Macrophage heterogeneity in respiratory diseases

Phytochemical determination and mechanistic investigation of Polygala tenuifolia root (Yuanzhi) extract for bronchitis: UPLC-MS/MS analysis, network pharmacology and in vitro/in vivo evaluation

ETHNOPHARMACOLOGICAL RELEVANCE

Bronchitis is a respiratory disease characterized by a productive cough. Polygala tenuifolia Willd., commonly known as Yuan zhi, is a traditional Chinese herbal medicine used for relieving cough and removing phlegm. Despite its historical use, studies are lacking on the effectiveness of P. tenuifolia in treating bronchitis. Furthermore, the molecular mechanisms underlying the action of its bioactive compounds remain unknown.

AIM OF THE STUDY

This study aims to identify the main bioactive compounds responsible for the effects of P. tenuifolia liquid extract (PLE) in treating bronchitis and to elucidate the associated molecular mechanisms.

MATERIALS AND METHODS

The main chemical compounds in PLE were identified and determined using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The antitussive, expectorant and anti-inflammatory activities of PLE were evaluated in an ammonia-induced mouse cough model, a tracheal phenol red excretion mouse model, and a xylene-induced ear swelling mouse model, respectively. A network pharmacology analysis was conducted to investigate the associated gene targets, gene ontology, and KEGG pathways related to the main bioactives in PLE targeting bronchitis. PLE and its five bioactive compounds were assessed for their potential anti-inflammatory activities in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Western blot analysis was conducted to elucidate the associated molecular mechanisms.

RESULTS

Thirty-seven compounds in PLE were identified, and twelve main compounds were further quantified in PLE using UPLC-MS/MS. PLE oral gavage administrations (0.6 and 0.12 mg/kg) for 7 days markedly reduced cough frequency, prolonged latency period of cough, reduced phlegm and inflammation in mice. The network pharmacology analysis identified 57 gene targets of PLE against bronchitis. The PI3K/AKT and MAPK signalling pathways were the top two modulated pathways. In RAW264.7 cells, PLE (12.5-50 μg/mL) significantly reduced cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α. PLE downregulated LPS-elevated protein targets in both PI3K/AKT and MAPK signaling pathways. In PLE, tenuifolin, polygalaxanthone ⅠⅠⅠ, polygalasaponin ⅩⅩⅤⅢ, tenuifoliside B, and 3,6'-Disinapoyl sucrose, were identified as the top five core components responsible for treating bronchitis. These compounds were also found to modulate the protein targets in the PI3K/AKT and MAPK signalling pathways.

CONCLUSIONS

This study demonstrated the potential therapeutic effects of PLE on bronchitis by reducing cough, phlegm and inflammation. The anti-inflammatory action and molecular mechanisms of the 5 main bioactive compounds in PLE were partly validated through the in vitro assays. The findings provide valuable insights into the mechanisms underlying the traditional use of PLE for bronchitis.

CKD-497 inhibits NF-kB signaling and ameliorates inflammation and pulmonary fibrosis in ovalbumin-induced asthma and particulate matter-induced airway inflammatory diseases

Introduction: Air pollution, allergens, and bacterial infections are major contributors to pathological respiratory disorders worldwide. CKD-497, derived from the rhizome of Atractylodes japonica and the fruits of Schisandra chinensis, is known for its ability to relieve cough and facilitate phlegm expectoration. However, its protective action against allergic asthma and fine dust-induced lung inflammation, along with its underlying mechanisms, have not been thoroughly investigated. Methods: In this study, we established mouse models of ovalbumin (OVA)-induced asthma and particulate matter (PM)-induced pulmonary inflammation to evaluate the effects of CKD-497. Mice were administered CKD-497 orally, and various parameters such as airway inflammation, mucus production, and proinflammatory cytokine levels (IL-1β, IL-6, TNF-α) were measured. Additionally, the macrophage cell line RAW264.7 was pretreated with CKD-497 and stimulated with lipopolysaccharide (LPS) to assess inflammation via the NF-kB signaling pathway. Results: Oral administration of CKD-497 effectively attenuated airway inflammation and mucus production in both OVA-induced asthma and PM-induced lung inflammation models. It also significantly decreased the production of proinflammatory cytokines IL-1β, IL-6, and TNF-α. CKD-497 alleviated leukocyte infiltration, including neutrophils, and reduced fibrillary collagen deposition in PM10-treated mice. In vitro, CKD-497 pretreatment inhibited LPS-induced inflammation in RAW264.7 cells through the suppression of the NF-kB signaling pathway. Discussion: CKD-497 shows potent anti-inflammatory effects in mouse models of asthma and PM-induced lung inflammation, potentially mediated by the inhibition of the NF-kB pathway. These findings suggest that CKD-497 could serve as a functional supplement to protect against respiratory diseases by mitigating pulmonary and airway inflammation induced by allergens and air pollution.

The human MIF polymorphism CATT7 enhances pro-inflammatory macrophage polarization in a clinically relevant model of allergic airway inflammation

High level expression of the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) has been associated with severe asthma. The role of MIF and its functional promotor polymorphism in innate immune training is currently unknown. Using novel humanized CATT7 MIF mice, this study is the first to investigate the effect of MIF on bone marrow-derived macrophage (BMDM) memory after house dust mite (HDM) challenge. CATT7 BMDMs demonstrated a significant primed increase in M1 markers following HDM and LPS stimulation, compared to naive mice. This M1 signature was found to be MIF-dependent, as administration of a small molecule MIF inhibitor, SCD-19, blocked the induction of this pro-inflammatory M1-like phenotype in BMDMs from CATT7 mice challenged with HDM. Training naive BMDMs in vitro with HDM for 24 h followed by a rest period and subsequent stimulation with LPS led to significantly increased production of the pro-inflammatory cytokine TNFα in BMDMs from CATT7 mice but not WT mice. Addition of the pan methyltransferase inhibitor MTA before HDM training significantly abrogated this effect in BMDMs from CATT7 mice, suggesting that HDM-induced training is associated with epigenetic remodelling. These findings suggest that trained immunity induced by HDM is under genetic control, playing an important role in asthma patients with the high MIF genotypes (CATT6/7/8).

Effects of lysine deacetylase inhibitor treatment on LPS responses of alveolar-like macrophages

Macrophages are key immune cells that can adapt their metabolic phenotype in response to different stimuli. Lysine deacetylases are important enzymes regulating inflammatory gene expression and lysine deacetylase inhibitors have been shown to exert anti-inflammatory effects in models of chronic obstructive pulmonary disease. We hypothesized that these anti-inflammatory effects may be associated with metabolic changes in macrophages. To validate this hypothesis, we used an unbiased and a targeted proteomic approach to investigate metabolic enzymes, as well as liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry, to quantify metabolites in combination with the measurement of functional parameters in primary murine alveolar-like macrophages after lipopolysaccharide-induced activation in the presence or absence of lysine deacetylase inhibition. We found that lysine deacetylase inhibition resulted in reduced production of inflammatory mediators such as tumor necrosis factor α and interleukin 1β. However, only minor changes in macrophage metabolism were observed, as only one of the lysine deacetylase inhibitors slightly increased mitochondrial respiration while no changes in metabolite levels were seen. However, lysine deacetylase inhibition specifically enhanced expression of proteins involved in ubiquitination, which may be a driver of the anti-inflammatory effects of lysine deacetylase inhibitors. Our data illustrate that a multiomics approach provides novel insights into how macrophages interact with cues from their environment. More detailed studies investigating ubiquitination as a potential driver of lysine deacetylase inhibition will help developing novel anti-inflammatory drugs for difficult-to-treat diseases such as chronic obstructive pulmonary disease.

Oral Administration of Sargassum horneri Suppresses Particulate Matter-Induced Oxidative DNA Damage in Alveolar Macrophages of Allergic Airway Inflammation: Relevance to PM-Mediated M1/M2 AM Polarization

SCOPE

Particulate matter (PM) can cause cellular oxidative damage and promote respiratory diseases. It has recently shown that Sargassum horneri ethanol extract (SHE) containing sterols and gallic acid reduces PM-induced oxidative stress in mice lung cells through ROS scavenging and metal chelating. In this study, the role of alveolar macrophages (AMs) is identified that are particularly susceptible to DNA damage due to PM-triggered oxidative stress in lungs of OVA-sensitized mice exposed to PM.

METHODS AND RESULTS

The study scrutinizes if PM exposure causes oxidative DNA damage to AMs differentially depending on their type of polarization. Further, SHE's potential is investigated in reducing oxidative DNA damage in polarized AMs and restoring AM polarization in PM-induced allergic airway inflammation. The study discovers that PM triggers prolonged oxidative stress to AMs, leading to lipid peroxidation in them and alveolar epithelial cells. Particularly, AMs are polarized to M2 phenotype (F4/80+ CD206+ ) with enhanced oxidative DNA damage when subject to PM-induced oxidative stress. However, SHE repairs oxidative DNA damage in M1- and M2-polarized AMs and reduces AMs polarization imbalance due to PM exposure.

CONCLUSION

These results suggest the possibility of SHE as beneficial foods against PM-induced allergic airway inflammation via suppression of AM dysfunction.

