Chronic in vivo or acute in vitro resveratrol attenuates endothelium-dependent cyclooxygenase-mediated contractile signaling in hypertensive rat carotid artery.

Exaggerated cyclooxygenase (COX) and thromboxane-prostanoid (TP) receptor-mediated endothelium-dependent contraction can contribute to endothelial dysfunction. This study examined the effect of resveratrol (RSV) on endothelium-dependent contraction and cell signaling in the common carotid artery (CCA) from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Acetylcholine (Ach)-stimulated endothelium-dependent nitric oxide synthase (NOS)-mediated relaxation in precontracted SHR CCA was impaired (maximum 73 ± 6% vs. 87 ± 5% in WKY) (P < 0.05) by competitive COX-mediated contraction. Chronic (28-day) treatment in vivo (drinking water) with a ∼0.075 mg·kg(-1)·day(-1) RSV dose affected neither endothelium-dependent relaxation nor endothelium-dependent contraction and associated prostaglandin (PG) production evaluated in non-precontracted NOS-blocked CCA. In contrast, a chronic ∼7.5 mg·kg(-1)·day(-1) RSV dose improved endothelium-dependent relaxation (94 ± 6%) and attenuated endothelium-dependent contraction (58 ± 4% vs. 73 ± 5% in No-RSV) and PG production (183 ± 43 vs. 519 ± 93 pg/ml) in SHR CCA, while U46619-stimulated TP receptor-mediated contraction was unaffected. In separate acute in vitro experiments, 20-µM RSV preincubation attenuated endothelium-dependent contraction (6 ± 4% vs. 62 ± 2% in No Drug) and PG production (121 ± 15 vs. 491 ± 93 pg/ml) and attenuated U46619-stimulated contraction (134 ± 5% vs. 171 ± 4%) in non-precontracted NOS-blocked SHR CCA. Compound C, a known AMP-activated protein kinase (AMPK) inhibitor, did not prevent the RSV attenuating effect on Ach- and U46619-stimulated contraction but did prevent the RSV attenuating effect on PG production (414 ± 58 pg/ml). These data demonstrate that RSV can attenuate endothelium-dependent contraction both by suppressing arterial wall PG production, which may be partially mediated by AMPK, and by TP receptor hyporesponsiveness, which does not appear to be mediated by AMPK.

The effects of buthionine sulfoximine treatment on diaphragm contractility and SERCA pump function in adult and middle aged rats.

This study examined the effects of 10 days of buthionine sulfoximine (BSO) treatment on in vitro contractility and sarcoplasmic reticulum calcium pump (SERCA) expression and function in adult (AD; 6-8 months old) and middle aged (MA; 14-17 months old) rat diaphragm in both the basal state and following fatiguing stimulation. BSO treatment reduced the cellular concentrations of free glutathione (GSH) by >95% and oxidized glutathione (GSSG) by >80% in both age cohorts. GSH content in AD Control diaphragm was 32% higher (P < 0.01) than in MA Control, with no differences in GSSG. The ratio of GSH:GSSG, an indicator of cellular oxidative state, was 34.6 ± 7.4 in MA Control, 52.5 ± 10.1 in AD Control, 10.6 ± 1.7 in MA BSO, and 9.5 ± 1.1 in AD BSO (BSO vs. Control, P < 0.05). Several findings suggest that the effects of BSO treatment are age dependent. AD BSO diaphragm had 26% higher twitch and 28% higher tetanic force (both P < 0.05) than AD Controls, whereas no significant difference existed between the two MA groups. In contrast to our previous work on BSO-treated AD rats, BSO treatment did not influence maximal SERCA ATPase activity in MA rat diaphragm, nor did SERCA2a expression increase in BSO-treated MA diaphragm. Biotinylated iodoacetamide binding to SERCA1a, a specific marker of free cysteine residues, was reduced by 35% (P < 0.05) in AD Control diaphragm following fatiguing stimulation, but was not reduced in any other group. Collectively, these results suggest an important role for redox regulation in both contractility and SERCA function which is influenced by aging.

Sustained hyperaemia stimulus is necessary to induce flow-mediated dilation of the human brachial artery.

