Endotoxemia in patients with alcoholic and non-alcoholic cirrhosis and in subjects with no evidence of chronic liver disease following acute alcohol excess

The presence of endotoxemia in peripheral venous blood was evaluated in 88 patients with alcoholic cirrhosis (AC) and in 42 patients with non-alcoholic cirrhosis (NAC). The two groups did not differ significantly with respect to mean age, liver function tests, and incidence of esophageal varices or ascites. In addition, a group of 24 patients with no evidence of chronic liver disease but with acute exposure to large quantities of alcoholic beverages was investigated. Endotoxin was determined by using the Limulus lysate test. The assays were carried out in the plasma samples by both the dilution technique and the chloroform extraction method. Endotoxemia was found more frequently in patients with AC (67.3%) than in patients with NAC (45.5%, P less than 0.025). The prevalence of endotoxemia was not significantly higher in cirrhotics with ascites or esophageal varices when compared to the subgroup without ascites or esophageal varices. Of the 24 patients with no evidence of chronic liver disease investigated because of acute alcohol excess immediately before admission 11 (45.7%) were found to have endotoxin in the peripheral venous blood. In 7 of these patients a second blood sample was tested 5-8 days later and no endotoxin could be detected. The latter results suggest that heavy alcohol abuse leads to transient endotoxemia even in patients with no signs of chronic liver disease. The findings support the hypothesis that gut-derived endotoxins might play a role in the initiation and aggravation of alcohol-induced liver disease.

The pulmonary vascular sequestration of neutrophils in endotoxemia is initiated by an effect of endotoxin on the neutrophil in the rabbit

Endotoxemia causes neutrophil sequestration in the pulmonary vascular bed. Such sequestration may be a critical initiating event in the generation of microvascular injury, although the mechanisms that lead to this localization are not understood. To investigate these phenomena, the following study employed intravenous pulses of 111Indium-tropolonate-labeled neutrophils (111In-neutrophils), which circulated in the rabbit with normal kinetics and responded in a manner indistinguishable from unlabeled, circulating neutrophils in response to an intravenous injection of purified endotoxic lipopolysaccharide (LPS) or epinephrine. Pulmonary sequestration of 111In-neutrophils was assessed by quantitative external gamma camera scintigraphy of a lung suprahilar region of interest. Noninvasive assessment of radioactivity by this method accurately reflected total lung radioactivity, which was shown by autoradiography to be confined to the injected 111In-neutrophils. Intravenously administered LPS caused a marked, dose-dependent sequestration of 111In-neutrophils in the pulmonary vasculature, and exhaustive ultrastructural autoradiography showed discretely radiolabeled neutrophils located within pulmonary capillaries. A distinct effect was seen with an intravenous injection of as little as 100 ng per rabbit (i.e., 500 pg/ml blood). A 5-min ex vivo pretreatment of 111In-neutrophils with 10 ng to 10 micrograms/ml LPS in heat-inactivated plasma (which resulted in retention of as little as 500 pg LPS per 10(7) neutrophils) also caused dose-dependent pulmonary sequestration of the pretreated 111In-neutrophils but did not cause generalized neutropenia in recipient rabbits. There was no evidence of complement activation on the surface of pretreated neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Low lipid concentrations in critical illness: implications for preventing and treating endotoxemia

OBJECTIVES

To determine the prevalence and clinical significance of hypolipidemia found in critically ill patients, and whether the addition of a reconstituted lipoprotein preparation could inhibit the generation of tumor necrosis factor-alpha (TNF-alpha) in acute-phase blood taken from these patients.

SETTING

Surgical intensive care unit (ICU) of a large urban university hospital.

DESIGN

Prospective case series.

PATIENTS

A total of 32 patients with a variety of critical illnesses had lipid and lipoprotein concentrations determined. Six patients and six age- and gender-matched control subjects had whole blood in vitro studies of the effect of lipoprotein on lipopolysaccharide mediated TNF-alpha production.

INTERVENTIONS

Blood samples were drawn on admission to the ICU and over a subsequent 8-day period.

