低剂量辐射诱导人骨髓间充质干细胞分子在P38MAPK通路的信号机制

Signal transduction mechanism on hormesis of human marrow mesenchymal stem cell induced by low dose radiation

目的:探讨低剂量辐射(LDR)对人骨髓间充质干细胞(MSCs)的增殖作用及相关信号传导机制。方法:将培养的人骨髓MSCs及K562细胞分别分成3组:对照组、照射组和SB203580组。3组照射剂量均为75 mGy,观察照射后24 h总P38MAPK、P53、P21表达水平及增殖指数(PI)的变化,同时观察K562及MSCs细胞75 mGy照射后即刻和4、12及24 h磷酸化P38MAPK(p-P38MAPK)表达。SB203580组根据培养液量将SB203580调节成5μmol.L-1终浓度,于实验前1 h加入。结果:人骨髓MSCs细胞p-P38MAPK表达以75 mGy照射后12 h达高峰;照射后24 h P53和P21蛋白表达水平下降,PI增高,但总P38MAPK无变化,SB203580抑制P38MAPK激酶活性后,P53、P21表达上调,PI下降;K562细胞p-P38MAPK、P53、P21、总P38MAPK表达水平及PI在75mGy照射后24 h均无任何改变,加SB203580后PI略有下降,P21蛋白表达略有上升。结论:LDR可诱导人骨髓MSCs增殖兴奋性反应,这种反应是通过P38MAPK信号通路介导的,且与P21下降有关,这种P21下降存在P53依赖性的。

Objective To investigate the hormesis effect on human marrow mesenchymal stem cells（MSCs）induced by low dose radiation（LDR） and its related signal transduction mechanism.Methods Human marrow MSCs and K562 cells were divided into control group,radiation group and SB203580 group.The dose of radiation was 75 mGy in three group.The expression levels of P38MAPK,P53,P21 and proliferation index（PI） were observed at 24 h after radiation,The expressions of phosphor-P38MAPK（p-P38MAPK） of K562 cells and MSCs were observed immediatly,4,12 and 24 h after radiation.SB203580 was adjusted to 5 μmol·L-1 end concentration according to the culture liquid volume in SB203580 group,and was added at 1 h before experiment.Results The expression of p-P38MAPK of human MSCs attained peak at 12 h after 75 mGy radiation,the expression levels of P53 and P21 protein were dereased,PI was increased,P38MAPK didn＇t change;P53 and P21were increased,PI was decreased after P38MAPK kinase activity was inhibited with SB203580;the expression levels of p-P38MAPK,P53,P21,P38MAPK and PI of K562 cells didn＇t change at 24 h after 75 mGy radiation;PI was slightly decreased,P21 was slightly increased after addition of SB203580.Conclusion LDR can induce hormesis of human MSCs,the proliferation hormesis is mediated by P38MAPK signal and related to down-regulation of P21 which is P53 dependent.