Oral administration of poly-γ-glutamic acid prevents the development of atopic dermatitis in NC/Nga mice

IL-7 Deficiency Exacerbates Atopic Dermatitis in NC/Nga Mice

Interleukin-7 (IL-7) plays a vital role in the homeostasis of CD4⁺ and CD8⁺ T cells. Although IL-7 has been implicated in T helper (Th)1- and Th17-mediated autoinflammatory diseases, its role in Th2-type allergic disorders, such as atopic dermatitis (AD), remains unclear. Thus, to elucidate the effects of IL-7 deficiency on AD development, we generated IL-7-deficient AD-prone mice by backcrossing IL-7 knockout (KO) B6 mice onto the NC/Nga (NC) mouse strain, a model for human AD. As expected, IL-7 KO NC mice displayed defective development of conventional CD4⁺ and CD8⁺ T cells compared with wild type (WT) NC mice. However, IL-7 KO NC mice presented with enhanced AD clinical scores, IgE hyperproduction, and increased epidermal thickness compared with WT NC mice. Moreover, IL-7 deficiency decreased Th1, Th17, and IFN-γ-producing CD8⁺ T cells but increased Th2 cells in the spleen of NC mice, indicating that a reduced Th1/Th2 ratio correlates with severity of AD pathogenesis. Furthermore, significantly more basophils and mast cells infiltrated the skin lesions of IL-7 KO NC mice. Taken together, our findings suggest that IL-7 could be a useful therapeutic target for treating Th2-mediated skin inflammations, such as AD.

Phosphorothioate-linked guanine/cytosine-based stem-loop oligonucleotides induce the extracellular release of mitochondrial DNA from peritoneal B1a cells

It has been previously demonstrated that phosphorothioate-linked GpC-based stem-loop oligonucleotides (GC-SL ODN) induce the release of mitochondrial DNA (mtDNA) from chronic lymphocytic leukemia (CLL) B cells. Although CLL B cells are believed to originate from CD5⁺ B cells because of their phenotypic similarities, it remains unclear whether GC-SL ODN can stimulate CD5⁺ B1 cells to secrete mtDNA. To explore this possibility, we compared the frequency of the mtDNA-producing population among peritoneal cells after GC-SL ODN treatment. We found that mtDNA-releasing cells are enriched for peritoneal CD19⁺ B cells upon GC-SL ODN challenge. Among peritoneal CD19⁺ B cells, the CD5⁺ B1a subpopulation was a primary cellular source of mtDNA secretion in GC-SL ODN-elicited immune responses. GC-SL ODN-stimulated mtDNA release by B1a cells was positively regulated by MyD88 and TRIF signaling pathways. In vivo GC-SL ODN treatment increased lipopolysaccharide-induced activation of innate immune cells such as NK cells, suggesting the immune-enhancing effects of mtDNA secretion. Furthermore, the loop size formed by GC-SL ODNs was a critical factor in inducing mtDNA release by B1a cells. Taken together, our results identified GC-SL ODN as promising biomaterials for enhancing immune responses.

A γ-PGA/KGM-based injectable hydrogel as immunoactive and antibacterial wound dressing for skin wound repair

Injectable hydrogels, of which the cover area and volume can be flexibly adjusted according to the shape and depth of the wound, are considered to be an ideal material for wound dressing. Konjac glucomannan (KGM) is a natural polysaccharide with immunomodulatory capability, while γ-polyglutamic acid (γ-PGA) is a single chain polyamino acid with moisturizing, water-retention and antibacterial properties. This work intended to combine the advantages of the two materials to prepare an injectable hydrogel (P-OK) by mixing the adipic acid dihydrazide (ADH) modified γ-PGA with oxidized KGM. The chemical structures, the physical and chemical properties, and the biological properties of the P-OK hydrogel were evaluated. The optimal conditions to form the P-OK hydrogel were fixed, and the cytotoxicity, qPCR, antibacterial and animal experiments were performed. Results showed that the P-OK hydrogel had a fast gelation time, good water-retention rate, little cytotoxicity, good immunomodulating and antibacterial capabilities, and could shorten the healing period in the rat full-thickness defect model, which makes it a potential candidate for wound repair dressing.

