Bleomycin Induces E-selectin Expression in Cultured Umbilical Vein Endothelial Cells by Increasing Its mRNA Levels through Activation of NF-κB/Rel

Abstract

Treatment with bleomycin (BLM) often results in the development of acute lung injury and subsequent fibrosis by mechanisms that are not well understood. It is hypothesized that active oxygen species and proteases generated by inflammatory cells that accumulate in the bronchoalveolus are responsible and that BLM-induced E-selectin expression on the endothelial surface has an essential role as a trigger in the accumulation of inflammatory cells. We aimed to understand the mechanisms of BLM-induced E-selectin expression in endothelial cells. The E-selectin antigen was induced on the surface of cultured human umbilical vein endothelial cells (HUVECs) exposed to BLM in a dose- and time-dependent manner, with an increase in mRNA levels. The binding of nuclear proteins to oligonucleotides containing the NF-κB/Rel or AP-1 binding motif of the promoter of the human E-selectin gene significantly increased in BLM-treated HUVECs compared with control cells. The increased E-selectin antigen levels induced by BLM were abrogated by pretreatment with MG132 (10 μM) or PDTC (100 μM), in parallel with inhibition of the NF-κB/Rel activation and nuclear translocation, although no inhibition of the AP-1 activation was observed. Supershift assays indicated that NF-κB/Rel bound with the NF-κB/Rel binding motif contained p65, p50, and c-Rel subunits. The AP-1 activation by BLM was inhibited by pretreatment of the cells with SB203580, although BLM-induced expression of E-selectin was not attenuated. These results suggest that BLM can directly induce E-selectin expression with an increase in transcription in endothelial cells through activation and nuclear translocation of NF-κB/Rel without mediation of inflammatory cytokines.