Bradykinin B1 receptors in rabbit aorta smooth muscle cells in culture

Optimal blood pressure in patients with peripheral artery disease following endovascular therapy

This study examined the associations between blood pressure (BP) and event incidence to define optimal BP after endovascular therapy (EVT) in patients who underwent EVT. BP was monitored every 6 months for 5 years, and the patients were divided into two groups by average BP: ≥ 140/90 mmHg and < 140/90 mmHg. The association of BP with several events was examined. Although no significant differences in total mortality were observed between the groups, restenosis rates were significantly higher among patients who did not achieve target BP (36.2%) than among those who did (18.2%) (p < 0.01). The percentage of patients with glycosylated haemoglobin > 7.0% was significantly higher among those who did not achieve target BP in the restenosis group (42.9%) than in the other group (10.8%) (p < 0.01). In the restenosis group, there was a significantly higher percentage of patients taking metformin (p < 0.01) than in the other group. Metformin seemed to be administered to patients with more severe diabetes mellitus. In conclusion, it is important to manage hypertension and diabetes to prevent restenosis after EVT.

Inhibition of human and rabbit arterial smooth muscle cell migration mediated by the kinin B1 receptor: role of receptor density and released mediators

Bradykinin (BK)-related peptides are suspected to negatively influence diverse functions in vascular smooth muscle cells (SMCs), notably via stimulation of the inducible B1 receptor (B1R), and have been shown to inhibit the migration of rat SMCs. The present study had several objectives: (i) to test whether B1R mediates the inhibition of migration of arterial SMCs from additional species (the human and the rabbit); (ii) whether B1R density influences this action and whether autocrine NO or prostanoid release modulate it; and (iii) the possible signaling interaction between the B1R and phosphatidylinositol-3 kinase (PI-3K) has been addressed. The peptidase resistant B1R agonist Sar-[D-Phe8]des-Arg9-BK (10 nmol/L – 1 μmol/L) was an inhibitor of migration in human or rabbit arterial SMCs in a wound closure assay, more effectively if the medium composition allowed a high B1R expression (20% fetal bovine serum (FBS) + interleukin-1β (IL-1β) in human SMCs, 10% FBS in rabbit cells). The effect of the B1R agonist on motility was abrogated by a B1R antagonist, B-9858, but not by the B2R antagonist Hoe 140; a peptidase-resistant B2R agonist, [Phe8Ψ(CH2-NH)-Arg9]BK, had a marginal or no effect on migration. Sar-[D-Phe8]des-Arg9-BK (1 μmol/L) did not significantly influence SMC proliferation. The B1R-mediated inhibition of SMC migration was not affected by pharmacological inhibition of the nitric oxide synthases or cyclooxygenases-1 or -2, but was correlated to an inhibition of PI-3K in both types of SMCs. The inhibition of SMC migration mediated by the kinin B1R is likely independent from NO or prostanoid release, applicable to several species, and correlated to receptor density and the inhibition of PI-3K.

Angiotensin I-converting enzyme inhibitors block protein kinase C epsilon by activating bradykinin B1 receptors in human endothelial cells

Angiotensin I-converting enzyme (ACE) inhibitors are widely used to treat patients with cardiovascular and kidney diseases, but inhibition of ACE alone does not fully explain the beneficial effects. We reported that ACE inhibitors directly activate bradykinin B1 receptor at the canonical Zn2+ binding site, leading to prolonged nitric oxide (NO) production in endothelial cells. Protein kinase C (PKC) epsilon, a novel PKC isoform, is up-regulated in myocardium after infarction, suggesting a role in the development of cardiac dysfunction. In cytokine-treated human lung microvascular endothelial cells, B1 receptor activation by ACE inhibitors (enalaprilat, quinaprilat) or peptide ligands (des-Arg10-Lys1-bradykinin, des-Arg9-bradykinin) inhibited PKC epsilon with an IC50 = 7 x 10(-9) M. Despite the reported differences in binding affinity to receptor, the two peptide ligands were equally active, even when inhibitor blocked the cleavage of Lys(1), thus the conversion by aminopeptidase. The synthetic undecapeptide (LLPHEAWHFAR) representing the binding site for ACE inhibitors on human B(1) receptors reduced PKC epsilon inhibition by enalaprilat but not by peptide agonist. A combination of inducible and endothelial NO synthase inhibitors, 1400W [N-(3(aminomethyl) benzyl) acetamidine dihydrochloride] and N omega-nitro-L-arginine (2 microM), significantly reduced inhibition by enalaprilat (100 nM), whereas the NO donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate (100 microM) inhibited PKC epsilon activity just as the B1 ligands did. In conclusion, NO generated by B1 receptor activation inhibits PKC epsilon.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Pharmacological characterization and radioligand binding properties of a high-affinity, nonpeptide, bradykinin B1 receptor antagonist

Compound A (N-[2-[4-(4,5-dihydro-1H-imidazol-2-yl)phenyl]ethyl]-2-[(2R)-1-(2-napthylsulfonyl)-3-oxo-1,2,3,4-tetrahydroquinoxalin-2-yl]acetamide) is a member of a new class of aryl sulfonamide dihydroquinoxalinone bradykinin B1 receptor antagonists that should be useful pharmacological tools. Here we report on some of the pharmacological properties of compound A as well as the characterization of [35S]compound A as the first nonpeptide bradykinin B1 receptor radioligand. Compound A inhibited tritiated peptide ligand binding to the cloned human, rabbit, dog, and rat bradykinin B1 receptors expressed in CHO cells with Ki values of 0.016, 0.050, 0.56, and 29 nM, respectively. It was inactive at 10 microM in binding assays with the cloned human bradykinin B2 receptor. In functional antagonist assays with the cloned bradykinin B1 receptors, compound A inhibited agonist-induced signaling with activities consistent with the competition binding results, but had no antagonist activity at the bradykinin B2 receptor. Compound A was also found to be a potent antagonist in a rabbit aorta tissue bath preparation and to effectively block des-Arg9 bradykinin depressor responses in lipopolysaccharide-treated rabbit following intravenous administration. The binding of [35S]compound A was evaluated with the cloned bradykinin B1 receptors. In assays with human, rabbit, and dog receptors, [35S]compound A labeled a single site with Kd values of 0.012, 0.064, and 0.37 nM, respectively, and with binding site densities equivalent to those obtained using the conventional tritiated peptide ligands. Binding assays with the cloned rat bradykinin B1 receptor were not successful, presumably due to the low affinity of the ligand for this species receptor. There was no specific binding of the ligand detected in CHO cells expressing the human bradykinin B2 receptor. In assays with the cloned human bradykinin B1 receptor, the pharmacologies of the binding of [35S]compound A and [3H][Leu9]des-Arg10-kallidin were the same. The high signal-to-noise ratio obtained with [35S]compound A will allow this ligand to be a very useful tool for future investigations of the bradykinin B1 receptor.

Cyclic AMP increases bradykinin receptor binding affinity in human endothelial cells

We demonstrated bradykinin receptors in human endothelial cells and studied whether bradykinin receptors might be regulated by cyclic AMP. Messenger RNA for bradykinin B(1) and B(2) receptors was detected with real-time PCR and B(2) receptor protein was confirmed by immunoblotting. Saturation binding experiments with increasing concentrations of (125)I-[Tyr(8)]-bradykinin (25-700 pM) were made to determine maximal binding capacity and dissociation constant. However, saturation binding experiments suggested one class of binding sites, maximal binding capacity of 39.3 +/- 1.3 fmol/mg protein and dissociation constant of 352 +/- 27 pM. Competition studies with bradykinin B(1) and B(2) receptor antagonists showed that binding was competed by a B(1) antagonist, and when internalization was inhibited with hypertonic buffer, by both B(1) and B(2) antagonists. Stimulating cells with dibutyryl-cAMP, cholera toxin and forskolin for 24 h increased (125)I-[Tyr(8)]-bradykinin (90 pM) binding with approximately 50%. Saturation binding experiments with dibutyryl-cAMP stimulated cells showed, that the dissociation constant was altered from 352 +/- 27 pM in non-stimulated cells, to 203 +/- 18 pM (P < 0.001) in stimulated cells, while maximal binding capacity remained unchanged. Binding was competed similarly by the B(1) antagonist in stimulated and control cells. These results suggest, that the dibutyryl-cAMP stimulated increase in (125)I-[Tyr(8)]-bradykinin binding is probably due to increased B(1) receptor affinity with no change in receptor capacity. In conclusion, bradykinin B(1) and B(2) receptor mRNA was shown in human endothelial cells. Binding studies suggest that bradykinin receptors are competable with bradykinin antagonists. Adenylate cyclase activators probably increase bradykinin B(1) receptor affinity, without changing capacity, and thus increase bradykinin binding.

