Role of bradykinin B1 and B2 receptors in normal blood pressure regulation

With inhibition or absence of the bradykinin B2 receptor (B2R), B1R is upregulated and assumes some of the hemodynamic properties of B2R, indicating that both participate in the maintenance of normal vasoregulation or to development of hypertension. Herein we further evaluate the role of bradykinin in normal blood pressure (BP) regulation and its relationship with other vasoactive factors by selectively blocking its receptors. Six groups of Wistar rats were treated for 3 wk: one control group with vehicle alone, one with concurrent administration of B1R antagonist R-954 (70 microg x kg(-1) x day(-1)) and B2R antagonist HOE-140 (500 microg x kg(-1) x day(-1)), one with R-954 alone, one with HOE 140 alone, one with concurrent administration of both R-954 and HOE-140 plus the angiotensin antagonist losartan (5 mg x kg(-1) x day(-1)), and one with only losartan. BP was measured continuously by radiotelemetry. Only combined administration of B1R and B2R antagonists produced a significant BP increase from a baseline of 107-119 mmHg at end point, which could be partly prevented by losartan and was not associated with change in catecholamines, suggesting no involvement of the sympathoadrenal system. The impact of blockade of bradykinin on other vasoregulating systems was assessed by evaluating gene expression of different vasoactive factors. There was upregulation of the eNOS, AT1 receptor, PGE2 receptor, and tissue kallikrein genes in cardiac and renal tissues, more pronounced when both bradykinin receptors were blocked; significant downregulation of AT2 receptor gene in renal tissues only; and no consistent changes in B1R and B2R genes in either tissue. The results indicate that both B1R and B2R contribute to the maintenance of normal BP, but one can compensate for inhibition of the other, and the chronic inhibition of both leads to significant upregulation in the genes of related vasoactive systems.     

The angiotensin II type 1 receptor antagonist Losartan binds and activates bradykinin B2 receptor signaling

The angiotensin II type 1 receptor (AT1R) blocker (ARB) Losartan has cardioprotective effects during ischemia-reperfusion injury and inhibits reperfusion arrhythmias -effects that go beyond the benefits of lowering blood pressure. The renin-angiotensin and kallikrein-kinin systems are intricately connected and some of the cardioprotective effects of Losartan are abolished by blocking the bradykinin B2 receptor (B2R) signaling. In this study, we investigated the ability of six clinically available ARBs to specifically bind and activate the B2R. First, we investigated their ability to activate phosphoinositide (PI) hydrolysis in COS-7 cells transiently expressing the B2R. We found that only Losartan activated the B2R, working as a partial agonist compared to the endogenous ligand bradykinin. This effect was blocked by the B2R antagonist HOE 140. A competitive binding analysis revealed that Losartan does not significantly compete with bradykinin and does not change the binding affinity of bradykinin on the B2R. Furthermore, Losartan but not Candesartan mimicked the ability of bradykinin to increase the recovery of contractile force after metabolic stress in rat atrial tissue strips. In conclusion, Losartan is a partial agonist of the B2R through direct binding and activation, suggesting that B2R agonism could partly explain the beneficial effects of Losartan.     

Changes in amino-terminal portion of human B2 receptor selectively increase efficacy of synthetic ligand HOE 140 but not of cognate ligand bradykinin

Recently, we have shown that a widely used antagonist of the human bradykinin B(2) receptor (B(2)R) HOE 140 acts as a full agonist of the chicken ornithokinin receptor (B(o)R). To understand the molecular mechanisms underlying differential efficacy of HOE 140 for the various kinin receptors, we have constructed chimeric kinin receptors (CKR) in which the amino-terminal portion including the first two transmembrane regions and the first extracellular loop (CKR-2) or only the second transmembrane region and the first extracellular loop (CKR-1) of B(2)R were substituted with the corresponding segments of B(o)R. Ligand efficacy of synthetic ligand HOE 140 decreased in the order B(o)R > CKR-2 > CKR-1 > B(2)R, whereas the efficacy of the endogenous kinin ligand was unchanged. Enhanced HOE 140 efficacy was not due to a structural change in the ligand binding site or to an enhanced receptor expression level. Rather, heterologous binding competition studies indicated that structural change(s) introduced into the engineered receptors caused a selective reduction in apparent affinity of HOE 140 for the uncoupled inactive receptor state R but not for the active G protein-coupled state R*, thereby increasing the ratio of R* over R for a given ligand concentration. Our results may help explain the unusually broad efficacy spectrum of HOE 140, which varies from inverse to full agonism, depending on kinin receptor subtype, tissue origin, or species.     

