Nitric oxide, atherosclerosis and the clinical relevance of endothelial dysfunction

Retinal Microcirculation Changes in Crohn’s Disease Patients under Biologics, a Potential Biomarker of Severity: A Pilot Study

Crohn’s disease (CD) is associated with increased cardiovascular risk and the retinal microcirculation is a reflection of the systemic microcirculation. Is the retinal microcirculation altered in relation to the severity of Crohn’s disease? This cross-sectional case-controlled study was conducted in a university hospital center from November 2020 to February 2021. We prospectively included patients with moderate (biologic therapy) or severe (biologic therapy + peri-anal disease and/or digestive resection) CD and age- and sex-matched controls. Individuals with diabetes, renal disease, cardiovascular disease, ophthalmological history or poor quality images were excluded. All participants underwent OCT angiography (OCT-A) imaging (Optovue, Fremont, CA). Analysis of covariance was used. 74 CD patients (33 moderate, 41 severe) and 74 controls (66 (44.6%) men; mean (SD) age 44 (14) years) were included. Compared with the controls, the severe CD patients showed a significantly reduced mean foveal avascular zone area (p = 0.001), superficial macular capillary plexus vessel density (p = 0.009) and parafoveal thickness (p < 0.001), with no difference in mean superficial capillary flow index (p = 0.06) or deep macular capillary plexus vessel density (p = 0.67). The mean foveal avascular zone was significantly lower in the severe than the moderate CD patients (p = 0.010). OCT-A can detect alterations in retinal microcirculation in patients with severe versus moderate CD and versus age- and sex-matched controls.

The Role of Zinc in Cardiovascular Disease

Zinc is an essential trace element due to its role as a key part of human enzymatic activity. As a cofactor in metalloenzymes and metalloproteins, zinc participates in diverse biological functions, including gene transcription, translation, and replication, phagocytosis, and immunoglobulin and cytokine production. In this review, we will focus on the role of zinc in the cardiovascular system, including heart failure, vascular calcification, and myocardial infarction. We will further highlight the role of zinc in cardiovascular pathology in individuals with chronic kidney disease, and type II diabetes mellitus, groups uniquely at risk for cardiovascular morbidity and mortality.

The Influence of an Acute Bout of Aerobic Exercise on Vascular Endothelial Function in Moderate Stages of Chronic Kidney Disease

Chronic kidney disease (CKD) is directly influenced by the deleterious effects of systemic inflammation and oxidative stress. The vascular endothelium may transiently respond to aerobic exercise and improve post-exercise vascular renal function in moderate stages of CKD. Brachial artery flow-mediated dilation (FMD) is a nitric-oxide-dependent measure of endothelial function that is transiently potentiated by exercise. The purpose of the study was to determine the acute influence of a single bout of high-intensity interval exercise (HIIE) or steady-state moderate-intensity exercise (SSE) on endothelial dysfunction in moderate stages of CKD. Twenty participants (n = 6 men; n = 14 women) completed 30 min of SSE (65%) and HIIE (90:20%) of VO_2reserve in a randomized crossover design. FMD measurements and blood samples were obtained before, 1 h, and 24 h post-exercise. FMD responses were augmented 1 h post-exercise in both conditions (p < 0.005). Relative to pre-exercise measures, total antioxidant capacity increased by 4.3% 24 h post-exercise (p = 0.012), while paraoxonase-1 was maintained 1 h and elevated by 6.1% 24 h after SSE, but not HIIE (p = 0.035). In summary, FMD can be augmented by a single episode of either HIIE or SSE in moderate stages of CKD. Modest improvements were observed in antioxidant analytes, and markers of oxidative stress were blunted in response to either SSE or HIIE.

Effects of anagliptin on the stress induced accelerated senescence of human umbilical vein endothelial cells

Background

Dipeptidyl peptidase 4 (DPP-4) inhibitors have been used to treat type 2 diabetes mellitus (T2DM) via inhibition of the enzymatic activity of DPP-4 in degrading active circulating glucagon-like peptide-1. In addition to their glucose-lowering effect, DPP-4 inhibitors have pleiotropic effects. Cellular senescence regarded as important pathophysiological mechanism underlying many degenerative diseases, including atherosclerosis. This study was performed to examine whether the DPP-4 inhibitor, anagliptin, can directly protect against stress-induced accelerated senescence (SIAS) of vascular endothelial cells, regardless of changes in ambient glucose level.

Methods

Cultured human umbilical vein endothelial cells (HUVECs) were exposed to various concentrations of H₂O₂, and a fixed high concentration of glucose (25 mM) with varying concentrations of palmitate. Changes in cell viability, senescence-associated beta-galactosidase (SA-β-Gal), p16 protein, markers of endoplasmic reticulum (ER) stress, NOX4, NLRP inflammasome, lactate dehydrogenase (LDH) release and interleukin (IL) 1β levels were measured by Cell Counting Kit-8 assay, immunofluorescent staining, Western blotting, and enzyme-linked immunosorbent assay, respectively before and after application of anagliptin.

Results

The application of oxidative and glucolipotoxic stresses markedly increased the degree of SIAS of HUVECs, represented by increased SA-β-Gal immunopositivity and p16 protein expression. Aggravation of ER stress and inflammatory response were also observed through increased levels of ATF4, CHOP, peIF2α, NOX4, NLRP inflammasome, LDH, and IL1β. These changes were markedly reversed by the administration of anagliptin.

Conclusions

The DPP-4 inhibitor anagliptin effectively protects HUVECs against SIAS, suggesting its potential use in the development of new treatment strategies for aging.

New views on endothelial dysfunction in gestational hypertension and potential therapy targets

The placenta has vital roles in metabolite exchange, fetal growth, and pre-eclampsia (PE). In this review, we discuss the pathogenesis of hypertension in pregnancy, focusing on four major theories to explain PE, discussing endothelial roles in those theories. We focus in particular on the roles of nitric oxide (NO) and prostacyclin (PGI₂) in placental endothelium, and propose new hypotheses for the influence and mechanisms of endothelial NO and PGI₂ signaling pathways in PE.

Mechanisms of Non-Alcoholic Fatty Liver Disease in the Metabolic Syndrome. A Narrative Review

Non-alcoholic fatty liver disease (NAFLD) and metabolic syndrome (MS) are two different entities sharing common clinical and physio-pathological features, with insulin resistance (IR) as the most relevant. Large evidence leads to consider it as a risk factor for cardiovascular disease, regardless of age, sex, smoking habit, cholesterolemia, and other elements of MS. Therapeutic strategies remain still unclear, but lifestyle modifications (diet, physical exercise, and weight loss) determine an improvement in IR, MS, and both clinical and histologic liver picture. NAFLD and IR are bidirectionally correlated and, consequently, the development of pre-diabetes and diabetes is the most direct consequence at the extrahepatic level. In turn, type 2 diabetes is a well-known risk factor for multiorgan damage, including an involvement of cardiovascular system, kidney and peripheral nervous system. The increased MS incidence worldwide, above all due to changes in diet and lifestyle, is associated with an equally significant increase in NAFLD, with a subsequent rise in both morbidity and mortality due to both metabolic, hepatic and cardiovascular diseases. Therefore, the slowdown in the increase of the "bad company" constituted by MS and NAFLD, with all the consequent direct and indirect costs, represents one of the main challenges for the National Health Systems.

