Pathogenesis of hemorrhage-induced bacteria/endotoxin translocation in rats. Effects of recombinant bactericidal/permeability-increasing protein

A bibliometric analysis of the role of microbiota in trauma

Introduction

Over the last several decades, the gut microbiota has been implicated in the formation and stabilization of health, as well as the development of disease. With basic and clinical experiments, scholars are gradually understanding the important role of gut microbiota in trauma, which may offer novel ideas of treatment for trauma patients. In this study, we purposed to summarize the current state and access future trends in gut microbiota and trauma research.

Methods

We retrieved relevant documents and their published information from the Web of Science Core Collection (WoSCC). Bibliometrix package was responsible for the visualized analysis.

Results

Totally, 625 documents were collected and the number of annual publications kept increasing, especially from 2016. China published the most documents while the USA had the highest local citations. The University of Colorado and Food & Function are respectively the top productive institution and journal, as PLOS One is the most local cited journal. With the maximum number of articles and local citations, Deitch EA is supported to be the most contributive author. Combining visualized analysis of keywords and documents and literature reading, we recognized two key topics: bacteria translocation in trauma and gut microbiota's effect on inflammation in injury, especially in nervous system injury.

Discussion

The impact of gut microbiota on molecular and pathological mechanism of inflammation is the focus now. In addition, the experiments of novel therapies based on gut microbiota's impact on trauma are being carried out. We hope that this study can offer a birds-eye view of this field and promote the gradual improvement of it.

Microbial Translocation and Perinatal Asphyxia/Hypoxia: A Systematic Review

The microbiome is vital for the proper function of the gastrointestinal tract (GIT) and the maintenance of overall wellbeing. Gut ischemia may lead to disruption of the intestinal mucosal barrier, resulting in bacterial translocation. In this systematic review, according to PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines, we constructed a search query using the PICOT (Patient, Intervention, Comparison, Outcome, Time) framework. Eligible studies reported in PubMed, up to April 2021 were selected, from which, 57 publications’ data were included. According to these, escape of intraluminal potentially harmful factors into the systemic circulation and their transmission to distant organs and tissues, in utero, at birth, or immediately after, can be caused by reduced blood oxygenation. Various factors are involved in this situation. The GIT is a target organ, with high sensitivity to ischemia–hypoxia, and even short periods of ischemia may cause significant local tissue damage. Fetal hypoxia and perinatal asphyxia reduce bowel motility, especially in preterm neonates. Despite the fact that microbiome arouse the interest of scientists in recent decades, the pathophysiologic patterns which mediate in perinatal hypoxia/asphyxia conditions and gut function have not yet been well understood.

The role of the sensor kinase, QseC, an adrenergic receptor of Escherichia coli, in bacterial translocation during hemorrhagic shock

BACKGROUND

Hemorrhagic shock results in ileal mucosa damage and intestinal bacterial translocation. Additionally, during hemorrhagic shock, norepinephrine levels increase. Past research has shown that the QseC sensor kinase of Escherichia coli modulates the quorum-sensing response to epinephrine and norepinephrine. Therefore, the aim of our study was to examine whether the absence of the ability of E. coli to sense epinephrine/norepinephrine would attenuate the bacterial translocation to extraintestinal organs in a rat model of hemorrhagic shock.

METHODS

An E. coli MC1000 qseC mutant was constructed, and E. coli MC1000 and MC1000ΔqseC with streptomycin resistance were used to track bacterial translocation after gavage in rats. A rat model of nonlethal hemorrhagic shock was used. The rats were divided into six groups: controls (SS), rats that received a sham shock and MC1000 (M-SS), rats that received a sham shock and MC1000ΔqseC (Δ-SS), rats that received a hemorrhagic shock alone (HS), rats that received a hemorrhagic shock and MC1000 (M-HS), and rats that received a hemorrhagic shock and MC1000ΔqseC (Δ-HS).

RESULTS

We found the incidence of bacterial translocation in the M-HS rats was higher than in the Δ-HS rats. The observed effects seem to be largely dependent on the inability to sense epinephrine/norepinephrine and the decreased motility of E. coli MC1000ΔqseC.

CONCLUSION

Therefore, a role for E. coli sensing epinephrine/norepinephrine in the pathophysiology of bacterial translocation following hemorrhagic shock is proposed. The demonstration of such an effect would suggest a new mechanism for the development of shock-induced sepsis.

Pathophysiological relevance of the CD14 receptor in surgical patients: biological activity of endotoxin is regulated by the CD14 receptor

Endotoxins (lipopolysaccharides, LPSs) are potent bacterial poisons, and they are always present in the intestine in considerable numbers. Stress, such that as a resulting from multiple injuries, burns, hypovolemia, hypoxia, intestinal ischemia, and surgery can lead to a breakdown of the gut barrier, allowing endotoxins to enter the systemic circulation via translocation. However, estimating the biological activity of translocated circulating endotoxins and identification of the mechanisms regulating their biological activities remain complex problems. CD14 has been found to exist as a soluble protein in the serum and as a glycosylphosphatidylinositol (GPI)-anchored protein of myeloid lineage cells. It plays key roles in both LPS-induced activation and in LPS internalization by cells. In this article, we outline: (i) the biological activity of circulating endotoxin; and (ii) the role of membrane and/or soluble CD14 regulating the bioactivity of circulating endotoxin in a human model of postoperative endotoxemia.

Cytokine synthesis in the liver of endotoxin-tolerant and normal rats during hemorrhagic shock

In the present study the effects of endotoxin tolerance on hemorrhagic shock were investigated with particular focus on hepatic alterations. The following questions were addressed: (i) does hemorrhagic shock induce cytokine formation and heat shock response in the liver; and (ii) does endotoxin tolerance alter these reactions. Endotoxin tolerance was induced by repetitive daily injections of LPS for 5 days. Hemorrhagic shock was induced by hypovolemia (MAP 35 ± 5 mmHg). After 3 h, the animals were resuscitated by re-infusion of homologous blood. m-RNA was isolated from liver biopsies and the mRNA levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10) and heat shock protein 70 (HSP-70) were determined by RT-PCR. TNF-α was measured by ELISA in serum samples and in the supernatants of whole blood cultures. It was found that endotoxin tolerance reduced mortality caused by hemorrhagic shock from 80% to 20%. In parallel, TNF-α production in response to LPS in vivo and in vitro was significantly decreased. During hemorrhage and after resuscitation. increased mRNA levels were detected in hepatic biopsies for TNF-α, IL-6, IL-10 and HSP-70, with highest levels immediately after re-infusion. Endotoxin-tolerant rats produced significantly lower levels of TNF-α, while no differences were found for IL-10 and HSP-70. Within 30 min after reperfusion, significantly higher levels of IL-6 mRNA were found in hepatic biopsies from tolerant rats; these differences disappeared 2 h after reperfusion.

The impact of bacterial DNA translocation on early postoperative outcomes in Crohn's patients undergoing abdominal surgery

BACKGROUND AND AIMS

Bacterial DNA (bactDNA) translocation occurs frequently in patients with Crohn's disease and can be present in patients with a negative blood microbiological culture. We aimed to determine the effects of bactDNA translocation on postoperative outcomes in Crohn's disease patients undergoing abdominal surgery.

METHODS

Patients with Crohn's disease who underwent abdominal surgery between January 2012 and March 2014 were identified. General and postoperative outcome-related information was retrieved from a database, and the data were compared between patients with and without bactDNA translocation. Multivariate analysis was used to determine the independent effect of bactDNA translocation on postoperative morbidity.

RESULTS

One hundred and seven patients who underwent abdominal surgery were included in our study. The presence of bactDNA in blood samples was identified in 29 patients (27.1%). There was a total of 55 complications in 28 patients (26.2%). Patients with bactDNA in their blood had a mean postoperative hospital stay of 12.7±4.2 days and patients without DNA translocation had a mean postoperative hospital stay of 10.1±4.8 days (p = 0.009). The readmission rate was increased in patients with bactDNA translocation (p = 0.032). A low preoperative level of serum albumin (p = 0.024), preoperative immunosuppressive agent use (p = 0.046), and the presence of bactDNA in blood (p = 0.005) were independently associated with increased postoperative adverse outcomes.

CONCLUSIONS

Preoperative bactDNA translocation into the blood increases the incidence of postoperative adverse outcomes in patients with Crohn's disease who undergo abdominal surgery.

