ABSTRACT
In cultured rat hippocampal neurons, gradual increases were seen in the expression of microtubule-associated protein-2 (MAP-2), neuronal nuclei (NeuN) and growth-associated protein-43 (GAP-43), in proportion to increased duration, up to 9 days in vitro (DIV). Sustained exposure to static magnetic fields at 100 mT for up to 9 DIV significantly decreased expression of MAP-2 and NeuN in cultured rat hippocampal neurons without markedly affecting GAP-43 expression. Although a significant increase was seen in the expression of glial fibrillary acidic protein (GFAP) in hippocampal neuronal preparations cultured for 6-9 DIV under sustained magnetism, GFAP and proliferating cell nuclear antigen expression were not affected markedly in cultured astrocytes prepared from rat hippocampus and neocortex, irrespective of cellular maturity. No significant alteration was seen in cell survivability of hippocampal neurons or astrocytes cultured under sustained magnetism. In hippocampal neurons cultured for 3 DIV under sustained magnetism, marked mRNA expression was seen for N-methyl-D-aspartate (NMDA) receptor subunits, NR1, NR2A-2C, NR2D, and NR3A. In addition, significant potentiation of the ability of NMDA to increase intracellular free Ca(2+) ions was observed. Differential display analysis revealed a significant decrease in mRNA expression for the transcription factor ALF1 in response to sustained magnetism for 3 DIV. These results suggest that sustained exposure to static magnetic fields may affect cellular functionality and maturity in immature cultured rat hippocampal neurons through modulation of expression of particular NMDA receptor subunits.
Subject(s)
Cell Differentiation/radiation effects , Electromagnetic Fields , Hippocampus/radiation effects , Nerve Tissue Proteins/radiation effects , Neural Pathways/radiation effects , Receptors, N-Methyl-D-Aspartate/radiation effects , Animals , Calcium/metabolism , Calcium Signaling/physiology , Calcium Signaling/radiation effects , Cell Differentiation/physiology , Cells, Cultured , Fetus , GAP-43 Protein/metabolism , GAP-43 Protein/radiation effects , Glial Fibrillary Acidic Protein/metabolism , Glial Fibrillary Acidic Protein/radiation effects , Hippocampus/cytology , Hippocampus/metabolism , Intracellular Fluid/metabolism , Intracellular Fluid/radiation effects , Magnetics , Microtubule-Associated Proteins/metabolism , Microtubule-Associated Proteins/radiation effects , Nerve Tissue Proteins/metabolism , Neural Pathways/growth & development , Neural Pathways/metabolism , Proliferating Cell Nuclear Antigen/metabolism , Proliferating Cell Nuclear Antigen/radiation effects , Protein Subunits/genetics , Protein Subunits/radiation effects , RNA, Messenger/metabolism , RNA, Messenger/radiation effects , Rats , Rats, Wistar , Receptors, N-Methyl-D-Aspartate/geneticsABSTRACT
We investigated the distribution and expression of growth associated protein-43 (GAP-43) in human glioma cells (MO54) after exposure to a magnetic field (60 Hz, 5 mT), with or without initial X-ionizing radiation (2 Gy), by using immunocytochemistry and the reverse transcription polymerase chain reaction (RT-PCR). GAP-43 was present in the cytoplasm, accumulating in the perinuclear area. An increase in GAP-43 expression was observed with a peak at 10 h at the mRNA level and at 12 h at the protein level, after exposure to the magnetic field. The increased level of GAP-43 protein returned to a normal level within 24 h of exposure to a 5 mT magnetic field. The kinetic pattern of GAP-43 expression induced by X-ionizing radiation was very similar to that induced by the magnetic field. These results suggest that the stimulation of GAP-43 expression could occur by a similar mechanism following exposure to X-rays or magnetic fields. We have provided the first evidence that exposure to a 5 mT magnetic field can induce GAP-43 gene expression in human glioma MO54 cells.
