Protein kinase C: a potential pathway of endothelial cell activation by endotoxin, tumor necrosis factor, and interleukin-1.

Human endothelial cells exposed to lipopolysaccharide (LPS), tumor necrosis factor (TNF), or interleukin-1 (IL-1) in vitro acquire a cell surface property that promotes the adherence of neutrophils (PMNs). The common mechanism by which endothelial cells are activated by these agents is unknown. We examined adherence of PMNs to cultured human umbilical vein endothelium (HUVE) pretreated with LPS (100 ng/ml), TNF (100 U/ml), and IL-1 (1 U/ml) in medium alone or medium containing protein kinase inhibitors H-7 or HA-1004. Both compounds inhibit a similar spectrum of protein kinases, but H-7 is an effective inhibitor of protein kinase C, whereas HA-1004 is not. We found that H-7 (25 mumol/L) reduced the adherence of PMNs to LPS-, TNF-, and IL-1-stimulated HUVE monolayers to 16.7% +/- 3.0%, 12.1% +/- 2.5%, and 18.3% +/- 2.9% of control, respectively (mean plus or minus standard error of three experiments); HA-1004 (25 mumol/L) did not inhibit endothelial adhesiveness. Cytotoxicity of H-7 was less than 10% in LPS-, TNF-, and IL-1-treated HUVE. Protein synthesis, as measured by the incorporation of tritiated amino acids, was not significantly impaired in LPS-treated HUVE concurrently exposed to H-7. We conclude that protein kinase C appears to be a necessary common mediator of endothelial cell activation by LPS, TNF, and IL-1.