The Immunosuppressive Receptor CD32b Regulation of Macrophage Polarization and Its Implications in Tumor Progression.

Macrophages, pivotal components of the immune system, orchestrate host defense mechanisms in humans and mammals. Their polarization into classically activated macrophages (CAMs or M1) and alternatively activated macrophages (AAMs or M2) dictates distinct functional roles in immunity and tissue homeostasis. While the negative regulatory role of CD32b within the FC gamma receptor (FCγR) family is recognized across various immune cell types, its influence on macrophage polarization remains elusive. This study aimed to elucidate the regulatory role of CD32b in macrophage polarization and discern the differential expression markers between the M1 and M2 phenotypes following CD32b siRNA transfection. The results revealed a decrease in the CD32b levels in lipopolysaccharide (LPS)-treated M1 and an increase in interleukin-4 (IL-4)-treated M2 macrophages, as observed in macrophage Raw264.7 cells. Furthermore, CD32b siRNA transfection significantly downregulated the M2 markers (IL-10, VEGF, Arg-1, and STAT6), while upregulating the M1 markers (IL-6, NF-κB, NOS2, and STAT1) in the Raw264.7 cells. Similar findings were recapitulated in macrophage-rich adherent cells isolated from mouse spleens. Additionally, the cytopathological analysis of pleural effusions and ascitic fluids from patients with cancer revealed a positive correlation between advanced tumor stages, metastasis, and elevated CD32b levels. In conclusion, this study highlights the regulatory influence of CD32b in suppressing M1 expression and promoting M2 polarization. Moreover, heightened M2 activation and CD32b levels appear to correlate with tumor progression. A targeted CD32b blockade may serve as a novel therapeutic strategy to inhibit M2 macrophage polarization and is promising for anti-tumor intervention.

M2 Macrophages Upregulated by Allergen Exposure in Seasonal Allergic Rhinitis.

INTRODUCTION: Macrophages play a central role in balancing the immune response by switching phenotypes between the M1 and M2 profiles according to a delicate equilibrium. Based on a previous clinical trial (NCT03649139), this study aimed to evaluate the change in M2 macrophages during pollen exposure in seasonal allergic rhinitis (SAR). METHODS: Nasal symptom scores were recorded. Peripheral M2 macrophages were investigated according to cell surface markers, and M2-associated cytokine/chemokine release in serum and nasal secretion were assessed. In vitro pollen stimulation tests were performed, and polarized macrophage subsets were analyzed by flow cytometry. RESULTS: Compared to baseline, the percentage of peripheral CD163+ M2 macrophages in CD14+ monocytes increased during the pollen season (p < 0.001) and at the end of treatment (p = 0.004) in the SLIT group. The percentage of CD206+CD86- M2 cells in M2 macrophages during the pollen season was higher than that at baseline and at the end of SLIT. On the other hand, the percentage of CD206-CD86+ M2 cells in M2 macrophages significantly increased at the end of treatment in the SLIT group compared to baseline (p = 0.049), the peak pollen period (p = 0.017), and the placebo group (p = 0.0023). M2-associated chemokines CCL26 and YKL-40 were significantly increased during the pollen season in the SLIT group and remained higher at the end of SLIT than at baseline. Correspondingly, in vitro study demonstrated that Artemisia annua promoted M2 macrophage polarization in pollen-induced AR patients. CONCLUSION: Significant M2 macrophage polarization was promoted when patients with SAR were exposed to the allergen, either naturally exposed in pollen seasons or subjectively continuously exposed during the course of SLIT.

Mizoribine halts kidney fibrosis in childhood IgA nephropathy: association with modulation of M2-type macrophages.

