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

Abstract

Radiotherapy inadvertently affects gastrointestinal (GI) epithelial cells, causing intestinal barrier disruption and increased permeability. 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. Eight-week-old male Swiss mice received a single-dose TBI (0, 1, 3, or 5Gy), 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. Saline-treated mice had a higher conductance at doses as low as 3Gy, and as early as 2 d post-TBI compared with 0Gy (P<0.001). Paracellular permeability and dilution potential were increased 6 d after 5Gy 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 5Gy 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 6d, whereas claudin-2 decreased indicating restitution of TJ proteins. 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.