Antioxidant Enzymatic Activities in Alzheimer's Disease: The Relationship to Acetylcholinesterase Inhibitors

Abstract

The mode of action of acetylcholinesterase inhibitors (AChEIs) in Alzheimer's disease (AD) is mainly by potentiating neuronal transmission. Animal studies have also consistently described a role for AChEIs in enhancement of antioxidants and attenuation of oxidative stress. The influence of AChEIs on blood antioxidants in AD patients has not been established before. Furthermore, AChEI treatment, or lack of it, may have contributed to the inconsistent antioxidant data reported by other studies so far. Here we sought to investigate the potential modulation effect of AChEIs on blood antioxidants in AD patients. Catalase (CAT) and glutathione reductase (GR) activities were analyzed in 25 drug naïve patients (Group A), 43 patients receiving AChEIs (Group B) and 34 cognitively unimpaired controls (Group C). A statistically significant difference for CAT and GR was observed between the two AD groups (A and B) when compared to the control group C (KW-H = 36.530, p < 0.001; post hoc tests p < 0.001 and KW-H = 37.814, p < 0.001; post hoc tests p < 0.001, respectively). In contrast, CAT and GR activities did not differ significantly between the two AD groups, and were not influenced by AChEI treatment. Hence, these results do not replicate the extensively reported data from animal studies and question whether AChEI efficacy in AD is mediated by processes beyond neuron to neuron enhancement of transmission. Studies assessing a wider range of oxidative/inflammatory markers taking into account type, dosage, and treatment duration of the various acetylcholinesterase inhibitors are now needed.