H.pylori Infection Alleviates Acute and Chronic Colitis with the Expansion of Regulatory B Cells in Mice

The yin and yang of B cells in a constant state of battle: intestinal inflammation and inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, defined by a clinical relapse-remitting course. Affecting people worldwide, the origin of IBD is still undefined, arising as a consequence of the interaction between genes, environment, and microbiota. Although the root cause is difficult to identify, data clearly indicate that dysbiosis and pathogenic microbial taxa are connected with the establishment and clinical course of IBD. The composition of the microbiota is shaped by plasma cell IgA secretion and binding, while cytokines such as IL10 or IFN-γ are important fine-tuners of the immune response in the gastrointestinal environment. B cells may also influence the course of inflammation by promoting either an anti-inflammatory or a pro-inflammatory milieu. Here, we discuss IgA-producing B regulatory cells as an anti-inflammatory factor in intestinal inflammation. Moreover, we specify the context of IgA and IgG as players that can potentially participate in mucosal inflammation. Finally, we discuss the role of B cells in mouse infection models where IL10, IgA, or IgG contribute to the outcome of the infection.

Regulatory B cells (Bregs) in Helicobacter pylori chronic infection

BACKGROUND

Helicobacter pylori (H. pylori) infection is linked with a wide variety of diseases and was reported in more than half of the world's population. Chronic H. pylori infection and its final clinical outcome depend mainly on the bacterial virulence factors and its ability to manipulate and adapt to human immune responses. Bregs blood levels have been correlated with increased bacterial load and infection chronicity, especially Gram-negative bacterial infection. This study aimed to identify prevalence and virulence factors of chronic H. pylori infection among symptomatic Egyptian patients and to examine its possible correlation to levels of regulatory B cells (Bregs) in blood.

MATERIALS AND METHODS

Gastric biopsies and blood samples from each of 113 adult patients, who underwent upper endoscopy, were examined for the detection of H. pylori by culture and PCR methods. Conventional PCR was used to determine various virulent genes prevalence and association to clinical outcome. Flow cytometry was used to evaluate Bregs levels.

RESULTS

Helicobacter pylori prevalence was 49.1% (55/112). Regarding virulence genes incidence, flaA gene was detected in 73% (40/55), vir B11 in 56.4% (31/55), hopZ1 in 34.5% (19/55), hopZ2 in 89% (49/55), babA2 in 52.7% (29/55), dupA jhp917 in 61.8% (34/55), vacA m1/m2 in 70.9% (39/55), and vacA s1/s2 in 69% (38/55) strains. Bregs levels were significantly lower in H. pylori-infected patients (p = 0.013), while total leukocyte count (TLC) showed no significant differences.

CONCLUSION

Helicobacter pylori infection prevalence was almost 49%, and the infection was found to be related to inflammatory conditions as gastritis and ulcers rather than malignant transformations. Also, we found that CD24⁺ CD38⁺ B cells were downregulated in H. pylori-infected patients.

Trends and Complication Rates in Ulcerative Colitis Patients With and Without Helicobacter pylori Infections

Background Previous studies have shown an inverse relationship between ulcerative colitis (UC) and Helicobacter pylori infections (HPI). Though these two conditions have opposite geographic distributions, there may also be a physiological explanation for the decreased incidence of H. pylori infections in patients with UC. The purpose of this study is to analyze trends and complication rates of ulcerative colitis patients with and without HPI. Materials and methods The National Inpatient Sample (NIS) database was queried for patients with a primary diagnosis of UC, stratified by the presence of H. pylori infection. Patient demographics, length of stay, total hospital charges, and mortality were compared by H. pylori status. Additionally, complication rates were also compared between the two groups. Chi-squared and independent t-tests were used to compare outcomes and demographics, and multiple logistic regression was used to analyze primary and secondary outcomes. Results Patients with UC and HPI had a lower mortality rate (8.22 vs. 3.48, P<0.05, adjusted odds ratio [AOR] 0.33) and lower hospital charges ($65,652 vs. $47,557, p<0.05, AOR 1) with similar length of stay. Patients with UC and HPI also had lower rates of intestinal perforation (2.16% vs. 1.12%, p=0.05, AOR 0.408) and intrabdominal abscess formation (0.89% vs. 0.12%, AOR 0.165, p=0.072), though this difference was not significant. From 2001 to 2013, the incidence of UC has increased while the incidence of HPI has decreased. Conclusions The lower hospital charges and mortality rate as well as decreased rates of intestinal perforation and abscess formation suggest that there may be a physiologic role that HPI plays in modulating UC. Further studies into the interaction of these two conditions would be beneficial in clarifying their relationship and may help guide treatment of UC.

