The relationship between Helicobacter pylori infection and the expression of TGF-β1 and B7-H1 in gastric mucosal epithelial cells

Abstract

Objective To explore the influence of different dose of Helicobacter pylori on the expression of transforming growth factorβ(TGF-β1) and B7-H1 in the infected gastric mucosal epithelial cell and the bacterial factors which influence the expression of TGF-β1.To confirm that H.pylorican induce the expression of TGF-β1 and B7-H1 to inhibit the host immune function in gastric mucosal epithelial cell.Methods (1) We investigated the expression of TGF-β1 of human gastric mucosal epithelial cells infected with different concentration(1.0 × 109 CFU/ml,4.0 × 109 CFU/ml,8.0 × 109 C FU/ml) of H.pylori(NCTC 11637) in different time-point(0 h,0.5 h,1 h,1.5 h,2 h,4 h,8 h,12 h),and compared with the expression of TGF-β1 between the deactivated H.pylori group and activated H.pylori group.The blank group is the gastric mucosa epithelial cells which does not infect H.pylori.To detect expression of TGF-β1 in infected cell culture supernatant by enzyme-linked immunosorbent assay(ELISA) and the expression of B7-H1 mRNA by in situ hybridization.(2)At the same time,the middle concentration of deactivated H.pyloriand in vitro gastric mucosal cells were incubated for 2 h and 12 h,to detect expression of TGF-β1 in the cells and cell culture supernatant.(3)In vitro gastric mucosal cells were incubated with H.pylori bacterial supernatant and sedimentation by ultrasonic crushing and centrifugation and with H.pyloribacterial supernatant and sedimentation after boiling respectively,to detect expression of TGF-β1 in the cells and cell culture supernatant after 2 h,12 h.Results (1)Compared to the control group,the expression of TGF-β1 was significantly increased after stimulation with different concentration of activated H.pylori in different time-point(P ＜0.05).The expression of TGF-β1 secretion group has a similar dynamic trend,and the highest expression is the middle concentration group(P ＜0.05).(2)There was no difference between the middle concentration of deactivated H.pylori group and the same concentration of activated H.pylorigroup(P ＞ 0.05).(3) The expression of TGF-β1 in the H.pylori bacterial supernatant group was significantly increased higher than the blank group and the H.pylori bacterial sedimentation group(P ＜0.05),and the H.pylori bacterial supernatant group after boiling was significantly lower than the H.pylori bacterial supernatant group(P ＜ 0.05),but there was no difference between H.pylori sedimentation group after boiling and not boiling(P ＞ 0.05).The B7-H1 expression of different concentration groups which the H.pylori and gastric mucosal epithelial cells cocultured 12 h are higher than the blank group(P ＜ 0.05) by in situ hybridization,and the middle concentration group is the highest expression.TGF-β1 and B7-H1 mRNA are positively correlated(r,=0.628,P ＜0.01).Conclusion H.pylori can induce the gastric mucosal epithelial cells to express the TGF-β1,the factor was the soluble protein in the H.pylori thalline.At the same time,H.pylorican induce the B7-H1 expression increased.In gastric mucosal epithelial cells,TGF-β1 and B7-H1 mRNA are positively correlated.So H.pylori can inhibit the host immune response and participate the process of immune escape by increased the expressions of TGF-β1 and B7-H1. Key words: Helicobacter pylori; Transforming growth factor β1; B7-H1; Gastric mucosal epithelial cells; Immune escape