Effect of fructooligosaccharide on endothelial function in CKD patients: a randomized controlled trial

BACKGROUND

Microbiota-derived uremic toxins have been associated with inflammation that could corroborate with endothelial dysfunction (ED) and increase cardiovascular risk in patients with chronic kidney disease (CKD). This trial aimed to evaluate the effect of the prebiotic fructooligosaccharide (FOS) on endothelial function and arterial stiffness in nondialysis CKD patients.

METHODS

In a double-blind controlled trial, 46 nondiabetic CKD patients were randomized to receive 12 g/day of FOS or placebo (maltodextrin) for 3 months. Total p-cresyl sulfate (PCS) and indoxyl sulfate by high-performance liquid chromatography, urinary trimethylamine N-oxide by mass spectrometry, C-reactive protein, interleukin-6 (IL-6), serum nitric oxide and stroma-derived factor-1 alfa were measured at baseline and at the end of follow-up; endothelial function was assessed through flow-mediated dilatation (FMD) and arterial stiffness by pulse wave velocity (PWV).

RESULTS

The mean (± standard deviation) age of the study participants was 57.6 ± 14.4 years, with an estimated glomerular filtration rate of 21.3 ± 7.3 mL/min/1.73 m2. During the follow-up, regarding the inflammatory markers and uremic toxins, there was a significant decrease in IL-6 levels (3.4 ± 2.1 pg/mL versus 2.6 ± 1.4 pg/mL; P = 0.04) and a trend toward PCS reduction (55.4 ± 38.1 mg/L versus 43.1 ± 32.4 mg/L, P = 0.07) only in the prebiotic group. Comparing both groups, there was no difference in FMD and PWV. In an exploratory analysis, including a less severe ED group of patients (FMD ≥2.2% at baseline), FMD remained stable in the prebiotic group, while it decreased in the placebo group (group effect P = 0.135; time effect P = 0.012; interaction P = 0.002).

CONCLUSIONS

The prebiotic FOS lowered circulating levels of IL-6 in CKD patients and preserved endothelial function only in those with less damaged endothelium. No effect of FOS in arterial stiffness was observed.

Combination of hyperglycaemia and hyperlipidaemia induces endothelial dysfunction: Role of the endothelin and nitric oxide systems

Endothelial dysfunction (ED) is a key feature of diabetes and is a major cause of diabetic vasculopathy. Diabetic patients who also exhibit hyperlipidaemia suffer from accelerated vascular complications. While the deleterious effects of high glucose levels (HG) and hyperlipidaemia alone on ED are well established, the effects of combined hyperlipidaemia and HG have not been thoroughly studied. Therefore, the current study examines whether HG and hyperlipidaemia exert synergistic ED, and explores the mechanisms underlying this phenomenon. We applied multi‐disciplinary approaches including cultured HUVECs and HMEC‐1 as well as knockout mice CByJ.129S7(B6)‐Ldlrtm1Her/J (LDLR^−/−) to investigate the mechanisms underlying combined HG and hyperlipidaemia‐induced ED. Incremental doses of glucose in the presence or absence of OxLDL were added to HUVECs and HMEC‐1. After 5 days, the status of nitric oxide (NO) and endothelin (ET)‐1 systems as well as their signal transduction were assessed using Western blot, ELISA and immunoreactive staining. The effects of chronic combination of HG and hyperlipidaemia on endothelial integrity and function as well as alterations in circulatory NO and ET‐1 systems were examined in knockout mice LDLR^−/− and their wild‐type. HUVEC cells exposed to HG and OxLDL displayed enhanced ET‐1 production, more than HG or OxLDL when added alone. Overproduction of ET‐1 stems from up‐regulation of endothelin converting enzyme (ECE)‐1 as observed under these conditions. In contrast, combination of HG and OxLDL dramatically decreased both total endothelial NO synthase (eNOS) by 60%, and activated eNOS (peNOS) by 80%. Moreover, NRF2 decreased by 42% and its active form (pNRF2) by 56%, as compared to baseline. Likewise, ET_B levels decreased by 64% from baseline on endothelial cells. Furthermore, diabetic LDLR^−/− mice displayed a higher blood pressure, plasma triglycerides, cholesterol, ET‐1 and NO2/NO3 levels, when compared with normoglycemic LDLR^−/− and BALB mice. Combined hyperglycaemia and hyperlipidaemia activates the ET system and attenuates the nitric oxide system with the Nrf2 signalling pathway. These findings suggest that perturbations in these paracrine systems may contribute to ED.

From short-term blood pressure variability to atherosclerosis: Relative roles of vascular stiffness and endothelial dysfunction

Both arterial blood pressure (BP) average levels and short-term BP variability (BPV) relate to hypertension-mediated organ damage, in particular increased carotid artery intima-media thickness (IMT) and carotid-femoral pulse wave velocity (PWV). Endothelial dysfunction possibly mediates such damage. The authors aimed at further investigating such role in hypertensive patients. In 189 recently diagnosed, untreated hypertensive patients the authors evaluated, in a cross-sectional design, the relationships of BP average levels and short-term systolic (S) BPV (standard deviation of awake SBP or of 24-hour-weighted SBP) with IMT and PWV, and how much these relationships are explained by endothelial function parameters-brachial artery flow-mediated dilation (FMD) and digital reactive hyperemia index (RHI). Multivariable models assessed the strength of these relationships to derive a plausible pathogenetic sequence. Both average SBP values and our measures of SBPV were significantly related to IMT (24-hour mean SBP: r = .156, P = .034; 24-hour-weighted SBPV: r = .157, P = .033) and to PWV (24-hour mean SBP: r = .179, P = .015; 24-hour-weighted SBPV: r = .175; P = .018), but only poorly related to FMD or RHI (P > .05 for all). At univariable regression analysis, FMD and RHI were both related to IMT, (P < .001), but not to PWV. When FMD and RHI were added to average SBP and SBPV parameters in a multivariable model, both significantly (P < .005) contributed to predict IMT, but not PWV. Thus, endothelial dysfunction relates to IMT independently of BP parameters, but appears to play a minor role in the association between BP variability-related variables and arterial stiffening.

