Relaxation Of Aortic Rings Research Articles

Saffron Induced Relaxation in Isolated Rat Aorta via Endothelium Dependent and Independent Mechanisms.

Crocus sativus L. (saffron) is a widely used food additive for its color and taste. The hypotensive effects of saffron have been shown in previous studies. The aim of this study was to evaluate the mechanism of vasodilatory effects induced by saffron on isolated rat aorta. To study the vasodilatory effects of saffron aqueous extract (0.5, 1 and 2 mg/mL), isolated rat thoracic aorta rings were contracted by 10-6 M phenylephrine (PE) or KCl 80 mM. The vasodilatory effect of saffron was also evaluated both on intact and denuded endothelium aortic rings. To study the role of nitric oxide and prostacyclin in relaxation induced by saffron, aortic rings were incubated by L-NAME (10-6 M) and indomethacin (10-5 M) respectively for 20 min. Saffron induced relaxation in endothelium-intact aortic rings precontracted with PE in a concentration dependent manner. The obtained relaxation induced by the highest saffron concentration in endothelium-intact aortic rings precontracted with KCl was less than that observed in endothelium-intact aortic rings precontracted with PE. The relaxant activity of saffron was abolished by incubation of aortic rings with L-NAME but not in the presence of indomethacin. Also, the vasodilatory activity of saffron was partially abolished in endothelium denuded aortic rings. Saffron induced relaxation in isolated rat aortic rings might be due particularly to its effect on endothelium via nitric oxide synthase pathway and partly due to the effect on vascular smooth muscle cells via L type voltage dependent calcium channels.

Vasorelaxant study of standardized extract of Pericarpium Citrus reticulatae

Event Abstract Back to Event Vasorelaxant study of standardized extract of Pericarpium Citrus reticulatae CHU SHAN TAN1 and MUN FEI YAM1* 1 School of Pharmaceutical Sciences, University of Science Malaysia, Malaysia Background Pericarpium Citrus reticulatae (Chen pi in Chinese) was widely used as an important ingredient in the prescription of Traditional Chinese Medicine (TCM) to treat hypertension and is one of the famous ingredients officially listed in Chinese Pharmacopoeia. Since Chen pi has been included in major TCM formulations to treat hypertension, it is a correlated and justifiable expectation that Chen pi possesses vasorelaxant properties. Methods This study is designed to investigate the vasorelaxant effect of Chen pi standardized extracts using Sprague Dawley rat isolated thoracic aortic ring assay. Results Among the different solvent extracts, water extract of Chen pi (CRW) exhibited the strongest vasorelaxant activity. CRW caused the relaxation of the phenylephrine pre-contracted aortic rings in the presence and absence of endothelium as well as in potassium chloride pre-contracted endothelium-intact aortic ring. The incubation of propranolol (β-adrenergic receptor blocker), atropine (muscarinic receptor blocker), Nω-nitro-L-arginine methyl ester (NO synthase inhibitor), ODQ (sGC inhibitor), indomethacin (COX inhibitor), 4-aminopyridine (KV blocker), barium chloride (Kir blocker), and glibenclamide (KATP blocker) significantly reduced the vasorelaxant effects of CRW. CRW was also found to be active in reducing calcium releases from the sarcoplasmic reticulum and suppressing the voltage-operated calcium channels. Conclusion The vasorelaxant effect of CRW on rat aorta involves NO/sGC, calcium and potassium channels, muscarinic and β-adrenergic receptors. Keywords: Pericarpium Citrus reticulatae, NO/sGC pathway, Potassium and calcium channels, Traditional Chinese Medicine, Vasorelaxation Conference: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”, Putrajaya, Malaysia, 3 Dec - 5 Feb, 2019. Presentation Type: Oral Presentation Topic: Metabolic diseases Citation: TAN C and YAM M (2019). Vasorelaxant study of standardized extract of Pericarpium Citrus reticulatae. Front. Pharmacol. Conference Abstract: International Conference on Drug Discovery and Translational Medicine 2018 (ICDDTM '18) “Seizing Opportunities and Addressing Challenges of Precision Medicine”. doi: 10.3389/conf.fphar.2018.63.00067 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 12 Oct 2018; Published Online: 17 Jan 2019. * Correspondence: Dr. MUN FEI YAM, School of Pharmaceutical Sciences, University of Science Malaysia, Penang, Malaysia, yammunfei@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers CHU SHAN TAN MUN FEI YAM Google CHU SHAN TAN MUN FEI YAM Google Scholar CHU SHAN TAN MUN FEI YAM PubMed CHU SHAN TAN MUN FEI YAM Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Direct actions of the flavonoids naringenin, quercetin and genistein on rat cardiac and vascular muscles

