Smoking status and anti-inflammatory macrophages in bronchoalveolar lavage and induced sputum in COPD

Involvement of M2 macrophages polarization in PM2.5-induced COPD by upregulating MMP12 via IL4/STAT6 pathway

Biomass-related airborne fine particulate matter (PM2.5) is an important risk factor for chronic obstructive pulmonary disease (COPD). Macrophage polarization has been reported to be involved in PM2.5-induced COPD, but the dynamic characteristics and underlying mechanism of this process remain unclear. Our study established a PM2.5-induced COPD mouse model and revealed that M2 macrophages predominantly presented after 4 and 6 months of PM2.5 exposure, during which a notable increase in MMP12 was observed. Single cell analysis of lung tissues from COPD patients and mice further revealed that M2 macrophages were the dominant macrophage subpopulation in COPD, with MMP12 being involved as a hub gene. In vitro experiments further demonstrated that PM2.5 induced M2 polarization and increased MMP12 expression. Moreover, we found that PM2.5 increased IL-4 expression, STAT6 phosphorylation and nuclear translocation. Nuclear pSTAT6 then bound to the MMP12 promoter region. Furthermore, the inhibition of STAT6 phosphorylation effectively abrogated the PM2.5-induced increase in MMP12. Using a coculture system, we observed a significantly reduced level of E-cadherin in alveolar epithelial cells cocultured with PM2.5-exposed macrophages, while the decrease in E-cadherin was reversed by the addition of an MMP12 inhibitor to the co-culture system. Taken together, these findings indicated that PM2.5 induced M2 macrophage polarization and MMP12 upregulation via the IL-4/STAT6 pathway, which resulted in alveolar epithelial barrier dysfunction and excessive extracellular matrix (ECM) degradation, and ultimately led to COPD progression. These findings may help to elucidate the role of macrophages in COPD, and suggest promising directions for potential therapeutic strategies.

Macrophage Polarization and Functions in Pathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD), the major leading cause of mortality worldwide, is a progressive and irreversible respiratory condition characterized by peripheral airway and lung parenchymal inflammation, accompanied by fibrosis, emphysema, and airflow limitation, and has multiple etiologies, including genetic variance, air pollution, and repetitive exposure to harmful substances. However, the precise mechanisms underlying the pathogenesis of COPD have not been identified. Recent multiomics-based evidence suggests that the plasticity of alveolar macrophages contributes to the onset and progression of COPD through the coordinated modulation of numerous transcription factors. Therefore, this review focuses on understanding the mechanisms and functions of macrophage polarization that regulate lung homeostasis in COPD. These findings may provide a better insight into the distinct role of macrophages in COPD pathogenesis and perspective for developing novel therapeutic strategies targeting macrophage polarization.

Clinical utility of circulating TWEAK and CD163 as biomarkers of iron-induced cardiac decompensation in transfusion dependent thalassemia major

BACKGROUND AND AIM

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) affects most of the cells involved in cardiac fibrosis like inflammatory cells, cardiomyocytes and fibroblasts. CD163, the receptor of TWEAK on the surface of type 2 macrophages, is shed into plasma upon macrophages activation. This work aimed to evaluate serum TWEAK and its decoy receptor CD163 as probable biomarkers to monitor myocardial iron overload (MIO) in transfusion dependent thalassemia major (TDTM) patients and to predict iron-induced cardiac decompensation (IICD).

METHODS

A total of 140 TDTM patients were enrolled. Patients were categorized into two groups; group I (n = 70) diagnosed with IICD while group II (n = 70) had no evidence of IICD. sTWEAK and sCD163 were quantitated utilizing Enzyme-linked-immunosorbent- assay.

RESULTS

sTWEAK was evidently lower in group I than group II (medians, 412 and 1052 pg/mL respectively). sCD163 was higher in group I than group II (medians, 615.5 and 323.5 ng/mL respectively). sTWEAK positively correlated with cardiac MRI-T2 mapping and ventricular ejection fractions and negatively correlated with B-Natriuretic peptide and cardiac troponin. An inverse relationship between TWEAK and CD163 was documented throughout the study. sTWEAK, sCD163 and TWEAK/CD163 ratio proved to be significant predictors of IICD in TDTM patients. TWEAK/CD163 ratio < 1.04 discriminated IICD in TDTM patients with 100 % clinical sensitivity and specificity.

CONCLUSION

Circulating TWEAK and CD163 appears to be promising biomarkers for monitoring MIO and predicting IICD in TDTM patients.

Interleukin-41 diminishes cigarette smoke-induced lung inflammation in mice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and other inflammatory lung illnesses are markedly exacerbated by cigarette smoke (CS). The novel cytokine interleukin (IL)-41 has immunoregulatory effects, but data on its function in lung inflammation caused by CS are limited and inconclusive. Our study aimed to investigate the ability of IL-41 to protect against CS-induced lung inflammation in vivo.

METHODS

In this model, mice were exposed to six cigarettes three times daily for 1 h, with 4-hour intervals between exposures, for 5 consecutive days. Mice received an intraperitoneal dose of IL-41 or a negative control 1 day prior to their initial exposure to CS. On day 6, mice were sacrificed to assess the impact of IL-41 on CS-induced lung inflammation.

RESULTS

We found that IL-41 pre-treatment alleviated pulmonary inflammatory infiltration and lung tissue lesions. IL-41 pre-treatment also limited CS-induced weight loss, and resulted in lower numbers of macrophages in the bronchoalveolar lavage fluid and lower percentages of neutrophils and monocytes in the blood. Furthermore, it promoted the polarization of M2 macrophages rather than M1 macrophages, as determined by immunohistochemistry. Consistent with its effects on M2 polarization, pre-treatment with IL-41 was associated with higher levels of IL-10 in the bronchoalveolar lavage fluid and lung tissues of CS-exposed animals and lower production of tumor necrosis factor-α, IL-6 and IL-1β in the serum and lung tissues.

CONCLUSIONS

These findings suggest that IL-41 could be used therapeutically to treat CS-induced lung inflammatory disorders as it inhibits CS-induced pulmonary inflammation when administered in vivo in mice.

Biomimetic System Based on Reconstituted Macrophage Membranes for Analyzing and Selection of Higher-Affinity Ligands Specific to Mannose Receptor to Develop the Macrophage-Focused Medicines

Progress in macrophage research is crucial for numerous applications in medicine, including cancer and infectious diseases. However, the existing methods to manipulate living macrophages are labor-intense and inconvenient. Here, we show that macrophage membranes can be reconstituted after storage for months at 4 °C, with their CD206 receptor selectivity and specificity being similar to those in the living cells. Then, we have developed a mannose ligand, specific to CD206, linked with PEG as an IR spectroscopy marker to detect binding with the macrophage receptor. PEG was selected due to its unique adsorption band of the C-O-C group at IR spectra, which does not overlap with other biomolecules' spectroscopic feature. Next, competitive binding assay versus the PEG-bound ligand has enabled the selection of other higher-affinity ligands specific to CD206. Furthermore, those higher-affinity ligands were used to differentiate activated macrophages in a patient's bronchoalveolar (BAL) or nasopharyngeal (NPL) lavage. CD206- control cells (HEK293T) showed only non-specific binding. Therefore, biochips based on reconstituted macrophage membranes as well as PEG-trimannoside as an IR spectroscopic marker can be used to develop new methods facilitating macrophage research and macrophage-focused drug discovery.

A Single-Cell Atlas of Small Airway Disease in Chronic Obstructive Pulmonary Disease: A Cross-Sectional Study

Rationale: Emerging data demonstrate that the smallest conducting airways, terminal bronchioles, are the early site of tissue destruction in chronic obstructive pulmonary disease (COPD) and are reduced by as much as 41% by the time someone is diagnosed with mild (Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage 1) COPD. Objectives: To develop a single-cell atlas that describes the structural, cellular, and extracellular matrix alterations underlying terminal bronchiole loss in COPD. Methods: This cross-sectional study of 262 lung samples derived from 34 ex-smokers with normal lung function (n = 10) or GOLD stage 1 (n = 10), stage 2 (n = 8), or stage 4 (n = 6) COPD was performed to assess the morphology, extracellular matrix, single-cell atlas, and genes associated with terminal bronchiole reduction using stereology, micro-computed tomography, nonlinear optical microscopy, imaging mass spectrometry, and transcriptomics. Measurements and Main Results: The lumen area of terminal bronchioles progressively narrows with COPD severity as a result of the loss of elastin fibers within alveolar attachments, which was observed before microscopic emphysematous tissue destruction in GOLD stage 1 and 2 COPD. The single-cell atlas of terminal bronchioles in COPD demonstrated M1-like macrophages and neutrophils located within alveolar attachments and associated with the pathobiology of elastin fiber loss, whereas adaptive immune cells (naive, CD4, and CD8 T cells, and B cells) are associated with terminal bronchiole wall remodeling. Terminal bronchiole pathology was associated with the upregulation of genes involved in innate and adaptive immune responses, the interferon response, and the degranulation of neutrophils. Conclusions: This comprehensive single-cell atlas highlights terminal bronchiole alveolar attachments as the initial site of tissue destruction in centrilobular emphysema and an attractive target for disease modification.

