Sequential expression of macrophage anti-microbial/inflammatory and wound healing markers following innate, alternative and classical activation

Microglia signaling in health and disease - Implications in sex-specific brain development and plasticity

Microglia, the intrinsic neuroimmune cells residing in the central nervous system (CNS), exert a pivotal influence on brain development, homeostasis, and functionality, encompassing critical roles during both aging and pathological states. Recent advancements in comprehending brain plasticity and functions have spotlighted conspicuous variances between male and female brains, notably in neurogenesis, neuronal myelination, axon fasciculation, and synaptogenesis. Nevertheless, the precise impact of microglia on sex-specific brain cell plasticity, sculpting diverse neural network architectures and circuits, remains largely unexplored. This article seeks to unravel the present understanding of microglial involvement in brain development, plasticity, and function, with a specific emphasis on microglial signaling in brain sex polymorphism. Commencing with an overview of microglia in the CNS and their associated signaling cascades, we subsequently probe recent revelations regarding molecular signaling by microglia in sex-dependent brain developmental plasticity, functions, and diseases. Notably, C-X3-C motif chemokine receptor 1 (CX3CR1), triggering receptors expressed on myeloid cells 2 (TREM2), calcium (Ca2+), and apolipoprotein E (APOE) emerge as molecular candidates significantly contributing to sex-dependent brain development and plasticity. In conclusion, we address burgeoning inquiries surrounding microglia's pivotal role in the functional diversity of developing and aging brains, contemplating their potential implications for gender-tailored therapeutic strategies in neurodegenerative diseases.

Whole Blood Reactivity to Viral and Bacterial Pathogens after Non-Emergent Cardiac Surgery during the Acute and Convalescence Periods Demonstrates a Distinctive Profile of Cytokines Production Compared to the Preoperative Baseline in Cohort of 108 Patients, Suggesting Immunological Reprogramming during the 28 Days Traditionally Recognized as the Post-Surgical Recovery Period

The release of danger signals from tissues in response to trauma during cardiac surgery creates conditions to reprogram the immune system to subsequent challenges posed by pathogens in the postoperative period. To demonstrate this, we tested immunoreactivity before surgery as the baseline (tbaseline), followed by subsequent challenges during the acute phase (t24h), convalescence (t7d), and long-term recovery (t3m). For 108 patients undergoing elective heart surgery, whole blood was stimulated with lipopolysaccharide (LPS), Influenza A virus subtype N2 (H3N2), or the Flublok™ vaccine to represent common pathogenic challenges. Leukocytosis, platelet count, and serum C-reactive protein (CRP) were used to measure non-specific inflammation. Cytokines were measured after 18 h of stimulation to reflect activation of the various cell types (activated neutrophils-IL-8; activated T cells-IL-2, IFNγ, activated monocyte (MO)-TNFα, IL-6, and deactivated or atypically activated MO and/or T cells-M-CSF, IL-10). IL-2 and IL-10 were increased at t7d, while TNFα was suppressed at t24h when LPS was utilized. Interestingly, M-CSF and IL-6 production was elevated at seven days in response to all stimuli compared to baseline. While some non-specific markers of inflammation (white cell count, IL-6, and IL-8) returned to presurgical levels at t3m, CRP and platelet counts remained elevated. We showed that surgical stimulus reprograms leukocyte response to LPS with only partial restoration of non-specific markers of inflammation.

Topically-applied collagen-binding serum albumin-fused interleukin-4 modulates wound microenvironment in non-healing wounds

Non-healing wounds have a negative impact on quality of life and account for many cases of amputation and even early death among patients. Diabetic patients are the predominate population affected by these non-healing wounds. Despite the significant clinical demand, treatment with biologics has not broadly impacted clinical care. Interleukin-4 (IL-4) is a potent modulator of the immune system, capable of skewing macrophages towards a pro-regeneration phenotype (M2) and promoting angiogenesis, but can be toxic after frequent administration and is limited by its short half-life and low bioavailability. Here, we demonstrate the design and characterization of an engineered recombinant interleukin-4 construct. We utilize this collagen-binding, serum albumin-fused IL-4 variant (CBD-SA-IL-4) delivered in a hyaluronic acid (HA)-based gel for localized application of IL-4 to dermal wounds in a type 2 diabetic mouse model known for poor healing as proof-of-concept for improved tissue repair. Our studies indicate that CBD-SA-IL-4 is retained within the wound and can modulate the wound microenvironment through induction of M2 macrophages and angiogenesis. CBD-SA-IL-4 treatment significantly accelerated wound healing compared to native IL-4 and HA vehicle treatment without inducing systemic side effects. This CBD-SA-IL-4 construct can address the underlying immune dysfunction present in the non-healing wound, leading to more effective tissue healing in the clinic.

15-F2t-Isoprostane Favors an Anti-Inflammatory Phenotype in RAW 264.7 Macrophages during Endotoxin Challenge

Dysregulated inflammation and oxidative stress are major underlying components of several diseases. Macrophages are critical effector cells in immune responses, functioning to progress and resolve inflammation during such diseases. These mononuclear cells regulate inflammatory responses by exhibiting a range of phenotypes that evolve with the process, first promoting inflammation but then switching to a proresolving subtype to restore tissue homeostasis. Furthermore, macrophages are a primary source of isoprostanes (IsoPs), a nonenzymatic byproduct of lipid peroxidation during inflammation. As highly sensitive and specific indicators of lipid damage, IsoPs are the gold standard biomarker of oxidative stress. However, the physiological role of IsoPs during inflammation is currently not well-established. This study determined how IsoPs affect macrophage phenotype during lipopolysaccharide (LPS) challenge. RAW 264.7 macrophages (n = 7) were challenged with 5 ng/mL LPS for 8 h, followed with or without 500 nM 15-F2t-IsoP for 1 h. Macrophage phenotype was determined using metabolic, transcriptomic, and proteomic markers. Phenotypic markers assessed included ATP production; transcription of proinflammatory Nos2, Il1β, and anti-inflammatory Il10; and translation markers IL1α and IL6 (proinflammatory) with G-CSF and IL17 (anti-inflammatory). Statistical analyses included one-way ANOVA followed by Tukey’s posthoc test. Significance was set at p < 0.05. In combination with LPS, 15-F2t-IsoP increased ATP production relative to LPS-only treated cells. Additionally, gene expression of Nos2 and Il1β were decreased while Il10 was increased. Cytokine production of IL6 was decreased while IL10, G-CSF, and IL17 were increased. Collectively, these results provide evidence that 15-F2t-IsoP promotes an anti-inflammatory macrophage phenotype during LPS challenge. These data support a novel physiological role of IsoPs, where these lipid mediators may participate in healing pathways during late-stage inflammation when they are elevated. Additionally, the promotion of an anti-inflammatory macrophage phenotype may contribute to preventing or mitigating inflammation during disease. Future studies should be directed towards defining the mechanisms in which IsoPs influence macrophage phenotype, such as receptor interactions and downstream signaling pathways.

Spinal cord injury target-immunotherapy with TNF-α autoregulated and feedback-controlled human umbilical cord mesenchymal stem cell derived exosomes remodelled by CRISPR/Cas9 plasmid

Human umbilical cord mesenchymal stem cell (hucMSC) derived exosomes (EXOs) have been investigated as a new treatment for spinal cord injury (SCI) because of their anti-inflammatory, anti-apoptotic, angiogenesis-promoting, and axonal regeneration properties. The CAQK peptide found in the brains of mice and humans after trauma has recently been found to specifically bind to the injured site after SCI. Thus, we developed a nanocarrier system called EXO-C@P based on hucMSC exosomes remodelled by the CRISPR/Cas9 plasmid to control inflammation and modified by the CAQK peptide. EXO-C@P was shown to effectively accumulate at the injury site and saturate the macrophages to significantly reduce the expression of inflammatory cytokines in a mouse model of SCI. Moreover, EXO-C@P treatment improved the performance of mice in behavioural assessments and upregulated soluble tumour necrosis factor receptor-1 (sTNFR1) in serum and at the trauma site after SCI surgery, but lowered the proportion of iNOS⁺ cells and the concentration of proinflammatory factors. In conclusion, EXO-C@P provides an effective alternative to multiple topical administration and drug delivery approaches for the treatment of SCI. STATEMENT OF SIGNIFICANCE: SCI is a serious disease characterised by a high incidence, high disability rate, and high medical costs, and has become a global medical problem. Several studies have shown that the inflammatory response is the critical inducer of secondary injury after SCI. The inflammatory cytokine TNF-α is considered to be one of the most significant therapeutic targets for autoimmune diseases. Antibodies targeting TNF-α and sTNFR1 are capable of neutralising free TNF-α. In this study, exosomes in the CRISPR/Cas9 system were used to establish stem cells with an autoregulated and feedback-controlled TNF-α response, with these cells secreting sTNFR1, which neutralised TNF-α and antagonised the inflammation stimulated by TNF-α. Moreover, the plasmid was combined with CAQK, which targeted the injury site and promoted the recovery of SCI function.