Context: Flavonoids are natural polyphenolic compounds that are ubiquitous in plants. Numerous prospective epidemiological studies have found beneficial effects of flavonoid consumption on overall cardiovascular mortality. These effects have been attributed to nonspecific antioxidant, anti-atherosclerotic and antithrombotic properties of flavonoids. However, little is known about direct actions of flavonoids on cardiac and vascular smooth muscles. Aims: To evaluate the effects of three flavonoids (naringenin, quercetin and genistein) on electrical and contractile activities of isolated rat hearts and on contraction of rat abdominal aortic rings. Methods: Surface electrogram (ECG) and force of contraction (FC) were recorded in isolated rat hearts. The ventricular fibrillation threshold was evaluated with the flavonoids. The effects on aortic contraction were assessed in rat abdominal aortic rings pre-contracted with 60 mM of KCl. Results: Genistein tended to prolong the QT interval while naringenin tended to decrease it. The effects of all flavonoids on QRS and RR interval were mild and not statistically significant. Genistein and naringenin produced a negative inotropic effect in isolated rat hearts with an IC50 of 13.8 μM and 33.8 μM, respectively. Quercetin at low concentrations had a positive inotropic effect; at high concentrations, it exerted a negative inotropic effect. Naringenin and quercetin increased the threshold for ventricular fibrillation, whereas genistein decreased it. Naringenin, quercetin, and genistein induced concentration-dependent relaxation in endothelium-denuded rat aortic rings. Conclusions: These flavonoids have direct actions on rat cardiac and vascular smooth muscles.

Vasorelaxant and Hypotensive Effects of Cheonwangbosimdan in SD and SHR Rats.

Historically, traditional herbal medicines (THMs) have been the conventional treatment strategy in the Korean medical system for treating many diseases. However, THMs have rarely been used to treat hypertension, and moreover few studies have investigated the interaction of blood pressure with the coadministration of synthetic antihypertensives. We aimed to evaluate the vasorelaxant and hypotensive effects of the traditional herbal prescription Cheonwangbosimdan (CWBSD; “Tianwangbuxindan” in Chinese) and the combination of CWBSD with amlodipine. CWBSD was extracted with distilled water at 100°C for 2 h. To investigate vasorelaxant activities, CWBSD with amlodipine (10 μg/ml) was added cumulatively (10–1,000 μg/ml) to isolated rat aortic rings precontracted using phenylephrine or potassium chloride in organ chambers. To investigate hypotensive effects, CWBSD (2,476 mg/kg) was orally administered with or without amlodipine (5 mg/kg) to spontaneously hypertensive rats (SHRs). CWBSD increased the relaxation of rat aortic rings induced by amlodipine (P < 0.01). In vivo, CWBSD coadministration with amlodipine also significantly decreased the blood pressure of SHRs compared to the amlodipine-treated group. These results suggested that CWBSD could be a useful herbal prescription to treat hypertension and we recommend establishing guidelines for the use of herbal medicines in conjunction with antihypertensive drugs, including amlodipine.

α-Isocubebene modulates vascular tone by inhibiting myosin light chain phosphorylation in murine thoracic aorta.

α-Iso-cubebene (ICB) is a dibenzocyclooctadiene lignin contained in Schisandra chinensis (SC), a well-known medicinal herb that ameliorates cardiovascular symptoms, but the mechanism responsible for this activity has not been determined. To determine the role played by ICB on the regulation of vascular tone, we investigated the inhibitory effects of ICB on vascular contractile responses by adrenergic α-receptor agonists. In addition, we investigated the role on myosin light chain (MLC) phosphorylation and cytosolic calcium concentration in vascular smooth muscle cells (VSMC). In aortic rings isolated from C57BL/6J mice, ICB significantly attenuated the contraction induced by phenylephrine (PE) and norepinephrine (NE), whereas ICB had no effects on KCl (60 mM)-induced contraction. In vasculatures precontracted with PE, ICB caused marked relaxation of aortic rings with or without endothelium, suggesting a direct effect on VSMC. In cultured rat VSMC, PE or NE increased MLC phosphorylation and increased cytosolic calcium levels. Both of these effects were significantly suppressed by ICB. In conclusion, our results showed that ICB regulated vascular tone by inhibiting MLC phosphorylation and calcium flux into VSMC, and suggest that ICB has anti-hypertensive properties and therapeutic potential for cardiovascular disorders related to vascular hypertension.

