Alveolar macrophages: plasticity in a tissue-specific context

Bone marrow mesenchymal stem cell-derived exosomes alleviating sepsis-induced lung injury by inhibiting ferroptosis of macrophages

OBJECTIVE

To investigate whether bone marrow mesenchymal stem cells derived exosomes (BMSCs-exo) can alleviate sepsis-induced lung injury and its related mechanism by inhibiting ferroptosis of macrophages.

METHODS

RAW264.7 cells were first stimulated with lipopolysaccharide (LPS) to observe whether macrophage ferroptosis occurred. After pre-treating BMSCs with the exosome inhibitor GW4869, the lung-protective effect was observed to determine if it was eliminated. Furthermore, BMSCs-exo was extracted to clarify if it could exert effects like BMSCs. Finally, key molecules responsible for the effects were identified through sequencing and other related techniques.

RESULTS

Following stimulation with LPS, the expression of GPX4 in RAW264.7 cells decreased significantly, while the expression of PTGS2 increased significantly. The intracellular GSH content decreased, while MDA content increased. BMSCs-exo reversed the decrease in GPX4 and increase in PTGS2, increased GSH and decreased MDA. Sequencing revealed that lncRNA SNHG12 in macrophages was significantly upregulated after co-culture with BMSCs-exo. Knockdown of lncRNA SNHG12 in BMSCs via siRNA resulted in a significant decrease in the inhibitory effect on macrophage ferroptosis both in vivo and in vitro.

CONCLUSION

BMSCs-exo can inhibit macrophage ferroptosis through lncRNA SNHG12, thereby alleviating the sepsis-induced lung injury and improving the survival rate.

Fibrous erionite modifications following THP-1 macrophage phagocytosis: An insight into the mechanisms of interaction with biological systems

Erionite is a ubiquitous natural zeolite, often occurring with fibrous habit, whose strong tumorigenic activity to humans has been certified by its inclusion in the Group 1 Human-Carcinogenic list by the International Agency for Research on Cancer. To date, the reason(s) of erionite toxicity are still unclear, albeit several hypotheses have been proposed. The present work, based on the combined analysis of the chemical and structural modifications of erionite fibres following incubation in human THP-1 macrophages and evaluation of cellular response, indicates that, upon macrophage phagocytosis, a large release of cations is counterbalanced by a significant sequestration of hydronium ions from lysosomes provoking a quick pH dysregulation. This would be restored by the hyperactivation of ATP-dependent proton pumps with significant energy expenditure for the cell, ultimately causing mitochondrial suffering, leading to chronic inflammation and eventually cancer development.

Exaggerated Lung Inflammation Induced by Lung-Targeted mRNA-LNP Dampens Vaccines against Tuberculosis

The challenges in developing a tuberculosis (TB) vaccine stem from the complex life cycle of Mycobacterium tuberculosis (Mtb) and various bacterial proteins encoded by approximately 4000 genes. mRNA is easy to design and can accommodate multiple antigens, suggesting that it may be an effective TB vaccine technology. Here, we designed an mRNA encoding Ag85B and ESAT6 that was delivered by lung targeted lipid nanoparticles (LNPlung-mRNAA-E), intending to stimulate lung immunity to combat TB. To enhance the vaccine efficacy, we further cofabricated monophosphoryl lipid A (MPLA) with mRNA to evaluate the adjuvanted mRNA vaccine (LNPlung-mRNAA-E-MPLA). Both vaccines elicited robust CD4+ T cell response, resulting in markedly locally higher production of IFN-γ, TNF-α, and IL-2. As anticipated, the addition of MPLA further enhanced the immunogenicity of LNPlung-mRNAA-E. However, the Mtb challenge experiment showed that LNPlung-mRNAA-E-MPLA neither provided effective protection nor enhanced the immune protection primed by BCG (Bacillus Calmette-Guérin). The subsequent HE staining of the lung revealed that the LNPlung-mRNAA-E-MPLA induced pulmonary inflammation, leading to tissue damage. Moreover, the inflammatory cytokines including IL-6, IL-1β, and MCP-1 were significantly increased and the MPLA additive exacerbated the inflammatory process. Therefore, the lung targeted mRNA vaccine and MPLA adjuvant synergistically induced lung inflammation and weakened protection from Mtb infection. Thus, this work provides valuable implications for developing targeted lung vaccines: Addressing chronic lung inflammation induced by vaccine systems is critical for lung-targeted mRNA vaccines.

mTOR inhibition impacts the flagellin-augmented inflammatory and antimicrobial response of human airway epithelial cells to Pseudomonas aeruginosa

OBJECTIVE

The airway epithelium provides a first line of defense against pathogens by release of antimicrobial factors and neutrophil-attracting chemokines. Pseudomonas (P.) aeruginosa, a Gram-negative bacterium that expresses flagellin as an important virulence factor, is a common cause of injurious airway inflammation. The aim of our study was to determine the contribution of flagellin to the inflammatory, antimicrobial, and metabolic responses of the airway epithelium to P. aeruginosa. Furthermore, as we previously showed that targeting mTOR limited the glycolytic and inflammatory response induced by flagellin, we assessed the effect of rapamycin on human bronchial epithelial (HBE) cells stimulated with flagellated and non-flagellated P. aeruginosa.

METHODS

Primary pseudostratified HBE cells, cultured on an air-liquid-interface, were treated on the basolateral side with medium, vehicle or rapamycin, exposed on the apical side with flagellated or flagellin-deficient P. aeruginosa, and analyzed for their inflammatory, antimicrobial, and glycolytic responses.

RESULTS

Flagellin augmented the P. aeruginosa-induced expression of antimicrobial factors and secretion of chemokines by HBE cells but did not further increase the glycolytic response. Treatment of HBE cells with rapamycin inhibited mTOR activation in general and flagellin-augmented mTOR activation in particular, but did not affect the glycolytic response. Rapamycin, however, diminished the flagellin-augmented inflammatory and antimicrobial response induced by Pseudomonas.

CONCLUSIONS

These results demonstrate that flagellin is a significant factor that augments the inflammatory and antimicrobial response of human airway epithelial cells upon exposure to P. aeruginosa and suggest that mTOR inhibition by rapamycin in the airway epithelium diminishes these exaggerated responses.

Cell type-specific efferocytosis determines functional plasticity of alveolar macrophages

Resolution of lung injuries is vital to maintain gas exchange, but there is an increased risk of secondary bacterial infections during this stage. Alveolar macrophages (AMs) are crucial to clear bacteria and control the resolution of inflammation, but environmental cues that switch functional phenotypes of AMs remain incompletely understood. Here, we found that AMs lack the capacity to mount an effective immune response against bacteria during resolution of inflammation. Neutrophil (PMN)-derived myeloperoxidase (MPO) fueled canonical glutaminolysis via the mitochondrial membrane transporter uncoupling protein-2 (UCP2), resulting in decreased mtROS-dependent killing of bacteria and secretion of pro-inflammatory cytokines. MPO-enhanced UCP2 expression inhibited mitochondrial hyperpolarization and boosted efferocytosis irrespective of the presence of bacterial pathogens. Conversely, efferocytosis of other cell types resulted in a distinct anti-inflammatory AM phenotype while maintaining antibacterial phenotypic plasticity. Overall, our findings indicate that the uptake of apoptotic PMNs or MPO switches AMs to prioritize resolution of inflammation over antibacterial responses, a feature that is conserved in murine extrapulmonary macrophages and human AMs.

Evaluating the evidence for GM-CSF as a host-directed therapy in respiratory infections

Novel therapeutic approaches are needed to treat respiratory infections due to the rising antimicrobial resistance and the lack of effective antiviral therapies. A promising avenue to overcome treatment failure is to develop strategies that target the host immune response rather than the pathogen itself. Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a critical role in controlling homeostasis in lungs, alveolar macrophages being the most sensitive cells to GM-CSF signaling. In this review, we discuss the importance of GM-CSF secretion for lung homeostasis and its alteration during respiratory infections. We also present the pre-clinical evidence and clinical investigations evaluating GM-CSF-based treatments (administration or inhibition) as a therapeutic strategy for treating respiratory infections, highlighting both supporting and contradictory findings.

