Classical M1 Macrophages Research Articles

Deletion of Myeloid GSK3α Attenuates Atherosclerosis and Promotes an M2 Macrophage Phenotype.

Glycogen synthase kinase (GSK)-3α/β has been implicated in the pathogenesis of diabetes mellitus, cancer, Alzheimer, and atherosclerosis. The tissue- and homolog-specific functions of GSK3α and β in atherosclerosis are unknown. This study examines the effect of hepatocyte or myeloid cell deletion of GSK3α or GSK3β on atherosclerosis in low-density lipoprotein receptor (LDLR)(-/-) mice. We ablated GSK3α or GSK3β expression in hepatic or myeloid cells of LDLR(-/-) mice, and mice were fed a high-fat diet for 10 weeks. GSK3α or GSK3β deficiency in hepatic or myeloid cells did not affect metabolic parameters, including plasma lipid levels. Hepatic deletion of GSK3α or GSK3β did not affect the development of atherosclerosis or hepatic lipid content. Myeloid deletion of GSK3α, but not of GSK3β, reduced atherosclerotic lesion volume and lesion complexity. Mice lacking GSK3α in myeloid cells had a less inflammatory and more anti-inflammatory plasma cytokine profile. Macrophages within atherosclerotic lesions of myeloid GSK3α-deficient mice, but not of GSK3β-deficient mice, displayed reduced expression of markers associated with M1 macrophage polarization and enhanced expression of the M2 markers. Finally, bone marrow-derived macrophages were isolated and differentiated into classical M1 macrophages or alternative M2 macrophages in vitro. GSK3α deletion, but not GSK3β deletion, attenuated the expression of genes associated with M1 polarization while promoting the expression of genes associated with M2 polarization by modulating STAT3 and STAT6 activation. Our findings suggest that deletion of myeloid GSK3α attenuates the progression of atherosclerosis by promoting an M2 macrophage phenotype.

Polarization and functional plasticity of macrophages in regulating innate immune response

Innate immune system is the first line of resistance that protects the host body from invasion of pathogens. During this innate immune response process, macrophages are well known to be the powerful leading players located throughout the body in defecting attacks. Originated from bone marrow, monocyte-macrophage lineage still manifests hallmarks of plasticity and diversity. Toll-like receptor (TLR) or interferon gamma (IFNγ) drives macrophages into M1 (classical) activation while IL-4/IL-13 or IL-10 induces M2 (alternative) activation. Different phenotypes of macrophages have distinct biological functions, transcriptional profiles, signaling pathways and cytokines along with chemokine framework. Classical M1 macrophages show strong pro-inflammatory and antimicrobial abilities while M2 macrophages are skilled at anti-inflammation, wound healing and fibrosis. Researches have shown that under different pathological conditions, macrophages are programmed to be different phenotypic subsets and play disparate immunomodulation. However, under the intricate microenvironment, there might be mixed populations instead of a kind of unique phenotypic macrophages. Evidences also show that macrophages can be converted from one phenotype to another according to microenvironmental signals (cytokines, chemokines, growth factors, and microbial-associated molecule patterns). A better understanding of the mechanisms of plasticity and polarization of macrophages will shine new lights into the mechanisms underlying the innate inflammation diseases and suggest promising therapeutic targets.

Macrophage phenotypes in atherosclerosis.

Initiation and progression of atherosclerosis depend on local inflammation and accumulation of lipids in the vascular wall. Although many cells are involved in the development and progression of atherosclerosis, macrophages are fundamental contributors. For nearly a decade, the phenotypic heterogeneity and plasticity of macrophages has been studied. In atherosclerotic lesions, macrophages are submitted to a large variety of micro-environmental signals, such as oxidized lipids and cytokines, which influence the phenotypic polarization and activation of macrophages resulting in a dynamic plasticity. The macrophage phenotype spectrum is characterized, at the extremes, by the classical M1 macrophages induced by T-helper 1 (Th-1) cytokines and by the alternative M2 macrophages induced by Th-2 cytokines. M2 macrophages can be further classified into M2a, M2b, M2c, and M2d subtypes. More recently, additional plaque-specific macrophage phenotypes have been identified, termed as Mox, Mhem, and M4. Understanding the mechanisms and functional consequences of the phenotypic heterogeneity of macrophages will contribute to determine their potential role in lesion development and plaque stability. Furthermore, research on macrophage plasticity could lead to novel therapeutic approaches to counteract cardiovascular diseases such as atherosclerosis. The present review summarizes our current knowledge on macrophage subsets in atherosclerotic plaques and mechanism behind the modulation of the macrophage phenotype.

