An upward 9.4 T static magnetic field inhibits DNA synthesis and increases ROS-P53 to suppress lung cancer growth

Studies have shown that 9.4 Tesla (9.4 T) high-field magnetic resonance imaging (MRI) has obvious advantages in improving image resolution and capacity, but their safety issues need to be further validated before their clinical approval. Meanwhile, emerging experimental evidences show that moderate to high intensity Static Magnetic Fields (SMFs) have some anti-cancer effects.We examined the effects of two opposite SMF directions on lung cancer bearing mice and found when the lung cancer cell-bearing mice were treated with 9.4 T SMFs for 88 h in total, the upward 9.4 T SMF significantly inhibited A549 tumor growth (tumor growth inhibition=41%), but not the downward 9.4 T SMF. In vitro cellular analysis shows that 9.4 T upward SMF treatment for 24 h not only inhibited A549 DNA synthesis, but also significantly increased ROS and P53 levels, and arrested G2 cell cycle. Moreover, the 9.4 T SMF-treatments for 88 h had no severe impairment to the key organs or blood cell count of the mice.Our findings demonstrated the safety of 9.4 T SMF long-term exposure for their future applications in MRI, and revealed the anti-cancer potential of the upward direction 9.4 T SMF.     

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

The magnetic flux density of MRI for clinical diagnosis has been steadily increasing. However, there remains very little biological data regarding the effect of strong static magnetic fields (SMFs) on human health. To evaluate the effects of strong SMFs on biological systems, we cultured insulin-secreting cells under exposure to sham and SMF conditions (3-10 T of magnetic flux density, and 0-41.7 T/m of magnetic field gradient) for 0.5 or 1 h, and analyzed insulin secretion, mRNA expression, glucose-stimulated insulin secretion, insulin content, cell proliferation and cell number. Exposure to SMF with a high magnetic field gradient for 1 h significantly increased insulin secretion and insulin 1 mRNA expression. Exposure to SMF with a high magnetic flux density for 0.5 h significantly enhanced responsiveness to glucose stimulation. Exposure to SMF did not affect the insulin content, cell proliferation or cell number. Our results suggested that MRI systems with a higher magnetic flux density might not cause cell proliferative or functional damages on insulin-secreting cells, and that SMF with a high magnetic field gradient might be used clinically after thorough in vivo investigations are conducted.     

Effects of homogeneous and inhomogeneous static magnetic fields combined with gamma radiation on DNA and DNA repair

The aim of this study was to reveal whether static magnetic fields (SMFs) influence the repair of radiation‐damaged DNA on leukocytes or has any effect on DNA. After 4 Gy of ⁶⁰Co‐γ irradiation, some of the samples were exposed to inhomogeneous SMFs with a lateral magnetic flux density gradient of 47.7, 1.2, or 0.3 T/m by 10 mm lateral periodicity, while other samples were exposed to homogeneous SMF of 159.2 ± 13.4 mT magnetic flux density for a time period of 0.5 min, 1, 2, 4, 6, 18, 20, or 24 h. Another set of samples was exposed to the aforementioned SMFs before gamma irradiation. The following three groups were examined: (i) exposed to SMF only, (ii) exposed to SMF following irradiation by ⁶⁰Co‐γ, and (iii) exposed to SMF before ⁶⁰Co‐γ irradiation. The analysis of the DNA damage was made by single‐cell gel electrophoresis technique (comet assay). Statistically significant differences were found at 1 h (iSMF), 4 h (hSMF), and 18 h (hSMF) if samples were exposed to only SMF, compared to control. When the SMF exposure followed the ⁶⁰Co‐γ irradiation, statistically significant differences were found at 1 h (iSMF) and 4 h (hSMF). If exposure to SMF preceded ⁶⁰Co‐γ irradiation, no statistically significant difference was found compared to 4 Gy gamma‐irradiated group. Bioelectromagnetics 31:488–494, 2010. © 2010 Wiley‐Liss, Inc.     