Electroacupuncture alleviates diesel exhaust particles-induced inflammatory response in lung through dopamine inhibition of NLRP3 signaling pathway

Fine particulate matter (PM2.5) remains a major environmental problem both in China and worldwide. Extensive researches have indicated that PM2.5 exposure can lead to various adverse health effects through pulmonary and systemic inflammation, making it crucial to explore effective individual intervention strategies. Electroacupuncture, an ancient Chinese medical treatment, has been proven safe and effective for treating some diseases, however, its potential in preventing PM2.5-induced toxicity remains unclear. This study aimed to explore the potential of electroacupuncture in mitigating pulmonary inflammation induced by diesel exhaust particles (DEP). Electroacupuncture was administered 15 minutes before intratracheal instillation of DEP, and the results showed that it markedly reduced DEP-induced pulmonary inflammation, as evidenced by significantly decreased pro-inflammatory markers at both gene and protein levels in lung, via regulating the macrophage polarization. Further analysis indicated that electroacupuncture promoted the production and release of dopamine from the adrenal medulla of mice, which then translocated to lung via circulation and inhibited the pulmonary NLRP3/caspase-1 signaling pathway. In addition, the time effectiveness experiment suggested that the anti-inflammatory effect of electroacupuncture against DEP can last for 48 hours. These findings suggest that electroacupuncture holds potential as a therapeutic intervention for health issues caused by PM2.5 exposure.

Aging-associated changes in immunological parameters: Implications for COVID-19 immune response in the elderly

Aging has a profound impact on the immune system, leading to a gradual decline in its function and increased systemic inflammation, collectively known as immunosenescence and inflammaging. These changes make older adults more susceptible to infections, including COVID-19, and contribute to worse clinical outcomes, such as higher morbidity and mortality rates. This review explores immunological changes associated with aging, including impaired innate immune responses, reduced T- and B-cell function, and altered cytokine profiles. A comprehensive literature search identified relevant studies on the topic, and inclusion criteria focused on studies addressing age-related immune changes and their impact on responses to COVID-19. The findings underscore the need for targeted healthcare strategies to mitigate the negative effects of aging on immunity and improve immune resilience, and ultimately clinical outcomes and quality of life for this vulnerable population.

The intricate interplay among microbiota, mucosal immunity, and viral infection in the respiratory tract

The mucosal system serves as the primary barrier against respiratory diseases and plays a crucial role in combating viral infections through mucosal immunity. The resident microbial community constitutes the main component of the mucosal system and exerts a significant inhibitory impact on the invasion of exogenous agents. However, the precise relationship between resident microbiota, mucosal immunity, and viral infections remains incomplete. This review aims to summarize the regulatory interactions between the resident microbiota of the mucosal system and innate immune components such as mucosal immunity and trained immunity. By clarifying these complex relationships, this review seeks to identify potential targets for augmenting respiratory disease prevention strategies and developing novel vaccine formulations. Furthermore, we propose the possibility of integrating the fields of microbiome-based therapeutics and vaccine development to create multifunctional vaccine formulations capable of targeting mucosal immunity induction. Such an approach holds great potential in offering novel pathways and strategies for the prevention and treatment of respiratory diseases.

Peroxisomes are critical for a unique metabolic demand and survival of alveolar macrophages

Tissue-resident macrophages (TRMs) populate throughout various tissues, and their homeostatic metabolism is heavily influenced by these microenvironments. Peroxisomes are organelles that contribute to lipid metabolism. However, the involvement of these organelles in the bioenergetics of TRMs remains undetermined. We conducted a developmental screen of TRMs using a conditional peroxisomal biogenesis factor 5 (Pex5) knockout mouse model that lacks functional peroxisomes in all immune cell subsets. Pulmonary alveolar macrophages (AMs) appeared as the only subset of TRMs that required functional peroxisomes for their development. Pex5 deficiency resulted in reduced AM survival due to increased sensitivity to lipotoxicity, in line with an excess accumulation of ceramides. The absence of peroxisomes had a significant effect on overall mitochondrial fitness and altered their metabolic program, allowing them to engage in glycolysis in addition to oxidative phosphorylation. Our results revealed that AMs have a unique metabolic regulation, where peroxisomes play a central role in their homeostatic development and maintenance.

Epigenetic Control of Alveolar Macrophages: Impact on Lung Health and Disease

Alveolar macrophages (AMs) are immune cells located in the alveoli-the tiny air sacs in the lungs where gas exchange occurs. Their functions are regulated by various epigenetic mechanisms, which are essential for both healthy lung function and disease development. In the lung's microenvironment, AMs play critical roles in immune surveillance, pathogen clearance, and tissue repair. This review examines how epigenetic regulation influences AM functions and their involvement in lung diseases. Key mechanisms, such as DNA methylation, histone modifications, and non-coding RNAs, regulate gene expression in response to environmental signals. In healthy lungs, these modifications enable AMs to quickly respond to inhaled threats. However, when these processes malfunction, they could contribute to diseases such as pulmonary fibrosis, COPD, and pulmonary hypertension. By exploring how epigenetic changes affect AM polarization, plasticity, and immune responses, we can gain deeper insights into their role in lung diseases and open new avenues for treating and preventing respiratory conditions. Ultimately, understanding the epigenetic mechanisms within AMs enhances our knowledge of lung immunology and offers potential for innovative interventions to restore lung health and prevent respiratory diseases.

Host responses to S. pneumoniae in wild type and Mertk mutant mice

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. Mertk is a receptor tyrosine kinase and a member of the TAM family. It serves as an efferocytosis receptor involved in the recognition and removal of apoptotic debris by phagocytic cells, dampening the inflammatory response. Here we show that at 24h post-inoculation with S. pneumoniae, Mertk-/- mice generated through homologous recombination and backcrossed (HRB-Mertk-/- mice) have fewer bacteria present in their pneumonic lung than wild type mice. This enhanced clearance was not observed in Mertk-/- mice generated by CRISPR technology. The enhanced clearance of HRB-Mertk-/- mice was associated with fewer neutrophils and more IFNγ in the bronchoalveolar lavage, but was not prevented by a neutralizing IFNγ antibody. Mertk is highly expressed on alveolar macrophages. Transcriptomic changes observed in HRB-Mertk-/- alveolar macrophages were associated with leukocyte activation, cellular motility, and response to stimulus, suggesting that they are primed for an inflammatory response. HRB-Mertk-/- mice similarly had enhanced host defense pathways in S. pneumoniae-stimulated alveolar macrophages in vitro and in pneumonic lung tissue. However, HRB-Mertk-/- alveolar macrophages demonstrated no defect in phagocytosis and acidification in vivo, and genes and gene sets describing phagocytic pathways were not enriched, suggesting that the enhanced clearance may be through alterations in the lung microenvironment. HRB-Mertk-/- mice are reported to have a long 129P2 DNA insert (~645 genes) in chromosome 2 adjacent to Mertk, as well as other alterations at multiple sites. Thus, while Mertk deficiency may contribute to the enhanced bacterial clearance, it is not solely responsible, because the phenotype is not seen in the CRISPR-Mertk-/- mice. The 129P2 DNA insert in the HRB-Mertk-/- mice must be mediating at least some of this phenotype. Understanding the mechanistic differences and the means by which this 129P2 DNA insert enhances bacterial clearance remains critically important.

Advanced MicroRNA delivery for lung inflammatory therapy: surfactant protein A controls cellular internalisation and degradation of extracellular vesicles

INTRODUCTION

Alveolar macrophages (AMs) are the first line of defence against pathogens that initiate an inflammatory response in the lungs and exhibit a strong affinity for surfactant protein A (SP-A). Extracellular vesicles (EVs) have emerged as a promising drug delivery platform due to their minimal cytotoxicity. However, precise targeting of specific cell types and the rapid lysosomal degradation of EVs within recipient cells remain persistent challenges.

METHOD

In this study, we explored the biological significance of SP-A-EVs as novel drug delivery systems for combating lung inflammation. We first verified that respiratory EVs express SP-A receptor (SP-R210), facilitating the conjugation of SP-A with EVs. The delivery efficiency, cellular internalisation pathways and therapeutic effects were evaluated using an in vivo mouse model.

RESULTS

SP-A-EVs were robustly internalised into AMs both in vitro and in vivo. Furthermore, our investigation revealed that the toll-like receptor 4-mediated endocytosis pathway was employed for the uptake of SP-A-EVs, significantly delaying their degradation compared with natural EVs, which primarily followed the conventional lysosomal degradation pathway within AMs. In a functional study, we successfully loaded anti-inflammatory microRNA (let-7b) into SP-A-EVs, leading to the suppression of AM activation and the alleviation of lung inflammation induced by lipopolysaccharide.

CONCLUSION

These findings underscore the potential of SP-A-EVs as highly effective drug delivery systems for targeted therapeutics in lung-related disorders, capitalising on the strong affinity between AMs and SP-A and the modulation of cellular internalisation.

