechanisms support ED in diabetic patients, frequently cross-talking each other: uncoupling of eNOS with impaired endothelium-dependent vascular response, increased ROS production, mitochondrial dysfunction, activation of polyol pathway, generation of advanced glycation end-products (AGEs), activation of protein kinase C (PKC), endothelial inflammation, endothelial apoptosis and senescence, and dysregulation of microRNAs (miRNAs). Metformin is a milestone in T2DM treatment. To date, according to most recent EASD/ADA guidelines, it still represents the first-choice drug in these patients. Intriguingly, several extraglycemic effects of metformin have been recently observed, among which large preclinical and clinical evidence support metformin’s efficacy against ED in T2DM. Metformin seems effective thanks to its favorable action on all the aforementioned pathophysiological ED mechanisms. AMPK pharmacological activation plays a key role, with metformin inhibiting inflammation and improving ED. Therefore, aim of this review is to assess metformin’s beneficial effects on endothelial dysfunction in T2DM, which could preempt development of atherosclerosis.

In vitro and ex vivo anti-diabetic and anti-hyperglycemic properties of Zataria multiflora essential oil

The underlying mechanism involved in the onset of many diseases such as diabetes is oxidative stress. Zataria multiflora has a very high antioxidant power that can be used in the antioxidant therapy of the diabetes symptom. The in vitro antioxidant and anti-diabetic capacity of Zataria multiflora essential oil (ZMEO) incorporated in dendrosome against glucose oxidation, lipid oxidation, protein oxidation, and protein glycation was analyzed. The ex vivo antioxidant capacity of dendrosomal ZMEO were explored against hyperglycemia (HG)-induced oxidative stress. Inhibition of oxidative stress markers; NADH oxidase (NOX), nuclear respiratory factor 2 (NRF2) and nuclear factor kappa B (NF-kB) were examined. Dendrosomal-ZMEO displayed low conductivity, low surface tension, low zeta-potential, nanoscale particle size and low viscosity that suggest dendrosomal-ZMEO could remain stable in biological fluids. FTIR spectra of dendrosomal-ZMEO indicated the non-covalent interactions between dendrosome and ZMEO and the entrapment of ZMEO droplets in the dendrosome network. Dendrosomal-ZMEO displayed good anti-glucose oxidation, anti-lipid peroxidation, anti-protein oxidation, and anti-protein glycation activity. Dendrosomal ZMEO strongly reduced intracellular hydrogen peroxide and NOX expression and activity in HG-treated macrophages while increased superoxide dismutase (SOD) and catalase (CAT) expression and activity in a synergistic manner. HG-treated murine macrophages showed an increased level of NF-kB expression while the decreased level of NRF2 expression compared to controls. The anti-diabetic activity of ZMEO by sequestering hydrogen peroxide and down-regulation of NOX activity is a recommended mechanism for diabetes and oxidative stress. The effect of ZMEO on decreasing NF-kB and increasing in NRF2, transcription factors involved in oxidative stress and hyperglycemia, may imply its clinical application.

Paracetamol-induced metabolic and cardiovascular changes are prevented by exercise training

Paracetamol (PAR) is the most frequently consumed non-prescription drug, yet it is well known to induce toxicity. Here, we have evaluated the effects of exercise training on vascular dysfunction induced by PAR. Rats were distributed among four groups: (a) Sedentary; (b) Exercise; (c) Sedentary+PAR; and (d) Exercise+PAR. The exercise comprised swimming 50 min/d, 5 d/wk for 6 weeks (+PAR in the last 2 weeks, at 400 mg/kg/d/p.o.). After killing, the rats' blood and aortas were collected for biochemical analysis of hepatic transaminases, TBARs reaction, glutathione, glutathione reductase, SOD, and catalase. In vitro vascular relaxation was measured using acetylcholine and sodium nitroprusside in the presence or absence of tiron (an antioxidant). Vascular protein expression (eNOS and sGC) also were analysed. Increased transaminases after PAR treatment were found to be reduced by exercise. Vasodilation was impaired by PAR only in the sedentary group. Exercise prevented alterations in lipoperoxidation and glutathione levels after PAR exposure. Glutaathione reductase and SOD also were increased by PAR but were normalized in the exercised group. Catalase activity and protein expressions did not change in any group. PAR treatment caused impairment in both vasodilation and redox balance; however, exercise training prevented the vascular and redox system dysfunction induced by PAR treatment.

Evaluation of apocynin in vitro on high glucose-induced oxidative stress on tenocytes

Aims

The purpose of this study was to evaluate the in vitro effects of apocynin, an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase (NOX) and a downregulator of intracellular reactive oxygen species (ROS), on high glucose-induced oxidative stress on tenocytes.

Methods

Tenocytes from normal Sprague-Dawley rats were cultured in both control and high-glucose conditions. Apocynin was added at cell seeding, dividing the tenocytes into four groups: the control group; regular glucose with apocynin (RG apo+); high glucose with apocynin (HG apo+); and high glucose without apocynin (HG apo–). Reactive oxygen species production, cell proliferation, apoptosis and messenger RNA (mRNA) expression of NOX1 and 4, and interleukin-6 (IL-6) were determined in vitro.

Results

Expression of NOX1, NOX4, and IL-6 mRNA in the HG groups was significantly higher compared with that in the RG groups, and NOX1, NOX4, and IL-6 mRNA expression in the HG apo+ group was significantly lower compared with that in the HG apo– group. Cell proliferation in the RG apo+ group was significantly higher than in the control group and was also significantly higher in the HG apo+ group than in the HG apo– group. Both the ROS accumulation and the amounts of apoptotic cells in the HG groups were greater than those in the RG groups and were significantly less in the HG apo+ group than in the HG apo– group.

Conclusion

Apocynin reduced ROS production and cell death via NOX inhibition in high-glucose conditions. Apocynin is therefore a potential prodrug in the treatment of diabetic tendinopathy.

Cite this article:Bone Joint Res 2020;9(1):23–28.

Serum Levels of Carbamylated LDL and Soluble Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 Are Associated with Coronary Artery Disease in Patients with Metabolic Syndrome

