Plasma Nitrite Levels Research Articles

SGLT2 inhibition improves endothelium-independent vasodilatory function in type 2 diabetes: A double-blind, randomized, placebo-controlled crossover trial.

The objective of this study was to examine the effects of empagliflozin on endothelium-dependent and endothelium-independent vasodilatation and systemic hemodynamic parameters and to assess the role of the nitric oxide (NO) system in patients with type 2 diabetes (T2DM). In this double-blind, placebo-controlled cross over trial, patients with T2DM were treated with either empagliflozin 10 mg or matching placebo for 4 weeks. Following a 2-week washout, participants were crossed over to 4 weeks of the opposite treatment. Forearm blood flow (FBF) was measured after each treatment period using venous occlusion plethysmography. Acetylcholine and sodium nitroprusside (SNP) were infused into the brachial artery to assess endothelium-dependent and endothelium-independent vasodilatory function, respectively. Total peripheral resistance, 24-h blood pressure (BP) and biochemical markers of NO activity were measured as well. Sixteen participants completed the trial. The mean age was 68 ± 8 years, and 69% were male. The SNP response increased by 21% (geometric mean ratio 1.21, 95% CI: 1.09; 1.33) during treatment with empagliflozin compared to placebo (p ≤ 0.001), but not during acetylcholine infusion (p = 0.290). Empagliflozin decreased 24-h systolic BP by 5 mmHg (95% CI: -9; -1 mmHg) (p = 0.015), diastolic BP by 2 mmHg (95% CI: -5; 0 mmHg) (p = 0.029) and systemic vascular resistance by 48 dyn×s/m5 (95% CI: -94; -1 dyn×s/m5) (p = 0.044). Furthermore, empagliflozin reduced plasma levels of nitrite and urinary levels of NOx. Empagliflozin improves endothelium-independent vasodilation, reduces vascular resistance and lowers 24-h BP in patients with T2DM, whereas no change in endothelial-dependent vasodilation was observed. EU Clinical Trials Register number: 2019-004303-12 (https://www.clinicaltrialsregister.eu/ctr-search/trial/2019-004303-12/DK).

Antidepressant Potential of Hispidulin Present in S. barbata D. Don: Mechanistic Insights through Neurochemical and Behavioral Assessments.

This study aims to investigate the antidepressant properties of Hispidulin, a flavonoid present in Scutellaria barbata D. Don. The selection of Hispidulin stems from its notable inhibitory activity against Xanthine Oxidase (XO), a parameter in the pathophysiology of depression. Mice were subjected to a rigorous evaluation using a murine model of Chronic Unpredictable Mild Stress (CUMS) to induce depression for 21 days and antidepressant properties were rigorously assessed using the Tail Suspension Test (TST), Forced Swim Test (FST), and Open Field Test (OFT). Imipramine and fluoxetine were used as standard drugs. Additionally, neurochemical analyses were conducted to quantify serotonin (5-HT), norepinephrine (NE), and dopamine (DA) levels in the cortex, hippocampus, and hypothalamus. Further mechanistic insights were sought through the estimation of monoamine oxidase (MAO) activity and assessment of antioxidant enzyme levels in the brain. Plasma nitrite and corticosterone levels were also measured to delineate the underlying mechanism of action. Hispidulin demonstrated significant antidepressant effects, as evidenced by reduced immobility time in TST and FST and increased exploratory behavior in OFT. Neurochemical analysis revealed restoration of 5-HT, NE, and DA levels in key brain regions. Furthermore, Hispidulin modulated MAO activity and enhanced antioxidant enzyme levels in the brain. Plasma nitrite levels were elevated, indicating enhanced nitric oxide synthesis, while corticosterone levels were reduced. Our findings indicate that Hispidulin exerts potent antidepressant effects, potentially mediated through its influence on monoaminergic neurotransmitters, MAO activity, and antioxidant defenses. These results provide valuable mechanistic insights into the antidepressant action of Hispidulin, supporting its potential therapeutic application in depressive disorders.

Unveiling the Predictive Model for Macrovascular Complications in Type 2 Diabetes Mellitus: microRNAs Expression, Lipid Profile, and Oxidative Stress Markers.

