Nitric Oxide Availability Research Articles

Impaired Neurovascular Function Underlies Poor Neurocognitive Outcomes and Is Associated with Nitric Oxide Bioavailability in Congenital Heart Disease.

We use a non-invasive MRI proxy of neurovascular function (pnvf) to assess the ability of the vasculature to supply baseline metabolic demand, to compare pediatric and young adult congenital heart disease (CHD) patients to normal referents and relate the proxy to neurocognitive outcomes and nitric oxide bioavailability. In a prospective single-center study, resting-state blood-oxygen-level-dependent (BOLD) and arterial spin labeling (ASL) MRI scans were successfully obtained from 24 CHD patients (age = 15.4 ± 4.06 years) and 63 normal referents (age = 14.1 ± 3.49) years. Pnvf was computed on a voxelwise basis as the negative of the ratio of functional connectivity strength (FCS) estimated from the resting-state BOLD acquisition to regional cerebral blood flow (rCBF) as estimated from the ASL acquisition. Pnvf was used to predict end-tidal CO2 (PETCO2) levels and compared to those estimated from the BOLD data. Nitric oxide availability was obtained via nasal measurements (nNO). Pnvf was compared on a voxelwise basis between CHD patients and normal referents and correlated with nitric oxide availability and neurocognitive outcomes as assessed via the NIH Toolbox. Pnvf was shown as highly predictive of PETCO2 using theoretical modeling. Pnvf was found to be significantly reduced in CHD patients in default mode network (DMN, comprising the ventromedial prefrontal cortex and posterior cingulate/precuneus), salience network (SN, comprising the insula and dorsal anterior cingulate), and central executive network (CEN, comprising posterior parietal and dorsolateral prefrontal cortex) regions with similar findings noted in single cardiac ventricle patients. Positive correlations of Pnvf in these brain regions, as well as the hippocampus, were found with neurocognitive outcomes. Similarly, positive correlations between Pnvf and nitric oxide availability were found in frontal DMN and CEN regions, with particularly strong correlations in subcortical regions (putamen). Reduced Pnvf in CHD patients was found to be mediated by nNO. Mediation analyses further supported that reduced Pnvf in these regions underlies worse neurocognitive outcome in CHD patients and is associated with nitric oxide bioavailability. Impaired neuro-vascular function, which may be non-invasively estimated via combined arterial-spin label and BOLD MR imaging, is a nitric oxide bioavailability dependent factor implicated in adverse neurocognitive outcomes in pediatric and young adult CHD.

Targeting SIRT1 Rescues Age- and Obesity-Induced Microvascular Dysfunction in Ex Vivo Human Vessels.

Background:Experimental evidence suggests a key role of SIRT1 (silent information regulator 1) in age- and metabolic-related vascular dysfunction. Whether these effects hold true in the human microvasculature is unknown. We aimed to investigate the SIRT1 role in very early stages of age- and obesity-related microvascular dysfunction in humans.Methods:Ninety-five subjects undergoing elective laparoscopic surgery were recruited and stratified based on their body mass index status (above or below 30 kg/m2) and age (above or below 40 years) in 4 groups: Young Nonobese, Young Obese, Old Nonobese, and Old Obese. We measured small resistance arteries’ endothelial function by pressurized micromyography before and after incubation with a SIRT1 agonist (SRT1720) and a mitochondria reactive oxygen species (mtROS) scavenger (MitoTEMPO). We assessed vascular levels of mtROS and nitric oxide availability by confocal microscopy and vascular gene expression of SIRT1 and mitochondrial proteins by qPCR. Chromatin immunoprecipitation assay was employed to investigate SIRT1-dependent epigenetic regulation of mitochondrial proteins.Results:Compared with Young Nonobese, obese and older patients showed lower vascular expression of SIRT1 and antioxidant proteins (FOXO3 [forkhead box protein O3] and SOD2) and higher expression of pro-oxidant and aging mitochondria proteins p66Shc and Arginase II. Old Obese, Young Obese and Old Nonobese groups endothelial dysfunction was rescued by SRT1720. The restoration was comparable to the one obtained with mitoTEMPO. These effects were explained by SIRT1-dependent chromatin changes leading to reduced p66Shc expression and upregulation of proteins involved in mitochondria respiratory chain.Conclusions:SIRT1 is a novel central modulator of the earliest microvascular damage induced by age and obesity. Through a complex epigenetic control mainly involving p66Shc and Arginase II, it influences mtROS levels, NO availability, and the expression of proteins of the mitochondria respiratory chain. Therapeutic modulation of SIRT1 restores obesity- and age-related endothelial dysfunction. Early targeting of SIRT1 might represent a crucial strategy to prevent age- and obesity-related microvascular dysfunction.

