Innate Immune Molecule NLRC5 Protects Mice From Helicobacter-induced Formation of Gastric Lymphoid Tissue

Adaptor molecules mediate negative regulation of macrophage inflammatory pathways: a closer look

Macrophages play a central role in initiating, maintaining, and terminating inflammation. For that, macrophages respond to various external stimuli in changing environments through signaling pathways that are tightly regulated and interconnected. This process involves, among others, autoregulatory loops that activate and deactivate macrophages through various cytokines, stimulants, and other chemical mediators. Adaptor proteins play an indispensable role in facilitating various inflammatory signals. These proteins are dynamic and flexible modulators of immune cell signaling and act as molecular bridges between cell surface receptors and intracellular effector molecules. They are involved in regulating physiological inflammation and also contribute significantly to the development of chronic inflammatory processes. This is at least partly due to their involvement in the activation and deactivation of macrophages, leading to changes in the macrophages' activation/phenotype. This review provides a comprehensive overview of the 20 adaptor molecules and proteins that act as negative regulators of inflammation in macrophages and effectively suppress inflammatory signaling pathways. We emphasize the functional role of adaptors in signal transduction in macrophages and their influence on the phenotypic transition of macrophages from pro-inflammatory M1-like states to anti-inflammatory M2-like phenotypes. This endeavor mainly aims at highlighting and orchestrating the intricate dynamics of adaptor molecules by elucidating the associated key roles along with respective domains and opening avenues for therapeutic and investigative purposes in clinical practice.

NLRC5 restricts dengue virus infection by promoting the autophagic degradation of viral NS3 through E3 ligase CUL2 (cullin 2)

NLRC5 has been reported to be involved in antiviral immunity; however, the underlying mechanism remains poorly understood. Here, we investigated the functional role of NLRC5 in the infection of a flavivirus, dengue virus (DENV). We found that the expression of NLRC5 was strongly induced by virus infection and IFNB or IFNG stimulation in different cell lines. Overexpression of NLRC5 remarkably suppressed DENV infection, whereas knockout of NLRC5 led to a significant increase in DENV infection. Mechanistic study revealed that NLRC5 interacted with the viral nonstructural protein 3 (NS3) protease domain and mediated degradation of NS3 through a ubiquitin-dependent selective macroautophagy/autophagy pathway. We demonstrated that NLRC5 recruited the E3 ubiquitin ligase CUL2 (cullin 2) to catalyze K48-linked poly-ubiquitination of the NS3 protease domain, which subsequently served as a recognition signal for cargo receptor TOLLIP-mediated selective autophagic degradation. Together, we have demonstrated that NLRC5 exerted an antiviral effect by mediating the degradation of a multifunctional protein of DENV, providing a novel antiviral signal axis of NLRC5-CUL2-NS3-TOLLIP. This study expands our understanding of the regulatory network of NLRC5 in the host defense against virus infection.

Anti-CD40L therapy prevents the formation of precursor lesions to gastric B-cell MALT lymphoma in a mouse model

Mucosa-associated lymphoid tissue (MALT) lymphoma is a B-cell tumour that develops over many decades in the stomachs of individuals with chronic Helicobacter pylori infection. We developed a new mouse model of human gastric MALT lymphoma in which mice with a myeloid-specific deletion of the innate immune molecule, Nlrc5, develop precursor B-cell lesions to MALT lymphoma at only 3 months post-Helicobacter infection versus 9-24 months in existing models. The gastric B-cell lesions in the Nlrc5 knockout mice had the histopathological features of the human disease, notably lymphoepithelial-like lesions, centrocyte-like cells, and were infiltrated by dendritic cells (DCs), macrophages, and T-cells (CD4+ , CD8+ and Foxp3+ ). Mouse and human gastric tissues contained immune cells expressing immune checkpoint receptor programmed death 1 (PD-1) and its ligand PD-L1, indicating an immunosuppressive tissue microenvironment. We next determined whether CD40L, overexpressed in a range of B-cell malignancies, may be a potential drug target for the treatment of gastric MALT lymphoma. Importantly, we showed that the administration of anti-CD40L antibody either coincident with or after establishment of Helicobacter infection prevented gastric B-cell lesions in mice, when compared with the control antibody treatment. Mice administered the CD40L antibody also had significantly reduced numbers of gastric DCs, CD8+ and Foxp3+ T-cells, as well as decreased gastric expression of B-cell lymphoma genes. These findings validate the potential of CD40L as a therapeutic target in the treatment of human gastric B-cell MALT lymphoma. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

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.