Effects of acute ethanol gavage on intestinal integrity after hemorrhage/resuscitation

BACKGROUND

In hemorrhagic shock with subsequent resuscitation (H/R), increased pro-inflammatory changes contribute to tissue injury and mortality in rodent models. Ethanol (EtOH) is assumed to modulate the inflammatory response and the subsequent organ injury after H/R. Therefore, we determined the contribution of acute ethanol gavage on intestinal inflammation and injury as well as survival after H/R in rats.

METHODS

Fourteen hours before H/R, female LEWIS rats were gavaged with single dose of EtOH or saline (5 g/kg, 30% EtOH, H/R_EtOH group or H/R_ctrl group). Then, rats were hemorrhaged to a mean arterial blood pressure of 30 ± 2 mmHg for 60 min and resuscitated. Control groups underwent surgical procedures and gavage without H/R (sham_ctrl group and sham_EtOH group). Tissue was harvested 2 h after resuscitation. Mortality was assessed 72 h after H/R.

RESULTS

Ethanol gavage increased survival after H/R from 20% to 80%, but amplified plasma alanineaminotransferase (ALT) release compared to saline gavage (2847 ± 406 vs. 1159 ± 200 IU/L, p < 0.05). Intestinal mucosal damage index, intestinal permeability, ileal myeloperoxidase levels as indicators of polymorphonuclear leukocyte (PMNL) infiltration and systemic IL-6 levels as well as ileal IL-6 and TNF gene expressions after H/R were reduced and partly restored after ethanol gavage when compared to the saline gavaged group after H/R.

CONCLUSIONS

Taken together, we propose that acute ethanol gavage prior to H/R 1) did not enhance intestinal mucosa injury after H/R and 2) suppressed the H/R-induced inflammatory response. Both findings seem to contribute to the ethanol-induced survival benefit after H/R in our model.

Increased circulating D-lactate levels predict risk of mortality after hemorrhage and surgical trauma in baboons

Patients with hemorrhagic shock and/or trauma are at risk of developing colonic ischemia associated with bacterial translocation that may lead to multiple organ failure and death. Intestinal ischemia is difficult to diagnose noninvasively. The present retrospective study was designed to determine whether circulating plasma D-lactate is associated with mortality in a clinically relevant two-hit model in baboons. Hemorrhagic shock was induced in anesthetized baboons (n = 24) by controlled bleeding (mean arterial pressure, 40 mmHg), base excess (maximum -5 mmol/L), and time (maximum 3 h). To mimic clinical setting more closely, all animals underwent a surgical trauma after resuscitation including midshaft osteotomy stabilized with reamed femoral interlocking nailing and were followed for 7 days. Hemorrhagic shock/surgical trauma resulted in 66% mortality by day 7. In nonsurvivor (n = 16) hemorrhagic shock/surgical trauma baboons, circulating D-lactate levels were significantly increased (2-fold) at 24 h compared with survivors (n = 8), whereas the early increase during hemorrhage and resuscitation declined during the early postresuscitation phase with no difference between survivors and nonsurvivors. Moreover, D-lactate levels remained elevated in the nonsurvival group until death, whereas it decreased to baseline in survivors. Prediction of death (receiver operating characteristic test) by D-lactate was accurate with an area under the curve (days 1-3 after trauma) of 0.85 (95% confidence interval, 0.72-0.93). The optimal D-lactate cutoff value of 25.34 μg/mL produced sensitivity of 73% to 99% and specificity of 50% to 83%. Our data suggest that elevation of plasma D-lactate after 24 h predicts an increased risk of mortality after hemorrhage and trauma.

C-Jun N-Terminal Kinase 2 Promotes Liver Injury via the Mitochondrial Permeability Transition after Hemorrhage and Resuscitation

Hemorrhagic shock leads to hepatic hypoperfusion and activation of mitogen-activated stress kinases (MAPK) like c-Jun N-terminal kinase (JNK) 1 and 2. Our aim was to determine whether mitochondrial dysfunction leading to hepatic necrosis and apoptosis after hemorrhage/resuscitation (H/R) was dependent on JNK2. Under pentobarbital anesthesia, wildtype (WT) and JNK2 deficient (KO) mice were hemorrhaged to 30 mm Hg for 3 h and then resuscitated with shed blood plus half the volume of lactated Ringer's solution. Serum alanine aminotransferase (ALT), necrosis, apoptosis and oxidative stress were assessed 6 h after resuscitation. Mitochondrial polarization was assessed by intravital microscopy. After H/R, ALT in WT-mice increased from 130 U/L to 4800 U/L. In KO-mice, ALT after H/R was blunted to 1800 U/l (P < 0.05). Necrosis, caspase-3 activity and ROS were all substantially decreased in KO compared to WT mice after H/R. After sham operation, intravital microscopy revealed punctate mitochondrial staining by rhodamine 123 (Rh123), indicating normal mitochondrial polarization. At 4 h after H/R, Rh123 staining became dim and diffuse in 58% of hepatocytes, indicating depolarization and onset of the mitochondrial permeability transition (MPT). By contrast, KO mice displayed less depolarization after H/R (23%, P < 0.05). In conclusion, JNK2 contributes to MPT-mediated liver injury after H/R.

Lipopolysaccharide binding protein inhibitory peptide alters hepatic inflammatory response post-hemorrhagic shock

Translocation of microorganisms and endotoxin (LPS) across the gastrointestinal mucosa may exacerbate the inflammatory response and potentiate hepatic injury associated with hemorrhagic shock. Lipopolysaccharide binding protein (LBP) augments LPS signaling through TLR4. In addition, evidence suggests that TLR4-mediated injury in liver ischemia/reperfusion occurs through the IRF-3/MyD88 independent pathway. We hypothesized that administration of LBP inhibiting peptide, LBPK95A, given at the time of resuscitation would reduce liver inflammation and injury in a murine model of hemorrhagic shock by limiting LPS-induced activation of the MyD88 independent pathway. Hemorrhagic shock was induced in male, C57BL/6 mice; a mean arterial blood pressure of 35 mmHg was maintained for 2.5 h. LBPK95A peptide or equal volume Lactated Ringer's solution was administered followed by fluid resuscitation. Mice were sacrificed at 2 and 6 h post-resuscitation. At 2 h, liver mRNA levels revealed a significant reduction in IFN-β, a cytokine produced via the MyD88 independent pathway, with LBPK95A treatment. However, mRNA levels of TNF-α, a cytokine associated with the MyD88 dependent pathway, were unaffected by treatment. The LBP inhibitory peptide did selectively reduce activation of TLR4 signaling via the IRF-3/MyD88 independent pathway. These results suggest that LBP promotes cytokine production through the MyD88 independent pathway during hemorrhagic shock.

Rons formation under restrictive reperfusion does not affect organ dysfunction early after hemorrhage and trauma

Reactive oxygen species have been implicated in the pathophysiology of early reperfusion. We aimed to determine 1) reactive oxygen and nitrogen species (RONS) formation in organs of rats and 2) its pathophysiological relevance during a phase of restrictive reperfusion after hemorrhagic/traumatic shock (HTS). Fifty-seven male Sprague-Dawley rats were subjected to a clinically relevant HTS model, featuring laparotomy, bleeding, and a phase of restrictive reperfusion. The RONS scavenger 1-hydroxy-3-carboxy-2,2,5,5-tetramethyl-pyrrolidine hydrochloride (continuous i.v. infusion) and electron paramagnetic resonance spectroscopy were applied for RONS (primarily superoxide and peroxynitrite) detection. Compared with sham-operated animals, the organ-specific distribution of RONS changed during restrictive reperfusion after HTS. Reactive oxygen and nitrogen species formation increased during restrictive reperfusion in red blood cells and ileum only but decreased in the kidney and remained unchanged in other organs. Hemorrhagic traumatic shock followed by restrictive reperfusion resulted in metabolic acidosis, dysfunction of liver and kidney, and increased oxidative burst capacity in circulating cells. Plasma RONS correlated with shock severity and organ dysfunction. However, RONS scavenging neither affected organ dysfunction nor oxidative burst capacity nor myeloperoxidase activity in lung when compared with the shock controls. In summary, a phase of restrictive reperfusion does not increase RONS formation in most organs except in intestine and red blood cells. Moreover, scavenging of RONS does not affect the early organ dysfunction manifested at the end of a phase of restrictive reperfusion.

