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Biomedical subjects

C E Hack

Publications and source records attributed to C E Hack.

At least 145 records · Page 8Linked to original sources
PubMed1997

Potentiation of C1 inhibitor by glycosaminoglycans: dextran sulfate species are effective inhibitors of in vitro complement activation in plasma.

Activation of the complement system may contribute to the pathogenesis of many diseases. Hence, an effective inhibitor of complement might be useful to reduce tissue damage. Some glycosaminoglycans (GAG), such as heparin, are known to inhibit the interaction of C1q with activators and the assembly of the classical and the alternative pathway C3 convertases. Furthermore, they may potentiate C1 inhibitor-mediated inactivation of C1s. To search for potential complement inhibitors, we systematically investigated the complement inhibitory properties of various synthetic and naturally occurring GAG (dextran sulfates 500,000 and 5,000, heparin, N-acetylheparin, heparan sulfate, dermatan sulfate, and chondroitin sulfates A and C). First, we assessed the effect of GAG on the second-order rate constant of the inactivation of C1s by C1 inhibitor. This rate constant increased 6- to 130-fold in the presence of the GAG, dextran sulfate being the most effective. Second, all tested GAG were found to reduce deposition of C4 and C3 on immobilized aggregated human IgG (AHG) and to reduce fluid phase formation of C4b/c and C3b/c in recalcified plasma upon incubation with AHG. Dextran sulfate again was found to be most effective. We conclude that GAG modulate complement activation in vitro and that the low molecular weight dextran sulfate (m.w. 5000) may be a candidate for pharmacologic manipulation of complement activation via potentiation of C1 inhibitor.

Complement Activation↗
PubMed1997

Interleukin-6 downregulates factor XII production by human hepatoma cell line (HepG2).

Involvement of the contact system of coagulation in the pathogenesis of various inflammatory diseases is suggested by reduced plasma levels of factor XII (Hageman factor) and prekallikrein generally considered to result from activation of the contact system. However, in many of these diseases patients develop an acute-phase response and, therefore, an alternative explanation for the decreased levels of factor XII could be the downregulation of factor XII gene expression in the liver as described for negative acute-phase proteins. We report here that interleukin-6 (IL-6), the principal cytokine mediating the synthesis of most acute-phase proteins in the liver, downregulates the production of factor XII by the human hepatoma cell line HepG2 by up to 75%. The decrease in protein secretion correlated with an equivalent decrease of factor XII mRNA likely indicating a pretranslational control of factor XII gene expression by IL-6. Downregulation of factor XII production by IL-6 in vitro parallelled that of transthyretin, a known negative acute-phase protein. Moreover, we show that, in patients developing an acute-phase response after immunotherapy with IL-2, plasma levels of factor XII correlate (r = .76, P < .0001) with those of transthyretin. Taken together, these results suggest that factor XII behaves as a negative acute-phase protein.

Acute-Phase Reaction↗
PubMed1997

Effect of a recombinant dimeric tumor necrosis factor receptor on inflammatory responses to intravenous endotoxin in normal humans.

To determine the role of tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-induced inflammation, 12 healthy subjects received an intravenous injection with LPS (2 ng/kg) preceded by infusion of either a recombinant human dimeric TNF receptor type II-IgG fusion protein (TNFR:Fc; 6 mg/m2; n = 6) or vehicle (n = 6) from -30 minutes to directly before LPS injection. LPS elicited a transient increase in plasma TNF activity, peaking after 1.5 hours (219 +/- 42 pg/mL; P < .05). Infusion of TNFR:Fc completely neutralized endogenous TNF activity. LPS administration was associated with an early activation of fibrinolysis (plasma concentrations of tissue-type plasminogen activator, plasminogen activator activity, and plasmin-alpha2-antiplasmin complexes), followed by inhibition (plasma plasminogen activator inhibitor type I), changes that were completely prevented by TNFR:Fc. By contrast, TNFR:Fc did not influence LPS-induced activation of coagulation (plasma levels of prothrombin fragment F1 + 2 and thrombin-antithrombin III complexes). TNFR:Fc strongly inhibited endothelial cell activation (plasma levels of soluble E-selectin), modestly reduced neutrophil responses (neutrophilia and plasma concentrations of elastase-alpha1-antitrypsin complexes and lactoferrin), but did not affect the release of secretory phospholipase A2 or lipopolysaccharide-binding protein (P > .05). Infusion of TNFR:Fc only (without LPS) in another 6 normal subjects did not induce any inflammatory response. These data indicate that TNF is involved in only some inflammatory responses to intravenous LPS in humans.

