Background & AimsAtrophic gastritis caused by chronic inflammation in the gastric mucosa leads to the loss of gastric glandular cells, including acid-secreting parietal cells. Parietal cell atrophy in a setting of chronic inflammation induces spasmolytic polypeptide expressing metaplasia, a critical step in gastric carcinogenesis. However, the mechanisms by which inflammation causes parietal cell atrophy and spasmolytic polypeptide expressing metaplasia are not well defined. We investigated the role of interleukin-17A (IL-17A) in causing parietal cell atrophy.MethodsA mouse model of autoimmune atrophic gastritis was used to examine IL-17A production during early and late stages of disease. Organoids derived from corpus glands were used to determine the direct effects of IL-17A on gastric epithelial cells. Immunofluorescent staining was used to examine IL-17A receptors and the direct effect of signaling on parietal cells. Mice were infected with an IL-17A-producing adenovirus to determine the effects of IL-17A on parietal cells in vivo. Finally, IL-17A neutralizing antibodies were administered to mice with active atrophic gastritis to evaluate the effects on parietal cell atrophy and metaplasia.ResultsIncreased IL-17A correlated with disease severity in mice with chronic atrophic gastritis. IL-17A caused caspase-dependent gastric organoid degeneration, which could not be rescued with a necroptosis inhibitor. Parietal cells expressed IL-17A receptors and IL-17A treatment induced apoptosis in parietal cells. Overexpressing IL-17A in vivo induced caspase-3 activation and terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling staining in parietal cells. Finally, IL-17A neutralizing antibody decreased parietal cell atrophy and metaplasia in mice with chronic atrophic gastritis.ConclusionsThese data identify IL-17A as a cytokine that promotes parietal cell apoptosis during atrophic gastritis, a precursor lesion for gastric cancer.

Chronic inflammation of the gastric mucosa, often caused by autoimmune gastritis and/or infection with Helicobacter pylori, can lead to atrophy of acid‐secreting parietal cells with metaplasia of remaining cells. The histological pattern marks a critical step in the progression from chronic gastritis to gastric cancer, yet underlying mechanism(s) of inflammation‐induced cell death of gastric epithelial cells are poorly understood. We investigated direct effects of a type 1 cytokine associated with autoimmunity and infection, interferon‐γ (IFN‐γ), on gastric epithelial cells. IFN‐γ was applied to three‐dimensional organoid cultures of gastric epithelial cells derived from gastric corpus gland (gastroids) of control and IFN‐γ receptor‐deficient mice. Gastroids were also treated with supernatants from activated immune cells isolated from a mouse model of autoimmune‐mediated atrophic gastritis (TxA23) with and without IFN‐γ expression. Finally, histopathological analysis of atrophy and metaplasia severity was performed in TxA23 mice and compared to TxA23 × Ifng−/− mice. Gastric epithelial cells in gastroid cultures expressed IFN‐γ receptor in the basolateral membrane, and gastroids died when treated with IFN‐γ in an IFN‐γ receptor‐dependent manner. Supernatants from immune cells containing high levels of IFN‐γ were highly toxic to gastroids, and toxicity was tempered when IFN‐γ was either neutralized using a monoclonal antibody or when supernatants from Ifng−/− mouse immune cells were used. Finally, TxA23 × Ifng−/− mice showed near‐complete abrogation of pre‐cancerous histopathological atrophy and metaplasia versus IFN‐γ‐sufficient controls. We identify IFN‐γ as a critical promoter of parietal cell atrophy with metaplasia during the progression of gastritis to gastric atrophy and metaplasia. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Background & Aims The association between chronic inflammation and gastric carcinogenesis is well established, but it is not clear how immune cells and cytokines regulate this process. We investigated the role of interleukin 27 (IL27) in the development of gastric atrophy, hyperplasia, and metaplasia (preneoplastic lesions associated with inflammation-induced gastric cancer) in mice with autoimmune gastritis. Methods We performed studies with TxA23 mice (control mice), which express a T-cell receptor against the H+/K+ adenosine triphosphatase α chain and develop autoimmune gastritis, and TxA23x Ebi3 -/- mice, which develop gastritis but do not express IL27. In some experiments, mice were given high-dose tamoxifen to induce parietal cell atrophy and spasmolytic polypeptide-expressing metaplasia (SPEM). Recombinant IL27 was administered to mice with mini osmotic pumps. Stomachs were collected and analyzed by histopathology and immunofluorescence; we used flow cytometry to measure IL27 and identify immune cells that secrete IL27 in the gastric mucosa. Single-cell RNA sequencing was performed on immune cells that infiltrated stomach tissues. Results We identified IL27-secreting macrophages and dendritic cell in the corpus of mice with chronic gastritis (TxA23 mice). Mice deficient in IL27 developed more severe gastritis, atrophy, and SPEM than control mice. Administration of recombinant IL27 significantly reduced the severity of inflammation, atrophy, and SPEM in mice with gastritis. Single-cell RNA sequencing showed that IL27 acted almost exclusively on stomach-infiltrating CD4+ T cells to suppress expression of inflammatory genes. Conclusions In studies of mice with autoimmune gastritis, we found that IL27 is an inhibitor of gastritis and SPEM, suppressing CD4+ T-cell–mediated inflammation in the gastric mucosa.

