Protective Role of Extracellular Superoxide Dismutase in Hemodialysis Patients

Background: The superoxide anion and other oxygen radicals have been implicated in the progression of chronic renal failure, and are removed by extracellular superoxide dismutase (EC-SOD) in the extracellular space on the surface of the endothelium. A single-base substitution of the EC-SOD gene which reduces the binding capability to endothelial cells resulting in an increased serum concentration, has been identified in healthy persons and hemodialysis patients.

Results: The proportion of patients with this mutation among hemodialysis patients in each 20 months' duration after the initiation of hemodialysis was retrospectively studied. The percentage of substitution-positive patients declined 80 months after the start of hemodialysis in non-DM patients. In contrast, in DM patients, the rapid decrease was obvious as early as 40 months after the initiation of hemodialysis. By prospective study for 5 years, there were significant differences in the survival rate between patients with and without R213G in DM, but not in non-DM patients. Among those who died, the incidence of ischemic heart disease and cerebrovascular disease in cases with R213G was significantly higher than in cases without R213G.

Conclusion: These results suggest that the presence of a substitution in the EC-SOD gene at the heparin-binding domain could be a prognostic marker of dialysis patients.