Growth hormone-releasing peptide ghrelin inhibits homocysteine-induced endothelial dysfunction in porcine coronary arteries and human endothelial cells.
OBJECTIVE
Ghrelin, a novel growth hormone-releasing peptide, is implicated to play a protective role in cardiovascular tissues. However, it is not clear whether ghrelin protects vascular tissues from injury secondary to risk factors such as homocysteine (Hcy). This study investigated the effect and potential mechanisms of ghrelin on Hcy-induced endothelial dysfunction.


METHODS
Porcine coronary artery rings were incubated for 24 hours with ghrelin (100 ng/mL), Hcy (50 microM), or ghrelin plus Hcy. Endothelial vasomotor function was evaluated using the myograph tension model. The response to the thromboxane A(2)analog U46619, bradykinin, and sodium nitroprusside was analyzed. Endothelial nitric oxide synthase (eNOS) expression was determined using real-time polymerase chain reaction and immunohistochemistry staining, and superoxide anion production was documented lucigenin-enhanced chemiluminescence analysis. Human coronary artery endothelial cells (HCAECs) were treated with different concentrations of Hcy, ghrelin, or antighrelin receptor antibody for 24 hours, and eNOS protein levels were determined by Western blot analysis.


RESULTS
Maximal contraction with U46619 and endothelium-independent vasorelaxation with sodium nitroprusside were not different among the four groups. However, endothelium-dependent vasorelaxation with bradykinin (10(-6) M) was significantly reduced by 34% with Hcy compared with controls (P < .05). The addition of ghrelin to Hcy had a protective effect, with 61.6% relaxation, which was similar to controls (64.7%). Homocysteine significantly reduced eNOS expression, whereas ghrelin cotreatment effectively restored eNOS expression to the control levels. Superoxide anion levels, which were increased by 100% with Hcy, returned to control levels with ghrelin cotreatment. Ghrelin also effectively blocked the Hcy-induced decrease of eNOS protein levels in HCAECs in a concentration-dependent manner. Antighrelin receptor antibody effectively inhibited the effect of ghrelin.


CONCLUSIONS
Ghrelin has a protective effect in the porcine coronary artery by blocking Hcy-induced endothelial dysfunction, improving eNOS expression, and reducing oxidative stress. Ghrelin also shows a protective effect on HCACEs from the Hcy-induced decrease in eNOS protein levels. The effect of ghrelin is receptor-dependent. Thus, ghrelin administration may have beneficial effects in the treatment of vascular disease in patients with hyperhomocysteinemia.
Hedayati
Nasim
N
Michael E DeBakey Department of Surgery, Division of Vascular Surgery and Endovascular Therapy, Molecular Surgeon Research Center, Baylor College of Medicine , Houston, Texas 77030-3411, USA.
Annambhotla
Suman
S
Jiang
Jun
J
Wang
Xinwen
X
Chai
Hong
H
Lin
Peter H
PH
Yao
Qizhi
Q
Chen
Changyi
C
D000818:Animals; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D054439:Ghrelin / Q000378:metabolism*; D006710:Homocysteine / Q000378:metabolism*; D006801:Humans; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D013552:Swine; D046509:Tissue Culture Techniques; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
C515349:GHRL protein, human; D054439:Ghrelin; D012333:RNA, Messenger; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D006710:Homocysteine; D013481:Superoxides; D009569:Nitric Oxide; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III