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PubMed1995

Limitation of reperfusion injury by a monoclonal antibody to C5a during myocardial infarction in pigs.

The complement system has been implicated in reperfusion injury during acute myocardial infarction. We therefore attempted to reduce reperfusion injury with a monoclonal antibody (MAb) to the complement component, C5a. In 13 control pigs and 9 pigs pretreated with this MAb, ischemia was induced by a 50-min occlusion of the left anterior descending coronary artery, followed by 3 h of reperfusion. Infarct area (as percent of risk area) was reduced from 58 +/- 5% in controls to 38 +/- 7% (P < 0.05) in MAb-treated animals. Heart rate-systolic blood pressure product, left ventricular (LV) first derivative of pressure, LV end-diastolic pressure, and coronary blood flow were similar (P > 0.05) in the two groups. At 15 min of reperfusion, immunoreactive factor Bb began to increase significantly (P < 0.05) in regional coronary venous plasma, consistent with activation of the alternative complement pathway. The anti-C5a MAb did not attenuate formation of the membrane attack complex (C5b-9) as assessed by a hemolytic complement assay. Myocardial myeloperoxidase activity, a marker of tissue neutrophil concentration, was similar in the risk regions of the two groups, suggesting that neutrophil infiltration was unaltered by the MAb. However, in vitro the MAb (15 and 30 micrograms/ml) reduced C5a-stimulated neutrophil aggregation (67.4 and 70.9%), chemotaxis (52.5 and 81.4%), degranulation (66.7 and 75.8%), and superoxide generation (26.7 and 100%). In conclusion, myocardial infarction-reperfusion is associated with activation of the alternative complement pathway. Furthermore, a MAb to C5a that inhibits neutrophil cytotoxic activity, but neither the membrane attack complex nor myocardial neutrophil accumulation, decreases infarct size in pigs. These data suggest an important role of the alternative complement pathway and C5a in the propagation of ischemia cardiac damage during reperfusion.

Animals↗
PubMed1995

Binding of Gc globulin (vitamin D binding protein) to C5a or C5a des Arg is not necessary for co-chemotactic activity.

Gc globulin (vitamin D binding protein) has been shown to augment significantly the leukocyte chemotactic activity of the activated complement peptides C5a and C5a des Arg. However, the mechanism of chemotaxis enhancement is not known. Natural C5-derived peptides contain a carbohydrate side chain that comprises approximately 25% of the mass of the 11-kDa peptides. Previous studies have demonstrated that Gc globulin binds to C5-derived peptides via sialic acid residues on this carbohydrate side chain. The necessity of this carbohydrate side chain for chemotaxis enhancement by Gc globulin was investigated by using both natural (glycosylated) and recombinant (carbohydrate-free) peptides. The dose-response curves of neutrophil chemotaxis to recombinant C5a or C5a des Arg plus Gc globulin were identical to those observed with the naturally derived peptides, despite the fact that natural C5a bound to Gc globulin while the recombinant C5a failed to bind this protein. Moreover, neutrophils pretreated with Gc globulin then washed before addition to the chemotaxis assay displayed significantly enhanced movement to C5a alone. These results indicate that the binding of C5a/C5a des Arg to Gc globulin is not necessary for their chemotactic activity to be augmented. Furthermore, these results demonstrate that the co-chemotactic activity of Gc globulin is generated on the cell surface, independent of C5a binding to its receptor.

Chemotaxis, Leukocyte↗
PubMed1988

Human C5a and C5a des Arg exhibit chemotactic activity for fibroblasts.

C5a and C5a des Arg are chemotactic factors for inflammatory cells but it is not known whether these agents are chemoattractants for fibroblasts. Accordingly, C5a, purified from zymosan-activated human, and C5a des Arg, prepared by incubating C5a with immobilized porcine carboxypeptidase B, were studied for fibroblast chemotactic activity. We observed that both C5a and C5a des Arg stimulated human skin fibroblasts and fetal bovine ligament fibroblasts to migrate in a concentration-dependent fashion, and that the migratory responses were similar in magnitude to the responses achieved with optimal concentrations of two known fibroblast chemoattractants, platelet-derived growth factor and human fibrinopeptide B. The peak responses to C5a and C5a des Arg occurred at approximately 10(-9)M. With ligament fibroblasts, there was a greater response to C5a des Arg than to C5a, but with human fibroblasts there was no difference. Cochemotaxin, which enhances the chemotactic activity of C5a des Arg for neutrophils, had no effect on C5a des Arg fibroblast chemotactic activity but appeared to increase the fibroblast chemotactic activity of C5a. These results indicate that the effects of C5a and C5a des Arg in vivo may extend to the recruitment of mesenchymal cells. Moreover, the findings represent another example of an activity retained by C5a after removal of its carboxyl terminal arginine.