Periodontal ligament stem cells promote polarization of M2 macrophages

Macrophages are widely distributed in a variety of tissues, and the different state of macrophages polarization is closely related to the occurrence, development, and prognosis of inflammation, including periodontitis, a chronic inflammatory disease leading to tooth loss worldwide. Periodontal ligament stem cells (PDLSCs) play a key role in immune regulation and periodontal tissues regeneration, contributing to cell-based therapy of periodontitis. However, the interactions between PDLSCs and macrophages are still elusive. The purpose of present study is to investigate the effect of PDLSCs conditioned medium (PDLSCs-CM) on the macrophage polarization and the possible mechanism. PDLSCs were isolated using tissue explant methods and characterized via multipotent differentiation test and examination of expression profiles of mesenchymal stem cells (MSCs) markers. The supernatant of PDLSCs was collected, centrifuged, filtered, and used as PDLSCs-CM. Then, PDLSCs-CM was cocultured with M0 macrophages or IL-4- and IL-13-induced M2 macrophages. The level of surface markers of M1/M2 macrophages and production of several proinflammatory or anti-inflammatory factors were evaluated by flow cytometric analysis and enzyme-linked immunosorbent assay, respectively. The associated genes and proteins involved in the JNK pathway were investigated to explore the potential mechanism that may regulate PDLSCs-CM-mediated macrophage polarization. PDLSCs expressed MSCs markers, including STRO-1, CD146, CD90, and CD73, and were negative for CD34 and CD45, could undergo osteogenic and adipogenic differentiation when cultured in defined medium. After incubation with PDLSCs-CM, no significant increase of CD80+ and HLA-DR+ M1 macrophages was shown while evaluated CD209+ and CD206+ M2 macrophages were observed. In addition, the levels of anti-inflammatory factors such as IL-10, TGF-β, and CCL18 were increased instead of proinflammatory factors such as IL-1β, TNF-α with PDLSC-CM treatment. There was a decrease of JNK expression on M0 macrophages by qRT-PCR analysis and an increase of protein phosphorylation on M0 macrophages after incubation with PDLSCs-CM. Furthermore, as for the enhancement of IL-4- and IL-13-mediated M2 polarization by PDLSCs-CM, the mRNA level of JNK decreased, and the protein phosphorylation level of JNK increased. In addition, the treatment of JNK pathway inhibitor, SP600125, could inhibit the expression and secretion level of anti-inflammatory factor such as IL-10 in M2 polarization induced by PDLSCs-CM. Collectively, PDLSCs were able to induce M2 macrophage polarization instead of M1 polarization, and capable of enhancing M2 macrophage polarization induced by IL-4 and IL-13. The JNK pathway was involved in the promotion of M2 macrophage polarization.

Ongoing Exposure to Peritoneal Dialysis Fluid Alters Resident Peritoneal Macrophage Phenotype and Activation Propensity

Peritoneal dialysis (PD) is a more continuous alternative to haemodialysis, for patients with chronic kidney disease, with considerable initial benefits for survival, patient independence and healthcare costs. However, long-term PD is associated with significant pathology, negating the positive effects over haemodialysis. Importantly, peritonitis and activation of macrophages is closely associated with disease progression and treatment failure. However, recent advances in macrophage biology suggest opposite functions for macrophages of different cellular origins. While monocyte-derived macrophages promote disease progression in some models of fibrosis, tissue resident macrophages have rather been associated with protective roles. Thus, we aimed to identify the relative contribution of tissue resident macrophages to PD induced inflammation in mice. Unexpectedly, we found an incremental loss of homeostatic characteristics, anti-inflammatory and efferocytic functionality in peritoneal resident macrophages, accompanied by enhanced inflammatory responses to external stimuli. Moreover, presence of glucose degradation products within the dialysis fluid led to markedly enhanced inflammation and almost complete disappearance of tissue resident cells. Thus, alterations in tissue resident macrophages may render long-term PD patients sensitive to developing peritonitis and consequently fibrosis/sclerosis.

Differential expression of complement receptors CR1/2 and CR4 by murine M1 and M2 macrophages

Macrophages polarize into functionally divergent phenotypes - M1 and M2 - which express distinct receptors. These cells are known to express complement receptors, including CR1, CR3, and CR4. However, whether these complement receptors are differentially expressed on M1 and M2 macrophages is not yet known. Herein, we have examined the expression of CR1 to CR4 on murine bone marrow-derived M1 (stimulated with IFN-γ or LPS) and M2 (stimulated with IL-4 or IL-4 + IL-13) macrophages. We show that M1 cells exhibit increased expression of CR1/2, whereas M2 cells display the higher expression of CR4; CR3 is equally expressed on both the phenotypes. Thus, M1 cells are CR1/2⁺CR4⁺, and M2 are CR1/2^-CR4⁺. Functional probing of these cells for their phagocytic ability indicates that M1 cells, which express higher CR1/2, internalize a significantly greater number of C3b-opsonized erythrocytes. Both M1 and M2 cells, on the other hand, internalize iC3b-opsonized erythrocytes to a similar extent. Interestingly, the phagocytic receptor involved in phagocytosis of iC3b-opsonized erythrocytes is only CR3 with no contribution of CR4. We, thus, propose that complement receptor expression can be used in combination with the expression of other known polarization markers to better locate a macrophage along its phenotypic spectrum.

Assessing the Anti-Inflammatory Activity of the Anxiolytic Drug Buspirone Using CRISPR-Cas9 Gene Editing in LPS-Stimulated BV-2 Microglial Cells

Buspirone is an anxiolytic drug with robust serotonin receptor 1A (Htr1a) agonist activities. However, evidence has demonstrated that this drug also targets the dopamine D3 receptor (Drd3), where it acts as a potent antagonist. In vivo, Drd3 blockade is neuroprotective and reduces inflammation in models of Parkinson’s disease. To test if buspirone also elicited anti-inflammatory activities in vitro, we generated stable Drd3^−/− and Htr1a^−/− BV2 microglial cell lines using CRISPR-Cas9 technology and then tested the effects of buspirone after lipopolysaccharide (LPS) challenge. We found that LPS exposure had no effect on cell viability, except in Htr1a^−/− cells, where viability was reduced (p < 0.001). Drug treatment reduced viability in Drd3^−/− cells, but not in WT or Htr1a^−/− cells. Buspirone counteracted LPS-induced NO release, NOS2, IL-1β and TNF-α gene expression in WT cells, whereas it exerted limited effects in Drd3^−/− or Htr1a^−/− microglia. In summary, our findings indicate that buspirone attenuates microglial polarization after LPS challenge. These results also highlight some major effects of Drd3 or Htr1a genetic ablation on microglial biology, raising important questions on the complex role of neurotransmitters in regulating microglia functions.

Activated Beta-Catenin Signaling Ameliorates Radiation-Induced Skin Injury by Suppressing Marvel D3 Expression

Radiation-induced skin injury remains a serious concern for cancer radiotherapy, radiation accidents and occupational exposure, and the damage mainly occurs due to apoptosis and reactive oxygen species (ROS) generation. There is currently no effective treatment for this disorder. The β-catenin signaling pathway is involved in the repair and regeneration of injured tissues. However, the role of the β-catenin signaling pathway in radiation-induced skin injury has not been reported. In this study, we demonstrated that the β-catenin signaling pathway was activated in response to radiation and that its activation by Wnt3a, a ligand-protein involved in the β-catenin signaling pathway, inhibited apoptosis and the production of ROS in irradiated human keratinocyte HaCaT cells and skin fibroblast WS1 cells. Additionally, Wnt3a promoted cell migration after irradiation. In a mouse model of full-thickness skin wounds combined with total-body irradiation, Wnt3a was shown to facilitate skin wound healing. The results from RNA-Seq revealed that 24 genes were upregulated and 154 were downregulated in Wnt3a-treated irradiated skin cells, and these dysregulated genes were mainly enriched in the tight junction pathway. Among them, Marvel D3 showed the most obvious difference. We further found that the activated β-catenin signaling pathway stimulated the phosphorylation of JNK by silencing Marvel D3. Treatment of irradiated cells with SP600125, a JNK inhibitor, augmented ROS production and impeded cell migration. Furthermore, treatment with Wnt3a or transfection with Marvel D3-specific siRNAs could reverse the above effects. Taken together, these findings illustrate that activated β-catenin signaling stimulates the activation of JNK by negatively regulating Marvel D3 to ameliorate radiation-induced skin injury.

