Concentration-dependent Vasorelaxation Research Articles

The vasodilator effect of Eugenol on uterine artery – potential therapeutic applications in pregnancy-associated hypertension

Preeclampsia, a gestational associated hypertension, has been reported in 6–8% of pregnant women worldwide leading to premature delivery and low birth weight of newborn due to reduced blood flow to placenta. Although several vasodilators (Methyl dopa, hydralazine, β-blockers and diuretics) are currently in use to treat preeclampsia, still there is a search for safer drugs with better efficacy. Lately, antihypertensive vasodilators from natural sources are gaining importance in treating preeclampsia. Eugenol (Eug), a natural essential oil, has been traditionally used in health and food products without any risk. In the present study, ex vivo experiments were designed to examine the vasorelaxation effect of Eug and its signaling pathways in a middle uterine artery (MUA) of pregnant Capra hircus (Ch). In presence of different blockers (L-NAME, indomethacin, ODQ, Ouabain, glibenclamide, 4-AP, Ba2, Carbenoxolone and 18β Glycyrrhetinic acid), Eug-induced concentration-dependent vasorelaxation response was elicited. The results showed that Eug caused a greater vasorelaxation effect in the MU of pregnant animals, which is mediated by potential activation of eNOS, KATP channels, and Kir channels with moderate activation of Na+- K+- ATPase and sGC and MEGJ. These findings provide a strong basis for developing Eug as a therapeutic candidate in the treatment of pregnancy-associated hypertension.

Sulodexide Inhibits Arterial Contraction via the Endothelium-Dependent Nitric Oxide Pathway.

Background/Objectives: Sulodexide (SDX) is a drug known for restoring the glycocalyx, thereby offering endothelial protection and regulating permeability. Additionally, it has antithrombotic and anti-inflammatory properties and has shown arterial vasodilatory effects. Endothelial cells play a crucial role in maintaining homeostasis, with their dysfunction being a key contributor to loss in vasodilatory response, especially in arterial pathologies. The aim of this study was to investigate the effects of SDX on stimulated vascular tonus in human arterial samples and to assess the function of the endothelial layer as a source of nitric oxide (NO). Methods: A total of 16 internal mammary artery remnants from coronary artery bypass graft surgeries were dissected into endothelium-intact and endothelium-denuded groups (n = 8 each). The arterial rings were equilibrated under tension, with their basal tonus recorded before and after phenylephrine stimulation. SDX's impact on arterial contraction was assessed through cumulative dose-response curves. NO synthase inhibitor (Nω-nitro-L-arginine methyl ester) was used to assess SDX's vasodilatory effect over the NO pathway. Results: SDX application resulted in concentration-dependent vasorelaxation in both endothelium-intact and endothelium-denuded groups at certain doses. However, the inhibitory effect of SDX was more pronounced in endothelium-intact rings at higher doses compared to endothelium-denuded rings (p < 0.05). Similar inhibition of contraction curves was achieved for both endothelium-intact and endothelium-denuded rings after L-NAME pre-incubation, suggesting a necessity for NO-related endothelial pathways. Conclusions: SDX exerts a concentration-dependent inhibition on arterial contraction, emphasizing the critical role of an intact endothelium and NO-mediated pathways in this process. This underscores SDX's potential in treating endothelial dysfunction-related pathologies.

Vasorelaxant and Blood Pressure-Lowering Effects of Cnidium monnieri Fruit Ethanol Extract in Sprague Dawley and Spontaneously Hypertensive Rats.

Cnidium monnieri (L.) Cusson, a member of the Apiaceae family, is rich in coumarins, such as imperatorin and osthole. Cnidium monnieri fruit (CM) has a broad range of therapeutic potential that can be used in anti-bacterial, anti-cancer, and sexual dysfunction treatments. However, its efficacy in lowering blood pressure through vasodilation remains unknown. This study aimed to assess the potential therapeutic effect of CM 50% ethanol extract (CME) on hypertension and the mechanism of its vasorelaxant effect. CME (1-30 µg/mL) showed a concentration-dependent vasorelaxation on constricted aortic rings in Sprague Dawley rats induced by phenylephrine via an endothelium-independent mechanism. The vasorelaxant effect of CME was inhibited by blockers of voltage-dependent and Ca2+-activated K+ channels. Additionally, CME inhibited the vascular contraction induced by angiotensin II and CaCl2. The main active compounds of CM, i.e., imperatorin (3-300 µM) and osthole (1-100 µM), showed a concentration-dependent vasorelaxation effect, with half-maximal effective concentration values of 9.14 ± 0.06 and 5.98 ± 0.06 µM, respectively. Orally administered CME significantly reduced the blood pressure of spontaneously hypertensive rats. Our research shows that CME is a promising treatment option for hypertension. However, further studies are required to fully elucidate its therapeutic potential.

