A study of the biologic activity of trauma-hemorrhagic shock mesenteric lymph over time and the relative role of cytokines

Intestinal Lymphatic Dysfunction in Kidney Disease

Kidney disease is associated with adverse consequences in many organs beyond the kidney, including the heart, lungs, brain, and intestines. The kidney-intestinal cross talk involves intestinal epithelial damage, dysbiosis, and generation of uremic toxins. Recent studies reveal that kidney injury expands the intestinal lymphatics, increases lymphatic flow, and alters the composition of mesenteric lymph. The intestinal lymphatics, like blood vessels, are a route for transporting potentially harmful substances generated by the intestines. The lymphatic architecture and actions are uniquely suited to take up and transport large macromolecules, functions that differentiate them from blood vessels, allowing them to play a distinct role in a variety of physiological and pathological processes. Here, we focus on the mechanisms by which kidney diseases result in deleterious changes in intestinal lymphatics and consider a novel paradigm of a vicious cycle of detrimental organ cross talk. This concept involves kidney injury-induced modulation of intestinal lymphatics that promotes production and distribution of harmful factors, which in turn contributes to disease progression in distant organ systems.

Synapomorphic features of hepatic and pulmonary vasculatures include comparable purinergic signaling responses in host defense and modulation of inflammation

Hepatosplanchnic and pulmonary vasculatures constitute synapomorphic, highly comparable networks integrated with the external environment. Given functionality related to obligatory requirements of "feeding and breathing," these organs are subject to constant environmental challenges entailing infectious risk, antigenic and xenobiotic exposures. Host responses to these stimuli need to be both protective and tightly regulated. These functions are facilitated by dualistic, high-low pressure blood supply of the liver and lungs, as well as tolerogenic characteristics of resident immune cells and signaling pathways. Dysregulation in hepatosplanchnic and pulmonary blood flow, immune responses, and microbiome implicate common pathogenic mechanisms across these vascular networks. Hepatosplanchnic diseases, such as cirrhosis and portal hypertension, often impact lungs and perturb pulmonary circulation and oxygenation. The reverse situation is also noted with lung disease resulting in hepatic dysfunction. Others, and we, have described common features of dysregulated cell signaling during liver and lung inflammation involving extracellular purines (e.g., ATP, ADP), either generated exogenously or endogenously. These metabokines serve as danger signals, when released by bacteria or during cellular stress and cause proinflammatory and prothrombotic signals in the gut/liver-lung vasculature. Dampening of these danger signals and organ protection largely depends upon activities of vascular and immune cell-expressed ectonucleotidases (CD39 and CD73), which convert ATP and ADP into anti-inflammatory adenosine. However, in many inflammatory disorders involving gut, liver, and lung, these protective mechanisms are compromised, causing perpetuation of tissue injury. We propose that interventions that specifically target aberrant purinergic signaling might prevent and/or ameliorate inflammatory disorders of the gut/liver and lung axis.

The Gut-Lung Axis in Systemic Inflammation. Role of Mesenteric Lymph as a Conduit

Emerging evidence shows that after injury or infection, the mesenteric lymph acts as a conduit for gut-derived toxic factors to enter the blood circulation, causing systemic inflammation and acute lung injury. Neither the cellular and molecular identity of lymph factors nor their mechanisms of action have been well understood and thus have become a timely topic of investigation. This review will first provide a summary of background knowledge on gut barrier and mesenteric lymphatics, followed by a discussion focusing on the current understanding of potential injurious factors in the lymph and their mechanistic contributions to lung injury. We also examine lymph factors with antiinflammatory properties as well as the bidirectional nature of the gut-lung axis in inflammation.

Mesenteric Lymph Duct Drainage Attenuates Lung Inflammatory Injury and Inhibits Endothelial Cell Apoptosis in Septic Rats

The present study was to investigate the effect of mesenteric lymph duct drainage on lung inflammatory response, histological alteration, and endothelial cell apoptosis in septic rats. Animals were randomly assigned into four groups: control, sham surgery, sepsis, and sepsis plus mesenteric lymph drainage. We used the colon ascendens stent peritonitis (CASP) procedure to induce the septic model in rats, and mesenteric lymph drainage was performed with a polyethylene (PE) catheter inserted into mesenteric lymphatic. The animals were sacrificed at the end of CASP in 6 h. The mRNA expression levels of inflammatory mediators were measured by qPCR, and the histologic damage were evaluated by the pathological score method. It was found that mesenteric lymph drainage significantly reduced the expression of TNF-α, IL-1β, and IL-6 mRNA in the lung. Pulmonary interstitial edema and infiltration of inflammatory cells were alleviated by mesenteric lymph drainage. Moreover, increased mRNA levels of TNF-α, IL-1β, IL-6 mRNA, and apoptotic rate were observed in PMVECs treated with septic lymph. These results indicate that mesenteric lymph duct drainage significantly attenuated lung inflammatory injury by decreasing the expression of pivotal inflammatory mediators and inhibiting endothelial apoptosis to preserve the pulmonary barrier function in septic rats.

Sustained bile drainage decreases the organs injuries via inflammation-associated factors modulation in a severe acute pancreatitis rat model

The timely and effective treatment for severe acute pancreatitis (SAP) is favorable to prognosis. Decompression of the bile duct might be a feasible way to decrease the progression of SAP. The present study investigated the effects of sustained bile external drainage on organs injury caused by SAP in Sprague-Dawley (SD) rats and the mechanisms involved. A total of 72 female SD rats weighting 190-230 g were randomly divided into four groups (n=18): Sham operation group (SOG), SOG + bile drainage group (BDG), SAP group, and SAP + BDG. Sodium taurocholate solution (4%; 1 mg/kg body weight) was used to set up SAP model via injection of retrograde puncture of biliopancreatic duct through the duodenum. A cannula was inserted into the bile duct and fixed externally to establish BDG model. At each time points (t=3, 6, 12; n=6), tissues from the liver, lung, and pancreas, and blood samples were collected. Serum amylase (AMY) was analyzed in all the samples. The levels of tumor necrosis factor-α (TNF-α), heme oxygenase-1 (HO-1), interleukin-10 (IL-10) and high mobility group box 1 (HMGB1) were detected by ELISA. Hematoxylin-eosin staining was performed to observe the histopathological changes, and nuclear transcription factor (NF)-κB-p65 levels in the pancreas were analyzed by western blotting. The data indicated that BDG alleviated the SAP progression and multiple organs injuries. Meanwhile, the histopathological changes of the pancreas, liver, and lungs were improved by BDG. BDG decreased the pathological scores of pancreas significantly (P<0.05). The levels of AMY, TNF-α, HMGB1, and NF-κB-p65 were significantly downregulated by BDG (P<0.05), while the level of HO-1 was upregulated and IL-10 was unchanged. In summary, BDG may attenuate the multiple organs injuries caused by SAP via downregulation of TNF-α, HMGB1, NF-κB-p65 and upregulation of HO-1.

Lymphatic Vessel Network Structure and Physiology

The lymphatic system is comprised of a network of vessels interrelated with lymphoid tissue, which has the holistic function to maintain the local physiologic environment for every cell in all tissues of the body. The lymphatic system maintains extracellular fluid homeostasis favorable for optimal tissue function, removing substances that arise due to metabolism or cell death, and optimizing immunity against bacteria, viruses, parasites, and other antigens. This article provides a comprehensive review of important findings over the past century along with recent advances in the understanding of the anatomy and physiology of lymphatic vessels, including tissue/organ specificity, development, mechanisms of lymph formation and transport, lymphangiogenesis, and the roles of lymphatics in disease. © 2019 American Physiological Society. Compr Physiol 9:207-299, 2019.

Biliary tract external drainage protects against multiple organs injuries of severe acute pancreatitis rats via heme oxygenase-1 upregulation

OBJECTIVE

To investigate the effect of biliary tract external drainage (BTED) on severe acute pancreatitis (SAP) in rats and the relationship with heme oxygenase-1 (HO-1) pathway.

METHODS

Thirty SD rats weighing 250-300 g were randomly assigned into five groups (n = 6): sham surgery (SS) group, SAP group, SAP + BTED group, SAP + zinc protoporphyrin IX (ZnPP) group, SAP + BTED + ZnPP group. The SAP model was induced via retrograde injection of 4% sodium taurocholate (1 mL/kg) into biliopancreatic duct through duodenal wall. BTED was performed by inserting a cannula into the bile duct of SAP rats. Tissue and blood samples were collected 24 h after surgery. Pathological changes in organs were scored. The level of amylase, alanine transaminase (ALT), aspartate aminotransferase (AST), diamine oxidase (DAO), lipopolysaccharide (LPS), myeloperoxidase (MPO) and ability to inhibit hydroxyl radical(·OH) in serum were measured. The expression of hemeoxygenase-1 (HO-1), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in tissues were analyzed by RT- PCR and western-blot.

RESULTS

Organs damage in SAP rats was significantly alleviated by BTED (p < 0.05). Compared to the SAP group, the serum level of amylase, ALT, AST, DAO, MPO, and LPS were significantly lower in the SAP + BTED group, and the ability to inhibit ·OH was significantly higher (p < 0.05). The BETD treatment led to a significant reduction of TNF-α, IL-6 level and a significant increase of HO-1 level in tissues than in SAP rats (p < 0.05). ZnPP significantly inhibited all above mentioned changes.

CONCLUSIONS

BTED protected multiple organs against SAP related injuries via HO-1 upregulation.

Lymphatic Pump Treatment as an Adjunct to Antibiotics for Pneumonia in a Rat Model

Background: Lymphatic pump treatment (LPT) is a technique used by osteopathic physicians as an adjunct to antibiotics for patients with respiratory tract infections, and previous studies have demonstrated that LPT reduces bacterial load in the lungs of rats with pneumonia. Currently, it is unknown whether LPT affects drug effcacy.

