Dependent Dilation Research Articles

Vascular Function and Structure in Veteran Athletes after Myocardial Infarction.

Although athletes demonstrate lower cardiovascular risk and superior vascular function compared with sedentary peers, they are not exempted from cardiac events (i.e., myocardial infarction [MI]). The presence of an MI is associated with increased cardiovascular risk and impaired vascular function. We tested the hypothesis that lifelong exercise training in post-MI athletes, similar as in healthy controls, is associated with a superior peripheral vascular function and structure compared with a sedentary lifestyle in post-MI individuals. We included 18 veteran athletes (ATH) (>20 yr) and 18 sedentary controls (SED). To understand the effect of lifelong exercise training after MI, we included 20 veteran post-MI athletes (ATH + MI) and 19 sedentary post-MI controls (SED + MI). Participants underwent comprehensive assessment using vascular ultrasound (vascular stiffness, intima-media thickness, and endothelium (in)dependent mediated dilatation). Lifetime risk score was calculated for a 30-yr risk prediction of cardiovascular disease mortality of the participants. ATH demonstrated a lower vascular stiffness and smaller femoral intima-media thickness compared with SED. Vascular function and structure did not differ between ATH + MI and SED + MI. ATH (4.0% ± 5.1%) and ATH + MI (6.1% ± 3.7%) had a significantly better lifetime risk score compared with their sedentary peers (SED: 6.9% ± 3.7% and SED + MI: 9.3% ± 4.8%). ATH + MI had no secondary events versus two recurrent MI and six elective percutaneous coronary interventions within SED + MI (P < 0.05). Although veteran post-MI athletes did not have a superior peripheral vascular function and structure compared with their sedentary post-MI peers, benefits of lifelong exercise training in veteran post-MI athletes relate to a better cardiovascular risk profile and lower occurrence of secondary events.

5,6-δ-DHTL, a stable metabolite of arachidonic acid, is a potential EDHF that mediates microvascular dilation

ObjectiveProminent among the endothelium-derived hyperpolarizing factors (EDHFs) are the Cytochrome P450 (CYP) epoxygenase-derived arachidonic acid metabolites—the epoxyeicosatrienoic acids (EETs), that are known as vasodilators in the microcirculation. Among the EET isomers, 5,6-EET undergoes rapid lactonization in aqueous solution to the more stable 5,6-δ DHTL (5,6-dihydroxytrienoic lactone) isomer. It is unclear whether this metabolic transformation maintains its vasodilator potential and what is the mechanism of action. Thus, the aim of this study was to investigate the capacity of the lactone isomer, 5,6- δ DHTL, to induce dilation of arterioles and explore the endothelial Ca2+ response mechanism. Approach and resultsIn isolated human microvessels 5,6- δ DHTL induced a dose dependent vasodilation, that was inhibited by mechanical denudation of the endothelial layer. This 5,6- δ DHTL -dependent dilation was partially reduced in the presence of L-NAME (NOS inhibitor) or the NO-scavenger, cPTIO (by 19.7%, which was not statistically significantly). In human endothelial cells, 5,6- δ DHTL induced an increase in intracellular Ca2+([Ca2+]i) in a dose dependent manner. This increase in [Ca2+]i was similar to that induced by the 5,6-EET isomer, and significantly higher than observed by administering the hydrolytic dihydroxy isomer, 5,6-DHET. Further experiments aimed to investigate the mechanism of action revealed, that the 5,6-δ DHTL-mediated ([Ca2+]i elevation was reduced by IP3 and ryanodine antagonists, but not by antagonists to the TRPV4 membrane channel. Similar to their effect on the dilation response in the arteries, NO inhibitors reduced the 5,6-δ DHTL-mediated ([Ca2+]i elevation by 20%. Subsequent 5,6-δ DHTL -dependent K+ ion efflux from endothelial cells, was abolished by the inhibition of small and intermediate conductance KCa. ConclusionsThe present study shows that 5,6-δ DHTL is a potential EDHF, that dilates microvessels through a mechanism that involves endothelial dependent Ca2+ entry, requiring endothelial hyperpolarization. These results suggest the existence of additional lactone-containing metabolites that can be derived from the PUFA metabolism and which may function as novel EDHFs.

Tetrahydrobiopterin rescues impaired responses of cerebral resistance arterioles during type 1 diabetes.

