Aspects of nitric oxide in health and disease: a focus on hypertension and cardiovascular disease

Ameliorative effect of mussel-derived ACE inhibitory peptides on spontaneous hypertension rats

PURPOSE

The purpose of this study was to prepare the novel mussel-derived ACE inhibitory peptides (MEPs) by enzymatic hydrolysis of Mytilus edulis and investigate their antihypertensive effects in vivo.

METHODS

After assessing the stability of MEPs in vitro, we investigated the effect of MEPs on hypertension using spontaneously hypertensive rats (SHRs). Subsequently, MEPs were purified and identified by ultrafiltration, gel filtration chromatography and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

Our study demonstrated that MEPs could keep stable ACE inhibitory activity after treatment with heat, acid, alkali, metal ions and simulated gastrointestinal digestive fluid. Additionally, the animal experiments showed that both short-term and long-term treatment with MEPs resulted in a significant reduction in systolic and diastolic blood pressure in SHRs. Mechanistically, the results suggested that MEPs could reduce vascular remodeling, regulate renin-angiotensin system (RAS), and inhibit kidney and myocardial fibrosis. Finally, we isolated and identified five peptides from MEPs, with the peptide Ile-Leu-Thr-Glu-Arg showed the highest ACE inhibition rate.

CONCLUSION

Our findings demonstrate the potential use of MEPs as active components in functional foods designed to lower blood pressure.

Oral Nicorandil effectively attenuates the incidence of contrast-induced nephropathy in patients undergoing cardiac catheterization: a randomized, controlled, open-label clinical trial

PURPOSE

The contrast-induced nephropathy (CIN) rate is increasing globally and can increase the rate of mortality and long-term problems. This study aims to determine the effect of Nicorandil on preventing CIN among patients undergoing cardiac catheterization.

METHODS

In a controlled randomized open-labeled clinical trial, all included patients undergoing cardiac catheterization due to coronary problems and possessing at least two risk factors of contrast nephropathy were divided into two groups of intervention and control. The intervention group received oral Nicorandil and normal saline, while the control group was treated with intravenous normal saline. Serum creatinine was measured before and 48 h after the procedure, and patients were assessed regarding CIN.

RESULTS

In this study, 172 patients entered each group; 41.86% and 45.34% were male in the control and Nicorandil groups. We showed that the incidence of CIN was meaningfully lower in the Nicorandil group (12, 7%) than in the control group (34, 19.8%, P = 0.001). Additionally, the incidence of CIN was notably lower in the female patients in the Nicorandil (85.7%) than in the control group (14.3%, P = 0.001); however, these numbers were not significantly different among men (64.0% and 36.0%, respectively, P = 0.850). After the injection of the contrast agent, the serum levels of blood urea nitrogen (P = 0.248), creatinine (P = 0.081), and glomerular filtration rate (P = 0.386) showed no significant differences between the control and Nicorandil groups. Multivariate regression analysis showed that Nicorandil significantly lowered the odds of CIN [odds ratio (OR) = 0.299, 95% confidence interval (CI) 0.149-0.602; P = 0.001] after adjustment for baseline creatinine (OR = 1.404, 95% CI 0.431-4.572; P = 0.574).

CONCLUSION

Our results indicate that pre-procedural treatment with Nicorandil may be effective against CIN in contrast to agent-exposed patients.

Thrombosis in Pregnant Women with Hemolytic Anemia

Hemolytic anemias are a group of uncommon disorders affecting both genders, frequently occurring at the reproductive age. While a link between hemolysis and hypercoagulability has been suggested based on the elucidation of certain involved pathophysiological mechanisms, the extent of thrombotic risk in pregnant women with hemolytic anemia remains debatable. Due to the paucity of pregnancy-related data, risk assessment of gestations in women with hemolytic anemia is complicated. This review will highlight the latest advances in the diagnosis and management of these challenging disorders in pregnancy.