Macrophage Plasticity and Function in the Lung Tumour Microenvironment Revealed in 3D Heterotypic Spheroid and Explant Models

In non-small cell lung cancer (NSCLC), stroma-resident and tumour-infiltrating macrophages may facilitate an immunosuppressive tumour microenvironment (TME) and hamper immunotherapeutic responses. Analysis of tumour-associated macrophage (TAM) plasticity in NSCLC is largely lacking. We established a novel, multi-marker, dual analysis approach for assessing monocyte-derived macrophage (Mφ) polarisation and M1/M2 phenotypic plasticity. We developed a flow cytometry-based, two-marker analysis (CD64 and CD206) of CD14⁺ cells. The phenotype and immune function of in vitro-induced TAMs was studied in a heterotypic spheroid and tumour-derived explant model of NSCLC. Heterotypic spheroids and NSCLC explants skewed Mφs from an M1- (CD206^loCD64^hi) to M2-like (CD206^hiCD64^lo) phenotype. Lipopolysaccharide (LPS) and IFNγ treatment reversed M2-like Mφ polarisation, indicating the plasticity of Mφs. Importantly, antigen-specific CD8⁺ T cell responses were reduced in the presence of tumour explant-conditioned Mφs, but not spheroid-conditioned Mφs, suggesting explants are likely a more relevant model of the immune TME than cell line-derived spheroids. Our data indicates the importance of multi-marker, functional analyses within Mφ subsets and the advantages of the ex vivo NSCLC explant model in immunomodulation studies. We highlight the plasticity of the M1/M2 phenotype using the explant model and provide a tool for studying therapeutic interventions designed to reprogram M2-like Mφ-induced immunosuppression.

Effects of 9-t-butyl doxycycline on the innate immune response to CNS ischemia-reperfusion injury

Cerebral ischemia triggers a cascade of neuroinflammatory and peripheral immune responses that contribute to post-ischemic reperfusion injury. Prior work conducted in CNS ischemia models underscore the potential to harness non-antibiotic properties of tetracycline antibiotics for therapeutic benefit. In the present study, we explored the immunomodulatory effects of the tetracycline derivative 9-tert-butyl doxycycline (9-TB) in a mouse model of transient global ischemia that mimics immunologic aspects of the post-cardiac arrest syndrome. Pharmacokinetic studies performed in C57BL/6 mice demonstrate that within four hours after delivery, levels of 9-TB in the brain were 1.6 and 9.5-fold higher than those obtained using minocycline and doxycycline, respectively. Minocycline and 9-TB also dampened inflammation, measured by reduced TNFα-inducible, NF-κβ-dependent luciferase activity in a microglial reporter line. Notably, daily 9-TB treatment following ischemia-reperfusion injury in vivo induced the retention of polymorphonuclear neutrophils (PMNs) within the spleen while simultaneously biasing CNS PMNs towards an anti-inflammatory (CD11b^LowYm1+) phenotype. These studies indicate that aside from exhibiting enhanced CNS delivery, 9-TB alters both the trafficking and polarization of PMNs in the context of CNS ischemia-reperfusion injury.

Combination of gemcitabine and anti-PD-1 antibody enhances the anticancer effect of M1 macrophages and the Th1 response in a murine model of pancreatic cancer liver metastasis

BACKGROUND

Pancreatic ductular adenocarcinoma (PDAC) is among the most dreadful of malignancies, in part due to the lack of efficacious chemotherapy. Immune checkpoint inhibitors, including anti-programmed cell death 1 (anti-PD-1) antibodies, are novel promising forms of systemic immunotherapy. In the current study, we assessed whether gemcitabine (GEM) combined with anti-PD-1 antibody treatment was efficacious as immunochemotherapy for advanced PDAC using a murine model of liver metastasis.

METHODS

The murine model of PDAC liver metastasis was established by intrasplenically injecting the murine pancreatic cancer cell line PAN02 into immunocompetent C57BL/6J mice. The mice were treated with an anti-PD-1 antibody, GEM, or a combination of GEM plus anti-PD-1 antibody, and compared with no treatment (control); liver metastases, immune cell infiltration, gene expression, immune cell response phenotypes, and overall survival were investigated.

RESULTS

In the metastatic tumor tissues of mice treated with GEM plus anti-PD-1 antibody, we observed the increased infiltration of Th1 lymphocytes and M1 macrophages. Gene expression profile analysis of peripheral blood cells obtained from mice treated with GEM plus anti-PD-1 antibody clearly highlighted T cell and innate immune signaling pathways. Survival of PDAC liver metastasis mice was significantly prolonged by the combination therapy (median survival, 66 days) when compared with that of GEM alone treatment (median survival, 56 days). Expanded lymphocytes, which were isolated from the splenocytes of PDAC liver metastasis mice treated with GEM plus anti-PD-1 antibody, had an increased number of M1 macrophages.

CONCLUSION

The combination of anti-PD-1 antibody immunotherapy with GEM was beneficial to treat a murine model of PDAC liver metastasis by enhancing the immune response mediated by Th1 lymphocytes and M1 macrophages and was associated with CD8+ T cells.

Hemorrhagic Shock/Resuscitation Reduces the M2 Phenotype of Alveolar Macrophages: A Potential Mechanism Contributing to Increased LPS-Induced Lung Injury

Major hemorrhage is a significant contributor to the morbidity and mortality resulting from traumatic injury. In addition to its role in in early mortality, hemorrhagic shock followed by resuscitation (HS/R) is known to initiate immunological events that contribute to the development of organ dysfunction. The pathogenesis of acute lung injury following HS/R involves macrophage activation. Recent studies have shown that macrophage function may in part be regulated by polarization toward classical M1 pro-inflammatory cells or alternatively activated anti-inflammatory M2 cells. We hypothesized that alteration in the M1/M2 phenotypic balance of alveolar macrophages in the lung may contribute to a pro-inflammatory state following HS/R. Using a murine model, we show that HS/R causes a rapid reduction in surface cluster of differentiation (CD)206 and CD36, markers of M2 cells, as well as in CD206 messenger ribonucleic acid (mRNA). M1 markers including surface CD80 and tumour necrosis factor alpha and inducible nitric oxide synthase mRNA were increased, albeit in a somewhat delayed time course. The prostaglandin 5-deoxyDelta12,14 prostaglandin J2 (15d-PGJ2), known to polarize cells toward M2, restored levels of M2 macrophages toward control and prevented lung injury, as assessed by bronchoalveolar protein content. Adoptive cell transfer of in vitro M2 polarized macrophages also reduced lung inflammation/injury following hemorrhagic shock. Together, these studies demonstrate that HS/R increases M1/M2 ratio, predominantly by lowering M2 cells, and thus enhances the proinflammatory state. Various strategies aimed at promoting M2 polarization may lessen the magnitude of inflammation and injury. This represents a novel approach to the prevention/treatment of lung injury in critically ill trauma patients.

Relationship of Inflammatory Cytokines From M1-Type Microglia/Macrophages at the Injured Site and Lumbar Enlargement With Neuropathic Pain After Spinal Cord Injury in the CCL21 Knockout (plt) Mouse

Spinal cord injury (SCI) causes loss of normal sensation and often leads to debilitating neuropathic pain (NeP). Chronic NeP develops at or below the SCI lesion in as many as 80% of patients with SCI and may be induced by modulators of neuronal excitability released from activated microglia and macrophages. In the inflammatory response after SCI, different microglia/macrophage populations that are classically activated (M1 phenotype) or alternatively activated (M2 phenotype) have become of great interest. Chemokines have also recently attracted attention in neuron-microglia communication. CCL21 is a chemokine that activates microglia in the central nervous system (CNS) and is expressed only in neurons with an insult or mechanical injury. In this study using an SCI model in mutant (plt) mice with deficient CCL21 expression, we assessed post-SCI NeP and expression of microglia/macrophages and inflammatory cytokines at the injured site and lumbar enlargement. SCI-induced hypersensitivities to mechanical and thermal stimulation were relieved in plt mice compared with those in wild-type (C57BL/6) mice, although there was no difference in motor function. Immunohistochemistry and flow cytometry analysis showed that the phenotype of microglia/macrophages was M1 type-dominant in both types of mice at the lesion site and lumbar enlargement. A decrease of M1-type microglia/macrophages was seen in plt mice compared with wild-type, while the number of M2-type microglia/macrophages did not differ between these mice. In immunoblot analysis, expression of M1-induced cytokines [tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ)] was decreased in plt mice, while that of M2-induced cytokines interleukin-4 (IL-4, IL-10) did not differ in the two types of mice. The results of this study indicate that suppression of expression of inflammatory cytokines by decreasing the number of M1-type microglia/macrophages at the injured site and lumbar enlargement is associated with provision of an environment for reduction of NeP. These findings may be useful for the design of new therapies to alleviate NeP after SCI.

MSC-Derived Exosome Promotes M2 Polarization and Enhances Cutaneous Wound Healing

Mesenchymal stem cell transplantation (MSCT) promotes cutaneous wound healing. Numerous studies have shown that the therapeutic effects of MSCT appear to be mediated by paracrine signaling. However, the cell-cell interaction during MSCT between MSCs and macrophages in the region of cutaneous wound healing is still unknown. In this study, early depletion of macrophages delayed the wound repair with MSC injection, which suggested that MSC-mediated wound healing required macrophages. Moreover, we demonstrated that systemically infused bone marrow MSCs (BMMSCs) and jaw bone marrow MSCs (JMMSCs) could translocate to the wound site, promote macrophages toward M2 polarization, and enhance wound healing. In vitro coculture of MSCs with macrophages enhanced their M2 polarization. Mechanistically, we found that exosomes derived from MSCs induced macrophage polarization and depletion of exosomes of MSCs reduced the M2 phenotype of macrophages. Infusing MSCs without exosomes led to lower number of M2 macrophages at the wound site along with delayed wound repair. We further showed that the miR-223, derived from exosomes of MSCs, regulated macrophage polarization by targeting pknox1. These findings provided the evidence that MSCT elicits M2 polarization of macrophages and may accelerate wound healing by transferring exosome-derived microRNA.

