Daily Respiratory Research Analysis
Analyzed 122 papers and selected 3 impactful papers.
Summary
Analyzed 122 papers and selected 3 impactful articles.
Selected Articles
1. Epithelial SLC39A1 prevents acute lung injury through zinc-mediated transcriptional activation of autophagy in male mice.
This mechanistic study identifies SLC39A1 in alveolar type II cells as a gatekeeper of a zinc–autophagy protective axis in ALI/ARDS. Genetic ablation worsened injury, while zinc or SLC39A1 overexpression was protective; zinc failed to rescue SLC39A1-deficient mice, placing SLC39A1 upstream of TFEB/TFE3/MITF-driven autophagy that suppresses apoptosis/pyroptosis.
Impact: It uncovers a druggable epithelial defense pathway linking zinc transport to autophagy and cell-death control in ALI/ARDS, offering a mechanistic basis for targeted interventions beyond non-specific supportive care.
Clinical Implications: Suggests therapeutic strategies that enhance SLC39A1 function or activate TFEB/TFE3/MITF-driven autophagy in alveolar epithelium; zinc supplementation may benefit selected patients but appears contingent on epithelial SLC39A1 competence and warrants stratification.
Key Findings
- SLC39A1 is upregulated in AT2 cells in murine ALI and human ARDS and is required for epithelial protection.
- Zinc or SLC39A1 overexpression attenuates lung injury, but zinc cannot rescue Slc39a1-deficient mice, placing SLC39A1 upstream of protection.
- Zinc likely activates TFEB/TFE3/MITF to drive autophagy, limiting mitochondrial damage and apoptosis/pyroptosis; Lc3b or Tfe3 deficiency abolishes zinc’s benefit.
- Epistasis (AAV-shLc3b in AT2 Slc39a1-deficient mice) supports a linear SLC39A1→autophagy pathway.
Methodological Strengths
- Multi-system validation across murine ALI models and human ARDS samples with cell-type specificity (AT2-targeted genetics).
- Mechanistic epistasis and pathway interrogation (TFEB/TFE3/MITF, LC3b, Tfe3) linking zinc transport to autophagy and cell-death programs.
Limitations
- Preclinical work primarily in male mice; sex differences and human dose–response to zinc are not established.
- Translational readiness of SLC39A1-targeted or TFEB/TFE3-directed therapies requires safety and efficacy studies.
Future Directions: Validate the zinc–autophagy axis in female models and diverse ARDS etiologies; develop small molecules that enhance SLC39A1 activity or selectively activate TFEB/TFE3 in alveolar epithelium; explore patient stratification by epithelial SLC39A1 status.
Zinc transporters regulate intracellular zinc homeostasis, but their role in acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) remains underexplored. Here, we show that the zinc transporter SLC39A1 is highly upregulated in alveolar type II (AT2) cells from male murine ALI models and patients with ARDS. AT2-specific Slc39a1 deletion or zinc chelation exacerbates lung injury, whereas overexpression or zinc supplementation attenuates it. Notably, zinc supplementation fails to rescue Slc39a1-deficient mice, indicating SLC39A1 governs zinc uptake to control ALI. Zinc likely directly binds to and activates TFEB, TFE3, and MITF, inducing transcriptional activation of autophagy to eliminate damaged mitochondria and suppress apoptosis/pyroptosis in AT2 cells. Lc3b- or Tfe3-deficient mice show heightened lung injury, which remain unmitigated by zinc supplementation. Importantly, administration of AAV-shLc3b to AT2 Slc39a1-deficient mice did not further aggravate lung injury beyond that caused by either intervention alone. This epistatic relationship places SLC39A1 upstream of autophagy activation within a linear pathway. Collectively, we define an essential role for epithelial SLC39A1 in host defense against ALI/ARDS, which is mediated by a protective zinc-autophagy axis.
2. Dietary intake and BCAA metabolism regulate pulmonary fibrosis through KDM4A-mediated epigenetic remodeling in male mice.
