The Effect Of PHA-543613 On Neuronal Apoptosis And Cognition Of Presenilin1 And Presenilin2 Conditional Double Knockout Mice

Alzheimer's diease(AD)is the most common progressive neurodegenerative disorder.AD patients were characterized clinically by progressive deterioration of memory and other cognitive abilities,by dysfunction of hippocampus and cortex,by loss of neurons and by formation of neurofibrillary tangles and amyloid plaques.Mutations in three genes including APP,PSEN1,PSEN2 are the major cause of early-onset familial Alzheimer's disease(FAD).The mechanism by which presenilin mutations cause memory loss and neurodegeneration remains unclear.The?7-nicotinic ACh receptors(a7nAChRs)dysfunction is involved in the pathophysiology of AD and thus make itself a therapeutic target in AD,however the mechanism is still not clear.Here,by using Presenilin-1 and Presenilin-2 double knockout mice(cDKO mice),combined behavioral techniques with molecular biology,we examine the role of PSEN1 and PSEN2 in neuronal apoptosis and cognition,we test the effect of PHA-543613 treatment on the cognition and neuronal apopopsis of cDKO mice.We also reveal a variety of underlying mechanisms of how PHA-543613 treatment improve the cognition and decrease the neuronal apoptosis of cDKO mice.Our results are as follows:1.The knockout of PSEN1 and PSEN2 impaired ?-secretase activity1)The results of western blotting suggested the level of PS1-CTF was decreased in 6 months old cDKO mice.2)The results of Elisa suggested the level of A?1-42 was decreased in 6 months old cDKO mice,these results demonstrate that the knockout of PSEN1 and PSEN2 disrupt y-secretase activity.2.The knockout of PSEN1 and PSEN2 cause loss of neurons1)Results showed the level of caspase-3 was significantly increased in cDKO mice,demonstrate that loss of presenilin cause increasing neuronal apoptosis.2)We found the level of proteins related to PI3K signals were reduced in 6 months old cDKO mice,indicated that the activity of PI3K signals were inhibitied,and the ability of PI3K signals to protect neuron from death were abnormal.3.The knockout of PSEN1 and PSEN2 impair the hippocampal memory1)The results of water maze task suggested the spatial reference memory were damaged in cDKO mice.2)The results of passive avoidance task suggested the aversive fear memory were also damaged in cDKO mice.4.PHA-543613 decrease the neuronal apoptosis of cDKO mice1)The PHA-543613 treatment decrease the level of caspase-3,indicated that the PHA-543613 treatment decrease neuronal apoptosis of cDKO mice.2)The PHA-543613 treatment reverse the level of proteins which are related to PI3K signals,indicated that the PHA-543613 treatment activates PI3K signals,and decrease neuronal apoptosis of cDKO mice.5.PHA-543613 rescue the hippocampal memory of cDKO mice.1)The results of water maze task suggested the PHA-543613 treatment reverse the spatial reference memory of cDKO mice.2)The results of passive avoidance task suggested the PHA-543613 treatment reverse the aversive fear memory of cDKO mice.3)The results of western blotting suggested the PHA-543613 treatment increase the level of GluN2A,GluN2B,GluA1,GluA2 which were related to synaptic plasticity of cDKO mice,indicated the PHA-543613 treatment reverse hippocampal memory by increasing the level of these receptors.To sum up,the knockout of PS1 and PS2 lead to the neural death and impaired cognition of cDKO mice,the underlying mechanism of this may be that,loss of presenilin impaired the activity of y-secretase,leading to decreaseing level of A?1-42,and then resulting in abnormal function of a7nAChRs.Dysfunction of a7nAChRs may inhibit the activity of PI3K signals and then reduce the level of NMDAR,at last leading to impaired cognition of cDKO mice.PHA-543613 treatment rescue the dysfunction of a7nAChRs,and then increase the activity of PI3K signals,decrease neuronal apoptosis of cDKO mice.PHA-543613 treatment also increase the level of GluN2A,GluN2B,GluAl and GluA2 and reverse the learning and memory deficiency of cDKO mice.Our results may not only provided new experimental data to the uderlying mechanisms of the AD sympotoms in cDKO mice,but also proposed a promising therapeutic strategy for impaired cognition in AD patients.