Contraction Of Rat Aorta Research Articles

Saponins from seeds of Zizyphus jujuba Mill. var. spinosa exhibit vasorelaxant effects on rat isolated aorta

AbstractAimThe vasorelaxant saponins jujuboside A(1), A1(2), B(3), and acetyljujuboside B(4) were isolated from 50% MeOH extracts of seeds of Zizyphus jujuba Mill. var. spinosa Hu ex H.F. Chou (Rhamnaceae), and their effects were studied using isolated rat aortic rings.MethodDried jujube seeds were crushed and extracted with 50% MeOH, and the extracts were concentrated under reduced pressure. Vasorelaxant effects of this extracts were assessed on rat isolated aorta rings. The aorta rings were placed in a well‐oxygenated bath of modified Krebs–Henseleit solution and the mechanical tension was measured isometrically.ResultsThe crude extract was fractionated by chromatographic methods with the guidance of vasorelaxant activity, and four saponins (1~4) were isolated. These compounds were identified using nuclear magnetic resonance (NMR) studies. Compounds 1~4 showed slow relaxation activity against norepinephrine (NE)‐induced contractions of rat aorta with/without endothelium. Treatment with 1~4 did not significantly inhibit NE‐induced vasoconstrictions. Compounds 1~4 inhibited vasoconstriction induced by high‐concentration potassium (60 mM) and NE in the presence of nicardipine but did not affect phorbol 12‐myristate 13‐acetate‐induced vasoconstriction.ConclusionThese results suggest that inhibition of NE‐induced vasoconstriction by 1~4 is due to the inhibition of receptor‐operated Ca2+ channels and voltage‐dependent Ca2+ channels or inhibition of intracellular calcium modulations.

Role of protein kinase D1 in vasoconstriction and haemodynamics in rats

AimsProtein kinase D (PKD), once considered an effector of protein kinase C (PKC), now plays many pathophysiological roles in various tissues. However, little is known about role of PKD in vascular function. We investigated the role of PKD in contraction of rat aorta and human aortic smooth muscle cells (HASMCs) and in haemodynamics in rats. Methods and resultsIsometric tension of rat aortic was measured to examine norepinephrine-induced contraction in the presence of PKD, PKC and Rho-kinase inhibitors. Phosphorylation of PKD1, myosin targeting subunit-1 (MYPT1), myosin light chain (MLC), CPI-17 and heat-shock protein 27 (HSP27), and actin polymerization were measured in the aorta. Phosphorylation of MYPT1 and MLC was also measured in HASMCs knocked down with specific siRNAs of PKD 1, 2 and 3. Intracellular calcium concentrations and cell shortening were measured in HASMCs.Norepinephrine-induced aortic contraction was accompanied by increased phosphorylation of PKD1, MYPT1 and MLC and actin polymerization, all of which were attenuated with PKD inhibitor CRT0066101. PKD1 phosphorylation was not inhibited by PKC inhibitor, chelerythrine or Rho kinase inhibitor, fasudil. In HASMCs, the phosphorylation of MYPT1 and MLC was attenuated by PKD1, but not PKD2, 3 knockdown. In HASMCs, CRT0066101 inhibited norepinephrine-induced cell shortening without affecting calcium concentration. Administration of CRT0066101 decreased systemic vascular resistance and blood pressure without affecting cardiac output in rats. ConclusionsPKD1 may play roles in aorta contraction and haemodynamics via phosphorylation of MYPT1 and actin polymerization in a calcium-independent manner.

Involvement of α1B-adrenoceptors and Rho kinase in contractions of rat aorta and mouse spleen.

