Superior Mesenteric Artery Rings Research Articles

New paeonol derivative C302 reduces hypertension in spontaneously hypertensive rats through endothelium-dependent and endothelium-independent vasodilation

Hypertension is a major risk factor for cardiovascular disease and Chinese herb monomers could provide new structural skeletons for anti-hypertension new drug development. Paeonol is a Chinese herbal monomer extracted from Cortex moutan, exhibited some anti-hypertensive activity. The study focused on the structural optimization of paeonol to provide promising lead compounds for anti-hypertension new drug development. Herein, twelve new paeonol derivatives (PD) were designed and synthesized and their vasodilation activity was evaluated by in vitro vasodilation drug screening platform based on Myograph. Its anti-hypertension activity, PD-C302 (2-hydroxy-4-methoxyvalerophenone) as a representative with the optimal vasodilation activity, was determined by its response to blood pressure in spontaneously hypertensive rats (SHR) in vivo. Moreover, its molecular mechanism was probed by the vasodilation activity of rat superior mesenteric artery rings with or without endothelium pre-contracted by potassium chloride (KCl) or phenylephrine hydrochloride (PE). It was indicated that PD-C302 significantly reduced the blood pressure in SHR, which would involve in PD-C302-induced vasodilation. Furthermore, endothelium-dependent pathways and endothelium-independent pathways both contributed importantly to PD-C302-induced vasodilation at low concentration of PD-C302. Endothelium-independent pathways (vascular smooth muscle cell-mediated vasodilation), were mainly responsible for the PD-C302-induced vasodilation at high concentration of PD-C302, which involved in opening multiple K+ channels to restrain Ca2+ channels, and then triggered vasodilation to reduce blood pressure. PD-C302 has a simple structure and favorable anti-hypertensive activity in vivo, which could be a promising lead compound for anti-hypertension new drug development.

Electroacupuncture attenuates vascular hyporeactivity in a rat model of portal hypertension induced by bile duct ligation.

A hyperdynamic circulation and impaired vascular responsiveness to vasoconstrictors are observed in portal hypertension (PHT) rats. Inflammation is a major contributor to the hyperdynamic circulation state in murine models of PHT. Electroacupuncture (EA) may ameliorate the inflammatory response and limit arterial vasodilatation and portal pressure. This study investigated the possible mechanisms underlying putative hemodynamics effects of EA in normal and PHT rats. PHT was induced by bile duct ligation (BDL) surgery over 4 weeks in rats. Sham-operated and BDL rats were treated with low-frequency EA (2 Hz) at ST36 10 min three times weekly for one or two consecutive weeks (for a total of 3 or 7 treatments, respectively). Serum tumor necrosis factor-α (TNF-α), nitrite/nitrate (NOx) and 6-keto-prostaglandin F1α (6-keto-PGF1α) were analyzed, and hemodynamic variation and contractile responses to phorbol-12,13-dibutyrate and phenylephrine in aortic and superior mesenteric arterial rings were recorded. Inducible (i) and endothelial (3) nitric oxide synthase (NOS), cyclooxygenase-1 (COX-1), and protein kinase C-α (PKC-α) levels were determined by Western blotting. EA significantly reduced portal pressure and serum TNF-α, NOx and 6-keto-PGF1α levels compared to the untreated BDL group, enhanced maximum contractile responses in the aorta, up-regulated PKC-α, and down-regulated iNOS and COX-1 levels. In addition, EA decreased the aortic angiogenesis signaling cascade, reflected by down-regulation of vascular endothelial growth factor (VEGF) abundance and transforming growth factor β receptor (TGFβR)I/II expression, as assessed by immunostaining. EA attenuates TNF-α, NO and 6-keto-PGF1α overproduction, modulates the vascular levels of constitutive NOS and PKC-α, blunts the development of the angiogenesis cascade, and enhances vascular contractile force in PHT rats.

Vasorelaxant Effect Induced by the Essential Oil of Ocotea duckei Vattimo Leaves and Its Main Constituent, Trans-caryophyllene, in Rat Mesenteric Artery

Aims: To evaluate the vasorelaxant effect induced by the essential oil of the leaves of O. duckei Vattimo (ODEO) and its main constituent, trans-caryophyllene, in rat superior mesenteric arteries.
 Methodology: Isolated rat superior mesenteric rings were suspended by cotton threads for isometric tension recordings in Tyrode’s solution at 37ºC, gassed with 95% O2 and 5% CO2 and different ODEO concentrations (0.1-300 μg/mL) or trans-caryophyllene (1-1000 μg/mL) were added cumulatively to the organ baths.
 Results: Vasorelaxant effect induced by the essential oil of Ocotea duckei leaves (ODEO) and its main constituent, trans-caryophyllene (60.54 %), was evaluated in this work. In intact isolated rat superior mesenteric rings ODEO (0.1-300 μg/mL, n=6) induced concentration-dependent relaxation of tonus induced by phenylephrine (10 µM) or K+-depolarizing solution (KCl 80 mM) (IC50=31±5, 5±0.4 µg/mL, respectively, n=6). The relaxations of phenylephrine-induced contractions were not significantly attenuated after removal of the vascular endothelium (IC50=25±5 µg/mL). ODEO antagonized the concentration-response curves to CaCl2 (10-6-3x10-2 M) and Bay K 8644 (10-10-3x10-6 M). Furthermore, in nominally without calcium solution, ODEO significantly inhibited, in a concentration-dependent manner, transient contractions induced by 10 µM phenylephrine or 20 µM caffeine. Trans-caryophyllene induced vasorelaxations, however, this effect was 18.6 times less potent when compared to ODEO-induced vasorelaxations.
 Conclusion: The relaxant effect induced by ODEO in rat superior mesenteric artery rings is endothelium-independent and seems to be related to both, inhibition of Ca2+ influx through L-type voltage-gated Ca2+-channels sensitive to dihydropyridines and inhibition of the calcium release from intracellular IP3-and caffeine-sensitive stores.

