Bilirubin Against The Acute Lung Injury In The Formation Mechanism Of Action

Aim To explore the effects of bilirubin on the development of acute lung injury(ALI) in rats and its mechanisms.Methods 40 healthy Wistar rats were randomly divided into four groups: normalgroup(group A), ALI group(group L),bilirubin group(group B) and treatedgroup(group BL) (n=12, for each group). Rats in group L and in group B werepretreated bilirubin for 6 continual days(40mg/kg/d). Rats in group L wereinjected endotoxin(5mg/kg) to make ALI models and in group BL the rats wereinjected endotoxin 1 hour after last pretreated of bilirubin. The rats weresacrificed two hours after the LPS injection. Pathological examination wasperformed and the contents of OH^-,H₂O₂,O^-₂ and MDA were detected in thehomogemate of the lungs . The activity of MPO in the lungs was also detected.And the activity of Caspase3 was investigated by immunochemistry. Results Ingroup L, interstitial edema with massive infiltration of the inflammatory cells wasobserved. In group BL, infiltration of inflammatory cells and edema decreased.Both alveoli and alveolar septum appeared normal in size and shape in group Nand group B.Contents of OH^-,H₂O₂,O^-₂ and MDA in the homogenate of thelungs in group L was higher than those in group N (P<0.05). In group BL, theywere lower than those in group L (P<0.05), but was higher compared with groupN (P<0.05). They were similar in the group B with those in group N. Activityof MPO and Caspase3 in the lungs in group L (59.7±5.1) was higher than those ingroup N (P<0.05). In group BL, they decreased significantly compared withgroup L (P<0.05), but higher than those in group N (P<0.05). They were similarin the group B with those in group N. Conclusions Bilirubin was shown to beable to ameliorate apoptosis in ALI rats. The increasing of the content or activityof OH^-,H₂O₂,O^-₂ ,MPO and MDA in group L indicating the infiltration ofpolymorphonuclear neutrophils and the development of oxidative lung injury.Histopathological and immunohistochemical assessment also confirmed that themodel of CLP used here substantially injured lung tissue, which was associatednot only with necrosis but with apoptosis as well.