Caffeine inhibits monocyte and neutrophil chemotaxis at concentrations relevant to normal human consumption

The objective of this study was to determine the effects of caffeine, and its major metabolite paraxanthine, on monocyte and neutrophil chemotaxis, at concentrations relevant to normal human consumption. In order to determine circulating levels of caffeine and paraxanthine, their concentrations were measured in plasma samples from 6 volunteers both prior to, and following, consumption of coffee and chocolate. One hour following caffeine consumption, plasma caffeine concentrations were 27 + - 2.1muM, and plasma paraxanthine concentrations were 10 + - 1.4muM. The chemotactic response of human monocytcs and neutrophils to fMLP was then assessed following in vitro exposure to caffeine or paraxanthinc (10-500muM). Caffeine significantly suppressed chemotaxis at concentrations as low as 20muM, and paraxanthine at concentrations as low as 10muM. These data indicate that caffeine and paraxanthinc inhibit leucocyte chemotaxis at concentrations relevant to human consumption.