Endothelium-intact Aortic Rings Research Articles

Root essential oil of Chrysopogon zizanioides relaxes rat isolated thoracic aorta - an ex vivo approach.

Root of Chrysopogon zizanioides (L.) Roberty has been used in Siddha system of medicine to treat hypertension. The present study was therefore to investigate the vasorelaxation effect of root essential oil of C. zizanioides using rat isolated thoracic aortic rings. Chemical characterization of root essential oil was carried out using Gas Chromatography-Flame Ionization Detector (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS). Essential oil nanoemulsion (EONE) was prepared and characterized. Vasorelaxant effect of EONE in endothelium-intact aortic rings precontracted with phenylephrine (PE) (1µM) or KCl (80mM) was investigated. Role of Ca2+, nitric oxide and K+ channels in precontracted aortic rings were investigated to elucidate the mechanism of action of the essential oil. Further, the role of muscarinic and prostacyclin receptors in EONE induced relaxation was studied. The EONE significantly induced relaxation (Emax 77.1±4.87%) in PE precontracted aortic rings. The nitric oxide synthase, and cyclooxygenase inhibitors and potassium channel blockers have not significantly inhibited the vasorelaxation induced by EONE. However, EONE induced relaxation in precontracted endothelium-intact aortic rings was significantly inhibited by muscarinic receptor and calcium channel. The root essential oil of C. zizanioides possesses vasorelaxant effect through muscarinic pathway as well as acts as calcium channel blocker.

Anti-hypertensive vasodilatory action of Gynura procumbens mediated by kaempferol 3-O-rutinoside

Introduction: Gynura procumbens (GP), otherwise known as longevity spinach or “Sambung Nyawa” in Malay, is an evergreen herb found in Africa and Southeast Asian countries (including Brunei) used traditionally to treat various diseases such as fever, diabetes and hypertension. We examined GP’s vasodilatory action to determine its possible role via the cholinergic-mediated pathway. Methods: GP leaves were prepared by filtration and evaporation to obtain the aqueous (AEGP) and methanol (MEGP) extracts followed by screening for phytochemical constituents. The total phenol, total flavonoid and flavonol contents were determined using the corresponding Folin–Ciocalteau, and aluminium colorimetric methods and the presence of kaempferol 3-O-rutinoside in the extracts was detected using HPLC analysis. Organ bath studies were conducted to determine the vasodilatory activity using intact and denuded isolated rat aortic rings by exposure to either increasing concentration of extracts (0.25, 0.5, 1.0, and 2.0 mg/mL) or 10 µg/mL kaempferol 3-O-rutinoside in the presence or absence of acetylcholine (ACh) after pre-contraction by noradrenaline (NA). Results: MEGP contained more phytochemical constituents and higher content of total flavonoid and total flavonol but less phenolic content than AEGP. Furthermore, MEGP yielded a 20% elevated amount of kaempferol 3-O-rutinoside than AEGP. Both extracts significantly amplified ACh-endothelium dependent vasodilation and mediated relaxation at 1 mg/mL in endothelium-intact and endothelium-denuded aortic rings with MEGP as a more effective vasodilator than AEGP. Overall, these results imply the involvement of extracts in potentiating cholinergic pathway, which might be mediated by kaempferol, as shown by its vasorelaxation effects in endothelium-intact and –denuded aorta. Conclusions: The present findings demonstrate that the vasodilatory activities of the two Gynura procumbens extracts, AEGP and MEGP, in thoracic aorta rings isolated from rats are potentially mediated via a cholinergic pathway through the action of a flavonoid particularly kaempferol 3-O-rutinoside.

The Involvement of ATP-Sensitive Potassium Channels in the Nebivolol-Induced Relaxation of Endothelium-Intact Aorta Isolated from Rats

Objective: Nebivolol is a highly selective beta-1 adrenergic receptor blocker with additional vasorelaxant properties. The vasorelaxant effect of nebivolol has been mainly attributed to endothelium-dependent mechanisms including beta-adrenergic receptors. However, the involvement of ATP-sensitive potassium (KATP) channels, another potential mechanism for vasorelaxant effect, in the vasorelaxant response to nebivolol remains unclear. Therefore, this study was aimed to investigate the role of KATP channels in the nebivolol-induced vasorelaxation in the isolated rat aorta Methods: The rat thoracic aortic rings isolated from Sprague-Dawley rats were mounted in organ bath chambers containing Krebs-Henseleit solution at 37 oC continuously bubbled with 95% O2 and 5% CO2. After an equilibration period, the presence of endothelium was confirmed by the response (more than 50%) to acetylcholine (10 μM) in aortic rings precontracted with phenylephrine (1 μM). After washout, in control group, the endothelium-intact aortic rings were contracted by potassium chloride (30 mM) before the cumulative addition of nebivolol (0.0001-100 μM). In some experiments, the relaxant response to nebivolol (0.0001-100 μM) was also obtained in the presence of glibenclamide (KATP channel blocker, 10 μM) or Nω-Nitro-L-arginine methyl ester (L-NAME: eNOS inhibitor, 100 μM) in the endothelium-intact aortic rings precontracted with potassium chloride (30 mM). Data were presented as means±SEM. Multiple comparisons of groups were performed by using ANOVA followed by post-hoc Bonferroni test. Results: Nebivolol elicited a concentration dependent vasorelaxant effect in the endothelium-intact aortic rings. Relaxant response to nebivolol was significantly inhibited by the presence of glibenclamide or L-NAME (p< 0.05). Although Emax values were not found significantly different among groups, pD2 values of nebivolol were reduced in the endothelium-intact aortic rings incubated with glibenclamide or L-NAME. Conclusion: These results demonstrate for the first time the involvement of KATP channels in the nebivolol-induced vasorelaxation in the endothelium-intact aorta precontracted with potassium chloride.

