Immunomodulatory effects in vitro of vitamin K antagonist acenocoumarol

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.