Therapeutic potential of nitric oxide donors in the prevention and treatment of atherosclerosis

Linking endothelial dysfunction with endothelial cell activation

The thin layer of cells that lines the interior of blood vessels, known as the endothelium, plays a complex role in vascular biology. The endothelium mediates blood vessel tone, hemostasis, neutrophil recruitment, hormone trafficking, and fluid filtration. Endothelial dysfunction, as defined by a lack of NO, has been linked to a variety of disease states, including atherosclerosis, diabetes mellitus, coronary artery disease, hypertension, and hypercholesterolemia. Indeed, restoration of endothelial function is one of the earliest recognizable benefits of statin therapy. In 1995, James Liao and colleagues published a study in the JCI demonstrating that NO is a vascular protective factor that limits endothelial activation and prevents leukocyte adhesion to the vessel wall.

Beneficial effects of the active principle component of Korean cabbage kimchi via increasing nitric oxide production and suppressing inflammation in the aorta of apoE knockout mice

The present study investigated the effects of 3'-(4'-hydroxyl-3',5'-dimethoxyphenyl)propionic acid (HDMPPA), the active principle compound of kimchi, on vascular damage in the experimental atherosclerotic animal. HDMPPA was administrated by an intraperitoneal injection of 10 mg/kg per d for 8 weeks to apoE knockout (KO) mice with an atherogenic diet containing 1 % cholesterol, and its effects were compared with vehicle-treated control mice. HDMPPA increased NO content in the aorta, accompanied by a decrease in reactive oxygen species (ROS) concentration. Furthermore, in the HDMPPA-treated group, aortic endothelial NO synthase (eNOS) expression was up-regulated compared with the control group. These results suggested that HDMPPA could maintain NO bioavailability through an increasing eNOS expression and preventing NO degradation by ROS. Furthermore, HDMPPA treatment in apoE KO mice inhibited eNOS uncoupling through an increase in vascular tetrahydrobiopterin content and a decrease in serum asymmetric dimethylarginine levels. Moreover, HDMPPA ameliorates inflammatory-related protein expression in the aorta of apoE KO mice. Therefore, the present study suggests that HDMPPA, the active compound of kimchi, a Korean functional food, may exert its vascular protective effect through the preservation of NO bioavailability and suppression of the inflammatory response.

Nitric oxide: orchestrator of endothelium-dependent responses

The present review first summarizes the complex chain of events, in endothelial and vascular smooth muscle cells, that leads to endothelium-dependent relaxations (vasodilatations) due to the generation of nitric oxide (NO) by endothelial nitric oxide synthase (eNOS) and how therapeutic interventions may improve the bioavailability of NO and thus prevent/cure endothelial dysfunction. Then, the role of other endothelium-derived mediators (endothelium-derived hyperpolarizing (EDHF) and contracting (EDCF) factors, endothelin-1) and signals (myoendothelial coupling) is summarized also, with special emphasis on their interaction(s) with the NO pathway, which make the latter not only a major mediator but also a key regulator of endothelium-dependent responses.

Early treatment of radiation-induced heart damage in rats by caffeic acid phenethyl ester

The study is designed to determine the therapeutic effect of caffeic acid phenethyl ester (CAPE) in minimizing radiation-induced injuries in rats. Rats were exposed to 7Gy gamma radiation, 30min later rats were injected with CAPE (10μmol/kg body, i.p.) for 7 consecutive days. Rats were sacrificed at 8 and 15 days after starting the experiment. Gamma-irradiation induced significant increase in malondialdehyde (MDA) level and xanthine oxidase (XO) and adenosine deaminase (ADA) activities, and significant decrease in total nitrate/nitrite (NO(x)) level and glutathione peroxidise (GPx), superoxide dismutase (SOD) and catalase activities in heart tissue and augmented lipid fractions levels and activities of lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and aspartate transaminase (AST) in serum. Irradiated rats early treated with CAPE showed significant decrease in MDA, XO and ADA and significant increase in NO(x) and SOD in heart tissue and in serum enzymes compared with irradiated group. Serum lipid profiles and cardiac enzymes were restored.

CONCLUSION

CAPE could exhibits curable effects on gamma irradiation-induced cardiac-oxidative impairment in rats.

Gomisin J from Schisandra chinensis induces vascular relaxation via activation of endothelial nitric oxide synthase

Gomisin J (GJ) is a lignan contained in Schisandra chinensis (SC) which is a well-known medicinal herb for improvement of cardiovascular symptoms in Korean. Thus, the present study examined the vascular effects of GJ, and also determined the mechanisms involved. Exposure of rat thoracic aorta to GJ (1-30μg/ml) resulted in a concentration-dependent vasorelaxation, which was more prominent in the endothelium (ED)-intact aorta. ED-dependent relaxation induced by GJ was markedly attenuated by pretreatment with L-NAME, a nitric oxide synthase (NOS) inhibitor. In the intact endothelial cells of rat thoracic aorta, GJ also enhanced nitric oxide (NO) production. In studies using human coronary artery endothelial cells, GJ enhanced phosphorylation of endothelial NOS (eNOS) at Ser(1177) with increased cytosolic translocation of eNOS, and subsequently increased NO production. These effects of GJ were attenuated not only by calcium chelators including EGTA and BAPTA-AM, but also by LY294002, a PI3K/Akt inhibitor, indicating calcium- and PI3K/Akt-dependent activation of eNOS by GJ. Moreover, the levels of intracellular calcium were increased immediately after GJ administration, but Akt phosphorylation was started to increase at 20min of GJ treatment. Based on these results with the facts that ED-dependent relaxation occurred rapidly after GJ treatment, it was suggested that the ED-dependent vasorelaxant effects of GJ were mediated mainly by calcium-dependent activation of eNOS with subsequent production of endothelial NO.

