LAT alleviates Th2/Treg imbalance in an OVA-induced allergic asthma mouse model through LAT-PLC-γ1 interaction

Introduction: Low expression of linker for activation of T cells (LAT) is observed in asthma. LAT and its downstream regulator, phospholipase Cgamma 1 (PLC-gamma 1) play important roles in the T cell antigen receptor signaling pathway, and their interaction is associated with CD4(+) cell polarization. Here, we investigated whether LAT can alleviate the imbalance among CD4(+) cell subgroups and the possible mechanism. Methods: An ovalbumin-induced allergic asthma mouse model was established and LAT plasmid was delivered. The pathological changes in lung were evaluated by hematoxylin and eosin and periodic acidSchiff staining. The typical cytoldnes released by T helper 2 (Th2) and regulatory T (Treg) cells were measured using enzymelinked immunosorbent assay and the number of Thl, Th2, and Treg cells were determined using flow cytometry. Lung CD4(+) T cells were isolated by magnetic isolation. The mRNA expression of LAT and PLC-gamma l was determined by real-time PCR. Co-Immunoprecipitation was performed to confirm the interaction between LAT and PLC-gamma 1. The protein expression of LAT, PLC gamma 1 and corresponding downstream signaling factors were determined by western blotting. Results: The delivery of LAT DNA to the lung could suppress an overactive Th2 response by decreasing allergicsesponse and Th2 cytokine secretion, and by increasing Treg cytokine secretion. The Th2/Freg imbalance in lung and decreased phosphorylated PLC-gamma 1 expression in lung CD4(+) T cells were rectified by LAT DNA delivery. Excessive activation of the Raf-MEK-ERK and PI3K-AICT-CREB pathways after asthma is attenuated by LAT. Conclusion: The sitespecific delivery of EAT DNA to the lung could suppress an overactive Th2 response and rectify the Th2/Treg imbalance in asthmatic mouse model. LAT-PLC-gamma 1 interaction may contribute to LAT activity in vivo and LAT protects against asthma partly via Raf-MEK-ERK and PI3K-AKT-CREB pathways. The delivery of LAT DNA could offer a novel and safe strategy for asthma prevention. (C) 2016 Elsevier B.V. All rights reserved.