Protective Effects Of Gelsolin On Acute Radiation Sickness

With more and more widely utilize of nuclear energy in economic and military, the underlying damage of ionization radiation to human being increases. Populations and emergency staff will be exposed to medium and high doses of ionizing radiation in a variety of unexpected and outbreak radiation accident so that pathological changes of acute radiation injury will emerge in their body. Therefore, safely and effectively rescuing of exposed population becomes an important issue to be solved in radiation medical research. Acute radiation sickness is a severe systemic disease and traumatic syndrome which is caused by exposing to large doses of ionizing radiation (IR) in a short time. According to the quantity of the radiation dose, acute radiation sickness can be divided into three types including the bone marrow type (exposure doses≤10Gy), intestinal type (10Gy≤exposure doses<50Gy) and brain type (exposure doses≥50Gy). Among the three categories, the bone marrow acute radiation sickness can also be divided into light degree (dose range 1-2Gy), media degree (dose range 2-4Gy), heavy degree (dose range 4-6Gy) and critical degree (6Gy≤dose≤10Gy) according to exposure doses. Currently, the therapeutic principle of hematopoietic reconstruction is only effective to bone marrow acute radiation sickness of the light and media degree and is not very satisfactory in the treatment over heavy degree in practicing. In the treatment of heavy type acute radiation sickness although hematopoietic reconstruction is successful the patient finally dies from multiple organ failure. Since people know a little about the occurrence, development and regulating factors of the multiple organ failure induced by radiation till now there are not good ways to solve the problems of radiation-induced multiple organ failure. To address these issues it is necessary that catches up development of the science and technology and renews our past ideals about pathological developing process of radiation injury. Meanwhile, accurate and in-depth scientific researches with new theories and methods should also be launched. Solutions of these problems have great significance in rising levels of prevention and treatment of radiation injury and in promoting ability of safely and effectively using nuclear energy in our nation.Gelsolin is a member of the gelsolin superfamily and belongs to the ABPs (actin binding proteins).It widely distributes in tissues and cells of mammals and non-mammals and its molecular weights is about 82-84KDa. It exists as both cytoplasmic (cGSN) and plasma isform (pGSN) originating from the same gene. Geloslin has primary biological function to regulate the actin dynamics in a Ca2+-dependent manner so that it plays a key role in the conversion from cytoplasm sol state to gel state (gel). In addition to modulate actin reorganization, gelsolin also play important roles in many cell processes such as cell movement, cell viability, apoptosis, ion channel regulation and some signal transduction ways. It has been reported that pGSN significantly decreases in a variety of injuries and diseases because abnormal accumulation of large quantity of blood-actin released from the damaged cells and tissue needs to be scavenged by gelsolin. However, in many pathological situations the actin was so much in amount that gelsolin was used up soon to eliminate. The excess actin in blood vessel can induce microthrombus formation and blood vessel injury. Whereas delivering the patients and experimental animals with gelsolin as an actin scavenging reagent can significantly relieve the progress of inflammation and improve the prognosis. A number of studies suggested that gelsolin might involve in the pathological processes of acute injuries, chronic and genetic diseases and play active protective roles in the process of injuries and diseases.The pathological development of acute radiation injury shows microcirculation disturbance in the early stage and extensive bleeding and severe infection in the late stage. Are these pathological changes correlate with massive actin released from the damage cells induced by radiation? Can gelsolin engage in the developing process of the acute radiation sickness pathology as a protein of plasma actin scavenging system? Can the exogenous gelsolin supplement scavenge the poisoning effect induced by actin accumulation and protect the body from irradiated injury? Clarification of these issues will help us to deepen our understanding on the pathological development of acute radiation injury and regulatory and influencing factors that direct us to seek new ways of improving or mitigating the severe acute radiation sickness.To comprehend the relationship between gelsolin changes and the prognosis of acute radiation sickness, we observed changes occurring in the expression and content of cGSN and pGSN in radiation-sensitive cells and mice after irradiation with different doses and evaluated the protect effects of gelsolin on the hemorrhagic injury, oxidative damage and survival rate in irradiated mice by detecting some biochemical indicators such as PT,APTT,FIB,GSH,MDA and SOD.Research contents:1. Observing the relationships between changes of two gelsolin isoforms expression and the acute radiation injury. 