Nitric oxide insufficiency and atherothrombosis

Antiphospholipid Syndrome: Thrombotic and Vascular Complications

Antiphospholipid syndrome is a rare, autoimmune thrombophilia defined by vascular thrombosis and pregnancy morbidity, in the setting of documented persistent antiphospholipid antibodies including the lupus anticoagulant, anticardiolipin antibodies, or anti-β2 glycoprotein I antibodies. The presence of antiphospholipid antibodies can be completely asymptomatic, or they can lead to clinical manifestations as severe as catastrophic antiphospholipid syndrome, which involves widespread coagulopathy over a very short period of time. The degree of risk associated with antiphospholipid syndrome depends on the characteristics of the antiphospholipid antibody profile and on the presence of additional thrombotic risk factors. The current standard treatment for unprovoked thrombosis is long-term warfarin. Treatment to prevent recurrent obstetric complications is low-dose aspirin and prophylactic heparin in pregnant patients. The use of direct oral anticoagulants in patients with antiphospholipid syndrome is still being debated. Their use is generally contraindicated, especially in high-risk patients, such as those with all 3 antiphospholipid antibodies present, but they may potentially be of some use in some low-risk patients.

Nitric Oxide Oxygenation Reactions of Cobalt-Peroxo and Cobalt-Nitrosyl Complexes

Here, we report a comparative study of nitric oxide oxidation (NOO) reactions of Co^III-peroxo (Co^III-O₂^2-) and Co-nitrosyl ({CoNO}⁸) complexes bearing the same N₄-donor ligand (HMTETA) framework. In this regard, we prepared and characterized two new [(HMTETA)Co^III(O₂^2-)]⁺ (2, S = 2) and [(HMTETA)Co(NO)]²⁺ (3, S = 1) complexes from [(HMTETA)Co^II(CH₃CN)₂]²⁺ (1). Both complexes (2 and 3) are characterized by different spectroscopic measurements, including their DFT-optimized structures. Complex 2 produces Co^II-nitrato [(HMTETA)Co^II(NO₃^-)]⁺ (Co^II-NO₃^-, 4) complex in the presence of NO. In contrast, when 3 reacted with a superoxide (O₂^•-) anion, it generated Co^II-nitrito [(HMTETA)Co^II(NO₂^-)]⁺ (Co^II-NO₂^-, 5) with O₂ evolution. Experiments performed using ^18/16O-labeled superoxide (¹⁸O₂^•-/¹⁶O₂^•-) showed that O₂ originated from the O₂^•- anion. Both the NOO reactions are believed to proceed via a presumed peroxynitrite (PN) intermediate. Although we did not get direct spectral evidence for the proposed PN species, the mechanistic investigation using 2,4-di-tert-butylphenol indirectly suggests the formation of a PN intermediate. Furthermore, tracking the source of the N-atom in the above NOO reactions using ¹⁵N-labeled nitrogen (¹⁵NO) revealed N-atoms in 4 (Co^II-¹⁵NO₃^-) and 5 (Co^II-¹⁵NO₂^-) derived from the ¹⁵NO moiety.

Why Intermolecular Nitric Oxide (NO) Transfer? Exploring the Factors and Mechanistic Aspects of NO Transfer Reaction

Small molecule activation & their transfer reactions in biological or catalytic reactions are greatly influenced by the metal-centers and the ligand frameworks. Here, we report the metal-directed nitric oxide (NO)...

Inflammation and Oxidative Stress: Potential Targets for Improving Prognosis After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) has a high mortality rate and causes long-term disability in many patients, often associated with cognitive impairment. However, the pathogenesis of delayed brain dysfunction after SAH is not fully understood. A growing body of evidence suggests that neuroinflammation and oxidative stress play a negative role in neurofunctional deficits. Red blood cells and hemoglobin, immune cells, proinflammatory cytokines, and peroxidases are directly or indirectly involved in the regulation of neuroinflammation and oxidative stress in the central nervous system after SAH. This review explores the role of various cellular and acellular components in secondary inflammation and oxidative stress after SAH, and aims to provide new ideas for clinical treatment to improve the prognosis of SAH.

Endothelial nitric oxide synthase polymorphism and venous thromboembolism: A meta-analysis of 9 studies involving 3993 subjects

BACKGROUND

Endothelial nitric oxide synthase (eNOS) polymorphism may influence the risk of venous thromboembolism (VTE). However, data from published studies with low statistical power are inconclusive. The present meta-analysis aimed to assess the relationship between eNOS polymorphism and the risk of VTE.

METHOD

Case-control studies evaluating the association between the eNOS polymorphism and VTE were searched in PubMed, Embase, Web of Science, Google Scholar, Wanfang, Chinese National Knowledge Infrastructure (CNKI), the Chongqing VIP Chinese Science and Technology Periodical Database (VIP), and Chinese Biomedical Literature Database (CBM).

RESULTS

A total of 1588 cases and 2405 controls from 9 studies were included in the analysis. The results showed that eNOS G894T polymorphism was related to VTE susceptibility and the difference was statistically significant [T vs G: OR = 1.41, 95% CI (1.13, 1.75), P = 0.002; TT + GG vs TG: OR = 0.71, 95% CI (0.60, 0.84), P = 0.000; TT + TG vs GG: OR = 1.45, 95% CI (1.23, 1.70), P = 0.000]. Additionally, eNOS Intron 4 VNTR polymorphism was related to VTE susceptibility and the difference was statistically significant [4b4b vs 4a4a + 4a4b: OR = 2.77, 95% CI (1.01, 7.61), P = 0.048].

CONCLUSION

ENOS G894T and eNOS Intron 4 VNTR polymorphisms were associated with VTE susceptibility, especially in Asian populations. However, multicenter studies with larger samples should be conducted to further clarify this association and verify our findings.

Priapism in sickle cell disease: Associations between NOS3 and EDN1 genetic polymorphisms and laboratory biomarkers

Priapism is a urologic emergency characterized by an uncontrolled, persistent and painful erection in the absence of sexual stimulation, which can lead to penile fibrosis and impotence. It is highly frequent in sickle cell disease (SCD) associated with hemolytic episodes. Our aim was to investigate molecules that may participate in the regulation of vascular tone. Eighty eight individuals with SCD were included, of whom thirty-seven reported a history of priapism. Priapism was found to be associated with alterations in laboratory biomarkers, as well as lower levels of HbF. Patients with sickle cell anemia using hydroxyurea and those who received blood products seemed to be less affected by priapism. Multivariate analysis suggested that low HbF and NOm were independently associated with priapism. The frequency of polymorphisms in genes NOS3 and EDN1 was not statistically significant between the studied groups, and the presence of the variant allele was not associated with alterations in NOm and ET-1 levels in patients with SCD. The presence of the variant allele in the polymorphisms investigated did not reveal any influence on the occurrence priapism. Future studies involving larger samples, as well as investigations including patients in priapism crisis, could contribute to an enhanced understanding of the development of priapism in SCD.

