Silencing Angiopoietin‐Like Protein 4 (ANGPTL4) Protects Against Lipopolysaccharide‐Induced Acute Lung Injury Via Regulating SIRT1 /NF‐kB Pathway

Lung inflammation and alveolar epithelial cell death are critical events in the development and progression of acute lung injury (ALI). Although angiopoietin-like protein 4 (ANGPTL4) participates in inflammation, whether it plays important roles in ALI and alveolar epithelial cell inflammatory injury remains unclear. We therefore investigated the role of angptl4 in lipopolysaccharide (LPS)-induced ALI and the associated mechanisms. Lentivirus-mediated short interfering RNA targeted to the mouse angptl4 gene (AngsiRNA) and a negative control lentivirus (NCsiRNA) were intranasally administered to mice. Lung inflammatory injury and the underlying mechanisms for regulation of angptl4 on the LPS-induced ALI were subsequently determined. We reported that angptl4 levels were increased both in human alveolar epithelial A549 cells and lung tissues obtained from a mouse model of LPS-induced ALI. Angptl4 expression was induced by LPS in alveolar epithelial cells, whereas LPS-induced lung inflammation (neutrophils infiltration in the lung tissues, tumor necrosis factor α, interleukin 6), lung permeability (lung wet/dry weight ratio and bronchoalveolar lavage fluid (BALF) protein concentration), tissue damage (caspase3 activation), and mortality rates were attenuated in AngsiRNA-treated mice. The inflammatory reaction (tumor necrosis factor α, interleukin 6) and apoptosis rates were reduced in AngsiRNA(h)-treated A549 cells. Moreover, angptl4 promoted NF-kBp65 expression and suppressed SIRT1 expression both in mouse lungs and A549 cells. Additionally, SIRT1 antagonist nicotinamide (NAM) attenuated the inhibitory effects of AngsiRNA both on LPS-induced NF-kBp65 expression and IL6 expression. These findings suggest that silencing angptl4 protects against LPS-induced ALI via regulating SIRT1/NF-kB signaling pathway.