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) mono layers to [I-125]-labelled bovine serum albumin (BSA) was examined fol lowing pretreatment of the cells with various cytokines. The electrica l resistance measured across untreated, confluent, intact HUVEC monola yers was 18.2 +/- 3.8 OMEGA.cm2 (mean +/- S.D. of 4 observations). Hum an recombinant (hr) interleukin-1 alpha/beta (IL-1 alpha/beta), hr tum or necrosis factor-alpha (TNF-alpha), and hr interferon-gamma (IFN-gam ma) each increased HUVEC monolayer permeability in a time- and dose-de pendent manner. These effects were inhibitable by neutralizing antibod ies (nAb) to the corresponding cytokines, and were not due to contamin ation by endotoxin (abolition of cytokine effect by heat treatment, an d 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 permeabili ty) and the effect of hrTNF-alpha could not be accounted for by induct ion of IL-I (effect not inhibited by hrIL-1 alpha/beta nAb). The effec ts 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) great er than that seen with either cytokine alone. hrTNF-alpha and hrIL-1 a lpha/beta in combination however produced an enhanced effect only at l ow concentrations, high concentrations in combination producing an eff ect no greater than either agent alone. These results highlight the im portance of investigating actions of cytokine combinations on in vitro models of endothelial cell activation.