BACKGROUND: The immunosuppressant mizoribine (Miz) can reduce progression of childhood IgA nephropathy (IgAN). This study examined whether Miz affects CD163+ M2-type macrophages which are associated with kidney fibrosis in childhood IgAN. METHODS: A retrospective cohort of 90 children with IgAN were divided into groups treated with prednisolone (PSL) alone (P group; n = 42) or PSL plus Miz (PM group; n = 48) for a 2-year period. Normal human monocyte-derived macrophages were stimulated with dexamethasone (Dex), or Dex plus Miz, and analyzed by DNA microarray. RESULTS: Clinical and histological findings at first biopsy were equivalent between patients entering the P and PM groups. Both treatments improved proteinuria and haematuria, and maintained normal kidney function over the 2-year course. The P group exhibited increased mesangial matrix expansion, increased glomerular segmental or global sclerosis, and increased interstitial fibrosis at 2-year biopsy; however, the PM group showed no progression of kidney fibrosis. These protective effects were associated with reduced numbers of glomerular and interstitial CD163+ macrophages in the PM versus P group. In cultured human macrophages, Dex induced upregulation of cytokines and growth factors, which was prevented by Miz. Miz also inhibited Dex-induced expression of CD300E, an activating receptor which can prevent monocyte apoptosis. CD300e expression by CD163+ macrophages was evident in the P group, which was reduced by Miz treatment. CONCLUSION: Miz halted the progression of kidney fibrosis in PSL-treated pediatric IgAN. This was associated with reduced CD163+ and CD163+CD300e+ macrophage populations, plus in vitro findings that Miz can suppress steroid-induced macrophage expression of pro-fibrotic molecules. A higher resolution version of the Graphical abstract is available as Supplementary information.

Trichinella-induced immunomodulation: Another tale of helminth success.

Trichinella spiralis is a unique parasite in that both the adults and larvae survive in two different intracellular niches in the same host. The immune response, albeit intense, is highly modulated to ensure the survival of both the host and the parasite. It is skewed to T helper 2 and regulatory arms. Diverse cells from both the innate and adaptive compartments of immunity, including dendritic cells, T regulatory cells, and alternatively activated macrophages are thought to mediate such immunomodulation. The parasite has also an outstanding ability to evade the immune system by several elaborate processes. The molecules derived from the parasites including Trichinella, particularly the components of the excretory-secretory products, are being continually identified and explored for the potential of ameliorating the immunopathology in animal models of diverse inflammatory and autoimmune human diseases. Herein we discuss the various aspects of Trichinella-induced immunomodulation with a special reference to the practical implications of the immune system manipulation in alleviating or possibly curing human diseases.

Developing a clinical grade human adipose decellularized biomaterial.

While tissue engineering investigators have appreciated adipose tissue as a repository of stromal/stem cells, they are only now beginning to see its value as a decellularized tissue resource. Independent academic investigators have successfully extracted lipid, genomic DNA and proteins from human fat to create a decellularized extracellular matrix enriched in collagen, glycoproteins, and proteoglycans. Pre-clinical studies have validated its compatibility with stromal/stem cells and its ability to support adipogenesis in vitro and in vivo in both small (murine) and large (porcine) subcutaneous implant models. Furthermore, Phase I safety clinical trials have injected decellularized human adipose tissue scaffolds in human volunteers without incident for periods of up to 127 days. This commentary takes an opinionated look at the under-appreciated but potential benefits of obesity as an increasingly available biomaterial resource.

Polarization of infiltrating macrophages in the outer annulus fibrosus layer associated with the process of intervertebral disc degeneration and neural ingrowth in the human cervical spine.

