Distinct Properties of Human M-CSF and GM-CSF Monocyte-Derived Macrophages to Simulate Pathological Lung Conditions In Vitro: Application to Systemic and Inflammatory Disorders with Pulmonary Involvement

Emerging diagnostic and therapeutic challenges for skin fibrosis in systemic sclerosis

Systemic sclerosis (also called scleroderma, SSc) is a chronic autoimmune disorder characterized by excessive collagen deposition leading to skin fibrosis and various internal organ manifestations. The emergent diagnostics and therapeutic strategies for scleroderma focus on early detection and targeted interventions to improve patient outcomes and quality of life. Diagnostics for SSc have evolved significantly in recent years, driven by advancements in serological markers and imaging techniques. Autoantibody profiling, especially antinuclear antibodies (ANA) and specific scleroderma-associated autoantibodies, aids in identifying subsets of scleroderma and predicting disease progression. Furthermore, novel imaging modalities, such as high-frequency ultrasonography and optical coherence tomography, enable early detection of skin fibrosis and internal organ involvement, enhancing the diagnostic precision and allowing for tailored management. Therapeutic strategies for SSc are multifaceted, targeting immune dysregulation, vascular abnormalities, and fibrotic processes. Emerging biologic agents have shown promise in clinical trials, including monoclonal antibodies directed against key cytokines involved in fibrosis, such as transforming growth factor-β (TGF-β) and interleukin-6 (IL-6). Additionally, small-molecule inhibitors that disrupt fibrotic pathways, like tyrosine kinase inhibitors, have exhibited potential in limiting collagen deposition and preventing disease progression. Stem cell therapy, cell ablation and gene editing techniques hold great potential in regenerating damaged tissue and halting fibrotic processes. Early intervention remains crucial in managing SSc, as irreversible tissue damage often occurs in advanced stages. Novel diagnostic methods, such as biomarkers and gene expression profiling, are being explored to identify individuals at high risk for developing progressive severe disease and intervene proactively. Furthermore, patient-tailored therapeutic approaches, employing a combination of immunosuppressive agents and targeted anti-fibrotic therapies, are being investigated to improve treatment efficacy while minimizing adverse effects. The emergent diagnostics and therapeutic strategies in scleroderma are transforming the management of this challenging disease. Nevertheless, ongoing research and clinical trials are needed to optimize the efficacy and safety of these novel approaches in the complex and diverse spectrum of SSc manifestations.

Mycobacterium tuberculosis impairs human memory CD4+ T cell recognition of M2 but not M1-like macrophages

Direct recognition of Mycobacterium tuberculosis (Mtb)-infected cells is required for protection by CD4+ T cells. While impaired T cell recognition of Mtb-infected macrophages was demonstrated in mice, data are lacking for humans. Using T cells and monocyte-derived macrophages (MDMs) from individuals with latent Mtb infection (LTBI), we quantified the frequency of memory CD4+ T cell activation in response to autologous MDMs infected with virulent Mtb. We observed robust T cell activation in response to Mtb infection of M1-like macrophages differentiated using GM-CSF, while M2-like macrophages differentiated using M-CSF were poorly recognized. However, non-infected GM-CSF and M-CSF MDMs loaded with exogenous antigens elicited similar CD4+ T cell activation. IL-10 was preferentially secreted by infected M-CSF MDMs, and neutralization improved T cell activation. These results suggest that preferential infection of macrophages with an M2-like phenotype limits T cell-mediated protection against Mtb. Vaccine development should focus on T cell recognition of Mtb-infected macrophages.

Regeneration of the cerebral cortex by direct chemical reprogramming of macrophages into neuronal cells in acute ischemic stroke

Theoretically, direct chemical reprogramming of somatic cells into neurons in the infarct area represents a promising regenerative therapy for ischemic stroke. Previous studies have reported that human fibroblasts and astrocytes transdifferentiate into neuronal cells in the presence of small molecules without introducing ectopic transgenes. However, the optimal combination of small molecules for the transdifferentiation of macrophages into neurons has not yet been determined. The authors hypothesized that a combination of small molecules could induce the transdifferentiation of monocyte-derived macrophages into neurons and that the administration of this combination may be a regenerative therapy for ischemic stroke because monocytes and macrophages are directly involved in the ischemic area. Transcriptomes and morphologies of the cells were compared before and after stimulation using RNA sequencing and immunofluorescence staining. Microscopic analyses were also performed to identify cell markers and evaluate functional recovery by blinded examination following the administration of small molecules after ischemic stroke in CB-17 mice. In this study, an essential combination of six small molecules [CHIR99021, Dorsomorphin, Forskolin, isoxazole-9 (ISX-9), Y27632, and DB2313] that transdifferentiated monocyte-derived macrophages into neurons in vitro was identified. Moreover, administration of six small molecules after cerebral ischemia in model animals generated a new neuronal layer in the infarct cortex by converting macrophages into neuronal cells, ultimately improving neurological function. These results suggest that altering the transdifferentiation of monocyte-derived macrophages by the small molecules to adjust their adaptive response will facilitate the development of regenerative therapies for ischemic stroke.

The temporal characteristics of the disruption of gut microbiota, serum metabolome, and cytokines by silica exposure in wistar rats

Silicosis is one of the most frequent, rapidly developing, and lethal types of pneumoconiosis. However, our understanding of the underlying mechanisms of its pathogenesis and progress remains unclear. We investigated the fundamental processes of silicosis incidence and progression using a combination of lung function testing, histopathology, 16 S rRNA, untargeted metabolomics, and cytokine chips at different exposure times (4 or 8 weeks). The results show that silica exposure damages lung tissue reduces lung function, and increases with time. Cytokines with time-specific properties were found in lung lavage fluid: IFN-γ (4 weeks; P＜0.05), TNF-α, M-CSF, GM-CSF (8 weeks; P＜0.01). In addition, silica exposure for different periods interferes to varying degrees with the metabolism of lipids. The composition of the intestinal microbiota changed with increasing exposure time and there were time-specific: Allobaculum, Turicibacter、Jeotgalicoccu、Coprococcus 1 (4 weeks; P＜0.05), Ruminococcaceae NK4A214 group、Ruminiclostridium 5 (8 weeks; P＜0.05). We found strong associations between cytokines, gut microbiota changes, and metabolic disturbances at different exposure times. These results suggest that time-specific changes in crosstalk among cytokines, the gut microbiota, and metabolites may be a potential mechanism for silica-induced lung injury.

Influence of the irradiated pulmonary microenvironment on macrophage and T cell dynamics

BACKGROUND

The lung is sensitive to radiation, increasing normal tissue toxicity risks following radiation therapy. Adverse outcomes include pneumonitis and pulmonary fibrosis, which result from dysregulated intercellular communication within the pulmonary microenvironment. Although macrophages are implicated in these pathogenic outcomes, the impact of their microenvironment is not well understood.