Effects of acute hypervolaemic haemodilution on the expression of plasma interferon-inducible protein-10 and bactericidal/permeability-increasing protein in patients undergoing total hip replacement

This prospective, randomized controlled study evaluated the effects of acute hypervolaemic haemodilution (AHH) on the expression of plasma interferon-inducible protein-10 (IP-10) and bactericidal/permeability-increasing protein (BPI) in patients undergoing elective total hip replacement. Twenty patients were randomized to receive an infusion of either hydroxyethyl starch (HES group) or lactated Ringer's solution (LR group) immediately after anaesthesia. Plasma concentrations of IP-10 and BPI were measured before anaesthesia (baseline), at the start of surgery, 30 min after the start of surgery and at the end of surgery. Blood loss and the volume of blood transfused were significantly lower in the HES group compared with the LR group. Compared with baseline, IP-10 and BPI concentrations increased significantly in both groups 30 min after the start of surgery. The IP-10 concentrations were significantly lower and BPI concentrations significantly higher in the HES group compared with the LR group 30 min after the start of surgery and at the end of surgery. It is concluded that AHH with HES may be helpful in ameliorating immune function during total hip replacement and in reducing blood loss and the extent of blood transfusion.

RECOMBINANT BACTERICIDAL/PERMEABILITY-INCREASING PROTEIN INHIBITS ENDOTOXIN-INDUCED HIGH-MOBILITY GROUP BOX 1 PROTEIN GENE EXPRESSION IN SEPSIS

We investigated in vivo the effect of recombinant bactericidal/permeability-increasing protein (rBPI21) on high-mobility group box 1 protein (HMGB1) expression in sepsis and its potential mechanism. Using a sepsis model induced by cecal ligation and puncture (CLP), rats were randomly divided into four groups as follows: normal control group, sham-operated group, CLP group, and BPI treatment group. Animals were killed at designated time points, and blood and tissue samples from liver, lungs, kidneys, and small intestine were harvested to determine related variables. In addition, we observed the effect of treatment with rBPI21 on survival rate in septic rats. The results showed that endotoxin content and expression levels of HMGB1 and LPS binding protein/CD14 mRNA in various organs were significantly increased at 12 and 24 h after CLP, which can be attenuated by treatment with rBPI21 (P<0.05-0.01). Meanwhile, treatment with rBPI21 in septic rats can markedly reduce serum alanine aminotransferase, creatinine levels, and pulmonary myeloperoxidase activity at 12 and 24 h after CLP, increase diamine oxidase activity at both time points (P<0.05-0.01), and improve the 1- to 10-day survival rates in animals subjected to CLP (P=0.012). These findings suggest that treatment with rBPI21 can significantly reduce endotoxin contents and expression levels of HMGB1 and LPS binding protein/CD14 mRNA in various organs in sepsis induced by CLP, and can protect against multiple organ damage resulting from sepsis. The effect of rBPI21 inhibiting HMGB1 gene expression in sepsis might be associated with endotoxin-dependent mechanisms.

Bactericidal/permeability increasing protein attenuates the myocardial inflammation/dysfunction that occurs with burn complicated by subsequent infection

Intubation and mechanical ventilation after burn contribute to pneumonia-related infection. Although postburn presence or absence of endotoxin has been described, inactivation of Toll-like receptor 4 signaling has been shown to improve postburn organ function, suggesting that LPS participates in burn-related susceptibility to infection. We hypothesized that bactericidal/permeability-increasing protein (rBPI) given postburn would attenuate myocardial inflammation/dysfunction associated with postburn septic challenge given 7 days postburn. Rats were given burn over 40% total body surface area, lactated Ringer 4 ml.kg(-1).% burn(-1); burns received either vehicle or rBPI, 1 mg.kg(-1).h(-1) for 48 h postburn. Postburn day 7, subgroups of burns and shams were given intratracheal Klebsiella pneumoniae, 4 x 10(6) CFU to produce burn complicated by sepsis; additional sham and burn subgroups received intratracheal vehicle to produce sham sepsis. Vehicle-treated groups: 1) sham burn + sham sepsis 2) sham burn + sepsis, 3) burn + sham sepsis, 4) burn + sepsis. rBPI-treated groups: 5) sham burn + sham sepsis, 6) sham burn + sepsis, 7) burn + sham sepsis, 8) burn + sepsis. Cardiomyocyte cytokine secretion and myocardial function were studied 24 h after septic challenge, postburn day 8. Pneumonia-related infection 8 days after vehicle-treated burn produced myocyte cytokine secretion (pg/ml), indicated by increased myocyte TNF-alpha, 549 +/- 46; IL-1beta, 50 +/- 8; IL-6, 286 +/- 3 levels compared with levels in sham myocytes (TNF-alpha, 88 +/- 11; IL-1beta, 7 +/- 1; IL-6, 74 +/- 10; P < 0.05). Contractile dysfunction was evident from lower left ventricular pressure +/-dP/dt values in this group compared with sham. rBPI attenuated myocyte cytokine responses to septic challenge and improved contractile function, suggesting that burn-related mobilization of microbial-like products contribute to postburn susceptibility to infection.

Does noncomplicated acute appendicitis cause bacterial translocation?

It is unknown whether noncomplicated acute appendicitis cause bacterial translocation. In this study, we aimed to test development of the bacterial translocation in the patients who were operated for acute appendicitis. In this prospective study, 10 control patients who underwent elective operations because of other reasons, and 18 patients with noncomplicated acute appendicitis were evaluated. No patients took prophylactic antibiotic. After laparotomy, samples were obtained from peritoneal leaf just close to wound edge, and peritoneal swab culture from right paracolic region. Before appendectomy, a mesenteric lymph node (MLN) adjacent to the terminal ileum was taken out. Tissue samples were placed in a sterile container for microbiological analysis, and 10% formalin for histopathological analysis. Control samples had no bacterial translocation. Only 3 of 18 (16.6%) patients with appendicitis included bacterial translocation to MLN. There was no significant difference between both groups. No bacterial colonization was detected in the peritoneal tissue and peritoneal swab culture. Peritoneal tissue injury score was 2 +/- 1.4 in controls and 2.8 +/- 1.7 in the patients with appendicitis (P>0.05). MLN injury score was 2.5 +/- 1.3 in controls and 3.2 +/- 1.5 in the patients with appendicitis (P>0.05). No patient developed wound and systemic infection. No significant bacterial translocation frequency and tissue injury score was identified in the children with noncomplicated acute appendicitis. This result suggests that antibiotic prophylaxis may be unnecessary in such patients.

Large animal models: baboons for trauma, shock, and sepsis studies

A few limited examples of large animal models are outlined, with the main emphasis on baboon models. The baboon offers all the advantages of a large animal and is comparable with humans in nearly all physiological and immunological aspects. In addition, cross-reactivity with human therapeutic and diagnostic reagents allows testing of new species-specific therapies such as antihuman antibodies, on the one hand, and monitoring with available human analytical procedures, on the other.

Lipopolysaccharide-binding protein modulates hepatic damage and the inflammatory response after hemorrhagic shock and resuscitation

Hemorrhagic shock and resuscitation cause endotoxemia and hepatocellular damage. Because lipopolysaccharide-binding protein (LBP) enhances cellular responses to endotoxin, our aim was to determine whether LBP contributes to hemorrhage/resuscitation-induced injury by comparing LBP knockout and wild-type mice. Under pentobarbital anaesthesia, wild-type and LBP-deficient mice were hemorrhaged to 30 mmHg for 3 h and then resuscitated with shed blood plus half the volume of lactated Ringer solution. Serum alanine aminotransferase (ALT) necrosis, neutrophil infiltration, and 4-hydroxynonenal by histology/cytochemistry and stress kinase activation by immunoblot analysis were then determined. ALT in wild-type mice was 2,461 +/- 383 and 1,418 +/- 194 IU/l (means +/- SE), respectively, at 2 and 6 h after resuscitation versus sham ALT of 102 +/- 6 IU/l. In LBP-deficient mice, ALT was blunted at both time points to 1,108 +/- 340 and 619 +/- 171 IU/l (P < 0.05). Liver necrosis after 6 h was also attenuated from 3.5 +/- 0.8% in wild-type mice to 1.3 +/- 0.5% in LBP-deficient mice (P < 0.05). After hemorrhage/resuscitation, neutrophil infiltration increased 71% more in wild-type than LBP knockout mice. Similarly, hepatic 4-hydroxynonenal staining, indicative of lipid peroxidation, decreased from 33.8 +/- 4.5% in wild-type mice to 11.6 +/- 1.9% in knockout mice (P < 0.05). After hemorrhage/resuscitation, activation of MAPKs, JNK and ERK, occurred in wild-type mice, which was largely blocked in LBP-deficient mice. However, endotoxin in portal blood after resuscitation was not significantly different between wild-type and knockout mice. In conclusion, hemorrhagic shock and resuscitation to mice cause severe, LBP-mediated hepatocellular damage. An absence of LBP blunts hepatocellular injury with decreased neutrophil infiltration, oxidative stress, and c-Jun and ERK activation.

