Pulmonary Alveolar Research Articles

Spatiotemporal modeling quantifies cellular contributions to uptake of Aspergillus fumigatus in the human lung

The human lung is confronted daily with thousands of microbial invaders reaching the lower respiratory tract. An efficient response by the resident type 1 and type 2 alveolar epithelial cells (AECs) and alveolar macrophages (AMs) cells during the early hours of innate immunity is a prerequisite to maintain a non-inflammatory state, but foremost to rapidly remove harmful substances. One such human-pathogenic invader is the opportunistic fungus Aspergillus fumigatus. If the spherical conidia are not cleared in time, they swell reaching approximately twice of their initial size and germinate to develop hyphae around six hours post-infection. This process of morphological change is crucial as it enables the pathogen to invade the alveolar epithelium and to reach the bloodstream, but also makes it conspicuous for the immune system. During this process, conidia are first in contact with AECs then with migrating AMs, both attempting to internalize and clear the fungus. However, the relative contribution of AMs and AECs to uptake of A. fumigatus remains an open question, especially the capabilities of the barely investigated type 1 AECs. In this study, we present a bottom-up modeling approach to incorporate experimental data on the dynamic increase of the conidial diameter and A. fumigatus uptake by AECs and AMs in a hybrid agent-based model (hABM) for the to-scale simulation of virtual infection scenarios in the human alveolus. By screening a wide range of parameters, we found that type 1 AECs, which cover approximately 95% of the alveolar surface, are likely to have a greater impact on uptake than type 2 AECs. Moreover, the majority of infection scenarios across the regime of tested parameters were cleared through uptake by AMs, whereas the contribution to conidial uptake by AECs was observed to be limited, indicating that their crucial support might mostly consist in mediating chemokine secretion for AM recruitment. Regardless, as the first host cell being confronted with A. fumigatus conidia, our results evidence the large potential impact of type 1 AECs antimicrobial activities, underlining the requirement of increasing experimental efforts on this alveolar constituent.

Combined exercise hinders the progression of pulmonary and right heart harmful remodeling in monocrotaline-induced pulmonary arterial hypertension.

The aim of this study was to test whether combined physical exercise training of moderate intensity executed during the development of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) hinders the progression of pulmonary and right heart harmful functional and structural remodeling in rats. Wistar rats were injected with MCT (60 mg/kg) and after 24 hours were exposed to a combined exercise training program: aerobic exercise (Treadmill running - 60 min/day; 60% of maximum running speed); and resistance exercise (Vertical ladder climbing - 15 climbs; 60% of maximum carrying load), on alternate days, 5 days/week, for approximately 3 weeks. After euthanasia, lung, and right ventricle (RV) were excised and processed for histological, single myocyte and biochemical analyses. Combined exercise increased the tolerance to physical effort (time until fatigue and relative maximum load), and prevented increases in pulmonary artery resistance (TA/TE) and reductions in RV function (TAPSE). Moreover, in myocytes isolated from the RV, combined exercise preserved contraction amplitude, as well as contraction and relaxation velocities, and inhibited reductions in the amplitude and maximum speeds to peak and to decay of the intracellular Ca2+ transient. Furthermore, combined exercise avoided RV (RV weight, cardiomyocyte, extracellular matrix, collagen, inflammatory infiltrate, and extracellular matrix) and lung (pulmonary alveoli and alveolar septum) harmful structural remodeling. Additionally, combined exercise restricted RV (NO and CP) and lung (CAT, GST, and NO) oxidative stress. In conclusion, the applied combined exercise regime hinders the progression of pulmonary and right heart functional and structural harmful remodeling in rats with MCT-induced PAH.

