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Cardiovascular Research 1999 41(3):654-662; doi:10.1016/S0008-6363(98)00275-2
© 1999 by European Society of Cardiology
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Copyright © 1999, European Society of Cardiology

Reactive oxygen species modulate endothelin-I-induced c-fos gene expression in cardiomyocytes

T.H. Chenga, N.L. Shihb, S.Y. Chenb,1,1, D.L. Wangb and J.J. Chenb,c,*

aGraduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, ROC
bCardiovascular Division, Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529 Taiwan, ROC
cDepartment of Internal Medicine, Medical College of National Taiwan University, Taipei, Taiwan, ROC

* Corresponding author. Tel.: +886-2-2789-9135; Fax: +886-2-2782-9143.

Objectives: Recent evidence indicates that reactive oxygen species (ROS) may act as second messengers in receptor-mediated signaling pathways. The possible role of ROS during Et-1 stimulation in cardiomyocytes was therefore investigated. Methods: Intracellular ROS levels were measured with fluorescence probe 2',7'-dichlorofluorescin diacetate by confocal microscopy in cultured neonatal rat cardiomyocytes. The ROS-inducible c-fos expression was analyzed by Northern blotting and promoter activity. Results: Et-1 applied to cardiomyocytes dose-dependently increased intracellular ROS levels. The increase of ROS levels was attenuated by pretreating cardiomyocytes with Et-A receptor antagonist-BQ485, but not with Et-B receptor antagonist. Cardiomyocytes pretreated with catalase or an antioxidant N-acetylcysteine (NAC) reduced Et-1-induced ROS levels. Et-1 or H2O2 treatment of cardiomyocytes rapidly induced the expression of an immediate early gene c-fos. Et-1-treated cardiomyocytes enhanced the c-fos gene expression as revealed by functional analysis using a reporter gene construct containing c-fos promoter region (–2.25 kb) and reporter gene chloramphenicol acetyltransferase. The induction of mRNA levels and the promoter activities of c-fos gene by Et-1 or H2O2 were abolished by pretreating cardiomyocytes with catalase or NAC. Cells transiently transfected with the dominant positive mutant of p21ras (RasL61) led to a significant increase in intracellular ROS. Concomitantly, the mRNA levels and the promoter activities of c-fos were also induced. In contrast, cells transfected with the dominant negative mutant of Ras (RasN17) inhibited Et-1-induced ROS. Consistently, the increase of c-fos mRNA levels and promoter activities by Et-1 were also inhibited. Conclusions: These findings clearly indicate that Et-1 treatment to cardiomyocytes can induce ROS via Ras pathway and the increased ROS are involved in the increase of c-fos expression. Our studies thus emphasize the importance of ROS as second messengers in Et-1-induced responses in cardiomyocytes.

KEYWORDS Endothelin-1; Reactive oxygen species; c-fos; Gene expression; Ras; Rat, Cardiomyocyte

1 Present address: Faculty of Art and Science, University of Toronto, Toronto, Ontario, Canada.


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