Differences in IL-10 and IL-12 production patterns and differences in the effects of acute ethanol treatment on macrophages in vivo and in vitro

Abstract 

Several recent studies have documented that signaling can be fundamentally different in vivo and in vitro. However, studies of signaling and cytokine production by macrophages are often conducted in vitro, without confirmation in vivo. In addition, the direct effects of drugs and chemicals, including ethanol, on these processes are also often investigated in vitro. The purpose of the present study was to compare production of interleukin-6 (IL-6), IL-10, and IL-12 by macrophages in response to two different ligands for toll-like receptors and the effects of acute ethanol exposure on these responses in vivo and in vitro. The macrophage-like cell line RAW 264.7 is also widely used in cytokine and signaling studies, so these cells were also evaluated in this study. The results indicate that IL-6 production and the effects of Ethanol on IL-6 were similar in vivo and in vitro. In contrast, IL-10 was produced to a much greater extent in vitro than in vivo, and IL-12 was often undetectable in vitro even though it was produced at greater concentrations than IL-10 in vivo. To determine the role of altered secretion of preformed IL-10 as compared to new synthesis, cells were treated in vitro with protein and mRNA synthesis inhibitors. The results suggest that preformed IL-10 is released in vivo, but almost all IL-10 secreted in vitro is newly synthesized. Ethanol suppressed IL-12 and enhanced or had no effect on IL-10 production in vivo, whereas it decreased IL-10 production in vitro. These effects were similar at different times and using different concentrations of toll-like receptor ligands. In general, RAW 264.7 cells responded similarly to peritoneal macrophages in vitro. This suggests that results for cytokine studies and probably signaling studies as well that are conducted in vitro should be interpreted with caution and confirmed in vivo, particularly if they involve IL-10 and IL-12.

Keywords: Ethanol, Toll-like receptor, Macrophage, Lipopolysaccharide, Cytokine, In vitro