Accumulation Of M2 Macrophages Research Articles

Abstract 116: IGFBP2 promotes tumor progression by inducing alternative polarization of macrophages in pancreatic ductal adenocarcinoma

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the most lethal and aggressive malignancy. Tumor-associated macrophages (TAMs) mainly represent the M2-like phenotype, with potent immunosuppressive activity, and play a pro-tumor role in nearly all aspects of PDAC biology. Elevated infiltration of M2 TAMs is associated with poor prognosis in PDAC. Insulin-like growth factor binding protein 2 (IGFBP2) is a pleiotropic oncogene that induces PDAC progression and is involved in the regulation of immune responses. Our recent study demonstrated that IGFBP2 potentiates signal transducer and activator of transcription 3 (STAT3) transactivation activities in glioma. Considering the essential role of IGFBP2 in governing tumor progression and immune evasion of PDAC, we hypothesized that IGFBP2 promotes tumor progression by inducing alternatively activated macrophages in PDAC. In this study, immunohistochemical (IHC) staining for human PDAC clinical samples was used to reveal the relationship among IGFBP2 expression, M2 TAM accumulation and patient survival. The function of IGFBP2 in inducing alternative polarization of macrophages and promoting tumor progression in PDAC through the STAT3 pathway were evaluated using in vitro and in vivo assays. Ingenuity pathway and gene set enrichment analyses were used to identify the correlation of IGFBP2 gene expression with all other genes in the genome and enriched pathways associated with IGFBP2 gene expression. Our results provide evidence that IGFBP2 expression is associated with M2 macrophage accumulation in the tumor microenvironment and with poor prognosis in PDAC. IGFBP2 augments the production and secretion of IL-10 through activation of STAT3 in PDAC cells, thus reprogramming the TAMs polarization toward an M2 phenotype and promoting tumor progression. These findings established IGFBP2 as an immune-suppressor in the PDAC microenvironment and suggested a strategy for targeting IGFBP2 to improve PDAC immunotherapy. Citation Format: Longhao Sun, Liang Liu, Weijun Tian, Zhixiang Zhang, Ya'an Kang, Huamin Wang, Jason B. Fleming, Boris C. Pasche, Wei Zhang. IGFBP2 promotes tumor progression by inducing alternative polarization of macrophages in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 116.

Galectin-3 in M2 Macrophages Plays a Protective Role in Resolution of Neuropathology in Brain Parasitic Infection by Regulating Neutrophil Turnover.

Macrophages/microglia with M2-activation phenotype are thought to play important anti-inflammatory and tissue reparative functions in the brain, yet the molecular bases of their functions in the CNS remain to be clearly defined. In a preclinical model of neurocysticercosis using brain infection with a parasite Mesocestoides corti, we previously reported the presence of large numbers of M2 cells in the CNS. In this study using female mice, we report that M2 macrophages in the parasite-infected brain display abundant galectin-3 expression. Disease severity was increased in Galectin-3-/- mice correlating with increased neurological defects, augmented cell death and, importantly, massive accumulation of neutrophils and M2 macrophages in the CNS of these mice. Because neutrophil clearance by efferocytosis is an important function of M2 macrophages, we investigated a possible role of galectin-3 in this process. Indeed, galectin-3-deficient M2 macrophages exhibited a defect in efferocytic clearance of neutrophils in vitro Furthermore, adoptive transfer of M2 macrophages from galectin-3-sufficient WT mice reduced neutrophilia in the CNS and ameliorated disease severity in parasite-infected Galectin-3-/- mice. Together, these results demonstrate, for the first time, a novel role of galectin-3 in M2 macrophage function in neutrophil turnover and resolution of inflammatory pathology in the CNS. This likely will have implications in neurocysticercosis and neuroinflammatory diseases.SIGNIFICANCE STATEMENT Macrophages/microglia with M1-activation phenotype are thought to promote CNS pathology, whereas M2-anti-inflammatory phenotype promote CNS repair. However, the mechanisms regulating M2 cell-protective functions in the CNS microenvironment are undefined. The current study reports that helminth infection of the brain induces an increased expression of galectin-3 in M2 macrophages accumulated in the CNS. Using multiple experimental models in vivo and in vitro, they show that galectin-3 in M2 macrophages functions to clear neutrophils accumulated in the CNS. Importantly, galectin-3 in M2 macrophages plays a central role in the containment of neuropathology and disease severity. These results provide a direct mechanistic evidence of the protective function of M2 macrophages in the CNS.

