Hypertension, stroke, and endothelium

Beneficial Effects of Citrus Bergamia Polyphenolic Fraction on Saline Load-Induced Injury in Primary Cerebral Endothelial Cells from the Stroke-Prone Spontaneously Hypertensive Rat Model

High salt load is a known noxious stimulus for vascular cells and a risk factor for cardiovascular diseases in both animal models and humans. The stroke-prone spontaneously hypertensive rat (SHRSP) accelerates stroke predisposition upon high-salt dietary feeding. We previously demonstrated that high salt load causes severe injury in primary cerebral endothelial cells isolated from SHRSP. This cellular model offers a unique opportunity to test the impact of substances toward the mechanisms underlying high-salt-induced vascular damage. We tested the effects of a bergamot polyphenolic fraction (BPF) on high-salt-induced injury in SHRSP cerebral endothelial cells. Cells were exposed to 20 mM NaCl for 72 h either in the absence or the presence of BPF. As a result, we confirmed that high salt load increased cellular ROS level, reduced viability, impaired angiogenesis, and caused mitochondrial dysfunction with a significant increase in mitochondrial oxidative stress. The addition of BPF reduced oxidative stress, rescued cell viability and angiogenesis, and recovered mitochondrial function with a significant decrease in mitochondrial oxidative stress. In conclusion, BPF counteracts the key molecular mechanisms underlying high-salt-induced endothelial cell damage. This natural antioxidant substance may represent a valuable adjuvant to treat vascular disorders.

Comparisons of the Nonlinear Relationship of Cerebral Blood Flow Response and Cerebral Vasomotor Reactivity to Carbon Dioxide under Hyperventilation between Postural Orthostatic Tachycardia Syndrome Patients and Healthy Subjects

Postural orthostatic tachycardia syndrome (POTS) typically occurs in youths, and early accurate POTS diagnosis is challenging. A recent hypothesis suggests that upright cognitive impairment in POTS occurs because reduced cerebral blood flow velocity (CBFV) and cerebrovascular response to carbon dioxide (CO₂) are nonlinear during transient changes in end-tidal CO₂ (P_ETCO2). This novel study aimed to reveal the interaction between cerebral autoregulation and ventilatory control in POTS patients by using tilt table and hyperventilation to alter the CO₂ tension between 10 and 30 mmHg. The cerebral blood flow velocity (CBFV), partial pressure of end-tidal carbon dioxide (P_ETCO2), and other cardiopulmonary signals were recorded for POTS patients and two healthy groups including those aged >45 years (Healthy-Elder) and aged <45 years (Healthy-Youth) throughout the experiment. Two nonlinear regression functions, Models I and II, were applied to evaluate their CBFV-P_ETCO2 relationship and cerebral vasomotor reactivity (CVMR). Among the estimated parameters, the curve-fitting Model I for CBFV and CVMR responses to CO₂ for POTS patients demonstrated an observable dissimilarity in CBFV_max (p = 0.011), mid-P_ETCO2 (p = 0.013), and P_ETCO2 range (p = 0.023) compared with those of Healthy-Youth and in CBFV_max (p = 0.015) and CVMR_max compared with those of Healthy-Elder. With curve-fitting Model II for POTS patients, the fit parameters of curvilinear (p = 0.036) and P_ETCO2 level (p = 0.033) displayed significant difference in comparison with Healthy-Youth parameters; range of change (p = 0.042), P_ETCO2 level, and CBFV_max also displayed a significant difference in comparison with Healthy-Elder parameters. The results of this study contribute toward developing an early accurate diagnosis of impaired CBFV responses to CO₂ for POTS patients.

Enzymatically modified isoquercitrin improves endothelial function in volunteers at risk of cardiovascular disease