Objective: To determine whether the combination of antibiotics and LPT would reduce bacterial load in the lungs of rats with acute pneumonia.

Methods: Rats were infected intranasally with 5×107 colony-forming units (CFU) of Streptococcus pneumoniae. At 24, 48, and 72 hours after infection, the rats received no therapy (control), 4 minutes of sham therapy, or 4 minutes of LPT, followed by subcutaneous injection of 40 mg/kg of levofoxacin or sterile phosphate-buffered saline. At 48, 72, and 96 hours after infection, the spleens and lungs were collected, and S pneumoniae CFU were enumerated. Blood was analyzed for a complete blood cell count and leukocyte differential count.

Results: At 48 and 72 hours after infection, no statistically significant differences in pulmonary CFU were found between control, sham therapy, or LPT when phosphate-buffered saline was administered; however, the reduction in CFU was statistically significant in all rats given levofoxacin. The combination of sham therapy and levofoxacin decreased bacterial load at 72 and 96 hours after infection, and LPT and levofoxacin significantly reduced CFU compared with sham therapy and levofoxacin at both time points (P<.05). Colony-forming units were not detected in the spleens at any time. No statistically significant differences in hematologic findings between any treatment groups were found at any time point measured.

Conclusion: The results suggest that 3 applications of LPT induces an additional protective mechanism when combined with levofoxacin and support its use as an adjunctive therapy for the management of pneumonia; however, the mechanism responsible for this protection is unclear.

Portal cytokine response and metabolic markers in the early stages of abdominal sepsis in pigs

BACKGROUND

The portal vein could play a major role in disseminating the local inflammation of acute bacterial peritonitis since it is responsible for the venous drainage of the gastrointestinal tract. We hypothesized that after peritoneal exposure to Escherichia coli, a gradient between the portal and systemic levels of cytokines would be expected.

METHODS

Acute peritonitis was induced by depositing 200 ml of broth with live E. coli in the peritoneal cavity of the animals in the B-group (n = 7). They were then observed for 4 h and compared with a control group (C-group, n = 7). Tumour necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-10 and vascular endothelial growth factor were measured repeatedly in the portal vein and the femoral artery. Portal vein metabolic markers (microdialysis), haemodynamics, biochemistry, plasma volume (PV), fluid shifts and total tissue water content were recorded or calculated.

RESULTS

The intervention led to PV contraction, increased fluid extravasation, increased pulmonary vascular resistance and reduced urinary output in the B-group as compared with the C-group. The levels of glucose in the portal vein were reduced in both study groups with no between-group differences. The levels of TNF-α and IL-6 increased markedly in the portal vein as well as in the systemic circulation of the B-group, but no gradient was seen between them. The corresponding levels of TNF-α and IL-6 remained low and stable in the C-group.

CONCLUSION

The portal vein appears to play a minor role in supplying TNF-α and IL-6 to the systemic circulation after peritoneal exposure to a substantial dose of E. coli.

CCK1-receptor stimulation protects against gut mediator-induced lung damage during endotoxemia

Background/Aims

Cholecystokinin 1-receptor (CCK1-R) activation by long chain fatty acid (LCFA) absorption stimulates vago-vagal reflex pathways in the brain stem. The present study determines whether this reflex also activates the cholinergic anti-inflammatory pathway, a pathway known to modulate cytokine release during endotoxemia.

Methods

Mesenteric lymph was obtained from wild type (WT) and CCK1-R knockout (CCK1-R^−/−) mice intraperitoneally challenged with Lipopolysaccharid (LPS) (endotoxemic lymph, EL) and intestinally infused with vehicle or LCFA-enriched solution. The lymph was analyzed for TNFα, IL-6 and IL-10 concentration and administered to healthy recipient mice via jugular infusion. Alveolar wall thickness, myeloperoxidase (MPO) and TUNEL positive cells were determined in lung tissue of recipient mice.

Results

LCFA infusion in WT mice reduced TNFα concentration in EL by 49% compared to vehicle infusion, but had no effect in CCK1-R^−/− mice. EL significantly increased the alveolar wall thickness, the number of MPO-positive and TUNEL-positive cells compared to control lymph administration. LCFA infusion in WT, but not in CCK1R^−/− mice, significantly reduced these pathological effects of EL.

Conclusion

During endotoxemia enteral LCFA absorption reduces TNFα release into mesenteric lymph and attenuates histomorphologic parameters of lung dysfunction. Failure to elicit this effect in CCK1R^−/− mice demonstrates that anti-inflammatory properties of LCFAs are mediated through CCK1-Rs.

Role of lipase-generated free fatty acids in converting mesenteric lymph from a noncytotoxic to a cytotoxic fluid

Recent studies have shown that mesenteric lymph plays a very important role in the development of multiple-organ dysfunction syndrome under critical conditions. Great efforts have been made to identify the biologically active molecules in the lymph. We used a trauma-hemorrhagic shock (T/HS) model and the superior mesenteric artery occlusion (SMAO) model, representing a global and a localized intestinal ischemia-reperfusion insult, respectively, to investigate the role of free fatty acids (FFAs) in the cytotoxicity of mesenteric lymph in rats. Lymph was collected before, during, and after (post) shock or SMAO. The post-T/HS and SMAO lymph, but not the sham lymph, manifested cytotoxicity for human umbilical vein endothelial cells (HUVECs). HUVEC cytotoxicity was associated with increased FFAs, especially the FFA-to-protein ratio. Addition of albumin, especially delipidated albumin, reduced this cytotoxicity. Lipase treatment of trauma-sham shock (T/SS) lymph converted it from a noncytotoxic to a cytotoxic fluid, and its toxicity correlated with the FFA-to-protein ratio in a fashion similar to that of the T/HS lymph, further suggesting that FFAs were the key components leading to HUVEC cytotoxicity. Analysis of lymph by gas chromatography revealed that the main FFAs in the post-T/HS or lipase-treated T/SS lymph were palmitic, stearic, oleic, and linoleic acids. When added to the cell culture at levels comparable to those in T/HS lymph, all these FFAs were cytotoxic, with linoleic acid being the most potent. In conclusion, this study suggests that lipase-generated FFAs are the key components resulting in the cytotoxicity of T/HS and SMAO mesenteric lymph.

Activation of toll-like receptor 4 is necessary for trauma hemorrhagic shock-induced gut injury and polymorphonuclear neutrophil priming

Interactions of toll-like receptors (TLRs) with nonmicrobial factors play a major role in the pathogenesis of early trauma-hemorrhagic shock (T/HS)-induced organ injury and inflammation. Thus, we tested the hypothesis that TLR4 mutant (TLR4 mut) mice would be more resistant to T/HS-induced gut injury and polymorphonuclear neutrophil (PMN) priming than their wild-type littermates and found that both were significantly reduced in the TLR4 mut mice. In addition, the in vivo and ex vivo PMN priming effect of T/HS intestinal lymph observed in the wild-type mice was abrogated in TLR4 mut mice as well the TRIF mut-deficient mice and partially attenuated in Myd88 mice, suggesting that TRIF activation played a more predominant role than MyD88 in T/HS lymph-induced PMN priming. Polymorphonuclear neutrophil depletion studies showed that T/HS lymph-induced acute lung injury was PMN dependent, because lung injury was totally abrogated in PMN-depleted animals. Because the lymph samples were sterile and devoid of endotoxin or bacterial DNA, we investigated whether the effects of T/HS lymph was related to endogenous nonmicrobial TLR4 ligands. High-mobility group box 1 protein 1, heat shock protein 70, heat shock protein 27, and hyaluronic acid all have been implicated in ischemia-reperfusion-induced tissue injury. None of these "danger" proteins appeared to be involved, because their levels were similar between the sham and shock lymph samples. In conclusion, TLR4 activation is important in T/HS-induced gut injury and in T/HS lymph-induced PMN priming and lung injury. However, the T/HS-associated effects of TLR4 on gut barrier dysfunction can be uncoupled from the T/HS lymph-associated effects of TLR4 on PMN priming.

Osteopathic lymphatic pump techniques to enhance immunity and treat pneumonia

Pneumonia is a common cause of morbidity and mortality worldwide. While antibiotics are generally effective for the treatment of infection, the emergence of resistant strains of bacteria threatens their success. The osteopathic medical profession has designed a set of manipulative techniques called lymphatic pump techniques (LPT), to enhance the flow of lymph through the lymphatic system. Clinically, LPT is used to treat infection and oedemaand might be an effective adjuvant therapy in patients with pneumonia.The immune system uses the lymphatic and blood systems to survey to rid the body of pathogens; however, only recently have the effects of LPT on the lymphatic and immune systems been investigated. This short review highlightsclinical and basic science research studies that support the use of LPT to enhance the lymphatic and immune systems and treat pneumonia, and discusses the potential mechanisms by which LPT benefits patients with pneumonia.

Anticoagulants influence the in vitro activity and composition of shock lymph but not its in vivo activity

Many models of trauma-hemorrhagic shock (T/HS) involve the reinfusion of anticoagulated shed blood. Our recent observation that the anticoagulant heparin induces increased mesenteric lymph lipase activity and consequent in vitro endothelial cell cytotoxicity prompted us to investigate the effect of heparin-induced lipase activity on organ injury in vivo as well as the effects of other anticoagulants on mesenteric lymph bioactivity in vitro and in vivo. To investigate this issue, rats subjected to trauma-hemorrhage had their shed blood anticoagulated with heparin, the synthetic anticoagulant arixtra (fondaparinux sodium), or citrate. Arixtra, in contrast to heparin, did not increase lymph lipase activity or result in high levels of endothelial cytotoxicity. Yet, the arixtra-treated rats subjected to T/HS still manifested lung injury, neutrophil priming, and red blood cell dysfunction, which was totally abrogated by lymph duct ligation. Furthermore, the injection of T/HS mesenteric lymph, but not sham-shock lymph, collected from the arixtra rats into control mice recreated the pattern of lung injury, polymorphonucleocyte (PMN) priming, and red blood cell dysfunction observed after actual shock. Consistent with these observations, citrate-anticoagulated rats subjected to T/HS developed lung injury, and the injection of mesenteric lymph from the citrate-anticoagulated T/HS rats into control mice also resulted in lung injury. Based on these results, several conclusions can be drawn. First, heparin-induced increased mesenteric lymph lipase activity is not responsible for the in vivo effects of T/HS mesenteric lymph. Second, heparin should be avoided as an anticoagulant when studying the biology or composition of mesenteric lymph because of its ability to cause increases in lymph lipase activity that increase the in vitro cytotoxicity of these lymph samples.

