published_or_final_version / Biochemistry / Master / Master of Philosophy

Autosomal-dominant mutations in the amyloid precursor protein (APP) gene increase the production and aggregation of toxic amyloid-β (Aβ) peptides and cause early-onset Alzheimer’s disease (AD). Noradrenergic cell loss is well documented in AD and has been posited to play a role in cognitive symptoms as well as disease progression. We investigated memory and affect, tissue levels of catecholamines, brain-derived neurotrophic factor (BDNF) mRNA and bioenergetic homeostasis in TgCRND8 mice that express a double mutant (K670N/M671L + V717F) human APP695 transgene. We found that TgCRND8 mice develop object memory impairment and behavioural despair, as well as reductions in noradrenaline and BDNF expression in the hippocampus and cortex, before the appearance of Aβ plaques. Animals with more advanced Aβ pathology exhibit disruptions in energetic status, along with diminished complex I+III activity in the electron transport chain. To test whether the AD-like phenotypes of TgCRND8 mice might be due to altered noradrenergic tone, pre-plaque mice were treated with dexefaroxan, an antagonist of presynaptic inhibitory α2-adrenoceptors that are highly expressed on both noradrenergic and cholinergic terminals. Effects of dexefaroxan were compared to those of rivastigmine, a cholinesterase inhibitor. Both dexefaroxan and rivastigmine improved behavioural phenotypes and BDNF expression without affecting tissue Aβ load. Drug treatments also restored complex I+III mitochondrial activity and increased ATP levels. Reductions in noradrenergic tone appear to underlie Aβ-induced functional impairment in TgCRND8 mice, in addition to BDNF deficits and bioenergetic stress. These studies suggest that α2-adrenoceptor targeting may warrant consideration as a therapeutic strategy in AD.

Autosomal-dominant mutations in the amyloid precursor protein (APP) gene increase the production and aggregation of toxic amyloid-β (Aβ) peptides and cause early-onset Alzheimer’s disease (AD). Noradrenergic cell loss is well documented in AD and has been posited to play a role in cognitive symptoms as well as disease progression. We investigated memory and affect, tissue levels of catecholamines, brain-derived neurotrophic factor (BDNF) mRNA and bioenergetic homeostasis in TgCRND8 mice that express a double mutant (K670N/M671L + V717F) human APP695 transgene. We found that TgCRND8 mice develop object memory impairment and behavioural despair, as well as reductions in noradrenaline and BDNF expression in the hippocampus and cortex, before the appearance of Aβ plaques. Animals with more advanced Aβ pathology exhibit disruptions in energetic status, along with diminished complex I+III activity in the electron transport chain. To test whether the AD-like phenotypes of TgCRND8 mice might be due to altered noradrenergic tone, pre-plaque mice were treated with dexefaroxan, an antagonist of presynaptic inhibitory α2-adrenoceptors that are highly expressed on both noradrenergic and cholinergic terminals. Effects of dexefaroxan were compared to those of rivastigmine, a cholinesterase inhibitor. Both dexefaroxan and rivastigmine improved behavioural phenotypes and BDNF expression without affecting tissue Aβ load. Drug treatments also restored complex I+III mitochondrial activity and increased ATP levels. Reductions in noradrenergic tone appear to underlie Aβ-induced functional impairment in TgCRND8 mice, in addition to BDNF deficits and bioenergetic stress. These studies suggest that α2-adrenoceptor targeting may warrant consideration as a therapeutic strategy in AD.

Alzheimer's disease (AD) is the leading cause of dementia. Amyloid plaques in the brain remain a pathological feature of AD. These plaques are primarily composed of amyloid β-protein (Aβ). It has been postulated that glycogen synthase kinase-3β (GSK3β) activity might exert a central role in the development of AD. GSK3β activity has been implicated in tau phosphorylation, APP processing, Aβ production and neurodegeneration. Quetiapine is frequently used to treat psychoses in AD patients at the late stage and has inhibitory effects on GSK3β activity in mouse brains after acute/subchronic treatment. Therefore, the proposed hypothesis is that chronic quetiapine administration after amyloid plaque onset reduces AD like pathology and alleviates AD like behaviours in APP/PS1 transgenic mice by inhibiting GSK3β activity. APP/PS1 transgenic mice were treated with quetiapine (2.5, 5 mg/kg/day) in drinking water starting from 3.5 months of age, for a period of 8 months. One week after behaviour testing, mice were sacrificed at 12 months of age. Half of the hemispheres were rapidly frozen for immunoblot and ELISA analyses and the other half were fixed with 4% paraformaldehyde for histological analyses. Quetiapine treatment reduced amyloid plaques formation in the cortex and hippocampus of AD mice. It also improved the behavioural deficits in these mice, including attenuating impaired memory and anxiety-like phenotypes. In addition, chronic quetiapine administration inhibited GSK3β, which resulted in reduced production of Aβ in cortices and hippocampi of transgenic mice. Quetiapine treatment also significantly decreased the activation of astrocytes and attenuated synapse integrity impairment in transgenic mice. These findings suggest that early application of quetiapine can alleviate memory deficits and pathological changes in the APP/PS1 transgenic mouse model of AD, and further support that modulation of GSK3β activity by quetiapine may be a therapeutic option for AD.