Effects of nitrite and far-red light on coagulation

Nitric oxide, NO, has been explored as a therapeutic agent to treat thrombosis. In particular, NO has potential in treating mechanical device-associated thrombosis due to its ability to reduce platelet activation and due to the central role of platelet activation and adhesion in device thrombosis. Nitrite is a unique NO donor that reduces platelet activation in that it's activity requires the presence of red blood cells whereas NO activity of other NO donors is blunted by red blood cells. Interestingly, we have previously shown that red blood cell mediated inhibition of platelet activation by adenosine diphosophate (ADP) is dramatically enhanced by illumination with far-red light that is likely due to photolysis of red cell surface bound NO congeners. We now report the effects of nitrite, far-red light, and their combination on several measure of blood coagulation using a variety of agonists. We employed turbidity assays in platelet rich plasma, platelet activation using flow cytometry analysis of a fluorescently labeled antibody to the activated platelet fibrinogen binding site, multiplate impedance-based platelet aggregometry, and assessment of platelet adhesion to collagen coated flow-through microslides. In all cases, the combination of far-red light and nitrite treatment decreased measures of coagulation, but in some cases mono-treatment with nitrite or light alone had no effect. Perhaps most relevant to device thrombosis, we observed that platelet adhesions was inhibited by the combination of nitrite and light treatment while nitrite alone and far-red light alone trended to decrease adhesion, but the results were mixed. These results support the potential of combined far-red light and nitrite treatment for preventing thrombosis in extra-corporeal or shallow-tissue depth devices where the far-red light can penetrate. Such a combined treatment could be advantageous due to the localized treatment afforded by far-red light illumination with minimal systemic effects. Given the role of thrombosis in COVID 19, application to treatment of patients infected with SARS Cov-2 might also be considered.

Acute platelet response to aneurysmal subarachnoid hemorrhage depends on severity and distribution of bleeding: an observational cohort study

Microthrombosis after aneurysmal subarachnoid hemorrhage (aSAH) is considered to initiate neuroinflammation, vessel remodeling, and blood-brain barrier leakage. We aimed to verify the hypothesis that the intensity of thrombogenicity immediately after aSAH depends on the amount and distribution of extravasated blood. This observational cohort study included 37 consecutive aSAH patients admitted no longer than 24 h after ictus. Volumes of subarachnoid and intraventricular hemorrhages as well as the Subarachnoid Hemorrhage Early Brain Edema Scale (SEBES) score were calculated in each case. Platelet system status was described by platelet count (PLT), mean platelet volume (MPV), MPV to PLT ratio, and platelet-large cell ratio (P-LCR). Median hemorrhage volume amounted to 11.4 ml (interquartile range 2.8-26.8 ml). Patients with more severe hemorrhage had lower PLT and higher MPV to PLT ratio (ρ =  - 0.49, p < .002; ρ = 0.50, p < .002, respectively). PLT decreased by 2.80 G/l per 1 ml of hemorrhage volume (95% CL 1.30-4.30, p < .001). Further analysis revealed that intraventricular hemorrhage volume was associated with P-LCR and MPV (ρ = 0.34, p < .039; ρ = 0.33, p < .048, respectively), whereas SAH volume with PLT and MPV:PLT ratio (ρ =  - 0.40, p < .013; ρ = 0.41, p < .013, respectively). The odds of unfavorable neurological outcome increased 3.95 times per 1 fl of MPV (95% CI 1.19-13.12, p < .025). MPV was independently correlated with SEBES (ρ = 0.44, p < .006). This study demonstrated that the extent and distribution of aneurysmal subarachnoid hemorrhage are related to different types of acute platelet response, which may be interpreted as local and systemic thrombogenicity. Increased mean platelet volume measured in the acute phase of aSAH may identify patients at risk for unfavorable neurological outcomes and may serve as a marker of early brain injury.

A Brief Overview on Antioxidant Activity Determination of Silver Nanoparticles

Our objective in this review article is to find out relevant information about methods of determination of antioxidant activity of silver nanoparticles. There are many studies dealing with mentioned problem and herein we summarize the knowledge about methods evaluating the antioxidant activity of silver nanoparticles reported so far. Many authors declare better antioxidant activity of silver nanoparticles compared to the extract used for synthesis of them. In this review, we focused on methods of antioxidant activity determination in detail to find out novel and perspective techniques to solve the general problems associated with the determination of antioxidant activity of silver nanoparticles.

A Review of Hematoma Components Clearance Mechanism After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a complicated clinical syndrome, which is caused by several kinds of cerebrovascular disorders, with high morbidity, disability and mortality rate. In recent years, several studies have shown that early brain injury (EBI) is an important factor leading to the poor prognosis of SAH. A major cause of EBI has been attributed that hematoma components invade into the brain parenchyma, resulting in neuronal cell death. Therefore, the clearance of hematoma components is essential in the clinical outcome of patients after SAH. Here, in the review, we provide a summary of the current known hematoma components clearance mechanisms and simultaneously propose a new hypothesis for hematoma components clearance.

Nitric oxide dioxygenation (NOD) reactions of CoIII-peroxo and NiIII-peroxo complexes: NODversusNO activation

A comparative study of “nitric oxide dioxygenationversusdioxygen or nitric oxide activation”.

Haemoglobin scavenging in intracranial bleeding: biology and clinical implications

Haemoglobin is released into the CNS during the breakdown of red blood cells after intracranial bleeding. Extracellular free haemoglobin is directly neurotoxic. Haemoglobin scavenging mechanisms clear haemoglobin and reduce toxicity; these mechanisms include erythrophagocytosis, haptoglobin binding of haemoglobin, haemopexin binding of haem and haem oxygenase breakdown of haem. However, the capacity of these mechanisms is limited in the CNS, and they easily become overwhelmed. Targeting of haemoglobin toxicity and scavenging is, therefore, a rational therapeutic strategy. In this Review, we summarize the neurotoxic mechanisms of extracellular haemoglobin and the peculiarities of haemoglobin scavenging pathways in the brain. Evidence for a role of haemoglobin toxicity in neurological disorders is discussed, with a focus on subarachnoid haemorrhage and intracerebral haemorrhage, and emerging treatment strategies based on the molecular pathways involved are considered. By focusing on a fundamental biological commonality between diverse neurological conditions, we aim to encourage the application of knowledge of haemoglobin toxicity and scavenging across various conditions. We also hope that the principles highlighted will stimulate research to explore the potential of the pathways discussed. Finally, we present a consensus opinion on the research priorities that will help to bring about clinical benefits.

Antioxidant and antihyperlipidemic activity of Costus speciosus against atherogenic diet-induced hyperlipidemia in rabbits

OBJECTIVE

An extract of Costus speciosus (CSE), a herb widely used in folk medicine, was evaluated for its antioxidant, antihyperlipidemic and ameliorating effects on histopathological changes in atherogenic rabbits.

