Alternative Macrophage Research Articles

Investigation of the interplay between plasma lipids and macrophage polarization in small oral squamous cell carcinomas with different outcome: A pilot study of 17 cases.

Growing evidence suggests a correlation of alternative polarization of macrophages (M2) with a bad outcome of oral cancer. Macrophage polarization plays a significant role in the progression of hyperlipidemia and atherosclerosis, being influenced from plasma cholesterol. On the other hand plasma lipids have been studied epidemiologically as risk factors in carcinogenesis. Goal of our pilot study was the investigation of a possible association of plasma lipids with tumor outcome through their potential influence on macrophage polarization. 17 patients with small pN0 OSCC with different clinical outcome, treated operatively without postoperative R(C)T constituted our patient collective. Plasma lipids (total cholesterol and triglycerides) were studied in relation to macrophage polarization (determined through the expression of CD68, CD11c, CD163 and MRC1 antibodies) and tumor outcome. Patients with pathological chronic course of either plasma cholesterol or triglycerides demonstrated an increased infiltration with alternatively polarized macrophages in their specimens. Patients with pathological chronic course of plasma cholesterol showed moreover a bad tumor outcome. A role of plasma lipids in the tumor outcome via alternative macrophage polarization could be assumed. A larger prospective study is needed to confirm our preliminary results.

Abstract 12656: Phosphodiesterase 4 (PDE4) Inhibition Induces Weight Loss and Improves Insulin Resistance via cAMP-EPAC-AMPK Mediated Reprogramming of Macrophages

Objective: Recent evidence suggests an important role for cAMP-dependent pathways in modulation of innate immune function. Phosphodiesterase 4 (PDE4) is widely expressed in innate immune cells such as macrophages/dendritic cells with potent anti-inflammatory effects on pharmacologic inhibition of the enzyme. We investigated the importance of PDE4 in diet-induced obesity (DIO) and hypothesized that PDE4 inhibition will improve insulin sensitivity and reduce inflammation. Methods and Results: PDE4 was upregulated in both visceral and subcutaneous (SubQ) white adipose tissue (WAT) in DIO mice (12 weeks of high-fat diet, HFD, 60% fat) compared to normal-chow diet (NCD) mice (↑4∼10-folds, p<0.01). The degree of expression was correlated with macrophage infiltration in stromal vascular fraction from WAT (CD11b + F4/80 + cells, r=0.56, p<0.05). Treatment with Roflumilast (3mg/kg/day), a high affinity inhibitor of PDE4 (IC 50 0.39 nM) versus vehicle control (n=6∼10 in each group) for 21 days concomitant with HFD, resulted in rapid and substantial weight loss (↓45.8% fat content), enhanced thermogenesis [(∼20% higher oxygen consumption and heat production, 0.7∼1.1°C higher core body temperature in a cold environment (4°C)], brown adipose reprogramming, improvement in insulin resistance (HOMA-IR ↓ from 0.69±0.04 to 0.44±0.01, p<0.01) and hepatic steatosis. These changes were paralleled by increased alternative macrophage activation (Altf), reduced inflammation in WAT [↑CD206 and CD301 by flow cytometry with ↓ TNF/IL-6 gene expression] and activation of thermogenic genes in brown adipose tissue. In-vitro treatment of mouse bone marrow-derived macrophages (BMDM) promoted Altf and increased expression of tyrosine hydroxylase (↑2.5 folds) and catecholamines secretion. Additional experiments with agents that augment/reduce intracellular cAMP/EPAC/AMPK revealed an essential role for this cascade in Altf activation and catecholamine release. Conclusions: PDE4 antagonism improves obese diabetic symptoms through convergent pathways involving Altf activation and enhancing thermogenesis via cAMP dependent modulation of macrophage catecholamine release.

