M2A and M2C Macrophage Subsets Ameliorate Inflammation and Fibroproliferation in Acute Lung Injury Through Interleukin 10 Pathway. Shock. 2017;48:119-129. [PMID: 27941591 DOI: 10.1097/shk.0000000000000820]

Mechanism of Astragaloside IV in Treatment of Renal Tubulointerstitial Fibrosis

Tubulointerstitial fibrosis (TIF) is one of the key indicators in evaluating the renal function of patients. Mild TIF can cause a vicious cycle of renal tubular glomerular injury and aggravate renal disease. Therefore, studying the mechanisms underlying TIF is essential to identify therapeutic targets, thereby protecting the renal function of patients with timely intervention. Astragaloside IV (AS-IV) is a Chinese medicine component that has been shown to inhibit the occurrence and progression of TIF via multiple pathways. Previous studies have reported that AS-IV protected against TIF by inhibiting inflammation, autophagy, endoplasmic reticulum stress, macrophages, and transforming growth factor-β1, which laid the foundation for the development of a new preventive and therapeutic option for TIF.

Renal macrophages and NLRP3 inflammasomes in kidney diseases and therapeutics

Macrophages are exceptionally diversified cell types and perform unique features and functions when exposed to different stimuli within the specific microenvironment of various kidney diseases. In instances of kidney tissue necrosis or infection, specific patterns associated with damage or pathogens prompt the development of pro-inflammatory macrophages (M1). These M1 macrophages contribute to exacerbating tissue damage, inflammation, and eventual fibrosis. Conversely, anti-inflammatory macrophages (M2) arise in the same circumstances, contributing to kidney repair and regeneration processes. Impaired tissue repair causes fibrosis, and hence macrophages play a protective and pathogenic role. In response to harmful stimuli within the body, inflammasomes, complex assemblies of multiple proteins, assume a pivotal function in innate immunity. The initiation of inflammasomes triggers the activation of caspase 1, which in turn facilitates the maturation of cytokines, inflammation, and cell death. Macrophages in the kidneys possess the complete elements of the NLRP3 inflammasome, including NLRP3, ASC, and pro-caspase-1. When the NLRP3 inflammasomes are activated, it triggers the activation of caspase-1, resulting in the release of mature proinflammatory cytokines (IL)-1β and IL-18 and cleavage of Gasdermin D (GSDMD). This activation process therefore then induces pyroptosis, leading to renal inflammation, cell death, and renal dysfunction. The NLRP3-ASC-caspase-1-IL-1β-IL-18 pathway has been identified as a factor in the development of the pathophysiology of numerous kidney diseases. In this review, we explore current progress in understanding macrophage behavior concerning inflammation, injury, and fibrosis in kidneys. Emphasizing the pivotal role of activated macrophages in both the advancement and recovery phases of renal diseases, the article delves into potential strategies to modify macrophage functionality and it also discusses emerging approaches to selectively target NLRP3 inflammasomes and their signaling components within the kidney, aiming to facilitate the healing process in kidney diseases.

Structural Characterization of Polygonatum Cyrtonema Polysaccharide and Its Immunomodulatory Effects on Macrophages

A neutral Polygonatum cyrtonema polysaccharide (NPCP) was isolated and purified from Polygonatum cyrtonema by various chromatographic techniques, including DEAE-52 and Sephadex-G100 chromatography. The structure of NPCP was characterized by HPLC, HPGPC, GC-MS, FT-IR, NMR, and SEM. Results showed that NPCP is composed of glucose (55.4%) and galactose (44.6%) with a molecular weight of 3.2 kDa, and the sugar chain of NPCP was →1)-α-D-Glc-(4→1)-β-D-Gal-(3→. In vitro bioactivity experiments demonstrated that NPCP significantly enhanced macrophages proliferation and phagocytosis while inhibiting the M1 polarization induced by LPS as well as the M2 polarization induced by IL-4 and IL-13 in macrophages. Additionally, NPCP suppressed the secretion of IL-6 and TNF-α in both M1 and M2 cells but promoted the secretion of IL-10. These results suggest that NPCP could serve as an immunomodulatory agent with potential applications in anti-inflammatory therapy.

Targeting Macrophages: Therapeutic Approaches in Diabetic Kidney Disease

Diabetes is not solely a metabolic disorder but also involves inflammatory processes. The immune response it incites is a primary contributor to damage in target organs. Research indicates that during the initial phases of diabetic nephropathy, macrophages infiltrate the kidneys alongside lymphocytes, initiating a cascade of inflammatory reactions. The interplay between macrophages and other renal cells is pivotal in the advancement of kidney disease within a hyperglycemic milieu. While M1 macrophages react to the inflammatory stimuli induced by elevated glucose levels early in the disease progression, their subsequent transition to M2 macrophages, which possess anti-inflammatory and tissue repair properties, also contributes to fibrosis in the later stages of nephropathy by transforming into myofibroblasts. Comprehending the diverse functions of macrophages in diabetic kidney disease and regulating their activity could offer therapeutic benefits for managing this condition.

Intermittent Fasting Modulates Immune Response by Generating Tregs via TGF-β Dependent Mechanisms in Obese Mice with Allergic Contact Dermatitis

People with obesity maintain low levels of inflammation; therefore, their exposure to foreign antigens can trigger an excessive immune response. In people with obesity or allergic contact dermatitis (ACD), symptoms are exacerbated by a reduction in the number of regulatory T cells (Tregs) and IL-10/TGF-β-modified macrophages (M2 macrophages) at the inflammatory site. Benefits of intermittent fasting (IF) have been demonstrated for many diseases; however, the immune responses regulated by macrophages and CD4+T cells in obese ACD animal models are poorly understood. Therefore, we investigated whether IF suppresses inflammatory responses and upregulates the generation of Tregs and M2 macrophages in experimental ACD animal models of obese mice. The IF regimen relieved various ACD symptoms in inflamed and adipose tissues. We showed that the IF regimen upregulates Treg generation in a TGF-β-dependent manner and induces CD4+T cell hypo-responsiveness. IF-M2 macrophages, which strongly express TGF-β and inhibit CD4+T cell proliferation, directly regulated Treg differentiation from CD4+T cells. These results indicate that the IF regimen enhances the TGF-β-producing ability of M2 macrophages and that the development of Tregs keeps mice healthy against ACD exacerbated by obesity. Therefore, the IF regimen may ameliorate inflammatory immune disorders caused by obesity.

Artificially induced in situ macrophage polarization: An emerging cellular therapy for immuno-inflammatory diseases

Macrophages are the mature form of monocytes that have high plasticity and can shift from one phenotype to another by the process of macrophage polarization. Macrophage has several vital pharmacological tasks like eliminating microorganism invasion, clearing dead cells, causing inflammation, repairing damaged tissues, etc. The function of macrophages is based on their phenotype. M1 macrophages are mostly responsible for the body's immune responses and M2 macrophages have healing properties. Inappropriate activation of any one of the phenotypes often leads to ROS-induced tissue damage and affects wound healing and angiogenesis. Therefore, maintaining tissue macrophage homeostasis is necessary. Studies are being done to find techniques for macrophage polarization. But, the process of macrophage polarization is very complex as it involves multiple signalling pathways involving innate immunity. Thus, identifying the right pathways for macrophage polarization is essential to apply the polarizing technique for the treatment of various inflammatory diseases where macrophage physiology influences the disease pathology. In this review, we highlighted the various techniques so far used to change macrophage plasticity. We believe that soon macrophage targeting therapeutics will hit the market for the management of inflammatory disease. Hence this review will help macrophage researchers choose suitable methods and materials/agents to polarize macrophages artificially in various disease models.

