Alveolar Epithelial Injury Research Articles

Aberrant activation of wound healing programs within the metastatic niche facilitates lung colonization by osteosarcoma cells.

Lung metastasis is responsible for most deaths caused by osteosarcoma. How malignant bone cells coerce the lung microenvironment to support metastatic growth remains unclear. We sought to identify metastasis-specific therapeutic vulnerabilities by delineating the cellular and molecular mechanisms essential to metastatic niche formation in the lung. We used single-cell transcriptomics (scRNA-seq) to characterize molecular changes induced within lung tissues by disseminated osteosarcoma cells. We then evaluated the ability of nintedanib to reverse metastasis-specific changes in both immunocompetent mouse and immunodeficient xenograft models. Molecular pharmacodynamic studies used single-nucleus and spatial transcriptomics to define the tumor-intrinsic and -extrinsic changes induced by the drug. Osteosarcoma cells induced acute alveolar epithelial injury upon lung dissemination. scRNA-seq demonstrated that the surrounding lung stroma adopts a chronic, non-resolving wound-healing phenotype similar to diseases associated with lung injury. Accordingly, metastasis-associated lung demonstrated marked fibrosis, likely due to the accumulation of pathogenic, pro-fibrotic, partially differentiated epithelial intermediates and macrophages. Our data suggested that nintedanib prevented metastatic progression in multiple murine and human xenograft models by inhibiting osteosarcoma-induced fibrosis. Fibrosis is essential to osteosarcoma lung metastasis and represents a targetable vulnerability. Our data support a model where interactions between osteosarcoma and epithelial cells induce the deposition of extracellular matrix proteins-a reaction disrupted by the anti-fibrotic TKI nintedanib. Our data shed light on the non-cell autonomous effects of TKIs on metastasis and provide a roadmap for using single-cell and spatial transcriptomics to define the mechanism of action of TKIs on metastases in animal models.

Astragaloside IV Inhibits Lung Injury and Fibrosis Induced by PM2.5 by Targeting RUNX1 Through miR-362-3p.

To discover the molecular mechanism of Astragaloside IV (AS IV) in PM2.5-induced lung injury and pulmonary fibrosis (PF). A lung injury rat model was induced by PM2.5 and injected intraperitoneally with AS IV. Lungs were harvested to evaluate lung tissue injury and apoptosis. Rat alveolar epithelial cells L2 were exposed to PM2.5 and treated with AS IV. After cellular transfection, cell proliferation, LDH production, and apoptosis were measured. In both models, inflammatory factors and fibrotic indices were measured by ELISA and Western blot. miR-362-3p and RUNX1 interplay was explored and confirmed. Administration of AS IV attenuated PM2.5-induced lung tissue injury, inflammation, apoptosis, and PF in rats. AS IV enhanced proliferation and reduced LDH release, apoptosis, inflammation, and PF in PM2.5-treated L2 cells. MiR-362-3p upregulation improved PM2.5-induced L2 cell injury. AS IV improved PM2.5-induced lung injury by upregulating miR-362-3p. miR-362-3p had an inhibition effect on RUNX1 expression. RUNX1 upregulation weakened the therapeutic effect of AS IV on PM2.5-induced alveolar epithelial cell injury. AS IV inhibits lung injury and PF induced by PM2.5 by targeting RUNX1 through upregulation of miR-362-3p.

TRIM13 Reduces Damage to Alveolar Epithelial Cells in COPD by Inhibiting Endoplasmic Reticulum Stress-Induced ER-Phagy

PurposeTripartite motif-containing protein 13 (TRIM13) directly or indirectly participates in autophagy and apoptosis. However, it remains unclear whether TRIM13 participates in chronic obstructive pulmonary disease (COPD) progression. This study aimed to reveal the molecular mechanisms through which TRIM13 regulates alveolar epithelial cell injury in COPD to provide new molecular targets for COPD treatment.MethodsThe TRIM13 expression levels were determined in clinical COPD patients and a rat emphysema model. A cigarette smoke-induced model of endoplasmic reticulum stress (ERS) and endoplasmic reticulum autophagy (ER-phagy) was developed using A549 cells, and the effects of TRIM13 gene overexpression/knockdown on ERS, ER-phagy, and cell apoptosis were assessed in these cells.ResultsTRIM13 expression was significantly decreased in the lung tissues of COPD patients and rats with emphysema. Moreover, the apoptosis level was significantly increased in the lung tissues of rats with emphysema. TRIM13 gene overexpression reduced the expression levels of ERS-related molecules (GRP78, GRP94, XBP-1, and eIF2a) in the COPD model; it also lowered the ER-phagy level, as evidenced by decreased number of autolysosomes observed by transmission electron microscopy, improved endoplasmic reticulum structure, reduced LC3-II/LC3-I and Beclin1 expression levels, and increased expression level of the autophagy inhibitory molecule Bcl-2. TRIM13 gene knockdown, however, led to opposite results.ConclusionTRIM13 expression attenuated alveolar epithelial cell injury in COPD by inhibiting ERS-induced ER-phagy.

