Isolation and Differentiation of Human Macrophages

A Simple and Rapid Microscale Method for Isolating Bacterial Lipopolysaccharides

Bacterial endotoxins (lipopolysaccharides (LPSs)) are important mediators of inflammatory processes induced by Gram-negative microorganisms. LPSs are the key inducers of septic shock due to a Gram-negative bacterial infection; thus, the structure and functions of LPSs are of specific interest. Often, highly purified bacterial endotoxins must be isolated from small amounts of biological material. Each of the currently available methods for LPS extraction has certain limitations. Herein, we describe a rapid and simple microscale method for extracting LPSs. The method consists of the following steps: ultrasonic destruction of the bacterial material, LPS extraction via heating, LPS purification with organic solvents, and treatment with proteinase K. LPSs that were extracted by using this method contained less than 2-3% protein and 1% total nucleic acid. We also demonstrated the structural integrity of the O-antigen and lipid A via the sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) methods, respectively. We demonstrated the ability of the extracted LPSs to induce typical secretion of cytokines and chemokines by primary macrophages. Overall, this method may be used to isolate purified LPSs with preserved structures of both the O-antigen and lipid A and unchanged functional activity from small amounts of bacterial biomass.

Apoptosis recognition receptors regulate skin tissue repair in mice

Apoptosis and clearance of apoptotic cells via efferocytosis are evolutionarily conserved processes that drive tissue repair. However, the mechanisms by which recognition and clearance of apoptotic cells regulate repair are not fully understood. Here, we use single-cell RNA sequencing to provide a map of the cellular dynamics during early inflammation in mouse skin wounds. We find that apoptotic pathways and efferocytosis receptors are elevated in fibroblasts and immune cells, including resident Lyve1+ macrophages, during inflammation. Interestingly, human diabetic foot wounds upregulate mRNAs for efferocytosis pathway genes and display altered efferocytosis signaling via the receptor Axl and its ligand Gas6. During early inflammation in mouse wounds, we detect upregulation of Axl in dendritic cells and fibroblasts via TLR3-independent mechanisms. Inhibition studies in vivo in mice reveal that Axl signaling is required for wound repair but is dispensable for efferocytosis. By contrast, inhibition of another efferocytosis receptor, Timd4, in mouse wounds decreases efferocytosis and abrogates wound repair. These data highlight the distinct mechanisms by which apoptotic cell detection coordinates tissue repair and provides potential therapeutic targets for chronic wounds in diabetic patients.

Comparative Infections of Zika, Dengue, and Yellow Fever Viruses in Human Cytotrophoblast-Derived Cells Suggest a Gating Role for the Cytotrophoblast in Zika Virus Placental Invasion

The Zika virus (ZIKV) is teratogenic and considered a TORCH pathogen (toxoplasmosis [Toxoplasma gondii], rubella, cytomegalovirus, herpes simplex virus [HSV], and other microorganisms capable of crossing the blood-placenta barrier). In contrast, the related flavivirus dengue virus (DENV) and the attenuated yellow fever virus vaccine strain (YFV-17D) are not. Understanding the mechanisms used by ZIKV to cross the placenta is necessary. In this work, parallel infections with ZIKV of African and Asian lineages, DENV, and YFV-17D were compared for kinetics and growth efficiency, activation of mTOR pathways, and cytokine secretion profile using cytotrophoblast-derived HTR8 cells and monocytic U937 cells differentiated to M2 macrophages. In HTR8 cells, ZIKV replication, especially the African strain, was significantly more efficient and faster than DENV or YFV-17D. In macrophages, ZIKV replication was also more efficient, although differences between strains were reduced. Greater activation of the mTORC1 and mTORC2 pathways in HTR8 cells infected with ZIKV than with DENV or YFV-17D was observed. HTR8 cells treated with mTOR inhibitors showed a 20-fold reduction in ZIKV yield, versus 5- and 3.5-fold reductions for DENV and YFV-17D, respectively. Finally, infection with ZIKV, but not DENV or YFV-17D, efficiently inhibited the interferon (IFN) and chemoattractant responses in both cell lines. These results suggest a gating role for the cytotrophoblast cells in favoring entry of ZIKV, but not DENV and YFV-17D, into the placental stroma. IMPORTANCE Zika virus acquisition during pregnancy is associated with severe fetal damage. The Zika virus is related to dengue virus and yellow fever virus, yet fetal damage has not been related to dengue or inadvertent vaccination for yellow fever during pregnancy. Mechanisms used by the Zika virus to cross the placenta need to be deciphered. By comparing parallel infections of Zika virus strains belonging to the African and Asian lineages, dengue virus, and the yellow fever vaccine virus strain YFV-17D in placenta-derived cytotrophoblast cells and differentiated macrophages, evidence was found that Zika virus infections, especially by the African strains, were more efficient in cytotrophoblast cells than dengue virus or yellow fever vaccine virus strain infections. Meanwhile, no significant differences were observed in macrophages. Robust activation of the mTOR signaling pathways and inhibition of the IFN and chemoattractant response appear to be related to the better growth capacity of the Zika viruses in the cytotrophoblast-derived cells.

