Gut-derived mesenteric lymph but not portal blood increases endothelial cell permeability and promotes lung injury after hemorrhagic shock

Intestinal ischemia/reperfusion injury: defining the role of the gut microbiome

Intestinal ischemia/reperfusion (I/R) injury initiates a systemic inflammatory response syndrome with a high associated mortality rate. Early diagnosis is essential for reducing surgical mortality, yet current clinical biomarkers are insufficient. Metabonomics is a novel strategy for studying intestinal I/R, which may be used as part of a systems approach for quantitatively analyzing the intestinal microbiome during gut injury. By deconvolving the mammalian–microbial symbiotic relationship systems biology thus has the potential for personalized risk stratification in patients exposed to intestinal I/R. This review describes the mechanism of intestinal I/R and explores the essential role of the intestinal microbiota in the initiation of systemic inflammatory response syndrome. Furthermore, it analyzes current and future approaches for elucidating the mechanism of this condition.

Albumin resuscitation protects against traumatic/hemorrhagic shock-induced lung apoptosis in rats

OBJECTIVE

To determine the effects of albumin administration on lung injury and apoptosis in traumatic/hemorrhagic shock (T/HS) rats.

METHODS

Studies were performed on an in vivo model of spontaneously breathing rats with induced T/HS; the rats were subjected to femur fracture, ischemia for 30 min, and reperfusion for 20 min with Ringer's lactate solution (RS) or 5% (w/v) albumin (ALB), and the left lower lobes of the lungs were resected.

RESULTS

Albumin administered during reperfusion markedly attenuated injury of the lung and decreased the concentration of lactic acid and the number of in situ TdT-mediated dUTP nick-end labelling (TUNEL)-positive cells. Moreover, immunohistochemistry performed 24 h after reperfusion revealed increases in the level of nuclear factor kappaB (NF-kappaB), and phosphorylated p38 mitogen-activated protein kinase (MAPK) in the albumin-untreated group was down-regulated by albumin treatment when compared with the sham rats.

CONCLUSION

Resuscitation with albumin attenuates tissue injury and inhibits T/HS-induced apoptosis in the lung via the p38 MAPK signal transduction pathway that functions to stimulate the activation of NF-kappaB.

Pentoxifylline modulates intestinal tight junction signaling after burn injury: effects on myosin light chain kinase

BACKGROUND

Burn injury can result in loss of intestinal barrier function, leading to systemic inflammatory response syndrome and multiorgan failure. Myosin light chain kinase (MLCK), a tight junction protein involved in the regulation of barrier function, increases intestinal epithelial permeability when activated. Prior studies have shown that tumor necrosis factor (TNF)-alpha activates MLCK, in part through a nuclear factor (NF)-kappa B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-alpha synthesis and NF-kappaB activation in models of shock. Therefore, we postulate that PTX will attenuate activation of the tight junction protein MLCK, which may decrease intestinal tight junction permeability after severe burn.

METHODS

Male balb/c mice undergoing a severe burn were randomized to resuscitation with normal saline (NS) or NS + PTX (12.5 mg/kg). Intestinal TNF-alpha levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IkappaB-alpha, and NF-kappaB p65 levels by immunoblotting.

RESULTS

Burn injury increased intestinal MLCK protein levels threefold in animals resuscitated with NS, whereas those receiving PTX had MLCK levels similar to control (p < 0.01). Treatment with PTX attenuated burn-induced intestinal permeability. PTX decreased cytoplasmic IKK, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS).

CONCLUSION

Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-alpha synthesis and NF-kappaB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.

Pentoxifylline modulates intestinal tight junction signaling after burn injury: effects on myosin light chain kinase

BACKGROUND

Burn injury can result in loss of intestinal barrier function, leading to systemic inflammatory response syndrome and multiorgan failure. Myosin light chain kinase (MLCK), a tight junction protein involved in the regulation of barrier function, increases intestinal epithelial permeability when activated. Prior studies have shown that tumor necrosis factor (TNF)-alpha activates MLCK, in part through a nuclear factor (NF)-kappa B-dependent pathway. We have previously shown that pentoxifylline (PTX) decreases both TNF-alpha synthesis and NF-kappaB activation in models of shock. Therefore, we postulate that PTX will attenuate activation of the tight junction protein MLCK, which may decrease intestinal tight junction permeability after severe burn.

METHODS

Male balb/c mice undergoing a severe burn were randomized to resuscitation with normal saline (NS) or NS + PTX (12.5 mg/kg). Intestinal TNF-alpha levels were evaluated using enzyme linked immunosorbent assay. Gut extracts were obtained to assess MLCK, phosphorylated IKK, IkappaB-alpha, and NF-kappaB p65 levels by immunoblotting.

RESULTS

Burn injury increased intestinal MLCK protein levels threefold in animals resuscitated with NS, whereas those receiving PTX had MLCK levels similar to control (p < 0.01). Treatment with PTX attenuated burn-induced intestinal permeability. PTX decreased cytoplasmic IKK, IkappaB-alpha phosphorylation, and nuclear NF-kappaB p65 translocation to sham levels (p < 0.05 vs. NS).

CONCLUSION

Treatment with PTX attenuates activation of the tight junction protein MLCK, likely through its ability to decrease local TNF-alpha synthesis and NF-kappaB activation after burn. PTX may have therapeutic utility by decreasing intestinal barrier breakdown after burn.

Starvation-induced proximal gut mucosal atrophy diminished with aging

BACKGROUND

Starvation induces small bowel atrophy with increased intestinal epithelial apoptosis and decreased proliferation. The authors examined these parameters after starvation in aged animals.

METHODS

Sixty-four 6-week-old and 26-month-old C57BL/6 mice were randomly assigned to either an ad libitum fed or fasted group. The small bowel was harvested at 12, 48, and 72 hours following starvation. Proximal gut mucosal height was measured and epithelial cells counted. Apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining. Proliferation was determined by immunohistochemical staining for proliferating cell nuclear antigen. Comparison of fed vs fasted and adult vs old groups was done by one-way ANOVA with Tukey's test and unpaired Student's t test. Significance was accepted at P < .05.

RESULTS

Aged mice had higher proximal gut weights, mucosal heights, and cell numbers at baseline compared with the adult group (P < .05). The rate of apoptosis was lower in the aged (P < .05), but proliferation was not different between groups before starvation. After starvation, proximal gut wet weight decreased only in adult mice (P < .05). Gut mucosal height and mucosal cell number decreased more in adult than in aged mice (P < .05). This was related to decreased proliferation only in the adult group (P < .05). The fold of epithelial apoptosis that increased was higher in the aged group than in the adult group after starvation (P < .05).

CONCLUSIONS

Gut mucosal kinetics change with age and have lower rates of apoptosis and greater mucosal mass; the character of starvation-induced atrophy is diminished with aging.

Defects in innate immunity predispose C57BL/6J-Leprdb/Leprdb mice to infection by Staphylococcus aureus

Foot and ankle infections are the most common cause of hospitalization among diabetic patients, and Staphylococcus aureus is a major pathogen implicated in these infections. Patients with insulin-resistant (type 2) diabetes are more susceptible to bacterial infections than nondiabetic subjects, but the pathogenesis of these infections is poorly understood. C57BL/6J-Lepr(db)/Lepr(db) (hereafter, db/db) mice develop type 2 diabetes due to a recessive, autosomal mutation in the leptin receptor. We established a S. aureus hind paw infection in diabetic db/db and nondiabetic Lepr(+/+) (+/+) mice to investigate host factors that predispose diabetic mice to infection. Nondiabetic +/+ mice resolved the S. aureus hind paw infection within 10 days, whereas db/db mice with persistent hyperglycemia developed a chronic infection associated with a high bacterial burden. Diabetic db/db mice showed a more robust neutrophil infiltration to the infection site and higher levels of chemokines in the infected tissue than +/+ mice. Blood from +/+ mice killed S. aureus in vitro, whereas db/db blood was defective in bacterial killing. Compared with peripheral blood neutrophils from +/+ mice, db/db neutrophils demonstrated a diminished respiratory burst when stimulated with S. aureus. However, bone marrow-derived neutrophils from +/+ and db/db mice showed comparable phagocytosis and bactericidal activity. Our results indicate that diabetic db/db mice are more susceptible to staphylococcal infection than their nondiabetic littermates and that persistent hyperglycemia modulates innate immunity in the diabetic host.