Effect of Physical Activity/Exercise on Oxidative Stress and Inflammation in Muscle and Vascular Aging.

Functional status is considered the main determinant of healthy aging. Impairment in skeletal muscle and the cardiovascular system, two interrelated systems, results in compromised functional status in aging. Increased oxidative stress and inflammation in older subjects constitute the background for skeletal muscle and cardiovascular system alterations. Aged skeletal muscle mass and strength impairment is related to anabolic resistance, mitochondrial dysfunction, increased oxidative stress and inflammation as well as a reduced antioxidant response and myokine profile. Arterial stiffness and endothelial function stand out as the main cardiovascular alterations related to aging, where increased systemic and vascular oxidative stress and inflammation play a key role. Physical activity and exercise training arise as modifiable determinants of functional outcomes in older persons. Exercise enhances antioxidant response, decreases age-related oxidative stress and pro-inflammatory signals, and promotes the activation of anabolic and mitochondrial biogenesis pathways in skeletal muscle. Additionally, exercise improves endothelial function and arterial stiffness by reducing inflammatory and oxidative damage signaling in vascular tissue together with an increase in antioxidant enzymes and nitric oxide availability, globally promoting functional performance and healthy aging. This review focuses on the role of oxidative stress and inflammation in aged musculoskeletal and vascular systems and how physical activity/exercise influences functional status in the elderly.

Reduced nitric oxide synthesis in winter: A potential contributing factor to increased cardiovascular risk

BackgroundNitric oxide is a key signalling molecule that elicits a range of biological functions to maintain vascular homeostasis. A reduced availability of nitric oxide is implicated in the progression of cardiovascular diseases and increases the risk of pathogenic events. AimsTo compare the concentration of nitric oxide metabolites in healthy adults between winter and summer months. DesignAn observational study of healthy adults (age 32 ± 9 years) living in central Scotland. MethodsThirty-four healthy adults (13 females) were monitored for 7 days in summer and winter to record sunlight exposure (ultraviolet-A (UV-A) radiation), diet, and physical activity. At the end of each phase, blood pressure was measured, and samples of blood and saliva collected. The samples were analysed to determine the concentrations of plasma and salivary nitrate and nitrite and serum 25-hydroxyvitamin D (25(OH)D). ResultsThe participants maintained similar diets in each measurement phase but were exposed to more UV-A radiation (550%) and undertook more moderate-vigorous physical activity (23%) in the summer than in winter. Plasma nitrite (46%) and serum 25(OH)D (59%) were higher and blood pressure was lower in the summer compared to winter months. Plasma nitrite concentration was negatively associated with systolic, diastolic, and mean arterial blood pressure. ConclusionsPlasma nitrite, an established marker of nitric oxide synthesis, is higher in healthy adults during the summer than in winter. This may be mediated by a greater exposure to UV-A which stimulates the release of nitric oxide metabolites from skin stores. While it is possible that seasonal variation in nitric oxide availability may contribute to an increased blood pressure in the winter months, the overall impact on cardiovascular health remains to be determined.