The hypertensive effect of sorafenib is abolished by sildenafil

BackgroundContrasting to the well documented tyrosine kinase inhibitor (TKI)-induced hypertension, little is known on their intrinsic vasomotor effects. We investigated the vasomotor effects of sorafenib, a widely used multikinase inhibitor in the treatment of hepatocellular and renal cell carcinoma and tested the hypothesis that sildenafil, a phosphodiesterase-5 (PDE-5) inhibitor, could represent a pharmacological strategy for the treatment of TKI-induced hypertension.MethodsConcentration-response curves of sorafenib were constructed in endothelium-intact or denuded precontracted rat aorta, in the presence or absence of several inhibitors. Acute intravenous effects of sorafenib on arterial blood pressure were also investigated in anaesthetized rats. Finally, rats were chronically treated with sorafenib during 4 weeks in the presence and absence of sildenafil.ResultsIn endothelium intact aortic ring, sorafenib induced a potent concentration-dependent relaxation of precontracted rat aorta. Removal of the endothelium shifted the concentration-response curve of sorafenib to the right and significantly reduced its maximal effects, demonstrating that sorafenib-induced vasorelaxation is endothelium-dependent and endothelium-independent. Inhibition of the different pathways implicated in the endothelium-dependent and independent vasorelaxation revealed that the endothelium-dependent effects of sorafenib result mainly from the activation of prostaglandin and the nitric oxide (NO) pathways. The endothelium-independent vasodilatory effects of sorafenib may result mainly from the activation of Na/K-ATPase and soluble guanylate cyclase. These vasodilatory effects observed in vitro were confirmed by the decrease in arterial blood pressure observed during acute administrations of sorafenib in anesthetized rats. Finally, and most importantly, we report here for the first time that chronic administration of sorafenib in rats induced an increase in SBP that was abolished by sildenafil.ConclusionThe multikinase inhibitor sorafenib induced in vitro vasorelaxation of large conductance artery, primary by activating soluble guanylate cyclase. Its chronic administration led to arterial blood hypertension that was counteracted by a PDE-5 inhibitor, sildenafil. Our results suggest that targeting the cGMP pathway including NO signalling might be an interesting pharmacological strategy for the treatment of TKI-induced hypertension.

Comparative study of acute in vitro and short-term in vivo triiodothyronine treatments on the contractile activity of isolated rat thoracic aortas.

We aimed to characterize the participation of rapid non-genomic and delayed non-genomic/genomic or genomic mechanisms in vasoactive effects to triiodothyronine (T3), emphasizing functional analysis of the involvement of these mechanisms in the genesis of nitric oxide (NO) of endothelial or muscular origin. Influences of in vitro and in vivo T3 treatments on contractile and relaxant responsiveness of isolated rat aortas were studied. In vivo T3-treatment was 500 μg•kg–1•d–1, subcutaneous injection, for 1 (T31d) and 3 (T33d) days. In experiments with endothelium-intact aortic rings contracted with phenylephrine, increasing concentrations of T3 did not alter contractility. Likewise, in vitro T3 did not modify relaxant responses induced by acetylcholine or sodium nitroprusside (SNP) nor contractile responses elicited by phenylephrine or angiotensin II in endothelium-intact aortas. Concentration-response curves (CRCs) to acetylcholine and SNP in endothelium-intact aortic rings from T31d and T33d rats were unmodified. T33d, but not T31d, treatment diminished CRCs to phenylephrine in endothelium-intact aortic rings. CRCs to phenylephrine remained significantly depressed in both endothelium-denuded and endothelium-intact, nitric oxide synthase inhibitor-treated, aortas of T33d rats. In endothelium-denuded aortas of T33d rats, CRCs to angiotensin II, and high K+ contractures, were decreased. Thus, in vitro T3 neither modified phenylephrine-induced active tonus nor CRCs to relaxant and contractile agonists in endothelium-intact aortas, discarding rapid non-genomic actions of this hormone in smooth muscle and endothelial cells. Otherwise, T33d-treatment inhibited aortic smooth muscle capacity to contract, but not to relax, in an endothelium- and NO-independent manner. This effect may be mediated by delayed non-genomic/genomic or genomic mechanisms.