Our goal was to test the hypothesis that administration of tetrahydrobiopterin (BH4) would improve impaired endothelial nitric oxide synthase-dependent dilation of cerebral arterioles during type 1 diabetes. In addition, we examined the influence of BH4 on levels of superoxide in brain tissue. In vivo diameter of cerebral arterioles in nondiabetic and diabetic rats was measured in response to endothelial nitric oxide synthase-dependent agonists (acetylcholine and adenosine 5'-diphosphate) and an endothelial nitric oxide synthase-independent agonist (nitroglycerine) before and during application of BH4 (1.0 µM). We also measured levels of superoxide from cortex tissue in nondiabetic and diabetic rats under basal states and during BH4 Acetylcholine and adenosine 5'-diphosphate dilated cerebral arterioles in nondiabetic rats, but this vasodilation was significantly impaired in diabetic rats. In contrast, nitroglycerine produced similar vasodilation in nondiabetic and diabetic rats. Application of BH4 did not enhance vasodilation in nondiabetic rats but improved impaired cerebral vasodilation in diabetic rats. Basal superoxide levels were increased in cortex tissue from diabetic rats, and BH4 reduced these levels to that found in nondiabetic rats. Thus, BH4 is an important mediator of endothelial nitric oxide synthase-dependent responses of cerebral arterioles in diabetes and may have therapeutic potential for the treatment of cerebral vascular disease.

Abstract 12197: Increased Angiotensin II Sensitivity Contributes to Microvascular Endothelial Dysfunction in Women Who Have Had Preeclampsia

Introduction: Women with a history of preeclampsia have increased cardiovascular disease risk, however the mechanisms responsible for this association remain unclear. Microvascular damage sustained during a preeclamptic pregnancy may persist post-partum. The putative mechanisms mediating this dysfunction include a reduction in nitric oxide (NO)-dependent dilation, and an increased sensitivity to angiotensin II (ang II). In this study, we evaluated endothelium-dependent dilation, ang II sensitivity, and the therapeutic effect of ang II receptor blockade (losartan) on endothelium-dependent dilation in vivo in the microvasculature of women with a history of preeclampsia (PrEC, n=7) and control women who had a healthy pregnancy (HC, n=9). We hypothesized that PrEC would have 1) reduced endothelium-dependent dilation, 2) reduced NO-mediated dilation, and 3) increased sensitivity to ang II. We further hypothesized that losartan would increase endothelium-dependent dilation in PrEC. Methods: We assessed microvascular function by measurement of cutaneous vascular conductance responses to graded infusion of acetylcholine (ACh; 10 -10 -10 -1 M) and ang II (10 -20 -10 -4 M); and during ACh co-infusion with 15mM L-NAME (NO-synthase inhibitor) or 43μM losartan. Results: ACh-induced vasodilation was attenuated in PrEC compared to HC (PrEC -3.3±0.2 vs. HC -4.7±0.1 logEC50; p&lt;0.05). There was no difference between PrEC and HC during ACh co-infusion with L-NAME (PrEC -4.4±0.2 vs. HC -4.6±0.2 logEC50; NS). NO-mediated dilation was attenuated in PrEC compared to HC (PrEC 10±4 vs. HC 35±4%; p&lt;0.01). PrEC had a greater vasoconstriction response to ang II (PrEC -11.8±0.2 vs. HC -9.7±0.2 logEC50; p&lt;0.05. Losartan co-infusion improved the vasodilation response to ACh in PrEC (losartan -4.6±0.2 vs. ACh alone -3.3±0.2 logEC50; NS). Conclusions: These findings suggest that women who have had preeclampsia have impaired endothelium-dependent vasodilation which is mediated, in part, by reductions in NO signaling and increased sensitivity to ang II. Furthermore, losartan improved endothelium-dependent dilation, suggesting that ang II receptor blockade may have therapeutic potential to treat microvascular dysfunction in women who have had preeclampsia.

