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

Kinin B1- and B2-Receptor Subtypes Contract Isolated Bovine Ciliary Muscle: Their Role in Ocular Lens Function and Intraocular Pressure Reduction

Background: Bradykinin is an endogenously produced nonapeptide with many physiological and pathological functions that are mediated by two pharmacologically defined receptor subtypes, B1- and B2-receptors. Current studies sought to characterize the functional bradykinin (BK) receptors present in freshly isolated bovine ciliary muscle (BCM) using an organ-bath tissue contraction system. Methods: Cumulative longitudinal isometric tension responses of BCM strips (4-5 mm) were recorded before and after the addition of test compounds to BCM strips hooked up to an isometric strain gauge transducer system. Results: BK and its analogs (7-11 concentrations) contracted BCM in a biphasic concentration-dependent manner. The first high affinity/potency phase accounted for 40-60% of the maximal contraction by each of BK (potency, EC50 = 0.9 ± 0.3 nM), Lys-BK (EC50 = 0.7 ± 0.1 nM), Met-Lys-BK (EC50 = 1 ± 0.1 nM), Hyp3-BK (EC50 = 1 ± 0.2 nM), RMP-7 (EC50 = 3.5 ± 0.5 nM), and Des-Arg9-BK (EC50 = 10 ± 0.4nM) (mean ± SEM, n = 3-8). The second lower activity phase of contraction potency values for these peptides ranged between 100 nM and 3 µM. In the presence of a selective B1-receptor antagonist (R715; 0.1-10 µM), the concentration-response curves to Des-Arg9-BK (B1-receptor agonist) were still observed, indicating activation of B2-receptors by this kinin. Likewise, when B2-receptors were completely blocked by using a B2-selective antagonist (WIN-64338; 1-10 µM), BK still induced BCM contraction, now by stimulating B1-receptors. Conclusions: This agonist/antagonist profile of BCM receptors indicated the presence of both B1- and B2-receptor subtypes, both being responsible for contracting this smooth muscle. The BCM kinin receptors may be involved in changing the shape of the ocular lens to influence accommodation, and since the ciliary muscle is attached to the trabecular meshwork through which aqueous humor drains, endogenously released kinins may regulate intraocular pressure.

Serping1 associated with α-synuclein increase in colonic smooth muscles of MPTP-induced Parkinson's disease mice

Patients with Parkinson's disease (PD) have gastrointestinal motility disorders, which are common non-motor symptoms. However, the reasons for these motility disorders remain unclear. Increased alpha-synuclein (α-syn) is considered an important factor in peristalsis dysfunction in colonic smooth muscles in patients with PD. In this study, the morphological changes and association between serping1 and α-syn were investigated in the colon of the 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine-induced chronic PD model. Increased serping1 and α-syn were noted in the colon of the PD model, and decreased serping1 also induced a decrease in α-syn in C2C12 cells. Serping1 is a major regulator of physiological processes in the kallikrein-kinin system, controlling processes including inflammation and vasodilation. The kinin system also comprises bradykinin and bradykinin receptor 1. The factors related to the kallikrein-kinin system, bradykinin, and bradykinin receptor 1 were regulated by serping1 in C2C12 cells. The expression levels of bradykinin and bradykinin receptor 1, modulated by serping1 also increased in the colon of the PD model. These results suggest that the regulation of increased serping1 could alleviate Lewy-type α-synucleinopathy, a characteristic of PD. Furthermore, this study could have a positive effect on the early stages of PD progression because of the perception that α-syn in colonic tissues is present prior to the development of PD motor symptoms.

The kinin-kallikrein system: physiological roles, pathophysiology and its relationship to cancer biomarkers

The kinin-kallikrein system (KKS) is an endogenous multiprotein cascade, the activation of which leads to triggering of the intrinsic coagulation pathway and enzymatic hydrolysis of kininogens with the consequent release of bradykinin-related peptides. This system plays a crucial role in inflammation, vasodilation, smooth muscle contraction, cardioprotection, vascular permeability, blood pressure control, coagulation and pain. In this review, we will outline the physiology and pathophysiology of the KKS and also highlight the association of this system with carcinogenesis and cancer progression.

Characterization of kinin receptors in human cultured detrusor smooth muscle cells

BACKGROUND AND PURPOSE

Kinins have an important role in inflammatory cystitis and in animal pathophysiological models, by acting on epithelium, fibroblasts, sensory innervation and smooth muscle. The aim of this study was to characterize the receptors responsible for direct motor responses induced by kinins on human detrusor.

