Study On The Inflammation Injury Of Irradiated Skin And Distant Organs By X-Ray Irradiation

Radiotherapy is one of the important methods to treat malignant tumor in clinical.Radiation therapy kills not only irradiated tumor cells,but also unirradiated cells around them,a phenomenon known as the "radiation-induced bystander effect," Its biological effects include DNA damage,cell apoptosis,inflammatory response,and cancer formation.The mechanisms and time effects of radiation-induced bystander effect are still unknown.Meanwhile,most of the current research results are focused on the cell level or the tissue level in vitro,but there are few animals experiments in vivo.The signal transduction pathway in vivo is not clear and still needs to be further studied.DNA damage plays an important role in the occurrence of bystander effect.Researches showed that ionizing radiation caused water molecules to ionize,forming free radicals that causes DNA double-strand breaks,eventually leading to cell apoptosis and the release of inflammatory factors.Studies have shown that inflammation played a key role in the early and late stage of ionizing radiation-induced bystander effects.NLRP3,as the early inflammatory factor and high mobility group protein B1(HMGB1),as the late inflammatory factor,have received wide attention in the research of inflammation.However,little is known about the relationship and mechanisms between DNA damage and two inflammatory factors in the radiation-induced bystander effect.At the same time,HMGB1-related drugs were used in the clinical treatment of radioactive skin injury,but there is no literature report on the injury of other parts of the body after irradiation.So in this study,on the basis of the acute radiation skin injury model established by the previous research of a dose of 38 Gy irradiation on the posterior hip skin of Wistar rats,the effects of radiation and drugs on DNA damage,expressions of NLRP3,HMGB1 and downstream pathways in the skin and immune organ thymus,non-immune organ liver of the irradiated rats,as well as the relationship among the three,were investigated.The main contents and results of this study are as follows:(1)To investigate the effects of radiation on DNA damage and inflammatory response in rat skin and distant organs(thymus,liver).Immunohistochemistry,immunofluorescence,ELISA,q RT-PCR and Western Blot were used to detect the DNA damage in the skin at different times after irradiation,as well as the expression and changes of NLRP3 inflammasome,HMGB1 and downstream factors.The expressions of DNA damage,NLRP3 inflammasome and HMGB1 in the distant organs(thymus,liver)of rats at specific times after irradiation were detected by q RT-PCR and Western Blot.The results showed that after radiation acted on the skin of rats,the expression of the oxidative stress marker 8-oxo G increased at 6 h after irradiation,leading to DNA damage and cell apoptosis,releasing inflammatory factors,and activating NLRP3 inflammasome,HMGB1 inflammatory factors and their downstream pathways.The expression of NLRP3 inflammasome reached peak at 48 h-15 d after irradiation,while the expression of HMGB1 reached peak at 15 d-18 d after irradiation.Meanwhile,the skin injury of rats affected the thymus and liver of distant organs through the release of a large number of inflammatory factors in serum.The expression of DNA damage and inflammatory responses in the skin peaked first,then the thymus,and finally the liver.(2)To investigate the effects of drugs on DNA damage and inflammatory response in rat skin and distant organs(thymus,liver)after irradiation.At 15 d when the most severe wound occured,rats were intraperitoneal injection of pro-inflammatory HMGB1 solution and anti-inflammatory glycyrrhizic acid(GA)solution,DNA damage,expression and change trends of NLRP3 inflammasome,HMGB1 and downstream pathways in the radiation area skin were observed by immunohistochemistry,immunofluorescence,ELISA,q RT-PCR and Western Blot.After injecting with pro-inflammatory HMGB1 solution and anti-inflammatory glycyrrhizic acid(GA)solution for 1 d,q RT-PCR and Western Blot were used to observe the expression of DNA damage,NLRP3 inflammasome,HMGB1 in the distant organs(thymus,liver).The results showed that HMGB1 solution promoted the expression of skin DNA damage,while glycyrrhizic acid(GA)solution inhibited the expression.Pro-inflammatory drug HMGB1 solution promoted the irradiation effects on NLRP3 pathway,while anti-inflammatory drug glycyrrhizic acid(GA)solution inhibited the irradiation effects on HMGB1 pathway.The pro-inflammatory drug HMGB1 solution promoted the damage of irradiation effects on the thymus,while the anti-inflammatory drug glycyrrhizic acid(GA)solution reduced the damage of irradiation effects on the liver.It can be seen from the experimental results: after the skin of rats was irradiated,oxidative stress occurred,causing DNA damage and cell apoptosis,inducing inflammatory response.Moreover,it can cause damage to non-irradiated organs through the release of a large number of inflammatory factors in the blood.Anti-inflammatory drugs can alleviate the injury of non-irradiated organs and provide a theoretical basis for clinical use.