Alzheimer’s disease (AD) is a deleterious neurodegenerative disease caused in major part by the aberrant processing and accumulation of amyloid beta peptides. In this dissertation, we systematically investigated the role of N-terminal region (NTR) residues of amyloid (1-40) (Aβ40) peptide in amyloidogenesis, lipid bilayer membrane interaction and damage, as well as neurotoxicity. Herein, we investigated the role of NTR residues on the aggregation and amyloid fibril formation process, to gain understanding on the electrostatic and hydrophobic constituents of the mechanism. This was achieved by substituting specific charged residues located in the NTR of Aβ40 and investigating their effects through a variety of techniques. We also investigated the role of NTR charged residues in their interaction with supported phospholipid bilayer membranes through the use of Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring to gain insight on the mechanistic details of the interaction. To further understand the implications of substituting charged NTR residues on membrane interaction, pore formation and damage, we utilized a carboxyfluorescein dye leakage assay to quantify the membrane damage caused by Aβ40 and the NTR mutants. We also performed neurotoxicity assay with SH-SY5Y neuroblastoma cells to shed light on the effects of NTR substitutions on cellular toxicity. Finally, we synthesized a polymer, trimethyl chitosan (TMC), and utilized it as a polyelectrolyte monitor of electrostatic interactions occurring between TMC and the NTR of Aβ40. Our results demonstrate that the NTR charged residues of Aβ40 contribute significantly to the aggregation process, amyloidogenesis, and phospholipid membrane interaction and perturbation by means of electrostatic, thermodynamic and hydrophobic forces. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Cognitive impairment after stroke or transient ischemic attack (TIA) is a prototype of vascular cognitive impairment (VCI). 30% of subjects with poststroke cognitive impairment are detected Alzheimer’s disease (AD)-like amyloid-beta (Aβ) retention with reference to ¹¹C-Pittsburgh compound B (PiB) positron emission tomography (PET). Therefore, poststroke cognitive impairment provides a good clinical context for the study about contribution of comorbid Alzheimer’s and cerebrovascular disease (CVD) pathologies to cognition. In this thesis, there are four studies addressing the effect of Aβ on poststroke cognitive impairment. / The first study investigated the accuracy of diagnosing cognitive impairment subtype in subjects with stroke/TIA using current clinical diagnostic criteria with reference to ¹¹C-PiB PET. We found the agreement between the pre and the post-PET diagnoses was poor (Kappa=0.194). The overall accuracy of clinical diagnosis of pure VCI (pVCI) was 66.7%, while that of mixed (i.e., AD with CVD) VCI (mVCI) was 68.0%. / Dementia may occur after stroke/TIA within 3-6 months (early poststroke dementia [PSD]) or from 3-6 months onward (delayed PSD). In the second study, apart from age and history of diabetes mellitus, chronic small vessel disease (SVD) lesions including lacunes and white matter changes (WMC) predicted delayed PSD as they did for early PSD. With comparable levels of SVD, the presence