BACKGROUND CONTEXT: As no infiltrating macrophages exist in healthy discs, understanding the role of infiltrating macrophages including their polarity (M1 and M2 phenotypes) in intervertebral discs (IVDs) is important in the assessment of the pathomechanisms of disc degeneration. PURPOSE: To determine the relationship between infiltrating macrophage polarization and the progression of human cervical IVD degeneration. STUDY DESIGN: Histopathological study using harvested human cervical IVDs. METHODS: IVDs collected during anterior cervical decompression from 60 patients were subjected to immunostaining and immunoblotting. The samples were classified as type 0-3 according to the percentage of CD16- and CD206-positive cells to CD68-positive cells in the outer annulus fibrosus layer. The number of vessels and nerve fibers and the severity of chronic inflammation with a focus on inflammatory cell infiltration, fibrosis, and capillary proliferation were also assessed. RESULTS: The number of CD16-positive cells was the highest in type 2 IVDs, and was suppressed following the infiltration of CD206-positive cells. The degree of chronic inflammation was significantly higher in type 2 and type 3 IVDs, and the number of nerve fibers was significantly higher in type 3 IVDs. The endothelial cells of small vessels were positive for nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 expression. Staining for tropomyosin receptor kinase (Trk)-A, Trk-B, and Trk-C was positive in aberrant fibers. In immunoblot analysis, the expression levels of these neurotrophic factors and receptors were significantly higher in type 2 and 3 IVDs. CONCLUSIONS: The polarity of macrophages around newly developed microvasculature might be altered with cervical IVD degeneration. A higher number of infiltrating M1 macrophages around the vessels was associated with chronic inflammation; however, their number got suppressed following the infiltration of M2 macrophages. The expression of neurotrophins in the capillaries of small vessels might contribute to neural ingrowth into degenerated IVDs. CLINICAL SIGNIFICANCE: Clarifying macrophages polarity change around new microvasculature associated with progression of IVD degeneration could enhance our understanding of the underlying mechanisms of neural ingrowth into degenerated IVDs and lead to development of a novel therapeutic target for prevention of IVD.

Interleukin-5-induced eosinophil population improves cardiac function after myocardial infarction.

AIMS: Interleukin (IL)-5 mediates the development of eosinophils (EOS) that are essential for tissue post-injury repair. It remains unknown whether IL-5 plays a role in heart repair after myocardial infarction (MI). This study aims to test whether IL-5-induced EOS population promotes the healing and repair process post-MI and to reveal the underlying mechanisms. METHODS AND RESULTS: MI was induced by permanent ligation of the left anterior descending coronary artery in wild-type C57BL/6 mice. Western blot and real-time polymerase chain reaction revealed elevated expression of IL-5 in the heart at 5 days post-MI. Immunohistostaining indicated that IL-5 was secreted mainly from macrophages and CD127+ cells in the setting of experimental MI. External supply of recombinant mouse IL-5 (20 min, 1 day, and 2 days after MI surgery) reduced the infarct size and increased ejection fraction and angiogenesis in the border zone. A significant expansion of EOS was detected in both the peripheral blood and infarcted myocardium after IL-5 administration. Pharmacological depletion of EOS by TRFK5 pretreatment muted the beneficial effects of IL-5 in MI mice. Mechanistic studies demonstrated that IL-5 increased the accumulation of CD206+ macrophages in infarcted myocardium at 7 days post-MI. In vitro co-culture experiments showed that EOS shifted bone marrow-derived macrophage polarization towards the CD206+ phenotypes. This activity of EOS was abolished by IL-4 neutralizing antibody, but not IL-10 or IL-13 neutralization. Western blot analyses demonstrated that EOS promoted the macrophage downstream signal transducer and activator of transcription 6 (STAT6) phosphorylation. CONCLUSION: IL-5 facilitates the recovery of cardiac dysfunction post-MI by promoting EOS accumulation and subsequent CD206+ macrophage polarization via the IL-4/STAT6 axis.

Meta-Inflammation and Metabolic Reprogramming of Macrophages in Diabetes and Obesity: The Importance of Metabolites.

Diabetes mellitus type II and obesity are two important causes of death in modern society. They are characterized by low-grade chronic inflammation and metabolic dysfunction (meta-inflammation), which is observed in all tissues involved in energy homeostasis. A substantial body of evidence has established an important role for macrophages in these tissues during the development of diabetes mellitus type II and obesity. Macrophages can activate into specialized subsets by cues from their microenvironment to handle a variety of tasks. Many different subsets have been described and in diabetes/obesity literature two main classifications are widely used that are also defined by differential metabolic reprogramming taking place to fuel their main functions. Classically activated, pro-inflammatory macrophages (often referred to as M1) favor glycolysis, produce lactate instead of metabolizing pyruvate to acetyl-CoA, and have a tricarboxylic acid cycle that is interrupted at two points. Alternatively activated macrophages (often referred to as M2) mainly use beta-oxidation of fatty acids and oxidative phosphorylation to create energy-rich molecules such as ATP and are involved in tissue repair and downregulation of inflammation. Since diabetes type II and obesity are characterized by metabolic alterations at the organism level, these alterations may also induce changes in macrophage metabolism resulting in unique macrophage activation patterns in diabetes and obesity. This review describes the interactions between metabolic reprogramming of macrophages and conditions of metabolic dysfunction like diabetes and obesity. We also focus on different possibilities of measuring a range of metabolites intra-and extracellularly in a precise and comprehensive manner to better identify the subsets of polarized macrophages that are unique to diabetes and obesity. Advantages and disadvantages of the currently most widely used metabolite analysis approaches are highlighted. We further describe how their combined use may serve to provide a comprehensive overview of the metabolic changes that take place intracellularly during macrophage activation in conditions like diabetes and obesity.