静磁场对小鼠黑色素瘤细胞B16生长和氧化应激的影响

目的:利用小鼠黑色素瘤细胞B16,研究静磁场对肿瘤细胞生长和氧化应激的影响,探讨氧化应激介导静磁场影响肿瘤细胞生长的机制,为磁场在肿瘤疾病的治疗中的应用提供理论依据。方法:采用MTT法测定磁场对B16细胞活力的影响;利用流式细胞仪测定静磁场暴露对B16细胞周期分布的影响;利用生物化学方法测定磁场暴露对细胞氧化防御系统相关蛋白酶活性的影响。结果:24 h内50 m T-200 m T静磁场暴露可以抑制B16生长,但超过24 h的磁场暴露可以促进B16生长;100 m T和200 m T静磁场暴露对B16的细胞周期分布没有影响;B16暴露于100 m T和200 m T静磁场48 h,GST活性和GSH/GSSG水平表现为先上升后下降,SOD活性和T-AOC水平先下降后上升,CAT活性没有受到影响。结论:50 m T-200 m T静磁场可以抑制小鼠黑色素瘤细胞B16的生长,诱导肿瘤细胞产生氧化应激。     

Nitric oxide modulates the responses of osteoclast formation to static magnetic fields

Nitric oxide (NO) is involved in osteoclast differentiation. Our previous studies showed that static magnetic fields (SMFs) could affect osteoclast differentiation. The inhibitory effects of 16 T of high SMF (HiMF) on osteoclast differentiation was correlated with increased production of NO. We raised the hypothesis that NO mediated the regulatory role of SMFs on osteoclast formation. In this study, 500 nT of hypomagnetic field (HyMF), 0.2 T of moderate SMF (MMF) and 16 T of high SMF (HiMF) were utilized as SMF treatment. Under 16 T, osteoclast formation was markedly decreased with enhanced NO synthase (NOS) activity, thus producing a high level of NO. When treated with NOS inhibitor N-Nitro-L-Arginine Methyl Ester (L-NAME), NO production could be inhibited, and osteoclast formation was restored to control group level in a concentration-dependent manner. However, 500 nT and 0.2 T increased osteoclast formation with decreased NOS activity and NO production. When treated with NOS substrate L-Arginine (L-Arg) or NO donor sodium nitroprusside (SNP), the NO level in the culture medium was obviously elevated, thus inhibiting osteoclast differentiation in a concentration-dependent manner under 500 nT or 0.2 T. Therefore, these findings indicate that NO mediates the regulatory role of SMF on osteoclast formation.     

Effects of static magnetic fields on bone microstructure and mechanical properties in mice

All the living organisms originate, evolve and live under geomagnetic field (GMF, 20–70 µT). With rapid development in science and technology, exposure to various static magnetic fields (SMFs) from natural and man-made sources remains a public environmental topic in consideration of its probable health risk for humans. Many animal studies related to health effect have demonstrated that SMF could improve bone formation and enhance bone healing. Moreover, most of the studies focused on local SMF generated by rod-type magnet. It was difficult to come to a conclusion that how SMF affected bone metabolism in mice. The present study employed hypomagnetic field (HyMF, 500 nT), and moderate SMF (MMF, 0.2 T) to systematically investigate the effects of SMF with continuous exposure on microstructure and mechanical properties of bone. Our results clearly indicated that 4-week MMF exposure did not affect bone biomechanical properties or bone microarchitecture, while HyMF significantly inhibited the growth of mice and elasticity of bone. Furthermore, mineral elements might mediate the biological effect of SMF.     

The role of the calmodulin‐dependent pathway in static magnetic field‐induced mechanotransduction

While the effects of static magnetic fields (SMFs) on osteoblastic differentiation are well demonstrated, the mechanotransduction pathways of SMFs are still unclear. The aim of this study was to explore the role of calmodulin in the biophysical effects of SMFs on osteoblastic cells. MG63 cells were exposed to a 0.4 T SMF. The expression of phosphodiesterase RNA in the cytoplasm was tested using real‐time polymerase chain reaction. The differentiation of the cells was assessed by detecting changes in alkaline phosphatase activity. The role of calmodulin antagonist W‐7 was used to evaluate alterations in osteoblastic proliferation and differentiation after the SMF simulations. Our results showed that SMF exposure increased alkaline phosphatase activity and phosphodiesterase 1C gene expression in MG63 cells. Addition of W‐7 significantly inhibited the SMF‐induced cellular response. We suggest that one possible mechanism by which SMFs affects osteoblastic maturation is through a calmodulin‐dependent mechanotransduction pathway. Bioelectromagnetics 31:255–261, 2010. © 2009 Wiley‐Liss, Inc.     

