The Effects And Mechanisms Of New Antiepileptic Drugs On Neuropathology And Behavioral Impairments In APPswe/PS1dE9Transgenic Mice

Alzheimer’s disease (AD) has become an enormous public health issue duringthe global aging process, which has caused huge economic burden. AD ischaracterized clinically by progressive cognitive decline and pathologically bydeposition of amyloid beta (Aβ) and formation of neurofibrillary tangles in the brain.To date, no “disease-modifying” drug has shown therapeutic benefits and acceptablesafety. Elevated activity of neuronal network has been observed in AD patients and anumber of conditions that confer risk of AD. Experimental evidence has demonstratedthe closer relationship between the activity of neuronal network and Aβ-inducedneuropathology and cognition impairment.The inhibitory effect of antiepileptic drugs on the activity of neuronal networkhas been demonstrated in animal models of various diseases, including AD, epilepsyand normal aging. The traditional antiepileptic drug valproic acid (VPA) significantlyalleviated memory deficits and reduced neuropathology in AD transgenic mice. VPAexerted protective effects via suppressing the activity of neuronal network andinhibiting the activity of histone deacetylase (HDAC). Published studies haveindicated that both Topiramate (TPM) and Levetiracetam (LEV) could exertinhibitory effects on HDAC activity. The effects and mechanisms of TPM and LEVon neuropathology and behavioral impairments in AD transgenic mice have not been investigated.The activity of neuronal network and HDAC activity have been regarded astherapeutic strategies for AD. Considering that the new antiepileptic drugs TPM andLEV could modify the activity of neuronal network and HDAC activity, we proposedthe following questions. First, could the new antiepileptic drugs TPM and LEV exertprotective effects on neuropathology and behavioral impairments in AD transgenicmice? Then, how the new antiepileptic drugs TPM and LEV impact on Aβ clearanceand production pathway? Finally, which signal pathways are involved in themechanisms? All the questions are currently unresolved and are desired furtherinvestigations.PART I The effects of new antiepileptic drugson neuropathology and behavioral impairmentsin APPswe/PS1dE9transgenic miceAims: To determine the effects of new antiepileptic drugs on neuropathologyand behavioral impairments in APPswe/PS1dE9transgenic mice.Materials and Methods: Forty APPswe/PS1dE9transgenic mice (7monthsold) were divided into four groups. Mice were injected with20mg/kg TPM,50mg/kg LEV or30mg/kg VPA i.p., respectively, once daily at the same time, for30days. Mice in control group were injected with PBS. C57BL/6J mice (7months old)were chosen as non-transgenic control. Aβ1-42immunohistochemistry and ThioflavinT staining were used to detect the deposition of Aβ1-42in brains of APPswe/PS1dE9transgenic mice. Western blotting was used to detect the expression of p-tau in brainsof APPswe/PS1dE9transgenic mice. Morris water maze was used to evaluatebehavioral impairments in APPswe/PS1dE9transgenic mice.Results: Compared with the non-transgenic control, there were abundant Aβdeposition in the cortex and hippocampus of APPswe/PS1dE9transgenic mice. In thehidden platform trial of Morris water maze, APPswe/PS1dE9transgenic mice showed longer escape latency and swimming distance than did non-transgenic control. In theprobe trial, APPswe/PS1dE9transgenic mice traveled into the southeastern quadrant,where the hidden platform was placed, significantly less times than didnon-transgenic control. TPM and LEV significantly reduced Aβ deposition and thelevel of p-tau. In the hidden platform trial of Morris water maze, TPM-, LEV-treatedmice traveled into the southeastern quadrant, where the hidden platform was placed,significantly more times than did mice in control group.Conclusion: The results indicated that TPM and LEV reduced amyloid plaquesand tau phosphorylation and alleviated memory deficits in APPswe/PS1dE9transgenic mice.PART II The effects of new antiepileptic drugson Aβ clearance and production pathwayin APPswe/PS1dE9transgenic miceAims: To determine the effects of new antiepileptic drugs on Aβ clearance andproduction pathway in APPswe/PS1dE9transgenic mice.Materials and Methods: In vivo, Forty APPswe/PS1dE9transgenic mice (7months old) were divided into four groups. Mice were injected with20mg/kg TPM,50mg/kg LEV or30mg/kg VPA i.p., respectively, once daily at the same time, for30days. Mice in control group were injected with PBS. In vitro, Human SH-SY5Yneuroblastoma cells were chosen. In different groups,0.25mM TPM,0.25mM LEVor1.0mM VPA was added into the culture media, PBS as a control. The Aβ1-42concentration in brains and peripheral blood of APPswe/PS1dE9transgenic mice wasdetected by ELISA. Western blotting was used to detect the levels of Low densitylipoprotein receptor-related protein1(LRP1) and receptor for advanced glycosylationend products (RAGE) in brains of APPswe/PS1dE9transgenic mice. Western blottingwas used to detect the levels of Microtubule-associated protein light chain3(LC3),Beclin1, amyloid precursor protein (APP), beta-site APP cleaving enzyme1(BACE1), amyloid precursor protein carboxy terminal fragments (APP-CTFs), p-GSK-3β (Ser9),p-Akt (Ser473), p-AMPKα (Ser172), Acetyl-Histone H4(Lys5) in brains ofAPPswe/PS1dE9transgenic mice and SH-SY5Y cells.Results: Both TPM and LEV reduced the brain soluble and insoluble Aβ42concentration and enhanced peripheral blood Aβ42concentration in APPswe/PS1dE9transgenic mice. TPM, LEV treatment significantly increased the LRP1level inbrains of APPswe/PS1dE9transgenic mice. TPM, LEV treatment significantlyincreased the levels of LC3, Beclin1, APP-CTFs, p-GSK-3β (Ser9), p-Akt (Ser473),p-AMPKα (Ser172), Acetyl-Histone H4(Lys5) in brains of APPswe/PS1dE9transgenic mice and SH-SY5Y cells.Conclusion: Both TPM and LEV increased Aβ clearance by up-regulation ofAβ transport and autophagic degradation. TPM and LEV inhibited Aβ generation bysuppressing γ-secretase. The inhibitory effects on the activity of GSK-3β, Akt andAMPKα might be involved in the mechasnisms. Further, TPM and LEV inhibitedHDAC activity in vivo and in vitro.In summary, the novel findings of this study are as follows:1. The new antiepileptic drugs TPM and LEV alleviated neuropathologyand memory deficits in APPswe/PS1dE9transgenic mice.The new antiepileptic drugs TPM and LEV reduced amyloid plaques and tauphosphorylation and alleviated memory deficits and in APPswe/PS1dE9transgenicmice. The present work provides evidence for the “aberrant activity in neuronalnetwork” hypothesis. The results suggest that aberrant activity in neuronal networkmight become a new therapeutic target in AD.2. The new antiepileptic drugs TPM and LEV modified Aβ clearance andproduction pathwayThe new antiepileptic drugs TPM and LEV increased Aβ clearance byup-regulation of Aβ transport and autophagic degradation. The new antiepilepticdrugs TPM and LEV inhibited Aβ generation by suppressing γ-secretase activity.Both might be ascribed to GSK-3β inhibition and HDAC inhibition. The results suggest that HDAC might become a new therapeutic target in AD treatment.