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.

Acute effects of "delayed postconditioning" with periodic acceleration after asphyxia induced shock in pigs

Asphyxia cardiac arrest and shock are models for whole body ischemia reperfusion injury. Periodic acceleration (pGz) achieved by moving the body on a platform is a novel method for inducing pulsatile vascular shear stress and endogenous production of endothelial nitric oxide, prostaglandin E2, tissue plasminogen activator, and adrenomedullin. The aforementioned are cardioprotective during and after ischemia reperfusion injury. We investigated whether pGz, applied 15 min after return of spontaneous circulation (ROSC) would serve as an effective "delayed" post conditioning tactic to lessen acute reperfusion injury markers in a pediatric swine model of asphyxia induced shock. Asphyxia shock was induced in 20 swine weight 3.9 +/- 0.6 kg. Fifteen minutes after ROSC, the animals were randomized to receive conventional mechanical ventilation (CMV, [Control]) or CMV with pGz. All animals had ROSC and no significant differences in blood gases or hemodynamics after ROSC. pGz treated had significantly less myocardial dysfunction post resuscitation, (i.e. better % ejection fraction (EF), % fractional shortening (FS), and wall motion score index) and lower biochemical indices of reperfusion injury (lower TNF-alpha, IL-6, and Troponin I, and myeloperoxidase activity). Delayed postconditioning with pGz ameliorates acute post resuscitation reperfusion injury and improves myocardial dysfunction after asphyxia-induced shock.

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.

Hypertonic saline reduces neutrophil-epithelial interactions in vitro and gut tissue damage in a mouse model of colitis

Transepithelial migration of polymorphonuclear neutrophils (PMN) plays a crucial role in inflammatory conditions of the intestine, such as inflammatory bowel diseases. Hypertonic saline (HS) exerts various inhibitory effects on PMN function. We hypothesized that HS could inhibit transepithelial migration of PMN and thereby prevent inflammatory events in experimental colitis. Isolated human PMN were treated with HS (40 mM), and their transmigration across a monolayer of T84 epithelial cells was induced by N-formyl-methionyl-leucyl-phenylalanine. Monolayer disruption was assessed by monitoring changes in transepithelial conductance in an Ussing chamber. Colitis in mice was induced by oral administration of dextran sulfate sodium (DSS). Animals were treated with 4 or 8 ml/kg of 7.5% saline intraperitoneally two times daily for 7 days. Controls received equivalent volumes of normal saline (NS, n = 6) or no intraperitoneal treatment (DSS, n = 12). The severity of inflammation was evaluated based on disease activity index and histology score. HS treatment of PMN in vitro significantly reduced cell migration and the disruption of T84 monolayers compared with untreated control cells (n = 5, P < 0.05). This effect of HS was dose dependent. HS treatment in vivo also reduced colitis-induced gut tissue damage, as indicated by an improved histology score compared with the NS and DSS groups. We conclude that HS inhibits transepithelial migration of PMN in vitro and gut tissue damage in vivo in a mouse model of colitis. Thus HS may have clinical value to reduce PMN-mediated intestinal damage.

Second hit post burn increased proximal gut mucosa epithelial cells damage

Secondary infections after burn are common and are a major contributor to morbidity and mortality. We previously showed that burn disrupted proximal gut mucosal homeostasis through increased epithelial cell apoptosis. In the present study, we sought to determine whether proximal gut mucosal disruption is additively affected by secondary endotoxemia after a severe burn. C57BL/6 mice received 30% total body surface area full-thickness scald burns and were randomized to receive saline or LPS 1 mg/kg body weight given intraperitoneally 72 h after burn. Proximal small bowel was harvested 12 h after LPS injection. Mucosal height and epithelial cell number were assessed on hematoxylin-eosin sections, intestinal epithelial cell apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen. Results showed that proximal gut mucosa impairment occurred 12 h after injury, including significantly decreased proximal gut wet weight, gut mucosal height, and epithelial cell number associated with increased proximal gut epithelial apoptosis (P < 0.05). This impairment diminished 72 h after burn. Second-hit endotoxemia caused additional proximal gut mucosa damage with decreased proximal gut weight, cell number, and mucosal height (P < 0.05) and significantly increased small intestinal epithelial apoptosis and mucosal atrophy, even after the first event, indicating a second detrimental effect of endotoxemia after the initial injury.

IFN-gamma regulated chemokine production determines the outcome of Staphylococcus aureus infection

Immunomodulatory therapy represents an attractive approach in treating multidrug-resistant infections. Developing this therapy necessitates a lucid understanding of host defense mechanisms. Neutrophils represent the first line of systemic defense during Staphylococcus aureus infections. However, recent research suggests that survival of S. aureus inside neutrophils may actually contribute to pathogenesis, indicating that neutrophil trafficking to the infection site must be tightly regulated to ensure efficient microbial clearance. We demonstrate that neutrophil-regulating T cells are activated during S. aureus infection and produce cytokines that control the local neutrophil response. S. aureus capsular polysaccharide activates T cell production of IFN-gamma in a novel MHC class II-dependent mechanism. During S. aureus surgical wound infection, the presence of IFN-gamma at the infection site depends upon alphabetaTCR+ cells and functions to regulate CXC chemokine production and neutrophil recruitment in vivo. We note that the reduced neutrophil response seen in IFN-gamma-/- mice during S. aureus infection is associated with reduced tissue bacterial burden. CXC chemokine administration to the infection site resulted in an increased survival of viable S. aureus inside neutrophils isolated from the wound. These data demonstrate that T cell-derived IFN-gamma generates a neutrophil-rich environment that can potentiate S. aureus pathogenesis by facilitating bacterial survival within the neutrophil. These findings suggest avenues for novel immunomodulatory approaches to control S. aureus infections.

Ghrelin improves burn-induced multiple organ injury by depressing neutrophil infiltration and the release of pro-inflammatory cytokines

Mechanisms of burn-induced skin and remote organ injury involve oxidant generation and the release of pro-inflammatory cytokines. In this study the possible antioxidant and anti-inflammatory effects of ghrelin were evaluated in a rat model of thermal trauma. Wistar albino rats were exposed to 90 degrees C bath for 10 s to induce thermal trauma. Ghrelin, was administered subcutaneously (10 ng/kg/day) after the burn injury and repeated twice daily. Rats were decapitated at 6 h and 48 h after burn injury and blood was collected for the analysis of pro-inflammatory cytokines (TNF-alpha and IL-1beta), lactate dehydrogenase (LDH) activity and antioxidant capacity (AOC). In skin, lung and stomach tissue samples malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) and Na(+)-K(+)-ATPase activity were measured in addition to the histological analysis. DNA fragmentation ratio in the gastric mucosa was also evaluated. Burn injury caused significant increase in both cytokine levels, and LDH activity, while plasma AOC was found to be depleted after thermal trauma. On the other hand, in tissue samples the raised MDA levels, MPO activity and reduced GSH levels, Na(+)-K(+)-ATPase activity due to burn injury were found at control levels in ghrelin-treated groups, while DNA fragmentation in the gastric tissue was also reduced. According to the findings of the present study, ghrelin possesses a neutrophil-dependent anti-inflammatory effect that prevents burn-induced damage in skin and remote organs and protects against oxidative organ damage.

