Intravenous Injection of Mesenteric Lymph Produced During Hemorrhagic Shock Decreases RBC Deformability in the Rat

Abstract

Objective To test the hypothesis that gut-derived factors carried in trauma-hemorrhagic shock (T/HS) lymph are sufficient to induce red blood cells (RBC) injury, to investigate their potential mechanisms of action, and to define the time post-T/HS that these factors appear in the lymph. Methods Mesenteric lymph collected from T/HS or trauma-sham shock (T/SS) rats over different time periods was injected intravenously into male rats at a rate of 1 mL/h for 3 hours. RBC deformability was measured using laser-assisted ektacytometer to calculate the elongation index. From the shear-stress elongation curve, the stress required for the erythrocytes to reach 50% of their maximal elongation was also determined. RBC deformability was measured before lymph infusion and at 1 hour and 3 hours after the initiation of lymph infusion. The effect of the lymph samples (5% v/v) was also determined in vitro by incubating naïve whole blood with the lymph samples. The potential role of T/HS lymph-induced RBC oxidant injury mediated by inducible nitric oxide synthase (iNOS)-generated oxidants and/or white blood cells (WBC) was investigated using iNOS inhibitors and WBC depletion, respectively. In all the in vivo studies, five to seven rats were studied per group. Results The intravenous injection of T/HS lymph but not T/SS lymph caused in vivo RBC injury. The biological activity of T/HS lymph varied over time with the RBC-injurious factors being produced only during the first 3 hours postshock. The in vivo inhibition of iNOS did not prevent lymph-induced RBC injury. T/HS lymph incubated in vitro with naïve whole blood resulted in RBC injury, but this injury was not observed in blood depleted of WBC. Conclusions These results indicate that T/HS lymph produced during the initial 3-hour postshock period is sufficient to induce RBC injury in otherwise normal rats and that the lymph-induced RBC injury is not dependent on activation of the iNOS pathway but seems to require WBC.

Modulating the Biologic Activity of Mesenteric Lymph after Traumatic Shock Decreases Systemic Inflammation and End Organ Injury

“…CPSI-121, a guanylhydrazone-derived compound, has been shown to result in efferent vagal fiber activation after systemic administration and thus can be used to provide VNS through pharmacologic means [33]. While the exact therapeutic window is unknown, VNS appears to have the greatest benefit 1–2 hours following injury [10, 63]. Given the greater clinically feasibility of administering a pharmacologic agent over direct, electrical stimulation of the vagus nerve, pharmacologic VNS is an attractive option that may yield higher therapeutic potential.…”

“…Newer theories have focused on the mesenteric lymph (ML) as the inciting source for the development of SIRS [2, 9]. These theories propose that pro-inflammatory mediators are produced in the gut after trauma, which can be released into the systemic circulation via the ML to cause and propagate the systemic inflammatory response [2, 10, 11]. …”

“…In vitro application of shock-derived ML causes endothelial cell dysfunction [15–17], neutrophil activation [17–19] and red blood cell deformation [10, 20]. In-vivo studies have shown that shock-derived ML contributes to the development of acute lung injury (ALI) [21–23] and cardiac dysfunction [24, 25] and that these effects are abrogated with mesenteric duct ligation prior to injury [16, 26].…”

The Initial Common Pathway of Inflammation, Disease, and Sudden Death

“…Condon et al demonstrated that intravenously injected mesenteric lymph produced during hemorrhagic shock decreased RBC deformability in the rat [276]. The in vivo inhibition of inducible nitric oxide synthase (iNOS) did not prevent lymph-induced RBC injury.…”

Cross-transfusion of Postshock Mesenteric Lymph Provokes Acute Lung Injury

“…37 Postshock mesenteric lymph may be toxic through a variety of mechanisms, including endothelial inflammation, 6,26 neutrophil priming, 38,39,40 enhanced apoptosis, 41 pulmonary epithelial inflammation, 42 and RBC hemolysis. 43,32 In this study, we demonstrate that postshock mesenteric lymph is necessary and sufficient to provoke ALI in the naïve rat. These data further support a central mechanistic role of PSML in the pathogenesis of ALI.…”