Prophylactic feeding with immune-enhanced diet ameliorates chemoradiation-induced gastrointestinal injury in rats

Screening of radiation gastrointestinal injury biomarkers in rat plasma by high-coverage targeted lipidomics

INTRODUCTION

In the event of radiological accidents and cancer radiotherapies in clinic, the gastrointestinal (GI) system is vulnerable to ionizing radiation and shows GI injury. Accessible biomarkers may provide means to predict, evaluate, and treat GI tissue damage. The current study investigated radiation GI injury biomarkers in rat plasma.

MATERIAL AND METHODS

High-coverage targeted lipidomics was employed to profile lipidome perturbations at 72 h after 0, 1, 2, 3, 5 and 8 Gy (⁶⁰Co γ-rays at 1 Gy/min) total-body irradiation in male rat jejunum. The results were correlated with previous plasma screening outcomes.

RESULTS

In total, 93 differential metabolites and 28 linear dose-responsive metabolites were screened in the jejunum. Moreover, 52 lipid species with significant differences both in jejunum and plasma were obtained. Three lipid species with linear dose-response relationship both in jejunum and plasma were put forth, which exhibited good to excellent sensitivity and specificity in triaging different exposure levels.

DISCUSSION

The linear dose-effect relationship of lipid metabolites in the jejunum and the triage performance of radiation GI injury biomarkers in plasma were studied for the first time.

CONCLUSION

The present study can provide insights into expanded biomarkers of IR-mediated GI injury and minimally invasive assays for evaluation.

Irradiation-Induced Intestinal Damage Is Recovered by the Indigenous Gut Bacteria Lactobacillus acidophilus

The intestinal tract is one of the most sensitive organs following irradiation. The protective effect of specific indigenous microbiota on irradiation-induced damage to intestinal epithelial cells has not been reported. Mice were irradiated with a single dose of 6 Gy of gamma rays. The intestinal damage was analyzed by histopathology. Intestinal stemness and differentiation were determined by intestinal organoid culture. Microbiota community was observed by high-throughput 16S rRNA gene sequencing and oligotyping analysis. We showed that distal small intestine was damaged by sublethal dose of gamma irradiation. Intestinal organoids derived from the irradiated mice showed defects in budding and mucin expression, suggesting the detrimental effect of irradiation on the intestinal stemness and differentiation. In addition, irradiation reduced intestinal immunoglobulin A level, concomitant with decreased microbiota diversity based on our high-throughput 16S rRNA gene sequencing data. Especially, the relative abundance of Lactobacillus was reduced at early time point post-irradiation; however, it was recovered at late time point. Oligotyping analysis within the Lactobacillus genus indicated that Lactobacillus-related oligotype 1 (OT1) including Lactobacillus acidophilus might drive recovery after irradiation as it was associated with increased long-term numbers post-exposure. We showed that treatment with heat-killed L. acidophilus rescued the budding-impaired organoids and induced sufficient differentiation in epithelial cells, and particularly mucin-producing cells, in intestinal organoids. This study provides the first evidence that the indigenous gut bacteria L. acidophilus enhance intestinal epithelial function with respect to irradiation-induced intestinal damage by improving intestinal stem cell function and cell differentiation.

Beta-Hydroxy-Beta-Methyl-Butyrate, L-glutamine, and L-arginine Supplementation Improves Radiation-Induce Acute Intestinal Toxicity

We aimed to evaluate effects of β-hydroxy-β-methylbutyrate, L-glutamine, and L-arginine (HMB/GLN/ARG) on radiation-induced acute intestinal toxicity. Forty rats were divided into four groups: group (G) 1 was defined as control group, and G2 was radiation therapy (RT) control group. G3 and G4 were HMB/GLN/ARG control and RT plus HMB/GLN/ARG groups, respectively. HMB/GLN/ARG started from day of RT and continued until the animals were sacrificed 10 days after RT. The extent of surface epithelium smoothing, villous atrophy, lamina propria inflammation, cryptitis, crypt distortion, regenerative atypia, vascular dilatation and congestion, and fibrosis were quantified on histological sections of intestinal mucosa. Statistical analyses were performed using the analysis of variance (ANOVA) test. There were significant differences between study groups regarding extent of surface epithelium smoothing, villous atrophy, lamina propria inflammation, cryptitis and crypt distortion, regenerative atypia, vascular dilatation and congestion, and fibrosis (p values were 0.019 for fibrosis, <.001 for the others). Pair-wise comparisons revealed significant differences regarding surface epithelium smoothing, villous atrophy, lamina propria inflammation, cryptitis, vascular dilatation, and congestion between G2 and G4 (p values were <.001, .033, <.001, .007, and <.001, respectively). Fibrosis score was significantly different only between G1 and G2 (p = .015). Immunohistochemical TGF-β score of G2 was significantly higher than G1 and G3 (p values were .006 and .017, respectively). There was no difference between TGF-β staining scores of G2 and G4. Concomitant use of HMB/GLN/ARG appears to ameliorate radiation-induced acute intestinal toxicity; however, this finding should be clarified with further studies.

