TH2 cytokines and allergic challenge induce Ym1 expression in macrophages by a STAT6-dependent mechanism

Antimycobacterial and healing effects of Pranlukast against MTB infection and pathogenesis in a preclinical mouse model of tuberculosis

It is essential to understand the interactions and relationships between Mycobacterium tuberculosis (Mtb) and macrophages during the infection in order to design host-directed, immunomodulation-dependent therapeutics to control Mtb. We had reported previously that ornithine acetyltransferase (MtArgJ), a crucial enzyme of the arginine biosynthesis pathway of Mtb, is allosterically inhibited by pranlukast (PRK), which significantly reduces bacterial growth. The present investigation is centered on the immunomodulation in the host by PRK particularly the activation of the host's immune response to counteract bacterial survival and pathogenicity. Here, we show that PRK decreased the bacterial burden in the lungs by upregulating the population of pro-inflammatory interstitial macrophages (IMs) and reducing the population of Mtb susceptible alveolar macrophages (AMs), dendritic cells (DCs), and monocytes (MO). Additionally, we deduce that PRK causes the host macrophages to change their metabolic pathway from fatty acid metabolism to glycolytic metabolism around the log phage of bacterial multiplication. Further, we report that PRK reduced tissue injury by downregulating the Ly6C-positive population of monocytes. Interestingly, PRK treatment improved tissue repair and inflammation resolution by increasing the populations of arginase 1 (Arg-1) and Ym1+Ym2 (chitinase 3-like 3) positive macrophages. In summary, our study found that PRK is useful not only for reducing the tubercular burden but also for promoting the healing of the diseased tissue.

Dynamics of ex vivo cytokine transcription during experimental Toxocara canis infection in Balb/c mice

The cytokine microenvironment is crucial in generating and polarizing the immune response. A means of monitoring this environment would be of great value for better understanding Toxocara canis immune modulation. The aim of this study was to analyze the dynamics of cytokine transcription ex vivo, during early (24-48 hours) and late (15-30 days) times post-infection, in the mesenteric lymph nodes, spleen and intestinal mucosa of Balb/c mice experimentally infected with T. canis larvae. Mice in the treated group were infected with 100 third-stage larvae (L3), whereas mice in the control group were not infected. Analyses were performed at different times: 24-48 hours post-infection (HPI), 15-30 days post-infection (DPI). IL4, IL10, IL12 and Ym1 mRNA transcriptions were analyzed through qPCR. This study showed cytokine transcription mediated by migrating larvae in the mesenteric lymph nodes and spleen at 24-48 HPI, whereas cytokine transcription in the intestinal mucosa was observed only at late times (15-30 DPI). These results suggest that the T. canis larvae migration during infection might play a role in cytokine dynamics. Since the cytokine microenvironment is crucial in modulating immune response, knowledge of cytokine dynamics during T. canis infections pave the way to better understand its interaction with the host.

Eosinophil Phenotypes Are Functionally Regulated by Resolvin D2 during Allergic Lung Inflammation

Eosinophils (Eos) reside in multiple organs during homeostasis and respond rapidly to an inflammatory challenge. Although Eos share chemical staining properties, they also demonstrate phenotypic and functional plasticity that is not fully understood. Here, we used a murine model of allergic lung inflammation to characterize Eos subsets and determine their spatiotemporal and functional regulation during inflammation and its resolution in response to resolvin D2 (RvD2), a potent specialized proresolving mediator. Two Eos subsets were identified by CD101 expression with distinct anatomic localization and transcriptional signatures at baseline and during inflammation. CD101low Eos were predominantly located in a lung vascular niche and responded to allergen challenge by moving into the lung interstitium. CD101high Eos were predominantly located in bronchoalveolar lavage (BAL) and extravascular lung, only present during inflammation, and had transcriptional evidence for cell activation. RvD2 reduced total Eos numbers and changed their phenotype and activation by at least two distinct mechanisms: decreasing interleukin 5-dependent recruitment of CD101low Eos and decreasing conversion of CD101low Eos to CD101high Eos. Collectively, these findings indicate that Eos are a heterogeneous pool of cells with distinct activation states and spatiotemporal regulation during resolution of inflammation and that RvD2 is a potent proresolving mediator for Eos recruitment and activation.

Kinin B1 Receptor Antagonism Prevents Acute Kidney Injury to Chronic Kidney Disease Transition in Renal Ischemia-Reperfusion by Increasing the M2 Macrophages Population in C57BL6J Mice

BACKGROUND

Chronic kidney disease (CKD) is a multifactorial, world public health problem that often develops as a consequence of acute kidney injury (AKI) and inflammation. Strategies are constantly sought to avoid and mitigate the irreversibility of this disease. One of these strategies is to decrease the inflammation features of AKI and, consequently, the transition to CKD.

METHODS

C57Bl6J mice were anesthetized, and surgery was performed to induce unilateral ischemia/reperfusion as a model of AKI to CKD transition. For acute studies, the animals received the Kinin B1 receptor (B1R) antagonist before the surgery, and for the chronic model, the animals received one additional dose after the surgery. In addition, B1R genetically deficient mice were also challenged with ischemia/reperfusion.

RESULTS

The absence and antagonism of B1R improved the kidney function following AKI and prevented CKD transition, as evidenced by the preserved renal function and prevention of fibrosis. The protective effect of B1R antagonism or deficiency was associated with increased levels of macrophage type 2 markers in the kidney.

CONCLUSIONS

The B1R is pivotal to the evolution of AKI to CKD, and its antagonism shows potential as a therapeutic tool in the prevention of CKD following AKI.

Cutting edges and therapeutic opportunities on tumor-associated macrophages in lung cancer

Lung cancer is a disease with remarkable heterogeneity. A deep understanding of the tumor microenvironment (TME) offers potential therapeutic strategies against this malignant disease. More and more attention has been paid to the roles of macrophages in the TME. This article briefly summarizes the origin of macrophages, the mutual regulation between anti-tumoral immunity and pro-tumoral statuses derived from macrophage polarization, and the therapeutic opportunities targeting alternately activated macrophages (AAM)-type macrophage polarization. Among them, cellular components including T cells, as well as acellular components represented by IL-4 and IL-13 are key regulators driving the polarization of AAM macrophages. Novel treatments targeting macrophage-associated mechanisms are mainly divided into small molecule inhibitors, monoclonal antibodies, and other therapies to re-acclimate AMM macrophages. Finally, we paid special attention to an immunosuppressive subgroup of macrophages with T cell immunoglobulin and mucin domain-3 (TIM-3) expression. Based on cellular interactions with cancer cells, TIM3+ macrophages facilitate the proliferation and progression of cancer cells, yet this process exposes targets blocking the ligand-receptor recognition. To sum up, this is a systematic review on the mechanism of tumor-associated macrophages (TAM) polarization, therapeutic strategies and the biological functions of Tim-3 positive macrophages that aims to provide new insights into the pathogenesis and treatment of lung cancer.

Protection against influenza-induced Acute Lung Injury (ALI) by enhanced induction of M2a macrophages: possible role of PPARγ/RXR ligands in IL-4-induced M2a macrophage differentiation

