Abstract 167: A Cell-Autonomous Role for Endothelial GTP Cyclohydrolase 1 and Tetrahydrobiopterin in Blood Pressure Regulation

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Surawee Chuaiphichai ◽  
Eileen McNeill ◽  
Gillian Douglas ◽  
Mark J Crabtree ◽  
Jennifer K Bendall ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Endothelial Cell ◽  
De Novo ◽  
Soluble Guanylate Cyclase ◽  
Ex Vivo ◽  
Mesenteric Arteries ◽  
Gtp Cyclohydrolase ◽  
Enos Uncoupling

Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide synthase (eNOS) function and nitric oxide (NO) generation. Augmentation of BH4 levels can prevent eNOS uncoupling and improve endothelial dysfunction in vascular disease states. However, the physiological requirement for de-novo endothelial cell BH4 biosynthesis in eNOS function remains unclear. We generated a novel mouse model with endothelial cell-specific deletion of GCH1, encoding GTP cyclohydrolase 1, an essential enzyme for BH4 biosynthesis, to test the cell-autonomous requirement for endothelial BH4 biosynthesis in vivo. Mice with a floxed GCH1 allele ( GCH1 fl/fl ) were crossed with Tie2cre mice to delete GCH1 in endothelial cells. GCH1 fl/fl Tie2cre mice demonstrated virtually absent NO bioactivity and significantly greater O 2 • - production. GCH1 fl/fl Tie2cre aortas and mesenteric arteries had enhanced vasoconstriction to phenylephrine and impaired endothelium-dependent vasodilatations to acetylcholine and SLIGRL. Endothelium-dependent vasodilatations in GCH1 fl/fl Tie2cre aortas were in part mediated by NOS-derived hydrogen peroxide (H 2 O 2 ), which mediated vasodilatation through soluble guanylate cyclase. Ex vivo supplementation of aortic rings with the BH4 analogue sepiapterin restored normal endothelial function and abolished eNOS-derived H 2 O 2 production in GCH1 fl/fl Tie2cre aortas. GCH1 fl/fl Tie2cre mice had higher systemic blood pressure than wild-type littermates, which was normalised by NOS inhibitor, L-NAME. Taken together, these studies reveal an endothelial cell-autonomous requirement for GCH1 and BH4 in regulation of vascular tone and blood pressure, and identify endothelial cell BH4 as a pivotal regulator of NO vs. H 2 O 2 as alternative eNOS-derived endothelial derived relaxing factors.

Abstract 322: Acute Inhibition of GTP Cyclohydrolase 1 Uncouples Endothelial Nitric Oxide Synthase and Elevates Blood Pressure

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Shuangxi Wang ◽  
Jian Xu ◽  
Ping Song ◽  
Yong Wu ◽  
Junhua Zhang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Nitric Oxide Synthase ◽  
Endothelial Nitric Oxide Synthase ◽  
De Novo ◽  
Gtp Cyclohydrolase ◽  
South Central ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide ◽  
Endothelium Dependent Relaxation

