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PubMed1980

Inhibition of the hypotensive effect of plasma protein solutions by C1 esterase inhibitor.

The hypotensive effect of stable plasma protein solution (SPPS) is a well-known phenomenon, causing serious problems in surgical patients and patients supported by cardiopulmonary bypass. Kinins are believed to be responsible. A study was made to prevent this hypotension by adding C1 esterase inhibitor to the SPPS and comparing this with 5% human albumin. The results shows a significant difference between the effects of SPPS and SPPS plus C1 esterase inhibitor infusion on bypass. Five percent human albumin did not cause hypotension. Possible sequelae are discussed.

Blood Pressure↗
PubMedDate not supplied

An IgG autoantibody which inactivates C1-inhibitor.

Antibodies are considered to play a specific pathogenic role in certain disease states such as myasthenia gravis, Graves' disease and autoimmune haemolytic anaemia. Autoantibodies which interfere with the function of enzyme cascade systems have also been described in diseases such as acquired haemophilia (anti-factor VIII antibodies) and glomerulonephritis (C3 nephritic factor). The identification of these autoantibodies is crucial to an understanding of the aetiology of such diseases and is also of importance in revealing the inter-relationships of the immune system with other biological pathways. This is the first report of an immunoglobulin G (IgG) autoantibody reactive with C1-inhibitor (C1-Inh), a pivotal inhibitor of the inflammatory response which is known to inactivate proteins of the complement, kinin, fibrinolytic and 'contact phase' systems. This autoantibody was isolated from a patient with a novel variant of acquired angioedema and C1-Inh dysfunction. This finding highlights the involvement of the immune system in the pathogenesis of disorders characterized by the presence of dysfunctional inflammatory response proteins.

Autoantibodies↗
PubMed1988

Effects of fibroblasts and endothelial cells on inactivation of target proteases by protease nexin-1, heparin cofactor II, and C1-inhibitor.

Previous studies have shown that glycosaminoglycans in the extracellular matrix accelerate the inactivation of target proteases by certain protease inhibitors. It has been suggested that the ability of the matrix of certain cells to accelerate some inhibitors but not others might reflect the site of action of the inhibitors. Previous studies showed that fibroblasts accelerate the inactivation of thrombin by protease nexin-1, an inhibitor that appears to function at the surface of cells in extravascular tissues. The present experiments showed that endothelial cells also accelerate this reaction. The accelerative activity was accounted for by the extracellular matrix and was mostly due to heparan sulfate. Fibroblasts but not endothelial cells accelerated the inactivation of thrombin by heparin cofactor II, an abundant inhibitor in plasma. This is consistent with previous suggestions that heparin cofactor II inactivates thrombin when plasma is exposed to fibroblasts and smooth muscle cells. Neither fibroblasts nor endothelial cells accelerated the inactivation of C1s by plasma C1-inhibitor.

Amyloid beta-Protein Precursor↗
PubMed1992

Influence of 4 different membrane oxygenators on inflammation-like processes during extracorporeal circulation with pulsatile and non-pulsatile flow.

The influence of four different membrane oxygenators (HF 4000, BOS-CM 50, CML 2, Maxima) on leucocyte count, concentrations of PMN-elastase, clotting factor XII, AT-III, C1-INH, alpha 2-antiplasmin and C3a was registered before, during and after CPB with pulsatile and nonpulsatile flow in 80 male patients aged between 36 and 67 years. With all systems tested, there was a drop in the concentrations of clotting factor XII, AT-III, C1-INH and alpha 2-antiplasmin in the early extracorporeal circulation (ECC) phase, exceeding the average hematocrit reduction accounted for by dilution. This drop was the least distinct with CML 2 systems, both with pulsatile and nonpulsatile perfusion, indicating system-inherent influences. Leucocyte cound and PMN-elastase concentration rose significantly during ECC irrespective of oxygenator tested of flow type applied. The rise in leucocyte count even continued for about 4 h after ECC. During the first 40 min of ECC, these changes were paralleled by a significant rise in C3a concentration, suggesting complement activation as a main cause for PMN activation. However, there is reason to suppose involvement of further mechanisms operating in PMN activation, since the elevated C3a-concentrations began to fall off while leucocyte count and PMN-elastase concentrations were still increasing.

Acute-Phase Proteins↗
PubMed1989

Inhibition of human bronchial kallikrein in asthma.

Human bronchial kallikrein (HBK) is the major kinin-generating enzyme in the airways of asthmatic subjects. We examined the in vitro inhibition of HBK and its in vivo regulation in asthma. HBK kininogenase activity was measured by cleavage of radiolabeled purified high molecular weight kininogen (HMWK) (125I HMWK). Functional inhibition of the enzyme was present after co-incubation with either normal human plasma (NHP) or preparations of alpha-1-proteinase inhibitor (alpha 1-PI). Stable HBK inhibitor complex was detected at 92 K by immunoblotting employing anti-HUK as a probe. Anti alpha 1-PI probes did not demonstrate the 92 K complex under identical conditions, raising the possibility of an additional co-purifying protein involved in HBK binding. alpha 1-PI antigenic and activity levels were measured in asthmatic bronchoalveolar lavage (BAL) fluid. In only a single sample of the six examined was alpha 1-PI activity detected. In two of the remaining five samples, low levels of alpha 1-PI antigen were present which were functionally inactive. In the BAL fluid containing alpha 1-PI activity, progressive functional inhibition of kininogenase activity correlating with HBK inhibitor complex formation occurred during BAL fluid incubation. In contrast, BAL fluid lacking alpha 1-PI activity failed to show progressive kininogenase inhibition or complex formation under identical conditions. In all experiments, the time course of HBK inhibitor interaction was markedly prolonged, requiring 150-min co-incubation with either NHP or the alpha 1-PI preparation for greater than 80% inhibition of function and near maximal complex formation. The slow rate of inhibition of HBK may allow for its continued activity and kinin generation in the airways of asthmatic subjects.

