The two faces of endothelial nitric oxide synthase in the pathophysiology of atherosclerosis

Association Between Serine Concentration and Coronary Heart Disease: A Case-Control Study

Purpose

Early identification of new residual risk factors for coronary heart disease (CHD) is warranted. In this study, we aim to investigate the association between the serine concentration, an important amino acid in one-carbon metabolism, and CHD in Chinese hospitalized patients.

Patients and Methods

This case-control study included 428 case-control pairs comprising patients with CHD with a maximum coronary artery stenosis degree of >70% and controls with stenosis of <30%. The individuals were matched by age, sex, and date of coronary angiography at Peking University First Hospital from January 1, 2016, to December 31, 2019. Conditional logistic regression was used to investigate the associations between the serine concentration and CHD.

Results

Patients with CHD were aged 63.48 ± 10.38 years, and 43.73% were male. Compared with controls, patients with CHD had a slightly lower serine concentration (13.35 ± 4.20 vs 13.77 ± 4.08 μg/mL), but the difference was not significant. In the multivariable conditional logistic regression analysis, for every 1 μg/mL increase in serine concentration, the odds of CHD decreased by 6% (95% confidence interval [CI] 0.90-0.99; P = 0.010). Patients with a serine concentration of ≥13.41 μg/mL had a lower CHD risk than those with a serine concentration of <13.41 μg/mL (odds ratio [OR] 0.57, 95% CI 0.39-0.84; P = 0.004). Subgroup analyses showed that sex interacted with the relationship between serine concentration and CHD (P interaction = 0.039), which was more significant in males (OR 0.93, 95% CI 0.87-0.98; P = 0.013) than in females.

Conclusion

This study observed an inverse association between the serine concentration and CHD prevalence in Chinese hospitalized patients, which revealed that serine might play a protective role in CHD.

Hemodynamic parameters and diabetes mellitus in community-dwelling middle-aged adults and elders: a community-based study

Hemodynamic parameters have been correlated with stroke, hypertension, and arterial stenosis. While only a few small studies have examined the link between hemodynamics and diabetes mellitus (DM). This case-control study enrolled 417 DM patients and 3475 non-DM controls from a community-based cohort. Peak systolic velocity (PSV), end-diastolic velocity (EDV), blood flow velocity (MFV), pulsatility index (PI), and the resistance index (RI) of the common carotid arteries were measured by color Doppler ultrasonography. Generalized linear regression analyses showed that as compared to the non-DM controls, the age-sex-adjusted means of PSV, EDV, and MFV were - 3.28 cm/sec, - 1.94 cm/sec, and - 2.38 cm/sec, respectively, lower and the age-sex-adjusted means of RI and PI were 0.013 and 0.0061, respectively, higher for the DM cases (all p-values < 0.0005). As compared to the lowest quartiles, the multivariable-adjusted ORs of DM for the highest quartiles of PSV, EDV, MFV, RI, and PI were 0.59 (95% confidence interval [CI] 0.41-0.83), 0.45 (95% CI 0.31-0.66), 0.53 (95% CI 0.37-0.77), 1.61 (95% CI 1.15-2.25), and 1.58 (95% CI 1.12-2.23), respectively. More importantly, the additions of EDV significantly improved the predictabilities of the regression models on DM. As compared to the model contained conventional CVD risk factors alone, the area under the receiver operating curve (AUROC) increased by 1.00% (95% CI 0.29-1.73%; p = 0.0059) and 0.80% (95% CI 0.15-1.46%; p = 0.017) for models that added EDV in continuous and quartile scales, respectively. Additionally, the additions of PSV and MFV also significantly improved the predictabilities of the regression models (all 0.01 < p-value < 0.05). This study reveals a significant correlation between DM and altered hemodynamic parameters. Understanding this relationship could help identify individuals at higher risk of DM and facilitate targeted preventive strategies to reduce cardiovascular complications in DM patients.

Vascular endothelial cell morphology and alignment regulate VEGF-induced endothelial nitric oxide synthase activation

Nitric oxide (NO) production by endothelial nitric oxide synthase (eNOS) inhibits platelet and leukocyte adhesion while promoting vasorelaxation in smooth muscle cells. Dysfunctional regulation of eNOS is a hallmark of various vascular pathologies, notably atherosclerosis, often associated with areas of low shear stress on endothelial cells (ECs). While the link between EC morphology and local hemodynamics is acknowledged, the specific impact of EC morphology on eNOS regulation remains unclear. Morphological differences between elongated, aligned ECs and polygonal, randomly oriented ECs correspond to variations in focal adhesion and cytoskeletal organization, suggesting differing levels of cytoskeletal prestress. However, the functional outcomes of cytoskeletal prestress, particularly in the absence of shear stress, are not extensively studied in ECs. Some evidence suggests that elongated ECs exhibit decreased immunogenicity and enhanced NO production. This study aims to elucidate the signaling pathways governing VEGF-stimulated eNOS regulation in the aligned EC phenotype characterized by elongated and aligned cells within a monolayer. Using anisotropic topographic cues, bovine aortic endothelial cells (BAECs) were elongated and aligned, followed by VEGF treatment in the presence or absence of cytoskeletal tension inhibitors. Phosphorylation of eNOS ser1179, AKT ser437 and FAK Tyr397 in response to VEGF challenge were significantly heightened in aligned ECs compared to unaligned ECs. Moreover this response proved to be robustly tied to cytoskeletal tension as evinced by the abrogation of responses in the presence of the myosin II ATPase inhibitor, blebbistatin. Notably, this work demonstrates for the first time the reliance on FAK phosphorylation in VEGF-mediated eNOS activation and the comparatively greater contribution of the cytoskeletal machinery in propagating VEGF-eNOS signaling in aligned and elongated ECs. This research underscores the importance of utilizing appropriate vascular models in drug development and sheds light on potential mechanisms underlying vascular function and pathology that can help inform vascular graft design.

Platelet-derived growth factor-stimulated pulmonary artery smooth muscle cells regulate pulmonary artery endothelial cell dysfunction through extracellular vesicle miR-409-5p

Platelet-derived growth factor (PDGF)-induced changes in vascular smooth muscle cells (VSMCs) stimulate vascular remodeling, resulting in vascular diseases such as pulmonary arterial hypertension. VSMCs communicate with endothelial cells through extracellular vesicles (EVs) carrying cargos, including microRNAs. To understand the molecular mechanisms through which PDGF-stimulated pulmonary artery smooth muscle cells (PASMCs) interact with pulmonary artery endothelial cells (PAECs) under pathological conditions, we investigated the crosstalk between PASMCs and PAECs via extracellular vesicle miR-409-5p under PDGF stimulation. miR-409-5p expression was upregulated in PASMCs upon PDGF signaling, and it was released into EVs. The elevated expression of miR-409-5p was transported to PAECs and led to their impaired function, including reduced NO release, which consequentially resulted in enhanced PASMC proliferation. We propose that the positive regulatory loop of PASMC-extracellular vesicle miR-409-5p-PAEC is a potential mechanism underlying the proliferation of PASMCs under PDGF stimulation. Therefore, miR-409-5p may be a novel therapeutic target for the treatment of vascular diseases, including pulmonary arterial hypertension.

Hypotheses on Atherogenesis Triggering: Does the Infectious Nature of Atherosclerosis Development Have a Substruction?

Since the end of the 20th century, it has been clear that atherosclerosis is an inflammatory disease. However, the main triggering mechanism of the inflammatory process in the vascular walls is still unclear. To date, many different hypotheses have been put forward to explain the causes of atherogenesis, and all of them are supported by strong evidence. Among the main causes of atherosclerosis, which underlies these hypotheses, the following can be mentioned: lipoprotein modification, oxidative transformation, shear stress, endothelial dysfunction, free radicals' action, homocysteinemia, diabetes mellitus, and decreased nitric oxide level. One of the latest hypotheses concerns the infectious nature of atherogenesis. The currently available data indicate that pathogen-associated molecular patterns from bacteria or viruses may be an etiological factor in atherosclerosis. This paper is devoted to the analysis of existing hypotheses for atherogenesis triggering, and special attention is paid to the contribution of bacterial and viral infections to the pathogenesis of atherosclerosis and cardiovascular disease.