The Role of Single-Nucleotide Variants of NOS1, NOS2, and NOS3 Genes in the Comorbidity of Arterial Hypertension and Tension-Type Headache

Patients with tension-type headache (TTH) have an increased risk of developing arterial hypertension (AH), while hypertensive subjects do seem to have an increased risk of TTH. We searched for full-text English publications in databases using keywords and combined word searches over the past 15 years. In addition, earlier publications of historical interest were included in the review. In our review, we summed up the single nucleotide variants (SNVs) of Nitric Oxide Synthases (NOSs) genes involved in the development of essential AH and TTH. The results of studies we discussed in this review are contradictory. This might be due to different designs of the studies, small sample sizes in some of them, as well as different social and geographical characteristics. However, the contribution of genetic and environmental factors remains understudied. This makes the issue interesting for researchers, as understanding these mechanisms can contribute to a search for new approaches to pathogenetic and disease-modifying treatment of the AH and TTH phenotype. New drugs against AH and TTH can be based on inhibition of nitric oxide (NO) production, blockade of steps in the NO-cGMP pathway, or NO scavenging. Indeed, selective neuronal NOS (n-NOS) and inducible NOS (i-NOS) inhibitors are already in early clinical development.

Hypoxic training improves blood pressure, nitric oxide and hypoxia-inducible factor-1 alpha in hypertensive patients

PURPOSE

To examine the effects of intermittent hypoxic breathing at rest (IHR) or during exercise (IHT) on blood pressure and nitric oxide metabolites (NOx) and hypoxia-inducible factor-1 alpha levels (HIF-1α) over a 6-week period.

METHODS

47 hypertensive patients were randomly allocated to three groups: hypertensive control (CON: n = 17; IHR: n = 15 and IHT: n = 15. The CON received no intervention; whereas, IH groups received eight events of hypoxia (F_IO₂ 0.14), and normoxia (F_IO₂ 0.21), 24-min hypoxia and 24-min normoxia, for 6 weeks. The baseline data were collected 2 days before the intervention; while, the post-test data were collected at days 2 and 28 after the 6-week intervention.

RESULTS

We observed a significant decrease of the SBP in both IH groups: IHR (- 12.0 ± 8.0 mmHg, p = 0.004 and - 9.9 ± 8.8 mmHg, p = 0.028, mean ± 95% CI) and IHT (- 13.0 ± 7.8 mmHg, p = 0.002 and - 10.0 ± 8.4 mmHg, p = 0.016) at days 2 and 28 post-intervention, respectively. Compared to CON, IHR and IHT had increased of NOx (IHR; 8.5 ± 7.6 μmol/L, p = 0.031 and IHT; 20.0 ± 9.1 μmol/L, p < 0.001) and HIF-1α (IHR; 170.0 ± 100.0 pg/mL, p = 0.002 and IHT; 340.5 ± 160.0 pg/mL, p < 0.001). At 2 days post-intervention, NOx and HIF-1α were negatively correlated with SBP in IHT.

CONCLUSION

IH programs may act as an alternative therapeutic strategy for hypertension patients probably through elevation of NOx and HIF-1α production.

Enhanced endothelin-1/Rho-kinase signalling and coronary microvascular dysfunction in hypertensive myocardial hypertrophy

AIMS

Hypertensive cardiac hypertrophy is associated with reduced coronary flow reserve, but its impact on coronary flow regulation and vasomotor function remains incompletely understood and requires further investigation.

METHODS AND RESULTS

Left ventricular hypertrophy was induced in mice by transverse aortic coarctation (TAC) for 4 weeks. The left coronary artery blood velocity (LCABV) and myocardium lactate level were measured following the metabolic activation by isoproterenol. Septal coronary arterioles were isolated and pressurized for functional studies. In TAC mice, the heart-to-body weight ratio was increased by 45%, and cardiac fractional shortening and LCABV were decreased by 51 and 14%, respectively. The resting myocardial lactate level was 43% higher in TAC mice. Isoproterenol (5 µg/g, i.p.) increased heart rate by 20% in both groups of animals, but the corresponding increase in LCABV was not observed in TAC mice. The ventricular hypertrophy was associated with elevation of myocardial endothelin-1 (ET-1), increased vascular expression of rho-kinases (ROCKs), and increased superoxide production in the myocardium and vasculature. In coronary arterioles from TAC mice, the endothelial nitric oxide (NO)-mediated dilation to acetylcholine (ACh) was reversed to vasoconstriction and the vasoconstriction to ET-1 was augmented. Inhibition of ROCK by H-1152 alleviated oxidative stress and abolished enhanced vasoconstriction to ET-1. Both H-1152 and superoxide scavenger Tempol abolished coronary arteriolar constriction to ACh in a manner sensitive to NO synthase blocker NG-nitro-L-arginine methyl ester.

