Increased oxidative damage and free radical generation in lymphoblasts from autism

Background: Recent studies have suggested increased oxidative stress in autism.  Most of these studies were done with serum, plasma or erythrocyes. The studies with cell cultures are lacking in autism. Under normal conditions, a dynamic equilibrium exists between the production of free radicals (reactive oxygen species -ROS and reactive nitrogen species- RNS) and the anti-oxidant capacity of the cell. The free radicals are highly reactive, and their elevated levels lead to oxidative/ nitrosative stress and cell death.

Objectives: The aim was to study the status of oxidative/ nitrosative stress in lymphoblasts from autism by analyzing lipid peroxidation, generation of free radicals (ROS/RNS) and extent of membrane damage.

Methods: The lymphoblasts from autistic and control subjects were obtained from Autism Genetic Resources Exchange Program, and the cell lysates were prepared. Lipid peroxidation was assessed by measuring malonyldialdehyde, an end product of fatty acid oxidation. ROS levels (basal and upon induction by Fenton reaction) were determined by using dichlorofluorescin-diacetate (DCFH-DA) as a fluorescent  probe. RNS levels were measured by  nitric oxide fluorometric assay kit. Damage of the plasma membrane was evaluated by measuring the amount of intracellular lactate dehydrogenase (LDH) that was released into the conditioned medium.

Results: Lipid peroxidation was significantly increased in lymphoblasts from autism as compared with control lymphoblasts, suggesting increased oxidative damage in autism. The levels of ROS and RNS were significantly increased in the lymphoblasts from autism as compared with control lymphoblasts, suggesting increased generation of free radicals in autism. LDH leakage was also increased in lymphoblasts of autism as compared with controls, suggesting that membrane integrity is affected in autism.

Conclusions: Autism is associated with increased formation of free radicals (ROS and RNS), which leads to increased oxidative damage and membrane damage.