Role of NOS2 in pulmonary injury and repair in response to bleomycin

Nitric oxide (NO) is derived from multiple isoforms of the Nitric Oxide Synthases (NOSs) within the lung for a variety of functions; however, NOS2-derived nitrogen oxides seem to play an important role in inflammatory regulation. In this study, we investigate the role of NOS2 in pulmonary inflammation/fibrosis in response to intratracheal bleomycin instillation (ITB) and to determine if these effects are related to macrophage phenotype. Systemic NOS2 inhibition was achieved by administration of 1400W, a specific and potent NOS2 inhibitor, via osmotic pump starting six days prior to ITB. 1400W administration attenuated lung inflammation, decreased chemotactic activity of the broncheoalveolar lavage (BAL), and reduced BAL cell count and nitrogen oxide production. S-nitrosylated SP-D (SNO-SP-D), which has a pro-inflammatory function, was formed in response to ITB; but this formation, as well as structural disruption of SP-D, was inhibited by 1400W. mRNA levels of IL-1β, CCL2 and Ptgs2 were decreased by 1400W treatment. In contrast, expression of genes associated with alternate macrophage activation and fibrosis Fizz1, TGF-β and Ym-1 was not changed by 1400W. Similar to the effects of 1400W, NOS2−/− mice displayed an attenuated inflammatory response to ITB (day 3 and day 8 post-instillation). The DNA-binding activity of NF-κB was attenuated in NOS2−/− mice; in addition, expression of alternate activation genes (Fizz1, Ym-1, Gal3, Arg1) was increased. This shift towards an increase in alternate activation was confirmed by western blot for Fizz-1 and Gal-3 that show persistent up-regulation 15 days after ITB. In contrast arginase, which is increased in expression at 8 days post ITB in NOS2−/−, resolves by day 15. These data suggest that NOS2, while critical to the development of the acute inflammatory response to injury, is also necessary to control the late phase response to ITB.

P53 in the Myeloid Lineage Modulates an Inflammatory Microenvironment Limiting Initiation and Invasion of Intestinal Tumors.

Chronic inflammation promotes the development and progression of various epithelial tumors. Wild-type p53 suppresses inflammation, but it is unclear whether the role of p53 in suppression of inflammation is linked to its tumor suppression function. Here, we established mouse models of myeloid lineage-specific p53 deletion or activation to examine its role in inflammation-related intestinal tumorigenesis. Impaired p53 in the myeloid linage resulted in elevated levels of inflammatory mediators and stimulated adenoma initiation in Apc(Min/+) mice. In contrast, mice with mild p53 activation in the myeloid lineage attenuated the inflammatory response and were more resistant to intestinal tumor development and invasion, which were initiated through Apc(Min/+) mutation or carcinogen and promoted by colitis. Furthermore, p53 activation also suppressed alternative (M2) macrophage polarization together with c-MYC downregulation. Therefore, as a regulator of macrophage function, p53 is critical to protection against tumorigenesis in a non-cell-autonomous manner.

High salt reduces the activation of IL-4- and IL-13-stimulated macrophages.

A high intake of dietary salt (NaCl) has been implicated in the development of hypertension, chronic inflammation, and autoimmune diseases. We have recently shown that salt has a proinflammatory effect and boosts the activation of Th17 cells and the activation of classical, LPS-induced macrophages (M1). Here, we examined how the activation of alternative (M2) macrophages is affected by salt. In stark contrast to Th17 cells and M1 macrophages, high salt blunted the alternative activation of BM-derived mouse macrophages stimulated with IL-4 and IL-13, M(IL-4+IL-13) macrophages. Salt-induced reduction of M(IL-4+IL-13) activation was not associated with increased polarization toward a proinflammatory M1 phenotype. In vitro, high salt decreased the ability of M(IL-4+IL-13) macrophages to suppress effector T cell proliferation. Moreover, mice fed a high salt diet exhibited reduced M2 activation following chitin injection and delayed wound healing compared with control animals. We further identified a high salt-induced reduction in glycolysis and mitochondrial metabolic output, coupled with blunted AKT and mTOR signaling, which indicates a mechanism by which NaCl inhibits full M2 macrophage activation. Collectively, this study provides evidence that high salt reduces noninflammatory innate immune cell activation and may thus lead to an overall imbalance in immune homeostasis.

MicroRNA-223 is a crucial mediator of PPARγ-regulated alternative macrophage activation.