Effect of chronic L-Arginine supplementation on aortic fatty streak formation and serum nitric oxide concentration in normal and high-cholesterol fed rabbits

Several reports indicated the beneficial effects of short-term L-Arginine (L-Arg) administration on atherosclerosis processes. The aim of this study was to evaluate the effect of chronic L-Arg supplementation on serum lipid profile, aortic Fatty Streak (FS) formation, and serum Nitric oxide (NO) concentration in Normal Diet (ND) and High-Cholesterol Diet (HCD) fed rabbits. 24 male rabbits were randomly divided into four groups (n=6 in each group) (i): ND for seven months; (ii): ND for 1 month plus ND + L-Arg for six months; (iii): HCD (1%) for 1 month plus HCD (0.5%) for six months; (iv): HCD (1%) for 1 month plus HCD (0.5%) + L-Arg for six months. At the end of the study, histological evaluation of aortic FS formation was performed. Blood samples were taken for serum lipid profile and NO concentrations. L-Arg did not change serum total cholesterol, triglyceride, LDL and LDL/HDL ratio in normal and hypercholesterolemic rabbits (p>0.05). Histological examination of thoracic aortae revealed that the HCD group had higher FS formation compared to the ND group (2.1 ± 0.16 vs. 0 ± 0; respectively; p<0.05) and L-Arg supplementation did not attenuate FS formation in the HCD group (1.93 ± 0.17 compare to 2.1 ± 0.16; p>0.05). Serum NO level in the HCD group was higher than ND groups (p<0.05). Chronic L-Arg supplementation did not alter serum NO concentration either in the hypercholesterolemic or in the ND group (p>0.05). It seems that chronic L-Arg supplementation does not have beneficial effects on aortic fatty streak formation, serum lipids and NO concentrations in this model of experimental hypercholesterolemia.

Chronic deficiency of nitric oxide affects hypoxia inducible factor-1α (HIF-1α) stability and migration in human endothelial cells

BACKGROUND

Endothelial dysfunction in widely diffuse disorders, such as atherosclerosis, hypertension, diabetes and senescence, is associated with nitric oxide (NO) deficiency. Here, the behavioural and molecular consequences deriving from NO deficiency in human umbilical vein endothelial cells (HUVECs) were investigated.

RESULTS

Endothelial nitric oxide synthase (eNOS) was chronically inhibited either by N(G)-Nitro-L-arginine methyl ester (L-NAME) treatment or its expression was down-regulated by RNA interference. After long-term L-NAME treatment, HUVECs displayed a higher migratory capability accompanied by an increased Vascular Endothelial Growth Factor (VEGF) and VEGF receptor-2 (kinase insert domain receptor, KDR) expression. Moreover, both pharmacological and genetic inhibition of eNOS induced a state of pseudohypoxia, revealed by the stabilization of hypoxia-inducible factor-1α (HIF-1α). Furthermore, NO loss induced a significant decrease in mitochondrial mass and energy production accompanied by a lower O(2) consumption. Notably, very low doses of chronically administered DETA/NO reverted the HIF-1α accumulation, the increased VEGF expression and the stimulated migratory behaviour detected in NO deficient cells.

CONCLUSION

Based on our results, we propose that basal release of NO may act as a negative controller of HIF-1α levels with important consequences for endothelial cell physiology. Moreover, we suggest that our experimental model where eNOS activity was impaired by pharmacological and genetic inhibition may represent a good in vitro system to study endothelial dysfunction.

Effect of DETA-NONOate and papaverine on vasodilation of human internal mammary artery

In this study, the relaxatory effect of DETA-NONOate is compared with that of papaverine on isolated human internal mammary artery. We investigated the inhibitory effects of DETA-NONOate and papaverine on phenylephrine-induced contractile response in internal mammary artery segments. The internal mammary artery segments, taken from methodologically matched patients who underwent coronary artery bypass grafting, were prepared, placed in an organ bath, and contracted with phenylephrine (10−9 to 10−4 mol/L) to investigate their relaxatory response to DETA-NONOate or papaverine. Phenylephrine dose–response contraction was obtained after 1, 2, and 3 h in segments pre-incubated with DETA-NONOate or papaverine for 30 min. The EC50 that presented for internal mammary artery segments incubated with DETA-NONOate was 3.523 ± 1.2696 × 10–7 mol/L, and for papaverine was 3.467 ± 1.2145 × 10–6 mol/L. In segments pre-incubated with DETA-NONOate, the contractile response to phenylephrine was suppressed in the first 2 h post-incubation, compared with control responsive groups (p < 0.05), but this inhibition was revoked after 3 h post-incubation. We showed that DETA-NONOate has a more significant relaxative effect by comparison with papaverine; moreover, continuous and long-lasting nitric oxide production by DETA-NONOate might be of great importance for the outcome from coronary artery bypass grafting, when internal mammary artery is used as a conduit.

Ginsenoside Rb1 preconditioning enhances eNOS expression and attenuates myocardial ischemia/reperfusion injury in diabetic rats

Diabetes mellitus is associated with decreased NO bioavailability in the myocardium. Ginsenoside Rb1 has been shown to confer cardioprotection against ischemia reperfusion injury. The aim of this study was to investigate whether Ginsenoside Rb1 exerts cardioprotective effects during myocardial ischemia-reperfusion in diabetic rats and whether this effect is related to increase the production of NO via enhancing eNOS expression in the myocardium. The myocardial I/R injury were induced by occluding the left anterior descending artery for 30 min followed by 120 min reperfusion. An eNOS inhibitor L-NAME or Rb1 were respectively administered 25 min or 10 min before inducing ischemia. Ginsenoside Rb1 preconditioning reduced myocardial infarct size when compared with I/R group. Ginsenoside Rb1 induced myocardial protection was accompanied with increased eNOS expression and NO concentration and reduced plasma CK and LDH (P < 0.05). Moreover, the myocardial oxidative stress and tissue histological damage was attenuated by Ginsenoside Rb1 (P < 0.05). L-NAME abolished the protective effects of Ginsenoside Rb1. It is concluded that Ginsenoside Rb1 protects against myocardium ischemia/reperfusion injury in diabetic rat by enhancing the expression of eNOS and increasing the content of NO as well as inhibiting oxidative stress.

