title: Homocysteine impaired endothelial function through compromised vascular endothelial growth factor/Akt/endothelial nitric oxide synthase signalling.
abstract: 1. Hyperhomocysteinaemia (HHcy) is associated with endothelial dysfunction and has been recognized as a risk factor of cardiovascular disease. The present study aimed to investigate the effect of homocysteine (Hcy) on endothelial function in vivo and in vitro, and the underlying signalling pathways. 2. The HHcy animal model was established by intragastric administration with l-methionine in rats. Plasma Hcy and nitric oxide (NO) concentration were measured by fluorescence immunoassay or nitrate reductase method, respectively. Vasorelaxation in response to acetylcholine and sodium nitroprusside were carried out on aortic rings. Human umbilical vein endothelial cells (HUVEC) were treated with indicated concentrations of Hcy in the in vitro experiments. Intracellular NO level and NO concentration in culture medium were assayed. The alterations of possible signalling proteins were detected by western blot analysis. 3. l-methionine administration induced a significant increase in plasma Hcy and decrease in plasma NO. Endothelium-dependent relaxation of aortic rings in response to acetylcholine was impaired in l-methionine-administrated rats. The in vitro study showed that Hcy reduced both intracellular and culture medium NO levels. Furthermore, Hcy decreased phosphorylation of endothelial nitric oxide synthase (eNOS) at serine-1177 and phosphorylation of Akt at serine-473. Hcy-induced dephosphorylation of eNOS at Ser-1177 was partially reversed by insulin (Akt activator) and GF109203X (PKC inhibitor). Furthermore, Hcy reduced vascular endothelial growth factor (VEGF) expression in a dose-dependent manner. 4. In conclusion, Hcy impaired endothelial function through compromised VEGF/Akt/endothelial nitric oxide synthase signalling. These findings will be beneficial for further understanding the role of Hcy in cardiovascular disease.
authors.affiliation: Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
authors.forename: Ting-Ting
authors.initials: TT
authors.lastname: Yan
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Xuan-Hong
authors.initials: XH
authors.lastname: Zhang
authors.forename: Wei-Kang
authors.initials: WK
authors.lastname: Wu
authors.forename: Juan
authors.initials: J
authors.lastname: Sun
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Quan
authors.initials: Q
authors.lastname: Zhang
authors.forename: Hong-Mei
authors.initials: HM
authors.lastname: Tan
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D015153:Blotting, Western; D018929:Cell Culture Techniques; D002460:Cell Line; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D006710:Homocysteine / Q000097:blood / Q000494:pharmacology*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood / Q000201:enzymology / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008715:Methionine; D009569:Nitric Oxide / Q000096:biosynthesis / Q000097:blood; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D006710:Homocysteine; D009569:Nitric Oxide; D008715:Methionine; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D051057:Proto-Oncogene Proteins c-akt