Tissue-resident Klebsiella quasipneumoniae contributes to progression of idiopathic pulmonary fibrosis by triggering macrophages mitophagy in mice

Idiopathic pulmonary fibrosis (IPF) is a progressive and chronic interstitial lung disease with unclear underlying pathogenic mechanisms. Dysbiosis of the lung microbiota is believed to be associated with the development of fibrosis; however, the roles of the microbiome in the respiratory functions of hosts with IPF remain poorly understood. To investigate the relationship between the lung microbiome and the pathological processes of idiopathic pulmonary fibrosis under laboratory conditions, C57BL/6 J mice were exposed to bleomycin and observed at 7, 14, 21, and 28 days post-exposure. 16S rDNA analysis revealed that the lung microbial community exhibited dysbiosis in the bleomycin-induced pulmonary fibrosis model, characterized by an abnormally high proportion of Klebsiella quasipneumoniae (K. quasipneumoniae), as confirmed by RNA fluorescence in situ hybridization. Throughout the progression of experimental pulmonary fibrosis, Tax4Fun analysis indicated that the abundance of K. quasipneumoniae differed significantly between model mice and control mice, correlating with the sustained activation of reactive oxygen species (ROS) pathways. Importantly, the dysbiosis of K. quasipneumoniae may serve as a critical factor triggering increased ROS levels, accompanied by macrophage mitophagy, ultimately leading to the overexpression of TGF-β1, a key player in the pathogenesis of pulmonary fibrosis. These findings suggest that lung microbiota dysbiosis exacerbates the progression of bleomycin-induced pulmonary fibrosis related to macrophage mitophagy.

Chemokine CXCL14 Inhibits the Survival of Mycobacterium smegmatis inside Macrophages by Upregulating A20 to Promote ROS Production

Tuberculosis remains a major global health threat, with traditional antibiotic treatments facing challenges such as drug resistance. Host-directed therapy (HDT) has emerged as a promising approach to combat tuberculosis by enhancing the host immune response. CXCL14, a chemokine family member, plays a crucial role in regulating host antipathogenic immune responses. To elucidate the role of CXCL14 and its key regulatory molecules in mycobacterial infections, we identified new targets for host-directed therapy. RAW264.7 macrophages were pretreated with CXCL14 and infected with Mycobacterium smegmatis. CFU, ROS levels, and apoptosis were assessed. Cell RNA was extracted for high-throughput sequencing, and significantly differentially expressed genes were screened and identified. The effects of candidate genes were verified using knockdown and overexpression techniques. A mouse model of mycobacterial infection was established to validate the role of CXCL14 in vivo. CXCL14 pretreatment significantly reduced intracellular mycobacteria and increased ROS levels in macrophages without affecting apoptosis. Transcriptome analysis identified A20 as a key differentially expressed gene. A20 overexpression promoted ROS production and decreased intracellular mycobacteria, while A20 knockdown reversed these effects. The combination of CXCL14 and A20 overexpression effectively inhibited mycobacterial survival in macrophages. CXCL14 significantly inhibited mycobacterial survival in mice and reduced organ damage in vivo. CXCL14 promoted ROS production in macrophages by upregulating A20 expression, thereby inhibiting mycobacterial survival. In the mouse model, CXCL14 alleviated inflammatory responses and histopathological damage caused by mycobacterial infection. These findings suggest that CXCL14 is a promising new HDT molecule for the treatment of mycobacterial infections.

HIF-1 regulates mitochondrial function in bone marrow-derived macrophages but not in tissue-resident alveolar macrophages

HIF-1α plays a critical role in shaping macrophage phenotype and effector function. We have previously shown that tissue-resident alveolar macrophages (TR-AMs) have extremely low glycolytic capacity at steady-state but can shift toward glycolysis under hypoxic conditions. Here, we generated mice with tamoxifen-inducible myeloid lineage cell specific deletion of Hif1a (Hif1afl/fl:LysM-CreERT2+/-) and from these mice, we isolated TR-AMs and bone marrow-derived macrophages (BMDMs) in which Hif1a is deleted. We show that TR-AM HIF-1α is required for the glycolytic shift under prolyl hydroxylase inhibition but is dispensable at steady-state for inflammatory effector function. In contrast, HIF-1α deletion in BMDMs led to diminished glycolytic capacity at steady-state and reduced inflammatory capacity, but higher mitochondrial function. Gene set enrichment analysis revealed enhanced c-Myc transcriptional activity in Hif1a-/- BMDMs, and upregulation of gene pathways related to ribosomal biogenesis and cellular proliferation. We conclude that HIF-1α regulates mitochondrial function in BMDMs but not in TR-AMs. The findings highlight the heterogeneity of HIF-1α function in distinct macrophage populations and provide new insight into how HIF-1α regulates gene expression, inflammation, and metabolism in different types of macrophages.

Cross one single body 49 tissues single-cell transcriptome reveals detailed macrophage heterogeneity during pig pregnancy

Introduction

Pregnancy involves complex physiological adaptations across maternal organs and the immune system to support fetal development. Macrophages play a dual role during pregnancy: defending against pathogens and supporting tissue adaptation. However, comprehensive and in-depth studies of cross-tissue transcriptional heterogeneity of macrophages during healthy pregnancy at the single-cell level remain elusive.

Methods

We performed single-cell RNA sequencing (scRNA-seq) to profile macrophages from a healthy pregnant pig across 49 tissues. Immunofluorescence was performed to verify the specific expression of transcription factors.

Results

In this study, we generated a macrophage atlas containing 114,881 macrophages from 49 tissues/organs within one single healthy pregnant pig, identified 33 subtypes, and revealed extensive tissue-specific diversity. We observed significant heterogeneity of macrophage subtypes across five different anatomical sites of adipose tissue. Notably, the Mφ MARCO+ subtype, primarily derived from mesenteric adipose tissue, showed higher activity in pattern recognition receptor signaling pathways compared to subtypes in other tissues, including different fat depots. Cross-tissue analysis revealed distinct expression patterns of transcription factors, cytokines, and cell surface receptors, including the transcription factor PLSCR1, specifically expressed in lung macrophages and verified by immunofluorescence. Cross-species analysis unveiled conservation and heterogeneity among macrophages in pigs, humans, and mice.

Conclusion

We constructed a multiple-tissue single-cell transcriptome atlas of macrophages in one single healthy pregnant pig, revealing their molecular differences and commonalities across tissues and species. Our study provides a valuable resource for understanding macrophage diversity and tissue-specific macrophage adaptations during pregnancy in pigs.

Dynamic Alterations in DNA Methylation of CD4+ T Cells and Macrophages in a Murine Model of Tuberculous Pleural Infection Induced by BCG Vaccination

Tuberculous pleural effusion (TPE) is a prevalent form of extrapulmonary tuberculosis, and immune abnormalities play a crucial role in promoting its development. However, the dynamic changes and regulatory characteristics of immune cells during TPE progression remain incompletely understood. This study analyzed DNA methylation and transcriptome data from macrophages and CD4+ T cells from pleural lavage fluid of BCG-induced tuberculous pleurisy mouse models at specific time points (Days 0, 1, 7, and 14). The results revealed substantial alterations in DNA methylation patterns associated with inflammatory factors and interferon genes. Notably, macrophages exhibited the most pronounced differences in DNA methylation profiles on Day 1, while CD4+ T cells demonstrated gradual changes over time. The investigation further indicated that DNA methylation primarily regulated the differentiation of Th1, Th17, and Th22 cells but not Th9 cells. Additionally, single-cell RNA sequencing analysis revealed an increasing expression of C1q during infection, which was regulated by DNA methylation. Importantly, C1q+ and C1q- macrophages demonstrated distinct roles in modulating immune responses during infection. This research provides valuable insights into the DNA methylation profile of immune cells during Mycobacterium bovis infection-induced pleurisy in a mouse model, enhancing our understanding of the upstream regulatory mechanisms underlying immune response development in TPE.

The Interplay Between Innate Immunity and Nonimmune Cells in Lung Damage, Inflammation, and Repair

As the site of gas exchange, the lung is critical for organismal survival. It is also subject to continual environmental insults inflicted by pathogens, particles, and toxins. Sometimes, these insults result in structural damage and the initiation of an innate immune response. Operating in parallel, the immune response aims to eliminate the threat, while the repair process ensures continual physiological function of the lung. The inflammatory response and repair processes are thus inextricably linked in time and space but are often studied in isolation. Here, we review the interplay of innate immune cells and nonimmune cells during lung insult and repair. We highlight how cellular cross talk can fine-tune the circuitry of the immune response, how innate immune cells can facilitate or antagonize proper organ repair, and the prolonged changes to lung immunity and physiology that can result from acute immune responses and repair processes.