Radiation as a risk factor for cardiovascular disease

Abstract population are ubiquitous background radiation and medical exposure of patients. From the early 1980s to 2006, the average dose per individual in the United States for all sources of radiation increased by a factor of 1.7-6.2 mSv, with this increase due to the growth of medical imaging procedures. Radiation can place individuals at an increased risk of developing cardiovascular disease. Excess risk of cardiovascular disease occurs a long time after exposure to lower doses of radiation as demonstrated in Japanese atomic bomb survivors. This review examines sources of radiation (atomic bombs, radiation accidents, radiological terrorism, cancer treatment, space exploration, radiosurgery for cardiac arrhythmia, and computed tomography) and the risk for developing cardiovascular disease. The evidence presented suggests an association between cardiovascular disease and exposure to low-to-moderate levels of radiation, as well as the well-known association at high doses. Studies are needed to define the extent that diagnostic and therapeutic radiation results in increased risk factors for cardiovascular disease, to understand the mechanisms involved, and to develop strategies to mitigate or treat radiation-induced cardiovascular disease.

Making prudent recommendations for return-to-play in adult athletes with cardiac conditions

Clinicians who treat millions of adult athletes throughout the world may be faced with participation or return-to-play decisions in individuals with known or suspected cardiac conditions. Here we review existing published participation guidelines and analyze emerging data from ongoing registries and population-based studies pertaining to return-to-play decisions for cardiac conditions specifically affecting adult athletes. Considerations related to return-to-play decisions will vary according to age of the athlete, with inherited disorders being the main consideration in younger adult athletes aged 18 to 40 yr, and coronary artery disease being the main consideration in older adult athletes aged 40 yr and older. Although this arbitrary division is based on the epidemiology of underlying heart disease in these populations, the essential return-to-play decision process for both age groups is quite similar. Among the most widely used guidelines to make return-to-play decisions in this group of athletes are the 36th Bethesda Conference Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities. These have long been considered the "gold standard" for determining return-to-play decisions in young athletes in the United States. Other guidelines are available for unique purposes, including The European Society of Cardiology guidelines, and the American Heart Association published recommendations regarding participation of young patients (younger than 40 yr) with genetic cardiovascular diseases in recreational sports. The latter are consistent with the 36th Bethesda guidelines and cover common genetically based diseases such as inherited cardiomyopathies, channelopathy, and connective tissue disorders like Marfan's syndrome. The consensus on masters athletes (older than 40 yr) provides return-to-play decisions for a wide variety of conditioned states, from elite older athletes to walk-up athletes. For any adult athlete with a cardiac condition, return-to-play decisions following use of medications, ablation procedures, device implantation, corrective surgery, or coronary intervention depend on whether the procedure has sufficiently altered the risk for sudden cardiac events, and whether there is a potential for unfavorable interaction with cardiac performance.

Anti-atherogenic effect of laminar shear stress via Nrf2 activation

Fluid shear stress plays a critical role in the regulation of vascular biology and its pathology, such as atherosclerosis, via modulation of redox balance. Both pro-atherogenic (either oscillatory or turbulent, nonunidirectional) shear stress and anti-atherogenic (either steady or pulsatile, unidirectional laminar) shear stress stimulate production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) that are involved in signal transduction of gene expression. Nonunidirectional shear stress induces pro-atherogenic genes encoding adhesion molecules and chemokines in a manner dependent on production of both superoxide and nitric oxide. Steady or pulsatile laminar shear stress induces expression of genes encoding cytoprotective enzymes for glutathione biosynthesis and detoxification, which are regulated by the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). We show that pulsatile laminar shear stress (PLSS)-induced expression of adhesion molecules and chemokines was enhanced in human umbilical vein endothelial cells (HUVEC) treated with Nrf2 siRNA and arterial endothelial cells isolated from Nrf2 knockout mice. Hence, we propose the hypothesis that PLSS maintains the endothelium in an anti-atherogenic state via intracellular antioxidant levels increased as a result of Nrf2 activation, thereby preventing excess ROS/RNS production required for pro-atherogenic gene expression.

The effect of Hypericum perforatum on isolated rat aorta

CONTEXT

Different Hypericum species such as Hypericum perforatum (HP) L. and Hypericum triquetrifolium Turra are well known and widely used traditional medicine in Turkey.

OBJECTIVES

We investigated the effect of standardized HP extract on endothelium and vascular function.

MATERIALS AND METHODS

After suspending the aortas with endothelium in organ baths containing Krebs solution, contractile and relaxant responses were assessed in the absence and presence of HP (0.05 mg/ml).

RESULTS

Although there were significant reductions in the contractile responses to phenylephrine (1113.73 ± 164.11; 477.40 ± 39.94; p < 0.05) and potassium chloride (745.58 ± 66.73; 112.58 ± 26.58; p < 0.05), no differences in the relaxant responses to acetylcholine (94.61 ± 2.65; 87.79 ± 9.40) and sodium nitroprusside (108.82 ± 5.06; 106.43 ± 7.45) were observed.

DISCUSSION AND CONCLUSION

These data suggest that even the high dose of HP intervention does not bring any harmful effect on endothelium and smooth muscle function; meanwhile it might be beneficial on some of diseases accompanied with increased vascular contraction.

XJP-1, a novel ACEI, with anti-inflammatory properties in HUVECs

AIM

We investigated whether 8-dihydroxy-3-methyl-isochromanone (XJP-1), a novel angiotensin-converting enzyme inhibitor (ACEI), exhibited inhibitory activity to lipopolysaccharide (LPS)-accelerated vascular inflammation.

METHODS

Human umbilical vein endothelial cells (HUVECs) were isolated from human umbilical cords and cultured. The direct effect of XJP-1 on the activation of endothelial cells was measured using MTT assay. Nitric oxide (NO) in the culture medium was measured using Griess method. The expression of cell adhesion molecules (ICAM-1 and VCAM-1) was determined by flow cytometry and RT-PCR. The protein expression levels of tumor necrosis factor-α (TNF-α), monocyte chemotactic protein (MCP)-1, and endothelin-1 (ET-1) secretion were measured using ELISA. Quantitative analysis of eNOS, iNOS, inhibitory factor NF-κB (IκB) and MAPKs were determined using Western blot analysis. The translocation of NF-κB from the cytoplasm to the nucleus was determined using immunofluorescence.