Ubiquitous Overexpression of Chromatin Remodeling Factor SRG3 Exacerbates Atopic Dermatitis in NC/Nga Mice by Enhancing Th2 Immune Responses

The SWItch (SWI)3-related gene (SRG3) product, a SWI/Sucrose Non-Fermenting (SNF) chromatin remodeling subunit, plays a critical role in regulating immune responses. We have previously shown that ubiquitous SRG3 overexpression attenuates the progression of Th1/Th17-mediated experimental autoimmune encephalomyelitis. However, it is unclear whether SRG3 overexpression can affect the pathogenesis of inflammatory skin diseases such as atopic dermatitis (AD), a Th2-type immune disorder. Thus, to elucidate the effects of SRG3 overexpression in AD development, we bred NC/Nga (NC) mice with transgenic mice where SRG3 expression is driven by the β-actin promoter (SRG3^β-actin mice). We found that SRG3^β-actin NC mice exhibit increased AD development (e.g., a higher clinical score, immunoglobulin E (IgE) hyperproduction, and an increased number of infiltrated mast cells and basophils in skin lesions) compared with wild-type NC mice. Moreover, the severity of AD pathogenesis in SRG3^β-actin NC mice correlated with expansion of interleukin 4 (IL4)-producing basophils and mast cells, and M2 macrophages. Furthermore, this accelerated AD development is strongly associated with Treg cell suppression. Collectively, our results have identified that modulation of SRG3 function can be applied as one of the options to control AD pathogenesis.

Selective Expansion of Double-Negative iNKT Cells Inhibits the Development of Atopic Dermatitis in Vα14 TCR Transgenic NC/Nga Mice by Increasing Memory-Type CD8+ T and Regulatory CD4+ T Cells

Spontaneous development of atopic dermatitis (AD) in NC/Nga (NC) mice has been attributed to a deficiency in invariant NK T (iNKT) cells. To elucidate the precise role of iNKT cells in AD development of NC mice, we employed two distinct murine models of iNKT cell over-representation: Vβ8 TCR congenic and Vα14 TCR transgenic NC mice. We found that Vα14 TCR transgenic (Vα14^Tg) but not Vβ8 TCR congenic (Vβ8^Cg) NC mice exhibited reduced AD development, which was attributed to both quantitative and qualitative changes in iNKT cells such as a biased expansion of the double-negative iNKT subset. Adoptive transfer experiments confirmed that iNKT cells from Vα14^Tg mice but not from Vβ8^Cg mice were responsible for protecting NC mice from AD development. Double-negative iNKT cells from Vα14^Tg NC mice showed a T helper type-1‒dominant cytokine profile, which may account for the expansion of CD4⁺ regulatory T cells and memory-type CD8⁺ T cells. Furthermore, the adoptive transfer of CD8⁺ T cells from Vα14^Tg NC mice into AD-susceptible wild-type NC mice suppressed AD in recipient NC mice. Taken together, our results have identified double-negative iNKT cells as promising cellular targets to prevent AD pathogenesis.

The microbiome and its impact on food allergy and atopic dermatitis in children

Food allergy (FA) affects 4-10% of children, especially children with atopic dermatitis (AD). During infancy the gut microbiome may determine both the course of FA and tolerance to food allergens. Analogically, the skin microbiome changes in the course of AD. Most studies have associated FA with a lower abundance and diversity of Lactobacillales and Clostridiales, but greater numbers of Enterobacterales, while AD in children has been associated with lower numbers of Staphylococcus epidermidis and S. hominis but an abundance of S. aureus and Streptococcus species. An understanding of the impact of the microbiome on the clinical course of FA and AD may allow for the development of new models of allergy treatment and prevention.

