Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi, China.
School of Basic Medical Sciences, Ningxia Medical University, Yinchuan, 750004, China.
Histochem Cell Biol. 2020 May;153(5):357-366. doi: 10.1007/s00418-020-01847-z. Epub 2020 Mar 2.
The proliferation, migration, and cellular morphology of vascular smooth muscle cells (VSMCs) play important roles in the pathogenesis of atherosclerosis (AS). Homocysteine (Hcy) is a sulfur-containing amino acid, which is an intermediate product of methionine metabolism. Hcy can induce proliferation, migration, and phenotypic switch of VSMCs, but details of these mechanisms are still unclear. The phosphatidylinositol 3-kinase (PI3K/Akt/mTOR) signaling pathway is involved in a host of cellular functions. In this study, we sought to determine if this multifunctional pathway played a role in Hcy-induced proliferation, migration, and phenotypic transformation of VSMCs, which has not been previously reported. miR-145 has been previously reported to suppress the effects of Hcy in VSMCs. In our study, using qRT-PCR, we found that Hcy itself reduced the expression of miR-145 in VSMCs, while overexpression of miR-145 reduced the proliferation, migration, and phenotypic transformation of VSMCs caused by Hcy. Using Western blot analysis, we found that VSMCs exposed to Hcy exhibited significant increases in the levels of PI3K, Akt, and mTOR proteins. Additionally, overexpression of miR-145 dramatically decreased PI3K, Akt, and mTOR expression. Using qRT-PCR we found that miR-145 expression increased after blocking PI3K using an inhibitor. Inhibition of the PI3K signaling pathway also prevented Hcy-induced VSMC proliferation, migration, and phenotypic switch. Taken together, our results suggest that miR-145 could inhibit VSMC proliferation, migration, and phenotype switching by preventing activation of the PI3K/Akt/mTOR signaling pathway.
血管平滑肌细胞（VSMCs）的增殖、迁移和细胞形态在动脉粥样硬化（AS）的发病机制中起重要作用。同型半胱氨酸（Hcy）是一种含硫氨基酸，是蛋氨酸代谢的中间产物。Hcy 可诱导 VSMCs 的增殖、迁移和表型转换，但这些机制的细节尚不清楚。磷脂酰肌醇 3-激酶（PI3K/Akt/mTOR）信号通路参与多种细胞功能。在本研究中，我们试图确定该多功能通路是否在 Hcy 诱导的 VSMCs 增殖、迁移和表型转化中发挥作用，这在以前的研究中尚未报道过。miR-145 先前被报道可抑制 Hcy 对 VSMCs 的作用。在我们的研究中，通过 qRT-PCR，我们发现 Hcy 本身降低了 VSMCs 中 miR-145 的表达，而 miR-145 的过表达降低了 Hcy 引起的 VSMCs 的增殖、迁移和表型转化。通过 Western blot 分析，我们发现暴露于 Hcy 的 VSMCs 中 PI3K、Akt 和 mTOR 蛋白水平显著增加。此外，miR-145 的过表达显著降低了 PI3K、Akt 和 mTOR 的表达。通过 qRT-PCR，我们发现用抑制剂阻断 PI3K 后 miR-145 的表达增加。PI3K 信号通路的抑制也阻止了 Hcy 诱导的 VSMC 增殖、迁移和表型转换。综上所述，我们的结果表明，miR-145 可以通过阻止 PI3K/Akt/mTOR 信号通路的激活来抑制 VSMC 的增殖、迁移和表型转换。