CD16+ Macrophages Mediate Fibrosis in Inflammatory Bowel Disease.

Fibrosis is a common complication of Crohn's disease [CD], and is related to dysregulated tissular repair following inflammation, in which macrophages play a central role. We have previously observed that STAT6-/- mice present delayed mucosal recovery after 2,4,6-trinitrobenzenesulfonic acid [TNBS]-induced colitis due to a deficiency in reparatory interleukin-4 [IL4]/STAT6-dependent M2 macrophages, which can be reverted by the exogenous transfer of this cell type. In the present study, we analyse the role of STAT6-dependent macrophages in intestinal fibrosis. Colitis was induced by weekly intra-rectal administration of TNBS [6 weeks] to STAT6-/- mice and wild-type [WT] animals. Colonic surgical resections were obtained from CD patients and from colon cancer patients. Chronic colitis provoked a fibrogenic response in STAT6-/- mice, but not in WT animals. An accumulation of M2 macrophages, defined as CD206+ cells, was observed in WT mice, but not in STAT6-/- animals. Instead, the latter group showed an increase in CD16+ macrophages that correlated with the expression of fibrogenic markers. CD16+ macrophages were also increased in the damaged mucosa of Crohn's disease patients with stenotic or penetrating complications. Finally, administration of IL4-treated WT macrophages to STAT6-/- mice reduced TNBS-induced fibrosis. Our study demonstrates that STAT6 deficiency dysregulates the macrophage response to inflammatory outbursts by increasing the presence of a population of CD16+ macrophages that seems to contribute to intestinal fibrosis.

Apoptosis inhibitor of macrophage depletion decreased M1 macrophage accumulation and the incidence of cardiac rupture after myocardial infarction in mice.

BackgroundCardiac rupture is an important cause of death in the acute phase after myocardial infarction (MI). Macrophages play a pivotal role in cardiac remodeling after MI. Apoptosis inhibitor of macrophage (AIM) is secreted specifically by macrophages and contributes to macrophage accumulation in inflamed tissue by maintaining survival and recruiting macrophages. In this study, we evaluated the role of AIM in macrophage accumulation in the infarcted myocardium and cardiac rupture after MI.Methods and resultsWild-type (WT) and AIM‒/‒ mice underwent permanent left coronary artery ligation and were followed-up for 7 days. Macrophage accumulation and phenotypes (M1 pro-inflammatory macrophage or M2 anti-inflammatory macrophage) were evaluated by immunohistological analysis and RT-PCR. Matrix metalloproteinase (MMP) activity levels were measured by gelatin zymography. The survival rate was significantly higher (81.1% vs. 48.2%, P<0.05), and the cardiac rupture rate was significantly lower in AIM‒/‒ mice than in WT mice (10.8% vs. 31.5%, P<0.05). The number of M1 macrophages and the expression levels of M1 markers (iNOS and IL-6) in the infarcted myocardium were significantly lower in AIM‒/‒ mice than in WT mice. In contrast, there was no difference in the number of M2 macrophages and the expression of M2 markers (Arg-1, CD206 and TGF-β1) between the two groups. The ratio of apoptotic macrophages in the total macrophages was significantly higher in AIM‒/‒ mice than in WT mice, although MCP-1 expression did not differ between the two groups. MMP-2 and 9 activity levels in the infarcted myocardium were significantly lower in AIM‒/‒ mice than in WT mice.ConclusionsThese findings suggest that AIM depletion decreases the levels of M1 macrophages, which are a potent source of MMP-2 and 9, in the infarcted myocardium in the acute phase after MI by promoting macrophage apoptosis, and leads to a decrease in the incidence of cardiac rupture and improvements in survival rates.