NOTCH4 potentiates the IL-13 induced genetic program in M2 alternative macrophages through the AP1 and IRF4-JMJD3 axis

IL-13 signaling polarizes macrophages to an M2 alternatively activated phenotype, which regulates tissue repair and anti-inflammatory responses. However, an excessive activation of this pathway leads to severe pathologies, such as allergic airway inflammation and asthma. In this work, we identified NOTCH4 receptor as an important modulator of M2 macrophage activation. We show that the expression of NOTCH4 is induced by IL-13, mediated by Janus kinases and AP1 activity, probably mediated by the IL-13Rα1 and IL-13Rα2 signaling pathway. Furthermore, we demonstrate an important role for NOTCH4 signaling in the IL-13 induced gene expression program in macrophages, including various genes that contribute to pathogenesis of the airways in asthma, such as ARG1, YM1, CCL24, IL-10, or CD-163. We also demonstrate that NOTCH4 signaling modulates IL-13-induced gene expression by increasing IRF4 activity, mediated, at least in part, by the expression of the histone H3K27me3 demethylase JMJD3, and by increasing AP1-dependent transcription. In summary, our results provide evidence for an important role of NOTCH4 signaling in alternative activation of macrophages by IL-13 and suggest that NOTCH4 may contribute to the increased severity of lesions in M2 inflammatory responses, such as allergic asthma, which points to NOTCH4 as a potential new target for the treatment of these pathologies.

Chemical exposure and alveolar macrophages responses: 'the role of pulmonary defense mechanism in inhalation injuries'

Epidemiological and clinical studies have indicated an association between particulate matter (PM) exposure and acute and chronic pulmonary inflammation, which may be registered as increased mortality and morbidity. Despite the increasing evidence, the pathophysiology mechanism of these PMs is still not fully characterised. Pulmonary alveolar macrophages (PAMs), as a predominant cell in the lung, play a critically important role in these pathological mechanisms. Toxin exposure triggers events associated with macrophage activation, including oxidative stress, acute damage, tissue disruption, remodelling and fibrosis. Targeting macrophage may potentially be employed to treat these types of lung inflammation without affecting the natural immune response to bacterial infections. Biological toxins, their sources of exposure, physical and other properties, and their effects on the individuals are summarised in this article. Inhaled particulates from air pollution and toxic gases containing chemicals can interact with alveolar epithelial cells and immune cells in the airways. PAMs can sense ambient pollutants and be stimulated, triggering cellular signalling pathways. These cells are highly adaptable and can change their function and phenotype in response to inhaled agents. PAMs also have the ability to polarise and undergo plasticity in response to tissue damage, while maintaining resistance to exposure to inhaled agents.

Identification and Characterization of Alveolar and Recruited Lung Macrophages during Acute Lung Inflammation

To precisely identify mouse resident alveolar macrophages (AMs) and bone marrow (BM)-derived macrophages, we developed a technique to separately label AMs and BM-derived macrophages with a fluorescent lipophilic dye followed by FACS. We showed that this technique overcomes issues in cell identification related to dynamic shifts in cell surface markers that occurs during lung inflammation. We then used this approach to track macrophage subsets at different time points after intratracheal (i.t.) instillation of Escherichia coli LPS. By isolating BM-derived macrophages and AMs, we demonstrated that BM-derived macrophages were enriched in expression of genes in signal transduction and immune system activation pathways whereas resident AMs were enriched in cellular processes, such as lysosome/phagosome pathways, efferocytosis, and metabolic pathways related to fatty acids and peroxisomes. Taken together, these data indicate that more accurate identification of macrophage origin can result in improved understanding of differential phenotypes and functions between AMs and BM-derived macrophages in the lungs.

Caspase Inhibition Modulates Monocyte-Derived Macrophage Polarization in Damaged Tissues

Circulating monocytes are recruited in damaged tissues to generate macrophages that modulate disease progression. Colony-stimulating factor-1 (CSF-1) promotes the generation of monocyte-derived macrophages, which involves caspase activation. Here, we demonstrate that activated caspase-3 and caspase-7 are located to the vicinity of the mitochondria in CSF1-treated human monocytes. Active caspase-7 cleaves p47^PHOX at aspartate 34, which promotes the formation of the NADPH (nicotinamide adenine dinucleotide phosphate) oxidase complex NOX2 and the production of cytosolic superoxide anions. Monocyte response to CSF-1 is altered in patients with a chronic granulomatous disease, which are constitutively defective in NOX2. Both caspase-7 down-regulation and radical oxygen species scavenging decrease the migration of CSF-1-induced macrophages. Inhibition or deletion of caspases prevents the development of lung fibrosis in mice exposed to bleomycin. Altogether, a non-conventional pathway that involves caspases and activates NOX2 is involved in CSF1-driven monocyte differentiation and could be therapeutically targeted to modulate macrophage polarization in damaged tissues.

Curcumin Ameliorates Particulate Matter-Induced Pulmonary Injury through Bimodal Regulation of Macrophage Inflammation via NF-κB and Nrf2

The direct effects of particulate matter (PM) on lung injury and its specific molecular mechanisms are unclear. However, experimental evidence has shown that oxidative stress-mediated inflammation in macrophages is the main pathological outcome of PM exposure. Curcumin has been reported to protect organs against the disturbance of homeostasis caused by various toxic agents through anti-inflammatory and antioxidative effects. However, the protective action of curcumin against PM-induced pulmonary inflammation and the underlying mechanism have not been thoroughly investigated. In this study, we established a PM-induced pulmonary inflammation mouse model using the intratracheal instillation method to investigate the protective ability of curcumin against PM-induced pulmonary inflammation. Compared to the mice treated with PM only, the curcumin-treated mice showed alleviated alveolar damage, decreased immune cell infiltration, and reduced proinflammatory cytokine production in both lung tissue and BALF. To evaluate the underlying mechanism, the mouse macrophage cell line RAW264.7 was used. Pretreatment with curcumin prevented the production of PM-induced proinflammatory cytokines by deactivating NF-κB through the suppression of MAPK signaling pathways. Furthermore, curcumin appears to attenuate PM-induced oxidative stress through the activation of Nrf2 and downstream antioxidant signaling. Our findings demonstrate that curcumin protects against PM-induced lung injury by suppressing oxidative stress and inflammatory activation in macrophages.

The impact of the PCSK-9/VLDL-Receptor axis on inflammatory cell polarization

BACKGROUND

Studies have shown that lipoproteins, such as LDL and VLDL, as well as its major protein component ApoE2 impact on macrophage polarization important in atherosclerosis. Proprotein convertase subtilisin/kexin 9 (PCSK9) is a key regulator of lipoprotein receptor expression. The present study investigated the effect of the VLDL/VLDL-receptor (VLDL-R) axis on mononuclear cell polarization, as well as the role of PCSK9 and PCSK9 inhibitors (PCSK9i) within this network.

METHODS

Human monocytic THP-1 cells and human monocyte-derived macrophages isolated from peripheral blood mononuclear cells (PBMC) were treated with either LPS/IFN-γ to induce a pro-inflammatory phenotype, or with IL-4/IL-13 to induce an anti-inflammatory phenotype. Cells were then subjected to further treatments by lipoproteins, PCSK9, PCSK9i and lipoprotein receptor blockers.

RESULTS

LPS/IFN-γ treatment promoted a pro-inflammatory state with an increased expression of pro-inflammatory mediators such as TNF-α, CD80 and IL-1β. VLDL co-treatment induced a switch of this pro-inflammatory phenotype to an anti-inflammatory phenotype. In pro-inflammatory cells, VLDL significantly decreased the expression of pro-inflammatory markers e.g., TNF-α, CD80, and IL-1β. These effects were eliminated by PCSK9 and restored by co-incubation with a specific anti-PCSK9 monoclonal antibody (PCSK9i). Migration assays demonstrated that pro-inflammatory cells displayed a significantly higher invasive capacity when compared to untreated cells or anti-inflammatory cells. Moreover, pro-inflammatory cell chemotaxis was significantly decreased by VLDL-mediated acquisition of the anti-inflammatory phenotype. PCSK9 significantly lessened this VLDL-mediated migration inhibition, which was reversed by the PCSK9i.

CONCLUSION

VLDL promotes mononuclear cell differentiation towards an anti-inflammatory phenotype. PCSK9, via its capacity to inhibit VLDL-R expression, reverses the VLDL-mediated anti-inflammatory action, thereby promoting a pro-inflammatory phenotype. Thus, PCSK9 targeting therapies may exert anti-inflammatory properties within the vessel wall.

Explaining the polarized macrophage pool during murine allergic lung inflammation

Introduction

Differentially polarized macrophages, especially YM1+ and MHCII+ macrophages, play an important role in asthma development. The origin of these polarized macrophages has not been elucidated yet. We therefore aimed to investigate how proliferation, monocyte recruitment, and/or switching of polarization states contribute to this specific pool of polarized interstitial and alveolar macrophages during development of house dust mite (HDM)-induced allergic lung inflammation in mice.

Methods

Male and female mice were first treated intranasally with PKH26 to label lung-resident macrophages and were then exposed to either HDM or phosphate-buffered saline (PBS) for two weeks. Different myeloid immune cell types were quantified in lung tissue and blood using flow cytometry.