RESULTS

XJP-1 significantly inhibited LPS-mediated endothelial cell dysfunction, as measured by NO production, iNOS expression, adhesion molecule (ICAM-1, VCAM-1) expression, and chemokine (TNF-α, MCP-1) production in vitro. It up-regulated eNOS expression in the same experimental setting. XJP-1 alone was found non-cytotoxic at the concentration up to 1000μM. The mechanistic investigations of XJP-1 suppression LPS-induced inflammation in HUVECs revealed that XJP-1 blocked NF-κB nuclear entry in an IκB-dependent manner, as well as inhibited MAPK activation induced by LPS. XJP-1 reduced endothelin-1 secretion and increased nitric oxide metabolite production by HUVECs. However, the effect of XJP-1 on nitric oxide and endothelin-1 metabolite production is mediated by the activation of bradykinin B(2) receptor being counteracted, at least in part, by a specific antagonist.

CONCLUSION

XJP-1 inhibited LPS-induced cytotoxicity and inflammatory response. The mechanism underlying this protective effect might be related to the inhibition of MAPK and NF-κB signaling pathway activation, suggesting the potential inhibition of the atherosclerotic process by suppressing the expression of chemoattractant molecules and monocyte adhesion. XJP-1 also has an effect in improving endothelin-1 through activating bradykinin B(2) receptor. These findings indicated that XJP-1 is potentially a novel therapeutic candidate for the treatment of atherosclerosis.

Cardioprotective effect of NO-metoprolol in murine coxsackievirus B3-induced myocarditis

The effect of NO-metoprolol, that is, 3-nitrooxypivaloyl metoprolol-amide, a novel NO-releasing derivative of the β1-blocking drug metoprolol was investigated in A.CA/SnJ mice infected with coxsackievirus B3 (CVB3) and compared to metoprolol and placebo. Daily treatment of mice with the respective drug started immediately (experiment A) or 3 days after virus infection (experiment B) and was continued until day 13 post-infection (p.i.). Two doses of NO-metoprolol were administered. Body mass differences, viral load, and histopathological signs of myocarditis were compared between the several groups. As a result, NO-metoprolol diminished significantly the body weight loss, the viral load and the histopathology, whereas metoprolol treatment led solely to a significant attenuation of myocardial damage. In experiment A, low dose NO-metoprolol decreased significantly enteroviral copy numbers. Both doses of NO-metoprolol had a significant effect on reduction of myocardial infiltrates and fibrosis. The data suggest that delayed drug administration might more advantageous. Both doses of NO-metoprolol reduced significantly the scores of four tested parameters compared to placebo. Body weight loss, virus titers, plus-strand as well as minus-strand enteroviral RNA levels, infiltration and fibrosis scores were diminished significantly when NO-metoprolol was given 3 days p.i. In addition, a significant difference regarding the enteroviral copy numbers was observed between low dose NO-metoprolol- and metoprolol-treated mice. Treatment with metoprolol reduced insignificantly the viral load and body weight loss (experiment A and B) but led to a significant reduction of myocardial histopathology in experiment A. The results indicate that NO-metoprolol treatment has a greater therapeutic benefit than metoprolol.

The mechanism of opiorphin-induced experimental priapism in rats involves activation of the polyamine synthetic pathway

Intracorporal injection of plasmids encoding opiorphins into retired breeder rats can result in animals developing a priapic-like condition. Microarray analysis demonstrated that following intracorporal gene transfer of plasmids expressing opiorphins the most significantly upregulated gene in corporal tissue was the ornithine decarboxylase gene (ODC). Quantitative RT-PCR confirmed the upregulation of ODC, as well as other genes involved in polyamine synthesis, such as arginase-I and -II, polyamine oxidase, spermidine synthase, spermidine acetyltransferase (SAT), and S-adenosylmethionine decarboxylase. Western blot analysis demonstrated upregulation of arginase-I and -II, ODC, and SAT at the protein level. Levels of the polyamine putrescine were upregulated in animals treated with opiorphin-expressing plasmids compared with controls. A direct role for the upregulation of polyamine synthesis in the development of the priapic-like condition was supported by the observation that the ODC inhibitor 1,3-diaminopropane, when added to the drinking water of animals treated with plasmids expressing opiorphins, prevented experimental priapism. We also demonstrate that in sickle cell mice, another model of priapism, there is increased expression of the mouse opiorphin homologue in corporal tissue compared with the background strain at a life stage prior to evidence of priapism. At a life stage when there is onset of priapism, there is increased expression of the enzymes involved in polyamine synthesis (ODC and arginase-I and -II). Our results suggest that the upregulation of enzymes involved in the polyamine synthetic pathway may play a role in the development of experimental priapism and represent a target for the prevention of priapism.

Gomisin A induces Ca2+-dependent activation of eNOS in human coronary artery endothelial cells

AIM OF THE STUDY

Gomisin A (GA) is a small molecular weight lignan contained in Fructus Schisandrae, the dried seed of Schisandra chinensis which is widely used as a tonic in traditional Korean medicine. We previously demonstrated that GA induces endothelium-dependent and -independent relaxation in rat thoracic aorta, however the signaling pathways involved was not clarified. In this study, we examined whether GA could actually induce nitric oxide (NO) production and clarified the mechanism in cultured human coronary artery endothelial cells (HCAEC).

RESULTS

Treatment of HCAEC with GA induced NO production in a time- and concentration-dependent manner in association with an enhanced endothelial NO synthase (eNOS) activity with an increased cytosolic translocation of eNOS. Both GA-induced NO production and eNOS activation were attenuated by pretreatment of the cells with EGTA, an extracellular Ca(2+) chelator, and BAPTA-AM, an intracellular Ca(2+) chelator, but not by LY 294002, a PI3-kinase/Akt inhibitor, suggesting involvement of Ca(2+). Furthermore, GA rapidly increased the intracellular Ca(2+) concentration, which was abolished in Ca(2+) free media.

CONCLUSION

Taken together, our results suggest that GA induces Ca(2+)-dependent activation and translocation of eNOS in HCAEC, events linked to NO production and thereby endothelial-dependent vasorelaxation.