Nutritional stimulation of cholecystokinin receptors inhibits inflammation via the vagus nerve

The immune system in vertebrates senses exogenous and endogenous danger signals by way of complex cellular and humoral processes, and responds with an inflammatory reaction to combat putative attacks. A strong protective immunity is imperative to prevent invasion of pathogens; however, equivalent responses to commensal flora and dietary components in the intestine have to be avoided. The autonomic nervous system plays an important role in sensing luminal contents in the gut by way of hard-wired connections and chemical messengers, such as cholecystokinin (CCK). Here, we report that ingestion of dietary fat stimulates CCK receptors, and leads to attenuation of the inflammatory response by way of the efferent vagus nerve and nicotinic receptors. Vagotomy and administration of antagonists for CCK and nicotinic receptors significantly blunted the inhibitory effect of high-fat enteral nutrition on hemorrhagic shock-induced tumor necrosis factor-α and interleukin-6 release (P < 0.05). Furthermore, the protective effect of high-fat enteral nutrition on inflammation-induced intestinal permeability was abrogated by vagotomy and administration of antagonists for CCK and nicotinic receptors. These data reveal a novel neuroimmunologic pathway, controlled by nutrition, that may help to explain the intestinal hyporesponsiveness to dietary antigens, and shed new light on the functionality of nutrition.

Tissue lipopolysaccharide-binding protein expression in rats after thermal injury: potential role of TNF-alpha

Recent studies have suggested that levels of lipopolysaccharide-binding protein (LBP) might play a harmful role by up-regulating the host's sensitivity to endotoxin. Our previous studies demonstrated that local endotoxin could up-regulate LBP expression after acute insults, however, the definite molecular mechanisms downstream of endotoxin action remain unclear. This study investigates whether tumor necrosis factor (TNF-alpha) might be responsible for the LBP formation during endogenous endotoxemia postburn. Wistar rats were anesthetized, and a 35% TBSA full-thickness burn was created. Animals were randomly divided into normal control, thermal injury and anti-TNF-alpha mAb treatment group. A significant elevation of plasma endotoxin concentration was observed after acute insults. TNF-alpha levels in plasma also rapidly increased after thermal injury. Meanwhile, LBP mRNA expression markedly increased in liver, lungs, kidneys and intestine postburn. There was no detectable TNF-alpha in the plasma of anti-TNF-alpha mAb treated animals. Treatment with anti-TNF-alpha mAb also resulted in significantly lower concentrations of LBP mRNA in local tissues. Additionally, several organ function parameter levels in plasma significantly decreased in treatment group. These results demonstrated that an increase of plasma TNF-alpha levels caused by burns might be associated with a marked elevation of tissue LBP mRNA expression, which could contribute to the development of multiple organ damage.

Enteral administration of high-fat nutrition before and directly after hemorrhagic shock reduces endotoxemia and bacterial translocation

OBJECTIVE

To determine whether potential enhancement of endotoxin neutralization via high-fat enteral nutrition affects endotoxemia and bacterial translocation after hemorrhage.

SUMMARY BACKGROUND DATA

Endotoxin and bacterial translocation due to gut barrier failure are important initiating events in the pathogenesis of sepsis after hemorrhage. Systemic inhibition of endotoxin activity attenuates bacterial translocation and distant organ damage. Triacylglycerol-rich lipoproteins constitute a physiological means of binding and neutralizing endotoxin effectively. We hypothesized that enhancement of triacylglycerol-rich lipoproteins via high-fat enteral nutrition would reduce endotoxemia and prevent bacterial translocation.

METHODS

A rat model of nonlethal hemorrhagic shock was used. Hemorrhagic shock (HS) rats were divided into 3 groups: rats starved overnight (HS-S); rats fed with a low-fat enteral diet (HS-LF), and rats receiving a high-fat enteral diet (HS-HF).

RESULTS

Circulating triacylglycerol and apolipoprotein B, reflecting the amount of triacylglycerol-rich lipoproteins, were elevated in HS-HF rats compared with both HS-S rats (P

CONCLUSION

This study is the first to show that high-fat enteral nutrition, leading to increased plasma triacylglycerol and apolipoprotein B levels, significantly decreases endotoxemia and bacterial translocation after hemorrhage.

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Key Words Collapse

MESH Headings

• Animals
• Apolipoproteins B/blood
• Bacterial Translocation
• Dietary Fats/administration & dosage
• Endotoxins/blood
• Enteral Nutrition
• Liver/microbiology
• Lymph Nodes/microbiology
• Male
• Mesentery
• Rats
• Rats, Sprague-Dawley
• Shock, Hemorrhagic/blood
• Shock, Hemorrhagic/microbiology
• Spleen/microbiology
• Triglycerides/blood

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Grants Collapse

Affiliation(s)

Misha D P Luyer Department of Surgery, University of Maastricht and University Hospital Maastricht, the Netherlands
Jan A Jacobs
Anita C E Vreugdenhil
M'hamed Hadfoune
Cornelis H C Dejong
Wim A Buurman
Jan Willem M Greve

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Pretreatment With High-Fat Enteral Nutrition Reduces Endotoxin and Tumor Necrosis Factor-?? and Preserves Gut Barrier Function Early After Hemorrhagic Shock

Gram-negative sepsis is a potentially fatal clinical syndrome characterized by a proinflammatory response (tumor necrosis factor-alpha) to bacterial (endo)toxins and gut barrier function loss. Recently, we found that high-fat enteral nutrition protects against late bacterial translocation in a model of hemorrhagic shock in rats. However, the basis for this protection is unknown. We hypothesized that the observed protection is the result of an early inhibition of endotoxin and the subsequent inflammatory response resulting in a preserved gut barrier function. Sprague-Dawley rats were divided into a group that was starved overnight (HS-S), fed with a low-fat enteral diet (HS-LF) or fed wih a high-fat enteral diet (HS-HF), and subsequently subjected to a nonlethal hemorrhagic shock. Ninety minutes after hemorrhage, arterial endotoxin significantly decreased in HS-HF rats (4.0 +/- 0.6 pg/mL) compared with HS-LF rats (10.7 +/- 0.9 pg/mL, P = 0.002) and HS-S rats (15.2 +/- 2.2 pg/mL P = 0.001). Interestingly, arterial tumor necrosis factor-alpha was also decreased in HS-HF rats (17.9 +/- 10.4 pg/mL) compared with HS-LF (83.5 +/- 16.7 pg/mL, P < 0.01) and HS-S rats (180.9 +/- 67.9 pg/mL, P < 0.02). Loss of tight junction structure (ZO-1) observed in ileum and colon of control hemorrhagic shock rats was prevented in HS-HF rats. In parallel, intestinal barrier function was preserved in HS-HF rats, evidenced by a reduced permeability to horseradish peroxidase (P < 0.05), less bacterial invasion, and a 10-fold reduction of bacterial translocation early after hemorrhagic shock. This report describes a new strategy to nutritionally prevent endotoxemia, the subsequent inflammatory response and gut barrier failure following hemorrhagic shock. High-fat enteral nutrition requires further evaluation as an intervention to prevent a potentially fatal systemic inflammatory response in patients at risk for sepsis.

Increased plasma D-lactate is associated with the severity of hemorrhagic/traumatic shock in rats

D-lactate is produced by indigenous bacteria in the gastrointestinal tract. Mammals do not have the enzyme systems to metabolize D-lactate rapidly. The present study was designed to determine the kinetics of circulating D-lactate levels and to examine whether the severity of shock affects circulating D-lactate levels in rats subjected to hemorrhagic/traumatic shock. Anesthetized rats underwent midline laparotomy (duration 30 min) and were bled to 30-35 mmHg mean arterial pressure (MAP). After the onset of decompensation, MAP was either increased to 40-45 mmHg immediately by administration of Ringer's solution (moderate shock) or after 40% of shed blood volume had been re-infused as Ringer's solution (severe shock). MAP was then maintained at 40-45 mmHg for 40 min by further administration of Ringer's solution (inadequate resuscitation). Subsequently, adequate resuscitation was performed for 60 min with shed blood and additional Ringer's solution. Metabolic acidosis was significantly more pronounced in severe than in moderate hemorrhagic/traumatic shock. Plasma D-lactate levels were already significantly increased at the end of severe hemorrhagic/traumatic shock and remained high during inadequate resuscitation. D-lactate levels were significantly higher after severe than after moderate shock. Endotoxin levels did not correlate with shock severity. Damage to the intestinal mucosa was more profound in severe shock than in moderate shock. Our data suggest that hemorrhagic/traumatic shock is associated with mucosal damage and increased plasma D-lactate levels. The severity of shock affects D-lactate concentrations in plasma. Plasma D-lactate may be a useful marker of intestinal injury after hemorrhagic/traumatic shock.