TARGETING SIRT1 RESCUES AGE- AND OBESITY-INDUCED HUMAN MICROVASCULAR DYSFUNCTION

Objective: Experimental evidence suggests a relevant role of SIRT1 in age- and metabolic-related vascular dysfunction. Whether these effects hold true in the human microvasculature is unknown. We aimed to investigate the role of SIRT1 in age- and obesity-related microvascular dysfunction in humans. Design and method: Individuals (n = 95) undergoing laparoscopic surgery were stratified by BMI status (above or below 30 Kg/m2) and age (above or below 40 years) and classified as young control (YC), young obese (YO), old control (OC) and old obese (OO). Endothelial function was assessed in small resistance arteries by pressurized micromyography, before and after incubation with a SIRT1 agonist (SRT1720) and a mitochondria reactive oxygen species (mtROS) scavenger (MitoTEMPO). We assessed vascular levels of mtROS and nitric oxide availability by confocal microscopy and vascular gene expression of SIRT1 and mitochondrial proteins by qPCR. ChIP assay was employed to investigate SIRT1-dependent epigenetic regulation of mitochondrial proteins. Results: Endothelial function showed a graded decrease from YC to OO, with reduced nitric oxide availability and increased mtROS levels. Similarly, SIRT1 and mitochondrial antioxidant proteins (FOXO3 and SOD2) expression levels were reduced while there was a higher expression of pro-oxidant and ageing mitochondria proteins p66Shc and Arginase II. OO, YO and OC endothelial function was rescued by SRT1720 (Figure). The improvement in endothelial function showed a linear relationship with age, BMI and vascular emodelling. The restoration was comparable to the one obtained with mitoTEMPO in the same groups. These effects were explained by SIRT1-dependent chromatin changes leading to reduced p66Shc expression and upregulation of proteins involved in mitochondria respiratory chain: ATP synthase 6, cytochrome B, NADH dehydrogenase 2, NADH dehydrogenase 5. Conclusions: Restoring SIRT1 activity rescues obesity and age-related endothelial dysfunction. Its epigenetic control on mitochondrial pathways influences mtROS levels, NO availability, and the expression of the mitochondria respiratory chain proteins. SIRT1 is a novel central regulator of a homeostatic axis connecting vascular phenotype to systemic metabolism and ageing and to exposure to external adverse stimuli. Early targeting of SIRT1 might represent a crucial strategy to prevent the microvascular dysfunction related to age and obesity.

Loss of eNOS in Endothelial Cells Promotes Proliferation

BackgroundEndothelial cells help maintain vascular homeostasis mainly by balancing interplay between vasorelaxation and vasoconstriction via regulating availability of Nitric Oxide (NO). Endothelial nitric oxide synthase (eNOS) is one of three NOS isoforms that catalyses the synthesis of NO to regulate endothelial function. To date, however, eNOS’s role in endothelial cell proliferation, remains unclear.Methods and ResultsTo gain a better understanding about eNOS and cell proliferation, we genetically inhibited eNOS viasilencing by transfecting cultured human umbilical vein endothelial cells with sieNOS or scrambled control. Successful eNOS silencing was confirmed at transcript and protein levels, and then endothelial cell proliferation was evaluated. Surprisingly, loss of eNOS significantly induced endothelial cell proliferation, concomitant with significant downregulation of both cell cycle inhibitor p21 and cell proliferation antigen Ki‐67. To confirm the specificity of eNOS silencer, we used another sieNOS molecule, which also showed the similar results as endothelial proliferation was significantly induced in eNOS‐silenced endothelial cells. Later, to demonstrate that the induced endothelial cell proliferation is due to eNOS inhibition, we pharmacologically inhibited eNOS by treating endothelial cells with L‐NAME. Contrastingly, L‐NAME‐treatment significantly inhibited endothelial cell proliferation in a dose‐dependent manner.ConclusionOur findings, for the first time, indicate that eNOS regulate endothelial function by directly controlling endothelial cell proliferation. Observed inhibition of endothelial cell proliferation by L‐NAME, may be due to its non‐specific effects. The findings also indicate that eNOS and L‐NAME might employ different pathways regulating endothelial cell proliferation warranting further investigation.

Reduced Abundance of Nitrate-Reducing Bacteria in the Oral Microbiota of Women with Future Preeclampsia.

The oral microbiota can contribute to the regulation of blood pressure by increasing the availability of nitric oxide through the reduction of nitrate to nitrite, which can be converted into nitric oxide in the stomach and then enter the circulation. It is unclear if the composition of the oral microbiota is different between women who do and do not develop preeclampsia. This study aimed to compare the composition of the buccal microbiota just prior to the development of symptoms at 36 weeks gestation in 12 women who developed late-onset preeclampsia and 24 matched women who remained normotensive throughout pregnancy by 16S rRNA gene amplicon sequencing. The abundance of the nitrate-reducing Veillonella spp V. parvula and V. dispar and a subunit of nitrate reductase narH was compared using real-time PCR. The abundance of bacteria was correlated with maternal blood pressure and dietary intake of nitrate-containing vegetables. The results showed that the abundance of nitrate-reducing bacteria including Veillonella, specifically V. parvula, and Prevotella was reduced in women who developed preeclampsia. Veillonella but not Prevotella abundance was negatively correlated with maternal blood pressure. The dietary intake of nitrate-containing vegetables did not differ between the groups and was not correlated with the abundance of Veillonella. There was no difference in the abundance of the nitrate reductase subunit narH between the groups. These results suggest that the abundance of nitrate-reducing bacteria is reduced in the oral microbiota of women who later develop preeclampsia, indicating a potential pathway for prevention.

