Intracellular Osteopontin Induced by CagA-positive Helicobacter pylori Promotes Beta-catenin Accumulation and Interleukin-8 Secretion in Gastric Epithelial cells.
BACKGROUND
Osteopontin, an important immune modulator and oncogenic promoter, is upregulated in H. pylori-infected gastric mucosa. However, the underlying mechanisms and biological significance are poorly understood. We investigated whether osteopontin was upregulated in gastric epithelial cells by H. pylori and the virulence factors involved. Moreover, cellular component changes caused by osteopontin were also investigated.


METHODS
The gastric epithelial cell line MKN45 was cocultured with wild-type and mutant H. pylori to analyze osteopontin expression. Beta-catenin levels in cell lysate and interleukin-8 levels in supernatant were analyzed. The difference in osteopontin expression levels in both gastric epithelium and plasma was compared between H. pylori-infected patients and uninfected controls.


RESULTS
H. pylori induced intracellular, but not secretory, osteopontin expression in MKN45 cells. Accordingly, osteopontin expression intensity in gastric epithelium was higher in H. pylori-infected patients than in controls, but osteopontin levels in plasma were similar between both patient groups. H. pylori virulence factor CagA delivered via the type IV secretion system was essential for intracellular osteopontin upregulation. H. pylori induced β-catenin accumulation and interleukin-8 secretion, whereas osteopontin knockdown completely abrogated these effects, in MKN45 cells. TLR2 antagonist abolished iOPN expression induced by H. pylori gastritis strain, but not by H. pylori cancer strain.


CONCLUSIONS
H. pylori is dependent on CagA translocation via the type IV secretion system to induce intracellular osteopontin expression in gastric epithelial cells. Upregulated intracellular osteopontin may promote gastric carcinogenesis via increased β-catenin accumulation and interleukin-8 secretion.
Departments of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.|Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Wei-Lun
WL
Chang
Department of Pathology, Ton-Yen General Hospital, Hsin-Chu, Taiwan.
Hsiao-Bai
HB
Yang
Departments of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Hsiu-Chi
HC
Cheng
Departments of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Yi-Chun
YC
Yeh
Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Cheng-Yen
CY
Kao
Medical Laboratory Science and Biotechnology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Jiunn-Jong
JJ
Wu
Department of Pathology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Cheng-Chan
CC
Lu
Departments of Internal Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.|Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Bor-Shyang
BS
Sheu
D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology*; D016480:Helicobacter pylori / Q000472:pathogenicity*; D054884:Host-Pathogen Interactions; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D053495:Osteopontin / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D016209:Interleukin-8; D051176:beta Catenin; C080866:cagA protein, Helicobacter pylori; D053495:Osteopontin
CagA; Helicobacter pylori; Osteopontin; T4SS; interleukin-8; β-catenin