Identificação e caracterização de proteína β-amiloide em camundongos bitransgênicos para Alzheimer através de espectroscopia Raman: primeiro passo para o estabelecimento de uma plataforma de espectroscopia intraocular para fins de diagnóstico precoce

• Ano de defesa: 2020
• Autor(a) principal: Emerson Alberto da Fonseca
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICX - DEPARTAMENTO DE QUÍMICA; Programa de Pós-Graduação em Inovação Tecnológica e Biofarmacêutica; UFMG
• Palavras-chave em Português: Espectroscopia Raman; Alzheimer; Diagnóstico; Retina; Alzheimer's disease (AD); Raman spectroscopy (RS); Inovações tecnológicas; Alzheimer, Doença de; Raman, Espectroscopia de; Retina - Doenças; Neurônios; Demência; Cérebro - Doenças - Diagnóstico; Microscopia eletrônica de varredura
• Link de acesso: http://hdl.handle.net/1843/36236; https://orcid.org/0000-0002-7971-1686

In the last decades, there has been a significant increase in the life expectancy of the world population. This increase in years of life brought a greater incidence of diseases related to aging, among them, as age-dependent neurodegenerative diseases, with a significant increase in patients with dementia. Alzheimer's disease (AD) is the most common form of dementia. It is estimated that it represents 60 to 80% of dementia cases. In 2019, at least 50 million people were living with some form of dementia worldwide. This number is expected to increase to more than 152 million by 2050. With a survival rate of 6 to 8 years after clinical diagnosis, AD is already the fifth leading cause of death in the world among people over 65 years of age. The main histopathological alteration of the disease is the deposition of the amyloid β (Aβ) peptide followed by the tangled neurofibrillary, which is related to neuronal death, leading to the cognitive deficit characteristic of the disease. The Aβ peptide accumulates in extensive extracellular plaques (amyloid plaques) and the identification of these amyloid plaques is used to confirm the diagnosis, which occurs post mortem. As a disease originating in the Central Nervous System (CNS), the AD exhibis the biochemical and histopathological changes also in the retina, a tissue composed mainly of neurons, which are part of the CNS and connect directly to the brain through the optic nerve. Studies show that the deposition of βA in the retina leads to deposition in the brain, and in humans, it is believed that this event can happen 15 to 20 years before plaques accumulate in the patient's brain. In this sense, an intraocular diagnosis that detects amyloid plaques in the retina, using only a light source, would be able to prove an early diagnosis in a fast and safe way. For this reason, we propose the use of Raman spectroscopy (RS) as an alternative for the early diagnosis of AD. This technique uses a laser as probe to identify a particular molecule of interest, with high specificity, without the need for dye or contrast. For this purpose, we developed a work to characterize amyloid plaques aiming at an early diagnosis protocol via Intraocular Spectroscopy. This characterization using RS included the study of synthetic amyloid plaques previously characterized with microscopy (electronic and scanning probe), and of naturally appearing plaques in the brains of transgenic mice specific for AD. Our results show that the amyloid plaque has, not one, but a complex multifeatured spectrum that serves as a molecular marker for diagnostic purposes (phenylalanine, amide III, amide I, CH2 stretch, and CH3 stretch of protein and lipid). We also demonstrated that an RS is able to differentiate its disease evolution stage. We were able to identify a clear trend that differentiates animals between 6 and 12 months according to biochemical changes in brain tissue in bitransgenic mice. In addition, we demonstrate that RS is able to identify, not only amyloid plaques, but also the eurodegeneration associated with plaque. We developed such characterization based on spontaneous and also stimulated Raman spectroscopy, this second intense enough to provide a complete imaging of the retina in seconds or fractions of seconds, an important technical aspect for the implementation of the technique as a diagnostic method. We conclude, therefore, the characterization and identification of the amyloid plaque in a brain tissue. The next phase of this project will be to apply this knowledge acquired in the identification of amyloid plaques in retinas of animal models and humans.