IL-33-induced metabolic reprogramming controls the differentiation of alternatively activated macrophages and the resolution of inflammation.

Alternatively activated macrophages (AAMs) contribute to the resolution of inflammation and tissue repair. However, molecular pathways that govern their differentiation have remained incompletely understood. Here, we show that uncoupling protein-2-mediated mitochondrial reprogramming and the transcription factor GATA3 specifically controlled the differentiation of pro-resolving AAMs in response to the alarmin IL-33. In macrophages, IL-33 sequentially triggered early expression of pro-inflammatory genes and subsequent differentiation into AAMs. Global analysis of underlying signaling events revealed that IL-33 induced a rapid metabolic rewiring of macrophages that involved uncoupling of the respiratory chain and increased production of the metabolite itaconate, which subsequently triggered a GATA3-mediated AAM polarization. Conditional deletion of GATA3 in mononuclear phagocytes accordingly abrogated IL-33-induced differentiation of AAMs and tissue repair upon muscle injury. Our data thus identify an IL-4-independent and GATA3-dependent pathway in mononuclear phagocytes that results from mitochondrial rewiring and controls macrophage plasticity and the resolution of inflammation.

Protective effects of recombinant 53-kDa protein of Trichinella spiralis on acute lung injury in mice via alleviating lung pyroptosis by promoting M2 macrophage polarization.

Trichinella spiralis represents an effective treatment for autoimmune and inflammatory diseases. The effects of recombinant T. spiralis (TS) 53-kDa protein (rTsP53) on acute lung injury (ALI) remain unclear. Here, mice were divided randomly into a control group, LPS group, and rTsP53 + LPS group. ALI was induced in BALB/c mice by LPS (10 mg/kg) injected via the tail vein. rTsP53 (200 µl; 0.4 µg/µl) was injected subcutaneously three times at an interval of 5 d before inducing ALI in the rTsP53+LPS group. Lung pathological score, the ratio and markers of classic activated macrophages (M1) and alternatively activated macrophages (M2), cytokine profiles in alveolar lavage fluid, and pyroptosis protein expression in lung tissue were investigated. RTsP53 decreased lung pathological score. Furthermore, rTsP53 suppressed inflammation by increasing IL-4, IL-10, and IL-13. There was an increase in alveolar M2 macrophage numbers, with an increase in CD206 and arginase-1-positive cells and a decrease in alveolar M1 markers such as CD197 and iNOS. In addition, the polarization of M2 macrophages induced by rTsP53 treatment could alleviate ALI by suppressing lung pyroptosis. RTsP53 was identified as a potential agent for treating LPS-induced ALI via alleviating lung pyroptosis by promoting M2 macrophage polarization.

Steroid treatment promotes an M2 anti-inflammatory macrophage phenotype in childhood lupus nephritis.