α1-adrenoceptors link via the G-protein Gq/G11 to both Ca2+ entry and release from stores, but may also activate Rho kinase, which causes calcium sensitization. This study aimed to identify the subtype(s) of α1-adrenoceptor involved in Rho kinase-mediated responses in both rat aorta and mouse spleen, tissues in which contractions involve multiple subtypes of α1-adrenoceptor. Tissues were contracted with cumulative concentrations of noradrenaline (NA) in 0.5 log unit increments, before and in the presence of an antagonist or vehicle. Contractions produced by NA in rat aorta are entirely α1-adrenoceptor mediated as they are competitively blocked by prazosin. The α1A-adrenoceptor antagonist RS100329 had low potency in rat aorta. The α1D-adrenoceptor antagonist BMY7378 antagonized contractions in rat aorta in a biphasic manner: low concentrations blocking α1D-adrenoceptors and high concentrations blocking α1B-adrenoceptors. The Rho kinase inhibitor fasudil (10 μM) significantly reduced aortic contractions in terms of maximum response, suggesting inhibition of α1B-adrenoceptor mediated responses. In the mouse spleen, a tissue in which all 3 subtypes of α1-adrenoceptor are involved in contractions to NA, fasudil (3 μM) significantly reduced both early and late components to the NA contraction, the early component involving α1B- and α1D-adrenoceptors, and the late component involving α1B- and α1A-adrenoceptors. This suggests that fasudil inhibits α1B-adrenoceptor mediated responses. It is concluded that α1D- and α1B-adrenoceptors interact in rat aorta and α1D-, α1A- and α1B-adrenoceptors interact in the mouse spleen to produce contractions and these interactions suggest that one of the receptors preferentially activates Rho kinase, most likely the α1B-adrenoceptor.

Effects of RS17053 on α1 -adrenoceptors in rat vas deferens and aorta.

RS17053 is classed as an α1A -adrenoceptor selective antagonist. We have examined its profile of action at all subtypes of α1 -adrenoceptor. Noradrenaline (NA) evoked contractions of rat vas deferens involve α1D -adrenoceptors in phasic contractions and α1A -adrenoceptors in tonic contractions. Contractions of rat aorta to NA involve α1D - and α1B -adrenoceptors. RS17053 (10-5 M) shifted NA potency and virtually abolished tonic contractions to NA, with little or limited effect on phasic contractions. The α1D -adrenoceptor antagonist BMY7378 (3 × 10-7 M) significantly inhibited the remaining phasic component of the contractions, and the α1A -adrenoceptor antagonist RS100329 (10-7 M) inhibited further the residual tonic contraction. Hence, RS17053 shows high selectivity for α1A -adrenoceptors over α1D -adrenoceptors in rat vas deferens. However, RS17053 (10-5 M) produced a large shift in the potency of NA in rat aorta, with a pKB of 6.82. Large shifts of NA potency in rat aorta involve α1B -adrenoceptor blockade. Results in rat vas deferens demonstrate low potency of RS17053 at α1D -adrenoceptors, but results from rat aorta can only be explained as demonstrating α1B -adrenoceptor antagonism by RS17053. RS17053 may be a useful pharmacological tool when reclassified as a mainly α1A - and to a lesser extent α1B -adrenoceptor antagonist with little effect at α1D -adrenoceptors.

Vasoconstrictor and hemodynamic effects of a methanolic extract from Rhinella marina toad poison

Rhinella marina toad is abundant in Brazil. Its poison contains cardiac glycosides called bufadienolides, which are extensively investigated for their bioactivity. Our aim was to characterize the vasoactivity of Rhinella marina poison (RmP) on the aorta of male Wistar rats. For this, the RmP was first collected and processed to obtain an alcoholic extract. To determine cardiovascular effects of RmP, we performed in vivo tests by administering RmP intravenously in doses of 0.1–0.8 mg/kg. Vascular reactivity was also performed through concentration-response curves to RmP (10 ng/mL to 200 μg/mL) in aortic segments with and without endothelium. RmP induced a concentration-dependent contraction in rat aorta which was partly endothelium-mediated. Nitric oxide contributes with this response in view that incubation with L-NAME increased the contractile response. Additionally, treatment with indomethacin [cyclooxygenase, (COX) inhibitor], nifedipine (L-type voltage-gated calcium channels blocker), and BQ-123 (ETA receptors antagonist) decreased maximum response, and ketanserin (5-HT2 receptors antagonist) decreased pEC50, suggesting active participation of these pathways in the contractile response. On the other hand, apocynin (NADPH oxidase inhibitor) did not alter contractility. Incubation with prazosin (α1-adrenergic receptor antagonist) abolished the contractile response, suggesting that the RmP-induced contraction is dependent on the adrenergic pathway. In the Na+/K+ ATPase protocol, a higher Emax was observed in the RmP experimental group, suggesting that RmP potentiated Na+/K+ATPase hyperpolarizing response. When this extract was injected (i.v.) in vivo, increase in blood pressure and decrease in heart rate were observed. The results were immediate and transitory, and occurred in a dose-dependent manner. Overall, these data suggest that the poison extract of R. marina toad has an important vasoconstrictor action and subsequent vasopressor effects, and its use can be investigated to some cardiovascular disorders.