Obesity enhances carcinogen 7, 12-Dimethylbenz [a] anthracene -induced tumorigenesis in vitro and in vivo

Growing body of evidence shows that extra adiposity influences on the progression of multiple cancers, including breast cancer. The aim of this study is to investigate whether obesity correlates with mammary tumor development in vitro and in vivo. We found that obesity-related mediators, 3T3-L1 adipocyte conditioned medium, enhanced formation of cancerous foci induced by the carcinogen 7,12-Dimethylbenz[a]anthracene (DMBA) in NIH/3T3 fibroblasts, in vitro. Additionally, we tested the effect of obesity in mouse model of DMBA-induced breast cancer. C57BL/6J female mice were fed a low fat (LF), or high fat (HF) diet, and DMBA was administered by oral gavage (LF plus DMBA [LFD] and HF plus DMBA [HFD]). Our results indicated that HFD mouse developed a tumor which weight was 169mg, whereas the LFD mouse developed a tumor weight of 77mg. Histological analysis of the mammary tumor from HFD group showed morphological aggressiveness and multiple cell type infiltration compared to LFD group. The epididymal adipose tissue from the DMBA groups showed more macrophage infiltration, polarized towards an M1 phenotype compared to the non-DMBA mice. HF mice showed less accumulation of M2 macrophages in the adipose tissue. In summary, obese mediators enhanced DMBA induced tumorigenesis in vitro and in vivo.

Dynamic stroma reorganization drives blood vessel dysmorphia during glioma growth

Glioma growth and progression are characterized by abundant development of blood vessels that are highly aberrant and poorly functional, with detrimental consequences for drug delivery efficacy. The mechanisms driving this vessel dysmorphia during tumor progression are poorly understood. Using longitudinal intravital imaging in a mouse glioma model, we identify that dynamic sprouting and functional morphogenesis of a highly branched vessel network characterize the initial tumor growth, dramatically changing to vessel expansion, leakage, and loss of branching complexity in the later stages. This vascular phenotype transition was accompanied by recruitment of predominantly pro‐inflammatory M1‐like macrophages in the early stages, followed by in situ repolarization to M2‐like macrophages, which produced VEGF‐A and relocate to perivascular areas. A similar enrichment and perivascular accumulation of M2 versus M1 macrophages correlated with vessel dilation and malignancy in human glioma samples of different WHO malignancy grade. Targeting macrophages using anti‐CSF1 treatment restored normal blood vessel patterning and function. Combination treatment with chemotherapy showed survival benefit, suggesting that targeting macrophages as the key driver of blood vessel dysmorphia in glioma progression presents opportunities to improve efficacy of chemotherapeutic agents. We propose that vessel dysfunction is not simply a general feature of tumor vessel formation, but rather an emergent property resulting from a dynamic and functional reorganization of the tumor stroma and its angiogenic influences.

Tissue-type plasminogen activator modulates macrophage M2 to M1 phenotypic change through annexin A2-mediated NF-κB pathway.

