PGC-1? Ameliorates Cognitive Impairment Induced By Chronic Cerebral Hypoperfusion In Mice Via A Reduction In ROS Production

Background&Purpose:Vascular dementia?VaD?refers to the cerebrovascular pathological changes as a result of brain damage caused by dementia,Whitch is the second common cause of dementia after Alzheimer's disease?AD?.Therefore,its clinical manifestations include cognitive dysfunction and neurological dysfunction associated with cerebrovascular disease.Mitochondrial dysfunction and oxidative stress occur in VaD,but the specific molecular mechanism remain unclear.Peroxisome proliferator-activated receptor-?co-activator-1??PGC-1??is a master regulator of mitochondrial function and respiration.Since the mitochondrial electrontransport chain is the main producer of reactive oxygen species?ROS?in most cells,we examined the effect of PGC-1?on the metabolism of ROS.Many studies have shown that increasing PGC-1?levels dramatically protects neural cells in culture from oxidativestressor-mediated death.These studies reveal that PGC-1?is a broad and powerful regulator of ROS metabolism,providing a potential target for the therapeutic manipulation of these important endogenous toxins.Previous researches have shown PGC-1?plays a key role in many neurodegenerative diseases,such as alzheimer's disease?AD?,Multiple sclerosis?MS?,and so on.This study aimed to investigate whether PGC-1?is involved in the pathophysiology of VaD and ROS production in VaD.Methods:First,we divided normal mice into two groups:sham and BCAS,to explore the expression level of PGC-1?in mice.The results showed that the expression level of PGC-1?was decreased in the mice in the BCAS group,so as the mitochondrial uncoupling protein and mitochondrial antioxidant.Secondly,we used Cre/loxP system to realize the knockout of PGC-1?gene in mice under specific conditions,and obtained two transgenic mice:PGC-1?^f/f mice and PGC-1?^f/f/f Eno2-Cre mice.The later can express PGC-1?in neuron cells,but also express IRES-eGFP.The experimental group and control group all of the mice used in this study were were housed under specific pathogen-free conditions and with a 12-hour light/dark cycle.The experiment was divided into three groups:sham,PGC-1?^f/f+BCAS and PGC-1?^f/f Eno2-Cre+BCAS.Chronic cerebral hypoperfusion was induced in mice via bilateral common carotid artery stenosis?BCAS?.The mice were exposed to long-term hypoxia and ischemia,and the cognitive performance of the mice in the BCAS and the control group ware detected by Morris water maze experiment.After completion of MWM-probe testing,the mice were prepared for electrophysiological recording.Long-term potentiation?LTP?in perforant pathway?PP?synapses of the dentate gyrus?DG?was recorded electrophysiologically to assess synaptic plasticity in the various groups of mice.Immunofluorescent staining was used to localize PGC-1?,ionized calcium-binding adaptor molecule 1?Iba1?,glial fibrillary acidic protein?GFAP?,acetylcholinesterase?AChE?,choline acetyltransferase?ChAT?,vesicle acetylcholine transporter?VAChT?,and high-affinity choline transporter?ChT1?in hippocampal CA1 area.Use Real-time quantitative PCR analysis showed that different experimental rat hippocampus mitochondrial antioxidant mRNA?SOD2,Prx3,Trx2,GPx?of the content and the expression of uncoupling protein,including uncoupling protein 2,uncoupling protein4,uncoupling protein 5.Western blot is used to analyze the different experimental mice in expressing PGC-1?,brain derived neurotrophic factor,ChAT in the hippocampus in mice,VAChT and ChT1 expression.Dihydroethidium?DHE,Sigma-Aldrich?was used to detect in situ ROS production in the hippocampus.All analyses was performed using GraphPad Prism 5.0 software to compare differences among groups.Data were presented as means±SEM.Two-way analysis of variance?ANOVA?was used to compare time-course data.One-way ANOVA?Kruskal-Wallis test?followed by appropriate post-hoc test was applied to test differences among multiple groups.For data with nonnormal distribution,the Mann-Whitney U test was used to compare differences between two groups.Conclusions:1.Decreased expression of hippocampal PGC-1?and impaired MWM performance in chronic cerebral hypoperfusion.2.PGC-1?overexpression in neurons is correlated with improved cognitive performance in mice with chronic cerebral hypoperfusion.3.PGC-1?protects against neuronal damage in chronic cerebral hypoperfusion.4.PGC-1?partly ameliorates the cholinergic imbalance in hippocampus in chronic cerebral hypoperfusion.5.PGC-1?reduces glial activation in chronic cerebral hypoperfusion.6.PGC-1?upregulates the expression of mitochondrial antioxidants and UCPs,and reduced oxidative stress in chronic cerebral hypoperfusion.Result:In summary,we observed a significant reduction in PGC-1?levels in the hippocampus of mice with cognitive deficits,which are likely to underlie the decrease in mitochondrial antioxidant enzymes and UCPs expression.Next,we investigated how PGC-1?might affect neurological function after chronic cerebral hypoperfusion by testing mice that overexpress PGC-1?specifically in neurons.After the MWM test,we assessed hippocampal synaptic plasticity of the mice using a LTP assay,these data suggest that PGC-1?contributes to remodeling of synaptic plasticity.These results suggest that PGC-1?overexpression increases BDNF expression.The number of neurons in the hippocampus also appeared to be affected by PGC-1?overexpression.These results suggest that PGC-1?exerts a neuroprotective effect,which partly may be attributable to the restoration of BDNF expression.Several studied have demonstrated that there is cholinergic deficit in dementia.We study cholinergic system molecules,including ChAT,VAChT,ChT1 and AChE in the hippocampus in our VaD mouse model,suggesting that PGC-1?overexpression in neurons protects against the cognitive impairments that ensue after chronic cerebral hypoperfusion,and this may occur partly through positive influences on cholinergic system components.Previous studies indicated that PGC-1?reduces glial activation in chronic cerebral hypoperfusion,PGC-1?upregulates the expression of mitochondrial antioxidants and UCPs,and reduced oxidative stress in chronic cerebral hypoperfusion.In summary,these results suggest that the function of PGC-1?is to protect the vascular dementia by inhibiting the excessive expression of ROS and inhibiting the inflammation of the hippocampus.