Vasorelaxant and antiproliferative effects of berberine

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Abstract

The present study was intended to examine the relaxant effects of berberine in rat isolated mesenteric arteries. Berberine produced a rightward shift of the concentration–response curve to phenylephrine and significantly reduced the maximal contractile response to phenylephrine. Berberine (10−7–3×10−5 M) also relaxed the phenylephrine- and 9,11-dideoxy-11α,9α-epoxy-methanoprostaglandin F-precontracted arteries with respective IC50 values of 1.48±0.16×10−6 and 2.23±0.22×10−6 M. Removal of a functional endothelium significantly attenuated the berberine-induced relaxation (IC50: 4.73±0.32×10−6 M) without affecting the maximum relaxant response. Pretreatment with NG-nitro-l-arginine methyl ester (l-NAME) or methylene blue reduced the relaxant effect of berberine, and l-arginine (10−3 M) partially antagonized the effect of l-NAME. In contrast, pretreatment with 10−6 M glibenclamide or 10−5 M indomethacin had no effect. Berberine (10−5 M) reduced over by 50% the transient contraction induced by caffeine or phenylephrine in endothelium-denuded rings bathed in Ca2+-free Krebs solution. Pretreatment with putative K+ channel blockers, such as tetrapentylammonium ions (1–3×10−6 M), 4-aminopyridine (10−3 M), or Ba2+ (3×10−4 M), significantly attenuated the berberine-induced relaxation in endothelium-denuded arteries. In contrast, tetraethylammonium ions (3×10−3 M), charybdotoxin (10−7 M) or glibenclamide (10−6 M) were without effect. Berberine reduced the high-K+-induced sustained contraction and the relaxant response to berberine was greater in rings with endothelium (IC50: 4.41±0.47×10−6 M) than in those without endothelium (IC50: 8.73±0.74×10−6 M). However, berberine (10−6–10−4 M) did not affect the high-K+-induced increase of intracellular [Ca2+] in cultured aortic smooth muscle cells. Berberine did not affect active phorbol ester-induced contraction in Ca2+-free Krebs solution. In addition, berberine inhibited proliferation of cultured rat aortic smooth muscle cells with an IC50 of 2.3±0.43×10−5 M. These findings suggest that berberine could act at both endothelium and the underlying vascular smooth muscle to induce relaxation. Nitric oxide from endothelium may account primarily for the berberine-induced endothelium-dependent relaxation, while activation of tetrapentylammonium-, 4-aminopyridine- and Ba2+-sensitive K+ channels, inhibition of intracellular Ca2+ release from caffeine-sensitive pools, or a direct relaxant effect, is likely responsible for the berberine-induced endothelium-independent relaxation. Mechanisms related to either Ca2+ influx or protein kinase C activation may not be involved. Both vasorelaxant and antiproliferative effects may contribute to a long-term benefit of berberine in the vascular system.

Introduction

Berberine, an isoquinoline alkaloid, derived from the Chinese herb Huanglian and many other plants, such as the Berberidaceae family, has a varied pharmacology, including antibiotic activity (Hahn and Cuak, 1975), antitumor action (Nishino et al., 1986) and antimotility properties (Yamamoto et al., 1993). Extracts of berberine-containing plants have been used for many centuries in the treatment of diarrhea Dutta et al., 1972, Sack and Froehlich, 1982, Chang and But, 1987, probably through inhibition of mucosal Cl secretion (Taylor et al., 1999). Several studies indicate important cardiovascular effects of berberine. Berberine exerts both positive ionotropic and negative chronotropic effects in isolated guinea-pig atria (Shaffer, 1985), and an antifibrillatory effect (Pang et al., 1986). Berberine was also used in the treatment of congestive heart failure (Martin-Neto et al., 1988). In vivo, berberine lowers blood pressure in mammals Sabir and Bhide, 1971, Chun et al., 1979. In isolated vascular preparations, berberine causes relaxation (Chiou et al., 1991). More recently, Chiou et al. (1998) have reported that berberine possessed a relaxant effect on rabbit corpus cavernosal tissues. Activation of some K+ channels may contribute to the endothelium-independent relaxation induced by berberine (Chiou et al., 1998). Besides, a phospholipase C-mediated contractile mechanism may be partially involved in the berberine-induced vascular response (Bova et al., 1992). Nevertheless, the vascular sites for a hypotensive activity of berberine are not clear. It is possible that berberine acts on both endothelium and the underlying vascular smooth muscle to induce vasorelaxation via multiple cellular mechanisms. In this study, we attempted to examine the roles of endothelium-derived vasoactive factors, K+ channel activation, Ca2+ influx, intracellular Ca2+ release and protein kinase C-mediated pathway in the berberine-induced relaxation of rat isolated mesenteric artery, and to examine a possible antiproliferative effect of berberine on cultured aortic smooth muscle cells, which could account for its long-term beneficial effect in the cardiovascular system.

