OBJECTIVETo study the effects of extremely low frequency magnetic fields(ELF MF) on the amount and localization of connexin 43(Cx43) gap-junction protein in the Chinese hamster lung(CHL) cells, and to explore the mechanism of ELF MF suppression on gap-junctional intercellular communication(GJIC).

METHODSThe cells were irradiated for 24 h with 50 Hz sinusoidal magnetic field at 0.8 mT without or with 12-O-tetrade-canoylphorbol-3-acetate(TPA), 5 ng/ml for 1 h. The localization of Cx43 proteins were performed by indirect immunofluorescence histochemical analysis and detected by confocal microscopy. The second experiment was conducted to examine the quantity of Cx43 proteins level in nuclei or cytoplasm and detected by Western blotting analysis.

RESULTSThe cells exposed to TPA for 1 h displayed less bright labelled spots in the regions of intercellular junction than the normal cells. Most of Cx43 labelled spots occurred in the cytoplasm and aggregated near the nuclei. At the same time, the amount of Cx43 protein in cytoplasm were increased[(2.03 +/- 0.89) in ELF group, (2.43 +/- 0.82) in TPA group] as compared to normal control(1.04 +/- 0.17) (P < 0.01).

CONCLUSIONInhibition on GJIC function by ELF MF alone or combined with TPA may be related with the shift of Cx43 from the regions of intercellular junction to the cytoplasm.

Animals ; Cell Communication ; radiation effects ; Connexin 43 ; biosynthesis ; Cricetinae ; Cricetulus ; Cytoplasm ; metabolism ; Electromagnetic Fields ; adverse effects ; Gap Junctions ; radiation effects ; Lung ; metabolism ; radiation effects ; Tetradecanoylphorbol Acetate ; pharmacology

BACKGROUNDClinical combination of some traditional Chinese medical herbs, including berberine, with irradiation is demonstrated to improve efficacy of tumor radiotherapy, yet the mechanisms for such effect remain largely unknown. The present study investigated the effect of berberine on apoptosis induced by X-rays irradiation and the relation between this effect and gap junction intercellular communication (GJIC).

METHODSThe role of gap junctions in the modulation of X-rays irradiation-induced apoptosis was explored by manipulation of connexin (Cx) expression, and gap junction function, using oleamide, a GJIC inhibitor, and berberine.

RESULTSIn transfected HeLa cells, Cx32 expression increased apoptosis induced by X-rays irradiation, while inhibition of gap junction by oleamide reduced the irradiation responses, indicating the dependence of X-rays irradiation-induced apoptosis on GJIC. Berberine, at the concentrations without cytotoxicity, enhanced apoptosis induced by irradiation only in the presence of functional gap junctions.

CONCLUSIONSThese results suggest that berberine potentizes cell apoptosis induced by X-rays irradiation, probably through enhancement of gap junction activity.

Apoptosis ; drug effects ; Berberine ; pharmacology ; Gap Junctions ; drug effects ; metabolism ; radiation effects ; HeLa Cells ; Humans ; Oleic Acids ; pharmacology ; X-Rays

OBJECTIVEIn order to explore if power frequency magnetic field (PFMF) can act as cancer promoter or be synergistic with phorbol 12-myristate 13-acetate (TPA) in cancer promotion, the effects of 50 Hz MF on gap junction intercellular communication (GJIC) of astrocytes were observed.

METHODSFluorescence redistribution after photobleaching (FRAP) was adopted to observe the recovery of fluorescence intensity in the bleached cells thus to estimate intercellular communication by gap junction. Comparative fluorescence intensity recovery rate (CFIRR) was as evaluation index. The effects of 50 Hz MF alone or with TPA on GJIC of astrocytes were studied.

RESULTSAfter 3 ng/ml TPA treatment for 1 hour, M(d) of CFIRR was 4.53%/min, whereas that in the control group was 9.74%/min (H = 12.084, P < 0.005). After exposure to 0.8 and 1.6 mT magnetic field for 24 hours respectively, M(d) of CFIRR was 8.25%/min and 6.68%/min respectively, no significant difference from that of control (H = 32.617, P > 0.05). After exposure to 0.8 and 1.6 mT magnetic field for 23 hours then combined with 3 ng/ml TPA treatment for 1 hour, M(d) of CFIRR was 3.32%/min and 2.85%/min respectively, also no significant difference from that in the group treated with 3 ng/ml TPA alone (H = 2.589, P > 0.05).