Results

We found that macrophage polarization only starts up in the second week of HDM exposures. Before this happened, unpolarized alveolar and interstitial macrophages transiently increased in HDM-exposed mice. This transient increase was mostly local proliferation of alveolar macrophages, while interstitial macrophages also contained unlabeled macrophages suggesting monocyte contribution. After two weeks of exposures, the number of interstitial and alveolar macrophages was similar between HDM and PBS-exposed mice, but the distribution of polarization states was remarkably different. HDM-exposed mice selectively developed YM1+ alveolar macrophages and MHCII-hi interstitial macrophages while nonpolarized macrophages were lost compared to PBS-exposed mice.

Discussion

In this HDM model we have shown that development of a polarized macrophage pool during allergic inflammation is first dependent on proliferation of nonpolarized tissue-resident macrophages with some help of infiltrating unlabeled cells, presumably circulating monocytes. These nonpolarized macrophages then acquire their polarized phenotype by upregulating YM1 on alveolar macrophages and MHCII on interstitial macrophages. This novel information will help us to better understand the role of macrophages in asthma and designing therapeutic strategies targeting macrophage functions.

Detection of Radiolabeled Inflammatory Cell Macrophage Subpopulations in Chronic Respiratory Diseases: Results from Preliminary Analyses

Chronic respiratory diseases (CRDs) like asthma and chronic obstructive pulmonary disease (COPD) are the leading causes of morbidity and mortality worldwide. Alveolar macrophages (AM) are immune cells that exist in different polarization states/phenotypes and have been shown to play a critical role during an inflammatory process. In this paper, differently polarized mouse bone marrow-derived macrophages (BMDM (M1-proinflammatory or M2-immunomodulator)) were radiolabeled with either 99mTc-D,L-hexamethylene-propyleneamine oxime (^99mTc-HMPAO), 2-deoxy-2-[18F] fluoro-D-glucose (¹⁸F-FDG), or ⁶⁷Ga-citrate. Biocompatibility and in vivo biodistribution of radionuclide-labeled macrophages after intravenous injection were evaluated. Radioactivity measurements were performed using Packard Cobra Quantum 5002 Gamma Counter. Both M1 and M2 macrophages showed a higher uptake for ¹⁸F-FDG and ^99mTc-HMPAO, than ⁶⁷Ga-citrate. M2 macrophages showed a higher uptake of radionuclides than M1 macrophages. The used radionuclides were biocompatible for both M1 and M2 macrophages. At 2-hour postinjection, ¹⁸F-FDG-labeled M1 and M2 macrophages were found significantly higher in the lung of inflammatory animals (12.54 ± 1.58% and 14.13 ± 1.03%, respectively) than in control mice. Labeling macrophages with either ¹⁸F-FDG or ^99mTc-HMPAO did not affect their biodistribution. The results from these initial experiments indicate that radionuclide-labeled macrophages may allow a higher sensitivity detection in nuclear imaging techniques such as PET and SPECT. Further confirmatory studies are needed to noninvasively image radiolabeled BMDM to understand their role in the inflammatory processes inherent to CRDs.

The Emerging Role of Macrophages in Chronic Obstructive Pulmonary Disease: The Potential Impact of Oxidative Stress and Extracellular Vesicle on Macrophage Polarization and Function

Chronic obstructive pulmonary disease (COPD) is one of the most common airway diseases, and it is considered a major global health problem. Macrophages are the most representative immune cells in the respiratory tract, given their role in surveying airways, removing cellular debris, immune surveillance, and resolving inflammation. Macrophages exert their functions by adopting phenotypical changes based on the stimuli they receive from the surrounding tissue. This plasticity is described as M1/M2 macrophage polarization, which consists of a strictly coordinated process leading to a difference in the expression of surface markers, the production of specific factors, and the execution of biological activities. This review focuses on the role played by macrophages in COPD and their implication in inflammatory and oxidative stress processes. Particular attention is on macrophage polarization, given macrophage plasticity is a key feature in COPD. We also discuss the regulatory influence of extracellular vesicles (EVs) in cell-to-cell communications. EV composition and cargo may influence many COPD-related aspects, including inflammation, tissue remodeling, and macrophage dysfunctions. These findings could be useful for better addressing the role of macrophages in the complex pathogenesis and outcomes of COPD.

Effect of Acinetobacter lwoffii on the modulation of macrophage activation and asthmatic inflammation

BACKGROUND

Although lung macrophages are directly exposed to external stimuli, their exact immunologic roles in asthma are still largely unknown. The aim of this study was to investigate the anti-asthmatic effect of Acinetobacter lwoffii in terms of lung macrophage modulation.

METHODS

Six-week-old female BALB/c mice were sensitized and challenged with ovalbumin (OVA) with or without intranasal administration of A. lwoffii during the sensitization period. Airway hyperresponsiveness and inflammation were evaluated. Using flow cytometry, macrophages were subclassified according to their activation status. In the in vitro study, a murine alveolar macrophage cell line (MH-S) treated with or without A. lwoffii before IL-13 stimulation were analysed by quantitative RT-PCR.

RESULTS

In a murine asthma model, the number of inflammatory cells, including macrophages and eosinophils, decreased in mice treated with A. lwoffii (A. lwoffii/OVA group) compared with untreated mice (OVA group). The enhanced expression of MHCII in macrophages in the OVA group was decreased by A. lwoffii treatment. M2 macrophage subtypes were significantly altered. A. lwoffii treatment decreased CD11b⁺ M2a and CD11b⁺ M2c macrophages, which showed strong positive correlations with Th2 cells, ILC2 and eosinophils. In contrast, CD11b⁺ M2b macrophages were significantly increased by A. lwoffii treatment and showed strong positive correlations with ILC1 and ILC3. In vitro, A. lwoffii down-regulated the expression of M2 markers related but up-regulated those related to M2b macrophages.

CONCLUSIONS AND CLINICAL RELEVANCE

Intranasal A. lwoffii exposure suppresses asthma development by suppressing the type 2 response via modulating lung macrophage activation, shifting M2a and M2c macrophages to M2b macrophages.

Carbon Monoxide Regulates Macrophage Differentiation and Polarization toward the M2 Phenotype through Upregulation of Heme Oxygenase 1

Carbon monoxide (CO) is generated by heme oxygenase (HO), and HO-1 is highly induced in monocytes and macrophages upon stimulation. Monocytes differentiate into macrophages, including pro-inflammatory (M1) and anti-inflammatory (M2) cells, in response to environmental signals. The present study investigated whether CO modulates macrophage differentiation and polarization, by applying the CO-releasing molecule-3 (CORM-3). Results showed that murine bone marrow cells are differentiated into macrophages by CORM-3 in the presence of macrophage colony-stimulating factor. CORM-3 increases expressions of macrophage markers, including F4/80 and CD11b, and alters the cell morphology into elongated spindle-shaped cells, which is a typical morphology of M2 cells. CORM-3 upregulates the expressions of genes and molecules involved in M2 polarization and M2 phenotype markers, such as STAT6, PPARγ, Ym1, Fizz1, arginase-1, and IL-10. However, exposure to CORM-3 inhibits the iNOS expression, suggesting that CO enhances macrophage differentiation and polarization toward M2. Increased HO-1 expression is observed in differentiated macrophages, and CORM-3 further increases this expression. Hemin, an HO-1 inducer, results in increased macrophage differentiation, whereas the HO-1 inhibitor zinc protoporphyrin IX inhibits differentiation. In addition, CORM-3 increases the proportion of macrophages in peritoneal exudate cells and enhances the expression of HO-1 and arginase-1 but inhibits iNOS. Taken together, these results suggest that the abundantly produced CO in activated macrophages enhances proliferation, differentiation, and polarization toward M2. It will probably help clear apoptotic cells, resolve inflammation, and promote wound healing and tissue remodeling.

Meta-Inflammation and Metabolic Reprogramming of Macrophages in Diabetes and Obesity: The Importance of Metabolites

Diabetes mellitus type II and obesity are two important causes of death in modern society. They are characterized by low-grade chronic inflammation and metabolic dysfunction (meta-inflammation), which is observed in all tissues involved in energy homeostasis. A substantial body of evidence has established an important role for macrophages in these tissues during the development of diabetes mellitus type II and obesity. Macrophages can activate into specialized subsets by cues from their microenvironment to handle a variety of tasks. Many different subsets have been described and in diabetes/obesity literature two main classifications are widely used that are also defined by differential metabolic reprogramming taking place to fuel their main functions. Classically activated, pro-inflammatory macrophages (often referred to as M1) favor glycolysis, produce lactate instead of metabolizing pyruvate to acetyl-CoA, and have a tricarboxylic acid cycle that is interrupted at two points. Alternatively activated macrophages (often referred to as M2) mainly use beta-oxidation of fatty acids and oxidative phosphorylation to create energy-rich molecules such as ATP and are involved in tissue repair and downregulation of inflammation. Since diabetes type II and obesity are characterized by metabolic alterations at the organism level, these alterations may also induce changes in macrophage metabolism resulting in unique macrophage activation patterns in diabetes and obesity. This review describes the interactions between metabolic reprogramming of macrophages and conditions of metabolic dysfunction like diabetes and obesity. We also focus on different possibilities of measuring a range of metabolites intra-and extracellularly in a precise and comprehensive manner to better identify the subsets of polarized macrophages that are unique to diabetes and obesity. Advantages and disadvantages of the currently most widely used metabolite analysis approaches are highlighted. We further describe how their combined use may serve to provide a comprehensive overview of the metabolic changes that take place intracellularly during macrophage activation in conditions like diabetes and obesity.