A higher intake of food rich in flavonoids such as quercetin can reduce the risk of CVD. Enzymatically modified isoquercitrin (EMIQ®) has a bioavailability 17-fold higher than quercetin aglycone and has shown potential CVD moderating effects in animal studies. The present study aimed to determine whether acute ingestion of EMIQ® improves endothelial function, blood pressure (BP) and cognitive function in human volunteers at risk of CVD. Twenty-five participants (twelve males and thirteen females) with at least one CVD risk factor completed this randomised, controlled, crossover study. In a random order, participants were given EMIQ® (2 mg aglycone equivalent)/kg body weight or placebo alongside a standard breakfast meal. Endothelial function, assessed by flow-mediated dilatation (FMD) of the brachial artery was measured before and 1·5 h after intervention. BP, arterial stiffness, cognitive function, BP during cognitive stress and measures of quercetin metabolites, oxidative stress and markers of nitric oxide (NO) production were assessed post-intervention. After adjustment for pre-treatment measurements and treatment order, EMIQ® treatment resulted in a significantly higher FMD response compared with the placebo (1·80 (95 % CI 0·23, 3·37) %; P = 0·025). Plasma concentrations of quercetin metabolites were significantly higher (P < 0·001) after EMIQ® treatment compared with the placebo. No changes in BP, arterial stiffness, cognitive function or biochemical parameters were observed. In this human intervention study, the acute administration of EMIQ® significantly increased circulating quercetin metabolites and improved endothelial function. Further clinical trials are required to assess whether health benefits are associated with long-term EMIQ® consumption.

Chronic Fish Oil Consumption with Resistance Training Improves Grip Strength, Physical Function, and Blood Pressure in Community-Dwelling Older Adults

Fish oil (FO) has received great attention for its health-enhancing properties. However, its potential synergistic effects with resistance training (RT) are not well established. The purpose of this study was to investigate the effects of FO supplementation during 12-weeks of RT on handgrip strength, physical function, and blood pressure (BP) in community-dwelling older adults. Twenty-eight healthy older adults (10 males, 18 females; 66.5 ± 5.0 years) were randomly assigned to three groups: Control (CON), resistance training (RT), resistance training with FO (RTFO). Handgrip strength, physical function [five times sit-to-stand (5T-STS), timed up and go (TUG), 6-m walk (6MW), 30-s sit-to-stand (30S-STS)], and BP were measured pre- and post-intervention. ANOVA was used with significance set at P ≤ 0.05. Handgrip strength significantly increased in RT (+5.3%) and RTFO (+9.4%) but decreased in CON (−3.9%). All physical function outcomes increased in RT and RTFO. CON exhibited significantly decreased TUG and 30S-STS with no change in 5T-STS and 6MW. BP substantially decreased only in RTFO, systolic blood pressure (−7.8 mmHg), diastolic blood pressure (−4.5 mmHg), mean arterial pressure (−5.6 mmHg), while no change was found in CON and RT. Chronic RT enhanced strength and physical function, while FO consumption combined with RT improved BP in community-dwelling older adults.

Predictors of inadequate bowel preparation for colonoscopy: a systematic review and meta-analysis

The aim of this study was to investigate factors contributing to poor bowel preparation in patients undergoing colonoscopy procedures. We used a reproducible search strategy to identify studies, searching 10 medical databases, including PubMed, Ovid, Medline, and Cochrane Library Database for reports published between 2000 and 2016. Fully published studies, evaluating risk factors for inadequate bowel preparation, were included. Two reviewers independently scored the identified studies for methodology and abstracted pertinent data. Pooling was conducted with both fixed-effects and random-effects models; results were presented from the random effects model when heterogeneity was significant. Odds ratios (OR) estimates with 95% confidence interval were calculated. Heterogeneity was assessed by I statistics. Twenty-four studies with a total of 49 868 patients met the inclusion criteria. Age (OR: -1.20), male sex (OR: 0.85), inpatient status (OR: 0.57), diabetes mellitus (OR: 0.58), hypertension (OR: 0.58), cirrhosis (OR: 0.49), narcotic use (OR: 0.59), constipation (OR: 0.61), stroke (OR; 0.51), and tricyclic antidepressant (TCA) use (0.51), were associated with inadequate bowel preparation. In our sensitivity analysis comparing Western and Asian countries, we found that diabetes, cirrhosis, male sex, history of stroke and TCA use were stronger risk factors for inadequate bowel preparation in Western countries than in Asian countries. We also found that history of stroke, TCA use, and race were risk factors for inadequate bowel preparation in patients receiving conventional bowel preparation compared with those receiving split-dose bowel preparation. Multiple risk factors affect the quality of bowel preparation and specific risk factors can be intervened upon, in different populations, to optimize preparation.