Experimental reduction of miR-92a mimics arterial aging

MicroRNAs (miRs) are small non-coding RNAs that are important regulators of aging and cardiovascular diseases. MiR-92a is important in developmental vascular growth and tumorigenesis and two of its putative targets, tumor necrosis factor alpha receptor 1 (TNFR1) and collagen type 1, play a role in age-related arterial dysfunction. We hypothesized that reduced miR-92a expression contributes to age-related arterial dysfunction characterized by endothelial dysfunction and increased large artery stiffness. MiR-92a is reduced 39% (RT-PCR, p<0.05) in arteries of older adults compared to young adults. Similarly, there was a 40% reduction in miR-92a in aortas of old (29months, n=13) compared to young (6months, n=11) B6D2F1 mice, an established model of vascular aging. To determine if reduced miR-92a contributes to arterial dysfunction; miR-92a was inhibited in vivo in young mice using antagomirs (I.P., 4wks). Antagomir treatment was associated with a concomitant 48% increase in TNFR1 (Western blot, p<0.05), 19% increase in type 1 collagen (immunohistochemistry, p<0.01), and a reduction in endothelial dependent dilation (max dilation: 93±1 vs. 73±5%, p<0.01) in response to acetylcholine (ACh, 10−9 to 10−4M). Treatment with the nitric oxide (NO) synthase inhibitor, L-NAME (10−4M), revealed that impaired ACh dilation after antagomir treatment resulted from reduced NO bioavailability. Inhibition of miR-92a also increased arterial stiffness (pulse wave velocity, 309±13 vs. 484±52cm/s, p<0.05). Together, these results suggest that experimental reductions in arterial miR-92a partially mimic the arterial aging phenotype and we speculate that modulating miR-92a may provide a therapeutic strategy to improve age-related arterial dysfunction.

The influence of silica nanoparticles on small mesenteric arterial function.

To determine the influence of silica nanoparticles (SiNPs) on small arterial function; both ex vivo and in vivo. Mono-dispersed dye-encapsulated SiNPs (97.85 ± 2.26 nm) were fabricated and vasoconstrictor and vasodilator responses of mesenteric arteries assessed. We show that while exposure to SiNPs under static conditions, attenuated endothelial dependent dilator responses ex vivo, attenuation was only evident at lower agonist concentrations, when exposed under flow conditions or after intravenous administration in vivo. Pharmacological inhibition studies suggest that SiNPs may interfere with the endothelial dependent hyperpolarizing factor vasodilator pathway. The dosage dependent influence of SiNPs on arterial function will help identify strategies for their safe clinical administration.

P66 Shc Contributes to Susceptibility to Cerebrovascular Injury and Intracerebral Hemorrhages

BackgroundBreakdown of the blood brain barrier (BBB) and loss of cerebral vessels autoregulation in response to elevated systemic pressure are closely linked to intracerebral hemorrhage and micro bleeds. Presently no established models to study the causes of intracerebral hemorrhage exist that does not rely on surgical interventions and existing models have failed to improve clinical understanding of this condition. Overproduction of reactive oxygen species (ROS) following ischaemia/reperfusion (I/R) is considered a key mechanism leading to BBB damage. It has been shown that the adaptor protein p66(Shc) is crucial regulator for ROS production in several disease states including I/R injury of the brain. p66shc when activated translocates to the mitochondria where it sequesters cytochrome C and generates hydrogen peroxide. The contribution of mitochondria to myogenic tone and autoregulation of the cerebral vasculature is not well defined.We have found previously that rats expressing constitutively active form of p66 Shc (Shc‐CA) have decreased long term survival and increased incidences of stoke despite no significant difference in systemic blood pressure.HypothesisWe hypothesis that p66Shc signaling via mitochondrial translocation contribute to vascular dysfunction of cerebral arteries and intracerebral hemorrhage in hypertensive rats by decreasing mitochondrial ATP while elevating mitochondrial ROS.ResultsVessels from WT rats, lacking p66 Shc protein (Shc‐KO), or expressing Shc‐CA were used for video microscopy. Endothelial dependent dilation to flow was assessed in vessels from Shc‐KO animals compared to their littermate controls (%Max Dilation 100 cm H2O: WT = 1.3±3 vs. Shc‐KO=39±3*; N≥3 P&lt;0.05 one way ANOVA). Shc‐CA failed to develop tone spontaneously or to pharmacological stimuli (as a result no dilator function could be studied) suggesting a defect in vascular smooth muscle function. No difference in tone were observed in WT vs. Shc‐KO. Further evaluation revealed loss of myogenic tone in MCAs of Shc‐CA (% Tone at 150 cm H2O relative to Ca2+ free: WT = 19±6; Shc‐KO = 28±12; Shc‐CA =3±2, n≥2). In vivo cerebral vascular flow was evaluated using Doppler laser probe and revealed an inability of cerebral vessels to respond to altered systemic pressure in vivo. Shc‐CA showed decreased levels of ATP (pmol/mg Protein WT=1±0.2; Shc‐KO=0.7±0.2; Shc‐CA=0.1±0.1*; N≥3 P&lt;0.05 one way ANOVA) and mitochondrial respiration, confirming decreased mitochondrial function in rats that express Shc‐CA.To investigate an underling physiological relevance, rats were perfused with methylene blue (MB). A substantial increase in MB staining in the brain of Shc‐CA was observed, suggesting an increase in permeability of the BBB.

