Involvement of reactive oxygen species in angiotensin II-induced endothelin-1 gene expression in rat cardiac fibroblasts.
OBJECTIVE
The aim of this study was to investigate the effects of angiotensin II (Ang II) on fibroblast proliferation and endothelin-1 (ET-1) gene induction, focusing especially on reactive oxygen species (ROS)-mediated signaling in cardiac fibroblasts.


BACKGROUND
Angiotensin II increases ET-1 expression, which plays an important role in Ang II-induced fibroblast proliferation. Angiotensin II also stimulates ROS generation in cardiac fibroblasts. However, whether ROS are involved in Ang II-induced proliferation and ET-1 expression remains unknown.


METHODS
Cultured neonatal rat cardiac fibroblasts were stimulated with Ang II, and then [(3)H]thymidine incorporation and the ET-1 gene expression were examined. We also examined the effects of antioxidants on Ang II-induced proliferation and mitogen-activated protein kinase (MAPK) phosphorylation to elucidate the redox-sensitive pathway in fibroblast proliferation and ET-1 gene expression.


RESULTS
Both AT(1) receptor antagonist (losartan) and ET(A) receptor antagonist (BQ485) inhibited Ang II-increased DNA synthesis. Endothelin-1 gene was induced with Ang II as revealed by Northern blotting and promoter activity assay. Angiotensin II increased intracellular ROS levels, which were inhibited with losartan and antioxidants. Antioxidants further suppressed Ang II-induced ET-1 gene expression, DNA synthesis, and MAPK phosphorylation. PD98059, but not SB203580, fully inhibited Ang II-induced ET-1 expression. Truncation and mutational analysis of the ET-1 gene promoter showed that AP-1 binding site was an important cis-element in Ang II-induced ET-1 gene expression.


CONCLUSIONS
Our data suggest that ROS are involved in Ang II-induced proliferation and ET-1 gene expression. Our findings imply that the combination of AT(I) and ET(A) receptor antagonists plus antioxidants may be beneficial in preventing the formation of excessive cardiac fibrosis.
Cheng
Tzu-Hurng
TH
Department of Medicine, Taipei Medical University-Wan Fang Hospital, and Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan. thcheng@gate.sinica.edu.tw
Cheng
Pao-Yun
PY
Shih
Neng-Lang
NL
Chen
Iuan-Bor
IB
Wang
Danny Ling
DL
Chen
Jin-Jer
JJ
D000804:Angiotensin II / Q000378:metabolism*; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001381:Azepines / Q000494:pharmacology; D018929:Cell Culture Techniques; D002455:Cell Division / Q000502:physiology; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology*; D006321:Heart / Q000502:physiology; D019808:Losartan / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000378:metabolism; D017466:Receptors, Endothelin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D015854:Up-Regulation
D057911:Angiotensin Receptor Antagonists; D000959:Antihypertensive Agents; D001381:Azepines; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D009842:Oligopeptides; D017382:Reactive Oxygen Species; D011945:Receptors, Angiotensin; D017466:Receptors, Endothelin; D000804:Angiotensin II; C083116:BQ 485; D020928:Mitogen-Activated Protein Kinases; D019808:Losartan