N-(Heteroaryl)thiophene sulfonamides as angiotensin AT2 receptor ligands

Two series of N-(heteroaryl)thiophene sulfonamides, encompassing either a methylene imidazole group or a tert-butylimidazolylacetyl group in the meta position of the benzene ring, have been synthesized. An AT2R selective ligand with a Ki of 42 nM was identified in the first series and in the second series, six AT2R selective ligands with significantly improved binding affinities and Ki values of <5 nM were discovered. The binding modes to AT2R were explored by docking calculations combined with molecular dynamics simulations. Although some of the high affinity ligands exhibited fair stability in human liver microsomes, comparable to that observed with C21 undergoing clinical trials, most ligands displayed a very low metabolic stability with t½ of less than 10 min in human liver microsomes. The most promising ligand, with an AT2R Ki value of 4.9 nM and with intermediate stability in human hepatocytes (t½ = 77 min) caused a concentration-dependent vasorelaxation of pre-contracted mouse aorta.

PS-BPB03-2: VASORELAXANT-MEDIATED ANTIHYPERTENSIVE EFFECT OF THE SEED AQUEOUS EXTRACT OF AFRAMOMUM PRUINOSUM GAGNEP. (ZINGIBERACEAE)

Objective: Despite the existing therapies, arterial hypertension is still a prevalent and a worldwide major public health concern, prompting the search for new therapeutic alternatives. The present study investigated the antihypertensive and the related mechanisms of action of the seed aqueous extract of Aframomum pruinosum (AEAP), a plant used in Cameroon traditional medicine against cardiovascular ailments. Design and method: Male Wistar rats were rendered hypertensive by chronic oral administration of L-NAME (30 mg/kg/day) for three consecutive weeks, and hypertensive rats were selected and treated with L-NAME alone or in combination with AEAP at doses of 75 or 150 mg/kg/day for an additional 3 consecutive weeks. Captopril (25 mg/kg/day, p.o) was used as reference drug. Blood pressure and heart rate were monitored weekly. At the end of the experiment, the heart was harvested, weighed, and sections of cardiac tissue were stained with hematoxylin and eosin for histological analysis. Cumulative concentrations of the aqueous extract (3, 10, 30, 100, and 300 μg/mL) were tested on intact or endothelium-denuded aorta rings precontracted with norepinephrine (NE; 1 μM) or KCl (90 mM) in absence or presence of L-NAME (a nitric oxide synthase inhibitor, 100 μM), indomethacin (a prostaglandin synthesis inhibitor; 10 μM), methylene blue (a guanylate cyclase inhibitor, 1 μM), tetraethylammonium (TEA; a non-specific potassium channel blocker; 5 μM) or glibenclamide (an ATP-sensitive potassium channel blocker; 10 μM). The contractile response to NE, or CaCl2 was also assessed in the presence or absence of the plant extract. Results: AEAP completely reversed (p &lt; 0.001) L-NAME-induced elevated systolic and diastolic blood pressure, and increased heart rate. AEAP partially reversed cardiac hypertrophy, leucocyte infiltration, and prevent cardiac necrosis. AEAP induced a concentration-dependent vasorelaxant effect on NE- and KCl-evoked contraction with EC50 values of 13.46 and 49.37 μg/mL, respectively. Removal of the endothelium and the preincubation of aorta rings with L-NAME significantly (p &lt; 0.05) reduced the vasorelaxant effect of the plant extract, while indomethacin and methylene blue had no effect (p &gt; 0.05). Glibenclamide, similar to TEA, significantly (p &lt; 0.001) inhibited the vasorelaxant response to AEAP. Also, the extract significantly (p &lt; 0.01 and p &lt; 0.001) inhibited NE- and CaCl2-induced contraction. Conclusion: AEAP possesses antihypertensive effects that are at least partially mediated by its vasorelaxant activity. Nitric oxide release, opening of KATP channels, blockade of alpha-1 receptors, and inhibition of Ca2+ influx account for this vasorelaxant activity.

Potassium Channels Contributes to Apelin-induced Vasodilation in Rat Thoracic Aorta.