Semicarbazide-sensitive amine oxidase activity and total nitrite and nitrate concentrations in serum: novel biochemical markers for type 2 diabetes?

The aim of this study was to evaluate the activity of semicarbazide-sensitive amine oxidase (SSAO) and the total nitrite and nitrate (NO( x )) concentrations in serum from type 2 diabetic patients and control subjects in order to evaluate if they could be used as novel diabetic markers. We studied 38 type 2 diabetic patients and 35 control subjects. Serum samples from those subjects were evaluated by radiochemical methods for SSAO activity using (14)C-benzylamine. Serum NO( x ) concentrations were obtained as an index of nitric oxide production by the Griess reaction. Serum SSAO activity was higher in type 2 diabetic patients than in control group and serum SSAO in type 2 diabetic correlated with age, serum creatinine and total cholesterol. Serum NO( x ) levels in type 2 diabetic patients were also significantly higher than those in the control group. Serum NO( x ) levels in control group correlated with serum SSAO activity. In conclusion, the increase in the SSAO activity and NO( x ) levels observed in type 2 diabetic patients could be parameters to take in account and play relevant role in diabetes development. SSAO and NO( x ) are suggested as markers for prognostic of diabetes.

Actions and interactions of nitric oxide, carbon monoxide and hydrogen sulphide in the cardiovascular system and in inflammation--a tale of three gases!

Nitric oxide (NO), carbon monoxide (CO) and hydrogen sulphide (H(2)S) together make up a family of biologically active gases (the so-called 'gaseous triumvirate') with an increasingly well defined range of physiological effects plus roles to play in a number of disease states. Over the years, most researchers have concentrated their attention on understanding the part played by a single gas in one or more body systems. It is becoming more clear that all three gases are synthesised naturally in the body, often by the same cells within the same organs, and that all three gases exert essentially similar biological effects albeit via different mechanisms. Within the cardiovascular system, for example, all are vasodilators, promote angiogenesis and vascular remodelling and are protective towards tissue damage in for example, ischaemia-reperfusion injury in the heart. Similarly, all exhibit complex effects in inflammation with both pro- and anti-inflammatory effects recognised. It seems likely that cell function is controlled not by the activity of single gases working in isolation but by the concerted activity of all three of these gases working together.

Smoking increases salivary arginase activity in patients with dental implants

It is believed that an increased arginase activity may lead to less nitric oxide production, which consequently increases the susceptibility to bacterial infection. Considering the hypothesis that smoking may alter the arginase activity and that smoking is considered a risk factor to dental implant survival, the present study aimed at evaluating the effect of smoking on the salivary arginase activity of patients with dental implants. Salivary samples of 41 subjects were collected: ten non-smoking and with no dental implants (group A), ten non-smoking subjects with dental implants (group B), ten smoking subjects with implants (group C), and 11 smoking subjects with no dental implants (group D). The levels of salivary arginase activity were determined by the measurement of L-ornithine and expressed as mIU/mg of protein. A significant increase in the salivary arginase activity was verified in groups C (64.26 +/- 16.95) and D (49.55 +/- 10.01) compared to groups A (10.04 +/- 1.95, p = 0.00001 and p = 0.0110, groups C and D, respectively) and B (11.77 +/- 1.45, p = 0.00001 and p = 0.0147, groups C and D, respectively). No significant difference was found between groups C and D (p = 0.32). Within the limits of the present study, it can be concluded that salivary arginase activity is increased in smoking subjects with dental implants in contrast to non-smoking subjects with dental implants, therefore suggesting a possible mechanism by which cigarette smoking may lead to implant failure. The analysis of salivary arginase activity may represent an important tool to prevent implant failure in the near future.

The Asp298 allele of endothelial nitric oxide synthase is a risk factor for myocardial infarction among patients with type 2 diabetes mellitus

BACKGROUND

Endothelial dysfunction plays a central role in atherosclerotic progression and cardiovascular complications of type 2 diabetes mellitus (T2DM). Given the role of nitric oxide in the vascular system, we aimed to test hypotheses of synergy between the common endothelial nitric oxide synthase (eNOS) Asp298 allele and T2DM in predisposing to acute myocardial infarction (AMI).

METHODS

In a population-based patient survey with 403 persons with T2DM and 799 healthy subjects from the population without diabetes or hypertension, we analysed the relation between T2DM, sex and the eNOS Asp298 allele versus the risk for AMI.

RESULTS

In an overall analysis, T2DM was a significant independent risk factor for AMI. In patients with T2DM, homozygosity for the eNOS Asp298 allele was a significant risk factor (HR 3.12 [1.49-6.56], p = 0.003), but not in subjects without diabetes or hypertension. Compared to wild-type non-diabetic subjects, all patients with T2DM had a significantly increased risk of AMI regardless of genotype. This risk was however markedly higher in patients with T2DM homozygous for the Asp298 allele (HR 7.20 [3.01-17.20], p < 0.001), independent of sex, BMI, systolic blood pressure, serum triglycerides, HDL -cholesterol, current smoking, and leisure time physical activity. The pattern seemed stronger in women than in men.

CONCLUSION

We show here a strong independent association between eNOS genotype and AMI in patients with T2DM. This suggests a synergistic effect of the eNOS Asp298 allele and diabetes, and confirms the role of eNOS as an important pathological bottleneck for cardiovascular disease in patients with T2DM.

Endothelial nitric oxide deficiency reduces MMP-13-mediated cleavage of ICAM-1 in vascular endothelium: a role in atherosclerosis

OBJECTIVE

Lack of endothelial nitric oxide synthase worsens atherosclerosis at least by increasing monocyte adhesion to endothelial cells. The purpose of this study was to elucidate the molecular mechanism elicited by NO.

