Migratory responses of polymorphonuclear leukocytes to kinin peptides.

The present study examines the influence of kinins on the migratory capacity of human polymorphonuclear leukocytes under in vitro conditions using the Boyden chamber technique. By means of checkerboard analysis the migration of neutrophils induced by bradykinin could be characterized as true chemotaxis. The stimulation of human neutrophils with bradykinin, with the nonpeptide B(2) receptor agonist FR190997 as well as with des-Arg(9)-bradykinin and des-Arg(10)-kallidin results in a concentration-dependent migration. Pretreatment of the neutrophils with the B(2) receptor antagonist HOE-140 (icatibant) inhibited the bradykinin-induced migration but not that induced by B(1) receptor agonists, whereas the B(1 )receptor antagonist des-Arg(10)HOE-140 abolished the migration elicited by des-Arg(9)-bradykinin or des-Arg(10)-kallidin but not that evoked by bradykinin. Pretreatment of the neutrophils with the leukotriene B(4) (LTB(4)) antagonist ZK158252 inhibited the LTB(4)-induced chemotaxis as well as the chemotaxis produced by bradykinin and des-Arg(10)-kallidin. An involvement of interleukin-1beta and of the chemokine IL-8 in the bradykinin-induced migration in vitro could be excluded during the migration time of the neutrophils. In conclusion, the present study provides pharmacological evidence showing that B(1) and B(2) kinin receptors are involved in the migration of human neutrophils in vitro, that LTB(4) participates in the downstream pathway and that the B(1) kinin receptor seems to be expressed already under physiological conditions.

Degradation of bradykinin by peritoneal and alveolar macrophages of the guinea pig.

Peptidase inhibitors and identification of the peptide fragments were used for the characterization of the bradykinin metabolism by alveolar and peritoneal macrophages. Both cell types show differences in the rate of inactivation and in the quantity of the metabolites generated. BK(1-5), BK(1-8), and BK(1-7) are the predominant direct metabolites. Metalloendopeptidase 24.15, carboxypeptidase M, and an unidentified peptidase are responsible for their formation. Angiotensin-converting enzyme and neutral endopeptidase 24.11 do not play a crucial role in the degradation of bradykinin by macrophages. In the bronchoalveolar space, other cells than the macrophages are more important to the breakdown of this peptide.

Structure activity relationships for bradykinin antagonists on the inhibition of cytokine release and the release of histamine.

Highly potent bradykinin antagonists were found to inhibit bradykinin-induced release of cytokines but to stimulate histamine release. Both actions show structural requirements completely different from those for bradykinin B1 and B2 receptors, indicating that the release of some cytokines from spleen mononuclear cells and of histamine from rat mast cells is not mediated by these receptors. Most potent bradykinin antagonists release histamine at lower concentrations than does bradykinin itself. Dimers of bradykinin antagonists are the most potent compounds for histamine release. In contrast to enhanced histamine release, potent inhibition of cytokine release enhances the applicability of these compounds as anti-inflammatory drugs. Many of the peptides designed for high B2-receptor antagonism were found to be compared by their concentrations far more potent for inhibition of cytokine release than for smooth muscle contraction. Thus, for some antagonists inhibition of cytokine release was detected at concentrations as low as 10(-15) M. The rational design of peptide and nonpeptide bradykinin antagonists for therapeutic use requires not only knowledge about the potency but also knowledge about the structure-activity relationships of such important side effects as cytokine and histamine release.

A new type of bradykinin B2 receptor antagonists: bradykinin analogs with N-alkyl amino acids at position 2.

It is commonly assumed that bradykinin B2 receptor antagonists bind to a receptor site partially different from that for agonists. Thus, it is likely that there exists more than one key modification to convert bradykinin receptor agonists into antagonists. In this respect, [L-NMePhe2]-BK represents the basic structure of a new type of bradykinin B2 receptor antagonists without any replacement at position 7. This compound inhibits both in vitro bradykinin-induced contraction of the guinea pig lung strip and in vivo bradykinin-induced bronchoconstriction. Furthermore, this analog shows analgesic activity, blocks in a dose-dependent manner the bradykinin-induced Ca2+ release from macrophages and inhibits at a concentration of 10(-13) M the bradykinin-induced cytokine release from mononuclear cells. Combinations with structural modifications previously performed for other B2 receptor antagonists rather reduce than enhance the potency.

Induction of histamine release from rat mast cells by bradykinin analogues.

Independently of their agonistic or antagonistic activity on different isolated tissue preparations, the kinin analogues investigated induce histamine release on rat peritoneal mast cells. The effectivity of most compounds is 10 to 100 times higher than that of bradykinin. Beside the positively charged amino acids, the elongation at the N-terminus with hydrophobic amino acids and the replacement of amino acids in the bradykinin sequence (especially at position 7) with aromatic residues is important for a high histamine-releasing activity.

Release of cytokines from isolated lung strips by bradykinin.

Bradykinin as an inflammatory mediator was assayed for its ability to release cytokines from isolated lung tissue derived from guinea pigs, mice and in some cases from patients. Bradykinin elicited in concentrations, which were able to induce a contraction of isolated lung strips, a secretion of different cytokines from the tissue into organ baths as well as from lung tissue incubated in petri dishes (4h, 37 degrees C). Using enzyme immuno assays and the tanned erythrocyte electrophoretic mobility (TEEM)-test in combination with monoclonal antibodies the cytokines could be identified preferably as interleukin(IL)-1, IL-2, sIL-2R and IL-6. Tyrode solution as a control and carbachol in a concentration causing also a contraction were not able to release cytokines in a significant amount. The bradykinin B2 receptor antagonist icatebant (HOE 140) inhibited the bradykinin-induced IL-2 and IL-6 release. The results show that bradykinin can elicit the secretion of the cytokine cascade via a receptor-mediated process.

On the mode of action of antiphlogistically active DL-omega-phenyl amino acid esters.

DL-omega-phenyl amino acid esters turned out to be inhibitors of the sheep vesicular gland prostaglandin H synthase in addition to their antiphlogistic action on the carrageenan-induced oedema of the rat paw and weak antihistaminic actions. The inhibition of the prostaglandin H synthase was dose-dependent, the inhibitory potencies were however much lower than that of indomethacin. Some but not all derivatives, such as DL-4-amino-4-phenylbutyric acid octyl ester, also caused inhibition of the pure lipoxygenase from rabbit reticulocytes and the conversion of arachidonic acid to leukotriene B4 and 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid by human polymorphonuclear leukocytes as well as inhibition of antigen-induced release of histamine from mast cells of ovalbumin-sensibilized rats. Since no clear relations between the data of the in vitro and in vivo models were obtained, further studies on the pharmacokinetics and possible biotransformations are required.

Bradykinin action in the rat duodenum through the cyclic AMP system.

Activators of the adenylate cyclase or inhibitors of the cAMP-phosphodiesterase, respectively, potentiate the bradykinin-induced relaxation of the rat duodenum, whereas imidazole as a stimulator of the cAMP-phosphodiesterase reduces the relaxation. The experiments indicate a linkage between the adenylate cyclase system with the biological action of bradykinin on the rat duodenum. In contrast, no similar effect has been observed on the rat uterus.