Apelin is a newly discovered peptide hormone and originally discovered endogenous apelin receptor ligand. In this study, we aimed to investigate the possible roles of potassium channel subtypes in the vasorelaxant effect mechanisms of apelin. The vascular rings obtained from the thoracic aortas of the male Wistar Albino rats were placed into the isolated tissue bath system. The resting tension was set to 2 g. After the equilibration period, the aortic rings were precontracted with 10-5 M phenylephrine (PHE) or 45 mM KCl. Pyroglutamyl-apelin-13 ([Pyr1]apelin-13), which is the dominant apelin isoform in the human cardiovascular tissues and human plasma, was applied cumulatively (10-10-10-6 M) to the aortic rings in the plateau phase. The experimental protocol was repeated in the presence of specific K+ channel subtype blockers to determine the role of K+ channels in the vasorelaxant effect mechanisms of apelin. [Pyr1]apelin-13 induced a concentration-dependent vasorelaxation (p < 0.001). The maximum relaxation level was approximately 52%, according to PHE-induced contraction. Tetraethylammonium, iberiotoxin, 4-Aminopyridine, glyburide, anandamide, and BaCl2 statistically significantly decreased the vasorelaxant effect level of [Pyr1]apelin-13 (p < 0.001). However, apamin didn't statistically significantly change the vasorelaxant effect level of [Pyr1]apelin-13. In conclusion, our findings suggest that BKCa, IKCa, Kv, KATP, Kir, and K2P channels are involved in the vasorelaxant effect mechanisms of apelin in the rat thoracic aorta.

Vascular Effects of Polyphenols from Agrimonia eupatoria L. and Role of Isoquercitrin in Its Vasorelaxant Potential in Human Arteries

Agrimonia eupatoria L. has been traditionally used for the treatment of inflammatory diseases but also as a hypotensive. To our knowledge, only one study has previously suggested an improvement in vascular endothelial function in diabetic conditions, as the underlying mechanisms and responsible compounds are unknown. In this study, we aimed to assess the direct vascular effects of Agrimonia eupatoria L. in human arteries. The infusion elicited a mild increase in basal vascular tone and a significant potentiation of the adrenergic contraction of 49.18% at 0.02 mg/mL, suggesting the presence of compounds with mild vasoconstrictor activity. In contrast, the ethyl acetate fraction inhibited adrenergic contraction by 80.65% at 2 mg/mL and elicited no effect on basal vascular tone. A potent concentration-dependent vasorelaxation was observed for both the infusion and the ethyl acetate fraction (maximal relaxation above 76% and 47%, respectively). Inhibition of nitric oxide synthase and cyclooxygenase elicited significant decreases in the vasorelaxation to the infusion, as, for the ethyl acetate fraction, only the cyclooxygenase pathway appeared to be involved. Isoquercitrin elicited a vasoactivity consistent with the ethyl acetate fraction, suggesting this is a major component responsible for the vasorelaxant properties of A. eupatoria. Further research is warranted to fully evaluate its vasoprotective properties with therapeutic potential in several conditions, e.g., atherosclerosis.

Vasorelaxant and Antioxidant Effects of Aframomum pruinosum Gagnep. (Zingiberaceae) Seed Extracts May Mediate Their Cardioprotective Activity against Isoproterenol-Induced Myocardial Infarction.

Aframomum pruinosum seeds are traditionally used in Cameroon to treat cardiac palpitations. The present work evaluates the cardioprotective effects of the aqueous (AE) and ethanolic (EE) extracts from A. pruinosum seeds against isoproterenol-induced myocardial infarction. Male Wistar rats were pretreated for 14 days with AE or EE at doses of 75 and 150 mg/kg/day or propranolol (10 mg/kg/day). On days 15 and 16, they were injected subcutaneously with isoproterenol (85 mg/kg/day). Blood pressure and heart rate were weekly recorded by tail-cuff plethysmography during pretreatment and 24 hours after the second dose of isoproterenol. At the end of the treatment period, serum Lactate Dehydrogenase (LDH), Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), cardiac nitric oxide (NO), myeloperoxidase (MPO), and oxidative stress parameters (SOD, catalase, MDA, and GSH) were assayed. Sections of left ventricle tissue were subjected to histological analysis. The vasorelaxant effects of cumulative concentrations of AE or EE (3–300 µg/mL) were evaluated on intact or endothelium-denuded isolated aorta rings precontracted with noradrenaline (1 µM). The vasorelaxant effects of the plant extracts were also tested in the presence of Nω-nitro-L-arginine methyl ester (L-NAME; 100 µM). AE and EE significantly prevented blood pressure decrease and heart rate increase elicited by isoproterenol. Both plant extracts inhibited the increase in ALT, AST, NO, and MPO but did not prevent LDH surge. Oxidative stress parameters were improved following A. pruinosum pretreatment. AE and EE highly reduced cardiomyocyte necrosis and fibrosis but did not prevent leukocyte infiltration. Both extracts induced a concentration-dependent vasorelaxation that was significantly inhibited by the destruction of the endothelium and by L-NAME. Extracts of A. pruinosum exhibited cardioprotective effects, and EE was the most active. The cardioprotective effects of A. pruinosum extracts could be ascribed to their antioxidant, antinecrotic, and endothelium-dependent vasorelaxant effects.

