Effect Of Aβ_1-42 On The Neuroglobin Expression In Cultured Primitary Rat Basal Forebrain Neurons

BackgroundAlzheimer's disease(AD) is worldwide the leading cause of dementia in the elderly.Senile plaques and neurofibrillary tangles together with neuronal loss and cortical atrophy are characteristic neuropathological features of the disease.Excessive accumulation of amyloid-beta(Aβ) peptide has been proposed as a pivotal event in the pathogenesis of AD.Although the precise mechanism by which Aβinduces neuronal death is still unknown.Possible mechanisms include excess production of reactive oxidative species(ROS) and apoptosis.Several studies suggest that the oxidative stress and apoptosis play a key role in Aβ-mediated neuronal cytotoxicity by triggering or facilitating neurodegeneration through a wide range of molecular events which eventually lead to neuronal cell loss.Neuroglobin(Ngb) is a heme protein belonging to the extended globin family and binds 02 and other gaseous messengers,which was discovered in 2000 by Burmester.The protein in many brain sites including the cerebral cortex, hippocampal,thalamus,hypothalamus,brainstem and cerebellum.We found that its expression in neurons is up-regulated under conditions of hypoxia and the extent of ischemic damage after experimental stroke in the rat is reduced when the amount of Ngb expressed in the brain suggesting a role as an endogenous neuroprotectant.The expression of Ngb increased in cerebral ischemia and hypoxia,oxidative stress,toxic injury and so on.However,the effects of neruoglobin in cultured primitary rat basal forebrain cholinergic neurons exposed to Aβremain unclear. ObjectiveTo investigate the effects of Beta-amyloid peptides(Aβ_1-42) on the neuroglobin expression in cultured primitary rat basal forebrain cholinergic neurons.MethodsPrimary rat basal forebrain cholinergic neurons were cultured and evaluated by Immunocytochemistry.The cells were randomly divided into 4 groups:the control group,the Aβ_1-42 (24h)group,the Aβ_1-42(48h) group and Aβ_1-42(72h) group.The neuroglobin expressing change was observed by RT-PCR and Immunoblotting when the neurons were exposed to Aβ_1-42(2μmol/L) for different time(24h,48h and 72h).ResultsImmunocytochemistry:More than 90%cells were cholinergic neuron.RT-PCR:Being exposed to Aβ_1-42 for 24h,the expression of neuroglobin mRNA was increased significantly compared with the controls(P＜0.05).After being exposed to Aβ_1-42 for 48h,the expression of the neuroglobin mRNA was still increased significantly compared with the controls(P＜0.05),athough it was decresed compared with the 24h.After being exposed to Aβ_1-42 for 72h,the expression of the neuroglobin mRNA showed no significantly chang.Immunoblotting:the expression of neuroglobin changes compared with the controls as neuroglobin mRNA.ConclusionBeing exposed to Aβ_1-42 for different time(24h,48h and 72h) induces differential expressions of neuroglobin in cultured primitary rat basal forebrain cholinergic neurons.Being exposed to Aβ_1-42 for 24h and 48h,the expression of the neuroglobin was increased significantly compared with the controls(P＜0.05),but after being exposed to Aβ_1-42 for 72h,the expression of the neuroglobin showed no significantly chang(P＞0.05).The changes in the expression of the neuroglobin may contribute to resist that Ngb may plays a neuronal protective role in the early of Alzheimer's disease.