MATERIALS AND METHODS

C57BL/6J mice received 6Gyx5 irradiation to the right lung. Macrophage and T cell dynamics were investigated in ipsilateral right lungs, contralateral left lungs and non-irradiated control lungs 4-26wk post exposure. Lungs were evaluated by flow cytometry, histology and proteomics.

RESULTS

Following uni-lung irradiation, focal regions of macrophage accumulation were noted in both lungs by 8wk, however by 26wk fibrotic lesions were observed only in ipsilateral lungs. Infiltrating and alveolar macrophages populations expanded in both lungs, however transitional CD11b + alveolar macrophages persisted only in ipsilateral lungs and expressed lower CD206. Concurrently, arginase-1 + macrophages accumulated in ipsilateral but not contralateral lungs at 8 and 26wk post exposure, while CD206 + macrophages were absent from these accumulations. While radiation expanded CD8 + T cells in both lungs, T regulatory cells only increased in ipsilateral lungs. Unbiased proteomics analysis of immune cells revealed a substantial number of differentially expressed proteins in ipsilateral lungs when compared to contralateral lungs and both differed from non-irradiated controls.

CONCLUSIONS

Pulmonary macrophage and T cell dynamics are impacted by the microenvironmental conditions that develop following radiation exposure, both locally and systemically. While macrophages and T cells infiltrate and expand in both lungs, they diverge phenotypically depending on their environment.

Towards an artificial human lung: modelling organ-like complexity to aid mechanistic understanding

Respiratory diseases account for over 5 million deaths yearly and are a huge burden to healthcare systems worldwide. Murine models have been of paramount importance to decode human lung biology in vivo, but their genetic, anatomical, physiological and immunological differences with humans significantly hamper successful translation of research into clinical practice. Thus, to clearly understand human lung physiology, development, homeostasis and mechanistic dysregulation that may lead to disease, it is essential to develop models that accurately recreate the extraordinary complexity of the human pulmonary architecture and biology. Recent advances in micro-engineering technology and tissue engineering have allowed the development of more sophisticated models intending to bridge the gap between the native lung and its replicates in vitro Alongside advanced culture techniques, remarkable technological growth in downstream analyses has significantly increased the predictive power of human biology-based in vitro models by allowing capture and quantification of complex signals. Refined integrated multi-omics readouts could lead to an acceleration of the translational pipeline from in vitro experimental settings to drug development and clinical testing in the future. This review highlights the range and complexity of state-of-the-art lung models for different areas of the respiratory system, from nasal to large airways, small airways and alveoli, with consideration of various aspects of disease states and their potential applications, including pre-clinical drug testing. We explore how development of optimised physiologically relevant in vitro human lung models could accelerate the identification of novel therapeutics with increased potential to translate successfully from the bench to the patient's bedside.

Exercise-induced specialized proresolving mediators stimulate AMPK phosphorylation to promote mitochondrial respiration in macrophages

OBJECTIVE

Physical activity has been shown to reduce the risk of CVD mortality in large-cohort longitudinal studies; however, the mechanisms underpinning the beneficial effects of exercise remain incompletely understood. Emerging data suggest that the risk reducing effect of exercise extends beyond changes in traditional CVD risk factors alone and involves alterations in immunity and reductions in inflammatory mediator production. Our study aimed to determine whether exercise-enhanced production of proresolving lipid mediators contribute to alterations in macrophage intermediary metabolism, which may contribute to the anti-inflammatory effects of exercise.

METHODS

Changes in lipid mediators and macrophage metabolism were assessed in C57Bl/6 mice following 4 weeks of voluntary exercise training. To investigate whether exercise-stimulated upregulation of specialized proresolving lipid mediators (SPMs) was sufficient to enhance mitochondrial respiration, both macrophages from control mice and human donors were incubated in vitro with SPMs and mitochondrial respiratory parameters were measured using extracellular flux analysis. Compound-C, an ATP-competitive inhibitor of AMPK kinase activity, was used to investigate the role of AMPK activity in SPM-induced mitochondrial metabolism. To assess the in vivo contribution of 5-lipoxygenase in AMPK activation and exercise-induced mitochondrial metabolism in macrophages, Alox5^-/- mice were also subjected to exercise training.

RESULTS

Four weeks of exercise training enhanced proresolving lipid mediator production, while also stimulating the catabolism of inflammatory lipid mediators (e.g., leukotrienes and prostaglandins). This shift in lipid mediator balance following exercise was associated with increased macrophage mitochondrial metabolism. We also find that treating human and murine macrophages in vitro with proresolving lipid mediators enhances mitochondrial respiratory parameters. The proresolving lipid mediators RvD1, RvE1, and MaR1, but not RvD2, stimulated mitochondrial respiration through an AMPK-dependent signaling mechanism. Additionally, in a subset of macrophages, exercise-induced mitochondrial activity in vivo was dependent upon 5-lipoxygenase activity.

CONCLUSION

Collectively, these results suggest that exercise stimulates proresolving lipid mediator biosynthesis and mitochondrial metabolism in macrophages via AMPK, which might contribute to the anti-inflammatory and CVD risk reducing effect of exercise.

The Human Myofibroblast Marker Xylosyltransferase-I: A New Indicator for Macrophage Polarization

Chronic inflammation and excessive synthesis of extracellular matrix components, such as proteoglycans (PG), by fibroblast- or macrophage-derived myofibroblasts are the hallmarks of fibrotic diseases, including systemic sclerosis (SSc). Human xylosyltransferase-I (XT-I), which is encoded by the gene XYLT1, is the key enzyme that is involved in PG biosynthesis. Increased cellular XYLT1 expression and serum XT-I activity were measured in SSc. Nothing is known so far about the regulation of XT-I in immune cells, and their contribution to the increase in measurable serum XT-I activity. We utilized an in vitro model, with primary human CD14+CD16+ monocyte-derived macrophages (MΦ), in order to investigate the role of macrophage polarization on XT-I regulation. The MΦ generated were polarized towards two macrophage phenotypes that were associated with SSc, which were classified as classical pro-inflammatory (M1-like), and alternative pro-fibrotic (M2-like) MΦ. The fully characterized M1- and M2-like MΦ cultures showed differential XT-I gene and protein expressions. The fibrotic M2-like MΦ cultures exhibited higher XT-I secretion, as well as increased expression of myofibroblast marker α-smooth muscle actin, indicating the onset of macrophage-to-myofibroblast transition (MMT). Thus, we identified XT-I as a novel macrophage polarization marker for in vitro generated M1- and M2-like MΦ subtypes, and broadened the view of XT-I as a myofibroblast marker in the process of MMT.