Recombinant human erythropoietin improves gut barrier function in a hemorrhagic shock and resuscitation rat model

BACKGROUND

Gut injury and bacterial translocation develop and persist after limited periods of hemorrhagic shock. Erythropoietin (EPO) can exert hemodynamic, anti-inflammatory, and tissue protective effects. We tested the hypothesis that EPO given at the time of resuscitation with saline will reduce functional ileal injury 24 hours after shock.

METHODS

Sprague-Dawley rats (n = 6 per group) were randomized to sham surgery or hemorrhagic shock maintained at mean arterial pressure 40 mm Hg for 60 minutes and then treated with either saline resuscitation (three times the volume of shed blood) or saline + recombinant human EPO (rHuEPO) resuscitation. Intravenous rHuEPO (1,000 U/kg) was given at the start of saline resuscitation, and at 24 hours ileal function was evaluated using quantitative cultures of mesenteric lymph nodes to assess for bacterial translocation (colony-forming units per gram of tissue [CFU/g]), determination of portal vein plasma endotoxin levels and histopathological evaluation using semi-thin plastic sections of the distal ileum. In a second series of animals, fluorescein isothiocyanate-dextran 4000 (FD-4) was used to assess mucosal permeability of the distal ileum to macromolecules.

RESULTS

At 24 hours, the saline group had morphologic evidence of intestinal injury when compared with the sham group, and the degree of mucosal injury was less in the saline + rHuEPO when compared with the saline group, which demonstrated significantly reduced bacterial translocation to the mesenteric lymph nodes (383 CFU/g ± 111 CFU/g vs. 1130 CFU/g ± 297 CFU/g; p < 0.05) and decreased terminal ileum permeability to FD-4 (3.08 μg/mL ± 0.31 μg/mL vs. 5.14 μg/mL ± 0.88 μg/mL; p < 0.05). No significant difference was found in the portal vein endotoxin levels between the two groups. Histopathological evaluation demonstrated a trend for decreased enterocyte disarray or disruption and vacuolization in the saline + rHuEPO versus saline group.

CONCLUSION

Using rHuEPO at time of saline resuscitation resulted in decreased bacterial translocation and permeability to macromolecules 24 hours after shock. These observations suggest that rHuEPO can mediate a protective effect on intestinal mucosal barrier function during ischemic injury.

Lymphatic pump manipulation mobilizes inflammatory mediators into lymphatic circulation

Lymph stasis can result in edema and the accumulation of particulate matter, exudates, toxins and bacteria in tissue interstitial fluid, leading to inflammation, impaired immune cell trafficking, tissue hypoxia, tissue fibrosis and a variety of diseases. Previously, we demonstrated that osteopathic lymphatic pump techniques (LPTs) significantly increased thoracic and intestinal duct lymph flow. The purpose of this study was to determine if LPT would mobilize inflammatory mediators into the lymphatic circulation. Under anesthesia, thoracic or intestinal lymph of dogs was collected at resting (pre-LPT), during four minutes of LPT, and for 10 min following LPT (post-LPT), and the lymphatic concentrations of interleukin-2 (IL-2), IL-4, IL-6, IL-10, interferon- γ, tissue necrosis factor α,  monocyte chemotactic protein-1 (MCP-1), keratinocyte chemoattractant, superoxide dismutase (SOD) and nitrotyrosine (NT) were measured. LPT significantly increased MCP-1 concentrations in thoracic duct lymph. Further, LPT increased both thoracic and intestinal duct lymph flux of cytokines and chemokines as compared with their respective pre-LPT flux. In addition, LPT increased lymphatic flux of SOD and NT. Ten minutes following cessation of LPT, thoracic and intestinal lymph flux of cytokines, chemokines, NT and SOD were similar to pre-LPT, demonstrating that their flux was transient and a response to LPT. This re-distribution of inflammatory mediators during LPT may provide scientific rationale for the clinical use of LPT to enhance immunity and treat infection.

Cross-transfusion of postshock mesenteric lymph provokes acute lung injury

OBJECTIVE

Substantial investigation has implicated mesenteric lymph as the mechanistic link between gut ischemia/reperfusion (I/R) and distant organ injury. Specifically, lymph diversion prevents acute lung injury (ALI) in vitro, and bioactive lipids and proteins isolated from postshock mesenteric lymph (PSML) maintain bioactivity in vitro. However, Koch's postulates remain to be satisfied via direct cross-transfusion into a naïve animal. We therefore hypothesized that real time cross-transfusion of postshock mesenteric lymph provokes acute lung injury.

METHODS

One set of Sprague-Dawley rats (lymph donors) was anesthetized, with the mesenteric lymph ducts cannulated and exteriorized to drain freely into a siliconates plastic cup; concurrently, a second group of rats ( lymph recipients) was anesthetized, with a cannula inserted into the animal's right internal jugular vein. Blood was removed from the donor rats to induce hemorrhagic shock (MAP of 35 mmHg × 45 min). The recipient rats were positioned 10 cm below the plastic cup, which emptied into the jugular vein cannula. Thus, mesenteric lymph from the shocked donor rat was delivered to the recipient rat at the rate generated during shock and the subsequent 3 h of resuscitation.

RESULTS

Neutrophil (PMN) accumulation in the lungs was substantially elevated in the postshock lymph cross-transfusion group compared to both sham lymph cross-transfusion and instrumented control (MPO: 9.42 ± 1.55 versus 2.81 ± 0.82 U/mg lung tissue in postshock versus sham lymph cross-transfusion, n = 6 in each group, P = 0.02). Additionally, cross-transfusion of PSML induced oxidative stress in the lung (0.21 ± 0.03 versus 0.10 ± 0.01 micromoles MDA per mg lung tissue in lymph cross-transfusion versus instrumented control, n = 6 in each group, P = 0.046). Furthermore, transfusion of PSML provoked lung injury (BAL protein 0.77 ± 0.18 versus 0.15 ± 0.02 mg/mL protein in BALF, postshock versus sham lymph cross-transfusion, n = 6 in each group, P = 0.004).

CONCLUSION

Cross-transfusion of PSML into a naïve animal leads to PMN accumulation and provokes ALI. These data provide evidence that postshock agents released into mesenteric lymph are capable of provoking distant organ injury.

Lymph duct ligation during ischemia/reperfusion prevents pulmonary dysfunction in a rat model with ω-3 polyunsaturated fatty acid and glutamine

OBJECTIVE

The release of injurious factors into the mesenteric lymph from the ischemic intestine has been shown to contribute to lung injury and systemic inflammation after severe injury. We studied the effects of lung injury and systemic inflammatory reaction after intestinal ischemia/reperfusion and mesenteric lymph duct ligation with different nutritional statuses.

METHODS

Rats (n = 72) were fed with a normal diet or received one of three diets (enteral nutrition, glutamine, or ω-3 polyunsaturated fatty acid) that were isocaloric and isonitrogenous. After 7 d, rats were subjected to 60 min of intestinal ischemia, ischemia plus mesenteric lymph duct ligation, or sham procedures. After 3 d of ischemia, the lymph nodes, lung, intestinal, liver, and blood were harvested and analyzed.

RESULTS

In the different groups, lung injury, including levels of myeloperoxidase, nitric oxide, nitric oxide synthase, and the index of alveolar apoptosis, were partly prevented by mesenteric lymph duct ligation (P < 0.05). Likewise, the rats with ischemia/reperfusion, but not those with duct ligation plus ischemia/reperfusion, had a significant increase in intestinal permeability and decreased mucosal thickness. The serum cytokine and endotoxin concentrations were also lower in the lymph duct ligation groups, although there was no significant difference between lymph duct ligation and sham procedure. The lung and intestinal injuries were attenuated in the groups fed with glutamine and ω-3 polyunsaturated fatty acid.

CONCLUSION

These results indicate that lymph duct ligation prevents lung injury, a systemic inflammation reaction, and gut-barrier dysfunction. Enteral glutamine and ω-3 polyunsaturated fatty acid modified the gut inflammation, prevented lung injury, and attenuated the systemic inflammation reaction.

Mesenteric lymph from rats with trauma-hemorrhagic shock causes abnormal cardiac myocyte function and induces myocardial contractile dysfunction

Myocardial contractile dysfunction develops following trauma-hemorrhagic shock (T/HS). We have previously shown that, in a rat fixed pressure model of T/HS (mean arterial pressure of 30-35 mmHg for 90 min), mesenteric lymph duct ligation before T/HS prevented T/HS-induced myocardial contractile depression. To determine whether T/HS lymph directly alters myocardial contractility, we examined the functional effects of physiologically relevant concentrations of mesenteric lymph collected from rats undergoing trauma-sham shock (T/SS) or T/HS on both isolated cardiac myocytes and Langendorff-perfused whole hearts. Acute application of T/HS lymph (0.1-2%), but not T/SS lymph, induced dual inotropic effects on myocytes with an immediate increase in the amplitude of cell shortening (1.4 ± 0.1-fold) followed by a complete block of contraction. Similarly, T/HS lymph caused dual, positive and negative effects on cellular Ca²⁺ transients. These effects were associated with changes in the electrophysiological properties of cardiac myocytes; T/HS lymph initially prolonged the action potential duration (action potential duration at 90% repolarization, 3.3 ± 0.4-fold), and this was followed by a decrease in the plateau potential and membrane depolarization. Furthermore, intravenous infusion of T/HS lymph, but not T/SS lymph, caused myocardial contractile dysfunction at 24 h after injection, which mimicked actual T/HS-induced changes; left ventricular developed pressure (LVDP) and the maximal rate of LVDP rise and fall (±dP/dt(max)) were decreased and inotropic response to Ca²⁺ was blunted. However, the contractile responsiveness to β-adrenergic receptor stimulation in the T/HS lymph-infused hearts remained unchanged. These results suggest that T/HS lymph directly causes negative inotropic effects on the myocardium and that T/HS lymph-induced changes in myocyte function are likely to contribute to the development of T/HS-induced myocardial dysfunction.

