Expression of integrins to control migration direction of electrotaxis.

Proper control of cell migration is critically important in many biologic processes, such as wound healing, immune surveillance, and development. Much progress has been made in the initiation of cell migration; however, little is known about termination and sometimes directional reversal. During active cell migration, as in wound healing, development, and immune surveillance, the integrin expression profile undergoes drastic changes. Here, we uncovered the extensive regulatory and even opposing roles of integrins in directional cell migration in electric fields (EFs), a potentially important endogenous guidance mechanism. We established cell lines that stably express specific integrins and determined their responses to applied EFs with a high throughput screen. Expression of specific integrins drove cells to migrate to the cathode or to the anode or to lose migration direction. Cells expressing αMß2, ß1, α2, αIIbß3, and α5 migrated to the cathode, whereas cells expressing ß3, α6, and α9 migrated to the anode. Cells expressing α4, αV, and α6ß4 lost directional electrotaxis. Manipulation of α9 molecules, one of the molecular directional switches, suggested that the intracellular domain is critical for the directional reversal. These data revealed an unreported role for integrins in controlling stop, go, and reversal activity of directional migration of mammalian cells in EFs, which might ensure that cells reach their final destination with well-controlled speed and direction.-Zhu, K., Takada, Y., Nakajima, K., Sun, Y., Jiang, J., Zhang, Y., Zeng, Q., Takada, Y., Zhao, M. Expression of integrins to control migration direction of electrotaxis.

A voxel-based analysis of neurobiological mechanisms in placebo analgesia in rats.

Placebo analgesia is the beneficial effect that follows despite a pharmacologically inert treatment. Modern neuroimaging studies in humans have delineated the hierarchical brain regions involved in placebo analgesia. However, because of the lack of proper approaches to perform molecular and cellular manipulations, the detailed molecular processes behind it have not been clarified. To address this issue, we developed an animal model of placebo analgesia in rats and analyzed the placebo analgesia related brain activity using small-animal neuroimaging method. We show here that gabapentin-based Pavlovian conditioning successfully induced placebo analgesia in neuropathic pain model rats and hierarchical brain regions are involved in placebo analgesia in rats, including the prelimbic cortex (PrL) of the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), ventrolateral periaqueductal gray matter (vlPAG), etc. The functional couplings in placebo responders between the mPFC and vlPAG was interrupted by naloxone, an antagonist of µ opioid receptor. Moreover, both local chemical lesion and microinfusion of naloxone in the mPFC suppressed the placebo analgesia. These results suggest that the intrinsic µ opioid system in the mPFC causally contribute to placebo analgesia in rats, and the small-animal neuroimaging approach could provide important insights toward understanding the placebo effect in great detail.

cAMP and cGMP Play an Essential Role in Galvanotaxis of Cell Fragments.

Cell fragments devoid of the nucleus and major organelles are found in physiology and pathology, for example platelets derived from megakaryocytes, and cell fragments from white blood cells and glioma cells. Platelets exhibit active chemotaxis. Fragments from white blood cells display chemotaxis, phagocytosis, and bactericidal functions. Signaling mechanisms underlying migration of cell fragments are poorly understood. Here we used fish keratocyte fragments and demonstrated striking differences in signal transduction in migration of cell fragments and parental cells in a weak electric field. cAMP or cGMP agonists completely abolished directional migration of fragments, but had no effect on parental cells. The inhibition effects were prevented by pre-incubating with cAMP and cGMP antagonists. Blocking cAMP and cGMP downstream signaling by inhibition of PKA and PKG also recovered fragment galvanotaxis. Both perturbations confirmed that the inhibitory effect was mediated by cAMP or cGMP signaling. Inhibition of cathode signaling with PI3K inhibitor LY294002 also prevented the effects of cAMP or cGMP agonists. Our results suggest that cAMP and cGMP are essential for galvanotaxis of cell fragments, in contrast to the signaling mechanisms in parental cells.

