17 Sep 1998

Mutations in the enzyme for superoxide dismutase (SOD1) have been linked to 15 to 20 percent of cases of amyotrophic lateral sclerosis (ALS), leading to a theory that the disease results when the defective enzyme allows super oxide radicals to build up to damaging levels and killing motor neurons and resulting in paralysis. New findings reported in tomorrow's issue of Science, however, cast doubt on this idea. L.I. Bruijn and colleagues decided to test the theory by studying the effects of eliminating or raising levels of normal SOD1 in mice. They found that, contrary to what the theory predicts, manipulating SOD1 levels had no effect. The finding casts doubt on the idea that nerve cell death in ALS arises from oxidative stress tied to abnormal SOD1, the authors say. Their work suggests that drugs designed to scavenge oxygen radicals are unlikely to help patients with ALS.—June Kinoshita