Coffee and Maillard products activate NF-κB in macrophages via H ₂O₂ production

In this study, we investigated the immunomodulatory activity of coffee and Maillard reaction products on macrophages in vitro. Stimulation of macrophages with coffee, but not with raw coffee extract in PBS, led to a 13-fold increased nuclear NF-κB translocation. A Maillard reaction mixture (25 mM D-ribose/L-lysine, 30 min at 120°C) increased NF-κB translocation 18-fold (in PBS) or six-fold (in medium). MRPs also induced a two-fold increased NF-κB translocation in untransfected human embryonic kidney (HEK) cells as well as in HEK cells stably transfected with the receptor for advanced glycation endproducts (RAGE), indicating that the effect was not RAGE mediated. On the other hand, catalase totally abolished coffee- and MRP-induced NF-κB translocation. Consequently, up to 366 μM hydrogen peroxide was measured in the coffee preparation and Maillard mixtures used for cell stimulation. Stimulation of macrophages with MRPs did not lead to significantly increased IL-6 or NO release. Thus, it can be concluded that coffee and MRPs induce NF-κB translocation in macrophages via the generation of hydrogen peroxide.