The History and Mystery of Alveolar Epithelial Type II Cells: Focus on Their Physiologic and Pathologic Role in Lung

AECII-derived miR-21a-5p exosomes alleviate HALI via targeting and regulating PGAM5-mediated necroptosis

Hyperoxic Acute Lung Injury (HALI) is a serious complication of prolonged high-concentration oxygen therapy, primarily leading to Acute Respiratory Distress Syndrome (ARDS), which primarily affects alveolar epithelial cells (AECs). Exosomes (Exos) derived from type II alveolar epithelial cells (AEC IIs) play a crucial role in lung protection through their contained microRNAs (miRNAs). Previous research has established miR-21a-5p as a key player in pulmonary defense mechanisms. In this study, we utilized a C57BL/6 mouse model of HALI established by hyperoxic conditions (FiO2 > 90 %) to demonstrate a gradual decrease in miR-21a-5p levels concomitant with an increase in PGAM5 levels with prolonged hyperoxia exposure. Exosomal transcriptome sequencing suggested significant downregulation of miR-21a-5p expression in hyperoxia-stimulated AECII exosomes. We employed dual-luciferase reporter assays and Chromatin Isolation by RNA Purification (ChIRP) to confirm the direct interaction between miR-21a-5p and PGAM5. AECII-derived exosomal miR-21a-5p effectively attenuated lung injury and inhibited the expression of proteins associated with PGAM5-mediated necroptosis (RIPK1, RIPK3, p-MLKL). Furthermore, in vitro assays using MLE-12 cells confirmed that AECII-derived exosomal miR-21a-5p intervention reversed the elevated levels of necroptotic apoptotic proteins in hyperoxia-stimulated MLE-12 cells. These findings collectively demonstrate that AECII-derived exosomal miR-21a-5p inhibits necroptosis pathway activity by modulating PGAM5, thereby exerting lung-protective effects. Therefore, exosomal miR-21a-5p may serve as a novel therapeutic target for attenuating HALI via modulation of the PGAM5-mediated necroptotic pathway.

Basal and AT2 cells promote IPF-lung cancer co-occurrence via EMT: Single-cell analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrotic interstitial lung disease. With IPF, the probability of complication with lung cancer (LCA) increases considerably, and the prognosis is worse than that of simple IPF. To understand the pathological mechanisms and molecular pathways shared by these two diseases, we used the single-cell analysis from the Gene Expression Omnibus (GEO) database, and find that basal cells (BCs) and alveolar type 2 cells (AT2 cells) are important components of lung epithelial cells. Changes in molecular pathways in BCs and AT2 cells may be involved in the common pathogenesis of IPF and LCA. KRT17 and S100A14 in BCs may promote the IPF co-occurrence with LCA by mediating the EMT. WFDC2 and KRT19 may be the elements in AT2 cells that activate the EMT process to promote IPF co-occurrence with LCA. In both IPF and LCA, FN1-WNT axis may be involved in the interaction between BCs and AT2 cells. Importantly, the results of immunofluorescence colocalization experiments on tissue samples from patients with IPF and LCA were consistent with these conclusions. Basal-macrophage interactions may have also induced the IPF co-occurrence with LCA via the CYBA-ERK1/2 axis. The regulation of M2 macrophage polarization by JUN/SOD2-glycolysis axis may therefore be involved in the co-morbidity mechanism of IPF and LCA. Therefore, our results suggest that molecular changes in BCs, AT2 cells and macrophages may play important roles in the pathogenesis of IPF co-occurrence with LCA, and the cellular interactions between these cells may be critical for the progression of both diseases.

A novel role for the regulatory NRP1 in immune and inflammatory reactions during radiation-induced lung injury

Neuropilin-1 (NRP1) is a transmembrane protein with diverse functions in tumor biology and immune system regulation. Despite extensive research, its specific function in radiation-induced lung injury (RILI) remains unclear. In this study, we aimed to explore the influence of NRP1 on immune and inflammatory responses mediated by regulatory T cells (Tregs) in RILI. Initial findings revealed that radiation increases the number of NRP1-expressing Tregs, which correlated with RILI severity. Inhibiting Tregs in mice effectively suppressed radiation-induced Treg differentiation and promoted helper T cell 1 (Th1) and Th2 cytokine expression, thereby shifting T cell polarization toward a Th1 phenotype and slowing RILI progression. However, Treg inhibition alone did not entirely prevent RILI, as skin damage and inflammatory factor expression persisted. Subsequent specific NRP1 knockdown in alveolar epithelial cell-II altered the inflammatory gene network, suppressed TGF-β signaling, reduced Treg levels, decreased IL-17 A and INF-γ expression, and shifted Th cell polarization toward Th2, alleviating RILI. In conclusion, this study reveals a novel mechanism by which NRP1 regulates immune and inflammatory responses in RILI, offering a promising avenue for developing innovative therapeutic strategies.

Glucagon-like peptide-1 receptor signaling activation in alveolar type II cells enhances lung development in neonatal rats exposed to hyperoxia

BACKGROUND

Many studies have reported the important role of glucagon-like peptide-1 receptor (GLP-1R) in regulating glucose homeostasis. However, in addition to the pancreas, GLP-1R is distributed in organs such as the lungs. A few researches have reported the mechanism of action of GLP-1R in acute and chronic lung diseases. Nevertheless, its effect on lung development remains unclear. In this research, we aimed to explore the role of GLP-1R in regulating lung development and its potential mechanisms in in vivo and in vitro bronchopulmonary dysplasia (BPD) models.

METHODS

Neonatal Sprague-Dawley rats were divided into hyperoxia (FIO2 = 0.85) and control (FIO2 = 0.21) groups. Lung tissues were extracted at 3, 7, 10, and 14 postnatal days and subjected to hematoxylin and eosin staining for histopathological and morphological observation. Single-cell RNA sequencing was performed to explore the role of GLP-1R in lung development. Western blotting was conducted to assess the expression of GLP-1R, dynamin-related protein 1 (DRP1), and glycolysis-associated enzymes, including phosphofructokinase (PFKM), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), in the lung tissues, primary alveolar type II (ATII) cells, and RLE-6TN cells. Double immunofluorescence staining was performed to confirm the co-localization of GLP-1R, DRP1, and ATII cells. A Seahorse XF96 metabolic extracellular flux analyzer was used to perform real-time analyses of extracellular acidification rate and oxygen consumption rate in ATII cells isolated from lung tissues and RLE-6TN cells. The adenosine triphosphate (ATP) concentrations in ATII and RLE-6TN cells were measured using an ATP kit. Mitochondria were stained with MitoTracker and observed using HiS-SIM. GLP-1R gene levels in lung tissues, primary ATII cells, and RLE-6TN cells were tested using RT-qPCR. We used MeRIP-qPCR to determine the m6A modification level of GLP-1R mRNA in RLE-6TN cells. A reporter gene was used to verify the modification site and key methyltransferases.

RESULTS

We observed that GLP-1R signaling regulates lung development and plays a key role in ATII cells, particularly after birth. Hyperoxia inhibits GLP-1R protein and gene expression in ATII cells and accelerates BPD development. ATP production decreased and glycolysis levels increased in ATII cells under hyperoxia. Activation of GLP-1R signaling promotes ATP production and downregulates glycolysis by regulating DRP1 induced mitochondria fission. In RLE-6TN cells, we verified that the m6A modification level of GLP-1R mRNA decreased; the modification site was tested by MeRIP-qPCR and was primarily induced by the methyltransferase-like 14 (METTL14).

CONCLUSION

GLP-1R is primarily expressed in ATII cells of neonatal rats and can promote lung development during the early postnatal period. The GLP-1R signaling pathway modulates mitochondrial fission and glucose metabolism in ATII cells under hyperoxia. Hyperoxia can inhibit the activation of GLP-1R by inhibiting m6A methylation during BPD pathogenesis.

Tissue-Informed Biomaterial Innovations Advance Pulmonary Regenerative Engineering

Irreversible progressive pulmonary diseases drastically reduce the patient quality of life, while transplantation remains the only definitive cure. Research into lung regeneration pathways holds significant potential to expand and promote the discovery of new treatment options. Polymeric biomaterials designed to replicate key tissue characteristics (i.e., biochemical composition and mechanical cues) show promise for creating environments in which to study chronic lung diseases and initiate lung tissue regeneration. In this Viewpoint, we explore how naturally derived materials can be employed alone or combined with engineered polymer systems to create advanced tissue culture platforms. Pulmonary tissue models have historically leveraged natural materials, including basement membrane extracts and a decellularized extracellular matrix, as platforms for lung regeneration studies. Here, we provide an overview of the progression of pulmonary regenerative engineering, exploring how innovations in the growing field of tissue-informed biomaterials have the potential to advance lung regeneration research by bridging the gap between biological relevance and mechanical precision.

The Role of Cuproptosis in Hyperoxia-Induced Lung Injury and Its Potential for Treatment

Background

Oxygen supplementation is essential for patients with a multitude of diseases but can cause severe hyperoxia-induced lung injury (HLI), necessitating the identification of therapeutic targets to improve clinical outcomes. Cuproptosis, a novel copper-dependent form of cell death characterized by proteotoxic stress resulting from lipoylated protein aggregation and loss of iron-sulfur cluster proteins, is distinct from other forms of cell death. However, the role of cuproptosis in HLI remains unclear.

Methods

We established an HLI model in MLE-12 cells and C57BL/6 mice to investigate the involvement of cuproptosis in hyperoxia-induced toxicity.

Results

We observed a time-dependent increase in the cuproptosis-related gene Fdx1 under hyperoxia. Moreover, hyperoxia activated the membrane-associated copper transporter SLC31A1 and significantly elevated copper levels in MLE-12 cells, as well as in the serum and lung tissue of C57BL/6 mice. Further analysis revealed that hyperoxia significantly altered the expression of cuproptosis-related genes without affecting DLAT levels, but significantly increased lipoylated-DLAT levels. ELISA, CCK-8 assays, HE staining, lung wet-to-dry weight ratio, and bronchoalveolar lavage fluid analysis demonstrated that treatment with the cuproptosis inhibitor TTM reduced pro-inflammatory cytokines (TNF-α and IL-1β) and alleviated hyperoxia-induced injury in both MLE-12 cells and C57BL/6 mice.