Immune Biology and Persistence of Helicobacter pylori in Gastric Diseases

Helicobacter pylori is a prevalent pathogen, which affects more than 40% of the global population. It colonizes the human stomach and persists in its host for several decades or even a lifetime, if left untreated. The persistent infection has been linked to various gastric diseases, including gastritis, peptic ulcers, and an increased risk for gastric cancer. H. pylori infection triggers a strong immune response directed against the bacterium associated with the infiltration of innate phagocytotic immune cells and the induction of a Th1/Th17 response. Even though certain immune cells seem to be capable of controlling the infection, the host is unable to eliminate the bacteria as H. pylori has developed remarkable immune evasion strategies. The bacterium avoids its killing through innate recognition mechanisms and manipulates gastric epithelial cells and immune cells to support its persistence. This chapter focuses on the innate and adaptive immune response induced by H. pylori infection, and immune evasion strategies employed by the bacterium to enable persistent infection.

Unraveling the role of Breg cells in digestive tract cancer and infectious immunity

Over the past two decades, regulatory B cells (Breg cells or Bregs) have emerged as an immunosuppressive subset of B lymphocytes playing a key role in inflammation, infection, allergy, transplantation, and cancer. However, the involvement of Bregs in various pathological conditions of the gastrointestinal tract is not fully understood and is the subject of much recent research. In this review, we aimed to summarize the current state of knowledge about the origin, phenotype, and suppressive mechanisms of Bregs. The relationship between the host gut microbiota and the function of Bregs in the context of the disturbance of mucosal immune homeostasis is also discussed. Moreover, we focused our attention on the role of Bregs in certain diseases and pathological conditions related to the digestive tract, especially Helicobacter pylori infection, parasitic diseases (leishmaniasis and schistosomiasis), and gastrointestinal neoplasms. Increasing evidence points to a relationship between the presence and number of Bregs and the severity and progression of these pathologies. As the number of cases is increasing year by year, also among young people, it is extremely important to understand the role of these cells in the digestive tract.

Probiotic Cocktail Alleviates Intestinal Inflammation Through Improving Gut Microbiota and Metabolites in Colitis Mice

The modulation of the gut microbiome has been widely suggested as a promising therapeutic strategy for inflammatory bowel disease (IBD). Here, we established a novel probiotic cocktail to investigate its therapeutic role in acute colitis mice. During dextran sulfate sodium (DSS)-induced colitis, the mice were treated with the probiotic cocktail, fecal microbiota transplantation (FMT) from a healthy mice donor, or 5-aminosalicylic acid (5-ASA), respectively. The inflammatory responses were assessed by symptoms, serum inflammatory factors, and histological scoring. The intestinal barrier function was assessed by detecting tight junction proteins. Gut microbiota and its metabolites were further identified using 16S rDNA sequencing and a liquid chromatograph mass spectrometer (LC-MS/MS). Compared with FMT and 5-ASA treatment, the probiotic cocktail performed better in alleviating symptoms of colitis and decreasing disease activity score and mucosal inflammation. The probiotic cocktail also significantly decreased serum IL-17 level and increased JAM-1 expression in colon. The gut microbiota analysis confirmed that the beneficial effects of the probiotic cocktail were attributed to increasing anti-inflammatory bacteria Akkermansia, Bifidobacterium, and Blautia, while decreasing pro-inflammatory bacteria Parasutterella. The targeted metabolome analysis further indicated a rise in the production of Bifidobacterium-related short-chain fatty acids (SCFAs) such as propanoic acid and isobutyric acid after probiotics treatment. Taken together, the probiotic cocktail effectively alleviated intestinal inflammation through improving gut microbiota and metabolites in colitis mice, suggesting its great potential to be a novel therapeutic approach for IBD patients.

Exosomal CagA from Helicobacter pylori aggravates intestinal epithelium barrier dysfunction in chronic colitis by facilitating Claudin-2 expression

BACKGROUND

The chronic infection with Helicobacter pylori (H. pylori), especially cytotoxin-associated gene A-positive (CagA⁺) strains, has been associated with various extragastric disorders. Evaluating the potential impacts of virulence factor CagA on intestine may provide a better understanding of H. pylori pathogenesis such as colitis. The intestinal mucosal barrier is essential for maintaining its integrity and functions. However, how persistent CagA⁺ H. pylori colonization influences barrier disruption and thereby affects chronic colitis is not fully understood.

