Since an increased serum unconjugated bilirubin (UCB) level has been proposed as an independent protective factor against atherosclerotic disease, we investigated the molecular events at the basis of this effect. HUVEC and H5V cells were treated with TNF alpha and UCB and the effects assessed on E-selectin, VCAM-1 and ICAM-1. In HUVEC cells, UCB blunted the TNF alpha-induced gene upregulation of E-selectin VCAM-1 and ICAM-1. The same pattern was observed in H5V cells except for ICAM-1. UCB also inhibited the PMN endothelial adhesion in HUVEC H5V cells. Western blot and FACS analysis confirmed that UCB prevented TNF alpha-induced over-expression of adhesion molecules proteins in H5V cells. These data contribute to further explain the protective effect of bilirubin against development of atherosclerosis. (C) 2009 Elsevier Inc. All rights reserved.