ACh-induced Relaxation Research Articles

367 - Tocomin Attenuates Oxidative Stress and Improves NO Mediated Relaxation in Aortaefrom Rats Fed a High Fat Diet

We have previously reported that tocomin, a mixture high in tocotrienol content and also containing tocopherol, acutely preserves endothelial function in the presence of oxidative stress. We investigated whether tocomin treatment would preserve endothelial function in aortae isolated from rats fed a high fat diet. Wistar hooded rats were fed a western diet (WD, 21% fat) or control rat chow (SD, 6% fat) for 12 weeks. Tocomin (40 mg/kg/day sc) or its vehicle was administered for the last 4 weeks of feeding. Aortae from WD rats showed an impairment of endothelium-dependent relaxation that was associated with an increased expression of the NADPH oxidase Nox2 subunit and an increase in the generation of superoxide. The increase in vascular oxidative stress was accompanied by a decrease in basal NO release and impairment of the contribution of NO to ACh-induced relaxation. The impaired relaxation is likely contributed to by a decreased expression of eNOS, calmodulin and phosphorylated Akt and an increase in caveolin. Tocomin prevented the diet-induced changes in vascular function, reduced vascular superoxide production and abolished the diet-induced changes in eNOS and other protein expression. Using selective inhibitors of nitric oxide synthase (NOS), soluble guanylate cyclase (sGC) and calcium activated potassium (KCa) channels we demonstrated that tocomin selectively increased NO mediated relaxation. The beneficial actions of tocomin suggests that it may have potential to be used as a therapeutic agent to prevent vascular disease in obesity.

Tocotrienol-Rich Tocomin Attenuates Oxidative Stress and Improves Endothelium-Dependent Relaxation in Aortae from Rats Fed a High-Fat Western Diet.

We have previously reported that tocomin, a mixture high in tocotrienol content and also containing tocopherol, acutely preserves endothelial function in the presence of oxidative stress. In this study, we investigated whether tocomin treatment would preserve endothelial function in aortae isolated from rats fed a high-fat diet known to cause oxidative stress. Wistar hooded rats were fed a western diet (WD, 21% fat) or control rat chow (standard diet, 6% fat) for 12 weeks. Tocomin (40 mg/kg/day sc) or its vehicle (peanut oil) was administered for the last 4 weeks of the feeding regime. Aortae from WD rats showed an impairment of endothelium-dependent relaxation that was associated with an increased expression of the NADPH oxidase Nox2 subunit and an increase in the vascular generation of superoxide measured using L-012 chemiluminescence. The increase in vascular oxidative stress was accompanied by a decrease in basal NO release and impairment of the contribution of NO to ACh-induced relaxation. The impaired relaxation is likely contributed to by a decreased expression of eNOS, calmodulin, and phosphorylated Akt and an increase in caveolin. Tocotrienol rich tocomin, which prevented the diet-induced changes in vascular function, reduced vascular superoxide production and abolished the diet-induced changes in eNOS and other protein expression. Using selective inhibitors of nitric oxide synthase (NOS), soluble guanylate cyclase (sGC) and calcium-activated potassium (KCa) channels we demonstrated that tocomin increased NO-mediated relaxation, without affecting the contribution of endothelium-dependent hyperpolarization type relaxation to the endothelium-dependent relaxation. The beneficial actions of tocomin in this diet-induced model of obesity suggest that it may have potential to be used as a therapeutic agent to prevent vascular disease in obesity.

Endothelial dysfunction of internal thoracic artery graft in patients with chronic kidney disease

ObjectivesThe present study was designed to evaluate the association between chronic kidney disease and the endothelial function of internal thoracic artery (ITA) grafts in patients undergoing coronary bypass surgery. An isometric tension study was performed in ITA strips obtained during surgery. Concentration-response curves for acetylcholine (ACh) and sodium nitroprusside were constructed in ITA strips partially precontracted with phenylephrine under the inhibition of cyclooxygenase. The integrity of the endothelium was verified histologically by en-face staining of the luminal surface with the use of silver nitrate solution. ResultsIn endothelium-intact ITA strips, ACh produced a concentration-dependent relaxation in patients with glomerular filtration rate (GFR, mL/min/1.73 m2) > 60. A concentration-dependent relaxation response also was observed in patients with GFR 30 to 60, but it was reduced significantly compared with those with GFR > 60. In both groups, removal of endothelium or treatment with nitric oxide (NO) synthase inhibitors almost abolished the ACh-induced relaxation. On the other hand, in patients with GFR < 30, mild contraction rather than relaxation was induced at a high concentration of ACh, which was modified neither by treatment with NO synthase inhibitors nor by removal of the endothelium. Vasodilator responses to sodium nitroprusside were comparable among the 3 groups. The relaxation of endothelium-intact strips to a peak ACh concentration correlated positively with GFR. This relationship held true in a multiple linear regression model, and interaction terms between GFR and other risk factors were not statistically significant. ConclusionsEndothelial function of ITA grafts to release NO is impaired at the time of surgery in patients with chronic kidney disease.

