Anaphylactic release of a prekallikrein activator from human lung in vitro

Mediators of Anaphylaxis, Anaphylactoid Reactions, and Rhinitis

Besides histamine, a large and increasing number of mediators of allergic reactions are being found to be released by mast cells or basophils during anaphylactic reactions. Many of these same substances are released by stimuli other than allergen-IgE interactions, and this type of phenomenon (anaphylactoid or pseudo-allergic reaction) may account for some nasal symptoms that simulate allergy. In addition to rapidly developing reactions of these types, numerous recent investigations have emphasized the importance of late-phase reactions that occur as a consequence of the immediate reactivity. Besides mast cells and/or basophils, these late effects seem to involve a complex network of cellular interactions, which may include neutrophils, eosinophils, lymphocytes, macrophages, and platelets.

Studies of nasal washings following allergen challenges in humans have provided cogent in vivo support of earlier hypotheses about mediator release based on in vitro experimentation.

Activation of the kallikrein-kinin system and release of new kinins through alternative cleavage of kininogens by microbial and human cell proteinases

Kinins are released from kininogens through the activation of the Hageman factor-prekallikrein system or by tissue kallikrein. These peptides exert various biological activities, such as vascular permeability increase, smooth muscle contraction, pain sensation and induction of hypotension. In many instances kinins are thought to be involved in the pathophysiology of various diseases. Recent studies have revealed that microbial and human cell proteinases activate Hageman factor and/or prekallikrein, or directly release kinin from kininogens. This review discusses the activation of the kinin-release system by mast-cell tryptase and microbial proteinases, including gingipains, which are cysteine proteinases from Porphyromonas gingivalis , the major pathogen of periodontal disease. Each enzyme is evaluated in the context of its association to allergy and infectious diseases, respectively. Furthermore, a novel system of kinin generation directly from kininogens by the concerted action of two proteinases is described. An interesting example of this system with implications to bacterial pathogenicity is the release of kinins from kininogens by neutrophil elastase and a synergistic action of cysteine proteinases from Staphylococcus aureus . This alternative production of kinins by proteinases present in diseased sites indicates a significant contribution of proteinases other than kallikreins in kinin generation. Therefore kinin receptor antagonists and proteinase inhibitors may be useful as therapeutic agents.

Potent 'new pressor protein' related to coagulation factor XII is potentiated by inhibition of angiotensin converting enzyme

BACKGROUND

'New pressor protein' was observed after tryptic activation of human and rat plasma in vitro, which is done conventionally for prorenin measurements.

RESULTS

It is potently pressor, heat labile, possesses enzyme activity, and has a relative molecular mass > 30 kDa with isoelectric point(s) 4.7-4.9. New pressor protein equivalent to only 0.01 ml human, or rat, plasma injected intravenously quickly raises systolic blood pressure in 300 g anesthetized, ganglion-blocked, bioassay rats by about 15 mmHg. For unknown reasons, this is potentiated to about 45 mmHg after treatment with angiotensin I converting enzyme inhibitors (such as captopril and enalapril). New pressor protein activity in rats remains normal 24 h after bilateral nephrectomy, suggesting that it has an extrarenal origin and, furthermore, excluding the possibility of an association with renin-angiotensin system. Systolic blood pressure elevation is greater than the diastolic one, implicating cardiotonic effects. Human plasma new pressor protein was purified using standard biochemical techniques and its N-terminal sequence (19 residues) found to be homologous with the beta factor XIIa fragment of coagulation factor XII. This was supported by demonstrating inhibition of new pressor protein activity in vitro using the factor XII-specific corn trypsin inhibitor. Also, human new pressor protein activity in humans congenitally deficient in coagulation factor XII is very low. The high potency and multiphasic, cardiotonic effects of injected new pressor protein suggest that it interacts synergistically with other systems in the body. This was confirmed by showing that, within 10 min of total bilateral adrenalectomy, responses to new pressor protein decreased markedly.

