Infusion Of Acetylcholine Research Articles

Acute cardiovascular effects of controlled exposure to dilute Petrodiesel and biodiesel exhaust in healthy volunteers: a crossover study

BackgroundAir pollution derived from combustion is associated with considerable cardiorespiratory morbidity and mortality in addition to environmental effects. Replacing petrodiesel with biodiesel may have ecological benefits, but impacts on human health remain unquantified.The objective was to compare acute cardiovascular effects of blended and pure biodiesel exhaust exposure against known adverse effects of petrodiesel exhaust (PDE) exposure in human subjects.In two randomized controlled double-blind crossover studies, healthy volunteers were exposed to PDE or biodiesel exhaust for one hour. In study one, 16 subjects were exposed, on separate occasions, to PDE and 30% rapeseed methyl ester biodiesel blend (RME30) exhaust, aiming at PM10 300 μg/m3. In study two, 19 male subjects were separately exposed to PDE and exhaust from a 100% RME fuel (RME100) using similar engine load and exhaust dilution. Generated exhaust was analyzed for physicochemical composition and oxidative potential. Following exposure, vascular endothelial function was assessed using forearm venous occlusion plethysmography and ex vivo thrombus formation was assessed using a Badimon chamber model of acute arterial injury. Biomarkers of inflammation, platelet activation and fibrinolysis were measured in the blood.ResultsIn study 1, PDE and RME30 exposures were at comparable PM levels (314 ± 27 μg/m3; (PM10 ± SD) and 309 ± 30 μg/m3 respectively), whereas in study 2, the PDE exposure concentrations remained similar (310 ± 34 μg/m3), but RME100 levels were lower in PM (165 ± 16 μg/m3) and PAHs, but higher in particle number concentration. Compared to PDE, PM from RME had less oxidative potential. Forearm infusion of the vasodilators acetylcholine, bradykinin, sodium nitroprusside and verapamil resulted in dose-dependent increases in blood flow after all exposures. Vasodilatation and ex vivo thrombus formation were similar following exposure to exhaust from petrodiesel and the two biodiesel formulations (RME30 and RME100). There were no significant differences in blood biomarkers or exhaled nitric oxide levels between exposures.ConclusionsDespite differences in PM composition and particle reactivity, controlled exposure to biodiesel exhaust was associated with similar cardiovascular effects to PDE. We suggest that the potential adverse health effects of biodiesel fuel emissions should be taken into account when evaluating future fuel policies.Trial registrationClinicalTrials.gov, NCT01337882/NCT01883466. Date of first enrollment March 11, 2011, registered April 19, 2011, i.e. retrospectively registered.

Pulmonary Microcirculation during Experimental Pulmonary Thromboembolism under Conditions of Activation and Blockade of Muscarinic Acetylcholine Receptors.

Changes in pulmonary microcirculation were studied in isolated perfused rabbit lungs during modelling pulmonary thromboembolism under conditions of acetylcholine infusion against the background of treatment with M1 acetylcholine receptor blocker pirenzepine or blockade of muscarinic acetylcholine receptors with atropine. In the first case, the increase in pulmonary artery pressure was less pronounced than in case of atropine treatment. In response to pulmonary embolism after acetylcholine infusion against the background of pirenzepine pretreatment, the capillary hydrostatic pressure and postcapillary resistance did not change, while after atropine treatment, these parameters increased. In case of pulmonary embolism after acetylcholine infusion combined with selective blockade of M1 muscarinic acetylcholine receptors, the capillary filtration coefficient increased to a greater extent, than in the control and after blockade of muscarinic acetylcholine receptors.

Changes in vascular function during breast cancer treatment.

AimsBreast cancer (BC) survivors are at increased risk of cardiovascular disease. We evaluated whether chemotherapy induces early or late vascular dysfunction in vivo.MethodsEarly‐stage BC patients (n = 33) underwent measurements of forearm blood flow (FBF), 24‐hour blood pressure (BP), aortic pulse wave velocity and inflammatory markers before (T0), 14 days after (T1) and 12 months after (T2) chemotherapy. FBF was assessed during intra‐arterial infusion of acetylcholine (ACh), ACh during simultaneous nitric oxide synthase inhibition with L‐NG‐monomethyl arginine, and during infusion of sodium nitroprusside. Controls matched by age and menopausal status were examined for baseline comparison.ResultsAt T0, absolute FBF in the BC patients did not differ from controls. At T1, ACh‐induced absolute FBF was higher compared to T0. ACh‐induced FBF decreased significantly at T2, evaluated as area under the dose–response curve, and when corrected for FBF in the contralateral arm (FBF ratio at T0: 4.05, 95% confidence interval [2.54; 5.74] and T2: 2.77 [2.41; 3.50]), without difference evident during L‐NG‐monomethyl arginine infusion. FBF during sodium nitroprusside infusion remained unchanged. Pulse wave velocity and BP remained unchanged. Asymmetric dimethylarginine (T0: 0.68 μmol/L ± 0.17, T1: 0.75 μmol/L ± 0.16) and the inflammation‐related biomarkers Cd163 (T0: 1.86 mg/L [1.68; 2.05], T1: 2.04 mg/L [1.76; 2.4]) and Cd206 (T0: 0.22 mg/L [0.19; 0.26], T1: 0.27 mg/L [0.23; 0.30]) all increased significantly at T1, but returned to baseline values at T2. L‐arginine was significantly increased at both T1 (78.5 μmol/L [68.9; 86.6]) and T2 (76.8 μmol/L [66.9; 90.6]), compared to T0 (59.6 μmol/L [53.7; 68.0]).ConclusionChemotherapy for BC seems associated with early amplification of endothelium‐dependent vasodilation and inflammation. One year after chemotherapy, microvascular dysfunction persists in terms of reduced NO‐dependent vasodilation without alterations in BP or arterial stiffness.

