Endothelial Nitric Oxide Signaling Research Articles

ZFYVE21 promotes endothelial nitric oxide signaling and vascular barrier function in the kidney during aging

ZFYVE21 is an ancient, endosome-associated protein that is highly expressed in endothelial cells (ECs) but whose function(s) invivo are undefined. Here, we identified ZFYVE21 as an essential regulator of vascular barrier function in the aging kidney. ZFYVE21 levels significantly decline in ECs in aged human and mouse kidneys. To investigate attendant effects, we generated EC-specific Zfyve21-/- reporter mice. These knockout mice developed accelerated aging phenotypes including reduced endothelial nitric oxide (ENOS) activity, failure to thrive, and kidney insufficiency. Kidneys from Zfyve21 EC-/- mice showed interstitial edema and glomerular EC injury. ZFYVE21-mediated phenotypes were not programmed developmentally as loss of ZFYVE21 in ECs during adulthood phenocopied its loss prenatally, and a nitric oxide donor normalized kidney function in adult hosts. Using live cell imaging and human kidney organ cultures, we found that in a GTPase Rab5- and protein kinase Akt-dependent manner, ZFYVE21 reduced vesicular levels of inhibitory caveolin-1 and promoted transfer of Golgi-derived ENOS to a perinuclear Rab5+ vesicular population to functionally sustain ENOS activity. Thus, our work defines a ZFYVE21- mediated trafficking mechanism sustaining ENOS activity and demonstrates the relevance of this pathway for maintaining kidney function with aging.

Endothelial Hemoglobin Alpha Mediates Iron Regulation of Endothelial Nitric Oxide

Iron deficiency is associated with heart failure, chronic kidney disease, and chronic inflammation. All of these pathologies are associated with endothelial dysfunction and impaired nitric oxide (NO) signaling. Previous clinical studies have found iron deficiency anemia (IDA) increases endothelial NO signaling and attributed this change to the reduction in circulating hemoglobin. However, while free hemoglobin is a potent scavenger of NO, it has been shown in ex vivo preparations that endothelial NO signaling is unaffected by the presence of erythrocytes suggesting changes in circulating hemoglobin do not alter NO signaling. For these reasons we focused on endothelial iron regulation. Using single cell RNA sequencing data of isolated mesenteric and adipose endothelial cells generated by our lab, we have observed arterial endothelial cells have higher transferrin receptor expression compared to capillary, veinous, and lymphatic endothelial cells. This suggests that the arterial endothelium, which controls blood flow and is especially susceptible to endothelial dysfunction, may be particularly sensitive to changes in iron status. Additionally, our lab has previously shown the alpha chain of hemoglobin (Hbα) is expressed in the endothelium of small arteries and scavenges NO. We therefore hypothesized endothelial Hbα, rather than blood hemoglobin is responsible for the increased NO signaling in IDA. We first tested this hypothesis in a mouse model of IDA in which we were able to replete vascular iron stores. C57BL/6 mice were fed an iron deficient (2-6 ppm Fe) or nutrient matched control diet (48 ppm Fe) beginning at weaning. IDA mice underwent phlebotomies (10% blood volume) at 9 and 11 weeks old to aid in the progression of anemia. To restore vascular iron stores, a subset of IDA mice received a single i.p. injection of iron dextran (FeDex; 20 mg/kg) at 12 weeks. One week later complete blood counts were assessed, tissues were collected, and blood flow studies were performed. As expected, IDA mice had low blood hemoglobin (Con: 15.54 ± 0.43 vs. IDA: 6.04 ± 0.35 g/dL; p < 0.0001). FeDex did not rescue the anemia (8.55 ± 0.74 g/dL; p < 0.0001 vs. Con), but did rescue vascular iron stores as measured by ferritin light chain protein. To investigate NO signaling, we used laser speckle contrast imaging to measure changes in in vivo blood flow in response to the NO synthase inhibitor L-NAME. The magnitude of the response to L-NAME is an indicator of NO signaling. IDA mice exhibited an exaggerated response to L-NAME indicating increased NO signaling. Rescuing vascular iron stores with FeDex restored the L-NAME response back to control levels suggesting vascular iron stores, rather than the anemia itself increased NO signaling. In order to investigate the role of endothelial Hbα, we repeated these studies in endothelial specific Hbα knockout mice (Hba1 fl/fl-Cdh5-CreER T2+) developed by us. Lack of endothelial Hbα did not prevent the increased response to L-NAME in IDA mice, but did prevent the rescue by FeDex. These data suggest a model in which endothelial Hbα participates in regulating NO in response to iron, but not the increased NO in IDA.

