Alzheimer’s disease (AD) is the most common form of dementia. The cause of AD is closely related to the
accumulation of amyloid beta peptide in the neuritic plaques. The use of animal model systems represents
a good strategy to elucidate the molecular mechanism behind the development of this pathology.
Here we use the Paracentrotus lividus embryo to identify molecules and pathways that can be involved in
the degenerative process. As a first step, we identified the presence of an antigen related to the human
APP, called PlAPP. This antigen, after gastrula stage, is processed producing a polypeptide of about
10 kDa. By immunohistochemistry we localized the PlAPP antigen in some serotonin expressing cells.
Similarly, after 48 or 96 h incubation, a recombinant b-amyloid peptide, rAb42, accumulates around
the intestinal tube and oesophagus. In addition, incubation of sea urchin embryos with two different
solutions rich in oligomers and fibrillar aggregates of rAb42 induce activation of apoptosis as detected
by TUNEL assay. Moreover, we demonstrate that aggregates induce apoptosis by extrinsic pathway activation,
whereas oligomers induce apoptosis both by extrinsic and intrinsic pathway activation. Utilizing
an apoptotic inhibitor, caspases activation was offset and morphological damage rescued. Taken together
all these observations suggest that the sea urchin may be a simple and suitable model to characterize the
mechanism underlining the cytotoxicity of Ab42