Adult↗
PubMed1997

Epinephrine exerts anticoagulant effects during human endotoxemia.

To determine the effect of a physiologically relevant elevation in the plasma concentrations of epinephrine on the activation of the hemostatic mechanism during endotoxemia, 17 healthy men were studied after intravenous injection of lipopolysaccharide (LPS, 2 ng/kg), while receiving a continuous infusion of epinephrine (30 ng/kg/min) started either 3 h (n = 5) or 24 h (n = 6) before LPS injection, or an infusion of normal saline (n = 6). Activation of the coagulation system (plasma concentrations of thrombin-antithrombin III complexes and prothrombin fragment F1+2) was significantly attenuated in the groups treated with epinephrine when compared with subjects injected with LPS only (P <0.05). Epinephrine enhanced LPS-induced activation of fibrinolysis (plasma levels of tissue-type plasminogen activator and plasmin-alpha2-antiplasmin complexes; P <0.05), but did not influence inhibition of fibrinolysis (plasminogen activator inhibitor type I). In subjects infused with epinephrine, the ratio of maximal activation of coagulation and maximal activation of fibrinolysis was reduced by >50%. Hence, epinephrine exerts antithrombotic effects during endotoxemia by concurrent inhibition of coagulation, and stimulation of fibrinolysis. Epinephrine, whether endogenously produced or administered as a component of treatment, may limit the development of disseminated intravascular coagulation during systemic infection.

Adult↗
PubMed1997

Effects of IL-10 on systemic inflammatory responses during sublethal primate endotoxemia.

IL-10 protects mice from LPS-induced lethality. To determine the effects of IL-10 on LPS-induced inflammatory responses, six Papio anubis baboons were i.v. injected with a sublethal dose of LPS (Salmonella typhimurium; 500 microg/kg) directly preceded by either human rIL-10 (n = 3, 500 microg/kg) or diluent (n = 3). IL-10 strongly inhibited LPS-induced release of TNF, IL-6, IL-8, and IL-12 (all p < 0.05). By contrast, IL-10 did neither influence the activation of the coagulation system (plasma levels of thrombin/antithrombin III complexes), nor the activation of the fibrinolytic system (plasma levels of tissue-type plasminogen activator, plasminogen activator inhibitor type I, and plasmin/alpha 2-antiplasmin complexes). IL-10 modestly attenuated neutrophilic leukocytosis and neutrophil degranulation (plasma concentrations of elastase/alpha1-antitrypsin complexes) (both p < 0.05). Changes in surface TNF receptor expression on circulating granulocytes were not affected by IL-10. These results suggest that during sublethal endotoxemia the predominant anti-inflammatory effect of IL-10 treatment is inhibition of proinflammatory cytokine release.

Animals↗
PubMed1997

Partial coverage of phospholipid model membranes with annexin V may completely inhibit their degradation by phospholipase A2.

Phospholipase A2 (PLA2)-mediated hydrolysis of membrane phospholipids was measured by ellipsometry, and the inhibition of this process by annexin V was studied. Planar membranes, consisting of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine (PC/PE/PS; 54:33:13, on molar basis), were degraded by pancreatic PLA2, and the rate of hydrolysis was limited to about 0.7%/min. The influence of graded coverage of the membrane with annexin V was studied. The degree of PLA2 inhibition was nonlinearly related to the amount of membrane-bound annexin V, and binding of only 12% and 54% of full membrane coverage resulted in, respectively, 50% and 93% inhibition. These findings indicate that the inhibition of PLA2-mediated hydrolysis by annexin V cannot be simply explained by shielding of phospholipid substrates from the enzyme. Moreover, the present results leave room for a role of endogenous annexin V in regulating phospholipid turnover in the plasma membrane of parenchymal cells such as cardiomyocytes.

