Semester

Spring

Date of Graduation

2025

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Microbiology, Immunology, and Cell Biology

Committee Chair

Candice M Brown

Committee Co-Chair

James Simpkins

Committee Member

James Simpkins

Committee Member

John Hollander

Committee Member

Aminata Coulibaly

Committee Member

Gordon Meares

Abstract

Ischemic stroke and sepsis-associated encephalopathy (SAE) are two distinct conditions that share common pathophysiological mechanisms affecting brain microvascular endothelial cells (BMECs). Ischemic stroke results from an acute reduction in cerebral blood flow due to thrombosis or embolism, leading to energy failure, oxidative stress, and blood-brain barrier (BBB) dysfunction. SAE, a neurological complication of sepsis, arises from systemic inflammation, endothelial activation, and BBB disruption, leading to cognitive impairment and neuroinflammation. Despite their different etiologies, both conditions involve BMEC dysfunction as a central mediator of neurovascular injury. This dissertation aims to investigate the immunometabolic dysfunction of BMECs in ischemic stroke and sepsis, with a particular focus on the role of tissue-nonspecific alkaline phosphatase (TNAP) in regulating endothelial metabolism and inflammation. By elucidating BMEC-specific metabolic adaptations and inflammatory responses, this research seeks to identify potential therapeutic targets for mitigating neurovascular damage. Experimental models of ischemic stroke and sepsis were utilized to assess metabolic and bioenergetic changes in BMECs. Seahorse metabolic assays were employed to measure glycolysis and oxidative phosphorylation, while high-dimensional flow cytometry and metabolomic profiling were used to characterize immune and metabolic shifts. Transgenic mouse models with endothelial-specific deletion of TNAP were utilized to determine its role in immunometabolic regulation. Findings indicate that both ischemic stroke and SAE trigger BMEC metabolic reprogramming, shifting towards fatty acid metabolism with slight alternation in glycolysis and oxidative phosphorylation. TNAP was found to modulate endothelial metabolism by regulating fatty acid metabolism enzymes and metabolites and increased microglia and B cell migration to the site of inflammation. Loss of TNAP activity exacerbated BBB breakdown and neurovascular inflammation in ischemic stroke. Our results indicate that BMEC dysfunction serves as a critical driver of neurovascular injury in ischemic stroke and SAE. The immunometabolic interplay within these endothelial cells presents a novel target for therapeutic intervention. TNAP emerges as a key regulator of endothelial metabolism, and its modulation could provide a potential strategy for preserving BBB integrity and mitigating neuroinflammatory responses in ischemic and septic brain injuries.

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