Oxidative stress and endothelial nitric oxide bioactivity

The effect of sesame oil consumption compared to sunflower oil on lipid profile, blood pressure, and anthropometric indices in women with non-alcoholic fatty liver disease: a randomized double-blind controlled trial

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in the world. There is strong evidence that dyslipidemia and other cardio-metabolic disorders are highly prevalent in patients with NAFLD. This trial aimed at examining the effect of sesame oil (SO) in the context of a weight loss program on lipid profile, blood pressure, and anthropometric indices in women with NAFLD.

METHODS

This randomized, double-blind, controlled trial was carried out on 60 women with NAFLD. Subjects were randomly assigned to the SO group (n = 30) and sunflower oil (SFO) group (n = 30), each person consuming 30 g of oil per day for 12 weeks. All the participants received a hypocaloric diet (- 500 kcal/day) during the study. Lipid profile, blood pressure, and anthropometric indices were assessed at pre- and post-intervention phases.

RESULTS

In total, 53 participants completed the study. Following 12 weeks of intervention, anthropometric indices (p < 0.001) and systolic blood pressure (SBP) (p < 0.05) were significantly decreased in both groups and diastolic blood pressure (DBP) was significantly decreased in So group (p = 0.03). There was no significant change in lipid profile in both groups (p > 0.05). After adjusting for confounders, DBP (p = 0.031) and total cholesterol (TC) divided by high-density lipoprotein cholesterol (HDL-C) (p = 0.039) in the SO group were significantly reduced compared to the SFO group (p < 0.05).

CONCLUSIONS

The present clinical trial revealed that SO and SFO may not differently affect anthropometric indices, SBP, and lipid profile except for TC/HDL-C. In addition, SO may be effective in improvement of DBP and TC/HDL-C compared to the SFO group.

TRIAL REGISTRATION

Ethical approval of this trial was obtained at Isfahan University of Medical Sciences with the reference number of IR.MUI.

RESEARCH

REC.1399.548 ( https://ethics.

RESEARCH

ac.ir/ProposalCertificateEn.php?id=158942&Print=true&NoPrintHeader=true&NoPrintFooter=true&NoPrintPageBorder=true&LetterPrint=true ), and it was registered before the start of the patient recruitment on December 12^th, 2020 in the Iranian Registry of Clinical Trials (IRCT) with the registration number of IRCT20140208016529N6 .

The effects of sesame oil on metabolic biomarkers: a systematic review and meta-analysis of clinical trials

Background

Clinical evidences showing the effects of sesame oil on metabolic biomarkers led to inconsistent results.

Propose

This meta-analysis was designed to examine the effects of sesame oil on metabolic biomarkers in adults, including the maximum number of clinical trials.

Methods

Google Scholar, PubMed, Web of Science, and Scopus were systematically searched to date up to July 2021 to identify eligible clinical trial studies. We obtained the pooled estimates of weighted mean differences (WMDs) with their 95% confidence intervals (CIs) using random-effects meta-analysis.

Result

Meta-analysis showed that sesame oil consumption significantly lowered the levels of fasting blood glucose (FBG) (WMD: -3.268 mg/dl; 95% CI: -4.677, -1.86; P < 0.001), and malondialdehyde (MDA) (WMD: -4.847 nmol/dL; 95% CI: -7.051, -2.698; P < 0.001) between the intervention and control groups. Also, this study showed sesame oil consumption significantly decreased HbA1C (WMD: -2.057%; 95% CI: -3.467, -0.646; P = 0.004), systolic blood pressure (SBP) (WMD: -2.679 mmHg; 95% CI: -5.257, -0.101; P < 0.001), diastolic blood pressure (DBP) (WMD: -1.981 mmHg; 95% CI: -3.916, -0.046; P = 0.045), body weight (WMD: -0.346 kg; 95% CI: -0.641, -0.051; P = 0.021), and body mass index (BMI) (WMD: -0.385 kg/m2; 95% CI:-0.721, -0.049; P = 0.025) after intervention. No significant effect was seen in serum insulin levels (p > .05).

Conclusions

The current study provided some evidence regarding the beneficial effects of sesame oil on metabolic biomarkers. Further studies are still required to confirm our results.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-022-00997-2.

Chewing Behavior Attenuates the Tumor Progression-Enhancing Effects of Psychological Stress in a Breast Cancer Model Mouse

We examined whether chewing behavior affects the tumor progression-enhancing impact of psychological stress. Human breast cancer cell line (MDA-MB-231) cells were inoculated into the mammary fat pads of athymic nude mice. The mice were assigned randomly to control, stress, and stress+chewing groups. Psychological stress was created by keeping mice in a transparent restraint cylinder for 45 min, three times a day, for 35 days after cell inoculation. Animals in the stress+chewing group were provided with a wooden stick for chewing on during the psychological stress period. Chewing behavior remarkably inhibited the tumor growth accelerated by the psychological stress. Immunohistochemical and Western blot findings revealed that chewing behavior during psychological stress markedly suppressed tumor angiogenesis and cell proliferation. In addition, chewing behavior decreased serum glucocorticoid levels and expressions of glucocorticoid and β2-adrenergic receptors in tumors. Chewing behavior decreased expressions of inducible nitric oxide synthase and 4-hydroxynonenal, and increased expression of superoxide dismutase 2 in tumors. Our findings suggest that chewing behavior could ameliorate the enhancing effects of psychological stress on the progression of breast cancer, at least partially, through modulating stress hormones and their receptors, and the subsequent signaling pathways involving reactive oxygen and nitrogen species.

Endothelial-transcytosed myeloperoxidase activates endothelial nitric oxide synthase via a phospholipase C-dependent calcium signaling pathway

During vascular inflammation, the leukocyte-derived enzyme myeloperoxidase (MPO) is transcytosed across the endothelium and into the sub-endothelial extracellular matrix, where it promotes endothelial dysfunction by catalytically consuming nitric oxide (NO) produced by endothelial NO synthase (eNOS). In the presence of chloride ions and hydrogen peroxide (H2O2), MPO forms the oxidant hypochlorous acid (HOCl). Here we examined the short-term implications of HOCl produced by endothelial-transcytosed MPO for eNOS activity. Incubation of MPO with cultured aortic endothelial cells (ECs) resulted in its transport into the sub-endothelium. Exposure of MPO-containing ECs to low micromolar concentrations of H2O2 yielded enhanced rates of H2O2 consumption that correlated with HOCl formation and increased eNOS enzyme activity. The MPO-dependent activation of eNOS occurred despite reduced cellular uptake of the eNOS substrate l-arginine, which involved a decrease in the maximal activity (Vmax), but not substrate affinity (Km), of the major endothelial l-arginine transporter, cationic amino acid transporter-1. Activation of eNOS in MPO-containing ECs exposed to H2O2 involved a rapid elevation in cytosolic calcium and increased eNOS phosphorylation at Ser-1179 and de-phosphorylation at Thr-497. These signaling events were attenuated by intracellular calcium chelation, removal of extracellular calcium and inhibition of phospholipase C. This study shows that stimulation of endothelial-transcytosed MPO activates eNOS by promoting phospholipase C-dependent calcium signaling and altered eNOS phosphorylation at Ser-1179 and Thr-497. This may constitute a compensatory signaling response of ECs aimed at maintaining eNOS activity and NO production in the face of MPO-catalyzed oxidative stress.

NOVEL antioxidant and oxidant biomarkers related to sarcopenia in COPD

BACKGROUND

The relation between oxidative stress (OS) and sarcopenia in COPD remains unknown.

OBJECTIVE

To analyze OS levels and its association with sarcopenia in COPD.

METHODS

Thirty-nine individuals with COPD (69±7years; 41%female) and thirty-five for the control group (69±7years; 43%female) were included. Advanced oxidation protein products (AOPP), paraoxonase-1 (PON1), superoxide dismutase activity (SOD), catalase dismutase activity (CAT), sulfhydryl group (SH), nitric oxide metabolites (NOX), total radical trapping antioxidant parameter (TRAP) were analysed. OS markers were correlated with handgrip and quadriceps strength, gait speed, skeletal muscle mass index, fat-free mass index, maximum inspiratory and expiratory pressure. European criteria were used to identify sarcopenia.