PP.03.16] INCREASED ROS GENERATION INVOLVES MITOCHONDRIA IN MR-OVEREXPRESSING ADIPOCYTES – IMPACT ON VASCULAR FUNCTION.

Objective: Visceral adipose tissue (VAT) influences vascular function through aldosterone and mineralocorticoid receptors (MR). We demonstrated that adipocyte MR over-activation in mice leads to metabolic changes. Whether this is associated with vascular dysfunction remains unclear. Design and method: To address this, we generated mice with conditional MR overexpression targeted to adipocytes (Adipo-MROE) and studied the effect of fat conditioned medium (Fcm, collected from visceral adipose tissue) on vascular reactivity of resistant mesenteric arteries and associated molecular mechanisms. Endothelial-dependent relaxation to acetylcholine (ACh), in the presence or absence of Fcm, was assessed by wire myography. Levels of reactive oxygen species (ROS) were determined in mitochondria isolated from adipose tissues (mito-AT) by electron paramagnetic spin resonance and Amplex Red kit. Inhibitors of NADPH oxidases and mitochondrial ROS were used in our experiments. Results: We previously showed that 1) ROS were increased in adipose tissues from Adipo-MROE vs control (CTR) mice; b) Fcm from Adipo-MROE (Fcm-MR) induced endothelial dysfunction in control arterie, through redox-sensitive mechanisms. Here, we identified the source of ROS in adipocytes, with the hypothesis that NADPH oxidases and mitochondria may play an important role. Levels of superoxide were 3 fold-increased in mito-AT from Adipo-MROE compared to CTR mice (n = 7 mice per group, p < 0.01). We pre-incubated Fcm-MR with either the inhibitor of NADPH oxidase isoforms 1 and 2 (ML171, 10–6 M), either a specific inhibitor of mitochondrial-derived ROS (mito-TEMPO, 10–7 M), and assessed ACh-induced relaxation (10–6 M) in CTR arteries. Normal relaxation was restored by mito-TEMPO (% relaxation: CTR+Fcm-MR, without vs with mito-TEMPO: 47.5 ± 4.4 vs 87.1 ± 2.2, n = 6 mice per group, p < 0.05), whereas Nox1/2 inhibitor-ML171 did not improve endothelial function (% relaxation: 47.7 ± 4.2, ns). Conclusions: Our data demonstrate that adipocyte MR over-activation leads to increased mitochondrial-derived ROS generation in visceral adipose tissue, which contributes to endothelial dysfunction. We describe a novel mechanism that directly links adipose tissue and vascular function. Our study identifies novel mechanisms linking vascular/adipose tissue biology and aldosterone/MR activation, which may be particularly important in vascular dysfunction associated with metabolic syndrome.

Hydrogen sulfide: A novel mechanism for the vascular protection by resveratrol under oxidative stress in mouse aorta

Reactive oxygen species (ROS) decreases bioavailability of nitric oxide (NO) and impairs NO-dependent relaxations. Like NO, hydrogen sulfide (H2S) is an antioxidant and vasodilator; however, the effect of ROS on H2S-induced relaxations is unknown. Here we investigated whether ROS altered the effect of H2S on vascular tone in mouse aorta and determined whether resveratrol (RVT) protects it via H2S. Pyrogallol induced ROS formation. It also decreased H2S formation and relaxation induced by l-cysteine and in mouse aorta. Pyrogallol did not alter sodium hydrogensulfide (NaHS)-induced relaxation suggesting that the pyrogallol effect on l-cysteine relaxations was due to endogenous H2S formation. RVT inhibited ROS formation, enhanced l-cysteine-induced relaxations and increased H2S level in aortas exposed to pyrogallol suggesting that RVT protects against “H2S-dysfunctions” by inducing H2S formation. Indeed, H2S synthesis inhibitor AOAA inhibited the protective effects of RVT. RVT had no effect on Ach-induced relaxation that is NO dependent and the stimulatory effect of RVT on H2S-dependent relaxation was also independent of NO. These results demonstrate that oxidative stress impairs endogenous H2S-induced relaxations and RVT offers protection by inducing H2S suggesting that targeting endogenous H2S pathway may prevent vascular dysfunctions associated by oxidative stress.

