Nitric Oxide Bioavailability Research Articles

Auto/Paracrine C-Type Natriuretic Peptide/Cyclic GMP Signaling Prevents Endothelial Dysfunction.

Endothelial dysfunction is cause and consequence of cardiovascular diseases. The endothelial hormone C-type natriuretic peptide (CNP) regulates vascular tone and the vascular barrier. Its cGMP-synthesizing guanylyl cyclase-B (GC-B) receptor is expressed in endothelial cells themselves. To characterize the role of endothelial CNP/cGMP signaling, we studied mice with endothelial-selective GC-B deletion. Endothelial EC GC-B KO mice had thicker, stiffer aortae and isolated systolic hypertension. This was associated with increased proinflammatory E-selectin and VCAM-1 expression and impaired nitric oxide bioavailability. Atherosclerosis susceptibility was evaluated in such KO and control littermates on Ldlr (low-density lipoprotein receptor)-deficient background fed a Western diet for 10 weeks. Notably, the plaque areas and heights within the aortic roots were markedly increased in the double EC GC-B/Ldlr KO mice. This was accompanied by enhanced macrophage infiltration and greater necrotic cores, indicating unstable plaques. Finally, we found that EC GC-B KO mice had diminished vascular regeneration after critical hind-limb ischemia. Remarkably, all these genotype-dependent changes were only observed in female and not in male mice. Auto/paracrine endothelial CNP/GC-B/cGMP signaling protects from arterial stiffness, systolic hypertension, and atherosclerosis and improves reparative angiogenesis. Interestingly, our data indicate a sex disparity in the connection of diminished CNP/GC-B activity to endothelial dysfunction.

Brain endothelial cell activation and dysfunction associate with and contribute to the development of enlarged perivascular spaces and cerebral small vessel disease.

Multiple injurious stimuli to the brain's endothelium results in brain endothelial cell activation and dysfunction (BECact/dys) with upregulation of inflammatory signaling cascades and a decrease in bioavailable nitric oxide respectively. These injurious stimuli initiate a brain injury and a response to injury wound healing genetically programed cascade of events, which result in cellular remodeling of the neurovascular unit and blood-brain barrier with increased inflammation and permeability. These remodeling changes also include the perivascular spaces that become dilated to form enlarged perivascular spaces (EPVS) that may be identified noninvasively by magnetic resonance imaging. These EPVS are associated with and considered to be a biomarker for cerebral small vessel disease (SVD) and a dysfunctional glymphatic system with impaired removal of neurotoxic waste, which ultimately results in neurodegeneration with impaired cognition and dementia. The penultimate section discusses the understudied role of venous cerebral circulation in relation to EPVS, SVD, and the vascular contribution to cognitive impairment (VCID). The focus of this review will be primarily on BECact/dys that associates with and contributes to the development of EPVS, SVD, and impaired glymphatic system efflux. Importantly, BECact/dys may be a key piece of the puzzle to unlock this complicated story of EPVS and SVD. Multiple transmission electron micrographs and illustrations will be utilized to depict anatomical ultrastructure and allow for the discussion of multiple functional molecular cascades.

Eicosapentaenoic Acid Improves Endothelial Nitric Oxide Bioavailability Via Changes in Protein Expression During Inflammation.

Endothelial cell (EC) dysfunction involves reduced nitric oxide (NO) bioavailability due to NO synthase uncoupling linked to increased oxidation and reduced cofactor availability. Loss of endothelial function and NO bioavailability are associated with inflammation, including leukocyte activation. Eicosapentaenoic acid (EPA) administered as icosapent ethyl reduced cardiovascular events in REDUCE-IT (Reduction of Cardiovascular Events With Icosapent Ethyl-Intervention Trial) in relation to on-treatment EPA blood levels. The mechanisms of cardiovascular protection for EPA remain incompletely elucidated but likely involve direct effects on the endothelium. In this study, human ECs were treated with EPA and challenged with the cytokine IL-6 (interleukin-6). Proinflammatory responses in the ECs were confirmed by ELISA capture of sICAM-1 (soluble intercellular adhesion molecule-1) and TNF-α (tumor necrosis factor-α). Global protein expression was determined using liquid chromatography-mass spectrometry tandem mass tag. Release kinetics of NO and peroxynitrite were monitored using porphyrinic nanosensors. IL-6 challenge induced proinflammatory responses from the ECs as evidenced by increased release of sICAM-1 and TNF-α, which correlated with a loss of NO bioavailability. ECs pretreated with EPA modulated expression of 327 proteins by >1-fold (P<0.05), compared with IL-6 alone. EPA augmented expression of proteins involved in NO production, including heme oxygenase-1 and dimethylarginine dimethylaminohydrolase-1, and 34 proteins annotated as associated with neutrophil degranulation. EPA reversed the endothelial NO synthase uncoupling induced by IL-6 as evidenced by an increased [NO]/[peroxynitrite] release ratio (P<0.05). These direct actions of EPA on EC functions during inflammation may contribute to its distinct cardiovascular benefits.

