Institute of Cellular and System Medicine, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 35053, Taiwan.
Arterioscler Thromb Vasc Biol. 2012 Nov;32(11):2751-60. doi: 10.1161/ATVBAHA.112.300302. Epub 2012 Sep 20.
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.
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.
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.
血管平滑肌细胞（VSMCs）从中膜迁移到内膜有助于动脉粥样硬化的发生。基因缺失实验表明 Toll 样受体 2（TLR2）在动脉粥样形成中起作用。然而，其潜在机制尚不清楚。我们假设 TLR2 通过增强白细胞介素（IL）-6 的产生来促进 VSMC 迁移。
迁移实验表明 TLR2 激动剂促进 VSMC 迁移，但不促进细胞增殖或活力。TLR2 缺陷或用抗 TLR2 抗体抑制 TLR2 信号转导抑制 TLR2 激动剂诱导的 VSMC 迁移和 IL-6 产生，这是通过 p38 丝裂原激活的蛋白激酶和细胞外信号调节激酶 1/2 信号通路介导的。中和抗 IL-6 抗体可损害 TLR2 介导的 VSMC 迁移和丝状肌动蛋白纤维和片状伪足的形成。抑制 p38 丝裂原激活的蛋白激酶或细胞外信号调节激酶 1/2 激活可抑制 TLR2 激动剂 pam3CSK4 诱导的 cAMP 反应元件结合蛋白磷酸化，该蛋白通过 cAMP 反应元件位点调节 IL-6 启动子活性。此外，cAMP 反应元件结合蛋白小干扰 RNA 抑制 pam3CSK4 诱导的 IL-6 产生和 VSMC 迁移。另外，Rac1 小干扰 RNA 抑制 pam3CSK4 诱导的 VSMC 迁移，但不抑制 IL-6 产生。
我们的结果表明，在配体结合后，TLR2 在 VSMCs 中激活 p38 丝裂原激活的蛋白激酶和细胞外信号调节激酶 1/2 信号通路。这些信号通路协同作用激活 cAMP 反应元件结合蛋白，随后 IL-6 产生，这反过来又通过 Rac1 介导的肌动蛋白细胞骨架重排促进 VSMC 迁移。
