title: Ceramide and Toll-like receptor 4 are mobilized into membrane rafts in response to Helicobacter pylori infection in gastric epithelial cells.
abstract: Helicobacter pylori infection is thought to be involved in the development of several gastric diseases. Two H. pylori virulence factors (vacuolating cytotoxin A and cytotoxin-associated gene A) reportedly interact with lipid rafts in gastric epithelial cells. The role of Toll-like receptor (TLR)-mediated signaling in response to H. pylori infection has been investigated extensively in host cells. However, the receptor molecules in lipid rafts that are involved in H. pylori-induced innate sensing have not been well characterized. This study investigated whether lipid rafts play a role in H. pylori-induced ceramide secretion and TLR4 expression and thereby contribute to inflammation in gastric epithelial cells. We observed that both TLR4 and MD-2 mRNA and protein levels were significantly higher in H. pylori-infected AGS cells than in mock-infected cells. Moreover, significantly more TLR4 protein was detected in detergent-resistant membranes extracted from H. pylori-infected AGS cells than in those extracted from mock-infected cells. However, this effect was attenuated by the treatment of cells with cholesterol-usurping agents, suggesting that H. pylori-induced TLR4 signaling is dependent on cholesterol-rich microdomains. Similarly, the level of cellular ceramide was elevated and ceramide was translocated into lipid rafts after H. pylori infection, leading to interleukin-8 (IL-8) production. Using the sphingomyelinase inhibitor imipramine, we observed that H. pylori-induced TLR4 expression was ceramide dependent. These results indicate the mobilization of ceramide and TLR4 into lipid rafts by H. pylori infection in response to inflammation in gastric epithelial cells.
authors.affiliation: College of Life Science, China Medical University, Taichung, Taiwan.
authors.forename: Dah-Yuu
authors.initials: DY
authors.lastname: Lu
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Chen
authors.forename: Mei-Shiang
authors.initials: MS
authors.lastname: Yang
authors.forename: Yuan-Man
authors.initials: YM
authors.lastname: Hsu
authors.forename: Hwai-Jeng
authors.initials: HJ
authors.lastname: Lin
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Tang
authors.forename: Che-Hsin
authors.initials: CH
authors.lastname: Lee
authors.forename: Cheng-Kuo
authors.initials: CK
authors.lastname: Lai
authors.forename: Chun-Jung
authors.initials: CJ
authors.lastname: Lin
authors.forename: Woei-Cherng
authors.initials: WC
authors.lastname: Shyu
authors.forename: Fong-Yan
authors.initials: FY
authors.lastname: Lin
authors.forename: Chih-Ho
authors.initials: CH
authors.lastname: Lai
mesh_terms: D002460:Cell Line; D002518:Ceramides / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology*; D005786:Gene Expression Regulation / Q000502:physiology; D016480:Helicobacter pylori / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism*; D015398:Signal Transduction; D013270:Stomach / Q000166:cytology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: C508606:CXCL8 protein, human; D002518:Ceramides; D016209:Interleukin-8; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4