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PubMed1981

Identification of classical anaphylatoxin as the des-Arg form of the C5a molecule: evidence of a modulator role for the oligosaccharide unit in human des-Arg74-C5a.

A functionally active and potentially lethal fragment of the fifth component of complement (C5) is generated during complement activation in serum from animals of various species. This factor, termed the "classical" anaphylatoxin, was isolated from porcine serum and was identified chemically as the des-Arg derivative of the well-characterized C5a molecule. Unlike the C3a and C4a anaphylatoxins, porcine C5a does not require the COOH-terminal arginyl residue for spasmogenic activity. Further degradation of porcine des-Arg(74)-C5a by carboxypeptidase Y removed glycine-73 and leucine-72 and decreased the intrinsic spasmogenic activity by >90%. Hence, we conclude that, although the arginyl residue is not essential, the COOH-terminal sequence Leu-Gly-Arg contributes structural information that accounts for >90% of C5a activity. Human des-Arg(74)-C5a, like its porcine counterpart, has instrinsic anaphylatoxin activity; however, higher concentrations were needed to contract the guinea pig ileal tissue (i.e., 1 muM for human des-Arg(74)-C5a versus 1 nM for porcine des-Arg(74)-C5a). Furthermore, the des-Arg form of human C5a was only 0.1% as active as porcine des-Arg(74)-C5a for enhancing vascular permeability in guinea pig skin. In addition to these biological differences, numerous chemical differences exist between the human and porcine des-Arg(74)-C5a molecules, the most prominent feature being an oligosaccharide entity associated uniquely with the human C5a. When the oligosaccharide unit of human des-Arg(74)-C5a was removed by glycosidases, leaving a single glucosamine residue attached to the side chain of asparagine-64, activity was enhanced. The human des-Arg(74)-C5a molecule devoid of the complex oligosaccharide unit exhibited 10-fold stronger spasmogenic activity and 20- to 50-fold greater permeability-enhancing activity than did human des-Arg(74)-C5a containing the oligosaccharide. Consequently, the oligosaccharide associated with human C5a modulates or suppresses potentially harmful activities of this anaphylatoxin. The relatively high levels of spasmogenic activity associated with porcine des-Arg(74)-C5a indicate that this factor is poorly controlled by endogenous serum carboxypeptidase, whereas human C5a is virtually inactivated by the enzyme. Hence, the influence of this oligosaccharide in suppressing human des-Arg(74)-C5a activity is of major physiologic importance in protecting man from potentially toxic effects of this complement factor.

Amino Acid Sequence↗
PubMed1992

Localization and characterization of human salivary kininases.

The human saliva of normal subjects containing large amounts of basic carboxypeptidase produces decarboxylated non inflammatory peptides, for instance, kinins and anaphilotoxins C3a, C4a and C5a. A reduction of epithelial cell-bonded enzyme (carboxypeptidase M-type or kininase I), produces inflammations by the active intact kinins and the initiation of the alternative activating pathway of complement by active anaphilotoxins, which generate complement cleavage products, containing potential destructive mechanism.

Complement System Proteins↗
PubMed1988

Quantitative analyses of the relationship between C3 consumption, C3b capture, and immune adherence of complement-fixing antibody/DNA immune complexes.

We have studied the turnover of the third component of C (C3) and capture of the major cleavage fragment of C3 produced during C activation (C3b) that occurs when soluble antibody/DNA immune complexes (IC) active C. We used the Amersham RIA kit for the minor cleavage fragment of C3 produced during C activation (C3a), and a new assay utilizing mAb to C3b to measure the fraction of active C3 in a C source after the IC activate C. These mAb, along with a mAb to human IgG, allowed us to measure IC stoichiometries. The efficiency of C3 turnover by the IC is quite high, and under conditions of Ab excess, the maximum number of IgG bound per dsDNA corresponds to 1 IgG/20 to 30 base pairs. The maximum number of C3b found in the IC corresponds to less than 1 C3b/IgG, and the vast majority of the captured C3b is bound to the IgG, and not to the DNA. We identified several IC that consumed large amounts of C3, and captured large amounts of C3b, but did not bind to human E via C3b receptors (C receptor type 1). This finding suggests that the ability of IC to bind to human E depends upon the number and distribution of captured C3b molecules and the conformation and size of the DNA Ag, which reflects the need for multivalent binding between several properly arrayed C3b and a "cluster" of C receptor type 1 on the human E membrane. IC that activate C3 but do not bind to E would presumably "escape" the E IC clearance mechanism, but could deposit in susceptible organs and tissues and play a role in the pathogenesis of SLE because of their potential to generate the inflammatory products of C activation.

