Effects of huperzine A on amyloid precursor protein processing and β‐amyloid generation in human embryonic kidney 293 APP Swedish mutant cells

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Abstract
The amyloid precursor protein (APP) is cleaved enzymatically by nonamyloidogenic and amyloidogenic pathways. α‐Secretase (α‐secretase), cleaves APP within the β‐amyloid (Aβ) sequence, resulting in the release of a secreted fragment of APP (αAPPs) and precluding Aβ generation. In this study, we investigated the effects of an acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Aβ generation in human embryonic kidney 293 cells transfected with human APP bearing the Swedish mutation (HEK293 APPsw). Hup A dose dependently (0–10 μM) increased αAPPs release and membrane‐coupled APP CTF‐C83, suggesting increased APP metabolism toward the nonamyloidogenic α‐secretase pathway. The metalloprotease inhibitor TAPI‐2 inhibited the Hup A‐induced increase in αAPPs release, further suggesting a modulatory effect of Hup A on α‐secretase activity. The synthesis of full‐length APP and cell viability were unchanged after Hup A incubation, whereas the level of AβTotalwas significantly decreased, suggesting an inhibitory effect of Hup A on Aβ production. Hup A‐induced αAPPs release was significantly reduced by the protein kinase C (PKC) inhibitors GF109203X and Calphostin C. These data, together with the finding that the PKCα level was enhanced prior to the increase of αAPPs secretion, indicate that PKC may be involved in Hup A‐induced αAPPs secretion by HEK293 APPsw cells. Our data suggest alternative pharmacological mechanisms of Hup A relevant to the treatment of Alzheimer's disease.

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