Cinnamaldehyde Alleviates Alveolar Epithelial Cell Injury in ALI by Inhibiting the CaMKII Pathway.

Alveolar epithelial cell injury plays a key role in acute lung injury (ALI) and is a vital determinant of its severity. Here, we aimed to assess the protective effects of cinnamaldehyde (CA) on lipopolysaccharide (LPS)-induced A549 cells and elucidate the underlying mechanisms. A549 cells were stimulated with 1 μg/mL LPS for 24 h to establish an alveolar epithelial cell injury model and subsequently treated with CA or Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN93. Flow cytometry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, and lactate dehydrogenase release assays were used to evaluate apoptosis, cell viability, and lactate dehydrogenase activity, respectively. Levels of inflammatory cytokines (interleukin-6, interleukin-1β, tumor necrosis tactor-α, and interferon-γ) and oxidative stress markers (reactive oxygen species, superoxide dismutase, catalase, and malondialdehyde) were determined using enzyme-linked immunosorbent assay and specific assay kits, respectively. Furthermore, levels of apoptosis-related proteins (cleaved caspase-3, Bcl-2-associated X, and Bcl-2) and CaMKII were assessed via western blotting. CA did not exhibit significant cytotoxicity in A549 cells. It dose-dependently improved the cell viability, suppressed apoptosis, decreased cleaved caspase-3 and Bcl-2-associated X levels, and increased Bcl-2 levels in LPS-treated A549 cells. It also inhibited inflammatory factor release and oxidative stress in LPS-induced A549 cells. Similar results were observed in the KN93- and CA-treated groups. Western blotting assay revealed that CA and KN93 inhibited CaMKII pathway activation, as indicated by the reduced p-CaMKII and p-phospholamban (PLN) levels and p-CaMKII/CaMKII and p-PLN/PLN ratios. Overall, CA alleviated alveolar epithelial cell injury by inhibiting the inflammatory response and oxidative stress and inducing cell apoptosis in LPS-induced A549 cells by regulating the CaMKII pathway, serving as a potential candidate for ALI prevention and treatment.

Aberrant activation of wound healing programs within the metastatic niche facilitates lung colonization by osteosarcoma cells.

Lung metastasis is responsible for nearly all deaths caused by osteosarcoma, the most common pediatric bone tumor. How malignant bone cells coerce the lung microenvironment to support metastatic growth is unclear. The purpose of this study is to identify metastasis-specific therapeutic vulnerabilities by delineating the cellular and molecular mechanisms underlying osteosarcoma lung metastatic niche formation. Using single-cell transcriptomics (scRNA-seq), we characterized genome- and tissue-wide molecular changes induced within lung tissues by disseminated osteosarcoma cells in both immunocompetent murine models of metastasis and patient samples. We confirmed transcriptomic findings at the protein level and determined spatial relationships with multi-parameter immunofluorescence and spatial transcriptomics. Based on these findings, we evaluated the ability of nintedanib, a kinase inhibitor used to treat patients with pulmonary fibrosis, to impair metastasis progression in both immunocompetent murine osteosarcoma and immunodeficient human xenograft models. Single-nucleus and spatial transcriptomics was used to perform molecular pharmacodynamic studies that define the effects of nintedanib on tumor and non-tumor cells within the metastatic microenvironment. Osteosarcoma cells induced acute alveolar epithelial injury upon lung dissemination. scRNA-seq demonstrated that the surrounding lung stroma adopts a chronic, non-resolving wound-healing phenotype similar to that seen in other models of lung injury. Accordingly, metastasis-associated lung demonstrated marked fibrosis, likely due to the accumulation of pathogenic, pro-fibrotic, partially differentiated epithelial intermediates and macrophages. Our data demonstrated that nintedanib prevented metastatic progression in multiple murine and human xenograft models by inhibiting osteosarcoma-induced fibrosis. Fibrosis represents a targetable vulnerability to block the progression of osteosarcoma lung metastasis. Our data support a model wherein interactions between osteosarcoma cells and epithelial cells create a pro-metastatic niche by inducing tumor deposition of extracellular matrix proteins such as fibronectin that is disrupted by the anti-fibrotic TKI nintedanib. Our data shed light on the non-cell autonomous effects of TKIs on metastasis and provide a roadmap for using single-cell and spatial transcriptomics to define the mechanism of action of TKI on metastases in animal models.