A Pilot Cross-Sectional Study of Immunological and Microbiome Profiling Reveals Distinct Inflammatory Profiles for Smokers, Electronic Cigarette Users, and Never-Smokers

Smokers (SM) have increased lung immune cell counts and inflammatory gene expression compared to electronic cigarette (EC) users and never-smokers (NS). The objective of this study is to further assess associations for SM and EC lung microbiomes with immune cell subtypes and inflammatory gene expression in samples obtained by bronchoscopy and bronchoalveolar lavage (n = 28). RNASeq with the CIBERSORT computational algorithm were used to determine immune cell subtypes, along with inflammatory gene expression and microbiome metatranscriptomics. Macrophage subtypes revealed a two-fold increase in M0 (undifferentiated) macrophages for SM and EC users relative to NS, with a concordant decrease in M2 (anti-inflammatory) macrophages. There were 68, 19, and 1 significantly differentially expressed inflammatory genes (DEG) between SM/NS, SM/EC users, and EC users/NS, respectively. CSF-1 and GATA3 expression correlated positively and inversely with M0 and M2 macrophages, respectively. Correlation profiling for DEG showed distinct lung profiles for each participant group. There were three bacteria genera-DEG correlations and three bacteria genera-macrophage subtype correlations. In this pilot study, SM and EC use were associated with an increase in undifferentiated M0 macrophages, but SM differed from EC users and NS for inflammatory gene expression. The data support the hypothesis that SM and EC have toxic lung effects influencing inflammatory responses, but this may not be via changes in the microbiome.

Immunoprofiling bronchoalveolar lavage cells reveals multifaceted smoking-associated immune dysfunction

Background

Bronchoalveolar lavage (BAL) is an underutilised tool in the search for pulmonary disease biomarkers. While leukocytes with effector and suppressor function play important roles in airway immunity and tumours, it remains unclear if frequencies and phenotypes of BAL leukocytes can be useful parameters in lung cancer studies and clinical trials. We therefore explored the utility of BAL leukocytes as a source of biomarkers interrogating the impact of smoking, a major lung cancer risk determinant, on pulmonary immunity.

Methods

In this "test case" observational study, BAL samples from 119 donors undergoing lung cancer screening and biopsy procedures were evaluated by conventional and spectral flow cytometry to exemplify the comprehensive immune analyses possible with this biospecimen. Proportions of major leukocyte populations and phenotypic markers levels were found. Multivariate linear rank sum analysis considering age, sex, cancer diagnosis and smoking status was performed.

Results

Significantly increased frequencies of myeloid-derived suppressor cells and PD-L1-expressing macrophages were found in current and former smokers compared to never-smokers. While cytotoxic CD8 T-cells and conventional CD4 helper T-cell frequencies were significantly reduced in current and former smokers, expression of immune checkpoints PD-1 and LAG-3 as well as Tregs proportions were increased. Lastly, the cellularity, viability and stability of several immune readouts under cryostorage suggested BAL samples are useful for correlative end-points in clinical trials.

Conclusions

Smoking is associated with heightened markers of immune dysfunction, readily assayable in BAL, that may reflect a permissive environment for cancer development and progression in the airway.

PPARγ inhibits small airway remodeling through mediating the polarization homeostasis of alveolar macrophages in COPD

The role of Peroxisome Proliferator-Activated Receptor-γ (PPARγ) in alveolar macrophages(AMs) polarization homeostasis is closely associated with airway remodeling in COPD, but the definite mechanism remains unclear. In this study, elevated percentage of M1-type AMs and the expression of functionally cytokines were found in COPD patients and mice, which closely related to the disease severity. PPARγ was markedly up-regulated in M2-type AMs and down-regulated in M1-type AMs, and was associated with disease severity in COPD. Co-cultured with M1- or M2-type AMs promoted the epithelial-mesenchymal transition (EMT) of airway epithelial cells and the proliferation of airway smooth muscle cells. Moreover, airway remodeling and functional damage were observed in both IL4R-/- COPD mice with runaway M1-type AMs polarization and TLR4-/- COPD mice with runaway M2-type AMs polarization. Cigarette extract (CS) or lipopolysaccharide (LPS) stimulated PPARγ-/- AMs showed more serious polarization disorder towards M1, as well as CS induced PPARγ-/- COPD mice, which led to more severe airway inflammation, lung function damage, and airway remodeling. Treatment with PPARγ agonist significantly improved the polarization disorder and function activity in CS/LPS stimulated-AMs by inhibiting the JAK-STAT, MAPK and NF-κB pathways, and alleviated the airway inflammation, restored the lung function and suppressed airway remodeling in CS induced-COPD mice. Our research demonstrates that polarization homeostasis of AMs mediated by PPARγ has the protective effect in airway remodeling, and may be a novel therapeutic target for the intervention and treatment of airway remodeling in COPD.

Ectodomain shedding of proteins important for SARS-CoV-2 pathogenesis in plasma of tobacco cigarette smokers compared to electronic cigarette vapers: a cross-sectional study

The impact of tobacco cigarette (TCIG) smoking and electronic cigarette (ECIG) vaping on the risk of development of severe COVID-19 is controversial. The present study investigated levels of proteins important for SARS-CoV-2 pathogenesis present in plasma because of ectodomain shedding in smokers, ECIG vapers, and non-smokers (NSs). Protein levels of soluble angiotensin-converting enzyme 2 (ACE2), angiotensin (Ang) II (the ligand of ACE2), Ang 1-7 (the main peptide generated from Ang II by ACE2 activity), furin (a protease that increases the affinity of the SARS-CoV-2 spike protein for ACE2), and products of ADAM17 shedding activity that predict morbidity in COVID-19 (IL-6/IL-6R alpha (IL-6/IL-6Rα) complex, soluble CD163 (sCD163), L-selectin) were determined in plasma from 45 NSs, 30 ECIG vapers, and 29 TCIG smokers using ELISA. Baseline characteristics of study participants did not differ among groups. TCIG smokers had increased sCD163, L-selectin compared to NSs and ECIG vapers (p < 0.001 for all comparisons). ECIG vapers had higher plasma furin compared to both NSs (p < 0.001) and TCIG smokers (p < 0.05). ECIG vaping and TCIG smoking did not impact plasma ACE2, Ang 1-7, Ang II, and IL-6 levels compared to NSs (p > 0.1 for all comparisons). Further studies are needed to determine if increased furin activity and ADAM17 shedding activity that is associated with increased plasma levels of sCD163 and L-selectin in healthy young TCIG smokers may contribute to the future development of severe COVID-19 and cardiovascular complications of post-acute COVID-19 syndrome.

MicroRNA Let-7 Induces M2 Macrophage Polarization in COPD Emphysema Through the IL-6/STAT3 Pathway

Background

M2 polarized macrophages are involved in the occurrence and development of emphysema in COPD patients. However, the molecular mechanism of M2 macrophage polarization is still unclear. This study investigated the molecular mechanism of let-7 differentially expressed in bronchial epithelial cells of COPD patients participating in COPD emphysema by regulating the expression of IL-6 and inducing M2 polarization of alveolar macrophages (AM).

Materials and Methods

We measured let-7c expression in human lung tissue, serum and the lung tissue of cigarette smoke (CS)-exposed mice by qRT‒PCR. We observed the M1/M2 AM polarization in the lungs of COPD patients and COPD model mice by immunofluorescence analysis. Western blotting was used to determine the expression of MMP9/12 in the lung tissue of COPD patients and CS-exposed mice. An in vitro experiment was performed to determine the molecular mechanism of let-7c-induced macrophage polarization.

Results

Let-7c expression was downregulated in COPD patients, CS-exposed mice, and CS extract (CSE)-treated human bronchial epithelial (HBE) cells. AMs in COPD patients and CS-exposed mice were dominated by the M2 type, and the release of MMP9/12 was increased. In vitro, the transfection of mimics overexpressing let-7 or the use of tocilizumab to block signal transduction between HBE cells and macrophages inhibited the IL-6/STAT3 pathway. M2 macrophage polarization was inhibited, and MMP9/12 release was reduced.

Conclusion

Our results indicate that CS decreased let-7c expression in HBE cells, and M2 AM polarization was dominant in COPD. In HBE cells, let-7c could inhibit M2 polarization of AMs through the IL-6/STAT3 pathway, providing potential diagnostic and therapeutic value for slowing COPD emphysema.

Expansion of Phenotypically Altered Dendritic Cell Populations in the Small Airways and Alveolar Parenchyma in Patients with Chronic Obstructive Pulmonary Disease

Contrasting the antigen-presenting dendritic cells (DCs) in the conducting airways, the alveolar DC populations in human lungs have remained poorly investigated. Consequently, little is known about how alveolar DCs are altered in diseases such as chronic obstructive pulmonary disease (COPD). This study maps multiple tissue DC categories in the distal lung across COPD severities. Specifically, single-multiplex immunohistochemistry was applied to quantify langerin/CD207+, CD1a+, BDCA2+, and CD11c+ subsets in distal lung compartments from patients with COPD (GOLD stage I-IV) and never-smoking and smoking controls. In the alveolar parenchyma, increased numbers of CD1a+langerin- (p < 0.05) and BDCA-2+ DCs (p < 0.001) were observed in advanced COPD compared with controls. Alveolar CD11c+ DCs also increased in advanced COPD (p < 0.01). In small airways, langerin+ and BDCA-2+ DCs were also significantly increased. Contrasting the small airway DCs, most alveolar DC subsets frequently extended luminal protrusions. Importantly, alveolar and small airway langerin+ DCs in COPD lungs displayed site-specific marker profiles. Further, multiplex immunohistochemistry with single-cell quantification was used to specifically profile langerin DCs and reveal site-specific expression patterns of the maturation and activation markers S100, fascin, MHC2, and B7. Taken together, our results show that clinically advanced COPD is associated with increased levels of multiple alveolar DC populations exhibiting features of both adaptive and innate immunity phenotypes. This expansion is likely to contribute to the distal lung immunopathology in COPD patients.