Progress in internal/external stimuli responsive fluorescent carbon nanoparticles for theranostic and sensing applications

In the past decade, fluorescent carbon nanoparticles (FNPs) prepared from natural resources and biomaterials have been attractive due to their various properties, such as unique optical properties, great biocompatibility, water dispersion, and facile surface functionalization. Depending on the properties of the carbon sources and the subsequent carbonization processes, internal/external stimuli responsive carbon nanoparticles have been generated that are useful for theranostic and sensing applications. In this review, we highlight the recent developments in the use of FNPs in nanomedicine in great detail, particularly for FNPs responding to internal stimuli, including redox, pH, and enzymes, and external stimuli, including temperature, light, and magnetic fields, for drug delivery and sensing applications. Furthermore, we hope to provide insight that could stimulate further research aiming for unparalleled useful applications. As a result, there are many possibilities that can be explored from this smart material.

Physical Exercise Is a Potential "Medicine" for Atherosclerosis

Cardiovascular disease (CVD) has been recognized as the number one killer for decades. The most well-known risk factor is atherosclerosis. Unlike the acuity of CVD, atherosclerosis is a chronic, progressive pathological change. This process involves inflammatory response, oxidative reaction, macrophage activity, and different interaction of inflammatory factors. Physical exercise has long been known as good for health in general. In recent studies, physical exercise has been demonstrated to be a therapeutic tool for atherosclerosis. However, its therapeutic effect has dosage-dependent effect. Un-proper over exercise might also cause damage to the heart. Here we summarize the mechanism of Physical exercise's beneficial effects and its potential clinical use.

Clopidogrel Improves Skin Microcirculatory Endothelial Function in Persons With Heightened Platelet Aggregation

Background

Platelet activation can lead to enhanced oxidative stress, inflammatory response, and endothelial dysfunction. To quantify the effects of platelet inhibition on endothelial function, we assessed platelet activity of healthy persons before and after clopidogrel administration and evaluated its effects on endothelial function. We hypothesized that clopidogrel, by attenuating platelet activity, would result in enhanced endothelial function.

Methods and Results

Microcirculatory endothelial function was quantified by laser Doppler flowmetry (LDF) mediated by thermal hyperemia (TH) and postocclusive reactive hyperemia, respectively, in 287 and 241 relatively healthy and homogenous Old Order Amish persons. LDF and platelet aggregation measures were obtained at baseline and after 7 days of clopidogrel administration. Our primary outcome was percentage change in post‐ versus preclopidogrel LDF measures. Preclopidogrel TH‐LDF and platelet aggregation were higher in women than in men (P<0.001). Clopidogrel administration was associated with ≈2‐fold higher percentage change in TH‐LDF in participants with high versus low baseline platelet aggregation (39.4±10.1% versus 17.4±5.6%, P=0.03). Clopidogrel also increased absolute TH‐LDF measures in persons with high platelet aggregation (1757±766 to 2154±1055, P=0.03), with a more prominent effect in women (1909±846 to 2518±1048, P=0.001). There was no evidence that clopidogrel influenced postocclusive reactive hyperemia LDF measures.

Conclusions

The administration of clopidogrel in healthy persons with high baseline platelet aggregation results in improved TH‐induced microcirculatory endothelial function. These data suggest that clopidogrel may have a beneficial effect on microcirculatory endothelial function, presumably through antiplatelet activity, and may confer additional vascular benefits.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00799396.

Flow Mediated Dilatation, Carotid Intima Media Thickness, Ankle Brachial Pressure Index and Pulse Pressure in Young Male Post Myocardial Infarction Patients in India

INTRODUCTION

Due to increase in Coronary Artery Disease (CAD) at a younger age, we should try to diagnose atherosclerotic process and population at risk, at the earliest. Flow Mediated Dilatation (FMD), Carotid Intima-Media Thickness (CIMT) and Ankle-Brachial Pressure Index (ABI) are probable markers for early atherosclerosis and may be useful in coronary risk stratification.

AIM

To compare and correlate the FMD, CIMT, ABI and Pulse Pressure (PP) in young male patients of Myocardial Infarction (MI) with age and sex matched healthy controls.

MATERIALS AND METHODS

Eighty male patients of MI aged ≤45 years, who presented to the Cardiac Care Unit and Department of Medicine of Guru Teg Bahadur Hospital, Delhi, India, from November 2010 to April 2012 were recruited consecutively for this case control study and same number of age and sex matched healthy controls were also analyzed. Six weeks after MI, FMD of the brachial artery, intima media thickness of carotid artery, ABPI and PP were measured in the cases and compared with healthy controls.

RESULTS

The FMD was lower among young patients of MI than controls (p<0.001). CIMT was higher among cases than controls (p=0.001). ABI was lower among cases than controls (p<0.001). Compared to controls, PP was higher among cases (p=0.001). In all subjects, a negative correlation between FMD and CIMT (r=-0.220, p=0.005) and a positive correlation between FMD and ABPI (r=0.304, p<0.001) was found. A statistically significant negative correlation was found between endothelial dependent FMD and PP among cases and control groups (r=-0.209, p=0.007).

CONCLUSION

Biophysical parameters were deranged in young post MI patients. Majority of our young male patients fell in low risk Framingham risk score but still they manifested with CAD. Despite six weeks of treatment among young male patients of MI, various biophysical parameters were still deranged.

Electrostatic Control of Isoform Selective Inhibitor Binding in Nitric Oxide Synthase

Development of potent and isoform selective nitric oxide synthase (NOS) inhibitors is challenging because of the structural similarity in the heme active sites. One amino acid difference between NOS isoforms, Asp597 in rat neuronal NOS (nNOS) versus Asn368 in bovine endothelial NOS (eNOS), has been identified as the structural basis for why some dipeptide amide inhibitors bind more tightly to nNOS than to eNOS. We now have found that the same amino acid variation is responsible for substantially different binding modes and affinity for a new class of aminopyridine-based inhibitors.

Chlorthalidone Improves Endothelial-Mediated Vascular Responses in Hypertension Complicated by Nondiabetic Metabolic Syndrome

Background: The study was conducted to evaluate the vascular effects of chlorthalidone, a distal tubule-acting natriuretic agent, in hypertensive patients with nondiabetic metabolic syndrome, an insulin-resistant condition characterized by endothelial dysfunction and high risk for diabetes mellitus development.