Polarized activation of adipose tissue macrophages (ATMs) is crucial for maintaining adipose tissue function and mediating obesity-associated cardiovascular risk and metabolic abnormalities; however, the regulatory network of this key process is not well defined. Here, we identified a PPARγ/microRNA-223 (miR-223) regulatory axis that controls macrophage polarization by targeting distinct downstream genes to shift the cellular response to various stimuli. In BM-derived macrophages, PPARγ directly enhanced miR-223 expression upon exposure to Th2 stimuli. ChIP analysis, followed by enhancer reporter assays, revealed that this effect was mediated by PPARγ binding 3 PPARγ regulatory elements (PPREs) upstream of the pre-miR-223 coding region. Moreover, deletion of miR-223 impaired PPARγ-dependent macrophage alternative activation in cells cultured ex vivo and in mice fed a high-fat diet. We identified Rasa1 and Nfat5 as genuine miR-223 targets that are critical for PPARγ-dependent macrophage alternative activation, whereas the proinflammatory regulator Pknox1, which we reported previously, mediated miR-223-regulated macrophage classical activation. In summary, this study provides evidence to support the crucial role of a PPARγ/miR-223 regulatory axis in controlling macrophage polarization via distinct downstream target genes.

Neither classical nor alternative macrophage activation is required for Pneumocystis clearance during immune reconstitution inflammatory syndrome.

Pneumocystis is a respiratory fungal pathogen that causes pneumonia (Pneumocystis pneumonia [PcP]) in immunocompromised patients. Alveolar macrophages are critical effectors for CD4(+) T cell-dependent clearance of Pneumocystis, and previous studies found that alternative macrophage activation accelerates fungal clearance during PcP-related immune reconstitution inflammatory syndrome (IRIS). However, the requirement for either classically or alternatively activated macrophages for Pneumocystis clearance has not been determined. Therefore, RAG2(-/-) mice lacking either the interferon gamma (IFN-γ) receptor (IFN-γR) or interleukin 4 receptor alpha (IL-4Rα) were infected with Pneumocystis. These mice were then immune reconstituted with wild-type lymphocytes to preserve the normal T helper response while preventing downstream effects of Th1 or Th2 effector cytokines on macrophage polarization. As expected, RAG2(-/-) mice developed severe disease but effectively cleared Pneumocystis and resolved IRIS. Neither RAG/IFN-γR(-/-) nor RAG/IL-4Rα(-/-) mice displayed impaired Pneumocystis clearance. However, RAG/IFN-γR(-/-) mice developed a dysregulated immune response, with exacerbated IRIS and greater pulmonary function deficits than those in RAG2 and RAG/IL-4Rα(-/-) mice. RAG/IFN-γR(-/-) mice had elevated numbers of lung CD4(+) T cells, neutrophils, eosinophils, and NK cells but severely depressed numbers of lung CD8(+) T suppressor cells. Impaired lung CD8(+) T cell responses in RAG/IFN-γR(-/-) mice were associated with elevated lung IFN-γ levels, and neutralization of IFN-γ restored the CD8 response. These data demonstrate that restricting the ability of macrophages to polarize in response to Th1 or Th2 cytokines does not impair Pneumocystis clearance. However, a cell type-specific IFN-γ/IFN-γR-dependent mechanism regulates CD8(+) T suppressor cell recruitment, limits immunopathogenesis, preserves lung function, and enhances the resolution of PcP-related IRIS.

ID: 48: Hck activation enhances colorectal tumourigenesis by facilitating alternative macrophage polarisation