of acute infarcts and AD-like Aβ retention were associated with the early dementia after stroke/ TIA. / So far, there is a lack of research on the long-term effect of Alzheimer’s pathology on cognitive impairment in the context of stroke/TIA. We hypothesized that comorbid AD-like Aβ deposition played a key role in progressive cognitive decline after stroke/TIA. To test this hypothesis, we conducted a 3-year longitudinal study as study 3. Over 3 years, there was significant difference between mVCI and pVCI on the changes of the Mini-Mental State Examination (MMSE) score over time. We observed a significant decline in MMSE in the mVCI group but not the pVCI group. The annual rates of decline in MMSE and Montreal Cognitive Assessment (MoCA) score were greater in the mVCI group compared to the pVCI group. Of all MoCA domains measured, memory, executive and visuospatial functions were related to Aβ deposition. / In study 4, we investigated the relative contribution of Aβ deposition and CVD lesions to neuropsychological profiles in subjects with cognitive impairment after stroke/TIA. We found that in mVCI, Aβ retention in deep region or parietal lobe was predominantly associated with memory or executive function, respectively. In pVCI, frontal WMC and global large acute infarcts could affect memory or executive function via brain atrophy. / The conclusion of these studies reported herein can be summarized as follows: First, the overall accuracy of clinical diagnosis for cognitive impairment subtypes after stroke/TIA was low. Second, subjects with AD-like Aβ deposition tended to have dementia early after stroke/TIA, and they were more likely to experience a continuous and more severe cognitive decline 3 years later. Finally, Aβ deposition could affect both memory and executive function directly as a predominant factor in subjects with mixed Alzheimer’s and CVD pathologies. / 中風或短暫性腦缺血發作後的認知障礙被普遍視為血管性認知障礙的一種原型。通過澱粉樣蛋白正電子發射計算機斷層掃描技術（¹¹C-PiB PET），30%的中風或短暫性腦缺血發作後認知障礙患者具有阿爾茲海默氏病型的澱粉樣蛋白(Aβ)沈積。因此，中風或短暫性腦缺血發作後認知障礙是一種研究共存的阿爾茲海默氏病和腦血管疾病對認知功能的影響的良好模型。該論文通過四個研究，闡述了Aβ對中風或短暫性腦缺血發作後認知功能的影響。 / 第一個研究通過藉助¹¹C-PiB PET,調查了臨床診斷中對中風或短暫性腦缺血發作後認知障礙的分型的準確性。我們發現，對不同認知障礙類型的臨床診斷準確率較低（Kappa=0.194）。其中，對血管性認知障礙的臨床診斷準確率為66.7％，對混合性(阿爾茲海默氏病和腦血管疾病混合型)認知障礙的臨床診斷準確率為68.0％。 / 通常，我們把於中風或短暫性腦缺血發作後3至6個月內發生的癡呆定義為早髮型中風或短暫性腦缺血發作後癡呆，3至6個月后發生的癡呆定義為晚髮型中風或短暫性腦缺血發作後癡呆。在第二個研究中，我們發現，慢性小血管病（腔隙性梗塞和腦白質病變）不僅可以導致早髮型中風或短暫性腦缺血發作後癡呆，而且和晚髮型中風或短暫性腦缺血發作後癡呆也有關聯。然而，如果在相同程度的小血管病損傷的情況下，具有急性缺血性損傷和阿爾茲海默氏型Aβ沈積的患者更易提早發生中風或短暫性腦缺血發作後癡呆。 / 迄今，尚無關於共存的阿爾茲海默氏病和腦血管疾病對認知功能的長期影響的研究。我們假設合併的阿爾茲海默氏病可以導致患者中風或短暫性腦缺血發作後認知功能持續下降。為了驗證這一假設，我們進行了一個為期3年的長期隨訪研究（研究三）。在三年的隨訪中，混合性認知障礙患者和血管性認知障礙患者的簡短認知檢測（MMSE）評分變化有著顯著不同：混合性認知障礙患者的MMSE評分顯著下降，而血管性認知障礙患者的MMSE評分則無明顯改變。而且，混合性認知障礙患者的MMSE和蒙特利爾認知評估量表（MoCA）評分每年下降的平均速度皆高於血管性認知障礙患者。此外，藉助MoCA，我們發現中風或短暫性腦缺血發作後認知障礙患者的記憶、執行能力和視覺空間能力的損傷都和Aβ沉積有關。 / 在第四個研究中，我們研究了Aβ和腦血管病損傷對中風或短暫性腦缺血發作後患者不同認知功能的影響。我們發現，在混合性認知障礙患者中，腦深部的Aβ沉積和記憶功能損害直接相關，腦頂葉的Aβ沉積則和執行功能損害直接相關。在血管性認知障礙患者中，額葉腦白質病變和全腦大型腦梗病灶則可通過腦萎縮的介導，影響記憶或執行功能。 / 總之，我們的研究發現: 1.目前關於中風或短暫性腦缺血發作後患者認知障礙分型的臨床診斷的準確性較低。2.具有阿爾茲海默氏型Aβ沉積的患者不僅易於在中風或短暫性腦缺血發作後早期發生認知障礙，而且其認知水平在長期隨訪中也會不斷下降。3. Aβ沉積可以作為主導因素直接影響混合性認知障礙患者的記憶和執行功能。 / Liu, Wenyan. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references (leaves 164-187). / Abstracts also in Chinese; appendixes in Chinese. / Title from PDF title page (viewed on 12, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