Thermoneutrality induces vascular dysfunction and impaired metabolic function in male Wistar rats: a new model of vascular disease

OBJECTIVE

Cardiovascular disease is of paramount importance, yet there are few relevant rat models to investigate its pathology and explore potential therapeutics. Housing at thermoneutral temperature (30 °C) is being employed to humanize metabolic derangements in rodents. We hypothesized that housing rats in thermoneutral conditions would potentiate a high-fat diet, resulting in diabetes and dysmetabolism, and deleteriously impact vascular function, in comparison to traditional room temperature housing (22 °C).

METHODS

Male Wistar rats were housed at either room temperature or thermoneutral temperatures for 16 weeks on either a low or high-fat diet. Glucose and insulin tolerance tests were conducted at the beginning and end of the study. At the study's conclusion, vasoreactivity and mitochondrial respiration of aorta and carotid were conducted.

RESULTS

We observed diminished vasodilation in vessels from thermoneutral rats ( P  < 0.05), whereas high-fat diet had no effect. This effect was also observed in endothelium-denuded aorta in thermoneutral rats ( P  < 0.05). Vasoconstriction was significantly elevated in aorta of thermoneutral rats ( P  < 0.05). Diminished nitric oxide synthase activity and nitrotyrosine, and elevated glutathione activity were observed in aorta from rats housed under thermoneutral conditions, indicating a climate of lower nitric oxide and excess reactive oxygen species in aorta. Thermoneutral rat aorta also demonstrated less mitochondrial respiration with lipid substrates compared with the controls ( P  < 0.05).

CONCLUSION

Our data support that thermoneutrality causes dysfunctional vasoreactivity, decreased lipid mitochondrial metabolism, and modified cellular signaling. These are critical observations as thermoneutrality is becoming prevalent for translational research models. This new model of vascular dysfunction may be useful for dissection of targetable aspects of cardiovascular disease and is a novel and necessary model of disease.

Differences in Tolerance to Hypoxia: Physiological, Biochemical, and Molecular-Biological Characteristics

Hypoxia plays an important role in the development of many infectious, inflammatory, and tumor diseases. The predisposition to such disorders is mostly provided by differences in basic tolerance to oxygen deficiency, which we discuss in this review. Except the direct exposure of different-severity hypoxia in decompression chambers or in highland conditions, there are no alternative methods for determining organism tolerance. Due to the variability of the detection methods, differences in many parameters between tolerant and susceptible organisms are still not well-characterized, but some of them can serve as biomarkers of susceptibility to hypoxia. At the moment, several potential biomarkers in conditions after hypoxic exposure have been identified both in experimental animals and humans. The main potential biomarkers are Hypoxia-Inducible Factor (HIF)-1, Heat-Shock Protein 70 (HSP70), and NO. Due to the different mechanisms of various high-altitude diseases, biomarkers may not be highly specific and universal. Therefore, it is extremely important to conduct research on hypoxia susceptibility biomarkers. Moreover, it is important to develop a method for the evaluation of organisms' basic hypoxia tolerance without the necessity of any oxygen deficiency exposure. This can contribute to new personalized medicine approaches' development for diagnostics and the treatment of inflammatory and tumor diseases, taking into account hypoxia tolerance differences.

(-)-Epicatechin Modulates Mitochondrial Redox in Vascular Cell Models of Oxidative Stress

Diabetes mellitus affects 451 million people worldwide, and people with diabetes are 3-5 times more likely to develop cardiovascular disease. In vascular tissue, mitochondrial function is important for vasoreactivity. Diabetes-mediated generation of excess reactive oxygen species (ROS) may contribute to vascular dysfunction via damage to mitochondria and regulation of endothelial nitric oxide synthase (eNOS). We have identified (–)-epicatechin (EPICAT), a plant compound and known vasodilator, as a potential therapy. We hypothesized that mitochondrial ROS in cells treated with antimycin A (AA, a compound targeting mitochondrial complex III) or high glucose (HG, global perturbation) could be normalized by EPICAT, and correlate with improved mitochondrial dynamics and cellular signaling. Human umbilical vein endothelial cells (HUVEC) were treated with HG, AA, and/or 0.1 or 1.0 μM of EPICAT. Mitochondrial and cellular superoxide, mitochondrial respiration, and cellular signaling upstream of mitochondrial function were assessed. EPICAT at 1.0 μM significantly attenuated mitochondrial superoxide in HG-treated cells. At 0.1 μM, EPICAT nonsignificantly increased mitochondrial respiration, agreeing with previous reports. EPICAT significantly increased complex I expression in AA-treated cells, and 1.0 μM EPICAT significantly decreased mitochondrial complex V expression in HG-treated cells. No significant effects were seen on either AMPK or eNOS expression. Our study suggests that EPICAT is useful in mitigating moderate ROS concentrations from a global perturbation and may modulate mitochondrial complex activity. Our data illustrate that EPICAT acts in the cell in a dose-dependent manner, demonstrating hormesis.

L-sepiapterin restores SLE serum-induced markers of endothelial function in endothelial cells

OBJECTIVE

SLE serves as an independent risk factor` for endothelial dysfunction (ED) not explained by Framingham risk factors. We sought to understand the development of SLE-induced ED on a cellular level in order to develop strategies aimed at reversing cellular abnormalities. This study assessed the impact of SLE patient serum on endothelial nitric oxide synthase (eNOS), nitric oxide (NO) production and functional changes in the cell.

METHODS

Human umbilical vein endothelial cells (HUVECs) cultured in serum of either SLE (n=25) or healthy patients (n=14) or endothelial basal medium 2 (EBM-2) culture media supplemented with fetal bovine serum with or without L-sepiapterin were used for our studies. We applied the fluorescent probe DAF-FM diacetate for intracellular NO detection using flow cytometry. Total RNA isolates were analysed using reverse transcription PCR for eNOS mRNA expression. Oxygen consumption rate was determined using seahorse analysis. Neutrophil adhesion and migration were determined using a calcein AM microscopy assay.

RESULTS

The mRNA expression of eNOS was increased in SLE cultured HUVECs compared with healthy control (p<0.05). The SLE eNOS mRNA level correlated with SLE patient age (p=0.008); however, this trend was not observed with healthy patients. SLE serum reduced NO production in HUVECs compared with EBM-2 cultured cells (p<0.05). Co-treatment of endothelial cells with L-sepiapterin preserved HUVEC capacity to produce NO in SLE conditions (p<0.01). SLE serum enhanced neutrophil migration (p<0.01) but not neutrophil adhesion compared with healthy controls. The bioenergetic health index was not different.

CONCLUSIONS

SLE likely causes disruption of endothelial cell eNOS function and NO modulated pathways.

Sepiapterin Improves Vascular Reactivity and Insulin-Stimulated Glucose in Wistar Rats

In the vasculature, sedentary behavior leads to endothelial abnormalities, resulting in elevated cardiovascular disease risk. Endothelial nitric oxide synthase (eNOS) aberrations characterize endothelial dysfunction; eNOS also regulates mitochondrial function. We hypothesized that sepiapterin (a precursor to eNOS cofactor tetrahydrobiopterin (BH₄)) supplementation would improve endothelium-dependent vascular relaxation in sedentary animals via modulation of NOS function and mitochondrial activity. Sedentary male Wistar rats were fed ad libitum for a total of 10 weeks. Sepiapterin was administered in diet during the final 5 weeks. Intraperitoneal insulin and glucose tolerance tests (IP-ITT/IP-GTT) were conducted at baseline and endpoint. Aorta was assessed for vasoreactivity and mitochondrial respiration. Insulin tolerance, determined by IP-ITT, significantly improved in rats treated with sepiapterin (p < 0.05, interaction of time and treatment). Acetylcholine- (ACh-) driven vasodilation was significantly greater in aorta from sepiapterin-treated rats as compared with control (76.4% versus 54.9% of phenylephrine contraction at 20 μM ACh, p < 0.05). Sepiapterin treatment resulted in significantly elevated state 3 (9.00 oxygen pmol/sec^∗mg versus 8.17 oxygen pmol/sec^∗mg, p < 0.05) and 4 (7.28 oxygen pmol/sec^∗mg versus 5.86 oxygen pmol/sec^∗mg, p < 0.05) aortic mitochondrial respiration with significantly lower respiratory control ratio (p < 0.05) during octanoylcarnitine-driven respiration. Vasodilation and insulin sensitivity were improved through targeting NOS via sepiapterin supplementation.