To assay new circulating markers related to macrovascular complications (MVC) in type 2 diabetes mellitus (T2DM), we carried out a descriptive cross-sectional study. We recruited 30 controls (CG), 34 patients with T2DM (DG), and 28 patients with T2DM and vascular complications (DG+C); among them, 22 presented MVC. Peripheral blood was used to determine redox status (superoxide dismutase, SOD; catalase, CAT; glutathione reductase, GRd; glutathione peroxidase, GPx; glucose-6-phosphate dehydrogenase, G6PD) and markers of oxidative damage (advanced oxidation protein products, AOPP; lipid peroxidation, LPO), nitrite levels in plasma (NOx). Inflammatory markers (IL-1β, IL-6, IL-10, IL-18, MCP-1, TNF-α) and the relative expression of c-miRNAs were analyzed. The real-time PCR results showed that the expressions of miR-155-5p, miR-21-5p, miR-146a-3p, and miR-210-3p were significantly higher in the DG group compared to the CG. The DG+C group presented statistically relevant differences with CG for four miRs: the increased expression of miR-484-5p, miR-21-5p, and miR-210-3p, and decreased expression of miR-126a-3p. Moreover, miR-126a-3p was significantly less expressed in DG+C compared to DG. The application of binary logistic regression analysis and construction of receiving operator characteristic curves (ROC) revealed two models with high predictive values for vascular complications presence: (1) HbAc1, creatinine, total cholesterol (TC), LPO, GPx, SOD, miR-126, miR-484 (Exp(B) = 0.926, chi2 = 34.093, p < 0.001; AUC = 0.913). (2) HbAc1, creatinine, TC, IL-6, LPO, miR-126, miR-484 (Exp(B) = 0.958, Chi2 = 33.863, p < 0.001; AUC = 0.938). Moreover, our data demonstrated that gender, TC, GPx, CAT, and miR-484 were associated with MVC and exhibited higher predictive values (Exp(B) = 0.528, p = 0.024, Chi2 = 28.214, AUC = 0.904) than classical variables (Exp(B) 0.462, p = 0.007, Chi2 = 18.814, AUC = 0.850). miR-126, miR-484, IL-6, SOD, CAT, and GPx participate in vascular damage development in the studied diabetic population and should be considered for future studies.

Evaluation of Anti-Depressant Potential of Standardized Hydroethanolic Extract of S. barbata D. Don Using Chronic Unpredictable Mild Stress Model

Background: S. barbata D. Don is a Chinese herb, that belongs to the family Lami-aceae. It has established traditional use in ethnomedicine for treating various ailments, includ-ing mood disorders and sleep disorders, which led to growing interest in exploring its neuro-logical potential, particularly as a potential anti-depressant agent. Aims: This study explores the anti-depressant potential of the HSBE utilizing a Chronic Un-predictable Mild Stress-induced depression model in mice. Additionally, the research aims to elucidate the underlying mechanisms of action. Methods: Swiss albino mice were subjected to a 3-week CUMS paradigm and subsequently administered HSBE at doses of 200 and 400 mg/kg via oral administration. The behavioral alterations were evaluated using the FST, TST, OFT, and SPT. Brain levels of serotonin, dopa-mine, and nor-epinephrine were estimated in different brain regions (cortex, hippocampus, and hypothalamus) to uncover the molecular mechanism. Additionally, assays for monoamine oxi-dase-A, monoamine oxidase-B, and antioxidant enzyme activities were conducted. Plasma ni-trite and corticosterone levels were also measured to get further insight into potential mecha-nisms underlying the anti-depressant effects of HSBE. Results: HSBE significantly ameliorated depressive-like behavior induced by CUMS para-digm, as evidenced by reduced immobility in FST and TST, increased locomotor activity in OFT, and improved sucrose preference in SPT. Neurochemical analysis revealed a significant increase in serotonin, dopamine, and norepinephrine levels in the cortex, hippocampus, and hypothalamus of HSBE-treated mice, implying a potential regulation of monoaminergic neuro-transmitter levels. Moreover, biochemical analyses demonstrated a significant inhibition of both MAO-A and MAO-B activity, contributing to the increase of the brain levels of neuro-transmitters. The administration of HSBE also led to a significant enhancement of antioxidant enzyme activities and reduced brain lipid peroxidation, indicating a pronounced antioxidant effect of HSBE. Furthermore, decreased plasma nitrite and corticosterone levels provided ad-ditional insights into HSBE's potential multi-targeted anti-depressant mechanism. Conclusion: This study indicates that HSBE exhibits robust anti-depressant properties, sup-ported by behavioral, neurochemical, and biochemical alterations. These findings underscore the therapeutic promise of HSBE as a natural intervention for depressive disorders, warranting further clinical exploration.