Effects of short-term dietary nitrate supplementation on exercise and coronary blood flow responses in patients with peripheral artery disease.

Peripheral arterial disease (PAD) is a prevalent vascular disorder characterized by atherosclerotic occlusion of peripheral arteries, resulting in reduced blood flow to the lower extremities and poor walking ability. Older patients with PAD are also at a markedly increased risk of cardiovascular events, including myocardial infarction. Recent evidence indicates that inorganic nitrate supplementation, which is abundant in certain vegetables, augments nitric oxide (NO) bioavailability and may have beneficial effects on walking, blood pressure, and vascular function in patients with PAD. We sought to determine if short-term nitrate supplementation (via beetroot juice) improves peak treadmill time and coronary hyperemic responses to plantar flexion exercise relative to placebo (nitrate-depleted juice) in older patients with PAD. The primary endpoints were peak treadmill time and the peak coronary hyperemic response to plantar flexion exercise. Eleven PAD patients (52-80 yr.; 9 men/2 women; Fontaine stage II) were randomized (double-blind) to either nitrate-rich (Beet-IT, 0.3 g inorganic nitrate twice/day; BRnitrate) or nitrate-depleted (Beet-IT, 0.04 g inorganic nitrate twice/day, BRplacebo) beetroot juice for 4 to 6 days, followed by a washout of 7 to 14 days before crossing over to the other treatment. Patients completed graded plantar flexion exercise with their most symptomatic leg to fatigue, followed by isometric handgrip until volitional fatigue at 40% of maximum on day 4 of supplementation, and a treadmill test to peak exertion 1-2 days later while continuing supplementation. Hemodynamics and exercise tolerance, and coronary blood flow velocity (CBV) responses were measured. Although peak walking time and claudication onset time during treadmill exercise did not differ significantly between BRplacebo and BRnitrate, the diastolic blood pressure response at the peak treadmill walking stage was significantly lower in the BRnitrate condition. Increases in CBV from baseline to peak plantar flexion exercise after BRplacebo and BRnitrate showed a trend for a greater increase in CBV at the peak workload of plantar flexion with BRnitrate (p = 0.06; Cohen's d = 0.56). Overall, these preliminary findings suggest that inorganic nitrate supplementation in PAD patients is safe, well-tolerated, and may improve the coronary hyperemic and blood pressure responses when their calf muscles are most predisposed to ischemia.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT02553733.

Endothelial Protection by Sodium-Glucose Cotransporter 2 Inhibitors: A Literature Review of In Vitro and In Vivo Studies.

Endothelial dysfunction often precedes the development of cardiovascular diseases, including heart failure. The cardioprotective benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2is) could be explained by their favorable impact on the endothelium. In this review, we summarize the current knowledge on the direct in vitro effects of SGLT2is on endothelial cells, as well as the systematic observations in preclinical models. Four putative mechanisms are explored: oxidative stress, nitric oxide (NO)-mediated pathways, inflammation, and endothelial cell survival and proliferation. Both in vitro and in vivo studies suggest that SGLT2is share a class effect on attenuating reactive oxygen species (ROS) and on enhancing the NO bioavailability by increasing endothelial nitric oxide synthase activity and by reducing NO scavenging by ROS. Moreover, SGLT2is significantly suppress inflammation by preventing endothelial expression of adhesion receptors and pro-inflammatory chemokines in vivo, indicating another class effect for endothelial protection. However, in vitro studies have not consistently shown regulation of adhesion molecule expression by SGLT2is. While SGLT2is improve endothelial cell survival under cell death-inducing stimuli, their impact on angiogenesis remains uncertain. Further experimental studies are required to accurately determine the interplay among these mechanisms in various cardiovascular complications, including heart failure and acute myocardial infarction.

S-Nitroso Human Serum Albumin Enhances Left Ventricle Hemodynamic Performance and Reduces Myocardial Damage after Local Ischemia-Reperfusion Injury.

