Endothelium-independent Dilation Research Articles

Evaluation of Statin Therapy on Endothelial Function in Hypercholesterolemic Rabbits by Automatic Measurement of Arterial Wall Movement Using Ultrasound Images

The aim of this study was to evaluate arterial endothelial function, assessed as acetylcholine-mediated dilation (AMD), in a hypercholesterolemic atherosclerotic rabbit model to investigate the effects of atorvastatin in the atherosclerotic process, using a new computerized analysis model and ultrasound images. Twenty-seven rabbits were fed a high-cholesterol (2%) diet for 6 wk and then divided into three groups for an additional 9 wk: Group A received regular chow food, group B received a 2% cholesterol-rich diet plus atorvastatin drug, and group C received regular chow food plus atorvastatin. Ultrasound examinations of endothelial function of the rabbit abdominal aorta artery were performed immediately after the 6 weeks (0 wk) and then 3, 6 and 9 wk after that. For off-line analysis, a computerized analysis method for evaluating instantaneous changes in the wall of the rabbit abdominal aorta was used. As parameters of improvement resulting from treatment, endothelium-dependent acetylcholine-induced dilation and endothelium-independent nitroglycerin-induced dilation were evaluated in treated rabbits. Differences among groups were tested using analysis of variance. On histopathology, intima-media thickness decreased after treatment in all groups. There were no significant differences in arterial diameter and blood velocity changes among treated rabbits at 0, 3, 6 and 9 wk of treatment in all groups, except in end-diastolic velocity, radial strain percentage, pulse index and resistance index in group C. In group A, AMD did not significantly improve after 3, 6 and 9 wk, as compared with 0 wk. Atorvastatin treatment significantly increased AMD (18%) at 3 wk in group B, compared with week 0. AMD significantly increased after 3 (26%), 6 (124%) and 9 (182%) wk in group C, compared with 0 wk. It is concluded that the new automatic method enables accurate and repeated evaluation of endothelial function during the progression and regression of atherosclerosis. Also, the results obtained in this study indicate that short-term administration of atorvastatin can improve endothelial function in cholesterol-fed rabbits.

Functional changes of the coronary microvasculature with aging regarding glucose tolerance, energy metabolism, and oxidative stress.

This study was aimed at characterizing the functional progression of the endothelial (ECs) and smooth muscle cells (SMCs) of the coronary microvasculature between youth and old age, as well as at determining the mechanisms of the observed changes on the basis of the glucose tolerance, mitochondrial energy metabolism, and oxidative stress. Male rats were divided into four age groups (3, 6, 11, and 17 months for the young (Y), young adult (YA), middle-aged (MA), and old (O) animals). The cardiac mechanical function, endothelial-dependent dilatation (EDD) and endothelial-independent dilatation (EID) of the coronary microvasculature were determined in a Langendorff preparation. The mitochondrial respiration and H2O2 production were evaluated and completed by ex vivo measurements of oxidative stress. EDD progressively decreased from youth to old age. The relaxation properties of the SMCs, although high in the Y rats, decreased drastically between youth and young adulthood and stabilized thereafter, paralleling the reduction of mitochondrial oxidative phosphorylation. The ECs dilatation activity, low at youth, was stimulated in YA animals and returned to their initial level at middle age. That parameter followed faithfully the progression of the amount of active cardiac endothelial nitric oxide synthase and whole body glucose intolerance. In conclusion, the progressive decrease in EDD occurring with aging is due to different functional behaviors of the ECs and SMCs, which appear to be associated with the systemic glucose intolerance and cardiac energy metabolism.

