人参皂苷Rg1对辐射致造血干/祖细胞衰老的影响及其机制

Effect of ginsenoside Rg1 on radiation-induced senescence of hematopoietic stem / progenitor cells and relevant mechanism

目的探讨人参皂苷Rg1对辐射致造血干/祖细胞(hematopoietic stem/progenitor cell,HSC/HPC)衰老的影响及其机制。方法将C57BL/6小鼠随机分为假照射组、照射组和照射+Rg1组,照射组与照射+Rg1组利用6.5 Gy的X射线全身一次性辐射小鼠。照射+Rg1组于照射前第7天起连续经腹腔注射人参皂苷Rg1 20 mg/(kg·d),照射后继续注射同剂量人参皂苷Rg1直至处死;照射组同时注射等剂量的生理盐水;假照射组小鼠处理同照射组,但不照射。辐射后不同时间点处死各组动物,改良免疫磁性吸附细胞分选(magnetic activated cell sorting,MACS)法分离、纯化骨髓Sca-1+HSC/HPC并计数;SA-β-gal染色检测衰老细胞百分率;流式细胞术分析细胞周期;造血祖细胞混合集落(colony forming unit-mixture,CFU-Mix)体外培养评价人参皂苷Rg1对辐射小鼠HSC/HPC衰老的影响;彗星试验测定细胞DNA损伤;并检测细胞内SOD活性和MDA含量。结果经MACS分离纯化后,Sca-1+HSC/HPC的纯度可达93.66%,活性可达99.4%。照射组Sca-1+HSC/HPC数量显著降低,且恢复缓慢,照射+Rg1组Sca-1+HSC/HPC数量下降在照射后第3天和第7天得到阻止,与照射组比较,差异有统计学意义(P<0.01或P<0.001);照射组SA-β-gal阳性细胞率明显高于假照射组和照射+Rg1组(P<0.001);照射组Sca-1+HSC/HPC与假照射组相比出现G1期阻滞,照射+Rg1组第3和第7天G1期细胞比例较照射组降低(P<0.05或P<0.01);照射组Sca-1+HSC/HPC形成CFU-Mix的数量明显低于假照射组(P<0.001),照射+Rg1组形成CFU-Mix的数量较照射组明显增加(P<0.001);照射组DNA彗星尾长和Olive尾矩均明显大于假照射组和照射+Rg1组(P<0.001);与假照射组相比,照射组Sca-1+HSC/HPC的SOD活性明显降低(P<0.001),MDA含量明显升高(P<0.001),与照射组相比,照射+Rg1组Sca-1+HSC/HPC SOD活性明显升高(P<0.01),MDA含量明显降低(P<0.001)。结论辐射损伤可导致HSC/HPC衰老;人参皂苷Rg1具有抗辐射致HSC/HPC衰老的作用,其机制可能与抑制辐射致HSC/HPC氧化应激反应,减少氧化应激介导的DNA损伤密切相关。本实验为人参皂苷抗辐射损伤致细胞衰老提供了实验依据。

Objective To investigate the effect of ginsenoside Rgl on the senescence of hematopoietic stem/progenitor cells （HSCs/HPCs） induced by radiation as well as the relevant mechanism. Methods C57BL/6 mice were randomly divided into sham radiation, radiation and radiation ＋ Rgl groups. The mice in radiation and radiation ＋ Rgl groups were exposed to total body irradiation （TBI） with 6. 5 Gy X-ray, while those in radiation ＋ Rgl group were injected i.p. with Rgl （20 mg/kg· d） once a day starting from 7 d before TBI until being killed, and those in radiation group were injected with physiological saline. However, the mice in sham irradiation group were unexposed to TBI, while were injected with physiological saline. The mice in various groups were killed at different time points after TBI, of which bone marrow Sea-1^＋HSCs/HPCs were isolated and purified by magnetic activated cell sorting （MACS）. The percentage of aged cells was de-termined by β-galactosidase（SA-β-gal） staining, while the cell cycle was analyzed by flow cytometry. The effect of Rgl on senescence of HSCs/HPCs of radiated mice was evaluated in vitro by colony forming unit-mixture（CFU-Mix） culture. The damage of cell DNA was determined by comet assay. Meanwhile, the SOD activity and MDA content were determined. Re-suits The purity and activity of Sca-1^＋ HSCs/HPCs after purification by MACS reached 93. 66% and 99. 4% respectively. The count of Sca-1^＋ HSCs/HPCs decreased remarkably and recovered slowly in radiation group. However, the count of Sca-1^＋ HSCs/HPCs recovered significantly in irradiation ＋ Rgl group on days 3 and 7 after TBI, which showed significant difference with that in irradiation group （P 〈 0. 01 or P 〈 0. 001 ）. The percentage of SA-β-gal positive cells in irradiation group was significantly higher than those in sham irradiation and irradiation ＋ Rgl group （P 〈 0. 001 ）. The percentage of cells at G1 stage was higher in irradiation group than in sham irradiation group. However, the percentage of cells at G1 stage in irradiation ＋ Rgl group on days 3 and 7 after TBI decreased as compared with those in irradiation group （P 〈 0. 05 or P 〈 0. 01 ）. The number of CFU-Mix was significantly higher in irradiation group was significantly lower than in sham irradia- tion group （P 〈 0. 001 ）, while was significantly higher in irradiation ＋ Rgl group than in irradiation group （P 〈 0. 001 ）. The DNA tail length and Olive moment in irradiation group was significantly larger than those in sham irradiation and irradia-tion ＋ Rgl group（P 〈 0. 001 ）. The SOD activity of Sca-1^＋ HSCs/HPCs in irradiation group decreased signficiantly （P 〈 0. 001）, while the MDA content increased significantly （P 〈 0. 001 ）, as compared with those in sham irradiation group. However, as compared with those in irradiation group, the SOD activity in irradiation ＋ Rgl group increased significantly （P 〈 0. 01 ）, while the MDA content decreased significantly （P 〈 0. 001 ）. Conclusion Irradiation induced the senescence of HSCs/HPCs, which was resisted by ginsenoside Rgl by a possible mechanism associated with inhibiting the oxidative stress reaction induced by irradiation and reducing the DNA damage mediated by oxidative stress. This study provided an experimental basis for delaying the irradiation-induced cell senescence by ginsenoside.