METHODS

Twenty-four male rabbits (Oryctolagus cuniculus) were divided into 4 groups. Three groups were fed a diet containing 3% saturated fat and 1.3% cholesterol for 40 d. One of these was sacrificed on the 40th day and was called the pathogenic (P) group; the other two groups received treatment for another 30 d as follows: one received 0.8 g/(kg·d) of CSE and the other was given 0.01 g/(kg·d) of simvastatin. The normal group was sacrificed on the 70th day and used as a control.

RESULTS

CSE showed radical-scavenging ability. Administration of CSE for a 30-day period resulted in a significant decrease in total cholesterol, triacylglycerol, low-density lipoprotein and aspartate aminotransferase compared to the P group, while levels of hemoglobin, packed corpuscular volume and red blood cells were elevated. With respect to studies performed on the heart, a decrease in malondialdehyde and an increase in reduced glutathione were noted. Total protein increased in the liver, heart and aorta after treatment with CSE and also a marked improvement in histopathological parameters was demonstrated.

CONCLUSION

The present findings indicate that the C. speciosus rhizome possesses antiatherogenic and antioxidant properties which may provide protective effects against oxidative stress in atherosclerotic rabbits.

Association between eNOS Gene Polymorphism (T786C and VNTR) and Sickle Cell Disease Patients in Ghana

Endothelial nitric oxide synthase (eNOS) variants have been found to be associated with several vascular disorders as well as the pathogenesis of sickle cell disease (SCD) complications such as vaso-occlusive crises (VOC). Studies on eNOS gene variants among SCD patients are rare in Ghana and several other African countries. The current study aimed to determine a possible association between variants of the eNOS gene (variable number of tandem repeats in intron 4 and T786C) in SCD complications among Ghanaian patients. This was a cross-sectional study involving 89 HbSS patients with complications and 46 HbSS patients without complications. Genomic DNA was extracted from leukocytes in the buffy coat and separated from collected whole blood samples of the study participants. PCR amplification, followed by restriction fragment length polymorphism (RFLP) was used to genotype T786C (rs2070744) variants. Variable number of tandem repeats (VNTR) in intron 4 was genotyped by PCR and direct electrophoresis. There was a significant difference in the genotype frequency of the T786C variant between HbSS patients with complications and those without complications (p = 0.0165). However, there was no significant difference in the VNTR intron 4 variant of the eNOS gene between patients with complications and those without complications (p > 0.05). The study shows an association between the eNOS gene variant (T786C) and complications in SCD.

Implication of the Kallikrein-Kinin system in neurological disorders: Quest for potential biomarkers and mechanisms

Neurological disorders represent major health concerns in terms of comorbidity and mortality worldwide. Despite a tremendous increase in our understanding of the pathophysiological processes involved in disease progression and prevention, the accumulated knowledge so far resulted in relatively moderate translational benefits in terms of therapeutic interventions and enhanced clinical outcomes. Aiming at specific neural molecular pathways, different strategies have been geared to target the development and progression of such disorders. The kallikrein-kinin system (KKS) is among the most delineated candidate systems due to its ubiquitous roles mediating several of the pathophysiological features of these neurological disorders as well as being implicated in regulating various brain functions. Several experimental KKS models revealed that the inhibition or stimulation of the two receptors of the KKS system (B1R and B2R) can exhibit neuroprotective and/or adverse pathological outcomes. This updated review provides background details of the KKS components and their functions in different neurological disorders including temporal lobe epilepsy, traumatic brain injury, stroke, spinal cord injury, Alzheimer's disease, multiple sclerosis and glioma. Finally, this work will highlight the putative roles of the KKS components as potential neurotherapeutic targets and provide future perspectives on the possibility of translating these findings into potential clinical biomarkers in neurological disease.

Unique Contribution of Haptoglobin and Haptoglobin Genotype in Aneurysmal Subarachnoid Hemorrhage

Survivors of cerebral aneurysm rupture are at risk for significant morbidity and neurological deficits. Much of this is related to the effects of blood in the subarachnoid space which induces an inflammatory cascade with numerous downstream consequences. Recent clinical trials have not been able to reduce the toxic effects of free hemoglobin or improve clinical outcome. One reason for this may be the inability to identify patients at high risk for neurologic decline. Recently, haptoglobin genotype has been identified as a pertinent factor in diabetes, sickle cell, and cardiovascular disease, with the Hp 2-2 genotype contributing to increased complications. Haptoglobin is a protein synthesized by the liver that binds free hemoglobin following red blood cell lysis, and in doing so, prevents hemoglobin induced toxicity and facilitates clearance. Clinical studies in patients with subarachnoid hemorrhage indicate that Hp 2-2 patients may be a high-risk group for hemorrhage related complications and poor outcome. We review the relevance of haptoglobin in subarachnoid hemorrhage and discuss the effects of genotype and expression levels on the known mechanisms of early brain injury (EBI) and cerebral ischemia after aneurysm rupture. A better understanding of haptoglobin and its role in preventing hemoglobin related toxicity should lead to novel therapeutic avenues.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Genetic risk factors for restenosis after percutaneous coronary intervention in Kazakh population

BACKGROUND

After coronary stenting, the risk of developing restenosis is from 20 to 35 %. The aim of the present study is to investigate the association of genetic variation in candidate genes in patients diagnosed with restenosis in the Kazakh population.

METHODS

Four hundred fifty-nine patients were recruited to the study; 91 patients were also diagnosed with diabetes and were excluded from the sampling. DNA was extracted with the salting-out method. The patients were genotyped for 53 single-nucleotide polymorphisms. Genotyping was performed on the QuantStudio 12K Flex (Life Technologies). Differences in distribution of BMI score among different genotype groups were compared by analysis of variance (ANOVA). Also, statistical analysis was performed using R and PLINK v.1.07. Haplotype frequencies and LD measures were estimated by using the software Haploview 4.2.

RESULTS

A logistic regression analysis found a significant difference in restenosis rates for different genotypes. FGB (rs1800790) is significantly associated with restenosis after stenting (OR = 2.924, P = 2.3E-06, additive model) in the Kazakh population. CD14 (rs2569190) showed a significant association in the additive (OR = 0.08033, P = 2.11E-09) and dominant models (OR = 0.05359, P = 4.15E-11). NOS3 (rs1799983) was also highly associated with development of restenosis after stenting in additive (OR = 20.05, P = 2.74 E-12) and recessive models (OR = 22.24, P = 6.811E-10).

CONCLUSIONS

Our results indicate that FGB (rs1800790), CD14 (rs2569190), and NOS3 (rs1799983) SNPs could be genetic markers for development of restenosis in Kazakh population. Adjustment for potential confounder factor BMI gave almost the same results.

