Abstract 12316: Insulin-like Growth Factor-1 Prevents Oxidative Stress-Induced Cell Senescence in Vascular Endothelial Cells, via Upregulation of GPX1 Expression: a Novel Mechanism for IGF-1 Prevention of Endothelial Dysfunction
Premature senescence of endothelial cells (ECs) is a key underlying mechanism for the development of endothelial dysfunction, a critical early event in atherogenesis. Insulin-like growth factor 1 (IGF-1) has vascular anti-inflammatory and anti-oxidant effects, thereby preventing atherogenesis in Apo E-/- mice; however precise mechanisms are unclear. We investigated potential effects of IGF-1 on oxidative stress-induced cell senescence in vascular ECs. Human aortic ECs were exposed to 0-100 ng/mL IGF-1 for 24 hr, and then to 100 µM H2O2 for 1 hr, prior to replating, culture to subconfluency, and detection of senescence-associated β-galactosidase (β-gal) expression. H2O2 increased β-gal positivity (2.2±0.2-fold, P<0.05, n=3) and preconditioning with IGF-1 completely prevented this effect. 100 ng/mL IGF-1 upregulated glutathione peroxidase 1 (GPX1) expression and activity (2.6±0.2-fold increase and 4.8±0.5-fold increase, respectively, at 24h (n=4, p<0.01), thereby suppressing reactive oxygen species levels by 83±2 % (determined by 2’,7’-dichlorofluorescein, P<0.01, n=4). These results strongly suggest that IGF-1’s antioxidant effect contributes to prevention of cell senescence in ECs and that the effect is, at least in part, mediated by upregulation of GPX1. IGF-1 did not change GPX1 mRNA levels, and 10 µg/mL cycloheximide inhibited the IGF-1 upregulation, suggesting translational mechanisms. GPX1 is one of a family of selenoproteins, so-called because the rate limiting step for their synthesis is a unique step of selenocysteine (Sec) incorporation upon translation, controlled by Sec-incorporation sequence Binding Protein 2 (SBP2) and eukaryotic elongation factor Sec-specific (eEFsec). IGF-1 did not alter SBP2 and eEFsec expression levels but decreased GPX1 mRNA levels which co-immunoprecipitated with SBP2 by 40 % (P<0.01, n=8), indicating that IGF-1 modulated complex formation between SBP2 and GPX1 mRNA, leading to upregulation of GPX1. In summary, IGF-1 regulates Sec-incorporation and GPX1 translation in ECs, thereby upregulating GPX1 synthesis and antioxidant activity and preventing premature EC senescence. This effect of IGF-1 likely plays a critical role in preventing endothelial dysfunction and atherosclerosis.
- © 2012 by American Heart Association, Inc.