Recombinant Human Granulocyte Colony Stimulating Factor (rhg-csf) In The Neutron Severe Bone Marrow Form Of Acute Radiation Sickness Than The Experimental Treatment Of Beagle Dogs

At present, nations which own nuclear weapons still insist on the core thinking of nuclear threaten. Nuclear weapons are deemed as important safeguard to protect nation safety and benefits. Nations which do not own nuclear weapons are actively developing nuclear weapons. Dangers of our country threatened by nuclear weapons from perimeter countries are increasing. In addition, terror activities are outbreak currently. Simple explosion devices maybe used to destroyed nuclear facilities. Besides, in the process of application of nuclear energy and nuclear technology, criticality accidents occurred occasionally due to the operation fault and so on. Either nuclear weapon explosion or great nuclear radiation accidents would result in large crowd received different ratio of mixed fission neutron and gamma ray radiation. Numerous studies demonstrated that the higher the percentage of neutrons, the more severe the biologic response. In order to prepare for nuclear radiation medical emergency, it is important to carry out sdudies on the treatment of high ratio neutron-gamma irradiation evoked acute radiation sickness (ARS).It is well known that hematopoietic injury is the basic injury of myeloid ARS. At present, recombinant hematopoietic growth factors synthesized through gene engineering recombination technology are the choice drug to promote hematopoietic recovery in ARS treatments. Among the total, recombinant human granulocyte colony-stimulating factor (rhG-CSF) could promote proliferation and differentiation of bone marrow hematopoietic cells into granulocyte colony, induce terminal differentiation of neutrophils and enhance neutrophils'function. RhG-CSF had positive therapeutic effect for gamma ray induced myeloid ARS and received international recognition for its use in ARS treatment. But reports on the treatment of rhG-CSF in severe myeloid ARS induced by high proportion neutron-γray irradiation have rarely been seen yet. Moreover, there were many controversial issues on the usage and dosage of rhG-CSF. We carried out two aspects work to answer the questions above.First, Beagles were exposed to a unilateral irradiation with a single dose of 2.3Gy 90% neutrons to prepare animal model of neutron severe myeloid ARS. The results showed that 75% animals in the irradiation control group were died. The survival time of decedents was 10.8 days. All of the irradiated dogs showed early signs of gastrointestinal syndromes including loss of appetite, vomiting and diarrhea, one of whom even showed bloody diarrhea. They also exhibited profound cytopenia. Histopathologic evaluation of sternum of died animals showed that there were few hematopoietic cells left in cavitas medullaris accompanying haemorrhage. Analyzed the conditions mentioned above, 2.3Gy neutron unilateral irradiation mainly induced a severe hematopoietic syndrome in this study. Compared with isoeffect dose gamma ray irradiated Beagles, the incidence of early death (within 7 days) in 2.3Gy neutron radiated dogs increased, death time was advanced, the time occurred early gastrointestinal symptom, infection and clinical bleeding was earlier and the degree was more severe, and injuries on skin were more serious. Peripheral blood leucocytes decreased more rapidly, but the nadir of leucocytes under both radiation conditions was equivalent. Moreover, we also found that the blood clotting system was in hypercoagulabale state in the early days after 2.3Gy neutron irradiation, and became hypocoagulabale at acme. Changes of blood clotting function were mainly on intrinsic coagulation pathway. Fibrinogen increased markedly during the course of disease. Platelet counts and aggregation function were decreased at the same time. The main cause of death maybe the hypocoagulabale state and the augmentation of capillary fragility and permeability at the early stage after irradiation.After the model was prepared, one group of animals was administered 10μg rhG-CSF/kg/d subcutaneously daily from day 0 to day 20 starting within 1 hour post exposure. Results indicated that low dose rhG-CSF administered continuously in combination with supportive care could improve the quality of life of irradiated animals, enhance the nadirs of peripheral blood leucocyte and neutrophil counts, effectively control the infection syndrome, and make irradiated dogs survived eventually (Compared with irradiation control group, P<0.05). Additionally, we also found that low dose rhG-CSF administered daily could also correct hypercoagulabale state induced by 2.3Gy neutron irradiation at the early time post exposure, shorten the thromboplatin generation time, accelerate the formation speed of coagula, improve intrinsic coagulation functional disorder, down regulate the abnormal increase of fibrinogen, and ameliorate platelet aggregation function. Coagulation disorders of irradiated dogs at early time and acme were improved accordingly, which provided an important clue for treatment of hemorrhage at early stage and acme of ARS.Another group of animals was subcutaneously injected with rhG-CSF at a dose of 200μg/kg early at 0.5 and 24 hours post irradiation. Results showed that twice injection of rhG-CSF early at the first 24 hours in combination with supportive care could also reduce duration of neutropenia, enhance neutrophil nadir and promote neutrophil recovery on the whole, and rescue lethally (2.3Gy neutron) irradiated canines from hematopoietic death (Compared with irradiation control group, P<0.05). Moreover, the apoptosis of peripheral blood cells decreased. The numbers of colony-forming cells (CFU-GM, CFU-E, and BFU-E) in peripheral blood of rhG-CSF treated canines were increased on day 3. In addition, we also found that high dose rhG-CSF early intervention could not only mitigate the injuries of immune organ, but also reinforce the immune function of spleen. What's more important is that all canines treated with rhG-CSF achieved hematopoietic reconstruction, showing that the quantity and density of myeloid elements were normal in view of pathological section of sternum. The results indicated that rhG-CSF enhanced hematopoietic recovery through mobilizing myeloid elements into peripheral blood early and mitigate the effects of cell apoptosis and necrosis on bone marrow hemopoietic microenvironment.Finally, in order to observe the non-hematopoietic organ damage induced by 2.3Gy neutron irradiation, pathohistology examination and serum enzymatic methods were used. Results showed that gastrointestinal impairments evoked by 2.3Gy neutron were mainly functional disorder, while structural changes were not apparent. The early changes of immune system were cell population diminished, spleen and lymphoid node atrophied, structure vanished and immunoglobulin production suppressed. Administration of rhG-CSF could promote immune tissues recovery, especially high dose rhG-CSF. Pulmonary impairments induced by mixed fission neutron-gamma irradiation were more severe than that of simple gamma ray, but the pathological changes were basically in accordance with gamma ray. Genital system and kidney damages in 2.3Gy neutron irradiated dogs could recover on their own. However, the dropsy around the minute blood vessel in cerebral cortex was hardly to recover. 2.3Gy neutron irradiation provoked myocardial function impairments at early stage, but did not provoke pathohistology changes.In conclusion, combination of supportive care and low dose rhG-CSF daily injection or high dose rhG-CSF early intervention was effective in alleviating neutropenia and promoting reconstitution of myelopoiesis, and enhanced survival of 2.3Gy mixed neutron and gamma ray irradiated dogs.