Cerebrospinal fluid inflammatory markers in amnestic mild cognitive impairment

Inflammatory processes might play a significant role at the pathophysiology of Alzheimer's disease (AD). Neuroinflammation is characterized by activation of microglia and the release of inflammatory cytokines, such as interleukin (IL)-1β, IL-6 and tumor necrosis factor-α. Although, it is unknown what the real contribution of these inflammatory markers in the development of AD is. The purpose of the present study was to assess the possible relationship between inflammatory markers in the cerebrospinal fluid (CSF) of amnestic mild cognitive impairment patients (aMCI), aged 60 years or older, and compare with aged healthy controls.

We examined concentrations of IL-1β, IL-6 and tumor necrosis factor-α in the CSF of aMCI patients and controls by enzyme immunoassay. aMCI diagnoses were based on anamnesis and Petersen criteria, corroborated by the Clinical Dementia Rating. Cognitive function was assessed by neuropsychological tests.

CSF levels of IL-1β (13.735 vs 22.932 pg/mL; P < 0.001) and tumor necrosis factor-α (1.913 vs 2.627 pg/mL; P = 0.002), but not IL-6 (4.178 vs 5.689 pg/mL; P = 0.106), were significantly reduced in the aMCI samples as compared with controls. Individuals with IL-1β < 17 pg/mL were at a 7.2 (CI 1.5-36; P: 0.016) increased odds of aMCI. There was a positive correlation between IL-1β levels and the Consortium to Establish a Registry for Alzheimer's Disease word list score (r_s  = 0.299; P = 0.046). Linear regression analysis showed that IL-1β levels might explain 13.7% (β = 24.545; P = 0.012) of the variance on this Consortium to Establish a Registry for Alzheimer's Disease subscore.

The present results show a pattern of cytokines expression in the CSF of aMCI patients that might be relevant to the pathogeny of prodromal AD. Geriatr Gerontol Int 2017; 17: 239-245.