Conclusion

Our study identifies the involvement of cuproptosis in HLI, providing new insights into the pathogenesis of hyperoxic lung injury and potential therapeutic strategies.

N‑acetyl‑L‑cysteine protects rat lungs and RLE‑6TN cells from cigarette smoke‑induced oxidative stress

Cigarette smoke (CS) is a key contributor of chronic obstructive pulmonary disease (COPD); however, its role in the pathogenesis of COPD has not been fully elucidated. N‑acetyl‑L‑cysteine (NAC), as an antioxidant, has been used in the treatment of COPD; however, the mechanisms of action of NAC are not fully understood. Alveolar epithelial type 2 (ATII) cells serve an essential role in the maintenance of alveolar integrity. The aim of the present study was to identify the effect of CS on rat lungs and ATII cells. A subacute lung injury model of Wistar rats was established using CS exposure for 4 weeks. Interalveolar septa widening, infiltration of inflammatory cells, edema fluid in airspaces and abnormal enlargement of airspaces were observed through H&E staining. ELISA revealed that NAC could protect against CS‑induced increases in serum levels of malondialdehyde and decreases in serum levels of superoxide dismutase. Additionally, 8‑hydroxy‑deoxyguanosine was detected using immunohistochemical staining, and this was also expressed at increased levels in the lung tissue of the CS‑exposed group. In addition, the expression levels of Bcl‑2, BAX and caspase‑3 p12 in lung tissue were detected by western blotting or immunohistochemical staining. The expression levels of Bcl‑2 decreased and those of caspase3 p12 were increased in response to CS exposure when compared with those in the control group. These effects were prevented by treatment with NAC. In vitro, the effect of CS extract (CSE) on rat lung epithelial‑6‑T‑antigen negative (RLE‑6TN) cells was observed, flow cytometry was used to detect intracellular reactive oxygen species (ROS) levels and the occurrence of apoptosis, and the content of glutathione (GSH) was detected using a colorimetric assay. Additionally, the expression levels of heme oxygenase‑1 (HO‑1), p53 and Bcl‑2 were examined by western blotting, and HO‑1 mRNA expression was also examined using reverse transcription‑quantitative PCR. The results of the present study revealed that CSE induced apoptosis of RLE‑6TN cells, accompanied by increased levels of intracellular ROS and exhaustion of GSH. Significantly increased protein levels of HO‑1 and p53, as well as decreased protein levels of Bcl‑2 were also observed. These effects were prevented by administration of NAC. Overall, these findings suggested that CS could promote apoptosis in rat lung tissues and alveolar epithelial cells by inducing intracellular oxidative injury, and NAC may serve an antioxidant role by replenishing the intracellular GSH content.

A combination of alveolar type 2-specific p38α activation with a high-fat diet increases inflammatory markers in mouse lungs

Chronic respiratory diseases such as asthma and chronic obstructive pulmonary disease afflict millions of individuals globally and are significant sources of disease mortality. While the molecular mechanisms underlying such diseases are unclear, environmental and social factors, such as cigarette smoke and obesity, increase the risk of disease development. Yet, not all smokers or obese individuals will develop chronic respiratory diseases. The mitogen-activated protein kinase p38α is abnormally active in such maladies, but its contribution, if any, to disease etiology is unknown. To assess whether p38α activation per se in the lung could impose disease symptoms, we generated a transgenic mouse model allowing controllable expression of an intrinsically active variant, p38αD176A+F327S, specifically in lung alveolar type 2 pneumocytes. Sustained expression of p38αD176A+F327S did not appear to induce obvious pathological outcomes or to exacerbate inflammatory outcomes in mice challenged with common respiratory disease triggers. However, mice expressing p38αD176A+F327S in alveolar type 2 cells and fed with a high-fat diet exhibited increased numbers of airway eosinophils and lymphocytes, upregulated levels of proinflammatory cytokines and chemokines including interleukin-1β and eotaxin, as well as a reduction in levels of leptin and adiponectin within the lung. Neither high-fat diet nor p38αD176A+F327S alone induced such outcomes. Perhaps in obese individuals with associated respiratory diseases, elevated p38α activity which happens to occur is the factor that promotes their development.

Radiation-induced lung injury: from mechanism to prognosis and drug therapy

Radiation induced lung injury, known as the main complication of thoracic radiation, remains to be a major resistance to tumor treatment. Based on the recent studies on radiation-induced lung injury, this review collated the possible mechanisms at the level of target cells and key pathways, corresponding prognostic models including predictors, patient size, number of centers, radiotherapy technology, construction methods and accuracy, and pharmacotherapy including drugs, targets, therapeutic effects, impact on anti-tumor treatment and research types. The research priorities and limitations are summarized to provide a reference for the research and management of radiation-induced lung injury.

Transcriptomic changes in oxidative stress, immunity, and cancer pathways caused by cannabis vapor on alveolar epithelial cells

As legalization of cannabis increases worldwide, vaping cannabis is gaining popularity due to the belief that it is less harmful than smoking cannabis. However, the safety of cannabis vaping remains untested. To address this, we developed a physiologically relevant method for in vitro assessment of cannabis vapor on alveolar epithelial cell cultures. We compared the transcriptional response in three in vitro models of cannabis vapor exposure using A549 epithelial cells in submerged culture, pseudo-air liquid interface (ALI) culture, and ALI culture coupled with the expoCube™ advanced exposure system. Baseline gene expression in ALI-maintained A549 cells showed higher expression of type 2 alveolar epithelial (AEC2) genes related to surfactant production, ion movement, and barrier integrity. Acute exposure to cannabis vapor significantly affected gene expression in AEC2 cells belonging to pathways related to cancer, oxidative stress, and the immune response without being associated with a DNA damage response. This study identifies potential risks of cannabis vaping and underscores the need for further exploration into its respiratory health implications.

Coral calcium hydride promotes peripheral mitochondrial division and reduces AT-II cells damage in ARDS via activation of the Trx2/Myo19/Drp1 pathway

Acute respiratory distress syndrome (ARDS) is a common respiratory emergency, but current clinical treatment remains at the level of symptomatic support and there is a lack of effective targeted treatment measures. Our previous study confirmed that inhalation of hydrogen gas can reduce the acute lung injury of ARDS, but the application of hydrogen has flammable and explosive safety concerns. Drinking hydrogen-rich liquid or inhaling hydrogen gas has been shown to play an important role in scavenging reactive oxygen species and maintaining mitochondrial quality control balance, thus improving ARDS in patients and animal models. Coral calcium hydrogenation (CCH) is a new solid molecular hydrogen carrier prepared from coral calcium (CC). Whether and how CCH affects acute lung injury in ARDS remains unstudied. In this study, we observed the therapeutic effect of CCH on lipopolysaccharide (LPS) induced acute lung injury in ARDS mice. The survival rate of mice treated with CCH and hydrogen inhalation was found to be comparable, demonstrating a significant improvement compared to the untreated ARDS model group. CCH treatment significantly reduced pulmonary hemorrhage and edema, and improved pulmonary function and local microcirculation in ARDS mice. CCH promoted mitochondrial peripheral division in the early course of ARDS by activating mitochondrial thioredoxin 2 (Trx2), improved lung mitochondrial dysfunction induced by LPS, and reduced oxidative stress damage. The results indicate that CCH is a highly efficient hydrogen-rich agent that can attenuate acute lung injury of ARDS by improving the mitochondrial function through Trx2 activation.

The application and prospects of drug delivery systems in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease primarily affecting elderly individuals aged >65 years and has a poor prognosis. No effective treatment is currently available for IPF. The two antipulmonary fibrosis drugs nintedanib and pirfenidone approved by the FDA in the United States have somewhat decelerated IPF progression. However, the side effects of these drugs can lead to poor patient tolerance and compliance with the medications. Researchers have recently developed various methods for IPF treatment, such as gene silencing and pathway inhibitors, which hold great promise in IPF treatment. Nevertheless, the nonselectivity and nonspecificity of drugs often affect their efficacies. Drug delivery systems (DDS) are crucial for delivering drugs to specific target tissues or cells, thereby minimizing potential side effects, enhancing drug bioavailability, and reducing lung deposition. This review comprehensively summarizes the current state of DDS and various delivery strategies for IPF treatment (e.g., nano-delivery, hydrogel delivery, and biological carrier delivery) to completely expound the delivery mechanisms of different drug delivery carriers. Subsequently, the advantages and disadvantages of different DDS are fully discussed. Finally, the challenges and difficulties associated with the use of different DDS are addressed so as to accelerate their rapid clinical translation.

Clinical analysis and predictive value of early serum lipid levels in very premature and extremely preterm infants with bronchopulmonary dysplasia: a 4 years retrospective study

BACKGROUND

Lipid metabolism plays an important role in fetal growth and development, but its role in lung maturation is currently unknown. We investigated the relationship between early serum lipid levels and clinical characteristics of bronchopulmonary dysplasia (BPD) in very preterm and extremely preterm infants.

METHODS

This study analyzed the clinical data of preterm infants with gestational age ≤ 32 weeks between January 2020 and February 2024, while clinical risk factors, maternal comorbidities, treatment methods and prognosis were retrospectively reviewed for subjects (n = 341) recruited from neonatal intensive care unit (NICU).

RESULTS

Of 228 BPD and 113 non-BPD extremely preterm infants, univariate analysis found that triglyceride (TG, P < 0.01) and high-density lipoprotein (HDL, P = 0.04) levels on the first day of admission were significantly lower in BPD infants, however, apolipoprotein A1 levels were higher than those in the non-BPD group (P < 0.01). Multivariable model further revealed that apolipoprotein A1 (Apo-A1) was a dominant determinant (OR 6.55, 95% CI 2.61,6.12). Regarding perinatal risk factors, maternal gestational hypertension was a risk factor for the morbidity of BPD (P = 0.04), while prenatal hormone exposure displayed a positive performance (P = 0.01). Kaplan-Meier curve showed no statistical difference in survival between low and normal serum lipid level groups (P > 0.05).

