PLD2 deficiency alleviates endothelial glycocalyx degradation in LPS-induced ARDS/ALI

Abstract

- Acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) is a life-threatening condition marked by severe lung inflammation and increased lung endothelial barrier permeability. Endothelial glycocalyx deterioration is the primary factor of vascular permeability changes in ARDS/ALI. Although previous studies have shown that phospholipase D2 (PLD2) is closely related to the onset and progression of ARDS/ALI, its role and mechanism in the damage of endothelial cell glycocalyx remains unclear. We used LPS-induced ARDS/ALI mice (in vivo) and LPS-stimulated injury models of EA.hy926 endothelial cells (in vitro). We employed C57BL/6 mice, including wild-type and PLD2 knockout (PLD2−/−) mice, to establish the ARDS/ALI model. We applied immunofluorescence and ELISA to examine changes in syndecan-1 (SDC-1), matrix metalloproteinase-9 (MMP9), inflammatory cytokines (TNF-α, IL-6, and IL-1β) levels and the effect of external factors, such as phosphatidic acid (PA), 1-butanol (a PLD inhibitor), on SDC-1 and MMP9 expression levels. We found that PLD2 deficiency inhibits SDC-1 degradation and MMP9 expression in LPS-induced ARDS/ALI. Externally added PA decreases SDC-1 levels and increases MMP9 in endothelial cells, hence underlining PA's role in SDC-1 degradation. Additionally, PLD2 deficiency decreases the production of inflammatory cytokines (TNF-α, IL-6, and IL-1β) in LPS-induced ARDS/ALI. In summary, these findings suggest that PLD2 deficiency plays a role in inhibiting the inflammatory process and protecting against endothelial glycocalyx injury in LPS-induced ARDS/ALI.