Nitric Oxide-dependent Dilation Research Articles

Effect of home-based heat therapy on 24-h blood pressure and cutaneous microvascular function in post-menopausal women with hypertension

Hypertension is a leading risk factor for cardiovascular morbidity and mortality and is often accompanied by microvascular dysfunction. Despite a clear effcacy in men, standard antihypertensive medications are less effective in post-menopausal women. Consequently, adjuvant therapies are needed to improve blood pressure control and microvascular function in post-menopausal women. Heat therapy may fill this therapeutic gap as it has been shown to reduce blood pressure and improve microvascular function in healthy and certain clinical populations. Therefore, the purpose of this study was to test the hypothesis that 8 weeks of home-based heat therapy would improve 24-h blood pressure and cutaneous nitric oxide-dependent vasodilation in post-menopausal women with hypertension. Post-menopausal women (69 ± 5 y) with hypertension were randomized to 8 weeks of sham ( N = 15) or heat therapy ( N = 13). Participants immersed their lower legs ~33 cm into a circulated and temperature-controlled (sham: 35 °C; heat therapy: 42 °C) water bath 4 days per week, and 45 min per session. Blood pressure and cutaneous microvascular function and were assessed before (pre) and after (post) the 8-week intervention. Mean arterial blood pressure was measured across 24-h using an ambulatory monitor. To assess microvascular function, an intradermal microdialysis probe was inserted in the anterior aspect of the lower leg at a site directly exposed to water (immersed) and at another site not directly exposed (non-immersed). Red blood cell flux was measured (laser doppler flowmetry) during cutaneous hyperemia induced by 39 °C local heating. N(G)-nitro-L-arginine methyl ester (L-NAME; 20mM) was then infused in each probe until a nadir in red blood cell flux was achieved. Cutaneous vascular conductance was calculated as red blood cell flux divided by mean arterial pressure and normalized to maximal vasodilation (42 °C heating + 56 mM sodium nitroprusside; CVC%max). Nitric oxide-dependent dilation was calculated as the difference between CVC%max measured during the 39 °C plateau and the L-NAME nadir. Mean arterial blood pressure did not differ across time or between groups (sham: pre, 96 ± 5 mmHg vs. post, 96 ± 6 mmHg; heat therapy: pre, 97 ± 4 mmHg vs. 99 ± 7 mmHg; P = 0.5 for interaction). Cutaneous vasodilation induced by local heating did not differ across time for either group (sham: pre, 60 ± 19 CVC%max vs. post, 64 ± 12 CVC%max; heat therapy: pre, 68 ± 15 CVC%max vs. post, 63 ± 13 CVC%max) or between immersed and non-immersed sites ( P = 0.9 for interaction). Similarly, nitric oxide-dependent vasodilation did not differ across time or between sites for either group ( P = 1.0 for interaction). Taken together, 8 weeks of home-based heat therapy does not improve blood pressure or cutaneous microvascular function in post-menopausal women with hypertension. This work was supported by grants from the National Institutes of Health (T32 AG020494; R01AG059314; F32HL167556) and the American Heart Association (TPA958179). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Oxidative stress contributes to reductions in microvascular endothelial- and nitric oxide-dependent dilation in women with a history of gestational diabetes.

Women with a history of gestational diabetes mellitus (GDM) are twice as likely to develop cardiovascular disease (CVD) and ∼7 times as likely to develop type 2 diabetes as their age-matched counterparts. However, the mechanism(s) mediating these associations remain unclear. We hypothesized that endothelium- and (nitric oxide) NO-dependent dilation would be attenuated through oxidant stress mechanisms in the microvasculature of women with a history of GDM compared with control women with a history of uncomplicated pregnancy (HC). Ten HC (35 ± 4 yr) and 10 GDM (34 ± 4 yr) underwent a standard local heating protocol (42°C; 0.1°C·s-1). Two intradermal microdialysis fibers were placed in the ventral forearm for local delivery of lactated Ringer's (control) or 5 mM l-ascorbate. After full expression of the local heating response, 15 mM NG-nitro-l-arginine methyl ester (NO synthase inhibition) was perfused. Red cell flux was measured continuously by laser-Doppler flowmetry, and cutaneous vascular conductance (CVC = flux/MAP) was standardized to maximum (% CVCmax; 28 mM SNP + 43°C). Urine albumin:creatinine ratio (ACR) was measured. GDM had attenuated endothelium-dependent (GDM: 67 ± 7 vs. HC: 90 ± 4% CVCmax; P < 0.001) and NO-dependent (GDM: 54 ± 7 vs. HC: 71 ± 3% CVCmax; P = 0.001) dilation at the control site and tended to have higher urine ACR (P = 0.06). Both endothelium-dependent (R2 = 0.53, P = 0.02) and NO-dependent (R2 = 0.56, P = 0.01) dilation were related to urine ACR in GDM. l-ascorbate perfusion improved endothelium-dependent (82 ± 5% CVCmax; P = 0.03 vs. control) and NO-dependent (68 ± 5% CVCmax; P = 0.02 vs. control) dilation in GDM but had no effect in HC (P > 0.05). Otherwise healthy women with a history of GDM have attenuated microvascular endothelial function and this dysfunction is mediated, in part, by oxidative stress.NEW & NOTEWORTHY Women who have gestational diabetes during pregnancy are at greater risk for cardiovascular disease and type 2 diabetes in the decade following pregnancy. However, the mechanisms mediating this increased risk are unclear. Herein, we demonstrate that microvascular dysfunction, mediated by increase in oxidative stress, persists after pregnancy in women who had gestational diabetes, despite the remission of glucose tolerance.

