<p dir="ltr">Neurodegenerative disease (ND) is a debilitating neurological disorder characterized by progressive loss of neurons in central nervous system (CNS), resulting in the decline in memory, cognition and motor functions. Alzheimer's disease (AD) and Parkinson's disease (PD) are the two of the most prevalent NDs, affecting millions of individuals in the United States. While hundreds of genetic risk factors have been identified in association with ND, familial cases with genetic origin only account for 10% and 15% of diagnosed AD and PD incidences, respectively. The majority of ND cases occur sporadically. Mounting evidence from epidemiology studies suggests that environmental stressors are one of the key ND associated risk factors where exposure to environmental stressors leads to the on-set of ND years or decades later. Little is known about the molecular mechanism facilitating the establishment of the persistent and potentially permanent neurotoxic state after exposures, particularly at a developmental stage. Hence, there is a pressing need in understanding the cellular machineries involved in establishment of a persistent neurotoxic state resulting from early-life exposure to environmental toxins. Subcellular compartments are crucial for the maintenance of neuronal homeostasis. Alterations in various subcellular compartments, including the nucleus, mitochondria, and lysosomes, have been commonly noted in cases of AD and PD; and are believed to play a crucial role in the establishment of a persistent neurotoxic state. The primary goal of my thesis is thus to uncover the dysregulation in multiple subcellular compartments and their contributes to ND pathogenesis induced by early-in-life exposure to environmental stressors, including atrazine (ATZ), per-and polyfluoroalkyl substances (PFAS), and neurofibrillary tangles.</p><p dir="ltr">I started by developing live-cell compatible tools to track cellular and sub-cellular changes. Mitochondria DNA methylation is of particular interest, due to its potential regulatory role in the expression of electron transport chain (ETC) subunits and thus mitochondrial activity. Thus, I started expanding the mitochondria probe tool set by designing a novel probe targeting methylated CpGs of mitochondrial DNA (mtDNA). We demonstrated the capability of our probe to reveal spatial distribution of methylated mtDNA and capture mtDNA methylation change at single cell level. Combined with our previously developed probe for nuclear DNA methylation, we monitored mtDNA and nuclear DNA methylation simultaneously on the single-cell level where unsynchronized dynamics of DNA methylation from nucleus and mitochondria were discovered.</p><p dir="ltr">Our tool offers a unique opportunity to understand epigenetic regulation of mtDNA and its dynamic response to microenvironment and cellular changes. Later, I further extended these efforts to develop in situ probes for tracking the formation of tau aggregates based on fluorescence resonance energy transfer (FRET); and demonstrated the superior performance of our engineered probes compared to the current state-of-the-art.</p><p dir="ltr">I explored two neuronal culture systems, namely SH-SY5Y- and human induced pluripotent stem cell (hiPSC)-derived neurons; and their feasibility in studying neurotoxic effects of developmental exposure to environmental stressors. Specifically, I used SH-SY5Y derived neuron-like cells to study the impact of pre-differentiation exposure to PFOA, abundant chemical in environment due to its historical uses in consumer products and industrial applications. hiPSC-derived neurons were used to study the effects of developmental exposure to ATZ. Both studies identified cellular changes, for example neurite morphology and expression of enzyme catalyzing the production of neurotransmitters, that last after completion of differentiation. We also identified changes of pathogenic markers aligning with increased PD risks associated with developmental PFOA and ATZ exposure. Compared to SH-SY5Y, hiPSC-derived neurons were more advantageous due to their ability to recapitulate neuronal activity and pathogenic changes related to ND, and thus were used in my follow-up studies.</p><p dir="ltr">I adopted hiPSC derived neuron model to study the molecular mechanism of ND using established ND etiology. Patients with neurodegenerative disorders (ND) exhibit varying levels and temporal patterns of aggregated β-amyloid (Aβ) and tau protein. We exposed neurons derived from hiPSC with preformed fibrils (PFFs) of Aβ, tau and Aβ+tau, respectively. These treatments result in significant alterations in neurite network morphology, nuclear morphology, chromatin compactness and synaptic density. Interestingly, Aβ and tau fibrils seem to have opposite effects on mitochondrial membrane potential on neurites. Increased quantity of lysosomes was found in neurons treated with Aβ, tau and Aβ+tau, while decrease of lysosomal acidity was only observed in neurons treated with Aβ and tau sequentially. Collectively, our data suggests the potential synergy between Aβ and tau in establishing a neurotoxic state.</p><p dir="ltr">In summary, my thesis work has developed enabling engineering tools to monitor cellular and subcellular changes in neurons; identified hiPSC-derived neurons as a promising platform for studying developmental neurotoxicity; and paved the way towards understanding multi-etiology and its molecular underpinning for ND.</p>

No description available.

