Introduction: Vagal nerve stimulation has been shown to have significant immunomodulatory effects following injury. We have recently shown that vagal nerve stimulation activates enteric glia cells, which are known to play an important role in maintaining gut barrier function. Activated enteric glia cells have been shown to modulate intestinal barrier integrity and tight junction protein expression through secretion of s-nitrosoglutathione (GSNO). We hypothesized that vagal nerve stimulation would decrease burn-induced intestinal barrier injury through modulation of the tight junction proteins myosin light chain kinase (MLCK) and phosphorylated myosin light chain (MLC). We also postulated that injection of GSNO immediately following burn would improve intestinal barrier integrity and modulate tight junction protein expression.

Methods: Male balb/c mice underwent electrical cervical vagal nerve stimulation for 10 minutes prior to 30% total body surface area steam burn. Segments of distal ileum were obtained 4 hours following injury to assess intestinal TNF-a using ELISA, and MLCK protein expression by Western blot. Confocal microscopy was utilized to demonstrate changes in phosphorylated MLC localization. Animals were also given an intraperitoneal injection of GSNO (10mg/kg) immediately following burn. Intestinal barrier integrity was assessed using histology and by measuring in vivo intestinal permeability to 4 kilodalton FITC-Dextran.

Results: Severe burn injury results in a 4-fold increase in intestinal MLCK protein expression which is associated with elevated gut TNF-a. Stimulation of the vagus nerve immediately prior to burn decreases intestinal MLCK expression to sham levels. There is no difference in intestinal TNF-a between sham and burned animals undergoing vagal nerve stimulation. Confocal microscopy images demonstrate that vagal nerve stimulation attenuates the burn-induced phosphorylation of intestinal MLC. Injection of GSNO following burn injury improved gut barrier function (see Figure), decreased burn-induced histologic gut injury, and was associated with decreased phosphorylation of MLC compared to burn alone.

Conclusion: Vagal nerve stimulation attenuates gut barrier injury following burn by modulating expression of the intestinal tight junction protein MLCK. These results further demonstrate the immunomodulatory effects of vagal nerve stimulation, suggesting a novel mechanism by which activation of enteric glia maintains intestinal barrier integrity following injury through secretion of GSNO.