Panax notoginseng saponins ameliorate LPS-induced acute lung injury by promoting STAT6-mediated M2-like macrophage polarization

BACKGROUND

Acute lung injury (ALI) is a severe inflammatory condition characterized by dysregulated immune responses and high mortality rates, with limited effective therapeutic options currently available. Panax notoginseng saponins (PNS), bioactive compounds derived from Panax notoginseng, have shown promise in mitigating lipopolysaccharide (LPS)-induced ALI. However, the molecular mechanisms underlying their therapeutic effects remain poorly understood. Given the critical role of M2-like macrophage polarization in resolving inflammation and promoting tissue repair, we investigated whether PNS exerts its protective effects in ALI by modulating this process. Furthermore, we explored the specific involvement of the signal transducer and activator of transcription 6 (STAT6) pathway in mediating these effects.

METHODS

Chemical profiling of PNS was performed using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), followed by quantitative analysis of its major bioactive components via high-performance liquid chromatography (HPLC). To evaluate the therapeutic efficacy of PNS and its principal constituents, we established an ALI mouse model through intratracheal administration of LPS. Comprehensive assessments included lung field shadowing, oxygen saturation levels, pulmonary function, and systematic histopathological examination. The regulatory effects of PNS on macrophage polarization were examined in THP-1 cells and bone marrow-derived macrophages (BMDMs), with cellular phenotypes analyzed by flow cytometry. To elucidate the mechanistic role of STAT6 in PNS-mediated protection, experiments were conducted using Stat6-deficient BMDMs and Stat6 knockout mice.

RESULTS

UPLC-Q-TOF-MS and HPLC identified and quantified the principal components of PNS: Notoginsenoside R1, Ginsenoside Rg1, Ginsenoside Re, and Ginsenoside Rb1. PNS treatment dose-dependently reduced inflammatory responses in LPS-induced ALI mice, as evidenced by decreased cytokine levels. Each of the four major PNS components independently alleviated ALI symptoms in mice. Pathway analysis revealed 56 potential ALI-related targets, with Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment suggesting that PNS exerts its protective effects by modulating inflammatory signaling pathways. In vitro studies demonstrated that PNS promoted STAT6 phosphorylation and nuclear translocation, enhancing M2-like macrophage polarization and interleukin-10 (IL-10) secretion in a STAT6-dependent manner. Genetic ablation of Stat6 partially reversed the protective effects of PNS on ALI, macrophage polarization, and IL-10 production, confirming the pivotal role of STAT6 in mediating PNS activity.

CONCLUSION

This study demonstrates that PNS alleviates LPS-induced ALI by promoting STAT6-dependent M2-like macrophage polarization, highlighting its potential as a therapeutic agent for ALI. These findings provide mechanistic insights into the anti-inflammatory actions of PNS and underscore the importance of STAT6 signaling in its protective effects.

Autophagy and Its Association with Macrophages in Clonal Hematopoiesis Leading to Atherosclerosis

Atherosclerosis, a chronic inflammatory disease characterized by lipid accumulation and immune cell infiltration, is linked to plaque formation and cardiovascular events. While traditionally associated with lipid metabolism and endothelial dysfunction, recent research highlights the roles of autophagy and clonal hematopoiesis (CH) in its pathogenesis. Autophagy, a cellular process crucial for degrading damaged components, regulates macrophage homeostasis and inflammation, both of which are pivotal in atherosclerosis. In macrophages, autophagy influences lipid metabolism, cytokine regulation, and oxidative stress, helping to prevent plaque instability. Defective autophagy exacerbates inflammation, impairs cholesterol efflux, and accelerates disease progression. Additionally, autophagic processes in endothelial cells and smooth muscle cells further contribute to atherosclerotic pathology. Recent studies also emphasize the interplay between autophagy and CH, wherein somatic mutations in genes like TET2, JAK2, and DNMT3A drive immune cell expansion and enhance inflammatory responses in atherosclerotic plaques. These mutations modify macrophage function, intensifying the inflammatory environment and accelerating atherosclerosis. Chaperone-mediated autophagy (CMA), a selective form of autophagy, also plays a critical role in regulating macrophage inflammation by degrading pro-inflammatory cytokines and oxidized low-density lipoprotein (ox-LDL). Impaired CMA activity leads to the accumulation of these substrates, activating the NLRP3 inflammasome and worsening inflammation. Preclinical studies suggest that pharmacologically activating CMA may mitigate atherosclerosis progression. In animal models, reduced CMA activity accelerates plaque instability and increases inflammation. This review highlights the importance of autophagic regulation in macrophages, focusing on its role in inflammation, plaque formation, and the contributions of CH. Building upon current advances, we propose a hypothesis in which autophagy, programmed cell death, and clonal hematopoiesis form a critical intrinsic axis that modulates the fundamental functions of macrophages, playing a complex role in the development of atherosclerosis. Understanding these mechanisms offers potential therapeutic strategies targeting autophagy and inflammation to reduce the burden of atherosclerotic cardiovascular disease.

Design, fabrication, and in vitro-in vivo evaluation of surface-engineered pyrazinamide-loaded lipid nanoparticles for tuberculosis therapy

Pyrazinamide (PYZ), a nicotinamide derivative, is an essential first-line anti-TB drug. However, its dose-dependent hepatotoxicity poses a considerable challenge, accentuating the need for improved delivery approaches. The key objective of the research work was to develop mannose-appended pyrazinamide-containing solid-lipid nanoparticles (Mn-PYZ-SNs) for the targeted management of TB. The developed Mn-PYZ-SNs depicted a particle size of 422±09 nm, which was slightly higher than that of unconjugated PYZ-SNs (Un-PYZ-SNs)(401±08 nm), with a minimal reduction in entrapment efficiency(83.64±1.42%). The in vitro drug release studies demonstrated comparable sustained release patterns for both formulations, with a similarity factor (f2) of 77.33, indicating that the structural integrity of PYZ-SNs was maintained during mannose conjugation. Fluorescence imaging and flow cytometric analysis revealed significantly enhanced cellular uptake of Mn-C6-SNs, with a 1.60-fold increase compared to Un-C6-SNs. The in vivo pharmacokinetic studies conducted on Sprague-Dawley rats showed a 4.7-fold improvement in relative bioavailability for Mn-PYZ-SNs. Biodistribution studies demonstrated significantly higher lung accumulation of Mn-PYZ-SNs (1.93-fold) compared to Un-PYZ-SNs at 24 hours. The aforementioned results imply that the developed Mn-PYZ-SNs could be a promising carrier for the treatment of TB. via the oral intestinal lymphatic pathway, circumventing its hepatic first-pass metabolism, and thereby preventing hepatic adverse effects.

Coculture of mesenchymal stem cells and macrophage: A narrative review

Stem cell transplantation is a promising treatment for repairing damaged tissues, but challenges like immune rejection and ethical concerns remain. Mesenchymal stem cells (MSCs) offer high differentiation potential and immune regulatory activity, showing promise in treating diseases such as gynecological, neurological, and kidney disorders. With scientific progress, MSC applications are overcoming traditional treatment limitations. In MSCs-macrophage coculture, MSCs transform macrophages into anti-inflammatory M2 macrophages, reducing inflammation, whereas macrophages enhance MSCs osteogenic differentiation. This coculture is vital for immune modulation and tissue repair, with models varying by contact type and dimensional arrangements. Factors such as coculture techniques and cell ratios influence outcomes. Benefits include improved heart function, wound healing, reduced lung inflammation, and accelerated bone repair. Challenges include optimizing coculture conditions. This study reviews the methodologies, factors, and mechanisms of MSC-macrophage coculture, providing a foundation for tissue engineering applications. SIGNIFICANCE STATEMENT: This review underlines the significant role of mesenchymal stem cell-macrophage coculture, providing a foundation for tissue engineering application.

Integrating Pulmonary and Systemic Transcriptomic Profiles to Characterize Lung Injury after Pediatric Hematopoietic Stem Cell Transplant

Hematopoietic stem cell transplantation (HCT) is potentially curative for numerous malignant and non-malignant diseases but can lead to lung injury due to chemoradiation toxicity, infection, and immune dysregulation. Bronchoalveolar lavage (BAL) is the most commonly used procedure for diagnostic sampling of the lung but is invasive, cannot be performed in medically fragile patients, and is challenging to perform serially. We previously showed that BAL transcriptomes representing pulmonary inflammation and cellular injury can phenotype post-HCT lung injury and predict mortality outcomes. However, whether peripheral blood testing is a suitable minimally-invasive surrogate for pulmonary sampling in the HCT population remains unknown. To address this question, we compared 210 paired BAL and peripheral blood transcriptomes obtained from 166 pediatric HCT patients at 27 children's hospitals. BAL and blood mRNA abundance showed minimal overall correlation at the level of individual genes, gene set enrichment scores, imputed cell fractions, and T- and B-cell receptor clonotypes. Instead, we identified significant site-specific transcriptional programs. In BAL, expression of innate and adaptive immune pathways was tightly co-regulated with expression of epithelial mesenchymal transition and hypoxia pathways, and these signatures were associated with mortality. In contrast, in blood, expression of endothelial injury, DNA repair, and cellular metabolism pathways was associated with mortality. Integration of paired BAL and blood transcriptomes dichotomized patients into two groups, of which one group showed twice the rate of hypoxia and significantly worse outcomes within 7 days of enrollment. These findings reveal a compartmentalized injury response, where BAL and peripheral blood transcriptomes provide distinct but complementary insights into local and systemic mechanisms of post-HCT lung injury.

