Nitric Oxide Availability Research Articles

Increased nitric oxide availability worsens the cardiac performance during early re-perfusion period in adult rats.

Re-perfusion is the standard therapy for acute myocardial infarction, despite the associated pathologies that may contribute to irreversible myocardial injury. The present study aims to clarify the alterations in cardiac activities in response to experimental cardiac ischemic arrest followed by re-perfusion in isolated hearts perfused with nitric oxide (NO) donor, l-arginine, or NO inhibitor, Nω-Nitro-l-arginine methyl ester hydrochloride (l-NAME), to shed light on the possible role of NO in the re-perfusion process. Hearts isolated from adult Wistar rats were studied on Langendorff preparation under basal conditions and during 30min re-perfusion following 30min of total global ischemia. Rats were randomly divided into three groups; control and l-arginine or l-NAME infused heart groups. Cardiac tissue content of malondialdhyde, catalase and nitrite was also measured. Compared to the control group, both l-arginine and l-NAME infused hearts showed increased basal chronotropy and myocardial flow rate. Following ischemia and during the whole period of re-perfusion, the three groups demonstrated significant deterioration in the inotropic activity and compromised myocardial flow rate. l-arginine infused hearts revealed depressed inotropy and chronotropy, weak systolic and diastolic functions with compromised myocardial flow at early 5min of re-perfusion, yet with significantly higher myocardial flow rate by the end of re-perfusion. Reducing NO availability by l-NAME revealed mild impact on the ischemia re-perfusion induced contractile dysfunction, whereas excess NO worsens cardiac performance at the early re-perfusion period.

Relationship between endothelin and nitric oxide pathways in the onset and maintenance of hypertension in children and adolescents

The mechanisms that regulate blood pressure are numerous and complex; one mechanism that plays an important role in this scenario is represented by the balance between the vasoconstrictor effect of endothelin-1 and the vasodilator effect of nitric oxide. While there is agreement on the fact that increased endothelin-1 activity and decreased nitric oxide bioavailability are present in hypertensive adults, the situation is less clear in children and adolescents. Not all studies agree on the finding of an increase in plasma endothelin-1 levels in hypertensive children and adolescents; in addition, the picture is often confused by the concomitant presence of obesity, a condition that stimulates the production of endothelin-1. Furthermore, there is recent evidence that, in younger obese and hypertensive subjects, there is an overproduction of nitric oxide, rather than a reduction. This condition may change over time, causing endothelial dysfunction due to a reduced availability of nitric oxide in hypertensive adolescents. The purpose of this review is to address the main biochemical and pathophysiological aspects of endothelin and nitric oxide involvement in hypertension and to summarize the available scientific evidence on their role in the onset and maintenance of high blood pressure in children and adolescents.

Divergent Dimethylarginine Dimethylaminohydrolase Isoenzyme Expression in the Central Nervous System

The endogenous methylated derivative of ʟ-arginine, Nω,Nω′-dimethyl-ʟ-arginine (asymmetric dimethylarginine, ADMA), an independent risk factor in many diseases, inhibits the activity of nitric oxide synthases and, consequently, modulates the availability of nitric oxide. While most studies on the biological role of ADMA have focused on endothelial and inducible nitric oxide synthases modulation and its contribution to cardiovascular, metabolic, and renal diseases, a role in regulating neuronal nitric oxide synthases and pathologies of the central nervous system is less understood. The two isoforms of dimethylarginine dimethylaminohydrolase (DDAH), DDAH1 and DDAH2, are thought to be the main enzymes responsible for ADMA catabolism. A current impediment is limited knowledge on specific tissue and cellular distribution of DDAH enzymes within the brain. In this study, we provide a detailed characterization of the regional and cellular distribution of DDAH1 and DDAH2 proteins in the adult murine and human brain. Immunohistochemical analysis showed a wide distribution of DDAH1, mapping to multiple cell types, while DDAH2 was detected in a limited number of brain regions and exclusively in neurons. Our results provide key information for the investigation of the pathophysiological roles of the ADMA/DDAH system in neuropsychiatric diseases and pave the way for the development of novel selective therapeutic approaches.