MEASUREMENTS AND MAIN RESULTS

Mean serum lipid and lipoprotein values obtained from patients within 24 hrs of transfer to the surgical ICU were extremely low: mean total cholesterol was 117 mg/dL (3.03 mmol/L), low-density lipoprotein cholesterol 71 mg/dL (1.84 mmol/L), and high-density lipoprotein cholesterol 25 mg/dL (0.65 mmol/L). Only the mean triglyceride concentration of 105 mg/dL (1.19 mmol/L), and the mean lipoprotein(a) concentration of 25 mg/dL (0.25 g/L) were within the normal range. During the first 8 days following surgical ICU admission, there were trends toward increasing lipid and lipoprotein concentrations that were significant for triglycerides and apolipoprotein B. Survival did not correlate with the lipid or lipoprotein concentrations, but patients with infections had significantly lower (p = .008) high-density lipoprotein cholesterol concentrations compared with noninfected patients. Lipopolysaccharide-stimulated production of TNF-alpha in patient and control blood samples was completely suppressed by the addition of 2 mg/mL of a reconstituted high-density lipoprotein preparation.

CONCLUSIONS

Patients who are critically ill from a variety of causes have extremely low cholesterol and lipoprotein concentrations. Correction of the hypolipidemia by a reconstituted high-density lipoprotein preparation offers a new strategy for the prevention and treatment of endotoxemia.

High plasma levels of von Willebrand factor as a marker of endothelial perturbation in cirrhosis: relationship to endotoxemia

The aim of this study was to evaluate whether there is endothelial dysfunction in patients with cirrhosis and to detect the mechanism that may account for it. We measured plasma levels of von Willebrand factor (vWF), a marker of endothelial perturbation, and endotoxin, which releases vWF from endothelial cells in vitro, in 32 patients (18 men, 14 women, aged 39-70 years) with cirrhosis classified as mild (class A, n = 10), moderate (class B, n = 16), or severe (class C, n = 6) according to Child-Pugh's classification. vWF antigen (P < .0001) and endotoxemia (P < .0001) progressively increased from A to class C; but the increase of vWF antigen was not strictly related to liver failure, as shown by the lack of correlation between vWF and several indexes of liver protein synthesis. Analysis of the vWF subunit showed no sign of proteolytic fragmentation of the molecule. Multimeric analysis indicated intact vWF multimeric structure. In all patients, there was a strong correlation between vWF antigen and endotoxemia (rho = .92; P = .0001). In 20 selected patients, vWF antigen and endotoxemia were measured before and after 7 days of standard therapy (n = 10) or standard therapy plus nonabsorbable antibiotics. There was a significant decrease of vWF antigen (P < .02) concomitantly with the decrease of endotoxemia (P < .006) in patients taking nonabsorbable antibiotics. Human umbilical vein endothelial cells incubated in vitro with 125 to 500 pg/mL endotoxin released vWF antigen into the medium dose dependently. These results demonstrate that there is endothelial perturbation in cirrhosis and that endotoxemia may play a key role in its occurrence.

Clinical detection of LPS and animal models of endotoxemia

The interest in the study of endotoxemia in the clinical area has increased recently as a result of a) improved and simplified endotoxin determination e.g. chromogenic-kinetic microplate methods (also an improved blood sampling tool is available), b) incidence of sepsis has increased due to improvement in early (e.g. posttraumatic) survival, c) interest in and good evidence for gut translocation as a source of endotoxemia, d) agents have developed, which can antagonize endotoxins. There is evidence that patients with positive endotoxin test in the ICU have a higher incidence of organ failure. To study the pathophysiological consequences of endotoxemia and possible ways of intervention animal models are necessary. The choice of the experimental setting depends on the aim of the study e.g. whether prolonged observation is necessary in survival studies or whether hemodynamic variables have to be measured or whether therapeutic agents only crossreact with primates. Since LPS levels are quite low in clinical studies, an important factor for selection of a relevant animal might be LPS sensitivity, or the use of additional sensitization techniques e.g. galactosamine. Another important aspect in this context is whether LPS is given as bolus or infused up to several days. In this review the dose, time, and route of LPS administration is also discussed. For screening purposes rodents are usually used, or sometimes rabbits due to their higher LPS sensitivity. Another very sensitive animal model is the sheep, which can be chronically instrumented and as a specialty allows lung lymph drainage and thus studies of LPS effects on pulmonary permeability. Pigs are used for hemodynamic studies and often in therapeutical studies if species-specificity of the drug tested is not important, in cases where a large animal is necessary. Finally the non-human primates offer a number of advantages due to human-like physiology, due to the cross-reactivity of human assay systems and accordingly also cross-reactivity of human therapeutic agents. While the chimpanzee also shares the LPS sensitivity of humans, baboons are insensitive like rodents. Thus each model serves to provide some useful purpose and the selection must be made to meet the requirements of the specific questions to be asked, with special emphasis of the chosen endotoxin model on relevance for the human sepsis state.

