Lehmann Lab

The immunoproteasome is a specialized type of proteasome involved in MHC class I antigen presentation, antiviral adaptive immunity, autoimmunity, and is also part of a broader response to stress. Whether the immunoproteasome is regulated by DNA stress, however, is not known. We here demonstrate that mitochondrial DNA stress upregulates the immunoproteasome and MHC class I antigen presentation pathway via cGAS/STING/type I interferon signaling resulting in cell autonomous activation of CD8+ T cells. The cGAS/STING-induced adaptive immune response is also observed in response to genomic DNA and is conserved in epithelial and mesenchymal cells of mice and men. In patients with idiopathic pulmonary fibrosis, chronic activation of the cGAS/STING-induced adaptive immune response in aberrant lung epithelial cells concurs with CD8+ T-cell activation in diseased lungs. Genetic depletion of the immunoproteasome and specific immunoproteasome inhibitors counteract DNA stress induced cytotoxic CD8+ T-cell activation. Our data thus unravel cytoplasmic DNA sensing via the cGAS/STING pathway as an activator of the immunoproteasome and CD8+ T cells. This represents a novel potential pathomechanism for pulmonary fibrosis that opens new therapeutic perspectives.

The 9th biennial conference titled "Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases" was hosted virtually, due to the ongoing COVID-19 pandemic, in collaboration with the University of Vermont Larner College of Medicine, the National Heart, Lung, and Blood Institute, the Alpha-1 Foundation, the Cystic Fibrosis Foundation, and the International Society for Cell & Gene Therapy. The event was held from July 12th through 15th, 2021 with a pre-conference workshop held July 9th. As in previous years the objectives remained to review and discuss the status of active research areas involving stem cells, cellular therapeutics, and bioengineering as they relate to the human lung. Topics included: 1) technological advancements in the in situ analysis of lung tissues, 2) new insights into stem cell signalling and plasticity in lung remodelling and regeneration, 3) the impact of extracellular matrix in stem cell regulation and airway engineering in lung regeneration, 4) differentiating and delivering stem cell therapeutics to the lung, 5) regeneration in response to viral infection, and 6) ethical development of cell-based treatments for lung diseases. This selection of topics represents some of the most dynamic and current research areas in lung biology. The virtual workshop included active discussion on state-of-the-art methods relating to the core features of the 2021 conference, including in-situ protemics, lung-on-chip, iPSC-airway differentiation, and light sheet microscopy. The conference concluded with an open discussion to suggest funding priorities and recommendations for future research directions in basic and translational lung biology.

Background and purpose: Emphysema is an incurable disease characterized by loss of lung tissue leading to impaired gas exchange. Wnt/β-catenin signaling is reduced in emphysema and exogenous activation of the pathway in experimental models in vivo and in human ex vivo lung tissue improves lung function and structure. We sought to identify a pharmaceutical able to activate Wnt/β-catenin signaling and asses its potential to activate lung epithelial cells and repair. Experimental approach: We screened 1216 human-approved compounds for Wnt/β-catenin signaling activation using luciferase reporter cells, and selected candidates based on their computational predicted protein targets. We further performed confirmatory luciferase reporter and metabolic activity assays. Finally, we studied the regenerative potential in murine adult epithelial cell derived lung organoids and in vivo using a murine elastase-induced emphysema model. Key results: The primary screen identified 16 compounds that significantly induced Wnt/β-catenin-dependent luciferase activity. Selected compounds activated Wnt/β-catenin signaling without inducing cell toxicity or proliferation. Two compounds were able to promote organoid formation, which was reversed by pharmacological Wnt/β-catenin inhibition, confirming the Wnt β-catenin-dependent mechanism of action. Amlexanox was used for in vivo evaluation and preventive treatment resulted in improved lung function and structure in emphysematous mouse lungs. Moreover, gene expression of Hgf, an important alveolar repair marker, was increased, whereas disease marker Eln was decreased, indicating that amlexanox induces pro-regenerative signaling in emphysema. Conclusion and implications: Using a drug screen based on Wnt/β-catenin activity, organoid assays, and a murine emphysema model, amlexanox was identified as a novel potential therapeutic for emphysema.