COVID-19: A Redox Disease-What a Stress Pandemic Can Teach Us About Resilience and What We May Learn from the Reactive Species Interactome About Its Treatment.

Significance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), affects every aspect of human life by challenging bodily, socioeconomic, and political systems at unprecedented levels. As vaccines become available, their distribution, safety, and efficacy against emerging variants remain uncertain, and specific treatments are lacking. Recent Advances: Initially affecting the lungs, COVID-19 is a complex multisystems disease that disturbs the whole-body redox balance and can be long-lasting (Long-COVID). Numerous risk factors have been identified, but the reasons for variations in susceptibility to infection, disease severity, and outcome are poorly understood. The reactive species interactome (RSI) was recently introduced as a framework to conceptualize how cells and whole organisms sense, integrate, and accommodate stress. Critical Issues: We here consider COVID-19 as a redox disease, offering a holistic perspective of its effects on the human body, considering the vulnerability of complex interconnected systems with multiorgan/multilevel interdependencies. Host/viral glycan interactions underpin SARS-CoV-2's extraordinary efficiency in gaining cellular access, crossing the epithelial/endothelial barrier to spread along the vascular/lymphatic endothelium, and evading antiviral/antioxidant defences. An inflammation-driven "oxidative storm" alters the redox landscape, eliciting epithelial, endothelial, mitochondrial, metabolic, and immune dysfunction, and coagulopathy. Concomitantly reduced nitric oxide availability renders the sulfur-based redox circuitry vulnerable to oxidation, with eventual catastrophic failure in redox communication/regulation. Host nutrient limitations are crucial determinants of resilience at the individual and population level. Future Directions: While inflicting considerable damage to health and well-being, COVID-19 may provide the ultimate testing ground to improve the diagnosis and treatment of redox-related stress diseases. "Redox phenotyping" of patients to characterize whole-body RSI status as the disease progresses may inform new therapeutic approaches to regain redox balance, reduce mortality in COVID-19 and other redox diseases, and provide opportunities to tackle Long-COVID. Antioxid. Redox Signal. 35, 1226-1268.

Decreased availability of nitric oxide and hydrogen sulfide is a hallmark of COVID-19

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is involved in a global outbreak affecting millions of people who manifest a variety of symptoms. Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 is increasingly associated with cardiovascular complications requiring hospitalizations; however, the mechanisms underlying these complications remain unknown. Nitric oxide (NO) and hydrogen sulfide (H2S) are gasotransmitters that regulate key cardiovascular functions. MethodsBlood samples were obtained from 68 COVID-19 patients and 33 controls and NO and H2S metabolites were assessed. H2S and NO levels were compared between cases and controls in the entire study population and subgroups based on race. The availability of gasotransmitters was examined based on severity and outcome of COVID-19 infection. The performance of H2S and NO levels in predicting COVID-19 infection was also analyzed. Multivariable regression analysis was performed to identify the effects of traditional determinants of gasotransmitters on NO and H2S levels in the patients with COVID-19 infection. ResultsSignificantly reduced NO and H2S levels were observed in both Caucasian and African American COVID-19 patients compared to healthy controls. COVID-19 patients who died had significantly higher NO and H2S levels compared to COVID-19 patients who survived. Receiver-operating characteristic analysis of NO and H2S metabolites in the study population showed free sulfide levels to be highly predictive of COVID-19 infection based on reduced availability. Traditional determinants of gasotransmitters, namely age, race, sex, diabetes, and hypertension had no effect on NO and H2S levels in COVID-19 patients. ConclusionThese observations provide the first insight into the role of NO and H2S in COVID-19 infection, where their low availability may be a result of reduced synthesis secondary to endotheliitis, or increased consumption from scavenging of reactive oxygen species.