Liquid crystalline nanoparticles enable a multifunctional approach for topical psoriasis therapy by co-delivering triptolide and siRNAs

Liquid crystalline nanoparticles (LCNs) are an attractive drugs topical delivery system due to the great internal ordering, wide interfacial area and structural similarities with the skin. In this work, LCNs were designed to encapsulate triptolide (TP) and to complex on its surface small interfering RNAs (siRNA) targeting TNF-α and IL-6, aiming at topical co-delivery and regulating multi-targets in psoriasis. These multifunctional LCNs showed appropriate physicochemical properties for topical application, such as a mean size of 150 nm, low polydispersion, TP encapsulation greater than 90% and efficient complexation with siRNA. The internal reverse hexagonal mesostructure of LCNs was confirmed by SAXS while their morphology was assessed by cryo-TEM. In vitro permeation studies revealed an increase of more than 20-fold in the distribution of TP through the porcine epidermis/dermis was achieved after the application of LCN-TP or LCN TP in hydrogel. In cell culture, LCNs showed good compatibility and rapid internalization, which was attributed to macropinocytosis and caveolin-mediated endocytosis. Anti-inflammatory potential of multifunctional LCNs was assessed by reducing of TNF-α, IL-6, IL-1β and TGF-β1 levels in LPS-stimulated macrophages. These results support the hypothesis that the co-delivery of TP and siRNAs by LCNs may be a new strategy for psoriasis topical therapy.

M2 Macrophage-Derived sEV Regulate Pro-Inflammatory CCR2+ Macrophage Subpopulations to Favor Post-AMI Cardiac Repair

Tissue-resident cardiac macrophage subsets mediate cardiac tissue inflammation and repair after acute myocardial infarction (AMI). CC chemokine receptor 2 (CCR2)-expressing macrophages have phenotypical similarities to M1-polarized macrophages, are pro-inflammatory, and recruit CCR2+ circulating monocytes to infarcted myocardium. Small extracellular vesicles (sEV) from CCR2̶ macrophages, which phenotypically resemble M2-polarized macrophages, promote anti-inflammatory activity and cardiac repair. Here, the authors harvested M2 macrophage-derived sEV (M2EV ) from M2-polarized bone-marrow-derived macrophages for intramyocardial injection and recapitulation of sEV-mediated anti-inflammatory activity in ischemic-reperfusion (I/R) injured hearts. Rats and pigs received sham surgery; I/R without treatment; or I/R with autologous M2EV treatment. M2EV rescued cardiac function and attenuated injury markers, infarct size, and scar size. M2EV inhibited CCR2+ macrophage numbers, reduced monocyte-derived CCR2+ macrophage recruitment to infarct sites, induced M1-to-M2 macrophage switching and promoted neovascularization. Analysis of M2EV microRNA content revealed abundant miR-181b-5p, which regulated macrophage glucose uptake, glycolysis, and mitigated mitochondrial reactive oxygen species generation. Functional blockade of miR-181b-5p is detrimental to beneficial M2EV actions and resulted in failure to inhibit CCR2+ macrophage numbers and infarct size. Taken together, this investigation showed that M2EV rescued myocardial function, improved myocardial repair, and regulated CCR2+ macrophages via miR-181b-5p-dependent mechanisms, indicating an option for cell-free therapy for AMI.

