Anemoside A₃-induced Relaxation in Rat Renal Arteries: Role of Endothelium and Ca²⁺ Channel Inhibition

Abstract

Anemoside A₃, a lupane-type triterpenoid saponin, exists in the roots of Pulsatilla chinensis, but its pharmacological properties are largely unknown. The present study aimed to investigate the mechanisms underlying anemoside A₃-induced relaxation in rat renal arteries. Changes of isometric force were determined on arteries with a myograph. Anemoside A₃ caused concentration-dependent relaxation in precontracted aortas, mesenteric, left coronary, and renal arteries. Removal of endothelium or treatment with charybdotoxin plus apamin slightly but significantly attenuated the relaxation in renal arteries. TEA⁺ inhibited the relaxation caused by anemoside A₃ in renal arteries with and without endothelium while glibenclamide, BaCl₂, or capsaicin had no effect on it. Anemoside A₃ produced less relaxation in rings contracted by 60 mM KCl compared with rings contracted by receptor-dependent constrictors. It further inhibited contractions induced by Ca²⁺ influx through nifedipine-sensitive voltage-gated Ca²⁺ channels, nifedipine-insensitive receptor-operated Ca²⁺ channels, and by intracellular Ca²⁺ release. Pretreatment with nifedipine attenuated anemoside A₃-induced relaxation. Taken together, the present results indicate that anemoside A₃ produces relaxation in rat renal arteries through multiple mechanisms. The release of CTX/apamin-sensitive endothelium-derived hyperpolarizing factor, stimulation of TEA⁺-sensitive K⁺ channel, and inhibition of Ca²⁺ influx jointly contribute to the relaxation.

Key words

Pulsatilla chinensis - Ranunculaceae - anemoside A₃ - vasorelaxation - Ca²⁺ channel - endothelium - rat renal arteries

References

• 1 Grassi D, Desideri G, Croce G, Tiberti S, Aggio A, Ferri C. Flavonoids, vascular function and cardiovascular protection.  Curr Pharm Des. 2009;  15 1072-1084
• 2 Chen Z Y, Peng C, Jiao R, Wong Y M, Yang N, Huang Y. Anti-hypertensive nutraceuticals and functional foods.  J Agric Food Chem. 2009;  57 4485-4499
• 3 Kim N D, Kang S Y, Kim M J, Park J H, Schini-Kerth V B. The ginsenoside Rg₃ evokes endothelium-independent relaxation in rat aortic rings: role of K⁺ channels.  Eur J Pharmacol. 1999;  367 51-57
• 4 Zhou W, Chai H, Lin P H, Lumsden A B, Yao Q, Chen C, Tex H. Ginsenoside Rb₁ blocks homocysteine-induced endothelial dysfunction in porcine coronary arteries.  J Vasc Surg. 2005;  41 861-868
• 5 Kwan C Y, Kwan T K. Effects of Panax notoginseng saponins on vascular endothelial cells in vitro.  Acta Pharmacol Sin. 2000;  21 1101-1105
• 6 Ye W C, Zhao S X, Liu J H. Chemical constituents of Pulsatilla chinensis (I).  J China Pharm Univ. 1990;  21 264-266
• 7 Li Q, Shi Y H, Gao Y G, Ye W C, Yao X S. Determination of the three-dimensional structure of anemoside A₃ in solution by NMR and molecular simulation.  J China Pharm Univ. 2006;  37 123-126
• 8 Gao X D, Ye W C, Yu C H, Zhang Y, Tan R X, Li M, Wendy Hsiao W L. Pulsatilloside A and anemoside A₃ protect PC12 cells from apoptosis induced by sodium cyanide and glucose deprivation.  Planta Med. 2003;  69 171-174
• 9 Tsang S Y, Yao X Q, Essin K, Wong C M, Chan F L, Gollasch M, Huang Y. Raloxifene relaxes rat cerebral arteries in vitro and inhibits L-type voltage-sensitive Ca²⁺ channels.  Stroke. 2004;  35 1709-1714
• 10 Leung F P, Yao X Q, Lau C W, Ko W H, Lu L, Huang Y. Raloxifene relaxes rat intrarenal arteries by inhibiting Ca²⁺ influx.  Am J Physiol Renal Physiol. 2005;  289 F137-F144
• 11 Standen N B, Quayle J M, Davies N W, Brayden J E, Huang Y, Nelson M T. Hyperpolarizing vasodilators activate ATP-sensitive K⁺ channels in arterial smooth muscle.  Science. 1989;  245 177-180
• 12 Langton P D, Nelson M T, Huang Y, Standen N B. Block of calcium-activated potassium channels in mammalian arterial myocytes by tetraethylammonium ions.  Am J Physiol. 1991;  260 H927-H934
• 13 Quayle J M, McCarron J G, Brayden J E, Nelson M T. Inward rectifier K⁺ currents in smooth muscle cells from rat resistance-sized cerebral arteries.  Am J Physiol. 1993;  265 C1363-C1370
• 14 Huang Y, Ho I H. Separate activation of intracellular Ca²⁺ release, voltage-dependent and receptor-operated Ca²⁺ channels in the rat aorta.  Chin J Physiol. 1996;  39 1-8
• 15 Gössl M, Lerman A. Endothelin: beyond a vasoconstrictor.  Circulation. 2006;  113 1156-1158
• 16 Sakariassen K S, Alberts P, Fontana P, Mann J, Bounameaux H, Sorensen A S. Effect of pharmaceutical interventions targeting thromboxane receptors and thromboxane synthase in cardiovascular and renal diseases.  Future Cardiol. 2009;  5 479-493
• 17 Edwards G, Dora K A, Gardener M J, Garland C J, Weston A H. K⁺ is an endothelium-derived hyperpolarizing factor in rat arteries.  Nature. 1998;  396 269-272

1 DMZ and SML contributed equally.