Underlying mechanism of vasorelaxant effect exerted by 3,5,7,2′,4′-pentahydroxyflavone in rats aortic ring

Morin (3,5,7,2′,4′-pentahydroxyflavone) is a yellow coloured natural flavonoid found in plants of the Moraceae family. This favonoid is easily sources from readily available fruits, vegetables and eve certain beverages. Among the sources that was identified, it is clear that morin is most abundantly found in almond, old fustic, Indian guava, and Osage orange. Multiple studies have suggested that morin has multiple therapeutic actions and possess potential to be a functional potent drug. Previous studies demonstrated that morin is capable of resolving deoxycorticosterone acetate-salt-induced hypertension and possess strong vasorelaxant properties. However, the exact mechanisms remains unknown. Therefore, this study is designed to investigate the in vitro mechanism of morin-induced vasorelaxant effects. The underlying mechanisms of morin's vasorelaxant activities were evaluated on thoracic aortic rings isolated from Sprague-Dawley rats. Results from the study demonstrated morin causing vasodilatory reaction in phenylephrine and potassium chloride pre-contracted endothelium-intact aortic rings with the effect being significantly affected in endothelium-denuded aortic rings. Pre-incubation of the aortic rings with ODQ (selective cGMP-independent sGC inhibitor), indomethacin (nonselective COX inhibitor), L-NAME (endothelial nitric oxide inhibitor), propranolol (β2-adrenegic receptors blocker), and atropine (muscarinic receptors blocker) significantly reduced the vasorelaxant effect of morin. It was also found to be able to reduce the intracellular calcium level by blocking VOCC and calcium intake from the extracellular environment and the intracellular release of calcium from the sarcoplasmic reticulum. The present study showed that the vasorelaxant effect of morin potentially involves the NO/sGC, muscarinic receptors, β2-adrenegic receptors, and calcium channels.

Vaso‐relaxant Effect of Zingiber officinale Extract Involves Release of Nitric Oxide from the Endothelium

IntroductionZingiber officinale (ZO) is an important plant with several medicinal, nutritional and ethnomedical values. The blood pressure lowering effect of ZO has been reported in experimental animals and human and some mechanisms have been postulated, including; blockage of voltage dependent calcium channel, stimulation of muscarinic receptors and serotonergic antagonistic property. The aim of this study is to investigate the vaso‐relaxant effect of the extract of ZO and the mechanism by which it is produced.MethodRhizomes of ZO were extracted in 80% methanol. Thoracic aorta isolated from male rabbits were cut into rings of 3–5 mm, mounted in organ baths containing 25 ml Krebs physiological solution maintained at 37 °C and bubbled continuously with a mixture of 95% O2 and 5% CO2. The aortic rings were equilibrated for 30 min at a resting tension of 1 g. Responses were recorded isometrically via a force displacement transducer connected to a recording system. The presence of functional endothelium was checked by the ability of acetylcholine (1μM) to induce relaxation on phenylepherine (PE, 1μM) contracted rings. The relaxant responses to ZO was recorded by adding cumulative concentrations (10, 20, 40, 80, 100, 500, 1000 μg/ml) of ZO. To investigate the involvement of endothelium in the vaso‐relaxant action, endothelium was removed by gently rubbing the luminal surface of the ring with a polyethylene tube. To investigate which endothelium‐derived vasorelaxant factors were involved, the rings were pre‐incubated with Nitro‐L‐arginine methyl ester (L‐NAME, 10 μM) or indomethacin (10 μM) for 30 min before addition of the spasmogen and ZO. Relaxant responses were expressed as percentage relaxation from PE‐precontraction levels. The EC50 (the concentration required to cause half‐maximal relaxation) was calculated from the concentration‐response curve. Results were expressed as means ± s.e.m. Student t‐test was used to assess the significant differences at (p < 0.05)ResultsZO produced a vaso‐relaxation effect on rings pre‐contracted with PE (1μM) at concentrations of 20–100 μg/ml in endothelium intact rings with an EC50 of 14.8±1.2 μg/ml (Figure 1). This relaxation was not however seen at 500–1000 μg/ml but rather a vaso‐contraction was observed. In endothelium denuded rings, the vaso‐relaxation effect of ZO at 20–100 μg/ml was abolished while vaso‐relaxation was observed with 500–1000 μg/ml, the concentrations that otherwise produced contraction in endothelium intact aortic rings. Pre‐incubation of the tissues with L‐NAME (10μM) abolished the relaxant effect of ZO at 20–100μg/ml but caused relaxation effect with 500–1000 μg/ml similar to that observed with endothelium denuded rings. Pretreatment with indomethacin abolished the relaxant effect of ZO at 20μg/ml but not at 40 μg/ml and above (Figure 2).ConclusionVaso‐relaxant effect of ZO is seen at lower concentrations, endothelium dependent and may involve the release of nitric oxide from the endothelium. There may be interplay between contractile and relaxant compounds in crude extract of ZO at concentrations above 500 μg/ml.Support or Funding InformationThe PhD study grant awarded to I.M Adebisi by Usmanu Danfodiyo University, Sokoto, Nigeria is acknowledgedRelaxation effect of methanol extract of Zingiber officinale (ZO) on phenylephrine‐precontracted aortic rings with intact endothelium. Data represent the mean ± s.e.m. of four individual experiments. * is p<0.05Figure 1Relaxation effect of methanol extract of Zingiber officinale (ZO) on phenylephrine‐precontracted aortic rings with endothelium, without endothelium and effect of L‐NAME (10 μM), and Indomethacin (10 μM) on ZO induced vasorelaxation on phenylephrine‐precontracted aortic rings with endothelium. Data represent the mean ± s.e.m. of four individual experiments. * is p<0.05Figure 2

