Effect of Fatty Acid Profiles on the Susceptibility of Cultured Rabbit Tracheal Epithelial Cells to Hyperoxic Injury

Abstract

Abstract To investigate the role of cellular fatty acid content on the susceptibility of airway epithelial cells to hyperoxic injury, monolayer cultures of rabbit tracheal epithelial (TE) cells were grown to confluence in serum-free media with or without a commercial mixture of cholesterol esters and phospholipid-rich lipo-proteins (Excyte III, Miles-Pentex, Kankakee, IL) in conjunction with arachidonic acid complexed to BSA. Monolayer cultures were then exposed to control (5% CO2/air) or hyperoxic atmospheres (95% oxygen/5% CO2) for 2 h using an in vitro system in which cells were maintained at a gas-liquid interface analogous to in vivo conditions. Hyperoxic injury was assessed by cell viability (trypan blue exclusion) and by the generation of lipid peroxides measured as thiobarbituric acid (TBA) reactive substances. Changes in TE cell and cell culture effluent fatty acid content induced by exposure to control or hyperoxic atmospheres were analyzed by gas chromatography. TE cells grown in lipid-unsupplemented media had fatty acid profiles characteristic of essential fatty acid deficiency, whereas the fatty acid content of lipid-supplemented TE cells more closely resembled those of acutely recovered TE cells. Lipid-unsupplemented cells were more susceptible to hyperoxic injury as demonstrated by decreased viability and increased production of TBA-reactive substances compared to cells maintained in lipid-supplemented media. In both lipid-supplemented and unsupplemented cells, hyperoxic exposure was associated with a decreased relative cellular content of the monounsaturated and polyunsaturated fatty acids (PUFA) and an increased content of saturated fatty acids. The fatty acid content of cell culture effluents from lipid-supplemented and unsupplemented cells contained little to no PUFA and this did not change after exposures. Our observations suggest that differences in hyperoxia-induced cytotoxicity between the lipid-supplemented and unsupplemented TE cells may be due to varying susceptibilities of constituent membrane fatty acids to lipid peroxidation and provide further evidence for a protective effect of PUFA against hyperoxic injury.