Expression And Function Of Phosphodiseterases(PDEs) In The Brain Of 3×Tg-AD Mice

Background:Alzheimer’s disease（AD）is a neurodegenerative disease with progressive impairments of memory and cognition functions in elderly.The pathogenesis of AD has not been fully elucidated and there is no effective therapeutic drugs to date.Phosphodiesterases（PDEs）,which hydrolyze c AMP and/or c GMP,have been considered as potential targets for treatment of AD.While PDEs have been widely investigated in AD-associated studies,few reports have been published on the changes in PDEs in APP_Swe/PS1_{d E91}/Tau_P301L triple transgenic（i.e.3×Tg-AD）mice,an animal model to simulate human AD.Objective:To observe the expression of PDEs in the brain of 3×Tg-AD mice and identify dominant PDEs involved in AD.Methods:1.Evaluation of 3×Tg-AD mouse model and screening of dominant PDEs11-month-old 3×Tg-AD mice were used,in comparison with age-matched wild-type C57BL/6J（Wild Type,WT）mice with the same genetic background.The AD model was evaluated using behavioral analysis,expression of APP,PS1,Tau,Aβ_1-42protein,and senile plaques（SP）and neurofibrillary tangles（NFT）;expression of PDEs in the cerebral cortex and hippocampus of 3×Tg-AD mice were detected by Western blot,and dominant PDEs were identified and changes in m RNA levels detected by q RT-PCR.2.To observe the changes of dominant PDEs in the brain of 3×Tg-AD mice at different ages3×Tg-AD mice of 1,5 and 10 months old were tested for cognitive functions by Morris water maze（MWM）and passive avoidance test.The expression of dominant PDEs in the cerebral cortex and hippocampus of mice at each age was detected by Western blot.The changes of the dominant PDEs in the AD model was further confirmed.3.Effects of the PDE7A inhibitor ASB16165 on learning and memory in3×Tg-AD miceThe effect of PDE7A inhibitor ASB16165 on learning and memory ability of3×Tg-AD mice was observed by Morris water maze（MWM）and passive avoidance test.4.Data analysisAll data were statistically analyzed with SPSS16.0 software.Two-sample T-test was used for comparison between samples.Statistical difference was observed at P<0.05.Result:1.Evaluation of 3×Tg-AD mouse model and screening of dominant PDEsIn MWM,compared with WT mice,the escape latency to the platform in 3×Tg-AD mice was significantly prolonged,and the latency entering the previous area of the escape platform for the first time was significantly prolonged,and entries to the target quadrant were reduced,the exploration time in the target quadrant was significantly reduced.Consistently,in the passive avoidance test,3×Tg-AD mice had a longer time in the dark compartment,more entries to the dark side and shorter latency of entering the dark compartment compared to the WT mice.These results demonstrated that the cognitive function of 3×Tg-AD mice at 11 months was decreased.Western blot results showed that the expression of APP,PS1,Tau and Aβ_1-42 protein in the brain of 3×Tg-AD mice was significantly increased.Moreover,the SP and NFT were observed in the brain of 3×Tg-AD mice.The above results indicate that 11-month-old 3×Tg-AD mice have significant AD characteristic changes.Further detection of the expression of PDEs showed that PDE1B,PDE2A,PDE4D,PDE5A and PDE7A proteins had obvious changes in 11-month-old3×Tg-AD mice compared with WT,which were consistent with the changes in the m RNA levels.In addition,the changes of protein and m RNA showed different trends in both sexes and brain regions,in particular in the cerebral cortex and hippocampus.2.Changes of dominant PDE in the brain of 3×Tg-AD mice at different ages3×Tg-AD mice at 1,5,10 months were used to evaluate the change of dominant PDEs.Results showed that the learning and memory abilities of 3×Tg-AD mice at different age for the experiment were significantly reduced compared with WT mice,and the dominant PDEs changed significantly with age,especially PDE7A.The expression of PDE7A was increased significantly in both female and male mice,the cerebral cortex and hippocampus with the increase of month age,but decreased in females compared with WT mice,and increased significantly in males compared with WT mice.3.Effects of PDE7A inhibitor ASB16165 on learning and memory in 3×Tg-AD miceIn water maze place navigation test,compared with WT mice,the escape latency to the platform in 3×Tg-AD mice was significantly prolonged,the exploration time in the target quadrant was significantly reduced compared with 3×Tg-AD mice;the escape latency to the platform in the drug-treated animals was significantly reduced,the exploration time in the quadrant was significantly prolonged,especially at the low dose（1mg/kg）of ASB16165.In the passive avoidance test,3×Tg-AD mice had more entries to the dark compartment and shorter latency of entering the dark side compared with the WT mice.memory was improved when given ASB16165,especially at the low dose.Conclusion:1.11-month-old 3×Tg-AD mice had cognitive dysfunction and characteristic pathological changes of AD in the present study.2.Compared with WT mice,PDE1B,PDE2A,PDE4D,PDE5A and PDE7A were changed significantly in the brain of 11-month-old 3×Tg-AD mice.3.Compared with WT mice,the learning and memory ability of 3×Tg-AD mice at 1,5 and 10 months was decreased,and the dominant PDEs also had significant changes,especially PDE7A,which appeared to change in a sex-specific manner.4.PDE7A inhibitors improved the cognitive function of 3×Tg-AD mice.