Dual-target Inhibitory Activity And In Vivo And In Vitro Biological Efficacy Of Small-molecule Isoquinoline Derivatives In Alzheimer’s Disease

Alzheimer’s disease(AD)is the most common,complex neurodegenerative disease,and it is predicted that the number of patients may increase to 100 million by 2050.Though the tremendous global efforts have been made to combat AD,the disease remains as a great challenge for modern medicine.In the past decades,the development of single-target drugs has not led to any successful treatment for AD.Therefore,in order to prevent the rapid progression of AD,new therapeutic approaches need to target multiple targets in AD.This thesis is divided into three main parts.The first part describes the current treatment and complex pathological hypotheses of AD.The latest research advances in multi-target therapeutic strategies for AD are reviewed and classified.It is expected to provide some reference for the rational design of multi-target therapy for AD.The second and third parts focus on the evaluation of the anti-AD efficacy of two small molecule isoquinoline derivatives,that is,compounds 9S and 9R,with dual inhibitory effects on cholinesterase and Aβ aggregation in vitro,as reported by the group of Associate Professor Kin Yip Tam.Specifically,in the second part,the biological activity and efficacy of 9S against both cholinesterase and Aβ in in vitro models including protein/enzyme and cellular models were first systematically evaluated.Compound 9S exhibited good in vitro inhibitory activity and anti-Aβ aggregation against acetylcholinesterase(AChE)and butyrylcholinesterase(BuChE),and attenuated synaptic dysfunction and reduced Aβaggregation.Secondly,the neuroprotective effects and pharmacokinetic characteristics of9 S were evaluated in triple transgenic AD(3×Tg AD)mice.As a result,compound 9S penetrated the blood-brain barrier,increased the levels of acetylcholine in brain,significantly improved cognitive dysfunction and reduced amyloid burden in 3×Tg AD mice.In particular,mice in the administered group performed significantly better than control mice in behavioral assessments.Treatment with high doses of 9S led to significant reduction in the amyloid plaques in brain tissue in 3×Tg AD mice,and the treatment effect was better for early-stage AD than for late-stage.In addition,various chemical biology studies were applied to further elucidate the possible mechanisms of action of 9S and the possible reasons for the neuroprotective effect in AD models.As a consequence,compound9 S regulates neuronal apoptosis by modulating GSK-3β phosphorylation and ROS levels.Given the finding that compound 9S has an inhibitory effect on GSK-3βphosphorylation,in the third part,compound 9R was combined with GSK-3β inhibitor LiCl.It was expected that the combination would act synergistically to reduce the drug dose while achieving the goal of treating AD.Study on the in vitro and in vivo efficacy of the combination of 9R and LiCl suggested that the combination had better neuroprotective effects than either 9R or LiCl alone at both cellular level and in vivo in 3×Tg AD mice.In particular,after one month of administration,mice showed superior performance in behavioural assessments and had significantly less amyloid plaques in their brain tissue than the control mice.In summary,this thesis focused on evaluating the dual-target inhibitory activity,in vitro and in vivo efficacy and possible mechanisms of small molecule isoquinoline derivative 9S as well as the synergistic ability of 9R and LiCl combination against AD in vivo and in vitro.The present findings suggest that the use of multi-target compounds and combination may be a potential approach for the treatment of AD,and further may provide some reference for systematically evaluating the multiple inhibition toward Aβ aggregation,cholinesterase and GSK-3β,and in vitro in vivo efficacy of a new compound as a potential chemotherapeutic agent for AD.