CONCLUSIONS

New pressor protein's action requires adrenal (medullary?) involvement, but its mechanism of action and that of its potentiation by angiotensin converting enzyme inhibitors remain unknown. The physiologic and clinical relevance of these observations depends on whether activation of new pressor protein can occur in vivo.

Activation of the coagulation pathway during ongoing allergic cutaneous reactions in humans

The levels of histamine, fibrinopeptide A (FPA), and IgG were determined in chamber fluids overlying sites of antigen versus buffer incubation for up to 7 hours in seven atopic and four antigen-nonreactive subjects. Significant increases in histamine were observed at antigen versus buffer sites in the atopic subjects throughout the 7-hour period. FPA and IgG levels were higher in antigen than in buffer sites from 0 to 5 hours in the atopic subjects. Furthermore, FPA levels correlated with the magnitude of induration at 6 hours after antigen injection in atopic subjects. There were no differences in the levels of histamine, FPA, or IgG at antigen versus buffer sites in the skin test-negative subjects. We suggest that the combination of vascular leakage of proteins, induced by vasoactive mediator release, and activation of these proteins during ongoing cutaneous reactions is responsible for fibrin formation that contributes to the pathophysiology of late-phase allergic responses in the skin.

Release of elastase from purified human lung mast cells and basophils. Identification as a Hageman factor cleaving enzyme

Elastase, a serine protease, is capable of inducing severe lung destruction in experimental animal models. We now report that this proteinase exists preformed in neutrophil-free sonicates of purified human lung mast cells (greater than 98% purity) and in circulating peripheral blood basophils (greater than 97% purity). The elastase levels in both cell types (41-174 ng/10(6) cells) represents approximately 3-20% of those found in human neutrophils; both cell types released their elastase following anti-IgE and ionophore A23187 challenge. The apparent molecular size of the mast cell enzyme on Sephadex G-100 gel filtration, as well as its inhibition profile, was identical to that of purified human neutrophil elastase. This mast cell elastase is identical to our previously reported mast cell-derived Hageman factor cleaving activity. Mast cell-, basophil-, and neutrophil-derived elastases cleave Hageman factor into fragments of 52,000 and 28,000 Da; cleavage by all three enzymes is inhibited by preincubation with polyclonal antibodies directed against human neutrophil elastase.

The Hageman factor-dependent system in the vascular permeability reaction

The mechanism by which the Hageman factor-dependent system induces vascular permeability has been analyzed. The Mr-28,000 active fragment of guinea pig Hageman factor (beta-HFa), injected intradermally, induces an increase in local vascular permeability. Inhibition of vascular permeability resulted from pretreatment of the beta-HFa with immunopurified anti-Hageman factor F(ab')2 antibody at concentrations of 10(-6)-10(-7) M as well as by incubation with corn and pumpkin seed inhibitors of beta-HFa. To determine whether prekallikrein and kallikrein participated in the permeability induced by beta-HFa, circulating prekallikrein was depleted by intra-arterial injections of anti-prekallikrein F(ab')2 antibody. This resulted in about 80% diminution of the vascular permeability response to beta-HFa, without affecting the permeability reaction to bradykinin. Soybean trypsin inhibitor (10(-6) M), injected at the same cutaneous site as the beta-HFa, inhibited the vascular permeability response to beta-HFa by more than 90%. This concentration of soybean inhibitor blocked more than 90% of the activity of guinea pig plasma kallikrein, but did not inhibit the amidolytic capacity of beta-HFa. The permeability activity of beta-HFa (but not its amidolytic activity) was augmented 10-fold by simultaneous injection of a synthetic kinin potentiator, SQ 20,881 (Glu-Tyr-Pro-Arg-Pro-Gln-Ile-Pro-Pro-OH), and was almost completely inhibited by the simultaneous injection of a kinin-destroying enzyme, carboxypeptidase B. These results support the hypothesis that the greatest proportion of vascular permeability induced by beta-HFa is produced by the activation of prekallikrein followed by the release of kinin in the cutaneous tissue. These data offer the first in vivo evidence that the Hageman factor-dependent system by itself can induce inflammatory changes.