Tumor-associated macrophages as major players in the tumor microenvironment.

During tumor progression, circulating monocytes and macrophages are actively recruited into tumors where they alter the tumor microenvironment to accelerate tumor progression. Macrophages shift their functional phenotypes in response to various microenvironmental signals generated from tumor and stromal cells. Based on their function, macrophages are divided broadly into two categories: classical M1 and alternative M2 macrophages. The M1 macrophage is involved in the inflammatory response, pathogen clearance, and antitumor immunity. In contrast, the M2 macrophage influences an anti-inflammatory response, wound healing, and pro-tumorigenic properties. Tumor-associated macrophages (TAMs) closely resemble the M2-polarized macrophages and are critical modulators of the tumor microenvironment. Clinicopathological studies have suggested that TAM accumulation in tumors correlates with a poor clinical outcome. Consistent with that evidence, experimental and animal studies have supported the notion that TAMs can provide a favorable microenvironment to promote tumor development and progression. In this review article, we present an overview of mechanisms responsible for TAM recruitment and highlight the roles of TAMs in the regulation of tumor angiogenesis, invasion, metastasis, immunosuppression, and chemotherapeutic resistance. Finally, we discuss TAM-targeting therapy as a promising novel strategy for an indirect cancer therapy.

Abstract P6-09-04: M2 macrophages induced by mammary carcinoma are switched to M1 macrophages by Escherichia coli maltose-binding protein

Abstract Background: The maltose-binding protein (MBP) is a component of the maltose transport system in the Escherichia coli. It is used to increase the stability and solubility of proteins in bacterial protein expression systems and is increasingly being used to facilitate the production and delivery of subunit vaccine. Tumor-associated macrophages (TAMs) are alternatively activated macrophages (M2) within the tumor microenvironment, which directly promoting tumor cell growth, extracellular matrix remodeling, and angiogenesis. Our previous studies revealed that MBP could nonspecifically induce Th1 cells activation and classically activate macrophages (M1). In the present study, we investigated the effect of MBP on re-polarization of mammary carcinoma induced M2 macrophage to pro-inflammatory M1 macrophages, in order to develop a novel antitumor immune adjuvant. Methods: We mimicked a tumor microenvironment by in vitro coculturing RAW264.7 macrophages with conditioned media (CM) from two different kinds of mammary carcinoma cell lines EMT6 and 4T1. In the absence or presence of MBP, the mammary carcinoma CM-induced macrophages were tested for their polarization types. The production of IL-12 and IL-10 were assessed by ELISA, the mRNA expression of iNOS and Arg-1 were detected by RT-PCR, and the expression of CD206 and CD16/32 were determined by flow cytometry and immunofluorescence staining. All of these important factors were taken as criteria for M1 and M2 polarization. The expression levels of TLR2 and TLR4 on the surface of RAW264.7 cells were determined by flow cytometry. By the addition of TLR2 or TLR4 blocking antibody, the ratio of IL-12 and IL-10 production was used to distinguish M1 and M2 macrophages in the absence or presence of MBP. For the investigation of the signal transduction pathways, the expression level of MyD88 and the phosphorylation levels of IκB-α, NF-κB, PI3K, Akt, MAPKs, JNK were analyzed by western blotting. Results: The mammary carcinoma CM induced the RAW264.7 macrophage to polarize to M2 macrophages. In the mammary carcinoma CM-induced macrophages, the expression level of CD206 was increased, the ratio of IL-12/IL-10 production was decreased, and the gene expression of Arg-1 was increased. In the presence of MBP, M2 polarization was attenuated as shown by the increase of CD16/32 and iNOS, the decrease of CD206 and Arg-1, an altered ratio of IL-12/IL-10, and accompanied with the up-regulation of TLR2 and TLR4 expressions. The effect of MBP on mammary carcinoma CM-induced macrophages was blocked by anti-TLR2 antibody, but not anti-TLR4 antibody or TLR4 inhibitor polymyxin B. Further studies confirmed that the effects of MBP on switching mammary carcinoma induced M2 macrophages to M1 depended on the activation of NF-κB and MAPKs. Conclusion: Our results provide new insights into the modulation of TAM polarization. MBP can be used as a novel antitumor adjuvant, which may stimulate a tumor-rejecting environment by switching M2 macrophages to classical pro-inflammatory M1 macrophages through TLR2 signaling and a combination of transcription factors including NK-κB and MAPKs. Accordingly, MBP may have the therapeutic potential in mammary carcinoma. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-09-04.

