Alternatively activated alveolar macrophages in pulmonary fibrosis-mediator production and intracellular signal transduction

Icariside II modulates pulmonary fibrosis via PI3K/Akt/β-catenin pathway inhibition of M2 macrophage program

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a debilitating interstitial lung disorder characterized by its limited therapeutic interventions. Macrophages, particularly the alternatively activated macrophages (M2 subtype), have been acknowledged for their substantial involvement in the development of pulmonary fibrosis. Hence, targeting macrophages emerges as a plausible therapeutic avenue for IPF. Icariside II (ISE II) is a natural flavonoid glycoside molecule known for its excellent anti-tumor and anti-fibrotic activities. Nevertheless, the impact of ISE II on pulmonary fibrosis and the intricate mechanisms through which it operates have yet to be elucidated.

OBJECTIVE

To scrutinize the impact of ISE II on the regulation of M2 macrophage polarization and its inhibitory effect on pulmonary fibrosis, as well as to delve deeper into the underlying mechanisms of its actions.

METHODS

The effect of ISE II on proliferation and apoptosis in RAW264.7 cells was assessed through the use of EdU-488 labeling and the Annexin V/PI assay. Flow cytometry, western blot, and qPCR were employed to detect markers associated with the M2 polarization phenotype. The anti-fibrotic effects of ISE II in NIH-3T3 cells were investigated in a co-culture with M2 macrophages. Si-Ctnnb1 and pcDNA3.1(+)-Ctnnb1 plasmid were used to investigate the mechanism of targeted intervention. The murine model of pulmonary fibrosis was induced by intratracheal administration of bleomycin (BLM). Pulmonary function, histopathological manifestations, lung M2 macrophage infiltration, and markers associated with pulmonary fibrosis were evaluated. Furthermore, in vivo transcriptomics analysis was employed to elucidate differentially regulated genes in lung tissues. Immunofluorescence, western blot, and immunohistochemistry were conducted for corresponding validation.

RESULTS

Our investigation demonstrated that ISE II effectively inhibited the proliferation of RAW264.7 cells and mitigated the pro-fibrotic characteristics of M2 macrophages, exemplified by the downregulation of CD206, Arg-1, and YM-1, Fizz1, through the inhibition of the PI3K/Akt/β-catenin signaling pathway. This impact led to the amelioration of myofibroblast activation and the suppression of nuclear translocation of β-catenin of NIH-3T3 cells in a co-culture. Consequently, it resulted in decreased collagen deposition, reduced infiltration of profibrotic macrophages, and a concurrent restoration of pulmonary function in mice IPF models. Furthermore, our RNA sequencing results showed that ISE II could suppress the expression of genes related to M2 polarization, primarily by inhibiting the PI3K/Akt and β-catenin signaling pathway. In essence, our findings suggest that ISE II holds potential as an anti-fibrotic agent by orchestrating macrophage polarization. This may have significant implications in clinical practice.

CONCLUSION

This study has provided evidence that ISE II exerts a significant anti-fibrotic effect by inhibiting macrophage M2 polarization through the suppression of the PI3K/Akt/β-catenin signaling pathway. These findings underscore the potential of ISE II as a promising candidate for the development of anti-fibrotic pharmaceuticals in the future.

IL20Rb aggravates pulmonary fibrosis through enhancing bone marrow derived profibrotic macrophage activation

Idiopathic pulmonary fibrosis (IPF) is one of the most fatal chronic interstitial lung diseases with unknown pathogenesis, current treatments cannot truly reverse the progression of the disease. Pulmonary macrophages, especially bone marrow derived pro-fibrotic macrophages, secrete multiple kinds of profibrotic mediators (SPP1, CD206, CD163, IL-10, CCL18…), thus further promote myofibroblast activation and fibrosis procession. IL20Rb is a cell-surface receptor that belongs to IL-20 family. The role of IL20Rb in macrophage activation and pulmonary fibrosis remains unclear. In this study, we established a bleomycin-induced pulmonary fibrosis model, used IL4/13-inducing THP1 cells to induce profibrotic macrophage (M2-like phenotype) polarization models. We found that IL20Rb is upregulated in the progression of pulmonary fibrosis, and its absence can alleviate the progression of pulmonary fibrosis. In addition, we demonstrated that IL20Rb promote the activation of bone marrow derived profibrotic macrophages by regulating the Jak2/Stat3 and Pi3k/Akt signaling pathways. In terms of therapeutic strategy, we used IL20Rb neutralizing antibodies for animal administration, which was found to alleviate the progression of IPF. Our results suggest that IL20Rb plays a profibrotic role by promoting profibrotic macrophage polarization, and IL20Rb may become a potential therapeutic target for IPF. Neutralizing antibodies against IL20Rb may become a potential drug for the clinical treatment of IPF.

The causality between systemic inflammatory regulators and chronic respiratory diseases: A bidirectional Mendelian-randomization study

INTRODUCTION

Accumulative evidence suggests the associations between systemic inflammatory regulators and chronic respiratory diseases (CRDs). However, the intrinsic causation remains implicit. Therefore, this study aimed to examine causative associations by mendelian randomization (MR) and to identify valuable active factors.

METHODS

Based on data from the GWAS database, we performed MR analyses of 41 serum cytokines from 8,293 Finnish and European descent cohorts from GBMI and UKBB for five major CRDs. We mainly applied inverse variance weighted regression, supplemented by MR-Egger regression, weighted median, maximum likelihood, weighted mode, and simple mode algorithms. Moreover, sensitivity analyses were conducted using Cochrane's Q test, MR-Egger intercept, MR-PRESSO Global test and MR-Steiger filtering. Eventually, the consistency of MR results was assessed by leave-one-out.

RESULTS

Our results suggest that 12 genetically predicted systemic inflammatory regulators probably participate in the progression of CRDs, including four risk factors (IL-1RA, IL-4, MIP-1A, PDGF-BB) and one protective factor (IL-6) in IPF, two protective factors (SCF, SDF-1A) in COPD, and two protective factors (SCF, SDF-1A) in asthma, two protective factors (GROA, IL-2RA) were also included in asthma, whereas only one factor (HGF) was protective against bronchiectasis. Additionally, two protective factors (FGF-BASIC, G-CSF) were identified in sarcoidosis. Sensitivity analyses showed no horizontal pleiotropy and significant heterogeneity. Finally, based on the findings of inverse MR analysis, no inverse causal association was uncovered, confirming the robustness of results.

CONCLUSION

Our study unearths potential associations between systemic inflammatory modulators and common CRDs, providing new insights for inflammation-mediated CRD prevention and therapeutic approaches.

Azithromycin Augments Bacterial Uptake and Anti-Inflammatory Macrophage Polarization in Cystic Fibrosis

BACKGROUND

Azithromycin (AZM) is widely being used for treating patients with cystic fibrosis (pwCF) following clinical trials demonstrating improved lung function and fewer incidents of pulmonary exacerba-tions. While the precise mechanisms remain elusive, immunomodulatory actions are thought to be involved. We previously reported impaired phagocytosis and defective anti-inflammatory M2 macrophage polarization in CF. This study systematically analyzed the effect of AZM on the functions of unpolarized and M1/M2 polarized macrophages in CF.

METHODS

Monocytes, isolated from the venous blood of patients with CF (pwCF) and healthy controls (HCs), were differentiated into monocyte-derived macrophages (MDMs) and subsequently infected with P. aeruginosa. P. aeruginosa uptake and killing by MDMs in the presence or absence of AZM was studied. M1 and M2 macrophage polarizations were induced and their functions and cytokine release were analyzed.

RESULTS

Following AZM treatment, both HC and CF MDMs exhibited a significant increase in P. aeruginosa uptake and killing, however, lysosomal acidification remained unchanged. AZM treatment led to higher activation of ERK1/2 in both HC and CF MDMs. Pharmacological inhibition of ERK1/2 using U0126 significantly reduced P. aeruginosa uptake in HC MDMs. M1 macrophage polarization remained unaffected; however, AZM treatment led to increased IL-6 and IL-10 release in both HC and CF M1 macrophages. AZM also significantly increased the phagocytic index for both pHrodo E. coli and S. aureus in CF M1 macrophages. In CF, AZM treatment promoted anti-inflammatory M2 macrophage polarization, with an increased percentage of CD209+ M2 macrophages, induction of the M2 gene CCL18, along with its secretion in the culture supernatant. However, AZM d'd not restore endocytosis in CF, another essential feature of M2 macrophages.

CONCLUSIONS

This study highlights the cellular functions and molecular targets of AZM which may involve an improved uptake of both Gram-positive and Gram-negative bacteria, restored anti-inflammatory macrophage polarization in CF. This may in turn shape the reduced lung inflammation observed in clinical trials. In addition, we confirmed the role of ERK1/2 activation for bacterial uptake.