Genetics of guanylyl cyclase pathways in the cochlea and their influence on hearing

Although hearing loss is the most common sensory deficit in Western societies, there are no successful pharmacological treatments for this disorder. Recent experiments have demonstrated that manipulation of intracellular cyclic guanosine monophosphate (cGMP) concentrations can have both beneficial and harmful effects on hearing. In this review, we will examine the role of cGMP as a key second messenger involved in many aspects of cochlear function and discuss the known functions of downstream effectors of cGMP in sound processing. The nitric oxide-stimulated soluble guanylyl cyclase system (sGC) and the two natriuretic peptide-stimulated particulate GCs (pGCs) will be more extensively covered because they have been studied most thoroughly. The cochlear GC systems are attractive targets for medical interventions that improve hearing while simultaneously representing an under investigated source of sensorineural hearing loss.

Polycystic ovarian syndrome-associated cardiovascular complications: An overview of the association between the biochemical markers and potential strategies for their prevention and elimination

Polycystic ovarian syndrome (PCOS) is associated with multiple cardiovascular risk factors (CVRF) including endothelial dysfunction (ED) and presence of metabolic syndrome (MS). The probable reason suggested for elevated CVRF in PCOS is oxidative stress (OS), which is an integral factor in cardiometabolic complications (CMC) seen in PCOS women. The interrelated mechanisms by which CVRF instigate clinical manifestation plays a crucial role in identification of a strategy to treat different comorbidities in PCOS. The existing treatment for PCOS mostly focuses on management of individual disorders, however, therapeutic strategies or novel targets to address cardiovascular complications in PCOS deserve extensive analysis.

Novel rhynchophylline analogues as microvascular relaxation agents for the treatment of microvascular dysfunction caused by diabetes

Dysfunction in vascular reactivity in the micro- and macrocirculation is well established in cardiovascular disease. However, little is known about methods that may improve vascular reactivity in patients likely to develop microvascular dysfunction. One of the racemic analogues of rhynchophylline (G2) and its stereoisomers (G2-a and G2-b) were synthesized to address this knowledge gap. The preliminary pharmaceutical studies on the relaxation of the rat thoracic aorta showed that G2 and its stereoisomers are more potent (at least 30-fold) than the natural product rhynchophylline, which encouraged us to further investigate their functions and mechanisms as treatments for microvascular dysfunction caused by diabetes. G2-a displayed the best microvascular relaxation activity on rat mesenteric arteries among the three compounds, and G2 or G2-a caused relaxation in an endothelium-dependent manner. In ex vivo tests, G2 and G2-a exhibited a weaker potency in inducing microvascular relaxation in mesenteric arteries from diabetic rats than from normal rats, most likely, due to microvascular endothelium damage caused by diabetes. However, based on the animal studies, G2 ameliorated diabetes-induced endothelial dysfunction in rat mesenteric arteries in vivo. Further investigations of the mechanism showed that G2 mainly induced the recovery of endothelial function by upregulating endothelial nitric oxide synthase (eNOS) expression and further increasing the concentration of nitric oxide (NO), which is required for vascular relaxation.

H2S regulates endothelial nitric oxide synthase protein stability by promoting microRNA-455-3p expression

The aims of the present study are to determine whether hydrogen sulfide (H₂S) is involved in the expression of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production, and to identify the role of microRNA-455-3p (miR-455-3p) during those processes. In cultured human umbilical vein endothelial cells (HUVECs), the expression of miR-455-3p, eNOS protein and the NO production was detected after administration with 50 μM NaHS. The results indicated that H₂S could augment the expression of miR-455-3p and eNOS protein, leading to the increase of NO level. We also found that overexpression of miR-455-3p in HUVECs increased the protein levels of eNOS whereas inhibition of miR-455-3p decreased it. Moreover, H₂S and miR-455-3p could no longer increase the protein level of eNOS in the presence of proteasome inhibitor, MG-132. In vivo, miR-455-3p and eNOS expression were considerably increased in C57BL/6 mouse aorta, muscle and heart after administration with 50 μmol/kg/day NaHS for 7 days. We also identified that H₂S levels and miR-455-3p expression increased in human atherosclerosis plaque while H₂S levels decreased in plasma of atherosclerosis patients. Our data suggest that the stability of eNOS protein and the NO production could be regulated by H₂S through miR-455-3p.

Curcumin inhibits angiotensin II-induced inflammation and proliferation of rat vascular smooth muscle cells by elevating PPAR-γ activity and reducing oxidative stress

Angiotensin II (AngII)-induced production of inflammatory factors and proliferation in vascular smooth muscle cells (VSMCs) play an important role in the progression of atherosclerotic plaques. Growing evidence has demonstrated that activation of peroxisome proliferator-activated receptor-γ (PPAR-γ) effectively attenuates AngII-induced inflammation and intercellular reactive oxygen species (iROS) production. Curcumin (Cur) inhibits inflammatory responses by enhancing PPAR-γ activity and reducing oxidative stress in various tissues. The aim of the present study was to ascertain whether Cur inhibits AngII-induced inflammation and proliferation, and its underlying molecular mechanism, in VSMCs. Enzyme-linked immunosorbent assay (ELISA) and real-time PCR were used to measure the protein and mRNA expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Nitric oxide (NO) production was measured by Griess reaction. Western blot analysis and a DNA-binding assay were used to measure PPAR-γ activity. iROS production was measured using the DCFH-DA method. In rat VSMCs, Cur attenuated AngII‑induced expression of IL-6 and TNF-α mRNA and protein in a concentration-dependent manner, inhibited NO production by suppressing inducible NO synthase (iNOS) activity, and suppressed proliferation of VSMCs. This was accompanied by increased PPAR-γ expression and activation in Cur-pretreated VSMCs. GW9662, a PPAR-γ antagonist, reversed the anti-inflammatory effect of Cur. Moreover, Cur attenuated AngII-induced oxidative stress by downregulating the expression of p47phox, which is a key subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In conclusion, Cur inhibited the expression of IL-6 and TNF-α, decreased the production of NO, and suppressed the proliferation of VSMCs, by elevating PPAR-γ activity and suppressing oxidative stress, leading to attenuated AngII-induced inflammatory responses in VSMCs.

Posttranscriptional and transcriptional regulation of endothelial nitric-oxide synthase during hypoxia: the role of microRNAs

Understanding the cellular pathways that regulate endothelial nitric oxide (eNOS, NOS3) expression and consequently nitric oxide (NO) bioavailability during hypoxia is a necessary aspect in the development of novel treatments for cardiovascular disorders. eNOS expression and eNOS-dependent NO cellular signaling during hypoxia promote an equilibrium of transcriptional and posttranscriptional molecular mechanisms that belong to both proapoptotic and survival pathways. Furthermore, NO bioavailability results not only from eNOS levels, but also relies on the presence of eNOS substrate and cofactors, the phosphorylation status of eNOS, and the presence of reactive oxygen species (ROS) that can inactivate eNOS. Since both NOS3 levels and these signaling pathways can also be a subject of posttranscriptional modulation by microRNAs (miRNAs), this class of short noncoding RNAs contribute another level of regulation for NO bioavailability. As miRNA antagomirs or specific target protectors could be used in therapeutic approaches to regulate NO levels, either by changing NOS3 mRNA stability or through factors governing eNOS activity, it is critical to understand their role in governing eNOS activity during hypoxa. In contrast to a large number of miRNAs reported to the change eNOS expression during hypoxia, only a few miRNAs modulate eNOS activity. Furthermore, impaired miRNA biogenesis leads to NOS3 mRNA stabilization under hypoxia. Here we discuss the recent studies that define miRNAs’ role in maintaining endothelial NO bioavailability emphasizing those miRNAs that directly modulate NOS3 expression or eNOS activity.