CONCLUSIONS

Myocardial hypertrophy induced by pressure overload leads to cardiac and coronary microvascular dysfunction and ischaemia possibly due to oxidative stress, enhanced vasoconstriction to ET-1 and compromised endothelial NO function via elevated ROCK signalling.

Soluble analog of ApoER2 targeting beta2-glycoprotein I in immune complexes counteracts hypertension in lupus-prone mice with spontaneous antiphospholipid syndrome

Essentials (NZWxBXSB)F1 male mice develop antibodies beta2-glycoprotein I (β2GPI) and hypertension. A1-A1 is a soluble analogue of ApoE receptor 2 with a high affinity for β2GPI/antibody complexes. A1-A1 improved blood pressure and arterial elastance in (NZWxBXSB)F1 male mice. A1-A1 had no adverse effects on the hemodynamics of healthy mice.

SUMMARY

Background Antiphospholipid syndrome (APS) is diagnosed based on the presence of antiphospholipid antibodies and clinical thrombosis or fetal loss during pregnancy. Lupus-prone (NZWxBXSB)F1 male mice are the mouse model of spontaneous APS. They develop anti-β2GPI antibodies, microinfarcts and hypertension. ApoER2 is a receptor that contributes to anti-β2GPI-dependent thrombosis in APS by down-regulating endothelial nitric oxide synthase activation. Objectives A1-A1 is a small protein constructed from two identical ligand-binding modules from ApoER2, containing the binding site for β2GPI. We studied how treatment with A1-A1 affects the development of hypertension in (NZWxBXSB)F1 male mice. Methods We treated (NZWxBXSB)F1 male mice with A1-A1 for up to 4 weeks and examined changes in hemodynamics by left ventricular pressure-volume loop measurements. Results We observed improvements in blood pressure in the A1-A1 treated mice. A1-A1 prevented the deterioration of arterial elastance by decreasing systemic resistance and improving vessel compliance. We did not detect any adverse effects of the treatment in either male mice or in apparently healthy female (NZWxBXSB)F1 mice. Conclusions We demonstrated that A1-A1, which is a soluble analog of ApoER2 that binds pathological β2GPI/anti-β2GPI complexes, has a positive impact on hemodynamics in lupus-prone mice with spontaneous anti-β2GPI antibodies and hypertension.

Two N-(2-phenylethyl)nitroaniline derivatives as precursors for slow and sustained nitric oxide release agents

Notwithstanding its simple structure, the chemistry of nitric oxide (NO) is complex. As a radical, NO is highly reactive. NO also has profound effects on the cardiovascular system. In order to regulate NO levels, direct therapeutic interventions include the development of numerous NO donors. Most of these donors release NO in a single high-concentration burst, which is deleterious. N-Nitrosated secondary amines release NO in a slow, sustained, and rate-tunable manner. Two new precursors to sustained NO-releasing materials have been characterized. N-[2-(3,4-Dimethoxyphenyl)ethyl]-2,4-dinitroaniline, C16H17N3O6, (I), crystallizes with one independent molecule in the asymmetric unit. The adjacent amine and nitro groups form an intramolecular N-H...O hydrogen bond. The anti conformation about the phenylethyl-to-aniline C-N bond leads to the planes of the arene and aniline rings being approximately perpendicular. Molecules are linked into dimers by weak intermolecular N-H...O hydrogen bonds such that each amine H atom participates in a three-center interaction with two nitro O atoms. The dimers pack so that the arene rings of adjacent molecules are not parallel and π-π interactions do not appear to be favored. N-(4-Methylsulfonyl-2-nitrophenyl)-L-phenylalanine, C16H16N2O6S, (II), with an optically active center, also crystallizes with one unique molecule in the asymmetric unit. The L enantiomer was established via the configuration of the starting material and was confirmed by refinement of the Flack parameter. As in (I), there is an intramolecular N-H...O hydrogen bond between adjacent amine and nitro groups. The conformation of the molecule is such that the arene rings display a dihedral angle of ca 60°. Unlike (I), molecules are not linked via intermolecular N-H...O hydrogen bonds. Rather, the carboxylic acid H atom forms a classic, approximately linear, O-H...O hydrogen bond with a sulfone O atom. Pairs of molecules related by twofold rotation axes are linked into dimers by two such interactions. The packing pattern features a zigzag arrangement of the arene rings without apparent π-π interactions. These structures are compared with reported analogues, revealing significant differences in molecular conformation, intermolecular interactions, and packing that result from modest changes in functional groups. The structures are discussed in terms of potential NO-release capability.

