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PubMed1988

Dialysis leukopenia, hypoxemia, and anaphylatoxin formation: effect of membrane, bath, and citrate anticoagulation.

The goal of these prospective studies was to determine the effect of different dialyzer membranes and dialysate composition on leukopenia and hypoxemia during hemodialysis with citrate anticoagulation. Significant early leukopenia was found with a cuprophane membrane, while a cellulose acetate membrane was associated with mild early leukopenia. Bath composition had no effect. Bicarbonate dialysate, compared with acetate, eliminated hypoxemia in cellulose acetate membranes and reduced its degree and duration with cuprophane. Membrane composition had no effect on hypoxemia during acetate dialysis. The findings indicate that leukopenia is directly and exclusively related to membrane composition while hypoxemia only relates in part to membrane effects. Serial determinations of complement components C3a and C5a showed significant increases in parallel with leukopenia during heparin anticoagulation, but the anaphylatoxin concentration changes were dissociated during dialysis with citrate anticoagulation. The concentrations of anaphylatoxins C3a and C5a appear not to be directly related to dialysis-induced leukopenia. The dissociation between anaphylatoxin concentrations and leukopenia may be related to changes in generation or unmasked changes in leukocyte response. Citrate anticoagulation may provide a useful probe for further studies on membrane-leukocyte interactions in vivo.

Acetates↗
PubMed1987

Activation of the complement system by recombinant tissue plasminogen activator.

Recent trials have shown that recombinant tissue plasminogen activator (rt-PA) is an effective thrombolytic agent in patients with acute myocardial infarction. Because rt-PA converts plasminogen to plasmin, which is known to activate complement in vitro, we tested the hypothesis that rt-PA can induce in vivo activation of complement. Studies were performed in 12 patients with acute myocardial infarction. Six control patients had patent coronary arteries and did not receive rt-PA; these patients had normal values of the components of the complement system C4a (409 +/- 111 ng/ml) and C5a (8.8 +/- 1.8 ng/ml) with a slight elevation of C3a (204 +/- 6.6 ng/ml) in samples collected before coronary arteriography (253 +/- 25 minutes after onset of pain). After coronary arteriography, there was a slight decrease in the values of C4a (224 +/- 37 ng/ml), C5a (7.3 +/- 1.3 ng/ml) and C3a (164 +/- 35 ng/ml). The remaining six patients had complete coronary occlusion and received rt-PA (80 to 150 mg intravenously). In this treated group, before coronary arteriography the values of C4a (406 +/- 51.6 ng/ml) and C5a (8.1 +/- 1.9 ng/ml) were normal, and those of C3a were slightly elevated (250 +/- 76 ng/ml). All complement values obtained before rt-PA were similar to those in the untreated group. However, after administration of rt-PA (but before any angiographically detectable reperfusion), there was a striking increase in C4a (2,265 +/- 480 ng/ml; p less than 0.01), C3a (600 +/- 89 ng/ml; p less than 0.05) and C5a (30.0 +/- 4.5 ng/ml; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

[A new case of bronchospasm under extracorporeal circulation].

A case of bronchospasm occurring after the termination of cardiopulmonary bypass is reported. The complement fractions C3a, C4a and C5a were measured before and right after CPB. Complement activation is not specific to CPB but may occur in any thoracotomy. The statistically significant increase in complement C3a without any pulmonary symptomatology has been reported by several authors. Complement activation cannot therefore be considered as the explanation of this bronchospasm.

Bronchial Spasm↗
PubMed1992

The mechanism by which microorganisms avoid complement attack.

The complement system provides a critical level of defense against bacterial invasion. Various microorganisms have evolved a variety of mechanisms to allow them to avoid complement lytic and opsonic activity. These range from the formation of factors that destroy activity of complement proteins to the evolution of surface structures that fail to bind, facilitate degradation of, or shed, complement proteins. The range of factors associated with bacterial complement resistance is reviewed here.

Animals↗
PubMed1986

Interaction of complement proteins C5b-6 and C5b-7 with phospholipid vesicles: effects of phospholipid structural features.