Varied effects of tobacco smoke and e-cigarette vapor suggest that nicotine does not affect endothelium-dependent relaxation and nitric oxide signaling

Chronic smoking causes dysfunction of vascular endothelial cells, evident as a reduction of flow-mediated dilation in smokers, but the role of nicotine is still controversial. Given the increasing use of e-cigarettes and other nicotine products, it appears essential to clarify this issue. We studied extracts from cigarette smoke (CSE) and vapor from e-cigarettes (EVE) and heated tobacco (HTE) for their effects on vascular relaxation, endothelial nitric oxide signaling, and the activity of soluble guanylyl cyclase. The average nicotine concentrations of CSE, EVE, and HTE were 164, 800, and 85 µM, respectively. At a dilution of 1:3, CSE almost entirely inhibited the relaxation of rat aortas and porcine coronary arteries to acetylcholine and bradykinin, respectively, while undiluted EVE, with a 15-fold higher nicotine concentration, had no significant effect. With about 50% inhibition at 1:2 dilution, the effect of HTE was between CSE and EVE. Neither extract affected endothelium-independent relaxation to an NO donor. At the dilutions tested, CSE was not toxic to cultured endothelial cells but, in contrast to EVE, impaired NO signaling and inhibited NO stimulation of soluble guanylyl cyclase. Our results demonstrate that nicotine does not mediate the impaired endothelium-dependent vascular relaxation caused by smoking.

Allyl Isothiocianate Induces Ca2+ Signals and Nitric Oxide Release by Inducing Reactive Oxygen Species Production in the Human Cerebrovascular Endothelial Cell Line hCMEC/D3.

Nitric oxide (NO) represents a crucial mediator to regulate cerebral blood flow (CBF) in the human brain both under basal conditions and in response to somatosensory stimulation. An increase in intracellular Ca2+ concentrations ([Ca2+]i) stimulates the endothelial NO synthase to produce NO in human cerebrovascular endothelial cells. Therefore, targeting the endothelial ion channel machinery could represent a promising strategy to rescue endothelial NO signalling in traumatic brain injury and neurodegenerative disorders. Allyl isothiocyanate (AITC), a major active constituent of cruciferous vegetables, was found to increase CBF in non-human preclinical models, but it is still unknown whether it stimulates NO release in human brain capillary endothelial cells. In the present investigation, we showed that AITC evoked a Ca2+-dependent NO release in the human cerebrovascular endothelial cell line, hCMEC/D3. The Ca2+ response to AITC was shaped by both intra- and extracellular Ca2+ sources, although it was insensitive to the pharmacological blockade of transient receptor potential ankyrin 1, which is regarded to be among the main molecular targets of AITC. In accord, AITC failed to induce transmembrane currents or to elicit membrane hyperpolarization, although NS309, a selective opener of the small- and intermediate-conductance Ca2+-activated K+ channels, induced a significant membrane hyperpolarization. The AITC-evoked Ca2+ signal was triggered by the production of cytosolic, but not mitochondrial, reactive oxygen species (ROS), and was supported by store-operated Ca2+ entry (SOCE). Conversely, the Ca2+ response to AITC did not require Ca2+ mobilization from the endoplasmic reticulum, lysosomes or mitochondria. However, pharmacological manipulation revealed that AITC-dependent ROS generation inhibited plasma membrane Ca2+-ATPase (PMCA) activity, thereby attenuating Ca2+ removal across the plasma membrane and resulting in a sustained increase in [Ca2+]i. In accord, the AITC-evoked NO release was driven by ROS generation and required ROS-dependent inhibition of PMCA activity. These data suggest that AITC could be exploited to restore NO signalling and restore CBF in brain disorders that feature neurovascular dysfunction.

Alpha globin gene copy number and incident ischemic stroke risk among Black Americans.