Background and objectives: Lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) has been recognized as the primary receptor for carbamylated low-density lipoproteins (cLDL) and is increasingly being viewed as a critical mediator of vascular inflammation and atherosclerosis. The aim of the current study was to evaluate the possible role of circulating cLDL and soluble LOX-1 (sLOX-1) as potential biomarkers of metabolic syndrome (MetS) as well as of coronary artery disease (CAD) among MetS patients. Materials and Methods: The serum levels of cLDL and sLOX-1 were measured by ELISA in 30 MetS patients without CAD, 30 MetS patients with CAD, and 30 healthy controls. Results: Patients with MetS had significantly higher serum levels of both cLDL and sLOX-1 than the healthy controls but lower in comparison to MetS + CAD subjects. Serum sLOX-1 concentration correlated significantly with fasting glucose (r_s = 0.414, p = 0.001) and high-density lipoprotein (HDL)-cholesterol (r_s = −0.273, p = 0.035) in the whole MetS cohort, whereas it correlated with cLDL only in the MetS + CAD subgroup (r_s = 0.396, p = 0.030). The receiver-operating characteristic (ROC) curves of cLDL and sLOX-1 for MetS diagnosis had area under the curve (AUC) values of 0.761 and 0.692, respectively. AUC values of cLDL and sLOX-1 for CAD diagnosis among MetS patients were 0.811 and 0.739. Elevated serum levels of cLDL and sLOX-1 were associated with a higher risk of MetS development [odds ratio (OR) 24.28, 95% confidence interval (CI): 5.86–104.61, p < 0.001 and OR 4.75; 95% CI: 1.58–14.25, p = 0.009] as well as with presence of CAD among MetS subjects (OR 11.23; 95% CI: 3.10–40.71, p < 0.001 and OR 4.03; 95% CI: 1.73–11.84, p = 0.019, respectively). Conclusions: The present study underscores the potential of cLDL and sLOX-1 as promising biomarkers for diagnosis and risk assessment of MetS and CAD among the MetS population.

Endothelial Dysfunction: Is There a Hyperglycemia-Induced Imbalance of NOX and NOS?

NADPH oxidases (NOX) are enzyme complexes that have received much attention as key molecules in the development of vascular dysfunction. NOX have the primary function of generating reactive oxygen species (ROS), and are considered the main source of ROS production in endothelial cells. The endothelium is a thin monolayer that lines the inner surface of blood vessels, acting as a secretory organ to maintain homeostasis of blood flow. The enzymatic production of nitric oxide (NO) by endothelial NO synthase (eNOS) is critical in mediating endothelial function, and oxidative stress can cause dysregulation of eNOS and endothelial dysfunction. Insulin is a stimulus for increases in blood flow and endothelium-dependent vasodilation. However, cardiovascular disease and type 2 diabetes are characterized by poor control of the endothelial cell redox environment, with a shift toward overproduction of ROS by NOX. Studies in models of type 2 diabetes demonstrate that aberrant NOX activation contributes to uncoupling of eNOS and endothelial dysfunction. It is well-established that endothelial dysfunction precedes the onset of cardiovascular disease, therefore NOX are important molecular links between type 2 diabetes and vascular complications. The aim of the current review is to describe the normal, healthy physiological mechanisms involved in endothelial function, and highlight the central role of NOX in mediating endothelial dysfunction when glucose homeostasis is impaired.

CTRP3 Protects against High Glucose-Induced Cell Injury in Human Umbilical Vein Endothelial Cells

Aims

Inflammation was closely associated with diabetes-related endothelial dysfunction. C1q/tumor necrosis factor-related protein 3 (CTRP3) is a member of the CTRP family and can provide cardioprotection in many cardiovascular diseases via suppressing the production of inflammatory factors. However, the role of CTRP3 in high glucose- (HG-) related endothelial dysfunction remains unclear. This study evaluates the effects of CTRP3 on HG-induced cell inflammation and apoptosis.

Materials and Methods

To prevent high glucose-induced cell injury, human umbilical vein endothelial cells (HUVECs) were pretreated with recombinant CTRP3 for 1 hour followed by normal glucose (5.5 mmol/l) or high glucose (33 mmol/l) treatment. After that, cell apoptosis and inflammatory factors were determined.

Results

Our results demonstrated that CTRP3 mRNA and protein expression were significantly decreased after HG exposure in HUVECs. Recombinant human CTRP3 inhibited HG-induced accumulation of inflammatory factors and cell loss in HUVECs. CTRP3 treatment also increased the phosphorylation levels of protein kinase B (AKT/PKB) and the mammalian target of rapamycin (mTOR) in HUVECs. CTRP3 lost its inhibitory effects on HG-induced cell inflammation and apoptosis after AKT inhibition. Knockdown of endogenous CTRP3 in HUVECs resulted in increased inflammation and decreased cell viability in vitro.

Conclusions

Taken together, these findings indicated that CTRP3 treatment blocked the accumulation of inflammatory factors and cell loss in HUVECs after HG exposure through the activation of AKT-mTOR signaling pathway. Thus, CTRP3 may be a potential therapeutic drug for the prevention of diabetes-related endothelial dysfunction.

Effect of oral magnesium sulfate administration on lectin-like oxidized low-density lipoprotein receptor-1 gene expression to prevent atherosclerosis in diabetic rat vessels

AIMS/INTRODUCTION

The purpose of the present study was to investigate the possible effect of oral magnesium sulfate (MgSO4 ) in the reduction of atherosclerosis plaques through inhibition of lectin-like low-density lipoprotein receptor-1 (LOX-1) gene expression in diabetic vessels.

MATERIALS AND METHODS

A total of 50 rats were divided into five groups, including non-diabetic control, Mg-treated non-diabetic control, chronic diabetic, Mg-treated chronic diabetic and insulin-treated chronic diabetic. The induction of diabetes was carried out by streptozotocin. The Mg-treated chronic diabetic and Mg-treated non-diabetic control groups were treated with 10 g/L of MgSO4 added to their drinking water. The insulin-treated chronic diabetic group received 2.5 U/kg of insulin twice per day. The fasting blood glucose level and bodyweight were determined weekly. Blood pressure measurement and the intraperitoneal glucose tolerance test were carried out after 16 weeks, and the plasma levels of Mg, lipid profile and oxidized low-density lipoprotein cholesterol (oxLDL) were determined. The mesenteric bed was isolated and perfused according to the McGregor method. The aorta was isolated for LOX-1 genes and proteins expression, and pathological investigation.

RESULTS

MgSO4 administration improved blood pressure, sensitivity to phenylephrine, intraperitoneal glucose tolerance test, lipid profile and plasma ox-LDL level, and also lowered the blood glucose level to the normal range, and decreased LOX-1 gene and protein expressions. Insulin decreased blood pressure, sensitivity to phenylephrine, blood glucose, lipid profiles and plasma oxLDL level, but it did not decrease LOX-1 gene and protein expressions.

CONCLUSIONS

The present findings suggested that MgSO4 improves blood pressure and vessel structure through decreasing oxLDL, and LOX-1 gene and protein expressions; however, insulin did not repair vessel structure, and LOX-1 gene and protein expressions.

Blocking CXCR3 with AMG487 ameliorates the blood-retinal barrier disruption in diabetic mice through anti-oxidative

Oxidative stress and blood-retinal barrier (BRB) damage induced by hyperglycemia are the principal processes involved in the early stages of diabetic retinopathy (DR). CXC chemokine receptor 3 (CXCR3)-mediated inflammatory infiltration exists in many disease models. The main objective of the present study was to determine whether AMG487, a CXCR3 antagonist, can ameliorate BRB disruption and reactive oxygen species generation in the DR model. The retinal endothelial cell and ganglion cell ultrastructures were observed using a transmission electron microscope. The pericyte marker PDGFR-β, tight junction occludin, and leaking albumin were evaluated. The oxidative stress level, CCAAT-enhancer-binding protein homologous protein (CHOP), and p-p38 expression were also investigated in vivo and in vitro. The results indicated that AMG487 application might alleviate PDGFR-β and occludin loss, and decreased the residual content of retinal albumin in the streptozocin-induced DR mouse model via the inhibition of oxidative and endoplasmic reticulum stress, in which p38 activation was also involved. Thus, CXCR3 inhibition might be a target to prevent the early stage of DR injury.