Exposure to 50 Hz Extremely-Low-Frequency Magnetic Fields Induces No DNA Damage in Cells by Gamma H2AX Technology.

The current results for extremely-low-frequency magnetic fields (ELF-MF) on DNA damage are still debated. A sensitive indicator and systematic research are needed to assess the effects of ELF-MF. In this study, we used γH2AX as an early and sensitive molecular marker to evaluate the DNA damage effects of ELF-MF in vitro. Human amnion epithelial cells (FLs), human skin fibroblast cells (HSFs), and human umbilical vein endothelial cells (HUVECs) were exposed to 50 Hz ELF-MF at 0.4, 1, and 2 mT for 15 min, 1 h, and 24 h, respectively. After exposure, cells were subjected to γH2AX immunofluorescence and western blot. The results showed no significant difference in the average number of foci per cell, the percentage of γH2AX foci-positive cells, or the expression of γH2AX between the sham and 50 Hz ELF-MF exposure groups (P > 0.05). In conclusion, 50 Hz ELF-MF did not induce DNA damage in FLs, HSFs, or HUVECs, which was independent of the intensity or duration of the exposure.

Effect of superposed electromagnetic noise on DNA damage of lens epithelial cells induced by microwave radiation.

PURPOSE: To investigate the influence of the 1.8-GHz radiofrequency fields (RFs) of the Global System for Mobile Communications on DNA damage, intracellular reactive oxygen species (ROS) formation, cell cycle, and apoptosis in human lens epithelial cells (hLECs) and whether the effects induced by RF could be blocked by superposing of electromagnetic noise. METHODS: After 24-hour intermittent exposure at the specific absorption rate of 1 W/kg, 2 W/kg, 3 W/kg, and 4 W/kg, the DNA damage of hLECs was examined by alkaline comet assay and immunofluorescence microscope detection of the phosphorylated form of histone variant H2AX (gammaH2AX) foci, respectively. ROS production was quantified by the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). Cell cycle and cell apoptosis were determined by flow cytometry. RESULTS: DNA damage examined by alkaline comet assay was significantly increased after 3 W/kg and 4 W/kg radiation (P < 0.05), whereas the double-strand breaks (DSBs) evaluated by gammaH2AX foci were significantly increased only after 4 W/kg radiation (P < 0.05). Significantly elevated intracellular ROS levels were also detected in the 3-W/kg and 4-W/kg groups (P < 0.05). After exposure to 4 W/kg for 24 hours, hLECs exhibited significant G(0)/G(1) arrest (P < 0.05). There was no detectable difference in cell apoptosis between the microwave radiation and sham exposure groups (P > 0.05). All the effects mentioned were blocked when the RF was superposed with 2 muT electromagnetic noise. CONCLUSIONS: Microwave radiation induced hLEC DNA damage after G(0)/G(1) arrest does not lead to cell apoptosis. The increased ROS observed may be associated with DNA damage. Superposed electromagnetic noise blocks microwave radiation-induced DNA damage, ROS formation, and cell cycle arrest.

[Effects of different cell lysis buffers on protein quantification].

OBJECTIVE: To observe the effects of different cell lysis buffers on protein quantification with Bradford method and bicinchoninic acid (BCA) method. METHODS: Bradford method and BCA method were used to determine the concentration of bovine serum albumin (BSA) in different solutions (distilled water, cell lysis buffer used in two-dimensional differential in-gel electrophoresis and three kinds of cell lysis buffers used in conventional two dimensional gel electrophoresis), as well as the protein concentrations of cell lysates using these different lysis buffers. Bradford method was also applied to determine the protein concentrations of samples with repeated freeze thaw cycle, in different colorimetric cylinders, or using different standard curves from different periods. RESULT: The protein measurements increased for 1.2 to 2 fold when different cell lysis buffers were used in Bradford method, but the measurements increased with the increased concentration of BSA (r=0.989 approximately 0.996, P<0.05). For BCA, measurement reading increased about thousands times higher, even overflowed the limits of machine. Protein measurements didn't change significantly, only showed a declined trend after repeated freeze thaw cycle, while no significant changes were found using different colorimetric cylinders or standard curves from different periods. CONCLUSION: Bradford method may be the choice of the protein quantification in proteomics. However, optimization is required for specific experimental conditions.

