Rapid disruption of intestinal epithelial tight junction and barrier dysfunction by ionizing radiation in mouse colon in vivo: protection byN-acetyl-l-cysteine

Abstract

The goals of this study were to evaluate the effects of ionizing radiation on apical junctions in colonic epithelium and mucosal barrier function in mice in vivo. Adult mice were subjected to total body irradiation (4 Gy) with or without N-acetyl-l-cysteine (NAC) feeding for 5 days before irradiation. At 2-24 h postirradiation, the integrity of colonic epithelial tight junctions (TJ), adherens junctions (AJ), and the actin cytoskeleton was assessed by immunofluorescence microscopy and immunoblot analysis of detergent-insoluble fractions for TJ and AJ proteins. The barrier function was evaluated by measuring vascular-to-luminal flux of fluorescein isothiocyanate (FITC)-inulin in vivo and luminal-to-mucosal flux in vitro. Oxidative stress was evaluated by measuring protein thiol oxidation. Confocal microscopy showed that radiation caused redistribution of occludin, zona occludens-1, claudin-3, E-cadherin, and β-catenin, as well as the actin cytoskeleton as early as 2 h postirradiation, and this effect was sustained for at least 24 h. Feeding NAC before irradiation blocked radiation-induced disruption of TJ, AJ, and the actin cytoskeleton. Radiation increased mucosal permeability to inulin in colon, which was blocked by NAC feeding. The level of reduced-protein thiols in colon was depleted by radiation with a concomitant increase in the level of oxidized-protein thiol. NAC feeding blocked the radiation-induced protein thiol oxidation. These data demonstrate that radiation rapidly disrupts TJ, AJ, and the actin cytoskeleton by an oxidative stress-dependent mechanism that can be prevented by NAC feeding.

N‐Acetylcysteine alleviates gut dysbiosis and glucose metabolic disorder in high‐fat diet‐fed mice

“…In the present study, NAC treatment reduced the damage to intestinal integrity and the mucus barrier (Fig. ), consistent with the findings of a recent study in which NAC protected radiation‐induced mice against disruption of intestinal tight junctions and barrier dysfunction …”

Rebamipide alleviates radiation‐induced colitis through improvement of goblet cell differentiation in mice

“…31 An irradiated colonic epithelium displayed a rapid redistribution of tight junctional complexes in the acute phase. 4 However, in this in vivo and in vitro study, rebamipide was able to prevent the irradiation-induced destruction of TJs in the colonic epithelium. These findings suggested that the TJ recovery upon rebamipide treatment attenuated the radiation-induced colonic damage.…”

“…The condition may also lead to alterations of the gut microbiota and induce colonic endotoxemia. 4,25 Therefore, we focused on the effects of rebamipide against colonic injury using a GI-ARS model.…”

“…[2][3][4] Bacterial translocation is defined as the passage of viable endogenous bacteria and endotoxins from the gastrointestinal tract to extraintestinal sites such as the mesenteric lymph node (mLN) complex, liver, spleen, kidney, and bloodstream. 5,6 Endotoxemia and bacteremia are critical events in the pathogenesis of GI-ARS, and the colon is the primary source of endotoxins, which thus highlights the importance of this tissue's injury during radiation exposure.…”

“…5,6 Endotoxemia and bacteremia are critical events in the pathogenesis of GI-ARS, and the colon is the primary source of endotoxins, which thus highlights the importance of this tissue's injury during radiation exposure. 4 Goblet cells are columnar epithelial cells specializing in the secretion of high-molecular-weight glycoproteins, called mucins, which consist of a protein core, rich in threonine, proline, or serine residues, supplemented with an O-linked oligosaccharide. 7 These cells play a pivotal role in epithelial defense against luminal stimulants and pathogens.…”