CONCLUSIONS

TG, HDL, Apo-A1 levels provide an insight risk and prognostication stratification in very preterm BPD infants, thus, neonatologists should emphasize high-risk features and optimize preventive therapy.

Effect of aging on pulmonary cellular responses during mechanical ventilation

Acute respiratory distress syndrome (ARDS) results in substantial morbidity and mortality, especially in elderly people. Mechanical ventilation, a common supportive treatment for ARDS, is necessary for maintaining gas exchange but can also propagate injury. We hypothesized that aging leads to alterations in surfactant function, inflammatory signaling, and microvascular permeability within the lung during mechanical ventilation. Young and aged male mice were mechanically ventilated, and surfactant function, inflammation, and vascular permeability were assessed. Additionally, single-cell RNA-Seq was used to delineate cell-specific transcriptional changes. The results showed that, in aged mice, surfactant dysfunction and vascular permeability were significantly augmented, while inflammation was less pronounced. Differential gene expression and pathway analyses revealed that alveolar macrophages in aged mice showed a blunted inflammatory response, while aged endothelial cells exhibited altered cell-cell junction formation. In vitro functional analysis revealed that aged endothelial cells had an impaired ability to form a barrier. These results highlight the complex interplay between aging and mechanical ventilation, including an age-related predisposition to endothelial barrier dysfunction, due to altered cell-cell junction formation, and decreased inflammation, potentially due to immune exhaustion. It is concluded that age-related vascular changes may underlie the increased susceptibility to injury during mechanical ventilation in elderly patients.

Copper-enriched automotive brake wear particles perturb human alveolar cellular homeostasis

BACKGROUND

Airborne fine particulate matter with diameter < 2.5 μm (PM2.5), can reach the alveolar regions of the lungs, and is associated with over 4 million premature deaths per year worldwide. However, the source-specific consequences of PM2.5 exposure remain poorly understood. A major, but unregulated source is car brake wear, which exhaust emission reduction measures have not diminished.

METHODS

We used an interdisciplinary approach to investigate the consequences of brake-wear PM2.5 exposure upon lung alveolar cellular homeostasis using diesel exhaust PM as a comparator. This involved RNA-Seq to analyse global transcriptomic changes, metabolic analyses to investigate glycolytic reprogramming, mass spectrometry to determine PM composition, and reporter assays to provide mechanistic insight into differential effects.

RESULTS

We identified brake-wear PM from copper-enriched non-asbestos organic, and ceramic brake pads as inducing the greatest oxidative stress, inflammation, and pseudohypoxic HIF activation (a pathway implicated in diseases associated with air pollution exposure, including cancer, and pulmonary fibrosis), as well as perturbation of metabolism, and metal homeostasis compared with brake wear PM from low- or semi-metallic pads, and also, importantly, diesel exhaust PM. Compositional and metal chelator analyses identified that differential effects were driven by copper.

CONCLUSIONS

We demonstrate here that brake-wear PM may perturb cellular homeostasis more than diesel exhaust PM. Our findings demonstrate the potential differences in effects, not only for non-exhaust vs exhaust PM, but also amongst different sources of non-exhaust PM. This has implications for our understanding of the potential health effects of road vehicle-associated PM. More broadly, our findings illustrate the importance of PM composition on potential health effects, highlighting the need for targeted legislation to protect public health.

YAP as a potential therapeutic target for myofibroblast formation in asthma

Myofibroblasts accumulation contributes to airway remodeling, with the mechanisms being poorly understood. It is steroid-insensitive and has not been therapeutically targeted in asthma. In this study, we explored the potential of yes-associated protein (YAP) as a therapeutic target for myofibroblasts formation in asthma, by revealing the novel role and mechanisms by which YAP activation in type II alveolar epithelial (ATII) cells promotes the fibroblast-to-myofibroblast transition in vitro and in vivo. By performing immunofluorescence staining, we showed that myofibroblasts were increased in the bronchial walls and alveolar parenchyma in clinical asthmatic and house dust mite (HDM)-induced mouse lung samples. This was accompanied by YAP overexpression and nuclear translocation in ATII cells, and connective tissue growth factor (CTGF) upregulation. In vitro, HDM or combination of rhIL-1β with rhTNF-α upregulated and activated YAP in human primary ATII cells and A549 cells, but not in the bronchial epithelial cells, BEAS-2B. This effect was mediated by F-actin polymerization and could be suppressed by pretreatment with latrunculin A but not budesonide. Inhibition of YAP/transcriptional coactivator with PDZ-binding motif (TAZ) in A549 cells by pretreatment with YAP/TAZ siRNA or verteporfin, but not budesonide, impaired the fibroblast-to-myofibroblast transition in vitro. In vivo, verteporfin partly or completely prevented HDM-induced bronchial or alveolar myofibroblast accumulation, and significantly suppressed CTGF expression and collagen deposition in mouse lungs, without profoundly affecting airway inflammation. Our results provide novel mechanistic insights into airway remodeling, and holds promise for the development of novel therapeutic strategies.

Regulation of lung progenitor plasticity and repair by fatty acid oxidation

Idiopathic pulmonary fibrosis (IPF) is an age-related interstitial lung disease, characterized by inadequate alveolar regeneration and ectopic bronchiolization. While some molecular pathways regulating lung progenitor cells have been described, the role of metabolic pathways in alveolar regeneration is poorly understood. We report that expression of fatty acid oxidation (FAO) genes is significantly diminished in alveolar epithelial cells of IPF lungs by single-cell RNA sequencing and tissue staining. Genetic and pharmacological inhibition in AT2 cells of carnitine palmitoyltransferase 1a (CPT1a), the rate-limiting enzyme of FAO, promoted mitochondrial dysfunction and acquisition of aberrant intermediate states expressing basaloid, and airway secretory cell markers SCGB1A1 and SCGB3A2. Furthermore, mice with deficiency of CPT1a in AT2 cells show enhanced susceptibility to developing lung fibrosis with an accumulation of epithelial cells expressing markers of intermediate cells, airway secretory cells, and senescence. We found that deficiency of CPT1a causes a decrease in SMAD7 protein levels and TGF-β signaling pathway activation. These findings suggest that the mitochondrial FAO metabolic pathway contributes to the regulation of lung progenitor cell repair responses and deficiency of FAO contributes to aberrant lung repair and the development of lung fibrosis.

Inhalable spray-dried porous microparticles containing dehydroandrographolide succinate phospholipid complex capable of improving and prolonging pulmonary anti-inflammatory efficacy in mice

Due to the unique physiological barriers within the lungs, there are considerable challenges in developing drug delivery systems enabling prolonged drug exposure to respiratory epithelial cells. Here, we report a PulmoSphere-based dry powder technology that incorporates a drug-phospholipid complex to promote intracellular retention of dehydroandrographolide succinate (DAS) in respiratory epithelial cells following pulmonary delivery. The DAS-phospholipid complex has the ability to self-assemble into nanoparticles. After spray-drying to produce PulmoSphere microparticles loaded with the drug-phospholipid complex, the rehydrated microparticles discharge the phospholipid complex without altering its physicochemical properties. The microparticles containing the DAS-phospholipid complex exhibit remarkable aerodynamic properties with a fine particle fraction of ∼ 60% and a mass median aerodynamic diameter of ∼ 2.3 μm. These properties facilitate deposition in the alveolar region. In vitro cell culture and lung tissue explants experiments reveal that the drug-phospholipid complex prolongs intracellular residence time and lung tissue retention due to the slow intracellular disassociation of drug from the complex. Once deposited in the lungs, the DAS-phospholipid complex loaded microparticles increase and extend drug exposure to the lung tissues and the immune cells compared to the free DAS counterpart. The improved drug exposure to airway epithelial cells, but not immune cells, is related to a prolonged duration of pulmonary anti-inflammation at decreased doses in a mouse model of acute lung injury induced by lipopolysaccharide. Overall, the phospholipid complex loaded microparticles present a promising approach for improved treatment of respiratory diseases, e.g. pneumonia and acute respiratory distress syndrome.

Functional analysis of yak alveolar type II epithelial cells at high and low altitudes based on single-cell sequencing

The adaptation of lung cells to high-altitude environments represents a notable gap in our understanding of how animals cope with hypoxic conditions. Alveolar epithelial cells type II (AEC II) are crucial for lung development and repair. However, their, specific role in the adaptation of yaks to high-altitude environments remains unclear. In this study, we aimed to address this gap by investigating the differential responses of AEC II in yaks at high and low altitudes (4000 m and 2600 m, respectively). We used the 10 × scRNA-seq technology to construct a comprehensive cell atlas of yak lung tissue, and identified 15 distinct cell classes. AEC II in high-altitude yaks revealed increased immunomodulatory, adhesive, and metabolic activities, which are crucial for maintaining lung tissue stability and energy supply under hypoxic conditions. Furthermore, alveolar epithelial progenitor cells within AEC II can differentiate into both Alveolar epithelial cell type I (AEC I) and AEC II. SHIP1 and other factors are promoters of AEC I transdifferentiation, whereas SFTPC and others promote AEC II transdifferentiation. This study provides new insights into the evolutionary adaptation of lung cells in plateau animals by elucidating the molecular mechanisms underlying AEC II adaptation to high-altitude environments.