Exploring the Antidepressant-like Effects of Wogonin: Analysis of Behavioural, Neurochemical, and Biochemical Parameters

Background: Wogonin, a bioactive compound isolated from S. barbata D. Don, has been identified in the literature as a potential inhibitor of monoamine oxidase (MAO), a key enzyme involved in the degradation of neurotransmitters associated with mood regulation. This study aims to investigate the antidepressant-like activity of wogonin in vivo, utilizing a preclinical model. The rationale for selecting wogonin stems from its documented MAO inhibitory properties, suggesting a potential role in modulating neurotransmitter levels implicated in depressive disorder. Method: The study employs a multifaceted approach, incorporating behavioural, neurochemical, and biochemical assessments. The Chronic Unpredictable Mild Stress model is utilized to induce depression-like behavior in rodents for 21 days. Two doses of wogonin (20 and 40 mg/kg per orally) and standard (fluoxetine, 20 mg/kg, and imipramine, 15 mg/kg) were administered to albino mice. Behavioural paradigms, including the Tail Suspension Test, Forced Swim Test, and Open Field Test, are employed to assess the impact of wogonin on depressive-like symptoms on the 21st day. Neurochemical analyses focus on alterations in 5-HT, NE, and DA levels within relevant brain regions, and MAO activity is quantified to ascertain wogonin's potential as an MAO inhibitor on the 22nd day. Biochemical assessments emphasize wogonin's antioxidant properties and its ability to mitigate oxidative stress, a significant factor in depression pathophysiology. Plasma nitrite levels are measured to elucidate wogonin's impact on nitric oxide signalling. Plasma corticosteroid levels are also quantified to delineate wogonin's effect on the hypothalamicpituitary- adrenal (HPA) axis, a central regulator of stress response. Results: Wogonin demonstrates significant antidepressant effects in a dose-dependent manner in the behavioural assessments, showing a marked reduction in depressive-like behaviours across all paradigms. Neurochemical analyses revealed a significant (p ≤ 0.05) restoration of monoamine neurotransmitter levels in the relevant brain regions as compared to CUMS-induced stress group. Additionally, wogonin exhibits a potent (p ≤ 0.05) inhibitory effect on MAO activity. Biochemical assessments demonstrate a significant (p ≤ 0.05) increase in antioxidant capacity and a reduction in oxidative stress markers. Plasma nitrite levels indicate an enhancement of nitric oxide signalling. Corticosteroid levels showed a modulation of the HPA axis, suggesting a regulatory effect on stress response. Conclusion: This comprehensive study establishes wogonin as a promising MAO inhibitor with notable antidepressant potential. The findings provide crucial insights into its mechanisms of action, indicating a multifaceted approach to alleviating depression. Wogonin's demonstrated efficacy across behavioural, neurochemical, and biochemical parameters presents a strong foundation for further research and development of wogonin-based antidepressant interventions.

Gut Microbiota and Cytokine Profile in Cirrhosis.

Gut dysbiosis and abnormal cytokine profiles are common in cirrhosis. This study aimed to evaluate the correlations between them. In the blood plasma of cirrhosis patients and controls, 27 cytokines were examined using a multiplex assay. The plasma levels of nitrites (stable metabolites of the endothelial dysfunction biomarker nitric oxide) and lipopolysaccharide (LPS) were examined. The fecal microbiota was assessed by 16S rRNA gene sequencing. Levels of IL-1b, IL-2, IL-6, IL-13, IP-10, IFN-g, TNF-a, LPS, and nitrites were higher in cirrhosis patients than in controls, while levels of IL-4, IL-7, and PDGF-BB were lower. The LPS level was directly correlated with the levels of IL-1b, IL1-Ra, IL-9, IL-17, PDGF-BB, IL-6, TNF-a, and nitrites. The nitrite level was significantly directly correlated with the levels of TNF-a, GM-CSF, IL-17, and IL-12, and inversely correlated with the IL-7 level. TNF-a levels were directly correlated with ascites severity and the abundance of Negativicutes, Enterobacteriaceae, Veillonellaceae, and Klebsiella, while inversely correlated with the abundance of Firmicutes, Clostridia, and Subdoligranulum. IFN-g levels were directly correlated with the abundance of Bacteroidaceae, Lactobacillaceae, Bacteroides, and Megasphaera, and inversely correlated with the abundance of Verrucomicrobiota, Akkermansiaceae, Coriobacteriaceae, Akkermansia, Collinsella, and Gemella. IL-1b levels were directly correlated with the abundance of Comamonadaceae and Enterobacteriaceae and inversely correlated with the abundance of Marinifilaceae and Dialister. IL-6 levels were directly correlated with the abundance of Enterobacteriaceae, hepatic encephalopathy, and ascites severity, and inversely correlated with the abundance of Peptostreptococcaceae, Streptococcaceae, and Streptococcus. The abundance of harmful gut microbiota taxa and endotoxinemia directly correlates with the levels of proinflammatory cytokines.

Perioperative Changes in Plasma Nitrite and IL-6 Levels Predict Postoperative Atrial Fibrillation (POAF) and Acute Kidney Injury (AKI) after Cardiac Surgery.

