Abstract
Mechanotransduction represents an integral part of vascular homeostasis and contributes to vascular lesion formation. Previously, we demonstrated a mechanosensitive activation of phosphoinositide 3-kinase (PI3-K)/protein kinase B (Akt) resulting in p27Kip1 transcriptional downregulation and cell cycle entry of vascular smooth muscle cells (VSMC). In this study, we further elucidated the signaling from outside-in toward PI3-K/Akt in vitro and in an in vivo model of elevated tensile force. When VSMC were subjected to cyclic stretch (0.5 Hz at 125% resting length), PI3-K, Akt, and Src kinases were found activated. Disrupting caveolar structures with beta-cyclodextrin or transfection of VSMC with caveolin-1 antisense oligonucleotides (ODN) prevented PI3-K and Akt activation and cell cycle entry. Furthermore, PI3-K and Akt were resistant to activation when Src kinases were inhibited pharmacologically or by overexpression of a kinase-dead c-Src mutant. alpha(V)beta3 integrins were identified to colocalize with PI3-K/caveolin-1 complexes, and blockade of alpha(V)beta3 integrins prevented Akt activation. The central role of caveolin-1 in mechanotransduction was further examined in an in vivo model of elevated tensile force. Interposition of wild-type (WT) jugular veins into WT carotid arteries resulted in a rapid Akt activation within the veins that was almost abolished when veins of caveolin-1 knockout (KO) mice were used. Furthermore, late neointima formation within the KO veins was significantly reduced. Our study provides evidence that PI3-K/Akt is critically involved in mechanotransduction of VSMC in vitro and within the vasculature in vivo. Furthermore, caveolin-1 is essential for the integrin-mediated activation of PI3-K/Akt.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Anastomosis, Surgical
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Androstadienes / pharmacology
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Animals
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Aorta / cytology
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Carotid Artery, Common / surgery
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Caveolae / drug effects
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Caveolae / physiology
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Caveolae / ultrastructure
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Caveolin 1
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Caveolins / deficiency
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Caveolins / genetics
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Caveolins / physiology*
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Cells, Cultured / enzymology
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Cells, Cultured / physiology
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Cholesterol / metabolism
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Chromones / pharmacology
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Enzyme Activation
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Extracellular Signal-Regulated MAP Kinases / physiology
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Focal Adhesions / metabolism
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Integrin alphaVbeta3 / physiology
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Jugular Veins / transplantation
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Male
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Membrane Lipids / metabolism
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Morpholines / pharmacology
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Muscle, Smooth, Vascular / cytology
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Myocytes, Smooth Muscle / enzymology
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Myocytes, Smooth Muscle / physiology
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Phosphatidylinositol 3-Kinases / physiology*
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Phosphoinositide-3 Kinase Inhibitors
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Protein Serine-Threonine Kinases / physiology*
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins pp60(c-src) / physiology
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Pyrazoles / pharmacology
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Pyrimidines / pharmacology
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Rats
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Rats, Sprague-Dawley
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Signal Transduction / physiology*
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Stress, Mechanical*
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Tunica Intima / pathology
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Wortmannin
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beta-Cyclodextrins / pharmacology
Substances
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4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine
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Androstadienes
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Cav1 protein, mouse
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Cav1 protein, rat
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Caveolin 1
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Caveolins
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Chromones
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Integrin alphaVbeta3
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Membrane Lipids
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Morpholines
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins
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Pyrazoles
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Pyrimidines
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beta-Cyclodextrins
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Cholesterol
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Proto-Oncogene Proteins pp60(c-src)
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Akt1 protein, rat
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Extracellular Signal-Regulated MAP Kinases
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betadex
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Wortmannin