Autism spectrum disorder (ASD) has been associated with brain inflammation as indicated by the activation of microglia, but the triggers are not known. Extracellular vesicles (EVs) are secreted from many cells in the blood and other biological fluids and carry molecules that could influence the function of target cells. EVs have been recently implicated in several diseases, but their presence or function in ASD has not been studied.
EVs were isolated from the serum of children with ASD (n = 20, 16 males and 4 females, 4–12 years old) and unrelated age and sex-matched normotypic controls (n = 8, 6 males and 2 females, 4–12 years old) using the exoEasy Qiagen kit. EVs were characterized by determining the CD9 and CD81 membrane-associated markers with Western blot analysis, while their morphology and size were assessed by transmission electron microscopy (TEM). Human microglia SV40 were cultured for 24 h and then stimulated with EVs (1 or 5 μg/mL), quantitated as total EV-associated protein, for 24 or 48 h. IL-1β secretion was measured by ELISA. The results were analyzed using the Mann-Whitney U non-parametric test, and all statistical analyses were performed using Graph Pad Prism 5.
EVs were isolated and shown to be spherical structures (about 100 nm) surrounded by a membrane. Total EV-associated protein was found to be significantly increased (p = 0.02) in patients as compared to normotypic controls. EVs (5 μg/mL) isolated from the serum of patients with ASD stimulated cultured human microglia to secrete significantly more of the pro-inflammatory cytokine interleukin IL-1β (163.5 ± 13.34 pg/mL) as compared to the control (117.7 ± 3.96 pg/mL, p < 0.0001). The amount of mitochondrial DNA (mtDNA7S) contained in EVs from children with ASD was found to be increased (p = 0.046) compared to the normotypic controls.
These findings provide novel information that may help explain what triggers inflammation in the brain of children with ASD and could lead to novel effective treatments.
Centers for Disease Control and Prevention (2018) CDC estimates 1 in 59 children has been identified with autism spectrum disorder, https://www.cdc.gov/features/new-autism-data/index.html Access date July 11 2018.
Geschwind DH, State MW. Gene hunting in autism spectrum disorder: on the path to precision medicine. Lancet Neurol. 2015;11:1109–20. CrossRef
Ruggeri B, Sarkans U, Schumann G, Persico AM. Biomarkers in autism spectrum disorder: the old and the new. Psychopharmacology (Berl). 2014;231:1201–16. CrossRef
Leigh JP, Du J. Brief report: forecasting the economic burden of autism in 2015 and 2025 in the United States. J Autism Dev Disord. 2015;12:4135–9. CrossRef
Bryniarski K, Ptak W, Jayakumar A, Pullmann K, Caplan MJ, Chairoungdua A, Lu J, Adams BD, Sikora E, Nazimek K, Marquez S, Kleinstein SH, Sangwung P, Iwakiri Y, Delgato E, Redegeld F, Blokhuis BR, Wojcikowski J, Daniel AW, Groot KT, Askenase PW. Antigen-specific, antibody-coated, exosome-like nanovesicles deliver suppressor T-cell microRNA-150 to effector T cells to inhibit contact sensitivity. J Allergy Clin Immunol. 2013;132:170–81. CrossRefPubMedPubMedCentral
Angelidou A, Francis K, Vasiadi M, Alysandratos K-D, Zhang B, Theoharides A, Lykouras L, Kalogeromitros D, Theoharides T. Neurotensin is increased in serum of young children with autistic disorder. J Neuroinflam. 2010;7:48. CrossRef
Tsilioni I, Dodman N, Petra AI, Taliou A, Francis K, Moon-Fanelli A, Shuster L, Theoharides TC. Elevated serum neurotensin and CRH levels in children with autistic spectrum disorders and tail-chasing bull terriers with a phenotype similar to autism. Transl Psychiatry. 2014;4:e466. CrossRefPubMedPubMedCentral
Banigan MG, Kao PF, Kozubek JA, Winslow AR, Medina J, Costa J, Schmitt A, Schneider A, Cabral H, Cagsal-Getkin O, Vanderburg CR, Delalle I. Differential expression of exosomal microRNAs in prefrontal cortices of schizophrenia and bipolar disorder patients. PLoS One. 2013;8:e48814. CrossRefPubMedPubMedCentral
Van GV, An SS. Emergence of exosomal miRNAs as a diagnostic biomarker for Alzheimer’s disease. J Neurol Sci. 2016;360:141–52. CrossRef
- Extracellular vesicles are increased in the serum of children with autism spectrum disorder, contain mitochondrial DNA, and stimulate human microglia to secrete IL-1β
Theoharis C. Theoharides
- BioMed Central