Severity and prognosis of COVID-19 complicated by autoimmune pulmonary alveolar proteinosis

BackgroundThe prognosis of patients with coronavirus disease 2019 (COVID-19) was poor although its survival rate has been improved after the occurrence of the Omicron strain. Autoimmune pulmonary alveolar proteinosis (APAP), a lung disease caused by macrophage dysfunction induced by anti-granulocyte-macrophage colony-stimulating factor (GM–CSF)–neutralizing autoantibodies, is characterized by the deposition of proteinaceous material in the alveolar spaces. The clinical course of COVID-19 in patients with APAP remains unclear and this study aimed to clarify it. MethodsThe data of 23 patients with APAP, who were diagnosed with COVID-19 between January 2020 and May 2023 and collected through a nationwide questionnaire surveillance system, were retrospectively reviewed. ResultsBased on the epidemiological frequency at disease onset, suspected strains of severe acute respiratory syndrome coronavirus 2 were Omicron (n = 18) and non-Omicron (n = 5). Fifteen patients were vaccinated. Six and three patients received anti-viral drugs and corticosteroids, respectively. One patient in the third trimester of pregnancy died despite treatment in the intensive care unit. Six patients were complicated by pneumonia and/or required supplemental oxygen. These patients were suspected to have non-Omicron strains (p = 0.087). Vaccination status showed a significant association with suspected Omicron strains. The radiological findings in four patients and shortness of breath improved in two of the four patients after COVID-19. ConclusionsThe severity and prognosis of the patients were not worse than those predicted based on the results of a previous study. The transition from a non-Omicron strain to an Omicron strain and the vaccination status may have affected these results.

Whole lung and sequential bronchoscopic lavage for pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a diffuse lung disease that results from the accumulation of lipoproteinaceous material in the alveoli due to abnormal surfactant homeostasis. Since its introduction in the 1960s, whole lung lavage (WLL) has been the primary treatment for PAP. This review focuses on WLL, including its technique modifications, and sequential bronchoscopic lavage. Autoimmune PAP, which accounts for the majority of cases, occurs when antigranulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies lead to the deficiency of bioavailable GM-CSF. At present, there are no international guidelines or consensus statements for PAP treatment. Traditionally, therapeutic decisions are made based on the severity and type of PAP. Despite emerging data on GM-CSF-based therapies, WLL remains a central component in the therapeutic strategy for PAP. Although the technique of WLL has evolved over time, there is still no universally adopted, standardized protocol. However, key periprocedural aspects - such as preprocedural planning, patient evaluation, anesthetic technique, lavage protocol, and postprocedural care - remain essential to ensuring the safety and success of WLL.

Abstract A001: Reciprocal activation of breast cancer metastases and the lung epithelium during metastatic outgrowth

Abstract Introduction. During metastasis, tumor cells interact extensively with endogenous cells in distant organs. These interactions change the behavior of these surrounding cell populations, often inducing a more pro-tumor microenvironment. The lung is one of the most common sites of breast cancer (BC) metastasis, and in the lung, alveolar epithelial cells are the most common cell type. My data suggest that the lung alveolar epithelium contributes to metastatic outgrowth, and I hypothesize that BC lung micrometastases activate surrounding lung epithelial cells which, in turn, support the outgrowth of BC metastases within the lung. The overall purpose of these studies is to identify factors secreted by resident lung epithelial cells that could be used as metastasis-specific therapeutic targets and/or agents. Methods. To test this hypothesis, I utilized immunocompetent preclinical BC metastasis models to study lung metastatic outgrowth, the stage at which most patients are diagnosed with metastatic disease. A custom imaging panel was developed to quantify lung wound repair, and single-cell RNA-sequencing (scRNAseq) was performed on mouse lungs with high or low metastatic burden to identify genes in the lung epithelium that produce potentially targetable pro-metastatic secreted factors. No-contact co-culture experiments were used to directly study reciprocal paracrine interactions between lung type II alveolar epithelial (AT2) and BC cells. Results. A wound repair-related phenotype, characterized by chronic inflammation, developed within the lung microenvironment during metastatic outgrowth, including an increase in the number and activation of AT2 cells surrounding metastases as they grow. Single-cell RNA-sequencing of mouse lungs with a high vs. low metastatic burden showed that metastatic outgrowth significantly changed AT2 gene expression resulting in a modified secretome. No-contact co-culture experiments indicated that TNBC cells directly alter AT2 gene expression, while AT2 secreted factors promoted TNBC growth. I investigated the possible mechanism(s) responsible for these effects and discovered that AT2 pulmonary surfactant protein and lipid levels are altered by BC-derived secreted factors. Interestingly, treatment with the naturally derived calf surfactant Infasurf, which contains native surfactant proteins/lipids and is FDA-approved for use in premature infants, inhibited BC proliferation. Conclusion. Low levels of surfactant are commonly associated with pulmonary disease and lung cancer. My BC lung metastasis data suggest that something similar may be occurring in the lungs during metastatic outgrowth. Overall, my studies demonstrate the potential for targeting lung epithelial cells in the metastatic microenvironment, in addition to directly targeting malignant cells, as an effective way to treat and manage BC lung metastases. Citation Format: Jessica L. Christenson, Nicole S. Spoelstra, Jennifer K. Richer. Reciprocal activation of breast cancer metastases and the lung epithelium during metastatic outgrowth [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A001.

