Enhanced secretion of prostaglandin E₂ from osteoblasts by exposure to a strong static magnetic field

Abstract

Exposure to static magnetic fields (SMFs) has been reported to promote osteoblast differentiation in vitro, and increase bone formation in vivo and in clinical studies. Prostaglandins respond early to exogenous mechanical loading, and play an important role in bone formation. In this study, we investigated whether exposure to a strong SMF affects prostaglandin E(2) (PGE(2)) secretion from a mouse osteoblastic cell line, MC3T3-E1. We also investigated the PGE(2)-synthesizing enzyme, cyclooxygenase 2 (Cox-2), and translocation of the transcription factor nuclear factor kappa B (NF-kappaB), which is involved in the induction of Cox-2 expression. In the SMF exposures, experiments were performed at the 10 T-exposure position, at which the magnetic flux density was highest, and at the 6 T-exposure position, at which the magnetic field gradient was highest (41.7 T/m). PGE(2) secretion was not affected by exposure at the 10 T-exposure position compared to sham-exposure, but was enhanced at the 6 T-exposure position (about 1.5-fold). Similarly, Cox-2 expression and NF-kappaB translocation were not enhanced at the 10 T-exposure position, but increased at the 6 T-exposure position (about twofold, two- to threefold, respectively). These findings suggested that exposure to a high magnetic field gradient induced secretion of PGE(2) and expression of the Cox-2 protein, which was mediated through increased translocation of NF-kappaB.

Effects of strong static magnetic fields used in magnetic resonance imaging on insulin‐secreting cells

“…We previously reported that magnetic field gradient and/or the product of magnetic field gradient and magnetic flux density played a critical role in the effects on biological systems [Hirose et al, 2003;Sakurai et al, 2008b]. In this study, we also detected the effects of magnetic field gradient and/or the product of magnetic field gradient and magnetic flux density, not magnetic flux density, on insulin secretion.…”

“…In this study, to evaluate the effects of exposure to strong SMF on insulin-secreting cells, we cultured INS-1 cells under exposure to sham and SMF conditions, and analyzed insulin secretion, mRNA expression, glucosestimulated insulin secretion, insulin content, cell proliferation, and cell number. We exposed the cells to SMF for 0.5 or 1 h, because MRI diagnosis is usually performed within 1 h. We previously reported that strong SMF affected the assembly pattern of smooth muscle cells [Iwasaka et al, 2003] and osteoblasts [Kotani et al, 2000;Iwasaka and Ueno, 2005], depending on the magnetic flux density, and gene expression in HL-60 cells [Hirose et al, 2003] and prostaglandin E 2 secretion from osteoblasts by exposure to a high magnetic field gradient, but not by exposure to a high magnetic flux density [Sakurai et al, 2008b]. Therefore, we evaluated the effects of strong SMF from the viewpoint of magnetic flux density and magnetic field gradient in this study.…”

Extremely low frequency electromagnetic fields modulate expression of inducible nitric oxide synthase, endothelial nitric oxide synthase and cyclooxygenase-2 in the human keratinocyte cell line HaCat: potential therapeutic effects in wound healing

“…Previously, this effect of EMF on COX‐2 and PGE 2 expression has been demonstrated also for other cell types such as fibroblasts 38 . However, there are also contrasting data in the literature, demonstrating an upregulation of PGE 2 , probably due to the different types of magnetic fields and cells used 39 …”

Effects of 7 T static magnetic fields on the expression of biological markers and the formation of bone in rats

“…Previous studies examining the effects of SMF on MSCs have also supported this hypothesis [Chuo et al, ; Kim et al, ]. Moreover, Sakurai et al [] reported that 10 T exposure alone had no effect on prostaglandin E2 secretion in osteoblasts, whereas a strong magnetic field (6 T) with a high gradient (41.7 T/m) showed progressive effects. Kotani et al [] reported that 8 T SMFs with a field gradient (approximately 4 T/100 mm) enhanced osteogenesis in vitro and in vivo [Kotani et al, ].…”