People with African ancestry have greater stroke risk and greater heritability of stroke risk than people of other ancestries. Given the importance of nitric oxide (NO) in stroke, and recent evidence that alpha globin restricts nitric oxide release from vascular endothelial cells, we hypothesized that alpha globin gene (HBA) deletion would be associated with reduced risk of incident ischemic stroke. We evaluated 8,947 participants self-reporting African ancestry in the national, prospective Reasons for Geographic And Racial Differences in Stroke (REGARDS) cohort. Incident ischemic stroke was defined as non-hemorrhagic stroke with focal neurological deficit lasting ≥ 24 hours confirmed by the medical record or focal or non-focal neurological deficit with positive imaging confirmed with medical records. Genomic DNA was analyzed using droplet digital PCR to determine HBA copy number. Multivariable Cox proportional hazards regression was used to estimate the hazard ratio (HR) of HBA copy number on time to first ischemic stroke. Four-hundred seventy-nine (5.3%) participants had an incident ischemic stroke over a median (IQR) of 11.0 (5.7, 14.0) years' follow-up. HBA copy number ranged from 2 to 6: 368 (4%) -α/-α, 2,480 (28%) -α/αα, 6,014 (67%) αα/αα, 83 (1%) ααα/αα and 2 (<1%) ααα/ααα. The adjusted HR of ischemic stroke with HBA copy number was 1.04; 95%CI 0.89, 1.21; p = 0.66. Although a reduction in HBA copy number is expected to increase endothelial nitric oxide signaling in the human vascular endothelium, HBA copy number was not associated with incident ischemic stroke in this large cohort of Black Americans.

Novel identification and modulation of the mechanosensitive Piezo1 channel in human myometrium.

Approximately 10% of US births deliver preterm before 37weeks of completed gestation. Premature infants are at risk for life-long debilitating morbidities and death, and spontaneous preterm labour explains 50% of preterm births. In all cases existing treatments are ineffective, and none are FDA approved. The mechanisms that initiate preterm labour are not well understood but may result from dysfunctional regulation of quiescence mechanisms. Human pregnancy is accompanied by large increases in blood flow, and the uterus must enlarge by orders of magnitude to accommodate the growing fetus. This mechanical strain suggests that stretch-activated channels may constitute a mechanism to explain gestational quiescence. Here we identify for the first time that Piezo1, a mechanosensitive cation channel, is present in the uterine smooth muscle and microvascular endothelium of pregnant myometrium. Piezo is downregulated during preterm labour, and stimulation of myometrial Piezo1 in an organ bath with the agonist Yoda1 relaxes the tissue in a dose-dependent fashion. Further, stimulation of Piezo1 while inhibiting protein kinase A, AKT, or endothelial nitric oxide synthase mutes the negative inotropic effects of Piezo1 activation, intimating that actions on the myocyte and endothelial nitric oxide signalling contribute to Piezo1-mediated contractile dynamics. Taken together, these data highlight the importance of stretch-activated channels in pregnancy maintenance and parturition, and identify Piezo1 as a tocolytic target of interest. KEY POINTS: Spontaneous preterm labour is a serious obstetric dilemma without a known cause or effective treatments. Piezo1 is a stretch-activated channel important to muscle contractile dynamics. Piezo1 is present in the myometrium and is dysregulated in women who experience preterm labour. Activation of Piezo1 by the agonist Yoda1 relaxes the myometrium in a dose-dependent fashion, indicating that Piezo1modulation may have therapeutic benefits to treat preterm labour.

Alpha globin gene copy number and hypertension risk among Black Americans.

BackgroundAlpha globin is expressed in the endothelial cells of human resistance arteries where it binds to endothelial nitric oxide synthase and limits release of the vasodilator nitric oxide. Genomic deletion of the alpha globin gene (HBA) is common among Black Americans and could lead to increased endothelial nitric oxide signaling and reduced risk of hypertension.MethodsCommunity-dwelling US adults aged 45 years or older were enrolled and examined from 2003 to 2007, followed by telephone every 6 months, and reexamined from 2013 to 2016. At both visits, trained personnel performed standardized, in-home blood pressure measurements and pill bottle review. Prevalent hypertension was defined as systolic blood pressure ≥ 140mmHg or diastolic blood pressure ≥ 90mmHg or anti-hypertensive medication use. Droplet digital PCR was used to determine HBA copy number. The associations of HBA copy number with prevalent hypertension, resistant hypertension, and incident hypertension were estimated using multivariable regression.ResultsAmong 9,684 Black participants, 7,439 (77%) had hypertension at baseline and 1,044 of those had treatment-resistant hypertension. 1,000 participants were not hypertensive at baseline and participated in a follow up visit; 517 (52%) developed hypertension over median 9.2 years follow-up. Increased HBA copy number was not associated with prevalent hypertension (PR = 1.00; 95%CI 0.98,1.02), resistant hypertension (PR = 0.95; 95%CI 0.86,1.05), or incident hypertension (RR = 0.96; 95%CI 0.86,1.07).ConclusionsThere were no associations between increased HBA copy number and risk of hypertension. These findings suggest that variation in alpha globin gene copy number does not modify the risk of hypertension among Black American adults.