[Effects of 50 Hz magnetic fields on DNA double-strand breaks in human lens epithelial cells].

OBJECTIVE: To investigate the effects of 50 Hz magnetic fields (MF) on DNA double-strand breaks in human lens epithelial cells (hLECs). METHODS: The cultured human lens epithelial cells were exposed to 0.4 mT 50 Hz MF for 2 h, 6 h, 12 h, 24 h and 48 h. Cells exposed to 4-nitroquinoline-1-oxide, a DNA damage agent, at a final concentration of 0.1 micromol/L for 1 h were used as positive controls.After exposure, cells were fixed with 4 % paraformaldehyde and for H2AX (gamma H2AX) immunofluorescence measurement. gamma H2AX foci were detected at least 200 cells for each sample. Cells were classified as positive when more than three foci per cell were observed. Mean values of foci per cell and percentage of foci positive cells were adopted as indexes of DNA double-strand breaks. RESULT: The mean value of foci per cell and the percentage of gamma H2AX foci positive cells in 50 Hz MF exposure group for 24 h were (2.93 +/-0.43) and (27.88 +/-2.59)%, respectively, which were significantly higher than those of sham-exposure group [(1.77 +/-0.37) and (19.38+/-2.70)%, P <0.05], and the mean value of foci per cell and the percentage of gamma H2AX foci positive cells in 50 Hz MF exposure group for 48 h were (3.14 +/-0.35) and (31.00 +/-3.44)%, which were significantly higher than those of sham-exposure group (P <0.01). However there was no significant difference between 50 Hz MF exposure groups for 2 h, 6 h, 12 h and sham-exposure group for above two indexes (P >0.05). CONCLUSION: 0.4 mT 50 Hz MF exposure for longer duration might induce DNA double-strand breaks in human lens epithelial cells in vitro.

[Surface markers and functions of human dendritic cells exposed to mobile phone 1800 MHz electromagnetic fields].

OBJECTIVE: To investigate the effects of mobile phone 1800 MHz electromagnetic fields (EMF) on the surface markers and the functions of human dendritic cells (DC). METHODS: Human DCs were exposed to intermittent 5 min on/10 min off EMF with specific absorption rates (SAR) 4 W/kg for 0 h, 1 h, 12 h or 24 h, respectively. FACS analysis was used to detect the positive percentage of DC surface markers including HLA-DR and co-stimulatory molecules such as CD80, CD86, CD40 and CD11c. CCK-8 kit was adopted to examine the function of allo-mixed lymphocyte reaction (allo-MLR) of DC, and enzyme linked immunosorbent assay (ELISA) to identify the levels of IL-12p70 and TNF-alpha secreted by DC. RESULT: Compared with the sham radiation group, after exposure to the electromagnetic fields for 1 h, 12 h, or 24 h, HLA-DR, CD80,CD86 and CD40 were all declined except CD11c. The ability of DC allo-MLR in each exposure group was decreased significantly (P<0.05), especially in the 24 h exposure group. However, the secreted levels of IL-12p70 and TNF-alpha of DC in each exposure group remained no changed. CONCLUSION: The study showed that EMF exposure could down-regulate the surface molecules and stimulation ability of human DC.

Corrigendum: Diabetic cornea wounds produce significantly weaker electric signals that may contribute to impaired healing.

This corrects the article DOI: 10.1038/srep26525.

Src activation decouples cell division orientation from cell geometry in mammalian cells.