Sequential drug delivery to modulate macrophage behavior and enhance implant integration

Macrophages are major upstream regulators of the inflammatory response to implanted biomaterials. Sequential functions of distinct macrophage phenotypes are essential to the normal tissue repair process, which ideally results in vascularization and integration of implants. Improper timing of M1 or M2 macrophage activation results in dysfunctional healing in the form of chronic inflammation or fibrous encapsulation of the implant. Thus, biphasic drug delivery systems that modulate macrophage behavior are an appealing approach to promoting implant integration. In this review, we describe the timing and roles of macrophage phenotypes in healing, then highlight current drug delivery systems designed to sequentially modulate macrophage behavior.

Different Approaches to Modulation of Microglia Phenotypes After Spinal Cord Injury

Microglial cells, which are highly plastic, immediately respond to any change in the microenvironment by becoming activated and shifting the phenotype toward neurotoxicity or neuroprotection. The polarization of microglia/macrophages after spinal cord injury (SCI) seems to be a dynamic process and can change depending on the microenvironment, stage, course, and severity of the posttraumatic process. Effective methods to modulate microglia toward a neuroprotective phenotype in order to stimulate neuroregeneration are actively sought for. In this context, available approaches that can selectively impact the polarization of microglia/macrophages regulate synthesis of trophic factors and cytokines/chemokines in them, and their phagocytic function and effects on the course and outcome of SCI are discussed in this review.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Neuroinflammation and microglia in glaucoma: time for a paradigm shift

Glaucoma is a complex neurodegenerative disease with many clinical subtypes. Some of its rare forms include pigmentary glaucoma, uveitic glaucoma and congenital glaucoma. While they all share common features of progressive retinal ganglion cell (RGC) loss, optic nerve damage and corresponding visual field loss, the exact mechanisms underlying glaucomatous neuron loss are not clear. This has largely hindered the development of a real cure for this disease. Elevated intraocular pressure (IOP) is a known major risk factor of glaucoma; however, progressive degeneration of RGCs and axons can also be found in patients with a normal IOP, i.e., normal tension glaucoma (NTG). Interestingly, patients who carry the gain-of-function mutation of the pro-inflammatory gene TBK1 - tumor necrosis factor (TNF) receptor associated factor NF-κB activator (TANK) binding kinase 1 - are at increased risk to develop NTG. This finding suggests a causal link between neuroinflammatory processes and glaucoma. Various studies have reported the presence of neuroinflammatory responses by microglia, astrocytes and other blood-born immune cells in the optic nerve head (ONH) at early stages of experimental glaucoma. Inhibition of certain pro-inflammatory pathways, particularly those associated with microglial activation, appears to be neuroprotective. In this review, we will focus on the inflammatory responses, in particular the proposed roles of microglia, in the pathogenesis of glaucoma.

Imaging Reporter Strategy to Monitor Gene Activation of Microglia Polarisation States under Stimulation

Microglial cells as innate immune key players have a critical and unique role in neurodegenerative disorders. They strongly interact with their microenvironment in a complex manner and react to changes by switching their phenotype and functional activation states. In order to understand the development of brain diseases, it is imperative to elucidate up- or down-regulation of genes involved in microglia polarisation in time-profile by a simple-to-use strategy. Here, we present a new imaging strategy to follow promoter activity of genes involved in microglia polarisation. We lentivirally transduced BV-2 microglia cells in culture with constructs consisting of the induced nitric oxide synthase (iNOS), Fc gamma receptor III (Fcgr3) (both resembling the pro-inflammatory M1-like phenotype) or Chitinase-like 3 (Chil3/Ym1) (resembling the anti-inflammatory M2-like phenotype) promoters and stimulated transgenic cells with potent activators for pro- or anti-inflammatory response, such as lipopolysaccharide (LPS) + interferon gamma (IFN-γ) or interleukin (IL)-4, respectively. Promoter activities upon polarisation phases were quantitatively assessed by the two imaging reporters Luc2 for bioluminescence and eGFP for fluorescence.

Mesenchymal stem cells and extracellular matrix scaffold promote muscle regeneration by synergistically regulating macrophage polarization toward the M2 phenotype

Background

Skeletal muscle plays an important role in the body’s physiology but there are still no effective treatments for volumetric muscle loss (VML) resulting from severe traumatic injury or tumor excision. Recent studies show that a tissue engineering strategy using a compound containing mesenchymal stem cells (MSCs) and decellularized extracellular matrix (ECM) scaffold generates significant regenerative effects on VML injury, but the underlying mechanisms are not fully understood.

Methods

The characteristics of human umbilical cord MSCs, including multiplication capacity and multidifferentiation ability, were determined. We constructed a compound containing MSCs and decellularized ECM scaffold which was used for tissue regeneration in a VML model.

Results

We found that MSCs and decellularized ECM scaffold generated synergistic effects on promoting skeletal muscle tissue regeneration. Interestingly, both MSCs and decellularized ECM scaffold could promote macrophage polarization toward the M2 phenotype and suppress macrophage polarization toward the M1 phenotype, which is widely regarded as an important promoting factor in tissue regeneration. More importantly, MSCs and decellularized ECM scaffold generate synergistic promoting effects on macrophage polarization toward the M2 phenotype, not just an additive effect.

Conclusions

Our findings uncover a previously unknown mechanism that MSCs and decellularized ECM scaffold promote tissue regeneration via collaboratively regulating macrophage polarization.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0821-5) contains supplementary material, which is available to authorized users.

One-pot preparation of polymer microspheres with different porous structures to sequentially release bio-molecules for cutaneous regeneration

Herein, we reveal a double emulsion method combining the sol–gel method to prepare poly(lactic-co-glycolic acid) microspheres with different porous structures for sequential release of two types of biomolecules.

Deconvolution of heterogeneous wound tissue samples into relative macrophage phenotype composition via models based on gene expression

Macrophages, the primary cell of the innate immune system, act on a spectrum of phenotypes that correspond to diverse functions. Dysregulation of macrophage phenotype is associated with many diseases. In particular, defective transition from pro-inflammatory (M1) to anti-inflammatory (M2) behavior has been implicated as a potential source of sustained inflammation that prevents healing of chronic wounds such as diabetic ulcers. In order to design effective treatments, an understanding of the relative presence of macrophage phenotypes during tissue repair is necessary. Inferring the relative phenotype composition is currently challenging due to the heterogeneous nature of the macrophages themselves and also of tissue samples. We propose here a method to deconvolute gene expression from heterogeneous tissue samples into the composition of two primary macrophage phenotypes (M1 and M2). Our final method uses gene expression signatures for each phenotype cultivated in vitro as input to a predictive model that infers sample composition with an average error of 0.16, and whose predictions fit known compositions prepared in vitro with an R² value of 0.90. Finally, we apply this model to describe macrophage behavior in human diabetic ulcer healing using clinically isolated ulcer tissue samples. The model predicted that non-healing diabetic ulcers contained higher proportions of M1 macrophages compared to healing diabetic ulcers, in agreement with numerous studies that have implicated a dysfunctional M1-to-M2 transition in the impaired healing of diabetic ulcers. These results show proof of concept that the model holds utility in making predictions regarding macrophage behavior in heterogeneous samples, with potential application as a wound healing diagnostic.

Bone marrow-derived mesenchymal stem cells propagate immunosuppressive/anti-inflammatory macrophages in cell-to-cell contact-independent and -dependent manners under hypoxic culture

Immunosuppressive/anti-inflammatory macrophage (Mφ), M2-Mφ that expressed the typical M2-Mφs marker, CD206, and anti-inflammatory cytokine, interleukin (IL)-10, is beneficial and expected tool for the cytotherapy against inflammatory diseases. Here, we demonstrated that bone marrow-derived lineage-positive (Lin+) blood cells proliferated and differentiated into M2-Mφs by cooperation with the bone marrow-derived mesenchymal stem cells (MSCs) under hypoxic condition: MSCs not only promoted proliferation of undifferentiated M2-Mφs, pre-M2-Mφs, in the Lin+ fraction via a proliferative effect of the MSCs-secreted macrophage colony-stimulating factor, but also promoted M2-Mφ polarization of the pre-M2-Mφs through cell-to-cell contact with the pre-M2-Mφs. Intriguingly, an inhibitor for intercellular adhesion molecule (ICAM)-1 receptor/lymphocyte function-associated antigen (LFA)-1, Rwj50271, partially suppressed expression of CD206 in the Lin+ blood cells but an inhibitor for VCAM-1 receptor/VLA-4, BIO5192, did not, suggesting that the cell-to-cell adhesion through LFA-1 on pre-M2-Mφs and ICAM-1 on MSCs was supposed to promoted the M2-Mφ polarization. Thus, the co-culture system consisting of bone marrow-derived Lin+ blood cells and MSCs under hypoxic condition was a beneficial supplier of a number of M2-Mφs, which could be clinically applicable to inflammatory diseases.

