Parasympathetic stimulation via the vagus nerve prevents systemic organ dysfunction by abrogating gut injury and lymph toxicity in trauma and hemorrhagic shock

Abstract

We tested if vagus nerve stimulation (VNS) would prevent gut injury, mesenteric lymph toxicity, and systemic multiple organ dysfunction syndrome following trauma-hemorrhagic shock (T/HS). Four groups of experiments were performed. The first tested whether VNS (5 V for 10 min) would protect against T/HS-induced increases in gut and lung permeability as well as neutrophil priming. In the second experiment, mesenteric lymph was collected from rats subjected to T/HS or trauma-sham shock with or without VNS and then injected into naive mice to assess its biologic activity. Lung permeability, neutrophil priming, and red blood cell deformability were measured. Next, the role of the spleen in VNS-mediated protection was tested by measuring gut and lung injury in splenectomized rats subjected to sham or actual VNS. Lastly, the ability of nicotine to replicate the gut-protective effect of VNS was tested. Vagus nerve stimulation protected against T/HS-induced gut injury, lung injury, and neutrophil priming (P < 0.05). Not only did VNS limit organ injury after T/HS, but in contrast to the mesenteric lymph collected from the sham-VNS T/HS rats, the mesenteric lymph from the VNS T/HS rats did not cause lung injury, neutrophil priming, or loss of red blood cell deformability (P < 0.05) when injected into naive mice. Removal of the spleen did not prevent the protective effects of VNS on gut or lung injury after T/HS. Similar to VNS, the administration of nicotine also protected the gut from injury after T/HS. Vagus nerve stimulation prevents T/HS-induced gut injury, lung injury, neutrophil priming, and the production of biologically active mesenteric lymph. This protective effect of VNS was not dependent on the spleen but appeared to involve a cholinergic nicotinic receptor, because its beneficial effects could be replicated with nicotine.

FIG 1

In vivo effect of the injection of mesenteric lymph from rats subjected to T/HS or T/SS with or without VNS on (A) lung permeability to EBD, (B) neutrophil respiratory burst, and (C) RBC deformability as measured by the elongation index and (D) stress forces required to deform RBC as measured by Kei. Data expressed as mean (SEM). *P G 0.05 T/HS versus all other groups; +P G 0.01 versus all other groups; **P G 0.05 versus T/SS. n = 6Y7 in T/HS groups, n = 4Y7 in T/SS groups.

FIG 2

A, T/HS-induced plasma TNF is not prevented by VNS; (B) VNS remains protective after splenectomy, because VNS protects against T/Hsinduced gut injury and (C) lung injury after splenectomy (SPX). D, VNS does not reduce the increased base deficit observed after T/HS. Data expressed as mean (SEM). n = 6 in T/HS groups, n = 4 in the T/SS groups. *P G 0.01 versus T/SS groups; +P G 0.05 versus all other groups.

FIG 3

Nicotine protects against T/HS-induced gut injury. n = 5 in T/HS groups, n = 3 in T/SS groups. Data expressed as mean (SEM). *P G 0.05 versus all other groups.