Flavonoid-Rich Apple Improves Endothelial Function in Individuals at Risk for Cardiovascular Disease: A Randomized Controlled Clinical Trial

SCOPE

The cardioprotective effects of apples are primarily attributed to flavonoids, found predominantly in the skin. This study aimed to determine if acute and/or chronic (4 weeks) ingestion of flavonoid-rich apples improves endothelial function, blood pressure (BP), and arterial stiffness in individuals at risk for cardiovascular diseases (CVD).

METHODS AND RESULTS

In this randomized, controlled cross-over trial, acute and 4 week intake of apple with skin (high flavonoid apple, HFA) is compared to intake of apple flesh only (low flavonoid apple, LFA) in 30 participants. The primary outcome is endothelial function assessed using flow-mediated dilation (FMD) of the brachial artery, while main secondary outcomes are 24 h ambulatory BP and arterial stiffness. Other outcomes include fasting serum glucose and lipoprotein profile, plasma heme oxygenase-1 (Hmox-1), F₂ -isoprostanes, flavonoid metabolites, and plasma and salivary nitrate (NO₃^- ) and nitrite (NO₂^- ) concentrations. Compared to LFA control, the HFA results in a significant increase in FMD acutely (0.8%, p < 0.001) and after 4 weeks chronic intake (0.5%, p < 0.001), and in plasma flavonoid metabolites (p < 0.0001). Other outcomes are not altered significantly.

CONCLUSION

A lower risk of CVD with higher apple consumption could be mediated by the beneficial effect of apple skin on endothelial function, both acutely and chronically.

Docosahexaenoic acid regulates vascular endothelial cell function and prevents cardiovascular disease

Docosahexaenoic acid (DHA) is present in high concentrations in salmon, herring, and trout. Epidemiologic studies have shown that high dietary consumption of these and other oily fish is associated with reduced rates of myocardial infarction, atherosclerosis, and other ischemic pathologies. Atherosclerosis is induced by inflammation and can lead to acute cardiovascular events and extensive plaque. DHA inhibits the development of inflammation in endothelial cells, alters the function and regulation of vascular biomarkers, and reduces cardiovascular risk. It also affects vascular relaxation and constriction by controlling nitric oxide and endothelin 1 production in endothelial cells. DHA also contributes to the prevention of arteriosclerosis by regulating the expression of oxidized low density lipoprotein receptor 1, plasminogen activator inhibitor 1, thromboxane A2 receptor, and adhesion molecules such as vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, and intercellular adhesion molecule 1 in endothelial cells. Recent research showed that DHA reduces the increase in adhesion factor expression induced by lipopolysaccharide by suppressing toll-like receptor 4. A new mechanism of action of DHA has been described that is mediated through endothelial free fatty acid receptor 4, associated with heme oxygenase 1 induction by Nrf2. However, the efficacy and mechanisms of action of DHA in cardiovascular disease prevention are not yet completely understood. The aim of this paper was to review the effects of DHA on vascular endothelial cells and recent findings on their potential for the prevention of circulatory diseases.

Acute effects of quercetin-3-O-glucoside on endothelial function and blood pressure: a randomized dose-response study

BACKGROUND

Epidemiologic studies have suggested that a flavonoid-rich diet can reduce the risk of developing cardiovascular disease. Certain flavonoids, in particular quercetin, have been shown to ameliorate endothelial dysfunction and reduce blood pressure (BP), possibly by increasing the bioavailability of the potent vasodilator nitric oxide (NO). Several studies have indicated that improvements in measures of cardiovascular health do not occur linearly, but rather, plateau or decrease with an increasing dose of flavonoids.

OBJECTIVES

We determined whether the acute administration of increasing doses of a common quercetin glycoside (quercetin-3-O-glucoside) improves endothelial function and reduces BP in a dose-dependent manner. We also explored whether any effects were correlated with changes in plasma NO production.

DESIGN

A randomized, controlled, crossover study was performed in 15 healthy volunteers who each completed 5 visits with a minimum washout period of 1 wk between testing days. Participants received each of the following 5 interventions in a random order: 1) 0, 2) 50, 3) 100, 4) 200, or 5) 400 mg quercetin-3-O-glucoside. Endothelial function and BP were assessed before and 60 min after intervention. A blood sample was taken before and 90 min after intervention for the analysis of plasma nitrate and nitrite as markers of NO production as well as of plasma quercetin metabolites.