Sodium Houttuyniae attenuates ferroptosis by regulating TRAF6-c-Myc signaling pathways in lipopolysaccharide-induced acute lung injury (ALI)

The impact of Sodium Houttuyniae (SH) on lipopolysaccharide (LPS)-induced ALI has been investigated extensively. However, it remains ambiguous whether ferroptosis participates in this process. This study aimed to find out the impacts and probable mechanisms of SH on LPS-induced ferroptosis. A rat ALI model and type II alveolar epithelial (ATII) cell injury model were treated with LPS. Enzyme-linked immunosorbent assay (ELISA), hematoxylin-eosin (HE) staining, and Giemsa staining were executed to ascertain the effects of SH on LPS-induced ALI. Moreover, Transmission electron microscopy, Cell Counting Kit-8 (CCK8), ferrous iron colorimetric assay kit, Immunohistochemistry, Immunofluorescence, Reactive oxygen species assay kit, western blotting (Wb), and qRT-PCR examined the impacts of SH on LPS-induced ferroptosis and ferroptosis-related pathways. Theresults found that by using SH treatment, there was a remarkable attenuation of ALI by suppressing LPS-induced ferroptosis. Ferroptosis was demonstrated by a decline in the levels of glutathione peroxidase 4 (GPX4), FTH1, and glutathione (GSH) and a surge in the accumulation of malondialdehyde (MDA), reactive oxygen species (ROS), NOX1, NCOA4, and Fe2+, and disruption of mitochondrial structure, which were reversed by SH treatment. SH suppressed ferroptosis by regulating TRAF6-c-Myc in ALI rats and rat ATII cells. The results suggested that SH treatment attenuated LPS-induced ALI by repressing ferroptosis, and the mode of action can be linked to regulating the TRAF6-c-Myc signaling pathway in vivo and in vitro.

Association of Acute Systemic Inflammation with Patient-Centric Postoperative Pulmonary Complications After Elective Cardiac Surgery.

Postoperative pulmonary complications (PPCs) occur frequently after cardiac surgery. Absolute postoperative values of biomarkers of inflammation (interleukin [IL]-6, IL-8, and tumor necrosis factor-alpha [TNF-α]) and alveolar epithelial injury (soluble receptor for advanced glycation end-products [sRAGE]) have been associated with hypoxia and prolonged ventilation. However, relationships between these biomarkers and PPCs, contextualized to preoperative inflammation and perioperative lung injury risk factors, are uncertain. We aimed to determine associations between perioperative increases in biomarkers of inflammation and alveolar epithelial injury with a patient-centric PPC definition in adult cardiac surgical patients, accounting for the influence of intraoperative risk factors for lung injury. Adults undergoing elective cardiac surgery were eligible for this observational cohort study. Blood concentrations of IL-6, IL-8, TNF-α, and sRAGE were collected after anesthesia induction (baseline) and on postoperative day 1 (POD 1). The primary outcome was the occurrence of moderate or severe PPCs, graded using a validated scale, in POD 0 to 7. We estimated the association between POD 1 IL-6, IL-8, TNF-α, and sRAGE concentrations and moderate/severe PPC presence using separate logistic regression models for each biomarker, adjusted for baseline biomarker values and risk factors for postoperative lung injury (age, baseline PaO2/FiO2, left ventricle ejection fraction [LVEF], procedural type, cardiopulmonary bypass duration, and transfusions). Covariables were chosen based on relevance to lung injury and unadjusted between-group differences among patients with versus without PPCs. The secondary outcome was postoperative ventilation duration, which was log-transformed and analyzed using linear regression, adjusted using the same variables as the primary outcome. We enrolled 204 patients from 2016 to 2018. Biomarkers were analyzed in 2023 among 175 patients with complete data. In adjusted analyses, POD 1 IL-8 and IL-6 were significantly associated with moderate/severe PPCs. The odds ratio (OR) for developing a PPC for every 50 pg/mL increase in POD 1 IL-8 was 7.19 (95% confidence interval [CI], 2.13-28.53, P = .003) and 1.42 (95% CI, 1.13-1.93, P = .01) for every 50 pg/mL increase in POD 1 IL-6. In adjusted analyses, postoperative ventilation duration was significantly associated with POD 1 sRAGE; each 50 pg/mL increase in sRAGE was associated with a 25% (95% CI, 2%-52%, P = .03) multiplicative increase in hours of ventilation. TNF-α was not significantly associated with PPCs or ventilation duration. Acute systemic inflammation is significantly associated with PPCs after elective cardiac surgery in adults when taking into consideration preoperative inflammatory burden and perioperative factors that may influence postoperative lung injury.