Autoantibodies targeting interferons and GM-CSF are associated with adverse outcome risk, comorbidities, and pathogen in community-acquired pneumonia.

Cytokine autoantibodies (c-aAb) have been associated with pulmonary diseases, including severe novel coronavirus disease 2019 (COVID-19) and pulmonary alveolar proteinosis. This study aimed to determine c-aAb association with community-acquired pneumonia (CAP) etiology (SARS-CoV-2, influenza, or bacteria) and c-aAb associations with CAP-related clinical outcomes and pulmonary comorbidities. In a cohort of 665 patients hospitalized with CAP, c-aAb targeting interferon α (IFNα), IFNβ, IFNγ, interleukin-1α (IL-1α), IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor (GM-CSF) were measured in plasma samples. Associations between c-aAb and baseline characteristics, pulmonary comorbidities, pathogen, intensive care unit (ICU) transferal, time to clinical stability, and mortality were estimated, with results stratified by sex. More men infected with SARS-CoV-2 were had high-titer type 1 IFN c-aAb compared to other pathogens. Among patients with CAP, asthma and bronchiectasis comorbidities were associated with high-titer GM-CSF c-aAb in men, and men with high-titer IFNβ c-aAb had increased odds for ICU transferal. High-titer IL-10 c-aAb were associated with faster clinical stability in women. In men with CAP, various c-aAb-including type 1 IFN and GM-CSF c-aAb-were associated with adverse clinical events and comorbidities, whereas c-aAb targeting an autoinflammatory cytokine were associated with a positive outcome in women. This suggests that the potentially immunomodulatory effects of c-aAb depend on pathogen, autoantibody specificity, comorbidity, and sex.

Repeated inhalation of GM-CSF by nonhuman primates induces bronchus-associated lymphoid tissue along the lower respiratory tract

BackgroundRepeated inhalation of granulocyte-macrophage colony-stimulating factor (GM-CSF) was recently approved in Japan as a treatment for autoimmune pulmonary alveolar proteinosis. However, the detailed physiological and pathological effects of repeated inhalation in the long term, especially at increasing doses, remain unclear.MethodsIn this chronic safety study, we administered 24 cynomolgus monkeys (Macaca fascicularis) aged 2–3 years with aerosolized sargramostim (a yeast-derived recombinant human GM-CSF [rhGM-CSF]) biweekly for 26 weeks across four dosing groups (0, 5, 100, and 500 µg/kg/day). We measured the serum GM-CSF antibody (GM-Ab) concentration by an ELISA and assessed the neutralizing capacity of GM-Ab using the GM-CSF-dependent cell line TF-1. We subjected lung tissue samples taken from all monkeys at 27 weeks to histopathological assessment using a sargramostim-specific monoclonal antibody to detect localization of residual sargramostim.ResultsAll the animals maintained good body condition and showed steady weight gain throughout the study. The pathological analyses of the lung revealed the formation of induced bronchus-associated lymphoid tissue (iBALT) in the lower respiratory tract, even at the clinical dose of 5 µg/kg/day. There was a relationship between the number or size of BALT and sargramostim dose or the serum GM-Ab levels. Immunohistochemical analyses revealed GM-Ab–producing cells in the follicular region of iBALT, with residual sargramostim in the follicles. Leucocyte counts were inversely correlated with GM-Ab levels in the high-dose groups. Additionally, serum GM-Ab from the treated animals significantly suppressed the alveolar macrophage proliferation activity of both Cynomolgus recombinant and rhGM-CSF in vitro.ConclusionLong-term repeated inhalation of sargramostim led to iBALT formation in the lower respiratory tract, even at the clinical dose of 5 µg/kg/day, with the extent of iBALT formation increasing in a dose-dependent manner. Inhaled sargramostim was localized to the follicular region of iBALT nodules, which may induce the production of GM-Ab.