Colorectal cancer is the second most commonly diagnosed cancer worldwide, and may develop sporadically or due to chronic colitis. Macrophages are a major component of the colorectal tumour microenvironment and may be broadly classified as classically-activated (CAM) ‘inflammatory’ or alternatively-activated (AAM) ‘pro-angiogenic’ macrophages. Hematopoietic Cell Kinase (Hck) is a myeloid-specific Src family kinase involved in alternative macrophage polarisation, which correlates with a poor prognosis in human colorectal cancer. To investigate the role of Hck in colorectal tumourigenesis, Hck mutant mice that express a constitutively active form of Hck (HckCA) were subjected to models of sporadic and colitis-associated colorectal cancer. In both models, HckCA mice demonstrated increased tumour size and multiplicity compared to wild-type animals. FACS analysis of tumour immune-cell infiltrates did not reveal a difference in the number of tumour-associated macrophages (TAMs) between genotypes; however, CD206+ alternatively-activated TAMs were significantly greater in HckCA mice compared to wild-type. Furthermore, qPCR analysis highlighted a significant increase in genes associated with alternative-macrophage activation in HckCA TAMs. To confirm the role of macrophages in HckCA-driven tumourigenesis, wild-type mice were reconstituted with HckCA bone-marrow, and subjected to sporadic or colitis-associated colon cancer induction, after which we observed an increased tumour burden and an AAM phenotype compared to wild-type bone-marrow recipients. Finally, we have shown that the inhibition of Hck using a small molecule inhibitor reduces alternative macrophage polarisation. Collectively, our results suggest that excessive Hck activation enhances colorectal tumourigenesis by facilitating alternative macrophage polarisation, which may be alleviated through the therapeutic targeting of this kinase.

ID: 43: The IL-13 receptor-alpha 1 chain is essential for induction of the alternative macrophage activation pathway by IL-13 but not IL-4

Macrophages coexpress both the interleukin (IL)-2R-gamma chain ( γ c) and IL-13R-alpha 1. These receptor chains can heterodimerize with IL-4R α to form type I or type II IL-4 receptor complexes, respectively. We used macrophages derived from Il2rg and Il13ra1 knockout (KO) mice to evaluate the requirements for these receptor chains for induction of the alternative macrophage activation (AMA) pathway by IL-4 and IL-13. Absence of γ c significantly decreased activation of STAT6 by IL-4 but not IL-13. However, although activation of STAT6 by IL-4 was markedly reduced in Il2rg KO macrophages, it was not abolished, indicating that IL-4 can still signal through type II IL-4 receptors via the IL-13R α 1 chain. IL-13 failed to activate STAT6 in macrophages derived from Il13ra1 KO mice; however, these cells remained fully responsive to IL-4. The inability of IL-13 but not IL-4 to signal in Il13ra1−/− macrophages correlated with the inability of IL-13 but not IL-4 to induce expression of genes such as Arg1, Retnla and Ccl11 that are characteristically expressed by alternatively activated macrophages. In addition, IL-13 but not IL-4 failed to induce membrane fusion and giant cell formation by Il13ra1 KO macrophages. These findings demonstrate that the IL-13R α 1 chain is essential for induction of the AMA pathway by IL-13 but not IL-4. Furthermore, the IL-13R-alpha 1 chain represents an excellent target for development of neutralizing monoclonal antibodies to inhibit the pro-inflammatory activities of IL-13.

Effect of shock waves on macrophages: A possible role in tissue regeneration and remodeling

IntroductionExtracorporeal Shock Wave Therapy (ESWT) is broadly used as a non-surgical therapy in various diseases for its pro-angiogenic and anti-inflammatory effects. However, the molecular mechanisms translating tissue exposure to shock waves (SW) in a biological response with potential therapeutic activity are largely unknown. As macrophages take part in both the onset and amplification of the inflammatory response, and well in its resolution, we investigated the effect of SW on their biology. MethodsHuman monocyte-derived macrophages were polarized to classic (M1) pro-inflammatory macrophages or alternative (M2) anti-inflammatory macrophages and exposed to SW ad different intensities. Expression levels of marker genes of macrophage activation were measured by qPCR at different time points. ResultsSW did not induce activation of resting macrophages at any energy level used. Conversely, when used at low energy SW caused a significant inhibition of some M1 marker genes (CD80, COX2, CCL5) in M1 macrophages and a significant synergistic effect for some M2 marker genes (ALOX15, MRC1, CCL18) in M2 macrophages. SW also affected cytokine and chemokine production, inducing in particular a significant increase in IL-10 and reduction in IL-1β production. ConclusionsMacrophage exposure to low energy SW dampens the induction of the pro-inflammatory profile characterizing M1 macrophages and promotes the acquisition of an anti-inflammatory profile synergizing with macrophage alternative activation.