CONCLUSION50 Hz MF (within 0 - 1.6 mT) alone could not inhibit GJIC of astrocytes; with TPA, could not enhance the inhibition of TPA on GJIC of astrocytes. But with MF intensity increasing, the inhibition of MF on GJIC showed elevated tendency.

Animals ; Astrocytes ; radiation effects ; ultrastructure ; Cell Communication ; radiation effects ; Electromagnetic Fields ; adverse effects ; Gap Junctions ; radiation effects ; Ornithine Decarboxylase ; metabolism ; Rats ; Rats, Sprague-Dawley ; Tetradecanoylphorbol Acetate ; pharmacology

This study investigated that whether a 2 mT, 60 Hz, sinusoidal electromagnetic field (EMF) alters the structure and function of cells. This research compared the effects of EMF on four kinds of cell lines: hFOB 1.19 (fetal osteoblast), T/G HA-VSMC (aortic vascular smooth muscle cell), RPMI 7666 (B lymphoblast), and HCN-2 (cortical neuronal cell). Over 14 days, cells were exposed to EMF for 1, 3, or 6 hours per day (hrs/d). The results pointed to a cell type-specific reaction to EMF exposure. In addition, the cellular responses were dependent on duration of EMF exposure. In the present study, cell proliferation was the trait most sensitive to EMF. EMF treatment promoted growth of hFOB 1.19 and HCN-2 compared with control cells at 7 and 14 days of incubation. When the exposure time was 3 hrs/d, EMF enhanced the proliferation of RPMI 7666 but inhibited that of T/G HA- VSMC. On the other hand, the effects of EMF on cell cycle distribution, cell differentiation, and actin distribution were unclear. Furthermore, we hardly found any correlation between EMF exposure and gap junctional intercellular communication in hFOB 1.19. This study revealed that EMF might serve as a potential tool for manipulating cell proliferation.
Signal Transduction ; Microfilaments/radiation effects ; Humans ; Gap Junctions/metabolism/radiation effects ; *Electromagnetic Fields ; Cell Proliferation/radiation effects ; Cell Physiology/*radiation effects ; Cell Line ; Cell Differentiation/radiation effects ; Cell Cycle/radiation effects

This study investigated that whether a 2 mT, 60 Hz, sinusoidal electromagnetic field (EMF) alters the structure and function of cells. This research compared the effects of EMF on four kinds of cell lines: hFOB 1.19 (fetal osteoblast), T/G HA-VSMC (aortic vascular smooth muscle cell), RPMI 7666 (B lymphoblast), and HCN-2 (cortical neuronal cell). Over 14 days, cells were exposed to EMF for 1, 3, or 6 hours per day (hrs/d). The results pointed to a cell type-specific reaction to EMF exposure. In addition, the cellular responses were dependent on duration of EMF exposure. In the present study, cell proliferation was the trait most sensitive to EMF. EMF treatment promoted growth of hFOB 1.19 and HCN-2 compared with control cells at 7 and 14 days of incubation. When the exposure time was 3 hrs/d, EMF enhanced the proliferation of RPMI 7666 but inhibited that of T/G HA- VSMC. On the other hand, the effects of EMF on cell cycle distribution, cell differentiation, and actin distribution were unclear. Furthermore, we hardly found any correlation between EMF exposure and gap junctional intercellular communication in hFOB 1.19. This study revealed that EMF might serve as a potential tool for manipulating cell proliferation.
Signal Transduction ; Microfilaments/radiation effects ; Humans ; Gap Junctions/metabolism/radiation effects ; *Electromagnetic Fields ; Cell Proliferation/radiation effects ; Cell Physiology/*radiation effects ; Cell Line ; Cell Differentiation/radiation effects ; Cell Cycle/radiation effects