Epigenetic reprogramming of airway macrophages promotes polarization and inflammation in muco-obstructive lung disease

Lung diseases, such as cystic fibrosis and COPD, are characterized by mucus obstruction and chronic airway inflammation, but their mechanistic link remains poorly understood. Here, we focus on the function of the mucostatic airway microenvironment on epigenetic reprogramming of airway macrophages (AM) and resulting transcriptomic and phenotypical changes. Using a mouse model of muco-obstructive lung disease (Scnn1b-transgenic), we identify epigenetically controlled, differentially regulated pathways and transcription factors involved in inflammatory responses and macrophage polarization. Functionally, AMs from Scnn1b-transgenic mice have reduced efferocytosis and phagocytosis, and excessive inflammatory responses upon lipopolysaccharide challenge, mediated through enhanced Irf1 function and expression. Ex vivo stimulation of wild-type AMs with native mucus impairs efferocytosis and phagocytosis capacities. In addition, mucus induces gene expression changes, comparable with those observed in AMs from Scnn1b-transgenic mice. Our data show that mucostasis induces epigenetic reprogramming of AMs, leading to changes favoring tissue damage and disease progression. Targeting these altered AMs may support therapeutic approaches in patients with muco-obstructive lung diseases.

Macrophage exosomes transfer angiotensin II type 1 receptor to lung fibroblasts mediating bleomycin-induced pulmonary fibrosis

BACKGROUND

Macrophages are involved in the pathogenesis of idiopathic pulmonary fibrosis, partially by activating lung fibroblasts. However, how macrophages communicate with lung fibroblasts is largely unexplored. Exosomes can mediate intercellular communication, whereas its role in lung fibrogenesis is unclear. Here we aim to investigate whether exosomes can mediate the crosstalk between macrophages and lung fibroblasts and subsequently induce fibrosis.

METHODS

In vivo, bleomycin (BLM)-induced lung fibrosis model was established and macrophages infiltration was examined. The effects of GW4869, an exosomes inhibitor, on lung fibrosis were assessed. Moreover, macrophage exosomes were injected into mice to observe its pro-fibrotic effects. In vitro, exosomes derived from angiotensin II (Ang II)-stimulated macrophages were collected. Then, lung fibroblasts were treated with the exosomes. Twenty-four hours later, protein levels of α-collagen I, angiotensin II type 1 receptor (AT1R), transforming growth factor-β (TGF-β), and phospho-Smad2/3 (p-Smad2/3) in lung fibroblasts were examined. The Student's t test or analysis of variance were used for statistical analysis.

RESULTS

In vivo, BLM-treated mice showed enhanced infiltration of macrophages, increased fibrotic alterations, and higher levels of Ang II and AT1R. GW4869 attenuated BLM-induced pulmonary fibrosis. Mice with exosomes injection showed fibrotic features with higher levels of Ang II and AT1R, which was reversed by irbesartan. In vitro, we found that macrophages secreted a great number of exosomes. The exosomes were taken by fibroblasts and resulted in higher levels of AT1R (0.22 ± 0.02 vs. 0.07 ± 0.02, t = 8.66, P = 0.001), TGF-β (0.54 ± 0.05 vs. 0.09 ± 0.06, t = 10.00, P < 0.001), p-Smad2/3 (0.58 ± 0.06 vs. 0.07 ± 0.03, t = 12.86, P < 0.001) and α-collagen I (0.27 ± 0.02 vs. 0.16 ± 0.01, t = 7.01, P = 0.002), and increased Ang II secretion (62.27 ± 7.32 vs. 9.56 ± 1.68, t = 12.16, P < 0.001). Interestingly, Ang II increased the number of macrophage exosomes, and the protein levels of Alix (1.45 ± 0.15 vs. 1.00 ± 0.10, t = 4.32, P = 0.012), AT1R (4.05 ± 0.64 vs. 1.00 ± 0.09, t = 8.17, P = 0.001), and glyceraldehyde-3-phosphate dehydrogenase (2.13 ± 0.36 vs. 1.00 ± 0.10, t = 5.28, P = 0.006) were increased in exosomes secreted by the same number of macrophages, indicating a positive loop between Ang II and exosomes production.

CONCLUSIONS

Exosomes mediate intercellular communication between macrophages and fibroblasts plays an important role in BLM-induced pulmonary fibrosis.

Anti-F4/80 treatment attenuates Th2 cell responses: Implications for the role of lung interstitial macrophages in the asthmatic mice

Lung interstitial macrophages (IMs) can be polarized towards an alternative activation phenotype in ovalbumin (OVA)-induced asthmatic mice. However, the role of alternative activation of lung IMs in Th2 cell responses in the asthmatic murine is still unclear. Here, we leverage an anti-F4/80 treatment which has been shown to selectively deplete IMs in mice and investigate how this treatment modulates Th2 cell responses in lung and whether the modulation is dependent on lung IMs in murine models of asthma. We show that anti-F4/80 treatment alleviates Th2 cell responses in mice immunized and challenged with OVA or house dust mite (HDM). The anti-F4/80 treatment does not target lung alveolar macrophages (AMs) in OVA-induced asthmatic mice or impact the abundance of other immune cell types, including B cells, T cells, and NK cells in wild-type mice. However, this treatment does inhibit the expression of polarized markers of alternatively activated macrophages, including arginase-1, Ym-1, and Fizz-1 in the lung tissues from OVA-induced asthmatic mice. Furthermore, we find that the inhibitory effects of anti-F4/80 treatment on Th2 cell responses can be reversed upon adoptive transfer of lung IMs. Taken together, our data show that anti-F4/80 treatment attenuates Th2 cell responses, which is at least partially related to depletion of lung IMs in murine models of asthma. This suggests that targeted lung IMs may provide a potential therapeutic protocol for the treatment of asthmatics.

Tranglutaminase 2 contributes to the asthmatic inflammation by modulating activation of alveolar macrophages

BACKGROUND

Transglutaminase 2 (TG2), a multifunctional calcium-dependent acyltransferase, is upregulated in asthmatic airways and reported to play a role in the pathogenesis of allergic asthma. However, the underlying mechanism is not fully understood.

OBJECTIVE

To investigate the role of TG2 in alternative activation of alveolar macrophages by using murine asthma model.

METHODS

TG2 expression was assessed in induced sputum of 21 asthma patients and 19 healthy controls, and lung tissue of ovalbumin (OVA)-induced murine asthma model. To evaluate the role of TG2 in asthma, we developed an OVA asthma model in both TG2 null and wild-type mice. The expression of M2 macrophage markers was measured by fluorescence-activated cell sorting (FACS) after OVA sensitization and challenge. To evaluate the effect of TG2 inhibition in vitro, interleukin 4 (IL-4) or IL-13-stimulated expression of M2 macrophage markers was measured in CRL-2456 cells in the presence and absence of a TG2 inhibitor.

RESULTS

The expression of both TG2 and M2 markers was increased in the sputum of asthmatics compared with that of healthy controls. The expression of TG2 was increased in macrophages of OVA mice. Airway hyperresponsiveness, and the number of inflammatory cells, including eosinophils, was significantly reduced in TG2 null mice compared with wild-type mice. Enhanced expression of M2 markers in OVA mice was normalized by TG2 knockout. IL-4 or IL-13-stimulated expression of M2 markers in alveolar macrophages was also attenuated by TG2 inhibitor treatment in vitro.

CONCLUSION

Our results suggest that TG2-mediated modulation of alveolar macrophage polarization plays important roles in the pathogenesis of asthma.

The Role of Macrophages in the Development of Acute and Chronic Inflammatory Lung Diseases

Macrophages play an important role in the innate and adaptive immune responses of organ systems, including the lungs, to particles and pathogens. Cumulative results show that macrophages contribute to the development and progression of acute or chronic inflammatory responses through the secretion of inflammatory cytokines/chemokines and the activation of transcription factors in the pathogenesis of inflammatory lung diseases, such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), ARDS related to COVID-19 (coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)), allergic asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). This review summarizes the functions of macrophages and their associated underlying mechanisms in the development of ALI, ARDS, COVID-19-related ARDS, allergic asthma, COPD, and IPF and briefly introduces the acute and chronic experimental animal models. Thus, this review suggests an effective therapeutic approach that focuses on the regulation of macrophage function in the context of inflammatory lung diseases.

Casticin Improves Respiratory Dysfunction and Attenuates Oxidative Stress and Inflammation via Inhibition of NF-ĸB in a Chronic Obstructive Pulmonary Disease Model of Chronic Cigarette Smoke-Exposed Rats

Objective

The present study was conducted to elucidate the protective effect of Casticin against chronic obstructive pulmonary disease (COPD) in rats.

