L-type amino acid transporter 1 inhibitor suppresses murine Th2 cell-mediated bronchial hyperresponsiveness independently of eosinophil accumulation

BACKGROUND: The activation of Th2 cells that play a pivotal role in the development of allergic eosinophilic inflammation is regulated by an L-type amino acid transporter (LAT) 1. However, the contribution of LAT1 to the pathogenesis of Th2 cell-mediated airway inflammation has not been investigated. OBJECTIVE: In this study, we investigated the effect of a LAT1 inhibitor, JPH203, on Th2 cell-mediated airway eosinophilic inflammation. METHODS: BALB/c mice were transferred with ovalbumin (OVA)-specific Th2 cell and challenged by corresponding allergen with or without administration of JPH203. Then, the infiltration of inflammatory cells including eosinophils and allergen-specific Th2 cells in the lungs and bronchial hyperresponsiveness (BHR) was assessed. RESULTS: Inflammatory responses in the lungs with massive accumulation of eosinophils and BHR were induced in Th2 cell-transferred mice upon challenge with OVA. The treatment with JPH203 significantly suppressed the allergen-induced BHR but not eosinophil infiltration. The infused Th2 cells were also accumulated in the lungs upon allergen challenge, though the response was not affected by JPH203 treatment. CONCLUSION: JPH203 suppressed Th2 cell-mediated BHR through the mechanisms independently of the lung accumulation of eosinophils and Th2 cells.