title: 22R-Hydroxycholesterol protects neuronal cells from beta-amyloid-induced cytotoxicity by binding to beta-amyloid peptide.
abstract: 22R-hydroxycholesterol, a steroid intermediate in the pathway of pregnenolone formation from cholesterol, was found at lower levels in Alzheimer's disease (AD) hippocampus and frontal cortex tissue specimens compared to age-matched controls. beta-Amyloid (Abeta) peptide has been shown to be neurotoxic and its presence in brain has been linked to AD pathology. 22R-hydroxycholesterol was found to protect, in a dose-dependent manner, against Abeta-induced rat sympathetic nerve pheochromocytoma (PC12) and differentiated human Ntera2/D1 teratocarcinoma (NT2N) neuron cell death. Other steroids tested were either inactive or acted on rodent neurons only. The effect of 22R-hydroxycholesterol was found to be stereospecific because its enantiomer 22S-hydroxycholesterol failed to protect the neurons from Abeta-induced cell death. Moreover, the effect of 22R-hydroxycholesterol was specific for Abeta-induced cell death because it did not protect against glutamate-induced neurotoxicity. The neuroprotective effect of 22R-hydroxycholesterol was seen when using Abeta1-42 but not the Abeta25-35 peptide. To investigate the mechanism of action of 22R-hydroxycholesterol we examined the direct binding of this steroid to Abeta using a novel cholesterol-protein binding blot assay. Using this method the direct specific binding, under native conditions, of 22R-hydroxycholesterol to Abeta1-42 and Abeta17-40, but not Abeta25-35, was observed. These data suggest that 22R-hydroxycholesterol binds to Abeta and the formed 22R-hydroxycholesterol/Abeta complex is not toxic to rodent and human neurons. We propose that 22R-hydroxycholesterol offers a new means of neuroprotection against Abeta toxicity by inactivating the peptide.
authors.affiliation: Division of Hormone Research, Departments of Cell Biology, Pharmacology and Neurosciences and Samaritan Research Laboratories, Georgetown University School of Medicine, Washington DC 20057, USA.
authors.forename: Zhi-Xing
authors.initials: ZX
authors.lastname: Yao
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Brown
authors.forename: Gary
authors.initials: G
authors.lastname: Teper
authors.forename: Janet
authors.initials: J
authors.lastname: Greeson
authors.forename: Vassilios
authors.initials: V
authors.lastname: Papadopoulos
mesh_terms: D000368:Aged; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D016923:Cell Death; D002460:Cell Line; D003198:Computer Simulation; D005260:Female; D005625:Frontal Lobe / Q000737:chemistry; D018698:Glutamic Acid / Q000633:toxicity; D006624:Hippocampus / Q000737:chemistry; D006801:Humans; D006888:Hydroxycholesterols / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D008958:Models, Molecular; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology*; D016716:PC12 Cells; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D016229:Amyloid beta-Peptides; D006888:Hydroxycholesterols; D018696:Neuroprotective Agents; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); C074636:amyloid beta-protein (25-35); C003585:22-hydroxycholesterol; D018698:Glutamic Acid