Individual Variabilities in Adipose Stem Cell Proliferation, Gene Expression and Responses to Lipopolysaccharide Stimulation

Adipose stem cells (ASCs) are reported to play a role in normal physiology as well as in inflammation and disease. The objective of this work was to elucidate inter-individual differences in growth, gene expression and response to inflammatory stimuli in ASCs from different donors. Human ASC1 (male donor) and ASC2 (female donor) were purchased from Lonza (Walkersville, MD). Cell proliferation was determined by the sulforhodamine B assay. After time-dependent treatment of ASCs with or without bacterial lipopolysaccharide (LPS), marker gene mRNAs for proliferation, steroid hormones, and xenobiotic and immune pathways were determined using RT-PCR, and secreted cytokine levels in media were measured using the Bio-Plex cytokine assay kit. ASCs from both donors expressed androgen receptors but not estrogen receptors. ASC2 had a 2-fold higher proliferation rate and a 6-fold higher level of proliferation marker Ki67 mRNA than ASC1. ASC2 exhibited significantly greater fold induction of TNF-α and CCL2 by LPS compared to ASC1. TNF-α and GM-CSF protein levels were also significantly higher in the LPS-induced ASC2 media, but IL-6 secretion was higher in the LPS-induced ASC1 media. Our findings suggest that inter-individual variability and/or possible sex differences exist in ASCs, which may serve as a key determinant to inflammatory responses of ASCs.

Trichoderma stromaticum spores induce autophagy and downregulate inflammatory mediators in human peripheral blood-derived macrophages

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T. stromaticum biocontrol agent induces autophagy, up-regulating autophagy-related genes

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T. stromaticum modulates expression of micro RNAs that control imune response

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T. stromaticum dow-nregulates expression of TLR2, TLR4, CLEC7A, NLRP3, IL-10, IL1β and IL18

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T. stromaticum modulates ROS production

Trichoderma spp. are usually considered safe and normally used as biocontrol and biofertilization. Safety for human health is evaluated by several tests that detect various effects such as allergenicity, toxicity, infectivity, and pathogenicity. However, they do not evaluate the effects of the agent upon the immune system. The aim of this study was to investigate the interaction between T. stromaticum spores and mammalian cells to assess the immunomodulatory potential of the spores of this fungus. First, mouse macrophage cell line J774 and human macrophages were exposed to fungal spores and analyzed for structural features, through scanning and transmission electron microscopy. Then, various analysis were performed in human macrophages as to their effect in some functional and molecular aspects of the immune system through immunocytochemistry, flow cytometry and gene expression assays. We demonstrated that T. stromaticum spores induces autophagy and autophagy-related genes (ATGs) and downmodulate inflammatory mediators, including ROS, NLRP3, the cytokines IL-1β, IL-18, IL-12 and IL-10, as well as TLR2, TLR4, miR-146b and miR-155, which may lead to an augmented susceptibility to pathogens. Our study shows the extension of damages the biofungicide Tricovab® can cause in the innate immune response. Further studies are necessary to elucidate other innate and adaptive immune responses and, consequently, the safety of this fungus when in contact with humans.

Towards in silico Models of the Inflammatory Response in Bone Fracture Healing

In silico modeling is a powerful strategy to investigate the biological events occurring at tissue, cellular and subcellular level during bone fracture healing. However, most current models do not consider the impact of the inflammatory response on the later stages of bone repair. Indeed, as initiator of the healing process, this early phase can alter the regenerative outcome: if the inflammatory response is too strongly down- or upregulated, the fracture can result in a non-union. This review covers the fundamental information on fracture healing, in silico modeling and experimental validation. It starts with a description of the biology of fracture healing, paying particular attention to the inflammatory phase and its cellular and subcellular components. We then discuss the current state-of-the-art regarding in silico models of the immune response in different tissues as well as the bone regeneration process at the later stages of fracture healing. Combining the aforementioned biological and computational state-of-the-art, continuous, discrete and hybrid modeling technologies are discussed in light of their suitability to capture adequately the multiscale course of the inflammatory phase and its overall role in the healing outcome. Both in the establishment of models as in their validation step, experimental data is required. Hence, this review provides an overview of the different in vitro and in vivo set-ups that can be used to quantify cell- and tissue-scale properties and provide necessary input for model credibility assessment. In conclusion, this review aims to provide hands-on guidance for scientists interested in building in silico models as an additional tool to investigate the critical role of the inflammatory phase in bone regeneration.

