C3a triggers formation of sub-retinal pigment epithelium deposits via the ubiquitin proteasome pathway.

The mechanisms that connect complement system activation and basal deposit formation in early stages of age-related macular degeneration (AMD) are insufficiently understood, which complicates the design of efficient therapies to prevent disease progression. Using human fetal (hf) retinal pigment epithelial (RPE) cells, we have established an in vitro model to investigate the effect of complement C3a on RPE cells and its role in the formation of sub-RPE deposits. The results of these studies revealed that C3a produced after C3 activation is sufficient to induce the formation of sub-RPE deposits via complement-driven proteasome inhibition. C3a binds the C3a receptor (C3aR), stimulates deposition of collagens IV and VI underneath the RPE, and impairs the extracellular matrix (ECM) turnover by increased MMP-2 activity, all mediated by downregulation of the ubiquitin proteasome pathway (UPP). The formation of basal deposits can be prevented by the addition of a C3aR antagonist, which restores the UPP activity and ECM turnover. These findings indicate that the cell-based model can be used to test potential therapeutic agents in vitro. The data suggest that modulation of C3aR-mediated events could be a therapeutic approach for treatment of early AMD.

Role of complement and perspectives for intervention in ischemia-reperfusion damage.

Reperfusion of an organ following prolonged ischemia instigates the pro-inflammatory and pro-coagulant response of ischemia / reperfusion (IR) injury. IR injury is a wide-spread pathology, observed in many clinically relevant situations, including myocardial infarction, stroke, organ transplantation, sepsis and shock, and cardiovascular surgery on cardiopulmonary bypass. Activation of the classical, alternative, and lectin complement pathways and the generation of the anaphylatoxins C3a and C5a lead to recruitment of polymorphonuclear leukocytes, generation of radical oxygen species, up-regulation of adhesion molecules on the endothelium and platelets, and induction of cytokine release. Generalized or pathway-specific complement inhibition using protein-based drugs or low-molecular-weight inhibitors has been shown to significantly reduce tissue injury and improve outcome in numerous in-vitro, ex-vivo, and in-vivo models. Despite the obvious benefits in experimental research, only few complement inhibitors, including C1-esterase inhibitor, anti-C5 antibody, and soluble complement receptor 1, have made it into clinical trials of IR injury. The results are mixed, and the next objectives should be to combine knowledge and experience obtained in the past from animal models and channel future work to translate this into clinical trials in surgical and interventional reperfusion therapy as well as organ transplantation.

Inhibitory effects of C4a on chemoattractant and secretagogue functions of the other anaphylatoxins via Gi protein-adenylyl cyclase inhibition pathway in mast cells.

A recombinant complement anaphylatoxin, C4a, inhibited chemotaxis, respiratory burst and histamine release in mast cell-like HMC-1 cells that were treated with recombinant C5a anaphylatoxin. C4a also inhibited histamine release from HMC-1 cells that were induced by recombinant C3a. The inhibition of C5a- and C3a-induced leukocyte reactions by C4a was recapitulated in peripheral blood CD133(+) cell-derived differentiated mast cells. In HMC-1 cells, C4a inhibited cytoplasmic Ca(2+) influx, an event that precedes anaphylatoxin-induced chemotactic and secretary responses. A conditioned medium of HMC-1 cells after shortly treated with C4a also inhibited the anaphylatoxin-induced Ca(2+) influx even after removal of C4a, indicating that the effect of C4a is to liberate an autocrine inhibitor from the mast cells. The inhibitor secretion by C4a was prevented with pertussis toxin or with a phosphodiesterase inhibitor. Conversely, an adenylyl cyclase inhibitor reproduced the effect of C4a. C4a decreased the intracellular cyclic AMP concentration of HMC-1 cells, indicating that C4a elicited the Gi protein-adenylyl cyclase inhibition pathway. Neither C4a nor the conditioned medium, however, inhibited Ca(2+) influx and respiratory burst in C5a- or C3a-stimulated peripheral neutrophils, suggesting that these cells lack this inhibitory system. Additionally, in HMC-1 cells, C4a did not inhibit Ca(2+)-independent, Leu72Gln-C5a-stimulated chemotactic response. In agreement with this finding, C4a treatment inhibited ERK1/2 phosphorylation in HMC-1 cells stimulated with other anaphylatoxins but did not inhibit p38MAPK phosphorylation in cells stimulated with Leu72Gln-C5a. Taken together, these findings suggest that the autocrine inhibitory effect elicited by C4a is attributed to interruption of Ca(2+)-dependent intracellular signaling pathway.