Methods: Thirteen untreated hypertensive patients with Adult Treatment Panel-III-defined nondiabetic metabolic syndrome were assigned to 3-month treatment with chlorthalidone. The end-points were baseline and post-treatment evaluation of (1) forearm blood flow (strain-gauge plethysmography) responses to graded intra-arterial acetylcholine infusion to test endothelial-mediated vasomotor function, with sodium nitroprusside as a control for endothelium-independent vasodilatation; (2) minimum forearm vascular resistance, the ratio of mean blood pressure and maximal blood flow in response to 13-minute arterial occlusion, as a hemodynamic correlate of arteriolar structure; and (3) transcapillary albumin escape rate (the 1-hour decay rate of 125I-albumin, 6-8 μC ev) as a measure of systemic capillary permeability. Additional measurements included baseline and posttreatment lipids, fasting, and postload glucose and insulin as well as the homeostasis model assessment, an index of insulin sensitivity.

Results: Chlorthalidone reduced blood pressure, augmented acetylcholine-mediated vasodilatation, decreased minimum forearm resistance, and slowed the transcapillary albumin escape rate. Metabolic parameters did not change significantly except for an increase in low-density lipoprotein cholesterol levels.

Conclusions: Chlorthalidone improved endothelial function, reversed abnormal arteriolar structure, and slowed albumin permeation in hypertensive patients with nondiabetic metabolic syndrome.

Cellular mechanisms and consequences of glycation in atherosclerosis and obesity

Post-translational modification of proteins imparts diversity to protein functions. The process of glycation represents a complex set of pathways that mediates advanced glycation endproduct (AGE) formation, detoxification, intracellular disposition, extracellular release, and induction of signal transduction. These processes modulate the response to hyperglycemia, obesity, aging, inflammation, and renal failure, in which AGE formation and accumulation is facilitated. It has been shown that endogenous anti-AGE protective mechanisms are thwarted in chronic disease, thereby amplifying accumulation and detrimental cellular actions of these species. Atop these considerations, receptor for advanced glycation endproducts (RAGE)-mediated pathways downregulate expression and activity of the key anti-AGE detoxification enzyme, glyoxalase-1 (GLO1), thereby setting in motion an interminable feed-forward loop in which AGE-mediated cellular perturbation is not readily extinguished. In this review, we consider recent work in the field highlighting roles for glycation in obesity and atherosclerosis and discuss emerging strategies to block the adverse consequences of AGEs. This article is part of a Special Issue entitled: The role of post-translational protein modifications on heart and vascular metabolism edited by Jason R.B. Dyck & Jan F.C. Glatz.

Genistein supplementation prevents weight gain but promotes oxidative stress and inflammation in the vasculature of female obese ob/ob mice

Obesity, a state of chronic low-grade inflammation, is strongly associated with the development of hypertension and diabetes. Superoxide, a free radical elevated in obese individuals, promotes hypertension through scavenging the endogenous vasodilator nitric oxide. The hypothesis was a genistein-enriched diet would promote weight loss and reduce oxidative stress and inflammation in the vasculature of intact female ob/ob mice. Aortas and mesenteric arteries were isolated from female ob/ob mice fed genistein-free (0mg genistein/kg diet; n=6), standard chow (200-300mg genistein/kg diet; n=11) or genistein-enriched (600mg genistein/kg diet; n=9) diets for 4weeks. Sections of isolated vessels were labeled with the superoxide indicator dihydroethidium and fluorescence was measured by confocal microscopy. Protein expression of the inflammatory marker inducible nitric oxide synthase (iNOS) was measured in the perivascular adipose tissue (PVAT) surrounding each vessel and plasma concentrations of superoxide dismutase (SOD) were quantified. Genistein-enriched diet promoted less weight gain compared to animals fed standard chow (P=.008). Standard chow promoted increased superoxide in the aorta (P=.030) and mesenteric arteries (P=.024) compared to a diet devoid of genistein. At all tested concentrations, genistein significantly increased iNOS expression in mesenteric artery PVAT (vs. standard chow, P<.001; vs. genistein-enriched, P=.002) and tended to increase iNOS within the aortic PVAT (standard chow, P=.075) compared to the genistein-free group. Plasma SOD activity was significantly downregulated in genistein-enriched animals as compared to those fed a genistein-free diet (P=.028). In summary, although genistein prevents weight gain, it promotes vascular oxidative stress and inflammation in obese ovarian-intact female mice.

Hypertension and physical exercise: The role of oxidative stress

Oxidative stress is associated with the pathogenesis of hypertension. Decreased bioavailability of nitric oxide (NO) is one of the mechanisms involved in the pathogenesis. It has been suggested that physical exercise could be a potential non-pharmacological strategy in treatment of hypertension because of its beneficial effects on oxidative stress and endothelial function. The aim of this review is to investigate the effect of oxidative stress in relation to hypertension and physical exercise, including the role of NO in the pathogenesis of hypertension. Endothelial dysfunction and decreased NO levels have been found to have the adverse effects in the correlation between oxidative stress and hypertension. Most of the previous studies found that aerobic exercise significantly decreased blood pressure and oxidative stress in hypertensive subjects, but the intense aerobic exercise can also injure endothelial cells. Isometric exercise decreases normally only systolic blood pressure. An alternative exercise, Tai chi significantly decreases blood pressure and oxidative stress in normotensive elderly, but the effect in hypertensive subjects has not yet been studied. Physical exercise and especially aerobic training can be suggested as an effective intervention in the prevention and treatment of hypertension and cardiovascular disease via reduction in oxidative stress.

Cardiovascular complications in inflammatory bowel disease

Over the past years, a growing number of studies have indicated that patients suffering from inflammatory bowel disease (IBD) have an increased risk of developing cardiovascular disease. Both are chronic inflammatory diseases and share certain pathophysiological mechanisms that may influence each other. High levels of cytokines, C-reactive protein (CRP), and homocysteine in IBD patients may lead to endothelial dysfunction, an early sign of atherosclerosis. IBD patients, in general, do not show the typical risk factors for cardiovascular disease but changes in lipid profiles similar to the ones seen in cardiovascular events have been reported recently. Higher levels of coagulation factors frequently occur in IBD which may predispose to arterial thromboembolic events. Finally, the gut itself may have an impact on atherogenesis during IBD through its microbiota. Microbial products are released from the inflamed mucosa into the circulation through a leaky barrier. The induced rise in proinflammatory cytokines could contribute to endothelial damage, artherosclerosis and cardiovascular events. Although large retrospective studies favor a link between IBD and cardiovascular diseases, the mechanisms behind still remain to be determined.