The Effects of L-Citrulline on Blood-Lactate Removal Kinetics Following Maximal-Effort Exercise

The accumulation of lactate in muscle and blood during high-intensity exercise is negatively correlated with the duration exercise can be sustained. Removal of lactate is a key component of acute recovery between consecutive bouts of such exercise. Low-intensity exercise enhances recovery by accelerating lactate turnover in metabolically active tissues, largely mediated by blood flow to these tissues. Therefore, the purpose of this research was to clarify if L-citrulline, a nutritional supplement purported to promote vasodilation via enhanced nitric oxide availability, would augment the removal of blood lactate during active recovery (AR). L-citrulline ingestion will augment the rate of blood lactate concentration decrease during AR, reduce the oxygen-cost of submaximal exercise, and increase time-to-exhaustion and peak oxygen uptake (V̇O2peak) during a test of maximal aerobic power. Healthy university students (five males & five females) participated in this double-blind, randomized, placebo-controlled study. Participants exercised on a cycle ergometer at submaximal steady-state intensities followed by progressively increasing intensity to exhaustion, 10 min of AR, and then supramaximal intensity exercise to exhaustion. Oxygen uptake was measured throughout the trial and blood lactate was sampled repeatedly during AR. The protocol elicited very high peak blood lactate concentrations after exercise (11.3 + 1.3 mmol/L). L-citrulline supplementation did not significantly alter blood lactate kinetics during AR, the oxygen cost of exercise, V̇O2peak, or time-to-exhaustion. Despite a strong theoretical basis by which L-citrulline could augment lactate removal from the blood, L-citrulline supplementation showed no effect as an exercise-recovery supplement.

Chocolate enriched by extra virgin olive oil improves endothelial function and oxidative stress in patients with diabetes

ObjectiveEndothelial dysfunction and oxidative stress are among the most relevant mechanisms underlying the atherosclerotic process in patients with type 2 diabetes mellitus (T2 DM). Extra virgin olive oil (EVOO) reduces postprandial glycemia with a mechanism counteracting oxidative stress–mediated incretin down-regulation in healthy subjects and in patients with impaired fasting glucose. The aim of this study was to evaluate if the intake of chocolate enriched by EVOO had positive effects on endothelial function and oxidative stress in patients with T2 DM. MethodsIn this study we enrolled and randomly assigned 25 consecutive patients with T2 DM to receive 40 g of EVOO-enriched chocolate or 40 g of control chocolate spread. Participants were assessed at baseline and 2 h after chocolate intake. Endothelial function was assessed by arterial brachial flow-mediated dilation (FMD); oxidative stress was evaluated by the measurement of serum nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (Nox2) levels, nitric oxide availability, and serum hydrogen peroxide breakdown activity (HBA). ResultsWe observed a significant increase of FMD, nitric oxide (NO) availability, and HBA in the EVOO-enriched chocolate group (P < 0.001). Conversely, soluble Nox2-derived peptide (sNox2-dp) levels significantly decreased (P < 0.001). No significant change was observed in the control chocolate group. To assess the relation of EVOO-enriched chocolate to endothelial function and oxidative stress, a general linear model (GLM) analysis was performed; a significant difference for treatments was found with respect to FMD, NO availability, HBA, and sNox-dp. ConclusionsAdministration of 40 g of EVOO-enriched chocolate is associated with increased endothelial function and reduction of oxidative stress in patients with T2 DM. Future studies are needed to analyze the effect of chronic assumption of EVOO-enriched chocolate on vascular function, oxidative stress, and cardiovascular complications in patients with T2 DM.