N-dihydrogalactochitosan (GC) is developed for inducing immune responses. Synthesized from chitosan and galactose, GC is a new chemical entity that significantly enhances the immune-stimulating properties of its parental material, chitosan, making it a promising therapeutic agent. When used in combination with antigenic material, GC stimulates innate and adaptive antitumor and antiviral immunities. However, the mechanism of GC has not been fully investigated. Herein we demonstrate that GC drives type I IFN production and IFN responses in antigen presenting cells (APCs) and has superior potency compared to its corresponding chitosan. More importantly, GC drives alternative activation of STING leading to inflammatory cell death that enhances dendritic cell (DC) activation, which triggers a variety of nucleic acid sensing pattern recognition receptors (PRRs) and IL-1b production. In vivo, GC induced a potent response of type I IFN and upregulated genes associated with STING signaling within the tumor microenvironment (TME). Moreover, intratumoral delivery of GC reduced the numbers of M2-like macrophages residing within the TME, while subsequently increasing the number of DCs. Our findings demonstrate GC's unique ability to activate STING and stimulate a broad type I IFN response which holds therapeutic promise in generating antitumor and antiviral immunities.

The ability to analyze individual epithelial cells in the gastric mucosa would provide important insight into gastric disease, including chronic gastritis and progression to gastric cancer. However, the successful isolation of viable gastric epithelial cells (parietal cells, neck cells, chief cells, and foveolar cells) from gastric glands has been limited due to difficulties in tissue processing. Furthermore, analysis and interpretation of gastric epithelial cell flow cytometry data has been difficult due to the varying sizes and light scatter properties of the different epithelial cells, high levels of autofluorescence, and poor cell viability. These studies were designed to develop a reliable method for isolating viable single cells from the corpus of stomachs and to optimize analyses examining epithelial cells from healthy and diseased stomach tissue by flow cytometry. We performed a two stage enzymatic digestion in which collagenase released individual gastric glands from the stromal tissue of the corpus, followed by a Dispase II digestion that dispersed these glands into greater than 1 × 106 viable single cells per gastric corpus. Single cell suspensions were comprised of all major cell lineages found in the normal gastric glands. A method describing light scatter, size exclusion, doublet discrimination, viability staining, and fluorescently-conjugated antibodies and lectins was used to analyze individual epithelial cells and immune cells. This technique was capable of identifying parietal cells and revealed that gastric epithelial cells in the chronically inflamed mucosa significantly upregulated major histocompatibility complexes (MHC) I and II but not CD80 or CD86, which are costimulatory molecules involved in T cell activation. These studies describe a method for isolating viable single cells and a detailed description of flow cytometric analysis of cells from healthy and diseased stomachs. These studies begin to identify effects of chronic inflammation on individual gastric epithelial cells, a critical consideration for the study of gastric cancer.