Many respiratory viruses cause lung damage that may evolve into acute lung injury (ALI), a cytokine storm, acute respiratory distress syndrome, and ultimately, death. Peroxisome proliferator activated receptor gamma (PPARγ), a member of the nuclear hormone receptor (NHR) family of transcription factors, regulates transcription by forming heterodimers with another NHR family member, Retinoid X Receptor (RXR). Each component of the heterodimer binds specific ligands that modify transcriptional capacity of the entire heterodimer by recruiting different co-activators/co-repressors. However, the role of PPARγ/RXR ligands in the context of influenza infection is not well understood. PPARγ is associated with macrophage differentiation to an anti-inflammatory M2 state. We show that mice lacking the IL-4Rα receptor, required for M2a macrophage differentiation, are more susceptible to mouse-adapted influenza (A/PR/8/34; "PR8")-induced lethality. Mice lacking Ptgs2, that encodes COX-2, a key proinflammatory M1 macrophage mediator, are more resistant. Blocking the receptor for COX-2-induced Prostaglandin E2 (PGE2) was also protective. Treatment with pioglitazone (PGZ), a PPARγ ligand, increased survival from PR8 infection, decreased M1 macrophage gene expression, and increased PPARγ mRNA in lungs. Conversely, conditional knockout mice expressing PPARγ-deficient macrophages were significantly more sensitive to PR8-induced lethality. These findings were extended in cotton rats: PGZ blunted lung inflammation and M1 cytokine gene expression after challenge with non-adapted human influenza. To study mechanisms by which PPARγ/RXR transcription factors induce canonical M2a genes, WT mouse macrophages were treated with IL-4 in the absence or presence of rosiglitazone (RGZ; PPARγ ligand), LG100754 (LG; RXR ligand), or both. IL-4 dose-dependently induced M2a genes Arg1, Mrc1, Chil3, and Retnla. Treatment of macrophages with IL-4 and RGZ and/or LG differentially affected induction of Arg1 and Mrc1 vs. Chil3 and Retnla gene expression. In PPARγ-deficient macrophages, IL-4 alone failed to induce Arg1 and Mrc1 gene expression; however, concurrent treatment with LG or RGZ + LG enhanced IL-4-induced Arg1 and Mrc1 expression, but to a lower level than in WT macrophages, findings confirmed in the murine alveolar macrophage cell line, MH-S. These findings support a model in which PPARγ/RXR heterodimers control IL-4-induced M2a differentiation, and suggest that PPARγ/RXR agonists should be considered as important tools for clinical intervention against influenza-induced ALI.

An update on Ym1 and its immunoregulatory role in diseases

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

Fungal-mediated lung allergic airway disease: The critical role of macrophages and dendritic cells

Fungi are abundant in the environment, causing our lungs to be constantly exposed to a diverse range of species. While the majority of these are cleared effectively in healthy individuals, constant exposure to spores (especially Aspergillus spp.) can lead to the development of allergic inflammation that underpins and worsen diseases such as asthma. Despite this, the precise mechanisms that underpin the development of fungal allergic disease are poorly understood. Innate immune cells, such as macrophages (MΦs) and dendritic cells (DCs), have been shown to be critical for mediating allergic inflammation to a range of different allergens. This review will focus on the crucial role of MΦ and DCs in mediating antifungal immunity, evaluating how these immune cells mediate allergic inflammation within the context of the lung environment. Ultimately, we aim to highlight important future research questions that will lead to novel therapeutic strategies for fungal allergic diseases.

The effect of short-chain fatty acids on M2 macrophages polarization in vitro and in vivo

Alternatively activated macrophages (M2 polarization) play an important role in asthma. Short-chain fatty acids (SCFAs) possessed immune-regulatory functions, but their effects on M2 polarization of alveolar macrophages and its underlying mechanisms are still unclear. In our study, murine alveolar macrophage MH-S cell line and human monocyte-derived macrophages were used to polarize to M2 subset with interleukin-4 (IL-4) treatment. The underlying mechanisms involved were investigated using molecule inhibitors/agonists. In vivo, female C57BL/6 mice were divided into five groups: CON group, ovalbumin (OVA) asthma group, OVA+Acetate group, OVA+Butyrate group, and OVA+Propionate group. Mice were fed with or without SCFAs (Acetate, Butyrate, Propionate) in drinking water for 20 days before developing OVA-induced asthma model. In MH-S, SCFAs inhibited IL-4-incuced protein or mRNA expressions of M2-associated genes in a dose-dependent manner. G-protein-coupled receptor 43 (GPR43) agonist 4-CMTB and histone deacetylase (HDAC) inhibitor (trichostatin A, TSA), but not GPR41 agonist AR420626 could inhibit the protein or mRNA expressions M2-associated genes. 4-CMTB, but not TSA, had no synergistic role in the inhibitory effect of SCFAs on M2 polarization. In vivo study indicated Butyrate and Propionate, but not Acetate, attenuated OVA-induced M2 polarization in the lung and airway inflammation. We also found the inhibitory effect of SCFAs on M2 polarization in human-derived macrophages. Therefore, SCFAs inhibited M2 polarization in MH-S likely through GPR43 activation and/or HDAC inhibition. Butyrate and Propionate but not Acetate could inhibit M2 polarization and airway inflammation in asthma model. SCFAs also abrogated M2 polarization in human-derived macrophages.

IL-4 and IL-13 Promote Proliferation of Mammary Epithelial Cells through STAT6 and IRS-1

T helper (Th)2 cytokines such as interleukin (IL)-4 and IL-13 control immune function by acting on leukocytes. They also regulate multiple responses in non-hematopoietic cells. During pregnancy, IL-4 and IL-13 facilitate alveologenesis of mammary glands. This particular morphogenesis generates alveoli from existing ducts and requires substantial cell proliferation. Using 3D cultures of primary mouse mammary epithelial cells, we demonstrate that IL-4 and IL-13 promote cell proliferation, leading to enlargement of mammary acini with partially filled lumens. The mitogenic effects of IL-4 and IL-13 are mediated by STAT6 as inhibition of STAT6 suppresses cell proliferation and improves lumen formation. In addition, IL-4 and IL-13 stimulate tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1). Prolonged treatment with these cytokines leads to increased IRS-1 abundance, which, in turn, amplifies IL-4- and IL-13-stimulated IRS-1 tyrosine phosphorylation. Through signaling crosstalk between IL-4/IL-13 and insulin, a hormone routinely included in mammary cultures, IRS-1 tyrosine phosphorylation is further enhanced. Lowering IRS-1 expression reduces cell proliferation, suggesting that IRS-1 is involved in IL-4- and IL-13-stimulated cell proliferation. Thus, a Th2-dominant cytokine milieu during pregnancy confers mammary gland development by promoting cell proliferation.

HSPB1 inhibitor J2 attenuates lung inflammation through direct modulation of Ym1 production and paracrine signaling

Heat shock protein beta-1 (HSPB1) is a multifaceted protein that controls cellular stress, modulates cell differentiation and development, and inhibits apoptosis of cancer cells. Increased HSPB1 expression is highly associated with poor outcomes in lung cancer by enhancing cell migration and invasion; therefore, targeting HSPB1 may be a promising therapeutic for lung cancer and fibrosis. Although the HSPB1 inhibitor J2 has been reported to exhibit potent antifibrotic effects, it remains unclear whether and how J2 directly modulates inflammatory immune responses in pulmonary fibrosis. In this study, we found that J2 potently attenuated irradiation or bleomycin-induced pulmonary fibrosis by significantly inhibiting the infiltration and activation of T cells and macrophages. J2 inhibited T-cell proliferation and subsequently suppressed T helper cell development. Although there was no significant effect of J2 on cell proliferation of M1 and M2 macrophages, J2 specifically increased the expression of Ym1 in M2 macrophages without affecting the expression of other M2 markers. Interestingly, J2 increased lysosomal degradation of HSPB1 and inhibited HSPB1-induced repression of signal transducer and activator of transcription 6 (STAT6), which simultaneously increased STAT6 and Ym1 expression. Ym1 production and secretion by J2-treated M2 macrophages substantially decreased IL-8 production by airway epithelial cells in vitro and in vivo, resulting in attenuation of airway inflammation. Taken together, we suggest that J2 has potential as a therapeutic agent for pulmonary fibrosis with increased HSPB1 expression through direct immune suppression by Ym1 production by M2 macrophages as well as T-cell suppression.

Altered Macrophage Function Associated with Crystalline Lung Inflammation in Acid Sphingomyelinase Deficiency

Deficiency of ASM (acid sphingomyelinase) causes the lysosomal storage Niemann-Pick disease (NPD). Patients with NPD type B may develop progressive interstitial lung disease with frequent respiratory infections. Although several investigations using the ASM-deficient (ASMKO) mouse NPD model revealed inflammation and foamy macrophages, there is little insight into the pathogenesis of NPD-associated lung disease. Using ASMKO mice, we report that ASM deficiency is associated with a complex inflammatory phenotype characterized by marked accumulation of monocyte-derived CD11b⁺ macrophages and expansion of airspace/alveolar CD11c⁺ CD11b^- macrophages, both with increased size, granularity, and foaminess. Both the alternative and classical pathways were activated, with decreased in situ phagocytosis of opsonized (Fc-coated) targets, preserved clearance of apoptotic cells (efferocytosis), secretion of Th2 cytokines, increased CD11c⁺/CD11b⁺ cells, and more than a twofold increase in lung and plasma proinflammatory cytokines. Macrophages, neutrophils, eosinophils, and noninflammatory lung cells of ASMKO lungs also exhibited marked accumulation of chitinase-like protein Ym1/2, which formed large eosinophilic polygonal Charcot-Leyden-like crystals. In addition to providing insight into novel features of lung inflammation that may be associated with NPD, our report provides a novel connection between ASM and the development of crystal-associated lung inflammation with alterations in macrophage biology.