Gastrointestinal disorders of the critically ill. Bacterial translocation in the gut

The human gastrointestinal tract is colonized by a dense population of microorganisms, referred to as the bacterial flora. Although the gut provides a functional barrier between these organisms and the host, bacterial translocation is a common event in the healthy person. However, in critically ill patients, with various underlying diseases, this bacterial translocation may lead to infections and consequently to a further reduction in general health status. The mechanism of bacterial translocation is widely, and somehow controversially investigated in vitro and in animal models. In human studies, several diseases have been associated with bacterial translocation. However, methodological shortcomings, insufficient populations and conflicting results leave many open questions. This is also reflected in the various published therapeutic strategies. To overcome this problem more investigations in humans are needed, especially in techniques for detecting bacterial translocation.

Attenuated metabolic response to surgery in tumor-bearing rats

BACKGROUND

During cancer, proteins are chronically wasted, including proteins of the gut. Surgical stress acutely increases protein breakdown of the gut. Surgery in cancer patients may thus have a double effect on the gut and lead to exhaustion and functional loss of the gut.

METHODS

Female Lewis rats (+/-200 g) were studied bearing a subcutaneous tumor or after sham implantation. Hysterectomy was performed in half of the rats as a standardized operative procedure. Postoperative protein kinetics of the gut were determined using a primed constant infusion of L-[2,6-(3)H]-phenylalanine. Gut function was assessed by testing its permeability for sugar probes lactulose and L-rhamnose. Villus height and crypt depth were measured and polyamine concentrations were measured as markers for mucosal proliferation and differentiation.

RESULTS

In control rats, gut protein breakdown increased from 6 +/- 3 to 32 +/- 8 nmol phenylalanine x 100 g body wt x min after hysterectomy. This was accompanied by increased amino acid membrane transport rates and metabolic shunting. In tumor-bearing rats, increased protein breakdown in response to surgery was attenuated (8 +/- 4 vs 17 +/- 4 nmol x 100 g body wt x min). Surgery increased the lactulose/L-rhamnose recovery ratio, indicating increased gut permeability. In the presence of a tumor gut permeability also increased and it increased further after surgery. No changes in villus height or polyamine levels could explain the increased permeability of the gut.

CONCLUSION

The study shows that a mild surgical trauma increases protein breakdown of the gut and simultaneously increases gut permeability. In the presence of a tumor the metabolic response to surgery is attenuated. Gut barrier loss was highest in the combined presence of cancer and the surgical insult.

Nitric oxide synthase inhibitors affect nitric oxide synthesis in normoxic but not in ischemic organs during intestinal ischemia and early reperfusion

Inhibition of endogenous nitric oxide (NO) synthesis during early intestinal ischemia/reperfusion (I/R(i)) enhances remote organ damage related to I/R(i). However, the effects of NO synthase (NOS) inhibitors on NO formation in various organs have not yet been specified. We therefore investigated the effects of N-G-monomethyl-L-arginine (L-NMMA), a nonspecific NOS inhibitor, and L-arginine, the NOS substrate, on NO formed in ischemic intestine versus normoxic remote organs (lung and liver). We used electron paramagnetic resonance spectroscopy and a specific NO trap to assay NO in blood, intestine, lung, and liver of rats subjected to local I/R(i), with and without L-NMMA and L-arginine supplementation. We found that I/R(i) increased NO levels in the intestine and blood, but not in the remote organs lung and liver. Administration of L-NMMA before I/R(i) decreased I/R(i)-independent basal NO levels in normoxic lung and liver without influencing I/R(i)-induced increase in NO levels in intestinal tissue or in blood. L-arginine supplementation increased circulating levels of NO, with sensitivity to L-NMMA, without affecting NO levels in normoxic or ischemic tissue. Our data suggest that NOS activity controls the NO generated in normally perfused remote organs during early I/R(i). Hence NOS inhibitors, when administered during I/R(i), decrease physiological NO levels in normoxic remote organs without affecting increased NO levels originating from ischemic intestine. This may explain the harmful effect of nonspecific NOS inhibitors during early I/R(i). In addition, the generation of NO in remote organs is not limited by tissue L-arginine concentrations and, therefore, not influenced by exogenous L-arginine. The protective effect of L-arginine supplementation during I/R(i) is probably related to increasing intravascular NO formation.

Effect of hemorrhagic shock on gut barrier function and expression of stress-related genes in normal and gnotobiotic mice

We sought to determine whether gut-derived microbial factors influence the hepatic or intestinal inflammatory response to hemorrhagic shock and resuscitation (HS/R). Conventional and gnotobiotic mice contaminated with a defined microbiota without gram-negative bacteria were subjected to either a sham procedure or HS/R. Tissue samples were obtained 4 h later for assessing ileal mucosal permeability to FITC dextran and hepatic and ileal mucosal steady-state IL-6, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, and TNF mRNA levels. Whereas HS/R significantly increased ileal mucosal permeability in conventional mice, this effect was not apparent in gnotobiotic animals. HS/R markedly increased hepatic mRNA levels for several proinflammatory genes in both conventional and gnotobiotic mice. HS/R increased ileal mucosal IL-6 and COX-2 mRNA expression in conventional but not gnotobiotic mice. If gnotobiotic mice were contaminated with Escherichia coli C25, HS/R increased ileal mucosal permeability and upregulated expression of IL-6 and COX-2. These data support the view that the hepatic inflammatory response to HS/R is largely independent of the presence of potentially pathogenic gram-negative bacteria colonizing the gut, whereas the local mucosal response to HS/R is profoundly influenced by the microbial ecology within the lumen during and shortly after the period of hemorrhage.

The significance of changes in high mobility group-1 protein mRNA expression in rats after thermal injury

There has been a widespread impression that tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mediate the toxicity of high doses of lipopolysaccharide (LPS, endotoxin) and are key factors in septic shock. However, the clinical efficacy of treatment with antagonists of TNF-alpha and IL-1beta is still controversial, suggesting that mediators other than TNF-alpha and IL-1beta might contribute causally to endotoxin-induced death. Recent studies implicated high mobility group-1 (HMG-1) protein as a late mediator of endotoxin lethality in mice. However, the role of HMG-1 in mediating multiple organ damage-associating trauma has not been studied. This study was designed to investigate changes in HMG-1 gene expression in vital organs, and its potential role in mediating multiple organ damage following major burns. Wistar rats were subjected to a 35 percent full-thickness thermal injury, and randomly divided into three groups as follows: normal controls (n = 7), thermal injury (n = 24), and recombinant bactericidal/permeability-increasing protein (rBPI21) treatment (n = 12). Tissue samples from liver and lungs were collected to measure tissue endotoxin levels and HMG-1 mRNA expression. In addition, blood samples were obtained for measurement of organ function parameters. Our data demonstrated a significant increase in HMG-1 gene expression in tissues at 24 h postburn, which remained markedly elevated up to 72 h after thermal injury (P< 0.05-0.01). Treatment with rBPI21 could significantly decrease tissue HMG-1 mRNA expression in the liver and lung (P < 0.01). In addition, there were high positive correlations between hepatic HMG-1 mRNA and serum aminoleucine transferase (ALT) and aspartate aminotransferase (AST) levels, and also between pulmonary HMG-1 mRNA and myeloperoxidase activities (P < 0.05-0.01). Taken together, these findings indicate that thermal injury per se can markedly enhance HMG-1 gene expression in various organs. Up-regulation of HMG-1 expression may be involved in the pathogenesis of endogenous endotoxin-mediated multiple organ damage secondary to major burns.

Effect of recombinant bactericidal/permeability-increasing protein on endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression in rats after thermal injury

OBJECTIVE

To investigate the potential mechanisms underlying the in vivo effect of recombinant bactericidal/permeability-increasing protein (rBPI21) on endogenous bacteria or endotoxin translocation and lipopolysaccharide-binding protein/CD14 expression secondary to thermal injury.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

College hospital animal research laboratory.

SUBJECTS

Thirty-six male Wistar rats weighing 250-300 g.

