Pro-inflammatory M1 Macrophage Polarization Research Articles

The TFPI2–PPARγ axis induces M2 polarization and inhibits fibroblast activation to promote recovery from post-myocardial infarction in diabetic mice

BackgroundDiabetes mellitus is one of the causes of poor ventricular remodelling and poor cardiac recovery after myocardial infarction (MI). We previously reported that tissue factor pathway inhibitor-2 (TFPI2) was downregulated in response to hyperglycaemia and that it played a pivotal role in extracellular matrix (ECM) degradation and cell migration. Nonetheless, the function and mechanism of TFPI2 in post-MI remodelling under diabetic conditions remain unclear. Therefore, in the present study, we investigated the role of TFPI2 in post-MI effects in a diabetic mouse model.ResultsTFPI2 expression was markedly decreased in the infarcted myocardium of diabetic MI mice compared with that in non-diabetic mice. TFPI2 knockdown in the MI mouse model promoted fibroblast activation and migration as well as matrix metalloproteinase (MMP) expression, leading to disproportionate fibrosis remodelling and poor cardiac recovery. TFPI2 silencing promoted pro-inflammatory M1 macrophage polarization, which is consistent with the results of TFPI2 downregulation and M1 polarization under diabetic conditions. In contrast, TFPI2 overexpression in diabetic MI mice protected against adverse cardiac remodelling and functional deterioration. TFPI2 overexpression also inhibited MMP2 and MMP9 expression and attenuated fibroblast activation and migration, as well as excessive collagen production, in the infarcted myocardium of diabetic mice. TFPI2 promoted an earlier phenotype transition of pro-inflammatory M1 macrophages to reparative M2 macrophages via activation of peroxisome proliferator-activated receptor gamma.ConclusionsThis study highlights TFPI2 as a promising therapeutic target for early resolution of post-MI inflammation and disproportionate ECM remodelling under diabetic conditions.

Less Severe Sepsis in Cecal Ligation and Puncture Models with and without Lipopolysaccharide in Mice with Conditional Ezh2-Deleted Macrophages (LysM-Cre System).

Despite a previous report on less inflammatory responses in mice with an absence of the enhancer of zeste homologue 2 (Ezh2), a histone lysine methyltransferase of epigenetic regulation, using a lipopolysaccharide (LPS) injection model, proteomic analysis and cecal ligation and puncture (CLP), a sepsis model that more resembles human conditions was devised. As such, analysis of cellular and secreted protein (proteome and secretome) after a single LPS activation and LPS tolerance in macrophages from Ezh2 null (Ezh2flox/flox; LysM-Crecre/-) mice (Ezh2 null) and the littermate control mice (Ezh2fl/fl; LysM-Cre-/-) (Ezh2 control) compared with the unstimulated cells from each group indicated fewer activities in Ezh2 null macrophages, especially by the volcano plot analysis. Indeed, supernatant IL-1β and expression of genes in pro-inflammatory M1 macrophage polarization (IL-1β and iNOS), TNF-α, and NF-κB (a transcription factor) were lower in Ezh2 null macrophages compared with the control. In LPS tolerance, downregulated NF-κB compared with the control was also demonstrated in Ezh2 null cells. In CLP sepsis mice, those with CLP alone and CLP at 2 days after twice receiving LPS injection, representing sepsis and sepsis after endotoxemia, respectively, symptoms were less severe in Ezh2 null mice, as indicated by survival analysis and other biomarkers. However, the Ezh2 inhibitor improved survival only in CLP, but not LPS with CLP. In conclusion, an absence of Ezh2 in macrophages resulted in less severe sepsis, and the use of an Ezh2 inhibitor might be beneficial in sepsis.

A Matrix-Metalloproteinase-Responsive Hydrogel System for Modulating the Immune Microenvironment in Myocardial Infarction.