Endothelial nitric oxide (NO) production is crucial in maintaining vascular homeostasis. However, in the context of ischemia-reperfusion (I/R) injury, uncoupled endothelial nitric oxide synthase (eNOS) can exacerbate reactive oxygen species (ROS) generation. Supplementation with S-nitroso human serum albumin (S-NO-HSA) offers a potential solution by mitigating eNOS uncoupling, thereby enhancing NO bioavailability. In a study conducted at the University of Verona, male rats underwent thoracotomy followed by 30 min left anterior descendant coronary (LAD) occlusion and subsequent reperfusion. Hemodynamic parameters were meticulously assessed using a conductance catheter inserted via the carotid artery. The rats were stratified into two main groups based on reperfusion duration and the timing of drug infusion, with the effects of S-NO-HSA evaluated after 2 or 24 h. Remarkably, intravenous administration of S-NO-HSA, initiated before or during ischemia, exhibited notable benefits. It significantly improved left ventricular function, safeguarded energetic substrates such as phosphocreatine and ATP, and sustained glutathione levels akin to basal conditions, indicative of diminished oxidative stress. The data from this study strongly suggest a protective role for S-NO-HSA in mitigating I/R injury induced by LAD artery occlusion, a phenomenon observed at both 2 and 24 h post-reperfusion. These findings underscore the promising therapeutic potential of NO supplementation in alleviating myocardial damage subsequent to ischemic insult.

Isoflurane increases the activity of the vascular matrix metalloproteinase-2 in non-pregnant rats and increases the nitric oxide metabolites in pregnancy.

Surgeries that require general anesthesia occur in 1.5-2% of gestations. Isoflurane is frequently used because of its lower possibility of affecting fetal growth. Therefore, we examined the isoflurane anesthesia-induced effects on maternal hemodynamic and vascular changes. We hypothesized that isoflurane would enhance endothelium-dependent vasodilation as a consequence of increased nitric oxide and decreased metalloproteinases (MMPs). Female rats (n=28) were randomized into 4 groups (7 rats/group): conscious (non-anesthetized) non-pregnant group, non-pregnant anesthetized group, conscious pregnant group, and pregnant anesthetized group. Anesthesia was performed on the 20th pregnancy day, and hemodynamic parameters were monitored. Nitric oxide metabolites, gelatinolytic activity of MMP-2 and MMP-9, and the vascular function were assessed. Isoflurane caused no significant hemodynamic changes in pregnant compared with non-pregnant anesthetized group. Impaired acetylcholine-induced relaxations were observed only in conscious non-pregnant group (by approximately 62%) versus 81% for other groups. Phenylephrine-induced contractions were greater in endothelium-removed aorta segments of both pregnant groups (with or without isoflurane) compared with non-pregnant groups. Higher nitric oxide metabolites were observed in anesthetized pregnant in comparison with the other groups. Reductions in the 75 kDa activity and concomitant increases in 64 kDa MMP-2 isoforms were observed in aortas of pregnant anesthetized (or not) groups compared with conscious non-pregnant group. Isoflurane anesthesia shows stable effects on hemodynamic parameters and normal MMP-2 activation in pregnancy. Furthermore, there were increases in nitric oxide bioavailability, suggesting that isoflurane provides protective actions to the endothelium in pregnancy.

Controversies in the pathophysiology of leg ulcers in sickle cell disease.

Patients with sickle cell disease (SCD) often experience painful vaso-occlusive crises and chronic haemolytic anaemia, as well as various acute and chronic complications, such as leg ulcers. Leg ulcers are characterized by their unpredictability, debilitating pain and prolonged healing process. The pathophysiology of SCD leg ulcers is not well defined. Known risk factors include male gender, poor social conditions, malnutrition and a lack of compression therapy when oedema occurs. Leg ulcers typically start with spontaneous pain, followed by induration, hyperpigmentation, blister formation and destruction of the epidermis. SCD is characterized by chronic haemolysis, increased oxidative stress and decreased nitric oxide bioavailability, which promote ischaemia and inflammation and consequently impair vascular function in the skin. This cutaneous vasculopathy, coupled with venostasis around the ankle, creates an ideal environment for local vaso-occlusive crises, which can result in the development of leg ulcers that resemble arterial ulcers. Following the development of the ulcer, healing is hindered as a result of factors commonly observed in venous ulceration, including venous insufficiency, oedema and impaired angiogenesis. All of these factors are modulated by genetic factors. However, our current understanding of these genetic factors remains limited and does not yet enable us to accurately predict ulceration susceptibility.

Dietary NO3− does not enhance endothelial dependent cutaneous vascular conductance in older women