Oxidative Stress in Arterial Hypertension (HTN): The Nuclear Factor Erythroid Factor 2-Related Factor 2 (Nrf2) Pathway, Implications and Future Perspectives.

Arterial hypertension (HTN) is one of the most prevalent entities globally, characterized by increased incidence and heterogeneous pathophysiology. Among possible etiologies, oxidative stress (OS) is currently extensively studied, with emerging evidence showing its involvement in endothelial dysfunction and in different cardiovascular diseases (CVD) such as HTN, as well as its potential as a therapeutic target. While there is a clear physiological equilibrium between reactive oxygen species (ROS) and antioxidants essential for many cellular functions, excessive levels of ROS lead to vascular cell impairment with decreased nitric oxide (NO) availability and vasoconstriction, which promotes HTN. On the other hand, transcription factors such as nuclear factor erythroid factor 2-related factor 2 (Nrf2) mediate antioxidant response pathways and maintain cellular reduction–oxidation homeostasis, exerting protective effects. In this review, we describe the relationship between OS and hypertension-induced endothelial dysfunction and the involvement and therapeutic potential of Nrf2 in HTN.

Full-Face Mask Use during SCUBA Diving Counters Related Oxidative Stress and Endothelial Dysfunction.

Impaired flow mediated dilation (FMD), an index of vascular stress, is known after SCUBA diving. This is related to a dysfunction of nitric oxide (NO) availability and a disturbance of the redox status, possibly induced by hyperoxic/hyperbaric gas breathing. SCUBA diving is usually performed with a mask only covering “half face” (HF) and therefore forcing oral breathing. Nasal NO production is involved in vascular homeostasis and, as consequence, can significantly reduce NO possibly promoting vascular dysfunction. More recently, the utilization of “full-face” (FF) mask, allowing nasal breathing, became more frequent, but no reports are available describing their effects on vascular functions in comparison with HF masks. In this study we assessed and compared the effects of a standard shallow dive (20 min at 10 m) wearing either FF or a HF mask on different markers of vascular function (FMD), oxidative stress (ROS, 8-iso-PGF2α) and NO availability and metabolism (NO2, NOx and 3-NT and iNOS expression). Data from a dive breathing a hypoxic (16% O2 at depth) gas mixture with HF mask are shown allowing hyperoxic/hypoxic exposure. Our data suggest that nasal breathing might significantly reduce the occurrence of vascular dysfunction possibly due to better maintenance of NO production and bioavailability, resulting in a better ability to counter reactive oxygen and nitrogen species. Besides the obvious outcomes in terms of SCUBA diving safety, our data permit a better understanding of the effects of oxygen concentrations, either in normal conditions or as a strategy to induce selected responses in health and disease.

The role of nitric oxide in renovascular hypertension: from the pathophysiology to the treatment.

Renovascular hypertension is one of the most relevant causes of secondary hypertension, mostly caused by atherosclerotic renovascular stenosis or fibromuscular dysplasia. The increase in angiotensin II production, oxidative stress, and formation of peroxynitrite promotes the decrease in nitric oxide (NO) availability and the development of hypertension, renal and endothelial dysfunction, and cardiac and vascular remodeling. The NO produced by nitric oxide synthases (NOS) acts as a vasodilator; however, endothelial NOS uncoupling (eNOS) also contributes to NO reduced availability in renovascular hypertension. NO donors and NO-derived metabolites have been investigated in experimental renovascular hypertension and have shown promissory effects in attenuating blood pressure and organ damage in this condition. Therefore, understanding the role of decreased NO in the pathophysiology of renovascular hypertension promotes the study and development of NO donors and molecules that can be converted into NO (such as nitrate and nitrite), contributing for the treatment of this condition in the future.

Administration of L-citrulline prevents Plasmodium growth by inhibiting/ modulating T-regulatory cells during malaria pathogenesis.

