Maximal Vasodilation Research Articles

Abstract 138: Angiotensin Converting Enzyme (ACE) Inhibition Reverses Vasoconstriction and Impaired Dilation of Pial Collaterals During Chronic Hypertension

Introduction: Leptomeningeal anastomoses (LMAs) are pial collaterals that perfuse the penumbra and are important for stroke outcome. In the current study, we investigated mechanisms by which hypertension causes LMA vasoconstriction that is known to limit the amount of salvageable tissue when stroke occurs during chronic hypertension. We hypothesized that increased vasoreactivity of LMAs from hypertensive rats is angiotensin II (Ang II)-dependent. Methods: Spontaneously hypertensive rats (SHRs, n=8/group) were treated with the ACE inhibitor captopril, hydralazine to lower blood pressure (BP) independent of AngII, or vehicle for 5 weeks in drinking water. A group of normotensive Wistar rats (n=8) had regular drinking water served as controls. BP was measured twice weekly by tail cuff. LMAs were isolated and studied in pressurized conditions. Vasoactivity of LMAs, including myogenic responses, reactivity to the Rho-kinase inhibitor Y-27632 and nitric oxide (NO) were measured. Results: Both captopril and hydralazine lowered BP in SHRs similar to Wistar rats. LMAs from untreated SHRs had increased myogenic tone vs. Wistar that was normalized by captopril but not hydralazine (Fig. 1A). LMAs from all groups constricted similarly to NO synthase inhibition; however, the vasodilatory response of LMAs to the NO donor sodium nitroprusside, was impaired in SHRs vs. Wistar rats that was restored by captopril and not hydralazine (Fig. 1B). Maximum vasodilatory response of LMAs to Y-27632 was impaired in SHRs compared to Wistar rats (28±3% vs. 81±4%, p<0.01) that was restored by captopril (84±5%) and partially by hydralazine (59±4%) treatment. Conclusions: ACE inhibition during chronic hypertension reversed vascular dysfunction and hyperconstriction of LMAs, an effect that could improve stroke outcome by increasing collateral perfusion. In addition, lowering BP alone without inhibition of Ang II, may not provide the same protective effect on pial collaterals.

Regional contributions of nitric oxide synthase to cholinergic cutaneous vasodilatation and sweating in young men.

What is the central question of this study? We evaluated whether regional variations exist in NO-dependent cutaneous vasodilatation and sweating during cholinergic stimulation. What is the main finding and its importance? Peak cutaneous vasodilatation and sweating were greater on the torso than the forearm. Furthermore, we found that NO was an important modulator of cholinergic cutaneous vasodilatation, but not sweating, across body regions, with a greater contribution of NO to cutaneous vasodilatation in the limb compared with the torso. These findings advance our understanding of the mechanisms influencing regional variations in cutaneous vasodilator and sweating responses to pharmacological stimulation. Regional variations in cutaneous vasodilatation and sweating exist across the body. Nitric oxide (NO) is an important modulator of these heat loss responses in the forearm. However, whether regional differences in NO-dependent cutaneous vasodilatation and sweating exist remain uncertain. In 14 habitually active young men (23±4years of age), cutaneous vascular conductance (CVC%max ) and local sweat rates were assessed at six skin sites. On each of the dorsal forearm, chest and upper back (trapezius), sites were continuously perfused with either lactated Ringer solution (control) or 10mmNω -nitro-l-arginine (l-NNA; an NO synthase inhibitor) dissolved in Ringer solution, via microdialysis. At all sites, cutaneous vasodilatation and sweating were induced by co-administration of the cholinergic agonist methacholine (1, 10, 100, 1000 and 2000mm; 25min per dose) followed by 50mm sodium nitroprusside (20-25min) to induce maximal vasodilatation. The l-NNA attenuated CVC%max relative to the control conditions for all regions (all P<0.05), and NO-dependent vasodilatation was greater at the forearm compared with the back and chest (both P<0.05). Furthermore, maximal vasodilatation was higher at the back and chest relative to the forearm (both P<0.05). Conversely, l-NNA had negligible effects on sweating across the body (all P>0.05). Peak local sweat rate was higher at the back relative to the forearm (P<0.05), with a similar trend observed for the chest. In habitually active young men, NO-dependent cholinergic cutaneous vasodilatation varied across the body, and the contribution to cholinergic sweating was negligible. These findings advance our understanding of the mechanisms influencing regional variations in cutaneous vasodilatation and sweating during pharmacological stimulation.

Sub-segmental quantification of single (stress)-pass perfusion CMR improves the diagnostic accuracy for detection of obstructive coronary artery disease