The Role of Microglia in Retinal Neurodegeneration: Alzheimer's Disease, Parkinson, and Glaucoma

Microglia, the immunocompetent cells of the central nervous system (CNS), act as neuropathology sensors and are neuroprotective under physiological conditions. Microglia react to injury and degeneration with immune-phenotypic and morphological changes, proliferation, migration, and inflammatory cytokine production. An uncontrolled microglial response secondary to sustained CNS damage can put neuronal survival at risk due to excessive inflammation. A neuroinflammatory response is considered among the etiological factors of the major aged-related neurodegenerative diseases of the CNS, and microglial cells are key players in these neurodegenerative lesions. The retina is an extension of the brain and therefore the inflammatory response in the brain can occur in the retina. The brain and retina are affected in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and glaucoma. AD is an age-related neurodegeneration of the CNS characterized by neuronal and synaptic loss in the cerebral cortex, resulting in cognitive deficit and dementia. The extracellular deposits of beta-amyloid (Aβ) and intraneuronal accumulations of hyperphosphorylated tau protein (pTau) are the hallmarks of this disease. These deposits are also found in the retina and optic nerve. PD is a neurodegenerative locomotor disorder with the progressive loss of dopaminergic neurons in the substantia nigra. This is accompanied by Lewy body inclusion composed of α-synuclein (α-syn) aggregates. PD also involves retinal dopaminergic cell degeneration. Glaucoma is a multifactorial neurodegenerative disease of the optic nerve, characterized by retinal ganglion cell loss. In this pathology, deposition of Aβ, synuclein, and pTau has also been detected in retina. These neurodegenerative diseases share a common pathogenic mechanism, the neuroinflammation, in which microglia play an important role. Microglial activation has been reported in AD, PD, and glaucoma in relation to protein aggregates and degenerated neurons. The activated microglia can release pro-inflammatory cytokines which can aggravate and propagate neuroinflammation, thereby degenerating neurons and impairing brain as well as retinal function. The aim of the present review is to describe the contribution in retina to microglial-mediated neuroinflammation in AD, PD, and glaucomatous neurodegeneration.

Acanthamoeba Activates Macrophages Predominantly through Toll-Like Receptor 4- and MyD88-Dependent Mechanisms To Induce Interleukin-12 (IL-12) and IL-6

Acanthamoeba castellanii is a ubiquitous free-living amoeba with a worldwide distribution that can occasionally infect humans, causing particularly severe infections in immunocompromised individuals. Dissecting the immunology of Acanthamoeba infections has been considered problematic due to the very low incidence of disease, despite the high exposure rates. While macrophages are acknowledged as playing a significant role in Acanthamoeba infections, little is known about how this facultative parasite influences macrophage activity. Therefore, in this study we investigated the effects of Acanthamoeba on the activation of resting macrophages. Consequently, murine bone marrow-derived macrophages were cocultured with trophozoites of either the laboratory Neff strain or a clinical isolate of A. castellaniiIn vitro real-time imaging demonstrated that trophozoites of both strains often established evanescent contact with macrophages. Both Acanthamoeba strains induced a proinflammatory macrophage phenotype characterized by the significant production of interleukin-12 (IL-12) and IL-6. However, macrophages cocultured with the clinical isolate of Acanthamoeba produced significantly less IL-12 and IL-6 than the Neff strain. The utilization of macrophages derived from MyD88-, TRIF-, Toll-like receptor 2 (TLR2)-, TLR4-, and TLR2/4-deficient mice indicated that Acanthamoeba-induced proinflammatory cytokine production was through MyD88-dependent, TRIF-independent, TLR4-induced events. This study shows for the first time the involvement of TLRs expressed on macrophages in the recognition of and response to Acanthamoeba trophozoites.

Long-term Monocyte Dysfunction after Sepsis in Humanized Mice Is Related to Persisted Activation of Macrophage-Colony Stimulation Factor (M-CSF) and Demethylation of PU.1, and It Can Be Reversed by Blocking M-CSF In Vitro or by Transplanting Naïve Autologous Stem Cells In Vivo

The duration of post-sepsis long-term immune suppression is poorly understood. Here, we focused on the role of monocytes (MO) as the pivotal cells for long-term regulation of post-sepsis milieu. Lost ability of MO to adapt is seen in several acute conditions, but it is unclear for how long MO aberrancy post-sepsis can persist. Interestingly, the positive feedback loop sustaining secretion of macrophage-colony stimulation factor (M-CSF) can persist even after resolution of sepsis and significantly alters performance of MO. Here, we investigated the activation of M-CSF, and it as critical regulator of PU.1 in mice surviving 28 days after sepsis. Our primary readout was the ability of MO to differentiate into dendritic cells (DCs; MO→iDC) in vitro since this is one of the critical processes regulating a successful transition from innate to acquired immunity. We utilized a survival modification of the cecal ligation and puncture (CLP) model of sepsis in humanized mice. Animals were sacrificed 28 days after CLP (t_CLP+28d). Untouched (CONTR) or sham-operated (SHAM) animals served as controls. Some animals received rescue from stem cells originally used for grafting 2 weeks after CLP. We found profound decrease of MO→iDC in the humanized mice 28 days after sepsis, demonstrated by depressed expression of CD1a, CD83, and CD209, diminished production of IL-12p70, and depressed ability to stimulate T cells in mice after CLP as compared to SHAM or CONTR. In vitro defect in MO→iDC was accompanied by in vivo decrease of BDCA-3⁺ endogenous circulating DC. Interestingly, post-CLP MO had persistent activation of M-CSF pathway, shown by exaggerated secretion of M-CSF, activation of PU.1, and demethylation of SPII. Neutralization of the M-CSF in vitro reversed the post-CLP MO→iDC aberration. Furthermore, transplantation of naïve, autologous stem cell-derived MO restored CLP-deteriorated ability of MO to become DC, measured as recovery of CD1a expression, enhanced production of IL-12p70, and ability of IL-4 and GM-CSF MO to stimulate allogeneic T cells. Our results suggest the role of epigenetic mediated M-CSF aberration in mediating post-sepsis immune system recovery.

Immunomodulatory Potential of Chitosan-graft-poly(ε-caprolactone) Copolymers toward the Polarization of Bone-Marrow-Derived Macrophages

In tissue engineering, the use of biomaterials as templates or scaffolds to guide tissue development in vivo provokes the inevitable action of the immune system of the host. This induced immune response often determines the success of the scaffold, including angiogenesis and regeneration or failure causing inflammation and fibrosis. Therefore, it is crucial to predict or even better to promote the proper immune response following implantation. The aim of the present study was to evaluate the immunomodulatory potential of chitosan-graft-poly(ε-caprolactone) copolymers (CS-g-PCL) by analyzing the differentiation of primary bone marrow derived macrophages (BMDM) cultured in vitro on copolymer thin films. In order to evaluate the role of the chitosan content of the copolymer on macrophage polarization, two different copolymers containing 50 and 78% w/w chitosan were studied. Our data from cytokines secretion detection by ELISA show that the CS-g-PCL copolymer significantly decreases the secretion of the inducible levels of pro-inflammatory cytokines IL-12/23 by 31% ± 6, and thus possesses anti-inflammatory ability. Moreover, this anti-inflammatory action is correlated with the increased chitosan content of the copolymer. In addition, the CS-g-PCL copolymer significantly enhances the production of Arg1, the hallmark of M2 polarized macrophages, as shown by semiquantitative RT-PCR analysis, and this enhancement is 4-fold higher for the copolymer with the lower chitosan content. Although further in vivo experimentation is required to predict the outcome of the in situ engraftment of the copolymer, our results so far suggest that the CS-g-PCL copolymers possess anti-inflammatory activity and favor the transition of M1 to M2 macrophages, which are essential prerequisites for proper tissue remodeling.

Protective effect of curcumin on TNBS-induced intestinal inflammation is mediated through the JAK/STAT pathway

Background

Curcumin displays a protective role in rat models of intestinal inflammation. However, the mechanism of how curcumin affects on intestinal inflammation is less known. The purpose of the current study is to explore the signal pathway in which the curcumin protecting rat from intestinal inflammation.

Methods

The intestinal inflammation rat models were made by TNBS treatment. Curcumin was added to their diet 5 days before the TNBS instillation. After that, body weight change, score of macroscopic assessment of disease activity and microscopic scoring were utilized to analyse the severity of the induced inflammation. In addition, the level of pro-inflammatory cytokines and anti-inflammatory were detected to determine the effect of curcumin on intestinal inflammation. The JAK/STAT pathway of pro-inflammation response was also evaluated. Finally, the impact of curcumin on apoptosis in intestinal inflammation was assessed by TUNEL staining.

