Formyl peptide chemotactic receptor. Evidence for an active proteolytic fragment

We have developed a radioiodinated photoaffinity label, N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys-N-6-(4'-azido-2'-nitrophenylamino) hexanoate (where Nle represents norleucine) (125I-PAL), which forms a covalent complex with the formyl peptide chemotactic receptor of living human neutrophils. Labeling was 12 to 16% efficient and did not alter cell viability. The receptor on live neutrophils and neutrophil membranes has an apparent molecular weight of 50,000 to 70,000 by sodium dodecyl sulfate-polyacrylamide electrophoresis. The receptor on intact cells possesses one predominant papain cleavage site, yielding a 35,000-Da fragment. This receptor fragment retains an affinity for N-formyl-Nle-Leu-Phe-Nle-125I-Tyr-Lys indistinguishable from the receptor on control cells (KD = 1.9 and 1.8 nM, respectively). The 35,000-Da papain fragment was biologically active as evidenced by an unchanged dose-response curve for peptide-stimulated beta-glucuronidase release and fluorescent peptide uptake. Papain treatment of 125I-PAL-labeled neutrophil membranes or of digitonin-soluble 125I-PAL-labeled receptors produced a predominant 28,000-Da fragment without evidence of the 35,000-Da fragment seen with whole cells. Pronase, which did not cleave the receptor on intact cells, produced multiple receptor fragments when used to treat 125I-PAL-labeled membranes.

Encapsulation of exogenous agents in erythrocytes and the circulating survival of carrier erythrocytes

Erythrocytes can be made to entrap enzymes, lipids, drugs, pesticides, and large macromolecules by a variety of encapsulation procedures. Methods of encapsulation include hypotonic dilution and dialysis, lipid fusion, electrical hemolysis, and chemical perturbation. The survival of carrier erythrocytes is dependent on the method of encapsulation as is the encapsulation efficiency. Research has led to utilization of carrier cells for drug and enzyme-replacement therapies, for incorporation of DNA and antibodies into living cells, and for enhancement of the oxygen-carrying capacity of hemoglobin. Many of the possible uses of erythrocytes as carriers are explored.

Quantitative cytochemistry of blood neutrophils in acute myeloid leukaemia

Blood neutrophils were studied by quantitative cytochemistry in patients with acute myeloid leukemia at diagnosis (17 patients), during remission (17 patients) and in relapse (seven patients). Scanning and integrating microdensitometry was used to quantify components of azurophilic granules (myeloperoxidase, chloroacetate esterase, beta-glucuronidase, acid phosphatase, acid mucosubstance) and also specific granules (lactoferrin). At diagnosis, neutrophil myeloperoxidase, chloroacetate esterase, and lactoferrin were significantly decreased, compared with normal neutrophils from 25 controls, with 13 of the 17 patients showing a partial or complete deficiency of at least one granule constituent. Five of seven patients, followed serially from remission into relapse, showed a fall in activity of azurophilic or specific granule components before overt blast cell infiltration of the marrow had occurred and this may predict relapse.

Evidence that abnormal platelet functions in human Chédiak-Higashi syndrome are the result of a lack of dense bodies

The structure and functions of platelets from three patients with the Chédiak-Higashi syndrome were examined. Electron-microscopic observations revealed a large reduction in the number of serotonin-storage granules or dense bodies but otherwise normal ultrastructure and normal amounts of alpha-granules and catalase-positive granules. The number of mepacrine-labeled granules was also reduced. Platelets contained normal amounts of beta-thromboglobulin and Platelet Factor 4. The platelet release reaction studied with thrombin as the inducer was impaired. The serotonin uptake by the patients' platelets was low and not inhibited by reserpine, and its metabolism was increased. These findings clearly show that platelets from human Chédiak-Higashi syndrome are deficient in the storage pool of dense granule substances and suggest that this granule defect has an influence on the release mechanism of other granule constituents.

Protective effects of thromboxane A2 synthetase inhibitors on endotoxin shock

To elucidate the role of thromboxane A2 in the development of endotoxin shock following administration of endotoxin, the effects of three thromboxane A2 synthetase inhibitors, (E)-3-(4-(1-imidazolyl)phenyl)-2-propenoic acid hydrochloride monohydrate (OKY-046), sodium (E)-3-(4-(3-pyridylmethyl)phenyl)-2-methylacrylate (OKY-1581) and imidazole were examined. Intravenous administration of E. Coli endotoxin (3 mg/kg) produced shock and all rats died within ten hours. Pretreatment with thromboxane A2 synthetase inhibitors markedly improved the survival rates. The untreated endotoxin shock group showed marked increase in thromboxane B2 levels in the venous blood, while no such changes were seen in the pretreated groups. There were no statistically significant differences in 6-keto prostaglandin F1 alpha levels in the venous blood. In the untreated shock group, microthrombi were observed in 64% of the glomeruli in the kidneys two hours after endotoxin injection. In the groups pretreated with OKY-046, OKY-1581 and imidazole, microthrombi were seen only in 22, 19 and 24%, respectively. Thus, thromboxane A2 plays an important role in the development of endotoxin shock and thromboxane A2 synthetase inhibitors, in particular OKY-046 and -1581, are prophylactic.