Identification of non-coding RNA signatures in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a deadly, chronic, progressive, irreversible interstitial lung disease characterized by the formation of scar tissue resulting in permanent lung damage. The average survival time following diagnosis is only 3-5years, with a 5-year survival rate shorter than that of many cancers. Alveolar epithelial cell injury followed by irregular repair is the primary pathological process observed in patients with IPF. An evident characteristic of IPF is the development of fibroblastic foci representing active fibrotic areas. Most of the cells within these foci are believed to be myofibroblasts, which are thought to be the primary source of abnormal extracellular matrix production in IPF. The lung phenotype in IPF is characterized by significantly different processes from healthy lungs, including irregular apoptosis, oxidative stress, and epithelial-mesenchymal transition (EMT) pathways. The exact cause of IPF is not fully understood and remains mysterious. It is not suppressing that non-coding RNAs are involved in the development and progression of IPF. Accordingly, here we aimed to identify non-coding RNA molecules during TGFβ-induced myofibroblast activation. Differential expression and functional enrichment analysis were employed to reveal the impact of non-coding RNAs during TGFβ-associated lung fibrosis. Remarkably, LOC101448202, CZ1P-ASNS, LINC01503, IER3-AS1, MIR503HG, CLMAT3, LINC02593, ACTA2-AS1, LOC102723692, LOC107985728, and LOC105371064 were identified to be differentially altered during TGFβ-stimulated myofibroblast activation. These findings strongly suggest that the mechanism of lung fibrosis is heavily under control of non-coding RNAs, and RNA-based therapies could be a promising approach for future therapeutic interventions to lung fibrosis.

Early inflammatory profiles predict maximal disease severity in COVID-19: An unsupervised cluster analysis

BackgroundThe inflammatory changes that underlie the heterogeneous presentations of COVID-19 remain incompletely understood. In this study we aimed to identify inflammatory profiles that precede the development of severe COVID-19, that could serve as targets for optimised delivery of immunomodulatory therapies and provide insights for the development of new therapies. MethodsWe included individuals sampled <10 days from COVID-19 symptom onset, recruited from both inpatient and outpatient settings. We measured 61 biomarkers in plasma, including markers of innate immune and T cell activation, coagulation, tissue repair and lung injury. We used principal component analysis and hierarchical clustering to derive biomarker clusters, and ordinal logistic regression to explore associations between cluster membership and maximal disease severity, adjusting for known risk factors for severe COVID-19. ResultsIn 312 individuals, median (IQR) 7 (4–9) days from symptom onset, we found four clusters. Cluster 1 was characterised by low overall inflammation, cluster 2 was characterised by higher levels of growth factors and markers of endothelial activation (EGF, VEGF, PDGF, TGFα, PAI-1 and p-selectin). Cluster 3 and 4 both had higher overall inflammation. Cluster 4 had the highest levels of most markers including markers of innate immune activation (IL6, procalcitonin, CRP, TNFα), and coagulation (D-dimer, TPO), in contrast cluster 3 had the highest levels of alveolar epithelial injury markers (RAGE, ST2), but relative downregulation of growth factors and endothelial activation markers, suggesting a dysfunctional inflammatory pattern. In unadjusted and adjusted analysis, compared to cluster 1, cluster 3 had the highest odds of progressing to more severe disease (unadjusted OR (95%CI) 9.02 (4.53–17.96), adjusted OR (95%CI) 6.02 (2.70–13.39)). ConclusionEarly inflammatory profiles predicted subsequent maximal disease severity independent of risk factors for severe COVID-19. A cluster with downregulation of growth factors and endothelial activation markers, and early evidence of alveolar epithelial injury, had the highest risk of severe COVID-19.

Interference with Histone Deacetylase 4 Regulates c-Jun N-terminal Kinase/Activating Protein-1 Signaling to Ameliorate Sepsis-induced Alveolar Epithelial Cell Injury.

Sepsis is a syndrome of systemic inflammatory response resulting from infection, which can lead to severe lung injury. Histone deacetylase 4 (HDAC4) is a key protein known to regulate a wide range of cellular processes. This study was designed to investigate the role of HDAC4 in lipopolysaccharide (LPS)-induced alveolar epithelial cell injury as well as to disclose its potential molecular mechanisms. The alveolar epithelial cell injury model was established by inducing A549 cells with LPS. A549 cell viability was detected by cell counting kit-8 assay and the transfection efficiency of small interfering RNA targeting HDAC4 was appraised utilizing Western blot. The levels of inflammatory cytokines and oxidative stress markers were detected using corresponding assay kits. Dichloro-dihydro-fluorescein diacetate assay was used for the measurement of reactive oxygen species (ROS) content. Flow cytometry, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl-carbocyanine iodide-1 staining, adenosine triphosphate (ATP) assay kits, and MitoSOX Red assay kits were employed to estimate cell apoptosis, mitochondrial membrane potential, ATP level, and mitochondrial ROS level, respectively. The oxygen consumption rate of A549 cells was evaluated with XF96 extracellular flux analyzer. Western blot was applied for the evaluation of HDAC4, apoptosis- and c-Jun N-terminal kinase (JNK)/activating protein-1 (AP-1) signaling pathway-related proteins. HDAC4 expression was found to be increased in LPS-induced A549 cells and HDAC4 silence inhibited inflammatory damage, repressed oxidative stress, alleviated cell apoptosis, improved mitochondrial function, and blocked JNK/AP-1 signaling in A549 cells stimulated by LPS, which were all reversed by JNK activator anisomycin. Collectively, the interference with HDAC4 could ameliorate LPS-induced alveolar epithelial cell injury, and such protective effect may be potentially mediated through the JNK/AP-1 signaling pathway.