Therapeutic effects of hypertonic saline on peritonitis-induced septic shock with multiple organ dysfunction syndrome in rats

OBJECTIVE

Significant mortality in patients with sepsis results from the development of multiple organ dysfunction syndrome. Small-volume resuscitation with 7.5% NaCl hypertonic saline has been proposed to restore physiologic hemodynamics in hemorrhagic shock. Therefore, we hypothesized that hypertonic saline resuscitation could alleviate the development of multiple organ dysfunction syndrome in sepsis induced by cecal ligation and puncture.

DESIGN

Randomized, prospective animal experiment.

SETTING

Academic research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

The animals were randomly allocated to one of four groups: 1) sham operation (0.9% NaCl, 4 mL/kg intravenously, at 3 hrs after laparotomy); 2) sham operation plus hypertonic saline (7.5% NaCl, 4 mL/kg intravenously, at 3 hrs after laparotomy); 3) cecal ligation and puncture (0.9% NaCl, 4 mL/kg intravenously, at 3 hrs after cecal ligation and puncture); and 4) cecal ligation and puncture plus hypertonic saline (7.5% NaCl, 4 mL/kg intravenously, at 3 hrs after cecal ligation and puncture).

MEASUREMENTS AND MAIN RESULTS

Cecal ligation and puncture for 18 hrs was associated with circulatory failure (i.e., hypotension and vascular hyporeactivity to norepinephrine), multiple organ dysfunction syndrome (examined by biochemical variables and histologic studies), and 18-hr mortality. Hypertonic saline not only ameliorated the deterioration of hemodynamic changes but also attenuated neutrophil infiltration in the lung and the liver of septic animals. Hypertonic saline increased the survival rate at 9 and 18 hrs compared with the cecal ligation and puncture group. Moreover, hypertonic saline reduced plasma nitric oxide and interleukin-1beta and organ O2-* levels in rats that underwent cecal ligation and puncture.

CONCLUSIONS

Hypertonic saline prevented circulatory failure, alleviated multiple organ dysfunction syndrome, and decreased the mortality rate in animals receiving cecal ligation and puncture. These beneficial effects of hypertonic saline may be attributed to reducing the plasma concentration of nitric oxide and interleukin-1beta as well as the organ O2-* level and decreasing lung neutrophil infiltration and liver necrosis. Our study suggests that hypertonic saline could be a potential and inexpensive therapeutic agent in the early sepsis of animals or patients.

Tryptophan catabolites in mesenteric lymph may contribute to pancreatitis-associated organ failure

Background

Multiple organ failure (MOF) is the key determinant of mortality in acute pancreatitis (AP). Mesenteric lymph cytotoxicity contributes to organ failure in experimental models of systemic inflammation. The aim of this study was to evaluate the mesenteric lymph pathway and the lymph injury proteome in experimental AP-associated MOF, and to test the hypothesis that immunoregulatory tryptophan catabolites contribute to mesenteric lymph cytotoxicity.

Methods

Using an experimental model of AP in rats, the humoral component of mesenteric lymph in AP was compared with that from sham-operated control animals, using in vitro and in vivo cytotoxicity assays, high-throughput proteomics and high-performance liquid chromatography. The experimental findings were corroborated in a cohort of 34 patients with AP.

Results

Compared with biologically inactive lymph from sham-operated rats, mesenteric lymph in AP became cytotoxic 3 h after induction. Hierarchical clustering of lymph proteomic mass spectra predicted the biological behaviour of lymph. Levels of the immunoregulatory tryptophan catabolite, 3-hydroxykynurenine, were increased in cytotoxic lymph and re-created cytotoxicity in vitro. In humans with AP, plasma kynurenine concentrations correlated in real time with MOF scores and preceded a requirement for mechanical ventilation and haemodialysis.

Conclusion

These results support the concept that mesenteric lymph-borne kynurenines may contribute to pancreatitis-associated MOF.

Role of gut-lymph factors in the induction of burn-induced and trauma-shock-induced acute heart failure

Acute injury-induced cardiac contractile dysfunction occurs even in young and otherwise healthy individuals after major injuries, and significantly contributes to morbidity and mortality in patients with pre-existent cardiac diseases as well as in patients who develop multiple organ dysfunction syndrome. Recent studies indicate that post-injury acute cardiac failure is the result of an exaggerated cardiac inflammatory response resulting in an inflammatory cardiomyopathy characterized by decreased cardiac contractility. Over the past decade, many of the effector molecules involved in this process have been identified as having some involvement in generating a myocardial inflammatory response. However, less is known about the agents and processes involved in triggering this inflammation-induced decrease in cardiac contractility. Consequently, in this review, the concept of the heart responding to major injury like an innate immune organ will be presented, the various effector molecules and mechanisms leading to myocyte contractile dysfunction will be reviewed and data indicating that the acute cardiac contractile dysfunction observed after trauma is due to gut-derived intestinal lymph factors will be reviewed.

Arachidonic acid in postshock mesenteric lymph induces pulmonary synthesis of leukotriene B4

Mesenteric lymph is the mechanistic link between splanchnic hypoperfusion and acute lung injury (ALI), but the culprit mediator(s) remains elusive. Previous work has shown that administration of a phospholipase A(2) (PLA(2)) inhibitor attenuated postshock ALI and also identified a non-ionic lipid within the postshock mesenteric lymph (PSML) responsible for polymorphonuclear neutrophil (PMN) priming. Consequently, we hypothesized that gut-derived leukotriene B(4) (LTB(4)) is a key mediator in the pathogenesis of ALI. Trauma/hemorrhagic shock (T/HS) was induced in male Sprague-Dawley rats and the mesenteric duct cannulated for lymph collection/diversion. PSML, arachidonic acid (AA), and a LTB(4) receptor antagonist were added to PMNs in vitro. LC/MS/MS was employed to identify bioactive lipids in PSML and the lungs. T/HS increased AA in PSML and increased LTB(4) and PMNs in the lung. Lymph diversion decreased lung LTB(4) by 75% and PMNs by 40%. PSML stimulated PMN priming (11.56 +/- 1.25 vs. 3.95 +/- 0.29 nmol O(2)(-)/min; 3.75 x 10(5) cells/ml; P < 0.01) that was attenuated by LTB(4) receptor blockade (2.64 +/- 0.58; P < 0.01). AA stimulated PMNs to produce LTB(4), and AA-induced PMN priming was attenuated by LTB(4) receptor antagonism. Collectively, these data indicate that splanchnic ischemia/reperfusion activates gut PLA(2)-mediated release of AA into the lymph where it is delivered to the lungs, provoking LTB(4) production and subsequent PMN-mediated lung injury.

Mesenteric lymph duct ligation attenuates lung injury and neutrophil activation after intraperitoneal injection of endotoxin in rats

BACKGROUND

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 shock and trauma. Since endotoxemia is also associated with gut injury, we tested the hypothesis that mesenteric lymph contributes to the lung injury seen in endotoxemia and that the ligation of the mesenteric lymph duct will attenuate this injury.

