Analysis of the activation profile of dendritic cells derived from the bone marrow of interleukin-12/interleukin-23-deficient 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.

Mechanisms and Effects of Isorhamnetin on Imiquimod-Induced Psoriasiform Dermatitis in Mice

Isorhamnetin (IRh), which has a wide range of pharmacological effects, is one of the most significant active components in the fruits of Hippophae rhamnoides L. and the leaves of Ginkgo biloba L. It protects the heart and brain, in addition to possessing anti-tumor, anti-inflammatory, antioxidant, organ protection, and anti-obesity properties. We sought to assess IRh's anti-psoriatic activity, explore its immunomodulatory properties in reducing the severity of psoriatic symptoms, and evaluate its potential immunotherapeutic effects. We used IRh to treat imiquimod (IMQ)-induced psoriasis in BALB/C mice and examined the underlying mechanisms. The outcomes demonstrated that IRh reduced epidermal hyperplasia, lowered PASI scores, and improved histopathological psoriasiform lesions in IMQ-induced mice. IRh attenuated the accumulation of malondialdehyde (MDA), and also reversed the reduction caused by IMQ of superoxide dismutase (SOD) and catalase (CAT) in skin tissues. Additionally, IRh effectively inhibited IMQ's ability to increase proinflammatory cytokines such as TNF-α, IL-6, IL-17A, and transcription factor NF-κB. Furthermore, IRh significantly reduced the percentage of Th1 and Th17 in the spleens of mice treated with IMQ and suppressed the maturation of splenic dendritic cells. Overall, our research suggests that IRh protects against oxidative stress and inflammation in the pathogenesis of psoriasis, with potential for the development of new and potent medication for the treatment of psoriasis.

IL-23 in axial spondyloarthritis and psoriatic arthritis: a good fit for biological treatment?

INTRODUCTION

Interleukin 23 (IL-23) is a pro-inflammatory cytokine that plays a protective role against bacterial and fungal infections. However, the dysregulation of the IL-23/IL-17 axis provides a solid substrate for the development of various inflammatory diseases, such as psoriatic arthritis (PsA) and ankylosing spondylitis (AS).

AREAS COVERED

In different clinical trials, several drugs against IL-23 have shown efficacy and safety towards PsA, with excellent results on skin and joint scores. However, the same drugs did not show the same efficacy in AS, suggesting that IL-23 may not be a relevant driver of the pathobiology and clinical symptoms of active axial spondyloarthritis (axSpA).

EXPERT OPINION

These drugs have shown an excellent efficacy and a good safety profile towards PsA, while in AS the efficacy of the IL-23 blockade is lacking for reasons not yet known. Several hypotheses have been reported, but further studies will be needed for a greater understanding. This suggests the involvement of pathways or mechanisms for the development of SpA that remain unknown. In order to allow a wide use of IL-23 inhibitors, further clinical trials and long-term prospective studies are necessary.

Role of the IL-23/IL-17 Pathway in Rheumatic Diseases: An Overview

Interleukin-23 (IL-23) is a pro-inflammatory cytokine composed of two subunits, IL-23A (p19) and IL-12/23B (p40), the latter shared with Interleukin-12 (IL-12). IL-23 is mainly produced by macrophages and dendritic cells, in response to exogenous or endogenous signals, and drives the differentiation and activation of T helper 17 (Th17) cells with subsequent production of IL-17A, IL-17F, IL-6, IL-22, and tumor necrosis factor α (TNF-α). Although IL-23 plays a pivotal role in the protective immune response to bacterial and fungal infections, its dysregulation has been shown to exacerbate chronic immune-mediated inflammation. Well-established experimental data support the concept that IL-23/IL-17 axis activation contributes to the development of several inflammatory diseases, such as PsA, Psoriasis, Psoriatic Arthritis; AS, Ankylosing Spondylitis; IBD, Inflammatory Bowel Disease; RA, Rheumatoid Arthritis; SS, Sjogren Syndrome; MS, Multiple Sclerosis. As a result, emerging clinical studies have focused on the blockade of this pathogenic axis as a promising therapeutic target in several autoimmune disorders; nevertheless, a greater understanding of its contribution still requires further investigation. This review aims to elucidate the most recent studies and literature data on the pathogenetic role of IL-23 and Th17 cells in inflammatory rheumatic diseases.