Peptide fragments of bradykinin show unexpected biological activity not mediated by B1 or B2 receptors.

Bradykinin (BK-(1-9)) is an endogenous nonapeptide involved in multiple physiological and pathological processes. Peptide fragments of bradykinin are believed to be biologically inactive. We have now tested the two major peptide fragments of bradykinin in human and animals. BK peptides were quantified by MS in male rats. NO release was quantified from human, mouse and rat cells loaded with DAF-FM. Rat aortic rings were used to measure vascular reactivity. Changes in BP and HR were measured in conscious male rats. To evaluate pro-inflammatory effects both vascular permeability and nociception were measured in adult mice. BK-(1-7) and BK-(1-5) are produced in vivo from BK-(1-9). Both peptides induced NO production in all cell types tested. However, unlike BK-(1-9), NO production elicited by BK-(1-7) or BK-(1-5) was not inhibited by B1 or B2 receptor antagonists. BK-(1-7) and BK-(1-5) induced concentration-dependent vasorelaxation of aortic rings, without involvement of B1 or B2 receptors. Intravenous or intra-arterial administration of BK-(1-7) or BK-(1-5) induced similar hypotensive response in vivo. Nociceptive responses of BK-(1-7) and BK-(1-5) were reduced compared to BK-(1-9), and no increase in vascular permeability was observed for BK-(1-9) fragments. BK-(1-7) and BK-(1-5) are endogenous peptides present in plasma. BK-related peptide fragments show biological activity, not mediated by B1 or B2 receptors. These BK fragments could constitute new, active components of the kallikrein-kinin system.

Calcium Channel Blockade Mediates the Vasorelaxant Activity of Dichloromethane Extract from Roots of Oncidium cebolleta on Isolated Rat Aorta

Oncidium cebolleta belongs to the Orchidaceae family, and it is used in preparations in Mexican traditional medicine to treat several diseases. This research aimed to study the vasorelaxant activity of dichloromethane extract from the roots of Oncidium cebolleta (DEROc) on endothelium-intact and -removed rat aorta segments to determine its mode of vasorelaxant action. Several extracts (hexane, dichloromethane, and methanol) obtained from leaves and roots were evaluated on isolated rat aorta rings with and without endothelium to determine their vasorelaxant effect. Except for methanolic extract from leaves, all extracts induced a concentration-dependent vasorelaxant effect on endothelium-intact rat aorta rings pre-contracted with noradrenaline (NA, 0.1 µM). Dichloromethane extract from roots (DEROc) was the most potent and efficient, and the effect was endothelium-independent. Also, DEROc could relax KCl-induced contraction (80 mM) and inhibit the contraction induced by CaCl2-cumulative concentration on endothelium-denuded rings. However, DEROc was less potent than control nifedipine (L-type calcium channel blocker), but its effectiveness was similar. Contractions induced by NA and 5-HT [0.001 µM to 0.1 µM] were significantly reduced by DEROc. However, DEROc vasorelaxation was not reduced by TEA (potassium channel blocker, 10 mM) nor by ODQ (soluble guanylyl cyclase inhibitor, 0.1 µM) in endothelium-denuded aortic rings. Our functional results suggest that DEROc induces its relaxant effect by an endothelium-independent mechanism due to a Ca2+ channels blockade in rat aortic rings.

The role of potassium channels on vasorelaxant effects of elabela in rat thoracic aorta.