Relationship between Glycosylated Hemoglobin, Serum Nitric Oxide and Mean Arterial Blood Pressure

BACKGROUND

Hypertension is about twice as frequent in individuals with diabetes as in those without diabetes. Formation of glycosylated conjugates like HbA1c is implicated to have many effects on the vascular endothelium which leads to the development of hypertension in diabetes. Nitric oxide (NO)-dependent vasodilatation has been shown to be an important factor in the maintenance and regulation of peripheral vascular tone. Studies correlating these parameters give conflicting results. Hence the present study was designed to correlate HbA1c, Serum NO & mean arterial blood pressure.

AIMS

To study the relationship between glycosylated hemoglobin, serum nitric oxide & mean arterial blood pressure.

SETTINGS AND DESIGN

It is a case control study with 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives).

MATERIALS & METHODS

The study subjects included 28 type 2 diabetic hypertensives, 32 type 2 diabetic normotensives and 51 controls (non diabetic normotensives) [ADA 2010 and JNC7]. FBS, PPBS, PCV, Hb, HbA1c & serum NO estimation and BP recording was done in all the study subjects. Normalised mean arterial blood pressure (MAPn) and calculated glycosylated hemoglobin (cHbA1c) were calculated from mean arterial BP (MAP) and HbA1c respectively.

STATISTICAL ANALYSIS

was done using R commander software. The difference in the distribution of cHbA1c, MAPn & NO levels between all 3 groups was measured using ANOVA and Kruskal-Wallis test. Correlation between the parameters was measured by Correlation coefficient and logistic regression (Spearman linear regression) analysis (univariate and multivariate).

RESULTS

There was a significant difference in the distribution of cHbA1c, MAPn & NO levels (p<0.001) between all 3 groups, whether measured by ANOVA or Kruskal-Wallis test. On univariate analysis, there was a positive correlation between cHbA1c & MAPn (ρ= +0.26), a negative correlation between NO & MAPn (ρ = -0.54) and cHbA1c & NO (ρ= -0.66) .On multivariate analysis, not only NO, but contrary to univariate analysis, cHbA1c also showed a negative association with MAPn.

CONCLUSION

As the severity of diabetes increases, there is increase in BP, which is mainly due to the marked decrease in NO level which masks the negative correlation between HbA1c on MAPn.

Therapeutic potential of intermittent hypoxia: a matter of dose

Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in multiple physiological systems. Here, we review the extensive literature concerning IH and its impact on the respiratory, cardiovascular, immune, metabolic, bone, and nervous systems. One major goal is to define relevant IH characteristics leading to safe, protective, and/or therapeutic effects vs. pathogenesis. To understand the impact of IH, it is essential to define critical characteristics of the IH protocol under investigation, including potentially the severity of hypoxia within episodes, the duration of hypoxic episodes, the number of hypoxic episodes per day, the pattern of presentation across time (e.g., within vs. consecutive vs. alternating days), and the cumulative time of exposure. Not surprisingly, severe/chronic IH protocols tend to be pathogenic, whereas any beneficial effects are more likely to arise from modest/acute IH exposures. Features of the IH protocol most highly associated with beneficial vs. pathogenic outcomes include the level of hypoxemia within episodes and the number of episodes per day. Modest hypoxia (9-16% inspired O2) and low cycle numbers (3-15 episodes per day) most often lead to beneficial effects without pathology, whereas severe hypoxia (2-8% inspired O2) and more episodes per day (48-2,400 episodes/day) elicit progressively greater pathology. Accumulating evidence suggests that "low dose" IH (modest hypoxia, few episodes) may be a simple, safe, and effective treatment with considerable therapeutic potential for multiple clinical disorders.

A series of N-(2-phenylethyl)nitroaniline derivatives as precursors for slow and sustained nitric oxide release agents