Interleukin-12p35 knockout promotes macrophage differentiation, aggravates vascular dysfunction, and elevates blood pressure in angiotensin II-infused mice

AIMS

Numerous studies have demonstrated that inflammation is involved in the progression of hypertension. Inflammatory cytokines interleukin (IL)-12 and IL-35 belong to the IL-12 cytokine family and share the same IL-12p35 subunit. Accumulating evidence has demonstrated that IL-12p35 knockout (IL-12p35 KO) leads to cardiovascular disease by regulating the inflammatory response. This study aimed to investigate whether IL-12p35 KO elevates blood pressure in a hypertension mouse model.

METHODS AND RESULTS

Mice with angiotensin (Ang) II infusion showed marked aortic IL-12p35 expression; thus, aortic macrophages may be the main source of IL-12p35. Wild-type and IL-12p35 KO mice were infused with Ang II or saline. IL-12p35 KO promoted M1 macrophage differentiation, amplified the inflammatory response, aggravated vascular dysfunction, and elevated blood pressure in Ang II-treated mice. Then, some Ang II-infused mice were given phosphate buffer saline, mouse recombinant IL-12 (rIL-12), or rIL-35, and the results showed that rIL-12 but not rIL-35 treatment had an antihypertensive effect on Ang II-infused mice. In addition, detection of human plasma IL-12 levels in hypertensive patients and control subjects showed that IL-12 was significantly increased in hypertensive patients when compared with control subjects. In hypertensive patients, IL-12 levels were positively correlated with blood pressure.

CONCLUSION

IL-12p35 KO amplifies the inflammatory response and promotes blood pressure elevation in Ang II-treated mice. In addition, IL-12, but not IL-35, plays a protective role in the Ang II-induced hypertension model. Thus, IL-12 may be a novel therapeutic agent for the prevention and treatment of clinical hypertension.

Reversing Ongoing Chronic Intestinal Inflammation and Fibrosis by Sustained Block of IL-12 and IL-23 Using a Vaccine in Mice

Interleukin (IL)-12 and IL-23 that share subunit p40 are important cytokines in the pathogenesis of inflammatory bowel disease. We reported that mouse p40 peptide-based vaccines ameliorated intestinal inflammation in the prevention of trinitrobenzene sulfonic acid (TNBS)–induced murine colitis model. Here, we evaluated whether administration of the vaccine after establishment of colitis would be effective in modifying both TNBS-induced and dextran sulfate sodium (DSS)–induced chronic colitis and the underlying immune mechanisms. We further examined whether vaccination could exacerbate infections. Chronic colitis was developed by either intrarectally administrating TNBS or drinking 4% DSS water. Vaccination started after two TNBS administrations or 7 days of DSS treatment. Results showed that administrating p40 vaccine induced high tittered antibodies to IL-12 and IL-23, improved clinical scores, reduced intestinal inflammation and fibrosis, and down-regulated proinflammatory cytokine productions in colon tissue, compared with control mice. Furthermore, in lamina propria mononuclear cells and/or mesenteric lymph nodes, mice immunized with p40 peptide vaccine exhibited high ratios of Treg/Th1 and Treg/Th17 cells and increased IL-10 expression in CD11c⁺IL-10⁺cells. In mice infected with lung chlamydia, in which the protective role of Th1/Th17 is well documented, vaccine immunization did not increase lung bacterial burden. We conclude that p40 vaccine may provide a potential and safe approach for treatment of IBD.

