Soluble cell adhesion molecules in monocytes of Alzheimer's disease and mild cognitive impairment.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with characteristic neuropathological features that are accompanied by inflammatory processes and release of pro-inflammatory cytokines. There is evidence that microglial cells are a key mediator of damage in AD. The microglial compartment may arise to a greater part from activation and transmigration of circulating monocytes. The aim of the present pilot study was to explore, if different cell adhesion molecules (ICAM-1 and -3, PECAM-1, VCAM-1, P-, L- and E-selectins, E-cadherin), RAGE and CD14 are affected in monocytes of healthy subjects compared to patients suffering from AD or mild cognitive impairment (MCI). Monocytes were isolated by negative magnetic selection (MACS) from EDTA blood samples, and extracts were analyzed by Searchlight Multiplex ELISAs. When compared to healthy subjects, the ratio of monocytic ICAM-3/CD14 was significantly decreased in MCI and AD patients and the ratio of the monocytic P-selectin/CD14 was specifically decreased in AD patients. In conclusion, our data show that monocytic cell adhesion molecules are decreased in AD and MCI patients. Further larger longitudinal studies should then clarify whether any of these parameters may be useful as a diagnostic biomarker.