title: Elevation of cystatin C in susceptible neurons in Alzheimer's disease.
abstract: A common polymorphism in the cystatin C gene is associated with increased risk of developing Alzheimer's disease (AD). To explore possible neuropathological consequences of this genetic association, we examined expression of cystatin C in brains from 22 AD and 11 control patients by immunohistochemistry. In the temporal cortex of all AD brains, there was strong cystatin C immunostaining of neurons and activated glia, whereas staining was absent or minimal in 7 of the 11 control brains. Neuronal staining of cystatin C in AD brains was primarily limited to pyramidal neurons in cortical layers III and V, which are the neurons most susceptible to cell death in AD. The increase in cystatin C staining in AD was independent of cystatin C genotype. Immunostaining of cystatin C within neurons showed a punctate distribution, which co-localized with the endosomal/lysosomal proteinase, cathepsin B. A primarily glial source for cystatin C was suggested by parallel studies using in situ hybridization of mouse brain. In human AD brain, there was little co-localization of cystatin C with parenchymal Abeta deposits, although a small fraction of cerebral blood vessels and neurofibrillary tangles were cystatin C-positive. The regional distribution of cystatin C neuronal immunostaining also duplicated the pattern of neuronal susceptibility in AD brains: the strongest staining was found in the entorhinal cortex, in the hippocampus, and in the temporal cortex; fewer pyramidal neurons were stained in frontal, parietal, and occipital lobes. These neuropathological observations reinforce the association between cystatin C and AD, and support a model of cystatin C involvement in the process of neuronal death in AD.
authors.affiliation: Memory Disorders Clinic and the Alzheimer's Research Unit, Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, USA.
authors.forename: A
authors.initials: A
authors.lastname: Deng
authors.forename: M C
authors.initials: MC
authors.lastname: Irizarry
authors.forename: R M
authors.initials: RM
authors.lastname: Nitsch
authors.forename: J H
authors.initials: JH
authors.lastname: Growdon
authors.forename: G W
authors.initials: GW
authors.lastname: Rebeck
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000378:metabolism / Q000473:pathology; D055316:Cystatin C; D015891:Cystatins / Q000378:metabolism*; D004351:Drug Resistance; D020022:Genetic Predisposition to Disease; D006801:Humans; D008875:Middle Aged; D009474:Neurons / Q000378:metabolism*
chemical_list: C525030:CST3 protein, human; C525031:Cst3 protein, mouse; D055316:Cystatin C; D015891:Cystatins