Principal role of IL-12p40 in the decreased Th1 and Th17 responses driven by dendritic cells of mice lacking IL-12 and IL-18

IL-12 and IL-18 are cytokines which are mainly secreted by endothelial cells and monocytes including dendritic cells. The well-known effects of IL-12 and IL-18 in the protection against bacteria and virus infection as well as tumor development are associated with their characteristics in synergistically driving the development of T helper type 1 (Th1) cells and inducing IFN-γ production. In this study, we compared the knockout effects of IL-12 and/or IL-18 genes on phenotypes and functional capabilities of dendritic cells (DCs) including their ability to polarize naive CD4(+) T cells. The expression levels of surface molecules such as MHC II, CD80, CD86 and ICOSL, and endocytic capacity were not significantly differences between DCs of wild type (WT) mice and double knockout (DKO) mice of IL-12p40 and IL-18. Additionally, DCs lacking IL-12p40 and/or IL-18 genes were equivalently efficient in inducing T cell proliferation, compared with the WT-DCs. Interestingly, IL-10 production significantly decreased in DKO-DCs, while production of other inflammation-related cytokines were unaffected in WT-DCs and DKO-DCs. Importantly, IL-12p40(-/-)-DCs and DKO-DCs severely impaired the ability to induce IFN-γ and IL-17 production from CD4(+) T cells. IL-18(-/-)-DCs also moderately decreased IL-17 production and IL-17-expressing CD4(+) T cells when co-cultured with CD4(+) T cells, demonstrating the involvement of IL-18 in driving IL-17 differentiation. Taken together, these results suggest the principal contribution of IL-12p40 in inducing Th1 and Th17 polarization, regardless of similar surface phenotypes of DCs.

Interleukin-12p35 Deletion Promotes CD4 T-Cell–Dependent Macrophage Differentiation and Enhances Angiotensin II–Induced Cardiac Fibrosis

Objective—

Interleukin-12 is essential for the differentiation of naïve T cells into interferon-γ–producing T cells, which regulate inflammatory responses. We investigated this process of regulating hypertension-induced cardiac fibrosis.

Methods and Results—

Mice infused with angiotensin II showed a marked increase in interleukin-12p35 expression in cardiac macrophages. The degree of cardiac fibrosis was significantly enhanced in interleukin-12p35 knockout (p35-KO) mice compared with wild-type (WT) littermates in response to angiotensin II. Fibrotic hearts of p35-KO mice showed increased accumulation of alternatively activated (M2) macrophages and expression of M2 genes such as Arg-1 and Fizz1. Bone marrow–derived macrophages from WT or p35-KO mice did not differ in differentiation in response to angiotensin II treatment; however, in the presence of CD4 + T cells, macrophages from p35-KO mice differentiated into M2 macrophages and showed elevated expression of transforming growth factor-β. Moreover, CD4 + T-cell–treated p35-KO macrophages could stimulate cardiac fibroblasts to differentiate into α-smooth muscle actin–positive and collagen I–positive myofibroblasts in 3-dimensional nanofiber gels. Neutralizing antibodies against transforming growth factor-β inhibited myofibroblast formation induced by M2 macrophages.

Conclusion—

Deficiency in interleukin-12p35 regulates angiotensin II–induced cardiac fibrosis by promoting CD4 + T-cell–dependent differentiation of M2 macrophages and production of transforming growth factor-β.

Interleukin-23: as a drug target for autoimmune inflammatory diseases

Interleukin-23 (IL-23) is a member of the IL-12 family of cytokines with pro-inflammatory properties. Its ability to potently enhance the expansion of T helper type 17 (Th17) cells indicates the responsibility for many of the inflammatory autoimmune responses. Emerging data demonstrate that IL-23 is a key participant in central regulation of the cellular mechanisms involved in inflammation. Both IL-23 and IL-17 form a new axis through Th17 cells, which has evolved in response to human diseases associated with immunoactivation and immunopathogeny, including bacterial or viral infections and chronic inflammation. Targeting of IL-23 or the IL-23 receptor or IL-23 axis is a potential therapeutic approach for autoimmune diseases including psoriasis, inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. The current review focuses on the immunobiology of IL-23 and summarizes the most recent findings on the role of IL-23 in the pre-clinical and ongoing clinical studies.