Animals↗
PubMed1997

C-reactive protein colocalizes with complement in human hearts during acute myocardial infarction.

BACKGROUND: Rises in circulating C-reactive protein (CRP), the prototypical acute-phase protein in humans, correlate with clinical outcome in patients with myocardial ischemia and infarction. We hypothesized that these correlations might reflect active participation of CRP in the local inflammatory response ensuing in the jeopardized myocardium because on binding to a ligand, CRP is able to activate the classic pathway of complement, and in addition, complement activation has been shown to occur locally in infarcted myocardium. METHODS AND RESULTS: To verify our hypothesis, we investigated localization of CRP in relation to deposition of complement in tissue specimens of infarcted and healthy heart tissue obtained from 17 patients who had died after acute myocardial infarction. CRP was found to be deposited only in infarcted regions and not in normal-appearing areas of the myocardium, being colocalized with depositions of C4 and C3 activation fragments of the complement system. Deposition of CRP and complement in infarcted myocardium appeared to be time dependent, because it was found in all infarctions except for one of young age (< 12 hours old) and two of greater age (> 1 year old), whereas another tissue specimen of an infarct < 12 hours old showed only moderate but positive staining for both CRP and complement in comparison with older infarctions. CONCLUSIONS: We conclude that in humans, CRP may localize in infarcted heart tissue and suggest that this acute-phase protein promotes local complement activation, and hence tissue damage, in acute myocardial infarction.

Aged↗
PubMed1997

Interleukin 12 levels during the initial phase of septic shock with purpura in children: relation to severity of disease.

Plasma levels of interleukin 12 (IL-12), a cytokine consisting of two different polypeptide subunits (p40 and p35), were measured together with interferon gamma (IFN-gamma) and other cytokines in 46 children with septic shock and purpura. The median (range) plasma IL-12 p40 level on admission was 457 (244-2677) pg/ml in non-survivors vs 189 (< 40-521) pg/ml in survivors (P = < 0.001). IL-12 p70 levels were elevated in only nine patients. IL-12 p40 plasma levels were positively correlated with tumour necrosis factor alpha (TNF-alpha), IL-6, IL-8, IL-10 and PRISM-score, whereas they were negatively correlated with C-reactive protein (CRP), whole blood cell (WBC) and serum glucose levels. Twelve (29%) of the patients had detectable levels of IFN-gamma. Thus, circulating levels of IL-12 p40 and to a lesser extent those of IL-12 p70, are elevated in children with septic shock and purpura, and correlate with severity of disease and outcome.

Adolescent↗
PubMed1997

Both plasma- and leukocyte-associated C5a are essential for assessment of C5a generation in vivo.

BACKGROUND: Measurement of C5a in plasma is hampered by the rapid clearance of C5a as a result of cell binding. Therefore, an assessment of whether cell-bound C5a might better reflect C5a generation in vivo is essential. METHODS: We quantified plasma and leukocyte-bound C5a in samples from patients undergoing cardiopulmonary bypass, which is known to be associated with complement activation. C3 activation products and the terminal complement complex were measured as well. RESULTS: Plasma levels of C3 activation products and the terminal complement complex increased rapidly and significantly after the onset of cardiopulmonary bypass until they reached a plateau after 30 minutes. The concentration of plasma C5a increased steadily to twice baseline at the end of bypass. The concentration of leukocyte-associated C5a increased threefold after 10 minutes of cardiopulmonary bypass, when a plateau was reached. A positive correlation was found between levels of plasma C3 activation products or terminal complement complex and plasma C5a plus cell-associated C5a but not between C3 activation products or terminal complement complex and either one of the C5a variables. CONCLUSIONS: We conclude that both plasma C5a and leukocyte-associated C5a are needed for monitoring in vivo C5a generation.

Cardiopulmonary Bypass↗
PubMed1997

A baboon model for hematologic studies of cardiopulmonary bypass.

