Fibrinogen regulates the expression of inflammatory chemokines through NF-κB activation of endothelial cells

The objective of this study was to characterize the role of fibrinogen in stimulating expression of inflammatory chemokines in endothelial cells through NF-κB activation. Human umbilical vein endothelial cells (HUVEC) were exposed to fibrinogen up to 3,000 μg/ml, and NF-κB activation was assessed using electrophoretic mobility shift assay (EMSA). Fibrinogen exposure resulted in a concentration dependent increase in NF-κB activation that reached a maximum at 1,000 μg/ml after 4 hours and was sustained up to 24 hours. The effect was inhibited by antibodies to α_vβ₃ and α₅β₁ and by the GRGDS peptide, indicating integrin involvement. Preincubation with Mn₂₊ lowered the fibrinogen concentration-dependence, consistent with integrin activation. Supershift assays demonstrated involvement of the p50, p65 and c-Rel components of NF-κB. Fibrinogen exposure also resulted in up-regulation of expression of monocyte chemoattractant protein-I (MCP-I and of interleukin-8 as shown by RNase protection assays and by real-time RT-PCR. Increased secretion of MCP-I was confirmed by ELISA. Parthenolide, an IκB kinase inhibitor, prevented up-regulation of MCP-I by fibrinogen, linking this response to NF-κB activation. From our findings, we conclude that fibrinogen regulates NF-κB activation and expression of inflammatory chemokines in endothelial cells and may be involved in mediating inflammatory processes.