Pharmacokinetics and Antihypertensive effect of linalool is improved after incorporation in β‐cyclodextrin as a drug delivery system

Linalool (LIN) is a monoterpene alcohol present in some aromatic medicinal plants with biological activities that can impact cardiovascular disease. Previous studies from our research group have shown that LIN has antihypertensive activity, but as an essential oil it has some administration restrictions. The study aimed to investigate the pharmacokinetics (PK) and cardiovascular effects of LIN complexed with beta‐cyclodextrin (LIN/β‐CD) as a potential antihypertensive drug. All the experiments were conducted in accordance with FASEB statement of principles for the use of animals in research and education and approved by the ethics committee under the protocol CEUA‐ICS/UFBA n° 085/2015. For PK studies, LIN and LIN/β‐CD were administered to male normotensive wistar rats orally and LIN plasma concentrations were validated by HPLC‐UV. The individual and mean PK parameters of elimination rate, absorption rate, clearance, volume of distribution, half‐life, mean residence time, absolute bioavailability and relative bioavailability were estimated for LIN free or complexed form. For the cardiovascular experiments, spontaneously hypertensive rats (SHR) and wistar were used. Rats were randomly divided into 3 groups, each treated daily for 60 days, in the following manner: group 1 (vehicle solution); group 2 (LIN; 50 mg/kg/day); group 3 group (LIN/β‐CD; 50 mg/kg/day). Blood pressure, daily body weight and vascular reactivity were studied. The results of PK parameters showed that bioavailability of the LIN/β‐CD was approximately 20‐fold higher compared to LIN, after oral administration. Population modeling studies demonstrated that LIN/β‐CD had less tissues distribution compared to non‐complexed form, consequently remaining in the bloodstream or more irrigated organ and tissues. In addition, LIN/β‐CD, but not LIN, was able to induce acute hypotensive effect after oral administration. Furthermore, during the 60 days of chronic treatment, SHR treated with vehicle (192 ± 2.5 mmHg, p<0.05; 40th day) demonstrated progressive increase in mean arterial pressure compared to wistar normotensive rats (103 ± 5 mmHg, 40th day). However, the blood pressure of the SHR treated by LIN/β‐CD was significantly reduced during the treatment, presenting similar levels to the normotensive healthy animals (113 ± 5 mmHg; 40th day). This antihypertensive effect induced by complexed form was not observed with linalool free (167 ± 8 mmHg 40th day). Vascular reactivity assays using superior mesenteric artery rings demonstrated that LIN/β‐CD or LIN ameliorated the vascular function of SHR, increasing vasodilator responsiveness and reducing sensitivity to the sympathetic agonist. Taking together, our results suggested that incorporation of linalool into β‐cyclodextrin improved the bioavailability and antihypertensive effect of this monoterpene, making it a possible new pharmaceutical formulation for the treatment of hypertension in the future.Support or Funding InformationFIOCRUZ, National Council for Scientific and Technological Development (CNPq) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior ‐ Brasil (CAPES).

English

Hypertension is associated with endothelial dysfunction characterized by decreased vasorelaxation. Our research group recently demonstrated that hydroalcoholic extract of Syzygium cumini leaves (HESc) reduces the blood pressure in spontaneously hypertensive rats (SHR). This study evaluated the ability of HESc and chloroform fraction (CF) in promoting vasorelaxation on resistance arteries rings. Endothelium-deprived superior mesenteric artery rings were suspended in organ baths containing warm perfusion medium that was continuously bubbled with carbogen and then the vasorelaxant ability of HESc and CF were assayed. The cumulative additions of HESc (0.1 to 10 mg/mL) caused a concentration-dependent relaxant response, in precontracted preparations by NE or KCl. CF (0.1 to 1.0 mg/mL) exhibited remarkable vasorelaxant activity in preparations endothelium-denuded pre-contracted with NE, in a concentration-dependent manner. The pretreatment of TEA did not decrease significantly in relaxation. The incubation of CF (0.25 and 0.5 mg/ml) reduced in a concentration-dependent way, the Emax induced by NE in mesenteric artery, however, did not altered the pD2 of the NE. Additionally, CF promoted concentration-dependent manner, maximal effect inhibition and also led to a significant rightward shift in the concentration-response curve for Ca2+ in endothelium-denuded rings. This finding indicates that S. cumini acts as a vasorelaxant agent and interfere with the responsiveness of vascular smooth muscle cell, probably acting on the regulation of intracellular Ca2+ levels through voltage-operated calcium channels.   Key words: S. cumini, calcium channels, vasorelaxant, medicinal plant, antihypertensive.