Effects of the Rho Kinase Inhibitor Fasudil on Adrenergic Contractions of Rat Aorta and Mouse Spleen

G‐protein coupled receptors such as α1‐adrenergic receptors (AR) are linked via the G‐protein Gq/G11 to both Ca2+ entry and release of Ca2+ from stores, but can also activate the small GTP binding protein RhoA and Rho kinase to produce contractions involving Ca2+ sensitization. In rat portal vein, tonic but not phasic components of contractions to the α1‐AR agonist phenylephrine involve predominantly the α1B‐AR subtype, and are at least partly mediated by mechanisms involving Rho kinase sensitive to fasudil (Alsufyani & Docherty, 2021). In this study we examined the involvement of Rho Kinase in contractions involving α1‐AR in two further tissues to investigate the predominant α1‐AR subtype involved. We have examined the Rho kinase inhibitor fasudil in rat aorta and mouse spleen, tissues containing multiple α1‐AR subtypes. Male Wistar rats (250‐300g) and C57 mice were killed by CO2 overdose and cervical dislocation, and rat aortic rings and mouse spleens were mounted in organ baths under 0.5 g tension, and bathed with Krebs‐Henseleit solution at 37oC. Tissues were contracted with cumulative additions of norepinephrine (NE) in 0.5 log unit increments, over the concentration range 10‐8‐10‐3M. Both α2‐ and α1‐ARs mediate contractions of mouse spleen and the major α1‐AR involved is the α1B‐adrenoceptor, and this receptor interacts with an α1D‐AR at low, and an α1A‐AR at high, NE concentrations (Alsufyani et al., 2021). In mouse spleen, fasudil (3 μM) reduced contractions to both low and high concentrations of NE. In rat aorta, contractions to NE are reported to be mediated by two subtypes of α1‐AR: α1B‐ and α1D‐ARs, with responses to low but not high concentrations of NE being sensitive to the antagonist BMY7378. Responses to high concentrations of NE in rat aorta are sensitive to the non‐selective α1‐AR antagonist prazosin and the putative α1B‐AR antagonist cyclazosin. Fasudil (3 and 10 μM) significantly reduced contractions to both low and high concentrations of NE in rat aorta in a dose dependent manner in terms of maximum response. It is concluded that α1‐AR mediated contractions to NE in both rat aorta and mouse spleen are sensitive to non‐competitive block by the Rho kinase inhibitor fasudil in concentrations of 3‐10 μM. Although multiple subtypes of α1‐adrenoceptor are involved in contractions of both rat aorta and mouse spleen, the evidence suggests that, as previously reported in rat portal vein, α1B‐adrenoceptors are most likely linked to the Rho kinase pathwayAlsufyani HA & Docherty, J.R. Can J Physiol Pharmacol. 2021 Jun;99(6):654‐659. Alsufyani HA, et al. Basic Clin Pharmacol Toxicol. 2021 Dec;129(6):416‐426.

Improved nonclinical safety profile of a novel, highly selective inhibitor of the immunoproteasome subunit LMP7 (M3258)

M3258 is the first selective inhibitor of the immunoproteasome subunit LMP7 (Large multifunctional protease 7) in early clinical development with the potential to improve therapeutic utility in patients of multiple myeloma (MM) or other hematological malignancies. Safety pharmacology studies with M3258 did not reveal any functional impairments of the cardiovascular system in several in vitro tests employing human cardiomyocytes and cardiac ion channels (including hERG), guinea pig heart refractory period and force contraction, and rat aortic contraction as well as in cardiovascular function tests in dogs. Following single dose M3258 administration to rats, no changes were observed on respiratory function by using whole body plethysmography, nor did it change (neuro)behavioral parameters in a battery of tests. Based on pivotal 4-week toxicity studies with daily oral dosing of M3258, the identified key target organs of toxicity were limited to the lympho-hematopoietic system in rats and dogs, and to the intestine with its local lymphoid tissues in dogs only. Importantly, the stomach, nervous system, heart, lungs, and kidneys, that may be part of clinically relevant toxicities as reported for pan-proteasome inhibitors, were spared with M3258. Therefore, it is anticipated that by targeting highly selective and potent inhibition of LMP7, the resulting favorable safety profile of M3258 together with the maintained potent anti-tumor activity as previously reported in mouse MM xenograft models, may translate into an improved benefit-risk profile in MM patients.