High agonist-independent clearance of rabbit kinin B1 receptors in cultured cells

We hypothesized that the inducible kinin B(1) receptor (B(1)R) is rapidly cleared from cells when its synthesis subsides. The agonist-independent degradation of the rabbit B(1)Rs and related B(2) receptors (B(2)Rs) was investigated. Endocytosis of the B(1)R-yellow fluorescent protein (YFP) conjugate was more intense than that of B(2)R-green fluorescent protein (GFP) based on fluorescence accumulation in HEK 293 cells treated with a lysosomal inhibitor. The cells expressing B(1)R-YFP contained more GFP/YFP-sized degradation product(s) than those expressing B(2)R-GFP (immunoblot, antibodies equally reacting with both fluorescent proteins). The binding site density of B(1)R-YFP decreased in the presence of protein synthesis or maturation inhibitors (anisomycin, brefeldin A), whereas that of B(2)R-GFP remained constant. Wild-type B(1)Rs were also cleared faster than B(2)Rs in rabbit smooth muscle cells treated with metabolic inhibitors. Contractility experiments based on brefeldin A-treated isolated rabbit blood vessels also functionally support that B(1)Rs are more rapidly eliminated than B(2)Rs (decreased maximal effect of agonist over 2 h). The highly regulated B(1)R is rapidly degraded, relative to the constitutive B(2)R.

Overexpression of kinin B1 receptors induces hypertensive response to des-Arg9-bradykinin and susceptibility to inflammation

We demonstrated that rat kinin B(1) receptors displayed a ligand-independent constitutive activity, assessed through inositol phosphate production in transiently or stably transfected human embryonic kidney 293A cells. Substitution of Ala for Asn(130) in the third transmembrane domain resulted in additional constitutive activation of the B(1) receptor. The constitutively active mutant N130A receptor could be further activated by the B(1) receptor agonist des-Arg(9)-bradykinin. To gain insights into the physiological function of the B(1) receptor, we have generated transgenic mice overexpressing wild-type and constitutively active mutant receptors under the control of human cytomegalovirus immediately early gene enhancer/promoter. The rat B(1) receptor transgene expression was detected in the aorta, brain, heart, lung, liver, kidney, uterus, and prostate of transgenic mice by reverse transcription-polymerase chain reaction/Southern blot analysis. Transgenic mice were fertile and normotensive. Overexpression of B(1) receptors exacerbated paw edema induced by carrageenan and rendered transgenic mice more susceptible to lipopolysaccharide-induced endotoxic shock. Interestingly, the hemodynamic response to kinins was altered in transgenic mice, with des-Arg(9)-bradykinin inducing blood pressure increase when intravenously administered. Our study supports an important role for B(1) receptors in modulating inflammatory responses and for the first time demonstrates that B(1) receptors mediate a hypertensive response to des-Arg(9)-bradykinin.

Expression of kinin B(1) receptor in fresh or cultured rabbit aortic smooth muscle: role of NF-kappa B

Kinin B(1) receptor (B(1)R) expression and the importance of the transcription factor nuclear factor (NF)-kappa B in this process were evaluated in models based on the rabbit aorta: freshly isolated tissue (postisolation induction) and cultured smooth muscle cells (SMCs). A 3-h incubation of freshly isolated tissues determined a sharp B(1)R mRNA increase (RT-PCR). Coincubation of tissues with a stimulus (interleukin-1 beta, fetal bovine serum, epidermal growth factor, or cycloheximide) further increased mRNA levels. Cultured SMCs possessed a basal population of surface B(1)Rs ([(3)H]Lys-des-Arg(9)-bradykinin binding) that was upregulated by treatments with the same set of stimuli (binding, mRNA, nuclear runon). Pharmacological inhibitors of NF-kappa B (MG-132, BAY 11-7082, dexamethasone) or actinomycin D reduced the postisolation induction of B(1)Rs in fresh aortic tissue (contractility or mRNA) and the cytokine effect on cells (mRNA, binding). NF-kappa B may be a common mediator of various stimuli that increase B(1)R gene transcription in the rabbit aorta, including tissue isolation, but cycloheximide also stabilizes B(1)R mRNA. The SMC models faithfully mimic the in vivo situation with regard to B(1)R regulation.

Kallikrein cascade and cytokines in inflamed joints

Rheumatoid arthritis is a chronic multi-system disease of unknown aetiology. The current hypothesis is that an unknown antigen triggers an autoimmune response in a genetically susceptible individual. The predominant pathological change is that of an inflammatory synovitis, characterised by cellular infiltrates and angiogenesis, with subsequent bone and cartilage destruction. These pathological changes are as a result of the activation of a variety of cells, inflammatory mediators, and effector molecules. The pro-inflammatory kinins and cytokines appear to play a central role in the pathogenesis of rheumatoid arthritis. Sufficient evidence exists that establishes a key role for the kallikrein-kinin cascade in inflamed joints. In addition, there appears to be an inter-relationship between cytokines and kinins in the inflammatory process. Kinins induce the release of cytokines, and cytokines have been shown to augment the effects of kinins. This may lead to an enhancement and perpetuation of the inflammatory process. In this review, we report a first study, correlating markers of disease with the kallikrein-kinin cascade and with cytokines.

Absence of ligand-induced regulation of kinin receptor expression in the rabbit

The induction of B(1) receptors (B(1)Rs) and desensitization or down-regulation of B(2) receptors (B(2)Rs) as a consequence of the production of endogenous kinins has been termed the autoregulation hypothesis. The latter was investigated using two models based on the rabbit: kinin stimulation of cultured vascular smooth muscle cells (SMCs) and in vivo contact system activation (dextran sulphate intravenous injection, 2 mg kg(-1), 5 h). Rabbit aortic SMCs express a baseline population of B(1)Rs that was up-regulated upon interleukin-1beta treatment ([(3)H]-Lys-des-Arg(9)-BK binding or mRNA concentration evaluated by RT - PCR; 4 or 3 h, respectively). Treatment with B(1)R or B(2)R agonists failed to alter B(1)R expression under the same conditions. Despite consuming endogenous kininogen (assessed using the kinetics of immunoreactive kinin formation in the plasma exposed to glass beads ex vivo) and producing hypotension mediated by B(2)Rs in anaesthetized rabbits, dextran sulphate treatment failed to induce B(1)Rs in conscious animals (RT - PCR in several organs, aortic contractility). By contrast, lipopolysaccharide (LPS, 50 microg kg(-1), 5 h) was an effective B(1)R inducer (kidney, duodenum, aorta) but did not reduce kininogen reserve. We tested the alternate hypothesis that endogenous kinin participate in LPS induction of B(1)Rs. Kinin receptor antagonists (icatibant combined to B-9858, 50 microg kg(-1) of each) failed to prevent or reduce the effect of LPS on B(1)R expression. Dextran sulphate or LPS treatments did not persistently down-regulate vascular B(2)Rs (jugular vein contractility assessed ex vivo). The kinin receptor autoregulation hypothesis is not applicable to primary cell cultures derived from a tissue known to express B(1)Rs in a regulated manner (aorta). The activation of the endogenous kallikrein-kinin system is ineffective to induce B(1)Rs in vivo in an experimental time frame sufficient for B(1)R induction by LPS.

Detection of bradykinin B1 receptors in rat aortic smooth muscle cells

The tritiated bradykinin B1 receptor agonist [3H]des-Arg(10)-kallidin bound to a single class of high-affinity binding sites (K(d) = 0.5 +/- 0.16 nM; B(max) = 15,000 +/- 8,000 sites/cell) on cultured rat aortic smooth muscle cells. [3H]Des-Arg(10)-kallidin association and dissociation kinetics were monoexponential, making it possible to determine the association and dissociation rate constants (k(+1) = 1.5 10(5) M(-1) sec(-1); k(-1) = 4.2 10(-5) sec(-1)). [3H]Des-Arg(10)-kallidin binding was inhibited by specific ligands of bradykinin B1 and B2 receptors with a rank order of potency consistent with that known for bradykinin B1 receptors in other species (des-Arg(9)-[Leu(8)]bradykinin = des-Arg(10)-kallidin = des-Arg(9)-bradykinin = des-Arg(10)-[Leu(9)]kallidin > des-Arg(10)-HOE-140 >> bradykinin >> HOE-140). Bradykinin B1 receptor mRNA was also detected in these cells. Des-Arg(10)-kallidin increased cytosolic free Ca2+ levels, phosphoinositide turnover, and arachidonic acid release at nanomolar concentrations (respective EC(50) values: 16 +/- 2, 4 +/- 2.7, 6 +/- 2 nM). These functional effects of des-Arg(10)-kallidin could be blocked by the bradykinin B1 receptor antagonist des-Arg(9)-[Leu(8)]bradykinin, but were not sensitive to bradykinin B2 receptor antagonists. These results therefore show that rat aortic smooth muscle cells in culture express functional bradykinin B1 receptors.