Antibodies↗
PubMed1987

Rapid and simple measurement of human C5a-des-Arg level in plasma or serum using monoclonal antibodies.

A new sandwich immunoassay method for measuring human C5a-des-Arg was developed using monoclonal antibody specifically reactive with C5a-des-Arg. Monoclonal antibodies were obtained from a panel of hybridomas produced by fusion of mouse myeloma cells, P3 X 63-AG8,653, with spleen cells from a CBF1(C57BL/6 X BALB/c) mouse immunized with purified C5a. The reactivities of these monoclonal antibodies against C5a, C5a-des-Arg and C5 were tested by solid-phase radioimmunoassay. One of the antibodies reacted with C5a-des-Arg, but not with C5a and C5. By use of this antibody for capturing antibody in sandwich immunoassay, a rapid and simple method was developed for measuring C5a-des-Arg without previous removal of C5. The sensitivity of this assay system was approximately 1 ng/ml for C5a-des-Arg.

Animals↗
PubMed1976

Induction of platelet aggregation by the complement-derived peptides C3a and C5a.

The effect of two complement-derived peptides, hog serum C3a and C5a, on platelet aggregation in platelet-rich plasma and suspensions in Tyrode solution was investigated. 1. Guinea-pig platelets were aggregated by both C3a and C5a; the spasmogenically inactive product of C3a, C3ai, also induced aggregation. Threshold concentrations were in the range of 10(-6)--10(-9) M depending on the peptide and platelet preparation. 2. Cat platelets were aggregated by C5a (threshold concentrations 10(-7)--10(-8) M) but not by C3a. 3. Platelets from pig, rabbit and man were not aggregated by either of the two peptides in concentrations of up to 5 X 10(-6) M. 4. When C5a was administered repeatedly in subthreshold doses guinea-pig platelets became tachyphylactic to C5a but were still aggregable by C3a or ADP. Conversely, platelets desensitized to C3a still reacted to C5a or ADP. Tachyphylaxis towards C5a developed also when platelets were incubated with C5a in the absence of free Ca2+ under which condition they do not react. The tachyphylaxis in this case became evident after recalcification of the medium. The lack of cross-desensitization indicates that C3a and C5a react via different receptors. 5. C3a and C5a were injected i.v. into guinea pigs. Histological examination of the lungs revealed that some of the smaller vessels (20-30 mu in diameter) were occluded by platelet aggregates. In addition signs of severe acute emphysema were seen in animals treated with C5a, but only slight emphysema in C3a-treated animals. Intravenous injections of C3a into guinea pigs caused but weak respiratory distress and drowsiness and never killed an animal (at doses of up to 20 mg per kg body weight), whereas C5a caused the well-known severe respiratory failure and death already at doses of 0.03 mg/kg body weight.

Anaphylatoxins↗
PubMed1991

FUT-175 as a potent inhibitor of C5/C3 convertase activity for production of C5a and C3a.

We examined the inhibitory effect of FUT-175 on the C3/C5 convertase activity of the cobra venom factor-derived enzyme CVF,Bb by measuring C5b6-mediated reactive lysis of unsensitized guinea pig erythrocytes and by measuring directly the released fragments C3-des-Arg and C5a-des-Arg. In this study, we showed that the concentration of 4.5 X 10(-6) M of FUT-175 caused 50% inhibition of C5 convertase activity of CVF,Bb in reactive hemolysis assays, and that 4.0 X 10(-6) M FUT-175 caused 50% inhibition of the production of C3a and C5a generated by the C3/C5 convertase activity of CVF,Bb.

Animals↗
PubMed1986

Chemotactic peptides modulate adherence of human polymorphonuclear leukocytes to monolayers of cultured endothelial cells.

