American Journal of Respiratory Cell and Molecular Biology最新文献

Contractile myofibroblasts immersed in stiffened remodeled extracellular matrix characterize fibrotic lesions in idiopathic pulmonary fibrosis. Lipofibroblasts are lipid droplet-containing interstitial fibroblasts that support functional homeostasis of the developing and adult lung. We show that stiff substrates augment myofibroblast differentiation and extracellular matrix production in vitro under basal conditions and following TGF-β1 (transforming growth factor-β1) incubation when cultured on tissue culture plastic, whereas culture in soft microenvironments (as spheroids or on soft collagen-coated substrate) redirects myofibroblasts to a lipofibroblast-like phenotype (identified by expression of ADRP [adipose differentiation-related protein] and intracellular lipid droplets), with reduced basal α-SMA (α-smooth muscle actin), collagen I, vimentin, and fibronectin expression. The fibrogenic effects of TGF-β1 are prevented in fibroblasts cultured in soft settings. Global proteomics showed similar numbers of TGF-β1-induced differentially expressed proteins in stiff and soft settings (271 and 436, respectively). Of these, only 33 were similarly altered by TGF-β1; 200 were exclusively altered by TGF-β1 in the stiff setting and 365 in the soft setting; 38 showed opposite responses. Reductions in YAP/TAZ, β-catenin, and SMAD expression and their limited nuclear levels in soft settings may explain the "afibrogenic" characteristic of these lipofibroblasts. Thus, in spheroids of lipofibroblasts, TGF-β1 intracellular signaling is redirected and uncoupled from fibrogenesis, including YAP/TAZ, β-catenin, and SMAD. Understanding the proximal causal mechanotransduction signaling networks that are differentially active in soft and stiff microenvironments may reveal novel drug targets for fibrosis treatment.

Bronchopulmonary dysplasia (BPD) is a serious lung disease that affects premature infants born with developmentally immature lungs. Supplemental oxygen, although a lifesaving treatment, provokes inflammation and oxidative stress, causing microvasculature injury, pulmonary edema, and abnormal lung development. Impaired pulmonary vascular development is implicated in BPD; however, the role of the lymphatics is poorly understood. Studies used an established animal model, in which mice were exposed on the day of birth for 14 days to 75% oxygen to induce hallmark features of BPD, including pulmonary edema. Single-cell RNA sequencing data were analyzed to examine VEGF-D (vascular endothelial growth factor-D) expression in the neonatal lung and to define how fibroblasts and lymphatics were altered in response to hyperoxia. VEGF-D biology was interrogated by using mice with a null mutation in Vegfd, and quantitative PCR was used to define mechanisms underlying phenotypes. Hyperoxia elicited expression of VEGF-D, a powerful lymphangiogenic growth factor that is expressed exclusively in lung fibroblasts. In response to hyperoxia, alveolar fibroblasts exhibited significant alterations to their transcriptional profile and changed signaling dynamics within the BPD microenvironment. Probing VEGF-D biology by genetic deletion revealed that VEGF-D deficiency worsened alveolar simplification in response to hyperoxia, exacerbated alveolar fluid accumulation, worsened inflammation, and deranged lymphatic architecture. These data identify an important interplay between alveolar fibroblasts, VEGF-D, and lymphatics in regulating functional lymphangiogenesis and lymphatic vessel patterning in BPD that inform therapeutic and regenerative medicine strategies for this incurable disease.

Ozone (O₃) is an air pollutant that induces pulmonary inflammation and injury, leading to increased susceptibility and exacerbation of chronic lung diseases. Furthermore, ambient O₃ concentrations are expected to rise with increasing global temperatures. Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid found primarily in oily fish that reduces inflammation and enhances the resolution of inflammation. This is attributed partially to DHA-derived oxylipins termed specialized proresolving mediators that have antiinflammatory and/or proresolving properties. However, whether dietary DHA protects the lungs from O₃-induced inflammation and injury is unclear. We hypothesized that dietary DHA supplementation increases pulmonary specialized proresolving mediators and thereby decreases O₃-induced pulmonary inflammation. To test this, C57BL/6J mice were fed a control diet or a DHA-enriched diet (2% kcal from DHA) for 6 weeks, exposed to filtered air or 1 ppm O₃ for 3 hours (comparable with an O₃ action day for humans), and necropsied 24 or 48 hours after exposure. DHA supplementation reduced airspace neutrophilia, decreased cytokine production, and promoted transcriptomic signatures for leukocyte chemotaxis and fatty acid oxidation. Furthermore, dietary DHA increased pulmonary DHA and its oxylipins while decreasing proinflammatory omega-6 polyunsaturated fatty acids and their oxylipins. Oropharyngeal aspiration of DHA oxylipins monohydroxylated 14-hydroxy-DHA and maresin 1 decreased O₃-induced airspace neutrophilia and reduced bone marrow-derived macrophage production of neutrophil chemokines Cxcl1 and Cxcl2. These findings reveal that dietary DHA protects the lungs from O₃ exposure by driving monohydroxylated 14-hydroxy-DHA and maresin 1 production, which reduces neutrophil-recruiting chemokine production by macrophages. This pathway highlights a potential therapeutic dietary approach for mitigating air pollution-induced pulmonary inflammation.

