Novel features of nitric oxide, endothelial nitric oxide synthase, and atherosclerosis

Noninvasive Assessment of Vascular Function: From Physiological Tests to Biomarkers

Vascular function is impaired by conditions such as hypertension, dyslipidemia, and diabetes as well as coronary risk factors including age, smoking, obesity, menopause and physical inactivity. Measurement of vascular function is useful not only for assessment of atherosclerosis itself but also in many other aspects such as understanding the pathophysiology, assessing treatment efficacy, and predicting prognosis of cardiovascular events. It is therefore important to accurately assess the extent of vascular function. A variety of vascular function assessments are currently used in clinical practice, including flow-mediated vasodilation, reactive hyperemia index, strain-gauge pulse plethysmographs, pulse wave velocity, augmentation index, intima media thickness, and chemical biomarkers. However, it is also true that there is no gold standard method for measuring vascular function in humans. To use vascular function effectively, it is necessary to understand the measurement-related pitfalls.

Multi-proteomic Biomarker Risk Scores for Predicting Risk and Guiding Therapy in Patients with Coronary Artery Disease

PURPOSE OF REVIEW

Patients with established coronary artery disease (CAD) are at high residual risk for adverse events, despite guideline-based treatments. Herein, we aimed to determine whether risk scores based on multiple circulating biomarkers that represent activation of various pathophysiologically important pathways involved in atherosclerosis and myocardial dysfunction help identify those at greatest residual risk.

RECENT FINDINGS

Numerous circulating proteins, representing dysregulation of the pathways involved in the development and stability of coronary and myocardial diseases, have been identified. When aggregated together, biomarker risk scores (BRS) more accurately stratify patients with established CAD that may help target interventions in those individuals who are at elevated risk. Moreover, intensification of guideline-based therapies has been associated with parallel improvements in both BRS and outcomes, indicating that these risk scores may be employed clinically to target therapy. Multi-protein BRS are predictive of risk, independent of, and in addition to traditional risk factor assessments in patients with CAD. Those with elevated risk may benefit from optimization of therapies, and improvements in the BRS will identify those with improved outcomes.

Diosgenin and Its Analogs: Potential Protective Agents Against Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the artery wall associated with lipid metabolism imbalance and maladaptive immune response, which mediates most cardiovascular events. First-line drugs such as statins and antiplatelet drug aspirin have shown good effects against atherosclerosis but may lead to certain side effects. Thus, the development of new, safer, and less toxic agents for atherosclerosis is urgently needed. Diosgenin and its analogs have gained importance for their efficacy against life-threatening diseases, including cardiovascular, endocrine, nervous system diseases, and cancer. Diosgenin and its analogs are widely found in the rhizomes of Dioscore, Solanum, and other species and share similar chemical structures and pharmacological effects. Recent data suggested diosgenin plays an anti-atherosclerosis role through its anti-inflammatory, antioxidant, plasma cholesterol-lowering, anti-proliferation, and anti-thrombotic effects. However, a review of the effects of diosgenin and its natural structure analogs on AS is still lacking. This review summarizes the effects of diosgenin and its analogs on vascular endothelial dysfunction, vascular smooth muscle cell (VSMC) proliferation, migration and calcification, lipid metabolism, and inflammation, and provides a new overview of its anti-atherosclerosis mechanism. Besides, the structures, sources, safety, pharmacokinetic characteristics, and biological availability are introduced to reveal the limitations and challenges of current studies, hoping to provide a theoretical basis for the clinical application of diosgenin and its analogs and provide a new idea for developing new agents for atherosclerosis.

Peroxynitrous acid-modified extracellular matrix alters gene and protein expression in human coronary artery smooth muscle cells and induces a pro-inflammatory phenotype

Leukocytes produce oxidants at inflammatory sites, including within the artery wall during the development of atherosclerosis. Developing lesions contain high numbers of activated leukocytes that generate reactive nitrogen species, including peroxynitrite/peroxynitrous acid (ONOO^-/ONOOH), as evidenced by the presence of oxidized/nitrated molecules including extracellular matrix (ECM) proteins. ECM materials are critical for arterial wall integrity, function, and determine cell phenotype, with smooth muscle cells undergoing a phenotypic switch from quiescent/contractile to proliferative/synthetic during disease development. We hypothesized that ECM modification by ONOO^-/ONOOH might drive this switch, and thereby potentially contribute to atherogenesis. ECM generated by primary human coronary artery smooth muscle cells (HCASMCs) was treated with increasing ONOO^-/ONOOH concentrations (1-1000 μM). This generated significant damage on laminin, fibronectin and versican, and lower levels on collagens and glycosaminoglycans, together with the increasing concentrations of the damage biomarker 3-nitrotyrosine. Adhesion of naïve HCASMC to ECM modified by 1 μM ONOO^-/ONOOH was enhanced, but significantly diminished by higher ONOO^-/ONOOH treatment. Cell proliferation and metabolic activity were significantly enhanced by 100 μM ONOO^-/ONOOH pre-treatment. These changes were accompanied by increased expression of genes involved in mitosis (PCNA, CCNA1, CCNB1), ECM (LAMA4, LAMB1, VCAN, FN1) and inflammation (IL-1B, IL-6, VCAM-1), and corresponding protein secretion (except VCAM-1) into the medium. These changes induced by modified ECM are consistent with HCASMC switching to a synthetic/proliferative/pro-inflammatory phenotype, together with ECM remodelling. These changes model those in atherosclerosis, suggesting a link between oxidant-modified ECM and disease progression, and highlight the potential of targeting oxidant generation as a therapeutic strategy.

Single Donor Infusion of S-Nitroso-Human-Serum-Albumin Attenuates Cardiac Isograft Fibrosis and Preserves Myocardial Micro-RNA-126-3p in a Murine Heterotopic Heart Transplant Model

Objectives: Cold ischemia and subsequent reperfusion injury are non-immunologic cornerstones in the development of graft injury after heart transplantation. The nitric oxide donor S-nitroso-human-serum-albumin (S-NO-HSA) is known to attenuate myocardial ischemia-reperfusion (I/R)-injury. We assessed whether donor preservation with S-NO-HSA affects isograft injury and myocardial expression of GATA2 as well as miR-126-3p, which are considered protective against vascular and endothelial injury.