Enhancement of natural killer cell cytotoxicity by using static magnetic field to increase their viability

Natural killer (NK) cells are innately immune to the body’s immune system and can actively recognize and kill cancer cells. This study explores the potential for enhancing the killing ability of NK cells by co-culturing the NK cells with the target cells under a static magnetic field (SMF). In this study, NK92-MI cell lines were cultured in the presence of a 0.4-T SMF. The effect of the SMF on NK cell viability was evaluated by means of an MTT assay. Culturing tests were performed with inhibitors of the DAG/IP3, STAT3, ERK, JNK and p38 pathways in order to examine the possible signaling cascade responsible for the SMF effect on the NK92-MI cell viability. Finally, the effect of the SMF on the cytotoxicity of the NK92-MI cells was evaluated by co-culturing the NK cells with K562 leukemia cell lines. The results showed that the application of a 0.4-T SMF significantly increased (p < 0.05) the viability of the NK92-MI cells. Furthermore, the inhibitor tests indicated that the SMF affected cell viability by activating multiple MAPK signaling pathways (ERKs, JNKs, and p38-MAPK). Finally, SMF pre-exposure for 48 hr significantly improved the killing activity of the NK92-MI cells (p < 0.05). That is, pre-exposure to SMF increased the viability of the NK92-MI cells and improved their killing ability against K562 tumor cells. In general, the present results suggest that NK cells pre-exposed to 0.4-T SMF show potential as a tool for immune-therapy treatment of cancer.     

Regulation of osteoclast differentiation by static magnetic fields

Static magnetic field (SMF) modulates bone metabolism, but little research is concerned with the effects of SMF on osteoclast. Our previous studies show that osteogenic differentiation is strongly correlated with magnetic strength from hypo (500 nT), weak (geomagnetic field, GMF), moderate (0.2 T) to high (16 T) SMFs. We speculated that the intensity that had positive (16 T) or negative (500 nT and 0.2 T) effects on osteoblast differentiation would inversely influence osteoclast differentiation. To answer this question, we examined the profound effects of SMFs on osteoclast differentiation from pre-osteoclast Raw264.7 cells. Here, we demonstrated that 500 nT and 0.2 T SMFs promoted osteoclast differentiation, formation and resorption, while 16 T had an inhibitory effect. Almost all the osteoclastogenic genes were highly expressed under 500 nT and 0.2 T, including RANK, matrix metalloproteinase 9 (MMP9), V-ATPase, carbonic anhydrase II (Car2) and cathepsin K (CTSK), whereas they were decreased under 16 T. In addition, 16 T disrupted actin formation with remarkably decreased integrin β3 expression. Collectively, these results indicate that osteoclast differentiation could be regulated by altering the intensity of SMF, which is just contrary to that on osteoblast differentiation. Therefore, studies of SMF effects could reveal some parameters that could be used as a physical therapy for various bone disorders.     

Effects of static magnetic fields on the growth of various types of human cells

The effects of a static magnetic field (SMF) on the proliferation of various types of human cells were determined. All cultures were maintained at 37 °C throughout the experiment. SMF was generated by placing two magnets oppositely oriented on either side of a T25 flask. The flux density in the flask ranged from 35 to 120 mT. Growth curves were constructed by plotting cell number at 18 h and 4, 7, 11, and 14 days after seeding, with the 18‐h point being a measure of attachment efficiency. Exposure to SMF significantly decreased initial attachment of fibroblasts and decreased subsequent growth compared to sham‐exposed control. Significant effects were observed in both fetal lung (WI‐38) and adult skin fibroblasts, but they were generally larger in the fetal lung fibroblast line. SMF did not affect attachment of human melanoma cells, but inhibited their growth by 20% on day 7. SMF produced no effects in a human adult stem cell line. Oxidant production increased 37% in WI‐38 cells exposed to SMF (230–250 mT) during the first 18 h after seeding, when cell attachment occurs. Conversely, no elevation in oxidant levels was observed after a prolonged 5‐day exposure. These results indicate that exposure to SMF has significant biological effects in some, but not all types of human cells. Bioelectromagnetics 32:140–147, 2011. © 2010 Wiley‐Liss, Inc.     

Exposure to a MRI‐type high‐strength static magnetic field stimulates megakaryocytic/erythroid hematopoiesis in CD34+ cells from human placental and umbilical cord blood