Early effects of irradiation on laryngeal mucosa in a gastroesophageal reflux model: an experimental study

OBJECTIVE

The aim of this study was to evaluate the early histopathological changes of gastroesophageal reflux and irradiation on laryngeal mucosa in rats.

STUDY DESIGN

Animal study.

SETTING

Experimental animal laboratory, tertiary referral center.

SUBJECT AND METHOD

Twenty-four adult female Wistar Albino rats were grouped as: control (n = 6), reflux and irradiation (n = 10), and irradiation (n = 8). Rats were operated to create a reflux model 30 days before irradiation. Ionizing radiation was administered in a single fraction of a 20 Gy to the larynx. Laryngeal tissue samples were taken at the 4th day of irradiation and all specimens underwent histopathological examination.

RESULTS

Edema and vascular dilation in lamina propria were higher in the reflux and irradiation, and irradiation groups than control group. Inflammation was higher in the reflux and irradiation group than the control group. Inflammation in squamous epithelium was higher in the reflux and irradiation and irradiation groups compared to the control group. Inflammation in the squamous epithelium of the irradiation group was higher than the reflux and irradiation group. In the respiratory tract epithelium, inflammation was higher in the reflux and irradiation group; additionally, a significant loss of cilia was present in the reflux and irradiation and irradiation groups while pseudostratification was higher in the reflux and irradiation group.

CONCLUSION

Ionizing radiation-induced inflammation may increase on previously inflammated area due to gastroesophageal reflux. Therefore, it may be helpful to investigate and treat the reflux in laryngeal cancer patients that will receive ionizing radiation.

Rebamipide ameliorates radiation-induced intestinal injury in a mouse model

Radiation-induced enteritis is a major side effect in cancer patients undergoing abdominopelvic radiotherapy. Radiation exposure produces an uncontrolled inflammatory cascade and epithelial cell loss leading to impaired epithelial barrier function. The goal of this study was to determine the effect of rebamipide on regeneration of the intestinal epithelia after radiation injury. The abdomens of C57BL/6 mice were exposed to 13Gy of irradiation (IR) and then the mice were treated with rebamipide. Upon IR, intestinal epithelia were destroyed structurally at the microscopic level and bacterial translocation was increased. The intestinal damage reached a maximum level on day 6 post-IR and intestinal regeneration occurred thereafter. We found that rebamipide significantly ameliorated radiation-induced intestinal injury. In mice treated with rebamipide after IR, intestinal barrier function recovered and expression of the tight junction components of the intestinal barrier were upregulated. Rebamipide administration reduced radiation-induced intestinal mucosal injury. The levels of proinflammatory cytokines and matrix metallopeptidase 9 (MMP9) were significantly reduced upon rebamipide administration. Intestinal cell proliferation and β-catenin expression also increased upon rebamipide administration. These data demonstrate that rebamipide reverses impairment of the intestinal barrier by increasing intestinal cell proliferation and attenuating the inflammatory response by inhibiting MMP9 and proinflammatory cytokine expression in a murine model of radiation-induced enteritis.

Development of a new minipig model to study radiation-induced gastrointestinal syndrome and its application in clinical research

Because of insufficient clinical data regarding acute radiation damage after single high-dose radiation exposure, acute radiation-induced gastrointestinal (GI) syndrome remains difficult to treat. The goal of this study was to establish an appropriate and efficient minipig model to study high-dose radiation-induced GI syndrome after radiation exposure. For endoscopic access to the ileum, ileocutaneous anastomosis was performed 3 weeks before irradiation in six male Göttingen minipigs. Minipigs were locally irradiated at the abdominal area using a gamma source as follows: 1,000 cGy (n = 3) and 1,500 cGy (n = 3). Endoscopic evaluation for the terminal ileum was periodically performed via the ileocutaneous anastomosis tract. Pieces of tissue were serially taken for histological examination. The irradiated intestine presented characteristic morphological changes over time. The most obvious changes in the ileum were mucosal atrophy and telangiectasia from day 1 to day 17 after abdominal irradiation. Microscopic findings were characterized as architectural disorganization, loss of villi and chronic active inflammation. Increase in cyclooxygenase-2 (COX-2) expression was closely correlated with severity of tissue damage and inflammation. Particularly, the plasma citrulline level (PCL), a potential marker for radiation-induced intestinal damage, was significantly decreased the day after irradiation and recovered when irradiated mucosa was normalized. Our results also showed that PCL changes were positively correlated with microscopic changes and the endoscopic score in radiation-induced mucosal damage. In conclusion, the ileocutaneous anastomosis model using the minipig mimics human GI syndrome and allows the study of sequential changes in the ileum, the main target tissue of abdominal irradiation. In addition, PCL could be a simple biomarker for radiation-induced intestinal damage.