Objective: GTP cyclohydrolase 1 (GTPCH1) is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for endothelial nitric oxide synthase (eNOS) dictating at least partly, the balance of nitric oxide (NO) and superoxide (O 2 .− ) produced by this enzyme. The aim of this study is to determine the effects of acute inhibition of GTPCH1 on BH4, eNOS function, and blood pressure. Methods: The biopterin content was detected by HPLC. O 2 .− and NO productions were assayed by using DHE and DAF fluorescence respectively. The vessel relaxation was assayed by organ chamber. The blood pressure in wild-type (WT) or eNOS −/− mice was determined by a carotid catheter method. Results: Exposure of bovine or mouse aortic endothelial cells to GTPCH1 inhibitors (10 mM DAHP or 1 mM NAS) for 24 hours or GTPCH1 siRNA transfection significantly reduced both BH4 and NO levels, but increased O 2 .− levels. This increase was abolished by 10 μM L-sepiapterin (BH4 precursor) or 1 mM L-NAME (non-selective NOS inhibitor). Incubation of isolated WT mice aortas with DAHP or NAS for 24 hours impaired acetylcholine-induced endothelium-dependent relaxation, but not endothelium-independent relaxation. Aortas from GTPCH1 siRNA-injected mice, but not their control-siRNA injected mice, also exhibited impaired endothelium-dependent relaxation. Furthermore, GT-PCH1 siRNA injection in mice reduced BH4 levels in aortas, associated with increased aortic levels of O 2 .− , 3-nitrotyrosine, and adhesion molecules (ICAM1 and VCAM1). In addition, an elevated mean, systolic, and diastolic blood pressure was induced by GTPCH1 siRNA injection in vivo , but not control siRNA (mean blood pressure: 114.28±4.48 vs . 136.81±2.45 mmHg) in WT mice. GTPCH1 siRNA was unable to elicit the similar effects in eNOS −/− mice, including increased oxidative stress (O 2 .− , 3-nitrotyrosine, ICAM1, VCAM1) and blood pressure. Finally, sepiapterin supplementation, which had no effect on high blood pressure in eNOS −/− mice, partially reversed GTPCH1 siRNA-induced elevation of systemic blood pressure in WT mice. Conclusion: GTPCH1 via BH4 maintains normal blood pressure and endothelial function by preserving eNOS-dependent NO biosynthesis. This research has received full or partial funding support from the American Heart Association, AHA South Central Affiliate (Arkansas, New Mexico, Oklahoma & Texas).

scholarly journals 3-Hydroxyphenylacetic Acid: A Blood Pressure-Reducing Flavonoid Metabolite

Nutrients ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 328
Author(s):  
Patrícia Dias ◽  
Jana Pourová ◽  
Marie Vopršalová ◽  
Iveta Nejmanová ◽  
Přemysl Mladěnka
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Ex Vivo ◽  
Laboratory Animals ◽  
Spontaneously Hypertensive ◽  
Porcine Coronary Artery ◽  
Arterial Blood ◽  
Hydroxyphenylacetic Acid ◽  
Dose Dependent Decrease

Regular intake of polyphenol-rich food has been associated with a wide variety of beneficial health effects, including the prevention of cardiovascular diseases. However, the parent flavonoids have mostly low bioavailability and, hence, their metabolites have been hypothesized to be bioactive. One of these metabolites, 3-hydroxyphenylacetic acid (3-HPAA), formed by the gut microbiota, was previously reported to exert vasorelaxant effects ex vivo. The aim of this study was to shed more light on this effect in vivo, and to elucidate the mechanism of action. 3-HPAA gave rise to a dose-dependent decrease in arterial blood pressure when administered i.v. both as a bolus and infusion to spontaneously hypertensive rats. In contrast, no significant changes in heart rate were observed. In ex vivo experiments, where porcine hearts from a slaughterhouse were used to decrease the need for laboratory animals, 3-HPAA relaxed precontracted porcine coronary artery segments via a mechanism partially dependent on endothelium integrity. This relaxation was significantly impaired after endothelial nitric oxide synthase inhibition. In contrast, the blockade of SKCa or IKCa channels, or muscarinic receptors, did not affect 3-HPAA relaxation. Similarly, no effects of 3-HPAA on cyclooxygenase nor L-type calcium channels were observed. Thus, 3-HPAA decreases blood pressure in vivo via vessel relaxation, and this mechanism might be based on the release of nitric oxide by the endothelial layer.

