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Mechanism of vasorelaxation induced by 3'-hydroxy-5,6,7,4'-tetramethoxyflavone in the rats aortic ring assay

Tan CS, Yam MF

Naunyn Schmiedebergs Arch Pharmacol, 2018 06;391(6):561-569.
PMID: 29552696 DOI: 10.1007/s00210-018-1481-9

Previous studies have demonstrated that 3'-hydroxy-5,6,7,4'-tetramethoxyflavone (TMF) content in Orthosiphon stamineus fractions correlate with its vasorelaxation activity. Even with the availability of previous studies, there is still very little information on the vasorelaxation effect of TMF, and few scientific studies have been carried out. Therefore, the present study was designed to investigate the vasorelaxation activity and mechanism of action of the TMF. The vasorelaxation activity and the underlying mechanisms of TMF were evaluated on thoracic aortic rings isolated from Sprague Dawley rats. TMF caused the relaxation of aortic rings with endothelium pre-contracted with phenylephrine. However, the vasorelaxant effect of TMF was significantly decreased in PE-primed endothelium-denuded and potassium chloride-primed endothelium-intact aortic rings. In the presence of Nω-nitro-L-arginine methyl ester, methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, indomethacin, tetraethylammonium, 4-aminopyridine, barium chloride, atropine and propranolol, the relaxation stimulated by TMF was significantly reduced. TMF was also found to reduce Ca2+ release from sarcoplasmic reticulum (via IP3R) and block calcium channels (VOCC). The present study demonstrates the vasorelaxant effect of TMF involves NO/sGC/cGMP and prostacyclin pathways, calcium and potassium channels and muscarinic and beta-adrenergic receptors.

Matched MeSH terms: Soluble Guanylyl Cyclase/physiology
Vasorelaxant effect of sinensetin via the NO/sGC/cGMP pathway and potassium and calcium channels

Yam MF, Tan CS, Shibao R

Hypertens Res, 2018 Oct;41(10):787-797.
PMID: 30111856 DOI: 10.1038/s41440-018-0083-8

Orthosiphon stamineus Benth. (Lambiaceae) is an important traditional plant for the treatment of hypertension. Previous studies have demonstrated that the sinensetin content in O. stamineus is correlated with its vasorelaxant activity. However, there is still very little information regarding the vasorelaxant effect of sinensetin due to a lack of scientific studies. Therefore, the present study was designed to investigate the underlying mechanism of action of sinensetin in vasorelaxation using an in vitro precontraction aortic ring assay. The changes in the tension of the aortic ring preparations were recorded using a force-displacement transducer and the PowerLab system. The mechanisms of the vasorelaxant effect of sinensetin were determined in the presence of antagonists. Sinensetin caused relaxation of the aortic ring precontracted with PE in the presence and absence of the endothelium and with potassium chloride in endothelium-intact aortic rings. In the presence of Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), ODQ (selective soluble guanylate cyclase inhibitor), indomethacin (a nonselective cyclooxygenase inhibitor), tetraethylammonium (nonselective calcium activator K+ channel blocker), 4-aminopyridine (voltage-dependent K+ channel blocker), barium chloride (inwardly rectifying Kir channel blocker), glibenclamide (nonspecific ATP-sensitive K+ channel blocker), atropine (muscarinic receptor blocker), or propranolol (β-adrenergic receptor blocker), the relaxation stimulated by sinensetin was significantly reduced. Sinensetin was also active in reducing Ca2+ release from the sarcoplasmic reticulum (via IP3R) and in blocking calcium channels (VOCC). The present study demonstrates the vasorelaxant effect of sinensetin, which involves the NO/sGC/cGMP and indomethacin pathways, calcium and potassium channels, and muscarinic and beta-adrenergic receptors.

Matched MeSH terms: Soluble Guanylyl Cyclase/metabolism*
Fulltext Possible Participation of Ionotropic Glutamate Receptors and l-Arginine-Nitric Oxide-Cyclic Guanosine Monophosphate-ATP-Sensitive K+ Channel Pathway in the Antinociceptive Activity of Cardamonin in Acute Pain Animal Models

Pui Ping C, Akhtar MN, Israf DA, Perimal EK, Sulaiman MR

Molecules, 2020 Nov 18;25(22).
PMID: 33217904 DOI: 10.3390/molecules25225385

The perception of pain caused by inflammation serves as a warning sign to avoid further injury. The generation and transmission of pain impulses involves various pathways and receptors. Cardamonin isolated from Boesenbergia rotunda (L.) Mansf. has been reported to exert antinociceptive effects in thermal and mechanical pain models; however, the precise mechanism has yet to be examined. The present study investigated the possible mechanisms involved in the antinociceptive activity of cardamonin on protein kinase C, N-methyl-d-aspartate (NMDA) and non-NMDA glutamate receptors, l-arginine/cyclic guanosine monophosphate (cGMP) mechanism, as well as the ATP-sensitive potassium (K+) channel. Cardamonin was administered to the animals intra-peritoneally. Present findings showed that cardamonin significantly inhibited pain elicited by intraplantar injection of phorbol 12-myristate 13-acetate (PMA, a protein kinase C activator) with calculated mean ED50 of 2.0 mg/kg (0.9-4.5 mg/kg). The study presented that pre-treatment with MK-801 (NMDA receptor antagonist) and NBQX (non-NMDA receptor antagonist) significantly modulates the antinociceptive activity of cardamonin at 3 mg/kg when tested with glutamate-induced paw licking test. Pre-treatment with l-arginine (a nitric oxide precursor), ODQ (selective inhibitor of soluble guanylyl cyclase) and glibenclamide (ATP-sensitive K+ channel inhibitor) significantly enhanced the antinociception produced by cardamonin. In conclusion, the present findings showed that the antinociceptive activity of cardamonin might involve the modulation of PKC activity, NMDA and non-NMDA glutamate receptors, l-arginine/nitric oxide/cGMP pathway and ATP-sensitive K+ channel.