Microwave Assisted Synthesis of 4-Phenylquinazolin-2(1H)-one Derivatives that Inhibit Vasopressor Tonus in Rat Thoracic Aorta.

Quinazolinones have pharmacological effects on vascular reactivity through different mechanisms. We synthesized 4-phenylquinazolin-2(1H)-one derivatives under microwave irradiation and tested them on the rat thoracic aorta. The prepared compounds 2a–2f were obtained in about 1 h with suitable yields (31–92%). All derivatives produced vasorelaxant effects with IC50 values ranging from 3.41 ± 0.65 µM to 39.72 ± 6.77 µM. Compounds 2c, 2e and 2f demonstrated the highest potency in endothelium-intact aorta rings (IC50 4.31 ± 0.90 µM, 4.94 ± 1.21 µM and 3.41 ± 0.65 µM respectively), and they achieved around 90% relaxation (30 μM). In aorta rings without an endothelium, the effect of compound 2f was abolished. Using the MTT assay to test for cell viability, only compound 2b induced cytotoxicity at the maximum concentration employed (30 µM). The results show that vasorelaxation by 4-phenylquinazolin-2(1H)-one derivatives might depend on the activation of a signalling pathway triggered by endothelium-derived factors.

Vasorelaxant effect of 3,5,4′-trihydroxy-trans-stilbene (resveratrol) and its underlying mechanism

Resveratrol is found in numerous plant-based foods and beverages and is known to have an impact on the cardiovascular system. The aim of this study was to investigate the vasorelaxant effect of resveratrol and its underlying mechanisms by employing an aortic ring assay model. Resveratrol caused relaxation of aortic rings that had been precontracted with phenylephrine in the presence of endothelium or with potassium chloride in endothelium-intact aortic rings. The vasorelaxant effect was decreased in the absence of an endothelium. The mechanisms underlying the vasorelaxant effect of resveratrol were determined through the addition of antagonists. In the presence of the endothelium, indomethacin (a nonselective cyclooxygenase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, selective soluble guanylate cyclase inhibitor), Nω-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), tetraethylammonium (TEA, nonselective calcium activator potassium channel blocker), 4-aminopyridine (4-AP, voltage-dependent K+ channel blocker), barium chloride (BaCl2, inwardly rectifying K+ channel blocker), glibenclamide (non-specific ATP-sensitive K+ channel blocker) and propranolol (β-adrenergic receptor blocker) led to a significant reduction in the vasorelaxation effect induced by resveratrol. Resveratrol was also found to reduce Ca2+ release from the sarcoplasmic reticulum and block calcium channels. In conclusion, resveratrol targets multiple signalling pathways for exerting its vasorelaxant effects in the rat aortic ring model in both the presence and absence of endothelium.

Blood pressure lowering effect and vascular activity of Phyllanthus niruri extract: The role of NO/cGMP signaling pathway and β-adrenoceptor mediated relaxation of isolated aortic rings.