Cardiovascular complications in inflammatory bowel disease

Over the past years, a growing number of studies have indicated that patients suffering from inflammatory bowel disease (IBD) have an increased risk of developing cardiovascular disease. Both are chronic inflammatory diseases and share certain pathophysiological mechanisms that may influence each other. High levels of cytokines, C-reactive protein (CRP), and homocysteine in IBD patients may lead to endothelial dysfunction, an early sign of atherosclerosis. IBD patients, in general, do not show the typical risk factors for cardiovascular disease but changes in lipid profiles similar to the ones seen in cardiovascular events have been reported recently. Higher levels of coagulation factors frequently occur in IBD which may predispose to arterial thromboembolic events. Finally, the gut itself may have an impact on atherogenesis during IBD through its microbiota. Microbial products are released from the inflamed mucosa into the circulation through a leaky barrier. The induced rise in proinflammatory cytokines could contribute to endothelial damage, artherosclerosis and cardiovascular events. Although large retrospective studies favor a link between IBD and cardiovascular diseases, the mechanisms behind still remain to be determined.

High-Risk Cardiovascular Patients: Clinical Features, Comorbidities, and Interconnecting Mechanisms

Cardiovascular disease is the leading cause of death in the Western world with an increase over the last few decades. Atherosclerosis with its different manifestations in the coronary artery tree, the cerebral, as well as peripheral arteries is the basis for cardiovascular events, such as myocardial infarction, stroke, and cardiovascular death. The pathophysiological understanding of the mechanisms that promote the development of vascular disease has changed over the last few decades, leading to the recognition that inflammation and inflammatory processes in the vessel wall are major contributors in atherogenesis. In addition, a subclinical inflammatory status, e.g., in patients with diabetes or the presence of a chronic inflammatory disease, such as rheumatoid arthritis, have been recognized as strong risk factors for cardiovascular disease. The present review will summarize the different inflammatory processes in the vessel wall leading to atherosclerosis and highlight the role of inflammation in diabetes and chronic inflammatory diseases for cardiovascular morbidity and mortality.

The vulnerable blood. Coagulation and clot structure in diabetes mellitus

Patients with diabetes are at increased risk of cardiovascular morbidity and mortality. While arteriosclerotic lesions have long been recognized as the underlying cause more recent studies suggest that alterations of the blood are also critically involved. Following plaque rupture, adherence of platelets is followed by the formation of a cross-linked fibrin clot. Patients with diabetes exhibit a prothrombotic milieu consisting of hyper reactive platelets, a tight and rigid clot structure which is due to up-regulation of coagulation factors and prolongation of clot lysis. Metabolic alterations as well as inflammatory processes, which are up-regulated in diabetes, are thought to be the main underlying causes. More recently, the complement cascade has emerged as a potential new player in this context with several complement components directly influencing both platelet function and coagulation. This review provides an overview concerning the changes that lead to alterations of platelet function and clot structure in diabetes.

Role of inorganic nitrate and nitrite in driving nitric oxide-cGMP-mediated inhibition of platelet aggregation in vitro and in vivo

BACKGROUND

Nitric oxide (NO) is a critical negative regulator of platelets that is implicated in the pathology of thrombotic diseases. Platelets generate NO, but the presence and functional significance of NO synthase (NOS) in platelets is unclear. Inorganic nitrate/nitrite is increasingly being recognized as a source of bioactive NO, although its role in modulating platelets during health and vascular dysfunction is incompletely understood.

METHODS

We investigated the functional significance and upstream sources of NO-cGMP signaling events in platelets by using established methods for assessing in vitro and in vivo platelet aggregation, and assessed the bioconversion of inorganic nitrate to nitrite during deficiency of endothelial NOS (eNOS).

RESULTS

The phosphodiesterase 5 (PDE5) inhibitor sildenafil inhibited human platelet aggregation in vitro. This inhibitory effect was abolished by a guanylyl cyclase inhibitor and NO scavengers, but unaffected by NOS inhibition. Inorganic nitrite drove cGMP-mediated inhibition of human platelet aggregation in vitro and nitrate inhibited platelet function in eNOS(-/-) mice in vivo in a model of thromboembolic radiolabeled platelet aggregation associated with an enhanced plasma nitrite concentration as compared with wild-type mice.

CONCLUSIONS

Platelets generate transient, endogenous cGMP signals downstream of NO that are primarily independent of NOS and may be enhanced by inhibition of PDE5. Furthermore, nitrite can generate transient NO-cGMP signals in platelets. The absence of eNOS leads to enhanced plasma nitrite levels following nitrate administration in vivo, which negatively impacts on platelet function. Our data suggest that inorganic nitrate exerts an antiplatelet effect during eNOS deficiency, and, potentially, that dietary nitrate may reduce platelet hyperactivity during endothelial dysfunction.

Protein-bound uremic toxins: new culprits of cardiovascular events in chronic kidney disease patients

Chronic kidney disease (CKD) has been considered a major risk factor for cardiovascular diseases. Although great advances have recently been made in the pathophysiology and treatment of cardiovascular diseases, CKD remains a major global health problem. Moreover, the occurrence rates of cardiovascular events among CKD patients increase even in cases in which patients undergo hemodialysis, and the mechanisms underlying the so-called “cardiorenal syndrome” are not clearly understood. Recently, small-molecule uremic toxins have been associated with cardiovascular mortality in CKD and/or dialysis patients. These toxins range from small uncharged solutes to large protein-bound structures. In this review, we focused on protein-bound uremic toxins, such as indoxyl sulfate and p-cresyl sulfate, which are poorly removed by current dialysis techniques. Several studies have demonstrated that protein-bound uremic toxins, especially indoxyl sulfate, induce vascular inflammation, endothelial dysfunction, and vascular calcification, which may explain the relatively poor prognosis of CKD and dialysis patients. The aim of this review is to provide novel insights into the effects of indoxyl sulfate and p-cresyl sulfate on the pathogenesis of atherosclerosis.

Circulating anti-beta2-glycoprotein I antibodies are associated with endothelial dysfunction, inflammation, and high nitrite plasma levels in patients with intermittent claudication

Our aim is to investigate a possible association of circulating anti-beta2-glycoprotein I antibodies (ABGPI) with the endothelial dysfunction, nitric oxide bioactivity dysregulation, and the inflammatory status that surrounds peripheral arterial disease. We carried out an observational translational study, including 50 male patients with intermittent claudication and a healthy control group of 10 male subjects, age and sex matched with the cases. Flow-mediated arterial dilatation (FMAD) was assessed as a surrogate of endothelial dysfunction, and C-reactive protein (hsCRP) was determined as a marker of inflammation. Nitrite plasma levels were measured by colorimetric analysis. Circulating ABGPI titer was detected with indirect immunofluorescence. Titers <1 : 10 represented the reference range and the lower detection limit of the test. Circulating ABGPI titer ≥1 : 10 was detected in 21 (42%) patients and in none of the control subjects (P < 0.01). Patients with ABGPI titer ≥1 : 10 had a lower FMAD (P = 0.01). The CRP levels were higher in patients with ABGPI titer ≥1 : 10 (P = 0.04). The nitrite plasma levels were higher in patients with ABGPI titer ≥1 : 10 (P < 0.01). These data suggest that these circulating ABGPI may collaborate in the development of atherosclerosis; however, further prospective studies are required to establish a causal relationship.