Acidosis potentiates endothelium-dependent vasorelaxation and gap junction communication in the superior mesenteric artery

Extracellular pH is an important physiological determinant of vascular tone that is normally maintained within 7.35–7.45. Any change outside this range leads to severe pathological repercussions. We investigated the unknown effects of extracellular acidosis on relaxation in the superior mesenteric artery (SMA) of goat. SMA rings were employed to maintain isometric contractions at extracellular pH (pHo) 7.4 and 6.8. We analyzed the effect of acidosis (pHo 6.8) compared to physiological pH (pHo 7.4) on three signaling mediators of endothelium-dependent hyperpolarization: nitric oxide (NO), prostaglandin I2 (PGI2), and myoendothelial gap junctions (MEGJ). NO and cyclic guanosine monophosphate (cGMP) levels were compared between normal and acidic pH. Quantitative real-time PCR (qPCR) studies determined the change in expression of vascular connexin (Cx), Cx37, Cx40, and Cx43. Under acidosis, acetyl choline-induced relaxation was augmented in an endothelium-dependent manner via eNOS-NO-cGMP signaling. Conversely, at normal pH, acetyl choline-induced vasorelaxation was mediated primarily via COX-PGI2 pathway. The functional activity of MEGJ was increased under acidosis as evident from increased sensitivity of connexin blockers and upregulated gene and protein expression of connexins. In conclusion, acetyl choline-induced augmented vasorelaxation under acidosis is mediated by NOS-NO-cGMP, with a partial role of MEGJ as EDH mediators in the SMA. Present data suggest a novel role of connexin as therapeutic targets to attenuate the detrimental effect of acidosis on vascular tone.

Risk assessment of bis-ethylhexyloxyphenol methoxyphenyl triazine in cosmetic products

Animal toxins are natural resources for pharmacological studies. The venom of Crotalus durissus cascavella (C.d. cascavella) may be a source in the bio-prospecting of new anti-hypertensive agents. The aim of this study was to investigate vascular effects of the venom of C.d. cascavella in normotensive rats. Studies were performed using isolated mesenteric artery segments and aortic endothelial cells. The cumulative administration of the venom of C.d. cascavella (0.001–30 μg/mL) on phenylephrine (Phe; 10 μM) pre-contracted rings induced a concentration-dependent vasorelaxation in the presence of vascular endothelium (Emax = 47.9 ± 5.0% n = 8), and its effect was almost abolished in the absence of endothelium (Emax = 5.8± 2.4% n = 5 (∗∗∗p < 0.001)). Tissue viability was maintained as there was no difference in the contractile capacity of rings before and after the administration of venom. The vasorelaxant effect of the venom was also abolished when arteries were pre-contracted with potassium chloride (KCl; 80 mM) (Emax = 6.4± 0.9% n = 5, ∗∗∗p < 0.001). When assessing the participation of endothelium-derived relaxing factors, it was noted that non-selective COX inhibition with indomethacin (10 μM) caused a significant reduction in the vasorelaxant effect of C.d. cascavella (*p < 0.05). When investigating the participation of NO released by endothelium, there was a significant reduction of the vasorelaxant effect of venom in rings treated with L-NAME (100 μM; Emax = 17.5± 2.2% n = 6; **p < 0.01). Similar results were noted in the presence of ODQ (10 μM), an inhibitor of soluble guanylyl cyclase (Emax = 11.2± 3.5%, n = 6) and PTIO (100 μM), a stable radical scavenger for nitric oxide (Emax = 10.77± 3.6%, n = 6). Moreover, the venom induced the release of NO by isolated aortic endothelial cells through amperometric studies. When assessing the participation of K+ channels on the vasodilatory response of the venom, tyrode solution with 20 mM of KCl caused a significant reduction in the relaxation response (p < 0.001) (Emax = 21.3 ± 8%, n = 7), as did inhibitor of delayed rectifier K+ channels (4-amynopiridine 1 mM; Emax = 9.5 ± 1.3, %, n = 5, ***p < 0.001), and vasorelaxation was almost abolished in the presence of Iberiotoxin (IbTx 100 nM). Therefore, these results suggest that the venom of C.d. cascavella induces vasorelaxation in superior mesenteric artery rings of normotensive rats in an endothelium-dependent manner. Specifically, the venom stimulates the generation of endothelium-derived relaxing factors, especially NO, and activates vascular smooth muscle hyperpolarization through K+ channels. These data illustrate that C.d. cascavella is a source of bioactive molecules and therefore has therapeutic potential in the treatment of cardiovascular diseases such as hypertension.

