Autism Spectrum Disorder (ASD) is characterized by impairments in social and communicative function and repetitive behaviors. Recent work suggests that oxidative stress (arising from both genetic and environmental causes) is a contributing factor to the neuropathology of ASD. Emerging evidence suggests that increased oxidative stress may contribute to the neuronal and cognitive impairments seen in children with Autism Spectrum Disorder (ASD). Glutathione (GSH) is the main redox compound in the brain, and reduced GSH during development may lead to such increases in oxidative stress and may be a primary cause of secondary neurophysiological impairments in ASD.
GSH can be measured using edited Magnetic Resonance Spectroscopy (MRS). Here, we propose using a new MRS technique (HERMES) to measure GSH in the brain of children with ASD and investigate its relation to functional behavioral measures of autism, and peripheral markers of oxidative stress, work not previously performed. Increased oxidative stress, and associated GSH dysfunction, may be an important contributor to autism-associated alterations in brain development, contributing in turn to cognitive and social impairments common in ASD.
Understanding the role of oxidative stress in ASD is important for understanding the emergence of ASD and offers a promising target for future early interventions to increase GSH concentration in the brain.
The underlying pathophysiology of ASD remains unclear, with a large variety of genetic and environmental factors contributing to development of the disorder. Recent work suggests that oxidative stress (arising from both genetic and environmental causes) may be a contributing factor to the neuropathology of ASD. Studies have revealed increased plasma nitric oxide and decreased plasma levels of antioxidants; however, there has been limited examination of brain measures of oxidative stress. The ‘redox’ hypothesis argues that increased oxidative stress in the brain and reduced clearance of free radicals during brain development lead to neuronal damage, which in turn leads to neurological deficits.
Glutathione (GSH) is the main endogenous redox compound in the brain. As such, it plays a key role in neutralizing reactive oxygen species (ROS) by dimerizing to its oxidized form GSSG, thereby preventing cellular damage. GSH is also involved in the maintenance of other antioxidants, regulation of DNA repair, and regulation of apoptosis. Reduced protection against oxidative stress, e.g. through reduced GSH, has been associated with abnormal inhibitory GABAergic neurotransmission, as well as with cognitive and neurological deficits. Increased oxidative stress, and associated GSH dysfunction, may therefore be an important contributor to autism-associated alterations in brain development, and in turn, to the cognitive and social impairments of ASD.
GSH can be measured in vivo in the human brain using edited Magnetic Resonance Spectroscopy (MRS). Quantification of GSH using conventional MRS methods is problematic due to its low concentration and overlap in the default mode network (also altered in ASD); we have previously shown that metabolic abnormalities in SM1 (reduced GABA levels) are associated with behavioral outcomes in ASD.