Objective investigation of new inhibitors of blood protein or cellular systems that are activated during cardiopulmonary bypass (CPB) is impeded by the absence of a satisfactory animal model. Because most baboon hematologic proteins immunologically cross-react with those used for human assays, we developed a robust, reusable baboon model of CPB. Blood samples were obtained from adult baboons at six time intervals before, during, and after 60 minutes of partial CPB at 37 degrees C with peripheral cannulas. Both membrane (n = 7) and bubble oxygenators (n = 7) were investigated. We measured platelet and white blood cell counts; platelet response to adenosine diphosphate and release of beta-thromboglobulin; fibrinopeptide A, prothrombin fragment F1.2, thrombin-antithrombin complex, D-dimer, and plasmin-antiplasmin complex; activated complement (C3b/c and C4b/c); elastase-alpha1 proteinase inhibitor complex; and bleeding times. Adherent glycoprotein IIIa antigen in Triton X-100 washes of the perfusion circuit was also measured. Markers of baboon platelet, complement, and neutrophil activation and thrombosis significantly increased during CPB with bubble oxygenator systems but did not change appreciably in membrane oxygenator circuits. Markers of fibrinolysis, D-dimer, and plasmin-antiplasmin complex did not change with either oxygenator. The baboon model of CPB, when a bubble oxygenator is used, is a robust, reusable animal model for evaluating inhibitors of platelet, complement, and neutrophil activation and thrombosis during and after CPB.

Adenosine Diphosphate↗
PubMed1997

Heparin coating of extracorporeal circuits inhibits contact activation during cardiac operations.

OBJECTIVE: Heparin coating reduces complement activation on the surface of extracorporeal circuits. In this study we investigated its effect on activation of the contact system in 30 patients undergoing coronary artery bypass grafting with the use of a heparin-coated (Duraflo II, Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.; n = 15) or an uncoated extracorporeal circuit (n = 15). METHODS: Plasma markers that reflect activation of contact (kallikrein-C1-inhibitor complexes), coagulation (prothrombin fragments F1 + 2), or fibrinolytic (plasmin-alpha 2-antiplasmin complexes) systems were determined before and during the operation. The generation of kallikrein-C1-inhibitor complexes was reduced by 62% (p = 0.06) after the onset of cardiopulmonary bypass and by 43% (p = 0.026) after the cessation of bypass in the group in which a heparin-coated circuit was used compared with the group in which the circuit was uncoated. Generation was reduced by 58% (p = 0.06) when the ratio of kallikrein-C1-inhibitor to prekallikrein after onset of bypass was considered. We detected significant increases in F1 + 2 levels in both groups and increases in plasmin-alpha 2-antiplasmin complexes in the heparin-coated group at cessation of bypass, but no intergroup differences were observed. Thus use of heparin-coated extracorporeal circuits during cardiac operations reduces formation of kallikrein-C1-inhibitor complexes when compared with use of uncoated circuits. The heparin coating is not accompanied by similar reductions in coagulation or fibrinolysis, suggesting that thrombin and plasmin formation during cardiopulmonary bypass occurs mainly independently of the contact system activation.

Aged↗
PubMed1997

Effect of whole and fractionated intravenous immunoglobulin on complement in vitro.

Intravenous immunoglobulins (IVIG) are increasingly used for treatment of inflammatory diseases, and the modulation of complement may contribute to some of its beneficial effects. IVIG may bind C1q and activated C3 and C4, and enhance inactivation of C3b. We have previously shown that IVIG inhibited complement-mediated lysis solely via its Fc part through interaction with the classical pathway. In the present study we have investigated whole IVIG (Octagam, and Sandoglobulin) and the monomer, dimer and multimer fractions of Octagam with respect to complement activation in serum and inhibition of complement lysis of red cells. The isolated fractions were found to be stable, homogeneous (monomer, dimer or multimer) and pure (virtually only IgG). Both whole IVIG and its fractions significantly activated complement in serum and inhibited hemolysis compared with human albumin. These effects were most pronounced in the monomer, less in the multimer and least in the dimer fraction. The complement activation was shown to be mediated through the classical pathway since formation of C1rs-C1inh complexes and C4bc were increased, in contrast to Bb. Surprisingly, heat aggregation of Octagam was not followed by a corresponding increase in complement activation, as would be expected, unless it was dialysed before heating, suggesting that it is stabilized to avoid excess activation. In conclusion, the results support the hypothesis that IVIG causes a mild activation of complement in vitro. We suggest that this effect may contribute to the complement inhibitory properties of IVIG by diverting complement deposition from the target to the fluid phase.

