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

In this study, we tested the synergy between histamine and LPS, and histamine and TNF-alpha, on endothelial cell production of interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1). Human coronary artery endothelial cells (HCAEC) were cultured in vitro with histamine (0.1 to 1000 muM) in the presence or absence of LPS or TNF-alpha for 24 h, and the secreted IL-6, IL-8 and MCP-1 were quantified. Unactivated HCAEC 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. Stimulation of HCAEC with LPS or TNF-alpha caused dose-dependent increase in cytokine production. In the presence of all stimulatory concentrations of LPS and TNF-alpha tested, histamine was shown to further enhance IL-6 and IL-8 production. The effect of histamine on endothelial cell production of cytokines was completely inhibited by the H-1 receptor antagonist, diphenhydramine, and not by the H-2 antagonist, famotidine. Electrophoretic mobility shift assays of nuclear proteins extracted from HCAEC treated with histamine and LPS, or histamine and TNF-alpha, revealed amplified translocation of NF-kappaB proteins to the nuclei. Since both LPS and TNF-alpha potentiated histamine-induced cytokine production, it is possible that these activators stimulate H-l receptor expression and/or augment the signal transduction pathways leading to the expression of IL-6 and IL-8. These results indicate the importance of synergy between histamine and other inflammatory stimuli on endothelial cell activation and implicate their cooperative participation in vascular leak and inflammation. (C) 2001 Academic Press.