Decreased Levels of Intrathecal Interleukin 1 Receptor Antagonist in Alzheimer’s Disease

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Abstract
A growing body of evidence points out the potential role of inflammatory mechanisms in the pathophysiology of brain damage in dementia. In previous studies, we have demonstrated intrathecal production of the proinflammatory cytokine tumor necrosis factor (TNF)α in patients with Alzheimer’s disease (AD). The aim of the present study was to investigate the downstream products of TNF-α expression including interleukin (IL)1β and its naturally occurring antagonist IL-1 receptor agonist (ra) in patients with AD. The cytokine levels were related to neuronal damage, as measured by intrathecal τ and β-amyloid concentration and certain clinical features of the disease. Fifty-two patients with AD and 25 healthy controls were analyzed with respect to cerebrospinal fluid (CSF) levels of IL-1β and IL-1ra. CSF IL-1β was neither detectable in CSF of AD nor in control CSF. In contrast, a significantly lower (p < 0.01) number of patients (24 of 49) than of controls (20 of 24) showed detectable levels of IL-1ra in the CSF. The intrathecal levels of IL-1ra were significantly lower in patients with AD than in the controls. Our study demonstrates a decreased production of the anti-inflammatory compound IL-1ra, suggesting a propensity towards inflammation in patients with AD.