Background This study aims to investigate the roles of potassium channel subtypes in the vasorelaxant effect mechanism of elabela, which is a recently discovered endogenous apelin receptor ligand. Methods The vascular rings (4-mm) obtained from the thoracic aortas of 20 male Wistar Albino rats were placed into the isolated tissue bath system. The resting tension was set to 1 g. The aortic rings were contracted with 10-5 molar phenylephrine after the equilibration period (90 min). Elabela was applied cumulatively (10-10-10-6 molar) to the aortic rings in the plateau phase. The experimental protocol was repeated in the presence of specific potassium channel subtype inhibitors to determine the role of potassium channels in the vasorelaxant effect mechanism of elabela. Results Elabela induced a concentration-dependent vasorelaxation (p<0.001). The maximum relaxation level was approximately 51% according to phenylephrineinduced contraction. Vasorelaxant effect level of elabela statistically significantly decreased after removal of the endothelium (p<0.05). Tetraethylammonium (1 milimolar), 4-Aminopyridine (1 milimolar), glyburide (10 micromolar), and barium chloride (30 micromolar) statistically significantly decreased the vasorelaxant effect level of elabela (p<0.001, p<0.001, p<0.01, and p<0.05 respectively). However, anandamide (10 micromolar) and apamin (100 nanomolar) did not statistically significantly change the vasorelaxant effect level of elabela. Conclusion Our results suggest that large-conductance calciumactivated, voltage-gated, adenosine triphosphate-sensitive, and inward-rectifier potassium channels are involved in the vasorelaxant effect mechanism of elabela in the rat thoracic aorta.

Comparison of Pinoresinol and its Diglucoside on their ADME Properties and Vasorelaxant Effects on Phenylephrine-Induced Model.

Pinoresinol (PINL) and pinoresinol diglucoside (PDG), two natural lignans found in Eucommia ulmoides Oliv. (Duzhong), have several pharmacological activities. However, there is no report available on their absorption, distribution, metabolism, and elimination (ADME) properties. Given the possible wide spectrum of their application in therapeutic areas, this area should be investigated. This work studied the in vitro ADME properties of PDG and PINL, including their kinetic solubility, permeability across monolayer cells (PAMPA), protein binding, and metabolic stabilities in liver microsomes. The in vivo pharmacokinetic study and in vitro vasorelaxant effects on isolated phenylephrine-induced aortic rings of PINL and PDG were also investigated. It was found that both of their kinetic solubility in PBS (pH 7.4) was greater than 100 μM, indicating that they are both soluble compounds. The permeability investigations (P eff) by PAMPA indicated that PINL had higher permeability than PDG (p < 0.05). Both components represented moderate plasma protein binding activities (average binding rate in human plasma: PINL 89.03%, PDG 45.21%) and low metabolic rate (t 1/2 in human liver microsome: PINL 1509.5 min, PDG 1004.8 min). Furthermore, the results of pharmacokinetic studies indicated that PINL might be eliminated less quickly than PDG from the rat plasma, and its cumulative urinary excretion was much lower than that of PDG. The phenylephrine-induced aortic rings demonstrated concentration-dependent vasorelaxation in PDG, PINL, or their combination group. The vasorelaxant effects of PINL were more obvious than those of PDG, whereas the vasorelaxant effect of the combinations was significantly better than that of the single component (p < 0.05). The similarity or difference between PINL and its diglucoside in these pharmaceutical aspects may offer valuable insights into the further exploration of lignans and might contribute to relevant studies involving natural products with similar molecular structure and their glucosides.

Vasodilatory action of trans-4-methoxy-β-nitrostyrene in rat isolated pulmonary artery.

Trans-4-methoxy-β-nitrostyrene (T4MN) induced more potent vasorelaxant effects in resistance arteries from hypertensive rats than its parent drug, β-nitrostyrene 1-nitro-2-phenylethene (NPe). To better understand the influence of insertion of the electron-releasing methoxy group in the aromatic ring of NPe, we investigated vasorelaxant effects of T4MN in isolated pulmonary artery and compared them with those of NPe in view of the potential interest of T4MN in pulmonary arterial hypertension. T4MN and NPe both caused concentration-dependent vasorelaxation in pulmonary artery rings pre-contracted with either phenylephrine (1µmol/L) or KCl (60mmol/L), an effect unaffected by endothelium removal. In endothelium-intact preparations pre-contracted with phenylephrine, the vasorelaxant effect of T4MN was more potent than that of NPe. However, unlike NPe, this effect was significantly reduced following pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10µmol/L, a guanylate cyclase inhibitor) or tetraethylammonium (5mmol/L, a potassium channel blocker). T4MN abolished the CaCl2 -induced contractions in pulmonary artery preparations stimulated with phenylephrine (PHE) under Ca2+ -free conditions in the presence of verapamil, to preferentially activate receptor-operated calcium channels. From these findings, we propose that T4MN evokes endothelium-independent vasorelaxant effects in isolated rat pulmonary artery, partially by inhibiting Ca2+ influx through L-type Ca2+ channels, as well as by activating soluble guanylate cyclase and potassium channels. The present results suggest the therapeutic potential of T4MN in treating pulmonary arterial hypertension.