Injectable hydrogels carrying therapeutic factors to modulate the infarct immune microenvironment show great potential in the treatment of myocardial infarction (MI). However, conventional injectable hydrogels release therapeutic factors in an uncontrolled manner, which leads to poor treatment efficacy and acute side effects on normal tissues. Inthiswork, a matrix metalloproteinase (MMP)2/9-responsive hydrogel system (MPGC4) is developed, considering the characteristics of the post-MI microenvironment. MPGC4 consists of tetra-poly(ethylene glycol) (PEG) hydrogels and a composite gene nanocarrier (CTL4) that is composed of carbon dots (CDots) coupled with interleukin-4 plasmid DNA via electrostatic interactions. MPGC4 can be automatically triggered to release CTL4 on demand after MI to regulate the infarct immune microenvironment. In addition, due to the photoluminescence properties of CDots, a large amount of viscoelastic MPGC4 is found to be retained in situ after injection into the infarct region without leakage. The in vitro results demonstrate that CTL4 promotes proinflammatory M1 macrophage polarization to the anti-inflammatory M2 subtype and contributes to cardiomyocyte survival through macrophage transition. In a rat model of MI, MPGC4 clears MMPs and precisely targets CTL4 to the infarcted region. In particular, MPGC4 improves cardiac function by modulating macrophage transition to reduce early inflammatory responses and proangiogenic activity.

On the Potential Therapeutic Roles of Taurine in Autism Spectrum Disorder

Contemporary research has found that people with autism spectrum disorder (ASD) exhibit aberrant immunological function, with a shift toward increased cytokine production and unusual cell function. Microglia and astroglia were found to be significantly activated in immuno-cytochemical studies, and cytokine analysis revealed that the macrophage chemoattractant protein-1 (MCP-1), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and transforming growth factor β-1 (TGFB-1), all generated in the neuroglia, constituted the most predominant cytokines in the brain. Taurine (2-aminoethanesulfonic acid) is a promising therapeutic molecule able to increase the activity of antioxidant enzymes and ATPase, which may be protective against aluminum-induced neurotoxicity. It can also stimulate neurogenesis, synaptogenesis, and reprogramming of proinflammatory M1 macrophage polarization by decreasing mitophagy (mitochondrial autophagy) and raising the expression of the markers of the anti-inflammatory and pro-healing M2 macrophages, such as macrophage mannose receptor (MMR, CD206) and interleukin 10 (IL-10), while lowering the expression of the M1 inflammatory factor genes. Taurine also induces autophagy, which is a mechanism that is impaired in microglia cells and is critically associated with the pathophysiology of ASD. We hypothesize here that taurine could reprogram the metabolism of M1 macrophages that are overstimulated in the nervous system of people suffering from ASD, thereby decreasing the neuroinflammatory process characterized by autophagy impairment (due to excessive microglia activation), neuronal death, and improving cognitive functions. Therefore, we suggest that taurine can serve as an important lead for the development of novel drugs for ASD treatment.

A Pathogenic Role for FcγRI in the Immune Response against Chlamydial Respiratory Infection.

FcγRI is an important cell surface receptor reported to be involved in multiple immune responses, although it has not yet been extensively studied in intracellular bacterial infections. Here, using a mouse model of C. muridarum respiratory infection, we were able to determine how FcγRI regulates the host resistance against chlamydial invasion. According to our findings, the chlamydial loads and pulmonary pathology were both reduced in FcγRI deficient (Fcgr1-/-) animals. Being infected, monocytes, macrophages, neutrophils, DCs, CD4+/CD8+ T cells, and effector Th1 subsets displayed increased FcγRI expression patterns. Altered infiltration of these cells in the lungs of Fcgr1-/- mice further demonstrated the regulation of FcγRI in the immune system and identified Th1 cells and macrophages as its target cell populations. As expected, we observed that the Th1 response was augmented in Fcgr1-/- mice, while the pro-inflammatory M1 macrophage polarization was constrained. These findings might indicate FcγRI as a potential regulator for host immunity and inflammatory response during chlamydial infection.

Phenotypic and Transcriptional Changes of Pulmonary Immune Responses in Dogs Following Canine Distemper Virus Infection.

Canine distemper virus (CDV), a morbillivirus within the family Paramyxoviridae, is a highly contagious infectious agent causing a multisystemic, devastating disease in a broad range of host species, characterized by severe immunosuppression, encephalitis and pneumonia. The present study aimed at investigating pulmonary immune responses of CDV-infected dogs in situ using immunohistochemistry and whole transcriptome analyses by bulk RNA sequencing. Spatiotemporal analysis of phenotypic changes revealed pulmonary immune responses primarily driven by MHC-II+, Iba-1+ and CD204+ innate immune cells during acute and subacute infection phases, which paralleled pathologic lesion development and coincided with high viral loads in CDV-infected lungs. CD20+ B cell numbers initially declined, followed by lymphoid repopulation in the advanced disease phase. Transcriptome analysis demonstrated an increased expression of transcripts related to innate immunity, antiviral defense mechanisms, type I interferon responses and regulation of cell death in the lung of CDV-infected dogs. Molecular analyses also revealed disturbed cytokine responses with a pro-inflammatory M1 macrophage polarization and impaired mucociliary defense in CDV-infected lungs. The exploratory study provides detailed data on CDV-related pulmonary immune responses, expanding the list of immunologic parameters potentially leading to viral elimination and virus-induced pulmonary immunopathology in canine distemper.