Mitochondria‐targeted antioxidant (MitoQ) ameliorates age‐related arterial endothelial dysfunction in mice

Age-related arterial endothelial dysfunction, a key antecedent of the development of cardiovascular disease (CVD), is largely caused by a reduction in nitric oxide (NO) bioavailability as a consequence of oxidative stress. Mitochondria are a major source and target of vascular oxidative stress when dysregulated. Mitochondrial dysregulation is associated with primary ageing, but its role in age-related endothelial dysfunction is unknown. Our aim was to determine the efficacy of a mitochondria-targeted antioxidant, MitoQ, in ameliorating vascular endothelial dysfunction in old mice. Ex vivo carotid artery endothelium-dependent dilation (EDD) to increasing doses of acetylcholine was impaired by ∼30% in old (∼27 months) compared with young (∼8 months) mice as a result of reduced NO bioavailability (P < 0.05). Acute (ex vivo) and chronic (4 weeks in drinking water) administration of MitoQ completely restored EDD in older mice by improving NO bioavailability. There were no effects of age or MitoQ on endothelium-independent dilation to sodium nitroprusside. The improvements in endothelial function with MitoQ supplementation were associated with the normalization of age-related increases in total and mitochondria-derived arterial superoxide production and oxidative stress (nitrotyrosine abundance), as well as with increases in markers of vascular mitochondrial health, including antioxidant status. MitoQ also reversed the age-related increase in endothelial susceptibility to acute mitochondrial damage (rotenone-induced impairment in EDD). Our results suggest that mitochondria-derived oxidative stress is an important mechanism underlying the development of endothelial dysfunction in primary ageing. Mitochondria-targeted antioxidants such as MitoQ represent a promising novel strategy for the preservation of vascular endothelial function with advancing age and the prevention of age-related CVD.

Response to comment on Goldfine et al. Targeting inflammation using salsalate in patients with type 2 diabetes: effects on flow-mediated dilation (TINSAL-FMD). Diabetes care 2013;36:4132-4139.

In our study to target inflammation using salsalate in patients with type 2 diabetes, we demonstrate improvement in glycemia but no change in either flow-mediated, endothelium-dependent (FMD) or nitroglycerin-mediated, endothelium-independent dilation over 6 months in salsalate (3.5 g/day) compared with placebo-treated patients (1). It is important to note that no adverse cardiovascular safety signal for endothelial function was demonstrated. Our findings differ from Pierce and colleagues (2,3), who demonstrated improvement in vascular function and …

Adipose dysfunction with aging is associated with resistance artery endothelial dysfunction and impaired angiogenic capacity (688.3)

Although tissue dysfunction is reported in aging, effects of aging on adipose tissue per se are not well studied. To address this, we assessed metabolic homeostasis, adipose tissue structure‐function and adipose artery endothelial function from young (6 mo) and old (29 mo) male B6D2F1 mice. Fasted blood glucose was not different with age but plasma insulin, homeostatic model assessment (HOMA‐) of insulin resistance (IR), and beta cell function (‐B) were increased by 84%, 54%, 57% respectively (P&lt;0.05) in old mice. Old mice also were glucose intolerant (P&lt;0.05), concomitant with increased plasma free fatty acids (P&lt;0.05) and liver triglycerides (P&lt;0.05). Despite no difference in body mass, epididymal white adipose tissue (eWAT) mass was 40% lower in old mice. There was ~60% reduction in mean adipocyte area (p&lt;0.01), 7‐fold increase in fibrosis (p&lt;0.01) and ~50% reduction in vascular density (p&lt;0.01) in old eWAT. There also was a 2‐fold reduction in in vitro eWAT angiogenesis and a ~25% reduction in endothelium dependent dilation to acetylcholine in eWAT arteries (p&lt;0.01) from old mice, without a reduction in endothelium independent dilation. Thus, aging results in metabolic dysfunction associated with increased circulating and ectopic lipids, altered adipose tissue morphology and reduced vascular density, concomitant with impaired angiogenic potential and endothelial dysfunction in adipose arteries.Grant Funding Source: Supported by R21 AG033755, K01 AG033196, R01 AG040297

SIRT1 overexpression protects against high fat diet‐induced cerebral artery endothelial dysfunction (1070.10)