Tissue kallikrein protects cortical neurons against hypoxia/reoxygenation injury via the ERK1/2 pathway

Systemic or local delivery of human tissue kallikrein gene (hTK) has been shown to be an effective strategy to alleviate cerebral ischemia/reperfusion (I/R) injury, and tissue kallikrein (TK) administration can suppress glutamate- or acidosis-mediated neurotoxicity in vitro. In the present study, the role of TK in hypoxia/reoxygenation (H/R) induced neuronal cell death was investigated. We found that TK administration could remarkably alleviate H/R-induced neuronal injury by reduction of LDH release and promotion of neuron viability. The protective effects of TK could be counteracted by bradykinin B2 receptor (B2R) antagonist HOE140, which could suppress up-regulation of TK on the ERK signal pathway under H/R condition. These results indicate that TK plays an important role in preventing neurons from H/R damage at least partially through the TK-B2R-ERK1/2 pathway.     

Age-related changes of bradykinin B1 and B2 receptors in rat heart

Aging is a major risk factor for the development of vascular diseases, such as hypertension and atherosclerosis, that leads to end organ damage and especially heart failure. Bradykinin has been demonstrated to have a cardioprotective role by affecting metabolic processes and tissue perfusion under conditions of myocardial ischemia. Its actions are exerted via the bradykinin B1- and B2-type receptors (B1Rs and B2Rs), but the functional status of these receptors during the aging process is poorly understood. This study aims to investigate whether changes in B1R and B2R gene and protein expression in rat heart are associated with the age-related alterations of cardiac structure and function. Using real-time PCR, we found that B1R mRNA expression increased 2.9-fold in hearts of older rats (24 mo of age) compared with younger rats (3 mo of age), whereas B2R gene expression remained unchanged. Western blot analysis showed that expression of B2R at the protein level is approximately twofold higher in young rats compared with old rats, whereas the B1R protein is approximately twofold higher in old rats compared with young rats. The present results provide clear functional and molecular evidence that indicate age-related changes of bradykinin B1Rs and B2Rs in heart. Because the cardioprotective actions of bradykinin are physiologically mediated via the B2Rs, whereas the B1Rs become induced by tissue damage, these results suggest that age-related decreases in B2R protein levels may leave the heart vulnerable to ischemic damage, and increases in B1R expression and activity may represent a compensatory reaction in aging hearts.     

Modulation of vasoconstrictor and dilator pancreatic metabolites in streptozotocine diabetic rats: effect of bradykinin blockage and NO inhibition.

This study was designed to investigate the effect of HOE 140 (a bradykinin beta2 receptor antagonist) and N(w)-nitro-L-arginine methyl-ester (L-NAME, a nitric oxide synthase inhibitor) on endothelial and beta-cell function in induced streptozotocine (Stz) diabetic rats. The decrease in the insulinogenic index after Stz effect (control 286.03+/-104.12 and Stz 18.22+/-10.77, P<0.001 vs. Control) was partially prevented by L-NAME (46.54+/-10.12, P<0.001) and HOE 140 (105.12+/-23.06, P<0.001). It was observed in diabetic rats: L-NAME increased the pancreatic endothelin-1 (ET-1) production and HOE 140 did not. L-NAME and HOE 140 decreased the nitric oxide (NO) synthesis, increased prostacyclin 1-2 (PGI2), and did not modify thromboxane A-2 (TxA2). These results indicate that L-NAME and HOE 140 had a protective effect on the development of diabetes in the rat. The protective effect of L-NAME and HOE 140 on the insulinogenic index could be related to ET-1, bradykinin, PGI2, and NO.     

