Deletion of PLD2 Alleviates LPS Induced Acute Lung Injury by Inhibiting STAT3 Phosphorylation and Regulating Endothelial Tight Junctions

Abstract

Background: Acute respiratory distress syndrome (ARDS) is the leading cause of acute respiratory failure. Endothelial cell damage and increased permeability are critical in developing acute lung injury (ALI). Phospholipase D2 (PLD2) and its metabolite phosphatidic acid (PA) regulate many physiological activities in cells, disrupting cell barrier integrity. However, the exact mechanism remains unexplored. Therefore, we elucidated the role and action mechanism of PLD2 in lipopolysaccharide (LPS)-induced endothelial cell integrity.Methods: We used wild-type (WT) and PLD2 knockout (PLD2-/-) mouse models of LPS-induced ALI. Altered pulmonary endothelial permeability was assessed using histopathological analysis. The relative permeability of the pulmonary vascular endothelial cell culture model was assessed using transwell chamber assays for FITC-dextran and TEER transcellular resistance. The PA content, a downstream product of PLD2, was detected using ELISA, and the mRNA expression of tight junction proteins was detected by real-time quantitative polymerase chain reaction (RT-PCR). Changes in tight junction protein levels and STAT3 pathway phosphorylation, a critical endothelial barrier component, were assessed using immunofluorescence and western blotting analyses in vivo and in vitro.Results: PLD2-/- could significantly improve the histopathological changes, lung wet-dry ratio, and endothelial cell permeability in LPS-induced ALI mice. Simultaneously, PLD2-/- could reduce PA-induced STAT3 phosphorylation, resulting in reduced endothelial tight junction degradation.Conclusion: Loss or inhibition of PLD2 significantly inhibits tight junction injury and alleviates lung injury. LPS-induced PA production leads to STAT3 pathway phosphorylation and tight junction protein targeting, resulting in increased barrier permeability. Collectively, PA is crucial in ARDS pathogenesis.