Vasodilator and hypotensive effects of the spider peptide Lycosin-I in vitro and in vivo

Lycosin-I, a spider peptide isolated from the venom of the spider Lycosa singoriensis, has anti-bacteria and anti-cancer properties in organisms. However, cardiovascular effects of Lycosin-I have not been studied. In this study, we investigated for the first time the vasodilator and hypotensive effects of Lycosin-I and the possible mechanisms, in order to develop a promising treatment for hypertension-related diseases. For in vitro experiments, thoracic aortas were isolated, and divided into two groups, endothelium-intact and endothelium-denuded aortic rings. Lycosin-I induced a remarkable dose-dependent relaxation in endothelium-intact aortic rings pre-treated with phenylephrine (p < 0.05), while it showed no obvious vasodilator effects in endothelium-denuded aortic rings (p > 0.05). The vasodilator effects of Lycosin-I were significantly weakened by a nitric oxide synthase (NOS) inhibitor, L-NAME (p < 0.001) and a selective inhibitor of nitric oxide (NO)-sensitive soluble guanylate cyclase (sGC), ODQ (p < 0.05), respectively. The levels of endothelial nitric oxide synthase (eNOS) phosphorylation and the NO production were significantly higher in human umbilical vascular endothelial cells pre-cultured with Lycosin-I than the control (p < 0.001), determined via western blot analysis and ozone-chemiluminescence technology. For in vivo experiments, arterial and venous catheters were inserted for mean arterial pressure (MAP) recording and drug administration in anaesthetized spontaneously hypertensive rats. Lycosin-I caused a transient drop of MAP 2 min after the administration compared with the control (p < 0.001). In conclusion, Lycosin-I has the potential to be an anti-hypertensive drug by endothelium-dependent vasodilatation, in which eNOS and NO-sensitive sGC are two main involved factors.

The vasorelaxant effect of Canarium odontophyllum Miq. (Dabai) extract in rat thoracic aorta

Background/aimCanarium odontophyllum (CO) (Miq.) (Burseraceae) has been traditionally consumed for its antioxidant benefit in maintaining longetivity. However, there is no report concerning its pharmacological activity on blood vessels. This study was aimed to investigate the effects of CO aqueous leaf extract on isolated aortic rings. MethodsIsolated thoracic aortic rings were suspended in a tissue bath and placed between 2 tungsten wires and connected to an isometric force transducer. The tension changes were recorded to a data acquisition system. ResultsThe leaf aqueous extract (3–15 mg/ml) induced relaxation in endothelium-intact and endothelium-denuded aortic rings precontracted with PE. Incubation with nitric oxide enzyme inhibitor L-NAME, however, did not alter the CO-induced vasorelaxant on endothelium-intact aortic ring. The vasorelaxant effect of CO was endothelium-independent as it reduced the contraction induced by extracellular Ca2+ in endothelium-denuded aortic ring precontracted by PE and KCl in Ca2+-free Krebs solution. However, CO did not inhibit the release of intracellular Ca2+ from sarcoplasmic reticulum. ConclusionThis study suggests that the vasorelaxant effect of aqueous extract from CO leaves was endothelium-independent and was possibly mediated through the blockade of voltage-dependent calcium channel and receptor-operated calcium channel.

Endothelium-derived contraction in a model of rheumatoid arthritis is mediated via angiotensin II type 1 receptors

A role for endothelium-derived constricting factors (EDCF), and the angiotensin II type 1 receptor (AT1R) pathway, in the vascular impairment found in the rat Freund's complete adjuvant (FCA)-model of rheumatoid arthritis (RA) was examined. FCA arthritis was induced in rats±losartan. Vehicle-treated rats served as controls. Knee-joint swelling and red blood cell (RBC) aggregation were measured as indicators of inflammation and endothelium reactivity assessed by response to acetylcholine (ACh) on aortic rings. Results show that knee-joint swelling and RBC aggregation were elevated in the FCA+vehicle group and restored to control levels in the FCA+losartan-treated animals. ACh-induced relaxation of aortic rings taken from FCA+vehicle animals was significantly impaired compared to vehicle-controls and this vasoreactivity was restored to control levels in the FCA+losartan-treated group. Further examination of aorta from the FCA+vehicle animals revealed an EDCF that was reliant on cyclooxygenase-2 (but not cyclooxygenase-1), generation of superoxide anion generation (but not hydrogen peroxide) and activation of thromboxane-prostanoid receptor. Losartan administration in vivo or ex vivo (to aortic rings) prevented the generation of the EDCF. In summary, this is the first evidence of an EDCF in a model of RA and identifies this mechanism as potentially significant in the cardiovascular disorder associated with the disease.