Differential Mitochondrial Adaptation in Primary Vascular Smooth Muscle Cells from a Diabetic Rat Model

Diabetes affects more than 330 million people worldwide and causes elevated cardiovascular disease risk. Mitochondria are critical for vascular function, generate cellular reactive oxygen species (ROS), and are perturbed by diabetes, representing a novel target for therapeutics. We hypothesized that adaptive mitochondrial plasticity in response to nutrient stress would be impaired in diabetes cellular physiology via a nitric oxide synthase- (NOS-) mediated decrease in mitochondrial function. Primary smooth muscle cells (SMCs) from aorta of the nonobese, insulin resistant rat diabetes model Goto-Kakizaki (GK) and the Wistar control rat were exposed to high glucose (25 mM). At baseline, significantly greater nitric oxide evolution, ROS production, and respiratory control ratio (RCR) were observed in GK SMCs. Upon exposure to high glucose, expression of phosphorylated eNOS, uncoupled respiration, and expression of mitochondrial complexes I, II, III, and V were significantly decreased in GK SMCs (p < 0.05). Mitochondrial superoxide increased with high glucose in Wistar SMCs (p < 0.05) with no change in the GK beyond elevated baseline concentrations. Baseline comparisons show persistent metabolic perturbations in a diabetes phenotype. Overall, nutrient stress in GK SMCs caused a persistent decline in eNOS and mitochondrial function and disrupted mitochondrial plasticity, illustrating eNOS and mitochondria as potential therapeutic targets.

The Role of Systemic Arterial Stiffness in Open-Angle Glaucoma with Diabetes Mellitus

PURPOSE

To investigate the role of systemic arterial stiffness in glaucoma patients with diabetes mellitus (DM).

DESIGN

Retrospective, cross-sectional study.

PARTICIPANTS

DM subjects who underwent brachial-ankle pulse wave velocity (baPWV) were recruited.

METHODS

Glaucoma patients (n = 75) and age-matched control subjects (n = 92) were enrolled. Systemic examination including BaPWV and detailed eye examination were performed. The glaucoma group was divided into subgroups of normal tension glaucoma (NTG, n = 55) and primary open-angle glaucoma (POAG) based on an IOP of 21 mmHg. BaPWV was used to stratify the population into 4 groups based on the rate. Stepwise multiple logistic regression analysis by baPWV quartiles was used to compare the glaucoma group with the control group.

MAIN OUTCOME MEASURES

BaPWV in glaucoma with DM patients.

RESULTS

Faster baPWV was positively associated with glaucoma (odds ratio: 3.74; 95% CI: 1.03-13.56, stepwise multiple logistic regression analysis) in patients with DM. Increasing baPWV was also positively associated with glaucoma (p for trend = 0.036). The NTG subgroup showed similar results to those of the glaucoma group.

CONCLUSIONS

In this study, increased arterial stiffness was shown to be associated with glaucoma and may contribute to the pathogenesis of glaucoma in DM patients.

Endothelial Dysfunction in Type 2 Diabetes Mellitus

Endothelial dysfunction is an imbalance in the production of vasodilator factors and when this balance is disrupted, it predisposes the vasculature towards pro-thrombotic and pro-atherogenic effects. This results in vasoconstriction, leukocyte adherence, platelet activation, mitogenesis, pro-oxidation, impaired coagulation and nitric oxide production, vascular inflammation, atherosclerosis and thrombosis. Endothelial dysfunction is focussed as it is a potential contributor to the pathogenesis of vascular disease in diabetes mellitus. Under physiological conditions, there is a balanced release of endothelial-derived relaxing and contracting factors, but this delicate balance is altered in diabetes mellitus and atherosclerosis, thereby contributing to further progression of vascular and end-organ damage. This review focuses on endothelial dysfunction in atherosclerosis, insulin resistance, metabolic syndrome, oxidative stress associated with diabetes mellitus, markers and genetics that are implicated in endothelial dysfunction.

A Novel Arginase Inhibitor Derived from Scutellavia indica Restored Endothelial Function in ApoE-Null Mice Fed a High-Cholesterol Diet

Elevated endothelial arginase activity decreases nitric oxide (NO) production by competing with the substrate l-arginine, previously reported, and reciprocally regulating endothelial nitric oxide synthase (eNOS) activity. Thus, arginase inhibitors may help treat vascular diseases associated with endothelial dysfunction. A screening of metabolites from medicinal plants revealed that (2S)-5,2',5'-trihydroxy-7,8-dimethoxy flavanone (TDF) was a noncompetitive inhibitor of arginase. We investigated whether TDF reciprocally regulated endothelial NO production and its possible mechanism. TDF noncompetitively inhibited arginase I and II activity in a dose-dependent manner. TDF incubation decreased arginase activity and increased NO production in human umbilical vein endothelial cells and isolated mouse aortic vessels and reduced reactive oxygen species (ROS) generation in the endothelium of the latter. These TDF-mediated effects were associated with increased eNOS phosphorylation and dimerization but not with changes in protein content. Endothelium-dependent vasorelaxant responses to acetylcholine (Ach) were significantly increased in TDF-incubated aortic rings and attenuated by incubation with soluble guanylyl cyclase inhibitor. Phenylephrine-induced vasoconstrictor responses were markedly attenuated in TDF-treated vessels from wild-type mice. In atherogenic-prone ApoE(-/-) mice, TDF attenuated the high-cholesterol diet (HCD)-induced increase in arginase activity, which was accompanied by restoration of NO production and reduction of ROS generation. TDF incubation induced eNOS dimerization and phosphorylation at Ser1177. In addition, TDF improved Ach-dependent vasorelaxation responses and attenuated U46619-dependent contractile responses but did not change sodium nitroprusside-induced vasorelaxation or N-NAME-induced vasoconstriction. The findings suggest that TDF may help treat cardiovascular diseases by reducing pathophysiology derived from HCD-mediated endothelial dysfunction.

High prevalence of cardiovascular disease in South Asians: Central role for brown adipose tissue?

Cardiovascular disease (CVD) is the leading cause of death in modern society. Interestingly, the risk of developing CVD varies between different ethnic groups. A particularly high risk is faced by South Asians, representing over one-fifth of the world's population. Here, we review potential factors contributing to the increased cardiovascular risk in the South Asian population and discuss novel therapeutic strategies based on recent insights. In South Asians, classical ('metabolic') risk factors associated with CVD are highly prevalent and include central obesity, insulin resistance, type 2 diabetes, and dyslipidemia. A contributing factor that may underlie the development of this disadvantageous metabolic phenotype is the presence of a lower amount of brown adipose tissue (BAT) in South Asian subjects, resulting in lower energy expenditure and lower lipid oxidation and glucose uptake. As it has been established that the increased prevalence of classical risk factors in South Asians cannot fully explain their increased risk for CVD, other non-classical risk factors must underlie this residual risk. In South Asians, the prevalence of "inflammatory" risk factors including visceral adipose tissue inflammation, endothelial dysfunction, and HDL dysfunction are higher compared with Caucasians. We conclude that a potential novel therapy to lower CVD risk in the South Asian population is to enhance BAT volume or its activity in order to diminish classical risk factors. Furthermore, anti-inflammatory therapy may lower non-classical risk factors in this population and the combination of both strategies may be especially effective.

