M2b macrophage subset decrement as an indicator of cognitive function in Alzheimer's disease

Abstract

Alzheimer's disease (AD) is a chronic neurodegenerative disease. Various inflammatory processes account for the pathology of AD, and macrophages in particular have a distinct polarization phenotype related to M1/M2 classification. We aimed to investigate macrophage polarization patterns as an indicator of cognitive function in AD. We recruited 54 non-demented individuals as control and 105 AD patients as experimental groups respectively. Percentages of macrophage (PM2K+ CD14+ and PM2K+ CD14- ) and macrophage polarization subsets (M1, M2a, M2b, and M2c) were assessed using flow cytometry. All AD patients were classified by dementia severity using clinical Dementia Rating scale (CDR) as CDR 0.5, 1 and ≧2. AD patients had cognitive function evaluation using Mini-Mental State Examination (MMSE) and Cognitive Assessment Screening Instrument (CASI). We compared the macrophage polarization patterns between control and patient groups. Cognitive function was evaluated in association with macrophage polarization patterns in AD patients. The percentages of PM2K+ CD14+ and PM2K+ CD14- macrophages were higher in AD patients than in controls. M2b macrophage subset decrement and M1 macrophage subset increment of PM2K+ CD14+ and PM2K+ CD14- macrophages were observed in AD patients compared with controls. Although percentages of macrophage subsets were not consistent with CDR staging, PM2K+ CD14+ M2b macrophage subset decrement was correlated with worse cognitive functioning by MMSE and CASI in AD patients. M2b macrophage subset decrement and M1 macrophage subset increment were noted in AD patients, while PM2K+ CD14+ M2b macrophage subset decrement indicated worse cognitive function in such patients.