Abstract Alzheimer’s disease (AD) is a major public health concern worldwide, with an increasing prevalence in the elderly population. AD is a progressive neurological disorder of multi-faceted origin, where factors such as genetic mutations, biochemical changes, along with inflammatory cascade and soluble beta amyloid (Aβ) peptide, are thought to play a pivotal role in synaptic failure and neuronal death, ultimately leading to cognitive and neuropsychiatric decline in patients suffering from the disease. At present, there is no long-term cure for the disease, although there is access to pharmacotherapy that might improve cognitive and neuropsychiatric symptoms early in the course of the disease. The current pharmacological therapy for AD only provides symptomatic relief for a very short period of time. It is therefore of utmost importance to discover other pharmacological strategies that might delay the development of AD and slow down the disease progression in terms of cognitive decline and neurodegeneration. Elucidating the pathogenic mechanisms involved in AD neuropathogenesis is a major goal to find efficacious disease-modifying treatments. What remains to be understood completely are the intracellular pathways affected by Aβ protein which may lead to neurodegeneration in AD. Since phosphorylation and dephosphorylation mechanisms are crucial in the β-amyloid precursor protein (APP) metabolism, protein kinase C has emerged as one of the key regulators of the APP metabolism. Indeed, dysregulation of the PKC pathway might play a role in the intracellular mechanisms of neurodegeneration, but their effective involvement still remains elusive. Therefore, a detailed analysis of PKC pathways in established models of AD neurodegeneration is necessary and will form part of this work. Fucoidin is a sulphated polysaccharide extracted from edible brown seaweed, which has been shown to exhibit anti-inflammatory and anti-oxidant effects as well as being a neuroprotectant in various inflammatory diseases including hypoxic ischemia, atherosclerosis and Heyman nephritis. Therefore, fucoidin may have an inhibitory effect on the inflammatory mechanisms of AD. Little is known, however, about the effect of fucoidin on AD. Animal models of AD are extremely valuable for the discovery and development of new treatments. Rodents have been one of the preferred models for pharmacological and behavioural studies in AD. In this thesis, first aim was to establish a non-transgenic Aβ-induced AD model in rats. AD was induced utilising a published protocol which involved the bilateral injection of aggregated Aβ (1-42) into the CA3 subfield of the hippocampus in rat brain. Behavioural assessment with well defined tools such as the Morris water maze and T-maze were utilised to assess the impairment in spatial working memory in rats. Behavioural impairments along with increased astrocytosis and microgliosis were observed in this particular Aβ-induced AD model. In the established disease model, fucoidin (50 mg/kg/day and 25 mg/kg/day) and ibuprofen (50 mg/kg/day) were shown to provide a partial protective effect on impairment in memory function in the MWM behavioural task in rats treated prior to disease initiation and throughout the course of the study. In addition, the histopathological and quantitative analysis of AD brain sections showed a marked reduction in reactive glial fibrillary acidic protein (GFAP) and microglia in fucoidin (low and high dose) and ibuprofen treated Aβ injected rats compared to untreated Aβ injected rats. These results indicate that fucoidin may serve as a possible effective therapeutic approach to improve AD symptoms. There is strong evidence that PKC α and ε signalling pathways regulate important molecular events in memory impairment and neurodegenerative pathophysiology in AD. A possible neuroprotective mechanism of fucoidin involving attenuation of an Aβ-induced decrease in PKC ε phosphorylation using cultured SHSY5Y neuroblastoma cells as a model system was examined. Co-administration of fucoidin (2μM and 5 μM) with Aβ (1μM) abolished the inhibitory effect of Aβ on the phosphorylation of PKCε in a concentration-dependent manner as revealed by western blot analysis. These findings suggest that a possible mechanism underpinning the neuroprotective effect of fucoidin may be through prevention of A-induced inhibition of PKC phosphorylation and may serve as a possible therapeutic approach to improve AD symptoms. As cellular events that involve PKC are affected by Aβ in in vitro systems, it was necessary to examine whether PKC activity is also modulated by the Aβ treatment in vivo in our Aβ-peptide induced AD model. Therefore, the next aim was to assess the potential for fucoidin use as an intervention therapy in an established disease stage in the Aβ-peptide induced AD model. Intervention with fucoidin (50 mg/kg/day, i.p.) in the established disease stage partially prevented Aβ (1-42) mediated damage with respect to memory impairment, neuroinflammation and PKC ε phosphorylation in the in vivo AD model consistent with the in vitro findings in SHSY5Y cells.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, June 1999. / Includes bibliographical references. Also available on the Internet

Thesis (Ph. D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (March 3, 2007) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 121-158).

