American journal of physiology. Lung cellular and molecular physiology最新文献

The increasing use of electronic cigarettes (e-cigs) among adolescents poses significant public health risks. This study investigates the impact of e-cigs on the airway epithelial barrier, focusing on apical junctional complexes (AJCs), including tight junctions (TJs) and adherens junctions (AJs). We hypothesized that e-cigs disrupt AJCs in a mouse model, leading to increased airway barrier permeability. C57BL/6 mice were exposed to 36 mg/mL e-cig aerosols (3 puffs/min) for 1 h daily over 4 days. Bronchoalveolar lavage (BAL) fluid analysis, lung inflammation assessment, immunohistochemistry (IHC) staining, Western blotting (WB), and permeability assays were performed to evaluate the structure and function of the airway barrier. E-cig-exposed mice showed weight loss and elevated serum cotinine levels. BAL fluid analysis revealed elevated white blood cells. Histological analysis confirmed lung inflammation, whereas IHC and WB showed significant AJC disruption. Notably, claudin-2 levels were elevated in e-cig-exposed mice compared with controls. Claudin-2, known for its role in promoting permeability in "leaky" epithelia, increased alongside decreases in other TJ components, signifying structural barrier impairment. After e-cig exposure, instilling fluorescein isothiocyanate (FITC)-dextran into the airway increased serum FITC-dextran levels, indicating enhanced barrier permeability. E-cig aerosol exposure disrupts airway epithelial barrier structure and function, primarily through the disassembly of TJs and AJs. These findings suggest potential pathways for further clinical investigation into the health risks of e-cig use.NEW & NOTEWORTHY The rising use of e-cigs among youth has become a significant public health concern. This study, using a mouse model, demonstrates that exposure to e-cig aerosol leads to airway inflammation, structural damage to the airway epithelial barrier, and increased epithelial barrier permeability.

Recent studies have linked deficiencies in β-carotene ingestion and its metabolites with an increased risk and severity of asthma exacerbations. We demonstrate that β-ionone, a β-carotene metabolite, dose-dependently relaxes upper and lower airways in vitro using wire myography of tracheal rings and phase-contrast microscopy of precision-cut lung slices (PCLSs). We demonstrate that β-ionone-induced relaxation is mediated through extraocular opsin-3 (OPN3) receptor activation via pharmacological competitive inhibition with chromophore 9-cis retinal and through the decreased relaxation demonstrated in Opn3-null PCLSs. We implicate a mechanistic pathway suggestive of G_αs activation that is in agreement with our previous findings. Finally, we confirmed OPN3 expression in airway smooth muscle cells by immunofluorescence and mRNA expression. Our findings implicate β-ionone as a potential therapeutic agent for conditions characterized by bronchoconstriction, such as asthma and COPD. Moreover, this study underscores the significance of dietary intake, particularly of β-carotene-rich foods, in maintaining respiratory health.NEW & NOTEWORTHY This research investigates β-ionone's potential as a therapeutic agent for bronchoconstriction. It sheds light on the mechanism of action of β-ionone's activation of extraocular opsin-3 receptors, offering insights into dietary influences on respiratory health. Notably, β-ionone induces dose-dependent relaxation in both upper and lower airways, with attenuated relaxation in Opn3-knockout models confirming receptor selectivity. This study presents a novel approach to addressing respiratory ailments and underscores the significance of dietary components in managing airway pathology.

