Author ORCID Identifier

https://orcid.org/0009-0002-7002-9469

Date Available

7-10-2026

Year of Publication

2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Pharmacy

Department/School/Program

Pharmaceutical Sciences

Faculty

Jill R. Turner

Faculty

Dr. David Feola

Abstract

Nicotine use disorder (NUD) remains a leading cause of preventable disease, yet the neurobiological mechanisms underlying nicotine withdrawal are incompletely understood. Emerging evidence implicates neuroimmune signaling and astrocytic regulation of glutamate in shaping the withdrawal-associated affective phenotype. This dissertation investigated these processes using multiple nicotine administration paradigms including osmotic minipump implant, cigarette smoke exposure, and nicotine vapor inhalation to model diverse routes of human nicotine intake.

Chapter 2 examines the effects of these three modes of administration on neuroinflammation and validation of nicotine delivery. Nicotine exposure was confirmed through receptor [3H]Epibatidine nAChR binding assay and serum cotinine measurements. Results demonstrated that only cigarette smoke exposure induced upregulation of NOX2, accompanied by a reduction in IBA1-positive cells in the ventral hippocampus. Cell-to-cell communication was further assessed by analyzing astrocyte-specific genes in a microglia-depleted environment achieved through PLX5622 chow treatment. Although three of the four genes were significantly downregulated in the withdrawal group compared to saline controls, only two returned to baseline following PLX5622 chow treatment. This indicates that microglial depletion partially normalizes astrocytic gene expression altered by withdrawal.

Chapter 3 explores Fingolimod (FTY720) as an off-label therapeutic in targeting behavioral impairments caused by NUD withdrawal. To enhance translational relevance, FTY720 was administered intranasally (IN) and compared to an intraperitoneal injection (IP). Fingolimod acts on sphingosine-1-phosphate receptors (S1PRs) on astrocytes, which were evaluated in both naïve (nicotine free) and nicotine withdrawal mice. Naïve and withdrawal cohorts exhibited variability across S1PR subtypes and routes of administration. Behavioral testing assessing anxiety-like phenotypes revealed correlations between FTY720 and gene expression of GAD67, suggesting that decreased GABA levels may contribute to altered anxiety states. Gene expression analyses were conducted for markers of glutamate dysfunction, astrocyte activity, proinflammatory microglial, mitochondria impairment and metabolism, and FTY720-depedent signaling.

Collectively, these studies indicate that chronic nicotine withdrawal induces classic markers of microglia activation in the cigarette smoke model, both in mRNA and protein levels of the ventral hippocampus. PLX5622 experiments demonstrate that microglia and astrocytes are closely interconnected, as microglial depletion alters the astrocyte-specific genes regulation. While FTY720 administration does not directly modulate anxiolytic behavior during nicotine withdrawal, cellular signaling mediated by FTY720 may help mitigate the neuroinflammatory environment associated with NUD withdrawal. Overall, IN FTY720 administration shows potential as a translatable pharmacotherapeutic for treating NUD-related neuroimmune dysfunction.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.568

Funding Information

This study was supported by the National Institute on Drug Abuse Grant (no.: 5R01DA044311-06) in 2022.

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Available for download on Friday, July 10, 2026

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