Abstract

Purpose

We previously showed that a 0.5-mT, 50-Hz sinusoidal magnetic field (LFMF) enhanced DNA single-strand breaks (SSB) and necrosis in RAW264 macrophages that had been stimulated by bacterial endotoxin (lipopolysaccharide; LPS). LPS enhances production of nitric oxide (NO) and superoxide anion (O₂ ⁻) that react with each other to generate peroxynitrite (ONOO⁻). ONOO⁻ causes DNA strand breaks. Hence, we anticipated that 0.5-mT, 50-Hz sinusoidal magnetic field increased production of NO, thereby increasing intracellular ONOO⁻ concentration and promoted DNA strand breaks. However, the NO production was not increased. In this study, we examined if the exposure of the cell to 0.5-mT, 50-Hz magnetic field for 24 h (1) promotes O₂ ⁻ production, (2) elevated the degree of apoptosis, because apoptosis is an upstream event of necrosis, (3) lowers mitochondrial membrane potential (ΔΦ_m), because it would also promote necrosis.

Materials and methods

O₂ ⁻, was measured with nitroblue tetrazolium and water-soluble tetrazolium salt. Necrosis and apoptosis were quantified with propidium iodide and fluorescence labelling of caspases, respectively. The ΔΦ_m was measured with a fluorescent probe (JC-1) that reflects ΔΦ_m.

Results and conclusions: In the LPS-stimulated macrophage, the LFMF did not promote O₂ ⁻ production. Thus, the LFMF-promoted DNA strand breaks did not result from the increase in the O₂ ⁻ production. The LFMF did not promote apoptosis, whereas it tended to increase the degree of necrosis, as we showed previously. The ΔΦ_m slightly declined in the LFMF-exposed cell without statistical significance.

摘要

目的：我们以前显示了0.5mT，50Hz的正弦磁场（LFMF）增强了细菌内毒素（脂多糖； LPS）刺激的RAW264巨噬细胞的DNA单链断裂（SSB）和坏死。LPS提高生产一氧化氮（NO）和超氧阴离子（O ₂ ^- ），其与彼此反应以生成过氧化亚硝酸盐（ONOO ^- ）。ONOO ^-引起DNA链断裂。因此，我们预期，0.5 mT的，50赫兹的正弦磁场增加NO的产生，从而提高了细胞内的ONOO ^-集中和促进DNA链断裂。但是，NO的产量没有增加。在本研究中，我们检查，如果细胞以0.5 mT的，50赫兹的磁场的24小时（1）曝光促进Ò ₂ ^-生产，（2）升高的细胞凋亡的程度，因为细胞凋亡是的上游事件坏死，（3）降低了线粒体膜电位（ΔΦ_米），因为它也将促进坏死。

材料和方法：o ₂ ^- ，混合物用氮蓝四唑和水溶性四唑盐测得。分别用碘化丙啶和胱氨酸蛋白酶的荧光标记定量坏死和凋亡。所述ΔΦ_米用反映ΔΦ的荧光探针（JC-1）测得的_米。

结果和结论：在LPS刺激的巨噬细胞的LFMF不促进ö ₂ ^-生产或凋亡。因此，LFMF促进的DNA链断裂并没有从澳增加导致₂ ^-生产。如前所述，LFMF不会促进细胞凋亡，而却倾向于增加坏死的程度。该ΔΦ_米略有下降在LFMF暴露细胞无统计学意义。