Mechanisms of NK cell-macrophage Bacillus anthracis crosstalk: a balance between stimulation by spores and differential disruption by toxins

NK cells are important immune effectors for preventing microbial invasion and dissemination, through natural cytotoxicity and cytokine secretion. Bacillus anthracis spores can efficiently drive IFN-γ production by NK cells. The present study provides insights into the mechanisms of cytokine and cellular signaling that underlie the process of NK-cell activation by B. anthracis and the bacterial strategies to subvert and evade this response. Infection with non-toxigenic encapsulated B. anthracis induced recruitment of NK cells and macrophages into the mouse draining lymph node. Production of edema (ET) or lethal (LT) toxin during infection impaired this cellular recruitment. NK cell depletion led to accelerated systemic bacterial dissemination. IFN-γ production by NK cells in response to B. anthracis spores was: i) contact-dependent through RAE-1-NKG2D interaction with macrophages; ii) IL-12, IL-18, and IL-15-dependent, where IL-12 played a key role and regulated both NK cell and macrophage activation; and iii) required IL-18 for only an initial short time window. B. anthracis toxins subverted both NK cell essential functions. ET and LT disrupted IFN-γ production through different mechanisms. LT acted both on macrophages and NK cells, whereas ET mainly affected macrophages and did not alter NK cell capacity of IFN-γ secretion. In contrast, ET and LT inhibited the natural cytotoxicity function of NK cells, both in vitro and in vivo. The subverting action of ET thus led to dissociation in NK cell function and blocked natural cytotoxicity without affecting IFN-γ secretion. The high efficiency of this process stresses the impact that this toxin may exert in anthrax pathogenesis, and highlights a potential usefulness for controlling excessive cytotoxic responses in immunopathological diseases. Our findings therefore exemplify the delicate balance between bacterial stimulation and evasion strategies. This highlights the potential implication of the crosstalk between host innate defences and B. anthracis in initial anthrax control mechanisms.

NK cells are important immune effectors that perform a surveillance task and react to transformed, stressed, and virally infected cells. They represent a first-line defence against cancer and pathogen invasion. Different pathogens trigger distinct NK-cell activation pathways. The Bacillus anthracis spore is the highly resistant form that enters the host and provokes anthrax. This microbe kills through a combination of acute bacterial infection and devastating toxemia. In the present study, we characterise the crosstalk between NK cells and spores, as well as the strategies used by B. anthracis to evade initial control mechanisms and impact anthrax pathogenesis. Our findings exemplify the spores' property to efficiently drive a high production of IFN-γ by NK cells, as well as the complex pathways used for activation which require both cytokine and cellular signaling. B. anthracis subverts this response through its toxins by paralysing essential NK cell functions. Furthermore, edema toxin from B. anthracis blocks natural cytotoxicity without affecting IFN-γ secretion. The CyaA toxin of Bordetella pertussis possesses the same enzymatic activity and has a similar effect. The high efficiency of these toxins in blocking cytotoxicity in vivo implies possible exploitation of their subverting activity to modulate excessive cytotoxic responses in immunopathological diseases.

Dendritic cells transduced with lentiviral-mediated RelB-specific ShRNAs inhibit the development of experimental autoimmune myasthenia gravis

Dendritic cells (DC) are professional APC that are able to modulate immune response in either a positive or negative manner depending upon their lineage and state of maturation. RelB is a NF-kappaB family member which plays a key role in the differentiation and maturation of DC. In this study, we constructed lentiviral vector expressing RelB-specific short hairpin RNAs (ShRNAs) that efficiently silenced the RelB gene in bone marrow-derived dendritic cells (BMDCs). These RelB-silenced BMDCs were maturation resistant and could functionally decrease antigen-specific T cells proliferation. We tested the therapeutic effect of RelB-silenced BMDCs in C57BL/6 mice with experimental autoimmune myasthenia gravis (EAMG). Injection i.v. with RelB-silenced BMDCs plused with Torpedo acetylcholine receptor (TAChR) dominant peptide Talpha(146-162) on days 3, 33, and 63 after first immunization decreased the incidence and severity of clinical EAMG with suppressed IFN-gamma production and increased IL-10 and IL-4 production in vitro and in vivo, and also leads to a decreased serum anti-AChR IgG, IgG1, IgG2b Ab levels. Furthermore, RelB-silenced BMDCs promoted regulatory T cell profiles as indicated by a marked increase of FoxP3 in splenocyte. Our data suggested that lentiviral-mediated RNAi targeting RelB was effective methods to inhibit the maturation of BMDCs, thus possess therapeutic potential to prevent autoimmune disorders such as EAMG or human MG.