Spatial targeting of fibrosis-promoting macrophages with nanoscale metal-organic frameworks for idiopathic pulmonary fibrosis therapy

Targeted delivery of therapeutic drugs to fibrosis-promoting macrophages (FPMs) holds promise as a challenging yet effective approach for the treatment of idiopathic pulmonary fibrosis (IPF). Here, nanocarriers composed of Mn-curcumin metal-organic frameworks (MOFs) were utilized to deliver the immune inhibitor BLZ-945 to the lungs, with the goal of depleting fibrosis-promoting macrophages (FPMs) from fibrotic lung tissues. FPM targeting was achieved by functionalizing the nanocarrier surface with an M2-like FPM binding peptide (M2pep). As a result, significant therapeutic benefits were observed through the successful depletion of approximately 80 % of the M2-like macrophages (FPMs) in a bleomycin-induced fibrosis mouse model treated with the designed M2-like FPM-targeting nanoparticle (referred to as M2NP-BLZ@Mn-Cur). Importantly, the released Mn2+ and curcumin after the degradation of M2NP-BLZ@Mn-Cur accumulated in the fibrotic lung tissue, which can alleviate inflammation and oxidative stress reactions, thereby further improving IPF therapy. This study presents a novel strategy with promising prospects for molecular-targeted fibrosis therapy. STATEMENT OF SIGNIFICANCE: Metal-organic frameworks (MOFs)- based nanocarriers equipped with both fibrosis-promoting macrophage (FPM)-specific targeting ability and therapeutic drugs are appealing for pulmonary fibrosis treatment. Here, we prepared M2pep (an M2-like FPM binding peptide)-modified and BLZ945 (a small molecule inhibitor of CSF1/CSF-1R axis)-loaded Mn-curcumin MOF nanoparticles (M2NP-BLZ@Mn-Cur) for pulmonary fibrosis therapy. The functionalized M2NP-BLZ@Mn-Cur nanoparticles can be preferentially taken up by FPMs, resulting in their depletion from fibrotic lung tissues. In addition, Mn2+and curcumin released from the nanocarriers have anti-inflammation and immune regulation effects, which further enhance the antifibrotic effect of the nanoparticles.

Systemic sclerosis interstitial lung disease: unmet needs and potential solutions

Systemic sclerosis (SSc), or scleroderma, is a rare, complex, systemic autoimmune disease of unknown aetiology, characterized by high morbidity and mortality often resulting from cardiopulmonary complications such as interstitial lung disease and pulmonary arterial hypertension. Despite substantial progress in unravelling the pathways involved in the pathogenesis of SSc and the increasing number of therapeutic targets tested in clinical trials, there is still no cure for this disease, although several proposed treatments might limit the involvement of specific organs, thereby slowing the natural history of the disease. A specific focus of recent research has been to address the plethora of unmet needs regarding the global management of SSc-related interstitial lung disease, including its pathogenesis, early diagnosis, risk stratification of patients, appropriate treatment regimens and monitoring of treatment response, as well as the definition of progression and predictors of progression and mortality. More refined stratification of patients on the basis of clinical features, molecular signatures, identification of subpopulations with distinct clinical trajectories and implementation of outcome measures for future clinical trials could also improve therapeutic management strategies, helping to avoid poor outcomes related to lung involvement.

Clinical Manifestations and Management of Fibrotic Pulmonary Sarcoidosis

Fibrotic pulmonary sarcoidosis represents a distinct and relatively uncommon manifestation within the spectrum of sarcoidosis and has substantial morbidity and mortality. Due to the scarcity of research focused on this specific disease subtype, our current understanding of pathogenesis and optimal management remains constrained. This knowledge gap underscores the need for further investigation into areas such as targeted therapies, lung transplantation, and quality of life of patients with fibrotic pulmonary sarcoidosis. The primary aim of this review is to discuss recent developments within the realm of fibrotic pulmonary sarcoidosis to foster a more comprehensive understanding of the underlying mechanisms, prognosis, and potential treatment modalities.

Icariside Ⅱ attenuates bleomycin-induced pulmonary fibrosis by modulating macrophage polarization

ETHNOPHARMACOLOGICAL RELEVANCE

Numerous studies have provided evidence supporting the significant roles of icariin, in the prevention of multiple chronic diseases like diabetes, liver fibrosis, cardiac fibrosis, renal fibrosis, and pulmonary fibrosis. In particular, Icariside II (ISE II), a prominent flavonoid glycoside derived from Epimedium brevicornum Maxim, the principal metabolite of icariin, has demonstrated noteworthy anti-inflammatory and anti-oxidant properties, along with its ability to protect against lung remodeling. However, the research exploring ISE Ⅱ's application in treating pulmonary fibrosis remains limited.

AIM OF THE STUDY

The aim of this study was to assess the therapeutic efficacy of ISE II in models of pulmonary fibrosis, while also investigating its potential mechanisms of action in cell signaling pathways.

MATERIALS AND METHODS

An in vitro model of pulmonary fibrosis was established by treating NIH-3T3 cells with transforming growth factor-β1 (TGF-β1). Western blot, RT-qPCR, and scratch test were performed to assess the effect of ISE Ⅱ. In addition, a murine model of pulmonary fibrosis was induced by intratracheal instillation of bleomycin, and the therapeutic effect of ISE Ⅱ was tested by orally administering ISE Ⅱ at a dose of 10 mg/kg. Three weeks later, lung function, micro-CT, hydroxyproline content, pathological staining, and cytokines detection of BALF or serum were used to assess the anti-fibrosis effects of ISE Ⅱ. Next, immunofluorescence staining, flow cytometry, and in vivo transcriptomics were used to investigate the underlying mechanisms of action.

RESULTS

Our data revealed a significant inhibitory effect of ISE Ⅱ on the upregulation of α-smooth muscle actin (α-SMA) and collagen production induced by TGF-β1 in fibroblasts. Meanwhile, ISE Ⅱ exerted a therapeutic effect against bleomycin-induced pulmonary fibrosis in mice by improving lung function, decreasing collagen deposition, and reducing the expression of interleukin (IL)-1β, tumor necrosis factor α (TNF-α), TGF-β1 and platelet-derived growth factor (PDGF) in serum and bronchoalveolar lavage fluid (BALF). Additionally, ISE Ⅱ treatment effectively attenuated the infiltration of M2 macrophages, concurrently downregulating the expression level of M2 marker genes, such as CD206, arginase-1(Arg-1), and Chitinase-Like Protein 3 (YM-1). Importantly, we observed a statistically significant reduction in the M2 phenotype of interstitial macrophages (IMs). However, the impact of ISE Ⅱ on the M2 polarization of alveolar macrophages (AMs) did not reach statistical significance. Lastly, transcriptome sequencing results suggested that the anti-pulmonary fibrosis effects of ISE Ⅱ may be mediated by the suppression of the WNT/β-catenin signaling pathway, which modulated M2 polarization in macrophages and contributed to the amelioration of pulmonary fibrosis. By immunohistochemical analysis, it was verified that ISE Ⅱ treatment dramatically inhibited the activation of β-catenin in fibrosis murine.

CONCLUSION

Our findings indicated that ISE Ⅱ exerted anti-fibrotic effects by inhibiting pro-fibrotic macrophage polarization. The underlying mechanism of action might be mediated by modulating the WNT/β-catenin signaling pathway to inhibit the M2 program in IMs.

Study on Potential Differentially Expressed Genes in Idiopathic Pulmonary Fibrosis by Bioinformatics and Next-Generation Sequencing Data Analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with reduced quality of life and earlier mortality, but its pathogenesis and key genes are still unclear. In this investigation, bioinformatics was used to deeply analyze the pathogenesis of IPF and related key genes, so as to investigate the potential molecular pathogenesis of IPF and provide guidance for clinical treatment. Next-generation sequencing dataset GSE213001 was obtained from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) were identified between IPF and normal control group. The DEGs between IPF and normal control group were screened with the DESeq2 package of R language. The Gene Ontology (GO) and REACTOME pathway enrichment analyses of the DEGs were performed. Using the g:Profiler, the function and pathway enrichment analyses of DEGs were performed. Then, a protein-protein interaction (PPI) network was constructed via the Integrated Interactions Database (IID) database. Cytoscape with Network Analyzer was used to identify the hub genes. miRNet and NetworkAnalyst databaseswereused to construct the targeted microRNAs (miRNAs), transcription factors (TFs), and small drug molecules. Finally, receiver operating characteristic (ROC) curve analysis was used to validate the hub genes. A total of 958 DEGs were screened out in this study, including 479 up regulated genes and 479 down regulated genes. Most of the DEGs were significantly enriched in response to stimulus, GPCR ligand binding, microtubule-based process, and defective GALNT3 causes HFTC. In combination with the results of the PPI network, miRNA-hub gene regulatory network and TF-hub gene regulatory network, hub genes including LRRK2, BMI1, EBP, MNDA, KBTBD7, KRT15, OTX1, TEKT4, SPAG8, and EFHC2 were selected. Cyclothiazide and rotigotinethe are predicted small drug molecules for IPF treatment. Our findings will contribute to identification of potential biomarkers and novel strategies for the treatment of IPF, and provide a novel strategy for clinical therapy.