METHODS AND RESULTS

We evaluated atherosclerosis in apoE and NOS3/apoE-deficient mice fed with high-cholesterol diet. We found significant increase in aortic lesion size, and infiltration of macrophages in NOS3/apoE-null mice when compared to apoE-deficient animals. To test the relevance of cellular adhesion as well as extracellular matrix degradation, we evaluated ICAM-1, VCAM-1, PECAM-1, MMP-2, MMP-9, MMP-12, MT1-MMP, and MMP-13 levels in mouse aortas. Lack of NO inhibits MMP-13 and increases ICAM-1 levels in atherosclerosis as compared to apoE-null mice. Ectopically expression of ICAM-1 in eukaryotic cells revealed that extracellular domain of ICAM-1 harbors a substrate recognized by MMP-13. Incubation of COS-7 cells expressing ectopic ICAM-1 in the presence of active MMP-13 induced inhibition of RAW 264.7 cell adhesion to COS-7 monolayers. MALDI-TOF MS analysis combined to Liquid chromatography coupled to Ion Trap MS on ICAM-1 incubated with MMP-13 allowed us to determine the cleavage sites of MMP-13 at positions E61 and G98 of ICAM-1. G98 is part of a PDGQS moiety, which shows homology with the consensus PDGLS substrate located at the MMP-13 cleaved site of type II collagen I-alpha.

CONCLUSIONS

Taking together, these results point toward MMP-13 as a mechanism for the NO-mediated protection of atherosclerosis.

An integrated view of insulin resistance and endothelial dysfunction

Endothelial dysfunction and insulin resistance are frequently comorbid states. Vasodilator actions of insulin are mediated by phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathways that stimulate production of nitric oxide from vascular endothelium. This helps to couple metabolic and hemodynamic homeostasis under healthy conditions. In pathologic states, shared causal factors, including glucotoxicity, lipotoxicity, and inflammation selectively impair PI3K-dependent insulin signaling pathways that contribute to reciprocal relationships between insulin resistance and endothelial dysfunction. This article discusses the implications of pathway-selective insulin resistance in vascular endothelium, interactions between endothelial dysfunction and insulin resistance, and therapeutic interventions that may simultaneously improve both metabolic and cardiovascular physiology in insulin-resistant conditions.

Exogenous nitric oxide regulates activity and synthesis of vascular endothelial nitric oxide synthase

BACKGROUND

Nitric oxide (NO) - a major signalling molecule of the vascular system - is constitutively produced in endothelial cells (EC) by the endothelial NO synthase (eNOS). Since a reduced NO synthesis is an early sign of endothelial dysfunction and NO delivering drugs are used to substitute the impaired endothelial NO production, we addressed the effect of exogenous NO on eNOS in human umbilical venous endothelial cell cultures.

MATERIALS AND METHODS

The synthetic NO donor DETA/NO (trade name, but in the following we refer to detNO), that releases NO in a strictly first order reaction with a half life of 20 h, was used in our experiments.

RESULTS

Short-term (20-30 min) detNO treatment of EC increases the Ser(1177) phosphorylation of the constitutively expressed endothelial NOS and the production of endogenous NO generated by eNOS from [(3)H]arginine. The phosphorylation of eNOS is Akt-dependent and completely reverted by the phosphatidylinositol-3 kinase (PI-3K) inhibitor LY294002. A prolonged continuous exposure of EC to detNO 150 micromol L(-1) over a period of 24-48 h causes a reversible cell cycle arrest at G(1)-phase associated with a larger cell volume and increased cell protein content (hypertrophic phenotype of EC). The eNOS protein and mRNA of the hypertrophic cells and the generation of endogenous NO are reduced but eNOS phosphorylation could still be elevated by stimulation with vascular endothelial growth factor.

CONCLUSIONS

Our data explain clinical studies describing a short-term but not a long-term benefit of NO treatment for patients with cardiovascular risk factors. The results could be a rational approach to develop a generation of NO donors accomplishing a retarded release from NO donors that mimic the low continuous pulsatile stress-induced release of endogenous NO.

Selective depletion of macrophages in atherosclerotic plaques via macrophage-specific initiation of cell death

Macrophages play a central role in atherosclerotic plaque destabilization, leading to acute coronary syndromes and sudden death. Removal of macrophages from plaques via pharmacological therapy may therefore represent a promising approach to stabilize vulnerable, rupture-prone lesions. In this review, we summarize the current therapeutic means to induce macrophage cell death in atherosclerotic plaques without affecting smooth muscle cell viability, and their potential pitfalls.

Dietary nitrite supplementation protects against myocardial ischemia-reperfusion injury

Nitrite has emerged as an endogenous signaling molecule with potential therapeutic implications for cardiovascular disease. Steady-state levels of nitrite are derived in part from dietary sources; therefore, we investigated the effects of dietary nitrite and nitrate supplementation and deficiency on NO homeostasis and on the severity of myocardial ischemia-reperfusion (MI/R) injury. Mice fed a standard diet with supplementation of nitrite (50 mg/liter) in their drinking water for 7 days exhibited significantly higher plasma levels of nitrite, exhibited significantly higher myocardial levels of nitrite, nitroso, and nitrosyl-heme, and displayed a 48% reduction in infarct size (Inf) after MI/R. Supplemental nitrate (1 g/liter) in the drinking water for 7 days also increased blood and tissue NO products and significantly reduced Inf. A time course of ischemia-reperfusion revealed that nitrite was consumed during the ischemic phase, with an increase in nitroso/nitrosyl products in the heart. Mice fed a diet deficient in nitrite and nitrate for 7 days exhibited significantly diminished plasma and heart levels of nitrite and NO metabolites and a 59% increase in Inf after MI/R. Supplementation of nitrite in the drinking water for 7 days reversed the effects of nitrite deficiency. These data demonstrate the significant influence of dietary nitrite and nitrate intake on the maintenance of steady-state tissue nitrite/nitroso levels and illustrate the consequences of nitrite deficiency on the pathophysiology of MI/R injury. Therefore, nitrite and nitrate may serve as essential nutrients for optimal cardiovascular health and may provide a treatment modality for cardiovascular disease.

Nitric oxide selectively depletes macrophages in atherosclerotic plaques via induction of endoplasmic reticulum stress

BACKGROUND AND PURPOSE

Macrophages in atherosclerotic plaques have a tremendous impact on atherogenesis and plaque destabilization. We previously demonstrated that treatment of plaques in cholesterol-fed rabbits with the nitric oxide (NO) donor molsidomine preferentially eliminates macrophages, thereby favouring features of plaque stability. In this study, we investigated the underlying mechanism.

