The B1-agonist [des-Arg10]-kallidin activates transcription factor NF-kappaB and induces homologous upregulation of the bradykinin B1-receptor in cultured human lung fibroblasts.

The bradykinin B1-receptor is strongly upregulated under chronic inflammatory conditions. However, the mechanism and reason are not known. Because a better understanding of the mechanism of the upregulation will help in understanding its potential importance in inflammation, we have studied the molecular mechanism of B1-receptor upregulation in cultured human lung fibroblasts (IMR 90) in response to IL-1beta and the B1-agonist [des-Arg10]-kallidin. We show that treatment of human IMR 90 cells by IL-1beta stimulates the expression of both B1-receptor mRNA and protein. The latter was studied by Western blot analysis using antipeptide antibodies directed against the COOH-terminal part of the human B1-receptor. We furthermore report the novel observation that the B1-receptor is upregulated by its own agonist which was completely blocked by the specific B1-antagonist [des-Arg10-Leu9]-kallidin, indicating an upregulation entirely mediated through cell surface B1-receptors. The increased population of B1-receptors was functionally coupled as exemplified by an enhancement of the B1-agonist induced increase in free cytosolic calcium. Upregulation by the B1-agonist was blocked by a specific protein kinase C inhibitor. B1-agonist-induced upregulation was correlated to the induction of transcription factor nuclear factor kappaB (NF-kappaB) which efficiently bound to the NF-kappaB-like sequence located in the promoter region of the human B1-receptor gene. This correlation was further confirmed by reporter gene assays which showed that this NF-kappaB-like sequence, in the B1-receptor promoter context, could contribute to IL-1beta and DLBK-induced B1-receptor transcription activation, and by the effect of NF-kappaB inhibitor pyrrolidinedithiocarbamate which diminished both B1-receptor upregulation and NF-kappaB activation. NF-kappaB is now recognized as a key inflammatory mediator which is activated by the B1-agonist but which is also involved in B1-receptor upregulation.

Pharmacological characterization of bradykinin receptors in canine cultured tracheal smooth muscle cells.

1. [3H]-bradykinin was used to characterize the bradykinin receptors associated with canine cultured tracheal smooth muscle cells (TSMCs). Receptor binding assay showed that TSMCs had specific, saturable, high-affinity binding sites for [3H]-bradykinin. 2. The specific [3H]-bradykinin binding increased linearly with increasing cell concentrations. The equilibrium for association of [3H]-bradykinin with the bradykinin receptors was attained within 2 h at 4 degrees C and 1 h at room temperature, respectively. 3. Analysis of binding isotherms yielded an apparent equilibrium dissociation constant (KD) of 2.5 +/- 0.3 nM and a maximum receptor density (Bmax) of 25.1 +/- 0.3 fmol mg-1 protein. The Hill coefficient for [3H]-bradykinin binding was 1.00 +/- 0.02. The association (K1) and dissociation (K-1) rate constants were (8.67 +/- 2.60) x 10(6) M-1 min-1 and 0.024 +/- 0.005 min-1, respectively. KD, calculated from the ratio of K-1 and K1 was 2.8 +/- 0.5 nM, a value close to that of KD calculated from Scatchard plots of binding isotherms. 4. The B1 receptor selective agonist, (des-Arg9-bradykinin, 0.1 nM-10 microM) and antagonist ([Leu8, des-Arg9]-bradykinin, 0.1 nM-10 microM) did not did not inhibit the [3H]-bradykinin binding to TSMCs, which excludes the presence of B1 receptors in canine TSMCs. 5. The specific binding of [3H]-bradykinin to canine TSMCs was inhibited by B2 receptor selective antagonists ([D-Arg0, Hyp3, Thi5, D-Tic7, Oicl-bradykinin, Hoe 140, 0.1 nM-10 micro M and [D-Arg0, Hyp3,Thi5,8, D-Phe7-bradykinin, 0.1 nM-10 micro M) and agonists (bradykinin and kallidin, 0.1 nM-10 micro M) with a best fit by a one-binding site model. The order of potency for the inhibition of [3H]-bradykinin binding was kallidin = bradykinin = Hoe 140> [D-Arg0, Hyp3, Thi5,8, D-Phel-bradykinin.6. Preincubation of TSMCs with forskolin for 24 h led to an up-regulation of B2 receptors, increasing in Bmax from 25.1 +/- 0.3 to 218 +/- 24 fmol mg-1 protein without changing the KD values. [3H]-bradykinin binding to TSMCs was inhibited by the B2 receptor selective antagonists and agonists, but not by the B1 receptor selective reagents. The up-regulation of the B2 receptor by forskolin was mediated through protein synthesis, since cycloheximide blocked this response.7 It is concluded that the pharmacological characteristics of the bradykinin receptors in canine cultured TSMCs are primarily of the B2 receptor subtype.

Regulation by interleukin-1beta of gene expression of bradykinin B1 receptor in MH-S murine alveolar macrophage cell line.

The effects of recombinant murine interleukin (IL)-1beta on gene expression of murine bradykinin B1 receptor (BDKRB1) in MH-S murine alveolar macrophage cell line were evaluated. BDKRB1 mRNA expression in MH-S cells was increased by IL-1beta (1, 3, and 10 ng/ml) in a time-dependent manner, peaking at 3-4 h by 100-1000 fold. IL-1beta (5 ng/ml, 24h) also induced significant binding to [3H]-des-Arg10-kallidin with a dissociation constant (Kd) of 2.95 nM and a maximal binding density (Bmax) of 670 sites/cell. Des-Arg10-kallidin (10 microM), a BDKRB1 agonist, increased intracellular calcium ion ([Ca2+]i) in IL-1beta (5 ng/ml, 24 h)-exposed cells, an increase not observed in the cells not exposed to IL-1beta. A significant increase of tumor necrosis factor (TNF)-alpha secretion occurred in the IL-1beta (5 ng/ml, 24 h)-exposed cells following addition of des-Arg10-kallidin (the IL-1beta-exposed group: 57. 8 +/- 13.7 vs. the vehicle-exposed group: 16.7 +/- 4.3 pg/ml, p < 0.05 after a 100 nM des-Arg10-kallidin for 8 h), with an optimal effect at 3-100 nM. These data suggest that IL-1beta may up-regulate BDKRB1-mediated functions of alveolar macrophages via an induction of BDKRB1 gene expression.