Methods: Donor C57BL/6 mice received intravenous (0.1 μmol/kg/h) S-NO-HSA (n = 12), or 0.9% saline (control, n = 11) for 20 min. Donor hearts were stored in cold histidine-tryptophan-α-ketoglutarate-N solution for 12 h and underwent heterotopic, isogenic transplantation, except 5 hearts of each group, which were analysed immediately after preservation. Fibrosis was quantified and expression of GATA2 and miR-126-3p assessed by RT-qPCR after 60 days or immediately after preservation.

Results: Fibrosis was significantly reduced in the S-NO-HSA group (6.47% ± 1.76 vs. 11.52% ± 2.16; p = 0.0023; 12 h-S-NO-HSA-hHTX vs. 12 h-control-hHTX). Expression of miR-126-3p was downregulated in all hearts after ischemia compared to native myocardium, but the effect was significantly attenuated when donors received S-NO-HSA (1 ± 0.27 vs. 0.33 ± 0.31; p = 0.0187; 12 h-S-NO-HSA-hHTX vs. 12 h-control-hHTX; normalized expression to U6 snRNA).

Conclusion: Donor pre-treatment with S-NO-HSA lead to reduced fibrosis and preservation of myocardial miR-126-3p and GATA2 levels in murine cardiac isografts 60 days after transplantation.

Increased Fetal Cardiovascular Disease Risk: Potential Synergy Between Gestational Diabetes Mellitus and Maternal Hypercholesterolemia

Cardiovascular diseases (CVD) remain a major cause of death worldwide. Evidence suggests that the risk for CVD can increase at the fetal stages due to maternal metabolic diseases, such as gestational diabetes mellitus (GDM) and maternal supraphysiological hypercholesterolemia (MSPH). GDM is a hyperglycemic, inflammatory, and insulin-resistant state that increases plasma levels of free fatty acids and triglycerides, impairs endothelial vascular tone regulation, and due to the increased nutrient transport, exposes the fetus to the altered metabolic conditions of the mother. MSPH involves increased levels of cholesterol (mainly as low-density lipoprotein cholesterol) which also causes endothelial dysfunction and alters nutrient transport to the fetus. Despite that an association has already been established between MSPH and increased CVD risk, however, little is known about the cellular processes underlying this relationship. Our knowledge is further obscured when the simultaneous presentation of MSPH and GDM takes place. In this context, GDM and MSPH may substantially increase fetal CVD risk due to synergistic impairment of placental nutrient transport and endothelial dysfunction. More studies on the separate and/or cumulative role of both processes are warranted to suggest specific treatment options.

Carnosine, Small but Mighty-Prospect of Use as Functional Ingredient for Functional Food Formulation

Carnosine is a dipeptide synthesized in the body from β-alanine and L-histidine. It is found in high concentrations in the brain, muscle, and gastrointestinal tissues of humans and is present in all vertebrates. Carnosine has a number of beneficial antioxidant properties. For example, carnosine scavenges reactive oxygen species (ROS) as well as alpha-beta unsaturated aldehydes created by peroxidation of fatty acid cell membranes during oxidative stress. Carnosine can oppose glycation, and it can chelate divalent metal ions. Carnosine alleviates diabetic nephropathy by protecting podocyte and mesangial cells, and can slow down aging. Its component, the amino acid beta-alanine, is particularly interesting as a dietary supplement for athletes because it increases muscle carnosine, and improves effectiveness of exercise and stimulation and contraction in muscles. Carnosine is widely used among athletes in the form of supplements, but rarely in the population of cardiovascular or diabetic patients. Much less is known, if any, about its potential use in enriched food. In the present review, we aimed to provide recent knowledge on carnosine properties and distribution, its metabolism (synthesis and degradation), and analytical methods for carnosine determination, since one of the difficulties is the measurement of carnosine concentration in human samples. Furthermore, the potential mechanisms of carnosine's biological effects in musculature, metabolism and on immunomodulation are discussed. Finally, this review provides a section on carnosine supplementation in the form of functional food and potential health benefits and up to the present, neglected clinical use of carnosine.

The Molecular Basis of Predicting Atherosclerotic Cardiovascular Disease Risk

Atherosclerotic cardiovascular disease (ASCVD) proceeds through a series of stages: initiation, progression (or regression), and complications. By integrating known biology regarding molecular signatures of each stage with recent advances in high-dimensional molecular data acquisition platforms (to assay the genome, epigenome, transcriptome, proteome, metabolome, and gut microbiome), snapshots of each phase of atherosclerotic cardiovascular disease development can be captured. In this review, we will summarize emerging approaches for assessment of atherosclerotic cardiovascular disease risk in humans using peripheral blood molecular signatures and molecular imaging approaches. We will then discuss the potential (and challenges) for these snapshots to be integrated into a personalized movie providing dynamic readouts of an individual's atherosclerotic cardiovascular disease risk status throughout the life course.

Arginine and Endothelial Function

Arginine (L-arginine), is an amino acid involved in a number of biological processes, including the biosynthesis of proteins, host immune response, urea cycle, and nitric oxide production. In this systematic review, we focus on the functional role of arginine in the regulation of endothelial function and vascular tone. Both clinical and preclinical studies are examined, analyzing the effects of arginine supplementation in hypertension, ischemic heart disease, aging, peripheral artery disease, and diabetes mellitus.

Atherosclerosis

Atherosclerosis, the formation of fibrofatty lesions in the artery wall, causes much morbidity and mortality worldwide, including most myocardial infarctions and many strokes, as well as disabling peripheral artery disease. Development of atherosclerotic lesions probably requires low-density lipoprotein, a particle that carries cholesterol through the blood. Other risk factors for atherosclerosis and its thrombotic complications include hypertension, cigarette smoking and diabetes mellitus. Increasing evidence also points to a role of the immune system, as emerging risk factors include inflammation and clonal haematopoiesis. Studies of the cell and molecular biology of atherogenesis have provided considerable insight into the mechanisms that link all these risk factors to atheroma development and the clinical manifestations of this disease. An array of diagnostic techniques, both invasive (such as selective coronary arteriography) and noninvasive (such as blood biomarkers, stress testing, CT and nuclear scanning), permit assessment of cardiovascular disease risk and targeting of therapies. An expanding armamentarium of therapies that can modify risk factors and confer clinical benefit is available; however, we face considerable challenge in providing equitable access to these treatments and in maximizing adherence. Yet, the clinical application of the fruits of research has advanced preventive strategies, enhanced clinical outcomes in affected individuals, and improved their quality of life. Rapidly accelerating knowledge and continued research promise to provide further progress in combating this common chronic disease.

