Vascular Smooth Muscle Cell Proliferation and Regrowth after Mechanical Injury in Vitro Are. Egr-1/NGFI-A-Dependent

Abstract

Smooth muscle cell (SMC) proliferation is a key event in renarrowing of blood vessels after balloon angioplasty. Mechanical injury imparted to the arterial wall in experimental models induces the expression of the immediate-early gene , egr-1. Egr-1 binds to and activates expression from the proximal promoters of multiple genes whose products can , in turn , influence the vascular response to injury. Here , we used antisense strategies in vitro to inhibit rat vascular SMC proliferation by directly targeting Egr-1. A series of phosphorothioate antisense oligonucleotides of 15 base length and complementary to various theoretically accessible regions within Egr-1 mRNA were synthesized and assessed for their ability to selectively inhibit SMC proliferation in an Egr-1-dependent manner. Western blot analysis revealed that two oligonucleotides , AS2 and E11 , inhibited Egr-1 synthesis in cells exposed to serum without affecting levels of the zinc finger protein Sp1. AS2 and E11 inhibited seruminducible [ 3 H]thymidine incorporation into DNA, as well as serum stimulation of total cell numbers. Sizematched phosphorothioate oligonucleotides with random , scrambled , sense or mismatch sequences failed to inhibit. Antisense Egr-1 inhibition was nontoxic and reversible. These oligonucleotides also inhibited SMC regrowth after mechanical injury in vitro. Egr-1 thus plays a key regulatory role in SMC proliferation and repair following injury. (Am J Pathol 1999, 155:897-905)

Berberine suppresses MEK/ERK-dependent Egr-1 signaling pathway and inhibits vascular smooth muscle cell regrowth after in vitro mechanical injury

“…Previous reports indicated that transcription factors Egr-1 and c-Fos play a key regulatory role in SMC proliferation and repair following injury [27]. As shown in Fig.…”

“…In injured vascular cells, Egr-1 is rapidly activated and found to be involved in profound chemotactic and mitogenic effects, which may contribute to the structural remodeling that typically occurs in the pathogenesis of vascular diseases [7,43]. Antisense oligonucleotides or DNA enzymes targeting Egr-1 inhibited SMC proliferation after mechanic injury in vitro [6,27,30,44]. These DNA enzymes also block Egr-1 induction and neointima formation in a rat carotid angioplasty model [30] and after stenting pig coronary arteries in vivo [6].…”

“…Several studies reported that ERK-dependent expression of Egr-1 and c-Fos in response to mechanical injury were observed in both in vivo and in vitro cultured endothelial cells and SMCs [24,[27][28][29][30]. We therefore tested the effect of mechanical injury on ERK phosphorylation and activation in SMCs.…”

Egr-1 Expression During Neointimal Development in Flow-Associated Pulmonary Hypertension

“…In systemic vessels, the importance of Egr-1 expression during vascular remodeling has been confirmed given that neointima formation is reduced when Egr-1 expression is blocked. [33][34][35][36] In addition, these studies demonstrate that Egr-1-induced neointima formation is mediated through both proliferative and inflammatory pathways. [33][34][35][36] Taken together, this is the first study to demonstrate the spatiotemporal correlation between increased Egr-1 expression and increased pulmonary blood flow, as an inductor of neointimal development.…”

“…[33][34][35][36] In addition, these studies demonstrate that Egr-1-induced neointima formation is mediated through both proliferative and inflammatory pathways. [33][34][35][36] Taken together, this is the first study to demonstrate the spatiotemporal correlation between increased Egr-1 expression and increased pulmonary blood flow, as an inductor of neointimal development. These data suggest that Egr-1 may be able to initiate and maintain the process of neointimal development in flow-associated PAH and therefore also justifies further exploration of the exact role of Egr-1 in pulmonary vascular remodeling in PAH.…”