Activation of the Central Renin-Angiotensin System Causes Local Cerebrovascular Dysfunction.

Hypertension is a leading risk factor for cerebrovascular disease and loss of brain health. While the brain renin-angiotensin system (RAS) contributes to hypertension, its potential impact on the local vasculature is unclear. We tested the hypothesis that activation of the brain RAS would alter the local vasculature using a modified deoxycorticosterone acetate (DOCA) model. C57BL/6 mice treated with DOCA (50 mg SQ; or shams) were given tap H2O and H2O with 0.9% NaCl for 1 to 3 weeks. In isolated cerebral arteries and parenchymal arterioles from DOCA-treated male mice, endothelium- and nitric oxide-dependent dilation was progressively impaired, while mesenteric arteries were unaffected. In contrast, cerebral endothelial function was not significantly affected in female mice treated with DOCA. In males, mRNA expression of renal Ren1 was markedly reduced while RAS components (eg, Agt and Ace) were increased in both brain and cerebral arteries with central RAS activation. In NZ44 reporter mice expressing GFP (green fluorescent protein) driven by the angiotensin II type 1A receptor (Agtr1a) promoter, DOCA increased GFP expression ≈3-fold in cerebral arteries. Impaired endothelial responses were restored to normal by losartan, an AT1R (angiotensin II type 1 receptor) antagonist. Last, DOCA treatment produced inward remodeling of parenchymal arterioles. These findings suggest activation of the central and cerebrovascular RAS impairs endothelial (nitric oxide dependent) signaling in brain through expression and activation of AT1R and sex-dependent effects. The central RAS may be a key contributor to vascular dysfunction in brain in a preclinical (low renin) model of hypertension. Because the brain RAS is also activated during aging and other diseases, a common mechanism may promote loss of endothelial and brain health despite diverse cause.

Connexins: Key Players in the Control of Vascular Plasticity and Function.

Of the 21 members of the connexin family, 4 (Cx37, Cx40, Cx43, and Cx45) are expressed in the endothelium and/or smooth muscle of intact blood vessels to a variable and dynamically regulated degree. Full-length connexins oligomerize and form channel structures connecting the cytosol of adjacent cells (gap junctions) or the cytosol with the extracellular space (hemichannels). The different connexins vary mainly with regard to length and sequence of their cytosolic COOH-terminal tails. These COOH-terminal parts, which in the case of Cx43 are also translated as independent short isoforms, are involved in various cellular signaling cascades and regulate cell functions. This review focuses on channel-dependent and -independent effects of connexins in vascular cells. Channels play an essential role in coordinating and synchronizing endothelial and smooth muscle activity and in their interplay, in the control of vasomotor actions of blood vessels including endothelial cell reactivity to agonist stimulation, nitric oxide-dependent dilation, and endothelial-derived hyperpolarizing factor-type responses. Further channel-dependent and -independent roles of connexins in blood vessel function range from basic processes of vascular remodeling and angiogenesis to vascular permeability and interactions with leukocytes with the vessel wall. Together, these connexin functions constitute an often underestimated basis for the enormous plasticity of vascular morphology and function enabling the required dynamic adaptation of the vascular system to varying tissue demands.

Deficiency of T-type voltage-gated calcium channels results in attenuated weight gain and improved endothelium-dependent dilatation of resistance vessels induced by a high-fat diet in mice.

