C1 inhibitor: the main inhibitor of human plasma kallikrein.
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Complement C1 Inactivator Proteins↗
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Pre-operative plasma levels of C-reactive protein, albumin and various plasma protease inhibitors for the pre-operative assessment of operability and recurrence in cancer surgery.
Pre-operative levels of the acute phase protein C-reactive protein (CRP), albumin (assessing nutritional status), the tumour marker CEA and three plasma protease inhibitors, i.e. C1-esterase inhibitor, alpha-2-macroglobulin and antithrombin III, were prospectively studied in 183 patients with various solid cancers. First, the predictive value of abnormal levels for operability at the primary operation was studied. Secondly, the predictive value of abnormal levels for cancer recurrence and metastases was evaluated during 2 years of follow-up. The results show that malignancy induces increased CRP and C1-esterase inhibitor levels and decreased albumin levels in serum. These changes, as well as raised alkaline phosphatase and lowered haemoglobin levels, also correlate to the 'overall' tumour burden. The most important conclusion is, that increased pre-operative CRP levels (CRP > or = 10 mg/l; sensitivity, 79%; specificity, 71%) and/or low albumin levels (albumin <37 g/l; sensitivity, 94%; specificity, 54%) are seen in inoperable cancer patients compared with patients having operable cancers. The second main important conclusion is, that high pre-operative C1-esterase inhibitor levels (C1-esterase inhibitor >152%; sensitivity, 45%; specificity, 90%), and in some patients a high alkaline phosphatase level, are seen in patients exhibiting early cancer recurrence (within 2 years post-operatively).
Aged↗
[Comparative studies of the adsorption behavior of plasma proteins to heparin-coated surfaces].
Over the past 10 years, investigations have shown that heparin coating optimizes haemocompatibility in extracorporeal circulation systems. To date, however, the mechanisms involved have not been identified. 20 ml of fresh human blood were circulated in an in vitro closed-loop model with and without heparin coating. Using a newly developed ELISA, a quantitative analysis of the adsorbed plasma proteins was done. In addition, changes in coagulation, complement and blood cell releasing factors were measured by ELISA methods: prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin-III complex (TAT), PMN-elastase, beta-thromboglobulin (beta-TG) and terminal complement-complex (TCC). In uncoated tubing, high concentrations of fibrinogen, fibronectin, prothrombin, vitronectin, alpha 2-macroglobulin, von Willebrand factor and complement factor C3 were found. Large amounts of antithrombin-III, HMWK and C1-esterase inhibitor were found on the heparinized surfaces. In addition, the concentrations of the soluble plasma protein markers F1 + 2, FPA, PMN-elastase, TCC and beta-TG were significantly lower (p < 0.05) in the presence of heparin coating. The haemocompatibility of "foreign" surfaces depends largely on the extent to which the processes of activation and inhibition of humoral and cellular mediators permanently occurring at the natural endothelium can be simulated. Owing to the low adsorption of procoagulatory and proinflammatory enzymes, heparin-coated surfaces demonstrate significantly improved haemocompatibility.
Adsorption↗
[Congenital angioneurotic edema in an 11-year-old girl].
A case of a 11-year girl with the inherited angioedema is presented. Lack of improvement following antiallergic therapy and familial history of the disease were the base of studies leading to the diagnosis of this rare syndrome. Preliminary diagnosis was confirmed by C1q inhibitor and blood level of C4 assays.
Angioedema↗
Clinical presentation and diagnosis of hereditary angio-oedema in five families.
The clinical features of 16 patients with deficiency of C1 esterase inhibitor are described. Severity ranged from no symptoms in 2 young subjects to repeated and severe abdominal pain and angio-oedema. Diagnostic techniques are described and the ease with which the diagnosis can be established is emphasized. A functional assay is required in addition to immunological determination of the protein in order to detect a minority of patients who have ineffective inhibitor. Experience of treatment with tranexamic acid is reviewed and its place in management in relation to androgens is discussed.
Adult↗
Identification of the complement regulatory protein CD59 in human colostrum and milk.