Animals↗
PubMed1997

A role for secretory phospholipase A2 and C-reactive protein in the removal of injured cells.

The acute phase response is initiated in response to infection or physical trauma and is characterized by an increase in the levels of some plasma proteins. Here, Erik Hack and colleagues suggest that the combined actions of two of these acute phase proteins, secretory phospholipase A2 and C-reactive protein, may serve to promote phagocytosis of injured cells and tissue debris, thereby enhancing inflammation and tissue damage.

Acute-Phase Reaction↗
PubMed1997

The inflammatory response to vascular surgery-associated ischaemia and reperfusion in man: effect on postoperative pulmonary function.

OBJECTIVES: To characterise the inflammatory response to vascular surgery and ischaemia/reperfusion (I/R) in man, regarding release of inflammatory mediators, recruitment and activation of neutrophils, and their relation to postoperative pulmonary function. DESIGN: Prospective cohort study. MATERIALS AND METHODS: Circulating neutrophil counts and plasma levels of elastase-alpha 1-antitrypsin (AT), a neutrophil degranulation product, were measured before and approx. 2.5 h (group 1, n = 19) after elective abdominal aortic surgery, and approx. 2.9 h after elective peripheral vascular surgery (group 2, n = 6), together with concentrations of neutrophil agonists, including activated complement (C3a), secretory phospholipase A2 (sPLA2), tumor necrosis factor (TNF-alpha), interleukin (IL)-6, IL-8 and granulocyte colony-stimulating factor (G-CSF). At the time of blood sampling, respiratory variables allowing computation of the lung injury score (LIS) were obtained in patients admitted after surgery in the intensive care unit (ICU), i.e. all group 1 patients and one group 2 patient. RESULTS: Median (range) neutrophil counts rose by 80% (-28-208) and 90% (10-147) in groups 1 and 2, respectively (n.s. between groups). The increase (p < 0.05) in elastase-alpha 1-AT level was 121% (-5-439) in group 1 and 82% (18-792) in group 2 (n.s. between groups). There was a rise (p < 0.05) in C3a level by 93% (-42-751) and of sPLA2 level by 68% (-40-1400) after surgery for the groups together (n.s. between groups), and the rise of the elastase-alpha 1-AT related to that of the C3a levels. IL-6 and G-CSF concentrations increased more in group 1 than 2. The IL-8 concentration increased in group 1 only, and TNF-alpha was unchanged in all groups. In ICU patients, the LIS related to the postoperative rise in IL-6 level only, even though the rise in plasma concentrations of cytokines interrelated. No patient developed ARDS and all survived. CONCLUSIONS: Vascular surgery and I/R in man activates complement, releases cytokines (except for TNF-alpha), and induces neutrophil recruitment and degranulation, which may primarily depend on complement activation. In contrast to the latter, the release of cytokines may depend on the extent of I/R and may contribute to transient pulmonary dysfunction after extensive I/R.

Adult↗
PubMed1997

Isolated hepatic perfusion in the pig with TNF-alpha with and without melphalan.

