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Biomedical subjects

T van der Poll

Publications and source records attributed to T van der Poll.

At least 109 records · Page 6Linked to original sources
PubMed1997

Pretreatment with a 55-kDa tumor necrosis factor receptor-immunoglobulin fusion protein attenuates activation of coagulation, but not of fibrinolysis, during lethal bacteremia in baboons.

Baboons (Papio anubis) receiving a lethal intravenous infusion with live Escherichia coli were pretreated with either a 55-kDa tumor necrosis factor (TNF) receptor-IgG fusion protein (TNFR55:IgG) (n = 4, 4.6 mg/kg) or placebo (n = 4). Neutralization of TNF activity in TNFR55:IgG-treated animals was associated with a complete prevention of mortality and a strong attenuation of coagulation activation as reflected by the plasma concentrations of thrombin-antithrombin III complexes (P < .05). Activation of fibrinolysis was not influenced by TNFR55:IgG (plasma tissue-type plasminogen activator and plasmin-alpha2-antiplasmin complexes), whereas TNFR55:IgG did inhibit the release of plasminogen activator inhibitor type I (P < .05). Furthermore, TNFR55:IgG inhibited neutrophil degranulation (plasma levels of elastase-alpha1-antitrypsin complexes, P < .05) and modestly reduced release of secretory phospholipase A2. These data suggest that endogenous TNF contributes to activation of coagulation, but not to stimulation of fibrinolysis, during severe bacteremia.

Animals↗
PubMed1997

Interleukin-6 gene-deficient mice show impaired defense against pneumococcal pneumonia.

Induction of pneumonia in C57Bl/6 mice by intranasal inoculation with 10(6) cfu of Streptococcus pneumoniae resulted in sustained expression of interleukin (IL)-6 mRNA in lungs and increases in lung and plasma IL-6 concentrations. In IL-6-deficient (IL-6-/-) mice, pneumonia was associated with higher lung levels of the proinflammatory cytokines tumor necrosis factor-alpha, IL-1beta, and interferon-gamma and of the antiinflammatory cytokine IL-10 than in wild type (IL-6+/+) mice (all P < .05). Also, the plasma concentrations of soluble tumor necrosis factor receptors were higher in IL-6-/- mice (P < .05), while the acute-phase protein response was strongly attenuated (P < .01). Lungs harvested from IL-6-/- mice 40 h after inoculation contained more S. pneumoniae colonies (P < .05). IL-6-/- mice died significantly earlier from pneumococcal pneumonia than did IL-6+/+ mice (P < .05). During pneumococcal pneumonia, IL-6 down-regulates the activation of the cytokine network in the lung and contributes to host defense.

Acute-Phase Proteins↗
PubMed1997

Antiinflammatory cytokine responses during clinical sepsis and experimental endotoxemia: sequential measurements of plasma soluble interleukin (IL)-1 receptor type II, IL-10, and IL-13.

Plasma concentrations of soluble interleukin (IL)-1 receptor type II, IL-10, and IL-13 were measured in 42 patients with clinically defined sepsis during a 3-day follow-up and in 7 healthy humans after intravenous injection of endotoxin (2 ng/kg). Levels of soluble IL-1 receptor type II were persistently elevated in patients with sepsis than in healthy controls and higher in nonsurviving patients (n = 22) than in surviving patients (n = 20) at all time points. IL-10 was found in the circulation of 81% of patients with sepsis, while it was not detectable in normal plasma. During follow-up, IL-10 remained invariably high only in nonsurviving patients, while it significantly decreased in survivors. Endotoxin induced IL-10, while soluble IL-1 receptor type II remained unchanged. IL-13 remained undetectable in the vast majority of patients and was not induced by endotoxin. Enhanced IL-13 production does not seem to be part of an inducible host defense mechanism during sepsis.

Adult↗
PubMed1997

Lipopolysaccharide-induced interleukin 8 production by human whole blood is enhanced by epinephrine and inhibited by hydrocortisone.