RESULTS

Chronic colitis models of CagA⁺ H. pylori-colonized mice treated with 2% Dextran sulphate sodium (DSS) were established to assess the disease activity and pertinent expression of tight junction proteins closely related to mucosal integrity. The aggravating effect of CagA⁺ H. pylori infection on DSS-induced chronic colitis was confirmed in mouse models. In addition, augmented Claudin-2 expression was detected in CagA⁺ H. pylori infection conditions and selected for mechanistic analysis. Next, GES-1 human gastric epithelial cells were cultured with CagA⁺ H. pylori or a recombinant CagA protein, and exosomes isolated from conditioned media were then identified. We assessed the Claudin-2 levels after exposure to CagA⁺ exosomes, CagA^- exosomes, and IFN-γ incubation, revealing that CagA⁺ H. pylori compromised the colonic mucosal barrier and facilitated IFN-γ-induced intestinal epithelial destruction through CagA-containing exosome-mediated mechanisms. Specifically, CagA upregulated Claudin-2 expression at the transcriptional level via a CDX2-dependent mechanism to slow the restoration of wounded mucosa in colitis in vitro.

CONCLUSIONS

These data suggest that exosomes containing CagA facilitate CDX2-dependent Claudin-2 maintenance. The exosome-dependent mechanisms of CagA⁺ H. pylori infection are indispensable for damaging the mucosal barrier integrity in chronic colitis, which may provide a new idea for inflammatory bowel disease (IBD) treatment.

Helicobacter-stimulated IL-10-producing B cells suppress differentiation of lipopolysaccharide/Helicobacter felis-activated stimulatory dendritic cells

Regulatory B cells (Bregs) produce antiinflammatory cytokines and inhibits proinflammatory response. Recently, immunosuppressive roles of Bregs in the effector functions of dendritic cells (DCs) were demonstrated. However, cross talk between Bregs and DCs in Helicobacter infection remains unknown. Here, we showed that direct stimulation of bone marrow-derived DCs (BM-DCs) with Helicobacter felis (H. felis) antigen upregulates their CD86 surface expression and causes the production of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and interleukin-10 (IL-10). Furthermore, prestimulation of DCs with supernatants derived from both Helicobacter-stimulated IL-10^– B (Hf_stim-IL-10^– B) or IL-10⁺ B (Hf_stim-IL-10⁺) cells suppresses the secretion of TNF-α and IL-6, but does not affect the expression of CD86 and secretion of IL-12 by lipopolysaccharide (LPS) or H. felis-activated BM-DCs. Remarkably, soluble factors secreted by Hf_stim-IL-10^– B cells, but not by Hf_stim-IL-10⁺ B cells, suppress the secretion of IL-10 by BM-DCs upon subsequent LPS stimulation. In contrast, prestimulation with BM-DCs with supernatants of Hf_stim-IL-10⁺ B cells before H. felis antigen stimulation induces significantly their IL-10 production. Collectively, our data indicated that prestimulation with soluble factors secreted by Hf_stim-IL-10⁺ B cells, DCs exhibit a tolerogenic phenotype in response to LPS or Helicobacter antigen by secreting high levels of IL-10, but decreased levels of IL-6 and TNF-α.

New insights into regulatory B cells biology in viral, bacterial, and parasitic infections

B lymphocytes are primarily well known for their contribution to immunity by antibody production, antigen presentation and, the production of cytokines. In recent years several studies demonstrated the existence of B cells with regulatory functions, which have been termed regulatory B cells (B_regs), similar to regulatory T cells (T_regs). B_regs are a subpopulation of B cells that have immunosuppressive effects via the production of regulatory cytokines including interleukin-10 (IL-10), transforming growth factor-β (TGF-β), and IL-35. B_regs limit host defense against various pathogens. In addition, B_regs contribute to increased levels of regulatory cytokines and leads to an induction of suppressive T_regs, which exert broader suppressive functions against various pathogens. The high percentage of B_regs is positively associated with viral and bacterial load and can contribute to poor vaccine responses. B_regs can also facilitate pathogen survival at an early stage of infection, and subsequently cause increased severity of disease by inhibiting pro-inflammatory cytokine production, macrophage activation, and inflammatory T cells activation such as Th1, Th17, and Th22. Also, B_regs afford protection against the hyper-inflammatory response in parasitic infections. Here we review the central role of B_regs in many major bacterial and viral human infections, and provide an overview of the immunoregulatory mechanisms used by B_regs.