Non-competitive pharmacological antagonism at the rabbit B(1) receptor

The B(1) receptor for kinins, stimulated by kinin metabolites without the C-terminal Arg residue (e.g., des-Arg(9)-bradykinin (BK) and Lys-des-Arg(9)-BK), is an increasingly recognized molecular target for the development of analgesic and anti-inflammatory drugs. Recently developed antagonists of this receptor were compared to a conventional antagonist, Ac-Lys-[Leu(8)]-des-Arg(9)-BK, in pharmacological assays based on the rabbit B(1) receptor. B-9858 (Lys-Lys-[Hyp(3), Igl(5), D-Igl(7), Oic(8)]des-Arg(9)-BK) and three other analogues possessing the alpha-2-indanylglycine(5) (Igl(5)) residue (order of potency B-9858 approximately B-10146>B-10148>B-10050) were partially insurmountable antagonists of des-Arg(9)-BK in the contractility assay based on rabbit aortic rings. B-9858-induced depression of the maximal effect was more pronounced in tissues treated with the protein synthesis inhibitor cycloheximide to block the spontaneous increase of response attributed to the post-isolation formation of B(1) receptors, and only partly reversible on washing. By comparison, Ac-Lys-[Leu(8)]des-Arg(9)-BK was a surmountable antagonist (pA(2) 7. 5), even in cycloheximide-treated tissues. B-9958 (Lys-[Hyp(3), CpG(5), D-Tic(7), CpG(8)]des-Arg(9)-BK) was also surmountable (pA(2) 8.5). The binding of [(3)H]-Lys-des-Arg(9)-BK to recombinant rabbit B(1) receptors expressed in COS-1 cells was influenced by two of the antagonists: while Ac-Lys-[Leu(8)]des-Arg(9)-BK competed for the radioligand binding without affecting the B(max), B-9858 decreased the B(max) in a time-dependent and washout-resistant manner. B-9858 and analogues possessing Igl(5) are the first reported non-competitive, non-equilibrium antagonists of the kinin B(1) receptor.

Bradykinin B(1) receptor mediates inhibition of neointima formation in rat artery after balloon angioplasty

We evaluated the effects of the kallikrein-kinin system on the proliferation and migration of primary cultured vascular smooth muscle cells (VSMCs) in vitro and neointima formation in balloon-injured rat carotid arteries in vivo. In cultured rat VSMCs, tissue kallikrein inhibited cell proliferation, and this inhibitory effect was blocked by Sar-Tyr-Aca(epsilon)-Lys [D-betaNal(7), Ile(8)]-des-Arg(9)-bradykinin, a bradykinin B(1) receptor antagonist, and by icatibant, a bradykinin B(2) receptor antagonist. Platelet-derived growth factor significantly increased the expression of the B(1) receptor but not the B(2) receptor in VSMCs. Platelet-derived growth factor-induced cell migration was significantly attenuated by des-Arg(9)-bradykinin and to a lesser degree by bradykinin. Endogenous B(1) receptor mRNA increased in rat carotid arteries after balloon angioplasty. After local delivery of adenovirus carrying the human tissue kallikrein gene into the rat carotid artery, we observed a 54% reduction in the intima/media ratio at the injured site compared with the control ratio (n=7, P:<0.01). Administration of the B(1) receptor antagonist via minipumps blocked the protective effect of kallikrein and partially reversed the intima/media ratio toward the control ratio. Kallikrein gene delivery results in the regeneration of endothelium compared with the control groups, and the B(1) receptor antagonist abolished this effect. Nitrite/nitrate, cGMP, and cAMP levels in balloon-injured arteries significantly increased after kallikrein gene delivery, whereas the B(1) receptor antagonist abolished these increases (n=4 or 5, P:<0.05). These results indicate that the B(1) receptor contributes to the reduction of neointima formation via the promotion of reendothelialization and inhibition of VSMC proliferation and migration through NO-cGMP and cAMP signaling pathways. This study provides significant implications in treating restenosis after revascularization.

Regulation of bradykinin receptor gene expression in human lung fibroblasts

In WI-38 human fibroblasts, interleukin-1 beta and tumour necrosis factor-alpha (TNF-alpha) increased bradykinin B(1) receptor mRNA, which peaked between 2 and 4 h, remaining elevated for 20 h. Binding of the bradykinin B(1) receptor selective ligand [3H]des-Arg(10)-kallidin, also increased, peaking at 4 h and remaining elevated for 20 h. The B(max) value for [3H]des-Arg(10)-kallidin rose from 280+/-102 fmol/mg (n=3) to 701+/-147 fmol/mg (n=3), but the K(D) value remained unaltered (control, 1.04+/-0.33 nM (n=3); interleukin-1 beta, 0.88+/-0.41 nM (n=3)). The interleukin-1 beta-induced [3H]des-Arg(10)-kallidin binding sites were functional receptors, as bradykinin B(1) receptor agonist-induced responses increased in treated cells. Bradykinin B(2) receptor mRNA and [3H]bradykinin binding were upregulated by interleukin-1 beta, but not TNF-alpha. The effect of interleukin-1 beta on bradykinin B(2) receptors was smaller than for bradykinin B(1) receptors. Cycloheximide prevented interleukin-1 beta-mediated increases in B(1) and B(2) binding, but not mRNA suggesting that de novo synthesis of a transcriptional activator was unnecessary.

Expression of kininogen, kallikrein and kinin receptor genes by rat cardiomyocytes

To ascertain the existence of the kallikrein-kinin system in the heart, we have studied in vivo and in vitro whether rat cardiac tissue expresses kininogen, kallikrein and kinin receptor mRNAs. The reverse transcription-polymerase chain reaction demonstrated that the ventricular myocardium of adult male rats expressed mRNAs for T- and low-molecular-weight (L-) kininogens, tissue kallikreins such as true kallikrein and T-kininogenase, and bradykinin B2 receptor, but not those for high-molecular-weight kininogen and B1 receptor. Lipopolysaccharide (LPS; 0.5 mg/kg, i.v.) increased the levels of mRNA for T-kininogen at 12 h and the bradykinin B1 receptor at 24 h without affecting that for other components. All of these mRNAs for the kallikrein-kinin system were also detected in cultured cardiomyocytes derived from neonatal rat ventricles; dibutyryl cyclic AMP, LPS or inflammatory cytokines such as interleukin-1 and tumor necrosis factor, up-regulated mRNA expression of T-kininogen, T-kininogenase, or B1 receptor in these cells in vitro. These results suggest that there are two kinin-generating systems in rat myocardium comprising T-kininogen/T-kininogenase and L-kininogen/true kallikrein respectively, and that the former may be relatively important in inflammatory diseases or conditions in which cAMP levels increase in cardiomyocytes.

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.

Pathophysiology of the kallikrein-kinin system in mammalian nervous tissue

The nervous system and peripheral tissues in mammals contain a large number of biologically active peptides and proteases that function as neurotransmitters or neuromodulators in the nervous system, as hormones or cellular mediators in peripheral tissue, and play a role in human neurological diseases. The existence and possible functional relevance of bradykinin and kallidin (the peptides), kallikreins (the proteolytic enzymes), and kininases (the peptidases) in neurophysiology and neuropathological states are discussed in this review. Tissue kallikrein, the major cellular kinin-generating enzyme, has been localised in various areas of the mammalian brain. Functionally, it may assist also in the normal turnover of brain proteins and the processing of peptide-hormones, neurotransmitters, and some of the nerve growth factors that are essential for normal neuronal function and synaptic transmission. A specific class of kininases, peptidases responsible for the rapid degradation of kinins, is considered to be identical to enkephalinase A. Additionally, kinins are known to mediate inflammation, a cardinal feature of which is pain, and the clearest evidence for a primary neuronal role exists so far in the activation by kinins of peripherally located nociceptive receptors on C-fibre terminals that transmit and modulate pain perception. Kinins are also important in vascular homeostasis, the release of excitatory amino acid neurotransmitters, and the modulation of cerebral cellular immunity. The two kinin receptors, B2 and B1, that modulate the cellular actions of kinins have been demonstrated in animal neural tissue, neural cells in culture, and various areas of the human brain. Their localisation in glial tissue and neural centres, important in the regulation of cardiovascular homeostasis and nociception, suggests that the kinin system may play a functional role in the nervous system.