Antigen-Antibody Complex↗
PubMed1993

[Evaluation of antimicrobial system of polymorphonuclear leukocytes and opsonic activity in patients with congenital biliary atresia].

Postoperative ascending cholangitis (AC) is a serious problem in patients with biliary atresia (BA). It was reported that this complication was due to impaired functions of polymorphonuclear leukocytes (PMNs). We investigated the oxygen-dependent bactericidal activities including the ability to generate O2-, Myeloperoxidase (MPO) activity and opsonic activity using chemiluminescence method. The serum complement level and fibronectin level were also examined. O2- generating ability was 30.7 +/- 4.5 x 10(4) counts/min (cpm) in BA and 37.4 +/- 4.4 x 10(4) cpm in controls (p < 0.01). There was a significant difference in serum C4 between these two groups. No difference was found in opsonic activity, MPO activity, C3A, C3 and fibronectin. The O2- generating ability of the PMNs in BA was decreased but the opsonic and MPO activity were not depressed. From these results it is suggested that the frequent occurrence of AC in BA is not caused by low opsonic activity but may be associated with decreased O2- generation. Because of low C4 concentration, activation of classical pathway may also be impaired in BA.

Biliary Atresia↗
PubMed1986

Treatment of cancer ascites by intraperitoneal administration of a streptococcal preparation OK-432 with fresh human complement--role of complement-derived chemotactic factor to neutrophils.

The role of complement in the polymorphonuclear leukocyte (PMN)-mediated tumor cell destruction in cancer ascites was investigated in relation to a streptococcal preparation OK-432, a so-called biological response modifier. Incubation of OK-432 with fresh human serum at 37 degrees C for 60 min resulted in the generation of C3a and C5a chemotactic factors. Intraperitoneal (i.p.) injection of the mixture to a patient with cancer ascites revealed an accumulation of PMNs in the ascitic fluid for a longer period with a rapid reduction of the ascitic fluid, than an intraperitoneal injection of OK-432 alone examined in the same patient. PMNs were found to invade clusters of the tumor cells and then form rosettes followed by the destruction of tumor cells. These findings induced by OK-432 continued over 10 days in the presence of fresh serum, while diminished within 3-4 days when OK-432 alone was injected. When fresh human plasma or fresh frozen plasma was used instead of serum and i.p. injected with OK-432 avoiding preincubation, the same cytological and clinical changes were observed in other patients. These data strongly indicate that OK-432 activates human complement either in vitro or in the peritoneal cavity, and induces PMNs to accumulate in the ascitic fluid. Although the mechanism of killing of tumor cells by PMNs is obscure, addition of human serum or plasma to i.p. use of OK-432 seems to be valuable for the management of patients with malignant ascites.

Ascites↗
PubMed1988

Acute pulmonary vasoconstriction and thromboxane release during protamine reversal of heparin anticoagulation in awake sheep. Evidence for the role of reactive oxygen metabolites following nonimmunological complement activation.

When protamine (2 mg/kg) was injected intravenously into awake sheep 5 minutes after infusing heparin (200 units/kg), there was transient diffuse pulmonary vasoconstriction with mean pulmonary arterial pressure increasing from 18.0 +/- 0.7 to 43.8 +/- 2.7 mm Hg at 1 minute (x +/- SEM; n = 10). In addition, there was profound leukopenia (36.9 +/- 7.7% of baseline values at 2 minutes) with transpulmonary leukocyte sequestration and transiently elevated plasma concentrations of C3a (from 420 +/- 146 to 1,599 +/- 249 ng/ml; n = 3, p less than 0.01) and thromboxane B2 (from 0.30 +/- 0.05 to 6.3 +/- 2.8 ng/ml; n = 10, p less than 0.0001), without significant increases of plasma 6-keto-prostaglandin F1 alpha, prostaglandin F2 alpha, leukotrienes, or histamine. Intravenous injection of protamine alone produced no hemodynamic effects and did not increase plasma levels of vasoconstrictor eicosanoids. Intravenous pretreatment with either a cyclooxygenase inhibitor or a hydrogen peroxide scavenger (dimethylthiourea) blocked both the increases of thromboxane levels and the pulmonary vasoconstriction.

Animals↗
PubMed1989

Plasma concentrations of complement-activation complexes correlate with disease activity in patients diagnosed with isolated central nervous system vasculitis.