To determine the effect of epinephrine and hydrocortisone on lipopolysaccharide (LPS)-induced interleukin 8 (IL-8) production, human whole blood was stimulated with LPS in the presence or absence of these stress hormones. Epinephrine caused a dose-dependent increase in LPS-induced IL-8 production, which was mediated exclusively via beta-adrenergic receptors, as reflected by the facts that beta (but not alpha) receptor blockade reversed the epinephrine effect and beta (but not alpha) receptor stimulation reproduced the epinephrine effect. Further, elevating cellular cyclic AMP (cAMP) concentrations, a known effect of beta-adrenergic stimulation, by addition of dibutyryl cAMP also enhanced LPS-induced IL-8 production. Epinephrine-induced upregulation of IL-10 production masked an even more pronounced stimulating effect of this hormone on IL-8 synthesis, as indicated by the finding that the extent of IL-8 upregulation was greater in the presence of anti-IL-10 than in the absence of anti-IL-10. Hydrocortisone dose-dependently inhibited LPS-induced IL-8 production and reversed epinephrine-induced enhancement of IL-8 production. Epinephrine and hydrocortisone have opposite effects on IL-8 production, which may be relevant for the understanding of endogenous and therapeutic stress hormone influences on IL-8 mediated inflammation.

Bucladesine↗
PubMed1997

Passive immunization against tumor necrosis factor-alpha impairs host defense during pneumococcal pneumonia in mice.

Streptococcus pneumoniae is the most frequent cause of community-acquired pneumonia. We sought to determine the role of tumor necrosis factor-alpha (TNF) in the pathogenesis of pneumococcal pneumonia. Induction of pneumonia in C57B1/6 mice by intranasal inoculation with 10(6) colony-forming units (cfu) S. pneumoniae resulted in a sustained increase in TNF activity in lung homogenates reaching a plateau between 12 and 72 h (72 h: 185.49 +/- 54.41 ng/g), while plasma TNF activity remained low or undetectable. Treatment with a neutralizing anti-TNF monoclonal antibody 2 h before inoculation strongly reduced lung TNF activity, but only modestly diminished lung interleukin (IL)-1beta levels, and did not significantly influence lung IL-6, IL-10, and interferon-gamma concentrations. Anti-TNF-treated mice had fourfold more S. pneumoniae cfu isolated from lungs than control mice 40 h after inoculation (p < 0.05), although lung myeloperoxidase activities were similar in both treatment groups. Anti-TNF-treated mice died significantly earlier from pneumococcal pneumonia than control mice (p < 0.05). Endogenously produced TNF is important for host defense during pneumococcal pneumonia.

Animals↗
PubMed1997

Differential effects of reconstituted high-density lipoprotein on coagulation, fibrinolysis and platelet activation during human endotoxemia.

High-density lipoproteins (HDL) can bind and neutralize lipopolysaccharides (LPS) in vitro and in vivo. HDL can also affect fibrinolytic activity and can directly influence platelet function by reducing platelet aggregation. In this study, the effects of reconstituted HDL (rHDL) on LPS-induced coagulation, fibrinolysis and platelet activation in humans were investigated. In a double-blind, randomized, placebo-controlled, cross-over study, eight healthy male volunteers were injected with LPS (4 ng/kg) on two occasions, once in conjunction with rHDL (40 mg/kg, given as a 4 h infusion starting 3.5 h prior to LPS injection), and once in conjunction with placebo. rHDL significantly reduced LPS-induced activation of coagulation (plasma levels of prothrombin fragment F1 + 2) and fibrinolysis (plasma levels of tissue type plasminogen activator antigen, t-PA). No effect was observed on LPS-induced inhibition of the fibrinolytic pathway (PAI-1) or on the transient thrombocytopenia elicited by LPS. Furthermore, rHDL treatment significantly enhanced the inhibition of collagen-stimulated inhibition of platelet aggregation during endotoxemia, but had no such effect on arachidonate-stimulated platelet aggregation. rHDL treatment per se also reduced collagen-induced platelet aggregation. These results indicate that rHDL modifies the procoagulant state associated with endotoxemia.

Adult↗
PubMed1996

Antiinflammatory effects of reconstituted high-density lipoprotein during human endotoxemia.

High-density lipoprotein (HDL) has been found to neutralize LPS activity in vitro and in animals in vivo. We sought to determine the effects of reconstituted HDL (rHDL) on LPS responsiveness in humans in a double-blind, randomized, placebo-controlled, cross-over study. rHDL, given as a 4-h infusion at 40 mg/kg starting 3.5 h before endotoxin challenge (4 ng/kg), reduced flu-like symptoms during endotoxemia, but did not influence the febrile response. rHDL potently reduced the endotoxin-induced release of TNF, IL-6, and IL-8, while only modestly attenuating the secretion of proinflammatory cytokine inhibitors IL-1ra, soluble TNF receptors and IL-10. In addition, rHDL attenuated LPS-induced changes in leukocyte counts and the enhanced expression of CD11b/CD18 on granulocytes. Importantly, rHDL infusion per se, before LPS administration, was associated with a downregulation of CD14, the main LPS receptor, on monocytes. This effect was biologically relevant, since monocytes isolated from rHDL-treated whole blood showed reduced expression of CD14 and diminished TNF production upon stimulation with LPS. These results suggest that rHDL may inhibit LPS effects in humans in vivo not only by binding and neutralizing LPS but also by reducing CD14 expression on monocytes.

