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

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 immediately, 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 decreased, 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. (authors)