Biochemical and molecular inducers and modulators of M2 macrophage polarization in clinical perspective

Macrophages as innate immune cells with great plasticity are of great interest for cell therapy. There are two main macrophage populations - pro- and anti-inflammatory cells also known as M1 and M2. High potential in cancer research contributed to the in-depth study of the molecular processes leading to the polarization of macrophages into the M1 phenotype, and much less attention has been paid to anti-inflammatory M2 macrophages, which can be successfully used in cell therapy of inflammatory diseases. This review describes ontogenesis of macrophages, main functions of pro- and and-inflammatory cells and four M2 subpopulations characterized by different functionalities. Data on agents (cytokines, microRNAs, drugs, plant extracts) that may induce M2 polarization through the changes in microenvironment, metabolism, and efferocytosis are summarized. Finally, recent attempts at stable macrophage polarization using genetic modifications are described. This review may be helpful for researchers concerned with the problem of M2 macrophage polarization and potential use of these anti-inflammatory cells for the purposes of regenerative medicine.

Therapeutic strategies targeting pro-fibrotic macrophages in interstitial lung disease

Idiopathic pulmonary fibrosis (IPF) is the representative phenotype of interstitial lung disease where severe scarring develops in the lung interstitium. Although antifibrotic treatments are available and have been shown to slow the progression of IPF, improved therapeutic options are still needed. Recent data indicate that macrophages play essential pro-fibrotic roles in the pathogenesis of pulmonary fibrosis. Historically, macrophages have been classified into two functional subtypes, "M1" and "M2," and it is well described that "M2" or "alternatively activated" macrophages contribute to fibrosis via the production of fibrotic mediators, such as TGF-β, CTGF, and CCL18. However, highly plastic macrophages may possess distinct functions and phenotypes in the fibrotic lung environment. Thus, M2-like macrophages in vitro and pro-fibrotic macrophages in vivo are not completely identical cell populations. Recent developments in transcriptome analysis, including single-cell RNA sequencing, have attempted to depict more detailed phenotypic characteristics of pro-fibrotic macrophages. This review will outline the role and characterization of pro-fibrotic macrophages in fibrotic lung diseases and discuss the possibility of treating lung fibrosis by preventing or reprogramming the polarity of macrophages. We also utilized a systematic approach to review the literature and identify novel and promising therapeutic agents that follow this treatment strategy.

The generation, activation, and polarization of monocyte-derived macrophages in human malignancies

Macrophages are immune cells that originate from embryogenesis or from the differentiation of monocytes. They can adopt numerous phenotypes depending on their origin, tissue distribution and in response to different stimuli and tissue environment. Thus, in vivo, macrophages are endowed with a continuum of phenotypes that are rarely strictly pro-inflammatory or anti-inflammatory and exhibit a broad expression profile that sweeps over the whole polarization spectrum. Schematically, three main macrophage subpopulations coexist in human tissues: naïve macrophages also called M0, pro-inflammatory macrophages referred as M1 macrophages, and anti-inflammatory macrophages also known as M2 macrophages. Naïve macrophages display phagocytic functions, recognize pathogenic agents, and rapidly undergo polarization towards pro or anti-inflammatory macrophages to acquire their full panel of functions. Pro-inflammatory macrophages are widely involved in inflammatory response, during which they exert anti-microbial and anti-tumoral functions. By contrast, anti-inflammatory macrophages are implicated in the resolution of inflammation, the phagocytosis of cell debris and tissue reparation following injuries. Macrophages also play important deleterious or beneficial roles in the initiation and progression of different pathophysiological settings including solid and hematopoietic cancers. A better understanding of the molecular mechanisms involved in the generation, activation and polarization of macrophages is a prerequisite for the development of new therapeutic strategies to modulate macrophages functions in pathological situations.

Emerging roles of the Hippo signaling pathway in modulating immune response and inflammation-driven tissue repair and remodeling

Inflammation is an evolutionarily conserved process and part of the body's defense mechanism. Inflammation leads to the activation of immune and non-immune cells that protect the host tissue/organs from injury or intruding pathogens. The Hippo pathway is an evolutionarily conserved kinase cascade with an established role in regulating cell proliferation, survival, and differentiation. It is involved in diverse biological processes, including organ size control and tissue homeostasis. Recent clinical and pre-clinical studies have shown that the Hippo signaling pathway is also associated with injury- and pathogen-induced tissue inflammation and associated immunopathology. In this review, we have summarized the recent findings related to the involvement of the Hippo signaling pathway in modulating the immune response in different acute and chronic inflammatory diseases and its impact on tissue repair and remodeling.

How to tame your genes: mechanisms of inflammatory gene repression by glucocorticoids

Glucocorticoids (GCs) are widely used therapeutic agents to treat a broad range of inflammatory conditions. Their functional effects are elicited by binding to the glucocorticoid receptor (GR), which regulates transcription of distinct gene networks in response to ligand. However, the mechanisms governing various aspects of undesired side effects versus beneficial immunomodulation upon GR activation remain complex and incompletely understood. In this review, we discuss emerging models of inflammatory gene regulation by GR, highlighting GR's regulatory specificity conferred by context-dependent changes in chromatin architecture and transcription factor or co-regulator dynamics. GR controls both gene activation and repression, with the repression mechanism being central to favorable clinical outcomes. We describe current knowledge about 3D genome organization and its role in spatiotemporal transcriptional control by GR. Looking beyond, we summarize the evidence for dynamics in gene regulation by GR through cooperative convergence of epigenetic modifications, transcription factor crosstalk, molecular condensate formation and chromatin looping. Further characterizing these genomic events will reframe our understanding of mechanisms of transcriptional repression by GR.

Pyroptosis-Induced Inflammation and Tissue Damage

Programmed cell deaths are pathways involving cells playing an active role in their own destruction. Depending on the signaling system of the process, programmed cell death can be divided into two categories, pro-inflammatory and non-inflammatory. Pyroptosis is a pro-inflammatory form of programmed cell death. Upon cell death, a plethora of cytokines are released and trigger a cascade of responses from the neighboring cells. The pyroptosis process is a double-edged sword, could be both beneficial and detrimental in various inflammatory disorders and disease conditions. A physiological outcome of these responses is tissue damage, and sometimes death of the host. In this review, we focus on the inflammatory response triggered by pyroptosis, and resulting tissue damage in selected organs.

CircN4bp1 Facilitates Sepsis-Induced Acute Respiratory Distress Syndrome through Mediating Macrophage Polarization via the miR-138-5p/EZH2 Axis

We recently reported the differential circRNA expression patterns of the pulmonary macrophages in sepsis-induced acute respiratory distress syndrome (ARDS) mice model by microarray analysis. However, their function and hidden molecular mechanism in regulation of macrophage activation and inflammation remain poorly understood. In this study, we found that circN4bp1was overexpressed in PBMC and monocytes, and its expression levels were correlated with a poor prognosis in sepsis induced ARDS patients induced by sepsis. Knockdown of circN4bp1 inhibited the lung injury and improved the long-time survival through blunting the M1 macrophage activation in cecal ligation and puncture- (CLP-) induced ARDS mice. Moreover, bioinformatics analysis predicated a circN4bp1/miR-138-5p ceRNA network, which was confirmed by luciferase reporter assay and RNA binding protein immunoprecipitation (RIP). CircN4bp1 affected macrophage differentiation by binding to miR-138-5p, thus regulating the expression of EZH2 in vivo and ex vivo. Lastly, the m6A level of circN4bp1was found to be elevated in ARDS mice; inhibition of m6A methyltransferase METTL3 blocked this response in vitro. Therefore, circN4bp1 can function as a miR-138-5p sponge for the modulation of macrophage polarization through regulation the expression of EZH2 and may serve as a potential target and/or prognostic marker for ARDS patients following sepsis.

Dimethyl fumarate prevents acute lung injury related cognitive impairment potentially via reducing inflammation

OBJECTIVE

Dimethyl fumarate (DMF) has been reported to exert a protective role against diverse lung diseases and cognitive impairment-related diseases. Thus this study aimed to investigate its role on acute lung injury (ALI) and related cognitive impairment in animal model.