Quantification of superoxide radical production in 4 vital organs of rats subjected to hemorrhagic shock

OBJECTIVE

The aim of this study was to measure the production of superoxide radical (O2-), a direct indicator of oxidative stress, in 4 vital organs of rats subjected to hemorrhagic shock. For this purpose, and for the first time, a new quantitative assay for the ex vivo measurement of O2- via an established 1:1 molar relationship between O2- and 2-OH-ethidium was used. The production of lipid hydroperoxides (LOOHs), a standard method of evaluation of oxidative stress, was also used for reasons of comparison.

METHODS

Sixteen male Wistar rats were divided into 2 groups: sham and hemorrhagic shock, targeting to a mean arterial pressure of 30 to 40 mm Hg for 60 minutes. Three hours after resuscitation, tissues were collected for measurement of LOOHs and O2- production.

RESULTS

Hemorrhagic shock induced increased production of LOOHs in the gut, liver, and lungs (P<.001), whereas the production of O2- was also increased in the gut (P<.001), liver (P<.001), and, to a lesser extent, in the lungs (P<.05). The oxidative load of the kidneys, as estimated by both techniques, remained unaffected.

CONCLUSION

The results of this new O2- assay were comparable with the results of the established LOOHs method, and this assay proved to be accurate and sensitive in the detection and quantification of O2- production in all organs tested. Thus, the proposed direct measurement of O2- in critically ill patients often facing in extremis situations could be used as a prognostic tool and as a method to evaluate therapeutic interventions in the setting of emergency medicine.

Tumor necrosis factor is not associated with intestinal ischemia/reperfusion-induced lung inflammation

Intestinal ischemia-reperfusion (I/R) injury may cause acute systemic and lung inflammation. Here, we revisited the role of TNF-alpha in an intestinal I/R model in mice, showing that this cytokine is not required for the local and remote inflammatory response upon intestinal I/R injury using neutralizing TNF-alpha antibodies and TNF ligand-deficient mice. We demonstrate increased neutrophil recruitment in the lung as assessed by myeloperoxidase activity and augmented IL-6, granulocyte colony-stimulating factor, and KC levels, whereas TNF-alpha levels in serum were not increased and only minimally elevated in intestine and lung upon intestinal I/R injury. Importantly, TNF-alpha antibody neutralization neither diminished neutrophil recruitment nor any of the cytokines and chemokines evaluated. In addition, the inflammatory response was not abrogated in TNF and TNF receptors 1 and 2-deficient mice. However, in view of the damage on the intestinal barrier upon intestinal I/R with systemic bacterial translocation, we asked whether Toll-like receptor (TLR) activation is driving the inflammatory response. In fact, the inflammatory lung response is dramatically reduced in TLR2/4-deficient mice, confirming an important role of TLR receptor signaling causing the inflammatory lung response. In conclusion, endogenous TNF-alpha is not or minimally elevated and plays no role as a mediator for the inflammatory response upon ischemic tissue injury. By contrast, TLR2/4 signaling induces an orchestrated cytokine/chemokine response leading to local and remote pulmonary inflammation, and therefore disruption of TLR signaling may represent an alternative therapeutic target.

Claude H. Organ, Jr. memorial lecture: splanchnic hypoperfusion provokes acute lung injury via a 5-lipoxygenase-dependent mechanism

Postinjury multiple organ failure (MOF) is the net result of a dysfunctional immune response to injury characterized by a hyperactive innate system and a suppressed adaptive system. Acute lung injury (ALI) is the first clinical manifestation of organ failure, followed by renal and hepatic dysfunction. Circulatory shock is integral in the early pathogenesis of MOF, and the gut has been invoked as the motor of MOF. Mesenteric lymph is recognized as the mechanistic link between splanchnic ischemia/reperfusion and distant organ dysfunction, but the specific mediators remain to be defined. Current evidence suggests the lipid fraction of postshock mesenteric lymph is central in the etiology of ALI. Specifically, our recent work suggests that intestinal phospholipase A2 generated arachidonic acid and its subsequent 5-lipoxygenase products are essential in the pathogenesis of ALI. Proteins conveyed via postshock mesenteric lymph also may have an important role. Elucidating these mediators and the timing of their participation in pulmonary inflammation is critical in translating our current knowledge to new therapeutic strategies at the bedside.

Gut lymph and lymphatics: a source of factors leading to organ injury and dysfunction

Major trauma, shock, sepsis, and other conditions can lead to the acute respiratory distress syndrome (ARDS), which may progress to the highly lethal multiple organ dysfunction syndrome (MODS). Although a number of therapeutic strategies have been initiated, their success has been limited largely due to an incomplete understanding of the biology of MODS. However, recent studies indicate that the intestinal lymphatics serve as the primary route for nonbacterial, tissue injurious gut-derived factors, which can induce acute ARDS and MODS. The gut lymph hypothesis of ARDS and MODS thus helps clarify several important issues. First, because the lung is the first organ exposed to mesenteric lymph and not the liver (i.e., mesenteric lymph enters the subclavian vein via the thoracic duct, which, in turn, empties directly into the heart and lungs), it would explain the clinical observation that the lung is generally the first organ to fail. Second, this hypothesis provides new pathophysiologic information, thereby providing a basis for novel therapies. Finally, by studying the composition of lymph, MODS-inducing factors can be isolated and identified.

Therapeutic distant organ effects of regional hypothermia during mesenteric ischemia-reperfusion injury

INTRODUCTION

Mesenteric ischemia-reperfusion injury (IRI) leads to systemic inflammation and multiple organ failure in clinical and laboratory settings. We investigated the lung structural, functional, and genomic response to mesenteric IRI with and without regional intraischemic hypothermia (RIH) in rodents and hypothesized that RIH would protect the lung and preferentially modulate the distant organ transcriptome under these conditions.

METHODS

Sprague-Dawley rats underwent sham laparotomy or superior mesenteric artery occlusion (SMAO) for 60 minutes with or without RIH. Gut temperature was maintained at 15°-20°C during SMAO, and systemic normothermia (37°C) was maintained throughout the study period. At 6 or 24 hours, lung tissue was collected for (1) histology, (2) myeloperoxidase activity, (3) bronchoalveolar lavage (BAL) fluid protein concentrations, (4) lung wet/dry ratios, and (5) total RNA isolation and hybridization to Illumina's Sentrix BeadChips (>22,000 probes) for gene expression profiling. Significantly affected genes (false discovery rate <5% and fold change ≥1.5) were linked to gene ontology (GO) terms using MAPPFinder, and hypothermia-suppressed genes were further analyzed with Pubmatrix.

RESULTS

Mesenteric IRI-induced lung injury, as evidenced by leukocyte trafficking, alveolar hemorrhage, and increased BAL protein and wet/dry ratios, and activated a proinflammatory lung transcriptome compared with sham. In contrast, rats treated with RIH exhibited lung histology, BAL protein, and wet/dry ratios similar to sham. At 6 hours, GO analysis identified 232 hypothermia-suppressed genes related to inflammation, innate immune response, and cell adhesion, and 33 hypothermia-activated genes related to lipid and amine metabolism and defense response. Quantitative real-time polymerase chain reaction validated select array changes in top hypothermia-suppressed genes lipocalin-2 (lcn-2) and chemokine ligand 1 (CXCL-1), prominent genes associated with neutrophil activation and trafficking.

CONCLUSIONS

Therapeutic hypothermia during SMAO provides distant organ protection and preferentially modulates the IRI-activated transcriptome in the rat lung. This study identifies potential novel diagnostic and therapeutic targets of mesenteric IRI and provides a platform for further mechanistic study of hypothermic protection at the cellular and subcellular level.

Effect of biliary tract external drainage on cytokine expression and histomorphology of intestine, liver, and lung in rats with hemorrhagic shock

OBJECTIVE

To investigate the protective effect of biliary tract external drainage on cytokine expression and pathomorphism of intestine, liver, and lung in rats with hemorrhagic shock.

DESIGN

Randomized, control animal study.

SETTING

This study was conducted at The Institution Digestive Surgery Research Laboratory of Shanghai Jiao Tong University.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Biliary tract external drainage was performed by inserting a cannula into the bile duct. Hemorrhagic shock was induced by drawing blood from the carotid artery.