Abstract P212: Sphingolipid De Novo Pathway is a Novel Regulator of Blood Pressure Homeostasis

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Anna Cantalupo ◽  
Yi Zhang ◽  
Xian-Cheng Jiang ◽  
Annarita Di Lorenzo
Keyword(s):  
Blood Pressure ◽  
Endothelial Cells ◽  
High Blood Pressure ◽  
Vascular Reactivity ◽  
De Novo ◽  
Ex Vivo ◽  
Mesenteric Arteries ◽  
Serine Palmitoyltransferase ◽  
Sphingosine 1 Phosphate

Background and objectives: Sphingolipids, particularly sphingosine 1-phosphate (S1P), play an important role in the cardiovascular homeostasis. Recently, we revealed that endothelial de novo biosynthesis of sphingolipids is very important to control vascular functions and blood pressure. We discovered that in blood vessels, particularly in endothelial cells, Nogo-B, a membrane protein of the endoplasmic reticulum, inhibits serine palmitoyltransferase (SPT), the first and rate-limiting enzyme of de novo production of sphingolipids, to impact vascular tone and blood pressure. Indeed, mice lacking Nogo-B are protected from angiotensin II-induced hypertension, and pharmacological inhibition of SPT by myriocin reinstates high blood pressure in absence of Nogo-B, suggesting that the upregulation of SPT activity exerts anti-hypertensive functions. Thus, the goal of this study is to investigate the role of SPT in vascular functions and blood pressure regulation by using novel genetic mouse models. Methods: The SBP was evaluated in 14 weeks old mice heterozygous for Sptlc2 ( Sptlc2 +/- ) or lacking Sptlc2 specifically in endothelial cells (ECKO Sptlc2 ) and smooth muscle cells (SMCKO Sptlc2 ) by using tail-cuff system. Vascular reactivity of isolated mesenteric arteries was assessed ex-vivo by using the pressure myograph system. Results: Sptlc2 +/- , ECKO Sptlc2 and SMCKO Sptlc2 mice were hypertensive compared to their respective controls ( Sptlc2 +/- 128.9±2.6 vs. WT 112.1±2.6 mmHg; ECKO Sptlc2 125.5±1.8, SMCKO Sptlc2 127.2±0.6 vs. Sptlc2 f/f 106±0.84 mmHg) and developed endothelial dysfunction as shown by the impaired vasodilation in response to acetylcholine (EC 50 Sptlc2 +/- 1.48x10 -6 M vs. WT 4.46x10 -7 M; Emax ECKO Sptlc2 73.2±3.3% vs. Sptlc2 f/f 95.3±1.1%), as well as to flow (Emax: Sptlc2 +/- 23.3±1.4 μm vs. WT 42.9±4.4 μm; ECKO Sptlc2 19.9±0.9 μm vs. Sptlc2 f/f 41.3±3.1 μm). Conclusion: This study demonstrates the important role of SPT, thus the de novo production of sphingolipids, in controlling blood flow and pressure homeostasis, and provides the ground for the development of alternative therapeutic strategies to manage high blood pressure.

scholarly journals Metastatic Melanoma Progression Is Associated with Endothelial Nitric Oxide Synthase Uncoupling Induced by Loss of eNOS:BH4 Stoichiometry

2021 ◽  
Vol 22 (17) ◽  
pp. 9556
Author(s):  
Fabiana Henriques Machado de Melo ◽  
Diego Assis Gonçalves ◽  
Ricardo Xisto de Sousa ◽  
Marcelo Yudi Icimoto ◽  
Denise de Castro Fernandes ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Metastatic Melanoma ◽  
Endothelial Nitric Oxide Synthase ◽  
De Novo ◽  
Melanoma Cells ◽  
Enos Uncoupling ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Melanoma is the most aggressive type of skin cancer due to its high capability of developing metastasis and acquiring chemoresistance. Altered redox homeostasis induced by increased reactive oxygen species is associated with melanomagenesis through modulation of redox signaling pathways. Dysfunctional endothelial nitric oxide synthase (eNOS) produces superoxide anion (O2−•) and contributes to the establishment of a pro-oxidant environment in melanoma. Although decreased tetrahydrobiopterin (BH4) bioavailability is associated with eNOS uncoupling in endothelial and human melanoma cells, in the present work we show that eNOS uncoupling in metastatic melanoma cells expressing the genes from de novo biopterin synthesis pathway Gch1, Pts, and Spr, and high BH4 concentration and BH4:BH2 ratio. Western blot analysis showed increased expression of Nos3, altering the stoichiometry balance between eNOS and BH4, contributing to NOS uncoupling. Both treatment with L-sepiapterin and eNOS downregulation induced increased nitric oxide (NO) and decreased O2• levels, triggering NOS coupling and reducing cell growth and resistance to anoikis and dacarbazine chemotherapy. Moreover, restoration of eNOS activity impaired tumor growth in vivo. Finally, NOS3 expression was found to be increased in human metastatic melanoma samples compared with the primary site. eNOS dysfunction may be an important mechanism supporting metastatic melanoma growth and hence a potential target for therapy.