Prior work has yet to determine whether the reduction of dietary nitrate (NO3−) to NO, via the enterosalivary pathway, may modify cutaneous vascular conductance (CVC) responses to local heating in older women. Changes occurring with the transition to menopause related to hormonal flux, increased adiposity, and/or decreased physical activity may further compound the negative influence of aging on nitric oxide (NO)-dependent CVC. Herein, we characterized changes in NO-dependent CVC following acute ingestion of 140 mL of NO3−-rich beetroot juice in 24 older women (age: 65 ± 5 y, BMI: 31.2 ± 3.7 kg/m2). Red blood cell (RBC) flux was measured continuously via laser-Doppler flowmetry on the dorsal aspect of the forearm during local skin heating to 39 °C/44 °C before and 3 h after NO3− ingestion. NO-dependent changes in CVC were calculated as RBC flux/mean arterial blood pressure at 39 °C and normalized as a proportion of maximal CVC at 44 °C (%CVCmax). Changes (Δ) in fractional exhaled NO (FeNO) following NO3− ingestion were used an index of NO bioavailability. Despite increased FeNO (+81 ± 70 %, P < 0.001), %CVCmax at 39 °C was reduced (−16 ± 10 %, P < 0.001) following NO3− ingestion. A greater reduction in %CVCmax was weakly to moderately associated with higher body fat% (r = 0.45 [0.05–0.72], P = 0.029), central adiposity% (r = 0.50 [0.13–0.75], P = 0.012), neutrophil% (r = 0.42 [0.02–0.70], P = 0.041), and higher neutrophil to lymphocyte ratio (r = 0.49 [0.11–0.75], P = 0.016). These findings demonstrate a single dose of dietary NO3− does not promote CVC responses to local heating in sedentary older women with overweight and obesity. Correlation with multiple biomarkers suggest systemic inflammation may be involved.

The relationship between endothelial-dependent flow-mediated dilation and diastolic function in type 2 diabetes

AimsDiastolic dysfunction represents the earliest and most common manifestation of diabetic cardiomyopathy. Nitric oxide (NO), a potent vasodilator and anti-inflammatory mediator released from the subendocardial and coronary endothelium, favors left ventricular distensibility and relaxation. In type 2 diabetes (T2D), the NO bioavailability is reduced due to the oxidative stress and inflammatory state of the endothelium, because of chronic hyperglycemia. The aim of the present research is to evaluate the relationship between endothelial function and diastolic function in subjects with T2D.MethodSubjects with T2D and age and sex-matched healthy controls were consecutively recruited. All participants underwent flow-mediated dilation (FMD) to assess endothelial function, and echocardiography to evaluate diastolic function.ResultsThirty-five patients (6 women, 29 men) and 35 healthy controls were included in the final analysis. FMD was significantly lower in T2D than controls (4.4 ± 3.4 vs. 8.5 ± 4.3%, p = 0.001). T2D presented different abnormalities in diastolic function compared to controls: lower E/A (early to late diastolic transmitral flow velocity), lower septal and lateral e′ (early diastolic myocardial tissue velocity at septum and lateral wall), and higher E/e′ (surrogate of filling pressure). In subjects with T2D, we observed a significant correlation between FMD and E/e′ (r = −0.63, p = 0.001), lateral e′ (r = 0.44, p = 0.03), and septal e′ (r = 0.39, p = 0.05).ConclusionsOur observational study demonstrated a link between FMD and diastolic dysfunction in subjects with type 2 diabetes.

Facilitating Nitrite-Derived S-Nitrosothiol Formation in the Upper Gastrointestinal Tract in the Therapy of Cardiovascular Diseases.

Cardiovascular diseases (CVDs) are often associated with impaired nitric oxide (NO) bioavailability, a critical pathophysiological alteration in CVDs and an important target for therapeutic interventions. Recent studies have revealed the potential of inorganic nitrite and nitrate as sources of NO, offering promising alternatives for managing various cardiovascular conditions. It is now becoming clear that taking advantage of enzymatic pathways involved in nitrite reduction to NO is very relevant in new therapeutics. However, recent studies have shown that nitrite may be bioactivated in the acidic gastric environment, where nitrite generates NO and a variety of S-nitrosating compounds that result in increased circulating S-nitrosothiol concentrations and S-nitrosation of tissue pharmacological targets. Moreover, transnitrosation reactions may further nitrosate other targets, resulting in improved cardiovascular function in patients with CVDs. In this review, we comprehensively address the mechanisms and relevant effects of nitrate and nitrite-stimulated gastric S-nitrosothiol formation that may promote S-nitrosation of pharmacological targets in various CVDs. Recently identified interfering factors that may inhibit these mechanisms and prevent the beneficial responses to nitrate and nitrite therapy were also taken into consideration.