BackgroundMyocardial perfusion with cardiovascular magnetic resonance (CMR) imaging is an established diagnostic test for evaluation of myocardial ischaemia. For quantification purposes, the 16 segment American Heart Association (AHA) model poses limitations in terms of extracting relevant information on the extent/severity of ischaemia as perfusion deficits will not always fall within an individual segment, which reduces its diagnostic value, and makes an accurate assessment of outcome data or a result comparison across various studies difficult. We hypothesised that division of the myocardial segments into epi- and endocardial layers and a further circumferential subdivision, resulting in a total of 96 segments, would improve the accuracy of detecting myocardial hypoperfusion. Higher (sub-)subsegmental recording of perfusion abnormalities, which are defined relatively to the normal reference using the subsegment with the highest value, may improve the spatial encoding of myocardial blood flow, based on a single stress perfusion acquisition.ObjectiveA proof of concept comparison study of subsegmentation approaches based on transmural segments (16 AHA and 48 segments) vs. subdivision into epi- and endocardial (32) subsegments vs. further circumferential subdivision into 96 (sub-)subsegments for diagnostic accuracy against invasively defined obstructive coronary artery disease (CAD).MethodsThirty patients with obstructive CAD and 20 healthy controls underwent perfusion stress CMR imaging at 3 T during maximal adenosine vasodilation and a dual bolus injection of 0.1 mmol/kg gadobutrol. Using Fermi deconvolution for blood flow estimation, (sub-)subsegmental values were expressed relative to the (sub-)subsegment with the highest flow. In addition, endo−/epicardial flow ratios were calculated based on 32 and 96 (sub-)subsegments. A receiver operating characteristics (ROC) curve analysis was performed to compare the diagnostic performance of discrimination between patients with CAD and healthy controls. Observer reproducibility was assessed using Bland-Altman approaches.ResultsSubdivision into more and smaller segments revealed greater accuracy for #32, #48 and # 96 compared to the standard #16 approach (area under the curve (AUC): 0.937, 0.973 and 0.993 vs 0.820, p < 0.05). The #96-based endo−/epicardial ratio was superior to the #32 endo−/epicardial ratio (AUC 0.979, vs. 0.932, p < 0.05). Measurements for the #16 model showed marginally better reproducibility compared to #32, #48 and #96 (mean difference ± standard deviation: 2.0 ± 3.6 vs. 2.3 ± 4.0 vs 2.5 ± 4.4 vs. 4.1 ± 5.6).ConclusionsSubsegmentation of the myocardium improves diagnostic accuracy and facilitates an objective cut-off-based description of hypoperfusion, and facilitates an objective description of hypoperfusion, including the extent and severity of myocardial ischaemia. Quantification based on a single (stress-only) pass reduces the overall amount of gadolinium contrast agent required and the length of the overall diagnostic study.

Effect of a Strategy of Comprehensive Vasodilation vs Usual Care on Mortality and Heart Failure Rehospitalization Among Patients With Acute Heart Failure

Short-term infusions of single vasodilators, usually given in a fixed dose, have not improved outcomes in patients with acute heart failure (AHF). To evaluate the effect of a strategy that emphasized early intensive and sustained vasodilation using individualized up-titrated doses of established vasodilators in patients with AHF. Randomized, open-label blinded-end-point trial enrolling 788 patients hospitalized for AHF with dyspnea, increased plasma concentrations of natriuretic peptides, systolic blood pressure of at least 100 mm Hg, and plan for treatment in a general ward in 10 tertiary and secondary hospitals in Switzerland, Bulgaria, Germany, Brazil, and Spain. Enrollment began in December 2007 and follow-up was completed in February 2019. Patients were randomized 1:1 to a strategy of early intensive and sustained vasodilation throughout the hospitalization (n = 386) or usual care (n = 402). Early intensive and sustained vasodilation was a comprehensive pragmatic approach of maximal and sustained vasodilation combining individualized doses of sublingual and transdermal nitrates, low-dose oral hydralazine for 48 hours, and rapid up-titration of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or sacubitril-valsartan. The primary end point was a composite of all-cause mortality or rehospitalization for AHF at 180 days. Among 788 patients randomized, 781 (99.1%; median age, 78 years; 36.9% women) completed the trial and were eligible for primary end point analysis. Follow-up at 180 days was completed for 779 patients (99.7%). The primary end point, a composite of all-cause mortality or rehospitalization for AHF at 180 days, occurred in 117 patients (30.6%) in the intervention group (including 55 deaths [14.4%]) and in 111 patients (27.8%) in the usual care group (including 61 deaths [15.3%]) (absolute difference for the primary end point, 2.8% [95% CI, -3.7% to 9.3%]; adjusted hazard ratio, 1.07 [95% CI, 0.83-1.39]; P = .59). The most common clinically significant adverse events with early intensive and sustained vasodilation vs usual care were hypokalemia (23% vs 25%), worsening renal function (21% vs 20%), headache (26% vs 10%), dizziness (15% vs 10%), and hypotension (8% vs 2%). Among patients with AHF, a strategy of early intensive and sustained vasodilation, compared with usual care, did not significantly improve a composite outcome of all-cause mortality and AHF rehospitalization at 180 days. ClinicalTrials.gov Identifier: NCT00512759.

P5635Predictive ability of lipdic burden for FFR-derived physiological measures: insights from near-infrared spectroscopy imaging analysis

Abstract Background Fractional flow reserve (FFR) has enabled to physiologically assess the myocardial ischemia of coronary artery with intermediate stenosis. Mechanistically, not only the severity of coronary stenosis but also the extent of maximal vasodilatation within the entire coronary artery potentially affects this physiological measure. Since the accumulation of lipidic materials within vessel wall increases vascular stiffness via inducing endothelial dysfunction, the presence of lipidic atheroma burden may affect physiological measures. Purpose To investigate the association of FFR with lipidic coronary atheroma by near-infrared spectroscopy/intravascular ultrasound (NIRS/IVUS) imaging, which quantitatively visualize lipidic burden in vivo. Methods We analyzed 61 coronary arteries (LAD/RCA/LCX=52/5/4) with FFR≤0.80 in 59 stable coronary artery disease subjects receiving PCI. Following FFR measurement, NIRS/IVUS imaging was conducted to evaluate the extent of atheroma burden (maximum percent plaque area=max%PA) and lipidic materials (lipid core burden index within the entire vessel=LCBIvessel). The analyzed vessels were stratified according to FFR: definite FFR group (FFR≤0.74, n=34) and gray-zone FFR group (0.75≤FFR≤0.80, n=27). Results NIRS/IVUS imaging analysis (analyzed longitudinal length=77±7mm) was more likely to exhibit a significantly higher LCBIvessel and a larger max%PA in the definite FFR group (Table). Of note, FFR was significantly correlated to LCBIvessel (ρ=-0.299, p=0.02), but not max%PA (ρ=-0.255, p=0.07). Multivariate analysis demonstrated that an independent determinant of FFR≤0.74 was LCBIvessel [odds ratio (OR)=1.016, 95% confidential interval (CI)=1.002–1.031, p=0.02], but not max%PA [OR=1.084, 95% CI=0.994–1.182, p=0.07]. Area under the receiver-operating characteristic curve analysis elucidated that the addition of LCBIvessel to angiography- and IVUS-derived measures resulted in a significant improvement for detecting FFR≤0.74 (picture). Definite FFR Group (FFR≤0.74, n=34) Gray-zone FFR Group (0.75≤FFR≤0.80, n=27) p value Fractional flow reserve (FFR) 0.68±0.05 0.78±0.02 &lt;0.01 Percent diameter stenosis (%) 56.2±13.1 51.9±7.8 0.16 Maximum percent plaque area (max%PA, %) 84.3±6.9 79.9±7.2 0.01 Lipid core burden index within the entire vessel (LCBIvessel) 102.0±60.2 65.6±51.6 0.01 ROC analysis for detecting FFR≦0.74 Conclusion The propagation of lipidic burden associates with the physiological measures. The present findings indicate the possibility that vessel characteristics or instability may have influence for causing ischemia on the coronary artery.