LOW DOSE-EPLERENONE TREATMENT DECREASES AORTIC STIFFNESS IN PATIENTS WITH METABOLIC SYNDROME

Objective: Metabolic syndorme is a well-established cardiovascular risk factor with increasing prevalence and incidence globally. Our aim in this study was to analyse the effect of a low dose steroidal mineralocorticoid receptor antagonist on metabolic parameters, aortic stiffness parameters and endothelial function (as assessed by measuring baseline nitric oxide activity) of the macrovasculature in patients with metabolic syndrome. Design and method: Patients with mild uncomplicated primary arterial hypertension and at least 2 of the following traits of the metabolic syndrome (Adult Treatment Panel III criteria: abdominal obesity (abdominal girth &gt; 102 cm in males), triglyceride level &gt; 150 mg/dL or treatment for elevated triglycerides, HDL &lt; 40 mg/dL or treatment for low HDL, fasting blood glucose &gt; 100 mg/dL and &lt; 126 mg/dl) were included in the study. After the wash-out of antihypertensive medication (if applicable), patients were treated with eplerenone (EPL) 25 mg for the next 10 weeks. Pulse wave analysis was performed before and after infusion of L-NMMA (=nitric oxide-synthase inhibitor) at baseline and after treatment with EPL. Results: In patients with metabolic syndrome (n = 23), HbA1c (5.8 ± 0.3 vs. 6.0 ± 0.3 %; p = 0.012) and HDL (41.5 ± 8.1 vs. 44.1 ± 10 mg/dl; p = 0.046) increased significantly with EPL treatment. Central systolic pressure (132 ± 11.6 vs. 124.8 ± 12.9 mmHg; p = 0.015), augmentation pressure (15.2 ± 26.9 vs. 11.9 ± 23.1 mmHg; p = 0.011), augmentation index (22.5 ± 7.8 vs. 18 ± 11.1 %; p = 0.028, independent of systolic office blood pressure (BP) reduction), and augmentation index normalized to heart rate of 75/min (18.6 ± 7.8 vs. 14.5 ± 8.8 %; p = 0.006, independent of systolic office BP reduction) reduced significantly with EPL treatment. Augmentation index normalized to heart rate of 75/min increased significantly with infusion of L-NMMA after treatment with EPL (14.7 ± 8.8 vs. 17.6 ± 8.3 %; p = 0.004), whereas no such difference could be noticed at baseline (p = 0.230) thereby indicating an increased nitric oxide availability. Conclusions: Our data show that EPL beneficially affects markers of arterial stiffness in patients with metabolic syndrome, independent of systolic office BP reduction. Whether the observed benefits could be noticed with nonsteroidal mineralocorticoid receptor antagonists without change in metabolic parameters warrants further investigation.

Association Between 17β-Estradiol Receptors and Nitric Oxide Signaling Augments High-Altitude Adaptation of Ladakhi Highlanders.

Pooja, Vandana Sharma, Manish Sharma, Rajeev Varshney, Bhuvnesh Kumar, and Niroj Kumar Sethy. Association between 17β-estradiol receptors and nitric oxide signaling augments high-altitude adaptation of Ladakhi highlanders. High Alt Med Biol. 22: 174-183, 2021. Background: Genomic studies have identified positive natural selection of plasma membrane estrogen receptor signaling pathway for Himalayan highlanders. We sought to investigate significance of this pathway for high-altitude adaptation by studying Ladakhi highlanders. Materials and Methods: We recruited 25 healthy Ladakhi males (age range: 19-37, height: 164 ± 6 cm, and weight 59 ± 4 kg) at Leh (altitude 3,520 m) and age matched sea level volunteers at Delhi (altitude 215 m), India. We evaluated circulatory levels of 17β-estradiol (E2) and testosterone (T) and levels of E2 biosynthesis pathway proteins. In addition, we analyzed mRNA levels of E2 pathway genes and their association with nitric oxide (NO) availability. Results: We observed higher circulatory E2 and lower testosterone (T) in Ladakhi highlanders compared to lowlanders. Studying E2 pathway genes, we identified higher transcript levels of E2 receptors ESR1 (2.02-fold) and ESR2 (3.87-fold) in Ladakhi highlanders. Higher NOS3 mRNA, plasma level of endothelial NO synthase (eNOS), p-eNOS Ser1177, NOx (nitrate and nitrite), and cGMP were observed for Ladakhi highlanders. In addition, we observed a positive correlation between E2 with plasma NOx (r = 0.52, p = 0.002) and cGMP (r = 0.72, p = 0.007) for Ladakhi highlanders. Conclusion: Our results demonstrate higher circulatory E2 and lower T levels in Ladakhi highlanders. Higher levels of E2 and its receptors (ESR1 and ESR2) are positively associated with observed higher levels of eNOS signaling pathway metabolites. These results highlight the functional importance of E2 and its receptors for Himalayan pattern of high-altitude adaptation.