We have used a new centrifugation assay to examine the effects of highly purified human C5a and C5a des Arg, as well as effects of N-formyl-methionyl-leucyl-phenylalanine (FMLP), on both the extent and strength of human polymorphonuclear leukocyte (PMN) adherence to monolayers of cultured human umbilical vein endothelial cells. At concentrations that were chemotactic for PMN, C5a (0.1 nM), C5a des Arg (5.0 nM), and FMLP (1.0 nM) significantly reduced the percentage of PMN that adhered to endothelial monolayers. Adherence also was reduced by C5a des Arg that was generated by incubating (37 degrees C, 30 min) fresh human serum with either zymosan or purified C5a. High concentrations of C5a (greater than 1.0 nM) and FMLP (greater than 50 nM) that diminished PMN chemotaxis significantly enhanced the percentage of PMN that adhered tightly to endothelial cells (adherent cells resisted a dislodgment force of 1200 X G). Tight adherence of PMN to endothelial cells also was increased by high concentrations of C5a that were added to human serum in which carboxypeptidase N activity was destroyed by heating (56 degrees C, 30 min), and by C5a that was generated by incubating (37 degrees C, 30 min) fresh human serum with zymosan in the presence of the carboxypeptidase N inhibitor, epsilon-aminocaproic acid. High concentrations of C5a des Arg (up to 80 nM) neither enhanced adherence of PMN to endothelial cells nor decreased PMN migration. Thus, a reciprocal relation exists between PMN migration and PMN adherence to endothelial cells in response to chemotactic factors. At concentrations that are chemotactic for human PMN, C5-derived peptides and FMLP reduce the adherence of PMN to endothelial monolayers. Only at concentrations that decrease PMN migration do C5a and FMLP augment PMN adherence.

Adult↗
PubMed1994

Inactivation of human anaphylatoxin C5a and C5a des-Arg through cleavage by the plasminogen activator activity of a human fibrosarcoma cell line.

The HT-1080 human fibrosarcoma cell line exhibited a plasminogen-dependent ability to inactivate recombinant anaphylatoxin C5a or zymosan-activated serum. The inactivation was obtained at physiological levels of both plasminogen (2 microM) and C5a (1-5 nM). Inactivated C5a and zymosan-activated serum were no longer able to induce chemotaxis and degranulation of neutrophils. Inactivation of C5a paralleled the emergence of plasmin activity, assayed by cleavage of the synthetic substrate H-D-valyl-L-leucyl-L-lysine-p-nitroanilide (S-2251). Both C5a inactivation and S-2251 cleavage were inhibited by the plasmin inhibitor alpha 2-antiplasmin, the urokinase inhibitor amiloride, and by anti-urokinase antibodies. In a cell-free system, inactivation of C5a was shown to depend on the simultaneous presence of urokinase and plasminogen and was inhibited by alpha 2-antiplasmin and by anti-urokinase antibodies. SDS-polyacrylamide electrophoresis demonstrated the cleavage of C5a by the plasminogen activation system and inhibition of the cleavage by amiloride. Amino acid sequencing of the band corresponding to the C5a degradation product revealed that C5a was cleaved at positions Lys14-His15 and Arg40-Ile41; cleavage at position Arg40-Ile41 seemed to be responsible for the loss of activity. Since neoplastic cells extensively produce and exhibit plasminogen activator activity, the present observations suggest that plasminogen activation may, by inactivation of C5a, reduce the anti-tumor immune response and support the immunological escape phenomenon of tumors.

Amino Acid Sequence↗
PubMed1986

Anaphylatoxin C5a generation and dialysis-induced leukopenia with different hemodialyzer membranes.

Leukocyte counts and plasma C5a anaphylatoxin levels were studied during hemodialysis in patients using Cuprophan, polycarbonate and polyacrylonitrile membrane dialyzers. Cuprophan induced a marked leukopenia with significant plasma C5a generation. Polycarbonate promoted the same trend of changes in both parameters but significantly less pronounced, while polyacrylonitrile did not affect leukocyte counts nor plasma C5a levels. These data suggest that complement-derived C5a generation may be an important factor in the mechanism of hemodialysis-induced leukopenia.

Acrylic Resins↗
PubMed1983

A specific enzyme-linked immunosorbent assay (ELISA) for the determination of human C5a antigen.

An enzyme-linked immunosorbent assay has been developed to detect human C5a antigen. This ELISA methodology has been shown to be a highly sensitive technique capable of detecting C5a antigen concentrations below 10 ng/ml. The microELISA technique used in this study is specific for human C5a and C5a des arg (C5a antigen) but not for human C5. Conditions to establish sensitivity and specificity are outlined in ths report.