IL10-driven STAT3 signalling in senescent macrophages promotes pathological eye angiogenesis.

Macrophage dysfunction plays a pivotal role during neovascular proliferation in diseases of ageing including cancers, atherosclerosis and blinding eye disease. In the eye, choroidal neovascularization (CNV) causes blindness in patients with age-related macular degeneration (AMD). Here we report that increased IL10, not IL4 or IL13, in senescent eyes activates STAT3 signalling that induces the alternative activation of macrophages and vascular proliferation. Targeted inhibition of both IL10 receptor-mediated signalling and STAT3 activation in macrophages reverses the ageing phenotype. In addition, adoptive transfer of STAT3-deficient macrophages into eyes of old mice significantly reduces the amount of CNV. Systemic and CD163+ eye macrophages obtained from AMD patients also demonstrate STAT3 activation. Our studies demonstrate that impaired SOCS3 feedback leads to permissive IL10/STAT3 signalling that promotes alternative macrophage activation and pathological neovascularization. These findings have significant implications for our understanding of the pathobiology of age-associated diseases and may guide targeted immunotherapy.

Abstract LB-133: Excessive activation of the Src-kinase HCK in the tumor stroma promotes progression of solid tumors

Abstract Hemopoietic cell kinase, HCK, is a Src-family kinase expressed in myeloid and B-lymphoid cells, regulates innate immune cell functions, and is aberrantly activated and/or expressed (incl HCK gene amplification) in solid tumors of the colon, stomach, lung and other organs. Here we exploit the Hck(CA) mouse model, which carries a constitutively activating germline mutation and spontaneously develops pulmonary inflammation, airspace enlargement and cellular consolidation highly reminiscent of patient with chronic obstructive pulmonary disease, COPD [1]. To establish whether aberrant activation of endogenous Hck promotes tumorigenesis, we tested three established cancer models. First, we found lung adenocarcinoma burden in Hck(CA)x Kras(LSL-G12D) mice compared to Kras(LSL-G12D) mice, where the oncogenic KrasG12D transgene becomes activated in response to transnasal administration of adenovirus-encoded Cre recombinase. Second, using gp130(F/+) mice as a strain predisposed to the development of intestinal-type gastric cancer [2], we established that compound Hck(CA)x gp130(F/+), developed tumor burden similar to that of gp130(F/F) animals. Furthermore, tumors from Hck(CA)x gp130(F/+) mice, but not from gp130(F/F) mice, showed sub-mucosal invasion. Third, we modeled sporadic colorectal cancer by weekly administration of the alkylating agent azoxymethane for 6 consecutive weeks [3]. Compared to wild-type mice, Hck(CA) mice exhibited increased tumor frequency and multiplicity, and colonic tumors in Hck(CA) mice showed mucosal invasion, which was absent from tumors in wild-type mice. In all models the Hck(CA) allele increased tumor cell proliferation and associated Stat3, Erk, Akt and S6 cytoplasmic signaling, although the total number of tumor-associated macrophages remained unchanged by the presence of the Hck(CA) allele. However gene expression profiling of the latter cells revealed excessive alternative macrophage activation from Hck(CA) mice with prominent expression of Il4, Il10, Il13, Arg1 and Ym1. Accordingly, adoptive transfer of Hck(CA) bone-marrow was sufficient to confer increase tumor burden and promote alternative macrophage polarisation, while reconstitution with triple Hck(KO)x Fgr(KO)x Lyn(KO) bone marrow reduced tumor burden. Collectively, our data suggest that mutations affecting the stroma, and macrophage polarization specifically, confer tumor progression and that HCK may provide a novel target for rational cancer drug development. References 1) J. Exp. Med. 196:589-604 (2002) 2) Nat Med 11:845 (2005) 3) Cancer Cell 24:25 (2013) Citation Format: Robert O'Donoghue, Ashleigh Poh, Adele Preaudet, Matthias Ernst. Excessive activation of the Src-kinase HCK in the tumor stroma promotes progression of solid tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-133. doi:10.1158/1538-7445.AM2015-LB-133

The cholesterol-binding protein NPC2 restrains recruitment of stromal macrophage-lineage cells to early-stage lung tumours.

