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Chest Jun 2013In healthy individuals, billions of cells die by apoptosis each day. Clearance of these apoptotic cells, termed "efferocytosis," must be efficient to prevent secondary... (Review)
Review
In healthy individuals, billions of cells die by apoptosis each day. Clearance of these apoptotic cells, termed "efferocytosis," must be efficient to prevent secondary necrosis and the release of proinflammatory cell contents that disrupt tissue homeostasis and potentially foster autoimmunity. During inflammation, most apoptotic cells are cleared by macrophages; the efferocytic process actively induces a macrophage phenotype that favors tissue repair and suppression of inflammation. Several chronic lung diseases, particularly airways diseases such as chronic obstructive lung disease, asthma, and cystic fibrosis, are characterized by an increased lung burden of uningested apoptotic cells. Alveolar macrophages from individuals with these chronic airways diseases have decreased efferocytosis relative to alveolar macrophages from healthy subjects. These two findings have led to the hypothesis that impaired apoptotic cell clearance may contribute causally to sustained lung inflammation and that therapies to enhance efferocytosis might be beneficial. This review of the English-language scientific literature (2006 to mid-2012) explains how such existing therapies as corticosteroids, statins, and macrolides may act in part by augmenting apoptotic cell clearance. However, efferocytosis can also impede host defenses against lung infection. Thus, determining whether novel therapies to augment efferocytosis should be developed and in whom they should be used lies at the heart of efforts to differentiate specific phenotypes within complex chronic lung diseases to provide appropriately personalized therapies.
Topics: Apoptosis; Homeostasis; Humans; Lung Diseases; Macrophages, Alveolar; Phagocytosis; Phenotype; Precision Medicine; Smoking
PubMed: 23732585
DOI: 10.1378/chest.12-2413 -
European Respiratory Review : An... Sep 2015Bacterial and viral infections (exacerbations) are particularly problematic in those with underlying respiratory disease, including post-viral infection, asthma, chronic... (Review)
Review
Bacterial and viral infections (exacerbations) are particularly problematic in those with underlying respiratory disease, including post-viral infection, asthma, chronic obstructive pulmonary disease and pulmonary fibrosis. Patients experiencing exacerbations tend to be at the more severe end of the disease spectrum and are often difficult to treat. Most of the unmet medical need remains in this patient group. Airway macrophages are one of the first cell populations to encounter airborne pathogens and, in health, exist in a state of reduced responsiveness due to interactions with the respiratory epithelium and specific factors found in the airway lumen. Granulocyte-macrophage colony-stimulating factor, interleukin-10, transforming growth factor-β, surfactant proteins and signalling via the CD200 receptor, for example, all raise the threshold above which airway macrophages can be activated. We highlight that following severe respiratory inflammation, the airspace microenvironment does not automatically re-set to baseline and may leave airway macrophages more restrained than they were at the outset. This excessive restraint is mediated in part by the clearance of apoptotic cells and components of extracellular matrix. This implies that one strategy to combat respiratory exacerbations would be to retune airway macrophage responsiveness to allow earlier bacterial recognition.
Topics: Adaptation, Physiological; Animals; Cellular Microenvironment; Host-Pathogen Interactions; Humans; Inflammation Mediators; Lung; Macrophage Activation; Macrophages, Alveolar; Phenotype; Pneumonia, Bacterial; Pneumonia, Viral; Risk Assessment; Risk Factors; Signal Transduction
PubMed: 26324813
DOI: 10.1183/16000617.0030-2015 -
Life Sciences Oct 2021Respiratory disorders are a prominent component of Gulf War Illness. Although much of the underlying mechanisms of Gulf War Illness remain undefined, chronic immune...