Dexmedetomidine Activates Akt, STAT6 and IRF4 Modulating Cytoprotection and Macrophage Anti-Inflammatory Phenotype Against Acute Lung Injury in vivo and in vitro.

PurposeThis study aims to investigate the cytoprotective and anti-inflammatory effects of an α2-adrenoreceptor (α2-AR) agonist, dexmedetomidine (Dex), on lipopolysaccharides (LPS)-induced acute lung injury and underlying mechanisms with focus on alveolar macrophage polarization modulation.MethodsC57BL/6 mice were intraperitoneally injected LPS (10 mg/kg) with or without Dex (25 µg/kg) and/or α2-AR antagonist atipamezole (Atip, 500 µg/kg). Lung tissues were then analysed to determine injuries. In vitro, human pulmonary epithelial cells (A549) and mice alveolar macrophages (MH-S) were exposed to LPS (10 ng/mL) with or without different concentrations of Dex (0.1–100 nM). Alveolar macrophage polarization, NLRP3 inflammasome activation and inflammatory responses were determined. PTEN/Akt signaling and its downstream transcriptional factors as targets for macrophage polarization were assessed.ResultsDex treatment significantly reduced pro-inflammatory M1 macrophage polarization and NLRP3 inflammasome activation in the lungs relative to the mice treated with LPS. The similar pattern reduction of NLRP3 inflammasome activation by Dex was also found in A549 cells. Atip partly reversed the anti-inflammatory effects of Dex. In cultured alveolar macrophages, Dex reduced LPS-mediated expression of IL-1, −6 and TNF-α receptors while promoting alveolar macrophages differentiation towards a M2 anti-inflammatory phenotype. Additionally, LPS increased Akt signaling activation in a time-dependent manner, which was further activated by Dex via inhibiting phosphatase and tensin homolog (PTEN). The action of Dex on Akt signaling shifted alveolar macrophages from M1 to M2 phenotype through increasing STAT6 and IRF4 transcriptional factors.ConclusionDex protected against LPS-induced lung injury and suppressed LPS-induced pulmonary inflammatory responses by attenuating the NLRP3 inflammasome activation and promoting anti-inflammatory M2 macrophage polarization.

RNA editing enzyme APOBEC3A promotes pro-inflammatory M1 macrophage polarization

Pro-inflammatory M1 macrophage polarization is associated with microbicidal and antitumor responses. We recently described APOBEC3A-mediated cytosine-to-uracil (C > U) RNA editing during M1 polarization. However, the functional significance of this editing is unknown. Here we find that APOBEC3A-mediated cellular RNA editing can also be induced by influenza or Maraba virus infections in normal human macrophages, and by interferons in tumor-associated macrophages. Gene knockdown and RNA_Seq analyses show that APOBEC3A mediates C>U RNA editing of 209 exonic/UTR sites in 203 genes during M1 polarization. The highest level of nonsynonymous RNA editing alters a highly-conserved amino acid in THOC5, which encodes a nuclear mRNA export protein implicated in M-CSF-driven macrophage differentiation. Knockdown of APOBEC3A reduces IL6, IL23A and IL12B gene expression, CD86 surface protein expression, and TNF-α, IL-1β and IL-6 cytokine secretion, and increases glycolysis. These results show a key role of APOBEC3A cytidine deaminase in transcriptomic and functional polarization of M1 macrophages.