Adult↗
PubMed1996

Tumor necrosis factor-alpha induces activation of coagulation and fibrinolysis in baboons through an exclusive effect on the p55 receptor.

Tumor necrosis factor-alpha (TNF-alpha) can bind to two distinct transmembrane receptors, the p55 and p75 TNF receptors. We compared the capability of two mutant TNF proteins with exclusive affinity for the p55 or p75 TNF receptor with that of wild type TNF, to activate the hemostatic mechanism in baboons. Both activation of the coagulation system, monitored by the plasma levels of thrombin-antithrombin III complexes, and activation of the fibrinolytic system (plasma levels of tissue-type plasminogen activator, and plasminogen activator inhibitor type I), were of similar magnitude after intravenous injection of wild type TNF or the TNF mutant with affinity only for the p55 receptor. Likewise, wild type TNF and the TNF p55 specific mutant were equally potent in inducing neutrophil degranulation (plasma levels of elastase-alpha 1-antitrypsin complexes). Wild type TNF tended to be a more potent inducer of secretory phospholipase A2 release than the p55 specific TNF mutant. Administration of the TNF mutant binding only to the p75 receptor did not induce any of these responses. We conclude that TNF-Induced stimulation of coagulation, fibrinolysis, neutrophil degranulation, and release of secretory phospholipase A2 are predominantly mediated by the p55 TNF receptor.

Animals↗
PubMed1996

Release of bactericidal/permeability-increasing protein in experimental endotoxemia and clinical sepsis. Role of tumor necrosis factor.

Bactericidal/permeability-increasing protein (BP]) is contained within the azurophilic granules of neutrophils and is able to neutralize endotoxin and kill Gram-negative bacteria. TNF has been implicated as a mediator of endotoxin-induced neutrophil degranulation. To assess the role of TNF in the elevated BPI levels during sepsis, the following studies were performed. 1) In 31 consecutive patients with sepsis syndrome, plasma BPI levels were markedly elevated compared with those in healthy controls, but showed no correlation with simultaneously measured TNF concentrations. 2) In four healthy men, i.v. injection of recombinant human TNF (50 microg/m2) induced a rapid rise in plasma BPI levels. 3) In eight normal subjects, i.v. administration of Escherichia coli endotoxin (4 ng/kg) elicited subsequent increases in the plasma concentrations of TNF and BPI. 4) Eight healthy chimpanzees were investigated after i.v. injection of endotoxin (4 ng/kg); four animals received endotoxin only, and four animals received an anti-TNF mAb simultaneously. Although anti-TNF completely prevented the endotoxin-induced appearance of TNF activity, the rise in BPI levels remained unaltered. These results suggest that TNF is not critical for the release of BPI from neutrophils during experimental endotoxemia or clinical sepsis.

Adult↗
PubMed1996

Epinephrine inhibits tumor necrosis factor-alpha and potentiates interleukin 10 production during human endotoxemia.

Short-term preexposure of mononuclear cells to epinephrine inhibits LPS-induced production of TNF, whereas preexposure for 24 h results in increased TNF production. To assess the effects of epinephrine infusions of varying duration on in vivo responses to LPS, the following experiments were performed: (a) Blood obtained from eight subjects at 4-24 h after the start of a 24-h infusion of epinephrine (30 ng/kg per min) produced less TNF after ex vivo stimulation with LPS compared with blood drawn before the start of the infusion, and (b) 17 healthy men who were receiving a continuous infusion of epinephrine (30 ng/kg per min) started either 3 h (EPI-3; n = 5) or 24 h (EPI-24; n = 6) were studied after intravenous injection of LPS (2 ng/kg, lot EC-5). EPI-3 inhibited LPS-induced in vivo TNF appearance and also increased IL-10 release (both P < 0.005 versus LPS), whereas EPI-24 only attenuated TNF secretion (P = 0.05). In separate in vitro experiments in whole blood, epinephrine increased LPS-induced IL-10 release by a combined effect on alpha and beta adrenergic receptors. Further, in LPS-stimulated blood, the increase on IL-10 levels caused by epinephrine only marginally contributed to concurrent inhibition of TNF production. Epinephrine, either endogenously produced or administered as a component of sepsis treatment, may have a net antiinflammatory effect on the cytokine network early in the course of systemic infection.