Exposure to acetaminophen impairs vasodilation, increases oxidative stress and changes arterial morphology of rats

Acetaminophen (APAP) is one of the most widely consumed drugs in the world. Studies have shown renal and hepatic damage as the direct result of high oxidative stress induced by APAP. Since the cardiovascular system is sensitive to oxidative stress and literature describes increased cardiovascular dysfunction in APAP consumers, this work aimed to evaluate harmful effects of APAP on the vascular system. Rats were exposed to APAP (400 mg/kg/day in drinking water) for 14 days. Plasma and aortas were collected and stored in - 80 °C and a selection of arteries was prepared for isometric tension recordings, morphological, immunohistochemical and protein expression analysis. The APAP-treated group presented increased transaminases (ALT/AST) and malondialdehyde levels in the plasma compared to controls. Lipid peroxidation, glutathione reductase and superoxide dismutase levels were increased in the plasma and arteries of the APAP group. Nevertheless, glutathione level was reduced as compared to control group. The vasodilation response to acetylcholine and sodium nitroprusside (0.1 nM to 10 µM) was also impaired after APAP treatment; however, the vascular relaxation was restored after treatment with vitamin C (100 µM). Arteries from the APAP group presented reduced wall thickness, collagen deposition, elastic fibers and increased immunoreactivity to nitrotyrosine. eNOS and sGC protein expression remained unchanged and were at similar levels as controls. These findings showed higher oxidative stress and impaired vasodilation in rats exposed to APAP. Furthermore, arteries presented reduced cell layers, collagen, elastin deposition and significantly increased immunoreactivity to nitrotyrosine after APAP treatment.

Overexpression of scavenger receptor and infiltration of macrophage in epicardial adipose tissue of patients with ischemic heart disease and diabetes

Background

Oxidized low-density lipoproteins and scavenger receptors (SRs) play an important role in the formation and development of atherosclerotic plaques. However, little is known about their presence in epicardial adipose tissue (EAT). The objective of the study was to evaluate the mRNA expression of different SRs in EAT of patients with ischemic heart disease (IHD), stratifying by diabetes status and its association with clinical and biochemical variables.

Methods

We analyzed the mRNA expression of SRs (LOX-1, MSR1, CXCL16, CD36 and CL-P1) and macrophage markers (CD68, CD11c and CD206) in EAT from 45 patients with IHD (23 with type 2 diabetes mellitus (T2DM) and 22 without T2DM) and 23 controls without IHD or T2DM.

Results

LOX-1, CL-P1, CD68 and CD11c mRNA expression were significantly higher in diabetic patients with IHD when compared with those without T2DM and control patients. MSR1, CXCL16, CD36 and CD206 showed no significant differences. In IHD patients, LOX-1 (OR 2.9; 95% CI 1.6–6.7; P = 0.019) and CD68 mRNA expression (OR 1.7; 95% CI 0.98–4.5; P = 0.049) were identified as independent risk factors associated with T2DM. Glucose and glycated hemoglobin were also shown to be risk factors.

Conclusions

SRs mRNA expression is found in EAT. LOX-1 and CD68 and were higher in IHD patients with T2DM and were identified as a cardiovascular risk factor of T2DM. This study suggests the importance of EAT in coronary atherosclerosis among patients with T2DM.

Efficacy of High-Dose and Low-Dose Simvastatin on Vascular Oxidative Stress and Neurological Outcomes in Patient with Acute Ischemic Stroke: A Randomized, Double-Blind, Parallel, Controlled Trial

Backgrounds

Stroke is the leading cause of death and long-term disability. Oxidative stress is elevated during occurrence of acute ischemic stroke (AIS). Soluble LOX-1 (sLOX-1) and NO are used as biomarkers for vascular oxidative stress that can reflect stabilization of atherosclerotic plaque. Previous study showed that simvastatin can reduce oxidative stress and LOX-1 expression.

Objectives

To evaluate neurological outcomes and serum sLOX-1 and NO levels in patients with AIS treatment with low dose 10 mg/day and high dose 40 mg/day of simvastatin.

Methods

65 patients with AIS within 24 hours after onset were randomized to treatment with simvastatin 10 mg/day or 40 mg/day for 90 days. Personal data and past history of all patients were recorded at baseline. The blood chemistries were measured by standard laboratory techniques. Serum sLOX-1 and NO levels and neurological outcomes including NIHSS, mRS, and Barthel index were tested at baseline and Day 90 after simvastatin therapy.

Results

Baseline characteristics were not significantly different in both groups except history of hypertension. Serum sLOX-1 and NO levels significantly reduce in both groups (sLOX-1 = 1.19 ± 0.47 and 0.98 ± 0.37 ng/ml; NO = 49.28 ± 7.21 and 46.59 ± 9.36 μmol/l) in 10 mg/day and 40 mg/day simvastatin groups, respectively. Neurological outcomes including NIHSS, mRS, and Barthel index significantly improve in both groups. However, no difference in NO level and neurological outcomes was found at 90 days after treatment as compared between low dose 10 mg/day and high dose 40 mg/day of simvastatin.

Conclusion

High-dose simvastatin might be helpful to reduce serum sLOX-1. But no difference in clinical outcomes was found between high- and low-dose simvastatin. Further more intensive clinical trial is needed to confirm the appropriate dosage of simvastatin in patients with acute ischemic stroke. This trial is registered with ClinicalTrials.gov ID: NCT03402204.

CFTR ameliorates high glucose-induced oxidative stress and inflammation by mediating the NF-κB and MAPK signaling pathways in endothelial cells

Diabetic cardiovascular diseases are characterized by progressive hyperglycemia, which results in excessive production of oxidative stress and pro-inflammatory cytokines. Cystic fibrosis (CF) is characterized by chronic inflammation due to mutations in CF transmembrane conductance regulator (CFTR). However, little information is available about the role of CFTR in hyperglycemia‑induced endothelial cell oxidative stress and inflammation. In the present study, a high glucose‑treatment was applied in human umbilical vein endothelial cells with CFTR overexpression or inhibition, and the oxidative and inflammatory characteristics were measured. It was shown that CFTR protein and mRNA expression were reduced by glucose in a concentration‑dependent manner. Overexpression of CFRT via adenoviral infection significantly inhibited the production of reactive oxygen species and inflammatory biomediators induced by high glucose. Conversely, pharmacological inhibition of CFTR led to the opposite effects. Mechanistically, nuclear factor‑κB (NF‑κB) and mitogen‑activated protein kinase (MAPK) signaling were activated following high glucose treatment, which were inhibited by CFTR overexpression and enhanced by CFTR inhibition. The pro‑inflammatory effect of CFTR inhibition was abolished by pharmacological inhibition of the NF‑κB or MAPK pathways. Moreover, inhibition of MAPK abrogated CFTR inhibition‑induced NF‑κB nuclear translocation, whereas NF‑κB inhibitor produced no effects on MAPK activation. Additionally, antioxidant treatment inhibited the high glucose‑induced decrease in CFTR expression and the increase in inflammatory responses. Collectively, these findings revealed that CFTR attenuates high glucose‑induced endothelial cell oxidative stress and inflammation through inactivation of NF‑κB and MAPK signaling, indicating that elevation of CFRT expression may be a novel strategy in preventing endothelial dysfunction in diabetes.