New strategies for the treatment of pulmonary hypertension in sickle cell disease : the rationale for arginine therapy

Nitric oxide (NO) is inactivated in sickle cell disease (SCD), while bioavailability of arginine, the substrate for NO synthesis, is diminished. Impaired NO bioavailability represents the central feature of endothelial dysfunction, and is a key factor in the pathophysiology of SCD. Inactivation of NO correlates with the hemolytic rate and is associated with erythrocyte release of cell-free hemoglobin and arginase during hemolysis. Accelerated consumption of NO is enhanced further by the inflammatory environment of oxidative stress that exists in SCD. Based upon its critical role in mediating vasodilation and cell growth, decreased NO bioavailability has also been implicated in the pathogenesis of pulmonary arterial hypertension (PHT). Secondary PHT is a common life-threatening complication of SCD that also occurs in most hereditary and chronic hemolytic disorders. Aberrant arginine metabolism contributes to endothelial dysfunction and PHT in SCD, and is strongly associated with prospective patient mortality. The central mechanism responsible for this metabolic disorder is enhanced arginine turnover, occurring secondary to enhanced plasma arginase activity. This is consistent with a growing appreciation of the role of excessive arginase activity in human diseases, including asthma and PHT. Decompartmentalization of hemoglobin into plasma consumes endothelial NO and thus drives a metabolic requirement for arginine, whose bioavailability is further limited by arginase activity. New treatments aimed at maximizing both arginine and NO bioavailability through arginase inhibition, suppression of hemolytic rate, or oral arginine supplementation may represent novel therapeutic strategies.

Chemical Changes in Nonthermal Plasma-Treated N-Acetylcysteine (NAC) Solution and Their Contribution to Bacterial Inactivation

In continuation of our previous reports on the broad-spectrum antimicrobial activity of atmospheric non-thermal dielectric barrier discharge (DBD) plasma treated N-Acetylcysteine (NAC) solution against planktonic and biofilm forms of different multidrug resistant microorganisms, we present here the chemical changes that mediate inactivation of Escherichia coli. In this study, the mechanism and products of the chemical reactions in plasma-treated NAC solution are shown. UV-visible spectrometry, FT-IR, NMR, and colorimetric assays were utilized for chemical characterization of plasma treated NAC solution. The characterization results were correlated with the antimicrobial assays using determined chemical species in solution in order to confirm the major species that are responsible for antimicrobial inactivation. Our results have revealed that plasma treatment of NAC solution creates predominantly reactive nitrogen species versus reactive oxygen species, and the generated peroxynitrite is responsible for significant bacterial inactivation.

The effect of prolonged dietary nitrate supplementation on atherosclerosis development

BACKGROUND

Short term dietary nitrate or nitrite supplementation has nitric oxide (NO)-mediated beneficial effects on blood pressure and inflammation and reduces mitochondrial oxygen consumption, possibly preventing hypoxia. As these processes are implicated in atherogenesis, dietary nitrate was hypothesized to prevent plaque initiation, hypoxia and inflammation.

AIMS

Study prolonged nitrate supplementation on atherogenesis, hypoxia and inflammation in low density lipoprotein receptor knockout mice (LDLr(-/-)).

METHODS

LDLr(-/-) mice were administered sodium-nitrate or equimolar sodium-chloride in drinking water alongside a western-type diet for 14 weeks to induce atherosclerosis. Plasma nitrate, nitrite and hemoglobin-bound nitric oxide were measured by chemiluminescence and electron parametric resonance, respectively.

RESULTS

Plasma nitrate levels were elevated after 14 weeks of nitrate supplementation (NaCl: 40.29 ± 2.985, NaNO3: 78.19 ± 6.837, p < 0.0001). However, prolonged dietary nitrate did not affect systemic inflammation, hematopoiesis, erythropoiesis and plasma cholesterol levels, suggesting no severe side effects. Surprisingly, neither blood pressure, nor atherogenesis were altered. Mechanistically, plasma nitrate and nitrite were elevated after two weeks (NaCl: 1.0 ± 0.2114, NaNO3: 3.977 ± 0.7371, p < 0.0001), but decreased over time (6, 10 and 14 weeks). Plasma nitrite levels even reached baseline levels at 14 weeks (NaCl: 0.7188 ± 0.1072, NaNO3: 0.9723 ± 0.1279 p = 0.12). Also hemoglobin-bound NO levels were unaltered after 14 weeks. This compensation was not due to altered eNOS activity or conversion into peroxynitrite and other RNI, suggesting reduced nitrite formation or enhanced nitrate/nitrite clearance.

CONCLUSION

Prolonged dietary nitrate supplementation resulted in compensation of nitrite and NO levels and did not affect atherogenesis or exert systemic side effects.

Stimulation of nitric oxide production contributes to the antiplatelet and antithrombotic effect of new peptide pENW (pGlu-Asn-Trp)

INTRODUCTION

New peptide pGlu-Asn-Trp (pENW), initially extracted from snake venom, significantly attenuates the formation of arterial and venous thrombi in vivo, and has modest in-vitro antiplatelet activity. This study was designed to investigate the underlying mechanisms.

METHODS

The rat carotid thrombosis model induced by FeCl3 was established to evaluate the antithrombotic activity of pENW. The effects of pENW on the production of nitric oxide (NO), as well as the expression and activity of endothelial nitric oxide synthase (eNOS), were determined. The vasorelaxant effect of pENW was evaluated using isolated rat aortic rings in the absence or presence of N(G)-nitro-L-arginine methyl ester (L-NAME, eNOS inhibitor). Furthermore, the in-vitro antiplatelet activity of pENW was investigated with the addition of sodium nitroprusside (SNP, NO donor) and/or L-NAME to further prove the role of NO and eNOS in the inhibitory effect of pENW on platelet aggregation.

RESULTS

In vivo, pENW inhibited thrombus formation induced by endothelial injury in a dose-dependent manner, with a significantly prolonged time to the occurrence of arterial occlusion. It was shown that pENW offered protection for blood vessels from oxidative injury. pENW significantly increased NO production in rats treated with pENW at 4 or 2mg/kg body weight. Furthermore, the production of NO from the cultured vascular endothelial cells was increased with the treatment of 10(-4)M and 10(-5)M pENW; pENW also enhanced eNOS expression and activity both in vivo and in vitro, and elicited a concentration-dependent vasorelaxation which was significantly inhibited by L-NAME. Notably, pENW inhibited ADP-induced platelet aggregation, and the inhibition was more significant in the presence of NO. The inhibition of platelet aggregation by pENW was significantly abolished by L-NAME.

CONCLUSIONS

The in-vivo antiplatelet and antithrombotic effects of pENW are at least partly mediated by the increased production of endogenous NO via up-regulation and stimulation of eNOS. The findings suggest that pENW could potentially be developed as a novel therapeutic agent in the treatment of platelet-driven disorders.

