Elevated levels of peripheral and central nervous system immune markers reflect innate immune dysregulation in autism spectrum disorder
Attila Szabó, Kevin S. O’Connell, Ibrahim A. Akkouh, Thor Ueland, Ida E. Sønderby, Sigrun Hope, Anne Roe, Monica Stolen Dønnum, Ingrid Sjaastad, Nils Eiel Steen, Torill Ueland, Linn Sofie Sæther, Jordi Requena Osete, Ole A. Andreassen, Terje Nærland, Srdjan Djurovic
Abstract
• People with ASD display higher plasma levels of IL-18, ICAM-1, MADCAM1, and PSEL relative to CTRL. • In ASD, mRNA levels of ICAM1 is increased in postmortem brain samples relative to controls. • Higher levels and activity of the NLRP3 inflammasome-caspase-1 system in immune cells in ASD. • Higher levels of secreted IL-18, IL-1β, and IL-8 from PBMC in ASD, both at baseline and following inflammasome activation. Evidence suggests dysregulated immune functions in the pathophysiology of Autism spectrum disorder (ASD), although specific immune mechanisms are yet to be identified. We assessed circulating levels of 25 immune/neuroinflammatory markers in a large ASD sample ( n = 151) and matched controls ( n = 72) using linear models. In addition, we performed global brain transcriptomics analyses of relevant immune-related genes. We also assessed the expression and function of factors and pathway elements of the inflammasome system in peripheral blood mononuclear cells (PBMC) isolated from ASD and controls using in vitro methods. We found higher circulating levels of IL-18 and adhesion factors (ICAM-1, MADCAM1) in individuals with ASD relative to controls. Consistent with this, brain levels of ICAM1 mRNA were also higher in ASD compared to controls. Furthermore, we found higher expression/activity of Caspase-1 and the inflammasome sensor NLRP3 in PBMCs in ASD, both at baseline and following inflammatory challenge. This corresponded with higher levels of secreted IL-18, IL-1β, and IL-8, as well as increased expression of adhesion factors following inflammasome activation in ASD PBMC cultures. Inhibition of the NLRP3-inflammasome rescued the observed immune phenotype in ASD in vitro . Our results suggest a role for inflammasome dysregulation in ASD pathophysiology.