Relationship between NLRC5 gene polymorphisms and gastric cancer susceptibility

BACKGROUND

The NF-κB signaling pathway exerts a synergistic effect on gastric carcinogenesis. NLRC5 is an upstream regulator of the NF-κB signaling pathway, which is closely related to gastric carcinogenesis. Since NLRC5 expression is different among gastric cancer patients, we speculated that it might be related to NLRC5 gene polymorphisms. We explored the associations between NLRC5 gene polymorphism and gastric carcinogenesis through gene sequencing.

AIM

To investigate the associations of the NLRC5 rs56315364 and rs289726 gene polymorphisms with gastric cancer susceptibility and prognosis.

METHODS

A total of 75 gastric cancer patients and 59 healthy volunteers (age- and sex-matched) were enrolled in the study from September 2014 to October 2016. The NLRC5 rs56315364 and rs289726 genotypes were determined by first-generation sequencing of PCR products. Sequencing products were analyzed using MegAlign and Chromas 2.4.3 software. Differences in NLRC5 gene polymorphisms between patients with gastric cancer and healthy volunteers were identified to investigate the relationship between NLRC5 gene polymorphisms and the prognosis of gastric cancer.

RESULTS

The NLRC5 rs56315364 CC genotype increased the risk of gastric cancer [odds ratio (OR) = 7.06, 95% confidence interval (CI): 2.81-17.72], as did the rs289726 TC and CC genotypes (OR = 11.04, 95%CI: 4.29-28.43; OR = 4.77, 95%CI: 1.57-14.48, respectively). There was no significant difference in the genotype frequency of NLRC5 rs56315364 and rs289726 between the Helicobacter pylori (H. pylori)-negative group and the H. pylori-positive group (P > 0.05). Survival analysis showed that the NLRC5 rs289726 genotype was correlated with the prognosis of gastric cancer (P < 0.05), and the NLRC5 rs289726 CC genotype was associated with the worst prognosis. Multivariate Cox regression analysis showed that age and tumor-node-metastasis (TNM) stage were correlated with the prognosis of gastric cancer patients (P < 0.05)

CONCLUSION

The NLRC5 rs56315364 CC and rs289726 TC genotypes significantly increase the risk of gastric cancer. Older age and higher TNM stage are associated with the worse prognosis of patients with gastric cancer. The prognosis of gastric cancer patients with NLRC5 rs289726 CC genotype is the worst.

NLRC5 modulates bone metabolism and plays a role in periodontitis

INTRODUCTION

NOD-like receptor C5 (NLRC5) plays a significant role in the immune system, and is one of the largest members of the pattern recognition receptor family. Previous studies have found that NLRC5 might be involved in the regulation of various diseases, such as fibrotic diseases and cancers; however, its effect on bone metabolism-related diseases has not been reported.

METHODS

Skeletons of Nlrc5^-/- mice generated by CRISPR/Cas9 and wild-type (WT) mice were compared using X-ray, micro-computed tomography, double labeling, and histological examination. Tartrate-resistant acid phosphatase and pit-absorption assays were performed to evaluate the effect of NLRC5 on osteoclasts differentiation and osteoclastic capacity. The influence of NLRC5 on osteoblasts differentiation and bone formation were studied using alkaline phosphatase and alizarin red staining, respectively. Experimental periodontitis was induced by Porphyromonas gingivalis infection and ligature to investigate the role of NLRC5 in inflammatory periodontal bone loss.

RESULTS

Adenovirus-mediated NLRC5 overexpression in human bone marrow mesenchymal stem cells regulated osteogenesis positively. The femoral osteogenesis ability was significantly weakened in Nlrc5^-/- mice. Histology showed that the area of the femoral trabeculae in the Nlrc5^-/- mice was less than that in the WT mice, and radiology suggested that the Nlrc5^-/- mice had fewer trabeculae and a thinner bone cortex than those of the WT mice. Nlrc5 knockout decreased osteoblast mineralization and increased osteoclastogenesis in vitro. NLRC5 was downregulated in periodontitis and P. gingivalis infection. In the experimental periodontitis model, the alveolar bone loss, inflammatory cell infiltration, and inflammatory cytokines secretion (interleukin [IL]-1β, IL-6, and tumor necrosis factor alpha [TNF-α]) in the Nlrc5^-/- mice were significantly enhanced compared to WT mice.

