The Mechanism Of Rat Fecal Microbiota As Bio-dosimeters For Acute Radiation Injury In Intestine

Objective Radiation-induced intestinal injury is mainly found in sudden nuclear accidents,and it is also one of the important complications caused by radiotherapy in clinical abdominal tumors.Intestine is one of the most sensitive tissues in response to acute radiation injury.During the period of irradiation,the stem cells and intestinal villi structures in the small intestine crypts are destroyed to a certain extent,resulting in destruction of the intestinal mucosa structure,impaired intestinal epithelial barrier function,and intestinal bacteria in the ectopic place,posing a serious threat to patient’s lifetime as well as quality of life.However,the pathogenesis of intestinal damage caused by ionizing radiation remains unclear.Therefore,the aim of this study was to investigate the effects of ionizing radiation on the expression of inflammatory factor proteins in intestine of rats and intestinal microflora,in order to study its possible mechanism.Materials and Methods Forty eight 2-month old rats were randomized into radiation group and sham control group.Radiation group received whole body irradiation at a single dose of 4 Gy,8 Gy,12 Gy.The intestine were separated from rats at 1h,6h,1d,and 3d after irradiation.Western-Blot was applied to detect the protein levels.The status of intestinal microflora was detected by 16 s rDNA fluorescent quantificative PCR.HE staining was performed to observe the villous and crypt appearance of the small intestine under electron microscope.Dates were expressed with mean ± SD and analyzed with two tiered Student’s t test or one-oway ANOVA by Oringin(version 8.0).A value of P < 0.05 was considered to be statistically significant.Results 1.Protein levels of IL-1β,IL-6 and TNF-α increased significantly.The higher the dose,the later the peak time appeared,and then gradually decreased.In addition,the values in radiation groups were still higher than the control group after 3 days.2.16 s rDNA results showed that the structure of gut microbiota significantly changed after irradiation.The abundance of Bacteroidales S24-7 group(conditional pathogenic bacteria)increased significantly,and the abundance of Lachnospiraceae and Ruminococcaceae significant decreased.3.Three days after irradiation,the villus lengths of the small intestine in the control group,4Gy group,8Gy group and 12 Gy group were(303.84±42.19),(242.95±25.29),(149.65±19.83),(68.77±13.96)μm respectively.The irradiation groups were significantly lower than the control group(p<0.05).The number of intestinal crypts in the control group,4Gy group,8Gy group,and 12 Gy group was(138.45±10.90),(98.86±9.62),(67.38±5.77),(24.75±2.82),Compared with control group,the number of intestinal crypts significantly decreased after irradiation(p<0.05).Conclusion Under the experimental condition,the expression of IL-1β,IL-6,and TNF-α after whole body irradiation may play an important role in the damage of intestinal tissue caused by ionizing radiation.After the whole body irradiation,the intestinal microbiota structure changes significantly,the abundance of the pathogenic bacteria genus is significantly increased and the abundance of the probiotic bacteria significantly reduced,which may be related to the expression of IL-1β,IL-6,and TNF-α.Conditioned pathogens in the feces Bacteroides S24-7 group can be used as a potential biomarker of radiation damage in the intestine.