Complement components C5b-6 and C7 assemble to form C5b-7, which then interacts with membranes and commits the membrane attack complex to a target site. This protein-membrane association event was investigated to determine possible structural features that could contribute to a selective membrane attack. This system may also suggest general properties of protein-membrane insertion events. Initial binding of C5b-6 to membranes could potentially determine the site of assembly. However, binding of C5b-6 to membranes required phosphatidylglycerol or phosphatidic acid produced from egg phosphatidylcholine while binding of C5b-6 to phosphatidylcholine, phosphatidylserine, or phosphatidylinositol was undetectable. Binding to phosphatidic acid was irreversible, and the bound C5b-6 could no longer interact with C7. In contrast, C5b-7 interacted with all phospholipids tested. The rate-limiting process was the interaction of C5b-6 and C7, which displayed bimolecular properties and an activation energy of 37 kcal/mol. The C5b-7 complex showed 20-fold selectivity for small unilamellar phospholipid vesicles over large unilamellar vesicles. Vesicles carrying high negative charge densities were selected over neutral vesicles by a factor of about 5. Vesicles formed from phospholipids with short, saturated hydrocarbon side chains (dimyristoylphosphatidylcholine and dipalmitoylphosphatidylcholine) were about 5-fold less effective than those formed from phospholipids with natural fatty acid distributions. The gel vs. fluid state had little influence on C5b-7 insertion.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1988

Sequence-specific assignments in the 1H NMR spectrum of the human inflammatory protein C5a.

Full sequence-specific assignments for the 1H NMR lines of the backbone protons of the human complement factor C5a are described and documented. The results were obtained by largely following the methodology developed by Wüthrich et al. [Wüthrich, K., Wider, G., Wagner, G., & Braun, W. (1982) J. Mol. Biol. 155, 311]. Assignments for the majority of the amino acid side chain protons were obtained by using a comparison of double- and triple-quantum-filtered two-dimensional correlated experiments together with the analysis of relayed coherence transfer spectra. The assignments provide the basis for the determination of the thus far unknown three-dimensional structure of C5a from nuclear Overhauser enhancement distance constraints.

Amino Acid Sequence↗
PubMed1989

Tertiary structure of human complement component C5a in solution from nuclear magnetic resonance data.

The tertiary structure for the region 1-63 of the 74 amino acid human complement protein C5a in solution was calculated from a large number of distance constraints derived from nuclear Overhauser effects with an angular distance geometry algorithm. The protein consists of four helices juxtaposed in an approximately antiparallel topology connected by peptide loops located at the surface of the molecule. The structures obtained for the helices are compatible with alpha-helical hydrogen-bonding patterns, which provides an explanation for the observed slow solvent exchange kinetics of the amide protons in these peptide regions. In contrast to the peptide region 1-63, no defined structure could be assigned to the C-terminal region 64-74, which increasingly acquires dynamic random coil characteristics as the end of the peptide chain is approached. An average root-mean-square deviation of 1.6 A was obtained for the alpha-carbons of the first 63 residues in the calculated ensemble of C5a structures, while the alpha-helices were determined with an average root-mean-square deviation of 0.8 A for the alpha-carbons. A comparison between the solution structure of C5a and the crystal structure of the functionally related C3a protein, as well as inferences for the interaction of C5a with its receptor on polymorphonuclear leukocytes, is discussed.

Amino Acid Sequence↗
PubMed1989

Heteronuclear three-dimensional NMR spectroscopy of the inflammatory protein C5a.

The utility of three-dimensional heteronuclear NMR spectroscopy for the assignment of 1H and 15N resonances of the inflammatory protein C5a (MW 8500), uniformly labeled with 15N, is demonstrated at a protein concentration of 0.7 mM. It is shown that dramatic simplification of the 2D nuclear Overhauser effect spectrum (NOESY) is obtained by editing with respect to the frequency of the 15N heteronucleus in a third dimension. The improved resolution in the 3D experiment largely facilitates the assignment of protein NMR spectra and allows for the determination of distance constraints from otherwise overlapping NOE cross peaks for purposes of 3D structure determination. The results show that 15N heteronuclear 3D NMR can facilitate the structure determination of small proteins and promises to be a useful tool for the study of larger systems that cannot be studied by conventional 2D NMR techniques.

Amino Acid Sequence↗
PubMed1983

Symptoms and activation of granulocytes and complement with two dialysis membranes.