CONCLUSION

We verified a novel role of NLRC5 in bone metabolism by regulating both osteoclasts activity and osteoblasts activity. Our results revealed a protective effect of NLRC5 against periodontal inflammation and alveolar bone destruction. NLRC5 could be a novel treatment target to prevent periodontal bone destruction.

Toll-like Receptor 9 Promotes Initiation of Gastric Tumorigenesis by Augmenting Inflammation and Cellular Proliferation

BACKGROUND & AIMS

Gastric cancer (GC) is strongly linked with chronic gastritis after Helicobacter pylori infection. Toll-like receptors (TLRs) are key innate immune pathogenic sensors that mediate chronic inflammatory and oncogenic responses. Here, we investigated the role of TLR9 in the pathogenesis of GC, including Helicobacter infection.

METHODS

TLR9 gene expression was profiled in gastric tissues from GC and gastritis patients and from the spontaneous gp130^F/F GC mouse model and chronic H felis-infected wild-type (WT) mice. Gastric pathology was compared in gp130^F/F and H felis infection models with or without genetic ablation of Tlr9. The impact of Tlr9 targeting on signaling cascades implicated in inflammation and tumorigenesis (eg, nuclear factor kappa B, extracellular signal-related kinase, and mitogen-activated protein kinase) was assessed in vivo. A direct growth-potentiating effect of TLR9 ligand stimulation on human GC cell lines and gp130^F/F primary gastric epithelial cells was also evaluated.

RESULTS

TLR9 expression was up-regulated in Helicobacter-infected gastric tissues from GC and gastritis patients and gp130^F/F and H felis-infected WT mice. Tlr9 ablation suppressed initiation of tumorigenesis in gp130^F/F:Tlr9^-/- mice by abrogating gastric inflammation and cellular proliferation. Tlr9^-/- mice were also protected against H felis-induced gastric inflammation and hyperplasia. The suppressed gastric pathology upon Tlr9 ablation in both mouse models associated with attenuated nuclear factor kappa B and, to a lesser extent, extracellular signal-related kinase, mitogen-activated protein kinase signaling. TLR9 ligand stimulation of human GC cells and gp130^F/F GECs augmented their proliferation and viability.

CONCLUSIONS

Our data reveal that TLR9 promotes the initiating stages of GC and facilitates Helicobacter-induced gastric inflammation and hyperplasia, thus providing in vivo evidence for TLR9 as a candidate therapeutic target in GC.

The Helicobacter pylori CagY Protein Drives Gastric Th1 and Th17 Inflammation and B Cell Proliferation in Gastric MALT Lymphoma

Background: the neoplastic B cells of the Helicobacter pylori-related low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma proliferate in response to H. pylori, however, the nature of the H. pylori antigen responsible for proliferation is still unknown. The purpose of the study was to dissect whether CagY might be the H. pylori antigen able to drive B cell proliferation. Methods: the B cells and the clonal progeny of T cells from the gastric mucosa of five patients with MALT lymphoma were compared with those of T cell clones obtained from five H. pylori–infected patients with chronic gastritis. The T cell clones were assessed for their specificity to H. pylori CagY, cytokine profile and helper function for B cell proliferation. Results: 22 of 158 CD4⁺ (13.9%) gastric clones from MALT lymphoma and three of 179 CD4⁺ (1.7%) clones from chronic gastritis recognized CagY. CagY predominantly drives Interferon-gamma (IFN-γ) and Interleukin-17 (IL-17) secretion by gastric CD4⁺ T cells from H. pylori-infected patients with low-grade gastric MALT lymphoma. All MALT lymphoma-derived clones dose dependently increased their B cell help, whereas clones from chronic gastritis lost helper activity at T-to-B-cell ratios greater than 1. Conclusion: the results obtained indicate that CagY drives both B cell proliferation and T cell activation in gastric MALT lymphomas.