Isolated limb perfusion with tumour necrosis factor alpha (TNF-alpha) and melphalan is well tolerated and highly effective in irresectable sarcoma and melanoma. No data are available on isolated hepatic perfusion (IHP) with these drugs for irresectable hepatic malignancies. This study was undertaken to assess the feasibility of such an approach by analysing hepatic and systemic toxicity of IHP with TNF-alpha with and without melphalan in pigs. Ten healthy pigs underwent IHP. After vascular isolation of the liver, inflow catheters were placed in the hepatic artery and portal vein, and an outflow catheter was placed in the inferior vena cava (IVC). An extracorporeal veno-venous bypass was used to shunt blood from the lower body and intestines to the heart. The liver was perfused for 60 min with (1) 50 microg kg(-1) TNF-alpha (n = 5), (2) 50 microg kg(-1) TNF-alpha plus 1 mg kg(-1) melphalan (n = 3) or (3) no drugs (n = 2). The liver was washed with macrodex before restoring vascular continuity. All but one pigs tolerated the procedure well. Stable perfusion was achieved in all animals with median perfusate TNF-alpha levels of 5.1 +/- 0.78 x 10(6) pg ml(-1) (+/- s.e.m). Systemic leakage of TNF-alpha from the perfusate was consistently < 0.02%. Following IHP, a transient elevation of systemic TNF-alpha levels was observed in groups 1 and 2 with a median peak level of 23 +/- 3 x 10(3) pg ml(-1) at 10 min after washout, which normalized within 6 h. No significant systemic toxicity was observed. Mild transient hepatotoxicity was seen to a similar extent in all animals, including controls. IHP with TNF-alpha with(out) melphalan in pigs is technically feasible, results in minimal systemic drug exposure and causes minor transient disturbances of liver biochemistry and histology.

Alanine Transaminase↗
PubMed1997

Initiation of contact system activation in plasma is dependent on factor XII autoactivation and not on enhanced susceptibility of factor XII for kallikrein cleavage.

Various mechanisms have been hypothesized to explain the initiation of contact system activation in plasma. We investigated the capability of dextran sulphate (DS) of different molecular weights to initiate contact system activation in normal human plasma, and compared this with their capability to support factor XII autoactivation and to enhance factor XII susceptibility for cleavage by kallikrein. Dextran sulphate of Mr 500,000 (DS500) and 50,000 (DS50) was able to initiate contact system activation in plasma (determined by measuring the amount of factor XIIa-C1-inhibitor, kallikrein-C1-inhibitor and factor XIa-C1-inhibitor complexes generated) as well as to support factor XII autoactivation and to enhance factor XII susceptibility for cleavage by kallikrein (as measured with amidolytic assays using purified proteins). In contrast, dextran sulphate of Mr 15,000 (DS15) and 5000 (DS5) neither induced contact system activation in plasma, nor supported autoactivation of factor XII, although both of these DS species enhanced the rate of activation of factor XII by kallikrein in the purified system. Based on these properties (i.e. binding of factor XII without inducing autoactivation), DS15 and DS5 were predicted to be inhibitors of contact system activation induced in plasma by DS500, which indeed was observed. We conclude that enhanced factor XII susceptibility for kallikrein activation and factor XII autoactivation are distinct phenomena, the latter being necessary to support activation of the contact system in plasma.

Dextran Sulfate↗
PubMed1997

A neoepitope-based enzyme immunoassay for quantification of C1-inhibitor in complex with C1r and C1s.

Monoclonal antibodies (MoAb) recognizing neoepitopes exposed on activation products of complement proteins but hidden in the native components have been used for quantification of activated complement. A previously produced and characterized mouse MoAb, recognizing a neoepitope on the human plasma protein C1-inhibitor complexed with its substrates, was used to design an enzyme immunoassay for detection of C1-inhibitor complexed with C1r and C1s. These complexes are indicators of early classical complement pathway activation. The standard was serum activated with heat aggregated IgG defined to contain 1000 arbitrary units (AU)/ml. The lower detection limit was approximately 0.05 AU/ml corresponding to 0.005% of fully activated serum. The reliability of the assay, including day-to-day variation, was tested. Intra-assay variation coefficients were 12% for low plasma control and 13% for high plasma control (n = 12 for both). Inter-assay variation coefficients were 12% for low control (n = 6), 19% for high control (n = 6) and 15% for the normal plasma control (n = 9). A 2.5-97.5 percentile reference range (normal blood donors) was 16-33 AU/ml. Two patients with systemic lupus erythematosus had considerably elevated plasma levels of the activation product (56 and 62 AU/ml), and six patients with hereditary angioedema had normal plasma levels despite considerably reduced C1-inhibitor concentration. We conclude that the present method is sensitive and reliable for detection of early classical pathway activation and superior to previously published methods by utilizing neoepitope specificity and non-radiolabelled reagents.

Animals↗