Metformin regulates oxLDL-facilitated endothelial dysfunction by modulation of SIRT1 through repressing LOX-1-modulated oxidative signaling

It is suggested that oxLDL is decisive in the initiation and development of atherosclerotic injuries. The up-regulation of oxidative stress and the generation of ROS act as key modulators in developing pro-atherosclerotic and anti-atherosclerotic processes in the human endothelial wall. In this present study, we confirmed that metformin enhanced SIRT1 and AMPK expression in human umbilical vein endothelial cells (HUVECs). Metformin also inhibited oxLDL-increased LOX-1 expression and oxLDL-collapsed AKT/eNOS levels. However, silencing SIRT1 and AMPK diminished the protective function of metformin against oxidative injuries. These results provide a new insight regarding the possible molecular mechanisms of metformin.

Glycosylation with O-linked β-N-acetylglucosamine induces vascular dysfunction via production of superoxide anion/reactive oxygen species

Overproduction of superoxide anion (•O₂^-) and O-linked β-N-acetylglucosamine (O-GlcNAc) modification in the vascular system are contributors to endothelial dysfunction. This study tested the hypothesis that increased levels of O-GlcNAc-modified proteins contribute to •O₂^- production via activation of NADPH oxidase, resulting in impaired vasodilation. Rat aortic segments and vascular smooth muscle cells (VSMCs) were incubated with vehicle (methanol) or O-(2-acetamido-2-deoxy-d-glucopyranosylidenamino) N-phenylcarbamate (PUGNAc) (100 μM). PUGNAc produced a time-dependent increase in O-GlcNAc levels in VSMC and decreased endothelium-dependent relaxation, which was prevented by apocynin and tiron, suggesting that •O₂^- contributes to endothelial dysfunction under augmented O-GlcNAc levels. Aortic segments incubated with PUGNAc also exhibited increased levels of reactive oxygen species, assessed by dihydroethidium fluorescence, and augmented •O₂^- production, determined by lucigenin-enhanced chemiluminescence. Additionally, PUGNAc treatment increased Nox-1 and Nox-4 protein expression in aortas and VSMCs. Translocation of the p47^phox subunit from the cytosol to the membrane was greater in aortas incubated with PUGNAc. VSMCs displayed increased p22^phox protein expression after PUGNAc incubation, suggesting that NADPH oxidase is activated in conditions where O-GlcNAc protein levels are increased. In conclusion, O-GlcNAc levels reduce endothelium-dependent relaxation by overproduction of •O₂^- via activation of NADPH oxidase. This may represent an additional mechanism by which augmented O-GlcNAc levels impair vascular function.

Myeloperoxidase amplified high glucose-induced endothelial dysfunction in vasculature: Role of NADPH oxidase and hypochlorous acid

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (H₂O₂), have emerged as important molecules in the pathogenesis of diabetic endothelial dysfunction. Additionally, neutrophils-derived myeloperoxidase (MPO) and MPO-catalyzed hypochlorous acid (HOCl) play important roles in the vascular injury. However, it is unknown whether MPO can use vascular-derived ROS to induce diabetic endothelial dysfunction. In the present study, we demonstrated that NADPH oxidase was the main source of ROS formation in high glucose-cultured human umbilical vein endothelial cells (HUVECs), and played a critical role in high glucose-induced endothelial dysfunction such as cell apoptosis, loss of cell viability and reduction of nitric oxide (NO). However, the addition of MPO could amplify the high glucose-induced endothelial dysfunction which was inhibited by the presence of apocynin (NADPH oxidase inhibitor), catalase (H₂O₂ scavenger), or methionine (HOCl scavenger), demonstrating the contribution of NADPH oxidase-H₂O₂-MPO-HOCl pathway in the MPO/high glucose-induced vascular injury. In high glucose-incubated rat aortas, MPO also exacerbated the NADPH oxidase-induced impairment of endothelium-dependent relaxation. Consistent with these in vitro data, in diabetic rat aortas, both MPO expresion and NADPH oxidase activity were increased while the endothelial function was simultaneously impaired. The results suggested that vascular-bound MPO could amplify high glucose-induced vascular injury in diabetes. MPO-NADPH oxidase-HOCl may represent an important pathogenic pathway in diabetic vascular diseases.

Toll-like receptors 2 and 4 mediate hyperglycemia induced macrovascular aortic endothelial cell inflammation and perturbation of the endothelial glycocalyx

OBJECTIVES

Hyperglycemia-induced inflammation is central to the vascular complications in diabetes. Toll-like receptors (TLRs) are key players in regulating inflammatory responses. There are sparse data on the role of TLR2 and TLR4 in regulating human macrovascular aortic endothelial cells (HMAECs) inflammation and glycocalyx dysfunction under hyperglycemia. We examined the role of TLR2/4 in the above dysfunctions in HMAEC under high glucose (HG) conditions.

METHODS

HMAECs were treated with high or normal glucose and TLR-2, TLR-4, MyD88, IRF3, TRIF, nuclear NF-κB p65, IL-8, IL-1β, TNF-α, MCP-1, ICAM-1, sVCAM-1, monocyte adhesion to HMAECs, heparan sulfate and hyaluronic acid were measured.

RESULTS

HG upregulated TLR2 and TLR4 mRNA and protein and increased both MyD88 and non-MyD88 pathways, NF-κB p65, inflammatory biomediators, and monocyte adhesion to HMAECs. Heparan sulfate protein expression was reduced and hyaluronic acid secretion was increased on HG exposure. Inhibition of TLR2 and TLR4 signaling by inhibitory peptides and knockdown of TLR-2 and TLR-4 gene expression by siRNA attenuated HG induced inflammation, leukocyte adhesion and glycocalyx dysfunction. An increase in ROS paralleled the increase in TLR-2/4 and antioxidants treatment reduced TLR-2/4 expression and downstream inflammatory biomediators.

CONCLUSION

Thus hyperglycemia induces HMAEC inflammation and glycocalyx dysfunction through TLR-2/4 pathway activation via increased ROS.