Helicobacter pylori infection reduces TAMs infiltration in a mouse model of AOM/DSS induced colitis-associated cancer

Inflammatory bowel disease (IBD) increases the risk of colitis-associated cancer (CAC). Evidences suggest that Helicobacter pylori (H. pylori) infection is associated with a low risk of IBD and protects against experimental colitis in mouse models. However, the effect of H. pylori infection in CAC remains unclear. We previously reported that H. pylori infection increased M2 macrophages in dextran sodium sulfate (DSS)-induced chronic colitis. Tumor-associated macrophages (TAMs) play a pivotal role in colon cancer. Therefore, we established a H. pylori-infected CAC mouse model induced by azoxymethane and DSS to explore the effect of H. pylori infection on TAMs in CAC. Here, we demonstrated that H. pylori infection attenuated the development of CAC by decreasing tumor multiplicity, tumor size, tumor grade and colitis scores. Moreover, H. pylori infection reduced the infiltration of TAMs, particularly M2-like TAMs in CAC tumors, accompanied with the down-regulated pro-inflammatory and pro-tumorigenic factors TNF-α, IL-1β, IL-6 and IL-23 in tumors of CAC mice. Our study suggests that H. pylori infection can reduce TAMs infiltration and regulate cytokines expression in CAC.

Synthesis of Interleukin-10 in Patients with Ulcerative Colitis and Helicobacter pylori Infection

METHODS

Detection of H. pylori infection was performed by a 13C-urea breath test in 31 patients with UC. In each patient, a serum sample was drawn to measure IL-10 by the ELISA technique. Based on the primary breath test result, two groups were formed and serum IL-10 was measured.

RESULTS

Serological IL-10 levels in patients with UC and negative 13C-urea breath test was 10.28 pg/ml whereas in patients with UC and positive 13C-urea breath test was 5.5 pg/ml (P = 0.035). IL-10 levels were higher in the inflammatory endoscopic and histological active groups which tested positive in the 13C-urea breath tests for H. pylori (P < 0.05).

CONCLUSIONS

The role of IL-10 secretion in patients with UC in determining the clinicopathological outcome of infection merits further study. This study suggests an association between serum IL-10 and disease severity in patients with UC and HP infection.

Probiotic mixtures with aerobic constituent promoted the recovery of multi-barriers in DSS-induced chronic colitis

AIMS

Gut microbiota has been closely linked to the mucosal immune and been regarded as a reliable target for intestinal inflammation. This study aimed to explore the therapeutic roles of probiotic mixtures of Bifidobacterium infantis, Lactobacillus acidophilus, Enterococcus faecalis with (quadruple probiotics, P-qua) or without (triple probiotics, P-tri) aerobic Bacillus cereus in colitis, focusing on the multiple barrier functions.

MATERIALS AND METHODS

Chronic colitis was induced by dextran sulfate sodium (DSS) in C57BL/6 mice. The probiotic mixtures P-qua or P-tri was gavage administrated respectively, while fecal microbiota transplantation (FMT) as a positive control. The intestinal inflammation and functions of multiple barriers were assessed, including the mucus barrier, epithelial barrier and endothelial barrier known as gut-vascular barrier (GVB). Altered composition and diversity in gut microbiota were observed via sequencing analysis.

KEY FINDINGS

Both P-qua and P-tri relieved the intestinal inflammation and improved the functions of multiple barriers with increased integrity of mucous layer, enhanced transepithelial electrical resistance, declined epithelial and endothelial permeability to macromolecules in DSS-colitis. Aerobe-contained P-qua revealed a more active role in barrier recovering relative to P-tri, while FMT as a positive control seemed to get better results than pure probiotics. Indeed, P-qua was effective in rebuilding the structure and diversity of gut flora in DSS-colitis, especially increased abundance of Bifidobacterium, Akkermansia, Lactobacillus and Bacteroides.

SIGNIFICANCE

Aerobe-contained P-qua was a powerful adjuvant therapy for chronic colitis, via restoring the intestinal microflora and recovering the multi-barriers in the inflamed gut.