EXPERIMENTAL APPROACH

Human detrusor cells from biopsies were isolated and maintained in culture. B(1) and B(2) kinin receptors were characterized by means of radioligand and functional experiments (PI accumulation and PGE(2) release).

KEY RESULTS

[(3)H]-[desArg(9)]-Lys-BK and [(3)H]-BK saturation studies indicated receptor density (B(max)) and K (d) values of 19 or 113 fmol mg(-1), and 0.16 or 0.11 nM for the B(1) or B(2) receptors, respectively. Inhibition binding studies indicated the selectivity of the B(1) receptor antagonist [desArg(9)Leu(8)]-Lys-BK and of the B(2) receptor antagonists Icatibant and MEN16132. [DesArg(9)]-Lys-BK and BK induced PI accumulation with an EC(50) of 1.6 and 1.4 nM and different maximal responses (E(max) of [desArg(9)]-Lys-BK was 10% of BK). BK also induced prostaglandin E(2) release (EC(50) 2.3 nM), whereas no response was detected with the B(1) receptor agonist. The incubation of detrusor smooth muscle cells with interleukin 1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha) (10 ng ml(-1)) induced a time-dependent increase in radioligand-specific binding, which was greater for the B(1) than for the B(2) receptor.

CONCLUSIONS AND IMPLICATIONS

Human detrusor smooth muscle cells in culture retain kinin receptors, and represent a suitable model to investigate the mechanisms and changes that occur under chronic inflammatory conditions.

Kallikrein protects against ischemic stroke by inhibiting apoptosis and inflammation and promoting angiogenesis and neurogenesis

Stroke-induced neurological deficits and mortality are often associated with timing of treatment after the onset of stroke. We showed that local delivery of the human tissue kallikrein gene into rat brain immediately after middle cerebral artery occlusion (MCAO) exerts neuroprotection. In this study, we investigated the effect of systemic delivery of the kallikrein gene 8 hr after MCAO. Expression of recombinant human tissue kallikrein after gene transfer was identified in the ischemic brain region and blood vessels. Intravenous injection of adenovirus encoding the kallikrein gene significantly reduced neurological deficit scores 2 and 7 days after gene transfer. Kallikrein gene transfer also reduced ischemia-reperfusion (I/R)-induced cerebral infarction and promoted the survival and migration of glial cells from penumbra to the ischemic core from 3 to 14 days after gene delivery. Kallikrein reduced I/R-induced apoptosis of neuronal cells and inhibited inflammatory cell accumulation in the ischemic brain. These effects were blocked by the kinin B2 receptor antagonist icatibant. In addition, kallikrein enhanced angiogenesis and promoted neurogenesis after I/R and the stimulatory effect of kinin on neuronal cell proliferation was confirmed in primary cultured neuronal cells. The protective effects of kallikrein, through the kinin B2 receptor, were accompanied by increased cerebral nitric oxide and Bcl-2 levels, Akt phosphorylation, and reduced NAD(P)H oxidase activity, superoxide production, Bax levels, and caspase-3 activity. These results indicate that delayed systemic administration of the kallikrein gene after onset of stroke protects against ischemic brain injury by inhibiting apoptosis and inflammation and by promoting angiogenesis and neurogenesis.

Pharmacology of the lower urinary tract: basis for current and future treatments of urinary incontinence

The lower urinary tract constitutes a functional unit controlled by a complex interplay between the central and peripheral nervous systems and local regulatory factors. In the adult, micturition is controlled by a spinobulbospinal reflex, which is under suprapontine control. Several central nervous system transmitters can modulate voiding, as well as, potentially, drugs affecting voiding; for example, noradrenaline, GABA, or dopamine receptors and mechanisms may be therapeutically useful. Peripherally, lower urinary tract function is dependent on the concerted action of the smooth and striated muscles of the urinary bladder, urethra, and periurethral region. Various neurotransmitters, including acetylcholine, noradrenaline, adenosine triphosphate, nitric oxide, and neuropeptides, have been implicated in this neural regulation. Muscarinic receptors mediate normal bladder contraction as well as at least the main part of contraction in the overactive bladder. Disorders of micturition can roughly be classified as disturbances of storage or disturbances of emptying. Failure to store urine may lead to various forms of incontinence, the main forms of which are urge and stress incontinence. The etiology and pathophysiology of these disorders remain incompletely known, which is reflected in the fact that current drug treatment includes a relatively small number of more or less well-documented alternatives. Antimuscarinics are the main-stay of pharmacological treatment of the overactive bladder syndrome, which is characterized by urgency, frequency, and urge incontinence. Accepted drug treatments of stress incontinence are currently scarce, but new alternatives are emerging. New targets for control of micturition are being defined, but further research is needed to advance the pharmacological treatment of micturition disorders.