Función endotelial y microvascular distal a stents farmacoactivos sin polímero y captadores de células endoteliales. Estudio aleatorizado FUNCOMBO

Introduction and objectivesThe vasomotor function of new-generation drug-eluting stents designed to enhance stent healing and reendothelialization is unknown. This study aimed to compare the endothelial function of the infarct-related artery (IRA) treated with bioactive circulating endothelial progenitor cell-capturing sirolimus-eluting stents (COMBO) vs polymer-free biolimus-eluting stents (BioFreedom) in ST-segment elevation myocardial infarction patients at 6 months. Secondary objectives were to compare the microcirculatory function of the IRA and stent healing at 6 months. MethodsSixty patients were randomized to bioactive sirolimus-eluting stent vs polymer-free biolimus-eluting stents implantation. At 6 months, patients underwent coronary angiography with vasomotor, microcirculatory and optical coherence tomography examinations. Endothelial dysfunction of the distal coronary segment was defined as ≥ 4% vasoconstriction to intracoronary acetylcholine infusion. ResultsEndothelial dysfunction was similarly observed between groups (64.0% vs 62.5%, respectively; P=.913). Mean lumen diameter decreased by 16.0 ±20.2% vs 16.1 ±21.6% during acetylcholine infusion (P=.983). Microcirculatory function was similar in the 2 groups: coronary flow reserve was 3.23 ±1.77 vs 3.23±1.62 (P=.992) and the index of microcirculatory resistance was 24.8±16.8 vs 21.3±12.0 (P=.440). Optical coherence tomography findings were similar: uncovered struts (2.3% vs 3.2%; P=.466), malapposed struts (0.1% vs 0.3%; P=.519) and major evaginations (7.1% vs 5.6%; P=.708) were observed in few cases. ConclusionsEndothelial dysfunction of the IRA was frequent and was similarly observed with new-generation drug-eluting stents designed to enhance stent reendothelialization at 6 months. Endothelial dysfunction was observed despite almost preserved microcirculatory function and complete stent coverage. Larger and clinically powered studies are needed to assess the role of residual endothelial dysfunction in ST-segment elevation myocardial infarction patients.Registered in ClinicalTrials.gov: NCT04202172Full English text available from:www.revespcardiol.org/en

Glycemic management is inversely related to skeletal muscle microvascular endothelial function in patients with type 2 diabetes.

Microvascular endothelial dysfunction precipitates cardiovascular disease mortality in patients with type 2 diabetes mellitus (T2DM). However, the relationship between glycemic management and microvascular endothelial function of these patients remains ill defined. We investigated the association between skeletal muscle microvascular endothelial function with glycemic management (HbA1c) and responses to an oral glucose challenge (OGTT) in 30 patients with T2DM (59 ± 9 years, 31.2 ± 5.1 kg/m2, HbA1c = 7.3 ± 1.3%). On study day 1, microvascular endothelial function was quantified as the increase (Δ from rest) in forearm vascular conductance (FVC, ml/min/100 mmHg) during intra‐arterial acetylcholine infusion at 4.0 and 8.0 μg/dl forearm volume/min (ACh4 and ACh8, respectively). [Glucose] and [insulin] were measured in a fasted state as well as following a 75 g OGTT on a second day with an additional fasting blood sample collected to measure HbA1c. FVC increased (Δ) 221 ± 118 and 251 ± 144 ml/min/100 mm Hg during ACh4 and ACh8 trials, respectively (p < 0.05 between doses). [Glucose] and [insulin] increased at the 1‐h time point, relative to fasting levels, and remained elevated 2 h post‐consumption (p < 0.05 for both variables and time points). [Glucose] nor [insulin], fasting or during the OGTT, were associated with ΔFVC during ACh4 or ACh8, respectively (p = 0.11–0.86), although HbA1c was inversely related (r = −0.47 and −0.46, respectively, p < 0.01 for both). Patients whose HbA1c met the ADA’s therapeutic target of ≤7.0% had greater ΔFVC to ACh4 (272 ± 147 vs. 182 ± 74 ml/100 mm Hg/min) and ACh8 (324 ± 171 vs. 196 ± 90 ml/100 mm Hg/min, p < 0.05 for both trials) compared to those with >7.0%, respectively. Our data show glycemic management is related to acetylcholine‐mediated vasodilation (e.g., microvascular endothelial function) in skeletal muscle of patients with T2DM.

Coronary endothelial and microvascular function distal to polymer-free and endothelial cell-capturing drug-eluting stents. The randomized FUNCOMBO trial