BACKGROUND: M1-type proinflammatory macrophages (MΦ) promote glomerular injury in lupus nephritis (LN). However, whether this phenotype is altered by steroid therapy is unclear. Therefore, we investigated the effect of steroid treatment on MΦ phenotype in LN. METHODS: Patients with LN (7-18 years old) were divided into 2 groups: those with no treatment (N) before biopsy (n = 17) and those who underwent steroid (S) treatment (3-73 days) before biopsy (n = 15). MΦ number and phenotype were assessed by immunofluorescence. In vitro studies used monocyte-derived MΦ from healthy volunteers. RESULTS: Age at biopsy, urine findings, and kidney function (eGFR) were comparable between the two groups. Biopsies in N group had higher levels of active lesions such as endocapillary hypercellularity, necrosis, and cellular crescent formation (p < 0.05). The total CD68+ MΦ infiltrate was comparable between N and S groups. However, N group had more M1 MΦ (CD68+ CD86+ cells) (p < 0.05) and fewer M2 MΦ (CD68+ CD163+ cells) (p < 0.05), giving a 6-fold increase in the M2/M1 ratio in S vs. N groups. Dexamethasone treatment of cultured MΦ induced upregulation of CD163 expression, increased production of anti-inflammatory (IL-10, IL-19) and profibrotic factors (FGF-22, PDGF), and upregulated the scavenger receptor, stabilin-1. Upregulation of stabilin-1 in CD163+ M2 MΦ was confirmed in biopsies from S group. CONCLUSIONS: Initial steroid treatment induces MΦ phenotypic change from proinflammatory M1 to anti-inflammatory or profibrotic M2 in LN with acute/active lesions. Although steroid treatment is effective for resolution of M1-medated injury, promotion of fibrotic lesions via M2 MΦ is a potential downside of steroid single therapy in LN.

Monocyte and Macrophage-Mediated Pathology and Protective Immunity During Schistosomiasis.

Infection by Schistosoma parasites culminates in a chronic granulomatous disease characterized by intense tissue fibrosis. Along the course of schistosomiasis, diverse leukocytes are recruited for inflammatory foci. Innate immune cell accumulation in Th2-driven granulomas around Schistosoma eggs is associated with increased collagen deposition, while monocytes and macrophages exert critical roles during this process. Monocytes are recruited to damaged tissues from blood, produce TGF-ß and differentiate into monocyte-derived macrophages (MDMs), which become alternatively activated by IL-4/IL-13 signaling via IL-4Rα (AAMs). AAMs are key players of tissue repair and wound healing in response to Schistosoma infection. Alternative activation of macrophages is characterized by the activation of STAT6 that coordinates the transcription of Arg1, Chi3l3, Relma, and Mrc1. In addition to these markers, monocyte-derived AAMs also express Raldh2 and Pdl2. AAMs produce high levels of IL-10 and TGF-ß that minimizes tissue damage caused by Schistosoma egg accumulation in tissues. In this review, we provide support to previous findings about the host response to Schistosoma infection reusing public transcriptome data. Importantly, we discuss the role of monocytes and macrophages with emphasis on the mechanisms of alternative macrophage activation during schistosomiasis.

Depletion of microRNA-451 in response to allergen exposure accentuates asthmatic inflammation by regulating Sirtuin2.

The incidence of asthma has increased from 5.5% to near 8% of the population, which is a major health concern. The hallmarks of asthma include eosinophilic airway inflammation that is associated with chronic airway remodeling. Allergic airway inflammation is characterized by a complex interplay of resident and inflammatory cells. MicroRNAs (miRNAs) are small noncoding RNAs that function as posttranscriptional modulators of gene expression. However, the role of miRNAs, specifically miR-451, in the regulation of allergic airway inflammation is unexplored. Our previous findings showed that oxidant stress regulates miR-451 gene expression in macrophages during an inflammatory process. In this paper, we examined the role of miR-451 in regulating macrophage phenotype using an experimental poly-allergenic murine model of allergic airway inflammation. We found that miR-451 contributes to the allergic induction of CCL17 in the lung and plays a key role in proasthmatic macrophage activation. Remarkably, administration of a Sirtuin 2 (Sirt2) inhibitor diminished alternate macrophage activation and markedly abrogated triple-allergen [dust mite, ragweed, Aspergillus fumigatus (DRA)]-induced lung inflammation. These data demonstrate a role for miR-451 in modulating allergic inflammation by influencing allergen-mediated macrophages phenotype.

IL33 attenuates ventricular remodeling after myocardial infarction through inducing alternatively activated macrophages ethical standards statement.