Bronchial epithelial cells derived from the tracheobronchial regions of human airways (HBECs) provide a valuable in vitro model for studying pathological mechanisms and evaluating therapeutics. This cell population comprises a mixed population of basal cells (BCs), the predominant stem cell in airways capable of both self-renewal and functional differentiation. Despite their potential for regenerative medicine, BCs exhibit significant phenotypic variability in culture. To investigate how culture conditions influence BC phenotype and function, we expanded three independent BC isolates in three media: airway epithelial cell growth medium (AECGM), dual-SMAD inhibitor (DSI)-enriched AECGM, and PneumaCult Ex plus (PEx+). Analysis through RNA sequencing, immune assays, and impedance measurements revealed that PEx+ media significantly drove cell proliferation and a broad proinflammatory phenotype in BCs. In contrast, BCs expanded in AECGM and displayed increased expression of structural and extracellular matrix components at higher passage. AECGM increased expression of some cytokines at high passage, whereas DSI suppressed inflammation implicating the involvement TGF-β in BC inflammatory processes. Differentiation capacity of BCs declined with time in culture irrespective of expansion media. This was associated with an increase in PLUNC expressing secretory cells in AECGM and PEx+ media consistent with the known immune modulatory role of PLUNC in the airways. These findings highlight the profound impact of media conditions on inflammatory niche established by, and function of, in vitro expanded BCs. The broad proinflammatory phenotype driven by PEx+ media, in particular, should be considered in the development of cell-based models for airway diseases and therapeutic applications.NEW & NOTEWORTHY Airway basal cells, vital for airway regeneration and potential therapies, show significant changes based on culture conditions. Our study reveals that media composition and culture duration greatly affect basal cell properties with profound changes in the proinflammatory phenotype and extracellular matrix deposition driven by changes in growth conditions. These results underscore the critical impact of culture conditions on BC phenotype, influencing cell-based models for airway disease research and therapy.

Tartrate-resistant acid phosphatase [TRAP, gene acid phosphatase 5 (Acp5; gene name for TRAP)] is highly expressed in alveolar macrophages with proposed roles in lung inflammation and lung fibrosis development. We previously showed that its expression and activity are higher in lung macrophages of smokers and patients with chronic obstructive pulmonary disease (COPD), suggesting involvement in smoke-induced lung damage. In this study, we explored the function of TRAP and regulation of its different mRNA transcripts (Acp5 201-206) in lung tissue exposed to cigarette smoke to elucidate its function in alveolar macrophages. In mice exposed to cigarette smoke or air for 4-6 wk, higher Acp5 mRNA expression in lung tissue after smoking was mainly driven by transcript Acp5-202, which originates from macrophages. The expression of Acp5-202 correlated with transcription factors previously found to drive proliferation of macrophages. Treating fetal liver progenitor-derived alveolar-like macrophages [Max Planck Institute (MPI; macrophages derived from fetal liver progenitors) macrophages] with cigarette smoke extract resulted in more proliferation compared with nontreated cells. In contrast, Acp5-deficient MPI macrophages and MPI macrophages treated with a TRAP inhibitor proliferated significantly less than control macrophages. Mechanistically, this lack of proliferation after TRAP inhibition was associated with higher presence of phosphorylated Beta-catenin (β-catenin; a signaling protein) compared with nontreated controls. Phosphorylation of β-catenin is known to mark it for ubiquitination and degradation by the proteasome, preventing its activity in promoting cell proliferation. In conclusion, our findings provide strong evidence for TRAP stimulating alveolar macrophage proliferation by dephosphorylating β-catenin. By driving proliferation, TRAP likely helps sustain alveolar macrophage populations during smoke exposure, either compensating for their loss due to smoking or increasing their numbers to better manage smoke-induced damage.NEW & NOTEWORTHY This study has uncovered that the enzyme tartrate-resistant acid phosphatase (TRAP) is crucial for alveolar macrophage proliferation through a β-catenin-dependent pathway. Importantly, TRAP influences this important ability of alveolar macrophages through the Acp5-202 mRNA transcript. The increase in TRAP expression following smoke exposure suggests that it plays a key role in promoting cell renewal, potentially helping to mitigate smoke-induced lung damage.