We studied the relative importance of the magnitude and duration of the shear stimulus to induce flow-mediated dilation (FMD) in the brachial artery of 10 healthy men by ultrasound imaging. The shear stress stimulus was induced by different durations of reactive hyperaemia following 15-min forearm occlusion. The control condition of continuous postocclusion hyperaemia was compared to 20, 40 and 60 s of reactive hyperaemia followed by reapplication of circulatory arrest for 2 min and a second cuff release. In response to the first cuff release, peak shear rate was not different between conditions; total shear during the first minute was reduced in the 40 s and further reduced in the 20 s conditions. FMD in control (10·0 ± 3·0%), 60 s (10·5 ± 3·2%) and 40 s (7·8 ± 3·6%) were greater than the 20-s condition (2·9 ± 2·8%). At second cuff release, peak shear of the 20-s condition was slightly reduced from the first release, but 40 and 60-s conditions were progressively reduced. Total shear to peak dilation was reduced after the second cuff release for the 20 and 40-s conditions and further after the 60-s condition. FMD was maintained in the 20-s condition (8·3 ± 3·7%) but reduced in the 40-s (3·7 ± 1·7%) and 60-s conditions (1·5 ± 2·6%). FMD was not related to peak shear rate after the first occlusion (r = 0·003) but was after the second cuff release (r = 0·32, P = 0·004). The FMD response was correlated with the total shear to time of peak diameter after the first (r = 0·35, P<0·001) and the second (r = 0·25, P = 0·009) cuff release.

Effects of glutathione-depleting drug buthionine sulfoximine and aging on activity of endothelium-derived relaxing and contracting factors in carotid artery of Sprague-Dawley rats.

The role of the antioxidant glutathione (GSH) in mediating endothelial (dys)function, and how that role may depend on age, is unclear. The main purpose of the current study was to investigate the effect of 10-day treatment with the GSH-depleting drug l-buthionine sulfoximine (BSO) on endothelium-derived relaxing factor and endothelium-derived contracting factor activities in the isolated common carotid artery (CCA) of Adult and Aging animals. CCA blood pressure and flow were unaffected by age or BSO. Endothelium-derived relaxing factor activity, examined in precontracted CCA as relaxation to cumulative acetylcholine (ACh), was largely nitric oxide synthase (NOS) mediated and was not different between Adult and Aging animals at lower ACh; however, at higher ACh, relaxation was blunted in Aging CCA, an effect abolished by cyclooxygenase (COX) inhibition but not by NOS inhibition nor by the reactive oxygen species (ROS) inhibitors 4-hydroxy-TEMPO or Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin,tetratosylate,hydroxide. Specific examination of endothelium-derived contracting factor activity in quiescent NOS-inhibited CCA established that higher ACh elicited a contractile response, ∼3.5-fold greater in Aging versus Adult CCA, which was abolished by COX-1-specific inhibition but unaffected by ROS inhibitors. Aging was unrelated to changes in liver or vascular tissue GSH or ROS content. BSO was effective in significantly decreasing GSH and increasing ROS content in both animal cohorts. However, NOS-mediated endothelium-derived relaxing factor activity was well preserved and age-related COX-mediated endothelium-derived contracting factor activity was unaffected in response to these BSO-induced perturbations, as were exogenous H2O2-stimulated NOS/non-NOS-mediated relaxation and COX-mediated contractile activities. These data suggest that, regardless of age, chronic partial depletion of GSH in vivo does not necessarily cause endothelium-dependent vasomotor dysfunction.

RhoA-Rho kinase signaling mediates endothelium- and endoperoxide-dependent contractile activities characteristic of hypertensive vascular dysfunction.

