From the Cardiovascular Research Institute (Y.K., U.Y., C.Y., M.U., T.F., Y.I.) and Department of Immunology (D.K., T.T.), Yokohama City University, Graduate School of Medicine, Yokohama, Japan; Department of Microbiology and Immunology, Tokyo Medical and Dental University Graduate School of Health Care Sciences, Tokyo, Japan (Y.K., R.I., T.K.); Department of Physiology, Tsurumi University School of Dental Medicine, Yokohama, Japan (S.O.); and Department of Cardiovascular Medicine, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan (M.S.).
Arterioscler Thromb Vasc Biol. 2015 Dec;35(12):2617-25. doi: 10.1161/ATVBAHA.115.306534. Epub 2015 Oct 1.
Vascular smooth muscle cell (SMC) migration causes neointima, which is related to vascular remodeling after mechanical injury and atherosclerosis development. We previously reported that an exchange protein activated by cAMP (Epac) 1 was upregulated in mouse arterial neointima and promoted SMC migration. In this study, we examined the molecular mechanisms of Epac1-induced SMC migration and the effect of Epac1 deficiency on vascular remodeling in vivo.
Platelet-derived growth factor-BB promoted a 2-fold increase in SMC migration in a primary culture of aortic SMCs obtained from Epac1(+/+) mice (Epac1(+/+)-ASMCs), whereas there was only a 1.2-fold increase in Epac1(-/-)-ASMCs. The degree of platelet-derived growth factor-BB-induced increase in intracellular Ca(2+) was smaller in Fura2-labeled Epac1(-/-)-ASMCs than in Epac1(+/+)-ASMCs. In Epac1(+/+)-ASMCs, an Epac-selective cAMP analog or platelet-derived growth factor-BB increased lamellipodia accompanied by cofilin dephosphorylation, which is induced by Ca(2+) signaling, whereas these effects were rarely observed in Epac1(-/-)-ASMCs. Furthermore, 4 weeks after femoral artery injury, prominent neointima were formed in Epac1(+/+) mice, whereas neointima formation was significantly attenuated in Epac1(-/-) mice in which dephosphorylation of cofilin was inhibited. The chimeric mice generated by bone marrow cell transplantation from Epac1(+/+) into Epac1(-/-) mice and vice versa demonstrated that the genetic background of vascular tissues, including SMCs rather than of bone marrow-derived cells affected Epac1-mediated neointima formation.
These data suggest that Epac1 deficiency attenuates neointima formation through, at least in part, inhibition of SMC migration, in which a decrease in Ca(2+) influx and a suppression of cofilin-mediated lamellipodia formation occur.
血管平滑肌细胞（SMC）迁移导致新生内膜形成，这与机械损伤后的血管重构和动脉粥样硬化的发展有关。我们之前的研究报告表明，环腺苷酸激活的交换蛋白（Epac）1 在小鼠动脉新生内膜中上调，并促进 SMC 迁移。在本研究中，我们研究了 Epac1 诱导的 SMC 迁移的分子机制以及 Epac1 缺失对体内血管重构的影响。
血小板衍生生长因子-BB 促进了 Epac1(+/+)小鼠主动脉 SMC 原代培养物（Epac1(+/+)-ASMCs）中 SMC 迁移增加了 2 倍，而 Epac1(-/-)-ASMCs 中只有 1.2 倍的增加。Fura2 标记的 Epac1(-/-)-ASMCs 中血小板衍生生长因子-BB 诱导的细胞内 Ca(2+)增加程度小于 Epac1(+/+)-ASMCs。在 Epac1(+/+)-ASMCs 中，Epac 选择性 cAMP 类似物或血小板衍生生长因子-BB 增加了由 Ca(2+)信号诱导的片状伪足，并伴有丝切蛋白去磷酸化，而在 Epac1(-/-)-ASMCs 中很少观察到这些效应。此外，股动脉损伤 4 周后，Epac1(+/+)小鼠形成明显的新生内膜，而 Epac1(-/-)小鼠的新生内膜形成明显减弱，其中丝切蛋白的去磷酸化受到抑制。从 Epac1(+/+)到 Epac1(-/-)小鼠和反之亦然的骨髓细胞移植产生的嵌合体小鼠表明，包括 SMC 在内的血管组织的遗传背景，而不是骨髓细胞的遗传背景，影响了 Epac1 介导的新生内膜形成。
这些数据表明，Epac1 缺失通过至少部分抑制 SMC 迁移来减轻新生内膜形成，其中 Ca(2+)内流减少和抑制丝切蛋白介导的片状伪足形成。