The Curcumin-Induced Vasorelaxation in Rat Superior Mesenteric Arteries

Curcumin (Cur) is a natural lipophilic polyphenol compound extracted from the rhizome of turmeric. Recently, protective effect of Cur on cardiovascular system is paid close attention. Some researches demonstrated that Cur could induce vascular relaxation in many arterial beds. However, relaxant effect of Cur on rat superior mesenteric artery is not clear. This present study will investigate the vasorelaxant effect of Cur on rat superior mesenteric arteries and the mechanisms involved. The isometric tension of rat superior mesenteric arterial rings was recorded by a sensitive myograph system invitro. The vasodilation of Cur at various concentrations (range: 10-8-10-4 M) on potassium chloride (KCl; 60mmol/L)-precontracted or phenylephrine hydrochloride (PE; 10μmol/L)-precontracted arterial rings were observed. We also observed vasorelaxant effect of Cur on KCl (60mM)-preconstricted rat superior mesenteric arterial rings after incubating the inhibitors of endothelial mechanism, including the endothelial nitric oxide synthase inhibitor Nω-nitro-L-arginine methyl ester, the guanylate cyclase inhibitor 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one, and the cyclooxygenase inhibitor indomethacin, and inhibitors of potassium ion channel, including 4-aminopyridine (Voltage-sensitive K+ channel blockers), and tetraethylammonium chloride (Ca2+ activated K+ channel blockers), and BaCl2 (Inward rectifying K+ channel blockers), and glibenclamide (ATP -sensitive K+ channel blockers), respectively. The effects of Cur are expressed as percentage of relaxation from the precontraction induced by KCl (60mmol/L) or PE (10μmol/L). The Emax value refers to the maximum relaxation. The pD2 value refers to the negative logarithmic value of the drug concentration that produces 50% Emax. Cur concentration dependently relaxed the superior mesenteric artery rings with endothelium precontracted by PE (Emax=84.33±1.11 and pD2=5.03±0.02) or KCl (Emax=80.96±2.12% and pD2=4.32±0.01). The vasorelaxant effect of Cur on the superiormesenteric artery rings relied on endothelium partially. Indomethacin (5μM) significantlyinhibited the effect. However, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (10μM) and Nω-nitro-L-arginine methyl ester (100μM) had no effect on the action. In artery rings without endothelium, vasorelaxation induced by Cur was attenuated by 4-aminopyridine (100μM). However, barium chloride dehydrate (10μM), glibenclamide (10μM), and traethylammonium chloride (1mM) did not affect vasorelaxation induced by Cur. Moreover, Cur also significantly inhibited contraction induced by increasing external calcium in Ca2+-free medium plus K+ (60mM) and releasing intracellular Ca2+ in the Ca2+-free solution. Our results suggested that Cur induces relaxation in superior mesenteric arterial rings through an endothelium-dependent pathway, involving prostanoid, and also through an endothelium-independent pathway, opening K+ channel, and blockade of Ca2+ influx and intracellular Ca2+ release.

Total flavonoids from Astragalus alleviate endothelial dysfunction by activating the Akt/eNOS pathway.

ObjectiveTo investigate the vasodilative and endothelial-protective effects and the underlying mechanisms of total flavonoids from Astragalus (TFA).MethodsThe vasodilative activities of TFA were measured with a myograph ex vivo using rat superior mesenteric arterial rings. The primary human umbilical vein endothelial cell (HUVEC) viabilities were assayed using the cell counting kit-8 after hypoxia or normoxia treatment with or without TFA. Akt, P-Akt, eNOS, P-eNOS, Erk, P-Erk, Bcl-2 and Bax expression were analyzed using western blotting.ResultsTFA showed concentration-dependent vasodilative effects on rat superior mesenteric arterial rings, but had no effects on normal or potassium chloride precontracted arterial rings. TFA did not affect HUVEC viabilities in normoxia, but dramatically promoted cell proliferation in the concentration range of 1 to 30 µg/mL under hypoxia. Moreover, TFA significantly increased the ratios of P-Akt/Akt and P-eNOS/eNOS in vascular endothelial cells under hypoxic conditions, but did not change the P-Erk/Erk or Bcl-2/Bax ratios.ConclusionsTFA might exhibit vasorelaxant and endothelial-protective effects via the Akt/eNOS signaling pathway.

O11 Endothelium-dependent relaxation by a hydroethanolic extract of Adansonia digitata leaves in porcine coronary artery rings and rat thoracic aorta, mesenteric, carotid artery rings: Role of NO and EDH

Introduction Adansonia digitata leaves are used for the traditional treatment of hypertension in Senegal. This study evaluated the relaxant effect of a hydroethanolic extract of leaves of Adansonia digitata (ADF) in artery rings, and investigated the underlying mechanism. Methods Vascular reactivity was assessed in organ chambers. Rings were either untreated or incubated with a pharmacological tool for 30 min before contraction of coronary artery rings with either U46619 or phenylephrine, and the subsequent addition of ADF. In some experiments, the endothelium was removed mechanically. The phosphorylation level of target proteins was assessed by Western blot analysis. Results ADF induced concentration-dependent relaxations in coronary artery rings with endothelium, which reached 100% at a concentration as low as 10 μg/ml. The relaxation to ADF was significantly reduced by NLA (NO synthase inhibitor) and by the combination of Tram-34 and apamin (inhibitors of intermediate and small conductance calcium-dependent K+ channels, respectively), not affected by indomethacin (cyclooxygenase inhibitor), and abolished by wortmannin (PI3-kinase inhibitor) and MnTMPyP (membrane permeant superoxide dismutase mimetic). ADF caused relaxations in the rat superior mesenteric artery, carotid artery and aortic rings but not in the secondary mesenteric artery and femoral artery rings. ADF induced a sustained phosphorylation of Akt and eNOS at Ser1177 in cultured porcine coronary artery endothelial cells. Conclusion The Adansonia digitata leave extract induced potent endothelium-dependent relaxations, involving predominantly NO and endothelium-dependent hyperpolarization. Such vasorelaxant effects may explain the antihypertensive use of this plant in traditional African medicine.

