Cardiopulmonary bypass: studies on its damaging effects

Despite the widespread safe application of cardiopulmonary bypass (CPB) for cardiac surgery, it is inherently a pathologic state. CPB produces a generalized inflammatory reaction involving at least the complement, coagulation, kallikrein, and fibrinolytic cascades. Marked alterations in organ perfusion and metabolism occur during CPB which are further affected by the perfusion flow rate. During hypothermic CPB at 20 degrees C, there is a progressive decrease in perfusion of the microcirculation at flow rates less than 1.2 liters/min/m2. Experimental studies suggest that brain oxygen consumption and resistance remain relatively constant as flow rates are reduced during hypothermia, and the brain becomes the passive recipient of proportionally more blood flow. Recent ultrafiltration studies have demonstrated a specific increase in microvascular permeability to proteins after 2 h of normothermic CPB. This provides experimental support to the well-known clinical observation of increased interstitial fluid following CPB. The development of uniformly safe CPB depends upon prevention of the abnormalities of the microcirculation and upon neutralization of the deleterious effects of inflammatory mediators.

Ex vivo and in vivo protein A perfusion: background, basic investigations, and first clinical experiences

During the past several years clinical protein A perfusion has attracted much attention because it allows to selectively remove IgG subclasses 1, 2, 4 and probably IgG-containing immune complexes, and has a tumoricidal effect in experimental animals and in some cancer patients. Due to several drawbacks, this therapy is not yet generally accepted. Our first experience with laboratory and clinical protein A perfusions confirms several limitations of this new apheresis therapy. Plasma IgG extraction in the ex vivo system under investigation and during clinical application of protein A perfusion reached a 10:1 ratio of grams IgG removed per gram solid-phase protein A only in 2 of 5 runs. Nevertheless, the absolute amount of IgG removed was very low in all runs due to the restricted protein A load (maximum 200 mg) per column. Removal capacity can be increased by a two-column switch-over system with subsequent perfusion and elution. Furthermore, the side effects observed in both in vivo treatments exceeded by far those of other extracorporeal therapies and had not been observed in more than 1,200 unselective plasma exchanges or in 50 cascade filtrations in our center. C3a generation in protein A perfusion is, however, comparable to cascade filtration, but exceeds that of unselective plasma exchange and is lower than in hemodialysis. Consequently, side effects in protein A perfusion cannot be correlated with the total amount of anaphylatoxin generated but may be due to a leakage of protein A or contaminants. Clinical application of protein A perfusion needs a more detailed elaboration in respect to biocompatibility, removal capacity, and the significance of the induced biological effects.

Effect of dialyzer geometry on granulocyte and complement activation

During hemodialysis with cuprophan membranes, the complement system as well as leukocytes become activated. In order to clarify the role of dialyzer geometry, the effect of hollow-fiber versus flat-sheet dialyzers and of different surface areas on C3a generation and leukocyte degranulation was investigated. Plasma levels of leukocyte elastase in complex with alpha 1-proteinase inhibitor were significantly increased after 1 h (+55%) and 3 h (+62%) of hemodialysis with flat-sheet dialyzers as compared to hollow-fiber devices. In addition, plasma levels of lactoferrin, released from the specific granules of leukocytes during activation, were significantly higher (+42%) 3 h after the onset of dialysis treatment with flat-sheet than with hollow-fiber dialyzers. With respect to surface area, larger dialyzers tended to cause more release of leukocyte elastase as compared to dialyzers with smaller surface areas, irrespectively of the configuration of the dialyzer used. On the other hand, activation of the complement system, as measured by the generation of C3a-desarg, did not differ with both types of configurations. The same held true for leukopenia, which was almost identical for hollow-fiber and flat-sheet dialyzers. From these findings two lines of evidence emerge: First, not only the type of membrane material used in a dialyzer may influence its biocompatibility, but the geometry of the extracorporeal device also determines the degree of compatibility. Hence, the extent of leukocyte activation correlated with both configuration of the dialyzer and surface area of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatibility of different hemodialysis and plasmapheresis membranes

The biocompatibility of different membranes was assessed by measuring changes in different white blood cell counts, PGE2 concentrations, thromboplastin activity, production of anaphylatoxins and clinical parameters during treatment. The in vivo recorded complement activation was compared with in vitro experiments. Hemodialysis (HD) treatment was performed with 5 different membranes. Plasmapheresis was run with cellulose diacetate membranes in single (SMF) and double (DMF) membrane filtration and with a new polycarbonate membrane in SMF. The polysulfone membrane was found to be the most, and the cuprophane membrane the least biocompatible membrane in HD. However, large individual differences from one HD patient to the other were found. In contrast to the cellulose diacetate membrane, the polycarbonate membrane apparently activated no complement along the blood-membrane interface during plasmapheresis, but activated large amounts within the membrane matrix. High blood concentrations of C5a were promptly cleared in the body, while high concentrations of C3a seemed to block the removal of this substance from the blood compartment. Even when the patients had high blood concentrations of anaphylatoxins throughout the plasmapheresis treatments using cellulose diacetate membranes and when a significant activation of PGE2 was found in patient plasma, no activation of thromboplastin was recorded on the surface circulating monocytes.