Methods

The COPD in rats was induced by the controlled cigarette smoke, and CST (10, 20, and 30 mg/kg) was injected into the cigarette-smoke exposed rats. Blood was taken from the abdominal vein and centrifuged (1500×g, 4°C, 15min); plasma was collected and used for the determination of various biochemical parameters.

Results

The results of the study suggested that CST significantly improved the lung functions of the rats in a dose-dependent manner. It also causes a reduction of white blood cells, neutrophils, and macrophages in BALF of rats. The plasma level of leptin and C-reactive protein together with pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) were also significantly restored to near to normal in CST-treated group. In Western blot analysis, CST causes significant inhibition of the NF-ĸB and iNOS pathway.

Conclusion

Our study demonstrated that the CST protects lungs against COPD via improving lung functions and inhibition of oxidative stress and inflammation.

Can Dasatinib Ameliorate the Hepatic changes, Induced by Long Term Western Diet, in Mice?

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a worldwide disease that progresses into steatohepatitis (NASH) that has no current effective treatment. This study aimed, for the first time, to investigate the effect of Dasatinib; a tyrosine kinase inhibitor showing anti-PDGFR activity with a macrophage modulating efficacy, on NASH.

METHODS

NASH was induced, in C57BL/6 mice by western diet (WD). Control groups received either DMSO or Dasatinib. After 12 weeks, WD-fed mice received DMSO, Dasatinib (4 mg/kg) or Dasatinib (8 mg/kg) once daily, for four weeks. Serum was examined for ALT and lipid profile. Immunohistochemical staining for SREBP1 (lipogenesis marker), iNOS, arginase-1, CD68, CD163 (macrophage polarization markers), TGF-β (fibrosis marker) and ASMA (a marker for activated hepatic stellate cell), hepatic mRNA expression for SREBP-1, iNOS, arginase-1, TGF-β and PDGFA genes; and western blotting for phosphorylated PDGFR α and β, SREBP1, iNOS, arginase-1, IL1α, COX2, TGF-β and ASMA were performed. Liver sections were stained also for H & E, Oil red O and Sirius red.

RESULTS

Dasatinib could ameliorate the WD-induced disturbance of serum ALT, lipid profile and significantly reduced hepatic expression of PDGFA, phosphorylated PDGFR α and β, IL1α, COX2, SREBP-1, iNOS, CD68, TGF-β and ASMA but increased expression for arginase-1 and CD163 (M2 macrophage markers). Moreover, Dasatinib reduced the steatosis, inflammation, hepatocellular ballooning, hepatic fibrosis and the high NAFLD activity scoring induced by WD.

CONCLUSION

Dasatinib can prevent the progression of WD-induced NASH by attenuating lipogenesis, and inducing M2 macrophage polarization with antifibrotic activity.

Macrophage TLR4 and PAR2 Signaling: Role in Regulating Vascular Inflammatory Injury and Repair

Macrophages play a central role in dictating the tissue response to infection and orchestrating subsequent repair of the damage. In this context, macrophages residing in the lungs continuously sense and discriminate among a wide range of insults to initiate the immune responses important to host-defense. Inflammatory tissue injury also leads to activation of proteases, and thereby the coagulation pathway, to optimize injury and repair post-infection. However, long-lasting inflammatory triggers from macrophages can impair the lung's ability to recover from severe injury, leading to increased lung vascular permeability and neutrophilic injury, hallmarks of Acute Lung Injury (ALI). In this review, we discuss the roles of toll-like receptor 4 (TLR4) and protease activating receptor 2 (PAR2) expressed on the macrophage cell-surface in regulating lung vascular inflammatory signaling.

A review of Sulfur Mustard-induced pulmonary immunopathology: An Alveolar Macrophage Approach

Despite many studies investigating the mechanism of Sulfur Mustard (SM) induced lung injury, the underlying mechanism is still unclear. Inflammatory and subsequent fibroproliferative stages of SM-toxicity are based upon several highly-related series of events controlled by the immune system. The inhalation of SM gas variably affects different cell populations within the lungs. Various studies have shown the critical role of macrophages in triggering a pulmonary inflammatory response as well as its maintenance, resolution, and repair. Importantly, macrophages can serve as either pro-inflammatory or anti-inflammatory populations depending on the present conditions at any pathological stage. Different characteristics of macrophages, including their differentiation, phenotypic, and functional properties, as well as interactions with other cell populations determine the outcomes of lung diseases and the extent of long- or short-term pulmonary damage induced by SM. In this paper, we summarize the current state of knowledge regarding the role of alveolar macrophages and their mediators in the pathogenesis of SM in pulmonary injury. Investigating the specific cells and mechanisms involved in SM-lung injury may be useful in finding new target opportunities for treatment of this injury.

In situ evidence of collagen V and signaling pathway of found inflammatory zone 1 (FIZZ1) is associated with silicotic granuloma in lung mice

Inhalation of silica particles causes silicosis: an occupational lung disease characterized by persistent inflammation with granuloma formation that leads to tissue remodeling and impairment of lung function. Although silicosis has been studied intensely, little is known about the crucial cellular mechanisms that initiate and drive the process of inflammation and fibrosis. Recently, found in inflammatory zone 1 (FIZZ1) protein, produced by alveolar macrophages and fibroblasts have been shown to induce the proliferation of myofibroblasts and their transdifferentiation, causing tissue fibrosis. Moreover, autoimmunogenic collagen V, produced by alveolar epithelial cells and fibroblasts, is involved in the pathophysiology of interstitial pulmonary fibrosis and bleomycin-induced lung fibrosis. Based on the aforementioned we hypothesized that FIZZ1 and collagen V may be involved in the silicotic granuloma process in mice lungs. Male C57BL/6 mice (N = 20) received intratracheal administration of silica particles (Silica; 20 mg in 50 μL saline) or saline (Control; 50 μL). After 15 days, the lung histology was performed through immunohistochemistry and morphometric analysis. Within silicotic granulomas, collagen V and FIZZ1 increased, while peroxisome proliferator-activated receptor gamma (PPARγ) positive cells decreased. In addition, the expression of proteins Notch-1, alpha smooth muscle actin (α-SMA) and macrophages163 (CD163) were higher in silicotic granulomas than control lungs. A significant positive correlation was found between collagen V and FIZZ1 (r = 0.70; p < 0.05), collagen V and Notch-1 (r = 0.72; p < 0.05), whereas Collagen V was inversely associated with peroxisome proliferator-activated receptor gamma (r=-0.69; p < 0.05). These findings suggested that collagen V association with FIZZ1, Notch-1 and PPARγ might be a key pathogenic mechanism for silicotic granulomas in mice lungs.

Use of Tripterygium wilfordii Hook F for immune-mediated inflammatory diseases: progress and future prospects

Tripterygium wilfordii Hook F has significant anti-inflammatory and immunosuppressive properties and is widely used for treating autoimmune and inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus, and kidney disease, especially in traditional Chinese medicine. The mechanisms underlying its effects may be diverse but they remain unclear, and its toxicity and side effects limit its wider clinical application. This review summarizes the clinical application of Tripterygium wilfordii Hook F in recent years, as well as the results of studies into its mechanisms and toxicity, to provide a reference for its future clinical application.

Using toponomics to characterize phenotypic diversity in alveolar macrophages from male mice treated with exogenous SP-A1

Background

We used the Toponome Imaging System (TIS) to identify “patterns of marker expression”, referred to here as combinatorial molecular phenotypes (CMPs) in alveolar macrophages (AM) in response to the innate immune molecule, SP-A1.

Methods

We compared 114 AM from male SP-A deficient mice. One group (n = 3) was treated with exogenous human surfactant protein A1 (hSP-A1) and the other with vehicle (n = 3). AM obtained by bronchoalveolar lavage were plated onto slides and analyzed using TIS to study the AM toponome, the spatial network of proteins within intact cells. With TIS, each slide is sequentially immunostained with multiple FITC-conjugated antibodies. Images are analyzed pixel-by-pixel identifying all of the proteins within each pixel, which are then designated as CMPs. CMPs represent organized protein clusters postulated to contribute to specific functions.

Results

1) We compared identical CMPs in KO and SP-A1 cells and found them to differ significantly (p = 0.0007). Similarities between pairs of markers in the two populations also differed significantly (p < 0.0001). 2) Focusing on the 20 most abundant CMPs for each cell, we developed a method to generate CMP “signatures” that characterized various groups of cells. Phenotypes were defined as cells exhibiting similar signatures of CMPs. i) AM were extremely diverse and each group contained cells with multiple phenotypes. ii) Among the 114 AM analyzed, no two cells were identical. iii) However, CMP signatures could distinguish among cell subpopulations within and between groups. iv) Some cell populations were enriched with SP-A1 treatment, some were more common without SP-A1, and some seemed not to be influenced by the presence of SP-A1. v) We also found that AM were more diverse in mice treated with SP-A1 compared to those treated with vehicle.

Conclusions

AM diversity is far more extensive than originally thought. The increased diversity of SP-A1-treated mice points to the possibility that SP-A1 enhances or activates several pathways in the AM to better prepare it for its innate immune functions and other functions shown previously to be affected by SP-A treatment. Future studies may identify key protein(s) responsible for CMP integrity and consequently for a given function, and target it for therapeutic purposes.