Emerging Risk Markers; Nitric Oxide and Oxidized Low-Density Lipoprotein in Predicting Coronary Heart Disease in Young subjects

NO is a free radical gas, identified as Endothelial Derived Releasing Factor (EDRF) and synthesized from L-arginine which plays a dynamic role in defence against onset and development of coronary heart disease. Decreased availability of nitric oxide is one of the important cause for the pathogenesis of atherosclerosis. An accumulation of Low Density Lipoprotein cholesterol (LDL) in the intimal wall is the early step in atherosclerosis. Reduced NO level in the endothelium makes it vulnerable and increase the passage of leukocyte and undergo LDL oxidation in the sub endothelial space which ultimately lead to coronary heart disease. The aim of the study is to assess role of Nitric Oxide and oxidized LDL in CHD subjects. This cross-sectional study was conducted in SRM Medical college Hospital and Research centre on subjects attending the Department of Cardiology and Medicine OP. The study was conducted on 194 subjects in age group &lt;40 years and were age and sex matched. After overnight fasting blood samples were collected for analysis for Lipid Profile and Nitric oxide and ox-LDL. Nitric Oxide and ox-LDL measured by ELISA method. Statistical analysis was done using Student‘t’ test and Pearson correlation analysis for the comparison between two groups. The mean level of Nitric Oxide were decreased (12.97± 1.20) significantly in CHD group compared to controls (19.08±4.74) (p &lt;0.001). And Oxidized LDL showed significant increase (41.53± 8.72) in CHD group when compared to controls (16.73± 3.55) (p &lt;0.001). Reduction in the levels of NO in the arterial wall impairs endothelial function. The study concludes that there is a strong association between NO and ox-LDL in progression of CHD. Interestingly, these analyses can help as diagnostic and monitoring markers in young CHD patients.

Protective Effects of Curcumin on Pulmonary Arterial Hypertension.

Pulmonary hypertension is one of the most common diseases among older people. This disease is usually associated with complications such as vascular changes, vascular remodeling, vasoconstriction, endothelial dysfunction, right ventricular failure, and reduction in nitric oxide availability. Many chemical drugs have been used to treat pulmonary hypertension, but result in limited efficacy and several side effects, and these medications are not always available worldwide. Various studies in traditional medicine have shown that changes in lifestyle and nutritional habits can be extremely effective in both the prevention and treatment of various diseases. One treatment method related to changing nutritional habits is the use of curcumin as a nutritional supplement. Curcumin plays an important role in treating pulmonary hypertension and positively alters the aforementioned complications.

Relation of asymmetric dimethylarginine with pulmonary morbidities in neonatal respiratory distress syndrome.

Asymmetric Dimethyl Arginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS) is important in different diseases characterized by decreased nitric oxide (NO) availability. We aimed to assess the serum ADMA level in preterm infants suffering from respiratory distress syndrome (RDS) and its relationship with pulmonary outcomes. This prospective study included 50 preterm neonates suffering from RDS aging≤32 weeks and weighing≤1500 gm. Serum ADMA levels were estimated in the 1st and 28th day of life by ELISA, and its correlation with surfactant requirement, duration of ventilation, and development of BPD was assessed. Fifty preterm infants with RDS were included, 30 infants were treated with surfactant within 12 hours after birth, the 1stday ADMA level was higher significantly in infants who required surfactant treatment than infants without surfactant treatment, At 36 weeks postmenstrual age, 16 infants were diagnosed with BPD, the 28th day ADMA level was significantly higher in infants with BPD than others without BPD. 1st-day ADMA level was significantly correlated with days on mechanical ventilation but there were no significant correlations between 1st day ADMA and days on CPAP and days on supplemental O2. Elevated serum ADMA level in preterm neonates with RDS estimated in the 1st and 28th day of life is a good predictor for pulmonary morbidities such as surfactant requirement, duration of mechanical ventilation, and development of BPD.