The respiratory tract possesses a highly regulated innate defense system that includes cilia-mediated mucociliary clearance (MCC). Efficient MCC relies on appropriate hydration of airway surfaces, which is controlled by a blend of transepithelial sodium and liquid absorption, as well as anion and liquid secretion. The latter is mediated primarily by the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel. Succinate is derived from parasites, microorganisms, and inflammatory cells, and its concentration increases in the airway surface liquid during infections, activating the G protein-coupled succinate receptor (SUCNR1), which acts as a succinate sensor. Because MCC is tightly regulated by second messengers, we tested the hypothesis that succinate signaling was linked to CFTR activity. We observed that SUCNR1 activation stimulated anion secretion, increased mucus transport, and induced tracheal constriction in mouse airways. In the Cftr^{ΔF508/ΔF508} mouse, increased mucus transport and tracheal constriction were not observed, whereas succinate-induced electrogenic anion secretion remained unaffected. Stimulation of normal human bronchial epithelial cells with succinate activated CFTR-dependent anion secretion and increased airway surface liquid height. Moreover, human bronchial epithelial cells derived from ΔF508-CF individuals that lacked succinate-induced anion secretion, unless incubated with elexacaftor-tezacaftor-ivacaftor, which restored succinate-induced anion secretion, confirmed the tight relationship between SUCNR1 signaling and CFTR function. We have identified a novel mechanism for regulating CFTR/MCC activation that is defective in cystic fibrosis airways. We propose that succinate acts as a danger molecule that alerts the airways to the presence of pathogens leading to a flushing out of the airways.

As medical and scientific communities, we have enjoyed exciting advances in our mechanistic understanding, diagnosis, and therapy of different types of lung fibrosis. However, much still needs to be learned as we are challenged to make earlier diagnoses; improve our ability to assess active disease and risks for disease progression; advance our understanding of the complex interplay of molecular, genetic, and cellular cross-talk processes that underly the disease; and develop transformative therapeutic options to treat and prevent progressive lung fibrosis. Elucidating cellular phenotypes, function and signaling, and the interplay with matrices and aspects of mechanobiology has the potential to help us identify future targets and even reprogram or rebuild a damaged lung. Key to potential future opportunities will be understanding what aspects of fibrogenesis can be prevented or reversed. Bringing together a group of respected medical and scientific thought leaders, the 66th Annual Thomas L. Petty Aspen Lung Conference was titled "Pulmonary Fibrosis-Focusing on the Future." The conference topics included concepts and technologies for identification of early disease and progression using imaging and -omics approaches, identifying and understanding cellular phenotypes and their function, and cross-talk between different cell types, matrices, and matrix receptors. A central theme throughout was the integration of these scientific advances to advance novel targets for therapy, including aspects of reprogramming and rebuilding a damaged lung. The conference provided a forum for discussion, debate, and exchange of ideas with leaders and trainees in the field with the goal to help advance our shared mission of preventing and curing pulmonary fibrotic disease.

Allergic asthma is a widespread disease of the airway stemming from the actions of multiple cell types, including eosinophils and epithelial cells. The urokinase plasminogen activator receptor (uPAR) is a membrane bound protein that can contribute to the activation and mobilization of leukocytes and is present at increased levels in asthmatics. However, its role in allergic asthma remains poorly understood. Here, we used multiple mouse strains and different models of allergic airway disease to study the function of uPAR in the pathogenesis of this disease. Plaur, the gene encoding uPAR, was rapidly induced following allergic sensitization through the airway, and again following subsequent allergen challenge. Plaur-deficient mice displayed both increased numbers of eosinophils and heightened airway hyperresponsiveness (AHR) in multiple models of allergic asthma. Mice selectively lacking Plaur in eosinophils also had more robust eosinophilia than did WT mice, and eosinophils lacking Plaur displayed increased activity in an ex vivo assay of chemokine-dependent migration. However, those mice did not have increased AHR compared with WT mice. Conversely, although mice selectively lacking Plaur in lung epithelial cells did not have increased inflammation compared with wild type (WT) mice, they displayed heightened AHR. These findings suggest that uPAR controls both airway inflammation and AHR, but through distinct mechanisms. Targeting uPAR might have therapeutic potential for treating inflammation and AHR in asthma.