Chronic exposure to diesel particles worsened emphysema and increased M2-like phenotype macrophages in a PPE-induced model

Chronic exposure to ambient levels of air pollution induces respiratory illness exacerbation by increasing inflammatory responses and apoptotic cells in pulmonary tissues. The ineffective phagocytosis of these apoptotic cells (efferocytosis) by macrophages has been considered an important factor in these pathological mechanisms. Depending on microenvironmental stimuli, macrophages can assume different phenotypes with different functional actions. M1 macrophages are recognized by their proinflammatory activity, whereas M2 macrophages play pivotal roles in responding to microorganisms and in efferocytosis to avoid the progression of inflammatory conditions. To verify how exposure to air pollutants interferes with macrophage polarization in emphysema development, we evaluated the different macrophage phenotypes in a PPE- induced model with the exposure to diesel exhaust particles. C57BL/6 mice received intranasal instillation of porcine pancreatic elastase (PPE) to induce emphysema, and the control groups received saline. Both groups were exposed to diesel exhaust particles or filtered air for 60 days according to the groups. We observed that both the diesel and PPE groups had an increase in alveolar enlargement, collagen and elastic fibers in the parenchyma and the number of macrophages, lymphocytes and epithelial cells in BAL, and these responses were exacerbated in animals that received PPE instillation prior to exposure to diesel exhaust particles. The same response pattern was found inCaspase-3 positive cell analysis, attesting to an increase in cell apoptosis, which is in agreement with the increase in M2 phenotype markers, measured by RT-PCR and flow cytometry analysis. We did not verify differences among the groups for the M1 phenotype. In conclusion, our results showed that both chronic exposure to diesel exhaust particles and PPE instillation induced inflammatory conditions, cell apoptosis and emphysema development, as well as an increase in M2 phenotype macrophages, and the combination of these two factors exacerbated these responses. The predominance of the M2-like phenotype likely occurred due to the increased demand for efferocytosis. However, M2 macrophage activity was ineffective, resulting in emphysema development and worsening of symptoms.

Modeling Progressive Fibrosis with Pluripotent Stem Cells Identifies an Anti-fibrotic Small Molecule

Progressive organ fibrosis accounts for one-third of all deaths worldwide, yet preclinical models that mimic the complex, progressive nature of the disease are lacking, and hence, there are no curative therapies. Progressive fibrosis across organs shares common cellular and molecular pathways involving chronic injury, inflammation, and aberrant repair resulting in deposition of extracellular matrix, organ remodeling, and ultimately organ failure. We describe the generation and characterization of an in vitro progressive fibrosis model that uses cell types derived from induced pluripotent stem cells. Our model produces endogenous activated transforming growth factor β (TGF-β) and contains activated fibroblastic aggregates that progressively increase in size and stiffness with activation of known fibrotic molecular and cellular changes. We used this model as a phenotypic drug discovery platform for modulators of fibrosis. We validated this platform by identifying a compound that promotes resolution of fibrosis in in vivo and ex vivo models of ocular and lung fibrosis.

M1-polarized alveolar macrophages are crucial in a mouse model of transfusion-related acute lung injury

BACKGROUND

The pathogenesis of transfusion-related acute lung injury (TRALI) progress is incompletely understood, and specific therapies for TRALI are lacking. Alveolar macrophages (AMs) are critical for initiation and resolution of lung inflammation. However, the role of AMs in the pathogenesis of TRALI-associated lung failure is poorly understood.

STUDY DESIGN AND METHODS

Mouse model for in vivo imaging of interleukin (IL)-6 activation in AMs was established by intratracheal instillation of a lentiviral vector carrying the luciferase reporter gene. The TRALI mouse model was produced by intraperitoneal lipopolysaccharide plus intravenous major histocompatibility complex Class I monoclonal antibody treatment. We focused on the changes in AMs in the lung during TRALI and examined whether targeting AMs is an effective strategy to alleviate this condition.

MEASUREMENTS AND MAIN RESULTS

We confirmed that TRALI progress is accompanied by IL-6 activation in AMs. Further study showed that AMs undergo M1 activation during TRALI progress. AM depletion protected mice from TRALI, and transfusion of M1-polarized AMs into 34-1-2 s-treated mice elevated acute lung injury, indicating that the severity of TRALI was able to be ameliorated by targeting AM polarization. Next, we showed that α₁ -antitrypsin (AAT) expression improved lung injury by modulating the production of IL-6 in AMs and decreased polarization of AMs toward the M1 phenotype.

CONCLUSIONS

M1-polarized AMs are crucial in a mouse model of TRALI, and AAT may serve as a future treatment for TRALI by regulating the polarization of AMs.

ATP/P2X7r axis mediates the pathological process of allergic asthma by inducing M2 polarization of alveolar macrophages

Recent studies revealed that macrophages are polarized towards the M2 phenotype in an ovalbumin (OVA)-induced asthmatic model. Alveolar macrophages (AMs) are immune barriers in alveoli to various pathogens in the respiratory tract; AMs suppress Th2 cell proliferation, inhibit interleukin (IL)-4, IL-5, and IL-13 secretion, and protect against airway hyperresponsiveness in allergic asthma. However, the polarization status and effects of different types of AMs in the pathogenesis of asthma are not known. ATP/P2X7r, expressed mainly on macrophages and dendritic cells, is associated with acute and chronic asthmatic airway inflammation and Th2 immune responses in mice and humans and functions by activating the NLRP3 inflammasome complex and inducing proinflammatory cytokine release (IL-1β and IL-18). Therefore, we evaluated the association between the ATP/P2X7r axis and different types of AMs in the pathology of allergic asthma. A murine AM-depleted asthma model was established by administration of clodronate-encapsulated liposomes, and M1-or M2-AMs were adoptively transferred to confirm the effects of different AMs in allergic asthma. Brilliant Blue G and BzATP were administered to OVA/HDM-induced mice in vivo. Lipopolysaccharide + OVA, ATP, Brilliant Blue G, and BzATP were used to stimulate AMs isolated from control and asthmatic mice. We found that selective depletion of AMs aggravated lung inflammation in asthmatic mice. Further, M2-type AMs may play a key role in mediating asthmatic inflammatory responses via the adoptive transfer of M2-type AMs to AM-depleted asthmatic mice, and the phenotype of AMs differentiated to M2 type in asthma. P2X7r expression in M2-type AMs was higher than that in M1-type AMs. Activating P2X7r induced polarization of M2-type AMs and inhibited polarization of M1-type AMs, while blockage of P2X7r had the opposite effect. The ATP/P2X7r axis may participate in the pathogenesis of asthma by mediating the M2-type AM polarization.

A Flow Cytometric Method for Isolating Cystic Fibrosis Airway Macrophages from Expectorated Sputum

Research to understand the contribution of macrophages to nonresolving airway inflammation in cystic fibrosis (CF) and other chronic suppurative airways diseases has been hindered by a lack of methods for isolating and studying these cells. With the development of technologies that can characterize small numbers of cells or individual cells, there is an even greater need for methodologies to isolate rare cells in heterogeneous specimens. Here, we describe a method that overcomes the technical obstacles imposed by sputum debris and apoptotic cells, and allows isolation of pure populations of macrophages from CF sputum. In addition to enhancing our ability to study human CF airway macrophages, this protocol can be adapted to study cells in sputum from other chronic suppurative lung diseases (e.g., chronic obstructive pulmonary disease) and used for isolation of individual cells for single cell analyses.

miR-30c-5p Reduces Renal Ischemia-Reperfusion Involving Macrophage

Background

Ischemia-reperfusion (I/R) leads to kidney injury. Renal I/R frequently occurs in kidney transplantations and acute kidney injuries. Recent studies reported that miR-30 stimulated immune responses and reductions in renal I/R related to anti-inflammation. Our study investigated the effects of miR-30c-5p on renal I/R and the relationship among miR-30c-5p, renal I/R, and macrophages.

Material/Methods

Sprague Dawley rats received intravenous tail injections of miR-30c-5p agomir. Then a renal I/R model were established by removing the left kidney and clamping the right renal artery. Serum creatinine (Cr) was analyzed using a serum Cr assay kit, and serum neutrophil gelatinase associated lipocalin (NGAL) was measured using a NGAL ELISA (enzyme-linked immunosorbent assay) kit. Rat kidney tissues were analyzed using hematoxylin and eosin staining. THP-1 cells treated with miR-30c-5p agomir and miR-30c-5p antagomir were measured with quantitative reverse transcription-polymerase chain reaction. Protein levels were analyzed by western blot.

Results

MiR-30c-5p agomir reduced serum Cr, serum NGAL, and renal I/R injury. MiR-30c-5p agomir inhibited the expression of CD86 (M1 macrophage marker), inducible nitric oxide synthase (iNOS), and tumor necrosis factor-alpha (TNF-α) and promoted the expression of CD206 (M2 macrophage marker), interleukin (IL)-4, and IL-10 in rat kidneys. MiR-30c-5p agomir reduced the expression of CD86 and iNOS, and increased the expression of CD206 and IL-10 in THP-1 cells.

Conclusions

We preliminarily demonstrated that miR-30c-5p agomir might decrease renal I/R through transformation of M1 macrophages to M2 macrophages and resulted in changes in inflammatory cytokines.