Antibody Specificity↗
PubMed1991

A sensitive enzyme immunoassay for the quantitation of human C5a/C5a(desArg) anaphylatoxin using a monoclonal antibody with specificity for a neoepitope.

The direct quantitation of C5a/C5a(desArg) in human plasma was achieved by a specific and highly sensitive ELISA which is based on the neoepitope-specific monoclonal antibody C17/5. The error-prone removal of C5 from plasma prior to the assay is therefore not required. With a detection limit of 20 pg C5a/ml plasma, the sensitivity of this assay allowed to define normal ranges (1.94 +/- 1.49 ng C5a/nl, mean +/- SD) of C5a/C5a(desArg) in human blood plasma. This assay will also be applicable to the quantitation of C5a in specimens with low protein content where precipitation-based assays fail to accurately determine C5a. In addition, the mAb C17/5 turned out to efficiently block the binding of C5a/C5a (desArg) to its cellular receptor and therefore provides a valuable tool in the delineation of C5a effects in complex biologic systems in the presence of native C5, such as under in vivo conditions.

Adenosine Triphosphate↗
PubMed1986

Attachment of human C5a des Arg to its cochemotaxin is required for maximum expression of chemotactic activity.

The chemotactic activity of human C5a des Arg is enhanced significantly by an anionic polypeptide (cochemotaxin) in normal human serum and plasma. We have found that the cochemotaxin attaches to the oligosaccharide chain of native C5a des Arg to form a complex with potent chemotactic activity for human polymorphonuclear leukocytes. Although capable of enhancing the chemotactic activity of native C5a des Arg, the cochemotaxin had no effect on the chemotactic activity of either deglycosylated C5a des Arg, native C5a, or N-formyl-methionyl-leucyl-phenylalanine. Of the known components of the oligosaccharide chain, only sialic acid prevented enhancement by the cochemotaxin of the chemotactic activity exhibited by native C5a des Arg. Sialic acid also prevented the formation of C5a des Arg-cochemotaxin complexes, detected by acid polyacrylamide gel electrophoresis, molecular sieve chromatography on polyacrylamide gels, and sucrose density gradient ultracentrifugation.

Anaphylatoxins↗
PubMed1989

Inflammatory properties of human C5a and C5a des Arg/ in mast cell-depleted human skin.

C5a and its degradation product, C5a des Arg, elicit immediate cutaneous inflammatory reactions after intradermal injection. Histologically, these reactions are characterized by neutrophil-rich leukocytic infiltrates, leukocytoclasis, edema, and dermal mast cell degranulation. It has not been possible to assess in vivo the relative contributions of resident mast cells and circulating leukocytes to this reaction because the accumulation of leukocytes and degranulation of mast cells occur simultaneously after injection of these anaphylatoxins. To assess the role of mast cells in these inflammatory reactions, we have examined the reactivity of human skin selectively depleted of dermal mast cells by local corticosteroid treatment. Corticosteroid-treated skin became virtually devoid of dermal mast cells within 4-6 wk as assessed by light microscopy, immunofluorescence with fluorescein-conjugated avidin, or electron microscopy. Mast cell-depleted skin demonstrated normal vasopermeability and vasodilatory responsiveness to intradermal injection of histamine, but the reactivity of these sites to the mast cell secretagogue, morphine, was absent. Moreover, no clinical reactions were detectable in mast cell-depleted human skin after intradermal challenge with 50 ng of either C5a or C5a des Arg, despite the fact that biopsies of these sites revealed substantial, neutrophil-rich infiltrates. These infiltrates were qualitatively and quantitatively identical to C5a or C5a des Arg-induced infiltrates in mast cell replete skin. This experimental approach in vivo has allowed the independent analysis of the anaphylactogenic and chemoattractant activities of human C5a and C5a des Arg in human skin, demonstrated the importance of dermal mast cells in these clinical responses, and shown that leukocytes can accumulate at these injection sites directly in response to these mediators.

Adrenal Cortex Hormones↗
PubMed1986

Chemotactic activity for polymorphonuclear and mononuclear leukocytes in rheumatoid synovial fluids.