Phyllanthus niruri have a long history of use in the traditional treatment of various ailments including hypertension. Literature reports have indicated that it is a potent antihypertensive herbal medication used traditionally. This study was carried out to investigate the antihypertensive and vasodilatory activity of four solvents extracts of P. niruri namely; petroleum ether (PEPN), chloroform (CLPN), methanol (MEPN) and water (WEPN), with the aim of elucidating the mechanism of action and identifying the phytochemical constituents. Male Spontaneous Hypertensive Rats (SHRs) were given oral gavage of P. niruri extract daily for two weeks and the blood pressure was recorded in vivo. We also determine the vasodilation effect of the extracts on rings of isolated thoracic aorta pre-contracted with phenylephrine (PE, 1μM). Endothelium-intact or endothelium-denuded aorta rings were pre-incubated with various antagonists like 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10μM) and Methylene blue (MB 10μM), sGC inhibitors; Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME, 10μM) a nitric oxide synthase (NOS) inhibitor; atropine (10μM), a cholinergic receptor blocker; indomethacin (10μM), a cyclooxygenase inhibitor and various K+ channel blockers such as glibenclamide (10μM) and tetraethyl ammonium (TEA 10μM) for mechanism study. SHRs receiving P. niruri extracts showed a significant decrease in their blood pressure (BP) when compared to the baseline value, with PEPN being more potent. The extracts (0.125-4mg/mL) also induced vasorelaxation on endothelium-intact aorta rings. PEPN elicited the most potent maximum relaxation effect (Rmax). Mechanism assessment of PEPN showed that its relaxation effect is significantly suppressed in endothelium-denuded aorta rings. Pre-incubation of aorta rings with atropine, L-NAME, ODQ, indomethacin, and propranolol also significantly attenuated its relaxation effect. Conversely, incubation with TEA and glibenclamide did not show a significant effect on PEPN-induced relaxation. This study indicates that the antihypertensive activity of P. niruri extract is mediated by vasoactive phytoconstituents that dilate the arterial wall via endothelium-dependent pathways and β-adrenoceptor activity which, in turn, cause vasorelaxation and reduce blood pressure.

Effects of six weeks consumption of coconut milk oil on vascular functions and fasting blood glucose and lipid profile in middle-aged male rats

Background: Coconut milk consumption in middle-aged male rats can cause increased blood vessel endothelial nitric oxide synthase (eNOS) and cystathionine-γ-lyase (CSE) protein expression, and decreased fasting blood glucose.Objective: The present study aimed to investigate whether coconut milk oil (CO), the major constituents of the coconut milk, was responsible for those effects.Methods: CO was isolated from dried fresh coconut milk and gavaged (1 and 3 ml/kg) to middle-aged male rats for 6 weeks. Blood biochemistry, lipid profile and vascular functions were investigated.Results: In comparison to a distilled water control group, no differences were observed in any of the parameters studied in the group fed 1 ml/kg of CO except for an increase in retroperitoneal fat accumulation. Feeding 3 ml/kg of CO caused decreased fasting blood glucose, plasma alkaline phosphatase and blood urea nitrogen and liver cell lipid accumulation, but increased retroperitoneal fat tissue. It also caused decreased maximal contractile response of endothelium-intact thoracic aortic rings to phenylephrine although the effect disappeared in the presence of N-nitro-L-arginine (L-NA) or removal of the endothelium. DL-propargylglycine together with L-NA caused a higher contraction to phenylephrine in the CO-treated groups than in the control group. It also caused an increase in vasodilatation to acetylcholine, but not to glyceryl trinitrate, of the phenylephrine pre-contracted aortic rings. CO treatment caused increased vascular wall eNOS and CSE protein expression.Conclusion: CO at a dose of 3 ml/kg causes some decrease in cardiovascular risk factors in middle-aged male rats, although the amount of CO consumption should be limited as it caused an increase in retroperitoneal fat.

Mechanisms underlying Eugenia mattosii D. Legrand leaves extract, fractions and compounds induce relaxation of the aorta from normotensive and hypertensive rats.

The present study aimed to verify the effect of methanolic extract, fractions, and phenolic compounds of Eugenia mattosii D. Legrand leaves on the aorta relaxation. Isometric tensions were measured on the aorta of normotensive (NTR) and spontaneously hypertensive rats (SHR). The results showed that both methanolic extracts of leaves and stems, as well as, fractions obtained from leaves were able to induce a concentration-dependent relaxation in both endothelium-intact and -denuded aortas. The methanolic extract of leaves (ME-leaves) was the most effective since the maximal relaxation (≈ 83%) obtained was at the concentration of 300μg/mL. As the endothelium-dependent relaxation was more significant, we investigated the mechanisms by which ME-leaves induced this effect. After the pretreatment with LNAME, ME-leaves-induced relaxation was decreased in the aorta of NTR and SHR. However, the pretreatment with methylene blue only reduced the relaxation in the aorta of NTR. Furthermore, pretreatment with ME-leaves decreased phenylephrine-induced contraction in preparation Ca2+-free only in aortic rings from NTR. This study also reveals that both compounds, cryptostrobin isolated from chloroform fraction and catechin from the ethyl acetate fraction induced a marked relaxation in endotheliumintact aortic rings of NTR. In conclusion, ME-leaves induces relaxation in the rat aorta involves the modulation of NO/cGMP dependent signaling pathway, this mechanism may at least, in part, explain the endothelium-dependent relaxation. Furthermore, cryptostrobin and catechin also induced relaxation, which may contribute synergistically to the vasorelaxation effect of the ME-leaves.

