Macrophage Phenotype Transition Research Articles

Tunable Sulfated Alginate-based Hydrogel Platform with enhanced anti-inflammatory and antioxidant capacity for promoting burn wound repair

Amidst progressive advancements in tissue engineering, there has been a significant enhancement in the efficacy of anti-inflammatory hydrogel dressings, addressing a myriad of clinical challenges on wound healing. A frequent complication during the initial stages of deep second-degree burn wound healing is the onset of an inflammatory storm, typically occurring without effective intervention. This event disrupts normal biological healing sequences, leading to undesirable regression. In response, we have customized a tunable, multidimensional anti-inflammatory hydrogel platform based on sulfated alginates (Algs), loaded with Prussian blue (PB) nanozymes. This platform competently eliminates surplus reactive oxygen species (ROS) present in the wound bed. Algs, functioning as a mimic of sulfated glycosaminoglycans (including heparin, heparan sulfate, and chondroitin sulfate) in the extracellular matrices (ECM), demonstrate a high affinity towards inflammatory chemokines such as interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). This affinity effectively impedes the infiltration of inflammatory cells into the wound. Concurrently, Algs markedly modulate the macrophage phenotype transition from M1 to M2. Ultimately, our potent anti-inflammatory hydrogels, which strategically target inflammatory chemokines, M1 macrophages, and ROS, successfully attenuate dysregulated hyperinflammation in wound sites. Precise immunomodulation administered to deep second-degree burn wounds in mice has demonstrated promotion of neovascular maturation, granulation tissue formation, collagen deposition, and wound closure. Our biomimetic hydrogels, therefore, represent a significant expansion in the repertoire of anti-inflammatory strategies available for clinical practice.

Microenvironment-responsive Cu-phenolic networks coated nanofibrous dressing with timely macrophage phenotype transition for chronic MRSA infected wound healing.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a pressing clinical issue that impedes wound healing. Pro-inflammatory M1 macrophages is required to clear bacteria and recruit various cell types during the initial phase of wound healing, but timing of this process is crucial. Herein, a microenvironment-responsive nanofibrous dressing capable of timely macrophage phenotype transition in vivo is constructed by coating copper ions (Cu2+)-polydopamine (PDA) networks on poly (ε-caprolactone) fiber (PCL-fiber) membrane. During the initial post-implantation period, the nanofibrous dressing show pH-sensitive Cu2+ release in the acidic infection microenvironment. The release Cu2+ have a direct killing effect on MRSA, and promote the proinflammatory M1 phenotype of macrophages to enhance the antibacterial macrophage response. Later, PDA to become a reactive oxygen species (ROS) scavenger when in microenvironments with elevated ROS levels, which conferred the dressing with an immunomodulatory activity that convert M1 macrophages into M2 macrophages. In vivo examination in an MRSA infected full-thickness skin wounds of rat model demonstrates that this dressing significantly facilitated infection eradication and wound healing through modulating local inflammatory phenotype. Overall, this study offers a simple and effective approach for timely manipulation of inflammation progression to promote infected wound healing.

Biomimetic hydrogel derived from decellularized dermal matrix facilitates skin wounds healing.

Cutaneous wound healing affecting millions of people worldwide represents an unsolvable clinical issue that is frequently challenged by scar formation with dramatical pain, impaired mobility and disfigurement. Herein, we prepared a kind of light-sensitive decellularized dermal extracellular matrix-derived hydrogel with fast gelling performance, biomimetic porous microstructure and abundant bioactive functions. On account of its excellent cell biocompatibility, this ECM-derived hydrogel could induce a marked cellular infiltration and enhance the tube formation of HUVECs. In vivo experiments based upon excisional wound splinting model showed that the hydrogel prominently imparted skin wound healing, as evidenced by notably increased skin appendages and well-organized collagen expression, coupled with significantly enhanced angiogenesis. Moreover, the skin regeneration mediated by this bioactive hydrogel was promoted by an accelerated M1-to-M2 macrophage phenotype transition. Consequently, the decellularized dermal matrix-derived bioactive hydrogel orchestrates the entire skin healing microenvironment to promote wound healing and will be of high value in treatment of cutaneous wound healing. As such, this biomimetic ddECMMA hydrogel provides a promising versatile opinion for the clinical translation.