High fat (HF) diet is associated with increased cerebrovascular disease risk, but interventional targets to protect cerebral artery function with HF diet have not been elucidated. Sirtuins control cellular energy metabolism and SIRT1 transgenic overexpressing (SIRT‐TG) mice are protected against some of the negative consequences of HF diet, such as glucose intolerance. However, the effect of SIRT1‐TG on cerebral artery function after HF diet is unknown. We measured middle cerebral artery (MCA) endothelium‐dependent dilation to acetylcholine (ACh) in normal chow (NC) and HF diet fed SIRT‐TG and wildtype (WT) mice (6 mo, n=6‐8/group). In NC mice, MCA dilation to ACh did not differ between SIRT1‐TG and WT (max: 66±13% vs. 67±14%, P=0.90). HF WT mice had impaired MCA dilation to ACh (46±11%, P&lt;0.01 vs. NC WT). However, MCA dilation to ACh for HF SIRT‐TG mice was greater than HF WT mice (63±10%, P=0.01) and not different from NC groups (P&gt;0.05). There were no group differences after nitric oxide (NO) synthase inhibition with L‐NAME (P&gt;0.05), indicating that the impaired dilation to ACh in HF WT mice resulted from reduced NO bioavailability. Endothelium‐independent dilation did not differ between groups (P&gt;0.05). In conclusion, HF diet induced cerebral artery endothelial dysfunction by reducing NO bioavailability in WT mice. SIRT1‐TG mice are protected against cerebral artery endothelial dysfunction induced by HF diet.Grant Funding Source: AG029337, AG040297, AG033196, HL007576

Divergence in depressive symptom severity and vascular dysfunction with gender in rats with unpredictable chronic mild stress (680.20)

Chronic stress leads to many negative health outcomes proportional to the severity of developed depressive symptoms. This includes vascular reactivity, as endothelial function is compromised by 8 weeks of unpredictable chronic mild stress (UCMS). To extend this, we imposed 8 weeks of UCMS on healthy rats of both genders from 9 weeks of age. In males, plasma cortisol and depressive symptom severity (coat status, anhedonia, delayed grooming) were elevated. Endothelial‐dependent dilation to methacholine/acetylcholine was impaired in conduit arteries/skeletal muscle arterioles, indicating a near complete loss of NO bioavailability and increased production of TxA2 with elevated ROS. Endothelium‐independent dilation was intact. However, in females, depressive symptoms and plasma cortisol increases were more severe, although impairments to vascular reactivity were attenuated. The effects of elevated ROS and constrictor prostanoids were also blunted. These results suggest that, in comparison to males, female rats are more susceptible to chronic stress in terms of the severity of depressive behaviors, but that the subsequent development of vasculopathy is blunted.Grant Funding Source: Supported by National Institutes of Health and American Heart Association

Effects of aging and high fat diet on endothelial function in middle cerebral arteries is not additive (1070.11)

Vascular dysfunction in cerebral arteries has been associated with cognitive impairments with advancing age and disease. It is not known, however, how aging and consumption of a high fat (HF) obesigenic diet interact to impact cerebrovascular function. We examined endothelium dependent dilation (EDD) to acetylcholine in the middle cerebral arteries of young (6‐8 mo) and old (29‐31 mo) normal chow (NC) and HF diet fed mice. Maximal EDD was reduced with aging (68 ± 6 vs. 40 ± 2%, P&lt;0.01) in NC mice. HF reduced EDD in young (41 ± 3%, P&lt;0.01) but was without effect in old (34 ± 5%, P=0.3) mice. Differences in maximal EDD with aging and after HF diet were eliminated after inhibition of nitric oxide (NO) synthase by L‐NAME, indicating that the impairments resulted from reduced NO bioavailability. There were no differences in endothelium independent dilation to sodium nitroprusside between groups (P’s&gt;0.5). Advancing age and consumption of a HF diet independently reduce cerebrovascular endothelial function through reductions in NO, but there is no further decrement in old mice fed HF diet.Grant Funding Source: Supported by NIH grants: R21 AG033755, K01 AG033196, R01 AG040297

Impaired Vascular Function in Physically Active Premenopausal Women With Functional Hypothalamic Amenorrhea Is Associated With Low Shear Stress and Increased Vascular Tone