Hyperuricemia is Associated with Increased Apo AI Fractional Catabolic Rates and Dysfunctional HDL in New Zealand Rabbits.

The potential cause-effect relationship between uric acid plasma concentrations and HDL functionality remains elusive. Therefore, this study aimed to explore the effect of oxonic acid (OA)-induced hyperuricemia on the HDL size distribution, lipid content of HDL subclasses, and apo AI turnover, as well as HDL functionality in New Zealand white rabbits. Experimental animals received OA 750mg/kg/day by oral gavage during 21days. The HDL-apo AI fractional catabolic rate (FCR) was determined by exogenous labeling with 125I, and HDL subclasses were determined by sequential ultracentrifugation and PAGE. Paraoxonase-1 activity (PON-1) and the effect of HDL on relaxation of aorta rings in vitro were determined as an indication of HDL functionality. Oxonic acid induced a sixfold increase of uricemia (0.84±0.06 vs. 5.24±0.12mg/dL, P<0.001), and significant decreases of triglycerides and phospholipids of HDL subclasses, whereas HDL size distribution and HDL-cholesterol remained unchanged. In addition, HDL-apo AI FCR was significantly higher in hyperuricemic rabbits than in the control group (0.03697±0.0038 vs. 0.02605±0.0017h-1 respectively, P<0.05). Such structural and metabolic changes were associated with lower levels of PON-1 activities and deleterious effects of HDL particles on endothelium-mediated vasodilation. In conclusion, hyperuricemia is associated with structural and metabolic modifications of HDL that result in impaired functionality of these lipoproteins. Our data strongly suggest that uric acid per se exerts deleterious effects on HDL that contribute to increase the risk of atherosclerosis.

Curcumin inhibits cardiac hypertrophy and improves cardiovascular function via enhanced Na+/Ca2+ exchanger expression after transverse abdominal aortic constriction in rats.

This study tested the hypothesis that inhibition of cardiac hypertrophy and preservation of cardiac/endothelial function by the natural yellow pigment curcumin are associated with upregulated expression of Na+/Ca2+ exchanger (NCX) after transverse aortic constriction (TAC). Male Wistar rats were subjected to TAC for 10 weeks and curcumin (50 mg/kg/day) was fed by gastric gavage during TAC. Expression of NCX and endothelial nitric oxide synthase (eNOS) was analyzed by Western blot and immunohistochemistry. Compared with the animals in the TAC group, curcumin significantly increased the survival rate and reduced the ratio of heart or left ventricle (LV) to body weight and the cross sectional area of cardiomyocytes. In coincidence with improved LV systolic pressure and reduced LV end-diastolic pressure, curcumin significantly reduced LV end-systolic and diastolic diameter/dimension, and enhanced LV ejection fraction and LV fractional shortening as measured by echocardiography. Furthermore, endothelium-dependent relaxation of aortic rings in response to acetylcholine was significantly improved by curcumin. Along with these modifications, the expression and localization of NCX and eNOS in the myocardium and vascular endothelium were significantly upregulated by curcumin. The protective effect of curcumin on endothelium-dependent relaxation was partly blocked by pretreatment with the NCX inhibitor, KB-R7943. These results demonstrate that inhibition of cardiac hypertrophy, improvement of cardiac systolic/diastolic function and preservation of vascular endothelium by curcumin might be associated with upregulated NCX expression level in response to increased afterload.