Introduction and objectivesThe vasomotor function of new-generation drug-eluting stents designed to enhance stent healing and reendothelialization is unknown. This study aimed to compare the endothelial function of the infarct-related artery (IRA) treated with bioactive circulating endothelial progenitor cell-capturing sirolimus-eluting stents (COMBO) vs polymer-free biolimus-eluting stents (BioFreedom) in ST-segment elevation myocardial infarction patients at 6 months. Secondary objectives were to compare the microcirculatory function of the IRA and stent healing at 6 months. MethodsSixty patients were randomized to bioactive sirolimus-eluting stent vs polymer-free biolimus-eluting stents implantation. At 6 months, patients underwent coronary angiography with vasomotor, microcirculatory and optical coherence tomography examinations. Endothelial dysfunction of the distal coronary segment was defined as ≥ 4% vasoconstriction to intracoronary acetylcholine infusion. ResultsEndothelial dysfunction was similarly observed between groups (64.0% vs 62.5%, respectively; P=.913). Mean lumen diameter decreased by 16.0 ±20.2% vs 16.1 ±21.6% during acetylcholine infusion (P=.983). Microcirculatory function was similar in the 2 groups: coronary flow reserve was 3.23 ±1.77 vs 3.23±1.62 (P=.992) and the index of microcirculatory resistance was 24.8±16.8 vs 21.3±12.0 (P=.440). Optical coherence tomography findings were similar: uncovered struts (2.3% vs 3.2%; P=.466), malapposed struts (0.1% vs 0.3%; P=.519) and major evaginations (7.1% vs 5.6%; P=.708) were observed in few cases. ConclusionsEndothelial dysfunction of the IRA was frequent and was similarly observed with new-generation drug-eluting stents designed to enhance stent reendothelialization at 6 months. Endothelial dysfunction was observed despite almost preserved microcirculatory function and complete stent coverage. Larger and clinically powered studies are needed to assess the role of residual endothelial dysfunction in ST-segment elevation myocardial infarction patients.Registered in ClinicalTrials.gov: NCT04202172

Endothelial dysfunction and C-reactive protein predict the incidence of heart failure in hypertensive patients.

AimsEndothelial dysfunction and heart failure are associated, but no prospective studies demonstrated that impaired endothelium‐dependent vasodilation predicts incident heart failure. We designed this study to test whether endothelial dysfunction is associated with incident heart failure in a group of hypertensives.Methods and resultsWe enrolled 735 White never‐treated hypertensive outpatients free from heart failure, diabetes, chronic kidney disease, and previous cardiovascular events. Endothelium‐dependent vasodilation was investigated by intra‐arterial infusion of acetylcholine, and laboratory determinations were obtained by standard procedures. During the follow‐up [median 114 months (range 26–206)], there were 208 new cases of heart failure (3.1 events/100 patient‐years). Dividing the study population in progressors and non‐progressors, we observed that progressors were older, showed a higher prevalence of being female, and had a higher baseline heart rate, glucose, insulin, Homeostatic Model Assessment (HOMA), creatinine, and high‐sensitivity C‐reactive protein (hs‐CRP) mean values, while estimated glomerular filtration rate and maximal acetylcholine‐stimulated forearm blood flow were lower. In the multiple Cox regression analysis, female gender [hazard ratio (HR) = 1.454, 95% CI = 1.067–1.981], fasting glucose (HR = 1.186, 95% CI = 1.038–1.357), hs‐CRP (HR = 1.162, 95% CI = 1.072–1.259), HOMA (HR = 1.124, 95% CI = 1.037–1.219), acetylcholine‐stimulated forearm blood flow (HR = 0.779, 95% CI = 0.695–0.874), and estimated glomerular filtration rate (HR = 0.767, 95% CI = 0.693–0.849) maintained an independent association with the outcome. Successively, testing the interaction between forearm blood flow and hs‐CRP, we observed that patients who have hs‐CRP values above the median and forearm blood flow under the median show a higher risk of developing heart failure (HR = 7.699, 95% CI = 4.407–13.451).ConclusionsThe present data demonstrate that an impaired endothelium‐dependent vasodilation and hs‐CRP predict development of incident heart failure in hypertensives.

A prospective, randomized, comparison of the coronary vasomotion associated with drug-coated balloon versus drug-eluting stent

Abstract Background It is widely known that even new-generation drug-eluting stent (DES) induce coronary vasomotion abnormality. On the other hand, recent studies reported that drug-coated balloon (DCB) for native coronary artery was non-inferior to DES in medium term outcomes. However, there is no available information about vasomotion after treatment with DCB. Purpose The aim of this study was to prospectively compare coronary vasomotion in patients treated with DCB versus new-generation DES. Methods Twenty-seven patients were randomly treated with angioplasty with DCB (n=12) versus implantation of bioabsorbable polymer everolimus-eluting stent (BP-EES, n=15) after successful predilation. At 8 months after treatment, endothelium-dependent and -independent vasomotion were evaluated by intracoronary infusion of incremental doses of acetylcholine (for right coronary artery: low-dose 5μg, high-dose 50μg and for left coronary artery: low-dose 10μg, high-dose 100μg) and nitroglycerine (200μg). Mean luminal diameter of the distal segments, beginning 5 mm and ending 15 mm distal to the edge of the treated segment was quantitatively measured by angiography. Results Clinical and procedural characteristics were not different between two groups. Vasoconstriction after acetylcholine infusion was less pronounced in the DCB group than the BP-EES group (low-dose: 4±13% vs −4±14%, p=0.158, high-dose: −2±14% vs −28±30%, p=0.013). The response to nitroglycerin was not different between two groups (17±13% vs 18±24%, p=0.838). Conclusion Vasoconstriction after acetylcholine infusion in the peri-treated region was more pronounced in the BP-EES group than in the DCB group, which suggests that endothelial function of coronary vessel treated by DCB can be more preserved than new-generation DES. Figure 1 Funding Acknowledgement Type of funding source: None

Atrial dilation as a substrate for atrial fibrillation in the canine complete chronic atrioventricular block model