Rapamycin Promotes ROS-Mediated Cell Death via Functional Inhibition of xCT Expression in Melanoma Under γ-Irradiation

Although many cancer patients are administered radiotherapy for their treatment, the interaction between tumor cells and macrophages in the tumor microenvironment attenuates the curative effects of radiotherapy. The enhanced activation of mTOR signaling in the tumors promotes tumor radioresistance. In this study, the effects of rapamycin on the interaction between tumor cells and macrophages were investigated. Rapamycin and 3BDO were used to regulate the mTOR pathway. In vitro, tumor cells cocultured with macrophages in the presence of each drug under normoxic or hypoxic conditions were irradiated with γ–rays. In vivo, mice were irradiated with γ–radiation after injection with DMSO, rapamycin and 3BDO into tumoral regions. Rapamycin reduced the secretion of IL-4 in tumor cells as well as YM1 in macrophages. Mouse recombinant YM1 decreased the enhanced level of ROS and the colocalized proportion of both xCT and EEA1 in irradiated tumor cells. Human recombinant YKL39 also induced results similar to those of YM1. Moreover, the colocalized proportion of both xCT and LC3 in tumor tissues was elevated by the injection of rapamycin into tumoral regions. Overall, the suppression of mTOR signaling in the tumor microenvironment might be useful for the improvement of tumor radioresistance.

Charcot-Leyden crystals and other protein crystals driving type 2 immunity and allergy

Protein crystals derived from innate immune cells have been synonymous with a Type-2 immune response in both mouse and man for over 150 years. Eosinophilic Galectin-10 (Charcot-Leyden) crystals in humans, and Ym1/Ym2 crystals in mice are frequently found in the context of parasitic infections, but also in diseases such as asthma and chronic rhinosinusitis. Despite their notable presence, these crystals are often overlooked as trivial markers of Type-2 inflammation. Here, we discuss the source, context, and role of protein crystallization. We focus on similarities observed between Galectin-10 and Ym1/2 crystals in driving immune responses; the subsequent benefit to the host during worm infection, and conversely the detrimental exacerbation of inflammation and mucus production during asthma.

Tumor-Associated Macrophages-Implications for Molecular Oncology and Imaging

Tumor-associated macrophages (TAMs) represent the largest group of leukocytes within the tumor microenvironment (TME) of solid tumors and orchestrate the composition of anti- as well as pro-tumorigenic factors. This makes TAMs an excellent target for novel cancer therapies. The plasticity of TAMs resulting in varying membrane receptors and expression of intracellular proteins allow the specific characterization of different subsets of TAMs. Those markers similarly allow tracking of TAMs by different means of molecular imaging. This review aims to provides an overview of the origin of tumor-associated macrophages, their polarization in different subtypes, and how characteristic markers of the subtypes can be used as targets for molecular imaging and theranostic approaches.

Cutaneous Immune Cell-Microbiota Interactions Are Controlled by Epidermal JunB/AP-1

Atopic dermatitis (AD) is a multi-factorial skin disease with a complex inflammatory signature including type 2 and type 17 activation. Although colonization by S. aureus is common in AD, the mechanisms rendering an organism prone to dysbiosis, and the role of IL-17A in the control of S. aureus-induced skin inflammation, are not well understood. Here, we show several pathological aspects of AD, including type 2/type 17 immune responses, elevated IgE, barrier dysfunction, pruritus, and importantly, spontaneous S. aureus colonization in JunB^Δep mice, with a large transcriptomic overlap with AD. Additionally, using Rag1^−/− mice, we demonstrate that adaptive immune cells are necessary for protection against S. aureus colonization. Prophylactic antibiotics, but not antibiotics after established dysbiosis, reduce IL-17A expression and skin inflammation, examined using Il17a-eGFP reporter mice. Mechanistically, keratinocytes lacking JunB exhibit higher MyD88 levels in vitro and in vivo, previously shown to regulate S. aureus colonization. In conclusion, our data identify JunB as an upstream regulator of microbiota-immune cell interactions and characterize the IL-17A response upon spontaneous dysbiosis.

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JunB^Δep mice display several defining features of atopic dermatitis

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Skin of JunB^Δep mice are colonized by human-derived S. aureus

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Adaptive immune system is necessary for protection against S. aureus

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JunB is an upstream regulator of the microbiota-immune cell interactions

A DNA Hypomethylating Drug Alters the Tumor Microenvironment and Improves the Effectiveness of Immune Checkpoint Inhibitors in a Mouse Model of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer that has proven refractory to immunotherapy. Previously, treatment with the DNA hypomethylating drug decitabine (5-aza-dC; DAC) extended survival in the KPC-Brca1 mouse model of PDAC. Here we investigated the effects of DAC in the original KPC model and tested combination therapy with DAC followed by immune checkpoint inhibitors (ICI). Four protocols were tested: PBS vehicle, DAC, ICI (anti-PD-1 or anti-VISTA), and DAC followed by ICI. For each single-agent and combination treatment, tumor growth was measured by serial ultrasound, tumor-infiltrating lymphoid and myeloid cells were characterized, and overall survival was assessed. Single-agent DAC led to increased CD4⁺ and CD8⁺ tumor-infiltrating lymphocytes (TIL), PD1 expression, and tumor necrosis while slowing tumor growth and modestly increasing mouse survival without systemic toxicity. RNA-sequencing of DAC-treated tumors revealed increased expression of Chi3l3 (Ym1), reflecting an increase in a subset of tumor-infiltrating M2-polarized macrophages. While ICI alone had modest effects, DAC followed by either of ICI therapies additively inhibited tumor growth and prolonged mouse survival. The best results were obtained using DAC followed by anti-PD-1, which extended mean survival from 26 to 54 days (P < 0.0001). In summary, low-dose DAC inhibits tumor growth and increases both TILs and a subset of tumor-infiltrating M2-polarized macrophages in the KPC model of PDAC, and DAC followed by anti-PD-1 substantially prolongs survival. Because M2-polarized macrophages are predicted to antagonize antitumor effects, targeting these cells may be important to enhance the efficacy of combination therapy with DAC plus ICI. SIGNIFICANCE: In a pancreatic cancer model, a DNA hypomethylating drug increases tumor-infiltrating effector T cells, increases a subset of M2 macrophages, and significantly prolongs survival in combination with immune checkpoint inhibitors.See related commentary by Nephew, p. 4610.

Mechanisms of ultrafine particle-induced respiratory health effects

Particulate matter (PM) is the principal component of air pollution. PM includes a range of particle sizes, such as coarse, fine, and ultrafine particles. Particles that are <100 nm in diameter are defined as ultrafine particles (UFPs). UFPs are found to a large extent in urban air as both singlet and aggregated particles. UFPs are classified into two major categories based on their source. Typically, UFPs are incidentally generated in the environment, often as byproducts of fossil fuel combustion, condensation of semivolatile substances or industrial emissions, whereas nanoparticles are manufactured through controlled engineering processes. The primary exposure mechanism of PM is inhalation. Inhalation of PM exacerbates respiratory symptoms in patients with chronic airway diseases, but the mechanisms underlying this response remain unclear. This review offers insights into the mechanisms by which particles, including UFPs, influence airway inflammation and discusses several mechanisms that may explain the relationship between particulate air pollutants and human health, particularly respiratory health. Understanding the mechanisms of PM-mediated lung injury will enhance efforts to protect at-risk individuals from the harmful health effects of air pollutants.

