Investigation of Tight Junction Protein Alterations in ADHD: The Role of Claudin-5, β-Catenin and Paxillin

Objective: Blood-brain barrier permeability (BBB) has been suggested to be involved in the etiopathogenesis of ADHD. Claudin-5, β-catenin and paxillin are important molecules with different roles in this barrier. Alterations in these molecules may disrupt the neurodevelopmental process by affecting various critical processes in the developing brain. Therefore, this study aimed to evaluate whether the peripheral levels of these molecules differ in children and adolescents with ADHD. Method: A total of 90 patients with ADHD aged between 8 and 18 years and 60 healthy controls were included in this study. The severity of ADHD symptoms was determined with the Atilla Turgay Scale. Child Anxiety-Depression Scale-Revised was completed to evaluate additional psychiatric problems of the patients. Serum levels of biochemical parameters were measured using enzyme-linked immunosorbent assay kits. Results: Serum claudin-5 levels were significantly lower and β-catenin levels were significantly higher in the ADHD group compared to the control group. However, there was no significant difference in paxillin serum levels between the groups. Conclusion: This study suggests that claudin-5 and beta-catenin may play a role in the pathogenesis of ADHD. These proteins may affect the brain by causing a dysregulation in BBB permeability or through other mechanisms.