Metabolites and growth factors produced by airway epithelial cells induce tolerance in macrophages

Macrophages play a role in preventing inflammation in the respiratory tract. To investigate the mechanisms that lead to tolerance in macrophages, we examined the crosstalk between airway epithelial cells (AECs) and macrophages using a 2D coculture model. Culture of macrophages with AECs led to a significant inhibition of LPS induced pro-inflammatory responses. More importantly, AECs induced the secretion of TGF-β and IL-10 from macrophages even in the absence of LPS stimulation. In addition, the expression of inhibitory molecule, CD200R was also upregulated on AEC exposed macrophages. Furthermore, the AECs exposed macrophages induced significantly increased level of T regulatory cells. Investigation into the possible mechanisms indicated that a combination of growth factor, G-CSF, and metabolites, Kynurenine and lactic acid produced by AECs is responsible for inducing tolerance in macrophages. Interestingly, all these molecules had differential effect on macrophages with G-CSF inducing TGF-β, Kynurenine elevating IL-10, and lactic acid upregulating CD200R. Furthermore, a cocktail of these factors/metabolites induced similar changes in macrophages as AEC exposure. Altogether, these data identify factors secreted by AECs that enhance tolerance in the respiratory tract. These mediators thus have the potential to be used for therapeutic purposes to modulate respiratory inflammation following local viral infections and lung diseases.

Recent Insights Into the Role of Macrophages in Acute Gout

Gout is a common type of inflammatory arthritis characterized by the presence of monosodium urate crystals (MSU) in the joints. Macrophages are believed to be involved in gout flares. It has long been recognized that resident macrophage and monocyte derived macrophages are distinct subsets and there have been attempts to investigate their roles in acute gout, respectively. Previous studies revealed that resident macrophages initiate and drive the inflammation, while monocyte derived macrophages differentiated into M1-like macrophages in response to MSU crystals. With the advancement of technologies, subpopulations of synovial resident macrophages have been defined with the characteristics more accurately described. Resident macrophages in the synovial lining layer showed an anti-inflammatory effect in rheumatoid arthritis, but specific Trpv4 depletion of them reduced MSU crystals induced murine arthritis. CD14+ monocytes in the synovial fluid from patients with gout exhibit phenotypes of anti-inflammatory as well as pro-inflammatory characteristics. Here, we review the main aspects of macrophages in the initiation and resolution of acute gout and try to clarify the specific role of each subpopulation. Building a reliable diagram of the effect of monocytes and macrophages during MSU crystals induced arthritis will bring us closer to targeting macrophages for improving the management of gout.

Membrane-Tethered Mucin 1 Is Stimulated by Interferon and Virus Infection in Multiple Cell Types and Inhibits Influenza A Virus Infection in Human Airway Epithelium

Influenza A virus (IAV) causes significant morbidity and mortality in the human population. Tethered mucin 1 (MUC1) is highly expressed in airway epithelium, the primary site of IAV replication, and also by other cell types that influence IAV infection, including macrophages. MUC1 has the potential to influence infection dynamics through physical interactions and/or signaling activity, yet MUC1 modulation and its impact during viral pathogenesis remain unclear. Thus, we investigated MUC1-IAV interactions in an in vitro model of human airway epithelium (HAE). Our data indicate that a recombinant IAV hemagglutinin (H3) and H3N2 virus can bind endogenous HAE MUC1. Notably, infection of HAE with H1N1 or H3N2 IAV strains does not trigger MUC1 shedding but instead stimulates an increase in cell-associated MUC1 protein. We observed a similar increase after type I or III interferon (IFN) stimulation; however, inhibition of IFN signaling during H1N1 infection only partially abrogated this increase, indicating that multiple soluble factors contribute to MUC1 upregulation during the antiviral response. In addition to HAE, primary human monocyte-derived macrophages also upregulated MUC1 protein in response to IFN treatment and conditioned media from IAV-infected HAE. Then, to determine the impact of MUC1 on IAV pathogenesis, we developed HAE genetically depleted of MUC1 and found that MUC1 knockout cultures exhibited enhanced viral growth compared to control cultures for several IAV strains. Together, our data support a model whereby MUC1 inhibits productive uptake of IAV in HAE. Infection then stimulates MUC1 expression on multiple cell types through IFN-dependent and -independent mechanisms that further impact infection dynamics.

Genetic Screening of Candida albicans Inactivation Mutants Identifies New Genes Involved in Macrophage-Fungal Cell Interactions

Candida albicans, an important fungal pathogen of humans, displays different morphologies, such as yeast, pseudo-hyphae and hyphae, which are recognized unequally by phagocytic cells of the innate immune response. Once C. albicans cells invade host tissues, immune cells such as macrophages are attracted to the site of infection and activated to recognize, engulf and kill the pathogen. We have investigated this fungal cell-macrophage interface by using high-throughput screening of the C. albicans GRACE library to identify genes that can influence this interaction and modify the kinetics of engulfment. Compared with the wild-type (WT) strain, we identified generally faster rates of engulfment for those fungal strains with constitutive pseudo-hyphal and hyphal phenotypes, whereas yeast-form-locked strains showed a reduced and delayed recognition and internalization by macrophages. We identified a number of GRACE strains that showed normal morphological development but exhibited different recognition and engulfment kinetics by cultured macrophages and characterized two mutants that modified interactions with the murine and human-derived macrophages. One mutant inactivated an uncharacterized C. albicans open reading frame that is the ortholog of S. cerevisiae OPY1, the other inactivated CaKRE1. The modified interaction was monitored during a 4 h co-culture. Early in the interaction, both opy1 and kre1 mutant strains showed reduced recognition and engulfment rates by macrophages when compared with WT cells. At fungal germ tube initiation, the engulfment kinetics increased for both mutants and WT cells, however the WT cells still showed a higher internalization by macrophages up to 2 h of interaction. Subsequently, between 2 and 4 h of the interaction, when most macrophages contain engulfed fungal cells, the engulfment kinetics increased for the opy1 mutant and further decreased for the kre1 mutant compared with Ca-WT. It appears that fungal morphology influences macrophage association with C. albicans cells and that both OPY1 and KRE1 play roles in the interaction of the fungal cells with phagocytes.

Opportunistic Infection Associated with Elevated GM-CSF Autoantibodies: A Case Series and Review of the Literature

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to play a key role in enhancing multiple immune functions that affect response to infectious pathogens including antigen presentation, complement- and antibody-mediated phagocytosis, microbicidal activity, and neutrophil chemotaxis. Reduced GM-CSF activity and immune response provides a mechanism for increased infection risk associated with autoimmune pulmonary alveolar proteinosis (aPAP) and other disorders involving the presence of GM-CSF autoantibodies. We present a case series of five patients with persistent or unusual pulmonary and central nervous system opportunistic infections (Cryptococcus gattii, Flavobacterium, Nocardia) and elevated GM-CSF autoantibody levels, as well as 27 cases identified on systematic review of the literature.