Inflammatory response in human lung cells stimulated with plasma from COPD patients

Background: Chronic obstructive pulmonary disease (COPD) is a condition resulting from a persistent inflammatory state in the airways even after smoking cessation. Intriguingly, the reasons behind this persistence of the inflammatory influx without smoking exposure have not been fully unraveled. We aimed to explore the hypothesis that systemic inflammation in COPD patients influences lung cell inflammatory response. Methods: We cultured human lung fibroblast and human airway epithelial cell lines with plasma from COPD patients (four emphysematous-COPD, four asthma-COPD overlap, four chronic bronchitis-COPD, and four bronchiectasis-COPD), and four smokers or ex-smokers without COPD as controls. We measured Interleukine-8 (IL-8), C-reactive protein (CRP) and matrix metalloproteinase-9 (MMP-9) in plasma and culture supernatants by ELISA. Results: Cells stimulated with plasma from COPD patients and control subjects produced higher CRP, IL-8 and MMP-9 levels, an increase for COPD in CRP(p=0.039) in epithelial cells and IL-8(p=0.039) in fibroblasts and decrease for MMP-9(p=0.039) in fibroblasts. The response was higher in epithelial cells for IL-8(p=0.003) and in fibroblasts for MMP-9(p=0.063). The plasma from chronic bronchitis and bronchiectasis phenotypes induced higher IL-8 in fibroblasts. Conclusions: Plasma from COPD patients increases the inflammatory response in lung epithelial cells and lung fibroblasts, with a different response depending on the cell type and clinical phenotype.

Macrophage programming is regulated by a cooperative interaction between fatty acid binding protein 5 and peroxisome proliferator-activated receptor γ

Resolution of inflammation is an active process that is tightly regulated to achieve repair and tissue homeostasis. In the absence of resolution, persistent inflammation underlies the pathogenesis of chronic lung disease such as chronic obstructive pulmonary disease (COPD) with recurrent exacerbations. Over the course of inflammation, macrophage programming transitions from pro-inflammatory to pro-resolving, which is in part regulated by the nuclear receptor Peroxisome Proliferator-Activated Receptor γ (PPARγ). Our previous work demonstrated an association between Fatty Acid Binding Protein 5 (FABP5) expression and PPARγ activity in peripheral blood mononuclear cells of healthy and COPD patients. However, a role for FABP5 in macrophage programming has not been examined. Here, using a combination of in vitro and in vivo approaches, we demonstrate that FABP5 is necessary for PPARγ activation. In turn, PPARγ acts directly to increase FABP5 expression in primary human alveolar macrophages. We further illustrate that lack of FABP5 expression promotes a pro-inflammatory macrophage programming with increased secretion of pro-inflammatory cytokines and increased chromatin accessibility for pro-inflammatory transcription factors (e.g., NF-κB and MAPK). And finally, real-time cell metabolic analysis using the Seahorse technology shows an inhibition of oxidative phosphorylation in FABP5-deficient macrophages. Taken together, our data indicate that FABP5 and PPARγ reciprocally regulate each other's expression and function, consistent with a novel positive feedback loop between the two factors that mediates macrophage pro-resolving programming. Our studies highlight the importance of defining targets and regulatory mechanisms that control the resolution of inflammation and may serve to inform novel interventional strategies directed towards COPD.

Proteomic Network Analysis of Bronchoalveolar Lavage Fluid in Ex-Smokers to Discover Implicated Protein Targets and Novel Drug Treatments for Chronic Obstructive Pulmonary Disease

Bronchoalveolar lavage of the epithelial lining fluid (BALF) can sample the profound changes in the airway lumen milieu prevalent in chronic obstructive pulmonary disease (COPD). We compared the BALF proteome of ex-smokers with moderate COPD who are not in exacerbation status to non-smoking healthy control subjects and applied proteome-scale translational bioinformatics approaches to identify potential therapeutic protein targets and drugs that modulate these proteins for the treatment of COPD. Proteomic profiles of BALF were obtained from (1) never-smoker control subjects with normal lung function (n = 10) or (2) individuals with stable moderate (GOLD stage 2, FEV1 50−80% predicted, FEV1/FVC < 0.70) COPD who were ex-smokers for at least 1 year (n = 10). After identifying potential crucial hub proteins, drug−proteome interaction signatures were ranked by the computational analysis of novel drug opportunities (CANDO) platform for multiscale therapeutic discovery to identify potentially repurposable drugs. Subsequently, a literature-based knowledge graph was utilized to rank combinations of drugs that most likely ameliorate inflammatory processes. Proteomic network analysis demonstrated that 233 of the >1800 proteins identified in the BALF were significantly differentially expressed in COPD versus control. Functional annotation of the differentially expressed proteins was used to detail canonical pathways containing the differential expressed proteins. Topological network analysis demonstrated that four putative proteins act as central node proteins in COPD. The drugs with the most similar interaction signatures to approved COPD drugs were extracted with the CANDO platform. The drugs identified using CANDO were subsequently analyzed using a knowledge-based technique to determine an optimal two-drug combination that had the most appropriate effect on the central node proteins. Network analysis of the BALF proteome identified critical targets that have critical roles in modulating COPD pathogenesis, for which we identified several drugs that could be repurposed to treat COPD using a multiscale shotgun drug discovery approach.

Chronic exposure to biomass ambient particulate matter triggers alveolar macrophage polarization and activation in the rat lung

The role of alveolar macrophages (AMs) in chronic obstructive pulmonary disease is unclear. We characterized the function of AMs in rats chronically exposed to biomass fuel smoke (BMF) and studied the signal pathways that regulate AMs polarization. One hundred and eighty male Sprague‐Dawley rats were divided into BMF group and clean air control (CON) group. After BMF smoke exposure for 4 days, 1 month and 6 months, the cytokine secretion and function of AMs were determined by flow cytometry, quantitative polymerase chain reaction, Western blotting and immunofluorescence. Bone marrow‐derived macrophages were cultured and exposed to particulate matter (PM) from the smoke. Exposure initially promoted pro‐inflammatory factors, but pro‐inflammatory macrophages shared features of anti‐inflammatory macrophages. Consistent with IL‐4 upregulated in bronchoalveolar lavage fluid, p‐Stat6 and peroxisome proliferator‐activated receptor γ (PPARγ) in AMs elevated at 4 days of exposure. After 6 months of exposure, CD206, TGF‐β1 and p‐Smad3 were significantly higher than the control groups. PPARγ reversed the M1 phenotype induced by PM in vitro and drove the macrophages into the M2 phenotype. Altogether, the study demonstrates the dynamic phenotype and functional changes in AMs during exposure to BMF smoke.

Changes in systemic inflammation after pulmonary rehabilitation in patients with COPD and severe physical inactivity - an exploratory study

Background: Severe physical inactivity (SPI) in patients with COPD is associated with a poor prognosis. It is unknown whether there is a link between SPI and systemic inflammation, and if systemic inflammation in SPI changes following pulmonary rehabilitation (PR).

Methods: A prospective, observational study of patients referred for at least 7 weeks of PR comprising 2 h of exercise therapy and education twice weekly. At baseline and after PR, daily physical activity level (PAL) was measured with a validated activity monitor, SenseWear^® as well as systemic inflammation: b-eosinophils, p-fibrinogen, p-CRP, s-IL-6 and s-CD 163. SPI was defined as PAL <1.4.

Results: At baseline, SPI was present in 31 of the 57 patients included, and 23% (7/31) improved to non-SPI after PR. We observed no differences between patients with SPI and non-SPI, except baseline plasma fibrinogen level was slightly yet significantly higher in patients with SPI (median 13.3 [6.2–23.6] vs 11.2 [6.5–16.7] µmol/l) but change in fibrinogen levels differed insignificantly between patients who improved to non-SPI at follow-up compared to patients with persistent SPI (−0.6 [−16.9–9.9] vs −0.4 [−11.2–1.2] µmol/l).

Conclusion: SPI in COPD appears not to be associated with a distinct inflammatory profile compared to less sedentary COPD patients attending pulmonary rehabilitation. Currently biomarkers have no role in the detection of SPI in COPD.

Dysregulation of the CD163-Haptoglobin Axis in the Airways of COPD Patients

Pulmonary iron levels are increased in chronic obstructive pulmonary disease (COPD) patients. Iron causes oxidative stress and is a nutrient for pathogenic bacteria. Iron may therefore play an important role in the pathophysiology of COPD. The CD163-haptglobin axis plays a central role in the regulation of iron bioavailability. The aim of this study was to examine dysregulation of the CD163-haptglobin axis in COPD. We measured soluble CD163 (sCD163) and haptoglobin levels in sputum supernatants by enzyme-linked immunosorbent assay (ELISA) and sputum macrophage CD163 and haptoglobin expression by flow cytometry in COPD patients and controls. SCD163 levels were lower in COPD patients compared to controls (p = 0.02), with a significant correlation to forced expiratory volume in 1 s (FEV1)% predicted (rho = 0.5, p = 0.0007). Sputum macrophage CD163 expression was similar between COPD patients and controls. SCD163 levels and macrophage CD163 expression were lower in COPD current smokers compared to COPD ex-smokers. Haptoglobin levels were not altered in COPD patients but were regulated by genotype. Macrophage CD163 and haptolgobin expression were significantly correlated, supporting the role of CD163 in the cellular uptake of haptoglobin. Our data implicates a dysfunctional CD163-haptoglobin axis in COPD, which may contribute to disease pathophysiology, presumably due to reduced clearance of extracellular iron.

