The antipsychotic agent clozapine induces autophagy via the AMPK-ULK1-Beclin1 signaling pathway in the rat frontal cortex

Clozapine, a representative atypical antipsychotic, has superior efficacy compared to other antipsychotic agents and is used for the treatment of severe psychotic disorders. Therefore, studies on its mechanisms of action are important for understanding the mechanisms of therapeutic approaches to psychosis. Adenosine monophosphate-activated protein kinase (AMPK) is a serine-threonine kinase that plays a major role in maintaining metabolic homeostasis. Unc-51-like kinase 1 (ULK1) and Beclin1 are downstream substrates of AMPK and activate the autophagic process. In this study, we examined the effects of clozapine on the AMPK-ULK1-Beclin1 signaling pathway and autophagy in the frontal cortex of the rat. Clozapine (10 mg/kg) administration increased the immunoreactivity of p-Thr172-AMPK alpha in the rat frontal cortex at 1, 2, and 4 h after injection, as we previously reported. The immunoreactivity of p-Ser317-ULK1 and p-Ser93-Beclin1 was also increased at 2 and 4 h after clozapine injection. At the same time, the immunoreactivity of LC3-II and the Atg5-Atg12 conjugate, which indicate activation of autophagy, was increased. Transmission electron microscopy clearly showed an increase in autophagosome number in the rat frontal cortex at 2 h after clozapine injection. To investigate the role of AMPK in clozapine-induced autophagy, the effects of intracerebroventricular injection of compound C, an AMPK inhibitor, were examined. Administration of compound C attenuated the clozapine-induced increase in ULK1 and Beclin1 phosphorylation, as well the protein levels of LC3-II and the Atg5-Atg12 conjugate in the frontal cortex. In summary, the results showed that clozapine activates autophagy through the AMPK-ULK1-Beclin1 signaling pathway in the frontal cortex of the rat.