MEASUREMENTS AND MAIN RESULTS

Twenty-four Sprague-Dawley rats were randomized to three equal groups of eight: sham shock; hemorrhagic shock; and hemorrhagic shock plus bile duct drainage. The messenger RNA expression of tumor necrosis factor-alpha, interleukin-6 in the intestine, liver, and lung tissue from the three groups were analyzed by reverse transcription-polymerase chain reaction. Tumor necrosis factor-alpha was analyzed in the bile of the rats by enzyme-linked immunosorbent assay. Histology of intestine, liver, and lung was performed in all groups by hematoxylin and eosin staining. The messenger RNA expression of tumor necrosis factor-alpha was significantly increased in the hemorrhagic shock group compared with the sham shock group (intestine 0.54 +/- 0.07 vs. 0.37 +/- 0.05, liver 1.01 +/- 0.06 vs. 0.56 +/- 0.07, lung 0.94 +/- 0.07 vs. 0.62 +/- 0.06). The messenger RNA expression of interleukin-6 was also significantly increased in the hemorrhagic shock group compared with the sham shock group (intestine 0.89 +/- 0.12 vs. 0.50 +/- 0.09, liver 1.07 +/- 0.10 vs. 0.57 +/- 0.12, lung 1.09 +/- 0.09 vs. 0.67 +/- 0.06). Biliary tract external drainage reduced significantly the messenger RNA expression of tumor necrosis factor-alpha (intestine 0.43 +/- 0.06 vs. 0.54 +/- 0.07, liver 0.74 +/- 0.18 vs. 1.01 +/- 0.06, lung 0.87 +/- 0.15 vs. 0.94 +/- 0.07) and interleukin-6 (intestine 0.60 +/- 0.11 vs. 0.89 +/- 0.12, liver 0.71 +/- 0.16 vs. 1.07 +/- 0.10, lung 0.88 +/- 0.25 vs. 1.09 +/- 0.09). The concentration of tumor necrosis factor-alpha in bile was significantly higher in the hemorrhagic shock group compared with the sham shock group (31.22 +/- 6.44 ng/mL vs. 15.49 +/- 3.64 ng/mL, p < .01). The histologic observation of the intestine, liver, and lung showed that the biliary tract external drainage significantly attenuate the putrescence and exfoliation of intestinal villi, denaturation and putrescence of hepatocytes, edema, and inflammatory cells infiltration of lung.

CONCLUSIONS

Biliary tract external drainage decreases the messenger RNA expression of tumor necrosis factor-alpha, interleukin-6 and attenuate the tissue injury of the intestine, liver, and lung in rats model of hemorrhagic shock. The gut-liver axis was implicated to play a crucial role in hemorrhagic shock-induced multiple organ dysfunction syndrome.

Nitric oxide mediates lung vascular permeability and lymph-borne IL-6 after an intestinal ischemic insult

Acute lung injury following intestinal I/R depends on neutrophil-endothelial cell interactions and on cytokines drained from the gut through the lymph. Among the mediators generated during I/R, increased serum levels of IL-6 and NO are also found and might be involved in acute lung injury. Once intestinal ischemia itself may be a factor of tissue injury, in this study, we investigated the presence of IL-6 in lymph after intestinal ischemia and its effects on human umbilical vein endothelial cells (HUVECs) detachment. The involvement of NO on the increase of lung and intestinal microvascular permeability and the lymph effects on HUVEC detachment were also studied. Upon anesthesia, male Wistar rats were subjected to occlusion of the superior mesenteric artery during 45 min, followed by 2-h intestinal reperfusion. Rats were treated with the nonselective NO synthase (NOS) inhibitor L-NAME (N(omega)-nitro-L-arginine methyl ester) or with the selective inhibitor of iNOS aminoguanidine 1 h before superior mesenteric artery occlusion. Whereas treatment with L-NAME during ischemia increased both IL-6 levels in lymph and lung microvascular permeability, aminoguanidine restored the augmented intestinal plasma extravasation due to ischemia and did not induce IL-6 in lymph. On the other hand, IL-6 and lymph of intestinal I/R detached the HUVECs, whereas lymph of ischemic rats upon L-NAME treatment when incubated with anti-IL-6 prevented HUVEC detachment. It is shown that the intestinal ischemia itself is sufficient to increase intestinal microvascular permeability with involvement of iNOS activation. Intestinal ischemia and absence of constitutive NOS activity leading to additional intestinal stress both cause release of IL-6 and increase of lung microvascular permeability. Because anti-IL-6 prevented the endothelial cell injury caused by lymph at the ischemia period, the lymph-borne IL-6 might be involved with endothelial cell activation. At the reperfusion period, this cytokine does not seem to be modulated by NO.

Systemic not just mesenteric lymph causes neutrophil priming after hemorrhagic shock

BACKGROUND

Inflammatory mediators in postshock mesenteric lymph have been causally linked to systemic polymorphonuclear cells (PMNs) priming resulting in acute lung injury (ALI) and multiple organ failure. Earlier human and animal studies demonstrated ALI after lower limb ischemia/reperfusion (I/R) injury. As hemorrhagic shock (HS) is in essence a systemic I/R insult, we postulated that systemic lymph after HS would exhibit PMN priming and this was studied in vitro.

METHODS

Lymph was collected at intervals from the hind limb of dogs subjected to sham or HS and crystalloid resuscitation. Human PMNs isolated from heparinized blood of normal volunteers were incubated with buffer, sham lymph, or lymph after 120 minutes of shock or resuscitation. PMN priming was indexed by CD11b expression (mean fluorescence intensity), superoxide anion (O2(-)) generation (nanomoles/mg protein), and elastase release (%) after the addition of fMLP (1 micromol). PMNs with buffer served as control.

RESULTS

PMN priming after exposure to either shock or postshock resuscitation lymph was noted by increased expression of CD11b, superoxide generation, and elastase release after exposure to fMLP. No priming effect was noted with sham lymph. Maximal bioactivity of shock or postresuscitation shock lymph was noted at 2 hours postresuscitation.

CONCLUSIONS

Exposure with systemic lymph after HS resulted in PMN priming. These results question the unique properties attributed to post-HS lymph from the splanchnic bed in causing PMN priming and ALI after shock. The causal agent(s) for these effects are unclear.

Mesenteric lymph duct ligation improves survival in a lethal shock model

The goal of this study was to test the hypothesis that factors released from the gut and carried in the mesenteric lymph contribute to mortality in a lethal gut I/R model. To test this hypothesis, a lethal splanchnic artery occlusion (SAO) shock model was used in male Sprague-Dawley rats. In the first set of experiments, ligation of the mesenteric lymph duct (LDL), which prevents gut-derived factors carried in the intestinal lymphatics from reaching the systemic circulation, significantly improved 24-h survival after a 20-min SAO insult (0% vs. 60% survival; P < 0.05). This increase in survival in the LDL-treated rats was associated with a blunted hypotensive response. Because increased iNOS-induced NO levels have been implicated in SAO-induced shock, we measured plasma nitrite/nitrate levels and liver iNOS protein levels in a second group of animals. Ligation of the mesenteric lymph duct significantly abrogated the SAO-induced increase in plasma nitrite/nitrate levels and the induction of hepatic iNOS (P < 0.05). In an additional series of studies, we documented that LDL increased not only 24-h but also long-term 7-day survival. During the course of these studies, we made the unexpected finding that Sprague-Dawley rats from different animal vendors had differential resistance to SAO, and that the time of the year that the experiments were carried out also influenced the results. Nonetheless, in conclusion, these studies support the hypothesis that factors carried in the mesenteric lymph significantly contribute to the development of irreversible shock after SAO.

Trauma-hemorrhagic shock-induced pulmonary epithelial and endothelial cell injury utilizes different programmed cell death signaling pathways

Intestinal ischemia after trauma-hemorrhagic shock (T/HS) results in gut barrier dysfunction and the production/release of biologically active and tissue injurious factors in the mesenteric lymph, which, in turn, causes acute lung injury and a systemic inflammatory state. Since T/HS-induced lung injury is associated with pulmonary endothelial and epithelial cell programmed cell death (PCD) and was abrogated by mesenteric lymph duct ligation, we sought to investigate the cellular pathways involved. Compared with trauma-sham shock (T/SS) rats, a significant increase in caspase-3 and M30 expression was detected in the pulmonary epithelial cells undergoing PCD, whereas apoptosis-inducing factor (AIF), but not caspase-3, was detected in endothelial cells undergoing PCD. This AIF-mediated pulmonary endothelial PCD response was validated in an in situ femoral vein assay where endothelial cells were found to express AIF but not caspase-3. To complement these studies, human umbilical vein endothelial cell (HUVEC), human lung microvascular endothelial cell (HLMEC), and human alveolar type II epithelial cell (A549) lines were used as in vitro models. T/HS lymph induced the nuclear translocation of AIF in HUVEC and HLMEC, and caspase inhibition in these cells did not afford any cytoprotection. For proof of principle, AIF silencing in HUVEC reversed the cytotoxic effects of T/HS on cell viability and DNA fragmentation. In A549 cells, T/HS lymph activated caspase-3-mediated apoptosis, which was partially abrogated by N-benzyloxycarbonyl-Val-Ala-Asp (zVAD). Additionally, T/HS lymph did not cause the nuclear translocation of AIF in A549 cells. Collectively, T/HS-induced pulmonary endothelial PCD occurs via an AIF-dependent caspase-independent pathway, whereas epithelial cells undergo apoptosis by a caspase-dependent pathway.

Mesenteric lymph duct ligation prevents trauma/hemorrhage shock-induced cardiac contractile dysfunction

Clinical and experimental studies have shown that trauma combined with hemorrhage shock (T/HS) is associated with myocardial contractile dysfunction. However, the initial events triggering the cardiac dysfunction are not fully elucidated. Thus we tested the hypothesis that factors carried in intestinal (mesenteric) lymph contribute to negative inotropic effects in rats subjected to a laparotomy (T) plus hemorrhagic shock (HS; mean arterial blood pressure of 30-40 Torr for 90 min) using a Langendorff isolated heart preparation. Left ventricular (LV) function was assessed 24 h after trauma plus sham shock (T/SS) or T/HS by recording the LV developed pressure (LVDP) and the maximal rate of LVDP rise and fall ( +/- dP/dt(max)) in five groups of rats: 1) naive noninstrumented rats, 2) rats subjected to T/SS, 3) rats subjected to T/HS, 4) rats subjected to T/SS with mesenteric lymph duct ligation (T/SS+LDL), or 5) rats subjected to T/HS+LDL. Cardiac function was comparable in hearts from naive, T/SS, and T/SS+LDL rats. Both LVDP and +/- dP/dt(max) were significantly depressed after T/HS. The T/HS hearts also manifested a blunted responsiveness to increases in coronary flow rates and Ca(2+), and this was prevented by LDL preceding T/HS. Although electrocardiograms were normal under physiological conditions, when the T/HS hearts were perfused with low Ca(2+) levels ( approximately 0.5 mM), prolonged P-R intervals and second-degree plus Wenckebach-type atrioventricular blocks were observed. No such changes occurred in the control or T/HS+LDL hearts. The effects of T/HS were similar to those of the Ca(2+) channel antagonist diltiazem, indicating that an impairment of cellular Ca(2+) handling contributes to T/HS-induced cardiac dysfunction. In conclusion, gut-derived factors carried in mesenteric lymph are responsible for acute T/HS-induced cardiac dysfunction.

