An Amino Acid–Based Oral Rehydration Solution Regulates Radiation-Induced Intestinal Barrier Disruption in Mice

Abstract

ABSTRACT Background Radiotherapy inadvertently affects gastrointestinal (GI) epithelial cells, causing intestinal barrier disruption and increased permeability. Objective We examined the effect of amino acid–based oral rehydration solution (AA-ORS) on radiation-induced changes of intestinal barrier function and epithelial tight junctions (TJs) in a randomized experimental study using a total-body irradiation (TBI) mouse model. Methods Eight-week-old male Swiss mice received a single-dose TBI (0, 1, 3, or 5 Gy), and subsequent gastric gavage with AA-ORS (threonine, valine, serine, tyrosine, and aspartic acid) or saline for 2 or 6 d. Intestinal barrier function of mouse ileum was characterized by electrophysiological analysis of conductance, anion selectivity, and paracellular permeability [fluorescein isothiocyanate (FITC)-dextran]. Ultrastructural changes of TJs were evaluated by transmission electron microscopy. Membrane protein and mRNA expression of claudin-1, -2, -3, -5, and -7, occludin, and E-cadherin were analyzed with western blot, qPCR, and immunohistochemistry. Nonparametric tests were used to compare treatment-dose differences for each time point. Results Saline-treated mice had a higher conductance at doses as low as 3 Gy, and as early as 2 d post-TBI compared with 0 Gy (P < 0.001). Paracellular permeability and dilution potential were increased 6 d after 5 Gy TBI (P < 0.001). Conductance decreased with AA-ORS after 2 d in 3-Gy and 5-Gy mice (P < 0.05 and P < 0.001), and on day 6 after 5 Gy TBI (P < 0.001). Anion selectivity and FITC permeability decreased from 0.73 ± 0.02 to 0.61 ± 0.03 pCl/pNa (P < 0.01) and from 2.7 ± 0.1 × 105 to 2.1 ± 0.1 × 105 RFU (P < 0.001) in 5-Gy mice treated with AA-ORS for 6 d compared with saline. Irradiation-induced ultrastructural changes of TJs characterized by decreased electron density and gap formation improved with AA-ORS. Reduced claudin-1, -3, and -7 membrane expression after TBI recovered with AA-ORS within 6 d, whereas claudin-2 decreased indicating restitution of TJ proteins. Conclusions Radiation-induced functional and structural disruption of the intestinal barrier in mice is reversed by AA-ORS rendering AA-ORS a potential treatment option in prospective clinical trials in patients with gastrointestinal barrier dysfunction.