Results

Rats pretreated with curcumin significantly reversed the decrease of body weight and increase of colon weight derived from TNBS-induced colitis. Histological improvement was observed in response to curcumin. In addition, curcumin attenuated TNBS-induced secretion of pro-inflammatory cytokines and M1/M2 ratio, while stimulated the secretion of anti-inflammatory cytokines. The inhibition of pro-inflammation response was mediated by SOCS-1, which could efficiently suppress JAK/STAT pathways. Furthermore, curcumin efficiently suppressed the TNBS-induced apoptosis, and reduced the accumulation of cytochrome C in cytosol.

Conclusion

The anti-inflammatory effect of curcumin is realized by enhancing SOCS-1 expression and inhibiting JAK/STAT pathways. Curcumin also plays an anti-apoptotic role in TNBS-induced intestinal inflammation. We propose that curcumin may have therapeutic implications for human intestinal inflammation.

Mangiferin inhibits macrophage classical activation via downregulating interferon regulatory factor 5 expression

Mangiferin is a natural polyphenol and the predominant effective component of Mangifera indica Linn. leaves. For hundreds of years, Mangifera indica Linn. leaf has been used as an ingredient in numerous traditional Chinese medicine preparations for the treatment of bronchitis. However, the pharmacological mechanism of mangiferin in the treatment of bronchitis remains to be elucidated. Macrophage classical activation is important role in the process of bronchial airway inflammation, and interferon regulatory factor 5 (IRF5) has been identified as a key regulatory factor for macrophage classical activation. The present study used the THP-1 human monocyte cell line to investigate whether mangiferin inhibits macrophage classical activation via suppressing IRF5 expression in vitro. THP-1 cells were differentiated to macrophages by phorbol 12-myristate 13-acetate. Macrophages were polarized to M1 macrophages following stimulation with lipopolysaccharide (LPS)/interferon-γ (IFN-γ). Flow cytometric analysis was conducted to detect the M1 macrophages. Reverse transcription-quantitative polymerase chain reaction was used to investigate cellular IRF5 gene expression. Levels of proinflammatory cytokines and IRF5 were assessed following cell culture and cellular homogenization using enzyme-linked immunosorbent assay. IRF5 protein and nuclei co-localization was performed in macrophages with laser scanning confocal microscope immunofluorescence analysis. The results of the present study demonstrated that mangiferin significantly inhibits LPS/IFN-γ stimulation-induced classical activation of macrophages in vitro and markedly decreases proinflammatory cytokine release. In addition, cellular IRF5 expression was markedly downregulated. These results suggest that the inhibitory effect of mangiferin on classical activation of macrophages may be exerted via downregulation of cellular IRF5 expression levels.

Novel grooved substrata stimulate macrophage fusion, CCL2 and MMP-9 secretion

Rough surface topographies on implants attract macrophages but the influence of topography on macrophage fusion to produce multinucleated giant cells (MGC) and foreign body giant cells (FBGC) is unclear. Two rough novel grooved substrata, G1 and G2, fabricated by anisotropic etching of Silicon <110> crystals without the use of photolithographic patterning, and a control smooth surface (Pol) were produced and replicated in epoxy. The surfaces were compared for their effects on RAW264.7 macrophage morphology, gene expression, cyto/chemokine secretion, and fusion for one and five days. Macrophages on grooved surfaces exhibited an elongated morphology similar to M2 macrophages and increased cell alignment with surface directionality, roughness and cell culture time. Up-regulated expression of macrophage chemoattractants at gene and protein level was observed on both grooved surfaces relative to Pol. Grooved surfaces showed time-dependent increase in soluble mediators involved in cell fusion, CCL2 and MMP-9, and an increased proportion of multinucleated cells at Day 5. Collectively, this study demonstrated that a rough surface with surface directionality produced changes in macrophage shape and macrophage attractant chemokines and soluble mediators involved in cell fusion. These in vitro results suggest a possible explanation for the observed accumulation of macrophages and MGCs on rough surfaced implants in vivo. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2243-2254, 2016.

Apolipoprotein E-/- Mice Lacking Hemopexin Develop Increased Atherosclerosis via Mechanisms That Include Oxidative Stress and Altered Macrophage Function

OBJECTIVE

We previously reported that hemopexin (Hx), a heme scavenger, is significantly increased and associated with proinflammatory high-density lipoprotein under atherogenic conditions. Although it is established that Hx together with macrophages plays a role in mitigating oxidative damage, the role of Hx in the development of atherosclerosis is unknown.

APPROACH AND RESULTS

We used Hx and apoE double-knockout mice (HxE(-/-)) to determine the role of Hx in the development of atherosclerosis. HxE(-/-) mice had significantly more free heme, reactive oxygen species, and proinflammatory high-density lipoprotein in their circulation, when compared with control apoE(-/-) mice. Atherosclerotic plaque area (apoE(-/-)=9.72±2.5×10(4) μm(2) and HxE(-/-)=27.23±3.6×10(4) μm(2)) and macrophage infiltration (apoE(-/-)=38.8±5.8×10(3) μm(2) and HxE(-/-)=103.4±17.8×10(3) μm(2)) in the aortic sinus were significantly higher in the HxE(-/-) mice. Atherosclerotic lesions in the aortas were significantly higher in the HxE(-/-) mice compared with apoE(-/-) mice. Analysis of polarization revealed that macrophages from HxE(-/-) mice were more M1-like. Ex vivo studies demonstrated that HxE(-/-) macrophage cholesterol efflux capacity was significantly reduced when compared with apoE(-/-) mice. Injection of human Hx into HxE(-/-) mice reduced circulating heme levels and human Hx pretreatment of naive bone marrow cells ex vivo resulted in a shift from M1- to M2-like macrophages.

CONCLUSIONS

We conclude that Hx plays a novel protective role in alleviating heme-induced oxidative stress, improving inflammatory properties of high-density lipoprotein, macrophage phenotype and function, and inhibiting the development of atherosclerosis in apoE(-/-) mice.

Platelets and plasma stimulate sheep rotator cuff tendon tenocytes when cultured in an extracellular matrix scaffold

The addition of platelet-rich plasma (PRP) to rotator cuff repair has not translated into improved outcomes after surgery. However, recent work stimulating ligament healing has demonstrated improved outcomes when PRP or whole blood is combined with an extracellular matrix carrier. The objective of this study was to evaluate the effect of three components of blood (plasma, platelets, and macrophages) on the in vitro activity of ovine rotator cuff cells cultured in an extracellular matrix environment. Tenocytes were obtained from six ovine infraspinatus tendons and cultured over 14 days in an extracellular matrix scaffold with the following additives: (1) plasma (PPP), (2) plasma and platelets (PAP), (3) plasma and macrophages (PPPM), (4) plasma, platelets and macrophages (PAPM), (5) phosphate buffered saline (PBS), and (6) PBS with macrophages (PBSM). Assays measuring cellular metabolism (AlamarBlue), proliferation (Quantitative DNA assay), synthesis of collagen and cytokines (SIRCOL, TNF-α and IL-10 ELISA, and MMP assay), and collagen gene expression (qPCR) were performed over the duration of the experiment, as well as histology at the conclusion. Plasma was found to stimulate cell attachment and spreading on the scaffold, as well as cellular proliferation. Platelets also stimulated cell proliferation, cellular metabolism, transition of cells to a myofibroblast phenotype, and contraction of the scaffolds. The addition of macrophages did not have any significant effect on the sheep rotator cuff cells in vitro. In vivo studies are needed to determine whether these changes in cellular function will translate into improved tendon healing.

Flagellin preconditioning enhances the efficacy of mesenchymal stem cells in an irradiation-induced proctitis model

The success of mesenchymal stem cell transplantation for proctitis depends not only on cell donors but also on host microenvironmental factors, which play a major role in conditioning mesenchymal stem cell immunosuppressive action and repair. This study sought to determine if flagellin, a TLR5 ligand, can enhance the mesenchymal stem cell treatment efficacy in radiation-induced proctitis. With the use of a colorectal model of 27 Gy irradiation in rats, we investigated and compared the effects on immune capacity and remodeling at 28 d after irradiation of the following: 1) systemic mesenchymal stem cell (5 × 10(6)) administration at d 7 after irradiation, 2) administration of flagellin at d 3 and systemic mesenchymal stem cell administration at d 7, and 3) in vitro preconditioning of mesenchymal stem cells with flagellin, 24 h before their administration on d 7. The mucosal CD8(+) T cell population was normalized after treatment with flagellin-preconditioned mesenchymal stem cells or flagellin plus mesenchymal stem cells, whereas mesenchymal stem cells alone did not alter the radiation-induced elevation of CD8(+) T cell frequency. Mesenchymal stem cell treatment returned the irradiation-elevated frequency of CD25(+) cells in the mucosa-to-control levels, whereas both flagellin-preconditioned mesenchymal stem cell and flagellin-plus-mesenchymal stem cell treatment each significantly increased not only CD25(+) cell frequency but also forkhead box p3 and IL-2Rα expression. Specifically, IL-10 was overexpressed after flagellin-preconditioned mesenchymal stem cell treatment. Analysis of collagen expression showed that the collagen type 1/collagen type 3 ratio, an indicator of wound-healing maturation, was low in the irradiated and mesenchymal stem cell-treated groups and returned to the normal level only after the flagellin-preconditioned mesenchymal stem cell treatment. This was associated with a reduction in myofibroblast accumulation. In a proctitis model, flagellin-preconditioned mesenchymal stem cells improved colonic immune capacity and enhanced tissue remodeling.