Complement-mediated neutrophil activation in sepsis- and trauma-related adult respiratory distress syndrome. Clarification with radioaerosol lung scans

Complement-mediated neutrophil activation (CMNA) has been proposed as an important pathogenic mechanism causing acute microvascular lung injury in the adult respiratory distress syndrome (ARDS). To clarify the relationship between CMNA and evolving lung injury, we studied 26 patients with multiple trauma and sepsis within 24 hours of risk establishment for ARDS. Pulmonary alveolar-capillary permeability (PACP) was quantified as the clearance rate of a particulate radioaerosol. Seventeen patients (65%) had increased PACP (six developed ARDS) while nine (35%) had normal PACP (none developed ARDS; clearance rates of 3.4%/min and 1.5%/min, respectively). These patients, regardless of evidence of early lung injury, had elevated plasma C3adesArg levels and neutrophil chemotactic desensitization to C5a/C5adesArg. Plasma C3adesArg levels correlated weakly, but significantly, with PACP. Thus, CMNA may be a necessary, but not a sufficient, pathogenic mechanism in the evolution of ARDS.

The predictive and discriminative value of biologically active products of eosinophils, neutrophils and complement in bronchoalveolar lavage and blood in patients with adult respiratory distress syndrome

To determine whether biologically active products of eosinophils, neutrophils and complement contribute to the development of adult respiratory distress system (ARDS) we measured eosinophil cationic protein (ECP), lactoferrin (LF) and C3a in bronchoalveolar lavage (BAL) and blood by means of radioimmunoassays. Seventeen patients served as controls. Fifteen patients were studied before and after major surgery to evaluate the influence of the surgical procedure, and 12 patients with ARDS were investigated 4-12 h after the onset of the disease. Major surgery per se significantly increased ECP in BAL, LF in serum and C3a in BAL and plasma. ECP, LF and C3a levels in BAL and blood were all significantly higher in ARDS patients as compared with levels in controls and those observed after major surgery. The higher ECP levels in BAL were associated with the more severe ARDS as was also the case for C3a in BAL and plasma and LF in serum. One out of 15 patients subjected to major surgery developed ARDS postoperatively and had very high levels of ECP, LF and C3a in BAL and blood at sampling 3 h prior to onset of ARDS, and these levels were similar to those observed in ARDS patients. One out of 12 ARDS patients died from the disease and this patient had the highest level of ECP in BAL and serum. Our results strongly support the role of activated polymorphonuclears, and notably the activated eosinophils, in the pathogenesis of ARDS. Evidence is also presented that ECP can be used as a predictor of impending ARDS.

Anaphylatoxin C5a fails to promote prostacyclin release in cultured endothelial cells from human umbilical veins

Subcultured endothelial cells from human umbilical veins respond to histamine and melittin with increased prostacyclin production, measured as 6-keto-prostaglandin F1 alpha by radioimmunoassay. However, no response to leukotriene C4 was observed. Primary cultured cells, on the other hand, respond to leukotriene C4 and the histamine response was 7 times more potent for these cells than for subcultured cells. In contrast, neither primary cultures nor subcultures of endothelial cells released prostacyclin following application of either human anaphylatoxin C5a (100 nM) or C3a (1 microM). In addition, these endothelial cells appear to have no specific binding sites for 125I-C5a. However, endothelial cells released prostacyclin in the presence of human polymorphonuclear leukocytes that were activated with C5a. We conclude that involvement of endothelial cells in the haemodynamic response to anaphylatoxin is an indirect function, i.e. C5a activates circulating or tissue cells which in turn stimulate the endothelial cell to produce prostacyclin.

Complement activation after aortic endothelial injury

Ischemic endothelial cell injury results in C activation that precedes partially via the classic pathway. This may be relevant to clinical situations of ischemia such as occur during embolization or thrombus formation. The generation of C activation products (such as C3a and C5a) may mediate many of the inflammatory changes observed in infarcted tissues.