The deletion of T-type Cav3.1 channels may reduce high-fat diet (HFD)-induced weight gain, which correlates positively with obesity and endothelial dysfunction. Therefore, experiments were designed to study the involvement of T-type Cav3.1 channels in HFD-induced endothelial dysfunction in mice. Wildtype (WT) and Cav3.1-/- mice were fed either a normal diet (ND) or an HFD for 8weeks. Body composition was assessed, and thoracic aortae and mesenteric arteries were harvested for myography to assess endothelium-dependent responses. Changes in intracellular calcium were measured by fluorescence imaging, and behavior was assessed with the open-field test. Cav3.1-/- mice had attenuated HFD-induced weight gain and lower total fat mass compared with WT mice. Cav3.1-/- mice on an HFD had reduced plasma cholesterol levels compared with WT mice on the same diet. Increased feeding efficiency, independent of food intake, was observed in WT mice on an HFD compared with an ND, but no difference in feeding efficiency between diets was observed for Cav3.1-/- mice. Nitric oxide-dependent dilatation was increased in mesenteric arteries of Cav3.1-/- mice compared with WT mice on an HFD, with no difference observed in aortae. No differences in mouse locomotor activity were observed between the experimental groups. Mice on an HFD lacking T-type channels have reduced weight gain, lower total cholesterol levels, and increased dilatation of resistance vessels compared with WT mice on an HFD, suggesting that Cav3.1 deletion protects against endothelial dysfunction in resistance vessels but not in large conduit vessels.

High salt intake shifts the mechanisms of flow-induced dilation in the middle cerebral arteries of Sprague-Dawley rats.

The goal of the present study was to examine the effect of 1 wk of high salt (HS) intake and the role of oxidative stress in changing the mechanisms of flow-induced dilation (FID) in isolated pressurized middle cerebral arteries of male Sprague-Dawley rats ( n = 15-16 rats/group). Reduced FID in the HS group was restored by intake of the superoxide scavenger tempol (HS + tempol in vivo group). The nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester, cyclooxygenase inhibitor indomethacin, and selective inhibitor of microsomal cytochrome P-450 epoxidase activity N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide significantly reduced FID in the low salt diet-fed group, whereas FID in the HS group was mediated by NO only. Cyclooxygenase-2 mRNA (but not protein) expression was decreased in the HS and HS + tempol in vivo groups. Hypoxia-inducible factor-1α and VEGF protein levels were increased in the HS group but decreased in the HS + tempol in vivo group. Assessment by direct fluorescence of middle cerebral arteries under flow revealed significantly reduced vascular NO levels and increased superoxide/reactive oxygen species levels in the HS group. These results suggest that HS intake impairs FID and changes FID mechanisms to entirely NO dependent, in contrast to the low-salt diet-fed group, where FID is NO, prostanoid, and epoxyeicosatrienoic acid dependent. These changes were accompanied by increased lipid peroxidation products in the plasma of HS diet-fed rats, increased vascular superoxide/reactive oxygen species levels, and decreased NO levels, together with increased expression of hypoxia-inducible factor-1α and VEGF. NEW & NOTEWORTHY High-salt (HS) diet changes the mechanisms of flow-induced dilation in rat middle cerebral arteries from a combination of nitric oxide-, prostanoid-, and epoxyeicosatrienoic acid-dependent mechanisms to, albeit reduced, a solely nitric oxide-dependent dilation. In vivo reactive oxygen species scavenging restores flow-induced dilation in HS diet-fed rats and ameliorates HS-induced increases in the transcription factor hypoxia-inducible factor-1α and expression of its downstream target genes.

Effect of short-term estrogen therapy on endothelial function: a double-blinded, randomized, controlled trial

Objective: To evaluate the effect of short-term hormone replacement therapy with 0.625 mg conjugated estrogens daily on endothelial function of healthy postmenopausal women, using flow-mediated dilation (FMD) of the brachial artery.Methods: We performed a double-blinded, randomized, controlled trial over 3 years. Randomization was performed using computer-generated sorting. All participants were blinded to the use of conjugated equine estrogens (CEE) or placebo and FMD was assessed by a blinded examiner, before and after 28 days of medication. A total of 64 healthy postmenopausal women were selected and randomly assigned into two groups of treatment: 0.625 mg of CEE or placebo.Results: FMD values were statistically different between the groups (p = 0.025): the group receiving CEE showed a FMD value of 0.011 compared to the placebo group (FMD = −0.082). The two groups were additionally evaluated for homogeneity through the Shapiro–Wilk test in respect to variables that could interfere with endothelial function such as age (p = 0.729), body mass index (p = 0.891), and time since menopause (p = 0.724). Other variables were excluded during selection of the participants such as chronic vascular conditions, smoking, and sedentary lifestyle.Conclusion: Our results demonstrate that the administration of 0.625 mg CEE for 28 days is effective in improving vascular nitric oxide-dependent dilation assessed by FMD of the brachial artery in postmenopausal women.Clinical trial registration: NCT01482416

Passive heat therapy improves cutaneous microvascular function in sedentary humans via improved nitric oxide-dependent dilation.

