Oxidant-mediated lung epithelial cell tolerance: the role of intracellularglutathione and nuclear factor-kappaB

The airway epithelium is injured by oxidants inhaled as atmospheric polluta nts or produced during inflammatory responses. We studied the effect of mod ulating the antioxidant intracellular glutathione, both using thiol compoun ds and by the adaptive effect of hyperoxia, on oxidant-induced injury and a ctivation of the nuclear factor-kappaB (NF-kappaB) in two cell lines: the h uman bronchial (16HBE) and type II alveolar epithelial cells (A549). The th iol antioxidants glutathione (GSH) and glutathione monoethyl ester (GSH-MEE ) [2 mM] increased GSH levels (nmol/mg protein) in A549 cells (GSH 383 +/- 26 and GSH-MEE 336 +/- 23 vs control 171 +/- 13, P < 0.001) and in 16HBE ce lls (GSH 405 +/- 33, GSH-MEE 362 +/- 37 vs control 198 +/- 12, P < 0.001, N = 3). Treatment of hyperoxia (95% oxygen) also increased GSH levels betwee n 4 and 24 hr exposure compared with control (P < 0.01). Hydrogen peroxide (H2O2) (0.01 mM) induced NF-kappaB activation, whereas hyperoxia exposure d id not affect NF-kappaB activation in either cell line. Pretreatment with D L-buthionine (SR)sulfoximine, which decreased intracellular glutathione, in creased NF-kappaB binding induced by H2O2 and increased lactate dehydrogena se (LDH) release (P < 0.001). Pretreatment with the thiol compounds and hyp eroxia totally inhibited H2O2-induced NF-kappaB binding and cell injury as measured by LDH release. These data indicate the importance of intracellula r glutathione and inhibition of NF-kappaB in both protection/tolerance agai nst oxidant-induced epithelial cell injury, and NF-kappaB activation in res ponse to oxidative stress which may be important in lung inflammation. Thus , increasing intracellular glutathione may be of therapeutic relevance if a ble to modulate NF-kappaB activation and hence attenuate inflammation. (C) 2001 Elsevier Science Inc. All rights reserved.