Taurine improves obesity‐induced inflammatory responses and modulates the unbalanced phenotype of adipose tissue macrophages

It is increasingly accepted that chronic inflammation is a feature of obesity. Obesity-induced inflammation triggers enhanced recruitment of macrophages into the adipose tissue. Depending on their phenotype, macrophages can be designated either as pro-inflammatory M1 macrophages or anti-inflammatory M2 macrophages. We have therefore investigated the effects of taurine, a sulfated amino acid that is abundant in seafood, on obesity-related inflammation. In high-fat diet fed C57BL/6J mice, taurine treatment reduced the infiltration of macrophages and promoted an M2-like phenotype of macrophages in adipose tissues. In addition, taurine decreased the production of inflammatory cytokines, and suppressed the development of hyperglycemia in diet-induced obese mice. Moreover, in vitro experiments that involved bone marrow derived macrophages indicated that taurine treatment induced alternative M2 macrophage activation, and its chloride, taurine chloramines, inhibited classical M1 macrophage activation. Our findings indicate that taurine treatment attenuates the infiltration of adipose tissue by macrophages and modulates the phenotype of macrophages, which suggest that taurine is a valuable food constituent with a potential to attenuate chronic inflammation in adipose tissue and improve obesity-related insulin resistance.

Tumor associated macrophages and neutrophils in cancer

The tumor microenvironment is a complex framework, in which myeloid cells play important roles in sculpting cancer development from tumor initiation to metastasis. Immune cells are key participants of the tumor microenvironment where they can promote or inhibit cancer formation and development. Plasticity is a widely accepted hallmark of myeloid cells and in particular of the monocyte–macrophage lineage. It includes the ability to display a wide spectrum of activation states in response to distinct signals and classical M1 or alternative M2 macrophages represent a paradigm of this feature. Neutrophils have long been viewed as terminally differentiated effector cells, playing a major role during the acute phase of inflammation and resistance against microbes. Recent evidence questioned this limited point of view, indicating that neutrophils can interact with distinct cell populations and produce a wide number of cytokines and effector molecules. Therefore, macrophages and neutrophils are both integrated in the regulation of the innate and adaptive immune responses in various inflammatory situations, including cancer.

AB0189 Macrophages polarization in the gut of patients with ankylosing spondylitis

BackgroundSubclinical gut inflammation occurs in patients with Ankylosing Spondylitis (AS) and long term evolution to overt Crohn’s disease (CD) has been described in these patients. Gut mucosal macrophages represent the...

S130 Exogenous Macrophages Are Retained in Mouse Lungs After Injury and Target Therapeutic Transgenes to the Injured Lung Parenchyma

IntroductionPulmonary fibrosis evolves in response to epithelial injury in a number of lung diseases, and carries a poor prognosis; novel therapies are urgently needed. The epithelial mitogen keratinocyte growth factor...

M2 Macrophages Induced by Prostaglandin E2 and IL-6 from Cervical Carcinoma Are Switched to Activated M1 Macrophages by CD4+ Th1 Cells