Phosphodiesterase inhibition attenuates alterations to the tight junction proteins occludin and ZO-1 in immunostimulated Caco-2 intestinal monolayers

AIMS

Under normal conditions, the intestinal mucosa acts as a local barrier to prevent the influx of luminal contents. The intestinal epithelial tight junction is comprised of several membrane associated proteins, including zonula occludens-1 (ZO-1) and occludin. Disruption of this barrier can lead to the production of pro-inflammatory mediators and ultimately multiple organ failure. We have previously shown that Pentoxifylline (PTX) decreases histologic gut injury and pro-inflammatory mediator synthesis. We hypothesize that PTX prevents the breakdown of ZO-1 and occludin in an in vitro model of immunostimulated intestinal cell monolayers.

MAIN METHODS

Caco-2 human enterocytes were grown as confluent monolayers and incubated under control conditions, or with PTX (2 mM), Cytomix (TNF-alpha, IFN-gamma, IL-1), or Cytomix+PTX for 24 h. Occludin and ZO-1 protein levels were analyzed by Western blot. Confocal microscopy was used to assess the cytoplasmic localization of ZO-1 and occludin.

KEY FINDINGS

Cytomix stimulation of Caco-2 cells resulted in a 50% decrease in both occludin and ZO-1 protein. Treatment with Cytomix+PTX restored both occludin and ZO-1 protein to control levels. Confocal microscopy images show that Cytomix caused an irregular, undulating appearance of ZO-1 and occludin at the cell junctions. Treatment with PTX prevented the Cytomix-induced changes in ZO-1 and occludin localization.

SIGNIFICANCE

Treatment with PTX decreases the pro-inflammatory cytokine induced changes in the intestinal tight junction proteins occludin and ZO-1. Pentoxifylline may be a useful adjunct in the treatment of sepsis and shock by attenuating intestinal barrier breakdown.

Gut ischemia/reperfusion induced acute lung injury is an alveolar macrophage dependent event

BACKGROUND

Although the role of the lung alveolar macrophage (AM) as a mediator of acute lung injury (ALI) after lung ischemia/reperfusion (I/R) has been suggested by animal experiments, it has not been determined whether AMs mediate ALI after intestinal I/R. The objective of this study was to determine the effect of AM elimination on ALI after intestinal I/R in rats.

METHODS

Male Wistar rats (n = 90) were randomly divided into three groups: the clodronate-liposomes (CLOD-LIP) group received intratracheal treatment with CLOD-LIP; the liposomes (LIP) group received intratracheal treatment with LIP; and the nontreated (UNTREAT) group received no treatment. Twenty-four hours later each group was randomly divided into three subgroups: the intestinal I/R subgroup was subjected to 45-minute intestinal ischemia and 2-hour reperfusion; the laparotomy (LAP) subgroup was subjected to LAP and sham procedures; the control (CTR) subgroup received no treatment. At the end of reperfusion, ALI was quantitated in all the animals by the Evans blue dye (EBD) method.

RESULTS

ALI values are expressed as EBD lung leakage (microg EBD/g dry lung weight). EBD lung leakage values in the CLOD-LIP group were 32.59 +/- 12.74 for I/R, 27.74 +/- 7.99 for LAP, and 33.52 +/- 10.17 for CTR. In the LIP group, lung leakage values were 58.02 +/- 18.04 for I/R, 31.90 +/- 8.72 for LAP, and 27.17 +/- 11.48 for CTR. In the UNTREAT group, lung leakage values were 55.60 +/- 10.96 for I/R, 35.99 +/- 6.89 for LAP, and 30.83 +/- 8.41 for CTR. Within each group, LAP values did not differ from CTR values. However, in the LIP and UNTREAT groups, values for both the LAP and CTR subgroups were lower than values for the I/R subgroup (p < 0.001). The CLOD-LIP I/R subgroup value was less (p < 0.001) than the I/R subgroup values in the LIP and UNTREAT groups. These results indicated that I/R provokes ALI that can be prevented by CLOD-LIP treatment, and further suggested that AMs are essential for ALI occurrence induced by intestinal I/R in rats.

Introduction of an agent-based multi-scale modular architecture for dynamic knowledge representation of acute inflammation

Background

One of the greatest challenges facing biomedical research is the integration and sharing of vast amounts of information, not only for individual researchers, but also for the community at large. Agent Based Modeling (ABM) can provide a means of addressing this challenge via a unifying translational architecture for dynamic knowledge representation. This paper presents a series of linked ABMs representing multiple levels of biological organization. They are intended to translate the knowledge derived from in vitro models of acute inflammation to clinically relevant phenomenon such as multiple organ failure.

Results and Discussion

ABM development followed a sequence starting with relatively direct translation from in-vitro derived rules into a cell-as-agent level ABM, leading on to concatenated ABMs into multi-tissue models, eventually resulting in topologically linked aggregate multi-tissue ABMs modeling organ-organ crosstalk. As an underlying design principle organs were considered to be functionally composed of an epithelial surface, which determined organ integrity, and an endothelial/blood interface, representing the reaction surface for the initiation and propagation of inflammation. The development of the epithelial ABM derived from an in-vitro model of gut epithelial permeability is described. Next, the epithelial ABM was concatenated with the endothelial/inflammatory cell ABM to produce an organ model of the gut. This model was validated against in-vivo models of the inflammatory response of the gut to ischemia. Finally, the gut ABM was linked to a similarly constructed pulmonary ABM to simulate the gut-pulmonary axis in the pathogenesis of multiple organ failure. The behavior of this model was validated against in-vivo and clinical observations on the cross-talk between these two organ systems

Conclusion

A series of ABMs are presented extending from the level of intracellular mechanism to clinically observed behavior in the intensive care setting. The ABMs all utilize cell-level agents that encapsulate specific mechanistic knowledge extracted from in vitro experiments. The execution of the ABMs results in a dynamic representation of the multi-scale conceptual models derived from those experiments. These models represent a qualitative means of integrating basic scientific information on acute inflammation in a multi-scale, modular architecture as a means of conceptual model verification that can potentially be used to concatenate, communicate and advance community-wide knowledge.

Pancreatic duct ligation abrogates the trauma hemorrhage-induced gut barrier failure and the subsequent production of biologically active intestinal lymph

The studies of the mechanisms by which trauma-hemorrhagic shock leads to gut injury and dysfunction have largely ignored the nonbacterial factors contained within the lumen of the intestine. Yet, there is increasing evidence suggesting that intraluminal pancreatic proteases may be involved in this process. Thus, we tested the hypothesis that pancreatic proteases are necessary for the trauma-hemorrhagic shock-induced gut injury and the production of biologically active mesenteric lymph by determining the extent to which pancreatic duct ligation (PDL) would limit gut injury and mesenteric lymph bioactivity. To assess the effect of PDL on gut injury and dysfunction gut morphology, the mucus layer structure and the gut permeability were measured in the following four groups of male rats subjected to laparotomy (trauma) and hemorrhagic shock (pressure, 30 mmHg for 90 min): (1) rats subjected to trauma plus sham-shock (T/SS), (2) T/SS rats undergoing PDL (T/SS + PDL), (3) rats subjected to trauma and hemorrhagic shock (T/HS), and (4) rats subjected to T/HS + PDL. The ability of mesenteric lymph from these four rat groups to kill endothelial cells and activate neutrophils was tested in vitro. The PDL did not affect any of the parameters studied because there were no differences between the T/SS and the T/SS + PDL groups. However, PDL protected the gut from injury and dysfunction because PDL significantly abrogated T/HS-induced mucosal villous injury, loss of the intestinal mucus layer, and gut permeability. Likewise, PDL totally reversed the endothelial cell cytotoxic activity of T/HS lymph and reduced the ability of T/HS lymph to prime naive neutrophils for an augmented respiratory burst. Thus, it seems that intraluminal pancreatic proteases are necessary for the T/HS-induced gut injury and the production of bioactive mesenteric lymph.

Intravenous injection of trauma-hemorrhagic shock mesenteric lymph causes lung injury that is dependent upon activation of the inducible nitric oxide synthase pathway

OBJECTIVE

To test the hypothesis that gut-derived factors carried in trauma-hemorrhagic shock (T/HS) lymph is sufficient to induce lung injury. Additionally, because our previous studies showed that T/HS-induced nitric oxide production was associated with lung injury, we examined whether T/HS lymph-induced lung injury occurs via an inducible nitric oxide synthase (iNOS)-dependent pathway.

BACKGROUND

We have previously shown that T/HS-induced lung injury is mediated by gut-derived humoral factors carried in the mesenteric lymph. However, it remains unclear whether T/HS lymph itself is sufficient to induce lung injury, or requires the activation of other factors during the T/HS period to exert its effect.

METHODS

Mesenteric lymph collected from T/HS or trauma-sham shock (T/SS) animals was injected intravenously into male rats at a rate of 1 mL/h for 3 hours. At the end of infusion, lung injury was assessed by lung permeability and lung histology. The effect of iNOS inhibition on T/HS lymph-induced lung injury was studied and this was further confirmed in iNOS knockout mice. Finally, iNOS immunohistochemistry was performed to identify the cells of origin of iNOS.

