Albumin peptide: A molecular marker for trauma/hemorrhagic-shock in rat mesenteric lymph
Introduction
It has been recognized for over 25 years that the development of a dysregulated inflammatory response as well as acute lung injury and multiple organ failure (MOF) complicates the recovery of patients with severe trauma [11]. In spite of this recognition, advances in medical care have done little to reduce the incidence or mortality rate of trauma-induced acute lung injury or MOF. This failure of medical therapy appears to be related, at least in part, to an incomplete understanding of the mechanisms by which trauma–hemorrhage leads to acute organ dysfunction. Although the relationship between trauma–hemorrhage and acute pulmonary dysfunction as well as systemic inflammation has been recognized for many years, the pathogenesis of trauma/shock-induced pulmonary microvascular dysfunction is not well understood [11]. Nevertheless, it is clear that hemorrhagic-shock and major trauma are associated with intestinal ischemia and loss of gut barrier function [10], [12], [16], [19], [27]. Experimental animal models have been developed to investigate the events that lead to successive organ failure following trauma with hemorrhagic-shock (T/HS). The data from these experiments lend strong evidence that factors contributing to post-T/HS organ failure originate in the ischemic gut and are introduced systemically via the mesenteric lymphatics [1], [2], [3], [12], [13], [14], [31], [33], [34]. First, these data show that lymph duct ligation prior to shock can abrogate the lung damage, gut permeability, bone marrow (BM) suppression, neutrophil (PMN) activation and endothelial cell damage that is normally seen in these animals after T/HS [3], [33]. Second, the deleterious in vivo effects on BM, PMN and endothelial cells can be recreated in vitro by incubating these cells with post-T/HS lymph but not pre-T/HS or lymph collected from animals subjected to trauma without shock (T/SS). These data therefore indicate that factors responsible for this damage are present in post-T/HS lymph and are produced or increased due to T/HS [2], [13], [22], [23], [34].
Previous studies have excluded translocating bacteria [12], endotoxin [12], cytokines and xanthine oxidase (12, 13) as factors responsible for the biologic activity in post-shock lymph. We have, however, recently reported that a modified form of rat serum albumin (RSA) and multiple lipid factors are implicated in T/HS lymph-induced endothelial cell toxicity [17]. In this study, we have continued our efforts in the identification of factors present in post-T/HS lymph that are responsible for endothelial cell toxicity and report the finding of a novel 24-amino acid peptide that is significantly increased in post-T/HS mesenteric lymph.
Section snippets
Animals
Male Sprague-Dawley rats (pathogen-free, Taconic, Long Island, NY) were housed in barrier-sustained conditions under 12 h light/12 h dark cycles, and allowed free access to water and chow (Teklad 22/5 rodent diet W-8640, Harlan Teklad, Madison, WI). Rat maintenance was performed in accordance with the “Guide for the Care and Use of Laboratory Animals” and all procedures were approved by the New Jersey Medical School Animal Care Committee.
Trauma/hemorrhagic-shock model and lymph collection
Mesenteric lymph was collected from male rats (300–350 g)
Analysis of lymph
Lymph collected from animals following trauma with hemorrhagic-shock has been shown to be toxic to endothelial cells, whereas the lymph collected prior to shock or from animals subjected to trauma without shock is not [13], [23]. We therefore hypothesized that T/HS results in the production or increase of a factor(s) in mesenteric lymph that is toxic to endothelial cells. To test this hypothesis, pre-T/HS lymph was compared to lymph collected during and up to 3 h post-T/HS in order to identify
Discussion
Endothelial cell injury, bone marrow suppression, neutrophil activation and increased red blood cell rigidity are in vivo systemic effects that have been observed in studies of rats subjected to trauma with hemorrhagic-shock [1], [2], [3], [23], [33]. Although the factors responsible for these effects are unknown, experimental data suggest they are produced by the gut and transported to the general circulation through the mesenteric lymphatics. Since the endothelium plays a central role in
Acknowledgements
The authors thank Dr. G. Diamond for critical reading of the manuscript, J. Kaiser for editing, Dr. A. Haag and R. Jones for technical assistance. This study was supported by National Institutes of Health Grant GM59841 (to EAD).
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