Pharmacological and functional characterization of bradykinin B2 receptor in human prostate

The objective of this study was to pharmacologically characterize bradykinin receptors, a component of the kallikrein-kinin system, in normal human prostate cells. In primary cultured human prostate stromal cells, bradykinin, but not [des-Arg9]bradykinin or [des-Arg10]kallidin, produced calcium mobilization or inositol phosphates accumulation with potencies (pEC50) of 8.8+/-0.2 and 8.2+/-0.2, respectively. This was consistent with abundance of bradykinin B2 mRNA over bradykinin B1 mRNA in prostate stromal cells. Although the prostate epithelial cells (prostate epithelium, BPH-1, and PC-3) expressed mRNA for bradykinin B2 receptors (albeit in lesser amounts than stromal cells), bradykinin was not functionally efficacious in the epithelial cells. Increasing concentrations of D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thienyl)-L-alanyl-L-seryl-D-1,2,3,4-tetrahhydro-3-isoquinolinecarbonyl-L-(2alpha,3beta,7alphabeta)-octahydro-1H-indole-2-carbonyl-L-arginine (HOE-140), a bradykinin B2-selective peptide antagonist, attenuated bradykinin concentration-response curves in human prostate stromal cells with apparent estimate of affinity similar to that for the human bradykinin B2 receptor. Bradykinin (10 nM) caused proliferation of prostate stromal cells and phosphorylated extracellular signal-regulated kinases (ERK-1 and ERK-2) that were blocked by HOE-140 (1 microM). This study demonstrated that, in primary cultures of normal human prostate stromal cells, bradykinin activates bradykinin B2 receptors that may play a significant role in proliferation via activation of ERK-1/2 pathways.

Bradykinin B1 receptor stimulates the proximal tubule Na+-ATPase activity through protein kinase C pathway

Recently, our group described a B1-mediated stimulatory effect of des-Arg(9)-bradykinin (DABK) on the Na(+)-ATPase activity of proximal tubule basolateral membranes (BLM) [Biochim. Biophys. Acta 1431 (1999) 483.]. Data in the present report suggest the participation of a phosphatidylinositol-specific PLC (PI-PLC)/protein kinase C (PKC) pathway as the molecular mechanism of DABK-mediated stimulation of the Na(+)-ATPase activity since (i) 10(-8) M DABK activates PI-PLC activity; (ii) 10(-9) M U73122, a PI-PLC inhibitor, abolishes the effect of 10(-8) M DABK on the Na(+)-ATPase activity; (iii) 10(-8) M DABK increases phosphoprotein formation by 34%. This effect is completely reversed by 10(-7) M calphostin C, an inhibitor of PKC; (iv) 20 ng/ml TPA, an activator of PKC, and 10(-8) M DABK stimulate the Na(+)-ATPase activity in a similar and nonadditive manner. Furthermore, the effect of 10(-8) M DABK is completely reversed by calphostin C; (v) 10(-8) M DABK increases phosphoserine residue levels by 54%. This effect is completely reversed by 10(-7) M calphostin C.

Development of an intact cell reporter gene beta-lactamase assay for G protein-coupled receptors for high-throughput screening

G protein-coupled receptors (GPCRs) are involved in a large variety of physiological disorders, and are thus important pharmaceutical drug targets. Here, we describe the development and characterization of a beta-lactamase reporter gene assay as a functional readout for the ligand-induced activation of the human bradykinin B1 receptor, expressed recombinantly in CHO cells. The beta-lactamase reporter gene assay provides high sensitivity due to the absence of endogenous beta-lactamase activity in mammalian cells. The cell-permeable fluorogenic substrate allows single-cell cloning of cells expressing functional BK1 receptors. Pharmacological characterization reveals comparable sensitivity and potency of known BK1 receptor agonists and antagonists between the beta-lactamase assay, competition-binding assay, and other direct measurements of second messengers. The beta-lactamase assay has been optimized for cell density, time of agonist stimulation, and DMSO sensitivity. This CHO-hBK1-beta-lactamase assay is well suited to automation and miniaturization required for high-throughput screening.