RESULTS

In COPD, antioxidant capacity was correlated with muscle mass and strength (r from 0.5 to 0.64) P<0.05 for all. TRAP≤ 850 μM/trolox and AOPP≤65 μM/l were associated with sarcopenia (OR:8.3; 95% CI: 1.4-49.6 and OR:14; 95%CI: 2.2-87.1, respectively; P<0.05 for both).

CONCLUSION

OS is associated with sarcopenia in COPD.

NOS cofactor tetrahydrobiopterin contributes to anesthetic preconditioning induced myocardial protection in the isolated ex vivo rat heart

Anesthetic preconditioning (APC) may decrease the myocardium injury nearly 50% following ischemia/reperfusion (I/R) by enhancing recovery of cardiac function, reducing myocardial enzyme release and lowering infarct size when utilized as pretreatment or posttreatment agents. I/R increases nitric oxide (NO) production through endothelial NO synthase (NOS3) and heat shock protein 90 (HSP90). The present study aimed to observe the role of BH4 availability and the association of HSP90 with NOS3 in APC‑mediated cardioprotection against I/R injury. Isolated rat hearts were subjected to no‑flow ischemia for 30 min and reperfusion for 120 min. Sevoflurane (3.5%) was administered for 15 min followed by a 15 min washout prior to ischemia. 2,4-Diamino-6-hydroxypyrimidine (DAHP) or sepiapterin (SP) was administered for 40 min until the onset of ischemia. The results revealed that compared with pre‑ischemic basal levels, BH4 levels decreased and BH2 levels increased following I/R. BH4 levels were significantly increased and BH2 levels were significantly decreased in the APC + I/R hearts compared with the I/R group hearts. The BH4:BH2 ratio in the APC‑treated hearts was also increased compared with that in the I/R group hearts. SP increased the recovery of contractile function and the production of NO, and decreased the production of superoxide anion (O2·‑) in I/R heart, but did not elicit these effects in APC‑treated hearts. DAHP treatment inhibited the APC‑mediated recovery of contractile function, increased O2·‑ levels and decreased NO production, but had no effect in I/R hearts. The cardioprotection of APC was demonstrated to be modulated by the BH4 precursor SP, which increased BH4 levels, or DAHP, which inhibited GTP cyclohydrolase I. Both APC and SP treatments increased the combination of HSP90 and NOS3, which improved the NOS3 activity and function. The results suggested that BH4, which servesas a cofactor for NOS, mediated the resistance of APC to I/R injury by promoting the binding of HSP90 and NOS3.

The Peroxisome Proliferator-Activated Receptor γ Agonist Pioglitazone Protects Vascular Endothelial Function in Hypercholesterolemic Rats by Inhibiting Myeloperoxidase

Objective

Hypercholesterolemia- (HC-) induced endothelial dysfunction is the first step of atherogenesis, and the peroxisome proliferator-activated receptor γ (PPARγ (PPARγ (PPARγ) has been reported to attenuate atherosclerosis formation; however, the underlying mechanisms are not fully understood. The present study was designed to determine whether myeloperoxidase (MPO) mediates HC-induced endothelial dysfunction and the role of the PPARγ agonist pioglitazone (PIO) in attenuating endothelial dysfunction.

Methods

Male Wistar rats were fed with normal or high cholesterol diets for 8 weeks. HC rats were randomized to receive dapsone (DDS, the MPO inhibitor) during the last 6 days or PIO for the remaining 4 weeks. Vascular endothelial function was determined by comparing vasorelaxation to ACh, an endothelium-dependent vasodilator, and SNP, an endothelium-independent vasodilator in vascular rings in vitro. The vascular MPO activity, NO_x content, and cGMP level were measured by the MPO activity assay kit, NO assay kit, and cGMP RIA kit.

Results

Compared with rats fed with normal diet, endothelium-dependent vasodilation, NO_x content, and cGMP level were decreased, and MPO activity was increased in thoracic aortas of rats fed with HC diet. There was a negative correlation between vascular endothelial function, NO_x content or cGMP level, and MPO activity. PIO obviously reduced the MPO activity, increased NO_x content and cGMP level, and improved endothelium-dependent vasodilation function in HC rats, which was essentially the same as that seen with DDS. And, there was a negative correlation between vascular endothelial function, NO_x content or cGMP level, and MPO activity in the HC group and the PIO intervention group.

Conclusion

MPO might provoke vascular endothelial dysfunction in hypercholesterolemic rats by reducing the NO biological activity and impairing the NO/cGMP/cGK signaling pathway. PIO might inhibit vascular MPO activity and increase NO bioavailability with the net result of reversing endothelial dysfunction.

Can sesame consumption improve blood pressure? A systematic review and meta-analysis of controlled trials

Hypertension is a major risk factor for cardiovascular disease, myocardial infarction, stroke and renal failure. Sesame consumption may benefit blood pressure (BP) owing to its high polyunsaturated fatty acid, fibre, phytosterol and lignan contents. To clarify this, a systematic review and meta-analysis of controlled trials was conducted. The PubMed (MEDLINE), Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Cochrane Library (Central) databases were systematically searched until August 2016. Eight controlled trials with a total of 843 participants met the eligibility criteria. A random effect meta-analysis showed that sesame consumption can reduce systolic BP (-7.83 mmHg, 95% CI: -14.12, -1.54; P < 0.05, I²  = 99%) and diastolic BP (-5.83 mmHg, 95% CI: -9.58, -2.08; P < 0.01, I²  = 98%). To reduce the heterogeneity, the meta-analysis was limited to high methodology quality trials (n = 4), which resulted in a significant reduction in systolic BP (-3.23 mmHg, 95% CI: -5.67, -0.79; I²  = 33%) and a non-significant reduction in diastolic BP (-2.08 mmHg, 95% CI: -4.85, 0.69; I²  = 62%). This study concluded that sesame consumption can reduce systolic and diastolic BP. However, further investigations with larger sample sizes and better methodology quality are required to confirm the BP-lowering effect of sesame consumption. © 2017 Society of Chemical Industry.

Effects of the Intake of Sesame Seeds (Sesamum indicum L.) and Derivatives on Oxidative Stress: A Systematic Review

This study is aimed at assessing the scientific evidence on the effect of the intake of sesame seeds and derivatives on oxidative stress of individuals with systemic hypertension, dyslipidemia, and type 2 diabetes mellitus. A systematic review was conducted in seven databases (Lilacs, PubMed, ISI Web of Knowledge, Cochrane Library, Scopus, Trip Database, and Scielo) from September 2013 to January 2014. Clinical trials on the intake of sesame seeds and derivatives assessing the outcomes related to oxidative stress were retrieved. The risk of bias in the results of the studies selected was assessed according to the criteria of the Cochrane Handbook for Systematic Reviews of Interventions. This review included seven clinical trials showing that the intake of sesame resulted in the increase in enzymatic and nonenzymatic antioxidants, as well as in a reduction in oxidative stress markers. This was mainly observed with the use of sesame oil for hypertensive individuals during 2 months and black sesame meal capsules for prehypertensive individuals during four weeks. Most studies involved a small number of participants, sample size being considered a limiting factor for this review. In addition, a significant heterogeneity was observed in the type of population studied and the type of sesame and derivatives used, as well as their amount. The follow-up time was considered a limiting factor, because it varied in the different studies. The high risk of randomization and blinding biases found in the studies assessed determines lower scientific evidence of the results. Despite the limitations and biases identified in this systematic review, sesame showed relevant effects on oxidative stress, suggesting it could increase the antioxidant capacity.

