Abstract

Initially in our study, we evaluated the effect of PA on NGF Differentiated PC 12 cells at concentrations levels that mimic pathological conditions. PA exposure resulted to be toxic to NGFDPC12 cells. PA treatment decreased cell viability and triggered cell death with apparent apoptotic features. Further morphological studies revealed the classical features of apoptosis response; including cell shrinking, cell blebbing, chromatin and nucleus condensation (Kerr et al. 1972). Our findings in summary, suggest that FFA-induced lipotoxicity requires full activation of PA, targeting the mitochondria, leading to membrane potential disruption and up-regulation of reactive oxygen free radicals. PA-induced-lipotoxicity decreased cell viability and triggered cell death with apoptotic features in PCI2 cells and Cortical Neurons. DHA induces PC 12 cells differentiation and significantly protect both NGFDPC12 cells and primary neonatal cortical cells from PA-induced lipotoxicity. In addition, Bromo-PA, a metabolically inactive FA exposure did not induce the lipotoxicity characteristic of Palmitic Acid. Thus, FA metabolism is essential for FA induced lipotoxicity. FA uptake and metabolism in the cellular environment is mediated ACS. Silencing ACS gene expression lead to inhibition of PA induced cell death and lipotoxicity. Treatment with FA metabolism inhibitors like EDYA, Etomoxir, or Malonyl CoA also improved cell viability after PA-induced lipotoxicity. Furthermore, Palmitic Acid induced lipotoxicity may be mediated downstream by lysosomal dysfunction. Accordingly, inhibition of lysosomal proteases in particular Cathepsin L led to decreased PA induced lipotoxicity and cell death.

Importantly, DHA protection mechanism from FA induced lipotoxicity in neurons may be centered at the FA metabolism and ACS checkpoint. In addition, DHA neuroprotection may be related to its incorporation into the lysosomal and mitochondrial phospholipids stabilizing their membrane structure. Increasing the organelles resistance may prevent the mitochondrial-lysosomal crosstalk. Neuroprotection is achieved by preventing the early lysosomal dysfunction, further release of cathepsins which leads to mitochondrial dysfunction and cell death.

LLU Discipline

Physiology

Department

Physiology

School

School of Medicine

First Advisor

Marino De Leon

Second Advisor

Carlos A. Casiano

Third Advisor

Michael Kirby

Fourth Advisor

Lawrence Longo

Fifth Advisor

Lubo Zhang

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2010

Date (Title Page)

6-2010

Language

English

Library of Congress/MESH Subject Headings

Lipids -- metabolism; Phospholipids -- metabolism; Docosahexaenoic Acids -- analysis; Palmitic Acid -- analysis; Fatty Acid-Binding Proteins; Mitochondria -- physiology; Intracellular Membranes; Oxidative Stress -- drug effects; Rats.

Type

Dissertation

Page Count

xiii; 209 [pgs 135 & 144 skipped]

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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