Abstract 253: The Direct Renin Inhibitor Aliskiren Prevents Endothelial Dysfunction in Spontaneously Hypertensive Rat Aortas

Introduction: Hypertension is a significant medical problem. Aliskiren is a novel anti-hypertensive agent that inhibits renin directly. We tested the hypothesis that aliskiren prevents endothelial dysfunction in spontaneously hypertensive rats (SHRs). Methods: SHRs and age-matched Wistar Kyoto (WKY) rats were randomly divided and subjected to oral administration of aliskiren (10 mg/kg/day) or vehicle for 8 weeks. Blood pressure was monitored bi-weekly by a tail-cuff method. After an initial equilibration period, each ring was contracted by elevated KCl (60 mmol/L) to ensure a level of contractility suitable for subsequent experimentation. To examine endothelium-dependent relaxations in phenylephrine-contracted rings, two consecutive concentration-response curves to acetylcholine (ACh; 3 nmol/L -30 μmol/L) were constructed. In some phenylephrine-contracted rings without intact endothelium, sodium nitroprusside (SNP; 3 nmol/L – 10μmol/L) were applied cumulatively to the bathing solution to test the sensitivity of vascular smooth muscle cells (VSMCs) to NO. Results: Aliskiren reduced systolic blood pressure (SBP) to 155.6 ± 1.87 mmHg as compared to 165.3 ± 3.2 mmHg in vehicle-treated SHRs (n = 7), while chronic aliskiren administration did not affect SBP in WKY rats. SHR aortas with endothelium relaxed less in response to different concentrations of ACh than age-matched WKY rat aortas and ACh failed to cause relaxations of aortic rings without endothelium. By contrast, endothelium-independent relaxations caused by sodium nitroprusside (SNP) were comparable in aortas from SHR and WKY rats. Chronic aliskiren administration improved endothelium-dependent dilatations of aortas from SHRs compared to vehicle-treated SHRs, but this was unaffected in WKY rats. Endothelium-independent relaxations to SNP were not significantly different in aortas from the four treatment groups. Conclusions: Aliksiren reduces blood pressure and improves endothelium-dependent dilatations of SHRs. Figure 1. Effects of 8-week treatment of aliskiren on acetylcholine (ACh)-induced endothelium-dependent dilatations in SHR (A) and WKY (B) aortas. Results are mean ± SEM of 7 experiments. *p&lt;0.05.

Treatment with Captopril Enhances the Vascular Relaxation Induced by the Angiotensin II Type 2 Receptor (AT2R) Agonist CGP42112 in Diabetic Rats

The role of the AT2 receptor (AT2R) in physiological and pathophysiological processes is still controversial. Some studies suggest that expression of AT2R increases in certain diseases like diabetes mellitus. This could have beneficial effects as signaling through the AT2 receptor has been shown to counter the effects of angiotensin II mediated through the AT1 receptor, which are believed to contribute to pathological changes; this is supported by the favorable effects of ACE inhibitors and Angiotensin receptor blockers on the course of diabetes induced complications in renal function. We examined the effect of diabetes and of treatment with captopril on the vascular responses to CGP42112 (CGP), an AT2R selective agonist, in Sprague Dawley rats with streptozotocin (85 mg/kg i.v.) induced diabetes. Rats were followed for either 2, 4 or 12 weeks, at the end of which period thoracic aortas were isolated and used for measurement of relaxant responses to CGP42112 after pre‐contraction with phenylephrine. In a subset of the 4‐week study, osmotic pumps were implanted at week 2 to deliver either captopril (50 mg/kg/day) or losartan (5 mg/kg/day) s.c. for 2 weeks. All aortic ring studies were conducted in the presence of losartan (100 μM) to prevent interactions of CGP with the AT1R. CGP induced a mild (10%) relaxation in aortic rings at 2 weeks, 4 weeks and 12 weeks in the control animals. The response to CGP in aortic rings from diabetic rats was not different from controls. Treatment with losartan for 2 weeks did not alter the responses to CGP observed after 4 weeks. However, treatment with captopril for 2 weeks resulted in a markedly exaggerated relaxant response to CGP reaching up to 50% relaxation. These preliminary results suggest that while diabetes, per se, may not alter responses to CGP, treatment of diabetic rats (but not control rats) with captopril produces a marked increase in the sensitivity of the AT2R. Considering the known anti‐proliferative and anti‐ischemic effects of AT2R activation, these results potentially imply that the use of ACE inhibitors together with AT2R agonists could amplify the protective effect of ACE inhibitors against diabetes induced complications. Thus, the pathophysiological and therapeutic implications of this finding require further study.Support or Funding InformationSupported by funds from the Medical Practice Plan, AUB Faculty of Medicine

Vasorelaxant properties of Vernonia amygdalina ethanol extract and its possible mechanism