Arsenic Exposure and Predicted 10-Year Atherosclerotic Cardiovascular Risk Using the Pooled Cohort Equations in U.S. Hypertensive Adults

This study was to evaluate the association of urine arsenic with predicted 10-year atherosclerotic cardiovascular disease (ASCVD) risk in U.S. adults with hypertension. Cross-sectional analysis was conducted in 1570 hypertensive adults aged 40-79 years in the 2003-2012 National Health and Nutrition Examination Survey (NHANES) with determinations of urine arsenic. Predicted 10-year ASCVD risk was estimated by the Pooled Cohort Equations, developed by the American College of Cardiology/American Heart Association in 2013. For men, after adjustment for sociodemographic factors, urine dilution, ASCVD risk factors and organic arsenic intake from seafood, participants in the highest quartiles of urine arsenic had higher 10-year predicted ASCVD risk than in the lowest quartiles; the increases were 24% (95% confidence interval (CI): 2%, 53%) for total arsenic, 13% (95% CI: 2%, 25%) for dimethylarsinate and 22% (95% CI: 5%, 40%) for total arsenic minus arsenobetaine separately. For women, the corresponding increases were 5% (95% CI: -15%, 29%), 10% (95% CI: -8%, 30%) and 0% (95% CI: -15%, 19%), respectively. Arsenic exposure, even at low levels, may contribute to increased ASCVD risk in men with hypertension. Furthermore, our findings suggest that particular circumstances need urgently to be considered while elucidating cardiovascular effects of low inorganic arsenic levels.

Heterozygous eNOS deficiency is associated with oxidative stress and endothelial dysfunction in diet-induced obesity

Heterozygous endothelial nitric oxide synthase (eNOS) deficiency is associated with normal endothelium-dependent responses, however, little is known regarding the mechanisms that maintain or impair endothelial function with heterozygous eNOS deficiency. The goals of this study were to (1) determine mechanism(s) which serve to maintain normal endothelial function in the absence of a single eNOS gene; and (2) to determine whether heterozygous eNOS deficiency predisposes blood vessels to endothelial dysfunction in response to a high-fat diet (HFD). Responses of carotid arteries were examined in wild-type (eNOS(+/+)) and heterozygous eNOS-deficient (eNOS(+/-)) treated with either vehicle (saline), N(G)-nitro-L-arginine (L-NNA, 100 μmol/L), an inhibitor of nitric oxide synthase, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 1 μmol/L), an inhibitor of soluble guanylyl cyclase (sGC), and in eNOS(+/+) and eNOS(+/-) mice fed a control (10%) or a 45% HFD (kcal from fat). Responses to acetylcholine (ACh) were similar in vehicle-treated arteries from eNOS(+/+) and eNOS(+/-) mice, and were equally inhibited by L-NNA and ODQ. Phosphorylation of eNOS Ser1176, a site associated with increased eNOS activity, was significantly greater in eNOS(+/-) mice most likely as a compensatory response for the loss of a single eNOS gene. In contrast, responses to ACh were markedly impaired in carotid arteries from eNOS(+/-), but not eNOS(+/+), mice fed a HFD. Vascular superoxide levels as well as plasma levels of the pro-inflammatory cytokine interleukin-6 (IL-6) were selectively increased in HFD-fed eNOS(+/-) mice. In reconstitution experiments, IL-6 produced concentration-dependent impairment of endothelial responses as well as greater increases in NADPH-stimulated superoxide levels in arteries from eNOS(+/-) mice fed a control diet compared to eNOS(+/+) mice. Our findings of increased Ser1176-phosphorylation reveal a mechanism by which NOS- and sGC-dependent endothelial function can be maintained with heterozygous eNOS deficiency. In addition, heterozygous eNOS deficiency predisposes blood vessels to developing endothelial dysfunction in response to a HFD. The impairment produced by a HFD in eNOS(+/-) mice appears to be mediated by IL-6-induced increases in vascular superoxide. These findings serve as an important example of eNOS haploinsufficiency, one that may contribute to the development of carotid artery disease in obese humans.

Melatonin modulates the fetal cardiovascular defense response to acute hypoxia

Experimental studies in animal models supporting protective effects on the fetus of melatonin in adverse pregnancy have prompted clinical trials in human pregnancy complicated by fetal growth restriction. However, the effects of melatonin on the fetal defense to acute hypoxia, such as that which may occur during labor, remain unknown. This translational study tested the hypothesis, in vivo, that melatonin modulates the fetal cardiometabolic defense responses to acute hypoxia in chronically instrumented late gestation fetal sheep via alterations in fetal nitric oxide (NO) bioavailability. Under anesthesia, 6 fetal sheep at 0.85 gestation were instrumented with vascular catheters and a Transonic flow probe around a femoral artery. Five days later, fetuses were exposed to acute hypoxia with or without melatonin treatment. Fetal blood was taken to determine blood gas and metabolic status and plasma catecholamine concentrations. Hypoxia during melatonin treatment was repeated during in vivo NO blockade with the NO clamp. This technique permits blockade of de novo synthesis of NO while compensating for the tonic production of the gas, thereby maintaining basal cardiovascular function. Melatonin suppressed the redistribution of blood flow away from peripheral circulations and the glycemic and plasma catecholamine responses to acute hypoxia. These are important components of the fetal brain sparing response to acute hypoxia. The effects of melatonin involved NO-dependent mechanisms as the responses were reverted by fetal treatment with the NO clamp. Melatonin modulates the in vivo fetal cardiometabolic responses to acute hypoxia by increasing NO bioavailability.

[NOS UNCOUPLING IS ACCOMPANIED WITH INDUCTION OF THE OXIDATIVE STRESS AND THE CARDIOHEMODYNAMICS DISTURBANCES IN HYPERTENSION]

We compared the performance of cardiaohemodynamics and indicators of oxidative and nitrosative stress in the heart and aorta in normotensive Wistar rats (WKR) and spontaneously hypertensive rats (SHR). On the basis of experimentally determined parameters to calculate cNOS uncoupling index and biochemical index of function (BIF) in these organs of the cardiovascular system. In the heart, and especially in the aorta of SHR develop a combined oxidative and nitrosative stress that leads to cNOS uncoupling, BIF lowering that correlate with lowering of systolic and diastolic functions, inhibition of the efficiency Frank-Starling mechanism, oxygen consumption of the heart and increasing arterial stiffness. We made the assumption of the existence of the vicious circle of enhancing oxidative stress in organs of the cardiovascular system due to additional superoxide generation by uncoupling cNOS.

Equine digital veins are more sensitive to superoxide anions than digital arteries

This work was designed to investigate (i) the effect of superoxide dismutase (SOD) inhibition on endothelial function and (ii) the free radical-induced endothelial dysfunction in equine digital veins (EDVs) and equine digital arteries (EDAs) isolated from healthy horses. EDV and EDA rings were suspended in a 5 ml organ bath containing Krebs solution. After a 60 min equilibration period, EDV and EDA rings were contracted with phenylephrine. Then, cumulative concentration-response curves (CCRCs) to acetylcholine were performed. In both EDVs and EDAs, acetylcholine (1 nM to 10 µM) produced concentration-dependent relaxation. We investigated the influence of SOD inhibition by diethyldithiocarbamate (DETC; 100 µM), a CuZnSOD inhibitor, on EDAs and EDVs relaxant responses to acetylcholine. Acetylcholine -mediated relaxation was impaired by DETC only in EDVs. SOD activity assayed by a xanthine-xanthine oxidase method was higher in EDAs compared with EDVs (P<0.05). CCRCs to acetylcholine established in the presence of pyrogallol (30 µM) or homocysteine (20 µM), two superoxide anions generating systems showed that in both EDVs and EDAs, the acetylcholine-mediated relaxation was significantly impaired by pyrogallol and homocysteine. This impairment was more pronounced in EDVs than in EDAs. Moreover, the pyrogallol-induced impairment of acetylcholine-mediated relaxation was potentiated by DETC to a greater extent in EDVs. We concluded that due to the lower activity of SOD, EDVs are more sensitive to superoxide anions than EDAs. So, any alteration of superoxide anions metabolism is likely to have a more important impact on venous rather than arterial relaxation.

Hypertension and chronic ethanol consumption: What do we know after a century of study?

The influences of life habits on the cardiovascular system may have important implications for public health, as cardiovascular diseases are among the leading causes of shorter life expectancy worldwide. A link between excessive ethyl alcohol (ethanol) consumption and arterial hypertension was first suggested early last century. Since then, this proposition has received considerable attention. Support for the concept of ethanol as a cause of hypertension derives from several epidemiologic studies demonstrating that in the general population, increased blood pressure is significantly correlated with ethanol consumption. Although the link between ethanol consumption and hypertension is well established, the mechanism through which ethanol increases blood pressure remains elusive. Possible mechanisms underlying ethanol-induced hypertension were proposed based on clinical and experimental observations. These mechanisms include an increase in sympathetic nervous system activity, stimulation of the renin-angiotensin-aldosterone system, an increase of intracellular Ca²⁺ in vascular smooth muscle, increased oxidative stress and endothelial dysfunction. The present report reviews the relationship between ethanol intake and hypertension and highlights some mechanisms underlying this response. These issues are of interest for the public health, as ethanol consumption contributes to blood pressure elevation in the population.