AIMS
Respiratory disorders are a prominent component of Gulf War Illness. Although much of the underlying mechanisms of Gulf War Illness remain undefined, chronic immune dysfunction is a consistent feature of this multi-symptomatic, multi-organ disorder. Alveolar macrophages represent the predominant mononuclear phagocytes of the pulmonary mucosa, orchestrating the host response to pathogens and environmental stimuli. Herein, we sought to characterize the innate immune response of the pulmonary mucosa, with a focus on macrophages, to experimental respiratory exposure to two putative Gulf War Toxins (GWTs).
MATERIALS AND METHODS
Utilizing commercially available instrumentation, we evaluated the effect of aerosolized exposure to the pesticide malathion and diesel exhaust particulate (DEP) on the immune composition and inflammatory response of the lung in FVB/N mice using multiparametric spectral cytometry, cytokine analysis, and histology.
KEY FINDINGS
Aerosolized GWTs induced gross pulmonary pathology with transient recruitment of neutrophils and sustained accumulation of alveolar macrophages to the lung for up to two weeks after exposure cessation. High-dimensional cytometry and unbiased computational analysis identified novel myeloid subsets recruited to the lung post-exposure driven by an influx of peripheral monocyte-derived progenitors. DEP and malathion, either alone or in combination, induced soluble mediators in bronchoalveolar lavage indicative of oxidative stress (PGFα), inflammation (LTB, TNFα, IL-12), and immunosuppression (IL-10), that were sustained or increased two weeks after exposures concluded.
SIGNIFICANCE
These findings indicate that macrophage accumulation and pulmonary inflammation induced by GWTs continue in the absence of toxin exposure and may contribute to the immunopathology of respiratory Gulf War Illness.
Topics: Animals; Bronchoalveolar Lavage; Female; Gulf War; Humans; Macrophages, Alveolar; Male; Mice; Pneumonia; Vehicle Emissions
PubMed: 34293400
DOI: 10.1016/j.lfs.2021.119839 -
BMC Immunology Oct 2012Alveolar macrophages are one of the first lines of defence against invading pathogens and play a central role in modulating both the innate and acquired immune systems....
BACKGROUND
Alveolar macrophages are one of the first lines of defence against invading pathogens and play a central role in modulating both the innate and acquired immune systems. By responding to endogenous stimuli within the lung, alveolar macrophages contribute towards the regulation of the local inflammatory microenvironment, the initiation of wound healing and the pathogenesis of viral and bacterial infections. Despite the availability of protocols for isolating primary alveolar macrophages from the lung these cells remain recalcitrant to expansion in-vitro and therefore surrogate cell types, such as monocyte derived macrophages and phorbol ester-differentiated cell lines (e.g. U937, THP-1, HL60) are frequently used to model macrophage function.
METHODS
The availability of high throughput gene expression technologies for accurate quantification of transcript levels enables the re-evaluation of these surrogate cell types for use as cellular models of the alveolar macrophage. Utilising high-throughput TaqMan arrays and focussing on dynamically regulated families of integral membrane proteins, we explore the similarities and differences in G-protein coupled receptor (GPCR) and ion channel expression in alveolar macrophages and their widely used surrogates.
RESULTS
The complete non-sensory GPCR and ion channel transcriptome is described for primary alveolar macrophages and macrophage surrogates. The expression of numerous GPCRs and ion channels whose expression were hitherto not described in human alveolar macrophages are compared across primary macrophages and commonly used macrophage cell models. Several membrane proteins known to have critical roles in regulating macrophage function, including CXCR6, CCR8 and TRPV4, were found to be highly expressed in macrophages but not expressed in PMA-differentiated surrogates.
CONCLUSIONS
The data described in this report provides insight into the appropriate choice of cell models for investigating macrophage biology and highlights the importance of confirming experimental data in primary alveolar macrophages.
Topics: Cells, Cultured; Cluster Analysis; Gene Expression Profiling; Gene Expression Regulation; Humans; Ion Channels; Macrophages, Alveolar; Oligonucleotide Array Sequence Analysis; Receptors, G-Protein-Coupled; Reproducibility of Results; Tetradecanoylphorbol Acetate
PubMed: 23102269
DOI: 10.1186/1471-2172-13-57 -
Infection and Immunity Mar 2015Although the importance of alveolar macrophages for host immunity during early Streptococcus pneumoniae lung infection is well established, the contribution and relative...