Dexmedetomidine Blocks NCOA4-Dependent Ferritinophagy to Confer Ferroptosis Resistance in Lung Ischemia Reperfusion Injury via Targeting NRF2

Lung ischemia reperfusion injury (LIRI) represents an evitable but significant pathologic complication post pulmonary transplantation. Dexmedetomidine (Dex) that is extensively applied as an anesthetic adjuvant in the intensive care setting has increasingly presented outstandingly protective effect on LIRI. This article concerns the elaborate role of Dex in ferroptosis after LIRI and the correlative downstream mechanism. Upon hypoxia/reoxygenation (H/R) in human (A549) and mouse (MLE-12) alveolar epithelial cells, reverse transcription-quantitative PCR and western blot analysis tested nuclear receptor coactivator 4 (NCOA4) expression. CCK-8 kit determined cell viability. Western blot analysis and immunofluorescence assay estimated ferritinophagy. C11-BODIPY 581/591 staining, western blot analysis, assay kits and ferro-orange staining appraised ferroptosis. Molecular docking technology investigated the binding affinity between Dex and nuclear factor erythroid 2-related factor 2 (NRF2). Cell viability was eliminated and ferritinophagy was aggravated in A549 and MLE-12 cells in response to H/R. Disturbance of NCOA4 or treatment with Dex suppressed the ferroptosis in H/R-stimulated cells. Also, Dex docked with NRF2 and upregulated NRF2 to concentration-dependently obstruct NCOA4-mediated ferritinophagy and ferroptosis in H/R-challenged cells. Collectively, Dex might protect against NCOA4-mediated ferritinophagy through targeting NRF2, thereby alleviating ferroptosis during LIRI.

Characterizing SV40-hTERT Immortalized Human Lung Microvascular Endothelial Cells as Model System for Mechanical Stretch-Induced Lung Injury

Drug development for human disease relies on preclinical model systems such as human cell cultures and animal experiments before therapeutic treatments can ultimately be tested on humans in clinical studies. We here describe the generation of a novel human cell line (HLMVEC/SVTERT289) that we generated by transfection of microvascular endothelial cells from healthy donor lung tissue with the catalytic domain of telomerase and the SV40 large T/small t-antigen. These cells exhibited satisfactory growth characteristics and largely maintained their native characteristics, including morphology, cell surface marker expression, angiogenic potential and the protein composition of secreted extracellular vesicles. In order to test their suitability as a disease model, we simulated mechanical stress induced by cyclic stretch as encountered in ventilator-induced lung injury using the FlexCell® system and compared their performance to primary lung endothelial cells. In this setting, HLMVEC/SVTERT289 cells exhibited significantly higher neprilysin activity on the cell surface and extracellular vesicles secreted from the cell line exhibited higher Tissue Factor and ACE2 expression but lower ACE expression and ACE activity than vesicles released from the primary cells. This study provides an unprecedented and detailed characterization of the HLMVEC/SVTERT289 cell line, which should help to appraise its suitability in different molecular studies.

The pathogenesis and management of heatstroke and heatstroke-induced lung injury

In the past two decades, record-breaking heat waves have caused an increasing number of heat-related deaths, including heatstroke, globally. Heatstroke is a life-threatening systemic condition characterized by a core body temperature >40°C and the subsequent development of multiple organ dysfunction syndrome. Lung injury is a well-documented complication of heatstroke and is usually the secondary cause of patient death. In recent years, extensive research has been conducted to investigate the underlying causes of heatstroke and heatstroke-induced lung injury. This review aims to consolidate and present the current understanding of the key pathogenic mechanisms involved in heatstroke and heatstroke-induced lung injury. In addition, systemic factors such as heat cytotoxicity, systemic inflammation, oxidative stress, endothelial cell dysfunction, and other factors are involved in the pathogenesis of lung injury in heatstroke. Furthermore, we also established current management strategies for heatstroke and heatstroke-induced lung injury. However, further investigation is required to fully understand the detailed pathogenesis of heatstroke so that potentially effective means of treating and preventing heatstroke and heatstroke-induced lung injury can be developed and studied.

Wenshen Yiqi Granule Alleviates Chronic Obstructive Pulmonary Disease via the Long Noncoding RNA-XIST/MicroRNA-200c-3p Axis

Chronic obstructive pulmonary disease (COPD) is a major challenge to global public health. Evidence showed that long noncoding RNA (lncRNA)-XIST/microRNA (miRNA)-200c-3p axis regulated apoptosis and inflammation in cigarette smoke extract (CSE)-exposed human bronchial epithelial cells. Wenshen Yiqi granule (WSYQG) is a Traditional Chinese medicine compound prescription and often used for treating COPD. However, the current understanding of the mechanism by which WSYQG improves COPD is still limited, which has somewhat restrained its widespread application. Therefore, this study aims to investigate the effects and biological mechanisms of WSYQG on CSE-exposed type II alveolar epithelial (AEC II) cells with cell transfection and miRNA mimics/inhibitors intervention. Cell counting kit-8, flow cytometry, Transwell, Western blot, real-time quantitative reverse transcription PCR, and fluorescence in situ hybridization assays were used. Results showed that WSYQG intervention increased cell viability and decreased levels of IFN-γ, TNF-α and apoptosis, also preventing cell migration in CSE-exposed ACE II cells. Additionally, expression of epithelial marker (ZO-1), Notch1/4 decreased, and mesenchymal markers (vimentin) and Notch2 expression increased in CSE-exposed ACE II cells, while WSYQG intervention antagonized them and also decreased N-cadherin and increased E-cadherin. Silencing lncRNA-XIST enhanced WSYQG's effects on CSE-exposed ACE II cells, while inhibiting miR-200c-3p reversed silencing lncRNA-XIST's effects. Furthermore, dual-luciferase reporter assay system and RNA immunoprecipitation assay proved that lncRNA-XIST acts as a miR-200c-3p sponge. This study highlights the importance of the lncRNA-XIST/miR-200c-3p axis in WSYQG improving COPD, providing a research basis for WSYQG to improve COPD and expanding the possibility of expanding its clinical application.

Metabolic dysfunction and insulin sensitizers in acute and chronic disease

INTRODUCTION

The concept of insulin resistance has been a major topic for more than 5 decades. While there are several treatments that may impact insulin resistance, this pathology is uniquely addressed by mitochondrially directed thiazolidinedione (TZD) insulin sensitizers. Understanding of this mechanism of action and consideration of 'insulin resistance' as a consequence of metabolic inflammation allows a new paradigm for approaching chronic diseases.

AREAS COVERED

We review evolving understanding of the mitochondrial pyruvate carrier (MPC) as a mitochondrial mechanism of action of the TZD insulin sensitizers and discuss how reprogramming of mitochondrial metabolism impacts pleotropic pharmacology in multiple tissues. Additional lines of investigation are proposed.

EXPERT OPINION

A change in paradigm can facilitate rethinking of insulin sensitizers in clinical trials, specifically beyond the treatment of frank type 2 diabetes. There should be broader clinical evaluation of insulin sensitizers in combination with weight loss and lifestyle approaches across diseases/syndromes associated with insulin resistance. Finally, 'connecting all the dots' to unwind the interconnectedness of cell biology involved in the syndromes impacted by metabolic dysfunction and the efficacy of TZD insulin sensitizers may also uncover new molecular targets. New studies should facilitate the discovery and development of novel pharmacologic agents.

Understanding the cellular dynamics, engineering perspectives and translation prospects in bioprinting epithelial tissues

The epithelium is one of the important tissues in the body as it plays a crucial barrier role serving as a gateway into and out of the body. Most organs in the body contain an epithelial tissue component, where the tightly connected, organ-specific epithelial cells organize into cysts, invaginations, or tubules, thereby performing distinct to endocrine or exocrine secretory functions. Despite the significance of epithelium, engineering functional epithelium in vitro has remained a challenge due to it is special architecture, heterotypic composition of epithelial tissues, and most importantly, difficulty in attaining the apico-basal and planar polarity of epithelial cells. Bioprinting has brought a paradigm shift in fabricating such apico-basal polarized tissues. In this review, we provide an overview of epithelial tissues and provide insights on recapitulating their cellular arrangement and polarization to achieve epithelial function. We describe the different bioprinting techniques that have been successful in engineering polarized epithelium, which can serve as in vitro models for understanding homeostasis and studying diseased conditions. We also discuss the different attempts that have been investigated to study these 3D bioprinted engineered epithelium for preclinical use. Finally, we highlight the challenges and the opportunities that need to be addressed for translation of 3D bioprinted epithelial tissues towards paving way for personalized healthcare in the future.

The triple combination DBDx alleviates cytokine storm and related lung injury

Cytokine storm is a life-threatening disorder, and therapeutic treatments are urgently needed. Here, we investigated the anti-cytokine storm efficacy of DBDx, a triple drug combination composed of dipyridamole, ubenimex and dexamethasone. Evaluated by lipopolysaccharide (LPS)-induced cytokine storm murine model, DBDx significantly improved survival rate and prolonged survival time of the model mice. Notably, the efficacy of DBDx was higher than that of dipyridamole, ubenimex and dexamethasone. Determined by ELISA, DBDx significantly reduced the LPS-stimulated serum levels of TNF-α, IL-6 and IL-1β in mice. Luminex assay showed that DBDx suppressed the serum levels of a wide variety of inflammatory cytokines and chemokines, which was more potent than dexamethasone alone. Otherwise, DBDx exerted similar inhibitory effects on cytokine profiles in bronchoalveolar lavage fluid. Histopathological observation showed that DBDx significantly reduced the LPS-induced thickening of alveolar septum, indicating its suppression of capillary congestion, edema and neutrophil infiltration in the lung. Ultra-structure analysis showed that DBDx suppressed the LPS-induced morphological changes of microvilli in type II pneumocytes. In vitro experiment showed that DBDx inhibited IL-6 and TNF-α secretion in THP-1 cells, and downregulated TLR4/NF-κB/HIF-1α signaling pathway. All of these results demonstrate that DBDx, a triple combination of clinical orally-administered drugs, can alleviate cytokine storm and related lung injury. DBDx is beneficial for treating cytokine storm disorders.