Hypertensive vasomotor dysfunction is defined by endothelium-dependent contractions involving prostaglandins and ROS. Since both thromboxane-prostanoid receptor (TPr) signaling and ROS activate RhoA-Rho kinase (ROCK) in vascular smooth muscle (VSM) preparations, we hypothesized that enhanced endothelium-dependent contraction in the common carotid artery (CCA) of spontaneously hypertensive rats (SHRs) is ROCK mediated. ACh-stimulated contractions were approximately twofold greater in SHRs versus normotensive Wistar-Kyoto (WKY) rats, abolished by endothelial denudation or cyclooxygenase (COX)-1 inhibition, and nearly eliminated by TPr blockade. RhoA but not ROCK-II protein expression was increased ( approximately 50%) in the SHR CCA. Inhibition of ROCK, but not protein kinase C, caused a dose-dependent reduction in endothelium-dependent contractions to ACh across strains, with the highest dose mirroring the effect of high-dose TPr antagonism. Conversely, ROCK inhibition caused dose-dependent and endothelium- and nitric oxide-independent relaxation in CCAs precontracted with the TPr agonist U-46619. Prostacyclin was the predominant prostaglandin produced by ACh-stimulated CCAs, with greater than twofold more prostacyclin released from SHR versus WKY rats, and its production was unaffected by ROCK inhibition. RhoA activation was approximately twofold higher in quiescent SHR CCAs compared with those from WKY rats and was significantly increased by ACh stimulation. Augmentation of chemical superoxide quenching with tiron or inhibition of the NADPH oxidase-derived superoxide-producing pathway with apocynin reduced ACh-stimulated contractile activity in SHR more than in WKY rats, whereas the SOD mimetic tempol amplified the response. Exposure of CCAs to exogenous H(2)O(2) caused contractions, similar to ACh stimulation, that were greater in SHR than in WKY rats, abolished by COX-1 inhibition, and highly attenuated by TPr blockade or ROCK inhibition. These results indicate that RhoA-ROCK may act as a molecular switch, transducing signals from endothelium-derived prostaglandin(s) and ROS, which are overproduced in SHR CCAs, to "turn on" VSM contractile pathways, thus mediating the enhanced endothelium- and endoperoxide-dependent vascular contractions characteristic of hypertension, among other cardiovascular disease states, such as diabetes and aging.

Impaired hemodynamics and endothelial vasomotor function via endoperoxide-mediated vasoconstriction in the carotid artery of spontaneously hypertensive rats.

The fact that endothelium removal increases diameter and compliance in the common carotid artery (CCA) of spontaneously hypertensive rats (SHR) and that improving CCA endothelium-dependent vasorelaxation has been shown to normalize a reduced systolic blood flow through the SHR CCA compared with normotensive Wistar-Kyoto rats (WKY) suggests that endothelial vasomotor dysfunction may be linked to altered large artery hemodynamics in hypertension. The experiments herein were designed to further investigate WKY and SHR CCA hemodynamics and endothelium-dependent vasomotor functions. It was hypothesized that CCA blood flow and conductance would be reduced throughout the cardiac cycle in SHR and that endothelium-dependent contractile activity would impair SHR CCA vasorelaxation. We report that mean, maximal systolic, and diastolic blood flow was reduced in SHR vs. WKY CCA, as was vascular conductance. Pressure was augmented in SHR CCA and accompanied by late systolic flow augmentation so that total flow during systole was indeed no different between strains, possibly explained by earlier lower body wave reflection. While ACh stimulation in isolated precontracted WKY CCA caused a robust nitric oxide (NO)-mediated vasorelaxation, endothelium-dependent, cyclooxygenase (COX)-mediated contractile activity stimulated by high ACh concentration impaired NO- and non-NO/non-COX-mediated vasorelaxation in precontracted SHR CCA. In quiescent CCA, this endothelium-dependent contractile response was COX-1 and thromboxane-prostanoid receptor mediated and modulated by the availability of NO. These data collectively suggest that endothelium-dependent, COX-mediated endoperoxide signaling in the CCA of SHR may elicit vasoconstriction, which could shift the mechanical properties of this conduit artery and contribute to reduced CCA blood flow in vivo.

Effect of short-term lycopene supplementation and postprandial dyslipidemia on plasma antioxidants and biomarkers of endothelial health in young, healthy individuals.

The objective of this study was to test the hypothesis that the effect of a high-fat meal (HFm) on plasma lipid-soluble antioxidants and biomarkers of vascular oxidative stress and inflammation would be attenuated by short-term lycopene supplementation in young healthy subjects. Following restriction of lycopene-containing foods for 1-wk (LYr), blood was collected in a fasting state and 3 h after a HFm and a low-fat meal (LFm) in N = 18 men aged 23 +/- 2 years, and after a HFm only in N = 9 women aged 23 +/- 1 years. Blood was also sampled pre- and post-meals following 1-wk of 80 mg/day lycopene supplementation (LYs) under continued dietary LYr. In the fasting state, LYs compared with LYr not only evoked a >2-fold increase in plasma lycopene but also increased plasma beta-carotene and alpha-tocopherol (p < 0.01), though LYs did not affect plasma nitrate/nitrite (biomarker of nitric oxide), malondialdehyde (biomarker of lipid oxidative stress), vascular- and intercellular-adhesion molecules or C-reactive protein (biomarkers of inflammation). Contrary to the hypothesis, the HFm-induced dyslipidemic state did not affect plasma malondialdehyde, C-reactive protein, or adhesion molecules in either LYr or LYs. Both the HFm and LFm were associated with decreases in the nitric oxide metabolites nitrate/nitrite and lipid-soluble antioxidants (p < 0.05). The data revealed that 1-wk of LYs increased plasma lycopene, beta-carotene, and alpha-tocopherol yet despite these marked changes to the plasma lipid-soluble antioxidant pool, biomarkers of vascular oxidative stress and inflammation were unaffected in the fasted state as well as during dyslipidemia induced by a HFm in young healthy subjects.

