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

COVID-19 commonly presents as pneumonia, with those most severely affected progressing to respiratory failure. Patient responses to SARS-CoV-2 infection are varied, with comorbidities acting as major contributors to varied outcomes. Focusing on one such major comorbidity, we assessed whether pharmacological induction of type 1 diabetes mellitus (T1DM) would increase the severity of lung injury in a murine model of COVID-19 pneumonia utilizing wild-type mice infected with mouse-adapted SARS-CoV-2. Hyperglycemic mice exhibited increased weight loss and reduced blood oxygen saturation in comparison with their euglycemic counterparts, suggesting that these animals indeed experienced more severe lung injury. Transcriptomic analysis revealed a significant impairment of the adaptive immune response in the lungs of diabetic mice compared with those of control. To expand the limited options available for tissue analysis due to biosafety restrictions, we also employed a new technique to digest highly fixed tissue into a single-cell suspension, originally designed for scRNA-Seq, which we then adapted for flow cytometric analysis. Flow immunophenotyping and scRNA-Seq confirmed impaired recruitment of T-cells into the lungs of T1DM animals. In addition, scRNA-Seq revealed a distinct, highly inflammatory macrophage profile in the diabetic cohort that correlates with the more severe infection these mice experienced clinically, allowing insight into a possible mechanism for this phenomenon. Recognizing the near certainty that respiratory viruses will continue to present significant public health concerns for the foreseeable future, our study provides key insights into how T1DM results in a much more severe infection and identifies possible targets to ameliorate comorbidity-associated severe disease.NEW & NOTEWORTHY We define the exacerbating effects of type 1 diabetes mellitus (T1DM) on COVID-19 pneumonia severity in mice. Hyperglycemic mice experienced increased weight loss and reduced oxygen saturation. Transcriptomic analysis revealed impaired immune responses in diabetic mice, while flow cytometry and single-cell RNA sequencing confirmed reduced T-cell recruitment and an inflammatory macrophage profile. In addition, we introduced a novel technique for tissue analysis, enabling flow cytometric analysis on highly fixed tissue samples.

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with limited therapeutic options. Fibroblast growth factor receptor-4 (FGFR4) is a known receptor for several paracrine fibroblast growth factors (FGFs). FGFR4 is also the main receptor for FGF19, an endocrine FGF that was demonstrated by our group to have antifibrotic properties in the lung. We aimed to determine whether FGFR4 could modulate pulmonary fibrogenesis. We assessed FGFR4 mRNA and protein levels in IPF and control lungs. In vitro, we determined the effect of transforming growth factor-β (TGF-β), endothelin-1, and platelet-derived growth factor (PDGF) on FGFR4 expression in human lung fibroblasts. We determined the effect of FGFR4 inhibition, using a specific pharmacological inhibitor (FGF401), or genetic deletion in murine embryonic fibroblasts (MEFs) on TGF-β-induced myofibroblastic differentiation. In vivo, we evaluated the development of bleomycin-induced lung fibrosis in Fgfr4-deficient (Fgfr4^-/-) mice compared with wild-type littermates (WT) and after FGF401 treatment in WT mice compared with a control group receiving the solvent only. FGFR4 was decreased in IPF lungs, as compared with control lungs, at mRNA and protein levels. In vitro, FGFR4 was downregulated after treatment with TGF-β, endothelin-1, and PDGF. In vitro, FGFR4 inhibition by FGF401 prevented TGF-β1-induced collagen and ACTA2 increase in lung fibroblasts. Similar results were observed in Fgfr4^-/- MEFs. In vivo, FGFR4 genetic deficiency or FGFR4 pharmacological inhibition did not modulate bleomycin-induced pulmonary fibrosis. Our data suggest that FGFR4 exerts profibrotic properties by enhancing TGF-β signaling in vitro. However, the inhibition of FGFR4 is not sufficient to prevent the development of pulmonary fibrosis in vivo.NEW & NOTEWORTHY FGFR4 has been reported to have antifibrotic effects in the liver. We aimed to determine the involvement of FGFR4 during IPF. Our data suggest that FGFR4 exerts profibrotic properties by enhancing TGF-β signaling in vitro. However, the inhibition of FGFR4 is not sufficient to prevent the development of pulmonary fibrosis in vivo. To our knowledge, this is the first study to assess the profibrotic action of FGFR4 during pulmonary fibrosis.