Background: Postoperative atrial fibrillation (POAF) and acute kidney injury (AKI) are common yet significant complications after cardiac surgery, with incidences of up to 40% for each. Here, we assessed plasma nitrite and serum interleukin-6 (IL-6) levels before and after cardiac surgery to quantify the extent to which oxidative stress and inflammation contribute to POAF and AKI occurrence. Methods: We prospectively enrolled 206 cardiac surgical patients. Plasma nitrite and serum IL-6 levels were determined preoperatively and at 24 h, 48 h and 72 h postoperatively. The patients had continuous EKG monitoring for occurrence of POAF, while daily serum creatinine was measured for determination of stage 1 + AKI. Results: Postoperatively, 78 (38%) patients experienced AF, and 47 (23%) patients experienced stage 1 + AKI. POAF analysis: Age, ACE-inhibitor use, valve surgery and percent change in baseline plasma nitrite at 24 h postoperatively were associated with POAF in multiple logistic regression analysis. The inclusion of this new biomarker significantly improved the POAF prediction model (AUC 0.77 for clinical risk factors alone, to AUC 0.81). AKI analysis: A history of diabetes mellitus was associated with AKI in multiple logistic regression analysis, and the addition of preoperative IL-6 levels improved the prediction model for AKI occurrence (AUC 0.69 to AUC 0.74). Conclusions: We previously observed selective upregulation of NADPH oxidase isoform 4 (NOX4) in patients with AF, a critical causal role of NOX4 for AF in zebrafish and a robust inhibitory effect of nitric oxide (NO) on NOX4. Our data innovatively demonstrate that a reduction in circulating nitrite levels, likely implicative of elevated NOX4-mediated oxidative stress, independently associates with POAF and improves POAF prediction, whereas the inclusion of circulating IL-6 levels improves the prediction model for AKI. Therefore, therapeutic strategies to mitigate these pathophysiological sequalae of surgical stress may reduce the incidence of severe postoperative complications of POAF and AKI.

Mild hyperbaric oxygen exposure protects heart during ischemia/reperfusion and affects vascular relaxation.

Mild hyperbaric oxygen therapy (mHBOT) is an adjuvant therapy used in conditions where tissue oxygenation is reduced and is implemented using pressures less than 1.5 ATA and 100% O2 (instead of the classical HBOT at 1.9-3 ATA) which results in cheaper, easier to implement, and equally effective. mHBOT is offered for wellness and beauty and as an anti-aging strategy, in spite of the absence of studies on the cardiovascular system. Consequently, we investigated the impact of mHBOT on the cardiovascular system. Mechanical and energetic parameters of isolated heart submitted to ischemia/reperfusion injury and arterial contractile response from mHBOT-exposed rats were evaluated. In the heart, mHBOT increased pre-ischemic velocity of contraction and ischemic end-diastolic pressure and developed pressure and contractile economy during reperfusion. mHBOT decreased infarct size and increased the plasma nitrite levels. In the artery, mHBOT increased acetylcholine sensitivity. mHBOT protects the heart during ischemia/reperfusion and affects vascular relaxation.

Arginine ingestion inhibits phagocyte invasion in eccentrically contracted rat fast-twitch muscle

Eccentric contraction (ECC) has been shown to induce leukocyte invasion into skeletal muscle, resulting in muscle inflammation. This study aimed to investigate whether prior ingestion of L-arginine (ARG), a nitric oxide precursor, inhibits ECC-induced macrophage invasion. Male Wistar rats received ARG in water for 7 days, beginning 3 days prior to ECC. ECCs were induced in the anterior crural muscles for 200 cycles. Three days later, the tibialis anterior and extensor digitorum longus muscles were excised for biochemical analysis and force measurement, respectively. ARG ingestion increased nitrite and nitrate levels in plasma and muscle, inhibiting force depression and reducing CD68 content in muscles subjected to ECC. ARG ingestion also ameliorated an ECC-induced increase in protein nitration, although neither ARG ingestion nor ECC induction affected protein carbonyl levels. The present results suggest that ingestion of ARG or ARG-rich foods may alleviate inflammation by attenuating phagocyte invasion in eccentrically contracted skeletal muscles.

Neutrophil and Plasma Nitrite Levels and Neuronal Nitric Oxide Synthase Expression in Schizophrenia: A Case-Control Study

Background: In neural tissues, neuronal nitric oxide synthase (nNOS) primarily leads to nitric oxide (NO) synthesis which acts as a neurotransmitter. NO is also an oxidant produced during oxidative stress states and has been implicated in the etiopathogenesis of schizophrenia. Thus, it can be a potential biomarker of schizophrenia.Aims: In this study, we aimed to determine the differences in the levels of nNOS (in circulating neutrophil) and nitrite (in circulating neutrophil and plasma) in the drug naïve or drug-free patients of first-episode schizophrenia, their first-degree relatives (FDR) and healthy controls (HC).Methods: Drug-free adults with schizophrenia, and age and sex-matched FDRs, and HCs were tested for nNOS expression (in circulating neutrophil) and nitrite levels (in circulating neutrophil and plasma). Kruskal Wallis H test was used to compare continuous variables.Results: The final sample consisted of 31 participants in each group. The nNOS expression was significantly higher in schizophrenia patients compared to FDRs and HCs. In patients the plasma and neutrophil nitrite levels were significantly lower compared to HCs, but not FDRs. The nNOS expression among FDRs was also significantly higher compared to HCs. There was no correlation among nNOS expression, plasma nitrite level, and neutrophil nitrite level.Conclusions: Plasma and neutrophil nitrite could be potential trait markers for schizophrenia. There is no straightforward association between nNOS expression, and nitrite levels in plasma and circulating neutrophils.