Role and mechanism of ginsenoside Rg1 in ameliorating sepsis-induced acute lung injury based on PERK/eIF2α/ATF4/CHOP-induced alveolar epithelial cell apoptosis

The study investigates the therapeutic effects and mechanisms of ginsenoside Rg_1(GRg_1) on sepsis-induced acute lung injury(SALI). A murine model of SALI was created using cecal ligation and puncture(CLP) surgery, and mice were randomly assigned to groups for GRg_1 intervention. Survival and body weight changes were recorded, lung function was assessed with a non-invasive lung function test system, and lung tissue damage was evaluated through HE staining. The content and expression of inflammatory factors were measured by ELISA and qRT-PCR. Apoptosis was examined using flow cytometry and TUNEL staining. The activation and expression of apoptosis-related molecules cysteinyl aspartate specific proteinase 3(caspase-3), B-cell lymphoma-2(Bcl-2), Bcl-2 associated X protein(Bax), and endoplasmic reticulum stress-related molecules protein kinase R-like endoplasmic reticulum kinase(PERK), eukaryotic initiation factor 2α(eIF2α), activating transcription factor 4(ATF4), and C/EBP homologous protein(CHOP) were studied using Western blot and qRT-PCR. In addition, an in vitro model of lipopolysaccharide(LPS)-induced lung alveolar epithelial cell injury was used, with the application of the endoplasmic reticulum stress inducer tunicamycin to validate the action mechanism of GRg_1. RESULTS:: indicated that, when compared to the model group, GRg_1 intervention significantly enhanced the survival time of CLP mice, mitigated body weight loss, and improved impaired lung function indices. The GRg_1-treated mice also displayed reduced lung tissue pathological scores, a reduced lung tissue wet-to-dry weight ratio, and lower protein content in the bronchoalveolar lavage fluid. Serum levels of interleukin-6(IL-6), interleukin-1β(IL-1β), and tumor necrosis factor-α(TNF-α), as well as the mRNA expressions of these cytokines in lung tissues, were decreased. There was a notable decrease in the proportion of apopto-tic alveolar epithelial cells, and down-regulated expressions of caspase-3, Bax, PERK, eIF2α, ATF4, and CHOP and up-regulated expression of Bcl-2 were observed. In vitro findings showed that the apoptosis-lowering and apoptosis-related protein down-regulating effects of GRg_1 were significantly inhibited with the co-application of tunicamycin. Altogether, GRg_1 reduces apoptosis of alveolar epithelial cells, inhibits inflammation in the lungs, alleviates lung injury, and enhances lung function, possibly through the PERK/eIF2α/ATF4/CHOP pathway.

Vinpocetine alleviated alveolar epithelial cells injury in experimental pulmonary fibrosis by targeting PPAR-γ/NLRP3/NF-κB and TGF-β1/Smad2/3 pathways

This study aimed to investigate the potential anti-fibrotic activity of vinpocetine in an experimental model of pulmonary fibrosis by bleomycin and in the MRC-5 cell line. Pulmonary fibrosis was induced in BALB/c mice by oropharyngeal aspiration of a single dose of bleomycin (5 mg/kg). The remaining induced animals received a daily dose of pirfenidone (as a standard anti-fibrotic drug) (300 mg/kg/PO) and vinpocetine (20 mg/kg/PO) on day 7 of the induction till the end of the experiment (day 21). The results of the experiment revealed that vinpocetine managed to alleviate the fibrotic endpoints by statistically improving (P ≤ 0.05) the weight index, histopathological score, reduced expression of fibrotic-related proteins in immune-stained lung sections, as well as fibrotic markers measured in serum samples. It also alleviated tissue levels of oxidative stress and inflammatory and pro-fibrotic mediators significantly elevated in bleomycin-only induced animals (P ≤ 0.05). Vinpocetine managed to express a remarkable attenuating effect in pulmonary fibrosis both in vivo and in vitro either directly by interfering with the classical TGF-β1/Smad2/3 signaling pathway or indirectly by upregulating the expression of Nrf2 enhancing the antioxidant system, activating PPAR-γ and downregulating the NLRP3/NF-κB pathway making it a candidate for further clinical investigation in cases of pulmonary fibrosis.

