The Preliminary Application of Faeces Microbiome as Biodosimeters of Intestinal Acute Radiation Injury

Abstract

Intestine is one of the most sensitive tissues in acute radiation injury(ARI）characterized by infection, diarrhea and lethality. Development of robust biodosimeters based on individual biological response is crucial for accurate assessment of exposure level and important decisions of medical therapy in Intestinal ARI. In our study, with the increase of radiation dosage, faeces flora constitute revealed corresponding variation tendency in accord with Intestinal radiotoxicity ,including diarrhea and weight decline, intestinal proliferation inhibition and DNA damage, apoptosis and inflamation induction. Because of the feasibility in dosage prediction and evaluation of intestinal ARI, such results supported the preliminary application of faeces microbiome as biodosimeters of intestinal ARI. A total of 120 adult SD rats (SPF) were randomly divided into four groups and received respectively whole-body exposure of 6MeV electron beam, namely 0, 4, 8 and 12Gy. The rats were sacrificed at 24h post-radiation. Faeces flora constitution was analyzed with 16SRNA gene sequencing. We evaluated the rats’ general condition by diarrhea and weight, lethality observation. Intestinal proliferation and DNA damage, morphology were respectively examined with Brdu staining, γ-H2AX staining and HE staining. Protein expression was judged by Western blot. Endotoxemia was tested by serum lipopolysaccharide (LPS) with limulus chromogenic assay. A P-value＜0.05 was considered statistically significant. Faeces flora constitution varied corresponding to the radiation dosage of 0, 4, 8 and 12Gy. The decreased rate of faeces flora proportion was as follows: Prevotella (36%,53%,76%), Ruminococcus (24%,33%,81%), Bifidobacterium (61%,89%,95%), Lactobacillus (54%,88%,92%), versus control group. The increased proportion of Bacteroides and Enterubacterium was 0.4%, 1.2%, 3.1 %and 0.7%, 2.8%, 3.6%, versus control group. The ratio of Enterubacterium to Bifidobacterium ranged from 0.26 to 1.6,15,41. With the variation tendency of radiation dosage and faeces flora constitute, intestinal radiotoxicity involving diarrhea and weight decrease, lethality exacerbated rapidly. More and more significant inhibition of intestinal proliferation and obvious DNA damage were observed, accompanied by increasing expression of apoptosis protein caspase3 and inflammatory factors like IL-1β,IL-6,TNFα (p < 0.05). Radiation caused the most dramatic morphology destruction and endotoxemia in the last group than others (p < 0.05). Our study demonstrate that faeces microbiome as biodosimeters is relatively stable and convenient for sample collection compared with conditional technologies ,which may bring about fast and accurate dosage prediction and radiotoxicity evaluation for intestinal ARI .This will provide a proof of principal for future precision medicine of ARI.