Lentiviral-Mediated Netrin-1 Overexpression Improves Motor and Sensory Functions in SCT Rats Associated with SYP and GAP-43 Expressions

Spinal cord injury (SCI), as a major cause of disability, usually causes serious loss of motor and sensory functions. As a bifunctional axonal guidance cue, netrin-1 can attract axons via the deleted in colorectal cancer (DCC) receptors and repelling others via Unc5 receptors, but its exact role in the recovery of motor and sensory function has not well been studied, and the mechanisms remains elusive. The aim of this experiment is to determine whether lentiviral (LV)-mediated overexpression of netrin-1 or RNA interference (RNAi) can regulate the functional recovery in rats subjected to spinal cord transection (SCT). Firstly, two lentiviral vectors including Lv-exNtn-1 (netrin-1 open reading frame (ORF)) and Lv-shNtn-1 (netrin-1 sh) were constructed and injected into spinal cords rostral and caudal to the transected lesion site. Overexpressing netrin-1 enhanced significantly locomotor function, and reduced thermal and mechanical stimuli in vivo, compared with the control, while silencing netrin-1 did not significantly change the situation. Western blot and immunostaining analysis confirmed that netrin-1 ORF treatment not only effectively increased the expression level of netrin-1, also up-regulated the level of synaptophysin (SYP) in spinal cord rostral to the lesion, but also enhanced growth-associated protein-43 (GAP-43) expression in spinal cord caudal to the lesion site. Comparatively, knockdown of netrin-1 did not give rise to positive findings in our experimental condition. These findings therefore pointed that Lv-mediated netrin-1 overexpression could promote motor and sensory functional recoveries following SCT, and the underlying mechanisms were associated with SYP and GAP-43 expressions. The present study therefore provided a novel strategy for the treatment of SCI and explained the possible mechanisms for the functional improvement.

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.

The effects of immunomodulation by macrophage subsets on osteogenesis in vitro

Background

Bone formation and remodeling are influenced by the inflammatory state of the local microenvironment. In this regard, macrophages are postulated to play a crucial role in modulating osteogenesis. However, the differential effects of macrophage subsets and their plasticity on bone formation are currently unknown.

Methods

Polarized primary murine macrophages and preosteoblastic MC3T3 cells were co-cultured to investigate the effect of non-activated M0, pro-inflammatory M1, and tissue-regenerative M2 macrophages on the osteogenic ability of MC3T3-E1 cells in vitro. Furthermore, to model the physiological transition from inflammation to tissue regeneration, M1-MC3T3 co-cultures were treated with interleukin-4 (IL-4) at different time points to modulate the M1 phenotype towards M2. Macrophage phenotypic markers were assessed by flow cytometry and enzyme-linked immunosorbent assay. A time course study of osteogenic markers at different time points was conducted: alkaline phosphatase (ALP) mRNA levels were evaluated at week 1, ALP activity and osteocalcin and osteopontin mRNA levels at week 2, and matrix mineralization and osteocalcin and osteopontin protein concentrations at week 3. Supernatant collected 72 hours after seeding or IL-4 treatment, whichever was later, was analyzed for oncostatin M, a cytokine released by macrophages that has been recognized to enhance osteogenesis. Unpaired t test or one-way ANOVA with Tukey’s or Dunnett’s post hoc tests were used for statistical comparison of the groups.

Results

Co-culture with any of the macrophage subtypes increased the osteogenic ability of MC3T3 cells as indicated by increases in ALP activity and matrix mineralization. Increased ALP activity, osteocalcin concentration, and matrix mineralization demonstrated that osteogenesis by M1-MC3T3 co-cultures was further enhanced by macrophage phenotype modulation to M2 via IL-4 treatment 72 hours after seeding. Increased oncostatin M protein concentration in untreated M1-MC3T3 co-cultures and M1-MC3T3 co-cultures treated with IL-4 at 72 hours correlated with greater ALP activity and matrix mineralization.

Conclusions

These results suggest that a transient inflammatory phase is crucial for enhanced bone formation. Macrophage plasticity may offer new strategies for modulating the local inflammatory microenvironment with the aim of potentially enhancing bone repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0276-5) contains supplementary material, which is available to authorized users.

Key mechanisms involved in ionizing radiation-induced systemic effects. A current review

Organisms respond to physical, chemical and biological threats by a potent inflammatory response, aimed at preserving tissue integrity and restoring tissue homeostasis and function. Systemic effects in an organism refer to an effect or phenomenon which originates at a specific point and can spread throughout the body affecting a group of organs or tissues. Ionizing radiation (IR)-induced systemic effects arise usually from a local exposure of an organ or part of the body. This stress induces a variety of responses in the irradiated cells/tissues, initiated by the DNA damage response and DNA repair (DDR/R), apoptosis or immune response, including inflammation. Activation of this IR-response (IRR) system, especially at the organism level, consists of several subsystems and exerts a variety of targeted and non-targeted effects. Based on the above, we believe that in order to understand this complex response system better one should follow a 'holistic' approach including all possible mechanisms and at all organization levels. In this review, we describe the current status of knowledge on the topic, as well as the key molecules and main mechanisms involved in the 'spreading' of the message throughout the body or cells. Last but not least, we discuss the danger-signal mediated systemic immune effects of radiotherapy for the clinical setup.

OsteoMacs: Key players around bone biomaterials

Osteal macrophages (OsteoMacs) are a special subtype of macrophage residing in bony tissues. Interesting findings from basic research have pointed to their vast and substantial roles in bone biology by demonstrating their key function in bone formation and remodeling. Despite these essential findings, much less information is available concerning their response to a variety of biomaterials used for bone regeneration with the majority of investigation primarily focused on their role during the foreign body reaction. With respect to biomaterials, it is well known that cells derived from the monocyte/macrophage lineage are one of the first cell types in contact with implanted biomaterials. Here they demonstrate extremely plastic phenotypes with the ability to differentiate towards classical M1 or M2 macrophages, or subsequently fuse into osteoclasts or multinucleated giant cells (MNGCs). These MNGCs have previously been characterized as foreign body giant cells and associated with biomaterial rejection, however more recently their phenotypes have been implicated with wound healing and tissue regeneration by studies demonstrating their expression of key M2 markers around biomaterials. With such contrasting hypotheses, it becomes essential to better understand their roles to improve the development of osteo-compatible and osteo-promotive biomaterials. This review article expresses the necessity to further study OsteoMacs and MNGCs to understand their function in bone biomaterial tissue integration including dental/orthopedic implants and bone grafting materials.

IL-4 regulates specific Arg-1(+) macrophage sFlt-1-mediated inhibition of angiogenesis

One of the main drivers for neovascularization in age-related macular degeneration is activation of innate immunity in the presence of macrophages. Here, we demonstrate that T helper cell type 2 cytokines and, in particular, IL-4 condition human and murine monocyte phenotype toward Arg-1(+), and their subsequent behavior limits angiogenesis by increasing soluble fms-like tyrosine kinase 1 (sFlt-1) gene expression. We document that T helper cell type 2 cytokine-conditioned murine macrophages neutralize vascular endothelial growth factor-mediated endothelial cell proliferation (human umbilical vein endothelial cell and choroidal vasculature) in a sFlt-1-dependent manner. We demonstrate that in vivo intravitreal administration of IL-4 attenuates laser-induced choroidal neovascularization (L-CNV) due to specific IL-4 conditioning of macrophages. IL-4 induces the expression of sFlt-1 by resident CD11b(+) retinal microglia and infiltrating myeloid cells but not from retinal pigment epithelium. IL-4-induced suppression of L-CNV is not prevented when sFlt-1 expression is attenuated in retinal pigment epithelium. IL-4-mediated suppression of L-CNV was abrogated in IL-4R-deficient mice and in bone marrow chimeras reconstituted with myeloid cells that had undergone lentiviral-mediated shRNA silencing of sFlt-1, demonstrating the critical role of this cell population. Together, these data establish how lL-4 directly drives macrophage sFlt-1 production expressing an Arg-1(+) phenotype and support the therapeutic potential of targeted IL-4 conditioning within the tissue to regulate disease conditions such as neovascular age-related macular degeneration.

