Experimental Lung Research最新文献

Background: Sepsis has become one of the main factors inducing the development of acute lung injury (ALI) in clinical practice. Currently, inhibiting the activation of NLRP3 mediated pyroptosis is the target of multiple drugs in the treatment of sepsis induced ALI. This study aimed to explore the effects of METTL14 on the pyroptosis in the sepsis induced ALI progression.Methods: LPS-stimulated A549 cells and cecal ligation and puncture (CLP)-treated mice were used to establish the ALI model in vitro and in vivo. Then, the cell viability was measured by CCK-8 assay. ELISA kits were used to determine the IL-18 and IL-1β contents. Pyroptosis rate was tested by flow cytometry. M6A dot blot was conducted to analyze the global m6A levels and MeRIP assay was performed to detect the m6A levels of NLRP3. The relationship between METTL14 and NLRP3 was confirmed by RIP and dual-luciferase report assays.Results: The global m6A levels were significantly increased in the LPS-stimulated A549 cells and CLP-treated mice. METTL14 knockdown decreased the cell viability, IL-18 and IL-1β contents, and pyroptosis rate of the LPS-stimulated A549 cells. Furthermore, the increase of pyroptosis-related proteins in LPS-stimulated A549 cells was significantly decreased after METTL14 knockdown. Additionally, METTL14 knockdown decreased the m6A and mRNA levels of NLRP3, and NLRP3 overexpression reversed the effects of METTL14 knockdown on the pyroptosis in the LPS-stimulated A549 cells. In CLP-treated mice, METTL14 knockdown relieved the injury and decreased the IL-18 and IL-1β contents in the lung tissues, serum and bronchoalveolar lavage fluid.Conclusion: This study demonstrated that METTL14 knockdown inhibited the pyroptosis in the sepsis-induced ALI progression through decreasing the NLRP3 levels dependent on m6A methylation modification.

Purpose: Growth hormone-releasing hormone (GHRH) is a 44-amino acid peptide that regulates growth hormone (GH) secretion. We hypothesized that GHRH receptor (GHRH-R) in alveolar type 2 (AT2) cells could modulate pro-inflammatory and possibly subsequent pro-fibrotic effects of lipopolysaccharide (LPS) or cytokines, such that AT2 cells could participate in lung inflammation and fibrosis. Methods: We used human alveolar type 2 (iAT2) epithelial cells derived from induced pluripotent stem cells (iPSC) to investigate how GHRH-R modulates gene and protein expression. We tested iAT2 cells' gene expression in response to LPS or cytokines, seeking whether these mechanisms caused endogenous production of pro-inflammatory molecules or mesenchymal markers. Quantitative real-time PCR (RT-PCR) and Western blotting were used to investigate differential expression of epithelial and mesenchymal markers. Result: Incubation of iAT2 cells with LPS increased expression of IL1-β and TNF-α in addition to mesenchymal genes, including ACTA2, FN1 and COL1A1. Alveolar epithelial cell gene expression due to LPS was significantly inhibited by GHRH-R peptide antagonist MIA-602. Incubation of iAT2 cells with cytokines like those in fibrotic lungs similarly increased expression of genes for IL1-β, TNF-α, TGFβ-1, Wnt5a, smooth muscle actin, fibronectin and collagen. Expression of mesenchymal proteins, such as N-cadherin and vimentin, were also elevated after prolonged exposure to cytokines, confirming epithelial production of pro-inflammatory molecules as an important mechanism that might lead to subsequent fibrosis. Conclusion: iAT2 cells clearly expressed the GHRH-R. Exposure to LPS or cytokines increased iAT2 cell production of pro-inflammatory factors. GHRH-R antagonist MIA-602 inhibited pro-inflammatory gene expression, implicating iAT2 cell GHRH-R signaling in lung inflammation and potentially in fibrosis.

Background: To investigate the protective effect of p14ARF in a nitric acid (NA) aerosol inhalation-induced bronchiolitis obliterans (BO) mouse model and its potential regulatory mechanism.