PROBLEM: Complement lytic activity has been demonstrated, and a potential for its activation is present in human colostrum and milk. This necessitates the presence of regulatory mechanisms protecting epithelial cells in the oropharynx and the gastrointestinal tract of the infant, the milk cellular elements, and bacteria colonizing the oropharynx and the gastrointestinal tract. Lactoferrin and C1 inhibitor have been attributed such a role. However, it is likely that additional protection against the cytolytic activity of the membrane attack complex is required. This has lead us to investigate the presence of the complement regulatory protein CD59 in human colostrum and milk, and to further characterize the source of secretion. METHOD: Samples of human colostrum and milk were obtained from volunteers at different stages of lactation, and separated into fat, skim milk, and milk cellular elements by centrifugation. Normal human mammary gland tissues were obtained from patients undergoing biopsy for benign conditions. SDS-PAGE and Western blotting, and an immuno dot-blot assay were used to identify CD59 in human milk. Immunohistochemistry was performed on all tissue samples and cytospins of the milk cellular elements, using monoclonal antibodies to CD59. RESULTS: CD59 was present in cell-free colostrum and milk as a 19-25 kDa glycoprotein. No variation in CD59 levels was detected between colostrum and milk. CD59 was present in great amounts in the cytoplasm and was highly expressed on the surface membrane on mammary gland acinar and ductal epithelial cells, while the milk cellular elements contained CD59 mainly in their cytoplasm. CONCLUSION: The complement regulatory protein CD59 present in cell-free human colostrum and milk may exert its effects both in the mammary gland and in the oropharynx and gastrointestinal tract of the infant. The lobuloalveolar epithelial cells in the mammary gland are the likely source of secretion.
Breast↗
An autoantibody to C1-inhibitor recognizes the reactive center of the inhibitor.
An autoantibody to C1-inhibitor produced a clinical disorder resembling that of patients with hereditary angioneurotic edema. The antibody could not interact with C1-inhibitor after exposure to synthetic peptides representing the primary structure of the reactive center region of the protein. Therefore the antibody recognized this domain of the inhibitor, and it probably impaired the function of C1-inhibitor by altering its conformational properties.
Amino Acid Sequence↗
Functional analysis of the serpin domain of C1 inhibitor.
To analyze the role of the heavily glycosylated amino-terminal domain of C1 inhibitor in protease inhibitory activity, two truncated C1 inhibitor molecules were constructed. The abilities of the recombinant truncated inhibitors to complex with target proteases were compared with that of the wild-type recombinant protein. One recombinant truncated molecule consisted of amino acid residues 76 to 478 (C-serp(76)) and the other of residues 98 to 478 (C-serp(98)). The recombinant proteins were each expressed in similar quantities. The thermal denaturation profiles of the two truncated proteins were similar to that of the wild-type protein. Identical binding of C1s, C1r, kallikrein, and beta factor XIIa was observed with the three molecules. Furthermore, the truncated molecules also effectively inhibited C1 activity in hemolytic assays. These studies therefore clearly demonstrate that the amino-terminal domain of C1 inhibitor does not influence complex formation with target proteases.
Complement C1 Inactivator Proteins↗
Activation of first component of complement (C1) in guinea pig serum by a polysaccharide is prevented by C1 inhibitor.
A polysaccharide (PS) purified from venom of the ant Pseudomyrmex sp. causes the activation of the classical complement (C) pathway in normal serum, but not in guinea pig serum. To investigate why C was not activated in guinea pig serum, we partially purified guinea pig C1 in the presence of the protease inhibitor p-nitrophenyl, p'-guanidinobenzoate (NPGB). This C1 preparation was activated (mu = 0.15, pH 7.5) by the PS in a dose-dependent reaction after NPGB was eliminated by dilution. The PS decreased the action of the C1 inhibitor for C1 in diluted guinea pig serum, and it also inhibited the activity of highly purified guinea pig C1 inhibitor for C1. There was a direct correlation between the concentration of the guinea pig C1 inhibitor and the loss of ability of the PS to activate C1 in mixtures of constant concentrations of purified guinea pig C1 and purified venom PS, and increasing concentrations of purified guinea pig C1 inhibitor. The activity of the human C1 inhibitor, either in diluted serum or highly purified, was not decreased by the PS. These results show that the PS does not activate guinea pig C1 in serum because its action is blocked by the C1 inhibitor.
Animals↗
Effect of some hydroxycoumarins on complement-mediated hemolysis in human serum.