Whole lung lavage: considerations from the anesthesiology perspective.

Whole lung lavage (WLL) remains the standard treatment for pulmonary alveolar proteinosis (PAP). The procedure involves meticulous preparation, including a multidisciplinary team and appropriate facilities, to ensure patient safety and procedural success. Effective anesthesia management is essential to allow for successful completion of the procedure and prevent complications. Effective anesthesia management, including total intravenous anesthesia (TIVA) and careful intraoperative monitoring, is essential to prevent complications such as hypoxemia and fluid overload. Proper airway control with a double-lumen tube, careful positioning, and continuous monitoring during the lavage phase are key to minimizing risks. Challenges such as fluid spillage and ventilation-perfusion mismatch must be managed proactively with techniques such as fiberoptic bronchoscopy and recruitment maneuvers. In cases of severe hypoxemia, advanced options like extra-corporeal membrane oxygenation (ECMO) or sequential lavage may be required. WLL is a pivotal treatment for PAP, offering significant relief and improvement for many patients despite the challenges in standardizing the procedure due to the rare nature of the condition. Involvement of a multidisciplinary team involving pulmonologist, anesthesiologist, critical care personnel, operating room personnel and in some cases and centers, cardiothoracic surgeon and perfusionist is critical to the success of the procedure.

Baicalein suppresses inflammation and attenuates acute lung injury by inhibiting glycolysis via HIF‑1α signaling.

Baicalein, a flavonoid monomer compound isolated from the dried root of the traditional Chinese herb Scutellaria baicalensis, has several pharmacological activities, such as anti‑inflammatory, anti‑angiogenic, antitumor, antimicrobial and antiviral properties. Acute lung injury (ALI) is characterized by injury of the alveolar epithelium and capillary endothelium, which results in decreased lung volume, decreased lung compliance, ventilation/perfusion mismatch, intrapulmonary edema, alveolar edema and even acute hypoxemic respiratory failure. The present study aimed to investigate the effects of baicalein on lung injury and inflammation. Bioinformatics analysis using network pharmacology predicted that the hypoxia inducible factor‑1α (HIF‑1α) and glycolysis signaling pathways were involved in the mechanism underlying the therapeutic effects of baicalein. Further in vitro and in vivo experiments, such as immunohistochemistry, immunofluorescence and PCR, verified that baicalein could inhibit HIF‑1α signaling, thus suppressing glycolysis, and improving inflammatory responses and ALI. Taken together, the results of the present study suggested that the anti‑inflammatory effects of baicalein on treating ALI were associated with its ability to suppress glycolysis via the HIF‑1α signaling pathway.