M2 macrophage-derived exosomes carry miR-1271-5p to alleviate cardiac injury in acute myocardial infarction through down-regulating SOX6

BACKGROUND

Emerging evidence has indicated that exosomes serve as key regulators in acute myocardial infarction (AMI). This study was determined to investigate the effect of M2 macrophage-derived exosomes (M2-Exos) in AMI and the further mechanism.

METHODS

M2 macrophages were induced and M2-exos were isolated and verified. The AMI mouse model was prepared by ligation of the left anterior descending coronary artery (LAD) and then intravenously injected with the isolated M2-exos. The mouse cardiac function was assessed by echocardiography. Hematoxylin and eosin (HE) staining and TUNEL assay were conducted to examine myocardial lesion and apoptosis in cardiac tissues. The expressions of associated molecules were detected by quantitative real time-PCR (qRT-PCR) and western blot. MTT assay, Flow cytometry and Dual-luciferase reporter assay were carried out to detect cell viability, apoptosis and the interaction of miRNA and the target.

RESULT

M2-Exos could promote cardiac repair in AMI mice. M2-Exos suppressed apoptosis and enhanced viability of hypoxia-induced cardiomyocytes through delivery of miR-1271-5p. SOX6 is a direct target of miR-1271-5p. miR-1271-5p decreased cardiomyocyte apoptosis induced by hypoxia and alleviated cardiac injury in AMI via down-regulating SOX6 expression.

CONCLUSION

We identified that M2-Exos could carry miR-1271-5p to reduce apoptosis of cardiomyocytes and promote cardiac repair via down-regulating SOX6.

Colorectal Cancer and Immunity: From the Wet Lab to Individuals

Simple Summary

Tackling the current dilemma of colorectal cancer resistance to immunotherapy is puzzling and requires novel therapeutic strategies to emerge. However, characterizing the intricate interactions between cancer and immune cells remains difficult because of the complexity and heterogeneity of both compartments. Developing rationales is intellectually feasible but testing them can be experimentally challenging and requires the development of innovative procedures and protocols. In this review, we delineated useful in vitro and in vivo models used for research in the field of immunotherapy that are or could be applied to colorectal cancer management and lead to major breakthroughs in the coming years.

Abstract

Immunotherapy is a very promising field of research and application for treating cancers, in particular for those that are resistant to chemotherapeutics. Immunotherapy aims at enhancing immune cell activation to increase tumor cells recognition and killing. However, some specific cancer types, such as colorectal cancer (CRC), are less responsive than others to the current immunotherapies. Intrinsic resistance can be mediated by the development of an immuno-suppressive environment in CRC. The mutational status of cancer cells also plays a role in this process. CRC can indeed be distinguished in two main subtypes. Microsatellite instable (MSI) tumors show a hyper-mutable phenotype caused by the deficiency of the DNA mismatch repair machinery (MMR) while microsatellite stable (MSS) tumors show a comparatively more “stable” mutational phenotype. Several studies demonstrated that MSI CRC generally display good prognoses for patients and immunotherapy is considered as a therapeutic option for this type of tumors. On the contrary, MSS metastatic CRC usually presents a worse prognosis and is not responsive to immunotherapy. According to this, developing new and innovative models for studying CRC response towards immune targeted therapies has become essential in the last years. Herein, we review the in vitro and in vivo models used for research in the field of immunotherapy applied to colorectal cancer.

The Emerging Role of Galectins and O-GlcNAc Homeostasis in Processes of Cellular Differentiation

Galectins are a family of soluble β-galactoside-binding proteins with diverse glycan-dependent and glycan-independent functions outside and inside the cell. Human cells express twelve out of sixteen recognized mammalian galectin genes and their expression profiles are very different between cell types and tissues. In this review, we summarize the current knowledge on the changes in the expression of individual galectins at mRNA and protein levels in different types of differentiating cells and the effects of recombinant galectins on cellular differentiation. A new model of galectin regulation is proposed considering the change in O-GlcNAc homeostasis between progenitor/stem cells and mature differentiated cells. The recognition of galectins as regulatory factors controlling cell differentiation and self-renewal is essential for developmental and cancer biology to develop innovative strategies for prevention and targeted treatment of proliferative diseases, tissue regeneration, and stem-cell therapy.