Role of bradykinin in acid-induced mesenteric hyperemia and duodenal villous damage

Intestinal mucosal capsaicin-sensitive afferent nerves mediate, in part, the mesenteric hyperemia after intraduodenal acidification. The hyperemia plays a role in protecting the duodenal mucosa against acid damage. We tested the hypothesis that bradykinin contributes to this protective hyperemia. A specific antagonist of bradykinin will attenuate the hyperemia and exacerbate duodenal villous damage induced by acid. Study 1: Intravenous vehicle, or the specific bradykinin B2 receptor antagonist (HOE 140) was administered to anesthetized rats. This was followed by intraduodenal bolus administration of 160 microM capsaicin or 0.1 N HCl, and then intravenous bradykinin. Study 2: Intravenous administration of vehicle or HOE 140 was followed by duodenal perfusion with 0.1 N HCl. Superior mesenteric artery blood flow (pulsed Doppler flowmetry) (Study 1) and duodenal villous damage (histology) (Study 2) were recorded. HOE 140 significantly reduced the hyperemia induced by bradykinin and intraduodenal capsaicin or acid. Deep villous injury was significantly increased after treatment with HOE 140. These findings support the hypothesis that acid-induced and afferent nerve-mediated mesenteric hyperemia is modulated by a mechanism that involves bradykinin B2 receptor. Antagonism of bradykinin B2 receptor also increased acid-induced deep duodenal villous damage. Thus, maintenance of bradykinin-mediated mesenteric hyperemia, is a previous unrecognized mechanism associated with protection of the rat duodenal mucosa against acid-induced damage.     

缓激肽B1受体与疼痛

摘要：缓激肽B1受体（bradykinin 1 receptors,B1Rs）是与Gq蛋白相偶联的受体。正常状态下,B1R除了在神经系统中（如脊髓背角浅层和感觉神经节）有少数表达外,其他机体组织中几乎不存在。在炎症或者神经受损的情况下,脊髓背角浅层和感觉神经节B1R表达量大大上升,参与炎性疼痛和神经病理性疼痛的产生和维持。近年来的研究表明,B1R在糖尿病性神经病理疼痛的发病中起着重要的作用。阻断B1R能有效抑制糖尿病诱发的热痛觉过敏和冷觉及触觉超敏。此外,B1R和癌症痛的发生也有密切关系,所以,对B1R的研究可能会为治疗这些临床顽症提供新的靶点。关键词：缓激肽B1受体;炎性痛;神经病理性痛中图分类号：Q189;Q42;R338文献标志码：A     

Bradykinin‐mediated Ca2+ signalling regulates cell growth and mobility in human cardiac c‐Kit+ progenitor cells

Our recent study showed that bradykinin increases cell cycling progression and migration of human cardiac c‐Kit⁺ progenitor cells by activating pAkt and pERK1/2 signals. This study investigated whether bradykinin‐mediated Ca²⁺ signalling participates in regulating cellular functions in cultured human cardiac c‐Kit⁺ progenitor cells using laser scanning confocal microscopy and biochemical approaches. It was found that bradykinin increased cytosolic free Ca²⁺ () by triggering a transient Ca²⁺ release from ER IP3Rs followed by sustained Ca²⁺ influx through store‐operated Ca²⁺ entry (SOCE) channel. Blockade of B2 receptor with HOE140 or IP3Rs with araguspongin B or silencing IP3R3 with siRNA abolished both Ca²⁺ release and Ca²⁺ influx. It is interesting to note that the bradykinin‐induced cell cycle progression and migration were not observed in cells with siRNA‐silenced IP3R3 or the SOCE component TRPC1, Orai1 or STIM1. Also the bradykinin‐induced increase in pAkt and pERK1/2 as well as cyclin D1 was reduced in these cells. These results demonstrate for the first time that bradykinin‐mediated increase in free via ER‐IP3R3 Ca²⁺ release followed by Ca²⁺ influx through SOCE channel plays a crucial role in regulating cell growth and migration via activating pAkt, pERK1/2 and cyclin D1 in human cardiac c‐Kit⁺ progenitor cells.     