Nox2-derived superoxide contributes to cerebral vascular dysfunction in diet-induced obesity

BACKGROUND AND PURPOSE

Obesity is an increasing epidemic worldwide; however, little is known about effects of obesity produced by high-fat diet (HFD) on the cerebral circulation. The purpose of this study was to examine the functional and temporal effects of a HFD on carotid and cerebral vascular function and to identify mechanisms that contribute to such functional alterations.

METHODS

Responses of cerebral arterioles (in vivo) and carotid arteries (in vitro) were examined in C57Bl/6 (wild-type) and Nox2-deficient (Nox2(-/-)) mice fed a control (10%) or a HFD (45% or 60% kcal of fat) for 8, 12, 30, or 36 weeks.

RESULTS

In wild-type mice, a HFD produced obesity and endothelial dysfunction by 12 and 36 weeks in cerebral arterioles and carotid arteries, respectively. Endothelial function could be significantly improved with Tempol (a superoxide scavenger) treatment in wild-type mice fed a HFD. Despite producing a similar degree of obesity in both wild-type and Nox2(-/-) mice, endothelial dysfunction was observed only in wild-type, but not in Nox2(-/-), mice fed a HFD.

CONCLUSIONS

Endothelial dysfunction produced by a HFD occurs in a temporal manner and appears much earlier in cerebral arterioles than in carotid arteries. Genetic studies revealed that Nox2-derived superoxide plays a major role in endothelial dysfunction produced by a HFD. Such functional changes may serve to predispose blood vessels to reduced vasodilator responses and thus may contribute to alterations in cerebral blood flow associated with obesity.

Endothelial dysfunction occurs prior to clinical evidence of polycystic kidney disease

OBJECTIVE

Polycystic kidney disease (PKD), a monogenic disease with an autosomal dominant or an autosomal recessive form of inheritance (ARPKD), is the most common genetic cause of renal dysfunction and end-stage renal failure. In addition to the development of cysts, the autosomal form of PKD is associated with vascular endothelial dysfunction, a marker of vascular disease. Whether vascular endothelial dysfunction is also present in ARPKD, and its relationship with renal dysfunction remain to be determined.

METHODS

ARPKD rats (PCK model) and controls were studied at 6 and 10 weeks of age, and mean arterial pressure and renal function were measured. Aortic endothelial function was assessed using organ chamber techniques. Aortic endothelial cells (ECs) were isolated, characterized and their function studied.

RESULTS

Compared to controls, ARPKD animals had a decrease in the vasorelaxation to endothelium-dependent vasodilators, even prior to changes in mean arterial pressure or renal function. The abnormal vasoreactivity was corrected with L-arginine (a precursor of nitric oxide, NO), while the expression of endothelial NO synthase (eNOS) was unchanged. Furthermore, isolated ECs from 6-week-old ARPKD animals showed increased oxidative stress, with preserved eNOS expression and abnormal patterns of migration and angiogenic capacity (measured by the scratch and tube formation assays, respectively).

CONCLUSION

ARPKD leads to impairments in aortic vascular function and ECs at an early stage, which can have significant functional consequences, potentially representing a novel therapeutic target in this disease.

HBOC vasoactivity: interplay between nitric oxide scavenging and capacity to generate bioactive nitric oxide species

SIGNIFICANCE

Despite many advances in blood substitute research, the development of materials that are effective in maintaining blood volume and oxygen delivery remains a priority for emergency care and trauma. Clinical trials on hemoglobin (Hb)-based oxygen carriers (HBOCs) have not provided information on the mechanism of toxicity, although all commercial formulations have safety concerns. Specifically, it is important to reconcile the different hypotheses of Hb toxicity, such as nitric oxide (NO) depletion and oxidative reactions, to provide a coherent molecular basis for designing a safe HBOC.

RECENT ADVANCES

HBOCs with different sizes often exhibit differences in the degree of HBOC-induced vasoactivity. This has been attributed to differences in the degree of NO scavenging and in the extent of Hb extravasation. Additionally, it is appears that Hb can undergo reactions that compensate for NO scavenging by generating bioactive forms of NO.

CRITICAL ISSUES

Engineering modifications to enhance bioactive NO production can result in diminished oxygen delivery by virtue of increased oxygen affinity. This strategy can prevent the HBOC from fulfilling the intended goal on preserving oxygenation; however, the NO production effects will increase perfusion and oxygen transport.

FUTURE DIRECTIONS

Hb modifications influence NO scavenging and the capacity of certain HBOCs to compensate for NO scavenging through nitrite-mediated reactions that generate bioactive NO. Based on the current understanding of these NO-related factors, possible synthetic strategies are presented that address how HBOC formulations can be prepared that: (i) effectively deliver oxygen, (ii) maintain tissue perfusion, and (iii) limit/reverse underlying inflammation within the vasculature.

Cholestasis is associated with hepatic microvascular dysfunction and aberrant energy metabolism before and during ischemia-reperfusion

AIMS

The aim was to investigate the impact of ischemia-reperfusion (I/R) on intrahepatic oxidative stress, oxidative phosphorylation, and nucleotide metabolism in relation to liver damage and inflammation in cholestatic rats to elucidate the molecular mechanisms responsible for post-I/R pathogenesis during cholestasis.

RESULTS

Pre-I/R cholestatic livers exhibited mild hepatopathology in the form of oxidative/nitrosative stress, perfusion defects, necrosis and apoptosis, inflammation, and fibrosis. Plasma bilirubin concentration in cholestatic livers was 190 μM. I/R in cholestatic livers exacerbated hepatocellular damage and leukocyte infiltration. However, myeloperoxidase activity in neutrophils at 6 h reperfusion was not elevated in cholestatic livers compared to pre-I/R levels and to control (Ctrl) livers. At 6 h reperfusion, cholestatic livers exhibited severe histological damage, which was absent in Ctrl livers. Despite a lower antioxidative capacity after I/R, no cardiolipin peroxidation and equivalent reduced glutathione/oxidized glutathione ratios and Hsp70 levels were found in cholestatic livers versus Ctrls. Bilirubin acted as a potent and protective antioxidant. Postischemic resumption of oxidative phosphorylation in Ctrl livers proceeded rapidly and encompassed reactive hyperemia, which was significantly impaired in cholestatic livers owing to extensive vasoconstriction and perfusion defects. Normalization of intrahepatic energy status and nucleotide-based metabolic cofactors was delayed in cholestatic livers during reperfusion. Innovation and

CONCLUSIONS

Cholestatic livers possess sufficient antioxidative capacity to ameliorate radical-mediated damage during I/R. I/R-induced damage in cholestatic livers is predominantly caused by microvascular perfusion defects rather than exuberant oxidative/nitrosative stress. The forestalled rate of oxidative phophorylation and recovery of bioenergetic and possibly metabolic parameters during the early reperfusion phase are responsible for extensive liver damage.