Interleukin 33 (IL33) has been found to be cardioprotective on various cardiovascular pathologies. However, it is not clear whether IL33 may inhibit myocardial infarction-related ventricular remodeling through inducing macrophage polarization. The objective of present study is to assess whether IL33 can improve ventricular remodeling after myocardial infarction by inducing macrophage polarization. In this study, the direct influence of IL33 on the polarization of macrophages and its mechanism in vitro were investigated. The potential protective effects of IL33 on acute and chronic myocardial infarction (MI) in vivo as well as its underlying mechanism through macrophage polarization were also determined. We found that IL33 significantly enhanced M2 macrophage and decreased the proportion of M1 macrophage. Importantly, IL33 induced M2 macrophage polarization by activating the JAK/STAT signaling pathway. In vivo, IL33 weaken the inflammatory level and myocardial apoptosis after MI and improved the systolic and diastolic function of the heart. Furthermore, IL33 significantly reduced infarct area and prevented the progression of fibrosis by inducing M2 macrophage polarization. The protective effects of IL33 were suppressed by JAK/STAT signaling pathway inhibitor. Our findings highlighted that IL33 not only reduced the early inflammatory response and inhibited myocardial apoptosis, but also increased the number of M2 macrophage in the infarcted area, significantly reduced infarct area and prevented the progression of fibrosis by activating JAK/STAT pathway. Therefore, IL33 may be a novel cardiac protective cytokine for myocardial infarction.

Effect of protein kinase C β inhibitor on renal ischemia-reperfusion injury and expression level of macrophage subtypes in rat models / 器官移植

Objective To investigate the effect of protein kinase C (PKC) β inhibitor on the renal ischemia-reperfusion injury (RIRI) in rat models and detect the expression level of macrophage subtypes. Methods Eighteen healthy SD male rats were randomly divided into the Sham operation group (Sham group, n=6), RIRI group (n=6), PKCβ inhibitor +RIRI group (Inhibitor+RIRI group, n=6). Serum and left renal tissue samples were collected at postoperative 24 h. The contents of serum creatinine (Scr) and blood urea nitrogen (BUN) were detected by automatic biochemical analyzer. The infiltration of inflammatory cells and pathological injury in the renal tissues were observed by hematoxylin-eosin (HE) staining. The expression levels of CD68, inducible nitric oxide synthase (iNOS) and CD206 proteins in the renal tissues of rats in each group were assessed by immunohistochemistry and Western blot. Results The contents of serum Scr and BUN in the RIRI group were significantly higher than those in the Sham group (both P < 0.05). The contents of serum Scr and BUN in the Inhibitor+RIRI group were considerably lower than those in the RIRI group (both P < 0.05). No obvious renal injury was noted in the Sham group, whereas renal inflammatory cell infiltration and renal tubular structural damage were observed in the RIRI group. The renal inflammatory cell infiltration and renal tubular structural damage in the Inhibitor+RIRI group was slighter than that in the RIRI group. The protein expression levels of CD68, iNOS and CD206 in the renal tissue of rats in the RIRI group were significantly higher than those in the Sham group (all P < 0.05). The protein expression levels of CD68 and iNOS in the Inhibitor+RIRI group were remarkably lower than those in the RIRI group (all P < 0.05). The expression level of CD206 protein in the Inhibitor+RIRI group was significantly higher than that in the RIRI group (P < 0.05). Conclusions PKC β inhibitor can alleviate the RIRI in rat models to certain extent, which may be correlated with the role of PKC β inhibitor in mitigating inflammatory cell infiltration in ischemic renal tissues and promoting the expression of alternatively activated macrophage

Protostemonine attenuates alternatively activated macrophage and DRA-induced asthmatic inflammation.