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.

Pharmacological and molecular evidence for kinin B1 receptor expression in urinary bladder of cyclophosphamide-treated rats

1. In the present study, we developed an experimental model of cystitis induced by cyclophosphamide (CYP). In order to characterize des-Arg9-BK-induced contraction on the urinary bladder (UB) during the development of inflammation and to quantify kinin B1 receptor gene expression using a quantitative RT - PCR technique. 2. In the presence of peptidase inhibitors captopril (10 microM), DL-thiorphan (1 microM) and DL-2-mercaptomethyl-3-guanidino-ethylthiopropanoic acid (MERGEPTA 5 microM), bradykinin (BK) (0.3 - 3,000 nM) evoked a concentration-dependent contraction of rat UB which was not different between the CYP- and vehicle-treated groups. Unlike BK, des-Arg9-BK (0.3 - 100,000 nM) did not contract UB from vehicle-treated rats but contracted vigorously bladder strips from CYP-treated rats 14, 24 and 168 h after treatment. In UB of 24 h treated rat, the pD2 value of des-Arg9-BK was 7.3+/-0.1. 3. The cyclo-oxygenase inhibitor indomethacin (3 microM) reduced by 30% the maximal response of des-Arg9-BK. Both the kinin B1 receptor antagonists des-Arg9-[Leu8]BK (10 microM) and des-Arg10-Hoe 140 (10 microM) produced a rightward shift of the concentration-response curve to des-Arg9-BK yielding pKB values of 6.8+/-0.2 and 7.2+/-0.1, respectively, whilst the kinin B2 receptor antagonist Hoe 140 (1 microM) had no effect. 4. After CYP treatment, mRNA coding for the kinin B1 receptor appeared predominantly in UB. In this organ, the induction was progressive, reaching a maximum 48 h after CYP treatment. 5. In conclusion, the present study provides strong evidence for an induction of kinin B1 receptors in UB of CYP-treated rats. This was associated at a molecular level with an increase in mRNA expression of the gene coding for the kinin B1 receptor. This kinin receptor displayed the whole features of a classical rat kinin B1 receptor.

Small molecule antagonists of the bradykinin B1 receptor

Screening Pharmacopeia's encoded combinatorial libraries has led to the identification of potent, selective, competitive antagonists at the bradykinin B1 receptor. Libraries were screened using a displacement assay of [3H]-des-Arglo-kallidin ([3H]-dAK) at IMR-90 cells expressing an endogenous human B1 receptor (Bmax = 20,000 receptors/cell, K(D) = 0.5+/-0.1 nM) or against membranes from 293E cells expressing a recombinant human B1 receptor (Bmax = 8,000 receptors/cell, K(D) = 0.5 +/- 0.3 nM). Compound PS020990, an optimized, representative member from the class of compounds, inhibits specific binding of 3H-dAK at IMR-90 cells with a KI of 6 +/- 1 nM. The compound inhibits dAK-induced phosphatidyl inositol turnover (K(Bapp) = 0.4 +/- 0.2 nM) and calcium mobilization (K(Bapp) = 17 +/- 2 nM) in IMR-90 cells. Compounds from the lead series are inactive at the B2 receptor and are > 1000-fold specific for B1 vs. a variety of other receptors, ion channels and enzymes. PS020990 and other related chemotypes therefore offer an excellent opportunity to explore further the role of B1 receptors in disease models and represent a potential therapeutic avenue.

Lipopolysaccharide upregulates bradykinin 1 receptors in the isolated mouse bladder

PURPOSE

Bradykinin 1 (B1) receptors have been shown to be upregulated at sites of inflammation. The purpose of this study was to determine the effect of lipopolysaccharide (LPS) on B1 receptor modulation in the isolated mouse bladder.

MATERIALS AND METHODS

The contractile responses of isolated mouse bladder to B1 and B2 agonists were determined in vitro following prolonged incubation with LPS or saline.