As a first project, collision-induced dissociation experiments were carried out using electrospray ionisation mass spectrometry on gas phase complexes involving different poly(methylmetacrylate) oligomers with three amino acids: glycine, leucine, and phenylalanine. After acquiring breakdown diagrams, RRKM modeling was used to fit the experimental data in order to obtain the 0 K activation energy and the entropy of activation. These thermodynamic data were then used to understand the competing dissociation channels observed (except for gas phase complexes involving glycine that had only one dissociation channel). Molecular dynamics simulated annealing calculations were carried on the gas phase complexes to understand further the energetic and entropic effects involved as well as the 3D conformation of these complexes. Valuable insight information was found on the 3D conformations, on a qualitative level. Using rotational constants and vibrational harmonic frequencies, it was possible to evaluate the entropy variation between the experimentally observed competing channels. Reasonable agreement was found between the experimental and theoretical variations of entropies. Finally, the proton affinity of poly(methylmetacrylate) oligomers is being discussed. Even though no absolute values for the proton affinity were found, the experimental and computational results help to understand the variation that accompanies the oligomers length. The second project presents the development an efficient and reproducible screening method for identifying low molecular weight compounds that bind to amyloid beta peptides (Abeta) peptides using electrospray ionization mass spectrometry (ESI-MS). Low molecular weight (LMW) compounds capable of interacting with soluble Abeta may be able to modulate/inhibit the Abeta aggregation process and serve as potential disease-modifying agents for Alzheimer’s disease. The present approach was used to rank the binding affinity of a library of compounds to Abeta1-40 peptide. The results obtained show that low molecular weight compounds bind similarly to Abeta1-42, Abeta1-40, as well as Abeta1-28 peptides and they underline the critical role of Abeta peptide charge motif in binding at physiological pH. Finally, some elements of structure-activity relationship (SAR) involved in the binding affinity of homotaurine to soluble Abeta peptides are discussed. As a third project, the gas phase binding of small molecules to the Abeta1-40 peptide generated by electrospray ionization has been explored with collision-induced dissociation mass spectrometry and kinetic rate theory. This project presents a simple procedure used to theoretically model the experimental breakdown diagrams for the Abeta1-40 peptide complexed with a series of aminosulfonate small molecules, namely homotaurine, 3-cyclohexylamino-2-hydroxy-1-propanesulfonic acid (CAPSO), 3-(1,3,4,9-tetrahydro-2H-beta-carbolin-2-yl) propane-1-sulfonic acid, 3-(1,3,4,9-tetrahydro-2H-beta-carbolin-2-yl)butane-1-sulfonic acid, and 3-(cyclohexylamino) propane-1-sulfonic acid. An alternative method employing an extrapolation procedure for the microcanonical rate constant, k(E), is also discussed.

