PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of gutGutVisit this articleSubmit a manuscriptReceive email alertsContact usBMJ
 
Gut. 2001 July; 49(1): 18–22.
PMCID: PMC1728350

Helicobacter pylori induced transactivation of SRE and AP-1 through the ERK signalling pathway in gastric cancer cells

Abstract

BACKGROUND AND AIMS—Helicobacter pylori infection induces expression of proinflammatory cytokines such as interleukin (IL)-8 and tumour necrosis factor α (TNF-α) in gastric mucosa, and their genes have AP-1 binding sites in the promoter region. c-Fos is important for transactivation of AP-1 which has SRE in the promoter region. We conducted this study to confirm H pylori induced transactivation of these binding sites.
METHODS—Transactivation of SRE and AP-1 was evaluated in human gastric cancer cells TMK1 and MKN45 by luciferase reporter assay in transient transfection. We compared the effects of coculture with four H pylori strains, a cag pathogenicity island (PAI) positive strain TN2, its isogenic vacA negative (TN2-ΔvacA) or cagE negative (TN2-ΔcagE) mutants, and a cag PAI negative clinical isolate T68. Phosphorylation of ERK1/2, JNK, and c-Jun was measured by immunoblot, induction of IL-8 secretion by ELISA, and the effects of MEK by inhibitor U0126.
RESULTS—Both SRE and AP-1 were transactivated by coculture with TN2. Although TN2-ΔvacA induced comparable transactivation, TN2-ΔcagE and T68 showed decreased transactivation of SRE (65% and 51%) and AP-1 (71% and 54%, respectively, of TN2). Heat killed TN2 or indirect contact using a permeable membrane inhibited transactivation. Levels of phosphorylated ERK1/2, JNK, and c-Jun were increased by coculture with TN2. MEK inhibitor U0126 reduced TN2 induced transactivation of SRE and AP1, as well as secretion of IL-8, by 83%, 87%, and 53%, respectively, of TN2.
CONCLUSIONS—Transactivation of SRE and AP-1, through ERK/MAPK and JNK/SAPK cascades, respectively, was found in gastric cancer cells cocultured with H pylori. Direct contact with viable bacteria possessing intact cag PAI is a prerequisite for the onset of intracellular signalling leading to AP-1 transactivation.


Keywords: Helicobacter pylori; SRE; AP-1; cag pathogenicity island PAI; gastric cancer

Figure 1
Transactivation of SRE by Helicobacter pylori. Transactivation of SRE in TMK1 (A) and MKN45 (B) cells induced by H pylori was measured by luciferase assay using pSRE-Luc. The TN2 strain was positive for two known virulence factors, CagA and VacA, and ...
Figure 2
Transactivation of AP-1 induced by Helicobacter pylori. Transactivation of AP-1 in TMK1 (A) and MKN45 (B) cells induced by H pylori was measured by luciferase assay using pAP-1-Luc. The TN2 strain was positive for two known virulence factors, CagA and ...
Figure 3
Phosphorylation of ERK1/2 by Helicobacter pylori (HP). Immunoblot analysis showing phospho-ERK1/2 (top panel) and total ERK1/2 (bottom panel) in TMK1 cells cocultured with H pylori. Antibodies used react with both ERK1 and ERK2. Stimulation by epidermal ...
Figure 4
Phosphorylation of JNK/SAPK by Helicobacter pylori (HP). Immunoblot analysis showing phospho JNK (top panel) and total JNK (bottom panel) in TMK1 cells cocultured with H pylori. Stimulation by interleukin 1β (IL-1β 10 ng/ml for ...
Figure 5
Phosphorylation of c-Jun by Helicobacter pylori (HP). Immunoblot analysis showing phospho c-JUN (top panel) and total c-JUN (bottom panel) in TMK1 cells cocultured with H pylori. Stimulation by interleukin 1β (IL-1β 10 ng/ml for ...
Figure 6
Effects of MEK inhibitor on Helicobacter pylori induced transactivation of SRE and AP-1. Transactivation of SRE and AP-1 in TMK1 cells induced by H pylori was measured by luciferase assay using pSRE-Luc and pAP-1-Luc with (+) or without (−) the ...
Figure 7
Effects of MEK inhibitor on Helicobacter pylori induced interleukin 8 (IL-8) secretion. TMK1 cells were cultured alone as control or were cocultured with H pylori with (+) or without (−) the MEK inhibitor U0126 (10 µM). ...

Articles from Gut are provided here courtesy of BMJ Group