Methods: A BO mouse model was established by NA aerosol inhalation. The expressions of p14ARF, phosphatidylinositol-3-kinase (PI3K), and protein kinase B (AKT) were detected by quantitative reverse transcription PCR (qRT-PCR) and western blot (WB). Hematoxylin (HE) staining, Masson staining, and periodic acid-Schiff (PAS) staining observed pulmonary histological changes. TdT-mediated dUTP nick end labeling (TUNEL) staining detected pulmonary cell apoptosis, and enzyme-linked immunosorbent assay (ELISA) measured matrix metalloproteinase-2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), interleukon-6 (IL-6), and transforminh growth factor-β (TGF-β) levels in lung tissue and bronchoalveolar lavage fluid (BALF).

Results: The expressions of p14ARF, PI3K, and AKT showed a time gradient change, with a decrease trend (*P < 0.05 and **P < 0.01). Severe inflammatory infiltration and tracheal fibrosis were found in lung tissue in the modeling group (BO group) compared with the control group (Con group). The pH, PaO₂, and PaO₂/FiO₂ values significantly reduced, while the PaCO₂ value and the number of TUNEL-positive cells increased in BO group (P < 0.05). In addition, MMP-2, MMP-9, IL-6, and TGF-β levels remarkably increased, with an increase in the number of white blood cells, neutrophils, and lymphocytes in BO group (P < 0.05). Furthermore, p14ARF up-regulation reversed the trend of the aforementioned indexes in BO mice.

Conclusions: p14ARF ameliorated the inflammatory response and airway remodeling in a BO mouse model via the PI3K/AKT pathway.

Background: Lung ischemia-reperfusion injury (LIRI) remains the major cause of primary lung dysfunction after lung transplantation. Diabetes mellitus (DM) is an independent risk factor for morbidity and mortality following lung transplantation. Mitochondrial dysfunction is recognized as a key mediator in the pathogenesis of diabetic LIRI. Melatonin has been reported to be a safe and potent preserving mitochondrial function agent. This study aimed at investigating the potential therapeutic effect and mechanisms of melatonin on diabetic LIRI. Methods: High-fat-diet-fed streptozotocin-induced type 2 diabetic rats were exposed to melatonin, with or without administration of the SIRT3 short hairpin ribonucleic acid (shRNA) plasmid following a surgical model of ischemia-reperfusion injury of the lung. Lung function, inflammation, oxidative stress, cell apoptosis, and mitochondrial function were examined. Results: The SIRT3 signaling and mitophagy were suppressed following diabetic LIRI. Treatment with melatonin markedly induced mitophagy and restored SIRT3 expression. Melatonin treatment also attenuated subsequent diabetic LIRI by improving lung functional recovery, suppressing inflammation, decreasing oxidative damage, diminishing cell apoptosis, and preserving mitochondrial function. However, either administration of SIRT3 shRNA or an autophagy antagonist 3-methyladenine (3-MA) suppressing mitophagy, and compromised the protective action of melatonin. Conclusion: Data indicated that melatonin attenuates diabetic LIRI through activation of SIRT3 signaling-mediated mitophagy.

Objective: Chronic pulmonary inflammation caused by long-term smoking is the core pathology of COPD. Alveolar macrophages (AMs) are involved in the pulmonary inflammation of COPD. The accumulation of damaged materials caused by impaired autophagy triggers inflammatory response in macrophages. As a key transcription regulator, transcription factor EB (TFEB) activates the transcription of target genes related autophagy and lysosome by binding to promoters, whereas it is unclarified for the relationship between inflammatory response induced by cigarette smoke extract (CSE) and TFEB-mediated autophagy. Thus, we investigated the role of TFEB-mediated autophagy in inflammatory response induced by CSE in NR8383 cells, and to explore its potential mechanism. Methods: Based on cell viability and autophagy, cells treated with 20% concentration of CSE for 24 h were selected for further studies. Cells were divided into control group, chloroquine (CQ, the autophagy inhibitor) group, CSE group, CSE + rapamycin (the autophagy inducer) group and CSE + fisetin (the TFEB inducer) group. The levels of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-6 in supernatant were detected by ELISA kits. The protein expressions were tested by western blot. The intensity of fluorescence of Lysosome-associated membrane protein 1 (LAMP1) and TFEB was detected by immunofluorescence. Lyso-Tracker Red staining was applied to detect the lysosome environment. Results: CSE inhibited the cell viability, increased the contents of TNF-α, IL-1β, IL-6, the ratio of LC3II/I, and the level of P62 protein. Besides, CSE decreased the fluorescence intensity of LAMP1 protein and Lyso-Tracker Red staining, as well as the ratio of nucleus/cytosol of TFEB protein. Activating autophagy with rapamycin alleviated CSE-induced inflammatory response. The activation of TFEB via fisetin alleviated CSE-induced autophagy impairment and lysosomal dysfunction, thus alleviated inflammatory response in NR8383 cells. Conclusion: CSE-induced inflammatory response in NR8383 cells, which may be related to the inhibition of TFEB-mediated autophagy.