Tryptase from human mast cells does not activate purified human Hageman factor

The effect of tryptase, a neural protease released from human lung mast cell secretory granules, on purified human Hageman Factor (Factor XII) was examined. No increase in Hageman Factor enzymatic activity was detected after incubation with tryptase at 37 degrees C; activation of Hageman Factor by bovine trypsin served as a positive control. Furthermore, pre-incubation of Hageman Factor with tryptase did not diminish the subsequent activation of Hageman Factor by trypsin. Polyacrylamide gel electrophoresis was also performed to show that incubation with tryptase does not alter the molecular weight of Hageman Factor. Therefore, tryptase neither activates nor destroys human Hageman Factor.

Immunologic aspects of vessel injury and thrombosis

A large and rapidly growing quantity of information gained from both clinical and experimental observation strongly indicate that perturbations of the immune system can contribute to the pathogenesis of vessel injury and thrombosis. This is, in part, because the immune system functions to amplify and diversify the host response to a given stimulus often resulting in activation of associated pathways such as the hemostatic system and modulation of endothelial cell function. Studying the pathogenesis of arteriosclerosis and its complications, as well as other vascular disease, from an immunologic or immunopathologic perspective may provide a better understanding of why some some individuals appear to be at greater risk of cardiovascular disease than others, a more precise identification of the mechanisms leading to the expression of increased risk, and because of the structural specificity implicit in immunologic reactions, identification of those environmental factors responsible for inciting such immunologic perturbation. It is conceivable that identification of at least some of the risk factors associated with the 50% of deaths from heart attack that are not associated with known risk factors may be achieved through a consideration of the role of immunologic mechanisms in the pathogenesis cardiovascular disease.

Detection of tissue kallikrein in the bronchoalveolar lavage fluid of asthmatic subjects

Kininogenase activity was detected by cleavage of radiolabeled substrate (125I-high molecular weight kininogen [HMWK]) in 22 of 24 bronchoalveolar lavage (BAL) fluid samples from 17 asthmatics who either responded to aerosolized allergen challenge or had symptoms of active asthma. In contrast, six of seven normal controls lacked enzymatic activity. Levels of free immunoreactive kinin found in BAL fluid correlated with the presence of kininogenase activity (P = 0.002). The cleavage pattern of 125I-HMWK by the BAL fluid kininogenase (a dominant 65,000-mol wt fragment), and synthetic inhibitor profile (phe-phe-arg-CH2Cl and phenylmethylsulfonyl fluoride) were compatible with a tissue kallikrein. Peak kininogenase activity eluted at an apparent molecular weight of 20,000-34,000 by HPLC gel filtration. Its antigenic identity was established by immunoblotting with anti-human urinary kallikrein antibody and its activity was inhibited by this antibody. Lysylbradykinin was generated during incubation of fractionated BAL fluid and purified HMWK, the characteristic cleavage product of the tissue kallikreins. We conclude that elevated amounts of tissue kallikrein and kinin are present in the bronchoalveolar spaces of asthmatic subjects. Kinin generation may contribute to the asthmatic response directly through edema formation and smooth muscle contraction and by augmenting release and/or production of preformed (histamine) and secondary mediators such as leukotrienes and platelet-activating factor.

The IgE-dependent release of a Hageman factor cleaving factor from human lung

Passively sensitized human lung fragments were shown to release a protease by an IgE-dependent mechanism which can cleave human Hageman factor (Coagulation Factor XII). This enzyme, lung Hageman factor cleaving factor, was partially purified by ion exchange chromatography and gel filtration and was shown to be a serine protease with an apparent molecular weight of 12,000-13,000. This protease appears to be unrelated to any known activator of Hageman factor by molecular weight and inhibition profile and was shown to be distinct from an IgE-dependent prekallikrein activator, as well as the kininogenase activity defined as basophil kallikrein of anaphylaxis. Although it appears marginally capable of activating Hageman factor, it rapidly cleaves and inactivates the activated form so that the net effect is a loss of activatable Hageman factor. The result suggests that diminished levels of Hageman factor that may be seen associated with IgE-dependent reactions can be due to digestion and depletion rather than activation, and other criteria for activation of the contact system must be employed.

