Hegner Björn, Lange Maria, Kusch Angelika, Essin Kirill, Sezer Orhan, Schulze-Lohoff Eckhard, Luft Friedrich C, Gollasch Maik, Dragun Duska
Clinic for Nephrology and Intensive Care Medicine, Charité Campus Virchow Klinihum, Augustenburger Platz 1, 13353 Berlin, Germany.
Arterioscler Thromb Vasc Biol. 2009 Feb;29(2):232-8. doi: 10.1161/ATVBAHA.108.179457. Epub 2008 Dec 12.
Vascular smooth muscle cells (VSMCs) and circulating mesenchymal progenitor cells (MSCs) with a VSMC phenotype contribute to neointima formation and lumen loss after angioplasty and during allograft arteriosclerosis. We hypothesized that phosphoinositol-Akt-mammalian target of rapamycin-p70S6 kinase (PI3K/Akt/mTOR/p70S6K) pathway activation regulates VSMC differentiation from MSCs.
We studied effects of PI3K/Akt/mTOR signaling on phenotypic modulation of MSC and VSMC marker expression, including L-type Ca(2+) channels. Phosphorylation of Akt and p70S6K featured downregulation of VSMC markers in dedifferentiated MSCs. mTOR inhibition with rapamycin at below pharmacological concentrations blocked p70S6K phosphorylation and induced a differentiated contractile phenotype with smooth muscle (sm)-calponin, sm-alpha-actin, and SM protein 22-alpha (SM22alpha) expression. The PI3K inhibitor Ly294002 abolished Akt and p70S6K phosphorylation and reversed the dedifferentiated phenotype via induction of sm-calponin, sm-alpha-actin, SM22alpha, and myosin light chain kinase. Rapamycin acted antiproliferative without impairing MSC viability. In VSMCs, rapamycin increased a homing chemokine for MSCs, stromal cell-derived factor-1-alpha, at mRNA and protein levels. The CXCR4-mediated MSC migration toward conditioned medium of rapamycin-treated VSMCs was enhanced.
We describe novel pleiotropic effects of rapamycin at very low concentrations that stabilized differentiated contractile VSMCs from MSCs in addition to exerting antiproliferative and enhanced homing effects.
血管平滑肌细胞（VSMC）和具有VSMC表型的循环间充质祖细胞（MSC）在血管成形术后以及同种异体移植动脉硬化过程中促进新生内膜形成和管腔狭窄。我们假设磷酸肌醇-蛋白激酶B-雷帕霉素哺乳动物靶蛋白-p70核糖体蛋白S6激酶（PI3K/Akt/mTOR/p70S6K）信号通路激活调节MSC向VSMC的分化。
我们研究了PI3K/Akt/mTOR信号对MSC表型调节及VSMC标志物表达的影响，包括L型钙通道。Akt和p70S6K的磷酸化表现为去分化的MSC中VSMC标志物的下调。用低于药理浓度的雷帕霉素抑制mTOR可阻断p70S6K磷酸化，并诱导出具有平滑肌（sm）-钙调蛋白、sm-α-肌动蛋白和SM蛋白22-α（SM22α）表达的分化收缩表型。PI3K抑制剂Ly294002消除了Akt和p70S6K的磷酸化，并通过诱导sm-钙调蛋白、sm-α-肌动蛋白 SM22α和肌球蛋白轻链激酶逆转去分化表型。雷帕霉素具有抗增殖作用而不损害MSC的活力。在VSMC中，雷帕霉素在mRNA和蛋白水平增加了一种针对MSC的归巢趋化因子——基质细胞衍生因子-1-α。CXCR4介导的MSC向雷帕霉素处理的VSMC条件培养基的迁移增强。
我们描述了极低浓度雷帕霉素的多种新作用，除了发挥抗增殖和增强归巢作用外，还能使来自MSC的分化收缩型VSMC稳定。
