Background: Bronchial smooth muscle (BSM) remodelling in asthma is related to an increased mitochondrial biogenesis and enhanced BSM cell proliferation in asthma. Since mitochondria produce the highest levels of cellular energy and fatty acid β-oxidation is the most powerful way to produce ATP, we hypothesised that, in asthmatic BSM cells, energetic metabolism is shifted towards the β-oxidation of fatty acids.Objectives: We aimed to characterise BSM cell metabolism in asthma bothin vitroandex vivoto identify a novel target for reducing BSM cell proliferation.Methods: 21 asthmatic and 31 non-asthmatic patients were enrolled. We used metabolomic and proteomic approaches to study BSM cells. Oxidative stress, ATP synthesis, fatty acid endocytosis, metabolite production, metabolic capabilities, mitochondrial networks, cell proliferation and apoptosis were assessed on BSM cells. Fatty acid content was assessedin vivousing matrix-assisted laser desorption/ionisation spectrometry imaging.Results: Asthmatic BSM cells were characterised by an increased rate of mitochondrial respiration with a stimulated ATP production and mitochondrial β-oxidation. Fatty acid consumption was increased in asthmatic BSM bothin vitroandex vivo. Proteome remodelling of asthmatic BSM occurredviatwo canonical mitochondrial pathways. The levels of carnitine palmitoyl transferase (CPT)2 and low-density lipoprotein (LDL) receptor, which internalise fatty acids through mitochondrial and cell membranes, respectively, were both increased in asthmatic BSM cells. Blocking CPT2 or LDL receptor drastically and specifically reduced asthmatic BSM cell proliferation.Conclusion: This study demonstrates a metabolic switch towards mitochondrial β-oxidation in asthmatic BSM and identifies fatty acid metabolism as a new key target to reduce BSM remodelling in asthma.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections initiate in the bronchi of the upper respiratory tract and are able to disseminate to the lower respiratory tract, where infections can cause an acute respiratory distress syndrome with a high degree of mortality in elderly patients. We used reconstituted primary bronchial epithelia from adult and child donors to follow the SARS-CoV-2 infection dynamics. We show that, in epithelia from adult donors, infections initiate in multiciliated cells and spread within 24 to 48 h throughout the whole epithelia. Syncytia formed of ciliated and basal cells appeared at the apical side of the epithelia within 3 to 4 d and were released into the apical lumen, where they contributed to the transmittable virus dose. A small number of reconstituted epithelia were intrinsically more resistant to virus infection, limiting virus spread to different degrees. This phenotype was more frequent in epithelia derived from children versus adults and correlated with an accelerated release of type III interferon. Treatment of permissive adult epithelia with exogenous type III interferon restricted infection, while type III interferon gene knockout promoted infection. Furthermore, a transcript analysis revealed that the inflammatory response was specifically attenuated in children. Taken together, our findings suggest that apical syncytia formation is an underappreciated source of virus propagation for tissue or environmental dissemination, whereas a robust type III interferon response such as commonly seen in young donors restricted SARS-CoV-2 infection. Thus, the combination of interferon restriction and attenuated inflammatory response in children might explain the epidemiological observation of age-related susceptibility to COVID-19.

Rhinovirus (RV) infection of the bronchial epithelium is implicated in the vast majority of severe asthma exacerbations. Interestingly, the susceptibility of bronchial epithelium to RV infection is increased in persons with asthma. Bronchial smooth muscle (BSM) remodeling is an important feature of severe asthma pathophysiology, and its reduction using bronchial thermoplasty has been associated with a significant decrease in the exacerbation rate. We hypothesized that asthmatic BSM can play a role in RV infection of the bronchial epithelium. Using an original co-culture model between bronchial epithelium and BSM cells, we show that asthmatic BSM cells increase RV replication in bronchial epithelium following RV infection. These findings are related to the increased production of CCL20 by asthmatic BSM cells. Moreover, we demonstrate an original downregulation of the activity of the epithelial protein kinase RNA-activated (PKR) antiviral pathway. Finally, we identify a direct bottom-up effect of asthmatic BSM cells on bronchial epithelium susceptibility to RV infection.

Patients with severe asthma show an increase in both exacerbation frequency and bronchial smooth muscle (BSM) mass. Rhinovirus (RV) infection of the bronchial epithelium (BE) is the main trigger of asthma exacerbations. Histological analysis of biopsies shows that a close connection between BE and hypertrophic BSM is a criterion for severity of asthma. We hypothesized that RV infection of BE specifically increases BSM-cell migration from patients with asthma. Serum samples, biopsies, or BSM cells were obtained from 86 patients with severe asthma and 31 subjects without asthma. BE cells from subjects without asthma were cultured in an air-liquid interface and exposed to RV-16. Migration of BSM cells was assessed in response to BE supernatant using chemotaxis assays. Chemokine concentrations were analyzed by transcriptomics and ELISAs. Immunocytochemistry, western blotting, and flow cytometry were used to quantify CXCR3 isoform distribution. CXCR3 downstream signaling pathways were assessed by calcium imaging and western blots. BSM cells from patients with severe asthma specifically migrated toward RV-infected BE, whereas those from subjects without asthma did not. This specific migration is driven by BE C-X-C motif chemokine ligand 10, which was increased in vitro in response to RV infection as well as in vivo in serum from exacerbating patients with severe asthma. The mechanism is related to both decreased expression and activation of the CXCR3-B-specific isoform in BSM cells from those with severe asthma. We have demonstrated a novel mechanism of BSM remodeling in patients with severe asthma following RV exacerbation. This study highlights the C-X-C motif chemokine ligand 10/CXCR3-A axis as a potential therapeutic target in severe asthma.

Chronic obstructive pulmonary disease (COPD) is a prevalent respiratory disease lacking effective treatment. Focusing on early COPD should help to discover disease modifying therapies. We examined the role of the CXCL12/CXCR4 axis in early COPD using human samples and murine models. Blood samples and lung tissues from both individuals with early COPD and controls were analyzed for CXCL12 and CXCR4 levels. To generate an early-like COPD model, 10-week-old male C57BL/6J mice were exposed to cigarette smoke for 10 weeks and intranasal instillations of polyinosinic–polycytidylic acid (poly(I:C)) for the last 5 weeks to mimic exacerbations. The number of cells expressing CXCR4 was increased in the blood of individuals with COPD, as well as in the blood of exposed mice. Lung CXCL12 expression was higher in both patients with early COPD and exposed mice. Exposed mice presented mild airflow obstruction, peribronchial fibrosis, and right heart thickening. The density of fibrocyte-like cells expressing CXCR4 increased in the bronchial submucosa of these mice. Conditional inactivation of CXCR4, as well as pharmacological inhibition of CXCR4 with plerixafor injections, improved lung function, reduced inflammation, and protected against cigarette smoke and poly(I:C)-induced airway and cardiac remodeling. CXCR4−/−-treated and plerixafor-treated mice also had fewer CXCR4-expressing circulating cells and a lower density of peribronchial fibrocyte-like cells. We demonstrate that targeting CXCR4 has beneficial effects in an animal model mimicking early COPD. Although these preclinical findings are encouraging, further research is needed to explore the potential for transferring these insights into clinical applications, including drug repurposing.