The Effect of Probiotics for Preventing Radiation-Induced Morphological Changes in Intestinal Mucosa of Rats

Radiation therapy is an important treatment modality for abdominal or pelvic cancer, but there is a common and serious complication such as radiation-induced enteritis. Probiotics is reported to have positive effects against radiation-induced enteropathy. In this study, morphological changes of bowel mucosa were analyzed in rats to presume the effect of probiotics on radiation-induced enteritis and its correlation with radiation dose. A total of 48 adult male Sprague-Dawley rats were randomly assigned to two groups and received a solution containing 1.0×108 colony-forming units of Lactiobacillus acidophilus or water once daily for 10 days. Each of two groups was divided into three subgroups and abdomino-pelvic area of each subgroup was irradiated with 10, 15, and 20 Gy, respectively on the seventh day of feeding the solutions. All rats were sacrificed 3 days after irradiation and the mucosal thickness and villus height of jejunum, ileum and colon were measured. The morphological parameters of the small intestine represented significant differences between two solution groups irradiated 10 or 15 Gy, except for villus height of jejunum in 15 Gy-subgroup (P=0.065). There was no significant morphometric difference between two groups irradiated with 20 Gy of radiation. Probiotics appear to be effective for the morphological shortening of small intestinal mucosa damaged by radiation less than or equal to 15 Gy. Graphical Abstract Keywords: Probiotics, Radiation Therapy, Enteritis, Rats INTRODUCTION Radiation-induced enteritis is a common and serious complication after abdominal or pelvic irradiation for gastrointestinal, gynecologic and urologic cancer (1, 2, 3). More than 70% of patients receiving pelvic radiation therapy suffered from bowel symptoms caused by inflammatory changes, and 50% of them developed into chronic bowel disease with permanent intestinal changes (4). Therefore, the methods to prevent or decrease the occurrence of the acute radiation-induced enteritis may be the one of the important issues to reduce the chronic toxicity. Although the more conformal irradiation techniques such as three-dimensional radiation therapy or intensity-modulated radiation therapy allowed a significant improvement in normal organ sparing, the radiation-induced enteropathy still has been reported with high incidence rate in patients receiving pelvic irradiation (5). While the highly accurate irradiation techniques can reduce the dose to the bowels, they may increase the intestinal volume exposed to relatively lower radiation dose because of multiple directions of radiation beams (6). The advanced irradiation techniques may be an insufficient solution of radiation-induced intestinal injury. Probiotics are defined as live microorganisms such as Lactobacillus acidophilus that exert specific favorable effects on the host. Continuous intake of them is thought to restore bowel microflora to optimal levels and reinforce the intestinal barrier capacity. Probiotics have been reported to prevent radiation-induced enteropathy and diarrhea (7). Experimental animal studies of acute radiation-induced enteritis have revealed that probiotics have a positive role on the mucosal integrity (8, 9). However, the effect of probiotics for radiation-induced diarrhea is still controversial issue in clinical studies (10, 11, 12). The morphological damages of acute radiation-induced enteritis were known as architectural changes of intestinal mucosa such as villus shortening by apoptosis (13, 14). In the present study, morphometric analysis of bowels was performed in rats to evaluate the effect of L. acidophilus on the morphological changes of intestinal mucosa by irradiation and their correlation with radiation dose.