P719Endothelial expression of adenylate cyclase type 9 (Adcy9) regulates endothelial cell signalling and vasodilation

Abstract Background/Introduction The clinical benefits of the cholesterol ester transfer protein (CETP) inhibitor dalcetrapib are dependent on the ADCY9 gene, which encodes adenylate cyclase (AC) type 9 (AC9). AC9 is one of nine membrane-bound isoforms of AC producing cyclic adenosine monophosphate (cAMP). We demonstrated that Adcy9 inactivation in the mouse protects from atherosclerosis, but only in absence of CETP. Adcy9 inactivation is also associated with improved endothelial function, including greater endothelial-dependent vasodilation (EDV) in response to acetylcholine (ACh). This suggests that Adcy9 may control endothelial Ca2+, an essential mediator of endothelial cell (EC) signalling. We hypothesized that Adcy9 is expressed in the endothelium and controls EC signalling. Purpose Our aim was to study AC9 expression in the vascular endothelium and the role of AC9 expression on endothelial cAMP signalling and Ca2+ dynamics. Methods The effects of Adcy9 inactivation were studied using wild-type (WT) and Adcy9-inactivated (Adcy9Gt/Gt) mice and siRNA-mediated inactivation of ADCY9 in human coronary artery endothelial cells (HCAEC). In the mouse, AC9 expression was quantified in whole aorta (± endothelium) and primary cultures of lung EC (LEC) by Western blot. Endothelial Ca2+ pulsars were monitored in mouse femoral arteries in response to acetylcholine (ACh, 10 μM). cAMP accumulation to AC activators VIP and forskolin were measured in LEC and HCAEC. EDV to VIP was studied ex vivo in mouse femoral arteries using pressurized arteriography. Results AC9 is expressed in LEC and the aorta, and its detection in the latter decreased by 33% after mechanical removal of the endothelium (P&lt;0.05). AC activation with forskolin (10–4 M) in LEC led to increased cAMP accumulation in response to Adcy9 inactivation (WT: 1129±138 pmol cAMP/mg of protein, Adcy9Gt/Gt: 1965±169, n=3; P&lt;0.01). ADCY9 inactivation in HCAEC also increased cAMP accumulation to forskolin 10–4M (control siRNA: 85±17, ADCY9 siRNA: 150±6, n=3; P&lt;0.01). In LEC, receptor-dependent accumulation of cAMP to VIP (10–5 M) was higher in Adcy9Gt/Gt (1509±258)) compared to WT (915±170, n=3; P&lt;0.05) mice. In mouse femoral arteries, VIP-induced maximal vasodilation was increased by Adcy9 inactivation in the presence of the endothelium (Adcy9Gt/Gt: 85±4%, n=6; WT: 52±9%, n=5, P&lt;0.05), but not in its absence (Adcy9Gt/Gt: 67±12%, n=6 and WT: 59±15%, n=5). In the femoral artery endothelium, ACh increased Ca2+ pulsar frequency more in Adcy9Gt/Gt (243±32%, n=4) than in WT (178±19%, n=5; P&lt;0.05) mice. Conclusion ADCY9 is expressed in the endothelium, and its inactivation potentiates endothelial cell Ca2+ dynamics, cAMP accumulation and VIP-induced vasodilation. We therefore identify ADCY9 as a new molecular pathway regulating endothelial-dependent vasodilation. This suggests that ADCY9's endothelial biology could be involved in the ADCY9 genotype-dependent clinical effects of dalcetrapib. Acknowledgement/Funding DalCor

TCT-230 Myocardial Ischemia Is Present and Mostly Reversible in Patients With a Chronic Total Occlusion and a Viable Perfusion Territory: The DISTAL CTO Study

The highest benefit of revascularization is found in patients with very low fractional flow reserve (FFR). In chronic total occlusion (CTO) patients, instant wave-free ratio (iFR, Philips) may be more appropriate to evaluate ischemia as it does not require maximal microvascular vasodilation, which

