Preliminary study on γ-ray induced expression and regulation of calcium-binding protein S100A8 in mouse macrophage cell line RAW264.7

Objective To study the expression and regulation of S100A8,a calcium-binding protein,in mouse macrophage cell line RAW264.7,which was used as cellular model of radiation injury.Methods RAW264.7 cells were exposed to γ-ray irradiation and/or lipopolysaccharide(LPS),then the mRNA level of S100A8 was detected by RT-PCR and real-time quantitative PCR methods.Real-time quantitative PCR was used to investigate the mRNA level of S100A8 in H2O2 or camptothecin treated cells.The second messenger in signal-transduction pathway was explored.To find γ-ray irradiation response element in the region 5' to the transcription start site,a series of 5' deletion fragments of this sequence linking luciferase reporter gene were constructed,and relative luciferase activity was measured after transfection and irradiation.Results The expression level of S100A8 mRNA was increased by irradiation.The expression of S100A8 in H2O2 treated cells was increased.However,no change was found in the expression of camptothecin treated cells.The expression level of luciferase reporter gene didn't change either after irradiation.Conclusions It has been revealed in present study that γ-ray irradiation or LPS challenge can induce the mRNA expression of S100A8,and that the cooperative effect between γ-rays and LPS can further increase the mRNA expression of S100A8 in RAW264.7.The second messenger of γ-ray induced S100A8 expression appears to be ROS rather than DNA damage.The responsive element to γ-ray radiation was not at position-877 to 0.It is likely that γ-ray radiation may regulate the expression of S100A8 by increasing its mRNA stability rather than influencing transcription frequency.