The Cardioprotective Role of Nitrate-Rich Vegetables.

Nitric oxide (NO) is an inorganic radical produced by both the non-enzymatic nitrate (NO3-)-nitrite (NO2-)-NO pathway and enzymatic reactions catalyzed by nitric oxide synthase (NOS). Also, as nitrate and nitrite from dietary and other endogenous sources can be reduced back to nitric oxide in vivo, the endogenous NO level can be increased through the consumption of nitrate-rich vegetables. Ingestion of dietary NO3- has beneficial effects which have been attributed to a subsequent increase in NO: a signaling molecule that may regulate various systems, including the cardiovascular system. A diet rich in NO3- from green leafy and root vegetables has cardioprotective effects, with beetroot products being particularly good sources of NO3-. For example, various studies have demonstrated a significant increase in nitrite levels (regarded as markers of NO) in plasma after the intake of beetroot juice. The present review describes the current literature concerning the role of nitrate-rich vegetables (especially beetroot products) in the prophylaxis and treatment of cardiovascular diseases (CVDs). This review is based on studies identified in electronic databases, including PubMed, ScienceDirect, Web of Knowledge, Sci Finder, Web of Science, and SCOPUS.

Gut Microbiota and Biomarkers of Endothelial Dysfunction in Cirrhosis.

Our aim was to study the association of endothelial dysfunction biomarkers with cirrhosis manifestations, bacterial translocation, and gut microbiota taxa. The fecal microbiome was assessed using 16S rRNA gene sequencing. Plasma levels of nitrite, big endothelin-1, asymmetric dimethylarginine (ADMA), presepsin, and claudin were measured as biomarkers of endothelial dysfunction, bacterial translocation, and intestinal barrier dysfunction. An echocardiography with simultaneous determination of blood pressure and heart rate was performed to evaluate hemodynamic parameters. Presepsin, claudin 3, nitrite, and ADMA levels were higher in cirrhosis patients than in controls. Elevated nitrite levels were associated with high levels of presepsin and claudin 3, the development of hemodynamic circulation, hypoalbuminemia, grade 2-3 ascites, overt hepatic encephalopathy, high mean pulmonary artery pressure, increased abundance of Proteobacteria and Erysipelatoclostridium, and decreased abundance of Oscillospiraceae, Subdoligranulum, Rikenellaceae, Acidaminococcaceae, Christensenellaceae, and Anaerovoracaceae. Elevated ADMA levels were associated with higher Child-Pugh scores, lower serum sodium levels, hypoalbuminemia, grade 2-3 ascites, milder esophageal varices, overt hepatic encephalopathy, lower mean pulmonary artery pressure, and low abundance of Erysipelotrichia and Erysipelatoclostridiaceae. High big endothelin-1 levels were associated with high levels of presepsin and sodium, low levels of fibrinogen and cholesterol, hypocoagulation, increased Bilophila and Coprobacillus abundances, and decreased Alloprevotella abundance.

Nitrate reduction capacity of the oral microbiota is impaired in periodontitis: potential implications for systemic nitric oxide availability

The reduction of nitrate to nitrite by the oral microbiota has been proposed to be important for oral health and results in nitric oxide formation that can improve cardiometabolic conditions. Studies of bacterial composition in subgingival plaque suggest that nitrate-reducing bacteria are associated with periodontal health, but the impact of periodontitis on nitrate-reducing capacity (NRC) and, therefore, nitric oxide availability has not been evaluated. The current study aimed to evaluate how periodontitis affects the NRC of the oral microbiota. First, 16S rRNA sequencing data from five different countries were analyzed, revealing that nitrate-reducing bacteria were significantly lower in subgingival plaque of periodontitis patients compared with healthy individuals (P < 0.05 in all five datasets with n = 20–82 samples per dataset). Secondly, subgingival plaque, saliva, and plasma samples were obtained from 42 periodontitis patients before and after periodontal treatment. The oral NRC was determined in vitro by incubating saliva with 8 mmol/L nitrate (a concentration found in saliva after nitrate-rich vegetable intake) and compared with the NRC of 15 healthy individuals. Salivary NRC was found to be diminished in periodontal patients before treatment (P < 0.05) but recovered to healthy levels 90 days post-treatment. Additionally, the subgingival levels of nitrate-reducing bacteria increased after treatment and correlated negatively with periodontitis-associated bacteria (P < 0.01). No significant effect of periodontal treatment on the baseline saliva and plasma nitrate and nitrite levels was found, indicating that differences in the NRC may only be revealed after nitrate intake. Our results suggest that an impaired NRC in periodontitis could limit dietary nitrate-derived nitric oxide levels, and the effect on systemic health should be explored in future studies.