Low dose dietary nitrate improves endothelial dysfunction and plaque stability in the ApoE−/− mouse fed a high fat diet

BackgroundNitric oxide (NO) is an important vascular signalling molecule. NO is synthesised endogenously by endothelial nitric oxide synthase (eNOS). An alternate pathway is exogenous dietary nitrate, which can be converted to nitrite and then stored or further converted to NO and used immediately. Atherosclerosis is associated with endothelial dysfunction and subsequent lesion formation. This is thought to arise due to a reduction in the bioavailability and/or bioactivity of endogenous NO. AimTo determine if dietary nitrate can protect against endothelial dysfunction and lesion formation in the ApoE−/− mouse fed a high fat diet (HFD). Methods and resultsApoE−/− fed a HFD were randomized to receive (i) high nitrate (10mmol/kg/day, n=12), (ii) moderate nitrate (1mmol/kg/day, n=8), (iii) low nitrate (0.1mmol/kg/day, n=8), or (iv) sodium chloride supplemented drinking water (control, n=10) for 10 weeks. A group of C57BL6 mice (n=6) received regular water and served as a healthy reference group. At 10 weeks, ACh-induced vessel relaxation was significantly impaired in ApoE−/− mice versus C57BL6. Mice supplemented with low or moderate nitrate showed significant improvements in ACh-induced vessel relaxation compared to ApoE−/− mice given the high nitrate or sodium chloride. Plaque collagen expression was increased and lipid deposition reduced following supplementation with low or moderate nitrate compared to sodium chloride, reflecting increased plaque stability with nitrate supplementation. Plasma nitrate and nitrite levels were significantly increased in all three groups fed the nitrate-supplemented water. ConclusionLow and moderate dose nitrate significantly improved endothelial function and atherosclerotic plaque composition in ApoE−/− mice fed a HFD.

Tert-butylhydroquinone lowers blood pressure in AngII-induced hypertension in mice via proteasome-PTEN-Akt-eNOS pathway.

Tert-butylhydroquinone (tBHQ), as an antioxidant, has been widely used for many years to prevent oxidization of food products. The aim of this study was to investigate whether tBHQ activates endothelial nitric oxide synthase (eNOS) to prevent endothelial dysfunction and lower blood pressure. The role of Akt in tBHQ-induced eNOS phosphorylation was examined in human umbilical vein endothelial cells (HUVEC) or in mice. tBHQ treatment of HUVEC increased both Akt-Ser473 phosphorylation, accompanied with increased eNOS-Ser1177 phosphorylation and NO release. Mechanically, pharmacologic or genetic inhibition of Akt abolished tBHQ-enhanced NO release and eNOS phosphorylation in HUVEC. Gain-function of PTEN or inhibition of 26S proteasome abolished tBHQ-enhanced Akt phosphorylation in HUVEC. Ex vivo analysis indicated that tBHQ improved Ach-induced endothelium-dependent relaxation in LPC-treated mice aortic arteries, which were abolished by inhibition of Akt or eNOS. In animal study, administration of tBHQ significantly increased eNOS-Ser1177 phosphorylation and acetylcholine-induced vasorelaxation, and lowered AngII-induced hypertension in wildtype mice, but not in mice deficient of Akt or eNOS. In conclusion, tBHQ via proteasome-dependent degradation of PTEN increases Akt phosphorylation, resulting in upregulation of eNOS-derived NO production and consequent improvement of endothelial function in vivo. In this way, tBHQ lowers blood pressure in hypertensive mice.

Adipocytokine, progranulin, augments acetylcholine-induced nitric oxide-mediated relaxation through the increases of cGMP production in rat isolated mesenteric artery.