Вивчення функціонального стану ендотелію за допомогою комплексу показників проби з реактивною гіперемією

Diagnosis of endothelial dysfunction is a key point in the prevention and treatment of cardiovascular diseases. In scientific research the study of the state of the endothelium used test with reactive hyperemia of brachial artery wich present as the value of endothelium dependent and independent artery dilatation. However, the disadvantage of this marker is ignoring the size of arteries, well know that small arteries has a greater degree of dilation more than big arterias, this fact making difficult to compare results between different patients.The aim of our study was to examine the state of endothelium using a complex of markers, compare them informative in children with JRA who are at risk for the development of endothelial dysfunction.Materials and Methods. The study was included 40 children with juvenile rheumatoid arthritis who were treated at the department of children's cardiorheumatology Kyiv City Children's Hospital #1 and Kiev Regional Hospital m. Boyarka.Results. The study found a development of endothelial dysfunction changes in endothelium dependent vasodilation, reactive hyperemia and coefficient of vasodilation. Simultaneous marked change of endothelium vasodilation of the brachial artery and coefficient of vasodilatation. There were no pathological changes in endothelial shear stress in patients compared with healthy children.Conclusions. Evaluate the state of the endothelium is necessary with the help of a set of indicators (RH, EDVD, VC) that will help to avoid diagnostic mistakes during the test with the reactive hyperemia.Key words: endothelial dysfunction, reactive hyperemia, endothelium dependent vasodilation, tension shear, coefficient of vasodilation.

Abstract TP455: Treatment With Trifluoromethoxyphenyl-3 (1propionylpiperidin-4-yl) Urea Improves Cognitive Functions and Endothelium Dependent Dilation in Penetrating Arterioles From Hypertensive Rats With Bilateral Common Carotid Stenosis

Soluble epoxide hydrolase (sEH) converts epoxyeicosatrienoic acids (EETs), arachidonic acid metabolites produced by cytochrome 450 enzymes, into less metabolically active compounds. sEH inhibitors have been proposed to have vascular and neural protective effects in stroke models. Studies from our lab showed that bilateral carotid artery stenosis (BCAS), a physiologically relevant model of cognitive impairment, impairs endothelium dependent dilation in penetrating arterioles (PAs) from stroke prone spontaneously hypertensive rats (SHRSPs). We hypothesized that treatment of SHRSPs with BCAS with the sEH inhibitor, trifluoromethoxyphenyl-3 (1propionylpiperidin-4-yl) urea (TPPU) would alleviate cognitive dysfunction and improve endothelium dependent dilation in PAs. Data are shown as mean ± SEM, vehicle vs TPPU, and p &lt;0.05 (an n=3 to 12 in each group). After 8 weeks of BCAS, TPPU treated rats showed improved short-term memory (novel exploration quotient, 90 minutes retention time: 0.5 ± 0.06 vs 0.6 ± 0.04), evaluated by novel object recognition test. PA reactivity and structure was assessed by pressure myography. TPPU restored endothelial function of PAs from SHRSP with BCAS, as evidenced by increased dilation to carbachol (% dilation at 10-6M: 2.7 ± 2.9 vs 16.5 ± 3.9). Inhibition of EET production with MS-PPOH (10-5M), enhanced dilation in PAs from TPPU treated SHRSP with BCAS (% dilation at 10-5M of carbachol, TPPU vs TPPU+MS-PPOH: 14.9 ± 2.9 vs 23.4 ± 3.5), while dilation in vehicle treated SHRSPs remained unaltered (% dilation at 10-5M, vehicle vs vehicle+MS-PPOH: 2.9 ± 2.9 vs -0.7 ± 5.1, p=0.96). This suggests that inhibiting EET production may unmask a compensatory dilatory mechanism in PAs from TPPU treated rats. Interestingly, PAs from TPPU treated rats were less sensitive to NO as evidenced by a reduction in the EC50 for NO- donor, sodium nitroprusside (logEC50: -7.1±0.14 vs -5.7± 0.2). This reduced sensitivity may be due to an overproduction of NO in PAs from TPPU treated rats. There was no difference in passive structure of the PAs with chronic TPPU administration. These data suggest that TPPU improves short-term memory after BCAS and this may be associated with improved endothelium-dependent dilation in the PAs.

