IL-12/23p40 overproduction by dendritic cells leads to an increased Th1 and Th17 polarization in a model of Yersinia enterocolitica-induced reactive arthritis in TNFRp55-/- mice

Mast cell-derived interleukin-4 mediates activation of dendritic cell during toll-like receptor 2-mediated inflammation

Introduction

During an innate inflammation, immune cells form distinct pro- and anti-inflammatory regions around pathogen-containing core-regions. Mast cells are localized in an anti-inflammatory microenvironment during the resolution of an innate inflammation, suggesting antiinflammatory roles of these cells.

Methods

High-content imaging was used to investigated mast cell-dependent changes in the regional distribution of immune cells during an inflammation, induced by the toll-like receptor (TLR)-2 agonist zymosan.

Results

The distance between the zymosan-containing core-region and the anti-inflammatory region, described by M2-like macrophages, increased in mast cell-deficient mice. Absence of mast cells abolished dendritic cell (DC) activation, as determined by CD86-expression and localized the DCs in greater distance to zymosan particles. The CD86- DCs had a higher expression of the pro-inflammatory interleukins (IL)-1β and IL-12/23p40 as compared to activated CD86+ DCs. IL-4 administration restored CD86 expression, cytokine expression profile and localization of the DCs in mast cell-deficient mice. The IL-4 effects were mast cell-specific, since IL-4 reduction by eosinophil depletion did not affect activation of DCs.

Discussion

We found that mast cells induce DC activation selectively at the site of inflammation and thereby determine their localization within the inflammation. Overall, mast cells have antiinflammatory functions in this inflammation model and limit the size of the pro-inflammatory region surrounding the zymosan-containing core region.

The Multiple Faces of Nitric Oxide in Chronic Granulomatous Disease: A Comprehensive Update

Nitric oxide (NO), a signaling molecule, regulates multiple biological functions, including a variety of physiological and pathological processes. In this regard, NO participates in cutaneous inflammations, modulation of mitochondrial functions, vascular diseases, COVID-19, neurologic diseases, and obesity. It also mediates changes in the skeletal muscle function. Chronic granulomatous disease (CGD) is a primary immunodeficiency disorder characterized by the malfunction of phagocytes caused by mutations in some of the genes encoding subunits of the superoxide-generating phagocyte NADPH (NOX). The literature consulted shows that there is a relationship between the production of NO and the NADPH oxidase system, which regulates the persistence of NO in the medium. Nevertheless, the underlying mechanisms of the effects of NO on CGD remain unknown. In this paper, we briefly review the regulatory role of NO in CGD and its potential underlying mechanisms.

Insights into the biology and therapeutic implications of TNF and regulatory T cells

Treatments that block tumour necrosis factor (TNF) have major beneficial effects in several autoimmune and rheumatic diseases, including rheumatoid arthritis. However, some patients do not respond to TNF inhibitor treatment and rare occurrences of paradoxical disease exacerbation have been reported. These limitations on the clinical efficacy of TNF inhibitors can be explained by the differences between TNF receptor 1 (TNFR1) and TNFR2 signalling and by the diverse effects of TNF on multiple immune cells, including FOXP3⁺ regulatory T cells. This basic knowledge sheds light on the consequences of TNF inhibitor therapies on regulatory T cells in treated patients and on the limitations of such treatment in the control of diseases with an autoimmune component. Accordingly, the next generation of drugs targeting TNF is likely to be based on agents that selectively block the binding of TNF to TNFR1 and on TNFR2 agonists. These approaches could improve the treatment of rheumatic diseases in the future.