Inactivation of the complement anaphylatoxin C5a by secreted products of parasitic nematodes.

Given the importance of the complement anaphylatoxins in cellular recruitment during infection, the ability of secreted products from larval stages of Brugia malayi and Trichinella spiralis to influence C5a-mediated chemotaxis of human peripheral blood granulocytes in vitro was examined. Secreted products from B. malayi microfilariae almost completely abolished chemotaxis. This inhibition was blocked by phenylmethylsulphonyl fluoride, indicating the presence of a serine protease, which was subsequently shown to cleave C5a. In contrast, secreted products from T. spiralis infective larvae showed modest inhibition of C5a-mediated granulocyte chemotaxis, and this was blocked by potato carboxypeptidase inhibitor, an inhibitor of several metallocarboxypeptidases. Adult and larval stages of both parasites were demonstrated to secrete carboxypeptidases which cleaved hippuryl-L-lysine and hippuryl-L-arginine, and the T. spiralis enzyme was partially characterised. The data are discussed with reference to inflammation in parasitic nematode infection.

Neuroprotection in stroke by complement inhibition and immunoglobulin therapy.

Activation of the complement system occurs in a variety of neuroinflammatory diseases and neurodegenerative processes of the CNS. Studies in the last decade have demonstrated that essentially all of the activation components and receptors of the complement system are produced by astrocytes, microglia, and neurons. There is also rapidly growing evidence to indicate an active role of the complement system in cerebral ischemic injury. In addition to direct cell damage, regional cerebral ischemia and reperfusion (I/R) induces an inflammatory response involving complement activation and generation of active fragments, such as C3a and C5a anaphylatoxins, C3b, C4b, and iC3b. The use of specific inhibitors to block complement activation or their mediators such as C5a, can reduce local tissue injury after I/R. Consistent with therapeutic approaches that have been successful in models of autoimmune disorders, many of the same complement inhibition strategies are proving effective in animal models of cerebral I/R injury. One new form of therapy, which is less specific in its targeting of complement than monodrug administration, is the use of immunoglobulins. Intravenous immunoglobulin (IVIG) has the potential to inhibit multiple components of inflammation, including complement fragments, pro-inflammatory cytokine production and leukocyte cell adhesion. Thus, IVIG may directly protect neurons, reduce activation of intrinsic inflammatory cells (microglia) and inhibit transendothelial infiltration of leukocytes into the brain parenchyma following an ischemic stroke. The striking neuroprotective actions of IVIG in animal models of ischemic stroke suggest a potential therapeutic potential that merits consideration for clinical trials in stroke patients.

A rapid and sensitive assay for the quantitation of carboxypeptidase N, an important regulator of inflammation.

BACKGROUND: Carboxypeptidase N is a plasma zinc metallocarboxypeptidase which is constitutively expressed in the liver and was identified as the enzyme responsible for inactivating bradykinin and kallidin by removing the C-terminal arginine. Because CPN can cleave the C-terminal arginine of C3a, C4a and C5a it is often referred to as anaphylatoxin inactivator. Markedly reduced levels of circulating CPN are associated with recurrent angioedema and abnormal cutaneous polymorphonuclear cell infiltration. METHODS: In this paper we describe a fast kinetic coupled enzymatic assay for the sensitive measurement of carboxypeptidase N activities in serum samples. The assay makes use of the excellent CPN substrate Benzoyl-L-Alanyl-L-Arginine. RESULTS: This novel assay is very fast, easy to perform and combines good reliability and reproducibility with excellent correlation with the HPLC-assisted assay (r=0.927; n=140). CONCLUSION: The presented assay can be used for high throughput screening of this important regulator of inflammation in clinical plasma or serum samples.