Can selective digestive decontamination avoid the endotoxemia and cytokine activation promoted by cardiopulmonary bypass?

OBJECTIVE

To evaluate the effect of selective digestive decontamination on endotoxemia and cytokine activation during the ischemic phase of cardiopulmonary bypass surgery.

DESIGN

Prospective, open, randomized, controlled trial.

SETTING

Two multidisciplinary intensive care units in tertiary care hospitals.

PATIENTS

Eighty consecutive patients randomly allocated to two groups: selective digestive decontamination (group 1, n = 40) and controls (group 2, n = 40).

INTERVENTIONS

Preoperative administration of oral antibiotics (polymyxin E, tobramycin, and amphotericin B) vs. untreated controls.

MEASUREMENTS AND MAIN RESULTS

Assessment of decontamination by bacteriologic evaluation of rectal swabs (colony-forming units [cfu]/mL) were made in each group, along with circulating endotoxin, tumor necrosis factor and interleukin-6 (IL-6) determinations before surgery, during ischemic and reperfusion phases of bypass, and at 4 hrs and at 24 hrs after surgery. Group 1 patients showed that rectal bacteria decreased ten-fold after treatment for 24 hrs, thousand-fold after 48 hrs, and registered 0 cfu/mL after digestive decontamination was administered for > 72 hrs. Endotoxin and IL-6 assays showed significantly lower values in this latter group vs. those circulating concentrations of control patients. On the other hand, both endotoxin and IL-6 concentrations correlated positively with the duration of surgical ischemia.

CONCLUSIONS

Selective digestive decontamination reduces the gut content of enterobacteria, with complete elimination after 3 days of treatment. This fact could explain the lower endotoxin and cytokine concentrations found in the blood samples of patients who had been fully decontaminated. Duration of aortic cross-clamping is an important factor in generating endotoxemia and in the activation of cytokines.

Sepsis and pathophysiology of anthrax in a nonhuman primate model

Studies that define natural responses to bacterial sepsis assumed new relevance after the lethal bioterrorist attacks with Bacillus anthracis (anthrax), a spore-forming, toxigenic gram-positive bacillus. Considerable effort has focused on identifying adjunctive therapeutics and vaccines to prevent future deaths, but translation of promising compounds into the clinical setting necessitates an animal model that recapitulates responses observed in humans. Here we describe a nonhuman primate (Papio c. cynocephalus) model of B. anthracis infection using infusion of toxigenic B. anthracis Sterne 34F2 bacteria (5 x 10(5) to 6.5 x 10(9) CFU/kg). Similar to that seen in human patients, we observed changes in vascular permeability, disseminated intravascular coagulation, and systemic inflammation. The lung was a primary target organ with serosanguinous pleural effusions, intra-alveolar edema, and hemorrhagic lesions. This animal model reveals that a fatal outcome is dominated by the host septic response, thereby providing important insights into approaches for treatment and prevention of anthrax in humans.

Endotoxaemia, pulmonary complications, and thrombocytopenia in liver transplantation

Plasma endotoxin was measured in 64 patients undergoing primary liver replacement. Endotoxin concentrations increased during the anhepatic phase of the operations, and remained high for several days. Although the severity of endotoxaemia did not correlate with duration of the anhepatic phase, there was a correlation between endotoxaemia and the need for perioperative platelet transfusions, ventilator dependency postoperatively, and one-month case-fatality.