Endothelial nitric oxide synthase gene intron 4 variable number tandem repeat polymorphism in β-thalassemia major: relation to cardiovascular complications

Endothelial nitric oxide synthase (eNOS), an enzyme that generates nitric oxide, is a major determinant of endothelial function. Several eNOS gene polymorphisms have been reported as 'susceptibility genes' in various human diseases states, including cardiovascular, pulmonary and renal diseases. We studied the 27-base pair tandem repeat polymorphism in intron 4 of eNOS gene in 60 β-thalassemia major (β-TM) patients compared with 60 healthy controls and assessed its role in subclinical atherosclerosis and vascular complications. Patients were evaluated stressing on transfusion history, splenectomy, thrombotic events, echocardiography and carotid intima-media thickness (CIMT). Analysis of eNOS intron 4 gene polymorphism was performed by PCR. No significant difference was found between β-TM patients and controls with regard to the distribution of eNOS4 alleles or genotypes. The frequency of eNOS4a allele (aa and ab genotypes) was significantly higher in β-TM patients with pulmonary hypertension or cardiomyopathy. Logistic regression analysis revealed that eNOS4a allele was an independent risk factor for pulmonary hypertension in β-TM patients [odds ratio (OR) 2.2, 95% confidence interval (95% CI) 1.19-5.6; P < 0.001]. We suggest that eNOS intron 4 gene polymorphism is related to endothelial dysfunction and subclinical atherosclerosis and could be a possible genetic marker for prediction of increased susceptibility to cardiovascular complications.

Antiphospholipid antibodies attenuate endothelial repair and promote neointima formation in mice

Background

Antiphospholipid syndrome patients have antiphospholipid antibodies (aPLs) that promote thrombosis, and they have increased cardiovascular disease risk. Although the basis for the thrombosis has been well delineated, it is not known why antiphospholipid syndrome patients also have an increased prevalence of nonthrombotic vascular occlusion. The aims of this work were to determine if aPLs directly promote medial hypertrophy or neointima formation in mice and to identify the underlying mechanisms.

Methods and Results

Medial hypertrophy and neointima formation invoked by carotid artery endothelial denudation were evaluated in mice administered normal human IgG or aPLs. While aPLs had no effect on medial hypertrophy, they caused exaggerated neointima development. This was related to an aPL‐induced impairment in reendothelialization post denudation, and scratch assays in cell culture revealed that there are direct effects of aPLs on endothelium that retard cell migration. Further experiments showed that aPL antagonism of endothelial migration and repair is mediated by antibody recognition of β2‐glycoprotein I, apolipoprotein E receptor 2, and a decline in bioavailable NO. Consistent with these mechanisms, the adverse impacts of aPLs on reendothelialization and neointima formation were fully prevented by the NO donor molsidomine.

Conclusions

APLs blunt endothelial repair, and there is related aPL‐induced exaggeration in neointima formation after endothelial injury in mice. The initiating process entails NO deficiency mediated by β2‐glycoprotein I recognition by aPLs and apolipoprotein E receptor 2. The modulation of endothelial apolipoprotein E receptor 2 function or NO bioavailability may represent new interventions to prevent the nonthrombotic vascular occlusion and resulting cardiovascular disorders that afflict antiphospholipid syndrome patients.

Regulation of soluble guanylate cyclase by matricellular thrombospondins: implications for blood flow

Nitric oxide (NO) maintains cardiovascular health by activating soluble guanylate cyclase (sGC) to increase cellular cGMP levels. Cardiovascular disease is characterized by decreased NO-sGC-cGMP signaling. Pharmacological activators and stimulators of sGC are being actively pursued as therapies for acute heart failure and pulmonary hypertension. Here we review molecular mechanisms that modulate sGC activity while emphasizing a novel biochemical pathway in which binding of the matricellular protein thrombospondin-1 (TSP1) to the cell surface receptor CD47 causes inhibition of sGC. We discuss the therapeutic implications of this pathway for blood flow, tissue perfusion, and cell survival under physiologic and disease conditions.

Interfacial residues promote an optimal alignment of the catalytic center in human soluble guanylate cyclase: heterodimerization is required but not sufficient for activity

Soluble guanylate cyclase (sGC) plays a central role in the cardiovascular system and is a drug target for the treatment of pulmonary hypertension. While the three-dimensional structure of sGC is unknown, studies suggest that binding of the regulatory domain to the catalytic domain maintains sGC in an autoinhibited basal state. The activation signal, binding of NO to heme, is thought to be transmitted via the regulatory and dimerization domains to the cyclase domain and unleashes the full catalytic potential of sGC. Consequently, isolated catalytic domains should show catalytic turnover comparable to that of activated sGC. Using X-ray crystallography, activity measurements, and native mass spectrometry, we show unambiguously that human isolated catalytic domains are much less active than basal sGC, while still forming heterodimers. We identified key structural elements regulating the dimer interface and propose a novel role for residues located in an interfacial flap and a hydrogen bond network as key modulators of the orientation of the catalytic subunits. We demonstrate that even in the absence of the regulatory domain, additional sGC domains are required to guide the appropriate conformation of the catalytic subunits associated with high activity. Our data support a novel regulatory mechanism whereby sGC activity is tuned by distinct domain interactions that either promote or inhibit catalytic activity. These results further our understanding of heterodimerization and activation of sGC and open additional drug discovery routes for targeting the NO–sGC–cGMP pathway via the design of small molecules that promote a productive conformation of the catalytic subunits or disrupt inhibitory domain interactions.

Genetic polymorphism of NOS3 with susceptibility to deep vein thrombosis after orthopedic surgery: a case-control study in Chinese Han population

Deep vein thrombosis is one of the common complications of orthopedic surgery. Studies indicated that genetic factors played a considerable role in the pathogenesis of deep vein thrombosis. Endothelial nitric oxide synthase which encoded by nitric oxide synthase 3 (NOS3), can generate nitric oxide in endothelial cells. As a predominant regulator for vascular homeostasis, nitric oxide might be involved in the pathogenesis of thrombosis. It had been proved that the NOS3 polymorphism (rs1799983) was associated with the development of cardiovascular diseases. Our objective was to evaluate the association between the NOS3 polymorphism (rs1799983) and deep vein thrombosis after orthopedic surgery in Chinese Han population. The polymorphism was genotyped in 224 subjects with deep vein thrombosis after orthopedic surgery and 580 controls. Allele and genotype frequencies were compared between subjects with deep vein thrombosis and control subjects. The allele and genotype frequencies of the NOS3 polymorphism (rs1799983) were significantly different between subjects with deep vein thrombosis and control subjects. There were also significant differences when the subjects were stratified by gender, surgery type and hypertension status. These findings suggested that the NOS3 polymorphism (rs1799983) was associated with susceptibility to the deep vein thrombosis after orthopedic surgery in Chinese Han population, and NOS3 might play a role in the development of deep vein thrombosis after orthopedic surgery.

