Plasma and urinary HPLC-ED determination of the ratio of 8-OHdG/2-dG in Parkinson's disease.

BACKGROUND

Oxidative stress may be directly or indirectly involved in the pathogenesis of Parkinson's disease (PD). 8-hydroxy-2'deoxyguanosine (8-OHdG) is the major product of DNA oxidative damage but its determination in plasma or urine may have controversial significance. The concentration of 8-OHdG not only depends on its oxidation rate but also on the efficacy of the DNA repairing systems.

METHODS

We studied the ratio between 8-OHdG and 2-dG (the corresponding not hydroxylated base 2'-deoxyguanosine) in plasma and urine as a marker of oxydative stress in PD. This enabled the determination of the real DNA damage in terms of oxidation rate regardless of the efficacy of the DNA repairing mechanisms.

RESULTS

We optimized two different analytical methods: one for 8-OHdG and the other for 2-dG, both based on a common preliminary solid-phase extraction step (SPE) followed by two different HPLC analytical separations with electrochemical detection (HPLC-ED). The reliability of these methods was confirmed by analysing plasma and urine samples collected in parkinsonian patients and in age-matched healthy control subjects.

CONCLUSIONS

In urine samples, the measurement of 8-OHdG alone as well as the ratio 8-OHdG/2-dG were significantly different in healthy controls and PD patients. In plasma samples, only the ratio 8-OHdG/2-dG was significantly higher in PD compared to healthy controls showing that the ratio 8-OHdG/2-dG is a reliable diagnostic tool in studies on DNA oxydative damage.