Methamphetamine (METH) is a highly abused psychostimulant that is neurotoxic to dopaminergic (DAergic) nerve terminals in the striatum and increases the risk of developing Parkinson’s disease (PD). In vivo, METH-mediated DA release, followed by DA-mediated oxidative stress and mitochondrial dysfunction in pre- and postsynaptic neurons, mediates METH neurotoxicity. METH-triggered oxidative stress damages parkin, a neuroprotective protein involved in PD etiology via its involvement in the maintenance of mitochondria. It is not known whether METH itself contributes to mitochondrial dysfunction and whether parkin regulates complex I, an enzymatic complex downregulated in PD. To determine this, we separately assessed the effects of METH or DA alone on electron transport chain (ETC) complexes and the protein parkin in isolated striatal mitochondria. We show that METH decreases the levels of selected complex I, II, and III subunits (NDUFS3, SDHA, and UQCRC2, respectively), whereas DA decreases the levels only of the NDUFS3 subunit in our preparations. We also show that the selected subunits are not decreased in synaptosomal mitochondria under similar experimental conditions. Finally, we found that parkin overexpression does not influence the levels of the NDUFS3 subunit in rat striatum. The presented results indicate that METH itself is a factor promoting dysfunction of striatal mitochondria; therefore, it is a potential drug target against METH neurotoxicity. The observed decreases in ETC complex subunits suggest that DA and METH decrease activities of the ETC complexes via oxidative damage to their subunits and that synaptosomal mitochondria may be somewhat “resistant” to DA- and METH-induced disruption in mitochondrial ETC complexes than perikaryal mitochondria. The results also suggest that parkin does not regulate NDUFS3 turnover in rat striatum.

In recent years, methamphetamine (METH) misuse in the US has been rapidly increasing, and there is no FDA-approved pharmacotherapy for METH use disorder (MUD). We previously determined that ubiquitin-protein ligase parkin is involved in the regulation of METH addictive behaviors in rat models of MUD. Parkin is not yet a “druggable” drug target; therefore, this study aimed to determine which biological processes, pathways, and proteins downstream of parkin are likely drug targets against MUD. Employing young adult Long Evans male rats with parkin deficit or excess in the nucleus accumbens (NAc), label-free proteomics, and molecular biology, we determined that the pathways downstream of parkin that are candidates for regulating METH addictive behaviors in young adult male rats are mitochondrial respiration, oxidative stress, AMPA receptor trafficking, GABAergic neurotransmission, and actin cytoskeleton dynamics.