Polymorphisms of Cytochromes P450 and Glutathione S-Transferases Synergistically Modulate Risk for Parkinson's Disease.

Background: Environmental substances such as pesticides are well-known in link with Parkinson's disease (PD) risk. Enzymes including cytochromes P450 (CYPs), esterases and glutathione S-transferases (GSTs) are responsible for the xenobiotic metabolism and may functionally compensate each other for subtypes in the same class. We hypothesize that the genetic effects of each class modulate PD risk stronger in a synergistic way than individually. Methods: We selected 14 polymorphic loci out of 13 genes which encode enzymes in the classes of CYP, esterase, and GST, and recruited a cohort of 1,026 PD and control subjects from eastern China. The genotypes were identified using improved multiplex ligation detection reaction and analyzed using multiple models. Results: A total of 13 polymorphisms remained after Hardy-Weinberg equilibrium analysis. None of the polymorphisms were independently associated with PD risk after Bonferroni correction either by logistic regression or genetic models. In contrast, interaction analyses detected increased resistance to PD risk in individuals carrying the rs12441817/CC (CYP1A1) and rs2070676/GG + GC (CYP2E1) genotypes (P = 0.002, OR = 0.393, 95% CI = 0.216-0.715), or carrying the GSTM1-present, GSTT1-null, rs156697/AG + GG (GSTO2) and rs1695/AA (GSTP1) genotypes (P = 0.003, OR = 0.348, 95% CI = 0.171-0.706). The synergistic effect of GSTs on PD was primarily present in females (P = 0.003). No synergistic effect was observed within genotypes of esterases. Conclusion: We demonstrate a presence of synergistic but not individual impact on PD susceptibility in polymorphisms of CYPs and GSTs. The results indicate that the genetic interplay leads the way to PD development for xenobiotic metabolizing enzymes.

An antisense Alu transposon insertion/deletion polymorphism of ALDH1A1 may functionally associate with Parkinson's disease.

BACKGROUND: Aldehyde dehydrogenase 1 (encoded by ALDH1A1) has been shown to protect against Parkinson's disease (PD) by reducing toxic metabolites of dopamine. We herein revealed an antisense Alu element insertion/deletion polymorphism in intron 4 of ALDH1A1, and hypothesized that it might play a role in PD.  METHODS: A Han Chinese cohort comprising 488 PD patients and 515 controls was recruited to validate the Alu insertion/deletion polymorphism following a previous study of tag-single nucleotide polymorphisms, where rs7043217 was shown to be significantly associated with PD. Functional analyses of the Alu element insertion were performed. RESULTS: The Alu element of ALDH1A1 was identified to be a variant of Yb8 subfamily and termed as Yb8c4. The antisense Yb8c4 insertion/deletion polymorphism (named asYb8c4ins and asYb8c4del, respectively) appeared to be in a complete linkage disequilibrium with rs7043217 and was validated to be significantly associated with PD susceptibility with asYb8c4ins serving as a risk allele (P = 0.030, OR = 1.224, 95% CI = 1.020-1.470). Multiple functional analyses including ALDH1A1 mRNA expression in blood cells of carriers, and reporters of EGFP and luciferase showed that the asYb8c4ins had a suppressive activity on gene transcription. Mechanistic explorations suggested that the asYb8c4ins induced no changes in CpG methylation and mRNA splicing of ALDH1A1 and appeared no binding of transcription factors. CONCLUSIONS: Our results consolidate an involvement of ALDH1 in PD pathogenesis. The asYb8c4 polymorphism may be a functional output of its linkage disequilibrium-linked single nucleotide polymorphisms.

Autoimmune Disease Associated CLEC16A Variants Convey Risk of Parkinson's Disease in Han Chinese.

CLEC16A is a membrane-associated endosomal protein implicated in regulating autophagy and antigen presentation. Its genetic variants are broadly associated with multiple autoimmune diseases. Parkinson's disease (PD), which undergoes autophagy disruption and neuroinflammation, has been clinically observed, for an extensive amount of time, to be associated with autoimmune diseases. In this study, we aimed to understand whether the autoimmune disease associated CLEC16A variants pleiotropically modulate PD risk. Five of such CLEC16A variants, including rs6498169, rs12708716, rs12917716, rs7200786, and rs2903692, were selected and analyzed in a Han Chinese cohort comprising 515 sporadic PD patients and 504 controls. Results showed that rs6498169 and rs7200786 were significantly associated with PD susceptibility (p = 0.005 and 0.004, respectively; recessive model, p = 0.002 and 0.001, respectively). Rs6498169 was also associated with the PD subtype of postural instability/gait difficulty (p = 0.002). Haplotype analysis showed that the AAG module in order of rs6498169, rs12708716, and rs2903692 was associated with the highest risk for PD (p = 0.0047, OR = 1.42, 95% CI = 1.11-1.82). Functional annotation analyses suggested that rs6498169 had high probability to affect transcription factor binding and target gene expression. In summary, the current study demonstrates that the autoimmune disease associated CLEC16A variants convey risk of PD in Han Chinese. Our findings suggest a pleiotropic role of CLEC16A and strengthen the link between PD and autoimmune diseases.