METHODS

C57BL/6 mice were divided into four groups: control group, DMF group, ALI group, and ALI + DMF group. For ALI group, the ALI mice model was created by airway injection of LPS (50 μL, 1 μg/μL); for ALI + DMF group, DMF (dissolved in 0.08% methylcellulose) was treated twice a day for 2 days, and on the third day, mice were injected with LPS for ALI modeling. Mice pre-administered with methylcellulose or DMF without LPS injection (PBS instead) were used as the control group and DMF group, respectively. Morris water maze test was performed before any treatment (0 h) and 6 h after LPS-induction (54 h) to evaluate the cognitive impairment of mice. Next, the brain edema and blood brain barrier (BBB) permeability of ALI mice were assessed by brain water content, Evans blue extravasation and FITC-Dextran uptake assays. In addition, the effect of DMF on the numbers of total cells and neutrophils, protein content in BALF were quantified; the inflammatory factors in BALF, serum, and brain tissues were examined by ELISA, qRT-PCR, and Western blot assays. The effect of DMF on the cognitive impairment-related factor HIF-1α level in lung and brain tissues was also examined by Western blot.

RESULTS

DMF reduced the numbers of total cells, neutrophils and protein content in BALF of ALI mice, inhibited the levels of IL-6, TNF-α and IL-1β in BALF, serum and brain tissues of ALI mice. The protein expressions of p-NF-κB/NF-κB and p-IKBα/IKBα was also suppressed by DMF in ALI mice. Morris water maze test showed that DMF alleviated the cognitive impairment in ALI mice by reducing the escape latency and path length. Moreover, DMF lessened the BBB permeability by decreasing cerebral water content, Evans blue extravasation and FITC-Dextran uptake in ALI mice. The HIF-1α levels in lung and brain tissues of ALI mice were also lessened by DMF.

CONCLUSION

In conclusion, DME had the ability to alleviate the lung injury and cerebral cognitive impairment in ALI model mice. This protective effect partly associated with the suppression of inflammation by DMF.

The Role of Macrophages in Kidney Fibrosis

The phenotypic heterogeneity and functional diversity of macrophages confer on them complexed roles in the development and progression of kidney diseases. After kidney injury, bone marrow-derived monocytes are rapidly recruited to the glomerulus and tubulointerstitium. They are activated and differentiated on site into pro-inflammatory M1 macrophages, which initiate Th1-type adaptive immune responses and damage normal tissues. In contrast, anti-inflammatory M2 macrophages induce Th2-type immune responses, secrete large amounts of TGF-β and anti-inflammatory cytokines, transform into αSMA+ myofibroblasts in injured kidney, inhibit immune responses, and promote wound healing and tissue fibrosis. Previous studies on the role of macrophages in kidney fibrosis were mainly focused on inflammation-associated injury and injury repair. Apart from macrophage-secreted profibrotic cytokines, such as TGF-β, evidence for a direct contribution of macrophages to kidney fibrosis is lacking. However, under inflammatory conditions, Wnt ligands are derived mainly from macrophages and Wnt signaling is central in the network of multiple profibrotic pathways. Largely underinvestigated are the direct contribution of macrophages to profibrotic signaling pathways, macrophage phenotypic heterogeneity and functional diversity in relation to kidney fibrosis, and on their cross-talk with other cells in profibrotic signaling networks that cause fibrosis. Here we aim to provide an overview on the roles of macrophage phenotypic and functional diversity in their contribution to pro-fibrotic signaling pathways, and on the therapeutic potential of targeting macrophages for the treatment of kidney fibrosis.

M2 macrophages have unique transcriptomes but conditioned media does not promote profibrotic responses in lung fibroblasts or alveolar epithelial cells in vitro

Macrophages are critical regulators of pulmonary fibrosis. Their plasticity, proximity, and ability to cross talk with structural cells of the lung make them a key cell type of interest in the regulation of lung fibrosis. Macrophages can express a variety of phenotypes, which have been historically represented through an "M1-like" to "M2-like" delineation. In this classification, M1-like macrophages are proinflammatory and have increased phagocytic capacity compared with alternatively activated M2-like macrophages that are profibrotic and are associated with wound healing. Extensive evidence in the field in both patients and animal models aligns pulmonary fibrosis with M2 macrophages. In this study, we performed RNA sequencing (RNAseq) to fully characterize M1- vs. M2-skewed bone marrow-derived macrophages (BMDMs) and investigated the profibrotic abilities of M2 BMDM conditioned media (CM) to promote fibroblast migration and proliferation, alveolar epithelial cell (AEC) apoptosis, and mRNA expression of key fibrotic genes in both fibroblasts and AECs. Although M2 CM-treated fibroblasts had increased migration and M2 CM-treated fibroblasts and AECs had increased expression of profibrotic proteins over M1 CM-treated cells, all differences can be attributed to M2 polarization reagents IL-4 and IL-13 also present in the CM. Collectively, these data suggest that the profibrotic effects associated with M2 macrophage CM in vitro are attributable to effects of polarization cytokines rather than additional factors secreted in response to those polarizing cytokines.

The Mechanism of CD8+ T Cells for Reducing Myofibroblasts Accumulation during Renal Fibrosis

Renal fibrosis is a hallmark of chronic kidney disease (CKD) and a common manifestation of end-stage renal disease that is associated with multiple types of renal insults and functional loss of the kidney. Unresolved renal inflammation triggers fibrotic processes by promoting the activation and expansion of extracellular matrix-producing fibroblasts and myofibroblasts. Growing evidence now indicates that diverse T cells and macrophage subpopulations play central roles in the inflammatory microenvironment and fibrotic process. The present review aims to elucidate the role of CD8⁺ T cells in renal fibrosis, and identify its possible mechanisms in the inflammatory microenvironment.

Inhibition of EZH2 prevents acute respiratory distress syndrome (ARDS)-associated pulmonary fibrosis by regulating the macrophage polarization phenotype

Background

We recently reported histone methyltransferase enhancer of zeste homolog 2 (EZH2) as a key epigenetic regulator that contributes to the dysfunction of innate immune responses to sepsis and subsequent lung injury by mediating the imbalance of macrophage polarization. However, the role of EZH2 in acute respiratory distress syndrome (ARDS)-associated fibrosis remains poorly understood.

Methods

In this study, we investigated the role and mechanisms of EZH2 in pulmonary fibrosis in a murine model of LPS-induced ARDS and in ex-vivo cultured alveolar macrophages (MH-S) and mouse lung epithelial cell line (MLE-12) by using 3-deazaneplanocin A (3-DZNeP) and EZH2 the small interfering (si) RNA.

Results

We found that treatment with 3-DZNeP significantly ameliorated the LPS-induced direct lung injury and fibroproliferation by blocking EMT through TGF-β1/Smad signaling pathway and regulating shift of macrophage phenotypes. In the ex-vivo polarized alveolar macrophages cells, treatment with EZH2 siRNA or 3-DZNeP suppressed the M1 while promoted the M2 macrophage differentiation through modulating the STAT/SOCS signaling pathway and activating PPAR-γ. Moreover, we identified that blockade of EZH2 with 3-DZNeP suppressed the epithelial to mesenchymal transition (EMT) in co-cultured bronchoalveolar lavage fluid (BALF) and mouse lung epithelial cell line through down-regulation of TGF-β1, TGF-βR1, Smad2 while up-regulation of Smad7 expression.

Conclusions

These results indicate that EZH2 is involved in the pathological process of ARDS-associated pulmonary fibrosis. Targeting EZH2 may be a potential therapeutic strategy to prevent and treat pulmonary fibrosis post ARDS.