Nuclear Receptor Nr4a2 Promotes Alternative Polarization of Macrophages and Confers Protection in Sepsis

The orphan nuclear receptor Nr4a2 is known to modulate both inflammatory and metabolic processes, but the mechanism by which it regulates innate inflammatory homeostasis has not been adequately addressed. This study shows that exposure to ligands for Toll-like receptors (TLRs) robustly induces Nr4a2 and that this induction is tightly regulated by the PI3K-Akt signaling axis. Interestingly, exogenous expression of Nr4a2 in macrophages leads to their alternative phenotype with induction of genes that are prototypical M2 markers. Moreover, Nr4a2 transcriptionally activates arginase 1 expression by directly binding to its promoter. Adoptive transfer experiments revealed that increased survival of animals in endotoxin-induced sepsis is Nr4a2-dependent. Thus our data identify a previously unknown role for Nr4a2 in the regulation of macrophage polarization.

Temporal phenotypic features distinguish polarized macrophages in vitro

Macrophages are important in vascular inflammation and environmental factors influence macrophage plasticity. Macrophage transitions into pro-inflammatory (M1) or anti-inflammatory (M2) states have been defined predominately by measuring cytokines in culture media (CM). However, temporal relationships between cellular and secreted cytokines have not been established. We measured phenotypic markers and cytokines in cellular and CM of murine bone marrow-derived macrophages at multiple time points following stimulation with IFN-γ + LPS (M1), IL-4 (M2a) or IL-10 (M2c). Cytokines/proteins in M1-polarized macrophages exhibited two distinct temporal patterns; an early (0.5-3 h), transient increase in cellular cytokines (GM-CSF, KC-GRO, MIP-2, IP-10 and MIP-1β) and a delayed (3-6 h) response that was more sustained [IL-3, regulated on activation normal T cell expressed and secreted (RANTES), and tissue inhibitor of metalloproteinases 1 (TIMP-1)]. M2a-related cytokine/cell markers (IGF-1, Fizz1 and Ym1) were progressively (3-24 h) increased post-stimulation. In addition, novel patterns were observed. First, and unexpectedly, cellular pro-inflammatory chemokines, MCP-1 and MCP-3 but not MCP-5, were comparably increased in M1 and M2a macrophages. Second, Vegfr1 mRNA was decreased in M1 and increased in M2a macrophages. Finally, VEGF-A was increased in the CM of M1 cultures and strikingly reduced in M2a coinciding with increased Vegfr1 expression, suggesting decreased VEGF-A in M2a CM was secondary to increased soluble VEGFR1. In conclusion, macrophage cytokine production and marker expression were temporally regulated and relative levels compared across polarizing conditions were highly dependent upon the timing and location (cellular versus CM) of the sample collection. For most cytokines, cellular production preceded increases in the CM suggesting that cellular regulatory pathways should be studied within 6 h of stimulation. The divergent polarization-dependent expression of Vegfr1 may be essential to controlling VEGF potentially regulating angiogenesis and inflammatory cell infiltration in the vascular niche. The current study expands the repertoire of cytokines produced by polarized macrophages and provides insights into the dynamic regulation of macrophage polarization and resulting cytokines, proteins and gene expression that influence vascular inflammation.

Solubilized extracellular matrix from brain and urinary bladder elicits distinct functional and phenotypic responses in macrophages

Extracellular matrix (ECM) derived from a variety of source tissues has been successfully used to facilitate tissue reconstruction. The recent development of solubilized forms of ECM advances the therapeutic potential of these biomaterials. Isolated, soluble components of ECM and matricryptic peptides have been shown to bias macrophages toward a regulatory and constructive (M2-like) phenotype. However, the majority of studies described thus far have utilized anatomically and morphologically similar gastrointestinal derived ECMs (small intestine, esophagus, urinary bladder, etc.) and a small subset of macrophage markers (CD206, CD86, CCR7) to describe them. The present study evaluated the effect of solubilized ECM derived from molecularly diverse source tissues (brain and urinary bladder) upon primary macrophage phenotype and function. Results showed that solubilized urinary bladder ECM (U-ECM) up-regulated macrophage PGE2 secretion and suppressed traditional pro-inflammatory factor secretion, consistent with an M2-like phenotype. The hyaluronic acid (HA) component in solubilized U-ECM played an important role in mediating this response. Brain ECM (B-ECM) elicited a pro-inflammatory (M1-like) macrophage response and contained almost no HA. These findings suggest that the molecular composition of the source tissue ECM plays an important role in influencing macrophage function and phenotype.

Function of microglia and macrophages in secondary damage after spinal cord injury

Spinal cord injury (SCI) is a devastating type of neurological trauma with limited therapeutic opportunities. The pathophysiology of SCI involves primary and secondary mechanisms of injury. Among all the secondary injury mechanisms, the inflammatory response is the major contributor and results in expansion of the lesion and further loss of neurologic function. Meanwhile, the inflammation directly and indirectly dominates the outcomes of SCI, including not only pain and motor dysfunction, but also preventingneuronal regeneration. Microglia and macrophages play very important roles in secondary injury. Microglia reside in spinal parenchyma and survey the microenvironment through the signals of injury or infection. Macrophages are derived from monocytes recruited to injured sites from the peripheral circulation. Activated resident microglia and monocyte-derived macrophages induce and magnify immune and inflammatory responses not only by means of their secretory moleculesand phagocytosis, but also through their influence on astrocytes, oligodendrocytes and demyelination. In this review, we focus on the roles of microglia and macrophages in secondary injury and how they contribute to the sequelae of SCI.

Borrelia burgdorferi arthritis-associated locus Bbaa1 regulates Lyme arthritis and K/B×N serum transfer arthritis through intrinsic control of type I IFN production

Localized upregulation of type I IFN was previously implicated in development of Borrelia burgdorferi-induced arthritis in C3H mice, and was remarkable due to its absence in the mildly arthritic C57BL/6 (B6) mice. Independently, forward genetics analysis identified a quantitative trait locus on Chr4, termed B. burgdorferi-associated locus 1 (Bbaa1), that regulates Lyme arthritis severity and includes the 15 type I IFN genes. Involvement of Bbaa1 in arthritis development was confirmed in B6 mice congenic for the C3H allele of Bbaa1 (B6.C3-Bbaa1), which developed more severe Lyme arthritis and K/B×N model of rheumatoid arthritis (RA) than did parental B6 mice. Administration of a type I IFN receptor blocking mAb reduced the severity of both Lyme arthritis and RA in B6.C3-Bbaa1 mice, formally linking genetic elements within Bbaa1 to pathological production of type I IFN. Bone marrow-derived macrophages from Bbaa1 congenic mice implicated this locus as a regulator of type I IFN induction and downstream target gene expression. Bbaa1-mediated regulation of IFN-inducible genes was upstream of IFN receptor-dependent amplification; however, the overall magnitude of the response was dependent on autocrine/paracrine responses to IFN-β. In addition, the Bbaa1 locus modulated the functional phenotype ascribed to bone marrow-derived macrophages: the B6 allele promoted expression of M2 markers, whereas the C3H allele promoted induction of M1 responses. This report identifies a genetic locus physically and functionally linked to type I IFN that contributes to the pathogenesis of both Lyme and RA.

Brazilian green propolis modulates inflammation, angiogenesis and fibrogenesis in intraperitoneal implant in mice

BACKGROUND

Chronic inflammatory processes in the peritoneal cavity develop as a result of ischemia, foreign body reaction, and trauma. Brazilian green propolis, a beeswax product, has been shown to exhibit multiple actions on inflammation and tissue repair. Our aim was to investigate the effects of this natural product on the inflammatory, angiogenic, and fibrogenic components of the peritoneal fibroproliferative tissue induced by a synthetic matrix.

METHODS

Chronic inflammation was induced by placing polyether-polyurethane sponge discs in the abdominal cavity of anesthetized Swiss mice. Oral administration of propolis (500/mg/kg/day) by gavage started 24 hours after injury for four days. The effect of propolis on peritoneal permeability was evaluated through fluorescein diffusion rate 4 days post implantation. The effects of propolis on the inflammatory (myeloperoxidase and n-acetyl-β-D-glucosaminidase activities and TNF-α levels), angiogenic (hemoglobin content-Hb), and fibrogenic (TGF-β1 and collagen deposition) components of the fibrovascular tissue in the implants were determined 5 days after the injury.

RESULTS

Propolis was able to decrease intraperitoneal permeability. The time taken for fluorescence to peak in the systemic circulation was 20±1 min in the treated group in contrast with 15±1 min in the control group. In addition, the treatment was shown to down-regulate angiogenesis (Hb content) and fibrosis by decreasing TGF-β1 levels and collagen deposition in fibroproliferative tissue induced by the synthetic implants. Conversely, the treatment up-regulated inflammatory enzyme activities, TNF-α levels and gene expression of NOS2 and IFN-γ (23 and 7 fold, respectively), and of FIZZ1 and YM1 (8 and 2 fold) when compared with the untreated group.

CONCLUSIONS

These observations show for the first time the effects of propolis modulating intraperitoneal inflammatory angiogenesis in mice and disclose important action mechanisms of the compound (downregulation of angiogenic components and activation of murine macrophage pathways).