Low-level laser therapy activates NF-kB via generation of reactive oxygen species in mouse embryonic fibroblasts.

BACKGROUND: Despite over forty years of investigation on low-level light therapy (LLLT), the fundamental mechanisms underlying photobiomodulation at a cellular level remain unclear. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we isolated murine embryonic fibroblasts (MEF) from transgenic NF-kB luciferase reporter mice and studied their response to 810 nm laser radiation. Significant activation of NF-kB was observed at fluences higher than 0.003 J/cm(2) and was confirmed by Western blot analysis. NF-kB was activated earlier (1 hour) by LLLT compared to conventional lipopolysaccharide treatment. We also observed that LLLT induced intracellular reactive oxygen species (ROS) production similar to mitochondrial inhibitors, such as antimycin A, rotenone and paraquat. Furthermore, we observed similar NF-kB activation with these mitochondrial inhibitors. These results, together with inhibition of laser induced NF-kB activation by antioxidants, suggests that ROS play an important role in the laser induced NF-kB signaling pathways. However, LLLT, unlike mitochondrial inhibitors, induced increased cellular ATP levels, which indicates that LLLT also upregulates mitochondrial respiration. CONCLUSION: We conclude that LLLT not only enhances mitochondrial respiration, but also activates the redox-sensitive NFkB signaling via generation of ROS. Expression of anti-apoptosis and pro-survival genes responsive to NFkB could explain many clinical effects of LLLT.

The zinc ionophore PCI-5002 radiosensitizes non-small cell lung cancer cells by enhancing autophagic cell death.

INTRODUCTION: A major focus of cancer research is to identify compounds that sensitize resistant cancer cells to radiation treatment. Lung cancer cells, in particular, have high rates of radioresistance that lead to treatment failure. We have previously shown that the autophagy induced in the context of decreased apoptosis confers radiosensitivity to prostate and lung cancer cells. Zinc supplementation has antiapoptotic effects in cell culture. In addition, the accumulation of zinc in response to oxidative stress has been associated with increased autophagy in astrocyte and breast cancer cells. METHODS: In this study, we hypothesized that the zinc ionophore PCI-5002 radiosensitizes lung cancer cells by inducing autophagic cell death. To test this hypothesis, we used a combination of in vitro and in vivo approaches, including clonogenic assays to test for radiosensitivity, biochemical analyses of apoptosis and autophagy, and a xenograft mouse model of tumor growth. RESULTS: We found that PCI-5002 reduced clonogenic survival in treated cells compared with untreated cells (0.03% versus 0.1% surviving fraction, p < 0.001). The increased radiosensitive fraction of PCI-5002-treated cells was accompanied by increased autophagy. PCI-5002 treatment also reduced caspase-3 cleavage. In an irradiated xenograft mouse model, the tumor growth of irradiated, PCI-5002-treated mice was slower than untreated, irradiated mice (25 days versus 22 days to reach a 1.0 cm tumor size). CONCLUSIONS: PCI-5002 treatment sensitizes lung cancer cells to radiation, both in vitro and in vivo. This data suggest that PCI-5002 could potentially treat radioresistant/locally advanced lung cancer by amplifying the effects of radiotherapy.

Anticipation of radiation dose to the conceptus from occupational exposure of pregnant staff during fluoroscopically guided electrophysiological procedures.

UNLABELLED: Conceptus dose from occupational exposure. INTRODUCTION: A female employee working in the electrophysiology suite has the right to know potential radiation hazards to the unborn child before she is pregnant or before she decides to formally declare her pregnancy. Moreover, the employer of a declared pregnant worker must evaluate the work situation and ensure that the conceptus dose is kept below the maximum permissible level during the remaining gestation period. The aim of this study was to develop a method for conceptus dose anticipation and determination of maximum workload allowed for the pregnant employee who participates in fluoroscopically guided electrophysiological procedures. METHODS AND RESULTS: A C-arm fluoroscopy system, an anthropomorphic phantom, and a radiation meter were used to obtain scattered air kerma dose rates separately for each of the three fluoroscopic projections typically used in the electrophysiology suite. Air kerma to conceptus dose conversion factors for all trimesters of gestation were calculated using Monte Carlo simulation. A formula is presented for the anticipation of the conceptus dose from occupational exposure of pregnant staff during fluoroscopically guided electrophysiological procedures. Normalized data are provided for conceptus dose estimation from occupational exposure of pregnant staff working in any electrophysiology laboratory. A methodology for estimation of maximum workload allowed for each month of the remaining gestation period of a worker who declared her pregnancy is proposed, which ensures that the regulatory dose limits are not exceeded. CONCLUSION: Data presented may be used for the implementation of a radiation protection program designed for pregnant staff working in an electrophysiological suite.

