Time evolution of the aggregation process of peptides involved in neurodegenerative diseases and preventing aggregation effect of phosphorus dendrimers studied by EPR.
A key pathological event of prion and Alzheimer diseases is the formation of prion and amyloid plaques generated by peptide aggregation in the form of fibrils. Dendrimers have revealed their ability to prevent fibril formation and therefore cure neurodegenerative diseases. To provide information about the kinetics and the mechanism of peptide fibril formation and about the ability of the dendrimers to prevent peptide aggregation, we performed a computer-aided EPR analysis of the selected nitroxide spin probe 4-octyl-dimethylammonium,2,2,6,6-tetramethyl-piperidine-1-oxyl bromide (CAT8) in water solutions of the β-amyloid peptide Aβ 1-28 and the prion peptide PrP 185-208, which contain the fibril nucleation sites, in the absence and in the presence of phosphorus dendrimers. After a careful selection of the experimental conditions that allow aggregation to occur and to be monitored by EPR analysis over time, it was found that the Aβ 1-28 fibrils formed in 220 min at 0.5 mM peptide, 0.05 mM CAT8, 0.04 mg/mL heparin, and pH = 5. As a consequence, the interacting sites available for cooperative interactions with CAT8 were engaged in the peptide-peptide interactions and a fraction of the probe was extracted in the fluid fibril/water interphase, while another fraction was trapped at the peptide/peptide interphase, showing a decrease in mobility. Conversely, in the presence of the dendrimer (at the selected, after several trials, peptide/dendrimer molar ratio = 50), due to dipole-dipole interactions with peptide monomers, the probe remained at the dendrimer/peptide interphase and the spectral parameters negligibly changed over time. A fraction of probes inserted in PrP 185-208 low-packed aggregates and monitored their fast formation after 90 min. However, the binding organization of the prion peptide negligibly changed upon aggregation in comparison to Aβ 1-28. It is proposed that dendrimers mainly interfere in the lag (nucleation) phase of the prion peptide.
Department of Geological Sciences, Chemical and Environmental Technologies, University of Urbino, Loc. Crocicchia, 61029 Urbino, Italy, Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse, Cedex 04, France, and Department of General Biophysics, University of Lodz, 12/16 Banacha Street, 90-237 Lodz, Poland.
M Francesca
MF
Ottaviani
Roberto
R
Mazzeo
Michela
M
Cangiotti
Luigi
L
Fiorani
Jean Pierre
JP
Majoral
Anne Marie
AM
Caminade
Elzbieta
E
Pedziwiatr
Maria
M
Bryszewska
Barbara
B
Klajnert
D050091:Dendrimers / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D015394:Molecular Structure; D019636:Neurodegenerative Diseases / Q000473:pathology*; D010455:Peptides / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D017510:Protein Folding; D013997:Time Factors
D050091:Dendrimers; D010455:Peptides; D010758:Phosphorus