Protective effects of liposome-entrapped superoxide dismutase on posttraumatic brain edema

Oxygen‐derived free radicals and membrane lipid peroxidation have been postulated to be involved in brain edema and cell death, secondary to ischemia and traumatic injury. Using a model of brain edema induced by cold‐induced injury, we have demonstrated an early elevation of superoxide radicals followed by permeability changes in the blood‐‐brain barrier and development of edema in injured brain. Intravenous injection of liposome‐entrapped copper‐zinc‐‐superoxide dismutase 5 minutes before the injury‐enhanced entry of the enzyme into endothelial cells of the blood‐‐brain barrier of injured brain reduced the brain level of superoxide radicals and ameliorated blood‐‐brain barrier permeability changes and brain edema. Identical treatment 5 minutes after injury was also effective. These data demonstrate that superoxide radicals play an important role in the delayed development of vasogenic brain edema following brain injury.