SOD-surfactant Liposomes Protect Against Hyperoxic Lung Injury In Rats

Objective: The acute lung injury following cardiopulmonary bypass(CPB) is one of the main causes of serious complications and high mortality . Similarly with hyperoxic lung injury, the effect of oxygen free radical is the most important mechanism. The purpose of this study is to observe the effects of SOD-pulmonary surfactant (SOD-PS) liposomes, superoxide dismutase(SOD), Pulmonary surfactant(PS) and SOD+PS in protecting against hyperoxic lung injury comparatively, so as to explore an efficient method to prevent acute lung injury following CPB. Methods : Forty male Wistar rats were divided into five groups randomly. All the animals were pretreated after, anesthesia: The first group, SOD-PS liposomes (2ml/kg) were administrated by intratracheal injection ; the second group, SOD(8000u/kg) was instilled; the third group , pulmonary surfactant (lml/kg);the forth group, SOD (8000u/kg) plus PS (1ml/kg);the fifth group was control group, received equal volume normal saline .Then all the animals were exposed to normobaric hyperoxia(>95% oxygen) for 60 hours at the same time. Then the rats were killed and explored and the pleural fluid volume were measured. Lung wet-to-dry weight ratios wore calculated after tissue samples were dried for 96 hoursat 60. Tissue was examined by light microscopy and electron-microscopy after it was sectioned and stained . The concentration of TNF-a in bronchoalveolar lavage fluid (BALF) and the concentration of MDA in lung homogenates were investigated as well. Results: The control rats got serious respiratory distress after normobaric hyperoxic exposition; SOD group and PS group rats had light respiration distress; while SOD plus PS group and the SOD-surfactant liposomes group rats had no respiratory distress . Compared with control group , every treated group has less pleural fluid volume, wet-to-dry weight ratios, TNF-a in BALF and MDA in lung homogenates significantly (KO. 01). These data of SOD-PS liposomes group and SOD plus PS group were lower than SOD group or PS group . The pleural fluid volume, wet-to-dry weight ratios, TNF-a in BALF of SOD-PS liposomes group were similar with SOD plus PS group (P>0.05) .while the concentration of MDA in lung homogenates were lower significantly (/<0.01) . Furthermore, the morphometric characters of lung injury, such as edema, capillary congestion, neutrophil infiltration and hyaline membrane formation were lighter in SOD-PS liposomes group. Conclusions : Intratracheal instillation of SOD or PS can lessen hyperoxic lung injury . The effects of SOD-PS liposomes in protecting against hyperoxic lung injury is superior to SOD or PS significantly .So intratracheal instillation of SOD-surfactant liposomes is an ideal method to prevent hyperoxic lung injury or other acute lung injury.