Xyloketal B attenuates atherosclerotic plaque formation and endothelial dysfunction in apolipoprotein e deficient mice

Our previous studies demonstrated that xyloketal B, a novel marine compound with a unique chemical structure, has strong antioxidant actions and can protect against endothelial injury in different cell types cultured in vitro and model organisms in vivo. The oxidative endothelial dysfunction and decrease in nitric oxide (NO) bioavailability are critical for the development of atherosclerotic lesion. We thus examined whether xyloketal B had an influence on the atherosclerotic plaque area in apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet and investigated the underlying mechanisms. We found in our present study that the administration of xyloketal B dose-dependently decreased the atherosclerotic plaque area both in the aortic sinus and throughout the aorta in apoE-/- mice fed a high-fat diet. In addition, xyloketal B markedly reduced the levels of vascular oxidative stress, as well as improving the impaired endothelium integrity and NO-dependent aortic vasorelaxation in atherosclerotic mice. Moreover, xyloketal B significantly changed the phosphorylation levels of endothelial nitric oxide synthase (eNOS) and Akt without altering the expression of total eNOS and Akt in cultured human umbilical vein endothelial cells (HUVECs). Here, it increased eNOS phosphorylation at the positive regulatory site of Ser-1177, while inhibiting phosphorylation at the negative regulatory site of Thr-495. Taken together, these findings indicate that xyloketal B has dramatic anti-atherosclerotic effects in vivo, which is partly due to its antioxidant features and/or improvement of endothelial function.

Synthesis and evaluation of multi-functional NO-donor/insulin-secretagogue derivatives for the treatment of type II diabetes and its cardiovascular complications

Although there is a significant effort in the discovery of effective therapies to contrast both the pathological endocrine and metabolic aspects of diabetes and the endothelial dysfunction associated with this disease, no hypoglycemic drug has been proven to defeat the cardiovascular complications associated with type II diabetes. The aim of this research was to design new compounds exhibiting a double profile of hypoglycemic agents/NO-donors. The synthesis of molecules obtained by the conjunction of NO-donor moieties with two oral insulin-secretagogue drugs (repaglinide and nateglinide) was reported. NO-mediated vasorelaxing effects of the synthesized compounds were evaluated by functional tests on isolated endothelium-denuded rat aortic rings. The most potent molecule (4) was tested to evaluate the hypoglycemic and the anti-ischemic cardioprotective activities. This study indicates that 4 should represent a new insulin-secretagogue/NO-donor prodrug with an enhanced cardiovascular activity, which may contrast the pathological aspects of diabetes and endowed of cardioprotective activity.

Neferine inhibits the upregulation of CCL5 and CCR5 in vascular endothelial cells during chronic high glucose treatment

We investigated whether the expressions of CCL5 and CCR5 participate in dysfunctional changes in human umbilical vein endothelial cells (HUVECs) induced by chronic high glucose treatment and examined whether neferine exerts its therapeutic effects by blocking the development of dysfunctional vascular endothelium. HUVECs were cultured with control or high concentrations of glucose in the absence or presence of neferine for 5 days. Nitric acid reductase method was used to detect the concentration of nitric oxide (NO) released into culture media. The level of intracellular reactive oxygen species (ROS) was measured by fluorescent DCFH-DA probe. The expressions of 84 genes related to endothelial cell biology were assessed by Human Endothelial Cell Biology RT(2) Profiler PCR Array. The expressions of the chemokine CCL5 and its receptor CCR5 were further determined by real-time RT-PCR and western blotting. PCR array indicated that CCL5 was the most significantly upregulated when HUVECs were exposed to chronic high glucose; the intracellular ROS level and the expressions of CCL5 and CCR5 at both mRNA and protein levels were significantly increased, whereas NO production was decreased simultaneously. The increased level of ROS and elevated expressions of CCL5 and CCR5 at high glucose were significantly inhibited by neferine; meanwhile the decreased NO production upon chronic high glucose treatment was relieved. An antioxidant (vitamin E) exerted similar beneficial effects. These data indicate that neferine can reduce the upregulation of CCL5 and CCR5 of vascular endothelium exposure to chronic high glucose and prevent or inhibit subsequent occurrence of inflammation in blood vessels possibly through antioxidation.

Arginase inhibition by piceatannol-3'-O-β-D-glucopyranoside improves endothelial dysfunction via activation of endothelial nitric oxide synthase in ApoE-null mice fed a high-cholesterol diet

Elevated plasma cholesterol is a hallmark of numerous cardiovascular diseases that are closely linked to endothelial dysfunction indicating decreased nitric oxide (NO) production in the endothelium. It has been previously demonstrated that piceatannol-3'-O-β-D-glucopyranoside (PG) inhibits arginase activity and reciprocally regulates NO production. Here, we aimed to ascertain whether PG ameliorates vascular function in wild-type (WT) and atherogenic model mice [apolipoprotein E-null mice (ApoE-/-)] and to investigate the possible underlying mechanism. Preincubation of aortic vessels from WT mice fed a normal diet (ND) with PG attenuated vasoconstriction response to U46619 and phenylephrine (PE), while the vasorelaxant response to acetylcholine (Ach) was markedly enhanced in an endothelium-dependent manner. However, the endothelium-independent NO donor, sodium nitroprusside (SNP), did not change vessel reactivity. In thoracic aorta from ApoE-/- mice, a high-cholesterol diet (HCD) induced an increase in arginase activity, a decrease in NO release and an increase in reactive oxygen species generation that was reversed by treatment with PG. The effect of PG was associated with enhanced stability of the eNOS dimer and was not dependent on the expression levels of arginase II and eNOS proteins, although eNOS expression was increased in ApoE-/- mice fed an HCD. Furthermore, PG treatment attenuated the PE-dependent contractile response, and significantly improved the Ach-dependent vasorelaxation response in aortic rings from ApoE-/- mice fed an HCD. On the other hand, PG incubation neither altered the contractile response to a high K+ solution nor the relaxation response to SNP. When analyzing the L-arginine content using high-performance liquid chromatography, PG incubation increased the intracellular L-arginine concentration. PG administration in the drinking water significantly reduced fatty streak formation in ApoE-/- mice fed an HCD. These data indicate that PG improves the pathophysiology of cholesterol-mediated endothelial dysfunction. Therefore, we conclude that the development of PG as a novel effective therapy for preventing atherosclerotic diseases is warranted.

Is it merely a myth that alcoholic beverages such as red wine can be cardioprotective?

It has been suggested that although the negative impact of alcohol consumption varies from person to person, on a global level the adverse effect of alcohol on cardiovascular disease outweighs any protective effect by between two- and three-fold. This is inaccurate. There is a proven positive relationship between alcohol consumption and cardiovascular disease that is acknowledged by the World Health Organization. For example, moderate alcohol consumption reduces the risk of cardiovascular disease by approximately 25%, such that alcohol consumption per se accounts for -4.7% of the total cardiovascular disease burden in Australia. Correspondingly, cardiovascular disease accounted for 34% of the total number of deaths in Australia in 2008, and 18% of the overall burden of disease in Australia in 2003, with coronary heart disease and stroke contributing over 80% of this burden. Australia is not substantially different from other developed countries having similar demographics to, and the same leading causes of burden as, other high-income developed countries. This article examines the suggestions and evidence surrounding the relationship between light-to-moderate alcohol consumption and benefits to human health.

Increase of arginase activity in old apolipoprotein-E deficient mice under Western diet associated with changes in neurovascular unit

Aging and atherosclerosis are well-recognized risk factors for cardiac and neurovascular diseases. The Apolipoprotein E deficient (ApoE-/-) mouse on a high-fat diet is a classical model of atherosclerosis, characterized by the presence of atherosclerotic plaques in extracranial vessels but not in cerebral arteries. Increase in arginase activity was shown to participate in vascular dysfunction in the peripheral arteries of atherosclerotic mice by changing the level of nitric oxide (NO). NO plays a key role in the physiological functions of the neurovascular unit (NVU). However, the regulation of arginase expression and activity in the brain was never investigated in association with changes in the NVU, ApoE deficiency and high fat diet.Fourteen-month-old ApoE-/- mice on high-fat diet exhibited deposition of lipids in the NVU, impairment of blood-brain barrier properties, astrogliosis and an increase of aquaporin 4 staining. In association with these changes, brain arginase activity was significantly increased in the old ApoE-/- mice as compared to old wild type mice, with an increase in the level of arginase type I in the blood vessels.In conclusion, aging in this classical mouse model of atherosclerosis induces an increase in the level and activity of arginase I that may impair NO synthesis and contribute to changes in the NVU leading to blood-brain barrier leakage and inflammation.