Orientation of cell division plane plays a crucial role in morphogenesis and regeneration. Misoriented cell division underlies many important diseases, such as cancer. Studies with Drosophila and C. elegance models show that Src, a proto-oncogene tyrosine-protein kinase, is a critical regulator of this aspect of mitosis. However, the role for Src in controlling cell division orientation in mammalian cells is not well understood. Using genetic and pharmacological approaches and two extracellular signals to orient cell division, we demonstrated a critical role for Src. Either knockout or pharmacological inhibition of Src would retain the fidelity of cell division orientation with the long-axis orientation of mother cells. Conversely, re-expression of Src would decouple cell division orientation from the pre-division orientation of the long axis of mother cells. Cell division orientation in human breast and gastric cancer tissues showed that the Src activation level correlated with the degree of mitotic spindle misorientation relative to the apical surface. Examination of proteins associated with cortical actin revealed that Src activation regulated the accumulation and local density of adhesion proteins on the sites of cell-matrix attachment. By analyzing division patterns in the cells with or without Src activation and through use of a mathematical model, we further support our findings and provide evidence for a previously unknown role for Src in regulating cell division orientation in relation to the pre-division geometry of mother cells, which may contribute to the misoriented cell division.

[Effect of 50 Hz power frequency magnetic field on microfilament cytoskeleton assembly of human amnion FL cells].

OBJECTIVE: Investigations were carried out to understand the effect of 50 Hz power frequency magnetic field on microfilament assembly of human amniotic cells and on expression of actin and epidermal growth factor receptor. METHODS: Human amnion FL cells were exposed to 0.1, 0.2, 0.3, 0.4, 0.5 mT power frequency magnetic field for 30 minutes. Microfilaments were marked using Phalloidin-TRITC, and then were observed under a fluorescence microscope. An optical method was used to detect the relative content of microfilament in cells. A scanning electron microscope was used to detect the cell shape. The content of actin and epidermal growth factor receptor in the preparation of the detergent-insoluble cytoskeleton were measured by western-blotting to analyse the potential mechanism of the change induced by magnetic field. RESULTS: Intracellular stress fibers were found to decrease after exposing cells to a 0.2 mT power frequency magnetic field for 30 minutes. New microfilament and filopodia bundles appeared at the cell periphery after exposure, but the detected total F-actin content per cell was not significantly changed, detected by a F-actin-specific dye. The change in the amount of microfilaments caused by the field could be recovered 2 hours later when the field was withdrawn. The mean height of microfilament cytoskeleton decreased from (12.37 +/- 1.28) microm to (9.97 +/- 0.38) microm (t = 6.96, P > 0.05) after exposure using a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure observed by a scanning electron microscope. By using Western blotting method, the intracellular contents of epidermal growth factor receptor and of actin in the preparation of the detergent-insoluble cytoskeleton which are associated with high-affinity epidermal growth factor receptors, increased about (31.2 +/- 4.1)% (t = 17.10, P < 0.05) and (16.8 +/- 2.3)% (t = 16.68, P < 0.05) respectively, compared with that of the control. CONCLUSION: These results suggest that a short time exposure to a 0.2 mT power frequency magnetic field induces re-organization of microfilament in human amnion FL cells. These changes could be recovered by field withdraw and may have something with the clustering of epidermal growth factor receptors induced by magnetic field.

[Study of toxicity to rats induced by nanosized SiO2 and standard SiO2].

