Summary. Elucidation of the biochemical steps leading to the 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP)-induced degeneration of the nigro-striatal dopamine (DA) pathway has provided new clues to the pathophysiology of Parkinson's Disease (PD). In line with the enhancement of MPTP toxicity by diethyldithiocarbamate (DDC), here we demonstrate how other CYP450 (2E1) inhibitors, such as diallyl sulfide (DAS) or phenylethylisothiocyanate (PIC), also potentiate the selective DA neuron degeneration in C57=bl mice. In order to provide direct evidence for this isozyme involvement, CYP 2E1 knockout mice were challenged with MPTP or the combined treatment. Here we show that these transgenic mice have a low sensitivity to MPTP alone, similarly to the wild type SVI, suggesting that it is likely that transgenic mice compensate for the missing enzyme. However, in these CYP 2E1 knockout mice, DDC pretreatment completely fails to enhance MPTP toxicity; this enhancement is instead regularly present in the SVI control animals. This study indicates that the occurrence of CYP 2E1 in C57=bl mouse brain is relevant for MPTP toxicity, and suggests that this isozyme may have a detoxificant role related to the efflux transporter of the toxin. Abbreviations DA dopamine; PD Parkinson's Disease; DDC diethyldithiocarbamate; PIC phenylethylisothiocyanate; DAS diallyl sulfide; MPTP 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine; MPP þ 1-methyl-4-phenylpyridinium; SN substantia nigra; TH tyrosine hydroxylase; SVI Cyp 2e1þ=þ (129S1=SvImJ); GONZ Cyp 2e1À=À (129=SV-Cyp 2e1 tm1Gonz )
