Hyperhomocystinemia impairs endothelial function and eNOS activity via PKC activation.
OBJECTIVE
A risk factor for cardiovascular disease, hyperhomocystinemia (HHcy), is associated with endothelial dysfunction. In this study, we examined the mechanistic role of HHcy in endothelial dysfunction.


RESULTS
Through the use of 2 functional models, aortic rings and intravital video microscopy of the cremaster, we found that arterial relaxation in response to the endothelium-dependent vessel relaxant, acetylcholine or the nitric oxide synthase (NOS) activator (A23187), was significantly impaired in cystathionine beta-synthase null (CBS(-/-)) mice. However, the vascular smooth muscle cell (VSMC) response to the nitric oxide (NO) donor (SNAP) was preserved in CBS(-/-) mice. In addition, superoxide dismutase and catalase failed to restore endothelium-dependent vasodilatation. Endothelial nitric oxide synthase (eNOS) activity was significantly reduced in mouse aortic endothelial cells (MAECs) of CBS(-/-) mice, as well as in Hcy-treated mouse and human aortic endothelial cells (HAECs). Hcy-mediated eNOS inhibition--which was not rescued by adenoviral transduction of superoxide dismutase and glutathione peroxidase, or by tetrahydrobiopterin, sepiapterin, and arginine supplementations in MAEC--was associated with decreased protein expression and increased threonine 495 phosphorylation of eNOS in HAECs. Ultimately, a protein kinase C (PKC) inhibitor, GF109203X (GFX), reversed Hcy-mediated eNOS inactivation and threonine 495 phosphorylation in HAECs.


CONCLUSIONS
These data suggest that HHcy impairs endothelial function and eNOS activity, primarily through PKC activation.
Jiang
Xiaohua
X
Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
Yang
Fan
F
Tan
Hongmei
H
Liao
Dan
D
Bryan
Robert M
RM
Randhawa
Jaspreet K
JK
Rumbaut
Rolando E
RE
Durante
William
W
Schafer
Andrew I
AI
Yang
Xiaofeng
X
Wang
Hong
H
D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000166:cytology; D001120:Arginine / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism / Q000494:pharmacology; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D003541:Cystathionine beta-Synthase / Q000235:genetics / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology*; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D005979:Glutathione Peroxidase / Q000235:genetics; D006710:Homocysteine / Q000097:blood; D006801:Humans; D020138:Hyperhomocysteinemia / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D011493:Protein Kinase C / Q000378:metabolism*; D011622:Pterins / Q000378:metabolism / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000235:genetics; D014664:Vasodilation / Q000502:physiology; D000094765:Glutathione Peroxidase GPX1
D000975:Antioxidants; D011622:Pterins; D006710:Homocysteine; D001708:Biopterins; C018524:N,N-dimethylarginine; D001120:Arginine; C016727:sepiapterin; D005979:Glutathione Peroxidase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D013482:Superoxide Dismutase; D011493:Protein Kinase C; D003541:Cystathionine beta-Synthase; C003402:sapropterin; D000094765:Glutathione Peroxidase GPX1