Context: Vernonia amygdalina Del. (VA) (Asteraceae) is commonly used to treat hypertension in Malaysia.Objective: This study investigates the vasorelaxant mechanism of VA ethanol extract (VAE) and analyzes its tri-step FTIR spectroscopy fingerprint.Materials and methods: Dried VA leaves were extracted with ethanol through maceration and concentrated using rotary evaporator before freeze-dried. The vasorelaxant activity and the underlying mechanisms of VAE using the cumulative concentration (0.01–2.55 mg/mL at 20-min intervals) were evaluated on aortic rings isolated from Sprague Dawley rats in the presence of antagonists.Results: The tri-step FTIR spectroscopy showed that VAE contains alkaloids, flavonoids, and saponins. VAE caused the relaxation of pre-contracted aortic rings in the presence and absence of endothelium with EC50 of 0.057 ± 0.006 and 0.430 ± 0.196 mg/mL, respectively. In the presence of Nω-nitro-l-arginine methyl ester (EC50 0.971 ± 0.459 mg/mL), methylene blue (EC50 1.203 ± 0.426 mg/mL), indomethacin (EC50 2.128 ± 1.218 mg/mL), atropine (EC50 0.470 ± 0.325 mg/mL), and propranolol (EC50 0.314 ± 0.032 mg/mL), relaxation stimulated by VAE was significantly reduced. VAE acted on potassium channels, with its vasorelaxation effects significantly reduced by tetraethylammonium, 4-aminopyridine, barium chloride, and glibenclamide (EC50 0.548 ± 0.184, 0.158 ± 0.012, 0.847 ± 0.342, and 0.304 ± 0.075 mg/mL, respectively). VAE was also found to be active in reducing Ca2+ released from the sarcoplasmic reticulum and blocking calcium channels.Conclusions: The vasorelaxation effect of VAE involves upregulation of NO/cGMP and PGI2 signalling pathways, and modulation of calcium/potassium channels, and muscarinic and β2-adrenergic receptor levels.

The Relaxant Activity of Safranal in Isolated Rat Aortas is Mediated Predominantly via an Endothelium-Independent Mechanism: -Vasodilatory mechanism of safranal.

Objectives:Safranal is a pharmacologically active component of saffron and is responsible for the unique aroma of saffron. The hypotensive effect of safranal has been shown in previous studies. This study evaluates the mechanism for the vasodilatory effects induced by safranal on isolated rat aortas.Methods:To study the vasodilatory effects of safranal (0.2, 0.4 and 0.8 mM), we contracted isolated rat thoracic aorta rings by using 10-6-M phenylephrine (PE) or 80-mM KCl. Dimethyl sulfoxide (DMSO) was used as a control. The vasodilatory effect of safranal was also evaluated both on intact and denuded endothelium aortic rings. Furthermore, to study the role of nitric oxide and prostacyclin in the relaxation induced by safranal, we incubated the aortic rings by using L-NAME (10-6 M) or indomethacin (10-5 M), each for 20 minutes.Results:Safranal induced relaxation in endothelium-intact aortic rings precontracted by using PE or KCl in a concentration-dependent manner, with a maximum relaxation of more than 100%. The relaxant activity of safranal was not eliminated by incubating the aortic rings with L-NAME (EC50 = 0.29 vs. EC50 = 0.43) or with indomethacin (EC50 = 0.29 vs. EC50 = 0.35), where EC50 is the half maximal effective concentration. Also, the vasodilatory activity of safranal was not modified by endothelial removal.Conclusion:This study indicated that relaxant activity of safranal is mediated predominantly through an endothelium- independent mechanism.

Intermittent parathyroid hormone administration attenuates endothelial dysfunction in old rats.

We have demonstrated that intermittent parathyroid hormone administration can rescue age-related vascular dysfunction by improving endothelial-dependent dilation in the aorta of older rodents. This demonstrates a novel potential benefit of parathyroid hormone administration in aging.

Deletion of AMPKα1 attenuates the anticontractile effect of perivascular adipose tissue (PVAT) and reduces adiponectin release.

