Tumor necrosis factor-alpha and interleukin-1beta mediate endothelial permeability induced by...

To investigate the role of endotoxin-induced inflammatory mediators in blood on the permeability of endothelial monolayers.

Whole blood of healthy volunteers was treated with bacterial lipopolysaccharide (Escherichia coli, B55:05), and the resultant plasma was added to human umbilical venular endothelial cells (HUVEC) cultured on semipermeable membrane inserts (Transwells).

University hospital laboratory.

Whole blood of healthy volunteers.

Donor plasma was treated with excess antibodies against either tumor necrosis factor-alpha, interleukin-1beta, or both, before the incubation on HUVEC.

The permeability of HUVEC monolayers to fluorescent-labeled albumin and dextran was measured over a 6-hr period, after removal of the stimulus. The production of tumor necrosis factor-alpha and interleukin-1beta in lipopolysaccharide-treated whole blood was determined by radioimmunoassay. Individually, lipopolysaccharide (10 microg/mL), tumor necrosis factor-alpha (10 ng/mL), and interleukin-1beta (50 ng/mL) all increased endothelial permeability by about 2.5-fold. A much larger increase could be achieved by preincubation of lipopolysaccharide (10 microg/mL) in whole blood: the resultant plasma induced a ten-fold increase of the permeability. The permeability response after preincubation of lipopolysaccharide in whole blood was time- and dose-dependent. Moreover, this treatment increased the sensitivity of endothelial monolayers to lipopolysaccharide by a factor of several thousand-fold: Whereas high doses of lipopolysaccharide were required for direct stimulation of the permeability, picomolar amounts of lipopolysaccharide in whole blood induced a similar increase. Significant amounts of tumor necrosis factor-alpha and interleukin-1beta were produced in blood at similar doses of lipopolysaccharide. The addition of antibodies against tumor necrosis factor-alpha or interleukin-1beta to plasma partially but significantly abrogated the permeability increase. However, a complete inhibition could be achieved by the simultaneous addition of anti-tumor necrosis factor-alpha and anti-interleukin-1beta to plasma.

Although lipopolysaccharide is capable of directly inducing endothelial permeability, blood-borne tumor necrosis factor-alpha and interleukin-1beta mediate lipopolysaccharide-induced endothelial permeability at low endotoxin concentrations. These findings support the idea that multifactorial inhibition of inflammatory mediators may improve survival in septic patients.