Impact of insulin-like growth factor-I on migration, proliferation and Akt-ERK signaling in early and late-passages of vascular smooth muscle cells.
Migration and proliferation of vascular smooth muscle cells (VSMCs) are important events in the progression of atherosclerosis. Insulin-like growth factor I (IGF-1) possesses both antiapoptotic and mitogenic/motogenic effects in VSMCs although the influence of life cycle on IGF-1-induced effects is unclear. This study was designed to evaluate the effect of IGF-1 on migration, proliferation, and signaling mechanisms in VSMCs from early (3-5) to late (20-22) passages. Migration, proliferation, and cell survival were measured using monolayer wounding, 3[H]-thymidine incorporation and MTT assay, respectively. Akt and ERK, which are critical to proliferation, differentiation and migration, were examined using Western blot analysis. DCF-DA fluorescence was used to quantify Reactive Oxygen Species (ROS) production. Late-passage VSMCs exhibited significantly higher basal cell proliferation and enhanced sensitivity to IGF-1-stimulated migration compared to cells from early-passages. Phosphorylated Akt and ERK levels were significantly higher in late-passage cells compared to early-passage, which was further enhanced by IGF-1 treatment. Late-passage cells exhibited higher levels of ROS production compared to early-passage, cells. IGF-1 did not significantly alter ROS levels in either passage. Expression of the cell cycle regulator p53, p21, and p16 was not affected by repeated passaging of cells. These results indicated that repeated passaging of VSMCs exhibits a phenotype which has higher proliferative capacity. Activation of trophic signaling molecules such as ERK1/2 and Akt and generation of ROS may represent the mechanisms by which repeated passages of VSMCs acquire a motogenic and mitogenic phenotype.
Stratton
Matthew S
MS
Division of Pharmaceutical Sciences, Center for Cardiovascular Research and Alternative Medicine, University of Wyoming, Laramie, WY 82071, USA.
Yang
Xiaoping
X
Sreejayan
Nair
N
Ren
Jun
J
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002465:Cell Movement / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D051058:Oncogene Protein v-akt / Q000502:physiology*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013778:Tetrazolium Salts; D013844:Thiazoles; D013936:Thymidine / Q000378:metabolism
D018797:Cell Cycle Proteins; D017382:Reactive Oxygen Species; D013778:Tetrazolium Salts; D013844:Thiazoles; D007334:Insulin-Like Growth Factor I; D004247:DNA; D051058:Oncogene Protein v-akt; D020928:Mitogen-Activated Protein Kinases; C022616:thiazolyl blue; D013936:Thymidine