Oxidative modification of the intestinal mucus layer is a critical but unrecognized component of trauma hemorrhagic shock-induced gut barrier failure

Recent studies demonstrate that mechanisms underlying gut barrier failure include systemic processes and less studied luminal processes. We thus tested the hypothesis that mucus layer oxidation is a component of trauma/hemorrhagic shock-induced gut injury and dysfunction. Male Sprague-Dawley rats underwent trauma/hemorrhagic shock. Controls underwent trauma only. Mucus from the terminal 30 cm of the ileum was collected, processed, and analyzed for reactive nitrogen intermediates (RNI)-mediated damage, reactive oxygen species (ROS)-induced damage, and total antioxidant capacity. The distal ileum was stained to quantify the mucus layer; gut permeability was assessed physiologically. A time course study was conducted to determine the temporal sequence of mucus layer damage. The role of free radical-mediated damage to the gut barrier was investigated by the effect of the free radical scavenger dimethyl sulfoxide on trauma/hemorrhagic shock-induced changes on the mucus and on gut permeability. Trauma/hemorrhagic shock increased intestinal permeability, which was associated with evidence of loss of the unstirred mucus layer. These changes correlated with increased ROS- and RNI-mediated mucus damage and loss of mucus total antioxidant capacity. Based on the time course study, ROS-mediated mucus damage and loss of total antioxidant capacity were present immediately following shock, whereas RNI-mediated damage was delayed for 3 h. Dimethyl sulfoxide ameliorated gut barrier loss, ROS-mediated changes to the mucus layer, and loss of total antioxidant capacity. There was no change in RNI-induced changes to the mucus layer. These results support the hypothesis that trauma/hemorrhagic shock leads to mucus damage and gut dysfunction through the generation of free radical species.