Impaired AMPK Control of Alveolar Epithelial Cell Metabolism Promotes Pulmonary Fibrosis
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ABSTRACT:
ORGANISM(S): Mus musculus Homo sapiens
PROVIDER: GSE296513 | GEO | 2025/06/24
REPOSITORIES: GEO
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Project description:Acute inflammatory exacerbations (AIEs) represent immune-driven deteriorations of many chronic lung conditions, including COPD, asthma, and pulmonary fibrosis (PF). The first line of therapy is represented by broad-spectrum immunomodulation. Among the several inflammatory populations mobilizing during AIEs, eosinophils have been identified as promising indicators of an active inflammatory exacerbation. To better study the eosinophil-parenchymal crosstalk during AIE-PF, this work leverages a clinically relevant model of inflammatory exacerbations triggered by mutation in the alveolar epithelial type 2 cell Surfactant Protein-C gene [SP-CI73T]. Unbiased single-cell sequencing analysis of controls and SP-CI73T mutants at a time coordinated with peak eosinophilia (14 d) defined heightened inflammatory activation, chemotaxis, and survival signaling (IL-6, IL-4/13, STAT3, Glucocorticoid Receptor, mTOR, and MYC) in eosinophils. To study the impact of eosinophils in inflammatory exacerbations, the SP-CI73T line was crossed with eosinophil lineage deficient mice (GATA1Δdbl, SP-CI73TGATA1KO). Time course analysis (7-42 d) demonstrated improved lung histology, survival, and reduced inflammation in SP-CI73TGATA1KO cohorts. Spectral flow cytometry of tissue digests confirmed eosinophil depletion in GATA1KO mice and the absence of a compensatory shift in neutrophils and immature monocyte recruitment. Eosinophil deletion was seen to boost accumulation of total monocyte-derived macrophages, 14 d post-injury, while declines in CD3+CD4+ lymphocyte abundance observed during SP-CI73T-induced injury were limited in SP-CI73TGATA1KO mice. Histochemical analysis 14 d post-injury revealed atypical inflammatory cell activation in SP-CI73TGATA1KO mice, with reduced numbers of Arg-1+ and iNOS+ cells, but increases in mcp1 and tgfb1 mRNA expression in BAL cells and tissue. To study corticosteroid efficacy in highly eosinophilic exacerbations, SP-CI73T mice received dexamethasone (1 mg/kg daily, i.p) starting 5 d post-induction. Dexamethasone successfully reduced total and eosinophil (CD11b+SigF+CD11c-) counts at 14 d and was linked to reduced evidence of structural damage and perivascular infiltrate. Together, these results illustrate the deleterious role of eosinophils in inflammatory events preceding lung fibrosis and demonstrate the efficacy of corticosteroid treatment in highly eosinophilic exacerbations induced by mutant SP-CI73T.
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Project description:Idiopathic pulmonary fibrosis (IPF) is an age-related interstitial lung disease, characterized by inadequate alveolar regeneration and ectopic bronchiolization. While some molecular pathways regulating lung progenitor cells have been described, the role of metabolic pathways in alveolar regeneration is poorly understood. We report that expression of fatty acid oxidation (FAO) genes significantly diminishes in alveolar epithelial cells of IPF lungs by single-cell RNA sequencing and tissue staining. Genetic and pharmacological inhibition in AT2 cells of carnitine palmitoyltransferase 1a (CPT1a), the rate-limiting enzyme of FAO, promoted mitochondrial dysfunction and acquisition of aberrant intermediate states expressing basaloid, and airway secretory cell markers SCGB1A1, and SCGB3A2. Further, mice with deficiency of CPT1a in AT2 cells show enhanced susceptibility to developing lung fibrosis with an accumulation of epithelial cells expressing markers of intermediate cells, airway secretory cells, and senescence. We found that deficiency of CPT1a causes a decrease in SMAD7 protein levels and TGF-β signaling pathway activation. These findings suggest that the mitochondrial FAO metabolic pathway contributes to the regulation of lung progenitor cell repair responses and deficiency of FAO contributes to aberrant lung repair and the development of lung fibrosis.
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Project description:Idiopathic pulmonary fibrosis (IPF) is an age-related interstitial lung disease, characterized by inadequate alveolar regeneration and ectopic bronchiolization. While some molecular pathways regulating lung progenitor cells have been described, the role of metabolic pathways in alveolar regeneration is poorly understood. We report that expression of fatty acid oxidation (FAO) genes significantly diminishes in alveolar epithelial cells of IPF lungs by single-cell RNA sequencing and tissue staining. Genetic and pharmacological inhibition in AT2 cells of carnitine palmitoyltransferase 1a (CPT1a), the rate-limiting enzyme of FAO, promoted mitochondrial dysfunction and acquisition of aberrant intermediate states expressing basaloid, and airway secretory cell markers SCGB1A1, and SCGB3A2. Further, mice with deficiency of CPT1a in AT2 cells show enhanced susceptibility to developing lung fibrosis with an accumulation of epithelial cells expressing markers of intermediate cells, airway secretory cells, and senescence. We found that deficiency of CPT1a causes a decrease in SMAD7 protein levels and TGF-β signaling pathway activation. These findings suggest that the mitochondrial FAO metabolic pathway contributes to the regulation of lung progenitor cell repair responses and deficiency of FAO contributes to aberrant lung repair and the development of lung fibrosis.
