S3I-201, a selective Stat3 inhibitor, restores neuroimmune function through upregulation of Treg signaling in autistic BTBR T Itpr3/J mice.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder whose symptoms include communication deficits, a lack of social skills, and stereotyped repetitive behaviors. We used BTBR T Itpr3/J (BTBR) mice, a model that demonstrates most of the core behavioral features of ASD, such as decreased sociability and high levels of repetitive behaviors. Currently, there is no treatment available that is able to improve most of the ASD disorder symptoms; thus, finding novel therapies is immediately required. Stat3 inhibitors are potential targets in the treatment of several immune disorders. The aim of the present study was to investigate the effects of S3I-201, a selective Stat3 inhibitor, to determine its potential mechanism in BTBR mice. In this study, we first examined the effects of S3I-201 on repetitive behavior and marble burying. We also examined the treatment of S3I-201 on Th1 (IFN-γ and T-bet), Th17 (IL-17A, RORγt, Stat3, IL-21, and IL-22), and T regulatory (Treg, Foxp3 and Helios) production in spleen CD4 T cells. We further assessed Th1, Th17, and Treg mRNA and protein expression levels in brain tissues. S3I-201 treatment in BTBR mice significantly prevents marble burying and repetitive behavior. Furthermore, S3I-201 administration causes a considerable decrease in IFN-γ, T-bet, IL-17A, RORγt, Stat3, IL-21, and IL-22 levels, and increases in Foxp3 and Helios production CD4 T cells in BTBR mice. Additionally, S3I-201 treatment also significantly decreases Th1 and Th17 levels, and increases Treg mRNA and protein expression levels. Therefore, these results suggest that S3I-201 could be considered as a therapeutic option for ASD.