Abstract Background Atrial fibrillation (AF) is the most common cardiac arrhythmia treated in clinical practice. Structural remodeling is characterized by atrial enlargement and contributes to the therapeutic resistance in patients with long-standing AF. Purpose To study the atrial arrhythmogenic and echocardiographic consequences induced by volume overload in the complete chronic atrioventricular block (CAVB) dog. Methods Echocardiographic and electrophysiological data was obtained in 14 anaesthetized Mongrel dogs, in acute AV-block (AAVB), after 6 weeks of CAVB (CAVB6) and CAVB10. Left atrial (LA) volume was determined with 2D echocardiography by using the biplane method. An electrocardiogram and monophasic action potentials (MAP) at the right atrial (RA) free wall were recorded. Atrial effective refractory period (AERP) was determined by continuous programmed electrical stimulation (PES) of 20 beats with a cycle length of 400 ms and an extrastimulus with decremental design until refractoriness was reached. A continuous PES protocol of 20 beats with an extrastimulus 5 ms longer than the AERP was applied for 150 seconds to trigger AF. After 5 min without arrhythmias, autonomic neuromodulation was performed by intravenous infusion (IV) of acetylcholine (1,5μg/kg/min to 6,0μg/kg/min) for 20 min followed by prompt IV infusion of isoprenaline (3μg/min) until the atrial heart rate increased by 20 bpm. PES with an extrastimulus was repeated for 150 seconds to induce AF. Results LA volume increased from 13.7±3.2 ml at AAVB to 20.5±5.9 ml* at CAVB6, and 22.7±6.0 ml* at CAVB10 (Fig. 1A). AERP was similar at AAVB, CAVB6, and CAVB10 (115.8±11.9, 117.3±11.7, and 106.8±12.1 ms respectively). Repetitive AF paroxysms of &amp;gt;10 seconds were induced in 1/14 (7%) dogs at AAVB, 1/11 (9%) at CAVB6, and 5/10 (50%)* at CAVB10 (*p&amp;lt;0.05) upon PES (Fig. 1B). Combined neuromodulation and PES did not increase the AF inducibility rate, but prolonged the longest episode of AF in the inducible dogs from 55±49 seconds to 236±202 seconds* at CAVB10 (Fig. 1C). LA volume was higher in inducible dogs 25.0±4.9 ml compared to 18.4±4.2 ml in non-inducible dogs at CAVB10. Conclusion Sustained atrial dilation forms a substrate for repetitive paroxysms of AF. Neuro-modulation prolongs AF episode duration in susceptible dogs. This animal model can be used to study structural remodeling of the atria and possible therapeutic advances in the management of AF. Figure 1 Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Amgen Research

Artificial intelligence-derived physiological aging is associated with coronary endothelial dysfunction

Abstract Background An Artificial intelligence (AI)-enabled algorithm can provide an age estimate from a single standard resting ECG. The gap between AI-estimated age (ECG age) and chronological age (Age-Gap) has been associated with total and cardiovascular mortality. We hypothesized that coronary endothelial dysfunction (CED), an early feature of coronary atherosclerosis, is associated with physiological aging, as measured by ECG age. Purpose The aim of this study is to investigate the association of CED, a potential index of cardiac aging, and AI-estimated physiological aging. Methods 1902 patients with signs and/or symptoms of ischemia and with non-obstructive coronary artery disease (&amp;lt;40% angiographic stenosis) who underwent functional coronary angiography with intracoronary (IC) acetylcholine (Ach) infusions and a resting ECG within one year were included in this analysis. CED was defined as coronary artery constriction [%ΔCoronary artery diameter (CAD) &amp;lt;0] in response to IC Ach. Patients were categorized as CED+ or CED−. The ECG age were calculated by a previously-trained AI algorithm that was built using the Keras framework with Tensorflow backend and Python. The association between ECG-age and Age-Gap, with CED was investigated. Results Average chronological age was 50.9±12.5, ECG age was 54.1±11.6, 1261 (66%) were females. Compared to CED−, the CED+ group had more males and hyperlipidaemia (p&amp;lt;0.05 for both). Age-gap was significantly higher in patients with CED+ (Fig. A). Multiple regression analysis showed that CED+ was associated with Age-gap (standardized β [sβ] coefficient = 0.08, P=0.001) even after adjustment for chronological age (sβ coefficient = 0.07, P=0.001), and even after adjusting for other cardiovascular risk factors like gender and obesity (sβ coefficient = 0.07, P&amp;lt;0.0001). Furthermore, there is a significant gradual increase in vasoconstriction, in response to IC Ach, with increasing Age-gap (Fig. B). Conclusion Abnormal coronary endothelial function is associated with an increased AI-estimated age which could indicate a higher physiological age. Funding Acknowledgement Type of funding source: None

Coronary microvascular dysfunction is associated with exertional haemodynamic abnormalities in patients with heart failure with preserved ejection fraction.