Isolated central nervous system (CNS) vasculitis is rare medium- sized vessel disease limited to intracerebral vessels. The two most common symptoms of this inflammatory disorder observed at entry to a hospital are headaches and mild memory deficits. Further progression of this disease may result in focal neurologic alterations and seizures. Currently, the most common laboratory abnormality noted is an elevated erythrocyte sedimentation rate. The complement (C) system is known to play a role in many inflammatory processes; it may also be involved in CNS vasculitis. In this longitudinal study of patients with CNS vasculitis, we detected C activation by highly sensitive and specific assays that are capable of identifying breakdown products formed after C activation: C3a des arg, C4a des arg, C5a des arg, C1rC1s-C1-inhibitor complex, and terminal C complex (C5b-9). We present two cases of documented CNS vasculitis in which serial measurements of these C-activation products correlate with disease activity. Our results indicate that a temporal association exists between C activation and the clinical presentation of CNS vasculitis. We conclude that physicians should monitor C-activation by-products in plasma when they attempt to follow the clinical course of CNS vasculitis.

Adult↗
PubMed1998

Adsorption of anaphylatoxins from the plasma of systemic lupus erythematosus patients using dextran sulfate cellulose columns.

Complement-derived anaphylatoxin may be one of the causes of vascular injury and an indicator of activity in systemic lupus erythematosus (SLE). The present study examines the effectiveness of dextran sulfate (DS) column immunoadsorption treatment to remove anaphylatoxins (C3a, C4a, and C5a) from the blood of patients with SLE. Seven SLE patients were subjected to immunoadsorption using DS-bound cellulose columns (Selesorb, Kaneka). Blood samples were taken both before and after the immunoadsorption session. Specimens were also obtained from both the inlets and outlets of the DS columns every 1,000 ml of treated plasma volume. The DS columns removed anaphylatoxins C3a and C4a from the separated plasma (from 775+/-334 ng/ml to 640+/-252 ng/ml, and from 1,303+/-847 ng/ml to 619+/-578 ng/ml, respectively) during the clinical anti-DNA apheresis procedure. In these study, the C5a levels in the circulating plasma of SLE patients were not elevated. To confirm whether DS-bound cellulose beads adsorbs anaphylatoxins in vitro, zymosan-activated plasma (ZAP) containing high levels of anaphylatoxins was incubated with DS-bound cellulose beads. The levels of C3a, C4a and C5a in the ZAP significantly decreased by mixing with DS-bound cellulose beads (P<0.05). Nevertheless, C3a and C4a in the peripheral blood were not significantly decreased after the immunoadsorption, suggesting that these anaphylatoxins bypass the DS columns in apheresis and return to the patient via the cell-rich fraction.

Adult↗
PubMed1980

Effects of histamine on monocyte complement production. I. Inhibition of C2 production mediated by its action on H2 receptors.

Histamine produced dose-dependent inhibition of the production of the second complement component (C2) by monocytes in tissue culture. The effect was not associated with either cell death, as ascertained by trypan blue exclusion, or loss of cells from the monolayer, as determined by measuring their DNA content. The specificity of the response was shown by the failure of histidine or histamine metabolites to inhibit C2 production. Preincubation of histamine with histaminase also abrogated the histamine effect. The kinetics of the effect were extremely rapid and irreversible, most of the reduction being achieved during a 5-min exposure to histamine. The H2 receptor antagonist cimetidine was able to prevent the histamine response, whereas chlorpheniramine, the H1 receptor antagonist, had no effect. Dimaprit and 4-methyl histamine, H2 receptor agonists, simulated the effect of histamine whereas the H1 receptor agonist 2-(2-aminoethylthiazole) was ineffective, confirming that the effect of histamine on C2 production by monocytes is mediated by the H2 receptors. Thus histamine, released from basophils or mast cells by the C3 and C5 cleavage products C3a and C5a respectively, may exert a negative feedback on further C3 and C5 cleavage by limiting the formation of the C3 (C42) and C5 (C423b) convertases.

Cells, Cultured↗
PubMed1988

Synergism between zymosan-activated serum and heparin in the induction of polymorphonuclear leukocyte aggregation.

During the course of extracorporeal circulation, leukocyte aggregation is known to occur in some patients. This is attributed to complement activation and release of the chemotactic factor C5a. We investigated the effect of heparin on in vitro complement induced aggregation of polymorphonuclear leukocytes (PMNAGG), since most patients undergo heparinization during the extracorporeal circulation. Our results indicate that sub-aggregating concentrations of zymosan-activated serum (ZAS) enhance heparin-induced PMNAGG and that sub-aggregating amounts of heparin increase the aggregation induced by ZAS. Heat inactivation of the serum prior to zymosan activation abrogated the aggregating activity of the ZAS. Furthermore, the combined ZAS and heparin-induced PMNAGG was partially inhibited by specific antibodies to C5a but not to C3a. Therefore, we suggest that heparin and C5a may have a synergistic effect on the aggregation of polymorphonuclear leukocytes. These data might be relevant to situations in which patients are subjected to extracorporeal circulation.