Antioxidant and Antihypertensive Effects of a Chemically Defined Fraction of Syrah Red Wine on Spontaneously Hypertensive Rats.

A particularly phenolic-rich fraction extracted from red wine from the São Francisco valley (Northeastern Brazil) was chemically characterized and its hypotensive and antioxidant effects on spontaneously hypertensive rats were studied both in vitro and in vivo. The liquid-liquid pH dependent fractionation scheme afforded a fraction with high content of bioactive phenolics such as flavonols, flavonol glycosides, phenolic acids and anthocyanins, whose identities were confirmed by liquid chromatography coupled to mass spectrometry analysis. Pretreatment of spontaneously hypertensive rats with this wine fraction at doses of 50 and 100 mg/kg by gavage for 15 days was able to decrease mean arterial pressure and heart rate as well as decrease serum lipid peroxidation. The fraction at concentrations of 0.01–1000 µg/mL induced concentration-dependent relaxation of isolated rat superior mesenteric artery rings pre-contracted with phenylephrine and this effect was not attenuated by endothelium removal. Our results demonstrate it is possible for phenolic constituents of red wine that are orally bioavailable to exert in vivo hypotensive and antioxidant effects on intact endothelial function.

NO production and potassium channels activation induced by Crotalus durissus cascavella underlie mesenteric artery relaxation

Animal toxins are natural resources for pharmacological studies. The venom of Crotalus durissus cascavella (C.d. cascavella) may be a source in the bio-prospecting of new anti-hypertensive agents. The aim of this study was to investigate vascular effects of the venom of C.d. cascavella in normotensive rats. Studies were performed using isolated mesenteric artery segments and aortic endothelial cells. The cumulative administration of the venom of C.d. cascavella (0.001–30 μg/mL) on phenylephrine (Phe; 10 μM) pre-contracted rings induced a concentration-dependent vasorelaxation in the presence of vascular endothelium (Emax = 47.9 ± 5.0% n = 8), and its effect was almost abolished in the absence of endothelium (Emax = 5.8± 2.4% n = 5 (∗∗∗p < 0.001)). Tissue viability was maintained as there was no difference in the contractile capacity of rings before and after the administration of venom. The vasorelaxant effect of the venom was also abolished when arteries were pre-contracted with potassium chloride (KCl; 80 mM) (Emax = 6.4± 0.9% n = 5, ∗∗∗p < 0.001). When assessing the participation of endothelium-derived relaxing factors, it was noted that non-selective COX inhibition with indomethacin (10 μM) caused a significant reduction in the vasorelaxant effect of C.d. cascavella (*p < 0.05). When investigating the participation of NO released by endothelium, there was a significant reduction of the vasorelaxant effect of venom in rings treated with L-NAME (100 μM; Emax = 17.5± 2.2% n = 6; **p < 0.01). Similar results were noted in the presence of ODQ (10 μM), an inhibitor of soluble guanylyl cyclase (Emax = 11.2± 3.5%, n = 6) and PTIO (100 μM), a stable radical scavenger for nitric oxide (Emax = 10.77± 3.6%, n = 6). Moreover, the venom induced the release of NO by isolated aortic endothelial cells through amperometric studies. When assessing the participation of K+ channels on the vasodilatory response of the venom, tyrode solution with 20 mM of KCl caused a significant reduction in the relaxation response (p < 0.001) (Emax = 21.3 ± 8%, n = 7), as did inhibitor of delayed rectifier K+ channels (4-amynopiridine 1 mM; Emax = 9.5 ± 1.3, %, n = 5, ***p < 0.001), and vasorelaxation was almost abolished in the presence of Iberiotoxin (IbTx 100 nM). Therefore, these results suggest that the venom of C.d. cascavella induces vasorelaxation in superior mesenteric artery rings of normotensive rats in an endothelium-dependent manner. Specifically, the venom stimulates the generation of endothelium-derived relaxing factors, especially NO, and activates vascular smooth muscle hyperpolarization through K+ channels. These data illustrate that C.d. cascavella is a source of bioactive molecules and therefore has therapeutic potential in the treatment of cardiovascular diseases such as hypertension.

Acute Treatment with Lauric Acid Reduces Blood Pressure and Oxidative Stress in Spontaneously Hypertensive Rats.