Adolescent↗
PubMed1986

Human inhibitor of the first component of complement, C1: characterization of cDNA clones and localization of the gene to chromosome 11.

C1 inhibitor is a heavily glycosylated plasma protein that regulates the activity of the first component of complement (C1) by inactivation of the serine protease subcomponents, C1r and C1s. C1 inhibitor cDNA clones have been isolated, and one of these (pC1INH1, 950 base pairs) has been partially sequenced. Sequence analysis demonstrates that the C1 inhibitor is a member of the serpin "superfamily" of protease inhibitors. In the region sequenced, C1 inhibitor has 22% identity with antithrombin III, 26% with alpha 1-antitrypsin and alpha 1-antichymotrypsin, and 18% with human angiotensinogen. C1 inhibitor has a larger amino-terminal extension than do the other plasma protease inhibitors. In addition, inspection of residues that are invariant among the other protease inhibitors shows that C1 inhibitor differs at 14 of 41 of these positions. Thus, it appears that C1 inhibitor diverged from the group relatively early in evolution, although probably after the divergence of angiotensinogen. Southern blot analysis of BamHI-digested DNA from normal individuals and from rodent-human somatic cell hybrid cell lines (that contain a limited but varied human chromosome complement) was used to localize the human C1 inhibitor gene to chromosome 11.

Amino Acid Sequence↗
PubMed2002

StcE, a metalloprotease secreted by Escherichia coli O157:H7, specifically cleaves C1 esterase inhibitor.

Escherichia coli O157:H7 causes diarrhoea, haemorrhagic colitis, and the haemolytic uraemic syndrome. We have identified a protein of previously unknown function encoded on the pO157 virulence plasmid of E. coli O157:H7, which is the first described protease that specifically cleaves C1 esterase inhibitor (C1-INH), a member of the serine protease inhibitor family. The protein, named StcE for secreted protease of C1 esterase inhibitor from EHEC (formerly Tagn), cleaves C1-INH to produce (unique) approximately 60-65 kDa fragments. StcE does not digest other serine protease inhibitors, extracellular matrix proteins or universal protease targets. We also observed that StcE causes the aggregation of cultured human T cells but not macrophage-like cells or B cells. Substitution of aspartic acid for glutamic acid at StcE position 435 within the consensus metalloprotease active site ablates its abilities to digest C1-INH and to aggregate T cells. StcE is secreted by the etp type II secretion pathway encoded on pO157, and extracellular StcE levels are positively regulated by the LEE-encoded regulator, Ler. StcE antigen and activity were detected in the faeces of a child with an E. coli O157:H7 infection, demonstrating the expression of StcE during human disease. Cleavage of C1-INH by StcE could plausibly cause localized pro-inflammatory and coagulation responses resulting in tissue damage, intestinal oedema and thrombotic abnormalities.

Blood Proteins↗
PubMed1998

Analysis of coagulation proteins as acute-phase reactants in horses with colic.

OBJECTIVES: To measure coagulation factor VIII:coagulant (F.VIII:C) and C1-esterase inhibitor (C1-INH), hemostasis-associated acute-phase reactant proteins and coagulation factors VII (F.VII), IX (F.IX), and X (F.X), hemostasis proteins not associated with an acute-phase response, in a select population of horses with colic and hemostasis abnormalities, and presumed to have acute-phase changes. To compare these values and other routine hemostasis test results in the horses with colic with values for a population of healthy horses. To correlate the values of known equine acute-phase reactants, F.VIII:C and fibrinogen, to those of other tests of hemostasis. To identify hemostasis-associated acute-phase reactant proteins and gain insights into the effects the acute-phase response has on hemostatic abnormalities in horses with colic syndrome. SAMPLE POPULATION: 54 plasma samples from horses with colic attributable to inflammatory (n = 39) or strangulating (n = 15) intestinal disorders. PROCEDURE: Plasma samples were evaluated for activities of F.VII, F.VIII:C, F.IX, F.X, C1-INH, antithrombin III, protein C, plasminogen, and alpha 2-antiplasmin (alpha 2AP); fibrinogen concentration; and prothrombin (PT) and activated partial thromboplastin (APTT) times. RESULTS: Horses with colic had significantly higher fibrinogen concentration, greater alpha 2AP and protein C activities, and longer PT and APTT than did healthy horses. Horses with colic also had significantly lower mean F.VII activity than did healthy horses. Significant positive correlations between fibrinogen concentration and F.VIII:C, C1-INH, and alpha 2AP values, and between F.VIII:C activity and fibrinogen, C1-INH, alpha 2AP, and plasminogen values were identified. CONCLUSIONS: An acute-phase response contributes to changes observed in coagulation proteins in horses with colic attributable to inflammatory and strangulating intestinal disorders. The data suggest that plasminogen, alpha 2AP, and C1-INH, should be considered equine acute-phase proteins.

Acute-Phase Proteins↗