The biological response after exposure to a high‐strength static magnetic field (SMF) has recently been widely discussed from the perspective of possible health benefits as well as potential adverse effects. To clarify this issue, CD34⁺ cells from human placental and umbilical cord blood were exposed under conditions of high‐strength SMF in vitro. The high‐strength SMF exposure system was comprised of a magnetic field generator with a helium‐free superconducting magnet with built‐in CO₂ incubator. Freshly prepared CD34⁺ cells were exposed to a 5 tesla (T) SMF with the strongest magnetic field gradient (41.7 T/m) or a 10 T SMF without magnetic field gradient for 4 or 16 h. In the harvested cells after exposure to 10 T SMF for 16 h, a significant increase of hematopoietic progenitors in the total burst‐forming unit erythroid‐ and megakaryocytic progenitor cells‐derived colony formation was observed, thus producing 1.72‐ and 1.77‐fold higher than the control, respectively. Furthermore, early hematopoiesis‐related and cell cycle‐related genes were found to be significantly up‐regulated by exposure to SMF. These results suggest that the 10 T SMF exposure may change gene expressions and result in the specific enhancement of megakaryocytic/erythroid progenitor (MEP) differentiation from pluripotent hematopoietic stem cells and/or the proliferation of bipotent MEP. Bioelectromagnetics 30:280–285, 2009. © 2009 Wiley‐Liss, Inc.     

Cytotoxicity of carboplatin on human glioblastoma cells is reduced by the concomitant exposure to an extremely low-frequency electromagnetic field (50 Hz, 70 G)

Glioblastoma multiforme (GBM) is a malignant brain cancer that causes high mortality in patients. GBM responds weakly to the common cancer treatments such as chemotherapy and radiotherapy and even surgery. Carboplatin is an alkylating agent widely used to treat cancer. However, resistance to this drug is a common problem in its use in cancer treatment. Concomitant exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) and carboplatin is one unexplored possibility for overcoming this resistance. Indeed, many lines of evidence show that EMF affects cancer cells and drug action. In this study, we evaluated the effect of concomitant administration of carboplatin and EMF (50 Hz, 70 G) and also concomitant administration of carboplatin and static magnetic field (SMF) (70 G) on human glioma cell line (U-87). The results showed that cotreatment reduced the efficiency of carboplatin in U-87 cells, by decreasing caspase-3 in comparison to drug groups. Overall, EMF reduced the apoptotic effect of carboplatin, possibly through a redox regulation mechanism. Therefore, we have to avoid coadministration of magnetic field (MF) and carboplatin in tumor area, because the MF decreased the toxicity of the drug. However, further studies are needed to reveal the action mechanism of this combination therapeutic method.     

ENHANCEMENT OF INVERTASE PRODUCTION BY Aspergillus niger OZ-3 USING LOW-INTENSITY STATIC MAGNETIC FIELDS

The aim of this study is to investigate the effect of low-intensity static magnetic fields (SMFs) on invertase activity and growth on different newly identified molds. The most positive effect of SMFs on invertase activity and growth was observed for Aspergillus niger OZ-3. The submerged production of invertase was performed with the spores obtained at the different exposure times (120, 144, 168, and 196 hr) and magnetic field intensities (0.45, 3, 5, 7, and 9 mT). The normal magnetic field of the laboratory was assayed as 0.45 mT (control). Optimization of magnetic field intensity and exposure time significantly increased biomass production and invertase activity compared to 0.45 mT. The maximum invertase activity (51.14 U/mL) and biomass concentration (4.36 g/L) were achieved with the spores obtained at the 144 hr exposure time and 5 mT magnetic field intensity. The effect of low-intensity static magnetic fields (SMFs) on invertase activities of molds was investigated for the first time in the present study. As an additional contribution, a new hyper-invertase-producing mold strain was isolated.

Supplemental materials are available for this article. Go to the publisher's online edition of Preparative Biochemistry and Biotechnology to view the supplemental file.     

The effect of 100 mT SMF on activation of the hsp70 promoter in a heat shock/luciferase reporter system

Human exposure to magnetic fields, increased through use of new technologies like magnetic resonance imaging (MRI), has prompted investigations into possible effects of static magnetic fields (SMFs) on cellular processes. However, controversy still remains between many studies, which likely results from a lack of uniformity across experimental parameters, including the length of magnetic field exposure, the strength of the magnetic field, and the cell type or organism under investigation. The purpose of this research was to monitor effects of SMF exposure using real‐time luminescence photometry. The study investigated the potential interaction of a 100 mT SMF on a heat shock protein (hsp70)/luciferase reporter construct in stably transfected NIH3T3 cells. Changes in heat shock promoter activation following 100 mT SMF exposure were analyzed and detected as bioluminescence in real‐time. Two heat parameters were considered in combination with sham‐ and 100 mT‐exposed experiments: no heat or 1,800 s heat. As expected, there was a significant increase in bioluminescence in response to 1,800 s of heat alone. However, no significant difference in average hsp70 promoter activation between sham and 100 mT experiments was observed for no heat or 1,800 s heat experiments. Therefore, a 100 mT SMF was shown to have no effect on the activation of the heat shock protein promoter during SMF exposure or when SMF exposure was combined with a heat insult. J. Cell. Biochem. 108: 956–962, 2009. © 2009 Wiley‐Liss, Inc.     