Plants against cancer: the immune-boosting herbal microbiome: not of the plant, but in the plant. Basic concepts, introduction, and future resource for vaccine adjuvant discovery.

The presence of microorganism communities (MOCs) comprised of bacteria, fungi, archaea, algae, protozoa, viruses, and the like, are ubiquitous in all living tissue, including plant and animal. MOCs play a significant role in establishing innate and acquired immunity, thereby influencing susceptibility and resistance to disease. This understanding has fostered substantial advancements in several fields such as agriculture, food science/safety, and the development of vaccines/adjuvants, which rely on administering inactivated-attenuated MOC pathogens. Historical evidence dating back to the 1800s, including reports by Drs Busch, Coley, and Fehleisen, suggested that acute febrile infection in response to "specific microbes" could trigger spontaneous tumor remission in humans. This discovery led to the purposeful administration of the same attenuated strains, known as "Coley's toxin," marking the onset of the first microbial (pathogen) associated molecular pattern (MAMPs or PAMPs)-based tumor immunotherapy, used clinically for over four decades. Today, these same MAMPS are consumed orally by billions of consumers around the globe, through "specific" mediums (immune boosting "herbal supplements") as carriers of highly concentrated MOCs accrued in roots, barks, hulls, sea algae, and seeds. The American Herbal Products Association (AHPA) mandates microbial reduction in botanical product processing but does not necessitate the removal of dead MAMP laden microbial debris, which we ingest. Moreover, while existing research has focused on the immune-modulating role of plant phytochemicals, the actual immune-boosting properties might instead reside solely in the plant's MOC MAMP laden biomass. This assertion is logical, considering that antigenic immune-provoking epitopes, not phytochemicals, are known to stimulate immune response. This review explores a neglected area of research regarding the immune-boosting effects of the herbal microbiome - a presence which is indirectly corroborated by various peripheral fields of study and poses a fundamental question: Given that food safety focuses on the elimination of harmful pathogens and crop science acknowledges the existence of plant microbiomes, what precisely are the immune effects of ingesting MAMPs of diverse structural composition and concentration, and where are these distributed in our botanicals? We will discuss the topic of concentrated edible MAMPs as acid and thermally stable motifs found in specific herbs and how these would activate cognate pattern recognition receptors (PPRs) in the upper gut-associated lymphoid tissue (GALT), including Peyer's patches and the lamina propria, to boost antibody titers, CD8+ and CD4+ T cells, NK activity, hematopoiesis, and facilitating M2 to M1 macrophage phenotype transition in a similar manner as vaccines. This new knowledge could pave the way for developing bioreactor-grown/heat-inactivated MOC therapies to boost human immunity against infections and improve tumor surveillance.

Sargentodoxa cuneata and Patrinia villosa extract inhibits LPS-induced inflammation by shifting macrophages polarization through FAK/PI3K/Akt pathway regulation and glucose metabolism reprogramming

