Alzheimer’s disease is the most common cause of dementia in the elderly and nowadays it affects an increasing number of people worldwide. The most recurring symptoms include behavioural changes and cognitive skills decline. The symptoms worsen during the course of the disease and finally lead to death. Although lots of researches have been carried out, currently no treatment to cure Alzheimer’s is available. The goal of recent studies is to develop therapies able to interfere with the activities of specific agents involved in the development of the disease. Beta-amyloid (Aβ) protein is one of these agents, as it is known to play a key role in Alzheimer’s pathogenesis. In the brain of people affected by Alzheimer’s, Aβ accumulates in the extraneuronal space in the form of neurotoxic aggregates, called fibrils. Alzheimer’s is part of a group of disorders called amyloidosis, that include tracheobronchial amyloidosis, caused by the accumulation of an amyloid protein in the respiratory tract. The successful results obtained by treating this disease with cycles of conventional radiation therapy led to the hypothesis, promoted in 2008, to extend the radiation treatment to other types of amyloidosis, like Alzheimer’s. Recently the hypothesis to investigate the feasibility of a treatment for Alzheimer’s with non-conventional radiation therapy, specifically Neutron Capture Therapy (NCT), has been proposed at Pavia University and at the Pavia section of the National Institute of Nuclear Physics. The long-term aim of the project is to test if a whole brain long-term low-dose and fractionated neutron irradiation in an animal model of Alzheimer’s, coupled with neutron capture reactions induced in beta-amyloid aggregates, could degrade these structures, resulting in altering the course of the disease and being at the same time tolerable for the brain. This last hypothesis is supported by the fact that lots of clinical trials of NCT are applied safely to some types of brain tumours. This thesis has developed in the first steps of the research and had the goal to study the effects of ionizing radiations on protein aggregates. On experimental level, solutions of Aβ protein and of bovine serum albumin (used as model of fibrillogenic protein) were used in aggregated state. They were irradiated with sources of α particles (Am-241), β- particles (Sr-90) and γ rays (Co-60). After the irradiation, the samples were analysed with different techniques, mainly electrophoresis, with the aim to understand if significant changes were present in the aggregates. Moreover, solutions of Aβ and albumin, prepared with the addition of compounds enriched in boron-10 and thus able to promote the neutron capture reactions, were irradiated at TRIGA Mark II nuclear reactor in Pavia. On computational level, Monte Carlo simulation codes were used both to find the most efficient irradiation setup with Am-241 source and to estimate the energy released in proteins depending upon the irradiation protocols. In the thesis the samples preparation, the irradiation procedures and the post-irradiation analysis are described, along with the geometries and the results of the simulations. The preliminary results obtained until now are then briefly discussed in the final part of the work.
Il morbo di Alzheimer è la causa più comune di demenza negli anziani e colpisce un numero crescente di persone in tutto il mondo. I sintomi più frequenti sono la diminuzione delle capacità cognitive e i cambiamenti comportamentali. Questi peggiorano progressivamente durante la malattia, fino alla morte del paziente. Sebbene molte ricerche siano state condotte in merito, ad oggi non esiste una cura definitiva per l’Alzheimer. L’obiettivo degli studi più recenti è quello di mettere a punto terapie in grado di interferire con l’attività di agenti specifici coinvolti nello sviluppo della malattia. Un esempio di questi agenti è la proteina beta-amiloide (Aβ), che ricopre un ruolo fondamentale nella patogenesi del morbo. Nel cervello delle persone affette da Alzheimer, l’Aβ si accumula nello spazio extraneuronale sotto forma di aggregati neurotossici chiamati fibrille. L’Alzheimer fa parte di una categoria di malattie dette amiloidosi, che includono l’amiloidosi tracheobronchiale, dovuta all’accumulo di una proteina amiloide nel tratto respiratorio. Il successo ottenuto nel trattamento di questa malattia con cicli di radioterapia convenzionale ha portato all’ipotesi, avanzata nel 2008, di estendere il trattamento radioterapico ad altri tipi di amiloidosi, compreso l’Alzheimer. Recentemente l’ipotesi di studio della fattibilità di un trattamento per l’Alzheimer basato su radioterapia non-convenzionale, in particolare sulla Terapia per Cattura Neutronica (NCT), è stata proposta presso l’Università di Pavia e la sezione di Pavia dell’Istituto Nazionale di Fisica Nucleare. Lo scopo a lungo termine del progetto è verificare se un irraggiamento neutronico del cervello a basse dosi, frazionato su un lungo periodo di tempo, in un modello animale di Alzheimer, accoppiato alle reazioni di cattura neutronica indotte negli aggregati di Aβ, possa degradare queste strutture, alterando il corso della malattia e risultando al contempo tollerabile per