Complement activation during systemic lupus erythematosus. C3a and C5a anaphylatoxins circulate during exacerbations of disease

To determine whether activated complement components appear in the circulation of patients with systemic lupus erythematosus (SLE), we measured C5a and C3a by radioimmunoassay. Mean C5a concentration in the plasma of acutely ill SLE patients was 46.0 ng/ml, compared with 17.1 ng/ml in normal controls (P less than 0.01). Mean C3a concentration in patients with severe disease was 526 ng/ml, compared with 134 ng/ml in controls (P less than 0.01). In patients with moderately active SLE, the mean C3a concentration, but not the mean C5a concentration, was also elevated. In addition, C3a was elevated in 15 or 21 patients with active SLE, whereas low levels of C3 or C4 were noted in only 7 of these 21 patients. We conclude that the measurement of complement-derived anaphylatoxins may be useful in the management of patients with SLE. In addition, we suggest that these circulating mediators may contribute to the pathogenesis of vascular injury in patients with the disease.

Inappropriate activation, deactivation, and probable autooxidative damage as a mechanism of neutrophil locomotory defect in trauma

We studied 46 patients who suffered from serious blunt trauma to examine the possible mechanism of their acquired neutrophil (PMN) locomotory dysfunction. Concentrations of plasma C3adesArg were higher in patients than in controls (310 +/- 190 ng/ml vs. 90 +/- 28 ng/ml, respectively; P = 3 X 10(-5)). Both resting and phagocytosing PMNs from the patients produced higher quantities of H2O2 (0.31 +/- 0.29 and 5.2 +/- 3.4 nmol/10(6) PMNs per hr, respectively). These levels resemble the H2O2 production of normal PMNs preactivated with chemotactic factor (0.85 +/- 0.03 for normal and 8.2 +/- 1.6 nmol/10(6) PMNs per hr for preactivated PMNs). Concentrations of oxidized glutathione were not significantly higher in PMNs from patients compared with PMNs from controls (0.053 +/- 0.057 vs. 0.037 +/- 0.046 nmol/10(6) PMNs, respectively; P = .5). A higher percentage of PMNs from trauma patients than from controls were capped with concanavalin A (66% +/- 11% vs. 37% +/- 14%, respectively; P = 4 X 10(-5)), a result indicating microtubular dysfunction. These findings suggest that in trauma, activation of intravascular complement results in inappropriate chemotactic stimulation and subsequent deactivation and autoxidative damage of circulating PMNs.

Unusual anaphylatoxin dynamics after head injury--case report

The case reported exemplifies a clinical picture markedly at variance with the chronology of symptoms and laboratory findings generally held to be typical in patients with post-traumatic shock. During a protracted clinical course this young man with a skull fracture and epidural haematoma experienced profound hypotension and adult respiratory distress syndrome (ARDS) well in advance of marked fourfold rise of circulating peripheral C3a desArg anaphylatoxin levels. This raises a note of caution with regard to diagnostic and/or therapeutic decisions based on anaphylatoxin assessment of neurosurgical trauma patients at risk of ARDS.

C3 activation by a new factor B-dependent enzyme detected in culture supernatant from guinea-pig peritoneal macrophages

Culture supernatants (c.s.) collected from thioglycollate-elicited macrophages were concentrated and incubated with purified C3. In this reaction mixture loss of haemolytic C3 according to classical enzyme kinetics was observed. As revealed by SDS-PAGE, c.s.-catalysed fragmentation of the C3 alpha-chain occurred. The cleavage products were identified by size and function as C3a and C3b. The apparent molecular weight of this C3-activating enzyme in c.s. was approximately 220,000 according to ultracentrifugation studies. This large enzyme showed the following characteristics: it had no activity against C5; it was inhibited by EDTA; Mg2+ was required for its optimal function; its half-life at 37 degrees was approximately 35 min; it was completely inhibited by anti-B IgG. Thus, we were able to detect a C3-activating enzyme in c.s. containing B but differing otherwise from a preformed C3 convertase of the alternative pathway. The exact component composition of this new enzyme is under further investigation.