Neonatal acute respiratory distress syndrome (NARDS) is a severe and potentially life-threatening form of lung injury recently defined by the International Neonatal ARDS Consensus. It is marked by extensive lung inflammation and damage to the alveolar epithelium and vascular endothelium. NARDS can be triggered by direct inflammatory exposures, such as pneumonia and aspiration, and indirect exposures, including sepsis, necrotizing enterocolitis, and chorioamnionitis. This review provides clinicians and researchers with the latest insights on NARDS. We adopt a cross-disciplinary approach to discuss the diagnostic criteria, pathobiology, triggers, epidemiology, and treatments of NARDS. In addition, we summarize existing clinical studies and advanced preclinical models that help address current knowledge gaps. Future research should focus on standardizing the Montreux consensus definition of NARDS in preclinical and clinical studies, identifying biomarkers, developing prediction models, and exploring novel therapies for affected infants.

When pulmonary surfactant was first detected in the 1950s by Pattle and Clements, many thousands of infants perished each year due to a respiratory illness termed hyaline membrane disease. Hyaline membranes are formed by plasma leaking through damaged endothelial barriers into the terminal bronchiolar: alveolar spaces. Since the leaking plasma lacks erythrocytes, these clots are opaque. Insightful research by Avery and Mead soon led to the suggestion that the neonatal respiratory distress syndrome (RDS) did not arise because of the presence of hyaline membranes, but rather was related to the lack of sufficient pulmonary surfactant, mainly as a result of immaturity. Unfortunately, initial attempts at treating RDS with aerosolized dipalmitoyl-phosphatidylcholine, the major single molecular component, proved unsuccessful. Almost 20 years later, it was demonstrated by Enhorning and Robertson that treating prematurely delivered rabbit pups with natural surfactant prevents respiratory failure. Initially, it appeared unlikely that animal surfactants could be used for therapy with human infants. However, in 1980, Fujiwara demonstrated that a modified bovine surfactant extract promoted gaseous exchange with infants suffering from RDS. Soon a number of bovine and porcine-modified surfactants and two wholly synthetic formulations were shown to alleviate RDS. The present review relates some of the key scientific findings and significant clinical contributions responsible for reducing the neonatal morbidity and mortality associated with RDS. It further describes some of the more recent findings on the biological, biophysical, and physiological significance of pulmonary surfactant in health and disease.

Introduction: Idiopathic pulmonary fibrosis(IPF) is a chronic progressive lung disease that leads to destruction of alveoli and replacement by fibrotic tissue. Metabolic profiling of lung tissue and serum from IPF patients has revealed that levels of tricarboxylic acid (TCA) cycle metabolites such as succinate are altered in patients with IPF. In our study, we aim to evaluate the role of succinate and its receptor- succinate receptor 1 (SUCNR1) in the pathogenesis of lung fibrosis, with a focus on fibroblasts, a central cell in IPF.

Methods: SUCNR1 expression was investigated using Western blots, qPCR, and FISH. In vitro assays with IPF and normal human lung fibroblasts(NHLF) were used to evaluate the effect of succinate treatment on the expression of fibrotic markers, fibroblast-myofibroblast transition, apoptosis and signaling mechanisms. Studies with the bleomycin mouse model of PF were used to evaluate the effect of succinate in vivo.

Results: Several cell types in the lung express SUCNR1 including ATII cells, fibroblasts, and macrophages. In IPF patient fibroblasts, succinate treatment increased expression of fibrosis associated markers such as alpha smooth muscle actin and collagen. Moreover, succinate exaggerated TGF-β-mediated fibroblast-to-myofibroblast transition in NHLF. In vivo, succinate treatment significantly increased collagen accumulation in the lung and enhanced weight loss in bleomycin-treated mice. Importantly, succinate-mediated elevation of fibrosis-associated markers was lost upon knockdown of SUCNR1 or inhibition of ERK activation in IPF patient-derived fibroblasts.

Conclusion: Succinate exerted pro-fibrotic effects in vitro and in vivo. Thus, SUCNR1 antagonism may be a potential therapeutic target for the treatment of IPF.