Systematic reviews and meta-analyses support the benefits of inspiratory muscle training (IMT) for sports and clinical populations. A typical application of "standalone" IMT intervention consists of breathing against an inspiratory load (IRL), twice daily, for 5-7 days/wk, for 4-12 wk. However, the application of IRL during aerobic exercise is often seen in a training routine of sports and rehabilitation centers with no evidence-based guide. In this Perspective, we will revisit putative mechanisms underlying the established benefits of "standalone" IMT to support our contention that IMT need not and should not be used during aerobic exercise.

To function effectively, pulmonary surfactant must adsorb rapidly to the alveolar air/water interface but avoid collapse from the surface when compressed to high interfacial densities. Prior studies show that phospholipids in the cylindrical monolayers of the inverse hexagonal (H_II) phase adsorb quickly. The monolayers have negative curvature, defined by the concave shape of the hydrophilic face. Formation of the H_II structures, however, involves significant disruption of chain-packing. Samples with significant spontaneous curvature, formed in the absence of applied force, may nonetheless have lamellar structures that optimize chain-packing. The experiments here tested whether planar lamellar bilayers formed by phospholipids with negative spontaneous curvature might adsorb rapidly but collapse slowly. Prior studies have shown that binary mixtures of dioleoyl phosphatidylcholine-dioleoyl phosphatidylethanolamine (DOPC-DOPE) with higher mol fractions of DOPE (X_PE) have more negative spontaneous curvature. Samples of DOPC-DOPE with higher X_PE studied here adsorbed more rapidly but also collapsed more quickly. Over that range of X_PE, small-angle X-ray scattering showed only lamellar structures. The H_II phase was undetectable. The results suggest that the innate tendency of the phospholipids to form curvature has primary importance for adsorption rather than the presence of the H_II phase. Planar structures are insufficient to minimize the tendency of spontaneous curvature to promote collapse. These findings are consistent with adsorption and collapse that occur via rate-limiting transient structures with significant negative curvature.NEW & NOTEWORTHY Pulmonary surfactant must adsorb rapidly to the surface of the alveolar liquid but collapse slowly when compressed. Prior studies show that cylindrical monolayers of the inverse hexagonal phase adsorb rapidly. These structures have negative curvature; the hydrophilic face of the phospholipid leaflet is concave. Our studies tested whether planar lamellar structures with a greater tendency to form negative curvature would adsorb rapidly but collapse slowly. Compositional change accelerated adsorption but also yielded faster collapse.

Semaphorin3E (Sema3E) is a member of axon guidance proteins that have emerged recently as essential regulators of cell migration and proliferation. It binds to PlexinD1 with high affinity and is expressed in different cell types, including immune, cancer, and epithelial cells. Recent work in our lab has revealed a critical immunoregulatory role of Sema3E in experimental allergic asthma; however, its role in chronic obstructive pulmonary disease (COPD) remains unclear. This study aimed to investigate the expression of Sema3E and its receptor, PlexinD1, in the airways of patients with COPD and whether Sema3E regulates airway smooth muscle (ASM) cell proliferation, a key feature of airway remodeling in COPD. We first demonstrate that human ASM cells obtained from COPD express Sema3E and PlexinD1 at both mRNA and protein levels. Also, bronchial sections from patients with COPD displayed immunoreactivity of Sema3E and its receptor PlexinD1, suggestive of functional contribution of Sema3E in airway remodeling. In contrast to ASM cells from healthy donors, Sema3E did not inhibit the platelet-derived growth factor (PDGF) induced cell proliferation in ASM cells of patients with COPD that were consistent with the binding of endogenous Sema3E to its receptors on the cell surface and the expression and release of p61KDa-Sema3E isoform. Our results support the Sema3E-PlexinD1 axis involvement in COPD airway smooth muscle remodeling.NEW & NOTEWORTHY Semaphorin3E (Sema3E), a protein guiding cell movement, is found in various cell types like neural, immune, cancer, and epithelial cells. This study examines Sema3E in chronic obstructive pulmonary disease (COPD) airways. In patients with COPD, airway smooth muscle cells express Sema3E and its receptor PlxD1. Unlike healthy cells, Sema3E does not hinder cell proliferation in COPD, indicating involvement in airway remodeling. These findings highlight the Sema3E-PlxD1 axis in COPD airway changes.

