The impact of aging on pulmonary microvascular endothelial cell barrier function

Abstract

Elderly individuals have substantially elevated morbidity and mortality during conditions of lung injury. However, the precise underlying mechanisms leading to this elevated mortality are ill-defined. Lung injury is associated with damage to pulmonary microvascular endothelial cells (PMVEC) leading to a compromised vascular barrier, fluid and protein leakage into the tissue, and subsequent respiratory dysfunction. Cell-cell junctions, including adherens junctions and tight junctions, are crucial for the maintenance of the endothelial barrier and have been shown to be dysregulated in various disease models. Pilot data from our lab demonstrated increased pulmonary vascular leak in aged mice during lung injury compared to young mice. We hypothesized that aging contributes to PMVEC barrier dysfunction due to impaired cell-cell junction integrity.To address our hypothesis, PMVEC isolated from young and aged mice were cultured in vitro until a confluent monolayer was formed. Endothelial barrier integrity was assessed by Evans blue-labelled albumin flux across the monolayers, as well as immunofluorescence staining of the adherens junction protein, vascular endothelial (VE)-cadherin, and tight junction protein, claudin-5. Localization of leak in relation to junctional proteins was performed using the fluorescently labelled macromolecule, NeutrAvidin. Proteomics analysis was conducted to identify differentially enriched pathways in young and aged PMVEC.Endothelial monolayers from aged mice exhibited a significant increase in albumin leak associated with augmented VE-cadherin and claudin-5 disruption vs. endothelial monolayers form young mice. Furthermore, NeutrAvidin staining localized to paracellular regions with VE-cadherin discontinuity was increased in PMVEC monolayers from aged mice vs. young mice, suggesting that the junctional disruption in aged PMVEC was directly associated with leak. Proteomics analysis revealed pathways known to be implicated in endothelial barrier dysfunction, including regulation of oxidoreduction and protein processing and trafficking, that were altered in PMVEC from aged mice.In summary, PMVEC from aged mice exhibit compromised barrier function, which is directly associated with impaired cell-cell junction integrity. We will next validate and target protein pathways identified in our proteomics analysis that were dysregulated in aged PMVEC to potentially rescue age-induced barrier dysfunction. These findings may highlight molecular pathways involved in predisposing aged individuals to worsened outcomes during lung injury, which can help in the development of therapeutics. Funded by Lawson Health Research Institute, CIHR, and Western University This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.