Lung Surfactant Gelation Induced by Epithelial Cells Exposed to Air Pollution or Oxidative Stress

Abstract

Lung surfactant lowers surface tension and adjusts interfacial rheology to facilitate breathing. A novel instrument, the interfacial stress rheometer (ISR), uses an oscillating magnetic needle to measure the shear viscosity and elasticity of a surfactant monolayer at the air-water interface. The ISR reveals that calf lung surfactant, Infasurf, exhibits remarkable fluidity, even when exposed to air pollution residual oil fly ash (ROFA), hydrogen peroxide (H 2 O 2 ), or conditioned media from resting A549 alveolar epithelial cells (AEC). However, when Infasurf is exposed to a subphase of the soluble fraction of ROFA-or H 2 O 2 -treated AEC conditioned media, there is a prominent increase in surfactant elasticity and viscosity, representing twodimensional gelation. Surfactant gelation is decreased when ROFA-AEC are pretreated with inhibitors of cellular reactive oxygen species (ROS), or with a mitochondrial anion channel inhibitor, as well as when A549-0 cells that lack mitochondrial DNA and functional electron transport are investigated. These results implicate both mitochondrial and nonmitochondrial ROS generation in ROFA-AEC-induced surfactant gelation. A549 cells treated with H 2 O 2 demonstrate a dose-dependent increase in lung surfactant gelation. The ISR is a unique and sensitive instrument to characterize surfactant gelation induced by oxidatively stressed AEC.

9,10-Phenanthrenequinone promotes secretion of pulmonary aldo-keto reductases with surfactant

“…As evidenced by the elevation of 8-hydroxydeoxyguanosine in the BALF from the 9,10-PQtreated rats, the accumulation of the abnormal surfactant observed during quinone exposure is possibly attributable to an enhanced level of ROS. The formation of the abnormal surfactant might also be explained by the findings that ROS modify the surfactant components and consequently cause the formation of conjugated dienes and protein carbonyls and SPA dysfunction (Andersson et al 1999) and that the chronic exposure of lung cells or of rats to DEP and ROS induces surfactant gelation and compositional changes in lipid components (Eskelson et al 1987;Anseth et al 2005). Thus, the unusual metabolism of the surfactant evoked by 9,10-PQ probably results from oxidative modifications of components by ROS; this is suggested to be a novel mechanism of alveolopathy caused by DEP inhalation.…”

Resistance of quiescent and proliferating airway epithelial cells to H2O2 challenge

“…In general, a trend was observed that cultures with a low thiol concentration contained the most MII cells and necrotic cells. H 2 O 2 incubations have been used [10][11][12][13]15]; this prompted the current authors to perform a detailed time-dependent dose-response study and to define limits for in vitro resistance and recovery. For this purpose, cells were challenged with H 2 O 2 at concentrations above levels implicated in cell signalling (50 mM) [23] but below levels that would lead to cell death within minutes (10 mM).…”

“…For this purpose, cells were challenged with H 2 O 2 at concentrations above levels implicated in cell signalling (50 mM) [23] but below levels that would lead to cell death within minutes (10 mM). In most described cases, A549 cells are maintained in medium containing serum up to the moment the experiment starts [11,12,15]. When the cultures are not 100% confluent it is likely that they are still proliferating at the start of the experiment.…”

“…To obtain a detailed description of recovery of cells after an oxidative challenge, the response of the alveolar epithelial cell line A549 to various concentrations of hydrogen peroxide (H 2 O 2 ) was investigated. The effect of H 2 O 2 on pulmonary epithelial cells has been studied in earlier investigations using different concentrations and different culture conditions [10][11][12][13][14][15]. However, the different abilities of proliferating and quiescent lung epithelial cells to recover from various concentrations of H 2 O 2 have not been studied in a time-dependent manner.…”

“…However, the different abilities of proliferating and quiescent lung epithelial cells to recover from various concentrations of H 2 O 2 have not been studied in a time-dependent manner. A549 is an adenocarcinoma cell line but is related to alveolar epithelial cells, as previous studies show [11,16], and is known to be sensitive to morphological changes under different stress conditions [17].…”