scholarly journals ET-CORM Mediated Vasorelaxation of Small Mesenteric Arteries: Involvement of Kv7 Potassium Channels

2021 ◽  
Vol 12 ◽  
Author(s):  
Danfeng Zhang ◽  
Bernhard M. Krause ◽  
Hans-Günther Schmalz ◽  
Paulus Wohlfart ◽  
Benito A. Yard ◽  
...  
Keyword(s):  
Soluble Guanylate Cyclase ◽  
Ex Vivo ◽  
Peripheral Resistance ◽  
Mesenteric Arteries ◽  
Kv7 Channels ◽  
Pre Treatment ◽  
Functional Relevance ◽  
Potential Use

Although the vasoactive properties of carbon monoxide (CO) have been extensively studied, the mechanism by which CO mediates vasodilation is not completely understood. Through-out published studies on CO mediated vasodilation there is inconsistency on the type of K+-channels that are activated by CO releasing molecules (CORMs). Since the vasorelaxation properties of enzyme triggered CORMs (ET-CORMs) have not been studied thus far, we first assessed if ET-CORMs can mediate vasodilation of small mesenteric arteries and subsequently addressed the role of soluble guanylate cyclase (sGC) and that of K-channels herein. To this end, 3 different types of ET-CORMs that either contain acetate (rac-1 and rac-4) or pivalate (rac-8) as ester functionality, were tested ex vivo on methoxamine pre-contracted small rat mesenteric arteries in a myograph setting. Pre-contracted mesenteric arteries strongly dilated upon treatment with both types of acetate containing ET-CORMs (rac-1 and rac-4), while treatment with the pivalate containing ET-CORM (rac-8) resulted in no vasodilation. Pre-treatment of mesenteric arteries with the sGC inhibitor ODQ abolished rac-4 mediated vasodilation, similar as for the known sGC activator SNP. Likewise, rac-4 mediated vasodilation did not occur in KCL pretreated mesenteric arteries. Although mesenteric arteries abundantly expressed a variety of K+-channels only Kv7 channels were found to be of functional relevance for rac-4 mediated vasodilation. In conclusion the current results identified Kv7 channels as the main channel by which rac-4 mediates vasodilation. In keeping with the central role of Kv7 in the control of vascular tone and peripheral resistance these promising ex-vivo data warrant further in vivo studies, particularly in models of primary hypertension or cardiac diseases, to assess the potential use of ET-CORMs in these diseases.

Abstract 15: Novel Functions of Small GTPase Rap1 in Regulating Endothelial Homeostasis: Control of Nitric Oxide Release, Vascular Function and Blood Pressure

2014 ◽  
Vol 34 (suppl_1) ◽  
Author(s):  
Sribalaji Lakshmikanthan ◽  
Xiaodong Zheng ◽  
Yoshinori Nishijima ◽  
Jeannette Vasquez-Vivar ◽  
David X Zhang ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Shear Flow ◽  
Knockout Mice ◽  
Ex Vivo ◽  
Left Ventricular ◽  
Small Gtpase ◽  
No Production ◽  
Endothelial Homeostasis