Although the importance of alveolar macrophages for host immunity during early Streptococcus pneumoniae lung infection is well established, the contribution and relative importance of other innate immunity mechanisms and of bacterial factors are less clear. We have used a murine model of S. pneumoniae early lung infection with wild-type, unencapsulated, and para-amino benzoic acid auxotroph mutant TIGR4 strains to assess the effects of inoculum size, bacterial replication, capsule, and alveolar macrophage-dependent and -independent clearance mechanisms on bacterial persistence within the lungs. Alveolar macrophage-dependent and -independent (calculated indirectly) clearance half-lives and bacterial replication doubling times were estimated using a mathematical model. In this model, after infection with a high-dose inoculum of encapsulated S. pneumoniae, alveolar macrophage-independent clearance mechanisms were dominant, with a clearance half-life of 24 min compared to 135 min for alveolar macrophage-dependent clearance. In addition, after a high-dose inoculum, successful lung infection required rapid bacterial replication, with an estimated S. pneumoniae doubling time of 16 min. The capsule had wide effects on early lung clearance mechanisms, with reduced half-lives of 14 min for alveolar macrophage-independent and 31 min for alveolar macrophage-dependent clearance of unencapsulated bacteria. In contrast, with a lower-dose inoculum, the bacterial doubling time increased to 56 min and the S. pneumoniae alveolar macrophage-dependent clearance half-life improved to 42 min and was largely unaffected by the capsule. These data demonstrate the large effects of bacterial factors (inoculum size, the capsule, and rapid replication) and alveolar macrophage-independent clearance mechanisms during early lung infection with S. pneumoniae.
Topics: 4-Aminobenzoic Acid; Animals; Bacterial Capsules; Bacterial Load; Female; Half-Life; Immunity, Innate; Lung; Macrophages, Alveolar; Male; Mice; Mice, Inbred Strains; Models, Statistical; Mutation; Phagocytosis; Pneumonia, Pneumococcal; Severity of Illness Index; Streptococcus pneumoniae; Time Factors
PubMed: 25583525
DOI: 10.1128/IAI.02788-14 -
Frontiers in Immunology 2021Lung diseases are an increasing global health burden affecting millions of people worldwide. Only a few new inhaled medicines have reached the market in the last 30...
INTRODUCTION
Lung diseases are an increasing global health burden affecting millions of people worldwide. Only a few new inhaled medicines have reached the market in the last 30 years, in part due to foamy alveolar macrophage (FAM) responses observed in pre-clinical rat studies. The induction mechanism and signaling pathways involved in the development of highly vacuolated 'foamy' phenotype is not known. Furthermore, it has not been determined if these observations are adaptive or adverse responses.
AIM
To determine if high content image analysis techniques can distinguish between alveolar macrophage activation (LPS/IFN-γ activated and IL-4 activated macrophages) and if this could be applied to understanding the generation of 'foamy' macrophage phenotypes.
METHODS
NR8383 rat alveolar macrophages were stimulated with a mix of cytokines (LPS/IFN-γ or IL-4) for 24 h. The cells were further exposed to FAM inducing-compounds amiodarone and staurosporine. Following 24 h incubation, phagocytosis and lipid accumulation were measured using flow cytometry and high content image analysis techniques. The alveolar macrophages responses after exposure to cytokines were assessed by evaluation: (i) cell surface and biochemical markers such as: nitric oxide production, arginase-1 activity and MRC-1 receptor expression (ii) cellular morphology (iii) cellular functionality (phagocytic activity and lipids accumulation).