Macrophage accumulation is one of the hallmarks of progressive kidney disease. In response to injury, macrophages undergo a phenotypic polarization to become two functionally distinct subsets: M1 and M2 macrophages. Macrophage polarization is a dynamic process, and recent work indicates that macrophages, in response to kidney injury, can shift their polarity. However, the underlying mechanisms remain largely unknown. Tissue-type plasminogen activator (tPA), a protease up-regulated in the chronically injured kidneys, has been shown to preferably promote M1 macrophage accumulation and renal inflammation. We hypothesized that tPA may be an endogenous factor that modulates macrophage M2 to M1 phenotypic change contributing to the accumulation of M1 macrophages in the injured kidneys. It was found that obstruction-induced renal M1 chemokine expression was alleviated in tPA knockout mice, and these knockout mice displayed increased M2 markers. In vitro, resting J774 macrophages were treated with IL-4 to induce M2 phenotype as indicated by de novo expression of arginase 1, Ym1, and IL-10, as well as suppression of iNOS, TNF-α, and IL-1β. Intriguingly, these IL-4-induced M2 macrophages, after tPA treatment, not only lost their M2 markers such as arginase 1, Ym1, and IL-10, but also displayed increased M1 chemokines including iNOS, TNF-α, and IL-1β. Possible endotoxin contamination was also excluded as heat-inactivated tPA lost its effect. Additionally, tPA-mediated macrophage M2 to M1 phenotypic change required its receptor annexin A2, and SN50, a specific NF-κB inhibitor, abolished tPA's effect. Thus, it's clear that tPA promotes macrophage M2 to M1 phenotypic change through annexin A2-mediated NF-κB pathway.

A positive-feedback loop between tumour infiltrating activated Treg cells and type 2-skewed macrophages is essential for progression of laryngeal squamous cell carcinoma

Background:Foxp3+ regulatory T (Treg) cells and M2 macrophages are associated with increased tumour progression. However, the interaction between Treg cells and M2 macrophages remains unclear.Methods:The expression of FoxP3 and CD163 was detected by immunohistochemistry in 65 cases of laryngeal squamous cell carcinoma (LSCC). In vitro, the generation of activated Treg (aTreg) cells and M2 macrophages by interactions with their precursor cells were analysed by flow cytometry and ELISA. In vivo, the antitumour effects were assessed by combined targeting aTreg cells and M2 macrophages, and intratumoural immunocytes were analysed by flow cytometry.Results:In LSCC tissue, accumulation of aTreg cells and M2 macrophages predicted a poor prognosis and were positively associated with each other. In vitro, aTreg cells were induced from CD4+CD25− T cells by cancer cell-activated M2-like macrophages. Consequently, these aTreg cells skewed the differentiation of monocytes towards an M2-like phenotype, thereby forming a positive-feedback loop. Combined targeting aTreg cells and M2 macrophages led to potent antitumour immunity in vivo.Conclusions:The positive-feedback loop between aTreg cells and M2 macrophages is essential to maintain or promote immunosuppression in the tumour microenvironment and may be a potential therapeutic target to inhibit tumour progression.

α-Linolenic acid-derived metabolites from gut lactic acid bacteria induce differentiation of anti-inflammatory M2 macrophages through G protein-coupled receptor 40.

Among dietary fatty acids with immunologic effects, ω-3 polyunsaturated fatty acids, such as α-linolenic acid (ALA), have been considered as factors that contribute to the differentiation of M2-type macrophages (M2 macrophages). In this study, we examined the effect of ALA and its gut lactic acid bacteria metabolites 13-hydroxy-9(Z),15(Z)-octadecadienoic acid (13-OH) and 13-oxo-9(Z),15(Z)-octadecadienoic acid (13-oxo) on the differentiation of M2 macrophages from bone marrow-derived cells (BMDCs) and investigated the underlying mechanisms. BMDCs were stimulated with ALA, 13-OH, or 13-oxo in the presence of IL-4 or IL-13 for 24 h, and significant increases in M2 macrophage markers CD206 and Arginase-1 (Arg1) were observed. In addition, M2 macrophage phenotypes were less prevalent following cotreatment with GPCR40 antagonists or inhibitors of PLC-β and MEK under these conditions, suggesting that GPCR40 signaling is involved in the regulation of M2 macrophage differentiation. In further experiments, remarkable M2 macrophage accumulation was observed in the lamina propria of the small intestine of C57BL/6 mice after intragastric treatments with ALA, 13-OH, or 13-oxo at 1 g/kg of body weight per day for 3 d. These findings suggest a novel mechanism of M2 macrophage differentiation involving fatty acids from gut lactic acid bacteria and GPCR40 signaling.-Ohue-Kitano, R., Yasuoka, Y., Goto, T., Kitamura, N., Park, S.-B., Kishino, S., Kimura, I., Kasubuchi, M., Takahashi, H., Li, Y., Yeh, Y.-S., Jheng, H.-F., Iwase, M., Tanaka, M., Masuda, S., Inoue, T., Yamakage, H., Kusakabe, T., Tani, F., Shimatsu, A., Takahashi, N., Ogawa, J., Satoh-Asahara, N., Kawada, T. α-Linolenic acid-derived metabolites from gut lactic acid bacteria induce differentiation of anti-inflammatory M2 macrophages through G protein-coupled receptor 40.