Design and synthesis of rosiglitazone-ferulic acid-nitric oxide donor trihybrids for improving glucose tolerance

Glucose intolerance is associated with metabolic syndrome and type 2 diabetes mellitus (T2DM) while some new therapeutic drugs, such as rosiglitazone (Rosi), for T2DM can cause severe cardiovascular side effects. Herein we report the synthesis of Rosi-ferulic acid (FA)-nitric oxide (NO) donor trihybrids to improve glucose tolerance and minimize the side effects. In comparison with Rosi, the most active compound 21 exhibited better effects on improving glucose tolerance, which was associated with its NO production, antioxidant and anti-inflammatory activities. Furthermore, 21 displayed relatively high stability in the simulated gastrointestinal environments and human liver microsomes, and released Rosi in plasma. More importantly, 21, unlike Rosi, had little stimulatory effect on the membrane translocation of aquaporin-2 (AQP2) in kidney collecting duct epithelial cells. These, together with a better safety profile, suggest that the trihybrids, like 21, may be promising candidates for intervention of glucose intolerance-related metabolic syndrome and T2DM.

Vasculoprotective Role of Olive Oil Compounds via Modulation of Oxidative Stress in Atherosclerosis

Existing evidence supports the significant role of oxidative stress in the endothelial injury, and there is a direct link between increased oxidative stress, and the development of endothelial dysfunction. Endothelial dysfunction precedes the development of atherosclerosis and subsequent cardiovascular disease (CVD). The overproduction of reactive oxygen species facilitates the processes, such as oxidative modification of low-density lipoproteins and phospholipids, reduction in the NOS-derived nitric oxide, and the functional disruption of high-density lipids that are profoundly involved in atherogenesis, inflammation, and thrombus formation in vascular cells. Thus, under oxidative stress conditions, endothelial dysfunction was found to be associated with the following endothelial alterations: reduced nitric oxide bioavailability, increased anticoagulant properties, increased platelet aggregation, increased expression of adhesion molecules, chemokines, and cytokines. In this review, we summarized the evidence indicating that endothelial damage triggered by oxidation can be diminished or reversed by the compounds of olive oil, a readily available antioxidant food source. Olive oil bioactive compounds exhibited a potent capability to attenuate oxidative stress and improve endothelial function through their anti-inflammatory, anti-oxidant, and anti-thrombotic properties, therefore reducing the risk and progression of atherosclerosis. Also, their molecular mechanisms of action were explored to establish the potential preventive and/or therapeutic alternatives to the pharmacological remedies available.

Effects of dietary arginine on antioxidant status and immunity involved in AMPK-NO signaling pathway in juvenile blunt snout bream

The present study assessed the effects of dietary arginine on antioxidant status and immunity involved in AMPK-NO signaling pathway in juvenile blunt snout bream. Fish were fed six practical diets with graded arginine levels ranging from 0.87% to 2.70% for 8 weeks. The results showed that compared with the control group (0.87% dietary arginine level), significantly higher mRNA levels of adenosine monophosphate activated protein kinase (AMPK) and nitric oxide synthetase (NOS), activities of total nitric oxide synthetase (T-NOS) and nitric oxide synthetase (iNOS), and plasma nitric oxide (NO) contents were observed in fish fed with 1.62%-2.70% dietary arginine levels. Significantly higher levels of NOS and iNOS were observed in fish fed with 1.62%-2.70% dietary arginine levels in enzyme-linked immune sorbent assay. At dietary arginine levels of 1.22%-2.70%, the mRNA levels of iNOS were significantly improved. Dietary arginine also significantly influenced plasma interleukin 8 (IL-8) and tumour necrosis factor-α (TNF-α) contents. Furthermore, dietary arginine significantly affected the activity and mRNA level of glutathione peroxidase (GPx), the mRNA levels of pro-inflammatory factor including IL-8 and TNF-α and plasma malondialdehyde (MDA) content. However, total superoxide dismutase (T-SOD) activity, plasma complement component 3 (C3) content, plasma immunoglobulin M (IgM) content, plasma interleukin 1β (IL-1β) content and the mRNA levels of copperzinc superoxide dismutase (Cu/Zn-SOD), manganese superoxide dismutase (Mn-SOD) and IL-1β were not significantly affected by dietary arginine. After Aeromonas hydrophila challenge, the death rate was significantly lowered in fish fed with 1.62%-1.96% dietary arginine levels. Furthermore, the mRNA levels of AMPK, NOS and iNOS, plasma NO content and the activities of T-NOS and iNOS showed an upward trend with increasing dietary arginine levels. Significantly higher levels of NOS and iNOS were observed in fish fed with 1.62%-2.70% dietary arginine levels in enzyme-linked immune sorbent assay. At dietary arginine levels of 1.96%-2.31%, T-SOD activities were significantly improved. Significantly higher GPx activities were observed in fish fed with 1.22%-2.70% dietary arginine levels. At dietary arginine levels of 1.22%-2.31%, the plasma TNF-α and IL-8 contents were significantly decreased. Significantly lower plasma IL-1β contents were observed in fish fed 1.62%-1.96% dietary arginine levels. Dietary arginine significantly influenced the mRNA levels of antioxidant and pro-inflammatory genes including Cu/Zn-SOD, Mn-SOD, GPx, IL-8, TNF-α and IL-1β. Significantly higher plasma C3 contents and significantly lower plasma MDA contents were observed in fish fed with 1.62%-1.96% arginine levels. Furthermore, plasma IgM contents were significantly improved at dietary arginine levels of 1.62%-2.31%. However, high dietary arginine group (2.70%) significantly improved the mRNA levels of pro-inflammatory genes including IL-8, TNF-α and IL-1β and plasma MDA, IL-8, TNF-α and IL-1β contents as compared with optimal dietary arginine levels (1.62% and 1.96%). The present results indicate that optimal arginine level (1.62% and 1.96%) could improve antioxidant capacity, immune response and weaken tissues inflammatory involved in arginine-AMPK-NO signaling pathway, while high arginine level resulted in excessive NO production, leading to increase oxidative stress damage and inflammatory response in juvenile blunt snout bream.