INTERVENTIONS

The rats were anesthetized, and a 35% total body surface area full-thickness burn was created. Animals were randomized to receive treatment with either rBPI21 or the control protein (albumin). rBPI21 (2 mg/kg body wt, BPI group) or a protein control preparation (burn group) in the same dose was administered in an intravenous bolus at 30 mins and 4 hrs after thermal injury. All animals were killed at 12 and 24 hrs postburn (six to ten rats for each interval). In addition, eight rats were taken as normal controls.

MEASUREMENT AND MAIN RESULTS

Our data showed that treatment with rBPI21 was effective in preventing endotoxin translocation secondary to severe burns. Meanwhile, tissue lipopolysaccharide-binding protein, CD14, and tumor necrosis factor-alpha mRNA expression in various organs were inhibited markedly by rBPI21 secondary to acute insults (p <.05-.01). Furthermore, significant reduction in serum aminoleucine transferase concentrations and elevation in intestinal diamine oxidase activities in the rBPI21-treated group were found compared with controls (p <.05-.01).

CONCLUSIONS

These findings indicate that endotoxin accumulated in local sites after thermal injury can markedly up-regulate lipopolysaccharide-binding protein/CD14 and tumor necrosis factor-alpha mRNA expression in various organs. Meanwhile, up-regulation of lipopolysaccharide-binding protein/CD14 expression would be the major molecular mechanism of increasing sensitivity to endogenous endotoxin response after burns. Early treatment with rBPI21may be effective in attenuating multiple organ damage resulting from gut-origin endotoxin translocation. This might be associated with the down-regulation effects of tissue lipopolysaccharide-binding protein and CD14 gene expression by the use of rBPI21.

Role of nitric oxide in hemorrhagic shock-induced bacterial translocation

BACKGROUND

Hemorrhagic shock-induced bacterial translocation is an etiologic factor in the pathogenesis of multiple system organ damage. Excessive production of nitric oxide (NO) during hemorrhagic shock may lead to cellular injury and gut barrier failure that promotes bacterial translocation. We investigated the effect of aminoguanidine (AG) and N(G)-nitro-l-arginine methyl ester (l-NAME), both inhibitors of NO synthase, on hemorrhagic shock- induced bacterial translocation in the rat.

MATERIALS AND METHODS

Anesthetized male Sprague-Dawley rats were subjected to a hemorrhagic shock protocol for 30 min followed by intravenous injection (1 mL/kg body wt) with normal saline, AG (100 mg/kg), or l-NAME (10 mg/kg). Tissues/organs were examined histologically for damage and bacterial translocation. Plasma nitrate/nitrite was measured using a procedure based on the Griess reaction, and nitric oxide synthase (NOS) expression was determined immunohistochemically.

RESULTS

The shocked animals treated with saline died within 90 min, and deaths were associated with 100% bacterial translocation, increased tissue/organ damage, and elevated nitrate/nitrite production. In contrast, both AG and l-NAME increased the survival time of shocked rats to >72 h, abrogated bacterial translocation, reduced tissue/organ damage, and prevented excessive nitrate/nitrite production and upregulation of expression of endothelial NOS and inducible NOS.

CONCLUSIONS

Prevention of bacterial translocation by pharmacologic agents such as aminoguanidine and l-NAME could be an important therapeutic approach to lessen mortality rates following hemorrhagic shock.

Recombinant bactericidal/permeability-increasing protein (rBPI21) as adjunctive treatment for children with severe meningococcal sepsis: a randomised trial. rBPI21 Meningococcal Sepsis Study Group

BACKGROUND

Endotoxin is a primary trigger of the inflammatory processes that lead to shock, multiorgan failure, and purpura fulminans in meningococcal sepsis. Bactericidal/permeability-increasing protein (BPI) is a natural protein, stored within the neutrophil granules, that binds to and neutralises the effects of endotoxin in vitro, in laboratory animals, and in humans. To establish whether a recombinant 21-kDa modified fragment of human BPI (rBPI21), containing the active antimicrobial and endotoxin-neutralising moiety, would decrease death and long-term disability from meningococcal sepsis, we did a randomised, double-blind, placebo-controlled trial of rBPI21 in children with severe meningococcal sepsis.

METHODS

We enrolled children (2 weeks to 18 years of age) presenting to 22 centres in the UK and the USA with a clinical picture suggestive of meningococcal sepsis, and with evidence of severe disease. Children were randomly assigned rBPI21 (2 mg/kg over 30 min followed by 2 mg/kg over 24 h) or placebo (0.2 mg/mL human albumin solution) in addition to conventional medical therapy. Primary outcome variables were mortality, amputations, and change in paediatric overall performance category (POPC) from before illness to day 60. Analysis was by intention to treat.

FINDINGS

Of 1287 patients screened, 892 were excluded, including 57 patients who died or who met criteria for imminent death before receiving the study drug. 190 patients received rBPI21, and 203 placebo. 34 (8.7%) of 393 patients died during the study: 14 (7.4%) in the rBPI21 group and 20 (9.9%) in the placebo group (odds ratio 1.31 [95% CI 0.62-2.74], p=0.48). Compared with patients randomised to placebo, fewer patients treated with rBPI21 had multiple severe amputations (six of 190 [3.2%] vs 15 of 203 [7.4%], odds ratio 2.47 [0.94-6.51], p=0.067), and more had a functional outcome similar to that before illness (as measured by the POPC scale) at day 60 (136 of 176 [77.3%] vs 126 of 190 [66.3%], p=0.019).

INTERPRETATION

Because most deaths occurred in the interval between identification of patients and study drug administration, the mortality rate in the placebo group was substantially lower than predicted. The trial was therefore underpowered to detect significant differences in mortality. However, patients receiving rBPI21 had a trend towards improved outcome in all primary outcome variables. Given the excellent severity match between placebo and rBPI21 groups at study entry, the results overall indicate that rBPI21 is beneficial in decreasing complications of meningococcal disease.

Hemorrhage and resuscitation induce delayed inflammation and pulmonary dysfunction in mice

BACKGROUND

It is well known that hemorrhagic shock induces inflammatory changes. Our objective was to study the histologic and biochemical changes in the lung and evaluate alterations in respiratory function after hemorrhage and resuscitation (H/R) in mice.

METHODS

After 30 min of hemorrhagic shock, mice were resuscitated with shed blood to restore mean arterial blood pressure to baseline. A sham group was anesthetized and instrumented for 30 min, but did not undergo hemorrhage. Myeloperoxidase (MPO) levels were measured and histologic analysis was performed on lung tissue. Pulmonary function was evaluated using whole-body plethysmography (WBP) 1, 3, and 5 days postprocedure. Alveolar function was evaluated by measuring carbon monoxide uptake via gas chromatography 5 days after H/R.

RESULTS

Five days after H/R, mice exposed to shock had significantly higher lung MPO levels and showed greater histologic evidence of lung injury. Airway resistance (Penh) in the sham mice was 0.91 +/- 0.06 versus 1.21 +/- 0.09 in the hemorrhage group (P < 0.01). Alveolar function was significantly decreased in the H/R group (70.8 +/- 3.6%) compared with shams (81.6 +/- 1.8%) (P < 0.05).

CONCLUSIONS

Hemorrhage and resuscitation cause delayed biochemical, histologic, and physiologic changes in the lung. These were marked by increased lung MPO, increased neutrophils, and decreased alveolar function. The alterations of pulmonary function and structure were most severe 5 days after H/R.

Gut gavage with antiendotoxin antibodies reduces the liberation of tumor necrosis factor-alpha after hemorrhage/resuscitation

OBJECTIVE

To evaluate the effect of gut gavage both alone and with enteral administration of monoclonal antibodies to endotoxin on the liberation of tumor necrosis factor (TNF)-alpha and subsequent hemodynamics after hemorrhage/resuscitation.

DESIGN

Dose response intervention, sham-controlled animal study.

SETTING

Research laboratory at a university medical center.

ANIMALS

Instrumented rats (250-325 g body weight) underwent standardized hemorrhage/resuscitation.

INTERVENTIONS

Animal groups received 4 hrs before hemorrhage/resuscitation: gastric gavage with Colyte alone (group 1), combined with E5 antiendotoxin at either 0.2 mg/100 g (group 2) or 2 mg/100 g body weight (group 3), or sham controls (group 4). There were six animals studied in each of the four groups.

