ABSTRACT
The interaction of extremely low frequency (ELF) magnetic fields (MF) with cells can induce alterations in various cell physiological processes. Here, we present evidence that exposure of mouse macrophages to 50 Hz, 1.0 mT MF lead to immune cell activation seen as increased production of reactive oxygen species (ROS), and also to modulation on the expression level of important proteins acting in redox regulatory processes and thus explaining the noted changes in ROS levels seen after exposure. The MF exposure caused slight and transient decreases after short term exposures (2h or less) of clathrin, adaptin, PI3-kinase, protein kinase B (PKB) and PP2A, whereas longer exposures had no effect. The levels of the NAD(P)H oxidase subunit gp91phox oscillated between increased and normal levels compared to controls. The stress proteins Hsp70 and Hsp110 exhibited increased levels at certain time points, but not generally. The effects of MF on protein levels are different from the effects exerted by 12-O-tetradecanolyphobol-13-acetate (TPA) or LPS, although all three factors cause increases in ROS release. This suggests that ELF MF interacts with other cellular constituents than these chemicals, although induced pathways at least partially converge.
Subject(s)
Electromagnetic Fields , Macrophages/radiation effects , Oxidation-Reduction/radiation effects , Protein Biosynthesis/radiation effects , Adaptor Protein Complex alpha Subunits/biosynthesis , Animals , Blotting, Western , Cell Line , Clathrin/biosynthesis , Flow Cytometry , HSP110 Heat-Shock Proteins/biosynthesis , HSP70 Heat-Shock Proteins/biosynthesis , Macrophages/metabolism , Macrophages/physiology , Mice , Oxidative Stress/radiation effects , Phosphatidylinositol 3-Kinases/biosynthesis , Proto-Oncogene Proteins c-akt/biosynthesis , Reactive Oxygen Species/metabolism , Reactive Oxygen Species/radiation effects , Signal Transduction/radiation effectsABSTRACT
We previously demonstrated that tensile stress (TS)-induced osteoblast differentiation eventually led to osteogenesis in an organ culture of mouse calvarial sutures. In the present study, we employed RNA-fingerprinting using an arbitrarily primed polymerase chain reaction (RAP-PCR) to identify alpha-adaptin C, a component of the endocytosis machinery AP2, as a TS-inducible gene. Protein production, as well as the gene expression of alpha-adaptin C, was induced by TS as early as 3 h following the initiation of loading. In situ hybridization and immunohistochemical analysis revealed that the induction of alpha-adaptin C mostly occurred in fibroblastic cells in the sutures, suggesting that it precedes TS-induced osteoblast differentiation. Consistent with this result, TS significantly increased the number of coated pits (CPs) and coated vesicles (CVs) in the undifferentiated fibroblastic cells but not in the osteoblastic cells around calvarial bones. Further, TS-induced osteoblast differentiation was suppressed when endocytosis was inhibited by potassium depletion. These results, taken together, suggest that TS accelerates osteoblast differentiation and osteogenesis, possibly through the induction of the alpha-adaptin C expression and consequent activation of receptor-mediated endocytosis.