Asthma is one of the most common pulmonary diseases that threatens human life because of lack of effective medicines. Protostemonine (PSN), an active alkaloid extracted from the roots of Stemona sesslifolia, has anti-inflammatory effects on acute lung injury and acute liver failure. However, it has not been defined whether PSN alleviates asthmatic inflammation. Here, we reported that PSN inhibits pulmonary eosinophil infiltration, goblet cell hyperplasia, mucus secretion, IgE and Th2 cytokine (IL-4, IL-5, IL-13 and IL-33) production by using DRA (dust mites, ragweed and aspergillus)-induced murine asthma model. Moreover, PSN also attenuated the expression of Arginase-1 (Arg-1), Ym-1 and Fizz-1, markers of AAM (alternatively activated macrophage) polarization, in lung tissues. In addition, PSN attenuated IL-4-induced expression of Arg-1, Ym-1 and Fizz-1 in bone marrow derived macrophages (BMDMs). Treatment with PSN decreased IL-4-induced STAT6 phosphorylation, KLF4 and IRF4 expression in BMDMs. Collectively, our results indicated that PSN ameliorates AAM polarization and asthmatic inflammation and might be a potential agent for treating asthma.

Emodin alleviates alternatively activated macrophage and asthmatic airway inflammation in a murine asthma model.

Alternatively activated macrophages (AAMs) are not only associated with asthma but also lead to asthmatic airway inflammation and remodeling. Inhibition of AAMs is an alternative therapeutic strategy for treating asthma. In this study we investigated whether emodin (1,3,8-trihydroxy-6-methylanthraquinone), isolated from the rhizome of Rheum palmatum, alleviated asthmatic airway inflammation and reduced AAM polarization in a murine asthma model. Mice were sensitized with a triple allergen mix containing dust mite, ragweed and aspergillus (DRA). In mice with DRA-induced asthma, asthmatic inflammation was significantly enhanced. Intraperitoneal injection of emodin (20 mg·kg-1·d-1, ip) 1 h prior to DRA challenge on days 12-14 significantly decreased pulmonary eosinophil and lymphocyte infiltration, mucus secretion and serum IgE production, as well as IL-4 and IL-5 production in bronchoalveolar lavage fluid. In response to emodin treatment, activated markers of AAM Ym-1, Fizz-1 and arginase-1 in the lung tissues were remarkably decreased. In mouse bone marrow-derived macrophages (BMDMs) in vitro, emodin (2-50 µmol/L) dose-dependently inhibited IL-4-induced AAM polarization and STAT6 phosphorylation. Collectively, our results suggest that emodin effectively ameliorates asthmatic airway inflammation and AAM polarization, and it may therefore become a potential agent for the treatment of asthma.

Promotion of neurological recovery in rat spinal cord injury by mesenchymal stem cells loaded on nerve-guided collagen scaffold through increasing alternatively activated macrophage polarization.

Mesenchymal stem cells (MSCs) are characterized by multidifferentiation and immunoregulatory potential and have been used in the treatment of spinal cord injury (SCI), but direct transplantation may limit effectiveness due to their quick diffusion. The role of macrophages in healing is being increasingly recognized because of their ability to polarize into pro- and anti-inflammatory phenotypes. In the present study, nerve-guide collagen scaffold (CS) combined with rat MSCs was developed. After CS was confirmed to minimize MSC distribution in vivo by positron emission tomography (PET) imaging, the repair capacity of combined implantation of CS and MSCs and the effect on classically activated macrophage/alternatively activated macrophage (M2) polarization was assessed in a hemisected SCI rat model. In vivo studies showed that, compared to the control group, the rats in the combined implantation group exhibited more significant recovery of nerve function evidenced by the 21-point Basso-Beattie-Bresnahan score and footprint analysis. Morphological staining showed less macrophage infiltration, apoptosis and glial fibrillary acidic protein, and more neurofilaments, and the fibres were guided to grow through the implant. More M2 were observed in the combined implantation group. The data suggest that the combined implantation could support MSCs to play a protective role of SCI, not only through inhibiting chronic scar formation and providing linear guidance for the nerve, but also benefitting M2 polarization to form an anti-inflammatory environment. Thus, the combination of biomaterial and MSCs might be a prominent therapeutic treatment for SCI. Copyright © 2016 John Wiley & Sons, Ltd.

All-Trans Retinoic Acid Promotes an M1- to M2-Phenotype Shift and Inhibits Macrophage-Mediated Immunity to Leishmania major.