The tumour microenvironment is known to play an integral role in facilitating cancer progression at advanced stages, but its function in some pre-cancerous lesions remains elusive. We have used the V600EBRAF-driven mouse lung model that develop premalignant lesions to understand stroma–tumour interactions during pre-cancerous development. In this model, we have found that immature macrophage-lineage cells (IMCs) producing PDGFA, TGFβ and CC chemokines are recruited to the stroma of premalignant lung adenomas through CC chemokine receptor 1 (CCR1)-dependent mechanisms. Stromal IMCs promote proliferation and transcriptional alterations suggestive of epithelial–mesenchymal transition in isolated premalignant lung tumour cells ex vivo, and are required for the maintenance of early-stage lung tumours in vivo. Furthermore, we have found that IMC recruitment to the microenvironment is restrained by the cholesterol-binding protein, Niemann-Pick type C2 (NPC2). Studies on isolated cells ex vivo confirm that NPC2 is secreted from tumour cells and is taken up by IMCs wherein it suppresses secretion of the CCR1 ligand CC chemokine 6 (CCL6), at least in part by facilitating its lysosomal degradation. Together, these findings show that NPC2 secreted by premalignant lung tumours suppresses IMC recruitment to the microenvironment in a paracrine manner, thus identifying a novel target for the development of chemopreventive strategies in lung cancer.

Hypoxia induces calpain activity and degrades SMAD2 to attenuate TGFβ signaling in macrophages.

BackgroundUnder inflammatory conditions or during tumor progression macrophages acquire distinct phenotypes, with factors of the microenvironment such as hypoxia and transforming growth factor β (TGFβ) shaping their functional plasticity. TGFβ is among the factors causing alternative macrophage activation, which contributes to tissue regeneration and thus, resolution of inflammation but may also provoke tumor progression. However, the signal crosstalk between TGFβ and hypoxia is ill defined.ResultsExposing human primary macrophages to TGFβ elicited a rapid SMAD2/SMAD3 phosphorylation. This early TGFβ-signaling remained unaffected by hypoxia. However, with prolonged exposure periods to TGFβ/hypoxia the expression of SMAD2 declined because of decreased protein stability. In parallel, hypoxia increased mRNA and protein amount of the calpain regulatory subunit, with the further notion that TGFβ/hypoxia elicited calpain activation. The dual specific proteasome/calpain inhibitor MG132 and the specific calpain inhibitor 1 rescued SMAD2 degradation, substantiating the ability of calpain to degrade SMAD2. Decreased SMAD2 expression reduced TGFβ transcriptional activity of its target genes thrombospondin 1, dystonin, and matrix metalloproteinase 2.ConclusionsHypoxia interferes with TGFβ signaling in macrophages by calpain-mediated proteolysis of the central signaling component SMAD2.Electronic supplementary materialThe online version of this article (doi:10.1186/s13578-015-0026-x) contains supplementary material, which is available to authorized users.

Prolonged Endoplasmic Reticulum-Stressed Hepatocytes Drive an Alternative Macrophage Polarization.

