Angiotensin II induces endothelin-1 gene expression via extracellular signal-regulated kinase pathway in rat aortic smooth muscle cells.
OBJECTIVE
Angiotensin II (Ang II) increases vascular endothelin-1 (ET-1) tissue levels, which in turn mediate a major part of Ang II-stimulated vascular growth and hypertension in vivo. Ang II also stimulates reactive oxygen species (ROS) generation in vascular smooth muscle cells (SMCs). However, whether ROS are involved in Ang II-induced ET-1 gene expression and the related intracellular mechanisms in vascular SMCs remains to be determined.


METHODS
Cultured rat aortic SMCs were stimulated with Ang II, [3H]thymidine incorporation and the ET-1 gene expression was examined. Antioxidants pretreatment on Ang II-induced extracellular signal-regulated kinase (ERK) phosphorylation were performed to elucidate the redox-sensitive pathway in proliferation and ET-1 gene expression.


RESULTS
Ang II-increased DNA synthesis was inhibited by AT(1) receptor antagonist (olmesartan) and ET(A) receptor antagonist (BQ485). ET-1 gene was induced with Ang II as revealed by Northern blotting and promoter activity assay. Ang II-increased intracellular ROS levels were inhibited by olmesartan and antioxidants. Antioxidants suppressed Ang II-induced ET-1 gene expression and ERK phosphorylation. An ERK inhibitor U0126 fully inhibited Ang II-induced ET-1 expression. Co-transfection of dominant negative mutant of Ras, Raf and MEK1 attenuated the Ang II-increased ET-1 promoter activity, suggesting that the Ras-Raf-ERK pathway is required for Ang II-induced ET-1 gene. Truncation and mutational analysis of the ET-1 gene promoter showed that activator protein-1 (AP-1) binding site was an important cis-element in Ang II-induced ET-1 gene expression. Moreover, Ang II- or H(2)O(2)-induced AP-1 reporter activities were also inhibited by antioxidants.


CONCLUSIONS
Our data suggest that ROS are involved in Ang II-induced proliferation and the redox-sensitive ERK pathway plays a role in ET-1 gene expression in rat aortic SMCs.
Hong
Hong-Jye
HJ
School of Chinese Medicine, China Medical University, Taichung, Taiwan, ROC.
Chan
Paul
P
Liu
Ju-Chi
JC
Juan
Shu-Hui
SH
Huang
Meng-Ting
MT
Lin
Jaung-Geng
JG
Cheng
Tzu-Hurng
TH
D000804:Angiotensin II / Q000494:pharmacology*; D047228:Angiotensin II Type 1 Receptor Blockers; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001011:Aorta; D001381:Azepines / Q000494:pharmacology; D001665:Binding Sites; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1 / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D020935:MAP Kinase Signaling System; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000032:analysis; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism
D047228:Angiotensin II Type 1 Receptor Blockers; D000975:Antioxidants; D001381:Azepines; D002070:Butadienes; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1; D009570:Nitriles; D009842:Oligopeptides; D017382:Reactive Oxygen Species; D018808:Transcription Factor AP-1; C113580:U 0126; D000804:Angiotensin II; C083116:BQ 485; D020928:Mitogen-Activated Protein Kinases