Kinin-forming and kinin-inactivating enzymes in human neutrophil leukocytes

Human leucocyte response to migration inhibitory activity from lymphocytes. Modification by aprotinin, Tranexamic acid and phenylmethyl sulfonylfluoride

Human lymphokines can elicit several effects associated with inflammation, e.g. leucocyte migration inhibition and fibrinolysis. These effects can be assessed in vitro by the leucocyte migration agarose technique (LMAT) and the leucocyte migration fibrinolysis technique (LMFT). The present study shows that preincubation of normal leucocytes with aprotinin, tranexamic acid and phenyl-methyl-sulfonylfluoride (PMSF) reduces or abolishes their migration inhibition response to leucocyte migration inhibition factor. The compounds exert this effect at non-toxic concentrations, which do not otherwise interfere with migration or fibrinolysis, and are non-toxic as estimated by PHA stimulation of lymphocytes. The LMFT is more sensitive to the modifying effect than the LMAT. The effect of aprotinin and tranexamic acid is reversible, the effect of PMSF is irreversible.

Induction of histamine release from human skin mast cells by bradykinin analogs

Kinins are potent proinflammatory peptides that induce histamine release from rodent mast cells. We examined the ability of bradykinin, lysylbradykinin and a series of kinin analogs to cause histamine release from human basophils, human lung mast cells and human skin mast cells. At concentrations ranging from 0.1 microM to 1 mM, bradykinin failed to cause histamine release from any of the human histamine-containing cells studied. Lysylbradykinin was also without effect on basophils and lung mast cells, but was a weak secretagogue for human skin mast cells, inducing 5.5 +/- 3% (mean +/- SD) of total cellular histamine release at a concentration of 10(-5) M. Similarly, when sixteen recently developed bradykinin antagonists were examined, these compounds had no effect on basophils or lung mast cells but all sixteen induced dose-dependent histamine release from skin mast cells. The release process was temperature dependent and, at a concentration of 10(-5) M, the antagonists induced 8-27% histamine release. Although preincubation of cells with 10(-3) M bradykinin or des(Arg9) bradykinin significantly inhibited antagonist-induced histamine release, the requirement for such high concentrations of these peptides to cause inhibition suggested that histamine release is not mediated by either B1 or B2 kinin receptors. To understand further the mechanism of histamine release, we examined a series of bradykinin analogs with single amino acid substitutions in the bradykinin sequence. Replacement of proline7 in the bradykinin sequence with D-phenylalanine is the essential change used to convert kinin analogs into antagonists, and 10(-5) M [DPhe7]-bradykinin induced 8-10% histamine release. Other analogs, devoid of antagonist activity, however, such as [DPhe6]-bradykinin and [LPhe7]-bradykinin were able to induce equivalent levels of histamine release. The ability to induce histamine release appears to be related, at least in part, to aromaticity, since [DTrp6]-bradykinin and [DTrp7]-bradykinin induced greater amounts of histamine release than equivalent [DPhe]-analogs, causing approximately 20% histamine release at 10(-5) M. By contrast, [DAla7]-bradykinin was an ineffective stimulus. In summary, a single amino acid substitution can convert bradykinin into a secretagogue for human skin mast cells. The ability of kinin analogs to induce histamine release from skin mast cells, but not lung mast cells or basophils, emphasizes the heterogeneity of human histamine-containing cells.

Generation of a vasoactive peptide by a neutral protease of human neutrophil leukocytes

Neutrophil leukocyte lysosomes contain a neutral protease capable of cleaving a peptide from kininogen. The protease has a molecular weight of about 27,000-28,000, as determined by SDS-disc gel electrophoresis and gel filtration in the presence of guanidine-HCl. Its S-value is 2.7 and the pI 10.0-11.8. Although homogeneous by some criteria (sucrose density gradient ultracentrifugation, gel filtration in Sephadex G-75, SDS-disc gel electrophoresis, immunoelectrophoresis), the protease is heterogeneous by other criteria (cation exchange chromatography, cationic disc gel electrophoresis and isoelectric focusing). The heterogeneity is attributable to charge isomerism. The enzyme is inhibited by DFP and a number of chloromethyl ketone inhibitors. It is also inhibited by the plasma protease inhibitors alpha1-antitrypsin, alpha2-macroglobulin and antithrombin III. The generated peptide has chemical and pharmacological properties similar to the undecapeptide methionyl-lysyl-bradykinin, but probably contains one or two additional amino acids.