Adult↗
PubMed1996

Monocyte tumor necrosis factor receptor levels as a predictor of risk in human sepsis.

OBJECTIVE: To assess peripheral blood monocyte tumor necrosis factor receptor (TNFR) levels and plasma soluble tumor necrosis factor receptor (sTNFR) concentrations in critically ill patients with sepsis syndrome. DESIGN: Prospective, descriptive cohort study with no interventions. SETTING: Surgical intensive care unit of a tertiary-care hospital associated with a university medical school. PATIENTS: Twenty-one patients with a documented source of infection who met currently accepted criteria for sepsis syndrome/septic shock. MAIN OUTCOME MEASURES: Plasma sTNFR p55 and p75 values were quantified by enzyme-linked immunosorbent assay, and monocyte TNFR levels were assessed by fluorescence flow cytometry after the monocytes were stained with biotinylated human recombinant TNF-alpha and streptavidin-phycoerythrin. RESULTS: Compared with healthy controls, plasma sTNFR p55 and p75 values were significantly higher (P <.01) in both surviving and nonsurviving patients with sepsis; in nonsurviving patients with sepsis, however, only sTNFR p55 values were significantly (P < .05) higher than in surviving patients with sepsis. By contrast, monocytes from the nonsurviving patients with sepsis manifested a significant (P < .01) and sustained (up to 4 days) decrease in cell surface TNFR values compared with either the normal controls or the surviving patients with sepsis. CONCLUSIONS: Assessment of monocyte surface TNFR values may provide a rapid prognostic indicator for patients with sepsis who are at increased risk of death.

Analysis of Variance↗
PubMed1996

Interleukin 10 release during endotoxaemia in chimpanzees: role of platelet-activating factor and interleukin 6.

Interleukin (IL-)10 has been demonstrated to inhibit endotoxin-induced production of a number of pro-inflammatory cytokines. The present study sought to compare the appearances in the circulation of IL-10, IL-6 and IL-8, and to assess the roles of endogenously produced platelet-activating factor (PAF) and IL-6 in IL-10 release during endotoxaemia in chimpanzees. Intravenous injection of endotoxin (lot EC-5, 4 ng/kg, n = 8) induced a transient rise in serum IL-10 concentrations, peaking after 2 h (213 +/- 70 pg/ml; P < 0.05). No correlations existed between peak IL-10 levels, and peak IL-6 and IL-8 levels. Neither infusion of the specific PAF antagonist TCV-309 (n = 4), nor infusion of a neutralizing anti-IL-6 monoclonal antibody (n = 4) influenced endotoxin-induced IL-10 release. IL-10 release elicited by injection of endotoxin is not mediated by PAF or IL6.

Animals↗
PubMed1996

Interleukin-10 impairs host defense in murine pneumococcal pneumonia.

The effects of recombinant interleukin (IL)-10 and the role of endogenous IL-10 were determined in C57B1/6 mice with pneumonia induced by intranasal inoculation with 10(6) cfu of Streptococcus pneumoniae. Pneumonia induced sustained expression of IL-10 mRNA and protein in lungs, but IL-10 remained undetectable in plasma. Intranasal inoculation of S. pneumoniae in combination with IL-10 (1500 U/mouse) resulted in decreased lung concentrations of tumor necrosis factor-alpha (TNF) and interferon (IFN)-gamma, increased bacterial counts in lungs and blood, and early lethality. Conversely, pretreatment (-2 h) of mice with an anti-IL-10 monoclonal antibody (2 mg/mouse) was associated with increased lung levels of TNF and IFN-gamma, reduced bacterial counts in lungs and plasma 40 h after the inoculation, and prolonged survival. These results indicate that during pneumococcal pneumonia, IL-10 attenuates the proinflammatory cytokine response within the lungs, hampers effective clearance of the infection, and shortens survival.

Animals↗
PubMed1996

Changes in endotoxin-induced cytokine production by whole blood after in vivo exposure of normal humans to endotoxin.