Perivascular adipose tissue (PVAT) surrounds most blood vessels and secretes numerous active substances, including adiponectin, which produce a net anticontractile effect in healthy individuals. AMPK is a key mediator of cellular energy balance and may mediate the vascular effects of adiponectin. In this study, we investigated the role of AMPK within PVAT in mediating the anticontractile effect of PVAT. Endothelium-denuded aortic rings from wild-type (WT; Sv129) and α1 AMPK knockout (KO) mice were mounted on a wire myograph. Dose-response curves to the AMPK-independent vasodilator cromakalim were studied in vessels with and without PVAT, and effect of pre-incubation with conditioned media and adiponectin on relaxation was also studied. The effect of AMPKα1 KO on the secretory profile of PVAT was assessed by elisa. Thoracic aortic PVAT from KO mice was morphologically indistinct from that of WT and primarily composed of brown adipose tissue. PVAT augmented relaxation to cromakalim in WT but not KO aortic rings. Addition of WT PVAT augmented relaxation in KO aortic rings but KO PVAT had no effect in WT rings. PVAT from KO mice secreted significantly less adiponectin and addition of adiponectin to either KO or WT aortic rings without PVAT augmented relaxation to cromakalim. An adiponectin blocking peptide significantly attenuated relaxation in WT rings with PVAT but not in KO rings. AMPKα1 has a critical role in maintaining the anticontractile actions of PVAT; an effect independent of the endothelium but likely mediated through altered adiponectin secretion or sensitivity. This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Crocin-Induced Endothelium-Dependent Relaxation in Isolated Rat Aorta

Background: Crocin, an active ingredient of saffron, has been found to possess hypotensive effects. Objectives: The aim of this study was to evaluate the mechanism of vasodilatory effects induced by crocin on isolated rat aorta. Methods: To study the vasodilatory effects of crocin (0.1, 0.2, 0.4 and 0.8 M), isolated rat thoracic aorta rings were contracted by 10-6 M Phenylephrine (PE) or 80 mM of KCl. To assess the role of nitric oxide in mechanism of relaxation, induced by crocin, aortic rings were incubated by L-NG-Nitroarginine methyl ester (L-NAME: 10-6 M) for 20 minutes. Furthermore, the relaxant effect of crocin was evaluated both in intact and denuded endothelium aortic rings. Results: Crocin induced relaxation in endothelium-intact aortic rings precontracted with PE in a concentration dependent manner yet not in KCl precontracted aortic rings. The relaxant activity of crocin was abolished by incubation of aortic rings with L-NAME. In addition, the endothelium removal inhibited the relaxant activity of crocin. Conclusions: This study indicated that relaxant activity of crocin is mainly mediated through an endothelium-dependent mechanism.

Attenuation of blood pressure in spontaneously hypertensive rats by acupuncture was associated with reduction oxidative stress and improvement from endothelial dysfunction.

BackgroundHypertension can be treated effectively by acupuncture; however, the association between acupuncture and endothelial function remains unknown. This study aimed to investigate the effects of acupuncture on endothelial dysfunction and oxidative stress-related parameters in spontaneously hypertensive animals.MethodsEighteen-week-old Wistar–Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) were arbitrarily divided into four groups: WKY control (n = 8), SHR control (n = 8), SHR sham-acupuncture (n = 8) and SHR acupuncture (n = 8). The SHR acupuncture group had electroacupuncture for 6 consecutive weeks on acupoints ST36 and LR3. Blood pressure was monitored during the treatment period, and animals were euthanized at the 6th week. Aortas were harvested for determination of angiotensin II levels, NADPH oxidase activity and nitrate/nitrite levels. The level of reactive oxygen species (ROS) was determined by dihydroethidium (DHE) imaging, and functional studies were performed to assess vascular reactivity. Endothelial nitric oxide synthase was measured by Western blot assay.ResultsBlood pressure at the end of treatment was significantly lower in the SHR acupuncture group (185.0 ± 5.6 mmHg) compared with the SHR sham-acupuncture and the SHR control groups (201.0 ± 5.4 and 197.4 ± 5.9 mmHg, respectively; P < 0.001). Serum angiotensin II level in the SHR control group was significantly higher than in the WKY control group (P < 0.001), while it was significantly attenuated by acupuncture treatment (P = 0.023). DHE staining showed that ROS level was reduced in the aortas (P = 0.0017) and carotid arteries (P = 0.039) of acupuncture-treated SHRs. Biochemical assays showed that acupuncture inhibited the NADPH oxidase activity (P = 0.022) and enhanced antioxidant capacity (P = 0.0039). In functional studies, endothelium-dependent relaxation of aortic rings (P = 0.018) and carotid arteries (P = 0.022) in response to acetylcholine was improved in the SHR acupuncture group. Aortas of SHRs receiving acupuncture also expressed an elevated level of eNOS (P > 0.001) and p-eNOS (P = 0.012) and a reduced nitrotyrosine level (P = 0.0012). The nitrate/nitrite level in aortic tissue was also attenuated after acupuncture (P = 0.0018).ConclusionThe effects of acupuncture in treating hypertension were associated with reduced oxidative stress, increased nitric oxide bioavailability and endothelial function in SHRs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13020-016-0110-0) contains supplementary material, which is available to authorized users.

