Vasorelaxant and antiproliferative effects of berberine.
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)-3x10(-5) M) also relaxed the phenylephrine- and 9,11-dideoxy-11alpha, 9alpha-epoxy-methanoprostaglandin F(2alpha)-precontracted arteries with respective IC(50) values of 1.48+/-0.16x10(-6) and 2.23+/-0. 22x10(-6) M. Removal of a functional endothelium significantly attenuated the berberine-induced relaxation (IC(50): 4.73+/-0. 32x10(-6) M) without affecting the maximum relaxant response. Pretreatment with N(G)-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 Ca(2+)-free Krebs solution. Pretreatment with putative K(+) channel blockers, such as tetrapentylammonium ions (1-3x10(-6) M), 4-aminopyridine (10(-3) M), or Ba(2+) (3x10(-4) M), significantly attenuated the berberine-induced relaxation in endothelium-denuded arteries. In contrast, tetraethylammonium ions (3x10(-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 (IC(50): 4.41+/-0.47x10(-6) M) than in those without endothelium (IC(50): 8.73+/-0.74x10(-6) M). However, berberine (10(-6)-10(-4) M) did not affect the high-K(+)-induced increase of intracellular [Ca(2+)] in cultured aortic smooth muscle cells. Berberine did not affect active phorbol ester-induced contraction in Ca(2+)-free Krebs solution. In addition, berberine inhibited proliferation of cultured rat aortic smooth muscle cells with an IC(50) of 2.3+/-0.43x10(-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 Ba(2+)-sensitive K(+) channels, inhibition of intracellular Ca(2+) release from caffeine-sensitive pools, or a direct relaxant effect, is likely responsible for the berberine-induced endothelium-independent relaxation. Mechanisms related to either Ca(2+) 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.
Ko
W H
WH
Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong, People's Republic of China.
Yao
X Q
XQ
Lau
C W
CW
Law
W I
WI
Chen
Z Y
ZY
Kwok
W
W
Ho
K
K
Huang
Y
Y
D000818:Animals; D001011:Aorta / Q000166:cytology; D001599:Berberine / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D017538:Mesenteric Artery, Superior / Q000187:drug effects / Q000502:physiology; D008751:Methylene Blue / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*
D010703:Phorbol Esters; D026902:Potassium Channel Blockers; D001599:Berberine; C008874:phorbol-12,13-diacetate; D000001:Calcimycin; D011188:Potassium; D002118:Calcium; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester