Cytochrome P450 2E1 gene polymorphisms/haplotypes and Parkinson's disease in a Swedish population.

Cytochrome P450 2E1 (CYP2E1), which inter alia is located in dopamine containing neurons in the substantia nigra, has been hypothesized to be of importance for the pathophysiology of Parkinson's disease (PD), either by its production of reactive oxygen species (ROS) or by its capability to detoxify putative neurotoxins. Numerous polymorphisms in the coding and non-coding regions of the gene for this enzyme have been reported. Different variants may account for inter-individual differences in the activity of the enzyme or production of ROS. In this study, the CYP2E1 gene was examined in a control population (n = 272) and a population with PD (n = 347), using a tag-single nucleotide polymorphism (tSNP) approach founded on HapMap Data. Six tSNPs were used in the analysis and haplotype block data were obtained. In case of significance, the SNP was further examined regarding early/late age of disease onset and presence of relatives with PD. We found an association between allele and genotype frequencies of the C/G polymorphism at intron 7 (rs2070676) of this gene and PD (P value of 0.026 and 0.027, respectively). Furthermore, analysis of the rs2070676 polymorphism in subgroups of patients with age of disease onset higher than 50 years and those not having a relative with PD also demonstrated a significant difference with controls. This was seen in both genotype (corresponding to P value = 0.039 and 0.032) and allele (P = 0.027 and 0.017 respectively) frequency. As a representative of many polymorphisms or in possible linkage disequilibrium with other functional variants, it is possible that rs2070676 could influence the regulation of the enzyme. In conclusion, our results display an association between the rs2070676 polymorphism and PD. Additional investigations are needed to elucidate the importance of this polymorphism for the activity of CYP2E1 and PD susceptibility.

Cytochrome P450 2E1 in the substantia nigra: relevance for dopaminergic neurotransmission and free radical production.

Cytochrome P450 2E1 (CYP2E1) has been detected in brain regions which are of relevance for the pathophysiology of Parkinson's disease, such as the substantia nigra (SN). Furthermore, CYP2E1 is known to generate reactive oxygen species (ROS), toxic molecules which have been implicated in the pathogenesis of the disease. We have previously reported that CYP2E1 inhibition increases extracellular dopamine (DA) in the SN. The aims of the present study were by using in vivo microdialysis in rat, to elucidate the mechanisms responsible for the increase in extracellular DA induced by CYP2E1 inhibition and to explore whether ROS is produced in the SN, both with and without the presence of an exogenous CYP2E1 substrate. The effect of inhibition of CYP2E1 by phenylethyl isothiocyanate (100 mg/kg) on extracellular DA in the SN was unaltered following pretreatment with gamma-butyrolactone and GBR-12909, drugs that inhibit firing of DA neurons and DA re-uptake, respectively. Preadministration of tetrodotoxin or reserpine, however, abolished the effect of CYP2E1 inhibition. Administration of isoflurane, an anesthetic which is metabolized by CYP2E1, increased the production of *OH in the SN, as measured by the transformation of 4-hydroxybenzoic acid to 3,4-dihydroxybenzoic acid during local perfusion compared with animals given other anesthetics. The results support the notion that CYP2E1 is located near or in the same compartment in the SN as stored DA, tentatively the endoplasmatic reticulum, and that the enzyme activity might modulate the amount of DA that is available for release. Furthermore, our findings indicate that the production of ROS can be stimulated by CYP2E1 substrates.

Association between the estrogen receptor beta gene and age of onset of Parkinson's disease.

The purpose of this study was to investigate the potential contribution of genetic variants in the estrogen receptor beta gene to the aetiology of Parkinson's disease (PD). Several lines of evidence from human and animal studies suggest a protective role for estrogen in PD. Recently the estrogen receptor beta subtype was reported to be an important mediator of estrogen actions in the nigrostriatal dopamine system. Two single nucleotide polymorphisms at position 1730 and 1082 in the ER beta gene were genotyped, using pyrosequencing, in 260 patients with PD and 308 controls recruited from the Swedish population. Neither of the two estrogen receptor beta polymorphisms was associated with an increased risk for PD. However, the G allele of the A1730G polymorphism was more frequent in patients with an early age of onset than in patients with a late age of onset of PD (P = 0.006). Patients carrying the GG genotype had an odds ratio of 2.2 for having an early onset of PD compared to non-carriers. In conclusion, our results indicate that genetic variation in the estrogen receptor beta gene may influence the age of onset of PD.