Attenuation of oxidative stress-induced vascular endothelial dysfunction by thymoquinone

This study aimed to assess the effects of thymoquinone (TQ) on pyrogallol-induced endothelial dysfunction in isolated rabbit aorta. The protective effects of TQ were examined by incubating aortic rings in TQ concomitant with pyrogallol. The results revealed that pyrogallol produced significant enhancement of phenylephrine-induced contraction and impairment of acetylcholine-induced relaxation. Pyrogallol caused a significant increase in lipid peroxidation and reduction in the level of superoxide dismutase and reduced glutathione in the aortic homogenates. In addition, pyrogallol produced a significant decrease in nitrite/nitrate concentrations (NOx), constitutive nitric oxide synthase (cNOS) activity and an increase in inducible nitric oxide synthase (iNOS) activity in the aortic homogenates. These changes were counteracted by TQ co-incubation as TQ attenuated pyrogallol-induced impairment in vascular reactivity in a dose-dependent manner. Furthermore, TQ showed potent antioxidant activity as well as causing a significant increase in NOx and cNOS activity, and depression in iNOS activity. These results suggest that TQ can protect against pyrogallol-induced endothelial dysfunction which probably results from its potent antioxidant capacity that leads to an increase in NO production as well as its ability to enhance the generation and bioavailability of NO.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Association of endothelial nitric oxide synthase and mitochondrial dysfunction in the hippocampus of scrapie-infected mice

The elevation of nitric oxide (NO) within the central nervous system (CNS) is known to be associated with the pathogenesis of neurodegenerative diseases such as HIV-associated dementia (HAD), brain ischemia, Parkinson's disease, and Alzheimer's disease. NO is enzymatically formed by the enzyme nitric oxide synthase (NOS). There are two forms of NOS, the constitutive and the inducible form. The constitutive form is present in endothelial cells (eNOS) and neurons (nNOS). The inducible form (iNOS) is expressed in various cell types including astroglia and microglia of the CNS. Using an animal model, we investigated the involvement of eNOS in the pathology of prion disease. We showed dramatic upregulation of eNOS immunoreactivity in reactive astroglial cells in the hippocampus in the prion disease animal model, scrapie in mice. Expression of eNOS was upregulated in cytosolic and mitochondrial fractions of whole brain. In the hippocampal region, eNOS was widely overexpressed in various components of the cell. We found that eNOS dramatically accumulated in hippocampal mitochondria and was particularly prevalent in structurally dysfunctional mitochondria. In association with the accumulation of eNOS in mitochondria, we showed that mitochondrial superoxide dismutase (Mn-SOD or SOD2), cytochrome c, and ATP activity were downregulated both in whole brain and in the hippocampal region. These results indicate that eNOS plays a role in the development of dysfunctional mitochondria and this, in turn, could induce some of the histopathological changes seen in prion diseases.

Modification of intracellular level of free radicals and apoptosis in cultured human endotheliocytes and carcinoma cells

The intracellular levels of superoxide O(2)(-)and nitric oxide NO were directly measured under intravital conditions in cultured human endotheliocytes ECV 304 and carcinoma cells HeLa G-63. Comparative analysis of changes in the intracellular levels of superoxide and NO induced by ascorbic acid revealed a negative correlation between NO and O(2)(-)levels, whose strength depended on concentration of the acid. In pharmacological concentrations, ascorbic acid induced apoptotic death of carcinoma cells, but did not trigger apoptosis of endotheliocytes. The study demonstrated a possible way of cytotoxic action of ascorbic acid in pharmacological concentrations.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Antihypertensive and antioxidant effects of dietary black sesame meal in pre-hypertensive humans

BACKGROUND

It has been known that hypertension is an independent risk factor for cardiovascular disease (CVD). CVD is the major cause of morbidity and mortality in developed and developing countries. Elevation of blood pressure (BP) increases the adverse effect for cardiovascular outcomes. Prevention of increased BP plays a crucial role in a reduction of those outcomes, leading to a decrease in mortality. Therefore, the purpose of this study was to investigate the effects of dietary black sesame meal on BP and oxidative stress in individuals with prehypertension.

METHODS

Twenty-two women and eight men (aged 49.8 ± 6.6 years) with prehypertension were randomly divided into two groups, 15 subjects per group. They ingested 2.52 g black sesame meal capsules or placebo capsules each day for 4 weeks. Blood samples were obtained after overnight fasting for measurement of plasma lipid, malondialdehyde (MDA) and vitamin E levels. Anthropometry, body composition and BP were measured before and after 4-week administration of black sesame meal or a placebo.

RESULTS

The results showed that 4-week administration of black sesame meal significantly decreased systolic BP (129.3 ± 6.8 vs. 121.0 ± 9.0 mmHg, P < 0.05) and MDA level (1.8 ± 0.6 vs. 1.2 ± 0.6 μmol/L, P < 0.05), and increased vitamin E level (29.4 ± 6.0 vs. 38.2 ± 7.8 μmol/L, P < 0.01). In the black sesame meal group, the change in SBP tended to be positively related to the change in MDA (R = 0.50, P = 0.05), while the change in DBP was negatively related to the change in vitamin E (R = -0.55, P < 0.05). There were no correlations between changes in BP and oxidative stress in the control group.

CONCLUSIONS

These results suggest the possible antihypertensive effects of black sesame meal on improving antioxidant status and decreasing oxidant stress. These data may imply a beneficial effect of black sesame meal on prevention of CVD.

Rutin attenuates metabolic changes, nonalcoholic steatohepatitis, and cardiovascular remodeling in high-carbohydrate, high-fat diet-fed rats

Metabolic syndrome (obesity, diabetes, and hypertension) increases hepatic and cardiovascular damage. This study investigated preventive or reversal responses to rutin in high-carbohydrate, high-fat diet-fed rats as a model of metabolic syndrome. Rats were divided into 6 groups: 2 groups were fed a corn starch-rich diet for 8 or 16 wk, 2 groups were fed a high-carbohydrate, high-fat diet for 8 or 16 wk, and 2 groups received rutin (1.6 g/kg diet) in either diet for the last 8 wk only of the 16-wk protocol. Metabolic changes and hepatic and cardiovascular structure and function were then evaluated in these rats. The corn starch-rich diet contained 68% carbohydrate (mainly cornstarch) and 0.7% fat, whereas the high-carbohydrate, high-fat diet contained 50% carbohydrate (mainly fructose) and 24% fat (mainly beef tallow) along with 25% fructose in drinking water (total 68% carbohydrate using mean food and water intakes). The high-carbohydrate, high-fat diet produced obesity, dyslipidemia, hypertension, impaired glucose tolerance, hepatic steatosis, infiltration of inflammatory cells in the liver and the heart, higher cardiac stiffness, endothelial dysfunction, and higher plasma markers of oxidative stress with lower expression of markers for oxidative stress and apoptosis in the liver. Rutin reversed or prevented metabolic changes such as abdominal fat pads and glucose tolerance, reversed or prevented changes in hepatic and cardiovascular structure and function, reversed oxidative stress and inflammation in the liver and heart, and normalized expression of liver markers. These results suggest a non-nutritive role for rutin to attenuate chronic changes in metabolic syndrome.

Ellagitannins, ellagic acid and vascular health

Hydrolysable tannins are phenolic phytochemicals that show high antioxidant and free-radical scavenging activities. For this reason their potential effects preventing oxidative related diseases, such as cardiovascular diseases, have been largely studied. In vitro studies show that ellagitannins, at concentrations in the range 10-100 μM, show some relevant anti-atherogenic, anti-thrombotic, anti-inflammatory and anti-angiogenic effects, supporting the molecular mechanisms for the vascular health benefits. While there is good evidence supporting the vascular effects in vitro, the evidence on animal models or humans is much scarcer. The in vitro results often do not match the findings in the in vivo studies. This could be explained by the low bioavailability of the antioxidant ellagitannins and ellagic acid. The main ellagitannin metabolites circulating in plasma are ellagic acid microbiota metabolites known as urolithins, and they have lost their free-radical scavenging activity. They are present in plasma as glucuronide or sulphate conjugates, at concentrations in the nM range. Future studies should focus in the bioavailable metabolites, urolithins, and in the form (conjugated with glucuronic acid or sulphate) and concentrations (nM range) in which they are found in plasma. In this review we critically discuss the role of ellagitannins and ellagic acid on vascular health.

Angiotensin II type 1 receptor-dependent oxidative stress mediates endothelial dysfunction in type 2 diabetic mice

The mechanisms underlying the effect of the renin-angiotensin-aldosterone system (RAAS) inhibition on endothelial dysfunction in type 2 diabetes are incompletely understood. This study explored a causal relationship between RAAS activation and oxidative stress involved in diabetes-associated endothelial dysfunction. Daily oral administration of valsartan or enalapril at 10 mg/kg/day to db/db mice for 6 weeks reversed the blunted acetylcholine-induced endothelium-dependent dilatations, suppressed the upregulated expression of angiotensin II type 1 receptor (AT(1)R) and NAD(P)H oxidase subunits (p22(phox) and p47(phox)), and reduced reactive oxygen species (ROS) production. Acute exposure to AT(1)R blocker losartan restored the impaired endothelium-dependent dilatations in aortas of db/db mice and also in renal arteries of diabetic patients (fasting plasma glucose level > or =7.0 mmol/l). Similar observations were also made with apocynin, diphenyliodonium, or tempol treatment in db/db mouse aortas. DHE fluorescence revealed an overproduction of ROS in db/db aortas which was sensitive to inhibition by losartan or ROS scavengers. Losartan also prevented the impairment of endothelium-dependent dilatations under hyperglycemic conditions that were accompanied by high ROS production. The present study has identified an initiative role of AT(1)R activation in mediating endothelial dysfunction of arteries from db/db mice and diabetic patients.

