Decreased IL-8 levels in CSF and serum of AD patients and negative correlation of MMSE and IL-1β

Background: It is widely accepted that neuroinflammatory processes play an important role in the pathogenesis of Alzheimer's disease (AD) and high levels of cytokines and chemokines are detected around A beta plaques. Methods: As neuroinflammation is involved in the development and progression of AD, we measured the pro-inflammatory cytokines interleukin 1 beta (IL-1 beta), IL-8 and tumor necrosis factor a (TNF-alpha) in serum and cerebrospinal fluid (CSF) samples from 45 AD patients and 53 age-matched control subjects using a highly sensitive multiplex electrochemiluminescence assay. To address the association with disease progression we correlated cognitive status with cytokine levels. Results: CSF as well as serum IL-8 levels were found to be significantly lower in AD patients than in controls (p = 0.02). A statistically significant inverse correlation was observed between the CSF level of IL-1 beta and the MMSE score (rs = -0.03, p = 0.02). We therefore stratified the AD patients by their MMSE scores into three equal groups and found that in the AD group with the most severe cognitive impairment CSF-IL-1 beta was significantly increased compared to age-matched controls (p < 0.05), whereas in the other investigated groups the increase was not statistically significant. Conclusion: Our results confirm data suggesting that cytokine alterations are involved in AD pathogenesis and may be helpful as a biomarker for monitoring disease progression.