Quercetin is a potent anti-atherosclerotic compound by activation of SIRT1 signaling under oxLDL stimulation

SCOPE

Atherosclerosis is believed to be an independent predictor of cardiovascular diseases. A growing body of evidence suggests that quercetin is a potent antioxidant and anti-inflammatory compound. The molecular mechanisms underlying its protective effects against oxidative stress in human endothelial cells remain unclear. This study was designed to confirm the hypothesis that quercetin inhibits oxidized LDL (oxLDL) induced endothelial oxidative damage by activating sirtuin 1 (SIRT1) and to explore the role of adenosine monophosphate activated protein kinase (AMPK), which is a negative regulator of Nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) and free radicals.

METHODS AND RESULTS

Human umbilical vein endothelial cells were treated with oxLDL with or without quercetin pretreatment. We found that quercetin pretreatment increased SIRT1 mRNA expression. In fact, quercetin protected against oxLDL-impaired SIRT1 and AMPK activities and reduced oxLDL-activated NOX2 and NOX4. However, silencing SIRT1 and AMPK diminished the protective function of quercetin against oxidative injuries. The results also indicated that oxLDL suppressed AKT/endothelial NO synthase, impaired mitochondrial dysfunction, and enhanced reactive oxygen species formation, activating the Nuclear Factor Kappa B (NF-κB) pathway.

CONCLUSION

These results provide new insight regarding the possible molecular mechanisms of quercetin. Quercetin suppresses oxLDL-induced endothelial oxidative injuries by activating SIRT1 and modulating the AMPK/NADPH oxidase/AKT/endothelial NO synthase signaling pathway.

Adiponectin as a link between type 2 diabetes and vascular NADPH oxidase activity in the human arterial wall: the regulatory role of perivascular adipose tissue

Oxidative stress plays a critical role in the vascular complications of type 2 diabetes. We examined the effect of type 2 diabetes on NADPH oxidase in human vessels and explored the mechanisms of this interaction. Segments of internal mammary arteries (IMAs) with their perivascular adipose tissue (PVAT) and thoracic adipose tissue were obtained from 386 patients undergoing coronary bypass surgery (127 with type 2 diabetes). Type 2 diabetes was strongly correlated with hypoadiponectinemia and increased vascular NADPH oxidase-derived superoxide anions (O2˙(-)). The genetic variability of the ADIPOQ gene and circulating adiponectin (but not interleukin-6) were independent predictors of NADPH oxidase-derived O2˙(-). However, adiponectin expression in PVAT was positively correlated with vascular NADPH oxidase-derived O2˙(-). Recombinant adiponectin directly inhibited NADPH oxidase in human arteries ex vivo by preventing the activation/membrane translocation of Rac1 and downregulating p22(phox) through a phosphoinositide 3-kinase/Akt-mediated mechanism. In ex vivo coincubation models of IMA/PVAT, the activation of arterial NADPH oxidase triggered a peroxisome proliferator-activated receptor-γ-mediated upregulation of the adiponectin gene in the neighboring PVAT via the release of vascular oxidation products. We demonstrate for the first time in humans that reduced adiponectin levels in individuals with type 2 diabetes stimulates vascular NADPH oxidase, while PVAT "senses" the increased NADPH oxidase activity in the underlying vessel and responds by upregulating adiponectin gene expression. This PVAT-vessel interaction is identified as a novel therapeutic target for the prevention of vascular complications of type 2 diabetes.

Nuclear cardiac myosin light chain 2 modulates NADPH oxidase 2 expression in myocardium: a novel function beyond muscle contraction

Recent studies demonstrated that NADPH oxidase 2 (NOX2) expression in myocardium after ischemia-reperfusion (IR) is significantly upregulated. However, the underlying mechanisms remain unknown. This study aims to determine if nuclear cardiac myosin light chain 2 (MYL2), a well-known regulatory subunit of myosin, functions as a transcription factor to promote NOX2 expression following myocardial IR in a phosphorylation-dependent manner. We examined the phosphorylation status of nuclear MYL2 (p-MYL2) in a rat model of myocardial IR (left main coronary artery subjected to 1 h ligation and 3 h reperfusion) injury, which showed IR injury and upregulated NOX2 expression as expected, accompanied by elevated H₂O₂ and nuclear p-MYL2 levels; these effects were attenuated by inhibition of myosin light chain kinase (MLCK). Next, we explored the functional relationship of nuclear p-MYL2 with NOX2 expression in H9c2 cell model of hypoxia-reoxygenation (HR) injury. In agreement with our in vivo findings, HR treatment increased apoptosis, NOX2 expression, nuclear p-MYL2 and H₂O₂ levels, and the increases were ameliorated by inhibition of MLCK or knockdown of MYL2. Finally, molecular biology techniques including co-immunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP), DNA pull-down and luciferase reporter gene assay were utilized to decipher the molecular mechanisms. We found that nuclear p-MYL2 binds to the consensus sequence AGCTCC in NOX2 gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and thus activates NOX2 gene transcription. Our results demonstrate that nuclear MYL2 plays an important role in IR injury by transcriptionally upregulating NOX2 expression to enhance oxidative stress in a phosphorylation-dependent manner.

Insulin reverses D-glucose-increased nitric oxide and reactive oxygen species generation in human umbilical vein endothelial cells

Vascular tone is controlled by the L-arginine/nitric oxide (NO) pathway, and NO bioavailability is strongly affected by hyperglycaemia-induced oxidative stress. Insulin leads to high expression and activity of human cationic amino acid transporter 1 (hCAT-1), NO synthesis and vasodilation; thus, a protective role of insulin on high D-glucose-alterations in endothelial function is likely. Vascular reactivity to U46619 (thromboxane A2 mimetic) and calcitonin gene related peptide (CGRP) was measured in KCl preconstricted human umbilical vein rings (wire myography) incubated in normal (5 mmol/L) or high (25 mmol/L) D-glucose. hCAT-1, endothelial NO synthase (eNOS), 42 and 44 kDa mitogen-activated protein kinases (p42/44mapk), protein kinase B/Akt (Akt) expression and activity were determined by western blotting and qRT-PCR, tetrahydrobiopterin (BH4) level was determined by HPLC, and L-arginine transport (0-1000 μmol/L) was measured in response to 5-25 mmol/L D-glucose (0-36 hours) in passage 2 human umbilical vein endothelial cells (HUVECs). Assays were in the absence or presence of insulin and/or apocynin (nicotinamide adenine dinucleotide phosphate-oxidase [NADPH oxidase] inhibitor), tempol or Mn(III)TMPyP (SOD mimetics). High D-glucose increased hCAT-1 expression and activity, which was biphasic (peaks: 6 and 24 hours of incubation). High D-glucose-increased maximal transport velocity was blocked by insulin and correlated with lower hCAT-1 expression and SLC7A1 gene promoter activity. High D-glucose-increased transport parallels higher reactive oxygen species (ROS) and superoxide anion (O2•-) generation, and increased U46619-contraction and reduced CGRP-dilation of vein rings. Insulin and apocynin attenuate ROS and O2•- generation, and restored vascular reactivity to U46619 and CGRP. Insulin, but not apocynin or tempol reversed high D-glucose-increased NO synthesis; however, tempol and Mn(III)TMPyP reversed the high D-glucose-reduced BH4 level. Insulin and tempol blocked the high D-glucose-increased p42/44mapk phosphorylation. Vascular dysfunction caused by high D-glucose is likely attenuated by insulin through the L-arginine/NO and O2•-/NADPH oxidase pathways. These findings are of interest for better understanding vascular dysfunction in states of foetal insulin resistance and hyperglycaemia.