OBJECTIVE: To study the pulmonary toxicity to rats induced by the nanosized SiO(2) or the standard SiO(2). METHODS: Seventy-two male SD rats were divided into three groups: the nanosized SiO(2) group, the standard SiO(2) group and the control group. 24 rats each group. The nanosized SiO(2) group and the standard SiO(2) group were instilled intratracheally with 0.5 ml suspension of 0.6 mg/ml nanosized SiO(2) or standard SiO(2) respectively while the control group was instilled with 0.5 ml physiological saline. On the 3rd, 7th, 14th, and 28th day after exposure, six rats were sacrificed at each time point and the total white cells counts and total protein in BALF and the histopathological changes were observed. The pulmonary toxicities of the two SiO(2) dusts were compared. RESULTS: Nanosized SiO(2) caused significant increase at 3rd, 7th, 14th day after the exposure [(16.0 +/- 6.0) x 10(6), (11.1 +/- 4.0) x 10(6), (12.2 +/- 4.6) x 10(6)] compared with saline (P < 0.05 or P < 0.01) in the total numbers of white cells and on the 3rd after the exposure compared with standard SiO(2) [(5.7 +/- 3.7) x 10(6), P < 0.01]. Meanwhile, Nanosized SiO(2) significantly increased the total protein on the 14th, 28th day after the exposure (0.41 +/- 0.14, 0.41 +/- 0.19 g/L) compared with saline or standard SiO(2) and nanosized SiO(2) on the 3rd, 7th day after the exposure (P < 0.05 or P < 0.01). Nanosized SiO(2)-treated rats showed marked white cell infiltration in alveolar space or around brondum the blood vessel. Standard SiO(2) caused similar but less severe responses compared with nanosized SiO(2). Van Gieson's-stained sections showed no significant fibrosis in these dust-exposed rats at 28th day after the exposure. CONCLUSION: Nanosized SiO(2) can cause severer and longer pulmonary toxicity in rats than standard SiO(2). The pulmonary particle load threshold of nanosized SiO(2) may be lower than that of standard SiO(2).

Effects of Single and Repeated Exposure to a 50-Hz 2-mT Electromagnetic Field on Primary Cultured Hippocampal Neurons.

The prevalence of domestic and industrial electrical appliances has raised concerns about the health risk of extremely low-frequency magnetic fields (ELF-MFs). At present, the effects of ELF-MFs on the central nervous system are still highly controversial, and few studies have investigated its effects on cultured neurons. Here, we evaluated the biological effects of different patterns of ELF-MF exposure on primary cultured hippocampal neurons in terms of viability, apoptosis, genomic instability, and oxidative stress. The results showed that repeated exposure to 50-Hz 2-mT ELF-MF for 8 h per day after different times in culture decreased the viability and increased the production of intracellular reactive oxidative species in hippocampal neurons. The mechanism was potentially related to the up-regulation of Nox2 expression. Moreover, none of the repeated exposure patterns had significant effects on DNA damage, apoptosis, or autophagy, which suggested that ELF-MF exposure has no severe biological consequences in cultured hippocampal neurons.

[Effects of GSM 1800 MHz radiofrequency electromagnetic fields on DNA damage in Chinese hamster lung cells].

OBJECTIVE: To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) on DNA damage in Chinese hamster lung (CHL) cells. METHODS: The cells were intermittently exposed or sham-exposed to GSM 1800 MHz RF EMF (5 minutes on/10 minutes off) at a special absorption rate (SAR) of 3.0 W/kg for 1 hour or 24 hours. Meanwhile, cells exposed to 2-acetylaminofluorene, a DNA damage agent, at a final concentration of 20 mg/L for 2 hours were used as positive control. After exposure, cells were fixed by using 4% paraformaldehyde and processed for phosphorylated form of H2AX (gammaH2AX) immunofluorescence measurement. The primary antibody used for immunofluorescence was mouse monoclonal antibody against gammaH2AX and the secondary antibody was fluorescein isothiocyanate (FITC)-conjugated goat anti-mouse IgG. Nuclei were counterstained with 4, 6-diamidino-2-phenylindole (DAPI). The gammaH2AX foci and nuclei were visualized with an Olympus AX70 fluorescent microscope. Image Pro-Plus software was used to count the gammaH2AX foci in each cell. For each exposure condition, at least 50 cells were selected to detect gammaH2AX foci. Cells were classified as positive when more than five foci were detected. The percentage of gammaH2AX foci positive cells was adopted as the index of DNA damage. RESULTS: The percentage of gammaH2AX foci positive cell of 1800 MHz RF EMF exposure for 24 hours (37.9 +/- 8.6)% or 2-acetylaminofluorene exposure (50.9 +/- 9.4)% was significantly higher compared with the sham-exposure (28.0 +/- 8.4)%. However, there was no significant difference between the sham-exposure and RF EMF exposure for 1 hour (31.8 +/- 8.7)%. CONCLUSION: 1800 MHz RF EMF (SAR, 3.0 W/kg) for 24 hours might induce DNA damage in CHL cells.