This study uniquely explored the relationship between coronary microvascular function and exercise haemodynamics using concurrent invasive testing. Fifty-one consecutive patients with unexplained cardiac exertion symptoms, non-obstructive coronary artery disease and normal left ventricular ejection fraction (>50%) underwent haemodynamic exercise assessment and concurrent coronary reactivity testing. Heart failure with preserved ejection fraction (HFpEF) was defined as a pulmonary arterial wedge pressure (PAWP) ≥15 mmHg at rest and/or ≥25 mmHg at peak exercise. Endothelium-independent coronary microvascular dysfunction (CMD) was defined as a coronary flow reserve (CFR) ≤2.5, while endothelium-dependent CMD was defined as ≤50% increase in coronary blood flow (CBF) in response to intracoronary acetylcholine infusions. Patients with HFpEF (n=22) had significantly lower CFR (2.5 ± 0.6 vs. 3.2 ± 0.7; P=0.0003) and median %CBF increase in response to intracoronary acetylcholine [1 (-35; 34) vs. 64 (-4; 133); P=0.002] compared to patients without HFpEF (n=29). PAWP was significantly higher in patients with endothelium-independent CMD compared to controls during both rest and exercise. This significant elevation was only present during exercise in patients with endothelium-dependent CMD compared to controls. CFR had significant inverse correlations with PAWP at rest (r=-0.31; P=0.03) and peak exercise (r=-0.47, P=0.001). CFR also had positive correlations with maximal exercise capacity (in W/kg) (r=0.33, P=0.02). Coronary microvascular function is inversely associated with filling pressures, particularly during exercise. Both types of CMD are associated with higher filling pressures at peak exercise. These findings underscore the potential mechanism and therapeutic target for CMD and HFpEF.

Microvascular Function Is Impaired after Short-Term Immobilization in Healthy Men.

We examined whether 2 wk of one-leg immobilization would impair leg microvascular function and to what extent a subsequent period of intense aerobic cycle training could restore function. Study participants were healthy young men (n = 12; 20-24 yr of age). Leg microvascular function was determined before the intervention, after the immobilization period, and after a 4-wk exercise training period. Microvascular function was assessed as the vasodilator response to intra-arterial infusion of acetylcholine and sodium nitroprusside and as the vasoconstrictor response to endogenous noradrenaline release induced by tyramine infusion. Vasodilator enzymes as well as prooxidant and antioxidant enzymes were assessed by protein analysis in skeletal muscle samples: endothelial nitric oxide synthase, NADPH oxidase (NOX p67 and NOX gp91), and superoxide dismutase 2 (SOD2). The acetylcholine-induced change in vascular conductance was reduced after the 2 wk of immobilization (P = 0.003), tended to increase (P = 0.061), and was back to baseline levels after the subsequent 4 wk of exercise training. Plasma prostacyclin levels in response to acetylcholine infusion were lower after immobilization than before (P = 0.041). The changes in vascular conductance with sodium nitroprusside and tyramine were similar during all conditions. Skeletal muscle protein levels of endothelial nitric oxide synthase in the experimental leg were unchanged with immobilization and subsequent training but increased 47% in the control leg with training (P = 0.002). NOX p67, NOX gp91, and SOD2 in the experimental leg remained unaltered with immobilization, and SOD2 was higher than preimmobilization after 4 wk of training (P < 0.001). The study shows that 2 wk of immobilization impairs leg microvascular endothelial function and prostacyclin formation but that 4 wk of intense aerobic exercise training restores the function. The underlying mechanism may reside in the prostacyclin system.

Electrical Propagation of Vasodilatory Signals in Capillary Networks.

We have developed a computational model to study electrical propagation of vasodilatory signals and arteriolar regulation of blood flow depending on the oxygen tension and agonist distribution in the capillary network. The involving key parameters of endothelial cell-to-cell electrical conductivity and plasma membrane area per unit volume were calibrated with the experimental data on an isolated endothelial tube of mouse skeletal feeding arteries. We have estimated the oxygen saturation parameters in terms of erythrocyte ATP release from the data of a left anterior descending coronary blood perfusion of dog. Regarding the acetylcholine-induced upstream conduction, our model shows that spatially uniform superfusion of acetylcholine attenuates the electrical signal propagation, and blocking calcium-activated potassium channels suppresses that attenuation. On the other hand, a local infusion of acetylcholine induces enhanced electrical propagation that corresponds to physiological relevance. Integrating the electrophysiology of endothelial tube and the electrophysiology/mechanics of a lumped arteriole, we show mechanistically that endothelial purinergic oxygen sensing of ATP released from erythrocytes and local infusion of acetylcholine are individually effective to induce vasodilatory signals to regulate blood flow in arterioles. We have recapitulated the upstream vasomotion in arterioles from the elevated oxygen tension in the downstream capillary domain. This study is a foundation for characterizing effective pharmaceutical strategies for ascending vasodilation and oxygenation.

Coronary Microvascular Dysfunction.

Many patients with chest pain undergoing coronary angiography do not show significant obstructive coronary lesions. A substantial proportion of these patients have abnormalities in the function and structure of coronary microcirculation due to endothelial and smooth muscle cell dysfunction. The coronary microcirculation has a fundamental role in the regulation of coronary blood flow in response to cardiac oxygen requirements. Impairment of this mechanism, defined as coronary microvascular dysfunction (CMD), carries an increased risk of adverse cardiovascular clinical outcomes. Coronary endothelial dysfunction accounts for approximately two-thirds of clinical conditions presenting with symptoms and signs of myocardial ischemia without obstructive coronary disease, termed “ischemia with non-obstructive coronary artery disease” (INOCA) and for a small proportion of “myocardial infarction with non-obstructive coronary artery disease” (MINOCA). More frequently, the clinical presentation of INOCA is microvascular angina due to CMD, while some patients present vasospastic angina due to epicardial spasm, and mixed epicardial and microvascular forms. CMD may be associated with focal and diffuse epicardial coronary atherosclerosis, which may reinforce each other. Both INOCA and MINOCA are more common in females. Clinical classification of CMD includes the association with conditions in which atherosclerosis has limited relevance, with non-obstructive atherosclerosis, and with obstructive atherosclerosis. Several studies already exist which support the evidence that CMD is part of systemic microvascular disease involving multiple organs, such as brain and kidney. Moreover, CMD is strongly associated with the development of heart failure with preserved ejection fraction (HFpEF), diabetes, hypertensive heart disease, and also chronic inflammatory and autoimmune diseases. Since coronary microcirculation is not visible on invasive angiography or computed tomographic coronary angiography (CTCA), the diagnosis of CMD is usually based on functional assessment of microcirculation, which can be performed by both invasive and non-invasive methods, including the assessment of delayed flow of contrast during angiography, measurement of coronary flow reserve (CFR) and index of microvascular resistance (IMR), evaluation of angina induced by intracoronary acetylcholine infusion, and assessment of myocardial perfusion by positron emission tomography (PET) and magnetic resonance (CMR).