Matched MeSH terms: Soluble Guanylyl Cyclase
Vasorelaxant effect of water fraction of Labisia Pumila and its mechanisms in spontaneously hypertensive rats aortic ring preparation

Manshor NM, Razali N, Jusoh RR, Asmawi MZ, Mohamed N, Zainol S, et al.

Int J Cardiol Hypertens, 2020 Mar;4:100024.
PMID: 33447753 DOI: 10.1016/j.ijchy.2020.100024

Introduction: Labisia pumila has been reported to possess activities including antioxidant, anti-aging and anti-cancer but there is no report on its vasorelaxant effects.
Objective: This study aims to fractionate water extract of Labisia pumila, identify the compound(s) involved and elucidate the possible mechanism(s) of its vasorelaxant effects.
Methods: Water extract of Labisia pumila was subjected to liquid-liquid extraction to obtain ethyl acetate, n-butanol and water fractions. In SHR aortic ring preparations, water fraction (WF-LPWE) was established as the most potent fraction for vasorelaxation. The pharmacological mechanisms of the vasorelaxant effect of WF-LPWE were investigated with and without the presence of various inhibitors. The cumulative dose-response curves of potassium chloride (KCl)-induced contractions were conducted to study the possible mechanisms of WF-LPWE in reducing vasoconstriction.
Results: WF-LPWE produced dose-dependent vasorelaxant effect in endothelium-denuded aortic ring and showed non-competitive inhibition of dose-response curves of PE-induced contraction, and at its higher concentrations reduced KCl-induced contraction. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) significantly inhibited vasorelaxant effect of WF-LPWE. WF-LPWE significantly reduced the release of intracellular calcium ion (Ca2+) from the intracellular stores and suppressed the calcium chloride (CaCal2)-induced contraction. Nω-nitro-L-arginine methyl ester (L-NAME), methylene blue, indomethacin and atropine did not influence the vasorelaxant effects of WF-LPWE.
Conclusion: WF-LPWE exerts its vasorelaxant effect independently of endothelium and possibly by inhibiting the release of calcium from intracellular calcium stores, receptor-operated calcium channels and formation of inositol 1,4,5- triphosphate. WF-LPWE vasorelaxant effect may also mediated via nitric oxide-independent direct involvement of soluble guanylate cyclase (sGC)/ cyclic guanosine monophosphate (cGMP) pathways.

Matched MeSH terms: Soluble Guanylyl Cyclase
Fulltext Methanolic Extract of Clinacanthus nutans Exerts Antinociceptive Activity via the Opioid/Nitric Oxide-Mediated, but cGMP-Independent, Pathways

Abdul Rahim MH, Zakaria ZA, Mohd Sani MH, Omar MH, Yakob Y, Cheema MS, et al.

Evid Based Complement Alternat Med, 2016;2016:1494981.
PMID: 27190528 DOI: 10.1155/2016/1494981

The objectives of the present study were to determine the mechanisms of antinociceptive effect of methanol extract of Clinacanthus nutans (Acanthaceae) leaves (MECN) using various animal nociceptive models. The antinociceptive activity of orally administered 10% DMSO, 100 mg/kg acetylsalicylic acid (ASA), 5 mg/kg morphine, or MECN (100, 250, and 500 mg/kg) was determined using the acetic acid-induced abdominal constriction (ACT), formalin-induced paw licking (FT), and hot plate tests (HPT). The role of opioid and nitric oxide/cyclic guanosine monophosphate (NO/cGMP) systems was also investigated. The results showed that MECN produced a significant (p < 0.05) antinociceptive response in all nociceptive models with the recorded ED50 value of 279.3 mg/kg for the ACT, while, for the early and late phases of the FT, the value was >500 mg/kg or 227.7 mg/kg, respectively. This antinociceptive activity was fully antagonized by naloxone (a nonselective opioid antagonist) but was partially reversed by l-arginine (l-arg; a nitric oxide [NO] precursor), Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME; an NO synthase inhibitor), or their combinations thereof. In contrast, 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ; a soluble guanylyl cyclase inhibitor) enhanced the extract's antinociception. UHPLC analysis revealed the presence of several flavonoid-based compounds with antinociceptive action. In conclusion, MECN exerted the peripherally and centrally mediated antinociceptive activity via the modulation of the opioid/NO-mediated, but cGMP-independent, systems.

Matched MeSH terms: Soluble Guanylyl Cyclase