​Estrogen Depletion Effects on Myelination and Lipid Regulation within the Central Nervous System

This dissertation has been split into two parts; Part 1 includes the generation and characterization of a novel menopausal mouse model of demyelination and Part 2 includes conformational studies of phytate with biologically relevant metals and macrocycles. Menopause has been associated with increased neurodegeneration experienced by multiple sclerosis patients, and this dissertation focuses on the investigation of menopausal estrogen depletion effects on myelin in the central nervous system (CNS). Multiple sclerosis is an inflammatory disease that causes demyelination, the breakdown of myelin sheaths, within the CNS, which results in neurodegenerative effects following repeated cycles of myelin damage. Animal models have been utilized in previous studies to investigate both menopause and multiple sclerosis separately, but menopause and demyelination models have not yet been combined to define the effects of estrogen depletion on myelin and myelination pathways. Therefore, this dissertation proposes the combination of ovariectomy surgery, the most common menopause model, with a demyelination model, the Plp1-iCKO-Myrf mouse model, to study the effects of estrogen depletion on myelin and myelination pathways. Chapter 2 outlines the generation and validation of this new model by combining ovariectomy surgeries with genetic ablation of the Myrf gene to induce demyelination followed by behavioral analysis. As demyelination results in motor disability in the Plp1-iCKO-Myrf model, mice underwent clinical scoring and rotarod testing that showed increased motor disability consistent with demyelination. Furthermore, estrogen depletion in both healthy and demyelinated mice caused increased motor disability. Chapter 3 expands upon the introduction of our new menopause model of demyelination to characterize the effects of menopausal estrogen depletion on myelin and myelination pathways. Myelin and cellular markers of myelin were analyzed by BlackGold II staining and immunofluorescence in collected brain tissue. These results showed ovariectomy effects in astrocytes, microglia, OPCs, and myelin levels. Lipidomic analysis was performed using tandem mass spectrometry to measure how phospholipids and sterols were altered with estrogen depletion in demyelination in the CNS. Thus, we have successfully combined ovariectomy surgery and a mouse model of demyelination to generate a new menopause model of demyelination and have begun to characterize the effects of menopausal estrogen depletion on myelin and myelination pathways within the CNS. In Part 2 of this dissertation, we introduce myo-inositol 1,2,3,4,5,6-hexakisphosphate, a biomolecule known for its numerous roles in eukaryotic species and commonly called phytate. Due to its complex polyphosphate nature, structural data is sorely lacking, especially with respect to its interactions with metal cations. In particular, metal ions tend to govern an abrupt conformation change (ring flip) at basic pHs. Here we propose supramolecular host-guest strategies using macrocyclic encapsulation of metals as a method to better define structural characteristics of these interactions. Chapter 7 explored supramolecular strategies using ether-based macrocycles, 2.2.2 cryptand and 18-crown-6, to trap metal cations in order to delay precipitation of phytate salts and define the influence of nearby counterions on phytate’s ring flip. Nuclear magnetic resonance (NMR) spectroscopy spectra showed that the 2.2.2 cryptand was capable of binding to sodium and potassium to delay the conformational flip of phytic acid. Additionally, NMR titrations with calcium and 2.2.2 cryptand led to a delay in precipitation of calcium-phytate complexes by 2 pH units. These findings suggest that disrupting direct metal ion-phytate contact by metal complexation with ether-based macrocycles can successfully delay precipitation, providing a new pathway to increase the solubilities of higher valent metal-phytate salts, facilitating future solution studies.

Grantor dc:publisher

University of Kansas

Year dc:date.issued

2025

Author dc:creator

• Holt, Esther

Advisor dc:contributor.advisor

• Hartley, Meredith

• Analytical chemistry
• Neurosciences
• Inorganic chemistry
• Demyelination
• Estrogen
• Inositol Hexaphosphates
• Lipids
• Menopause
• Phytate

Statement dc:rights

• This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.

Language dc:language.iso

en

Dc Identifier Other

https://www.proquest.com/LegacyDocView/DISSNUM/32167901

OAI identifier oai:identifier

oai:kuscholarworks.ku.edu:1808/37884