[Effects of GSM 1800 MHz radiofrequency electromagnetic fields on protein expression profile of human breast cancer cell MCF-7].

OBJECTIVE: To study the effects of GSM 1800 MHz radiofrequency electromagnetic fields (RF EMF) exposure on protein expression profile of human breast cancer cell line (MCF-7), as to exploring the possible effects on normal cell physiological function. METHODS: MCF-7 cells were continuously or intermittently (5 minutes field on followed by 10 minutes off) exposed to RF EMF for different duration (1 hour, 3 hours, 6 hours, 12 hours, or 24 hours) at an average specific absorption rate (SAR) of 3.5 W/kg. The extracted proteins were separated by 2-dimensional electrophoresis and the protein-spot distribution of the silver-stained gels was analyzed by using PDQuest software 7.1. Each experiment was repeated three times. RESULTS: On the average, around 1100 proteins were detected using pH 4 - 7 IPG strip. There were no differential proteins found under continuous exposure at SAR of 3.5 W/kg for 6 hours. Under other exposure conditions, we found various differentially expressed proteins in exposure groups as compared with the sham-exposed controls. Especially in 3 hours intermittent exposure and 12 hours continuous exposure, eighteen and seven differential proteins were detected, respectively. The categories and functions of these differentially expressed proteins were analyzed by searching of SWISS-PROT protein database, which suggested that these proteins should be related to the functions of biosynthesization, signal transduction, and DNA damage and repair. CONCLUSIONS: Data indicated that the protein expression changes induced by RF radiation might depend on exposure duration and mode. Many biological processes might be affected by RF exposure.

Extremely Low Frequency Magnetic Fields Do Not Induce DNA Damage in Human Lens Epithelial Cells In Vitro.

Non-ionizing radiations, e.g., radiofrequency electromagnetic fields, could induce DNA damage and oxidative stress in human lens epithelial cells (LECs) which can be early events in cataractogenesis. Extremely low frequency magnetic fields (ELF MF) as another common form of man-made electromagnetic fields has been considered as suspected human carcinogen by International Agency for Research on Cancer (IARC) and become a focus that people play more and more attentions to. This study aimed to determine whether ELF MF can induce DNA damage in cultured human LECs at a relatively low intensity. Human LECs were exposed or sham-exposed to a 50 Hz ELF MF which produced by a well-designed exposure system at the intensity of 0.4 mT. DNA damage in human LECs was examined by the phosphorylated form of histone variant H2AX (γH2AX) foci formation assay and further explored with western blot, flow cytometry, and alkaline comet assay. Immunofluorescence analysis showed that 0.4 mT ELF MF did not significantly increase γH2AX foci formation in human LECs after 2, 6, 12, 24, or 48 hr exposure. No significant differences had been detected in γH2AX expression level between the ELF MF- and sham-exposure groups, while no obvious chromosomal DNA fragmentation was detected by alkaline comet assay after ELF MF exposure. The results indicate an absence of genotoxicity in ELF MF-exposed human epithelial cells and do not support the hypothesis that environmental ELF MF might be causally led to genomic instability via chromosomal damage response processes. Neither short nor long term continuous exposure to 50 Hz ELF MF at 0.4 mT could induce DNA damage in human lens epithelial cells in vitro.

Diabetic cornea wounds produce significantly weaker electric signals that may contribute to impaired healing.