Relatively little is known about the effects of hepatocytes on hepatic macrophages, particularly under the situation of endoplasmic reticulum (ER) stress. We examined the effects of hepatocytes conditioned media (CM) from HepG2 treated with ER stress inducers, tunicamycin or thapsigargin, on the secretion of cytokines, expression of ER stress markers, and polarization of phorbol myristate acetate-activated THP-1 cells (pTHP-1). We found that CM decreased the production of the proinflammatory cytokines including tumor necrosis factor α, interleukin 6 (IL-6), and IL-1β as well as other cytokines and chemokines from pTHP-1 cells. These effects are mediated by the inhibition of TLR4 expression and nuclear factor κB signaling pathway. In addition, hepatocytes CM increased the expression of binding immunoglobulin protein and the transcription factor C/EBP homologous protein (CHOP) in pTHP-1 cells. Preconditioning with ER stress inhibitor, small molecular chaperone 4-phenylbutyrate before addition of ER stressors, attenuated the ER stress in macrophages, the property of hepatocytes CM to alter tumor necrosis factor α production and nuclear factor κB expression by macrophages. Remarkably, treatment of macrophage with these CM leads to an alternative activation of macrophages mediated by peroxisome proliferator-activated receptor γ signaling pathway, which might be resulted from the secretion of IL-10 and IL-4 as well as releasing apoptotic bodies from hepatocytes under ER stress. Our results highlight a mechanism of ER stress transmission from hepatocytes to macrophage that drives an alternative activation of macrophages, which depends on the exposure of hepatocytes to severe and prolonged ER stress.

The transcription factor PU.1 promotes alternative macrophage polarization and asthmatic airway inflammation.

The transcription factor PU.1 is involved in regulation of macrophage differentiation and maturation. However, the role of PU.1 in alternatively activated macrophage (AAM) and asthmatic inflammation has yet been investigated. Here we report that PU.1 serves as a critical regulator of AAM polarization and promotes the pathological progress of asthmatic airway inflammation. In response to the challenge of DRA (dust mite, ragweed, and Aspergillus) allergens, conditional PU.1-deficient (PU/ER(T)(+/-)) mice displayed attenuated allergic airway inflammation, including decreased alveolar eosinophil infiltration and reduced production of IgE, which were associated with decreased mucous glands and goblet cell hyperplasia. The reduced asthmatic inflammation in PU/ER(T)(+/-) mice was restored by adoptive transfer of IL-4-induced wild-type (WT) macrophages. Moreover, after treating PU/ER(T)(+/-) mice with tamoxifen to rescue PU.1 function, the allergic asthmatic inflammation was significantly restored. In vitro studies demonstrate that treatment of PU.1-deficient macrophages with IL-4 attenuated the expression of chitinase 3-like 3 (Ym-1) and resistin-like molecule alpha 1 (Fizz-1), two specific markers of AAM polarization. In addition, PU.1 expression in macrophages was inducible in response to IL-4 challenge, which was associated with phosphorylation of signal transducer and activator of transcription 6 (STAT6). Furthermore, DRA challenge in sensitized mice almost abrogated gene expression of Ym-1 and Fizz-1 in lung tissues of PU/ER(T)(+/-) mice compared with WT mice. These data, all together, indicate that PU.1 plays a critical role in AAM polarization and asthmatic inflammation.

Growth/differentiation factor-15 and its role in peripheral nervous system lesion and regeneration.

Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor beta (TGF-β) superfamily. It is widely distributed in the nervous system, where it has been shown to play an important role in neuronal maintenance. The present study investigates the role of endogenous GDF-15 in sciatic nerve (SN) lesions using wild-type (WT) and GDF-15 knock-out (KO) mice. SN of 5-6-month-old mice were crushed or transected. Dorsal root ganglia (DRG) and nerve tissue were analyzed at different time points from 6h to 9weeks post-lesion. Both crush and transection induced GDF-15 mRNA and protein in the distal portion of the nerve, with a peak at day 7. DRG neuron death did not significantly differ between the genotypes; similarly, remyelination of regenerating axons was not affected by the genotype. Alternative macrophage activation and macrophage recruitment were more pronounced in the KO nerve. Protrusion speed of axons was similar in the two genotypes but WT axons showed better maturation, as indicated by larger caliber at 9weeks. Furthermore, the regenerated WT nerve showed better performance in the electromyography test, indicating better functional recovery. We conclude that endogenous GDF-15 is beneficial for axon regeneration following SN crush.

Batf2/Irf1 induces inflammatory responses in classically activated macrophages, lipopolysaccharides, and mycobacterial infection.

