Interleukin-17C in Human Helicobacter pylori Gastritis

IL-17C is a driver of damaging inflammation during Neisseria gonorrhoeae infection of human Fallopian tube

The human pathogen Neisseria gonorrhoeae ascends into the upper female reproductive tract to cause damaging inflammation within the Fallopian tubes and pelvic inflammatory disease (PID), increasing the risk of infertility and ectopic pregnancy. The loss of ciliated cells from the epithelium is thought to be both a consequence of inflammation and a cause of adverse sequelae. However, the links between infection, inflammation, and ciliated cell extrusion remain unresolved. With the use of ex vivo cultures of human Fallopian tube paired with RNA sequencing we defined the tissue response to gonococcal challenge, identifying cytokine, chemokine, cell adhesion, and apoptosis related transcripts not previously recognized as potentiators of gonococcal PID. Unexpectedly, IL-17C was one of the most highly induced genes. Yet, this cytokine has no previous association with gonococcal infection nor pelvic inflammatory disease and thus it was selected for further characterization. We show that human Fallopian tubes express the IL-17C receptor on the epithelial surface and that treatment with purified IL-17C induces pro-inflammatory cytokine secretion in addition to sloughing of the epithelium and generalized tissue damage. These results demonstrate a previously unrecognized but critical role of IL-17C in the damaging inflammation induced by gonococci in a human explant model of PID.

Physiological roles of human interleukin-17 family

Interleukin-17 s (IL-17s) are well-known proinflammatory cytokines, and their antagonists perform excellently in the treatment of inflammatory skin diseases such as psoriasis. However, their physiological functions have not been given sufficient attention by clinicians. IL-17s can protect the host from extracellular pathogens, maintain epithelial integrity, regulate cognitive processes and modulate adipocyte activity through distinct mechanisms. Here, we present a systematic review concerning the physiological functions of IL-17s. Our goal is not to negate the therapeutic effect of IL-17 antagonists, but to ensure their safe use and reasonably explain the possible adverse events that may occur in their application.

The role of non-Helicobacter pylori bacteria in the pathogenesis of gastroduodenal diseases

Over the past decade, the development of next-generation sequencing for human microbiota has led to remarkable discoveries. The characterization of gastric microbiota has enabled the examination of genera associated with several diseases, including gastritis, precancerous lesions, and gastric cancer. Helicobacter pylori (H. pylori) is well known to cause gastric dysbiosis by reducing diversity, because this bacterium is the predominant bacterium. However, as the diseases developed into more severe stages, such as atrophic gastritis, premalignant lesion, and gastric adenocarcinoma, the dominance of H. pylori began to be displaced by other bacteria, including Streptococcus, Prevotella, Achromobacter, Citrobacter, Clostridium, Rhodococcus, Lactobacillus, and Phyllobacterium. Moreover, a massive reduction in H. pylori in cancer sites was observed as compared with noncancer tissue in the same individual. In addition, several cases of H. pylori-negative gastritis were found. Among these individuals, there was an enrichment of Paludibacter, Dialister, Streptococcus, Haemophilus parainfluenzae, and Treponema. These remarkable findings suggest the major role of gastric microbiota in the development of gastroduodenal diseases and led us to the hypothesis that H. pylori might not be the only gastric pathogen. The gastric microbiota point of view of disease development should lead to a more comprehensive consideration of this relationship.

IL-17C in human mucosal immunity: More than just a middle child

Interleukin-17C (IL-17C) is an understudied member of the IL-17 family of cytokines. Its synthesis is induced by both cytokines and pathogenic stimuli in a variety of cell types, most often expressed at mucosal and barrier surfaces. IL-17C expression is dysregulated in a variety of autoinflammatory and autoimmune diseases including inflammatory bowel disease, psoriasis, and atopic dermatitis, yet it is protective against bacterial infections of the gut, skin, and lungs. In this review we highlight studies on IL-17C regulation and its function at human mucosal surfaces. Understanding the relationship between IL-17C and autoinflammatory and autoimmune diseases of the mucosa and defining the beneficial and pathogenic functions of the cytokine in inflammatory responses are the first steps in determining the potential for IL-17C as a therapeutic target.

