Date of Award
Summer 2017
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Donaldson, William A.
Second Advisor
Sem, Daniel A.
Third Advisor
Kincaid, James R.
Abstract
Estrogens (17β-estradiol, E2) have garnered considerable attention in influencing cognitive process in relation to phases of the menstrual cycle, aging and menopausal symptoms. However, hormone replacement therapy can have deleterious effects leading to breast and endometrial cancer, predominantly mediated by estrogen receptor-alpha (ERα) the major isoform present in the mammary gland and uterus. Further evidence supports a dominant role of estrogen receptor-beta (ERβ) for improved cognitive effects such as enhanced hippocampal signaling and memory consolidation via estrogen activated signaling cascades. Creation of the ERβ selective ligands is challenging due to high structural similarity of both receptors. Thus far, several ERβ selective agonists have been developed, however, none of these have made it to clinical use due to their lower selectivity or considerable side effects. The research in this dissertation involved the design of non-steroidal ERβ selective agonists for hippocampal memory consolidation. The step-wise process to achieve the ultimate goal of this research includes: (1) design and synthesis of (4-hydroxyphenyl)cyclohexyl or cycloheptyl derivatives, (2) in vitro biological evaluation of synthesized compounds to identify highly potent and selective candidates, and (3) in vivo biological evaluation of selected candidates for hippocampal memory consolidation. Several (4-hydroxyphenyl)cyclohexyl or cycloheptyl derivatives were synthesized having structural alterations on both aromatic and cyclohexyl/heptyl ring scaffolds. ERβ agonist potency was initially evaluated in TR-FRET ERβ ligand binding assay and compounds having high potency were re-evaluated in functional cell based assays for potency and ERβ vs. ERα selectivity. Two compounds from each series, ISP 163-PK4 and ISP 358-2 were identified as most selective ERβ agonists. Both compounds revealed high metabolic stability, solubility and no cross reactivity towards other nuclear receptors. In vivo efficiency of ISP 358-2 was evaluated in ovariectomized mice (C57BL/6) with object recognition (OR) and object placement (OP) tasks. The results indicate improved memory consolidation at 100 pg/ hemisphere and 0.5 mg/Kg via DH infusion and IP injection respectively. The information learned from this project serves as a foundation for development of other cycloheptyl/hexyl based ERβ agonists or antagonists having acceptable pharmacological profiles.