Host defense against bacterial endotoxemia: mechanism in normal animals

The present study defines the early response of normal rabbits to the intravenous injection of a single, sublethal dose of endotoxin. Within the first few hours following endotoxin there occurs in the circulating plasma of recipients a decrease in ionized calcium, a threefold increase in the heat-stable, organo-phosphate-resistant esterase level, and a striking increase in the endotoxin-detoxifying capacity. These results are fully consistent with the thesis that circulating plasma represents a principal site of detoxification and that plasma esterases of the nonspecific, carboxylic type are of major concern in defense against circulating endotoxins.

Role of tissue hypoxia as the mechanism of lactic acidosis during E. coli endotoxemia

We compared the hemodynamic and metabolic alterations produced in rabbits by similar decreases in cardiac output created by inflating a balloon placed in the right ventricle (n = 6) with those produced by an intravenous bolus of Escherichia coli lipopolysaccharide (LPS; SEP group; n = 6). We measured O2 consumption (VO2), O2 transport (TO2), and O2 extraction ratio (ERO2) for the whole animal and also for the left hindlimb. Both groups experienced similar decreases in cardiac output, systemic TO2, and VO2 and similar increases in ERO2. For the hindlimb, TO2 was similar, but VO2 and ERO2 were lower for the SEP group 30 min after LPS administration (P less than 0.05); however, this difference disappeared during the remainder of the experiment. Arterial lactate concentration was greater (P less than 0.05) for the SEP group. There were no differences in skeletal muscle PO2, measured with a multiwire surface electrode, or in cardiac and skeletal muscle concentrations of high-energy phosphates. We hypothesize that a direct effect of LPS on cellular metabolism may have resulted in greater arterial lactate concentration for the SEP group.

Detection of tumor necrosis factor soluble receptor p55 in blood samples from healthy and endotoxemic humans

The tumor necrosis factor (TNF) soluble receptor derived from the cell surface p55 TNF receptor (TNFsRp55) is a naturally occurring substance generated during infection and inflammation. TNFsRp55 inhibits biologic effects of TNF. An RIA was developed to quantitate TNFsRp55 in human blood. Recovery of TNFsRp55 from blood anticoagulated with EDTA was optimal compared with recovery from serum or heparinized plasma. TNF did not interfere with the assay. With the RIA based on radiolabeled nonglycosylated Escherichia coli-derived recombinant TNFsRp55, a mean concentration of 198 +/- 15 pg/mL was found in 14 volunteers. When glycosylated CHO cell-derived TNFsRp55 was used, the mean level was 1656 +/- 95 pg/mL. Infusion of endotoxin into volunteers induced TNFsRp55, which peaked at 517 +/- 99 pg/mL for the E. coli-based RIA and 7300 +/- 1810 pg/mL for the CHO cell-based RIA. These findings demonstrate that blood collected in EDTA is optimal for measuring circulating TNFsRp55 and that this soluble receptor is present in health but elevated during endotoxemia.

Effects of methylene blue on blood pressure and reactivity to norepinephrine in endotoxemic rats

The effects of methylene blue, an inhibitor of the activation of the soluble guanylyl cyclase by nitric oxide (NO), were studied on blood pressure (BP) and on hyporesponsiveness to norepinephrine (NE) induced by Escherichia coli lipopolysaccharide (LPS) in pentobarbital-anesthetized rats. Methylene blue intravenous (i.v.) injection (3 mg/kg) produced a transient increase in BP which, in LPS-treated rats, was followed by a more sustained increase in BP. Methylene blue restored the reactivity to NE in LPS-treated rats but did not change either BP or reactivity to NE in saline-infused control rats. Cyclic GMP level was significantly increased in small femoral resistance arteries removed from LPS-treated rats as compared with controls (125.2 +/- 19.5 and 83.5 +/- 18.8 fmol/mg DNA, respectively, n = 8). In rats receiving methylene blue, there was no significant difference in cyclic GMP content of the arteries of LPS-treated rats as compared with controls (59.4 +/- 8.1 and 78.5 +/- 6.1 fmol/mg DNA, respectively, n = 8). These results support the involvement of increased stimulation of arterial guanylyl cyclase in hyporeactivity to NE elicited by LPS. They show that in vivo administration of methylene blue is able to restore both vascular cyclic GMP level and pressor responses to NE to control levels in LPS-treated rats.