Progranulin (PGRN) is a novel adipocytokine with anti-inflammatory effects in vascular cells. The aim of this study was to clarify the effects of PGRN on reactivity of isolated blood vessel. Isometric contraction of rat isolated superior mesenteric artery was measured. Pre-treatment with PGRN (10-100ngmL-1 , 30min) had no effect on noradrenaline- or 5-hydroxytriptamine-induced contraction. On the other hand, pre-treatment with PGRN (100ngmL-1 ) augmented acetylcholine (ACh; 30nm)-induced endothelium-dependent relaxation. Pre-treatment with PGRN (100ngmL-1 ) augmented ACh (10μm)-induced nitric oxide (NO)-mediated relaxation in the presence of indomethacin (10μm), a cyclooxygenase inhibitor, and tetraethyl ammonium (10mm), a non-selective potassium channel blocker. In contrast, pre-treatment with PGRN (100ngmL-1 ) had no effect on ACh-induced endothelium-derived hyperpolarizing factor-mediated relaxation. Pre-treatment with PGRN (100ngmL-1 ) had no effect on ACh (10μm, 1min)-induced endothelial NO synthase phosphorylation (at Ser1177) as determined by Western blotting. Pre-treatment with PGRN (100ngmL-1 ) augmented an NO donor, sodium nitroprusside (SNP; 30nm-1μm)- but not a membrane-permeable cGMP analogue, 8-bromo-cGMP-induced relaxation. In the presence of 3-isobutyl-1-methylxanthine (100μm), a phosphodiesterase inhibitor, pre-treatment with PGRN (100ngmL-1 ) increased SNP (30nm, 5min)-induced cGMP production as determined by enzyme immunoassay. We for the first time demonstrate that PGRN augments ACh-induced NO-mediated relaxation through the increases of cGMP production in smooth muscle. These results indicate PGRN as a possible pharmacotherapeutic target against cardiovascular diseases including obesity-related hypertension.

Restoring placental growth factor-soluble fms-like tyrosine kinase-1 balance reverses vascular hyper-reactivity and hypertension in pregnancy.

Preeclampsia (PE) is a pregnancy-related hypertensive disorder (HTN-Preg) with unclear mechanism. An imbalance between antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and angiogenic placental growth factor (PlGF) has been observed in PE, but the vascular targets and signaling pathways involved are unclear. We assessed the extent of sFlt-1/PlGF imbalance and vascular dysfunction in a rat model of HTN-Preg produced by reduction of uteroplacental perfusion pressure (RUPP), and tested whether inducing a comparable sFlt-1/PlGF imbalance by infusing sFlt-1 (10 μg·kg(-1)·day(-1)) in day 14 pregnant (Preg) rats cause similar increases in blood pressure (BP) and vascular reactivity. Using these guiding measurements, we then tested whether restoring sFlt-1/PlGF balance by infusing PIGF (20 μg·kg(-1)·day(-1)) in RUPP rats would improve BP and vascular function. On gestational day 19, BP was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP rats. Plasma sFlt-1/PlGF ratio was increased in Preg+sFlt-1, and RUPP and was reduced in RUPP+PlGF rats. In isolated endothelium-intact aorta, carotid, mesenteric, and renal artery, phenylephrine (Phe)- and high KCl-induced contraction was in Preg+sFlt-1 and RUPP > Preg, and in RUPP+PlGF < RUPP. The differences in vascular reactivity to Phe and KCl between groups were less apparent in vessels treated with the nitric oxide synthase (NOS) inhibitor l-NAME or guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) or endothelium-denuded, suggesting changes in endothelial NO-cGMP pathway. In Phe precontracted vessels, ACh-induced relaxation was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP, and was blocked by N(ω)-nitro-l-arginine methyl ester (l-NAME) or ODQ treatment or endothelium removal. Western blots revealed that aortic total endothelial NOS (eNOS) and activated phosphorylated-eNOS were in Preg+sFlt-1 and RUPP < Preg and in RUPP+PlGF > RUPP. ACh-induced vascular nitrate/nitrite production was in Preg+sFlt-1 and RUPP < Preg, and in RUPP+PlGF > RUPP. Vascular relaxation to the exogenous NO donor sodium nitroprusside was not different among groups. Thus, a tilt in the angiogenic balance toward anti-angiogenic sFlt-1 is associated with decreased vascular relaxation and increased vasoconstriction and BP. Restoring the angiogenic/antiangiogenic balance using PlGF enhances endothelial NO-cGMP vascular relaxation and decreases vasoconstriction and BP in HTN-Preg rats and could offer a new approach in the management of PE.