il cervello. Quest’ultima ipotesi è supportata dal fatto che molti trials clinici di NCT vengono applicati in modo sicuro ad alcuni tipi di tumori cerebrali. Questa tesi si è sviluppata durante le prime fasi della ricerca e ha avuto come obiettivo quello di studiare gli effetti delle radiazioni ionizzanti su aggregati proteici. Sul piano sperimentale, sono state usate soluzioni di proteina Aβ e di sieroalbumina bovina (usata come modello di proteina fibrillogenica) allo stato aggregato. Le soluzioni sono state irraggiate con sorgenti di particelle α (Am-241), particelle β- (Sr-90) e raggi γ (Co-60). Dopo l’irraggiamento i campioni sono stati analizzati con diverse tecniche (principalmente elettroforesi) con l’obiettivo di capire se fossero presenti significativi cambiamenti negli aggregati. Inoltre, soluzioni di Aβ e albumina, preparate con l’aggiunta di composti arricchiti in boro-10 e quindi in grado di favorire le reazioni per cattura neutronica, sono state irraggiate presso il reattore nucleare TRIGA Mark II di Pavia. Sul piano computazionale, sono stati utilizzati codici di simulazione Monte Carlo sia per trovare il setup d’irraggiamento più efficace con la sorgente di Am-241 sia per stimare l’energia rilasciata nelle proteine in base ai diversi protocolli di irraggiamento. Nella tesi vengono quindi descritte la preparazione dei campioni, le procedure di irraggiamento e le analisi condotte successivamente, così come le geometrie e i risultati delle simulazioni. I risultati preliminari fin qui ottenuti vengono quindi brevemente discussi nella parte finale del lavoro.
Studi preliminari degli effetti delle radiazioni ionizzanti su aggregati proteici di rilevanza per la malattia di Alzheimer
BIANCHINI, LINDA
2015/2016
Abstract
Alzheimer’s disease is the most common cause of dementia in the elderly and nowadays it affects an increasing number of people worldwide. The most recurring symptoms include behavioural changes and cognitive skills decline. The symptoms worsen during the course of the disease and finally lead to death. Although lots of researches have been carried out, currently no treatment to cure Alzheimer’s is available. The goal of recent studies is to develop therapies able to interfere with the activities of specific agents involved in the development of the disease. Beta-amyloid (Aβ) protein is one of these agents, as it is known to play a key role in Alzheimer’s pathogenesis. In the brain of people affected by Alzheimer’s, Aβ accumulates in the extraneuronal space in the form of neurotoxic aggregates, called fibrils. Alzheimer’s is part of a group of disorders called amyloidosis, that include tracheobronchial amyloidosis, caused by the accumulation of an amyloid protein in the respiratory tract. The successful results obtained by treating this disease with cycles of conventional radiation therapy led to the hypothesis, promoted in 2008, to extend the radiation treatment to other types of amyloidosis, like Alzheimer’s. Recently the hypothesis to investigate the feasibility of a treatment for Alzheimer’s with non-conventional radiation therapy, specifically Neutron Capture Therapy (NCT), has been proposed at Pavia University and at the Pavia section of the National Institute of Nuclear Physics. The long-term aim of the project is to test if a whole brain long-term low-dose and fractionated neutron irradiation in an animal model of Alzheimer’s, coupled with neutron capture reactions induced in beta-amyloid aggregates, could degrade these structures, resulting in altering the course of the disease and being at the same time tolerable for the brain. This last hypothesis is supported by the fact that lots of clinical trials of NCT are applied safely to some types of brain tumours. This thesis has developed in the first steps of the research and had the goal to study the effects of ionizing radiations on protein aggregates. On experimental level, solutions of Aβ protein and of bovine serum albumin (used as model of fibrillogenic protein) were used in aggregated state. They were irradiated with sources of α particles (Am-241), β- particles (Sr-90) and γ rays (Co-60). After the irradiation, the samples were analysed with different techniques, mainly electrophoresis, with the aim to understand if significant changes were present in the aggregates. Moreover, solutions of Aβ and albumin, prepared with the addition of compounds enriched in boron-10 and thus able to promote the neutron capture reactions, were irradiated at TRIGA Mark II nuclear reactor in Pavia. On computational level, Monte Carlo simulation codes were used both to find the most efficient irradiation setup with Am-241 source and to estimate the energy released in proteins depending upon the irradiation protocols. In the thesis the samples preparation, the irradiation procedures and the post-irradiation analysis are described, along with the geometries and the results of the simulations. The preliminary results obtained until now are then briefly discussed in the final part of the work.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
Per maggiori informazioni e per verifiche sull'eventuale disponibilità del file scrivere a: unitesi@unipv.it.
https://hdl.handle.net/20.500.14239/17976