Mechanisms of SGLT2 (Sodium-Glucose Transporter Type 2) Inhibition-Induced Relaxation in Arteries From Human Visceral Adipose Tissue.

As novel drug treatments for diabetes have shown favorable cardiovascular effects, interest has mounted with regard to their possible vascular actions, particularly in relation to visceral adipose tissue perfusion and remodeling in obesity. The present study tested the vasorelaxing effect of the SGLT2 (sodium-glucose transporter type 2) inhibitor canagliflozin in arteries from visceral adipose tissue of either nonobese or obese humans and investigated the underlying mechanisms. Also, the vasorelaxing effect of canagliflozin and the GLP-1 (glucagon-like peptide 1) agonist liraglutide were compared in arteries from obese patients. To these purposes, small arteries (116-734 μm) isolated from visceral adipose tissue were studied ex vivo in a wire myograph. Canagliflozin elicited a higher concentration-dependent vasorelaxation in arterioles from obese than nonobese individuals (P=0.02). The vasorelaxing response to canagliflozin was not modified (P=0.93) by inhibition of nitric oxide synthase (L-NAME) or prostacyclin (indomethacin), or by H2O2 scavenging (catalase); also, canagliflozin-induced relaxation was similar (P=0.23) in endothelium-intact or -denuded arteries precontracted with high potassium concentration, thereby excluding an involvement of endothelium-derived hyperpolarizing factors. The vasorelaxing response to canagliflozin was similar to that elicited by the Na+/H+ exchanger 1 inhibitor BIX (P=0.67), but greater than that to the Na+/Ca++ exchanger inhibitor SEA 0400 (P=0.001), hinting a role of Na+/H+ exchanger inhibition in canagliflozin-induced relaxation. In arterioles from obese patients, the vasorelaxing response to canagliflozin was greater than that to liraglutide (P=0.004). These findings demonstrate that canagliflozin induces endothelium-independent vasorelaxation in arterioles from human visceral adipose tissue, thereby suggesting that SGLT2 inhibition might favorably impact the processes linking visceral adipose burden to vascular disease in obesity.

N-(Methyloxycarbonyl)thiophene sulfonamides as high affinity AT2 receptor ligands

A series of meta-substituted acetophenone derivatives, encompassing N-(alkyloxycarbonyl)thiophene sulfonamide fragments have been synthesized. Several selective AT2 receptor ligands were identified, among those a tert-butylimidazole derivative (20) with a Ki of 9.3 nM, that demonstrates a high stability in human liver microsomes (t½ = 62 min) and in human hepatocytes (t½ = 194 min). This methyloxycarbonylthiophene sulfonamide is a 20-fold more potent binder to the AT2 receptor and is considerably more stable in human liver microsomes, than a previously reported and broadly studied structurally related AT2R prototype antagonist 3 (C38). Ligand 20 acts as an AT2R agonist and caused an AT2R mediated concentration-dependent vasorelaxation of pre-contracted mouse aorta. Furthermore, in contrast to imidazole derivative C38, the tert-butylimidazole derivative 20 is a poor inhibitor of CYP3A4, CYP2D6 and CYP2C9. It is demonstrated herein that smaller alkyloxycarbonyl groups make the ligands in this series of AT2R selective compounds less prone to degradation and that a high AT2 receptor affinity can be retained after truncation of the alkyloxycarbonyl group. Binding modes of the most potent AT2R ligands were explored by docking calculations combined with molecular dynamics simulations.

Antihypertensive effects of allicin on spontaneously hypertensive rats via vasorelaxation and hydrogen sulfide mechanisms

