Involvement of the Akt-dependent CREB signaling pathway in hydrogen-peroxide-induced early growth response protein-1 expression in rat vascular smooth muscle cells .

Increased generation of reactive oxygen species is believed to play a key role in the pathophysiology of cardiovascular diseases. Excessive growth and proliferation of vascular smooth muscle cells (VSMCs) have been suggested to be major contributors to vascular dysfunction. Potential involvement of early growth response protein-1 (Egr-1), a zinc finger transcription factor, in the development of vascular diseases has been suggested. Recent studies have shown that the reactive oxygen species hydrogen peroxide (HO) increases Egr-1 expression in VSMCs; however, signaling events leading to HO-induced Egr-1 expression are not fully understood. Therefore, we aimed to determine the signaling pathways implicated in HO-induced Egr-1 expression in rat VSMCs. Pharmacological blockade of the phosphatidylinositol 3-kinase/Akt pathway by wortmannin or SC66 significantly inhibited the protein and mRNA levels of Egr-1 induced by HO. HO-induced Egr-1 expression was associated with increased phosphorylation of cyclic AMP response element-binding (CREB) protein, and pharmacological inhibition or silencing of Akt attenuated both HO-induced CREB phosphorylation and Egr-1 expression. Moreover, RNA interference-mediated depletion of CREB almost completely suppressed the stimulatory effect of HO on Egr-1 expression. Pharmacological blockade or silencing of c-Src resulted in significant suppression of HO-induced Egr-1 expression as well as Akt and CREB phosphorylation. These data show that HO enhances the expression of Egr-1, which was associated with increased phosphorylation of Akt, and HO triggers its effects on Egr-1 expression through c-Src-mediated Akt and CREB-dependent signaling events in VSMCs.