MEASUREMENTS AND MAIN RESULTS

For animals receiving gut gavage and high-dose E5 antiendotoxin, plasma concentrations of TNF-alpha (pg/mL) at 120 mins after hemorrhage/resuscitation were significantly lower compared with sham controls (16+/-4 group 3; 65+/-36 group 4; mean +/- SD, p < .05). At 300 mins, this same treatment group had a significantly higher mean blood pressure (mm Hg) (110+/-6 group 3; 86+/-7 group 4: p < .05). Also at 300 mins after hemorrhage/resuscitation, plasma lactate concentrations (mmol/L) were significantly lower for all gut gavage treatment groups compared with sham control animals (1.9+/-0.2 group 1; 2.0+/-0.2 group 2; 1.8+/-0.2 group 3; 4.8+/-2.8 group 4, p < .05).

CONCLUSIONS

Prior treatment with gut gavage and enterally administered antiendotoxin antibodies reduces TNF-alpha liberation after hemorrhage/resuscitation and confers a subsequent improvement in hemodynamics and decreased plasma lactate concentrations. Such therapy may be efficacious in patients undergoing elective procedures where major hemorrhage is likely or in severely injured patients with continued or recurrent hemorrhage.

Endotoxin-induced aggravation of preservation-reperfusion injury of rat liver and its modulation

BACKGROUND/AIMS

In clinical transplantation, exposure of donors to gut-derived endotoxin occurs frequently and may adversely affect liver transplantation therapy. The aim of this study was to investigate: 1) whether brief exposure of rats to endotoxin before liver procurement aggravates the early phase of reperfusion injury of hepatic explants; and if so 2) whether Kupffer cell activation is a contributing factor to liver injury; and 3) whether heparin and pentoxifylline could minimize this effect.

METHODS

Male Wistar rats were injected with 0.2-4.0 mg/kg of Escherichia coli lipopolysaccharide 2 h prior to liver harvest. After preservation in University of Wisconsin cold-storage solution, the livers were reperfused using a blood-free perfusion model. To inactivate Kupffer cells, some rats were pretreated with gadolinium chloride or liposome-encapsulated dichloromethylene-diphosphonate before lipopolysaccharide administration. The other rats received lipopolysaccharide with heparin or pentoxifylline.

RESULTS

In a dose-independent fashion, lipopolysaccharide impaired portal flow during graft reperfusion. In a dose-dependent way, lipopolysaccharide increased lactate dehydrogenase release into the perfusate and decreased bile flow and bromosulfophthalein excretion. Gadolinium chloride, liposomal dichloromethylene-diphosphonate, heparin, and pentoxifylline reduced lactate dehydrogenase release by 34%, 43%, 59%, and 64%, respectively, and improved functional parameters of the liver. A 52-fold increased neutrophil infiltration in the liver sinusoids after lipopolysaccharide exposure was not affected significantly by the drugs studied; however, heparin reduced markedly neutrophil activation.

CONCLUSIONS

The results of this investigation provide direct evidence that aggravation of preservation-reperfusion injury of rat liver by endotoxin is mediated by Kupffer cell-dependent mechanism(s) and it can be minimized by heparin and pentoxifylline.

Changes in endotoxin-binding proteins during major elective surgery: important role for soluble CD14 in regulation of biological activity of systemic endotoxin

Assessment of circulating endotoxin during the perioperative period, which is only demonstrated by the Limulus amebocyte lysate (LAL) test, may be modulated by several endotoxin-binding proteins. Endotoxin-neutralizing capacity (ENC) and the plasma levels of soluble CD14 (sCD14), lipopolysaccharide-binding protein, and bactericidal/permeability-increasing protein (BPI) were determined in 40 patients 6 h prior to skin incision for major abdominal surgery. The bioactivity of plasma endotoxin was tested by the polymyxin B-inhibited stimulatory activity of the plasma samples on healthy monocytes as measured by the release of tumor necrosis factor alpha. Plasma endotoxin levels in almost all patients increased from 0.05 +/- 0.01 to 0.23 +/- 0.03 experimental units (EU) per ml (P < 0.001); more specifically, 17 of 40 samples showed endotoxin levels of greater than 0.2 EU per ml and corresponding reductions in ENC. Soluble CD14 plasma levels were decreased from 5. 6 +/- 0.3 to 4.6 +/- 0.3 microg per ml (P < 0.05). ENC was strongly correlated with the sCD14 plasma concentration throughout the period of observation. The addition of sCD14-neutralizing monoclonal anti-sCD14 antibodies reduced ENC both pre- and postoperatively. No correlation could be established between ENC and the plasma levels of BPI, high-density lipoproteins, or low-density lipoproteins determined by measuring the concentrations of apoprotein A and apoprotein B. Biologically active endotoxin was found in only 6 of 17 samples with endotoxin levels greater than 0.2 EU per ml in the LAL test. These samples could be characterized by their perioperative loss of at least 35% of their sCD14. No change in sCD14 was detected in the remaining 11 samples. The perioperative loss of ENC is partly caused by the loss of sCD14 resulting from its consumption by endotoxin reaching the bloodstream. This study demonstrated the role of sCD14 on the bioactivity of circulating endotoxin in a human model of endotoxemia after major abdominal surgery.

The gut's role in metabolism, mucosal barrier function, and gut immunology

The gastrointestinal tract functions not only to absorb nutrients, it also plays an important immunologic role during health and critical illness. Under experimental and certain clinical conditions, stimulating the gut attentuates the stress response and avoids mucosal atrophy and increases permeability. Gut stimulation prevents atrophy of the gut-associated lymphoid tissue, the body's major defender of moist mucosal surfaces. A better understanding of gut function and improved nutrient delivery has clinical implications in the treatment of critically ill patients.

Bactericidal/permeability-increasing protein (rBPI21) in patients with hemorrhage due to trauma: results of a multicenter phase II clinical trial. rBPI21 Acute Hemorrhagic Trauma Study Group

BACKGROUND

Infection and organ failure are the most common causes of death or serious complication in trauma patients surviving initial resuscitation and operation. Of the many possible causes of these complications, bacterial translocation and release of harmful cytokines and oxygen free radicals may play an important role in the pathogenesis of the complications associated with traumatic hemorrhage. Recombinant human bactericidal/permeability-increasing protein (rBPI21) has antibacterial and antiendotoxin properties, reduces cytokine levels, and increases survival in animal models of hemorrhagic shock. The primary objective of this study was to evaluate the safety and efficacy of prophylactic rBPI21 infusion in patients with hemorrhage due to trauma.

METHODS

This was a phase II, multicenter, randomized, double-blind, placebo-controlled trial. Patients who required at least 2 U of blood were randomized to receive rBPI21 (4 mg x kg(-1) x d(-1) for 2 consecutive days) or an equivalent volume of placebo by continuous infusion within 12 hours of injury. The primary efficacy end point was mortality or serious complication occurring during the first 15 days of the study. Safety was monitored clinically and by laboratory panels during the study period.

RESULTS

A total of 401 patients were treated (202 in the rBPI21 group and 199 in the placebo group). The composite end point rate of mortality or serious complication through day 15 was 46% in the placebo group and 39% in the rBPI21 group (hazard ratio = 0.79; p = 0.13). Secondary analysis, which adjusted for age, mechanism of injury, Injury Severity Score (1990 version), and units of blood received before study drug infusion showed similar results (hazard ratio = 0.79; p = 0.14). The proportion of patients who developed at least one serious organ dysfunction was 22% in the placebo group and 16% in the rBPI21 group (hazard ratio = 0.71; p = 0.14). The proportion of patients who developed either pneumonia or acute respiratory distress syndrome was 32% in the placebo group and 22% in the rBPI21 group (hazard ratio = 0.66; post hocp = 0.03). The beneficial trends of rBPI21 were observed in both blunt and penetrating trauma and were generally observed across different age groups, Injury Severity Scores, and units of blood transfused. No treatment difference was observed in mortality or resource utilization in this phase II study.

CONCLUSION

rBPI21 was well-tolerated and demonstrated a favorable trend in reducing the composite primary end point of mortality or serious complication through day 15, especially respiratory complications, in patients with hemorrhage due to trauma. A phase III study is currently in progress.

Protective effect of bactericidal/permeability-increasing protein (rBPI21) in baboon sepsis is related to its antibacterial, not antiendotoxin, properties

OBJECTIVE AND SUMMARY BACKGROUND DATA

The recombinant fragment of bactericidal/permeability-increasing protein, rBPI21, has potent bactericidal activity against gram-negative bacteria as well as antiendotoxin (lipopolysaccharide [LPS]) action. On the basis of these activities, the authors sought to discover whether rBPI21 would be protective in baboons with live Escherichia coli-induced sepsis and whether the potential protective effects of rBPI21 (together with antibiotics) would be more closely related to its antibacterial or LPS-neutralizing effects.