Soluble CD163 is produced by monocyte-derived and alveolar macrophages, and is not associated with the severity of idiopathic pulmonary fibrosis

The soluble form of the membrane hemoglobin scavenger receptor CD163 (sCD163), released by shedding, is a strong marker for macrophage activation. Serum sCD163 levels rise in several acute inflammatory states and some fibrosing diseases. Monocyte-derived macrophages (MoDM) differentiated by macrophage colony-stimulating factor (M-MoDM) contribute to the pathophysiology of idiopathic pulmonary fibrosis (IPF), an irreversible and rapidly fatal interstitial lung disease. Since M-MoDM express high membrane CD163 levels, we thus postulated that sCD163 could be a relevant biomarker for macrophage activation in IPF. We found that M-MoDM constitutively released higher amounts of sCD163 (49.5 ± 24.5 ng/ml) than monocytes (0.45 ± 0.32 ng/ml) or MoDM differentiated with granulocyte macrophage-stimulating factor (2.24 ± 0.98 ng/ml). The basal production of sCD163 by M-MoDM was increased following stimulation with lipopolysaccharide (123.4 ± 54.9 ng/ml) or ATP (168.9 ± 41.8 ng/ml). The sCD163 release was controlled by metalloproteases but not through ADAM17 activation. Moreover, CD163-positive macrophages and sCD163 were detected in pulmonary tissues and alveolar fluids of Caucasian patients with IPF, respectively. IPF alveolar macrophages constitutively secreted sCD163 amounts (67.6 ± 44.6 ng/µg RNA) which were significantly higher than those released by alveolar macrophages isolated from controls (19.2 ± 7.6 ng/µg RNA) or patients with other interstitial lung disease (31.5 ± 16.6 ng/µg RNA). However, the concentrations of sCD163 in blood serum collected from 155 patients with IPF did not correlate with the severity of their disease. In conclusion, our results show that M-MoDM constituted a pertinent model to study the regulation of sCD163 production. Yet, serum sCD163 values could not provide a prognostic biomarker for IPF in our cohort.

Systemic Sclerosis-Associated Interstitial Lung Disease: How to Incorporate Two Food and Drug Administration-Approved Therapies in Clinical Practice

Systemic sclerosis (SSc; scleroderma) has the highest individual mortality of all rheumatic diseases, and interstitial lung disease (ILD) is among the leading causes of SSc-related death. Two drugs are now approved by the US Food and Drug Administration (FDA) and indicated for slowing the rate of decline in pulmonary function in patients with SSc-associated ILD (SSc-ILD): nintedanib (a tyrosine kinase inhibitor) and tocilizumab (the first biologic agent targeting the interleukin-6 pathway in SSc). In addition, 2 generic drugs with cytotoxic and immunoregulatory activity, mycophenolate mofetil and cyclophosphamide, have shown comparable efficacy in a phase II trial but are not FDA-approved for SSc-ILD. In light of the heterogeneity of the disease, the optimal therapeutic strategy for the management of SSc-ILD is still to be determined. The objectives of this review are 2-fold: 1) review the body of research focused on the diagnosis and treatment of SSc-ILD; and 2) propose a practical approach for diagnosis, stratification, management, and therapeutic decision-making in this clinical context. This review presents a practical classification of SSc patients in terms of disease severity (subclinical versus clinical ILD) and associated risk of progression (low versus high risk). The pharmacologic and nonpharmacologic options for first- and second-line therapy, as well as potential combination approaches, are discussed in light of the recent approval of tocilizumab for SSc-ILD.

Cellular and Molecular Diversity in Scleroderma

With the increasing armamentarium of high-throughput tools available at manageable cost, it is attractive and informative to determine the molecular underpinnings of patient heterogeneity in systemic sclerosis (SSc). Given the highly variable clinical outcomes of patients labelled with the same diagnosis, unravelling the cellular and molecular basis of disease heterogeneity will be crucial to predicting disease risk, stratifying management and ultimately informing a patient-centered precision medicine approach. Herein, we summarise the findings of the past several years in the fields of genomics, transcriptomics, and proteomics that contribute to unraveling the cellular and molecular heterogeneity of SSc. Expansion of these findings and their routine integration with quantitative analysis of histopathology and imaging studies into clinical care promise to inform a scientifically driven patient-centred personalized medicine approach to SSc in the near future.

Contribution of monocytes and macrophages to the pathogenesis of systemic sclerosis: recent insights and therapeutic implications

PURPOSE OF REVIEW

To discuss recent studies addressing the role of monocytes and macrophages in the pathogenesis of systemic sclerosis (SSc) based on human and mouse models.

RECENT FINDINGS

Studies indicate that monocyte adhesion could be increased in SSc secondary to an interferon-dependent loss of CD52, and chemotaxis up-regulated through the CCR3/CCL24 pathway. Beyond the conventional M1/M2 paradigm of macrophage subpopulations, new subpopulations of macrophages have been recently described in skin and lung biopsies from SSc patients. Notably, single-cell ribonucleic acid sequencing has provided evidence for SPP1+ lung macrophages or FCGR3A+ skin macrophages in SSc. Impaired pro-resolving capacities of macrophages such as efferocytosis, i.e. the ability to phagocyte apoptotic cells, could also participate in the inflammatory and autoimmune features in SSc.

SUMMARY

Through their potential pro-fibrotic and pro-inflammatory properties, macrophages are at the cross-road of key SSc pathogenic processes and associated manifestations. Investigative drugs targeting macrophage polarization, such as pan-janus kinase inhibitors (tofacitinib or ruxolitinib) impacting both M1 and M2 activations, or Romilkimab inhibiting IL-4 and IL-13, have shown promising results in preclinical models or phase I/II clinical trials in SSc and other fibro-inflammatory disorders. Macrophage-based cellular therapy may also represent an innovative approach for the treatment of SSc, as initial training of macrophages may modulate the severity of fibrotic and autoimmune manifestations of the disease.

Therapeutic Approaches to Systemic Sclerosis: Recent Approvals and Future Candidate Therapies

Systemic sclerosis is the rheumatic disease with the highest individual mortality. The severity of the disease is determined by the extent of fibrotic changes to cutaneous and internal organ tissues, the most life-threatening visceral manifestations being interstitial lung disease, SSc-associated-pulmonary arterial hypertension and myocardial involvement. The heterogeneity of the disease has initially hindered the design of successful clinical trials, but considerations on classification criteria have improved patient selection in trials, allowing the identification of more homogeneous groups of patients based on progressive visceral manifestations or the extent of skin involvement with a focus of patients with early disease. Two major subsets of systemic sclerosis are classically described: limited cutaneous systemic sclerosis characterized by distal skin fibrosis and the diffuse subset with distal and proximal skin thickening. Beyond this dichotomic subgrouping of systemic sclerosis, new phenotypic considerations based on antibody subtypes have provided a better understanding of the heterogeneity of the disease, anti-Scl70 antibodies being associated with progressive interstitial lung disease regardless of cutaneous involvement. Two targeted therapies, tocilizumab (a monoclonal antibody targeting interleukin-6 receptors (IL-6R)) and nintedanib (a tyrosine kinase inhibitor), have recently been approved by the American Food & Drug Administration to limit the decline of lung function in patients with SSc-associated interstitial lung disease, demonstrating that such better understanding of the disease pathogenesis with the identification of key targets can lead to therapeutic advances in the management of some visceral manifestations of the disease. This review will provide a brief overview of the pathogenesis of SSc and will present a selection of therapies recently approved or evaluated in this context. Therapies evaluated and approved in SSc-ILD will be emphasized and a review of recent phase II trials in diffuse cutaneous systemic sclerosis will be proposed. We will also discuss selected therapeutic pathways currently under investigation in systemic sclerosis that still lack clinical data in this context but that may show promising results in the future based on preclinical data.

