Polyunsaturated Fatty Acids as Determinants of Redox Changes and Inflammatory Responses in Human Airway Epithelial Cells Exposed to Ozone

The health benefits of dietary fish oil consumption have been widely reported. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, two omega-3 fatty acids (ω-3 FA) found in fish oil, have been associated with anti-inflammatory effects through the reduction of pro-inflammatory mediators and their metabolism to specialized pro-resolving mediators (SPMs). However, the 5 and 6 double bonds in EPA and DHA respectively are targets for lipid peroxidation by ozone (O3), a major photochemical pollutant to which millions of Americans are exposed. Products of unsaturated fatty acid peroxidation by O3 have been proposed to mediate pulmonary inflammation resulting from O3 exposure. Thus, supplementation of the human airway epithelial cells (HAEC) with ω-3 FA has the potential to both support the inflammatory response induced by O3 inhalation as well as promote its resolution. This dissertation investigates the mechanisms involved in this potential paradox at the cellular level. The results presented here demonstrate that long-chain lipid hydroperoxides induce the oxidation of glutathione (GSH) through the action of glutathione peroxidase 4 (GPx4). It is further shown that exposure to lipid hydroperoxides causes the sulfenylation of redox-sensitive proteins and alters mitochondrial respiration. Exposure of HAEC supplemented with various FA to O3 revealed that ω-3 FA potentiate the O3-induced oxidation of GSH. This occurs through increased lipid peroxidation in ω-3 FA supplemented cells. Notably, the potentiation of GSH oxidation occurred at O3 concentrations approximating current regulatory standards. In contrast, supplementation with ω-3 FA did not significantly reduce the production of the pro-inflammatory mediators prostaglandin E2 (PGE2), interleukin (IL)-6, or IL-8, or increase the release of SPM in response to O3 exposure. These results suggest that supplementation with ω-3 FA exacerbates the oxidative effects without diminishing the pro-inflammatory effects induced by exposure to O3. Further, these findings highlight the role of lipid hydroperoxides in the disruption of cellular redox and metabolic homeostasis. Overall, this data may have implications for the use of unsaturated fatty acids, such as the ω-3 FA, as dietary supplements among populations exposed to O3.Doctor of Philosoph