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

•Colivelin (CL) is a potent neuroprotective peptide with unknown mechanism of action.•CL derivatives bearing tags were developed for biological evaluation experiments.•Fluorescence microscopy studies show specific association of CL with F11 cells.•Biodistribution experiments suggest the presence of radiolabeled CL in the brain.•ELISA type experiments reveal association of CL with Alzheimer’s β-amyloid peptide.

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 99mTc-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 β-amyloid peptide of AD was shown; finally, the 99mTc-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 2 min after injection. The above first successful applications of the CL probes demonstrate their potential to contribute in the field of neuroprotective peptides.