Endothelium-Independent Vasorelaxant Effects of Anthocyanins-Enriched Extract from Odontonema strictum (Nees) Kuntze (Acanthaceae) Flowers: Ca2+ Channels Involvement

Aims: We aimed in this study to investigate the mechanisms of the vasorelaxation effect caused by the anthocyanins-enriched extract of Odontonema strictum flowers.
 Study Design: Anthocyanins-enriched extract of Odontonema strictum flowers and vasorelaxantes activities of mice aortic rings.
 Place and Duration of Study: The flowers of Odontonema strictum (Nees) Kuntze (Acanthaceae) were collected in January 2015 at the “Institut de Recherche en Sciences de la Santé (IRSS)” experimental station in Ouagadougou. The experiments were conducted in October - November 2018 at the department of Medicine and Traditional Pharmacopeia-Pharmacy (MEPHATRA-PH)/IRSS.
 Methodology: The extract was enriched in anthocyanins using Amberlite XAD-7 non-ionic resin column. The vasorelaxant activity of anthocyanins-enriched extract of O. strictum flowers (OSF) was tested using isolated organ-chamber technique with mice aorta rings.
 Results: OSF showed concentration-dependent relaxant effects on mice endothelium intact or denuded aortic rings pre-contracted with U46619 (10-7 M) and KCl (80 mM). OSF induced relaxation in the mice aortic rings by stimulating smooth muscle cells. The vasorelaxant effect of OSF (10-1000 µg/mL) was similar in endothelium-intact and endothelium-denuded aortic rings. The maximum relaxant effect was 93.78 ± 4.69% and 92.30 ± 3.19% for endothelium-intact and endothelium-denuded aortic rings, respectively. Moreover, after incubation of the aorta rings with OSF (400 µg/mL) or vehicle (0.02% of DMSO) in PSS, OSF blocked the contraction through mechanism involving inhibition of CaCl2 and U46619 effect.
 Conclusions: The present study provides a pharmacological evidence for the antihypertensive medicinal use of Odontonema strictum by highlighting its vasorelaxant activity.

Cobalt-Induced Hypercontraction is Mediated by Generationof Reactive Oxygen Species and Influx of Calcium in Isolated RatAorta

To investigate the mechanism of cobalt-mediated phenylephrine (PE)-induced contraction in endothelium-intact isolated Wistar rat aortic rings. Effect of dose-dependent concentrations of cobalt on PE-induced contraction was investigated in isolated Wistar rat aortic rings using an organ bath system. Aortic rings were pre-incubated with verapamil (1μM and 20μM), gadolinium, apocynin, indomethacin or N-G-nitro-L-arginine methyl ester (L-NAME) separately before incubation with cobalt. Endothelium-intact aortic rings were incubated with 800nM, 1μM, 10μM, 50μM cobalt; we observed 20%, 22%, 32% and 27% increased contractions respectively, while no effect was seen in tension recording on cobalt exposure. Incubation of endothelium-intact aortic rings with 100μM apocynin and 100μM L-NAME suggested the role of NADPH oxidase in generation of reactive oxygen species (ROS) and decrease in bioavailability of nitric oxide (NO) from eNOS on exposure to cobalt. Aortic rings pre-incubated with 1μM and 20μM verapamil suggested role of both L-type and T-type calcium channels in influx of extracellular calcium in smooth muscle cells. We observed no role of store-operated calcium channels (SOCC) in calcium influx due to cobalt exposure and cyclooxygenase in generation of prostanoids in isolated aortic rings. Cobalt caused rise of PE-induced contractions as a result of the endothelial generation of ROS, by decreasing bioavailability of NO. Generation of ROS may be responsible for causing the influx of extracellular calcium through L-type and T-type Ca2+ channels in smooth muscle cells.

Curcumane C and (±)-curcumane D, an unusual seco-cadinane sesquiterpenoid and a pair of unusual nor-bisabolane enantiomers with significant vasorelaxant activity from Curcuma longa

A new seco-cadinane sesquiterpenoid (curcumane C, 1) and a pair of new nor-bisabolene enantiomers [(+)- and (−)-curcumane D, 2a and 2b] were isolated from C. longa. Compound 1 possesses an unusual 4,5-seco-cadinane skeleton with a tetrahydrophthalide moiety, while 2a and 2b contain an unusual 15-nor-bisabolene skeleton with a chromone core. All compounds exhibited significant vasorelaxant effects against KCl-induced contraction of rat aortic rings. Compound 1 also exhibited a vasorelaxant effect against phenylephrine-induced contraction of rat aortic rings. Meanwhile, compound 1 showed a stronger vasorelaxant effect in endothelium-intact rat aortic rings compared with endothelium-denuded rat aortic rings, indicating that vasodilation by 1 involved both endothelium-dependent and endothelium-independent pathways. Furthermore, compound 1 increased the NO content in human umbilical vein endothelial cells and its vasorelaxant effect could be attenuated by treatment with L-NAME, an endothelium NO synthase inhibitor. Thus, the underlying vasodilatory mechanisms of 1 may be mediated via abrogation of extracellular Ca2+ influx and regulation of NO release in vascular endothelial cells.