Background: The most common 'second strike' in mechanically ventilated patients is a pulmonary infection caused by the ease with which bacteria can invade and colonize the lungs due to mechanical ventilation. At the same time, metastasis of lower airway microbiota may have significant implications in developing intubation mechanical ventilation lung inflammation. Thus, we establish a rat model of tracheal intubation with mechanical ventilation and explore the effects of mechanical ventilation on lung injury and microbiological changes in rats. To provide a reference for preventing and treating bacterial flora imbalance and pulmonary infection injury caused by mechanical ventilation of tracheal intubation. Methods: Sprague-Dawley rats were randomly divided into Control, Mechanical ventilation under intubation (1, 3, 6 h) groups, and Spontaneously breathing under intubation (1, 3, 6 h). Lung histopathological injury scores were evaluated. 16SrDNA sequencing was performed to explore respiratory microbiota changes, especially, changes of bacterial count and alteration of bacterial flora. Results: Compared to groups C and SV, critical pathological changes in pulmonary lesions occurred in the MV group after 6 h (p < 0.05). The Alpha diversity and Beta diversity of lower respiratory tract microbiota in MV6, SV6, and C groups were statistically significant (p < 0.05). The main dominant bacterial phyla in the respiratory tract of rats were Proteobacteria, Firmicutes, Bacteroidetes, and Cyanobacteria. Acinetobacter radioresistens in group C was significant, Megaonas in group MV6 was significantly increased, and Parvibacter in group SV6 was significantly increased. Anaerobic, biofilm formation, and Gram-negative bacteria-related functional genes were altered during mechanical ventilation with endotracheal intubation. Conclusion: Mechanical ventilation under intubation may cause dysregulation of lower respiratory microbiota in rats.

Purpose: Airway epithelial barrier leak and the involvement of proinflammatory cytokines play a key role in a variety of diseases. This study evaluates barrier compromise by the inflammatory mediator Tumor Necrosis Factor-α (TNF-α) in the human airway epithelial Calu-3 model. Methods: We examined the effects of TNF-α on barrier function in Calu-3 cell layers using Transepithelial Electrical Resistance (TER) and transepithelial diffusion of radiolabeled probe molecules. Western immunoblot analyses of tight junctional (TJ) proteins in detergent soluble fractions were performed. Results: TNF-α dramatically reduced TER and increased paracellular permeability of both 14C-D-mannitol and the larger 5 kDa probe, 14C-inulin. A time course of the effects shows two separate actions on barrier function. An initial compromise of barrier function occurs 2-4 hours after TNF-α exposure, followed by complete recovery of barrier function by 24 hrs. Beginning 48 hrs. post-exposure, a second more sustained barrier compromise ensues, in which leakiness persists through 144 hrs. There were no changes in TJ proteins observed at 3 hrs. post exposure, but significant increases in claudins-2, -3, -4, and -5, as well as a decrease in occludin were seen at 72 hrs. post TNF-α exposure. Both the 2-4 hr. and the 72 hr. TNF-α induced leaks are shown to be mediated by the ERK signaling pathway. Conclusion: TNF-α induced a multiphasic transepithelial leak in Calu-3 cell layers that was shown to be ERK mediated, as well as involve changes in the TJ complex. The micronutrients, retinoic acid and calcitriol, were effective at reducing this barrier compromise caused by TNF-α. The significance of these results for airway disease and for COVID-19 specifically are discussed.

