Abstract

Hypoxic-ischemic and traumatic injury to the central nervous system (CNS) are major sources of morbidity and mortality. The broad goal of this dissertation research is to gain a better understanding of the cascade of injury events that follow hypoxic-ischemic and traumatic injury and how they may contribute to the cell death. To accomplish this goal, one of the major secondary events common to both traumatic and hypoxic-ischemic injury was investigated: the prolonged hydrolysis of membrane phospholipid with the release of massive quantities of free (non-esterified) fatty acid (FFA). The central hypothesis of this dissertation research is that elevated levels of FFA are toxic to neurons. This hypothesis is tested using cultures of nerve growth factor (NGF)-differentiated PCI 2 cells to approximate neurons and the cytotoxicity of various injury-relevant fatty acids assessed. In the series of studies comprising this dissertation, a non-toxic vehicle for the delivery of FFAs to NGF-differentiated PC12 cells in culture was developed using methyl-ß-cyclodextrin (MßCD). Cyclodextrins are widely used to facilitate the delivery of hydrophobic substances through aqueous environments and care was taken to characterize the cytotoxic effects of MßCD. Once an appropriate delivery vehicle was developed, stearic, palmitic, oleic, and arachidonic acids, which account for the bulk of FFA accumulating after injury, were tested for cytotoxic effects in cultures of NGF-differentiated PC12 cells. Palmitic and stearic acids were shown to be cytotoxic at concentrations similar to those found in the CNS following injury. Furthermore, the mode of cell death was likely apoptotic based on ultrastructural morphology, nuclear morphology, caspase activition[sic], and cleavage of specific cellular proteins. Further characterization of the cell death process revealed that earliest documented event is the upregulation of the Fas receptor mRNA. The Fas receptor is known to activate the apoptotic pathway in neurons and the early upregulation of this receptor has been shown by others to occur following traumatic and hypoxic-ischemic CNS injury. We conclude from these findings that palmitic and stearic acids are cytotoxic to neuron-like cells in concentrations similar to those reported following CNS injury. Furthermore, it is shown that fatty acid-induced cell death is apoptotic and associated with increased expression of Fas ligand. These results implicate elevated concentrations of FFAs in the pathogenesis of the apoptotic cell death that has been demonstrated following hypoxic-ischemic and traumatic CNS injury.

LLU Discipline

Physiology

Department

Physiology

School

Graduate School

First Advisor

Marino De Leon

Second Advisor

Carlos A. Casiano

Third Advisor

Michael A. Kirby

Fourth Advisor

Lawrence D. Longo

Fifth Advisor

Jonathan C. Salo

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2001

Date (Title Page)

12-2001

Language

English

Library of Congress/MESH Subject Headings

Cell Aging -- physiology; Neurons -- metabolism; Fatty Acids -- metabolism; Hypoxia- Ischemia, Brain -- physiopathology; Nerve Growth Factor; Cytotoxins; PC12 Cells; Apoptosis -- physiology

Type

Dissertation

Page Count

xii; 181

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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