RESULTS

Although we observed a significant correlation between the dose of quercetin-3-O-glucoside and plasma concentrations of total quercetin (R(2) = 0.52, P < 0.001) and isorhamnetin (R(2) = 0.12, P = 0.005), we showed no improvements in endothelial function or BP and no changes in NO production after any dose.

CONCLUSION

From these results, we conclude that there are no acute changes in BP or the NO-mediated endothelium-dependent relaxation of the brachial artery with doses of quercetin ranging from 50 to 400 mg in healthy men and women. This trial was registered at www.anzctr.org.au as ACTRN12615001338550.

Dietary flavonoids and nitrate: effects on nitric oxide and vascular function

Emerging evidence highlights dietary flavonoids and nitrate as candidates that may explain at least part of the cardioprotective effect of a fruit and vegetable diet. Nitric oxide plays a pivotal role in cardiovascular health. Components of a fruit and vegetable diet that are cardioprotective, in part through effects on nitric oxide status, could substantially reduce the cardiovascular risk profile of the general population with increased intake of such a diet. Epidemiological evidence suggests that dietary flavonoids and nitrate have a cardioprotective effect. Clinical trials with flavonoid- and nitrate-rich foods have shown benefits on measures of vascular health. While the molecular mechanisms by which flavonoids and nitrate are cardioprotective are not completely understood, recent evidence suggests both nonspecific and specific effects through nitric oxide pathways. This review presents an overview of nitric oxide and its key role in cardiovascular health and discusses the possible vascular benefits of flavonoids and nitrate, individually and in combination, through effects on nitric oxide status.

Markers of low-grade inflammation and endothelial dysfunction are related to reduced information processing speed and executive functioning in an older population - the Hoorn Study

Low-grade inflammation and endothelial dysfunction are related to cognitive decline and dementia, in a complex interplay with vascular factors and aging. We investigated, in an older population, low-grade inflammation and endothelial dysfunction in relation to detailed assessment of cognitive functioning. Furthermore, we explored this association within the context of vascular factors. 377 participants (73 ± 6 years) of the population-based Hoorn Study were included. In plasma samples of 2000-2001 (n=363) and/or 2005-2008 (n=323), biomarkers were determined of low-grade inflammation (CRP, TNF-alpha, IL-6, IL-8, SAA, MPO, and sICAM-1) and endothelial dysfunction (vWF, sICAM-1, sVCAM-1, sTM, sE-selectin). In 2005-2008, all participants underwent neuropsychological examination. Composite z-scores were computed for low-grade inflammation and endothelial dysfunction at both time points, and for six domains of cognitive functioning (abstract reasoning, memory, information processing speed, attention and executive functioning, visuoconstruction, and language). The association between low-grade inflammation and endothelial dysfunction, and cognitive functioning was evaluated with linear regression analysis. In secondary analyses, we explored the relation with vascular risk factors and cardiovascular disease. Low-grade inflammation and endothelial dysfunction were associated with worse performance on information processing speed and attention and executive functioning, in prospective and cross-sectional analyses (standardized betas ranging from -0.20 to -0.10). No significant relation with other cognitive domains was observed. Adjusting for vascular factors slightly attenuated the associations. Low-grade inflammation and endothelial dysfunction accounted for only 2.6% explained variance in cognitive functioning, on top of related vascular risk factors and cardiovascular disease. Bootstrapping analyses show that low-grade inflammation and endothelial dysfunction mediate the relation between vascular risk factors and cognitive functioning. This study shows that low-grade inflammation and endothelial dysfunction contribute to reduced information processing speed and executive functioning in an older population.

Suppression of endothelial P-selectin expression contributes to reduced cell trafficking in females: an effect independent of NO and prostacyclin

OBJECTIVE

Sex hormones underlie the lower incidence of cardiovascular disease in premenopausal women. Vascular inflammation is involved in the pathogenesis of several cardiovascular diseases and it has been reported that sex hormones modulate inflammatory responses but mechanisms responsible for these effects are not yet fully established. Herein, we assessed whether sex differences in leukocyte recruitment might exist and investigated the underlying mechanisms involved in this response.