EXPERIMENTAL APPROACH

Macrophages and smooth muscle cells (SMCs) were treated in vitro with the NO donors, spermine NONOate or S-nitroso-N-acetylpenicillamine (SNAP) as well as with the well-known endoplasmic reticulum (ER) stress inducers thapsigargin, tunicamycin, dithiothreitol or brefeldin A. Cell viability was analysed by Neutral Red viability assays. Cleavage of caspase-3, DNA fragmentation and ultrastructural changes were examined to characterize the type of macrophage death. Induction of ER stress was evaluated by measuring C/EBP homologous protein (CHOP) expression, phosphorylation of eukaryotic initiation factor 2 alpha (eIF2a), splicing of X-box binding protein 1 (XBP1) and inhibition of protein synthesis.

KEY RESULTS

Macrophages and SMCs treated with spermine NONOate or SNAP showed several signs of ER stress, including upregulation of CHOP expression, hyperphosphorylation of eIF2 alpha, inhibition of de novo protein synthesis and splicing of XBP1 mRNA. These effects were similar in macrophages and SMCs, yet only macrophages underwent apoptosis. Plaques from molsidomine-treated atherosclerotic rabbits showed a 2.7-fold increase in CHOP expression as compared to placebo. Beside NO, selective induction of macrophage death could be initiated with thapsigargin and tunicamycin.

CONCLUSIONS AND IMPLICATIONS

Induction of ER stress explains selective depletion of macrophages in atherosclerotic plaques by a NO donor, probably via inhibition of protein synthesis.

Recent developments in nitric oxide donor drugs

During the 1980s, the free radical, nitric oxide (NO), was discovered to be a crucial signalling molecule, with wide-ranging functions in the cardiovascular, nervous and immune systems. Aside from providing a credible explanation for the actions of organic nitrates and sodium nitroprusside that have long been used in the treatment of angina and hypertensive crises respectively, the discovery generated great hopes for new NO-based treatments for a wide variety of ailments. Decades later, however, we are still awaiting novel licensed agents in this arena, despite an enormous research effort to this end. This review explores some of the most promising recent advances in NO donor drug development and addresses the challenges associated with NO as a therapeutic agent.

Nitric oxide increases oxidative phosphorylation efficiency

We have studied the effect of nitric oxide (NO) and potassium cyanide (KCN) on oxidative phosphorylation efficiency. Concentrations of NO or KCN that decrease resting oxygen consumption by 10-20% increased oxidative phosphorylation efficiency in mitochondria oxidizing succinate or palmitoyl-L-carnitine, but not in mitochondria oxidizing malate plus glutamate. When compared to malate plus glutamate, succinate or palmitoyl-L-carnitine reduced the redox state of cytochrome oxidase. The relationship between membrane potential and oxygen consumption rates was measured at different degrees of ATP synthesis. The use of malate plus glutamate instead of succinate (that changes the H(+)/2e(-) stoichiometry of the respiratory chain) affected the relationship, whereas a change in membrane permeability did not affect it. NO or KCN also affected the relationship, suggesting that they change the H(+)/2e(-) stoichiometry of the respiratory chain. We propose that NO may be a natural short-term regulator of mitochondrial physiology that increases oxidative phosphorylation efficiency in a redox-sensitive manner by decreasing the slipping in the proton pumps.

Role of endothelial-derived nitric oxide in hypertension and renal disease

PURPOSE OF REVIEW

To highlight recent advances in the field of endothelial-derived nitric oxide regulation of blood pressure and renal homeostasis.

RECENT FINDINGS

Many laboratories have dissected a role for nitric oxide in regulating blood pressure and renal function. In models of hypertension, and chronic and acute renal disease, the loss of nitric oxide bioavailability may occur due to inactivation of endothelial nitric oxide synthase, synthesis of endogenous inhibitors or oxidative inactivation of nitric oxide.

SUMMARY

Understanding the molecular mechanisms of nitric oxide synthesis may lead to novel diagnostics and treatments for cardiovascular disorders.

Central blood pressures: do we need them in the management of cardiovascular disease? Is it a feasible therapeutic target?

It is well established that in young and healthy individuals central (aortic or carotid) systolic and pulse pressures are different from peripheral (brachial) corresponding pressures as a consequence of progressive changes in arterial stiffness and pressure wave reflections along the arterial tree. There is evidence indicating that in interventions with pharmaceutical and non-pharmaceutical agents, central pressures are subjected to greater changes than peripheral pressures, and they are more closely related to the pathophysiology of end-organ damage or cardiovascular risk. Therefore central blood pressures may be of higher clinical importance than peripheral pressures. The present review aims to provide an insight into the (patho)physiology of central blood pressures, to present the most accurate techniques for their estimation, and to discuss the available experimental and epidemiological data that support the emerging need for the evaluation of central blood pressures in clinical practice.

Signaling pathway of nitric oxide production induced by ginsenoside Rb1 in human aortic endothelial cells: a possible involvement of androgen receptor

Ginsenosides have been shown to stimulate nitric oxide (NO) production in aortic endothelial cells. However, the signaling pathways involved have not been well studied in human aortic endothelial cells. The present study was designed to examine whether purified ginsenoside Rb1, a major active component of ginseng could actually induce NO production and to clarify the signaling pathway in human aortic endothelial cells. NO production was rapidly increased by Rb1. The rapid increase in NO production was abrogated by treatment with nitric oxide synthetase inhibitor, L-NAME. Rb1 stimulated rapid phosphorylation of Akt (Ser473), ERK1/2 (Thr202/Thr204) and eNOS (Ser1177). Rapid phosphorylation of eNOS (Ser1177) was prevented by SH-5, an Akt inhibitor or wortmannin, PI3-kinase inhibitor and partially attenuated by PD98059, an upstream inhibitor for ERK1/2. Interestingly, NO production and eNOS phosphorylation at Ser1177 by Rb1 were abolished by androgen receptor antagonist, nilutamide. The results suggest that PI3kinase/Akt and MEK/ERK pathways and androgen receptor are involved in the regulation of acute eNOS activation by Rb1 in human aortic endothelial cells.

