Role of Endothelial Cells in Inflammatory Processes

We have studied human umbilical vein (HUVEC) and bovine aortic endothelial cells (BAEC) for the presence of elements of the kinin-kallikrein system. Kinin generation was measured in homogenates of endothelial cells using a radioimmunoassay with a human bradykinin antibody; it was measured after homogenization and was constant over a time interval of 120 min. Addition of exogenous kallikrein (50 mU) led to a five fold increase in kinin concentrations after 5 min in the homogenates, which declined within 2 h. Pretreatment of BAEC with dextran sulfate (0.1 mg/ml) resulted in a 80% reduction in kinin generation. Staining of endothelial cells using an antiserum against glandular kallikrein showed kallikrein immunoreactivity in all cells. Glandular kallikrein activity was measured in homogenates by a colorimetric method. Activities of 3.5 ± 0.4 mU/106 cells in HUVEC and 7.5 ± 0.8 mU/106 cells in BAEC were detected. These data indicate the presence of all key elements of the kinin-kallikrein system in the vascular endothelium. Thus, our results support the existence of a local kallikrein-kinin system in the vascular wall which may contribute to the regulation of local inflammatory processes and the regulation of vascular tone.