The objective of this work was to test the hypothesis that Intraluminal serine proteases are involved in trauma-hemorrhagic shock (T/HS)-induced intestinal and lung injury. Male Sprague-Dawley rats were administrated the serine protease inhibitor (6-amidino-2-naphthyl p-guanidinobenzoate dimethanesulfate, Nafamostat) either intraluminally into the gut or intravenously after a laparotomy (trauma) and then subjected to 90 min of hemorrhagic shock (T/HS) or sham shock (T/SS). Intestinal and lung injury was assessed at 3 h after resuscitation with Ringer's lactate solution. In a second set of experiments, mesenteric lymph was collected from the groups of rats subjected to T/HS or T/SS and its ability to activate normal neutrophils was tested. Lung permeability, pulmonary myeloperoxidase levels, and the bronchoalveolar lavage fluid protein to plasma protein ratio were increased after T/HS but were significantly decreased in the T/HS rats receiving intraluminal (P < 0.05), but not intravenous, nafamostat. Likewise, T/HS-induced intestinal villus injury was less in the nafamostat-treated shock rats (P < 0.05). Last, the ability of T/HS mesenteric lymph to increase PMN CD11b expression or prime neutrophils for an augmented respiratory burst was significantly reduced by the intraluminal administration of nafamostat. Because intraluminal nafamostat reduced T/HS-induced gut and lung injury as well as the neutrophil activating ability of intestinal T/HS lymph, the presence of serine proteases in the ischemic gut may play an important role in T/HS-induced gut and hence lung injury.

This large animal model validates rodent studies showing that the shock-injured gut releases biologically active factors into the mesenteric lymph and these factors activate neutrophils and injure endothelial cells.

Recent literature indicates that females are more resistant to shock-, trauma-, and sepsis-induced immune dysfunction and organ injury than are males. Consequently, using trauma-hemorrhagic shock (T/HS) and burn models, we tested whether the neutrophil response to trauma occurred in a sexually dimorphic fashion and, if so, the role of sex hormones. Neutrophil activation, as reflected by CD11b expression and respiratory burst activity, was increased to a greater extent in male rats than in female rats after T/HS or burn injury. Testosterone appeared to potentiate neutrophil activation, because castration reduced neutrophil activation, whereas ovariectomy had little effect. Mechanistically, this sexually dimorphic neutrophil response appeared to be due to both cellular and humoral factors. Evidence for a cellular difference between male and female neutrophils is based on the observation that naive female neutrophils were more resistant to activation by burn or T/HS plasma and lymph than naive male neutrophils and that this resistance varied over the estrus cycle. Additionally, the humoral environment was more neutrophil activating in male rats, because burn and T/HS plasma and lymph from male rats activated naive male neutrophils to a greater extent than comparable samples from females. Last, on the basis of in vitro experiments examining the effects of estrogen on calcium signaling, it appears that estrogen limits trauma-induced neutrophil activation, at least in part, by limiting the entry of calcium into the cell via store-operated calcium entry mechanisms. In conclusion, there is a striking sexual dimorphism in neutrophil responses after trauma, and these changes reflect both cellular resistance to activation as well as a less activating humoral environment.