Experimental pulmonary inflammatory injury in the monkey

Inflammatory pulmonary injury was induced in Macaca mulatta rhesus monkeys by the intrabronchial instillation of the formylated peptide norleu-leu-phe (FNLP) or phorbol myristate acetate (PMA). Indicators of pulmonary injury included an increase in mean protein content of bronchoalveolar lavage (BAL) fluid from 0.51 mg/ml in untreated animals to 3.74 mg/ml and 6.64 mg/ml in FNLP- and PMA-treated animals, respectively, the appearance of a diffuse pulmonary infiltrate in chest roentgenograms, and histologic evidence of a predominantly neutrophilic leukocytic infiltration. Concomitant with the appearance of pulmonary injury was the generation of proteases and oxidants in the BAL fluids. Neutrophil elastase, bound to alpha 1-protease inhibitor (alpha 1-PI), was found to increase from 0.47 micrograms/ml in untreated monkeys to 0.99 micrograms/ml in FNLP-treated animals and 1.23 micrograms/ml in monkeys receiving PMA. Radioiodinated human prekallikrein, instilled for 2 min into the inflammatory site and retrieved by lavaging, was found to have undergone proteolytic cleavage; this cleavage was not consistently inhibitable with the inclusion of antibody to elastase. BAL fluids were shown to contain an amidolytic activity when tested on the synthetic substrate H-D-pro-phe-arg-pNA. This activity was partially inhibitable with known inhibitors of active Hageman factor and kallikrein. beta-Glucuronidase levels in the BAL fluids increased from 0.85 U/ml to 4.36 U/ml and 8.25 U/ml in FNLP- and PMA-treated animals, respectively. Myeloperoxidase (MPO) levels also increased from 1.37 OD U/ml X min to 16.59 and 30.47 OD U/ml X min in the same groups of animals. Oxidant generation was also assessed in several different ways. The specific activity of the oxidant-sensitive inhibitor alpha 1-PI recovered in the BAL fluid decreased from 0.80 in control samples to 0.57 and 0.65 in FNLP- and PMA-treated animals. That this inactivation was due to oxidant injury of the molecule was confirmed by the return to full activity of four out of five BAL samples after their incubation with the reducing agent dithiothreitol in the presence of methionine sulfoxide peptide reductase. The specific activity of catalase in the BAL fluids of animals given 3-amino, 1,2,4 triazole (AT) 1 h before lavaging showed drops from 0.97 in untreated monkeys to 0.04 in FNLP-treated and 0.49 in PMA-treated monkeys. MPO levels also fell in the AT-treated injured animals from 16.59 to 0.85 delta OD/min X ml in FNLP animals in the absence and presence of AT, and 30.47 to 0.60 delta OD/min X ml in PMA-treated animals. Inhibition of MPO by AT was shown in vitro to be H2O2 dependent. Total glutathione levels in the BAL fluids did not change appreciably after FNLP or PMA treatment. These studies present substantial evidence of the generation of both proteases and oxidants during the establishment of acute pulmonary inflammatory injury in an experimental primate model.

The effect of tryptase from human mast cells on human prekallikrein

Tryptase, the dominant protease in human mast cells, was examined for its effect on human prekallikrein. Tryptase in the presence and absence of heparin failed to activate prekallikrein as shown in a spectrophotometric assay for kallikrein employing benzoy 1-pro-phe-arg-p-nitroanilide. Treated prekallikrein was converted to active kallikrein by bovine trypsin. Prekallikrein cleavage products were analyzed by electrophoresis in polyacrylamide gels under denaturing conditions (+/- reduction). Tryptase caused no apparent cleavage under conditions where trypsin caused complete cleavage. Thus, tryptase, which has previously been shown to lack kallikrein and kininase activities, neither activates nor destroys prekallikrein.