The influence of a 6 mT static magnetic field on apoptotic cell phagocytosis depends on monocyte/macrophage differentiation

In a previous work we showed that 6mT SMF interferes with monocyte/macrophage 12-Otetradecanoylphorbol- 13-acetate (TPA) -induced differentiation of promonocytes (U937 cells) and monocytes (THP-1 cells), in this work we investigate whether in the same cells and under the same conditions phagocytosis of apoptotic cells is influenced by 6 mT SMF exposure. Fluid phase endocytosis and phagocytosis of latex particles were also analysed for comparison. The results indicate that SMF exposure, whose influence was greater at the late stages of the macrophage differentiation (THP1 > U937 cells), has effects on phagocytosis but not on fluid phase endocytosis. Phagocytosis index and rate decreased under SMF exposure while the number of latex particles bound to the plasma membrane of TPA-differentiated U937 and THP1 cells increased. Conversely, phagocytosis rate of apoptotic cells increased under SMF exposure while the number of apoptotic cells bound to the plasma membrane of TPA-differentiated U937 and THP1 cells and Raw 264.7 macrophages decreased. Even in conditions of inability to phagocytose, i.e. non-differentiated U937 and THP-1 cells, the SMF exposure enhanced the number of cell surface bound apoptotic cells and latex beads.