Malaria affects around 228 million people all over the globe. Malaria causing parasite Plasmodium infection leads to activation of immune responses. The growth of parasite and immune activation requires semi essential amino acids like L-arginine. Malaria infection leads to condition of hyperargininemia and low availability of nitric oxide. However, the effect of L-arginine supplementation in malaria infected mice has not been explored in in-vivo studies. In this study we have compared the effect of oral supplementation of nitric oxide donor, L-arginine and L-citrulline, in malaria infected mice Methods: To examine the effect of oral supplementation of L-arginine and L-citrulline, Plasmodium berghei infected mice were divided in different groups and respective groups were fed with L- arginine and L-citrulline, parasitemia was measured on different days. Mice was sacrificed and immunophenotyping was done on 10 days post infection. our results show that supplementation of L-arginine induces conducive environment for Plasmodium growth due to which the infected mice dies earlier than control wild type infected mice whereas L-citrulline supplementation inhibits parasite growth and mice survives for longer period of time. Flow cytometric analysis shows that supplementation of L-arginine increases cTLA-4 on T cell population, increases Treg cells leading to immunosuppression while supplementation of L-citrulline does not have effect on T cells population and number of Treg cell decrease compared to P. berghei infected mice. our results show that L-citrulline can be a better alternative than L-arginine because of lower expression of inhibitory molecules and lower parasitemia as well as increased survival of infected mice.

Endothelial dysfunction in pathological processes of chronic liver disease during aging.

Aging is associated with gradual changes in liver structure and physiological/pathological functions in hepatic cells including hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). LSECs are specialized hepatic endothelial cells that regulate liver homeostasis. These cells actively impact the hepatic microenvironment as they have fenestrations and a thin morphology to allow substance exchange between circulating blood and the liver tissue. As aging occurs, LSECs have a reduction in both the number and size of fenestrations, which is referred to as pseudocapillarization. This along with the aging of the liver leads to increased oxidative stress, decreased availability of nitric oxide, decreased hepatic blood flow, and increased inflammatory cytokines in LSECs. Vascular aging can also lead to hepatic hypoxia, HSC activation, and liver fibrosis. In this review, we described the basic structure of LSECs, and the effect of LSECs on hepatic inflammation and fibrosis during aging process. We briefly summarized the changes of hepatic microcirculation during liver inflammation, the effect of aging on the clearance function of LSECs, the interactions between LSECs and immunity, hepatocytes or other hepatic nonparenchymal cells, and the therapeutic intervention of liver diseases by targeting LSECs and vascular system. Since LSECs play an important role in the development of liver fibrosis and the changes of LSEC phenotype occur in the early stage of liver fibrosis, the study of LSECs in the fibrotic liver is valuable for the detection of early liver fibrosis and the early intervention of fibrotic response.

Sodium nitrate supplementation improves blood pressure reactivity in patients with peripheral artery disease

Background & aimsPeripheral artery disease (PAD) is characterized by elevated blood pressure (BP), low nitric oxide availability (NO), and exaggerated pressor responses to sympatho-excitatory stressors. Inorganic nitrate reduces peripheral BP in healthy and chronically diseased populations. The objective of this study was to investigate the effects of eight-weeks of sodium nitrate (NaNO3) supplementation on indices of BP in PAD patients. Methods21 patients with PAD were recruited to participate in this study, undergoing 8-weeks of NaNO3 (n = 13; 73 ± 9 years) or placebo (n = 8; 69 ± 10 years) supplementation. BP responsiveness to a cold pressor test (CPT) were examined prior to and following the supplementation period. The systolic BP response (change from rest) during the first (26 ± 10 vs. 19 ± 11 mmHg) and second minutes (32 ± 10 vs. 26 ± 12 mmHg) of CPT were reduced following NaNO3 (P < 0.05 for both) but not after placebo (first minute: 22 ± 10 vs. 24 ± 10 mmHg, P = 0.30; second minute 26 ± 10 vs 27 ± 10 mmHg, P = 0.72) supplementation. ConclusionOur data suggest that eight-weeks of NaNO3 supplementation reduces BP responsiveness to sympatho-excitatory stimuli. Clinical trials registration numberNCT01983826.

Influence of anti-TNF therapy and homocysteine level on carotid intima-media thickness in rheumatoid arthritis patients.