Endothelial dysfunction in children with pyelonephritis

Aim. To study the characteristics of vascular endothelium system functioning as a marker of the balance between endothelium-dependent vasodilation and endothelium-dependent vasoconstriction in children with acute and chronic pyelonephritis.Materials and methods. 39 children with acute and 37 with chronic pyelonephritis aged 11–17 years, without exacerbation of the inflammatory process were examined. The control group consisted of 30 apparently healthy children. Endothelium-dependent vasodilatation test adapted to children was used.Results. In children with acute pyelonephritis, the initial index of the brachial artery diameter did not differ significantly from the norm (3.40 ± 0.19 mm, P &gt; 0.05), while it was significantly less in patients with chronic pyelonephritis (2.20 ± 0.12 mm, P &lt; 0.05). In the phase of maximal vasodilation, the brachial artery diameter index was significantly higher (4.10 ± 0.15 mm, P &lt; 0.05) in patients with acute pyelonephritis, and in patients with chronic pyelonephritis – significantly less than the norm (2.60 ± 0.17 mm, P &lt; 0.05). As a result, the brachial artery diameter increase was significantly less in children with chronic pyelonephritis than in healthy children (8.2 ± 0.2 %, P &lt; 0.05), while it was significantly higher (24.10 ± 0.53 %, P &lt; 0.05) in children with acute pyelonephritis. Linear blood flow velocity at rest was significantly lower than normal (111.80 ± 0.17, P &lt; 0.05) in children with acute pyelonephritis and it was significantly increased (148.70 ± 0.14 cm/s, P &lt; 0.05) in children with chronic pyelonephritis. In the phase of reactive hyperemia, the linear flow velocity was decreased in both groups of patients.Conclusions. Endothelial dysfunction is registered in 17.9 % of acute pyelonephritis and in 64.9 % of chronic pyelonephritis cases in children. Diverging paths are observed: in patients with acute pyelonephritis, activity of vasodilatory agents predominates, and in chronic pyelonephritis - vasoconstrictor agents. Endothelial dysfunction associated with chronic pyelonephritis has the risk of unfavorable course of the disease and requires differential management.

Genetic deletion of the DNA damage repair protein, ATM kinase, is not sufficient to induce vascular dysfunction in young mice

Ataxia telangiectasia mutated (ATM) kinase orchestrates the cellular response to double stranded DNA breaks, phosphorylating and activating downstream targets that lead to cell cycle arrest or apoptosis, as well as by recruiting the machinery necessary for DNA repair. In the vasculature, ATM may play a critical role in maintaining genomic stability, thereby preserving vascular function, as aberrant DNA repair has been implicated in vascular dysfunction. Here, we evaluated several measures of vascular function in ATM knockout (ATM −/−) and wildtype (ATM +/+) mice (4–6 mo, n=7–9/group). Aortic pulse wave velocity, a measure of large artery stiffness, was similar between groups (P&gt;0.05). Furthermore, using an automated capture and analysis system we assessed markers of microvascular perfusion and glycocalyx properties. Perfused microvascular density, a measure of the number of perfused microvessels in a given area, and red blood cell (RBC) fraction, a marker of the heterogeneity of RBCs between microvessel segments, were not significantly different between groups (P&gt;0.05). Likewise, perfused boundary region, a measure of endothelial glycocalyx barrier function, was not significantly different between ATM −/− and ATM +/+ controls (P&gt;0.05). Furthermore, we examined endothelium‐dependent dilation and nitric oxide (NO) bioavailability in mesenteric arteries by measuring vasodilation to acetylcholine (ACh) in the absence and presence of the nitric oxide synthase inhibitor, L‐NAME. Maximal vasodilation to ACh did not differ between groups (P&gt;0.05). Likewise, the contribution of NO to maximal vasodilation was similar between ATM −/− and ATM +/+ mice (P&gt;0.05). Next, we assessed smooth muscle responsiveness to NO by measuring vasodilation to the NO donor, sodium nitroprusside (SNP). Maximal vasodilation to SNP did not differ between groups (P&gt;0.05). Lastly, we evaluated the passive mechanical properties of isolated mesenteric arteries and found no differences in vessel lumen diameter in response to increasing pressure between ATM −/− and ATM +/+ mice (P&gt;0.05). In conclusion, these findings suggest that removal of a major kinase involved with double stranded DNA damage signaling does not affect vascular function in young mice. This could be due to several reasons. First, young mice may have not accumulated sufficient DNA damage and mutagenesis to induce dysfunction or second, signaling downstream from DNA damage may drive vascular dysfunction. Thus, future studies are warranted that examine the role of ATM kinase in vascular function in response to conditions that augment DNA damage.Support or Funding InformationFunding Information: Funded in part by awards from the NIH, R01 AG048366, R01 AG050238, K02 AG045339 and K99 AT010017, and by US Department of Veterans Affairs 1I01BX002151.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Reduced Sensory Nerve Function and Nitric Oxide Sensitivity in Non‐Hispanic Blacks Compared to Non‐Hispanic Whites

Microvascular function is known to be impaired in healthy non‐Hispanic Blacks (NHB) compared to non‐Hispanic Whites (NHW), but it remains unknown if sensory nerve function is also impaired in NHB. Mechanisms of reduced bioavailable nitric oxide (NO) or sensitivity to NO may play a role in this racial discrepancy. The purpose of this study was to assess sensory nerve activation and sensitivity to NO in young, healthy NHB and NHW. Eight participants who self‐identified as NHB (n=4) or NHW (n=4) were instrumented with three microdialysis fibers in the skin of the forearm: 1) lactated Ringer's (control), 2) 20 mM NG‐nitro‐L‐arginine methyl ester (L‐NAME)to inhibit NO synthase (NOS), and 3) 1μM low‐dose sodium nitroprusside (SNP). A slow local heating protocol was used to heat the skin from 33°C to 40°C at a rate of 0.1°C per minute. Maximal vasodilation was elicited by heating the skin to 43°C and infusion of 54 mM SNP. An index of skin blood flow was assessed using laser‐Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was calculated (LDF/MAP) and normalized to maximum (%CVCmax). At control sites, sensory nerve activation was shifted to a higher local temperature in NHB (39.4 ± 0.4°C) compared to NHW (38.1 ± 0.3°C). L‐NAME did not alter the temperature threshold for sensory nerve activation in either NHB (39.8 ± 0.2°C) or NHW (38.8 ± 0.6°C) compared to control. Low‐dose SNP did not alter the temperature threshold (38.7 ± 0.7°C) relative to control sites in NHB but did reduce the temperature threshold in NHB to a value similar to that observed at control sites in NHW (P &gt; 0.99). In NHW, low dose SNP reduced the temperature threshold (37.4 ± 0.6°C) compared to L‐NAME (P&lt; 0.001) but not control sites. The magnitude of vasodilation was significantly reduced in NHB (23 ± 9 %CVCmax) compared to NHW (45 ± 9 %CVCmax) at control sites. L‐NAME did not alter %CVCmax in NHB (21 ± 5) or NHW (32 ± 5) compared to control. Low‐dose SNP increased the magnitude of vasodilation in NHB (45 ± 1 %CVCmax) compared to both control and L‐NAME sites. Low‐dose SNP in NHB also increased the magnitude of vasodilation to a value similar to that observed at all sites in NHW. Conversely, low‐dose SNP did not affect the magnitude of vasodilation (49 ± 5 %CVCmax) compared to control or L‐NAME sites in NHW. These data suggest increasing bioavailable NO results in greater sensory nerve sensitivity and increased skin blood flow in NHB. Low‐dose SNP improved sensory nerve sensitivity and cutaneous microvascular vasodilation in NHB to comparable levels as that observed in NHW. As increasing bioavailable NO did not fully reduce the temperature threshold for sensory nerve activation in NHB, it appears other mechanisms may contribute to the differences in sensory nerve sensitivity between these racial groups and that other NO‐independent mechanisms help to increase skin blood flow in response to heat.Support or Funding InformationNIH R01HL141205This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of iNOS on Cutaneous Thermal Hyperemia in Non‐Hispanic Blacks versus Non‐Hispanic Whites