Increased oxidative stress alters coronary microvascular tone in exercising swine with multiple comorbidities

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch Cardiovascular Alliance Background/Objectives We have previously shown, in female swine that the combination of three cardiovascular risk factors (diabetes mellitus (DM), hypercholestolemia (HC) and chronic kidney disease (CKD)) induces systemic inflammation, oxidative stress, coronary endothelial dysfunction and impaired myocardial perfusion due to impaired nitric oxide (NO) bioavailability. In the present study we hypothesized that the reduced bioavailability of nitric oxide (NO) is the result of increased production of reactive oxygen species (ROS) and ROS scavenging will restore myocardial oxygen balance thereby improving myocardial perfusion. Methods 12 female swine, with DM (streptozotocin 3x50mg/kg iv), CKD (renal embolization), and HC (high fat, high sugar, high salt diet) and 9 female healthy swine on normal pig chow (Normal) were included. The effect of ROS scavenging on the coronary microvascular tone control was studied in vivo, at rest and during graded treadmill exercise before and after infusion of the ROS scavengers (MPG+Tempol). Additionally, vasodilation to bradykinin was studied in the presence of MPG and TEMPOL and after subsequent addition to catalase, in isolated left ventricle small coronary arteries, in vitro using wire-myography. Results 6 months of DM+HC+CKD resulted in hyperglycemia (18.0±1.3 vs 8.4±0.9mmol/L), hypercholesterolemia (13.4±2.1 vs 1.7±0.1mmol/l), renal dysfunction (plasma creatinine: 166±9 vs 119±3µmol/l), and systemic inflammation (TNFα: 63±8 vs 41±4pg/ml, all P&amp;lt;0.05) associated with impaired endothelium-dependent vasodilator response to bradykinin in vitro. Furthermore, myocardial oxidative stress was increased in DM+HC+CKD animals (8-isoprostane 13±1 vs 10±1pg/ml) and total antioxidant capacity was reduced (0.67±0.02 vs 0.72±0.01nmol Trolox eq./mg protein, both P&amp;lt;0.05). Surprisingly, in vivo ROS scavenging resulted in an even further increase in myocardial oxygen extraction in DM+HC+CKD while it had no effect in Normal, indicating the involvement of a vasodilator ROS (most likely H2O2) in the control of coronary microvascular tone. This was supported by increased activity of catalase in the myocardium of DM+HC+CKD animals (44±3 vs 31±4nmol/min/ml, both P&amp;lt;0.05) and the vascular relaxation response to bradykinin when catalase was added on top of the ROS scavenging in vitro. Conclusion In swine exposed for 6 months to multiple comorbidities, impaired myocardial perfusion is mediated by a loss of NO bioavailability due to increased oxidative stress which was partially compensated by increased H2O2-mediated coronary vasodilation.

Red blood cell-derived extracellular vesicles from type 2 diabetes patients induce endothelial dysfunction through a mechanism involving arginase 1

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Foundation for Geriatric Diseases Karolinska Institutet (2023-01860). Swedish Heart and Lung Foundation (20220210) Background The mechanisms driving the development of cardiovascular injury in type 2 diabetes (T2D) remain incompletely understood. We have recently demonstrated that red blood cells (RBCs) from patients with T2D (T2D-RBCs) act as mediators of endothelial dysfunction through the upregulation of arginase 1 and attenuation of nitric oxide bioavailability. However, the underlying mechanisms of this interaction remain unknown. It is increasingly clear that extracellular vesicles (EVs) are actively secreted by practically all cell types, including RBCs, and represent a novel mechanism of intercellular communication. However, the involvement of RBC-derived EVs in the development of endothelial dysfunction in T2D remains to be elucidated. Purpose To test the hypothesis that EVs are secreted by RBCs and transfer signalling to induce endothelial dysfunction in T2D through arginase 1. Methods EVs released from T2D-RBCs (T2D-RBCs EVs) and RBCs from age-matched healthy controls (H-RBCs EVs) were isolated using sequential ultracentrifugation or a membrane affinity column, co-incubated with mouse aortae to evaluate endothelium-dependent relaxation (EDR), and with human carotid artery endothelial cells (HCtAEC) to study the EV uptake and alteration in gene expression. EVs were characterized based on morphology, size and particle number, uptake in endothelial cells, and arginase 1 content. Functional involvement of EV uptake and arginase were investigated using pharmacological interventions. Arginase 1 was measured in EVs, HCtAEC, and mouse aortae after co-incubation with H-RBCs EVs and T2D-RBCs EVs. Results The uptake of T2D-RBCs EVs by endothelial cells was greater than that of EVs from H-RBCs (Fig. 1A, B) despite the reduced formation of EVs by T2D-RBCs (Fig. 1C). T2D-RBCs EVs significantly impaired EDR (Fig. 1D), and this impairment was prevented by inhibiting uptake of EVs with heparin (Fig. 1E). Arginase 1 was detected in RBC-derived EVs (Fig. 2A), and endothelial function was rescued by blocking arginase activity in EVs by the arginase inhibitor 2(S)-amino-6-boronohexanoic acid (ABH; Fig. 2B). Immunohistochemical staining revealed upregulation of arginase 1 in the vasculature following incubation with T2D-RBCs EVs (Fig. 2C, D). Additionally, co-incubation of HCtAEC and EVs derived from T2D-RBCs significantly increased endothelial cell arginase 1 (Fig. 2E, F). Administration of ABH to the aortae following the co-incubation also attenuated the impairment of EDR induced by T2D-RBCs EVs, suggesting the involvement of vascular arginase 1 (Fig. 2G). Conclusion T2D-RBCs EVs induce endothelial dysfunction. In addition to increased uptake of EVs in endothelial cells, the signalling behind this effect of EVs is mediated by arginase 1 to induce endothelial dysfunction. These results shed new important light on the mechanism underlying vascular injury mediated by RBCs in T2D.