Nitric oxide production and endothelium-dependent vasorelaxation ameliorated by N1-methylnicotinamide in human blood vessels

N(1)-methylnicotinamide (MNA(+)) has until recently been thought to be a biologically inactive product of nicotinamide metabolism in the pyridine nucleotides pathway. However, the latest observations imply that MNA(+) may exert antithrombotic and anti-inflammatory effects through direct action on the endothelium. We examined both in vivo and in vitro whether the compound might induce vasorelaxation in human blood vessels through the improvement of nitric oxide (NO) bioavailability and a reduction of oxidative stress mediated by endothelial NO synthase (eNOS) function. MNA(+) treatment (100 mg/m(2) orally) in healthy normocholesterolemic and hypercholesterolemic subjects increased the l-arginine (l-NMMA)-inhibitable flow-mediated dilation (FMD) of brachial artery responses that also positively correlated with MNA(+) plasma concentrations (r=0.73 for normocholesterolemics and r=0.78 for hypercholesterolemics; P<0.0001). MNA(+) increased FMD at the same concentration range at which it enhanced NO release from cultured human endothelial cells after stimulation with either the receptor-dependent (acetylcholine) or the receptor-independent endothelial NO synthase agonists (calcium ionophore A23187). MNA(+) restored the endothelial NO synthase agonist-stimulated NO release after the exposure of the cells to oxidized low-density lipoprotein. This effect was also associated with the normalization of the [NO]/[superoxide] balance in the endothelial cells. Taken together, the increased NO bioavailability in the endothelium contributes to the vasorelaxating properties of MNA(+). Targeting eNOS with MNA(+) might be therapeutically relevant for functional disorders of the endothelium, such as hypercholesterolemia and atherosclerosis.

The dual behavior of heat shock protein 70 and asymmetric dimethylarginine in relation to serum CRP levels in type 2 diabetes

BACKGROUND

Experimental evidence suggests that heat shock proteins (HSP) and asymmetric dimethylarginine (ADMA) are induced in the state of chronic inflammation and stress conditions. They are both inhibitors of nitric oxide synthase (NOS). The aim of this study was to evaluate the correlation between ADMA and HSP70, in patients with type 2 diabetes with respect to serum levels of C reactive protein (CRP).

METHODS

We quantified serum HSP70, ADMA and CRP in 80 newly-diagnosed patients with type 2 diabetes plus 80 age-, sex and BMI-matched healthy controls. The patients and controls were also stratified into groups of high and low CRP levels (cut-point: 2.5mg/ml).

RESULTS

Patients with type 2 diabetes had significantly higher serum HSP70 (0.52 [0.51-0.66] vs. 0.27 [0.26-0.36], p<0.001), ADMA (0.86 [0.81-0.92] vs. 0.72 [0.71-0.85], p<0.05) and CRP (2.9 [1.7-3.4] vs. 1.6[1.2-2.3], p<0.05) compared with healthy controls. Serum HSP70 and ADMA levels were significantly correlated in patients with high CRP levels (r=0.89, p<0.01), whereas there were no correlation in patients with low CRP (r=-0.37, p=0.07) and controls. This correlation was significant (r=0.77, p<0.001) in patients with high CRP and also in patients with low CRP levels (r=-0.51, p<0.05), after multiple adjustments for LDL and HDL levels.

DISCUSSION

We showed that, in a state of high inflammation; serum levels of ADMA parallel the HSP70 levels. However in low inflammation, they are negatively correlated. The duality in HSP70 and ADMA correlation may be related to the duality of NOS function in low and high CRP levels.

Cellular biomarkers of endothelial health: microparticles, endothelial progenitor cells, and circulating endothelial cells

Endothelial dysfunction, the shift from a healthy endothelium to a damaged pro-coagulative, pro-inflammatory, and pro-vasoconstrictive phenotype, is an early event in many chronic diseases that frequently precedes cardiovascular complications. Functional assessment of the endothelium can identify endothelial damage and predict cardiovascular risk; however, this assessment provides little information as to the mechanisms underlying development of endothelial dysfunction. Changes in plasma asymmetric dimethyl arginine levels, markers of lipid peroxidation, circulating levels of inflammatory mediators, indices of coagulation and cellular surrogates such as microparticles, circulating endothelial cells, and endothelial progenitor cells may reflect alterations in endothelial status and as such have been defined as "biomarkers" of endothelial function. Biomarkers may be chemical or cellular. This review examines some markers of endothelial dysfunction, with a particular focus on cellular biomarkers of endothelial dysfunction and their diagnostic potential.

Serum nitric oxide syntheses and lipid profile of the mothers with IUGR pregnancies uncomplicated with preeclampsia. Does insulin resistance matter?

Insulin resistance in late pregnancy increases nutrition availability in maternal circulation. Moreover, it is the leading cause of oxidative stress in pregnant women. Herein, we aimed to define the correlation between insulin resistance, serum inducible nitric oxide (iNOS) and serum lipid levels in patients with intrauterine growth retardation (IUGR) pregnancies and controls. We performed a cross sectional study of IUGR pregnancies uncomplicated with preeclampsia as cases and age, body mass index, parity and gestational age matched pregnant women as controls. We quantified serum insulin, fasting blood sugar (FBS), iNOS and lipid profile of the cases and controls. Serum total cholesterol and LDL-C were significantly lower when serum iNOS, FBS, insulin and homeostasis model assessment of insulin resistance (HOMA-IR) levels were significantly higher in patients with IUGR pregnancies. There was not any significant difference in serum iNOS levels between patients and controls (12.4 ± 2.1 vs. 11.1 ± 1.9; p = 0.52) after multiple adjustment for HOMA-IR. Serum iNOS levels were significantly correlated with maternal serum insulin, triglyceride and HOMA-IR levels in patients with IUGR pregnancies when there was not such a correlation in controls. We showed a positive correlation between insulin resistance and markers of oxidative stress like iNOS in IUGR pregnancies.

Impact of glycemic control on circulating endothelial progenitor cells and arterial stiffness in patients with type 2 diabetes mellitus

BACKGROUND

Patients with type 2 diabetes mellitus (DM) have increased risk of endothelial dysfunction and arterial stiffness. Levels of circulating endothelial progenitor cells (EPCs) are also reduced in hyperglycemic states. However, the relationships between glycemic control, levels of EPCs and arterial stiffness are unknown.

METHODS

We measured circulating EPCs and brachial-ankle pulse wave velocity (baPWV) in 234 patients with type 2 DM and compared them with 121 age- and sex-matched controls.

RESULTS

Patients with DM had significantly lower circulating Log CD34/KDR+ and Log CD133/KDR+ EPC counts, and higher Log baPWV compared with controls (all P < 0.05). Among those 120/234 (51%) of DM patients with satisfactory glycemic control (defined by Hemoglobin A1c, HbA1c < 6.5%), they had significantly higher circulating Log CD34/KDR+ and Log CD133/KDR+ EPC counts, and lower Log baPWV compared with patients with poor glycemic control (all P < 0.05). The circulating levels of Log CD34/KDR+ EPC (r = -0.46, P < 0.001) and Log CD133/KDR+ EPC counts (r = -0.45, P < 0.001) were negatively correlated with Log baPWV. Whilst the level of HbA1c positively correlated with Log baPWV (r = 0.20, P < 0.05) and negatively correlated with circulating levels of Log CD34/KDR+ EPC (r = -0.40, P < 0.001) and Log CD133/KDR+ EPC (r = -0.41, P < 0.001). Multivariate analysis revealed that HbA1c, Log CD34/KDR+ and Log CD133/KDR+ EPC counts were independent predictors of Log baPWV (P < 0.05).