The inhibitor miR-21 regulates macrophage polarization in an experimental model of chronic obstructive pulmonary disease

INTRODUCTION

In chronic obstructive pulmonary disease (COPD), macrophages play an indispensable role. In the lung tissues of COPD patients and smokers, macrophages can be observed to polarize towards M2 phenotype. The molecular mechanism of this process is unclear, and it has not been fully elucidated in COPD.

METHODS

We bought laboratory animals [C57BL/6 and miR-21^-/- C57BL/6(F1)] from the Jackson Laboratory. The model of COPD mice was established by cigarette smoke (CS) exposure combined with intraperitoneal injection of cigarette smoke extract (CSE). RT-PCR detected the expression levels of inflammatory factors and markers associated with M1 and M2 macrophages. The ratio of M2 macrophages to M1 macrophages was detected by immunohistochemical staining.

RESULTS

The level of miR-21 was increased in RAW264.7 cells intervened by CSE and in lung tissue and bone marrow-derived macrophages (BMDMs) from COPD mice. CSE can gradually over time increase the level of miR-21. The proportion of M2 macrophages to M1 macrophages had a positive correlation with miR-21. Knockdowning miR-21 can reduce lung tissue damage. CSE also increased the levels of related inflammatory factors and markers associated with M2 macrophages, and an miR-21 inhibitor can reverse this conversion.

CONCLUSIONS

We confirmed that CSE can lead to macrophage transformation to the M2 phenotype and an increase in the expression level of miR-21. Knockdown of the miR-21 gene could inhibit the transformation of macrophages to the M2 phenotype in COPD.

Abundance of Non-Polarized Lung Macrophages with Poor Phagocytic Function in Chronic Obstructive Pulmonary Disease (COPD)

Lung macrophages are the key immune effector cells in the pathogenesis of Chronic Obstructive Pulmonary Disease (COPD). Several studies have shown an increase in their numbers in bronchoalveolar lavage fluid (BAL) of subjects with COPD compared to controls, suggesting a pathogenic role in disease initiation and progression. Although reduced lung macrophage phagocytic ability has been previously shown in COPD, the relationship between lung macrophages' phenotypic characteristics and functional properties in COPD is still unclear. (1) Methods: Macrophages harvested from bronchoalveolar lavage (BAL) fluid of subjects with and without COPD (GOLD grades, I-III) were immuno-phenotyped, and their function and gene expression profiles were assessed using targeted assays. (2) Results: BAL macrophages from 18 COPD and 10 (non-COPD) control subjects were evaluated. The majority of macrophages from COPD subjects were non-polarized (negative for both M1 and M2 markers; 77.9%) in contrast to controls (23.9%; p < 0.001). The percentages of these non-polarized macrophages strongly correlated with the severity of COPD (p = 0.006) and current smoking status (p = 0.008). Non-polarized macrophages demonstrated poor phagocytic function in both the control (p = 0.02) and COPD (p < 0.001) subjects. Non-polarized macrophages demonstrated impaired ability to phagocytose Staphylococcus aureus (p < 0.001). They also demonstrated reduced gene expression for CD163, CD40, CCL13 and C1QA&B, which are involved in pathogen recognition and processing and showed an increased gene expression for CXCR4, RAF1, amphiregulin and MAP3K5, which are all involved in promoting the inflammatory response. (3) Conclusions: COPD is associated with an abundance of non-polarized airway macrophages that is related to the severity of COPD. These non-polarized macrophages are predominantly responsible for the poor phagocytic capacity of lung macrophages in COPD, having reduced capacity for pathogen recognition and processing. This could be a key risk factor for COPD exacerbation and could contribute to disease progression.

S100A9/CD163 Expression in Circulating Classical Monocytes in Chronic Obstructive Pulmonary Disease

Although many studies have characterized polarity of macrophages in chronic obstructive pulmonary disease (COPD), limited information is available regarding cellular phenotypes of circulating monocytes in this condition. This study aimed to determine the influence of cigarette smoking and COPD on the cellular phenotype of circulating monocytes. Thirty-two patients with COPD and 36 healthy volunteers (n = 17 and 19 in nonsmokers and smokers with normal lung functions, respectively) were enrolled in this study. The expression of two cell surface markers, pro-inflammatory-related S100A9 and anti-inflammatory-related CD163, on classical monocytes was analyzed by flow cytometry. The percentage of CD14^strongCD16^- classical monocytes in circulating monocytes showed no difference among the three groups. The percentage of S100A9⁺, S100A9⁺CD163^-, and S100A9⁺CD163⁺ cells in classical monocytes was significantly increased in COPD patients relative to nonsmoker controls. In contrast, the levels of S100A9^-CD163⁺ cells were significantly decreased in smokers with normal lung functions and in COPD patients relative to that in nonsmokers. Multivariate analyses revealed an independent association between S100A9⁺ cell rates and COPD (exponent 1.0336, 95% confidence interval [CI] 1.0063-1.0617, p value < 0.05). In Receiver operating characteristic (ROC) analyses, the ratio of S100A9⁺CD163^-/S100A9^-CD163⁺ cells yielded a receiver operating characteristic-area under the curve of 0.719 (95% CI = 0.567-0.871) for discrimination between smokers with normal lung functions and COPD patients. In conclusion, our results demonstrated increased pro-inflammatory phenotypes in circulating classical monocytes in COPD, providing novel insights to elucidate their roles in the pathogenesis of COPD.

Immunopathogenesis and therapeutic potential of macrophage influx in diffuse parenchymal lung diseases

INTRODUCTION

The diffuse parenchymal lung diseases (DPLD)/interstitial lung diseases (ILD) are progressive lung disorders with usually unclear etiology, poor long-term survival and no effective treatment. Their pathogenesis is characterized by alveolar epithelial cell injury, inflammation, epithelial-mesenchymal transition, and parenchymal fibrosis. Macrophages play diverse roles in their development, both in the acute phase and in tissue repair.

AREAS COVERED

In this review, we summarize the current state of knowledge regarding the role of macrophages and their phenotypes in the immunopathogenesis of DPLDs; CVD-ILD, UIP, NSIP, DIP, RB-ILD, AIP, HP, Sarcoidosis, etc. Our goal is to update the understanding of the immune mechanisms underlying the initiation and progression of fibrosis in DPLDs. This will help in identification of biomarkers and in developing novel therapeutic strategies for DPLDs. A thorough literature search of the published studies in PubMed (from 1975 to 2020) was done.

EXPERT OPINION

The macrophage associated inflammatory markers needs to be explored for their potential as biomarkers of disease activity and progression. Pharmacological targeting of macrophage activation may reduce the risk of macrophage activation syndrome (MAS) and help improving the survival and prognosis of these patients.

Modulation of Airway Epithelial Innate Immunity and Wound Repair by M(GM-CSF) and M(M-CSF) Macrophages

Airway epithelial cells and macrophages participate in inflammatory responses to external noxious stimuli, which can cause epithelial injury. Upon injury, epithelial cells and macrophages act in concert to ensure rapid restoration of epithelial integrity. The nature of the interactions between these cell types during epithelial repair is incompletely understood. We used an in vitro human coculture model of primary bronchial epithelial cells cultured at the air-liquid interface (ALI-PBEC) and polarized primary monocyte-derived macrophages. Using this coculture, we studied the contribution of macrophages to epithelial innate immunity, wound healing capacity, and epithelial exposure to whole cigarette smoke (WCS). Coculture of ALI-PBEC with lipopolysaccharide (LPS)-activated M(GM-CSF) macrophages increased the expression of DEFB4A, CXCL8, and IL6 at 24 h in the ALI-PBEC, whereas LPS-activated M(M-CSF) macrophages only increased epithelial IL6 expression. Furthermore, wound repair was accelerated by coculture with both activated M(GM-CSF) and M(M-CSF) macrophages, also following WCS exposure. Coculture of ALI-PBEC and M(GM-CSF) macrophages resulted in increased CAMP expression in M(GM-CSF) macrophages, which was absent in M(M-CSF) macrophages. CAMP encodes LL-37, an antimicrobial peptide with immune-modulating and repair-enhancing activities. In conclusion, dynamic crosstalk between ALI-PBEC and macrophages enhances epithelial innate immunity and wound repair, even upon concomitant cigarette smoke exposure.

Upregulation of miR-196b-5p attenuates BCG uptake via targeting SOCS3 and activating STAT3 in macrophages from patients with long-term cigarette smoking-related active pulmonary tuberculosis

Background

Cigarette smoking (CS) triggers an intense and harmful inflammatory response in lungs mediated by alveolar and blood macrophages, monocytes, and neutrophils and is closely associated with prevalence of tuberculosis (TB). The risk of death in patients with long-term cigarette smoking-related pulmonary tuberculosis (LCS-PTB) is approximately 4.5 times higher than those with nonsmoking pulmonary tuberculosis (N-PTB). However, the mechanisms underlying the harmful inflammatory responses in the setting of LCS-PTB have not been well documented.