Docosahexaenoic acid inhibits U46619- and prostaglandin F2α-induced pig coronary and basilar artery contractions by inhibiting prostanoid TP receptors

Docosahexaenoic acid (DHA, an n-3 polyunsaturated fatty acid) inhibits U46619 (a TP receptor agonist)- and prostaglandin F2α-induced contractions in rat aorta and mesenteric arteries. However, whether these effects could be replicated in vasospasm-prone vessels, such as coronary and cerebral arteries, remains unknown. Here, we evaluated the changes in pig coronary and basilar artery tensions and intracellular Ca2+ concentrations in human prostanoid TP or FP receptor-expressing cells. We aimed to clarify whether DHA inhibits U46619- and prostaglandin F2α-induced contractions in spasm-prone blood vessels and determine if the TP receptor is the primary target for DHA. In both pig coronary and basilar arteries, DHA suppressed U46619- and prostaglandin F2α-induced sustained contractions in a concentration-dependent manner, but did not affect contractions induced by 80 mM KCl. SQ 29,548 (a TP receptor antagonist) suppressed U46619- and prostaglandin F2α-induced contractions by approximately 100% and 60%, respectively. DHA suppressed both U46619- and prostaglandin F2α-induced increases in intracellular Ca2+ concentrations in human TP receptor-expressing cells. However, DHA did not affect prostaglandin F2α-induced increases in intracellular Ca2+ concentrations in human FP receptor-expressing cells. These findings suggest that DHA potently inhibits TP receptor-mediated contractions in pig coronary and basilar arteries, and the primary mechanism underlying its inhibitory effects on arterial contractions involves inhibiting TP receptors.

Effects Of F-18 On KCL And Phenylephrine - Induced Contractions Of Rat Aorta

The mechanism of action of the alkaloid 1-(2´-bromine-4´,5´-dimethoxyphenyl) - 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (F-18) on the functional activity of smooth muscle cells of the rat aorta was studied. Isometric contraction activity was recorded using a Grass FT – 03 (Grass Instrument, USA) mechanotron. The relaxant effect of the F-18 alkaloid was found to be associated with blockade of Ca2 + (IP3R) channels in the SR, along with voltage- dependent and receptor-operated Ca2+channels in the aorta smooth muscle cell plasmalemma.

Indoxyl sulfate enhances endothelin-1-induced contraction via impairment of NO/cGMP signaling in rat aorta.

The microbiome-derived tryptophan metabolite, indoxyl sulfate, is considered a harmful vascular toxin. Here, we examined the effects of indoxyl sulfate on endothelin-1 (ET-1)-induced contraction in rat thoracic aortas. Indoxyl sulfate (10-3 M, 60 min) increased ET-1-induced contraction but did not affect isotonic high-K+-induced contraction. The ET-1-induced contraction was enhanced by endothelial denudation in both control and indoxyl sulfate-treated groups. BQ123 (10-6 M), an ETA receptor antagonist, reduced the ET-1-induced contraction in both control and indoxyl sulfate groups. BQ788 (10-6 M), an ETB receptor antagonist, increased the contraction in the control group but had no effect on the indoxyl sulfate group. Conversely, indoxyl sulfate inhibited relaxation induced by IRL1620, an ETB receptor agonist. L-NNA, an NO synthase (NOS) inhibitor, increased the ET-1-induced contractions in both the control and indoxyl sulfate groups, whereas L-NPA (10-6 M), a specific neuronal NOS inhibitor, did not affect the ET-1-induced contraction in both groups. However, ODQ, an inhibitor of soluble guanylyl cyclase, increased the ET-1-induced contraction in both groups. Organic anion transporter (OAT) inhibitor probenecid (10-3 M) and antioxidant N-acetyl-L-cysteine (NAC; 5 × 10-3 M) inhibited the effects of indoxyl sulfate. A cell-permeant superoxide scavenger reduced the ET-1-induced contraction in the indoxyl sulfate group. The aortic activity of SOD was reduced by indoxyl sulfate. The present study revealed that indoxyl sulfate augments ET-1-induced contraction in rat aortae. This enhancement may be due to the impairment of NO/cGMP signaling and may be attributed to impairment of the antioxidant systems via cellular uptake through OATs.