Therapeutic applications of stem cell-derived exosomes in radiation-induced lung injury

Radiation-induced lung injury is a common complication of chest tumor radiotherapy; however, effective clinical treatments are still lacking. Stem cell-derived exosomes, which contain various signaling molecules such as proteins, lipids, and miRNAs, not only retain the tissue repair and reconstruction properties of stem cells but also offer improved stability and safety. This presents significant potential for treating radiation-induced lung injury. Nonetheless, the clinical adoption of stem cell-derived exosomes for this purpose remains limited due to scientific, practical, and regulatory challenges. In this review, we highlight the current pathology and therapies for radiation-induced lung injury, focusing on the potential applications and therapeutic mechanisms of stem cell-derived exosomes. We also discuss the limitations of existing stem cell-derived exosomes and outline future directions for exosome-based treatments for radiation-induced lung injury.

Porphyromonas gingivalis inducing autophagy-related biological dysfunction in alveolar epithelial cells: an in vitro study

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a respiratory disease with high morbidity and mortality. Notably, the pathogenesis and progression of COPD are related to lung infection, inflammatory response, and biological dysfunction in alveolar epithelial cells. Studies also found that periodontitis is an independent risk factor for COPD. The inhalation of periodontal pathogens into the respiratory system is the most common method for periodontal pathogens to promote the development of COPD. Porphyromonas gingivalis (P. gingivalis), the keystone pathogen in periodontitis, has been found to migrate to the lungs, triggering inflammatory reactions and causing decreased lung function. However, the impact of P. gingivalis infection on the biological function of alveolar epithelial cells remains unclear. Therefore, this study aimed to investigate the effects of P. gingivalis infection on the biological functions of alveolar epithelial cells.

METHODS

Mouse alveolar epithelial cells (MLE-12) were co-cultured with P. gingivalis and treated with autophagy inhibitor chloroquine (CQ) or LC3 siRNA in vitro. MTT assay and EdU staining were used to detect cell viability, and the TUNEL assay kit and Annexin V-FITC/PI method were used to detect cell apoptosis. Western blot was used to detect autophagic markers LC3 and P62, and mRFP-GFP-LC3 was used to observe autophagic flux.

RESULTS

P. gingivalis inhibited the viability of alveolar epithelial cells in a dose- and time-dependent manner. P. gingivalis also promoted autophagy and apoptosis of alveolar epithelial cells in a dose-dependent manner. Interestingly, we found that inhibiting autophagy using CQ or silencing LC3 with siRNA significantly reduced cell apoptosis and viability damage induced by P. gingivalis. Thus, these data indicated the synergistic effect of autophagy in P. gingivalis-induced biological dysfunction of alveolar epithelial cells.

CONCLUSION

P. gingivalis infection can cause biological dysfunction of alveolar epithelial cells, manifested as decreased cell viability, increased autophagy and apoptosis. Notably, the up-regulation of autophagy induced by P. gingivalis plays a synergistic role in this dysfunction.

Cytological changes in radiation-induced lung injury

Radiation-induced lung injury (RILI) is a prevalent complication associated with radiotherapy for thoracic tumors. Based on the pathological progression, it can be categorized into two stages: early radiation pneumonitis and late radiation pulmonary fibrosis. The occurrence of RILI not only constrains the therapeutic dose that can be administered to the tumor target area but also significantly impairs patients' health and quality of life, thereby limiting the efficacy and applicability of radiotherapy. To effectively prevent and mitigate the development of RILI, it is crucial to disclose its underlying mechanisms. This review aims to elucidate the specific mechanisms involved in RILI and to examine the roles of various cell types, including lung parenchymal cells and different immune cells. The functions and interactions of lung epithelial cells, pulmonary vascular endothelial cells, a variety of immune cells, and fibroblasts during different stages of inflammation, tissue repair, and fibrosis following radiation-induced lung injury are analyzed. A comprehensive understanding of the dynamic changes in these cellular components is anticipated to offer new strategies for the prevention of RILI.

Preventing human influenza and coronaviral mono or coinfection by blocking virus-induced sialylation

Influenza A viruses (IAVs) and endemic coronaviruses (eCoVs) are common etiologic agents for seasonal respiratory infections. The human H1N1 of IAV and coronavirus OC43 (HCoV-OC43) can result in hospitalization, acute respiratory distress syndrome (ARDS), and even death, particularly in immunocompromised individuals. They infect the epithelium of the respiratory tract by interacting with host cell sialic acid (Sia)- linked receptors whose synthesis is catalyzed by sialyltransferases (STs). Viral coinfection is challenging to treat because of the need to target specific components of two or more distinct pathogens. Emerging drug and vaccine resistance due to the high mutation rate of viral genomes further complicates the treatment and prevention of viral infection. Sialylation mediated by STs may be a potential drug target for treating viral diseases. ST is an attractive target because it could be effective before identifying the pathogen that has occurred, providing a novel direction for overcoming drug resistance and achieving a broad-spectrum antiviral effect. We developed an H1N1 and OC43 mono or coinfection model using 14 days post-plating (14 PP) human primary small airway epithelial cells (HSAEC) grown on transwell inserts at an air-fluid interface (ALI), mimicking in vivo cellular dynamics. Using this model, we have observed that mono or coinfection with OC43 and H1N1 results in increased sialic acid levels and synergistic viral infection. We showed for the first time that H1N1 and OC43 mono- and coinfection in HSAEC caused increased expression and activity of STs, which can be blocked by pan-STs inhibitor (3Fax-Peracetyl Neu5Ac) with no host cell toxicity.

Cadmium exposure triggers alveolar epithelial cell pyroptosis by inducing mitochondrial oxidative stress and activating the cGAS-STING pathway

BACKGROUND

Cadmium is a ubiquitous toxic metal and environmental pollutant. More and more studies have shown that cadmium exposure can damage lung function. Alveolar epithelial cells (AECs) are structural cells that maintain the stability of lung function. The injury of AECs is an essential determinant of many lung diseases. In the lung, cadmium accumulation can cause damage to AECs. However, the specific mechanism is still unclear. This study aimed to explore the key mechanism underlying the injury of AECs caused by cadmium exposure.

METHODS

The main modes of death of AECs induced by cadmium exposure were evaluated in vivo and in vitro. Transcriptomic changes of AECs induced by cadmium exposure were analyzed using RNA-sequence. Mitochondrial ROS scavengers (mitoQ), voltage-dependent anion channel 1 (VDAC1) oligomer inhibitor (VBIT4), and cyclic GMP-AMP synthase (cGAS) inhibitor (RU.521) were used to assess whether cadmium exposure triggered pyroptosis of AECs by inducing mitochondrial stress to activate the cGAS-STING-NLRP3 axis.

RESULTS

In this study, the expression of pyroptosis-related proteins was significantly up-regulated in the cadmium-exposed AECs, while the expression of apoptosis, necroptosis, and ferroptosis-related proteins had no significant up-regulated. The pan-caspase inhibitor ZVAD-FMK significantly reduced cell death. Thus, our research indicates that pyroptosis is the primary type of AEC death exported to cadmium. Mechanistically, RNA-seq and Western Blot results showed that cadmium exposure activated the cGAS-STING pathway in AECs and promoted pyroptosis by activating the NLRP3 inflammasome. Further investigation of the mechanism found that cadmium exposure caused mitochondrial oxidative stress, which led to mtDNA leakage into the cytoplasm and activated the cGAS-STING pathway. In addition, inhibition of the cGAS-STING pathway significantly alleviated lung injury induced by cadmium exposure in mice.

CONCLUSION

Our study confirmed that pyroptosis of AECs was a vital mechanism of lung injury after cadmium exposure in a cGAS-STING-dependent manner, which may provide a new target for the treatment of lung diseases induced by cadmium exposure.

Lung Single-Cell Transcriptomics Offers Insights into the Pulmonary Interstitial Toxicity Caused by Silica Nanoparticles

The adverse respiratory outcomes motivated by silica nanoparticles (SiNPs) exposure have received increasing attention. Herein, we aim to elucidate the interplay of diverse cell populations in the lungs and key contributors in triggering lung injuries caused by SiNPs. We conducted a subchronic respiratory exposure model of SiNPs via intratracheal instillation in Wistar rats, where rats were administered with 1.5, 3.0, or 6.0 mg/kg body weight SiNPs once a week for 12 times in total. We revealed that SiNPs caused pulmonary interstitial injury in rats by histopathological examination and pulmonary hydroxyproline determination. Further, a single-cell RNA-Seq via screening 10 457 cells in the rat lungs disclosed cell-specific responses to SiNPs and cell-to-cell interactions within the alveolar macrophages, epithelial cells, and fibroblasts from rat lungs. These disturbed responses were principally related to the dysregulation of protein homeostasis (proteostasis), accompanied by an inflammatory response in macrophages, cell death in epithelial, proliferation, and extracellular matrix deposition in fibroblast. These cell-specific responses may serve a synergistic role in the pathogenesis of pulmonary interstitial disease triggered by SiNPs. In particular, the analyses of gene interaction networks and gene-disease associations filtered out heat shock proteins (Hsps) family genes crucial to the observed pulmonary lesions caused by SiNPs. Of note, both GEO database analysis and our experiments' validation indicated that Hsps, especially Hspd1, may be a key contributor to pulmonary interstitial injury, possibly through triggering oxidative stress, immune response, and disrupting protein homeostasis. Taken together, our study provides insights into pulmonary toxic effects and underlying molecular mechanisms of SiNPs from a single-cell perspective.

The polysaccharide from purple sweet potato (Ipomoea batatas (L.) Lam) alleviates lipopolysaccharide-induced acute lung injury in mice via the VIP/cAMP/PKA/AQPs signaling pathway

BACKGROUND

The polysaccharide (PSP) from purple sweet potato has great potential for regulating apoptosis, but its regulatory role in acute lung injury (ALI) is unknown.

METHODS

The objective of this study was to investigate the protective effect of PSP on lipopolysaccharide (LPS)-induced ALI in mice and lung epithelial A549 cells and its mechanism. Moreover, subacute toxicity evaluation of PSP was carried out on ICR mice.