2,4-Dinitro-N-(2-phenylethyl)aniline, C14H13N3O4, (I), crystallizes with one independent molecule in the asymmetric unit. The adjacent amine and nitro groups form an intramolecular N-H...O hydrogen bond. The anti conformation about the ethyl C-C bond leads to the phenyl and aniline rings being essentially parallel. Molecules are linked into dimers by intermolecular N-H...O hydrogen bonds, such that each amine H atom participates in a three-centre interaction with two nitro O atoms. Though the dimers pack so that the arene rings of adjacent molecules are parallel, the rings are staggered and π-π interactions do not appear to be favoured. 4,6-Dinitro-N,N'-bis(2-phenylethyl)benzene-1,3-diamine, C22H22N4O4, (II), differs from (I) in the presence of a second 2-phenylethylamine group on the substituted ring. Compound (II) also crystallizes with one unique molecule in the asymmetric unit. Both amine groups are involved in intramolecular N-H...O hydrogen bonds with adjacent nitro groups. Although one ethyl group adopts an anti conformation as in (I), the other is gauche, with the result that the pendant phenyl rings are not parallel. The amine group that is part of the gauche conformation participates in a three-centre N-H...O hydrogen bond with the nitro group of a neighbouring molecule, leading to dimers as in (I). The other amine H atom does not form any intermolecular hydrogen bonds. The packing leads to separations of ca 3.4 Å of the parallel anti phenyl and aminobenzene rings. 2-Cyano-4-nitro-N-(2-phenylethyl)aniline, C15H13N3O2, (III), differs from (I) only in having a cyano group in place of the 2-nitro group. The absence of the adjacent nitro group eliminates the intramolecular N-H...O hydrogen bond. Molecules of (III) adopt the same anti conformation about the ethyl group as in (I), but crystallize in the higher-symmetry monoclinic space group P21/n. The molecules are linked into dimers via N-H...N amine-cyano hydrogen bonds, while the nitro groups are not involved in any N-H...O interactions. Owing to the different symmetry, the molecules pack in a herringbone pattern with fewer face-to-face interactions between the rings. The closest such interactions are about 3.5 Å between rings that are largely slipped past one another. 4-Methylsulfonyl-2-nitro-N-(2-phenylethyl)aniline, C15H16N2O4S, (IV), differs from (I) in having a methylsulfonyl group in place of the 4-nitro group. The intramolecular N-H...O hydrogen bond is present as in (I). However, unlike (I), the conformation about the ethyl group is gauche, so the two arene rings are nearly perpendicular rather than parallel. The packing is significantly different from the other three structures in that there are no intermolecular hydrogen bonds involving the N-H groups. The molecules are arranged in tetragonal columns running along the c axis, with the aniline rings mostly parallel and separated by ca 3.7 Å. Taken together, these structures demonstrate that modest changes in functional groups cause significant differences in molecular conformation, intermolecular interactions and packing.

Caveolin-1 knockout mice exhibit airway hyperreactivity

Caveolae are flask-shaped plasma membrane invaginations expressing the scaffolding caveolin proteins. Although caveolins have been found in endothelium and epithelium (where they regulate nitric oxide synthase activity), their role in smooth muscle is still under investigation. We and others have previously shown that caveolae of human airway smooth muscle (ASM), which express caveolin-1, contain Ca(2+) and force regulatory proteins and are involved in mediating the effects of inflammatory cytokines such as TNF-α on intracellular Ca(2+) concentration responses to agonist. Accordingly, we tested the hypothesis that in vivo, absence of caveolin-1 leads to reduced airway hyperresponsiveness, using a knockout (KO) (Cav1 KO) mouse and an ovalbumin-sensitized/challenged (OVA) model of allergic airway hyperresponsiveness. Surprisingly, airway responsiveness to methacholine, tested by use of a FlexiVent system, was increased in Cav1 KO control (CTL) as well as KO OVA mice, which could not be explained by a blunted immune response to OVA. In ASM of wild-type (WT) OVA mice, expression of caveolin-1, the caveolar adapter proteins cavins 1-3, and caveolae-associated Ca(2+) and force regulatory proteins such as Orai1 and RhoA were all increased, effects absent in Cav1 KO CTL and OVA mice. However, as with WT OVA, both CTL and OVA Cav1 KO airways showed signs of enhanced remodeling, with high expression of proliferation markers and increased collagen. Separately, epithelial cells from airways of all three groups displayed lower endothelial but higher inducible nitric oxide synthase and arginase expression. Arginase activity was also increased in these three groups, and the inhibitor nor-NOHA (N-omega-nor-l-arginine) enhanced sensitivity of isolated tracheal rings to ACh, especially in Cav1 KO mice. On the basis of these data disproving our original hypothesis, we conclude that caveolin-1 has complex effects on ASM vs. epithelium, resulting in airway hyperreactivity in vivo mediated by altered airway remodeling and bronchodilation.

