Immunomodulatory effects in vitro of vitamin K antagonist acenocoumarol

Abstract Neopterin production and tryptophan breakdown by indoleamine 2,3-dioxygenase (IDO) are induced within cell-mediated (= Th1-type) immune response, and in patients with coronary artery disease, serum neopterin and the kynurenine to tryptophan ratio (Kyn/Trp) are significantly predictive for cardiovascular and total mortality. To examine the potential impact of vitamin K-antagonist acenocoumarol (Sintrom) on the inflammatory response we investigated its effect on freshly isolated peripheral blood mononuclear cells (PBMC) from healthy donors, on myelomonocytic THP1-Blue and on intestinal Caco-2 cells in vitro . PBMC were incubated with increasing doses of acenocoumarol, and after 30 min either left unstimulated or stimulated with the mitogen phytohemagglutinin (PHA). Concentrations of neopterin, tryptophan, kynurenine, interferon-γ (IFN-γ) and tumor necrosis factor α (TNF-α) were measured in supernatants of PBMC after 48 h. Caco-2 cells were stimulated with IFN-γ and Kyn/Trp was used as readout. In THP1-Blue cells, the induction of NF-κB dependent reporter gene expression upon stimulation with lipopolysaccharide (LPS) was determined as an indicator of pro-inflammatory response. Upon stimulation, all measured immune response markers increased significantly compared to unstimulated cells. Acenocoumarol had no effect in unstimulated cells but in PHA-stimulated PBMC tryptophan breakdown and the formation of neopterin, as well as IFN-γ and TNF-α, were dose-dependently suppressed at concentrations as low as 10 μg/ml. Likewise, acenocoumarol dose-dependently inhibited tryptophan breakdown in IFN-γ stimulated Caco-2 cells. Interestingly, NF-κB expression was super-induced in the LPS treated cells. Data suggest that the immunomodulatory capacity of acenocoumarol contributes to its therapeutic efficacy.