ObjectiveThe epithelial layer of the GI tract is equipped with innate immune receptors to sense invading pathogens. Dysregulation in innate immune signalling pathways is associated with severe inflammatory diseases, but the responsiveness of GI epithelial cells to bacterial stimulation remains unclear.DesignWe generated 42 lines of human and murine organoids from gastric and intestinal segments of both adult and fetal tissues. Genome-wide RNA-seq of the organoids provides an expression atlas of the GI epithelium. The innate immune response in epithelial cells was assessed using several functional assays in organoids and two-dimensional monolayers of cells from organoids.ResultsResults demonstrate extensive spatial organisation of innate immune signalling components along the cephalocaudal axis. A large part of this organisation is determined before birth and independent of exposure to commensal gut microbiota. Spatially restricted expression of Toll-like receptor 4 (Tlr4) in stomach and colon, but not in small intestine, is matched by nuclear factor kappa B (NF-κB) responses to lipopolysaccharide (LPS) exposure. Gastric epithelial organoids can sense LPS from the basal as well as from the apical side.ConclusionWe conclude that the epithelial innate immune barrier follows a specific pattern per GI segment. The majority of the expression patterns and the function of TLR4 is encoded in the tissue-resident stem cells and determined primarily during development.

Summary Helicobacter pyloriis a bacterial pathogen that colonizes the gastric niche of ~50% of the human population worldwide and is known to cause peptic ulceration and gastric cancer. Pathology of infection strongly depends on a cag pathogenicity island (cagPAI)-encoded type IV secretion system (T4SS). Here, we aimed to identify as yet unknown bacterial factors involved in cagPAI effector function and performed a large-scale screen of an H. pylori transposon mutant library using activation of the pro-inflammatory transcription factor NF-κB in human gastric epithelial cells as a measure of T4SS function. Analysis of ~3000 H. pylori mutants revealed three non-cagPAI genes that affected NF-κB nuclear translocation. Of these, the outer membrane protein HopQ from H. pylori strain P12 was essential for CagA translocation and for CagA-mediated host cell responses such as formation of the hummingbird phenotype and cell scattering. Besides that, deletion of hopQ reduced T4SS-dependent activation of NF-κB, induction of MAPK signalling and secretion of interleukin 8 (IL-8) in the host cells, but did not affect motility or the quantity of bacteria attached to host cells. Hence, we identified HopQ as a non-cagPAI-encoded co-factor of T4SS function.

BackgroundWhile the immune pathogenesis caused by hepatitis B virus (HBV) infection has been studied extensively, little is known about direct pathogenic effects of HBV surface proteins. Here, we have investigated pathological cellular effects of HBV surface protein expression in the liver of transgenic mice with different genetic background.MethodsThe impact of HBV surface protein expression on the liver was studied in two mouse strains, BALB/c and C57BL/6. Histology and hydroxyproline assays were performed to investigate liver morphology and fibrosis. Gene expression and signaling were analyzed by microarray, qPCR and Western blotting.ResultsExpression of HBV surface proteins in the liver of transgenic mice induced activation of protein kinase-like endoplasmic reticulum kinase (PERK) and eukaryotic initiation factor 2α (eIF2α) phosphorylation. Phosphorylation of eIF2α resulted in activation of the ER stress markers glucose regulated protein (GRP) 78 and pro-apoptotic C/EBP homologous protein (CHOP) in transgenic mice on BALB/c genetic background leading to stronger liver injury and fibrosis in comparison with transgenic mice on C57BL/6 background. Hepatic stellate cells represented the main collagen-producing liver cells in HBV transgenic mice. The key regulators of hepatocyte proliferation, transcription factors c-Jun and STAT3 were activated in HBV transgenic mice. Tumour incidence in transgenic mice was strain- and sex-dependent.ConclusionsExtent of liver injury, fibrosis, and tumour development induced by hepatic HBV surface protein expression considerably depends on host genetic background.

During the early stages of infection, Neisseria gonorrhoeae triggers a phosphotyrosine-dependent Cav1-Vav2-RhoA signaling cascade that promotes the pathogen's extracellular state.

ERK3 is a ubiquitously expressed member of the atypical mitogen activated protein kinases (MAPKs) and the physiological significance of its short half-life remains unclear. By employing gastrointestinal 3D organoids, we detect that ERK3 protein levels steadily decrease during epithelial differentiation. ERK3 is not required for 3D growth of human gastric epithelium. However, ERK3 is stabilized and activated in tumorigenic cells, but deteriorates over time in primary cells in response to lipopolysaccharide (LPS). ERK3 is necessary for production of several cellular factors including interleukin-8 (IL-8), in both, normal and tumorigenic cells. Particularly, ERK3 is critical for AP-1 signaling through its interaction and regulation of c-Jun protein. The secretome of ERK3-deficient cells is defective in chemotaxis of neutrophils and monocytes both in vitro and in vivo. Further, knockdown of ERK3 reduces metastatic potential of invasive breast cancer cells. We unveil an ERK3-mediated regulation of IL-8 and epithelial secretome for chemotaxis.