Nrf2/HO-1信号通路抑制动脉粥样硬化中平滑肌源性泡沫细胞形成机制研究

Foam cells are the key components of atherosclerotic plaque. Previous studies have demonstrated that foam cells in early-stage atherosclerotic lesions are derived mainly from macrophages. However, in mid- and late-stage atherosclerosis, vascular smooth muscle cells become the main source of foam cells. Therefore, it is very important to investigate the mechanisms of inhibiting vascular smooth muscle-derived foam cells formation. Previous studies have indicated that Nrf2/HO-1 signaling pathway play inhibitory roles in macrophages-derived foam cells formation, but so far there have not been any studies regarding the association between Nrf2/HO-1 signaling pathway and vascular smooth muscle-derived foam cells. Based on preliminary research results, we intend to further investigate the molecular mechanism of vascular smooth muscle-derived foam cells formation from the view of inhibition of inflammation response and intracellular cholesterol ester synthesis. Briefly，the purpose of this study was to investigate whether Nrf2/HO-1 signaling pathway inhibits vascular smooth muscle-derived foam cells formation via affecting the following signal path: Nrf2→HO-1—TLR4→Cytokines（IL-1β, IL-6 and TNF-a）→ACAT1. There are sufficient evidence and preliminary research results supporting the present study. Our study could further uncover the mechanism of vascular smooth muscle-derived foam cells formation. Meanwhile, it will also present new target and avenue for prevention and therapy of atherosclerosis.

泡沫细胞是构成动脉粥样斑块的主要成分，早期动脉粥样硬化病变中的泡沫细胞主要来源于巨噬细胞，而在中晚期动脉粥样硬化病变中血管平滑肌细胞成为泡沫细胞的主要来源。因此，积极研究抑制血管平滑肌源性泡沫细胞形成机制对防治动脉粥样硬化具有重要的现实意义。之前有研究证实Nrf2/HO-1信号通路在调控巨噬细胞泡沫化过程中发挥重要抑制作用，但至今尚无关于Nrf2/HO-1信号通路调控血管平滑肌细胞泡沫化研究。本课题拟在前期研究基础之上，从Nrf2/HO-1信号通路调节炎症反应及胆固醇酯胞内合成的角度，结合国内外最新研究进展，以Nrf2→HO-1—TLR4→炎症细胞因子（IL-1β, IL-6和TNF-α）→ACAT1的调控作用为切入点，对平滑肌源性泡沫细胞形成的分子机制进行深入探讨。该项目有充分的立论依据及前期实验基础，将进一步揭示血管平滑肌细胞泡沫化机制，为动脉粥样硬化防治提供新的靶点和干预路径。

目的：据报道激活核因子-E2相关因子2（Nrf2）/血红素加氧酶-1（HO-1）信号通路阻碍动脉粥样硬化过程中泡沫细胞的形成。本研究旨在验证Nrf2 / HO-1通过抑制toll样受体4（TLR4）介导的炎症反应，进而阻碍血管平滑肌细胞（VSMCs）源性泡沫细胞的形成。方法：在本研究中，应用C57BL / 6J遗传背景的野生型（WT）、ApoE敲除（ApoE -/-）和TLR4-/-小鼠进行在体实验及离体实验。结果：高脂（HF）饮食诱导ApoE -/-小鼠体内动脉粥样硬化斑块形成，氧化低密度脂蛋白（oxLDL）诱导体外WT VSMC泡沫细胞形成。在以上过程中，我们还观察到TLR4和细胞因子表达的增加，这主要归因于核因子-κB（NF-κB）活性的增加。萝卜硫素（SFN）激活Nrf2 / HO-1信号通路后阻碍动脉粥样硬化斑块的形成，并抑制oxLDL诱导的VSMC泡沫细胞的形成，同时显著抑制TLR4和细胞因子的表达。 TLR4激动剂脂多糖（LPS）抵消SFN的以上抑制效应，而TLR4抑制剂依立托仑进一步促进SFN对oxLDL诱导的VSMC泡沫细胞形成的抑制作用。 TLR4缺陷阻碍HF饮食诱导的小鼠动脉粥样硬化斑块形成，并抑制oxLDL诱导的VSMC泡沫细胞形成；同时TLR4缺陷损害Nrf2对动脉粥样硬化和VSMC泡沫细胞形成的干预效果。结论：我们的结果提供证据表明：Nrf2 / HO-1信号通路通过抑制TLR4介导的炎症反应，进而抑制VSMC泡沫细胞形成，并最终阻碍动脉粥样硬化斑块形成。