Effects of gomisin A on vascular contraction in rat aortic rings

Vasorelaxant and Hypotensive Effects of Cheonwangbosimdan in SD and SHR Rats

Historically, traditional herbal medicines (THMs) have been the conventional treatment strategy in the Korean medical system for treating many diseases. However, THMs have rarely been used to treat hypertension, and moreover few studies have investigated the interaction of blood pressure with the coadministration of synthetic antihypertensives. We aimed to evaluate the vasorelaxant and hypotensive effects of the traditional herbal prescription Cheonwangbosimdan (CWBSD; "Tianwangbuxindan" in Chinese) and the combination of CWBSD with amlodipine. CWBSD was extracted with distilled water at 100°C for 2 h. To investigate vasorelaxant activities, CWBSD with amlodipine (10 μg/ml) was added cumulatively (10-1,000 μg/ml) to isolated rat aortic rings precontracted using phenylephrine or potassium chloride in organ chambers. To investigate hypotensive effects, CWBSD (2,476 mg/kg) was orally administered with or without amlodipine (5 mg/kg) to spontaneously hypertensive rats (SHRs). CWBSD increased the relaxation of rat aortic rings induced by amlodipine (P < 0.01). In vivo, CWBSD coadministration with amlodipine also significantly decreased the blood pressure of SHRs compared to the amlodipine-treated group. These results suggested that CWBSD could be a useful herbal prescription to treat hypertension and we recommend establishing guidelines for the use of herbal medicines in conjunction with antihypertensive drugs, including amlodipine.

Effects of Schisandra chinensis fruit extract and gomisin A on the contractility of penile corpus cavernosum smooth muscle: a potential mechanism through the nitric oxide - cyclic guanosine monophosphate pathway

BACKGROUND/OBJECTIVES

This study evaluated the effects and molecular mechanisms of the Schisandra chinensis fruit extract (SC) and its major compound gomisin A (GA), on the contractility of rabbit penile corpus cavernosum smooth muscle (PCCSM).

MATERIALS/METHODS

PCCSM was exposed to SC or GA after appropriate pretreatment with nitric oxide synthase (NOS) blocker, guanylate cyclase blocker, adenylyl cyclase blocker or protein kinase A blocker. Subsequently, we evaluated the cyclic nucleotide in the perfusate by radioimmunoassay, protein expression level of neuronal NOS (nNOS) and endothelial NOS (eNOS) by western blot, and the interaction of SC or GA with udenafil and rolipram.

RESULTS

Both SC and GA induce PCCSM relaxations in a concentration-dependent manner. Pretreatment with NOS blocker, guanylate cyclase blocker, adenylyl cyclase blocker or protein kinase A blocker result in significantly decreased relaxation. SC and GA also induce the levels of cyclic nucleotide in the perfusate in a concentration-dependent manner. Perfusion with GA also showed significantly higher levels of eNOS protein. Furthermore, the udenafil and rolipram induced relaxations of PCCSM were enhanced after exposure to SC and GA. Our results indicate that SC and GA induce the relaxation of PCCSM via the nitric oxide (NO)-cGMP and cAMP signaling pathways.

CONCLUSIONS

The SC and GA are potential alternative treatments for men who want to consume natural products to ameliorate erectile function, or who do not respond to the commercially available medicines.

Vasorelaxant and antihypertensive effects of methanolic fraction of the essential oil of Alpinia zerumbet

Alpinia zerumbet is used in folk medicine in Brazil to treat hypertension. However, several pathways involved in the mechanism of vasorelaxation are still unclear. This study was designed to verify the antihypertensive effect of the methanolic fraction of the essential oil of A. zerumbet (MFEOAz) and to characterize its mechanism of action. The thoracic aortic rings from the Wistar rats were perfused in the organ chambers filled with Kreb's solution, where the tension of each ring was measured. The antihypertensive effect of MFEOAz was assessed in rats submitted to chronic hypertension by inhibition of nitric oxide synthesis by indirect measurement of blood pressure with indirect tail cuff method. MFEOAz relaxed phenylephrine and KCl-induced contraction of either endothelium-intact or endothelium-denuded rat aortic rings in a concentration-dependent manner. Pre-incubation with MFEOAz (100 and 300 μg/mL) in Ca(2+)-free Krebs solution attenuated phenylephrine- or caffeine-induced contraction. Pre-incubation with L-NAME, ODQ, wortmannin, atropine, indomethacin, catalase, SOD, TEA, 4-aminopyridine, glibenclamide, apamin, charybdotoxin, or iberiotoxin did not affect MFEOAz-induced relaxation. The intragastric administration of MFEOAz induced an antihypertensive effect. MFEOAz it seems inhibited the calcium influx via voltage-operated calcium channels and receptor-operated calcium channels, as well as inhibition of calcium mobilization from intracellular stores.

