The Effect Of Beta-Amyloid Protein On Expression Of NADPH Oxidase Of Hippocampus In Rats And Its Mechanism

Background and ObjectiveThe pathological changes in encephalon with Alzheimer disease(AD) contain senile plaques and neurofibrillary tangles formation and secondary inflammatory reaction. Pathogenesis of AD is not clear. The theory of chronic inflammatory reaction within the brain has been attach more importance to.Inflammatory characteristics of AD include microglias activated byβ-amyloid(Aβ) protein sediment. CD11b is symbol of microglias activaton. Activated microglias secrete inflammatory substances and cellular factors, reactive oxygen species(ROS) among which can directly damage neurons and lead to the neurons degeneration and apoptosis. At present, studies of a lot of scholars show major source of ROS is nicotinamide adenine dinucleotide phosphate oxidase(NADPH oxidase).NADPH oxidase is a polybody protein, composed of p47phox, p67phox, p40phox, Rac, p22phox and gp91phox.P47phox is catalysis radicle of the enzyme, the increase of whose expression indicates that its power boosts up.The activation of NADPH oxidase is associated with non-receptor protein-tyrosine kinase Src family Fyn, Lyn and Syk. PP2 can inhibite Src kinase. The study discusses whether Fyn, Lyn and Syn result in Aβactivation of NADPH oxidase within microglias in hippocampus through observing the activation by Aβinduction of microglias and changed expression of NADPH oxidase. These provide theoretical foundation for elucidating inflammatory reaction mechanism and finding effective medicine to treat AD.MethodsSeventy-two rats sieved out through Morris water maze experiment were divided randomly into control group, model group and PP2 treating group. AD animal model was established by injected Aβ1-42 into the rat's hippocampus; PP2 was injected into the rat's hippocampus before Aβ1-42 injected into the rat's hippocampus in PP2 treating group; Same volume 0.9% N-S was injected into the rat's hippocampus in control group. Morris water maze was used to detect capacity of study and memory of the 72 rats on 14th day. After the experiment, the rats were executed. Immunofluorescence method detected Aβsediment in hippocampus; Immunohistochemistry method determined the expression of CD11b;RT-PCR was used to measure the expression of mRNA of main radicles of NADPH oxidase and Fyn, Western Blot to detect the expression of protein of p47phox, Fyn, Lyn and Syk in the hippocampus.Results1 Damages of study and memory of the rats in model group were more severe than the rats in control group and PP2 treating group. This difference had statistical significance.2 Aβ1-42 sediment was more prominent in the hippocampus of the rats in model group and PP2 treating group on 14th day, no Aβ1-42 sediment in the hippocampus of the rats in control group. 3 CD11b positive cells by Aβ1-42 induction significantly increased and were activated. the average of CD11b positive cells numbers among control group and model group and PP2 treating group was 100±1,589±25 and 525±23 respectively. This difference(model group vs.control group) had statistical significance.4 The expression of the mRNA of p47phox, p67phox, p40phox, p22phox, gp91phox and Fyn in the hippocampal area of the rats in model group was prominently more than it in control group(P<0.05)and PP2 treating group(P<0.05).It had statistical significance. The correlation of the expression of the mRNA of Fyn and p47phox was positive in model group(r=0.968, P<0.01).5 The expression of p47phox, Fyn, Lyn and Syk in the hippocampus of the rats in model group was significantly more than it in control group(P<0.05)and PP2 treating group(P<0.05).Conclusions1 we injected Aβ1-42 into the rat's hippocampus in order to found the model of AD. This model is an ideal model of groundwork study in AD.Aβsediment in brains may damage study and memory of rats.2 Aβdeposit in brains may lead to inflammatory reaction:Aβincreases the expression of NADPH oxidase. The function may depend on signal transduction pathway of Fyn, Lyn and Syk.