In ADbrains, the expression of MAO-B is increased in the hippocampusand cerebral cortex compared to healthy brains., A significantly higher level of active MAO-B is found in reactiveastrocytes surrounding amyloid-β deposits of the hippocampusand frontal cortex of the brains with AD. The overexpression of MAO-B in astrocytes is thought to promotethe excessive metabolism of monoamines, leading to an increased productionof free radicals and hydrogen peroxide (H2O2). This evidence concerns the gene MAOB and Alzheimer disease.