Ethnopharmacological relevanceSargentodoxa cuneata and Patrinia villosa (S&P) are two natural herbal medicine widely used for treatment of various inflammatory diseases in Traditional Chinese Medicine, whereas the mode of action needs to be further investigated. Aim of the studyThis study aimed to explore the anti-inflammatory effects and unravel the involved mechanism of S&P extract. Materials and methodsThe components of S&P extract were first detected using the liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of S&P extract on the viability and migration ability of macrophages were detected using CCK8, LDH, adhesion and transwell assays. Cytokine release and macrophage phenotype transition were measured using a cytometric bead array and flow cytometry. The potential mechanism was uncovered using an integrative approach combining RNA sequencing and LC-MS/MS-based metabolic analysis. The expression of related proteins was further validated using western blotting. ResultsS&P extract inhibited the proliferation and migration of LPS-induced macrophages, changed the morphology of macrophages, and inhibited the production of NO and the expression of iNOS. Furthermore, the extract inhibited tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production and the expression of the M1 phenotype markers CD11c and CD16/32, whereas it promoted interleukin-10 (IL-10) production and the expression of the M2 phenotype markers CD206 and arginase 1 (Arg1). RNA sequencing analysis demonstrated that the upregulated genes by S&P extract treatment were involved in M2 macrophages: Il10, Ccl17, Ccl22, Cd68. The downregulated genes were involved in M1 macrophages and glycolysis processes: Stat1, Il18, Cd80, Cd86, Nos2, Il6, Pik3ap1, Raf1, Pdhb, etc. Metabolomics results showed that the S&P extract strongly ameliorated lipopolysaccharide (LPS)-induced metabolic disturbances. KEGG analysis indicated that most of these metabolites were involved in glucose metabolism, which is involved in the tumor necrosis factor (TNF), phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt), Glycolysis, and mitogen-activated protein kinase (MAPK) pathways. In vitro experiments further confirmed that the extract significantly inhibited the phosphorylation of focal adhesion kinase (FAK), PI3K and Akt, and the expression of glucose metabolism-related proteins. Adding a FAK inhibitor (defactinib) further inhibited the expression of M1/M2 phenotypic markers and the phosphorylation of FAK, PI3K, and Akt. ConclusionsS&P extract can induce M2 polarization and shift macrophages from M1 to M2 tissue repair in LPS-induced inflammation by regulating glucose metabolism and the FAK/PI3K/Akt pathway.

Lactylation of PKM2 Suppresses Inflammatory Metabolic Adaptation in Pro-inflammatory Macrophages.

Emerging evidence suggests that metabolic adaptation is a vital hallmark and prerequisite for macrophage phenotype transition. Pyruvate kinase M2 (PKM2) is an essential molecular determinant of metabolic adaptions in pro-inflammatory macrophages. Post-translational modifications play a central role in the regulation of PKM2. However, doubt remains on whether lactylation in PKM2 exists and how lactylation modulates the function of PKM2. For the first time, our study reports that lactate inhibits the Warburg effect by activating PKM2, promoting the transition of pro-inflammatory macrophages towards a reparative phenotype. We identify PKM2 as a lactylation substrate and confirm that lactylation occurs mainly at the K62 site. We find that lactate increases the lactylation level of PKM2, which inhibits its tetramer-to-dimer transition, promoting its pyruvate kinase activity and reducing nuclear distribution. In short, our study reports a novel post-translational modification type in PKM2 and clarifies its potential role in regulating inflammatory metabolic adaptation in pro-inflammatory macrophages.

Barley β-glucan gelatin sponge improves impaired wound healing in diabetic and immunosuppressed mice by regulating macrophage polarization

β-glucan has been reported to improve chronic wound healing. Barley β-glucans are abundantly available, are easy to extract, and have high biological activity. Gelatin is a well-known hemostatic agent and can be processed into a variety of forms for clinical applications.Dysfunction in macrophage phenotype transition is one of the primary reasons for impaired wound healing. In this study, we evaluated the effects of barley β-glucan gelatin sponge on delayed wound healing and its’ effect on macrophage function. We observed that barley β-glucan gelatin sponge could alleviate delayed wound healing in immunosuppressed and diabetic db/db mice. Furthermore, it promoted macrophage recruitment to the wound site, decreased iNOS expression, and increased CD206 levels in granulation tissues. With regards to db/db mice, barley β-glucans gelatin sponge decreased the expression of M1 type cytokines (TNF-α mRNA and protein, IL-6/IL-12A mRNA) on day 7 post wounding and increased expression levels of M2 type cytokines (VEGF and IL-10mRNA, TGF-β protein) on day 14. In immunosuppressed mice, barley β-glucan gelatin sponge decreased IL-6 mRNA levels and increased TGF-β mRNA levels on days 3 and 7 post wound initiation. Furthermore, it increased VEGF levels during granulation. This suggested barley β-glucan gelatin sponge alleviated impaired wound healing by regulating macrophage phenotype transition. In conclusion, barley β-glucans gelatin sponge is a more effective and safer topical agent compared to traditional gelatin sponge for treating delayed wound healing and could be a treatment option for patients with chronic wounds.