Non‐Hispanic Blacks exhibit a blunted cutaneous microvascular response to local heating due, in part, to a decrease in nitric oxide (NO) bioavailability compared to non‐Hispanic Whites. Inducible NO synthase (iNOS) is known to contribute to vascular dysfunction; however, it is unknown whether iNOS contributes to microvascular dysfunction in NHB. The purpose of this study was to examine the role of iNOS on cutaneous microvascular function in NHB vs. NHW. Young, healthy non‐Hispanic Black and White participants (n = 4 per group) were instrumented with 2 microdialysis fibers for infusion of lactated Ringer's solution (control) and 0.1 mM 1400W (iNOS inhibitor), respectively. Following Ringer's and 1400W infusion, local skin temperature was increased via rapid local heating to 39°C at a rate of 0.1°C s−1. Once skin blood flow plateaued, 20 mM L‐NAME was infused to quantify endothelial NO synthase (eNOS)‐dependent vasodilation to the local heating response. Following L‐NAME infusion, the local heaters were increased to 43°C and 54mM of sodium nitroprusside was infused to elicit maximal endothelium‐independent cutaneous vasodilation. Skin blood flow was measured via laser‐doppler flowmetry (LDF) throughout the local heating protocol. Cutaneous vascular conductance (CVC) was calculated as LDF flow divided by mean arterial pressure and normalized to maximum (%CVCmax). iNOS inhibition minimally increased the initial peak in non‐Hispanic Blacks (33±6 vs. 41±8 %CVCmax) but had no effect in non‐Hispanic Whites (53±9 vs. 55±6 %CVCmax), suggesting an increased sensory nerve response in non‐Hispanic Blacks following blockade. Inhibition of iNOS (66±10 %CVCmax) did not alter microvascular function compared to control (70±14 %CVCmax) in non‐Hispanic Whites; however, microvascular function increased (47±11 vs. 60±10 %CVCmax) in non‐Hispanic Blacks, suggesting an increase in basal iNOS concentrations. Notably, iNOS inhibition in non‐Hispanic Blacks increased %CVCmax to a level similar to non‐Hispanic Whites. The %NO‐dependent vasodilation did not change in non‐Hispanic Whites with infusion of 1400W (60±5 vs. 61±5 %); however, infusion of 1400W increased the %NO‐dependent vasodilation in non‐Hispanic Blacks (44±6 vs. 57±3 %), suggesting increased levels of circulating iNOS impairs endothelial‐dependent vasodilation. These findings indicate iNOS‐derived NO contributes to reduced eNOS‐dependent microvascular vasodilation in young, healthy non‐Hispanic Blacks.Support or Funding InformationGrant Number: 1R01HL141205‐01This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Alterations in cutaneous microvascular function at high altitude in lowlanders and highlanders

Microvascular function is impaired in lowlanders at high altitude; however, this impairment was gauged using post‐occlusive reactive hyperemia and the contribution of nitric oxide (NO) to cutaneous vasodilation at high altitude remains unknown. Low molecular O2 at high altitude leads to production of reactive oxygen species (ROS) and reduced NO bioavailability. We therefore tested the hypothesis that vasodilation during a standard local heating protocol, and thus cutaneous microvascular function, is impaired in lowlanders at high altitude by ROS. We further tested whether lifelong residence at high altitude alters microvascular function compared to lowlanders. Four intradermal microdialysis membranes were inserted in the forearms of 11 male lowlanders [age: 30 (8) years; BMI: 24 (2) kg·m−2] at sea level and after two weeks at 4340 m in Cerro de Pasco, Peru. Andean highlanders [n=11; age: 26 (5) years; BMI: 24 (2) kg·m−2] residing permanently in Cerro de Pasco were also tested. The four sites were randomized and pre‐treated with infusions of 1) lactated Ringer's solution (control), 2) 100 μM Apocynin (NADPH oxidase inhibitor), 3) 10 μM Tempol (superoxide scavenger), and 4) 10 μM Allopurinol (xanthine oxidase inhibitor). Skin blood flux was measured continuously at each site via laser‐Doppler flowmetry during the 39°C local heating (NO‐dependent plateau phase), 20 mM L‐NAME (NO synthase inhibitor), and 44°C local heating combined with 28 mM sodium nitroprusside infusion to achieve maximal vasodilation. Data are presented as cutaneous vascular conductance (CVC; flux/mean arterial pressure) as a percentage of maximum.There was a main group effect (P&lt;0.001) on CVC during 39°C heating with impaired vasodilation in both lowlanders at high altitude and in Andeans [control site: 54 (14) vs. 50 (24)%, respectively] compared to lowlanders at sea level [control site: 73 (19)%]. Similarly, the NO contribution to vasodilation during the 39°C plateau portion (i.e. effect of L‐NAME) was impaired (main group effect P&lt;0.001) in lowlanders after 2 weeks at high altitude compared to sea level [control site: 41 (11) vs 49 (10)%, respectively], and this impairment was more pronounced in Andeans [control site: 32 (21)%]. There was no influence of ROS pathways, assessed via antioxidant infusions, on cutaneous vasodilation throughout the protocol in any group (all main drug effects P&gt;0.05). When values were pooled from both groups and altitudes, local heating plateau CVC (r2=0.18, P=0.02) and the NO contribution to vasodilation (r2=0.13, P=0.04) were both positively correlated with oxygen‐hemoglobin saturation.These results indicate that high altitude impairs NO‐mediated vasodilation independent of a ROS mechanism but is associated with oxygen‐hemoglobin desaturation. The extent of microvascular impairment is greater in lifelong high altitude residents.Support or Funding InformationCanada Research Chairs ProgramThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Sodium nitroprusside encapsulated in Silica nanoparticles as a strategy for safer nitric oxide delivery

