Genetic polymorphism of dopamine D2 receptors in Parkinson's disease and interactions with cigarette smoking and MAO-B intron 13 polymorphism

Genetic polymorphisms of dopamine D2 receptors (DRD2) may be susceptibility factors for Parkinson's disease due to their influence on dopamine respons e and association with cigarette smoking, which is inversely related to ris k of Parkinson's disease. Relations of TaqIA and TaqIB DRD2 genotypes with Parkinson's disease were investigated and tested for interactive effects wi th smoking and the monoamine oxidase B (MAO-B) intron 13 polymorphism previ ously found to be related to smoking. Study subjects were 152 cases of idio pathic Parkinson's disease and 231 controls. The smoking history of all gen otyped subjects was known. Subjects of genotype B12 were more frequent amon g cases than controls (27% and 23.8%, respectively), and were more frequent among "ever smokers" than "never smokers", among controls (27.8% and 17.2% , respectively), although these associations were not statistically signifi cant. Neither TaqIA or TaqIB genotypes modified the inverse relation of smo king and Parkinson's disease. When genotypes for DRD2 were considered in co mbination with genotypes for intron 13 of MAO-B, genotype combinations with high risk of Parkinson's disease were found; although the MAO-B/DRD2 inter action did not reach statistical significance after Bonferroni correction f or multiple comparisons, these results are suggestive of a possible synergi sm between MAOB and DRD2 genes with respect to Parkinson's disease.