TLR 2 Induces Vascular Smooth Muscle Cell Migration Through cAMP Response Element−Binding Protein−Mediated Interleukin-6 Production

Abstract

Objective-Migration of vascular smooth muscle cells (VSMCs) from the media into intima contributes to the development of atherosclerosis. Gene deletion experiments implicate a role for toll-like receptor 2 (TLR2) in atherogenesis. However, the underlying mechanisms remain unclear. We postulate that TLR2 promotes VSMC migration by enhancing interleukin (IL)-6 production. Methods and Results-Migration assays revealed that TLR2 agonists promoted VSMC migration but not cell proliferation or viability. TLR2 deficiency or inhibition of TLR2 signaling with anti-TLR2 antibody suppressed TLR2 agonist-induced VSMC migration and IL-6 production, which was mediated via p38 mitogen-associated protein kinase and extracellular signal-regulated kinase 1/2 signaling pathways. Neutralizing anti−IL-6 antibodies impaired TLR2-mediated VSMC migration and formation of filamentous actin fiber and lamellipodia. Blockade of p38 mitogen-associated protein kinase or extracellular signal-regulated kinase 1/2 activation inhibited TLR2 agonist pam3CSK4-induced phosphorylation of cAMP response element−binding protein, which regulates IL-6 promoter activity through the cAMP response element site. Moreover, cAMP response element−binding protein small interfering RNA inhibited pam3CSK4-induced IL-6 production and VSMC migration. Additionally, Rac1 small interfering RNA inhibited pam3CSK4-induced VSMC migration but not IL-6 production. Conclusion-Our results suggest that on ligand binding, TLR2 activates p38 mitogen-associated protein kinase and extracellular signal-regulated kinase 1/2 signaling in VSMCs. These signaling pathways act in concert to activate cAMP response element−binding protein and subsequent IL-6 production, which in turn promotes VSMC migration via Rac1-mediated actin cytoskeletal reorganization.

Toll-like Receptors in the Vascular System: Sensing the Dangers Within

“…The contribution of TLR2 to atherosclerosis has been observed with both the TLR2-TLR1 heterodimer (Mullick et al, 2005;Qi et al, 2009;Curtiss et al, 2012) and TLR2-TLR6 heterodimer (Curtiss et al, 2012) in the two prominent animal models of atherosclerosis, apolipoprotein E (ApoE)-and LDL receptor-deficient mice. Moreover, TLR2 activation causes macrophage lipid accumulation (Kazemi et al, 2005); induces a dedifferentiated, migratory, and proliferative phenotype in vascular smooth muscle cells (de Graaf et al, 2006;Lee et al, 2012); and initiates an inflammatory reaction in endothelial cells (Triantafilou et al, 2007). Similarly, TLR4 deficiency improved indices of atherosclerosis in both ApoE- (Michelsen et al, 2004) and LDL receptordeficient mice (Ding et al, 2012).…”

Role of vascular smooth muscle cell in the inflammation of atherosclerosis

“…According to recent studies, TLR2 can activate p38 MAPK, ERK1/2, JNK1/2 and AKT, in vSMCs from TLR2 KO mouse. Also, cAMP response element-binding protein (CREB)-dependent IL-6 production was highly related to TLR2, not TLR4, in vSMCs migration (52). Interestingly, Lee et al suggested a new role of TLR2 in vSMCs, where MMP2 and proinflammatory cytokines can be produced through TLR2-Nox1-dependent manner, leading to increasing monocyte-endothelial cell adhesion, and transendothelial migration of monocytic cells (53).…”

Complement anaphylatoxin C4a inhibits C5a-induced neointima formation following arterial injury

“…MCP-1 is a potent chemoattractant that is essential in various inflammatory diseases involving the recruitment of monocytes/macrophages (33). These factors all accelerate neointimal hyperplasia by promoting the migration and proliferation of VSMCs (13,34). …”