Sodium nitroprusside (SNP) has been used as a nitric oxide (NO) donor in medicine for several decades, even before any knowledge of the biological role of NO. This medicine is used in cases of emergency of hypertension due to its fast release of NO causing fast drop in blood pressure. Unfortunately, this compound also releases cyanide (CN-) as a side product. Nanoencapsulated nitroprusside was synthesized by using silica nanoparticles functionalized with primary amine (MPSi-NH2) (the final compound was named APTES). The compound was bioassayed using vascular tissues from Wistar rats, albine guinea-pigs and New Zealand rabbits. All the protocols were approved by the Ethic committee of the Ceará State University under the protocol # 2897836/15. The thoracic aorta, pulmonary artery or corpora cavernosa were carefully removed and mounted in a 5 mL organ bath containing Krebs–Henseleit solution at 37°C, gassed with 95% O2: 5% CO2, attached to isometric transducers coupled to a powerlab data acquisition system. After equilibration, the tissues were precontracted with phenylephrine (PE, 10−6–10−5 M) and after a plateau was achieved increasing concentrations of SNP or APTES (10−10 to 10−5 M) were cumulatively added in intervals of 5 minutes. The relaxant effect was measured as percentage of the maximal contraction induced by phenylephrine. In addition, we also measured the level of phosphorylation of Ser239 of VASP, a useful marker for monitoring cGMP-dependent protein kinase activation and signaling. SNP APTEs relaxed rat aortic rings with similar potency than non-modified SNP with a concentration necessary to induce 50% vasodilation (CE50) of 26 nM [95% confidence interval=20–33 nM] compared to 14 nM [95% confidence interval=7,9–21 nM] for non-modified SNP. However, the maximal vasodilation induced by SNP APTEs (177.4±7.1%) was higher than the maximal relaxation induced by nonmodified SNP (143.8±9.6%). When comparing different vascular beds, i.e., guinea pig thoracic aorta vs. pulmonary arteries vs. rabbit corpora cavernosa, SNP APTEs was shown to have similar potency and efficacy (119.6±5.7% and 130nM vs. 108±6.3% and 275nM vs. 116±4.5% and 98 nM, respectively). Interestingly, SNP increase VASP phosphorylation by 3.8-fold and APTES increased by 4.13-fold (P<0.05 vs. control). Our synthetic strategy to make functionalized silica nanoparticles showed quite efficient to incorporate sodium nitroprusside, where we succeeded to have up to 320 umol g−1. Remarkably, we noticed a minor release of cyanide or even NP, despite full effect of NO was observed during a series of biological assays. Indeed, EC50 and maximal response for relaxation in aorta, pulmonary arteries and Rabbit corpora cavernosa were quite similar. Support or Funding Information CAPES, CNPq and FUNCAP Vasorelaxant Effect of Sodium nitroprusside encapsulated in Silica nanoparticles Original tracings depicting the strong and potent vascular relaxant effect of SNP APTES (panel A). Effect of SNP APTES on the phenylephrine precontracted aortic rings compared with non-modified sodium nitroprusside (Panel B). Panel C depicts the Effect of 1 μM SNP or SNP APTES compared with the addition of vehicle only in the level of phosphorylation of the residues Serine 239 of the protein Vasodilator-stimulated phosphoprotein (VASP) a substrate of activated cGMP-activated protein kinase (PKG) *p<0.05 vs SNP at the same concentration This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endothelin Receptor‐dependent Responses in Overweight/Obese Postmenopausal Women