RESULTS

The injection of T/HS lymph, but not sham shock lymph, caused lung injury. This was associated with increased plasma nitrite/nitrate levels as well as induction of iNOS protein in the lung, liver, and gut. Treatment with the selective iNOS inhibitor aminoguanidine prevented T/HS lymph-induced lung injury. iNOS knockout mice, but not their wild-type controls, were resistant to T/HS lymph-induced lung injury. By immunohistochemistry, neutrophils and macrophages, rather than parenchymal cells, were the source of T/HS lymph-induced lung iNOS.

CONCLUSIONS

These results indicate that T/HS lymph is sufficient to induce acute lung injury and that lymph-induced lung injury occurs via an iNOS-dependent pathway.

Gelsolin is depleted in post-shock mesenteric lymph

BACKGROUND

Gelsolin is a plasma protein that functions to depolymerize actin filaments preventing capillary plug formation following tissue injury. It also functions to mediate the inflammatory response by binding proinflammatory lipids such as lysophosphatidic acid, sphingosine-1-phosphate and phosphoinositides. Clinically, reduced gelsolin concentrations have been associated with increased mortality in critically ill, trauma, and burn patients. We have previously shown that following hemorrhagic shock with splanchnic hypoperfusion, mesenteric lymph contains lipid components that cause neutrophil and EC activation and that protein concentrations are severely diluted due to resuscitation. We hypothesized that lipid binding proteins such as gelsolin may be depleted after trauma/hemorrhagic shock leading to increased lipid bioactivity.

METHODS

Shock was induced in SD rats by controlled hemorrhage and the mesenteric duct cannulated for lymph collection. Resuscitation was performed by infusing 2x SB volume in NS over 30 min, followed by 1/2 SB volume over 30 min, then 2x SB volume in NS over 60 min. Pre and post-shock lymph was loaded at equal protein concentrations on 2D-gels, followed by trypsin digestion and identification with mass spectrometry (MS-MS). Proteomics data were confirmed with Western blotting then quantitated by densitometry. Analysis of variance was used evaluate statistical data.

RESULTS

Gelsolin decreased in mesenteric lymph following hemorrhagic shock.

CONCLUSIONS

Gelsolin is found at high levels (comparable to plasma) in mesenteric lymph. Following hemorrhagic shock, gelsolin levels decrease significantly, possibly due to consumption by the actin scavenging system. The magnitude of this change in concentration could release lipid bioactivity and predispose the lung and other organs to capillary injury.

Postshock mesenteric lymph induces endothelial NF-kappaB activation

BACKGROUND

Posthemorrhagic shock mesenteric lymph (PSML) has been shown to activate pulmonary endothelial cells and cause lung injury. Although multiple mediators may be involved, most of these effects are mediated by nuclear factor-kappa B (NF-kappaB) activation. Degradation of the inhibitor of kappa B (IkappaB) is a key regulatory step in the activation of NF-kappaB. We therefore hypothesized that PSML would cause IkappaB degradation with subsequent NF-kappaB phosphorylation and nuclear translocation.

METHODS

Mesenteric lymph was collected from male rats before shock and each hour after shock for up to 3 h (n = 5). Buffer (control), buffer + 10% (v/v) lymph, or buffer + tumor necrosis factor (10 ng/mL) were incubated with human pulmonary endothelial cells for 30 min and then lysed. Immunoblots of lysates were probed for IkappaB and phospho-p65. Immunohistochemistry was performed on cells grown on glass slides and then treated as above with the third PSML sample. Cells were fixed and then probed for p65. Statistical analysis was performed with Student's t-test and analysis of variance with significance was set at P < 0.05.

RESULTS

Western blots of cell lysates for IkappaB demonstrated a steady decrease in total IkappaB with each lymph sample. Phosphorylation of NF-kappaB , p65 component, steadily increased with each PSML sample, with a maximum reached during the third PSML sample, which also significantly increased translocation of NF-kappaB to the nucleus.

CONCLUSION

Postshock mesenteric lymph bioactivity is mediated by pathways which involved IkappaB degradation. These pathways offer novel off targets for clinical intervention to prevent the distal organ injury caused by postinjury hemorrhagic shock.

Enteral immunonutrition during sepsis prevents pulmonary dysfunction in a rat model

BACKGROUND

Sepsis often results in severe pulmonary dysfunction. Via the thoracic duct, the lung is the first organ exposed to gut-derived inflammatory mediators released into mesenteric lymph during sepsis.

AIM

To investigate whether an enteral immunonutrition during sepsis improves pulmonary function.

METHODS

Mesenteric lymph was obtained from lymph fistula donor rats after intra peritoneal (i.p.) saline (control lymph) or lipopolysaccharide (sepsis lymph) injection. Sepsis lymph was also collected during enteral immunonutrition with omega-3 enriched, long-chain fatty acids (SMOF lipid). Control, sepsis, or sepsis-SMOF lymph was reinfused into the jugular vein of separate recipient rats. The lungs were then harvested, stained with hematoxylin-eosin, and analyzed for: (1) perpendicular parenchyma thickness of the alveolar wall; (2) myeloperoxidase-positive cells; and (3) terminal deoxynucleotidyl transferase Biotin-dUTP nick end labeling (TUNEL)-positive cells.

RESULTS

Enteral immunonutrition during sepsis reduced the release of TNFalpha into mesenteric lymph by about 4.5-fold within the first 2 h. Infusion of sepsis lymph into recipient rats induced thickening of alveolar walls, inflammatory reaction, and apoptosis. Infusion of sepsis lymph obtained during enteral immunonutrition did not cause anatomical changes, induced only a mild inflammatory reaction, and prevented apoptosis in the lungs of recipient rats.

CONCLUSIONS

Mediators in sepsis lymph induce pulmonary dysfunction such as an increased distance for oxygen transport, inflammatory reaction, and apoptosis. The lung may be protected by an enteral immunonutrition containing long-chain fatty acids.

Sex hormones affect bone marrow dysfunction after trauma and hemorrhagic shock

OBJECTIVE

Bone marrow (BM) dysfunction after trauma and hemorrhagic shock (T/HS) results in a decrease in clonogenic growth of BM progenitors through a plasma-mediated process. Although sex hormones have been shown to modulate some end-organ injury after shock, post-T/HS BM dysfunction has only been studied in male animals. Therefore, the present study examines the effects of sex hormones on post-T/HS BM dysfunction by measuring clonogenic growth of BM progenitors in castrated male rats and in ovariectomized and proestrus female rats.

DESIGN

Laboratory experiment.

SETTING

University surgical research laboratory.

SUBJECT

Castrated and noncastrated male and ovariectomized and proestrus female Sprague-Dawley rats.

INTERVENTION

All rats were subjected to either T/HS or sham shock with laparotomy (n = 3-5 per group). At 3 hrs after resuscitation, the rats were killed and plasma and BM mononuclear cells from bilateral femurs were harvested.

MEASUREMENTS AND MAIN RESULTS

BM mononuclear cells were cultured for erythroid burst-forming unit and granulocyte-macrophage colony-forming unit colonies to assess the extent of progenitor BM dysfunction. BM from noncastrated male rats subjected to T/HS demonstrated a significant decrease in granulocyte-macrophage colony-forming unit and erythroid burst-forming unit colony formation compared with BM of all the sham shock groups and with the castrated male and both female rat groups subjected to T/HS. In addition, plasma from noncastrated shocked male rats incubated in vitro with BM cells from unmanipulated male rats caused a significant suppression of BM granulocyte-macrophage colony-forming unit and erythroid burst-forming unit colonies compared with plasma from castrated rats subjected to either sham shock with laparotomy or T/HS.

CONCLUSION

The profound BM dysfunction observed in noncastrated male rats after T/HS is not observed in proestrus female rats and castrated male rats. In addition, the in vitro plasma-mediated BM suppression present in male rats after T/HS is also lost in castrated male rats. Sex hormones seem to play a significant role in BM dysfunction after T/HS.

Lymphatic thoracic duct ligation modulates the serum levels of IL-1beta and IL-10 after intestinal ischemia/reperfusion in rats with the involvement of tumor necrosis factor alpha and nitric oxide

Intestinal ischemia/reperfusion (I/R) causes local and remote injuries that are multifactorial and essentially inflammatory in nature. To study the putative influences of nitric oxide (NO) and tumor necrosis factor alpha (TNF-alpha) on the release of interleukin (IL) 1beta and IL-10 and the involvement of lymphatic system on a systemic inflammation caused by I/R, we have quantified the serum and lymph levels of IL-1beta and IL-10 in rats during I/R after treatment with inhibitors of NO synthase (N-nitro-L-arginine methyl ester hydrochloride [L-NAME]) or TNF-alpha (pentoxifylline [PTX]). Intestinal I/R was performed by means of a 45-min occlusion of the mesenteric artery, followed by 2-h reperfusion; groups of rats subjected to I/R had the thoracic lymph duct ligated immediately before the procedure. The I/R caused a significant increase of the serum levels of IL-1beta and IL-10 in rats with intact thoracic lymph duct, whereas the thoracic duct ligation blunted the serum release of IL-1beta and elevated that of IL-10. The levels of the cytokines collected in the lymph after I/R increased, and even more increase was observed in L-NAME-treated rats. L-NAME significantly increased the lymph levels of IL-1beta and IL-10; in serum, however, only IL-1beta increased in rats with either intact or ligated thoracic lymph duct. The treatment with PTX reduced the serum levels of IL-1beta irrespective of the lymph circulation interruption but was effective to increase the IL-10 levels in intact rats during I/R. The lymphatic levels of IL-1beta of rats subjected to I/R were reduced and those of IL-10 were increased after treatment with PTX. In conclusion, during I/R, the serum levels of IL-1beta seem modulated by stimulant mechanisms that could be associated with TNF-alpha and inhibited by NO and by the integrity of the thoracic lymphatic flow. On the other hand, IL-10 seems controlled by TNF-alpha-related, largely NO-independent mechanisms. Thus, it is reasonable to suppose that an endogenous mechanism that can limit the systemic inflammatory response ensuing an I/R splanchnic trauma exists.

