Muraoka_2009_Life.Sci_84_272

AIMS: To clarify the mechanism of the protective effect of non-steroidal anti-inflammatory drugs (NSAIDs) on Alzheimer's disease, inactivation of cholinesterase (ChE) induced by NSAIDs was examined. MAIN METHODS: Equine ChE and rat brain homogenate were incubated with NSAIDs and horseradish peroxidase (HRP) and H(2)O(2) (HRP-H(2)O(2)). ChE activity was measured by using 5,5'-dithiobis(nitrobenzoic acid). By using electron spin resonance, NSAID radicals induced by reaction with HRP-H(2)O(2) were detected in the presence of spin trap agents. KEY FINDINGS: Equine ChE was inactivated by mefenamic acid with HRP-H(2)O(2). ChE activity in rat brain homogenate decreased dependent on the concentration of mefenamic acid in the presence of HRP-H(2)O(2). NSAIDs diclofenac, indomethacin, phenylbutazone, piroxicam and salicylic acid inactivated ChE. Oxygen radical scavengers did not prevent inactivation of ChE induced by mefenamic acid with HRP-H(2)O(2). However, spin trap agents 5,5-dimethyl-1-pyrroline-l-oxide and N-methyl-nitrosopropane, reduced glutathione and ascorbic acid strongly inhibited inactivation of ChE, indicating participation of mefenamic acid radicals. Fluorescent emission of ChE peaked at 400 nm, and the Vmax value of ChE changed during interaction of mefenamic acid with HRP-H(2)O(2), indicating that ChE may be inactivated through modification of tyrosine residues by mefenamic radicals. SIGNIFICANCE: The protective effect of NSAIDs on Alzheimer's disease seems to occur through inactivation of ChE induced by NSAIDs radicals.