Endothelial dysfunction, resulting from decreased nitric oxide (NO) bioavailability is a pathology linked to endothelial vasomotor dysfunction and hypertension, inflammation and atherosclerosis, perturbed endothelial barrier and progression of diabetes. In blood vessels, NO is produced by the endothelial NO synthase (eNOS), the activity of which is regulated by Ca2+/calmodulin, binding of regulatory cofactors, and posttranslational modifications, including phosphorylation events on Ser1177, which stimulate NO production. Rap1 is a ubiquitously expressed small GTPase implicated in promoting vascular barrier. We have shown that endothelial cell (EC)-specific Rap1 deletion leads to defective angiogenesis in vivo due to faulty VEGFR2 activation and signaling. Importantly, EC-specific Rap1 knockout mice developed hypertension and pathological left ventricular hypertrophy. The objective of the study was to determine the role of small G protein Rap1 in regulating endothelial NO production and endothelial-dependent vasorelaxation in vivo and ex vivo. Using ex vivo myography and tamoxifen-inducible, endothelial-specific Rap1-knockout mice (Cadh5-CreERT2+/0;Rap1f/f), we demonstrate that Rap1 deficiency completely abrogates NO-dependent vasodilation and attenuates NO production. Mechanistically, we show that Rap1 is rapidly activated in response to receptor agonists that activate eNOS via Ca2+/calmodulin- dependent pathway and in response to shear flow, which modules eNOS activity by its phosphorylation. Rap1 deletion in human ECs, in vitro, leads to deficient NO release in response to both these stimuli, and interferes with PI3K/Akt pathway and eNOS Ser1177 phosphorylation. Further, we demonstrate Rap1 is required for transducing signals from the endothelial mechanosensing complex comprising PECAM-1, VE-cadherin and VEGFR2 in response to shear flow, leading to ligand-independent VEGFR2 activation and signaling to stimulate NO production. We conclude that Rap1 in endothelium is critically required for endothelial homeostasis and NO production, thereby affecting vascular tone and regulation of blood pressure. Furthermore, this study establishes Rap1 as a novel regulator of mechanotransduction in response to shear flow.

scholarly journals The Citrulline Recycling Pathway Sustains Cardiovascular Function in Arginine-Depleted Healthy Mice, but Cannot Sustain Nitric Oxide Production during Endotoxin Challenge

2018 ◽  
Vol 148 (6) ◽  
pp. 844-850 ◽  
Author(s):  
Yang Yuan ◽  
Mahmoud A Mohammad ◽  
Ancizar Betancourt ◽  
Inka C Didelija ◽  
Chandrasekar Yallampalli ◽  
...  
Keyword(s):  
Gene Expression ◽  
Nitric Oxide ◽  
Blood Pressure ◽  
Ex Vivo ◽  
Arginine Deiminase ◽  
Mesenteric Arteries ◽  
Saline Control ◽  
No Production ◽  
Endotoxin Challenge ◽  
Recycling Pathway

