[Effect of CagA(+) helicobacter pylori strain on the expression of connexin 43 and cell proliferation in BGC-823 cells].

OBJECTIVE: To determine the effect of CagA(+) Helicobacter pylori(H.pylori)strain and anti-H.pylori drugs on the expression of connexin 43(Cx43) and cell proliferation of BGC-823 cells in vitro,and to investigate the relation between the changes of Cx43 expression, cell proliferation of BGC-823 cells and CagA(+)H.pylori.
METHODS: BGC-823 cells were co-cultured with CagA(+) H.pylori strain(NCTC J99) or CagA(-) H.pylori strain(NCTC 12908)at bacteria/cells ratio of 20:1,100:1 and 500:1 for 24 hours and 48 hours respectively. anti-H.pylori drugs was given in the group co-cultured at bacteria/cells ratio of 100:1 after 16 hours. In the control group, BGC-823 cells were cultured for 24 hours and 48 hours respectively,but without H.pylori or antij H.pylori drugs. Immunocytochemical SABC method and the image analysis of the computer were applied to detect the changes of Cx43 expression in BGC-823 cells. The cell proliferation was examined by methyl tetrazolium (MTT) method.
RESULTS: (1)The expression of Cx43 in the control group after cultivation for 48 hours was higher than that for 24 hours (P< 0.05). The expression of Cx43 in the groups co-cultured with CagA(+) H.pylori strain after cultivation for 48 hours was lower than that co-cultured for only 24 hours, and that of the groups co-cultured with CagA(+) H.pylori strain was lower than that of the control group for both 24 hours and 48 hours (P< 0.05). The expression of Cx43 in the groups at bacteria/cells ratio of 500:1 was lower than that at bacteria/cells ratio of 20:1 and 100:1 for both 24 and 48 hours (P< 0.05),and that at bacteria/cells ratio of 100:1 was lower than that at bacteria/cells ratio of 20:1 for 48 hours (P< 0.05).However, there was no significant difference in Cx43 expression between 24 and 48 hours in the groups co-cultured with CagA(-) H.pylori strain (P>0.05). Cx43 expression in the groups co-cultured with CagA(-) H.pylori strain at the ratio of 100:1 and 500:1 was lower than that in the control group, and Cx43 expression at the ratio of 500:1 was lower than that at the ratio of 20:1 for 24 hours and 48 hours. Cx43 expression increased after the intervention with anti-H.pylori drugs for 48 hours. (2) In the groups co-cultured with CagA(+)H.pylori strain, the optical density value of MTT indicated that the cell proliferation at the bacteria/cells ratio of 100:1 was higher than that in the control group, but no significant difference was found in other two groups co-cultured for 24 hours. After co-culturing for 48 hours, the cell proliferation at the bacteria/cells ratio of 20:1 and 100:1 was significantly accelerated, while the cell proliferation at 500:1 was inhibited. In the groups co-cultured with CagA(-) H.pylori strain,there was no change in the cell proliferation. Intervention with anti-H.pylori drugs could suppress the cell proliferation.
CONCLUSION: CagA(+) H.pylori can down-regulate the expression of Cx43 in BGC-823 cells,which is related to the reaction time and the density of H.pylori. Low density of CagA(+)H.pylori suspensions can accelerate the proliferation of BGC-823 cells, while high density can suppress the cell proliferation. The CagA(-) H.pylori has no effect on the cell proliferation. Intervention with anti-H.pylori drugs can up-regulate the expression of Cx43,and suppress the cell proliferation of BGC-823 cells.