Effect Of Glycyrrhizic Acid On Vascular Endothelial Function In LPS-induced Acute Lung Injury Model

Objective: To study the regulation of glycyrrhizic acid(GA)on angiotensin converting enzyme 2(ACE2)and E-selectin and VCAM-1 in lipopolysaccharide-induced acute lung injury in mice,and to investigate the possible changes of GA effect on NF-κB signaling pathway and endothelial cell adhesion molecules including E-selectin and VCAM-1 after inhibition of ACE2 in endothelial cells.Methods:(1)In vivo: SPF Balb/c mice were randomly divided into four groups: solvent control group(Control,DMSO+PBS),GA control group(GA),LPS animal model group(LPS),GA pretreatment group(GA+LPS),mice in each group were given GA(200 mg/kg)or solvent with equal volume DMSO(DMSO as GA)pretreatment for 1 hour,intraperitoneal injection of LPS(10 mg/kg)or equal volume PBS.To observe and record the physiological responses of mice,8 hours later,mice were sacrificed,the lung tissue were isolated,and weighted.The lung coefficient of mice(lung coefficient= lung wet weight(g)/ body weight(kg)×100%)was calculated,the slides of lung tissue were underwent Hematoxylin-andeosin(HE)staining and photographed under microscope.Immunohistochemical staining and Western blot were used to detect the expression of ACE2 and cell adhesion molecules that are E-Selectin and VCAM-1.(2)In vitro: Human umbilical vein endothelial cell(HUVEC)were pretreated with GA(100 μg/mL)or equal volume DMSO for 1 hour,and then treated with LPS(1μg/mL)or PBS for 8 hour,the protein was extracted and detected the expression of ACE2,IκB-α,NF-κB,Caveolin-1,E-selectin,VCAM-1 by western blot.Cultured cells were also detected for ACE2,IκB-α,NF-κB,Caveolin-1,E-selectin,VCAM-1 by cellular immunofluorescence.After treatment with ACE2 inhibitor(MLN-4760),the effect of GA on the changes of IκB-α,NF-κB and Caveolin-1,Eselectin,VCAM-1 induced by LPS were also detected by WB and immunofluorescence.Results: 1.GA decreased the lung coefficient and alleviated the edema of lung tissue in LPS-induced acute lung injury model in mice.2.GA alleviated the inhibition of ACE2 in lung tissue of mice with acute lung injury induced by LPS and down-regulated the expression of adhesion molecules that are E-selectin and VCAM-1.3.GA up-regulates the expression of ACE2,decreased the activation of HUVEC NF-κB induced by LPS,reduced the expression of Caveolin-1,adhesion molecules that are E-selectin and VCAM-1,and played a protective role in endothelial cells.Conclusions: 1.GA can alleviate the acute lung injury induced by LPS in mice.2.GA protects damaged endothelial cells by up-regulating the expression of ACE2,inhibiting the activation of NF-κB signaling pathway and reducing the expression of endothelial cell adhesion molecules that are Eselectin and VCAM-1.