Role of p38MAPK pathway in protective effect of remifentanil or ischemic preconditioning against hepatic ischemia-reperfusion injury in rats

Objective To investigate the role of p38 mitogen-activated protein kinase (p38MAPK) pathway in the protective effect of remifentanil or ischemic preconditioning (IPC) against hepatic ischemia-reperfusion (I/R) injury in rats.Methods One hundred and forty-four male SD rats,weighing 200-250 g,were randomly assigned into 6 group ( n =24 each):sham operation group (group S),I/R group,remifentanil group (group R),IPC group,SB203580 (a specific p38MAPK inhibitor) + remifentanil group (group SB + R),and SB + IPC group.The animals were anesthetized with intraperitoneal 20％ urethane 1 mg/kg.Partial liver ischemia was produced by clamping the hepatic pedicle supplying left lobe and middle lobe for 30 min,followed by 120 min reperfusion.In group R,remifentanil was infused intravenously at 2μg· kg- 1 · min- 1 starting from 30 min before ischemia until the end of reperfusion.In IPC group,the rats were subjected to 3 episodes of 5 min ischemia at 5 min intervals before I/R.SB203580 0.2 mg/kg was injected intravenously at 5 min before remifentanil infusion or IPC in groups SB + R and SB + IPC,and the equal volume of normal saline was given in the other groups.Six rats in each group were selected at 30,60,90 and 120 min of reperfusion and venous blood samples were taken from inferior vena cava for measurement of serum ALT and AST activities and concentrations of TNF-a and 1L-1β.The rats were then sacrificed and liver tissues were taken for microscopic examination and determination of phosphor-p38MAPK expression by Western blot.Results Compared with group S,serum AST and ALT activities and serum levels of TNF-α and IL-1β were significantly increased at each time point (P ＜ 0.05) and pathological injury was aggravated in group I/R.Compared with group I/R,serum AST and ALT activities and serum levels of TNF-a and IL-lβ were significantly decreased and phosphor-p38MAPK expression was up-regulated at 90 min of reperfusion in groups R and IPC ( P ＜ 0.05).The serum AST and ALT activities and serum levels of TNF-α and IL-1β were significantly increased,phosphor-p38MAPK expression was down-regulated at 90 min of reperfusion ( P ＜ 0.05),and pathological injury was aggravated in group SB + R compared with group R,and in group SB + IPC compared with group IPC.Conclusion Activation of p38MAPK pathway and inhibition of inflammatory response may be involved in the mechanism by which remifentanil or IPC reduces the hepatic I/R injury in rats. Key words: p38 mitogen-activated protein kinases; Piperidines; Ischemic preconditioning; Reperfusion injury; Liver