Glucocorticoids activate Yes-associated protein in human vocal fold fibroblasts

Fibrosis of the vocal folds poses a substantive clinical challenge potentially underlying the rapid proliferation of direct steroid injections into the upper airway. The variable clinical response to glucocorticoids (GCs) in the vocal folds is likely related to diversity inherent to GCs and patient-specific, and upstream, cell-specific responses to GCs. Broadly, we hypothesize the disparity in clinical outcomes are due to undesirable effects of GCs on resident fibroblasts. Transcriptome analysis identified significant GC-mediated modulation of Hippo signaling, a known regulator of fibrotic gene expression. Subsequent analysis confirmed GC-mediated YAP activation, a transcriptional co-factor in the Hippo signaling pathway. YAP inhibition attenuated ACTA2 expression in GC-treated human vocal fold fibroblasts. Nuclear localization and phosphorylation at Ser211, however, was not affected by YAP inhibition, suggesting nuclear translocation of YAP is indirectly driven by GR. RNA-seq analysis confirmed the influence of GCs on Wnt signaling, and canonical Wnt signaling target genes were upregulated by GCs. These data implicate YAP and its downstream targets as putative mediators of a pro-fibrotic response to GCs. Therapeutic YAP inhibition may ultimately be clinically relevant and warrants further consideration.

Cerium oxide nanoparticle delivery of microRNA-146a for local treatment of acute lung injury

Acute respiratory distress syndrome (ARDS) is a devastating pulmonary disease with significant in-hospital mortality and is the leading cause of death in COVID-19 patients. Excessive leukocyte recruitment, unregulated inflammation, and resultant fibrosis contribute to poor ARDS outcomes. Nanoparticle technology with cerium oxide nanoparticles (CNP) offers a mechanism by which unstable therapeutics such as the anti-inflammatory microRNA-146a can be locally delivered to the injured lung without systemic uptake. In this study, we evaluated the potential of the radical scavenging CNP conjugated to microRNA-146a (termed CNP-miR146a) in preventing acute lung injury (ALI) following exposure to bleomycin. We have found that intratracheal delivery of CNP-miR146a increases pulmonary levels of miR146a without systemic increases, and prevents ALI by altering leukocyte recruitment, reducing inflammation and oxidative stress, and decreasing collagen deposition, ultimately improving pulmonary biomechanics.

Programmable immune activating electrospun fibers for skin regeneration

Immune cells play a crucial regulatory role in inflammatory phase and proliferative phase during skin healing. How to programmatically activate sequential immune responses is the key for scarless skin regeneration. In this study, an "Inner-Outer" IL-10-loaded electrospun fiber with cascade release behavior was constructed. During the inflammatory phase, the electrospun fiber released a lower concentration of IL-10 within the wound, inhibiting excessive recruitment of inflammatory cells and polarizing macrophages into anti-inflammatory phenotype "M2c" to suppress excessive inflammation response. During the proliferative phase, a higher concentration of IL-10 released by the fiber and the anti-fibrotic cytokines secreted by polarized "M2c" directly acted on dermal fibroblasts to simultaneously inhibit extracellular matrix overdeposition and promote fibroblast migration. The "Inner-Outer" IL-10-loaded electrospun fiber programmatically activated the sequential immune responses during wound healing and led to scarless skin regeneration, which is a promising immunomodulatory biomaterial with great potential for promoting complete tissue regeneration.

Rheumatoid cachexia: the underappreciated role of myoblast, macrophage and fibroblast interplay in the skeletal muscle niche

Although rheumatoid arthritis affects 1% of the global population, the role of rheumatoid cachexia, which occurs in up to a third of patients, is relatively neglected as research focus, despite its significant contribution to decreased quality of life in patients. A better understanding of the cellular and molecular processes involved in rheumatoid cachexia, as well as its potential treatment, is dependent on elucidation of the intricate interactions of the cells involved, such as myoblasts, fibroblasts and macrophages. Persistent RA-associated inflammation results in a relative depletion of the capacity for regeneration and repair in the satellite cell niche. The repair that does proceed is suboptimal due to dysregulated communication from the other cellular role players in this multi-cellular environment. This includes the incomplete switch in macrophage phenotype resulting in a lingering pro-inflammatory state within the tissues, as well as fibroblast-associated dysregulation of the dynamic control of the extracellular matrix. Additional to this endogenous dysregulation, some treatment strategies for RA may exacerbate muscle wasting and no multi-cell investigation has been done in this context. This review summarizes the most recent literature characterising clinical RA cachexia and links these features to the roles of and complex communication between multiple cellular contributors in the muscle niche, highlighting the importance of a targeted approach to therapeutic intervention.

Inflammatory Caspases Drive Pyroptosis in Acute Lung Injury

Acute lung injury (ALI), a critical respiratory disorder that causes diffuse alveolar injury leads to high mortality rates with no effective treatment. ALI is characterized by varying degrees of ventilation/perfusion mismatch, severe hypoxemia, and poor pulmonary compliance. The diffuse injury to cells is one of most important pathological characteristics of ALI. Pyroptosis is a form of programmed cell death distinguished from apoptosis induced by inflammatory caspases, which can release inflammatory cytokines to clear cells infected by pathogens and promote monocytes to reassemble at the site of injury. And pyroptosis not only promotes inflammation in certain cell types, but also regulates many downstream pathways to perform different functions. There is increasing evidence that pyroptosis and its related inflammatory caspases play an important role in the development of acute lung injury. The main modes of activation of pyroptosis is not consistent among different types of cells in lung tissue. Meanwhile, inhibition of inflammasome, the key to initiating pyroptosis is currently the main way to treat acute lung injury. The review summarizes the relationship among inflammatory caspases, pyroptosis and acute lung injury and provides general directions and strategies to conduct further research.

Skin regeneration is accelerated by a lower dose of multipotent mesenchymal stromal/stem cells-a paradigm change

Background

Multipotent mesenchymal stromal/stem cell (MSC) therapy is under investigation in promising (pre-)clinical trials for wound healing, which is crucial for survival; however, the optimal cell dosage remains unknown. The aim was to investigate the efficacy of different low-to-high MSC dosages incorporated in a biodegradable collagen-based dermal regeneration template (DRT) Integra®.

Methods

We conducted a porcine study (N = 8 Yorkshire pigs) and seeded between 200 and 2,000,000 cells/cm² of umbilical cord mesenchymal stromal/stem cells on the DRT and grafted it onto full-thickness burn excised wounds. On day 28, comparisons were made between the different low-to-high cell dose groups, the acellular control, a burn wound, and healthy skin.

Result

We found that the low dose range between 200 and 40,000 cells/cm² regenerates the full-thickness burn excised wounds most efficaciously, followed by the middle dose range of 200,000–400,000 cells/cm² and a high dose of 2,000,000 cells/cm². The low dose of 40,000 cells/cm² accelerated reepithelialization, reduced scarring, regenerated epidermal thickness superiorly, enhanced neovascularization, reduced fibrosis, and reduced type 1 and type 2 macrophages compared to other cell dosages and the acellular control.

Conclusion

This regenerative cell therapy study using MSCs shows efficacy toward a low dose, which changes the paradigm that more cells lead to better wound healing outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02131-6.

