CHARACTERIZATION OF THE RECEPTOR AND THE MECHANISMS UNDERLYING THE INFLAMMATORY RESPONSE INDUCED BY DES-ARG(9)-BK IN MOUSE PLEURISY

1 The characterization of the B-1 kinin receptor, and some mediators i nvolved in the inflammatory response elicited by intrathoracic (i.t.) administration of des-Arg(9)-bradykinin (BK) in the mouse model of ple urisy, was investigated.2 An i.t. injection of des-Arg(9)-BK (10-100 n mol per site), a selective B-1 agonist, caused a significant and dose- related increase in the vascular permeability observed after 5 min, wh ich peaked at 1 h, associated with an increase in cell influx, mainly neutrophils, and, to a lesser extent, mononuclear cell influx, peaking at 4 h and lasting for up to 48 h. The increase in fluid leakage caus ed by des-Arg(9)-BK was completely resolved 4 h after peptide injectio n. I.t, injection of Lys-des-Arg(9)-BK (30 nmol per site) caused a sim ilar inflammatory response. 3 Both the exudation and the neutrophil in flux elicited by i.t. injection of des-Arg(9)-BK were significantly an tagonized (P<0.01) by an i.t. injection of the selective B-1 antagonis ts des-Arg(9)-[Leu(8)]-BK (60 and 100 nmol per site) or des-Arg(9)-NPC 17731 (5 nmol per site), administered in association with des-Arg(9)- BK (P<0.01), or 30 and 60 min before the cellular peak, respectively. In contrast, an i.t. injection of the BZ bradykinin selective receptor antagonist Hoe 140 (30 nmol per site), at a dose which consistently a ntagonized bradykinin (10 nmol per site)-induced pleurisy, had no sign ificant effect on des-Arg(9)-BK-induced pleurisy. 4 An i.t. injection of the selective tachykinin receptor antagonists (NK1) FK 888 (1 nmol per site), (NK2) SR 48968 (20 nmol per site) or (NK3) SR 142801 (10 nm ol per site), administered 5 min before pleurisy induction, significan tly antagonized neutrophil migration caused by i.t. injection of des-A rg(9)-BK. In addition, FK 888 and SR 142801, but not SR 48968, also pr evented the influx of mononuclear cells in response to i.t. injection of des-Arg(9)-BK (P<0.01). However, the NK3 receptor antagonist SR 142 801 (10 nmol per site) also significantly inhibited des-Arg(9)-BK-indu ced plasma extravasation. An i.t. injection of the calcitonin gene-rel ated peptide (CGRP) receptor antagonist CGRP(8-37) (1 nmol per site), administered 5 min before pleurisy induction, inhibited des-Arg(9)-BK- induced plasma extravasation (P<0.01), without significantly affecting the total and differential cell migration. 5 The nitric oxide synthas e inhibitors L-NOARG and L-NAME (1 pmol per site), administered 30 min beforehand, almost completely prevented des-Arg(9)-BK (i.t.)-induced neutrophil cell migration (P<0.01), and, to a lesser extent, mononucle ar cell migration (P<0.01). The D-enantiomer D-NAME had no effect on d es-Arg(9)-BK-induced pleurisy. At the same dose range, L-NOARG and L-N AME inhibited the total cell migration (P<0.01). L-NAME, but not L-NOA RG caused significant inhibition of des-Arg(9)-BK-induced fluid leakag e. Indomethacin (1 mg kg(-1), i.p.), administered 1 h before des-Arg(9 )-BK (30 nmol per site), inhibited the mononuclear cell migration (P<0 .05), but, surprisingly, increased the neutrophil migration at 4 h wit hout interfering with plasma extravasation. The administration of terf enadine (50 mg kg(-1), i.p.), 30 min before des-Arg(9)-BK (30 nmol per site), did not interfere significantly with the total cell migration or with the plasma extravasation in the mouse pleurisy caused by i.t. injection of des-Arg(9)-BK. 6 Pretreatment of animals with the lipopol ysaccharide of E. coli (LPS; 10 mu g per animal, i.v.) for 24 h did no t result in any significant change of the inflammatory response induce d by i.t. injection of des-Arg(9)-BK compared with the saline treated group. However, the identical treatment of mice with LPS resulted in a marked enhancement of des-Arg(9)-BK induced paw oedema (P<0.01). 7 In conclusion, we have demonstrated that the inflammatory response induc ed by i.t. injection of des-Arg(9)-BK, in a murine model of pleurisy, is mediated by stimulation of constitutive B-1 receptors. These respon ses are largely mediated by release of neuropeptides such as substance P or CGRP and also by NO, but products derived from cyclo-oxygenase p athway and histamine seem not to be involved. Therefore, these results further support the notion that the B-1 kinin receptor has an importa nt role in modulating inflammatory responses, and it is suggested that selective B-1 antagonists may provide therapeutic benefit in the trea tment of inflammatory and allergic conditions.