Defense Date

2020

Document Type

Thesis

Degree Name

Doctor of Philosophy

Department

Pharmacology & Toxicology

First Advisor

Michael F. Miles

Abstract

Alcohol use disorder (AUD) is a prevalent neuropsychiatric disease with profound health, social, and economic consequences. With an estimated 50% heritability, identifying genes that engender risk and contribute to the underlying neurobiological mechanisms represents an important first step in developing effective treatments. Gene expression studies are an important source of candidate genes for studying AUD, providing windows into the molecular machinery engaged by the brain in response to ethanol. Our laboratory has implicated N-myc down-regulated gene 1 (Ndrg1) as a potential candidate gene that modulates ethanol-induced changes in myelin-related gene expression and acute sensitivity to ethanol. Analysis of mPFC expression data found that Ndrg1 expression was positively correlated with voluntary ethanol intake across the BXD panel of mice and demonstrated that the basal levels of Ndrg1 mRNA expression in the mPFC across seven different strains of mice was inversely correlated with LORR duration time. We found that mPFC Ndrg1 expression was up-regulated following 5 weeks of intermittent ethanol access in C57BL/6J (B6J) mice. We also observed an induction of Ndrg1 in the mPFC of female B6J mice following acute ethanol exposure. After observing the regulation of Ndrg1 in wild type mice, studies were performed in a mouse line that produces a myelinating cell-selective conditional knockout (KO) of Ndrg1, by inducing Cre Recombinase with tamoxifen treatment. Our findings demonstrate that Ndrg1 expression and its functional state, as determined by phosphorylation state and localization, are clearly modulated by acute ethanol.. We also found that deletion of Ndrg1 in myelinating cells alters ethanol-related behaviors in a way that suggests sensitivity to ethanol is modified. Additionally, we found altered ethanol concentration preferences and total ethanol preference between the KO and control groups in a 5-week drinking study. Mutations in Ndrg1 result in a demyelinating polyneuropathy: Charcot-MarieTooth Disease 4D. Given that mutations in Ndrg1 are known to cause peripheral neuropathies in multiple species, we characterized the peripheral nerve dysfunction that develops from conditional deletion of the gene in adult aged mice. Additionally, some evidence in clinical literature had suggested that nerve tissue levels of NDRG1 inversely correlates with chemotherapy-induced peripheral neuropathy (CIPN) following treatment with Paclitaxel for breast cancer. We demonstrated that low dose Paclitaxel accelerates the development of neuropathy symptoms in mice that have had Ndrg1 knocked out. The literature and our results suggest that cellular bio-lipids and lipid interactions with BK channels, such as Kcnma1, are key drivers for both the peripheral nerve dysfunction and the changes in ethanol sensitivity, but more studies are needed to prove this hypothesis. These results demonstrated the importance of Ndrg1 for peripheral nerve function and demonstrated that decreasing levels of Ndrg1 do increase the toxic effects of chemotherapeutics. Ultimately, the works presented here demonstrate the biological importance of Ndrg1 in the maintenance of peripheral nerve function and as an ethanol-related gene that modulates ethanol sensitivity, consumption, and risk for developing an AUD.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

12-4-2020

 
 
 
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