REVIEW ARTICLE


Alzheimer´s Disease in the Perspective of Neuroimmunology



Ricardo B. Maccioni*, Andrea González, Víctor Andrade, Nicole Cortés, José Pablo Tapia, Leonardo Guzmán-Martínez
Laboratory of Neuroscience, Faculty of Science, University of Chile & International Center for Biomedicine (ICC), Santiago, Chile


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© 2018 Maccioni et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence of this author at the 1Laboratory of Neuroscience, Faculty of Science, University of Chile and International Center for Biomedicine (ICC) Avda Vitacura 3568, D 513, Vitacura, Santiago, Chile; Tel: +56229536362; E-mail: icc@manquehue.net


Abstract

Background:

Alzheimer’s Disease (AD) is a severe neurodegenerative disorder that includes the occurrence of behavioral disorders as well as memory and cognitive impairment as major symptoms. AD affects around 12% of the aged population in the world. Considerable research efforts have pointed to the role of innate immunity as the main culprit in the pathogenesis of AD. In this context, and according to with our neuroimmunomodulation theory, microglial activation modifies the cross-talks between microglia and neurons. We postulated that glial activation triggered by “damage signals” activates a pathological molecular cascade that finally leads to hyperphosphorylation and oligomerization of the tau protein. Interestingly, these modifications correlate with the gradual cognitive impairment of patients with the AD. Microglial activation is determined by the nature and strength of the stimulus. In the AD, a continuous activation state of microglia appears to generate neuronal injury and neurodegeneration, producing the outflow of pathological tau from the inner of neurons to the extraneuronal space. Released tau, together with the contribution of ApoE4 protein, would then produce reactivation of microglia, thus inducing a positive feedback that stimulates the vicious cycle in neurodegeneration.

Conclusion:

Nevertheless, from the pathophysiological perspective AD is significantly more than a loss of memory. In the initial stages of AD pathogenesis, variations in the dopaminergic pathway along with serotonin diminution play an important role. This may explain why depression is associated with the onset of AD. All these pathophysiological events take place together with immunomodulatory changes that trigger tau oligomerization in the course of neurofibrillary tangles formation. Interestingly, mood disorders appear to be followed by neuroinflammatory processes and structural/functional alterations that lead to cognitive impairment in the context of AD.

Keywords: Alzheimer´s disease, Tau protein, Neuroimmunology, The neuroimmunomodulation theory, Microglial cells, Proinflammatory cytokines.