Oral Administration of Garcinia dulcis Flower Extract Lowers Arterial Blood Pressure of 2-kidneys-1-clip Renovascular Hypertensive Rat

The hexane insoluble fraction of the Garcinia dulcis (GD) flower extract comprises mainly camboginol and morelloflavone which possess potent in vivo and in vitro antioxidant properties. This study aimed to evaluate the effects of 4-week oral administration of GD flower extract on the arterial blood pressure (ABP) and the excretory function of the kidney in the 2-kidneys-1-clip (2K1C) renovascular hypertensive rats (total=12) compared to sham operated (SO) normotensive Wistar rats (total=12). Four weeks after hypertensive-induced surgery, either 50 mg/kg BW GD flower extract or vehicle was orally administered to the 2K1C or SO groups (n=6/group) daily for four weeks. ABP and the renal excretory function were studied in anesthetized rats, and expression of endothelial nitric oxide synthase (eNOS) mRNA in the isolated thoracic aorta were measured. In the 2K1C rats, GD flower extract significantly decreased ABP while increased significantly eNOS mRNA levels. GD flower extract did not exert a diuretic effect in either SO and 2K1C rats since there was no change in observed urine excretion, but it did tend to attenuated the renal tubular damage caused by renovascular hypertension. GD flower extract was anti-hypertensive in this model of renovascular hypertension and problably acts via the endothelial nitric oxide signaling pathway.

Alpha Globin Gene Copy Number Is Associated with Prevalent Chronic Kidney Disease and Incident End-Stage Kidney Disease among Black Americans.

α-Globin is expressed in endothelial cells of resistance arteries, where it limits endothelial nitric oxide signaling and enhances α-adrenergic-mediated vasoconstriction. α-Globin gene (HBA) copy number is variable in people of African descent and other populations worldwide. Given the protective effect of nitric oxide in the kidney, we hypothesized that HBA copy number would be associated with kidney disease risk. Community-dwelling Black Americans aged ≥45 years old were enrolled in a national longitudinal cohort from 2003 through 2007. HBA copy number was measured using droplet digital PCR. The prevalence ratio (PR) of CKD and the relative risk (RR) of incident reduced eGFR were calculated using modified Poisson multivariable regression. The hazard ratio (HR) of incident ESKD was calculated using Cox proportional hazards multivariable regression. Among 9908 participants, HBA copy number varied from 2 to 6. In analyses adjusted for demographic, clinical, and genetic risk factors, a one-copy increase in HBA was associated with 14% greater prevalence of CKD (PR, 1.14; 95% CI, 1.07 to 1.21; P<0.0001). While HBA copy number was not associated with incident reduced eGFR (RR, 1.06; 95% CI, 0.94 to 1.19; P=0.38), the hazard of incident ESKD was 32% higher for each additional copy of HBA (HR, 1.32; 95% CI, 1.09 to 1.61; P=0.005). Increasing HBA copy number was associated with a greater prevalence of CKD and incidence of ESKD in a national longitudinal cohort of Black Americans.

Sickle - Cell Disease

Sickle cell disease is a common inherited, multisystem, monogenic disorder of red blood cells (erythrocytes) caused due to polymorphic changes in hemoglobin. The most commonly known condition; Sickle cell anemia wherein there aren’t enough healthy RBCs to carry adequate oxygen throughout the body is considered to be a common form if Sickle-cell disease. Other type of Sickle cell disease is Hemoglobin SC disease (HbSC) caused due to inheritance of beta s and beta c alleles. The third type of such disease is HbS thalassemia caused due to beta-thalassemia mutation in the beta-globin gene leading to Sickle hemoglobin (HbS). Polymerization of HbS due to presence of fetal hemoglobin in the erythrocytes that in turn reduces the concentration of HbS which becomes the prominent determinant to check the severity of the disease. Reduced concentrations of HbS also reduce hemolysis that prevents acute vaso- occlusion. This pain is caused as the irregular shaped RBCs and WBCs get entrapped in the small blood vessels causing vascular obstruction and tissue ischemia. HbS polymerization can also lead to hemolytic anemia which is a state where in rate of RBC destruction is faster than formation; such patients are likely to develop vasculopathy. During the process of hemolysis, hemoglobin is released into plasma that inhibits endothelial nitric oxide signaling causing endothelial cell dysfunction. Hemolysis is also associated with formation of erythrocyte microvesicles that acts as a activator of tissue factor. Malaria is considered to cause HbS. Sickle cell disease is found to be highest in the African continent mostly affecting the new borns. The cause of deaths is hug in Africa due to poor diagnostic facilities. Measures taken against H influenzae and S pneumoniae that is profoundly detected in African children with Sickle cell disease can help reduce the disease proximity. Implementation of early life screening can thereby be effective in this case.

