The mechanism of vasorelaxation induced by ethanol extract of Sophora flavescens in rat aorta.

Sophora flavescens (SF) is a known medicinal herb for the treatment of cardiovascular symptoms associated with arrhythmia in China. However, the pharmacological action mechanisms involved have not been well studied. The aim of the present study was to define effects of roots of SF on the vascular tension and responsible mechanisms in rat thoracic aorta. Ethanol extract of the roots of SF (ESF) was examined for their vascular relaxant effect in isolated phenylephrine-precontracted rat thoracic aorta. ESF (0.1-100 μg/ml) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished the ESF-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with l-NAME, an inhibitor of nitric oxide synthase, and ODQ, an inhibitor of soluble guanylyl cyclase (sGC), inhibited ESF-induced vasorelaxation. ESF increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by l-NAME and ODQ. Inhibition of K(+) channels with glibenclamide and tetraethylammonium, cyclooxygenase inhibition with indomethacin, and β-adrenergic and muscarinic receptors blockade had no effect on the ESF-induced vasorelaxation. These findings suggest that ESF relaxes vascular smooth muscle via endothelium-dependent NO-sGC-cGMP signaling pathway.

Jin SN ，Wen JF ，Li X ，Kang DG ，Lee HS ，Cho KW ... -  《-》

Vasorelaxant effects of Cerebralcare Granule® are mediated by NO/cGMP pathway, potassium channel opening and calcium channel blockade in isolated rat thoracic aorta.

Cerebralcare Granule (CG), one of the famous classical recipes in traditional Chinese medicine, is developed from the "Decoction of Four Drugs". It has been used for treatment of cerebrovascular related diseases, such as hypertension. It is well known that vasodilatation plays a very important role in hypertensive. Despite the popular medicinal use of CG, little data was available to its activity and mechanism involved in vasodilatation. Therefore, we aimed to investigate the vasorelaxant effects of CG on isolated rat thoracic aorta so as to assess some of the possible mechanisms. The present study was performed to examine the vasodilative activity of CG and its mechanisms in isolated rat thoracic aorta. CG was studied on isolated rat thoracic aorta in vitro, including endothelium-intact and endothelium-denuded aortic rings. In present study, specific inhibitors including NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME), cyclooxygenase (COX) inhibitor indomethacin (INDO), non-selective K+ channel inhibitor tetraethylammonium chloride (TEA), Kir channel inhibitor BaCl2, KATP channel inhibitor Glibenclamide (Gli) and cholinergic receptor antagonist atropine were used, they were added 20 min before NE contraction and then added CG-induced vasodilation. Removal of endothelium or pretreatment of aortic rings (intact endothelium) with L-NAME (0.1 mM) or INDO (0.01 mM) significantly blocked the CG induced relaxation. Pretreatment with the non-selective K+ channel inhibitor TEA (1 mM), or the Kir channel inhibitor BaCl2 (0.1 mM), neither of them had no influence on the CG-induced response (p>0.05). However, pretreatment with the KATP channel inhibitor Gli (0.01 mM) produced significant inhibition on the CG-induced response (p<0.01). Besides, CG also inhibited the contraction triggered by NE in endothelium-denuded rings in Ca2+-free medium. CG (0.4, 0.8 and 3.2 mg/mL) produced rightward parallel displacement of CaCl2 curves and reduced the maximum contraction induced by 30 mM CaCl2 to 31.1±9.3%, 18.8±6.9% and 9.4±4.5%, respectively. The relaxation, induced by CG on endothelium-intact rat aortic rings pre-contracted with NE, was significantly attenuated in the presence of atropine (EC50=3.7 mg/mL, p<0.01). Our results suggest that CG induces relaxation in rat aortic rings through an endothelium-dependent pathway mediated by NO/cGMP pathway and an endothelium-independent pathway involving blockade of Ca2+ channels, inhibition of Ca2+ mobilization from intracellular stores, opening of KATP channel. In addition, the muscarinic receptor stimulation is also one of the vasorelaxant mechanisms.

Qu Z ，Zhang J ，Gao W ，Chen H ，Guo H ，Wang T ，Li H ，Liu C ... -  《-》

Water extract of Zanthoxylum piperitum induces vascular relaxation via endothelium-dependent NO-cGMP signaling.

The aim of the present study was to define the effects of extracts of leaves of Zanthoxylum piperitum (ZP) on the vascular tension and its mechanisms responsible in rat thoracic aortic rings. Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) were examined for their vascular relaxant effects in isolated phenylephrine-precontracted aortic rings. Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished the AZP-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N(G)-nitro-L-arginine methylester (L-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-alpha]-quinoxalin-1-one (ODQ) inhibited the AZP-induced vasorelaxation. Inhibition of Ca(2+) entry via L-type Ca(2+) channels failed to block the AZP-induced vasorelaxation. Extracellular Ca(2+) depletion slightly but significantly attenuated the AZP-induced vasorelaxation. Thapsigargin significantly attenuated the AZP-induced vasorelaxation. Further, Gd(3+) and 2-aminoethyl diphenylborinate (2-APB), inhibitors of store-operated Ca(2+) entry (SOCE), markedly attenuated the AZP-induced vasorelaxation. Also, wortmannin, an inhibitor of Akt, an upstream signaling molecule of eNOS, attenuated the AZP-induced vasorelaxation. AZP increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by L-NAME, ODQ, thapsigargin, Gd(3+), 2-APB, and wortmannin. K(+) channel inhibition with glibenclamide and tetraethylammonium, cyclooxygenase inhibition with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the AZP-induced vasorelaxation. Taken together, the present study suggests that AZP relaxes vascular smooth muscle via endothelium-dependent activation of NO-cGMP signaling through the Akt- and SOCE-eNOS pathways.