Background and aim: Pulmonary hypertension (PH) is a serious and even fatal disorder with limited treatment strategies. The hypoxia-induced pulmonary hypertension (HPH) rat model is commonly used in this field. While the HPH rat model has strong predictability and repeatability, the model is a chronic model, making it time-consuming, costly, and complicated and limiting the progress of the experiments. Currently, there is no uniform international standard for the HPH model. Our study aimed to find a relatively effective and efficient HPH modeling protocol. Methods: We established HPH rat models with different total hypoxia periods and different daily hypoxia times, and assessed different hypoxia modeling modes in multiple dimensions, such as haemodynamics, right ventricular (RV) hypertrophy, pulmonary arterial remodeling, muscularization, inflammation, and collagen deposition. Results: Longer daily hypoxia time resulted in higher mean pulmonary arterial pressure (mPAP)/right ventricular systolic pressure (RVSP) and more obvious RV hypertrophy, as well as more severe pulmonary arterial remodeling and muscularization, regardless of the total period of hypoxia (3- or 4-week). Moreover, pulmonary perivascular macrophages and collagen deposition showed daily hypoxia time-dependent increases, both in 3- and 4-week hypoxia groups. Conclusion: Our findings showed that the 3-week continuous hypoxia mode was a relatively efficient way to reduce the time needed to induce significant disease phenotypes, which offered methodological evidence for future studies in building HPH models.

Purpose: Alveolar epithelium dysfunction is associated with a very large spectrum of disease and an abnormal repair capacity of the airway epithelium has been proposed to explain the pathogenesis of Idiopathic Pulmonary Fibrosis (IPF). Following epithelium insult, the damaged cells will activate pathways implicated in the repair process, including proliferation and acquisition of migratory capacities to cover the denuded basement membrane. Induction of Endoplasmic Reticulum stress may be implicated in this process. Interestingly, ER stress excessive activation has been proposed as a central event associated with aberrant repair process and cellular dysfunction observed in IPF. Methods: We study by wound healing assay the molecular targets associated with Alveolar Epithelial Cells (AEC) repair. Results: We demonstrate that the wound recovery of AEC is associated with TGF-β1 signaling and increased transcriptional activity of ER stress and HIF-dependent genes. We further demonstrated that inhibition of TGF-β1 signaling, CHOP expression or HIF-1 expression, limits AECs wound closure. Conclusion: the use of pharmacological drugs targeting the ER/HIF-1 axis could be an attractive approach to limit AEC dysregulation in pathological condition, and confirmed a critical role of theses factor in response to alveolar injury.

Purpose: Endoplasmic reticulum (ER) stress regulates mucus hypersecretion, and may activate downstream factors via TBK1 signaling to induce gene expression. However, it remains unclear whether ER stress promotes airway mucus secretion through the TBK1 pathway. We aimed to investigate the role of the TBK1 pathway in the regulation of MUC5AC expression in a mouse model of house dust mite (HDM)-induced allergic asthma. Materials and Methods: Mice with HDM-induced asthma and human bronchial epithelial BEAS-2B cells were treated with amlexanox, an anti-allergy drug (25 μM), or 4-PBA (10 mM). Tissue and cell samples were collected. Tissue samples were stained with hematoxylin and eosin (H&E) or periodic acid Schiff (PAS) to evaluate pathology. Protein expression was analyzed by western blotting and immunofluorescence. Results: Mice exposed to HDM presented ER stress and hypersecretion of mucus Muc5ac from airway epithelial cells (p < 0.001). Similar results were observed in BEAS-2B cells following exposure to HDM. Both in vivo and in vitro studies revealed that HDM-induced ER stress induced MUC5AC overexpression via TBK1 signaling. Amlexanox and 4-PBA markedly reduced mucus production and weakened the TBK1 signal, which mediates MUC5AC hypersecretion. Conclusion: TBK1 plays a pivotal role in HDM-induced ER stress, leading to overproduction of MUC5AC in the asthmatic airway epithelium. The overproduction of MUC5AC can be significantly decreased by inhibiting TBK1 or ER stress using 4-PBA. These findings highlight potential target-specific therapies for patients with chronic allergic asthma.