Les proches qui accompagnent une personne âgée vivant avec un trouble neurocognitif majeur à un stade avancé (TNC) en centre d’hébergement et de soins de longue durée (nommé CHSLD au Québec) rencontrent de multiples défis au quotidien. Parmi ceux-ci se retrouve la responsabilité qui leur est conférée de prendre les décisions relatives aux soins de santé pour la personne vivant avec un TNC lorsque celle-ci devient incapable de le faire. Certaines de ces décisions placent les proches dans un processus complexe qui doit être accompagné par l’équipe soignante, notamment lorsque les décisions en question auront potentiellement une incidence sur la fin de vie de la personne âgée. Les infirmières et infirmiers, par leurs compétences relatives aux soins à la famille et leur présence quotidienne directe auprès des résidentes et résidents et de leurs proches, se retrouvent dans une position privilégiée pour offrir cet accompagnement. Toutefois, peu d’études se sont intéressées aux différentes composantes de cet accompagnement. Par conséquent, cette étude visait à proposer une théorie de l’accompagnement infirmier des proches qui doivent prendre des décisions concernant la fin de vie d’une personne âgée vivant avec un TNC en CHSLD. Inspirée par la philosophie herméneutique de Gadamer (1960/2018) et la théorie du human caring élaborée par Watson (2012), une théorisation ancrée constructiviste a été réalisée auprès de neuf infirmières ou infirmiers et 10 proches rencontrés dans le cadre d’une entrevue semi-structurée individuelle. Les infirmiers et infirmières occupaient toutes un poste régulier en CHSLD depuis au moins un an, alors que les proches étaient ou avaient été impliqués dans le processus de prise de décisions concernant la fin de vie d’une personne âgée vivant avec un TNC en CHSLD. L’analyse des données s’est appuyée sur les principes suggérés par Charmaz (2014), qui incluent entre autres la codification initiale, la codification ciblée, la comparaison constante et l’écriture de mémos. Il découle de la théorie proposée l’aspect fondamental du lien de confiance établi entre l’infirmière ou l’infirmier et les proches, celui-ci ayant un impact important sur le processus de prise de décisions vécu par les proches et la qualité de l’accompagnement offert par l’infirmière ou l’infirmier. Ensuite, l’exploration du refus des soins palliatifs et le soutien du besoin des proches d’être témoin de l’état de santé actuel de la personne âgée vivant avec un TNC se sont aussi avérés des composantes essentielles de l’accompagnement infirmier. Finalement, l’enseignement au moment opportun ainsi qu’une transmission claire de l’information complètent les thèmes centraux de la théorie. Ces connaissances permettent de mieux comprendre les principaux éléments d’un accompagnement infirmier de qualité, contribuant ainsi à soutenir la pratique infirmière basée sur des résultats probants et à guider la recherche dans le développement d’interventions efficaces afin de faciliter l’expérience des proches. En outre, ces résultats démontrent l’apport indispensable des infirmières et infirmiers au processus de prise de décisions des proches. / Relatives supporting an older person living with an advanced major neurocognitive disorder (NCD) in a long-term care home (called a CHSLD in Quebec) encounter multiple challenges every day. Among them is the responsibility of making healthcare decisions on behalf of a relative living with an NCD, who is no longer able to do so themself. Some of these decisions launch relatives into a complex process that requires guidance from the healthcare team, especially when the decisions may impact the end-of-life of the person living with an NCD. Through their skills in family care and their daily presence directly among residents and relatives, nurses have a privileged role to play in offering this support. However, few studies have examined its various components. The aim of this study is therefore to propose a theory on nurses’ support of relatives making end-of-life decisions for a resident living with an NCD in a CHSLD. Inspired by Gadamer’s hermeneutical philosophy (1960/2018) and Watson’s theory of human caring (2012), a constructivist grounded theory was conducted with nine nurses and 10 relatives, whom were met in individual semi-structured interviews. These nurses had all held regular positions in CHSLDs for at least one year, while relatives were or had been involved in the end-of-life decision-making process for a person living with an NCD in a CHSLD. The data analysis was based on principles suggested by Charmaz (2014), including initial coding, focus coding, constant comparison, and the writing of memos. The proposed theory highlights trust as the fundamental aspect in the nurse-relative relationship. Indeed, trust has a significant impact on families’ decision-making process and on the quality of the support nurses provide to relatives. Exploring the refusal of palliative care and supporting relatives’ need to witness and take stock of the state of health of the person living with an NCD for themselves are two other essential components of nursing care. Finally, nurses’ well-timed education of relatives and clear transmission of information are other themes that are central to this theory. Deepening the understanding of the main elements of quality nursing support, this study reinforces evidence-based nursing practice and guides research leading to effective interventions that will ultimately facilitate relatives’ experience. Our results also demonstrate nurses’ invaluable contribution to relatives’ decision-making process.