Cell Aggregation↗
PubMed1983

Inhibition of neutrophil function by fluid phase C3b of complement.

A high-molecular-weight fragment of C3 was isolated from normal human serum by column chromatography, was generated by incubation of serum at 37 degrees C with inulin, and was produced from highly purified C3 by limited digestion with trypsin. This product was shown to inhibit the antibacterial function of neutrophils by using Escherichia coli O75 as the main test organism. The inhibitor reacted with anti-C3b and anti-C3c, but not with anti-C3B (anti-native C3) or anti-C3a. The manner of preparation of the inhibitor, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern, and the amino acid composition of the inhibitor indicated that it was fluid phase C3b. The inhibitor of neutrophil function (fluid phase C3b) was shown to bind to C3b receptors or acceptors on sheep erythrocytes in a model system.

Amino Acids↗
PubMed1998

Comparative complement activation study of polypropylene hollow fibres of two different makes in static condition.

The complement activation is one of the major problems encountered in the use of extracorporeal devices. The complement-activating potential of two polypropylene hollow fibres (used in membrane oxygenator) of different make and designated as F1 and F2 was tested with time (10, 30, and 180 minutes). The fibres were brought in contact with human blood under in vitro static condition for the comparison. A direct measurement of unadsorbed concentration of the complement protein, C3, present in the liquid phase of human blood before and after the contact with polymer was made using human C3 antisera. This gave a measure of C3 adsorption on the fibres with time and probably also gave an indirect measure of C3a in the blood. IgG was also estimated using antisera of human IgG. The total protein and albumin concentration were measured to obtain an overall adsorption profile of these protein on the fibre surfaces with respect to time. The results showed that C3 adsorption was taking place mainly through the alternative pathway over and above the classical one, being more in the case of F2 than F1. SEM studies revealed poor adhesion of platelets on both fibres, though some activated platelets were also seen with slight deformation at 10 minutes and a few with prominent pseudopodia formations at a later time period on the surface of both fibres. The total protein adsorption was faster, and the surface pores of the F1 were found masked at 10 minutes observation. Later, desorption occurred making the pores visible at 180 minutes. The F2 surface examination showed a continuous deposition of protein layers with time, thereby masking the pores at 180 minutes. The present experimental finding and assessment favoured the F1 as a marginally better candidate to be considered for oxygenator development.

Adsorption↗
PubMed1996

Changes in platelet, granulocyte, and complement activation during cardiopulmonary bypass using heparin-coated equipment.

The effects of heparin-coated cardiopulmonary bypass (CPB) systems on platelet, granulocyte, and complement activation were investigated during cardiopulmonary bypass. Thirty patients underwent coronary artery bypass surgery with a heparin-coated (Carmeda Bio-Active Surface, CBAS, Medtronic, U.S.A.) CPB system (HC group, n = 10), a heparin-coated oxygenator and uncoated CPB circuit (HO group, n = 10), or an uncoated system (UC group, n = 10). In the HO group, plasma C3a (1667 +/- 632 ng/ml) and C4a (1088 +/- 319 ng/ml) concentrations were significantly (p < 0.05) lower than in the UC group (2846 +/- 1045 ng/ml and 1494 +/- 480 ng/ml, respectively) 10 min after the administration of protamine, but there were no significant differences in the platelet or granulocyte counts. In the HC group, granulocyte elastase concentrations 120 min after the onset of CPB (365 +/- 177 micrograms/L) and 10 min after the administration of protamine (676 +/- 314 micrograms/L) were significantly (p < 0.05) lower than in the other 2 groups (820 +/- 341 and 893 +/- 303 micrograms/L and 1365 +/- 595 and 1,258 +/- 622 micrograms/L). In addition, the increase in the plasma C3a concentration in the HC group 60 (p < 0.05) and 120 min after the onset of CPB (p < 0.05) was significantly less than in the other 2 groups. The C3a and C4a concentrations 10 min after the administration of protamine were significantly (p < 0.005 and p < 0.05) less in the HC group than in the UC group. Platelet counts 10 min after the administration of protamine were significantly higher (p < 0.05) and plasma beta-thromboglobulin concentrations during CPB were significantly lower in the HC group than in the other 2 groups 5 (p < 0.05), 60, and 120 min (p < 0.005) after the onset of CPB. Postoperative blood loss during the first 12 h in the HC group was significantly (p < 0.05) less than that in the UC group. The heparin-coated oxygenator and uncoated CPB circuit reduced complement activation but demonstrated no significant effects on the platelet and granulocyte systems. However, the heparin-coated CPB circuit (with all components making blood contact) reduced platelet, granulocyte, and complement activation and significantly reduced postoperative blood loss. Therefore, heparin coating of CPB systems improves biocompatibility.

