POLYETHYLENE GLYCOL-CONJUGATED SUPEROXIDE-DISMUTASE ATTENUATES SEPTIC LUNG INJURY IN GUINEA-PIGS

Reactive oxygen species (ROS), including superoxide anions, play an important role in mediating acute lung injury. We examined whether polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) attenuates lung injury in Escherichia coli-treated guinea pigs. Twenty-four guinea pigs were divided into four groups: (1) control group; (2) septic group, in which live E. coli (2 x 10(9)/kg) were injected intravenously; (3) pretreatment group, in which PEG-SOD (2,000 IU/kg) was injected intravenously 15 min before E. coli; and (4) posttreatment group, in which PEG-SOD (2,000 IU/kg) was injected intravenously 30 min after E. coli. Lung injury was assessed by the concentration ratio of I-125-labeled albumin in lung tissue and bronchoalveolar lavage (BAL) fluid relative to plasma (L/P and BAL/P), lung wet-to-dry weight ratio, and the number of neutrophils in BAL fluid. Plasma half-life of PEG-SOD in normal guinea pigs was 13.5 h. L/P, lung wet-to-dry weight ratio, and the number of neutrophils in BAL fluid decreased in both pretreatment and posttreatment groups compared with the septic group. BAL/P decreased in the pretreatment group but not in the posttreatment group compared with the septic group. After the animal model studies, we investigated the effect of PEG-SOD on the human neutrophil extracellular generation of ROS stimulated by phorbol myristate acetate (PMA) in lucigenin-dependent chemiluminescence (CL). PEG-SOD at concentrations greater-than-or-equal-to 0.1 U/ml inhibited PMA-induced CL in a dose-dependent manner. We also examined the effect of PEG-SOD on the neutrophil intracellular generation of ROS using flow cytometry to assess intracellular hydroethidine oxidation. PEG-SOD at concentrations of 10 and 100 U/ml reduced the fluorescence caused by hydroethidine oxidation in neutrophils stimulated by PMA. These results suggest that (1) pretreatment and posttreatment with PEG-SOD attenuated septic lung injury in guinea pigs; (2) PEG-SOD inhibited the extracellular generation of ROS in PMA-stimulated neutrophils; and (3) PEG-SOD reduced the intracellular generation of ROS in PMA-stimulated neutrophils.