METHODS AND RESULTS

Treatment with interleukin-1β (IL-1β) or tumor necrosis factor-α caused leukocyte rolling, adhesion, and emigration in mesenteric postcapillary venules in vivo that was substantially reduced in female mice compared with male mice; this difference was abolished by ovariectomy and partially restored by estrogen replacement. Deletion of endothelial nitric oxide (NO) synthase or cyclooxygenase-1 alone or in combination did not alter the leukocyte recruitment in IL-1β-treated females but significantly enhanced this response in male mice. Treatment of murine pulmonary endothelial cells with IL-1β increased expression of P-selectin in male but not female cells.

CONCLUSIONS

We have demonstrated a profound estrogen-dependent and NO and prostacyclin-independent suppression of leukocyte recruitment in females.

Reduced cerebral blood flow in older men with higher levels of blood pressure

OBJECTIVE

To examine relations of blood pressure (BP) with single photon emission computed tomography (SPECT)-derived estimates of cerebral blood flow in older men and women.

METHODS

Seventy-four stroke and dementia-free, community-dwelling older adults (ages 54-83 years; 68% men; 91% white) free of major medical, neurological, or psychiatric disease, engaged in clinical assessment of resting SBP and DBP, MRI rated for brain atrophy, and brain single photon emission computed tomography (SPECT) studies with computerized coding of cortical and select subcortical regions of interest.

RESULTS

Given significant interactions of BP and sex with respect to multiple SPECT outcomes, sex-stratified multiple regression models were computed. Models were adjusted for age, fasting glucose levels, antihypertensive medication, BMI, and MRI ratings of brain atrophy. In men (n = 50), higher levels of SBP and/or DBP were associated significantly with lower estimates of cerebral perfusion in the right and left frontal, temporal, parietal, and occipital cortex, thalamus, head of caudate, and cingulate cortex accounting for up to 28% of the variance in these measures (P < 0.05). In women (n = 24), higher DBP was related marginally to higher levels of perfusion in the right temporal cortex (P = 0.05).

CONCLUSION

Higher resting SBP or DBP was associated with lower levels of cerebral perfusion in otherwise healthy older men, but not women, in the present sample. Reduced cerebral blood flow may play a pathogenic role in increasing risk for stroke, dementia, and/or cognitive decline, particularly among older men with high BP.

Ventilatory, hemodynamic, sympathetic nervous system, and vascular reactivity changes after recurrent nocturnal sustained hypoxia in humans

Recurrent and intermittent nocturnal hypoxia is characteristic of several diseases including chronic obstructive pulmonary disease, congestive heart failure, obesity-hypoventilation syndrome, and obstructive sleep apnea. The contribution of hypoxia to cardiovascular morbidity and mortality in these disease states is unclear, however. To investigate the impact of recurrent nocturnal hypoxia on hemodynamics, sympathetic activity, and vascular tone we evaluated 10 normal volunteers before and after 14 nights of nocturnal sustained hypoxia (mean oxygen saturation 84.2%, 9 h/night). Over the exposure, subjects exhibited ventilatory acclimatization to hypoxia as evidenced by an increase in resting ventilation (arterial Pco(2) 41.8 +/- 1.5 vs. 37.5 +/- 1.3 mmHg, mean +/- SD; P < 0.05) and in the isocapnic hypoxic ventilatory response (slope 0.49 +/- 0.1 vs. 1.32 +/- 0.2 l/min per 1% fall in saturation; P < 0.05). Subjects exhibited a significant increase in mean arterial pressure (86.7 +/- 6.1 vs. 90.5 +/- 7.6 mmHg; P < 0.001), muscle sympathetic nerve activity (20.8 +/- 2.8 vs. 28.2 +/- 3.3 bursts/min; P < 0.01), and forearm vascular resistance (39.6 +/- 3.5 vs. 47.5 +/- 4.8 mmHg.ml(-1).100 g tissue.min; P < 0.05). Forearm blood flow during acute isocapnic hypoxia was increased after exposure but during selective brachial intra-arterial vascular infusion of the alpha-blocker phentolamine it was unchanged after exposure. Finally, there was a decrease in reactive hyperemia to 15 min of forearm ischemia after the hypoxic exposure. Recurrent nocturnal hypoxia thus increases sympathetic activity and alters peripheral vascular tone. These changes may contribute to the increased cardiovascular and cerebrovascular risk associated with clinical diseases that are associated with chronic recurrent hypoxia.

Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite

Diets rich in fruits and vegetables reduce blood pressure (BP) and the risk of adverse cardiovascular events. However, the mechanisms of this effect have not been elucidated. Certain vegetables possess a high nitrate content, and we hypothesized that this might represent a source of vasoprotective nitric oxide via bioactivation. In healthy volunteers, approximately 3 hours after ingestion of a dietary nitrate load (beetroot juice 500 mL), BP was substantially reduced (Delta(max) -10.4/8 mm Hg); an effect that correlated with peak increases in plasma nitrite concentration. The dietary nitrate load also prevented endothelial dysfunction induced by an acute ischemic insult in the human forearm and significantly attenuated ex vivo platelet aggregation in response to collagen and ADP. Interruption of the enterosalivary conversion of nitrate to nitrite (facilitated by bacterial anaerobes situated on the surface of the tongue) prevented the rise in plasma nitrite, blocked the decrease in BP, and abolished the inhibitory effects on platelet aggregation, confirming that these vasoprotective effects were attributable to the activity of nitrite converted from the ingested nitrate. These findings suggest that dietary nitrate underlies the beneficial effects of a vegetable-rich diet and highlights the potential of a "natural" low cost approach for the treatment of cardiovascular disease.

Human cerebrovascular and ventilatory CO2 reactivity to end-tidal, arterial and internal jugular vein PCO2

This study examined cerebrovascular reactivity and ventilation during step changes in CO(2) in humans. We hypothesized that: (1) end-tidal P(CO(2)) (P(ET,CO(2))) would overestimate arterial P(CO(2)) (P(a,CO(2))) during step variations in P(ET,CO(2)) and thus underestimate cerebrovascular CO(2) reactivity; and (2) since P(CO(2)) from the internal jugular vein (P(jv,CO(2))) better represents brain tissue P(CO(2)), cerebrovascular CO(2) reactivity would be higher when expressed against P(jv,CO(2)) than with P(a,CO(2)), and would be related to the degree of ventilatory change during hypercapnia. Incremental hypercapnia was achieved through 4 min administrations of 4% and 8% CO(2). Incremental hypocapnia involved two 4 min steps of hyperventilation to change P(ET,CO(2)), in an equal and opposite direction, to that incurred during hypercapnia. Arterial and internal jugular venous blood was sampled simultaneously at baseline and during each CO(2) step. Cerebrovascular reactivity to CO(2) was expressed as the percentage change in blood flow velocity in the middle cerebral artery (MCAv) per mmHg change in P(a,CO(2)) and P(jv,CO(2)). During hypercapnia, but not hypocapnia, P(ET,CO(2)) overestimated P(a,CO(2)) by +2.4 +/- 3.4 mmHg and underestimated MCAv-CO(2) reactivity (P < 0.05). The hypercapnic and hypocapnic MCAv-CO(2) reactivity was higher ( approximately 97% and approximately 24%, respectively) when expressed with P(jv,CO(2)) than P(a,CO(2)) (P < 0.05). The hypercapnic MCAv-P(jv,CO(2)) reactivity was inversely related to the increase in ventilatory change (R(2) = 0.43; P < 0.05), indicating that a reduced reactivity results in less central CO(2) washout and greater ventilatory stimulus. Differences in the P(ET,CO(2)), P(a,CO(2)) and P(jv,CO(2))-MCAv relationships have implications for the true representation and physiological interpretation of cerebrovascular CO(2) reactivity.

Early morning impairment in cerebral autoregulation and cerebrovascular CO2reactivity in healthy humans: relation to endothelial function

The reduction in cerebrovascular reactivity to CO(2) and/or endothelial function that occurs in the early hours after waking are potential causes for the increased risk for cardiovascular events at this time point. It is unknown whether cerebral autoregulation is reduced in the morning. We tested the hypothesis that early morning reduction in endothelium-dependent vascular reactivity would be linked to changes in cerebrovascular reactivity to CO(2) and cerebral autoregulation (CA). Overnight changes in a dynamic cerebral autoregulation index (ARI) were determined from continuous recordings of blood flow velocity in the middle cerebral artery (MCAv) and arterial blood pressure (BP) during transiently induced hypotension in 20 individuals. Frontal cortical oxygenation (near infrared spectroscopy) and cerebral haemodynamics were also monitored during hypercapnia and before and during 3 min of active standing. Brachial artery flow-mediated endothelium-dependent vasodilatation (FMD) and endothelium-independent dilatation (NFMD) were also monitored. From evening to morning, there was a significant lowering in ARI (5.3 +/- 0.5 versus 4.7 +/- 0.6 a.u.; P < 0.05), cerebrovascular reactivity to CO(2) (5.3 +/- 0.6 versus 4.6 +/- 1.1% mmHg(-1); P < 0.05) and FMD (7.6 +/- 0.9 versus 6.0 +/- 1.4%; P < 0.05). The lowered FMD was related to the decrease in cerebrovascular reactivity to CO(2) (r = 0.76; P < 0.05). Transient reductions in morning MCAv and cortical oxyhaemoglobin concentrations were observed upon resuming a supine-to-upright position (P < 0.05 versus evening). The early morning reduction in cerebral autoregulation may facilitate the onset of cerebrovascular accidents; this may be of particular relevance to at-risk groups, especially upon resuming the upright position.