Tumor-associated macrophage-derived exosomal microRNA-155-5p stimulates intracranial aneurysm formation and macrophage infiltration

Tumor-associated macrophages (TAMs) play a regulatory role in inflammation and cancer. Exosomes derived from macrophages carrying microRNAs (miRNAs or miRs) are of great value for cancer therapy. Gremlin 1 (GREM1), a member of the antagonists of secreted bone morphogenetic protein, has been implicated in the pathophysiology of multiple diseases or cancers. Based on the predictions of miRNA-mRNA interaction, GREM1 was found to be a target gene of miR-155-5p. Here, the present study aims to explore the role of TAM-derived exosomal miR-155-5p by regulating GREM1 in intracranial aneurysm (IA). The collected results showed that GREM1 was down-regulated in IA, while miR-155-5p was up-regulated in TAM-derived exosomes. Smooth muscle cells (SMCs) were co-cultured with TAMs or exposed to exosomes derived from TAMs transfected with either miR-155-5p mimic or miR-155-5p inhibitor for exploring their roles in proliferation and migration of SMCs in vitro. Accordingly, in vitro experiments showed that TAM-derived exosomal miR-155-5p could promote proliferation and migration of SMCs by targeting GREM1. The effects of TAM-derived exosomal miR-155-5p on IA formation and TAM activation and infiltration by regulation of GREM1 in vivo were measured in IA rats injected with exosomes or those from TAMs transfected with miR-155-5p inhibitor. In vivo experimental results consistently confirmed that TAM-derived exosomes carrying miR-155-5p promoted IA formation and TAM activation and infiltration. In conclusion, TAM-derived exosomal miR-155-5p promotes IA formation via GREM1, which points to miR-155-5p as a possible therapeutic target for IA.

Oleacein and Foam Cell Formation in Human Monocyte-Derived Macrophages: A Potential Strategy Against Early and Advanced Atherosclerotic Lesions

Background: Oleacein is a secoiridoid group polyphenol found mostly in Olea europea L. and Ligustrum vulgare L. (Oleaceae). The aim of the present study was to investigate a potential role of oleacein in prevention of the foam cell formation. Materials and Methods: Oleacein was isolated from Ligustrum vulgare leaves. Human monocyte-derived macrophages were obtained from monocytes cultured with Granulocyte-macrophage colony-stimulating factor (GM-CSF). Then, cells were incubated with 20 μM or 50 μM of oleacein and with oxidized low-density lipoprotein (oxLDL) (50 μg/mL). Visualization of lipid deposition within macrophages was carried out using Oil-Red-O. Expression of CD36, Scavenger receptor A1 (SRA1) and Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) was determined by Reverse transcription polymerase chain reaction (RT-PCR) and by flow cytometry. Apoptosis was determined by flow cytometry using Annexin V assay. STAT3 and Acyl-coenzyme A: cholesterol acyltransferase type 1 (ACAT1) levels were determined by ELISA. P-STAT3, P-JAK1, P-JAK2 expressions were determined by Western blot (WB). Results: Oleacein in dose-dependent manner significantly reduced lipid deposits in macrophages as well as their expression of selected scavenger receptors. The highest decrease of expression was found for CD36 and SRA1 receptors, from above 20% to more than 75% compared to oxLDL and the lowest for LOX-1 receptor, from approx. 8% to approx. 25% compared to oxLDL-stimulated macrophages. Oleacein significantly reduced (2.5-fold) early apoptosis of oxLDL-stimulated macrophages. Moreover, oleacein significantly increased the protein expression of JAK/STAT3 pathway and had no effect on ACAT1 level. Conclusions: Our study demonstrates, for the first time, that oleacein inhibits foam cell formation in human monocyte-derived macrophages and thus can be a valuable tool in the prevention of early and advanced atherosclerotic lesions.

Role of gingival mesenchymal stem cell exosomes in macrophage polarization under inflammatory conditions

OBJECTIVE

Exosomes have been shown to play a strong role in intercellular communication. While GMSCs have been extensively studied, less research exists on exosomes derived from GMSCs, especially on how exosomes affect macrophages. This study aimed to investigate the impact of GMSC-derived exosomes on macrophage polarization and phenotype under inflammatory conditions.