RESULTS

The results showed that compared with the ALI group, PSP significantly reduced the total protein content, wet-to-dry (W/D) ratio, the number of neutrophils, lymphocytes, and monocytes. Moreover, PSP was able to reduce cell apoptosis, the levels of macrophage inflammatory protein-2 (MIP-2), intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor-α (TNF-α), malondialdehyde (MDA) and myeloperoxidase (MPO) and increase the level of superoxide (SOD). In addition, PSP could up-regulate the levels of VIP, cAMP, p-PKA/PKA and AQP1 in mice and A549 cells. And PSP exhibited no apparent adverse effects on the mice.

CONCLUSIONS

PSP had a protective effect on LPS-induced ALI in mice and lung epithelial A549 cells, which may be related to the inflammatory response and via VIP/cAMP/PKA/AQPs signaling pathway. Thus, PSP may be a promising pharmacologic agent for ALI therapy.

Hyperoxia can Induce Lung Injury by Upregulating AECII Autophagy and Apoptosis Via the mTOR Pathway

Oxygen therapy is a crucial medical intervention, but it is undeniable that it can lead to lung damage. The mTOR pathway plays a pivotal role in governing cell survival, including autophagy and apoptosis, two phenomena deeply entwined with the evolution of diseases. However, it is unclarified whether the mTOR pathway is involved in hyperoxic acute lung injury (HALI). The current study aims to clarify the molecular mechanism underlying the pathogenesis of HALI by constructing in vitro and in vivo models using H2O2 and hyperoxia exposure, respectively. To investigate the role of mTOR, the experiment was divided into five groups, including normal group, injury group, mTOR inhibitor group, mTOR activator group, and DMSO control group. Western blotting, Autophagy double labeling, TUNEL staining, and HE staining were applied to evaluate protein expression, autophagy activity, cell apoptosis, and pathological changes in lung tissues. Our data revealed that hyperoxia can induce autophagy and apoptosis in Type II alveolar epithelial cell (AECII) isolated from the treated rats, as well as injuries in the rat lung tissues; also, H2O2 stimulation increased autophagy and apoptosis in MLE-12 cells. Noticeably, the experiments performed in both in vitro and in vivo models proved that the mTOR inhibitor Rapamycin (Rapa) functioned synergistically with hyperoxia or H2O2 to promote AECII autophagy, which led to increased apoptosis and exacerbated lung injury. On the contrary, activation of mTOR with MHY1485 suppressed autophagy activity, consequently resulting in reduced apoptosis and lung injury in H2O2-challenged MLE-12 cells and hyperoxia-exposed rats. In conclusion, hyperoxia caused lung injury via mTOR-mediated AECII autophagy.

Intranasal administration of Clostridium butyricum and its derived extracellular vesicles alleviate LPS-induced acute lung injury

Acute lung injury (ALI) is associated with high morbidity and mortality rates. However, its clinical treatment is limited. Currently, the treatment of lung diseases by regulating the lung microbiota has become a research hotspot. In this study, we investigated the protective effects of the intranasal administration of Clostridium butyricum and its derived extracellular vesicles (EVs) against lipopolysaccharide (LPS)-induced ALI. The results demonstrated that compared with the LPS group, the pre-treatment group with C. butyricum and its EVs reduced the expression of pro-inflammatory cytokines and alleviated the symptoms in ALI mice by inhibiting the TLR4/MyD88 signaling pathway. Moreover, C. butyricum and its derived EVs inhibited the expression of apoptosis-related proteins and increased the expression of lung barrier proteins. Additionally, the intervention of C. butyricum changed the composition of the pulmonary microbiota. At the species level, LPS significantly increased the relative abundance of Acinetobacter johnsonii, while C. butyricum reversed this effect. In conclusion, these data demonstrate that intranasal administration of C. butyricum and its EVs can prevent LPS-induced ALI by reducing inflammation, inhibiting apoptosis, and improving lung barrier function. Additionally, C. butyricum regulated the pulmonary microbiota of mice to alleviate LPS-induced ALI.IMPORTANCEThe disorder of pulmonary microbiota plays an important role in the progression of acute lung injury (ALI). However, very few studies have been conducted to treat ALI by modulating pulmonary microbiota. In this study, the diversity and composition of pulmonary microbiota were altered in lipopolysaccharide (LPS)-induced ALI mice, but the ecological balance of the pulmonary microbiota was restored by intranasal administration of Clostridium butyricum. Moreover, the study reported the mechanism of C. butyricum and its derived extracellular vesicles for the treatment of LPS-induced ALI. These results reveal the importance of pulmonary microbiota in ALI disease. It provides a new approach for the treatment of ALI with new-generation probiotics.

The Role of Mast Cells in the Remodeling Effects of Molecular Hydrogen on the Lung Local Tissue Microenvironment under Simulated Pulmonary Hypertension

Molecular hydrogen (H2) has antioxidant, anti-inflammatory, and anti-fibrotic effects. In a rat model simulating pulmonary fibrotic changes induced by monocrotaline-induced pulmonary hypertension (MPH), we had previously explored the impact of inhaled H2 on lung inflammation and blood pressure. In this study, we further focused the biological effects of H2 on mast cells (MCs) and the parameters of the fibrotic phenotype of the local tissue microenvironment. MPH resulted in a significantly increased number of MCs in both the pneumatic and respiratory parts of the lungs, an increased number of tryptase-positive MCs with increased expression of TGF-β, activated interaction with immunocompetent cells (macrophages and plasma cells) and fibroblasts, and increased MC colocalization with a fibrous component of the extracellular matrix of connective tissue. The alteration in the properties of the MC population occurred together with intensified collagen fibrillogenesis and an increase in the integral volume of collagen and elastic fibers of the extracellular matrix of the pulmonary connective tissue. The exposure of H2 together with monocrotaline (MCT), despite individual differences between animals, tended to decrease the intrapulmonary MC population and the severity of the fibrotic phenotype of the local tissue microenvironment compared to changes in animals exposed to the MCT effect alone. In addition, the activity of collagen fibrillogenesis associated with MCs and the expression of TGF-β and tryptase in MCs decreased, accompanied by a reduction in the absolute and relative content of reticular and elastic fibers in the lung stroma. Thus, with MCT exposure, inhaled H2 has antifibrotic effects involving MCs in the lungs of rats. This reveals the unknown development mechanisms of the biological effects of H2 on the remodeling features of the extracellular matrix under inflammatory background conditions of the tissue microenvironment.

BCAP31 Alleviates Lipopolysaccharide-Mediated Acute Lung Injury via Induction of PINK1/Parkin in Alveolar Epithelial Type II Cell

Background: B-cell receptor-associated protein 31 (BCAP31) has protective effects against alveolar epithelial type II cells (AECII) damage by inhibiting mitochondrial injury in acute lung injury (ALI) induced by lipopolysaccharide (LPS), whereas the precise mechanism is still unclear. It is known that PTEN-induced putative kinase 1 (PINK1)/Parkin-mediated mitophagy can remove damaged mitochondria selectively, which may be involved in BCAP31 protection against mitochondrial injury. Methods: In the current study, ALI mice models were established by using surfactant protein C (Sftpc)-BCAP31 transgenic mice (BCAP31TG mice) and AECII-specific BCAP31 knockout mice (BCAP31CKO mice) treated with LPS. Results: BCAP31 expression in lung tissue and AECII were inhibited in ALI mice. Under LPS challenge, lower level of BCAP31 was found to correlate positively with pathological injury of the lung, respiratory dysfunction, mortality rates, inflammation response, and AECII damage. Further study showed that down-regulation of BCAP31 induced decreased phosphorylation of PINK1 via reduced binding to PINK1, thereby restraining PINK1/Parkin-mediated mitophagy. Down-regulation of mitophagy promoted mitochondrial injury, as shown by the increase in mitochondrial permeability transition pore opening rate, together with enhanced mitochondrial reactive oxygen species (mROS), which were accompanied by increased cellular apoptosis and reactive oxygen species (ROS). The increased cellular ROS contributed to the inflammatory response via activation of nuclear factor κB (NF-κB). In contrast, BCAP31 overexpression promoted phosphorylation of PINK1 and PINK1/Parkin-mediated mitophagy, thus blocking the mROS/ROS/NF-κB pathway, favoring a protective condition that ultimately led to the inhibition of AECII apoptosis and inflammatory response in LPS-induced ALI. Conclusion: Ultimately, BCAP31 alleviated ALI by activating PINK1/Parkin-mediated mitophagy and blocking the mROS/ROS/NF-κB pathway in AECII.

Lung Progenitor and Stem Cell Transplantation as a Potential Regenerative Therapy for Lung Diseases

Chronic lung diseases are debilitating illnesses ranking among the top causes of death globally. Currently, clinically available therapeutic options capable of curing chronic lung diseases are limited to lung transplantation, which is hindered by donor organ shortage. This highlights the urgent need for alternative strategies to repair damaged lung tissues. Stem cell transplantation has emerged as a promising avenue for regenerative treatment of the lung, which involves delivery of healthy lung epithelial progenitor cells that subsequently engraft in the injured tissue and further differentiate to reconstitute the functional respiratory epithelium. These transplanted progenitor cells possess the remarkable ability to self-renew, thereby offering the potential for sustained long-term treatment effects. Notably, the transplantation of basal cells, the airway stem cells, holds the promise for rehabilitating airway injuries resulting from environmental factors or genetic conditions such as cystic fibrosis. Similarly, for diseases affecting the alveoli, alveolar type II cells have garnered interest as a viable alveolar stem cell source for restoring the lung parenchyma from genetic or environmentally induced dysfunctions. Expanding upon these advancements, the use of induced pluripotent stem cells to derive lung progenitor cells for transplantation offers advantages such as scalability and patient specificity. In this review, we comprehensively explore the progress made in lung stem cell transplantation, providing insights into the current state of the field and its future prospects.