The FGF21-CCL11 Axis Mediates Beiging of White Adipose Tissues by Coupling Sympathetic Nervous System to Type 2 Immunity

Type 2 cytokines are important signals triggering biogenesis of thermogenic beige adipocytes in white adipose tissue (WAT) during cold acclimation. However, how cold activates type 2 immunity in WAT remains obscure. Here we show that cold-induced type 2 immune responses and beiging in subcutaneous WAT (scWAT) are abrogated in mice with adipose-selective ablation of FGF21 or its co-receptor β-Klotho, whereas such impairments are reversed by replenishment with chemokine CCL11. Mechanistically, FGF21 acts on adipocytes in an autocrine manner to promote the expression and secretion of CCL11 via activation of ERK1/2, which drives recruitment of eosinophils into scWAT, leading to increases in accumulation of M2 macrophages, and proliferation and commitment of adipocyte precursors into beige adipocytes. These FGF21-elicited type 2 immune responses and beiging are blocked by CCL11 neutralization. Thus, the adipose-derived FGF21-CCL11 axis triggers cold-induced beiging and thermogenesis by coupling sympathetic nervous system to activation of type 2 immunity in scWAT.

Autophagy-dependent regulation of tumor metastasis by myeloid cells.

Autophagy is a vital process controlling the lysosomal degradation of cellular organelles and thereby regulating tissue homeostasis in an environment-dependent fashion. Recent studies have unveiled the critical role of tumor cell-derived autophagy in regulating pro-tumor and anti-tumor processes depending on different stages and tumor microenvironments. However, the precise mechanism whereby autophagy regulates tumor progression remains largely unclear. Since myeloid cells contribute to tumor progression and metastasis, we evaluated the role of myeloid cell-specific autophagy in the regulation of tumor progression. We found that the number and size of metastatic lesions were smaller in myeloid cell-specific autophagy-deficient mice. Furthermore, autophagy-mediated regulation of TGF-β in myeloid cells was associated with the induction of epithelial-mesenchymal transition (EMT), which increases the invasive and metastatic potentials of tumor cells. Myeloid-derived autophagy also plays a critical role in impairing antitumor immune responses and promoting the survival and accumulation of M2 macrophages in tumor tissues in a CSF-1 and TGF-β-dependent manner. Taken together, our findings elucidate previously unrecognized mechanisms by which myeloid cells promote tumor progression through autophagy-mediated regulation of malignancy and immune tolerance.

