Autophagy inhibition uncovers the neurotoxic action of the antipsychotic drug olanzapine

Abstract

We investigated the role of autophagy, a controlled cellular self-digestion process, in regulating survival of neurons exposed to atypical antipsychotic olanzapine. Olanzapine induced autophagy in human SH-SY5Y neuronal cell line, as confirmed by the increase in autophagic flux and presence of autophagic vesicles, fusion of autophagosomes with lysosomes, and increase in the expression of autophagy-related (ATG) genes ATG4B, ATG5, and ATG7. The production of reactive oxygen species, but not modulation of the main autophagy repressor MTOR or its upstream regulators AMP-activated protein kinase and AKT1, was responsible for olanzapine-triggered autophagy. Olanzapine-mediated oxidative stress also induced mitochondrial depolarization and damage, and the autophagic clearance of dysfunctional mitochondria was confirmed by electron microscopy, colocalization of autophagosome-associated MAP1LC3B (LC3B henceforth) and mitochondria, and mitochondrial association with the autophagic cargo receptor SQSTM1/p62. While olanzapine-triggered mitochondrial damage was not overtly toxic to SH-SY5Y cells, their death was readily initiated upon the inhibition of autophagy with pharmacological inhibitors, RNA interference knockdown of BECN1 and LC3B, or biological free radical nitric oxide. The treatment of mice with olanzapine for 14 d increased the brain levels of autophagosome-associated LC3B-II and mRNA encoding Atg4b, Atg5, Atg7, Atg12, Gabarap, and Becn1. The administration of the autophagy inhibitor chloroquine significantly increased the expression of proapoptotic genes (Trp53, Bax, Bak1, Pmaip1, Bcl2l11, Cdkn1a, and Cdkn1b) and DNA fragmentation in the frontal brain region of olanzapine-exposed animals. These data indicate that olanzapine-triggered autophagy protects neurons from otherwise fatal mitochondrial damage, and that inhibition of autophagy might unmask the neurotoxic action of the drug.

Inhibition of autophagy increased AGE/ROS-mediated apoptosis in mesangial cells

“…Furthermore, the results presented here also showed that AGE-induced autophagy involved mitophagy. This finding is consistent with the proposal suggesting that the ROS generated from damaged mitochondria lead to the collapse of the MMP and a transient increase in ROS generation via the electron transfer chain, which constitutes a positive feedback circle, 24 eventually leading to autophagic clearance of the impaired mitochondria, 42 and a reduction in oxidative stress. 26 In addition to mitophagy, general autophagy confers a cytoprotective role.…”

“…It is well established that enhanced ROS production induces autophagy, 22, 42, 43 which was confirmed in the present study. We found that treatment with the ROS scavenger NAC reversed LC3 conversion and puncta and decreased p62 expression in AGE-treated cells, suggesting that AGE-induced autophagy was related to ROS accumulation in mesangial cells.…”

Effects of Risperidone and Galantamine Treatment on Alzheimer’s Disease Biomarker Levels in Cerebrospinal Fluid

“…However, this effect may also be due to the anticholinergic or anti-histaminergic effects, or sedation. Recently another atypical antipsychotic drug Olanzapine was shown to exhibit neurotoxic effects by influencing autophagy, demonstrated both in vivo and in vitro [28]. Thus, the potential negative effect of risperidone on AD pathology may be mediated through an effect on autophagy in the neurons.…”

Mechanisms of Action of Autophagy Modulators Dissected by Quantitative Systems Pharmacology Analysis

“…As an antipsychotic drug, olanzapine mainly targets receptors of neurotransmitters such as dopamine, serotonin (5-HT), and γ-aminobutyric acid (GABA), which have been reported to regulate autophagy [32,40,41]. Further, olanzapine also induces autophagy by activating AMP-activated protein kinase (AMPK) signaling [42,43] and up-regulating the expression of the products of ATG genes such as ATG5 and Beclin-1 [44].…”