Histamine-induced production of interleukin-6 and interleukin-8 by human coronary artery endothelial cells is enhanced by endotoxin and tumor necrosis factor-alpha

In this study, we tested the synergy between histamine and LPS, and histami ne and TNF-alpha, on endothelial cell production of interleukin-6 (IL-6), i nterleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1). Human coronary artery endothelial cells (HCAEC) were cultured in vitro with hista mine (0.1 to 1000 muM) in the presence or absence of LPS or TNF-alpha for 2 4 h, and the secreted IL-6, IL-8 and MCP-1 were quantified. Unactivated HCA EC produced minimal levels of IL-6, IL-8, or MCP-1. The incubation of HCAEC with histamine resulted in low level induction of IL-6 and IL-8 production , which was dose-dependent and attained a plateau at a concentration of 10 muM. On the other hand, histamine failed to induce MCP-l production. Stimul ation of HCAEC with LPS or TNF-alpha caused dose-dependent increase in cyto kine production. In the presence of all stimulatory concentrations of LPS a nd TNF-alpha tested, histamine was shown to further enhance IL-6 and IL-8 p roduction. The effect of histamine on endothelial cell production of cytoki nes was completely inhibited by the H-1 receptor antagonist, diphenhydramin e, and not by the H-2 antagonist, famotidine. Electrophoretic mobility shif t assays of nuclear proteins extracted from HCAEC treated with histamine an d LPS, or histamine and TNF-alpha, revealed amplified translocation of NF-k appaB proteins to the nuclei. Since both LPS and TNF-alpha potentiated hist amine-induced cytokine production, it is possible that these activators sti mulate H-l receptor expression and/or augment the signal transduction pathw ays leading to the expression of IL-6 and IL-8. These results indicate the importance of synergy between histamine and other inflammatory stimuli on e ndothelial cell activation and implicate their cooperative participation in vascular leak and inflammation. (C) 2001 Academic Press.