Yun Sung Ji, Ha Jung Min, Kim Eun Kyoung, Kim Young Whan, Jin Seo Yeon, Lee Dong Hyung, Song Sang Heon, Kim Chi Dae, Shin Hwa Kyoung, Bae Sun Sik
MRC for Ischemic Tissue Regeneration, Department of Pharmacology, Pusan National University School of Medicine, Yangsan, Republic of Korea; Department of Pharmacology, Pusan National University School of Medicine, Yangsan, Republic of Korea.
Department of Obstetrics and Gynecology, Pusan National University School of Medicine, Yangsan, Republic of Korea.
Biochim Biophys Acta. 2014 Nov;1842(11):2184-92. doi: 10.1016/j.bbadis.2014.08.014. Epub 2014 Sep 6.
In this study, we investigated the role of Akt1 isoform in phenotypic change of vascular smooth muscle cells (VSMCs) and neointima formation. Laminin-induced conversion of synthetic VSMCs into contractile VSMCs was measured by expression of marker proteins for contractile VSMCs and collagen gel contraction assay. Culture of synthetic VSMCs on laminin-coated plates induced expression of marker proteins for contractile VSMCs and showed contraction in response to angiotensin II (AngII) stimulation. Silencing integrin-linked kinase attenuated activation of Akt and blocked phenotypic conversion of VSMCs resulting in the loss of AngII-dependent contraction. Laminin-induced phenotypic conversion of VSMCs was abrogated by phosphatidylinositol 3-kinase inhibitor or in cells silencing Akt1 but not Akt2. Proliferation of contractile VSMCs on laminin-coated plate was enhanced in cells silencing Akt1 whereas silencing Akt2 did not affect. Promoter activity of myocardin and SM22α was enhanced in contractile phenotype and overexpression of myocardin stimulated promoter activity of SM22α in synthetic phenotype. Promoter activity of myocardin and SM22α was reduced in cells silencing Akt1 and promoter activity of SM22α was restored by overexpression of myocardin in cells silencing Akt1. However, silencing of Akt2 affected neither promoter activity of myocardin nor SM22α. Finally, neointima formation in carotid artery ligation and high fat-diet-induced atherosclerosis was facilitated in mice lacking Akt1. This study demonstrates that Akt1 isoform stimulates laminin-induced phenotypic conversion of synthetic VSMCs by regulating the expression of myocardin. VSMCs become susceptible to shifting from contractile to synthetic phenotype by the loss of Akt1 in pathological conditions.
在本研究中，我们调查了Akt1亚型在血管平滑肌细胞（VSMC）表型变化和新生内膜形成中的作用。通过收缩型VSMC标记蛋白的表达和胶原凝胶收缩试验来检测层粘连蛋白诱导的合成型VSMC向收缩型VSMC的转化。在层粘连蛋白包被的平板上培养合成型VSMC可诱导收缩型VSMC标记蛋白的表达，并显示出对血管紧张素II（AngII）刺激的收缩反应。沉默整合素连接激酶可减弱Akt的激活，并阻断VSMC的表型转化，导致AngII依赖性收缩丧失。磷脂酰肌醇3激酶抑制剂或沉默Akt1而非Akt2的细胞可消除层粘连蛋白诱导的VSMC表型转化。沉默Akt1的细胞中，层粘连蛋白包被平板上收缩型VSMC的增殖增强，而沉默Akt2则无影响。在收缩型表型中，心肌素和SM22α的启动子活性增强，在合成型表型中，心肌素的过表达刺激了SM22α的启动子活性。在沉默Akt1的细胞中，心肌素和SM22α的启动子活性降低，在沉默Akt1的细胞中，通过心肌素的过表达可恢复SM22α的启动子活性。然而，沉默Akt对心肌素和SM22α的启动子活性均无影响。最后，在缺乏Akt1的小鼠中，颈动脉结扎和高脂饮食诱导的动脉粥样硬化中的新生内膜形成得到促进。本研究表明，Akt1亚型通过调节心肌素的表达来刺激层粘连蛋白诱导的合成型VSMC的表型转化。在病理条件下，VSMC因Akt1的缺失而易于从收缩型转变为合成型表型。