As a first project, collision-induced dissociation experiments were carried out using electrospray ionisation mass spectrometry on gas phase complexes involving different poly(methylmetacrylate) oligomers with three amino acids: glycine, leucine, and phenylalanine. After acquiring breakdown diagrams, RRKM modeling was used to fit the experimental data in order to obtain the 0 K activation energy and the entropy of activation. These thermodynamic data were then used to understand the competing dissociation channels observed (except for gas phase complexes involving glycine that had only one dissociation channel). Molecular dynamics simulated annealing calculations were carried on the gas phase complexes to understand further the energetic and entropic effects involved as well as the 3D conformation of these complexes. Valuable insight information was found on the 3D conformations, on a qualitative level. Using rotational constants and vibrational harmonic frequencies, it was possible to evaluate the entropy variation between the experimentally observed competing channels. Reasonable agreement was found between the experimental and theoretical variations of entropies. Finally, the proton affinity of poly(methylmetacrylate) oligomers is being discussed. Even though no absolute values for the proton affinity were found, the experimental and computational results help to understand the variation that accompanies the oligomers length. The second project presents the development an efficient and reproducible screening method for identifying low molecular weight compounds that bind to amyloid beta peptides (Abeta) peptides using electrospray ionization mass spectrometry (ESI-MS). Low molecular weight (LMW) compounds capable of interacting with soluble Abeta may be able to modulate/inhibit the Abeta aggregation process and serve as potential disease-modifying agents for Alzheimer’s disease. The present approach was used to rank the binding affinity of a library of compounds to Abeta1-40 peptide. The results obtained show that low molecular weight compounds bind similarly to Abeta1-42, Abeta1-40, as well as Abeta1-28 peptides and they underline the critical role of Abeta peptide charge motif in binding at physiological pH. Finally, some elements of structure-activity relationship (SAR) involved in the binding affinity of homotaurine to soluble Abeta peptides are discussed. As a third project, the gas phase binding of small molecules to the Abeta1-40 peptide generated by electrospray ionization has been explored with collision-induced dissociation mass spectrometry and kinetic rate theory. This project presents a simple procedure used to theoretically model the experimental breakdown diagrams for the Abeta1-40 peptide complexed with a series of aminosulfonate small molecules, namely homotaurine, 3-cyclohexylamino-2-hydroxy-1-propanesulfonic acid (CAPSO), 3-(1,3,4,9-tetrahydro-2H-beta-carbolin-2-yl) propane-1-sulfonic acid, 3-(1,3,4,9-tetrahydro-2H-beta-carbolin-2-yl)butane-1-sulfonic acid, and 3-(cyclohexylamino) propane-1-sulfonic acid. An alternative method employing an extrapolation procedure for the microcanonical rate constant, k(E), is also discussed.

A neurodegeneração é um processo onde ocorre morte celular progressiva. O tráfego neuronal anterógrado e retrógado, e entre os compartimentos é essencial para a viabilidade celular. As proteínas Rabs pertencem à família de pequenas GTPases, com funções de tráfego de vesículas e organelas, para realizarem sua função as proteínas Rab podem recrutar proteínas motoras como as KIF 1B e KIF 5, responsáveis pelo transporte anterógrado mitocondrial. A associação do distúrbio do tráfego intracelular com doenças neurodegenerativas tem sido tema de estudos recentes. Com isso o objetivo do presente trabalho é analisar a expressão das proteínas Rab, bem como estudar as proteínas motoras que podem contribuir para o esclarecimento sobre os distúrbios no tráfego intracelular que antecedem a formação de agregados proteicos envolvidos em neurodegeneração. Para tanto, utilizou-se o modelo de tratamento com rotenona para indução de agregados em Ratos Lewis idosos que foram expostos a rotenona durante 4 semanas, em seguida foram avaliados os níveis de expressão das proteínas Rab no hipocampo, substância negra e locus coeruleus, por western blotting. Foram analisados também os níveis de expressão das proteínas motoras KIF1B e KIF5 antes e durante a formação de agregados proteicos, em culturas de células, de ratos Lewis neonatos, do hipocampo, substância negra e locus