European Respiratory Society guidelines for the diagnosis and management of pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a rare syndrome caused by several distinct diseases leading to progressive dyspnoea, hypoxaemia, risk of respiratory failure and early death due to accumulation of proteinaceous material in the lungs. Diagnostic strategies may include computed tomography (CT) of the lungs, bronchoalveolar lavage (BAL), evaluation of antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), genetic testing and, eventually, lung biopsy. The management options are focused on removing the proteinaceous material by whole lung lavage (WLL), augmentation therapy with GM-CSF, rituximab, plasmapheresis and lung transplantation. The presented diagnostic and management guidelines aim to provide guidance to physicians managing patients with PAP. A European Respiratory Society Task Force composed of clinicians, methodologists and patients with experience in PAP developed recommendations in accordance with the ERS Handbook for Clinical Practice Guidelines and the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) approach. This included a systematic review of the literature and application of the GRADE approach to assess the certainty of evidence and strength of recommendations. The Task Force formulated five PICO (Patients, Intervention, Comparison, Outcomes) questions and two narrative questions to develop specific evidence-based recommendations. The Task Force developed recommendations for the five PICO questions. These included management of PAP with WLL, GM-CSF augmentation therapy, rituximab, plasmapheresis and lung transplantation. Also, the Task Force made recommendations regarding the use of GM-CSF antibody testing, diagnostic BAL and biopsy based on the narrative questions. In addition to the recommendations, the Task Force provided information on the hierarchy of diagnostic interventions and therapy. The diagnosis of PAP is based on CT and BAL cytology or lung histology, whereas the diagnosis of specific PAP-causing diseases requires GM-CSF antibody testing or genetic analysis. There are several therapies including WLL and augmentation therapy with GM-CSF available to treat PAP, but supporting evidence is still limited.

Whole Lung Lavage in Autoimmune Pulmonary Alveolar Proteinosis: Unique Challenges in a Resource-Limited Setting.

Autoimmune pulmonary alveolar proteinosis (PAP) is characterized by antibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF), alveolar macrophage dysfunction, and surfactant accumulation. Whole lung lavage (WLL) is the treatment of choice in patients with PAP and severe hypoxemia. In resource-limited settings, WLL can be performed in the intubated, anesthetized patient who is being one lung ventilated using a Y-type bladder irrigation catheter for saline instillation and drainage.

YAP Alleviates Pulmonary Fibrosis Through Promoting Alveolar Regeneration via Modulating the Stemness of Alveolar Type 2 Cells.

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with no cure except transplantation. Abnormal alveolar epithelial regeneration is a key driver of IPF development. The function of Yes1 Associated Transcriptional Regulator (YAP) in alveolar regeneration and IPF pathogenesis remains elusive. Here, we first revealed the activation of YAP in alveolar epithelium 2 cells (AEC2s) from human IPF lungs and fibrotic mouse lungs. Notably, conditional deletion of YAP in mouse AEC2s exacerbated bleomycin-induced pulmonary fibrosis. Intriguingly, we showed in both conditional knockout mice and alveolar organoids that YAP deficiency impaired AEC2 proliferation and differentiation into alveolar epithelium 1 cells (AEC1s). Mechanistically, YAP regulated expression levels of genes associated with cell cycle progression and AEC1 differentiation. Furthermore, overexpression of YAP in vitro promoted cell proliferation. These results indicate the critical role of YAP in alveolar regeneration and IPF pathogenesis. Our findings provide new insights into the regulation of alveolar regeneration and IPF pathogenesis, paving the road for developing novel treatment strategies.

Pathology of idiopathic pulmonary fibrosis with particular focus on vascular endothelium and epithelial injury and their therapeutic potential.

Idiopathic pulmonary fibrosis (IPF) remains a challenging disease with no drugs available to change the trajectory. It is a condition associated with excessive and highly progressive scarring of the lungs with remodelling and extracellular matrix deposition. It is a highly "destructive" disease of the lungs. The diagnosis of IPF is challenging due to continuous evolution of the disease, which also makes early interventions very difficult. The role of vascular endothelial cells has not been explored in IPF in great detail. We do not know much about their contribution to arterial or vascular remodelling, extracellular matrix changes and contribution to pulmonary hypertension and lung fibrosis in general. Endothelial to mesenchymal transition appears to be central to such changes in IPF. Similarly, for epithelial changes, the process of epithelial to mesenchymal transition seem to be the key both for airway epithelial cells and type-2 pneumocytes. We focus here on endothelial and epithelial cell changes and its contributions to IPF. In this review we revisit the pathology of IPF, mechanistic signalling pathways, clinical definition, update on diagnosis and new advances made in treatment of this disease. We discuss ongoing clinical trials with mode of action. A multidisciplinary collaborative approach is needed to understand this treacherous disease for new therapeutic targets.

