THP-1 cells are widely applied to mimic monocytes in cell culture models. In this study, we compared the cytokine release from THP-1, peripheral blood mononuclear cells (PBMC), monocytes, or whole blood after stimulation with lipopolysaccharide (LPS) and investigated the consequences of different cytokine profiles on human umbilical vein endothelial cell (HUVEC) activation. While Pseudomonas aeruginosa-stimulated (10 ng/mL) THP-1 secreted similar amounts of tumor necrosis factor alpha (TNF-α) as monocytes and PBMC, they produced lower amounts of interleukin(IL)-8 and no IL-6 and IL-10. Whole blood required a higher concentration of Pseudomonas aeruginosa (1000 ng/mL) to induce cytokine release than isolated monocytes or PBMC (10 ng/mL). HUVEC secreted more IL-6 and IL-8 after stimulation with conditioned medium derived from whole blood than from THP-1, despite equal concentrations of TNF-α in both media. Specific adsorption of TNF-α or selective cytokine adsorption from the conditioned media prior to HUVEC stimulation significantly reduced HUVEC activation. Our findings show that THP-1 differ from monocytes, PBMC, and whole blood with respect to cytokine release after stimulation with LPS. Additionally, we could demonstrate that adsorption of inflammatory mediators results in reduced endothelial activation, which supports the concept of extracorporeal mediator modulation as supportive therapy for sepsis.

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The aim of this work was to establish and characterize a cell culture model for lipopolysaccharide (LPS)-induced activation of human endothelial cells. Monocytic THP-1 cells were stimulated for 4 h with 10 ng/ml LPS from Pseudomonas aeruginosa in media containing 10% human plasma. Culture supernatants containing LPS and factors secreted by THP-1 in response to stimulation were applied to human umbilical vein endothelial cells (HUVECs). Nuclear factor-κB (NF-κB) activity, expression of adhesion molecules, and cytokine secretion were quantified. In addition, the effect of adsorptive removal of tumour necrosis factor-α (TNF-α) from the THP-1 culture supernatant on HUVEC activation was assessed. After 4 h of stimulation, THP-1 cells secreted various mediators including TNF-α (854 ± 472 pg/ml), interleukin (IL)-8 (2069 ± 710 pg/ml), IL-18 (305 ± 124 pg/ml), IL-10 (14 ± 5 pg/ml), and IL-1β (24 ± 11 pg/ml). Stimulated HUVECs showed significantly increased NF-κB activity and secreted high amounts of IL-6 and IL-8. Additionally, adhesion molecules ICAM-1 and E-selectin were increased both in the culture supernatant and at the cell surface. Removal of TNF-α from the THP-1 culture supernatant prior to HUVEC stimulation resulted in a decrease in NF-κB activity, expression of adhesion molecules, as well as IL-6 secretion. The cell culture model established in this study permits the monitoring of LPS-induced endothelial activation, which plays a central role in sepsis and may serve to assess the effect of mediator modulation by methods such as extracorporeal blood purification.

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Aim: In this study, the effect of specific or selective adsorption of inflammatory mediators on endothelial activation was assessed. Methods: Conditioned medium was obtained by stimulation of monocytic THP-1 cells with lipopolysaccharide and treated either with an adsorbent specific for tumour necrosis factor-α or with an albumin-coated polystyrene-divinylbenzene copolymer which selectively binds a range of cytokines. Thereafter, the conditioned medium was applied to endothelial cells in culture. Results: Adsorption of inflammatory mediators resulted in significantly decreased endothelial cell activation, as shown by reduced interleukin (IL)-6 and IL-8 secretion from endothelial cells as well as reduced surface expression of the adhesion molecules intercellular adhesion molecule-1 and E-selectin. The effect was more pronounced the earlier the mediator modulation was performed. Conclusion: Adsorptive modulation of inflammatory mediators dampens endothelial cell activation and may thus be beneficial as supportive therapy in sepsis.