title: Endolysosome involvement in LDL cholesterol-induced Alzheimer's disease-like pathology in primary cultured neurons.
abstract: OBJECTIVE
  Elevated levels of circulating cholesterol are extrinsic factors contributing to the pathogenesis of sporadic Alzheimer's disease (AD). We showed previously that rabbits fed a cholesterol-enriched diet exhibited blood-brain barrier (BBB) dysfunction, increased accumulation of apolipoprotein B (ApoB) in brain neurons, and endolysosomes in brain had disturbed structures and functions. These effects were linked to increased amyloid beta (Aβ) production, increased tau-pathology, and disrupted synaptic integrity. Because pathological changes to endolysosomes represent a very early event in sporadic AD, we determined here the extent to which ApoB-containing LDL cholesterol altered the structure and function of endolysosomes and contributed to the development of AD-like pathology in primary cultured neurons.
  
  
  METHODS
  Cholesterol distribution and endolysosome morphology were determined histologically. Endolysosome pH was measured ratio-metrically with LysoSensor dye. Endolysosome enzyme activity was measured for acid phosphatase, cathepsins B and D, and beta-site APP cleaving enzyme 1 (BACE-1). AD-like pathologies, including increased production of Aβ, increased tau-pathology, and disrupted synaptic integrity were determined using ELISA, immunoblotting, and immunostaining techniques.
  
  
  RESULTS
  Treatment of neurons with ApoB-containing LDL cholesterol increased endolysosome accumulation of cholesterol, enlarged endolysosomes, and elevated endolysosome pH. In addition, ApoB-containing LDL cholesterol increased endolysosome accumulation of BACE-1, enhanced BACE-1 activity, increased Aβ levels, increased levels of phosphorylated tau, and decreased levels of synaptophysin.
  
  
  CONCLUSIONS
  Our findings suggest strongly that alterations in the structure and function of endolysosomes play a key role in the exhibition of pathological features of AD that result from neuronal exposure to ApoB-containing LDL cholesterol.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Hui
authors.forename: Xuesong
authors.initials: X
authors.lastname: Chen
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Geiger
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology*; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001055:Apolipoproteins B / Q000032:analysis / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism; D002478:Cells, Cultured; D008078:Cholesterol, LDL / Q000737:chemistry / Q000494:pharmacology*; D017931:DNA Primers / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007150:Immunohistochemistry; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D016875:tau Proteins / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D001055:Apolipoproteins B; D008078:Cholesterol, LDL; D017931:DNA Primers; D016875:tau Proteins; D000135:Acid Phosphatase; D053829:Amyloid Precursor Protein Secretases; D002401:Cathepsin B; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human; D002402:Cathepsin D