Targeting Nitric Oxide With Drug Therapy

Increasing knowledge of the role of nitric oxide (NO) in physiology and disease has stimulated efforts to target the NO pathway pharmacologically. These therapeutic strategies include NO donors that directly or indirectly release NO and agents that increase NO bioactivity. Traditional organic nitrates such as nitroglycerin, which indirectly release NO, were believed to have limited long-term efficacy and tolerability, chiefly because of nitrate tolerance. Recent studies, however, suggest more effective ways of using these agents and new applications for them. Nicorandil, a hybrid organic nitrate that also activates potassium channels, has demonstrated significant benefits in acute coronary syndromes. Other nitrates are being investigated for use in neurodegenerative diseases. Direct NO donors include NO gas, which is useful in respiratory disorders, and the more recent classes of diazeniumdiolates, sydnonimines, and S-nitrosothiols. Preliminary data suggest that these agents may be effective as antiatherosclerotic agents as well as in other disease states. In addition, hybrid agents that consist of an NO donor coupled with a parent anti-inflammatory drug, including nonsteroidal anti-inflammatory drugs, have demonstrated enhanced efficacy and tolerability compared with the anti-inflammatory parent drug alone in diverse experimental models. Established drugs that enhance NO bioactivity include antihypertensive agents, particularly angiotensin-converting enzyme inhibitors, calcium channel blockers, and newer vasodilating beta-blockers. In addition, 3-methylglutaryl coenzyme A reductase inhibitors (statins) promote NO bioactivity, both through and independent of lipid lowering. The NO-promoting actions of these established drugs provide some insight into their known benefits and suggest possible therapeutic potential.

Cardioprotective effects of vegetables: Is nitrate the answer?

A diet rich in fruits and vegetables is associated with a lower risk of certain forms of cancer and cardiovascular disease, but the mechanisms behind this protection are not completely understood. Recent epidemiological studies suggest a cardioprotective action afforded specifically by green leafy vegetables. We here propose that these beneficial effects are related to the high content of inorganic nitrate, which in concert with symbiotic bacteria in the oral cavity is converted into nitrite, nitric oxide, and secondary reaction products with vasodilating and tissue-protective properties.

Novel therapies targeting vascular endothelium

Endothelial dysfunction has been identified as a major mechanism involved in all the stages of atherogenesis. Evaluation of endothelial function seems to have a predictive role in humans, and therapeutic interventions improving nitric oxide bioavailability in the vasculature may improve the long-term outcome in healthy individuals, high-risk subjects, or patients with advanced atherosclerosis. Several therapeutic strategies are now available, targeting both the synthesis and oxidative inactivation of nitric oxide (NO) in human vasculature. Statins seem to be currently the most powerful category of these agents, improving endothelial function and decreasing cardiovascular risk after long-term administration. Other cardiovascular agents improving endothelial function in humans are angiotensin-converting enzyme inhibitors/angiotensin receptors blockers, which increase NO bioavailability by modifying the rennin-angiotensin-aldosterone system. Newer therapeutic approaches targeting endothelial dysfunction in specific disease states include insulin sensitizers, L-arginine (the substrate for endothelial NO synthase [eNOS]) as well as substances that target eNOS "coupling," such as folates or tetrahydrobiopterin. Although there are a variety of strategies to improve NO bioavailability in human endothelium, it is still unclear whether they have any direct benefit at a clinical level.

Low-Density Lipoprotein Cholesterol Determines Oxidative Stress and Endothelial Dysfunction in Saphenous Veins From Patients With Coronary Artery Disease

OBJECTIVE

There is evidence for a relationship between endothelial dysfunction and cardiovascular disease, but a causative role for oxidative stress remains to be determined.

METHODS AND RESULTS

We studied 188 patients with severe coronary artery disease (CAD), of whom 51 were age and sex matched with 51 healthy controls undergoing varicose vein surgery. Relaxation of saphenous vein to calcium ionophore, apocynin, and allopurinol was studied together with the markers of oxidative stress, total antioxidant capacity and reduced/oxidized glutathione ratio. Vascular superoxide levels were measured using lucigenin chemiluminescence and hydroethidine. Relaxation to calcium ionophore was decreased in CAD compared with control patients (maximum relaxation 26+/-2% versus 60+/-1%; P<0.001). Total superoxide production was increased (0.89+/-0.09 versus 0.56+/-0.06 nmol/mg per min; P=0.008), whereas superoxide inhibition with apocynin or allopurinol had a greater effect on vasorelaxation in CAD patients. Low-density lipoprotein (LDL) cholesterol predicted relaxation to calcium ionophore (P<0.001) and oxidative stress markers (P<0.001) in CAD patients.

CONCLUSIONS

Endothelial dysfunction is associated with raised levels of superoxide and biomarkers of oxidative stress in saphenous veins from CAD patients. LDL cholesterol is a major determinant of endothelial dysfunction and oxidative stress in these patients. These results support intensive LDL cholesterol-lowering therapy as suggested by recent clinical trials.

Copper, oxidative stress, and human health

Copper (Cu), a redox active metal, is an essential nutrient for all species studied to date. During the past decade, there has been increasing interest in the concept that marginal deficits of this element can contribute to the development and progression of a number of disease states including cardiovascular disease and diabetes. Deficits of this nutrient during pregnancy can result in gross structural malformations in the conceptus, and persistent neurological and immunological abnormalities in the offspring. Excessive amounts of Cu in the body can also pose a risk. Acute Cu toxicity can result in a number of pathologies, and in severe cases, death. Chronic Cu toxicity can result in liver disease and severe neurological defects. The concept that elevated ceruloplasmin is a risk factor for certain diseases is discussed. In this paper, we will review recent literature on the potential causes of Cu deficiency and Cu toxicity, and the pathological consequences associated with the above. Finally, we will review some of the potential biochemical lesions that might underlie these pathologies. Given that oxidative stress is a characteristic of Cu deficiency, the role of Cu in the oxidative defense system will receive special attention. The concept that excess Cu may be a precipitating factor in Alzheimer's disease is discussed.