The role of monocytes and macrophages in idiopathic inflammatory myopathies: insights into pathogenesis and potential targets

Idiopathic inflammatory myopathies (IIMs) are heterogeneous autoimmune disorders characterized by muscle inflammation, weakness, and extramuscular manifestations such as interstitial lung disease, skin rash, arthritis, dysphagia, myocarditis and other systemic organ involvement. Although T and B cells have historically been central to the understanding of IIM immunopathology, monocytes and their differentiated progenitor cells, macrophages, are increasingly being recognized as critical mediators of both tissue damage and repair. In subtypes such as dermatomyositis, immune-mediated necrotizing myopathy and antisynthetase syndrome, macrophages infiltrate skeletal muscle and other affected tissues, contributing to inflammation via production of pro-inflammatory cytokines, chemokines, and reactive oxygen species. Dysregulated interferon signaling, mitochondrial stress, and aberrant metabolic states in these cells further perpetuate tissue injury in IIMs. Conversely, certain macrophage subsets can support muscle fiber regeneration and dampen inflammation, underscoring the dual roles these cells can play. Future research into the heterogeneity of monocytes and macrophages, including single-cell transcriptomic and metabolomic approaches, will help clarify disease mechanisms, identify biomarkers of disease activity and prognosis, and guide novel therapeutic strategies targeting these innate immune cells in IIM.

Macrophages hijack carbapenem-resistance hypervirulent Klebsiella pneumoniae by blocking SLC7A11/GSH-manipulated iron oxidative stress

Infection with carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKP) is life-threatening because of its pronounced virulence and antibiotic resistance. Recent studies revealed that iron and ROS enhance the ability of macrophages to eliminate intracellular pathogenic bacteria. However, whether and how iron-related oxygen stress responses in macrophages elicit a protective role against CR-hvKP infection remains largely unknown. In a mouse model of CR-hvKP pulmonary infection, the production of the Solute Carrier Family 7 member 11 (SLC7A11) was increased. Treatment with the ferroptosis agonist Erastin or Sorafenib decreased the SLC7A11 expression and the bacterial load in infected lung tissues, alleviating CR-hvKP-induced acute lung injury, increasing the content of TLR4, ROS and LPO. In vitro experiments showed that CR-hvKP infection resulted in a remarkable time-dependent changes in the expression of SLC7A11, GSH, ferrous iron, ROS and LPO in MH-S cells. Mechanically, blocking the expression of SLC7A11 in CR-hvKP-infected MH-S cells increased iron and ROS, improving the ability of macrophages to clear CR-hvKP in an LPO-dependent manner. Taken together, our study reveals that improving iron-related oxygen stress via blocking the SLC7A11/GSH pathway promoting the macrophages to phagocytose and eliminate CR-hvKP, which provides a new promising strategy against CR-hvKP infection.

Alveolar macrophages from persons with HIV mount impaired TNF signaling networks to M. tuberculosis infection

People living with HIV (PLWH) have an increased risk for developing tuberculosis after M. tuberculosis infection, despite anti-retroviral therapy (ART). To delineate the underlying mechanisms, we conducted single cell transcriptomics on bronchoalveolar lavage cells from PLWH on ART and HIV uninfected healthy controls infected with M. tuberculosis ex vivo. We identify an M1-like proinflammatory alveolar macrophage subset that sequentially acquires TNF signaling capacity in controls but not in PLWH. Cell-cell communication analyses reveal interactions between M1-like macrophages and effector memory T cells within TNF superfamily, chemokine, and costimulatory networks in the airways of controls. These interaction networks were lacking in PLWH infected with M. tuberculosis, where anti-inflammatory M2-like alveolar macrophages and T regulatory cells dominated along with dysregulated T cell signatures. Our data support a model in which impaired TNF-TNFR signaling, M2-like alveolar macrophages and aberrant macrophage-T cell crosstalk, lead to ineffective immunity to M. tuberculosis in PLWH on ART.

The Role of Inflammation in the Pathogenesis of Comorbidity of Chronic Obstructive Pulmonary Disease and Pulmonary Tuberculosis

The comorbid course of chronic obstructive pulmonary disease (COPD) and pulmonary tuberculosis is an important medical and social problem. Both diseases, although having different etiologies, have many overlapping relationships that mutually influence their course and prognosis. The aim of the current review is to discuss the role of different immune mechanisms underlying inflammation in COPD and pulmonary tuberculosis. These mechanisms are known to involve both the innate and adaptive immune system, including various cellular and intercellular interactions. There is growing evidence that immune mechanisms involved in the pathogenesis of both COPD and tuberculosis may jointly contribute to the tuberculosis-associated obstructive pulmonary disease (TOPD) phenotype. Several studies have reported prior tuberculosis as a risk factor for COPD. Therefore, the study of the mechanisms that link COPD and tuberculosis is of considerable clinical interest.

Mechanosensitivity of macrophage polarization: comparing small molecule leukadherin-1 to substrate stiffness

Macrophages sustain tissue homeostasis through host defense and wound repair. To promote host defense, macrophages upregulate surface markers associated with antigen processing and secrete pro-inflammatory mediators such as IL-6 and IL-1β. After pathogen clearance, macrophages shift phenotype to promote wound repair. Shifts in phenotypes are termed "polarization" and have historically been modeled by exposure to soluble mediators such as LPS+IFNγ (host defense) or IL-4+IL-13 (tissue repair). Greater emphasis is now being placed on understanding how the mechanical environment of macrophages, such as tissue compliance, regulates macrophages responses. Here, we compare incubation of primary macrophages on collagen-coated silica gels of varying stiffness to treatment with the small molecule integrin activator, leukadherin-1 (LA1), to examine how substrate stiffness alters macrophage polarization in response to multiple stimuli. LA1 was developed as an immunomodulator to treat inflammatory diseases by impairing trafficking of inflammatory cells. A recent clinical trial examining LA1 as an immunomodulator in solid tumors was terminated early because no benefit was observed. We hypothesized that LA1 treatment may exert additional, unexpected effects on macrophage polarization by replicating mechanotransduction. Specifically, we hypothesized that LA1 would mimic effects of incubation on stiffer substrates, as both conditions would be predicted to activate integrins. Our results show that soft substrate (0.2 kPa) trends towards upregulation of host defense molecules, in contrast to prior reports using different experimental systems. We further show that soft substrates enhance NLRP3-mediated IL-1β production, compared to stiff, in both primary mouse and human macrophages. LA1 mimicked incubation on stiff substrates in inhibiting NLRP3 activation and in regulating expression of several surface markers but differed by reducing IL-6 production. Our results show that macrophage inflammatory responses are regulated by adhesion-based, integrin-mediated mechanical signaling. Modulation of NLRP3-mediated IL-1β production by LA1 supports the possibility of repurposing LA1 to treat NLRP3-dependent inflammatory diseases.

Single cell transcriptomic analysis reveals tumor immune infiltration by macrophage cells gene signature in lung adenocarcinoma

BACKGROUND

Tumor-associated macrophages (TAMs) play pivotal roles in innate immunity and contribute to the advancement of lung cancer. We aimed to identify novel TAM-related biomarkers and significance of macrophage infiltration in lung adenocarcinoma (LUAD) through an integrative analysis of single-cell RNA-sequencing (scRNA-seq) data. To describe the cell atlas and construct a novel prognostic signature in LUAD.

METHODS

The gene signature linked to TAMs was identified utilizing Scanpy from the scRNA-seq dataset GSE131907. Subsequent analysis involved evaluating the expression levels of these genes, their potential molecular mechanisms, and prognostic significance in LUAD using data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. We also constructed a risk score models through LASSO Cox regression for these genes. The underlying mechanism was further elucidated through the application of GSEA, ESTIMATE, TIDE, and other bioinformatic algorithms.

