Abstract 4726: Phagocytic regulation through exogenous caffeine exposure in whole-blood macrophages.

Abstract

Abstract Caffeine is the most widely used neurostimulant in the world, and it has been shown that 79% of the United States population drinks coffee at least occasionally. Previous research has suggested that caffeine may be involved in the regulation of phagocytosis in immune cells through anti-inflammatory and pro-inflammatory signals. To investigate this effect, we used a macrophage engulfment assay, which was optimized in our lab to measure phagocytosis after exogenous caffeine exposure. Human leukocytes were isolated and incubated to allow for monocyte differentiation. After being allowed to differentiate for 1hr, 24hrs, 3-days, or 7-days, macrophages were incubated with varying concentrations of caffeine (35 μM-20 mM) for 1-24 hours. Cells were treated with lipopolysaccharide, and then incubated for 2 hours with fluorescently-labeled microspheres conditioned by incubation with fetal bovine serum. Engulfment was measured using flow cytometry, indicating the phagocytosis of microspheres in integral ratios. It was observed that engulfment was dependent on cell differentiation time, as well as caffeine concentration and exposure time. After <12 hour differentiation, cells exposed to caffeine showed a concentration-dependent reduction in engulfment when compared to those that were not treated. During incubation for 12 - 72 hours, however, results showed a 20% down-regulation of engulfment at <5 mM caffeine, whereas those cells exposed to 5-10 mM caffeine exhibited a 20% higher-engulfing phenotype, compared to the controls. At caffeine concentrations above 10 mM cell viability and engulfment was decreased up to 50%. It was concluded that the effect of caffeine on macrophages is dependent on incubation time and concentration, as well as the state of macrophage differentiation. Because of the implications of macrophage phenotype in many diseases involving inflammation, including cancer, these findings suggest further research should be continued to explore the therapeutic potential of caffeine and/or its analogs. Citation Format: Ryan Steck, Marcus Gustafsson, PingGuo Liu, Atif Elnaggar, Richard A. Robison, Kim L. O'Neill. Phagocytic regulation through exogenous caffeine exposure in whole-blood macrophages. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4726. doi:10.1158/1538-7445.AM2013-4726