稳恒磁场联合抗肿瘤药物协同杀伤肝癌细胞Hepa1-6

化学疗法为肿瘤临床治疗的常规方法,存在毒副作用大、抗药性强等缺陷。为了提高药物的利用效率,减少药物引起的毒副作用,将8.8 m T稳恒磁场分别与顺铂、阿霉素联用,经MTT检测发现磁场与药物联用可对肝癌细胞Hepa1-6生长具有协同抑制的效应,经HE染色发现联合处理组细胞发生明显的形态学改变。流式细胞仪检测显示磁场能增加顺铂对G2/M期细胞的滞留,而磁场与阿霉素共同作用可将细胞阻止于G1期和G2/M期。经彗星电泳检测表明磁场能够增强药物对DNA的损伤,且原子力显微镜观察发现联合处理组细胞膜表面出现较大且较深的孔洞,表面结构破坏严重。实验结果表明,抗肿瘤药物与磁场联用技术可有效抑制肿瘤细胞的生长,减少药物的使用浓度,为将抗肿瘤药物与磁场应用于临床治疗恶性肿瘤提供了一个全新的思路与策略。     

Static magnetic field increases survival rate of dental pulp stem cells during DMSO-free cryopreservation

Abstract

Successful and efficient cryopreservation of living cells and organs is a key clinical application of regenerative medicine. Recently, magnetic cryopreservation has been reported for intact tooth banking and cryopreservation of dental tissue. The aim of this study was to assess the cryoprotective effects of static magnetic fields (SMFs) on human dental pulp stem cells (DPSCs) during cryopreservation. Human DPSCs isolated from extracted teeth were frozen with a 0.4-T or 0.8-T SMF and then stored at ?196?°C for 24?h. During freezing, the cells were suspended in freezing media containing with 0, 3 or 10% DMSO. After thawing, the changes in survival rate of the DPSCs were determined by flow cytometry. To understand the possible cryoprotective mechanisms of the SMF, the membrane fluidity of SMF-exposed DPSCs was tested. The results showed that when the freezing medium was DMSO-free, the survival rates of the thawed DPSCs increased 2- or 2.5-fold when the cells were exposed to 0.4-T or 0.8-T SMFs, respectively (p?<?0.01). In addition, after exposure to the 0.4-T SMF, the fluorescence anisotropy of the DPSCs increased significantly (p?<?0.01) in the hydrophilic region. These results show that SMF exposure improved DMSO-free cryopreservation. This phenomenon may be due to the improvement of membrane stability for resisting damage caused by ice crystals during the freezing procedure.     

Cellular ATP content was decreased by a homogeneous 8.5 T static magnetic field exposure: role of reactive oxygen species

The literature on the impact of strong static magnetic fields (SMF) on human health is vast and contradictory. The present study focused on the cellular effects of strong homogeneous SMF in human–hamster hybrid (A_L) cells, mitochondria‐deficient (ρ⁰ A_L) cells, and double‐strand break (DSB) repair‐deficient (XRS‐5) cells. Adenosine triphosphate (ATP) content was significantly decreased in A_L cells exposed to 8.5 Tesla (T) but not 1 or 4 T SMF for either 3 or 5 h. In addition, ATP content significantly decreased in the two deficient cell lines exposed to 8.5 T SMF for 3 h. With further incubation of 12 or 24 h without SMF exposure, ATP content could retrieve to the control level in the A_L cells but not ρ⁰ A_L and XRS‐5 cells. Under a fluorescence reader, the levels of reactive oxygen species (ROS) in the three cell lines were significantly increased by exposure to 8.5 T SMF for 3 h. Concurrent treatment with ROS inhibitor, DMSO, dramatically suppressed the ATP content in exposed A_L cells. However, the CD59 mutation frequency and the cell cycle distribution were not significantly affected by exposure to 8.5 T SMF for 3 h. Our results indicated that the cellular ATP content was reduced by 8.5 T SMF for 3 h exposure, which was partially mediated by mitochondria and the DNA DSB repair process. Moreover, ROS were involved in the process of the cellular perturbations from the SMF. Bioelectromagnetics 32:94–101, 2011. © 2010 Wiley‐Liss, Inc.