Thrombosis in paroxysmal nocturnal hemoglobinuria

The most frequent and feared complication of paroxysmal nocturnal hemoglobinuria (PNH) is thrombosis. Recent research has demonstrated that the complement and coagulation systems are closely integrated with each influencing the activity of the other to the extent that thrombin itself has recently been shown to activate the alternative pathway of complement. This may explain some of the complexity of the thrombosis in PNH. In this review, the recent changes in our understanding of the pathophysiology of thrombosis in PNH, as well as the treatment of thrombosis, will be discussed. Mechanisms explored include platelet activation, toxicity of free hemoglobin, nitric oxide depletion, absence of other glycosylphosphatidylinositol-linked proteins such as urokinase-type plasminogen activator receptor and endothelial dysfunction. Complement inhibition with eculizumab has a dramatic effect in PNH and has a major impact in the prevention of thrombosis as well as its management in this disease.

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.

Regulation of Cell Signaling and Function by Endothelial Caveolins: Implications in Disease

Caveolae are cholesterol- and glycosphingolipid-rich omega-shaped invaginations of the plasma membrane that are very abundant in vascular endothelial cells and present in most cell types. Caveolins are the major coat protein components of caveolae. Multiple studies using knockout mouse, small interfering RNA, and cell-permeable peptide delivery approaches have significantly enhanced our understanding of the role of endothelial caveolae and caveolin-1 in physiology and disease. Several postnatal pulmonary and cardiovascular pathologies have been reported in caveolin-1 knockout mice, many of which have been recently rescued by selective re-expression of caveolin-1 in endothelium of these mice. A large body of experimental evidence mostly using caveolin-1 knockout mice suggests that, depending on the disease model, endothelial caveolin-1 may play either a protective or a detrimental role. For instance, physiological or higher expression levels of caveolin-1 in endothelium might be beneficial in such diseases as pulmonary hypertension, cardiac hypertrophy, or ischemic injury. On the other hand, endothelial caveolin-1 might contribute to acute lung injury and inflammation, atherosclerosis or pathological angiogenesis associated with inflammatory bowel disease. Moreover, depending on the specific model, endothelial caveolin-1 may either promote or suppress tumor-induced angiogenesis. In addition to overwhelming evidence for the role of endothelial caveolin-1, more recent studies also suggest that endothelial caveolin-2 could possibly play a role in pulmonary disease. The purpose of this review is to focus on how caveolin-1 expressed in endothelial cells regulates endothelial cell signaling and function. The review places particular emphasis on relevance to disease, including but not limited to Pulmonary and cardiovascular disorders as well as cancer. In addition to caveolin-1, possible importance of the less-studied endothelial caveolin-2 in pulmonary diseases will be also discussed.

Regulation of eNOS in caveolae

Caveolae are a specialized subset of lipid domains that are prevalent on the plasma membrane of endothelial cells. They compartmentalize signal transduction molecules which regulate multiple endothelial functions including the production of nitric oxide (NO) by the caveolae resident enzyme endothelial NO synthase (eNOS). eNOS is one of the three isoforms of the NOS enzyme which generates NO upon the conversion of L-arginine to L-citrulline and it is regulated by multiple mechanisms. Caveolin negatively impact eNOS activity through direct interaction with the enzyme. Circulating factors known to modify cardiovascular disease risk also influence the activity of the enzyme. In particular, high density lipoprotein cholesterol (HDL) maintains the lipid environment in caveolae, thereby promoting the retention and function of eNOS in the domain and it also causes direct activation of eNOS via scavenger receptor class B, Type I (SR-BI)-induced kinase signaling. Estrogen binding to estrogen receptors (ER) in caveolae also activates eNOS and this occurs through G protein coupling and kinase activation. Discrete domains within SR-BI and ER mediating signal initiation in caveolae have been identified. Counteracting the promodulatory actions of HDL and estrogen, C-reactive protein (CRP) antagonizes eNOS through FcγRIIB, which is the sole inhibitory receptor for IgG. Through their actions on eNOS, estrogen and CRP also regulate endothelial cell growth and migration. Thus, signaling events in caveolae invoked by known circulating cardiovascular disease risk factors have major impact on eNOS and endothelial cell phenotypes of importance to cardiovascular health and disease.

Nanocarriers for nitric oxide delivery

Nitric oxide (NO) is a promising pharmaceutical agent that has vasodilative, antibacterial, and tumoricidal effects. To study the complex and wide-ranging roles of NO and to facilitate its therapeutic use, a great number of synthetic compounds (e.g., nitrosothiols, nitrosohydroxyamines, N-diazeniumdiolates, and nitrosyl metal complexes) have been developed to chemically stabilize and release NO in a controlled manner. Although NO is currently being exploited in many biomedical applications, its use is limited by several factors, including a short half-life, instability during storage, and potential toxicity. Additionally, efficient methods of both localized and systemic in vivo delivery and dose control are needed. One strategy for addressing these limitations and thus increasing the utility of NO donors is based on nanotechnology.

New Insights into the Molecular Basis of the Antiphospholipid Syndrome

Antiphospholipid syndrome is an autoimmune disease characterized by the presence of circulating antiphospholipid antibodies (aPL) that promote thrombosis, pregnancy complications and cardiovascular diseases. Alterations in the function of vascular cells induced by aPL underlie these outcomes. This review will discuss recent findings that indicate a novel mechanism by which aPL antagonize endothelial cell production of nitric oxide and thereby promote thrombosis.

Antiphospholipid antibodies promote leukocyte-endothelial cell adhesion and thrombosis in mice by antagonizing eNOS via β2GPI and apoER2

In antiphospholipid syndrome (APS), antiphospholipid antibodies (aPL) binding to β2 glycoprotein I (β2GPI) induce endothelial cell-leukocyte adhesion and thrombus formation via unknown mechanisms. Here we show that in mice both of these processes are caused by the inhibition of eNOS. In studies of cultured human, bovine, and mouse endothelial cells, the promotion of monocyte adhesion by aPL entailed decreased bioavailable NO, and aPL fully antagonized eNOS activation by diverse agonists. Similarly, NO-dependent, acetylcholine-induced increases in carotid vascular conductance were impaired in aPL-treated mice. The inhibition of eNOS was caused by antibody recognition of domain I of β2GPI and β2GPI dimerization, and it was due to attenuated eNOS S1179 phosphorylation mediated by protein phosphatase 2A (PP2A). Furthermore, LDL receptor family member antagonism with receptor-associated protein (RAP) prevented aPL inhibition of eNOS in cell culture, and ApoER2-/- mice were protected from aPL inhibition of eNOS in vivo. Moreover, both aPL-induced increases in leukocyte-endothelial cell adhesion and thrombus formation were absent in eNOS-/- and in ApoER2-/- mice. Thus, aPL-induced leukocyte-endothelial cell adhesion and thrombosis are caused by eNOS antagonism, which is due to impaired S1179 phosphorylation mediated by β2GPI, apoER2, and PP2A. Our results suggest that novel therapies for APS can now be developed targeting these mechanisms.

