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1 Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto 606-8507; and 2 Second Department of Internal Medicine, Jikei University School of Medicine, Tokyo 10-8461, Japan
To elucidate the
significance of oxidative stress in the modulation of endothelial
functions, we examined the effects of H2O2 on
the expression of two endothelium-derived vasoactive peptides, endothelin (ET) and adrenomedullin (Am), and their interaction. H2O2 dose dependently suppressed ET secretion
and ET-1 mRNA expression in bovine carotid endothelial cells (ECs).
Menadion sodium bisulfate, a redox cycling drug, also decreased ET
secretion in a dose-dependent manner. Catalase, a
H2O2 reductase, and
dl-
-tocopherol (vitamin E) significantly inhibited
H2O2-induced suppression of ET secretion. Downregulation of ET-1 mRNA under oxidative stress was regulated at the
transcriptional level. In contrast, H2O2
increased Am secretion (and its mRNA expression) accompanied by the
augmentation of cAMP production. Am, as well as 8-bromo-cAMP and
forskolin decreased ET secretion in a dose-dependent fashion.
Furthermore, an anti-Am monoclonal antibody that we developed abolished
H2O2-induced suppression of ET secretion at
6-24 h after the addition of H2O2.
H2O2 increased the intracellular
Ca2+ concentration ([Ca2+]i).
Moreover, treatment with ionomycin, a Ca2+ ionophore, and
thapsigargin, an inhibitor of endoplasmic reticulum ATPase, decreased
ET secretion dose dependently for 3 h. These results suggest that
the production of ET was decreased via activation of the Am-cAMP
pathway and by the elevation of [Ca2+]i under
oxidative stress. These findings elucidate the coordinate expression of
two local vascular hormones, ET and Am, under oxidative stress, which
may protect against vascular diseases.
intracellular Ca2+; hydrogen peroxide; cAMP; nitric oxide; C-type natriuretic peptide
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