Patients in the intensive care unit (ICU) experience many ICU-specific factors that could impact their outcomes apart from their underlying acute illness. The precise function of sleep is not clear but its importance is suggested from literature of deleterious effects of poor sleep and sleep deprivation and may represent a modifiable opportunity in ICU patients. Investigation into the role of sleep in critical illness is impeded by lack of sufficient murine models. While many murine models of sleep disruption exist, these do not replicate the ICU patient experience. We modified a traditional model of sleep fragmentation, i.e. intermittent orbital shaking, with increased duration and intensity of shaking, and 2hr on and 2hr off light/dark cycles to create a ICU-associated sleep fragmentation model. Continuous electroencephalogram analyses identified significantly reduced total sleep time, significantly fragmented sleep and a loss of the diurnal sleep-wake cycle in mice exposed to the ICU sleep fragmentation protocol, but not in mice exposed to a traditional sleep fragmentation protocol when compared to baseline conditions. Using a S. pneumoniae murine model of pneumonia to mimic critical illness, we note a delay in resolution of markers of lung injury in mice exposed to the ICU sleep fragmentation protocol when compared to S. pneumoniae alone. We conclude that traditional sleep fragmentation models may not recapitulate the ICU patient sleep experience. Investigators could employ this ICU sleep fragmentation model for mechanistic studies of how sleep disruption in the ICU affects critical illness outcomes.

Impaired angiogenesis characterized by the reduced proliferation of pulmonary endothelial cells leads to reduced capillary density in patients with bronchopulmonary dysplasia (BPD). In a mouse model of BPD, perinatal hyperoxic injury decreases the number of the recently identified lung capillary stem cells termed as general capillary (gCap) cells, along with the specific reduction of Ntrk2, which encodes for Tropomyosin receptor kinase B (TrkB), within this subpopulation. Herein, we determine whether TrkB signaling is required for perinatal gCap cell proliferation and pulmonary angiogenesis in a hyperoxia mouse BPD model. TrkB activation by BDNF treatment led to enhanced tube-forming ability of endothelial cells in vitro. In vivo treatment of mice with BDNF increased the proliferation of gCap cells and alleviated gCap loss caused by hyperoxic injury. Conversely, inhibition of TrkB signaling disrupted the tube formation of endothelial cells and exaggerated the vascular endothelial damage caused by hyperoxia. We further show that MAPK/ERK signaling acts downstream of TrkB to modulate pulmonary angiogenesis. These data indicate that TrkB signaling plays a critical role in pulmonary angiogenesis upon perinatal lung injury, supporting the concept that TrkB activation might be a potential therapeutic for preserving endothelial cells for lung diseases associated with prematurity.

Preterm infants born to mothers with preeclampsia, a disease of vascular dysfunction, are at increased risk for bronchopulmonary dysplasia (BPD). Endothelial cells are critical in both maintaining proper vascular function and coordinating lung development. Understanding the mechanisms contributing to BPD in the setting of preeclampsia and how preeclampsia impacts pulmonary endothelial cells (PEC) in the newborn lung are required to decrease the burden of BPD. Vitamin D has been shown to improve lung angiogenesis and lung development in inflammatory models of BPD, but its therapeutic potential in the setting of preeclampsia is unknown. We hypothesized that intraamniotic (IA) treatment with the biologically active form of vitamin D, 1,25 dihydroxyvitamin D (1,25(OH)₂D), will preserve lung growth in an experimental model of BPD induced by antenatal exposure to soluble VEGF receptor-1 (sFlt- 1[soluble fms-like tyrosine kinase 1]). Fetal rats were exposed to saline (control), sFlt-1 alone, 1,25(OH)₂D alone, or simultaneous sFlt-1 + 1,25(OH)₂D via IA injection during the late canalicular stage of lung development and delivered 2 days later. IA treatment with 1,25(OH)₂D in sFlt-1 exposed pups improved lung alveolar and vascular growth and function at 14 days of life. PEC orchestrate alveolar development, and we demonstrate that IA sFlt-1 exposure alone decreased in vitro growth and tube formation of PEC isolated from newborn pups and that PEC from pups co-exposed to IA sFlt-1 and 1,25(OH)₂D demonstrated increased growth and tube formation. We conclude that IA 1,25(OH)₂D treatment improves distal lung development during sFlt-1 exposure through preservation of angiogenesis in the developing lung.