The Effect Of Helicobacter Pylori On The Cytokinetics Of Human Gastric Epithelial Cells And Its Mechanisms

Background: The infection rate of Helicobacter pylori in population is quite high, especially in Asian people. The infection of Helicobacter pylori plays an important role in the onset of peptic ulcer, chronic atrophic gastritis, as well as gastric mucosa associated lymphoid tissue lymphoma and gastric cancer. This kind of bacterium has been defined as class I carcinogen by World Health Organization (WHO) and International Agency for Research on Cancer (IARC). However, the pathogenic mechanism of H. pylori on these diseases remains unclear, which needs to be studied with the aspects including the bacterium, host and environmental agent.H. pylori would change the cytokinetics of infected gastric epithelial cell both in vivo and cell lines in vitro, but with different methods. The change of cytokinetics would destroy the balance between proliferation and apoptosis of the gastric epithelial cells, which contributes to the development of atrophic gastritis, intestinal metaplasia and gastric carcinoma. The study on the effect of H.pylori on the cytokinetics of AGS, as well as the related mechanisms, may disclose the relationship between H.pylori and host cells.Recent researches indicated that H.pylori would inhibit the expression of HSP70 in the cells. And HSP70 is an important molecular chaperone, which takes effects on promoting cells' proliferation and anti-apoptosis. Moreover, it is assumed that H.pylori may play roles in host cells' cytokinetics through regulating the expression ofHSP70 and related proteins, such as P21 and PCNA. And we tried to approve it through this study.â… , The effect of Helicobacter pylori on the cytokinetics of AGSAims: To observe the effect of H. pylori on cell growth, viability and cell cycle of human gastric epithelial cells in vitro.Methods: H. pylori with different concentrations were co-cultured with AGS cells. The cell growth and cell viability (examined by MTT) was observed at different time. And cell cycle influenced by H. pylori was analyzed by flow cytometry analysis. As a blank control, AGS cells were cultured without H.pylori.Results: Comparing with the control group, after 24 h a lot of AGS cells detached in study groups. And there was lots of bacterium, as well as residual granula resulted from cell disruption around attached cells and in the culture fluid. This phenomenon was more obvious in groups with higher H.pylori concentrations and prolonged culture time. After 4 h and 8h, the cell viability in all study groups was higher than control group, and with statistical differences in one group after 4h (bacterium/cell 500:1, p<0.05) and in some groups after 8h (200:1,p<0.05 and 100:1, p<0.01). However, after 24 h, the cell viability in all study groups was lower than control group, and with statistical differences in some groups (200:1, p<0.01 and 500:1, p<0.001). Moreover, after 48 h, the cell viability in all study groups was significantly lower than control group (p<0.001), and the higher bacterium concentration, the lower cell viability. The percentage of cells in G2 and/or M stage in total AGS cells in study group was different from that of control group at 6h, 12h and 24h.Conclusions: In vitro, H.pylori would impact on the cytokinetics of AGS, with promoting proliferation at early time as well as inhibiting proliferation after 24 hours by arresting cells in G2 and/or M. These effects would be affected by the concentration of H.pylori, as well as the culture time.â…¡, The effect of H.pylori on the expression of HSP70 in AGSAims: To observe the effect of H. pylori on the expression of HSP70 in AGS.Methods: AGS cells were co-cultured with H.pylori for 48h, and without H.pylori as a blank control. The expression of HSP70 in AGS was detected by Western blot.Results: The expression of HSP70 in the group in which AGS cells were co-cultured with H.pylori decreased comparing with control group.Conclusions: H.pylori would reduce the expression of HSP70 in AGS cells.â…¢, The effect of H.pylori on cytokinetics and expression of P21, PCNA of AGS with depletion of HSP70Aims: To discuss whether the effect of H.pylori on cytokenetics of AGS is related to the suppression of HSP70 and alteration of expression of P21 and PCNA.Methods: AGS cells which had been stably transfected with HSP70siRNA and with blank vector were involved in this study and co-cultured with H.pylori, respectively as a study group and control group. The cell growth and viability, as well as expression of P21 and PCNA, in both groups were detected.Results: The cell viability of the two groups decreased over time, which was more obvious after 48h and 72h. There were no statistical differences between the two groups at 4h, 8h and 24h. However, the cell viabilitiy in study group was lower than that in control group after 48h and 72h, with statistically differences (p<0.05). The expression of P21 increased in study group comparing with control group, while there was no obvious change of expression of PCNA.Conclusions: After the infection of H.pylori, the depletion of HSP70 in AGS cells would enhance the effect of antiproliferation which was induced by H.pylori. And it implies, that it may increase the expression of P21, which would contribute to cells' G2 and/or M arrest, and consequently inhibit cells' proliferation.