Activation of the contact system in cerebrospinal fluid of patients with Alzheimer disease

Several converging lines of evidence suggest that beta-amyloid and inflamma tion may be linked in the pathogenesis of Alzheimer disease (AD), but the m echanism of beta-amyloid neurotoxicity is unclear, in this study, by demons trating that high molecular weight kininogen may be massively cleaved in th e cerebrospinal fluid (CSF) of patients with AD, we provide evidence of the potential involvement of the contact system in the inflammatory processes taking place in this disease. In the CSF of patients with neuroimmune infla mmatory disease (multiple sclerosis, chronic inflammatory demyelinating pol yneuropathy), there was no evidence of increased cleavage of high molecular weight kininogen, suggesting that this finding maybe characteristic of the Alzheimer brain. The data obtained from in vitro experiments seem to indic ate that the cleavage of high molecular weight kininogen in vivo may be the result of the interaction of beta-amyloid with factor XII and of kallikrei n generation. The actual relevance of such a phenomenon remains to be estab lished in vivo. However, the demonstration that the contact system may be a ctivated in the brains of Alzheimer patients points to the potential involv ement of the kallikrein-kinin system in the inflammatory process of this di sease.