The effects of folic acid on vascular reactivity in a hyperhomocysteinemic rat model

Abstract
 Objective: This study aimed to investigate the antioxidant effects of folic acid and its effects on contraction and relaxation responses in rat aorta in hyperhomocysteinemic rats.
 Methods: Thirty-four male Wistar Albino rats were allocated into four groups. Rats in the hyperhomocysteinemia group (Group 1, n=9) received 1g/kg/day methionine via orogastric gavage for 30 days and then injected with intraperitoneal saline for the next 7 days. In the hyperhomocysteinemia+folic acid group (Group 2, n=9), following the administration of methionine for 30 days, folic acid (4mg/kg/day) was delivered intraperitoneally for 7 days. Sham group rats (Group 3, n=8) received orogastric saline for 30 days, which was followed by an IP injection of saline for another 7 days. Animals allocated into the folic acid group (Group 4, n= 7) had orogastric saline for 30 days and intraperitoneal folic acid for 7 days. After 5 weeks of treatment, blood samples were obtained, all animals were sacrificed, and hearts were harvested. Thoracic aortic segments were suspended on individual organ baths, and acetylcholine-induced (endothelium-dependent) relaxation responses of isolated aortic rings were evaluated. 
 Results: Relaxation responses in Group 1 thru 4 were 73.889.96, 76.159.28, 76.618.83, and 69.2615.68, respectively. There was no significant difference in the organ bath in terms of relaxation response to acetylcholine at a dose of 10-9 mM between the groups (F=0.716, p=0.550). 
 Conclusion: Folic acid therapy failed to produce a significant improvement in vascular reactivity. 
 Keywords: Hyperhomocysteinemia, folic acid, vascular reactivity

Abstract P061: Identification Of Piezo1 Channels In Perivascular Adipose Tissue (pvat) And Their Potential Role In Vascular Function

The vasculature constantly experiences distension/pressure exerted by the blood and responds accordingly to maintain homeostasis. Perivascular adipose tissue (PVAT) is gaining support as a formal blood vessel layer and also experiences these changes. We hypothesized that activation of the mechanotransducer Piezo1 directly increases vascular contraction in a way that might be modified by PVAT. The presence of Piezo1 was investigated at the mRNA level via PCR; protein via immunohistochemistry; and contractility via isolated tissue bath. Rat superior and mesenteric arteries, thoracic aortae, human mesenteric vessels and their PVATs were studied. Piezo1 mRNA (beta2 microglobulin calibrator) was expressed in the aortic vessel (2 -ΔC T =0.011); aortic PVAT (2 -ΔC T =0.0172); mesenteric vessel (2 -ΔC T =.00302), and mesenteric PVAT (2 -ΔC T =0.0219). Both adipocytes (2 -ΔC T =0.0249) and stromal vascular fraction (2 -ΔC T =0.0159) of mesenteric PVAT expressed Piezo1 mRNA. Piezo1 mRNA expression was greater in magnitude (one-way ANOVA) than that of the mechanotransducers Piezo2, TRPV4, TMEM16, and Panx1. Piezo1 protein was present in rat aortic PVAT, rat mesenteric (mes) artery, vein, and PVAT, as well as in human artery, vein, and PVAT. The Piezo1 agonists Yoda and Jedi (1 nM - 10 μM) did not stimulate rat aortic contraction [max <10% phenylephrine (PE) 10 μM contraction] or relaxation independent from vehicle in tissues + or - PVAT (relaxation as % of half maximal PE contraction was: Veh-PVAT=45.3±7.0; Yoda-PVAT=46.7±25.6; Jedi-PVAT= 40.4±10.3; Veh+PVAT= 71.8±19.7; Jedi+PVAT=39.1±13.2; Yoda +PVAT=21.6±10.9). Slightly K+ depolarizing the aorta did not unmask contraction to Yoda. Finally, the Piezo1 antagonist Dooku [10 μM] did not shift the PE curve (-log EC50 values [M]: Veh-PVAT= 7.96±0.12; Dooku-PVAT=7.26±0.22, Veh+PVAT=7.29±0.08; Dooku+PVAT=6.96±0.07). Surprisingly, Dooku [10 μM] directly caused aortic contraction in the absence of PVAT (Dooku 27.2±11.7 vs vehicle 13.5±11.2 %PE contraction), but not in the presence of PVAT vs vehicle (Dooku 2.9±1.9 vs Vehicle 7.3±5.2% PE contraction). Thus, Piezo1 is present and functional in the isolated aorta, important knowledge given that this molecule may serve as a translator of vascular pressure.

The Role of Two-Pore Channels in Norepinephrine-Induced [Ca2+]i Rise in Rat Aortic Smooth Muscle Cells and Aorta Contraction.