Effect of the Ca2+ antagonist nifedipine on the release of platelet-activating factor (PAF-acether), slow-reacting substance and beta-glucuronidase from human neutrophils

Ca2+ antagonists such as nifedipine (Nif) inhibit processes that depend on extracellular Ca2+ in many muscular and secretory cells. The effect of Nif on mediator release and Ca2+ uptake by human polymorphonuclear neutrophils (PMN) has been investigated. Nif caused a concentration-dependent inhibition of the Ca2+ ionophore-induced release of platelet-activating factor (PAF-acether), slow-reacting substance (SRS) and to a lesser degree beta-glucuronidase (beta-glu). Nif inhibited the synthesis of PAF-acether rather than its release. Increasing Ca2+ concentration in the bathing medium from 1.3 to 2.8 mM completely reversed the effect of Nif on PAF-acether secretion. Nif at 1 and 5 microM reduced PMN45Ca2+ uptake induced by the Ca2+ ionophore A 23187. These results indicate that the inhibition by Nif of mediator release depends probably on the Ca2+-antagonistic property of the drug. A preliminary ex vivo study suggests that this inhibitory effect on neutrophil functions exists during therapeutic use.

Serum lysosomal enzyme activities in silicosis and asbestosis

The serum activities of two lysosomal enzymes, beta-N-acetylglucosaminidase (EC 3.2.1.30) and beta-glucuronidase (EC 3.2.1.31) were analyzed for 28 silicosis and 34 asbestosis patients. The enzyme activities of the patients were compared with those of age-, sex- and exposure-matched controls with no radiological signs of pneumoconiosis, and with an additional reference group of blood donors. The serum activity of beta-N-acetylglucosaminidase was higher in the silicosis patients (32.5 +/- 11.7 U/l) than in the asbestosis patients (21.7 +/- 7.9 U/l, p less than 0.001), in the silica exposed controls (27.1 +/- 6.7 U/l, p less than 0.05) or in the blood donors (24.8 +/- 6.3 U/l, p less than 0.05). No significant differences were found in the serum activity of beta-glucuronidase in the studied groups. Although the mechanisms causing different levels of serum beta-N-acetylglucosaminidase activity in silicosis and asbestosis patients remain unresolved, they may be related to the different mechanisms of action of the two dusts on lung (10).

Effect of vitamin E on adjuvant arthritis in rats

Adjuvant arthritis was induced in rats fed a diet deficient in or supplemented with vitamin E, and its severity was scored according to the macroscopic findings of their legs, tails, and ears. The average score so obtained was higher in the vitamin E-deficient diet group than in the group of rats supplemented with vitamin E. Whereas the A/G ratio remained depressed in vitamin E-deficient rats, rats on a vitamin E-supplemented diet showed a fast recovery from A/G-ratio depression. The serum levels of beta-glucuronidase and acid phosphatase were elevated after administration of an adjuvant. The serum levels of these lysosomal enzymes showed a remarkable increase in rats fed a vitamin E-deficient diet, while the elevation in lysosomal enzyme levels in rats fed a vitamin E-supplemented diet was inhibited. The levels of thiobarbituric acid (TBA) reactants in the synovia were elevated at 2 weeks after exposure to the adjuvant and were decreased thereafter. In rats maintained on a diet supplemented with vitamin E, on the other hand, the increase in synovial level of TBA reactive substances was inhibited. These observations suggest that the aggravation of adjuvant arthritis may be associated with lipid peroxidation and that antioxidants, such as vitamin E, may be beneficial for arthritis.

Decreased release of lysosomal enzymes from peripheral leukocytes of patients with atopic dermatitis

Peripheral blood leukocytes from fifteen patients with atopic dermatitis and ten normal nonatopic volunteers were incubated with various stimuli in vitro, and the release of the lysosomal beta-glucuronidase into the supernatant was measured. beta-Glucuronidase release was significantly reduced in patients with severe atopic dermatitis after stimulation with aggregated IgG, horse antihuman lymphocyte globulin (ALG), zymosan, and yeast-activated serum. There was an indirect correlation (r = -0.83) between aggregated IgG-induced beta-glucuronidase release and the intensity of clinical symptoms; however, there was no correlation with serum IgE levels. The enzyme release measured was not caused by cellular lysis, except for high concentrations of antilymphocyte globulin, as determined by lactic dehydrogenase (LDH) activity in the supernatant. It is concluded that lysosomal enzyme release defects might be involved in the well-known decreased resistance to infections in patients with atopic dermatitis.