MiR-21-5p modulates LPS-induced acute injury in alveolar epithelial cells by targeting SLC16A10

Sepsis is a systemic inflammatory response syndrome resulting from the invasion of the human body by bacteria and other pathogenic microorganisms. One of its most prevalent complications is acute lung injury, which places a significant medical burden on numerous countries and regions due to its high morbidity and mortality rates. MicroRNA (miRNA) plays a critical role in the body's inflammatory response and immune regulation. Recent studies have focused on miR-21-5p in the context of acute lung injury, but its role appears to vary in different models of this condition. In the LPS-induced acute injury model of A549 cells, there is differential expression, but the specific mechanism remains unclear. Therefore, our aim is to investigate the changes in the expression of miR-21-5p and SLC16A10 in a type II alveolar epithelial cell injury model induced by LPS and explore the therapeutic effects of their targeted regulation. A549 cells were directly stimulated with 10 µg/ml of LPS to construct a model of LPS-induced cell injury. Cells were collected at different time points and the expression of interleukin 1 beta (IL-1β), tumor necrosis factor-α (TNF-α) and miR-21-5p were measured by RT-qPCR and western blot. Then miR-21-5p mimic transfection was used to up-regulate the expression of miR-21-5p in A549 cells and the expression of IL-1β and TNF-α in each group of cells was measured by RT-qPCR and western blot. The miRDB, TargetScan, miRWalk, Starbase, Tarbase and miR Tarbase databases were used to predict the miR-21-5p target genes and simultaneously, the DisGeNet database was used to search the sepsis-related gene groups. The intersection of the two groups was taken as the core gene. Luciferase reporter assay further verified SLC16A10 as the core gene with miR-21-5p. The expression of miR-21-5p and SLC16A10 were regulated by transfection or inhibitors in A549 cells with or without LPS stimulation. And then the expression of IL-1β and TNF-α in A549 cells was tested by RT-qPCR and western blot in different groups, clarifying the role of miR-21-5p-SLC16A10 axis in LPS-induced inflammatory injury in A549 cells. (1) IL-1β and TNF-α mRNA and protein expression significantly increased at 6, 12, and 24 h after LPS stimulation as well as the miR-21-5p expression compared with the control group (P < 0.05). (2) After overexpression of miR-21-5p in A549 cells, the expression of IL-1β and TNF-α was significantly reduced after LPS stimulation, suggesting that miR-21-5p has a protection against LPS-induced injury. (3) The core gene set, comprising 51 target genes of miR-21-5p intersecting with the 1448 sepsis-related genes, was identified. This set includes SLC16A10, TNPO1, STAT3, PIK3R1, and FASLG. Following a literature review, SLC16A10 was selected as the ultimate target gene. Dual luciferase assay results confirmed that SLC16A10 is indeed a target gene of miR-21-5p. (4) Knocking down SLC16A10 expression by siRNA significantly reduced the expression of IL-1β and TNF-α in A549 cells after LPS treatment (P < 0.05). (5) miR-21-5p inhibitor increased the expression levels of IL-1β and TNF-α in A549 cells after LPS stimulation (P < 0.05). In comparison to cells solely transfected with miR-21-5p inhibitor, co-transfection of miR-21-5p inhibitor and si-SLC6A10 significantly reduced the expression of IL-1β and TNF-α (P < 0.05). MiR-21-5p plays a protective role in LPS-induced acute inflammatory injury of A549 cells. By targeting SLC16A10, it effectively mitigates the inflammatory response in A549 cells induced by LPS. Furthermore, SLC16A10 holds promise as a potential target for the treatment of acute lung injury.

Inflammatory and tissue injury marker dynamics in pediatric acute respiratory distress syndrome.

BACKGROUNDThe molecular signature of pediatric acute respiratory distress syndrome (ARDS) is poorly described, and the degree to which hyperinflammation or specific tissue injury contributes to outcomes is unknown. Therefore, we profiled inflammation and tissue injury dynamics over the first 7 days of ARDS, and associated specific biomarkers with mortality, persistent ARDS, and persistent multiple organ dysfunction syndrome (MODS).METHODSIn a single-center prospective cohort of intubated pediatric patients with ARDS, we collected plasma on days 0, 3, and 7. Nineteen biomarkers reflecting inflammation, tissue injury, and damage-associated molecular patterns (DAMPs) were measured. We assessed the relationship between biomarkers and trajectories with mortality, persistent ARDS, or persistent MODS using multivariable mixed effect models.RESULTSIn 279 patients (64 [23%] nonsurvivors), hyperinflammatory cytokines, tissue injury markers, and DAMPs were higher in nonsurvivors. Survivors and nonsurvivors showed different biomarker trajectories. IL-1α, soluble tumor necrosis factor receptor 1, angiopoietin 2 (ANG2), and surfactant protein D increased in nonsurvivors, while DAMPs remained persistently elevated. ANG2 and procollagen type III N-terminal peptide were associated with persistent ARDS, whereas multiple cytokines, tissue injury markers, and DAMPs were associated with persistent MODS. Corticosteroid use did not impact the association of biomarker levels or trajectory with mortality.CONCLUSIONSPediatric ARDS survivors and nonsurvivors had distinct biomarker trajectories, with cytokines, endothelial and alveolar epithelial injury, and DAMPs elevated in nonsurvivors. Mortality markers overlapped with markers associated with persistent MODS, rather than persistent ARDS.FUNDINGNIH (K23HL-136688, R01-HL148054).