RESULTS

Bradykinin (BK), a B2 agonist, but not des-Arg9-bradykinin (DABK), a B1 agonist, was found to be a potent contractile agonist of the mouse urinary bladder under basal conditions. However, both sensitivity and maximal response to DABK increased during a second exposure to the agonist in a time-dependent manner. In vivo or in vitro treatment with LPS increased both sensitivity and maximal response of isolated bladders to DABK, whereas bladder contraction to BK and other peptides remained the same. Treatment of tissues with a B1 receptor antagonist 45 minutes prior to second exposure to DABK, or the prostaglandin synthesis inhibitor, indomethacin, 30 minutes prior to LPS or saline incubation, significantly inhibited the increase of both maximal response and sensitivity.

CONCLUSIONS

These results indicate that bladder B1 receptors can be upregulated by LPS, and that prostaglandins seem to mediate the effects of the B1 receptor activation in the isolated mouse bladder.

Characterization of bradykinin receptors in human lung fibroblasts using the binding of 3[H][Des-Arg10,Leu9]kallidin and [3H]NPC17731

Bradykinin (BK) receptors are involved in pain and inflammation. Two BK receptor subtypes, B1 and B2, have been defined based on their pharmacological properties. Both B1 and B2 receptors are G-protein coupled membrane receptors. B1 receptors are present in smooth muscle tissue, whereas B2 receptors are found in both smooth muscle tissue and neurons. [Des-Arg10,Leu9]kallidin (DALKD) is a selective B1 receptor antagonist, and NPC17731 is a selective B2 receptor antagonist. To develop binding assays for the two known BK receptor subtypes, [3H]DALKD and [3H]NPC17731 were used as selective ligands for B1 and B2 receptors respectively. Both ligands bound to the CCD-16 human lung fibroblast membranes reaching equilibrium at 25 degrees C within 30 min. Binding was stable for at least 60 min. The Kd of [3H]DALKD was 0.33 nM and Bmax was 52 fmol/mg membrane protein. The Kd of [3H]NPC17731 was 0.39 nM and Bmax was 700 fmol/mg membrane protein. Competition for [3H]DALKD binding with BK receptor agonists was in the order: [des-Arg10]KD (DAKD) > KD >> [des-Arg9]BK (DABK) > BK, and competition for [3H]DALKD binding with BK receptor antagonists was in the order: DALKD > [des-Arg10]Hoe 140 (DAHoe 140) > [des-Arg9,Leu8]BK (DALBK) > NPC17731 > Hoe 140 > DNMFBK, suggesting that [3H]DALKD bound selectively to B1 receptors. By contrast, competition for [3H]NPC17731 binding by BK agonists was in the order: BK > KD >> DAKD > DABK, and competition for [3H]NPC17731 binding by BK antagonists was in the order: NPC17731 = Hoe 140 >> DNMFBK > DAHoe 140 > DALBK > DALKD, indicating that [3H]NPC17731 labeled B2 receptors selectively. These results demonstrate that [3H]DALKD and [3H]NPC17731 can be used with CCD-16 human lung fibroblast membranes to provide a pair of binding assays for the simultaneous evaluation of B1 and B2 BK receptor subtypes.

Effects of bradykinin on signal transduction, cell proliferation, and cytokine, prostaglandin E2 and collagenase-1 release from human corneal epithelial cells