Synthesis and biological evaluation of Vinpocetine derivatives

A new series of Vinpocetine derivatives were synthesized and evaluated for their inhibitory activity on PDE1A in vitro. Seven compounds with higher inhibitory activity were selected for surface plasmon resonance (SPR) binding experiments. Compared with Vinpocetine, these high potency compounds presented a higher binding affinity with PDE1A, which was consistent with inhibitory activity. After further screening, compounds 5, 7, 21, 34 and Vinpocetine were selected to examine the vasorelaxant effects on endothelium-intact rat thoracic aortic rings. The study suggested that the effects of compounds 7 and 21 were the most significant with the maximum value of 93.46 ± 0.77% and 92.90 ± 0.78% (n = 5) at a concentration of 100 μM respectively. Based on these studies, compounds 7 and 21 were considered for further development as hit compounds.

Novel choline analog 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol produces sympathoinhibition, hypotension, and antihypertensive effects.

The search for new drugs remains an important focus for the safe and effective treatment of cardiovascular diseases. Previous evidence has shown that choline analogs can offer therapeutic benefit for cardiovascular complications. The current study investigates the effects of 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol (LQFM032) on cardiovascular function and cholinergic-nitric oxide signaling. Synthesized LQFM032 (0.3, 0.6, or 1.2mg/kg) was administered by intravenous and intracerebroventricular routes to evaluate the potential alteration of mean arterial pressure, heart rate, and renal sympathetic nerve activity of normotensive and hypertensive rats. Vascular function was further evaluated in isolated vessels, while pharmacological antagonists and computational studies of nitric oxide synthase and muscarinic receptors were performed to assess possible mechanisms of LQFM032 activity. The intravenous and intracerebroventricular administration of LQFM032 elicited a temporal reduction in mean arterial pressure, heart rate, and renal sympathetic nerve activity of rats. The cumulative addition of LQFM032 to isolated endothelium-intact aortic rings reduced vascular tension and elicited a concentration-dependent relaxation. Intravenous pretreatment with L-NAME (nitric oxide synthase inhibitor), atropine (nonselective muscarinic receptor antagonist), pirenzepine, and 4-DAMP (muscarinic M1 and M3 subtype receptor antagonist, respectively) attenuated the cardiovascular effects of LQFM032. These changes may be due to a direct regulation of muscarinic signaling as docking data shows an interaction of choline analog with M1 and M3 but not nitric oxide synthase. Together, these findings demonstrate sympathoinhibitory, hypotensive, and antihypertensive effects of LQFM032 and suggest the involvement of muscarinic receptors.

Comparative Study of the Effects of Acute In Vitro and Short‐term In Vivo Treatments with 3, 5, 3′ Triiodo‐L‐Thyronine on Contractile Responsiveness of Isolated Rat Thoracic Aorta

This work was aimed to study comparatively the influences of acute in vitro and short‐term in vivo treatments with 3, 5, 3′ triiodo‐L‐thyronine (T3) on the contractile responsiveness of isolated rat thoracic aortas. Previous studies have reported that T3 through nongenomic and genomic mechanisms can elicit endothelium‐dependent and ‐independent, nitric oxide (NO)‐mediated, depression of vascular tone. Short‐term in vivo treatment (hyperthyroidism) was established by subcutaneous injections of T3 (500 mg/kg/day) for 3 days (T33d); while control rats received vehicle (alkaline saline solution) for 3 days (V3d). T33d treatment was sufficient to cause both significant weight loss and elevation of T3 serum levels in the rat. In endothelium‐intact aortic rings contracted with phenylephrine, in vitro application of increasing cumulative concentrations of T3, each 30 minutes (0.01, 0.1, 1 and 10 mM), did not alter the contractile tone compared to vehicle treated tissues. Likewise, in vitro treatment with T3 (0.1, 1 and 10 mM for 30 min or 2 hs) did not modify the relaxant responses induced by either acetylcholine or sodium nitroprusside, in that order, in endothelium‐intact and ‐denuded aortic rings contracted with phenylephrine. (In aortic rings with and without endothelium, phenylephrine‐induced precontractions were not modified by preceding exposure to T3 compared to their corresponding vehicle‐treated tissues.) The concentration‐dependent contractions caused by phenylephrine and angiotensin II in aortic rings with endothelium, remained unchanged in the presence of T3 (0.1, 1 and 10 mM) applied 30 min or 2 h before. On the other hand, T33d treatment significantly decreased the contractile responses induced by phenylephrine and angiotensin II in aortic rings with and without endothelium, related to their respective controls. The absence of endothelium or the addition of the NO synthase inhibitor, L‐NAME, in the presence of endothelium (100 mM), independently, enhanced the contractile responses to phenylephrine in aortic rings of T33d and V3d rats. However, the contractile responses to phenylephrine remained similarly depressed in endothelium‐denuded and endothelium‐intact L‐NAME‐treated aortas of T33d compared to V3d rats. In conclusion, T3 applied in vitro does not alter the development of active tone in the endothelium‐intact and ‐denuded thoracic aortas, which rules out a direct action, by a rapid non‐genomic mechanism, of this hormone in smooth muscle and endothelial cells. On the other hand, short‐term in vivo administration of T3 depressed contractile responsiveness of the thoracic aorta, independently of endothelium and NO (whether of endothelial or muscle origin). It remains to elucidate if the T3‐induced depression of aortic contractility is due to direct hormonal effects or is secondary to a hyperdynamic cardiovascular state in hyperthyroid rats.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Trimebutine maleate relaxes the isolated rat thoracic aorta: The role of nitric oxide and L-type calcium channels.