METHODS

Exosomes were isolated from GMSCs-conditioned media by ultracentrifugation (UC) and characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot (WB). In vitro, GMSC-derived exosomes were co-incubated with macrophages for 24 h in the absence or presence of M1 polarizing conditions in the six-well plate. The protein and mRNA expression levels of M1 and M2 macrophage markers were detected and the supernatants were collected for an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Exosomes were successfully isolated from GMSCs. Macrophages co-cultured with exosomes showed significantly decreased levels of the M1 markers Tumor Necrosis Factor-α (TNF-α), Interleukin-12 (IL-12), CD86 and Interleukin-1β (IL-1β). By contrast, M2 marker Interleukin-10 (IL-10) levels moderately increased. Meanwhile, similar results were acquired in the cell culture supernatants.

CONCLUSION

GMSC-derived exosomes may promote M1 macrophage transformation into M2 macrophages, reducing the pro-inflammatory factors produced by M1 macrophages.

HDAC3 Inhibition Promotes Alternative Activation of Macrophages but Does Not Affect Functional Recovery after Spinal Cord Injury

After spinal cord injury (SCI), monocyte derived macrophages play a detrimental role. Histone deacetylases (HDACs) are central epigenetic regulators of macrophage-polarization. We hypothesized that HDAC3 inhibition suppresses the pro-inflammatory macrophage phenotype (M1), promotes the anti-inflammatory phenotype (M2) and improves functional recovery after SCI. Therefore, two inhibitors of HDAC3 were selected, namely scriptaid and RGFP966. The impact on macrophage polarization was studied by investigating the effect on gene and protein expression of selected M1 and M2 markers. We show that scriptaid differentially influences M1 and M2 markers. It increases CD86 and iNOS gene expression and decreases GPR18, CD38, FPR2 and Arg-1 gene expression as well as the production of IL-6 and NO. RGFP966 primarily increased the expression of the M2 markers Arg-1 and Ym1 and reduced the production of IL-6 (M1). RGFP966 and scriptaid reduced the formation of foamy macrophages. Finally, to investigate the impact of HDAC3 inhibition on functional recovery after SCI, we studied the effects of RGFP966 and scriptaid in an in vivo T-cut hemisection SCI model. Histological analyses were performed on spinal cord sections to determine lesion size and astrogliosis, demyelinated area and selected infiltrating immune cells. RGFP966 and scriptaid did not affect functional recovery or histopathological outcome after SCI. In conclusion, these results indicate that specific HDAC3 inhibition with RGFP966 promotes alternative activation of macrophages and reduces the formation of foamy macrophages, but does not lead to a better functional recovery after SCI.

NLRP3 regulates macrophage M2 polarization through up-regulation of IL-4 in asthma

Activation of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome received substantial attention recently in inflammatory diseases. Macrophages contribute to allergic inflammation in asthma. The present study was aimed to investigate the effect of NLRP3 inflammasome on the polarization of macrophages. We utilized human primary monocytes and monocyte-derived macrophages to study the expression of NLRP3 inflammasome components (NLRP3, apoptosis-associated specklike protein, and caspase-1) and its downstream cytokine interleukin-1β (IL-1β). By gain- or loss-of-function assays, we next explored the effects of NLRP3 inflammasome on M1/M2 polarization and secretion of IL-4, interferon-γ, tumor necrosis factor-α, and IL-1β. The results showed increased numbers of M2 cells in asthma. And NLRP3 inflammasome was activated and involved in the inflammation of asthma. Furthermore, silence of NLRP3 down-regulated IL-4 secretion and up-regulated M1/M2. In contrast, overexpression of NLRP3 increased IL-4 and decreased M1/M2. As expected, IL-4 was involved in NLRP3-mediated down-regulation of Ml/M2 ratio. Moreover, NLRP3 interacted with IRF4 and was required for optimal IRF4-dependent IL-4 transcription. Subsequently, deficiency of NLRP3 in ovalbumin-induced allergic asthmatic mice impaired lung inflammation and up-regulated M1/M2, and diminished IL-4 in bronchoalveolar lavage fluid. Collectively, we demonstrated here that activation of NLRP3 was engaged in the promotion of asthma. NLRP3, but not the inflammasome adaptor ASC or caspase-1, promoted the polarization of M2 macrophages through up-regulating the expression of IL-4, thereby contributing to its regulation of asthma.