B1 receptor involvement in the effect of bradykinin on venular endothelial cell proliferation and potentiation of FGF-2 effects

1. Bradykinin (BK) contributes to the inflammatory response inducing vasodilation of postcapillary venules and has been demonstrated to induce neovascular growth in subcutaneous rat sponges. 2. In this study the ability of BK to stimulate cell growth and migration in cultured endothelium from coronary postcapillary venules (CVEC) has been investigated. 3. [3H]-thymidine incorporation in subconfluent and synchronised CVEC was used to monitor DNA synthesis over 24 h. BK promoted a concentration-dependent increase of DNA synthesis with maximal activity at 100 nM. At this concentration BK also induced 18 fold accumulation of c-Fos protein immunoreactivity in the nucleus within 1 h from peptide exposure. 4. The total number of cells recovered after 48 h exposure to BK was increased in a concentration-dependent manner. Maximal effect was produced by 100 nM concentration of the peptide which produced 50% increase in cell number. The selective B1 receptor agonist Des-Arg9-BK mimicked the proliferative effect of BK, while the B2 receptor agonist kallidin was devoid of any activity. The proliferation induced by BK was abolished in a concentration-dependent manner by the addition of the B1 selective antagonist Des-Arg9-Leu8-BK, while the selective B2 receptor antagonist HOE140 did not modify BK-induced growth. 5. DNA synthesis and growth promoted by a threshold concentration of fibroblast growth factor-2 (FGF-2) (0.25 nM) were potentiated by increasing concentrations of BK and Des-Arg9-BK. 6. Endothelial cell migration assessed by the Boyden Chamber procedure was not promoted by BK or the selective B1 and B2 receptor agonists. 7. These data are the first demonstration that BK promotes growth of endothelial cells from postcapillary venules. The mitogenic activity of BK involves c-Fos expression and potentiates the growth promoting effect of FGF-2. Only the B1 receptor appears to be responsible for the proliferation induced by BK and suggests that this type of receptor might be implicated in favouring angiogenesis of coronary venules.

Possible mechanism of captopril induced endothelium-dependent relaxation in isolated rabbit aorta

The mechanism of captopril, an angiotensin converting enzyme (ACE) inhibitor with sulfhydryl group (SH) in its structure, to produce an endothelium-dependent vasorelaxation was studied. In rabbit aorta with intact endothelium and precontracted with phenylephrine, captopril and superoxide dismutase (SOD) produced dose-dependent relaxation. Lisinopril, an ACE inhibitor without a -SH group in its structure, did not produce endothelium-dependent relaxation. It was observed that captopril, like SOD, produced the relaxation by protecting the EDRF from getting inactivated by superoxide anions as pyrogallol and methylene blue inhibited both the captopril and SOD-mediated relaxation. The free radical scavenging action of captopril is further substantiated by the observation that captopril, but not lisinopril, inhibited FeCl3/ascorbic acid-induced lipid peroxidation in whole tissue homogenates of rabbit aorta to a level comparable to that of SOD. These results suggest that endothelium-dependent vasodilation produced by captopril may be due to its ability to scavenge superoxide anion and this property may be ascribed to the -SH group present in its structure.

Role of the Mitogen-Activated Protein Kinases in the Expression of the Kinin B1 Receptors Induced by Tissue Injury

Several cytokines and LPS regulate the population of the B1 receptors (B1Rs) for kinins; these are responsive to des-Arg9-bradykinin (BK) and Lys-des-Arg9-BK. B1R activation contributes to inflammatory vascular changes and pain. Aortic rings isolated from normal rabbits and incubated in vitro in Krebs physiological medium were used as a model of tissue injury. From a null level of response, these rings exhibit a time- and protein synthesis-dependent increase in the maximal contractile response to des-Arg9-BK. Exposure to exogenous IL-1β or epidermal growth factor (EGF) considerably increases the process of sensitization to the kinins. Freshly isolated control aortic rings showed high mitogen-activated protein (MAP) kinase activities (persistent activation of p38, but less prolonged for extracellular signal-regulated kinase and c-Jun-N-terminal kinase/stress-activated protein kinase pathways) relatively to the basal activities found in various types of cultured cells. IL-1β or EGF further increased the activities of the extracellular signal-regulated kinase and c-Jun-N-terminal kinase/stress-activated protein kinase MAP kinases. The inhibitor of the p38 MAP kinase, SB 203580 (10 μM), massively (∼75%) and selectively inhibited the spontaneous sensitization to des-Arg9-BK over 6 h. SB 203580 also significantly reduced the development of the response to des-Arg9-BK as stimulated by IL-1 or EGF. Both spontaneous and IL-1β-stimulated up-regulation of responsiveness to des-Arg9-BK were significantly inhibited by the MAP kinase extracellular signal-regulated kinase kinase 1 inhibitor PD 98059 (∼40%). The protein kinase inhibitors failed to inhibit protein synthesis and to acutely inhibit the contractile effect of des-Arg9-BK, suggesting that they do not influence B1 receptor transduction mechanisms. In cultured aortic smooth muscle cells stimulated with EGF, MAP kinase activation preceded B1R mRNA induction. Protein kinase inhibitors reveal the role of cell injury-controlled MAP kinase pathways, and singularly of the p38 pathway, in the induction of B1R.

Activation of endothelial cell kinin receptors leads to intracellular calcium increases and filamin translocation: regulation by protein kinase C

Membrane-associated cytoskeletal proteins provide support for endothelial cell (EC) junctional cell adhesion molecules. Nonmuscle filamin is a dimeric actin cross-linking protein that interacts with F-actin and membrane glycoproteins. Both bradykinin and des-Arg9-bradykinin cause filamin redistribution from the plasma membrane to the cytosol of confluent EC. Kinin-induced filamin translocation parallels the dynamics of intracellular Ca2+ increases. Pretreatment with kinin receptor antagonists blocks the Ca2+ response as well as filamin translocation induced by kinins. Protein kinase C activation prior to kinin stimulation attenuates intracellular Ca2+ increases and filamin translocation. BAPTA, a cell-permeable Ca2+ chelator, attenuates bradykinin-induced intracellular Ca2+ increases and filamin translocation. This study demonstrates that bovine pulmonary artery ECs express both kinin B1 and B2 receptors, and that activation of either receptor leads to intracellular Ca2+ increases. This Ca2+ signalling, which is downregulated by protein kinase C activation, is essential for kinin-induced filamin translocation.

Stable expression of human kinin B1 receptor in 293 cells: pharmacological and functional characterization

1. We compared the binding properties of [3H]-desArg10-[Leu9]-kallidin, a radiolabelled kinin B1 receptor antagonist, to membranes from IMR-90 human embryonic fibroblasts and from 293 cells transiently or stably transfected with the human B1 receptor. 2. The dissociation constant (KD) of [3H]-desArg10-[Leu9]-kallidin and the affinity of several kinin receptor agonists and antagonists were similar between the native and cloned receptor, either transiently or stably expressed in 293 cells. In IMR-90 cells, the rank order of potency was that expected for a kinin B1 receptor. 3. The receptors transiently or stably expressed in 293 cells were fully functional with respect to their signalling properties. Phosphoinositide hydrolysis was increased in a concentration-dependent manner by the B1 receptor agonist, desArg10-kallidin. Functional coupling to the calcium pathway was also demonstrated for the native and stably expressed human B1 receptor. 4. In conclusion, the established stable and functional 293 cell clone may provide an important tool for further analysis of the molecular mechanisms involved in binding, activation, and coupling of the kinin B1 receptor.

G-protein-mediated signaling in cholesterol-enriched arterial smooth muscle cells. 2. Role of protein kinase C-delta in the regulation of eicosanoid production

PGI2 generation by the vessel wall is an agonist for cyclic-AMP-dependent cholesteryl ester hydrolysis. The process of enhanced PGI2 synthesis is stimulated, in part, by G-protein-coupled receptor ligands. Cellular cholesterol enrichment has been hypothesized to alter G-protein-mediated PGI2 synthesis. In the studies reported herein, cells generated PGI2 in response to AlF4-, GTPgammaS, and ATP in a dose-dependent manner. G-protein agonists stimulated eicosanoid production principally by activating phospholipase A2, but not phospholipase C. This is in contrast to PDGF, which stimulated phospholipase A2 and PLCgamma activities. Galphai subunits mediate G-protein agonist-induced PGI2 synthesis, since ATP- and PDGF-induced PGI2 synthesis was inhibited by pertussis toxin. Although cholesterol enrichment reduced arachidonic acid- and PDGF-induced PGI2 synthesis, cholesterol enrichment enhanced PGI2 release in response to AlF4-, GTPgammaS, and ATP. The enhancement of PGI2 release in cholesterol-enriched cells was augmented by mevalonate, which inhibits the ability of cholesterol enrichment to reduce membrane-associated G-protein subunits. Since cholesterol enrichment inhibited PDGF and AlF4--induced MAP kinase activity [Pomerantz, K., Lander, H. M., Summers, B., Robishaw, J. D., Balcueva, E. A., & Hajjar, D. P. (1997) Biochemistry 36, 9523-9531] (the major mechanism by which phospholipase A2 is activated), these results suggest that cholesterol enrichment induces other alternative signaling pathways leading to phospholipase A2 activation. A PKC-dependent pathway is described herein that is involved in enhanced eicosanoid production in cholesterol-enriched cells. This conclusion is supported by two observations: (1) G-protein-linked PGI2 production is inhibited by calphostin, and (2) cholesterol enrichment augments the specific translocation of the delta-isoform of PKC from the cytosol to the plasma membrane following treatment of cells with phorbol ester. These data support the concept that, in cells possessing normal levels of cholesterol, MAP-kinase-dependent pathways mediate eicosanoid synthesis in response to G-protein activation; however, under conditions of high cellular cholesterol levels, augmented G-protein-linked eicosanoid production results from enhanced PKCdelta activity.

