Endothelial C-reactive protein increases platelet adhesion under flow conditions

While data regarding the pathogenetic role of C-reactive protein (CRP) in atherothrombosis are accumulating, it is still controversial whether local CRP secretion is of any pathobiological significance. The present study examined whether endothelial-derived CRP modulates autocrine prothrombotic activity. Endothelial cells were isolated from hearts of mice transgenic to human CRP and grown in primary cultures. Human CRP expression was confirmed in these cells compared with no expression in cultures derived from wild-type congenes. Adhesion of human platelets to endothelial cells was studied in the "cone and plate" flow system. Platelet adhesion to cells expressing CRP was significantly increased compared with that in controls (n = 6, P < 0.01). The proadhesive effect of CRP was significantly suppressed in mouse heart endothelial cells and in human umbilical vein endothelial cells following treatment with small interfering RNA for human CRP. Adhesion was modulated by an increase in P-selectin. P-selectin expression correlated with a proadhesive phenotype, and blocking P-selectin with neutralizing antibody significantly decreased the adhesion of platelets to CRP-expressing cells (40.4 ± 10.5 to 9.4 ± 6.9 platelets/high-power field, n = 5 to 6, P < 0.01). In conclusion, human CRP that is locally produced in endothelial cells increases platelet adhesion to endothelial cells under normal shear flow conditions. These findings indicate that CRP exerts a local effect on endothelial cells via P-selectin expression, which promotes platelet adhesion and subsequent thrombus formation.