Biomimetic Systems Involving Macrophages and Their Potential for Targeted Drug Delivery

The concept of targeted drug delivery can be described in terms of the drug systems' ability to mimic the biological objects' property to localize to target cells or tissues. For example, drug delivery systems based on red blood cells or mimicking some of their useful features, such as long circulation in stealth mode, have been known for decades. On the contrary, therapeutic strategies based on macrophages have gained very limited attention until recently. Here, we review two biomimetic strategies associated with macrophages that can be used to develop new therapeutic modalities: first, the mimicry of certain types of macrophages (i.e., the use of macrophages, including tumor-associated or macrophage-derived particles as a carrier for the targeted delivery of therapeutic agents); second, the mimicry of ligands, naturally absorbed by macrophages (i.e., the use of therapeutic agents specifically targeted at macrophages). We discuss the potential applications of biomimetic systems involving macrophages for new advancements in the treatment of infections, inflammatory diseases, and cancer.

Machine learning-based metabolism-related genes signature, single-cell RNA sequencing, and experimental validation in hypersensitivity pneumonitis

Metabolism is involved in the pathogenesis of hypersensitivity pneumonitis. To identify diagnostic feature biomarkers based on metabolism-related genes (MRGs) and determine the correlation between MRGs and M2 macrophages in patients with hypersensitivity pneumonitis (HP). We retrieved the gene expression matrix from the Gene Expression Omnibus database. The differentially expressed MRGs (DE-MRGs) between healthy control (HC) and patients with HP were identified using the "DESeq2" R package. The "clusterProfiler" R package was used to perform "Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses" on DE-MRGs. We used machine learning algorithms for screening diagnostic feature biomarkers for HP. The "receiver operating characteristic curve" was used to evaluate diagnostic feature biomarkers' discriminating ability. Next, we used the "Cell-type Identification by Estimating Relative Subsets of RNA Transcripts" algorithm to determine the infiltration status of 22 types of immune cells in the HC and HP groups. Single-cell sequencing and qRT-PCR were used to validate the diagnostic feature biomarkers. Furthermore, the status of macrophage polarization in the peripheral blood of patients with HP was determined using flow cytometry. Finally, the correlation between the proportion of M2 macrophages in peripheral blood and the diagnostic biomarker expression profile in HP patients was determined using Spearman analysis. We identified a total of 311 DE-MRGs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that DE-MRGs were primarily enriched in processes like steroid hormone biosynthesis, drug metabolism, retinol metabolism, etc. Finally, we identified NPR3, GPX3, and SULF1 as diagnostic feature biomarkers for HP using machine learning algorithms. The bioinformatic results were validated using the experimental results. The CIERSORT algorithm and flow cytometry showed a significant difference in the proportion of M2 macrophages in the HC and HP groups. The expression of SULF1 was positively correlated with the proportion of M2-type macrophages. In addition, a positive correlation was observed between SULF1 expression and M2 macrophage proportion. Finally, we identified NPR3, GPX3, and SULF1 as diagnostic feature biomarkers for HP. Further, a correlation between SULF1 and M2 macrophages was observed, providing a novel perspective for treating patients with HP and future studies.

Monocytes and macrophages: emerging mechanisms and novel therapeutic targets in pulmonary fibrosis

Pulmonary fibrosis results from a plethora of abnormal pathogenetic events. In idiopathic pulmonary fibrosis (IPF), inhalational, environmental, or occupational exposures in genetically and epigenetically predisposed individuals trigger recurrent cycles of alveolar epithelial cell injury, activation of coagulation pathways, chemoattraction, and differentiation of monocytes into monocyte-derived alveolar macrophages (Mo-AMs). When these events happen intermittently and repeatedly throughout the individual's life cycle, the wound repair process becomes aberrant leading to bronchiolization of distal air spaces, fibroblast accumulation, extracellular matrix deposition, and loss of the alveolar-capillary architecture. The role of immune dysregulation in IPF pathogenesis and progression has been underscored in the past mainly after the disappointing results of immunosuppressant use in IPF patients; however, recent reports highlighting the prognostic and mechanistic roles of monocytes and Mo-AMs revived the interest in immune dysregulation in IPF. In this review, we will discuss the role of these cells in the onset and progression of IPF, as well as potential targeted therapies.

Long-Term Radiological Pulmonary Changes in Mechanically Ventilated Patients with Respiratory Failure due to SARS-CoV-2 Infection

From the first reports of SARS-CoV-2, at the end of 2019 to the present, the global mortality associated with COVID-19 has reached 6,952,522 deaths as reported by the World Health Organization (WHO). Early intubation and mechanical ventilation can increase the survival rate of critically ill patients. This prospective study was carried out on 885 patients in the ICU of Mureș County Clinical Hospital, Romania. After applying inclusion and exclusion criteria, a total of 54 patients were included. Patients were monitored during hospitalization and at 6-month follow-up. We analyzed the relationship between invasive mechanical ventilation (IMV) and non-invasive mechanical ventilation (NIMV) and radiological changes on thoracic CT scans performed at 6-month follow-up and found no significant association. Regarding paraclinical analysis, there was a statistically significant association between patients grouped by IMV and ferritin level on day 1 of admission (p = 0.034), and between patients grouped by PaO2/FiO2 ratio with metabolic syndrome (p = 0.03) and the level of procalcitonin (p = 0.01). A significant proportion of patients with COVID-19 admitted to the ICU developed pulmonary fibrosis as observed at a 6-month evaluation. Patients with oxygen supplementation or mechanical ventilation require dynamic monitoring and radiological investigations, as there is a possibility of long-term pulmonary fibrosis that requires pharmacological interventions and finding new therapeutic alternatives.

Macrophage Implication in IPF: Updates on Immune, Epigenetic, and Metabolic Pathways

Idiopathic pulmonary fibrosis (IPF) is a lethal interstitial lung disease of unknown etiology with a poor prognosis. It is a chronic and progressive disease that has a distinct radiological and pathological pattern from common interstitial pneumonia. The use of immunosuppressive medication was shown to be completely ineffective in clinical trials, resulting in years of neglect of the immune component. However, recent developments in fundamental and translational science demonstrate that immune cells play a significant regulatory role in IPF, and macrophages appear to be among the most crucial. These highly plastic cells generate multiple growth factors and mediators that highly affect the initiation and progression of IPF. In this review, we will provide an update on the role of macrophages in IPF through a systemic discussion of various regulatory mechanisms involving immune receptors, cytokines, metabolism, and epigenetics.

Biomimetic Human Lung Alveolar Interstitium Chip with Extended Longevity

Determining the mechanistic causes of lung diseases, developing new treatments thereof, and assessing toxicity whether from chemical exposures or engineered nanomaterials would benefit significantly from a preclinical human lung alveolar interstitium model of physiological relevance. The existing preclinical models have limitations because they fail to replicate the key anatomical and physiological characteristics of human alveoli. Thus, a human lung alveolar interstitium chip was developed to imitate key alveolar microenvironmental factors including an electrospun nanofibrous membrane as the analogue of the basement membrane for co-culture of epithelial cells with fibroblasts embedded in 3D collagenous gels, physiologically relevant interstitial matrix stiffness, interstitial fluid flow, and 3D breathing-like mechanical stretch. The biomimetic chip substantially improved the epithelial barrier function compared to transwell models. Moreover, the chip having a gel made of a collagen I-fibrin blend as the interstitial matrix sustained the interstitium integrity and further enhanced the epithelial barrier, resulting in a longevity that extended beyond eight weeks. The assessment of multiwalled carbon nanotube toxicity on the chip was in line with the animal study.

Innovative Pre-Clinical Data Using Peptides to Intervene in the Evolution of Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, relentless, and deadly disease. Little is known about its pathogenetic mechanisms; therefore, developing efficient pharmacological therapies is challenging. This work aimed to apply a therapeutic alternative using immunomodulatory peptides in a chronic pulmonary fibrosis murine model. BALB/c mice were intratracheally instilled with bleomycin (BLM) and followed for 30 days. The mice were treated with the immune modulatory peptides ToAP3 and ToAP4 every three days, starting on the 5th day post-BLM instillation. ELISA, qPCR, morphology, and respiratory function analyses were performed. The treatment with both peptides delayed the inflammatory process observed in the non-treated group, which showed a fibrotic process with alterations in the production of collagen I, III, and IV that were associated with significant alterations in their ventilatory mechanics. The ToAP3 and ToAP4 treatments, by lung gene modulation patterns, indicated that distinct mechanisms determine the action of peptides. Both peptides controlled the experimental IPF, maintaining the tissue characteristics and standard function properties and regulating fibrotic-associated cytokine production. Data obtained in this work show that the immune response regulation by ToAP3 and ToAP4 can control the alterations that cause the fibrotic process after BLM instillation, making both peptides potential therapeutic alternatives and/or adjuvants for IPF.