Passive heat therapy (repeated hot tub or sauna use) reduces cardiovascular risk, but its effects on the mechanisms underlying improvements in microvascular function have yet to be studied. We investigated the effects of heat therapy on microvascular function and whether improvements were related to changes in nitric oxide (NO) bioavailability using cutaneous microdialysis. Eighteen young, sedentary, otherwise healthy subjects participated in 8 wk of heat therapy (hot water immersion to maintain rectal temperature ≥38.5°C for 60 min/session; n = 9) or thermoneutral water immersion (sham, n = 9), and participated in experiments before and after the 8-wk intervention in which forearm cutaneous hyperemia to 39°C local heating was assessed at three microdialysis sites receiving 1) Lactated Ringer's (Control), 2) N(ω)-nitro-l-arginine (l-NNA; nonspecific NO synthase inhibitor), and 3) 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol), a superoxide dismutase mimetic. The arm used for microdialysis experiments remained out of the water at all times. Data are means ± SE cutaneous vascular conductance (CVC = laser Doppler flux/mean arterial pressure), presented as percent maximal CVC (% CVCmax). Heat therapy increased local heating plateau from 42 ± 6 to 53 ± 6% CVCmax (P < 0.001) and increased NO-dependent dilation (difference in plateau between Control and l-NNA sites) from 26 ± 6 to 38 ± 4% CVCmax (P < 0.01), while no changes were observed in the sham group. When data were pooled across all subjects at 0 wk, Tempol had no effect on the local heating response (P = 0.53 vs. Control). There were no changes at the Tempol site across interventions (P = 0.58). Passive heat therapy improves cutaneous microvascular function by improving NO-dependent dilation, which may have clinical implications.

Genetic Deletion of P2Y 2 Receptor Induces Vascular Endothelial Dysfunction but not Large Artery Stiffening in Mice

The G-protein coupled and UTP/ATP-sensitive P2Y2 receptor has been linked to production of nitric oxide (NO) and prostaglandins in numerous cell types including endothelial and vascular smooth muscle cells. We hypothesized that genetic deletion of P2Y2 would induce generalized dysfunction in arteries. We measured endothelium dependent dilation to acetylcholine (ACh) in the presence or absence of the NO inhibitor, L-NAME, in large central (carotid) and small peripheral (gastrocnemius feed) arteries (N = 15) isolated from 5 – 8 months old P2Y2 deficient (-/-) or wild type (WT) mice. Maximal vasodilation to ACh was blunted in both carotid (Car) and gastrocnemius (Gas) feed arteries in the P2Y2 -/- compared to WT (Car: 88 ± 1 vs. 97 ± 2%; Gast: 86 ± 3 vs. 97 ± 2%; both p<0.05). L-NAME significantly reduced vasodilation in arteries from both groups (p<0.05), but abolished differences between P2Y2-/- and WT, indicating blunted NO dependent dilation in P2Y2-/- arteries. Smooth muscle function, assessed by dilation to sodium nitroprusside, was similar between P2Y2-/- and WT (Car: 98 ± 1 vs. 95 ± 2%; Gast: 91 ± 3 vs. 90 ± 2%; both p>0.05). Despite endothelial dysfunction in P2Y2-/- mice, in vivo large artery stiffness assessed via pulse wave velocity was similar between groups (p>0.05). Thus, deletion of the P2Y2 receptor induces endothelial dysfunction and reduces NO bioavailability in large and small arteries but does not impact smooth muscle vasodilation or large artery stiffness.

Rottlerin-Induced BKCa Channel Activation Impairs Specific Contractile Responses and Promotes Vasodilation

Activation of large conductance calcium-activated potassium (BKCa) channels is cardioprotective for ischemic injury and can enhance vasorelaxation. Rottlerin has recently been identified as a potent BKCa activator. We demonstrated that rottlerin improves cardiac function and increases coronary flow when used as a cardioplegia additive in rat and mouse models of cardioplegic arrest and reperfusion. In this study we examined the effectiveness and specificity of the putative BKCa activator rottlerin on vascular reactivity in response to specific contractile and dilatory agonists. Aortic rings from wild-type (wt) and BKCa knock-out (KO) mice were mounted in a tissue bath with force transducers. The vasodilatory effect of rottlerin was evaluated after pre-constriction with U46619. Dose responses to the contractile agonists U46619 and phenylephrine (PE), and vasodilation responses to rottlerin, hydrogen sulfide (H2S), and sodium nitroprusside (SNP) were performed after pretreatment with rottlerin. Similar studies were performed in pig coronary vessels. The BKCa KO mouse aortic rings exhibited spontaneous contraction and had greater contractile responses to U46619 and reduced vasodilation to SNP compared with wt mice. The wt and KO responses to phenylephrine were similar. Rottlerin dose dependently dilated wild-type vessels, but not in BKCa KO animals. Pretreatment with rottlerin caused depressed U46619 responses, but had no effect on PE, SNP, or H2S-mediated responses. However, pig coronary vessels pretreated with rottlerin exhibited reduced contractile responses and enhanced nitric oxide-dependent dilation. Rottlerin directly causes vasodilation through BKCa channel dependent mechanisms. The BKCa channel activator pretreatment enhances vasodilatory responses and impairs specific vasoconstrictive agonists.