Eosinophil-derived IL-13 promotes emphysema

The inflammatory responses in chronic airway diseases leading to emphysema are not fully defined. We hypothesised that lung eosinophilia contributes to airspace enlargement in a mouse model and to emphysema in patients with chronic obstructive pulmonary disease (COPD).A transgenic mouse model of chronic type 2 pulmonary inflammation (I5/hE2) was used to examine eosinophil-dependent mechanisms leading to airspace enlargement. Human sputum samples were collected for translational studies examining eosinophilia and matrix metalloprotease (MMP)-12 levels in patients with chronic airways disease.Airspace enlargement was identified in I5/hE2 mice and was dependent on eosinophils. Examination of I5/hE2 bronchoalveolar lavage identified elevated MMP-12, a mediator of emphysema. We showed, in vitro, that eosinophil-derived interleukin (IL)-13 promoted alveolar macrophage MMP-12 production. Airspace enlargement in I5/hE2 mice was dependent on MMP-12 and eosinophil-derived IL-4/13. Consistent with this, MMP-12 was elevated in patients with sputum eosinophilia and computed tomography evidence of emphysema, and also negatively correlated with forced expiratory volume in 1 s.A mouse model of chronic type 2 pulmonary inflammation exhibited airspace enlargement dependent on MMP-12 and eosinophil-derived IL-4/13. In chronic airways disease patients, lung eosinophilia was associated with elevated MMP-12 levels, which was a predictor of emphysema. These findings suggest an underappreciated mechanism by which eosinophils contribute to the pathologies associated with asthma and COPD.

Creation of RANKL mutants with low affinity for decoy receptor OPG and their potential anti-fibrosis activity

Fibrosis is characterized by the progressive alteration of the tissue structure due to the excessive production of extracellular matrix (ECM). The signaling system encompassing Receptor Activator of Nuclear factor NF‐κB Ligand (RANKL)/RANK/Osteoprotegerin (OPG) was discovered to play an important role in the regulation of ECM formation and degradation in bone tissue. However, whether and how this signaling pathway plays a role in liver or pulmonary ECM degradation is unclear up to now. Interestingly, increased decoy receptor OPG levels are found in fibrotic tissues. We hypothesize that RANKL can stimulate RANK on macrophages and initiate the process of ECM degradation. This process may be inhibited by highly expressed OPG in fibrotic conditions. In this case, RANKL mutants that can bind to RANK without binding to OPG might become promising therapeutic candidates. In this study, we built a structure‐based library containing 44 RANKL mutants and found that the Q236 residue of RANKL is important for OPG binding. We show that RANKL_Q236D can activate RAW cells to initiate the process of ECM degradation and is able to escape from the obstruction by exogenous OPG. We propose that the generation of RANKL mutants with reduced affinity for OPG is a promising strategy for the exploration of new therapeutics against fibrosis.

Distinctive Effects of GM-CSF and M-CSF on Proliferation and Polarization of Two Major Pulmonary Macrophage Populations

GM-CSF is required for alveolar macrophage (AM) development shortly after birth and for maintenance of AM functions throughout life, whereas M-CSF is broadly important for macrophage differentiation and self-renewal. However, the comparative actions of GM-CSF and M-CSF on AMs are incompletely understood. Interstitial macrophages (IMs) constitute a second major pulmonary macrophage population. However, unlike AMs, IM responses to CSFs are largely unknown. Proliferation, phenotypic identity, and M1/M2 polarization are important attributes of all macrophage populations, and in this study, we compared their modulation by GM-CSF and M-CSF in murine primary AMs and IMs. CSFs increased the proliferation capacity and upregulated antiapoptotic gene expression in AMs but not IMs. GM-CSF, but not M-CSF, reinforced the cellular identity, as identified by surface markers, of both cell types. GM-CSF, but not M-CSF, increased the expression of both M1 and M2 markers exclusively in AMs. Finally, CSFs enhanced the IFN-γ- and IL-4-induced polarization ability of AMs but not IMs. These first (to our knowledge) data comparing effects on the two pulmonary macrophage populations demonstrate that the activating actions of GM-CSF and M-CSF on primary AMs are not conserved in primary IMs.

Immunodeficiency in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), characterized by progressive airway inflammation and irreversible airflow limitation, leads to serious decline in life quality. The acute exacerbation of COPD (AECOPD) results in high healthcare costs as well as a significant mortality rate. The most common cause of acute exacerbation is infection. Immune deficiency, which induces dysfunction of anti-infection, plays an important role in the pathogenesis of acute exacerbation. As described in this review, the immune dysfunction in patients with AECOPD can be a major focus of efforts to therapeutic strategy.

Oxidative stress and macrophages: driving forces behind exacerbations of asthma and chronic obstructive pulmonary disease?

Oxidative stress is a common feature of obstructive airway diseases like asthma and chronic obstructive pulmonary disease (COPD). Lung macrophages are key innate immune cells that can generate oxidants and are known to display aberrant polarization patterns and defective phagocytic responses in these diseases. Whether these characteristics are linked in one way or another and whether they contribute to the onset and severity of exacerbations in asthma and COPD remain poorly understood. Insight into oxidative stress, macrophages, and their interactions may be important in fully understanding acute worsening of lung disease. This review therefore highlights the current state of the art regarding the role of oxidative stress and macrophages in exacerbations of asthma and COPD. It shows that oxidative stress can attenuate macrophage function, which may result in impaired responses toward exacerbating triggers and may contribute to exaggerated inflammation in the airways.

A hispanolone-derived diterpenoid inhibits M2-Macrophage polarization in vitro via JAK/STAT and attenuates chitin induced inflammation in vivo

Macrophages are highly plastic cells that adopt different functional phenotypes in response to environmental signals. Classically activated macrophages (M1) exhibit a pro-inflammatory role, mediating host defense against microorganisms or tumor cells; whereas alternatively activated macrophages (M2) perform a range of physiological processes, including inflammation, wound repair and tissue remodeling. Interestingly, M2 macrophages have been involved in pathological settings such as tumor progression, parasitic infection and respiratory disorders. Consequently, the search of new agents able to control macrophage polarization is on the basis of new therapeutic strategies. In the present study, we have evaluated the effect of the hispanolone derivative 8,9-dehydrohispanolone-15,16-lactol (DHHL) on M2 macrophage polarization. Our results reveal that DHHL significantly inhibited IL-4- or IL-13-stimulated M2 macrophage activation, as showed by reduced expression of M2 markers. In addition, DHHL suppressed IL-4-induced STAT-6 and JAK-1 tyrosine phosphorylation, suggesting that this compound inhibited M2 polarization by suppressing the JAK-STAT signaling pathway. Finally, DHHL prevented eosinophil recruitment and the presence of F4/80⁺-CD206⁺ M2-like macrophages in an in vivo model of M2 polarization via administration of chitin. Collectively, these results confirm DHHL as a novel regulator of macrophage polarization suitable to design future therapies towards M2-macrophages mediated pathologies.

Multi-cellular human bronchial models exposed to diesel exhaust particles: assessment of inflammation, oxidative stress and macrophage polarization

Background

Diesel exhaust particles (DEP) are a major component of outdoor air pollution. DEP mediated pulmonary effects are plausibly linked to inflammatory and oxidative stress response in which macrophages (MQ), epithelial cells and their cell-cell interaction plays a crucial role. Therefore, in this study we aimed at studying the cellular crosstalk between airway epithelial cells with MQ and MQ polarization following exposure to aerosolized DEP by assessing inflammation, oxidative stress, and MQ polarization response markers.

Method

Lung mucosa models including primary bronchial epithelial cells (PBEC) cultured at air-liquid interface (ALI) were co-cultured without (PBEC-ALI) and with MQ (PBEC-ALI/MQ). Cells were exposed to 12.7 μg/cm² aerosolized DEP using XposeALI^®. Control (sham) models were exposed to clean air. Cell viability was assessed. CXCL8 and IL-6 were measured in the basal medium by ELISA. The mRNA expression of inflammatory markers (CXCL8, IL6, TNFα), oxidative stress (NFKB, HMOX1, GPx) and MQ polarization markers (IL10, IL4, IL13, MRC1, MRC2 RETNLA, IL12 andIL23) were measured by qRT-PCR. The surface/mRNA expression of TLR2/TLR4 was detected by FACS and qRT-PCR.

Results

In PBEC-ALI exposure to DEP significantly increased the secretion of CXCL8, mRNA expression of inflammatory markers (CXCL8, TNFα) and oxidative stress markers (NFKB, HMOX1, GPx). However, mRNA expressions of these markers (CXCL8, IL6, NFKB, and HMOX1) were reduced in PBEC-ALI/MQ models after DEP exposure. TLR2 and TLR4 mRNA expression increased after DEP exposure in PBEC-ALI. The surface expression of TLR2 and TLR4 on PBEC was significantly reduced in sham-exposed PBEC-ALI/MQ compared to PBEC-ALI. After DEP exposure surface expression of TLR2 was increased on PBEC of PBEC-ALI/MQ, while TLR4 was decreased in both models. DEP exposure resulted in similar expression pattern of TLR2/TLR4 on MQ as in PBEC. In PBEC-ALI/MQ, DEP exposure increased the mRNA expression of anti-inflammatory M2 macrophage markers (IL10, IL4, IL13, MRC1, MRC2).