Plasma eNOS Concentration in Healthy Pregnancy and in Hypertensive Disorders of Pregnancy: Evidence of Reduced Concentrations in Pre-Eclampsia from Two Independent Studies.

Hypertensive disorders of pregnancy (HDP), comprising gestational hypertension (GH) and pre-eclampsia (PE), are leading causes of maternal and perinatal morbidity and mortality. Both GH and PE are characterized by new-onset hypertension, but PE additionally includes proteinuria and/or end-organ damage. Impaired nitric oxide (NO) bioavailability may lead to endothelial dysfunction in GH and PE, and the primary source of vascular NO is endothelial NO synthase (eNOS). However, no previous study has investigated plasma eNOS concentrations in patients with GH and PE. In this study, we compared plasma eNOS concentrations in healthy pregnancies and HDP in two independent cohorts. The primary study included 417 subjects, with 43 non-pregnant (NP) and 156 healthy pregnant (HP) women and 122 patients with GH and 96 with PE. The replication study included 85 pregnant women (41 healthy and 44 pre-eclamptic). Plasma concentrations of eNOS were measured using a commercial ELISA kit provided by R&D Systems, and plasma nitrite concentrations were assessed using two ozone-based chemiluminescence assays. Correlations between plasma eNOS concentrations and plasma nitrite concentrations, as well as clinical and biochemical parameters, were evaluated by either Spearman's or Pearson's tests. In the primary study, NP women and HDP had significantly lower plasma eNOS concentrations compared to HP; concentrations were even lower in PE compared to GH. Plasma eNOS concentrations were reduced but not significant in early-onset PE, PE with severe features, preterm birth, and intrauterine growth restriction. No correlation was observed between plasma eNOS and nitrite levels. In HDP, there was a significant positive correlation between levels of eNOS and hemoglobin (r = 0.1496, p = 0.0336) as well as newborn weight (r = 0.1487, p = 0.0316). Conversely, a negative correlation between eNOS levels and proteinuria was observed (r = -0.2167, p = 0.0179). The replication study confirmed significantly reduced plasma concentrations of eNOS in PE compared to HP. Our findings provide evidence of reduced plasma eNOS concentrations in HDP; they were particularly lower in PE compared to GH and HP in two independent studies.

Ascorbate mediates the non-enzymatic reduction of nitrite to nitric oxide

Nitric oxide (NO•) generated by nitric oxide synthases is involved in many physiological and pathophysiological processes. However, non-enzymatic formation of NO• also occurs in vivo. Here we investigated the production of NO• from nitrite, as facilitated by ascorbate, over the pH range of 2.4–7.4. Using a nitric oxide electrode, we observed at low pH a rapid generation of NO• from nitrite and ascorbate that slows with increasing pH. The formation of NO• was confirmed by its reaction with oxyhemoglobin. In the ascorbate/nitrite system a steady-state level of NO• was achieved, suggesting that a futile redox cycle of nitrite-reduction by ascorbate and NO•-oxidation by dioxygen was established. However, at pH-values of around 7 and greater, the direct reduction of nitrite by ascorbate is very slow; thus, this route to the non-enzymatic production of NO• is not likely to be significant process in vivo in environments having a pH around 7.4. The production of nitric oxide by nitrite and ascorbate would be important only in areas of lower pH, e.g. stomach/digestive system, sites of inflammation, and areas of hypoxia such as tumor tissue. In patients receiving very large doses of ascorbate delivered by intravenous infusion, plasma levels of ascorbate on the order of 20 - 30 mM can be achieved. After infusion, levels of nitrate and nitrite in plasma were unchanged. Thus, in blood and tissue that maintain a pH of about 7.4, the reduction of nitrite to nitric oxide by ascorbate appears to be insignificant, even at very large, pharmacological levels of ascorbate.

