Inhibitory effects of aripiprazole on interferon-γ-induced microglial activation via intracellular Ca2+ regulation in vitro

The activation of the inflammatory/immunological response system is suggested to be related to the pathophysiology of schizophrenia. Aripiprazole is a novel atypical antipsychotic, which is a high-affinity dopamine D-2 receptor partial agonist. Atypical antipsychotics, all of which have dopamine D-2 receptor antagonism, have recently reported to have significantly inhibitory effects on interferon (IFN)-gamma-induced microglial activation in vitro. In the present study, we investigated whether or not aripiprazole also has anti-inflammatory effect on IFN-gamma-induced microglial activation. Not quinpirole, dopamine D-2 full agonist, but aripiprazole significantly inhibited the generation of nitric oxide (NO) and tumor necrosis factor (TNF)-alpha from IFN-gamma-activated microglia and suppressed the IFN-gamma-induced elevation of intracellular Ca2+ concentrations ([Ca2+](i)) in murine microglial cells. Increased [Ca2+](i) has been reported to be required, but by itself not sufficient, for the release of NO and certain cytokines. As a result, we can speculate that aripiprazole may inhibit IFN-gamma-induced microglial activation through the suppression of IFN-gamma-induced elevation of [Ca2+](i) in microglia. Our results demonstrated that not only antipsychotics which have dopamine D-2 receptor antagonism but also aripiprazole have anti-inflammatory effects via the inhibition of microglial activation. Antipsychotics may therefore have a potentially useful therapeutic effect on patients with schizophrenia by reducing the microglial inflammatory reactions.