Pulsatility effects of flow on vascular tone in the fetoplacental circulation

IntroductionThe regulation of vascular tone in the fetoplacental circulation is governed by endocrine and mechanical forces yielding a relaxed basal state in normal pregnancy. Flow mediated vasodilation, induced by shear stress and endothelial nitric oxide signalling, is key to driving vasorelaxation in this circulation. The pulsatile property of blood flow, as opposed to the flow rate, could provide an additional factor in this regulation, but its effects and signalling have never been explored in the fetoplacental microvasculature. Methods: Here, we studied the effects of non-pulsatile and pulsatile flow modalities on vascular resistance in the fetoplacental microcirculation of the human placenta using an ex vivo perfusion model; and examined a potential role for nitric oxide. We also explored whether the placental Doppler velocimetry waveform is sustained within subchorial arteries in vivo. Results: Pulsatile flow reduced basal impedance to flow during steady state perfusion compared to non-pulsatile flow, signalled through enhanced nitric oxide production. Doppler velocimetry waveforms were visible within the subchorial arteries in vivo. Conclusion: This work suggests that the pulsatile property of flow through the fetoplacental circulation is sensed by the fetoplacental vasculature to mediate a signalling response and provide additional vasodilation of this microcirculation. We speculate that in pregnancy disease, altered amplitude and frequency of the subchorial pulse might impact on vascular function in a compromised high-resistance placental microcirculation.

Effects of a dammarane-type saponin, ginsenoside Rd, in nicotine-induced vascular endothelial injury

BackgroundPanax notoginseng (Burk.) F.H. Chen is a traditional medicinal plant widely used to prevent and treat cardiovascular diseases. Ginsenoside Rd (GRd) is a major bioactive component of P. notoginseng, but specific effects on cardiovascular disease-related pathogenic processes are rarely studied, especially vascular endothelial injury. PurposeThis study investigated the potential protective efficacy of GRd against nicotine-induced vascular endothelial cell injury, disruption of vascular nitric oxide (NO) signaling, aberrant endothelium–monocyte adhesion, platelet aggregation, and vasoconstriction. Study design/MethodsVascular endothelial injury and functional disruption were investigated in cultured human umbilical vein endothelial cells (HUVECs) by biochemical assays for nitric oxide (NO) and angiotensin II (Ang II), immunofluorescence (IF) and western blotting for expression analyses of apoptosis- related proteins, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), Ang II type receptor 1 (AGTR1), toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor-kappa B (NF-κB). In addition, vascular protection by GRd was examined in nicotine-administered Sprague-Dawley (SD) rats by serum NO and Ang II assays, and by hematoxylin-eosin (HE) and immunostaining of aorta. We also examined effects of GRd on monocyte (THP-1 cells) adhesion assays, adenosine diphosphate (ADP)-induced platelet aggregation, and phenylephrine (PE)-induced vasoconstriction of isolated rat aortic rings. ResultsIn HUVECs, nicotine significantly suppressed NO production, enhanced Ang II production, downregulated eNOS expression, and upregulated expression levels of AGTR1, TLR4, MyD88, NF-κB, iNOS, Bax/Bcl-2 ratio, cleaved caspase-3, and cytochrome c (cyt c). All of these changes were significantly reversed by GRd. In rats, oral GRd reversed the reduction NO and enhanced Ang II production in serum induced by nicotine administration, and HE staining revealed protection of aortic endothelial cells. In addition, GRd reversed nicotine-mediated enhancement of HUVECs-monocyte adhesion, inhibited ADP-induced platelet aggregation and PE-induced vasoconstriction. ConclusionGRd may prevent nicotine-induced cardiovascular diseases by preserving normal vascular endothelial NO signaling, suppressing platelet aggregation and vasoconstriction, and by preventing endothelial cell–monocyte adhesion.

Aging Alters Cerebrovascular Endothelial GPCR and K+ Channel Function: Divergent Role of Biological Sex.