Age‐related weight gain is greater in women compared to men, such that postmenopausal women are more likely to be overweight or obese (OW/Ob). Previous studies have demonstrated that OW/Ob older adults have impaired endothelial function in part due to endothelin‐1 mediated vasoconstriction via the ETA receptor. In addition, our laboratory has recently demonstrated an important role for ETB receptors and its contribution to vascular endothelial dysfunction in postmenopausal women.PURPOSEThe purpose of this study was to test the hypothesis that ETB and ETA receptors contribute to impaired vasodilatory function in OW/Ob postmenopausal women.METHODSFourteen postmenopausal women have completed the study: 8 normal weight (NW; 57±5 years, 22±2 kg/m2) and 6 OW/Ob (57±8 years, 28±3 kg/m2). We measured vasodilatory responses to local heating of the skin (laser Doppler flowmetry) during microdialysis perfusions of lactated Ringer's (Control), ETB receptor blockade (BQ‐788, 300nM), and ETA receptor blockade (BQ‐123, 500 nM). Cutaneous vascular conductance (CVC) was calculated during the plateau phase of local heating (42°C), and normalized to maximal vasodilation achieved by perfusion of sodium nitroprusside (28mM) and heating to 43°C. A two‐way ANOVA with post hoc Bonferroni correction was performed to compare the impact of weight on vascular responses to ETA and ETB mediated vasodilation compared to control. Data are presented as mean ± standard deviation.RESULTSETB receptor blockade increased vasodilation in NW women (Control: 88±4 vs. BQ‐788: 94±4 %CVC max; P=0.03), whereas ETA receptor blockade did not significantly alter vasodilation (BQ‐123: 88±3 %max CVC; P&gt;0.90 vs. Control). In OW/Ob, both ETB and ETA blockade increased vasodilation (Control: 89±4 vs. BQ‐788: 95±4, BQ‐123: 94±5 %max CVC; P&lt;0.05). Furthermore, the vasodilatory response to ETA receptor blockade was greater in OW/Ob compared to NW (P=0.03).CONCLUSIONThese preliminary data suggest that while blockade of ETB receptors improves vasodilatory function in postmenopausal women, there is a larger contribution of ETA receptors impacting endothelial function in OW/Ob postmenopausal women.Support or Funding InformationSupported by: NIH GRANT P20 GM 113125 and AHA 16SDG30700015This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Flap warming improves intraoperative indocyanine green angiography (ICGA) assessment of perfusion. An experimental study

Indocyanine green angiography (ICGA) is slowly replacing conventional methods of evaluating perfusion during flap surgery. Microcirculatory changes during flap elevation create a marked state of hypoperfusion intraoperatively leading to ICGA underestimation of tissue viability and consequent resection of viable tissue. We propose a novel method of flap warming to induce maximum vasodilation before performing ICGA to increase accuracy in assessing perfusion. Submental flaps harvested on a single perforator were created in 8 pigs. ICG angiography was performed in the intraoperative phase (ICGA-C), after inducing maximum vasodilatation by warming the flap at 42 °C (ICGA-W) and at 24H postoperative (ICGA-24). By setting a fluorescence threshold of 33% as indicative of necrosis, the flap surface deemed viable by ICGA was measured for ICGAC, ICGAW and ICGA24. The results were then compared to the actual flap survival observed clinically at 7 days. The mean of ICG-C predicted flap survival (FS-C = 49.17%) is 12.97% lower than the mean of actual flap survival on postoperative day 7 (FS=62.14%). The mean difference between ICG-W and ICG-24 predicted flap survival (FS-W and FS-24) and actual flap survival in the postoperative day 7 (FS) is lower, 3.13% and 2.15%, respectively. Average perfusion recovery over 24 h was 10.83% (FS-24-FS-C). Conventional intraoperative ICGA underestimated perfusion in all cases. Warming the flap intraoperatively and achieving maximum vasodilation mitigates the effects of vasoconstriction and mimics the microcirculatory environment encountered at 24 h. Performing angiography after induced vasodilation improves ICGA assessment of flap perfusion.

THE ROLE OF INSTANTANEOUS FLOW RESERVE FOR THE PHYSIOLOGICAL ASSESSMENT OF CORONARY ARTERY DISEASE IN PATIENTS WITH HEPATIC CIRRHOSIS

We hypothesize that instantaneous flow reserve (iFR) is a useful tool when assessing patients for percutaneous coronary intervention (PCI) with hepatic cirrhosis and obstructive coronary artery disease (CAD) despite being in a physiological state of maximal vasodilation. A 65 year old female with a

Seven consecutive days of remote ischaemic preconditioning improves cutaneous vasodilatory capacity in young adults.

Remote ischaemic preconditioning (RIPC), induced by brief bouts of ischaemia followed by reperfusion, confers vascular adaptations that protect against subsequent bouts of ischaemia; however, the effect of RIPC repeated over several days on the human microcirculation is unknown. Using skin as a model, microvascular function was assessed at a control and a NO-inhibited area of skin before 1day after and 1week after administering seven consecutive days of repeated RIPC on the contralateral arm. Maximal vasodilatation was increased by ∼20-50% following 7days of repeated RIPC, and this response remained elevated 1week after stopping RIPC; however, NO-mediated vasodilatation was not affected by the RIPC stimulus. These data indicate that repeated RIPC augments maximal vasodilatation, but the underlying mechanism for this improvement is largely independent of NO. This finding suggests a role for other endothelium-derived mediators and/or for endothelium-independent adaptations with repeated RIPC. Remote ischaemic preconditioning (RIPC), induced by intermittent periods of ischaemia followed by reperfusion, confers cardiovascular protection from subsequent ischaemic bouts. RIPC increases conduit and resistance vessel function; however, the effect of RIPC on the microvasculature remains unclear. Using human skin as a microvascular model, we hypothesized that cutaneous vasodilatory (VD) function elicited by localized heating would be increased following repeated RIPC. Ten participants (23± 1years, 6 males, 4 females) performed RIPC for seven consecutive days. Each daily RIPC session consisted of 4 repetitions of 5min of arm blood flow occlusion interspersed by 5min reperfusion. Before, 1day after and 1week after the 7days of RIPC, two microdialysis fibres were placed in ventral forearm skin for continuous infusion of Ringer solution or 20mM l-NAME. Red blood cell flux was measured by laser Doppler flowmetry at each fibre site during local heating (Tloc = 39°C) and during maximal VD elicited by heating (Tloc = 43°C) and 28mM sodium nitroprusside infusion. Data were normalized to cutaneous vascular conductance (flux/mmHg). Seven days of RIPC did not alter the nitric oxide (NO) contribution to the VD response to local heating (P> 0.05). However, the maximal VD was augmented (Pre: 2.5± 0.2, Post: 3.8± 0.5flux/mmHg; P< 0.05) and remained elevated 1week post RIPC (3.3± 0.4flux/mmHg; P< 0.05). Repeated RIPC improves maximal VD but does not affect NO-mediated VD in the cutaneous microvasculature. This finding suggests that other factors may explain the vasodilatory adaptations that occur following repeated RIPC.