Molecular Mechanism in the Development of Pulmonary Fibrosis in Patients with Sarcoidosis

Sarcoidosis is a multisystemic disease of unknown etiology characterized by the formation of granulomas in various organs, especially lung and mediastinal hilar lymph nodes. The clinical course and manifestations are unpredictable: spontaneous remission can occur in approximately two thirds of patients; up to 20% of patients have chronic course of the lung disease (called advanced pulmonary sarcoidosis, APS) resulting in progressive loss of lung function, sometimes life-threatening that can lead to respiratory failure and death. The immunopathology mechanism leading from granuloma formation to the fibrosis in APS still remains elusive. Recent studies have provided new insights into the genetic factors and immune components involved in the clinical manifestation of the disease. In this review we aim to summarize the clinical-prognostic characteristics and molecular pathways which are believed to be associated with the development of APS.

Prevention of M2 polarization and temporal limitation of differentiation in monocytes by extracellular ATP

BACKGROUND

Elevated levels of extracellular adenosine triphosphate (ATP) modulate immunologic pathways and are considered to be a danger signal in inflammation, lung fibrosis and cancer. Macrophages can be classified into two main types: M1 macrophages are classically activated, pro-inflammatory macrophages, whereas M2 macrophages are alternatively activated, pro-fibrotic macrophages. In this study, we examined the effect of ATP on differentiation of native human monocytes into these macrophage subtypes. We characterized M1 and M2 like macrophages by their release of Interleukin-1beta (IL-1β) and Chemokine (C-C motif) ligand 18 (CCL18), respectively.

RESULTS

Monocytes were stimulated with ATP or the P2X7 receptor agonist Benzoylbenzoyl-ATP (Bz-ATP), and the production of various cytokines was analyzed, with a particular focus on CCL18 and IL-1β, along with the expression of different purinergic receptors. Over a 72 h period of cell culture, monocytes spontaneously differentiated to M2 like macrophages, as indicated by an increased release of CCL18. Immediate stimulation of monocytes with ATP resulted in a dose-dependent reduction in CCL18 release, but had no effect on the concentration of IL-1β. In contrast, delayed stimulation with ATP had no effect on either CCL18 or IL-1β release. Similar results were observed in a model of inflammation using lipopolysaccharide-stimulated human monocytes. Stimulation with the P2X7 receptor agonist Bz-ATP mimicked the effect of ATP on M2-macrophage differentiation, indicating that P2X7 is involved in ATP-induced inhibition of CCL18 release. Indeed, P2X7 was downregulated during spontaneous M2 differentiation, which may partially explain the ineffectiveness of late ATP stimulation of monocytes. However, pre-incubation of monocytes with PPADS, Suramin (unselective P2X- and P2Y-receptor blockers) and KN62 (P2X7-antagonist) failed to reverse the reduction of CCL18 by ATP.

CONCLUSIONS

ATP prevents spontaneous differentiation of monocytes into M2-like macrophages in a dose- and time-dependent manner. These effects were not mediated by P2X and P2Y receptors.

Ubiquitin Ligases Siah1a/2 Control Alveolar Macrophage Functions to Limit Carcinogen-Induced Lung Adenocarcinoma

Cellular components of the tumor microenvironment, including myeloid cells, play important roles in the progression of lung adenocarcinoma (LUAD) and its response to therapy. Here, we characterize the function of the ubiquitin ligases Siah1a/2 in regulating the differentiation and activity of alveolar macrophages (AM) and assess the implication of Siah1a/2 control of AMs for carcinogen-induced LUAD. Macrophage-specific genetic ablation of Siah1a/2 promoted accumulation of AMs with an immature phenotype and increased expression of protumorigenic and pro-inflammatory Stat3 and β-catenin gene signatures. Administration of urethane to wild-type mice promoted enrichment of immature-like AMs and lung tumor development, which was enhanced by macrophage-specific Siah1a/2 ablation. The profibrotic gene signature seen in Siah1a/2-ablated immature-like macrophages was associated with increased tumor infiltration of CD14+ myeloid cells and poorer survival of patients with LUAD. Single-cell RNA-seq confirmed the presence of a cluster of immature-like AMs expressing a profibrotic signature in lungs of patients with LUAD, a signature enhanced in smokers. These findings identify Siah1a/2 in AMs as gatekeepers of lung cancer development.

SIGNIFICANCE

The ubiquitin ligases Siah1a/2 control proinflammatory signaling, differentiation, and profibrotic phenotypes of alveolar macrophages to suppress lung carcinogenesis.

Induced pluripotent stem cell-based therapies for organ fibrosis

Fibrotic diseases result in organ remodelling and dysfunctional failure and account for one-third of all deaths worldwide. There are no ideal treatments that can halt or reverse progressive organ fibrosis, moreover, organ transplantation is complicated by problems with a limited supply of donor organs and graft rejection. The development of new approaches, especially induced pluripotent stem cell (iPSC)-based therapy, is becoming a hot topic due to their ability to self-renew and differentiate into different cell types that may replace the fibrotic organs. In the past decade, studies have differentiated iPSCs into fibrosis-relevant cell types which were demonstrated to have anti-fibrotic effects that may have the potential to inform new effective precision treatments for organ-specific fibrosis. In this review, we summarize the potential of iPSC-based cellular approaches as therapeutic avenues for treating organ fibrosis, the advantages and disadvantages of iPSCs compared with other types of stem cell-based therapies, as well as the challenges and future outlook in this field.

4-OI ameliorates bleomycin-induced pulmonary fibrosis by activating Nrf2 and suppressing macrophage-mediated epithelial-mesenchymal transition

OBJECTIVES

Pulmonary fibrosis (PF) is a chronic and refractory interstitial lung disease with limited therapeutic options. 4-octyl itaconate (4-OI), a cell-permeable derivative of itaconate, has been shown to have anti-oxidative and anti-inflammatory properties. However, the effect and the underlying mechanism of 4-OI on PF are still unknown.

METHODS

WT or Nrf2 knockout (Nrf2^-/-) mice were intratracheally injected with bleomycin (BLM) to establish PF model and then treated with 4-OI. The mechanism study was performed by using RAW264.7 cells, primary macrophages, and conditional medium-cultured MLE-12 cells.

RESULTS

4-OI significantly alleviated BLM-induced PF and EMT process. Mechanism studies have found that 4-OI can not only directly inhibit EMT process, but also can reduce the production of TGF-β1 by restraining macrophage M2 polarization, which in turn inhibits EMT process. Moreover, the effect of 4-OI on PF and EMT depends on Nrf2.

CONCLUSION

4-OI ameliorates BLM-induced PF in an Nrf2-dependent manner, and its role in alleviating PF is partly due to the direct inhibition on EMT, and partly through indirect inhibition of M2-mediated EMT. These findings suggested that 4-OI has great clinical potential to develop as a new anti-fibrotic agent for PF therapy.

M2 macrophage polarization in systemic sclerosis fibrosis: pathogenic mechanisms and therapeutic effects

Systemic sclerosis (SSc, scleroderma), is an autoimmune rheumatic disease characterized by fibrosis of the skin and internal organs, and vasculopathy. Preventing fibrosis by targeting aberrant immune cells that drive extracellular matrix (ECM) over-deposition is a promising therapeutic strategy for SSc. Previous research suggests that M2 macrophages play an essential part in the fibrotic process of SSc. Targeted modulation of molecules that influence M2 macrophage polarization, or M2 macrophages, may hinder the progression of fibrosis. Here, in an effort to offer fresh perspectives on the management of scleroderma and fibrotic diseases, we review the molecular mechanisms underlying the regulation of M2 macrophage polarization in SSc-related organ fibrosis, potential inhibitors targeting M2 macrophages, and the mechanisms by which M2 macrophages participate in fibrosis.

Enhancer of zeste homolog 2 promotes renal fibrosis after acute kidney injury by inducing epithelial-mesenchymal transition and activation of M2 macrophage polarization

Long-term follow-up data indicates that 1/4 patients with acute kidney injury (AKI) will develop to chronic kidney disease (CKD). Our previous studies have demonstrated that enhancer of zeste homolog 2 (EZH2) played an important role in AKI and CKD. However, the role and mechanisms of EZH2 in AKI-to-CKD transition are still unclear. Here, we demonstrated EZH2 and H3K27me3 highly upregulated in kidney from patients with ANCA-associated glomerulonephritis, and expressed positively with fibrotic lesion and negatively with renal function. Conditional EZH2 deletion or pharmacological inhibition with 3-DZNeP significantly improved renal function and attenuated pathological lesion in ischemia/reperfusion (I/R) or folic acid (FA) mice models (two models of AKI-to-CKD transition). Mechanistically, we used CUT & Tag technology to verify that EZH2 binding to the PTEN promoter and regulating its transcription, thus regulating its downstream signaling pathways. Genetic or pharmacological depletion of EZH2 upregulated PTEN expression and suppressed the phosphorylation of EGFR and its downstream signaling ERK1/2 and STAT3, consequently alleviating the partial epithelial-mesenchymal transition (EMT), G2/M arrest, and the aberrant secretion of profibrogenic and proinflammatory factors in vivo and vitro experiments. In addition, EZH2 promoted the EMT program induced loss of renal tubular epithelial cell transporters (OAT1, ATPase, and AQP1), and blockade of EZH2 prevented it. We further co-cultured macrophages with the medium of human renal tubular epithelial cells treated with H₂O₂ and found macrophages transferred to M2 phenotype, and EZH2 could regulate M2 macrophage polarization through STAT6 and PI3K/AKT pathways. These results were further verified in two mice models. Thus, targeted inhibition of EZH2 might be a novel therapy for ameliorating renal fibrosis after acute kidney injury by counteracting partial EMT and blockade of M2 macrophage polarization.