It is a well-known fact that disruptions in the immune system and systemic inflammation are associated with accelerated atherosclerosis in rheumatoid arthritis (RA) patients. Elevated levels of tumor necrosis factor α (TNF-α), a major pro-inflammatory cytokine, are involved in endothelial cell activation of medium and large arteries, leading to increased endothelial permeability, generation of superoxide anion radical and hydrogen peroxide, and decreased availability of nitric oxide (NO). The present study aims to determine the influence of anti-TNF therapy and homocysteine (Hcy) levels on the carotid intima-media thickness (IMT) in patients with RA. Assessments were performed on 115 patients diagnosed with RA on biological treatment to determine the evolution of IMT and Hcy levels. Carotid ultrasonography was used to assess the IMT, as a fast and easy tool for the prediction of cardiovascular events in patients with RA. The first measurement of IMT was noted as IMT1, followed by a second measurement after 1 year, noted as IMT2. The group of patients was divided into approximately three equal groups, each being treated with a different biological product, respectively, etanercept, adalimumab, and infliximab. In the 3 groups, after 1 year of anti-TNF-α therapy, IMT2 progression was significantly reduced compared to baseline. No significant differences were found among the three groups of treatment. A strong association was observed between IMT1-IMT2 in the etanercept group (P<0.001, r=0.758), in the adalimumab group (P<0.001, r=0.761) and in the infliximab group (P<0.001, r=0.829). The low level of Hcy2 after 12 months of anti-TNF-α therapy was significantly correlated with a decrease in IMT2 (P<0.001) in patients who had a high level of Hcy and IMT >0.9 mm at baseline. The results from the present study showed that biological treatment and the low level of homocysteinemia reduced the cardiovascular risk in RA, regardless of the treatment chosen (infliximab, adalimumab, or etanercept).

Polyphenol consumption and endurance exercise performance: A systematic review and meta-analysis of randomised controlled trials

Introduction: Consumption of polyphenols is proposed to reduce oxidative damage and increase nitric oxide synthesis and availability, thereby inducing physiological effects that enhance endurance exercise performance. Thus, the objective of this study was to systematically review the literature to evaluate the effects of consuming polyphenol-rich foods on endurance exercise performance. Methods: This study comprised a subanalysis of a larger systematic review. Electronic searches of Scopus, Web of Science, Ovid Medline, EMBASE and SportDiscus databases were performed. Studies were included if they involved consumption of foods containing polyphenols, and a measure of endurance exercise performance was reported. Risk of bias was assessed using the Cochrane RoB 2.0 and random effects meta-analysis was conducted, with subgroup analyses performed based on food type, sex, fitness level, and supplementation dosage and duration. Results: Data from 58 studies met eligibility criteria, with 55 studies included in the meta-analysis. Meta-analysis identified trivial but significant benefits for the overall consumption of polyphenol-rich foods on endurance exercise performance (SMD= 0.17, p<0.001). When evaluated by food type, grape, (nitrate-depleted) beetroot, French maritime pine, Montmorency cherry and pomegranate exhibited significant ergogenic effects, while no significant effects were evident for New Zealand blackcurrant, cocoa, ginseng, green tea or raisins. Significant positive effects were evident following both acute and multiple-day supplementation and meta-regression indicated that total polyphenols consumed did not moderate effect size. No effect of polyphenol consumption on exercise performance was found in females (SMD= 0.01, p=0.95), but small to moderate effects (SMD=0.21-0.76, p<0.001) were found in males across a range of fitness levels (V̇O2max 41-71 ml.kg.min-1). Limited evidence supported polyphenol-rich foods enhancing nitric oxide availability, improving vascular function, reducing oxidative damage or other physiological indicators that may explain these ergogenic benefits. Considerable heterogeneity in effect sizes of included studies was present, which may reflect variation in polyphenol bioavailability between foods, differences in study designs and subject characteristics. Discussion: Foods rich in polyphenols provide benefits for endurance exercise performance in males, but not females. These sex-specific benefits were observed across a range of fitness levels, from untrained to well-trained athletes. There is limited direct evidence of the mechanisms underpinning these effects. Other: The review protocol was registered on the Open Science Framework (https://osf.io/u7nsj). My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.

Pathways of Microcirculatory Endothelial Dysfunction in Obstructive Sleep Apnea: A Comprehensive Ex Vivo Evaluation in Human Tissue.