The effects of obesity on the cerebral vasculature.

The incidence of obesity in the population is increasing at an alarming rate, with this comes an increased risk of insulin resistance (IR). Obesity and IR increase an individual's risk of having a stroke and they have been linked to several forms of dementia. Stroke and dementia are associated with, or exacerbated by, reduced cerebral blood flow, which has recently been described in obese patients. In this review we will discuss the effects of obesity on cerebral artery function and structure. Regarding their function, we will focus on the endothelium and nitric oxide (NO) dependent dilation. NO dependent dilation is impaired in cerebral arteries from obese rats, and the majority of evidence suggests this is a result of increased oxidative stress. We will also describe the limited studies showing that inward cerebral artery remodeling occurs in models of obesity, and that the remodeling is associated with an increase in the damage caused by cerebral ischemia. We will also discuss some of the more paradoxical findings associated with stroke and obesity, including the evidence that obesity is a positive factor for stroke survival. Finally we will discuss the evidence that links these changes in vascular structure and function to cognitive decline and dementia.

Gene deletion of protein tyrosine phosphatase 1B limits cardiovascular dysfunction and mortality during endotoxinic shock

Sepsis-associated cardiovascular dysfunction is one of the main causes of mortality in critically ill patients. PTP1B is negative regulator of insulin signaling and endothelial Nitric Oxide (NO) production, two mechanisms likely involved in the pathogenesis of sepsis. We recently showed that gene deletion or pharmacological inhibition of PTP1B improves endothelial dysfunction and reduces the severity of heart failure. The aim of the present study was to assess the effect of PTP1B gene deletion on lipopolysaccharide (LPS)-induced cardiovascular dysfunction and mortality in mice. PTP1B-/- or wild-type (WT) mice received LPS (15mg/kg) or vehicle followed by subcutaneous saline resuscitation (30ml/kg). LPS significantly enhanced cardiac and arterial PTP1B mRNA expression. Compared with WT, PTP1B-/- mice displayed markedly reduced mortality (Survival 4 days after LPS: WT: 0%; PTP1B-/- 70%, p<0.01), associated with a higher locomotor activity. Evaluation of vascular function 8h after LPS in isolated mesenteric resistance arteries (arteriograph system) showed that PTP1B-/- LPS mice had improved contractile response to phenylephrine, and restored flow mediated, NO dependent-dilatation (% dilatation to 200μl/min: WT 6,3±3; PTP1B-/- 16,5±2, p<0.05) associated with significant increases in phosphorylation of Akt and eNOS, and reduced mRNA expression of VCAM-1, ICAM-1, COX-2, IL-1β, iNOS and Gp91phox (PCR). Evaluation of left ventricular (LV) function by echocardiography, and pressure-volume curves 8h after LPS revealed reduced cardiac dysfunction in PTP1B-/- mice as shown by an increased LV fractional shortening (WT 17,3±1; PTP1B-/- 24±1, p<0.05) and LV end systolic pressure-volume relation (WT 16±2; PTP1B-/- 20±2, p<0.05) together with reduced LV end diastolic pressure-volume relation (WT 4,7±1,7; PTP1B-/- 2.4±0.9 mmHg/RVU, p<0.05). Improved cardiac contractility was also observed ex-vivo in hearts isolated and perfused 8h after LPS (LV Developed Pressure: WT 25±5; PTP1B-/- 50±5 mmHg, p<0.05). Improved cardiac function was associated with significant decreases in myocardial markers of inflammation and oxidative stress (VCAM-1, ICAM-1, CD45, IL-1β, TNF-α and Gp91phox), reduced P38 and ERK1/2 phosphorylation and limited decrease of phospholamban phosphorylation (WT -42%; PTP1B-/- -22.8, p<0.05). Thus, we demonstrate for the first time that PTP1B gene deletion protects against lipopolysaccharide-induced cardiovascular dysfunction and mortality. These results suggest that PTP1B is an attractive target for the treatment of sepsis.