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder, characterized by global cognitive decline and progressive memory loss. As many other neurological disorders characterized by “proteinopathy”, pathology of AD includes beta-amyloid plaques and tau neurofibrillary tangles, which imply a crucial role of the cellular degradation systems in maintaining homeostasis of protein turnover. This is especially important for post-mitotic neuronal cells since aggravating protein crisis cannot be alleviated by cell division. Autophagy is a cellular degradation process that removes or recycles long-lived proteins and damaged organelles, with its enhancement being remarkably implicated during the progression of Alzheimer’s disease (AD). The majority of studies have hitherto focused on the mechanism of how oligomeric Ah, as one of the potent toxic species in AD, activates autophagy. However, how autophagy is activated remains to be elucidated. The goal of this study is to reveal the underlying mechanisms of autophagy and the subsequent events. Using imaging and biochemical analysis in primary cultures of rat hippocampal neurons, I found that oligomeric An-induced autophagy was initiated by aggregation of the endoplasmic reticulum (ER), in an mTOR-independent pathway. Ao-triggered autophagosomes were derived from omegasomes, starting from the ER aggregation sites. Aggregation of the ER facilitated the clustering of Atg14L to propel the recruitment of Beclin1 and Vps34, which contributes to generation of omegasomes. I further found that p62 targeted to ER aggregates possibly through the enhanced ubiquitinated ER chaperones trapped at ER aggregation sites, implicating the underlying mechanism for how p62 are recruited to autophagosome formation sites (omegasomes). Herein, I report key steps for activation of AH-triggered autophagy, whereby a mechanistic link between ER aggregation, autophagic activation and recruitment of p62 to autophagosome formation sites is revealed. First, Ao-induced ER aggregation triggers autophagy, via the recruitment of Beclin 1 and Vps34 to Atg14L clusters, which is a promoting factor for omegasome formation at the ER aggregation site. Second, the recruitment of p62 to omegasomes is likely mediated by the attraction of the underlying accumulation of ubiquitinated ER chaperones at the ER aggregation site. Up-regulation of autophagy is an early sign of AD. The activation of autophagy without tightly manipulation may contribute to neuronal damage in AD. In addition, how the autophagic substrates can be efficiently incorporated into the autophagic pathway is important for understanding the sustainability of autophagy. Therefore, my study on elucidating how ER aggregation initiates autophagy and the autophagic substrate/cargo receptor p62 are loaded onto autophagosome formation sites may help us to identify a potential therapeutic strategy or target for AD patients. / published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

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Alzheimer’s disease (AD), a progressive age-related neurodegenerative disorder is characterized by impairments in memory and cognitive functions. The two main pathogenic hallmarks associated with the progression of this multifactorial disease include accumulation of amyloid-beta (Aβ) plaques and the deterioration of the cholinergic system in the brain. Using cost-effective synthetic procedures, mono-, di-, and tri- substituted sym-triazine derivatives incorporating acetylcholine substrate analogues and aromatic phenyl moieties were synthesized for the targeted modulation of Aβ aggregation and acetylcholinesterase (AChE) activity. A subset of these sym-triazines demonstrated dual inhibition of Aβ fibrillization and AChE hydrolytic activity in vitro studies. These highly effective compounds were also shown to be well tolerated by differentiated human neuronal cells in cell viability tests. These novel compounds have the potential to undergo future in vivo pharmaceutical analysis and have a positive impact on the quality of life of the people living with this devastating disease and their caretakers.

Alzheimer’s disease (AD), a progressive age-related neurodegenerative disorder is characterized by impairments in memory and cognitive functions. The two main pathogenic hallmarks associated with the progression of this multifactorial disease include accumulation of amyloid-beta (Aβ) plaques and the deterioration of the cholinergic system in the brain. Using cost-effective synthetic procedures, mono-, di-, and tri- substituted sym-triazine derivatives incorporating acetylcholine substrate analogues and aromatic phenyl moieties were synthesized for the targeted modulation of Aβ aggregation and acetylcholinesterase (AChE) activity. A subset of these sym-triazines demonstrated dual inhibition of Aβ fibrillization and AChE hydrolytic activity in vitro studies. These highly effective compounds were also shown to be well tolerated by differentiated human neuronal cells in cell viability tests. These novel compounds have the potential to undergo future in vivo pharmaceutical analysis and have a positive impact on the quality of life of the people living with this devastating disease and their caretakers.