Effects of Astragalus membranaceus and its main components on the acute phase endothelial dysfunction induced by homocysteine.
OBJECTIVE
This study was designed to investigate the effects of Astragalus membranaceus (AM) and its main components, astragalus saponin (ASP), astragalus polysaccharide (APS) and aminobutyric acid (GABA), on homocysteine (Hcy) induced acute impairment of vascular tone and to explore whether the antioxidant mechanism was involved in AM protective effect.


METHODS
Inhibitory effects of Hcy and protective effects of AM and its main components on endothelium-dependent relaxation of aortic rings were determined by isometric tension recordings and nitric oxide signaling was assayed with 125I-cGMP RIA Kit. Furthermore, generation of reactive oxygen species (ROS) in endothelial cells was detected using 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCF-DA).


RESULTS
Hcy significantly inhibited endothelium-dependent relaxation to acetylcholine (ACh) in a dose-dependent manner, and decreased cGMP levels increased by ACh in aorta. Furthermore, superoxide dismutase (SOD), AM, and ASP markedly attenuated inhibition of vasorelaxation and downregulation of cGMP level by Hcy, and APS exerted a tendency to reverse both of the depressive responses, while GABA had no similar effects. Additionally, partially impaired relaxation by Hcy was completely blocked due to the presence of N(omega)-nitro-L-arginine-methyl ester (L-NAME), which could not be further altered by treatment with AM, ASP, APS or GABA. Finally, Hcy significantly increased intracellular ROS levels in endothelial cells as measured by CM-H2DCF-DA fluorescence. SOD, AM, ASP, and APS, but not GABA, inhibited Hcy-stimulated ROS generation.


CONCLUSIONS
This study demonstrated that AM and ASP, potently protected endothelium-dependent relaxation against the acute injury from Hcy through nitric oxide regulatory pathways, in which antioxidation played a key role.
Zhang
Bi-Qi
BQ
Department of Cardiology, The First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79, Qingchun St, Hangzhou 310003, Zhejiang, PR China.
Hu
Shen-Jiang
SJ
Qiu
Li-Hong
LH
Zhu
Jian-hua
JH
Xie
Xian-Ji
XJ
Sun
Jian
J
Zhu
Zhao-Hui
ZH
Xia
Qiang
Q
Bian
Ka
K
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D027885:Astragalus propinquus; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018517:Plant Roots; D011134:Polysaccharides / Q000302:isolation & purification / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D012503:Saponins / Q000302:isolation & purification / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000302:isolation & purification / Q000494:pharmacology
D000975:Antioxidants; D010936:Plant Extracts; D011134:Polysaccharides; D017382:Reactive Oxygen Species; D012503:Saponins; D014665:Vasodilator Agents; D006710:Homocysteine; D009569:Nitric Oxide; D005680:gamma-Aminobutyric Acid; D013482:Superoxide Dismutase; D006152:Cyclic GMP; D000109:Acetylcholine