Differential vulnerability of skeletal muscle feed arteries to dysfunction in insulin resistance: impact of fiber type and daily activity

Functional and structural heterogeneity exists among skeletal muscle vascular beds related, in part, to muscle fiber type composition. This study was designed to delineate whether the vulnerability to vascular dysfunction in insulin resistance is uniformly distributed among skeletal muscle vasculatures and whether physical activity modifies this vulnerability. Obese, hyperphagic Otsuka Long-Evans Tokushima fatty rats (20 wk old) were sedentary (OSED) or physically active (OPA; access to running wheels) and compared with age-matched sedentary Long-Evans Tokushima Otsuka (LSED) rats. Vascular responses were determined in isolated, pressurized feed arteries from fast-twitch gastrocnemius (GFAs) and slow-twitch soleus (SFAs) muscles. OSED animals were obese, insulin resistant, and hypertriglyceridemic, traits absent in LSED and OPA rats. GFAs from OSED animals exhibited depressed dilation to ACh, but not sodium nitroprusside, and enhanced vasoconstriction to endothelin-1 (ET-1), but not phenylephrine, compared with those in LSED. Immunoblot analysis suggests reduced endothelial nitric oxide synthase phosphorylation at Ser1177 and endothelin subtype A receptor expression in OSED GFAs. Physical activity prevented reduced nitric oxide-dependent dilation to ACh, but not enhanced ET-1 vasoconstriction, in GFA from OPA animals. Conversely, vasoreactivity of SFAs to ACh and ET-1 were principally similar in all groups, whereas dilation to sodium nitroprusside was enhanced in OSED and OPA rats. These data demonstrate, for the first time, that SFAs from insulin-resistant rats exhibit reduced vulnerability to dysfunction versus GFAs and that physical activity largely prevents GFA dysfunction. We conclude that these results demonstrate that vascular dysfunction associated with insulin resistance is heterogeneously distributed across skeletal muscle vasculatures related, in part, to muscle fiber type and activity level.

Angiotensin-(1-7) and low-dose angiotensin II infusion reverse salt-induced endothelial dysfunction via different mechanisms in rat middle cerebral arteries

The goals of this study were to 1) determine the acute effect of ANG-(1-7) on vascular tone in isolated middle cerebral arteries (MCAs) from Sprague-Dawley rats fed a normal salt (NS; 0.4% NaCl) diet, 2) evaluate the ability of chronic intravenous infusion of ANG-(1-7) (4 ng·kg(-1)·min(-1)) for 3 days to restore endothelium-dependent dilation to acetylcholine (ACh) in rats fed a high-salt (HS; 4% NaCl) diet, and 3) determine whether the amelioration of endothelial dysfunction by ANG-(1-7) infusion in rats fed a HS diet is different from the protective effect of low-dose ANG II infusion in salt-fed rats. MCAs from rats fed a NS diet dilated in response to exogenous ANG-(1-7) (10(-10)-10(-5) M). Chronic ANG-(1-7) infusion significantly reduced vascular superoxide levels and restored the nitric oxide-dependent dilation to ACh (10(-10)-10(-5) M) that was lost in MCAs of rats fed a HS diet. Acute vasodilation to ANG-(1-7) and the restoration of ACh-induced dilation by chronic ANG-(1-7) infusion in rats fed a HS diet were blocked by the Mas receptor antagonist [D-ALA(7)]-ANG-(1-7) or the ANG II type 2 receptor antagonist PD-123319 and unaffected by ANG II type 1 receptor blockade with losartan. The restoration of ACh-induced dilation in MCAs of HS-fed rats by chronic intravenous infusion of ANG II (5 ng·kg(-1)·min(-1)) was blocked by losartan and unaffected by d-ALA. These findings demonstrate that circulating ANG-(1-7), working via the Mas receptor, restores endothelium-dependent vasodilation in cerebral resistance arteries of animals fed a HS diet via mechanisms distinct from those activated by low-dose ANG II infusion.

Endothelial dysfunction and vascular inflammation in Type 2 diabetes: interaction of AGE/RAGE and TNF-α signaling

the receptor for advanced glycation end products (RAGE) interacts with a diverse range of endogenous ligands termed advanced glycation end products (AGEs), which are formed by the Maillard reaction, a nonenzymatic process linking reducing sugar groups to proteins, lipids, and nucleic acids. AGEs

