Previous studies have reported that non-human primates and rodents exposed to lead during brain development may become dependent on the deposition of pre-determined β-amyloid protein （Aβ）,and exhibit upregulation ...Previous studies have reported that non-human primates and rodents exposed to lead during brain development may become dependent on the deposition of pre-determined β-amyloid protein （Aβ）,and exhibit upregulation of β-site amyloid precursor protein expression in old age.However,further evidence is required to elucidate the precise relationship and molecular mechanisms underlying the effects of early lead exposure on excessive Aβ production in adult mammals.The present study investigated the effects of lead exposure on expression of β-amyloid precursor protein cleavage enzyme-1 （BACE-1） in the rat retina and the production of Aβ in early development,using the retina as a window for studying Alzheimer＇s disease.Adult rats were intraocularly injected with different doses of lead acetate （10μmol/L,100μmol/L,1 mmol/L,10 mmol/L and 100 mmol/L）.The results revealed that retinal lead concentration,BACE-1 and its cleavage products β-C-terminal fragment and retina Aβ1-40 were all significantly increased in almost all of the lead exposure groups 48 hours later in a dose-dependent manner.The only exception was the 10μmol/L group.The distribution of BACE-1 in the retina did not exhibit obvious changes,and no distinctive increase in the activation of retinal microglia was apparent.Similarly,retinal synaptophysin expression did not exhibit any clear changes.These data suggest that lead exposure can result in the upregulation of retinal neuron BACE-1 expression in the early period of development and further increase the overproduction of Aβ1-40 in the retina.Our results provided novel insight into the molecular mechanisms underlying environmentally-induced Alzheimer＇s disease.展开更多
The deposition of amyloid-beta is a pathological hallmark of Alzheimer＇s disease, Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase （beta-site amyloid pr...The deposition of amyloid-beta is a pathological hallmark of Alzheimer＇s disease, Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase （beta-site amyloid precursor protein-cleaving enzyme 1） and r-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of AIzheimer＇s disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer＇s disease.展开更多
Because of a lack of sensitive biomarkers,the diagnosis of Alzheimer＇s disease（AD） cannot be made prior to symptom manifestation.Therefore,it is crucial to identify novel biomarkers for the presymptomatic diagnosis...Because of a lack of sensitive biomarkers,the diagnosis of Alzheimer＇s disease（AD） cannot be made prior to symptom manifestation.Therefore,it is crucial to identify novel biomarkers for the presymptomatic diagnosis of AD.While brain lesions are a major feature of AD,retinal pathological changes also occur in patients.In this study,we investigated the temporal changes in β-site APP-cleaving enzyme 1（BACE1） expression in the retina and brain to determine whether it could serve as a suitable biomarker for early monitoring of AD.APP/PS-1 transgenic mice,3,6 and 8 months of age,were used as an experimental group,and age-matched C57/BL6 wild-type mice served as the control group.In the Morris water maze test,there were no significant differences in escape latency or in the number of crossings in the target area among mice of different ages.Compared with wild-type mice,no changes in learning or memory abilities were detected in transgenic mice at 3 months of age.However,compared with wild-type mice,the escape latency was significantly increased in transgenic mice at 6 months,starting on day 3,and at 8 months,starting on day 2,during Morris water maze training.In addition,the number of crossings of the target area was significantly decreased in transgenic mice.The learning and memory abilities of transgenic mice were further worsened at 8 months of age.Immunohistochemical staining revealed no BACE1 plaques in wild-type mice at 3,6 or 8 months or in transgenic mice at 3 months,but they were clearly found in the entorhinal cortex,hippocampus and prefrontal cortex of transgenic mice at 6 and 8 months.BACE1 expression was not detected in the retina of wild-type mice at 3 months,but weak BACE1 expression was detected in the ganglion cell layer,inner plexiform layer and outer plexiform layer at 6 and 8 months.In transgenic mice,BACE1 expression in the ganglion cell layer was increased at 3 months,and BACE1 expression in the ganglion cell layer,inner plexiform layer and outer plexiform layer was significantly increased at 6 and 8 months,compared with age-matched wild-type mice.Taken together,these results indicate that changes in BACE1 expression appear earlier in the retina than in the brain and precede behavioral deficits.Our findings suggest that abnormal expression of BACE1 in the retina is an early pathological change in APP/PS-1 transgenic mice,and that BACE1 might have potential as a biomarker for the early diagnosis of AD in humans.展开更多
基金the National Natural Science Foundation of China,No.30900773the National University Basic Research Foundation of China,No.2010QZZD022