METHODS

To test this hypothesis, male Sprague-Dawley rats were given intraperitoneal injections (i.p.) of lipopolysaccharide (LPS) (10 mg/kg) with or without mesenteric lymph duct ligation (LDL). At 6 hours after injection of LPS, gut and lung injury, lung permeability, and neutrophil CD11b expression were measured. Lung permeability was quantified by calculating the percentage of Evan's Blue dye and the total protein concentration in the bronchoalveolar lavage fluid (BALF) when compared with the plasma and gut and lung injury were assessed morphologically.

RESULTS

LDL attenuated LPS- induced lung injury, lung permeability, and rat PMN CD11b expression but not villous injury. The magnitude of lung permeability as measured by Evan's Blue was approximately twofold greater in the LPS rats when compared with the LPS-treated rats with LDL. The expression of CD11b was greater in the LPS rats when compared with LPS rats with LDL or to sham controls (582 +/- 106 vs. 364 +/- 29 vs. 224 +/- 12 mean fluorescence intensity p < 0.001).

CONCLUSION

Based on the attenuation of lung injury and CD11b expression, these results suggest that LPS-induced lung injury and neutrophil activation is partially mediated through the release of factors from the injured gut into mesenteric lymph.

Intestinal crosstalk: a new paradigm for understanding the gut as the "motor" of critical illness

For more than 20 years, the gut has been hypothesized to be the "motor" of multiple organ dysfunction syndrome. As critical care research has evolved, there have been multiple mechanisms by which the gastrointestinal tract has been proposed to drive systemic inflammation. Many of these disparate mechanisms have proved to be important in the origin and propagation of critical illness. However, this has led to an unusual situation where investigators describing the gut as a "motor" revving the systemic inflammatory response syndrome are frequently describing wholly different processes to support their claim (i.e., increased apoptosis, altered tight junctions, translocation, cytokine production, crosstalk with commensal bacteria, etc). The purpose of this review is to present a unifying theory as to how the gut drives critical illness. Although the gastrointestinal tract is frequently described simply as "the gut," it is actually made up of (1) an epithelium; (2) a diverse and robust immune arm, which contains most of the immune cells in the body; and (3) the commensal bacteria, which contain more cells than are present in the entire host organism. We propose that the intestinal epithelium, the intestinal immune system, and the intestine's endogenous bacteria all play vital roles driving multiple organ dysfunction syndrome, and the complex crosstalk between these three interrelated portions of the gastrointestinal tract is what cumulatively makes the gut a "motor" of critical illness.

Alterations in intestinal microbial flora and human disease

PURPOSE OF REVIEW

To highlight the evidence supporting the role of altered commensal gut flora in human disease. While the contribution of the indigenous gut microbial community is widely recognized, only recently has there been evidence pointing to indigenous flora in disease.

RECENT FINDINGS

This review discusses recent evidence pointing to the role of altered commensal gut flora in such common conditions as irritable bowel syndrome and inflammatory bowel disease. Recent studies document the intricate relationship between the vast population of microbes that live in our gut and the human host. Since increased intestinal permeability and immune activation are consequences of an altered host-gut microbial relationship, what are the clinical effects of this shift in relationship?

SUMMARY

We focus on the example of an abnormal expansion of gut microbial flora into the small bowel or small intestinal bacterial overgrowth and discuss the effects of bacterial overgrowth on the human host in acute pancreatitis, bacterial gastroenteritis, irritable bowel syndrome, inflammatory bowel disease, hepatic encephalopathy, and fibromyalgia and burn injury. The identification of the underlying role of altered commensal gut microbiota in these and other human diseases could lead to novel diagnostic and therapeutic strategies that would improve clinical outcome.

Acute pancreatitis severity is exacerbated by intestinal ischemia-reperfusion conditioned mesenteric lymph

OBJECTIVE

To determine the effect of intestinal ischemia-reperfusion (IIR) on acute pancreatitis (AP) and the role of mesenteric lymph.

SUMMARY BACKGROUND DATA

Intestinal ischemia is an early feature of AP and is related to the severity of disease. It is not known whether this contributes to the severity of AP or is a consequence.

METHODS

Two experiments are reported here using intravital microscopy and a rodent model of mild acute pancreatitis (intraductal 2.5% sodium taurocholate). In the first, rats had an episode of IIR during AP that was produced by temporary occlusion of the superior mesenteric artery (30 min or 3 x 10 min) followed by 2h reperfusion. In a second study rats with AP had an intravenous infusion of mesenteric lymph collected from donor rats that had been subjected to IIR. In both experiments the pancreatic erythrocyte velocity (EV), functional capillary density (FCD), leukocyte adherence (LA), histology and edema index were measured.

RESULTS

The addition of IIR to AP caused a decline in the pancreatic microcirculation greater than that of AP alone (EV 42% of baseline vs. 73% of baseline AP alone, FCD 43% vs 72%, LA 7 fold increase vs 4 fold increase). This caused an increased severity of AP as evidenced by 1.4-1.8 fold increase of pancreatic edema index and histologic injury respectively. A very similar exacerbation of microvascular failure and increased pancreatitis severity was then demonstrated by the intravenous infusion of IIR conditioned mesenteric lymph from donor animals.

CONCLUSIONS

Unidentified factors released into the mesenteric lymph following IIR injury are capable of exacerbating AP. This highlights an important role for the intestine in the pathophysiology of AP pathogenesis and identifies mesenteric lymph as a potential therapeutic target.

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.

Mechanism of salutary effects of finasteride on post-traumatic immune/inflammatory response: upregulation of estradiol synthesis

OBJECTIVE

The aim of this study was to evaluate whether pretreatment with finasteride, a 5alpha-reductase inhibitor, improves immune functions after trauma-hemorrhage.

SUMMARY BACKGROUND DATA

A number of studies have provided evidence for a gender dimorphism in host defense after trauma. Under stress conditions, such as trauma-hemorrhage, androgenic hormones have immunosuppressive effects, leading to increased susceptibility to sepsis, morbidity, and mortality. Testosterone is converted by 5alpha-reductase to 5alpha-dihydrotestosterone (DHT), a more potent androgen.

METHODS

Male C3H/HeN mice (8-10 weeks) were randomly assigned to receive finasteride or vehicle for 2 days and were then subjected to trauma-hemorrhage or sham operation. Trauma-hemorrhage was induced by a midline laparotomy and approximately 90 minutes of hemorrhagic shock (blood pressure, 35 mm Hg), followed by fluid resuscitation. Animals were killed 2 hours after resuscitation or sham procedure. Plasma levels and Kupffer cell production of cytokines (TNF-alpha, IL-6, IL-10, MCP-1, KC, and MIP-1alpha), lung neutrophil infiltration, and edema were evaluated.

RESULTS

Finasteride administration prevented the increase in cytokine plasma levels, decreased DHT, and increased 17beta-estradiol plasma concentrations. In addition, neutrophil infiltration and edema formation in the lung were reduced by finasteride. The salutary effects of finasteride were abrogated after coadministration with an estrogen receptor inhibitor (ICI 182,780). Increased Kupffer cell cytokine production normally observed after trauma-hemorrhage was prevented by treatment with finasteride.

CONCLUSION

These results suggest that inhibition of 5alpha-reductase leads to the conversion of testosterone to 17beta-estradiol, which produces salutary effects on the post-traumatic immune response.

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.

Postresuscitation tissue neutrophil infiltration is time-dependent and organ-specific

BACKGROUND

Hemorrhagic shock with conventional resuscitation (CR) primes circulating neutrophils and activates vascular endothelium for increased systemic inflammation, superoxide release, and end-organ damage. Adjunctive direct peritoneal resuscitation (DPR) with intraperitoneal instillation of a clinical peritoneal dialysis solution decreases systemic inflammation and edema formation by enhancing tissue perfusion. The aim of this study is to determine the effect of adjunctive DPR on neutrophil and fluid sequestration.