Vascular endothelium dysfunction: a conservative target in metabolic disorders

AIM

Vascular endothelium plays a role in capillary transport of nutrients and drugs and regulates angiogenesis, homeostasis, as well as vascular tone and permeability as a major regulator of local vascular homeostasis. The present study has been designed to investigate the role of endothelium in metabolic disorders.

METHODS

The endothelium maintains the balance between vasodilatation and vasoconstriction, procoagulant and anticoagulant, prothrombotic and antithrombotic mechanisms.

RESULTS

Diabetes mellitus causes the activation of aldose reductase, polyol pathway and advanced glycation-end-product formation that collectively affect the phosphorylation status and expression of endothelial nitric oxide synthatase (eNOS) and causes vascular endothelium dysfunction. Elevated homocysteine levels have been associated with increase in LDL oxidation, generation of hydrogen peroxides, superoxide anions that increased oxidative degradation of nitric oxide. Hyperhomocysteinemia has been reported to increase the endogenous competitive inhibitors of eNOS viz L-N-monomethyl arginine (L-NMMA) and asymmetric dimethyl arginine (ADMA) that may contribute to vascular endothelial dysfunction. Hypercholesterolemia stimulates oxidation of LDL cholesterol, release of endothelins, and generation of ROS. The increased cholesterol and triglyceride level and decreased protective HDL level, decreases the activity and expression of eNOS and disrupts the integrity of vascular endothelium, due to oxidative stress. Hypertension also stimulates release of endothelins, vasoconstrictor prostanoids, angiotensin II, inflammatory cytokines, xanthine oxidase and, thereby, reduces bioavailability of nitric oxide.

CONCLUSION

Thus, the cellular and molecular mechanisms underlying diabetes mellitus, hyperhomocysteinemia, hypercholesterolemia hypertension and hyperuricemia leads to an imbalance of phosphorylation and dephosphorylation status of lipid and protein kinase that cause modulation of vascular endothelial L-arginine/nitric oxide synthetase (eNOS), to produce vascular endothelium dysfunction.

New Insights into the Role of Inflammation in the Pathogenesis of Atherosclerosis

Atherosclerosis is a chronic inflammatory disease characterized by the accumulation of lipids, smooth muscle cell proliferation, cell apoptosis, necrosis, fibrosis, and local inflammation. Immune and inflammatory responses have significant effects on every phase of atherosclerosis, and increasing evidence shows that immunity plays a more important role in atherosclerosis by tightly regulating its progression. Therefore, understanding the relationship between immune responses and the atherosclerotic microenvironment is extremely important. This article reviews existing knowledge regarding the pathogenesis of immune responses in the atherosclerotic microenvironment, and the immune mechanisms involved in atherosclerosis formation and activation.

Reactive Oxygen Species: A Key Hallmark of Cardiovascular Disease

Cardiovascular diseases (CVDs) have been the prime cause of mortality worldwide for decades. However, the underlying mechanism of their pathogenesis is not fully clear yet. It has been already established that reactive oxygen species (ROS) play a vital role in the progression of CVDs. ROS are chemically unstable reactive free radicals containing oxygen, normally produced by xanthine oxidase, nicotinamide adenine dinucleotide phosphate oxidase, lipoxygenases, or mitochondria or due to the uncoupling of nitric oxide synthase in vascular cells. When the equilibrium between production of free radicals and antioxidant capacity of human physiology gets altered due to several pathophysiological conditions, oxidative stress is induced, which in turn leads to tissue injury. This review focuses on pathways behind the production of ROS, its involvement in various intracellular signaling cascades leading to several cardiovascular disorders (endothelial dysfunction, ischemia-reperfusion, and atherosclerosis), methods for its detection, and therapeutic strategies for treatment of CVDs targeting the sources of ROS. The information generated by this review aims to provide updated insights into the understanding of the mechanisms behind cardiovascular complications mediated by ROS.

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.

Redox Roles of Reactive Oxygen Species in Cardiovascular Diseases

Cardiovascular disease (CVD), a major cause of mortality in the world, has been extensively studied over the past decade. However, the exact mechanism underlying its pathogenesis has not been fully elucidated. Reactive oxygen species (ROS) play a pivotal role in the progression of CVD. Particularly, ROS are commonly engaged in developing typical characteristics of atherosclerosis, one of the dominant CVDs. This review will discuss the involvement of ROS in atherosclerosis, specifically their effect on inflammation, disturbed blood flow and arterial wall remodeling. Pharmacological interventions target ROS in order to alleviate oxidative stress and CVD symptoms, yet results are varied due to the paradoxical role of ROS in CVD. Lack of effectiveness in clinical trials suggests that understanding the exact role of ROS in the pathophysiology of CVD and developing novel treatments, such as antioxidant gene therapy and nanotechnology-related antioxidant delivery, could provide a therapeutic advance in treating CVDs. While genetic therapies focusing on specific antioxidant expression seem promising in CVD treatments, multiple technological challenges exist precluding its immediate clinical applications.

Dipeptidyl peptidase-4 inhibitors and their potential role in the management of atherosclerosis--A review

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a relatively new class of anti-diabetic drugs that have therapeutic potential in the management of atherosclerosis. Of the numerous DPP-4 inhibitors in clinical practice no studies have been conducted to compare their anti-atherosclerotic effects despite growing evidence of their usefulness in the high risk population.

OBJECTIVE

The aim of the study was to review the anti-athero-thrombotic effects of DPP-4 inhibitors in atherosclerotic diseases.

METHOD

A literature search was conducted on MEDLINE and the COCHRANE Library using the terms "DPP-4 Inhibitors", "atherosclerosis", "GLP", "inflammation", "cytokines", "stroke", "ischaemic heart disease", "hypertension" and "peripheral vascular disease". A mathematical model devised by us was used to derive and compare the anti-inflammatory effects of the DPP-4 inhibitors using protective score [PS]. Data was analysed for alogliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin.

RESULTS

Sixty two published studies collected in the search were assessed for relevance to this study. Sitagliptin had the highest PS [n=5] while linagliptin and saxagliptin yielded the lowest PS [n=1]. This comparison and scoring system was limited to the data collected; which did not investigate for all athero-thrombotic factors selected in this study.

CONCLUSION

The findings suggest potential usefulness of DPP-4 in atherosclerotic diseases. It also reflected a possible superiority of sitagliptin over the other DPP-4 inhibitors in the management of atherosclerosis. Further investigations are required to establish specific inflammatory cytokines influenced by the DPP-4 inhibitors and to elucidate their clinical application in athero-thrombotic disease.

