Contribution of Lipopolysaccharide to Prolylcarboxypeptidase Activation in Endothelial Cells.

Bradykinin (BK) participates in the etiology of vascular inflammation and the regulation of local blood flow and blood pressure by causing a vascular hyperemia. The bradykinin generating pathway of human plasma consists of prolylcarboxypeptidase (PRCP), heat shock protein 90 (HSP90), coagulation factor XII (FXII, Hageman factor), and the heteromer complex of prekallikrein (PK) and high molecular weight kininogen (HK). In the presence of HK, PRCP activates PK to generate kallikrein on endothelial cells. Formed kallikrein then cleaves HK to liberate BK. PRCP-induced PK activation is independent of the activated FXII. The activity of PRCP leads to vasodilation. In inflamed tissues, tissue injury or hypotensive bacteremia, BK has been shown to accumulate in the blood or plasma of these patients. In this investigation, we have assessed the possible contribution of lipopolysaccharide (LPS) to PRCP activation in primary cultures of human umbilical vein endothelial cells (HUVECs) using multiple approaches. The role of LPS in HK binding to HUVECs was assessed. The effect of LPS on the endothelial permeability injury was evaluated by histological changes and analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The release of von Willebrand factor (VWF), endothelin-1 (ET-1) and intercellular adhesion molecule-1 (ICAM-1) induced by LPS in HUVEC was determined. PK activation on LPS-pretreated endothelial cells was higher than untreated cell. PRCP inhibitor, z-pro-prolinal, inhibited the production of kallikrein from PK compared to the control. These results suggest that LPS contributes to PRCP overactivation which results in the acceleration of the inflammatory process, exerting its effects via PK activation. Inhibiting the activity of PRCP may exert some beneficial therapeutic action in systemic inflammation, at least in part by inhibiting the production of BK and thus preventing vascular dysfunction.