Identification of hub genes and signaling pathways related to gastric cells infected by Helicobacter pylori

BACKGROUND

Helicobacter pylori is a pathogen involved in several gastroduodenal diseases, whose infection mechanisms have not been completely confirmed. To study the specific mechanism of gastropathy caused by H. pylori, we analyzed the gene microarray of gastric mucosa and gastric cells infected by H. pylori through bioinformatics analysis.

METHODS

We downloaded GSE60427 and GSE74492 from the Gene Expression Omnibus (GEO) database, screened differentially expressed genes (DEGs), and identified the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) through R software. The Search Tool for the Retrieval of Interacting Genes (STRING) was applied to establish a protein-protein interaction (PPI) network and Cytoscape was used to identify the top seven hub genes. Besides, we also constructed the gene-microRNA(gene-miRNA) interaction through the miRTarBase v8.0 database by using the NetworkAnalyst tool.

RESULTS

One hundred and fifteen DEGs were screened out, with 54 genes up-regulated and 61 genes down-regulated, among which seven hub genes, including "IGF1R," "APOE," "IRS1," "ATF3," "LCN2," "IL2RG," and "PI3," were considered as the main regulatory proteins in gastric cells when infected by H. pylori.

CONCLUSION

In this study, hub genes and related signal enrichment pathways of gastropathy infected by H. pylori were analyzed through bioinformatics analysis based on the GSE60427 and GSE74492 datasets.

DUOX2 variants associate with preclinical disturbances in microbiota-immune homeostasis and increased inflammatory bowel disease risk

A primordial gut-epithelial innate defense response is the release of hydrogen peroxide by dual NADPH oxidase (DUOX). In inflammatory bowel disease (IBD), a condition characterized by an imbalanced gut microbiota-immune homeostasis, DUOX2 isoenzyme is the highest induced gene. Performing multiomic analyses using 2872 human participants of a wellness program, we detected a substantial burden of rare protein-altering DUOX2 gene variants of unknown physiologic significance. We identified a significant association between these rare loss-of-function variants and increased plasma levels of interleukin-17C, which is induced also in mucosal biopsies of patients with IBD. DUOX2-deficient mice replicated increased IL-17C induction in the intestine, with outlier high Il17c expression linked to the mucosal expansion of specific Proteobacteria pathobionts. Integrated microbiota/host gene expression analyses in patients with IBD corroborated IL-17C as a marker for epithelial activation by gram-negative bacteria. Finally, the impact of DUOX2 variants on IL-17C induction provided a rationale for variant stratification in case control studies that substantiated DUOX2 as an IBD risk gene. Thus, our study identifies an association of deleterious DUOX2 variants with a preclinical hallmark of disturbed microbiota-immune homeostasis that appears to precede the manifestation of IBD.

The Roles of IL-17, IL-21, and IL-23 in the Helicobacter pylori Infection and Gastrointestinal Inflammation: A Review

Although millions of people have been infected by Helicobacter pylori (H. pylori), only a small proportion of infected individuals will develop adverse outcomes, ranging from chronic gastritis to gastric cancer. Advanced development of the disease has been well-linked with chronic inflammation, which is significantly impacted by the adaptive and humoral immunity response. From the perspective of cellular immunity, this review aims to clarify the intricate axis between IL-17, IL-21, and IL-23 in H. pylori-related diseases and the pathogenesis of inflammatory gastrointestinal diseases. CD4⁺ helper T (Th)-17 cells, with the hallmark pleiotropic cytokine IL-17, can affect antimicrobial activity and the pathogenic immune response in the gut environment. These circumstances cannot be separated, as the existence of affiliated cytokines, including IL-21 and IL-23, help maintain Th17 and accommodate humoral immune cells. Comprehensive understanding of the dynamic interaction between molecular host responses in H. pylori-related diseases and the inflammation process may facilitate further development of immune-based therapy.

