Background: Overproduction of nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) may be an important factor in the pathogenesis of amyotrophic lateral sclerosis (ALS). Owing to their ability to permeate through biological membranes, excess NO and H(2)O(2) may be present in the media surrounding motor neurones. Anti-oxidative defence enzymes (ADEs) in erythrocytes are capable of detoxifying reactive oxygen species (produced endogenously or exogenously), but may also be structurally modified and inactivated by reactive oxygen and nitrogen species. Both balanced and coordinated ADE activities are of utmost importance for their correct physiological function.
Methods: We determined activity of the following ADEs: copper-zinc superoxide dismutase (CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in erythrocytes from sporadic ALS patients [SALS (-/+)], familial ALS patients with the Leu144Phe mutation in the SOD1 gene [FALS (+/+)], asymptomatic carriers with the Leu144Phe mutation in the SOD1 gene (+/-), and control subjects (-/-). We also examined the in vitro effect of diethyldithiocarbamate (DDC) on CuZn SOD activity in erythrocytes from FALS patients, SALS patients and control subjects.
Results: The influence of the Leu144Phe mutation and/or disease was apparent for ADE activities measured in all three patient groups. The SOD1 gene mutation decreased CuZn SOD and GSH-Px activity (two-way ANOVA, significant mutation effect). We noted that the disease also contributed to decreased CuZn SOD activity in SALS patients in comparison with the control group (two-way ANOVA, mutation and disease effect). The disease also influenced CAT and GR activity. CAT activity was decreased in both SALS and FALS patients. In all three patient groups, GR activity was higher than in the control group. Finally, DDC inhibited CuZn SOD activity in erythrocytes from control subjects, FALS (Leu144Phe) patients and SALS patients; however, its effect was more pronounced and significant in FALS patients.
Conclusions: Changes in erythrocyte ADE activities suggest that oxidative stress, involved in the motor neurone pathogenesis of SALS and FALS, also has systemic effects. Differences in ADE systems between the study groups revealed the presence of different types of oxidative pressure, indicating the potential additional benefit of individually designed anti-oxidant cocktail therapies.