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

The bradykinin beta(1)-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 beta(1)-receptor upregulation in cultured human lung fibroblasts (IMR 90) in response to IL-1 beta and the B-1-agonist [des-Arg(10)]-kallidin. We show that treatment of human IMR 90 cells by IL-1 beta stimulates the expression of both B-1-receptor mRNA and protein. The latter was studied by Western blot analysis using antipeptide antibodies directed against the COOH-terminal part of the human B-1-receptor. We furthermore report the novel observation that the B-1-receptor is upregulated by its own agonist which was completely blocked by the specific B-1-antagonist [des-Arg(10)-Leu(9)]-kallidin, indicating an upregulation entirely mediated through cell surface B-1-receptors. The increased population of B-1-receptors was functionally coupled as exemplified by an enhancement of the B-1-agonist induced increase in free cytosolic calcium. Upregulation by the B-1-agonist was blocked by a specific protein kinase C inhibitor. B-1-agonist-induced upregulation was correlated to the induction of transcription factor nuclear factor kappa B (NF-kappa B) which efficiently bound to the NF-kappa B-Like sequence located in the promoter region of the human B-1-receptor gene. This correlation was further confirmed by reporter gene assays which showed that this NF-kappa B-like sequence, in the B-1-receptor promoter context, could contribute to IL-1 beta and DLBK-induced B-1-receptor transcription activation, and by the effect of NF-kappa B inhibitor pyrrolidinedithiocarbamate which diminished both B-1-receptor upregulation and NF-kappa B activation. NF-kappa B is now recognized as a key inflammatory mediator which is activated by the B-1-agonist but which is also involved in B-1-receptor upregulation.