RESULTS

Single-cell atlas was described by analyze 29 scRNA-seq samples from 19 LUAD patients. The TAMs-related gene signature (TGS) was identified as an independent prognostic factor by LASSO Cox regression analysis using differential expression genes (DEGs) derived from pro- and anti-inflammatory macrophage cells. Risk score model including nine TAMs-related genes (FOSL1, ZNF697, ADM, UBE2S, TICAM1, S100P, BIRC3, TLE1, and DEFB1) were obtained for prognosis construction. Moreover, the risk model underwent additional validation in four external GEO cohorts: GSE31210, GSE72094, GSE26939, and GSE30219. Interestingly, TGS-high tumors revealed enrichments in TGF-β signaling and hypoxia pathways, which shown low immune infiltration and immunosuppression by ESTIMATE and TIDE algorithm. The TGS-high risk group exhibited lower richness and diversity in the T-cell receptor (TCR) repertoire.

CONCLUSION

This study introduces a novel TGS score developed through LASSO Cox regression analysis, utilizing DEGs in pro- and anti-inflammatory macrophage cells. High TGS tumors exhibited enrichment in TGF-β signaling and hypoxia pathways, suggesting their potential utility in predicting prognosis and immune responses in patients with LUAD. These results offer promising implications for the development of therapeutic strategies for LUAD.

Polysialic acid-based nanoparticles for enhanced targeting and controlled dexamethasone release in pulmonary inflammation treatment

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions characterized by severe inflammation and respiratory failure. Despite the use of dexamethasone (Dex) in treatment, challenges such as poor solubility and systemic side effects persist, highlighting the need for novel therapeutic approaches. This study introduces an innovative nanoparticle delivery system based on chitosan (CS) and polysialic acid (PSA), engineered via electrostatic assembly, to improve the targeted delivery of Dex to inflamed lung tissues. To enhance drug encapsulation and stability, novel taurine-Vitamin E succinate amphiphilic molecules (TVES and TGVES) were synthesized. The unique ability of PSA to specifically target Siglec-1 receptors on M1 macrophages-key contributors to ALI/ARDS-related inflammation-positions this system as a promising strategy for targeted pulmonary therapies. In vitro targeting of M1 macrophages and in vivo reduction of inflammation demonstrate the potential to transform treatment by delivering therapeutic agents precisely to the site of need. This cutting-edge nanoparticle platform not only holds promise for improving ALI/ARDS outcomes but also paves the way for the application of functional additives like taurine in advanced medical therapies.

Hexahistidine-metal assembly encapsulated fibroblast growth factor 21 for lipopolysaccharide-induced acute lung injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) represents a spectrum of potentially fatal conditions that currently lack effective drug treatment. Recent researches suggest that Fibroblast Growth Factor 21 (FGF21) may protect against ALI/ARDS. However, the clinical use of FGF21 is limited by its rapid degradation, restricted targeting capabilities, and numerous adverse effects. Addressing this challenge, the study employs a pH-responsive nanoparticle delivery system known as Hexahistidine-metal Assembly (HmA) for administering FGF21. The entrapment efficiency (EE%) and loading capacity (LCwt%) of HmA exceed 90 % and 35 %, respectively, while the HmA@FGF21 nanoparticles exhibit an average size of 130 nm, a PDI value of approximately 0.28, and a zeta potential of 24 mV. In animal experiments, HmA@FGF21 administered in lipopolysaccharide (LPS)-induced lung injury significantly exceed those of standalone FGF21, including mitigating the pathological manifestations and reducing the wet/dry ratio, total protein concentration, and overall cell count in BALF of ALI, whether administered via the airway or intravenously. This therapeutic approach therefore shows promise for precise delivery of FGF21 to the lungs to treat ALI, and may offer a novel, and efficient method for delivery of potential pharmacological agents to address other lung diseases.

Differences in glycolytic metabolism between tissue-resident alveolar macrophages and recruited lung macrophages

Immunometabolism has emerged as a key area of focus in immunology and has the potential to lead to new treatments for immune-related diseases. It is well-established that glycolytic metabolism is essential for adaptation to hypoxia and for macrophage inflammatory function. Macrophages have been shown to upregulate their glycolytic metabolism in response to pathogens and pathogen-associated molecular patterns such as LPS. As a direct link to the external environment, the lungs' distinctive nutrient composition and multiple macrophage subtypes provide a unique opportunity to study macrophage metabolism. This review aims to highlight how the steady-state airway and severely inflamed airway offer divergent environments for macrophage glycolytic metabolism. We describe the differences in glycolytic metabolism between tissue-resident alveolar macrophages, and other lung macrophages at steady-state and during inflammation/injury. We also provide an overview of experimental guidelines on how to assess metabolism at the cellular level using Seahorse-based bioenergetic analysis including a review of pharmacologic agents used to inhibit or activate glycolysis.

Dual-Locked Fluorescence Probe for Monitoring the Dynamic Transition of Pulmonary Macrophages

Pulmonary macrophages undergo dynamic changes in population, proportion, and polarization during respiratory diseases. Monitoring these changes is critical for understanding their roles in pathology, improving the diagnosis, and guiding drug development. However, current analytic methods based on tissue biopsy are invasive and static, limiting their ability to provide such dynamic information. Herein, we report a dual-locked macrophage-specific renal-clearable probe (DMRPNOCas) for the dynamic monitoring of pulmonary macrophages during influenza A virus (IAV) infection. DMRPNOCas activates fluorescence in the presence of two biomarkers (caspase-1 and NO) only coexpressed by M1 macrophages. To optimize the NO reactivity, the scaffold of DMRPNOCas is screened from the hemicyanine derivatives with an o-phenylenediamine group positioned differently on the indole ring. Notably, the para-substituted o-phenylenediamine demonstrates a higher NO-activated fluorescence compared to its meta-substituted counterpart. This enhancement, as revealed by quantum chemical calculations, is attributed to differential inhibition of twisted intramolecular charge transfer induced by the NO reaction. DMRPNOCas specifically distinguishes M1 macrophages from other leukocytes including T cells, neutrophils, and M2 macrophages, a capability unmatched by single-locked control probes and other reported probes. Consequently, DMRPNOCas enables in vivo dynamic monitoring of pulmonary macrophages, uncovering extensive recruitment and M1 polarization of monocyte-derived macrophages within 48 h of IAV infection. This process is accompanied by a significant reduction in alveolar macrophages. These findings provide new insights into macrophage-mediated pulmonary inflammation and underscore the potential of dual-locked probes for precise diagnosis and monitoring of pathological processes.

Mouse mesenchymal stem cell-derived exosomal miR-205-5p modulates LPS-induced macrophage polarization and alleviates lung injury by regulating the USP7/FOXM1 axis

Exosomal microRNAs produced from mesenchymal stem cells (MSCs) are crucial in the management of acute lung injury (ALI). In this work, mMSCs separated from bone marrow were used to extract exosomes (MSC-Exos). MSC-Exos treatment attenuated pathological changes and scores, and edema in ALI mice. Also, MSC-Exos administration modulated the concentrations of inflammatory factors as well as the macrophage polarization both in vivo and in vitro. Upregulation of miR-205-5p in MSC-Exos regulated the macrophage polarization and the contents of inflammatory factors in animal and cell models. MiR-205-5p targeted USP7, and negatively modulated the expression of USP7. USP7 interacted with FOXM1, and reduced the ubiquitination degradation of FOXM1. MSC-derived exosomal miR-205-5p modulated ubiquitination of FOXM1 by targeting USP7. The ameliorative effect of MSC-Exos on the macrophage polarization and the inflammatory factors release was reversed with the overexpression of USP7 in animal and cell models. Collectively, MSC-derived exosomal miR-205-5p regulated lipopolysaccharide (LPS)-induced macrophage polarization and alleviated lung injury by the USP7/FOXM1 axis, which developed a potential target for the treatment of ALI.

A micro-lung chip with macrophages for targeted anti-fibrotic therapy

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease of unknown etiology. Macrophages are implicated in the fibrotic process, but exhibit remarkable plasticity in the activated immune environmentin vivo, presenting significant challenges as therapeutic targets. To explore the influence of macrophages on IPF and develop macrophage-targeted therapies, we engineered a micro-lung chip with a lung epithelium-interstitium tissue unit to establish a controlled immune environment containing only macrophages. We discovered that macrophages exacerbated inflammation and fibrosis by comparing microchips treated with bleomycin (BLM) in the presence and absence of macrophages. Based on the duration of BLM treatment, we established pathological models corresponding to inflammation and fibrosis stages. Transcriptome analysis revealed that activation of the PI3K-AKT signalling pathway facilitates the transition from inflammation to fibrosis. However, LY294002, a PI3K inhibitor, not only suppressed fibrosis and decreased the accumulation of M2 macrophages but also intensified the severity of inflammation. These findings suggest that macrophages play a pivotal role in the potential development at the tissue level. The micro-lung chip co-cultured with macrophages holds significant potential for exploring the pathological progression of IPF and elucidating the mechanisms of anti-fibrotic drugs.