Helicobacter urease suppresses cytotoxic CD8 + T cell responses through activating Myh9-dependent induction of PD-L1

As a key virulence factor for persistent colonization, Urease B subunit (UreB) is considered to be an ideal vaccine antigen against Helicobacter pylori (H. pylori) infection. However, the role and molecular mechanisms of UreB involved in immune microenvironment dysregulation still remains largely unknown. In the present study, we evaluated the effects of UreB on macrophage activation and found that UreB induced PD-L1 accumulation on Bone marrow-derived macrophages (BMDMs). Co-culture assays further revealed that UreB-induced PD-L1 expression on BMDMs significantly decreased the proliferation and secretion of cytolytic molecules (granzyme B and perforin) of splenic CD8 + T cells isolated from inactivated H. pylori-immunized mice. More importantly, myosin heavy chain 9 (Myh9) was confirmed to be a direct membrane receptor of UreB via using LC-MS/MS and Co-immunoprecipitation and required for PD-L1 upregulation on BMDMs. Molecular studies further demonstrated that the interaction between UreB and Myh9 decreased GCN2 autophosphorylation and enhanced intracellular pool of amino acids, leading to the upregulation of S6K phosphorylation, a commonly used marker for monitoring activation of mTORC1 signaling activity. Furthermore, blocking mTORC1 activation with its inhibitor Temsirolimus reversed UreB-induced PD-L1 upregulation and the subsequently inhibitory effects of BMDMs on activation of cytotoxic CD8 + T cell responses. Overall, our data unveil a novel immunosuppressive mechanism of UreB during H. pylori infection, which may provide valuable clue for the optimization of H. pylori vaccine.

The regulation of miR-320a/XBP1 axis through LINC00963 for endoplasmic reticulum stress and autophagy in diffuse large B-cell lymphoma

Background

This study incorporates fundamental research referring to considerable amounts of gene-sequencing data and bioinformatics tools to analyze the pathological mechanisms of diffuse large B-cell lymphoma (DLBCL).

Methods

A lncRNA-miRNA-mRNA ceRNA network of DLBCL was constructed through database analysis combining GTEx and TCGA. qPCR was used to detect the expression of LINC00963 and miR-320a in DLBCL cell lines. After LINC00963 or miR-320a overexpression in vitro, western blot was performed to assess the protein levels of UPR sensors (GRP78, p-IRE1, IRE1, active ATF6, ATF4 and XBP1), along with apoptosis markers (Bcl-2, Bax, caspase 3) and autophagy indicators (Beclin1, LC3II, LC3I and p62). Additionally, the expression of LC3 was analyzed through immunofluorescence (IF) assay. 

Results

Following LINC00963 overexpression in vitro, SUDHL4 cell line showed a marked increase in the level of UPR-related GRP78, p-IRE1 and spliced XBP-1/XBP-1(s), apoptosis-related Bax and cleaved caspase 3, as well as autophagy-related Beclin1 and LC3II, whereas miR-320a mimic greatly diminished the effects of LINC00963 overexpression. Moreover, LINC00963 targeted miR-320a while miR-320a bound to the 3’UTR of XBP1. It was also found that LINC00963 overexpression resulted in significantly delayed tumor growth in a xenograft model of DLBCL. 

Conclusion

Mechanistically, LINC00963/miR-320a regulated XBP1-apoptosis pathway and autophagy, implying the therapeutic potential of this pathway for selective targeting. The data presented here illustrated the mechanism of LINC00963/miR-320a/XBP1 in DLBCL for the first time.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01992-y.

Innate Immune Responses and Pulmonary Diseases

Innate immunity is the first defense line of the host against various infectious pathogens, environmental insults, and other stimuli causing cell damages. Upon stimulation, pattern recognition receptors (PRRs) act as sensors to activate innate immune responses, containing NF-κB signaling, IFN response, and inflammasome activation. Toll-like receptors (TLRs), retinoic acid-inducible gene I-like receptors (RLRs), NOD-like receptors (NLRs), and other nucleic acid sensors are involved in innate immune responses. The activation of innate immune responses can facilitate the host to eliminate pathogens and maintain tissue homeostasis. However, the activity of innate immune responses needs to be tightly controlled to ensure the optimal intensity and duration of activation under various contexts. Uncontrolled innate immune responses can lead to various disorders associated with aberrant inflammatory response, including pulmonary diseases such as COPD, asthma, and COVID-19. In this chapter, we will have a broad overview of how innate immune responses function and the regulation and activation of innate immune response at molecular levels as well as their contribution to various pulmonary diseases. A better understanding of such association between innate immune responses and pulmonary diseases may provide potential therapeutic strategies.

