Gene Transfer of Extracellular Superoxide Dismutase Increases Superoxide Dismutase Activity in Cerebrospinal Fluid

Abstract
Background and Purpose —Copper-zinc superoxide dismutase (CuZnSOD) is expressed intracellularly, while extracellular SOD (EC-SOD) is released from cells. The purpose of this study was to determine whether gene transfer of CuZnSOD increases SOD activity predominantly in tissues, and gene transfer of EC-SOD increases SOD activity in cerebrospinal fluid (CSF). We also determined whether heparin or dextran sulfate releases EC-SOD into CSF. Methods —We injected recombinant adenoviruses expressing EC-SOD (AdEC-SOD), CuZnSOD (AdCuZnSOD), or β-galactosidase (Adβ-gal) into the cisterna magna of rabbits. Results —Total SOD activity in CSF was 39±11 U/mL (mean±SE) before virus injection. Three days later, total SOD activity in CSF increased to 148±22 U/mL after AdEC-SOD and 92±10 U/mL after AdCuZnSOD ( P Conclusions —We have developed a method for intracranial gene transfer of CuZnSOD and EC-SOD. After gene transfer, CuZnSOD was expressed mainly in tissues, and EC-SOD was released into the CSF, especially after injection of heparin or dextran sulfate. Gene transfer of different isoforms of SOD may be useful in studies of cerebral vascular physiology and pathophysiology.

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