Prostaglandin E2 and Its Receptor EP2 Modulate Macrophage Activation and Fusion in Vitro

The foreign body response (FBR) has impaired progress of new implantable medical devices through its hallmark of chronic inflammation and foreign body giant cell (FBGC) formation leading to fibrous encapsulation. Macrophages are known to drive the FBR, but efforts to control macrophage polarization remain challenging. The goal for this study was to investigate whether prostaglandin E2 (PGE2), and specifically its receptors EP2 and/or EP4, attenuate classically activated (i.e., inflammatory) macrophages and macrophage fusion into FBGCs in vitro. Lipopolysaccharide (LPS)-stimulated macrophages exhibited a dose-dependent decrease in gene expression and protein production of tumor necrosis factor alpha (TNF-α) when treated with PGE2. This attenuation was primarily by the EP4 receptor, as the addition of the EP2 antagonist PF 04418948 to PGE2-treated LPS-stimulated cells did not recover TNF-α production while the EP4 antagonist ONO AE3 208 did. However, direct stimulation of EP2 with the agonist butaprost to LPS-stimulated macrophages resulted in a ∼60% decrease in TNF-α secretion after 4 h and corresponded with an increase in gene expression for Cebpb and Il10, suggesting a polarization shift toward alternative activation through EP2 alone. Further, fusion of macrophages into FBGCs induced by interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) was inhibited by PGE2 via EP2 signaling and by an EP2 agonist, but not an EP4 agonist. The attenuation by PGE2 was confirmed to be primarily by the EP2 receptor. Mrc1, Dcstamp, and Retlna expressions increased upon IL-4/GM-CSF stimulation, but only Retnla expression with the EP2 agonist returned to levels that were not different from controls. This study identified that PGE2 attenuates classically activated macrophages and macrophage fusion through distinct EP receptors, while targeting EP2 is able to attenuate both. In summary, this study identified EP2 as a potential therapeutic target for reducing the FBR to biomaterials.

Targeted delivery of Chil3/Chil4 siRNA to alveolar macrophages using ternary complexes composed of HMG and oligoarginine micelles

Cell-type-specific genes involved in disease can be effective therapeutic targets; therefore, the development of a cell-type-specific gene delivery system is essential. In this study, targeted delivery of Chil3 and Chil4 siRNA to activated macrophages was developed using a ligand called high mobility group (HMG) and oligoarginine (OR) micelles. HMG binds to TLR4 and RAGE located on the surface of activated macrophages. Since HMG is positively charged, it binds to the negatively charged siRNA by charge interaction. However, the stable formation of the siRNA/HMG complex requires an additional molecule to act as a carrier. In this study, OR micelles were used as the carrier. Gel retardation assays showed that siRNA, HMG, and OR micelles formed stable siRNA/HMG/OR micelle ternary complexes. In vitro transfection showed that the ternary complexes selectively delivered siRNA to TLR4 expressing macrophages. In addition, intratracheal administration of siRNA/HMG/OR ternary complexes delivered Chil3 and Chil4 siRNA specifically to alveolar macrophages. Furthermore, the siRNA that was delivered using ternary complexes reduced Chil3 and Chil4 expression and suppressed the symptoms of asthma, such as airway inflammation and mucin secretion.

The Endothelin-A Receptor Antagonist Zibotentan Induces Damage to the Nasal Olfactory Epithelium Possibly Mediated in Part through Type 2 Innate Lymphoid Cells

Zibotentan, an endothelin-A receptor antagonist, has been used in the treatment of various cardiovascular disorders and neoplasia. Castrated athymic nude mice receiving zibotentan for a preclinical xenograft efficacy study experienced weight loss, gastrointestinal bloat, and the presence of an audible respiratory click. Human side effects have been reported in the nasal cavity, so we hypothesized that the nasal cavity is a target for toxicity in mice receiving zibotentan. Lesions in the nasal cavity predominantly targeted olfactory epithelium in treated mice and were more pronounced in castrated animals. Minimal lesions were present in vehicle control animals, which suggested possible gavage-related reflux injury. The incidence, distribution, and morphology of lesions suggested direct exposure to the nasal mucosa and a possible systemic effect targeting the olfactory epithelium, driven by a type 2 immune response, with group 2 innate lymphoid cell involvement. Severe nasal lesions may have resulted in recurrent upper airway obstruction, leading to aerophagia and associated clinical morbidity. These data show the nasal cavity is a target of zibotentan when given by gavage in athymic nude mice, and such unanticipated and off-target effects could impact interpretation of research results and animal health in preclinical studies.

A chitinase-like protein from Sarcoptes scabiei as a candidate anti-mite vaccine that contributes to immune protection in rabbits

BACKGROUND

Scabies is caused by Sarcoptes scabiei burrowing into the stratum corneum of the host's skin and is detrimental to the health of humans and animals. Vaccines are an attractive alternative to replace the acaricides currently used in their control.

METHODS

In the present study, the S. scabiei chitinase-like protein 5 (SsCLP5) was characterized and recombinant SsCLP5 (rSsCLP5) was evaluated as a candidate vaccine protein for anti-mite protection in rabbits. The expression, characterization and immunolocalization of SsCLP5 were examined. Vaccination experiments were performed on three test groups (n = 12 per group) immunized with purified rSsCLP5. Control groups (n = 12 per group) were immunized with PBS, QuilA saponin or empty vector protein. After challenge, the inflammatory reaction and skin lesions were graded and rSsCLP5 indirect ELISA was used to detect antibody IgG levels in serum samples at the time of vaccination and post-challenge.

RESULTS

The results showed that rSsCLP5 had high immunoreactivity and immunogenicity. In S. scabiei, SsCLP5 had a wide distribution in the chewing mouthpart, legs and exoskeleton, especially the outer layer of the exoskeleton. Vaccination with rSsCLP5 resulted in 74.3% (26/35) of rabbits showing no detectable lesions after challenge with S. scabiei.

CONCLUSIONS

Our data demonstrate that rSsCLP5 is a promising candidate for a recombinant protein-based vaccine against S. scabiei. This study also provides a method for studying scabies vaccine using rabbit as an animal model and a basis for screening more effective candidate proteins.

Ym1 induces RELMα and rescues IL-4Rα deficiency in lung repair during nematode infection

Ym1 and RELMα are established effector molecules closely synonymous with Th2-type inflammation and associated pathology. Here, we show that whilst largely dependent on IL-4Rα signaling during a type 2 response, Ym1 and RELMα also have IL-4Rα-independent expression patterns in the lung. Notably, we found that Ym1 has opposing effects on type 2 immunity during nematode infection depending on whether it is expressed at the time of innate or adaptive responses. During the lung migratory stage of Nippostrongylus brasiliensis, Ym1 promoted the subsequent reparative type 2 response but once that response was established, IL-4Rα-dependent Ym1 was important for limiting the magnitude of type 2 cytokine production from both CD4+ T cells and innate lymphoid cells in the lung. Importantly, our study demonstrates that delivery of Ym1 to IL-4Rα deficient animals drives RELMα production and overcomes lung repair deficits in mice deficient in type 2 immunity. Together, Ym1 and RELMα, exhibit time and dose-dependent interactions that determines the outcome of lung repair during nematode infection.

Interactions of helminths with macrophages: therapeutic potential for inflammatory intestinal disease

Macrophages represent a highly heterogeneous and plastic cell type found in most tissues of the body; the intestine is home to enormous numbers of these cells. Considerable interest surrounds the 'M2 macrophage,' as it is able to control and regulate inflammation, while promoting tissue repair. Areas covered: As potent inducers of M2 macrophages, intestinal helminths and helminth-derived products are ideal candidates for small molecule drug design to drive M2 macrophage polarization. Several gastrointestinal helminths have been found to cause M2 macrophage-inducing infections. This review covers current knowledge of helminth products and their impact on macrophage polarization, which may in the future lead to new therapeutic strategies. A literature search was performed using the following search terms in PubMed: M2 macrophage, alternative activation, helminth products, helminth ES, helminth therapy, nanoparticle, intestinal macrophages. Other studies were selected by using references from articles identified through our original literature search. Expert commentary: While the immunomodulatory potential of helminth products is well established, we have yet to fully characterize many components of the intestinal helminth product library. Current work aims to identify the protein motifs responsible for modulation of macrophages and other components of the immune system.