Gomisin J from Schisandra chinensis induces vascular relaxation via activation of endothelial nitric oxide synthase

Gomisin J (GJ) is a lignan contained in Schisandra chinensis (SC) which is a well-known medicinal herb for improvement of cardiovascular symptoms in Korean. Thus, the present study examined the vascular effects of GJ, and also determined the mechanisms involved. Exposure of rat thoracic aorta to GJ (1-30μg/ml) resulted in a concentration-dependent vasorelaxation, which was more prominent in the endothelium (ED)-intact aorta. ED-dependent relaxation induced by GJ was markedly attenuated by pretreatment with L-NAME, a nitric oxide synthase (NOS) inhibitor. In the intact endothelial cells of rat thoracic aorta, GJ also enhanced nitric oxide (NO) production. In studies using human coronary artery endothelial cells, GJ enhanced phosphorylation of endothelial NOS (eNOS) at Ser(1177) with increased cytosolic translocation of eNOS, and subsequently increased NO production. These effects of GJ were attenuated not only by calcium chelators including EGTA and BAPTA-AM, but also by LY294002, a PI3K/Akt inhibitor, indicating calcium- and PI3K/Akt-dependent activation of eNOS by GJ. Moreover, the levels of intracellular calcium were increased immediately after GJ administration, but Akt phosphorylation was started to increase at 20min of GJ treatment. Based on these results with the facts that ED-dependent relaxation occurred rapidly after GJ treatment, it was suggested that the ED-dependent vasorelaxant effects of GJ were mediated mainly by calcium-dependent activation of eNOS with subsequent production of endothelial NO.

2-Morpholinoisoflav-3-enes as flexible intermediates in the synthesis of phenoxodiol, isophenoxodiol, equol and analogues: vasorelaxant properties, estrogen receptor binding and Rho/RhoA kinase pathway inhibition

Isoflavone consumption correlates with reduced rates of cardiovascular disease. Epidemiological studies and clinical data provide evidence that isoflavone metabolites, such as the isoflavan equol, contribute to these beneficial effects. In this study we developed a new route to isoflavans and isoflavenes via 2-morpholinoisoflavenes derived from a condensation reaction of phenylacetaldehydes, salicylaldehydes and morpholine. We report the synthesis of the isoflavans equol and deoxygenated analogues, and the isoflavenes 7,4'-dihydroxyisoflav-3-ene (phenoxodiol, haganin E) and 7,4'-dihydroxyisoflav-2-ene (isophenoxodiol). Vascular pharmacology studies reveal that all oxygenated isoflavans and isoflavenes can attenuate phenylephrine-induced vasoconstriction, which was unaffected by the estrogen receptor antagonist ICI 182,780. Furthermore, the compounds inhibited U46619 (a thromboxane A(2) analogue) induced vasoconstriction in endothelium-denuded rat aortae, and reduced the formation of GTP RhoA, with the effects being greatest for equol and phenoxodiol. Ligand displacement studies of rat uterine cytosol estrogen receptor revealed the compounds to be generally weak binders. These data are consistent with the vasorelaxation activity of equol and phenoxodiol deriving at least in part by inhibition of the RhoA/Rho-kinase pathway, and along with the limited estrogen receptor affinity supports a role for equol and phenoxodiol as useful agents for maintaining cardiovascular function with limited estrogenic effects.

Honokiol attenuates vascular contraction through the inhibition of the RhoA/Rho-kinase signalling pathway in rat aortic rings

Objectives

Honokiol is a small-molecule polyphenol isolated from the species Magnolia obovata. We hypothesized that honokiol attenuated vascular contractions through the inhibition of the RhoA/Rho-kinase signalling pathway.

Methods

Rat aortic rings were denuded of endothelium, mounted in organ baths, and subjected to contraction or relaxation. Phosphorylation of 20 kDa myosin light chains (MLC20), myosin phosphatase targeting subunit 1 (MYPT1) and protein kinase C (PKC)-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase (MLCP) of 17 kDa (CPI17) were examined by immunoblot. We also measured the amount of guanosine triphosphate RhoA as a marker for RhoA activation.

Key findings

Pretreatment with honokiol dose-dependently inhibited the concentration–response curves in response to sodium fluoride (NaF) or thromboxane A2 agonist U46619. Honokiol decreased the phosphorylation levels of MLC20, MYPT1Thr855 and CPI17Thr38 as well as the activation of RhoA induced by 8.0 mm NaF or 30 nm U46619.

Conclusions

These results demonstrated that honokiol attenuated vascular contraction through the inhibition of the RhoA/Rho-kinase signalling pathway.