Flow cytometry evaluation of CD14/CD16 monocyte subpopulations in systemic sclerosis patients: a cross sectional controlled study

BACKGROUND

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by vasculopathy and fibrosis, which can be subclassified into diffuse cutaneous (dSSc) and limited cutaneous (lSSc) subtypes. Previous studies suggest that an increase in monocytes can be a hallmark of various inflammatory diseases, including SSc. Our aim was to evaluate circulating blood monocyte subpopulations (classical, intermediate and non-classical) of SSc patients and their possible association with disease manifestations.

METHODS

Fifty consecutive patients fulfilling the 2013 ACR/EULAR classification criteria for SSc were included in a cross-sectional study. Monocyte subpopulations were identified based on their expression of CD64, CD14 and CD16, evaluated by flow cytometry, and were correlated with the clinical characteristics of the patients; furthermore, the expression of HLA-DR, CD163, CD169 and CD206 in the monocytes was studied. Thirty-eight age- and sex-matched healthy individuals were recruited as a control group.

RESULTS

SSc patients had an increased number of circulating peripheral blood monocytes with an activated phenotypic profile compared to healthy subjects. Absolute counts of CD16+ (intermediary and non-classical) monocyte subpopulations were higher in SSc patients. There was no association between monocyte subpopulations and the clinical manifestations evaluated.

CONCLUSION

We identified higher counts of all monocyte subpopulations in SSc patients compared to the control group. There was no association between monocyte subpopulations and major fibrotic manifestations. CD169 was shown to be more representative in dSSc, being a promising marker for differentiating disease subtypes.

Sulforaphane suppresses lipopolysaccharide- and Pam3CysSerLys4-mediated inflammation in chronic obstructive pulmonary disease via toll-like receptors

Chronic obstructive pulmonary disease (COPD) is a progressive inflammatory disease of the airway that represents a large global disease burden. Inflammation is a prominent feature of COPD and represents an important target for treatment. Toll‐like receptors (TLRs) are pattern recognition receptors that detect invading microorganisms and nonmicrobial endogenous molecules to trigger inflammatory responses during host defense and tissue repair. The TLR signaling pathway is closely linked to the pathogenesis of COPD. Sulforaphane (SFN), an isothiocyanate derived from cruciferous vegetables, is well known for its anti‐inflammatory activities. However, the molecular function of SFN in inhibition of COPD inflammation has yet to be fully elucidated. In this study, we investigated the effects of SFN on lipopolysaccharide (LPS)‐ or Pam3CysSerLys4 (Pam3CSK4)‐induced inflammation in monocyte‐derived macrophages (MDMs) from patients with COPD. MDMs from patients with COPD showed higher expression levels of TLR2, TLR4 and downstream myeloid differentiation factor 88 (MyD88) than healthy controls, along with increased secretion of interleukin‐6 (IL‐6) and tumor necrosis factor‐α (TNF‐α) (P < 0.05). Stimulation with TLR ligands (Pam3CSK4 and LPS) up‐regulated the levels of TLR2, TLR4 and MyD88 in MDMs from patients with COPD and induced the release of IL‐6 and TNF‐α (P < 0.05). Pretreatment of MDMs from patients with COPD with SFN significantly suppressed Pam3CSK4‐ or LPS‐induced TLR2, TLR4 and MyD88 expression, along with a reduction in the production of IL‐6 and TNF‐α (P < 0.05). Collectively, these data indicate that SFN exerts its anti‐inflammatory activity in COPD by modulating the TLR pathway. SFN may represent a potential therapeutic agent for the treatment of COPD.

Resolvin D1 and D2 reduce SARS-CoV-2-induced inflammatory responses in cystic fibrosis macrophages

An excessive, non‐resolving inflammatory response underlies severe COVID‐19 that may have fatal outcomes. Therefore, the investigation of endogenous pathways leading to resolution of inflammation is of interest to uncover strategies for mitigating inflammation in people with SARS‐CoV‐2 infection. This becomes particularly urgent in individuals with preexisting pathologies characterized by chronic respiratory inflammation and prone to bacterial infection, such as cystic fibrosis (CF). Here, we analyzed the immune responses to SARS‐CoV‐2 virion spike 1 glycoprotein (S1) of macrophages (MΦ) from volunteers with and without CF and tested the efficacy of resolvins (Rv) D1 and D2 in regulating the inflammatory and antimicrobial functions of MΦ exposed to S1. S1 significantly increased chemokine release, including interleukin (IL)‐8, in CF and non‐CF MΦ, while it enhanced IL‐6 and tumor necrosis factor (TNF)‐α in non‐CF MΦ, but not in CF cells. S1 also triggered the biosynthesis of RvD1 and modulated microRNAs miR‐16, miR‐29a, and miR‐103, known to control the inflammatory responses. RvD1 and RvD2 treatment abated S1‐induced inflammatory responses in CF and non‐CF MΦ, significantly reducing the release of select chemokines and cytokines including IL‐8 and TNF‐α. RvD1 and RvD2 both restored the expression of miR‐16 and miR‐29a, while selectively increasing miR‐223 and miR‐125a, which are involved in NF‐κB activation and MΦ inflammatory polarization. During Pseudomonas aeruginosa infection, S1 stimulated the MΦ phagocytic activity that was further enhanced by RvD1 and RvD2. These results provide a map of molecular responses to SARS‐CoV‐2 in MΦ, key determinants of COVID‐19‐related inflammation, unveiling some peculiarity in the response of cells from individuals with CF. They also demonstrate beneficial, regulatory actions of RvD1 and RvD2 on SARS‐CoV‐2‐induced inflammation.