BackgroundAllicin, the principle active constituent in garlic, has been reported to have antihypertensive effects on drug-induced hypertension or renal hypertension in rats, but reports on spontaneously hypertensive rats (SHRs) are rare. Allicin is comprised of a variety of sulfur-containing compounds, and hydrogen sulfide (H2S) has been shown to have specific vasomotor effects. We therefore hypothesize that allicin may exert a vasorelaxant activity by inducing H2S production, and this eventually result in a reduction in blood pressure in SHRs. MethodsThe in vivo antihypertensive effect of allicin was assessed using a tail-cuff method on SHRs. The in vitro vasorelaxant effect and in-depth mechanisms of allicin were explored on rat mesenteric arterial rings (RMARs) isolated from SD rats. ResultsIn the in vivo study, administration of allicin (7 mg/kg and 14 mg/kg, 4 weeks, i.g) dramatically decreased the blood pressure in SHRs, which was also shown to be attenuated by H2S synthase inhibitor (PAG, 32 mg/kg, i.g). In in vitro studies, allicin (2.50–15.77 mM) produced a concentration-dependent vasorelaxation on RMARs, which was obviously reduced by preincubation with PAG. The removal of endothelium led to a decline in allicin’s vasorelaxation, which was almost completely mitigated when treatment was followed with PAG. Inhibitors of nitric oxide (NO) and prostaglandin (PGI2) pathways separately suppressed the vasorelaxation induced by allicin to a certain degree. When the RMARs incubated with PAG were treated with or without the above inhibitors in separate groups, the relaxations caused by allicin were almost identical under both these conditions. Moreover, allicin treatment increased cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) levels (downstream products of NO and PGI2 pathways), which was decreased by PAG. Additionally, allicin increased the acetylcholine-induced endothelium-derived hyperpolarizing factor (EDHF) -mediated relaxation, which was unaffected by PAG. ConclusionAllicin exhibits a potent antihypertensive effect through vasodilatory properties and H2S mechanisms. Moreover, the vasodilation of allicin is partially dependent on endothelium. The endothelium-dependent vasodilation of allicin is mediated by the NO-sGC-cGMP, PGI2-AC-cAMP and EDHF pathways, of which H2S participates in the first two but not the third one. The endothelium independent vasodilation can be predominantly attributed to H2S production.

Vasorelaxant and Antihypertensive Effects of Neferine in Rats: An In Vitro and In Vivo Study.

The present study was performed to examine the antihypertensive effect of neferine in hypertensive rats and its relaxant mechanisms in isolated rat thoracic aorta. The antihypertensive effect was evaluated by tail-cuff methods on NG-nitro-L-arginine methyl ester (L-NAME) (40 mg/kg BW) 4-week hypertensive-induced hypertensive rats. The vasorelaxant effect and its mechanisms were studied by the organ bath technique in the thoracic aorta isolated from normotensive rats. The results indicated that the treatment of neferine (1 mg/kg and 10 mg/kg) markedly decreased the systolic blood pressure (SBP) when compared with the hypertension group (137.75 ± 10.14 mmHg and 132.23 ± 9.5 mmHg, respectively, p < 0.001), without affecting the heart rate. Moreover, neferine (10-12 - 10-4 M) exhibited concentration-dependent vasorelaxation in endothelium-intact rings (Emax values = 98.95 ± 0.66% and pD2 = 7.93 ± 0.28) and endothelium-denuded rings (Emax values = 90.61 ± 1.91% and pD2 = 6.85 ± 0.36). The effects of neferine were reduced by pre-incubation with L-NAME and 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one (ODQ) but not with pre-incubation with indomethacin and K+channel blockers. Neferine attenuated the contractions induced by phenylephrine and caffeine in a Ca2+-free solution and also inhibited in CaCl2- and phenylephrine-induced contracted rings. Our study suggests that neferine exhibited hypertensive potential, induced vasorelaxation through the endothelium nitric oxide synthase (eNOS)/nitric oxide (NO)/soluble guanylyl cyclase (sGC) pathway and involved the modulation of Ca2+ influx through Ca2+ channels and intracellular Ca2+ release from the sarcoplasmic reticulum.

Vasodilatory effects of cannabidiol in human pulmonary and rat small mesenteric arteries: modification by hypertension and the potential pharmacological opportunities.

