Electronic Theses and Dissertations

Identifier

6094

Date

2017

Document Type

Dissertation (Access Restricted)

Degree Name

Doctor of Philosophy

Major

Chemistry

Committee Chair

Thomas R Sutter

Committee Member

Gary L Emmert

Committee Member

Carrie H Sutter

Committee Member

Paul Simone

Abstract

We have previously hypothesized the existence of an intertwined, reciprocally regulated, network of transcription factors and enzymes involved in coordinating biochemical processes to efficiently restore or resist changes in redox homeostasis, termed the Soft Cysteine Signaling Network (SCSN). The individual components that comprise the SCSN contain unique low pKa cysteine residues, whereby chemical modification triggers changes in the activity of the reactive cysteine-containing protein. A central component of the mammalian SCSN is Nrf2. The Keap1-Nrf2 signaling pathway is currently the subject of clinical trials evaluating the pharmacological activation of this pathway for the prevention of cancer and the treatment of chronic kidney disease and multiple sclerosis. Leveraging a robust chemical genomics approach, we explored structure activity relationships between two distinct Nrf2-activating agents, 3H-1,2-dithiole-3-thione (D3T) and 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im). As thiol-reactive compounds with stark differences in potency, we sought to characterize the Nrf2-dependent and -independent effects unique to each treatment. At equally efficacious doses, D3T selectively up-regulated the expression of enzymes involved in cholesterol biosynthesis, while CDDO-Im showed preferential regulation of transcription factors contributing to lipid metabolism and beta-oxidation. In addition to these effects on metabolism, we observed significant alterations in the expression of genes that control molecular circadian rhythms in response to both compounds. Further biochemical characterization demonstrated that not only is Nrf2 required for normal circadian rhythmicity, but that Nrf2 transcriptionally regulates the expression of Cry2 and Nr1d1. Regulation of the circadian clock by Nrf2 in response to an oxidative signal corresponding to the time such a signal would be endogenously produced, resulted in significant reinforcement of the circadian amplitude. As a circadian output and a direct input into both the core and stabilizing circadian clock loops, these data characterize Nrf2 as a necessary component of the core clockwork. As a redox-sensitive transcription factor, changes in the intracellular redox flux are likely to be integrated into the clock via an Nrf2-dependent mechanism. Together these data expand on our understanding of the effects of clinically relevant Nrf2-activating compounds in addition to characterizing an endogenous function for Nrf2 in timekeeping.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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