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Though the etiology of Parkinson's disease (PD) is unresolved and may be heterogeneous involving both environmental and genetic factors, there are indications that oxidative stress plays an important role in dopaminergic neuronal death. And, it has been reported that inhibition of nitric oxide synthase (NOS) can prevent the destruction of dopaminergic neurons in mammals. To determine if NOS gene polymorphism affects the 5' flanking region that is immediately upstream of the transcription start site lying between the TATA element and CAATT boxes in PD, and differs significantly between patients with PD and normal controls, we studied genetic polymorphism in that region of the neuronal NOS gene in Chinese patients with PD living in Taiwan. The results indicate that the allele size distribution in that region was statistically significantly different between patients with PD and normal.

Debrisoquine 4-hydroxylase (CYP2D6) is one of the cytochrome P450 enzyme families that catalyze the breakdown of a variety of exogenous and endogenous compounds. Previous reports have suggested that genetic polymorphisms of debrisoquine 4-hydroxylase are associated with susceptibility to Parkinson's disease (PD) in Caucasians. To determine if CYP2D6 also confers susceptibility to PD in Chinese patients, we carried out a study of genetic association using three polymorphic markers of the CYP2D6 gene, 188C/T, 1934G/A (mutant B), and 4268G/C. No differences of allele or genotype frequencies of these three polymorphisms were detected upon comparison of primary PD patients (n=53) with normal controls (n=94). The 1934A allele (mutant B), which accounts for the majority of poor metabolizers in Caucasians, is extremely rare in Chinese. Our data do not support the suggestion that the CYP2D6 gene is related to PD susceptibility in Chinese.