| Objective:To explore the role of NF-κB activation in adaptive response induced by low dose microwave radiation via ROS. To study the relationship of low dose microwave radiation, ROS production, activation of NF-κB with adaptive response,as well as the possible mechanism of adaptive response induced by low dose microwave radiation.Methods:1. Establishing cell model of adaptive response induced by low dose microwave radiation with BMSCs.BMSCs were randomly divided into the following 6 groups:(a) un-exposed controls(cells kept in the incubator),(b) RF group(irradiated with 900 MHz microwave at 120μW /cm2 power intensity, 4 hours/day for 5 days),(c) sham group(cultured in microwave exposure system, but without microwave transmission),(d) γ-rays group(subjected to 1.5 Gy γ- rays),(e) RF+γ-rays group(irradiated with 1.5Gy γ-rays after microwave exposure),(f) Sham +γ-rays group(irradiated with 1.5Gy γ-rays after sham exposure).After exposure, the extent of primary DNA damage in the form of single strand breaks(SSBs) and double strand breaks(DSBs) was assessed using the alkaline comet assay and γ-H2 AX foci technique respectively.2. The role of ROS in adaptive response induced by low dose microwave radiation.(1) Intracellular reactive oxygen species influenced by low dose microwave radiationBMSCs were randomly divided into the following 6 groups:(a) un-exposed controls(cells kept in the incubator),(b) RF group(irradiated with 900 MHz microwave at 120μW /cm2 power intensity, 4 hours/day for 5 days),(c) sham exposure(Cells were cultured in microwave exposure system, but without microwave transmission),(d) MEL group(cells were subjected to 500 n M melatonin, a kind of ROS scavenger),(e) MEL+RF group(cells were subjected to 500 n M melatonin 4 h prior to microwave),(f) H2O2 group(positive control, cells were treated with hydrogen peroxide for 20~30 minutes).The production of intracellular reactive oxygen species(ROS) was determined immediately after the last RF exposure.(2) The role of ROS in adaptive response induced by low dose microwave radiationBMSCs were randomly divided into the following 6 groups:(a) un-exposed controls(cells kept in the incubator),(b) RF group(irradiated with 900 MHz microwave at 120μW /cm2 power intensity, 4 hours/day for 5 days),(c) MEL+ RF group(cells were subjected to 500 n M melatonin 4 h prior to microwave),(d) γ-rays group(cells were subjected to 1.5 Gy γ-rays),(e) RF+γ-rays group(irradiated with 1.5Gy γ-rays after microwave exposure),(f) MEL+RF+γ-rays group(Cells were subjected to 500 n M melatonin 4 h, then irradiated with 900 MHz microwave, 1.5 Gy γ-rays given 4h after microwave exposure).The extent of primary DNA damage in the form of single strand breaks(SSBs) and double strand breaks(DSBs) was assessed immediately, using an alkaline comet assay and γ-H2 AX foci technique, respectively.3. The role of NF- κ B activation in adaptive response induced by 900 MHz microwave radiation via reactive oxygen species.(1) NF- κ B activation induced by low dose microwave radiationBMSCs were randomly divided into the following 6 groups:(a) un-exposed controls(cells kept in the incubator),(b) RF group(irradiated with 900 MHz microwave at 120μW /cm2 power intensity, 4 hours/day for 5 days),(c) sham exposure(Cells were cultured in microwave exposure system, but without microwave transmission).The level of NF-κB protein in both plasma and nucleus of BMSCs were determined with western blot 0, 0.5, 1, 2, 4 and 6 hours after the last RF exposure.(2) The role of NF- κ B activation in adaptive response induced by 900 MHz microwave radiationBMSCs were randomly divided into the following 6 groups:(a) un-exposed controls(cells kept in the incubator),(b) RF group(irradiated with 900 MHz microwave at 120μW /cm2 power intensity, 4 hours/day for 5 days),(c) BAY group(Cells were subjected to 10μM BAY11-7082,an inhibitorfor NF- κ B, 30 mins prior to microwave),(d) γ-rays group(cells were subjected to 1.5 Gy γ-rays),(e) RF+γ-rays group(irradiated with 1.5Gy γ-rays after microwave exposure),(f) BAY+ RF+γ-rays group(Cells were subjected to 10μM BAY11-7082 30 mins, then irradiated with 900 MHz microwave, 1.5 Gy γ-rays given 4h after microwave exposure).The extent of primary DNA damage in the form of single strand breaks(SSBs) and double strand breaks(DSBs) was assessed immediately, using an alkaline comet assay and γ-H2 AX foci technique, respectively.4. The relationship of low dose microwave radiation, ROS production and activation of NF-κB.BMSCs were randomly divided into the following 3 groups:(a) un-exposed controls(cells kept in the incubator),(b) sham exposure(cells were cultured in microwave exposure system, but without microwave transmission),(c) MEL+ RF group(cells were subjected to 500 n M melatonin 4 h prior to microwave radiation).The level of NF-κB protein in both plasma and nucleus of BMSCs were determined with western blot 0, 0.5, 1, 2, 4 and 6 hours after the last microwave exposure.Results:1. There were no significant differences in tail length(TL)between control, sham and RF-group(P>0.05), and in contrast cells in γ-rays group showed significantly increased TL(P<0.0001). Compared to γ-rays group and Sham+γ-rays group, cells in RF+γ-rays group showed significantly decreased TL(P<0.0001). The results for the comet tail moment(TM) and γ-H2 AX foci/cell were similar with those of TL.2.(1) In RF group, a significantly increased ROS level was observed compared with that of the control and sham group(P<0.01) and this effect could be inhibited by pretreatment with melatonin.(2) Cells in RF+ γ-rays group showed significantly decreased SSBs and DSBs,but the cells in MEL+RF+ γ-rays group showed significantly increased SSBs and DSBs.3.(1) Compared with control group, cells in RF group showed a significantly increased expression of NF-κB.(2) Cells in RF+ γ-rays group showed significantly decreased SSBs and DSBs, but the cells in BAY+RF+ γ-rays group showed significantly increased SSBs and DSBs.4. There were no significant differences in the expressions of NF-κB between sham and MEL +RF group.Conclusions:1. 900 MHz microwave at 120 μW/cm2 power density could induce adaptive response, attenuate DNA damages caused by γ-rays in cultured mouse bone marrow stromal cells.2. 900 MHz microwave radiation could induce the production of ROS, activate NF-κ B, then induce adaptive response... |
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