Characterization of the receptor and the mechanisms underlying the inflammatory response induced by des-Arg9-BK in mouse pleurisy

1. The characterization of the B₁ kinin receptor, and some mediators involved in the inflammatory response elicited by intrathoracic (i.t.) administration of des-Arg⁹-bradykinin (BK) in the mouse model of pleurisy, was investigated.
2. An i.t. injection of des-Arg⁹-BK (10–100 nmol per site), a selective B₁ agonist, caused a significant and dose-related increase in the vascular permeability observed after 5 min, which 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 caused by des-Arg⁹-BK was completely resolved 4 h after peptide injection. I.t. injection of Lys-des-Arg⁹-BK (30 nmol per site) caused a similar inflammatory response.
3. Both the exudation and the neutrophil influx elicited by i.t. injection of des-Arg⁹-BK were significantly antagonized (P<0.01) by an i.t. injection of the selective B₁ antagonists des-Arg⁹-[Leu⁸]-BK (60 and 100 nmol per site) or des-Arg⁹-NPC 17731 (5 nmol per site), administered in association with des-Arg⁹-BK (P<0.01), or 30 and 60 min before the cellular peak, respectively. In contrast, an i.t. injection of the B₂ bradykinin selective receptor antagonist Hoe 140 (30 nmol per site), at a dose which consistently antagonized bradykinin (10 nmol per site)-induced pleurisy, had no significant effect on des-Arg⁹-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 nmol per site), administered 5 min before pleurisy induction, significantly antagonized neutrophil migration caused by i.t. injection of des-Arg⁹-BK. In addition, FK 888 and SR 142801, but not SR 48968, also prevented the influx of mononuclear cells in response to i.t. injection of des-Arg⁹-BK (P<0.01). However, the NK₃ receptor antagonist SR 142801 (10 nmol per site) also significantly inhibited des-Arg⁹-BK-induced plasma extravasation. An i.t. injection of the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP_8–37 (1 nmol per site), administered 5 min before pleurisy induction, inhibited des-Arg⁹-BK-induced plasma extravasation (P<0.01), without significantly affecting the total and differential cell migration.
5. The nitric oxide synthase inhibitors L-NOARG and L-NAME (1 pmol per site), administered 30 min beforehand, almost completely prevented des-Arg⁹-BK (i.t.)-induced neutrophil cell migration (P<0.01), and, to a lesser extent, mononuclear cell migration (P<0.01). The D-enantiomer D-NAME had no effect on des-Arg⁹-BK-induced pleurisy. At the same dose range, L-NOARG and L-NAME inhibited the total cell migration (P<0.01). L-NAME, but not L-NOARG caused significant inhibition of des-Arg⁹-BK-induced fluid leakage. Indomethacin (1 mg kg⁻¹, i.p.), administered 1 h before des-Arg⁹-BK (30 nmol per site), inhibited the mononuclear cell migration (P<0.05), but, surprisingly, increased the neutrophil migration at 4 h without interfering with plasma extravasation. The administration of terfenadine (50 mg kg⁻¹, i.p.), 30 min before des-Arg⁹-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-Arg⁹-BK.
6. Pretreatment of animals with the lipopolysaccharide of E. coli (LPS; 10 μg per animal, i.v.) for 24 h did not result in any significant change of the inflammatory response induced by i.t. injection of des-Arg⁹-BK compared with the saline treated group. However, the identical treatment of mice with LPS resulted in a marked enhancement of des-Arg⁹-BK induced paw oedema (P<0.01).
7. In conclusion, we have demonstrated that the inflammatory response induced by i.t. injection of des-Arg⁹-BK, in a murine model of pleurisy, is mediated by stimulation of constitutive B₁ receptors. These responses are largely mediated by release of neuropeptides such as substance P or CGRP and also by NO, but products derived from cyclo-oxygenase pathway and histamine seem not to be involved. Therefore, these results further support the notion that the B₁ kinin receptor has an important role in modulating inflammatory responses, and it is suggested that selective B₁ antagonists may provide therapeutic benefit in the treatment of inflammatory and allergic conditions.