The Effect And Mechanism Research Of Pioglitazone To The Memory Impairment Of AD Rats

BackgroundAlzheimer disease(AD) is the most common and important neurodegenerative disorders in the eldly,characterized by memory loss, especially recent recall,diminished cognitive ability and behavioral disorders.Mortality of AD has been the forth leading cause preceded by heart disease,cancer and stroke as the world population becoming old and life expectancy increasing.The pathologic feature of AD are neuro fibrillary tangles(NFT) which is in nerve cells and senile Plaque(SP)s which is out of nerve cells and mainly at frontal lobe and hippocampus. The etiological factors and pathogenesis of AD are unknown,and there is no effective therapy method,therefore more deeply studies on it are still needed.At Present,there is no ideal animal models simulating all aspects of AD,it limited the basic studies of AD and development of drugs on AD.So it is an earger to find an ideal and applied animal models of AD.Streptozotocin,a glucosamine derivative of nitorsourea,when injected intracerebroventricularly(ICV) in a subdiabetogenic dose in rat has been found to cause prolonged impairment of brain glucose and energy metabolism accompanied by impairment in leanring and memory. This model may be relevant to that of sporadic AD in humans as both are characterized by a progressive deterioration of both cognitive functions and of cerebral glucose and energy metabolism.Studies have found the changes of the synapses's numbers and structure in AD,however,no reports are available on whether the same changes would be found in intracerebral Streptozotocin injected rat.Treatment with Peroxisome Proliferator Activated Receptor gamma has been reported to produce beneficial effect in this model.Pioglitazone is one of the insulin-sensitizing compounds,thiazolidinedinoes(TZDs) and it is a ligand for Peroxisome Proliferator Activated Receptor gamma (PPAR gamma).Furthermore,it can be administered orally and crosses the blood-brian Barrier.In the present study,we evaluated the effects of pioglitazone on cognitive performance,and the injuries of neuron and synapse which caused by induced by intracerebroventricular(ICV) injection of streptozotocin.ObjectiveThis study discusses the relationship between CNS insulin receptor,synapse and AD as well as the molecular mechanisms about Pioglitazone's beneficial effect to AD through observing the spatial learning/memory,the ultramicrostructure of CA1 area,the changed expressionof Synaptophysin(SYP),Glycogen Synthase Kinase 3 beta (GSK 3 beta) extracellular signal-regulated kinase 1/2(ERK 1/2) in hippocampus of intracerebral Streptozotocin injected rat and Pioglitazone's effect to these factors.These provide theoretical for elucidating the pathogenesy of AD and finding effective medicine to treating AD.MethodAdult male SD rats weighing 300～350 g were procured from Central experimental animal centre of Central South university(CSU). Seventy-five rats were divided randomly into control group,model group and PIO group.Alzheimer disease animal model was established by intracerebroventricular(ICV) injection of streptozotocin.PIO group was intragastric administration by Pioglitazone(30mg/ kg.d),the control group and model group were intragastric administration 10% carboxymethylcellulose sodium.Morris water maze experiment was used to detect the escape latency,number of crossing of platform and percentage of time in aim quadrant after 15 days of opertation;HE staining and Nissl's staining were used to observe the neuronal morphous in CA1 area of the hippocampus after 22 days;Congo red staining and Aβ1-40 immunohistochemical method were used to view the deposition ofβ-amyloid;Electron microscope was used to view the structure of synapse in CA1 area of the hippocampus;and transmission electron microscope and image analyzer were utilized to survey and quantitative analysis texture parameters of the type Gray I synaptic interface in CA1 area of the hippocampus.The expression of Aβ1-40,Synaptophysin in CA1 area of the hippocampus was detectived by immunohistochemical method;RT-PCR was used to measured the expression of Synaptophysin in the hippocampus,and Western blotting to detect the expression of Synaptophysin,GSK-3β,p-GSK-3β,ERK1/2 and p-ERK1/2 in the hippocampus.Result1.Compared with the control group and PIO group,the mean escape latency in model rats was significantly longer and the number of crossing the platform and percentage of time spent in the target quadrant was significantly decreased(P＜0.05).2.The neurons in the CA1 areas of the rats in AD model decrease and distribute irregularly.The damages of the ultrastructure of neuronic organelles in CA1 area are more prominent.Compared with the model group,the neuron in the hippocampal CA1 area of the rats of the rats in PIO group increase and distribute more regularly and the damages of the ultrastructure of neuronic organelles in CA1 area are alleviative.3.The width of synaptic cleft in the CA1 area of the rats in AD group is remarkably increased,the thickness of PSD reduces apparently,flat synapses increase significantly,negative curve synapses and perforated synapses reduce apparently.But PIO can reverse these pathological change of the synaotic interface(P＜0.05).These above mentioned datas are differential between the AD model group and the PIO group and the difference has statistical significance(P＜0.05). 4.The expression of Aβ1-40,Synaptophysin in the hippocampal CA1 area of the rats in AD group is prominently less than that in control group(P＜0.05) and PIO group(P＜0.05).It has statistical significant.5.The expression of the mRNA of Synaptophysin in the hippocampal CA1 area of the rats in AD group is prominently less than that in control group(P＜0.05) and PIO group(P＜0.05).It has statistical significant.6.The expression of Synaptophysin in the hippocampus of the rats in AD group is significantly less than it in the control group(P＜0.05) and PIO group(P＜0.05),and the activity of GSK-3β,ERK1/2 in the hippocampus of the rats in AD group is higher than it in the control group and PIO group.Conclusion1.We ameliorated the method of injecting streptozotocin into the rat's lateral ventricles in order to found the model of AD.This model had a good reproducibility and stabilization.This model was an ideal model of groundwork study in AD.2.AD models established by intracerebroventricular injection of streptozotocin existed cognitive disorder may be because it could induce the structural impairment of neurons and synapse in the hippocampus. Pioglitazone could enhance the cognitive function of ICV STZ injected rats through protect them from the damage mentioned above. 3.Pioglitazone could protect the cognitive function of ICV STZ injected rats might be through the molecule mechanism of down-regulating of the activity of GSK-3βand ERK1/2 in the hippocampus.