Objective:Cannabidiol (CBD) has been suggested as a potential antihypertensive drug. The aim of our study was to investigate its vasodilatory effect in isolated human pulmonary arteries (hPAs) and rat small mesenteric arteries (sMAs).Methods:Vascular effects of CBD were examined in hPAs obtained from patients during resection of lung carcinoma and sMAs isolated from spontaneously hypertensive (SHR); 11-deoxycorticosterone acetate (DOCA-salt) hypertensive rats or their appropriate normotensive controls using organ bath and wire myography, respectively.Results:CBD induced almost full concentration-dependent vasorelaxation in hPAs and rat sMAs. In hPAs, it was insensitive to antagonists of CB1 (AM251) and CB2 (AM630) receptors but it was reduced by endothelium denudation, cyclooxygenase inhibitors (indomethacin and nimesulide), antagonists of prostanoid EP4 (L161982), IP (Cay10441), vanilloid TRPV1 (capsazepine) receptors and was less potent under KCl-induced tone and calcium-activated potassium channel (KCa) inhibitors (iberiotoxin, UCL1684 and TRAM-34) and in hypertensive, overweight and hypercholesteremic patients. The time-dependent effect of CBD was sensitive to the PPARγ receptor antagonist GW9662. In rats, the CBD potency was enhanced in DOCA-salt and attenuated in SHR. The CBD-induced relaxation was inhibited in SHR and DOCA-salt by AM251 and only in DOCA-salt by AM630 and endothelium denudation.Conclusion:The CBD-induced relaxation in hPAs that was reduced in hypertensive, obese and hypercholesteremic patients was endothelium-dependent and mediated via KCa and IP, EP4, TRPV1 receptors. The CBD effect in rats was CB1-sensitive and dependent on the hypertension model. Thus, modification of CBD-mediated responses in disease should be considered when CBD is used for therapeutic purposes.

Elucidating the Mechanism of Absorption of Fast-Acting Insulin Aspart: The Role of Niacinamide

PurposeFast-acting insulin aspart (faster aspart) is a novel formulation of insulin aspart containing two additional excipients: niacinamide, to increase early absorption, and L-arginine, to optimize stability. The aim of this study was to evaluate the impact of niacinamide on insulin aspart absorption and to investigate the mechanism of action underlying the accelerated absorption.MethodsThe impact of niacinamide was assessed in pharmacokinetic analyses in pigs and humans, small angle X-ray scattering experiments, trans-endothelial transport assays, vascular tension measurements, and subcutaneous blood flow imaging.ResultsNiacinamide increased the rate of early insulin aspart absorption in pigs, and pharmacokinetic modelling revealed this effect to be most pronounced up to ~30–40 min after injection in humans. Niacinamide increased the relative monomer fraction of insulin aspart by ~35%, and the apparent permeability of insulin aspart across an endothelial cell barrier by ~27%. Niacinamide also induced a concentration-dependent vasorelaxation of porcine arteries, and increased skin perfusion in pigs.ConclusionNiacinamide mediates the acceleration of initial insulin aspart absorption, and the mechanism of action appears to be multifaceted. Niacinamide increases the initial abundance of insulin aspart monomers and transport of insulin aspart after subcutaneous administration, and also mediates a transient, local vasodilatory effect.

Terminalia fagifolia Mart. & Zucc. elicits vasorelaxation of rat thoracic aorta through nitric oxide and K+ channels dependent mechanism.

ABSTRACTTerminalia fagifolia Mart. & Zucc. (Combretaceae) is a plant commonly found in the regions of the Brazilian cerrado, popularly used for the treatment of gastrointestinal disorders. There are no reports in the literature on the use of T. fagifolia for the treatment of the cardiovascular system conditions. Nevertheless, plants of the same genus, such as Terminalia arjuna (Roxb.) Wight & Arn and Terminalia superba Engler & Diels, present cardioprotective, hypotensive and vasodilatating effects. In light of this, the aim of the study was to investigate the effect of the ethanolic extract (Tf-EE) and of its aqueous (Tf-AQF), hexanic (Tf-HEXF) and hydroethanolic (Tf-HAF) partition fractions obtained from the stem bark of T. fagifolia Mart. & Zucc. The effects of the extract and partition fractions of T. fagifolia were evaluated on isometric tensions in the thoracic aorta rings of Wistar rats (250–300 g). Tf-EE, Tf-HEXF and Tf-HAF presented a concentration-dependent vasorelaxant effect, and Tf-AQF presented a vasorelaxant effect that was more potent in the presence of endothelium. The relaxation curves of the aorta promoted by the fraction investigated were attenuated in the presence of the following pharmacological tools: L-NAME, ODQ or PTIO. The vasorelaxant effect of the aorta promoted by Tf-AQF was attenuated in the presence of TEA and 4-AP. Tf-EE induced a concentration-dependent and endothelium-independent vasorelaxation. Tf-HAF and Tf-HEXF presented concentration-dependent and vascular-endothelium-independent vasorelaxation, but did not obtain 100% of relaxation. On the other hand, Tf-AQF presented concentration-dependent vasorelaxation that was more potent in aorta rings with vascular endothelium. The relaxant mechanism induced by the Tf-AQF involves the NO/sGC/cGMP pathway and channels Kv.