Rose Bengal induced formation of thrombosis in rats and an investigation of cardiovascular worries by haematological changes

BackgroundThe present investigation planned to study the cardiovascular worries in Rose Bengal (RB) induced thrombotic rats by analysing biochemical profile of plasma, platelet membrane and cardiac tissue. MethodsMale Wistar rats were categorized into two groups. The group I was Control (C) rats and received glucose, whereas group II was Rose Bengal (50 mg/kg) induced thrombotic rats. The animals sacrificed and biological samples collected were analysed for various biochemical parameters. ResultsIn rats RB induced heart damage/thrombosis showed significantly increased levels of lipid peroxidation (LPO), nitrate and nitrite. In RB administered group the antioxidant activities were lowered significantly i.e., reduced glutathione, glutathione S-transferase, glutathione peroxidase, superoxide dismutase and catalase when compared with control rats. Plasma enzymes SGOT, SGPT were decreased and Na+-K+ ATPase was significantly increased in group II in comparison with group I. There is no significant change in plasma hexokinase enzyme in RB administered rats when compared with control rats. The non-enzymatic and enzymatic antioxidants levels were decreased significantly in experimental groups II to compare with control group I rats. A significant increase in platelet membrane fluidity observed in group II rats when compared with group I rats in DPH and pyrene employed method. A significant raise in LPO of platelet membrane was observed in the experimental rats. Plasma nitrite and nitrate levels were increased in group II when compared to group I. Furthermore, the haematological parameters were also increased in group II when compared to group I rats. ConclusionThis investigation pointed out that the nitric oxide scavenging levels increased and might be protected the oxidative stress and free radicals generated by RB induced cardiac thrombosis in rats.

Protective effects of limb remote ischemic per-conditioning on the heart injury induced by renal ischemic-reperfusion through the interaction of the apelin with the RAS/iNOS pathway.

Remote ischemic conditioning upregulates endogenous protective pathways in response to ischemia-reperfusion injury. This study tested the hypothesis that limb remote ischemic per- conditioning (RIPerC) exerts cardioprotective effects via the renin-angiotensin system (RAS)/inducible nitric oxide synthase (iNOS)/apelin pathway. Renal ischemia-reperfusion injury (I/R) was induced by bilateral occlusion of the renal pedicles for 60 minutes, followed by 24 hours of reperfusion; sham-operated rats served as controls. RIPerC was induced by four cycles (5 minutes) of limb ischemia-reperfusion along with bilateral renal ischemia. The functional disturbance was evaluated by renal (BUN and creatinine) and cardiac (troponin I and lactate dehydrogenase) injury biomarkers. Renal I/R injury increased renal and cardiac injury biomarkers that were reduced in the RIPerC group. Histopathological findings of the kidney and heart were also suggestive of amelioration injury-induced changes in the RIPerC group. Assessment of cardiac electrophysiology revealed that RIPerC ameliorated the decline in P wave duration without significantly affecting other cardiac electrophysiological changes. Further, renal I/R injury increased the plasma (322.40±34.01 IU/L), renal (8.27±1.10 mIU/mg of Protein), and cardiac (68.28±10.28 mIU/mg of protein) angiotensin-converting enzyme (ACE) activities in association with elevations in the plasma and urine nitrite (25.47±2.01 & 16.62±3.05 μmol/L) and nitrate (15.47±1.33 & 5.01±0.96 μmol/L) levels; these changes were reversed by RIPerC. Further, renal ischemia-reperfusion injury significantly (P=0.047) decreased the renal (but not cardiac) apelin mRNA expression, while renal and cardiac ACE2 (P<0.05) and iNOS (P=0.043) mRNA expressions were significantly increased compared to the sham group; these effects were largely reversed by RIPerC. Our results indicated that RIPerC protects the heart against renal ischemia- reperfusion injury, likely via interaction of the apelin with the RAS/iNOS pathway.

The Probiotic Streptococcus salivarius M18 Increases Plasma Nitrite but Does Not Alter Blood Pressure: A Pilot Randomised Controlled Trial

Some species of oral bacteria can reduce dietary nitrate to nitrite, which can later be converted to nitric oxide in the nitrate—nitrite—nitic oxide pathway. Increasing nitric oxide availability can reduce blood pressure (BP) and improve exercise performance. Streptococcus salivarius M18 (Streptococcus salivarius M18) is a bacteriocin-producing probiotic that is known to improve oral health by inhibiting pathogenic oral bacteria. However, it is presently unclear whether probiotic-induced alterations to the oral microbiome will influence circulating levels of nitric oxide metabolites and BP. Purpose: To determine the effects of Streptococcus salivarius M18 supplementation on plasma and salivary nitrate and nitrite levels and BP. Methods: Ten healthy males (age 32 ± 8 y, body mass 88.2 ± 15.1 kg) completed 2 × 14-day supplementation phases in a randomized order at least 14 days apart. In one phase, participants consumed Streptococcus salivarius M18 probiotic lozenges (2.5 billion colony-forming units/dose) once per day, and in the other, they ingested water (placebo). The abundance of bacteria on the tongue was assessed via Illumina 16S rRNA gene sequencing, unstimulated saliva, and venous blood samples were collected, and BP was measured pre and post each phase. Saliva and plasma were analysed for nitrate and nitrite using chemiluminescence, and pH was measured in saliva. The change in each outcome from pre- to post-supplementation was compared between phases using repeated measures ANOVA. Results: Plasma nitrite increased from baseline following probiotic supplementation (from 173 ± 39 to 223 ± 63 nM, p = 0.003, 95% CI 192–250 nM). In comparison, there was no change in the placebo phase or between baselines (all p &gt; 0.05). The abundance of nitrite-producing bacteria was not altered, salivary nitric oxide metabolites and pH did not change, and the increase in plasma nitrite did not result in reductions in BP (all p &gt; 0.05). Conclusions: Supplementation with Streptococcus salivarius M18 increased plasma nitrite, a key marker of NO availability. Despite this, Streptococcus salivarius M18 did not lower BP in these healthy normotensive participants. Additionally, the increase in plasma nitrite was not associated with abundance changes in bacteria thought important to NO generation. Further research is required to determine the mechanism behind the increase in plasma nitrite and the potential therapeutic and ergogenic benefits of Streptococcus salivarius M18 supplementation.