Abstract 618: Targeted Delivery of microRNA-146a/-181b Protects Against Endothelial Dysfunction and Prevents Atherosclerosis

Objective: Atherosclerosis, which underlies most cardiovascular diseases (CVD), is a leading cause of mortality and disability in developed countries. The endothelium is an important site of vascular regulation, and its dysfunction initiates atherosclerosis and supports its progression. Current drug therapies, percutaneous angioplasty, and stenting alleviate symptoms but do not reverse atherosclerosis. Thus, more effective strategies that prevent or reverse atherosclerosis via improved endothelial function are needed. Approach: E-selectin serves as a surface marker of inflamed endothelial cells (ECs). We attempted to deliver microRNA (miR)-146a and miR-181b to inflamed endothelium covering atherosclerotic plaques with an E-selectin-targeting multistage vector (ESTA-MSV to inhibit atherosclerosis. Cy5-conjugated miR-146a and miR-181b were packaged in polyethylene glycol-polyethyleneimine (PEG/PEI) nanoparticles and then loaded into ESTA-MSV microparticles. Male apolipoprotein E-deficient mice were fed with Western diet and injected intravenously with the particles prepared as above biweekly for 12 weeks. Results: Atherosclerotic plaque size decreased with treatment of miRs packaged in ESTA-MSV but not in PEG/PEI. Moreover, vascular inflammation markers such as macrophages in aortic root lesion and expression of chemokines in aortic tissues were decreased while the vascular smooth muscle cells and collagen were increased in plaques from ESTA-MSV/miRs-treated mice compared with vehicle-treated group. Systemic delivery of miR-146a/-181b significantly improved the ACh-induced relaxation of aortas and carotid arteries and inhibited ACh-induced endothelium-dependent contraction of carotid arteries of ApoE-/- mice fed with Western diet for 12 weeks Conclusions: Our data demonstrate that the ESTA-MSV microparticle-mediated delivery of miR-146a/-181b ameliorates the endothelial dysfunction and prevents atherosclerosis.

Etanercept improves endothelial function via pleiotropic effects in rat adjuvant-induced arthritis.

To determine the effect of etanercept on endothelial dysfunction and on traditional cardiovascular (CV) risk factors in the adjuvant-induced arthritis (AIA) rat model. At the first signs of arthritis, etanercept (10 mg/kg/3 days, s.c.) or saline was administered for 3 weeks in AIA rats. Body weights and arthritis scores were monitored daily. Endothelial function was studied in aortic rings relaxed with acetylcholine (Ach) with or without inhibitors of nitric oxide synthase (NOS), cyclo-oxygenase (COX-2), arginase, endothelium-derived hyperpolarizing factor and superoxide anions (O2 (-)°) production. Aortic expression of endothelial nitic oxide synthase (eNOS), Ser1177-phospho-eNOS, COX-2, arginase-2, p22(phox) and p47(phox) was evaluated by western blotting analysis. Blood pressure, heart rate and blood levels of triglycerides, cholesterol and glucose were measured. Etanercept significantly reduced arthritis score (P < 0.001). It improved Ach-induced relaxation (P < 0.05) as a result of increased NOS activity, decreased COX-2/arginase activities and decreased O2 (-)° production. These functional effects relied on increased eNOS expression and phosphorylation, and decreased COX-2, arginase-2 and p22(phox) expressions. No correlation was found between arthritis score and Ach-induced relaxation. The treatment did not change triglycerides, cholesterol and glucose levels, but significantly increased systolic blood pressure and heart rate (P < 0.05). Our data demonstrated that efficient dosage of etanercept on inflammatory symptoms improved endothelial function in AIA. This beneficial effect on endothelial function is disconnected from its impact on CV risk factors and relates to pleiotropic effects of etanercept on endothelial pathways. These results suggest that etanercept could be a good choice for patients with rheumatoid arthritis at high risk of CV events.