The Bradykinin B2 receptor is required for full expression of renal COX-2 and renin

Angiotensin converting enzyme (ACE) inhibition leads to increased levels of bradykinin, cyclooxygenase-2 (COX-2), and renin. Since bradykinin stimulates prostaglandin release, renin synthesis may be regulated through a kinin-COX-2 pathway. To test this hypothesis, we examined the impact of bradykinin B2 receptor (B2R) gene disruption in mice on kidney COX-2 and renin gene expression. Kidney COX-2 mRNA and protein levels were significantly lower in B2R-/- mice by 40-50%. On the other hand, renal COX-1 levels were similar in B2R-/- and +/+ mice. Renal renin protein was 61% lower in B2R-/- compared to B2R+/+ mice. This was accompanied by a significant reduction in renin mRNA levels in B2R-/- mice. Likewise, intrarenal angiotensin I levels were significantly lower in B2R-/- mice compared to B2R+/+ mice. In contrast, kidney angiotensin II levels were not different and averaged 261+/-16 and 266+/-15fmol/g in B2R+/+ and B2R-/- mice, respectively. Kidney angiotensinogen, AT1 receptor and ACE activity were not different between B2R+/+ and B2R-/- mice. The results of these studies demonstrate suppression of renal renin synthesis in mice lacking the bradykinin B2R and support the notion that B2R regulation of COX-2 participates in the steady-state control of renin gene expression.     

Cannabidiol protects against hepatic ischemia/reperfusion injury by attenuating inflammatory signaling and response, oxidative/nitrative stress, and cell death

Ischemia/reperfusion (I/R) is a pivotal mechanism of liver damage after liver transplantation or hepatic surgery. We have investigated the effects of cannabidiol (CBD), the nonpsychotropic constituent of marijuana, in a mouse model of hepatic I/R injury. I/R triggered time-dependent increases/changes in markers of liver injury (serum transaminases), hepatic oxidative/nitrative stress (4-hydroxy-2-nonenal, nitrotyrosine content/staining, and gp91phox and inducible nitric oxide synthase mRNA), mitochondrial dysfunction (decreased complex I activity), inflammation (tumor necrosis factor α (TNF-α), cyclooxygenase 2, macrophage inflammatory protein-1α/2, intercellular adhesion molecule 1 mRNA levels; tissue neutrophil infiltration; nuclear factor κB (NF-κB) activation), stress signaling (p38MAPK and JNK), and cell death (DNA fragmentation, PARP activity, and TUNEL). CBD significantly reduced the extent of liver inflammation, oxidative/nitrative stress, and cell death and also attenuated the bacterial endotoxin-triggered NF-κB activation and TNF-α production in isolated Kupffer cells, likewise the adhesion molecule expression in primary human liver sinusoidal endothelial cells stimulated with TNF-α and attachment of human neutrophils to the activated endothelium. These protective effects were preserved in CB2 knockout mice and were not prevented by CB1/2 antagonists in vitro. Thus, CBD may represent a novel, protective strategy against I/R injury by attenuating key inflammatory pathways and oxidative/nitrative tissue injury, independent of classical CB1/2 receptors.     

Carboxypeptidase M and kinin B1 receptors interact to facilitate efficient b1 signaling from B2 agonists

Kinin B1 receptor (B1R) expression is induced by injury or inflammatory mediators, and its signaling produces both beneficial and deleterious effects. Kinins cleaved from kininogen are agonists of the B2R and must be processed by a carboxypeptidase to generate B1R agonists des-Arg(9)-bradykinin or des-Arg(10)-kallidin. Carboxypeptidase M (CPM) is a membrane protein potentially well suited for this function. Here we show that CPM expression is required to generate a B1R-dependent increase in [Ca(2+)](i) in cells stimulated with B2R agonists kallidin or bradykinin. CPM and the B1R interact on the cell membrane, as shown by co-immunoprecipitation, cross-linking, and fluorescence resonance energy transfer analysis. CPM and B1R are also co-localized in lipid raft/caveolin-enriched membrane fractions, as determined by gradient centrifugation. Treatment of cells co-expressing CPM and B1R with methyl-beta-cyclodextrin to disrupt lipid rafts reduced the B1R-dependent increase in [Ca(2+)](i) in response to B2R agonists, whereas cholesterol treatment enhanced the response. A monoclonal antibody to the C-terminal beta-sheet domain of CPM reduced the B1R response to B2R agonists without inhibiting CPM. Cells expressing a novel fusion protein containing CPM at the N terminus of the B1R also increased [Ca(2+)](i) when stimulated with B2R agonists, but the response was not reduced by methyl-beta-cyclodextrin or CPM antibody. A B1R- and CPM-dependent calcium signal in response to B2R agonist bradykinin was also found in endothelial cells that express both proteins. Thus, a close relationship of B1Rs and CPM on the membrane is required for efficiently generating B1R signals, which play important roles in inflammation.     