文摘Previous studies have reported that non-human primates and rodents exposed to lead during brain development may become dependent on the deposition of pre-determined β-amyloid protein （Aβ）,and exhibit upregulation of β-site amyloid precursor protein expression in old age.However,further evidence is required to elucidate the precise relationship and molecular mechanisms underlying the effects of early lead exposure on excessive Aβ production in adult mammals.The present study investigated the effects of lead exposure on expression of β-amyloid precursor protein cleavage enzyme-1 （BACE-1） in the rat retina and the production of Aβ in early development,using the retina as a window for studying Alzheimer＇s disease.Adult rats were intraocularly injected with different doses of lead acetate （10μmol/L,100μmol/L,1 mmol/L,10 mmol/L and 100 mmol/L）.The results revealed that retinal lead concentration,BACE-1 and its cleavage products β-C-terminal fragment and retina Aβ1-40 were all significantly increased in almost all of the lead exposure groups 48 hours later in a dose-dependent manner.The only exception was the 10μmol/L group.The distribution of BACE-1 in the retina did not exhibit obvious changes,and no distinctive increase in the activation of retinal microglia was apparent.Similarly,retinal synaptophysin expression did not exhibit any clear changes.These data suggest that lead exposure can result in the upregulation of retinal neuron BACE-1 expression in the early period of development and further increase the overproduction of Aβ1-40 in the retina.Our results provided novel insight into the molecular mechanisms underlying environmentally-induced Alzheimer＇s disease.
基金supported by the National Natural Science Foundation of China, No. 81171192XMU Basic Training Program of Undergraduate, No. CXB2011019Visiting Scholar Fellowship of Key Laboratory of Ministry of Education for Cell Biology and Tumor Cell Engineering of Xiamen University, No. 201101
文摘The deposition of amyloid-beta is a pathological hallmark of Alzheimer＇s disease, Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase （beta-site amyloid precursor protein-cleaving enzyme 1） and r-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of AIzheimer＇s disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer＇s disease.
基金supported by the National Natural Science Foundation of China(to JFH,DC,JBT),No.81371011,81400399,81471107a grant from the Project of Innovation-driven Plan of Central South University(to DC),No.2015CXS022+2 种基金a grant from the National Key Technologies Research and Development Program of China(to JFH),No.2012BAK14B03Fundamental Research Funds of Central South University of China(to HW),No.2010QZZD022Graduate Thesis Innovation Foundation of Central South University of China(to LL),No.2011ssxt106
文摘Because of a lack of sensitive biomarkers,the diagnosis of Alzheimer＇s disease（AD） cannot be made prior to symptom manifestation.Therefore,it is crucial to identify novel biomarkers for the presymptomatic diagnosis of AD.While brain lesions are a major feature of AD,retinal pathological changes also occur in patients.In this study,we investigated the temporal changes in β-site APP-cleaving enzyme 1（BACE1） expression in the retina and brain to determine whether it could serve as a suitable biomarker for early monitoring of AD.APP/PS-1 transgenic mice,3,6 and 8 months of age,were used as an experimental group,and age-matched C57/BL6 wild-type mice served as the control group.In the Morris water maze test,there were no significant differences in escape latency or in the number of crossings in the target area among mice of different ages.Compared with wild-type mice,no changes in learning or memory abilities were detected in transgenic mice at 3 months of age.However,compared with wild-type mice,the escape latency was significantly increased in transgenic mice at 6 months,starting on day 3,and at 8 months,starting on day 2,during Morris water maze training.In addition,the number of crossings of the target area was significantly decreased in transgenic mice.The learning and memory abilities of transgenic mice were further worsened at 8 months of age.Immunohistochemical staining revealed no BACE1 plaques in wild-type mice at 3,6 or 8 months or in transgenic mice at 3 months,but they were clearly found in the entorhinal cortex,hippocampus and prefrontal cortex of transgenic mice at 6 and 8 months.BACE1 expression was not detected in the retina of wild-type mice at 3 months,but weak BACE1 expression was detected in the ganglion cell layer,inner plexiform layer and outer plexiform layer at 6 and 8 months.In transgenic mice,BACE1 expression in the ganglion cell layer was increased at 3 months,and BACE1 expression in the ganglion cell layer,inner plexiform layer and outer plexiform layer was significantly increased at 6 and 8 months,compared with age-matched wild-type mice.Taken together,these results indicate that changes in BACE1 expression appear earlier in the retina than in the brain and precede behavioral deficits.Our findings suggest that abnormal expression of BACE1 in the retina is an early pathological change in APP/PS-1 transgenic mice,and that BACE1 might have potential as a biomarker for the early diagnosis of AD in humans.