The mechanism and markers of cardiovascular disease (CVD) in obstructive sleep apnea (OSA) remain unknown. The microcirculation is the site of early changes in OSA patients who are free of CVD risk. Patients with newly diagnosed moderate to severe OSA (n = 7) were studied before and 12 weeks after intensive treatment with continuous positive airway pressure (CPAP), along with weight and age matched controls (n = 7). Microcirculatory vessels were isolated from gluteal biopsies and changes in critical functional genes were measured. The following genes changed after 12 weeks of intensive CPAP therapy in the microcirculatory vessels: angiotensin receptor type 1 (AGTR-1) (11.6 (3.4) to 6 (0.8); P = 0.019); NADPH oxidase (NOX4) (0.85 (0.02) to 0.79 (0.11); P = 0.016); and dimethylarginine dimethylaminohydrolase (DDAH 1) (1 (0.31) to 0.55 (0.1); P = 0.028). Despite decreased nitric oxide (NO) availability as measured indirectly through brachial artery flow-mediated dilation, endothelial NO synthase (NOS3) did not change with CPAP. Other disease markers of OSA that changed with treatment in the microcirculation were endothelin, hypoxia inducible factor 1a, nuclear factor kappa B, interleukin-8, and interleukin-6. In this ex vivo evaluation of the microcirculation of patients with OSA and no CVD risk, several pathways of CVD were activated supporting that OSA independently induces microcirculatory endothelial dysfunction and serving as disease-specific markers for future pharmacological targeting of OSA-related CVD risk. The findings support the role of renin-angiotensin activation and endothelial oxidative stress in the decreased microcirculatory NO availability in OSA.

The associations of serum homoarginine to long-term prognosis in patients with chronic coronary syndrome and non-obstructive coronary artery disease

Abstract Background Although generally at lower risk than those with obstructive CAD, patients with non-obstructive CAD (NOCAD) are heterogeneous concerning long-term prognosis. Notably, reversible ischemia due to vascular dysfunction is a frequent finding in NOCAD patients (1). The endogenous, non-proteinogenic amino acid homoarginine (hArg) increases the availability of nitric oxide (NO) and thereby the NO-dependent vasodilatation (2). Several studies have reported a strong inverse relation between serum hArg levels and cardiovascular disease (CVD) risk among patients with obstructive CAD. However, the prognostic implications of serum hArg levels in NOCAD patients have not been explored previously. Purpose We evaluated serum hArg as a predictor of long-term risk of CVD mortality among patients with NOCAD. Methods 1046 patients with chronic coronary syndrome (CCS) underwent elective coronary angiography during 2000–2004, with the findings of NOCAD. Serum hArg was measured by liquid chromatography-tandem mass spectrometry in samples that had been frozen and stored at −80°C. The association of serum hArg to CVD mortality risk was visualized in a generalized additive regression plot and further explored using Cox regression. The models included age, sex, body mass index, hypertension, diabetes, smoking status, serum LDL cholesterol and estimated glomerular filtration rate as independent covariables. We evaluated model discrimination and risk classification by calculating C-statistics and net reclassification improvement (NRI &amp;gt;0), respectively. Results Median (25th-75th percentiles) age at inclusion was 57 (51–65) years, 48.5% were women and median (25th-75th percentiles) level of serum hArg was 1.87 (1.47–2.38) μmol/L. During median (25th- 75th percentiles) 14.1 (13.2–15.4) years of follow-up 5.7% of the patients died from CVD. The multivariable adjusted hazard ratio (95% confidence interval) per SD increment of (log transformed) hArg was 0.53 (0.40–0.70) in relation to CVD mortality. The multivariable model without biomarker provided a C- statistics for CVD mortality of 0.79 which increased to 0.82 by the addition of serum-hArg to the model (Δ area =0.03, P=0.01). Further, serum hArg provided a high NRI (95% CI) of 0.53 (0.40–0.70), P&amp;lt;0.001. Conclusion We demonstrated a strong inverse relationship between serum hArg and long-term risk of CVD mortality among patients with NOCAD. Our study adds to previous literature linking low hArg with vascular dysfunction and adverse CVD prognosis. The potential clinical usefulness of serum hArg measurements for the identification of a high-risk phenotype in NOCAD warrants further evaluation. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): The Western Norway Regional Health Authority

Deletion of the Gamma Subunit of ENaC in Endothelial Cells Does Not Protect against Renal Ischemia Reperfusion Injury.