RESULTS
Macrophages activated with LPS/IFN-γ showed distinct morphological (increased vacuolation) features and functionality (increased lipidosis, decreased phagocytic activity). Foamy macrophage phenotypes induced by amiodarone also displayed characteristics of proinflammatory macrophages (significantly increased nitric oxide production, increased vacuolation and lipidosis and decreased phagocytosis). In contrast, staurosporine treatment resulted in increased NO production, as well as arginase-1 activity.
CONCLUSION
High content image analysis was able to determine distinct differences in morphology between non-activated and LPS/IFN-γ activated macrophages, characterized by increased vacuolation and lipidosis. When exposed to compounds that induce a FAM phenotype, healthy non-activated macrophages displayed proinflammatory (amiodarone) or pro-apoptotic (staurosporine) characteristics but these responses were independent of a change in activation status. This technique could be applied in early drug discovery safety assessment to identify immune responses earlier and increase the understanding of alveolar macrophage responses to new molecules challenge in development of new inhalation therapies, which in turn will enhance decision-making in an early safety assessment of novel drug candidates.
Topics: Biomarkers; Cells, Cultured; Cytokines; Foam Cells; Immunophenotyping; Lipid Metabolism; Macrophage Activation; Macrophages; Macrophages, Alveolar; Molecular Imaging; Nitric Oxide; Phagocytosis
PubMed: 34539620
DOI: 10.3389/fimmu.2021.611280 -
The Journal of Veterinary Medical... Nov 2017Macrophage polarization is a process by which macrophages acquire a distinct phenotypic and functional profile in response to microenvironmental signals. The classically...
Macrophage polarization is a process by which macrophages acquire a distinct phenotypic and functional profile in response to microenvironmental signals. The classically and alternatively activated (M1 and M2, respectively) macrophage phenotypes are defined by the specific molecular characteristics induced in response to prototypic pro- and anti-inflammatory cues. In this study, we used LPS/IFN-γ and IL-4 to stimulate porcine alveolar macrophages (PAMs) in vitro and investigated the expression changes of several novel markers during macrophage polarization. Notably, we found that LPS/IFN-γ-stimulated PAMs express prototypical M1 molecules, whereas IL-4-stimulated PAMs express M2 molecules. We also demonstrated that replication of the highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) strain HuN4 was effectively suppressed in LPS/IFN-γ-stimulated M1 PAMs (M1 type), but not IL-4 stimulated M2 PAMs. However, this was not observed with the classic, less pathogenic CH-1a strain. Moreover, we found that M2 marker expression gradually increased after PAM infection with PRRSV, whereas no significant changes were found with M1 marker expression, suggesting that PRRSV infection may skew macrophage polarization towards an M2 phenotype. Finally, we found that anti-viral cytokine expression was significantly higher in M1 macrophages than in M2 macrophages or nonpolarized controls. In summary, our results show that PRRSV replication was significantly impaired in M1 PAMs, which may serve as a foundation for further understanding of the dynamic phenotypic changes during macrophage polarization and their effects on viral infection.
Topics: Animals; Cells, Cultured; Cytokines; Interferon-gamma; Interleukin-4; Lipopolysaccharides; Macrophage Activation; Macrophages, Alveolar; Phenotype; Porcine respiratory and reproductive syndrome virus; Swine; Virus Replication
PubMed: 28924090
DOI: 10.1292/jvms.17-0258 -
Journal of Cellular and Molecular... Feb 2022The role of alveolar macrophages (AMs) in chronic obstructive pulmonary disease is unclear. We characterized the function of AMs in rats chronically exposed to biomass...
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.
Topics: Animals; Biomass; Lung; Macrophage Activation; Macrophages, Alveolar; Male; Particulate Matter; Rats; Rats, Sprague-Dawley
PubMed: 34994052
DOI: 10.1111/jcmm.17169 -
JCI Insight Sep 2021Macrophage activation syndrome (MAS) is a life-threatening cytokine storm complicating systemic juvenile idiopathic arthritis (SJIA) driven by IFN-γ. SJIA and MAS are...
