Urban particulate matter induces the expression of receptors for early and late adhesion molecules on human monocytes
Highlights: • Inhalation of particles is related to local and systemic effects. • Activation of monocytes may play a role in the systemic effects induced by particles. • Monocytes may be activated by particles translocating from the lung into circulation, even at very low concentrations. • Expression of adhesion molecules receptors on monocytes increases the interaction between monocytes and endothelial cells. • Particles in concentration in the range of ng/mL are capable to induce the expression of receptors for adhesion molecules. Exposure to urban particulate matter (PM) is correlated with increases in the emergence of health services due to adverse events and deaths and is mainly related to cardiorespiratory complications. The translocation of particles from the lung into circulation has been proposed as a factor that may trigger systemic effects. Monocytes may be exposed to PM, and if the monocytes are activated, then they are likely to adhere to endothelial cells in a distant organ due to the expression of receptors for adhesion molecules. In the present study, we evaluated the expression of receptors for adhesion molecules (sLe{sup x}, PSGL-1, LFA-1, VLA-4 and α{sub V}β{sub 3}) in monocytes (U937 cells) exposed for 3 or 18 h to PM{sub 10} (0.001, 0.003, 0.010, 0.030, 0.300, 3 or 30 µg/mL). Exposed cells were co-cultured with human endothelial cells that were naive or previously exposed to the same particles. When U937 cells were exposed to PM{sub 10}, similar levels of expression for early and late receptors for adhesion molecules were observed from 30 ng/mL as those induced by TNF-α. Cells exposed to particles at concentrations above 30 ng/mL were more adhesive to naive or exposed human endothelial cells. Taken together, our results suggest that it is plausible that activated monocytes may play a role in systemic effects induced by PM{sub 10} due to the size distribution of the particles and the concentrations required to trigger the expression of receptors for adhesion molecules in monocytes.