Complement (C) activation, neutropenia, and mild pulmonary dysfunction attend hemodialysis (HD) with cellophane [for example, cuprophan (Cu)] membranes. While usually asymptomatic, these phenomena may cause distress in patients with cardiopulmonary disease, and "start-up" symptoms of HD might be mediated by C-stimulated granulocytes (PMNs). Cellulose acetate (CA) hemodialysis membranes have been devised and claimed more blood compatible than Cu. In a blinded series of HD patients, pruritus, fatigue, and sense of well-being were each scored statistically more favorably by the patients during HD with CA than during HD with Cu (P less than 0.05). Postulating that less C activation might underlie the benefit, we showed that neutropenia was less severe with CA (nadir 77.6% of initial count, +/- 4 SEM) than with Cu (38.3% +/- 2.9; P less than 0.01). In vitro, incubation of CA membranes with plasma led to less C3 conversion (20% vs. 40%), less PMN aggregating activity (5.9 ZAP units vs. 36.3) and less decrement in CH50 (6.5% vs. 22%) than like incubations of Cu. C activation was also less potent in vivo: During HD plasma C3a rose from a mean 401 ng/ml to a peak 6,325 in patients on Cu dialyzers, but from 426 to only 3,637 in patients on CA devices (P less than 0.05). Time-course studies suggested CA was initially as potent an activator as Cu but rapidly lost ability to activate C, possibly because of saturation of C3b binding sites. As an index of PMN activation, we also assayed plasma lactoferrin and found levels significantly higher during Cu than CA dialysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylatoxins↗
PubMed1983

Anaphylatoxin formation during hemodialysis: effects of different dialyzer membranes.

Measurable complement activation resulting in the formation of both C3a and C5a anaphylatoxins was observed in 12 patients undergoing maintenance dialysis treatment with cuprophan hollow fiber dialyzers. Specific radioimmunoassay measurements demonstrated that these patients displayed significantly elevated levels of C3a antigen in the venous (outflow) line of the dialyzer after only 2 min of dialysis. During hemodialysis, venous plasma C3a levels continued to increase and became maximally elevated after 15 min. Thereafter, C3a concentrations gradually declined, suggesting that the rate of complement activation abates with continued cuprophan hemodialysis. Complement activation, as judged by venous plasma C3a levels, was also temporally correlated with hemodialysis leukopenia. The factor believed to be responsible for pulmonary vascular leukosequestration, C5a, could also be detected in venous plasma, but levels of this antigen were not strikingly elevated until the later stages of dialysis. By contrast, six patients dialyzed with polyacrylonitrile dialyzers failed to exhibit hemodialysis leukopenia and displayed only very modest increases in their plasma C3a levels during the initial phases of hemodialysis. These observations provide direct evidence that anaphylatoxin formation during hemodialysis is a transient phenomenon and indicate that the biocompatibility of dialysis membranes, as reflected by their complement activating potential, may be significantly different.

Acrylic Resins↗
PubMed1983

Anaphylatoxin formation during hemodialysis: comparison of new and re-used dialyzers.

Hemodialysis of 11 endstage renal failure patients with new cuprophan hollow fiber dialyzers produced significant leukopenia as well as increased plasma levels of both C3a and C5a antigens during the initial phases of the procedure. Formalin-fixed new dialyzers produced quantitatively similar phenomena in eight of these same patients. By contrast, hemodialysis with re-used dialyzers, that is dialyzers exposed to blood prior to formalin sterilization, produced only a 20 to 30% decline in peripheral blood leukocyte counts. Correspondingly, C3a antigen formation within re-used dialyzers was only 20% of that observed in new dialyzers. Re-used dialyzers also differed significantly from either new or formalin-fixed new dialyzers in that C3b antigen could be readily detected within them even after extensive washing. These observations suggest that C3b deposition on the cellulosic membrane surface during first use markedly diminishes the complement activating potential of cuprophan dialyzers when they are subsequently re-used.

Adult↗
PubMed1986

Effects of the anaphylatoxin, C5a, on renal and glomerular hemodynamics in the rat.