Coumarin derivatives are known to possess antiinflammatory and antimetastatic properties due to their direct action on cells, predominantly on macrophages. In the present study the interactions between esculin, esculetin, fraxin, fraxetin, as well as their acetylated and methylated derivatives and non-cell system participating in inflammatory processes, comprised of serum complement proteins, were investigated in vitro. 7-Methylesculin, esculin 5Ac and esculetin 2Ac exhibited good inhibition on classical pathway (CP) activity and scoparone strongly reduced alternative pathway (AP) activity in normal human serum (NHS). Some of the hydroxycoumarins were able to enhance hemolysis. Seven derivatives were tested in C1 and C3 functional assays, as 7-methylesculin appeared to be the strongest inhibitor of both activities. Esculin (En) and scopoletin (St) altered the effect of other complement activators (heat aggregated IgG, suramin, and zymosan) when applied with them simultaneously in vitro.
Buffers↗
Coagulation inhibitor substitution during sepsis.
This review presents the rationale for and main results of coagulation inhibitor substitution during experimental and human sepsis. Activation of the contact system induces activation of the classical complement pathway with generation of anaphylatoxins, of the kinins pathway and of fibrinolysis. Physiologic inhibition depends on the C1-inhibitor (C1-Inh.). Septic patients exhibit a relative deficiency of biologically active C1-Inh. Substitution with concentrations of C1-Inh has been safely performed and preliminary results are consistent with a possible beneficial effect on hypotension and vasopressor requirement in septic shock. The extrinsic pathway is the main initial coagulation process involved in sepsis-induced DIC. Endothelial and monocyte generation of tissue factor (TF) is activated by bacterial products and endotoxin. Activation of TF is counteracted by a specific tissue factor pathway inhibitor (TFPI). The potential for TFPI substitution to inhibit the activation of the coagulation cascade in sepsis requires further study. Thrombin generation is inhibited by antithrombin III (AT III) and the protein C-protein S system. During sepsis, AT III is consumed and degraded by elastase. Animal studies have shown that DIC and death were prevented by high doses of AT III concentrates. Although a significant reduction in the duration of biological symptoms of DIC has been reported in most human studies, the usefulness of AT III substitution in human sepsis is still debated. None of the studies was able to document a statistically significant reduction in mortality. Protein C is activated by thrombomodulin and, with its cofactor protein S, inhibits factors Va and VIIIa. The free level of protein S depends on the level of the C4b binding protein (C4bBP), an acute-phase complement regulatory protein. During sepsis, protein C activity is significantly reduced, either by acute consumption or by thrombomodulin down-regulation, and increased levels of plasma C4bBP inhibit protein S. Infusion of activated protein C and protein S substitution both protect animals from the lethal effects of bacteria. Combining these different coagulation inhibitors should be carefully studied before its use in septic patients is recommended.
Animals↗
Angioedema responding to antiprotease treatment but without abnormalities of the complement system.
Four patients suffered from chronic or recurrent angioedema, of sudden onset in adult life, associated with visceral pain and impossible to control by dietary means. In spite of normal complement function they respond very well to tranexamic acid therapy. Antiprotease drugs need not be restricted to cases of ClsINH deficiency.
Adult↗
Complement C4 monitoring in the follow-up of chronic hepatitis C treatment.
The overall role of complement in the host--pathogen relationship is now well understood. However, its involvement at a chronic stage of infection, such as chronic hepatitis C, is less well documented. Here, results are reported which point to the use of specific C4 monitoring in the follow-up of HCV patients. This study concerns 66 patients with chronic HCV infection, treated with interferon alpha 2b alone or with interferon alpha 2b + ribavirin, and 50 healthy adults as controls. Complement blood tests were performed to measure C1q, C3, C4, mannan binding lectin (MBL), C1s-C1 inhibitor complexes, total (CH50) and C4 (C4H) haemolytic activity; specific C4 activity was taken as the C4H/C4 protein ratio. Rheumatoid factor (RF) levels were also measured. A significant reduction in CH50 and specific C4 activity in HCV patients, compared with the healthy controls, was observed before the onset of treatment; the other parameters were not affected and no C1s-C1 inhibitor complexes were detected. At the same time, a significant reduction in specific C4 activity was observed in relapsers compared with sustained responders. These results point to a potential predictive function of C4 specific activity to monitor the response to therapy. Restoration of specific C4 activity at 6 months was better in responders than in non-responders. Complement activation in chronic hepatitis C does not seem to involve the C1 stage of the classical pathway. A negative correlation between specific C4 activity and RF titres suggests a possible involvement of RF in C4 activation, via the lectin pathway. Specific C4 monitoring appears to be a valuable tool for the follow-up of chronic hepatitis C treatment, together with the other conventional investigations.