Use of a flow-mediated vasodilation technique to assess endothelial function in dogs

OBJECTIVE

To develop and assess the reproducibility of a protocol to noninvasively test endothelial function in dogs on the basis of the flow-mediated vasodilation (FMD) procedure used in humans.

ANIMALS

5 healthy spayed female dogs.

PROCEDURES

Luminal arterial diameter and blood flow velocity in the brachial and femoral arteries were measured with ultrasonography. The within-dog reproducibility of these ultrasonographic measurements was tested. An occlusion period of 1, 3, or 5 minutes with an inflatable cuff was used to create the FMD response. Measurements made at 15, 30, and 60 seconds following release of the occlusion were compared with measurements made immediately prior to each occlusion to assess the FMD response.

RESULTS

Within-dog reproducibility of measurements revealed moderate to high correlations. Change from baseline in luminal arterial diameter was most substantial when measured at 30 seconds following release of occlusion, whereas blood flow velocity changes were maximal when measured at 15 seconds following release. The brachial imaging site provided a larger number of significant FMD responses than the femoral site. The 3-minute occlusion period provided equal or better responses than the 5-minute occlusion period.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonographic measurement of the FMD responses was a feasible and reproducible technique and significant changes from baseline were detected. The FMD responses in dogs were most substantial when performed at the brachial artery with blood flow velocity and luminal arterial diameter changes from baseline measured at 15 and 30 seconds, respectively, following release of a 3-minute occlusion period.

Human VIP-alpha: a long-acting, biocompatible and biodegradable peptide nanomedicine for essential hypertension

We have previously shown that self-association of human vasoactive intestinal peptide with sterically stabilized liposomes (VIP-alpha) alters peptide conformation from random coil in aqueous solution to alpha-helix. This, in turn, protects the peptide from hydrolysis and amplifies and prolongs its bioactivity. The purpose of this study was to determine whether a single, intravenous injection of low-dose human VIP-alpha normalizes systemic arterial pressure in anesthetized spontaneously hypertensive hamsters for a prolonged period of time in a selective fashion. We found that intravenous injection of human VIP-alpha, VIP alone (each, 1.0 nmol) and empty liposomes had no significant effects on mean arterial pressure (MAP) in normotensive hamsters. By contrast, human VIP-alpha (0.01-1.0 nmol) evoked a significant concentration-dependent decrease in MAP to the normative range in spontaneously hypertensive hamsters that lasted throughout the observation period (6 h; p<0.05). VIP alone and empty liposomes had no significant effects on MAP in these animals. We conclude that a single, low-dose intravenous injection of human VIP-alpha normalizes systemic arterial pressure in spontaneously hypertensive hamsters for a prolonged period of time in a selective fashion. We suggest that human VIP-alpha should be further developed as a long-acting, biocompatible and biodegradable peptide nanomedicine for essential hypertension.

Salvianolic acid B modulates hemostasis properties of human umbilical vein endothelial cells