Glutathione depletion in vivo enhances contraction and attenuates endothelium-dependent relaxation of isolated rat aorta.

Ten-day administration of the glutamate-cysteine ligase inhibitor L-buthionine-[S,R]-sulfoximine (BSO; 20 or 30 mM in drinking water) to adult male Sprague-Dawley rats induced 50-60% glutathione depletion (p<0.001) and elevated aortic ring reactive oxygen species release and tissue and plasma H2O2 concentrations (p<0.001) compared to control animals (CON) that consumed normal drinking water. In contrast to previous studies using tail cuff plethysmography methods, BSO had no significant effect on systolic blood pressure assessed by indwelling femoral artery catheters in conscious animals (10-day values, 119+/-3 mn Hg vs 122+/-4 mm Hg in CON vs BSO, respectively). Thoracic aorta rings were excised for in vitro assessment of vasomotor function. BSO shifted the phenylephrine (PE) dose-response curve to the left (p=0.003), lowering the EC50 for PE contraction (from -6.752+/-0.056 to -7.056+/-0.055 log units; p=0.001). Endothelium-dependent relaxation to acetylcholine (ACh) was significantly blunted (p=0.019) and the EC50 for ACh relaxation was significantly increased (from -7.428+/-0.117 to -7.129+/-0.048 log units; p=0.02) in BSO vs CON. Endothelium-independent vasorelaxation to sodium nitroprusside was similar in BSO and CON groups. Thoracic aorta immunoblot analyses revealed increases in endothelial nitric oxide synthase, superoxide dismutase 1 and 2, and soluble guanylate cyclase in BSO vs CON (all p<0.01). Thus, enhanced PE contraction, blunted endothelium-dependent relaxation, and adaptations in nitric oxide bioavailability pathways provide the first evidence of chronic, in vivo BSO-induced, oxidative stress-mediated direct effects on the vasomotor function of arteries.

Vascular nitric oxide and oxidative stress: determinants of endothelial adaptations to cardiovascular disease and to physical activity.

Cardiovascular disease is the single leading cause of death and morbidity for Canadians. A universal feature of cardiovascular disease is dysfunction of the vascular endothelium, thus disrupting control of vasodilation, tissue perfusion, hemostasis, and thrombosis. Nitric oxide bioavailability, crucial for maintaining vascular endothelial health and function, depends on the processes controlling synthesis and destruction of nitric oxide as well as on the sensitivity of target tissue to nitric oxide. Evidence supports a major contribution by oxidative stress-induced destruction of nitric oxide to the endothelial dysfunction that accompanies a number of cardiovascular disease states including hypertension, diabetes, chronic heart failure, and atherosclerosis. Regular physical activity (exercise training) reduces cardiovascular disease risk. Numerous studies support the hypothesis that exercise training improves vascular endothelial function, especially when it has been impaired by preexisting risk factors. Evidence is emerging to support a role for improved nitric oxide bioavailability with training as a result of enhanced synthesis and reduced oxidative stress-mediated destruction. Molecular targets sensitive to the exercise training effect include the endothelial nitric oxide synthase and the antioxidant enzyme superoxide dismutase. However, many fundamental details of the cellular and molecular mechanisms linking exercise to altered molecular and functional endothelial phenotypes have yet to be discovered. The working hypothesis is that some of the cellular mechanisms contributing to endothelial dysfunction in cardiovascular disease can be targeted and reversed by signals associated with regular increases in physical activity. The capacity for exercise training to regulate vascular endothelial function, nitric oxide bioavailability, and oxidative stress is an example of how lifestyle can complement medicine and pharmacology in the prevention and management of cardiovascular disease.