Dysregulated Antioxidant Network and Increased iNOS Signaling in Platelets of Children with Autism Spectrum Disorder

Abstract

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by the significant involvement of both environmental and immunological factors. The pathophysiology of ASD has been linked to dysregulation of the antioxidant network and production of oxidants in immune cells. Previous studies have demonstrated disequilibrium in different enzymatic antioxidants in the plasma, red blood cells, and leukocytes of individuals with ASD; however, there has been no investigation thus far into the evaluation of these antioxidants in peripheral platelets in both individuals with ASD and typically developing control (TDC) children. Methods: Given this context, we investigated the levels and functions of key enzymatic antioxidants in peripheral platelets of TDC (n = 23)/ASD (n = 26) individuals, including superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and thioredoxin reductase (TRxR) through flow cytometric and enzymatic activity analyses. Further, levels of oxidative stress were evaluated by analysis of inducible nitric oxide synthase (iNOS) and nitrotyrosine formation in the platelets of both groups. Results: Our findings reveal a marked reduction in SOD1 (p < 0.0001) and TRxR1 (p < 0.01) expression in the platelets of ASD individuals, as evidenced by diminished SOD1+ and TRxR1+ immunostaining in CD42+ cells. SOD (p < 0.01) and TRxR (p < 0.01) activity were also significantly lower in ASD participants compared to the TDC group. In contrast, when comparing individuals with ASD to TDC group, GPx/GR activity/expression in platelets is either decreased or unaffected. A notable increase in iNOS (p < 0.0001) coupled with reduced SOD/TRxR activity in ASD platelets correlated with a significant rise in nitrotyrosine expression (p < 0.001), indicative of oxidant damage. Conclusions: Our findings demonstrate, for the first time, that ASD individuals have a disrupted enzymatic antioxidant system and heightened oxidative stress in their peripheral platelets. This imbalance in enzymatic antioxidants may significantly impact the development of ASD and its associated comorbidities.