Abstract P082: Elevated Circulating Endothelial-Derived Microvesicles Are Associated With Obesity-Related Endothelial Dysfunction

Background: Obesity reduces the number of years lived free of cardiovascular disease (CVD) and increases the number of years lived with CVD, contributing to increased morbidity and mortality risk across all ages. Experimental and clinical studies indicate that a proatherogenic endothelial phenotype is a major consequence of increased adiposity and a primary mechanism underlying obesity-related CVD. Extracellular microvesicles, particularly endothelial cell-derived microvesicles (EMVs), are seminal functional modulators of vascular health and disease. The purpose of this study was to determine: 1) if circulating EMV levels are elevated with obesity, independent of other cardiometabolic risk factors; and if so, 2) whether circulating EMVs are associated with obesity-related endothelial vasodilator dysfunction. Methods: Thirty sedentary, middle-aged adults (45-63 years) were studied: 15 normal weight (10M/5F; age: 56±1 yr; BMI: 23.2±0.4 kg/m2; body fat: 25.1±2.4 %) and 15 obese (10M/5F; age: 54±1 yr; BMI: 31.5±0.3 kg/m2; body fat: 37.2±1.7 %). All subjects were free of other cardiometabolic risk factors and overt disease. EMV identification (CD31 + /42b - ) and concentration in peripheral blood were determined by flow cytometry. Forearm blood flow (FBF: via plethysmography) was assessed in response to intra-arterial infusions of acetylcholine (4.0, 8.0 and 16.0 μg/100 mL tissue/min) and sodium nitroprusside (1.0, 2.0 and 4.0 μg/100 mL tissue/min). Results: Circulating EMV levels were ~100% higher (P&lt;0.05) in obese (182±14 EMV/μL) compared with normal weight (91±12 EMV/μL) adults. FBF response to acetylcholine was significantly lower (~35%) in the obese (from 4.0±0.2 to 10.3±0.6 mL/100 mL tissue/min vs 4.3±0.3 to 15.4±0.8 mL/100 mL tissue/min) group. Circulating EMVs were significantly and inversely associated with total FBF response to acetylcholine (r=-0.55). Conclusions: Obesity, independent of other cardiometabolic risk factors, is associated with elevated circulating levels of EMVs. Higher circulating EMVs in obese adults may contribute to adiposity-related endothelial dysfunction and vascular disease risk. Indeed, circulating EMVs have been linked to disease risk, severity and outcome in other high-risk populations.

Ischemic Preconditioning Improves Microvascular Endothelial Function in Remote Vasculature by Enhanced Prostacyclin Production.

BACKGROUNDThe mechanisms underlying the effect of preconditioning on remote microvasculature remains undisclosed. The primary objective was to document the remote effect of ischemic preconditioning on microvascular function in humans. The secondary objective was to test if exercise also induces remote microvascular effects.METHODS AND RESULTSA total of 12 healthy young men and women participated in 2 experimental days in a random counterbalanced order. On one day the participants underwent 4×5 minutes of forearm ischemic preconditioning, and on the other day they completed 4×5 minutes of hand‐grip exercise. On both days, catheters were placed in the brachial and femoral artery and vein for infusion of acetylcholine, sodium nitroprusside, and epoprostenol. Vascular conductance was calculated from blood flow measurements with ultrasound Doppler and arterial and venous blood pressures. Ischemic preconditioning enhanced (P<0.05) the remote vasodilator response to intra‐arterial acetylcholine in the leg at 5 and 90 minutes after application. The enhanced response was associated with a 6‐fold increase (P<0.05) in femoral venous plasma prostacyclin levels and with a transient increase (P<0.05) in arterial plasma levels of brain‐derived neurotrophic factor and vascular endothelial growth factor. In contrast, hand‐grip exercise did not influence remote microvascular function.CONCLUSIONSThese findings demonstrate that ischemic preconditioning of the forearm improves remote microvascular endothelial function and suggest that one of the underlying mechanisms is a humoral‐mediated potentiation of prostacyclin formation.