Impaired vasodilation in the pathogenesis of hypertension: focus on nitric oxide, endothelial-derived hyperpolarizing factors, and prostaglandins

Under resting conditions the arterial vasculature exists in a vasoconstricted state referred to as vascular tone. Physiological dilatation in response to increased flow, a function of normal endothelium is necessary to maintain normal blood pressure. Endothelial dysfunction in vascular smooth muscle cells thus results in loss of normal vasorelaxant function and the inability of arteries to appropriately dilate in response to increased blood flow in either a systemic or regional vascular bed, resulting in increased blood pressure, a sequence that may represent a common pathway to hypertension. Normal vasorelaxation is mediated by a number of endothelial systems including nitric oxide (NO), prostaglandins (PGI2 and PGE2), and a family of endothelial-derived hyperpolarizing factors (EDHF). In response to hemodynamic shear stress, endothelium continuously releases NO, EDHF, and PGI2 to provide vasodilatation. EDHF, not a single molecule but rather a group of molecules that includes epoxyeicosatrienoic acids, hydrogen peroxide, carbon monoxide, hydrogen sulfide, C-natriuretic peptide, and K+ itself, causes vasodilatation by activation of vascular smooth muscle cell K+ channels, resulting in hyperpolarization and thus vasorelaxation. The understanding and effective management of blood pressure requires an understanding of both physiologic and pathophysiologic regulation of vascular tone. This review describes molecular mechanisms underlying normal endothelial regulation and pathological states, such as increased oxidative stress, which cause loss of vasorelaxation. Possible pharmacological interventions to restore normal function are suggested.

Increased stability of S-nitrosothiol solutions via pH modulations

S-nitrosothiol (RSNO) solutions represent a valuable source of nitric oxide and could be used as topical vasodilators, but their fast decomposition rate poses a serious obstacle to their potentially widespread therapeutic use. Our aim was to characterize and quantify the effect of pH on S-nitrosothiol formation and decomposition in simple aqueous solutions of S-nitrosoglutathione (GSNO), S-nitroso-N-acetylcysteine (SNAC) and S-nitroso-3-mercaptopropionic acid (SN3MPA). Furthermore, we investigated the effect of storage pH on the stability of GSNO incorporated in poly(ethylene glycol)/ poly(vinyl alcohol) matrices. S-nitrosothiol concentrations were measured spectrophotometrically and laser Doppler scanning method was used to assess dermal blood flow. GSH and NAC solutions reached a complete transformation to nitrosothiols when synthesized using acidic NaNO(2) solution. The initial concentration of all investigated RSNOs decreased more slowly with pH adjusted to mildly basic values (8.4-8.8) for the storage period. Polymer gels of PVA/PEG compositions at mildly basic storage pH further reduced the decomposition rate succeeding to contain 46.8% of the initial GSNO concentration for 25 days. This amount of topically administered GSNO was still capable of increasing the dermal blood flow over 200% in human subjects.

Reactive oxygen species and endothelial function--role of nitric oxide synthase uncoupling and Nox family nicotinamide adenine dinucleotide phosphate oxidases

The healthy endothelium prevents platelet aggregation and leucocyte adhesion, controls permeability to plasma components and maintains vascular integrity. Damage to the endothelium promotes endothelial dysfunction characterized by: altered endothelium-mediated vasodilation, increased vascular reactivity, platelet aggregation, thrombus formation, increased permeability, leucocyte adhesion and monocyte migration. Molecular processes contributing to these phenomena include increased expression of adhesion molecules, synthesis of pro-inflammatory and pro-thrombotic factors and increased endothelin-1 secretion. Decreased nitric oxide bioavailability and increased generation of reactive oxygen species (ROS) are among the major molecular changes associated with endothelial dysfunction. A critical source of endothelial ROS is a family of non-phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, including the prototypic Nox2-based NADPH oxidases, Nox1, Nox4 and Nox5. Other possible sources include mitochondrial electron transport enzymes, xanthine oxidase, cyclooxygenase, lipoxygenase and uncoupled nitric oxide synthase (NOS). Cross-talk between ROS-generating enzymes, such as mitochondrial oxidases and Noxs, is increasingly implicated in cellular ROS production. The present review discusses the importance of endothelial ROS in health and disease and focuses on the major ROS-generating systems in the endothelium, namely uncoupled endothelial nitric oxide synthase and NADPH oxidases.

