Cigarette smoke increases the adhesion of human monocytes to endothelial cells

Authored by  M Lietz, C Berger, HP Lammerich, Y Steffen, K Stolle, S Lebrun, J Schueller, T Wallerath

Presented at European Atherosclerosis Society Congress     


Cigarette smoking is a well-known risk factor for the development and progression of atherosclerosis. However, the mechanisms involved are not well understood. One early step in the initiation of atherosclerosis is the adhesion of monocytes to the vascular endothelium. The objective of this project was to investigate the impact of cigarette smoke (CS) on the adhesion properties of human monocytic cell line Mono Mac 6 (MM6) to human umbilical vein endothelial cells (HUVECs) in vitro. CS was bubbled through phosphate-buffered saline (PBS) and further diluted with cell culture medium to concentrations of 0.045 or 0.09 puffs/ml. HUVECs were exposed to CS preparations for 2 or 4 hours, and a gene array analysis (affymetrix) was performed. Up-regulation of three different adhesion molecules—vascular adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and endothelial selectin (E-selectin)—was confirmed by real-time polymerase chain reaction (PCR) and InCell-Western. To test whether the CS-induced up-regulation of adhesion molecules on the surface of the HUVECs was sufficient for the adhesion of MM6 cells, an in-vitro adhesion assay under static conditions was established. Additional adhesion experiments with blocking antibodies against VCAM1, ICAM1, and E-selectin showed E-selectin to have the strongest impact on the CS-induced adhesion of MM6 cells to HUVECs. Adhesion of peripheral blood mononuclear cells is reported to be higher in smokers than non-smokers; therefore, the adhesion properties of CS-exposed MM6 cells to untreated HUVECs were also investigated. No increased adhesion was detected. Conclusion: exposure to CS increases the adhesion of human monocytes to HUVECs in vitro.