Effect of Helicobacter pylori on apoptosis and apoptosis related genes in gastric cancer cells - PubMed (original) (raw)

Y Yang et al. Mol Pathol. 2003 Feb.

Abstract

Background/aims: Helicobacter pylori induces the apoptosis of gastric epithelial cells in vivo and in vitro. However, the molecular mechanism has not been clarified. The aim of this study was to investigate the effect of H pylori on the apoptosis of gastric epithelial cells and the expression of apoptosis related genes in vitro.

Methods: Human gastric adenocarcinoma SGC-7901 cells were co-cultured with a cytotoxic H pylori strain, NCTC 11637, at various densities ranging from 3.2 x 10(4) to 1.0 x 10(8) colony forming units (CFU)/ml for 48 hours. Apoptosis in gastric cells was determined by transmission electron microscopy, Hoechst 33258 fluorochrome staining, and flow cytometry. The expression of apoptosis related proteins, Bcl-2, Bax, and c-Myc, was measured by an immunohistochemical method, and c-Myc mRNA expression was determined by the reverse transcription-polymerase chain reaction.

Results: Helicobacter pylori induces morphological changes typical of apoptosis. Both fluorochrome staining and flow cytometry showed that the apoptotic index began to increase when H pylori were at a density of > 1.6 x 10(4) CFU/ml, and in a density dependent manner (p < 0.01; one way ANOVA). The expression of the Bax and c-Myc proteins and of c-Myc mRNA was increased, whereas Bcl-2 expression was decreased after co-culture for 48 hours.

Conclusions: Helicobacter pylori induced apoptosis in gastric epithelial cells is mediated by altered expression of the products of the Bcl-2, Bax, and c-Myc genes.

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Figures

Figure 1

Figure 1

Transmission electron microscopy showing the ultrastructural apoptotic changes of SGC-7901 cells after co-culture with Helicobacter pylori for 48 hours: (A) condensation of irregular nuclear chromatin (arrow) (original magnification, ×10 000); and (B) formation of apoptotic bodies (arrow) (original magnification, ×20 000).

Figure 2

Figure 2

DNA specific fluorochrome staining showing condensation and fragmentation of nuclei of SGC-7901 cells (arrow) after co-culture with Helicobacter pylori (1.6 × 105 colony forming units/ml) for 48 hours (original magnification, ×400).

Figure 3

Figure 3

Positive immunohistochemical staining for (A) Bax (original magnification, ×200), (B) c-Myc (original magnification, ×400), and (C) Bcl-2 (original magnification, ×200) proteins in the cytoplasm of SGC-7901 cells (arrows) after co-culture with Helicobacter pylori (1.6 × 105 colony forming units/ml) for 48 hours.

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