Protecting the Brain With eNOS

See related article, pages 1132–1140 Nitric oxide (NO) plays a major role in both vascular and neural biology in health and disease. This concept is exemplified when one examines the role of NO in the brain and the cerebral circulation. NO is a potent vasodilator, and blood vessels in the brain are normally exposed to NO from 2 major sources—endothelium and neurons. Acting as a messenger molecule, NO mediates the majority of endothelium-dependent responses in the brain.1 The source of this NO is the endothelial isoform of NO synthase (eNOS). This prominent role for NO has been observed in a variety of blood vessels from multiple species including humans.1–3 Through this signaling mechanism, NO influences resting vascular tone and mediates responses to varied stimuli, including endothelium-dependent agonists and increases in blood flow (Figure).1,4,5 In addition, eNOS inhibits vasoconstrictor responses and cerebral vasospasm6–8 and can affect permeability of cerebral endothelium, the blood-brain barrier (Figure).9 eNOS normally inhibits cerebral vascular growth or hypertrophy (Figure),10 a structural change that can have functional consequences by impairing of maximal vasodilator capacity. Impairment of NO-mediated signaling is a key underlying mechanism of vascular dysfunction in diverse forms of disease and aging.1,11–13 Impairment of these eNOS-dependent mechanisms in the presence of cardiovascular risk factors may contribute to …

Editorial Comment: eNOS: Can We Exploit the Good?

HomeStrokeVol. 36, No. 1Editorial Comment: eNOS: Can We Exploit the Good? Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBEditorial Comment: eNOS: Can We Exploit the Good? Frank M. Faraci, PhD Frank M. FaraciFrank M. Faraci Departments of Internal Medicine and Pharmacology, Cardiovascular Center, University of Iowa Carver College of Medicine, Iowa City, Iowa Search for more papers by this author Originally published1 Jan 2005https://doi.org/10.1161/01.str.0000152179.37900.8dStroke. 2005;36:160–161One of the major functions of vascular endothelium is to regulate tone of underlying smooth muscle. This function is mediated in large part by release of diverse endothelium-derived relaxing factors (EDRFs).1,2 A major EDRF that regulates both cerebral vascular function and structure is nitric oxide (NO) produced by the endothelial isoform of NO synthase (eNOS).1,3 Most studies indicate that NO is the predominant EDRF in the cerebral circulation.1 Although dozens of studies in animal models support this view, it is important to recall that NO is also a major EDRF in both large arteries and microvessels in the human brain.1,4In the present study by Sorenson et al,5 the investigators examined effects of gene transfer of a mutant form of eNOS (S1179DeNOS) that is constitutively active (ie, active in the absence of agonist induced stimulation) on vascular function in human pial arteries obtained at the time of surgery. Because eNOS has many beneficial effects within the vessel wall, it was of interest to examine effects of expression of S1179DeNOS on vascular function.Expression of S1179DeNOS increased basal levels of cyclic GMP, a key second messenger in relation to NO-mediated signaling, and reduced responses to an endothelium-dependent agonist and an NO donor. Reduced responses to NO in vessels that express S1179DeNOS probably reflects a compensatory response within vascular muscle because of increase basal levels of NO.Reduced responses to NO in these experiments did not appear to be mediated by oxidative stress as a scavenger of the free radical superoxide had no effect on impaired responses. This observation is important as increased activity of eNOS could potentially deplete enzyme substrate (l-arginine) or cofactors (ie, tetrahydrobiopterin), resulting in ‘uncoupling’ of eNOS and production of superoxide rather than NO.The use of viral-mediated gene transfer of NOS isoforms to study the impact of NO on the vasculature is a relatively recent experimental approach. The strategy allows testing of basic biology of the vasculature but is also attractive as it may lay the framework, or at least establish proof-of-principle, for future therapeutic applications using viral vectors. To my knowledge, only two studies have used adenoviral vectors to express any gene in human cerebral arteries.6,7 The present work suggests that gene transfer of a constitutively active form of eNOS alters vascular function in these arteries. Because the vector used appears to increase basal levels of NO without increasing superoxide levels, it may have beneficial effects in models of cerebral vascular disease. This latter possibility remains to be tested.References1 Faraci FM, Heistad DD. Regulation of the cerebral circulation: role of endothelium. Physiological Reviews. 1998; 78: 53–97.CrossrefMedlineGoogle Scholar2 Bryan RM, You J, Golding EM, Marrelli SP. Endothelium-derived hyperpolarizing factor: a cousin to nitric oxide and prostacyclin. Anesthesiology. (In press).Google Scholar3 Baumbach GL, Sigmund CD, Faraci FM. Structure of cerebral arterioles in mice deficient in expression of the gene for endothelial NO synthase. Circulation Res. 2004; 95: 822–829.LinkGoogle Scholar4 Elhusseiny A, Hamel E. Muscarinic –but not nicotinic –acetylcholine receptors mediate a nitric oxide-dependent dilation in brain cortical arterioles: a possible role for the M5 receptor subtype. J Cerebral Blood Flow Metabol. 2000; 20: 298–305.CrossrefMedlineGoogle Scholar5 Sorenson J, Santhanam AVR, Smith LA, Akiyama M, Sessa WC, Katusic ZS. Expression and function of recombinant S1179D endothelial nitric oxide synthase in human pial arteries. Stroke. 2005; 36: 158–160.LinkGoogle Scholar6 Khurana VG, Smith LA, Weiler DA, Springett MJ, Parisi JE, Meyer FB, Marsh WR, O’Brien T, Katusic ZS. Adenovirus-mediated gene transfer to human cerebral arteries. J Cerebral Blood Flow Metabol. 2000; 20: 1360–1371.CrossrefMedlineGoogle Scholar7 Gunnett CA, Lund DD, Howard MA, Chu Y, Faraci FM, Heistad DD. Gene transfer of inducible nitric oxide synthase impairs relaxation in human and rabbit cerebral arteries. Stroke. 2002; 33: 2292–2296.LinkGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails January 2005Vol 36, Issue 1 Advertisement Article InformationMetrics https://doi.org/10.1161/01.str.0000152179.37900.8dPMID: 15618450 Originally publishedJanuary 1, 2005 PDF download Advertisement

