PKC delta knockout mice are protected from para-methoxymethamphetamine-induced mitochondrial stress and associated neurotoxicity in the striatum of mice

Abstract

Para-methoxymethamphetamine (PMMA) is a para-ring-substituted amphetamine derivative sold worldwide as an illegal psychotropic drug. Although PMMA use has been reported to lead to severe intoxication and even death, little is known about the mechanism(s) by which PMMA exerts its neurotoxic effects. Here we found that PMMA treatment resulted in phosphorylation of protein kinase CO (PKC delta) and subsequent mitochondrial translocation of cleaved PKCS. PMMA-induced oxidative stress was more pronounced in mitochondria than in the cytosol. Moreover, treatment with PMMA consistently resulted in significant reductions in mitochondrial membrane potential, mitochondrial complex I activity, and mitochondrial Mn superoxide dismutase-immunoreactivity. In contrast, PMMA treatment led to a significant increase in intramitochondrial Ca2+ level. Treatment with PMMA also significantly increased ionized calcium binding adaptor molecule 1 (Iba-1)-labeled microglial activation and upregulated tumor necrosis factor alpha (TNF-alpha) gene expression. PKC delta knockout attenuated these mitochondrial effects and dampened the neurotoxic effects of PMMA. Importantly, TNF-alpha knockout mice were significantly protected from PMMA-induced increases in phospho-PKC delta expression, mitochondrial translocation of cleaved PKC delta, and Iba-1-labeled microgliosis. Both rottlerin, a pharmacological inhibitor of WO, and etanercept, a pharmacological inhibitor of TNF-alpha, significantly protected against PMMA-mediated induction of apoptosis, as assessed by terminal deoxynucleotidyl transferase dUDP nick end labeling (TUNEL) assays. In addition, PKC delta knockout and TNF-alpha knockout both resulted in decreased PMMA-mediated induction of dopaminergic loss. Therefore, our results suggest that PKC delta mediates PMMA-induced neurotoxicity by facilitating oxidative stress (mitochondria > cytosol), mitochondrial dysfunction, microglial activation, and pro-apoptotic signaling. Our results also indicate that PMMA-induced PKC delta activation requires the proinflammatory cytokine TNF-alpha. (C) 2016 Published by Elsevier Ltd.