Importance of Toll-like Receptors in Pro-inflammatory and Anti-inflammatory Responses by Helicobacter pylori Infection

Sustained exposure to Helicobacter pylori induces immune tolerance by desensitizing TLR6

Helicobacter pylori (H. pylori, Hp) has been designated a class I carcinogen and is closely associated with severe gastric diseases. During colonization in the gastric mucosa, H. pylori develops immune escape by inducing host immune tolerance. The gastric epithelium acts as the first line of defense against H. pylori, with Toll-like receptors (TLRs) in gastric epithelial cells being sensitive to H. pylori components and subsequently activating the innate immune system. However, the mechanism of immune tolerance induced by H. pylori through the TLR signalling pathway has not been fully elucidated. In this research, we detected the expression of TLRs and inflammatory cytokines in GES-1 cells upon sustained exposure to H. pylori or H. pylori lysate from 1 to 30 generations and in Mongolian gerbils infected with H. pylori for 5 to 90 weeks. We found that the levels of TLR6 and inflammatory cytokines first increased and then dropped during the course of H. pylori treatment in vitro and in vivo. The restoration of TLR6 potentiated the expression of IL-1β and IL-8 in GES-1 cells, which recruited neutrophils and reduced the colonization of H. pylori in the gastric mucosa of gerbils. Mechanistically, we found that persistent infection with H. pylori reduces the sensitivity of TLR6 to bacterial components and regulates the expression of inflammatory cytokines in GES-1 cells through TLR6/JNK signaling. The TLR6 agonist obviously alleviated inflammation in vitro and in vivo. Promising results suggest that TLR6 may be a potential candidate immunotherapy drug for H. pylori infection.

Innate Immunity Crosstalk with Helicobacter pylori: Pattern Recognition Receptors and Cellular Responses

Helicobacter pylori is one of the most successful gastric pathogens that has co-existed with human for centuries. H. pylori is recognized by the host immune system through human pattern recognition receptors (PRRs), such as toll-like receptors (TLRs), C-type lectin like receptors (CLRs), NOD-like receptors (NLRs), and RIG-I-like receptors (RLRs), which activate downstream signaling pathways. Following bacterial recognition, the first responders of the innate immune system, including neutrophils, macrophages, and dendritic cells, eradicate the bacteria through phagocytic and inflammatory reaction. This review provides current understanding of the interaction between the innate arm of host immunity and H. pylori, by summarizing H. pylori recognition by PRRs, and the subsequent signaling pathway activation in host innate immune cells.

Multi-target regulation of intestinal microbiota by berberine to improve type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) and its complications are major public health problems that seriously affect the quality of human life. The modification of intestinal microbiota has been widely recognized for the management of diabetes. The relationship between T2DM, intestinal microbiota, and active ingredient berberine (BBR) in intestinal microbiota was reviewed in this paper. First of all, the richness and functional changes of intestinal microbiota disrupt the intestinal environment through the destruction of the intestinal barrier and fermentation/degradation of pathogenic/protective metabolites, targeting the liver, pancreas, visceral adipose tissue (VAT), etc., to affect intestinal health, blood glucose, and lipids, insulin resistance and inflammation. Then, we focus on BBR, which protects the composition of intestinal microbiota, the changes of intestinal metabolites, and immune regulation disorder of the intestinal environment as the therapeutic mechanism as well as its current clinical trials. Further research can analyze the mechanism network of BBR to exert its therapeutic effect according to its multi-target compound action, to provide a theoretical basis for the use of different phytochemical components alone or in combination to prevent and treat T2DM or other metabolic diseases by regulating intestinal microbiota.

Dietary intake of walnut prevented Helicobacter pylori-associated gastric cancer through rejuvenation of chronic atrophic gastritis