Translocation. Incidental phenomenon or true pathology?

OBJECTIVE

This study was conducted to determine if reduction of early postburn endotoxemia influences the cytokine cascade, clinical manifestations of sepsis, and mortality rate.

SUMMARY BACKGROUND DATA

Translocational endotoxemia has been demonstrated postburn in animals and humans. Endotoxin is known to induce the cytokine cascade, which leads to the clinical manifestations of sepsis. Whether reduction of postburn endotoxemia could influence the induction of cytokines has not been demonstrated.

METHODS

In a prospective, randomized study, 76 burn patients were given polymyxin intravenously or served as control subjects. Polymyxin B was given intravenously for 1 week postburn in doses designed to neutralize circulating endotoxemia.

RESULTS

In the polymyxin group, there was a statistically significant reduction in the plasma endotoxin concentration. There was, however, no reduction in the sepsis score or the interleukin-6 levels, and no differences in mortality rates were seen between the two groups.

CONCLUSIONS

Early postburn translocational endotoxemia can be treated with anti-endotoxin agents such as polymyxin B. This, however, does not influence the cytokine cascade or the mortality rate. The systemic inflammatory response syndrome is caused by cytokine induction from the injury and is unaffected by a reduction in the plasma endotoxin concentration.

Serum corticosterone, interleukin-1 and tumour necrosis factor in rat experimental endotoxaemia: comparison between Lewis and Wistar strains

1. Circulating corticosterone, interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF alpha) activities in serum of Lewis and Wistar rats were measured following injection of lipopolysaccharide (LPS). IL-1 was measured as 'lymphocyte activation factor' (LAF) activity following precipitation of inhibitory activity with polyethylene glycol. TNF alpha activity was measured as cytotoxic activity. 2. Compared to the Wistar, the Lewis rat had higher circulating LAF and TNF activities following LPS, and release of both cytokines was prolonged in this strain. 3. Corticosterone increases in response to LPS were less in the Lewis than in the Wistar rat following the initial peak at 1 h; basal corticosterone was lower in the Lewis rat. 4. Adrenalectomized Lewis rats had even greater amounts of circulating LAF and TNF activities following LPS than did intact animals; the effect of adrenalectomy was not however mimicked by acute treatment with the steroid receptor antagonist, RU486, suggesting that endogenous corticosteroids did not acutely control cytokine release. 5. Although in vivo administration of anti-murine IL-1 alpha antiserum significantly lowered LAF activity of serum, circulating corticosterone in response to LPS was not affected. Similarly, treatment with anti-murine TNF alpha monoclonal antibody (mAb) abrogated TNF activity without affecting corticosterone, suggesting that other mediators may be responsible for corticosterone release following LPS. 6. This 'overproduction' of inflammatory cytokines together with lower circulating corticosterone may contribute to the susceptibility of the Lewis rat to diseases such as adjuvant arthritis or experimental allergic encephalomyelitis.

The metabolic effects of platelet-activating factor antagonism in endotoxemic man

OBJECTIVE

To determine if the inflammatory phospholipid platelet-activating factor (PAF) participated in the symptomatologic, metabolic, and counterregulatory hormonal responses of human endotoxemia.

DESIGN

In a double-blind, placebo-controlled study, five subjects received 10 mg of the PAF antagonist Ro 24-4736 orally, while five control subjects received a placebo. Eighteen hours later, all subjects were administered 4 ng/kg of endotoxin (lipopolysaccharide) intravenously.

SETTING

The Clinical Research Center of The New York Hospital-Cornell Medical Center.

PARTICIPANTS

Healthy male volunteers.

MAIN OUTCOME MEASURES

Repeated measurements of vital signs, symptoms, cytokine and hormone levels, resting energy expenditure, platelet aggregation, and bleeding times were performed during a 24-hour period.