Strategies of therapeutic complement inhibition.

The involvement of complement in the pathogenesis of a great number of partly life threatening diseases defines the importance to develop inhibitors which specifically interfere with its deleterious action. Endogenous soluble complement-inhibitors, antibodies or low molecular weight antagonists, either blocking key proteins of the cascade reaction or neutralizing the action of the complement-derived anaphylatoxins have successfully been tested in various animal models over the past years. Promising results consequently led to first clinical trials. This review is focused on different approaches for the development of inhibitors, on their site of action in the cascade, on possible indications for complement inhibition based on experimental animal data, and on potential side effects of such treatment.

Carboxypeptidase R is an inactivator of complement-derived inflammatory peptides and an inhibitor of fibrinolysis.

Carboxypeptidase R (CPR) exists in precursor form (proCPR) in plasma in contrast to carboxypeptidase N (CPN), which is present in the active state. CPR plays two important roles, one of which appears to be the control of the inflammatory response by inactivation of anaphylatoxins such as complement-derived C3a and C5a. Therefore, an increase in CPR activity may facilitate rapid inactivation of these inflammatory mediators generated at the site of bacterial infection. Upregulation of proCPR expression during the inflammatory response initiated for instance by endotoxin (lipopolysaccharide) should play a role in suppressing hyper-reactivity as seen in septic shock. CPR also functions as an inhibitor of fibrinolysis, where its ability to prevent binding of plasminogen to lysine residues on fibrin clots significantly lengthens tissue plasminogen activator (tPA)-induced fibrinolysis time. Therefore, upregulation of proCPR production during the inflammatory response may exacerbate thrombosis contributing to the development of disseminated intravascular coagulation as well as other conditions involving thrombosis. Co-administration of tPA and a specific inhibitor of CPR, such as potato carboxypeptidase inhibitor, which does not affect CPN, may be useful in thrombolytic therapy.

Targeting complement in therapy.

With increasing evidence that complement activation significantly contributes to the pathogenesis of a large number of inflammatory diseases, strategies that interfere with its deleterious action have become a major focus in pharmacological research. Endogenous soluble complement inhibitors (C1 inhibitor, recombinant soluble complement receptor 1, antibodies) blocking key proteins of the cascade reaction, neutralizing the action of the complement-derived anaphylatoxin C5a, or interfering with complement receptor 3 (CR3, CD18/11b)-mediated adhesion of inflammatory cells to the vascular endothelium have successfully been tested in various animal models over the past years. Promising results consequently led to clinical trials. Furthermore, incorporation of membrane-bound complement regulators (decay-accelerating factor (CD55), membrane co-factor protein (CD46), CD59) in transgenic animals has provided a major step forward in protecting xenografts from hyperacute rejection. At the same time, the poor contribution of complement to the antitumor response, which is caused by multiple resistance mechanisms that hamper the efficacy of antibody-based tumor therapy, is increasingly recognized and requires pharmacologic intervention. First attempts have now been made to interfere with the resistance mechanisms, thereby improving complement-mediated tumor cell destruction.

C5a receptor antagonists.