Surface modification of electrospun fibers with mechano-growth factor for mitigating the foreign-body reaction

The implantation of synthetic polymeric scaffolds induced foreign-body reaction (FBR) seriously influence the wound healing and impair functionality recovery. A novel short peptide, mechano-growth factor (MGF), was introduced in this study to modify an electrospun polycaprolactone (PCL) fibrous scaffold to direct the macrophage phenotype transition and mitigate the FBR. In vitro studies discovered the cell signal transduction mechanism of MGF regulates the macrophage polarization via the expression of related genes and proteins. We found that macrophages response the MGF stimuli via endocytosis, then MGF promotes the histone acetylation and upregulates the STAT6 expression to direct an anti-inflammatory phenotype transition. Subsequently, an immunoregulatory electrospun PCL fibrous scaffold was modified by silk fibroin (SF) single-component layer-by-layer assembly, and the SF was decorated with MGF via click chemistry. Macrophages seeded on scaffold to identify the function of MGF modified scaffold in directing macrophage polarization in vitro. Parallelly, rat subcutaneous implantation model and rat tendon adhesion model were performed to detect the immunomodulatory ability of the MGF-modified scaffold in vivo. The results demonstrate that MGF-modified scaffold is beneficial to the transformation of macrophages to M2 phenotype in vitro. More importantly, MGF-functionalized scaffold can inhibit the FBR at the subcutaneous tissue and prevent tissue adhesion.

Harnessing noncoding RNA-based macrophage polarization: Emerging therapeutic opportunities for fibrosis.

AimOrgan fibrosis is a common pathological outcome of persistent tissue injury correlated with organ failure and death. Although current antifibrotic therapies have led to unprecedented successes, only a minority of patients with fibrosis benefit from these treatments. There is an urgent need to identify new targets and biomarkers that could be exploited in the diagnosis and treatment of fibrosis.MethodsMacrophages play a dual role in the fibrogenesis across different organs either by promoting pro‐inflammatory or anti‐inflammatory responses. Noncoding RNAs (ncRNAs) have been demonstrated to play key roles in macrophage functions by manipulating macrophage polarization. Therefore, understanding the mechanism of ncRNA‐associated macrophage polarization is important to move toward therapeutic interventions.ResultsIn this review, we provide an overview of recent insights into the role of ncRNAs in different fibrotic diseases by modulating macrophage phenotypic plasticity and functional heterogeneity. We also discuss the potential mechanisms of different ncRNAs integrate heterogeneous macrophages in fibrogenesis,including regulatory signatures, networks, and reciprocal interactions.ConclusionsA broader understanding of how ncRNA‐directed macrophage phenotype transition in immunity and fibrosis might promote the development of a novel strategy for antifibrotic treatment.

Tanshinone IIA-loaded aligned microfibers facilitate stem cell recruitment and capillary formation by inducing M2 macrophage polarization

Direct implantation of cell-free scaffolds capable of promoting tissue regeneration by manipulating immune responses has proven to be a promising therapeutic strategy for regenerative medicine. Here, we developed aligned microfiber scaffolds with sustained release of tanshinone ⅡA (Tan ⅡA) to modulate macrophages phenotypic transition, which subsequently promoted stem cell recruitment and capillary formation. Aligned microfibers scaffolds loaded with 1μM Tan ⅡA (AF-1) significantly down-regulated the expression of proinflammatory genes and proteins, while they upregulated anti-inflammatory genes and proteins, in RAW 264.7 macrophages. Conditioned medium collected from macrophages cultured on AF-1 scaffolds enhanced bone marrow-derived mesenchymal stem cell (BMSC) proliferation and migration, and also regulated their multiple biological functions as evidenced by RNA-Seq assays. Moreover, the conditioned medium also promoted human umbilical vein endothelial cell (HUVEC) proliferation, migration, and tube formation. Enhancement of endogenous stem cell recruitment and vascularization by regulating macrophage phenotype transition was further confirmed by utilizing rat subcutaneous implantation of the scaffolds. These results support the use of drug-loaded aligned microfiber scaffolds to enable immune modulation to stimulate stem cell recruitment and vascularization, which could potentially result in successful cell-free, scaffold-guided tissue regeneration.