RESULTS

Subjects who were pretreated with the PAF antagonist experienced fewer symptoms, including rigors at 1 hour (P < .05) and myalgias at 1 through 4 hours (P < .05) after administration of lipopolysaccharide. This was in concert with a diminished peak cortisol level (668 +/- 107 vs 959 +/- 159 nmol/L in controls; P < .05), epinephrine secretion (1057 +/- 165 vs 2029 +/- 431 nmol/L in controls; P < .05), and almost complete inhibition of PAF-induced platelet aggregation ex vivo.

CONCLUSIONS

These findings in the face of unaltered circulating cytokines tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6, as well as the tumor necrosis factor receptor-I s, suggest that PAF may influence some endotoxin-induced, counterregulatory hormonal responses and symptoms through cytokine-independent mechanisms. This study further supports the role of PAF antagonists as an adjunct to cytokine blockade in the treatment of gram-negative sepsis.

Leukocyte CD18 monoclonal antibody worsens endotoxemia and cardiovascular injury in canines with septic shock

We investigated the effects of a murine monoclonal antibody directed against the canine leukocyte CD11/18 adhesion complex (MAb R15.7) in a canine model of septic shock. Awake 2-yr-old purpose-bred beagles were studied 7 days before and 1, 2, 4, and 10 days after intraperitoneal placement of an Escherichia coli-infected fibrin clot. Starting 12 h before clot placement, animals received 0.5-1 mg/kg iv every 12 h (4 doses total) of either MAb R15.7 (MAb group, n = 8) or, as controls, murine serum protein (n = 8). After infected clot placement, all animals received antibiotic (ceftriaxne, 100 mg.kg-1.day-1 for 4 days). Two of eight control animals and four of eight MAb animals died (P = 0.4). During the first 8 h after clot placement, MAb animals, compared with control animals, had greater (P < 0.06) increases in serum endotoxin levels and higher (P < 0.05) neutrophil counts. Day 1 after clot placement, MAb animals, compared with control animals, had decreased (P < 0.05) central venous pressure and arterial pH and increased (P < 0.05) arterial lactate. Day 2 after clot placement, MAb animals, compared with control animals, had decreased (P < 0.05) cardiac index and mean arterial pressure. In summary, MAb R15.7, although associated with increased neutrophil counts, worsened serum endotoxemia, acidosis, and cardiovascular function in this canine model of septic shock. These data suggest that in septic shock, antibody directed against this leukocyte membrane protein complex may be harmful, possibly via impairment of normal leukocyte function.

Early fall of circulating iron and rapid rise of lactoferrin in septicemia and endotoxemia: an early defence mechanism

Total serum iron, plasma lactoferrin and circulating leukocytes were measured in piglets during the early phase of severe gram-negative septicemia and endotoxemia in 3 experimental settings: intravenous (i.v.) infusion of lipopolysaccharide (LPS) (n = 8), i.v. infusion of live Escherichia coli (n = 7) and intraperitoneal (i.p.) infusion of E. coli (n = 6). Iron dropped significantly during the first 30 min of LPS infusion from a median of 32 microM to 13.4 microM. A similar decrease in serum iron was demonstrated in the 2 other groups with minimum values at 120 min after the start of E. coli infusion. Plasma levels of lactoferrin increased significantly 120 min after the start of LPS infusion (median 6 mg/l) when compared to preinfusion values (0.25 mg/l). After i.v. infusion of E. coli a significant rise of plasma lactoferrin was demonstrated already 30 min after bacterial infusion (to 2.1 mg/l) compared to preseptic values (0.8 mg/l). This increase was accompanied with a significant drop of circulating leukocytes (to 7.3 x 10(9)/l) compared to before the infusion (17 x 10(9)/l) in the pigs given E. coli i.v. After i.p. E. coli infusion no significant change of plasma lactoferrin was observed. The rapid fall of total serum iron seen during endotoxemia and E. coli septicemia may in part be explained by the release of lactoferrin from granulocytes and the clearance of iron-bound lactoferrin in the blood or peritoneal cavity.