The anaphylatoxin C5a is an extremely potent proinflammatory peptide produced during activation of the complement system. The structure of C5a includes a core region (N-terminal residues 1-63) consisting of four, antiparallel alpha-helices held together by three disulfide linkages and a structured C-terminal tail (residues 64-74). The C5a receptor belongs to the large class of seven transmembrane, G-protein-linked receptors. C5a appears to interact with its receptor at two sites: the C5a core binds to the receptor s N-terminal extracellular domain while C5a s tail binds the receptor near Arg206, near the membrane surface of transmembrane helix V. C5a receptors are concentrated on blood granulocytes (neutrophils, eosinophils, and basophils) and tissue inflammatory cells (macrophages, mast cells, microglia); thus the main effects of C5a are manifest as inflammation. Additionally, C5a receptors are also present, albeit in lower concentrations, on non-myeloid cells, e.g. endothelial and smooth muscle cells where they may further influence inflammatory reactions such as blood cell emigration and tissue edema. C5a has been implicated in myriad disorders, both acute and chronic; therefore a C5a receptor antagonist is predicted to have utility as a therapeutic agent. Unfortunately, few specific C5a receptor antagonists have been reported, and only two have demonstrated activity in vivo. Furthermore, those reported are peptidic and hence have limited application therapeutically. The current state of C5a receptor antagonists is discussed as well as the potential for their use against various human disorders. A model of C5a receptor dimerization is presented to account for the high potency of the disulfide antagonist C5aRAD.

Anti-inflammatory and immunological effects of Centaurea cyanus flower-heads.

Centaurea cyanus flower-heads are used in European phytotherapy for the treatment of minor ocular inflammations. Different pharmacological experiments (inhibition of carrageenan, zymosan and croton oil-induced oedemas, inhibition of plasma haemolytic activity, induction of anaphylatoxin activity) showed that polysaccharides extracted from C. cyanus flower-heads had anti-inflammatory properties and interfered with complement. Moreover, these polysaccharides were found to be mainly composed of galacturonic acid, arabinose, glucose, rhamnose and galactose.

Controlling the complement system in inflammation.

Inappropriate or excessive activation of the complement system can lead to harmful, potentially life-threatening consequences due to severe inflammatory tissue destruction. These consequences are clinically manifested in various disorders, including septic shock, multiple organ failure and hyperacute graft rejection. Genetic complement deficiencies or complement depletion have been proven to be beneficial in reducing tissue injury in a number of animal models of severe complement-dependent inflammation. It is therefore believed that therapeutic inhibition of complement is likely to arrest the process of certain diseases. Attempts to efficiently inhibit complement include the application of endogenous soluble complement inhibitors (C1-inhibitor, recombinant soluble complement receptor 1- rsCR1), the administration of antibodies, either blocking key proteins of the cascade reaction (e.g. C3, C5), neutralizing the action of the complement-derived anaphylatoxin C5a, or interfering with complement receptor 3 (CR3, CD18/11b)-mediated adhesion of inflammatory cells to the vascular endothelium. In addition, incorporation of membrane-bound complement regulators (DAF-CD55, MCP-CD46, CD59) has become possible by transfection of the correspondent cDNA into xenogeneic cells. Thereby, protection against complement-mediated inflammatory tissue damage could be achieved in various animal models of sepsis, myocardial as well as intestinal ischemia/reperfusion injury, adult respiratory distress syndrome, nephritis and graft rejection. Supported by results from first clinical trials, complement inhibition appears to be a suitable therapeutic approach to control inflammation. Current strategies to specifically inhibit complement in inflammation have been discussed at a recent meeting on the 'Immune Consequences of Trauma, Shock and Sepsis', held from March 4-8, 1997, in Munich, Germany. The Congress (chairman: E. Faist, Munich, Germany), which was held in close cooperation with various national and international shock and trauma societies, was attended by about 2000 delegates from 40 countries. The major objective of the meeting was to provide an overview on the most state-of-the-art methods to prevent multiple organ dysfunction syndrome (MODS)/multiple organ failure (MOF) following the systemic inflammatory response (SIRS) to severe trauma. One of the largest symposia held within the Congress was devoted to current aspects of controlling complement in inflammation (for abstracts see: Shock 1997, 7 Suppl., 71-75). After providing the audience with information on the scientific background by addressing the clinical relevance of complement activation (G.O. Till, Ann Arbor, MI, USA) and discussing recent developments in modern complement diagnosis (J. Köhl, Hannover, Germany), B.P. Morgan (Cardiff, UK) introduced the symposium's special issue by giving an overview on complement regulatory molecules. Selected topics included overviews on the application of C1 inhibitor (C.E. Hack, Amsterdam, NL), sCR1 (U.S. Ryan, Needham, MA, USA), antibodies to C5 (Y. Wang, New Haven CT, USA) and to the anaphylatoxin C5a (M. Oppermann, Göttingen, Germany), and a report on complement inhibition in cardiopulmonary bypass (T.E. Mollnes, Bodø, Norway). The growing interest of clinicians in complement-directed anti-inflammatory therapy, and the fact that only some of the various aspects of therapeutic complement inhibition could be addressed on the meeting, has motivated the author to expand a Congress report into a short comprehensive review on recent strategies to control complement in inflammation.

