Résumé
? amyloid protein(A?) including A?40 and A?42 are the important bioactive substances in vivo.Their toxic and beneficial attributes in the body depend on its concentration.The brain A? level is maintained by two balances under the physiological condition.The first balance is the generation involved in ?-secretase and ?-secretase and the degradation involved in neprilysin(NEP) and insulin-degrading enzyme(IDE) of A?. The second one is the balance between the receptor for advanced end glycation products(RAGE)-mediated influx and low-density lipoprotein receptor related protein 1(LRP1)-mediated efflux of A? across the blood-brain barrier(BBB).Breakdowning any one of the two balances would result in the aggregation and precipitation of A? in the brain,which is a crucial event in the pathogenesis of Alzheimer's disease(AD).This paper reviews the regulation of brain A? level under the physiological condition and the reducing strategies on the level of brain A? under the pathological condition for developing new drugs in the treatment of AD.