Kaempferol-induces vasorelaxation via endothelium-independent pathways in rat isolated pulmonary artery

doi:10.1016/j.pharep.2018.03.006

Pharmacological Reports

Volume 70, Issue 5, October 2018, Pages 863-874

https://doi.org/10.1016/j.pharep.2018.03.006 Get rights and content

Abstract

Background

Kaempferol, a flavonoid, is the essential part of human diet. Flavonoids have different pharmacological activities like cardioprotective, anti-inflammatory and anti-oxidant. The aim of current study was to investigate vasorelaxant potential of kaempferol on rat isolated pulmonary artery and to assess the underling mechanisms.

Methods

Tension experiments were conducted on both the branches of main pulmonary artery of rats. Experiments were done using isolated organ bath system by recording tension with the help of data acquisition system, Power Lab.

Results

Kaempferol (10⁻⁸–10^−4.5 M) caused concentration-dependent relaxation (E_max 124.33 ± 4.37%; pD₂ 5.03 ± 0.084) of endothelium-intact pulmonary artery. In endothelium-denuded arterial rings, relaxation produced by kaempferol was not different from intact artery. L-NAME, indomethacin, combination of L-NAME and indomethacin did not show any effect on kaempferol-induced relaxation. Kaempferol-induced relaxation was reduced (E_max 55.53 ± 7.72%) in 60 mM K⁺ pre-contracted pulmonary arterial rings. Iberiotoxin significantly decreased (E_max 71.68 ± 11.84%) the relaxation response. However, glibenclamide, BaCl₂, 4-AP (1 mM) and ICI182780 did not reduce the kaempferol-induced relaxation. TEA (10 mM) and 4-AP (5 mM) significantly reduced relaxation. Kaempferol-induced relaxation was significantly attenuated (E_max 94.92 ± 19.60%) in presence of ODQ. H89 significantly decreased (E_max, 98.38 ± 8.55%) the kaempferol-induced relaxation in rat pulmonary arterial rings. HC067047 and apamin did not show any effect on kaempferol-induced relaxation. In endothelium-denuded K⁺ (80 mM)-depolarized arterial rings, kaempferol (10 μM) markedly reduced CaCl₂-induced contractions (E_max 35.14 ± 6.53% vs. control 69.04 ± 15.19%).

Conclusion

Kaempferol relaxes rat pulmonary artery in endothelium-independent manner through involvement of BK_Ca channel, sGC, PKA pathways and inhibition of Ca²⁺-influx through L-type calcium channels.

Introduction

Pulmonary hypertension is associated with vasoconstriction and vascular remodeling and leads to high mortality and morbidity [1]. This condition is considered as the main cause of right ventricular hypertrophy and heart failure [2]. Poor prognosis of the disease, heavy mortality rate and absence of proper curative treatment are existing in the condition of pulmonary hypertension [3]. Search of new relaxants of pulmonary artery disease is of high relevance for a better understanding of pulmonary signaling pathways and the development of new therapeutic strategies for pulmonary hypertension and related conditions [4].

Kaempferol is a flavonoid which is present in various edible plants such as tea, cabbage, kale, broccoli, grapefruit, beans, and further very commonly used in traditional medicine [5,6]. It is used for the management of various cardiovascular diseases including thrombosis, hypertension and coronary artery disease [7]. Kaempferol enhances the vasorelaxant effects in various blood vessels like porcine coronary artery [8,7], human umbilical vein endothelial cells [9], rat aorta [[10], [11], [12]]. Nevertheless, the possible vasorelaxant effect of kaempferol in the rat pulmonary artery and its underlying mechanisms are not known. Therefore, the first objective of the present study was to investigate the vasorelaxant potential of kaempferol in the rat isolated pulmonary artery through in vitro experiments. The second objective was to explore the underlying possible mechanisms of vasorelaxant activity of the kaempferol.

Section snippets

Experimental animals

Apparently healthy adult male Wistar rats (150–250 g) were procured from the Laboratory Animal Resource (LAR) Section of the institute. Rats were kept for acclimatization for a period of seven days before conduction of various tension experiments. All protocols followed in present study were approved by the Institutional Animal Ethics Committee (IAEC).

Tension recording experiments

Rats were killed by excising the abdominal aorta under urethane (1.2 g/kg body weight intraperitoneally) anesthesia. Further, heart and lungs enbloc

Effect of kaempferol on endothelium-intact and -denuded pulmonary arterial rings

The representative tracings in Fig. 1A and B show the effect of kaempferol on endothelium-intact and −denuded rat isolated pulmonary artery. Kaempferol (10⁻⁸–10^−4.5 M), added cumulatively at an increment of 0.5 log unit, caused concentration-dependent relaxation in endothelium-intact/denuded pulmonary arterial rings pre-contracted with 1 μM phenylephrine (0.309 ± 0.034 g)/(0.334 ± 0.041 g), respectively. The line diagram in Fig. 1C depicts concentration-response curves of kaempferol-induced relaxation

Discussion

The present study was conducted to investigate the kaempferol-induced relaxation in the rat isolated pulmonary artery. Kaempferol showed an endothelium-independent relaxation in this vessel. There are various factors released from the endothelium which contribute to regulate pulmonary vascular tone. In present study, L-NAME (NOS inhibitor), indomethacin (COX inhibitor) and combination of both did not show any effect on kaempferol-induced relaxations. A previous report suggested that kaempferol

Conflict of interest

There are no conflicts of interest.

Financial support

Financial support was provided by the ICAR-Indian Veterinary Research Institute, Izatnagar, India for completion of this work.

Acknowledgement

Authors are thankful to the Director, ICAR-Indian Veterinary Research Institute, Izatnagar, India for providing the necessary facilities to complete this work.

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Original articleKaempferol-induces vasorelaxation via endothelium-independent pathways in rat isolated pulmonary artery

Abstract

Background

Methods

Results

Conclusion

Introduction

Section snippets

Experimental animals

Tension recording experiments

Effect of kaempferol on endothelium-intact and -denuded pulmonary arterial rings

Discussion

Conflict of interest

Financial support

Acknowledgement

J Pharm Biomed Anal

Eur J Pharmacol

Toxicol Appl Pharmacol

Pharmacol Rep

Life Sci

Calorie restriction attenuates monocrotaline-induced pulmonary arterial hypertension in rats

J Cardiovasc Pharmacol

Echinacoside induces rat pulmonary artery vasorelaxation by opening the NO-cGMP-PKG-BKCa channels and reducing intracellular Ca2+ levels

Acta Pharmacol Sin

An evaluation of vardenafil as a calcium channel blocker in pulmonary artery in rats

Indian J Pharmacol

RGD peptides induce relaxation of pulmonary arteries and airways via β3-integrins

FASEB J

A review on the dietary flavonoid kaempferol

Mini Rev Med Chem

Kaempferol enhances endothelium-dependent relaxation in the porcine coronary artery through activation of large-conductance Ca(2+) −activated K(+) channels

Br J Pharmacol

Original article
Kaempferol-induces vasorelaxation via endothelium-independent pathways in rat isolated pulmonary artery

Echinacoside induces rat pulmonary artery vasorelaxation by opening the NO-cGMP-PKG-BKCa channels and reducing intracellular Ca²⁺ levels