Li X ，Kim HY ，Cui HZ ，Cho KW ，Kang DG ，Lee HS ... -  《-》

Vasorelaxant action of an ethylacetate fraction of Euphorbia humifusa involves NO-cGMP pathway and potassium channels.

Euphorbia humifusa Willd. (EH) is an important traditional Chinese medicine that has commonly been used for treating bacillary dysentery and enteritis in many Asian countries for thousands of years. EH has a wide variety of pharmacological actions such as antioxidant, hypotensive, and hypolipidemic effects. However, the mechanisms involved are to be defined. The present study was performed to evaluate the cardiovascular effects of EH in rats. Methanol extract of EH (MEH) and ethylacetate fraction of the MEH (EEH) was examined for their vascular relaxant effects in phenylephrine-precontracted aortic rings. Effects of EEH on systolic blood pressure and heart rate were tested in Sprague-Dawley rats. MEH and EEH induced vasorelaxation in a concentration-dependent manner. Endothelium-denudation abolished the EEH-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N(G)-nitro-L-arginine methylester (L-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ) significantly inhibited the EEH-induced vasorelaxation. EEH increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by L-NAME or ODQ. Extracellular Ca(2+) depletion and treatments with thapsigargin, Gd(3+), and 2-aminoethyl diphenylborinate significantly attenuated the EEH-induced vasorelaxation. Wortmannin markedly attenuated the EEH-induced vasorelaxation. In addition, tetraethylammonium, iberiotoxin, and charybdotoxin, but not apamin, attenuated the EEH-induced vasorelaxation. Glibenclamide, indomethacin, atropine, and propranolol had no effects on the EEH-induced vasorelaxation. Furthermore, EEH decreased systolic blood pressure and heart rate in a concentration-dependent manner in rats. The present study demonstrates that EEH induces endothelium-dependent vasorelaxation via eNOS-NO-cGMP signaling through the modification of intracellular Ca(2+), Ca(2+) entry, and large- and intermediate-conductance KCa channel homeostasis. The data also suggest that the Akt-eNOS pathway is involved in the EEH-induced vasorelaxation. EEH induces hypotension and bradycardia in vivo.

Wang TT ，Zhou GH ，Kho JH ，Sun YY ，Wen JF ，Kang DG ，Lee HS ，Cho KW ，Jin SN ... -  《-》

Mechanisms underlying the antihypertensive effect of Alstonia scholaris.

Alstonia scholaris has a long history of use in the Ayurveda traditional treatment of various ailments including hypertension. We have reported the blood pressure lowering activity of the extract of A. scholaris. The following research aim to delineate the pharmacological mechanism involve in the antihypertensive action. Vasorelaxant effect of the n-butanol fraction of A. scholaris (NBF-ASME) was evaluated on rat aorta pre-contracted with phenyelphrine (PE, 1 µM). Aortic rings preparation were pre-incubated with various antagonists like 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ 10 μM), methylene blue (MB 10 μM), Nω-nitro-L-arginine methyl ester hydrochloride (l-NAME 10 μM), atropine (10 μM), indomethacin (1 μM), ML-9 and various K(+) channel blockers such as glibenclamide (10 μM) and tetraethyl ammonium (TEA 10 μM) for mechanism study. The results showed that pre-incubation of aortic rings with the extract (0.5, 1 and 2mg/mL) significantly inhibit the contractile response of the rings to phenylephrine-induced contraction (p<0.05-0.001). Removal of endothelium, incubation with L-NAME, indomethacin, atropine and propranolol did not significantly affect the relaxation effect of NBF-ASME. Furthermore, the K(+) channel blockers, TEA and glibenclamide showed no inhibitory effect. However, aortic rings pretreated with ODQ and ML-9 showed a significant suppression of the relaxation curve of NBF-ASME (p<0.01-0.001). In Ca(2+)-free solution, NBF-ASME inhibits the release of intracellular Ca(2+) from the sarcoplasmic reticulum. NBF-ASME also inhibits calcium chloride (CaCl2)-induced contraction in endothelium-denuded aortic rings. The results from this study suggests that A. scholaris exerts vasodilation via calcium channels blockade, direct activation of soluble guanylate cyclase and possibly by also inhibiting the formation of inositol 1, 4, 5-triphosphate.

Bello I ，Usman NS ，Mahmud R ，Asmawi MZ ... -  《-》