Autophagy induced by H. pylori VacA regulated the survival mechanism of the SGC7901 human gastric cancer cell line

Juan Luo,Sufeng Luo,Lanqing Ma,Yunzhen Zhu,Yu Wen,Guangyu Pu,Mingke Li,Jun Tao,Luyan Bai

doi:10.1007/s13258-021-01151-7

Abstract

BackgroundVacuolating 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.ObjectiveWe 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.MethodsThe 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.ResultsThe 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.ConclusionsH. 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.

Highlights

Helicobacter pylori (H. pylori), a spiral-shaped, curved, gram staining-negative bacterium, is one of the most common pathogens in the human body
After H. pylori culture supernatants were concentrated by ultrafiltration, we examined the effect of the supernatants on autophagy in SGC7901 cells
We found that the H. pylori culture supernatants could induce autophagy in SGC7901 cells in a concentration-dependent manner (Fig. 1A, B)

Summary

Introduction

Helicobacter pylori (H. pylori), a spiral-shaped, curved, gram staining-negative bacterium, is one of the most common pathogens in the human body. H. pylori can secrete many virulence factors, including urease (Ure), cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA). VacA, one of the most important virulence factors in H. pylori, is named vacuolating toxin because it causes cellular vacuolar degeneration. 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. ATG7 silencing by siRNA inhibited VacA-induced autophagy. Conclusions H. pylori VacA is a key toxin that induces autophagy by increased ROS levels. Our findings demonstrated that VacA significantly inhibited proliferation in SGC7901 cells

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