Section snippets

Tissue preparation

Male Sprague–Dawley rats (supplied by Animal Services Center, Chinese University of Hong Kong, Hong Kong) weighing ∼250–300 g were killed by cervical dislocation and bled. The main branch of the superior mesenteric artery was dissected out and cut into three 3-mm wide ring segments. The ring was mounted between two stainless wire hooks in a 10-ml organ bath filled with Krebs solution. The upper wire was connected to a force-displacement transducer (Grass Instruments, USA) and the lower one

Vasorelaxant effect of berberine

Phenylephrine contracted the rat isolated mesenteric artery rings with an EC50 of 6.0±0.07×10−7 M and a maximum increase in tension of 10.1×0.6 mN (n=5). After a control curve for the phenylephrine-induced contractile response, the rings were incubated for 30 min with different concentrations of berberine and a concentration–response curve for phenylephrine was again obtained. A low concentration of berberine (10−7 M) caused an approximately parallel shift of the phenylephrine

Discussion

Berberine was found to exert a hypotensive action in rats (Chun et al., 1979) and to raise intracavernous pressure in rabbits (Chiou et al., 1998), however, the mechanism responsible for its vasodilator effect is not clear. The present study showed a relaxant action of berberine in rat isolated mesenteric arteries. Berberine at concentrations higher than 10−7 M showed a non-competitive antagonism against the phenylephrine-induced contraction. It was reported before that berberine derivatives

Acknowledgements

This work was supported by a grant from Hong Kong Research Grants Council (CUHK 4217/97M) and an UPGC Direct Grant (A/C 2040705).

References (31)

  • Y.T. Chun et al.

    A biochemical study on the hypotensive effect of berberine in rats

    Gen. Pharmacol.

    (1979)
  • C.T. Taylor et al.

    Berberine inhibits ion transport in human colonic epithelia

    Eur. J. Pharmacol.

    (1999)
  • A. Adeagbo et al.

    Varying extracellular [K+]: a functional approach to separate EDHF- and EDNO-related mechanisms in perfused rat mesenteric arterial bed

    J. Cardiovasc. Pharmacol.

    (1993)
  • S. Bova et al.

    On the mechanism of vasodilating action of berberine: possible role of inositol lipid signaling system

    J. Pharmacol. Exp. Ther.

    (1992)
  • J.E. Brayden et al.

    Regulation of arterial tone by activation of calcium-activated potassium channels

    Science

    (1992)
  • H.M. Chang et al.
  • G. Chen et al.

    Calcium dependency of the endothelium-dependent hyperpolarization in smooth muscle cells of the rabbit carotid artery

    J. Physiol.

    (1990)
  • W.F. Chiou et al.

    Mechanism of vasodilatory effect of berberine in rat mesenteric artery

    Eur. J. Pharmacol.

    (1991)
  • W.F. Chiou et al.

    Relaxation of corpus cavernosum and raised intracavernous pressure by berberine in rabbit

    Br. J. Pharmacol.

    (1998)
  • N.K. Dutta et al.

    Berberine in toxin induced experimental cholera

    Br. J. Pharmacol.

    (1972)
  • M. Félétou et al.

    Endothelium-dependent hyperpolarization of canine coronary smooth muscle

    Br. J. Pharmacol.

    (1988)
  • F.E. Hahn et al.

    Berberine

  • Y. Huang

    Inhibitory effect of noradrenaline uptake inhibitors on contractions of rat aortic smooth muscle

    Br. J. Pharmacol.

    (1996)
  • Y. Huang et al.

    Role of endothelium and K+ channels in dobutamine-induced relaxation in rat mesenteric artery

    Clin. Exp. Pharmacol. Physiol.

    (1998)
  • P. Langton et al.

    Block on calcium-activated potassium channels in mammalian arterial myocytes by tetraethylammonium ions

    Am. J. Physiol.

    (1991)
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