CC chemokines family in fibrosis and aging: From mechanisms to therapy

Fibrosis is a universal aging-related pathological process in the different organ, but is actually a self-repair excessive response. To date, it still remains a large unmet therapeutic need to restore injured tissue architecture without detrimental side effects, due to the limited clinical success in the treatment of fibrotic disease. Although specific organ fibrosis and the associated triggers have distinct pathophysiological and clinical manifestations, they often share involved cascades and common traits, including inflammatory stimuli, endothelial cell injury, and macrophage recruitment. These pathological processes can be widely controlled by a kind of cytokines, namely chemokines. Chemokines act as a potent chemoattractant to regulate cell trafficking, angiogenesis, and extracellular matrix (ECM). Based on the position and number of N-terminal cysteine residues, chemokines are divided into four groups: the CXC group, the CX3C group, the (X)C group, and the CC group. The CC chemokine classes (28 members) is the most numerous and diverse subfamily of the four chemokine groups. In this Review, we summarized the latest advances in the understanding of the importance of CC chemokine in the pathogenesis of fibrosis and aging and discussed potential clinical therapeutic strategies and perspectives aimed at resolving excessive scarring formation.

Immunometabolic Signature during Respiratory Viral Infection: A Potential Target for Host-Directed Therapies

RNA viruses are known to induce a wide variety of respiratory tract illnesses, from simple colds to the latest coronavirus pandemic, causing effects on public health and the economy worldwide. Influenza virus (IV), parainfluenza virus (PIV), metapneumovirus (MPV), respiratory syncytial virus (RSV), rhinovirus (RhV), and coronavirus (CoV) are some of the most notable RNA viruses. Despite efforts, due to the high mutation rate, there are still no effective and scalable treatments that accompany the rapid emergence of new diseases associated with respiratory RNA viruses. Host-directed therapies have been applied to combat RNA virus infections by interfering with host cell factors that enhance the ability of immune cells to respond against those pathogens. The reprogramming of immune cell metabolism has recently emerged as a central mechanism in orchestrated immunity against respiratory viruses. Therefore, understanding the metabolic signature of immune cells during virus infection may be a promising tool for developing host-directed therapies. In this review, we revisit recent findings on the immunometabolic modulation in response to infection and discuss how these metabolic pathways may be used as targets for new therapies to combat illnesses caused by respiratory RNA viruses.

Recent advances in the treatment of systemic sclerosis associated interstitial lung disease

Connective tissue diseases (CTDs) are a heterogenous group of systemic inflammatory disorders. The development of connective tissue disease-associated interstitial lung disease (CTD-ILD) is a key complication associated with significant morbidity and mortality. The aim of this review is to explore the pathogenesis of CTD-ILD and summarize the recent evidence from clinical trials for novel treatment options, including the role of antifibrotics and immunomodulatory therapies with a focus on systemic sclerosis associated ILD. Further clinical trials are ongoing to explore combination therapies and more targeted therapeutic options. Clinicians remain faced with the difficult challenge of appropriately selecting patients who will benefit from the available therapies and timing the start of therapy at the most suitable part of the disease course.

Immune mechanisms in fibrotic pulmonary sarcoidosis

Sarcoidosis is an immune-mediated disorder. Its immunopathology has been steadily mapped out over the past few decades. Despite this, the underpinning mechanisms for progressive fibrotic sarcoidosis is an almost uncharted area. Consequently, there has been little change in the clinical management of fibrotic sarcoidosis over the decades and an unfocused search for new therapeutics. In this review, we provide a comprehensive examination of the relevant immune findings in fibrotic and/or progressive pulmonary sarcoidosis and propose a unifying mechanism for the pathobiology of fibrosis in sarcoidosis.

Restoration of spinal cord injury: From endogenous repairing process to cellular therapy

Spinal cord injury (SCI) disrupts neurological pathways and impacts sensory, motor, and autonomic nerve function. There is no effective treatment for SCI currently. Numerous endogenous cells, including astrocytes, macrophages/microglia, and oligodendrocyte, are involved in the histological healing process following SCI. By interfering with cells during the SCI repair process, some advancements in the therapy of SCI have been realized. Nevertheless, the endogenous cell types engaged in SCI repair and the current difficulties these cells confront in the therapy of SCI are poorly defined, and the mechanisms underlying them are little understood. In order to better understand SCI and create new therapeutic strategies and enhance the clinical translation of SCI repair, we have comprehensively listed the endogenous cells involved in SCI repair and summarized the six most common mechanisms involved in SCI repair, including limiting the inflammatory response, protecting the spared spinal cord, enhancing myelination, facilitating neovascularization, producing neurotrophic factors, and differentiating into neural/colloidal cell lines.

Leveraging Nanodrug Delivery System for Simultaneously Targeting Tumor Cells and M2 Tumor-Associated Macrophages for Efficient Colon Cancer Therapy

Tumor-associated macrophages (TAMs) widely exist in the solid tumors, which participate in the entire course of tumor development and execute momentous impacts. Therefore, manipulating TAMs has been identified as an expecting strategy with immense potential for cancer therapy. Herein, a nanodrug delivery system was leveraged for simultaneously targeting tumor cells and M2-type TAMs for efficient colon cancer therapy. The broad-spectrum anticancer chemotherapeutic drug doxorubicin (DOX) was hitchhiked in a mannose-modified bovine serum albumin (MAN-BSA) carrier. The DOX@MAN-BSA nanodrug delivery system was verified to possess feasible physical performances for unhindered systemic circulation and active targeting on colon tumors. DOX@MAN-BSA nanoparticles could be preferentially swallowed by colon tumor cells and M2 TAMs through mannose receptor-mediated endocytosis. Further in vivo antitumor therapy in CT26 colon tumor-bearing mice has achieved remarkable suppression efficacy with satisfactory biosafety. Leveraging the nanodrug delivery system for simultaneously targeting tumor cells and M2 TAMs has contributed a feasible strategy to collaboratively repress the malignant tumor cells and the collusive M2 TAMs for efficient cancer therapy.

Small Tweaks, Major Changes: Post-Translational Modifications That Occur within M2 Macrophages in the Tumor Microenvironment

The majority of proteins are subjected to post-translational modifications (PTMs), regardless of whether they occur in or after biosynthesis of the protein. Capable of altering the physical and chemical properties and functions of proteins, PTMs are thus crucial. By fostering the proliferation, migration, and invasion of cancer cells with which they communicate in the tumor microenvironment (TME), M2 macrophages have emerged as key cellular players in the TME. Furthermore, growing evidence illustrates that PTMs can occur in M2 macrophages as well, possibly participating in molding the multifaceted characteristics and physiological behaviors in the TME. Hence, there is a need to review the PTMs that have been reported to occur within M2 macrophages. Although there are several reviews available regarding the roles of M2 macrophages, the majority of these reviews overlooked PTMs occurring within M2 macrophages. Considering this, in this review, we provide a review focusing on the advancement of PTMs that have been reported to take place within M2 macrophages, mainly in the TME, to better understand the performance of M2 macrophages in the tumor microenvironment. Incidentally, we also briefly cover the advances in developing inhibitors that target PTMs and the application of artificial intelligence (AI) in the prediction and analysis of PTMs at the end of the review.