METHODS

Anesthetized rats were hemorrhaged to 40% mean arterial pressure for 60 min. Animals were randomized for CR with the return of the shed blood plus two volumes of saline, or CR plus adjunctive DPR with 30 mL of intraperitoneal injection of a clinical peritoneal dialysis solution. Tissue myeloperoxidase (MPO) level, a marker of neutrophil sequestration, and total water content were assessed in the gut, lung, and liver in sham animals and at time-points 1, 2, 4, and 24 h postresuscitation.

RESULTS

Resuscitation from hemorrhagic shock increases MPO level in all tissues in a near-linear fashion during the first 4 h following resuscitation. This occurs irrespective of the resuscitation regimen used. Tissue MPO level returned to baseline at 24 h following resuscitation except in the liver where CR and not adjunctive DPR caused a significant rebound increase. Adjunctive DPR prevented the CR-mediated obligatory fluid sequestration in the gut and lung and maintained a relative normal tissue water in these organs compared with CR alone (n = 7, F = 10.1, P < 0.01).

CONCLUSION

Hemorrhagic shock and resuscitation produces time-dependent organ-specific trends of neutrophil sequestration as measured with tissue levels of myeloperoxidase, a marker of neutrophil infiltration. Modulation of the splanchnic blood flow by direct peritoneal resuscitation did not alter the time-dependent neutrophil infiltration in end-organs, suggesting a subordinate role of blood rheology in the hemorrhage-induced neutrophil sequestration. Vulnerable window for neutrophil-mediated tissue damage exists during the first 4 h following resuscitation from hemorrhagic shock in rats. Direct peritoneal resuscitation prevents the early obligatory fluid sequestration and promotes early fluid mobilization.

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.

Molecular signatures of trauma-hemorrhagic shock-induced lung injury: hemorrhage- and injury-associated genes

The etiology of trauma-hemorrhagic shock (T/HS)-induced acute lung injury has been difficult to elucidate because of, at least in part, the inability of in vivo studies to separate the noninjurious pulmonary effects of trauma-hemorrhage from the tissue-injurious ones. To circumvent this in vivo limitation, we used a model of T/HS in which T/HS lung injury was abrogated by dividing the mesenteric lymph duct. In this way, it was possible to separate the pulmonary injurious response from the noninjurious systemic response to T/HS by comparing the pulmonary molecular responses of rats subjected to T/HS, which did and did not develop lung injury, with those of nonshocked rats. Using high-density oligonucleotide arrays and treatment group comparisons of whole lung tissue collected at 3 h after the end of the shock or sham-shock period, 139 of 8,799 assessed genes were identified by significant analysis of microarrays. Hemorrhage without the secondary effects of lung injury modulated the expression of 21 genes such as interleukin 1beta, metallothionein-2, and myeloctomatosis oncogene (c-myc). In response to injury, 42 genes were identified to be differentially expressed. Upregulated genes included the L1 retroposon and guanine deaminase, whereas downregulated genes included catalase and superoxide dismutase 1. Real-time polymerase chain reaction confirmed the differential expression for selected genes. PathwayAssist analysis identified interleukin 1beta as a central regulator of two subpathways of stress response-related genes (c-myc and superoxide dismutase 1/catalase) as well as several unrelated genes such as lipoprotein lipase. Our model system provided a unique opportunity to distinguish the molecular changes associated with T/HS-induced acute lung injury from the systemic molecular response to T/HS.

Sphingosine 1-phosphate has dual functions in the regulation of endothelial cell permeability and Ca2+ metabolism

Ca2+ signaling plays an important role in endothelial cell (EC) functions including the regulation of barrier integrity. Recently, the endogenous lipid derivative, sphingosine-1-phosphate (S1P), has emerged as an important modulator of EC barrier function. We investigated the role of endogenously generated S1P in Ca2+ metabolism and barrier function in human umbilical endothelial cells (HUVECs) stimulated by thrombin, histamine, or other agonists. Barrier function was assessed by dextran diffusion through HUVEC monolayers, and Ca2+ transients were measured using a fluoroprobe. Thrombin or histamine increased Ca2+ release from the endoplasmic reticulum (ER) and Ca2+ entry through store-operated channels (SOCs) that was accompanied by increased EC permeability. Inhibition of S1P synthesis by a specific sphingosine kinase inhibitor (SKI) decreased thrombin or histamine-induced increased permeability and decreased Ca2+ entry via SOC in a concentration-dependent fashion. SKI had minuscule effects on thrombin or histamine-induced Ca2+ release from ER. SKI also inhibited thapsigargin or ionomycin-induced Ca2+ entry via SOC without affecting Ca2+ release from the ER. In contrast to the effects of endogenously generated S1P, when S1P was administered externally, it initiated Ca2+ release from ER similar to thrombin and histamine while decreasing EC permeability. These observations indicate that after agonist-induced conditions, endogenously generated S1P functions as a positive modulator of Ca2+ entry via SOC and a mediator of increased cell permeability. In contrast, extracellular exposure to S1P has different signaling mechanisms and effects. Thus, the potential dual roles of endogenous and exogenous S1P on EC function need to be considered in pharmacological studies targeting sphingosine metabolism.

Mechanisms of sepsis-induced organ dysfunction

BACKGROUND

The past several years have seen remarkable advances in understanding the basic cellular and physiologic mechanisms underlying organ dysfunction and recovery relating to sepsis. Although several new therapeutic approaches have improved outcome in septic patients, the far-reaching potential of these new insights into sepsis-associated mechanisms is only beginning to be realized.

AIM

The Brussels Round Table Conference in 2006 convened >30 experts in the field of inflammation and sepsis to review recent advances involving sepsis and to discuss directions that the field is likely to take in the near future.

FINDINGS

Current understanding of the pathophysiology underlying sepsis-induced multiple organ dysfunction highlights the multiple cell populations and cell-signaling pathways involved in this complex condition. There is an increasing appreciation of interactions existing between different cells and organs affected by the septic process. The intricate cross-talk provided by temporal changes in mediators, hormones, metabolites, neural signaling, alterations in oxygen delivery and utilization, and by modifications in cell phenotypes underlines the adaptive and even coordinated processes beyond the dysregulated chaos in which sepsis was once perceived. Many pathologic processes previously considered to be detrimental are now viewed as potentially protective. Applying systems approaches to these complex processes will permit better appreciation of the effectiveness or harm of treatments, both present and future, and also will allow development not only of better directed, but also of more appropriately timed, strategies to improve outcomes from this still highly lethal condition.

New advances in pancreatic surgery

PURPOSE OF REVIEW

New understanding of the dynamic of acute pancreatitis, the clinical impact of local pathology in chronic pancreatitis and cystic neoplastic lesions bearing high potential for malignant transformation has changed the management of pancreatic diseases.

RECENT FINDINGS

In acute pancreatitis, risk factors independently determining outcome in severe acute pancreatitis are early and persistent multiorgan failure, infected necrosis and extended sterile necrosis. The management of severe acute pancreatitis is based on early intensive-care treatment and late surgical debridement. In chronic pancreatitis, recent data from randomized controlled clinical trials have demonstrated duodenum-preserving pancreatic head resection with an inflammatory mass of the head as superior to pylorus-preserving Whipple resection. Cystic neoplasms are local lesions of the pancreas with high malignant potential. Local organ-preserving resection techniques have been applied with low morbidity and mortality, replacing a Whipple-type resection. Resection of pancreatic cancer is ineffective to cure patients. After an R0-resection, a significant survival benefit has been achieved when adjuvant chemotherapy has additionally been applied.