The effects of intrarenal infusion of the complement-derived anaphylatoxin, C5a, upon glomerular hemodynamics were examined in the Munich-Wistar rat, a strain with glomeruli on the kidney surface. Human C5a (1.5 micrograms/min) or vehicle was infused into the left renal artery for 12 min, and glomerular capillary (PG) and Bowman's space pressures, nephron plasma flow (SNPF) afferent and efferent arteriolar protein concentrations, nephron filtration rate (SNGFR) and the glomerular ultrafiltration coefficient (LpA) determined. Human C5a infusion resulted in a reduction in SNPF due to increased efferent arteriolar resistance, and PG increased which maintained SNGFR constant. LpA was numerically lower but not significantly decreased. Infusion of porcine C5ades Arg decreased glomerular filtration rate and renal blood flow. No polymorphonuclear leukocytes were observed within glomerular capillaries of C5a infused rats, and rat leukocytes did not exhibit receptors for human C5a infused. Renal artery infusion of either human C5a or porcine C5a resulted in renal hemodynamic alterations and, as documented for human C5a, effects of C5a upon renal vascular resistance can be added to the known effect of C5a on the polymorphonuclear leukocyte.

Animals↗
PubMed1986

Compartmental distribution of complement activation products in artificial kidneys.

The compartmental distribution of the human anaphylatoxins C3a and C5a has been defined during simulated hemodialysis performed with various types of hemodialyzers. New cuprophan hollow fiber dialyzers were found to activate human complement very readily in vitro, while re-used cuprophan dialyzers displayed only modest complement activating potential. The C3a and C5a antigens, formed as a result of complement activation in these dialyzers, accumulated predominantly in the blood path and were not adsorbed extensively on the membrane surface or transported into the dialysate compartment. Cellulose acetate membranes also produced complement activation in vitro, but to a lesser degree than new cuprophan hollow fibers. However, these membranes exhibited a significant capacity to bind the anaphylatoxins to their surface. Polyacrylonitrile membranes appeared to be unique in that they not only failed to activate complement significantly, but they rapidly adsorbed large quantities of C3a and C5a. These findings demonstrate that hemodialysis membranes may differ with regard to their complement activating potential as well as their ability to remove circulating anaphylatoxins from the blood path. Clinical measurements of anaphylatoxin production during hemodialysis reflect these dynamic events.

Complement Activation↗
PubMed1987

Effect of blood cooling on cuprophan-induced anaphylatoxin generation.

We investigated whether cooling of the extracorporeal blood during hemodialysis could prevent anaphylatoxin generation and leukopenia caused by blood-cuprophan contact. After preliminary in vitro studies confirming the temperature dependence of C5a generation, we carried out hypothermic dialysis on nine patients by manipulating blood and dialysate temperature in such a way that blood temperature within the dialyzer averaged 25 degrees C. In comparison with the control procedure (blood temperature within the dialyzer 35 degrees C) hypothermic dialysis reduced peak C5a generation from 41.7 +/- 17 ng/ml to 9.7 +/- 3.4 ng/ml (P less than 0.01), and white blood cell fall from 72 +/- 15 to 25 +/- 20% (P less than 0.01). Arterial PO2 decreased less in hypothermic dialysis (-19 +/- 9% of pre-HD value) than in the control procedure (-30 +/- 11%) (P less than 0.05). We conclude that blood cooling attenuates cuprophan-induced anaphylatoxin generation and leukopenia.

Adult↗
PubMed1988

Recruitment of actin to the cytoskeletons of human monocyte-like cells activated by complement fragment C5a. Is protein kinase C involved?

U-937 cells differentiated by exposure to dibutyryl cyclic AMP respond to complement fragment C5a with a marked increase in cytoskeletal F-actin, which can be detected by fluorescence-activated cell sorting (f.a.c.s.) analysis of their rhodamine phalloidin-stained cytoskeletons. The C5a-induced increase in F-actin content can be prevented by prior exposure of the cells to cytochalasin B and pertussis toxin. It is insensitive to removal of extra cellular Ca2+, to cholera toxin or to neomycin. Phorbol myristate acetate (PMA), an activator of protein kinase C, does not induce actin polymerization in the differentiated cells. Both C5a and PMA stimulate superoxide production. The action of C5a on superoxide formation is also inhibited by neomycin, a phospholipase inhibitor. These results suggest that the cytoskeletal response to C5a requires activation of a G protein, but probably does not involve phospholipase C and protein kinase C, and is not highly dependent on the availability of Ca2+. Phospholipase C and kinase C may, however, be components of the pathway leading from C5a binding to superoxide production.

Actins↗