Higher susceptibility of males to bleomycin-induced pulmonary inflammation is associated with sex-specific transcriptomic differences in myeloid cells

Idiopathic pulmonary fibrosis, a condition with likely genetic and environmental etiology, is relatively more prevalent with poor prognosis in human males. However, the underlying mechanisms for these gender-associated differences in the severity of fibrosis remain unknown. Here, we tested the hypothesis that the transcriptomic repertoire of myeloid cells determines the higher susceptibility of male mice to bleomycin (BLM)-induced lung fibrosis. Adult mice were oropharyngeally challenged with saline or BLM. Lung injury, inflammation, and fibrosis outcomes were assessed, and airspace myeloid-cells were subjected to RNA-sequencing. As compared with the female mice, the male mice manifested significantly increased lung injury, inflammation, proinflammatory cytokines (IL-6, IL-1β, IL-7, and IP-10), and fibrosis in response to BLM challenge. Interestingly, several pro-inflammatory and extracellular matrix-associated genes were significantly up-regulated in male myeloid-cells compared to female myeloid-cells in the saline-control group. Similarly, BLM challenge resulted in greater pro-inflammatory and pro-fibrotic transcriptomic changes in male compared to female myeloid cells. On the other hand, anti-inflammatory and regulatory cytokine, Il10 and Ifng respectively, were uniquely upregulated in BLM-challenged female but not in male myeloid cells when compared to their respective saline-control groups. Further, cross-sex bone marrow transplantation experiments revealed that male hematopoietic progenitor cells (HPCs) increased the granulocytic infiltration in female mice while female HPCs decreased the granulocytic infiltration in male mice post-BLM challenge. These findings suggest that there are inherent transcriptomic differences between the male and female lung myeloid cells and that the pro-inflammatory nature of male myeloid cells is sufficient to increase the susceptibility of female mice to BLM-induced inflammation.

Plasticity towards Rigidity: A Macrophage Conundrum in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, and ultimately fatal diffuse parenchymal lung disease. The molecular mechanisms of fibrosis in IPF patients are not fully understood and there is a lack of effective treatments. For decades, different types of drugs such as immunosuppressants and antioxidants have been tested, usually with unsuccessful results. Although two antifibrotic drugs (Nintedanib and Pirfenidone) are approved and used for the treatment of IPF, side effects are common, and they only slow down disease progression without improving patients’ survival. Macrophages are central to lung homeostasis, wound healing, and injury. Depending on the stimulus in the microenvironment, macrophages may contribute to fibrosis, but also, they may play a role in the amelioration of fibrosis. In this review, we explore the role of macrophages in IPF in relation to the fibrotic processes, epithelial–mesenchymal transition (EMT), and their crosstalk with resident and recruited cells and we emphasized the importance of macrophages in finding new treatments.

Destructive fibrotic teamwork: how both microenvironment stiffness and profibrotic interleukin 13 impair alveolar macrophage phenotype and function

The pulmonary fibrotic microenvironment is characterized by increased stiffness of lung tissue and enhanced secretion of profibrotic soluble cues contributing to a feedback loop that leads to dysregulated wound healing and lung failure. Pinpointing the individual and tandem effects of profibrotic stimuli in impairing immune cell response remains difficult and is needed for improved therapeutic strategies. We utilized a statistical design of experiment (DOE) to investigate how microenvironment stiffness and interleukin 13 (IL13), a profibrotic soluble factor linked with disease severity, contribute to the impaired macrophage response commonly observed in pulmonary fibrosis. We used engineered bioinspired hydrogels of different stiffness, ranging from healthy to fibrotic lung tissue, and cultured murine alveolar macrophages (MH-S cells) with or without IL13 to quantify cell response and analyze independent and synergistic effects. We found that, while both stiffness and IL13 independently influence macrophage morphology, phenotype, phagocytosis and efferocytosis, these factors work synergistically to exacerbate impaired macrophage phenotype and efferocytosis. These unique findings provide insights into how macrophages in fibrotic conditions are not as effective in clearing debris, contributing to fibrosis initiation/progression, and more broadly inform how underlying drivers of fibrosis modulate immune cell response to facilitate therapeutic strategies.

Sarcoidosis: Progression to the chronic stage and pathogenic based treatment (narrative review)

Many factors confirm the autoimmune nature of sarcoidosis and help in determining the strategy of patient management and treatment initiation. However, the causes and the mechanisms of disease progression that result in fibrosis and insufficiency of the affected organ remain unclear. This narrative review aims to analyse the mechanisms and biomarkers of sarcoidosis progression, as well as the pathogenetic basis of sarcoidosis therapy. The following characteristics of progressive chronic sarcoidosis were revealed: the disease develops in patients with a genetic predisposition (SNP in genes GREM1, CARD15, TGF-β3, HLA-DQB1^*06:02, HLA-DRB1^*07/14/15), which contributes either the decreased ability of antigen elimination or autoimmune inflammation. Various prognostic biomarkers of disease progression (decreased levels of neopterin, elastase, sIL-2R, chitotriosidase, glycoprotein Krebs von den Lungen, Th17 cell count, reduced quantity of TNF-α in peripheral blood or bronchoalveolar lavage fluid) have been described and can potentially be used to determine the group of patients who will benefit from the use of corticosteroids/cytostatic drugs/biologics.

The role of immune response in the pathogenesis of idiopathic pulmonary fibrosis: far beyond the Th1/Th2 imbalance

INTRODUCTION

. Idiopathic pulmonary fibrosis (IPF) is a chronic disease of unknown origin characterized by progressive scarring of the lung leading to irreversible loss of function. Despite the availability of two drugs that are able to slow down disease progression, IPF remains a deadly disease. The pathogenesis of IPF is poorly understood, but a dysregulated wound healing response following recurrent alveolar epithelial injury is thought to be crucial. Areas covered. In the last few years, the role of the immune system in IPF pathobiology has been reconsidered; indeed, recent data suggest that a dysfunctional immune system may promote and unfavorable interplay with pro-fibrotic pathways thus acting as a cofactor in disease development and progression. In this article, we review and critically discuss the role of T cells in the pathogenesis and progression of IPF in the attempt to highlight ways in which further research in this area may enable the development of targeted immunomodulatory therapies for this dreadful disease.

EXPERT OPINION

A better understanding of T cells interactions has the potential to facilitate the development of immune modulators targeting multiple T cell-mediated pathways thus halting disease initiation and progression.

Myeloid cell-specific deletion of Capns1 prevents macrophage polarization toward the M1 phenotype and reduces interstitial lung disease in the bleomycin model of systemic sclerosis

Background

Calpains are a family of calcium-dependent thiol proteases that participate in a wide variety of biological activities. In our recent study, calpain is increased in the sera of scleroderma or systemic sclerosis (SSc). However, the role of calpain in interstitial lung disease (ILD) has not been reported. ILD is a severe complication of SSc, which is the leading cause of death in SSc. The pathogenesis of SSc-related ILD remains incompletely understood. This study investigated the role of myeloid cell calpain in SSc-related ILD.

Methods

A novel line of mice with myeloid cell-specific deletion of Capns1 (Capns1-ko) was created. SSc-related ILD was induced in Capns1-ko mice and their wild-type littermates by injection 0.l mL of bleomycin (0.4 mg/mL) for 4 weeks. In a separate experiment, a pharmacological inhibitor of calpain PD150606 (Biomol, USA, 3 mg/kg/day, i.p.) daily for 30 days was given to mice after bleomycin injection on daily basis. At the end of the experiment, the animals were killed, skin and lung tissues were collected for the following analysis. Inflammation, fibrosis and calpain activity and cytokines were assessed by histological examinations and ELISA, and immunohistochemical analyses, western blot analysis and Flow cytometry analysis.

Results

Calpain activities increased in SSc-mouse lungs. Both deletion of Capns1 and administration of PD150606 attenuated dermal sclerosis as evidenced by a reduction of skin thickness and reduced interstitial fibrosis and inflammation in bleomycin model of SSc mice. These effects of reduced calpain expression or activity were associated with prevention of macrophage polarization toward M1 phenotype and consequent reduced production of pro-inflammatory cytokines including TNF-α, IL-12 and IL-23 in lung tissues of Capns1-ko mice with bleomycin model of SSc. Furthermore, inhibition of calpain correlated with an increase in the protein levels of PI3K and phosphorylated AKT1 in lung tissues of the bleomycin model of SSc mice.

Conclusions

This study for the first time demonstrates that the role of myeloid cell calpain may be promotion of macrophage M1 polarization and pro-inflammatory responses related PI3K/AKT1 signaling. Thus, myeloid cell calpain may be a potential therapeutic target for bleomycin model of SSc-related ILD.

Novel drug delivery systems and disease models for pulmonary fibrosis

Pulmonary fibrosis (PF) is a serious and progressive lung disease which is possibly life-threatening. It causes lung scarring and affects lung functions including epithelial cell injury, massive recruitment of immune cells and abnormal accumulation of extracellular matrix (ECM). There is currently no cure for PF. Treatment for PF is aimed at slowing the course of the disease and relieving symptoms. Pirfenidone (PFD) and nintedanib (NDNB) are currently the only two FDA-approved oral medicines to slow down the progress of idiopathic pulmonary fibrosis, a specific type of PF. Novel drug delivery systems and therapies have been developed to improve the prognosis of the disease, as well as reduce or minimize the toxicities during drug treatment. The drug delivery routes for these therapies are various including oral, intravenous, nasal, inhalant, intratracheal and transdermal; although this is dependent on specific treatment mechanisms. In addition, researchers have also expanded current animal models that could not fully restore the clinicopathology, and developed a series of in vitro models such as organoids to study the pathogenesis and treatment of PF. This review describes recent advances on pathogenesis exploration, classifies and specifies the progress of drug delivery systems by their delivery routes, as well as an overview on the in vitro and in vivo models for PF research.