A 21 day Daniel Fast improves selected biomarkers of antioxidant status and oxidative stress in men and women

BACKGROUND

Dietary modification via both caloric and nutrient restriction is associated with multiple health benefits, some of which are related to an improvement in antioxidant status and a decrease in the production of reactive oxygen species. The Daniel Fast is based on the Biblical book of Daniel, is commonly partaken for 21 days, and involves food intake in accordance with a stringent vegan diet. The purpose of the present study was to determine the effect of a 21 day Daniel Fast on biomarkers of antioxidant status and oxidative stress.

METHODS

43 subjects (13 men; 30 women; 35 ± 1 yrs; range: 20-62 yrs) completed a 21 day Daniel Fast following the guidelines provided by investigators. Subjects reported to the lab in a 12 hour post-absorptive state both pre fast (day 1) and post fast (day 22). At each visit, blood was collected for determination of malondialdehyde (MDA), hydrogen peroxide (H2O2), nitrate/nitrite (NOx), Trolox Equivalent Antioxidant Capacity (TEAC), and Oxygen Radical Absorbance Capacity (ORAC). Subjects recorded dietary intake during the 7 day period immediately prior to the fast and during the final 7 days of the fast.

RESULTS

A decrease was noted in MDA (0.66 ± 0.0.03 vs. 0.56 ± 0.02 μmol L-1; p = 0.004), while H2O2 demonstrated a trend for lowering (4.42 ± 0.32 vs. 3.78 ± 0.21 μmol L-1; p = 0.074). Both NOx (18.79 ± 1.92 vs. 26.97 ± 2.40 μmol L-1; p = 0.003) and TEAC (0.47 ± 0.01 vs. 0.51 ± 0.01 mmol L-1; p = 0.001) increased from pre to post fast, while ORAC was unchanged (5243 ± 103 vs. 5249 ± 183 μmol L-1 TE; p = 0.974). As expected, multiple differences in dietary intake were noted (p < 0.05), including a reduction in total calorie intake (2185 ± 94 vs. 1722 ± 85).

CONCLUSION

Modification of dietary intake in accordance with the Daniel Fast is associated with an improvement in selected biomarkers of antioxidant status and oxidative stress, including metabolites of nitric oxide (i.e., NOx).

Effects of Yinian Jiangya Decoction containing serum on cytokines secretion of vascular endothelium of spontaneously hypertensive rats

OBJECTIVE

To observe the effects of Yinian Jiangya Decoction (YNJYD) on cytokine secretion in spontaneoulsy hypertensive rats (SHRs) vascular endothelium.

METHODS

Aortic endothelial cells (ECs) were primarily cultured from SHRs; male SD rats were treated with different doses (high, medium, and low doses) of YNJYD, the blood was collected on the 21st day, and then, the serum was separated. ECs were cocultured with the serum for different time courses, and the culture supernatant concentrations of endothelin (ET)-1, nitric oxide (NO), tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitor (PAI-1) were determined by ABC-ELISA methods.

RESULTS

ET-1, NO, t-PA, and PAI-1 levels in endothelial cell culture supernatant were increased in a time-dependent manner; YNJYD could significantly elevate NO and t-PA expressions in ECs, while ET-1 and PAI-1 expressions were dramatically decreased; these effects of YNJYD were in a concentration-dependent manner.

CONCLUSION

The therapeutic effect of YNJYD on hypertension is attributed to its effect on regulating vessel dilation and blood coagulation, in which ET-1/NO and PAI-1/t-PA are two pairs of pivotal mediators.

Hydrogen sulfide and the vasculature: a novel vasculoprotective entity and regulator of nitric oxide bioavailability?

Hydrogen sulfide (H₂S) is a well known and pungent toxic gas that has recently been shown to be synthesised in man from the amino acids cystathionine, homocysteine and cysteine by at least two distinct enzymes; cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H₂S has emerged as a novel and increasingly important mediator in the cardiovascular system but delineating the precise physiology and pathophysiology of H₂S is proving to be complex and difficult to unravel with disparate findings reported with cell types, tissue types and animal species reported. Therefore, in this review we summarize the mechanisms by which H₂S has been proposed to regulate blood pressure and cardiac function, discuss the mechanistic discrepancies reported in the literature as well as the therapeutic potential of H₂S. We also examine the methods of H₂S detection in biological fluids, processes for H₂S removal and discuss the reported blood levels of H₂S in man and animal models of cardiovascular pathology. We also highlight the complex interaction of H₂S with nitric oxide in regulating cardiovascular function in health and disease.