Intracerebroventricular application of S100B selectively impairs pial arteriolar dilating function in rats

S100B is an astrocyte-derived protein that can act through the receptor for advanced glycation endproducts (RAGE) to mediate either “trophic” or “toxic” responses. Its levels increase in many neurological conditions with associated microvascular dysregulation, such as subarachnoid hemorrhage (SAH) and traumatic brain injury. The role of S100B in the pathogenesis of microvasculopathy has not been addressed. This study was designed to examine whether S100B alters pial arteriolar vasodilating function. Rats were randomized to receive (1) artificial cerebrospinal fluid (aCSF), (2) exogenous S100B, and (3) exogenous S100B+the decoy soluble RAGE (sRAGE). S100B was infused intracerebroventricularly (icv) using an osmotic pump and its levels in the CSF were adjusted to achieve a concentration similar to what we observed in SAH. After 48h of continuous icv infusion, a cranial window/intravital microscopy was applied to animals for evaluation of pial arteriolar dilating responses to sciatic nerve stimulation (SNS), hypercapnia, and topical suffusion of vasodilators including acetylcholine (ACh), s-nitroso-N-acetyl penicillamine (SNAP), or adenosine (ADO). Pial arteriolar dilating responses were calculated as the percentage change of arteriolar diameter in relation to baseline. The continuous S100B infusion for 48h was associated with reduced responses to the neuronal-dependent vasodilator SNS (p<0.05) and the endothelial-dependent vasodilator ACh (p<0.05), compared to controls. The inhibitory effects of S100B were prevented by sRAGE. On the other hand, S100B did not alter the responses elicited by vascular smooth muscle cell-dependent vasodilators, namely hypercapnia, SNAP, or ADO. These findings indicate that S100B regulates neuronal and endothelial dependent cerebral arteriolar dilation and suggest that this phenomenon is mediated through RAGE-associated pathways.

Effects of resistance training on cardiovascular health in non-obese active adolescents

To determine the benefits of a 10-wk resistance training programme on cardiovascular health in non-obese and active adolescents. This is a pragmatic randomised controlled intervention. The study was carried out in a Hong Kong Government secondary school. Thirty-eight lean and active boys and girls were randomised to either the resistance training group or the control group. Students in the resistance training group received in-school 10-wk supervised resistance training twice per week, with each session lasting 70 min. Main outcome measures taken before and after training included brachial endothelial dependent flow-mediated dilation, body composition, fasting serum lipids, fasting glucose and insulin, high sensitive C-reactive protein, 24-h ambulatory blood pressure and aerobic fitness. The only training related change was in endothelial dependent flow-mediated dilation which increased from 8.5% to 9.8%. A main effect of time and an interaction (P < 0.005) indicated that this improvement was a result of the 10-wk resistance training. Main effects for time (P < 0.05) in a number of anthropometric, metabolic and vascular variables were noted; however, there were no significant interactions indicating the change was more likely an outcome of normal growth and development as opposed to a training effect. Ten weeks of resistance training in school appears to have some vascular benefit in active, lean children.

Abstract P015: Bilateral Common Carotid Artery Stenosis in Hypertensive Rats Impairs Dilation in Penetrating Arterioles and Posterior Communicating Arteries