Surfactant Protein A Inhibits Human Rhinovirus C Binding and Infection of Airway Epithelial Cells from Pediatric Asthma.

Rhinovirus C (RV-C) infection can trigger asthma exacerbations in children and adults, and RV-C-induced wheezing illnesses in preschool children correlate with the development of childhood asthma. Surfactant protein A (SP-A) plays a critical role in regulating pulmonary innate immunity by binding to numerous respiratory pathogens. Mature SP-A consists of multiple isoforms that form the hetero-oligomers of SP-A1 and SP-A2, organized in 18-mers. In this report, we examined the efficacy of SP-A to antagonize RV-C infection using the wild-type (RV-C15) and reporter-expressing (RV-C15-GFP) viruses in differentiated nasal epithelial cells (NECs) from asthmatic and non-asthmatic children. We also determined the antiviral mechanism of action of SP-A on RV-C15 infection. The native SP-A was purified from alveolar proteinosis patients. The recombinant (r) SP-A1 and SP-A2 variants were expressed in FreeStyle™ 293-F cells. SP-A reduced the fluorescent focus-forming units (FFUs) after RV-C15-GFP infection of NECs by 99%. Both simultaneous and 4 h post-infection treatment with SP-A inhibited RV-C15 and RV-C15-GFP viral RNA load by 97%. In addition, the antiviral genes and chemokines (IFN-λ, IRF-7, MDA-5, and CXLC11) were not induced in the infected NECs due to the inhibition of RV-C propagation by SP-A. Furthermore, SP-A bound strongly to RV-C15 in a dose- and Ca2+-dependent manner, and this interaction inhibited RV-C15 binding to NECs. In contrast, rSP-A1 did not bind to solid-phase RV-C15, whereas the rSP-A2 variants, [A91, K223] and [P91, Q223], had strong binding affinities to RV-C15, similar to native SP-A. This study demonstrates that SP-A might have potential as an antiviral for RV infection and RV-induced asthma exacerbations.

Novel protocols of inhaled GM-CSF therapy for patients with pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a rare lung disease in which build-up of surfactant-derived lipo-proteinaceous material can cause respiratory failure. Effective treatment is paramount to saving lives and existing options include partial or whole lung lavage, however, as there are limitations to this the development of new treatment options is needed. Dr Ryushi Tazawa of Tokyo Medical and Dental University (TMDU) is a member of Japanese PAP multi-disciplinary research team which has been working on the potential to treat PAP through the inhalation of granulocyte-macrophage colony-stimulating factor (GM-CSF), an essential agent for maintaining biological functions of alveolar macrophages to clean up alveoli. Originally, Dr Koh Nakata and his colleagues found in 1999 that most patients with PAP have the autoantibody against GM-CSF. The anti-GM-CSF autoantibody blocks GM-CSF and deteriorates alveolar macrophages and alveolar cleanliness. GM-CSF inhalation would represent a simple treatment that can be prescribed on an outpatient basis and inhaled at home. It is believed that inhaled CM-CSF could help restore functions of impaired alveolar macrophages and renew alveolar macrophages. Following a pilot study published in 2005 and a phase II study in 2010, Dr Koh Nakata secured the budget for regulatory approval of GM-CSF inhalation therapy for autoimmune PAP (aPAP) and a clinical trial for the treatment in 2016. The Pulmonary Alveolar Proteinosis GM-CSF Inhalation Efficacy (PAGE) trial with twelve institutions nationwide successfully demonstrated the safety and efficacy of GM-CSF inhalation for aPAP. Based on PAGE trial data, Japanese pharmaceutical authority approved GM-CSF inhalation as a therapy for aPAP in 2024. The research team is currently interested in optimising the inhalation modes using mathematical models and a combination therapy of whole lung lavage and inhalation methods for severe cases.

Macrophage-specific lipid nanoparticle therapy blocks the lung's mechanosensitive immunity due to macrophage-epithelial interactions.