The intricate lung structure is crucial for gas exchange within the alveolar region. Despite extensive research, questions remain about the connection between capillaries and the vascular tree. We propose a computational approach combining three-dimensional (3-D) morphological modeling with computational fluid dynamics simulations to explore alveolar capillary network connectivity based on blood flow dynamics. We developed three-dimensional sheet-flow models to accurately represent alveolar capillary morphology and conducted simulations to predict flow velocities and pressure distributions. Our approach leverages functional features to identify plausible system architectures. Given capillary flow velocities and arteriole-to-venule pressure drops, we deduced arteriole connectivity details. Preliminary analyses for nonhuman species indicate a single alveolus connects to at least two 20-µm arterioles or one 30-µm arteriole. Hence, our approach narrows down potential connectivity scenarios, but a unique solution may not always be expected. Integrating our blood flow model results into our previously published gas exchange application, Alvin, we linked these scenarios to gas exchange efficiency. We found that increased blood flow velocity correlates with higher gas exchange efficiency. Our study provides insights into pulmonary microvasculature structure by evaluating blood flow dynamics, offering a new strategy to explore the morphology-physiology relationship that is applicable to other tissues and organs. Future availability of experimental data will be crucial in validating and refining our computational models and hypotheses.NEW & NOTEWORTHY The alveolus is pivotal for gas exchange. Its complex, dynamic nature makes structural experimental studies challenging. Computational modeling offers an alternative. We developed a data-based three-dimensional (3-D) model of the alveolar capillary network and performed blood flow simulations within it. Choosing a novel perspective, we inferred structure from function. We systematically varied the properties of vessels connected to our capillary network and analyzed simulation results for blood flow and gas exchange to obtain plausible vessel configurations.

Eosinophils contribute to metabolic homeostasis and airway hyperresponsiveness, but their specific role in obesity-related airway hyperresponsiveness remains unclear. To address this, we used transgenic mice that overexpress interleukin-5 (IL-5) in peripheral T cells (+IL-5T) and wild-type controls. On a normal diet, +IL-5T and wild-type mice have similar body weight, body fat, and airway nerve-mediated reflex bronchoconstriction in response to inhaled serotonin. Feeding wild-type mice a 61.6% high-fat diet resulted in significantly increased body weight, body fat, fasting glucose, fasting insulin, and reflex bronchoconstriction induced by serotonin, which was blocked by vagotomy. In contrast, +IL-5T mice on a high-fat diet gained less body weight and fat than wild-type mice on the same diet and did not exhibit potentiation in fasting glucose, fasting insulin, or reflex bronchoconstriction induced by serotonin. Compared with wild-type mice, +IL-5T mice on normal diet had significantly more adipose tissue eosinophils, and this was further increased by high-fat diet. High-fat diet did not increase adipose tissue eosinophils in wild-type mice. Our findings suggest that adipose tissue eosinophils may play a role in regulating body fat, thereby reducing insulin, which is a mediator of obesity-related airway hyperresponsiveness. Thus, our data indicate adipose tissue eosinophils may be an important avenue for research in obesity-related asthma.NEW & NOTEWORTHY This study investigates how eosinophils influence systemic metabolism and airway function in obesity. Known for their immune functions, eosinophils also mitigate obesity-related hyperinsulinemia, reducing airway hyperresponsiveness in obese mice models. The findings suggest potential therapeutic strategies targeting the intricate interplay among neurons, eosinophils, and the endocrine system to alleviate asthma in obesity. This research provides novel insights into the critical neuro-immune-endocrine interactions essential for managing obesity-related asthma.

Research on lung surfactant has exerted a great impact on newborn respiratory care and significantly improved survival and outcome of preterm infants with respiratory distress syndrome (RDS) due to surfactant deficiency because of lung immaturity. Current clinical, animal-derived, surfactants are among the most widely tested compounds in neonatology. However, limited availability, high production costs, and ethical concerns about using animal-derived products constitute important limitations in their universal application. Synthetic lung surfactant offers a promising alternative to animal-derived surfactants by providing improved consistency, quality and purity, availability and scalability, ease of production and lower costs, acceptance, and safety for the treatment of neonatal RDS and other lung conditions. Third-generation synthetic surfactants built around surfactant protein B (SP-B) and C (SP-C) peptide mimics stand at the forefront of innovation in neonatal pulmonary medicine, while nasal continuous positive airway pressure (nCPAP) has become the standard noninvasive respiratory support for preterm infants. nCPAP can prevent the risk of chronic lung disease (bronchopulmonary dysplasia) and reduce lung injury by avoiding intubation and mechanical ventilation, is a relatively simple technique, and can be initiated safely and effectively in the delivery room. Combining nCPAP with noninvasive, preferably aerosol, delivery of synthetic lung surfactant promises to improve respiratory outcomes for preterm infants, especially in low- and middle-income countries.