Melatonin improves nitric oxide bioavailability in isoproterenol induced myocardial injury

Isoproterenol administration is associated with cardiac inflammation and decreased NO availability. Melatonin has been reported to have cardioprotective effect. The aim of this study was to investigate the effect of melatonin on NO bioavailability and inflammation in myocardial injury induced by isoproterenol. Isoproterenol was administrated in male Wistar rats for 7 days to induce cardiac injury. The animals were divided into 3 groups: Control, Isoproterenol, Isoproterenol + Melatonin. Animals received melatonin for 7 days. Echocardiographic analysis was performed and the hearts were collected for molecular analysis. Animals that received isoproterenol demonstrated a reduction in left ventricle systolic and diastolic diameter, indicating the presence of concentric hypertrophy. Melatonin was able to attenuate this alteration. Melatonin also improved NO bioavailability and decreased NF-κβ, TNFα and IL-1β expression. In conclusion, melatonin exhibited a cardioprotective effect which was associated with improving NO bioavailability and decreasing the pro-inflammatory proteins.

Associations between Vegetable Nitrate Intake and Cardiovascular Disease Risk and Mortality: A Systematic Review.

Consumption of nitrate-rich vegetables increases nitric oxide bioavailability, lowers blood pressure, and improves endothelial function. These effects could also translate into reduced cardiovascular disease (CVD) risk and mortality. This systematic review aimed to investigate the associations between habitual vegetable nitrate intake and CVD incidence and mortality. A secondary aim was to identify factors that moderate the relationship between vegetable nitrate intake and CVD incidence/mortality. Seven databases (PubMed, MEDLINE, Embase, Scopus, Web of Science, CINAHL, and APA PsycINFO) were searched from inception to 13 February 2023. Observational studies quantifying vegetable nitrate intake in participants aged 18+ years through self-reported dietary exposure and assessing incidence or mortality from CVD overall, or individual CVD subtypes, were eligible. Five studies including a total of 63,155 participants were included. There was an inverse association between vegetable nitrate intake and most reported CVD outcomes. Reported risk reductions tended to plateau at moderate intake, suggesting a possible ceiling effect. The risk of bias across all studies was low. The results of this systematic review suggest a potential role for vegetable nitrate in reducing CVD risk and mortality. Further randomised controlled trials are now required to corroborate these findings.

2-(4-Methylthiazol-5-yl) Ethyl Nitrate Hydrochloride Ameliorates Cognitive Impairment via Modulation of Oxidative Stress and Nuclear Factor Kappa B (NF-κB) Signaling Pathway in Chronic Cerebral Hypoperfusion-Associated Spontaneously Hypertensive Rats.

Hypertension reduces the bioavailability of vascular nitric oxide (NO) and contributes to the onset of vascular dementia (VaD). A loss of NO bioavailability increases inflammation and oxidative stress. 2-(4-Methylthiazol-5-yl) ethyl nitrate hydrochloride (W1302) is a novel nitric oxide donor (NOD) which is undergoing phase I clinical trials in China for the treatment of VaD. In this study, we investigated the protective effects of W1302 in VaD rats induced by the permanent occlusion of a bilateral common carotid arteries model related to spontaneous hypertension (SHR-2VO), and we further explored the underlying mechanisms. Nimodipine was used as a positive control. Our results showed that W1302 treatment for 4 weeks (10 mg/Kg/day) exhibited stronger improvement in the spatial learning and memory deficits in SHR-2VO rats compared with nimodipine with slightly lower systolic blood pressure (SBP). Meanwhile, W1302 treatment significantly increased NO and cGMP production, restored mitochondrial membrane potential and attenuated oxidative stress as evidenced by increasing ATP production and reducing malondialdehyde (MDA) levels in the brain. Furthermore, W1302 treatment markedly inhibited the iNOS activity and decreased TNF-α expression via inhibiting the nuclear factor kappa B (NF-κB) signaling pathway. Nimodipine treatment also restored these aberrant changes, but its ATP production was weaker than that of W1302, and there was no significant effect on NO release. Taken together, W1302 exhibited beneficial effects on complications in VaD with hypertension, which is involved in suppressing oxidative damage, and the inflammatory reaction might be mediated by an increase in NO release. Therefore, W1302 has therapeutic potential for the treatment of VaD caused by chronic cerebral hypoperfusion-associated spontaneous hypertension.