Novel astaxanthin prodrug (CDX-085) attenuates thrombosis in a mouse model

BACKGROUND

Cardiovascular disease remains the leading cause of morbidity and premature mortality in most industrialized countries as well as in developing nations. A pro-oxidative state appears to promote and/or exacerbate vascular disease complications. Furthermore, a state of low-grade chronic inflammation can promote increased oxidative stress and lead to endothelial cell and platelet dysfunction ultimately contributing to thrombogenesis.

OBJECTIVES

In this study, the effect of a proprietary astaxanthin prodrug (CDX-085) on thrombus formation was investigated using a mouse model of arterial thrombosis. The influence of free astaxanthin, the active drug of CDX-085, on human endothelial cells and rat platelets was evaluated to investigate potential mechanisms of action.

METHODS AND RESULTS

Oral administration of CDX-085 (0.4% in chow, approximately 500 mg/kg/day) to 6-8 week old C57BL/6 male mice for 14 days resulted in significant levels of free astaxanthin in the plasma, liver, heart and platelets. When compared to control mice, the CDX-085 fed group exhibited significant increases in basal arterial blood flow and significant delays in occlusive thrombus formation following the onset of vascular endothelial injury. Primary human umbilical vein endothelial cells (HUVECs) and platelets isolated from Wistar-Kyoto rats treated with free astaxanthin demonstrated significantly increased levels of released nitric oxide (NO) and significantly decreased peroxynitrite (ONOO-) levels.

CONCLUSION

Observations of increased NO and decreased ONOO- levels in endothelial cells and platelets support a potential mechanism of action for astaxanthin (CDX-085 active drug). These studies support the potential of CDX-085 and its metabolite astaxanthin in the treatment or prevention of thrombotic cardiovascular complications.

Computational study of pulsatile blood flow in prototype vessel geometries of coronary segments

The spatial and temporal distributions of wall shear stress (WSS) in prototype vessel geometries of coronary segments are investigated via numerical simulation, and the potential association with vascular disease and specifically atherosclerosis and plaque rupture is discussed. In particular, simulation results of WSS spatio-temporal distributions are presented for pulsatile, non-Newtonian blood flow conditions for: (a) curved pipes with different curvatures, and (b) bifurcating pipes with different branching angles and flow division. The effects of non-Newtonian flow on WSS (compared to Newtonian flow) are found to be small at Reynolds numbers representative of blood flow in coronary arteries. Specific preferential sites of average low WSS (and likely atherogenesis) were found at the outer regions of the bifurcating branches just after the bifurcation, and at the outer-entry and inner-exit flow regions of the curved vessel segment. The drop in WSS was more dramatic at the bifurcating vessel sites (less than 5% of the pre-bifurcation value). These sites were also near rapid gradients of WSS changes in space and time - a fact that increases the risk of rupture of plaque likely to develop at these sites. The time variation of the WSS spatial distributions was very rapid around the start and end of the systolic phase of the cardiac cycle, when strong fluctuations of intravascular pressure were also observed. These rapid and strong changes of WSS and pressure coincide temporally with the greatest flexion and mechanical stresses induced in the vessel wall by myocardial motion (ventricular contraction). The combination of these factors may increase the risk of plaque rupture and thrombus formation at these sites.

Hyperoxia-induced lung injury in gamma-glutamyl transferase deficiency is associated with alterations in nitrosative and nitrative stress

gamma-Glutamyl transferase (GGT) regulates glutathione metabolism and cysteine supply. GGT inactivation in GGT(enu1) mice limits cysteine availability causing cellular glutathione deficiency. In lung, the resultant oxidant burden is associated with increased nitric oxide (NO) production, yet GGT(enu1) mice still exhibit higher mortality in hyperoxia. We hypothesized that NO metabolism is altered under severe oxidant stress and contributes to lung cellular injury and death. We compared lung injury, NO synthase (NOS) expression, nitrate/nitrite production, nitroso product formation, peroxynitrite accumulation, and cell death in wild-type and GGT(enu1) mice in normoxia and hyperoxia. The role of NOS activity in cell death was determined by NOS inhibition. Exposure of wild-type mice to hyperoxia caused increased lung injury, altered NO metabolism, and induction of cell death compared with normoxia, which was attenuated by NOS inhibition. Each of these lung injury indices were magnified in hyperoxia-exposed GGT(enu1) mice except nitrosation, which showed a diminished decrease compared with wild-type mice. NOS inhibition attenuated cell death only slightly, likely due to further exacerbation of oxidant stress. Taken together, these data suggest that apoptosis in hyperoxia is partially NO-dependent and reiterate the importance of cellular glutathione in lung antioxidant defense. Therefore, reduced denitrosylation of proteins, possibly resulting in impaired cellular repair, and excessive apoptotic cell death likely contribute to increased lung injury and mortality of GGT(enu1) mice in hyperoxia.

Identification of 13-hydroxy-14,15-epoxyeicosatrienoic acid as an acid-stable endothelium-derived hyperpolarizing factor in rabbit arteries

Arachidonic acid (AA) is metabolized by endothelial 15-lipoxygenase (15-LO) to several vasodilatory eicosanoids such as 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA) and its proposed unstable precursor 15-hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). In the present study, the acid-stable 13-hydroxy-trans-14,15-epoxy-eicosatrienoic acid (13-H-14,15-EETA) was identified and its vascular activities characterized. Rabbit aorta, mesenteric arteries, and the combination of 15-LO and cytochrome P450 2J2 converted AA to two distinct HEETA metabolites. The HEETA metabolites were resistant to acidic hydrolysis but were hydrolyzed by recombinant sEH to a more polar metabolite identified by mass spectrometry as 13,14,15-THETA. Mass spectrometric analyses and HPLC comigration identified the HEETAs as threo- and erythro-diastereomers of 13-H-trans-14,15-EETA. Erythro- and threo-diastereomers of 13-H-trans-14,15-EETA relaxed endothelium-denuded rabbit small mesenteric arteries with maximum relaxations of 22.6 +/- 6.0% and 8.6 +/- 4.3%, respectively. Apamin (10(-7) m) inhibited the relaxations to the erythro-isomer (maximum relaxation = 1.2 +/- 5.6%) and increasing [K(+)](o) from 4.6 to 30 mm blocked relaxations to both isomers. In cell-attached patches of mesenteric arterial smooth muscle cells (SMCs), erythro-13-H-trans-14,15-EETA (1-3 x 10(-6) m) increased mean open time of small conductance K(+) channels (13-14 pS) from 0.0007 +/- 0.0007 to 0.0053 +/- 0.0042. This activation was inhibited by apamin. The erythro, but not the threo, isomer blocked angiotensin II-stimulated aortic SMC migration. These studies demonstrate that 13-H-14,15-EETAs induces vascular relaxation via K(+) channel activation to cause SMC hyperpolarization. Thus, 13-H-14,15-EETA represents a new endothelial factor.