Immunolocalization and expression of kinin B1R and B2R receptors in human inflammatory bowel disease

Bradykinin is a mediator of inflammation, responsible for pain, vasodilation, and capillary permeability. Bradykinin receptor 1 (B(1)R) and bradykinin receptor 2 (B(2)R) are G protein-coupled receptors that mediate kinin effects. The latter is constitutive and rapidly desensitized; the former is induced by inflammatory cytokines and resistant to densensitization. The distribution of bradykinin receptors in human intestinal tissue was studied in patients with inflammatory bowel disease (IBD), namely ulcerative colitis (UC) and Crohn's disease (CD). Both B(2)R and B(1)R proteins are expressed in the epithelial cells of normal and IBD intestines. B(1)R protein is visualized in macrophages at the center of granulomas in CD. B(2)R protein is normally present in the apexes of enterocytes in the basal area and intracellularly in inflammatory tissue. In contrast, B(1)R protein is found in the basal area of enterocytes in normal intestine but in the apical portion of enterocytes in inflamed tissue. B(1)R protein is significantly increased in both active UC and CD intestines compared with controls. In patients with active UC, B(1)R mRNA is significantly higher than B(2)R mRNA. However, in inactive UC patients, the B(1)R and B(2)R mRNA did not differ significantly. Thus bradykinin receptors in IBD may reflect intestinal inflammation. Increased B(1)R gene and protein expression in active IBD provides a structural basis of the important role of bradykinin in chronic inflammation.     

The required role of endogenously produced lipoxin A4 and annexin-1 for the production of IL-10 and inflammatory hyporesponsiveness in mice

The appropriate development of an inflammatory response is central for the ability of a host to deal with any infectious insult. However, excessive, misplaced, or uncontrolled inflammation may lead to acute or chronic diseases. The microbiota plays an important role in the control of inflammatory responsiveness. In this study, we investigated the role of lipoxin A4 and annexin-1 for the IL-10-dependent inflammatory hyporesponsiveness observed in germfree mice. Administration of a 15-epi-lipoxin A4 analog or an annexin-1-derived peptide to conventional mice prevented tissue injury, TNF-alpha production, and lethality after intestinal ischemia/reperfusion. This was associated with enhanced IL-10 production. Lipoxin A4 and annexin-1 failed to prevent reperfusion injury in IL-10-deficient mice. In germfree mice, there was enhanced expression of both lipoxin A4 and annexin-1. Blockade of lipoxin A4 synthesis with a 5-lipoxygenase inhibitor or Abs against annexin-1 partially prevented IL-10 production and this was accompanied by partial reversion of inflammatory hyporesponsiveness in germfree mice. Administration of BOC-1, an antagonist of ALX receptors (at which both lipoxin A4 and annexin-1 act), or simultaneous administration of 5-lipoxygenase inhibitor and anti-annexin-1 Abs, was associated with tissue injury, TNF-alpha production, and lethality similar to that found in conventional mice. Thus, our data demonstrate that inflammatory responsiveness is tightly controlled by the presence of the microbiota and that the innate capacity of germfree mice to produce IL-10 is secondary to their endogenous greater ability to produce lipoxin A4 and annexin-1.     

IL-1-driven endogenous IL-10 production protects against the systemic and local acute inflammatory response following intestinal reperfusion injury

TNF-alpha release and action are central in the pathogenesis of the local and systemic inflammatory responses that occur after intestinal reperfusion. In this study we examined whether IL-1 participated in the cascade of events leading to TNF-alpha production and TNF-alpha-mediated injury following reperfusion of the ischemic superior mesenteric artery in rats. Blockade of the action of IL-1 by the use of anti-IL-1 antiserum or administration of IL-1R antagonist (IL-1ra), a natural antagonist of IL-1Rs, resulted in marked enhancement of reperfusion-associated tissue injury, TNF-alpha expression, and lethality. In contrast, there was marked decrease in IL-10 production. Facilitation of IL-1 action by administration of anti-IL-1ra, which antagonizes endogenous IL-1ra, or exogenous administration of rIL-1beta suppressed reperfusion-induced tissue pathology, TNF-alpha production, and lethality, but increased IL-10 production. Exogenous administration of IL-10 was effective in preventing the increase in tissue or plasma levels of TNF-alpha, the exacerbated tissue injury, and lethality. An opposite effect was observed after treatment with anti-IL-10, demonstrating a role for endogenous production of IL-10 in modulating exacerbated reperfusion-associated tissue pathology and lethality. Finally, pretreatment with anti-IL-10 reversed the protective effect of IL-1beta on reperfusion-associated lethality. Thus, IL-1 plays a major role in driving endogenous IL-10 production and protects against the TNF-alpha-dependent systemic and local acute inflammatory response following intestinal reperfusion injury.     