TLR4/MYD88-dependent, LPS-induced synthesis of PGE2 by macrophages or dendritic cells prevents anti-CD3-mediated CD95L upregulation in T cells

Antigen-presenting cells (APCs) control T-cell responses by multiple mechanisms, including the expression of co-stimulatory molecules and the production of cytokines and other mediators that control T-cell proliferation, survival and differentiation. Here, we demonstrate that soluble factor(s) produced by Toll-like receptor (TLR)-activated APCs suppress activation-induced cell death (AICD). This effect was observed in non-stimulated APCs, but it was significantly increased after lipopolysaccharide (LPS) treatment. Using different KO mice, we found that the LPS-induced protective factor is dependent on TLR4/MyD88. We identified the protective factor as prostaglandin E(2) (PGE(2)) and showed that both APC-derived supernatants and PGE(2) prevented CD95L upregulation in T cells in response to TCR/CD3 stimulation, thereby avoiding both AICD and activated T cell killing of target macrophages. The PGE(2) receptors, EP2 and EP4, appear to be involved since pharmacological stimulation of these receptors mimics the protective effect on T cells and their respective antagonists interfere with the protection induced by either APCs derived or synthetic PGE(2). Finally, the engagement of EP2 and EP4 synergistically activates protein kinase A (PKA) and exchange protein directly activated by cAMP pathways to prevent AICD. Taken together, these results indicate that APCs can regulate T-cell levels of CD95L by releasing PGE(2) in response to LPS through a TLR4/MyD88-dependent pathway, with consequences for both T cell and their own survival.

Dendritic cells transduced with SOCS-3 exhibit a tolerogenic/DC2 phenotype that directs type 2 Th cell differentiation in vitro and in vivo

Dendritic cells (DCs) have been suggested to direct a type of Th differentiation through their cytokine profile, e.g., high IL-12/IL-23 for Th1 (named DC1/immunogenic DCs) and IL-10 for Th2 (DC2/tolerogenic DCs). Suppressor of cytokine signaling (SOCS)-3 is a potent inhibitor of Stat3 and Stat4 transduction pathways for IL-23 and IL-12, respectively. We thus hypothesize that an enhanced SOCS-3 expression in DCs may block the autocrine response of IL-12/IL-23 in these cells, causing them to become a DC2-type phenotype that will subsequently promote Th2 polarization of naive T cells. Indeed, in the present study we found that bone marrow-derived DCs transduced with SOCS-3 significantly inhibited IL-12-induced activation of Stat4 and IL-23-induced activation of Stat3. These SOCS-3-transduced DCs expressed a low level of MHC class II and CD86 on their surface, produced a high level of IL-10 but low levels of IL-12 and IFN-gamma, and expressed a low level of IL-23 p19 mRNA. Functionally, SOCS-3-transduced DCs drove naive myelin oligodendrocyte glycoprotein-specific T cells to a strong Th2 differentiation in vitro and in vivo. Injection of SOCS-3-transduced DCs significantly suppressed experimental autoimmune encephalomyelitis, a Th1 cell-mediated autoimmune disorder of the CNS and an animal model of multiple sclerosis. These results indicate that transduction of SOCS-3 in DCs is an effective approach to generating tolerogenic/DC2 cells that then skew immune response toward Th2, thus possessing therapeutic potential in Th1-dominant autoimmune disorders such as multiple sclerosis.

Immune responses elicited by bacterial minicells capable of simultaneous DNA and protein antigen delivery

Recent events surrounding emerging infectious diseases, bioterrorism and increasing multidrug antibiotic resistance in bacteria have drastically increased current needs for effective vaccines. Many years of study have shown that live, attenuated pathogens are often more effective at delivering heterologous protein or DNA to induce protective immune responses. However, these vaccine carriers have inherent safety concerns that have limited their development and their use in many patient populations. Studies using nonliving delivery mechanisms have shown that providing both protein antigen and DNA encoding the antigen to an individual induces an improved, more protective immune response but rarely, if ever, are both delivered simultaneously. Here, non-replicating bacterial minicells derived from a commensal E. coli strain are shown to effectively induce antigen-specific immune responses after simultaneous protein and DNA delivery. These data demonstrate the potential use of achromosomal bacterial minicells as a vaccine carrier.