Restoration of electrical microenvironment enhances bone regeneration under diabetic conditions by modulating macrophage polarization

Macrophage-mediated inflammation compromises bone repair in diabetic patients. Electrical signaling cues are known to regulate macrophage functions. However, the biological effects of electrical microenvironment from charged biomaterials on the immune response for regulating osteogenesis under diabetic conditions remain to be elucidated. Herein the endogeneous electrical microenvironment of native bone tissue was recapitulated by fabricating a ferroelectric BaTiO3/poly (vinylidene fluoridetrifluoroethylene) (BTO/P(VDF-TrFE)) nanocomposite membrane. In vitro, the polarized BaTiO3/poly (vinylidene fluoridetrifluoroethylene) (BTO/P(VDF-TrFE)) nanocomposite membranes inhibited high glucose-induced M1-type inflammation, by effecting changes in cell morphology, M1 marker expression and pro-inflammatory cytokine secretion in macrophages. This led to enhanced osteogenic differentiation of human bone marrow mesenchymal stem cells (BM-MSCs). In vivo, the biomimetic electrical microenvironment recapitulated by the polarized nanocomposite membranes switched macrophage phenotype from the pro-inflammatory (M1) into the pro-healing (M2) phenotype, which in turn enhanced bone regeneration in rats with type 2 diabetes mellitus. Mechanistic studies revealed that the biomimetic electrical microenvironment attenuated pro-inflammatory M1 macrophage polarization under hyperglycemic conditions by suppressing expression of AKT2 and IRF5 within the PI3K-AKT signaling pathway, thereby inducing favorable osteo-immunomodulatory effects. Our study thus provides fundamental insights into the biological effects of restoring the electrical microenvironment conducive for osteogenesis under DM conditions, and offers an effective strategy to design functionalized biomaterials for bone regeneration therapy in diabetic patients.

Exosomal miRNA-19a and miRNA-614 Induced by Air Pollutants Promote Proinflammatory M1 Macrophage Polarization via Regulation of RORα Expression in Human Respiratory Mucosal Microenvironment.

Air pollution exposure leads to various inflammatory diseases in the human respiratory system. Chronic rhinosinusitis is an inflammatory disease caused by viruses, bacteria, or air pollutants. However, the underlying molecular mechanisms through which air particulate matter (PM) causes inflammation and disease remain unclear. In this article, we report that the induction of exosomal microRNAs (miRNAs) from human nasal epithelial cells upon airborne PM exposure promotes proinflammatory M1 macrophage polarization via downregulated RORα expression. Exposure of human nasal epithelial cells to PM results in inflammation-related miRNA expression, and more miRNA is secreted through exosomes delivered to macrophages. Among these, miRNA-19a and miRNA-614 directly bind to the 3'-untranslated region of RORα mRNA and downregulate RORα expression, which leads to inflammation due to inflammatory cytokine upregulation and induces macrophages to a proinflammatory M1-like state. Finally, we showed enhanced expression of miRNA-19a and miRNA-614 but reduced RORα expression in a chronic rhinosinusitis patient tissue compared with the normal. Altogether, our results suggest that PM-induced exosomal miRNAs might play a crucial role in the proinflammatory mucosal microenvironment and macrophage polarization through the regulation of RORα expression.

CB2R agonist JWH-133 attenuates chronic inflammation by restraining M1 macrophage polarization via Nrf2/HO-1 pathway in diet-induced obese mice

AimsCannabinoid receptor 2 (CB2R) is an important regulator of immunoinflammatory responses. Interestingly, studies have demonstrated that CB2R was expressed in metabolically active tissue, so we speculated that CB2R might have a crucial impact on energy balance. We thus examined the anti-inflammatory activities of CB2R and a CB2R agonist, JWH-133, in diet-induced obese in mice as well as in cultured macrophages. Materials and methodsWe evaluated the in vivo effect of JWH-133 on diet-induced adipose tissue inflammation. We also assessed the in vitro effects of JWH-133 on lipopolysaccharide (LPS)-induced inflammation in RAW264.7 macrophages, with a focus on the nuclear factor E2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling pathway. Key findingsWe found that JWH-133 reduced body weight gain, relieved glucose tolerance, and enhanced insulin sensitivity in a mouse model. It also down-regulated the expression of M1 macrophage biomarkers (tumor necrosis factor-α, interleukin (IL)-6, inducible nitric oxide synthase (iNOS), IL-1β, CC motif chemokine ligand 2, and C-X-C motif chemokine 10) in vivo and in vitro, but up-regulated levels of M2 macrophage biomarkers (IL-10 and arginase-1) in both mice and cultured macrophages. Furthermore, the underlying mechanisms were studied in an LPS-treated RAW264.7 cell line. We found a role for JWH-133 in controlling M1 macrophage polarization by activating the Nrf2/HO-1 pathway, while the effect of JWH-133 was diminished by a HO-1 inhibitor, Sn(IV) protoporphyrin IX dichloride. SignificanceJWH-133 showed anti-obesity effects that ameliorated pro-inflammatory M1 macrophage polarization through the Nrf2/HO-1 pathway. Therefore, our results provide a new proof for the potential use of the CB2R agonist, JWH-133, in the treatment of obesity.

