The molecular mechanism of angiotensin-converting enzyme 2 alleviating hepatocyte inflammation / 中华急诊医学杂志

ABSTRACT

Objective To observe the protective mechanism of angiotensin-converting enzyme (ACE) 2 on lipopolysaccharide (LPS)-induced hepatocyte inflammation by inhibiting P38 mitogen activated protein kinase (MAPK)/activator protein (AP)-1 pathway.Methods Rat liver BRL cells after immortalized culture were randomly divided into five kinds of groupscontrol group,LPS (10 μg/ mL) group,LPS + recombinant(r) ACE2 (5,10,20 ng/mL rACE2 for 30 min before cells stimulated with LPS) groups,LPS+ACE2 inhibitor MLN-4760 (10-7,10-6,105 mmol/L MLN-4760 for 30 min before cells stimulated with LPS) groups,LPS + rACE2 (20 ng/mL rACE2 for 30 min before cells stimulated with LPS) + P38MAPK inhibitor SB203580 (10-5 mmol/L SB203580 for 30 min before cells stimulated with LPS) groups.The changes in protein levels of ACE2,P38MAPK,p-P38MAPK and AP-1 were detected by western blot after LPS exposure for 6,12 and 24 hours,and the mRNA expressions of P38MAPK,AP-1 and tumor necrosis factor-α were quantified by real-time RT-PCR.Results Compared with control group,the protein levels of ACE2,P38MAPK and AP-1 were up-regulated in LPS-induced hepatic cells in a time-dependent manner,peaking at 12 h after LPS stimulation (all P＜0.05).Compared with LPS group,the mRNA expressions ofAP-l,P38MAPK,p-P38MAPK and tumor necrosis factor-oα decreased significantly in rACE2 group (all P＜0.05).The dose of 20 ng/mL rACE2 had the best inhibitory effects on the mRNA expression of AP-1 (0.12±0.002 vs.0.04±0.005,P＜0.01),P38MAPK (0.17±0.02 vs.0.02±0.002,P＜0.01) and p-P38MAPK(0.29±0.01 vs.0.02±0.01,P＜0.01)compared with LPS group.The mRNA expressions of AP-1,P38MAPK and p-P38MAPK increased in MLN-4760 group in a concentration dependent manner (all P＜0.05).Furthermore,the inhibitory effects of rACE2 on AP-1 and tumor necrosis factor-α levels were cancelled by SB203580.Conclusion The rACE2 can alleviate the LPS-induced hepatocyte injury by down regulating the P38MAPK/AP-1 signaling pathway.