coeruleus tratadas com rotenona por 24 horas ou 48 horas nas concentrações de 0,1nM, 0, 3nM e 0,5nM. Foi observado diminuição dos níveis de expressão das proteínas Rab 1 nas regiões do hipocampo e locus coeruleus. Houve aumento de expressão das Rab 4,5 e 6 no hipocampo, porém na substância negra a expressão da Rab 1 aumentou e da Rab 6 diminuiu. Já no locus coeruleus in vivo a Rab 6 aumentou, mas as Rab 1, 5 e 11 diminuíram sua expressão. Já a expressão da KIF 5 aumentou com o tratamento de 0,1nM de rotenona e diminuiu após 0,5nM do xenobiótico por 48 horas in vitro, na mesma região. Na substância negra aumentaram as KIFs 1B e 5 após o tratamento com 0,5nM por 48 horas in vitro, mas diminuíram as KIF 1B e 5 após o tratamento com 0,3nM por 24 horas e KIF 5 após o tratamento com 0,1nM por 48 horas. Esses resultados permitem concluir que a expressão de proteínas importantes para o tráfego mitocondrial e de vesículas encontram-se alteradas e fazem parte dos eventos intracelulares que antecedem a neurodegeneração / Neurodegeneration is a process that leads to progressive cell death. The anterograde and retrograde neuronal traffic as well as the traffic between compartments are essential for cell viability. The Rab proteins belong to the small GTPases family with function of vesicles and organelle trafficking. Rab proteins can recruit motor proteins such as KIF 1B and KIF 5 that are responsible for anterograde mitochondrial transport. The association of intracellular traffic disturb with neurodegenerative diseases have been theme of recent studies. Thereat the objective of this study is analyze the expression of Rab and motor proteins that can contribute for the understanding about the disturb of the intracellular traffic that precedes protein aggregation involved in neurodegeneration. For this purpose it was employed the model of rotenone treatment for induction of aggregation in aged Lewis rats that were exposed to rotenone during 4 weeks in order to evaluate Rabs expression. The levels of motor proteins KIF 1B and KIF 5 expression were evaluated before and during the formation of protein aggregates in hippocampus, substantia nigra and locus coeruleus cell cultures of neonates Lewis rats, exposed to rotenone for 24 hours or 48 hours in the concentrations of 0.1nM, 0.3nM or 0.5nM. It was observed decreased levels of Rab 1 expression in hippocampus and locus coeruleus. Rabs 4,5 and 6 were increased in the hippocampus, but in the substantia nigra the expression of Rab 1 increased and Rab 6 decreased. In the locus coeruleus the Rab 6 increased, but Rabs 1, 5 and 11 decreased. The expression of KIF 5 increased after 0.1nM of rotenone and decreased after the exposure to 0.5nM of for 48 hours in cultured cell from the locus coeruleus. In the substantia nigra the KIF1B and KIF 5 increased after treatment with 0.5nM for 48 hours in vitro, but these protein decreased after treatment with 0.3nM for 24 hours in vitro, and KIF 5 after treatment with 0.1nM for 48 hours. These results allow us conclude that the expression of important proteins for the mitochondrial and vesicles traffic are altered and participate of intracellular events that precede the neurodegeneration

A neurodegeneração é um processo onde ocorre morte celular progressiva. O tráfego neuronal anterógrado e retrógado, e entre os compartimentos é essencial para a viabilidade celular. As proteínas Rabs pertencem à família de pequenas GTPases, com funções de tráfego de vesículas e organelas, para realizarem sua função as proteínas Rab podem recrutar proteínas motoras como as KIF 1B e KIF 5, responsáveis pelo transporte anterógrado mitocondrial. A associação do distúrbio do tráfego intracelular com doenças neurodegenerativas tem sido tema de estudos recentes. Com isso o objetivo do presente trabalho é analisar a expressão das proteínas Rab, bem como estudar as proteínas motoras que podem contribuir para o esclarecimento sobre os distúrbios no tráfego intracelular que antecedem a formação de agregados proteicos envolvidos em neurodegeneração. Para tanto, utilizou-se o modelo de tratamento com rotenona para indução de agregados em Ratos Lewis idosos que foram expostos a rotenona durante 4 semanas, em seguida foram avaliados os níveis de expressão das proteínas Rab no hipocampo, substância negra e locus coeruleus, por western blotting. Foram analisados também os níveis de expressão das proteínas motoras KIF1B e KIF5 antes e durante a formação de agregados proteicos, em culturas de células, de ratos Lewis neonatos, do hipocampo, substância negra e locus