Age-related dementia entails impaired blood flow to and throughout the brain due, in part, to reduced endothelial nitric oxide signaling. However, it is unknown whether sex affects cerebrovascular Gq-protein-coupled receptors (GPCRs) and K+ channels underlying endothelium-derived hyperpolarization (EDH) during progressive aging. Thus, we simultaneously evaluated intracellular Ca2+ ([Ca2+]i) and membrane potential (Vm) of intact endothelial tubes freshly isolated from posterior cerebral arteries of young (4-6 mo), middle-aged (12-16 mo), and old (24-28 mo) male and female C57BL/6 mice. Purinergic receptor function (vs. muscarinic) was dominant and enhanced for [Ca2+]i increases in old females versus old males. However, Ca2+-sensitive K+ channel function as defined by NS309-evoked Vm hyperpolarization was mildly impaired in females versus males during old age. This sex-based contrast in declined function of GPCRs and K+ channels to produce EDH may support a greater ability for physiological endothelial GPCR function to maintain optimal cerebral blood flow in females versus males during old age. As reflective of the pattern of cerebral blood flow decline in human subjects, inward-rectifying K+ (KIR) channel function decreased with progressive age regardless of sex. Combined age-related analyses masked male versus female aging and, contrary to expectation, hydrogen peroxide played a minimal role. Altogether, we conclude a sex-based divergence in cerebrovascular endothelial GPCR and K+ channel function while highlighting a previously unidentified form of age-related endothelial dysfunction as reduced KIR channel function.

Alpha Globin Gene Copy Number Is Associated with Kidney Disease Among Black Individuals

Introduction: In addition to forming hemoglobin in red blood cells, alpha globin (HBA) has non-erythroid effects and is expressed in vascular endothelial cells where it interacts with endothelial nitric oxide (NO) synthase (eNOS) to limit nitric oxide diffusion across the myoendothelial junction. Reduced expression of HBA or disruption of HBA/eNOS interactions increases endothelial nitric oxide signaling. Humans have 0 to 3 copies of HBA per chromosome and Black individuals have increased variation in HBA allele count. Moreover, Black individuals are more likely to develop end-stage kidney disease (ESKD) and unexplained genetic factors may contribute to racial disparities in kidney disease not attributable to socioeconomic factors. Given that decreased endothelial NO signaling accelerates renal disease in mouse models, we hypothesized that lower HBA gene copy number would be associated with lower risk of kidney disease among Black individuals. Methods: We used droplet digital PCR to measure HBA copy number in Black individuals enrolled in the REasons for Geographic and Racial Differences in Stroke cohort. This national, prospective observational study enrolled 30,239 men and women &gt;45 years of age from the 48 contiguous United States. Prevalent chronic kidney disease (CKD) was defined as eGFR &lt;60 ml/min/1.73m2or urine albumin/creatinine ratio ≥30 mg/g at enrollment. Incident end-stage kidney disease (ESKD) was identified by linkage to the United States Renal Data System. The relative risk (RR) of prevalent CKD was calculated using modified Poisson multivariable regression employing a linear effect of HBA allele count and adjusting for 13 pre-specified genetic, biomedical, and socioeconomic factors. The hazard ratio (HR) for incident ESKD was calculated using Cox proportional hazards regression with the same covariates. Results: HBA copy number ranged from 2 to 6 among 9,918 Black participants (4% with 2 copies, 28% with 3, 67% with 4, and 1% with ≥ 5), with 25% of all participants having CKD at baseline. Participants were followed for a median (25th, 75thpercentile) of 10.1 (5.5, 12.5) years for the development of ESKD, with 2.4% of all participants developing ESKD. As shown in the table, after multivariable adjustment and calculated relative to the most common copy number (4), model-estimated CKD risk was 23% lower among those with 2 copies and 12% lower among those with 3 copies of HBA, while CKD risk was 14% higher among those with 5 or 6 copies of HBA. In addition, relative to 4 copies, ESKD risk was 40% lower among those with 2 copies and 22% lower among those with 3 copies, while the risk of ESKD increased by 29% in those with 5 or 6 copies of HBA. Conclusions: We identified a novel, independent genetic association of HBA copy number with CKD prevalence and ESKD incidence among Black individuals in a national, prospective cohort study in the US. The findings are consistent with our hypothesis that decreased alpha globin gene expression could increase endothelial NO signaling in small renal arteries and confer protection against renovascular injury, while increased alpha globin gene expression couldlimit endothelial NO signaling. These findings suggest that further study of the impact of HBA expression on normal renal physiology and susceptibility to injury is needed. Disclosures Naik: Elsevier: Other: Content Editor.

Krox20 Regulates Endothelial Nitric Oxide Signaling in Aortic Valve Development and Disease.

