1. Alzheimer’s disease (AD)
Alzheimer´s disease (AD) is the most common
form of dementia characterized mainly by massive
neuronal loss and impaired synaptic processes
located in the cerebral cortex, particularly
in the frontal and temporal lobes, and hippocampus
[1]. For over a century, pathologic features
have been used to define AD, whose phenotype
is composed of two main hallmarks: (i)
the deposition of senile plaques, which are extracellular
amyloid-β (Aβ) peptide aggregates
with axons and dendrites usually swollen or
atrophic, and (ii) the neurofibrillary tangles composed
of intracellular hyperphosphorylated TAU
protein and aggregated into paired helical filaments
[1].
Despite the intense research devoted to the
elucidation of the mechanisms underlying AD,
these are so far unknown. It is only welldocumented
the cause of a percentage less
than 1% of cases, known as familial AD (FAD),
which shows a pattern of autosomal dominant
inheritance and early onset of symptoms. FAD is
a monogenic disease associated with the presence
of specific mutations mainly in three
genes that increase the production of Aβ peptide
of 42 amino acids [2]: amyloid-β precursor
protein (APP), presenilin 1 (PSEN1), and to a
lesser extent the presenilin 2 (PSEN2). The rest
of the cases (>99%), called sporadic AD (SAD),
presents a complex interaction between genetic
susceptibility factors and environmental being
the main risk factor for AD, the allele ε4 of the
gene for apolipoprotein E (APOEε4) [3].