Impact of maternal obesity on fetal programming of cardiovascular disease

The in utero environment is a key determinant of long-term health outcomes; poor maternal metabolic state and placental insufficiency are strongly associated with these long-term health risks. Human epidemiological studies link maternal obesity and offspring cardiovascular disease in later life, but mechanistic studies in animal models are limited. Here, we review the literature pertaining to maternal consequences of obesity during pregnancy and the subsequent impact on fetal cardiovascular development.

Vascular Response to Graded Angiotensin II Infusion in Offspring Subjected to High-Salt Drinking Water during Pregnancy: The Effect of Blood Pressure, Heart Rate, Urine Output, Endothelial Permeability, and Gender

Introduction. Rennin-angiotensin system and salt diet play important roles in blood pressure control. We hypothesized that the high-salt intake during pregnancy influences the degree of angiotensin-dependent control of the blood pressure in adult offspring. Methods. Female Wistar rats in two groups (A and B) were subjected to drink tap and salt water, respectively, during pregnancy. The offspring were divided into four groups as male and female offspring from group A (groups 1 and 2) and from group B (groups 3 and 4). In anesthetized matured offspring mean arterial pressure (MAP), heart rate and urine output were measured in response to angiotensin II (AngII) (0-1000 ng/kg/min, iv) infusion. Results. An increase in MAP was detected in mothers with salt drinking water (P < 0.05). The body weight increased and kidney weight decreased significantly in male offspring from group 3 in comparison to group 1 (P < 0.05). MAP and urine volume in response to AngII infusion increased in group 3 (P < 0.05). These findings were not observed in female rats. Conclusion. Salt overloading during pregnancy had long-term effects on kidney weight and increased sex-dependent response to AngII infusion in offspring (adult) that may reveal the important role of diet during pregnancy in AngII receptors.

Effect of 7-difluoromethyl-5, 4'-dimethoxygenistein on aorta atherosclerosis in hyperlipidemia ApoE(-/-) mice induced by a cholesterol-rich diet

Purpose

7-Difluoromethyl–5, 4′-dimethoxygenistein (DFMG), prepared by the difluoromethylation and alkylation of Genistein, is an active new chemical entity. Its anti-atherosclerosis effect was found in a series of studies in vitro. In this article, we explored and evaluated the anti-atherosclerosis effect via its protection of endothelial function in ApoE^−/− mice that were fed a high-fat diet.

Methods

Five C57BL/6J mice were selected as a control group and were fed a 1% high-fat diet (control group, n = 5). Five ApoE^−/− mice that were fed a high-fat diet for 16 weeks were selected as the atherosclerosis model group (model group, n = 5). In the phase I study, 25 ApoE^−/− mice were provided a prophylactic treatment with different drugs at the beginning of the 16 week high-fat diet: 5 mg/gk genistein (genistein 1 group, n = 5), 5 mg/kg lovastatin (lovastatin1 group, n = 5), 2.5 mg/kg DFMG (DFMG L1 group, n = 5), 5 mg/kg DFMG (DFMG M1 group, n = 5), and 10 mg/kg DFMG (DFMG H1 group, n = 5). In the phase II study, 25 atherosclerosis model, ApoE^−/− mice were treated with different drugs and fed a high-fat diet for 16 weeks: 5 mg/gk genistein (genistein 2 group, n = 5), 5 mg/kg lovastatin (lovastatin 2 group, n = 5), 2.5 mg/kg DFMG (DFMG L2 group, n = 5), 5 mg/kg DFMG (DFMG M2 group, n = 5), and 10 mg/kg DFMG (DFMG H2 group, n = 5). The plasma levels of lipids, von Willebrand factor (vWF), and nitrite were compared between phases I and II. Endothelium-dependent relaxation (EDR), aortic lesion development, and quantification in thoracic aortas were measured during these two phase studies.

Results

Compared to the model group, the lipid and vWF plasma levels were significantly lower, the plasma nitrite levels were significantly higher, the fatty streaks of aortic lesions were significantly lower, and the endothelium dependent relaxation was significantly higher after both phase studies (P < 0.05). The DFMG supplementation led to significant plasma nitrite increment in all groups after both phase studies (P < 0.05). There were significantly decreased fatty streaks of aortic lesions in DFMG-prevented and DFMG-treated mice (P < 0.05). There was a significant increase in EDR in all prophylactic treatment groups and treatment groups (P < 0.05). We further demonstrated that the preventative effect was more obvious than the therapeutic effect.

Conclusion

Our results suggest that DFMG could work in prophylactic and therapeutic treatments for atherosclerosis development.

Effect of carvedilol and nebivolol on oxidative stress-related parameters and endothelial function in patients with essential hypertension

Oxidative stress and endothelial dysfunction have been associated with essential hypertension (EH) mechanisms. The purpose of this study was to evaluate the effect of carvedilol and nebivolol on the oxidative stress-related parameters and endothelial function in patients with EH. The studied population included 57 patients, either sex, between 30 and 75 years of age, with mild-to-moderate EH complications. Participants were randomized to receive either carvedilol (12.5 mg) (n = 23) or nebivolol (5 mg) (n = 21) for 12 weeks. Measurements included; 24-hr ambulatory blood pressure (BP), flow-mediated dilatation, levels of nitric oxide estimated as nitrite - a nitric oxide metabolite ( NO₂) - in plasma, and oxidative stress-related parameters in plasma and erythrocyte. EH patients who were treated with nebivolol or carvedilol showed systolic BP reductions of 17.4 and 19.9 mmHg, respectively, compared with baseline values (p < 0.01). Diastolic BP was reduced by 13.7 and 12.8 mmHg after the treatment with ebivolol and carvedilol, respectively (p < 0.01) (fig. 2B). Nebivolol and carvedilol showed 7.3% and 8.1% higher endothelium-dependent dilatation in relation to baseline values (p < 0.05). Ferric-reducing ability of plasma (FRAP) and reduced glutathione/oxidized glutathione (GSSH) ratio showed 31.5% and 29.6% higher levels in the carvedilol group compared with basal values; however, nebivolol-treated patients did not show significant differences after treatment. On the other hand, the NO₂ plasma concentration was not modified by the administration of carvedilol. However, nebivolol enhanced these levels in 62.1% after the treatment. In conclusion, this study demonstrated the antihypertensive effect of both beta-blockers. However, carvedilol could mediate these effects by an increase in antioxidant capacity and nebivolol through the raise in NO₂ concentration. Further studies are needed to determine the molecular mechanism of these effects.