CRTH2 Mediates Pro-fibrotic Macrophage Differentiation and Promotes Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a particularly deadly form of pulmonary fibrosis with unknown reason. In patients with IPF, high serum and lung levels of CHI3L1 can be detected and are associated with poor survival. However, the roles of CHI3L1 in these diseases have not been fully elucidated. We hypothesize that CHI3L1 interacts with CRTH2 to stimulate pro-fibrotic macrophage differentiation and the development of pulmonary fibrosis and that circulating blood monocytes from patients with IPF are hyperresponsive to CHI3L1-CRTH2 signaling. We used murine pulmonary fibrosis models to investigate the role of CRTH2 on pro-fibrotic macrophage differentiation and fibrosis development, and primary human PBMC cell culture to detect the difference of monocytes in the responses to CHI3L1 stimulation and CRTH2 inhibition between IPF patients and normal controls. Our results showed that null mutation or small molecule inhibition of CRTH2 prevents the development of pulmonary fibrosis in murine models. Furthermore, CHI3L1 stimulation induces a greater increase in CD206 expression in IPF monocytes than control monocytes. These results demonstrated that monocytes from IPF patients appear to be hyperresponsive to CHI3L1 stimulation. These studies support targeting CHI3L1-CRTH2 pathway as a promising therapeutic approach in IPF and that the sensitivity of blood monocytes to CHI3L1-induced pro-fibrotic differentiation may serve as a biomarker that predicts responsiveness to CHI3L1 or CRTH2 based interventions.

Multi-Platform Single-Cell Analysis Identifies Immune Cell Types Enhanced in Pulmonary Fibrosis

Immune cells have been implicated in Idiopathic Pulmonary Fibrosis (IPF), but the phenotypes and effector mechanisms of these cells remain incompletely characterized. We performed mass cytometry to quantify immune/inflammatory cell subsets in lungs of 12 patients with IPF and 15 organ donors without chronic lung disease and utilized existing single-cell RNA-sequencing (scRNA-seq) data to investigate transcriptional profiles of immune cells over-represented in IPF. Among myeloid cells, we found increased numbers of alveolar macrophages (AMØs) and dendritic cells (DCs) in IPF, as well as a subset of monocyte-derived DC. In contrast, monocyte-like cells and interstitial macrophages were reduced in IPF. Transcriptomic profiling identified an enrichment for interferon-γ (IFN-γ) response pathways in AMØs and DCs from IPF, as well as antigen processing in DCs and phagocytosis in AMØs. Among T cells, we identified three subset of memory T cells that were increased in IPF, including CD4+ and CD8+ resident memory T cells (TRM), and CD8+ effector memory (TEMRA) cells. The response to IFN-γ pathway was enriched in CD4 TRM and CD8 TRM cells in IPF, along with T cell activation and immune response-regulating signaling pathways. Increased AMØs, DCs, and memory T cells were present in IPF lungs compared to control subjects. In IPF, these cells possess an activation profile indicating increased IFN-γ signaling and up-regulation of adaptive immunity in the lungs. Together, these studies highlight critical features of the immunopathogenesis of IPF.

Pyroptosis executor gasdermin D plays a key role in scleroderma and bleomycin-induced skin fibrosis

The NLRP3 inflammasome and IL-1β are essential for scleroderma pathogenesis. Nevertheless, the role of pyroptosis executor gasdermin D(GSDMD), which is a downstream molecule of NLRP3 and is required for IL-1β release in some situations, has not yet been well elucidated in scleroderma. Here, we found that GSDMD was significantly up-regulated and activated in the skin of scleroderma patients and bleomycin-induced mouse model. What’s more, the ablation of GSDMD ameliorates bleomycin-induced skin fibrosis according to HE staining, Masson staining and the detection of hydroxyproline contents. GSDMD deficiency also impaired macrophages infiltration and reduced inflammation response. Furthermore, the loss of GSDMD reduced Th17 differentiation in vivo and in vitro. Collectively, these findings provide the first demonstration that GSDMD related pyroptosis plays an important role in scleroderma pathogenesis.

Emerging insights in sarcoidosis: moving forward through reverse translational research

Sarcoidosis is a chronic granulomatous disease of unknown etiology that primarily affects the lungs. The development of stage IV or fibrotic lung disease accounts for a significant proportion of the morbidity and mortality attributable to sarcoidosis. Further investigation into the active mechanisms of disease pathogenesis and fibrogenesis might illuminate fundamental mediators of injury and repair while providing new opportunities for clinical intervention. However, progress in sarcoidosis research has been hampered by the heterogeneity of clinical phenotypes and the lack of a consensus modeling system. Recently, reverse translational research, wherein observations made at the patient level catalyze hypothesis-driven research at the laboratory bench, has generated new discoveries regarding the immunopathogenic mechanisms of pulmonary granuloma formation, fibrogenesis, and disease model development. The purpose of this review is to highlight the promise and possibility of these novel investigative efforts.

Implications of the Immune Landscape in COPD and Lung Cancer: Smoking Versus Other Causes

Cigarette smoking is reported in about one third of adults worldwide. A strong relationship between cigarette smoke exposure and chronic obstructive pulmonary disease (COPD) as well as lung cancer has been proven. However, about 15% of lung cancer cases, and between one fourth and one third of COPD cases, occur in never-smokers. The effects of cigarette smoke on the innate as well as the adaptive immune system have been widely investigated. It is assumed that certain immunologic features contribute to lung cancer and COPD development in the absence of smoking as the major risk factor. In this article, we review different immunological aspects of lung cancer and COPD with a special focus on non-smoking related risk factors.

Targeting PI3K/AKT signaling for treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic interstitial pneumonia with unknown causes. The incidence rate increases year by year and the prognosis is poor without cure. Recently, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway can be considered as a master regulator for IPF. The contribution of the PI3K/AKT in fibrotic processes is increasingly prominent, with PI3K/AKT inhibitors currently under clinical evaluation in IPF. Therefore, PI3K/AKT represents a critical signaling node during fibrogenesis with potential implications for the development of novel anti-fibrotic strategies. This review epitomizes the progress that is being made in understanding the complex interpretation of the cause of IPF, and demonstrates that PI3K/AKT can directly participate to the greatest extent in the formation of IPF or cooperate with other pathways to promote the development of fibrosis. We further summarize promising PI3K/AKT inhibitors with IPF treatment benefits, including inhibitors in clinical trials and pre-clinical studies and natural products, and discuss how these inhibitors mitigate fibrotic progression to explore possible potential agents, which will help to develop effective treatment strategies for IPF in the near future.

Potential therapeutic targets to prevent organ damage in chronic pulmonary sarcoidosis

INTRODUCTION

Sarcoidosis is a granulomatous inflammatory disease with high chances of reduced quality of life, irreversible organ damage, and reduced life expectancy when vital organs are involved. Any organ system can be affected, and the lungs are most often affected. There is no preventive strategy as the exact etiology is unknown, and complex immunogenetic and environmental factors determine disease susceptibility and phenotype. Present-day treatment options originated from clinical practice and are effective in many patients. However, a substantial percentage of patients suffer from unacceptable side effects or still develop refractory, threatening pulmonary or extrapulmonary disease.

AREAS COVERED

As non-caseating granulomas, the pathological hallmark of disease, are assigned to divergent activation and regulation of the immune system, targets in relation to the possible triggers of granuloma formation and their sequelae were searched and reviewed.

EXPERT OPINION

:The immunopathogenesis underlying sarcoidosis has been a dynamic field of study. Several recent new insights give way to promising new therapeutic targets, such as certain antigenic triggers (e.g. from Aspergillus nidulans), mTOR, JAK-STAT and PPARγ pathways, the NRP2 receptor and MMP-12, which await further exploration. Clinical and trigger related phenotyping, and molecular endotyping in sarcoidosis will likely hold the key for precision medicine in the future.