CONCLUSIONS

In patients with type 2 DM, the level of circulating EPCs and arterial stiffness were closely related to their glycemic control. Furthermore, DM patients with satisfactory glycemic control had higher levels of circulating EPCs and were associated with lower arterial stiffness.

Adiponectin and sE-selectin Concentrations in Relation to Inflammation in Obese Type 2 Diabetic Patients With Coronary Heart Disease

Adipose tissue can release proinflammatory mediators, namely C-reactive protein (CRP), interleukin 1β (IL-1β), and monocyte chemotactic protein 1 (MCP-1), contributing to vascular injury and insulin resistance (IR). Other mediators namely, adiponectin and nitric oxide (NO) are protective. We enrolled type 2 diabetes mellitus (T2DM) obese male patients without coronary heart disease ([CHD] group II, n = 25) and T2DM obese patients with CHD (group III, n = 25). They were compared with 20 age- and body mass index (BMI)-matched nondiabetic control males (group I). Fasting blood glucose (FBG), glycated hemoglobin (HbA1c%), lipids, insulin, malondialdehyde ([MDA]; lipid peroxidation product), NO, high-sensitivity CRP (hsCRP), IL-1β, MCP-1, adiponectin as well as sE-selectin concentration were significantly different in patients with T2DM and CHD compared with patients without CHD and nondiabetic controls ( P = .01). There was a significant negative correlation between adiponectin and E-selectin ( P = .0001). Adipose tissue in T2DM obese patients may contribute to the pathogenesis of CHD.

Oxidative stress in diabetic nephropathy

Diabetic nephropathy is a leading cause of end-stage renal failure worldwide. Its morphologic characteristics include glomerular hypertrophy, basement membrane thickening, mesangial expansion, tubular atrophy, interstitial fibrosis and arteriolar thickening. All of these are part and parcel of microvascular complications of diabetes. A large body of evidence indicates that oxidative stress is the common denominator link for the major pathways involved in the development and progression of diabetic micro- as well as macro-vascular complications of diabetes. There are a number of macromolecules that have been implicated for increased generation of reactive oxygen species (ROS), such as, NAD(P)H oxidase, advanced glycation end products (AGE), defects in polyol pathway, uncoupled nitric oxide synthase (NOS) and mitochondrial respiratory chain via oxidative phosphorylation. Excess amounts of ROS modulate activation of protein kinase C, mitogen-activated protein kinases, and various cytokines and transcription factors which eventually cause increased expression of extracellular matrix (ECM) genes with progression to fibrosis and end stage renal disease. Activation of renin-angiotensin system (RAS) further worsens the renal injury induced by ROS in diabetic nephropathy. Buffering the generation of ROS may sound a promising therapeutic to ameliorate renal damage from diabetic nephropathy, however, various studies have demonstrated minimal reno-protection by these agents. Interruption in the RAS has yielded much better results in terms of reno-protection and progression of diabetic nephropathy. In this review various aspects of oxidative stress coupled with the damage induced by RAS are discussed with the anticipation to yield an impetus for designing new generation of specific antioxidants that are potentially more effective to reduce reno-vascular complications of diabetes.

Interactions of 5'-UTR thymidylate synthase polymorphism with 677C → T methylene tetrahydrofolate reductase and 66A → G methyltetrahydrofolate homocysteine methyl-transferase reductase polymorphisms determine susceptibility to coronary artery disease

AIM

The current study aimed to address the inconsistencies in association studies, specifically with reference to methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism in the light of gene-gene and gene-nutrient interactions.

METHODS

A case-control study was conducted to analyze four genetic polymorphisms i.e. thymidylate synthase (TYMS) 5'-UTR 28 bp tandem repeat, MTHFR C677T, methyltetrahydrofolate homocysteine methyltransferase (MTR) A2756G, methyltetrahydrofolate homocysteine methyltransferase reductase (MTRR) A66G using PCR-AFLP and PCR-RFLP methods; plasma folate and B12 using AxSYM kits; plasma homocysteine by reverse phase HPLC and nitric oxide using Griess reaction. Fisher's exact test, logistic regression analysis and multifactor dimensionality reduction analysis were used for statistical analysis of genetic parameters. Student's t-test was used for biochemical parameters.

RESULTS

MTHFR C677T and MTRR A66G were found to increase the risk for CAD by 1.61-fold (95% CI: 1.04-2.50) and 1.92-fold (95% CI: 1.29-2.87) whereas TYMS 2R allele was found to reduce the risk for CAD (OR: 0.66, 95% CI: 0.49-0.88) by counteracting MTHFR and MTRR variant alleles. Significant gene-gene interactions were observed among TYMS/MTRR (P < 0.0001), MTR/TYMS/MTRR (P < 0.0001), and MTHFR/MTR/TYMS/MTRR (P < 0.0001). MTHFR was found to increase the risk (OR: 2.36, 95% CI: 1.28-4.37) only in the absence of the TYMS 2R allele, with marked impairment of the remethylation process (P = 0.007). This impairment was predominant when the dietary folate was in the lowest tertile. In subjects with dietary folate intake in the highest tertile, no such impairment was observed.

CONCLUSION

Dietary folate status and TYMS 5'-UTR 28bp tandem repeat polymorphism are important effect modifiers of CAD risk associated with genetic variants in remethylating genes.

Endothelial dysfunction, inflammation, and apoptosis in diabetes mellitus

Endothelial dysfunction is regarded as an important factor in the pathogenesis of vascular disease in obesity-related type 2 diabetes. The imbalance in repair and injury (hyperglycemia, hypertension, dyslipidemia) results in microvascular changes, including apoptosis of microvascular cells, ultimately leading to diabetes related complications. This review summarizes the mechanisms by which the interplay between endothelial dysfunction, inflammation, and apoptosis may cause (micro)vascular damage in patients with diabetes mellitus.

Foxo1 links hyperglycemia to LDL oxidation and endothelial nitric oxide synthase dysfunction in vascular endothelial cells

OBJECTIVE

Atherosclerotic cardiovascular disease is the leading cause of death among people with diabetes. Generation of oxidized LDLs and reduced nitric oxide (NO) availability because of endothelial NO synthase (eNOS) dysfunction are critical events in atherosclerotic plaque formation. Biochemical mechanism leading from hyperglycemia to oxLDL formation and eNOS dysfunction is unknown.

RESEARCH DESIGN AND METHODS

We show that glucose, acting through oxidative stress, activates the transcription factor Foxo1 in vascular endothelial cells.

RESULTS

Foxo1 promotes inducible NOS (iNOS)-dependent NO-peroxynitrite generation, which leads in turn to LDL oxidation and eNOS dysfunction. We demonstrate that Foxo1 gain-of-function mimics the effects of hyperglycemia on this process, whereas conditional Foxo1 knockout in vascular endothelial cells prevents it.

CONCLUSIONS

The findings reveal a hitherto unsuspected role of the endothelial iNOS-NO-peroxynitrite pathway in lipid peroxidation and eNOS dysfunction and suggest that Foxo1 activation in response to hyperglycemia brings about proatherogenic changes in vascular endothelial cell function.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.

Chlamydia heat shock protein 60 decreases expression of endothelial nitric oxide synthase in human and porcine coronary artery endothelial cells

AIMS

Clinically, Chlamydia pneumoniae infection and its heat shock protein 60 (cHSP60) may contribute to atherogenesis; however, its underlying mechanisms are largely unknown. The objective of this study was to determine whether cHSP60 could cause endothelial dysfunction in human coronary artery endothelial cells (HCAECs) and porcine coronary arteries.

METHODS AND RESULTS

When HCAECs were treated with recombinant cHSP60, endothelial nitric oxide synthase (eNOS) mRNA and protein levels, enzyme activities, cellular NO levels, mRNA stability, and promoter activities were significantly decreased. Superoxide anion production was significantly increased due to the inhibition of mitochondrial membrane potential and catalase and superoxide dismutase (SOD) activities as well as activation of NADPH oxidase. Antioxidant seleno-l-methionine (SeMet) or SOD mimetic MnTBAP effectively blocked cHSP60-induced eNOS downregulation. In addition, cHSP60 activated mitogen-activated protein kinases (MAPKs) including p38, c-Jun-N-terminal kinase/stress-activated protein kinase, and extracellular signal-regulated kinases. Specific chemical inhibitors or their dominant-negative mutant forms of these MAPKs effectively blocked cHSP60-induced eNOS downregulation. cHSP60-induced eNOS downregulation and oxidative stress were also demonstrated in porcine coronary artery rings in vitro. Functionally, endothelium-dependent vasorelaxation was significantly reduced in cHSP60-treated vessels.

