The Role Of PARP-1 In Adaptive Response Induced By 900MHz Microwave Radiation In Mouse Bone Marrow Stromal Cells

Objective:To explore the role of PARP-1 in adaptive response induced by 900 MHz microwave radiation in mouse bone marrow stromal cells(BMSCs) exposed to γ-rays.Methods:1. Establishing cell model of adaptive response induced by 900 MHz microwave radiation with BMSCs.BMSCs were randomly divided into the following 6 groups: un-exposed controls, sham group(cultured in microwave exposure system, but without microwave exposure), RF group(irradiated with 900 MHz microwave at 120μW/cm2 power intensity, 3 hours/day for 5 days), γ-rays group(subjected to 1.5 Gy γ-rays), RF+γ group(irradiated with 1.5Gy γ-rays after microwave exposure), sham+γ-rays group(irradiated with 1.5Gy γ-rays after sham exposure). After exposure, the extent of primary DNA damage was measured using the alkaline comet assay.2. The expression of PARP-1 induced by 900 MHz microwave radiation in BMSCsBMSCs were exposed to sham-exposed(SH group), 1.5Gy gama-rays radiation(GR group) and 120μW/cm2 900 MHz radiofrequency fields, 3 hours/day for 5 days(RF group). SH and GR group were included as un-exposed and positive control group. The expression levels of PARP-1 mRNA and its protein levels were determined at different post-exposure times, viz., 0, 0.5, 1, 2, 4, 6, 8 and 10 hours, using RT-PCR and Western Blot analyses.3. Effects of PARP-1 on γ-rays induced DNA damages in BMSCsBMSCs were divided into the following groups:(1) unexposed control group,(2) RF group(900MHz at 120?W/cm2 power intensity for 3 hours/day for 5 days),(3) γ-ray group(acute 1.5 Gy γ-rays radiation alone),(4) RF+γ group(irradiated with 1.5 Gy γ-rays after microwave exposure),(5) RF+3-AB(cells were treated with 3-AB one hour before the last RF exposure on day 5),(6) RF+3-AB+γ group(cells were treated with 3-AB one hour before the last RF exposure on day 5, irradiated with γ-rays 3h after microwave exposure). After exposure, an aliquot of cells was immediately used for the alkaline comet assay to examine DNA damage, while the other aliquots were used to detect PARP-1 mRNA and protein expression levels.4. The role of PARP-1 on DNA damage repair in BMSCsBMSCs were exposed to the following 8 exposure conditions: unexposed control, SH, 900 MHz RF at 120?W/cm2 power intensity for 3 hours/day for 5 days, acute 1.5 Gy γ-radiation alone, RF+γ, SH+γ, RF+3-AB, RF+3-AB+γ. There was an interval of 3 hours between the last RF/SH and γ-ray exposure. PARP-1 mRNA expression was measured with RT-PCR, PARP protein level was analysed with western blot, alkaline comet assay was used to examine DNA strand breaks.Results:1. There were no significant differences between control, sham and RF group for TL and TM(p>0.05), while γ-rays group showed significantly increased TL and TM(p<0.0001). Compared to γ-rays group, cells in RF+γ group showed significantly decreased TL and TM(p<0.0001).2. BMSCs exposed to RF showed a significantly increased/up-regulated expression of PARP-1 mRNA and its protein levels at 0, 0.5, 1, 2, 4, 6, 8 and 10 hours post-exposure while such changes were not observed in SH-exposed cells.3. Cells exposed to RF showed a significantly increased PARP-1 mRNA expression and its protein levels compared with control group(p<0.001), and that effect was inhibited by pretreatment with 3-AB(p<0.01). Cells pre-exposed to RF showed significant decreased DNA damage compared with those exposed γ-radiation alone(p<0.001). However, when the cells were treated with 3-AB one hour before the last RF exposureand then exposed to γ-radiation(RF+3-AB+γ), the DNA damage was increased compared with those exposed to RF+γ(p<0.0001).4. Cells exposed to RF+γ showed significantly decreased DNA damage as well as faster kinetics of repair compared with those exposed to γ-radiation and SH+γ. However, cells exposed to RF+3-AB+γ showed increased DNA damage as well as slow kinetics of repair compared with those exposed RF+γ.Conclusions:1. 120μW/cm2 900 MHz microwave could induce adaptive response on DNA damage caused by γ-rays in mouse bone marrow stromal cells.2. 120μW/cm2 900 MHz microwave radiation is capable of up-regulating the PARP-1 expression, which contributes to efficient and faster of DNA repair. This is one of the potential mechanism of RF-induced adaptive response.