Synergistic effect of IFN-γ on breast cancer targeted therapy

Abstract ErbB2 is amplified in ~30% of breast cancer patients, and its amplification is associated with poor prognosis and worse survival outcome. We examined the synergistic effect of interferon-γ (IFN-γ) with anti-erbB2/neu mAb on erbB2-positive cancer model. IFN-γ showed marginal effects on its own, indicating that immune therapies mediated by this cytokine alone are unlikely to be beneficial. However, we discovered that treatment of the tumors with anti-erbB2/neu mAb concomitant with IFN-γ led to dramatic inhibition of in vivo tumor growth in the syngeneic tumor model and the preventional MMTV-neu transgenic mouse tumor model. We noted an increase of M1 macrophage accumulation in the tumor tissues as well as diminished myeloid derived suppressor cells, and increased CD8+ T cell cytotoxicity against tumor cells in the IFN-γ plus anti-erbB2/neu mAb treated mice. The tumor cells treated with both mAb and IFN-γ underwent changes in tumor stem cell marker ALDH-1, indicating a loss of stem cell-like properties, while mAb treatment alone did not accomplish this phenotypic change. We found that IFN-γ treatment significantly increase tumor PD-L1 expression, so we included anti-PD-1 or PD-L1 antibody with this combination therapy. Interestingly, anti-PD-L1 antibody further reduced tumor growth, while anti-PD-1 did not affect very much. These results indicate that the treatment of IFN-γ can improve targeted therapy, and further induce PD-L1 expression on tumor cells, creating a new target on the tumor cells for anti-PD-L1 therapy.

CD44 Promotes Inflammation and Extracellular Matrix Production During Arteriovenous Fistula Maturation.

Arteriovenous fistulae (AVF) remain the optimal conduit for hemodialysis access but continue to demonstrate poor patency and poor rates of maturation. We hypothesized that CD44, a widely expressed cellular adhesion molecule that serves as a major receptor for extracellular matrix components, promotes wall thickening and extracellular matrix deposition during AVF maturation. AVF were created via needle puncture in wild-type C57BL/6J and CD44 knockout mice. CD44 mRNA and protein expression was increased in wild-type AVF. CD44 knockout mice showed no increase in AVF wall thickness (8.9 versus 26.8 μm; P=0.0114), collagen density, and hyaluronic acid density, but similar elastin density when compared with control AVF. CD44 knockout mice also showed no increase in vascular cell adhesion molecule-1 expression, intercellular adhesion molecule-1 expression, and monocyte chemoattractant protein-1 expression in the AVF compared with controls; there were also no increased M2 macrophage markers (transglutaminase-2: 81.5-fold, P=0.0015; interleukin-10: 7.6-fold, P=0.0450) in CD44 knockout mice. Delivery of monocyte chemoattractant protein-1 to CD44 knockout mice rescued the phenotype with thicker AVF walls (27.2 versus 14.7 μm; P=0.0306), increased collagen density (2.4-fold; P=0.0432), and increased number of M2 macrophages (2.1-fold; P=0.0335). CD44 promotes accumulation of M2 macrophages, extracellular matrix deposition, and wall thickening during AVF maturation. These data show the association of M2 macrophages with wall thickening during AVF maturation and suggest that enhancing CD44 activity may be a strategy to increase AVF maturation.

Yeast-mediated mRNA delivery polarizes immuno-suppressive macrophages towards an immuno-stimulatory phenotype

Macrophages have increasingly gained interest as a therapeutic target since they represent an integral component of the tumor microenvironment. In fact, M2 macrophage accumulation in solid tumors is associated with poor prognosis and therapy failure. Therefore, reprogramming M2 macrophages towards an M1 phenotype with anti-tumor activity by gene therapy represents a promising therapeutic approach. Herein, we describe recombinant Saccharomyces cerevisiae as a novel gene delivery vehicle for primary human macrophages. Opsonized S. cerevisiae was taken up efficiently by M2 macrophages and initiated the expression of pro-inflammatory cytokines. Recombinant yeast delivered functional nucleic acids to macrophages, especially when constitutively biosynthesized mRNA was used as cargo. Interestingly, expression of the protein encoded for by the delivered nucleic acid was higher in M2 cells when compared to M1 macrophages. Finally, the delivery of mRNA coding for the pro-inflammatory regulators MYD88 and TNF to M2 macrophages induced a prolonged upregulation of pro-inflammatory and cytotoxic cytokines in these cells, suggesting their successful re-education towards an anti-tumor M1 phenotype. Our results suggest the use of yeast-based gene delivery as a promising approach for the treatment of pathologic conditions that may benefit from the presence of M1-polarized macrophages, such as cancer.