M2 Macrophage Subpopulations in Glomeruli Are Associated With the Deposition of IgG Subclasses and Complements in Primary Membranous Nephropathy

Objectives: The role of M2 macrophages in the pathogenesis and progression of primary membranous nephropathy (PMN) remains unknown. In this study, we aimed to investigate the relationship between M2 subsets and clinicopathological features of patients with PMN. Methods: A total of 55 patients with PMN confirmed by biopsy were recruited. The clinical and pathological data were recorded, respectively. Immunohistochemistry was used to detect the markers of M2 macrophages, including total macrophages (CD68+), M2a (CD206+), M2b (CD86+) and M2c (CD163+). Results: The numbers of glomerular macrophages, M2a, M2b, and M2c macrophages were 1.83 (1.00, 2.67), 0.65 (0.15, 1.15), 0.67 (0.33, 1.50), and 0.80 (0.05, 2.30) per glomerulus, respectively. Higher number of glomerular macrophages was found in stage II compared with stage III (2.08 vs. 1.16, P = 0.008). These macrophages also were negatively correlated with serum albumin level (r = -0.331, P = 0.014), while positively associated with complement 3 (C3) deposition (r = 0.300, P = 0.026) and the severity of glomerulosclerosis (r = 0.276, P = 0.041). Moreover, glomerular M2a macrophages were significantly correlated with the deposition of C3 (r = 0.300, P = 0.026), immunoglobulin G1 (IgG1) (r = 0.339, P = 0.011), immunoglobulin G2 (IgG2) (r = 0.270, P = 0.046) and immunoglobulin G3 (IgG3) (r = 0.330, P = 0.014) in glomerular basement membrane (GBM). In addition, M2b macrophages were positively associated with IgG1 (r = 0.295, P = 0.029) and IgG2 (r = 0.393, P = 0.003), while M2c macrophages were negatively correlated with complement 4d (C4d) (r = -0.347, P = 0.009) in GBM. Conclusions: Our results showed that M2 macrophage subpopulations in glomeruli are associated with the deposition of IgG subclasses and complements in renal tissue of PMN, which indicate that M2 macrophages may be involved in the pathogenesis and progression of PMN. Moreover, M2a and M2c macrophages might show different tendencies in the pathogenesis of PMN.

YAP Deficiency Attenuates Pulmonary Injury Following Mechanical Ventilation Through the Regulation of M1/M2 Macrophage Polarization

Background

Evidences indicate that the balance between macrophage M1 and M2 polarization is essential for the regulation of pulmonary inflammation during mechanical ventilation (MV). Yes-associated protein (YAP) is a key component of the Hippo pathway and was suggested to regulate macrophage polarization. This study was designed to investigate whether YAP contributes to pulmonary inflammation during MV.

Methods

Wild-type and macrophage YAP knockout mice were mechanically ventilated for 12 hours to induce pulmonary injuries. At the end of MV, animals were sacrificed for pulmonary tissue collection and macrophage isolation. In addition, the induction of macrophage polarization was performed in isolated macrophages with or without YAP overexpression in vitro. Pulmonary injuries, YAP expression, macrophage polarization and cytokines were measured.

Results

Here, we show that MV induces lung injury together with pulmonary inflammation as well as upregulated YAP expressions in pulmonary macrophages. In addition, our results indicate that YAP deficiency in macrophages attenuates pulmonary injury, accompanied with decreased production of pro-inflammatory cytokines including IL (interleukin)-1β, IL-6 and tumor necrosis factor-alpha (TNF-α). Moreover, both in vivo and in vitro studies indicate that YAP deficiency enhances M2 polarization while inhibits M1 polarization. In contrast, YAP overexpression inhibits the induction of M2 polarization but improves M1 polarization.

Conclusion

Our results report for the first time that the induction of YAP in macrophages contributes to pulmonary inflammation during MV through the regulation of M1/M2 polarization.

Complex fibroblast response to glucocorticoids may underlie variability of clinical efficacy in the vocal folds

Similar to the hypertrophic scar and keloids, the efficacy of glucorticoids (GC) for vocal fold injury is highly variable. We previously reported dexamethasone enhanced the pro-fibrotic effects of transforming growth factor (TGF)-β as a potential mechanism for inconsistent clinical outcomes. In the current study, we sought to determine the mechanism(s) whereby GCs influence the fibrotic response and mechanisms underlying these effects with an emphasis on TGF-β and nuclear receptor subfamily 4 group A member 1 (NR4A1) signaling. Human VF fibroblasts (HVOX) were treated with three commonly-employed GCs+ /-TGF-β1. Phosphorylation of the glucocorticoid receptor (GR:NR3C1) and activation of NR4A1 was analyzed by western blotting. Genes involved in the fibrotic response, including ACTA2, TGFBR1, and TGFBR2 were analyzed by qPCR. RNA-seq was performed to identify global changes in gene expression induced by dexamethasone. GCs enhanced phosphorylation of GR at Ser211 and TGF-β-induced ACTA2 expression. Dexamethasone upregulated TGFBR1, and TGFBR2 in the presence of TGF-β1 and increased active NR4A1. RNA-seq results confirmed numerous pathways, including TGF-β signaling, affected by dexamethasone. Synergistic pro-fibrotic effects of TGF-β were observed across GCs and appeared to be mediated, at least partially, via upregulation of TGF-β receptors. Dexamethasone exhibited diverse regulation of gene expression including NR4A1 upregulation consistent with the anti-fibrotic potential of GCs.

Anticytokine Activity Enhances Osteogenesis of Bioactive Implants

In dental clinical practice, systemic steroids are often applied at the end of implant surgeries to reduce postsurgical inflammation (tissue swelling, etc.) and to reduce patient discomfort. However, the use of systemic steroids is associated with generalized catabolic effects and with a temporarily reduced immunological competence. We hypothesize that by applying locally anticytokine antibodies (antitumor necrosis factor alpha and anti-interleukin-1 beta) together with a bioactive osteogenic implant at the time of the surgical intervention for the placement of a construct, we will be able to achieve the same beneficial effects as those using systemic steroids but are able to avoid the generalized antianabolic effects and the reduced immunocompetence effects, associated with the systemic use of steroids. In an adult rat model, a collagen sponge, soaked with the osteogenic agent bone morphogenetic protein-2, was used as an example for a bioactive implant material and was surgically placed subcutaneously. In the acute inflammatory phase after implantation (2 days after surgery) we investigated the local inflammatory tissue response, and 18 days postsurgically the efficiency of local osteogenesis (to assess possible antianabolic effects). We found that the negative control groups, treated postsurgically with systemic steroids, showed a significant suppression of both the inflammatory response and the osteogenetic activity, that is, they were associated with significant general antianabolic effects, even when steroids were used only at a low dose level. The local anticytokine treatment, however, was able to significantly enhance new bone formation activity, that is, the anabolic activity, over positive control values with BMP-2 only. However, the anticytokine treatment was unable to reduce the local inflammatory and swelling responses.

PAD4 selective inhibitor TDFA protects lipopolysaccharide-induced acute lung injury by modulating nuclear p65 localization in epithelial cells

Protein arginine deiminase 4 (PAD4) serves a critical role in differentiation, development and apoptosis through gene regulation and has emerged as a potential therapeutic target for the treatment of various diseases. However, the roles of PAD4 in lipopolysaccharide (LPS)-induced acute lung injury (ALI) remain largely unknown. To investigate the roles of PAD4 during LPS-induced ALI, the present study detected the trend of PAD4 expression in the lung tissues of ALI mice. Subsequently, the efficiency of TDFA on PAD4 and citrullinated H3 histone were detected. And then, histology, the wet/dry weight ratio, survival rate, activated cells infiltration, oxidative stress levels, tight junction proteins and proinflammatory cytokine expression were detected. In addition, the level of transepithelial electrical resistance (TEER) was assessed. Finally, the level of nuclear P65, total phosphorylated P65 and P65 were measured in vivo and in vitro. The results showed that PAD4 expression was upregulated in the lung tissues of LPS-induced ALI. TDFA efficiently decreased the severity of the lung edema, attenuated the severity of pulmonary injury and improved the survival rate following lethal LPS administration. Besides, TDFA reduced activated cells infiltration and suppressed inflammation related parameters, including proinflammatory cytokines production (TNF-α, IL-6 and IL-1β) and oxidative stress (MDA, GSH and SOD). Furthermore, TDFA reversed the TEER downregulation tendency and tight junction proteins (ZO-1, Occludin, Claudin-4) levels that represent the integrity of alveolar epithelium. Eventually, TDFA exerts its protective roles through modulating nuclear localization of transcription factor NF-κB P65 in epithelial cells. Taken together, these results indicate that PAD4 inhibition may serve as a promising therapeutic approach for LPS-induced ALI.