This study links BCAA influx (via SLC7A5) and impaired catabolism to fibroblast activation and lung fibrosis, with KDM4A mediating epigenetic remodeling of fibrotic genes. Inhibiting SLC7A5 or enhancing BCAA catabolism mitigated fibrosis in male mice; patient data connected BCAA dysregulation to disease severity.
Impact: It unveils a metabolic–epigenetic axis (BCAA–KDM4A) controlling fibrogenesis and identifies tractable targets (SLC7A5, KDM4A, catabolic enzymes) with direct therapeutic implications for pulmonary fibrosis.
Clinical Implications: Supports precision antifibrotic strategies targeting amino acid transport (SLC7A5), boosting BCAA catabolism, or inhibiting KDM4A; metabolic biomarkers could stratify patients and monitor response.
Key Findings
- Fibrotic lung fibroblasts show increased BCAA uptake and impaired BCAA catabolism.
- BCAA exposure promotes fibroblast activation and worsens bleomycin-induced fibrosis; BCAT2 loss exacerbates disease.
- SLC7A5 inhibition or enhancing BCAA catabolism attenuates fibrosis in male mice.
- ATF4 and PPARγ regulate SLC7A5 and catabolic gene expression; KDM4A mediates epigenetic regulation of fibrotic genes.
- Patient data link BCAA dysregulation with pulmonary fibrosis severity.
Methodological Strengths
- Integrated mechanistic approach combining transport biology, genetic perturbations (BCAT2), pharmacologic inhibition (SLC7A5), and in vivo fibrosis models.
- Human relevance supported by patient severity correlations.
Limitations
- Preclinical data predominantly in male mice; sex-specific effects and safety of long-term metabolic modulation remain unknown.
- Clinical sample size details and interventional translation to humans are not established.
Future Directions: Evaluate SLC7A5 inhibitors, KDM4A inhibitors, and catabolism enhancers in fibrosis models including females; develop metabolic biomarkers for patient stratification and test combinatorial regimens with approved antifibrotics.
Idiopathic pulmonary fibrosis is a progressive and fatal disorder characterized by abnormal activation of alveolar fibroblasts. However, the metabolic reprogramming of alveolar fibroblasts during lung injury remains unclear. Here we show that uptake of branched-chain amino acids is increased, whereas their catabolism is significantly impaired in fibrotic lung fibroblasts and mouse lung tissues. Branched-chain amino acids promote lung fibroblast activation and bleomycin-induced lung fibrosis. Genetic inactivation of branched-chain amino acid transaminase 2 exacerbates fibrosis, whereas inhibition of the corresponding transporter SLC7A5 or enhancement of catabolism attenuates pulmonary fibrosis in male mice. Mechanistically, ATF4 and PPARγ regulate the expression of SLC7A5 and BCAA catabolic genes, respectively. We identify KDM4A as a key mediator of the epigenetic regulation of fibrotic genes. Notably, dysregulated BCAA metabolism is associated with disease severity in patients, suggesting that targeting BCAA metabolism may serve as a promising therapeutic strategy for idiopathic pulmonary fibrosis.
3. Azurocidin-1 as a mediator of bronchiectasis severity, epithelial defence, and target of dipeptidyl peptidase-1 inhibition: an international, multicohort study.
Across multicohorts, sputum AZU1 tracked bronchiectasis severity (higher BSI, lower FEV1), radiological burden, symptoms, and P. aeruginosa infection and rose during exacerbations. In vitro, AZU1 impaired epithelial ciliary function; in WILLOW, brensocatib markedly reduced AZU1, linking a biomarker to a therapeutic mechanism.
Impact: It provides a clinically actionable biomarker (AZU1) tied to disease biology and modifiable by an approved class therapy (DPP1 inhibition), enabling stratification and pharmacodynamic monitoring in bronchiectasis.
Clinical Implications: AZU1 could support risk stratification, exacerbation monitoring, and serve as a pharmacodynamic readout for DPP1 inhibitors such as brensocatib; it may also guide microbiology-informed management (e.g., P. aeruginosa).