Impaired inflammatory resolution with severe SARS-CoV-2 infection in leptin knock out obese hamster

Comorbidities, such as obesity, increase the risk of severe COVID-19. However, the mechanisms underlying severe illnesses in individuals with obesity are poorly understood. Here, we used gene-edited leptin knock out (Leptin -/-) obese hamsters to establish a severe infection model. This model exhibits robust viral replication, severe lung lesions, pronounced clinical symptoms, and fatal infection, mirroring severe COVID-19 in patients with obesity. Using single-cell transcriptomics on lung tissues pre- and post-infection, we found that monocyte-derived alveolar macrophages (MD-AM) play a key role in lung hyper-inflammation, including two unique MD-AM cell fate branches specific to Leptin -/- hamsters. Notably, reduced Trem2-dependent efferocytosis pathways in Leptin -/- hamsters indicated weakened inflammation resolution, consistent with the scRNA-seq data from patients with obesity. In summary, our study highlights the obesity-associated mechanisms underlying severe SARS-CoV-2 infections and establishes a reliable preclinical animal model for developing obesity-specific therapeutics for critical COVID-19.

Measles vaccination in lung transplant candidates

Background

The incidence of measles is now increasing. Measles is especially dangerous for high-risk individuals, including lung transplant candidates with severe progressive bronchopulmonary disorders.

Objective

The objective of this study was to investigate how vaccine-induced immunity is developed in lung transplant candidates seronegative for measles. In order to study vaccine-induced measles immunity, the study subjects were divided in two groups. The main group consisted of 22 patients (11 males and 11 females) with severe bronchopulmonary disorders, aged 19 to 58. The control group was made up of healthcare providers who were matched with respect to age and gender to the patients in the main group. All study subjects were given a single dose of measles vaccine. Levels of anti-measles IgG antibodies (Ab) were measured by enzyme-linked immunosorbent assay (ELISA) using the VectoMeasles-IgG kit (Russia).

Results

One month after vaccination, both study groups showed a statistically significant increase in anti-measles IgG Ab compared to baseline levels. In the main group, vaccine-induced Ab levels were significantly lower than in the control group (0.41 [0.098; 1.75] IU/mL vs. 1.94 [0.96; 3.3] IU/mL; р<0.0001). The rates of seroconversion were 73% and 100% in the main and control groups, respectively. The majority of non-responders (83%) in the main group had restrictive pulmonary disease. One year after vaccination, anti-measles Ab were detected in 36% (5/14) of the patients in the main group.

Conclusion

Administration of a single dose of measles vaccine to seronegative lung transplant candidates with severe progressive bronchopulmonary disorders was safe and resulted in protective levels of antibodies in 73% of patients. One year after vaccination, anti-measles Ab were detected in 36% of the patients, which suggested that a single dose failed to induce a robust immune response in this patient population.

NLRP3 inflammasome mediates pyroptosis of alveolar macrophages to induce radiation lung injury

Alveolar macrophages play a crucial role in maintaining lung homeostasis. However, the mechanisms underlying alveolar macrophage pyroptosis and inflammasome activation in radiation-induced lung injury remain unclear. In this study, we employed multicolor flow cytometry and single-cell RNA sequencing to reveal the immune cell and cell death landscape in the tissue microenvironment of radiation-induced lung injury. Additionally, we utilized mass spectrometry, co-immunoprecipitation and Duolink techniques to investigate the core inflammasome responsible for mediating alveolar macrophage pyroptosis. We noticed that the percentage of alveolar macrophages, T, B and epithelial cells decreased significantly post-irradiation. Notably, the proportional changes in alveolar macrophages closely correlated with Szapiels' pneumonia score. Furthermore, alveolar macrophages emerged as the earliest cell type to initiate pyroptosis and act as pivotal regulators of cell communication. In vitro and in vivo experiments, we observed a significant increase in NLRP3 binding to the apoptosis-associated speck-like protein in irradiated alveolar macrophages. In vivo, MCC950 effectively inhibited alveolar macrophage pyroptosis and significantly reducing inflammatory cells recruitment. Subsequently, targeting AM pyroptosis ultimately inhibit the infiltration of interstitial macrophages and the activation of fibroblasts, decrease collagen deposition and alleviate the severity of radiation-induced lung fibrosis. Targeting alveolar macrophage pyroptosis and NLRP3 inflammasome activation hold substantial therapeutic potential for mitigating radiation-induced lung injury.

Extracellular vesicles in tumor immunity: mechanisms and novel insights

Extracellular vesicles (EVs), nanoscale vesicles secreted by cells, have attracted considerable attention in recent years due to their role in tumor immunomodulation. These vesicles facilitate intercellular communication by transporting proteins, nucleic acids, and other biologically active substances, and they exhibit a dual role in tumor development and immune evasion mechanisms. Specifically, EVs can assist tumor cells in evading immune surveillance and attack by impairing immune cell function or modulating immunosuppressive pathways, thereby promoting tumor progression and metastasis. Conversely, they can also transport and release immunomodulatory factors that stimulate the activation and regulation of the immune system, enhancing the body's capacity to combat malignant diseases. This dual functionality of EVs presents promising avenues and targets for tumor immunotherapy. By examining the biological characteristics of EVs and their influence on tumor immunity, novel therapeutic strategies can be developed to improve the efficacy and relevance of cancer treatment. This review delineates the complex role of EVs in tumor immunomodulation and explores their potential implications for cancer therapeutic approaches, aiming to establish a theoretical foundation and provide practical insights for the advancement of future EVs-based cancer immunotherapy strategies.

Role of TRIM29 in disease: What is and is not known

Tripartite motif-containing proteins (TRIMs), comprising the greatest subfamily of E3 ubiquitin ligases with approximately 80 members of this family, are widely distributed in mammalian cells. TRIMs actively participate in ubiquitination of target proteins, a type of post-translational modification associated with protein degradation and other functions. Tripartite motif-containing protein 29 (TRIM29), a member of the TRIM family, differs from other members of this family in that it lacks the RING finger structural domain containing cysteine and histidine residues that mediates DNA binding, protein-protein interactions, and ubiquitin ligase, at its N-terminus. The expression of TRIM29 was initially found to be associated with cancer and diabetic nephropathy progression, and antiviral immunity which is triggered by virus-derived nucleic acids binding to pattern recognition receptors (PRRs) on immune cells. Recently, TRIM29 has also been explored as a diagnostic biomarker and therapeutic target for some immune-related diseases. Here, we review the functions of TRIM29 in the progression of diseases and the inherent mechanisms, as well as the remaining gaps in the literature. A thorough understanding of the detailed regulatory mechanisms of TRIM29 will ultimately facilitate the development of different therapeutic strategies for various diseases.

Targeting ferroptosis offers therapy choice in sepsis-associated acute lung injury

Sepsis-associated acute lung injury (SALI) is a common complication of sepsis, consisting of a dysfunctional host response to infection-mediated heterogenous complexes. SALI is reported in up to 50 % of patients with sepsis and causes poor outcomes. Despite high incidence, there is a lack of understanding in its pathogenesis and optimal treatment. A better understanding of the molecular mechanisms underlying SALI may help produce better therapeutics. The effects of altered cell-death mechanisms, such as non-apoptotic regulated cell death (RCD) (i.e., ferroptosis), on the development of SALI are beginning to be discovered, while targeting ferroptosis as a meaningful target in SALI is increasingly being recognized. Here, we outline how a susceptible lung alveoli may develop SALI. Then we discuss the general mechanisms underlying ferroptosis, and how it contributes to SALI. We then outline the chemical structures of the emerging agents or compounds that can protect against SALI by inhibiting ferroptosis, summarizing their potential pharmacological effects. Finally, we highlight key limitations and possible strategies to overcome them. This review suggests that a detailed mechanistic and biological understanding of ferroptosis can foster the development of pharmacological antagonists in the treatment of SALI.