Sildenafil Slows Gastric Emptying in Patients with Previously Diagnosed Diabetic Gastroparesis

Objective: Delayed gastric emptying is a common complication of diabetes. Animal studies suggest that inhibition of phosphodiesterase type- 5 receptors with sildenafil improves pyloric nitric oxide availability and reverses gastroparesis in murine models of diabetic gastroparesis. We hypothesized that a single dose of sildenafil would improve gastric emptying in diabetic subjects with gastroparesis.

Obesity-Related Endothelial Dysfunction: moving from classical to emerging mechanisms

Human obesity is associated with vascular endothelial dysfunction, caused by a reduced nitric oxide availability secondary to an enhanced oxidative stress production. Pro-inflammatory cytokine generation, secreted by perivascular adipose tissue, is a major mechanism whereby obesity is associated with a reduced vascular NO availability. Vasculature also represents a source of low-grade inflammation and oxidative stress which contribute to endothelial dysfunction in obese patients. Recently, a direct influence of ghrelin and arginase on endothelial function by interfering with nitric oxide availability was demonstrated in small vessels from patients with obesity.

Effect of sildenafil on right ventricular performance in an experimental large-animal model of postcapillary pulmonary hypertension

Right ventricle (RV) dysfunction is a main determinant of morbidity and mortality in postcapillary pulmonary hypertension (PH). However, currently there are not available therapies. Since reduced nitric oxide (NO) availability and cyclic guanylate monophosphate (cGMP) levels are central in this disease, therapies targeting the NO pathway might have a beneficial effect on RV performance. In this regard, sildenafil has shown contradictory results. Our objective was to evaluate the effect of sildenafil on RV performance in an experimental pig model of postcapillary PH induced by a fixed banding of the venous pulmonary confluent. Animals were evaluated by right heart catheterization and cardiac magnetic resonance before randomization and after 8 weeks on sildenafil (n = 8) or placebo (n = 8), and myocardial tissues were analyzed with histology and molecular biology. At the end of the study, animals receiving sildenafil showed better RV performance as compared with those on placebo (improvement in RV ejection fraction of 7.3% ± 5.8% versus -0.6% ± 5.0%, P= 0.021) associated with less apoptotic cells and gene expression related with reduced oxidative stress and increased anti-inflammatory activity in the myocardium. No differences were observed in pulmonary hemodynamics. In conclusion, in a translational large animal model of chronic postcapillary PH, sildenafil improved RV systolic function independently of afterload. Further research with pharmacological approaches able to manipulate the NO-cGMP axis are needed to confirm this potential cardioprotective effect.

Intricacies of the endothelin system in human obesity: role in the development of complications and potential as a therapeutic target.

Activation of the vascular endothelin-1 (ET-1) system is a key abnormality in vascular dysfunction of human obesity, especially in patients developing complications, such as the metabolic syndrome, diabetes, and atherosclerosis. Vascular insulin resistance, an increased insulin-stimulated endothelial production of ET-1 combined with impaired nitric oxide availability, is the hallmark of obesity-related vasculopathy, but dysregulated adipokine release from obese adipose tissue may contribute to the predominance of ET-1-dependent vasoconstriction. ET-1, in turn, might determine unhealthy obese adipose tissue expansion, with visceral and perivascular adipose tissue changes driving the release of inflammatory cytokines and atherogenic chemokines. In addition, ET-1 might also play a role in the development of the metabolic complications of obesity. Studies have shown inhibition of lipoprotein lipase activity by ET-1, with consequent hypertriglyceridemia. Also, ET-1 in pancreatic islets seems to contribute to beta cell dysfunction, hence affecting insulin production and development of diabetes. Moreover, ET-1 may play a role in nonalcoholic steatohepatitis. Recent clinical trials using innovative design have demonstrated that antagonism of ET-type A receptors protects against some complications of obesity and diabetes, such as nephropathy. These findings encourage further investigation to evaluate whether targeting the ET-1 system could afford better protection against other consequences of the obesity epidemic.

