Alterations in the biophysical properties of the human endothelial cell plasma membrane induced by a chemotactic tripeptide: correlation with enhanced adherence of granulocytes.

Human umbilical vein endothelial cells in monolayer culture were used to study the effects of the chemotactic tripeptide, N-formylmethionylleucylphenylalanine (FMLP), on structure and function of the endothelium. Endothelial cell morphology was unaffected by concentrations of 10(-8)-10(-4)M. No effect on endothelial cell proliferative capacity, as measured by the DNA content of cultures, was seen at the FMLP concentrations studied (10(-8)-10(-6)M). Using fluorescent molecular probes to investigate FMLP-induced alterations in membrane structure, it was shown using the monomer-excimer method with pyrene decanoic acid that FMLP caused a marked restructuring of the plasma membrane. This took the form of a restriction of the surface available to the lipophile reporter molecules, probably caused by a molecular reorganization of the membrane protein component. Experiments with diphenylhexatriene indicated that FMLP did not make the plasma membrane of the endothelial cell more fluid. Concomitant with these changes in the physical properties of the membrane, an FMLP-induced increase in granulocyte adherence to the endothelial cells was observed. A theoretical model is presented correlating granulocyte adherence with the lateral mobility of lipids in the endothelial cell membrane. The significance of the FMLP-induced increase in granulocyte adherence to endothelial cells for the pathogenesis of sepsis is discussed.