Background

Mitophagy protects against cerebral ischemia/reperfusion (CI/R)–induced neuronal apoptosis via mitochondrial clearance. Although taurine-upregulated gene 1 (lncRNA TUG1) has been proposed to be involved in the neuronal apoptosis evoked by CI/R, its specific role in mitophagy during the progression of CI/R injury remains unknown.

Methods

The CI/R rat model was established using middle cerebral artery occlusion/reperfusion (MCAO/R). Human neuroblastoma cell line SH-SY5Y was subjected to oxygen-glucose deprivation and reoxygenation (OGD/R). Ubiquitination assay, co-immunoprecipitation assay, RNA pull-down, and RNA immunoprecipitation were used to determine the interplay among TUG1, sirtuin 1 (SIRT1), and F-box and WD repeat domain-containing 7 (FBXW7).

Results

The upregulation of the TUG1 level and downregulation of the mitophagy were observed in both MCAO/R-treated rats and OGD/R-treated cells. The administration of si-TUG1 (a siRNA directed against TUG1) potentiated mitophagy and suppressed neuronal apoptosis in OGD/R-treated cells. However, the neuroprotective effect of si-TUG1 was reversed by mitophagy inhibitor or SIRT1 knockdown in vitro. Functionally, TUG1 enhanced FBXW7-mediated SIRT1 ubiquitination by upregulating FBXW7 expression. The overexpression of FBXW7 abrogated the si-TUG1-reinforced mitophagy by decreasing SIRT1 expression, thus aggravating neuronal apoptosis in the OGD/R+si-TUG1-treated cells. In rats with MCAO/R, the interference of TUG1 clearly decreased neuronal apoptosis, lessened the infarct volume, and relieved the neurological deficits.

Conclusion

TUG1 knockdown promotes SIRT1-induced mitophagy by suppressing FBXW7-mediated SIRT1 degradation, thus relieving the neuronal apoptosis induced by CI/R injury.

Graphical abstract

LncRNA TUG1 promotes neuronal apoptosis through inhibition of mitophagy. TUG1 decreased SIRT1 expression by promoting FBXW7-mediated SIRT1 ubiquitination. FBXW7/SIRT1 axis mediated the effect of TUG1 on OGD/R-induced neuronal apoptosis by regulating mitophagy.

中文翻译：

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LncRNA TUG1 通过靶向 sirtuin 1 损害脑缺血/再灌注损伤中的神经元线粒体自噬

背景

线粒体自噬通过线粒体清除防止脑缺血/再灌注 (CI/R) 诱导的神经细胞凋亡。尽管已提出牛磺酸上调基因 1 (lncRNA TUG1) 参与 CI/R 诱发的神经细胞凋亡，但其在 CI/R 损伤进展过程中的线粒体自噬中的具体作用仍然未知。

方法

采用大脑中动脉闭塞/再灌注（MCAO/R）建立CI/R大鼠模型。对人神经母细胞瘤细胞系 SH-SY5Y 进行氧-葡萄糖剥夺和复氧 (OGD/R)。泛素化测定、共免疫沉淀测定、RNA pull-down 和 RNA 免疫沉淀用于确定 TUG1、sirtuin 1 (SIRT1) 和包含 F-box 和 WD 重复结构域的 7 (FBXW7) 之间的相互作用。

结果

在 MCAO/R 处理的大鼠和 OGD/R 处理的细胞中均观察到 TUG1 水平的上调和线粒体自噬的下调。si-TUG1（一种针对 TUG1 的 siRNA）的施用增强了线粒体自噬并抑制了 OGD/R 处理的细胞中的神经元凋亡。然而，si-TUG1 的神经保护作用在体外被线粒体自噬抑制剂或 SIRT1 敲低所逆转。在功能上，TUG1 通过上调 FBXW7 表达来增强 FBXW7 介导的 SIRT1 泛素化。FBXW7 的过表达通过降低 SIRT1 表达消除了 si-TUG1 增强的线粒体自噬，从而加剧了 OGD/R+si-TUG1 处理的细胞中的神经元凋亡。在 MCAO/R 大鼠中，TUG1 的干扰明显减少了神经细胞凋亡，减少了梗死体积，并减轻了神经功能缺损。

结论

TUG1 敲低通过抑制 FBXW7 介导的 SIRT1 降解促进 SIRT1 诱导的线粒体自噬，从而减轻 CI/R 损伤诱导的神经细胞凋亡。

图形概要

LncRNA TUG1 通过抑制线粒体自噬促进神经细胞凋亡。TUG1 通过促进 FBXW7 介导的 SIRT1 泛素化来降低 SIRT1 表达。FBXW7/SIRT1 轴通过调节线粒体自噬介导 TUG1 对 OGD/R 诱导的神经细胞凋亡的影响。