Conclusion

The cellular interaction of PBEC with MQ in response to DEP plays a pivotal role for MQ phenotypic alteration towards M2-subtypes, thereby promoting an efficient resolution of the inflammation. Furthermore, this study highlighted the fact that cell–cell interaction using multicellular ALI-models combined with an in vivo-like inhalation exposure system is critical in better mimicking the airway physiology compared with traditional cell culture systems.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0256-2) contains supplementary material, which is available to authorized users.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

Toxicity of orally inhaled drug formulations at the alveolar barrier: parameters for initial biological screening

Oral delivery is the most common mode of systemic drug application. Inhalation is mainly used for local therapy of lung diseases but may also be a promising route for systemic delivery of drugs that have poor oral bioavailability. The thin alveolar barrier enables fast and efficient uptake of many molecules and could deliver small molecules and proteins, which are susceptible to degradation and show poor absorption by oral application. The low rate of biotransformation and proteolytic degradation increases bioavailability of drugs but accumulation of not absorbed material may impair normal lung function. This limitation is more relevant for compounds that should be systematically active because higher doses have to be applied to the lung. The review describes processes that determine absorption of orally inhaled formulations, namely dissolution in the lung lining fluid and uptake and degradation by alveolar epithelial cells and macrophages. Dissolution testing in simulated lung fluid, screening for cytotoxicity and pro-inflammatory action in respiratory cells and study of macrophage morphology, and phagocytosis can help to identify adverse effects of pulmonary formulations.

Role of Monocyte/Macrophages during HIV/SIV Infection in Adult and Pediatric Acquired Immune Deficiency Syndrome

Monocytes/macrophages are a diverse group of cells that act as first responders in innate immunity and then as mediators for adaptive immunity to help clear infections. In performing these functions, however, the macrophage inflammatory responses can also contribute to pathogenesis. Various monocyte and tissue macrophage subsets have been associated with inflammatory disorders and tissue pathogeneses such as occur during HIV infection. Non-human primate research of simian immunodeficiency virus (SIV) has been invaluable in better understanding the pathogenesis of HIV infection. The question of HIV/SIV-infected macrophages serving as a viral reservoir has become significant for achieving a cure. In the rhesus macaque model, SIV-infected macrophages have been shown to promote pathogenesis in several tissues resulting in cardiovascular, metabolic, and neurological diseases. Results from human studies illustrated that alveolar macrophages could be an important HIV reservoir and humanized myeloid-only mice supported productive HIV infection and viral persistence in macrophages during ART treatment. Depletion of CD4+ T cells is considered the primary cause for terminal progression, but it was reported that increasing monocyte turnover was a significantly better predictor in SIV-infected adult macaques. Notably, pediatric cases of HIV/SIV exhibit faster and more severe disease progression than adults, yet neonates have fewer target T cells and generally lack the hallmark CD4+ T cell depletion typical of adult infections. Current data show that the baseline blood monocyte turnover rate was significantly higher in neonatal macaques compared to adults and this remained high with disease progression. In this review, we discuss recent data exploring the contribution of monocytes and macrophages to HIV/SIV infection and progression. Furthermore, we highlight the need to further investigate their role in pediatric cases of infection.

Characteristics and potential role of M2 macrophages in COPD

Background

COPD is a multi-pathogenesis disease mainly caused by smoking. A further understanding of the mechanism of smoking-related COPD might contribute to preventions and treatments of this disease in the early stages. This study was designed to identify the characteristics of M2 macrophages in COPD for a better understanding about their potential role.

Materials and methods

COPD models were built in the C57BL/6 mouse by cigarette smoke (CS) exposure combined with intraperitoneal injection of cigarette smoke extract (CSE). The modeling efficiency was evaluated by lung function and hematoxylin and eosin (H&E) staining. The number of different macrophage phenotypes was detected by immunohistochemical staining (IHS) of CD206, CD86 and CD68 on the lung tissue paraffin section. The RAW264.7 cells were polarized toward the M2 phenotype by interleukin IL-4 and confirmed by a flow cytometer. The gene expression levels of TGF-βRII, Smad2, Smad3 and Smad7 in CSE-treated M2 macrophages were detected by real-time reverse transcription polymerase chain reaction (RT-PCR). The expression levels of TGF-β/Smad pathway-related makers (TGF-βRII, p-Smad2, p-Smad3, Smad7 and TGF-β) in alveolar M2 macrophages were detected by two consecutive paraffin section IHS.

Results

The COPD model is well established, which is confirmed by the lung function test and lung H&E staining. The whole number of macrophages and the ratio of M2/M1 phenotype are both increased (p<0.05). The level of CD206⁺ cells in IL-4-stimulated RAW264.7 cells is up to 93.4%, which is confirmed by a flow cytometer. The gene expression of TGF-βRII, Smad2, Smad3 and Smad7 are all enhanced (p<0.05) in CES-treated M2 macrophages, which is detected by RT-PCR. The protein levels of TGF-β/Smad pathway-related markers are all increased in alveolar M2 macrophages of the model group.

Conclusion

This study found an increased deposition of alveolar M2 macrophages in the mouse COPD model and an increased expression level of TGF-β/Smad pathway in M2 macrophages, both in vitro and in vivo, induced by CSE and/or CS exposure, indicating that M2 macrophages might contribute to COPD through changing of phenotype and TGF-β/Smad pathway.

Carbon monoxide-releasing molecule, CORM-3, modulates alveolar macrophage M1/M2 phenotype in vitro

Alveolar macrophages are key contributors to both the promotion and resolution of inflammation in the lung and are categorized into pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes. The change in M1/M2 balance has been reported in various pulmonary diseases and is a target for therapeutic intervention. The aim of this study was to assess the modulation of M1/M2 phenotype in alveolar macrophages by water-soluble carbon monoxide-releasing molecule-3 (CORM-3). Rat alveolar macrophages (AM) (NR8383) in culture were stimulated with LPS (5 ng/ml)/IFN-γ (10 U/ml) or IL-4 (10 ng/ml)/IL-13 (10 ng/ml) to induce M1 and M2 phenotypes, respectively. Expression of M1 phenotype markers, iNOS and TNF-α, and M2 phenotype markers, CD206 and Ym-1, was assessed by western blotting after 1, 3, 6, or 24 h in the absence or presence of CORM-3 (0.15 mM) treatment. Inactive CORM-3 (iCORM-3) was used as a control. Treatment of naïve (unstimulated) AM with CORM-3 promoted progression of the M2 phenotype as evidenced by the increased expression of CD206 (at 1 h; 1.8-fold) and Ym-1 (at 3 h; 1.9-fold), respectively. Surprisingly, CORM-3 treatment also upregulated the expression of iNOS protein as assessed 6 h following stimulation of AM with CORM-3 (2.6-fold). On the contrary, CORM-3 effectively reduced LPS/IFN-γ-induced expression of iNOS protein (0.6-fold); however, it had no effect on TNF-α expression. Finally, CORM-3 acutely (1-3 h) upregulated CD206 (1.4-fold) and Ym-1 (1.6-fold) levels in IL-4-/IL-13-treated (M2-stimulus) macrophages. These findings indicate that CORM-3 modulates macrophage M1 and M2 phenotypes in vitro with respect to continuous suppression of iNOS expression in M1-polarized macrophages and transient (early-phase) upregulation of CD206 and Ym-1 proteins in M2-polarized macrophages.

Diversity of Human and Macaque Airway Immune Cells at Baseline and during Tuberculosis Infection

Immune cells of the distal airways serve as "first responders" of host immunity to the airborne pathogen Mycobacterium tuberculosis (Mtb). Mtb infection of cynomolgus macaques recapitulates the range of human outcomes from clinically silent latent tuberculosis infection (LTBI) to active tuberculosis of various degrees of severity. To further advance the application of this model to human studies, we compared profiles of bronchoalveolar lavage (BAL) cells of humans and cynomolgus macaques before and after Mtb infection. A simple gating strategy effectively defined BAL T-cell and phagocyte populations in both species. BAL from Mtb-naive humans and macaques showed similar differential cell counts. BAL T cells of macaques were composed of fewer CD4⁺cells but more CD8⁺ and CD4⁺CD8⁺ double-positive cells than were BAL T cells of humans. The most common mononuclear phagocyte population in BAL of both species displayed coexpression of HLA-DR, CD206, CD11b, and CD11c; however, multiple phagocyte subsets displaying only some of these markers were observed as well. Macaques with LTBI displayed a marked BAL lymphocytosis that was not observed in humans with LTBI. In macaques, the prevalence of specific mononuclear phagocyte subsets in baseline BAL correlated with ultimate outcomes of Mtb infection (i.e., LTBI versus active disease). Overall, these findings demonstrate the comparability of studies of pulmonary immunity to Mtb in humans and macaques. They also indicate a previously undescribed complexity of airway mononuclear phagocyte populations that suggests further lines of investigation relevant to understanding the mechanisms of both protection from and susceptibility to the development of active tuberculosis within the lung.