Serum VEGF-A levels on admission in COVID-19 patients correlate with SP-D and neutrophils, reflecting disease severity: A prospective study

Background and objectiveThe coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in significant global morbidity and mortality. This study aimed to investigate the clinical significance of serum vascular endothelial growth factor A (VEGF-A) in COVID-19 patients and its association with disease severity and pulmonary injury. MethodsWe prospectively collected data from 71 hospitalized COVID-19 patients between June 2020 and January 2021. Patients were classified as either mild or severe based on their oxygen requirements during hospitalization. Serum VEGF-A levels were measured using an ELISA kit. ResultsIn comparison to mild cases, significantly elevated serum VEGF-A levels were observed in severe COVID-19 patients. Furthermore, VEGF-A levels exhibited a positive correlation with white blood cell count, neutrophil count, and lymphocyte count. Notably, serum surfactant protein-D (SP-D), an indicator of alveolar epithelial cell damage, was significantly higher in patients with elevated VEGF-A levels. ConclusionThese results suggest that elevated serum VEGF-A levels could serve as a prognostic biomarker for COVID-19 as it is indicative of alveolar epithelial cell injury caused by SARS-CoV-2 infection. Additionally, we observed a correlation between VEGF-A and neutrophil activation, which plays a role in the immune response during endothelial cell injury, indicating a potential involvement of angiogenesis in disease progression. Further research is needed to elucidate the underlying mechanisms of VEGF-A elevation in COVID-19.

IRF4-mediated Treg phenotype switching can aggravate hyperoxia-induced alveolar epithelial cell injury

Bronchopulmonary dysplasia (BPD) is characterized by alveolar dysplasia, and evidence indicates that interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various inflammatory lung diseases. Nonetheless, the significance and mechanism of IRF4 in BPD remain unelucidated. Consequently, we established a mouse model of BPD through hyperoxia exposure, and ELISA was employed to measure interleukin-17 A (IL-17 A) and interleukin-6 (IL-6) expression levels in lung tissues. Western blotting was adopted to determine the expression of IRF4, surfactant protein C (SP-C), and podoplanin (T1α) in lung tissues. Flow cytometry was utilized for analyzing the percentages of FOXP3+ regulatory T cells (Tregs) and FOXP3+RORγt+ Tregs in CD4+ T cells in lung tissues to clarify the underlying mechanism. Our findings revealed that BPD mice exhibited disordered lung tissue structure, elevated IRF4 expression, decreased SP-C and T1α expression, increased IL-17 A and IL-6 levels, reduced proportion of FOXP3+ Tregs, and increased proportion of FOXP3+RORγt+ Tregs. For the purpose of further elucidating the effect of IRF4 on Treg phenotype switching induced by hyperoxia in lung tissues, we exposed neonatal mice with IRF4 knockout to hyperoxia. These mice exhibited regular lung tissue structure, increased proportion of FOXP3+ Tregs, reduced proportion of FOXP3+RORγt+ Tregs, elevated SP-C and T1α expression, and decreased IL-17 A and IL-6 levels. In conclusion, our findings demonstrate that IRF4-mediated Treg phenotype switching in lung tissues exacerbates alveolar epithelial cell injury under hyperoxia exposure.

Metformin alleviates benzo[a]pyrene-induced alveolar injury by inhibiting necroptosis and protecting AT2 cells

Exposure to benzo[a]pyrene (B[a]P) has been linked to lung injury and carcinogenesis. Airway epithelial cells express the B[a]P receptor AHR, so B[a]P is considered to mainly target airway epithelial cells, whereas its potential impact on alveolar cells remains inadequately explored. Metformin, a first-line drug for diabetes, has been shown to exert anti-inflammatory and tissue repair-promoting effects under various injurious conditions. Here, we explored the effect of chronic B[a]P exposure on alveolar cells and the impact of metformin on B[a]P-induced lung injury by examining the various parameters including lung histopathology, inflammation, fibrosis, and related signal pathway activation. MLKL knockout (Mlkl-/-) and AT2-lineage tracing mice (SftpcCre-ERT2;LSL-tdTomatoflox+/-) were used to delineate the role of necroptosis in B[a]P-induced alveolar epithelial injury and repair. Mice receiving weekly administration of B[a]P for 6 weeks developed a significant alveolar damaging phenotype associated with pulmonary inflammation, fibrosis, and activation of the necroptotic cell death pathway. These effects were significantly relieved in MLKL null mice. Furthermore, metformin treatment, which were found to promote AMPK phosphorylation and inhibit RIPK3, as well as MLKL phosphorylation, also significantly alleviated B[a]P-induced necroptosis and lung injury phenotype. However, the protective efficacy of metformin was rendered much less effective in Mlkl null mice or by blocking the necroptotic pathway with RIPK3 inhibitor. Our findings unravel a potential protective efficacy of metformin in mitigating the detrimental effects of B[a]P exposure on lung health by inhibiting necroptosis and protecting AT2 cells.