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.

Fetoplacental vascular endothelial dysfunction as an early phenomenon in the programming of human adult diseases in subjects born from gestational diabetes mellitus or obesity in pregnancy

Gestational diabetes mellitus (GDM) and obesity in pregnancy (OP) are pathological conditions associated with placenta vascular dysfunction coursing with metabolic changes at the fetoplacental microvascular and macrovascular endothelium. These alterations are seen as abnormal expression and activity of the cationic amino acid transporters and endothelial nitric oxide synthase isoform, that is, the "endothelial L-arginine/nitric oxide signalling pathway." Several studies suggest that the endogenous nucleoside adenosine along with insulin, and potentially arginases, are factors involved in GDM-, but much less information regards their role in OP-associated placental vascular alterations. There is convincing evidence that GDM and OP prone placental endothelium to an "altered metabolic state" leading to fetal programming evidenced at birth, a phenomenon associated with future development of chronic diseases. In this paper it is suggested that this pathological state could be considered as a metabolic marker that could predict occurrence of diseases in adulthood, such as cardiovascular disease, obesity, diabetes mellitus (including gestational diabetes), and metabolic syndrome.

Unresolved inflammation: 'immune tsunami' or erosion of integrity in immune-privileged and immune-responsive tissues and acute and chronic inflammatory diseases or cancer

INTRODUCTION

Unresolved inflammation is loss of balance between two biologically opposing arms of acute inflammation, 'Yin' (tumoricidal) and 'Yang' (tumorigenic) processes that cause disruption of protective mechanisms of immune system.

HYPOTHESIS

Unresolved inflammation-induced exaggerated expression of apoptotic and/or wound healing mediators lead to fundamental erosion ('immune tsunami' or 'immune meltdown') of integrity in tissues that are naturally immune-responsive (immune surveillance); or immune-privileged (immune tolerance). 'Immune tsunami' refers to end results of acute or chronic immune dysfunction leading to inflammatory diseases or cancer. Acute inflammatory diseases including drug-induced cancer cachexia, would fit features of 'immune meltdown' that are otherwise described for end results of age-associated diseases. Pathogens induce rapid destruction of vascular integrity, gain access to tissues and cause excessive expression of apoptotic factors leading to multiple organ failure (MOF). Significant disruptions of immunological barriers and response shifts lead to chronic neurodegenerative and autoimmune diseases, tumor growth, malignancies and angiogenesis and loss of natural immune response balances.

EXPERT OPINION

Strategies to promote (stabilize) inherent properties of innate immune cells ('tumoricidal' versus 'tumorigenesis') that would influence polarization of adaptive immune (T or B) cells are key in reducing or preventing incidence of inflammatory and vascular diseases or cancer during aging process.

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.

Adrenomedullin ameliorates the development of atherosclerosis in apoE-/- mice

Adrenomedullin (ADM) is a multifunctional peptide regulating cardiovascular homeostasis. We studied the role of ADM in the pathogenesis of atherosclerosis by investigating changes in ADM and its receptors - calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMPs) - in aorta of apoE-/- mice and the effect of exogenous ADM administration. ApoE-/- mice were fed an atherogenic diet for 4 weeks, and apoE-/-+ADM mice were additionally given subcutaneous injections of ADM, 300ng/kg/h, for 4 weeks. ApoE-/- mice fed an atherogenic diet showed hyperlipidemia, a large plaque area and increased vessel wall thickness. The mRNA expression and protein level of ADM/ADM receptors were increased in the aorta, compared with C57BL/6J mice. The elevated mRNA level of CRLR and RAMPs correlated positively with ADM mRNA level. Radioimmunoassay revealed a higher plasma and aorta ADM content, by 61.6% and 285% (both P<0.01), respectively, in apoE-/- mice than that in C57BL/6J mice. Exogenous ADM significantly ameliorated dyslipidemia in apoE-/- mice. ADM-treated mice showed fewer aortic plaques, decreased plaque area, by 76% (P<0.01), and reduced ratio of plaque area to luminal area, by 65% (P<0.01), and ultrasonography revealed significantly reduced intima-media thickness of the ascending branch and abdominal aorta. The results suggest that atherosclerotic apoE-/- mice fed an atherogenic diet showed upregulated endogenous ADM and its receptors, and exogenous ADM treatment ameliorated the dyslipidemia and vascular atherosclerotic lesions. ADM/ADM receptors might be an important protective system against atherosclerosis and could become a new target of prevention and therapy for atherosclerosis.

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.

Inflammation, aging, and cancer: tumoricidal versus tumorigenesis of immunity: a common denominator mapping chronic diseases

Acute inflammation is a highly regulated defense mechanism of immune system possessing two well-balanced and biologically opposing arms termed apoptosis ('Yin') and wound healing ('Yang') processes. Unresolved or chronic inflammation (oxidative stress) is perhaps the loss of balance between 'Yin' and 'Yang' that would induce co-expression of exaggerated or 'mismatched' apoptotic and wound healing factors in the microenvironment of tissues ('immune meltdown'). Unresolved inflammation could initiate the genesis of many age-associated chronic illnesses such as autoimmune and neurodegenerative diseases or tumors/cancers. In this perspective 'birds' eye' view of major interrelated co-morbidity risk factors that participate in biological shifts of growth-arresting ('tumoricidal') or growth-promoting ('tumorigenic') properties of immune cells and the genesis of chronic inflammatory diseases and cancer will be discussed. Persistent inflammation is perhaps a common denominator in the genesis of nearly all age-associated health problems or cancer. Future challenging opportunities for diagnosis, prevention, and/or therapy of chronic illnesses will require an integrated understanding and identification of developmental phases of inflammation-induced immune dysfunction and age-associated hormonal and physiological readjustments of organ systems. Designing suitable cohort studies to establish the oxido-redox status of adults may prove to be an effective strategy in assessing individual's health toward developing personal medicine for healthy aging.

