Insulin Regulation of Proliferation Involves Activation of AKT and ERK 1/2 Signaling Pathways in Vascular Smooth Muscle Cells

Abstract

This investigation used primary cultured rat vascular smooth muscle cells (VSMCs) to examine the effect of insulin (INS) on proliferation of VSMCs. In this study, we investigated the role of protein kinase B (Akt) and p42/44 mitogen-activated protein kinase (ERK 1/2) signaling pathways in mediating the mitogenic action of INS in VSMCs. Incubation of rat VSMCs with INS (100 nM) for 10 min resulted man increase of Akt phosphorylation by 6-fold (p LT 0.001) and ERK 1/2 phosphorylation by 3-fold (p LT 0.001). Pretreatment for 15 min with 10 mu M of PI3K/Akt inhibitor LY294002 or with 20 mu M PD98059, inhibitor of ERK 1/2, significantly reduced INS-stimulated Akt and ERK 1/2 phosphorylation by 76 and 75%, respectively. Prolonged treatment of VSMCs with INS for 24 h did not have an effect on either Akt or ERK 1/2 phosphorylation. Incubation of rat VSMCs with INS resulted in an increase of VSMCs proliferation by 87% (p LT 0.001.) The effect of INS on VSMCs proliferation was significantly reduced by 68% by pretreatment with LY294002 (p GT 0.01) and by 71% (p GT 0.01) by pretreatment with PD98059. These results indicate that INS acts through Akt and ERK 1/2 signaling pathways to Up-regulate proliferation of VSMCs.