834. Protective Effect of Bcl-XL Gene Expression on the Radiation-Induced Acute Intestinal Injuries

Abstract

Top of pageAbstract [Background] Intestinal injuries represent a major dose-limiting side effect of radiation treatment for many malignancies. Recent studies have demonstrated that mitochondrial damages occurred in the mucosal epithelial cells and subsequent release of cytochrome c from the damaged mitochondria resulting in apoptotic changes, are mainly involved in this type of injuries. The present study was designed to determine if transducing a Bcl-XL gene, a potent anti- apoptotic gene, to the epithelial cells could provide protective effects on the radiation-induced acute injuries of the small intestine. [Methods] C57Bl/6 mice were used in this study. Adenoviral vectors containing the human Bcl-XL gene (Ad-Bcl-XL) or ?-galactosidase gene (Ad-LacZ) driven by CAG promoter were generated. In order to increase the transduction efficiency to the mucosal epithelium, especially to the intestinal crypts, we first washed the intraluminal space of the small intestine with PBS and digested mucus components with pronase. Adenoviral vector infections were performed by injecting 2x10(8) pfu adenoviral vectors into 2cm portion of the pronase-treated small intestine that had been transiently clamped on both side. These clamps were removed 30 min after the vector infusion. Transduction efficiencies of the mucosal epithelial cells were examined by X-gal staining 24 hours after Ad-LacZ infection. Radiation-induced acute injuries of the small intestine were introduced by whole body irradiation (15 Gy) performed 24 hours after the adenoviral vector infection. Six hours after the radiation, apoptotic epithelial cells were visualized by TUNEL assay. Seventy-two hours after the radiation, morphological appearance of the small intestines was assessed by histological examination. [Results] With the method for adenoviral vector infection developed herein, successful transfection could be achieved to the intestinal mucosa determined by X-gal staining. When we irradiated to the mice after the vector infection, Ad-Bcl-XL group demonstrated significantly lower number of radiation-induced apoptotic mucosal epithelial cells compared with the other two control groups examined 6 hours after the irradiation (P<0.05). At 72 hours after the irradiation, morphological appearance of the small intestine of the Ad-Bcl-XL group showed significant prevention from the irradiation damages in terms of the mucosal thickness (P<0.001) compared with control groups. [Conclusion] The present study demonstrates in principle that Bcl-XL gene expression using adenoviral vector-mediated transfection could be a valuable approach in protecting intestinal injuries from ionizing radiation.