Effects of hypoxia on bronchial and alveolar epithelial cells linked to pathogenesis in chronic lung disorders

Rebecca Berggren-Nylund; Martin Ryde; Anna Löfdahl; Arturo Ibáñez-Fonseca; Monica Kåredal; Gunilla Westergren-Thorsson; Ellen Tufvesson; Anna-Karin Larsson-Callerfelt

doi:10.3389/fphys.2023.1094245

Effects of hypoxia on bronchial and alveolar epithelial cells linked to pathogenesis in chronic lung disorders

Front Physiol. 2023 Mar 13:14:1094245. doi: 10.3389/fphys.2023.1094245. eCollection 2023.

Authors

Rebecca Berggren-Nylund¹, Martin Ryde², Anna Löfdahl¹, Arturo Ibáñez-Fonseca¹, Monica Kåredal³, Gunilla Westergren-Thorsson¹, Ellen Tufvesson², Anna-Karin Larsson-Callerfelt¹

Affiliations

¹ Lung Biology, Department of Experimental Medical Science, Lund University, Lund, Sweden.
² Respiratory Medicine, Allergology and Palliative Medicine, Department of Clinical Sciences Lund, Lund University, Lund, Sweden.
³ Division of Occupational and Environmental Medicine, Lund University, Lund, Sweden.

Abstract

Introduction: Chronic lung disorders involve pathological alterations in the lung tissue with hypoxia as a consequence. Hypoxia may influence the release of inflammatory mediators and growth factors including vascular endothelial growth factor (VEGF) and prostaglandin (PG)E₂. The aim of this work was to investigate how hypoxia affects human lung epithelial cells in combination with profibrotic stimuli and its correlation to pathogenesis. Methods: Human bronchial (BEAS-2B) and alveolar (hAELVi) epithelial cells were exposed to either hypoxia (1% O₂) or normoxia (21% O₂) during 24 h, with or without transforming growth factor (TGF)-β1. mRNA expression of genes and proteins related to disease pathology were analysed with qPCR, ELISA or immunocytochemistry. Alterations in cell viability and metabolic activity were determined. Results: In BEAS-2B and hAELVi, hypoxia significantly dowregulated genes related to fibrosis, mitochondrial stress, oxidative stress, apoptosis and inflammation whereas VEGF receptor 2 increased. Hypoxia increased the expression of Tenascin-C, whereas both hypoxia and TGF-β1 stimuli increased the release of VEGF, IL-6, IL-8 and MCP-1 in BEAS-2B. In hAELVi, hypoxia reduced the release of fibroblast growth factor, epidermal growth factor, PGE₂, IL-6 and IL-8, whereas TGF-β1 stimulus significantly increased the release of PGE₂ and IL-6. TGF-β1 stimulated BEAS-2B cells showed a decreased release of VEGF-A and IL-8, while TGF-β1 stimulated hAELVi cells showed a decreased release of PGE₂ and IL-8 during hypoxia compared to normoxia. Metabolic activity was significantly increased by hypoxia in both epithelial cell types. Discussion: In conclusion, our data indicate that bronchial and alveolar epithelial cells respond differently to hypoxia and profibrotic stimuli. The bronchial epithelium appears more responsive to changes in oxygen levels and remodelling processes compared to the alveoli, suggesting that hypoxia may be a driver of pathogenesis in chronic lung disorders.

Keywords: BEAS-2B; fibrosis; growth factors; hAELVi; hypoxia; inflammation; lung epithelium.

Grants and funding

This work was supported by the Swedish Heart-Lung foundation (2020/0847, 2021/0382, and 2022/0847); Lund University Medical Faculty, Lund University library to cover the APC, Birgit and Sven Håkan Ohlsson Foundation, the Crafoord foundation (grant number 20200989 and 20221034) and Alfred Österlund foundation. Part of this work was also funded by the EMPIR 18HLT02 AeroTox project. The EMPIR program is co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation program. We are also grateful to the Fundación Ramón Areces (Spain; grant number BEVP33S12276) for the funding for AI-F postdoctoral position.