As key cells, able to host and kill Leishmania parasites, inflammatory monocytes/macrophages are potential vaccine and therapeutic targets to improve immune responses in Leishmaniasis. Macrophage phenotypes range from M1, which express NO-mediated microbial killing, to M2 macrophages that might help infection. Resistance to Leishmaniasis depends on Leishmania species, mouse strain, and both innate and adaptive immunity. C57BL/6 (B6) mice are resistant and control infection, whereas Leishmania parasites thrive in BALB/c mice, which are susceptible to develop cutaneous lesions in the course of infection with Leishmania major, but not upon infection with Leishmania braziliensis. Here, we investigated whether a deficit in early maturation of inflammatory monocytes into macrophages in BALB/c mice underlies increased susceptibility to L. major versus L. braziliensis parasites. We show that, after infection with L. braziliensis, monocytes are recruited to peritoneum, differentiate into macrophages, and develop an M1 phenotype able to produce proinflammatory cytokines in both B6 and BALB/c mice. Nonetheless, more mature macrophages from B6 mice expressed inducible NO synthase (iNOS) and higher NO production in response to L. braziliensis parasites, whereas BALB/c mice developed macrophages expressing an incomplete M1 phenotype. By contrast, monocytes recruited upon L. major infection gave rise to immature macrophages that failed to induce an M1 response in BALB/c mice. Overall, these results are consistent with the idea that resistance to Leishmania infection correlates with improved maturation of macrophages in a mouse-strain and Leishmania-species dependent manner. All-trans retinoic acid (ATRA) has been proposed as a therapy to differentiate immature myeloid cells into macrophages and help immunity to tumors. To prompt monocyte to macrophage maturation upon L. major infection, we treated B6 and BALB/c mice with ATRA. Unexpectedly, treatment with ATRA reduced proinflammatory cytokines, iNOS expression, and parasite killing by macrophages. Moreover, ATRA promoted an M1 to M2 transition in bone marrow-derived macrophages from both strains. Therefore, ATRA uncouples macrophage maturation and development of M1 phenotype and downmodulates macrophage-mediated immunity to L. major parasites. Cautions should be taken for the therapeutic use of ATRA, by considering direct effects on innate immunity to intracellular pathogens.

Calcitonin gene-related peptide exerts anti-inflammatory property through regulating murine macrophages polarization in vitro.

Acute lung injury (ALI) is a condition resulting from direct or indirect lung injury associated with high mortality and morbidity. The phenotype of macrophages in lung contributes to the pathological progress of ALI. Calcitonin gene-related peptide (CGRP) is one of the most abundant neuropeptides in lung, and attenuates lipopolysaccharide (LPS)-induced ALI in rats. However, the exact effect of CGRP on the activation of macrophages remains unknown. Here we investigate the effect of CGRP on the macrophages activation and inflammation in murine macrophages in vitro. We found that LPS increased the expression of CGRP in a LPS-induced ALI murine model and LPS-stimulated murine macrophages. Although CGRP didn't alter the expression of tumor necrosis factor-α (a marker of pro-inflammatory phenotype of macrophages, M1 macrophages) or Arginase 1 (Arg1, a marker of M2 macrophages) in non-differentiated macrophages, CGRP significantly reduced the NLRP3 and pro-IL-1ß mRNA expression induced by LPS, as well as NLRP3 protein and IL-1ß secretion induced by LPS+ATP in macrophages in vitro. On the other hand, CGRP dramatically enhanced the Arg1 expression and activity induced by IL-4 in the time- and dose-dependent manners. CGRP also promoted the expression of markers of M2 macrophages (IL-10, Fizz1 and Mrc1) induced by IL-4 in murine macrophages. These effects of CGRP were also observed in primary murine peritoneal macrophages. In addition, we found that CGRP regulated macrophages polarization partially through calmodulin, PKC and PKA pathways. Specifically, CGRP could inhibit the degradation of I-κB induced by LPS, and enhance the phosphorylation of STAT6 induced by IL-4 in macrophages. In conclusion, our results indicate that CGRP regulates macrophage polarization and inhibits inflammation in murine macrophages.