Syk and Src-targeted anti-inflammatory activity of aripiprazole, an atypical antipsychotic

Aripiprazole (ARP) is a partial agonist of dopamine D2 receptors that is commonly prescribed to treat schizophrenia and bipolar disorder. The anti-inflammatory effect of ARP was recently documented in a few studies, but its molecular mechanisms have not been fully elucidated. In this study, peptidoglycan (PGN)-treated macrophages (RAW264.7 cells), reporter gene assay, an overexpression strategy, immunoprecipitation, and immunoblotting analysis were employed to clarify the anti-inflammatory mechanism of ARP. ARP was found to dose-dependently inhibit production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) without exhibiting cytotoxicity. In agreement with this result, ARP was found to suppress the mRNA expression levels of inflammatory genes such as cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), and tumor necrosis factor (TNF)-α. Luciferase assay and immunoblotting analysis with nuclear fractions showed that activator protein-1 (AP-1) and nuclear factor (NF)-κB are targeted by ARP. Similar to these data, c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase kinase 4 (MKK4), MKK7, and transforming growth factor beta-activated kinase 1 (TAK1) for AP-1 activation, and inhibitor of κBα (IκBα), IκBαkinase α/β (IKKα/β), AKT, phosphatidylinositide 3-kinases (PI3K), spleen tyrosine kinase (Syk), and Src for NF-κB activation were revealed to be inhibited by ARP treatment. These results suggest that ARP can suppress inflammatory responses triggered by Gram positive bacteria through suppression of both AP-1 and NF-κB pathways.