Dose and time-dependent toxicological impact of pantoprazole on vascular endothelium and renal tissue

Proton pump inhibitors (PPIs) have wide pleiotropic action in addition to their therapeutic potential in gastroesophageal reflux diseases. Conversely, recent reports revealed a significant incidence of toxic events of PPIs including nephritis, osteoporosis, and cardiac damage. Thus, the study was designed to reconcile the deceptive contraindications. The present investigation targeted to reveal the toxic impact of sub-acute and sub-chronic administration of pantoprazole (PPZ) with different concentrations (low dose 4 mg/kg, medium-dose 8 mg/kg and high dose 16 mg/kg once a day) on normal vascular endothelium and renal tissue of rats. Vascular endothelial dysfunction (VED) was estimated by the contractility of an isolated aortic ring, nitrite/nitrate concentration, oxidative stress, and integrity of the endothelium layer. Moreover, the renal abnormalities were further confirmed by an increased level of serum creatinine, blood urea nitrogen (BUN), the incidence of microproteinuria, and structural alteration. Sub-acute administration of PPZ treatment did not produce any toxicological impact on endothelium and renal tissue. Whereas, sub-chronic administration of PPZ treatment causes moderate VED and renal dysfunction in a dose-dependent manner. Sub-chronic treatment of PPZ also influences the mitigation of NO and elevation of oxidative stress. Collecting all the evidence, it concludes that decreased nitric oxide availability and increased levels of oxidative stress may be a possible underlying mechanism of causing VED and renal abnormalities from high-dose PPZ treatment.

The Complex Relationship Between Serum Uric Acid, Endothelial Function and Small Vessel Remodeling in Humans.

Aims: The relationship between serum uric acid (SUA) and microvascular remodeling in humans remains largely unexplored. We assessed whether SUA provides additional information on the severity of microvascular remodeling than that obtained from the European Heart Score (HS), the patterns of microvascular remodeling associated with changes in SUA levels and the mediation by endothelial function and nitric oxide (NO) availability on this relationship. Methods: A total of 162 patients included in the microvascular dataset of the Italian Society of Hypertension with available information on SUA, media-to-lumen (M/L) ratio, media cross-sectional area (MCSA), endothelial function, NO availability and HS were included in the analysis. The top tertile of M/L ratio and MCSA were used to define severe microvascular remodeling. Results: A U-shaped association was observed between SUA and both M/L ratio and MCSA. Adjustment for HS did not affect these associations. SUA was able to reclassify a significant number of subjects without, and with, severe M/L ratio and MCSA remodeling over the HS alone. The microvascular remodeling associated with SUA levels presented a predominant hypertrophic pattern. SUA was inversely associated with endothelial function and NO availability. Structural equation modeling analysis controlling for the HS suggested that the association of SUA with M/L ratio and MCSA was mediated through changes in endothelial function and NO availability. Conclusions: The addition of SUA to the HS improves the identification of subjects with greater microvascular remodeling. The relationship between SUA and microvascular remodeling is mediated by endothelial function and NO availability.

Oxidative Stress and Thrombosis during Aging: The Roles of Oxidative Stress in RBCs in Venous Thrombosis.