Stable expression of the human kinin B1 receptor in Chinese hamster ovary cells. Characterization of ligand binding and effector pathways

To delineate ligand binding and functional characteristics of the human B1 kinin receptor, a stable clone of Chinese hamster ovary cells expressing a single class of binding sites for [3H]des-Arg10-lysylbradykinin with a Kd of 0.3 nM and a Bmax of 38 fmol/mg protein ( approximately 40,000 receptors/cell) was isolated. Studies with peptide analogs showed that a lysine residue at position 1 (based on the lysylbradykinin sequence) of ligands was essential for high affinity binding to the human B1 receptor. In marked contrast to cloned Chinese hamster ovary cells expressing the human kinin B2 receptor, which internalized approximately 80% of the ligand within 5 min upon exposure to 2 nM [3H]bradykinin, exposure of cells expressing the B1 receptor to 1 nM [3H]des-Arg10-lysylbradykinin resulted in minimal ligand internalization. Stimulation of the B1 receptor led to inositol phosphate generation and transient increases in intracellular calcium, confirming coupling to phospholipase C, while immunoprecipitation of photoaffinity-labeled G-proteins from membranes indicated specific coupling of the receptor to Galphaq/11 and Galphai1,2. The B1, unlike the B2, receptor does not desensitize (as demonstrated by continuous phosphoinositide hydrolysis), enhancing the potential role of this receptor during inflammatory events.

Bradykinin B1 receptors in human umbilical vein

The present study was undertaken to demonstrate the presence of bradykinin B1 receptors mediating contraction of human umbilical vein. The bradykinin B1 receptor selective agonist, des-Arg9-bradykinin, produced a dose-dependent contractile response of human umbilical vein rings. Furthermore, des-Arga-bradykinin-mediated response increased in a time-dependent manner in vitro. The maximal response to des-Arg9-bradykinin, expressed as percentage of the maximum elicited by serotonin, was: 10 +/- 2 at 15 min, 55 +/- 5 at 120 min and 80 +/- 3 at 300 min. Des-Arg9-bradykinin-mediated contractions were inhibited by the specific bradykinin B1 receptor antagonist des-Arg9-[Leu8]bradykinin which produced parallel shifts in the dose-response curve to the selective bradykinin B1 receptor agonist. Schild regression analysis of data established a pA2 value of 6.16 +/- 0.06. Kinin-induced contraction was not modified by pre-treatment with indomethacin (10 microM), a cyclo-oxygenase inhibitor. On the other hand, continuous exposure to the anti-inflammatory steroid dexamethasone (100 microM) or to the protein synthesis inhibitor cycloheximide (70 microM) largely prevented the sensitization to des-Arg9-bradykinin in incubated human umbilical vein rings. These results confirm the presence of bradykinin B1 receptors which mediate contraction in isolated human umbilical vein. These responses are up-regulated in a time- and protein synthesis-dependent process.

Novel subtype-selective nonpeptide bradykinin receptor antagonists FR167344 and FR173657

We describe the receptor binding and antagonistic properties of two novel nonpeptide antagonists, FR167344 (3-bromo-8-[2,6-dichloro-3-[N-[(E)-4-(N,N-dimethylcarbamoyl)cinnamido acetyl]-N-methylamino]benzyloxy]-2-methylimidazo[1,2-a]pyridine hydrochloride) and FR173657 (8-[3-[N-[(E)-3-(6-acetamidopyridin-3-yl)acryloylglycyl]-N-m ethylamino]-2,6-dichlorobenzyloxy]-2-methylquinoline), for the human bradykinin receptor subtypes (B1 and B2). In competitive experiments using membranes prepared from Chinese hamster ovary cells expressing the bradykinin receptor subtypes, FR167344 and FR173657 showed a high affinity binding to the B2 receptor with IC50 values of 65 and 8.9 nM, respectively, and no binding affinity for the B1 receptor. FR167344 and FR173657 inhibited the B2 receptor-mediated phosphatidylinositol (PI) hydrolysis and produced a concentration-dependent rightward shift in the dose-response curve to bradykinin. This shift was accompanied by a progressive reduction of maximal response. Estimated pA2 values for the antagonism of bradykinin-induced PI hydrolysis by FR167344 and FR173657 were 8.0 and 9.0, respectively. FR167344 and FR173657 showed no stimulatory effects on PI hydrolysis. Therefore, FR167344 and FR173657 are potent, highly selective, and insurmountable antagonists for the human bradykinin B2 receptor.

Selective labelling of bradykinin receptor subtypes in WI38 human lung fibroblasts

1. Binding of the B1 bradykinin receptor radioligand, [3H]-des-Arg10-kallidin (-KD) and the B2 receptor radioligand [3H]-bradykinin (-BK) was investigated in membranes prepared from WI38 human foetal lung fibroblasts. 2. One-site analysis of the saturation data for [3H]-des-Arg10-KD gave an equilibrium dissociation constant (KD) value of 0.51 +/- 0.12 nM and a maximum receptor density (Bmax) of 260 +/- 49 fmol mg-1 of protein. [3H]-des-Arg10-KD binding was displaced by ligands in the order: des-Arg10-KD > KD > > des-Arg9[Leu8]-BK > des-Arg9-BK > Hoe 140 > > BK, implying that it was binding selectively to B1 receptors. 3. One-site analysis of the binding of [3H]-BK to W138 membranes indicated that it had a KD value of 0.25 +/- 0.06 nM and a Bmax of 753 +/- 98 fmol mg-1 of protein. The potencies for displacement of [3H]-BK binding were: Hoe 140 > > BK = KD > > > des-Arg10-KD = des-Arg9[Leu8]-BK = des-Arg9-BK, which was consistent with binding to B2 receptors. 4. This is the first characterization of [3H]-des-Arg10-KD binding to include both kinetic and equilibrium data, and demonstrates that [3H]-des-Arg10-KD has a high affinity for human B1 bradykinin receptors and is sufficiently selective to be used as a radioligand for B1 receptors in human cells or tissues expressing an excess of B2 BK receptors.

B1 bradykinin receptors and sensory neurones

1. The location of the B1 bradykinin receptors involved in inflammatory hyperalgesia was investigated. 2. No specific binding of the B1 bradykinin receptor ligand [3H]-des-Arg10-kallidin was detected in primary cultures of rat dorsal root ganglion neurones, even after treatment with interleukin-1 beta (100 iu ml-1). 3. In dorsal root ganglion neurones, activation of B2 bradykinin receptors stimulated polyphosphoinositidase C. In contrast, B1 bradykinin receptor agonists (des-Arg9-bradykinin up to 10 microM and des-Arg10-kallidin up to 1 microM) failed to activate polyphosphoinositidase C, even in neurones that had been treated with interleukin-1 beta (100 iu ml-1), prostaglandin E2 (1 microM) or prostaglandin I2 (1 microM). 4. Dorsal root ganglion neurones removed from rats (both neonatal and 14 days old) that had been pretreated with inflammatory mediators (Freund's complete adjuvant, or carrageenan) failed to respond to B1 bradykinin receptor selective agonists (des-Arg9-bradykinin up to 10 microM and des-Arg10-kallidin up to 1 microM). 5. Bradykinin (25 nM to 300 nM) evoked ventral root responses when applied to peripheral receptive fields or central terminals of primary afferents in the neonatal rat spinal cord and tail preparation. In contrast, des-Arg9-bradykinin (50 nM to 500 nM) failed to evoke ventral root depolarizations in either control rats or in animals that developed inflammation following ultraviolet irradiation of the tail skin. 6. The results of the present study imply that the B1 bradykinin receptors that contribute to hypersensitivity in models of persistent inflammatory hyperalgesia are located on cells other than sensory neurones where they may be responsible for releasing mediators that sensitize or activate the nociceptors.

Autoradiographic visualization of B1 bradykinin receptors in porcine vascular tissues in the presence or absence of inflammation

B1 bradykinin receptors were visualized by using the B1 bradykinin receptor agonist [3H]des-Arg10-kallidin in receptor autoradiography experiments. Cryosections were prepared from arterial vessels from a healthy control pig, a pig with pre-existing inflammation and an animal with experimental sepsis induced by an infusion of bacterial lipopolysaccharide (LPS). Only diffusely scattered silver grains with no preference for a distinct tissue structure were detected on emulsion-coated coverslips above the cryosections from the healthy control animal. This indicates that under normal circumstances no or only minute amounts of B1 bradykinin receptors are present in these tissues. In contrast, a 3-fold increase in specific B1 bradykinin receptor binding was observed on both the corresponding preparations of the sick piglet and of that with experimentally induced sepsis. A similar enhancement of specific [3H]des-Arg10-kallidin binding occurred in preparations devoid of endothelium. By comparison with the stained cryosection on the slide the silver grains showed a preferential distribution above smooth muscle cells. Taken together our data are consistent with the hypothesis that B1 bradykinin receptors are induced in the muscle layer of large vessels not only after experimentally-induced sepsis but also in pre-existing inflammatory disease.