coeruleus tratadas com rotenona por 24 horas ou 48 horas nas concentrações de 0,1nM, 0, 3nM e 0,5nM. Foi observado diminuição dos níveis de expressão das proteínas Rab 1 nas regiões do hipocampo e locus coeruleus. Houve aumento de expressão das Rab 4,5 e 6 no hipocampo, porém na substância negra a expressão da Rab 1 aumentou e da Rab 6 diminuiu. Já no locus coeruleus in vivo a Rab 6 aumentou, mas as Rab 1, 5 e 11 diminuíram sua expressão. Já a expressão da KIF 5 aumentou com o tratamento de 0,1nM de rotenona e diminuiu após 0,5nM do xenobiótico por 48 horas in vitro, na mesma região. Na substância negra aumentaram as KIFs 1B e 5 após o tratamento com 0,5nM por 48 horas in vitro, mas diminuíram as KIF 1B e 5 após o tratamento com 0,3nM por 24 horas e KIF 5 após o tratamento com 0,1nM por 48 horas. Esses resultados permitem concluir que a expressão de proteínas importantes para o tráfego mitocondrial e de vesículas encontram-se alteradas e fazem parte dos eventos intracelulares que antecedem a neurodegeneração / Neurodegeneration is a process that leads to progressive cell death. The anterograde and retrograde neuronal traffic as well as the traffic between compartments are essential for cell viability. The Rab proteins belong to the small GTPases family with function of vesicles and organelle trafficking. Rab proteins can recruit motor proteins such as KIF 1B and KIF 5 that are responsible for anterograde mitochondrial transport. The association of intracellular traffic disturb with neurodegenerative diseases have been theme of recent studies. Thereat the objective of this study is analyze the expression of Rab and motor proteins that can contribute for the understanding about the disturb of the intracellular traffic that precedes protein aggregation involved in neurodegeneration. For this purpose it was employed the model of rotenone treatment for induction of aggregation in aged Lewis rats that were exposed to rotenone during 4 weeks in order to evaluate Rabs expression. The levels of motor proteins KIF 1B and KIF 5 expression were evaluated before and during the formation of protein aggregates in hippocampus, substantia nigra and locus coeruleus cell cultures of neonates Lewis rats, exposed to rotenone for 24 hours or 48 hours in the concentrations of 0.1nM, 0.3nM or 0.5nM. It was observed decreased levels of Rab 1 expression in hippocampus and locus coeruleus. Rabs 4,5 and 6 were increased in the hippocampus, but in the substantia nigra the expression of Rab 1 increased and Rab 6 decreased. In the locus coeruleus the Rab 6 increased, but Rabs 1, 5 and 11 decreased. The expression of KIF 5 increased after 0.1nM of rotenone and decreased after the exposure to 0.5nM of for 48 hours in cultured cell from the locus coeruleus. In the substantia nigra the KIF1B and KIF 5 increased after treatment with 0.5nM for 48 hours in vitro, but these protein decreased after treatment with 0.3nM for 24 hours in vitro, and KIF 5 after treatment with 0.1nM for 48 hours. These results allow us conclude that the expression of important proteins for the mitochondrial and vesicles traffic are altered and participate of intracellular events that precede the neurodegeneration

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Recently published research indicates that soluble oligomers of beta-amyloid (Abeta) may be the key neurotoxic species associated with the progression of Alzheimer's disease (AD) and that the process of Abeta aggregation may drive this event. Furthermore, soluble oligomers of Abeta and tau accumulate in the lipid rafts of brains from AD patients through an as yet unknown mechanism. Using cell culture models we report a novel action of Abeta on neuronal plasma membranes where exogenously applied Abeta in the form of ADDLs can be trafficked on the neuronal membrane and accumulate in lipid rafts. ADDL-induced dynamic alterations in lipid raft protein composition were found to facilitate this movement. We show clear associations between Abeta accumulation and redistribution on the neuronal membrane and alterations in the protein composition of lipid rafts. In addition, our data from fyn(-/-) transgenic mice show that accumulation of Abeta on the neuronal surface was not sufficient to cause cell death but that fyn is required for both the redistribution of Abeta and subsequent cell death. These results identify fyn-dependent Abeta redistribution and accumulation in lipid rafts as being key to ADDL-induced cell death and defines a mechanism by which oligomers of Abeta and tau accumulate in lipid rafts.