Bioinformatic identification of key pathways, hub genes, and microbiota for therapeutic intervention in Helicobacter pylori infection

The pathogenic mechanisms of Helicobacter pylori infection remain to be defined, and potential interventional microbiota are just beginning to be identified. In this study, gene-set enrichment analysis (GSEA) was used to integrate three H. pylori infection microarray data sets from the gene expression omnibus database and identified ten hallmark gene sets and 35 Kyoto encyclopedia of genes and genomes (KEGG) pathways that differed between healthy and Helicobacter pylori-infected individuals. Weighted gene co-expression network analysis (WGCNA) performed on two of the data sets identified three key gene coexpression modules. These modules contained 54 enriched KEGG pathways, 25 of which overlapped with the GSEA analysis, suggesting potentially important roles in H. pylori-infection. We selected 116 hub genes from the three key modules for in vitro validation at the transcriptional level using H. pylori Sydney Strain 1 and verified the upregulation of 80. WGCNA of the microbiomes based on 20 mucosal samples and a sequence read archive data set revealed four microbiota modules correlated with H. pylori infection. The negatively correlated modules contained 11 microbiome families. These findings provide new insight into the pathogenesis of H. pylori infection and systematically identify 25 key pathways, 80 upregulated hub genes, and 11 families of candidate interventional microbiota for further research.

Immunity and Vaccine Development Against Helicobacter pylori

Helicobacter pylori is a highly-adapted gastrointestinal pathogen of humans and the immunology of this chronic infection is extremely complex. Despite the availability of antibiotic therapy, the global incidence of H. pylori infection remains high, particularly in low to middle-income nations. Failure of therapy and the spread of antibiotic resistance among the bacteria are significant problems and provide impetus for the development of new therapies and vaccines to treat or prevent gastric ulcer, and gastric carcinoma. The expansion of knowledge on gastric conventional and regulatory T cell responses, and the role of T_H17 in chronic gastritis from studies in mouse models and patients have provided valuable insights into how gastritis is initiated and maintained. The development of human challenge models for testing candidate vaccines has meant a unique opportunity to study acute infection, but the field of vaccine development has not progressed as rapidly as anticipated. One clear lesson learned from previous studies is that we need a better understanding of the immune suppressive mechanisms in vivo to be able to design vaccine strategies. There is still an urgent need to identify practical surrogate markers of protection that could be deployed in future field vaccine trials. Important developments in our understanding of the chronic inflammatory response, progress and problems arising from human studies, and an outlook for the future of clinical vaccine trials will be discussed.

Decreased circulating interleukin-33 concentration in Helicobacter pylori-infected patients with peptic ulcer: Evaluation of its association with a cytokine gene polymorphism, gender of patients and bacterial virulence factor CagA

IL-33 has powerful immunoregulatory activities such as reinforcement of Th2 cell responses. The aim was to assess the circulating IL-33 levels and IL-33 rs1929992 polymorphism in H. pylori-infected peptic ulcer (PU) patients and asymptomatic (AS) subjects. Blood samples were obtained from 100 PU patients, 100 AS subjects and 100 uninfected individuals. Circulating IL-33 levels were detected by ELISA. After DNA extraction, the IL-33 rs1929992 polymorphism was determined using PCR-RFLP method. Serum IL-33 quantities were significantly lower in PU patients compared with AS and uninfected groups. IL-33 levels were higher in AS subjects compared with uninfected group. In PU, AS and uninfected groups, IL-33 levels were significantly higher in women than men. In PU and AS groups, the CagA⁺H. pylori-infected subjects exhibit higher IL-33 levels compared with carriers of CagA^-H. pylori strains. In PU patients, the frequency of genotype GG and allele G at IL-33 rs1929992 was significantly higher compared with all healthy subjects (AS + uninfected groups). The presence of genotypes GG and AG, and allele G in rs1929992 conferred greater risk for PU. In whole H. pylori-infected population (PU + AS groups), IL-33 levels in individuals with genotype AA or allele A at rs1929992 were higher than subjects with GG genotype or allele G. The reduced IL-33 production could contribute to the PU development during H. pylori infection. The IL-33 levels may be affected by individual gender, rs1929992 polymorphism, and the CagA status of bacteria. The rs1929992-related GG genotype and G allele may be associated with PU development.