Emergence of acetylcholine resistance and loss of rhythmic activity associated with the development of hypertension, obesity, and type 2 diabetes

The aim of this work was to study the influence of aging, obesity, metabolic syndrome (MS), hypertension (HT), and type 2 diabetes (T2D) on the endogenous rhythmic activity and the development acetylcholine resistance in aorta rings of male rats. T2D was produced by a free access to fat (lard). It was shown that phenylephrine (PE) or 5-hydroxytryptamine (5-HT) induces two types of rhythmic contractions: with periods T1 = 3–10 s and T2 = 50–70 s and amplitudes A1 = 1–5% and A2 = 20–40% of the maximal contraction force (Fmax), respectively. Such periodic modes can be caused by the operation of two known positive feedback loops (PFL) based on the Ca2+-induced activation of IP3 receptor (IP3R) or phospholipase C PFL1 and PFL2, respectively, and are not eliminated by L-NAME. Slow rhythmic activity induced by acetylcholine (Ach) with period T3 = 7–20 min and amplitude A3 = 20–30% of Fmax was observed only in young animals (under 6 months) and can be determined by the operation of PFL3, involving Ca2+, NO, kinase G, cADP-ribose, and the ryanodine receptor (RyR). Fast mode of contractions (T1, A1) is maintained regardless of age and the presence of MS and HT (140 mm Hg and higher) and disappears only at later stages of the T2D development. Probability of intermediate mode of contractions (T2, A2) decreases to 0.20–0.25 at the age of 14–16 months or during the development of HT and MS. In these circumstances, Ach could cause relaxation of preconstricted rings only to 40 and 60% of Fmax, respectively. At the stages of the T2D development characterized by high values of arterial pressure (above 150 mm Hg) and of the glucose (10–12 mM), ammonium (120–180 μM), and blood lipid levels, as well as by liver dysfunction (fibrosis/cirrhosis), the rhythmic activity of any type is lost and dysfunction of the initial part of the signaling cascade with the participation of PFL3 is manifested by the absence of responses to Ach or L-NAME. Coenzyme NAD (agonist of the P2Y receptors, К+ channel activator and a precursor of cADP-ribose) can exert a partial relaxation of aorta rings from healthy animals and animals with MS. Nicotinamide (product and an inhibitor of ADP-ribosyl cyclase) and SNP (donor of NO) produce an effective relaxation of aorta rings from healthy animals and animals with T2D. Relaxing effect of nicotinamide may suggest a tandem operation of IP3R and RyR in the control of intracellular Ca2+ stores in vascular cells.

The Effects of Glycerl Trinitrate and Adenosine 5-Triphosphate on Activation of Potassium Channel-Mediated Vasorelaxation in Female rats aortic Smooth Muscle.

Nitric oxide (NO) is produced from virtually all cell types composing the cardiovascular tissue and regulates vascular function through fine regulation of excitation–contraction coupling. Endogenous metabolites play a major role in coronary autoregulation. Therefore, the aim of the present study is to investigate the contribution of Glyceryl trinitrate (GTN) and Adenosine 5-triphosphate (ATP) mediated relaxation in rat aortic smooth muscle in intact and endothelium denuded endothelium rings precontracted with Phenylephrine (PE). The thoracic aorta was isolated, cut into rings, and mounted in organ-bath chambers and isometric tension was recorded using PowerLab Data Acquisition System (Model ML 870). The results showed that GTN as NO donor produced dose-dependent relaxation in intact aortic rings precontracted with PE (1 µM) that disinhibited in the presence of Glibenclamide (GLIB), while GLIB attenuate the response induced by ATP in intact aortic rings. L-nitroarginine methylester (L-NAME) an antagonist for nitric oxide synthases (NOS), not abolish the response induced by GTN (Emax 55.28% ± 0.18). Caffeine, ATP receptors antagonist, were partially inhibit the relaxation induced by ATP (vasodilation rate decreased by about 20.57 %). In endothelium denuded aortic rings, vasorelaxation induced by ATP were significantly attenuated , while GTN significantly increased relaxation by removing endothelium. These results suggested that (1) ATP-dependent potassium channel did not involve in GTN inducing vasorelaxation while KATP and A2Breceptors have a role in ATP mediated vasorelation (2) ATP partially dependent on endothelium in contrast to NO donors that independent to endothelium.