Exercise-trained hypoestrogenic premenopausal women with functional hypothalamic amenorrhea (ExFHA) exhibit impaired endothelial function. The vascular effects of an acute bout of exercise, a potent nitric oxide stimulus, in these women are unknown. Three groups were studied: recreationally active ExFHA women (n = 12; 24.2 ± 1.2 years of age; mean ± SEM), and recreationally active (ExOv; n = 14; 23.5 ± 1.2 years of age) and sedentary (SedOv; n = 15; 23.1 ± 0.5 years of age) ovulatory eumenorrheic women. Calf blood flow (CBF) and brachial artery flow-mediated dilation (FMD) were evaluated using plethysmographic and ultrasound techniques, respectively, both before and 1 hour after 45 minutes of moderate-intensity exercise. Endothelium-independent dilation was assessed at baseline using glyceryl trinitrate. Calf vascular resistance (CVR) and brachial peak shear rate, as determined by the area under the curve (SRAUCpk), were also calculated. FMD and glyceryl trinitrate responses were lower (P < .05) in ExFHA (2.8% ± 0.4% and 11.6% ± 0.7%, respectively) than ExOv (8.8% ± 0.7% and 16.7% ± 1.3%) and SedOv (8.0% ± 0.5% and 17.1% ± 1.8%). SRAUCpk was also lower (P < .05) in ExFHA. Normalization of FMD for SRAUCpk (FMD/SRAUCpk) did not alter (P > .05) the findings. CBF was lower (P < .05) and CVR higher (P < .05) in ExFHA. After exercise, FMD and SRAUCpk were augmented (P < .05), but remained lower (P < .05), in ExFHA. FMD/SRAUCpk no longer differed (P > .05) between the groups. CBF in ExFHA was increased (P < .05) and CVR decreased (P < .05) to levels observed in ovulatory women. Acute dynamic exercise improves vascular function in ExFHA women. Although the role of estrogen deficiency per se is unclear, our findings suggest that low shear rate and increased vasoconstrictor tone may play a role in impaired basal vascular function in these women.

Endothelial Dysfunction in an Ovine Model of Collagen-Induced Arthritis

Background: Rheumatoid arthritis (RA) induces systemic inflammation, producing a range of co-morbidities including cardiovascular disease. An early vascular change is endothelial dysfunction, characterized by reduced endothelium-dependent vasodilation. The aim of this study was to assess endothelial function in isolated coronary and digital arteries using an ovine model of collagen-induced RA. Methods: Sheep were culled following induction of arthritis, and their endothelial function was compared to that of normal sheep. Paired arterial segments were mounted in a wire myograph and dilated with endothelium-dependent vasodilators [bradykinin, serotonin, carbachol and adenosine diphosphate (ADP); linked to either Gi or Gq signalling pathways] and endothelium-independent dilators (adenosine and sodium nitroprusside) to construct cumulative concentration-response curves. Results: Coronary arteries from arthritic sheep exhibited a significantly greater EC₅₀ value for bradykinin-induced relaxation compared to non-arthritic controls (2.9 × 10^-8<smlcap>M</smlcap> for arthritic sheep vs. 8.6 × 10^-9<smlcap>M</smlcap> for controls). Digital arteries from arthritic sheep also exhibited a significantly greater EC₅₀ for relaxation to ADP and a significant decrease in the carbachol maximal response. Responses to sodium nitroprusside were unchanged in both coronary and digital arteries. Conclusion: Sheep with RA demonstrated attenuated arterial relaxation to endothelium-dependent vasodilators. This may provide a useful model of endothelial dysfunction in chronic inflammatory conditions. The dysfunction did not appear to be associated with one specific G-protein signalling pathway.