Antigen-cross presentation promotes development of terminally differentiated CD8 T cells in young individuals

Abstract Cancer immunotherapeutic approaches that rely on endogenous T cell responses have shown limited success in children, a pattern attributed to the low mutational burden of pediatric tumors. Here, we report that CD8 T cells isolated from a diverse set of pediatric solid tumors are enriched for an antigen-experienced phenotype. The limited ability of immune checkpoint blockade therapy (ICBT) to trigger anti-tumor responses in children, despite the presence of activated CD8 T cells, prompted us to explore alternative underlying mechanisms restricting anti-tumor responses. Using a novel mouse tumor model that expresses a well-characterized epitope coupled to an mCherry marker, we identified antigen cross-presentation by tumor infiltrating myeloid cells as a key regulator of CD8 T cell effector function in tumors. Strikingly, age-related changes in the TME resulted in a skewing of the CD8 T cell effector fate toward a terminally differentiated state in young tumor-bearing mice. Profiling of tumor infiltrating antigen presenting cells by scRNAseq revealed a proinflammatory M1 macrophage polarization in young tumors but a predominant M2 “wound healing” response in adult tumors. Consistent with our mouse findings, analysis of immune infiltrates from human pediatric solid tumors revealed a strong correlation between the expression of PDL1 on myeloid cells and enrichment of tumor-associated CD8 T cells with an exhaustion phenotype. Collectively, these data indicate that the “young” microenvironment of an actively developing tissue/individual contributes to the generation of an immune response skewed towards a terminally differentiated state with limited plasticity, thus narrowing the window for immunotherapeutic interventions.

MDM2 inhibitor APG-115 synergizes with PD-1 blockade through enhancing antitumor immunity in the tumor microenvironment

BackgroundProgrammed death-1 (PD-1) immune checkpoint blockade has achieved clinical successes in cancer therapy. However, the response rate of anti-PD-1 agents remains low. Additionally, a subpopulation of patients developed hyperprogressive disease upon PD-1 blockade therapy. Combination therapy with targeted agents may improve immunotherapy. Recent studies show that p53 activation in the myeloid linage suppresses alternative (M2) macrophage polarization, and attenuates tumor development and invasion, leading to the hypothesis that p53 activation may augment antitumor immunity elicited by anti-PD-1 therapy.MethodUsing APG-115 that is a MDM2 antagonist in clinical development as a pharmacological p53 activator, we investigated the role of p53 in immune modulation and combination therapy with PD-1 blockade.ResultsIn vitro treatment of bone marrow-derived macrophages with APG-115 resulted in activation of p53 and p21, and a decrease in immunosuppressive M2 macrophage population through downregulation of c-Myc and c-Maf. Increased proinflammatory M1 macrophage polarization was observed in the spleen from mice treated with APG-115. Additionally, APG-115 has co-stimulatory activity in T cells and increases PD-L1 expression in tumor cells. In vivo, APG-115 plus anti-PD-1 combination therapy resulted in enhanced antitumor activity in Trp53wt, Trp53mut, and Trp53-deficient (Trp53−/−) syngeneic tumor models. Importantly, such enhanced activity was abolished in a syngeneic tumor model established in Trp53 knockout mice. Despite differential changes in tumor-infiltrating leukocytes (TILs), including the increases in infiltrated cytotoxic CD8+ T cells in Trp53wt tumors and M1 macrophages in Trp53mut tumors, a decrease in the proportion of M2 macrophages consistently occurred in both Trp53wt and Trp53mut tumors upon combination treatment.ConclusionOur results demonstrate that p53 activation mediated by APG-115 promotes antitumor immunity in the tumor microenvironment (TME) regardless of the Trp53 status of tumors per se. Instead, such an effect depends on p53 activation in Trp53 wild-type immune cells in the TME. Based on the data, a phase 1b clinical trial has been launched for the evaluation of APG-115 in combination with pembrolizumab in solid tumor patients including those with TP53mut tumors.

