The Hemoprotective Effects Of A Rotary Magnetic Field In Mice Exposed To Irradiation

In course of nuclear war, nuclear radiation accident and radiation therapy of tumor, acute radiation syndrome (ARS) can be evoked by ionizing radiation. The treatment of ARS is the most important in the military medicine and radiomedicine, and hematopoietic damage is the fundamental injury of ARS. Therefore, the key problem in improving treatment of ARS is reducing the hematopoietic irradiation injury and promoting the hematopoietic repair. Departed findings had indicated that magnetic field had the effects of promoting the proliferation and differentiation of osteoplast, increasing the synthesis and secretion of the bone morphogenetic proteins (BMPs), bone alkaline phosphatase (BAP) and ecto-osteoblastic groundplasm. Most recently, some researches point out that the osteoplast is one of the important regulative compositions of the marrow hemopoietic microenvironment. All of these indicated that magnetic field might play a regulative role in hemopoietic microenvironment. In this research, we studied the rotary magnetic field (RMF) hemoprotective effects on radiation-injured mice and investigated the possible mechanisms. OBJECTIVE: To study the RMF hemoprotective effects on radiation-injured mice.METHODS:1. 94 male BALB/c mice were randomly divided into a control group and a magnetic treatment group according to the body weight. Then both groups were randomly divided into four groups, respectively. The mice were received total body irradiation (TBI) with 0Gy, 6Gy, 8Gy and 10Gy 60COγrays. The treatment group was treated with RMF for one and half an hour at a time, twice a day. The intensity of RMF was 0.6T. The 30-day survival rate and surviving days were observed.2. 132 male BALB/c mice were randomly divided into four groups: a normal group (N), a magnetic treatment group (M), an irradiation group (R) and an irradiation combining magnetic treatment group (R+M). Mice in the N group received no treatment. Mice in the R and R+M groups received TBI with 6Gy 60Coγrays. Mice in the M and R+M groups were treated with a RMF for one and half an hour at a time, twice a day, totally for 30 days. The frequency was 7.83Hz and the intensity was 0.6T.(1) On day 0, 5, 9, 15, 21 and 30, the subjects'peripheral blood cells were counted.(2) On day 9, 23 and 30, the number of bone marrow nucleated cells (BMNCs), colony forming unit-spleen (CFU-S), spleen-body ratio, the cell cycle and apoptosis of bone marrow cells were measured.(3) The HE staining of femur sections and the expression level of bone morphogenetic proteins (BMP2/4) in the bone marrow were evaluated.(4) On day 9, 23 and 30, the subjects'serum SOD activity and MDA content were determined. (5) On day 9, 23 and 30, the HYP contents of lung were determined and the HE staining and ultramicrostructure of lung sections were observed.RESULTS:1. The 30-day survival to different radiation dosesThe RMF treatment increased the survival rate and duration of the 6Gy dose irradiated mice, but it didn't increase the survival rate and duration of the mice irradiated with 10Gy and 8Gy doses. After RMF treatment, the survival rate of 6Gy dose irradiated mice increased from 21.41% to 71.43% (control vs. magnetic treated). As to the surviving days, the treatment group was (24.93±8.43) days and higher than that of control group (17.07±7.70 days).2. The correlative indexes of haematopoiesis(1)There was no remarkable difference between the N group and the M group in the number of blood cells, BMNCs and CFU-S (P>0.05). The R+M group and the R group compared with the N group and the M group, there were significant differences (P<0.05).(2) The RMF treatment increased the peripheral blood cells numbers of the R+M group. The number of BMNCs, CFU-S, and the proportation of G2+M phase in the R+M were markedly higher than that of the R group on the 9th day (P<0.05). Furthermore, the spleen index in the R+M group was also higher than that of the R group on the 23rd day (P<0.05). The proportation of the apoptosis of bone marrow cells in the R+M group was lower than that of the R group on the 9th day (P<0.05).(3) RMF could hasten the recovery of the bone marrow tissue and improve the expression level of BMP2/4 in the radiation-injury mice.(4) The rotary magnetic field could enhance the SOD activity and decrease the MDA content in the radiation-injured mice serum. However, there were little changes of the free radicals in the mice exposed to the RMF which were not irradiated. On the 9th day, the serum SOD activity of the R+M group was (272.602±34.058) U/ml, higher than that of the R group (229.611±42.433 U/ml) (P<0.05). The serum MDA content of the R+M group was (24.875±7.246) nmol/ml, lower than that of the R group (32.396±6.855 nmol/ml) (P<0.05). The R group compared with the M group and the N group, the serum SOD activity decreased and the MDA content increased (P<0.05). On the 23rd day, the serum MDA content of the R+M group was lower than that of the R group (16.494±3.912) vs. (25.000±7.266) nmol/ml and they were higher than that of the M and the N groups. There were no statistical differences of the two indexes between the M and the N groups at the same time.(5) Pathological change of lung tissue: HE staining showed that in the 9th day after radiation, there are pulmonary edema and pneumonia of radiation lung injury in the R and R+M groups.Microstructure of lung tissue: transmission electron microscopy results indicated that collagen fibers were increased and radiation pneumonia appears locally in lung tissues after radiation.CONCLUSION:In these experimental conditions, the RMF treatment had an obviously protective effect against the effects of 6Gy 60COγirradiation, and it accelerated the recovery of hematopoiesis and the hematopoietic microenvironment in mouse bone marrow. There was no significant effect of the RMF on the normal mice'hematopoietic function. The possible mechanism was that RMF could affect the haemopoietic stem cells, hemopoietic microenvironment, and the regulation of bone marrow cell cycle, apoptosis and the serum free radicals. The RMF treatment didn't evoke or add the lung injury in mice.