1. We recently demonstrated the presence of phospholipase C-coupled bradykinin (BK) B2-receptors in human primary and SV40 virus-immortalized corneal epithelial (CEPI) cells. 2. The aims of the present studies were to demonstrate the specific binding of [3H]-BK to CEPI cell membranes and to study its pharmacological characteristics. In addition, we wished to study the functional coupling of the BK receptors to various physiological and pathological mechanisms in the CEPI cells, including phosphoinositide (PI) turnover, intracellular Ca2+-mobilization ([Ca2+]i), cell proliferation (via [3H]-thymidine incorporation), and the release of various cytokines, collagenase-1 (matrix metalloproteinase-1) and prostaglandin E2 (PGE2). 3. Specific [3H]-BK binding comprised 83 +/- 2% of the total binding, and was of high affinity (Kd = 1.66 +/- 0.52 nM, n = 5), saturable (Bmax = 640 +/- 154 fmol g(-1) wet weight) and reversible. Competition studies yielded the following affinity values for BK and a number of BK-related peptides: Hoe-140 (D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]BK; icatibant): Ki = 0.17 +/- 0.07 nM; BK: Ki = 1.0 +/- 0.11 nM; [Tyr8]-BK: Ki = 12.9 +/- 2.3 nM; [des-Arg9]-BK: Ki > 9,200 nM (all n = 3-5)). 4. BK potently stimulated PI turnover (EC50 = 2.3 +/- 0.3 nM; n = 7) and [Ca2+]i mobilization (EC50 = 8-20 nM) in CEPI cells and both responses were inhibited in a concentration-dependent manner by 100 nM-10 microM Hoe-140, a selective B2-receptor antagonist, and also inhibited by the selective phospholipase C (PLC) inhibitor, U73122 (1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1 H-pyrrole-2,5-dione) (IC50 = 3.0 +/- 1.6 microM). BK-induced [Ca2+]i mobilization was reduced by about 30% in the presence of 4 mM EGTA, but was not significantly affected by 100 nM nifedipine. 5. BK (0.1 nM-10 microM) significantly (P<0.05-0.001) stimulated [3H]-thymidine incorporation into CEPI cellular DNA. However, while interleukin-1alpha (IL-1alpha; 10 ng ml(-1)) potently stimulated the release of IL-6, IL-8 and granulocyte macrophage colony-stimulating factor from CEPI cells, BK (0.1 nM-10 microM) was without effect. 6. Whilst phorbol-12-myristate-13-acetate (PMA; 3 microg ml(-1)) and 10% foetal bovine serum (positive control agents) significantly stimulated the release of both MMP-1 and PGE2 from CEPI cells, BK (0.1 nM-10 microM) was without any significant effect under these conditions. 7. In conclusion, these data indicate that the CEPI cells express high-affinity [3H]-BK binding sites representing B2-subtype BK receptors coupled to PI turnover and [Ca2+]i mobilization which appear to stimulate [3H]-thymidine incorporation into cellular DNA. In contrast, BK failed to elicit the release of PGE2, various cytokines and MMP-1 from CEPI cells. These results suggest that BK may have a potential role in corneal epithelium wound healing by stimulating cell proliferation.

Kinin receptors mediating the effect of bradykinin on gastric acid secretion

Kinins, and bradykinin in particular, can affect electrolyte transport in different segments of the intestine, thus being able to stimulate chloride secretion. Since the stomach is the main chloride secretory unit in the gastrointestinal tract, we have investigated the effect of bradykinin on acid secretion in the isolated frog (Rana catesbeiana) gastric mucosa. Bradykinin [2 x 10(-8) to 2 x 10(-6) M] and des-Arg9-bradykinin [2 x 10(-9) to 2 x 10(-7) M] were able to stimulate acid secretion in a dose-dependent manner. The bradykinin [2 x 10(-7) M] and des-Arg9-bradykinin (2 x 10(-8) M]-induced acid secretion was unaffected by Thi5,8,D-Phe7-bradykinin [2 x 10(-7) to 2 x 10(-5) M], a B2-kinin receptor antagonist. Interestingly, the B1-kinin receptor antagonist, des-Arg9-(Leu8)-bradykinin [2 x 10(-7) to 2 x 10(-5) M] blocked both bradykinin- and des-Arg9-bradykinin-stimulated acid secretion. Although the kininase I inhibitor, D-L-mercapto-methyl-3-guanidino-ethyl-propanoic acid [2 x 10(-6) and 2 x 10(-5) M] had no effect on des-Arg9-bradykinin-induced acid secretion, it inhibited the response to bradykinin. We conclude that bradykinin requires, at least in part, hydrolysis to des-Arg9-bradykinin to increase gastric acid secretion and that its effect is mediated by B1-kinin receptors.

The expression of functionally-coupled B2-bradykinin receptors in human corneal epithelial cells and their pharmacological characterization with agonists and antagonists