Regulation of Allergic Immune Responses by Microbial Metabolites

Emerging evidence demonstrates that the microbiota plays an essential role in shaping the development and function of host immune responses. A variety of environmental stimuli, including foods and commensals, are recognized by the host through the epithelium, acting as a physical barrier. Two allergic diseases, atopic dermatitis and food allergy, are closely linked to the microbiota, because inflammatory responses occur on the epidermal border. The microbiota generates metabolites such as short-chain fatty acids and poly-γ-glutamic acid (γPGA), which can modulate host immune responses. Here, we review how microbial metabolites can regulate allergic immune responses. Furthermore, we focus on the effect of γPGA on allergic T helper (Th) 2 responses and its therapeutic application.

iNKT Cells Are Responsible for the Apoptotic Reduction of Basophils That Mediate Th2 Immune Responses Elicited by Papain in Mice Following γPGA Stimulation

Recent studies have demonstrated that Bacillus subtilis-derived poly-gamma glutamic acid (γPGA) treatment suppresses the development of allergic diseases such as atopic dermatitis (AD). Although basophils, an innate immune cell, are known to play critical roles in allergic immune responses and repeated long-term administration of γPGA results in decreased splenic basophils in an AD murine model, the underlying mechanisms by which γPGA regulates basophil frequency remain unclear. To investigate how γPGA modulates basophils, we employed basophil-mediated Th2 induction in vivo model elicited by the allergen papain protease. Repeated injection of γPGA reduced the abundance of basophils and their production of IL4 in mice, consistent with our previous study using NC/Nga AD model mice. The depletion of basophils by a single injection of γPGA was dependent on the TLR4/DC/IL12 axis. CD1d-dependent Vα14 TCR invariant natural killer T (iNKT) cells are known to regulate a variety of immune responses, such as allergy. Because iNKT cell activation is highly sensitive to IL12 produced by DCs, we evaluated whether the effect of γPGA on basophils is mediated by iNKT cell activation. We found that in vivo γPGA treatment did not induce the reduction of basophils in iNKT cell-deficient CD1d KO mice, suggesting the critical role of iNKT cells in γPGA-mediated basophil depletion at the early time points. Furthermore, increased apoptotic basophil reduction triggered by iNKT cells upon γPGA stimulation was mainly attributed to Th1 cytokines such as IFNγ and TNFα, consequently resulting in inhibition of papain-induced Th2 differentiation via diminishing basophil-derived IL4. Taken together, our results clearly demonstrate that γPGA-induced iNKT cell polarization toward the Th1 phenotype induces apoptotic basophil depletion, leading to the suppression of Th2 immune responses. Thus, elucidation of the crosstalk between innate immune cells will contribute to the design and development of new therapeutics for Th2-mediated immune diseases such as AD.

Favourable effects of Bacillus subtilis and Bacillus licheniformis on experimental periodontitis in rats

OBJECTIVES

The purposes of this study were to evaluate, in rats: i) the effects of Bacillus species on the development of experimental periodontitis (EP) via microtomographic, immunological and hematological assays (Experiment 1-E1); ii) the effects of Bacillus species as adjuncts to scaling and root planing (SRP) for the treatment of EP via histomorphometric and immunohistochemical analyses (Experiment 2-E2).

METHODS

In E1, 24 rats were divided into groups C1 (control), PROB1, EP1 and EP-PROB1. In groups with EP, the mandibular first molar of each animal received a ligature for 14 days. In groups PROB1, animals received Bacillus species for 44 days, starting 30 days before EP induction in Group EP-PROB1. In E2, 24 rats were assigned to groups C2 (control), PROB2, EP-SRP2 and EP-SRP-PROB2. In groups with SRP, EP was induced as described in E1. The ligatures were removed after 14 days and SRP was performed. In groups PROB2, animals received Bacillus species for 15 days, starting after SRP in Group EP-SRP-PROB2.