Abstract 043: Targeting the Angiotensin Type 2 Receptor With Relaxin Confers Protection Against Renal Fibrosis and Vascular Dysfunction in Female Stroke Prone-Spontaneously Hypertensive Rats

The angiotensin type 2 receptor (AT 2 R) mediates cardiovascular and renal protection in females of reproductive age, a mechanism that is lost with advancing age. Recently, we demonstrated that the nitric oxide-promoting and transforming growth factor-β1 inhibitory actions of relaxin (RLX) involve an interaction between the relaxin-insulin like family peptide receptor 1 (RXFP1) and the AT 2 R. In the present study, we aimed to determine whether RLX induces cardio-renal protection and slows the progression of end-organ damage, via an AT 2 R-dependent mechanism. In female stroke prone-spontaneously hypertensive rats (SP-SHR) at 6 (young) and 14-15 (aged reproductively senescent) months of age arterial pressure, cardiac function, glomerular filtration rate (GFR) and proteinuria were measured before and after 4 weeks of treatment with vehicle (sodium acetate s.c.), RLX (serelaxin; 0.5mg/kg/day s.c.) or RLX+PD123319 (AT 2 R antagonist; 3mg/kg/day s.c). In addition, aortic endothelium-dependent relaxation in response to acetylcholine was assessed and cardiac and renal tissues were histologically analyzed for fibrosis. An age-related decline in GFR and increases in arterial pressure, proteinuria and cardiac and renal fibrosis were observed (all P&lt;0.05; n=4-8). RLX treatment had no significant effect on these variables in the aged group. However, in aged animals, RLX markedly improved endothelial function (~30% increase in maximal vasodilation as compared to vehicle counterparts, P=0.0002; n=4-6). This effect was partially reversed by co-infusion with PD123319, relative to RLX alone (~14% reduced maximal vasodilation, P=0.03; n=6). In young females, RLX+PD123319 as compared to RLX treatment alone, exacerbated glomerular (11.6±1.2% vs 8.5±0.7%, respectively, P=0.04) and tubulointerstitial (3.3±0.2% vs 1.6±0.2%, respectively, P=0.0002) fibrosis. In conclusion, the cardio-renal protective actions of relaxin are dependent in part, upon an interaction with the AT 2 R. Thus, targeting the RXFP1-AT 2 R axis may be a therapeutic option for the treatment of cardiovascular disease and associated end-organ damage in hypertensive women.

The Piezo1 cation channel mediates uterine artery shear stress mechanotransduction and vasodilation during rat pregnancy.

During mammalian pregnancy, the uterine circulation must undergo substantial vasodilation and growth to maintain sufficient uteroplacental perfusion. Although we and others have shown that nitric oxide (NO) is a key mediator of these processes, the mechanisms that augment uterine artery NO signaling during gestation have not been identified. We hypothesized that Piezo1, a recently discovered cation channel, may be involved in the process of shear stress mechanotransduction, as other studies have shown that it is both mechanosensitive and linked to NO production. Surprisingly, there are no studies on Piezo1 in the uterine circulation. Our aims in the present study were to determine whether this novel channel is 1) present in uterine arteries, 2) regulated by gestation, 3) functionally relevant (able to elicit rises in intracellular Ca2+ concentration and vasodilation), and 4) linked to NO. Immunohistochemistry confirmed that Piezo1 is present in uterine arteries, primarily but not exclusively in endothelial cells. Western blot analysis showed that its protein expression was elevated during gestation. In pressurized main uterine arteries, pharmacological activation of Piezo1 by Yoda1 produced near maximal vasodilation and was associated with significant increases in intracellular Ca2+ concentration in endothelial cell sheets. Shear stress induced by intraluminal flow produced reversible vasodilations that were inhibited >50% by GsMTx-4, a Piezo1 inhibitor, and by Nω-nitro-l-arginine methyl ester/ Nω-nitro-l-arginine, inhibitors of NO synthase. These findings are the first to implicate a functional role for Piezo1 in the uterine circulation as a mechanosensor of endothelial shear stress. Moreover, our data demonstrate that Piezo1 activation leads to vasodilation via NO and indicate that its molecular expression is upregulated during pregnancy. NEW & NOTEWORTHY This is the first study to highlight Piezo1 in the uterine circulation. As a potentially important endothelial mechanosensor of shear stress, Piezo1 may be linked to mechanisms that support increased uteroplacental perfusion during pregnancy. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/piezo1-mechanotransduction-in-the-uterine-circulation/ .

Blood flow simulation during flow‐mediated dilation

AbstractEndothelial dysfunction is known to be the early stage of arteriosclerosis. The flow‐mediated dilation (FMD) test is the most commonly used method to diagnose the endothelial function. The test measures the maximum vasodilation (FMD response) on the brachial artery induced by the increases in blood flow after cuff deflation on the forearm. The vessel diameter must be captured clearly with the ultrasonic probe during the test. The vasodilation is induced in response to changes in the mechanical property of the vessel wall due to the blood flow stimulation. The changes are supposed to affect the pulsatile flow, but the influence of continuous behavior of vascular property on hemodynamics has not been clarified. In this study, in order to clarify the influence of the FMD response on hemodynamics, we propose a mathematical model that can simulate hemodynamics and vasomotor responses. As a result, it was shown that vessel wall dynamics affected the pulsatile flow. This result suggests that the endothelial function can be evaluated from blood flow.