199-LB: Diabetes, Macrophage Dysfunction, and Mesh Complications

Objective: Diabetic women who receive polypropylene meshes in the surgical repair of stress urinary incontinence and/or pelvic organ prolapse have a ~5-fold increased risk in developing mesh complications, mainly mesh exposure and pain. Macrophage plays important roles in inflammation and mesh-tissue integration. This study aims to establish an association between diabetes and macrophage dysfunction at the mesh implantation site. Methods: Diabetic (n=20) vs. nondiabetic (n=28) mesh-tissue complexes excised from women with mesh complications were assessed for macrophage phenotype transition, efferocytosis and immune mediator production with TUNEL apoptotic cell labeling, immunofluorescence, NanoString and Luminex multiplex assays. Significance of all statistical tests was set at 0.05 level. Results: Demographic parameters were not different except that BMI was higher in diabetic women (p=0.04). In diabetic vs. nondiabetic specimens, the ratio of pro-healing M2 to pro-inflammatory M1 was 50% lower; the ratio of apoptotic cells/CD68+ macrophages was 50% higher; normal correlations of molecules involved in cell apoptosis (BCL10 and TRAF3) and CD68 were disrupted (Figure); and levels of chemokines CCL11, CCL13, CXCL10 were significantly increased (all p<0.05). Conclusion: Diabetes was associated with macrophage dysfunction at the mesh implantation site, which may contribute to short-term and long-term mesh complications. Disclosure R. Liang: None. S. Lopa: None. Funding Pennsylvania Department of Health

The BACH1–HMOX1 Regulatory Axis Is Indispensable for Proper Macrophage Subtype Specification and Skeletal Muscle Regeneration

The infiltration and subsequent in situ subtype specification of monocytes to effector/inflammatory and repair macrophages is indispensable for tissue repair upon acute sterile injury. However, the chromatin-level mediators and regulatory events controlling this highly dynamic macrophage phenotype switch are not known. In this study, we used a murine acute muscle injury model to assess global chromatin accessibility and gene expression dynamics in infiltrating macrophages during sterile physiological inflammation and tissue regeneration. We identified a heme-binding transcriptional repressor, BACH1, as a novel regulator of this process. Bach1 knockout mice displayed impaired muscle regeneration, altered dynamics of the macrophage phenotype transition, and transcriptional deregulation of key inflammatory and repair-related genes. We also found that BACH1 directly binds to and regulates distal regulatory elements of these genes, suggesting a novel role for BACH1 in controlling a broad spectrum of the repair response genes in macrophages upon injury. Inactivation of heme oxygenase-1 (Hmox1), one of the most stringently deregulated genes in the Bach1 knockout in macrophages, impairs muscle regeneration by changing the dynamics of the macrophage phenotype switch. Collectively, our data suggest the existence of a heme-BACH1--HMOX1 regulatory axis, that controls the phenotype and function of the infiltrating myeloid cells upon tissue damage, shaping the overall tissue repair kinetics.

STAT6 induces expression of Gas6 in macrophages to clear apoptotic neutrophils and resolve inflammation

Efferocytosis of apoptotic neutrophils (PMNs) by alveolar macrophages (AMФs) is vital for resolution of inflammation and tissue injury. Here, we investigated the role of AMФ polarization and expression of the efferocytic ligand Gas6 in restoring homeostasis. In the murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI), we observed augmented temporal generation of cytokines IL-4 and TSG6 in bronchoalveolar fluid (BALF). Interestingly, we also observed increased expression of antiinflammatory markers consistent with a phenotype shift in AMФs. In particular, AMФs expressed the efferocytic ligand Gas6. In vitro priming of bone marrow-derived macrophages (BMMФs) with IL-4 or TSG6 also induced MФ transition and expression of Gas6. TSG6- or IL-4-primed BMMФs induced efferocytosis of apoptotic PMNs compared with control BMMФs. Adoptive transfer of TSG6- or IL-4-primed BMMФs i.t. into LPS-challenged mice more rapidly and effectively cleared PMNs in lungs compared with control BMMФs. We demonstrated that expression of Gas6 during AMФ transition was due to activation of the transcription factor signal transducer and activator of transcription-6 (STAT6) downstream of IL-4 or TSG6 signaling. Adoptive transfer of Gas6-depleted BMMФs failed to clear PMNs in lungs following LPS challenge and mice showed severely defective resolution of lung injury. Thus, activation of STAT6-mediated Gas6 expression during macrophage phenotype transition resulting in efferocytosis of PMNs plays a crucial role in the resolution of inflammatory lung injury.

