Increased Vesicular Monoamine Transporter 2 (VMAT2; Slc18a2) Protects against Methamphetamine Toxicity

• Type of Material: Article
• Authors: Kelly M. Lohr, Emory University; Kristen A. Stout, Emory University; Amy R. Dunn, Emory University; Minzheng Wang, Emory University; Ali Salahpour, University of Toronto; Thomas S. Guillot, Emory University; Gary W Miller, Emory University
• Language: English
• Date: 2015-05-01
• Publisher: American Chemical Society
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2015 American Chemical Society.
• Final Published Version (URL): http://dx.doi.org/10.1021/acschemneuro.5b00010
• Title of Journal or Parent Work: ACS Chemical Neuroscience
• ISSN: 1948-7193
• Volume: 6
• Issue: 5
• Start Page: 790
• End Page: 799
• Grant/Funding Information: This work was supported by The National Institutes of Health Grants ES023839, P30ES019776, F31NS084739, F31DA037652, T32ES012870, and P50NS071669; The Canadian Institutes of Health Research Grant 210296; and The Lewis Dickey Memorial Fund.
• Keywords: SUBSTITUTED AMPHETAMINES; Life Sciences & Biomedicine; CYTOSOLIC DOPAMINE; MITOCHONDRIAL DYSFUNCTION; Neurosciences & Neurology; HUMAN DOPAMINE TRANSPORTER; Methamphetamine; Pharmacology & Pharmacy; PARKINSONS-DISEASE; neurodegeneration; OXIDATIVE STRESS; Biochemistry & Molecular Biology; Neurosciences; INDUCED NEUROTOXICITY; ALPHA-SYNUCLEIN; Chemistry, Medicinal; CONDITIONED PLACE PREFERENCE; VMAT2; vesicle; dopamine; inflammation; Science & Technology; MICROGLIAL ACTIVATION
• Research Categories: Environmental Sciences; Health Sciences, Pharmacology; Biology, Neuroscience

Abstract

The psychostimulant methamphetamine (METH) is highly addictive and neurotoxic to dopamine terminals. METH toxicity has been suggested to be due to the release and accumulation of dopamine in the cytosol of these terminals. The vesicular monoamine transporter 2 (VMAT2; SLC18A2) is a critical mediator of dopamine handling. Mice overexpressing VMAT2 (VMAT2-HI) have an increased vesicular capacity to store dopamine, thus augmenting striatal dopamine levels and dopamine release in the striatum. Based on the altered compartmentalization of intracellular dopamine in the VMAT2-HI mice, we assessed whether enhanced vesicular function was capable of reducing METH-induced damage to the striatal dopamine system. While wildtype mice show significant losses in striatal levels of the dopamine transporter (65% loss) and tyrosine hydroxylase (46% loss) following a 4 × 10 mg/kg METH dosing regimen, VMAT2-HI mice were protected from this damage. VMAT2-HI mice were also spared from the inflammatory response that follows METH treatment, showing an increase in astroglial markers that was approximately one-third of that of wildtype animals (117% vs 36% increase in GFAP, wildtype vs VMAT2-HI). Further analysis also showed that elevated VMAT2 level does not alter the ability of METH to increase core body temperature, a mechanism integral to the toxicity of the drug. Finally, the VMAT2-HI mice showed no difference from wildtype littermates on both METH-induced conditioned place preference and in METH-induced locomotor activity (1 mg/kg METH). These results demonstrate that elevated VMAT2 protects against METH toxicity without enhancing the rewarding effects of the drug. Since the VMAT2-HI mice are protected from METH despite higher basal dopamine levels, this study suggests that METH toxicity depends more on the proper compartmentalization of synaptic dopamine than on the absolute amount of dopamine in the brain.