The agonist selectivity of a mouse B1 bradykinin receptor differs from human and rabbit B1 receptors

A genomic clone encoding the mouse B1 receptor was isolated by homology to the human B1 receptor cDNA. The deduced amino acid sequence of the mouse B1 receptor is 72% identical to the human B1 receptor and 73% identical to the rabbit B1 receptor. Ligand binding studies of the mouse B1 receptor expressed in COS cells indicate that it has the pharmacological properties associated with the B1 receptor subtype. However the pharmacology of the mouse receptor is unique in that it possesses a 2-3-fold selectivity for the 'classical' B1 agonist des-Arg9BK over the agonist des-Arg10 kallidin. In contrast, the human and rabbit B1 receptors exhibit an approx. 2000- and 150-fold selectivity, respectively, for des-Arg10kallidin over des-Arg9BK. Thus relative to the human and rabbit B1 receptors the mouse B1 receptor has the opposite selectivity for kinin agonists. The DNA sequence of the region encoding bradykinin was determined for two different mouse kininogen cDNA clones, both encode the sequence Arg-BK. Antipeptide antibodies directed against a C-terminal peptide of the human B1 receptor were produced. Initial characterization of this antibody indicates that it detects specific bands by Western blot analyses that are present in membranes prepared from COS cells transfected with the human B1 receptor cDNA but not from mock transfected COS cells.

Cloning and pharmacological characterization of a rabbit bradykinin B1 receptor

A rabbit B1 bradykinin receptor cDNA was isolated from a rabbit aorta smooth muscle cell library. The 1223 bp cDNA clone encodes a protein of 352 amino acids which is 78% identical to the human bradykinin B1(3) receptor protein. Heterologous expression of the rabbit B1 receptor cDNA in COS-7 cells imparts a high affinity specific binding for 3H-labeled [des-Arg10,Leu9]kallidin. Scatchard analysis indicates that the receptor binds the radiolabeled ligand with a Kd of 0.5 nM. The ability of kallidin (Lys-bradykinin) and bradykinin analogues to compete with binding of 3H-labeled [des-Arg10,Leu9]kallidin was determined and defined a rank order of potency: [des-Arg10,Leu9]kallidin = [des-Arg10]kallidin > [des- Arg9]bradykinin = kallidin >> bradykinin. This receptor exhibits the classical B1 pharmacological property of preferentially binding to kinin analogues which lack the C-terminal arginine. In addition, the affinities for [des-Arg10]kallidin and [des-Arg10,Leu9]kallidin are 100-fold higher than those for the corresponding bradykinin analogues [des-Arg9]bradykinin and [des-Arg9,Leu8]bradykinin which lack the N-terminal lysine. This pharmacological profile is characteristic of the B1 receptor subtype.

Endothelium-dependent relaxations mediated by inducible B1 and constitutive B2 kinin receptors in the bovine isolated coronary artery

1. Rings of bovine left anterior descending coronary artery (LAD) were contracted with the thromboxane A2-mimetic, U46619 (1-30 nM), to approximately 40% of their maximum contraction to 125 mM KCl Krebs solution (KPSSmax) for comparison of responses to the B1 and B2 kinin receptor agonists, des-Arg9-bradykinin (des-Arg9-BK) and bradykinin (BK), respectively. Relaxation responses were normalized as percentages of the initial U46619-induced contraction level, while contractile responses were expressed as percentages of KPSSmax. 2. After 6 h of in vitro incubation in Krebs solution at 37 degrees C, des-Arg9-BK (pEC50, 8.00 +/- 0.08; maximum response (Rmax), 93.9 +/- 1.9%) and BK (pEC50, 9.75 +/- 0.07; Rmax, 100.1 +/- 0.7%) caused endothelium-dependent relaxations in precontracted rings of bovine LAD which were competitively and selectively antagonized by the B1 receptor antagonist, des-Arg9-[Leu8]-BK (pA2, 6.27 +/- 0.11) and the B2 receptor antagonist Hoc-140 (pA2, 9.63 +/- 0.14), respectively. 3. At 3 h of in vitro incubation, the sensitivity (pEC50, 7.45 +/- 0.10) and Rmax (84.6 +/- 3.3%) to des-Arg9-BK were significantly less than those obtained in the same tissues at 6 h (pEC50, 7.94 +/- 0.06; Rmax, 91.4 +/- 2.5%), whereas endothelium-dependent relaxations to BK and ACh were unaffected by incubation time. 4. Relaxation responses to des-ARg9-BK, but not BK, at both 3 h and 6 h were significantly attenuated by the protein synthesis inhibitors, cycloheximide (30 and 100 microM) and actinomycin D (2 microM). 5. At 6 h, the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine (L-NOARG, 100 microM), caused a significant 2 fold decrease in pEC50 (9.58 +/- 0.03) but had no effect on Rmax for BK. For des-Arg9-BK, L-NOARG (100 microM) caused a marked and significant decrease in both the pEC50 and Rmax and revealed contractions to low concentrations of des-Arg9-BK. In both cases, L-NOARG inhibition was reversed in the presence of L-arginine (10 mM). 6. At 6 h removal of the endothelium abolished relaxation responses to des-Arg9-BK and BK, and for des-Arg9-BK, but not BK, unmasked concentration-dependent contractions (pEC50, 7.57 +/- 0.09; Rmax, 83.4 +/- 9.1%). The sensitivity of contractions to des-Arg9-BK increased slightly from 3 h (pEC50, 7.37 +/- 0.08) to 6 h (pEC50, 7.62 +/- 0.12) of in vitro incubation; however, there was a small but significant depression in the maximum response over this time (Rmax, 126.8 +/- 8.5% and 103.3 +/- 8.6% for 3 h and 6 h of incubation respectively). 7. In conclusion, the bovine LAD contains inducible B1 and constitutive B2 endothelial cell kinin receptors, both of which mediate endothelium-dependent relaxation partly via the release of NO. B1 receptors were also present on the smooth muscle layer of the bovine LAD.

Inflammation modulates the contribution of receptor-subtypes to bradykinin-induced hyperalgesia in the rat

While B2 receptors mediate pain and hyperalgesia induced by bradykinin, in normal rats, recent reports indicate that, in the setting of inflammation, B1 receptors also mediate pain and hyperalgesia. Since bradykinin-induced hyperalgesia in normal rats is mediated by prostaglandins released from the postganglionic sympathetic neurons, we have evaluated the contribution of the sympathetic nervous system to the hyperalgesia induced by bradykinin, a preferential B2-receptor agonist, and des-Arg9-bradykinin, a major metabolite of bradykinin and a selective B1-receptor agonist. Mechanical hyperalgesia was quantified by the Randall-Selitto paw-withdrawal method. Inflammation was induced by injecting Complete Freund's Adjuvant into the left hindpaw of the rat and testing mechanical nociceptive threshold in the right hindpaw after injecting B1 or B2 agonists and/or antagonists. Sympathectomy was achieved by surgically removing sympathetic ganglia L1-L4. Rats were used 48 h post-adjuvant injection. In the normal rat, intradermal injection of bradykinin but not des-Arg9-bradykinin, into the dorsal surface of the hindpaw, produced a dose-dependent decrease in mechanical nociceptive threshold. NPC 17731, a B2-receptor antagonist, but not des-Arg9-[Leu8]-bradykinin, a B1-receptor antagonist, almost completely inhibited the decrease in mechanical threshold, suggesting that bradykinin hyperalgesia in the normal rat hindpaw was mediated by B2 receptors. In rats whose left paws were treated, 48 h earlier, with adjuvant, intradermal injection of bradykinin or des-Arg9-bradykinin, into the right paw produced dose-dependent hyperalgesia. Bradykinin hyperalgesia was partially inhibited by NPC 17731, and the residual part by des-Arg9,[Leu8]-bradykinin. des-Arg9-bradykinin hyperalgesia was inhibited by des-Arg9,[Leu8]-bradykinin but not by NPC17731. These results suggest that in the setting of inflammation, bradykinin hyperalgesia was mediated by both B1 and B2 receptors, and that des-Arg9-bradykinin hyperalgesia was mediated by the B1 receptor. Forty-eight hours after injection of complete Freund's adjuvant, in sympathectomized rats, bradykinin or des-Arg9-bradykinin failed to produce hyperalgesia, suggesting that intact sympathetic postganglionic neurons are required for the hyperalgesia produced by these agents in this model. These results are consistent with the suggestions that B2 receptors mediate bradykinin-induced cutaneous hyperalgesia in the normal rat hindpaw. The hyperalgesia induced by bradykinin, 48 h post injection of complete Freund's adjuvant is mediated by both B1 and B2 receptors, that by des-Arg9-bradykinin is mediated by B1 receptors. The hyperalgesia induced by both agents is dependent on the presence of intact sympathetic postganglionic neurons.