Inhibition of anaphylatoxin C3a- and C5a- but not nerve stimulation- or Noradrenaline-dependent increase in glucose output and reduction of flow in Kupffer cell-depleted perfused rat livers.

In isolated in situ perfused rat livers, infusion of anaphylatoxins C3a and C5a, activation peptides of the complement system, as well as stimulation of sympathetic hepatic nerves have been shown to increase hepatic glucose output and to reduce hepatic flow. These effects were mediated via an at least partially prostanoid-dependent intercellular signalling chain between nonparenchymal cells and hepatocytes. Kupffer cells have been implicated as the source of prostanoids in the anaphylatoxin-dependent signalling chain and Ito cells in the nerve stimulation-dependent signalling chain, because anaphylatoxins and noradrenaline increased prostanoid synthesis in isolated Kupffer and Ito cells, respectively. To further corroborate this hypothesis, anaphylatoxins were infused and hepatic nerves were stimulated in perfused rat livers in which Kupffer cells had been largely depleted by treatment of the animals with gadolinium chloride. Native human anaphylatoxin C3a (nhC3a) and recombinant rat anaphylatoxin C5a (rrC5a) increased prostanoid formation as well as glucose output and reduced flow in perfused rat liver. In Kupffer cell-depleted rat livers, the nhC3a- and rrC5a-mediated prostanoid formation was nearly abolished, and the increase in glucose output and the reduction of flow were reduced to between 30% and 50% (area under the curve [AUC]) of control livers. In contrast, stimulation of hepatic nerves increased glucose output and reduced flow to a similar extent in Kupffer cell-depleted livers as in control livers. These results indicate that Kupffer cells were not involved in the prostanoid-mediated nerve stimulation-dependent increase in glucose output and reduction of flow. Kupffer cells seemed, however, to be at least one major source of the anaphylatoxin-mediated prostanoid formation and, consequently, stimulation of glucose release and flow reduction in perfused liver. Because the metabolic and hemodynamic anaphylatoxin effects were not completely blocked in livers of gadolinium-treated animals, either Kupffer cells may not have been entirely eliminated, or yet another nonparenchymal cell type and mediator might be involved in the anaphylatoxin-elicited intercellular communication between nonparenchymal cells and hepatocytes.

The extracellular neutral cysteine proteinase of Entamoeba histolytica degrades anaphylatoxins C3a and C5a.

