Aripiprazole inhibits polyI: C-induced microglial activation possibly via TRPM7

Viral infections during fetal and adolescent periods, as well as during the course of schizophrenia itself have been linked to the onset and/or relapse of a psychosis. We previously reported that the unique antipsychotic aripiprazole, a partial D2 agonist, inhibits the release of tumor necrosis factor (TNF)-alpha from interferon-gamma-activated rodent microglial cells. Polyinosinic-polycytidylic acid (polyI:C) has recently been used as a standard model of viral infections, and recent in vitro studies have shown that microglia are activated by polyI:C. Aripiprazole has been reported to ameliorate behavioral abnormalities in polyI:C-induced mice. To clarify the anti-inflammatory properties of aripiprazole, we investigated the effects of aripiprazole on polyI: C-induced microglial activation in a cellular model of murine microglial cells and possible surrogate cells for human microglia. PolyI:C treatment of murine microglial cells activated the production of TNF-alpha and enhanced the p38 mitogen-activated protein kinase (MAPK) pathway, whereas aripiprazole inhibited these responses. In addition, polyI: C treatment of possible surrogate cells for human microglia markedly increased TNF-alpha mRNA expression in cells from three healthy volunteers. Aripiprazole inhibited this increase in cells from two individuals. PolyI: C consistently increased intracellular Ca2+ concentration ([Ca2+](i)) in murine microglial cells by influx of extracellular Ca2+. We demonstrated that transient receptor potential in melastatin 7 (TRPM7) channels contributed to this polyI: C-induced increase in [Ca2+](i). Taken together, these data suggest that aripiprazole may be therapeutic for schizophrenia by reducing microglial inflammatory reactions, and TRPM7 may be a novel therapeutic target for schizophrenia. Further studies are needed to validate these findings. (C) 2016 Elsevier B.V. All rights reserved.