Regulation of kinin-induced contraction and DNA synthesis by inflammatory cytokines in the smooth muscle of the rabbit aorta

1. In rabbit aortic rings, the contractile response to kinins is mediated by the B1 receptors for kinins; the response is upregulated from an initial null level in a time- and protein synthesis-dependent manner. Incubation (3 h) with human recombinant interleukin-1 beta (IL-1 beta) selectively amplified the contractile response to the B1 receptor agonist Sar-[D-Phe8]des-Arg9-BK, while it did not affect the contractile effect of other agents (angiotensin II, endothelin-1, phenylephrine). 2. Oncostatin M (OSM), but not macrophage migration inhibitory factor (MIF), increased the contractile response to the B1 receptor agonist, des-Arg9-bradykinin (des-Arg9-BK). 3. Cultured smooth muscle cells derived from the rabbit aorta exhibit a significant des-Arg9-BK-induced increase in [3H]-thymidine incorporation if pretreated with a cyclo-oxygenase inhibitor (diclofenac) and concomitantly treated with the cytokines IL-1 or OSM. Angiotensin II, endothelin-1 or phenylephrine, alone or in the presence of IL-1 beta, exerted little effect on DNA synthesis in these cells. 4. The pharmacological characterization of the mitogenic response to kinins using a set of agonist and antagonist analogues is consistent with mediation by B1 receptors. Des-Arg9-BK-induced DNA synthesis is suppressed by prostaglandin E2 by a prostacyclin mimetic (iloprost), by the Ser/Thr protein kinase inhibitor, H-7, and by a tyrosine kinase inhibitor (i.e. an erbstatin analogue). 5. B1 receptor-mediated responses and their capacity to be regulated by cytokines, are retained in rabbit aortic smooth muscle cells. Such responses could be relevant to tissue repair mechanisms and hypertrophic medial responses to injury in arteries.

Theodore Cooper Memorial Lecture. Kallikreins and kinins. Some unanswered questions about system characteristics and roles in human disease

Kinins can affect many aspects of cellular function, but their roles in human homeostatic mechanisms and disease are just beginning to be understood. In this brief review, some of the interesting new observations about kallikrein-kinin system characteristics, roles in cell behavior, and aberrancy in diseases of relevance to readers interested in hypertension will be discussed. Along the way, questions raised by these observations will be posed. They show that we still have much to learn about the contributions of kinins to human cardiovascular diseases but now have in addition both a strong rationale for asking them and the tools to make them operational.

Targeted disruption of a B2 bradykinin receptor gene in mice eliminates bradykinin action in smooth muscle and neurons

Mice that are homozygous for the targeted disruption of the gene encoding the B2 bradykinin receptor have been generated. The gene disruption results in a deletion of the entire coding sequence for the B2 receptor. The disruption of the B2 receptor gene has been confirmed by genetic, biochemical, and pharmacological analyses. Mice that are homozygous for the disruption of the B2 receptor gene are fertile and indistinguishable from their littermates by visual inspection. Bradykinin fails to produce responses in pharmacological preparations from ileum, uterus, and the superior cervical ganglia from these mice. Therefore, expression of a single gene appears to be responsible for conferring responsiveness to bradykinin in these tissues.

Kinin B1 receptors: a review

The kinin B1 receptor has been initially defined as the one mediating the contractile effect of bradykinin (BK)-related peptides in the isolated rabbit aorta. The B1 receptor is selectively sensitive to kinin metabolites without the C-terminal arginine residue, e.g. des-Arg9-BK and Lys-des-Arg9-BK; it is apparently rapidly up-regulated in immunopathology under the influence of cytokines and is further regulated by growth factors. Progress in the understanding of this pharmacologic entity is reviewed, including the development of B1 receptor agonists and antagonists, binding assays, physiopathological applications and the recent cloning and sequencing of the receptor cDNA.

Bradykinin receptors in mouse and rat isolated superior cervical ganglia

1. The ability of bradykinin and its analogues to depolarize rat and mouse superior cervical ganglia was studied by use of in vitro grease-gap recording techniques, and the ability of antagonists selective for bradykinin receptor subtypes to block their effects was examined. 2. Bradykinin (3 microM) depolarized ganglia from both species, although the magnitude of the maximal response was less in mouse (15 +/- 5%, n = 7) than rat tissue (33 +/- 6%, n = 7), relative to muscarine (1 microM). 3. Interleukin 1 beta (30 u ml-1 for 18 h at 37 degrees C) increased the depolarization caused by bradykinin (3 microM) in mouse ganglia from 15% to 54% (P < 0.001, n = 12). Responses to the B1 receptor agonist, [des-Arg10]-kallidin (3 microM) were similarly potentiated but this was only detected after inhibition of peptidase activity with 10 microM captopril (4% to 35%, n = 5). 4. In ganglia from both species the rank order of agonist potency was bradykinin = [Lys0]-bradykinin >> [des-Arg10]-kallidin. However, like responses to [des-Arg10]-kallidin in mouse tissue, both the potency of bradykinin and the maximal depolarization achieved (EC50 = 912 nM; 80%, n = 11) was enhanced following inhibition of angiotensin converting enzyme with 10 microM captopril (EC50 = 50 nM; 135%, n = 4). 5. Responses to bradykinin were selectively antagonized by the B2 receptor antagonist, Hoe 140 but not by the B1 antagonist, [Leu8]-bradykinin1-8. From Schild analysis the pA2 value for Hoe 140 in mouse tissue was 9.65, although the slope of the regression line was significantly greater than unity, indicating non-competitive kinetics (slope = 1.88 +/- 0.18, n = 9). The depolarization caused by [Lys0]-bradykinin was also antagonized by Hoe 140 (3 nM).6. Thus the predominant bradykinin receptor in mouse superior cervical ganglia is compatible with a B2 subtype. Furthermore the depolarizations caused by B1 and B2 agonists in this tissue can be increased following exposure to interleukin l beta, and by blocking peptide degradation with captopril.

Quantification of des-Arg9-bradykinin using a chemiluminescence enzyme immunoassay: application to its kinetic profile during plasma activation

There is a renewed interest in the kininase I pathway of kinin metabolism, because des-Arg9-bradykinin (des-Arg9-BK) and des-Arg10-Lys-BK are selective and potent agonists of the B1 receptors, that are apparently upregulated by tissue injury. We have developed a polyclonal rabbit antiserum against des-Arg10-Lys-BK. In a radioimmunoassay for des-Arg10-Lys-BK, this antiserum exhibited high specificity. Notably, native kinins with the C-terminal Arg residue, bradykinin (BK) and Lys-BK, did not cross-react to a significant extent, whereas des-Arg9-BK and digoxigenin (DIG)-des-Arg9-BK exhibited a complete cross-reactivity. The antibodies were used to set up a sensitive chemiluminescence enzyme immunoassay (CLEIA) using the DIG-anti-DIG system as intermediate for the revelation of the immune complexes. The detection limit and the half-maximal saturation concentration for des-Arg9-BK were 27 and 1530 fmol/ml respectively. This assay, as well as another for BK quantification, have been applied in vitro to rabbit plasma activated by kaolin. The conversion of BK into des-Arg9-BK was generally efficient, and the persistence and concentration of both peptides were increased in the presence of enalaprilat an inhibitor of the angiotensin converting enzyme (ACEI). Rabbits treated with bacterial lipopolysaccharide exhibited an increase of plasma immunoreactive des-Arg9-BK that was potentiated in animals also treated with ACEI. This CLEIA for des-Arg9-BK is a new analytical tool applicable to analyze of the kininase I metabolites of kinins in vitro and in vivo. Measurements of des-Arg9-BK may be useful indicators of the kallikrein-kinin system activation.

Development of a binding assay for the B1 receptors for kinins

A novel binding assay to kinin B1 receptors was developed, based on the design of a high-affinity agonist ligand, [125I]Tyr-Gly-Lys-Aca-Lys-des-Arg9-BK. Binding to rabbit aortic smooth muscle cells is highly temperature-dependent (optimal at 37 degrees C); apparent binding equilibrium is reached within 30 min, and competition by kinin analogs reveals the expected correlation with the B1 receptor pharmacology. The dissociation constant (Kd) of the labeled ligand is approx. 0.2 nM and this value does not change significantly as a function of cytokine pretreatment. However, the receptor abundance (Bmax) is significantly increased (1.5-fold) by pretreating the cells with interleukin-1 (IL-1), while oncostatin M (OSM) produces a marginal increase of the Bmax. This assay may be useful in documenting the regulation of B1 receptors in pathology.