METHODS

In a prospective, randomized, placebo-controlled subchronic laboratory study, the efficacy of rBPI21 or placebo was studied over 72 hours in chronically instrumented male baboons infused with live E. coli under antibiotic therapy.

RESULTS

Intravenous rBPI21 attenuated sepsis-related organ failure and increased survival significantly. Bacteremia was significantly reduced in the rBPI21 group at 2 hours after the start of the E. coli infusion, whereas circulating LPS was less affected. The in vivo formation of tumor necrosis factor was significantly suppressed by the rBPI21 treatment regimen. Microcirculation and organ function were improved.

CONCLUSIONS

In baboon live E. coli sepsis, the salutary effect of rBPI21 results from a more prevalent antibacterial than antiendotoxin activity.

Prostaglandin-induced recovery of barrier function in porcine ileum is triggered by chloride secretion

We have previously shown that PGI2 and PGE2 have a synergistic role in restoring electrical transepithelial resistance (R) in ischemia-injured porcine ileum via the second messengers Ca2+ and cAMP. Because Ca2+ and cAMP stimulate Cl- secretion, we assessed the role of PG-induced Cl- secretion in recovery of R. Mucosa from porcine ileum subjected to ischemia for 45 min was mounted in Ussing chambers and bathed in indomethacin and Ringer solution. Addition of PGs stimulated a twofold increase in R, which was preceded by elevations in short-circuit current (increase of 25 microA/cm2). The PG-induced effect on R was partially inhibited with bumetanide, an inhibitor of Cl- secretion. The remaining elevations in R were similar in magnitude to those induced in ischemic tissues by amiloride, an inhibitor of Na+ absorption. Treatment with 10(-4) M 8-bromo-cGMP or 300 mosM mucosal urea resulted in elevations in R similar to those attained with PG treatment. PGs signal recovery of R via induction of Cl- secretion and inhibition of Na+ absorption, possibly by establishing a transmucosal osmotic gradient.

Thoracic duct in patients with multiple organ failure: no major route of bacterial translocation

OBJECTIVE

To determine whether translocation of bacteria or endotoxin occurred into the thoracic duct in patients with multiple organ failure (MOF).

SUMMARY BACKGROUND DATA

Translocation of bacteria or endotoxin has been proposed as a causative factor for MOF in patients without an infectious focus, although it has rarely been demonstrated in patients at risk for MOF. Most studies have investigated the hematogenic route of translocation, but it has been argued that lymphatic translocation of bacteria or endotoxin by the thoracic duct is the major route of translocation.

METHODS

The thoracic duct was drained for 5 days in patients with MOF caused either by generalized fecal peritonitis (n = 4) or by an event without clinical and microbiologic evidence of infection (n = 4). Patients without MOF who were undergoing a transthoracic esophageal resection served as controls. In lymph and blood, concentrations of endotoxin, proinflammatory cytokines, and antiinflammatory cytokines were measured.

RESULTS

Endotoxin concentrations in lymph and blood of patients with MOF ranged from 39 to 63 units per liter and were not significantly different from concentrations in patients without MOF. The quantity of endotoxin transported by the thoracic duct in the study group was small. In patients with MOF, low levels of proinflammatory cytokines and high levels of antagonists of these cytokines were found.

CONCLUSION

This study provides evidence that translocation (especially of endotoxin) occurs into the thoracic duct. However, these data do not support the concept that the thoracic duct is a major route of bacterial translocation in patients with MOF.

Tumor necrosis factor-alpha hyporesponsiveness of rat intestinal mononuclear cells and whole portal venous blood after hemorrhagic shock

OBJECTIVE

To determine the effect of hemorrhagic shock on spontaneous and endotoxin-induced cytokine release from intestinal mononuclear cells compared with whole portal venous blood and splenic macrophages.

DESIGN

Random assignment to either unmanipulated control group, sham operation group, or hemorrhagic shock group.

SETTING

University animal laboratory.

SUBJECTS

Male Wistar rats, weighing between 300 and 350 g.

INTERVENTIONS

Rats were bled to 30 mm Hg for 30 mins by withdrawal/reinfusion of shed blood and Ringer's lactate equivalent to the shed blood volume.

MEASUREMENTS

Rats were killed immediately, 4 hrs, or 24 hrs after reperfusion. Portal venous blood, splenic macrophages, and small bowel mononuclear cells were obtained and spontaneous (unstimulated) and endotoxin-induced supernatant tumor necrosis factor (TNF)-alpha (WEHI 164 subclone 13) and interleukin (IL)-6 (B 13-29 clone 9) release was measured by bioassay.

MAIN RESULTS

Increased endotoxin-induced TNF release from gut mononuclear cells and portal venous blood was suppressed 4 and 24 hrs after reperfusion compared with sham operated animals (p < .05). TNF release from splenic macrophages could be significantly increased (p < .05) by addition of endotoxin in all groups with no difference between control, sham, and shock animals. In shock animals, endotoxin-stimulated IL-6 release was significantly greater (p < .05) than control and sham operated rats 4 hrs after reperfusion in portal blood and from splenic macrophages. In contrast to splenic macrophages, gut mononuclear cells and portal venous blood demonstrated high spontaneous IL-6 concentrations without further stimulation by endotoxin.

CONCLUSIONS

Hemorrhagic shock induced a hyporesponsiveness from gut mononuclear cells and whole portal venous blood 4 and 24 hrs after reperfusion. Spontaneous and endotoxin-induced stimulation of IL-6 indicates a different modulation of cytokines in gut, portal vein and spleen. The differences of gut mononuclear cells and portal blood compared with the splenic macrophages indicate a compartmentalized cytokine response.

Microbiology of bacterial translocation in humans

BACKGROUND

Gut translocation of bacteria has been shown in both animal and human studies. Evidence from animal studies that links bacteria translocation to the development of postoperative sepsis and multiple organ failure has yet to be confirmed in humans.

AIMS

To examine the spectrum of bacteria involved in translocation in surgical patients undergoing laparotomy and to determine the relation between nodal migration of bacteria and the development of postoperative septic complications.

METHODS

Mesenteric lymph nodes (MLN), serosal scrapings, and peripheral blood from 448 surgical patients undergoing laparotomy were analysed using standard microbiological techniques.

RESULTS

Bacterial translocation was identified in 69 patients (15.4%). The most common organism identified was Escherichia coli (54%). Both enteric bacteria, typical of indigenous intestinal flora, and non-enteric bacteria were isolated. Postoperative septic complications developed in 104 patients (23%). Enteric organisms were responsible in 74% of patients. Forty one per cent of patients who had evidence of bacterial translocation developed sepsis compared with 14% in whom no organisms were cultured (p < 0.001). Septic morbidity was more frequent when a greater diversity of bacteria resided within the MLN, but this was not statistically significant.

CONCLUSION

Bacterial translocation is associated with a significant increase in the development of postoperative sepsis in surgical patients. The organisms responsible for septic morbidity are similar in spectrum to those observed in the mesenteric lymph nodes. These data strongly support the gut origin hypothesis of sepsis in humans.

Plasma D (-)-lactate as a new marker for diagnosis of acute intestinal injury following ischemia-reperfusion

AIM: To observe the kinetics of D (-)-lactate alteration in both portal and systemic circulation systems, and its relationship with intestinal injury in rats subjected to acute intestinal ischemia-reperfusion.

METHODS: Anesthetized rats underwent a 75-min superior mesenteric artery occlusion followed by a 6-h reperfusion. Plasma D (-)-lactate levels were measured by an enzymatic spectrophotometric assay.

RESULTS: Intestinal ischemia for 75 min resulted in a significant elevation of D (-)-lactate levels in the portal vein, as compared with the baseline values (P < 0.05). Plasma D (-)-lactate levels had a tendency to further increase after reperfusion, up to 6 h. Similar alterations in D (-)-lactate were also found in systemic circulation, and there were no significant differences between the portal and systemic circulations at any time point. Moreover, the macropathological evaluation scores were significantly correlated to the portal D (-)-lactate levels in animals at various time points (r = 0.415, P < 0.01). In addition, there was a remarkable rise of endotoxin concentration within the portal vein at the end of the 75-min ischemic period (P < 0.05), reaching a peak at 2 h post-reperfusion.

CONCLUSION: Acute intestinal ischemia is associated with failure of the mucosal barrier resulting in increased plasma D (-)-lactate levels in both portal and systemic blood. The subsequent reperfusion might further increase D (-)-lactate levels, which are correlated to the macropathological alterations. Plasma D (-)-lactate may be a useful marker of intestinal injury following both ischemia and reperfusion insults.