Macrophage BACH1, a heme regulated transcriptional repressor, controls HMOX1 and skeletal muscle regeneration

Skeletal muscle regeneration following injury is a complex process that involves inflammatory components. Macrophage infiltration to damaged tissues upon injuries and their in‐situ differentiation into effector/inflammatory and repair macrophages is indispensable for necrotic debris clearance, and for coordination of tissue repair. Regulatory events controlling the highly dynamic macrophage phenotype switch are not well understood. Here, by using an acute sterile skeletal muscle injury model, and by studying macrophage chromatin accessibility (ATAC‐seq) and gene expression (RNA‐seq) dynamics during inflammation and tissue regeneration, we identified a heme‐ and MARE motif binding transcription factor, BTB Domain And CNC Homolog 1 (BACH1), as a novel regulatory molecule of the macrophage phenotype switch following tissue injury. We show that Bach1 deletion impairs muscle regeneration, alters the dynamics of the macrophage phenotype transition, impacts myoblast proliferation and leads to transcriptional deregulation of critical inflammatory and repair‐related genes. We also find that BACH1 directly binds and regulates distal regulatory elements of these genes, suggesting a role of BACH1 in controlling a spectrum of the inflammatory and tissue repair response genes in macrophages upon tissue injury. As proof of concept, inactivation of heme oxygenase 1 (Hmox1), a known downstream BACH1 target and the most deregulated gene in the Bach1 KO, in macrophages, impairs muscle regeneration by changing the dynamics of the macrophage phenotype switch. Collectively, our data suggest the existence of a regulatory axis, involving BACH1 and HMOX1 that control the phenotype and function of the infiltrating myeloid cells upon tissue damage, shaping the overall tissue repair kinetics.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Matrix bound nanovesicle-associated IL-33 activates a pro-remodeling macrophage phenotype via a non-canonical, ST2-independent pathway

The regenerative healing response of injured skeletal muscle is dependent upon an appropriately timed switch from a local type-I to a type-II immune response. Biologic scaffolds derived from extracellular matrix (ECM) have been shown to facilitate a macrophage phenotype transition that leads to downstream site-appropriate functional tissue deposition and myogenesis. However, the mechanisms by which ECM directs the switching of immune cell phenotype are only partially understood. Herein, we provide the first evidence that matrix bound nanovesicles (MBV) embedded within ECM-scaffolds are a rich and stable source of interleukin-33 (IL-33), an alarmin/cytokine with emerging reparative properties. We show that IL-33 encapsulated within MBV bypass the classical IL33/ST2 receptor signaling pathway to direct macrophage differentiation into the reparative, pro-remodeling M2 phenotype, which in turn facilitates myogenesis of skeletal muscle progenitor cells. Our results suggest the potential of IL-33+ MBV as a clinical therapy to augment the restorative efficacy of existing ECM-based and non-ECM based approaches.

Insulin promotes macrophage phenotype transition through PI3K/Akt and PPAR-γ signaling during diabetic wound healing.

Overactivation and persistent chronic inflammation are the major pathogenic characteristics of diabetic-impaired healing, and diabetic wound healing can be promoted by stimulating the transition of macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2). Our previous studies found that the application of insulin induced an advanced initiation and resolution of inflammatory response. To further explore the mechanism, we have investigated the effect of insulin on macrophage phenotype switch utilizing a diabetic rat model and a human monocytic THP-1 cell. We have utilized the high glucose (HG) and HG plus insulin to stimulate the M1 macrophages derived from lipopolysaccharide-treated THP-1 cells. We studied the secretion of inflammatory mediator and related signaling pathways by using western blot test, immunofluorescence, and Rac1 pull-down assay. We have found that the production of pro-inflammatory mediators, which thereafter induced macrophage polarization toward M1 phenotype, has been elevated due to consistent HG exposure. HG plus insulin stimulation, on the other hand, promoted anti-inflammatory effects. Experiments performed on diabetic burn wounds indicated that the insulin modulated macrophages transition from M1 to M2 phenotype. We found that PI3K/Akt/Rac-1 and PPAR-γ signaling pathways are involved in the anti-inflammatory effect of insulin. Insulin inhibited HG-induced activation of p38, NF-κB, and STAT1 transcriptional activity by activating Akt-Rac-1 signaling. Moreover, insulin performs anti-inflammatory effects through upregulation of PPAR-γ expression and induced P38-mediated dephosphorylation of PPAR-γ (Ser112). In conclusion, insulin downregulates inflammatory response, regulates M1 macrophage transition in response to HG, and thus improves chronic wound healing.