Resveratrol lowers blood pressure in spontaneously hypertensive rats via calcium-dependent endothelial NO production

ABSTRACTObjective: Resveratrol, a polyphenol of natural compounds, has beneficial cardiovascular effects, many of which are mediated by nitric oxide (NO). Resveratrol increases intracellular calcium and activates AMP-activated protein kinase (AMPK), all of which could increase NO production. We hypothesized that resveratrol via a calcium-dependent NO production lowers blood pressure (BP) in spontaneously hypertensive rats (SHR). Methods: Acetylcholine (Ach)-induced endothelium-dependent relaxations in rat aortas were examined by organ chamber. Blood pressures were determined by radiotelemetry methods. Results: Incubation of isolated aortas from SHR with resveratrol dramatically improved vasorelaxation induced by Ach. Preincubation of aortas with endothelial NO synthase (eNOS) inhibitor or calcium chelant blunted the effects of resveratrol on Ach-induced relaxation, as wells as NO production and eNOS phosphorylation. In animal studies, administration of resveratrol significantly lowered systemic BP in SHR. Conclusion: Resveratrol increases endothelial NO production to improve endothelial dysfunction and lowers BP in hypertensive rats, which depends on calcium-eNOS activation.

Vascular smooth muscle-specific deletion of the leptin receptor attenuates leptin-induced alterations in vascular relaxation.

Obesity is a risk factor for cardiovascular disease and is associated with increased plasma levels of the adipose-derived hormone leptin. Vascular smooth muscle cells (VSMC) express leptin receptors (LepR); however, their physiological role is unclear. We hypothesized that leptin, at levels to mimic morbid obesity, impairs vascular relaxation. To test this, we used control and VSM-LepR knockout mice (VSM-LepR KO) created with a tamoxifen-inducible specific Cre recombinase to delete the LepR gene in VSMC. Control (10-12 wk old) and VSM-LepR KO (10-12 wk old) mice were fed a diet containing tamoxifen (50 mg/kg) for 6 wk, after which vascular reactivity was studied in isolated carotid arteries using an organ chamber bath. Vessels were incubated with leptin (100 ng/ml) or vehicle (0.1 mM Tris·HCl) for 30 min. Leptin treatment resulted in significant impairment of vessel relaxation to the endothelial-specific agonist acetylcholine (ACh). When these experiments were repeated in the presence of the superoxide scavenger tempol, relaxation responses to ACh were restored. VSM-LepR deletion resulted in a significant attenuation of leptin-mediated impaired ACh-induced relaxation. These data show that leptin directly impairs vascular relaxation via a VSM-LepR-mediated mechanism, suggesting a potential pathogenic role for leptin to increase cardiovascular risk during obesity.

Nebivolol ameliorates asymmetric dimethylarginine-induced vascular response in rat aorta via β3 adrenoceptor-mediated mechanism

Background: Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, induces endothelial dysfunction. Nebivolol, a highly selective β1-adrenergic receptor (AR) blocker, is the only beta-blocker known to induce vascular production of nitric oxide. Objective: The present study was designed to evaluate the effect and mechanism of nebivolol on ADMA-induced vascular response in rat aorta in vitro. Methods: In vitro, the effects of nebivolol and ADMA on resting tone or contraction induced by phenylephrine (PE, 10−6 mol/L) and relaxation induced by acetylcholine (Ach, 10−10–10−5 mol/L) were evaluated. Results: ADMA in a concentration-dependent manner increased the resting and PE-induced tone and reduced Ach-induced relaxation. Nebivolol inhibited the ADMA-induced enhancements in tone and reversed the effects of ADMA on Ach-induced relaxation. These effects of nebivolol were blocked by selective β3 receptor blocker cyanopindolol (1 μM), but not by selective β2 receptor blocker butoxamine (50 μM). Conclusions: Nebivolol ameliorates the ADMA-induced vascular responses in rat aorta, at least in part, by mechanisms involving β3 adrenoceptor.

Methylmercury affects cerebrovascular reactivity to angiotensin II and acetylcholine via Rho-kinase and nitric oxide pathways in mice

AimsMethylmercury (MeHg) exposure results in increased risk of hypertension and cardiovascular diseases. In this study, we aimed to investigate whether the in vivo exposure of MeHg in mice affects blood pressure and basilar arterial responses to angiotensin II (Ang II) and acetylcholine (ACh), which are important modulators of cerebrovascular autoregulation. Main methodsMice were exposed to MeHg (40ppm) in drinking water for 21days. Blood pressure was measured in conscious mice by an indirect tail-cuff method. Functional studies of the isolated arteries' response to vasoactive substances were performed using a micro-organ-bath system. Key findingsSystolic and mean blood pressures were significantly increased after 2 and 3weeks of treatment with MeHg, respectively. Ang II-induced contraction in an isolated basilar artery, which is mediated via Rho-kinase activation, was increased in MeHg-treated mice. ACh-induced relaxation, which is dependent on NO production from the endothelial cells, was decreased in MeHg-treated mice. However, alterations of vascular responses to Ang II and ACh were not observed in the isolated thoracic aorta. SignificanceThis study demonstrated that the cerebral vasculature appears to be particularly sensitive to in vivo exposure of MeHg. Our results suggest that in vivo MeHg increases blood pressure and causes alterations in the cerebrovascular reactivity in response to Ang II and ACh through enhancement of Rho-kinase activity and inhibition of NO bioavailability, respectively.