Acute kidney injury due to renal ischemia-reperfusion injury (IRI) may lead to chronic or end stage kidney disease. A greater understanding of the cellular mechanisms underlying IRI are required to develop therapeutic options aimed at limiting or reversing damage from IRI. Prior work has shown that deletion of the α subunit of the epithelial Na+ channel (ENaC) in endothelial cells protects from IRI by increasing the availability of nitric oxide. While canonical ENaCs consist of an α, β, and γ subunit, there is evidence of non-canonical ENaC expression in endothelial cells involving the α subunit. We therefore tested whether the deletion of the γ subunit of ENaC also protects mice from IRI to differentiate between these channel configurations. Mice with endothelial-specific deletion of the γ subunit and control littermates were subjected to unilateral renal artery occlusion followed by 48 h of reperfusion. No significant difference was noted in injury between the two groups as assessed by serum creatinine and blood urea nitrogen, levels of specific kidney injury markers, and histological examination. While deletion of the γ subunit did not alter infiltration of immune cells or cytokine message, it was associated with an increase in levels of total and phosphorylated endothelial nitric oxide synthase (eNOS) in the injured kidneys. Our studies demonstrate that even though deletion of the γ subunit of ENaC may allow for greater activation of eNOS, this is not sufficient to prevent IRI, suggesting the protective effects of α subunit deletion may be due, in part, to other mechanisms.

Hyperuricemia-induced endothelial insulin resistance: the nitric oxide connection.

Hyperuricemia, defined as elevated serum concentrations of uric acid (UA) above 416µmol L-1, is related to the development of cardiometabolic disorders, probably via induction of endothelial dysfunction. Hyperuricemia causes endothelial dysfunction via induction of cell apoptosis, oxidative stress, and inflammation; however, it's interfering with insulin signaling and decreased endothelial nitric oxide (NO) availability, resulting in the development of endothelial insulin resistance, which seems to be a major underlying mechanism for hyperuricemia-induced endothelial dysfunction. Here, we elaborate on how hyperuricemia induces endothelial insulin resistance through the disruption of insulin-stimulated endothelial NO synthesis. High UA concentrations decrease insulin-induced NO synthesis within the endothelial cells by interfering with insulin signaling at either the receptor or post-receptor levels (i.e., proximal and distal steps). At the proximal post-receptor level, UA impairs the function of the insulin receptor substrate (IRS) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) in the insulin signaling pathway. At the distal level, high UA concentrations impair endothelial NO synthase (eNOS)-NO system by decreasing eNOS expression and activity as well as by direct inactivation of NO. Clinically, UA-induced endothelial insulin resistance is translated into impaired endothelial function, impaired NO-dependent vasodilation, and the development of systemic insulin resistance. UA-lowering drugs may improve endothelial function in subjects with hyperuricemia.

S-Nitrosylation of RhoGAP Myosin9A Is Altered in Advanced Diabetic Kidney Disease.

The molecular pathogenesis of diabetic kidney disease progression is complex and remains unresolved. Rho-GAP MYO9A was recently identified as a novel podocyte protein and a candidate gene for monogenic FSGS. Myo9A involvement in diabetic kidney disease has been suggested. Here, we examined the effect of diabetic milieu on Myo9A expression in vivo and in vitro. We determined that Myo9A undergoes S-nitrosylation, a post-translational modification dependent on nitric oxide (NO) availability. Diabetic mice with nodular glomerulosclerosis and severe proteinuria associated with doxycycline-induced, podocyte-specific VEGF164 gain-of-function showed markedly decreased glomerular Myo9A expression and S-nitrosylation, as compared to uninduced diabetic mice. Immortalized mouse podocytes exposed to high glucose revealed decreased Myo9A expression, assessed by qPCR, immunoblot and immunocytochemistry, and reduced Myo9A S-nitrosylation (SNO-Myo9A), assessed by proximity link assay and biotin switch test, functionally resulting in abnormal podocyte migration. These defects were abrogated by exposure to a NO donor and were not due to hyperosmolarity. Our data demonstrate that high-glucose induced decrease of both Myo9A expression and SNO-Myo9A is regulated by NO availability. We detected S-nitrosylation of Myo9A interacting proteins RhoA and actin, which was also altered by high glucose and NO dependent. RhoA activity inversely related to SNO-RhoA. Collectively, data suggest that dysregulation of SNO-Myo9A, SNO-RhoA and SNO-actin may contribute to the pathogenesis of advanced diabetic kidney disease and may be amenable to therapeutic targeting.