Adult↗
Molecular basis for the deficiency of complement 1 inhibitor in type I hereditary angioneurotic edema.
Hereditary angioneurotic edema (HANE) results from deficiency of complement 1 inhibitor (C1 INH). In type I HANE, C1 INH is present in serum at levels 5-30% of normals. Using cultured monocytes and biosynthetic labeling of proteins, C1 INH was detected in supernatants of cells from HANE patients at levels 20% of those detected in normals. The intracellular reduction of C1 INH in patients' monocytes approached 50%. The study of C1 INH messenger RNA (mRNA) by Northern blot analysis indicated that in HANE patients' monocytes a message of normal size is present at about half the concentration of that from normal cells. One of the patients analyzed showed the presence of a genetically inherited abnormal mRNA (1.9 kb) in addition to the normal mRNA (2.1 kb). Southern blot analysis of DNA from peripheral blood leukocytes did not show any difference in quantity or in sizes of endonuclease restriction fragments between patients and normals. The defect(s), therefore, in type I HANE is pretranslational, but is not due to a deletion or to a major chromosomal rearrangement.
Angioedema↗
In vivo study of the complement system during infusion of radiographic contrast media.
It has been claimed that activation of the complement system may play a role in reaction to radiographic contrast media (RCM) infusion. In order to clarify the effects of RCM on the complement system, three different parameters (CH50, C3a, and C1 inhibitor) were measured in 20 patients undergoing intravenous pyelography for diagnostic purposes. We found no significant changes in C3a levels, but CH50 and C1 inhibitor fell significantly at the different sampling times; however, the decreases lost significance when the data were corrected for hemodilution with the total protein content of each sample as a reference. We conclude that RCM infusion does not activate the complement system.
Complement Activation↗
[Physiologic inhibitors of blood coagulation. 2. Alpha 2-macroglobulin, alpha-antitrypsin and the C1 inhibitor of complement].
Three physiological inhibitors of blood coagulation - alpha-2-macroglobulin, alpha-1-antitrypsin, and C-1-inhibitor of complement - are dealt with in a brief survey. The point is that these are proteins of the organism with a defence character which are also able to inhibit an extraordinarily broad spectrum of proteases. Some recent findings about their molecular structure, manner of response, and inhibitory spectrum are represented. Comparisons are made to corresponding proteins in mammals, in alpha-2-macroglobulin and even in lower vertebrates. Moreover, the inherited deficiency of these three inhibitors are represented with respect to human diseases and changes of their blood level in the course of various diseases are referred to.
Animals↗
In vivo pharmacokinetics of calreticulin S-domain, an inhibitor of the classical complement pathway.
Inhibition of the complement system is potentially therapeutic in diseases where uncontrolled or overshooting complement activation plays a significant role in the pathogenesis of the disorder. Calreticulin (CRT) is a multifunctional protein whose cell-surface form (ectocalreticulin) is reported to be a C1q receptor. A 124-residue domain within CRT, the S-domain, binds to C1q, prevents the formation of C1 and so inhibits activation of the classical pathway. To assess the usefulness of CRT S-domain as a complement inhibitor, recombinant S-domain was expressed, radiolabeled, and the fate of the radiolabeled peptide followed in vivo. In rats, CRT-S-domain shows a half-life of 1.21 +/- 0.34 and 40.5 +/- 2.7 min in the distribution and elimination phases from plasma, respectively. The peptide remains largely intact, and is cleared from the circulation by the kidneys, where it accumulates in the proximal convoluted tubules, but is not excreted. Much smaller amounts of the peptide accumulate in other tissues, and essentially none crosses the blood-brain barrier.
Animals↗
C1 esterase inhibitor transfusions in patients with hereditary angioedema.
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Angioedema↗