The Role of Innate Lymphoid Cells in the Regulation of Immune Homeostasis in Sepsis-Mediated Lung Inflammation

Septic shock/severe sepsis is a deregulated host immune system response to infection that leads to life-threatening organ dysfunction. Lung inflammation as a form of acute lung injury (ALI) is often induced in septic shock. Whereas macrophages and neutrophils have been implicated as the principal immune cells regulating lung inflammation, group two innate lymphoid cells (ILC2s) have recently been identified as a new player regulating immune homeostasis. ILC2 is one of the three major ILC subsets (ILC1s, ILC2s, and ILC3s) comprised of newly identified innate immune cells. These cells are characterized by their ability to rapidly produce type 2 cytokines. ILC2s are predominant resident ILCs and, thereby, have the ability to respond to signals from damaged tissues. ILC2s regulate the immune response, and ILC2-derived type 2 cytokines may exert protective roles against sepsis-induced lung injury. This focused review not only provides readers with new insights into the signaling mechanisms by which ILC2s modulate sepsis-induced lung inflammation, but also proposes ILC2 as a novel therapeutic target for sepsis-induced ALI.

Sepsis Induces Deregulation of IL-13 Production and PD-1 Expression in Lung Group 2 Innate Lymphoid Cells

ABSTRACT

Deregulation of the immune system in sepsis plays the central role in the pathogenesis of multiple organ failure including septic lung injury. Group 2 innate lymphoid cells (ILC2s) have emerged as a new player in regulating immune homeostasis in the lung; however, the role of ILC2s in lung injury in sepsis remains poorly understood. Here, we investigated temporal changes in stimulatory and inhibitory receptor expression and intracellular type 2 cytokine expression of ILC2s in the lung using a cecal ligation and puncture mouse sepsis model. We found that IL-13 production by ILC2s, which were predominately composed of the resident natural ILC2 subset rather than the migratory inflammatory ILC2 subset, was reduced in the lungs of sepsis mice on day 1 and gradually restored through day 7. Although the expression levels of ST2 and inducible T-cell costimulator (stimulatory receptors) were high, IL-13 production by ILC2s was reduced while showing high programmed cell death 1 (PD-1) (inhibitory receptor) expression. Furthermore, using IL-33 knockout mice, we have shown that IL-33 regulates the capacity of ILC2s to produce IL-13, possibly through the modulation of ST2 and PD-1 expression and signaling in the septic lung. To the best of our knowledge, this is the first report showing differential costimulatory/inhibitory receptor expression on ILC2s in a septic lung in the context of an IL-33/IL-13 pathway-mediated type 2 immune response in the progression and resolution of inflammation. Our present findings contribute to a better understanding of the underlying immunological mechanism of ILC2s and may fill the critical knowledge gap regarding immune homeostasis in the lung that hampers the development of new therapeutic strategies for sepsis-induced acute lung injury.

Current Sarcoidosis Models and the Importance of Focusing on the Granuloma

The inability to effectively model sarcoidosis in the laboratory or in animals continues to hinder the discovery and translation of new, targeted treatments. The granuloma is the signature pathological hallmark of sarcoidosis, yet there are significant knowledge gaps that exist with regard to how granulomas form. Significant progress toward improved therapeutic and prognostic strategies in sarcoidosis hinges on tractable experimental models that recapitulate the process of granuloma formation in sarcoidosis and allow for mechanistic insights into the molecular events involved. Through its inherent representation of the complex genetics underpinning immune cell dysregulation in sarcoidosis, a recently developed in vitro human granuloma model holds promise in providing detailed mechanistic insight into sarcoidosis–specific disease regulating pathways at play during early stages of granuloma formation. The purpose of this review is to critically evaluate current sarcoidosis models and assess their potential to progress the field toward the goal of improved therapies in this disease. We conclude with the potential integrated use of preclinical models to accelerate progress toward identifying and testing new drugs and drug combinations that can be rapidly brought to clinical trials.

Androgen-Influenced Polarization of Activin A-Producing Macrophages Accompanies Post-pyelonephritic Renal Scarring

Ascending bacterial pyelonephritis, a form of urinary tract infection (UTI) that can result in hospitalization, sepsis, and other complications, occurs in ~250,000 US patients annually; uropathogenic Escherichia coli (UPEC) cause a large majority of these infections. Although UTIs are primarily a disease of women, acute pyelonephritis in males is associated with increased mortality and morbidity, including renal scarring, and end-stage renal disease. Preclinical models of UTI have only recently allowed investigation of sex and sex-hormone effects on pathogenesis. We previously demonstrated that renal scarring after experimental UPEC pyelonephritis is augmented by androgen exposure; testosterone exposure increases both the severity of pyelonephritis and the degree of renal scarring in both male and female mice. Activin A is an important driver of scarring in non-infectious renal injury, as well as a mediator of macrophage polarization. In this work, we investigated how androgen exposure influences immune cell recruitment to the UPEC-infected kidney and how cell-specific activin A production affects post-pyelonephritic scar formation. Compared with vehicle-treated females, androgenized mice exhibited reduced bacterial clearance from the kidney, despite robust myeloid cell recruitment that continued to increase as infection progressed. Infected kidneys from androgenized mice harbored more alternatively activated (M2) macrophages than vehicle-treated mice, reflecting an earlier shift from a pro-inflammatory (M1) phenotype. Androgen exposure also led to a sharp increase in activin A-producing myeloid cells in the infected kidney, as well as decreased levels of follistatin (which normally antagonizes activin action). As a result, infection in androgenized mice featured prolonged polarization of macrophages toward a pro-fibrotic M2a phenotype, accompanied by an increase in M2a-associated cytokines. These data indicate that androgen enhancement of UTI severity and resulting scar formation is related to augmented local activin A production and corresponding promotion of M2a macrophage polarization.

Macrophage regulation of graft-vs-host disease

Hematopoietic stem cell transplantation has become a curative choice of many hematopoietic malignancy, but graft-vs-host disease (GVHD) has limited the survival quality and overall survival of hematopoietic stem cell transplantation. Understanding of the immune cells’ reaction in pathophysiology of GVHD has improved, but a review on the role of macrophages in GVHD is still absent. Studies have observed that macrophage infiltration is associated with GVHD occurrence and development. In this review, we summarize and analyze the role of macrophages in GVHD based on pathophysiology of acute and chronic GVHD, focusing on the macrophage recruitment and infiltration, macrophage polarization, macrophage secretion, and especially interaction of macrophages with other immune cells. We could conclude that macrophage recruitment and infiltration contribute to both acute and chronic GVHD. Based on distinguishing pathology of acute and chronic GVHD, macrophages tend to show a higher M1/M2 ratio in acute GVHD and a lower M1/M2 ratio in chronic GVHD. However, the influence of dominant cytokines in GVHD is controversial and inconsistent with macrophage polarization. In addition, interaction of macrophages with alloreactive T cells plays an important role in acute GVHD. Meanwhile, the interaction among macrophages, B cells, fibroblasts, and CD4+ T cells participates in chronic GVHD development.

Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Attenuate LPS-Induced ARDS by Modulating Macrophage Polarization Through Inhibiting Glycolysis in Macrophages

Macrophages play a key role in the development of sepsis-induced acute respiratory distress syndrome (ARDS). Recent evidence has proved that glycolysis plays an important role in regulating macrophage polarization through metabolic reprogramming. Bone marrow mesenchymal stem cells (BMSCs) can alleviate sepsis-induced lung injury and possess potent immunomodulatory and immunosuppressive properties via secreting exosomes. However, it is unknown whether BMSCs-derived exosomes exert their therapeutic effect against sepsis-induced lung injury by inhibiting glycolysis in macrophages. Therefore, the present study aimed to evaluate the anti-inflammatory effects of exosomes released from BMSCs on acute lung injury induced by lipopolysaccharide (LPS) in mice and explored the possible underlying mechanisms in vitro and in vivo. We found that BMSCs inhibited M1 polarization and promoted M2 polarization in MH-S cells (a murine alveolar macrophage cell line) by releasing exosomes. Further experiments showed that exosomes secreted by BMSCs modulated LPS-treated MH-S cells polarization by inhibiting cellular glycolysis. Moreover, our results showed that BMSCs-derived exosomes down-regulated the expression of several essential proteins of glycolysis via inhibition of hypoxia-inducible factor 1 (HIF-1)α. Finally, a model of LPS-induced ARDS in mice was established, we found that BMSCs-derived exosomes ameliorated the LPS-induced inflammation and lung pathological damage. Meanwhile, we found that intratracheal delivery of BMSCs-derived exosomes effectively down-regulated LPS-induced glycolysis in mice lung tissue. These findings reveal new mechanisms of BMSCs-derived exosomes in regulating macrophage polarization which may provide novel strategies for the prevention and treatment of LPS-induced ARDS.