Nitrite decreases sickle hemoglobin polymerization in vitro independently of methemoglobin formation

The root cause of sickle cell disease (SCD) is the polymerization of sickle hemoglobin (HbS) leading to sickling of red blood cells (RBC). Earlier studies showed that in patients with SCD, high-dose nitrite inhibited sickling, an effect originally attributed to HbS oxidation to methemoglobin-S even though the anti-sickling effect did not correlate with methemoglobin-S levels. Here, we examined the effects of nitrite on HbS polymerization and on methemoglobin formation in a SCD mouse model. In vitro, at concentrations higher than physiologic (>1 μM), nitrite increased the delay time for polymerization of deoxygenated HbS independently of methemoglobin-S formation, which only occurred at much higher concentrations (>300 μM). In vitro, higher nitrite concentrations oxidized 100% of normal hemoglobin A (HbA), but only 70% of HbS. Dimethyl adipimidate, an anti-polymerization agent, increased the fraction of HbS oxidized by nitrite to 82%, suggesting that polymerized HbS partially contributed to the oxidation-resistant fraction of HbS. At low concentrations (10 μM-1 mM), nitrite did not increase the formation of reactive oxygen species but at high concentrations (10 mM) it decreased sickle RBC viability. In SCD mice, 4-week administration of nitrite yielded no significant changes in methemoglobin or nitrite levels in plasma and RBC, however, it further increased leukocytosis. Overall, these data suggest that nitrite at supra-physiologic concentrations has anti-polymerization properties in vitro and that leukocytosis is a potential nitrite toxicity in vivo. Therefore, to determine whether the anti-polymerization effect of nitrite observed in vitro underlies the decreases in sickling observed in patients with SCD, administration of higher nitrite doses is required.

#5878 PROTECTIVE EFFECTS OF VITAMIN D ON HYPERANDROGENEMIA-INDUCED-ACUTE KIDNEY INJURY THROUGH THE INTERACTION WITH THE RAS/INOS PATHWAY

Abstract Background and Aims The onset and development of metabolic abnormalities are closely related to polycystic ovary syndrome (PCOS). It has not yet been determined whether PCOS contributes to kidney injury, and the mechanism underlying the condition is not fully understood. Treatment with vitamin D has been shown to have beneficial effects on women with PCOS and renal disease. This study investigated the hypothesis that vitamin D supplementation exerts renoprotective effects via regulating the renin-angiotensin system (RAS)/inducible nitric oxide synthase (iNOS) pathway Method Female Sprague-Dawley rats were randomly divided into five groups (n = 10): (a) control, (b) sham, (c) dehydroepiandrosterone (DHEA, 6 mg/100 g day-1 S.Q.), (d) DHEA + vitamin D (1000 IU/Kg; 3 days/week), and (e) vitamin D. Plasma, ovary, and kidney levels of angiotensin-converting enzyme (ACE) activity was determined using FAPGG-based colorimetric method. The amount of NO was measured by determining the concentrations of nitrite and nitrate end products in the plasma and tissue samples using the Griess method. Histopathological changes in the ovary and kidney were also evaluated. Results Plasma testosterone increased in DHEA-treated rats compared with controls, indicating a hyperandrogenic state. Further, hyperandrogenemia-induced-acute kidney injury increased the plasma, renal, and ovarian angiotensin-converting enzyme (ACE) activities in association with elevations in the plasma and urine nitrite and nitrate levels; these changes were reversed by vitamin D treatment. Conclusion Hyperandrogenemia causes systemic abnormalities through RAS imbalance and NO metabolism disturbances, followed by apparent destruction of renal and ovarian tissues. Vitamin D supplementation attenuated these hyperandrogenemia-associated acute kidney injuries, likely via interaction with the RAS/iNOS pathway.