Neferine inhibits the upregulation of CCL5 and CCR5 in vascular endothelial cells during chronic high glucose treatment

We investigated whether the expressions of CCL5 and CCR5 participate in dysfunctional changes in human umbilical vein endothelial cells (HUVECs) induced by chronic high glucose treatment and examined whether neferine exerts its therapeutic effects by blocking the development of dysfunctional vascular endothelium. HUVECs were cultured with control or high concentrations of glucose in the absence or presence of neferine for 5 days. Nitric acid reductase method was used to detect the concentration of nitric oxide (NO) released into culture media. The level of intracellular reactive oxygen species (ROS) was measured by fluorescent DCFH-DA probe. The expressions of 84 genes related to endothelial cell biology were assessed by Human Endothelial Cell Biology RT(2) Profiler PCR Array. The expressions of the chemokine CCL5 and its receptor CCR5 were further determined by real-time RT-PCR and western blotting. PCR array indicated that CCL5 was the most significantly upregulated when HUVECs were exposed to chronic high glucose; the intracellular ROS level and the expressions of CCL5 and CCR5 at both mRNA and protein levels were significantly increased, whereas NO production was decreased simultaneously. The increased level of ROS and elevated expressions of CCL5 and CCR5 at high glucose were significantly inhibited by neferine; meanwhile the decreased NO production upon chronic high glucose treatment was relieved. An antioxidant (vitamin E) exerted similar beneficial effects. These data indicate that neferine can reduce the upregulation of CCL5 and CCR5 of vascular endothelium exposure to chronic high glucose and prevent or inhibit subsequent occurrence of inflammation in blood vessels possibly through antioxidation.

Reduced plasma zinc levels, lipid peroxidation, and inflammation biomarkers levels in hemodialysis patients: implications to cardiovascular mortality

Despite the fact that low plasma zinc (Zn) levels play important roles in the oxidative stress, the relationships between lipid peroxidation and inflammation biomarkers with low plasma Zn levels have not been investigated in chronic kidney disease (CKD) patients. The aim of this study was to evaluate the Zn plasma levels, electronegative LDL [LDL(-)] levels, and inflammation markers as predictors of cardiovascular (CV) mortality in hemodialysis (HD) patients. Forty-five HD patients (28 men, 54.2 ± 12.7 years, 62.2 ± 51.4 months on dialysis and BMI 24.3 ± 4.1 kg/m(2)) were studied and compared to 20 healthy individuals (9 men, 51.6 ± 15.6 years, BMI 25.2 ± 3.9 kg/m(2)) and followed for 24 months to investigate the risks for CV mortality. LDL(-) levels were measured by ELISA, plasma Zn levels by atomic absorption spectrophotometry, C-reactive protein (CRP) level by immunoturbidimetric method, and tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1) levels by a multiplex assay kit. HD patients presented low plasma Zn levels (54.9 ± 16.1 μg/dL) and high-LDL(-) (0.18 ± 0.12 U/L) and TNF-α (5.5 ± 2.2 pg/mL) levels when compared to healthy subjects (78.8 ± 9.4μ g/dL, 0.10 ± 0.08U/L, 2.4 ± 1.1 pg/mL, respectively, p < 0.05). Zn plasma levels were negatively correlated to TNF-α (r = -0.49; p = 0.0001) and LDL(-) (r = -0.33; p = 0.008). During the 2 years, 24.4% of the patients died, all due to CV disease. Analysis by the Cox model showed that high CRP, TNF-α, IL-6 levels, and long duration of HD were significant predictors of mortality. In conclusion, reduced Zn levels were associated with lipid peroxidation and inflammation, and we confirm here in a Brazilian cohort of HD patients that inflammation markers are strong predictors of CV death.

Tat-Mediated p66shc Transduction Decreased Phosphorylation of Endothelial Nitric Oxide Synthase in Endothelial Cells

We evaluated the role of Tat-mediated p66shc transduction on the activation of endothelial nitric oxide synthase in cultured mouse endothelial cells. To construct the Tat-p66shc fusion protein, human full length p66shc cDNA was fused with the Tat-protein transduction domain. Transduction of TAT-p66shc showed a concentration- and time-dependent manner in endothelial cells. Tat-mediated p66shc transduction showed increased hydrogen peroxide and superoxide production, compared with Tat-p66shc (S/A), serine 36 residue mutant of p66shc. Tat-mediated p66shc transduction decreased endothelial nitric oxide synthase phosphorylation in endothelial cells. Furthermore, Tat-mediated p66shc transduction augmented TNF-α-induced p38 MAPK phosphorylation in endothelial cells. These results suggest that Tat-mediated p66shc transduction efficiently inhibited endothelial nitric oxide synthase phosphorylation in endothelial cells.

Pyridoxine inhibits endothelial NOS uncoupling induced by oxidized low-density lipoprotein via the PKCα signalling pathway in human umbilical vein endothelial cells

BACKGROUND AND PURPOSE

One key mechanism for endothelial dysfunction is endothelial NOS (eNOS) uncoupling, whereby eNOS generates superoxide (O(2) (•-) ) rather than NO. We explored the effect of pyridoxine on eNOS uncoupling induced by oxidized low-density lipoprotein (ox-LDL) in human umbilical vein endothelial cells (HUVECs) and the potential molecular mechanism.

EXPERIMENTAL APPROACH

HUVECs were incubated with ox-LDL with/without pyridoxine, N(G) -nitro-L-arginine methylester (L-NAME), chelerythrine chloride (CHCI) or apocynin. Endothelial O(2) (•-) was measured using lucigenin chemiluminescence, and O(2) (•-) -sensitive fluorescent dye dihydroethidium (DHE). NO levels were measured by chemiluminescence, PepTag Assay for non-radioactive detection of PKC activity, depletion of PKCα and p47phox by siRNA silencing and the states of phospho-eNOS Thr495, total-eNOS, phospho-PKCα/βII, total PKC, phospho-PKCα, total PKCα and p47phox were measured by Western blot.

KEY RESULTS

Ox-LDL significantly increased O(2) (•-) production and reduced NO levels released from HUVECs; an effect reversed by eNOS inhibitor, L-NAME. Pyridoxine pretreatment significantly inhibited ox-LDL-induced O(2) (•-) generation and preserved NO levels. Pyridoxine also prevented the ox-LDL-induced reduction in phospho-eNOS Thr495 and PKC activity. These protective effects of pyridoxine were abolished by the PKC inhibitor, CHCI, or siRNA silencing of PKCα. However, depletion of p47phox or treatment with the NADPH oxidase inhibitor, apocynin, had no influence on these effects. Also, cytosol p47phox expression was unchanged by the different treatments.