SUMMARY

New knowledge about the nature of inflammatory diseases, cystic neoplastic lesions and malignant pancreatic tumours has changed the indication for surgical treatment and the application of organ-preserving surgical techniques.

Effect of hyperbarically oxygenated-perfluorochemical with University of Wisconsin solution on preservation of rat small intestine using an original pressure-resistant portable apparatus

BACKGROUND

Perfluorochemicals (PFC) are chemical substances that have a higher oxygen solubility under hyperbaric oxygen (HBO) pressure. This study investigated the effect of cold HBO-PFC/University of Wisconsin (UW) solution on preservation of rat small intestinal graft.

METHODS

We manufactured an air-tight, pressure-resistant tank made of stainless steel with high thermal conductivity. Rat ileal grafts were placed in a custom-made silicon-gum bag with UW solution, which was immersed in 5 atm HBO-PFC solution in the tank (Group P-5). The tank was kept at 4 degrees C. We compared the ATP concentration and mucosal permeability in Group P-5 with grafts preserved in 1 atm oxygenated-PFC/UW solution (Group P-1) and simple cold storage in UW solution (Group C). Histologic study was also performed.

RESULTS

PO(2) in UW solution after 48 h preservation were 1852 +/- 37, 499 +/- 13, and 173 +/- 3 mmHg (Group P-5, P-1 and C, respectively, mean +/- SD). At 48 h of preservation, graft ATP concentration was significantly greater in Group P-5 compared to that in Group P-1 and Group C. Mucosal hyperpermeability as well as mucosal morphologic changes were also ameliorated in Group P-5.

CONCLUSION

HBO-PFC can supply a greater amount of oxygen to UW solution. Indirect measures of oxygen metabolism such as ATP content and lactate production suggested improvement in maintaining graft oxygen metabolism.

Comparison of lung injury after normal or small volume optimized resuscitation in a model of hemorrhagic shock

OBJECTIVE

To compare lung injury induced by a hemorrhagic shock resuscitated with normal saline or with small volumes of a hypertonic/hyperoncotic solution.

DESIGN AND SETTING

Randomized, controlled, laboratory study in an animal research laboratory.

SUBJECTS

Nineteen pigs (43 +/- 4 kg).

INTERVENTIONS

After anesthesia and mechanical ventilation animals were bled to induce a 2-h deep shock and resuscitated for 2 h using normal saline (NS, 2 ml/kg per minute, n = 7) or the association of 7.2% NaCl with 6% hydroxyethylstarch 200/0.5 (HSHES, 4 ml/kg in 10 min followed by 0.2 ml/kg per minute, n = 7) to reach cardiac index and mixed venous oxygen saturation goals. Lungs were removed 6[Symbol: see text]h after the initiation of hemorrhage. Five animals were used as controls without hemorrhage.

MEASUREMENTS AND RESULTS

Resuscitation goals were achieved using 90 +/- 17 ml/kg NS or 6.8 +/- 1.9 ml/kg HSHES. Lung injury was noted in both hemorrhage groups but was not influenced by the type of resuscitation. Extravascular lung water was measured at 9.6 +/- 1.8 ml/kg in the NS group, 9.2 +/- 1.6 ml/kg in the HSHES, group and 6.4 +/- 1 m/kg in the control group. The degree of histological alveolar membrane focal thickening and interstitial neutrophil infiltration were significantly more pronounced in the hemorrhage groups with no difference between the two types of fluid loading. Finally, pulmonary levels of IL-8 were higher after hemorrhage regardless of the type of resuscitation.

CONCLUSIONS

When included in an optimized and goal directed resuscitation, the use of normal saline or a small volume of hypertonic/hyperoncotic solution does not result in a different early hemorrhage-induced lung injury.

Interleukin-1 mediates thermal injury-induced lung damage through C-Jun NH2-terminal kinase signaling

OBJECTIVE

The molecular mechanisms of lung damage following thermal injury are not clear. The purpose of this study was to determine whether interleukin (IL)-1 mediates burn-induced inducible nitric oxide synthase (iNOS) expression, peroxynitrite production, and lung damage through c-Jun NH2-terminal kinase (JNK) signaling.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Thermal injury models in the mice.

INTERVENTIONS

IL-1 receptor type 1 (IL-1R1) mice, Tnfrsf1a mice, and wild-type (WT) mice were subjected to 30% total body surface area third-degree burn. The JNK inhibitor, SP600125, was given to mice to study the involvement of the JNK pathway in thermal injury-induced lung damage. WT --> WT, WT --> IL-1R1, and IL-1R1 --> WT chimeric mice were generated to determine the role of hematopoietic cells in IL-1-mediated lung damage. Neutrophils were harvested and treated in vitro with N-formyl-methionyl-leucyl-phenylalanine (fMLP).

MEASUREMENTS AND MAIN RESULTS

IL-1R1 mice rather than Tnfrsf1a mice showed less thermal injury-induced lung damage. IL-1R1 mice displayed less lung JNK activity; intercellular adhesion molecule (ICAM), vascular cell adhesion molecule (VCAM), chemokine receptor 2 (CXCR2), and macrophage inflammatory protein-2 (MIP2), messenger RNA expression; myeloperoxidase activity; and neutrophil p38 mitogen-activated protein kinase (MAPK) phosphorylation after thermal injury. SP600125 significantly reduced thermal injury-induced blood dihydrorhodamine (DHR) 123 oxidation, iNOS expression, and lung permeability in WT mice but not in IL-1R1 mice. IL-1R1 --> WT chimeric mice rather than WT --> IL-1R1 chimeric mice showed less thermal injury-induced lung damage. fMLP increased reactive oxygen species (ROS) production of neutrophils in WT mice but not in IL-1R1 mice. SP600125 decreased ROS production of neutrophils in WT mice but not in IL-1R1 mice.

CONCLUSIONS

Thermal injury-induced lung JNK activation; lung ICAM, VCAM, CXCR2, and MIP2 expression; and DHR 123 oxidation are IL-1 dependent. JNK inhibition decreases IL-1-mediated thermal injury-induced lung damage. Given that the IL-1 receptor is critical in thermal injury-induced p38 MAPK phosphorylation and ROS production of neutrophils, we conclude that IL-1 mediates thermal injury-induced iNOS expression and lung damage through the JNK signaling pathway.

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.

Cellular mechanisms of burn-related changes in contractility and its prevention by mesenteric lymph ligation

Major burn injury results in impairment of left ventricular (LV) contractile function. There is strong evidence to support the involvement of gut-derived factor(s) transported in mesenteric lymph in the development of burn-related contractile dysfunction; i.e., mesenteric lymph duct ligation (LDL) prevents burn-related contractile depression. However, the cellular mechanisms for altered myocardial contractility of postburn hearts are largely unknown, and the cellular basis for the salutary effects of LDL on cardiac function have not been investigated. We examined contractility, Ca2+ transients, and L-type Ca2+ currents ( ICa) in LV myocytes isolated from four groups of rats: 1) sham burn, 2) sham burn with LDL (sham + LDL), 3) burn (≈40% of total body surface area burn), and 4) burn with LDL (burn + LDL). Myocytes isolated from hearts at 24 h postburn had a depressed contractility (≈20%) at baseline and blunted responsiveness to elevation of bath Ca2+. Myocyte contractility was comparable in sham + LDL and sham burn hearts. LDL completely prevented burn-related changes in myocyte contractility. Mechanistically, the decrease in contractility in myocytes from postburn hearts occurred with a decrease in the amplitude of Ca2+ transients (≈20%) without changes in resting Ca2+ or Ca2+ content of the sarcoplasmic reticulum. On the other hand, ICa density was decreased (≈30%) in myocytes from postburn hearts, with unaltered voltage-dependent properties. Thus burn-related myocardial contractile dysfunction is linked with depressed myocyte contractility associated with a decrease in ICa density. These findings also provide strong evidence that mesenteric lymph is involved in the onset of burn-related cardiomyocyte dysfunction.