In vivo veritas: Thrombosis mechanisms in animal models

Experimental models have enhanced our understanding of atherothrombosis pathophysiology and have played a major role in the search for adequate therapeutic interventions. Various animal models have been developed to simulate thrombosis and to study in vivo parameters related to hemodynamics and rheology that lead to thrombogenesis. Although no model completely mimics the human condition, much can be learned from existing models about specific biologic processes in disease causation and therapeutic intervention. In general, large animals such as pigs and monkeys have been better suited to study atherosclerosis and arterial and venous thrombosis than smaller species such as rats, rabbits, and dogs. On the other hand, mouse models of arterial and venous thrombosis have attracted increasing interest over the past two decades, owing to direct availability of a growing number of genetically modified mice, improved technical feasibility, standardization of new models of local thrombosis, and low maintenance costs. To simulate rupture of an atherosclerotic plaque, models of arterial thrombosis often involve vascular injury, which can be achieved by several means. There is no animal model that is sufficiently tall, that can mimic the ability of humans to walk upright, and that possesses the calf muscle pump that plays an important role in human venous hemodynamics. A number of spontaneous or genetically engineered animals with overexpression or deletion of various elements in the coagulation, platelet, and fibrinolysis pathways are now available. These animal models can replicate important aspects of thrombosis in humans, and provide a valuable resource in the development of novel concepts of disease mechanisms in human patients.

IMMUNOHISTOCHEMICAL LOCALIZATION OF ENDOTHELIAL ISOFORM (eNOS) IN HUMAN CEREBRAL ARTERIES AND THE AORTA

The common carotid, vertebral, posterior cerebral arteries, and the aorta were studied in the human in terms of its eNOS expression. In around 10 weeks of gestation, the developing intima began to express notable eNOS. In the adult, the positive eNOS sites were in the endothelial cells and the tunica media where the smooth muscles were. In the vessels with athrosclerotic changes, eNOS was down regulated in the endothelial layer and most of the tunica media but was significantly upregulated in the tunica media around the lesion. The protein changes are related to the onset of the athrosclerotic diseases.

Early prevention by L-Arginine attenuates coronary atherosclerosis in a model of hypercholesterolemic animals; no positive results for treatment

Background

Endothelial dysfunction (ED) is an independent predictor of cardiovascular events. ED is also a reversible disorder, and nitric oxide donors like L-arginine may promote this process. Despite the positive results from several studies, there are some studies that have shown that L-arginine administration did not improve endothelium-dependent dilation or the inflammatory state of patients. In this study the early and the late effects of L-arginine on coronary fatty streak formation and ED biomarkers were considered in hypercholesterolemic rabbits.

Methods

36 white male rabbits randomly assigned in 3 groups. Rabbits were fed 1% high-cholesterol diet (LP group, n = 15), or high-cholesterol diet with oral L-arginine (3% in drinking water) (EP group, n = 15) or standard diet (control group, n = 6) for 4 weeks (phase I). Afterward, all animals were fed normal diet for 4 weeks (phase II). In the second phase, L-arginine was discontinued for EP group and was begun for LP group. The plasma levels of lipids, von Willebrand factor (vWF), and nitrite were compared before and after 4 and 8 weeks of experiment. Coronary fatty streak formation was measure after 4 and 8 weeks of experiment.

Results

The plasma levels of lipids were increased significantly in both groups of LP and EP after phase I. The hypercholesterolemia induced significant increased vWF release in LP group. The L-arginine supplementation led to significant plasma nitrite increment in EP group. The vWF in LP group was higher than other groups (p < 0.05). By the end of phase II, despite of start of L-arginine supplementation for LP group and L-arginine discontinuation in EP group, there were significantly more fatty streaks lesions in LP group coronary arteries than EP group. Furthermore, L-arginine supplementation did not result in significant nitrite increment in LP group.

Conclusion

Early prevention by L-arginine may be helpful to prevent the ED, but our study did not suggest the treatment. It seems reasonable to consider ED-aside from control the cardiovascular risk factors in primary prevention of atherosclerosis and its clinical outcomes before development of irreversible vascular damage.

'Yin and Yang' in inflammation: duality in innate immune cell function and tumorigenesis

BACKGROUND

The two stages of the acute inflammatory process are apoptosis ('Yin') and wound healing or resolution ('Yang'). Inflammation defends the host against unwanted elements.

OBJECTIVE/METHODS

To present a discussion of pleiotropic roles of innate immune cells possessing 'tumoricidal' and/or 'tumorigenic' properties in inflammation-induced dysfunction of the immune system and the genesis of chronic inflammatory diseases, hyperplasia, precancer/neoplasia or tumor and angiogenesis.

RESULTS/CONCLUSIONS

Loss of maintenance of the balance between apoptosis and wound healing and co-existence of death and growth factors in tissues could create 'immunological chaos' with accumulation of 'immune response mismatches'. Unresolved inflammation plays a role in the genesis of chronic inflammatory and autoimmune diseases and cancer. Identification of accumulated 'mismatched' death and growth factors during the developmental phases of immune dysfunction in target tissues or cancer microenvironment presents challenges and opportunities for future studies on diagnosis, prevention and therapy of these diseases.

The prevention of endothelial dysfunction through endothelial cell apoptosis inhibition in a hypercholesterolemic rabbit model: the effect of L-arginine supplementation

BACKGROUND

The impact of L-arginine on atherogenesis and its ability to prevent endothelial dysfunction have been studied extensively during the past years. L-arginine is a substance for nitric oxide synthesis which involves in apoptosis. Hypercholesterolemia promotes endothelial dysfunction, and it is hypothesized that L-arginine prevents endothelial dysfunction through endothelial cells apoptosis inhibition. To test this hypothesis, thirty rabbits were assigned into two groups. The control group received 1% cholesterol diet for 4 weeks, and the L-arginine group received same diets plus 3% L-arginine in drinking water.

RESULTS

No significant differences were observed in cholesterol level between two groups, but the nitrite concentration in L-arginine group was significantly higher than other group (control group: 11.8 +/- 1; L-arginine group: 14.7 +/- 0.5 micromol/l); (p < 0.05). The aorta score of fatty streak in control group was 0.875 +/- 0.35, but no fatty streak lesion was detected in L-arginine group (p < 0.05). The number of intimal apoptotic cells/500 cells of aorta in two groups of experiment were statistically different (control group: 39.3 +/- 7.6; L-arginine group: 21.5 +/- 5.3) (p < 0.05).

CONCLUSION

The inhibition of endothelial cells apoptosis by L-arginine restores endothelial function in a model of hypercholesterolemia.