Effects of the fibrous topography-mediated macrophage phenotype transition on the recruitment of mesenchymal stem cells: An in vivo study

Host responses to a biomaterial critically influence its in vivo performance. Biomaterial architectures that can recruit endogenous host stem cells could be beneficial in tissue regeneration or integration. Here, we report that the fibrous topography of biomaterials promotes the recruitment of host mesenchymal stem cells (MSCs) by facilitating the macrophage phenotype transition from M1-to-M2. Electrospun poly (ε-caprolactone) fiber (PCL-fiber) films were implanted into the subcutaneous tissues of rats, and the response of host cells to the PCL-fiber was evaluated and compared with those of solid ones (PCL-solid). During the initial post-implantation period, greater numbers of cells were recruited and adhered to the PCL-fiber compared to the PCL-solid, and the cells exhibited the M1 phenotype, which was supported by the enhanced adsorption of complement C3a to the implanted PCL-fiber. Subsequently, the PCL-fiber supported the macrophage phenotype transition from M1-to-M2, which was confirmed by the ratio of M2/M1 marker (CD163/CCR7)-positive cells and by the expression of M2/M1 markers (arginase-1/iNOS). The PCL-fiber also reduced the formation of foreign body giant cells. MSC marker (CD29, CD44, and CD90)-positive cells began to appear as early as day 4 on the PCL-fiber, while few MSCs were observed on the PCL-solid. The MSCs migration ex vivo assay showed that MSCs substantially migrated across the trans-wells toward the implanted PCL-fiber. The cells on the implanted PCL-fiber expressed and secreted substantial levels of SDF-1 (CXCL-12), while anti-SDF-1 neutralizing antibody abrogated the MSCs migration. Taken together, these results provide evidence that the fibrous topography of biomaterials enhances the recruitment of MSCs by promoting macrophage recruitment, facilitating M1-to-M2 transition, and enhancing SDF-1 secretion.

C1q/Tumor necrosis factor-related protein-3 protects macrophages against LPS-induced lipid accumulation, inflammation and phenotype transition via PPARγ and TLR4-mediated pathways.

Macrophage inflammation and foam cell formation are critical events during the initiation and development of atherosclerosis (AS). C1q/tumor necrosis factor-related protein-3 (CTRP3) is a novel adipokine with anti-inflammatory and cardioprotection properties; however, little is known regarding the influence of CTRP3 on AS. As macrophages play a key role in AS, this study investigated the effects of CTRP3 on macrophage lipid metabolism, inflammatory reactions, and phenotype transition, as well as underlying mechanisms, to reveal the relationship between CTRP3 and AS. CTRP3 reduced the number of lipid droplets, lowered cholesteryl ester (CE), total cholesterol (TC), and free cholesterol (FC) levels, reduced the CE/TC ratio, and dose-dependently inhibited TNFα, IL-6, MCP-1, MMP-9 and IL-1β release in lipopolysaccharide (LPS)-stimulated THP-1 macrophages and mouse peritoneal macrophages. Pretreatment with CTRP3 effectively increased macrophage transformation to M2 macrophages rather than M1 macrophages. Western blotting showed that the specific NF-κB pathway inhibitor ammonium pyrrolidine dithiocarbamate (PDTC) or siRNA targeting PPARγ/LXRα markedly strengthened or abolished the above-mentioned effects of CTRP3, respectively. These results show that CTRP3 inhibits TLR4-NF-κB pro-inflammatory pathways but activates the PPARγ-LXRα-ABCA1/ABCG1 cholesterol efflux pathway. Taken together, CTRP3 participates in anti-lipid accumulation, anti-inflammation and macrophage phenotype conversion via the TLR4-NF-κB and PPARγ-LXRα-ABCA1/ABCG1 pathways and, thus, may have anti-atherosclerotic properties.