Dexamethasone Creates a Suppressive Microenvironment and Promotes Aspergillus fumigatus Invasion in a Human 3D Epithelial/Immune Respiratory Model

Lung immunity and susceptibility to infections is subject to interactions between the epithelial layer and immune cells residing in the pulmonary space. Aspergillus (A.) fumigatus, the most prevalent pathogenic fungus, affects both upper and lower respiratory tracts of immunocompromised hosts. Several reports implicate corticosteroids as a major risk factor due to their anti-inflammatory and immunosuppressive effects, which are exacerbated by long-term treatment regimens. Here we demonstrate for the first time the influence of dexamethasone when it comes to germination and hyphae formation of A. fumigatus in the presence of macrophages within a highly differentiated air–liquid interphase (ALI) epithelial/immune lung model. We illustrate suppressed mucus production within the highly differentiated 3D respiratory model as well as significantly decreased cilia beat frequencies by dexamethasone treatment. This goes along with corticosteroid-mediated macrophage M2 polarization within the epithelial/immune microenvironment. Therefore, we here showed that corticosteroids promote enhanced fungal growth and invasion A. fumigatus by creating a suppressive environment affecting both epithelial as well as immune cells.

Functions of CD169 positive macrophages in human diseases (Review)

CD169⁺ macrophages are a unique type of macrophage subset that differ from M1 and M2 macrophages. CD169⁺ macrophages are present in multiple tissues and organs throughout the body and are primarily expressed in secondary lymphoid organs. These cells are primarily divided across three locations in secondary lymphoid organs: The metallophilic marginal zone of the spleen, the subcapsular sinus and the medulla of the lymph nodes. Due to their unique location distribution in vivo and the presence of the CD169 molecule on their surfaces, CD169⁺ macrophages are reported to serve important roles in several processes, such as phagocytosis, antigen presentation, immune tolerance, viral infection and inflammatory responses. At the same time, it has been reported that CD169⁺ macrophages may also serve an important role in anti-tumour immunity. The present review focuses on the research progress surrounding the function of CD169⁺ macrophages in a variety of diseases, such as viral infection, autoimmune diseases and tumours.

Early macrophage infiltrates impair pancreatic cancer cell growth by TNF-α secretion

Background

Pancreatic ductal adenocarcinoma (PDAC) is a grim disease with high mortality rates. Increased macrophage influx in PDAC is a common hallmark and associated with poor prognosis. Macrophages have high cellular plasticity, which can differentiate into both anti- and pro-tumorigenic properties. Here, we investigated how naïve (M0) macrophages differ from other macrophages in their anti-tumorigenic activities.

Methods

In vitro BrdU proliferation and Annexin V cell death analyses were performed on PANC-1 and MIA PaCa-2 PDAC cell lines exposed to conditioned medium of different macrophage subsets. Macrophage secreted factors were measured by transcript analysis and ELISA. Therapeutic antibodies were used to functionally establish the impact of the identified cytokine on PDAC proliferation.

Results

Proliferation and cell death assays revealed that only M0 macrophages harbor anti-tumorigenic activities and that M1, M2, and TAMs do not. mRNA analysis and ELISA results suggested TNF-α as a potential candidate to mediate M0 macrophage induced cell death. To demonstrate the importance of TNF-α in M0 macrophage-induced cell death, PANC-1 and MIA PaCa-2 cell-lines were exposed to M0 macrophage conditioned medium in the presence of the TNF-α inhibitor Infliximab, which effectively diminished the anti-tumor activities of M0 macrophages.

Conclusion

Newly tumor-infiltrated naive M0 macrophages exert anti-tumorigenic activities via TNF-α secretion. Their subsequent differentiation into either M1, M2, or TAM subsets reduces TNF-α levels, thereby abolishing their cytotoxic activity on PDAC cells. These data suggest that reestablishing TNF-α secretion in differentiated macrophages might yield a therapeutic benefit.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07697-1.

Different Sensitivity of Macrophages to Phospholipidosis Induction by Amphiphilic Cationic Drugs

Phospholipidosis (PLD), the intracellular accumulation of phospholipids, is an adaptive response to toxic stimuli and serves as an important parameter in the biological assessment of compounds. Cationic amphiphilic drugs are the main inducers of PLD and may impair the function of alveolar macrophages. In vivo and in vitro models are used for PLD screening but the choice of the cellular model may be important because PLD develops in a cell- and species-specific manner. In this study, a panel of different staining (LysoSensor, Acridine Orange, Nile Red, HCS LipidTOX, LysoID) was evaluated in murine (DMBM-2, J774, RAW264.7) and human (THP-1, monocyte-derived macrophages from peripheral blood) cells to identify the most sensitive and easy to analyze staining method and to detect species-specific differences in the reaction pattern. Amiodarone and chloroquine served as inducers of PLD. High content screening was used to compare number, area, and intensity of the staining. Due to the fast staining protocol and the sensitivity of the detection, LysoID proved to be the most suitable dye of the testing. The lower induction of PLD by chloroquine reported in vivo was also seen in this study. THP-1 macrophages, followed by DMBM-2 cells, produced the most similar reaction pattern to human monocyte-derived macrophages.

Generation of a novel CD30+ B cell subset producing GM-CSF and its possible link to the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a T helper type 2 (Th2)-associated autoimmune disease characterized by vasculopathy and fibrosis. Efficacy of B cell depletion therapy underscores antibody-independent functions of B cells in SSc. A recent study showed that the Th2 cytokine interleukin (IL)-4 induces granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing effector B cells (GM-Beffs ) in humans. In this study, we sought to elucidate the generation mechanism of GM-Beffs and also determine a role of this subset in SSc. Among Th-associated cytokines, IL-4 most significantly facilitated the generation of GM-Beffs within memory B cells in healthy controls (HCs). In addition, the profibrotic cytokine transforming growth factor (TGF)-β further potentiated IL-4- and IL-13-induced GM-Beffs . Of note, tofacitinib, a Janus kinase (JAK) inhibitor, inhibited the expression of GM-CSF mRNA and protein in memory B cells induced by IL-4, but not by TGF-β. GM-Beffs were enriched within CD20+ CD30+ CD38-/low cells, a distinct population from plasmablasts, suggesting that GM-Beffs exert antibody-independent functions. GM-Beffs were also enriched in a CD30+ fraction of freshly isolated B cells. GM-Beffs generated under Th2 conditions facilitated the differentiation from CD14+ monocytes to DC-SIGN+ CD1a+ CD14- CD86+ cells, which significantly promoted the proliferation of naive T cells. CD30+ GM-Beffs were more pronounced in patients with SSc than in HCs. A subpopulation of SSc patients with the diffuse type and concomitant interstitial lung disease exhibited high numbers of GM-Beffs . Together, these findings suggest that human GM-Beffs are enriched in a CD30+ B cell subset and play a role in the pathogenesis of SSc.