The effects of acute administration of lauric acid (LA), the most abundant medium-chain fatty acid of coconut oil, on blood pressure, heart rate and oxidative stress were investigated in spontaneously hypertensive rats (SHR). Intravenous doses of LA reduced blood pressure in a dose-dependent fashion (1, 3, 4, 8 and 10 mg/kg) in both SHR and Wistar Kyoto rats. LA (10-8 to 3 × 10-3 M) induced vasorelaxation in isolated superior mesenteric artery rings of SHR in the presence (n = 7) or absence (n = 8) of functional endothelium [maximum effect (ME) = 104 ± 3 versus 103 ± 4%]. After exposure to KCl (60 mM), LA also induced concentration-dependent vasorelaxation (n = 7) compared to that under Phe-induced contraction (ME = 113.5 + 5.1 versus 104.5 + 4.0%). Furthermore, LA-induced vasorelaxation in vessels contracted with S(-)-BayK8644 (200 nM), a L-type Ca2+ channel agonist (ME = 91.4 + 4.3 versus 104.5 + 4.0%, n = 7). Lastly, LA (10-3 M) reduced NADPH-dependent superoxide accumulation in the heart (18 ± 1 versus 25 ± 1 MLU/min/μg protein, n = 4, p < 0.05) and kidney (82 ± 3 versus 99 ± 4 MLU/min/μg protein, n = 4, p < 0.05). Our data show that LA reduces blood pressure in normotensive and hypertensive rats. In SHR, this effect might involve Ca+2 channels in the resistance vessels and by its capability of reducing oxidative stress in heart and kidneys.

Mechanisms of simvastatin-induced vasodilatation of rat superior mesenteric arteries.

Independent of its lipid-lowering properties, simvastatin (Sim) induces vasorelaxation; however, the underlying mechanisms have remained elusive. The aim of the present study was to investigate the vasorelaxant effects of Sim on rat superior mesenteric arteries and the mechanisms involved. The isometric tension of rat superior mesenteric arterial rings was recorded in vitro on a myograph. The results showed that Sim concentration-dependently relaxed the superior mesenteric artery rings with endothelium pre-contracted by phenylephrine hydrochloride [maximum relaxation (Emax)=51.05±4.09%; negative logarithm of the concentration that caused 50% of the maximum response (pD2)=4.17±0.18] or KCl (Emax=41.65±1.32%; pD2=3.55±0.1). Nω-nitro-L-arginine methyl ester (100 µM) significantly inhibited this effect, while it was not affected by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 µM) and indomethacin (5 µM). In artery rings without endothelium, vasorelaxation induced by Sim was attenuated by 4-aminopyridine (100 µM), but was not affected by barium chloride dehydrate (10 µM), glibenclamide (10 µM) and traethylammonium chloride (1 mM). Moreover, Sim also inhibited the contraction induced by increasing external calcium in Ca2+-free medium with added KCl (60 mM). These results suggested that Sim induces relaxation of superior mesenteric arterial rings through an endothelium-dependent pathway, involving nitric oxide release and also through an endothelium-independent pathway, involving the opening of voltage-dependent K+ channels and blockade of extracellular Ca2+ influx.

Endothelium-dependent and-independent relaxation induced by resveratrol in rat superior mesenteric arteries.

Resveratrol (Res) is a specific agonist of sirtuin 1, and has many cardioprotective effects. Although Res is able to relax various vascular beds, its pharmacological properties in rat superior mesenteric arteries and the underlying mechanism are not well clarified. The aim of present study was to investigate the vasorelaxant effects of Res on rat superior mesenteric arteries and the mechanisms involved. The isometric tension of rat superior mesenteric arterial rings was recorded in vitro using myography. It was found that Res concentration-dependently relaxed endothelium-intact superior mesenteric artery rings pre-contracted by phenylephrine hydrochloride (Emax, 97.66±0.79%; pD2, 4.30±0.14) or KCl (Emax, 101.3±0.6%; pD2, 4.12±0.03). The vasorelaxant effect of Res on the superior mesenteric artery rings was partially endothelium-dependent. NG-nitro-L-arginine methyl ester (100 µM) significantly inhibited the Res-induced vasorelaxant effect. However, 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one (10 µM) and indomethacin (5 µM) each had no effect on the Res-induced vasorelaxation. In artery rings without endothelium, the vasorelaxation induced by Res was attenuated by 4-aminopyridine (100 µM) and glibenclamide (10 µM). However, barium chloride dehydrate (10 µM) and tetraethylammonium chloride (1 mM) did not affect the vasorelaxation induced by Res. Moreover, Res also inhibited the contraction induced by an increase in external calcium concentration in Ca2+-free medium plus KCl (60 mM). These results suggest that Res induces relaxation in superior mesenteric arterial rings through an endothelium-dependent pathway, involving nitric oxide release, and also through an endothelium-independent pathway, with opening of voltage-dependent K+ channels and ATP-sensitive K+ channels and blockade of extracellular Ca2+ influx.