In This Issue

HomeCirculation ResearchVol. 127, No. 2In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyRedditDiggEmail Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published2 Jul 2020https://doi.org/10.1161/RES.0000000000000419Circulation Research. 2020;127:204is related toIn Situ Expansion, Differentiation, and Electromechanical Coupling of Human Cardiac Muscle in a 3D Bioprinted, Chambered OrganoidGlobal Reach 2018 Heightened α-Adrenergic Signaling Impairs Endothelial Function During Chronic Exposure to Hypobaric Hypoxiais related toIdentification of Functional Variant Enhancers Associated With Atrial FibrillationIn Situ Differentiation to Produce Cardiac Tissues (p 207)Kupfer et al use 3D-printing to create beating human heart organoids.Download figureDownload PowerPointCultured human cardiac muscle is valuable for testing the efficacy and toxicity of drugs, studying diseases, assessing injury responses, and more. But growing such muscle in the lab is tricky. For one thing, adult cardiomyocytes don’t generally proliferate. For another, cells in a dish don’t recapitulate the forces and functions of a 3D heart. Generating cardiomyocytes from stem cells enables researchers to largely circumvent the issue of proliferation, so Kupfer and colleagues have focused their attention on the issue of 3D structure. They developed a photocrosslinkable bioink containing extracellular matrix proteins and pluripotent stem cells that can be printed within a supportive gel bath, and then stabilized with UV-induced crosslinking. After removal of the printed structure from the support gel, the stem cells proliferate to high density and are differentiated into cardiomyocytes. Using this approach, the team printed a chambered human heart organoid—approximately the size of a mouse heart—showing that it could propagate action potentials as well as beat and pump fluid. Furthermore, beat rate was pharmacologically modifiable. By showing the mechanical and electrical activities of this mini-heart, the work sets the stage for using such organoids in all manner of drug and disease studies.Functional Variant Elements in Atrial Fibrillation Models(p 229)van Ouwerkerk et al discover gene regulatory elements at atrial fibrillation associated loci.Download figureDownload PowerPointAtrial fibrillation (AF) is the most common form of arrhythmia and a major risk factor for heart failure, dementia, stroke, and sudden death. Genome-wide association studies have revealed more than 100 genetic loci linked to the condition, many of which are in intergenic or intronic regions and are enriched for transcription factor binding sites and epigenetic modifications suggesting potential gene regulatory roles. To test this idea, Ouwerkerk and colleagues used a method called self-transcribing active regulatory region sequencing (or STARR-Seq) to screen 12 of the strongest AF-linked regions of the genome—together containing more than 1600 AF-linked variants—for their gene regulatory activity in cultured rat atrial myocytes. From this screen, they found ≈400 regulatory elements, of which 24 exhibited variant-specific differences in regulatory activity. For one of these elements—upstream of the gene HCN4—deletion of the orthologous element in mice caused diminished transcriptional activity of the gene. Moreover, the mice had brachycardia and sinus node dysfunction. This proof-of-principle study confirms that such a regulatory element screen can provide insight into the consequences of variants associated with AF or, for that matter, other diseases.Vascular Function in Chronic Hypoxia(p e1)Tymko et al, examine how low oxygen at high altitudes affects vascular endothelium function.Download figureDownload PowerPointChronic hypoxia, whether due to disease or time spent at high altitude, is associated with increased sympathetic nerve activity and poor endothelial function—marked by reduced endothelial-dependent vasodilation. But whether the heightened nerve activity actually causes endothelial dysfunction was unclear. To investigate, Tymko and colleagues analyzed heart rate, nerve activity, and hemodynamics—including blood pressure, flow, and arterial diameter—in 9 people who normally live in lowlands after they spent 2-to-3 weeks at 4300 meters (14 000 feet) in the Andean highlands. The team found that, at high altitude, lowlanders had increased sympathetic nerve activity and reduced endothelial function—assessed by their vasodilatory responses to acetylcholine infusion. But also that administration of adrenergic blockers, which reduce sympathetic nerve activity, improved the subjects’ endothelial function. Similar results were seen in native Andean highlanders with excess red blood cell counts—a mark of endothelial dysfunction—compared with their healthy counterparts. The work provides the first direct link between sympathetic nerve activity and endothelial function as well as insights into the pathophysiological processes associated with low-oxygen conditions. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesIn Situ Expansion, Differentiation, and Electromechanical Coupling of Human Cardiac Muscle in a 3D Bioprinted, Chambered OrganoidMolly E. Kupfer, et al. Circulation Research. 2020;127:207-224Identification of Functional Variant Enhancers Associated With Atrial FibrillationAntoinette F. van Ouwerkerk, et al. Circulation Research. 2020;127:229-243Global Reach 2018 Heightened α-Adrenergic Signaling Impairs Endothelial Function During Chronic Exposure to Hypobaric HypoxiaMichael M. Tymko, et al. Circulation Research. 2020;127:e1-e13 July 3, 2020Vol 127, Issue 2Article InformationMetrics Download: 200 © 2020 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000419 Originally publishedJuly 2, 2020 PDF download