Suppression of epithelial abnormalities by nintedanib in induced-rheumatoid arthritis-associated interstitial lung disease mouse model

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is relevant for the prognosis in patients with RA. Nintedanib, which inhibits both receptor and non-receptor type tyrosine kinases, is an antifibrotic drug for the treatment of progressive fibrosing ILDs, such as idiopathic pulmonary fibrosis and systemic sclerosis-associated interstitial lung disease. Little is known about the effects of nintedanib on RA-ILD. We examined the characteristics of a novel induced RA-ILD (iRA-ILD) mouse model and the effects of nintedanib on the model. D1CC×D1BC mice are highly susceptible to arthritogenic antigens, such as bovine type II collagen, resulting in severe inflammatory arthritis. ILD develops after joint inflammation is alleviated. Serum surfactant protein D levels were monitored as an ILD marker. Nintedanib was orally administered to iRA-ILD mice for 2 months. The iRA-ILD model showed similar symptoms to those in patients with RA-ILD. The histopathological features of pulmonary disorder resembled nonspecific interstitial pneumonia, but with metaplastic epithelium. Histopathological analysis revealed that in addition to reducing fibrosis, nintedanib suppressed M2 macrophage polarisation and hyperplasia of Type 2 alveolar epithelial cells. The metaplastic epithelium acquired invasiveness because of the expression of E-cadherin, MMP7, Tgf-β, Col1a1, Padi2 and Padi4. Moreover, citrullinated peptides were detected in these invasive epithelial cells as well as in the bronchiolar epithelium. Administration of nintedanib reduced the expression of Pad4 and citrullinated peptides and eliminated invasive epithelial cells. The broad inhibitory effects of nintedanib on tyrosine kinases may contribute to the overall improvement in RA-ILD, including epithelial abnormalities associated with progressive lung fibrosis.

Targeting monocytes/macrophages in fibrosis and cancer diseases: Therapeutic approaches

Over almost 140 years since their identification, the knowledge about macrophages has unbelievably evolved. The 'big eaters' from being thought of as simple phagocytic cells have been recognized as master regulators in immunity, homeostasis, healing/repair and organ development. Long considered to originate exclusively from bone marrow-derived circulating monocytes, macrophages have been also demonstrated to be the first immune cells colonizing tissues in the developing embryo and persisting in adult life by self-renewal, as long-lived tissue resident macrophages. Therefore, heterogeneous populations of macrophages with different ontogeny and functions co-exist in tissues. Macrophages act as sentinels of homeostasis and are intrinsically programmed to lead the wound healing and repair processes that occur after injury. However, in certain pathological circumstances macrophages get dysfunctional, and impaired or aberrant macrophage activities become key features of diseases. For instance, in both fibrosis and cancer, that have been defined 'wounds that do not heal', dysfunctional monocyte-derived macrophages overall play a key detrimental role. On the other hand, due to their plasticity these cells can be 're-educated' and exert anti-fibrotic and anti-cancer functions. Therefore macrophages represent an important therapeutic target in both fibrosis and cancer diseases. The current review will illustrate new insights into the role of monocytes/macrophages in these devastating diseases and summarize new therapeutic strategies and applications of macrophage-targeted drug development in their clinical setting.

STAT6 Deficiency Attenuates Myeloid Fibroblast Activation and Macrophage Polarization in Experimental Folic Acid Nephropathy

Renal fibrosis is a pathologic feature of chronic kidney disease, which can lead to end-stage kidney disease. Myeloid fibroblasts play a central role in the pathogenesis of renal fibrosis. However, the molecular mechanisms pertaining to myeloid fibroblast activation remain to be elucidated. In the present study, we examine the role of signal transducer and activator of transcription 6 (STAT6) in myeloid fibroblast activation, macrophage polarization, and renal fibrosis development in a mouse model of folic acid nephropathy. STAT6 is activated in the kidney with folic acid nephropathy. Compared with folic-acid-treated wild-type mice, STAT6 knockout mice had markedly reduced myeloid fibroblasts and myofibroblasts in the kidney with folic acid nephropathy. Furthermore, STAT6 knockout mice exhibited significantly less CD206 and PDGFR-β dual-positive fibroblast accumulation and M2 macrophage polarization in the kidney with folic acid nephropathy. Consistent with these findings, STAT6 knockout mice produced less extracellular matrix protein, exhibited less severe interstitial fibrosis, and preserved kidney function in folic acid nephropathy. Taken together, these results have shown that STAT6 plays a critical role in myeloid fibroblasts activation, M2 macrophage polarization, extracellular matrix protein production, and renal fibrosis development in folic acid nephropathy. Therefore, targeting STAT6 may provide a novel therapeutic strategy for fibrotic kidney disease.

Tetraethylthiuram disulphide alleviates pulmonary fibrosis through modulating transforming growth factor-β signalling

Idiopathic pulmonary fibrosis (IPF) induces significant morbidity and mortality, for which there are limited therapeutic options available. Here, we found that tetraethylthiuram disulphide (disulfiram, DSF), a derivative of thiuram, used in the treatment of alcohol abuse, has an inhibitory effect on bleomycin (BLM)-induced pulmonary fibrosis via the attenuation of the fibroblast-to-myofibroblast transition, migration, and proliferation of fibroblasts. Furthermore, DSF inhibited the activation of primary pulmonary fibroblasts and fibroblast cell line under transforming growth factor-β 1 (TGF-β1) challenge. Mechanistically, the anti-fibrotic effect of DSF on fibroblasts depends on the inhibition of TGF-β signalling. We further determined that DSF interrupts the interaction between SMAD3 and TGF-β receptor Ι (TBR Ι), and identified that DSF directly binds with SMAD3, in which Trp326, Thr330, and Cys332 of SMAD3 are critical binding sites for DSF. Collectively, our results reveal a powerful anti-fibrotic function of DSF in pulmonary fibrosis through the inhibition of TGF-β/SMAD signalling in pulmonary fibroblasts, indicating that DSF is a promising therapeutic candidate for IPF.

Macrophage phenotypes in tissue repair and the foreign body response: Implications for biomaterial-based regenerative medicine strategies

Macrophages are a highly heterogeneous and plastic population of cells that are crucial for tissue repair and regeneration. This has made macrophages a particularly attractive target for biomaterial-directed regenerative medicine strategies. However, macrophages also contribute to adverse inflammatory and fibrotic responses to implanted biomaterials, typically related to the foreign body response (FBR). The traditional model in the field asserts that the M2 macrophage phenotype is pro-regenerative and associated with positive wound healing outcomes, whereas the M1 phenotype is pro-inflammatory and associated with pathogenesis. However, recent studies indicate that both M1 and M2 macrophages play different, but equally vital, roles in promoting tissue repair. Furthermore, recent technological developments such as single-cell RNA sequencing have allowed for unprecedented insights into the heterogeneity within the myeloid compartment, related to activation state, niche, and ontogenetic origin. A better understanding of the phenotypic and functional characteristics of macrophages critical to tissue repair and FBR processes will allow for rational design of biomaterials to promote biomaterial-tissue integration and regeneration. In this review, we discuss the role of temporal and ontogenetic macrophage heterogeneity on tissue repair processes and the FBR and the potential implications for biomaterial-directed regenerative medicine applications. STATEMENT OF SIGNIFICANCE: This review outlines the contributions of different macrophage phenotypes to different phases of wound healing and angiogenesis. Pathological outcomes, such as chronic inflammation, fibrosis, and the foreign body response, related to disruption of the macrophage inflammation-resolution process are also discussed. We summarize recent insights into the vast heterogeneity of myeloid cells related to their niche, especially the biomaterial microenvironment, and ontogenetic origin. Additionally, we present a discussion on novel tools that allow for resolution of cellular heterogeneity at the single-cell level and how these can be used to build a better understanding of macrophage heterogeneity in the biomaterial immune microenvironment to better inform immunomodulatory biomaterial design.

Adiponectin Inhibits the Production of TNF-α, IL-6 and Chemokines by Human Lung Macrophages

Background: Obesity is associated with an elevated risk of severe respiratory infections and inflammatory lung diseases. The objectives were to investigate 1) the production of adiponectin by human lung explants, 2) the expression of the adiponectin receptors AdipoR1 and AdipoR2 by human lung macrophages (LMs), and 3) the impact of recombinant human adiponectin and a small-molecule APN receptor agonist (AdipoRon) on LMs activation. Material and methods: Human parenchyma explants and LMs were isolated from patients operated for carcinoma. The LMs were cultured with recombinant adiponectin or AdipoRon and stimulated with lipopolysaccharide (10 ng ml^-1), poly (I:C) (10 µg ml^-1) or interleukin (IL)-4 (10 ng ml^-1) for 24 h. Cytokines or adiponectin, released by explants or LMs, were measured using ELISAs. The mRNA levels of AdipoR1 and AdipoR2 were determined using real-time quantitative PCR. AdipoRs expression was also assessed with confocal microscopy. Results: Adiponectin was released by lung explants at a level negatively correlated with the donor's body mass index. AdipoR1 and AdipoR2 were both expressed in LMs. Adiponectin (3-30 µg ml^-1) and AdipoRon (25-50 μM) markedly inhibited the LPS- and poly (I:C)-induced release of Tumor Necrosis Factor-α, IL-6 and chemokines (CCL3, CCL4, CCL5, CXCL1, CXCL8, CXCL10) and the IL-4-induced release of chemokines (CCL13, CCL17, CCL22) in a concentration-dependent manner. Recombinant adiponectin produced in mammalian cells (lacking low molecular weight isoforms) had no effects on LMs. Conclusion and implications: The low-molecular-weight isoforms of adiponectin and AdipoRon have an anti-inflammatory activity in the lung environment. Targeting adiponectin receptors may constitute a new means of controlling airways inflammation.