Trimebutine maleate (TMB), a widely prescribed drug for functional gastrointestinal disorders, has been reported to regulate smooth muscle contractility by modulating multiple ion channel activities in the gastrointestinal tract. However, its action on isolated aorta has not yet been reported. The aim of the present study was to evaluate in vitro vasorelaxant properties and the underlying pharmacological mechanisms of TMB in isolated rat thoracic aortic rings. Vascular activity experiments were performed on thoracic aorta isolated from Sprague-Dawley rats in vitro, including endothelium-intact and endothelium-denuded aortic rings. TMB (10-10 -10-5 mol/L) induced relaxation in endothelium-intact aortic rings precontracted by phenylephrine with a potency similar to that of carbachol. TMB-induced relaxation was not altered by glibenclamide and atropine in endothelium-intact aortic rings. However, L-NAME and endothelium denudation significantly reduced but not completely reversed the vasorelaxant effect of TMB. Also, TMB-induced relaxation wasn't affected by diclofenac in endothelium-intact aortic rings. TMB at 10-5 mol/L significantly reduced the CaCl2 -induced contractions in endothelium-intact aortic rings stimulated with KCl, but not stimulated with phenylephrine under Ca2+ free conditions. Moreover, TMB at 10-5 mol/L effectively attenuated Bay-K8644-induced contractions in aortic rings. These results suggest that TMB-induced relaxation was mediated by both endothelium-dependent and endothelium-independent manner in isolated rat thoracic aorta. The mechanism of TMB-induced relaxation at low concentrations is partially related to NO- and endothelium-dependent but unrelated to prostanoids formation. However, inhibition of Ca2+ influx through voltage-operated calcium channels and L-type Ca2+ channel blocking effect appears to be involved in the mechanism of vasorelaxant effect of TMB at high concentrations.

Vasorelaxant effect of the ethanol extract from Valeriana fauriei briquet root and rhizome on rat thoracic aorta

Background: Valeriana fauriei has been used to treat anxiety and cardiovascular disease in many countries; however, the mechanisms of the vasorelaxant effect of V. fauriei roots and rhizomes have not been elucidated. Purpose of the Study: Considering the increased use of traditional medicines for treating hypertension, the aim of this study was to examine the vasorelaxant effect and investigate the mechanisms of V. fauriei root and rhizome. Materials and Methods: Using an isolated organ-chamber technique, the vasorelaxant effects of 70% ethanol extract of V. fauriei root and rhizome (VFE) were tested in rat aortic ring segments. Results: VFE concentration dependently relaxed both endothelium-intact and endothelium-denuded aortic rings that were precontracted by phenylephrine (PE) or potassium chloride (KCl). VFE relaxed the aortic rings precontracted by PE (1 μM) irrespective of K+ channel blocker pretreatment such as tetraethylammonium, glibenclamide, or 4-aminopyridine. VFE inhibited vasoconstriction caused by extracellular Ca2+ influx through receptor-operative Ca2+ channels (ROCCs) or voltage-dependent Ca2+ channels (VDCCs) activated by PE or KCl, respectively, in Ca2+-free Krebs–Henseleit buffer. Conclusion: These results suggested that the vasorelaxant effects of VFE were endothelium independent and not related to K+ channels, such as Ca2+-activated K+ channels, ATP-sensitive K+ channels, and Voltage-gated K+ channels. In addition, VFE relaxed the aortic rings by blocking the influx of extracellular Ca2+ through ROCCs and VDCCs. Abbreviations used: ACE: Angiotensin-converting enzyme; VFE: The 70% EtOH extract of Valeriana fauriei root and rhizome; KH: Krebs–Henseleit; PE: Phenylephrine; KCl: Potassium chloride; TEA: Tetraethylammonium; 4-AP: 4-Aminopyridine; CaCl2: Calcium chloride; EGTA: Ethylene glycol-bis (2-aminoethylether)-N, N, N′, N′-tetraacetic acid; DMSO: Dimethyl sulfoxide; ROCCs: Receptor-operative Ca2+ channels; VDCCs: Voltage-dependent Ca2+ channels; KIR: Inward-rectifier K+ channels; KATP: ATP-sensitive K+ channels; KV: Voltage-gated K+ channels; KCa: Ca2+-activated K+ channels.