In this study, we show that the mitochondrially targeted CYP2D6 can efficiently catalyze MPTP-mimicking compounds, <i>i.e.</i> 2-methyl-1,2,3,4-tetrahydroisoquinoline, 2-methyl-1,2,3,4-tetrahydro-β-carboline, and 9-methyl-norharmon, suspected to induce PD in humans.
Despite several recent meta-analyses showing an association between several polymorphisms in genes related with detoxification mechanisms such as cytochrome P4502D6 (CYP2D6), and glutathione transferases M1 and T1 (GSTM1, and GSTT1), data on NAT2 gene polymorphisms obtained from the current meta-analysis do not support a major association with PD risk, except in Asian populations.
The pooled analyses showed a significant association between CYP2D6*4G/A polymorphism and PD risk in all of the comparisons (A vs. G allele: OR = 1.28, 95% CI = 1.14-1.43, P = 0.001; AA vs. GG: OR = 1.43, 95% CI = 1.06-1.93, P = 0.018; AG vs. GG: OR = 1.22, 95% CI = 1.06-1.40, P = 0.006; AG+AA vs. GG: OR = 1.26, 95% CI = 1.10-1.44, P = 0.001; AA vs. AG+GG: OR = 1.37, 95% CI = 1.02-1.83, P = 0.036).
In summary, the lower CYP2D6 levels in PD cases may have reduced their ability to inactivate PD-causing neurotoxins contributing to their disease risk.
Further, cases carrying combination of heterozygous genotypes of CYP2D6*4 or CYP2D6*10A(188C > T) and NAT2*5 were found to be at significantly higher risk for PD demonstrating the importance of gene-gene interactions in determining susceptibility to PD.
Multivariate logistic regression analysis revealed that heterozygous genotypes of cytochrome P4502D6*4(CYP2D6*4), CYP2E1*5B (RsaI) polymorphism and homozygous mutant genotypes of CYP2E1*6 (Dra1) were found to be overrepresented in PD cases when compared to the controls.
Polymorphisms of catechol-0-methyltransferase (COMT), monoamine oxidase B (MAOB), N-acetyltransferase 2 (NAT2) and cytochrome P450 2D6 (CYP2D6) gene in patients with early onset of Parkinson's disease.
No significant association was found between CYP2D6 genotype and PD, but subjects with extensive metabolizer (EM) CYP2D6 phenotype, and the variant GSTP1*B genotype were at significantly higher PD risk than the corresponding poor or intermediary metabolizers (CYP2D6 poor metabolizer phenotype+intermediary metabolizers).
Data from our group and others suggest that the CYP2D6 PM genotype interacts with certain environmental factors such as pesticide exposure and cigarette smoking to confer differential risk for PD.
Meanwhile, epidemiological studies from China have shown that the prevalence of PD is much lower than in the Caucasian population, explained by the low frequency of cytochrome P-450 CYP2D6 debrisoquine hydroxylase gene polymorphism.
Although they are based on a small group of subjects with the joint exposure, our findings are consistent with a gene-environment interaction disease model according to which (1) pesticides have a modest effect in subjects who are not CYP2D6 poor metabolizers, (2) pesticides' effect is increased in poor metabolizers (approximately twofold), and (3) poor metabolizers are not at increased PD risk in the absence of pesticide exposure.
Although they are based on a small group of subjects with the joint exposure, our findings are consistent with a gene-environment interaction disease model according to which (1) pesticides have a modest effect in subjects who are not CYP2D6 poor metabolizers, (2) pesticides' effect is increased in poor metabolizers (approximately twofold), and (3) poor metabolizers are not at increased PD risk in the absence of pesticide exposure.
Thus, a meta-analysis was conducted to determine if polymorphism, other than the B-mutation, within the CYP2D6 gene confers a greater susceptibility to PD outcome among Asian populations.