American Journal of Respiratory Cell and Molecular Biology最新文献

Chronic obstructive pulmonary disease (COPD) is characterized by progressive airflow limitation and emphysema development, associated with enhanced tissue destruction and defective repair. Supporting cells in the alveolar niche play a crucial role in guiding the activation of alveolar epithelial progenitor cells during repair. Despite their close anatomical proximity, understanding of the supportive role of the pulmonary microvascular endothelium in adult alveolar epithelial repair remains limited. We hypothesized that factors secreted by pulmonary endothelial cells support alveolar epithelial cell growth. Here, we report that human pulmonary microvasculature endothelial cells support murine and human alveolar organoid formation through paracrine signaling via the secretion of extracellular vesicles and soluble factors. Transcriptomic and proteomic analysis pinpointed human pulmonary microvasculature endothelial cell-derived BMP6 (bone morphogenetic protein 6) as a critical factor for alveolar organoid formation. BMP6 promoted alveolar epithelial cell growth, whereas function-blocking antibodies targeting BMP6 inhibited the beneficial effect of endothelial cells on murine alveolar organoid formation. Transcriptomic analysis revealed that BMP6 specifically enhances distal epithelial cell markers and increases Wnt signaling in epithelial progenitors. In contrast, BMP6 deficiency in mouse lungs was associated with reduced Wnt signaling and augmented oxidative stress signaling in murine lung tissue. Taken together, our findings highlight BMP6 as a key regulator of adult epithelial repair and suggest its potential as a therapeutic target for defective epithelial repair, particularly in individuals with early stages of COPD.

IL-33 released by injurious stimuli to airway epithelium activates innate lymphoid cells (ILCs) that express IL-13. IL-33 and ILCs have an important role in type 2 (T2)-high asthma, but their influence on airway dysfunction induced by irritants is unclear. We examined the effects of Cl₂ inhalation on IL-33 release, pulmonary ILCs, airway inflammation, and airway hyperresponsiveness (AHR). Cl₂ exposure resulted in IL-33 release and increased ILC2s in the airways of BALB/c mice. Inhibition of the IL-33 receptor did not alter AHR, but depletion of ILCs augmented AHR. Recombinant IL-33 given for 3 successive days to wild-type and Rag1^-/- (recombinant activating gene-deficient) mice, deficient in mature T and B cells, further increased ILC2s and inhibited Cl₂-induced neutrophilia and AHR, whereas Rag^-/- IL2rγ^-/- mice, lacking ILCs, did not show these effects. IL-33 increased IL-13 expression by ILC2s, and IL-13 neutralization exacerbated AHR, whereas IL-13 administration reduced AHR in Cl₂-exposed Rag1^-/- mice. IL-33 biased alveolar macrophages toward the M2 phenotype, partly mediated by IL-13. Depletion with clodronate liposomes abrogated the IL-33 protective effect on AHR. The data suggest that the expansion of ILC2s by IL-33 activates a protective pathway involving IL-13 and macrophages against airway dysfunction and inflammation after inhalation of Cl₂.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, interstitial lung disease lacking an efficient drug to reverse it. Thus, there is an urgent need to elucidate the complex pathogenesis of IPF and identify new therapeutic targets. It has been revealed that the pathophysiology of IPF is a highly orchestrated process that includes multiple cell types in which the contribution of endothelial cells (ECs) has attracted researchers' attention. However, although the involvement of ECs in fibrosis has been recognized, the underlying key molecules driving these changes are not well defined. In this study, we revealed that von Willebrand factor (VWF), a marker of damaged ECs, and endothelial dysfunction are positively correlated with IPF progression on the basis of reanalysis of gene expression profiles of patients with IPF. Next, we discovered that VWF deficiency attenuated fibrosis in experimental models, including human cell lines (in vitro) and mice (in vivo). Mechanistically, VWF deficiency inhibited endothelial-to-mesenchymal transition, regulated vascular abnormalities, and limited M2 macrophage infiltration, which were achieved, at least in part, by the inhibition of Wnt signaling. Our findings provided evidence for the pivotal role of ECs in IPF and revealed that VWF might be a driving factor of endothelial-to-mesenchymal transition, suggesting that VWF can be developed as a potential therapeutic target against IPF.

Surfactant protein (SP)-A, an octadecamer composed of SP-A1 and SP-A2, is secreted into the alveolar space. Heterozygous variations in SFTPA1 and SFTPA2, reported to impair protein secretion, have been associated with interstitial lung disease and lung adenocarcinoma. To date, no specific treatment is available. Here, the impact of wild-type (WT) SP-A1 or SP-A2 on the localization, oligomerization, and secretion of deleterious SP-A1 or SP-A2 variants is investigated. To achieve this, we used expression vectors carrying four previously described variations as well as a newly identified variation in SFTPA1 and SFTPA2 or WT sequences. Proteins were transiently expressed in HEK293T, and, after extraction, SP-A1 and SP-A2 were analyzed by Western blotting to assess their stability, ability to form oligomers, and secretion. In addition, the subcellular localization of these proteins in HEK293 cells was examined using immunofluorescence microscopy. Consistent with previous reports, we observed that all the variations impair SP-A1 or SP-A2 secretion. Localization of mutated proteins was also disrupted. Furthermore, all variations in SFTPA1 and SFTPA2 exhibited defects in oligomerization of mutated proteins, together with lower expression levels. Interestingly, coexpression of SP-A1 or SP-A2 WT resulted in an increased expression of the mutated proteins, restored a proper oligomerization profile, and partially restored SP-A secretion. This study reveals the beneficial effect of SP-A WT on oligomerization and secretion of mutant SP-A, suggesting that SP-A may be studied as a potential targeted treatment in interstitial lung disease linked to SP-A molecular variations.

Trisomy of chromosome 21 (TS21), also known as Down syndrome (DS), increases pediatric mortality risk due to respiratory syncytial virus (RSV) by ninefold. However, the underlying immunological basis remains unclear. To define the biological implications of TS21 in airway epithelial cells (AECs), the primary site of respiratory virus entry and host defense, in this study we investigated RSV-induced responses in primary nasal AECs from pediatric donors of euploid and trisomic cells. We used comprehensive approaches to assess baseline IFN-JAK-STAT signaling; viral infectivity; and the production of Type III IFN/λ1, proinflammatory cytokines, and chemokines before and after RSV exposure. TS21 AECs exhibited baseline hyperactive IFN-JAK-STAT signaling and reduced RSV infectivity but also showed impaired Type III IFN responses during viral infection. Furthermore, TS21 AECs demonstrated a robust proinflammatory state, with upregulated leukocyte/neutrophil chemotaxis pathways and heightened CXCL5/CXCL10 production before and after RSV exposure. This pattern was recapitulated in infants with DS who had severe viral bronchiolitis, exhibiting a dysregulated airway immune response characterized by diminished Type III IFN and excessive CXCL5/CXCL10 production. Our results suggest that RSV severity in DS is not due to enhanced viral infectivity but, rather, to dysregulated airway proinflammatory responses, offering new therapeutic opportunities to mitigate the severity of RSV infection in children with DS.