Dopamine Therapy and the Regulation of Oxidative Stress and Mitochondrial DNA Copy Number in Patients with Parkinson's Disease

Few studies have reported on changes to oxidative stress and mitochondrial DNA copy numbers in patients with Parkinson's disease (PD), particularly those undergoing long-term dopamine therapy. This study measured mitochondrial copy numbers, thiobarbituric acid reactive substances (TBARS), and thiols in 725 PD patients and 744 controls. The total prescribed dopamine dose was calculated for each PD patient. A decreased mitochondrial copy number and antioxidant thiols level, but an elevated oxidative TBARS level presented in PD patients. Stratification into age subgroups revealed a consistently lower mitochondrial copy number and thiols in all PD subgroups, but increased TBARS levels compared with those of the controls. Further study found an association between lower serum TBARS and dopamine administration. There appears to be an indirect relationship with the mitochondrial copy number, where a decrease in TBARS was found to diminish the effect of pathogenetic and age-related decrease in mitochondrial copy number in PD patients. Follow-up evaluations noted more significant decreases of mitochondrial copy numbers in PD patients over time; meanwhile, dopamine administration was associated with an initial decrease of the TBARS level which attenuated with high-dose and long-term therapy. Our study provides evidence that moderate dopamine dose therapy benefits PD patients through attenuation of oxidative stress and manipulation of the mitochondrial copy number.