Inhibitory effects of berberine on proinflammatory M1 macrophage polarization through interfering with the interaction between TLR4 and MyD88

BackgroundsInflammation is recognized as the key pathological mechanism of type 2 diabetes. The hypoglyceamic effects of berberine (BBR) are related to the inhibition of the inflammatory response, but the mechanism is not completely clear.MethodsThe inflammatory polarization of Raw264.7 cells and primary peritoneal macrophages were induced by LPS, and then effects and underlying mechanisms of BBR were explored. An inflammatory model was established by LPS treatment at different concentrations for different treatment time. An ELISA assay was used to detect the secretions of TNF-α. RT-PCR was applied to detect M1 inflammatory factors. The F4/80+ ratio and CD11c+ ratio of primary peritoneal macrophages were determined by flow cytometry. The expressions of p-AMPK and TLR4 were detected by Western blot. The cytoplasmic and nuclear distributions of NFκB p65 were observed by confocal microscopy. The binding of TLR4 to MyD88 was tested by CoIP, and the affinity of BBR for TLR4 was assessed by molecular docking.ResultsUpon exposure to LPS, the secretion of TNF-α and transcription of inflammatory factors in macrophages increased, cell morphology changed and protrusions appeared gradually, the proportion of F4/80+CD11c+ M1 macrophages increased, and the nuclear distribution of NFκB p65 increased. BBR pretreatment partially inhibited the changes mentioned above. However, the expression of TLR4 and p-AMPK did not change significantly after LPS intervention for 3 h. Meanwhile, CoIP showed that the interaction between TLR4 and MyD88 increased, and BBR inhibited the binding. Molecular docking suggested that BBR might interact with TLR4.ConclusionsInflammatory changes were induced in macrophages after LPS stimulation for 3 h, and BBR pretreatment inhibited inflammatory polarization. BBR might interact with TLR4 and disturb TLR4/MyD88/NFκB signalling pathway, and it might be the mechanism by which BBR attenuated inflammation in the early phase.

Irf5 deficiency in myeloid cells prevents necrotizing enterocolitis by inhibiting M1 macrophage polarization

Necrotizing enterocolitis (NEC) is a life-threatening inflammatory disease in newborns, but the mechanisms remain unclear. Interferon regulatory factor 5 (IRF5) is a master regulator of macrophage function and is essential for proinflammatory M1 macrophage polarization. Our previous data indicated that M1 macrophages promote NEC injury. Here, we investigated whether IRF5 is involved in the pathogenesis of NEC. First, we found that IRF5 was upregulated in infiltrated macrophages in human neonates with NEC compared to controls. We further confirmed IRF5 upregulation in macrophages in experimental murine NEC and that the infiltrated macrophages were predominantly polarized into the M1 but not the M2 phenotype. Myeloid-specific deficiency of Irf5, which was associated with reduced M1 macrophage polarization and systematic inflammation, dramatically prevented experimental NEC. Moreover, we found that the ablation of Irf5 in myeloid cells markedly suppressed intestinal epithelial cell apoptosis and further prevented intestinal barrier dysfunction in experimental NEC. Bioinformatic and chromatin immunoprecipitation analysis further showed that IRF5 binds to the promoters of the M1 macrophage-associated genes Ccl4, Ccl5, Tnf, and Il12b. Overall, our study provides evidence that IRF5 participates in the pathogenesis of NEC, while the deletion of Irf5 in myeloid cells prevents NEC via inhibiting M1 macrophage polarization.

Deficiency of Interferon Regulatory Factor 5 in Myeloid Cells Prevents Necrotizing Enterocolitis by Inhibiting M1 Macrophage Polarization

Necrotizing enterocolitis (NEC) is a severe inflammatory disease and is the most common cause of gastrointestinal mortality in newborns. However, the mechanisms remain unclear. Interferon regulatory factor 5 (IRF5) is a master regulator of macrophage function, which is essential for proinflammatory M1 macrophage polarization, and our previous data suggest the role of M1 macrophages promote NEC injury. Here, we investigated whether IRF5 is involved in the pathogenesis of NEC. We found that IRF5 was induced in infiltrated macrophages in neonates with NEC compared to the controls. We further confirmed IRF5 induction in macrophages in murine experimental NEC, and the infiltrated macrophages were predominantly polarized into M1 but not M2 phenotype in NEC. We generated the myeloid‐specific IRF5 defecient mice, and revealed that myeloid‐specific deficiency of IRF5 dramatically prevented experimental NEC, which was associated with reduced M1 macrophage polarization and systematic inflammation. Moreover, we found that ablation of IRF5 in myeloid cells markedly suppressed intestinal epithelial cells apoptosis and further prevented intestinal barrier dysfunction induced by experimental NEC. Overall, our study provides evidence that IRF5 in myeloid cells participates in the pathogenesis of NEC, while myeloid cell‐deletion of IRF5 prevents NEC via inhibiting M1 macrophage polarization.Support or Funding InformationThis study was supported by the National Natural Science Foundation of China (81501298, 81670390, and 81670259).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Selective activation of cannabinoid receptor-2 reduces neuroinflammation after traumatic brain injury via alternative macrophage polarization