Candesartan decreases carotid intima-media thickness by enhancing nitric oxide and decreasing oxidative stress in patients with hypertension

Candesartan has been reported to produce nitric oxide (NO) and to decrease oxidative stress in animal studies. We investigated candesartan's effect on the production of NO and oxidative stress as well as on carotid intima-media thickness (IMT) in hypertensive patients. One-hundred age-matched hypertensive patients were enrolled into an angiotensin II receptor blocker (ARB) group (n=50) or a non-ARB group (n=50). The ARB group was treated with candesartan 8 mg and, when needed, Ca channel blockers, angiotesin-converting enzyme (ACE) inhibitors, and/or beta-blockers. The non-ARB group was treated with drugs other than ARB. Carotid IMT was assessed by echocardiography before and 12 and 24 months after treatment. The urine levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), an indicator of oxidative stress, and the serum levels of NOx, an indicator of NO, were measured. Blood pressure decreased to below 140/90 mmHg to the same extent in both groups. Carotid IMT decreased significantly in the ARB group, but not in the non-ARB group, at 12 and 24 months after treatment. The urine levels of 8-OHdG decreased significantly at 6 and 12 months after treatment in the ARB group but did not decrease in the non-ARB group. The serum levels of NOx increased significantly at 6 and 12 months after treatment in the ARB group but not in the non-ARB group. In conclusion, candesartan decreases carotid IMT by enhancing NO production and decreasing oxidative stress in patients with hypertension.

Rosiglitazone stimulates nitric oxide synthesis in human aortic endothelial cells via AMP-activated protein kinase

The thiazolidinedione anti-diabetic drugs increase activation of endothelial nitric-oxide (NO) synthase by phosphorylation at Ser-1177 and increase NO bioavailability, yet the molecular mechanisms that underlie this remain poorly characterized. Several protein kinases, including AMP-activated protein kinase, have been demonstrated to phosphorylate endothelial NO synthase at Ser-1177. In the current study we determined the role of AMP-activated protein kinase in rosiglitazone-stimulated NO synthesis. Stimulation of human aortic endothelial cells with rosiglitazone resulted in the time- and dose-dependent stimulation of AMP-activated protein kinase activity and NO production with concomitant phosphorylation of endothelial NO synthase at Ser-1177. Rosiglitazone stimulated an increase in the ADP/ATP ratio in endothelial cells, and LKB1 was essential for rosiglitazone-stimulated AMPK activity in HeLa cells. Infection of endothelial cells with a virus encoding a dominant negative AMP-activated protein kinase mutant abrogated rosiglitazone-stimulated Ser-1177 phosphorylation and NO production. Furthermore, the stimulation of AMP-activated protein kinase and NO synthesis by rosiglitazone was unaffected by the peroxisome proliferator-activated receptor-gamma inhibitor GW9662. These studies demonstrate that rosiglitazone is able to acutely stimulate NO synthesis in cultured endothelial cells by an AMP-activated protein kinase-dependent mechanism, likely to be mediated by LKB1.

Versatile regulation of neuronal nitric oxide synthase by specific regions of its C-terminal tail

The C-terminal tail (CT) of neuronal nitric oxide synthase (nNOS) is a regulatory element that suppresses nNOS activities in the absence of bound calmodulin (CaM). A crystal structure of the nNOS reductase domain (nNOSr) (Garcin, E. D., Bruns, C. M., Lloyd, S. J., Hosfield, D. J., Tiso, M., Gachhui, R., Stuehr, D. J., Tainer, J. A., and Getzoff, E. D. (2004) J. Biol. Chem. 279, 37918-37927) revealed how the first half of the CT interacts with nNOSr and thus provided a template for detailed studies. We generated truncation mutants in nNOS and nNOSr to test the importance of 3 different regions of the CT. Eliminating the terminal half of the CT (all residues from Ile1413 to Ser1429), which is invisible in the crystal structure, had almost no impact on NADP+ release, flavin reduction, flavin autoxidation, heme reduction, reductase activity, or NO synthesis activity, but did prevent an increase in FMN shielding that normally occurs in response to NADPH binding. Additional removal of the CT alpha-helix (residues 1401 to 1412) significantly increased the NADP+ release rate, flavin autoxidation, and NADPH oxidase activity, and caused hyper-deshielding of the FMN cofactor. These effects were associated with increased reductase activity and slightly diminished heme reduction and NO synthesis. Further removal of residues downstream from Gly1396 (a full CT truncation) amplified the aforementioned effects and in addition altered NADP+ interaction with FAD, relieved the kinetic suppression on flavin reduction, and further diminished heme reduction and NO synthesis. Our results reveal that the CT exerts both multifaceted and regiospecific effects on catalytic activities and related behaviors, and thus provide new insights into mechanisms that regulate nNOS catalysis.

L-arginine chlorination results in the formation of a nonselective nitric-oxide synthase inhibitor

Reduced nitric oxide (NO) bioavailability and impaired vascular function are the key pathological characteristics of inflammatory diseases such as atherosclerosis. We have recently found that leukocyte-derived hypochlorous acid is able to react with the nitric-oxide synthase (NOS) substrate L-arginine to produce chlorinated L-arginine (cl-L-Arg). Interestingly, cl-L-Arg potently inhibits the formation of NO metabolites in cultured endothelial cells. It is unknown whether cl-L-Arg has a direct inhibitory effect on endothelial NOS (eNOS). In addition, the effect of cl-L-Arg on the other NOS isoforms, neuronal NOS (nNOS) and inducible NOS (iNOS), is also unknown. Therefore, we designed the current study to test the effects of cl-L-Arg on eNOS, nNOS, and iNOS. Using recombinant NOS, we found that cl-L-Arg had a direct inhibitory effect on the activity of NOS. The effect of cl-L-Arg on NOS activity is nonselective, as all three NOS isoforms were inhibited with a similar IC(50). We further determined the effect of cl-L-Arg on the three NOS isoforms at the tissue level. The results demonstrated that cl-L-Arg potently inhibited all three NOS isoform-mediated vessel reactivities, as well as the NOS signaling molecule cGMP. Cl-L-Arg might serve as a novel endogenous NOS inhibitor and an important mediator for vascular dysfunction under inflammatory conditions such as atherosclerosis. Blocking cl-L-Arg formation may be a new therapeutic approach to cardiovascular diseases.