Salviae miltiorrhizae (SM), a clinical, commonly used herb, can activate blood circulation and resolve stasis. We have investigated the effects of salvianolic acid B (Sal B), a pure compound extracted from the dried SM roots, on fibrinolytic (tissue-type plasminogen activator and plasminogen activator inhibitor, t-PA and PAI) and anticoagulant (thrombomodulin,TM) properties of cultured human umbilical vein endothelial cells (HUVECs). When HUVECs were treated with Sal B, a dose- (0.0125-0.5 mg/ml) and a time-dependent decrease in PAI activity were observed. PAI type 1 (PAI-1) antigen and PAI-1 mRNA expression significantly decreased compared to control values in the conditioned media of HUVECs pretreated with Sal B for 12 h. Moreover, TM activity reached a maximum stimulation of 1.25-fold over control levels in the pretreatment of Sal B for 12 h and t-PA and TM specific mRNA expression also increased (1.7- and 1.8-fold, respectively). In conclusion, Sal B increased the fibrinolytic and anticoagulant potential of cultured HUVECs by up-regulating the expression of t-PA and TM and by down-regulating the expression of PAI-1. These data suggest that Sal B is clinically effective because of its ability to change the gene expression profile of endothelial cells thereby preventing vascular events.

Intratracheal and subcutaneous liposomal VIP normalizes arterial pressure in spontaneously hypertensive hamsters

We determined whether a single intratracheal and subcutaneous administration of biocompatible and biodegradable vasoactive intestinal peptide self-associated with sterically stabilized liposomes (VIP-SSL) normalizes mean arterial pressure (MAP) in spontaneously hypertensive hamsters (SHH). We found that VIP-SSL (0.1 nmol) administered by either routes normalizes MAP (p < 0.05). Maximal effect was observed within 10-20 min and lasted for 6 h. VIP-SSL had no significant effects on heart rate. VIP alone (0.1 nmol) and empty SSL had no significant effects on MAP. VIP-SSL (0.1 nmol) had no significant effects on MAP and heart rate in age/genetically-matched control hamsters. Given these data, we suggest that pulmonary and subcutaneous delivery of VIP-SSL should be further developed as peptide nanomedicine for essential hypertension.

Sleep-disordered breathing and cerebrovascular disease: a mechanistic approach

The observations described in this article point to the existence of increased oxidative stress and systemic inflammation in sleep apnea and have paved the way for establishing sleep apnea as an independent risk factor for cardio- and cerebrovascular morbidities. The proposed course of events is summarized in Fig. 1. It is suggested that hypoxia/reoxygenation,characteristic of sleep apnea, promotes the formation of ROS, particularly during the reoxygenation period, and can be deleterious to cells and tissues. ROS, however, regulate the activation of critical transcription factors that are redox sensitive, resulting in increased expression of sets of genes that encode proteins essential to adaptation to hypoxia (via hypoxia inducible factor I [hypoxia inducible factor-la]). Yet, redox-sensitive transcription factors (NFKB and AP-1) that elicit inflammatory pathways also are activated, thereby affecting inflammatory and immune responses by promoting activation of endothelial cells, leukocytes, and platelets. These activated cells express adhesion molecules and proinflammatory cytokines that may lead to endothelial injury and dysfunction and consequently to the development of cardio- and cerebrovascular morbidities. These may be exaggerated in patients who have sleep apnea in response to the intermittent hypoxia.

Evidence of preserved endothelial function and vascular plasticity with age

We sought to identify the relationship between shear stimuli and flow-mediated vasodilation and to determine whether small muscle mass exercise training could provoke limb-specific improvements in endothelial function in older subjects. In five young (22 +/- 1 yr old) and six old (71 +/- 2 yr old) subjects, ultrasound Doppler measurements were taken in the arm (brachial artery) and leg (deep and superficial femoral arteries) after suprasystolic cuff occlusion with and without ischemic exercise to evaluate flow-mediated dilation (FMD) in both limbs. Older subjects were reevaluated after 6 wk of single-leg knee extensor exercise training. Before the training, a significant FMD was observed in the arm of young (3 +/- 1%) but not old (1 +/- 1%) subjects, whereas a significant leg FMD was observed in both groups (5 +/- 1% old vs. 3 +/- 1% young). However, arm vasodilation was similar between young and old when normalized for shear rate, and cuff occlusion with superimposed handgrip exercise provoked additional shear, which proportionately improved the FMD response in both groups. Exercise training significantly improved arm FMD (5 +/- 1%), whereas leg FMD was unchanged. However, ischemic handgrip exercise did not provoke additional arm vasodilation after training, which may indicate an age-related limit to shear-induced vasodilation. Together, these data demonstrate that vascular reactivity is dependent on limb and degree of shear stimuli, challenging the convention of diminished endothelial function typically associated with age. Likewise, exercise training improved arm vasodilation, indicating some preservation of vascular plasticity with age.