Graduation Date

Spring 5-9-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Pharmaceutical Sciences

First Advisor

Peter F. Kador, Ph.D.

Abstract

Aging is a complex biological process which stems from a growing imbalance between the regenerative capacity of an organism and endogenous as well as exogenous damaging factors. This imbalance leads to the slow deterioration of individual cells, organs, and eventually the entire organism. The free radical theory of aging combines the evolutionary and mechanistic aspects of aging, postulating that the innate process is caused by deleterious, irreversible, and inevitable changes in biological systems caused by oxidative damage that accumulates over the lifespan. Evidence of this phenomenon is supported by the pathogenesis of age-related diseases, such as age-related macular degeneration and Alzheimer’s disease, which show that there is an age-related decrease of cellular antioxidant defenses. This results in the dyshomeostasis of redox-active metals, such as iron, copper, and zinc, and in turn exacerbates the oxidative stress induced by reactive oxygen species and free radicals such as superoxide, hydrogen peroxide, and the hydroxyl radical. Our laboratory has developed two series of multifunctional antioxidants (MFAOs), the JHX and HK series, which can simultaneously chelate biologically active transition metals and scavenge free radicals. These orally-active compounds have demonstrated therapeutic effects against age-related eye diseases, such as cataract and macular degeneration. Despite their efficacy, little is known about the ocular biodistribution of these orally-administered molecules.

I have conducted a biodistribution study of 24 such molecules. These included the MFAOs, their monofunctional free radical scavenging (FRS) and biologically active transition metal chelating (CHL) analogs, as well as their nonfunctional (NF) analogs in Sprague Dawley rats. In Chapter Two, I demonstrate that all compounds can be detected unmetabolized in the cornea, iris with the ciliary body, lens, neural retina, retinal pigmented epithelium with the choroid, brain, sciatic nerve, kidney, and liver. In Chapter Three, I describe the predictive models of ocular, neural, and visceral tissue distribution, which I developed based on the biodistribution data from Chapter Two, using hierarchical cluster analysis (HCA) and quantitative structure activity relationship analysis (QSAR). The results indicated that both HCA and QSAR analysis yielded many predictive models which agree with other reported trends of drug delivery to ocular, neural, and visceral tissues. In Chapter Four, I present my investigation into the potential pharmacological chaperone activity of two oxysterols, lanosterol and 25-hydroxycholesterol, to three model αB-crystallin chaperone proteins in silico and compare their binding against the MFAOs. Our results confirm that the oxysterols fail to meet the predictive binding threshold, indicating weak binding affinity to the model αB-crystallin proteins. However, their predicted Kd values matched experimentally reported values. The MFAOs exceeded the threshold for predictive binding and support previous in vivo studies which suggest our molecules may have some chaperone activity. Finally, in Chapter Five, I will present several synthetic approaches for the preparation of various novel triphenylphosphonium-linked (TPP) JHXseries compounds. I will also discuss their in vitro evaluation in HEI-OC1 inner ear cells. Since mitochondrial dysfunction is linked to neurodegeneration, we hypothesized that directly linking a mitochondria-targeting moiety to our compounds would increase their potency by quenching free radicals at their main generation source. Our results indicate that the TPP compounds do not adversely affect mitochondria as shown using a viability assay and Rhodamine-123 fluorescence stain.

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