Aspirin-Triggered Resolvin D1-modified materials promote the accumulation of pro-regenerative immune cell subsets and enhance vascular remodeling.

This work is motivated by our efforts to explore the underlying mechanisms of inflammation resolution after injury and to develop biomaterial-based approaches to amplify endogenous mechanisms of resolution and repair. Though specific lipid mediators have been identified that actively promote the resolution of inflammation, biomaterial-based localized delivery of these mediators has been largely unexplored. We loaded Aspirin-Triggered Resolvin D1 into a PLGA scaffold and examined the effects of sustained, localized delivery on the innate immune response. We found that biomaterial delivery of resolvin was able to enhance the accumulation of pro-regenerative populations of immune cells, including anti-inflammatory monocytes, population that has never before been shown to respond to resolvin treatment, and also enhance vascular remodeling in response to tissue injury.

Adipose Tissue-Resident Regulatory T Cells.

Tissue-resident immune cells play critical roles in regulating tissue function and homeostasis. Obesity-associated visceral adipose tissue inflammation is attributed to the accumulation of M1 macrophages which produce inflammatory cytokines like TNF-α, IL-6, and expansion of effector T cells like Th1 cells, CD8+ cytotoxic T cells which produce interferon-γ to further add to the severity of inflammation in the visceral adipose tissue. Regulatory T cells have been reported to exert key roles in suppressing inflammation, thus maintaining the homeostasis of immune responses, and visceral adipose Tregs exert critical roles in defending against obesity-associated metabolic disorders. They inhibit the infiltration of effector T cells and facilitate the reconstitution of adipose tissue macrophages from M1 to M2 phenotype. What is more, they can take up lipids from the adipocytes through CD36 which is driven by PPARγ. Here we review the recent progress in adipose tissue-resident regulatory T cells (Tregs), a subpopulation of CD4+ T cells which suppress adipose tissue inflammation.

Loss of miR-140 is a key risk factor for radiation-induced lung fibrosis through reprogramming fibroblasts and macrophages.

Radiation-induced lung fibrosis (RILF) is a common side effect for patients with thoracic cancer receiving radiation therapy. RILF is characterized by excessive collagen deposition mediated by TGF-β1 and its downstream factor SMAD3, but the exact molecular mechanism leading to fibrosis is yet to be determined. The present study investigated the impact of miR-140 on RILF development. Herein, we first found that loss of miR-140 is a marker of fibrotic lung tissue in vivo one-year post-radiation treatment. We showed that miR-140 knockout primary lung fibroblasts have a higher percentage of myofibroblasts compared to wild type primary lung fibroblasts, and that loss of miR-140 expression leads to increased activation of TGF-β1 signaling as well as increased myofibroblast differentiation. We also identified fibronectin as a novel miR-140 target gene in lung fibroblasts. Finally, we have shown that miR-140 deficiency promotes accumulation of M2 macrophages in irradiated lung tissues. These data suggest that miR-140 is a key protective molecule against RILF through inhibiting myofibroblast differentiation and inflammation.

Adipocyte-derived microvesicles from obese mice induce M1 macrophage phenotype through secreted miR-155.