17beta-estradiol increases nitric oxide-dependent dilation in rat pulmonary arteries and thoracic aorta.

Past studies have demonstrated that 17beta-estradiol (E(2)beta) increases endothelial nitric oxide (NO) synthase (eNOS) activity in uterine, heart, and skeletal muscle and in cultured human endothelial cells. However, little is known about E(2)beta regulation of NO synthesis in the pulmonary vasculature. The present study evaluated E(2)beta regulation of eNOS function in pulmonary arteries and thoracic aortas. We hypothesized that E(2)beta upregulates vascular NO release by increasing eNOS expression. To test this, NO-dependent vasodilation was assessed in isolated perfused lungs and aortic rings from ovariectomized Sprague-Dawley rats treated for 1 wk with 20 microg/24 h of E(2)beta or vehicle. Expression of eNOS was evaluated by Western blot and immunohistochemistry. Also, a RNase protection assay determined eNOS mRNA levels in lung and aortic homogenates from control and treated rats. Vasodilation to ionomycin in lungs from the E(2)beta-treated group was enhanced compared with that in control animals. Endothelium-intact aortic rings from E(2)beta-treated animals also demonstrated augmented endothelium-dependent dilation. Both responses were blocked with NOS inhibition. Immunostaining for eNOS was greater in pulmonary arteries and aortas from E(2)beta-treated compared with control rats. However, mRNA levels did not differ between groups. Thus we conclude that in vivo E(2)beta treatment augments endothelium-dependent dilation in aorta and lung, increasing expression of eNOS independently of sustained augmented gene transcription.

Paradoxical increase in coronary flow velocity after termination of acetylcholine infusion is a marker of the impaired vasodilatation at coronary microvessels in patients with angina and normal coronary arteries.

Some patients with anginal chest pain and normal coronary arteries exhibit a paradoxical increase in coronary flow velocity after termination of acetylcholine infusion. The aim of this study was to investigate whether this paradoxical increase in the flow velocity is associated with the impaired microvascular dilatation to pharmacological stimuli. We infused graded doses of endothelium-dependent vasodilator acetylcholine (10, 50, and 100 microg/min for 2 min) and the endothelium-independent vasodilators, papaverine and nitroglycerin, into the left coronary artery in 15 patients with chest pain and normal coronary arteries. Coronary blood flow responses were evaluated by Doppler guidewire and quantitative angiography in the proximal left anterior descending coronary artery. Seven patients showed a paradoxical increase in coronary flow velocity after termination of acetylcholine infusion with the highest dose (100 microg/min), whereas eight showed no change or a decrease in the flow velocity. This was also observed in 50 microg/min of acetylcholine infusion. In patients with a paradoxical increase in the flow velocity, coronary flow velocity responses to acetylcholine during three graded doses were significantly blunted in comparison to those without a paradoxical increase. In contrast, coronary flow reserve to papaverine and nitroglycerin was similar in the two groups. Epicardial artery vasoreactivity to acetylcholine did not differ between the two groups. Papaverine and nitroglycerin also caused a similar degree of coronary dilatation in both groups. These results suggest that the paradoxical increase in coronary flow velocity observed immediately after termination of the intracoronary acetylcholine infusion is a marker of impaired nitric oxide-dependent dilatation of the coronary microvessels in patients with normal coronary arteries. Cathet. Cardiovasc. Intervent. 48:170-177, 1999.

Cardiopulmonary responses of male and female swine to simulated high altitude.

Cardiopulmonary responses of male and female swine to simulated high altitude.