We have shown previously that the extracellular cysteine proteinase of Entamoeba histolytica trophozoites activates the alternative pathway of complement by specifically cleaving C3. This unique mechanism of complement activation leads to passive lysis of nonpathogenic, but not of pathogenic strains. In an attempt to investigate the relationship between the cleavage of complement components C3 and C5 and the pathogenesis of amebiasis, we investigated the production of the anaphylatoxins C3a and C5a, which have diverse effects on the host immune response. The concentration of proteinase required to cleave purified C5 was at least 5 to 10 times that needed for C3 cleavage, but these levels are easily obtainable as demonstrated by cleavage of 125I-labeled C5 during incubation with purified trophozoites. When the C3a-like cleavage fragments were purified by gel filtration, they were found to be extensively degraded during a 1-h incubation of C3 with the proteinase. Subsequent evaluations of the C3a- and C5a-like cleavage products generated earlier in the reaction using immunoblots and cellulose acetate electrophoresis revealed rapid degradation, even during incubation periods as short as 5 min. Because C-terminal fragments as small as 20 amino acid residues can mimic the biologic functions of C3a or C5a, we tested cleavage products for activity. In sensitive bioassays, including guinea pig platelet aggregation for C3a activity and chemotaxis for C5a activity, we demonstrated that proteolysis renders these molecules inactive. These studies suggest that the extracellular cysteine proteinase of E. histolytica, which is capable of activating the complement system, may also provide a mechanism to circumvent normal host immunity by inactivating the proinflammatory factors C3a and C5a.

Anaphylatoxin generation in acute pancreatitis.

Fifty-one patients with elevated serum amylase and clinical signs of acute pancreatitis were studied prospectively. The concentrations of anaphylatoxins (C3a and C5a) were measured with a radioimmunoassay and the activity of their inactivator was determined. The pancreatitis was classified as mild, moderate, or severe according to Ranson's 11 signs, appearance of peritoneal fluid, and development of multisystem organ failure (MSOF). Plasma C3a and C5a concentrations were elevated during attacks of acute pancreatitis. Anaphylatoxin levels correlated with the severity of the disease (C3a, P less than 0.001; C5a, P less than 0.05). The highest and most persistent levels were found in the group with MSOF. C3a levels decreased rapidly during recovery. In patients with complications like abscess or pseudocyst, the C3a elevation persisted until adequate treatment was instituted. In this study, no significant changes of the inactivator levels were found, except at discharge when the inactivator level of the severe group was elevated compared to that of the moderate and mild groups (P less than 0.05).

Altered concentrations of terminal complement complexes, anaphylatoxins, and leukotrienes in the coronary sinus during cardiopulmonary bypass.

The aim of this study was to determine if the hypoperfused heart activates complement with formation of anaphylatoxins, terminal complement complexes (TCC), or leukotrienes during cardiopulmonary bypass. Fifteen patients undergoing elective cardiopulmonary bypass surgery were studied regarding complement and leukotriene activation. Blood samples were drawn serially from the radial artery and coronary sinus. The plasma concentrations of the complement components C1INH, C3, C4, and C5 decreased during the procedure, whereas C3a and TCC increased. Protamine reversal of heparin further increased the plasma levels of C3a and TCC. No significant changes in plasma levels of C5a and leukotriene C4 were observed during cardiopulmonary bypass. The activity of the anaphylatoxin inactivator (AI) decreased in both the radial artery and the coronary sinus. There were no significant differences between the concentrations of complement components and leukotriene C4 in blood from the radial artery and coronary sinus. The levels of C3a and TCC increased and C1INH, C3, C4, C5, and the anaphylatoxin inactivator activity decreased to the same extent in the coronary sinus and the radial artery. Thus, the heart does not appear to be the primary site for the altered concentrations of these endogenous vasoactive substances.

Inhibition of the covalent binding reaction of complement component C4 by penicillamine, an anti-rheumatic agent.

D(-)-Penicillamine [D(-)-beta beta-dimethylcysteine] is an anti-arthritic drug, but its use is limited by adverse side effects, which include problems in immune-complex clearance. Complement is important as a source of inflammatory mediators in rheumatoid arthritis and is also involved in immune-complex clearance. Thus inhibition of the complement cascade would be likely to contribute to both the therapeutic and the toxic effects of penicillamine. It is shown that penicillamine and cysteine are potent inhibitors of the covalent binding of activated complement component C4 to immune complexes. [35S]Cysteine itself becomes covalently bound to C4b through the thioester site. Penicillamine and cysteine are more reactive with the C4A isotype than with the C4B isotype of the HLA class III protein C4. The limited amino acid sequence differences between C4A and C4B include a cysteine/serine interchange, and it is suggested that the cysteine residue in C4A contributes to the increased rate of reaction of C4A with the alpha-amino-beta-thiol compounds.