2. Evaluating the effects of exogenous geloslin delivered to irradiate mice on the hemorrhagic and oxidative damage as well as mice survival rate.Methods:1. Western blot method was used for detecting the changes of cGSN expression in HIEC at different times after the cells were exposed to 8 and 12Gy irradiation; Commercial mouse gelsolin ELISA kit was used for detecting the changes of pGSN content in the plasma of BALB/c mice irradiated with 4 and 8Gy at different times.2. A blood coagulation instrument was used for determining of coagulation indicators of irradiated mice after recombinant human gelsolin was administrated twice within 24h postirradiation.3. Commercial GSH, SOD and MDA assay kits were respectively used for determining the oxidative and antioxidant indicators of irradiated mice after recombinant human gelsolin was administrated twice within 24h4. Observation the 30-day survival rate of the irradiated mice which recombinant human gelsolin was given.5. Statistical analysis was performed by SPSS 13.0 softwareResults:1. Relationships between changes of two gelsolin isoforms expression and the acute radiation injury.Lower pGSN levels in irradiated mice exposed with 4Gy and 8Gy radiation comparing to the non-irradiated mice were observed. The changes of pGSN at 24h,48h and 72h post-radiation in 4Gy and 8Gy radiation group were both statistical significant to the normal group (P<0.05). The pGSN decreased more pronounced at immediately and 72h post-radiation in 8Gy irradiation group than those in 4Gy irradiation group. The relative changes of cGSN in irradiated HIEC in vitro with 8Gy and 12Gy respectively were determined at the indicated times. To the 8Gy radiation group, the relative level of cGSN was below the normal level from 2h to 12h post-radiation but above the normal level at 24h after radiation, only the change of 12h postirradiation was significant difference (P<0.05). To the 12Gy radiation group, the relative level of cGSN was lower than normal level at 2h post-radiation but higher than the normal level from 4h to 24h after radiation. Differences of 6h and 12h time points versus the normal level respectively were statistical significant (P<0.05).2. The effects of exogenous geloslin on hemorrhagic damage induced by radiation. On the day from 4d to 7d after mice exposed to 6Gy, the PT and APTT values in plasma were significantly raising in gelsolin supplement groups (P<0.05) but FIB value were lower than those of irradiated control groups (P>0.05). From 14d to 18d postirradiation, the value of APTT,PT and FIB in gelsolin supplement groups were lower than those of only irradiated control groups, but only APTT value had prominent differences (P<0.05).3. The effects of exogenous gelsolin on oxidative damage induced by radiation.Levels of GSH and SOD in plasma of gelsolin treated mice after exposure to 6Gy radiation were conspicuous higher than those in control groups only by irradiation at 2d and 7d (P<0.05), whereas MDA level was significantly lower than that in the control groups only by irradiation (P<0.05).4. The effects of exogenous gelsolin on the survival rate of the irradiated mice.30-day survival rate of gelsolin treated mice was increased by 30% comapring to the non-treated mice (P>0.05)Primery conclusions:1. Lower pGSN levels in irradiated mice indicated that pGSN level was declined in acute radiation injury. The decreasing extent of pGSN is positive correlated with the radiation dose and the higher exposure dose, the poorer recovery of gelsolin level by the body itself. The relative changes of cGSN in HIEC postirradiation with 8Gy and 12Gy respectively had different variation tendency at the indiated times. The expression of the cGSN change may have a certain relationship with the radiation dose. Expressed as the cGSN might be up-regulated induced by a large dose irradiation, but to a relative small dose, its expression may be increased at a longer time after radiation. Clarification the relationship between the cGSN and radiation injury need to be a further in-depth study;2. Exogenous gelsolin could not improve the bleeding trend indicated by PT and APTT indexes in the early phase of pathological development of acute radiation injury but could markedly improve the bleeding trend induced by radiation in the later phase of the pathological development of acute radiation injury.3. The concentration of GSH and SOD increased but MDA, a lipid peroxidation product, decreased in the gelsolin treated mice after radiation indicated that gelsolin have some protective effects on oxidative damage induced by radiation. 4.30-day survival rate in gelsolin treated mice was 30% higher comapring to the non-gelsolin treated mice. The result indicated that gelsolin might be able to improve the survival rate of irradiated mice.