Whole blood of 6 healthy subjects, who were intravenously injected with lipopolysaccharide (LPS, 2 ng/kg), was stimulated ex vivo with LPS (10 ng/mL). Three and 6 h after injection of LPS, whole blood produced less tumor necrosis factor-alpha (TNF), interleukin (IL)-1beta, IL-6, and IL-10 (all P < .05). By contrast, the production of IL-1 receptor antagonist was enhanced after LPS injection (P < .05). Plasma obtained 2 h, but not 1 h, after in vivo administration of LPS showed a dose-dependent inhibition of TNF, IL-1beta, and IL-6 production by LPS-stimulated whole blood from 6 other healthy donors not previously exposed to LPS, while the production of IL-10 and IL-1 receptor antagonist were not or were marginally influenced. LPS tolerance represents a purposeful adaptation of the host, rather than a generalized hyporesponsiveness, and is at least partly mediated by soluble factors produced within 2 h after previous exposure to LPS.

Adult↗
PubMed1996

Hypercortisolemia increases plasma interleukin-10 concentrations during human endotoxemia--a clinical research center study.

Hypercortisolemia directly before the administration of endotoxin (LPS) to normal humans completely prevents the release of the proinflammatory cytokine tumor necrosis factor, whereas hypercortisolemia 12 h to 7 days before the injection of LPS is associated with enhanced tumor necrosis factor release. To determine the effect of elevated cortisol levels on the secretion of the antiinflammatory cytokine interleukin-10 (IL-10), 23 healthy men were given iv LPS (lot EC-5; 2 ng/kg) alone or in combination with a continuous iv infusion of hydrocortisone (3 micrograms/kg.min) for 6 h immediately before or 6, 12, or 144 h before LPS injection. LPS induced a monophasic increase in plasma IL-10 concentrations that peaked after 2 h (162 +/- 27 pg/mL; P < 0.0001). In subjects who were infused with hydrocortisone directly before LPS administration, IL-10 concentrations were much higher (1784 +/- 331 pg/mL; P < 0.0001 vs. LPS only), whereas hypercortisolemia 6, 12, or 144 h before LPS injection did not influence LPS-induced IL-10 levels. In human whole blood in vitro, hydrocortisone caused a dose-dependent reduction of LPS-induced IL-10 levels. Further, hydrocortisone reversed the increase in IL-10 concentrations by epinephrine in LPS-stimulated whole blood. Stimulation of IL-10 release may contribute to the antiinflammatory properties of glucocorticoids.

Adult↗
PubMed1996

Fat emulsion infusion potentiates coagulation activation during human endotoxemia.

Intravenous fat emulsions are frequently given to malnourished patients who are prone to suffer from infectious complications. As injection of low dose endotoxin represents a model to study the human response to acute infection, we sought to determine the effect of lipid emulsion infusion on endotoxin-induced activation of the hemostatic mechanism in man. Ten healthy men received a bolus intravenous injection of endotoxin (lot EC-5; 20 U/kg) midway through a 4-h infusion (125 ml/h) of either dextrose 5% (n = 5) or Intralipid 20% (n = 5). Lipid infusion potentiated endotoxin-induced coagulation activation, as indicated by higher plasma levels of the prothrombin fragment F1 + 2 and of thrombin-antithrombin III complexes (both p < 0.05 for the difference between groups). However, lipid infusion did not influence the fibrinolytic response to intravenous endotoxin, as reflected by similar increases in the levels of tissue-type plasminogen activator and plasmin-alpha 2-antiplasmin complexes in both groups. Endotoxin-induced appearance of plasminogen activator inhibitor type I was enhanced by lipid infusion (p < 0.05). These data suggest that fat emulsion infusion may enhance the tendency towards thrombotic complications in patients with infections.

Adult↗
PubMed1996

Interleukin-6 stimulates coagulation, not fibrinolysis, in humans.

The role of IL-6 as a mediator of haemostatic changes during severe inflammation is controversial. To assess the effect of IL-6 on haemostasis we conducted a controlled cross-over study in eight patients with metastatic renal cell cancer. In all subjects coagulation and fibrinolysis were monitored during and after a 4-h infusion of either 150 micrograms recombinant human (rh) IL-6, or during infusion of saline (control study). Mean maximum IL-6 concentrations were 1418.0 +/- 755.8 pg/ml. Compared to the control study, rhIL-6 induced activation of coagulation as reflected by a 190 +/- 55% increase in the plasma levels of thrombin-antithrombin III complexes (p < 0.001) and by a 24 +/- 11% increase in the plasma levels of in the prothrombin activation fragment F1 + 2 (p < 0.001). In contrast, fibrinolysis was not affected. We conclude that in severe inflammation IL-6 may contribute to the activation of coagulation, whereas other factors mediate changes in fibrinolysis.

Blood Coagulation↗