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.

Interleukin-35 reduces inflammation in acute lung injury through inhibiting TLR4/NF-κB signaling pathways

Acute lung injury (ALI) in children is a complex disease that is accompanied by an inflammatory response. The pathogenesis of ALI in children is not yet well understood. Mice with ALI exhibit inflammation of the lungs and decreased expression of interleukin (IL)-35. To investigate whether the function of IL-35 affects lipopolysaccharide (LPS)-induced ALI, IL-35 was overexpressed in cells. Enzyme-linked immunosorbent assays indicated decreased levels of IL-6 and tumor necrosis factor-α in LPS-induced and agomir-IL-35-treated murine RAW264.7 macrophages. Finally, toll-like receptor 4 (TLR4)/NF-κB signaling pathways were analyzed. The expression of TLR4, NF-κB p65 and NF-κB p50 were decreased, as was the degradation of NF-κB inhibitor-α, in LPS-induced and agomir-IL-35-treated murine RAW264.7 macrophages. The results of the present study demonstrated that IL-35 may exhibit a protective role in ALI by modulating the TLR4/NF-κB signaling pathways.

HuoXueTongFu Formula Alleviates Intraperitoneal Adhesion by Regulating Macrophage Polarization and the SOCS/JAK2/STAT/PPAR-γ Signalling Pathway

Intraperitoneal adhesion is a common complication after abdominal surgery, which seriously affects the quality of life of patients. HuoXueTongFu Formula (HXTF) plays an important role in the prevention and treatment of intraperitoneal adhesions. However, the molecular-related mechanisms are still not fully known. In this study, the model of Intrapetitoneal adhesion was established by cecum abrasion and treated with HXTF for one week. RAW264.7 cells were given LPS, IFN-γ, IL-4, HXTF-medicated serum, and PPAR-γ agonist/antagonist, respectively. Histopathology, flow cytometry, ELISA, real-time PCR, and Western blotting were used to further detect the related protein, M1/M2 polarization tendency, and PPAR-γ nuclear translocation. The deposition of collagen fibres reduced in the local area of rats after the operation with HXTF treatment. Similar to IL-4, HXTF induced a tendency for macrophages to polarize toward M2 and promoted peroxisome proliferator-activated receptor-gamma (PPAR-γ) nuclear translocation. Furthermore, the use of HXTF and PPAR-γ agonists downregulated macrophage M1 polarization-related factors IL-1, IL-6, and TNF-alpha and upregulated M2 polarization-related factors IL-4, IL-10, and TGF-beta 1. Meanwhile, the use of HXTF and PPAR-γ agonists downregulated the SOCS3/JAK2/STAT1 pathway and activated the SOCS1/STAT6/PPAR-γ pathway. These results show that HXTF may reduce intraperitoneal adhesion by inducing macrophage M2 polarization and regulating the SOCS/JAK2/STAT/PPAR-γ pathway.

Targeting cell signaling in allergic asthma

Asthma is chronic inflammation of the airways characterized by airway hyper-responsiveness, wheezing, cough, and dyspnea. Asthma affects >350 million people worldwide. The Th2 immune response is a major contributor to the pathophysiology of asthma. Targeted therapy modulating cell signaling pathways can be a powerful strategy to design new drugs to treat asthma. The potential molecular pathways that can be targeted include IL-4-IL-13-JAK-STAT-MAP kinases, adiponectin-iNOS-NF-κB, PGD2-CRTH2, IFNs-RIG, Wnt/β-catenin-FAM13A, FOXC1-miR-PI3K/AKT, JNK-Gal-7, Nrf2-ROS, Foxp3-RORγt, CysLTR, AMP, Fas-FasL, PTHrP/PPARγ, PAI-1, FcɛRI-LAT-SLP-76, Tim-3-Gal-9, TLRs-MyD88, PAR2, and Keap1/Nrf2/ARE. Therapeutic drugs can be designed to target one or more of these pathways to treat asthma.

Tim-3 Regulates Tregs' Ability to Resolve the Inflammation and Proliferation of Acute Lung Injury by Modulating Macrophages Polarization

We recently reported that CD4CD25 regulatory T cells (Tregs) contributed to the recovery of patients with acute lung injury (ALI) by upregulating T cell immunoglobulin and mucin-domain containing-3 (Tim-3). However, the molecular mechanism by which Tim-3 regulates Tregs' function in the resolution and fibroproliferation after ALI remains unknown. In this study, we adoptively transferred Tim-3Tregs or Tim-3Tregs into lipopolysaccharide -induced ALI mice model. Data demonstrated that Tim-3Tregs not only decreased indices of lung inflammation and injury but also mitigated lung fibrosis after ALI. Furthermore, we observed that the transfer of Tim-3Tregs led to M2-like macrophage differentiation as demonstrated by significantly upregulated levels of M2-associated phenotypic markers as well as downregulated expressions of M1-related markers in both the profibrotic lung tissue and sorted pulmonary monocytes after ALI. In addition, cytokines such as interleukin (IL)-10 and IL-4 were also upregulated in lung tissues after Tim-3Tregs transferring. In vitro experiments further demonstrated that cell-contact cocultures with Tregs lacking Tim-3 presented decreased polarization of M2-like macrophages partially mediated by a decreased expression and function of STAT-3. Therefore, these data demonstrate a previously unrecognized function of Tim-3 on Tregs in their ability to repress the fibroproliferation of ALI by inducing alternative macrophages polarization. Moreover, the data highlight that Tim-3Tregs-mediated induction of M2-like macrophages may be a novel treatment modality with transitional potential.

Macrophage Polarization Favors Epithelial Repair During Acute Respiratory Distress Syndrome

OBJECTIVES

Alveolar macrophage polarization and role on alveolar repair during human acute respiratory distress syndrome remain unclear. This study aimed to determine during human acute respiratory distress syndrome: the alveolar macrophage polarization, the effect of alveolar environment on macrophage polarization, and the role of polarized macrophages on epithelial repair.

DESIGN

Experimental ex vivo and in vitro investigations.

SETTING

Four ICUs in three teaching hospitals.

PATIENTS

Thirty-three patients with early moderate-to-severe acute respiratory distress syndrome were enrolled for assessment of the polarization of alveolar macrophages.

INTERVENTIONS

Polarization of acute respiratory distress syndrome macrophages was studied by flow cytometry and quantitative polymerase chain reaction. Modulation of macrophage polarization was studied in vitro using phenotypic and functional readouts. Macrophage effect on repair was studied using alveolar epithelial cells in wound healing models.

MEASUREMENTS AND MAIN RESULTS

Ex vivo, alveolar macrophages from early acute respiratory distress syndrome patients exhibited anti-inflammatory characteristics with high CD163 expression and interleukin-10 production. Accordingly, early acute respiratory distress syndrome-bronchoalveolar lavage fluid drives an acute respiratory distress syndrome-specific anti-inflammatory macrophage polarization in vitro, close to that induced by recombinant interleukin-10. Culture supernatants from macrophages polarized in vitro with acute respiratory distress syndrome-bronchoalveolar lavage fluid or interleukin-10 and ex vivo acute respiratory distress syndrome alveolar macrophages specifically promoted lung epithelial repair. Inhibition of the hepatocyte growth factor pathway in epithelial cells and hepatocyte growth factor production in macrophages both reversed this effect. Finally, hepatocyte growth factor and soluble form of CD163 concentrations expressed relatively to macrophage count were higher in bronchoalveolar lavage fluid from acute respiratory distress syndrome survivors.