Second messenger nicotinic acid adenine dinucleotide phosphate (NAADP) triggers Ca2+ release via two-pore channels (TPCs) localized in endolysosomal vesicles. The aim of the present work is to evaluate the role of TPCs in the action of norepinephrine (NE), angiotensin II (AngII), vasopressin (AVP), and 5-hydroxytriptamine (5-HT) on free cytoplasmic calcium concentration ([Ca2+]i) in smooth muscle cells (SMCs) isolated from rat aorta and on aorta contraction. To address this issue, the NAADP structural analogue and inhibitor of TPCs, NED 19, was applied. We have demonstrated a high degree of colocalization of the fluorescent signals of cis-NED 19 and endolysosmal probe LysoTracker in SMCs. Both cis- or trans-NED 19 inhibited the rise of [Ca2+]i in SMCs induced by 100 μM NE by 50–60%. IC50 for cis- and trans-NED 19 were 2.7 and 8.9 μM, respectively. The inhibition by NED 19 stereoisomers of the effects of AngII, AVP, and 5-HT was much weaker. Both forms of NED 19 caused relaxation of aortic rings preconstricted by NE, with relative potency of cis-NED 19 several times higher than that of trans-NED 19. Inhibition by cis-NED 19 of NE-induced contraction was maintained after intensive washing and slowly reversed within an hour of incubation. Cis- and trans-NED 19 did not cause decrease in the force of aorta contraction in response to Ang II and AVP, and only slightly relaxed aorta preconstricted by 5-HT and by KCl. Suppression of TPC1 in SMCs with siRNA caused a 40% decrease in [Ca2+]i in response to NE, whereas siRNA against TPC2 did not change NE calcium signaling. These data suggest that TPC1 is involved in the NE-stimulated [Ca2+]i rise in SMCs. Inhibition of TPC1 activity by NED 19 could be the reason for partial inhibition of aortic rings contraction in response to NE.

Propofol Relaxes Isolated Rat Aorta through BKCa Activation

Propofol is an intravenous anesthetic that can be used for the induction and maintenance of anesthesia. In the present study, it was aimed to investigate the mechanism of vasodilator action of propofol in the rat aorta (RA). The RA rings were suspended in isolated organ baths and tension was recorded isometrically. First, potassium chloride (KCl) and phenylephrine (PE) were added to organ baths to form precontraction. When the precontractions were stable, propofol (1, 10, and 100μM) was added cumulatively to the baths. The antagonistic effect of propofol on KCl (45mM), PE (1μM), 5-hydroxytryptamine (5-HT) (30μM), and calcium chloride (CaCl2) (10μM to 10mM) induced contractions in the vascular rings were investigated. Propofol-induced relaxations were alsotested in the presence of the K+ channel inhibitors tetraethylammonium (TEA, 1mM), glibenclamide (GLI, 10μM), 4-aminopyridine (4-AP, 1mM), and barium chloride (BaCl2, 30μM). Preincubation with propofol (1, 10, and 100μM) did not affect the basal tone but inhibited the contraction induced by KCl, PE, 5-HT, and CaCl2-induced contractions. Propofol-induced relaxation was not effected by 4-AP, GLI, and BaCl2. However, TEA inhibited propofol-induced relaxations significantly. The propofol induces relaxation in contracted RA and inhibits KCl, PE, 5-HT, andCaCl2-induced contractions. The results demonstrate that the mechanism of action of propofol-induced vasodilation in the RA may be related to large conductance Ca2+-activated K+ channel activation.

Endothelium-independent vasodilator effects of nobiletin in rat aorta

Nobiletin is a one of the polymethoxyflavones contained in the peel of citrus fruits, such as Citrus depressa. In this study, the effect of nobiletin-induced relaxation on phenylephrine (PE)-induced contraction of endothelium-denuded rat aorta was investigated. Nobiletin inhibited PE- or KCl-induced contractions in a concentration-dependent manner in endothelium-intact and -denuded aortas. However, this relaxation was stronger in PE-induced contractions than in KCl-induced contractions; moreover, the nobiletin-induced relaxation was significantly increased on PE-induced contraction in endothelium-intact aorta. ODQ significantly inhibited the nobiletin-induced relaxation in endothelium-denuded aorta; however, SQ22536 did not affect the relaxation. In addition, IBMX synergistically enhanced the nobiletin-induced relaxation. Nobiletin increased cGMP levels in aorta. Also, IBMX significantly increased cGMP content in aorta, and ODQ significantly reduced cGMP levels. Nobiletin-induced relaxation was significantly inhibited by the Ca2+-activated K+ (BK) channel inhibitor iberiotoxin (IbTX) and the ATP-sensitive K+ (KATP) channel inhibitor glybenclamide. Sodium nitroprusside-induced relaxation was suppressed by IbTX, but not by glybenclamide. These results suggest that nobiletin inhibits PE-induced contractions of endothelium-denuded rat aorta by increasing cGMP levels via GC activation. Moreover, the present findings indicate the possibility that nobiletin opened BK channels by a cGMP-related signal, but KATP channels were opened by a cGMP-nonrelated signal in rat aorta.