Endothelial function impairment in chronic venous insufficiency: effect of some cardiovascular protectant agents

In segments of human varicose veins, endothelial function was assessed by measuring relaxation induced by acetylcholine in noradrenaline-precontracted preparations. In addition, concentration-response curves to acetylcholine were obtained before and after incubation with the arterial endothelium protectant agents captopril, losartan, troglitazone, pravastatin, or simvastatin. The antivaricose agent escin was also tested. Mean acetylcholine-induced relaxation of varicose venous rings was about 13%, approximately one third of that reported for control saphenous veins. Concentration-response curves to acetylcholine were ''u'' shaped, the result of endothelium-mediated relaxation at low concentrations, superseded by subsequent smooth muscle contractile responses. Relaxation was enhanced by the endothelium-protecting agents and by escin, troglitazone being the least, and simvastatin the most effective. It was concluded that endothelial dysfunction is present in varicose veins, that this anomaly can be reverted by cardiovascular protecting agents, and that it can play a role in the pathogenesis and treatment of chronic venous insufficiency.

Association of endothelial nitric oxide synthase Glu298Asp, 4b/a, and -786T>C gene variants with diabetic nephropathy

BACKGROUND

Nitric oxide (NO) produced by endothelial NO synthase (eNOS) mediates a wide range of processes, and abnormal NO production mediated diabetes complications, including diabetic nephropathy (DN). In view of their impact on eNOS activity, polymorphisms in eNOS gene were described as candidates for atherosclerosis and DN.

AIMS

We evaluated the association of -786T>C (promoter region), Glu298Asp (Exon 7), and 4b4a (Intron 4) polymorphisms in eNOS gene with Type 2 diabetes mellitus (T2DM) and DN by haplotype analysis.

SUBJECTS AND METHODS

Study subjects comprised 515 DN patients, 402 normoalbuminuric [diabetes with no nephropathy (DWN)] T2DM patients, and 748 healthy subjects. -786T>C and Glu298Asp genotyping were done by PCR-RFLP analysis.

RESULTS

Higher prevalence of mutant Asp298, 4a, and -786C alleles and homozygous Asp298/Asp298 and 4a/4a genotypes were seen in T2DM patients compared to healthy subjects, with increased Asp298/Asp298 seen in DN compared to DWN patients (P<.05). Three-loci haplotype analysis demonstrated significant association between eNOS variants and T2DM, with protective, neutral, T2DM, and DN-susceptible haplotypes identified, the latter including Asp298/4b/-786T and the Asp298/4a/-786C haplotypes that were present at higher frequencies among DN than among DWN patients. Multivariate regression analysis identified only Asp298/4a/-786T haplotype to be associated with DN (P=.047) after controlling for potential covariates.

CONCLUSION

Genetic variation at the eNOS locus is associated with T2DM. It can serve as a useful genetic marker of increased susceptibility to T2DM and its complications, including the risk of nephropathy.

Intermittent hypoxia: cause of or therapy for systemic hypertension?

During acute episodes of hypoxia, chemoreceptor-mediated sympathetic activity increases heart rate, cardiac output, peripheral resistance and systemic arterial pressure. However, different intermittent hypoxia paradigms produce remarkably divergent effects on systemic arterial pressure in the post-hypoxic steady state. The hypertensive effects of obstructive sleep apnea (OSA) vs. the depressor effects of therapeutic hypoxia exemplify this divergence. OSA, a condition afflicting 15-25% of American men and 5-10% of women, has been implicated in the pathogenesis of systemic hypertension and is a major risk factor for heart disease and stroke. OSA imposes a series of brief, intense episodes of hypoxia and hypercapnia, leading to persistent, maladaptive chemoreflex-mediated activation of the sympathetic nervous system which culminates in hypertension. Conversely, extensive evidence in animals and humans has shown controlled intermittent hypoxia conditioning programs to be safe, efficacious modalities for prevention and treatment of hypertension. This article reviews the pertinent literature in an attempt to reconcile the divergent effects of intermittent hypoxia therapy and obstructive sleep apnea on hypertension. Special emphasis is placed on research conducted in the nations of the former Soviet Union, where intermittent hypoxia conditioning programs are being applied therapeutically to treat hypertension in patients. Also reviewed is evidence regarding mechanisms of the pro- and anti-hypertensive effects of intermittent hypoxia.