Zheng Haixiang, Fu Yucai, Huang Yusheng, Zheng Xinde, Yu Wei, Wang Wei
Department of Cardiology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong 515041, P.R. China.
Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong 515041, P.R. China.
Mol Med Rep. 2017 Sep;16(3):3315-3323. doi: 10.3892/mmr.2017.7032. Epub 2017 Jul 18.
Atherosclerosis (AS) is a chronic immuno‑inflammatory disease accompanied by dyslipidemia. The authors previously demonstrated that sirtuin 1 (SIRT1) may prevent atherogenesis through influencing the liver X receptor/C‑C chemokine receptor type 7/nuclear factor‑κB (LXR‑CCR7/NF‑κB) signaling pathway. Previous studies have suggested a role for mammalian target of rapamycin (mTOR) signaling in the pathogenesis of cardiovascular diseases. The present study investigated the potential association between mTOR signaling and SIRT1‑LXR‑CCR7/NF‑κB signaling (SIRT1 signaling) in AS pathogenesis. To induce foam cell formation, U937 cells were differentiated into macrophages by exposure to phorbol 12‑myristate 13‑acetate (PMA) for 24 h, followed by treatment with palmitate and oxidized low density lipoprotein for a further 24 h. Oil red O staining revealed a large accumulation of lipid droplets present in foam cells. Western blot analysis demonstrated increased protein levels of phosphorylated (p)‑mTOR and its downstream factor p‑ribosomal protein S6 kinase (p70S6K). Reverse transcription‑quantitative polymerase chain reaction and western blot analyses additionally revealed decreased expression of SIRT1, LXRα and CCR7 and increased expression of NF‑κB and its downstream factor tumor necrosis factor‑α (TNF‑α) in an atherogenetic condition induced by lysophosphatidic acid (LPA). In addition, abundant lipid droplets accumulated in U937‑LPA‑treated foam cells. Rapamycin, an mTOR inhibitor, suppressed the expression and activity of mTOR and p70S6K, however enhanced expression of SIRT1, LXRα, and CCR7. Conversely, rapamycin deceased TNF‑α and NF‑κB activity, the latter of which was further confirmed by immunofluorescence analysis demonstrating increased levels of NF‑κB present in the cytoplasm compared with the nucleus. The findings of the present study suggest that mTOR signaling promotes foam cell formation and inhibits foam cell egress via suppression of SIRT1 signaling.
动脉粥样硬化（AS）是一种伴有血脂异常的慢性免疫炎症性疾病。作者之前证明，沉默信息调节因子1（SIRT1）可能通过影响肝X受体/C-C趋化因子受体7/核因子-κB（LXR-CCR7/NF-κB）信号通路来预防动脉粥样硬化的发生。先前的研究表明，雷帕霉素靶蛋白（mTOR）信号在心血管疾病的发病机制中起作用。本研究调查了mTOR信号与AS发病机制中SIRT1-LXR-CCR7/NF-κB信号（SIRT1信号）之间的潜在关联。为诱导泡沫细胞形成，将U937细胞暴露于佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）24小时，使其分化为巨噬细胞，随后再用棕榈酸酯和氧化低密度脂蛋白处理24小时。油红O染色显示泡沫细胞中存在大量脂滴积累。蛋白质印迹分析表明，磷酸化（p）-mTOR及其下游因子p-核糖体蛋白S6激酶（p70S6K）的蛋白质水平升高。逆转录-定量聚合酶链反应和蛋白质印迹分析还显示，在溶血磷脂酸（LPA）诱导的动脉粥样硬化条件下，SIRT1、LXRα和CCR7的表达降低，NF-κB及其下游因子肿瘤坏死因子-α（TNF-α）的表达增加。此外，在经U937-LPA处理的泡沫细胞中积累了大量脂滴。mTOR抑制剂雷帕霉素抑制了mTOR和p70S6K的表达及活性，但增强了SIRT1、LXRα和CCR7的表达。相反，雷帕霉素降低了TNF-α和NF-κB的活性，免疫荧光分析进一步证实了这一点，该分析显示细胞质中NF-κB的水平高于细胞核。本研究结果表明，mTOR信号通过抑制SIRT1信号促进泡沫细胞形成并抑制泡沫细胞流出。
