Ethyl pyruvate modulates acute inflammatory reactions in human endothelial cells in relation to the NF-kappaB pathway

Endothelial cell activation plays a critical role in regulating leukocyte recruitment during inflammation and infection. Ethanol (EtOH) reduces host defence systems, including cell adhesion. However, well-known side effects of EtOH limit its clinical use as an anti-inflammatory drug. Instead, ethyl pyruvate (EtP) may represent a better alternative. Here, we compared effects of EtP and EtOH on neutrophil recruitment and activation of human umbilical vein endothelial cells (HUVECs).

Adhesion of neutrophils to HUVEC monolayers, surface expression of intercellular cell adhesion molecule, E-selectin, vascular cell adhesion molecule, release of interleukin (IL)-8 and granulocyte colony-stimulating factor (G-CSF) from HUVECs were assessed as well as translocation of interleukin-1 receptor-associated kinase (IRAK-1), the nuclear factor-kappa B (NF-kappaB) subunits p50, p65 and IkappaB-alpha. NF-kappaB activation was analysed with a luciferase reporter plasmid. Cells were stimulated with IL-1beta, lipopolysaccharide (LPS) or tumour necrosis factor-alpha.

EtP was several-fold more potent than EtOH in reducing adhesion of neutrophils to activated HUVECs, generation of IL-8 or G-CSF and surface expression of the adhesion molecules. This last reaction was decreased by EtP even when added after cytokines or LPS. Translocation of IRAK-1, IkappaBalpha and the NF-kappaB p65 subunit to the HUVEC nucleus was inhibited by EtP for all stimuli, whereas the diminished p50 translocation was stimulus specific. When p65 was constitutively expressed in Cos7 cells, stimulation of an NF-kappaB-dependent reporter gene was not affected by EtP, suggesting that EtP acted upstream of gene activation.

EtP impedes adhesive, secretory and signalling events typical of the early inflammatory response in endothelial cells, suggesting EtP as a possible treatment for acute inflammatory conditions.