1. Bradykinin (BK) and Lys-BK are peptides which are released at high nanomolar concentrations into the tear-film of ocular allergic patients. We hypothesized that these peptides may activate specific receptors on the ocular surface, especially the corneal epithelium (CE) and thus the CE cells may represent a potential target tissue for these kinins. 2. The purpose of the present studies, therefore, was to determine the presence of and the pharmacological characteristics of bradykinin receptors on normal cultured primary and SV40 virus-transformed human corneal epithelial (CEPI) cells by use of the accumulation of [3H]-inositol phosphates ([3H]-IPs) as a bioassay. 3. Bradykinin (BK) induced a maximal 1.95 +/- 0.24 fold (n = 17) and 2.51 +/- 0.29 fold (n = 26) stimulation of [3H]-IPs accumulation in normal, primary (P-CEPI) and SV40-immortalized (CEPI-17-CL4) cells, respectively. This contrasted with a maximal 3.2-4.5 fold and 2.0-2.9 fold stimulation by histamine (100 microM) and platelet activating factor (100 nM) in both cell-types, respectively. 4. The molar potencies of BK and some of its analogues in the CEPI-17-CL4 cells were as follows: BK (EC50 = 3.26 +/- 0.61 nM, n = 18), Lys-BK (EC50 = 0.95 +/- 0.16 nM, n = 5), Met-Lys-BK (EC50 = 2.3 +/- 0.42 nM, n = 5), Ile-Ser-BK (EC50 = 5.19 +/- 1.23 nM, n = 6), Ala3-Lys-BK (EC50 = 12.7 +/- 2.08 nM, n = 3), Tyr8-BK (EC50 = 19.3 +/- 0.77 nM, n = 3), Tyr5-BK (EC50 = 467 +/- 53 nM, n = 4) and des-Arg9-BK (EC50 = 14.1 +/- 2.7 microM, n = 4). The potencies of BK-related peptides in normal, P-CEPI cells were similar to those found in transformed cells, thus: BK, EC50 = 2.02 +/- 0.69 nM (n = 7), Tyr8-BK, EC50 = 14.6 +/- 2.7 nM (n = 3), Tyr5 = BK, EC50 = 310 +/- 70 nM (n = 4) and des-Arg9-BK, EC50 = 12.3 +/- 3.8 microM (n = 3). 5. The bradykinin-induced responses were competitively antagonized by the B2-receptor selective BK antagonists, Hoe-140 (D-Arg-[Hyp3, Thi5, D-Tic7, Oic8]BK; Icatibant; molar antagonist potency = 2.9 nM; pA2 = 8.54 +/- 0.06, n = 4; and slope = 1.04 +/- 0.08) and D-Arg0[Hyp3,Thi5,8, DPhe7]-BK (KB = 371 nM; pKB = 6.43 +/- 0.08, n = 4) in CEPI-17-CL4 cells. The antagonist potency of Hoe-140 against BK in normal, P-CEPI cells was 8.4 +/- 1.8 nM (pKi = 8.11 +/- 0.12, n = 4), this being similar to the potency observed in the immortalized cells. 6. This rank order of potency of agonist BK-related peptides, coupled with the antagonism of the BK-induced [3H]-IPs by the specific B2-receptor antagonists, strongly suggests that a B2-receptor subtype is involved in mediating functional phosphoinositide (PI) responses in the CEPI-17-CL4 and P-CEPI cells. 7. In conclusion, these data indicate that the P-CEPI and CEPI-17-CL4 cells express BK receptors of the B2-subtype coupled to the PI turnover signal transduction pathway. The CEPI-17-CL4 cells represent a good in vitro model of the human corneal epithelium in which to study further the role of BK receptors in its physiology and pathology, such as in allergic/inflammatory conditions, potential wound healing and other functions of the cornea.

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.

Bradykinin receptors

1. The last decade has witnessed a phenomenal increase in our understanding of the pharmacology of bradykinin receptors, and has led to an appreciation of a key role for the peptide kinins as proinflammatory mediators. This short review summarises the major changes that have taken place in the expanding area of bradykinin receptor pharmacology, and highlights important advances that we hope to anticipate in the future. 2. Bradykinin receptors are cell surface, G-protein coupled receptors of the seven-transmembrane domained family. The existence of two subtypes of bradykinin receptor, B1 and B2, has been confirmed through the use of high affinity peptide and nonpeptide receptor antagonists, radioligand binding studies and, recently, receptor cloning and expression studies. 3. Differences in the affinities of B2 receptor antagonists, including those of the [D-Phe7]-bradykinin series, D-Arg-[Hyp3, Thi5, D-Tic7, Oic8]-bradykinin (Hoe140, Icatibant) and the non-peptide, WIN64338, have led to proposals of the possible existence of further subtypes of bradykinin receptor (including a tracheal B3 receptor), and/or of species homologues of the B2 receptor. 4. Molecular cloning techniques have identified the gene encoding B1 receptors in the rabbit, human and mouse, and B2 receptors in the rat, human and mouse. B1 and B2 receptor show little (36%) overall sequence homology. Cloning studies reveal the potential for the existence of species homologues of receptors. 5. The use of bradykinin receptor antagonists in vivo has led to an appreciation of the involvement of bradykinin receptors in inflammation. Evidence suggests a role for B2 receptors in more classical acute inflammatory events, such as oedema and inflammatory pain, whereas B1 receptors appear to be involved in chronic inflammatory responses, including certain forms of persistent hyperalgesia. 6. The continuing advances in our knowledge of the characteristics of bradykinin receptors through the further development of selective receptor antagonists and molecular biology techniques will aid in the rational design of drugs effective in the therapeutic manipulation of inflammatory processes and in the control of inflammatory disease.