Basic leucine zipper transcription factor Batf2 is poorly described, whereas Batf and Batf3 have been shown to play essential roles in dendritic cell, T cell, and B cell development and regulation. Batf2 was drastically induced in IFN-γ-activated classical macrophages (M1) compared with unstimulated or IL-4-activated alternative macrophages (M2). Batf2 knockdown experiments from IFN-γ-activated macrophages and subsequent expression profiling demonstrated important roles for regulation of immune responses, inducing inflammatory and host-protective genes Tnf, Ccl5, and Nos2. Mycobacterium tuberculosis (Beijing strain HN878)-infected macrophages further induced Batf2 and augmented host-protective Batf2-dependent genes, particularly in M1, whose mechanism was suggested to be mediated through both TLR2 and TLR4 by LPS and heat-killed HN878 (HKTB) stimulation experiments. Irf1 binding motif was enriched in the promoters of Batf2-regulated genes. Coimmunoprecipitation study demonstrated Batf2 association with Irf1. Furthermore, Irf1 knockdown showed downregulation of IFN-γ- or LPS/HKTB-activated host-protective genes Tnf, Ccl5, Il12b, and Nos2. Conclusively, Batf2 is an activation marker gene for M1 involved in gene regulation of IFN-γ-activated classical macrophages, as well as LPS/HKTB-induced macrophage stimulation, possibly by Batf2/Irf1 gene induction. Taken together, these results underline the role of Batf2/Irf1 in inducing inflammatory responses in M. tuberculosis infection.

The novel biomarker of alternative macrophage activation, soluble mannose receptor (sMR/sCD206): Implications in multiple myeloma

Tumor-associated macrophages (TAMs) play an important role in the pathophysiology of human malignancies. They support growth of cancer cells by promoting angiogenesis, and by inhibiting tumour cell apoptosis and anti-tumor immune reactions. Several membrane proteins are well-described markers of human TAMs, including the haemoglobin scavenger receptor CD163 and the macrophage mannose receptor (MR/CD206). Interestingly, both CD163 and MR exist as soluble serum proteins (sCD163 and sMR) that may reflect the activation state of tissue macrophages, including TAMs. Here, we report the first data on sMR as a biomarker in patients with a malignant disease. We have measured concentrations of sMR in peripheral blood serum (n=104) from patients with newly diagnosed multiple myeloma (MM) by an enzyme-linked immunosorbent assay, and examined associations with data from medical records. At diagnosis, sMR levels were elevated in 27% of patients, and decreased after treatment. Further, sMR levels were associated with prognostic markers in MM, and elevated sMR (>0.43mg/L) was an independent marker of overall survival in a multivariate analysis (HR=2.20, P=0.006). Levels of sMR in blood samples showed significant association with sCD163, which may indicate common origin from CD163+MR+TAMs.

Tim-3 induces Th2-biased immunity and alternative macrophage activation during Schistosoma japonicum infection.

T cell immunoglobulin- and mucin-domain-containing molecule 3 (Tim-3) has been regarded as an important regulatory factor in both adaptive and innate immunity. Recently, Tim-3 was reported to be involved in Th2-biased immune responses in mice infected with Schistosoma japonicum, but the exact mechanism behind the involvement of Tim-3 remains unknown. The present study aims to understand the role of Tim-3 in the immune response against S. japonicum infection. Tim-3 expression was determined by flow cytometry, and increased Tim-3 expression was observed on CD4(+) and CD8(+) T cells, NK1.1(+) cells, and CD11b(+) cells from the livers of S. japonicum-infected mice. However, the increased level of Tim-3 was lower in the spleen than in the liver, and no increase in Tim-3 expression was observed on splenic CD8(+) T cells or CD11b(+) cells. The schistosome-induced upregulation of Tim-3 on natural killer (NK) cells was accompanied by reduced NK cell numbers in vitro and in vivo. Tim-3 antibody blockade led to upregulation of inducible nitric oxide synthase and interleukin-12 (IL-12) mRNA in CD11b(+) cells cocultured with soluble egg antigen and downregulation of Arg1 and IL-10, which are markers of M2 macrophages. In summary, we observed schistosome-induced expression of Tim-3 on critical immune cell populations, which may be involved in the Th2-biased immune response and alternative activation of macrophages during infection.