Increasing evidence suggests that the elevation of beta-amyloid (A beta) peptides in the brain is central to the pathogenesis of Alzheimer's disease (AD). Our recent studies have demonstrated that nobiletin, a polymethoxylated flavone from citrus peels, enhances cAMP/protein kinase A/extracellular signal-regulated kinase/cAMP response element-binding protein signaling in cultured hippocampal neurons and ameliorates A beta-induced memory impairment in AD model rats. For the first time, we report that this natural compound improves memory deficits in amyloid precursor protein (APP) transgenic mice that overexpress human APP695 harboring the double Swedish and London mutations [ APP-SL 7-5 transgenic (Tg) mice]. Our enzyme-linked immunosorbent assay (ELISA) also showed that administration of nobiletin to the transgenic mice for 4 months markedly reduced quantity of guanidine-soluble A beta(1-40) and A beta(1-42) in the brain. Furthermore, consistent with the results of ELISA, by immunohistochemistry with anti-A beta antibody, it was evidently shown that the administration of nobiletin decreased the A beta burden and plaques in the hippocampus of APP-SL 7-5 Tg mice. These findings suggest that this natural compound has potential to become a novel drug for fundamental treatment of AD.