Influence of acute dietary nitrate supplementation on oxygen delivery/consumption and critical impulse during maximal effort forearm exercise in males: a randomized crossover trial.

Beetroot juice supplementation (BRJ) should increase nitric oxide bioavailability under conditions of muscle deoxygenation and acidosis that are a normal consequence of the maximal effort exercise test used to identify forearm critical impulse. We hypothesized BRJ would improve oxygen delivery:demand matching and forearm critical impulse performance. Healthy males (20.8±2.4 years) participated in a randomized crossover trial between October 2017 and May 2018 (Queen's University, Kingston, ON). Participants completed 10 min of rhythmic maximal effort forearm handgrip exercise 2.5 h post placebo (PL) vs. BRJ (9 completed PL/BRJ vs. 4 completed BRJ/PL) within a 2 week period. Data are presented as mean±SD. There was a main effect of drink (PL>BRJ) for oxygen extraction (P=0.033, ηp2=0.351) and oxygen consumption/force (P=0.017, ηp2=0.417). There was a drink × time interaction (PL>BRJ) for oxygen consumption/force (P=0.035, ηp2=0.216) between 75 and 360s (1.25-6min) from exercise onset. BRJ did not influence oxygen delivery (P=0.953, ηp2=0.000), oxygen consumption (P=0.064, ηp2=0.278), metabolites ((lactate) (P=0.196, ηp2=0.135), pH (P=0.759, ηp2=0.008)) or power-duration performance parameters (critical impulse (P=0.379, d=0.253), W' (P=0.733, d=0.097)). BRJ during all-out handgrip exercise does not influence oxygen delivery or exercise performance. Oxygen cost of contraction with BRJ is reduced as contraction impulse is declining during maximal effort exercise resulting in less oxygen extraction.

Loss of nitric oxide bioavailability promotes arterial stiffening in a tissue transglutaminase-dependent manner

Although arterial stiffening undeniably contributes to cardiovascular disease, the cellular and molecular mechanisms leading to increased arterial stiffness are not well understood. Increased arterial stiffness in disease states such as obesity and type 2 diabetes typically coexists with indices of endothelial dysfunction including diminished nitric oxide (NO) bioavailability. In fact, it is commonly assumed that endothelial dysfunction precedes, and causally contributes to, arterial stiffening; yet the molecular underpinnings for this causal relationship remain elusive. We and others previously showed that activation of tissue transglutaminase (TG2), a crosslinking enzyme that also works as a G-protein and cellular scaffold, promotes cytoskeletal actin polymerization and stiffening of vascular smooth muscle cells (VSMC), thus contributing to whole-artery stiffening. It is also reported that NO is an endogenous inhibitor of TG2. Accordingly, herein, we tested the hypothesis that increased exposure of VSMC to NO suppresses TG2 activity and actin polymerization. Conversely, we hypothesized that loss of NO bioavailability promotes arterial stiffening, and that this effect is mediated by TG2 activity and downstream activation of LIM kinase (LIMK), an enzyme that modulates fibrillar (F)-actin severing via cofilin phosphorylation. All differences reported herein are significant at P&lt;0.05. In support of our hypotheses, we show that treatment of cultured human aortic VSMC with the NO donor S-nitrosoglutathione (200μM for 2 hours) reduces TG2 activity (N-epsilon gamma glutamyl Lysine presence) and F-actin formation (phalloidin staining) induced by TG2 activation (dithiothreitol, 200μM). Furthermore, we show that exposure of mouse isolated mesenteric arteries to the NO synthase inhibitor L-NAME (300μM for 18 hours) causes an increase in arterial stiffness ( i.e., increased incremental modulus of elasticity) as determined using pressure myography and videomicroscopy. Of note, L-NAME-induced arterial stiffening is prevented when arteries are co-treated with a TG2 inhibitor (cystamine, 1mM) or LIMK inhibitor (LIMKi, 1μM). Taken together, these findings support the notion that NO is a key downregulator of TG2 activity and demonstrate that reduced NO bioavailability promotes arterial stiffening in a VSMC TG2-LIMK-F-actin dependent manner. As such, this work provides insight into plausible molecular mechanisms by which endothelial dysfunction leads to arterial stiffening. R01HL153264 (to LAML and JP), and MU Research Excellence Program (REP) postdoctoral fellowship (to FIRP). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Relationships between nitric oxide biomarkers and physiological outcomes following dietary nitrate supplementation