In order to why polymorphonuclear leukocytes (PMNs) are predominant and mononuclear leukocytes (MNLs) are few in rheumatoid synovial fluids, chemotactic factor(s) for PMNs and MNLs were studied in the synovial fluids of rheumatoid arthritis (RA-SF) and osteoarthritis (OA-SF) using both Boyden's and agarose methods. The RA-SF showed strong chemotactic activity for human peripheral blood PMNs compared with non-rheumatoid OA-SF. The chemotactic activity for PMNs was well correlated with the number of PMNs in RA-SF, suggesting that it was a natural mediator for PMN emigration into rheumatoid joint cavity. The major chemotactic factor for PMN in RA-SF was of apparent molecular weight of 14,000 and its activity was suppressed to less than 10 percent by anti-C5a antibody, but it failed to show any anaphylatoxin activity which was an attribute of C5a. It was, therefore, suggested to be C5a-like molecule but not C5a itself. The possibility that the factor may be a C5a des-Arg was discussed. On the contrary, the chemotactic activity for MNLs was not found neither in RA-SF nor OA-SF. These findings may explain the fact that PMNs are predominant in rheumatoid synovial fluids.

Arthritis, Rheumatoid↗
PubMed1995

IgE-independent interleukin-4 expression and induction of a late phase of leukotriene C4 formation in human blood basophils.

T-helper cells can differentiate into at least two subtypes secreting distinct profiles of cytokines, Th1 and Th2, regulating immunoprotection and different immunopathologies. Interleukin-4 (IL-4) is both the product and the inducer of Th2 cells, raising the question whether IL-4 can be produced in response to antigen-independent stimuli. Here we show that human basophils produce IL-4 on stimulation with IL-3 and C5a or C5adesarg in similar amounts as induced by IgE-receptor-cross-linking. C5a-induced IL-4 production requires the presence of IL-3, with little effect of the sequence of stimuli addition. No "Th1-cytokines" (interferon-gamma and IL-2) and even no "Th2-cytokines" (IL-3, IL-5, IL-10, and granulocyte-macrophage colony-stimulating factor) are produced by basophils in response to either IgE-dependent or IgE-independent activation. The generation of leukotriene C4 (LTC4) is regulated in a similar manner. However, C5a induces a rapid, transient burst of leukotriene formation only if added after IL-3. Interestingly, upon prolonged culture, a late phase of continuous LTC4 production is observed, which also requires two signals (IL-3 and C5a), but rather depends on their continuous presence than on their sequence of action. These data describe an antigen-independent pathway of very restricted IL-4 expression. Thus, basophils must be considered as central immunoregulatory cells of the innate immune system. Furthermore, the results show that LTC4 can also be generated more continuously for many hours, a phenomenon that may be of particular importance in chornic allergic inflammation, such as asthma.

Basophils↗
PubMed1982

Cardiopulmonary bypass-induced complement activation. Evidence for C5a participation.

Plasma activity inducing polymorphonuclear neutrophils (PMN) aggregation, augmenting PMN adherence, plasma chemotactic activity as well as peripheral PMN count were estimated in patients during cardiopulmonary bypass. In the course of the surgical procedure the chemotactic activity and the activity inducing PMN aggregation were detected in plasma. The top of these two activities was always followed by the significant fall of the peripheral PMN count. The increase of the activity augmenting PMN adherence was observed in a part of cases, but when noticed, always preceded the maximum of the remaining evaluated activities.

Adult↗
PubMed1983

Acute lung inflammation induced in the rabbit by local instillation of 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine or of native platelet-activating factor.

The intratracheal instillation into rabbits of 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC) or native platelet-activating factor (PAF) was shown to induce a dose-dependent acute pulmonary inflammation characterized by accumulation of macrophages in the alveolar space, degenerative and necrotic changes of alveolar epithelium, and accumulation of polymorphonuclear leukocytes (PMNs) and platelets in the alveolar capillary lumens with degenerative changes of endothelial cells. Infiltration of alveolar septa by inflammatory cells and, in a later stage, pulmonary fibrosis were also observed. Intrabronchial instillation of lysoglyceryl ether phosphorylcholine (lyso-GEPC) produced no inflammatory changes or only mild ones. In comparison with acute inflammation induced by intratracheal instillation of C5a des Arg, which is mainly characterized by the presence of neutrophils, red blood cells, and fibrin in the alveolar space, AGEPC and native PAF seem to induce a more severe accumulation of macrophages in the alveolar space and septa and of platelet and PMNs in the lumens of alveolar capillaries. These results are compatible with the concept that during inflammatory reaction an intraalveolar release of PAF contributes to the development of pulmonary injury.

Acute Disease↗