Angiotensin II and vascular injury

Vascular injury, characterized by endothelial dysfunction, structural remodelling, inflammation and fibrosis, plays an important role in cardiovascular diseases. Cellular processes underlying this include altered vascular smooth muscle cell (VSMC) growth/apoptosis, fibrosis, increased contractility and vascular calcification. Associated with these events is VSMC differentiation and phenotypic switching from a contractile to a proliferative/secretory phenotype. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Among the many factors involved in vascular injury is Ang II. Ang II, previously thought to be the sole biologically active downstream peptide of the renin-angiotensin system (RAS), is converted to smaller peptides, [Ang III, Ang IV, Ang-(1-7)], that are functional and that modulate vascular tone and structure. The actions of Ang II are mediated via signalling pathways activated upon binding to AT1R and AT2R. AT1R activation induces effects through PLC-IP3-DAG, MAP kinases, tyrosine kinases, tyrosine phosphatases and RhoA/Rho kinase. Ang II elicits many of its (patho)physiological actions by stimulating reactive oxygen species (ROS) generation through activation of vascular NAD(P)H oxidase (Nox). ROS in turn influence redox-sensitive signalling molecules. Here we discuss the role of Ang II in vascular injury, focusing on molecular mechanisms and cellular processes. Implications in vascular remodelling, inflammation, calcification and atherosclerosis are highlighted.

A protective role of ciglitazone in ox-LDL-induced rat microvascular endothelial cells via modulating PPARγ-dependent AMPK/eNOS pathway

Thiazolidinediones, the antidiabetic agents such as ciglitazone, has been proved to be effective in limiting atherosclerotic events. However, the underlying mechanism remains elucidative. Ox-LDL receptor-1 (LOX-1) plays a central role in ox-LDL-mediated atherosclerosis via endothelial nitric oxide synthase (eNOS) uncoupling and nitric oxide reduction. Therefore, we tested the hypothesis that ciglitazone, the PPARγ agonist, protected endothelial cells against ox-LDL through regulating eNOS activity and LOX-1 signalling. In the present study, rat microvascular endothelial cells (RMVECs) were stimulated by ox-LDL. The impact of ciglitazone on cell apoptosis and angiogenesis, eNOS expression and phosphorylation, nitric oxide synthesis and related AMPK, Akt and VEGF signalling pathway were observed. Our data showed that both eNOS and Akt phosphorylation, VEGF expression and nitric oxide production were significantly decreased, RMVECs ageing and apoptosis increased after ox-LDL induction for 24 hrs, all of which were effectively reversed by ciglitazone pre-treatment. Meanwhile, phosphorylation of AMP-activated protein kinase (AMPK) was suppressed by ox-LDL, which was also prevented by ciglitazone. Of interest, AMPK inhibition abolished ciglitazone-mediated eNOS function, nitric oxide synthesis and angiogenesis, and increased RMVECs ageing and apoptosis. Further experiments showed that inhibition of PPARγ significantly suppressed AMPK phosphorylation, eNOS expression and nitric oxide production. Ciglitazone-mediated angiogenesis and reduced cell ageing and apoptosis were reversed. Furthermore, LOX-1 protein expression in RMVECs was suppressed by ciglitazone, but re-enhanced by blocking PPARγ or AMPK. Ox-LDL-induced suppression of eNOS and nitric oxide synthesis were largely prevented by silencing LOX-1. Collectively, these data demonstrate that ciglitazone-mediated PPARγ activation suppresses LOX-1 and moderates AMPK/eNOS pathway, which contributes to endothelial cell survival and function preservation.

Spironolactone improves endothelial dysfunction in streptozotocin-induced diabetic rats

Endothelial dysfunction is a critical initiator for developing diabetic vascular complications. Substantial clinical and experimental evidence suggests that aldosterone plays a crucial role in its pathogenesis. The present study aimed to investigate the effect of the mineralocorticoid receptor (MR) blocker, spironolactone, on diabetes-associated endothelial dysfunction and address the underlying mechanism(s) involved in this setting. Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ) to rats and spironolactone was orally administered (50 mg/kg/day). Our results showed a marked increase in aortic malondialdehyde (MDA) level and upregulation of the catalytic NADPH oxidase subunit, NOX2 gene expression alongside reducing catalase enzyme capacity, and the serum nitric oxide (NO) bioavailability in diabetic rats. This was associated with a significant reduction in endothelial nitric oxide synthase (eNOS) immunoreactivity and gene expression in diabetic aorta. The transforming growth factor-β (TGF-β) protein and the MR gene expression levels were significantly increased in the diabetic rat aorta. Moreover, the diabetic aorta showed a marked impairment in acetylcholine-mediated endothelium-dependent relaxation. Additionally, spironolactone significantly inhibited the elevated MDA, TGF-β, NOX2, and MR levels alongside correcting the dysregulated eNOS expression and the defective antioxidant function as well as NO bioavailability. Spironolactone markedly reversed the impaired endothelial function in the diabetic aorta. Collectively, our study demonstrates that spironolactone ameliorated the vascular dysfunction of diabetic aorta, at least partially via its anti-inflammatory and anti-oxidative effects alongside correcting the dysregulated eNOS and TGF-β expression. Thus, blockade of MR may represent a useful therapeutic approach against diabetic vasculopathy.

Endothelial NADPH oxidases: which NOX to target in vascular disease?

NADPH oxidases (NOXs) are reactive oxygen species (ROS)-generating enzymes implicated in the pathophysiology of vascular diseases such as hypertension and stroke. Endothelial cells express four NOX isoforms including the superoxide-generating enzymes NOX1, NOX2, and NOX5 and the hydrogen peroxide-generating enzyme NOX4. Studies on arteries from patients with coronary artery disease, and in animals with experimentally induced hypertension, diabetes, or atherosclerosis, suggest that NOX1, NOX2, and NOX5 promote endothelial dysfunction, inflammation, and apoptosis in the vessel wall, whereas NOX4 is by contrast vasoprotective in increasing nitric oxide bioavailability and suppressing cell death pathways. Based on these findings and promising preclinical studies with the NOX1/NOX2 antagonist, apocynin, we suggest that the field is poised for clinical evaluation of NOX inhibitors as therapeutics for cardiovascular disease.