Bacterial translocation: overview of mechanisms and clinical impact

Bacterial translocation (BT) is a phenomenon in which live bacteria or its products cross the intestinal barrier. Gut translocation of bacteria has been shown in both animal and human studies. BT and its complications have been shown clearly to occur in animal models, but its existence and importance in humans has been difficult to ascertain. We review the mechanisms of BT and its clinical impact based on the current literature.

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.

Hypertonic saline and pentoxifylline reduces hemorrhagic shock resuscitation-induced pulmonary inflammation through attenuation of neutrophil degranulation and proinflammatory mediator synthesis

BACKGROUND

Ringer's lactate (RL), the current standard resuscitation fluid, potentiates neutrophil activation and is associated with pulmonary inflammation. Resuscitation with hypertonic saline and pentoxifylline (HSPTX) has been shown to attenuate hemorrhagic shock-induced injury when compared with RL. Because the neutrophil plays a major role in postshock inflammation, we hypothesized that HSPTX reduces pulmonary inflammation after resuscitation in comparison to RL.

METHODS

Sprague-Dawley rats underwent controlled shock and were resuscitated with RL (32 mL/kg) or HSPTX (4 mL/kg 7.5% NaCl + pentoxifylline 25 mg/kg). Animals who did not undergo shock or resuscitation served as controls. After 24 hours, bronchoalveolar lavage fluid (BALF) and lung tissue were collected. Cytokine induced neutrophil chemoattractant (CINC) was measured in BALF by enzyme-linked immunosorbent assay. Matrix metalloproteinases (MMP)-2 and -9 were measured by zymography. Hemeoxygenase-1 (HO-1) was assessed by Western blot and immunohistochemistry.

RESULTS

HSPTX resuscitation led to a 62% decrease in CINC levels compared with RL (p < 0.01). BALF MMP-2 expression was attenuated by 11% with HSPTX (p = 0.09). Lung MMP-2 and MMP-9 expression was reduced by 89% (p < 0.01) and 76%, respectively (p < 0.05). Lung HO-1 expression declined by 34% with HSPTX in comparison to RL (p < 0.01), indicating less oxidative injury. Lung immunohistochemistry localized HO-1 to neutrophils, macrophages, and airway epithelial cells.

CONCLUSION

Collectively, the attenuation of pulmonary inflammation with HSPTX after shock when compared with RL is associated with downregulation of neutrophil activation, oxidative stress, and proinflammatory mediator production.

Relationship between disruption of the unstirred mucus layer and intestinal restitution in loss of gut barrier function after trauma hemorrhagic shock

BACKGROUND

The factors involved in shock-induced loss of gut barrier function remain to be defined fully and studies investigating gut injury have focused primarily on the systemic side of the intestine.

METHODS

Male Sprague-Dawley rats were subjected to a laparotomy (trauma) and 90 minutes of trauma sham shock (T/SS) or actual trauma (laparotomy) hemorrhagic shock (T/HS) (30 mm Hg). At 0, 30, 60, or 180 minutes after the end of shock and volume resuscitation (reperfusion), the animals were killed and samples of the ileum were collected for intestinal morphologic analysis, analysis of the unstirred mucus layer, and for barrier function by measuring permeability to flourescein dextran.

RESULTS

T/HS-induced morphologic evidence of mucosal injury as well as epithelial apoptosis was present at the end of the shock period and maximal after 60 minutes of reperfusion. At 3 hours after reperfusion, the degree of villous injury and enterocyte apoptosis had decreased. In contrast to the morphologic appearance of the villi, disruption of the mucus layer became progressively more severe over time and was manifest as a decrease in mucus thickness, progressive loss of coverage of the luminal surface by the mucus layer, and a change in mucus appearance from a dense to a loose structure. Studies of intestinal permeability documented that T/HS-induced loss of gut barrier function persisted throughout the 3-hour reperfusion period and were associated with injury to the mucus layer as well as the villi.

CONCLUSIONS

T/HS leads to changes in the intestinal mucus layer as well as increased villous injury, apoptosis, and gut permeability. Additionally, increased gut permeability was associated with loss of the intestinal mucus layer suggesting that T/HS-induced injury to the mucus layer may contribute to the loss of gut barrier function.

Intraperitoneal administration of hyperbarically oxygenated perfluorochemical enhances preservation of intestinal mucosa against ischemia/reperfusion injury

Perfluorochemicals (PFCs) have a high solubility for oxygen. We have previously demonstrated the effect of peritoneal lavage with oxygenated PFC (O2-PFC) on ameliorating ischemia/reperfusion (I/R)-induced intestinal ischemic damage in an animal model. In this study, we applied hyperbarically O2-PFC (HBO-PFC) to investigate whether a larger amount of oxygen carried by PFC could enhance the protective effect of O2-PFC during intestinal malperfusion. Rats were subjected to ischemia by clamping the superior mesenteric artery (SMA) for 90 min. The SMA was then declamped. Rats were divided into four groups. In group A, only anesthesia and abdominal incision were performed. In group B, SMA was clamped without O2-PFC. In group C, during the SMA clamp, 1 atm O2-PFC was injected into the abdominal cavity. In group D, 5 atm O2-PFC (HBO-PFC) was prepared using a custom-made hyperbaric oxygen tank and administered to the abdominal cavity during the SMA clamp. Ileal tissue adenosine triphosphate (ATP) levels 90 min after SMA declamping were determined using luciferase assay. To assess intestinal mucosal barrier function at 90 min after release of the SMA clip, everted gut sacs were prepared to measure the mucosal-to-serosal passage of fluorescein-conjugated dextran (FD4, molecular weight = 4 kDa). Thirty minutes after i.p. administration, partial pressure of oxygen in HBO-PFC remained around 1000 mmHg, whereas partial pressure of oxygen in 1 atm O2-PFC decreased to around 400 mmHg. The intestinal tissue ATP was significantly preserved in group D. Moreover, the mucosal hyperpermeability of the gut sac after I/R was significantly ameliorated in group D. Hyperbarically oxygenated perfluorochemical might supply a larger amount of oxygen to ischemic tissue during SMA clamp, which protected the small intestine from I/R injury, possibly caused by the maintenance of tissue ATP levels during 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.

Portal Triad Occlusion Induces Endotoxin Tolerance: Role of Portal Congestion

BACKGROUND

Portal triad occlusion (PTO) causes portal congestion and damages the intestinal mucosa, which is associated with portal endotoxemia. However, administration of a sublethal dose of endotoxin results in resistance to its toxic activities. We tested the hypothesis that portal congestion due to PTO induces endotoxin tolerance.

MATERIALS AND METHODS

Rats were subjected to PTO for 15 min. In Group 1, male rats underwent laparotomy and, 48 h after the surgery, a lethal dose of Escherichia coli lipopolysaccharide was administered. In Group 2, rats were subjected to PTO for 15 min. Then a lethal dose of LPS was administered 48 h after surgery. Group 3 was treated the same as Group 2, except that PTO was performed with portosystemic shunt. Group 4 was also treated same as Group 2, except that rats received polymixin B and neomycin by gavage to eliminate intestinal luminal bacteria before PTO. Survival was examined after the administration of a lethal dose of LPS. Changes in plasma levels of cytokine are also measured after the administration of LPS. The portal endotoxin level in each group after PTO was measured.