Dietary nitrate (NO3−) supplementation can increase nitric oxide (NO) bioavailability, reduce blood pressure (BP) and improve muscle contractile function in humans. Plasma nitrite concentration (plasma [NO2−]) is the most oft-used biomarker of NO bioavailability. However, it is unclear which of several NO biomarkers (NO3−, NO2−, S-nitrosothiols (RSNOs)) in plasma, whole blood (WB), red blood cells (RBC) and skeletal muscle correlate with the physiological effects of acute and chronic dietary NO3− supplementation. Using a randomized, double-blind, crossover design, 12 participants (9 males) consumed NO3−-rich beetroot juice (BR) (∼12.8 mmol NO3−) and NO3−-depleted placebo beetroot juice (PL) acutely and then chronically (for two weeks). Biological samples were collected, resting BP was assessed, and 10 maximal voluntary isometric contractions of the knee extensors were performed at 2.5–3.5 h following supplement ingestion on day 1 and day 14. Diastolic BP was significantly lower in BR (−2 ± 3 mmHg, P = 0.03) compared to PL following acute supplementation, while the absolute rate of torque development (RTD) was significantly greater in BR at 0–30 ms (39 ± 57 N m s−1, P = 0.03) and 0–50 ms (79 ± 99 N m s−1, P = 0.02) compared to PL following two weeks supplementation. Greater WB [RSNOs] rather than plasma [NO2−] was correlated with lower diastolic BP (r = −0.68, P = 0.02) in BR compared to PL following acute supplementation, while greater skeletal muscle [NO3−] was correlated with greater RTD at 0–30 ms (r = 0.64, P=0.03) in BR compared to PL following chronic supplementation. We conclude that [RSNOs] in blood, and [NO3−] in skeletal muscle, are relevant biomarkers of NO bioavailability which are related to the reduction of BP and the enhanced muscle contractile function following dietary NO3− ingestion in humans.

The impact of increased daily peanut consumption on indices of peripheral and cerebral vascular function in non-Hispanic Black individuals

Cardiovascular disease, neurocognitive conditions, and cerebral vascular diseases including cognitive impairment, stroke, and Alzheimer’s disease and related dementias disproportionately impact the Non-Hispanic Black (BL) population. The mechanisms are multifactorial but is related to reduced vascular function/health. Our lab, and others, have demonstrated that reduced nitric oxide (NO) bioavailability secondary to oxidative stress, systemic inflammation, and reduced L-arginine bioavailability contributes to reduced vascular function/health in this population. Increased dietary peanut consumption improves various physiological outcomes including blood pressure, cholesterol, type II diabetes, cognitive health, NO bioavailability, and vascular function/health. This improvement is related to increased bioavailability of L-arginine, reduced systemic inflammation, and antioxidant capacity. This study hypothesized that increased daily peanut consumption would improve indices of peripheral and cerebral vascular function/health in a cohort of BL individuals. Methods: Seventeen people participated (11 non-Hispanic White (WH) and 6 BL (age: WH 25±8, BL 21±2; BMI: WH 23±3, BL 22 ± 4; p&gt;0.05 for both). Measures were made before (pre) and after (post) 56 days of daily lightly salted peanut consumption (2 oz/day for females and 3 oz/day for males). Peripheral macro and microvascular function/health was assessed as brachial artery vasodilation (flow mediated dilation, %FMD) and forearm reactive hyperemia (peak mean forearm blood velocity (FBVmean) respectively following 5-min of suprasystolic cuff inflation. Cerebral vascular function/health was assessed as the cerebral vasodilator response during a hypercapnic challenge, i.e., the slope of % cerebral vascular conductance index (CVCi) relative to the change in end-tidal carbon dioxide concentration (ΔPETCO2). Results: There was no effect of race on peripheral macrovascular function assessed as %FMD (WH: 5.3 ±0.89, BL: 6.3 ±1.9 %, p=0.31) or peripheral microvascular function assessed as FBVmean (WH: 82.90 ± 4.5, BL: 72 ± 6.7 cm·s−1, p=0.13). Likewise, there no effect of treatment on %FMD (Pre: 5.4 ± 0.7, Post: 6.2 ± 2.1 %, p=0.46) or FBVmean (Pre: 81.4 ± 6.7, Post: 73.4 ± 8.8 cm·s−1, p=0.27). Lastly, there were no effect of race (WH: 4.0 ± 0.36, BL: 3.9 ± 0.6 %, p=0.85) or treatment (Pre: 3.9 ± 0.56, Post: 4.0 ± 0.39 %, p=0.79) on cerebral vascular function assessed as %CVCi during hypercapnia. Conclusion: The preliminary data suggest that 56 days of increased daily peanut consumption does not induce measurable improvements in indices of vascular function in a cohort of relatively young BL individuals. Future work will continue to assess this effect in a larger cohort of individuals as well as in individuals with existing conditions or diseases (i.e., hypertension, type II diabetes, etc.). Funding: Peanut Institute (982307). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.