IL-33 delays metastatic peritoneal cancer progression inducing an allergic microenvironment

Ovarian cancer is frequently diagnosed as peritoneal carcinomatosis. Unlike other tumor locations, the peritoneal cavity is commonly exposed to gut-breaching and ascending genital microorganisms and has a unique immune environment. IL-33 is a local cytokine that can activate innate and adaptive immunity. We studied the effectiveness of local IL-33 delivery in the treatment of cancer that has metastasized to the peritoneal cavity. Direct peritoneal administration of IL-33 delayed the progression of metastatic peritoneal cancer. Prolongation in survival was not associated with a direct effect of IL-33 on tumor cells, but with major changes in the immune microenvironment of the tumor. IL-33 promoted a significant increase in the leukocyte compartment of the tumor immunoenvironment and an allergic cytokine profile. We observed a substantial increase in the number of activated CD4⁺ T-cells accompanied by peritoneal eosinophil infiltration, B-cell activation and activation of peritoneal macrophages which displayed tumoricidal capacity. Depletion of CD4⁺ cells, eosinophils or macrophages reduced the anti-tumor effects of IL-33 but none of these alone were sufficient to completely abrogate its positive benefit. In conclusion, local administration of IL-33 generates an allergic tumor environment resulting in a novel approach for treatment of metastatic peritoneal malignancies, such as advanced ovarian cancer.

The phagosome and redox control of antigen processing

In addition to debris clearance and antimicrobial function, versatile organelles known as phagosomes play an essential role in the processing of exogenous antigen in antigen presenting cells. While there has been much attention on human leukocyte antigen haplotypes in the determination of antigenic peptide repertoires, the lumenal biochemistries within phagosomes and endosomes are emerging as equally-important determinants of peptide epitope composition and immunodominance. Recently, the lumenal redox microenvironment within these degradative compartments has been shown to impact two key antigenic processing chemistries: proteolysis by lysosomal cysteine proteases and disulfide reduction of protein antigens. Through manipulation of the balance between oxidative and reductive capacities in the phagosome-principally by modulating NADPH oxidase (NOX2) and γ-interferon-inducible lysosomal thiol reductase (GILT) activities-studies have demonstrated changes to antigen processing patterns leading to modified repertoires of antigenic peptides available for presentation, and subsequently, altered disease progression in T cell-driven autoimmunity. This review focuses on the mechanisms and consequences of redox-mediated phagosomal antigen processing, and the potential downstream implications to tolerance and autoimmunity.

Exopolysaccharide from Bifidobacterium longum subsp. longum 35624™ modulates murine allergic airway responses

Interactions between the host and the microbiota are thought to significantly influence immunological tolerance mechanisms at mucosal sites. We recently described that the loss of an exopolysaccharide (EPS) from Bifidobacterium longum 35624™ eliminated its protective effects in colitis and respiratory allergy murine models. Our goal was to investigate the immune response to purified EPS from B. longum 35624, determine if it has protective effects within the lung and identify the protective mechanisms. Isolated EPS from B. longum 35624 cultures was used for in vitro, ex vivo and in vivo studies. Human monocyte-derived dendritic cells (MDDCs) were used to investigate in vitro immunological responses to EPS. Cytokine secretion, expression of surface markers and signalling pathways were examined. The ovalbumin (OVA) respiratory allergy murine model was used to evaluate the in vivo immunomodulatory potential of EPS. In addition, interleukin (IL)-10 knockout (KO) mice and anti-Toll-like receptor (TLR)-2 blocking antibody were used to examine the underlying protective mechanisms of intranasal EPS administration. Stimulation of human MDDCs with EPS resulted in IL-10 secretion, but not proinflammatory cytokines. IL-10 secretion was TLR-2-dependent. Eosinophil recruitment to the lungs was significantly decreased by EPS intranasal exposure, which was associated with decreased expression of the Th2-associated markers C-C motif chemokine 11 (CCL11), C-C chemokine receptor type 3 (CCR3), IL-4 and IL-13. TLR-2-mediated IL-10 secretion was shown to be required for the reduction in eosinophils and Th2 cytokines. EPS-treatment reduced eosinophil recruitment within the lung in a respiratory inflammation mouse model, which is both TLR-2 and IL-10 mediated. EPS can be considered as a novel molecule potentially reducing the severity of chronic eosinophil-related airway disorders.

Regulation of chitinase-3-like-1 in T cell elicits Th1 and cytotoxic responses to inhibit lung metastasis

Chitinase-3-like-1 (Chi3l1) is known to play a significant role in the pathogenesis of Type 2 inflammation and cancer. However, the function of Chi3l1 in T cell and its clinical implications are largely unknown. Here we show that Chi3l1 expression was increased in activated T cells, especially in Th2 cells. In addition, Chi3l1-deficient T cells are hyper-responsive to TcR stimulation and are prone to differentiating into Th1 cells. Chi3l1-deficient Th1 cells show increased expression of anti-tumor immunity genes and decreased Th1 negative regulators. Deletion of Chi3l1 in T cells in mice show reduced melanoma lung metastasis with increased IFNγ and TNFα-producing T cells in the lung. Furthermore, silencing of Chi3l1 expression in the lung using peptide-siRNA complex (dNP2-siChi3l1) efficiently inhibit lung metastasis with enhanced Th1 and CTL responses. Collectively, this study demonstrates Chi3l1 is a regulator of Th1 and CTL which could be a therapeutic target to enhance anti-tumor immunity.

Toxoplasma gondii antigen SAG2A differentially modulates IL-1β expression in resistant and susceptible murine peritoneal cells

The cell surface of Toxoplasma gondii is covered by antigens (SAGs) from the SRS family anchored by glycosylphosphatidylinositol (GPI) and includes antigens from the SAG2 family. Among these, the SAG2A surface antigen shows great potential in activating humoral responses and has been used in characterizing the acute phase of infection and in the serological diagnosis of toxoplasmosis. In this study, we aimed to evaluate rSAG2A-induced proteins in BALB/c and C57BL/c mice macrophages and to evaluate the phenotypic polarization induced in the process. We treated the peritoneal macrophages from mouse strains that were resistant or susceptible to T. gondii with rSAG2A to analyze their proteomic profile by mass spectrometry and systems biology. We also examined the gene expression of these cells by RT-qPCR using the phenotypic markers of M1 and M2 macrophages. Differences were observed in the expression of proteins involved in the inflammatory process in both resistant and susceptible cells, and macrophages were preferentially induced to obtain a pro-inflammatory immune response (M1) via the overexpression of IL-1β in mice susceptible to this parasite. These data suggest that the SAG2A antigen induces phenotypic and classical activation of macrophages in both resistant and susceptible strains of mice during the acute phase of the disease.

Human Chitinases and Chitinase-Like Proteins as Indicators for Inflammation and Cancer

Human Glyco_18 domain-containing proteins constitute a family of chitinases and chitinase-like proteins. Chitotriosidase and AMCase are true enzymes which hydrolyse chitin and have a C-terminal chitin-binding domain. YKL-40, YKL-39, SI-CLP and murine YM1/2 proteins possess solely Glyco_18 domain and do not have the hydrolytic activity. The major sources of Glyco_18 containing proteins are macrophages, neutrophils, epithelial cells, chondrocytes, synovial cells, and cancer cells. Both macrophages and neutrophils use the regulated secretory mechanism for the release of Glyco_18 containing proteins. Glyco_18 containing proteins are established biomarkers for human diseases. Chitotriosidase is overproduced by lipid-laden macrophages and is a major marker for the inherited lysosomal storage Gaucher disease. AMCase and murine lectin YM1 are upregulated in Th2-environment, and enzymatic activity of AMCase contributes to asthma pathogenesis. YKL proteins act as soluble mediators for the cell proliferation and migration, and are also involved in rheumatoid arthritis, inflammatory bowel disease, hepatic fibrosis and cirrhosis. Chitotriosidase and YKL-40 reflect the macrophage activation in atherosclerotic plaques. Serum level of YKL-40 is a diagnostic and prognostic marker for numerous types of solid tumors. YKL-39 is a marker for the activation of chondrocytes and the progression of the osteoarthritis in human. Recently identified SI-CLP is upregulated by Th2 cytokine IL-4 as well as by glucocorticoids. This unique feature of SI-CLP makes it an attractive candidate for the examination of individual sensitivity of patients to glucocorticoid treatment and prediction of side effects of glucocorticoid therapy. Human chitinases and chitinase-like proteins are found in tissues and circulation, and can be detected by non-invasive technologies.

