Induction of IL-6 and inhibition of IL-8 secretion in the human airway cell line Calu-3 by urban particulate matter collected with a modified method of PM sampling

Exposure to particulate matter (PM) induces inflammatory cytokines. In the present study, we evaluated the secretion of IL-6 and IL-8 by an airway cell line exposed to PM with a mean aerodynamic size equal to or less than 10 or 2.5 μm (PM 10 and PM 2.5, respectively) collected in Mexico City, using a modified high-volume sampling method avoiding the use of solvents or introducing membrane components into the samples. PM was collected on cellulose-nitrate (CN) membranes modified for collection on high-volume samplers. Composition of the particles was evaluated by particle-induced X-ray emission (PIXE) and scanning electron microscopy. The particles (10–160 μg/cm 2) were tested on Calu-3 cells. Control cultures were exposed to LPS (10 ng/mL to 100 μg/mL) or silica (10–160 μg/cm 2). IL-6 and IL-8 secretions were evaluated by ELISA. An average of 10 mg of PM was recovered form each cellulose-nitrate filter. No evidence of contamination from the filter was found. Cells exposed to PM 10 presented an increase in the secretion of IL-6 (up to 400%), while IL-8 decreased (from 40% to levels below the detection limit). A similar but weaker effect was observed with PM 2.5. In conclusion, our modified sampling method provides a large amount of urban PM free of membrane contamination. The urban particles induce a decrease in IL-8 secretion that contrasts with the LPS and silica effects. These results suggest that the regulation of IL-8 expression is different for urban particles (complex mixture containing combustion-related particles, soil and biologic components) than for biogenic compounds or pure mineral particles.