P. Cavallaro1, F. Adiliaghdam1, Y. Liu1, M. Kaleko1, C. Furlan Freguia1, R. Hodin1 1Massachusetts General Hospital,General Surgery,Boston, MA, USA
Introduction: Radiation injury induces gut barrier dysfunction and local intestinal inflammation, a clinical entity known as radiation enteritis/colitis. The brush border enzyme intestinal alkaline phosphatase (IAP) has been shown to maintain the gut mucosal barrier and attenuate local and systemic inflammation in multiple mouse models of colitis. We wanted to determine if supplemental IAP can prevent radiation induced gut barrier dysfunction and local inflammation, and therefore be a potential therapy for radiation enteritis/colitis.
Methods: Adult WT C57BL/6J mice were subjected to whole body irradiation (IR) to a total of 850 or 1400 rads. Mice were administered either 100 U/mL IAP or vehicle in their drinking water starting 4 days prior to IR injury and then continued until mice were sacrificed 4 days after injury. Control “sham” mice received no IR injury. Gut barrier function, tissue and systemic inflammation were measured.
Results:There were no difference in food and water intake among any of the groups. Gut barrier function was first measured by FITC-dextran flux from intestinal lumen to systemic blood. Vehicle treated IR mice had a radiation dose dependent increase in FITC flux across the gut barrier compared to sham (10-fold increase in 850 rad group, 30-fold increase in 1400 rad group). Permeability to FITC was almost completely attenuated in IAP treated mice in both groups (p < 0.001). Quantitative PCR of tight junction proteins demonstrated a significant decrease in ileal ZO1, ZO3, and occludin that was partially restored by IAP supplementation in both IR groups. Quantitative PCR also showed a significant decrease in colonic ZO1, ZO3, and occludin, again partially restored by IAP. Similarly, Western blot analysis showed a significant decrease in TJPs in IR treated mice, restored with IAP therapy. Next, local inflammation was assessed by measuring cytokine expression. Relative ileal and colonic TNF-α expression was increased 10-fold in the 850 rad group and 30-fold in the 1400 rad group compared to sham mice and was decreased by 50-70% when treated with IAP (p <0.001). Systemic inflammation was measured by serum ELISA which showed a two-fold increase in TNF-α and IL-6. Again, this response was attenuated by IAP. Interestingly, there was no difference in serum LPS between groups.
Conclusion:Radiation-induced gut barrier dysfunction and both local and systemic inflammation can be attenuated with supplemental IAP. This may be a novel approach to the treatment and prevention of radiation enteritis/colitis.