Contribution of Hydrogen Sulfide to the Control of Coronary Blood Flow

This study examined the mechanisms by which H2 S modulates coronary microvascular resistance and myocardial perfusion at rest and in response to cardiac ischemia. Experiments were conducted in isolated coronary arteries and in open-chest anesthetized dogs. We found that the H2 S substrate l-cysteine (1-10mM) did not alter coronary tone of isolated arteries in vitro or coronary blood flow in vivo. In contrast, intracoronary (ic) H2 S (0.1-3mM) increased coronary flow from 0.49±0.08 to 2.65±0.13mL/min/g (p<0.001). This increase in flow was unaffected by inhibition of Kv channels with 4-aminopyridine (p=0.127) but was attenuated (0.23±0.02-1.13±0.13mL/min/g) by the KATP channel antagonist glibenclamide (p<0.001). Inhibition of NO synthesis (l-NAME) did not attenuate coronary responses to H2 S. Immunohistochemistry revealed expression of CSE, an endogenous H2 S enzyme, in myocardium. Inhibition of CSE with β-cyano-l-alanine (10μM) had no effect on baseline coronary flow or responses to a 15-second coronary occlusion (p=0.82). These findings demonstrate that exogenous H2 S induces potent, endothelial-independent dilation of the coronary microcirculation predominantly through the activation of KATP channels, however, our data do not support a functional role for endogenous H2 S in the regulation of coronary microvascular resistance.

Conduit artery structure and function in lowlanders and native highlanders: relationships with oxidative stress and role of sympathoexcitation

Research detailing the normal vascular adaptions to high altitude is minimal and often confounded by pathology (e.g., chronic mountain sickness) and methodological issues. We examined vascular function and structure in: (1) healthy lowlanders during acute hypoxia and prolonged (∼2 weeks) exposure to high altitude, and (2) high-altitude natives at 5050 m (highlanders). In 12 healthy lowlanders (aged 32 ± 7 years) and 12 highlanders (Sherpa; 33 ± 14 years) we assessed brachial endothelium-dependent flow-mediated dilatation (FMD), endothelium-independent dilatation (via glyceryl trinitrate; GTN), common carotid intima-media thickness (CIMT) and diameter (ultrasound), and arterial stiffness via pulse wave velocity (PWV; applanation tonometry). Cephalic venous biomarkers of free radical-mediated lipid peroxidation (lipid hydroperoxides, LOOH), nitrite (NO2-) and lipid soluble antioxidants were also obtained at rest. In lowlanders, measurements were performed at sea level (334 m) and between days 3-4 (acute high altitude) and 12-14 (chronic high altitude) following arrival to 5050 m. Highlanders were assessed once at 5050 m. Compared with sea level, acute high altitude reduced lowlanders' FMD (7.9 ± 0.4 vs. 6.8 ± 0.4%; P = 0.004) and GTN-induced dilatation (16.6 ± 0.9 vs. 14.5 ± 0.8%; P = 0.006), and raised central PWV (6.0 ± 0.2 vs. 6.6 ± 0.3 m s(-1); P = 0.001). These changes persisted at days 12-14, and after allometrically scaling FMD to adjust for altered baseline diameter. Compared to lowlanders at sea level and high altitude, highlanders had a lower carotid wall:lumen ratio (∼19%, P ≤ 0.04), attributable to a narrower CIMT and wider lumen. Although both LOOH and NO2- increased with high altitude in lowlanders, only LOOH correlated with the reduction in GTN-induced dilatation evident during acute (n = 11, r = -0.53) and chronic (n = 7, r = -0.69; P ≤ 0.01) exposure to 5050 m. In a follow-up, placebo-controlled experiment (n = 11 healthy lowlanders) conducted in a normobaric hypoxic chamber (inspired O2 fraction (F IO 2) = 0.11; 6 h), a sustained reduction in FMD was evident within 1 h of hypoxic exposure when compared to normoxic baseline (5.7 ± 1.6 vs. 8.0 ±1.3%; P < 0.01); this decline in FMD was largely reversed following α1-adrenoreceptor blockade. In conclusion, high-altitude exposure in lowlanders caused persistent impairment in vascular function, which was mediated partially via oxidative stress and sympathoexcitation. Although a lifetime of high-altitude exposure neither intensifies nor attenuates the impairments seen with short-term exposure, chronic high-altitude exposure appears to be associated with arterial remodelling.

