Background

Vacuolating cytotoxin (VacA) is an important virulence factor of Helicobacter pylori (H. pylori). It was previously believed that VacA can trigger the cascade of apoptosis on mitochondria to lead to cell apoptosis. Recently, it was found that VacA can induce autophagy. However, the molecular mechanism by which VacA induces autophagy is largely unknown.

Objective

We aimed to explore the molecular mechanism of autophagy induced by H. pylori in gastric cancer cells and the effect of autophagy on the survival of gastric cancer cells.

Methods

The autophagy of human gastric cancer cell line SGC7901 was detected by Western blot and RT-PCR in the treatment of VacA protein of H. pylori. The relationship between autophagy and reactive oxygen species (ROS) in the proliferation of gastric cancer cells were studied by gene expression silences (siRNA) and CM-H2DCFDA (DCF) staining.

Results

The results showed that VacA protein secreted by H. pylori in the supernatant stimulated autophagy in SGC7901 cells. After VacA protein treatment, the mRNA expressions of BECN1, ATG7 and PIK3C3, were up-regulated. ATG7 silencing by siRNA inhibited VacA-induced autophagy. Furthermore, our data demonstrated that VacA protein increased ROS levels. Addition of the antioxidant N-acetyl-l-cysteine (NAC) suppressed the levels of ROS, leading to inhibition of autophagy.

Conclusions

H. pylori VacA is a key toxin that induces autophagy by increased ROS levels. And our findings demonstrated that VacA significantly inhibited proliferation in SGC7901 cells.

中文翻译：

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H. pylori VacA诱导的自噬调控SGC7901人胃癌细胞系的生存机制

背景

空泡细胞毒素(VacA)是幽门螺杆菌( H. pylori )的重要毒力因子。以前认为 VacA 可以触发线粒体上的细胞凋亡级联反应，从而导致细胞凋亡。最近发现VacA可以诱导自噬。然而，VacA 诱导自噬的分子机制在很大程度上是未知的。

客观的

我们旨在探讨H. pylori诱导胃癌细胞自噬的分子机制以及自噬对胃癌细胞存活的影响。

方法

采用Western blot和RT-PCR检测人胃癌细胞株SGC7901在H. pylori VacA蛋白处理中的自噬作用。通过基因表达沉默（siRNA）和CM-H2DCFDA（DCF）染色研究了自噬与活性氧（ROS）在胃癌细胞增殖中的关系。

结果

结果表明，上清液中幽门螺杆菌分泌的VacA蛋白刺激了SGC7901细胞的自噬。VacA蛋白处理后，BECN1、ATG7和PIK3C3的mRNA表达上调。siRNA 对 ATG7 的沉默抑制了 VacA 诱导的自噬。此外，我们的数据表明 VacA 蛋白增加了 ROS 水平。添加抗氧化剂N-乙酰-l-半胱氨酸 (NAC) 可抑制 ROS 水平，从而抑制自噬。

结论

H. pylori VacA 是一种通过增加 ROS 水平诱导自噬的关键毒素。我们的研究结果表明，VacA 显着抑制了 SGC7901 细胞的增殖。