title: Aldosterone enhances IGF-I-mediated signaling and biological function in vascular smooth muscle cells.
abstract: The IGF-I pathway and renin-angiotensin-aldosterone axis are both involved in the pathogenesis of hypertension and atherosclerosis, but no information is available about IGF-I and aldosterone interaction or their potential synergistic effects in vascular smooth muscle cells (VSMCs). The aims of this study were to investigate whether aldosterone influences IGF-I signaling and to determine the mechanism(s) by which aldosterone affects IGF-I function. Aldosterone resulted in significant increases in the Akt (1.87 ± 0.24, P < 0.001), MAPK (1.78 ± 0.13, P < 0.001), p70S6kinase (1.92 ± 0.15, P < 0.001), IGF-I receptor (1.69 ± 0.05, P < 0.01), and insulin receptor substrate-1 (1.7 ± 0.04, P < 0.01) (fold increase, mean ± SEM, n = 3) phosphorylation responses to IGF-I compared with IGF-I treatment alone. There were also significant increases in VSMC proliferation, migration, and protein synthesis (1.63 ± 0.03-, 1.56 ± 0.08-, and 1.51 ± 0.04-fold increases compared with IGF-I alone, respectively, n = 3, P < 0.001). Aldosterone induced osteopontin (OPN) mRNA expression and activation of αVβ3-integrin as well as an increase in the synthesis of IGF-I receptor. The enhancing effects of aldosterone were inhibited by eplerenone (10 μmol/liter), actinomycin-D (20 nmol/liter), and an anti-αVβ3-integrin antibody that blocks OPN binding. The antioxidant N-acetylcysteine (2 mmol/liter) completely inhibited the ability of aldosterone to induce any of these changes. In conclusion, our results show that aldosterone enhances IGF-I signaling and biological actions in VSMCs through induction of OPN followed by its subsequent activation of the αVβ3-integrin and by increasing IGF-I receptor. These changes are mediated in part through increased oxidative stress. The findings suggest a new mechanism by which aldosterone could accelerate the development of atherosclerosis.
authors.affiliation: Department of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Cascella
authors.forename: Yashwanth
authors.initials: Y
authors.lastname: Radhakrishnan
authors.forename: Laura A
authors.initials: LA
authors.lastname: Maile
authors.forename: Walker H
authors.initials: WH
authors.lastname: Busby
authors.forename: Katherine
authors.initials: K
authors.lastname: Gollahon
authors.forename: Annamaria
authors.initials: A
authors.lastname: Colao
authors.forename: David R
authors.initials: DR
authors.lastname: Clemmons
mesh_terms: D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000166:cytology; D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D039302:Integrin alphaVbeta3 / Q000235:genetics / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000502:physiology*; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013552:Swine
chemical_list: D039302:Integrin alphaVbeta3; D053495:Osteopontin; D000450:Aldosterone; D007334:Insulin-Like Growth Factor I; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020929:Mitogen-Activated Protein Kinase Kinases