Abeta(1-40) peptide radiopharmaceuticals for brain amyloid imaging: (111)In chelation, conjugation to poly(ethylene glycol)-biotin linkers, and autoradiography with Alzheimer's disease brain sections.
The amyloid plaques of Alzheimer's disease (AD) are formed by the neuropeptide Abeta(1)(-)(42/43), and carboxyl terminal truncated forms of this neuropeptide, designated Abeta(1)(-)(40), bind to amyloid plaques of AD autopsy tissue sections. Therefore, Abeta(1)(-)(40) is a potential peptide radiopharmaceutical that could be used for imaging brain amyloid in living subjects with AD, should this neuropeptide be made transportable through the blood-brain barrier (BBB). To accomplish this, the neuropeptide must be modified to enable (i) attachment to a BBB drug targeting system and (ii) labeling with a radionuclide, e.g., 111-indium, suitable for brain imaging by external detection modalities such as single photon emission computed tomography (SPECT). The present studies describe the synthesis of an Abeta(1)(-)(40) analogue that contains a biotin at the amino terminus and a diethylenetriaminepentaacetic acid (DTPA) moiety conjugated to one of the internal lysine residues. The DTPA-[N-biotin]-Abeta(1)(-)(40) was purified by gel filtration fast-protein liquid chromatography (FPLC) using two Superose 12HR columns in series, and the structure of the purified peptide was confirmed by matrix-assisted laser desorption ionization (MALDI) mass spectrometry. The binding of the [(111)In]DTPA-[N-biotin]-Abeta(1)(-)(40) to amyloid plaques of AD autopsy tissue sections was demonstrated by film and emulsion autoradiography. A poly(ethylene glycol) (PEG) linker of 3400 Da molecular mass, designated PEG(3400), was inserted between the Abeta(1)(-)(40) and the biotin moiety, but this modification diminishes binding of Abeta(1)(-)(40) to the AD amyloid plaques. In summary, these studies describe a novel formulation of biotinylated Abeta(1)(-)(40) that allows radiolabeling with 111-indium. The peptide radiopharmaceutical may be conjugated to an avidin-based BBB drug targeting system to enable transport through the BBB and imaging of brain amyloid in vivo.
Kurihara
A
A
Department of Medicine, UCLA School of Medicine, Los Angeles, California 90095-1682, USA.
Pardridge
W M
WM
D000544:Alzheimer Disease / Q000378:metabolism*; D000682:Amyloid / Q000032:analysis*; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D001345:Autoradiography / Q000379:methods*; D019921:Biotinylation; D001923:Brain Chemistry; D002540:Cerebral Cortex / Q000737:chemistry; D006801:Humans; D007205:Indium Radioisotopes / Q000737:chemistry; D007553:Isotope Labeling; D004369:Pentetic Acid / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000682:Amyloid; D016229:Amyloid beta-Peptides; D007205:Indium Radioisotopes; D010446:Peptide Fragments; D019275:Radiopharmaceuticals; C078592:amyloid beta-protein (1-40); D011092:Polyethylene Glycols; D004369:Pentetic Acid