Monocytes attracted by tumor-induced chronic inflammation differentiate to APCs, the type of which depends on cues in the local tumor milieu. In this work, we studied the influence of human cervical cancer cells on monocyte differentiation and showed that the majority of cancer cells either hampered monocyte to dendritic cell differentiation or skewed their differentiation toward M2-like macrophages. Blocking studies revealed that M2 differentiation was caused by tumor-produced PGE(2) and IL-6. TGF-β, IL-10, VEGF, and macrophage colony-stimulating factor did not play a role. Notably, these CD14(+)CD163(+) M2 macrophages were also detected in situ. Activation of cancer cell-induced M2-like macrophages by several TLR-agonists revealed that compared with dendritic cells, these M2 macrophages displayed a tolerogenic phenotype reflected by a lower expression of costimulatory molecules, an altered balance in IL-12p70 and IL-10 production, and a poor capacity to stimulate T cell proliferation and IFN-γ production. Notably, upon cognate interaction with Th1 cells, these tumor-induced M2 macrophages could be switched to activated M1-like macrophages that expressed high levels of costimulatory molecules, produced high amounts of IL-12 and low amounts of IL-10, and acquired the lymphoid homing marker CCR7. The effects of the interaction between M2 macrophages and Th1 cells could partially be mimicked by activation of these APCs via CD40 in the presence of IFN-γ. Our data on the presence, induction, and plasticity of tumor-induced tolerogenic APCs in cervical cancer suggest that tumor-infiltrated Th1 cells can stimulate a tumor-rejecting environment by switching M2 macrophages to classical proinflammatory M1 macrophages.

Expression and function of semaphorin 3A and its receptors in human monocyte-derived macrophages

Semaphorins are a large family of secreted and membrane-bound proteins. Recently, several roles of semaphorins in the immune system have emerged. Several semaphorins and their receptors are expressed in a variety of lymphoid and myeloid cells and affect immune cell functions, including cell proliferation, differentiation, chemotaxis, and cytokine production. However, the roles of class 3 semaphorins in human myeloid cells are not well known. Here we examined the regulation of expression of class 3 semaphorins and their receptors by inflammatory stimuli and their function in human macrophages. We show that the expression of Sema3A receptors (neuropilin-1 (NRP-1), NRP-2, plexin A1, plexin A2, and plexin A3) significantly increased during M-CSF–mediated differentiation of monocytes into macrophages under conditions that promote an M2 alternatively activated macrophage phenotype. Consistent with increased NRP-1 expression, cell surface binding of Sema3A increased during M2 differentiation. Interferon (IFN)–γ and lipopolysaccharide, which promote classical M1 macrophage activation affected expression of NRP-1, NRP-2 and plexin A1. IFN-γ decreased NRP-1 expression and LPS suppressed NRP-2 and plexin A1 expression. Furthermore we show that Sema3A induced apoptosis in monocyte-derived macrophages and cooperated with anti-Fas CH11 antibody to augment apoptosis. Our results suggest that Sema3A plays a role in induction of apoptosis in monocyte-derived macrophages that are resistant to Fas-induced apoptosis, and that its function can be modulated in inflammatory conditions.

Transcriptome analysis reveals human cytomegalovirus reprograms monocyte differentiation toward an M1 macrophage.

Monocytes are primary targets for human CMV (HCMV) infection and are proposed to be responsible for hematogenous dissemination of the virus. Monocytes acquire different functional traits during polarization to the classical proinflammatory M1 macrophage or the alternative antiinflammatory M2 macrophage. We hypothesized that HCMV induced a proinflammatory M1 macrophage following infection to promote viral dissemination because, biologically, a proinflammatory state provides the tools to drive infected monocytes from the blood into the tissue. To test this hypothesis of monocyte conversion from a normal quiescent phenotype to an inflammatory phenotype, we used Affymetrix Microarray to acquire a transcriptional profile of infected monocytes at a time point our data emphasized is a key temporal regulatory point following infection. We found that HCMV significantly up-regulated 583 (5.2%) of the total genes and down-regulated 621 (5.5%) of the total genes>or=1.5-fold at 4 h postinfection. Further ontology analysis revealed that genes implicated in classical M1 macrophage activation were stimulated by HCMV infection. We found that 65% of genes strictly associated with M1 polarization were up-regulated, while only 4% of genes solely associated with M2 polarization were up-regulated. Analysis of the monocyte chemokinome at the transcriptional level showed that 44% of M1 and 33% of M2 macrophage chemokines were up-regulated. Proteomic analysis using chemokine Ab arrays confirmed the secretion of these chemotactic proteins from HCMV-infected monocytes. Overall, the results identify that the HCMV-infected monocyte transcriptome displayed a unique M1/M2 polarization signature that was skewed toward the classical M1 activation phenotype.