CONCLUSION

cHSP60 directly induces eNOS downregulation through oxidative stress and MAPK activation in both HCAECs and porcine coronary arteries, thereby causing endothelial dysfunction.

Plasma tetrahydrobiopterin/dihydrobiopterin ratio: a possible marker of endothelial dysfunction

BACKGROUND

Although endothelium-dependent vasodilatation has been used as a marker of endothelial dysfunction (ED), there have been no reliable plasma markers for ED. Oxidative stress, which is a major determinant of ED, oxidizes tetrahydrobiopterin (BH4), an essential cofactor of endothelial type nitric oxide synthase (eNOS), and resulted in the relative deficiency of BH4.

METHODS AND RESULTS

In 163 patients with cardiovascular disorders, the plasma levels of BH4 and 7, 8-dihydrobiopterin (BH2) by high performance liquid chromatography were measured and compared with the flow-mediated (FMD) vasodilatory response of the brachial artery, which was measured by ultrasonography. The effects of atorvastatin on plasma pteridine levels and FMD were examined in patients with multiple coronary risk factors. There was a positive relationship between FMD and plasma BH4 levels and a negative relationship between FMD and plasma BH2 levels. Subsequently, a strong positive relationship between FMD and the BH4/BH2 ratio (r=0.585, P<0.0001) was found. Although we did not find any significant relationship between pteridine levels and individual traditional risk factors, the BH4/BH2 ratio in patients with more than 2 risk factors showed significant reductions compared with that in those without risk factors. Statin treatment improved FMD in association with an increase in the plasma BH4/BH2 ratio.

CONCLUSIONS

Plasma pteridine levels were associated with endothelial dysfunction in cardiovascular disorders.

Reactive oxygen-induced reactive oxygen formation during human sperm capacitation

Physiological processes are often activated by reactive oxygen species (ROS), such as the superoxide anion (O(2)(*)(-)) and nitric oxide (NO*) produced by cells. We studied the interactions between NO* and O(2)(*)(-), and their generators (NO* synthase, NOS, and a still elusive oxidase), in human spermatozoa during capacitation (transformations needed for acquisition of fertility). Albumin, fetal cord serum ultrafiltrate, and L-arginine triggered capacitation and ROS generation (NO* and O(2)(*)(-)) and superoxide dismutase (SOD) and NOS inhibitors prevented all these effects. Surprisingly, capacitation due to exogenous NO* (or O(2)(*)(-)) was also blocked by SOD (or NOS inhibitors). Probes used were proven specific and innocuous on spermatozoa. Whereas O(2)(*)(-) was needed only for 30 min, the continuous NO* generation was essential for hours. Capacitation caused a time-dependent increase in protein tyrosine nitration that was prevented by SOD and NOS inhibitors, suggesting that O(2)(*)(-) and NO*. also act via the formation of ONOO(-). Spermatozoa treated with NO* (or O(2)(*)(-)) initiated a dose-dependent O(2)(*)(-) (or NO*) production, providing, for the first time in cells, a strong evidence for a two-sided ROS-induced ROS generation. Data presented show a close interaction between NO* and O(2)(*)(-) and their generators during sperm capacitation.

Angiotensin II type 1 receptor blocker ameliorates uncoupled endothelial nitric oxide synthase in rats with experimental diabetic nephropathy

BACKGROUND

Recent studies showed that angiotensin II type 1 receptor blocker (ARB) slows progression of chronic renal disease in patients with type 2 diabetes, regardless of changes in blood pressure. We showed that the imbalance of nitric oxide (NO) and reactive oxygen species (ROS) due to endothelial NO synthase (eNOS) uncoupling contributed to renal dysfunction in the diabetic nephropathy. The aim of this study was to determine the effects of ARB on uncoupled eNOS in rat diabetic nephropathy.

METHODS

Diabetes was induced in Sprague-Dawley rats with streptozotocin (65 mg/ kg body weight). After 6 weeks, rats were divided into saline (DM; n = 11) and ARB, losartan groups (DM+Los; n = 11). After 2-week treatment, glomerular ROS production was assessed by 2',7'-dichlorofluorescin diacetate (DCFH-DA)-derived chemiluminescence. Renal NO and ROS production were imaged by confocal laser microscopy after renal perfusion with DCFH-DA and diaminorhodamine-4M acetoxymethyl ester with L-arginine. The dimeric form of eNOS was measured by low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Serum tetrahydrobiopterin (BH4) concentrations were determined by high-performance liquid chromatography. Protein and mRNA expression of GTP cyclohydrolase 1 (GTPCH1), key enzyme of BH4 synthesis, were examined.

RESULTS

Losartan attenuated glomerular ROS production in DM. Accelerated ROS production and diminished bioavailable NO caused by NOS uncoupling were noted in DM glomeruli. Losartan reversed the decreased GTPCH1 and decreased dimeric form of eNOS and glomerular NO production by increased BH4 bioavailability.

CONCLUSIONS

ARB improved the NOS uncoupling in diabetic nephropathy by increasing BH4 bioavailability.

Serum amyloid A induces endothelial dysfunction in porcine coronary arteries and human coronary artery endothelial cells

The objective of this study was to determine the effects and mechanisms of serum amyloid A (SAA) on coronary endothelial function. Porcine coronary arteries and human coronary arterial endothelial cells (HCAECs) were treated with SAA (0, 1, 10, or 25 microg/ml). Vasomotor reactivity was studied using a myograph tension system. SAA significantly reduced endothelium-dependent vasorelaxation of porcine coronary arteries in response to bradykinin in a concentration-dependent manner. SAA significantly decreased endothelial nitric oxide (NO) synthase (eNOS) mRNA and protein levels as well as NO bioavailability, whereas it increased ROS in both artery rings and HCAECs. In addition, the activities of internal antioxidant enzymes catalase and SOD were decreased in SAA-treated HCAECs. Bio-plex immunoassay analysis showed the activation of JNK, ERK2, and IkappaB-alpha after SAA treatment. Consequently, the antioxidants seleno-l-methionine and Mn(III) tetrakis-(4-benzoic acid)porphyrin and specific inhibitors for JNK and ERK1/2 effectively blocked the SAA-induced eNOS mRNA decrease and SAA-induced decrease in endothelium-dependent vasorelaxation in porcine coronary arteries. Thus, SAA at clinically relevant concentrations causes endothelial dysfunction in both porcine coronary arteries and HCAECs through molecular mechanisms involving eNOS downregulation, oxidative stress, and activation of JNK and ERK1/2 as well as NF-kappaB. These findings suggest that SAA may contribute to the progress of coronary artery disease.

Endothelial arginase II: a novel target for the treatment of atherosclerosis

Oxidized low-density lipoproteins increase arginase activity and reciprocally decrease endothelial NO in human aortic endothelial cells. Here, we demonstrate that vascular endothelial arginase activity is increased in atherogenic-prone apolipoprotein E-null (ApoE(-/-)) and wild-type mice fed a high cholesterol diet. In ApoE(-/-) mice, selective arginase II inhibition or deletion of the arginase II gene (Arg II(-/-) mice) prevents high-cholesterol diet-dependent decreases in vascular NO production, decreases endothelial reactive oxygen species production, restores endothelial function, and prevents oxidized low-density lipoprotein-dependent increases in vascular stiffness. Furthermore, arginase inhibition significantly decreases plaque burden. These data indicate that arginase II plays a critical role in the pathophysiology of cholesterol-mediated endothelial dysfunction and represents a novel target for therapy in atherosclerosis.