1-Methyl-4-phenylpyridinium (MPP +) Decreases Mitochondrial Oxidation-Reduction (REDOX) Activity and Membrane Potential (Δψ m) in Rat Striatum

Abstract

Mitochondrial dysfunction has long been implicated in the death of nigrostriatal dopaminergic neurons in Parkinson's disease (PD) and its experimental models. Here we further analyzed changes in the mitochondrial oxidation-reduction (REDOX) activity and membrane potential (Δψ m) of striatal synaptosomes after the infusion of 1-methyl-4-phenylpyridinium (MPP +) into rat striatum. MPP + (40 nmol) treatment produced decreases in mitochondrial REDOX activity and Δψ m at 18 h, as measured by fluorometric analysis with both Alamar blue and JC-1 (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolyl-carbocyanine iodide) dyes. At this time point, tyrosine hydroxylase (TH) and dopamine transporter (DAT) protein levels were not altered, but both decreased at 7 days after MPP + (40 nmol) infusion. Both measures of mitochondrial dysfunction induced by MPP + (40 nmol) at 18 h were attenuated, at least in part, by pretreatment with a selective dopamine uptake inhibitor GBR-12909 (1-(2-(bis(4-fluorophenyl)methoxy)ethyl)-4-(3-phenylpropyl) piperazine). In addition, GBR-12909 partially attenuated MPP + (40 nmol)-caused a loss of striatal nerve terminal as indicated by decreases in TH and DAT immunoreactivities as well as dopamine and its metabolites levels. The present study indicates that decreases in mitochondrial REDOX activity and Δψ m may play a role in MPP +-induced dopaminergic neurotoxicity, and further provides that improvement of mitochondrial dysfunction may be a better way to slow progressive dopaminergic neurodegeneration commonly associated with PD.