Chlamydia pneumoniae infection promotes vascular smooth muscle cell migration via c-Fos/interleukin-17C signaling

Chlamydia pneumoniae (C. pneumoniae) infection is associated with the initiation and progression of atherosclerosis. The migration of vascular smooth muscle cell (VSMC) from the media to the intima is a key event in the development of atherosclerosis. Interleukin-17C (IL-17C) could enhance cell migration ability. The aim of our study is to investigate the role of IL-17C in C. pneumoniae infection-promoted VSMC migration, thereby possibly accelerating atherosclerosis. We firstly demonstrated that C. pneumoniae infection significantly increased IL-17C expression in VSMCs in the atherosclerotic lesion area from ApoE deficient mice. Our in vitro study further showed that IL-17C is required for C. pneumoniae infection-promoted VSMC migration, and its expression could be regulated by c-Fos through phosphorylating extracellular signal-regulated kinase (ERK). Unexpectedly, in the present study, we also found that IL-17C is critical for C. pneumoniae infection-induced c-Fos activation. c-Fos expression and activation induced by the exposure to recombinant IL-17C were markedly suppressed in the presence of the ERK inhibitor PD98059. These results suggest a possible positive feedback between c-Fos and IL-17C after C. pneumoniae infection. Taken together, our results indicate that C. pneumoniae infection promotes VSMC migration via c-Fos/IL-17C signaling.

TSLP Protects Corneas From Pseudomonas aeruginosa Infection by Regulating Dendritic Cells and IL-23-IL-17 Pathway

Purpose

We sought to determine the role of epithelium-produced thymic stromal lymphopoietin (TSLP) and its underlying mechanisms in corneal innate immune defense against Pseudomonas (P.) aeruginosa keratitis.

Methods

The expression of TSLP and TSLPR in cultured human corneal epithelial cells (HCECs) and mouse corneas was determined by PCR, Western, and/or ELISA. Cellular localization of TSLP receptor (TSLPR) was determined by whole mount confocal microscopy. TSLP-TSLPR signaling was downregulated by neutralizing antibodies and/or small interfering (si)RNA; their effects on the severity of P. aeruginosa–keratitis and cytokine expression were assessed using clinical scoring, bacterial counting, PMN infiltration, and real-time PCR. The role of dendritic cells (DCs) in corneal innate immunity was determined by local DC depletion using CD11c-DTR mice.

Results

P. aeruginosa–infection induced the expression of TSLP and TSLPR in both cultured primary HCECs and in C57BL/6 mouse corneas. While TSLP was mostly expressed by epithelial cells, CD11c-positive cells were positive for TSLPR. Targeting TSLP or TSLPR with neutralizing antibodies or TSLPR with siRNA resulted in more severe keratitis, attributable to an increase in bacterial burden and PMN infiltration. TSLPR neutralization significantly suppressed infection-induced TSLP and interleukin (IL)-17C expression and augmented the expression of IL-23 and IL-17A. Local depletion of DCs markedly increased the severity of keratitis and exhibited no effects on TSLP and IL-23 expression while suppressing IL-17A and C expression in P. aeruginosa–infected corneas.

Conclusions

The epithelium-expressed TSLP plays a protective role in P. aeruginosa keratitis through targeting of DCs and in an IL-23/IL-17 signaling pathway-related manner.