Cardiovascular expression of inflammatory signaling molecules, the kinin B1 receptor and COX2, in the rabbit: effects of LPS, anti-inflammatory and anti-hypertensive drugs

We first aimed to test the effect of anti-inflammatory drugs, etanercept and dexamethasone sodium phosphate (DSP), on the expression of inducible inflammatory signaling molecules (the bradykinin [BK] B(1) receptor [B(1)R], cyclooxygenase [COX]-2) in lipopolysaccharide (LPS)-treated rabbits. Preliminary experiments mostly based on a novel cellular model, rabbit dermis fibroblasts, showed that etanercept inhibited TNF-alpha-induced B(1)R expression ([(3)H]Lys-des-Arg(9)-BK binding), but that DSP also inhibited cytokine-induced B(1)R upregulation with less selectivity. LPS (100 microg/kg i.v.) induced the expression of the B(1)R (aortic contractility ex vivo, mRNA in hearts) and COX2 (immunoblots, heart extracts). However, the function of the BK B(2) receptor was unchanged (jugular vein contractility ex vivo). DSP pre-treatment profoundly reduced the induction of the B(1)R and COX2 whereas etanercept significantly inhibited only COX2 expression. The second aim was to verify whether chronic angiotensin converting enzyme (ACE) blockade in rabbits would induce B(1)R expression, as reported in other species. 14-Day enalapril oral dosing, but not treatment with the angiotensin receptor antagonist losartan, significantly increased aortic contractions mediated by B(1)Rs, however much less than LPS. Enalapril treatment did not increase COX2 expression but increased the ex vivo relaxation of the mesenteric artery mediated by endogenous prostaglandins. Chronic ACE inhibition recruits inflammatory signaling systems.     

Neurokinin-1 receptor agonists are involved in mediating neutrophil accumulation in the inflamed, but not normal, cutaneous microvasculature: an in vivo study using neurokinin-1 receptor knockout mice

We have used tachykinin neurokinin-1 receptor (NK1 receptor) knockout mice to learn of the link between NK1 receptors and neutrophil accumulation in normal naive skin, as compared with inflamed skin. Intradermal substance P (300 pmol) induced edema formation in wild-type mice, but not in NK1 knockout mice, as expected. However, in contrast to IL-1beta (0.3 pmol), substance P did not induce neutrophil accumulation in wild-type mice. IL-1beta-induced neutrophil accumulation was similar in wild-type and knockout mice, but a significant (p < 0.05) contributory effect of added NK1 agonists, which by themselves have no effect on neutrophil accumulation in normal skin, was observed. The results support the concept that NK1 agonists such as substance P cannot act on their own to mediate neutrophil accumulation in naive skin and provide direct evidence that in inflamed skin, under certain circumstances, the NK1 receptor can play a pivotal role in modulating neutrophil accumulation during the ongoing inflammatory process. We investigated responses to two inflammatory stimuli (carrageenin and zymosan). Neutrophil accumulation was significantly attenuated (p < 0.001) in carrageenin- but not zymosan-induced inflammation in NK1 knockout mice. The carrageenin (500 microg)-induced response was inhibited (p < 0.05) by a NK1 receptor antagonist, SR140333 (480 nmol/kg i.v. at -5 min), in the wild-type group. The bradykinin B1 and B2 receptor antagonists (desArg9[Leu8]bradykinin and HOE 140) each reduced neutrophil accumulation to carrageenin in wild-type animals (p < 0.05), but did not cause further reduction of the suppressed response of knockout mice. The results provide evidence that kinin receptors participate in NK1 receptor-dependent neutrophil accumulation in inflamed mouse skin.