Modulation of human endothelial cell permeability by combinations of the cytokines interleukin-1 alpha/beta, tumor necrosis factor-alpha and interferon-gamma.

The permeability of human umbilical vein endothelial cell (HUVEC) monolayers to [125I]-labelled bovine serum albumin (BSA) was examined following pretreatment of the cells with various cytokines. The electrical resistance measured across untreated, confluent, intact HUVEC monolayers was 18.2 +/- 3.8 omega.cm2 (mean +/- S.D. of 4 observations). Human recombinant (hr) interleukin-1 alpha/beta (IL-1 alpha/beta), hr tumor necrosis factor-alpha (TNF-alpha), and hr interferon-gamma (IFN-gamma) each increased HUVEC monolayer permeability in a time- and dose-dependent manner. These effects were inhibitable by neutralizing antibodies (nAb) to the corresponding cytokines, and were not due to contamination by endotoxin (abolition of cytokine effect by heat treatment, and no effect on cytokine action of the endotoxin inhibitor polymyxin B). The effects of these cytokines were not due to endothelial cell (EC) interleukin-6 (IL-6) induction (IL-6 shown not to increase permeability) and the effect of hrTNF-alpha could not be accounted for by induction of IL-1 (effect not inhibited by hrIL-1 alpha/beta nAb). The effects of three different combinations of the cytokines (each combination at two different concentrations) on HUVEC monolayer permeability were also examined. hrIFN-gamma with hrTNF-alpha or hrIL-1 alpha/beta gave an increase in permeability (at both concentration combinations) greater than that seen with either cytokine alone. hrTNF-alpha and hrIL-1 alpha/beta in combination however produced an enhanced effect only at low concentrations, high concentrations in combination producing an effect no greater than either agent alone. These results highlight the importance of investigating actions of cytokine combinations on in vitro models of endothelial cell activation.