Rifaximin improves survival and reduces intestinal injury in mice administered whole abdominal irradiation

The purpose of this study was to determine whether rifaximin reduces the radiation damages in the small intestine. Female C57BL/6 mice were treated with 15 Gy of whole abdominal irradiation (WAI) alone, oral rifaximin (30 mg/kg/day) for 2 days alone, oral rifaximin for 2 days before WAI, or oral rifaximin for 2 days after WAI. The survival rates and body weights of mice after the treatments were determined. From the histopathology preparations, the number of surviving crypt cells and the length of villi were determined. The frequency of apoptosis in crypt cells, proliferation of crypt cells, and expression of NF-kappa B were also determined. Administration of rifaximin for 2 days before 15 Gy WAI significantly improved the survival of mice. Rifaximin treatment after WAI was slightly less effective than that before WAI treatment to reduce the WAI-induced death of mice. Rifaximin treatment before WAI markedly reduced the WAI-induced depletion of crypts, shortening of villi, and increase of apoptosis in crypt cells. Rifaximin promoted the proliferation of crypt cells and increased the expression of NF-kappa B in crypt cells. Oral administration of rifaximin to C57BL/6 female mice for 2 days before WAI significantly reduced the radiation-induced damage in the small intestine and improved the survival of mice. Rifaximin also attenuated the damage in small intestine caused by 2 or 5 Gy WAI. Rifaximin may be useful for the attenuation of the radiation-induced gastrointestinal damages.