Methods

28 cases LCS-PTB patients, 22 cases N-PTB patients and 20 cases healthy volunteers were enrolled in this study. Monocytes were isolated from peripheral blood mononuclear cells. Differentiated human MDM and U937 cell were prepared with M-CSF and PMA stimulation, respectively. The miR-196b-5p, STAT1, STAT3, STAT4, STAT5A, STAT5B, STAT6, SOCS1 and SOCS3 mRNA expression were detected by qRT-PCR. Western blot was performed according to SOCS1, SOCS3, and pSTAT3 expression. The mycobacterial uptake by MDMs from different groups of patients after Bacillus Calmette–Guérin (BCG) infection and agomir-196b-5p or antagomir-196b-5p transfection were used by flow cytometry analysis. Human IL-6, IL-10 and TNF-α levels on the plasma and cell culture supernatant samples were measured using ELISA. For dual-luciferase reporter assay, the SOCS3 3′-UTR segments, containing the binding elements of miR-196b-5p or its mutant versions were synthesized as sense and antisense linkers.

Results

In this study, we found that IL-6, TNF-α production, SOCS3 mRNA expression were downregulated, while miR-196b-5p and STAT3 mRNA expression were upregulated in monocytes from LCS-PTB patients as compared to N-PTB patients. Meanwhile, we demonstrated that miR-196b-5p could target SOCS3 and activate STAT3 signaling pathway, which may possibly contribute to attenuation of BCG uptake and decrease in IL-6 and TNF-α production in macrophages.

Conclusions

Our findings revealed that CS exposure regulates inflammatory responses in monocyte/macrophages from LCS-PTB patients via upregulating miR-196b-5p, and further understanding of the specific role of miR-196b-5p in inflammatory responses mightfacilitate elucidating the pathogenesis of LCS-PTB, thus leading to the development of new therapeutic strategies for PTB patients with long-term cigarette smoking.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1654-9) contains supplementary material, which is available to authorized users.

Dysregulated Functions of Lung Macrophage Populations in COPD

Chronic obstructive pulmonary disease (COPD) is a diverse respiratory disease characterised by bronchiolitis, small airway obstruction, and emphysema. Innate immune cells play a pivotal role in the disease's progression, and in particular, lung macrophages exploit their prevalence and strategic localisation to orchestrate immune responses. To date, alveolar and interstitial resident macrophages as well as blood monocytes have been described in the lungs of patients with COPD contributing to disease pathology by changes in their functional repertoire. In this review, we summarise recent evidence from human studies and work with animal models of COPD with regard to altered functions of each of these myeloid cell populations. We primarily focus on the dysregulated capacity of alveolar macrophages to secrete proinflammatory mediators and proteases, induce oxidative stress, engulf microbes and apoptotic cells, and express surface and intracellular markers in patients with COPD. In addition, we discuss the differences in the responses between alveolar macrophages and interstitial macrophages/monocytes in the disease and propose how the field should advance to better understand the implications of lung macrophage functions in COPD.

Abnormal M1/M2 macrophage phenotype profiles in the small airway wall and lumen in smokers and chronic obstructive pulmonary disease (COPD)

We explore potential dysregulation of macrophage phenotypes in COPD pathogenesis through integrated study of human small airway tissue, bronchoalveolar lavage (BAL) and an experimental murine model of COPD. We evaluated human airway tissue and BAL from healthy controls, normal lung function smokers (NLFS), and COPD subjects. Both small airways and BAL cells were immunohistochemically stained with anti-CD68 for total macrophages and with anti-CD163 for M2, and anti-iNOS for M1 macrophages. Multiplex ELISA measured BAL cytokines. Comparable cigarette smoke-induced experimental COPD mouse model was assessed for relevant mRNA profiles. We found an increase in pro-inflammatory M1s in the small airways of NLFS and COPD compared to controls with a reciprocal decrease in M2 macrophages, which remained unchanged among pathological groups. However, luminal macrophages showed a dominant M2 phenotype in both NLFS and COPD subjects. BAL cytokine skewed towards an M2 profile with increase in CCL22, IL-4, IL-13, and IL-10 in both NLFS and COPDs. The mouse-model of COPD showed similar increase in mRNA for M2 markers. Our finding suggests abnormal macrophage switching in both mucosal and luminal areas of COPD patients, that strongly associated with cytokine balance. There may be potential for beneficial therapeutic cytokine manipulation of macrophage phenotypes in COPD.

Time Course of the Phenotype of Blood and Bone Marrow Monocytes and Macrophages in the Lung after Cigarette Smoke Exposure In Vivo

Alveolar macrophages play a central role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Monocytes are recruited from blood during inflammation and then mature into alveolar macrophages. The aim of this study was to investigate the effect of cigarette smoke (CS) at different times in lung macrophages and monocytes from blood and bone marrow in mice. Male mice (C57BL/6, n = 45) were divided into groups: control, CS 5 days, CS 14 days and CS 30 days. Five days’ CS exposure induced a pronounced influx of neutrophils and macrophages in the lung associated with increased levels of keratinocyte chemoattractant (KC), tumor necrosis factor-α (TNF-α), nitric oxide (NO) and matrix metalloproteinase (MMP)-12. After 14 days of CS exposure, neutrophil recruitment and cytokine production were greatly reduced. Moreover, chronic CS exposure led to increased recruitment of macrophages (with high expression of CD206), transforming growth factor-β (TGF-β) production as well as no detection of TNF-α, interleukin (IL)-6 and KC. CS can also change the monocyte phenotype in the blood and bone marrow, with an increase in Ly6C^low cells. These results show for the first time that CS can change not only macrophage polarization but also monocyte. These results suggest that continued recruitment of Ly6C^low monocytes may help the distinct renewing macrophage M2 population required for COPD progression.

Characterisation of lung macrophage subpopulations in COPD patients and controls

Lung macrophage subpopulations have been identified based on size. We investigated characteristics of small and large macrophages in the alveolar spaces and lung interstitium of COPD patients and controls. Alveolar and interstitial cells were isolated from lung resection tissue from 88 patients. Macrophage subpopulation cell-surface expression of immunological markers and phagocytic ability were assessed by flow cytometry. Inflammatory related gene expression was measured. Alveolar and interstitial macrophages had subpopulations of small and large macrophages based on size and granularity. Alveolar macrophages had similar numbers of small and large cells; interstitial macrophages were mainly small. Small macrophages expressed significantly higher cell surface HLA-DR, CD14, CD38 and CD36 and lower CD206 compared to large macrophages. Large alveolar macrophages showed lower marker expression in COPD current compared to ex-smokers. Small interstitial macrophages had the highest pro-inflammatory gene expression levels, while large alveolar macrophages had the lowest. Small alveolar macrophages had the highest phagocytic ability. Small alveolar macrophage CD206 expression was lower in COPD patients compared to smokers. COPD lung macrophages include distinct subpopulations; Small interstitial and small alveolar macrophages with more pro-inflammatory and phagocytic function respectively, and large alveolar macrophages with low pro-inflammatory and phagocytic ability.

A Review of Pulmonary Toxicity of Electronic Cigarettes in the Context of Smoking: A Focus on Inflammation

The use of electronic cigarettes (e-cigs) is increasing rapidly, but their effects on lung toxicity are largely unknown. Smoking is a well-established cause of lung cancer and respiratory disease, in part through inflammation. It is plausible that e-cig use might affect similar inflammatory pathways. E-cigs are used by some smokers as an aid for quitting or smoking reduction, and by never smokers (e.g., adolescents and young adults). The relative effects for impacting disease risk may differ for these groups. Cell culture and experimental animal data indicate that e-cigs have the potential for inducing inflammation, albeit much less than smoking. Human studies show that e-cig use in smokers is associated with substantial reductions in blood or urinary biomarkers of tobacco toxicants when completely switching and somewhat for dual use. However, the extent to which these biomarkers are surrogates for potential lung toxicity remains unclear. The FDA now has regulatory authority over e-cigs and can regulate product and e-liquid design features, such as nicotine content and delivery, voltage, e-liquid formulations, and flavors. All of these factors may impact pulmonary toxicity. This review summarizes current data on pulmonary inflammation related to both smoking and e-cig use, with a focus on human lung biomarkers. Cancer Epidemiol Biomarkers Prev; 26(8); 1175-91. ©2017 AACR.

Soluble CD163 predicts incident chronic lung, kidney and liver disease in HIV infection

OBJECTIVE

To examine if monocyte and macrophage activity may be on the mechanistic pathway to non-AIDS comorbidity by investigating the associations between plasma-soluble CD163 (sCD163) and incident non-AIDS comorbidities in well treated HIV-infected individuals.

DESIGN

Prospective single-center cohort study.

METHODS

Plasma sCD163 was quantified by ELISA technique at study entry in 2004/2005, and non-AIDS comorbidity was identified by International Classification of Disease Tenth revision diagnosis codes and registry linkage in 2015. Associations between sCD163 and incident comorbidity was examined using multivariable Cox proportional hazards models adjusted for pertinent covariates.

RESULTS

In HIV-1-infected individuals (n = 799), the highest quartile of plasma sCD163 was associated with incident chronic lung disease [adjusted hazard ratio (aHR), 3.2; 95% confidence interval (CI): 1.34; 7.46] and incident chronic kidney disease (aHR, 10.94; 95% CI: 2.32; 51.35), when compared with lowest quartiles. Further, (every 1 mg) increase in plasma sCD163 was positively correlated with incident liver disease (aHR, 1.12; 95% CI: 1.05; 1.19). The sCD163 level was not associated with incident cancer, cardiovascular disease or diabetes mellitus.