Wounds naturally produce electric signals which serve as powerful cues that stimulate and guide cell migration during wound healing. In diabetic patients, impaired wound healing is one of the most challenging complications in diabetes management. A fundamental gap in knowledge is whether diabetic wounds have abnormal electric signaling. Here we used a vibrating probe to demonstrate that diabetic corneas produced significantly weaker wound electric signals than the normal cornea. This was confirmed in three independent animal models of diabetes: db/db, streptozotocin-induced and mice fed a high-fat diet. Spatial measurements illustrated that diabetic cornea wound currents at the wound edge but not wound center were significantly weaker than normal. Time lapse measurements revealed that the electric currents at diabetic corneas lost the normal rising and plateau phases. The abnormal electric signals correlated significantly with impaired wound healing. Immunostaining suggested lower expression of chloride channel 2 and cystic fibrosis transmembrane regulator in diabetic corneal epithelium. Acute high glucose exposure significantly (albeit moderately) reduced electrotaxis of human corneal epithelial cells in vitro, but did not affect the electric currents at cornea wounds. These data suggest that weaker wound electric signals and impaired electrotaxis may contribute to the impaired wound healing in diabetes.

An Experimental Model for Simultaneous Study of Migration of Cell Fragments, Single Cells, and Cell Sheets.

Recent studies have demonstrated distinctive motility and responses to extracellular cues of cells in isolation, cells collectively in groups, and cell fragments. Here we provide a protocol for generating cell sheets, isolated cells, and cell fragments of keratocytes from zebrafish scales. The protocol starts with a comprehensive fish preparation, followed by critical steps for scale processing and subsequent cell sheet generation, single cell isolation, and cell fragment induction, which can be accomplished in just 3 days including a 36-48 h incubation time. Compared to other approaches that usually produce single cells only or together with either fragments or cell groups, this facile and reliable methodology allows generation of all three motile forms simultaneously. With the powerful genetics in zebrafish our model system offers a useful tool for comparison of the mechanisms by which cell sheets, single cells, and cell fragments respond to extracellular stimuli.

Exposure to 50Hz-sinusoidal electromagnetic field induces DNA damage-independent autophagy.

As electromagnetic field (EMF) is commonly encountered within our daily lives, the biological effects of EMF are of great concern. Autophagy is a key process for maintaining cellular homeostasis, and it can also reveal cellular responses to environmental stimuli. In this study, we aim to investigate the biological effects of a 50Hz-sinusoidal electromagnetic field on autophagy and we identified its mechanism of action in Chinese Hamster Lung (CHL) cells. CHL cells were exposed to a 50Hz sinusoidal EMF at 0.4mT for 30min or 24h. In this study, we found that a 0.4mT EMF resulted in: (i) an increase in LC3-II expression and increased autophagosome formation; (ii) no significant difference in the incidence of γH2AX foci between the sham and exposure groups; (iii) reorganized actin filaments and increased pseudopodial extensions without promoting cell migration; and (iv) enhanced cell apoptosis when autophagy was blocked by Bafilomycin A1. These results implied that DNA damage was not directly involved in the autophagy induced by a 0.4mT 50Hz EMF. In addition, an EMF induced autophagy balanced the cellular homeostasis to protect the cells from severe adverse biological consequences.

Effects of ELF magnetic fields on protein expression profile of human breast cancer cell MCF7.

Extremely Low Frequency Magnetic Fields (ELF MF) has been considered as a "possible human carcinogen" by International Agency for Research on Cancer (IARC) while credible mechanisms of its carcinogenicity remain unknown. In this study, a proteomics approach was employed to investigate the changes of protein expression profile induced by ELF MF in human breast cancer cell line MCF7, in order to determine ELF MF-responsive proteins. MCF7 cells were exposed to 50 Hz, 0.4 mT ELF MF for 24 h and the changes of protein profile were examined using two dimensional electrophoresis. Up to 6 spots have been statistically significantly altered (their expression levels were changed at least 5 fold up or down) compared with sham-exposed group. 19 ones were only detected in exposure group while 19 ones were missing. Three proteins were identified by LC-IT Tandem MS as RNA binding protein regulatory subunit, Proteasome subunit beta type 7 precursor and Translationally Controlled Tumor Protein. Our finding showed that 50 Hz, 0.4 mT ELF MF alternates the protein profile of MCF7 cell and may affect many physiological functions of normal cell and 2-DE coupled with MS is a promising approach to elucidating cellular effects of electromagnetic fields.