PARTICIPATION OF ADENYLYL CYCLASE/cAMP PATHWAY IN VASORELAXANT MECHANISM OF THE PYRANOCOUMARIN BRAYLIN IN MESENTERIC ARTERY

IntroductionBraylin is a pyranocoumarin isolated from the species Zanthoxylum tingoassuiba (Rutaceae). Previous studies have shown that Braylin has a possible inhibitory action in phosphodiesterase enzymes.AimsThe aim of this study was to investigate the mechanism involved in the vasorelaxant effect of Braylin.MethodsThe experiments were performed using wistar rats (12–16 weeks/250–300g), euthanized in CO2 camera and the superior mesenteric artery were isolated and free from connective tissue and cut into rings (1–2 mm), suspended by cotton threads for isometric tension recordings in a Tyrode's solution at 37 °C, gassed with a 95% O2 and 5% CO2, under a resting tension of 0.75g. All surgical and experimental procedures were approved by the local Animal use and care ethics committee – CEUA/ICS/UFBA by the number 089/2015.ResultsThe cumulative administration of Braylin (0.1–300 μM) in phenylephrine (Phe 10μM) pre‐contracted mesenteric rings, induced a concentration‐dependent vasorelaxation (Emax = 111.5 ± 7.9%, CE50 = 4.8 (3.0 – 7.7) × 10−5, n = 17), the removal of the endothelium did not change this effect (Emax = 127.6 ± 13.1%, CE50 =1.7 (4.0 – 7.3) × 10−5, n = 16). The presence of ODQ (100 μM), an inhibitor of soluble guanylyl cyclase, also did not change the effect induced by Braylin (Emax = 117.3 ± 2.6%, CE50 = 1.3 (1.9 – 8.9) × 10−5, n = 5). On the other hand, the presence of SQ 22536, an adenylyl cyclase inhibitor, reduced the relaxant effect (Emax = 115.6 ± 2.8, CE50 = 4.3 (3.0 – 6.2) × 10−5, n = 5). The incubation of the superior mesenteric rings with KT‐5720, an inhibitor of PKA, reduced the effect of Braylin (Emax = 110.4 ± 5.3%, CE50 = 2.9 (2.0 – 4.1) × 10−5, n = 5). Pre‐treatment with KCl 20 mM, TEA (1mM), BaCl2 (30μM), or 4‐aminopiridin (1mM) decreased the pharmacological potency of the Braylin significantly.ConclusionThose effects taken together suggest that Braylin induces vasorelaxant effects in isolated superior mesenteric artery rings from normotensive involving AC/cAMP pathway. K+ channels also seem to be important in the relaxant effect, probably BKca channels.Support or Funding InformationFundação de Amparo à Pesquisado Estado da Bahia (fapesb) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

PARTICIPATION OF NO/GC/cGMP/K+ CHANNELS IN THE RELATATION INDUCED BY Crotalus durissus cascavella IN MESENTERIC ARTERY

IntroductionThe studies with toxins from snakes poison have shown promising biological effects, especially those regarding to cardiovascular system, such as hypotensive and vasodilators.AimsTo investigate the vascular effect of Crotalus durissus cascavella poison (CDC), a high prevalence species in the state of Bahia ‐ Brazil, was used rat superior mesenteric artery.MethodsWistar rats (12–16 weeks/250–300g) were euthanized in CO2 camera and the mesenteric artery were isolated and free from connective tissue and cut into rings that was kept in Tyrode solution at 37°C carbonated with 95% of O2 and 5% of CO2. The amperometry technic was used to evaluate NO production in isolated aortic endothelial cells. The significant values was p&lt;0.05.ResultsCumulative administration of the CDC (0.001 – 30μg/mL) relaxed phenylephrine‐induced contractions in a concentration‐dependent manner (Emax = 47.9 ± 5.0%; n=8) in the endothelial vascular presence, this effect was practically abolished in the endothelial vascular absence (Emax= 5.8 ± 2.4%; n=5; *** p&lt;0.001). The vasorelaxant effect induced by CDC in KCl 80mM‐induced contraction was abolished (Emax= 6.4 ± 0.9%; n=5; *** p&lt;0.001. Pre‐treatment with Indomethacin (10μM), L‐NAME (100μM), and ODQ (10μM) significantly attenuated the relaxation effect induced by CDC (Emax = 29.1 ± 7.1%, n = 6, Emax = 17.5 ± 2.2%, n = 6, Emax = 11.2 ± 3.5%, n = 6, respectively). Additionally, in studies with isolated aortic endothelial cells demonstrated that CDC in concentration of 10 and 90 μg/mL induced significant increase in NO production. In mesenteric rings pre incubated with KCl 20mM, to evaluate K+ channels participation, the vasorelaxant effect induced by CDC was significantly reduced (Emax = 21.3 ± 8%, n = 7). Similar results was observed in the presence of Iberiotoxin (100nM), BaCl2 (30μM) and 4‐aminopiridin (1mM) [(Emax = 13.0 ± 3 %, n= 5, Emax = 21.7 ± 8 %, n= 5 e Emax = 9.5 ± 1.3, %, n=5, respectively).ConclusionThose results suggest that the CDC induces vasorelaxant effects in isolated superior mesenteric artery rings from normotensive rats in an endothelium‐dependent way, possibly trough endothelium‐derived relaxing factors, especially the NO, resulting in guanylyl cyclase activation, followed by GMPc production and probably K+ channels activation (BKca, Kv and Kir). Additionally, prostanoids derivated from cyclooxygenase also are involved in the relaxant effect induced by CDC.3012 ‐ ASPET Cardiovascular Pharmacology – General/OtherSupport or Funding InformationFundação de Amparo à Pesquisa do Estado da Bahia (FAPESB) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

