Correlation Between The Neuroprotective Effect Of Astrocytes Against Excitotoxicity And The Expression Of Amyloid Precursor Protein, Presenilin-1

Objective:Astrocytes is the most abundant glial cell in central nervous system,and it paly an important role in many central nervous system diseases such as stroke,Alzheimer disease, neurodegenerative disease . Astrocytes not only has the ability to up take glutamate , but also has the mechanism of releasing glutamate, especially in patho-logy conditions.so whether Astrocytes is good or not needs further discussion.Amyloid precursor protein (APP) is an integral membrane protein . APP is cleavage byα-Secretase(ADAM10,TACE and ADAM9) ,β-Secretase (BACE1) andγ-Secretase (Presenilin-1 , Presenilin-2,Nicastrin,Aph-1 and Pen-2 complexes) . Cleavage of APP releases secreted APP (sAPPα, sAPPβ) and amyloidβ-protein(Aβ) and other metabolic products.The products of APP cleavaged byγ-Secretase andβ- Secretase are Aβ40 and Aβ42 which associated with Alzheimer's disease.The proporation of Aβ40/Aβ42 is up toγ-Secretase site, however , Presenilin-1(PS1) is the key for activatedγ-Secretase.So PS1 will effect Aβquantity directly . The objective of this study is to observe the function of Astrocyes in excitotoxicity and it's effect to the expression of APP and PS1 in cultured rat hippocampal neurons and astrocyte-neuron co-culture, and to explore the effects of Astrocytes on damages and reparation of excitotoxicity, furthermore discuss the molecular mechanism of neuroprotective effect of Astrocytes, and hope to find a new strategy for neuroprotection and neurogenerative regulation.Methods:The primary hippocampal cultures from neonatal rat were treated with 50μM glutamate and 5μM glycine at 12 day in vitro. Trypan blue staining , Observed the neuroprotective effect of Astrocytes on neurons. Double immunofluorescent staining was used to observe the glutamate-induced expression and distribution changes of APP and PS1 in cultured hippocampal neurons and astrocyte-neuron co-culture , and effects of Astrocytes on this process.Results:1. Glutamate could induce marked damage in cultured hippocampal neurons.2. Death cell demonstrated by trypan blue staining in two cultured system is xˉ=11.2±2.9 and xˉ=10.8±3.3.3. Expressive location of APP and PS1 is uniform, both of them are expressed on nuclei, soma and processes of neurons.The immunofluorescent optical density of APP/ PS1 in neuron culture and neuon-astrocyte co-culture is 0.37/0.39 and 0.18/0.16 respectively.Conclusions:In the excitotocity model of 50μM[Glu] and 5μM[Gly]:Astrocytes aggravate the excitoxcity and inhibitate the expression of APP and PS1.