CONCLUSION

sCD163 was independently associated with incident chronic kidney disease, chronic lung disease and liver disease in treated HIV-1-infected individuals, suggesting that monocyte/macrophage activation may be involved in the pathogenesis of non-AIDS comorbidity and a potential target for therapeutic intervention.

Clinical significance of sCD163 and its possible role in asthma (Review)

Macrophages exert important functions in the balance and efficiency of immune responses, and participate in innate and adaptive immunity. The proinflammatory actions of macrophages are implicated in autoimmune diseases. Unlike classically activated M1 macrophages, the alternatively activated cluster of differentiation (CD)163⁺ and CD206⁺ M2 macrophages are involved in tissue repair and wound healing, and use oxidative metabolism to support their long-term functions. CD163 is a member of the scavenger receptor superfamily, categorized into class B, and its soluble(s) form, sCD163, is a marker of activated M2 macrophages. CD163 is selectively expressed in cells of the monocyte and macrophage lineages; however, its biological role has yet to be elucidated. The expression of sCD163 is markedly induced by anti-inflammatory mediators, such as glucocorticoids and interleukin-10, whereas it is inhibited by proinflammatory mediators, such as interferon-γ. These findings suggest that CD163 may serve as a potential target for the therapeutic modulation of inflammatory responses. The concentration of sCD163 in blood is associated with acute and chronic inflammatory processes in autoimmune disorders of connective tissue, fat metabolism and cardiovascular diseases, and it can be used for the assessment of cancer prognosis. A role for sCD163 in the pathogenesis of asthma has also been proposed. The present review serves to present the available knowledge concerning the implication of sCD163 in the pathophysiological mechanisms of asthma, and evaluate its potential as a biomarker and possible therapeutic target for asthma.

Dual polarization of human alveolar macrophages progressively increases with smoking and COPD severity

Background

It is known that tissue macrophages derive not only from blood monocytes but also from yolk sac or fetal liver, and the tissue of residence guides their function. When isolated, they lose tissue specific signatures, hence studies of human macrophages should be ideally done directly in the tissue. The aim of this study was to investigate directly in human lung tissue the polarization of alveolar macrophage (AM), classic (M1) or alternative (M2), in health and disease, using COPD as a model.

Methods

Surgical lungs from 53 subjects were studied: 36 smokers whose FEV₁ varied from normal to severe COPD, 11 non-smokers and 6 normal donors. iNOS and CD206 immunohistochemistry was used to quantify the percentage of AM polarized as M1 or M2 in lung sections.

Results and Discussion

The percentage of M1 and M2 increased progressively with smoking and COPD severity, from 26% to 84% for M1 and from 7% to 78% for M2. In donors 74% of AM were negative for M1 and 93% for M2. Confocal microscopy showed co-localization of M1 and M2 in the same AM in severe COPD.

Conclusion

In normal lungs alveolar macrophages were mostly non-polarized. With smoking and COPD severity, M1 and M2 polarization increased significantly and so did the co-expression of M1 and M2 in the same alveolar macrophage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0522-0) contains supplementary material, which is available to authorized users.

Serum levels of nitric oxide and cytokines in smokers at the beginning and after 4months of treatment for smoking cessation

INTRODUCTION

Nitric oxide (NO) modulates inflammatory reactions, having beneficial or toxic effects depending on the concentration. Its elevation can cause proinflammatory effects amplifying the inflammatory process with the participation of cytokines. Smoking has a negative impact on health and is considered one of the risk factors that influence disease development facilitating inflammatory processes.

AIM

To compare the serum concentration of NO and cytokines in smokers at baseline and after 4months of abstinence treatment.

METHODS

Blood samples which were collected to obtain the serum, at baseline and after 4months, were stored at -80°C until analysis. NO was measured by the total dose of nitrite determined by the Greiss method. CBA was the used technique to determine the concentration of cytokines in supernatants serum. The initial and final results of NO, TNF-α, IL-1, IL-6, IL-8, IL-10 and IL-12 that remained after 4months treatment were compared. Wilcoxon test was used to compare the data and Spearman test for correlations between NO and other variables. A significance level of p<0.05 was adopted.

RESULTS

The analysis of NO observed a significant reduction (p=0.001) of the initial median value of 18.80 (3.55-80.01) μmol/L to 8.10 (2.85-14.97) μmol/L after 4months of treatment. There were no significant differences in cytokines from baseline to the end of treatment.

CONCLUSION

The results may not mean harm to the body, but an adaptive process, decreasing the metabolism of abstinents due to the reduction of the use of nicotine.

Probing Cellular and Molecular Mechanisms of Cigarette Smoke-Induced Immune Response in the Progression of Chronic Obstructive Pulmonary Disease Using Multiscale Network Modeling

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disorder characterized by progressive destruction of lung tissues and airway obstruction. COPD is currently the third leading cause of death worldwide and there is no curative treatment available so far. Cigarette smoke (CS) is the major risk factor for COPD. Yet, only a relatively small percentage of smokers develop the disease, showing that disease susceptibility varies significantly among smokers. As smoking cessation can prevent the disease in some smokers, quitting smoking cannot halt the progression of COPD in others. Despite extensive research efforts, cellular and molecular mechanisms of COPD remain elusive. In particular, the disease susceptibility and smoking cessation effects are poorly understood. To address these issues in this work, we develop a multiscale network model that consists of nodes, which represent molecular mediators, immune cells and lung tissues, and edges describing the interactions between the nodes. Our model study identifies several positive feedback loops and network elements playing a determinant role in the CS-induced immune response and COPD progression. The results are in agreement with clinic and laboratory measurements, offering novel insight into the cellular and molecular mechanisms of COPD. The study in this work also provides a rationale for targeted therapy and personalized medicine for the disease in future.

Macrophage polarization in interstitial lung diseases

The role of bronchoalveolar lavage fluid (BALf) examination in differential diagnosis of interstitial lung diseases (ILD) was established. Currently, functional polarization into M1 (pro-inflammatory) and M2 (anti-inflammatory) subpopulations is emphasized. The aim of our study was to compare the proportion of M1 and M2 in BALf of patients with different ILD. BALf samples were collected from 75 ILD patients: sarcoidosis (SA, 36), hypersensitivity pneumonitis (HP, 10), non-specific interstitial pneumonia (NSIP, 8), idiopathic pulmonary fibrosis (IPF, 6) and other ILD (15). Phenotyping was performed by immunocytochemistry with anti-CD40 and CD163 antibodies (for M1 and M2, respectively). For both, CD40 and CD163, three populations of cells have been specified: small cells with strong (+++), large cells with weak (+) and cells with no (-) reaction. Due to lack of statistically significant differences between patients with HP, NSIP and IPF, they were classified into a common group and compared to the group of patients with sarcoidosis. The median proportion of macrophage population was as follows: for CD40: 61%, 35%, 2% in patients with SA and 49%, 47%, 3% in patients with other ILD and for CD163: 55%, 35%, 5% in SA and 53%, 43%, 1% in ILD patients, respectively. We found a significantly higher proportion of M1 in SA when compared with other ILD. Our study showed no evidence of defined polarization of alveolar macrophages in different types of interstitial lung diseases. However, we emphasized the role of CD40 positive cells in sarcoidosis and the role of CD163 positive cells in fibrotic diffuse lung diseases.

Disruption of Sirtuin 1-Mediated Control of Circadian Molecular Clock and Inflammation in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death, and it is characterized by abnormal inflammation and lung function decline. Although the circadian molecular clock regulates inflammatory responses, there is no information available regarding the impact of COPD on lung molecular clock function and its regulation by sirtuin 1 (SIRT1). We hypothesize that the molecular clock in the lungs is disrupted, leading to increased inflammatory responses in smokers and patients with COPD and its regulation by SIRT1. Lung tissues, peripheral blood mononuclear cells (PBMCs), and sputum cells were obtained from nonsmokers, smokers, and patients with COPD for measurement of core molecular clock proteins (BMAL1, CLOCK, PER1, PER2, and CRY1), clock-associated nuclear receptors (REV-ERBα, REV-ERBβ, and RORα), and SIRT1 by immunohistochemistry, immunofluorescence, and immunoblot. PBMCs were treated with the SIRT1 activator SRT1720 followed by LPS treatment, and supernatant was collected at 6-hour intervals. Levels of IL-8, IL-6, and TNF-α released from PBMCs were determined by ELISA. Expression of BMAL1, PER2, CRY1, and REV-ERBα was reduced in PBMCs, sputum cells, and lung tissues from smokers and patients with COPD when compared with nonsmokers. SRT1720 treatment attenuated LPS-mediated reduction of BMAL1 and REV-ERBα in PBMCs from nonsmokers. Additionally, LPS differentially affected the timing and amplitude of cytokine (IL-8, IL-6, and TNF-α) release from PBMCs in nonsmokers, smokers, and patients with COPD. Moreover, SRT1720 was able to inhibit LPS-induced cytokine release from cultured PBMCs. In conclusion, disruption of the molecular clock due to SIRT1 reduction contributes to abnormal inflammatory response in smokers and patients with COPD.

Antioxidant activity of pomegranate juice reduces emphysematous changes and injury secondary to cigarette smoke in an animal model and human alveolar cells

BACKGROUND

Cigarette smoke (CS) increases oxidative stress (OS) in the lungs. Pomegranate juice (PJ) possesses potent antioxidant activities, attributed to its polyphenols. This study investigates the effects of PJ on the damaging effects of CS in an animal model and on cultured human alveolar cells (A549).