Anaphylatoxin levels in human aqueous humor

Radioimmunoassay was used to measure levels of C3a, C4a, and C5a in aqueous humor from 13 normal eyes, 8 noninflamed eyes with a history of surgery or inflammation, and 14 eyes with anterior uveitis. The authors were unable to measure levels of C3a, C4a, or C5a in normal aqueous humor. In noninflamed aqueous humor from eyes with a history of surgery or inflammation, the authors were unable to measure levels of C4a or C5a, but were able to measure low levels of C3a in 3/8 patients. In aqueous humor from eyes with anterior uveitis, the authors were able to measure levels of C3a in all 14 patients, C4a in 9/14 patients, and C5a in 5/14 patients. Patients with severe anterior uveitis had higher levels of C3a than those with moderate anterior uveitis. The higher ratios of anaphylatoxin to protein levels in inflamed aqueous humor, when compared to normal plasma or noninflamed aqueous humor, suggested that complement was being activated by either the classical or alternative pathways in inflamed aqueous humor. Measurable levels of C3a without detectable C4a in five patients with anterior uveitis suggested alternative pathway activation of complement.

C5a receptor modulation on neutrophils and monocytes from chronic hemodialysis and peritoneal dialysis patients

Chronic renal failure patients have an increased risk for infection which may partially be due to altered chemotactic ability of their white blood cells. This study was designed to evaluate chemotactic factor and Fc receptor expression on neutrophils (PMN) and monocytes from chronic renal failure patients on hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). Analysis of these receptors was performed using flow cytometry and fluorescent chemotactic factors (C5a, f-Met-Leu-Phe-Lys [fMLPL] and casein) and heat-aggregated human IgG. Peripheral blood PMN and monocytes obtained from 14 HD patients (in the predialysis period) and 14 CAPD patients were analyzed for their ability to bind each of the fluoresceinated ligands. PMN and monocytes from both patient groups had a significant reduction in their ability to bind C5a. The average percentage (+/- s.e.m.) of PMN that bound C5a was 93.9 +/- 1.1 for the controls, 72.9 +/- 3.8 for HD patients, and 79.3 +/- 4.0 for CAPD patients. Similar results were obtained with monocytes with 69.7 +/- 1.9% for controls, 54.6 +/- 4.5% for HD patients, and 31.0 +/- 4.5% for CAPD patients. These differences in C5a binding were also reflected in the average intensity of fluorescence. There was no significant difference in the percentage or fluorescence intensity of PMN or monocytes that bound casein or aggregated IgG when either group of dialysis patients was compared to the control values. Binding of fMLPL by PMN and monocytes from the HD patients and PMN from the CAPD patients were similar to control values but the binding of fMLPL by monocytes from CAPD patients was significantly suppressed (p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Determination of anaphylatoxin concentrations in suction blisters in patients with psoriasis

Concentrations of C3a and C4a anaphylatoxins in suction blister fluids were determined by radioimmunoassay in patients with psoriasis and normal controls. Comparison of anaphylatoxin levels between serum samples and blister contents in the same subjects revealed that the levels of both C3a and C4a anaphylatoxins were significantly higher in the former than the latter even in those raised on normal skin, suggesting that the classic complement pathway is activated during suction procedure. Therefore we cannot regard suction blister fluid to be simply representative of undisturbed interstitial tissue fluid as far as the complement system is concerned. There was no difference in anaphylatoxin levels between those from uninvolved skin of psoriatic patients and those from normal controls. However, significantly high anaphylatoxin levels were noted in fluids of suction blisters raised on lesional skin as compared with those produced on uninvolved skin in psoriatic patients.

Interaction of prostaglandins, activated complement, and granulocytes in clinical sepsis and hypotension

Activated complement, thromboxane A2, prostacyclin, and activated granulocytes have been implicated in hemodynamic dysfunction after trauma, in sepsis, and in hypovolemic and septic shock. This study evaluated the interaction of plasma concentrations of complement components C3a and C5a, thromboxane B2 (TxB), prostaglandin 6-keto-F1 alpha (PGI), and granulocyte aggregation in clinical sepsis and hypotension. Forty-eight critically ill patients were followed clinically for as long as 10 days. Plasma C3a, C5a, TxB, and PGI were measured daily by the radioimmunoassay method. Granulocyte aggregation, the percentage of maximum aggregation of zymosan-activated plasma standard curves, was performed with patient plasma and normal human leukocytes. Patients were studied in four groups: group I, nonseptic, normotensive; group II, hypovolemic shock, group III, normotensive severe sepsis; and group IV, septic shock. Plasma from 12 normal adults was the control value. PGI, TxB, C3a, C5a, and granulocyte aggregation in patients were greater than that in the control subjects. Granulocyte aggregation was increased in groups III and IV versus groups I and II. C3a was increased in group IV versus groups II and III. C5a and TxB did not vary between groups. PGI was greatly increased in group IV compared with groups I through III. C3a and C5a decreased in nonsurvivors. PaO2/FiO2 ratios correlated directly with PGI and inversely with C3a and TxB/PGI. Plasma PGI and C3a are increased in septic shock. C3a and TxB/PGI imbalances are involved in hypovolemic and septic shock.

