Alterations in the activities of antioxidant enzymes in lymphoblasts from autism

Background: Recent evidence suggests that autistic subjects are under oxidative stress. Antioxidants enzymes scavenge the free radicals and play vital role in the intracellular defense mechanism against oxidative damage. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) are the primary enzymes involved in direct elimination of reactive oxygen species (free radicals), while glutathione reductase (GR) is a secondary antioxidant enzyme, which helps in maintaining a steady concentration of glutathione (GSH). GSH is the most important antioxidant for detoxification and elimination of environmental toxins. SOD protects from the damage caused by superoxide by catalyzing its conversion into hydrogen peroxide and oxygen, while CAT converts hydrogen peroxide to water and molecular oxygen, thereby reducing the amount of hydroxyl radical. GPx removes hydrogen peroxide in the presence of GSH.

Objectives: To understand the mechanism of oxidative stress in autism, the activities of antioxidant enzymes SOD, CAT, GPx and GR were analyzed in the lymphoblasts from autism and control subjects.

Methods: Cell lysates were prepared from lymphoblasts (control and autistic). SOD activity was measured by using assay kit from Calbiochem. CAT activity was measured spectrophotometrically by analyzing complex of ammonium molybdate with H₂O₂.  Measurement of GPx activity was based on the oxidation of GSH to oxidized glutathione (GSSG) catalyzed by GPx. Activity of GR was measured by the method based on the reduction of GSSH by NADPH.

Results: Activites of SOD, CAT, GPx and GR were reduced in lymphoblasts from autism as compared with control lymphoblasts.

Conclusions: The activities of antioxidant enzymes SOD, CAT, GPx and GR are decreased in autism, suggesting that defense mechanism against oxidative damage is impaired in autism. Reduced antioxidant capacity of the cell will lead to increased oxidative damage in autism.