Endothelial-Dependent and Independent Vascular Relaxation Effect of Tetrahydropalmatine on Rat Aorta.

Tetrahydropalmatine (THP) is an active natural alkaloid isolated from Corydalis yanhusuo W.T. Wang which has been widely used for treating pain and cardiovascular disease in traditional Chinese medicine. Previous studies suggested THP have various pharmacological effects in neural and cardio tissue while the vascular reactivity of THP was not fully established. The present study found that THP relaxed rat aorta which contracted by phenylephrine (Phe), KCl, and U46619. The vascular relaxation effect of THP was partially attenuated by PI3K inhibitor wortmannin, Akt inhibitor IV, endothelial nitric oxide synthetase (eNOS) inhibitor L-NAME, guanylate cyclase inhibitors and the mechanical removal of endothelium. Also, the eNOS substrate L-arginine reversed the inhibition effect of L-NAME on THP-induced vascular relaxation. THP also induced intracellular NO production in human umbilical vein endothelial cells. However, Pre-incubation with β-adrenergic receptor blocker propranolol, angiotensin II receptor 1 (AT1) inhibitor losartan, angiotensin II receptor 2 (AT1) inhibitor PD123319 or angiotensin converting enzyme inhibitor enalapril enhanced the vascular relaxation effect of THP. THP did not affect the angiotensin II induced vascular contraction. Cyclooxygenase-2 (COX2) inhibitor indomethacin did not affect the vascular relaxation effect of THP. Furthermore, pre-treatment THP attenuated KCl and Phe induced rat aorta contraction in standard Krebs solution. In Ca2+ free Krebs solution, THP inhibited the Ca2+ induced vascular contraction under KCl or Phe stress and reduced KCl stressed Ca2+ influx in rat vascular smooth muscle cells. THP also inhibited intracellular Ca2+ release induced vascular contraction by blocking Ryr or IP3 receptors. In addition, the voltage-dependent K+ channel (Kv) blocker 4-aminopyridine, ATP-sensitive K+ channel (KATP) blocker glibenclamide and inward rectifying K+ channel blocker BaCl2 attenuated THP induced vascular relaxation regardless of the Ca2+-activated K+ channel (KCa) blocker tetraethylammonium. Thus, we could conclude that THP relaxed rat aorta in an endothelium-dependent and independent manner. The underlying mechanism of THP relaxing rat aorta involved PI3K/Akt/eNOS/NO/cGMP signaling path-way, Ca2+ channels and K+ channels rather than COX2, β-adrenergic receptor and renin-angiotensin system (RAS). These findings indicated that THP might be a potent treatment of diseases with vascular dysfunction like hypertension.

Role of Calcium Sensitization in 5‐Hudroxytryptamine‐Induced Contraction of Rat Aorta with or without Perivascular Adipose Tissue

We have previously shown that the perivascular adipose tissue (PVAT) exerted an anti‐contractile effect against 5‐hydroxytryptamine (5‐HT)‐induced contraction of aorta segments from pregnant and non‐pregnant rats. This anti‐contractile effect was significantly reduced in aorta segments from pregnant rats. In the present investigation, we have examined the possible role of calcium sensitization involving ROCK and PKC in this loss of anti‐contractile effect of PVAT. Both Y‐27632 (10−6M) and GF 109203X (10−6M), inhibitors of calcium sensitization, significantly reduced 5‐HT‐induced contractions of PVAT‐free aorta segments from non‐pregnant and pregnant rats. However, they were less effective in aorta segments from pregnant rats. PVAT reduced the effectiveness of Y‐27632 and GF 109203X in aorta segments from pregnant and non‐pregnant rats. ROCK‐I and ROCK‐II protein were expressed in aorta segments and PVAT from pregnant and non‐pregnant rats. There was a reduction in the expression of both isoforms in aorta segments but not PVAT from pregnant rats. In addition, there was no significant difference in the expression of ROCK‐I and ROCK‐II in PVAT from pregnant and non‐pregnant rats. We concluded that the loss of anti‐contractile effect of PVAT in aorta segments from pregnant rats could not be explained by altered calcium‐sensitization mechanisms.Support or Funding InformationResearch Sector, Kuwait University, KuwaitThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Dental resin curing blue light induces vasoconstriction through release of hydrogen peroxide

