Airborne particulate matter upregulates expression of early and late adhesion molecules and their receptors in a lung adenocarcinoma cell line.

BACKGROUND: Epidemiological evidence associates chronic exposure to particulate matter (PM) with respiratory damage and lung cancer. Inhaled PM may induce systemic effects including inflammation and metastasis. This study evaluated whether PM induces expression of adhesion molecules in lung cancer cells promoting interaction with monocytes. METHODS: The expression of early and late adhesion molecules and their receptors was evaluated in A549 (human lung adenocarcinoma) cells using a wide range of concentrations of PM2.5 and PM10. Then we evaluated cellular adhesion between A549 cells and U937 (human monocytes) cells after PM exposure. RESULTS: We found higher expression of both early and late adhesion molecules and their ligands in lung adenocarcinoma cells exposed to PM2.5 and PM10 particles present in the air pollution at Mexico City from 0.03 µg/cm2 with a statistically significant difference (p ≤ 0.05). PM10 had stronger effect than PM2.5. Both PM also stimulated cellular adhesion between tumor cells and monocytes. CONCLUSIONS: This study reveals a comprehensive expression profile of adhesion molecules and their ligands upregulated by PM2.5 and PM10 in A549 cells. Additionally these particles induced cellular adhesion of lung cancer cells to monocytes. This highlights possible implications of PM in two cancer hallmarks i.e. inflammation and metastasis, underlying the high cancer mortality associated with air pollution.

Titanium dioxide nanoparticles induce the expression of early and late receptors for adhesion molecules on monocytes.

BACKGROUND: There is growing evidence that exposure to titanium dioxide nanoparticles (TiO2 NPs) could be harmful. Previously, we have shown that TiO2 NPs induces endothelial cell dysfunction and damage in glial cells. Considering that inhaled particles can induce systemic effects and the evidence that nanoparticles may translocate out of the lungs, we evaluated whether different types of TiO2 NPs can induce the expression of receptors for adhesion molecules on monocytes (U937 cell line). We evaluated the role of reactive oxygen spices (ROS) on these effects. METHODS: The expression of receptors for early (sLe(x) and PSGL-1) and late (LFA-1, VLA-4 and αVß3) adhesion molecules was evaluated in U937 cells on a time course (3-24 h) using a wide range of concentrations (0.001-100 µg/mL) of three types of TiO2 NPs (<25 nm anatase, 50 nm anatase-rutile or < 100 nm anatase). Cells exposed to TNFα were considered positive controls, and unexposed cells, negative controls. In some experiments we added 10 µmolar of N-acetylcysteine (NAC) to evaluate the role of ROS. RESULTS: All tested particles, starting at a concentration of 0.03 µg/mL, induced the expression of receptors for early and late adhesion molecules. The largest increases were induced by the different molecules after 3 h of exposure for sLe(x) and PSGL-1 (up to 3-fold of the positive controls) and after 18 h of exposure for LFA-1, VLA-4 and αVß3 (up to 2.5-fold of the positive controls). Oxidative stress was observed as early as 10 min after exposure, but the maximum peak was found after 4 h of exposure. Adhesion of exposed or unexposed monocytes to unexposed or exposed endothelial cells was tested, and we observed that monocytes cells adhere in similar amounts to endothelial cells if one of the two cell types, or both were exposed. When NAC was added, the expression of the receptors was inhibited. CONCLUSIONS: These results show that small concentrations of particles may activate monocytes that attach to endothelial cells. These results suggest that distal effects can be induced by small amounts of particles that may translocate from the lungs. ROS play a central role in the induction of the expression of these receptors.