Medulloblastoma is the most common pediatric brain cancer and accounts for 20% of all pediatric brain tumors. Upon diagnosis, patients undergo tumor-resection surgery followed by intense chemotherapy and cerebrospinal irradiation (CSI) regimens. CSI therapy is highly toxic and poorly tolerated in pediatric patients and is known to cause long-term neurocognitive, endocrine, and developmental deficits that often diminish the quality of life for medulloblastoma patients. The development of targeted therapies is necessary for both increasing the chance of survival and reducing treatment-related morbidities. A potential therapeutic target of interest in medulloblastoma is the polyamine biosynthesis pathway. Polyamines are metabolites present in every living organism and are essential for cellular processes such as growth, survival, and differentiation. Recent studies have shown that polyamine production is dysregulated in several cancers, including brain cancers, and have highlighted polyamine biosynthesis as a potential cancer growth dependency. Dysregulated polyamine metabolism has also been linked to several oncogenic drivers, including the WNT, SHH, and MYC signaling pathways that characterize genetically distinct medulloblastoma subgroups. One way to target polyamine biosynthesis is through the inhibition of the rate-limiting enzyme ornithine decarboxylase with difluoromethylornithine (DFMO), an analog of the polyamine precursor ornithine. DFMO is well-tolerated in pediatric populations and exerts minimal toxicities, as shown through neuroblastoma clinical trials, and is a therapy of interest for medulloblastoma. While DFMO has been tested clinically in multiple cancers, few in vitro studies have been performed to understand the exact mechanisms of anti-proliferation and cytotoxicity. Our study screened two immortalized medulloblastoma cell lines, DAOY (SHH) and D283 (non-WNT/non-SHH), and three patient-derived medulloblastoma cell lines, SL00024 (SHH), SL00668 (non-WNT/non-SHH), SL00870 (Unknown subgroup), for DFMO sensitivity and profiled the immortalized medulloblastoma cell line metabolome to understand the interactions between inhibition of polyamine metabolism with other essential metabolic processes and tumor cell growth. We found that medulloblastoma cell lines are sensitive to DFMO and the adaptive response to DFMO in medulloblastoma may be caused by increased oxidative stress and free radical scavenging. Our study hopes to inform the use of DFMO as an anti-cancer therapy in medulloblastoma by understanding the drug’s single-agent anti-proliferative mechanisms.

Approximately 2.8 million Americans seek medical care for traumatic brain injury (TBI) each year. Of this population, the majority are sufferers of diffuse TBI, or concussion. It is unknown how many more individuals decline to seek medical care following mild TBI. This likely sizeable population of un- or self-treated individuals combined with a lack of definitive biomarkers or objective post-injury diagnostics creates a unique need for practical therapies among diffuse TBI sufferers. Practical therapies stand to decrease the burden of TBI among those who would otherwise not seek treatment or do not meet clinical diagnostic criteria upon examination. For this unique treatment niche, practical therapies for TBI are defined as having one or more of the following qualities: common availability, easy administration, excellent safety profile, and cost-effectiveness. This dissertation identifies and critically examines the efficacy of four classes of practical treatments in improving rodent outcome from experimental diffuse traumatic brain injury.

Over-the-counter (OTC) analgesics, omega-3 fatty acids, specialized pro-resolving mediators (SPMs), and remote ischemic conditioning (RIC) were administered before or following midline fluid percussion injury. Behavioral, histological, and molecular analyses were used to assess treatment effects on functional outcome and secondary injury progression. Acute administration of common OTC analgesics had little effect on post-injury outcome in mice. Dietary supplementation with omega-3 fatty acid docosahexaenoic acid (DHA) prior to or following diffuse TBI significantly reduced injury-induced sensory sensitivity and markers of neuroinflammation with no effect on spatial learning. Intraperitoneal administration of omega-3 fatty acid-derived SPM resolvin E1 significantly increased post-injury sleep and suppressed microglial activation. Aspirin-triggered (AT) resolvin D1 administration improved both motor and cognitive outcome following diffuse TBI. RIC treatment in mice demonstrated little effect on functional outcome from diffuse TBI. Untargeted proteomic analysis of plasma samples from RIC-treated mice was used to identify candidate molecular correlates of RIC. Identification of these candidates represents a vital first step in elucidating the neuroprotective mechanisms underlying RIC. The overall findings suggest that omega-3 fatty acid supplementation, SPM administration, and RIC may serve as effective practical therapies to reduce the somatic, cognitive, and neurological burden of diffuse TBI felt by millions of Americans.

The stress response facilitates our ability to deal effectively with threatening situations, but exposure to severe or chronic stressors can lead to undesirable neural, physiological, and behavioral outcomes. Chronic stress is associated with structural changes in the rat hippocampus, with corresponding deficits in learning and memory. Recent studies have uncovered an inherent neuroplasticity that allows the hippocampus to recover from these stress-induced neural changes. Underlying mechanisms likely involve several different cellular and molecular pathways. In order to gain a more comprehensive understanding of these pathways, we investigated differences in protein expression throughout the timeline of chronic stress and recovery. Male Sprague-Dawley rats were randomly assigned to chronic restraint stress for 6hr/d/10d or 6hr/d/21d, stress for 6hr/d/21d followed by a recovery period of no stress for 10 or 21 days, or a control group. The proteome from the hippocampus of these rats was sequenced using liquid chromatography tandem mass spectrometry (LC-MS/MS) and analyzed. We hypothesized that chronic stress alters interneuronal signaling in the hippocampus by enhancing or attenuating the expression of proteins responsible for synaptic plasticity (functional) and neuronal structure (morphology). So far we have found that structural proteins, such as alpha-internexin, homer protein homolog 3, neurofilament light, and vimentin were significantly altered by chronic stress and recovery. In contrast, proteins necessary for or associated with myelination such as 2',3'-cyclic-nucleotide 3'-phosphodiesterase, myelin-associated glycoprotein, myelin basic protein S, and myelin proteolipid protein were significantly downregulated by chronic stress. Collectively, these results will provide a resource for further investigations into the mechanisms of the brain's recovery from chronic stress.