Clonal haematopoiesis is increased in early onset in systemic sclerosis

Objectives

SSc is an autoimmune disease characterized by fibrosis, microangiopathy and immune dysfunctions including dysregulation of proinflammatory cytokines. Clonal haematopoiesis of indeterminate potential (CHIP) is defined by the acquisition of somatic mutations in haematopoietic stem cells leading to detectable clones in the blood. Recent data have shown a higher risk of cardiovascular disease in patients with CHIP resulting from increased production of proinflammatory cytokines and accelerated atherosclerosis. Eventual links between CHIP and autoimmune diseases are undetermined. The aim of our study was to evaluate the prevalence of CHIP in SSc patients and its association with clinical phenotype.

Methods

Forty-one genes frequently mutated in myeloid malignancies were sequenced in peripheral blood mononuclear cells from 90 SSc patients and 44 healthy donors.

Results

A total of 15 somatic variants were detected in 13/90 SSc patients (14%) and four somatic variants in 4/44 (9%) healthy donors (HD) (P = 0.58). The prevalence of CHIP was significantly higher in younger SSc patients than in HD: 25% (6/24) vs 4% (1/26) (P = 0.045) under 50 years and 17% (7/42) vs 3% (1/38) (P = 0.065) under 60 years. The prevalence of CHIP in patients over 70 years was similar in SSc patients and healthy donors. The most common mutations occurred in DNMT3A (seven variants). No major clinical differences were observed between SSc patients with or without CHIP.

Conclusion

Whether CHIP increases the risk to develop SSc or is a consequence of a SSc-derived modified bone marrow micro-environment remains to be explored.

Models Contribution to the Understanding of Sarcoidosis Pathogenesis: "Are There Good Models of Sarcoidosis?"

Sarcoidosis is a systemic, granulomatous, and noninfectious disease of unknown etiology. The clinical heterogeneity of the disease (targeted tissue(s), course of the disease, and therapy response) supports the idea that a multiplicity of trigger antigens may be involved. The pathogenesis of sarcoidosis is not yet completely understood, although in recent years, considerable efforts were put to develop novel experimental research models of sarcoidosis. In particular, sarcoidosis patient cells were used within in vitro 3D models to study their characteristics compared to control patients. Likewise, a series of transgenic mouse models were developed to highlight the role of particular signaling pathways in granuloma formation and persistence. The purpose of this review is to put in perspective the contributions of the most recent models in the understanding of sarcoidosis.

Classic and new mediators for in vitro modelling of human macrophages

Macrophages are key immune cells in the activation and regulation of immune responses. These cells are present in all tissues under homeostatic conditions and in many disease settings. Macrophages can exhibit a wide range of phenotypes depending on local and systemic cues that drive the differentiation and activation process. Macrophage heterogeneity is also defined by their ontogeny. Tissue macrophages can either derive from circulating blood monocytes or are seeded as tissue-resident macrophages during embryonic development. In humans, the study of in vivo-generated macrophages is often difficult with laborious and cell-changing isolation procedures. Therefore, translatable, reproducible, and robust in vitro models for human macrophages in health and disease are necessary. Most of the methods for studying monocyte-derived macrophages are based on the use of limited factors to differentiate the monocytes into macrophages. Current knowledge shows that the in vivo situation is more complex, and a wide range of molecules in the tissue microenvironment promote and impact on monocyte to macrophage differentiation as well as activation. In this review, macrophage heterogeneity is discussed and the human in vitro models that can be applied for research, especially for monocyte-derived macrophages. We also focus on new molecules (IL-34, platelet factor 4, etc.) used to generate macrophages expressing different phenotypes.

Combined anti-fibrotic and anti-inflammatory properties of JAK-inhibitors on macrophages in vitro and in vivo: Perspectives for scleroderma-associated interstitial lung disease

Janus kinase (JAK) inhibitors (also termed Jakinibs) constitute a family of small drugs that target various isoforms of JAKs (JAK1, JAK2, JAK3 and/or tyrosine kinase 2 (Tyk2)). They exert anti-inflammatory properties linked, in part, to the modulation of the activation state of pro-inflammatory M1 macrophages. The exact impact of JAK inhibitors on a wider spectrum of activation states of macrophages is however still to be determined, especially in the context of disorders involving concomitant activation of pro-inflammatory M1 macrophages and profibrotic M2 macrophages. This is especially the case in autoimmune pulmonary fibrosis like scleroderma-associated interstitial lung disease (ILD), in which M1 and M2 macrophages play a key pathogenic role. In this study, we directly compared the anti-inflammatory and anti-fibrotic effects of three JAK inhibitors (ruxolitinib (JAK2/1 inhibitor); tofacitinib (JAK3/2 inhibitor) and itacitinib (JAK1 inhibitor)) on five different activation states of primary human monocyte-derived macrophages (MDM). These three JAK inhibitors exert anti-inflammatory properties towards macrophages, as demonstrated by the down-expression of key polarization markers (CD86, MHCII, TLR4) and the limited secretion of key pro-inflammatory cytokines (CXCL10, IL-6 and TNFα) in M1 macrophages activated by IFNγ and LPS or by IFNγ alone. We also highlighted that these JAK inhibitors can limit M2a activation of macrophages induced by IL-4 and IL-13, as notably demonstrated by the down-regulation of the M2a associated surface marker CD206 and of the secretion of CCL18. Moreover, these JAK inhibitors reduced the expression of markers such as CXCL13, MARCO and SOCS3 in alternatively activated macrophages induced by IL-10 and dexamethasone (M2c + dex) or IL-10 alone (M2c MDM). For all polarization states, Jakinibs with inhibitory properties over JAK2 had the highest effects, at both 1 μM or 0.1 μM. Based on these in vitro results, we also explored the effects of JAK2/1 inhibition by ruxolitinib in vivo, on mouse macrophages in a model of HOCl-induced ILD, that mimics scleroderma-associated ILD. In this model, we showed that ruxolitinib significantly prevented the upregulation of pro-inflammatory M1 markers (TNFα, CXCL10, NOS2) and pro-fibrotic M2 markers (Arg1 and Chi3L3). These results were associated with an improvement of skin and pulmonary involvement. Overall, our results suggest that the combined anti-inflammatory and anti-fibrotic properties of JAK2/1 inhibitors could be relevant to target lung macrophages in autoimmune and inflammatory pulmonary disorders that have no efficient disease modifying drugs to date.

