Role of interleukin-18 in experimental severe acute pancreatitis complicated with lung injury

Background Interleukin(IL)-18 is newly discovered proinflammatory cytokine,the serum level of IL-18 is closely associated with the severity and extrapancreatic organ dysfunction in acute pancreatitis(AP),however,few studies have focused on its changes and significance in lung injury in this disease.Aims To observe the expression of IL-18 in rat lung tissue from severe acute pancreatitis(SAP),and to evaluate the role of IL-18 in SAP with lung injury.Methods A rat model of SAP was induced in Sprague-Dawley rat by retrograde infusion of 4%sodium taurocholate into the biliary-pancreatic duct.Thirty-two rats were randomly divided into four groups:health control group(HC),SAP 6 h,SAP 12 h and SAP 18 h groups.The level of serum amylase,wet-dry ratio of lung weight was measured.The expression and distribution of IL-18 in lung tissue were measured by immunohistochemistry and Western blotting.Result The levels of serum amylase, wet-dry ratio of lung weight was significantly increased in the 6h,12h and 18h SAP groups compared with those in control group(P0.01).The histopathological injuries of pancreatic and lung tissues were gradually aggravating along with the time extension in different SAP groups.The expression of inactive and mature IL18 protein in lung detected by Western blotting and immunohistochemistry was significantly increased in pulmonary macrophage in all SAP groups.Conclusions Pulmonary macrophage are the main source of IL-18, IL-18 may play a pivotal role in the pathogenesis of SAP complicated with lung injury.