Abstract Background The recycling of citrulline by argininosuccinate synthase 1 (ASS1) and argininosuccinate lyase (ASL) is crucial to maintain arginine availability and nitric oxide (NO) production. Pegylated arginine deiminase (ADI-PEG20) is a bacterial enzyme used to deplete circulating arginine. Objective The goal of this research was to test the hypothesis that citrulline is able to sustain intracellular arginine availability for NO production in ADI-PEG20 arginine–depleted mice. Methods Six- to 8-wk-old male C57BL/6J mice injected with ADI-PEG20 (5 IU) or saline (control) were used in 4 different studies. Arginine, citrulline, and NO kinetics were determined by using stable isotopes in unchallenged (study 1) and endotoxin-challenged (study 2) mice. Blood pressure was determined by telemetry for 6 d after ADI-PEG20 administration (study 3), and vasomotor activity and ASS1 and ASL gene expression were determined in mesenteric arteries collected from additional mice (study 4). Results ADI-PEG20 administration resulted in arginine depletion (<1 compared with 111 ± 37 µmol/L) but in greater plasma citrulline concentrations (900 ± 123 compared with 76 ± 8 µmol/L; P < 0.001) and fluxes (402 ± 17 compared with 126 ± 4 µmol ⋅ kg−1 ⋅ h−1; P < 0.001) compared with controls. Endotoxin-challenged ADI-PEG20–treated mice produced less NO than controls (13 ± 1 compared with 27 ± 2 µmol ⋅ kg−1 ⋅ h−1; P < 0.001). No differences (P > 0.50) were observed for cardiovascular variables (heart rate, blood pressure) between ADI-PEG20–treated and control mice. Furthermore, no ex vivo vasomotor differences were observed between the 2 treatments. ADI-PEG20 administration resulted in greater gene expression of ASS1 (∼3-fold) but lower expression of ASL (–30%). Conclusion ADI-PEG20 successfully depleted circulating arginine without any effect on cardiovascular endpoints in healthy mice but limited NO production after endotoxin challenge. Therefore, the citrulline recycling pathway can sustain local arginine availability independently from circulating arginine, satisfying the demand of arginine for endothelial NO production; however, it is unable to do so when a high demand for arginine is elicited by endotoxin.

scholarly journals Cedrelopsis grevei induced hypotension and improved endothelial vasodilatation through an increase of Cu/Zn SOD protein expression

2004 ◽  
Vol 286 (2) ◽  
pp. H775-H781 ◽  
Author(s):  
Hantamalala Ralay Ranaivo ◽  
Olivier Rakotoarison ◽  
Angela Tesse ◽  
Christa Schott ◽  
Adolphe Randriantsoa ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Oral Administration ◽  
Ex Vivo ◽  
No Synthase ◽  
Mesenteric Arteries ◽  
Endothelial No Synthase ◽  
Enhanced Expression ◽  
Male Wistar Rats ◽  
Endothelium Dependent Relaxation

This study was designed to investigate the cardiovascular consequences of oral administration of Cedrelopsis grevei (CG) in normotensive rats. Experiments were designed to investigate hemodynamic parameters in vivo as well as the consequences of CG treatment on the vasoconstriction response to norepinephrine and the vasorelaxant response to ACh ex vivo in isolated aortas and small mesenteric arteries (SMA). Treatment of male Wistar rats with 80 mg/kg CG for 4 wk induced a progressive decrease in systolic blood pressure. In the aorta, CG did not significantly alter the response to norepinephrine despite the participation of extraendothelial nitric oxide (NO)-induced hyporeactivity. In the SMA, contraction to norepinephrine was not modified by CG treatment even though it enhanced the participation of endothelial NO. Endothelium-dependent relaxation to ACh was increased in both the aorta and SMA from CG-treated rats. In the aorta from CG-treated rats, the mechanism involved superoxide dismutase (SOD)- and catalase-sensitive free radical production. The latter was associated with enhanced expression of Cu/Zn SOD and endothelial NO synthase. These results suggest that oral administration of CG produces a decrease in blood pressure in normotensive rats. This hemodynamic effect was associated with enhanced endothelium-dependent relaxation and an induction of Cu/Zn SOD and endothelial NO synthase expressions in the vessel wall. They also show subtle mechanisms that compensate for the increased participation of NO to maintain unchanged agonist-induced contractility. These data provide a pharmacological basis for the empirical use of CG against cardiovascular diseases.

scholarly journals Role of endothelium-derived relaxing factor in regulation of renal hemodynamic responses

1990 ◽  
Vol 258 (3) ◽  
pp. H655-H662 ◽  
Author(s):  
J. P. Tolins ◽  
R. M. Palmer ◽  
S. Moncada ◽  
L. Raij
Keyword(s):  
Nitric Oxide ◽  
Blood Pressure ◽  
Intravenous Infusion ◽  
Soluble Guanylate Cyclase ◽  
Hemodynamic Responses ◽  
Relaxing Factor ◽  
Renal Hemodynamic ◽  
Endothelium Derived Relaxing Factor