Alveolar distribution of nebulized solution in health and lung injury assessed by confocal microscopy

Parenchymal distribution of nebulized drug in healthy and diseased lungs has not, as evident from a literature review, been well characterized. We use a vibrating mesh nebulizer to deliver fluorescein solution in vivo to healthy or intratracheal-lipopolysaccharide (LPS)-instilled anesthetized rats in dorsal recumbency, or ex vivo to the lungs of LPS-instilled rats. Following in vivo nebulization (healthy/LPS-instilled), we quantify fluorescein intensity distribution by confocal microscopy in standard locations on the surface of freshly isolated lungs. Following LPS instillation (in vivo/ex vivo nebulization), we quantify fluorescein intensity in visibly injured locations. In standard locations, there is uniform, low-intensity basal fluorescein deposition. Focal regions receive high deposition that is, in upper (cranial), middle, and lower (caudal) locations, 6.4 ± 4.9, 3.3 ± 3.0, and 2.3 ± 2.8 times greater, respectively, than average basal intensity. Following LPS instillation, deposition in moderately injured regions can be high or low; deposition in severely injured regions is low. Further, actively phagocytic cells are observed in healthy and LPS-instilled lungs. And LPS particularly impairs mechanics and activates phagocytic cells in the male sex. We conclude that a low level of nebulized drug can be distributed across the parenchyma excepting to severely injured regions.

3D cell culture models in research: applications to lung cancer pharmacology

Lung cancer remains one of the leading causes of cancer-related mortality worldwide, necessitating innovative research methodologies to improve treatment outcomes and develop novel strategies. The advent of three-dimensional (3D) cell cultures has marked a significant advancement in lung cancer research, offering a more physiologically relevant model compared to traditional two-dimensional (2D) cultures. This review elucidates the various types of 3D cell culture models currently used in lung cancer pharmacology, including spheroids, organoids and engineered tissue models, having pivotal roles in enhancing our understanding of lung cancer biology, facilitating drug development, and advancing precision medicine. 3D cell culture systems mimic the complex spatial architecture and microenvironment of lung tumours, providing critical insights into the cellular and molecular mechanisms of tumour progression, metastasis and drug responses. Spheroids, derived from commercialized cell lines, effectively model the tumour microenvironment (TME), including the formation of hypoxic and nutrient gradients, crucial for evaluating the penetration and efficacy of anti-cancer therapeutics. Organoids and tumouroids, derived from primary tissues, recapitulate the heterogeneity of lung cancers and are instrumental in personalized medicine approaches, supporting the simulation of in vivo pharmacological responses in a patient-specific context. Moreover, these models have been co-cultured with various cell types and biomimicry extracellular matrix (ECM) components to further recapitulate the heterotypic cell-cell and cell-ECM interactions present within the lung TME. 3D cultures have been significantly contributing to the identification of novel therapeutic targets and the understanding of resistance mechanisms against conventional therapies. Therefore, this review summarizes the latest findings in drug research involving lung cancer 3D models, together with the common laboratory-based assays used to study drug effects. Additionally, the integration of 3D cell cultures into lung cancer drug development workflows and precision medicine is discussed. This integration is pivotal in accelerating the translation of laboratory findings into clinical applications, thereby advancing the landscape of lung cancer treatment. By closely mirroring human lung tumours, these models not only enhance our understanding of the disease but also pave the way for the development of more effective and personalized therapeutic strategies.

Engraftment of wild-type alveolar type II epithelial cells in surfactant protein C deficient mice

Childhood interstitial lung disease (chILD) secondary to pulmonary surfactant deficiency is a devastating chronic lung disease in children. Clinical presentation includes mild to severe respiratory failure and fibrosis. There is no specific treatment, except lung transplantation, which is hampered by a severe shortage of donor organs, especially for young patients. Repair of lungs with chILD represents a longstanding therapeutic challenge but cell therapy is a promising strategy. As surfactant is produced by alveolar type II epithelial (ATII) cells, engraftment with normal or gene-corrected ATII cells might provide an avenue to cure. Here we used a chILD disease-like model, Sftpc -/- mice, to provide proof-of-principle for this approach. Sftpc -/- mice developed chronic interstitial lung disease with age and were hypersensitive to bleomycin. We could engraft wild-type ATII cells after low dose bleomycin conditioning. Transplanted ATII cells produced mature SPC and attenuated bleomycin-induced lung injury up to two months post-transplant. This study demonstrates that partial replacement of mutant ATII cells can promote lung repair in a mouse model of chILD-like disease.

Methylprednisolone alleviates lung injury in sepsis by regulating miR-151-5p/USP38 pathway

BACKGROUND

Acute lung injury (ALI) is manifested by increased blood vessel permeability within the lungs and subsequent impairment of alveolar gas exchange. Methylprednisolone (MP) is commonly used as a treatment for ALI to reduce inflammation, yet its molecular mechanism remains unclear. This study aims to explore the underlying mechanisms of MP on ALI in a model induced by lipopolysaccharide (LPS).

MATERIAL AND METHODS

The proliferation, viability, apoptosis, and miR-151-5p expression of alveolar type II epithelial cells (AECII) were detected using the cell EdU assay, Annexin V/PI Apoptosis Kit, counting kit-8 (CCK-8) assay, and RT-qPCR. Western blot analysis was used to detect the Usp38 protein level. IL-6 and TNF-α were measured by ELISA. The combination of miR-151-5p and USP38 was determined by chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase reporter assay.

RESULTS

MP greatly improved pulmonary function in vivo, reduced inflammation, and promoted the proliferation of the alveolar type II epithelial cells (AECII) in vitro. By comparing the alterations of microRNAs in lung tissues between MP treatment and control groups, we found that miR-151-5p exhibited a significant increase after LPS-treated AECII, but decreased after MP treatment. Confirmed by a luciferase reporter assay, USP38, identified as a downstream target of miR-151-5p, was found to increase after MP administration. Inhibition of miR-151-5p or overexpression of USP38 in AECII significantly improved the anti-inflammatory, anti-apoptotic, and proliferation-promotive effects of MP.

CONCLUSION

In summary, our data demonstrated that MP alleviates the inflammation and apoptosis of AECII induced by LPS, and promotes the proliferation of AECII partially via miR-151-5p suppression and subsequent USP38 activation.

Neutrophil extracellular traps trigger alveolar epithelial cell necroptosis through the cGAS-STING pathway during acute lung injury in mice

Extensive loss of alveolar epithelial cells (AECs) undergoing necroptosis is a crucial mechanism of acute lung injury (ALI), but its triggering mechanism needs to be thoroughly investigated. Neutrophil extracellular traps (NETs) play a significant role in ALI. However, the effect of NETs on AECs' death has not been clarified. Our study found that intratracheal instillation of NETs disrupted lung tissue structure, suggesting that NETs could induce ALI in mice. Moreover, we observed that NETs could trigger necroptosis of AECs in vivo and in vitro. The phosphorylation levels of RIPK3 and MLKL were increased in MLE12 cells after NETs treatment (P < 0.05). Mechanistically, NETs taken up by AECs through endocytosis activated the cGAS-STING pathway and triggered AECs necroptosis. The expression of cGAS, STING, TBK1 and IRF3 were increased in MLE12 cells treated with NETs (P < 0.05). Furthermore, the cGAS inhibitor RU.521 inhibited NETs-triggered AECs necroptosis and alleviated the pulmonary damage induced by NETs in mice. In conclusion, our study demonstrates that NETs taken up by AECs via endocytosis can activate the cGAS-STING pathway and trigger AECs necroptosis to promote ALI in mice. Our findings indicate that targeting the NETs/cGAS-STING/necroptosis pathway in AECs is an effective strategy for treating ALI.

LL37-mtDNA regulates viability, apoptosis, inflammation, and autophagy in lipopolysaccharide-treated RLE-6TN cells by targeting Hsp90aa1

Sepsis-induced acute lung injury is associated with lung epithelial cell injury. This study analyzed the role of the antimicrobial peptide LL37 with mitochondrial DNA (LL37-mtDNA) and its potential mechanism of action in lipopolysaccharide (LPS)-treated rat type II alveolar epithelial cells (RLE-6TN cells). RLE-6TN cells were treated with LPS alone or with LL37-mtDNA, followed by transcriptome sequencing. Differentially expressed and pivotal genes were screened using bioinformatics tools. The effects of LL37-mtDNA on cell viability, inflammation, apoptosis, reactive oxygen species (ROS) production, and autophagy-related hallmark expression were evaluated in LPS-treated RLE-6TN cells. Additionally, the effects of Hsp90aa1 silencing following LL37-mtDNA treatment were investigated in vitro. LL37-mtDNA further suppressed cell viability, augmented apoptosis, promoted the release of inflammatory cytokines, increased ROS production, and elevated LC3B expression in LPS-treated RLE-6TN cells. Using transcriptome sequencing and bioinformatics, ten candidate genes were identified, of which three core genes were verified to be upregulated in the LPS + LL37-mtDNA group. Additionally, Hsp90aa1 downregulation attenuated the effects of LL37-mtDNA on LPS-treated RLE-6TN cells. Hsp90aa1 silencing possibly acted as a crucial target to counteract the effects of LL37-mtDNA on viability, apoptosis, inflammation, and autophagy activation in LPS-treated RLE-6TN cells.

Long-term exposure to diesel exhaust particles induces concordant changes in DNA methylation and transcriptome in human adenocarcinoma alveolar basal epithelial cells

BACKGROUND

Diesel exhaust particles (DEP), which contain hazardous compounds, are emitted during the combustion of diesel. As approximately one-third of the vehicles worldwide use diesel, there are growing concerns about the risks posed by DEP to human health. Long-term exposure to DEP is associated with airway hyperresponsiveness, pulmonary fibrosis, and inflammation; however, the molecular mechanisms behind the effects of DEP on the respiratory tract are poorly understood. Such mechanisms can be addressed by examining transcriptional and DNA methylation changes. Although several studies have focused on the effects of short-term DEP exposure on gene expression, research on the transcriptional effects and genome-wide DNA methylation changes caused by long-term DEP exposure is lacking. Hence, in this study, we investigated transcriptional and DNA methylation changes in human adenocarcinoma alveolar basal epithelial A549 cells caused by prolonged exposure to DEP and determined whether these changes are concordant.

