Copyright © 2007, European Society of Cardiology
Cross-talk between aldosterone and angiotensin II in vascular smooth muscle cell senescence
Department of Molecular Cardiovascular Biology and Pharmacology, Ehime University, Graduate School of Medicine, Tohon, Ehime 791-0295, Japan
*Corresponding author. Tel.: +81 89 960 5248; fax: +81 89 960 5251. horiuchi{at}m.ehime-u.ac.jp
Objective Our aim was to examine the possible cross-talk of angiotensin II (Ang II) and aldosterone (Aldo) in the regulation of vascular cell senescence in cultured vascular smooth muscle cells (VSMC).
Methods VSMC were prepared from thoracic aorta of adult male Sprague–Dawley rats. Cellular senescence was evaluated by senescence-associated β-galactosidase (SA-β-gal) staining and expression of p21, p53, p16, and p27. Oxidative stress was determined by measuring NADPH oxidase activity and superoxide production. Signal transduction was examined by immunoblot analysis with or without RNA interference methods.
Results Persistent Ang II (100 nM) stimulation increased SA-β-gal-stained VSMC and enhanced expression of p21, p53, p16, p27 and Ki-ras2A. These effects of Ang II were markedly inhibited by treatment with a selective AT1 receptor blocker, valsartan, but partially attenuated by a mineralocorticoid receptor antagonist, spironolactone. The culture medium of VSMC treated with Ang II (100 nM) showed a time-dependent increase in Aldo concentration, which increased senescent VSMC. Antioxidant, N-acetyl-L-cysteine or superoxide dismutase attenuated Ang II- or Aldo-induced VSMC senescence and Ki-ras2A expression. A lower dose combination of Ang II (100 pM) and Aldo (1 pM) significantly enhanced SA-β-gal-stained VSMC with increases in expression of p21, p53, p16, p27 and Ki-ras2A, oxidative stress, and activity of transcription factors such as NF-
B, AP-1, whereas Ang II or Aldo alone at these doses did not affect these parameters. Ki-ras2A-siRNA treatment attenuated senescent VSMC, expression of p21, p53, p16 and p27, oxidative stress induced by Ang II or a lower dose combination of Ang II and Aldo.
Conclusion These results suggest that Ang II and Aldo exert cross-talk in VSMC senescence with involvement of oxidative stress and Ki-ras2A, and could provide a therapeutic benefit for age-related vascular disorders by blockade of both Ang II and Aldo.
KEYWORDS Renin–angiotensin system; Aging; Receptor; Signal transduction; Smooth muscle
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