The longitudinal muscle of rat ileum as a sensitive monoreceptor assay for bradykinin B1 receptors

1. Various bradykinin derivatives, acting preferentially at B1 or B2 receptors, were tested in the isolated longitudinal smooth muscle of rat ileum. Experiments were carried out in the presence of chlorpheniramine and atropine (both 1 microM), guanethidine and indomethacin (both 3 microM) and of the peptidase inhibitors (captopril, bestatin and thiorphan, all 1 microM). 2. The rank order of potency was (pD2 values +/- s.e.mean, n = 5 in parentheses, at 5 h from set-up): [des-Arg9]-BK (8.27 +/- 0.11) > or = [des-Arg10]-kallidin (7.67 +/- 0.24) > bradykinin (6.69 +/- 0.25). The B2 receptor selective agonist, [Hyp3,Tyr(Me)8]-BK, was approximately 10 fold less active than bradykinin. Contractile responses to all agonists increased with time. The maximal response to the B1 receptor agonist, [desArg9]-BK at 5 h (94 +/- 2%) was significantly (P < 0.05) greater than that measured at 2 h (74 +/- 2%). 3. The B2 receptor antagonist, D-Arg[Hyp3, Thi5, D-Tic7, Oic8]-BK (Hoe 140, 0.1 microM) did not affect responses to the B1 receptor agonist [des-Arg9]-BK (0.1 nM--1 microM) nor those to the B2 receptor agonist, [Hyp3,Tyr(Me)8]-BK (1 nM--10 microM). In control experiments performed in the longitudinal smooth muscle of guinea-pig ileum and rat isolated urinary bladder as bioassays for B2 receptors, the B2 receptor antagonist Hoe 140 (0.1 microM) antagonized bradykinin-induced contractions. 4. In the rat isolated ileum the B1 receptor antagonist, D-Arg[Hyp3, Thi5, D-Tic7, Oic8, des-Arg9]-BK ([des-Arg10]-Hoe 140, 0.3 - 10 microM) competitively antagonized contractile responses to [des-Arg9]-BK with an estimated pKB of 6.74 +/- 0.08 (Schild plot slope with confidence limits 1.22, (0.70 - 1.73) n = 13). In control experiments in the guinea-pig isolated ileum and rat isolated urinary bladder, [des-Arg10]-Hoe 140 (1 - 10 microM) did not inhibit B2 receptor-mediated contractile responses. 5. The putative B1 receptor antagonist, [Leu8,des-Arg9]-BK, behaved as a partial agonist when responses were determined 2 h from set-up (pD2 6.43 +/- 0.21, n = 5; Emax 30% of that evoked by [des-Arg9]-BK); at 5 h from set-up it behaved as a full agonist (pD2 7.48 +/- 0.12, n = 5; Emax 90% of that evoked by [des-Arg9]-BK). At this time the response to [Leu8,des-Arg9]-BK was antagonized in a concentration-dependent manner by [des-Arg10]-Hoe 140, which at 1 microM and 10 microM, produced dose-ratios of 6.33 +/- 3.66 (n = 4) and 103 +/- 40 (n = 4). 6. In view of the rank order of potency of agonists, the antagonist activity by [des-Arg10]-Hoe 140 and the lack of antagonist activity of Hoe 140, we conclude that the longitudinal smooth muscle of rat ileum, after histamine, acetylcholine, noradrenaline, and prostanoid production blockade, is a sensitive monoreceptor assay for studying the pharmacology of bradykinin B1 receptors. Further the preparation can also be used as a sensitive bioassay to identify partial agonist activity of B1 receptor antagonists such as [Leu8,desArg9]-BK.

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.