CONCLUSIONS AND IMPLICATIONS

Pyridoxine mitigated eNOS uncoupling induced by ox-LDL. This protectant effect was related to phosphorylation of eNOS Thr495 stimulated by PKCα, not via NADPH oxidase. These results provide support for the use of pyridoxine in ox-LDL-related vascular endothelial dysfunction.

Vasorelaxing Activity of Ulmus davidiana Ethanol Extracts in Rats: Activation of Endothelial Nitric Oxide Synthase

Ulmus davidiana var. japonica Rehder (Urticales: Ulmaceae) (UD) is a tree widespread in northeast Asia. It is traditionally used for anticancer and anti-inflammatory therapy. The present study investigated the effect of an ethanol extract of UD on vascular tension and its underlying mechanism in rats. The dried root bark of UD was ground and extracted with 80% ethanol. The prepared UD extract was used in further analysis. The effect of UD on the cell viability, vasoreactivity and hemodynamics were investigated using propidium iodide staining in cultured cells, isometric tension recording and blood pressure analysis, respectively. Low dose of UD (10~100µg/ml) did not affect endothelial cell viability, but high dose of UD reduced cell viability. UD induced vasorelaxation in the range of 0.1~10µg/ml with an ED₅₀ value of 2µg/ml. UD-induced vasorelaxation was completely abolished by removal of the endothelium or by pre-treatment with L-NAME, an inhibitor of nitric oxide synthase. UD inhibited calcium influx induced by phenylephrine and high K⁺ and also completely abolished the effect of L-NAME. Intravenous injection of UD extracts (10~100 mg/kg) decreased arterial and ventricular pressure in a dose-dependent manner. Moreover, UD extracts reduced the ventricular contractility (+dP/dt) in anesthetized rats. However, UD-induced hypotensive actions were minimized in L-NAME-treated rats. Taken together, out results showed that UD induced vasorelaxation and has antihypertensive properties, which may be due the activation of nitric oxide synthase in endothelium.

Effects of slow, sustained, and rate-tunable nitric oxide donors on human aortic smooth muscle cells proliferation

Smooth muscle cell (SMC) proliferation has been accepted as a common event in the pathophysiology of vascular diseases, including atherogenesis and intimal hyperplasia. Delivery of the nitric oxide synthase (NOS) substrate l-arginine, pharmacological nitric oxide (NO) donors, NO gas or overexpression of NOS proteins can inhibit SMC proliferation and reduce the injury responses within the blood vessel wall. Although commercial development of NO donors that attempt to provide exogenous delivery of NO has accelerated over the last few years, none of the currently available products can provide controlled, sustained, time-tunable release of NO. Nitrosamine-based NO donors, prepared in our laboratory, present a unique and innovative alternative for possible treatments for long-term NO deficiency-related diseases, including atherosclerosis, asthma, erectile dysfunction, cancer, and neurodegenerative diseases. A family of secondary amines prepared via nucleophilic aromatic displacement reactions could be readily N-nitrosated to produce NO donors. NO release takes place in three distinct phases. During the initial phase, the release rate is extremely fast. In the second phase, the release is slower and the rate remains essentially the same during the final stage. These compounds inhibited up to 35% human aortic smooth muscle cell proliferation in a concentration-dependent manner.

Roles of SIRT1 in high glucose-induced endothelial impairment: association with diabetic atherosclerosis

BACKGROUND AND AIMS

We undertook this study to investigate the roles of SIRT1 in high glucose-induced endothelial impairment and their association with diabetic atherosclerosis.

METHODS

Otsuka Long-Evans Tokushima Fatty (OLETF) rats and nondiabetic rats of the same genetic background were included. Real-time PCR was used to detect SIRT1 mRNA expression in abdominal aorta at week 42. To further investigate the roles of SIRT1 on the function of endothelial cells in high glucose, human endothelial cells were treated with SIRT1 activator resveratrol for 24 h before being cultured in high glucose medium for 48 h.

RESULTS

Along with the early manifestation of atherosclerosis, SIRT1 mRNA level in OLETF group was significantly lower than that in control group (p <0.05). Compared with control cells, high glucose decreased nitric oxide (NO) secretion, but resveratrol treatment increased the expression of SIRT1 and the secretion of NO. After interfering with the expression of SIRT1 using SIRT1 siRNA, the effects of resveratrol on NO secretion were impaired. SIRT1 also counteracted the other pro-atherosclerotic effects of high glucose including the upregulating roles of high glucose on the expression of E-selectin mRNA and the downregulating roles of high glucose on the expression of endothelial nitric oxide synthase.

CONCLUSIONS

Decreased expression of SIRT1 in artery may be involved in the initiation and development of diabetic atherosclerosis. Increasing SIRT1 expression may hold great promise in the prevention and therapy of atherosclerosis in diabetic patients.

Endothelial progenitor cells in cardiovascular disease and hypoxia--potential implications to obstructive sleep apnea

In recent years, endothelial progenitor cells (EPCs) have gained a central role in vascular regeneration and endothelial repair capacity through angiogenesis and restoring endothelial function of injured blood vessels. These bone-marrow-derived cells are capable of promoting neovascularization, improving blood perfusion, and facilitating the recovery of ischemic tissues through differentiation into functional endothelial cells and secretion of angiogenic mediators. Obstructive sleep apnea (OSA) syndrome is characterized by recurrent episodes of intermittent hypoxia (IH), which can lead to endothelial dysfunction, atherosclerosis, as well as cardiovascular morbidity and mortality. However, IH also may contribute to cardioprotection and the development of collateral vessels by mobilizing progenitor cells to the circulation and damaged myocardium. Accumulating evidence in recent years suggests that EPCs are decreased in patients with endothelial dysfunction and underlie an increased risk for cardiovascular morbidity in OSA. The current review highlights the potential role of EPCs in the pathogenesis of vascular diseases that is pertinent to OSA.