Relative contribution of eNOS and nNOS to endothelium-dependent vasodilation in the mouse aorta

In large vessels, endothelium-dependent vasodilation is mainly attributed to endothelial nitric oxide synthase (eNOS)-derived NO production. However, we have recently shown that neuronal nitric oxide synthase (nNOS)-derived H(2)O(2) is also an endothelium-dependent relaxing factor in the mouse aorta. The relative contribution of nNOS/eNOS, H(2)O(2)/NO remains to be characterized. This work was undertaken to determine the relative contribution of NO versus H(2)O(2), and eNOS versus nNOS to endothelium-dependent vasodilation in the mouse aorta. We used carbon microsensors placed next to the lumen of the vessels to simultaneously measure NO, H(2)O(2) and vascular tone. Acetylcholine produced a concentration-dependent increase in NO and H(2)O(2) production with a good coefficient of linearity with acetylcholine-induced relaxation (R(2)=0.93 and 0.96 for NO and H(2)O(2), respectively). L-NAME, a non-selective inhibitor of nitric oxide synthase, abolished NO and H(2)O(2) production, and impaired vasodilation. Selective pharmacological inhibition of nNOS with L-Arg(NO2)-L-Dbu-NH(2) 2TFA and specific knock-down of nNOS abrogated H(2)O(2) and decreased by half acetylcholine-induced vasodilation. Catalase, which specifically decomposes H(2)O(2), did not interfere with NO, but impaired H(2)O(2) and decreased vasodilation to the same level as those obtained with nNOS inhibition or knocking down. Specific knocking down of eNOS had no effect on H(2)O(2) production but greatly reduced NO and decreased vasodilation to levels similar to those found with nNOS inhibition. In eNOS knocked-down mice, pharmacological nNOS inhibition dramatically reduced H(2)O(2) production and further reduced the residual acetylcholine-induced vasodilation. It is concluded that nNOS/eNOS and H(2)O(2)/NO both contribute in a significant way to relaxation in the mouse aorta.

Role of tetrahydrobiopterin in resistance to myocardial ischemia in Brown Norway and Dahl S rats

Previously we showed that Brown Norway (BN/Mcw) rats are more resistant to myocardial ischemia-reperfusion (I/R) injury than Dahl S (SS/Mcw) rats due to increased nitric oxide (x NO) generation secondary to increased heat shock protein 90 (HSP90) association with endothelial nitric oxide synthase (NOS3). Here we determined whether increased resistance to I/R injury in BN/Mcw hearts is also related to tetrahydrobiopterin (BH(4)) and GTP cyclohydrolase I (GCH-1), the rate-limiting enzyme for BH(4) synthesis. We observed that BH(4) supplementation via sepiapterin (SP) and inhibition of GCH-1 via 2,4-diamino-6-hydroxypyrimidine (DAHP) differentially modulate cardioprotection and that SP alters the association of HSP90 with NOS3. BH(4) levels were significantly higher and 7,8-dihydrobiopterin (BH(2)) levels were significantly lower in BN/Mcw than in SS/Mcw hearts. The BH(4)-to-BH(2) ratio in BN/Mcw was more than two times that in SS/Mcw hearts. After I/R, BH(4) decreased and BH(2) increased in hearts from both strains compared with their preischemia levels. However, the increase in BH(2) in SS/Mcw hearts was significantly higher than in BN/Mcw hearts. Real-time PCR revealed that BN/Mcw hearts contained more GCH-1 transcripts than SS/Mcw hearts. SP increased recovery of left ventricular developed pressure (rLVDP) following I/R as well as decreased superoxide (O(2)(x-)) and increased x NO in SS/Mcw hearts but not in BN/Mcw hearts. DAHP decreased rLVDP as well as increased O(2)(x-) and decreased x NO in BN/Mcw hearts compared with controls but not in SS/Mcw hearts. SP increased the association of HSP90 with NOS3. These data indicate that BH(4) mediates resistance to I/R by acting as a cofactor and enhancing HSP90-NOS3 association.

Modulation of Nitric Oxide Synthase Activity in Brain, Liver, and Blood Vessels of Spontaneously Hypertensive Rats by Ascorbic Acid: Protection from Free Radical Injury

End organ damage in essential hypertension has been linked to increased oxygen free radical generation, reduced antioxidant defense, and/or attenuation of nitric oxide synthase (NOS) activity. Ascorbic acid (AA), a water-soluble antioxidant, has been reported as a strong defense against free radicals in both aqueous and nonaqueous environment. In this study we examined the hypothesis that antioxidant ascorbic acid may confer protection from increased free radical activity in brain, liver, and blood vessels of spontaneously hypertensive rats (SHR). Male SHRs were divided into groups: SHR + AA (treated with AA, 1 mg/rat/day; for 12 weeks) or SHR (untreated). Wister-Kyoto rats (WKY) served as the control. Mean systolic blood pressure (SBP) in treated and untreated SHR was 145 +/- 7 mmHg and 142 +/- 8 mmHg, respectively. AA treatment prevented the increase in systolic blood pressure in SHR by 37 +/- 1% (p < 0.05). NOS activity in the brain, liver, and blood vessels of WKY rat was 1.82 +/- 0.02, 0.14 +/- 0.003, and 1.54 +/- 0.06 pmol citruline/mg protein, respectively. In SHR, total NOS activity was significantly reduced by 52 +/- 1%, 21 +/- 3%, and 44 +/- 4%, respectively. AA increased NOS activity in brain, liver, and blood vessels of SHR from 0.87 +/-.03, 0.11 +/-.01, and 0.87 +/-.08 pmol citruline/mg protein to 0.93 +/- 0.01, 0.13 +/- 0.001, and 1.11 +/- 0.03 pmol citruline/mg protein (p < 0.05), respectively. Lipid peroxides in the brain, liver, and blood vessels from WKY rats were 0.87 +/- 0.06, 0.11 +/- 0.005, and 0.47 +/- 0.04 nmol MDA equiv/mg protein, respectively. In SHR, lipid peroxides in brain, liver, and blood vessels were significantly increased by 40 +/- 3%, 64 +/- 3%, and 104 +/- 13%, respectively. AA reduced lipid peroxidation in liver and blood vessels by 17 +/- 1% and 34 +/- 3% but not in brain. Plasma lipid peroxides were almost doubled in SHR (p < 0.01) together with a reduction in total antioxidant status (6 +/- 0.1%; p < 0.05), nitrite (53 +/- 2%; p < 0.05) and superoxide dismutase (SOD) activity (36 +/- 2%; p < 0.05). AA treatment reduced plasma lipid peroxide (p < 0.001), and increased TAS (p < 0.001), nitrite (p < 0.001), and SOD activity (p < 0.001). From this study, we conclude that brain, liver, and blood vessels in SHR are susceptible to free radical injury, which reduces the availability of NO either by scavenging it or by reducing its production via inhibiting NOS. In addition, brain, liver, and blood vessels in SHR; may be protected by antioxidant, which improves total antioxidant status, and SOD thus may prevent high blood pressure and its complications.