Hyperglycemia induces Toll-like receptor-2 and -4 expression and activity in human microvascular retinal endothelial cells: implications for diabetic retinopathy

Diabetic retinopathy (DR) causes visual impairment in working age adults and hyperglycemia-mediated inflammation is central in DR. Toll-like receptors (TLRs) play a key role in innate immune responses and inflammation. However, scanty data is available on their role in DR. Hence, in this study, we examined TLR2 and TLR4 mRNA and protein expression and activity in hyperglycemic human retinal endothelial cells (HMVRECs). HMVRECs were treated with hyperglycemia (HG) or euglycemia and mRNA and protein levels of TLR-2, TLR-4, MyD88, IRF3, and TRIF as well as NF-κB p65 activation were measured. IL-8, IL-1β, TNF-α and MCP-1, ICAM-1, and VCAM-1 as well as monocyte adhesion to HMVRECs were also assayed. HG (25 mM) significantly induced TLR2 and TLR4 mRNA and protein in HMVRECs. It also increased both MyD88 and non-MyD88 pathways, nuclear factor-κB (NF-κB), biomediators, and monocyte adhesion. This inflammation was attenuated by TLR-4 or TLR-2 inhibition, and dual inhibition by a TLR inhibitory peptide as well as TLR2 and 4 siRNA. Additionally, antioxidant treatment reduced TLR-2 and TLR4 expression and downstream inflammatory markers. Collectively, our novel data suggest that hyperglycemia induces TLR-2 and TLR-4 activation and downstream signaling mediating increased inflammation possibly via reactive oxygen species (ROS) and could contribute to DR.

Tempol ameliorates cardiac fibrosis in streptozotocin-induced diabetic rats: role of oxidative stress in diabetic cardiomyopathy

Long-standing diabetes is associated with increased oxidative stress and cardiac fibrosis. This, in turn, contributes to the progression of cardiomyopathy. The present study was sought to investigate whether the free radical scavenger, 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol) can protect against diabetic cardiomyopathy and to explore the specific underlying mechanism(s) in this setting. Diabetes was induced in rats by a single intraperitoneal injection dose of streptozotocin (50 mg/kg). These animals were treated with tempol (18 mg kg(-1) day(-1), orally) for 8 weeks. Our results showed significant increases in collagen IV and fibronectin protein levels and a marked decrease in matrix metalloproteinase-2 (MMP-2) activity measured by gelatin-gel zymography alongside elevated cardiac transforming growth factor (TGF)-β level determined using ELISA or immunohistochemistry in cardiac tissues of diabetic rats compared with control. This was accompanied by an increased in the oxidative stress as evidenced by increased reactive oxygen species (ROS) production and decreased antioxidant enzyme capacity along with elevated lactate dehydrogenase (LDH) and creatine kinase (CK-MB) serum levels as compared with the control. Tempol treatment significantly corrected the changes in the cardiac extracellular matrix, TGF-β, ROS or serum LDH, CK-MB levels, and normalized MMP-2 activity along with preservation of cardiac tissues integrity of diabetic rats against damaging responses. Moreover, tempol normalized the elevated systolic blood pressure and improved some cardiac functions in diabetic rats. Collectively, our data suggest a potential protective role of tempol against diabetes-associated cardiac fibrosis in rats via reducing oxidative stress and extracellular matrix remodeling.

Protective effect of hydrogen sulfide against cold restraint stress-induced gastric mucosal injury in rats

Hydrogen sulfide (H2S) is an endogenous gaseous mediator plays a potential role in modulating gastric inflammatory responses. However, its putative protective role remains to be defined. The present study aimed to evaluate role of the exogenously released and endogenously synthesized H2S in cold restraint stress (CRS)-induced oxidative gastric damage in rats. Rats were restrained, and maintained at 4 °C for 3 h. The H2S donor, sodium hydrosulfide (NaHS) (60 μmol/kg) was injected intraperitoneally (i.p.) before CRS. Our results revealed that NaHS pretreatment significantly attenuated ulcer index, free and total acid output, and pepsin activity in gastric juice along with decreased gastric mucosal carbonyl content and reactive oxygen species production. This was accompanied by increased gastric juice pH and mucin concentration in addition to restoring the deficits in the gastric reduced glutathione, catalase as well as superoxide dismutase enzyme activities. NaHS pretreatment markedly reduced the serum level of tumor necrosis factor (TNF-α) and myeloperoxidase activity compared to CRS-non-treated. Moreover, NaHS preadministration significantly abrogated the inflammatory and the deleterious responses of gastric mucosa in CRS. The protective effects of H2S were confirmed by gastric histopathological examination. However, pretreatment with the H2S-synthesizing enzyme, cystathionine-gamma-lyase inhibitor, beta-cyano-L-alanine (50 mg/kg, i.p.) reversed the gastroprotection afforded by the endogenous H2S. Collectively, our results suggest that H2S can protect rat gastric mucosa against CRS-induced gastric ulceration possibly through mechanisms that involve anti-oxidant and anti-inflammatory actions alongside enhancement of gastric mucosal barrier and reduction in acid secretory parameters.

Lectin-like oxidized low-density lipoprotein receptor 1 pathways

BACKGROUND

The role of lectin-like oxidized low-density lipoprotein receptor (LOX)-1 has been implicated in the pathogenesis of different diseases, including atherosclerosis, hypertension, obesity, diabetes mellitus and metabolic syndrome. To date, several studies aimed at partially investigating the mechanistic role of LOX-1 in these various pathologies. Still, so far, the precise signal transduction pathways involving LOX-1 have not yet been elucidated.

MATERIALS AND METHODS

The most recent data published by the authors as well as others concerning different pathways involving LOX-1 are collected to formulate the presented updated review.

RESULTS

One of the most prominent pathways highlighted in the present review is the relationship of LOX-1 to NADPH oxidase that acts as a major source of harmful free radicals causing oxidative stress in blood vessels. Other pathways involve lipid and glucose metabolism-mediated signal transduction.

DISCUSSION

The modulatory role of LOX-1 on nitric oxide and renin/angiotensin systems as well as on fibrosis, apoptosis and inflammatory pathways is discussed.

CONCLUSION

The current review revisits LOX-1 and its related pathways, implicating LOX-1 as a target for ameliorating various pathological conditions.

Celastrol prevents atherosclerosis via inhibiting LOX-1 and oxidative stress

Celastrol is a triterpenoid compound extracted from the Chinese herb Tripterygium wilfordii Hook F. Previous research has revealed its anti-oxidant, anti-inflammatory, anti-cancer and immunosuppressive properties. Here, we investigated whether celastrol inhibits oxidized low-density lipoprotein (oxLDL) induced oxidative stress in RAW 264.7 cells. In addition, the effect of celastrol on atherosclerosis in vivo was assessed in apolipoprotein E knockout (apoE^−/−) mouse fed a high-fat/high-cholesterol diet (HFC). We found that celastrol significantly attenuated oxLDL-induced excessive expression of lectin-like oxidized low density lipoprotein receptor-1(LOX-1) and generation of reactive oxygen species (ROS) in cultured RAW264.7 macrophages. Celastrol also decreased IκB phosphorylation and degradation and reduced production of inducible nitric oxide synthase (iNOS), nitric oxide (NO) and proinflammatory cytokines such as tumor necrosis factor (TNF)-α and IL-6. Celastrol reduced atherosclerotic plaque size in apoE^−/− mice. The expression of LOX-1 within the atherosclerotic lesions and generation of superoxide in mouse aorta were also significantly reduced by celastrol while the lipid profile was not improved. In conclusion, our results show that celastrol inhibits atherosclerotic plaque developing in apoE^−/− mice via inhibiting LOX-1 and oxidative stress.