Protamine inhibits plasma carboxypeptidase N, the inactivator of anaphylatoxins and kinins.

Protamine given to neutralize heparin after extracorporeal circulation can trigger a catastrophic reaction in some patients. While searching for a biochemical basis for this reaction, protamine was tested as an inhibitor of human plasma carboxypeptidase N (CPN) or kininase I, the inactivator of anaphylatoxins and kinins. Human plasma and CPN purified from human plasma, (Mr = 280 K) or its isolated active subunit (Mr = 48 K) were the sources of enzyme. The hydrolysis of furylacryloyl (FA)-Ala-Lys was measured in a UV spectrophotometer and that of bradykinin and the synthetic C-terminal octapeptide of anaphylatoxin C3a (C3a8) by high performance liquid chromatography. Protamine inhibited the hydrolysis of FA-Ala-Lys by CPN, (IC50 = 3.2 X 10(-7) M); added human serum albumin (30 mg/ml) increased the IC50 to 7 X 10(-6) M. When plasma was the source of CPN, the IC50 was 2 X 10(-6) M. Protamine more effectively inhibited the hydrolysis of bradykinin and C3a8. The IC50 for protamine was 5 X 10(-8) M with CPN and bradykinin, 7 X 10(-8) M with CPN and C3a8 and with the 48 K subunit and bradykinin it was 7 X 10(-8) M of protamine. Heparin competes with CPN for protamine, because in high concentration (18 U/ml) it reverses the inhibition by protamine. Protamine did not inhibit angiotensin I converting enzyme (kininase II) or the endopeptidase 24.11 (enkephalinase). Kinetic studies showed the mechanism of protamine inhibition to be partially competitive; about 10-20% of the hydrolysis of bradykinin by CPN was not inhibited by protamine. Thus, by blocking the inactivation of mediators released in shock, protamine inhibition of CPN may be partially responsible for the catastrophic reaction observed to occur in some patients.

Inhibition of complement activation by high-dose corticosteroids in total hip arthroplasty.

Anaphylatoxins are released during total hip arthroplasties (THA) when methylmethacrylate is used. These toxins may be responsible for hemodynamic and pulmonary instability during surgery. Recent studies have shown that the release of anaphylatoxins may be inhibited by high-dose corticosteroids (HDC). In a double-blind study 30 consecutive patients with osteoarthritis or failed hip fractures were randomized into two groups; 15 patients received HDC at the beginning of the operation and 15 patients, designated the control group, received infused saline. Anaphylatoxin formation, arterial oxygen tension, and blood pressure were determined preoperatively, during the operation, and one day postoperatively. The patients who received HDC had no significant alteration regarding the anaphylatoxins or arterial oxygen tension during surgery. However, in the control group elevated C3a levels and decreased PaO2 levels were found. Corticosteroids therefore inhibit complement activation and anaphylatoxin release in hip arthroplasty surgery.

Ixodes dammini: salivary anaphylatoxin inactivating activity.

Saliva of the tick, Ixodes dammini, antagonizes anaphylatoxin, abolishing both the effects of anaphylatoxin on guinea pig ileum preparations regularly stimulated with histamine and the local edema caused by intradermal injection of anaphylatoxin into guinea pigs. Saliva of these ticks, however, did not modify polymorphonuclear leukocyte aggregation induced by anaphylatoxin. Bradykinin and lysil-bradykinin were inactivated, but angiotensin I, angiotensin II, and substance P were not affected. Amino acids were released rapidly following incubation of saliva with bradykinin, but slowly from des-arg-9-bradykinin. These results suggest the presence of a salivary carboxypeptidase with specificity for terminal basic amino acids. Such activity may inactivate anaphylatoxin and bradykinin at the site of tick attachment.