Background Respiratory viruses cause chronic obstructive pulmonary disease (COPD) exacerbations. Rhinoviruses (RVs) are the most frequently detected. Some COPD patients experience frequent exacerbations ({greater than or equal to}2 exacerbations/ year). The relationship between exacerbation frequency and anti-viral immunity remains poorly understood. Objectives To investigate the relationship between exacerbation frequency and anti-viral immunity in COPD Methods Alveolar macrophages and bronchial epithelial cells (BECs) were obtained from COPD patients and healthy participants. Alveolar macrophages were infected with RV-A16 multiplicity of infection 5 (MOI 5) and BECs infected with RV-A16 MOI 1 for 24 hours. Interferons (IFN) and pro-inflammatory cytokines IL-1β, IL-6, CXCL8 and TNF were measured in cell supernatants using mesoscale discovery platform. Viral load and interferon stimulated genes were measured in cell lysates using qPCR. Results Spontaneous and RV induced IFN-β, IFN-γ and CXCL-11 release were significantly reduced in alveolar macrophages from COPD patients compared to healthy subjects. IFN-β was further impaired in uninfected alveolar macrophages from COPD patients with frequent exacerbations 82.0 pg/mL vs infrequent exacerbators 234.7 pg/mL P=0.008 and RV-infected alveolar macrophages from frequent exacerbators 158.1 pg/mL vs infrequent exacerbators 279.5 pg/mL P=0.022. Release of proinflammatory cytokines CXCL8, IL-6, TNF and IL-1β was higher in uninfected BECs from COPD patients compared to healthy subjects but there was no difference in pro-inflammatory response to RV between groups. Conclusions IFN responses to RV was impaired in alveolar macrophages from COPD patients and further reduced in patients with frequent exacerbations.

The objective of this study was to assess fibrinogen (FIB) co-modified with citrulline (CIT) and/or malondialdehyde-acetaldehyde (MAA) initiates macrophage-fibroblast interactions leading to extracellular matrix (ECM) deposition that characterizes rheumatoid arthritis-associated interstitial lung disease (RA-ILD). Macrophages (Mϕ) were stimulated with native-FIB, FIB-CIT, FIB-MAA or FIB-MAA-CIT. Supernatants (SN) (Mϕ-SN [U-937-derived] or MϕP-SN [PBMC-derived]) or direct antigens were co-incubated with human lung fibroblasts (HLFs). Gene expression was examined using RT-PCR. ECM deposition was quantified using immunohistochemistry and Western blot; cell signaling mechanisms were delineated. PDGF-BB and TGF- were measured in macrophage supernatants and inhibition studies performed using Su16f and SB431542, respectively. HLF gene expression of CD36, COL6A3, MMP-9, MMP-10, MMP-12 was increased following stimulations with Mϕ-SN generated from modified FIB but not from direct antigens. HLF stimulated with MϕP-SN^FIB-MAA-CIT derived from RA-ILD patients resulted in 4- to 30-fold increases in COL6A3 and MMP12 expression; up-regulation was greater in HLFs stimulated with MϕP-SN derived from RA-ILD vs. controls. HLF exposure to Mϕ-SN^FIB-MAA-CIT increased types I/VI collagen deposition vs. all other Mϕ-SN groups and was greater than FIB-MAA-CIT stimulation. PDGF-BB and TGF- signaling had the highest concentrations identified in Mϕ-SN^FIB-MAA-CIT and MϕP-SN^FIB-MAA-CIT, particularly from RA-ILD-derived cells. PDGF-BB and TGF- inhibitors, alone and in combination, significantly reduced HLF-mediated ECM deposition from Mϕ-SN stimulations. These results show that co-modified fibrinogen activates macrophages to produce PDGF-BB and TGF-β that promotes an aggressive HLF phenotype characterized increased ECM deposition. These results suggest that targeting CIT and/or MAA modifications or downstream cellular signals could represent novel approaches to RA-ILD treatment.