Hoi, Chu Peng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 81-103). / Abstracts in English and Chinese. / Acknowledgements --- p.II / Abstract --- p.III / Abstract (in Chinese) --- p.V / List of Abbreviations --- p.VI / List of Figures --- p.VIII / List of Tables --- p.X / Table of Contents --- p.XI / Chapter Chapter One --- General introduction --- p.1 / Chapter 1.1 --- Alzheimer's disease --- p.1 / Chapter 1.1.1 --- Epidemiology and risk factors --- p.2 / Chapter 1.1.2 --- Clinical manifestation and course --- p.4 / Chapter 1.1.3 --- Clinical diagnosis --- p.5 / Chapter 1.1.4 --- Neuropathology and pathogenesis of AD --- p.8 / Chapter 1.1.5 --- Drug therapy of AD --- p.11 / Chapter 1.1.5.1 --- Drugs for symptomatic treatment --- p.11 / Chapter 1.1.5.2 --- Drugs based on epidemiology --- p.12 / Chapter 1.1.5.3 --- Drugs with potential disease-modifying effects --- p.14 / Chapter 1.1.5.4 --- Herbal supplements --- p.15 / Chapter 1.2 --- Models for drug discovery in Alzheimer Disease --- p.15 / Chapter 1.2.1 --- In vivo (animal) models --- p.16 / Chapter 1.2.2 --- In vitro (cellular) models --- p.18 / Chapter 1.3 --- Chinese herbs for the treatment of AD --- p.20 / Chapter 1.3.1 --- Ginkgo biloba L --- p.21 / Chapter 1.3.2 --- Magnolia officinalis --- p.24 / Chapter 1.3.3 --- Acori graminei Rhizoma (AGR) --- p.26 / Chapter 1.3.4 --- Gastrodia elata (G. elata) --- p.27 / Chapter 1.3.5 --- Rhodiola rosea L.( R. rosea) --- p.29 / Chapter 1.3.6 --- Scutellariae baicalensis --- p.30 / Chapter 1.3.7 --- Curcuma longa L.(Zingiberaceae) --- p.31 / Chapter 1.4 --- Aims of the study --- p.33 / Chapter Chapter Two --- Materials and Methods --- p.34 / Chapter 2.1 --- Materials --- p.34 / Chapter 2.1.1 --- Chemicals and reagents --- p.34 / Chapter 2.1.2 --- Materials for cell culture --- p.35 / Chapter 2.1.3 --- Instruments --- p.35 / Chapter 2.2 --- Methods --- p.36 / Chapter 2.2.1 --- Cell culture --- p.36 / Chapter 2.2.2 --- MTT cell viability assay --- p.38 / Chapter 2.2.3 --- Characterization of the cytotoxicity of Aβ peptide in NGF-differentiated PC 12 cells --- p.38 / Chapter 2.2.4 --- Screening of the neuroprotective effect of major principles from selected herbs on PC 12 cells against Aβ-induced cytotoxicity --- p.39 / Chapter 2.2.5 --- Measurement of reactive oxygen species (ROS) --- p.40 / Chapter 2.2.6 --- Measurement of intracellular calcium levels --- p.41 / Chapter 2.2.7 --- Measurement of caspase-3 activity --- p.42 / Chapter 2.2.8 --- Propidium iodide (PI) staining to evaluate apoptosis and necrosis --- p.43 / Chapter 2.3 --- Statistics --- p.45 / Chapter Chapter Three --- Results --- p.46 / Chapter 3.1 --- NGF-differentiated PC 12 cells --- p.46 / Chapter 3.1.1 --- Determination of an appropriate cell density for the screening experiments --- p.46 / Chapter 3.1.2 --- Characterization of Aβ-induced cytotoxicity in NGF-differentiated PC 12 cells --- p.47 / Chapter 3.1.2.1 --- Cytotoxicity of Aβ-related fragments in NGF-differentiated PC 12 cells --- p.48 / Chapter 3.1.2.2 --- Dose-dependent cytotoxic effect of Aβ on PC 12 cells --- p.48 / Chapter 3.1.2.3 --- Time-dependent effect of Aβ-induced toxicity on PC12 cells --- p.50 / Chapter 3.1.3 --- Protective effect of selected active principles against Aβ1-4-induced toxicity in PC 12 cells --- p.51 / Chapter 3.2 --- Measurement of reactive oxygen species (ROS) --- p.54 / Chapter 3.2.1 --- Measurement of ROS induced by H202 --- p.54 / Chapter 3.2.2 --- Measurement of ROS induced by Aβ --- p.56 / Chapter 3.3 --- Measurement of Intracellular calcium levels --- p.57 / Chapter 3.4 --- Measurement of caspase-3 activity --- p.58 / Chapter 3.4.1 --- AMC reference standard curve --- p.59 / Chapter 3.4.2 --- Measurement of caspase-3 activity --- p.59 / Chapter 3.5 --- PI staining for evaluate apoptosis and necrosis --- p.60 / Chapter Chapter Four --- Discussion --- p.64 / Chapter 4.1 --- Aβ-induced cytotoxicity in NGF-differentiated PC 12 cells as an in vitro model of Alzheimer's disease --- p.64 / Chapter 4.1.1 --- Cell line selection --- p.65 / Chapter 4.1.2 --- Characterization of Aβ-induced cytotoxicity in NGF-differentiated PC 12 cells --- p.66 / Chapter 4.2 --- Screening of the neuroprotective effects of selected active principles against Aβ-induced cytotoxicity in NGF-differentiated PC 12 cells --- p.67 / Chapter 4.3 --- Neuroprotection via inhibition of the ROS generation --- p.71 / Chapter 4.4 --- Neuroprotection via suppression of calcium homeostasis --- p.73 / Chapter 4.5 --- Neuroprotective via inhibition of Aβ-induced apoptosis --- p.75 / Chapter 4.5.1 --- Inhibition of caspase-3 activation --- p.75 / Chapter 4.5.2 --- PI staining for evaluation of apoptosis and necrosis --- p.76 / Chapter Chapter Five --- Conclusion and future work --- p.79 / Chapter 5.1 --- Conclusion --- p.79 / Chapter 5.2 --- Future work --- p.80 / References --- p.81

Beta amyloid plays a main role in the pathophysiology of Alzheimer's disease by inducing oxidative stress in the brain. Curcumin, a natural antioxidant, is known to inhibit beta amyloid and beta amyloid induced oxidative stress. However, low bioavailability and photodegradation are the major concerns for the use of curcumin. In the present study, we have formulated apolipoprotein E3 mediated poly(butyl) cyanoacrylate nanoparticles containing curcumin (ApoE3-C-PBCA) to provide photostability and enhanced cell uptake of curcumin by targeting. Prepared nanoparticles were characterized for particle size, zeta potential, entrapment efficiency and in vitro drug release. The entrapment of curcumin inside the nanoparticles was confirmed by X-ray diffraction analysis. Physicochemical characterization confirmed the suitability of the method of preparation. The photostability of curcumin was increased significantly in nanoparticles compared to plain curcumin. In vitro cell culture study showed enhanced therapeutic efficacy of ApoE3-C-PBCA against beta amyloid induced cytotoxicity in SH-SY5Y neuroblastoma cells compared to plain curcumin solution. Beta amyloid is known to induce apoptosis in neuronal cells, therefore antiapoptotic activity of curcumin was studied using flow cytometry assays. From all the experiments, it was found that the activity of curcumin was enhanced with ApoE3-C-PBCA compared to plain curcumin solution suggesting enhanced cell uptake and a sustained drug release effect. The synergistic effect of ApoE3 and curcumin was also studied, since ApoE3 also possesses both antioxidant and antiamyloidogenic activity. It was found that ApoE3 did indeed have activity against beta amyloid induced cytotoxicity along with curcumin. Hence, ApoE3-C-PBCA offers great advantage in the treatment of beta amyloid induced cytotoxicity in Alzheimer's disease.