Effects of sham air and cigarette smoke on A549 lung cells: implications for iron-mediated oxidative damage

Abstract

Inhalation of airborne pollution particles that contain iron can result in a variety of detrimental changes to lung cells and tissues. The lung iron burden can be substantially increased by exposure to cigarette smoke, and cigarette smoke contains iron particulates, as well as several environmental toxins, that could influence intracellular iron status. We are interested in the effects of environmental contaminants on intracellular iron metabolism. We initiated our studies using lung A549 type II epithelial cells as a model, and we evaluated the effects of iron dose and smoke treatment on several parameters of intracellular iron metabolism. We show that iron at a physiological dose stimulates ferritin synthesis without altering the transferrin receptor (TfR) mRNA levels of these cells. This is mediated primarily by a reduction of iron regulatory protein 2. Higher doses of iron reduce iron regulatory protein-1 binding activity and are accompanied by a reduction in TfR mRNA. Thus, for A549 cells, different mechanisms influencing IRP-IRE interaction allow ferritin translation in the presence of TfR mRNA to provide for iron needs and yet prevent excessive iron uptake. More importantly, we report that smoke treatment diminishes ferritin levels and increases TfR mRNA of A549 cells. Ferritin serves as a cytoprotective agent against oxidative stress. These data suggest that exposure of lung cells to low levels of smoke as are present in environmental pollutants could result in reduced cytoprotection by ferritin at a time when iron uptake is sustained, thus enhancing the possibility of lung damage by iron-mediated oxidative stress.

Involvement of cigarette smoke-induced epithelial cell ferroptosis in COPD pathogenesis

“…Hence, to elucidate the molecular mechanisms for free iron accumulation linked to ferroptosis induction in COPD pathogenesis, we focused on NCOA4-mediated ferritinophagy in a CSE-treated bronchial epithelial cell. A recent study demonstrated that intracellular ferritin is transiently increased by CS, but declines after long time CS exposure, reflecting iron mobilization from ferritin in A549 cells 26 . In agreement with this observation, CSE treatment transiently increased ferritin expression, which was shifted to a time-dependent attenuation at 6 h with concomitant upregulation of NCOA4 in BEAS-2B (Fig.…”

Secreted ferritin: Mosquito defense against iron overload?

“…In vertebrate cells, IRP1 exists with a disulfide bridge; a form that does not bind to the IRE. The addition of reducing agent to cytoplasmic extracts of human cells (Mayo et al, 2004) or to the rHIRP1 (Gray et al, 1993) reduces this bridge and thereby, increases IRP1 binding activity. We evaluated the effects of b-mercaptoethanol (bME) on mosquito IRP1/ IRE interaction of cytoplasmic extracts from CCL-125 cells.…”

Characterization of a Human In Vitro Intestinal Model for the Hazard Assessment of Nanomaterials Used in Cancer Immunotherapy

“…Raji B, Caco-2, and HT29-MTX cells were seeded separately and in triple cell culture and incubated for 24 h at 37 • C in 5% CO 2 environment. MTS solution was added to each cell culture per the manufacturer's directions [38,39]. After a 2-h 37 • C incubation, the absorbance was measured at 490 nm using a plate reader (Synergy, BioTek, Winooski, VT, USA).…”