Nitric oxide, NAD(P)H oxidase, and atherosclerosis

The endothelial cell layer plays a major role in the development and progression of atherosclerosis. Endothelial NO synthase (eNOS) produces nitric oxide (NO) from L-arginine. NO can rapidly react with reactive oxygen species to form peroxynitrite. This reduces NO availability, impairs vasodilatation, and mediates proinflammatory and prothrombotic processes such as leukocyte adhesion and platelet aggregation. In the vessel wall, specific NAD(P)H oxidase complexes are major sources of reactive oxygen species. These NAD(P)H oxidases can transfer electrons across membranes to oxygen and generate superoxide anions. The short-lived superoxide anion rapidly dismutates to hydrogen peroxide, which can further increase the production of reactive oxygen species. This can lead to uncoupling of eNOS switching enzymatic activity from NO to superoxide production. This review describes the structure and regulation of different NAD(P)H oxidase complexes. We will also focus on NO/superoxide anion balance as modulated by hemodynamic forces, vasoconstrictors, and oxidized low-density lipoprotein. We will then summarize the recent advances defining the role of nitric oxide and NAD(P)H oxidase-derived reactive oxygen species in the development and progression of atherosclerosis. In conclusion, novel mechanisms affecting the vascular NO/superoxide anion balance will allow the development of therapeutic strategies in the treatment of cardiovascular diseases.

Apigenin protects endothelium-dependent relaxation of rat aorta against oxidative stress

Apigenin is shown to have cardiovascular effects, but the effects of apigenin on aortas injured by exogenous oxidants are unknown. The objective of this study was to investigate the effect of apigenin on endothelium-dependent vasorelaxation in isolated rat aortic rings exposed to superoxide anion produced by pyrogallol, and its mechanism. The male Sprague-Dawley rat thoracic aorta was rapidly dissected out and the effect of apigenin on tension of aortic rings pretreated with 500 microM pyrogallol, inducing oxidative stress injury, was measured. The activity of nitric oxide synthase (NOS), the level of nitric oxide (NO) and the inhibition of superoxide anion in aortic tissues were measured. We found that pretreatment with pyrogallol concentration-dependently decreased acetylcholine-induced endothelium-dependent vasorelaxation. Apigenin (0.5-72.0 microM) evoked a concentration-dependent relaxation in aortas (pD(2): 5.304+/-0.049), which was weakened by L-NAME (the maximal relaxation fell from 87.6+/-6.7% to 37.1+/-8.8%, P<0.01), but not by aminoguanidine and indomethacin. Apigenin markedly attenuated the inhibition of vasorelaxation induced by pyrogallol (the maximal relaxation elevated from 55.8%+/-6.6% to 69.5%+/-6.4%, and the pD(2) increased from 6.559+/-0.119 to 7.057+/-0.145, P<0.01) and increased the inhibition of superoxide anion (from 94.6% to 74.5%), the NO level (from 77.1% to 94.4%), and the constitutive NOS activity (from 35.1% to 62.5%). These results indicate that pyrogallol decreased endothelium-dependent vasorelaxation in rat aortas via oxidative stress, which was markedly attenuated by apigenin. This may be mediated by weakening the oxidative stress and the NO reduction.

Whole-body basal nitric oxide production is impaired in postprandial endothelial dysfunction in healthy rats

In healthy humans, a high-saturated-fat/high-sucrose meal induces vascular endothelial dysfunction, a hallmark of atherogenesis. This transient dysfunction indicates a loss in nitric oxide (NO) production and/or bioactivity in the vasculature but it remains unknown if this is the local manifestation of a general impairment in NO pathway in the postprandial state. Here, we studied whole-body NO production and systemic NO bioactivity in postprandial endothelial dysfunction, as induced by a high-saturated-fat, high-sucrose meal. We first developed a physiological test of endothelial function on conscious rats, based on the transient fall in blood pressure after iv acetylcholine, and showed that this response was NO-dependent. As assessed with this method in healthy rats, endothelial function decreased during the postprandial state, being 60+/-7% lower than baseline at 6h after the meal challenge, associated with important elevations in plasma triglycerides and hydroperoxides. Aortic superoxide anion production, as assessed by oxidative fluorescent detection, was higher 6h after the meal challenge than after the nutrients vehicle (water). During the postprandial period, plasma cGMP, but not plasma ANP, markedly decreased, indicating a general decrease in NO bioavailability, which was numerically maximal 4h after the meal challenge. As determined 4h after ingestion by a tracer-based method using iv [(15)N(2)-(guanido)]-arginine, the whole-body NO production fell by 27+/-9% postprandially. This is the first study evidencing that a meal challenge that impairs the stimulated, NO-mediated, vascular response also reduces whole-body basal NO production and bioavailability. Postprandial pathophysiology may build on this general, fundamental alteration in NO production.

Plasma oxidized low-density lipoprotein levels and arterial stiffness in older adults: the health, aging, and body composition study

Arterial stiffness is a prominent feature of vascular aging and is strongly related to cardiovascular disease. Oxidized low-density lipoprotein (ox-LDL), a key player in the pathogenesis of atherosclerosis, may also play a role in arterial stiffening, but this relationship has not been well studied. Thus, we examined the cross-sectional association between ox-LDL and aortic pulse wave velocity (aPWV), a marker of arterial stiffness, in community-dwelling older adults. Plasma ox-LDL levels and aPWV were measured in 2295 participants (mean age: 74 years; 52% female; 40% black) from the Health, Aging, and Body Composition Study. Mean aPWV significantly increased across tertiles of ox-LDL (tertile 1: 869+/-376 cm/s; tertile 2: 901+/-394 cm/s; tertile 3: 938+/-415 cm/s; P=0.002). In multivariate analyses, ox-LDL remained associated with aPWV after adjustment for demographics and traditional cardiovascular disease risk factors (P=0.008). After further adjustment for hemoglobin A1c, abdominal visceral fat, antihypertensive and antilipemic medications, and C-reactive protein, the association with ox-LDL was attenuated but remained significant (P=0.01). Results were similar when ox-LDL was expressed in absolute (milligrams per deciliter) or relative amounts (percentage of low-density lipoprotein). Moreover, individuals in the highest ox-LDL tertile were 30% to 55% more likely to have high arterial stiffness, defined as aPWV >75th percentile (P<or=0.02). In conclusion, we found that, among elderly persons, elevated plasma ox-LDL levels were associated with higher arterial stiffness, independent of cardiovascular disease risk factors. These data suggest that ox-LDL may be related to the pathogenesis of arterial stiffness.

Different extent of cardiac malfunction and resistance to oxidative stress in heterozygous and homozygous manganese-dependent superoxide dismutase-mutant mice

AIMS

The mitochondrially expressed manganese-dependent superoxide dismutase (MnSOD, SOD2) is an essential antioxidative enzyme that is necessary for normal heart function. In this study, we investigated the heart function of mice that were exposed to increased oxidative stress for time periods of up to 6 months due to decreased MnSOD activity caused by heterozygous deletion of the MnSOD gene.

METHODS AND RESULTS

We generated a mouse strain in which the gene encoding MnSOD was exchanged against a cassette containing the SOD cDNA under the control of the tetracycline response element. After breeding with mice carrying the tetracycline receptor, compound mice express MnSOD depending on the presence of tetracycline. Without tetracycline receptor the MnSOD gene is fully inactivated, and animals show an MnSOD-deficient phenotype. Using echocardiographic recordings, we found an impairment of left ventricular functions: MnSOD+/- mice displayed a decrease in fraction shortening and ejection fraction and an increase in left ventricular internal diameter in systole. Furthermore, MnSOD+/- mice developed heart hypertrophy with accompanying fibrosis and necrosis revealed by immunhistochemical analysis. Although we did not find an increase in apoptosis in MnSOD+/- hearts under normal conditions, we observed an increase of the number of apoptotic cells and vascular senescence after treatment with doxorubicin.

CONCLUSION

Our study demonstrates that lifelong reduction of MnSOD activity has a negative effect on normal heart function. This animal model presents a valuable tool to investigate the mechanism of heart pathology reported in patients bearing different polymorphic variants of the MnSOD gene and to develop new therapeutic strategies through manipulation of the antioxidative defence system.

Effects of Origanum onites on endothelial function and serum biochemical markers in hyperlipidaemic patients

The effects of Origanum onites on endothelial function and antioxidative status were investigated in 48 patients with mild hyperlipidaemia who required no drug therapy. All participants were given lifestyle and low-fat dietary advice, however 32 of the patients (study group) were also prescribed 25 ml of aqueous distillate of Origanum onites to be taken after each meal for 3 months. The remaining 16 patients were the control group. Various biochemical markers and endothelial function parameters were measured at baseline and after 3 months. A significantly greater increase in high density lipoprotein-cholesterol and significantly greater decreases in low density lipoprotein-cholesterol, apolipoprotein B, lipoprotein(a) and high sensitivity C-reactive protein occurred in the study group compared with the control group over the 3-month study period. Paraoxonase and arylesterase activities, and flow- and nitroglycerine-mediated dilatation of the brachial artery showed significantly greater increases in the study group compared with the changes in the control group. In conclusion, consumption of Origanum onites distillate had beneficial effects on lipid profiles, antioxidant status and endothelial function in patients with mild hyperlipidaemia.

Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities

The endothelium is essential for the maintenance of vascular homeostasis. Central to this role is the production of endothelium-derived nitric oxide (EDNO), synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelial dysfunction, manifested as impaired EDNO bioactivity, is an important early event in the development of various vascular diseases, including hypertension, diabetes, and atherosclerosis. The degree of impairment of EDNO bioactivity is a determinant of future vascular complications. Accordingly, growing interest exists in defining the pathologic mechanisms involved. Considerable evidence supports a causal role for the enhanced production of reactive oxygen species (ROS) by vascular cells. ROS directly inactivate EDNO, act as cell-signaling molecules, and promote protein dysfunction, events that contribute to the initiation and progression of endothelial dysfunction. Increasing data indicate that strategies designed to limit vascular ROS production can restore endothelial function in humans with vascular complications. The purpose of this review is to outline the various ways in which ROS can influence endothelial function and dysfunction, describe the redox mechanisms involved, and discuss approaches for preventing endothelial dysfunction that may highlight future therapeutic opportunities in the treatment of cardiovascular disease.

Environmental risk factors for heart disease

In this review, we discuss current evidence linking environmental pollutants to cardiovascular disease (CVD). Extensive evidence indicates that environmental factors contribute to CVD risk, incidence, and severity. Migrant studies show that changes in the environment could substantially alter CVD risk in a genetically stable population. Additionally, CVD risk is affected by changes in nutritional and lifestyle choices. Recent studies in the field of environmental cardiology suggest that environmental toxins also influence CVD. Exposure to tobacco smoke is paradigmatic of such environmental risk and is strongly and positively associated with increased cardiovascular morbidity and mortality. In animal models of exposure, tobacco smoke induces endothelial dysfunction and prothrombotic responses and exacerbates atherogenesis and myocardial ischemic injury. Similar mechanism may be engaged by other pollutants or food constituents. Several large population-based studies indicate that exposure to fine or ultrafine particulate air pollution increases CVD morbidity and mortality, and the plausibility of this association is supported by data from animal studies. Exposure to other chemicals such as polyaromatic hydrocarbons, aldehydes, and metals has also been reported to elevate CVD risk by affecting atherogenesis, thrombosis, or blood pressure regulation. Maternal exposure to drugs, toxins, and infection has been linked with cardiac birth defects and premature CVD in later life. Collectively, the data support the notion that chronic environmental stress is an important determinant of CVD risk. Further work is required to assess the magnitude of this risk fully and to delineate specific mechanisms by which environmental toxins affect CVD.

Low nitric oxide: a key factor underlying copper-deficiency teratogenicity

Copper (Cu)-deficiency-induced teratogenicity is characterized by major cardiac, brain, and vascular anomalies; however, the underlying mechanisms are poorly understood. Cu deficiency decreases superoxide dismutase activity and increases superoxide anions, which can interact with nitric oxide (NO), reducing the NO pool size. Given the role of NO as a developmental signaling molecule, we tested the hypothesis that low NO levels, secondary to Cu deficiency, represent a developmental challenge. Gestation day 8.5 embryos from Cu-adequate (Cu+) or Cu-deficient (Cu-) dams were cultured for 48 h in Cu+ or Cu- medium, respectively. We report that NO levels were low in conditioned medium from Cu-/Cu- embryos and yolk sacs, compared to Cu+/Cu+ controls under basal conditions and with NO synthase (NOS) agonists. The low NO production was associated with low endothelial NOS phosphorylation at serine 1177 and cyclic guanosine-3',5'-monophosphate (cGMP) concentrations in the Cu-/Cu- group. The altered NO levels in Cu-deficient embryos are functionally significant, as the administration of the NO donor DETA/NONOate increased cGMP and ameliorated embryo and yolk sac abnormalities. These data support the concept that Cu deficiency limits NO availability and alters NO-dependent signaling, which contributes to abnormal embryo and yolk sac development.

Thromboxane receptor activates the AMP-activated protein kinase in vascular smooth muscle cells via hydrogen peroxide

Thromboxane A2 receptor (TPr) stimulation induces cellular hypertrophy in vascular smooth muscle cells (VSMCs); however, regulation of VSMC hypertrophy remains poorly understood. Here we show that TPr stimulation activates AMP-activated kinase (AMPK), which in turn limits TPr-induced protein synthesis in VSMCs. Exposure of cultured VSMCs to either TPr agonists, IBOP and U46619, or exogenous hydrogen peroxide (H2O2) caused time- and dose-dependent AMPK activation, as evidenced by increased phosphorylation of both AMPK-Thr172 and acetyl-coenzyme A carboxylase-Ser79, a downstream enzyme of AMPK, whereas SQ29548, a selective TPr antagonist, significantly attenuated TPr-enhanced AMPK activation. In parallel, both IBOP and U46619 significantly increased the production of reactive oxygen species such as H2O2. Furthermore, adenoviral overexpression of catalase (an H2O2 scavenger) abolished, whereas superoxide dismutase (which catalyzes H2O2 formation) enhanced, IBOP-induced AMPK activation, suggesting that TPr-activated AMPK was mediated by H2O2. Consistently, exposure of VSMCs to either TPr agonists or exogenous H2O2 dose-dependently increased the phosphorylation of LKB1 (at serines 428 and 307), an AMPK kinase, as well as coimmunoprecipitation of AMPK with LKB1. In addition, direct mutagenesis of either Ser428 or Ser307 of LKB1 into alanine, like the kinase-dead LKB1 mutant, abolished both TPr-stimulated AMPK activation and coimmunoprecipitation. Finally, genetic inhibition of AMPK significantly accentuated IBOP-enhanced protein synthesis, whereas adenoviral overexpression of constitutively active AMPK abolished IBOP-enhance protein synthesis in VSMCs. We conclude that TPr stimulation triggers reactive oxygen species-mediated LKB1-dependent AMPK activation, which in return inhibits cellular protein synthesis in VSMCs.

The effect of oxidative stress on Ca2+ release and capacitative Ca2+ entry in vascular endothelial cells

Oxidative stress imposed by the accumulation of oxygen free radicals (reactive oxygen species, ROS) has profound effects on Ca2+ homeostasis in the vascular endothelium, leading to endothelial dysfunctions and the development of cardiovascular pathologies. We tested the effect of the oxidant and ROS generator tert-butyl-hydroperoxide (tBuOOH) on Ca2+ signaling in single cultured calf pulmonary artery endothelial (CPAE) cells loaded with the fluorescent Ca2+ indicator indo-1. Acute brief (5 min) exposures to tBuOOH had no effect on basal cytosolic free Ca2+ ([Ca2+](i)), agonist (ATP)-induced Ca2+ release from the endoplasmic reticulum (ER) and on Ca(2+) store depletion-dependent capacitative Ca2+ entry (CCE). Prolonged (60 min) exposure to tBuOOH did not affect intracellular Ca2+ release, but caused a profound inhibition of CCE. After 120 min of treatment with tBuOOH not only was CCE further reduced, but also ATP-induced Ca2+ release due to a slow depletion of the stores that resulted from CCE inhibition. The antioxidant Trolox (synthetic vitamin E analog) prevented the inhibition of CCE by tBuOOH and attenuated the increase of [ROS](i), indicating that inhibition of CCE was due to the oxidant effects of tBuOOH. The data suggest that in vascular endothelial cells oxidative stress primarily affects Ca2+ influx in response to Ca2+ loss from internal stores. [Ca2+](i) is an important signal for the production and release of endothelium-derived factors such as nitric oxide (NO). Since CCE is the preferential Ca2+ source for NO synthase activation, the finding that oxidative stress inhibits CCE may explain how oxidative stress contributes to endothelial dysfunction-related cardiovascular pathologies.