Hypertension and chronic cerebral hypoperfusion (CCH) are leading risk factors for cognitive impairment. We induced hypoperfusion in stroke prone spontaneously hypertensive rats (SHRSP) by bilateral carotid artery stenosis (BCAS) to create a novel, physiologically relevant model of cognitive impairment. We hypothesized that BCAS in SHRSP would impair endothelium dependent dilation and lead to outward remodeling of the penetrating arterioles (PAs) and posterior cerebral arteries (PCAs). The PAs are critical for maintaining parenchymal perfusion and controlling blood flow to the neurovascular unit, and the PCAs are integral in regulating the severity of CCH. Both artery types were studied by pressure myography and data are shown as mean±SEM, SHAM vs BCAS (an n =4 to 12 in each group) with p&lt;0.05. Short-term memory, evaluated by novel object recognition testing, was impaired 8 weeks after BCAS (novel exploration quotient: 0.60±0.1 vs 0.45±0.1). Endothelium-dependent dilation was assessed with carbachol (data shown as % dilation at 10 -6 M). BCAS impaired endothelial function in PAs, as evidenced by the abolition of the dilation (14±3.3% vs -10±4.7%) but did not significantly alter sodium nitroprusside induced dilation (60 ± 9.7% vs. 49 ± 6.4%). Inhibition of nitric oxide and prostacyclin production with L-NAME (100 μM) and indomethacin (10 μM), respectively, did not change dilation in either group. This suggests that endothelium-derived hyperpolarizing factor plays a role in PA dilation in SHRSP. PAs from BCAS rats had a reduced wall thickness (at 60 mmHg: 7±0.5 vs 5±0.6 μm), and wall-to-lumen ratio (at 60 mmHg: 0.10±0.002 vs 0.07±0.0001). BCAS increased wall stress in PAs (at 60 mmHg: 306±30.2 vs 427±48.3 dynes/cm 2 ). Endothelial dysfunction also was evident in the PCAs after BCAS (50 ± 13.0% vs 3 ± 14.9%) but the pattern of remodeling in these larger arteries was different. We did not observe a change in the wall thickness or wall-to-lumen ratio in PCAs after BCAS, but the lumen diameter was increased (at 80 mmHg: 105±7.7 vs 116±5.7 μm). These data suggest that endothelial dysfunction in the PAs and PCAs may worsen the severity of cerebral hypoperfusion and cognitive decline in SHRSP. The thinner walls in the PAs may also increase the risk of hemorrhage in the BCAS rats.

Can we reduce debris flow to an equivalent one-phase flow?

A recent extension of the discrete element method is reported for the simulation of dense mixtures of non-colloidal particles and viscous fluids in the non-inertial regime. As an application, we examine the interplay between rate dependent dilatancy and hydro-mechanical coupling which can be expected in debris flow. The numerical model includes sphere-sphere contacts using a soft contact approach [2], short range hydrodynamic interactions defined by frame-invariant expressions of forces and torques in the lubrication approximation, and drag forces resulting from the poromechanical coupling computed with the DEM-PFV technique [3]. The bulk shear stress is decomposed into contact stress and hydrodynamic stress. Both contributions are shown to be increasing functions of a dimensionless shear rate Iv, in agreement with experimental results [4]. Statistics of microstructural variables highlight a complex interplay between solid contacts and hydrodynamic interactions. In contrast with a popular idea, the results suggest that lubrication may not necessarily reduce the contribution of contact forces to the bulk shear stress. The proposed model is general and applies directly to sheared satured granular media in which pore pressure feedback plays a key role. We argue that it can be the case for debris fow, especially during the triggering phase, when run-out include transitional phases, and when the flow is stopped. It is then concluded that debris cannot be computed by assuming solely the rheological properties of an equivalent mixture.

Histamine Induces Vascular Hyperpermeability by Increasing Blood Flow and Endothelial Barrier Disruption In Vivo.

Histamine is a mediator of allergic inflammation released mainly from mast cells. Although histamine strongly increases vascular permeability, its precise mechanism under in vivo situation remains unknown. We here attempted to reveal how histamine induces vascular hyperpermeability focusing on the key regulators of vascular permeability, blood flow and endothelial barrier. Degranulation of mast cells by antigen-stimulation or histamine treatment induced vascular hyperpermeability and tissue swelling in mouse ears. These were abolished by histamine H1 receptor antagonism. Intravital imaging showed that histamine dilated vasculature, increased blood flow, while it induced hyperpermeability in venula. Whole-mount staining showed that histamine disrupted endothelial barrier formation of venula indicated by changes in vascular endothelial cadherin (VE-cadherin) localization at endothelial cell junction. Inhibition of nitric oxide synthesis (NOS) by L-NAME or vasoconstriction by phenylephrine strongly inhibited the histamine-induced blood flow increase and hyperpermeability without changing the VE-cadherin localization. In vitro, measurements of trans-endothelial electrical resistance of human dermal microvascular endothelial cells (HDMECs) showed that histamine disrupted endothelial barrier. Inhibition of protein kinase C (PKC) or Rho-associated protein kinase (ROCK), NOS attenuated the histamine-induced barrier disruption. These observations suggested that histamine increases vascular permeability mainly by nitric oxide (NO)-dependent vascular dilation and subsequent blood flow increase and maybe partially by PKC/ROCK/NO-dependent endothelial barrier disruption.