Macrophage activation syndrome (MAS) is a life-threatening cytokine storm complicating systemic juvenile idiopathic arthritis (SJIA) driven by IFN-γ. SJIA and MAS are also associated with an unexplained emerging inflammatory lung disease (SJIA-LD), with our recent work supporting pulmonary activation of IFN-γ pathways pathologically linking SJIA-LD and MAS. Our objective was to mechanistically define the potentially novel observation of pulmonary inflammation in the TLR9 mouse model of MAS. In acute MAS, lungs exhibit mild but diffuse CD4-predominant, perivascular interstitial inflammation with elevated IFN-γ, IFN-induced chemokines, and alveolar macrophage (AMϕ) expression of IFN-γ-induced genes. Single-cell RNA sequencing confirmed IFN-driven transcriptional changes across lung cell types with myeloid expansion and detection of MAS-specific macrophage populations. Systemic MAS resolution was associated with increased AMϕ and interstitial lymphocytic infiltration. AMϕ transcriptomic analysis confirmed IFN-γ-induced proinflammatory polarization during acute MAS, which switches toward an antiinflammatory phenotype after systemic MAS resolution. Interestingly, recurrent MAS led to increased alveolar inflammation and lung injury, and it reset AMϕ polarization toward a proinflammatory state. Furthermore, in mice bearing macrophages insensitive to IFN-γ, both systemic features of MAS and pulmonary inflammation were attenuated. These findings demonstrate that experimental MAS induces IFN-γ-driven pulmonary inflammation replicating key features of SJIA-LD and provides a model system for testing potentially novel treatments directed toward SJIA-LD.
Topics: Animals; Chemokines; Disease Models, Animal; Female; Gene Expression Regulation; Interferon-gamma; Macrophage Activation; Macrophage Activation Syndrome; Macrophages, Alveolar; Mice; Mice, Inbred C57BL; Pneumonia; RNA
PubMed: 34314387
DOI: 10.1172/jci.insight.147593 -
Oncotarget Dec 2016To study the impact of autophagy on alveolar macrophage apoptosis and its mechanism in the early stages of hypoxia, we established a cell hypoxia-reoxygenation model and...
To study the impact of autophagy on alveolar macrophage apoptosis and its mechanism in the early stages of hypoxia, we established a cell hypoxia-reoxygenation model and orthotopic left lung ischemia-reperfusion model. Rat alveolar macrophages stably expressing RFP-LC3 were treated with autophagy inhibitor (3-methyladenine, 3-MA) or autophagy promoter (rapamycin), followed by hypoxia-reoxygenation treatment 2 h, 4 h or 6 h later. Twenty Sprague-Dawley male rats were randomly divided into four different groups: no blocking of left lung hilum (model group), left lung hilum blocked for 1h with DMSO lavage (control group), left lung hilum blocked for 1 h with 100 ml/kg 3-MA (5 μmol/L) lavage (3-MA group), and left lung hilum blocked for 1 h with 100 ml/kg rapamycin (250 nmol/L) lavage (rapamycin group). Rapamycin decreased the unfolded protein response, which reduced endoplasmic reticulum stress-mediated apoptosis in the presence of oxygen deficiency. Rapamycin increased superoxide dismutase activities and decreased malondialdehyde levels, whereas 3-MA decreased superoxide dismutase activities and increased malondialdehyde levels. Thus, autophagy decreases alveolar macrophage apoptosis by attenuating endoplasmic reticulum stress and oxidative stress in the early stage of hypoxia in vitro and in vivo. This could represent a new approach to protecting against lung ischemia-reperfusion injury.
Topics: Adenine; Animals; Apoptosis; Autophagy; Caspase 3; Cell Hypoxia; Cells, Cultured; Endoplasmic Reticulum Stress; Macrophages, Alveolar; Male; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Sirolimus; Superoxide Dismutase
PubMed: 27888631
DOI: 10.18632/oncotarget.13560