Abstract:
Objective To study the protective effects of N-oxalyl-D-phenylalanine (NOFD) on the radiation injury of hematopoietic system in mice.
Methods Eighteen healthy C57BL/6J male mice aged 6−8 weeks were divided into three groups with six mice each according to randomized block design: a control group, a 4 Gy γ ray whole body irradiation group (TBI group), and a 4 Gy γ ray whole body irradiation + 5 mg/kg NOFD group (TBI+NOFD group). The mice in the TBI+NOFD group were intraperitoneally given with 5 mg/kg NOFD at 2, 16 h before irradiation, and 3 d after irradiation, respectively, while the control group and TBI group were intraperitoneally given with the same amount of normal saline at the same time as that in the TBI+NOFD group. The number of peripheral blood cells in each group of mice were analyzed using a blood cell counter. The percentage of B cells, T cells, and myeloid cells in peripheral blood were detected via flow cytometry. The number and percentage of hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) in bone marrow cells were detected via flow cytometry. Levels of phosphorylated histone H2AX (γ-H2AX) and mitochondrial reactive oxygen species in bone marrow cells were detected via flow cytometry. The proliferation ability of bone marrow cells was evaluated by counting colony-forming units-granulocyte-macrophage (CFU-GM) and colony-forming units-spleen(CFU-S). Student's t test was used for comparison between two groups.
Results Compared with that in the TBI group, the number of peripheral blood erythrocytes in the TBI+NOFD group substantially increased ((9.05±0.16)×109/mL vs. (9.57±0.15)×109/mL). The percentage of T cells increased ((11.54±0.20)% vs. (15.31±1.88)%), whereas the percentage of myeloid cells decreased ((32.67±2.87)% vs. (24.90±2.19)%). The number of HSC increased ((2.24±0.54)×103/femur vs. (6.77±1.67)×103/femur), whereas the percentage of HSC and HPC in bone marrow cells significantly increased ((0.09±0.02)% vs. (0.59±0.13)%, (0.62±0.14)% vs. (1.82±0.43)%; t=1.998−3.633, all P<0.05). The median fluorescence intensity (MFI) of mitochondrial reactive oxygen species (MitoSOX) in bone marrow nucleated cells (BMNC) and HPC in the TBI+NOFD group was significantly lower than that in the TBI group ((6.66±0.56)×103 vs. (3.19±0.25)×103, (2.51±0.46)×103 vs. (1.20±0.35)×103; t=6.350, 2.282, both P<0.05). Moreover, the MFI of γ-H2AX in BMNC, HPC, and HSC in the TBI+NOFD group was significantly lower than that in the TBI group ((10.25±0.77)×103 vs. (7.22±0.15)×103, (18.37±2.52)×103 vs. (12.44±0.34)×103, (26.05±2.64)×103 vs. (17.16±1.20)×103; t=4.356, 2.577, 3.070, all P<0.05). Compared with those in the TBI group, CFU-GM (12.33±1.48 vs. 24.00±3.92) and CFU-S (6.00±1.07 vs. 10.83±1.01) in the TBI+NOFD group significantly increased (t=2.788, 3.288; both P<0.05).
Conclusion NOFD exerts an obvious protective effect on the radiation injury of hematopoietic system in mice.