RESULTS

DNA methylation analysis using the Illumina Infinium MethylationEPIC BeadChips showed that the methylation levels of DEP-affected CpG sites in A549 cells changed in a dose-dependent manner; the extent of change increased with increasing dose reaching the statistical significance only in samples exposed to 30 µg/ml DEP. Four-week exposure to 30 µg/ml of DEP significantly induced DNA hypomethylation at 24,464 CpG sites, which were significantly enriched for DNase hypersensitive sites, genomic regions marked by H3K4me1 and H3K27ac, and several transcription factor binding sites. In contrast, 9,436 CpG sites with increased DNA methylation levels were significantly overrepresented in genomic regions marked by H3K27me3 as well as H3K4me1 and H3K27ac. In parallel, gene expression profiling by RNA sequencing demonstrated that long-term exposure to DEP altered the expression levels of 2,410 genes, enriching 16 gene sets including Xenobiotic metabolism, Inflammatory response, and Senescence. In silico analysis revealed that the expression levels of 854 genes correlated with the methylation levels of the DEP-affected cis-CpG sites.

CONCLUSIONS

To our knowledge, this is the first report of genome-wide transcriptional and DNA methylation changes and their associations in A549 cells following long-term exposure to DEP.

Using the sympathetic system, beta blockers and alpha-2 agonists, to address acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) manifests as an acute inflammatory lung injury characterized by persistent hypoxemia, featuring a swift onset, high mortality, and predominantly supportive care as the current therapeutic approach, while effective treatments remain an area of active investigation. Adrenergic receptors (AR) play a pivotal role as stress hormone receptors, extensively participating in various inflammatory processes by initiating downstream signaling pathways. Advancements in molecular biology and pharmacology continually unveil the physiological significance of distinct AR subtypes. Interventions targeting these subtypes have the potential to induce specific alterations in cellular and organismal functions, presenting a promising avenue as a therapeutic target for managing ARDS. This article elucidates the pathogenesis of ARDS and the basic structure and function of AR. It also explores the relationship between AR and ARDS from the perspective of different AR subtypes, aiming to provide new insights for the improvement of ARDS.

Aprotinin (I): Understanding the Role of Host Proteases in COVID-19 and the Importance of Pharmacologically Regulating Their Function

Proteases are produced and released in the mucosal cells of the respiratory tract and have important physiological functions, for example, maintaining airway humidification to allow proper gas exchange. The infectious mechanism of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), takes advantage of host proteases in two ways: to change the spatial conformation of the spike (S) protein via endoproteolysis (e.g., transmembrane serine protease type 2 (TMPRSS2)) and as a target to anchor to epithelial cells (e.g., angiotensin-converting enzyme 2 (ACE2)). This infectious process leads to an imbalance in the mucosa between the release and action of proteases versus regulation by anti-proteases, which contributes to the exacerbation of the inflammatory and prothrombotic response in COVID-19. In this article, we describe the most important proteases that are affected in COVID-19, and how their overactivation affects the three main physiological systems in which they participate: the complement system and the kinin-kallikrein system (KKS), which both form part of the contact system of innate immunity, and the renin-angiotensin-aldosterone system (RAAS). We aim to elucidate the pathophysiological bases of COVID-19 in the context of the imbalance between the action of proteases and anti-proteases to understand the mechanism of aprotinin action (a panprotease inhibitor). In a second-part review, titled "Aprotinin (II): Inhalational Administration for the Treatment of COVID-19 and Other Viral Conditions", we explain in depth the pharmacodynamics, pharmacokinetics, toxicity, and use of aprotinin as an antiviral drug.

Superoxide dismutase 1-modified dental pulp stem cells alleviate high-altitude pulmonary edema by inhibiting oxidative stress through the Nrf2/HO-1 pathway

High-altitude pulmonary edema (HAPE) is a deadly form of altitude sickness, and there is no effective treatment for HAPE. Dental pulp stem cells (DPSCs) are a type of mesenchymal stem cell isolated from dental pulp tissues and possess various functions, such as anti-inflammatory and anti-oxidative stress. DPSCs have been used to treat a variety of diseases, but there are no studies on treating HAPE. In this study, Sprague-Dawley rats were exposed to acute low-pressure hypoxia to establish the HAPE model, and SOD1-modified DPSCs (DPSCsHiSOD1) were administered through the tail vein. Pulmonary arterial pressure, lung water content (LWC), total lung protein content of bronchoalveolar lavage fluid (BALF) and lung homogenates, oxidative stress, and inflammatory indicators were detected to evaluate the effects of DPSCsHiSOD1 on HAPE. Rat type II alveolar epithelial cells (RLE-6TN) were used to investigate the effects and mechanism of DPSCsHiSOD1 on hypoxia injury. We found that DPSCs could treat HAPE, and the effect was better than that of dexamethasone treatment. SOD1 modification could enhance the function of DPSCs in improving the structure of lung tissue, decreasing pulmonary arterial pressure and LWC, and reducing the total lung protein content of BALF and lung homogenates, through anti-oxidative stress and anti-inflammatory effects. Furthermore, we found that DPSCsHiSOD1 could protect RLE-6TN from hypoxic injury by reducing the accumulation of reactive oxygen species (ROS) and activating the Nrf2/HO-1 pathway. Our findings confirm that SOD1 modification could enhance the anti-oxidative stress ability of DPSCs through the Nrf2/HO-1 signalling pathway. DPSCs, especially DPSCsHiSOD1, could be a potential treatment for HAPE. Schematic diagram of the antioxidant stress mechanism of DPSCs in the treatment of high-altitude pulmonary edema. DPSCs can alleviate oxidative stress by releasing superoxide dismutase 1, thereby reducing ROS production and activating the Nrf2/HO-1 signalling pathway to ameliorate lung cell injury in HAPE.

Cell Cross-Talk in Alveolar Microenvironment: From Lung Injury to Fibrosis

Alveoli are complex microenvironments composed of various cell types, including epithelial, fibroblast, endothelial, and immune cells, which work together to maintain a delicate balance in the lung environment, ensuring proper growth, development, and an effective response to lung injuries. However, prolonged inflammation or aging can disrupt normal interactions among these cells, leading to impaired repair processes and a substantial decline in lung function. Therefore, it is essential to understand the key mechanisms underlying the interactions among the major cell types within the alveolar microenvironment. We explored the key mechanisms underlying the interactions among the major cell types within the alveolar microenvironment. These interactions occur through the secretion of signaling factors and play crucial roles in the response to injury, repair mechanisms, and the development of fibrosis in the lungs. Specifically, we focused on the regulation of alveolar type 2 cells by fibroblasts, endothelial cells, and macrophages. In addition, we explored the diverse phenotypes of fibroblasts at different stages of life and in response to lung injury, highlighting their impact on matrix production and immune functions. Furthermore, we summarize the various phenotypes of macrophages in lung injury and fibrosis as well as their intricate interplay with other cell types. This interplay can either contribute to the restoration of immune homeostasis in the alveoli or impede the repair process. Through a comprehensive exploration of these cell interactions, we aim to reveal new insights into the molecular mechanisms that drive lung injury toward fibrosis and identify potential targets for therapeutic intervention.

Insights into the mechanism of action of pterostilbene against influenza A virus-induced acute lung injury

BACKGROUND

Severe respiratory system illness caused by influenza A virus infection is associated with excessive inflammation and abnormal apoptosis in alveolar epithelial cells (AEC). However, there are limited therapeutic options for influenza-associated lung inflammation and apoptosis. Pterostilbene (PTE, trans-3,5-dimethoxy-4-hydroxystilbene) is a dimethylated analog of resveratrol that has been reported to limit influenza A virus infection by promoting antiviral innate immunity, but has not been studied for its protective effects on virus-associated inflammation and injury in AEC.

PURPOSE

Our study aimed to investigate the protective effects and underlying mechanisms of PTE in modulating inflammation and apoptosis in AEC, as well as its effects on macrophage polarization during influenza virus infection.

STUDY DESIGN AND METHODS

A murine model of influenza A virus-mediated acute lung injury was established by intranasal inoculation with 5LD50 of mouse-adapted H1N1 viruses. Hematoxylin and eosin staining, immunofluorescence, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, western blotting, Luminex and flow cytometry were performed.

RESULTS

PTE effectively mitigated lung histopathological changes and injury induced by H1N1 viruses in vivo. These beneficial effects of PTE were attributed to the suppression of inflammation and apoptosis in AEC, as well as the modulation of M1 macrophage polarization. Mechanistic investigations revealed that PTE activated the phosphorylated AMP-activated protein kinase alpha (P-AMPKα)/sirtui1 (Sirt1)/PPARγ coactivator 1-alpha (PGC1α) signal axis, leading to the inhibition of nuclear factor kappa-B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) signaling induced by H1N1 viruses, thereby attenuating inflammation and apoptosis in AEC. PTE also forced activation of the P-AMPKα/Sirt1/PGC1α signal axis in RAW264.7 cells, counteracting the activation of phosphorylated signal transducer and activator of transcription 1 (P-STAT1) induced by H1N1 viruses and the augment of P-STAT1 activation in RAW264.7 cells with interferon-gamma (IFN-γ) pretreatment before viral infection, thereby reducing H1N1 virus-mediated M1 macrophage polarization as well as the enhancement of macrophages into M1 phenotypes elicited by IFN-γ pretreatment. Additionally, the promotion of the transition of macrophages towards the M2 phenotype by PTE was also related to activation of the P-AMPKα/Sirt1/PGC1α signal axis. Moreover, co-culturing non-infected AEC with H1N1 virus-infected RAW264.7 cells in the presence of PTE inhibited apoptosis and tight junction disruption, which was attributed to the suppression of pro-inflammatory mediators and pro-apoptotic factors in an AMPKα-dependent manner.

CONCLUSION

In conclusion, our findings suggest that PTE may serve as a promising novel therapeutic option for treating influenza-associated lung injury. Its ability to suppress inflammation and apoptosis in AEC, modulate macrophage polarization, and preserve alveolar epithelial cell integrity highlights its potential as a therapeutic agent in influenza diseases.