Neuroprotective Effect Of A Novel BACE1 Inhibitor And The Mechanistic Studies

Alzheimer's disease(AD)is a prevalent neurodegenerative disease in the elderly.The etiology of AD is still unknown to us as it's a very complex disease.Amyloid-?(A?)cascade and abnormal tau remain to be the two main hypotheses of AD pathogenesis.A?is generated by sequential proteolysis of amyloid precursor protein(APP)with?-site amyloid precursor protein cleaving enzyme 1(BACE1)and?-secretase.BACE1 is the rate-limiting enzyme for the production of A?,and subsequent research found that the expression level and activity of BACE1 are increased in AD patients.As a result,BACE1 is finally considered an effective drug target for AD treatment.To date,there is no BACE1 inhibitor which succeeds in the phase 3 clinical trial.So the discovering of drug candidate of AD is still very challenging.In fact,not only BACE1 inhibitor,other single-target drug candidate has also went to failure.Then researchers realized that AD is a complex and multifactorial disease and that promote some researchers to start the discovery of multi-target drug candidates.Growing evidence support that,in addition to A?and tau,other hypotheses such as oxidative stress also play an important role in the initiation and progression of AD.On the one hand,the initiation of AD accelerates oxidative stress.On the other hand,oxidative stress can promote or accelerate the progression of AD directly or indirectly.Specifically,the accumulation of A?will damage neuronal cell irreversibly by increasing oxidative stress.Then the increased oxidative stress will increase the activity of BACE1 and continue to increase the production of A?.This is a vicious circle that will accelerate the progression of AD.According to the fact,we hope to find a compound which will target both BACE1 and oxidative stress simultaneously to prevent the vicious circle.And we hope this can lay a foundation for the AD drug research.Fortunately,we found a compound named YS-5-23,which simultaneously target BACE1 and oxidative stress,from compounds previously synthesized by our team member.Firstly,YS-5-23 could protect SH-SY5Y cell against H₂O₂-induced cytotoxicity including alleviating H₂O₂-induced apoptosis,loss of mitochondria membrane potential and increase of ROS.Moreover,we found that PI3K/Akt/GSK3?and CREB signaling pathways are involved in YS-5-23's amelioration of cytotoxicity induced by H₂O₂.In addition,YS-5-23 reduced BACE1's expression in both SH-SY5Y and Swedish mutated APP overexpressed HEK293 cells.And concomitantly,s APP?and CTF?,products of proteolysis of APP by BACE1,were also reduced significantly.Moreover,YS-5-23 induced BACE1's transcriptional suppression by reducing BACE1's promoter activity.And PI3K/Akt signaling pathway was also proved to be involved in YS-5-23's inhibition of BACE1.At last,we verified that H₂O₂ could increase BACE1 protein expression at different levels.But YS-5-23 could suppress the up-regulation of BACE1 induced by H₂O₂.PI3K/Akt signaling pathway was also proved to be involved in YS-5-23's inhibition of BACE1's up-regulation induced by H₂O₂.In summary,we found a multifunctional compound YS-5-23 from a series of novel BACE1 inhibitors.YS-5-23 simultaneously inhibited the enzyme activity of BACE1,resisted the cytotoxicity caused by H₂O₂,reduced the protein expression of BACE1 and suppressed BACE1's expression induced by H₂O₂.Therefore,multitarget compound YS-5-23 has the advantage over other single-target candidate in the treatment or prevention of AD in the future.