Endothelial Nitric Oxide Synthase Gene Intron 4 (VNTR) Polymorphism and Vascular Access Graft Thrombosis

Vascular access thrombosis is a leading cause of vascular access failure in hemodialysis patients. Thrombosis is a multifactorial condition and genetic makeup can affect thrombosis risk. We conducted a study to investigate for possible associations between ecNOS gene intron 4 variable-number tandem repeat (VNTR) polymorphism and thrombosis of polytetrafluoroethylene hemodialysis arteriovenous access grafts (AVG) in Turkish patients. Fifty-five patients with end-stage renal disease who had AVGs implanted between 2000 and 2002 and 167 healthy individuals representing our healthy population were enrolled in this prospective study. Each subject provided a venous blood sample from which DNA was isolated, and polymerase chain reaction analysis was done to identify genotypes (aa, bb, ab) for ecNOS gene intron 4 VNTR polymorphism. All grafts were placed in brachioaxillary position. The subjects were divided into two groups based on duration of graft patency. The thrombosis group (Group I) comprised 26 patients who developed AVG thrombosis in the first 12 months after placement. The no-thrombosis group (Group II) comprised 29 patients whose grafts remained patient for at least 12 months. The frequency of the aa genotype in Group I was significantly higher than that in Group II (p = .005). At 6, 12, and 24 months, the primary patency rates for the AVGs in patients with the aa genotype were significantly lower than the corresponding rates for the bb and ab genotype groupings (p = .01, p = .01 and p = .04 for the three respective time points; Kaplan-Meier). ecNOS gene intron 4 VNTR polymorphism is linked with the pathogenesis of vascular access thrombosis in Turkish patients undergoing hemodialysis.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

Regulation of nitric oxide signalling by thrombospondin 1: implications for anti-angiogenic therapies

In addition to long-term regulation of angiogenesis, angiogenic growth factor signalling through nitric oxide (NO) acutely controls blood flow and haemostasis. Inhibition of this pathway may account for the hypertensive and pro-thrombotic side effects of the vascular endothelial growth factor antagonists that are currently used for cancer treatment. The first identified endogenous angiogenesis inhibitor, thrombospondin 1, also controls tissue perfusion, haemostasis and radiosensitivity by antagonizing NO signalling. We examine the role of these and other emerging activities of thrombospondin 1 in cancer. Clarifying how endogenous and therapeutic angiogenesis inhibitors regulate vascular NO signalling could facilitate development of more selective inhibitors.

Endothelial dysfunction: the first step toward coronary arteriosclerosis

The endothelium causes relaxations of the underlying vascular smooth muscle, by releasing nitric oxide (NO). The endothelial cells also can evoke hyperpolarization of the vascular smooth muscle cells (endothelium-dependent hyperpolarizations, endothelium-derived hyperpolarizing factors-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive Gi and pertussis toxin-insensitive Gq coupling proteins. The endothelial release of NO is reduced in diabetes and hypertension. Arteries covered with regenerated endothelium lose the pertussis-toxin sensitive pathway for NO-release. This dysfunction favors vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. Endothelial cells also release endothelium-derived contracting factors (EDCF). Most endothelium-dependent contractions are mediated by vasoconstrictor prostanoids (endoperoxides and prostacyclin), which activate thromboxane-prostanoid (TP)-receptors of the underlying vascular smooth muscle cells. EDCF-mediated responses are augmented by aging, hypertension and diabetes. Thus, endothelial dysfunction is the first step toward coronary arteriosclerosis.

Nitric oxide and arginine dysregulation: a novel pathway to pulmonary hypertension in hemolytic disorders

Secondary pulmonary hypertension (PH) is emerging as one of the leading causes of mortality and morbidity in patients with hemolytic anemias such as sickle cell disease (SCD) and thalassemia. Impaired nitric oxide (NO) bioavailability represents the central feature of endothelial dysfunction, and is a major factor in the pathophysiology of PH. Inactivation of NO correlates with hemolytic rate and is associated with the erythrocyte release of cell-free hemoglobin, which consumes NO directly, and the simultaneous release of the arginine-metabolizing enzyme arginase, which limits bioavailability of the NO synthase substrate arginine during the process of intravascular hemolysis. Rapid consumption of NO is accelerated by oxygen radicals that exists in both SCD and thalassemia. A dysregulation of arginine metabolism contributes to endothelial dysfunction and PH in SCD, and is strongly associated with prospective patient mortality. The central mechanism responsible for this metabolic disorder is enhanced arginine turnover, occurring secondary to enhanced plasma arginase activity. This is consistent with a growing appreciation of the role of excessive arginase activity in human diseases, including asthma and pulmonary arterial hypertension. New treatments aimed at improving arginine and NO bioavailability through arginase inhibition, suppression of hemolytic rate, oral arginine supplementation, or use of NO donors represent potential therapeutic strategies for this common pulmonary complication of hemolytic disorders.

Adenylic dinucleotides produced by CD38 are negative endogenous modulators of platelet aggregation

Diadenosine 5',5'''-P1,P2-diphosphate (Ap2A) is one of the adenylic dinucleotides stored in platelet granules. Along with proaggregant ADP, it is released upon platelet activation and is known to stimulate myocyte proliferation. We have previously demonstrated synthesis of Ap2A and of two isomers thereof, called P18 and P24, from their high pressure liquid chromatography retention time, by the ADP-ribosyl cyclase CD38 in mammalian cells. Here we show that Ap2A and its isomers are present in resting human platelets and are released during thrombin-induced platelet activation. The three adenylic dinucleotides were identified by high pressure liquid chromatography through a comparison with the retention times and the absorption spectra of purified standards. Ap2A, P18, and P24 had no direct effect on platelet aggregation, but they inhibited platelet aggregation induced by physiological agonists (thrombin, ADP, and collagen), with mean IC50 values ranging between 5 and 15 microm. Moreover, the three dinucleotides did not modify the intracellular calcium concentration in resting platelets, whereas they significantly reduced the thrombin-induced intracellular calcium increase. Through binding to the purinergic receptor P2Y11, exogenously applied Ap2A, P18, and P24 increased the intracellular cAMP concentration and stimulated platelet production of nitric oxide, the most important endogenous antiaggregant. The presence of Ap2A, P18, and P24 in resting platelets and their release during thrombin-induced platelet activation at concentrations equal to or higher than the respective IC50 value on platelet aggregation suggest a role of these dinucleotides as endogenous negative modulators of aggregation.