Genetic Polymorphisms in Inflammatory and Other Regulators in Gastric Cancer: Risks and Clinical Consequences

Helicobacter pylori infection is associated with the development of a chronic inflammatory response, which may induce peptic ulcers, gastric cancer (GC), and mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic H. pylori infection promotes the genetic instability of gastric epithelial cells and interferes with the DNA repair systems in host cells. Colonization of the stomach with H. pylori is an important cause of non-cardia GC and gastric MALT lymphoma. The reduction of GC development in patients who underwent anti-H. pylori eradication schemes has also been well described. Individual susceptibility to GC development depends on the host's genetic predisposition, H. pylori virulence factors, environmental conditions, and geographical determinants. Biological determinants are urgently sought to predict the clinical course of infection in individuals with confirmed H. pylori infection. Possible candidates for such biomarkers include genetic aberrations such as single-nucleotide polymorphisms (SNPs) found in various cytokines/growth factors (e.g., IL-1β, IL-2, IL-6, IL-8, IL-10, IL-13, IL-17A/B, IFN-γ, TNF, TGF-β) and their receptors (IL-RN, TGFR), innate immunity receptors (TLR2, TLR4, CD14, NOD1, NOD2), enzymes involved in signal transduction cascades (PLCE1, PKLR, PRKAA1) as well as glycoproteins (MUC1, PSCA), and DNA repair enzymes (ERCC2, XRCC1, XRCC3). Bacterial determinants related to GC development include infection with CagA-positive (particularly with a high number of EPIYA-C phosphorylation motifs) and VacA-positive isolates (in particular s1/m1 allele strains). The combined genotyping of bacterial and host determinants suggests that the accumulation of polymorphisms favoring host and bacterial features increases the risk for precancerous and cancerous lesions in patients.

Interleukin-17 family cytokines in protective immunity against infections: role of hematopoietic cell-derived and non-hematopoietic cell-derived interleukin-17s

Interleukin-17 family cytokines, consisting of six members, participate in immune response in infections and autoimmune and inflammatory diseases. The prototype cytokine of the family, IL-17A, was originally identified from CD4+ T cells which are now termed Th17 cells. Later, IL-17A-producing cells were expanded to include various hematopoietic cells, namely CD8+ T cells (Tc17), invariant NKT cells, γδ T cells, non-T non-B lymphocytes (termed type 3 innate lymphoid cells) and neutrophils. Some IL-17 family cytokines other than IL-17A are also expressed by CD4+ T cells: IL-17E by Th2 cells and IL-17F by Th17 cells. IL-17A and IL-17F induce expression of pro-inflammatory cytokines to induce inflammation and anti-microbial peptides to kill pathogens, whereas IL-17E induces allergic inflammation. However, the functions of other IL-17 family cytokines have been unclear. Recent studies have shown that IL-17B and IL-17C are expressed by epithelial rather than hematopoietic cells. Interestingly, expression of IL-17E and IL-17F by epithelial cells has also been reported and epithelial cell-derived IL-17 family cytokines shown to play important roles in immune responses to infections at epithelial sites. In this review, we summarize current information on hematopoietic cell-derived IL-17A and non-hematopoietic cell-derived IL-17B, IL-17C, IL-17D, IL-17E and IL-17F in infections and propose functional differences between these two categories of IL-17 family cytokines.

Bacterial pathogenesis and interleukin-17: interconnecting mechanisms of immune regulation, host genetics, and microbial virulence that influence severity of infection

Interleukin-17 (IL-17) is a pro-inflammatory cytokine involved in the control of many different disorders, including autoimmune, oncogenic, and diverse infectious diseases. In the context of infectious diseases, IL-17 protects the host against various classes of microorganisms but, intriguingly, can also exacerbate the severity of some infections. The regulation of IL-17 expression stems, in part, from the activity of Interleukin-23 (IL-23), which drives the maturation of different classes of IL-17-producing cells that can alter the course of infection. In this review, we analyze IL-17/IL-23 signalling in bacterial infection, and examine the interconnecting mechanisms that link immune regulation, host genetics, and microbial virulence in the context of bacterial pathogenesis. We consider the roles of IL-17 in both acute and chronic bacterial infections, with a focus on mouse models of human bacterial disease that involve infection of mucosal surfaces in the lungs, urogenital, and gastrointestinal tracts. Polymorphisms in IL-17-encoding genes in humans, which have been associated with heightened host susceptibility to some bacterial pathogens, are discussed. Finally, we examine the implications of IL-17 biology in infectious diseases for the development of novel therapeutic strategies targeted at preventing bacterial infection.