Abstract 9876: Long-Term Treatment With Sitagliptin Provides Multiple Ultrasonic Manifested Antiatherosclerotic Effects Independent of Diabetic Improvement for Type-2 Diabetics

Background: Diabetes mellitus is thought to be highly involved in complex atherothrombogenic processes, but the long-term antiatherosclerotic therapies in patients with type-2 diabetes mellitus have not been established. We previously demonstrated adverse prognostic impacts of endothelial dysfunction and intima-media thickening. Therefore we assessed hypothesis long-term treatment with sitagliptin, a dipeptidyl peptidase-4 inhibitor recently developed antidiabetic agent, chronically inhibits atherosclerotic progression in patients with type-2 diabetes mellitus. Methods: Thirty-four type-2 diabetic patients with stable coronary artery disease were randomized to group-S where they received sitagliptin (50mg/day), or to group-C where they received enhanced antidiabetic therapy without a dipeptidyl peptidase-4 inhibitor for 2 years. We quantified flow-mediated endothelium-dependent dilation of right brachial artery after transient forearm occlusion (FMD), endothelium-independent dilation of brachial artery after sublingual administration of nitroglycerin (TNG), and intima-media thickness of common carotid artery (IMT) using high-resolution ultrasonography. Changes in FMD, TNG, and IMT were compared between the two groups. Results: Group-S (n=17) manifested good compliance to the long-term treatment and improvements in diabetic and lipid variables represented by HbA1c and LDL after long-term medication of sitagliptin, while there were no improvements in group-C. FMD improved after medication in group-S (from 4.0±1.9% to 6.3±2.7%, p&lt;0.01) but not in group-C (from 4.1±2.0% to 4.0±1.9%, p=0.78). Changes of FMD in group-S did not correlate to those of HbA1c (r= 0.14, p=0.57). TNG (%) remained unchanged in both group-S and group-C. IMT did not increase in group-S (from 1.10±0.35mm to 1.08±0.40mm, p=0.17) but increased in group-C (from 1.09±0.47mm to 1.17±0.48mm, p&lt;0.01). Conclusion: This ultrasonic study suggests that long-term treatment of sitagliptin safely improves endothelial function of brachial artery independent of reversal for diabetic status and reduces progression of wall thickness in carotid artery, which may have beneficial potentials for long-term management of atherosclerosis in type-2 diabetics.

Endothelial nitric oxide synthase uncoupling and microvascular dysfunction in the mesentery of mice deficient in α-galactosidase A

A defect in the gene for the lysosomal enzyme α-galactosidase A (Gla) results in globotriaosylceramide (Gb3) accumulation in Fabry disease and leads to premature death from cardiac and cerebrovascular events. However, gastrointestinal symptoms are often first observed during childhood in these patients and are not well understood. In this study, we demonstrate an age-dependent microvasculopathy of the mesenteric artery (MA) in a murine model of Fabry disease (Gla-knockout mice) resulting from dysregulation of the vascular homeostatic enzyme endothelial nitric oxide synthase (eNOS). The progressive accumulation of Gb3 in the MA was confirmed by thin-layer chromatographic analysis. A total absence of endothelium-dependent dilation was observed in MAs from mice at 8 mo of age, while suppression of ACh-mediated vasodilation was evident from 2 mo of age. Endothelium-independent dilation with sodium nitroprusside was normal compared with age-matched wild-type mice. The microvascular defect in MAs from Fabry mice was endothelium-dependent and associated with suppression of the active homodimer of eNOS. Phosphorylation of eNOS at the major activation site (Ser(1179)) was significantly downregulated, while phosphorylation at the major inhibitory site (Thr(495)) was remarkably enhanced in MAs from aged Fabry mice. These profound alterations in eNOS bioavailability at 8 mo of age were observed in parallel with high levels of 3-nitrotyrosine, suggesting increased reactive oxygen species along with eNOS uncoupling in this vascular bed. Overall, the mesenteric microvessels in the setting of Fabry disease were observed to have an early and profound endothelial dysfunction associated with elevated reactive nitrogen species and decreased nitric oxide bioavailability.