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Project description:Idiopathic pulmonary fibrosis (IPF) is an age-related interstitial lung disease, characterized by inadequate alveolar regeneration and ectopic bronchiolization. While some molecular pathways regulating lung progenitor cells have been described, the role of metabolic pathways in alveolar regeneration is poorly understood. We report that expression of fatty acid oxidation (FAO) genes significantly diminishes in alveolar epithelial cells of IPF lungs by single-cell RNA sequencing and tissue staining. Genetic and pharmacological inhibition in AT2 cells of carnitine palmitoyltransferase 1a (CPT1a), the rate-limiting enzyme of FAO, promoted mitochondrial dysfunction and acquisition of aberrant intermediate states expressing basaloid, and airway secretory cell markers SCGB1A1, and SCGB3A2. Further, mice with deficiency of CPT1a in AT2 cells show enhanced susceptibility to developing lung fibrosis with an accumulation of epithelial cells expressing markers of intermediate cells, airway secretory cells, and senescence. We found that deficiency of CPT1a causes a decrease in SMAD7 protein levels and TGF-β signaling pathway activation. These findings suggest that the mitochondrial FAO metabolic pathway contributes to the regulation of lung progenitor cell repair responses and deficiency of FAO contributes to aberrant lung repair and the development of lung fibrosis.
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Project description:Mutation in the alveolar epithelial type 2 cell Surfactant Protein-C gene [SP-CI73T] is associated with pulmonary fibrosis (PF). We have previously demonstrated that inducible expression of the most common PF-linked mutation in the SP-C gene triggers inflammatory exacerbations of lung injury, progressing to fibrosis. We used single-cell sequencing to define the phenotype of epithelial, endothelial, immune and stromal cells accumulating in the lung at a time coordinated with peak injury (14 d post induction) and fibrotic remodeling (42 d post induction). The analysis showed at least 7 phenotypically distinct clusters of monocytes/macrophages during injury. Of these clusters, three exhibited distinctive pro-fibrotic signatures, based on expression of the prototypical markers TGFb1, osteopontin/SPP1 and fibronectin1. Notably SPP1+ cells expressed the highest levels of complement (C1qa, b, and c) and lipid associated genes (apoliporproteinE/ApoE, Cd36, Marco, Ldlr, Lrp1). We then set aim to examine the role of ApoE in inflammatory cell activation by crossing the SP-CI73T line with ApoE knock out mice. Mice heterozygous and homozygous for mutant ApoE were included to this analysis (both 14 and 42 da post injury). Survival analysis demonstrate unchanged inflammatory cell composition, but flow cytometric analysis noted a shift in myeloid (neutrophil and eosinophil) and lymphoid (B cells) cell recruitment in the ApoE mutant mice. Together, these results demonstrate time related changes in monocyte/macrophage dynamics and supports the notion that lipid homeostasis may be involved in their pro-fibrotic activation.
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Project description:Hermansky-Pudlak syndrome (HPS) is a genetic disorder of intracellular endosomal trafficking defects associated with pulmonary fibrosis. Double mutant HPS1/2 mice exhibit spontaneous fibrosis and single mutant HPS1 and HPS2 mice display increased fibrotic sensitivity. To identify mechanisms of AT2 cell dysfunction contributing to fibrosis in HPS, we examined lungs from aged HPS1/2 mice and observed regions of AT2 cell loss adjacent to areas of marked AT2 cell hyperplasia as compared to wild type (WT). Overall, there was accelerated loss of AT2 cells in HPS1/2, HPS1, and HPS2 mice with aging based on immunohistochemistry and lineage tracing studies. Lung organoids generated with HPS2 AT2 cells with WT fibroblasts were smaller in size and displayed significantly decreased colony forming efficiency compared to organoids with WT AT2 cells. Utilizing an H1N1 PR8 influenza model to examine AT2 cell regeneration after injury, there was a significant decrease in the percentage of proliferating AT2 cells in HPS1 and HPS2 mice compared to WT mice. RNA sequencing of AT2 cells isolated from unchallenged mice demonstrated upregulation of genes associated with proliferation and cellular senescence in HPS AT2 cells. Collectively, AT2 cells in HPS mice exhibit dysregulated proliferation with transcriptomic features suggesting subpopulations of senescent and hyperproliferative cells. Dysregulated maintenance of the alveolar epithelium with accelerated senescence and aberrant proliferation of AT2 cells appears to be a shared pathway underlying HPS and other sporadic and genetic forms of pulmonary fibrosis.
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