Among the aortic valve diseases, the bicuspid aortic valve (BAV) occurs when the aortic valve has two leaflets (cusps), rather than three, and represents the most common form of congenital cardiac malformation, affecting 1–2% of the population. Despite recent advances, the etiology of BAV is poorly understood. We have recently shown that Krox20 is expressed in endothelial and cardiac neural crest derivatives that normally contribute to aortic valve development and that lack of Krox20 in these cells leads to aortic valve defects including partially penetrant BAV formation. Dysregulated expression of endothelial nitric oxide synthase (Nos3) is associated with BAV. To investigate the relationship between Krox20 and Nos3 during aortic valve development, we performed inter-genetic cross. While single heterozygous mice had normal valve formation, the compound Krox20+/−;Nos3+/− mice had BAV malformations displaying an in vivo genetic interaction between these genes for normal valve morphogenesis. Moreover, in vivo and in vitro experiments demonstrate that Krox20 directly binds to Nos3 proximal promoter to activate its expression. Our data suggests that Krox20 is a regulator of nitric oxide in endothelial-derived cells in the development of the aortic valve and concludes on the interaction of Krox20 and Nos3 in BAV formation.

P1534Short time and short term of high-intensity intermittent exercise training reduces arterial stiffness via upregulation of endothelial nitric oxide signalling

Abstract Introduction Conventionally, as an exercise mode which leads to reduction of arterial stiffness, it is well used that moderate-intensity continuous exercise training (MICT). High-intensity interval training (HIIT), such as HIIT program with a total exercise time of 15–30 min is highly time-effective as an exercise mode for which reduces risks of cardiovascular disease. Recent study showed that even shorter HIIT leads to an effective reduction in arterial stiffness. Therefore, HIIT is an effectively exercise therapy which can use in patients with cardiovascular diseases. Although MICT induces vasodilation by acceleration of nitric oxide (NO) production via upregulating arterial endothelial NO synthase (eNOS)/protein kinase B (Akt) signalling pathway, an underlying mechanism of HIIT effects remains unclear. Purpose This study aimed to clarify the effects of short HIIT on arterial stiffness and arterial NO production in rats. Methods Forty 10-week-old male Sprague-Dawley rats were randomly divided into four groups; CON: 8-week sedentary control, MICT: treadmill running for 60 min at 30m/min, 5 days/wk for 8weeks, HIIT: fourteen 20 sec swimming sessions with a weight equivalent to 14–16% of each body weight and 10 sec pause was allowed between exercise sessions, 4 days/wk for 6 weeks from 12-week-old, and RT: ladder climbing, 8–10sets/day, 3 days/wk for 8 weeks groups (n=10 each group). After training session, we measured aortic pulse wave velocity (aortic PWV) as an index of arterial stiffness and plasma nitrite/nitrate (NOx) concentrations and phosphorylation of eNOS and Akt in the aorta. Results Aortic PWV was significantly reduced in both MICT and HIIT groups as compared to CON and RT groups (P&lt;0.05), whereas there was no difference between RT and CON groups. Additionally, arterial phosphorylations of eNOS and Akt and plasma NOx levels were significantly elevated in both MICT and HIIT groups as compared to CON and RT groups (P&lt;0.05), whereas there was no difference between RT and CON groups. Moreover, HIIT-induced reduction of aortic PWV and increase in eNOS and Akt phosphorylations and plasma NOx levels were equal to these MICT effects. Arterial eNOS phosphorylation was negatively correlated with aortic PWV in all groups (r=−0.38, P&lt;0.05). Further study was conducted whether a single-bout high-intensity intermittent exercise accelerates NO production. After acute high-intensity intermittent exercise, plasma NOx levels were significantly elevated (P&lt;0.05). Conclusion These results suggest that HIIT increases NO production via the upregulation of arterial Akt/eNOS signalling pathway, resulting in the reduction of arterial stiffness, despite a reduction in total exercise volume as compared with MICT. Acknowledgement/Funding JSPS KAKENHI (#17H02182 and #16K13059 for M. Iemitsu; #18H06423 for N. Hasegawa)

Clozapine Disrupts Endothelial Nitric Oxide Signaling and Antioxidant System for its Cardiovascular Complications.

Many drugs in current practice require additional safety labels in order to prevent potential risks to the major organ system. Psychotropic agent clozapine has been reported to produce myocarditis and other cardiac complications on repeated use. Our study aimed to establish the role of clozapine in vascular damage associated with nitric oxide metabolism. Isolated aortic strips incubated with clozapine at different dose levels were estimated for nitrite release and antioxidant systems such as glutathione and catalase. Vascular integrity assessment was performed by recording the acetylcholine induced relaxation of phenyephrine pre-contracted aorta. From our study, it was found that clozapine depletes the nitric oxide level in the endothelium and enhance the oxidative stress. The aorta fails to relax completely after the addition of acetylcholine indicates the deranged eNOS signaling in the endothelium. From the experimental findings, it was concluded that clozapine could depress the eNOS regulation and thereby perhaps initiates cardiovascular complications through subsequent vascular events.