Nicorandil modulated macrophages activation and polarization via NF-κb signaling pathway

Nicorandil, a drug with both nitrate-like and ATP-sensitive potassium (KATP) channel-activating properties, has been well demonstrated in various aspects of myocardial infarction (MI), especially in inhibiting cell apoptosis and increasing coronary flow. However, the role of nicorandil in regulating inflammation and angiogenesis following myocardial infarction is still unrevealed. In the present study, we explored the effect of nicorandil on macrophage phenotype transition and inflammation regulation and the potential underlying mechanisms. For the phenotype transition and phagocytosis ability of macrophages detection, flow cytometry analysis was used. The inflammation factors were measured with ELISA and qRT-PCR. Western blot was used to assess the levels of NF-κb and its target genes and VEGF expression. The tube formation ability of endothelial cells was examined on matrigel. We discovered that nicorandil can obviously inhibit the differentiation of monocytes into mature macrophages and decrease M1 phenotype transition both in peritoneal macrophages and cultured macrophage cell line in normal or hypoxia and serum deprivation (H/SD) conditions. Meanwhile, nicorandil can induce an anti-inflammatory M2 phenotype. Thereby, nicorandil regulated macrophages switching to M1/M2 status. Our data further showed that NF-κb and the expression of its target genes were pivotal players in the regulation of macrophages phenotype. Besides, we also showed that nicorandil can promote the tube formation and VEGF expression in endothelial cells. We concluded that nicorandil may serve as an effective modulator of NF-κb signaling pathway during the pathogenesis of MI via regulating M1/M2 status and promoting angiogenesis.

Dapagliflozin, a selective SGLT2 Inhibitor, attenuated cardiac fibrosis by regulating the macrophage polarization via STAT3 signaling in infarcted rat hearts

During myocardial infarction, infiltrated macrophages have pivotal roles in cardiac remodeling and delayed M1 toward M2 macrophage phenotype transition is considered one of the major factors for adverse ventricular remodeling. We investigated whether dapagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, attenuates cardiac fibrosis via regulating macrophage phenotype by a reactive oxygen and nitrogen species (RONS)/STAT3-dependent pathway in postinfarcted rats. Normoglycemic male Wistar rats were subjected to coronary ligation and then randomized to either saline, dapagliflozin (a specific SGLT2 inhibitor), phlorizin (a nonspecific SGLT1/2 inhibitor), dapagliflozin + S3I-201 (a STAT3 inhibitor), or phlorizin + S3I-201 for 4 weeks. There were similar infarct sizes among the infarcted groups at the acute and chronic stages of infarction. At day 3 after infarction, post-infarction was associated with increased levels of superoxide and nitrotyrosine, which can be inhibited by administering either dapagliflozin or phlorizin. SGLT2 inhibitors significantly increased STAT3 activity, STAT3 nuclear translocation, myocardial IL-10 levels and the percentage of M2 macrophage infiltration. At day 28 after infarction, SGLT2 inhibitors were associated with attenuated myofibroblast infiltration and cardiac fibrosis. Although phlorizin decreased myofibroblast infiltration, the effect of dapagliflozin on attenuated myofibroblast infiltration was significantly higher than phlorizin. The effects of SGLT2 inhibitors on cardiac fibrosis were nullified by adding S3I-201. Furthermore, the effects of dapagliflozin on STAT3 activity and myocardial IL-10 levels can be reversed by 3-morpholinosydnonimine, a peroxynitrite generator. Taken together, these observations provide a novel mechanism of SGLT2 inhibitors-mediated M2 polarization through a RONS-dependent STAT3-mediated pathway and selective SGLT2 inhibitors are more effective in attenuating myofibroblast infiltration during postinfarction remodeling.