METHODS

Male C57BL/6J mice were divided into the following groups: Control, CS, CS + PJ, and PJ. Acute CS exposure was for 3 days, while chronic exposure was for 1 and 3 months (5 days of exposure/week). PJ groups received daily 80 μmol/kg via bottle, while other groups received distilled water. At the end of the experiments, different parameters were studied: 1) expression levels of inflammatory markers, 2) apoptosis, 3) OS, and 4) histopathological changes. In vitro, A549 cells were pretreated for 48 hours with either PJ (0.5 μM) or vehicle. Cells were then exposed to increasing concentrations of CS extracted from collected filters. Cell viability was assessed by counting of live and dead cells with trypan blue staining.

RESULTS

Acutely, a significant increase in interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α expression, apoptosis, and OS was noted in CS when compared to Control. PJ significantly attenuated the expression of inflammatory mediators, apoptosis, and OS. Chronically (at 1 and 3 months), increased expression of TNF-α was observed, and lung sections demonstrated emphysematous changes when compared to Control. PJ supplementation to CS animals attenuated the increased expression of TNF-α and normalized lung cytoarchitecture. At the cellular level, CS extract reduced cellular proliferation and triggered cellular death. Pretreatment with PJ attenuated the damaging effects of CS extract on cultured human alveolar cells.

CONCLUSION

The expression of inflammatory mediators associated with CS exposure and the emphysematous changes noted with chronic CS exposure were reduced with PJ supplementation. In vitro, PJ attenuated the damaging effects of CS extract on cultured human alveolar cells.

COPD and squamous cell lung cancer: aberrant inflammation and immunity is the common link

Cigarette smoking has reached epidemic proportions within many regions of the world and remains the highest risk factor for chronic obstructive pulmonary disease (COPD) and lung cancer. Squamous cell lung cancer is commonly detected in heavy smokers, where the risk of developing lung cancer is not solely defined by tobacco consumption. Although therapies that target common driver mutations in adenocarcinomas are showing some promise, they are proving ineffective in smoking-related squamous cell lung cancer. Since COPD is characterized by an excessive inflammatory and oxidative stress response, this review details how aberrant innate, adaptive and systemic inflammatory processes can contribute to lung cancer susceptibility in COPD. Activated leukocytes release increasing levels of proteases and free radicals as COPD progresses and tertiary lymphoid aggregates accumulate with increasing severity. Reactive oxygen species promote formation of reactive carbonyls that are not only tumourigenic through initiating DNA damage, but can directly alter the function of regulatory proteins involved in host immunity and tumour suppressor functions. Systemic inflammation is also markedly increased during infective exacerbations in COPD and the interplay between tumour-promoting serum amyloid A (SAA) and IL-17A is discussed. SAA is also an endogenous allosteric modifier of FPR2 expressed on immune and epithelial cells, and the therapeutic potential of targeting this receptor is proposed as a novel strategy for COPD-lung cancer overlap.

Update on molecular mechanisms of corticosteroid resistance in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is an inflammatory and irreversible pulmonary disorder that is characterized by inflammation and airway destruction. In recent years, COPD has become a global epidemic due to increased air pollution and exposure to cigarette smoke. Current therapeutics using bronchiodialator and anti-inflammatory corticosteroids are most widely used for all patients with persistent COPD, but these approaches are disappointing due to limited improvement in symptom control and survival rate. More importantly, a certain number of COPD patients are resistant to the corticosteroid treatment and their symptoms worsen. Therefore, more effective anti-inflammatory drugs and combinational treatment are required. Understanding of the underlying molecular and immunological mechanisms is critical to developing new therapeutics. Lung inflammation and the released pro-inflammatory cytokines affect glucocorticoid receptor (GR), histone deacetylase 2 (HDAC2) and surfactant protein D (SP-D) activities in many cell types. Macrophages, neutrophils, airway epithelial cells and lymphocytes are involved in the induction of corticosteroid resistance. This review updated the recent advances in molecular and immunological mechanisms of steroid resistance among patients and animal models with COPD. Meanwhile we discussed novel therapeutic approaches in controlling lung inflammation and improving corticosteroid sensitivity among the steroid resistant patients with COPD.

Implications of the inflammatory response for the identification of biomarkers of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by both local and systemic inflammation. Because inflammation plays a critical role in the development, course and severity of COPD, inflammatory markers have the potential to improve the current diagnostic and prognostic approaches. Local inflammation in COPD is characterized by an infiltration of inflammatory cells, with an increased expression of cytokines, chemokines, enzymes, growth factors and adhesion molecules. Systemic low-grade inflammation is another common but nonspecific finding in COPD. Exacerbations of COPD are acute clinical events accompanied by an exaggerated inflammatory response. Future investigations in the field of COPD biomarkers should take into account different study designs and biochemical assays, disease course and duration, variations in symptom severity and timing of measurement.

The Role of Innate and Adaptive Immune Cells in the Immunopathogenesis of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a chronic and progressive inflammatory disease of the airways and lungs that results in limitations of continuous airflow and is caused by exposure to noxious gasses and particles. A major cause of morbidity and mortality in adults, COPD is a complex disease pathologically mediated by many inflammatory pathways. Macrophages, neutrophils, dendritic cells, and CD8+ T-lymphocytes are the key inflammatory cells involved in COPD. Recently, the non-coding small RNA, micro-RNA, have also been intensively investigated and evidence suggest that it plays a role in the pathogenesis of COPD. Here, we discuss the accumulated evidence that has since revealed the role of each inflammatory cell and their involvement in the immunopathogenesis of COPD. Mechanisms of steroid resistance in COPD will also be briefly discussed.

Regulation of YKL-40 expression by corticosteroids: effect on pro-inflammatory macrophages in vitro and its modulation in COPD in vivo

Background

Macrophages constitute a heterogeneous cell population with pro- (MΦ1) and anti-inflammatory (MΦ2) cells. The soluble chitinase-like-protein YKL-40 is expressed in macrophages and various other cell types, and has been linked to a variety of inflammatory diseases, including COPD. Dexamethasone strongly reduces YKL-40 expression in peripheral blood mononuclear cells (PBMC) in vitro. We hypothesized that: a) YKL-40 is differentially expressed by MΦ1 and MΦ2, b) is decreased by corticosteroids and c) that long-term treatment with inhaled corticosteroids (ICS) affects YKL-40 levels in serum and sputum of COPD patients.

Methods

Monocytes of healthy subjects were cultured in vitro for 7 days with either GM-CSF or M-CSF (for MΦ1 and MΦ2, respectively) and stimulated for 24 h with LPS, TNFα, or oncostatin M (OSM). MΦ1 and MΦ2 differentiation was assessed by measuring secretion of IL-12p40 and IL-10, respectively. YKL-40 expression in macrophages was measured by quantitative RT-PCR (qPCR) and ELISA; serum and sputum YKL-40 levels were analyzed by ELISA.

Results

Pro-inflammatory MΦ1 cells secreted significantly more YKL-40 than MΦ2, which was independent of stimulation with LPS, TNFα or OSM (p < 0.001) and confirmed by qPCR. Dexamethasone dose-dependently and significantly inhibited YKL-40 protein and mRNA levels in MΦ1. Serum YKL-40 levels of COPD patients were significantly higher than sputum YKL-40 levels but were not significantly changed by ICS treatment.

Conclusions

YKL-40 secretion from MΦ1 cells is higher than from MΦ2 cells and is unaffected by further stimulation with pro-inflammatory agents. Furthermore, YKL-40 release from cultured monocyte-derived macrophages is inhibited by dexamethasone especially in MΦ1, but ICS treatment did not change YKL-40 serum and sputum levels in COPD. These results indicate that YKL-40 expression could be used as a marker for MΦ1 macrophages in vitro, but not for monitoring the effect of ICS in COPD.

Trial registration

ClinicalTrials.gov, registration number: NCT00158847

Role of B Cell-Activating Factor in Chronic Obstructive Pulmonary Disease

RATIONALE

B cell-activating factor (BAFF) plays a major role in activation of B cells and in adaptive humoral immune responses. In chronic obstructive pulmonary disease (COPD), lymphoid follicles have been associated with disease severity, and overexpression of BAFF has been demonstrated within lymphoid follicles of patients with severe COPD.

OBJECTIVES

To investigate expression and localization of BAFF in the lungs of patients with COPD and to study the role of BAFF in COPD by antagonizing BAFF in a mouse model of chronic cigarette smoke (CS) exposure.

METHODS

We quantified and localized BAFF expression in lungs of never-smokers, smokers without COPD, and patients with COPD and in lungs of air- or CS-exposed mice by reverse-transcriptase polymerase chain reaction, ELISA, immunohistochemistry, and confocal imaging. Next, to investigate the role of BAFF in COPD, we antagonized BAFF by prophylactic or therapeutic administration of a soluble fusion protein of the BAFF-receptor, BAFFR-Fc, in mice exposed to air or CS for 24 weeks and evaluated several hallmarks of COPD and polarization of lung macrophages.

MEASUREMENTS AND MAIN RESULTS

BAFF expression was significantly increased in lungs of patients with COPD and CS-exposed mice. BAFF staining in lymphoid follicles was observed around B cells, CD4(+) cells, dendritic cells, follicular dendritic cells, and fibroblastic reticular cells. Prophylactic and therapeutic administration of BAFFR-Fc in mice reduced pulmonary B-cell numbers and prevented CS-induced formation of lymphoid follicles and increases in immunoglobulin levels. Interestingly, prophylactic BAFFR-Fc administration significantly attenuated pulmonary inflammation and destruction of alveolar walls. Moreover, antagonizing BAFF altered the phenotype of alveolar and interstitial macrophages.

