Little is known about the interactions between Helicobacter pylori, which specializes in colonizing the mucin layer that covers the gastric mucosa, and primary gastric epithelial cells. The expression pattern of Toll-like receptors (TLRs) in primary gastric epithelial cells and cell lines was compared. Primary cells did not express TLR4, whereas all cell lines expressed a nonsignaling form of TLR4. Because other cells within the mucosa expressed TLR4, it was next investigated whether H. pylori can be recognized by TLR4--they cannot. Moreover, H. pylori infection of primary cells induced a regulated production of interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha, whereas infection of cell lines only resulted in IL-8 production. The cytokine production in all cell types was strictly cag dependent. These findings indicate that, although the epithelium is important in directing the immune response against H. pylori infections, the response is independent of TLR4.

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The gastric pathogen Helicobacter pylori is known to activate multiple proinflammatory signaling pathways in epithelial cells. In this study, we addressed the question of whether expression of the interleukin-8 receptors IL-8RA (CXCR1) and IL-8RB (CXCR2) is upregulated in H. pylori-infected human gastric biopsy samples. Biopsy samples from patients infected with H. pylori strains harboring the cag pathogenicity island (PAI) expressed larger amounts of both receptors. In addition, IL-8RB expression was induced in the gastric epithelial cell line AGS upon infection with a clinical isolate containing the cag PAI, while a strain lacking the cag PAI did not. Our finding suggests that gastric epithelial cells express IL-8R in response to H. pylori infection.Helicobacter pylori is a gram-negative bacterium that is specialized in colonizing the human gastric mucosa, where it causes a variety of clinical outcomes ranging from asymptomatic carriage to gastritis, peptic ulcers, and cancer (12). One of the most important virulence determinants of H. pylori is the 40-kb pathogenicity island (PAI) that harbors the cag genes, which encode effector molecules and a type IV secretion system (4). The type IV secretion system is required for translocation of effector molecules, e.g., CagA, into host cells (14).Epithelial cells form tight mucosal barriers and are the first cells that encounter a microbial challenge and have evolved numerous ways to detect and respond to infectious agents (2). One of the most important effector molecules produced by the epithelium is the chemokine interleukin-8 (IL-8) (9, 11). Binding of IL-8 to two high-affinity receptors, IL-8RA (CXCR1) and IL-8RB (CXCR2), induces chemotaxis and transepithelial migration of neutrophils (8,10,13). The importance of IL-8R was shown in a urinary tract infection model in which mice deficient in the receptor were unable to clear an Escherichia coli infection (6). Because epithelial expression of IL-8R can be an effective means by which to augment the inflammatory response required for bacterial clearance, we examined whether epithelial cells express IL-8R in response to H. pylori infections. MATERIALS AND METHODSCollection of gastric biopsy samples. Clinical samples were obtained from 20 volunteers (18-to 50-year-old healthy males and females) enrolled in a clinical research trial (June 1999 to June 2000) in the Hepato-Gastroenterology Department at the Centre Hospitalier Universitaire Edouard Herriot (Lyon, France). Patients who had taken nonsteroidal anti-inflammatory drugs, proton pump inhibitors, or antibiotics during the preceding 3 months were excluded from the study. The H. pylori status of the volunteers was determined by serological Pyloriset Dry tests (Orion Diagnostica, Espoo, Finland) and enzyme-linked immunosorbent assays (ELISAs) as pre-endoscopy screening. Endoscopies were performed under local anesthesia, and two biopsy samples were obtained from adjacent areas of the gastric antrum. RNA and DNA were extracted with TRIZOL (Gibco BRL, Cergy Pontoise, Fran...

Although human mucosal linings are continuously exposed to microbes, the microbes rarely induce disease. This is because mucosal surfaces are protected by a first line of defence termed the innate immunity system. Inflammatory processes are activated as a consequence of a complex interplay between microbes and host target cells. Although inflammation is essential for clearing out infectious agents, it can also be harmful to the host and is therefore subjected to tight control at multiple levels. It was recently discovered that the bacterial protein toxin alpha-haemolysin (HlyA), secreted by uropathogenic Escherichia coli, induces constant, low-frequency Ca2+ oscillations in renal epithelial cells. Ca2+ oscillation occurs at a characteristic periodicity of 12 min, and affects gene expression in target epithelial cells. Specifically, the proinflammatory cytokine interleukin-6 (IL-6) and chemokine IL-8 were induced by HlyA-induced Ca2+ oscillations. A few additional bacterial protein toxins have been reported to induce Ca2+ oscillations in target epithelial cells, although their effects are poorly understood. However, the pioneering work on HlyA demonstrates a novel feature of bacterial protein toxins on host target cells: as inducers of second messenger responses which fine-tune gene expression in target epithelial cells.