Activation of endothelial nitric oxide synthase is dependent on its interaction with globular actin in human umbilical vein endothelial cells

Endothelial nitric oxide synthase (eNOS) has been reported to associate with globular actin, and this association increases eNOS activity. Adenosine, histamine, salbutamol and thrombin cause activation of eNOS through widely different mechanisms. Whether these eNOS agonists can regulate eNOS activity through affecting its association with actin is unknown. As previously reported, we confirmed in cultured human umbilical vein endothelial cells (HUVEC) that histamine and thrombin increased intracellular Ca(2+) whereas adenosine and salbutamol did not, and that these four agonists caused different effects on actin filament structure. Nevertheless, despite their divergent effects on intracellular Ca(2+) and on actin filament structure, we found by immunoprecipitation that adenosine, histamine, salbutamol and thrombin all caused an increase in association between eNOS and globular actin. This increase of association was inhibited by pre-treatment with phalloidin, an actin filament stabilizer. All of these agonists also increased phosphorylation of eNOS on serine residue 1177, eNOS activity, and cyclic guanosine-3', 5'-monophosphate, and these increases were all attenuated by phalloidin. Agonist-induced phosphorylation of eNOS on serine 1177 was attenuated by Akt inhibition, whereas association of eNOS with actin was not. We also found, in HEK-293 cells transfected with the eNOS mutants eNOS-S1177A or eNOS-S1177D, that the association between eNOS and globular actin was decreased as compared to cells transfected with wild-type eNOS. We conclude that association of globular actin with eNOS plays an essential and necessary role in agonist-induced eNOS activation, through enabling its phosphorylation by Akt at serine residue 1177.

Inflammation and thrombosis in diabetes

Patients with diabetes mellitus are at increased risk of cardiovascular morbidity and mortality. Atherothrombosis, defined as atherosclerotic lesion disruption with superimposed thrombus formation, is the most common cause of death among these patients. Following plaque rupture, adherence of platelets is followed by local activation of coagulation, the formation of a cross-linked fibrin clot and the development of an occlusive platelet rich fibrin mesh. Patients with diabetes exhibit a thrombotic risk clustering which is composed of hyper-reactive platelets, up regulation of pro-thrombotic markers and suppression of fibrinolysis. These changes are mainly mediated by the presence of insulin resistance and dysglycaemia and an increased inflammatory state which directly affects platelet function, coagulation factors and clot structure. This prothrombotic state is related to increased cardiovascular risk and may account for the reduced response to antithrombotic therapeutic approaches, underpinning the need for adequate antithrombotic therapy in patients with diabetes to reduce their cardiovascular mortality.

Association between inducible and neuronal nitric oxide synthase polymorphisms and recurrent depressive disorder

BACKGROUND

Major depression is characterised by increased nitric oxide (NO) levels. Inhibition of the NO synthesizing enzymes, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS), results in antidepressant-like effects, whereas the expression of iNOS and nNOS is increased in depression. Recent studies have indicated that NOS participates in the mechanisms of antidepressants. The aim of this study was to examine whether a single nucleotide polymorphism (SNP) present in the genes encoding iNOS and nNOS can contribute to the risk of developing recurrent depressive disorder (rDD).

METHODS

The study was carried out in a group of 181 depressive patients and 149 control subjects of Polish origin. SNPs were assessed using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses.

RESULTS

The genotype distributions of the polymorphisms in exon 22 of the NOS2A gene and in exon 29 of the nNOS gene were significantly different between rDD patients and controls. The results showed that the G/A SNP of the gene encoding iNOS was associated with an increased susceptibility to rDD, whereas A/A homozygous carriers had a decreased risk of developing rDD. There was also a significant association between the C/T SNP of the gene encoding nNOS; the presence of the CC homozygous genotype decreased the risk of rDD, whereas the T allele and T/T homozygous genotype increased the vulnerability to rDD.

CONCLUSIONS

Our results suggest that polymorphisms in the iNOS and nNOS genes confer an increased susceptibility or resistance to rDD. Future research should examine genetic variants and their associations to the expression of NOSs and NO level in depressive patients.

Cardiovascular protection afforded by caloric restriction: essential role of nitric oxide synthase

Caloric restriction is an established intervention, of which anti-aging effects are scientifically proven. It has pleiotropic effects on the cardiovascular system: vascular protection, improvement of myocardial ischemic tolerance and retardation of cardiac senescence. First, increasing evidence from both experimental and clinical studies supports the concept that "a man is as old as his arteries". Caloric restriction could prevent the progression of atherosclerosis and vascular aging through direct and indirect mechanisms. Second, the hearts of senescent animals are more susceptible to ischemia than those of young animals. We demonstrated that short-term and prolonged caloric restriction confers cardioprotection against ischemia/reperfusion injury in young and aged rodents. Furthermore, we showed that the increase in circulating adiponectin levels and subsequent activation of adenosine monophosphate-activated protein kinase are necessary for the cardioprotection afforded by short-term caloric restriction. In contrast, the mechanisms by which prolonged caloric restriction confers cardioprotection seem more complicated. Adiponectin, nitric oxide synthase and sirtuin may form a network of cardiovascular protection during caloric restriction. Recently, by using genetically engineered mice, we found that, in addition to endothelial nitric oxide synthase, neuronal nitric oxide synthase plays an essential role in the development of cardioprotection afforded by prolonged caloric restriction. Third, long-term caloric restriction has cardiac-specific effects that attenuate the age-associated impairment seen in left ventricular diastolic function. It is possible that long-term caloric restriction partially retards cardiac senescence by attenuating oxidative damage in the aged heart. Overall, we strongly believe that caloric restriction could reduce morbidity and mortality of cardiovascular events in humans.

Activation of vascular BK channels by docosahexaenoic acid is dependent on cytochrome P450 epoxygenase activity

AIMS

n-3 Polyunsaturated fatty acids (PUFAs) are known to protect the cardiovascular system and improve blood pressure control. These important dietary constituents are converted into bioactive metabolites, but their role in regulation of the cardiovascular system is unclear. In particular, the functions of the cytochrome P450 (CYP) metabolites of n-3 PUFAs remain virtually unexplored. In this study, we examined the effects of docosahexaenoic acid (DHA) on the regulation of large-conductance calcium-activated potassium (BK) channel activities in coronary arterial smooth muscle cells.

METHODS AND RESULTS

Using whole-cell patch-clamp techniques, we found that DHA is a potent activator of BK currents in rat coronary arterial smooth muscle cells with an EC(50) of 0.23 ± 0.03 µM. This effect was abolished by pre-incubation with the CYP epoxygenase inhibitor, SKF525A (10 µM). The effects of DHA on the BK channels were reproduced by 16,17-epoxydocosapentaenoic acid (16,17-EpDPE) with an EC(50) of 19.7 ± 2.8 nM. The physiological role of the CYP metabolites of DHA was confirmed by measuring DHA-mediated vasodilatation in isolated rat coronary arteries. DHA dilated pressurized isolated coronary arteries in a dose-dependent manner, and the DHA effects were abolished after pre-treatment with SKF525A (10 µM) or with iberiotoxin (100 nM). In addition, 16,17-EpDPE directly produced coronary vasodilatation that was iberiotoxin sensitive.

CONCLUSION

These results suggest that DHA-mediated vasodilatation is mediated through CYP epoxygenase metabolites by activation of vascular BK channels.