WSB1, a Hypoxia-Inducible E3 Ligase, Promotes Myofibroblast Accumulation and Attenuates Alveolar Epithelial Regeneration in Mouse Lung Fibrosis

Idiopathic pulmonary fibrosis is a progressive interstitial lung disease for which there is no curative therapy available. Repetitive alveolar epithelial injury repair, myofibroblast accumulation, and excessive collagen deposition are key pathologic features of idiopathic pulmonary fibrosis, eventually leading to cellular hypoxia and respiratory failure. The precise mechanism driving this complex maladaptive process remains inadequately understood. WD repeat and suppressor of cytokine signaling box containing 1 (WSB1) is an E3 ubiquitin ligase, the expression of which is associated strongly with hypoxia, and forms a positive feedback loop with hypoxia-inducible factor 1α (HIF-1α) under anoxic condition. This study explored the expression, cellular distribution, and function of WSB1 in bleomycin (BLM)-induced mouse lung injury and fibrosis. WSB1 expression was highly induced by BLM injury and correlated with the progression of lung fibrosis. Significantly, conditional deletion of Wsb1 in adult mice ameliorated BLM-induced pulmonary fibrosis. Phenotypically, Wsb1-deficient mice showed reduced lipofibroblast to myofibroblast transition, but enhanced alveolar type 2 proliferation and differentiation into alveolar type 1 after BLM injury. Proteomic analysis of mouse lung tissues identified caveolin 2 as a potential downstream target of WSB1, contributing to BLM-induced epithelial injury repair and fibrosis. These findings unravel a vital role for WSB1 induction in lung injury repair, thus highlighting it as a potential therapeutic target for pulmonary fibrosis.

Circ_0114428 knockdown inhibits ROCK2 expression to assuage lipopolysaccharide-induced human pulmonary alveolar epithelial cell injury through miR-574-5p

BackgroundSepsis-induced acute lung injury (ALI) accounts for about 40% of ALI, accompanied by alveolar epithelial injury. The study aimed to reveal the role of circular RNA_0114428 (circ_0114428) in sepsis-induced ALI.MethodsHuman pulmonary alveolar epithelial cells (HPAEpiCs) were treated with lipopolysaccharide (LPS) to mimic a sepsis-induced ALI cell model. RNA expression of circ_0114428, miR-574-5p and Rho-associated coiled-coil containing protein kinase 2 (ROCK2) was detected by qRT-PCR. Protein expression was checked by Western blotting. Cell viability, proliferation and apoptosis were investigated by cell counting kit-8, 5-Ethynyl-29-deoxyuridine (EdU) and flow cytometry analysis, respectively. The levels of pro-inflammatory factors were detected by enzyme-linked immunosorbent assay (ELISA). Oxidative stress was analyzed by lipid peroxidation Malondialdehyde (MDA) and Superoxide Dismutase (SOD) activity detection assays. The interplay among circ_0114428, miR-574-5p and ROCK2 was identified by dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation assays.ResultsCirc_0114428 and ROCK2 expression were significantly increased, but miR-574-5p was decreased in blood samples from sepsis patients and LPS-stimulated HPAEpiCs. LPS treatment led to decreased cell viability and proliferation and increased cell apoptosis, inflammation and oxidative stress; however, these effects were relieved after circ_0114428 knockdown. Besides, circ_0114428 acted as a miR-574-5p sponge and regulated LPS-treated HPAEpiC disorders through miR-574-5p. Meanwhile, ROCK2 was identified as a miR-574-5p target, and its silencing protected against LPS-induced cell injury. Importantly, circ_0114428 knockdown inhibited ROCK2 production by interacting with miR-574-5p.ConclusionCirc_0114428 knockdown protected against LPS-induced HPAEpiC injury through miR-574-5p/ROCK2 axis, providing a novel therapeutic target in sepsis-induced ALI.

Notch signaling regulates pulmonary fibrosis.

Pulmonary fibrosis is a progressive interstitial lung disease associated with aging. The pathogenesis of pulmonary fibrosis remains unclear, however, alveolar epithelial cell injury, myofibroblast activation, and extracellular matrix (ECM) accumulation are recognized as key contributors. Moreover, recent studies have implicated cellular senescence, endothelial-mesenchymal transition (EndMT), and epigenetic modifications in the pathogenesis of fibrotic diseases. Various signaling pathways regulate pulmonary fibrosis, including the TGF-β, Notch, Wnt, Hedgehog, and mTOR pathways. Among these, the TGF-β pathway is extensively studied, while the Notch pathway has emerged as a recent research focus. The Notch pathway influences the fibrotic process by modulating immune cell differentiation (e.g., macrophages, lymphocytes), inhibiting autophagy, and promoting interstitial transformation. Consequently, inhibiting Notch signaling represents a promising approach to mitigating pulmonary fibrosis. In this review, we discuss the role of Notch signaling pathway in pulmonary fibrosis, aiming to offer insights for future therapeutic investigations.