The Yersinia Phage X1 Administered Orally Efficiently Protects a Murine Chronic Enteritis Model Against Yersinia enterocolitica Infection

Yersinia enterocolitica is generally considered an important food-borne pathogen worldwide, especially in the European Union. A lytic Yersinia phage X1 (Viruses; dsDNA viruses, no RNA stage; Caudovirales; and Myoviridae) was isolated. Phage X1 showed a broad host range and could effectively lyse 27/51 Y. enterocolitica strains covering various serotypes that cause yersiniosis in humans and animals (such as serotype O3 and serotype O8). The genome of this phage was sequenced and analyzed. No toxin, antibiotic-resistance or lysogeny related modules were found in the genome of phage X1. Studies of phage stability confirmed that X1 had a high tolerance toward a broad range of temperatures (4–60°C) and pH values (4–11) for 1 h. The ability to resist harsh acidic conditions and enzymatic degradation in vitro demonstrated that phage X1 is suitable for oral administration, and in particular, that this phage can pass the stomach barrier and efficiently reach the intestine in vivo without losing infectious ability. The potential of this phage against Y. enterocolitica infection in vitro was studied. In animal experiments, a single oral administration of phage X1 at 6 h post infection was sufficient to eliminate Y. enterocolitica in 33.3% of mice (15/45). In addition, the number of Y. enterocolitica strains in the mice was also dramatically reduced to approximately 10³ CFU/g after 18 h compared with 10⁷ CFU/g in the mice without phage treatment. Treatment with phage X1 showed significant improvement by intestinal histopathologic observations. Moreover, proinflammatory cytokine levels (IL-6, TNF-α, and IL-1β) were significantly reduced (P < 0.05). These results indicate that phage X1 is a promising candidate to control infection by Y. enterocolitica in vivo.

Dendritic Cells of Mesenteric and Regional Lymph Nodes Contribute to Yersinia enterocolitica O:3-Induced Reactive Arthritis in TNFRp55-/- Mice

Dendritic cells (DCs) participate in the pathogenesis of several diseases. We investigated DCs and the connection between mucosa and joints in a murine model of Yersinia enterocolitica O:3-induced reactive arthritis (ReA) in TNFRp55^-/- mice. DCs of mesenteric lymph nodes (MLN) and joint regional lymph nodes (RLN) were analyzed in TNFRp55^-/- and wild-type mice. On day 14 after Y. enterocolitica infection (arthritis onset), we found that under TNFRp55 deficiency, migratory (MHC^highCD11c⁺) DCs increased significantly in RLN. Within these RLN, resident (MHC^intCD11c⁺) DCs increased on days 14 and 21. Similar changes in both migratory and resident DCs were also detected on day 14 in MLN of TNFRp55^-/- mice. In vitro, LPS-stimulated migratory TNFRp55^-/- DCs of MLN increased IL-12/23p40 compared with wild-type mice. In addition, TNFRp55^-/- bone marrow-derived DCs in a TNFRp55^-/- MLN microenvironment exhibited higher expression of CCR7 after Y. enterocolitica infection. The major intestinal DC subsets (CD103⁺CD11b^-, CD103^-CD11b⁺, and CD103⁺CD11b⁺) were found in the RLN of Y. enterocolitica-infected TNFRp55^-/- mice. Fingolimod (FTY720) treatment of Y. enterocolitica-infected mice reduced the CD11b^- subset of migratory DCs in RLN of TNFRp55^-/- mice and significantly suppressed the severity of ReA in these mice. This result was associated with decreased articular IL-12/23p40 and IFN-γ levels. In vitro FTY720 treatment downregulated CCR7 on Y. enterocolitica-infected bone marrow-derived DCs and purified MLN DCs, which may explain the mechanism underlying the impairment of DCs in RLN induced by FTY720. Taken together, data indicate the migration of intestinal DCs to RLN and the contribution of these cells in the immunopathogenesis of ReA, which may provide evidence for controlling this disease.