Different complement and granulocyte activation in patients dialyzed with PMMA dialyzers

Plasma C3a and C5a levels as well as plasma levels of granulocyte lactoferrin, granulocyte myeloperoxidase and granulocyte elastase in complex with alpha 1-proteinase inhibitor (E-alpha 1PI) were investigated in 10 patients (52.7 +/- 5.9 years) undergoing maintenance hemodialysis (39.4 +/- 12.4 months) with hollow fiber dialyzers made from polymethylmethacrylate. Plasma levels of lactoferrin increased from 166.5 +/- 28.5 to 712.5 +/- 165.9 ng/ml, myeloperoxidase from 59.0 +/- 15.3 to 210.5 +/- 33.9 ng/ml and E-alpha 1PI from 114.2 +/- 18.1 to 681.8 +/- 102.6 ng/ml during dialysis. In contrast, plasma C3a levels rose from 179.8 +/- 33.6 to maximal 276.2 +/- 45.4 ng/ml and C5a from 55.7 +/- 8.1 to maximal 101.1 +/- 14.8 ng/ml. Our data indicate that degranulation of granulocytes occurs during dialysis despite only little complement activation and mild initial granulocytopenia.

Complement cleavage products in the phototoxic reaction of porphyria cutanea tarda

We have measured C3, C4, CH50 and complement cleavage products C3a and C5a in in sera and plasma from PCT patients and normal controls 10 min and 1, 4 and 24 h after UVA irradiation. We found elevated C3a concentrations in PCT patients immediately after UVA irradiation and 24 h later. The same was true for CH50, whereas C3, C4 and C5a did not change significantly. No such changes occurred in normal controls. Our data suggest that activation of the complement cleavage product C3a by porphyrin and UV light triggers a series of events that cause tissue damage.

Complement mediated inhibition of immune precipitation and solubilization generate different concentrations of complement anaphylatoxins (C4a, C3a, C5a)

Complement prevents the formation of insoluble immune complexes (inhibition of immune precipitation (IIP], and solubilizes preformed immune aggregates (solubilization (SOL]. Since the mechanism of complement activation differs in these two reactions, it is possible that they differ also in the amount of complement fragments released, in particular the anaphylatoxins C3a, C5a and C4a. We measured C4 and C3 consumption, and the formation of complement anaphylatoxins during IIP and SOL using two different immune complex models (BSA, rabbit anti-BSA; tetanus toxoid (TT), human anti-TT). At equal immune complex concentrations in both models, SOL was more efficient than IIP at cleaving C3, and more C3a and C5a was released. Comparing the two reactions, C3a formation was followed by more C5 cleavage (C5a) during SOL. Similarly C4a formation (classical pathway activation) was followed by more C3 cleavage (C3a: classical and alternative pathway activations), during SOL. It is suggested that in vivo SOL of insoluble complexes is rapidly accompanied by a damaging phlogistic reaction, whereas IIP produces less inflammation.

Inactivation of C3a by a monocarboxypeptidase present in culture supernatants of stimulated guinea pig peritoneal macrophages

Hog C3a, as well as its derivative C3a-desArg were not found to act cytotoxically on starch gel-induced guinea pig peritoneal macrophages. Likewise, neither peptide significantly modified the secretion of N-acetyl-beta-D-glucosaminidase from these cells. However, C3a rapidly lost its spasmogenic activity during incubation in serum-free macrophage cultures and less rapidly in cellfree supernatants collected from cultured macrophages. The following results indicate that C3a is converted into its spasmogenically inactive derivative C3a-desArg by a macrophage-derived monocarboxypeptidase. The inactivated C3a product does not differ from native C3a in sodium dodecyl sulfate-polyacrylamide gel electrophoresis; it elutes from CM cellulose in the same position as purified C3a-desArg; and it is devoid of the carboxyl-terminal arginyl residue of C3a, but still contains the carboxyl-terminal sequence of C3a-desArg as determined by analysis after treatment with carboxypeptidases B or Y. Furthermore, inactivation of C3a in supernatants of macrophage cultures is completely blocked by the specific carboxypeptidase inhibitors guanidinopropylsuccinic acid and 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid in final concentrations of 10 mM and 2.1 mM, respectively. The monocarboxypeptidase is apparently supplied by biosynthesis of new material but is not stored as a preformed enzyme because cycloheximide markedly inhibits its expression.