Antioxidant-mediated augmentation of ozone-induced membrane oxidation

The pulmonary epithelial lining fluid (ELF) contains substrates, e.g., ascorbic acid (AH(2)) uric acid (UA), glutathione (GSH), proteins, and unsaturated lipids, which undergo facile reaction with inhaled ozone (03). Reactions near the ELF gas/liquid interface likely provide the driving force for O-3 absorption ("reactive absorption") and constrain O-3 diffusion to the underlying epithelium. To investigate the potential mechanisms wherein O-3/ELF interactions may induce cellular damage, we utilized a red cell membrane (RCM) model intermittently covered by an aqueous film to mimic the lung surface compartmentation, and evaluated exposure-mediated loss of acetylcholinesterase activity (AChE) and TBARS accumulation. In the absence of aqueous reactants, O-3 exposure induced no detectable changes in AChE or TBARS. AH(2) and GSH preferentially induced oxidative damage in a dose-dependent fashion. AH(2)-mediated RCM oxidation was not inhibited by superoxide dismutase, catalase, mannitol, or Fe chelators. O-3 reaction with UA, Trolox, or albumin produced no RCM oxidation but oxidation occurred when AH(2) was combined with UA or albumin. Rat bronchoalveolar lavage fluid (BALF) also induced RCM oxidation. However, in Vivo O-3 exposure dampened the extent of BALF-mediated RCM oxidation. Although we cannot completely rule Out O-3 diffusion to the RCM, product(s) derived front O-3 + AH(2)/GSH reactions (possibly O-3(.-) or O-1(2)) likely initiated RCM oxidation and may suggest that in vivo, such secondary species account for O-3 permeation through the ELF leading to cellular perturbations. (C) 2004 Elsevier Inc. All rights reserved.