PP.33.29

Objective: Obesity is associated with development of cardiovascular risk factors such as arterial hypertension, dyslipidemia, atherosclerosis and metabolic syndrome. RhoA associated kinase has been identified to play an important role in modulating vascular effects. In arterial hypertension abnormalities in RhoA/Rho-kinase signalling lead to augmented contractile response on vasoconstrictors. The pleiotrophic effect of statins is linked to this by inhibition of RhoA isoprenylation. Our aim was to explore the vascular changes of diet induced obesity leading to hypertension and the effects of Pravastatin incubation on vascular contractility. Design and method: Aortas from mice, fed with high-fat-diet (HFD, 51% of energy from fat) for two weeks, were incubated either with Pravastatin (10 μM) or without for 1 or 24 hours. A second group was treated with HFD and Pravastatin 50 mg/kg/d in drinking water. To examine vasoconstrictor response, dose-response-curves to norepinephrine, high potassium and acetylcholine were performed on a wired myograph. Blood pressure was measured by determining the tail blood volume. Results: Mice fed with HFD developed an increased blood pressure compared to normal weight mice. A two weeks treatment of Pravastatin showed a significant decrease in blood pressure compared to mice treated only with HFD (systolic blood pressure control: 138.5 ± 3.3 mmHg vs. 2wks Pravastatin: 125.3 ± 2.3mmHg). In vitro treatment with Pravastatin for 24 h attenuated the contractile response to norepinephrine and high potassium whereas incubation for one hour had no significant effect on vascular contractility (obese control: logEC50 -7.650 vs. Pravastatin 24 h: logEC50 -7.315). In vivo, a two week treatment with Pravastatin showed a significant reduction of contractile response to vasoconstrictors (obese control: logEC50 -6.880 vs. Pravastatin 2wks: logEC50 -6.593). Dose-response curves showed a shift to the right depending on length of treatment. Sensitivity against vasoconstrictors was significantly decreased. Acetylcholine dependent dilatation was not affected by treatment. A two weeks HFD treatment did not lead to endothelial dysfunction. Conclusions: Our study shows that a Pravastatin treatment of obese mice for just two weeks has beneficial effects on the cardiovascular system. The treatment prevented an increase in blood pressure and vascular smooth muscle cell contractility in obese mice.

Cardiorespiratory Fitness, Oxygen Uptake Efficiency Slope And Endothelial Function In Male Adolescents

PURPOSE: VO2 max defined as the point at which oxygen uptake reaches a plateau despite further increase in work rate, is an objective measure of an individual’s cardiorespiratory fitness (CRF). Due to its effort dependency, a true plateau in VO2 during incremental exercise is seldom attained particularly in chronic disease and pediatric populations. The oxygen uptake efficiency slope (OUES) is as an objective and effort independent submaximal measure of cardiopulmonary reserve. Children with high CRF have higher OUES values than those with low CRF. Furthermore, high CRF during adolescence is associated with a healthier cardiovascular profile. The purpose of this study was to examine the relation between OUES and endothelial function (EF) in healthy male adolescents with low, moderate and high CRF. METHODS: Low fit (n=14, VO2max = 43.2±5.3, mL·kg1·min-1), moderate fit (n=16, VO2max = 53.8±3.3, mL·kg1·min-1) and high fit (n=18, VO2max = 63.7±4.0 mL·kg1·min-1) healthy asymptomatic males (mean age 15.8 ± 0.5;) participated in the study. High-resolution ultrasonography was used to assess endothelial dependent (EDD) and endothelial independent dilation (EID) in response to brachial artery flow mediated dilation and glyceryl trinitrate. VO2max was measured using open circuit spirometry during an incremental treadmill test. OUES was determined by plotting VO2 (ml·min-1) against the logarithm of VE (L·min-1) and calculating the slope of this linear relation through single regression analysis. RESULTS: EDD and VO2max were significantly lower in the low fit than the moderate and high fit group. There was no between group difference in EID. Maximal OUES was higher in the high fit than the moderate (p<0.01) and low fit (p<0.05) group. There was a significant positive relation between maximal OUES and percentage change (r=0.33, p<0.01) and absolute change in EDD (r=0.44, p<0.01). VO2 max was also significantly related to percentage change (r=0.67, p<0.001) and absolute change in EDD (r=0.73, p<0.001) CONCLUSION: VO2 max and maximal OUES are significantly related to both absolute and percent change in EDD in adolescent males.