An endothelium-derived relaxing factor (EDRF) has recently been identified as nitric oxide (NO), originating from endothelial cell metabolism of L-arginine. In vitro studies suggest that EDRF/NO stimulates soluble guanylate cyclase and increases guanosine 3',5'-cyclic monophosphate (cGMP) levels in vascular smooth muscle cells, resulting in the vasorelaxant effects of endothelium-dependent vasodilators such as acetylcholine (ACh). The importance of EDRF/NO in normal physiology or disease states remains uncertain. We therefore investigated the relationship between ACh-induced hemodynamic responses, synthesis of EDRF/NO, and changes in the rate of urinary cGMP excretion in the anesthetized rat in vivo. Intravenous infusion of ACh resulted in hypotension, maintenance of glomerular filtration rate, and renal vasodilatation. ACh induced a dose-dependent increase in urinary cGMP excretion, an effect that was not observed with equihypotensive doses of the endothelium-independent vasodilator, prostacyclin. Rates of cGMP excretion were significantly correlated with the fall in systemic blood pressure induced by ACh. Treatment with NG-monomethyl-L-arginine (L-NMMA), an inhibitor of enzymatic synthesis of nitric oxide from L-arginine, prevented the ACh-induced increase in urinary cGMP excretion as well as the systemic and renal hemodynamic effects of ACh. Plasma levels of atrial natriuretic peptide were unchanged by ACh infusion. Intravenous infusion of L-NMMA was associated with increased blood pressure and decreased basal rates of urinary cGMP excretion. This hypertensive effect was reversed by administration of L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals eNOS uncoupling and endothelial dysfunction in aged vessels

2009 ◽  
Vol 297 (5) ◽  
pp. H1829-H1836 ◽  
Author(s):  
Yang-Ming Yang ◽  
An Huang ◽  
Gabor Kaley ◽  
Dong Sun
Keyword(s):  
Nitric Oxide ◽  
Endothelial Dysfunction ◽  
Mesenteric Arteries ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
Aged Mice ◽  
Sepiapterin Reductase ◽  
Enos Uncoupling ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Endothelial nitric oxide synthase (eNOS) uncoupling is a mechanism that leads to endothelial dysfunction. Previously, we reported that shear stress-induced release of nitric oxide in vessels of aged rats was significantly reduced and was accompanied by increased production of superoxide ( 18 , 27 ). In the present study, we investigated the influence of aging on eNOS uncoupling. Mesenteric arteries were isolated from young (3 mo) and aged (24 mo) C57 BL/6J mice. The expression of eNOS protein in young vs. aged mice was not significantly different. However, the aged mice had remarkable increases in the ratio of eNOS monomers to dimers and Nω-nitro-l-arginine methyl ester-inhibitable superoxide formation. The level of nitrotyrosine in the total protein and precipitated eNOS of aged vessels was increased compared with that in young vessels. HPLC analysis indicated a reduced level of tetrahydrobiopterin (BH4), an essential cofactor for eNOS, in the mesenteric arteries of aged mice. Quantitative PCR results implied that the diminished BH4 may result from the decreased expressions of GTP cyclohydrolase I and sepiapterin reductase, enzymes involved in BH4 biosynthesis. When isolated and cannulated second-order mesenteric arteries (∼150 μm) from aged mice were treated with sepiapterin, acetylcholine-induced, endothelium-dependent vasodilation improved significantly, which was accompanied by stabilization of the eNOS dimer. These data suggest that eNOS uncoupling and increased nitrosylation of eNOS, decreased expressions of GTP cyclohydrolase I and sepiapterin reductase, and subsequent reduced BH4 bioavailability may be important contributors of endothelial dysfunction in aged vessels.

Sign in / Sign up

Export Citation Format

Share Document