5-Hydroxytryptamine does not reduce sympathetic nerve activity or neuroeffector function in the splanchnic circulation

Infusion of 5-hydroxytryptamine (5-HT) in conscious rats results in a sustained (up to 30 days) fall in blood pressure. This is accompanied by an increase in splanchnic blood flow. Because the splanchnic circulation is regulated by the sympathetic nervous system, we hypothesized that 5-HT would: 1) directly reduce sympathetic nerve activity in the splanchnic region; and/or 2) inhibit sympathetic neuroeffector function in splanchnic blood vessels. Moreover, removal of the sympathetic innervation of the splanchnic circulation (celiac ganglionectomy) would reduce 5-HT-induced hypotension. In anaesthetized Sprague-Dawley rats, mean blood pressure was reduced from 101±4 to 63±3mm Hg during slow infusion of 5-HT (25μg/kg/min, i.v.). Pre- and postganglionic splanchnic sympathetic nerve activity were unaffected during 5-HT infusion. In superior mesenteric arterial rings prepared for electrical field stimulation, neither 5-HT (3, 10, 30nM), the 5-HT1B receptor agonist CP 93129 nor 5-HT1/7 receptor agonist 5-carboxamidotryptamine inhibited neurogenic contraction compared to vehicle. 5-HT did not inhibit neurogenic contraction in superior mesenteric venous rings. Finally, celiac ganglionectomy did not modify the magnitude of fall or time course of 5-HT-induced hypotension when compared to animals receiving sham ganglionectomy. We conclude it is unlikely 5-HT interacts with the sympathetic nervous system at the level of the splanchnic preganglionic or postganglionic nerve, as well as at the neuroeffector junction, to reduce blood pressure. These important studies allow us to rule out a direct interaction of 5-HT with the splanchnic sympathetic nervous system as a cause of the 5-HT-induced fall in blood pressure.

Vasorelaxation induced by a new naphthoquinone-oxime is mediated by NO-sGC-cGMP pathway.

It has been established that oximes cause endothelium-independent relaxation in blood vessels. In the present study, the cardiovascular effects of the new oxime 3-hydroxy-4–(hydroxyimino)-2-(3-methylbut-2-enylnaphtalen-1(4H)-one (OximeS1) derived from lapachol were evaluated. In normotensive rats, administration of Oxime S1 (10, 15, 20 and 30 mg/Kg, i.v.) produced dose-dependent reduction in blood pressure. In isolated aorta and superior mesenteric artery rings, Oxime S1 induced endothelium-independent and concentration-dependent relaxations (10−8 M to 10−4 M). In addition, Oxime S1-induced vasorelaxations were attenuated by hydroxocobalamin or methylene blue in aorta and by PTIO or ODQ in mesenteric artery rings, suggesting a role for the nitric oxide (NO) pathway. Additionally, Oxime S1 (30 and 100 µM) significantly increased NO concentrations (13.9 ± 1.6 nM and 17.9 ± 4.1 nM, respectively) measured by nitric oxide microsensors. Furthermore, pre-contraction with KCl (80 mM) prevented Oxime S1-derived vasorelaxation in endothelium-denuded aortic rings. Of note, combined treatment with potassium channel inhibitors also reduced Oxime S1-mediated vasorelaxation suggesting a role for potassium channels, more precisely Kir, Kv and KATP channels. We observed the involvement of BKCa channels in Oxime S1-induced relaxation in mesenteric artery rings. In conclusion, these data suggest that the Oxime S1 induces hypotension and vasorelaxation via NO pathway by activating soluble guanylate cyclase (sGC) and K+ channels.

Garcinielliptone FC, a polyisoprenylated benzophenone from Platonia insignis Mart., promotes vasorelaxant effect on rat mesenteric artery

Polyisoprenylated benzophenones represent a group of chemical compounds commonly identified in Clusiaceae species and are responsible for a large amount of biological activities. In this work, the vasorelaxant effect induced by garcinielliptone FC (GFC) isolated from Platonia insignis Mart. (Clusiaceae), a monotype species from Platonia genus, was investigated. GFC promoted an endothelium-independent vasorelaxation on phenylephrine (PHE, 10− 5 mol L− 1)-induced vasoconstriction, but not on KCl (80 mmol L− 1)-induced vasoconstriction, on rat superior mesenteric artery rings. In addition, a concentration-dependent decrease of PHE- or serotonin-induced cumulative concentration–response curves was observed for GFC, and a slight decrease of pD2 value on CaCl2-induced vasoconstriction. In a Ca2+-free medium, GFC interfered in calcium mobilisation from PHE (10− 5 mol L− 1)-sensitive intracellular stores. GFC-induced vasorelaxant effect is probably mediated by a dual effect on mobilisation of calcium intracellular stores and attenuation of transmembrane calcium influx.