RESULTS

On survival test, only rats in Group 2 and Group 4 showed significantly higher survival rates. The portal endotoxin level was significantly elevated only in Group 2. The elevation of plasma cytokine levels (IL-6, TNF-alpha) and NO production (NO(2)(-)/NO(3)(-)) in Groups 2 and 4 were inhibited compare to those in Groups 1 and 3.

CONCLUSIONS

PTO induced LPS tolerance possibly due to portal congestion and subsequent visceral congestion.

Post-resuscitation reperfusion injury: Comparison of periodic Gz acceleration versus Thumper CPR

The effects of whole body, periodic acceleration (pGz) on cardiopulmonary resuscitation outcome, organ blood flow and tissue inflammatory injury were examined in an experimental pig model, and compared with Thumper (TH)-CPR. VF was induced in 16 pigs, and remained untreated for 3 min, followed by either pGz-CPR or TH-CPR for 15 min. Defibrillation attempts were made at 18 min of VF. Six of eight animals had ROSC in both groups. Post-arrest myocardial dysfunction was present in both groups and progressed over hours. pGz-CPR animals had less wall motion abnormality and higher left ventricular ejection fraction than TH-CPR. The post-resuscitation haemodynamic variables returned to baseline after 3h of ROSC in pGz-CPR group, and remained low in TH-CPR group. The brain blood flow during CPR was similar between TH-CPR and pGz-CPR, 17% and 20% of pre-fibrillation values, respectively. The cardiac blood flow during CPR was significantly lower in pGz-CPR than TH-CPR (TH: 10.2% and pGz: 1.9% of pre-fibrillation value), as well as in other organs. The brain and heart blood flow was significantly higher than pre-fibrillation values after 30 min of ROSC in both groups. The pGz group had significantly higher blood flow in brain, heart and kidney than TH-CPR after 30 min of ROSC. Blood flow in all organs decreased below pre-fibrillation values at 2h of ROSC. Tissue inflammatory injury progressed over hours in the post-resuscitation phase. pGz-CPR group had significantly lower myeloperoxidase (MPO) activity and plasma creatine phosphokinase (CPK) and cardiac troponin I, TNF-alpha, and IL-6 than TH-CPR. Results from the present study demonstrate again that pGz-CPR is an effective method of cardiopulmonary resuscitation, with less post-reperfusion injury compared to TH-CPR.

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.

Amiloride moderates increased gut permeability and diminishes mesenteric lymph-mediated priming of neutrophils in trauma/hemorrhagic shock

BACKGROUND

Amiloride, an inhibitor of Na+/H+ exchangers and Na+ channels has been shown recently to ameliorate both gut and lung injury in rats subjected to a combined insult of trauma and hemorrhagic shock (T/HS). We have shown previously that mesenteric lymph duct ligation prevents T/HS-induced lung endothelial injury and neutrophil activation, suggesting that toxic inflammatory factors originating from the gut and carried in the lymph are responsible for the lung injury observed after T/HS. This study investigates whether the protective effect of amiloride against T/HS-induced lung injury was associated with decreased lymph toxicity and gut permeability.

METHODS

Male rats subjected to trauma (laparotomy) plus hemorrhagic shock (mean arterial pressure, 30 mm Hgx90 min) (T/HS) or trauma plus sham shock (T/SS) and treated with amiloride or its vehicle had their mesenteric lymph duct catheterized. Mesenteric lymph collected before and after shock was assayed for biologic activity on endothelial cells (cytotoxicity and permeability) and neutrophils (respiratory burst activity). Gut permeability was assessed by monitoring plasma concentrations of the fluorescent dye FITC-dextran after its injection into the ileum.

RESULTS

Amiloride administration reduced the capacity of post-shock mesenteric lymph to prime neutrophils for an increased respiratory burst. Amiloride failed to decrease the ability of mesenteric lymph to kill endothelial cells or increase their permeability. Amiloride decreased gut permeability.

CONCLUSIONS

The mechanisms of the lung protective effect of amiloride in rats undergoing T/HS may be secondary to decreased neutrophil activation, diminished gut permeability, or an effect on the end organ.

Conventional dose hypertonic saline provides optimal gut protection and limits remote organ injury after gut ischemia reperfusion

BACKGROUND

Hypertonic saline (HS) resuscitation prevents neutrophil mediated injury after shock. The optimal dose is not known, but appears as a result of osmotic stress. We hypothesized that a dose dependent effect exists related to increasing tonicity and that the optimal gut protective dose would provide better protection against remote organ injury than large volume isotonic crystalloids.

METHODS

In experiment 1, rats were assigned to controls (sham/no resuscitation, sham/4 mL/kg 7.5% HS, superior mesenteric artery occlusion [SMAO]/no resuscitation), SMAO/equal volume (4 mL/kg 0.9% NS, 4 mL/kg 2.5% HS, 4 mL/kg 5% HS, 4 mL/kg 7.5% HS and 4 mL/kg 10% HS) or SMAO/equal sodium (33 mL/kg 0.9% NS, 12 mL/kg 2.5% HS, 6 mL/kg 5% HS, 4 mL/kg 7.5% HS, and 3 mL/kg 10% HS). In experiment 2, rats were assigned to the same control groups, and to either SMAO/NS (33 mL/kg 0.9% NS, equal salt load) or SMAO/HS (4 mL/kg 7.5% HS). The SMAO was clamped for 60 minutes and boluses given 5 minutes before clamp removal. After 6 hours of reperfusion, ileum and lungs were harvested for analysis of histologic injury, myeloperoxidase (MPO) as an index of neutrophil mediated injury, and serum ALT and AST drawn as markers of liver injury.

RESULTS

In experiment 1, equal volume and equal sodium decreased injury and inflammation with increasing tonicity in a dose dependent fashion, with the optimal effect seen at 7.5%. In experiment 2, NS resuscitation resulted in minimal improvement of SMAO-induced lung injury and inflammation or increases in serum ALT and AST whereas HS resuscitation significantly decreased these parameters.

CONCLUSION

The protective effect of HS is related to increased tonicity. While NS had little effect on SMAO-induced remote organ injury, optimal dose HS resuscitation was quite protective. This supports the growing evidence that HS protection may be because of its gut protective effects.

Hydroxyethyl starch exhibits antiinflammatory effects in the intestines of endotoxemic rats

We performed the present in vivo study to investigate the effect of hydroxyethyl starch (HES) on intestinal production of inflammatory mediators and activation of transcription factors during endotoxemia. Rats with endotoxemia induced by lipopolysaccharide (LPS) (5 mg/kg, IV) were treated with HES (16 mL/kg, IV) or saline (64 mL/kg, IV). At 2, 3, or 6 h after the LPS challenge, the rat ileal tissues were collected. Various ileal inflammatory mediator levels (tumor necrosis factor-alpha, interleukin [IL]-6, cytokine-induced neutrophil chemoattractant-1, and IL-10), inflammatory mediator messenger RNAs (mRNAs), activities of nuclear factor (NF)-kappaB and activator protein (AP)-1, and ileal myeloperoxidase-positive cells were determined in each group. HES significantly reduced the increased intestinal levels of tumor necrosis factor-alpha, IL-6, cytokine-induced neutrophil chemoattractant-1, and the mRNAs in the endotoxemic rats. Similarly, HES could decrease the myeloperoxidase-positive cells induced by LPS and also inhibit ileal NF-kappaB and AP-1 activations. Our results suggest that during endotoxemia HES may down-regulate intestinal inflammatory mediator production, and this antiinflammatory effect of HES may act through suppression of NF-kappaB and AP-1 activations.