title: Influence of epithelial lining fluid lipids on NO(2)-induced membrane oxidation and nitration.
abstract: Within the pulmonary epithelial lining layer (ELF), antioxidants such as ascorbic acid (AH(2)) and glutathione (GSH) react with inhaled nitrogen dioxide ((*)NO(2)) to produce reactive oxygen species (ROS) that induce cellular oxidation. Because the ELF contains unsaturated fatty acids (UFA), which potentially react with (*)NO(2) and/or the antioxidant-derived ROS, we studied the influence of aqueous phase model UFA [egg phosphatidylcholine (EggPC) liposomes] on exposure-induced oxidation and nitration of membranes. Our lung surface model used gas phase (*)NO(2) exposures of immobilized red cell membranes (RCM) overlaid with defined aqueous phases. Acetyl cholinesterase (AChE) activity, TBARS, and 3-nitrotyrosine (3-NT) were used to assess protein and lipid oxidation and RCM nitration, respectively. During (*)NO(2) exposure, AH(2) and GSH induced AChE loss and TBARS, which were unchanged with buffer only. Exposures of EggPC generated extensive TBARS but not AChE loss; addition of AH(2)/GSH to EggPC resulted in smaller AChE declines and fewer TBARS. 3-NT formation occurred with or without EggPC, low concentration antioxidants, SOD, catalase, or DTPA, but was inhibitable by desferrioxamine or high antioxidant concentrations. The data suggest that reaction/diffusion limitations govern (*)NO(2) distribution, that (*)NO(2) per se directly nitrates tyrosine residues within hydrophobic regions, and that the induction of secondary oxidative processes is dependent on nonlinear relationships among (*)NO(2) flux rates, antioxidant concentrations, and diffusivity of secondary reactive species.
authors.affiliation: Department of Pathology, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: Leonard W
authors.initials: LW
authors.lastname: Velsor
authors.forename: Carol A
authors.initials: CA
authors.lastname: Ballinger
authors.forename: Jawaharlal
authors.initials: J
authors.lastname: Patel
authors.forename: Edward M
authors.initials: EM
authors.lastname: Postlethwait
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002374:Catalase / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D002614:Chelating Agents / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D004912:Erythrocytes / Q000201:enzymology / Q000502:physiology*; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D008297:Male; D009585:Nitrogen Dioxide / Q000494:pharmacology*; D010063:Ovum; D010084:Oxidation-Reduction; D004369:Pentetic Acid / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000975:Antioxidants; D002614:Chelating Agents; D008081:Liposomes; D010713:Phosphatidylcholines; D017392:Thiobarbituric Acid Reactive Substances; C002744:3-nitrotyrosine; D014443:Tyrosine; D004369:Pentetic Acid; D002374:Catalase; D013482:Superoxide Dismutase; D000110:Acetylcholinesterase; D005978:Glutathione; D001205:Ascorbic Acid; D009585:Nitrogen Dioxide