Korean J Physiol Pharmacol.  2013 Feb;17(1):31-36. 10.4196/kjpp.2013.17.1.31.

The Inhibitory Effect of Eupatilin on the Agonist-Induced Regulation of Vascular Contractility

• Je HD
• Kim HD
• Jeong JH

• KMID: 1432760
• DOI: http://doi.org/10.4196/kjpp.2013.17.1.31

Abstract

The present study was undertaken to investigate the influence of eupatilin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Eupatilin more significantly relaxed fluoride-induced vascular contraction than thromboxane A2 or phorbol ester-induced contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, eupatilin significantly inhibited fluoride-induced increases in pMYPT1 levels. On the other hand, it didn't significantly inhibit phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the primarily inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1. This study provides evidence regarding the mechanism underlying the relaxation effect of eupatilin on agonist-induced vascular contraction regardless of endothelial function.

Keyword

ERK1/2; Eupatilin; MYPT1; Rho-kinase; Vasodilation

MeSH Terms

Animals
Contracts
Flavonoids
Hand
Humans
Isometric Contraction
Male
Muscle, Smooth, Vascular
Nitric Oxide
Phorbols
Phosphorylation
Rats
Relaxation
rho-Associated Kinases
Thromboxane A2
Vasodilation
Flavonoids
Nitric Oxide
Phorbols
Thromboxane A2
rho-Associated Kinases

Figure

• 

  Fig. 1 A representative tracing of eupatilin-induced relaxation on the fluoride- (A), thromboxane A2- (B) or phorbol ester- (C) induced vasoconstriction in rat aorta.

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  Fig. 2 Effect of eupatilin on fluoride-induced vascular contraction. Each ring was equilibrated in the organ bath solution for 30~60 min before relaxation responses to eupatilin were measured. Data are expressed as the means of 3~5 experiments with vertical lines representing SEMs. Control respectively. *p<0.05, **p<0.01 versus.

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  Fig. 3 Effect of eupatilin on thromboxane A2-induced vascular contraction. Each ring was equilibrated in the organ bath solution for 30~60 min before relaxation responses to eupatilin were measured. Data are expressed as the means of 3~5 experiments with vertical lines representing SEMs. Control respectively. *p<0.05.

• 

  Fig. 4 Effect of eupatilin on phorbol ester-induced vascular contraction. Each ring was equilibrated in the organ bath solution for 30~60 min before relaxation responses to eupatilin were measured. Data are expressed as the means of 3~5 experiments with vertical lines representing SEMs. Control respectively. *p<0.05.

• 

  Fig. 5 Effect of eupatilin on fluoride-induced increases in phospho-MYPT1 levels. Phospho-MYPT1 protein levels were significantly decreased in quick frozen eupatilin-treated rat aorta in the absence of endothelium compared to vehicle-treated rat aorta precontracted with fluoride. The upper panel shows a typical blot and the lower panel shows average densitometry results for relative levels of phospho-MYPT1. Data are expressed as the means of 3~5 experiments with vertical lines representing SEMs. **p<0.01, ##p<0.01, versus control or normal group respectively. Eupa: 0.1 mM eupatilin; NaF: 8 mM sodium fluoride.

• 

  Fig. 6 Effect of eupatilin on phorbol ester-induced increases in phospho-ERK1/2 levels. Phospho-ERK1/2 protein levels were not decreased in quick frozen eupatilin-treated rat aortas in the absence of endothelium compared to vehicle-treated rat aortas precontracted with phorbol ester. The upper panel shows a typical blot and the lower panel shows average densitometry results for relative levels of phospho-ERK1/2. Data are expressed as the means of 3~5 experiments with vertical lines representing SEMs. ##p<0.01, versus normal group respectively. Eupa: 0.1 mM eupatilin; PDBu: 1 µM phorbol 12,13-dibutyrate.

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