Administration of bacterial lipopolysaccharide elicits circulating tumor necrosis factor-alpha in neonatal calves

The presence of tumor necrosis factor-alpha (TNF-alpha) during endotoxemia in ruminants has not been reported previously. In this study, we detected the in vivo release of bovine TNF-alpha by using WEHI-164 murine fibrosarcoma cells as targets in an 18-h cytotoxicity assay. Treatment of the WEHI-164 cells with 1 microgram of actinomycin D (dactinomycin) enhanced approximately twofold the susceptibility of the cells to TNF-alpha activity. TNF-alpha activity in sera from neonatal calves injected intravenously with 2.7 micrograms of Escherichia coli lipopolysaccharide (LPS) increased rapidly within the first 2 h postinjection and then declined until it was undetectable by 4 h postinjection. Sera taken before LPS administration had no TNF-alpha activity. LPS (10 micrograms/ml) and fetal, newborn, and pooled adult bovine sera alone and in combination had no direct cytotoxic effects on WEHI-164 cells. TNF-alpha cytotoxic activity is probably not due to the presence of interleukin-1 (IL-1), alpha interferon, or gamma interferon in the sera since recombinant human IL-1, natural bovine IL-1, and recombinant bovine alpha and gamma interferons had no direct cytotoxic effects on WEHI-164 cells. A monoclonal antibody that neutralizes recombinant human TNF-alpha significantly reduced the cytotoxic activity of sera from LPS-injected calves.

Identification of toxemia in patients with Clostridium difficile infection

Toxemia can develop in Clostridium difficile-infected animals, and correlates with severe and fulminant disease outcomes. Circumstantial evidence suggests that toxemia may occur in patients with C. difficile infection (CDI), but positive diagnosis is extremely rare. We analyzed the potential for C. difficile toxemia in patients, determined its characteristics, and assessed challenges. C. difficile toxins in serum from patients were tested using an ultrasensitive cell-based assay and further confirmed by Rac1 glucosylation assay. The factors that hinder a diagnosis of toxemia were assessed, including investigation of toxin stability, the level of toxins-specific neutralizing antibodies in sera and its effect on diagnosis limits. CDI patients develop detectable toxemia in some cases (2.3%). Toxins were relatively stable in stored sera. Neutralizing anti-toxin antibodies were present during infection and positively correlated with the diagnosis limits. Thus, the masking effect of toxin-specific neutralizing antibodies is the major obstacle in diagnosing C. difficile toxemia using cell-based bioassays.

Comparison of peripheral blood leukocyte kinetics after live Escherichia coli, endotoxin, or interleukin-1 alpha administration. Studies using a novel interleukin-1 receptor antagonist

OBJECTIVE

This study was undertaken to evaluate whether hematologic and immunologic effects observed after bacteremia and endotoxemia in the host could be replicated by administration of recombinant human interleukin-1 alpha (IL-1 alpha) in a primate model. Furthermore, to determine whether endogenously produced interleukin-1 (IL-1) contributes to the changes observed during endotoxemia or gram-negative septic shock, a specific IL-1 receptor antagonist (IL-1 ra) was administered.

SUMMARY BACKGROUND DATA

The lipopolysaccharide (LPS) component of the outer membrane of gram-negative bacteria initiates a constellation of metabolic and immunologic host responses. IL-1, a macrophage-derived cytokine, acts as a key mediator in the host response to infection and inflammation.

METHODS

Baboons were randomly assigned to receive either recombinant human IL-1 alpha, LPS, or live Escherichia coli both with or without concomitant administration of IL-1ra. Blood was collected hourly and analyzed using flow cytometric techniques.

RESULTS

Both endotoxemia and live E. coli bacteremia induced an acute granulocytopenia; however, the granulocytopenia gradually resolved in the endotoxemic group, but was sustained in the bacteremic group. An early lymphopenia and monocytopenia was elicited by LPS or E. coli and persisted throughout the experiment. Recombinant human IL-1 alpha induced the following: (1) an early, transient decline in granulocytes followed by a sustained granulocytosis; (2) a lymphopenia; and (3) a transient monocytopenia followed by a gradual return to baseline. Although IL-1ra had no effect on leukocyte kinetics with either live E. coli or LPS, the IL-1ra significantly abrogated the monocytopenia seen with recombinant human IL-1 alpha administration alone.