Inflammation is an important mediator of secondary neurological injury after traumatic brain injury (TBI). Endocannabinoids, endogenously produced arachidonate based lipids, have recently emerged as powerful anti-inflammatory compounds, yet the molecular and cellular mechanisms underlying these effects are poorly defined. Endocannabinoids are physiological ligands for two known cannabinoid receptors, CB1R and CB2R. In the present study, we hypothesized that selective activation of CB2R attenuates neuroinflammation and reduces neurovascular injury after TBI. Using a murine controlled cortical impact (CCI) model of TBI, we observed a dramatic upregulation of CB2R within infiltrating myeloid cells beginning at 72 h. Administration of the selective CB2R agonist, GP1a (1–5 mg/kg), attenuated pro-inflammatory M1 macrophage polarization, increased anti-inflammatory M2 polarization, reduced edema development, enhanced cerebral blood flow, and improved neurobehavioral outcomes after TBI. In contrast, the CB2R antagonist, AM630, worsened outcomes. Taken together, our findings support the development of selective CB2R agonists as a therapeutic strategy to improve TBI outcomes while avoiding the psychoactive effects of CB1R activation.

Natural product celastrol suppressed macrophage M1 polarization against inflammation in diet-induced obese mice via regulating Nrf2/HO-1, MAP kinase and NF-κB pathways.

Macrophage polarization is implicated in the inflammation in obesity. The aim of the present study was to examine the anti-inflammatory activities of botanical triterpene celastrol against diet-induced obesity. We treated diet-induced obese C57BL/6N male mice with celastrol (5, 7.5 mg/kg/d) for 3 weeks, and investigated macrophage M1/M2 polarization in adipose and hepatic tissues. Celastrol reduced fat accumulation and ameliorated glucose tolerance and insulin sensitivity. Celastrol down-regulated the mRNA levels of macrophage M1 biomarkers (e.g., IL-6, IL-1β, TNF-α, iNOS) in cell culture and in mice. The underlying mechanisms were investigated in murine macrophage RAW264.7 cells. Our results demonstrated that celastrol might control macrophage polarization through modulating the cross-talk between the following three mechanisms: 1) suppressing LPS-induced activation of MAP kinases (e.g., ERK1/2, p38, JNK) in a concentration dependent manner; 2) attenuating LPS-induced nuclear translocation of NF-κB p65 subunit in a time dependent manner; 3) activating Nrf2 and subsequently inducing HO-1 expression. HO-1 inhibitor SnPP diminished the inhibitory effects of celastrol on the activation of NF-κB pathway and the pro-inflammatory M1 macrophage polarization. Taken together, celastrol exhibited anti-obesity effects via suppressing pro-inflammatory M1 macrophage polarization. Thus, our results provide new evidence for the potential of celastrol in the treatment of obesity.

Treatment with long chain n-3 polyunsaturated fatty acids improves adipose tissue hypoxia and alters macrophage polarization in severely obese subjects

Introduction: Hypoxia is hypothesized to sustain adipose tissue inflammation and to initiate adipose tissue fibrotic remodeling, a newly found feature of obesity related pathological alterations. Relative adipose tissue hypoxia, which is characterized by increased expression of transcription factor HIF1-α (hypoxia inducible factor 1α) may facilitate the transition from M2 to proinflammatory M1 macrophage polarization. M1 macrophages produce high levels of chemokines which further recruit more macrophages to the tissue, promoting to the development of insulin resistance in humans. We hypothesized that long chain n-3 polyunsaturated fatty acids (PUFA) ameliorate adipose tissue inflammation, reduce adipose tissue hypoxia and may prevent adipose tissue remodeling.