The lung's mechanosensitive immune response, which occurs when pulmonary alveoli are overstretched, is a major impediment to ventilation therapy for hypoxemic respiratory failure. The cause is not known. We tested the hypothesis that alveolar stretch causes stretch of alveolar macrophages (AMs), leading to the immune response. In lungs viewed by optical imaging, sessile AMs expressed gap junctional protein connexin-43 (Cx43), and they communicated with the alveolar epithelium through gap junctions. Alveolar hyperinflation increased Ca2+ in the AMs but did not stretch the AMs. The Ca2+ response, and concomitant TNFα secretion by AMs were blocked in mice with AM-specific deletion of Cx43. The AM responses, as also lung injury due to mechanical ventilation at high tidal volume, were inhibited by AM-specific delivery of lipid nanoparticles containing Xestospongin C, which blocked the induced Ca2+ increases. We conclude, Cx43- and Ca2+-dependent AM-epithelial interactions determine the lung's mechanosensitive immunity, providing a basis for therapy for ventilator-induced lung injury.

Biomarkers of genotoxic damage in pulmonary alveolar macrophages: a review.

DNA damage is one of the primary mechanisms underlying cancer and other chronic degenerative diseases. Early evaluation of this damage in the affected cells and tissues is crucial for understanding pathogenesis and implementing effective prevention strategies. However, isolating target cells from affected organs, such as the lungs, can be challenging. Therefore, an alternative approach is to evaluate genotoxic damage in surrogate cells. Pulmonary alveolar macrophages are ideally suited for this purpose because they are in close contact with the target cells of the bronchial and alveolar epithelium, share the exact mechanisms and levels of exposure, and are easily recoverable in large numbers. This review comprehensively lists all studies using alveolar macrophages as surrogate cells to show genotoxic lung damage in humans or laboratory animals. These investigations provide fundamental information on the mechanisms of DNA damage in the lung and allow for better assessment and management of risk following exposure to inhalable genotoxic agents. Furthermore, they may be a valuable tool in cancer chemoprevention, helping the right choice of agents for clinical trials.

Leukocyte kinetics and bacterial clearance during S. pneumoniae pneumonia and contributions of ICAM-1.

Streptococcus pneumoniae is a leading cause of community-acquired pneumonia. Intercellular adhesion molecule-1 (ICAM-1) is an adhesion molecule that is highly expressed on the pulmonary capillary endothelium, alveolar epithelium and other cell types within the lung. ICAM-1 plays important roles in leukocyte adhesion, migration, and motility. To determine the contributions of ICAM-1 to bacterial clearance and leukocyte kinetics during pneumonia, mice were inoculated with S. pneumoniae and evaluated 1, 4 and 7 days later. Our results show that Icam1-/-mice have a greater number of viable bacteria within the lung at each time point. The impaired clearance observed in Icam1-/- mice was not due to an impediment in leukocyte recruitment. In fact, Icam1-/- mice had a greater number of neutrophils and recruited inflammatory macrophages in the lung tissue and the alveoli/airways on day 7. In contrast, fewer alveolar macrophages were present in the BAL of Icam1-/-mice. The loss of body weight and the concentrations of inflammatory mediators in the BAL were also significantly greater in Icam1-/- mice. Mechanistic studies to understand the defect in clearance show that neutrophils and macrophage subpopulations had no defect in phagocytosis or acidification of phagosomes. RNA sequencing reveals many differences in gene expression, but no suggestion of a defect in phagocytosis or killing. Thus, that ICAM-1 is necessary for the clearance of S. pneumoniae and for the resolution of pneumonia, but is not required for the recruitment of neutrophils or inflammatory macrophages into the pneumonic lung parenchyma or the alveoli/airways during S. pneumoniae-induced pneumonia.