Blood Flow Deficits and Cerebrovascular Changes in a Dietary Model of Hyperhomocysteinemia.

Elevated homocysteine in the blood, or hyperhomocysteinemia, is a recognized risk factor for multiple causes of dementia including Alzheimer’s disease. While reduction of homocysteine levels can generally be accomplished in a straightforward manner, the evidence regarding the cognitive benefits of this approach is less clear. To identify adjunct therapeutic targets that might more effectively restore cognition, the present series of experiments characterizes early and later cerebrovascular changes in a model of hyperhomocysteinemia. Sex-balanced groups of adult C57BL/6J mice were administered a diet deficient in vitamins B6, B12, and B9 (folate) and supplemented with excess methionine. They were subsequently assessed for changes in cerebral blood flow, memory, blood–brain barrier permeability, and selected vascular-associated genes. Blood flow deficits and barrier permeability changes occurred alongside changes in memory and in genes associated with metabolism, endothelial nitric oxide signaling, barrier integrity, and extracellular matrix remodeling. Significant sexually dimorphic responses to the diet were also detected. Taken together, these data deepen our understanding of a major contributor to dementia burden.

A4646 A novel endothelial NO-dependent vasorelaxing and anti-hypertensive peptide derived from rice bran

Objectives: We recently identified a novel anti-hypertensive peptide Leu-Arg-Ala (LRA) from the enzymatic digestion of rice bran protein (Shobako et al., Mol. Nutr. Food res., 2018). Orally administered LRA at a dose of 0.25 mg/kg potently reduced the systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs), but had low ACE inhibitory activity (IC50 = 62 μM), explaining its potent hypotensive activity. In this study, we investigated vasorelaxing activity of LRA and the involvement of nitric oxide (NO) signaling. Methods: The vasorelaxing activity was determined by the mesenteric artery isolated from SHRs. Changes in SBP of SHRs were measured by tail-cuff method. Results: A novel rice bran-derived hypotensive peptide LRA exhibited vasorelaxing activity in the mesenteric artery of SHRs. Pretreatment with NG-Nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase (NOS), diminished the LRA-induced vasorelaxing activity. L-NAME also inhibited the anti-hypertensive effects of LRA. LRA also activated phosphorylation of endothelial NOS in human umbilical vein endothelial cells (HUVECs). Thus, these data suggest that LRA-induced vasorelaxing and anti-hypertensive activites were mediated by the activation of endothelial NO signaling. Next, we investigated mechanisms upstream of NO signaling. The LRA-induced vasorelaxant activity was not blocked by HOE 140 (bradykinin B2 antagonist), A779 (MAS antagonist) and wortomannin (PI3 kinase inhibitor), implying that NO-mediated vasorelaxing activity by LRA is independent of the bradykinin B2/MAS receptor-PI3 kinase activation. Conclusion: We found that LRA possibly exhibited vasorelaxing and hypotensive effects in a novel endothelial NO signaling-dependent manner. This is the first example of a NO-dependent vasorelaxing peptide identified from rice bran.

Clozapine Disrupts Endothelial Nitric Oxide Signaling and Antioxidant System for its Cardiovascular Complications

: This article is now been retracted based on author requestObjective: Many drugs in current practice require additional safety labels in order to prevent potential risks to the major organ system. Psychotropic agent clozapine has been reported to produce myocarditis and other cardiac complications on repeated use. Our study aimed to establish the role of clozapine in vascular damage associated with nitric oxide metabolism. Method: Isolated aortic strips incubated with clozapine at different dose levels were estimated for nitrite release and antioxidant systems such as glutathione and catalase. Vascular integrity assessment was performed by recording the acetylcholine induced relaxation of phenyephrine precontracted aorta. Result: From our study, it was found that clozapine depilates the nitric oxide level in the endothelium and enhance the oxidative stress. The aorta fails to relax completely after adding acetylcholine indicates the deranged eNOS signaling in the endothelium. Conclusion: From the experimental findings, it was concluded that clozapine could depress the eNOS regulation and thereby perhaps initiates cardiovascular complications through subsequent vascular events.Key words: Endothelium, Nitric oxide, GSH, Catalase, Oxidation.