Dental resin curing blue light (BL) is frequently used during treatments in dental clinics. However, little is known about the influence of BL irradiation on pulpal blood vessels. The aim of the present study was to investigate the mechanism of effect of BL irradiation on vascular tone. Rat aorta (RA) rings were irradiated with a BL source in organ baths, and the responses were recorded isometrically. Effect of BL irradiation on phenylephrine (PE) -precontraction and acetylcholine (ACh) -induced relaxation after PE -precontraction were obtained and compared in BL -irradiated and control RA rings. Effect of 20 min preincubation with catalase (enzyme that breaks down hydrogene peroxide, 1200 u/ml) on PE -precontraced and BL-irradiated rings was also evaluated. Total oxidative stress (TOS) and total antioxidant capacity (TAC) in BL-irradiated and control RA preparations were measured with special assay kits and spectrophotometry. BL slightly decreased ACh -induced endothelium -dependent relaxations in PE (1 μM) -precontracted RA rings (n = 6, p > 0.05 vs. control). BL induced marked contraction 23.88 + 3.10% of PE (maximum contraction) in isolated RA ring segments precontracted with PE (p < 0.05 vs. control). The contractile effect of BL was inhibited by 1200 u/ml catalase (n = 6, p < 0.05 vs. control). BL irradiation increased the level of TOS in RA rings (n = 6, p < 0.05 vs. control). TAC levels were similar in BL-irradiated and control preparations. These results suggest that BL induces contraction in RA, and the mechanism of this effect may to be through release of hydrogen peroxide.

Quercetin-Induced AMP-Activated Protein Kinase Activation Attenuates Vasoconstriction Through LKB1-AMPK Signaling Pathway.

The vascular tone plays an important role in blood pressure and flow. It is influenced by the contraction of vascular smooth muscle cells (VSMCs), which in turn is regulated by the balance between the myosin light chain kinase (MLCK) and the phosphorylated myosin light chain (p-MLC). Quercetin is a common flavonoid which is found in many fruits and red wine. Although quercetin has been widely reported to be involved in cell proliferation, migration, and apoptosis in VSMCs, it has not yet been demonstrated whether quercetin is related to vasocontraction, a function regulated by the AMP-activated protein kinase (AMPK) signaling pathway. Accordingly, the aim of this study is to investigate the molecular mechanism through which the quercetin-activated LKB1-AMPK signaling pathway regulates the contraction of VSMCs. In cultured VSMCs, quercetin activated AMPK in a dose- and time-dependent manner. Quercetin inhibited the phenylephrine (PE)-induced expression of MLCK and p-MLC through the LKB1-AMPK signaling pathway and decreased the mRNA level of MLCK. Adenovirus-AMPK DN α1 and AMPK DN α2-transduced VSMCs displayed higher p-MLC expression. Moreover, quercetin inhibited the PE-mediated contraction in rat aorta. These data suggest that the quercetin-activated LKB1-AMPK signaling pathway regulates VSMC contraction by inhibiting MLCK and p-MLC; hence, it may be a therapeutic intervention for the treatment of cardiovascular disorders such as atherosclerosis and hypertension.

Gem-Dinitroalkyl Benzenes: A Novel Class of IOP-Lowering Agents for the Treatment of Ocular Hypertension.

Primary open angle glaucoma is the second most common cause of blindness worldwide. Nitric oxide has recently received particular attention as a potential antiglaucoma agent. In this work, gem-dinitroalkyl benzenes are evaluated for their capability to act as a new class of IOP lowering agents. These derivatives have been endowed with a variety of NO-release capacities and found to relax contracted rat aorta strips in a concentration-dependent manner. They have been studied for their IOP-lowering activity in a transient ocular hypertensive rabbit model at 1% dose. The most effective IOP-lowering products were compounds 9-11 and 13, whose activity was similar to that of Molsidomine 120 min after administration. Compounds 9 and 13 were selected for evaluation using carbomer-induced glaucoma as the chronic model of IOP. They cause a significant reduction in IOP in the first 24 h, and their activity is maintained over 5 days, displaying a Molsidomine-like profile.