Key Findings
- Higher sputum AZU1 associates with higher BSI, lower %FEV1, greater Reiff score, worse symptoms, and higher exacerbation frequency.
- AZU1 levels are highest with Pseudomonas aeruginosa infection and increase during bacterial/viral exacerbations; related to COPD severity and induced by experimental rhinovirus.
- In vitro, AZU1 impairs ciliary function and epithelial integrity, suggesting pathogenicity.
- Brensocatib (DPP1 inhibitor) significantly and persistently reduced airway AZU1 (WILLOW post-hoc), positioning AZU1 as a modifiable biomarker.
Methodological Strengths
- Convergent evidence from multiple independent cohorts, experimental challenge, in vitro assays, and post-hoc analysis of a randomized trial.
- Clinically meaningful endpoints (FEV1, exacerbations, microbiome) with consistent associations.
Limitations
- Heterogeneous study designs and sample sizes across cohorts; causality in humans is inferred but not proven.
- Post-hoc nature of the WILLOW analysis; standardized AZU1 assay thresholds for clinical use are not established.
Future Directions: Prospective studies validating AZU1 as a stratification and response biomarker; interventional trials integrating AZU1-guided DPP1 inhibition or adjunctive therapies; assay standardization and threshold setting.
BACKGROUND: Dipeptidyl peptidase-1 (DPP1) inhibitors prevent the activation of neutrophil serine proteases and reduce exacerbations in people with bronchiectasis. We previously identified a novel effect of DPP1 inhibitors in reducing the neutrophil pseudoenzyme azurocidin-1 (AZU1). The aim of this study was to investigate the role of AZU1 in the pathophysiology of bronchiectasis. METHODS: Sputum AZU1 concentrations were analysed in multiple cohorts. These consisted of two observational cohorts of patients with bronchiectasis (EMBARC BRIDGE cohort 1 and cohort 2) and a cohort of patients with chronic obstructive pulmonary disease (COPD; TARDIS COPD cohort) to correlate AZU1 with disease severity and exacerbations. A rhinovirus challenge study was used to investigate AZU1 concentrations during experimental exacerbation in COPD, people who smoke, and controls. A post-hoc analysis of the phase 2 WILLOW trial of brensocatib versus placebo was used to assess the effect of DPP1 inhibition on airway AZU1. FINDINGS: Higher AZU1 sputum concentration was associated with increased bronchiectasis disease severity index (p<0·0001), decreased percentage predicted forced expiratory volume in 1 second (r=-0·4662, p<0·001), and increased exacerbation frequency (p<0·0019; EMBARC cohort 1, n=197). AZU1 was associated with radiological severity (Reiff score), symptoms (quality of life bronchiectasis respiratory symptom score), and bacterial infection (sputum microbiology and 16S microbiome alpha diversity; highest levels of AZU1 were found in airway samples with Pseudomonas aeruginosa; p<0·0001; EMBARC cohort 2, n=144). Bronchiectasis patients with bacterial and viral exacerbations had increased concentrations of AZU1 (p=0·0003; n=96). These findings were extended to COPD, in which AZU1 was related to COPD severity (COPD cohort, n=101), and in patients with COPD challenged with rhinovirus A16, AZU1 was increased at day 9 post-challenge (p<0·001; n=9). In-vitro AZU1 impaired ciliary function and epithelial integrity, suggesting a mechanism by which AZU1 drives disease pathogenesis. In a post-hoc analysis of the WILLOW trial, AZU1 was the most downregulated protein with brensocatib treatment (brensocatib 10 mg, n=71; brensocatib 25 mg, n=73; and placebo, n=71). Over 24 weeks, AZU1 was significantly reduced by DPP1 inhibition (p<0·0001). INTERPRETATION: AZU1 was identified as a novel marker of disease severity in bronchiectasis, associated with bacterial infection and exacerbation, and targeted by DPP1 inhibition. FUNDING: EMBARC3 and Insmed.