Bradykinin B1 receptors in the rabbit urinary bladder: induction of responses, smooth muscle contraction, and phosphatidylinositol hydrolysis

1. The aim of this study was to analyse the pharmacological characteristics, and second-messenger coupling-mechanisms, of bradykinin B1 receptors in an intact tissue, the rabbit urinary bladder; and to investigate the influence of inhibition of endogenous peptidases on kinin activities. 2. In preparations of rabbit mucosa-free urinary bladder, at 90 min after mounting of the preparations, bradykinin (1 nM-10 microM) evoked contractile responses. In contrast, the B1 receptor-selective agonist [des-Arg9]-BK (10 mM-10 microM) was only weakly active at this time. Contractile responses to [des-Arg9]-BK increased with time of tissue incubation in the organ bath, reaching a maximum after 3 h, when the pD2 estimates were 6.4 +/- 0.3 for bradykinin, and 6.9 +/- 0.2 for [des-Arg9]-BK. 3. Once stabilized, responses to [des-Arg9]-BK in the bladder were competitively antagonized by the B1 receptor-selective antagonists [Leu8,des-Arg9]-BK and D-Arg-[Hyp3,Thi5,D-Tic7,Oic8,des-Arg9]-BK ([des-Arg10]-Hoe140) (pKB estimates were 6.1 +/- 0.1 and 7.1 +/- 0.1, respectively; n = 17-21), but responses were unaffected by the B2 receptor-selective antagonist D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]-BK (Hoe140) (100 nM; n = 4). Contractile responses to bradykinin itself were partially, but significantly, inhibited by the B1 receptor-selective antagonist, [Leu8,des-Arg9]-BK (10 microM) (P < 0.05), or by the B2 receptor-selective antagonist Hoe140 (100 nM) (P < 0.005) alone, and were largely blocked by a combination of the two antagonists (P < 0.0001). 4. The combined presence of the carboxypeptidase inhibitor DL-2-mercaptomethyl-3-guanidinoethylthiopropanoicacid (mergetpa; 10 microM), the neutral endopeptidase inhibitor, phosphoramidon (1 microM),and the angiotensin-converting enzyme inhibitor, enalaprilat (1 microM) increased the potency of bradykinin17 fold (P<0.001), but that of [des-Argl-BK was unchanged (P>0.05): pD2 estimates were 7.6 +/- 0.1 and 6.8 +/- 0.1 for bradykinin and [des-Argl-BK, respectively, in treated preparations. In the presence of peptidase inhibitors, the affinities of the antagonists [Leu8,des-Arg9]-BK and [des-Arg'j-Hoel4O were unchanged as compared with those determined in the absence of peptidase inhibitors (P> 0.05).[Leu8,des-Argj-BK inhibited responses to bradykinin under these conditions (n = 4).5. In endothelium-denuded preparations of the rabbit isolated aorta, an archetypal B1 receptor preparation,contractile responses to the B1 receptor-selective agonist [des-Argl-BK (10nM- 1O0 AM) (and to bradykinin) increased progressively with time of tissue incubation; and [des-Argl-BK responses were completely antagonized by the B. receptor antagonist [Leu8,des-Arg9]-BK (pKB 6.3 +/- 0.2; n = 13).6. In experiments measuring stimulation of hydrolysis of phosphatidylinositol in rabbit urinary bladder,[des-Argl-BK (10 microM- 1 mM), and bradykinin (100 microM) significantly increased accumulation of inositol phosphates (P<0.0001). The increase in accumulation of inositol phosphates evoked by [des-Arg9]-BK(10 microM - 1 mM) was significantly inhibited by [des-Arg'j-Hoe 140 (10 microM) (P <0.01).7. We conclude that in the mucosa-free rabbit urinary bladder, [des-Argl-BK evokes contraction largely via activation of B1 receptors which have similar properties, including time-dependent induction,to B1 receptors in the rabbit isolated aorta. Bradykinin evokes contraction via stimulation of both B1 and B2 receptors, but does not require conversion by peptidases in order to activate B1 receptors. We demonstrate, for the first time, B1 receptor-coupling to phosphatidylinositol hydrolysis in an intact tissue preparation.

Isolation and characterization of ovokinin, a bradykinin B1 agonist peptide derived from ovalbumin

A vasorelaxing peptide was purified from a peptic digest of ovalbumin, after three steps of reverse-phase HPLC. The structure of the peptide was Phe-Arg-Ala-Asp-His-Pro-Phe-Leu, which corresponded to residues 358-365 of ovalbumin. The peptide was named ovokinin. Ovokinin showed relaxing activity for a canine mesenteric artery (EC50 = 6.3 microM). The relaxing activity was blocked by the bradykinin B1 antagonist [des-Arg9] [Leu8]bradykinin, but not by the B2 antagonist Hoe 140. Ovokinin binds to B1 receptors (IC50 = 64 microM). Prostaglandin I2 was released from the artery after ovokinin stimulation as a relaxing factor. Thus, ovokinin is a weak bradykinin B1 agonist peptide derived from food proteins.

Further analysis of the upregulation of bradykinin B1 receptors in isolated rabbit aorta by using metabolic inhibitors

Kinins exert a contractile effect that develops as a function of the in vitro incubation time with isolated rabbit aorta. This response is mediated via receptors of the bradykinin B1 type and interleukin-1 amplifies this upregulation process. Tissues continuously treated with the protein synthesis inhibitor cycloheximide (71 microM) or with the protein trafficking inhibitor, brefeldin A (18 microM), failed to develop a contractile response to the bradykinin B1 receptor agonist, des-Arg9-bradykinin (1.7 microM) (72-100% inhibition of kinin response recorded at 3 or 6 h), whether or not they were exposed to interleukin-1 beta (290 pM). The protein glycosylation inhibitor tunicamycin exerted a selective and significant, but partial (50-76%), inhibition of des-Arg9-bradykinin-induced responses. The biochemical effect of the metabolic inhibitors on the tissue has been validated in assays involving incorporation of [3H]leucine and of [3H]mannose into protein or glycoprotein fractions, respectively. The modulatory effects of metabolic inhibitors on the responses to kinins of the isolated rabbit aorta support the idea that a de novo formation of membrane bradykinin B1 receptors is the molecular basis of both the spontaneous and the interleukin-1-stimulated upregulation phenomenon.

Up-regulation of [3H]-des-Arg10-kallidin binding to the bradykinin B1 receptor by interleukin-1 beta in isolated smooth muscle cells: correlation with B1 agonist-induced PGI2 production

1. Binding of the specific bradykinin B1 receptor agonist, [3H]-des-Arg10-kallidin (-KD) was investigated in smooth muscle cells (SMC) isolated from rabbit mesenteric arteries (RMA). 2. [3H]-des-Arg10-KD specifically bound to interleukin-1 (IL-1)-treated RMA-SMC in a saturable fashion with an equilibrium dissociation constant (KD) of 0.3-0.5 nM. The number of binding sites per cell was 20,000-35,000. Kinins inhibited [3H]-des-Arg10-KD binding to RMA-SMC with an order of potency very similar to that observed in typical B1 specific bioassays: des-Arg9-bradykinin (BK) approximately KD >> BK. Furthermore, the B1 receptor antagonist [Leu8]des-Arg9-BK inhibited [3H]-des-Arg10-KD binding with an IC50 of 43 nM as expected for its effect at B1 receptors. The B2 receptor antagonists, NPC 567 and Hoe 140 only affected [3H]-des-Arg10-KD binding at very high concentrations (IC50 = 0.8 microM and IC50 > 10 microM, respectively). 3. Des-Arg9-BK (B1 agonist) and [Hyp3]Tyr(Me)8-BK (B2 agonist) did not induce prostacyclin (PGI2) production by RMA-SMC. Lipopolysaccharide (LPS) treatment of the cells did not affect the B1 agonist response whereas IL-1 beta treatment produced a 7 fold increase in des-Arg9-BK-stimulated PGI2 production. IL-1 beta also stimulated the response to B2 agonists. 4. Des-Arg9-BK-induced PGI2 secretion in IL-1-primed RMA-SMC was mediated by B1 receptors since it was inhibited by [Leu8]des-Arg9-BK (IC50 = 56-73 nM) but not by Hoe 140. High concentrations of NPC 567 (IC5o = 2.4 micro M) were required to inhibit PGI2 production induced by B1 agonists.5. IL- 1-treated RMA-SMC displayed a 5 fold increase in the number of B1 receptors without modification of the affinity constant, thus establishing a possible relationship between the receptor density and the IL-i-primed B1 response.6. LPS treatment of the cells induced a 4 fold increase in B1 receptor number without modifying PGI2 secretion. This observation suggests that IL-1 but not LPS, in addition to increase in the number of receptors, signals the cell to permit the coupling of B1 receptors to the PLA2/cyclo-oxygenase pathway.