RESULTS

In E1, Group EP1 presented bone loss (BL) and eosinophil numbers greater than Group EP-PROB1 (P<0.05). In Group EP-PROB1, the receptor activator of nuclear factor-kB ligand (RANKL)/osteoprotegerin (OPG) ratio was similar to that of groups without EP. In E2, Group EP-SRP-PROB2 presented fewer TRAP-positive osteoclasts, lower immunolabeling pattern for a proinflammatory cytokine and decreased BL and attachment loss than Group EP-SRP2 (P<0.05).

CONCLUSIONS

Bacillus species supplementation provided a protective effect against BL and enhanced the effects of SRP in the treatment of EP in rats.

Ubiquitous Over-Expression of Chromatin Remodeling Factor SRG3 Ameliorates the T Cell-Mediated Exacerbation of EAE by Modulating the Phenotypes of both Dendritic Cells and Macrophages

Although SWI3-related gene (SRG3), a chromatin remodeling factor, is critical for various biological processes including early embryogenesis and thymocyte development, it is unclear whether SRG3 is involved in the differentiation of CD4⁺ T cells, the key mediator of adaptive immune responses. Because it is known that experimental autoimmune encephalomyelitis (EAE) development is determined by the activation of CD4⁺ T helper cells, here, we investigated the role of SRG3 in EAE development using SRG3 transgenic mouse models exhibiting two distinct SRG3 expression patterns: SRG3 expression driven by either the CD2 or β-actin promoter. We found that the outcome of EAE development was completely different depending on the expression pattern of SRG3. The specific over-expression of SRG3 using the CD2 promoter facilitated EAE via the induction of Th1 and Th17 cells, whereas the ubiquitous over-expression of SRG3 using the β-actin promoter inhibited EAE by promoting Th2 differentiation and suppressing Th1 and Th17 differentiation. In addition, the ubiquitous over-expression of SRG3 polarized CD4⁺ T cell differentiation towards the Th2 phenotype by converting dendritic cells (DCs) or macrophages to Th2 types. SRG3 over-expression not only reduced pro-inflammatory cytokine production by DCs but also shifted macrophages from the inducible nitric oxide synthase (iNOS)-expressing M1 phenotype to the arginase-1-expressing M2 phenotype during EAE. In addition, Th2 differentiation in β-actin-SRG3 Tg mice during EAE was associated with an increase in the basophil and mast cell populations and in IL4 production. Furthermore, the increased frequency of Treg cells in the spinal cord of β-actin-SRG3 Tg mice might induce the suppression of and accelerate the recovery from EAE symptoms. Taken together, our results provide the first evidence supporting the development of a new therapeutic strategy for EAE involving the modulation of SRG3 expression to induce M2 and Th2 polarization, thereby inhibiting inflammatory immune responses.

Immunomodulatory effect of poly-γ-glutamic acid derived from Bacillus subtilis on natural killer dendritic cells

Bacillus subtilis-derived poly-γ-glutamic acid (γPGA) stimulates dendritic cells (DCs) to produce IL12, leading to CD4(+) T cell differentiation toward the Th1 phenotype, but DCs consist of heterogeneous subpopulations with a variety of immune functions. Among these, natural killer dendritic cells (NKDCs) play an important role in anti-tumor immune responses. Herein, we demonstrate the role of NKDCs in γPGA-meditated anti-tumor immune responses. NK1.1(+) CD11c(+) NKDCs were stimulated upon γPGA stimulation in vitro and in vivo to up-regulate lymphocyte activation markers, MHC class I and II, and co-stimulatory molecules. In particular, NKDCs were activated by γPGA to produce IFNγ and TNFα, like NK cells, as well as IL12, like DCs, implying that NKDCs have unique and multifunctional roles. Importantly, NKDCs stimulated by γPGA conferred stronger anti-tumor effects in mice and showed increased cytotoxicity against various tumor cell lines in vitro. In conclusion, NKDCs are one of the key players in anti-tumor immunity induced by γPGA.