The sea urchin embryo: A model to study Alzheimer’s beta amyloid induced toxicity

Alzheimer’s disease (AD) is the most common form of dementia. The cause of AD is closely related to theaccumulation of amyloid beta peptide in the neuritic plaques. The use of animal model systems representsa 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 inthe degenerative process. As a first step, we identified the presence of an antigen related to the humanAPP, called PlAPP. This antigen, after gastrula stage, is processed producing a polypeptide of about10 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 aroundthe intestinal tube and oesophagus. In addition, incubation of sea urchin embryos with two differentsolutions rich in oligomers and fibrillar aggregates of rAb42 induce activation of apoptosis as detectedby TUNEL assay. Moreover, we demonstrate that aggregates induce apoptosis by extrinsic pathway activation,whereas oligomers induce apoptosis both by extrinsic and intrinsic pathway activation. Utilizingan apoptotic inhibitor, caspases activation was offset and morphological damage rescued. Taken togetherall these observations suggest that the sea urchin may be a simple and suitable model to characterize themechanism underlining the cytotoxicity of Ab42.