Aldosterone Decreases Nitric Oxide Mediated Dilatation through a Histamine H2 Dependent Mechanism in Intracerebral Arteries from Human and Mice

Background Prolonged exposure to aldosterone has a contractile effect through inhibition of NO-mediated vasodilatation in mice mesenteric arteries. This effect involves histamine release from perivascular mast cells. Furthermore, high plasma aldosterone gives exacerbated outcome after stroke. It was hypothesized that aldosterone affects intracerebral vessels by histamine receptor H2 activation resulting in vasospasms. Method: Changes in luminal diameter were measured in perfused intracerebral arteries (size 25–45 μm) from humans with operable brain tumors and mice. Results: Secondary dilatation (recovery) in response to high K+ was observed in human (50.4 %) and mice intracerebral arteries (52.5 %). Pretreatment with aldosterone (10-9M, 60 min) significantly inhibited recovery in mice (12.3 %). The inhibition was fully reversible. Pretreatment with N(G)-nitro-L-arginine methyl ester (10-5M) significantly inhibited recovery in response to high K+ in mice (13.5 %). Similar tendencies were seen on human intracerebral arteries. The effect of aldosterone on recovery in mice arteries was inhibited by the histamine H2 receptor antagonist cimetidine (10-5M, 55.3 %). RT-PCR showed expression of the mineralocorticoid receptor in human cerebral cortex and human intracerebral arteries. Conclusion Aldosterone inhibits NO dependent dilatation in both human and mice intracerebral arteries. The inhibition is mediated through the histamine H2 receptor. This mechanism could potentially be involved in cerebral vasospasms occurring after stroke. Foundation: Danish Research Council and Danish Heart Foundation.

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

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

Effects of Breathing O 2 at different Concentrations on Reactive Oxygen Species (ROS) and Endothelium Dependent Dilatation

Effects of Breathing O ₂ at different Concentrations on Reactive Oxygen Species (ROS) and Endothelium Dependent Dilatation

Abstract T P416: Bilateral Common Carotid Artery Stenosis in Normotensive Rats Impairs Short-Term Memory and Dilation in Penetrating Arterioles

Chronic cerebral hypoperfusion (CCH) is a risk factor for cognitive impairment. Reduced blood flow through the common carotid arteries induced by bilateral common carotid artery stenosis (BCAS) is a physiologically relevant model of CCH. We hypothesized that BCAS in Wistar Kyoto (WKY) rats would impair cognitive function, we further proposed that in an effort to compensate for the reduced blood flow BCAS would lead to increased dilation and outward remodeling in the penetrating arterioles (PAs). Data are shown as mean±SEM, SHAM vs BCAS. BCAS reduced pial artery perfusion in 20-week-old male WKY rats (469±8 vs 299±21 perfusion units p&lt;0.05). Short-term memory, evaluated by novel object recognition testing, was impaired (novel exploration quotient: 0.62±0.09 vs 0.46±0.14, p&lt;0.05). PA reactivity and structure were assessed by pressure myography. There was no difference in myogenic tone between the groups [SHAM (n=4) and BCAS (n=7), % average tone: 34.5±9.8]. Contrary to our hypothesis, BCAS impaired endothelial function of PAs from 28-29 weeks old WKY rats, as evidenced by reduced dilation to endothelium dependent dilator carbachol (% change in diameter from baseline at 10-5M: 7.0±4.1 vs -1.8±5.6, Student’s t-test p&lt;0.05). Inhibition of nitric oxide and prostacyclin production did not change the response to carbachol or the myogenic tone in either group. This suggests that endothelium derived hyperpolarizing factor (EDHF) plays a role in PA dilation in the SHAM rats; the role of EDHF in the PAs from the BCAS rats remains to be investigated but the lack of dilation to carbachol under any conditions suggests a general impairment in endothelial function. There was no difference in the PA passive structure between the groups. Work from our lab suggests that CCH leads to outward remodeling of the posterior communicating artery (PCA). Lumen diameter of the PCAs is important in regulating the severity of CCH. BCAS increased lumen diameter, wall-to-lumen ratio and distensibility of the PCAs (two-way ANOVA, p&lt;0.05). These data suggest that BCAS impairs short-term memory, and may contribute to impaired endothelium dependent dilation of the PAs. BCAS in normotensive WKY rats also leads to outward remodeling in the PCAs but it did not alter PA passive structure.