The MHC Class-I Transactivator NLRC5: Implications to Cancer Immunology and Potential Applications to Cancer Immunotherapy

The immune system constantly monitors the emergence of cancerous cells and eliminates them. CD8⁺ cytotoxic T lymphocytes (CTLs), which kill tumor cells and provide antitumor immunity, select their targets by recognizing tumor antigenic peptides presented by MHC class-I (MHC-I) molecules. Cancer cells circumvent immune surveillance using diverse strategies. A key mechanism of cancer immune evasion is downregulation of MHC-I and key proteins of the antigen processing and presentation machinery (APM). Even though impaired MHC-I expression in cancers is well-known, reversing the MHC-I defects remains the least advanced area of tumor immunology. The discoveries that NLRC5 is the key transcriptional activator of MHC-I and APM genes, and genetic lesions and epigenetic modifications of NLRC5 are the most common cause of MHC-I defects in cancers, have raised the hopes for restoring MHC-I expression. Here, we provide an overview of cancer immunity mediated by CD8⁺ T cells and the functions of NLRC5 in MHC-I antigen presentation pathways. We describe the impressive advances made in understanding the regulation of NLRC5 expression, the data supporting the antitumor functions of NLRC5 and a few reports that argue for a pro-tumorigenic role. Finally, we explore the possible avenues of exploiting NLRC5 for cancer immunotherapy.

APRIL-producing eosinophils are involved in gastric MALT lymphomagenesis induced by Helicobacter sp infection

The roles of the inflammatory response and production of a proliferation-inducing ligand (APRIL) cytokine in gastric mucosa-associated lymphoid tissue (MALT) lymphomagenesis induced by Helicobacter species infection are not clearly understood. We characterized the gastric mucosal inflammatory response associated with gastric MALT lymphoma (GML) and identified APRIL-producing cells in two model systems: an APRIL transgenic mouse model of GML induced by Helicobacter infection (Tg-hAPRIL) and human gastric biopsy samples from Helicobacter pylori-infected GML patients. In the mouse model, polarization of T helper 1 (tbet), T helper 2 (gata3), and regulatory T cell (foxp3) responses was evaluated by quantitative PCR. In humans, a significant increase in april gene expression was observed in GML compared to gastritis. APRIL-producing cells were eosinophilic polynuclear cells located within lymphoid infiltrates, and tumoral B lymphocytes were targeted by APRIL. Together, the results of this study demonstrate that the Treg-balanced inflammatory environment is important for gastric lymphomagenesis induced by Helicobacter species, and suggest the pro-tumorigenic potential of APRIL-producing eosinophils.

Review - Helicobacter, inflammation, immunology and vaccines

Understanding the mechanisms involved in induction and regulation of the immune and inflammatory response to Helicobacter pylori is extremely important in determining disease outcomes. H pylori expresses a plethora of factors that influence the host response. Vaccines against H pylori are desperately needed for the prevention of gastric carcinogenesis, especially with the increasing trends in antimicrobial resistance. This review summarizes some important findings, published between 1 April 2019 and 31 March 2020, in the areas of H pylori-mediated inflammation, immunity and vaccines.

Review: Other Helicobacter species

This review covers the most important, accessible, and relevant literature published between April 2019 and April 2020 in the field of non-Helicobacter pylori Helicobacter species (NHPH). The initial part of the review covers new insights regarding the presence of gastric and enterohepatic NHPH in humans and animals, while the subsequent section focuses on the progress in our understanding of animal models, the pathogenicity and omics of these species. Over the last year, the clinical relevance of gastric NHPH infections in humans was highlighted. With regard to NHPH in animals, the ancestral source of Helicobacter suis was further established showing that Cynomolgus macaques are the common ancestor of the pig-associated H. suis population, and 3 novel Helicobacter species isolated from the gastric mucosa of red foxes were described. "Helicobacter burdigaliensis" sp nov. and "Helicobacter labetoulli" sp nov. were proposed as novel enterohepatic Helicobacter species associated with human digestive diseases. An analysis of Helicobacter cinaedi recurrent infections in humans proposed long-term antibiotic therapies. Several studies using rodent models further elucidated the mechanisms underlying the development of NHPH-related disease, as well as intestinal immunity in inflammatory bowel disease models. Omics approaches supported Helicobacteraceae taxonomy and unraveled the transcriptomic signatures of H. suis and Helicobacter heilmannii upon adherence to the human gastric epithelium. With regard to virulence, data showed that the nuclear remodeling promoted by cytolethal distending toxin of Helicobacters involves the MAFB oncoprotein and is associated with nucleoplasmic reticulum formation in surviving cells.