Airway macrophage glycolysis controls lung homeostasis and responses to aeroallergen

The lungs represent a dynamic microenvironment where airway macrophages (AMs) are the major lung-resident macrophages. AMs dictate the balance between tissue homeostasis and immune activation and thus have contradictory functions by maintaining tolerance and tissue homeostasis, as well as initiating strong inflammatory responses. Emerging evidence has highlighted the connection between macrophage function and cellular metabolism. However, the functional importance of these processes in tissue-resident specialized macrophage populations such as those found in the airways, remain poorly elucidated. Here, we reveal that glycolysis is a fundamental pathway in AMs which regulates both lung homeostasis and responses to inhaled allergen. Using macrophage specific targeting in vivo, and multi-omics approaches, we determined that glycolytic activity in AMs is necessary to restrain type 2 (T2) immunity during homeostasis. Exposure to a range of common aeroallergens, including house dust mite (HDM), drove AM-glycolysis and furthermore, AM-specific inhibition of glycolysis altered inflammation in the airways and HDM-driven airway metabolic adaptations in vivo. Additionally, allergen sensitised asthmatics had profound metabolic changes in the airways, compared to non-sensitised asthmatic controls. Finally, we found that allergen driven AM-glycolysis in mice was TLR2 dependent. Thus, our findings demonstrate a direct relationship between glycolysis in AMs, AM-mediated homeostatic processes, and T2 immune responses in the lungs. These data suggest that glycolysis is essential for the plasticity of AMs. Depending on the immunological context, AM-glycolysis is required to exert homeostatic activity but once activated by allergen, AM-glycolysis influences inflammatory responses. Thus, precise modulation of glycolytic activity in AMs is essential for preserving lung homeostasis and regulating airway inflammation.

Silencing of lncRNA Gm26917 Attenuates Alveolar Macrophage-mediated Inflammatory Response in LPS-induced Acute Lung Injury Via Inhibiting NKRF Ubiquitination

The inflammatory response mediated by alveolar macrophages plays a crucial role in the development of acute lung injury. Numerous studies have reported that lncRNAs are highly expressed in acute lung injury in mouse models and cell lines, and acute lung injury (ALI) can be effectively alleviated by targeting these lncRNAs. The aim of this study was to explore the mechanism by LncRNA Gm26917 regulates the inflammatory response in alveolar macrophages during acute lung injury mouse model. We initially observed a significant upregulation of Gm26917 expression in both ALI conditions and in MH-S cells treated with LPS. Furthermore, the silencing of Gm26917 via lentivirus-mediated methods conferred protection against LPS-induced ALI. Additionally, siRNA-mediated knockdown of Gm26917 attenuated LPS-induced inflammatory responses and modulated the function of alveolar macrophages. Subsequent mechanistic studies revealed that Gm26917 interacts with NKRF, and its knockdown suppressed NKRF ubiquitination, thereby enhancing NKRF binding to p50 and subsequently inhibiting the NF-κB signaling pathway. In conclusion, our findings demonstrate that silencing Gm26917 can mitigate LPS-induced ALI by modulating the NF-κB signaling pathway in alveolar macrophages through interactions with NKRF.

The Importance of Lung Innate Immunity During Health and Disease

The lung is a vital organ for the body as the main source of oxygen input. Importantly, it is also an internal organ that has direct contact with the outside world. Innate immunity is a vital protective system in various organs, whereas, in the case of the lung, it helps maintain a healthy, functioning cellular and molecular environment and prevents any overt damage caused by pathogens or other inflammatory processes. Disturbances in lung innate immunity properties and processes, whether over-responsiveness of the process triggered by innate immunity or lack of responses due to dysfunctions in the immune cells that make up the innate immunity system of the lung, could be correlated to various pathological conditions. In this review, we discuss globally how the components of lung innate immunity are important not only for maintaining lung homeostasis but also during the pathophysiology of notable lung diseases beyond acute pulmonary infections, including chronic obstructive pulmonary disease (COPD), asthma, and pulmonary fibrosis.

Alveolar Macrophages in Viral Respiratory Infections: Sentinels and Saboteurs of Lung Defense

Respiratory viral infections continue to cause pandemic and epidemic outbreaks in humans and animals. Under steady-state conditions, alveolar macrophages (AlvMϕ) fulfill a multitude of tasks in order to maintain tissue homeostasis. Due to their anatomic localization within the deep lung, AlvMϕ are prone to detect and react to inhaled viruses and thus play a role in the early pathogenesis of several respiratory viral infections. Here, detection of viral pathogens causes diverse antiviral and proinflammatory reactions. This fact not only makes them promising research targets, but also suggests them as potential targets for therapeutic and prophylactic approaches. This review aims to give a comprehensive overview of the current knowledge about the role of AlvMϕ in respiratory viral infections of humans and animals.

High-dose intravenous BCG vaccination induces enhanced immune signaling in the airways

Intradermal Bacillus Calmette-Guérin (BCG) is the most widely administered vaccine, but it does not sufficiently protect adults against pulmonary tuberculosis. Recent studies in nonhuman primates show that intravenous BCG administration offers superior protection against Mycobacterium tuberculosis (Mtb). We used single-cell analysis of bronchoalveolar lavage cells from rhesus macaques vaccinated via different routes and doses of BCG to identify alterations in the immune ecosystem in the airway following vaccination. Our findings reveal that high-dose intravenous BCG induces an influx of polyfunctional T cells and macrophages in the airways, with alveolar macrophages from high-dose intravenous BCG displaying a basal activation state in the absence of purified protein derivative stimulation, defined in part by interferon signaling. Enhanced intercellular immune signaling and stronger T helper 1-T helper 17 transcriptional responses were observed following purified protein derivative stimulation. These results suggest that high-dose intravenous BCG vaccination creates a specialized immune environment that primes airway cells for effective Mtb clearance.

Collagen deposition in lung parenchyma driven by depletion of interstitial Lyve-1+ macrophages prevents cigarette smoke-induced emphysema and loss of airway function

Introduction

Collagen is essential for maintaining lung structure and function and its remodeling has been associated with respiratory diseases including chronic obstructive pulmonary disease (COPD). However, the cellular mechanisms driving collagen remodeling and the functional implications of this process in the pathophysiology of pulmonary diseases remain poorly understood.

Methods

To address this question, we employed Lyve1wt/cre ; Csf1rflox/flox mice with specific depletion of Lyve-1+ macrophages and assessed the content, types and organization of collagen in lung compartments at steady state and after chronic exposure to cigarette smoke (CS).

Results

Using this mouse model, we found that the absence of this subpopulation of tissue resident macrophage led to the deposition of type I collagen fibers around the alveoli and bronchi at steady state. Further analysis by polarized light microscopy and Sircol collagen assay revealed that the collagen fibers accumulating in the lungs depleted of Lyve-1+ macrophages were thicker and crosslinked. A decrease in MMP-9 gene expression and proteolytic activity together with an increase in Col1a1, Timp-3 and Lox expression accompanied the collagen alterations. Next, we investigated the effect of the collagen remodeling on the pathophysiology of COPD and airway function in mice lacking Lyve-1+ macrophages exposed chronically to cigarette smoke (CS), a well-established animal model of COPD. We found that deposition of collagen prior CS exposure protected these mice against destruction of alveoli (emphysema), and bronchi thickening and prevented loss of airway function.

Discussion

Thus, we uncover that interstitial Lyve-1+ macrophages regulate the composition, amount, and architecture of collagen network in the lungs at steady state and that such collagen remodeling functionally impacts the development of COPD. This study further supports the potential of targeting collagen as promising approaches to treat respiratory diseases.

Nebulized Immunotherapy of Orthotopic Lung Cancer by Mild Magnetothermal-Based Innate Immunity Activations

Advances in adaptive immunity have greatly contributed to the development of cancer immunotherapy. However, its over-low efficacy and insufficient invasion of immune cells in the tumor tissue, and safety problems caused by cytokine storm, have seriously impeded further clinical application for solid tumor immunotherapy. Notably, the immune microenvironment of the lungs is naturally enriched with alveolar macrophages (AMs). Herein, we introduce a novel nebulized magnetothermal immunotherapy strategy to treat orthotopic lung cancer by using magnetothermal nanomaterial (Zn-CoFe2O4@Zn-MnFe2O4-PEG, named ZCMP), which can release iron ions via an acid/thermal-catalytic reaction to maximize the use of lung's immune environment through the cascade activations of AMs and natural killer (NK) cells. Nebulized administration greatly enhance drug bioavailability by localized drug accumulation at the lesion site. Upon mild magnetic hyperthermia, the released iron ions catalyze endogenous H2O2 decomposition to produce reactive oxygen species (ROS), which triggers the M1 polarization of AMs, and the resultant inflammatory cytokine IFN-β, IL-1β and IL-15 releases to activate c-Jun, STAT5 and GZMB related signaling pathways, promoting NK cells proliferation and activation. This innovative strategy optimally utilizes the lung's immune environment and shows excellent immunotherapeutic outcomes against orthotopic lung cancer.