Mid-life stage adults are at higher risk of developing venous thrombosis (VT)/thromboembolism (VT/E). Aging is characterized by an overproduction of reactive oxygen species (ROS), which could evoke a series of physiological changes involved in thrombosis. Here, we focus on the critical role of ROS within the red blood cell (RBC) in initiating venous thrombosis during aging. Growing evidence has shifted our interest in the role of unjustifiably unvalued RBCs in blood coagulation. RBCs can be a major source of oxidative stress during aging, since RBC redox homeostasis is generally compromised due to the discrepancy between prooxidants and antioxidants. As a result, ROS accumulate within the RBC due to the constant endogenous hemoglobin (Hb) autoxidation and NADPH oxidase activation, and the uptake of extracellular ROS released by other cells in the circulation. The elevated RBC ROS level affects the RBC membrane structure and function, causing loss of membrane integrity, and decreased deformability. These changes impair RBC function in hemostasis and thrombosis, favoring a hypercoagulable state through enhanced RBC aggregation, RBC binding to endothelial cells affecting nitric oxide availability, RBC-induced platelet activation consequently modulating their activity, RBC interaction with and activation of coagulation factors, increased RBC phosphatidylserine exposure and release of microvesicles, accelerated aging and hemolysis. Thus, RBC oxidative stress during aging typifies an ultimate mechanism in system failure, which can affect major processes involved in the development of venous thrombosis in a variety of ways. The reevaluated concept of the critical role of RBC ROS in the activation of thrombotic events during aging will help identify potential targets for novel strategies to prevent/reduce the risk for VT/E or VT/E recurrences in mid-life stage adults.

P0089KEAP1/NRF2 PATHWAY REGULATES GFR BY INCREASING THE GLOMERULAR EFFECTIVE AREA WITHOUT AFFECTING THE AFFERENT/EFFERENT ARTERIOLE RATIO

Abstract Background and Aims The Keap1/Nrf2 pathway regulates the expression of a series of cytoprotective, anti-inflammatory and antioxidant genes. The Nrf2 activator, bardoxolone methyl (BARD), has consistently increased estimated GFR (eGFR) in clinical studies in patients with chronic kidney disease. BARD demonstrated improvement of renal function assessed by inulin clearance, the clinical gold standard for measuring GFR, in diabetic kidney disease patients. These findings suggest the Keap1/Nrf2 system is deeply involved in the regulatory mechanisms of GFR. However, the precise mechanisms are not fully elucidated. We pharmacologically and genetically investigated the mechanisms of GFR regulation by Keap1/Nrf2 system using in vivo multiphoton microscope (MPM) imaging techniques. Method C57BL/6 (Cont), Nrf2 knockout (Nrf2-KO), and Nrf2-activated Keap1-knockdown mice (Keap1-KD) were used. The mice were treated the synthetic triterpenoid RTA dh404 (10 mg/kg/day by gavage) which is a Nrf2 activator for rodents, for a week. We successfully developed the technique to evaluate single-nephron GFR (SNGFR) using MPM (Circulation 2019). The glomerular hemodynamics, diameter of the afferent/efferent arterioles and glomerular permeability were also evaluated. The calcium influx into cells in response to ATP and angiotensin II stimulation and the effect on [Ca2+]i by RTAdh404 were evaluated using Fluo 4 and Fura red in cultured mesangial cells and podocytes. Production of reactive oxygen species and nitric oxide (NO) availability were assessed by fluorescent method using CellROX® Deep Red and diaminofluorescein-FM diacetate (DAF-FM DA) upon the exposure to these stimuli. Results SNGFR in Keap1-KD mice was significantly higher than in the control (9.13±0.55 vs 4.40±0.39 nl/min, Figure 1). RTA dh404 increased SNGFR in the control but not in the Nrf2-KO mice (6.00±0.40 vs 4.66±0.35 nl/min, Figure 1). There was no significant change in the ratio of the glomerular afferent/efferent arteriole diameter in all groups. RTA dh404 treatment increased glomerular volume but did not affect the glomerular permeability of albumin and 40kd-dextran. RTA dh404-treatment inhibited calcium influx into cultured podocytes and mesangial cells induced by angiotensin II or ATP, thereby affecting contractile responses. Oxidative stress and NO-bioavailablity were also ameliorated with RTA dh404. Conclusion The Keap1/Nrf2 pathway plays a pivotal role in controlling GFR and presumably underlies the effect of BARD on GFR in patients.