New labeled derivatives of the neuroprotective peptide colivelin: synthesis, characterization, and first in vitro and in vivo applications.

Colivelin (CL), first reported in 2005, is the most potent member of the humanin family of neuroprotective peptides with in vitro and in vivo rescuing action against insults associated with Alzheimer's disease (AD). The objective of the present work is the design, synthesis and characterization of specific CL derivatives that can be used as molecular probes in the investigation of the unknown mechanism of CL action. Within this framework, three CL derivatives bearing suitable tags, i.e., the fluorescent moiety FITC, the streptavidin-counterpart biotinyl-group, and the (99m)Tc-radiometal chelating unit dimethylGly-Ser-Cys, were developed and subsequently applied in biological evaluation experiments. Specifically, the FITC-labeled derivative of CL was used in confocal microscopy, where specific binding at the periphery of F11 cells was observed; the biotin-labeled derivative of CL was used in an in-house developed ELISA-type assay, where specific and concentration-dependent binding with the ß-amyloid peptide of AD was shown; finally, the (99m)Tc-radiolabeled derivative of CL was used in in vivo biodistribution studies in healthy Swiss Albino mice, where 0.58% of the radioactivity administered was measured in the mouse brain 2min after injection. The above first successful applications of the CL probes demonstrate their potential to contribute in the field of neuroprotective peptides.

Oleuropein, an anti-oxidant polyphenol constituent of olive promotes α-secretase cleavage of the amyloid precursor protein (AßPP).

Over the past decade, intense focus has been dedicated on investigating processes involved in the proteolysis of amyloid precursor protein (AßPP) and ß-amyloid (Aß) peptide metabolism, as possible targets for Alzheimer's disease (AD) therapy. To this goal, considerable research has been targeted on potential therapeutic use of compounds promoting non-amyloidogenic processing of AßPP. One of these compounds, oleuropein, a polyphenol constituent of extra virgin olive oil exhibiting a wide range of pharmacological properties, was shown to interact non-covalently with Aß, an interaction that might be related to a potential protective role of oleuropein against Aß aggregation. In the present study, it was demonstrated that oleuropein treatment of HEK293 cells stably transfected with the isoform 695 of human AßPP (APP695) leads to markedly elevated levels of sAPPα and to significant reduction of Aß oligomers. These effects were associated with increased activity of matrix metalloproteinase 9 (MMP-9), whereas no significant alterations in the expression of secretases TACE, ADAM-10 or BACE-1 were observed. Similar results were obtained using the human neuroblastoma cell line SK-N-SH. The experimental data reveal an anti-amyloidogenic effect of oleuropein and suggest a possible protective role for oleuropein against AD, extending the spectrum of beneficial properties of this naturally occurring polyphenol.