RANKL-mediated harmonious dialogue between fetus and mother guarantees smooth gestation by inducing decidual M2 macrophage polarization

Decidual macrophages (dMφ) contribute to maternal–fetal tolerance. However, the mechanism of dMφ differentiation during pregnancy is still largely unknown. Here, we report that receptor activator for nuclear factor-κ B ligand (RANKL), secreted by human embryonic trophoblasts and maternal decidual stromal cells (DSCs), polarizes dMφ toward a M2 phenotype. This polarization is mediated through activation of Akt/signal transducer and activator of transcription 6 (STAT6) signaling, which is associated with the upregulation of histone H3 lysine-27 demethylase Jmjd3 and IRF4 in dMφ. Such differentiated dMφ can induce a Th2 bias that promotes maternal–fetal tolerance. Impaired expression of RANKL leads to dysfunction of dMφ in vivo and increased rates of fetal loss in mice. Transfer of RANK⁺Mφ reverses mouse fetal loss induced by Mφ depletion. Compared with normal pregnancy, there are abnormally low levels of RANKL/RANK in villi and decidua from miscarriage patients. These results suggest that RANKL is a pivotal regulator of maternal–fetal tolerance by licensing dMφ to ensure a successful pregnancy outcome. This observation provides a scientific basis on which a potential therapeutic strategy can be targeted to prevent pregnancy loss.

Ebi3 Prevents Trypanosoma cruzi-Induced Myocarditis by Dampening IFN-γ-Driven Inflammation

The identification of anti-inflammatory mediators can reveal important targetable molecules capable of counterbalancing Trypanosoma cruzi-induced myocarditis. Composed of Ebi3 and IL-27p28 subunits, IL-27 is produced by myeloid cells and is able to suppress inflammation by inducing IL-10-producing Tr1 cells, thus emerging as a potential candidate to ameliorate cardiac inflammation induced by T. cruzi. Although IL-27 has been extensively characterized as a suppressive cytokine that prevents liver immunopathogenesis after T. cruzi infection, the mechanisms underlying its effects on T. cruzi-induced myocarditis remain largely unknown. Here, wild-type (WT) and Ebi3-deficient animals were intraperitoneally infected with trypomastigotes of T. cruzi Y strain and used to evaluate the potential anti-inflammatory properties of Ebi3 during T. cruzi infection. The survival rates of mice were daily recorded, the frequency of inflammatory cells was analyzed by flow cytometry and inflammatory mediators were measured by ELISA, real-time PCR and PCR array. We reported that T. cruzi-induced myocarditis was prevented by Ebi3. Stressors mainly recognized by TLR2 and TLR4 receptors on myeloid cells were essential to trigger IL-27p28 production. In addition, Ebi3 regulated IFN-γ-mediated myocarditis by promoting an anti-inflammatory environment through IL-10, which was most likely produced by Tr1 cells rather than classical regulatory T cells (Tregs), in the heart tissue of T. cruzi-infected animals. Furthermore, in vivo IFN-γ blockade ameliorated the host survival without compromising the parasite control in the bloodstream. In humans, IL-27p28 was correlated with cardiac protection during Chagas disease. Patients with mild clinical forms of the disease produced high levels of IL-27p28, whereas lower levels were found in those with severe forms. In addition, polymorphic sites at Ebi3 gene were associated with severe cardiomyopathy in patients with Chagas disease. Collectively, we describe a novel regulatory mechanism where Ebi3 dampens cardiac inflammation by modulating the overproduction of IFN-γ, the bona fide culprit of Chagas disease cardiomyopathy.

Hyperoside attenuates OVA-induced allergic airway inflammation by activating Nrf2

Allergic airways disease (AAD) is one of the most common medical illnesses that is associated with an increased allergic airway inflammation. Hyperoside, an active compound isolated from Rhododendron brachycarpum G. Don, has been reported to have anti-inflammatory effect. The aim of this study was to analyze the protective effect of hyperoside on OVA-induced allergic airway inflammation in mice. In the present study, the mouse asthma model was induced by given OVA and hyperoside was administrated 1h before OVA challenge. The levels of IL-4, IL-5, IL-13, and IgE were detected by ELISA. H&E staining was used to assess lung histopathological changes. The expression of NF-κB p65, IκB, HO-1, and Nf-E2 related factor 2 (Nrf2) were measured by western blot analysis. The results showed that hyperoside significantly reduced the inflammatory cells infiltration and the levels of IL-4, IL-5, IL-13, and IgE. Hyperoside significantly inhibited OVA-induced oxidative stress as demonstrated by decreased MDA, and increased GSH and SOD levels. Treatment of hyperoside also inhibited OVA-induced airway hyperresponsiveness (AHR). Furthermore, the results showed that treatment of hyperoside significantly inhibited LPS-induced NF-κB activation. In addition, hyperoside was found to activate Nrf2/HO-1 signaling pathway. In conclusion, these results suggest that hyperoside ameliorates OVA-induced allergic airway inflammation by activating Nrf2 signaling pathway.

High glucose induces alternative activation of macrophages via PI3K/Akt signaling pathway

OBJECTIVE

It has been proved that lactate-4.25% dialysate could result in peritoneal fibrosis by inducing alternative activation of macrophages in our previous study, but the mechanism of high glucose-induced alternative activation has not been elucidated. This study was, therefore, to investigate the mechanism by high glucose stimuli.

METHODS

In this study, Raw264.7 (murine macrophage cell line) cells were cultured and stimulated by 4.25% glucose medium, and mannitol medium was used as osmotic pressure control. Cells were harvested at 0 h, 4 h, 8 h, and 12 h to examine the expression of Arg-1, CD206, and p-Akt. After blocking PI3K by LY294002, the expression of Arg-1, CD206, and p-Akt was examined again.

RESULTS

The expression of Arg-1 and CD206 was increased in a time-dependent manner induced by high glucose medium. On the contrary, there was mainly no Agr-1 or CD206 expressed in cells cultured in the mannitol medium with the same osmotic pressure. What's more, Akt was phosphorylated at the eighth hour stimulated by high glucose medium, and LY294002 inhibited the expression of Arg-1 and CD206 by blocking the phosphorylation of Akt.

CONCLUSIONS

Our study indicated that high glucose rather than high osmotic pressure induced M2 phenotype via PI3K/Akt signaling pathway.

Crosstalk between glucocorticoids and IL-4 modulates Ym1 expression in alternatively activated myeloid cells

Airway epithelial cells induce a tolerogenic microenvironment by modulating immune cells in the lung. We recently showed that the supernatant of airway epithelial cells induces two marker genes of alternative activation, Ym1 and Ms4a8a, in respiratory myeloid cells. This induction was partially mediated by glucocorticoids, secreted by airway epithelial cells. In this study, we further investigated Ym1 and Ms4a8a regulation in alternatively activated myeloid cells in the presence of the T_H2 cytokines IL-4 and IL-13. We show that Ym1 expression is boosted upon co-stimulation with airway epithelial cell supernatant and IL-4/IL-13, whereas Ms4a8a expression is down-regulated. This suggests that a crosstalk between IL-4/IL-13 and glucocorticoid signaling exists. Blocking protein synthesis indicated that dexamethasone-induced de novo protein synthesis is required for the interaction between glucocorticoid and IL-4 signaling regarding Ym1 regulation. Using reporter gene constructs, we demonstrate that the important regulatory region within the Ym1 promoter is found between -602bp and -969bp upstream of the start of translation. Bioinformatic analysis identified several glucocorticoid response elements (GREs) in this region. Further analysis identified overlapping but functionally active glucocorticoid receptor and STAT-6 binding sites, supporting the cooperative effect of glucocorticoids and IL-4 in the regulation of Ym1. These findings further prove the plasticity and complexity of alternatively activated myeloid cells and the importance of the local microenvironment. We believe that this regulation is of special importance in the pulmonary system, since both factors, glucocorticoids and IL-4/13, play a role in airway diseases such as asthma.

Chlorogenic acid inhibits glioblastoma growth through repolarizating macrophage from M2 to M1 phenotype

Glioblastoma is an aggressive tumor that is associated with distinctive infiltrating microglia/macrophages populations. Previous studies demonstrated that chlorogenic acid (5-caffeoylquinic acid, CHA), a phenolic compound with low molecular weight, has an anti-tumor effect in multiple malignant tumors. In the present study, we focused on the macrophage polarization to investigate the molecular mechanisms behind the anti-glioma response of CHA in vitro and in vivo. We found that CHA treatment increased the expression of M1 markers induced by LPS/IFNγ, including iNOS, MHC II (I-A/I-E subregions) and CD11c, and reduced the expression of M2 markers Arg and CD206 induced by IL-4, resulting in promoting the production of apoptotic-like cancer cells and inhibiting the growth of tumor cells by co-culture experiments. The activations of STAT1 and STAT6, which are two crucial signaling events in M1 and M2-polarization, were significantly promoted and suppressed by CHA in macrophages, respectively. Furthermore, In G422 xenograft mice, CHA increased the proportion of CD11c-positive M1 macrophages and decreased the distribution of CD206-positive M2 macrophages in tumor tissue, consistent with the reduction of tumor weight observed in CHA-treated mice. Overall these findings indicated CHA as a potential therapeutic approach to reduce glioma growth through promoting M1-polarized macrophage and inhibiting M2 phenotypic macrophage.

