Effects of a thrombomodulin-derived peptide on monocyte adhesion and intercellular adhesion molecule-1 expression in lipopolysaccharide-induced endothelial cells

PURPOSE: It has been documented that GC31, a 31-animo acid peptide from human thrombomodulin, has potent anti-inflammatory properties in endotoxin-induced uveitis and lipopolysaccharide (LPS)-induced RAW264.7 cells, while the role of GC31 in the endothelial cells has not yet been fully understood. Therefore, the aim of this study was to explore the effect of GC31 on intercellular adhesion molecule-1 (ICAM-1) expression in LPS-activated endothelial cells. METHODS: Human umbilical vein endothelial cells (HUVECs) were incubated with LPS (1 μg/ml) and peptide GC31 or control peptide VP30 simultaneously. ICAM-1 messenger RNA and protein levels were evaluated with real-time PCR and western blot. The adhesion of U937 cells labeled with CM-H2DCFDA to HUVECs was examined with fluorescence microscope. Extracellular signal-regulated kinase-1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) activation, inhibitor of nuclear factor kappa B alpha (IκBα) degradation, and nuclear factor kappa B (NF-κB) nuclear translocation were detected with western blot. RESULTS: Upon LPS stimulation, GC31 suppressed the mRNA and protein expression of ICAM-1 in HUVECs and remarkably reduced monocyte-endothelial cell adhesion in a dose-dependent manner. Furthermore, GC31 significantly inhibited the degradation of IκBα and nuclear translocation of NF-κB and moderately blocked the activation of p38 MAPK and ERK1/2 in activated HUVECs. CONCLUSIONS: Our results suggested that GC31 suppressed LPS-mediated ICAM-1 expression by inhibiting the activation of NF-κB and partially by attenuating the activity of ERK1/2 and p38 MAPK in vascular endothelium, which may contribute to ameliorating vascular inflammatory diseases, such as uveitis.