IL-4 receptor dependent expansion of lung CD169+ macrophages in microfilaria-driven inflammation

Lung disease is regularly reported in human filarial infections but the molecular pathogenesis of pulmonary filariasis is poorly understood. We used Litomosoides sigmodontis, a rodent filaria residing in the pleural cavity responsible for pleural inflammation, to model responses to human filarial infections and probe the mechanisms. Wild-type and Th2-deficient mice (ΔdblGata1 and Il-4receptor(r)a-/-/IL-5-/-) were infected with L. sigmodontis. Survival and growth of adult filariae and prevalence and density of microfilariae were evaluated. Cells and cytokines in the pleural cavity and bronchoalveolar space were characterized by imaging, flow cytometry and ELISA. Inflammatory pathways were evaluated by transcriptomic microarrays and lungs were isolated and analyzed for histopathological signatures. 40% of WT mice were amicrofilaremic whereas almost all mutant mice display blood microfilaremia. Microfilariae induced pleural, bronchoalveolar and lung-tissue inflammation associated with an increase in bronchoalveolar eosinophils and perivascular macrophages, production of mucus, visceral pleura alterations and fibrosis. Inflammation and pathology were decreased in Th2-deficient mice. An IL-4R-dependent increase of CD169 was observed on pleural and bronchoalveolar macrophages in microfilaremic mice. CD169+ tissue-resident macrophages were identified in the lungs with specific localizations. Strikingly, CD169+ macrophages increased significantly in the perivascular area in microfilaremic mice. These data describe lung inflammation and pathology in chronic filariasis and emphasize the role of Th2 responses according to the presence of microfilariae. It is also the first report implicating CD169+ lung macrophages in response to a Nematode infection.

Unfolded Protein Response Differentially Regulates TLR4-Induced Cytokine Expression in Distinct Macrophage Populations

Cellular stress responses are often engaged at sites of inflammation and can alter macrophage cytokine production. We now report that macrophages in distinct states of differentiation or in different temporal stages of inflammatory response exhibit differential sensitivity to cell stress mediated alterations in M1-like polarized inflammatory cytokine production. Tunicamycin (Tm) treatment of bone marrow derived macrophages (BMDM) cultured with M-CSF cultured bone marrow derived macrophages (M-BMDM) had markedly amplified M1-like responses to LPS, exhibiting higher levels of IL12p40 and IL12p35 mRNAs while BMDM cultured with GM-CSF, which normally express high IL12 subunit production in response to LPS, were relatively unaltered. Anti-inflammatory IL10 mRNA production in LPS-stimulated M-BMDM was greatly reduced by cell stress. These changes in cytokine mRNA levels resulted from altered rates of transcription and mRNA decay. Stress also altered cytokine protein production. Resident liver macrophages isolated from mice treated with Tm showed elevated levels of IL12 subunit mRNA production following LPS stimulation. Furthermore, macrophages infiltrating the liver during the early phase of acetaminophen injury (24 h) had little stress-mediated change in cytokine mRNA production while cells isolated in the later phase (48–72 h) exhibited higher sensitivity for stress elevated cytokine production. Hence cultured macrophages developed using different growth/differentiation factors and macrophages from different temporal stages of injury in vivo show markedly different sensitivity to cell stress for altered inflammatory cytokine production. These findings suggest that cellular stress can be an important modulator of the magnitude and character of myeloid inflammatory activity.

Alteration of human macrophage phenotypes by the anti-fibrotic drug nintedanib

The tyrosine kinase inhibitor, Nintedanib (NTD), has been approved for the treatment of idiopathic pulmonary fibrosis (IPF). In cell-free systems, NTD was recently shown to inhibit kinase activity of the human recombinant colony-stimulating factor 1 (CSF1) receptor (CSF1R) which mediates major functions of pulmonary macrophages. In the present study, we have investigated the effects of NTD on the phenotype of human monocyte-derived macrophages controlled by CSF1 in order to identify its anti-inflammatory properties via CSF1R inhibition. NTD (0.01 to 1 μM) prevented the CSF1-induced phosphorylation of CSF1R and activation of the downstream signaling pathways. NTD, like the CSF1R inhibitor GW2580, significantly decreased the adhesion of macrophages and production of the chemokine ligand (CCL) 2. NTD also altered the polarization of macrophages to classical M1 and alternative M2a macrophages. It reduced the secretion of several pro-inflammatory and/or pro-fibrotic cytokines (IL-1β, IL-8, IL-10 and CXCL13) by M1 macrophages but did not prevent the expression of M1 markers. While NTD (50-200 nM) partially blocked the synthesis of M2a markers (CD11b, CD200R, CD206, and CD209), it did not reduce synthesis of the M2a pro-fibrotic cytokines CCL22 and PDGF-BB, and increased CCL18 release when used at its highest concentration (1 μM). The effects of NTD on macrophage polarization only was partially mimicked by GW2580, suggesting that the drug inhibits other molecules in addition to CSF1R. In conclusion, NTD alters the CSF1-controlled phenotype of human macrophages mainly by blocking the activation of CSF1R that thus constitutes a new molecular target of NTD, at least in vitro.

A circulating cell population showing both M1 and M2 monocyte/macrophage surface markers characterizes systemic sclerosis patients with lung involvement

Background

Systemic sclerosis (SSc) is a disorder characterized by immune system alterations, vasculopathy and fibrosis. SSc-related interstitial lung disease (ILD) represents a common and early complication, being the leading cause of mortality.

Monocytes/macrophages seem to have a key role in SSc-related ILD. Interestingly, the classically (M1) and alternatively (M2) activated monocyte/macrophage phenotype categorization is currently under revision.

Our aim was to evaluate if circulating monocyte/macrophage phenotype could be used as biomarker for lung involvement in SSc. To this purpose we developed a wide phenotype characterization of circulating monocyte/macrophage subsets in SSc patients and we evaluated possible relations with lung involvement parameter values.

Methods

A single centre cross-sectional study was performed in fifty-five consecutive SSc patients, during the year 2017. All clinical and instrumental tests requested for SSc follow up and in particular, lung computed tomography (CT) scan, pulmonary function tests (PFTs), Doppler echocardiography with systolic pulmonary artery pressure (sPAP) measurement, blood pro-hormone of brain natriuretic peptide (pro-BNP) evaluation, were performed in each patient in a maximum one-month period. Flow cytometry characterization of circulating cells belonging to the monocyte/macrophage lineage was performed using specific M1 (CD80, CD86, TLR2 and TLR4) and M2 surface markers (CD204, CD163 and CD206). Non-parametric tests were used for statistical analysis.

Results

A higher percentage of circulating CD204⁺CD163⁺CD206⁺TLR4⁺CD80⁺CD86⁺ and CD14⁺CD206⁺CD163⁺CD204⁺TLR4⁺CD80⁺CD86⁺ mixed M1/M2 monocyte/macrophage subsets, was identified to characterize patients affected by SSc-related ILD and higher systolic pulmonary artery pressure. Mixed M1/M2 monocyte/macrophage subset showed higher percentages in patients positive for anti-topoisomerase antibody, a known lung involvement predictor.

Conclusions

The present study shows for the first time, through a wide flow cytometry surface marker analysis, that higher circulating mixed M1/M2 monocyte/macrophage cell percentages are associated with ILD, sPAP and anti-topoisomerase antibody positivity in SSc, opening the path for research on their possible role as pathogenic or biomarker elements for SSc lung involvement.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0891-z) contains supplementary material, which is available to authorized users.