Signs of early sub-clinical atherosclerosis in childhood cancer survivors

Cancer is the leading cause of death by disease among U.S. children ages 1-14 years; however, over the last few decades there has been a dramatic increase in survival in these individuals. Although free of cancer, survivors are faced with a variety of chronic health problems including an increased risk of cardiovascular and metabolic abnormalities. The effect of cancer treatments on vascular structure and function in childhood cancer survivors (CCS) has not been examined. Measures of carotid artery stiffness (compliance and distensibility) and thickness (IMT), brachial artery endothelial-dependent dilation (EDD), and endothelial-independent dilation (EID) were obtained from ultrasound imaging in 319 CCS (age: 14.6 ± 0.1 years; male/female: 112/96) who were >5 years from diagnosis and 208 (age: 13.6 ± 0.2 years; male/female: 171/148) siblings who had never been diagnosed with cancer. Participants were 9-18 years of age at examination. Survivors of leukemia had lower carotid distensibility and compliance, indicating increased arterial stiffness, when compared to controls. There were no significant differences in measures of carotid stiffness or EDD in survivors of solid tumors and central nervous system (CNS) tumors compared to controls. EDD was lower in leukemia survivors than in controls, and EID was greater in survivors of CNS tumors than in controls. These results demonstrate that early in life, CCS have arterial changes indicating increased risk for premature atherosclerosis and cardiovascular disease. Therefore, it is reasonable to advocate that efforts should be directed at monitoring and managing cardiovascular risk factors in CCS.

Improvement in Middle Cerebral Artery Structure and Endothelial Function in Stroke‐Prone Spontaneously Hypertensive Rats after Macrophage Depletion

Inflammation is involved in the pathogenesis of hypertension. Hypertensive animals have an increased number of perivascular macrophages in cerebral arteries. Macrophages might be involved in remodeling of the cerebral vasculature. We hypothesized that peripheral macrophage depletion would improve MCA structure and function in hypertensive rats. For macrophage depletion, six-week-old stroke-prone spontaneously hypertensive rats (SHRSP) were treated with CLOD, 10 mL/kg every three or four days, i.p., or vehicle (PBS lipo). MCA structure and function were analyzed by pressure and wire myography. Blood pressure was not affected by CLOD. The number of perivascular CD163-positive cells per microscopic field was reduced in the brain of SHRSP+CLOD. CLOD treatment caused an improvement in endothelium-dependent dilation after intralumenal perfusion of ADP and incubation with Ach. Inhibition of NO production blunted the Ach response, and endothelium-independent dilation was not altered. At an intralumenal pressure of 80 mmHg, MCA from SHRSP+CLOD showed increased lumen diameter, decreased wall thickness, and wall-to-lumen ratio. Cross-sectional area of pial arterioles from SHRSP+CLOD was higher than PBS lipo. These results suggest that macrophage depletion attenuates MCA remodeling and improves MCA endothelial function in SHRSP.

Prostaglandin E 2 Mediates Connecting Tubule Glomerular Feedback

Connecting tubule glomerular feedback (CTGF) is a mechanism in which Na reabsorption in the connecting tubule (CNT) causes afferent arteriole (Af-Art) dilation. CTGF is mediated by eicosanoids, including prostaglandins and epoxyeicosatrienoic acids; however, their exact nature and source remain unknown. We hypothesized that during CTGF, the CNT releases prostaglandin E2, which binds its type 4 receptor (EP4) and dilates the Af-Art. Rabbit Af-Arts with the adherent CNT intact were microdissected, perfused, and preconstricted with norepinephrine. CTGF was elicited by increasing luminal NaCl in the CNT from 10 to 80 mmol/L. We induced CTGF with or without the EP4 receptor blocker ONO-AE3-208 added to the bath in the presence of the epoxyeicosatrienoic acid synthesis inhibitor MS-PPOH. ONO-AE3-208 abolished CTGF (control, 9.4 ± 0.5; MS-PPOH+ONO-AE3-208, -0.6 ± 0.2 μm; P<0.001; n=6). To confirm these results, we used a different, specific EP4 blocker, L161982 (10(-5) mol/L), that also abolished CTGF (control, 8.5 ± 0.9; MS-PPOH+L161982, 0.8 ± 0.4 μm; P<0.001; n=6). To confirm that the eicosanoids that mediate CTGF are released from the CNT rather than the Af-Art, we first disrupted the Af-Art endothelium with an antibody and complement. Endothelial disruption did not affect CTGF (7.9 ± 0.9 versus 8.6 ± 0.6 μm; P=NS; n=7). We then added arachidonic acid to the lumen of the CNT while maintaining zero NaCl in the perfusate. Arachidonic acid caused dose-dependent dilation of the attached Af-Art (from 8.6 ± 1.2 to 15.3 ± 0.7 μm; P<0.001; n=6), and this effect was blocked by ONO-AE3-208 (10(-7) mol/L). We conclude that during CTGF, the CNT releases prostaglandin E2, which acts on EP4 on the Af-Art inducing endothelium-independent dilation.