Olive oil is more potent than fish oil to reduce septic pulmonary dysfunctions in rats

BACKGROUND

Abdominal sepsis is frequently the cause of severe pulmonary dysfunction. Via the thoracic duct, the lung is the first organ exposed to gut-derived mediators released into the mesenteric lymph.

AIM

The aim of this study is to investigate whether an enteral immunonutrition with long chain triglycerides prevents septic pulmonary dysfunctions.

MATERIALS AND METHODS

Mesenteric lymph was obtained from lymph fistula donor rats during sepsis (lipopolysaccharides [LPS], 5 mg/kg i.p.) with or without enteral immunonutrition (1% of olive oil or 1% of fish oil). Sepsis lymph was then reinfused into the jugular vein of separate recipient rats. Thereafter, the lung tissue was analyzed for the distance of oxygen diffusion, inflammatory response, and cell apoptosis.

RESULTS

Sepsis significantly increased TNFalpha release into the mesenteric lymph, whereas an enteral immunonutrition with olive oil significantly reduced the TNFalpha release into the mesenteric lymph by more than five-fold. Sepsis lymph induced a significant increase in alveolar wall thickness, inflammatory reaction, and apoptosis; whereas sepsis lymph collected during olive oil resorption prevented the thickening of the alveolar walls and induced only a mild inflammation, being more potent than fish oil to reduce septic pulmonary dysfunction.

CONCLUSIONS

Mediators in the sepsis lymph induce pulmonary dysfunction. The lung may be protected by an enteral immunonutrition containing long chain triglycerides such as olive oil.

Ischemic acute kidney injury induces a distant organ functional and genomic response distinguishable from bilateral nephrectomy

Acute kidney injury (AKI) is associated with significant mortality, which increases further when combined with acute lung injury. Experiments in rodents have shown that kidney ischemia-reperfusion injury (IRI) facilitates lung injury and inflammation. To identify potential ischemia-specific lung molecular pathways involved, we conducted global gene expression profiling of lung 6 or 36 h following 1) bilateral kidney IRI, 2) bilateral nephrectomy (BNx), and 3) sham laparotomy in C57BL/6J mice. Bronchoalveolar lavage fluid analysis revealed increased total protein, and lung histology revealed increased cellular inflammation following IRI, but not BNx, compared with sham controls. Total RNA from whole lung was isolated and hybridized to 430MOEA (22,626 genes) GeneChips (n = 3/group), which were analyzed by robust multichip average and significance analysis of microarrays and linked to gene ontology (GO) terms using MAPPFinder. The microarray power analysis predicted that the false discovery rate (q < 1%) and > or =50%-fold change compared with sham would represent significant changes in gene expression. Analysis identified 266 and 455 ischemia-specific, AKI-associated lung genes with increased expression and 615 and 204 with decreased expression at 6 and 36 h, respectively, compared with sham controls. Real-time PCR analysis validated select array changes in lung serum amyloid A3 and endothelin-1. GO analysis revealed significant activation (Z > 1.95) of several proinflammatory and proapoptotic biological processes. Ischemic AKI induces functional and transcriptional changes in the lung distinct from those induced by uremia alone. Further investigation using this lung molecular signature induced by kidney IRI will provide mechanistic insights and new therapies for critically ill patients with AKI.

Neuronal damage in rat brain and spinal cord after cardiac arrest and massive hemorrhagic shock*

OBJECTIVE

Severe global ischemia often results in severe damage to the central nervous system of survivors. Hind-limb paralysis is a common deficit caused by global ischemia. Until recently, most studies of global ischemia of the central nervous system have examined either the brain or spinal cord, but not both. Spinal cord damage specifically after global ischemia has not been studied in detail. Because the exact nature of the neuronal damage to the spinal cord and the differences in neuronal damage between the brain and spinal cord after global ischemia are poorly understood, we developed a new global ischemia model in the rat and specifically studied spinal cord damage after global ischemia. Further, we compared the different forms of neuronal damage between the brain and spinal cord after global ischemia.

DESIGN

Randomized, controlled study using three different global ischemia models in the rat.

SETTING

University research laboratory.

SUBJECTS

Male, adult Sprague-Dawley rats (300 g).

INTERVENTIONS

Animals were divided into three experimental groups, group A (n = 6, survived for 7 days), 12 mins of hemorrhagic shock; group B (n = 6, survived for 7 days), 5 mins of cardiac arrest; or group C (n = 6, each for 6 hrs, 12 hrs, 1 day, 3 days, and 7 days), 7 mins of hemorrhagic shock and 5 mins of cardiac arrest. Motor deficit of the hind limbs was studied 6 hrs to 7 days after resuscitation. Also, nonoperated animals (n = 6) were used as the control. Histologic analysis (hematoxylin and eosin, Fluoro-Jade B, terminal deoxynucleotidyl transferase- mediated dUTP end-labeling [TUNEL], Klüver-Barrera) and ultrastructural analysis using electron microscopy were performed on samples from the CA1 region of the hippocampus and lumbar spinal cord. Demyelination of the white matter of the lumbar spinal cord was analyzed semiquantitatively using Scion Image software.

MAIN RESULTS

No paraplegic animals were observed in either group A or B. All group C animals showed severe hind-limb paralysis. Severe neuronal damage was found in the CA1 region of the hippocampus in all groups, and the state of delayed neuronal cell death was similar among the three groups. Neuronal damage in the lumbar spinal cord was detected only in group C animals, mainly in the dorsal horn and intermediate gray matter. Demyelination was prominent in the ventral and ventrolateral white matter in group C. A significant difference was observed between control and group C rats with Scion Image software. Ultrastructural analysis revealed extensive necrotic cell death in the intermediate gray matter in the lumbar spinal cord in group C rats.

CONCLUSION

The combination in the global ischemia model (i.e., hemorrhagic shock followed by cardiac arrest) caused severe neuronal damage in the central nervous system. Thereby, hind-limb paralysis after global ischemia might result from spinal cord damage. These results suggest that therapeutic strategies for preventing spinal cord injury are necessary when treating patients with severe global ischemia.

Normal mesenteric lymph blunts the pulmonary inflammatory response to endotoxin

BACKGROUND

Mesenteric lymph may provide the mechanistic link between gut ischemia and acute lung injury after hemorrhagic shock (HS). Studies have focused on the toxic mediators that develop in the post-shock mesenteric lymph (PSML). However, a complementary possibility is that there is loss of protective mediators found in pre-shock normal mesenteric lymph (NML) after HS. We hypothesize that NML protects against inflammatory insults to the pulmonary endothelium and that this effect is lost in PSML.

MATERIALS AND METHODS

Primary human pulmonary endothelial cells (HMVECs) were incubated with NML or PSML collected from rats subjected to HS and resuscitation and then stimulated with 20 ng/mL LPS. ICAM-1 surface expression was measured by flow cytometry. In subsequent experiments, lipoproteins were extracted from NML before incubation and LPS-induced ICAM-1 expression determined.

RESULTS

Mean fluorescent intensity (MFI) of LPS-induced ICAM-1 in NML and PSML treated HMVECs were 10.1 +/- 2.3 versus 27.7 +/- 0.83, respectively (P < 0.05). This represented at 71% decrease in ICAM-1 expression by NML compared to ICAM-1 expression in LPS-induced controls (MFI: 34.6 +/- 6.9). Lipoprotein extraction from NML abolished this protective effect (MFI: 31.2 +/- 5.3 versus Control + LPS: 33.5 +/- 3.6, P > 0.05). Baseline ICAM-1 levels were not significantly different among control, NML, and PSML groups.

CONCLUSION

Lipoproteins in NML contain anti-inflammatory properties that decrease ICAM-1 expression induced by LPS in pulmonary endothelium. Decreased protective lipoproteins after HS and resuscitation may contribute to the toxicity associated with PSML from the ischemic gut.

BIOACTIVITY OF POSTSHOCK MESENTERIC LYMPH DEPENDS ON THE DEPTH AND DURATION OF HEMORRHAGIC SHOCK

Mesenteric hypoperfusion due to circulatory shock is a key event in the pathogenesis of subsequent distant organ injury. Postshock mesenteric lymph (PSML) has been shown to contain proinflammatory mediators elaborated from the ischemic gut. We hypothesize that the relative bioactivity of PSML depends on the depth and duration of circulatory shock. To first determine the timing of PSML bioactivity, we subjected rats to hemorrhagic shock (30 mm Hg x 45 min) and then resuscitation with 50 vol% of shed blood and normal saline (4x shed blood) over 2 h. Mesenteric lymph was collected hourly up to 6 h after shock. Superoxide release was measured from human neutrophils (polymorphonuclear neutrophils [PMNs]) incubated with lymph fractions collected from each of the hourly time points. Rats were then subjected to four different shock variations: (1) 30 mm Hg x 45 min, (2) 30 mm Hg x 15 min, (3) 45 mm Hg x 45 min, and (4) 45 mm Hg x 15 min, and were resuscitated. PSML flow depends on depth of shock, but not duration of shock or resuscitation volume. Maximal PSML bioactivity, as measured by PMN priming for the respiratory burst, occurred during the third postshock hour, which correlated with peak lymph flow rate. PSML bioactivity was greatest with 30 mm Hg x 45 min, followed by 30 mm Hg x 15 min, 45 mm Hg x 45 min, and 45 mm Hg x 15 min. Hemorrhagic shock provokes the release of bioactive agents in PSML that is dependent on both depth and duration of shock.