Regulation of ICAM-1 in Cells of the Monocyte/Macrophage System in Microgravity
ICAM-1 expression in U937 cells, macrophage-like differentiated U937 cells, and primary human macrophages in different gravity conditions during parabolic flight experiment. ICAM-1 expression was assessed by flow cytometry and fluorescent microscopy following immunocytochemical staining. Cells were cultured under standard cell culture conditions (incubator control) or exposed to different gravity conditions during the 19th DLR parabolic flight campaign. U937 cells were fixed either after PMA-activation in microgravity (μg group) or in 1 g (1 g control group). Differentiated U937 and primary macrophages were fixed after the microgravity phases (μg group) or after the 1 g phases before and after the μg phase (1 g control group). The level of ICAM-1 surface expression is represented by the mean fluorescent intensity assessed by flow cytometry. (a) ICAM-1 surface expression in myelomonocytic U937 cells (mon. U937) and macrophage-like differentiated U937 cells (max. U937) under standard cell culture conditions. (b) ICAM-1 surface expression in U937 cells with and without activation by PMA in different gravity conditions. (c) ICAM-1 surface expression in macrophage-like differentiated U937 cells in different gravity conditions. (d) ICAM-1 surface expression in primary macrophages in different gravity conditions. Data are given as median ± SE (, , and , according to one-way ANOVA followed by Wilcoxon or unpaired -test).