Endothelial Dysfunction in Rheumatoid Arthritis: Mechanistic Insights and Correlation with Circulating Markers of Systemic Inflammation.

ObjectivesTo determine mechanisms involved in endothelial dysfunction (ED) during the course of arthritis and to investigate the link between cytokines, chemokines and osteoprotegerin.Approach and ResultsExperiments were conducted on aortic rings at day 4 (preclinical), day 11 (onset of disease), day 33 (acute disease) and day 90 (chronic disease) after adjuvant-induced arthritis (AIA) in Lewis rats. At day 4, the unique vascular abnormality was a reduced norepinephrine-induced constriction. At day 11, endothelial function assessed by the relaxation to acetylcholine was normal despite increased cyclo-oxygenase-2 activity (COX-2) and overproduction of superoxide anions that was compensated by increased nitric oxide synthase (NOS) activity. At day 33, ED apparition coincides with the normalization of NOS activity. At day 90, ED was only observed in rats with a persisting imbalance between endothelial NOS and COX-2 pathways and higher plasma levels of IL-1β and TNFα. Plasma levels of IL-1β, TNFα and MIP-1α negatively correlated with Ach-induced relaxation throughout the course of AIA.ConclusionsOur data identified increased endothelial NOS activity as an important compensatory response that opposes the ED in the early arthritis. Thereafter, a cross-talk between endothelial COX-2/NOS pathways appears as an important element for the occurrence of ED. Our results encourage determining the clinical value of IL-1β, TNFα and MIP-1α as biomarkers of ED in RA.

Tunicamycin-Induced Alterations in the Vasorelaxant Response in Organ-Cultured Superior Mesenteric Arteries of Rats.

In cellular events, endoplasmic reticulum (ER) stress has an important role in the development of various diseases including cardiovascular diseases. Tunicamycin, an inhibitor of N-linked glycosylation, is known to be an inducer of ER stress. However, the extent to which tunicamycin affects the vasorelaxant function is not completely understood. Thus, we investigated the effect of tunicamycin on relaxations induced by various vasorelaxant agents, including acetylcholine (ACh; endothelium-dependent vasodilator), sodium nitroprusside (SNP; endothelium-independent vasodilator), isoprenaline (ISO; beta-adrenoceptor agonist), forskolin (FSK; adenylyl cyclase activator), and cromakalim [ATP-sensitive K(+) (KATP) channel activator] in organ-cultured superior mesenteric arteries of rats, which are treated with either a vehicle [dimethyl sulfoxide (DMSO)] or tunicamycin (20 µg/mL for 22-24 h). Protein levels of the ER stress marker binding immunoglobulin protein (BiP) were determined by Western blotting. Tunicamycin increased the expression of BiP in organ-cultured arteries. Tunicamycin impaired ACh-induced relaxation, but did not alter SNP-induced relaxation. Tunicamycin also impaired vasorelaxation induced by ISO, FSK, and cromakalim; moreover, it reduced basal nitric oxide (NO) formation. In conclusion, short-term treatment with tunicamycin not only caused endothelial dysfunction but also impaired cAMP- and KATP-mediated responses in the superior mesenteric arteries of rats. These alterations in tunicamycin-treated arteries may be due to reduced basal NO formation. This work provides new insight into ER stress in vascular dysfunction.

