Hydrogen peroxide-induced epithelial injury: the protective role of intracellular nonprotein thiols (NPSH)

Abstract

Injury to the alveolar region is a hallmark of the adult respiratory distress syndrome (ARDS) whereas injury to the epithelium of the conducting airways is a characteristic of asthma. Reactive oxygen species have been implicated as mediators of lung injury in both of these conditions. We have investigated the relationship between intracellular nonprotein thiols (NPSH), and the release of the cytosolic enzyme lactate dehydrogenase (LDH), as an index of cell injury, following treatment of the human alveolar type II-like epithelial cell line (A549 cells) or the human bronchial epithelial cell line (16HBE140-) with hydrogen peroxide (H2O2). We have also assessed the protective effects of pre-incubation of both of these cells lines with H2O2 or enhancement of intracellular NPSH against H2O2-induced cell injury. Exposure of A549 and 16HBE140- cells to H2O2 (0.1 mM and 1 mM respectively for 16 h) produced the release of 40% of the total cellular LDH. H2O2 exposure produced an initial dose-dependent decrease in NPSH in A549 cells, with a subsequent increase to above control values. 16HBE140- cells also showed a dose-dependent decrease in NPSH following exposure to H2O2. Pretreatment of A549 cells with 0.1 mM H2O2 followed by subsequent exposure to H2O2 did not protect against H2O2-induced LDH release in this epithelial cell line. Pre-incubation with 2 mM N-acetylcysteine (NAC) increased NPSH but not intracellular reduced glutathione and resulted in total inhibition of H2O2-induced LDH release in both cell types. Pretreatment with reduced glutathione protected both cell types against the injurious effects of H2O2, whereas glutathione monethyl ester (GSHMEE) only partially protected A549 cells and had no effect in 16HBE140- cells. Intracellular cysteine levels were increased in both cell lines following NAC exposure but not sufficiently to account for the increase in NPSH levels. These observations raise the possibility that a critical concentration of nonprotein thiols may be necessary to protect pulmonary epithelial cells against hydrogen peroxide-induced injury.

A Role for Forkhead Box A1 in Acute Lung Injury

“…AT-2 cells were stimulated with hydrogen peroxide (H 2 O 2 , 0.5 mM, Xilong Chemical Factory, China). A dose of H 2 O 2 was chosen that was consistent with previous reports [28,29] and with our pilot study, in which we found that a lower dose (0.25 mM) of H 2 O 2 did not induce obvious AT-2 cells injury. At 0, 1, 2, 4, 8, 16, 24 h after treatment, cells were harvested and mRNA and protein was extracted to determine FoxA1 expression.…”

Lipoteichoic Acid Induces HO-1 Expression via the TLR2/MyD88/c-Src/NADPH Oxidase Pathway and Nrf2 in Human Tracheal Smooth Muscle Cells

“…NAc is capable of scavenging hydrogen peroxide and hydroxyl radicals. Pretreatment of human alveolar and bronchial epithelial cells with NAc attenuates the injurious effects of hydrogen peroxide (45). In addition, DPI (a flavoprotein inhibitor) and APO (an inhibitor of translocation of the oxidase subunits) have been shown to prevent p47 phox translocation to the membrane (31,32).…”

Respiratory Syncytial Virus Infection: Mechanisms of Redox Control and Novel Therapeutic Opportunities

“…Moreover, it is able to scavenge H 2 O 2 , hydroxyl radicals, and hypochlorous acid (11). Pretreatment of human alveolar and bronchial epithelial cells with NAC protects both cell types against injurious effects of H 2 O 2 (174). It has also been shown that NAC protects against hypochlorous acid-induced contraction of guinea pig tracheal smooth muscles (19) and inhibits LPS-induced leukocyte accumulation in rat lungs.…”