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theses

The overall goal of this study is to investigate the role of reactive lipid mediators generated during oxidative and nitrosative stress on adaptive responses in corneal epithelial cells and skin keratinocytes. Adaptive responses include changes in enzymes in the detoxification of reactive intermediates, stress response genes and antioxidants. The skin and cornea are highly sensitive to oxidative stress induced environmental insults such as ultraviolet light and various chemical toxicants. Oxidative stress is associated with the excessive generation of highly toxic intermediates including superoxide anion, hydrogen peroxide and hydroxyl radicals. By initiating lipid peroxidation, these reactive oxygen species (ROS) can generate α, β-unsaturated hydroxyalkenals. One of these electrophilic species is 4-hydroxynonenal (4-HNE), a relatively abundant reactive aldehyde. Nitration products of unsaturated fatty acids including electrophilic fatty acid nitroalkenes represent another important class of endogenous lipid mediators formed in response to nitrosative stress. Nitro-fatty acids such as nitrooleic acid, as well as 4-HNE can form adducts with biomolecules via Michael addition, most notably, proteins. By reacting with signaling proteins, nitrooleic acids and 4-HNE can regulate their function and control expression of adaptive response proteins. In the present studies we characterized the effects of 4-HNE and nitrooleic acids on expression of adaptive response genes in corneal epithelial cells and keratinocytes. We also examined signal transduction pathways mediating changes of these genes including mitogen-activated protein kinases and phosphoinositide 3-kinase signaling. We also evaluated the role of caveolae in mediating the actions of 4-HNE and the nitro-fatty acids. This thesis is divided into four parts: 1. The generation of 4-hydroxynonenal in rabbit cornea organ cultures treated with UVB light and nitrogen mustard; 2. Modulation of keratinocyte expression of antioxidants by 4-HNE; 3. Regulation of keratinocyte expression of stress proteins and antioxidants by 9- and 10-nitrooleic acid; and 4. Differential metabolism of 4-HNE in liver, lung and brain of mice and rats. These findings indicate that 4-HNE and electrophilic nitrofatty acids effectively modulate expression of antioxidant enzymes in corneal epithelial cells and keratinocytes. Changes in expression of adaptive response genes in these cells may be important in protecting the eye and skin from oxidative stress.

ETD_5485

Ph.D.

Includes bibliographical references

by Ruijin Zheng

doi:10.7282/T3Z899Q3

ETD doctoral

The author owns the copyright to this work.