CONCLUSIONS

These results suggest that administration of recombinant human IL-1 alpha can replicate some of the characteristic patterns of hematologic change associated with bacteremia and endotoxemia. However, an endogenous IL-1 response is not required for these changes to occur. Rather, the data suggest that other inflammatory mediators induced by endotoxemia or gram-negative bacteremia, such as tumor necrosis factor-alpha (TNF alpha), may be involved.

Regulation of equine fibrinolysis in blood and peritoneal fluid based on a study of colic cases and induced endotoxaemia

Much of the pathophysiology associated with equine gastrointestinal diseases is attributed to the effects of endotoxin on haemostasis. Because little is known about the responses of the equine fibrinolytic system to endotoxin, regulation of the system was investigated. Tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type-1 (PAI-1) were identified as the primary plasminogen activator and plasminogen activator inhibitor, respectively, in equine blood. Under experimental conditions, the equine fibrinolytic system responded to endotoxin in a manner similar to that reported in man, with an early, transient increase in t-PA activity followed by an overwhelming and prolonged increase in activity of PAI-1. To investigate the response of the equine fibrinolytic system to clinical endotoxaemia, endotoxin concentrations were measured in plasma and peritoneal fluid, and activities of t-PA and PAI-1 were compared between healthy horses (n = 38) and horses with naturally occurring gastrointestinal diseases (n = 150). It was observed that plasma PAI-1 and peritoneal t-PA were increased concurrently in abnormal horses; and that these increases were associated with the presence of endotoxin. The results of this study suggest that 1) fibrinolysis is regulated in horses in a manner similar to that in man; 2) regulation of fibrinolysis is altered in endotoxaemic horses with gastrointestinal diseases; 3) events occurring in the vascular system may not reflect those in the peritoneal cavity; and 4) t-PA activity is increased in the peritoneal fluid of endotoxaemic horses with gastrointestinal diseases.

Assessment of limulus test for detecting endotoxaemia

The occurrence of endotoxaemia in 46 surgical patients has been investigated using a sensitive preparation of limulus lysate. Altogether 23 patients with local and systemic Gram-negative infections were shown to have endotoxaemia. An overt infection is not a prerequisite for a positive limulus test result, since endotoxin can be absorbed via the peritoneal cavity in patients with "chemical" peritonitis. Over 70% of the tests performed during episodes of Gram-negative infection or peritonitis gave positive results. In 23 patients without clinical evidence of infection or peritonitis only 15% of the limulus test results were positive. The implications of these findings and the use of the test in clinical practice are discussed.

Ursodeoxycholic acid modifies gut-derived endotoxemia in neonatal rats

We developed a model for the translocation of intraluminal endotoxin in the neonatal animal and used it to examine the capacity of a nonhepatotoxic bile acid, ursodeoxycholic acid (UDCA), to modify endotoxin translocation and cytokine response. Three-d-old Sprague-Dawley rats were randomized to receive enterally either no drug, lipopolysaccharide (LPS, 1 mg/animal), or UDCA (400 micrograms/animal) alone, or UDCA followed by LPS 1 h later. One h after LPS administration, the rats were killed and plasma endotoxin and tumor necrosis factor (TNF) were measured. Control animals had low circulating endotoxin (21.2 +/- 7.6 endotoxin units) and TNF (0.06 +/- 0.02 ng/mL). Enteral administration of LPS 1 h before the rats were killed resulted in significant elevation of endotoxin (249.5 +/- 71.3, p = 0.008) and TNF (3.6 +/- 1.3, p = 0.019). UDCA alone did not alter endotoxin levels (8.7 +/- 2.1). UDCA 1 h before LPS prevented the rise in endotoxin (38.9 +/- 11.2 endotoxin units) and TNF (0.2 +/- 0.05) significantly. Chenodeoxycholic acid was studied in a similar group of experiments and prevented neither the translocation of LPS nor the development of increased TNF levels in animals receiving LPS. In conclusion, LPS can cross the intestinal barrier in the normal neonatal rat. UDCA, administered before LPS, can decrease the translocation of LPS and prevent the cytokine response as measured by TNF levels. We speculate that UDCA, administered prophylactically, might reduce morbidity in clinical conditions leading to gut-derived endotoxemia.