Access to abstract permanently restricted to Ball State community only. / Access to thesis permanently restricted to Ball State community only. / Department of Biology

Both Immune cells and pathogenic microorganisms require iron for proliferation and multiplication. However, role of iron supplementation on immune function is still unclear. Studies show that iron-deficient mice are protected from developing Experimental Autoimmune Encephalomyelitis (EAE), an animal model of Multiple Sclerosis (MS) in humans. In this project, we developed a mice model of iron overload in (B6.Cg-Tg (Thy1-YFPH) 2Jrs/J mice). Seven mice were injected (ip), 100 μl iron dextran and seven with Phosphate buffered saline (PBS), five days/week for four weeks. Blood samples verified iron overload 170 versus 138μg/dl (P < 0.005). Flow Cytometry revealed high T-cells and low and CD8+ T-cell. Histological sections indicated perivascular immune cell infiltrations in the brain, but not in the spinal cord. Confocal microscopy of spinal cord sections showed myelinated axons with no breaks. The absence of demyelination and clinical signs, but high CD3+ with low CD4+ T-cells suggests an altered immune cell function in iron overload mice that needs further exploration. / Access to thesis permanently restricted to Ball State community only / Department of Physiology and Health Science

A number of neurodegenerative diseases like Multiple Sclerosis, Parkinson’s and Alzheimer’s have been linked with iron accumulation in the brain. Iron plays an important role in neural metabolism. However, mechanisms of neural degeneration in iron overload are complex and not clearly understood. We proposed that iron overload may lead to demyelination in B6.Cg-Tg (Thy1-YFPH) 2Jrs/J mice. These mice express spectral variants of GFP (yellow-YFP) at high levels in motor and sensory neurons. Serum iron levels were significantly higher in experimental versus control animals. Brain and spinal cords were harvested and fixed after 4 weeks of iron dextran injections. Tissue slices were stained with Prussian blue, H&E and fluromyelin for light and confocal microscopy. Immunological profile by Flow Cytometric analysis revealed significantly high numbers of CD3+T cells with no differences in CD4:CD8 ratio. This study indicates that iron overload caused a significant inflammation without demyelination in the CNS. / Department of Physiology and Health Science

Alzheimer's disease (AD) is the leading cause of dementia. Amyloid plaques in the brain remain a pathological feature of AD. These plaques are primarily composed of amyloid β-protein (Aβ). It has been postulated that glycogen synthase kinase-3β (GSK3β) activity might exert a central role in the development of AD. GSK3β activity has been implicated in tau phosphorylation, APP processing, Aβ production and neurodegeneration. Quetiapine is frequently used to treat psychoses in AD patients at the late stage and has inhibitory effects on GSK3β activity in mouse brains after acute/subchronic treatment. Therefore, the proposed hypothesis is that chronic quetiapine administration after amyloid plaque onset reduces AD like pathology and alleviates AD like behaviours in APP/PS1 transgenic mice by inhibiting GSK3β activity. APP/PS1 transgenic mice were treated with quetiapine (2.5, 5 mg/kg/day) in drinking water starting from 3.5 months of age, for a period of 8 months. One week after behaviour testing, mice were sacrificed at 12 months of age. Half of the hemispheres were rapidly frozen for immunoblot and ELISA analyses and the other half were fixed with 4% paraformaldehyde for histological analyses. Quetiapine treatment reduced amyloid plaques formation in the cortex and hippocampus of AD mice. It also improved the behavioural deficits in these mice, including attenuating impaired memory and anxiety-like phenotypes. In addition, chronic quetiapine administration inhibited GSK3β, which resulted in reduced production of Aβ in cortices and hippocampi of transgenic mice. Quetiapine treatment also significantly decreased the activation of astrocytes and attenuated synapse integrity impairment in transgenic mice. These findings suggest that early application of quetiapine can alleviate memory deficits and pathological changes in the APP/PS1 transgenic mouse model of AD, and further support that modulation of GSK3β activity by quetiapine may be a therapeutic option for AD.

Brain deposition of the $ beta$-amyloid protein is an early marker of Alzheimer's disease (AD). AD is a neurodegenerative disorder characterized by learning and memory impairments. Here, mice (B6C3, 8 and 20 months old) transgenic for a human $ beta$-amyloid fragment were compared to normal litter mates in spatial and non-spatial learning tasks in the Morris water maze, according to standard procedures. Four measures of learning and performance were analyzed statistically: latency, total distance swam, mean distance to a platform, and number of trials correct in reaching a platform. Transgenic mice were impaired relative to their litter mates in spatial learning and performed better in the non-spatial task than in the spatial task in the first three measures. An age effect for transgenics was observed in the total distance measure. The results suggest that expression of the human $ beta$-amyloid protein may produce a selective learning deficit in mice.

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