Adult↗
PubMed1979

Uptake of 125I-labelled C3a by cultured human endothelial cells.

The interactions of C3a anaphylatoxin with vascular endothelium were studied in vitro using human endothelial cells in culture and 125I-labelled human C3a. Cultured endothelial cells took up 125I-C3a in a time- and concentration-dependent manner and inactivated it. Uptake was not associated with binding to specific receptors since the amount of radioactivity accumulated by the cells was not influenced by treatment with excess unlabelled peptide, metabolic inhibitors or by low temperature. Further, we observed that uptake was not saturated during 90 min of incubation or within the concentration range of C3a tested (10(-9)--10(-6) M). C3a was taken up more rapidly than other labelled, less basic compounds, including Tyr5-bradykinin, lysozyme and albumin. Examination of the cells by autoradiographic electron microscopy revealed labelled material within the cell cysoplasm but not within specific intracellular structures, such as vesicles or vacuoles. C3a was partially inactivated after incubation with endothelial cells for 15 min, but some spasmogenic activity was retained even after 90 min incubation. Since the peptide is readily inactivated by the cells, the radioactivity in the cytoplasm may be inactive C3a and possibly C3a fragments. The combination of uptake and inactivation of C3a by endothelial cells may be an effective means of removing the peptide from circulation.

Anaphylatoxins↗
PubMed1984

Regulation of neutrophil migratory function in burn injury by complement activation products.

Polymorphonuclear neutrophils were isolated from patients with burn injury and random mobility, chemotaxis in response to C5adesArg (as agarose-activated control serum) and to N-formyl-methionyl-leucyl-phenylalanine (F-Met-Leu-Phe) were assessed. For a group of eight patients identified as not experiencing systemic infection, all three neutrophil migratory functions were observed to fall below control levels, beginning 4 to 6 days following burn injury, and to return to control levels after 21 to 30 days of hospitalization. Over this time the chemotactic differential (distance chemotactic migration-distance random migration) for F-Met-Leu-Phe remained positive, while the chemotactic differential for activated serum became nil after postburn day 4. This temporal, specific loss of a chemotactic response to activated serum was associated with rises in immunoreactive plasma C3a and C5a. This pattern of loss of chemotactic function was associated with a selective loss of C5a but not F-Met-Leu-Phe binding activity. These results demonstrate that burn injury can alter neutrophil migratory functions generally, and specifically depress chemotactic responsiveness to activated serum. The mechanism of the latter phenomenon appears to be related to desensitization of circulating neutrophils to C5a due to complement activation.

Adolescent↗
PubMed1992

Activation of complement components C3 and C5 by a cysteine proteinase (gingipain-1) from Porphyromonas (Bacteroides) gingivalis.

Complement components C3 and C5 are susceptible to limited proteolysis by an arginine-specific cysteine proteinase isolated from Porphyromonas gingivalis. This bacterium is an anaerobe commonly associated with severe periodontal disease. Infection by P. gingivalis is accompanied by an acute inflammatory response, complete with extensive neutrophil involvement. This prompted us to investigate a possible direct role for complement in periodontitis evoked by P. gingivalis. Exposure of C3 and C5 to the cysteine proteinase at molar ratios between 1:25 and 1:100 (enzyme to substrate ratios) resulted in a time-dependent, limited degradation of each component. C3 was converted in a stepwise manner to C3a-like and C3b-like fragments with evidence of extensive further degradation of the C3a-like portion of the molecule. We were unable to demonstrate C3a activity in the C3 digestion mixtures. C3 degradation appears to involve primarily the alpha-chain. Proteolysis of C5 also progresses in a stepwise manner producing an initial internal cleavage of the alpha-chain to generate 30- and 86-kDa fragments. Further digestion of the 86-kDa amino-terminal fragment of the alpha-chain leads to the release of C5a or a C5a-like fragment that is biologically active for neutrophil activation. The fact that a potent chemotactic factor, i.e. C5a, can be generated from C5 by a proteinase derived from P. gingivalis suggests a recruiting mechanism for attracting neutrophils to the gingival lesion site in periodontal disease.

Adhesins, Bacterial↗