What Is on the Horizon for Treatments in Idiopathic Pulmonary Fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a progressive and often fatal lung disease most commonly encountered in older individuals. Several decades of research have contributed to a better understanding of its pathogenesis, though only two drugs thus far have shown treatment efficacy, i.e., by slowing the decline of lung function. The pathogenesis of IPF remains incompletely understood and involves multiple complex interactions and mechanisms working in tandem or separately to result in unchecked deposition of extracellular matrix components and collagen characteristic of the disease. These mechanisms include aberrant response to injury in the alveolar epithelium, inappropriate communication between epithelial cells and mesenchymal cells, imbalances between oxidative injury and tissue repair, recruitment of inflammatory pathways that induce fibrosis, and cell senescence leading to sustained activation and proliferation of fibroblasts and myofibroblasts. Targeted approaches to each of these mechanistic pathways have led to recent clinical studies evaluating the safety and efficacy of several agents. This review highlights selected concepts in the pathogenesis of IPF as a rationale for understanding current or future therapeutic approaches, followed by a review of several selected agents and their recent or active clinical studies. Current novel therapies include approaches to attenuating or modifying specific cellular or signaling processes in the fibrotic pathway, modifying inflammatory and metabolic derangements, and minimizing inappropriate cell senescence.

N-acetylcysteine regulates NF-κB signaling pathway alleviates the pulmonary toxicity induced by indium-tin oxide nanoparticles in rats

Objective: The current study aimed to evaluate the possible protective effects of N-acetylcysteine (NAC) against Indum-tin oxide (ITO) nanoparticle (Nano-ITO) -induced pulmonary alveolar proteinosis (PAP) in rats, especially via modulation of nuclear factor kappa B (NF-κB) signaling. Methods: In October 2019, 50 adult male Sprague-Dawley rats were randomly allocated into five groups (10 rats each) as follows: blank control group, saline control group, NAC control group (200 mg/kg), Nano-ITO group (receiving a repeated intratracheal dose of 6 mg/kg Nano-ITO) and NAC intervention group (pre-treated intraperitoneally with 200 mg/kg NAC 1.5 h before the administration of an intratracheal dose of 6 mg/kg Nano-ITO). The rats were exposed twice a week for 12 weeks. Rats were then euthanized under anesthesia, and their lungs were removed for histopathological and immunohistochemical analysis. The comparison of indicators reflecting oxidative stress and pulmonary inflammation among groups was conducted using one-way analysis of variance (ANOVA) and Bonferroni's test. The effect of NAC on Nano-ITO induced NF-κB signaling pathway in rats was analyzed. Results: Histopathological examination of Nano-ITO exposed rats revealed diffuse alveolar damage, including PAP, cholesterol crystals, alveolar fibrosis, pulmonary fibrosis, and alveolar emphysema. Immunohistochemical results of Nano-ITO exposed rats showed strong positive for nuclear factor κB p65 (NF-κB p65) and nuclear factor Kappa B inhibitory factor kinase (IKK-β) and weak positive for nuclear factor κB inhibitory protein α (IκB-α) in the nuclei of bronchiolar and alveolar epithelial cells. Compared with blank control group, saline control group and NAC control group, the level of total protein (TP) in bronchoalveolar lavage fluid of rats in Nano-ITO group was significantly increased (P<0.05), and the activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA) content and total antioxidant capacity (T-AOC) were significantly increased (P<0.05), the levels of proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) were significantly increased (P<0.05), and the levels of NF-κB p65, IKK-β, inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) in lung tissue were significantly increased (P<0.05). Compared with Nano-ITO group, the levels of TP, T-AOC, MDA and TNF-α in bronchoalveolar lavage fluid of rats in NAC intervention group were significantly decreased (P<0.05), and the levels of NF-κB p65 and ROS in lung tissue were significantly decreased (P<0.05). Western blot results showed that compared with the control groups, the protein expressions of NF-κB p65 and IKK-β in the lung tissue of Nano-ITO group were increased, while the protein expression of IκB-α was decreased (P<0.05). Compared with Nano-ITO group, the protein expressions of NF-κB p65 and IKK-β in lung tissue of rats in NAC intervention group were decreased, while the protein expression of IκB-α was increased (P<0.05) . Conclusion: The study demonstrated that Nano-ITO might induce pulmonary toxicity through the activation of NF-κB signaling pathway, and NAC could antagonize the pulmonary toxicity of Nano-ITO by inhibiting the NF-κB signaling pathway.