CONCLUSIONS

Early acute respiratory distress syndrome alveolar environment drives an anti-inflammatory macrophage polarization favoring epithelial repair through activation of the hepatocyte growth factor pathway. These results suggest that macrophage polarization may be an important step for epithelial repair and acute respiratory distress syndrome recovery.

Functional aspects, phenotypic heterogeneity, and tissue immune response of macrophages in infectious diseases

Macrophages are a functionally heterogeneous group of cells with specialized functions depending not only on their subgroup but also on the function of the organ or tissue in which the cells are located. The concept of macrophage phenotypic heterogeneity has been investigated since the 1980s, and more recent studies have identified a diverse spectrum of phenotypic subpopulations. Several types of macrophages play a central role in the response to infectious agents and, along with other components of the immune system, determine the clinical outcome of major infectious diseases. Here, we review the functions of various macrophage phenotypic subpopulations, the concept of macrophage polarization, and the influence of these cells on the evolution of infections. In addition, we emphasize their role in the immune response in vivo and in situ, as well as the molecular effectors and signaling mechanisms used by these cells. Furthermore, we highlight the mechanisms of immune evasion triggered by infectious agents to counter the actions of macrophages and their consequences. Our aim here is to provide an overview of the role of macrophages in the pathogenesis of critical transmissible diseases and discuss how elucidation of this relationship could enhance our understanding of the host-pathogen association in organ-specific immune responses.

Characteristics of circular RNA expression of pulmonary macrophages in mice with sepsis-induced acute lung injury

Circular RNAs (circRNAs) make up a large class of non-coding RNAs and play important roles in the pathology of a variety of diseases. However, their roles in pulmonary macrophage polarization after sepsisinduced lung injury is unknown. In this study, mice were divided into two groups: Sham control group and cecal ligation and puncture (CLP)-induced ALI group. Macrophages were isolated from lung homogenates 24 hours after SCLP/CLP. We started with RNA-seq of circRNA changes in macrophages and validated by RT-PCR in the following experiments. A total of 4318 circRNAs were detected in the two groups. Of these, 11 and 126 circRNAs were found to be significantly upregulated and downregulated, respectively, compared to the control (p≤0.05, Fold Change ≥2). Differentially expressed circRNAs with a high foldchange (fold-change >4, P<0.05) were selected for validation by qRT-PCR, 10 of which were verified. Furthermore, the most differentially expressed circRNAs within all the comparisons were annotated in detail with circRNA/miRNA interaction information using miRNA target prediction software. The network of circRNA-miRNA-mRNA was illustrated by cytoscape software. Gene ontology analyses indicated the upregulated circRNAs were involved in the multiple biological functions such as regulation of mitochondrion distribution and Notch binding, while the down-regulated circRNAs mainly involved in the biological process as histone H3K27 methylation. KEGG pathway analysis revealed TGF-beta signaling pathway was related to the upregulated circRNAs. The present study provides a novel insight into the roles of circRNAs in pulmonary macrophage differentiation and polarization post septic lung injury.

Macrophages: versatile players in renal inflammation and fibrosis

Macrophages have important roles in immune surveillance and in the maintenance of kidney homeostasis; their response to renal injury varies enormously depending on the nature and duration of the insult. Macrophages can adopt a variety of phenotypes: at one extreme, M1 pro-inflammatory cells contribute to infection clearance but can also promote renal injury; at the other extreme, M2 anti-inflammatory cells have a reparative phenotype and can contribute to the resolution phase of the response to injury. In addition, bone marrow monocytes can differentiate into myeloid-derived suppressor cells that can regulate T cell immunity in the kidney. However, macrophages can also promote renal fibrosis, a major driver of progression to end-stage renal disease, and the CD206⁺ subset of M2 macrophages is strongly associated with renal fibrosis in both human and experimental diseases. Myofibroblasts are important contributors to renal fibrosis and recent studies provide evidence that macrophages recruited from the bone marrow can transition directly into myofibroblasts within the injured kidney. This process is termed macrophage-to-myofibroblast transition (MMT) and is driven by transforming growth factor-β1 (TGFβ1)-Smad3 signalling via a Src-centric regulatory network. MMT may serve as a key checkpoint for the progression of chronic inflammation into pathogenic fibrosis.

Bone marrow derived M2 macrophages protected against lipopolysaccharide-induced acute lung injury through inhibiting oxidative stress and inflammation by modulating neutrophils and T lymphocytes responses

Acute lung injury (ALI) is characterized by aggravated inflammatory responses and the subsequent alveolar-capillary injury for which there are no specific therapies available currently. The present study was designed to investigate the protective roles of bone marrow derived M₂ macrophages (M₂ BMDMs) in lipopolysaccharide (LPS) induced ALI. M₂ BMDMs were obtained from bone marrow cells stimulated with M-CSF and IL-4. Mice received M₂ BMDMs intratracheally 3 h after LPS administration. Histology and wet/dry (W/D) weight ratio, activated immune cells and total protein were detected. Cytokines production were measured in vivo and vitro study. The effects of PD-L1 blockade on M₂ BMDMs were calculated. The results showed that M₂ BMDMs administration reduced the infiltration of neutrophils, inhibited the oxidative stress, while increased the counts of CD3⁺T lymphocytes as well as CD4⁺CD25⁺ regulatory T lymphocytes. Further, M₂ BMDMs suppressed the TNF-α, IL-1β and IL-6 production, while increased the IL-10 production. Blockade of PD-L1/PD-1 pathway reversed cytokines production of M₂ BMDMs in the BALF. These findings indicated that M₂ BMDMs might be a promising therapeutic strategy for LPS-induced ALI through inhibiting oxidative stress and inflammation by modulating neutrophils and T lymphocytes responses.

Hypothermic Machine Perfusion's Protection on Porcine Kidney Graft Uncovers Greater Akt-Erk Phosphorylation

BACKGROUND

To investigate the potential mechanisms of hypothermic machine perfusion (HMP)'s beneficial effects on kidney graft over static cold storage (SCS) in vitro.

METHODS

Ten kidneys of 5 Bama miniature male pigs were paired into 2 groups: SCS group and HMP group. Preservation solutions were taken at 0, 1, 3, and 6 hours for the measurement of K⁺, Na⁺, Cl^-, blood urea nitrogen (BUN), creatinine (Cr), and lactate dehydrogenase (LDH) using the standard laboratory methods. Renal cortex were harvested at 6 hours for the following measurement: lactic acid (LD), adenosine triphosphate (ATP), malondialdehyde (MDA), neutrophil accumulation (MPO), interleukin-10 (IL-10), and transforming growth factor-β (TGF-β). Ischemia-induced apoptosis and the protein expression levels of total Akt, phospho-Akt, total Erk, and phospho-Erk were analyzed by Western blotting.

RESULTS

Almost all of the tested metabolites in preservation solutions were reduced with time in the HMP group. Levels of Na⁺, Cl^-, BUN, Cr, K⁺, and LDH were lower in the HMP group compared with the SCS group, with differences in the first 4 reaching statistical significance. HMP alleviated ATP degradation and LD accumulation, diminished the MDA (P < .05) and MPO (P = .227) levels, and greatly raised IL-10 and TGF-β (P < .05) expression. A marked decrease of proapoptotic and a large increase of antiapoptotic markers (P < .05) along with greatly raised Akt (P < .05) and Erk (P < .01) phosphorylation was observed in the kidney of the HMP group compared with the SCS group.

CONCLUSION

HMP's kidney graft protection involves inhibition of accumulation of toxic metabolites, oxidative damage, and apoptosis along with upregulation of the Akt and Erk signaling pathway.