CONCLUSIONS

BAFF is significantly increased in lungs of patients with COPD and is present around both immune and stromal cells within lymphoid follicles. Antagonizing BAFF in CS-exposed mice attenuates pulmonary inflammation and alveolar destruction.

Experimental progressive emphysema in BALB/cJ mice as a model for chronic alveolar destruction in humans

Emphysema, one of the major components of chronic obstructive pulmonary disease (COPD), is characterized by the progressive and irreversible loss of alveolar lung tissue. Even though >80% of COPD cases are associated with cigarette smoking, only a relatively small proportion of smokers develop emphysema, suggesting a potential role for genetic factors in determining individual susceptibility to emphysema. Although strain-dependent effects have been shown in animal models of emphysema, the molecular basis underlying this intrinsic susceptibility is not fully understood. In this present study, we investigated emphysema development using the elastase-induced experimental emphysema model in two commonly used mouse strains, C57BL/6J and BALB/cJ. The results demonstrate that mice with different genetic backgrounds show disparate susceptibility to the development of emphysema. BALB/cJ mice were found to be much more sensitive than C57BL/6J to elastase injury in both a dose-dependent and time-dependent manner, as measured by significantly higher mortality, greater body weight loss, greater decline in lung function, and a greater loss of alveolar tissue. The more susceptible BALB/cJ strain also showed the persistence of inflammatory cells in the lung, especially macrophages and lymphocytes. A comparative gene expression analysis following elastase-induced injury showed BALB/cJ mice had elevated levels of il17A mRNA and a number of classically (M1) and alternatively (M2) activated macrophage genes, whereas the C57BL/6J mice demonstrated augmented levels of interferon-γ. These findings suggest a possible role for these cellular and molecular mediators in modulating the severity of emphysema and highlight the possibility that they might contribute to the heterogeneity observed in clinical emphysema outcomes.

Therapeutic effects of LASSBio-596 in an elastase-induced mouse model of emphysema

Emphysema is an intractable pulmonary disease characterized by an inflammatory process of the airways and lung parenchyma and ongoing remodeling process in an attempt to restore lung structure. There is no effective drug therapy that regenerates lung tissue or prevents the progression of emphysema; current treatment is aimed at symptomatic relief. We hypothesized that LASSBio-596, a molecule with potent anti-inflammatory and immunomodulatory effects, might reduce pulmonary inflammation and remodeling and thus improve lung function in experimental emphysema. Emphysema was induced in BALB/c mice by intratracheal administration of porcine pancreatic elastase (0.1 IU) once weekly during 4 weeks. A control group received saline using the same protocol. After the last instillation of saline or elastase, dimethyl sulfoxide, or LASSBio-596 were administered intraperitoneally, once daily for 8 days. After 24 h, in elastase-induced emphysema animals, LASSBio-596 yielded: (1) decreased mean linear intercept, hyperinflation and collagen fiber content, (2) increased elastic fiber content, (3) reduced number of M1 macrophages, (4) decreased tumor necrosis factor-α, interleukin-1β, interleukin-6, and transforming growth factor-β protein levels in lung tissue, and increased vascular endothelial growth factor. These changes resulted in increased static lung elastance. In conclusion, LASSBio-596 therapy reduced lung inflammation, airspace enlargement, and small airway wall remodeling, thus improving lung function, in this animal model of elastase-induced emphysema.

Recruited alveolar macrophages, in response to airway epithelial-derived monocyte chemoattractant protein 1/CCl2, regulate airway inflammation and remodeling in allergic asthma

Although alveolar macrophages (AMs) from patients with asthma are known to be functionally different from those of healthy individuals, the mechanism by which this transformation occurs has not been fully elucidated in asthma. The goal of this study was to define the mechanisms that control AM phenotypic and functional transformation in response to acute allergic airway inflammation. The phenotype and functional characteristics of AMs obtained from human subjects with asthma after subsegmental bronchoprovocation with allergen was studied. Using macrophage-depleted mice, the role and trafficking of AM populations was determined using an acute allergic lung inflammation model. We observed that depletion of AMs in a mouse allergic asthma model attenuates Th2-type allergic lung inflammation and its consequent airway remodeling. In both human and mouse, endobronchial challenge with allergen induced a marked increase in monocyte chemotactic proteins (MCPs) in bronchoalveolar fluid, concomitant with the rapid appearance of a monocyte-derived population of AMs. Furthermore, airway allergen challenge of allergic subjects with mild asthma skewed the pattern of AM gene expression toward high levels of the receptor for MCP1 (CCR2/MCP1R) and expression of M2 phenotypic proteins, whereas most proinflammatory genes were highly suppressed. CCL2/MCP-1 gene expression was prominent in bronchial epithelial cells in a mouse allergic asthma model, and in vitro studies indicate that bronchial epithelial cells produced abundant MCP-1 in response to house dust mite allergen. Thus, our study indicates that bronchial allergen challenge induces the recruitment of blood monocytes along a chemotactic gradient generated by allergen-exposed bronchial epithelial cells.

Macrophages of M1 phenotype have properties that influence lung cancer cell progression

Stromal macrophages of different phenotypes can contribute to the expression of proteins that affects metastasis such as urokinase-type plasminogen activator (uPA), its receptor uPAR, and plasminogen activator inhibitor-1 (PAI-1), but knowledge of how essential their contribution is in comparison to the cancer cells in small cell lung cancer (SCLC) and lung squamous cell carcinoma (SCC) is lacking. The expression of uPA, uPAR, and PAI-1 and of the matrix metalloproteinases (MMP)-2 and MMP-9 were studied in human macrophages of M1 and M2 phenotype and compared to a lung SCC (NCI-H520) and a SCLC (NCI-H69) cell line. Effects of treatment with conditioned media (CM) from M1 and M2 macrophages on the expression of these genes in H520 and H69 cells as well as effects on the cell growth were investigated. In addition, data on the stromal macrophages immunoreactivity of uPAR, MMP-2, and MMP-9 in a few SCC and SCLC biopsies was included. uPAR, MMP-2, and MMP-9 were confirmed in stromal cells including macrophages in the SCC and SCLC biopsies. In vitro, both macrophage phenotypes expressed considerably higher mRNA levels of uPA, uPAR, PAI-1, and MMP-9 compared to the cancer cell lines, and regarding uPAR, the highest level was found in the M1 macrophage phenotype. Furthermore, M1 CM treatment not only induced an upregulation of PAI-1 in both H520 and H69 cells but also inhibited cell growth in both cell lines, giving M1 macrophages both tumor-promoting and tumor-killing potential.

Effects of different mesenchymal stromal cell sources and delivery routes in experimental emphysema

We sought to assess whether the effects of mesenchymal stromal cells (MSC) on lung inflammation and remodeling in experimental emphysema would differ according to MSC source and administration route. Emphysema was induced in C57BL/6 mice by intratracheal (IT) administration of porcine pancreatic elastase (0.1 UI) weekly for 1 month. After the last elastase instillation, saline or MSCs (1×105), isolated from either mouse bone marrow (BM), adipose tissue (AD) or lung tissue (L), were administered intravenously (IV) or IT. After 1 week, mice were euthanized. Regardless of administration route, MSCs from each source yielded: 1) decreased mean linear intercept, neutrophil infiltration, and cell apoptosis; 2) increased elastic fiber content; 3) reduced alveolar epithelial and endothelial cell damage; and 4) decreased keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8) and transforming growth factor-β levels in lung tissue. In contrast with IV, IT MSC administration further reduced alveolar hyperinflation (BM-MSC) and collagen fiber content (BM-MSC and L-MSC). Intravenous administration of BM- and AD-MSCs reduced the number of M1 macrophages and pulmonary hypertension on echocardiography, while increasing vascular endothelial growth factor. Only BM-MSCs (IV > IT) increased the number of M2 macrophages. In conclusion, different MSC sources and administration routes variably reduced elastase-induced lung damage, but IV administration of BM-MSCs resulted in better cardiovascular function and change of the macrophage phenotype from M1 to M2.

Role of alveolar macrophages in chronic obstructive pulmonary disease

Alveolar macrophages (AMs) represent a unique leukocyte population that responds to airborne irritants and microbes. This distinct microenvironment coordinates the maturation of long-lived AMs, which originate from fetal blood monocytes and self-renew through mechanisms dependent on GM-CSF and CSF-1 signaling. Peripheral blood monocytes can also replenish lung macrophages; however, this appears to occur in a stimuli specific manner. In addition to mounting an appropriate immune response during infection and injury, AMs actively coordinate the resolution of inflammation through efferocytosis of apoptotic cells. Any perturbation of this process can lead to deleterious responses. In chronic obstructive pulmonary disease (COPD), there is an accumulation of airway macrophages that do not conform to the classic M1/M2 dichotomy. There is also a skewed transcriptome profile that favors expression of wound-healing M2 markers, which is reflective of a deficiency to resolve inflammation. Endogenous mediators that can promote an imbalance in inhibitory M1 vs. healing M2 macrophages are discussed, as they are the plausible mechanisms underlying why AMs fail to effectively resolve inflammation and restore normal lung homeostasis in COPD.