High frequency electromagnetic fields (GSM signals) affect gene expression levels in tumor suppressor p53-deficient embryonic stem cells.

Effects of electromagnetic fields (EMF) simulating exposure to the Global System for Mobile Communications (GSM) signals were studied using pluripotent embryonic stem (ES) cells in vitro. Wild-type ES cells and ES cells deficient for the tumor suppressor p53 were exposed to pulse modulated EMF at 1.71 GHz, lower end of the uplink band of GSM 1800, under standardized and controlled conditions, and transcripts of regulatory genes were analyzed during in vitro differentiation. Two dominant GSM modulation schemes (GSM-217 and GSM-Talk), which generate temporal changes between GSM-Basic (active during talking phases) and GSM-DTX (active during listening phases thus simulating a typical conversation), were applied to the cells at and below the basic safety limits for local exposures as defined for the general public by the International Commission on Nonionizing Radiation Protection (ICNIRP). GSM-217 EMF induced a significant upregulation of mRNA levels of the heat shock protein, hsp70 of p53-deficient ES cells differentiating in vitro, paralleled by a low and transient increase of c-jun, c-myc, and p21 levels in p53-deficient, but not in wild-type cells. No responses were observed in either cell type after EMF exposure to GSM-Talk applied at similar slot-averaged specific absorption rates (SAR), but at lower time-averaged SAR values. Cardiac differentiation and cell cycle characteristics were not affected in embryonic stem and embryonic carcinoma cells after exposure to GSM-217 EMF signals. Our data indicate that the genetic background determines cellular responses to GSM modulated EMF. Bioelectromagnetics 25:296-307, 2004.

Radiological protection for diagnostic examination of pregnant women.

Application of diagnostic X-ray examination to pregnant women is complicated since risks to both mother and embryo/fetus must be considered. Embryos and fetuses are more sensitive to radiation than adults or children. The threshold doses for fetal death, malformations and mental retardation which are deterministic effects, are reported to be 100-200 mGy or higher. The relative risk for childhood cancer due to radiation at an absorbed dose of 10 mGy during embryonic/fetal development has been estimated at 1.4. However, the absorbed dose of the embryo/fetus during X-ray diagnostic examination in which the X-ray beam does not irradiate the embryo/fetus directly such as maternal skull and chest X-ray is extremely low, less than 0.01 mGy. Thus these diagnostic procedures are not a problem from the perspective of radiological protection of the embryo/fetus. However, for pelvic CT scan and barium enema in which the uterus is directly within the X-ray beam, the absorbed doses to the embryo/fetus are about 20-80 mGy and 10-20 mGy, respectively. Therefore, medical staff must pay careful attention to the embryo/fetus in application of these examinations. Pregnant women who were not aware of pregnancy at the time of their diagnostic exposure have great anxiety about radiation from such X-ray examinations. However, fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy.

Accidental embryo irradiation during barium enema examinations. An estimation of absorbed dose.

RATIONALE AND OBJECTIVES: To investigate the possibility of an embryo to receive a dose of more than 10 cGy, the threshold of malformations induction in embryos reported by the International Commission on Radiological Protection, during barium enema examinations. METHODS: Thermoluminescent dosimeters were placed in a phantom to calculate the depth-to-skin conversion coefficient needed for dose estimation at the average embryo depth in patients. Barium enema examinations were performed in 20 women of childbearing age with diagnostic problems demanding longer fluoroscopy times. Doses at 6 cm, the average embryo depth, were determined by measurements at the patients' skin followed by dose calculation at the site of interest. RESULTS: The range of doses estimated at embryo depth for patients was 1.9 to 8.1 cGy. The dose always exceeded 5 cGy when fluoroscopy time was longer than 7 minutes. CONCLUSION: The dose at the embryo depth never exceeded 10 cGy. This study indicates that fluoroscopy time should not exceed 7 minutes in childbearing-age female patients undergoing barium enema examinations.