P0978THE EFFECTS OF CHRONIC DAPAGLIFLOZIN TREATMENT ON THE RENAL MICROVASCULATURE IN A RAT MODEL OF TYPE 2 DIABETES

Abstract Background and Aims Chronic kidney disease (CKD) is an ever-growing concern and CKD associated with diabetes accounted for ∼ 35% of new cases of end-stage renal failure. Clinical trials with insulin-independent sodium-glucose co-transporter 2 (SGLT2) inhibitors not only showed significant improvements in hyperglycemia and thus renal damage, but also reduced the risk of adverse cardiovascular events. Microvessels supply local tissue oxygen demands and are important controllers of regional perfusion. Endothelial dysfunction has been posited to be an important factor driving the pathogenesis of diabetic nephropathy, largely through impaired eNOS activity and thus reduced nitric oxide bioavailability. Thus, we aim to determine the effects of SGLT2 inhibition on vasodilator function in the renal vasculature. We hypothesize that rats chronically treated with dapagliflozin, a SGLT2 inhibitor, improves renal endothelial function and the microvessels are better able to maintain perfusion in response to the inhibition of nitric oxide synthase and prostaglandin blockade. Method Male Zucker fatty diabetic rats (8 wk old), a model of type 2 diabetes, were given daily oral gavage of 1 mg/kg dapagliflozin or its vehicle for up to 22 wks of age (n=6/group). Renal excretory function, glomerular filtration rate (GFR) and indices of renal injury was assessed before treatment and after every 4 wks up until 22 wks of age. GFR was assessed via transcutaneous clearance of FITC-sinistrin. Vasodilator function of the renal microvasculature was assessed via X-ray microangiography. We conducted successive imaging of the microvessels before and during infusion of acetylcholine (ACh) and sodium nitroprusside (SNP) which facilitated the assessment of endothelium dependent and independent dilation respectively. After which, rats were given successive boluses of L-NAME and indomethacin to assess the vasodilatory function of the microvasculature independent of nitric oxide and prostaglandins respectively. These inhibitors were given under the conditions of SNP clamp which allowed for us to titrate the blood pressure to baseline levels. Lastly, we assessed the ability of endothelium hyperpolarizing factors (EDHFs) to maintain microvascular perfusion when SNP infusion ceased and an infusion of ACh commenced while still under the effects of L-NAME and indomethacin. Results As expected, dapagliflozin alleviated hyperglycemia across the treatment period. There was a tendency for dapagliflozin to ameliorate the decline of GFR, although this apparent effect was not statistically significant. Dapagliflozin did not appear to improve indices of renal injury. Treatment with dapagliflozin alleviated polyuria but did not appear to have an impact on urine osmolarity or sodium excretion. The responses (vessel diameter) of renal microvessels to ACh and SNP was greater in dapagliflozin than in vehicle fed rats. The microvessels of vehicle fed rats appeared to undergo relative constriction in response to L-NAME and indomethacin even under the effects of SNP clamp. In contrast, microvessels of dapagliflozin fed rats appeared to be relatively well-perfused after NOS and COX blockade. This suggests that dapagliflozin may improve endothelial dysfunction commonly associated with diabetic nephropathy. Following NOS and COX blockade, ACh was infused in rats to determine the status of vasodilatory function mediated by EDHFs. The microvessels in diabetic rats did not appear to be dilated after infusion of ACh, suggesting that vasodilatory effects of EDHFs on the vasculature is diminished in diabetic rats. Dapagliflozin appeared to improve this effect in that the renal microvessels were dilated even when NOS and COX production was blocked/inhibited. Conclusion Chronic treatment of dapagliflozin may improve endothelial dysfunction and thus retard the progression of diabetic nephropathy in a rat model of type 2 diabetes.

Increased prostacyclin formation after high-intensity interval training in late postmenopausal women.

Aging impairs vascular function in women, with the largest detrimental effects occurring during the menopausal transition. Deficiency in the nitric oxide system has been suggested to be responsible for impairment in vascular function with aging, but recent observations suggest that the prostacyclin system, acting in redundancy with the nitric oxide system, may be of importance too. Improvement in vascular function is a hallmark of exercise training and we hypothesize that leg vascular function is improved by exercise training in late postmenopausal women, and that the underlying mechanism is increased endothelial formation of prostacyclin and responsiveness to prostacyclin by the vascular smooth muscle cells. Femoral-arterial infusion of acetylcholine and epoprostenol was used to assess vascular function and prostacyclin release in ten late postmenopausal women (62 ± 7years) before and after 10weeks of high-intensity interval training (floorball conducted as small-sided games). The training intervention increased fitness level (V̇O2max) by 7 ± 7% and reduced systolic and diastolic blood pressure by 10 ± 10 and 5 ± 6mmHg, respectively. Leg vascular responsiveness to during acetylcholine and epoprostenol infusion was unchanged with training, whereas the release of prostacyclin during acetylcholine infusion increased by 125%. In late postmenopausal women, vascular function assessed by femoral-arterial infusion of acetylcholine was not improved after 10weeks of floorball training, but acetylcholine-induced prostacyclin formation and blood pressure were substantially improved. It is possible that a longer training period could lead to improvements in vascular function and that the observed increase in prostacyclin formation is one of the initial underlying changes.

Adjunctive mesenchymal stem/stromal cells augment microvascular function in poststenotic kidneys treated with low-energy shockwave therapy.

Effective therapeutic strategies are needed to preserve renal function in patients with atherosclerotic renal artery stenosis (ARAS). Low-energy shockwave therapy (SW) and adipose tissue-derived mesenchymal stem/stromal cells (MSCs) both stimulate angiogenesis repair of stenotic kidney injury. This study tested the hypothesis that intrarenal delivery of adipose tissue-derived MSCs would enhance the capability of SW to preserve stenotic kidney function and structure. Twenty-two pigs were studied after 16 weeks of ARAS, ARAS treated with a SW regimen (bi-weekly for 3 weeks) with or without subsequent intrarenal delivery of adipose tissue-derived MSCs and controls. Four weeks after treatment, single-kidney renal blood flow (RBF) before and after infusion of acetylcholine, glomerular filtration rate (GFR), and oxygenation were assessed in vivo and the renal microcirculation, fibrosis, and oxidative stress ex vivo. Mean arterial pressure remained higher in ARAS, ARAS + SW, and ARAS + SW + MSC compared with normal. Both SW and SW + MSC similarly elevated the decreased stenotic kidney GFR and RBF observed in ARAS to normal levels. Yet, SW + MSC significantly improved RBF response to acetylcholine in ARAS, and attenuated capillary loss and oxidative stress more than SW alone. Density of larger microvessels was similarly increased by both interventions. Therefore, although significant changes in functional outcomes were not observed in a short period of time, adjunct MSCs enhanced pro-angiogenic effect of SW to improve renal microvascular outcomes, suggesting this as an effective stratege for long-term management of renovascular disease.