Yersinia enterocolitica-specific modulation of innate immune responses in jejunal epithelial cells

Gut is often subject to infection by different pathogens like Y. enterocolitica. To date, biotypes (BTs) 1A have been considered as non-pathogenic, because they do not express plasmid of virulence pYV; however, BTs 1A strains present other chromosomic virulence genes and recent studies suggest an implication of this microorganism in reactive arthritis. Although many studies highlighted the molecular basis of pathogenesis of Ye infection, scanty data are available about several environmental BTs 1A strains, often isolated in cases of foodborne disease but not included in pathogenicity studies. The aim of our work was to verify the ability of different Ye 1A strains to adhere and penetrate IPEC-J2 cells and to modulate intestinal innate immunity. Our results showed that all strains under study were able to adhere and penetrate enterocytes, causing inflammatory responses. Indeed, adhesion and invasion of enterocytes is an essential step in Ye pathogenesis (Fàbrega and Vila, 2012). Moreover, our data suggest the possible involvement of strains Ye2/O:9 in reactive arthritis, due to their ability (i) to penetrate enterocytes as pathogenic Ye1/O:8 strains do, and (ii) to increase IL-6, IL-8, IL-12 and IL-18 release. Lastly, our results confirm that IPEC-J2 cells are a very good model to evaluate host-pathogen interaction, and indicate IL-8, TNF-α, TLRs1 and 4 as possible markers of the ability of Ye strains to penetrate enterocytes. Moreover, we showed that Ye strains differently affect the host's innate immune responses.

TLR4-dependent effects of ISAg treatment on conventional T cell polarization in vivo

We recently demonstrated that the polysaccharide component of the Korean medicinal herb Angelica gigas (immuno-stimulatory fraction of A. gigas; ISAg) induces anticancer effects in mice by activating natural killer (NK) and natural killer T (NKT) cells. However, it is unclear whether the use of ISAg in vivo can affect the differentiation of conventional T cells. Here, we investigated the effects of ISAg on the activation of conventional CD4⁺ and CD8⁺ T cells. We found that the administration of ISAg induced the polarization of CD4⁺ T cells toward the acquisition of the Th1 phenotype in vivo. Additionally, in mice treated with ISAg, CD8⁺ T cells produced more IFNγ than in control mice treated with PBS. Moreover, treatment with ISAg activated CD4⁺ and CD8⁺ T cells as well as NK and NKT cells, resulting in the secretion of Th1-type cytokines in a toll-like receptor 4 (TLR4)-dependent manner, implying that TLR4 is critical for an optimal Th1 response. Interestingly, ISAg treatment increased the number of Foxp3⁺ Treg cells, but not of Th2 cells, compared to control mice treated with PBS, indicating that ISAg possesses an immunomodulatory capacity that can control adaptive immune responses. Taken together, our results indicate that ISAg possesses a Th1-enhancing activity that could be used to treat Th2-mediated allergic immune diseases such as atopic dermatitis.

Direct activation of aryl hydrocarbon receptor by benzo[a]pyrene elicits T-helper 2-driven proinflammatory responses in a mouse model of allergic dermatitis

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that binds to various environmental chemicals and contributes to numerous toxicological effects. However, the direct effects of AhR on the development of allergic diseases are not fully understood. The main aim of this study was to elucidate the action of AhR in the development of cutaneous allergies. Initially, the potential for a direct relationship between AhR and the immune cells was investigated in vitro, using murine bone marrow-derived dendritic cells, human epidermal keratinocytes, and the mixed leukocyte reaction assay. Benzo[a]pyrene (BaP) and 6-formylindolo[3,2-b]carbazole were used as selective ligands for the AhR. Pretreatment with BaP and/or 6-formylindolo[3,2-b]carbazole significantly induced cytokine release by activated keratinocytes and T-cell proliferation, whereas interleukin-12 production in bone marrow-derived dendritic cells was reduced by AhR activation. To confirm the in vitro results, in vivo experiments were also performed in T-helper (Th)2-type hapten toluene-2,4-diisocyanate- and Th1-type hapten dinitrochlorobenzene-induced mouse models of allergic dermatitis. Mice were orally administered BaP at 48, 24 and 4 hours before the final allergen challenge. In the Th2 model, ear-swelling response and scratching behavior were promoted by BaP exposure, which supported the observed significant increases in local cytokine secretion. The infiltration of helper T cells, B cells and dendritic cells into the auricular lymph node was significantly enhanced by BaP administration, although Th1-type immune responses were not influenced by AhR activation. Our findings demonstrate that AhR activation directly activates keratinocytes and T cells, which leads to the exacerbation of Th2-type cutaneous allergy.