The fact that Fat-1 transgenic mice producing n-3 polyunsaturated fatty acids via overexpressed 3-desaturase significantly mitigated Helicobacter pylori (H. pylori)-associated gastric tumorigenesis through rejuvenation of chronic atrophic gastritis (CAG) led us to study whether dietary intake of walnut plentiful of n-3 PUFAs can be nutritional intervention to prevent H. pylori-associated gastric cancer. In our model that H. pylori-initiated, high salt diet-promoted gastric carcinogenesis, pellet diet containing 100 mg/kg and 200 mg/kg walnut was administered up to 36 weeks. As results, control mice (24 weeks) developed significant chronic CAG, in which dietary walnuts significantly ameliorated chronic atrophic gastritis. Expressions of COX-2/PGE₂/NF-κB/c-Jun, elevated in 24 weeks control group, were all significantly decreased with walnut (p<0.01). Tumor suppressive enzyme, 15-PGDH, was significantly preserved with walnut. Control mice (36 weeks) all developed significant tumors accompanied with severe CAG. However, significantly decreased tumorigenesis was noted in group treated with walnuts, in which expressions of COX-2/PGE₂/NF-κB/IL-6/STAT3, all elevated in 36 weeks control group, were significantly decreased with walnut. Defensive proteins including HO-1, Nrf2, and SOCS-1 were significantly increased in walnut group. Proliferative index as marked with Ki-67 and PCNA was significantly regulated with walnut relevant to 15-PGDH preservation. Conclusively, walnut can be an anticipating nutritional intervention against H. pylori.

Expression and Significance of MyD88 in Patients With Gastric Cardia Cancer in a High-Incidence Area of China

Background: Gastric cardia cancer (GCC) arises in the area of the stomach adjoining the esophageal-gastric junction and has unique risk factors. It was suggested that the involvement of Helicobacter pylori is associated with GCC from high-risk population. Myeloid differentiation factor 88 (MyD88) is a crucial adaptor molecule in Toll-like signaling pathway recognizing H. pylori. Its role in GCC has not been elucidated yet. In this study, our purpose is to investigate the expression and significance of MyD88 in GCC tissue. Methods: Expression of MyD88 and nuclear factor κB (NF-κB) p105/p50 and infection of H. pylori were detected by immunohistochemistry in gastric cardia tissue. The correlation of MyD88 expression to NF-κB p105/p50 expression, H. pylori infection, and clinicopathologic characteristics in gastric cardia tissue was analyzed. The involvement of MyD88 in patient prognosis was also analyzed. Results: Our data showed that the expression of MyD88 elevated from normal mucosa to inflammation (p = 0.071). The expression of MyD88 was enhanced in GCC tissues by contrast to non-malignant cardia mucosa (p = 0.025). What's more, overexpression of MyD88 was detected in intestinal-type adenocarcinoma with inflammation. Patients with high MyD88 staining revealed a better differentiation (p = 0.02). MyD88 also positively correlated with NF-κB p105/p50 expression (p = 0.012) in cancer tissue. Expression of MyD88 was increased but not significantly in biopsies with H. pylori infection compared with non-infected biopsies. Multivariate analyses revealed lymph node metastasis but not MyD88 expression was an independent predictor for patient survival. Conclusion: These findings provide pathological evidence that upregulating MyD88 and inducing inflammation might be involved in gastric cardia carcinogenesis in high-risk population. MyD88 plays a role in gastric cardia carcinogenesis with NF-κB pathway activation. Higher MyD88 expression is not a major prognostic determinant in GCC, but it may relate to the tumor cell differentiation.

Polyamine Transport Protein PotD Protects Mice against Haemophilus parasuis and Elevates the Secretion of Pro-Inflammatory Cytokines of Macrophage via JNK-MAPK and NF-κB Signal Pathways through TLR4

The potD gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system potABCD, encodes the bacterial substrate-binding subunit of the polyamine transport system. In this study, we found PotD in Haemophilus (Glaesserella) parasuis could actively stimulate both humoral immune and cellular immune responses and elevate lymphocyte proliferation, thus eliciting a Th1-type immune response in a murine immunity and infection model. Stimulation of Raw 264.7 macrophages with PotD validated that Toll-like receptor 4, rather than 2, participated in the positive transcription and expression of pro-inflammatory cytokines IL–1β, IL–6, and TNF–α using qPCR and ELISA. Blocking signal-regulated JNK–MAPK and RelA(p65) pathways significantly decreased PotD-induced pro-inflammatory cytokine production. Overall, we conclude that vaccination of PotD could induce both humoral and cellular immune responses and provide immunoprotection against H. parasuis challenge. The data also suggest that Glaesserella PotD is a novel pro-inflammatory mediator and induces TLR4-dependent pro-inflammatory activity in Raw 264.7 macrophages through JNK–MAPK and RelA(p65) pathways.