The Restorative Effects of Eucommia ulmoides Oliver Leaf Extract on Vascular Function in Spontaneously Hypertensive Rats

Eucommia ulmoides Oliv. leaf is a traditional Chinese antihypertensive and antidiabetic medicine. We examined the effects of chronic Eucommia leaf extract (ELE) administration on artery function and morphology in spontaneously hypertensive rats (SHRs). ELE was orally administered via normal diet ad libitum to six-week-old male SHRs at a concentration of 5% for seven weeks. Acetylcholine (ACh)-induced endothelium-dependent relaxation, sodium nitroprusside (SNP)-induced endothelium-independent relaxation, plasma nitric oxide (NO) levels, and media thickness were assessed. ELE significantly improved ACh-induced aortic endothelium-dependent relaxation but did not affect SNP-induced endothelium-independent relaxation in the SHRs, as compared to the animals receiving normal diet. Plasma NO levels and media thickness were significantly increased and decreased, respectively, in the ELE-treated SHRs. Therefore, long-term ELE administration may effectively improve vascular function by increasing plasma NO levels and bioavailability, and by preventing vascular hypertrophy in the SHR aorta.

Endothelial dysfunction in rats with ligature-induced periodontitis: Participation of nitric oxide and cycloxygenase-2-derived products

ObjectivesConsidering the evident relationship between periodontitis and cardiovascular diseases in humans, we aimed to study the in vitro vascular reactivity of aorta rings prepared from rats with ligature-induced periodontitis. MethodsSeven days after the induction of unilateral periodontitis, the animals were euthanised; rings were prepared from the descending abdominal aortas and mounted in tissue baths for the in vitro measurement of the isometric force responses to norepinephrine (NE) and acetylcholine (ACh), as well as in the presence of inhibitors of nitric oxide synthase (NOS) and cycloxygenase (COX) isoenzymes. Aortic COX and NOS gene expressions were analysed by RT-PCR, as well as protein COX-2 expression by Western blot. ResultsPeriodontitis resulted in significant alveolar bone loss and did not affect arterial pressure. However, both NE-induced contraction and ACh-induced relaxation were significantly decreased and related to the presence of endothelium. Diminished eNOS and augmented COX-2 and iNOS expressions were found in the aortas from rats with periodontitis, and the pharmacological inhibition of COX-2 or iNOS improved the observed vasomotor deficiencies. ConclusionsWe can thus conclude that periodontitis induces significant endothelial dysfunction in rat aorta which is characterized by decreased eNOS expression and mediated by upregulated iNOS and COX-2 products.

Chronic administration of the probiotic kefir improves the endothelial function in spontaneously hypertensive rats.

BackgroundThe beverage obtained by fermentation of milk with kefir grains, a complex matrix containing acid bacteria and yeasts, has been shown to have beneficial effects in various diseases. However, its effects on hypertension and endothelial dysfunction are not yet clear. In this study, we evaluated the effects of kefir on endothelial cells and vascular responsiveness in spontaneously hypertensive rats (SHR).MethodsSHR were treated with kefir (0.3 mL/100 g body weight) for 7, 15, 30 and 60 days and compared with non-treated SHR and with normotensive Wistar-Kyoto rats. Vascular endothelial function was evaluated in aortic rings through the relaxation response to acetylcholine (ACh). The balance between reactive oxygen species (ROS) and nitric oxide (NO) synthase was evaluated through specific blockers in the ACh-induced responses and through flow cytometry in vascular tissue.ResultsSignificant effects of kefir were observed only after treatment for 60 days. The high blood pressure and tachycardia exhibited by the SHR were attenuated by approximately 15 % in the SHR-kefir group. The impaired ACh-induced relaxation of the aortic rings observed in the SHR (37 ± 4 %, compared to the Wistar rats: 74 ± 5 %), was significantly attenuated in the SHR group chronically treated with kefir (52 ± 4 %). The difference in the area under the curve between before and after the NADPH oxidase blockade or NO synthase blockade of aortic rings from SHR were of approximately +90 and −60 %, respectively, when compared with Wistar rats. In the aortic rings from the SHR-kefir group, these values were reduced to +50 and −40 %, respectively. Flow cytometric analysis of aortic endothelial cells revealed increased ROS production and decreased NO bioavailability in the SHR, which were significantly attenuated by the treatment with kefir. Scanning electronic microscopy showed vascular endothelial surface injury in SHR, which was partially protected following administration of kefir for 60 days. In addition, the recruitment of endothelial progenitor cells was decreased in the non-treated SHR and partially restored by kefir treatment.ConclusionsKefir treatment for 60 days was able to improve the endothelial function in SHR by partially restoring the ROS/NO imbalance and the endothelial architecture due to endothelial progenitor cells recruitment.