Genetic Variants in CHIA and CHI3L1 Are Associated with the IgE Response to the Ascaris Resistance Marker ABA-1 and the Birch Pollen Allergen Bet v 1

Helminth infections and allergic diseases are associated with IgE hyperresponsiveness but the genetics of this phenotype remain to be defined. Susceptibility to Ascaris lumbricoides infection and antibody levels to this helminth are associated with polymorphisms in locus 13q33-34. We aimed to explore this and other genomic regions to identify genetic variants associated with the IgE responsiveness in humans. Forty-eight subjects from Cartagena, Colombia, with extreme values of specific IgE to Ascaris and ABA-1, a resistance marker of this nematode, were selected for targeted resequencing. Burden analyses were done comparing extreme groups for IgE values. One-hundred one SNPs were genotyped in 1258 individuals of two well-characterized populations from Colombia and Sweden. Two low-frequency coding variants in the gene encoding the Acidic Mammalian Chitinase (CHIA rs79500525, rs139812869, tagged by rs10494133) were found enriched in high IgE responders to ABA-1 and confirmed by genetic association analyses. The SNP rs4950928 in the Chitinase 3 Like 1 gene (CHI3L1) was associated with high IgE to ABA-1 in Colombians and with high IgE to Bet v 1 in the Swedish population. CHIA rs10494133 and ABDH13 rs3783118 were associated with IgE responses to Ascaris. SNPs in the Tumor Necrosis Factor Superfamily Member 13b gene (TNFSF13B) encoding the cytokine B cell activating Factor were associated with high levels of total IgE in both populations. This is the first report on the association between low-frequency and common variants in the chitinases-related genes CHIA and CHI3L1 with the intensity of specific IgE to ABA-1 in a population naturally exposed to Ascaris and with Bet v 1 in a Swedish population. Our results add new information about the genetic influences of human IgE responsiveness; since the genes encode for enzymes involved in the immune response to parasitic infections, they could be helpful for understanding helminth immunity and allergic responses. We also confirmed that TNFSF13B has an important and conserved role in the regulation of total IgE levels, which supports potential evolutionary links between helminth immunity and allergic response.

Co-exposure to zymosan A and heat-inactivated Asian sand dust exacerbates ovalbumin-induced murine lung eosinophilia

Background

Epidemiological studies have implicated Asian sand dust (ASD) in the increased prevalence of respiratory disorders, including asthma. It has been observed that fungal elements such as β-glucan can be adsorbed onto ASD. In the present study, the exacerbating effect of the combined exposure to zymosan A (ZymA) containing yeast β-glucan and heat-inactivated ASD on ovalbumin (OVA)-induced murine lung eosinophilia was investigated.

Methods

BALB/c mice were repeatedly instilled intratracheally with one of eight immunogenic formulations consisting of various combinations of (1) ZymA, (2) ASD that was briefly heated to remove organic substances (H-ASD), and (3) OVA in normal saline, or each of the above alone. Pathologic changes, cytological alterations in bronchoalveolar lavage fluid (BALF), changes in inflammatory cytokines and chemokines in BALF, and OVA-specific IgE and IgG₁ antibodies in serum were investigated.

Results

Exposure to ZymA with or without OVA had no effect on most indicators of lung inflammation. Exposure to H-ASD with OVA increased the recruitment of inflammatory cells to the lungs and the serum levels of OVA-specific IgE and IgG₁. The combination OVA + ZymA + H-ASD induced a marked recruitment of eosinophils and upregulation of T helper 2 (Th2) cytokines (interleukin [IL]-4 and IL-13), IL-6, eotaxin/CCL11, and monocyte chemotactic protein (MCP)-3/CCL7 in BALF and OVA-specific IgE in serum. This treatment also induced the most severe pathological changes in the lungs of mice. ZymA was found to boost the effects of H-ASD, thereby exacerbating the OVA-induced allergic inflammation, even though ZymA alone did not have such effect.

Conclusions

The results suggest that fungal elements such as β-1,3-glucan aggravate the allergic inflammation caused by ASD. Our findings may facilitate prophylaxis of some allergic diseases in Asia.

Targeting innate immunity for neurodegenerative disorders of the central nervous system

Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview of physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia and astrocyte cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article. Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer's disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview on physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article.

The activation of Wnt signaling by a STAT6-dependent macrophage phenotype promotes mucosal repair in murine IBD

The complete repair of the mucosa constitutes a key goal in inflammatory bowel disease (IBD) treatment. The Wnt signaling pathway mediates mucosal repair and M2 macrophages that coordinate efficient healing have been related to Wnt ligand expression. Signal transducer and activator of transcription 6 (STAT6) mediates M2 polarization in vitro and we hypothesize that a STAT6-dependent macrophage phenotype mediates mucosal repair in acute murine colitis by activating the Wnt signaling pathway. Our results reveal an impaired mucosal expression of M2 macrophage-associated genes and delayed wound healing in STAT6(-/-) mice treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). These mice also exhibited decreased mucosal expression of Wnt2b, Wnt7b, and Wnt10a, diminished protein levels of nuclear β-catenin that is mainly located in crypts adjacent to damage, and reduced mRNA expression of two Wnt/β-catenin target molecules Lgr5 and c-Myc when compared with wild-type (WT) mice. Murine peritoneal macrophages treated with interleukin-4 (IL-4) and polarized toward an M2a phenotype overexpressed Wnt2b, Wnt7b, and Wnt10a in a STAT6-dependent manner. Administration of a Wnt agonist as well as transfer of properly polarized M2a macrophages to STAT6(-/-) mice activated the Wnt signaling pathway in the damaged mucosa and accelerated wound healing. Our results demonstrate that a STAT6-dependent macrophage phenotype promotes mucosal repair in TNBS-treated mice through activation of the Wnt signaling pathway.

The adaptor protein insulin receptor substrate 2 inhibits alternative macrophage activation and allergic lung inflammation

Insulin receptor substrate 2 (IRS2) is an adaptor protein that becomes tyrosine-phosphorylated in response to the cytokines interleukin-4 (IL-4) and IL-13, which results in activation of the phosphoinositide 3-kinase (PI3K)-Akt pathway. IL-4 and IL-13 contribute to allergic lung inflammation. To examine the role of IRS2 in allergic disease, we evaluated the responses of IRS2-deficient (IRS2(-/-)) mice. Unexpectedly, loss of IRS2 resulted in a substantial increase in the expression of a subset of genes associated with the generation of alternatively activated macrophages (AAMs) in response to IL-4 or IL-13 in vitro. AAMs secrete factors that enhance allergic responses and promote airway remodeling. Moreover, compared to IRS2(+/+) mice, IRS2(+/-) and IRS2(-/-) mice developed enhanced pulmonary inflammation, accumulated eosinophils and AAMs, and exhibited airway and vascular remodeling upon allergen stimulation, responses that partially depended on macrophage-intrinsic IRS2 signaling. Both in unstimulated and IL-4-stimulated macrophages, lack of IRS2 enhanced phosphorylation of Akt and ribosomal S6 protein. Thus, we identified a critical inhibitory loop downstream of IRS2, demonstrating an unanticipated and previously unrecognized role for IRS2 in suppressing allergic lung inflammation and remodeling.