5-L-hydroxy-6,8,11,14-eicosatetraenoate potentiates the human neutrophil degranulating action of platelet-activating factor

Platelet-activating factor (AAGPC) and two of its structural analogues degranulated human neutrophils with respective potencies that were increased up to 100 to 1000-fold by 16 nM to 5 microM of 5-L-hydroxyeicosatetraenoate (5-L-HETE). 5-rac-HETE had similar actions but 8-rac-HETE was without effect. Furthermore, 5-L-HETE did not influence the degranulating actions of C5a, A23187 or a formalated oligopeptide chemotactic factor and none of the HETEs, by themselves, caused degranulation. Thus, 5-L-HETE and AAGPC selectively interact to induce degranulation. Since these products rapidly form in stimulated PMNs, they may serve as potentiator and agonist, respectively, to transduce biological signals into cell function.

Signals of monocyte activation in patients with SLE

The Fc receptor mediated reaction, the beta-glucuronidase and the lactic dehydrogenase activities of monocytes and the serum lysozyme level were tested together with the circulating immune complex content of patients with systemic lupus erythematosus. Simultaneously with the increasing FC receptor-mediated reaction and the elevated enzyme activities of patient monocytes, the secretion of lysozyme and the immune complex content of the sera were higher than those of the controls. A positive correlation was demonstrated between the Fc receptor-mediated reaction, the beta-glucuronidase activity, the lysozyme secretion and the immune complex content of the sera. Thus, the monocytes of patients appeared to be activated by the circulating immune complexes.

Cytochemical analysis of human peripheral blood lymphocyte subsets defined by monoclonal antibodies

Human blood lymphocyte subpopulations, revealed by a panel of commercially available monoclonal antibodies by means of a rosetting technique, were submitted to direct cytochemical analysis and were shown to have distinguishing characteristics. T cells reactive with OKT3 antibody (T3+) displayed higher beta-glucuronidase and dot-like alpha-naphthyl acetate acid esterase (ANAE) activity than T3- cells. Helper/inducer cells (T4+) were characterized by a high level of dot-like ANAE activity, whereas cytotoxic/suppressor cells (T8+) displayed selective naphthol-ASD-chloroacetate esterase activity. These results provide evidence for association of some cytoplasmic enzyme activities with the expression of membrane differentiation markers defined by monoclonal antibodies.

The effects of surgery on the activity of neutrophil granule proteins

Activities of the neutrophil granule-associated proteins beta-glucuronidase, lysozyme and vitamin B12 binding protein were measured, serially, in the cells and serum of 10 patients undergoing total abdominal hysterectomy. The neutrophil leucocytosis which followed total abdominal hysterectomy was accompanied by a fall in the intraneutrophilic activities of all three granule-associated proteins. Intraneutrophilic lysozyme activity and intraneutrophilic vitamin B12 binding capacity were maximally reduced within 4 h of surgery and fell to 62 +/- 13% (mean +/- SEM) and 63 +/- 9% of their preoperative levels, respectively. This contrasted with the activity of intraneutrophilic beta-glucuronidase which was not maximally reduced until 24 h post-surgery when a fall to 80 +/- 6% of the preoperative level was observed. By the fifth postoperative day activities of the three intraneutrophilic granule proteins were increasing and approaching those observed preoperatively. Serum lysozyme and plasma unsaturated vitamin B12 binding capacity (UBBC) rose steadily following surgery and were significantly elevated by the fifth postoperative day. It is suggested that activation and in vivo degranulation of circulating neutrophils may be responsible for these changes in activity of neutrophil granule proteins following surgery.

Effect of quercetin on human polymorphonuclear leukocyte lysosomal enzyme release and phospholipid metabolism

Quercetin inhibited in a concentration-dependent manner the release of beta-glucuronidase from human polymorphonuclear leukocytes stimulated with zymosan-activated serum. 3H-arachidonic acid-prelabelled polymorphonuclear leukocytes released 3H-arachidonic acid upon stimulation with zymosan-activated serum and this was associated with a decrease of radioactivity in the phospholipid fraction as determined by thin layer chromatography. Quercetin inhibited the release of 3H-arachidonic acid. These observations suggest that the zymosan-activated serum stimulus activates phospholipase A2 and that phospholipase A2 is inhibited by quercetin. Thus, quercetin alters polymorphonuclear leukocyte phospholipid metabolism and responses to stimulation.