The pro-inflammatory profile of M1 macrophage accumulation in adipose tissue is a central event leading to the metabolic complications of obesity. However, the mechanisms by which M1 macrophages are enriched in adipose tissue during weight gain remain incompletely understood. Here, we investigated the effects of adipocyte-derived microvesicles (ADM) on modulating macrophage phenotype in mice and explored the involved molecular signalling pathways. We found that, compared with ADM from lean mice (SD ADM), ADM from obese mice (HFD ADM) significantly enhanced M1 marker expression. The quantitative RT-PCR assay demonstrated that miR-155 was upregulated in both HFD ADM and HFD ADM-treated macrophages. By depleting miR-155 expression in HFD ADM and increasing miR-155 level in SD ADM, we further illustrated that miR-155 in ADM-induced M1 macrophage polarization. Functionally, in contrast to SD ADM, HFD ADM significantly decreased the protein level ofSOCS1, a proven miR-155 target, leading to activation of STAT1, and suppression of STAT6 signalling; these effects were reversed by silencing miR-155 in HFD ADM. Furthermore, the supernatant of bone marrow-derived macrophages pre-stimulated with miR-155-bearing ADM interfered with insulin signalling and insulin-induced glucose uptake in adipocytes. Collectively, these results provide the first evidence that M1 macrophage polarization can be mediated by miR-155-bearing ADM, which reciprocally regulates insulin signalling and glucose uptake in adipocytes. Our study reveals a novel mechanism through which obesity induces an imbalance in the M1-to-M2 macrophage ratio in adipose tissue, thus causing chronic inflammation and local insulin resistance.

Activation of the niacin receptor HCA2 reduces demyelination and neurofilament loss, and promotes functional recovery after spinal cord injury in mice

After spinal cord injury (SCI), there is an acute phase of alternatively activated (M2) macrophage infiltration, followed by a long-lasting phase of classically activated (M1) macrophage accumulation in the wound, which is believed to derail healing and compromize organ functions. Thus, agents which are able to modulate macrophage phenotypes may provide significant benefits to SCI patients. In the present study, we demonstrate that the niacin receptor HCA2 is specifically expressed on the cell surface of M1 but not M2 macrophages. Treatment of M1 macrophages with niacin (300μM) resulted in down-regulation of the p65 NF-κB phosphorylation, associated with a marked decrease in the levels of M1 markers, including CD86, IL-12, and IL-6, and a significant increase in the expressions of M2 markers, such as CD206, IL-10, and IL-13, suggesting that niacin causes a shift of M1 to M2. Moreover, treatment of the M1-oligodendrocyte precursor cell (OPC) co-cultures with niacin markedly promoted the expression of myelin binding protein (MBP). After SCI in C57/BL6 mice for a week, a marked accumulation of M1 macrophages, which expressed HCA2 receptor, was evident in the wound. Treatment of the SCI mice with niacin (100mg/kg) resulted in a dramatic decrease in the number of M1 macrophages and a significant increase in the number of M2 macrophages in the wound. This was associated with a robust inflammation resolution, attenuation of demyelination and neurofilament loss, and significant improvement of locomotor function. Thus, HCA2 receptor may serve as a therapeutic target to promote post-SCI recovery.

Olive oil, compared to a saturated dietary fat, has a protective role on atherosclerosis in niacin-treated mice with metabolic syndrome

We aimed to investigate the impact of high-fat low-cholesterol diets rich in saturated fatty acids (HFLCD-SFAs), monounsaturated FAs (HFLCD-MUFAs) or MUFAs + omega-3 long-chain polyunsaturated FAs (HFLCD-PUFAs) in combination with niacin (NA) on atherosclerotic plaque characteristics in a mouse model (Lepob/obLDLR−/−) of metabolic syndrome (MetS). Compared to a low-fat low-cholesterol diet (LFLCD), HFLCDs increased body weight, triglycerides, insulin, pro-inflammatory cytokines, and circulating monocytes, contributing the HFLCD-SFAs to a predominance of a classical pro-inflammatory Ly6Chi population, whereas HFLCD-MUFAs and HFLCD-PUFAs to a non-classical patrolling Ly6Clo population. HFLCDs promoted atherosclerosis in the aortic roots of animals but the plaque size, collagen, and macrophage content were higher with the HFLCD-SFAs than with the HFLCD-MUFAs or HFLCD-PUFAs. Furthermore, HFLCD-SFAs promoted the intra-plaque accumulation of M1 macrophages, whereas HFLCD-MUFAs and HFLCD-PUFAs favoured the accumulation of M2 macrophages. These data suggest that dietary MUFAs had advantage over SFAs to prevent atherosclerotic events in the NA-treated MetS.