Soluble antigen derived from IV larva of Angiostrongylus cantonensis promotes chitinase-like protein 3 (Chil3) expression induced by interleukin-13

Angiostrongyliasis caused by Angiostrongylus cantonensis (A. cantonensis) is an emerging food-borne parasitic disease, which refers basically to eosinophilic meningitis. Chitinase-like protein 3 (Chil3), a member of chitinase-like protein family which has chemotactic activity for eosinophils, is reported to be highly upregulated in brain of mouse infected with A. cantonensis. The mechanisms of high expression of Chil3 and the association between A. cantonensis and Chil3 are rarely reported. In order to understand the mechanism of high expression of Chil3 in A. cantonensis-infected mouse, we measured the level of Chil3 in RAW 264.7 and BV2 cell lines stimulated with soluble antigen of A. cantonensis by qPCR and ELISA. To explore the role of Chil3 in inflammation caused by A. cantonensis, we extracted and cultured brain mononuclear cells (BMNCs) and detected the eosinophil chemotactic activity of Chil3 using transwell assay and flow cytometer. Furthermore, we treated the infected mice by injection with rmChil3 and then counted the number of larvae in brains of infected mice and treated mice to examine the association between the worm and Chil3. Our results showed the soluble antigen from A. cantonensis could promote the Chil3 expression in macrophage and microglial cell lines induced by interleukin-13. In conclusion, we supposed that high expression of Chil3 enhanced by soluble antigens from A. cantonensis might be the reason of serious eosinophil infiltration in mouse brain after A. cantonensis infection.

Increased YKL-40 and Chitotriosidase in Asthma and Chronic Obstructive Pulmonary Disease

RATIONALE

Serum chitinases may be novel biomarkers of airway inflammation and remodeling, but less is known about factors regulating their levels.

OBJECTIVES

To examine serum chitotriosidase activity and YKL-40 levels in patients with asthma and chronic obstructive pulmonary disease (COPD) and evaluate clinically relevant factors that may affect chitinase levels, including genetic variability, corticosteroid treatment, disease exacerbations, and allergen exposure.

METHODS

Serum chitotriosidase (CHIT1) activity and YKL-40 (CHI3L1) levels, as well as the CHIT1 rs3831317 and CHI3L1 rs4950928 genotypes, were examined in subsets of patients with mild to moderate asthma (n = 76), severe asthma (n = 93), and COPD (n = 64) taking part in the European multicenter BIOAIR (Longitudinal Assessment of Clinical Course and Biomarkers in Severe Chronic Airway Disease) study. Blood was obtained at baseline, before and after a 2-week oral steroid intervention, up to six times during a 1-year period, and during exacerbations. Baseline chitinase levels were also measured in 72 healthy control subjects. The effect of allergen inhalation on blood and sputum YKL-40 levels was measured in two separate groups of patients with mild atopic asthma; one group underwent repeated low-dose allergen challenge (n = 15), and the other underwent high-dose allergen challenge (n = 16).

MEASUREMENTS AND MAIN RESULTS

Serum chitotriosidase and YKL-40 were significantly elevated in patients with asthma and those with COPD compared with healthy control subjects. Genotype and age strongly affected both YKL-40 and chitotriosidase activity, but associations with disease remained following adjustment for these factors. Correlations were observed with lung function but not with other biomarkers, including exhaled nitric oxide, blood eosinophils, periostin, and IgE. Generally, acute exacerbations, allergen-induced airway obstruction, and corticosteroid treatment did not affect circulating chitinase levels.

CONCLUSIONS

YKL-40 and chitotriosidase are increased in asthma and more so in COPD. The data in the present study support these substances as being relatively steroid-insensitive, non-T-helper cell type 2-type biomarkers distinctly related to chronic inflammatory disease processes.

Enhanced allergic responsiveness after early childhood infection with respiratory viruses: Are long-lived alternatively activated macrophages the missing link?

Early childhood infection with respiratory viruses, including human rhinovirus, respiratory syncytial virus (RSV) and influenza, is associated with an increased risk of allergic asthma and severe exacerbation of ongoing disease. Despite the long recognition of this relationship, the mechanism linking viral infection and later susceptibility to allergic lung inflammation is still poorly understood. We discuss the literature and provide new evidence demonstrating that these viruses induce the alternative activation of macrophages. Alternatively activated macrophages (AAM) induced by RSV or influenza infection persisted in the lungs of mice up to 90 days after initial viral infection. Several studies suggest that AAM contribute to allergic inflammatory responses, although their mechanism of action is unclear. In this commentary, we propose that virus-induced AAM provide a link between viral infection and enhanced responses to inhaled allergens.

Differential Roles of M1 and M2 Microglia in Neurodegenerative Diseases

One of the most striking hallmarks shared by various neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease (AD), and amyotrophic lateral sclerosis, is microglia-mediated neuroinflammation. Increasing evidence indicates that microglial activation in the central nervous system is heterogeneous, which can be categorized into two opposite types: M1 phenotype and M2 phenotype. Depending on the phenotypes activated, microglia can produce either cytotoxic or neuroprotective effects. In this review, we focus on the potential role of M1 and M2 microglia and the dynamic changes of M1/M2 phenotypes that are critically associated with the neurodegenerative diseases. Generally, M1 microglia predominate at the injury site at the end stage of disease, when the immunoresolution and repair process of M2 microglia are dampened. This phenotype transformation is very complicated in AD due to the phagocytosis of regionally distributed β-amyloid (Aβ) plaque and tangles that are released into the extracellular space. The endogenous stimuli including aggregated α-synuclein, mutated superoxide dismutase, Aβ, and tau oligomers exist in the milieu that may persistently activate M1 pro-inflammatory responses and finally lead to irreversible neuron loss. The changes of microglial phenotypes depend on the disease stages and severity; mastering the stage-specific switching of M1/M2 phenotypes within appropriate time windows may provide better therapeutic benefit.

Sustained Arginase 1 Expression Modulates Pathological Tau Deposits in a Mouse Model of Tauopathy

Tau accumulation remains one of the closest correlates of neuronal loss in Alzheimer's disease. In addition, tau associates with several other neurodegenerative diseases, collectively known as tauopathies, in which clinical phenotypes manifest as cognitive impairment, behavioral disturbances, and motor impairment. Polyamines act as bivalent regulators of cellular function and are involved in numerous biological processes. The regulation of the polyamines system can become dysfunctional during disease states. Arginase 1 (Arg1) and nitric oxide synthases compete for l-arginine to produce either polyamines or nitric oxide, respectively. Herein, we show that overexpression of Arg1 using adeno-associated virus (AAV) in the CNS of rTg4510 tau transgenic mice significantly reduced phospho-tau species and tangle pathology. Sustained Arg1 overexpression decreased several kinases capable of phosphorylating tau, decreased inflammation, and modulated changes in the mammalian target of rapamycin and related proteins, suggesting activation of autophagy. Arg1 overexpression also mitigated hippocampal atrophy in tau transgenic mice. Conversely, conditional deletion of Arg1 in myeloid cells resulted in increased tau accumulation relative to Arg1-sufficient mice after transduction with a recombinant AAV-tau construct. These data suggest that Arg1 and the polyamine pathway may offer novel therapeutic targets for tauopathies.

Along the Axis between Type 1 and Type 2 Immunity; Principles Conserved in Evolution from Fish to Mammals

A phenomenon already discovered more than 25 years ago is the possibility of naïve helper T cells to polarize into TH1 or TH2 populations. In a simplified model, these polarizations occur at opposite ends of an "immune 1-2 axis" (i1-i2 axis) of possible conditions. Additional polarizations of helper/regulatory T cells were discovered later, such as for example TH17 and Treg phenotypes; although these polarizations are not selected by the axis-end conditions, they are affected by i1-i2 axis factors, and may retain more potential for change than the relatively stable TH1 and TH2 phenotypes. I1-i2 axis conditions are also relevant for polarizations of other types of leukocytes, such as for example macrophages. Tissue milieus with "type 1 immunity" ("i1") are biased towards cell-mediated cytotoxicity, while the term "type 2 immunity" ("i2") is used for a variety of conditions which have in common that they inhibit type 1 immunity. The immune milieus of some tissues, like the gills in fish and the uterus in pregnant mammals, probably are skewed towards type 2 immunity. An i2-skewed milieu is also created by many tumors, which allows them to escape eradication by type 1 immunity. In this review we compare a number of i1-i2 axis factors between fish and mammals, and conclude that several principles of the i1-i2 axis system seem to be ancient and shared between all classes of jawed vertebrates. Furthermore, the present study is the first to identify a canonical TH2 cytokine locus in a bony fish, namely spotted gar, in the sense that it includes RAD50 and bona fide genes of both IL-4/13 and IL-3/ IL-5/GM-CSF families.