Nox as a target for diabetic complications

Oxidative stress has been linked to the pathogenesis of the major complications of diabetes in the kidney, the heart, the eye or the vasculature. NADPH oxidases of the Nox family are a major source of ROS (reactive oxygen species) and are critical mediators of redox signalling in cells from different organs afflicted by the diabetic milieu. In the present review, we provide an overview of the current knowledge related to the understanding of the role of Nox in the processes that control cell injury induced by hyperglycaemia and other predominant factors enhanced in diabetes, including the renin–angiotensin system, TGF-β (transforming growth factor-β) and AGEs (advanced glycation end-products). These observations support a critical role for Nox homologues in diabetic complications and indicate that NADPH oxidases are an important therapeutic target. Therefore the design and development of small-molecule inhibitors that selectively block Nox oxidases appears to be a reasonable approach to prevent or retard the complications of diabetes in target organs. The bioefficacy of these agents in experimental animal models is also discussed in the present review.

Oxidative stress augments pulmonary hypertension in chronically hypoxic mice overexpressing the oxidized LDL receptor

Chronic hypoxia is one of the main causes of pulmonary hypertension (PH) associated with ROS production. Lectin-like oxidized low-density lipoprotein receptor (LOX)-1 is known to be an endothelial receptor of oxidized low-density lipoprotein, which is assumed to play a role in the initiation of ROS generation. We investigated the role of LOX-1 and ROS generation in PH and vascular remodeling in LOX-1 transgenic (TG) mice. We maintained 8- to 10-wk-old male LOX-1 TG mice and wild-type (WT) mice in normoxia (room air) or hypoxia (10% O2 chambers) for 3 wk. Right ventricular (RV) systolic pressure (RVSP) was comparable between the two groups under normoxic conditions; however, chronic hypoxia significantly increased RVSP and RV hypertrophy in LOX-1 TG mice compared with WT mice. Medial wall thickness of the pulmonary arteries was significantly greater in LOX-1 TG mice than in WT mice. Furthermore, hypoxia enhanced ROS production and nitrotyrosine expression in LOX-1 TG mice, supporting the observed pathological changes. Administration of the NADPH oxidase inhibitor apocynin caused a significant reduction in PH and vascular remodeling in LOX-1 TG mice. Our results suggest that LOX-1-ROS generation induces the development and progression of PH.

Activation of renal haeme oxygenase-1 alleviates gentamicin-induced acute nephrotoxicity in rats

Objectives

This study aimed to investigate whether activation of haeme oxygenase (HO)-1 enzyme by haemin would have beneficial effects on the functional and histological outcome against gentamicin-induced renal damage in rats and sought to elucidate the underlying mechanisms of the therapeutic action.

Methods

Nephrotoxicity was induced by injection of gentamicin (80 mg/kg, i.p.) once daily for seven days. Haemin (50 μmol/kg, i.p.) was given to the control and gentamicin-treated rats in the presence or absence of a HO-1 inhibitor, zinc protoporphyrin IX (ZnPP, 50 μmol/kg per day, i.p.).

Key findings

Haemin treatment prevented gentamicin-induced elevated serum creatinine, urinary protein levels and ameliorated the impaired creatinine clearance. Haemin compensated the deficits in antioxidant enzyme activity and attenuated lipid peroxidation along with decreased reactive oxygen species (ROS) production in renal tissues due to gentamicin. Moreover, haemin pre-administration evoked increased renal HO-1 activity. Additionally, haemin significantly attenuated elevated renal tumour necrosis factor-α (TNF-α), nuclear factor-kappaB (NF-κB) levels and caspase-3 activity alongside ameliorating glomerular pathology. These therapeutic effects were abolished by ZnPP pretreatment.

Conclusions

Here is the first evidence demonstrating the protective effect of HO-1 against gentamicin-associated nephrotoxicity. Suppression of oxidative/inflammatory insults alongside the corresponding decline of apoptosis were presumably responsible for this renoprotection.

Effect of 5-hydroxymethylfurfural derived from processed Cornus officinalis on the prevention of high glucose-induced oxidative stress in human umbilical vein endothelial cells and its mechanism

The aim of this study was to investigate the protective effect of 5-HMF on human umbilical vein endothelial cells (HUVECs) injured by high glucose in vitro, and the mechanism underlying this process. Our results demonstrated that high glucose-induced oxidative stress in HUVECs was mainly mediated through activation of reactive oxygen species (ROS), Jun N-kinase 2/3 (JNK2/3) and plasma interleukin-8 (IL-8), and inactivation of phosphorylated protein kinase B (P-Akt). Treatment of HUVECs with media containing high glucose (4.5%) in the presence of 5-HMF (100, 200 and 400 μM) resulted in significant inhibition of high glucose-induced oxidative stress and expression of JNK1 and JNK2/3. Furthermore, 5-HMF rapidly inhibited high glucose-induced activation of IL-8, a downstream activator of P-Akt. Diabetes mellitus can cause a wide variety of vascular complications and high glucose can induce vascular endothelial cell apoptosis. Free radicals are formed disproportionately in diabetes by glucose oxidation. The finding of this study highlights the pharmacological application of 5-HMF for preventing cardiovascular and diabetes mellitus diseases, and provides the theoretical basis for further development of a Cornus officinalis agent for diabetes-associated vascular diseases.

Expression of NO synthases and redox enzymes in umbilical arteries from newborns born small, appropriate, and large for gestational age

BACKGROUND

Modified expression of nitric oxide synthases (NOSs) and an imbalance between the pro-oxidative and the antioxidative system accompany endothelial dysfunction, the first stage of atherosclerosis. Humans born small (SGA) or large (LGA) for gestational age are at higher risk of developing atherosclerosis later in life than humans born appropriate for gestational age (AGA). We hypothesized that indicators of endothelial dysfunction could be detectable at birth. The purpose of this study was to find out whether the expression patterns of NO synthases (endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS)), pro-oxidative enzymes (components of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, NADPH oxidase 1 (NOX1), NOX2, NOX4, p22phox, and p47phox), and antioxidative enzymes (superoxide dismutase 1-3 (SOD1-3), glutathione peroxidase 1 (GPX1), and catalase) in umbilical arteries differ among SGA, LGA, and AGA newborns.

METHODS

Thirty-six umbilical cords were obtained from healthy, normal, full-term SGA, AGA, and LGA newborns. The umbilical arteries were dissected and homogenized. mRNA expression was analyzed with quantitative real-time PCR. Western blotting was performed to determine protein expression.

RESULTS

mRNA and protein expression of NO synthases, pro-oxidative enzymes, and antioxidative enzymes did not differ in the umbilical arteries from newborns of the three groups.

CONCLUSION

Indicators of endothelial dysfunction in terms of differences in enzyme expression in SGA or LGA newborns vs. AGA newborns were not present at birth.