Helicobacter pylori lipopolysaccharides upregulate toll-like receptor 4 expression and proliferation of gastric epithelial cells via the MEK1/2-ERK1/2 mitogen-activated protein kinase pathway.
Helicobacter pylori is recognized as an etiological agent of gastroduodenal diseases. H. pylori produces various toxic substances, including lipopolysaccharide (LPS). However, H. pylori LPS exhibits extremely weakly endotoxic activity compared to the typical LPS, such as that produced by Escherichia coli, which acts through Toll-like receptor 4 (TLR4) to induce inflammatory molecules. The gastric epithelial cell lines MKN28 and MKN45 express TLR4 at very low levels, so they show very weak interleukin-8 (IL-8) production in response to E. coli LPS, but pretreatment with H. pylori LPS markedly enhanced IL-8 production induced by E. coli LPS by upregulating TLR4 via TLR2 and the MEK1/2-ERK1/2 pathway. The transcription factor NF-Y was activated by this signal and promoted transcription of the tlr4 gene. These MEK1/2-ERK1/2 signal-mediated activities were more potently activated by LPS carrying a weakly antigenic epitope, which is frequently found in gastric cancers, than by LPS carrying a highly antigenic epitope, which is associated with chronic gastritis. H. pylori LPS also augmented the proliferation rate of gastric epithelial cells via the MEK1/2-ERK1/2 pathway. H. pylori LPS may be a pathogenic factor causing gastric tumors by enhancing cell proliferation and inflammation via the MEK1/2-ERK1/2 mitogen-activated protein kinase cascade in gastric epithelial cells.
Department of Microbiology, Sapporo Medical University School of Medicine, South-1, West-17, Chuo-ku, Sapporo 060-8556, Japan. syokota@sapmed.ac.jp
Shin-Ichi
S
Yokota
Tamaki
T
Okabayashi
Michael
M
Rehli
Nobuhiro
N
Fujii
Ken-Ichi
K
Amano
D023081:CCAAT-Binding Factor / Q000378:metabolism; D002277:Carcinoma / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004247:DNA / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology; D048369:MAP Kinase Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048370:MAP Kinase Kinase 2 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D013274:Stomach Neoplasms / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D023081:CCAAT-Binding Factor; D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C402244:nuclear factor Y; D004247:DNA; C482128:MAP2K2 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human