Impact of Pubertal Development on Endothelial Function and Arterial Elasticity

Little is known about the relation of pubertal development on endothelial function and arterial elasticity in children and adolescents; therefore, we compared brachial artery flow-mediated dilation and carotid artery elasticity across Tanner (pubertal) stages in children and adolescents. Blood pressure, fasting lipids, glucose and insulin, body fat, insulin sensitivity adjusted for lean body mass, brachial flow-mediated dilation (percent dilation and area under the curve), endothelium-independent dilation (peak dilation and area under the curve), and carotid artery elasticity were evaluated across pubertal stages (Tanner I vs Tanner II-IV vs Tanner V) in 344 children and adolescents (184 males, 160 females; ages 6 to 21 years). One hundred twenty-four subjects (mean age 8.23 ± 0.15 years; 52 females) were Tanner stage I; 105 subjects (mean age 13.19 ± 0.17 years; 47 females) were Tanner stages II-IV; and 115 subjects (mean age 17.19 ± 0.16 years; 61 females) were Tanner stage V. There were no significant differences for any of the measures of vascular structure and function across pubertal stages. Results of the current study indicate that smooth-muscle and endothelial function, as well as carotid artery elasticity, do not differ throughout pubertal development and that accounting for pubertal stage when reporting vascular data in children and adolescents may be unnecessary.

Impact of non‐cardiovascular surgery on reactive hyperaemia and arterial endothelial function

Vascular reactivity is a surrogate marker for atherosclerosis and is predictive of cardiovascular outcome. Non-cardiovascular surgery is associated with perioperative cardiovascular complications in high-risk patients. To evaluate the impact of non-cardiovascular surgery on reactive hyperaemia and arterial endothelial function and to investigate the relationships between endothelial dysfunction and invasive (laparotomy) or minimally invasive (laparoscopic) surgery, we prospectively evaluated 106 patients undergoing abdominal surgery under general anaesthesia (71 laparotomy, 35 laparoscopy). Measurements of blood pressure, heart rate and pain (on a visual analogue scale (VAS)) were undertaken. Brachial endothelium-dependent flow-mediated dilation (FMD), endothelium-independent dilation, nitroglycerin (NTG)-induced dilation and reactive hyperaemia were measured with high-resolution B-mode ultrasound on preoperative Day 1 (baseline), as well as 2h and 1 and 7days postoperatively. Blood pressure and heart rate were significantly higher 2h postoperatively. Pain, as measured on the VAS, was higher (P<0.01) and reactive hyperaemia and FMD were significantly lower (P<0.001) at 2h and 1day postoperatively compared with values at baseline and on postoperative Day 7. By postoperative Day 7, FMD had recovered to baseline levels. Patients undergoing laparoscopic surgery had less FMD reduction on Days 1 and 7 (7.5±1.5% and 7.9±1.5%, respectively) compared with those undergoing laparotomy (6.4±1.6% (P=0.001) and 7.0±1.6% (P=0.006), respectively), consistent with potential cardiovascular benefit. Responses to NTG were stable throughout. Backward multivariate linear regression analysis indicated that FMD was independently related to age and VAS (model R=0.486; F=6.4; P<0.001). Reactive hyperaemia and arterial endothelial function are significantly reduced in the early postoperative period, particularly after laparotomy compared with laparoscopy, which may be related to postoperative cardiovascular events.

SAT0214 Elevated endothelial microparticle levels correlate with endothelial function in active SLE

BackgroundSystemic Lupus Erythematosus (SLE) is associated with an increased risk of clinical and subclinical cardiovascular disease (CVD), including endothelial dysfunction. This elevated CVD risk is multifactorial, but is in part...