Up-regulation of bradykinin receptors in a murine in-vitro model of chronic airway inflammation

The Role of Bradykinin Receptors in Hereditary Angioedema Due to C1-Inhibitor Deficiency

Background: Hereditary angioedema (HAE) is a rare, genetic disease caused by the decreased level or function of the C1 inhibitor. The primary mediator of symptoms in HAE is bradykinin acting through its two receptors, namely receptors 1 (BR1) and 2 (BR2). Although BR2 is well characterized, the role of BR1 remains unclear. Objective: To study the role of bradykinin receptors 1 (BR1) in the etiopathogenesis of HAE. Methods: A total of 70 individuals, 40 patients with HAE, and 30 healthy subjects were recruited to the study. HAE was diagnosed in accordance with the international guideline. The level of bradykinin receptors was determined in populations of CD3⁺, CD4⁺, CD8⁺, and CD14⁺⁺CD16⁻, CD14⁺⁺CD16⁺ monocytes. In addition, the level of disease activity-specific markers was measured. Results: There were statistically significant differences in the subpopulation of lymphocytes and monocytes between patients with HAE compared to healthy subjects. The level of BR1 and BR2 on PBMCs was comparable in healthy subjects and HAE patients during remission with significant overexpression of both receptors, triggered by HAE attack. Moreover, a significant increase in TNF-alpha and IL-1 plasma levels was observed among HAE patients. Conclusions: BR1 expression may play an important role in the pathomechanism of HAE.

Veno-Arterial Extracorporeal Membrane Oxygenation (ECMO) Impairs Bradykinin-Induced Relaxation in Neonatal Porcine Coronary Arteries

Extracorporeal membrane oxygenation (ECMO) is a lifesaving support for respiratory and cardiovascular failure. However, ECMO induces a systemic inflammatory response syndrome that can lead to various complications, including endothelial dysfunction in the cerebral circulation. We aimed to investigate whether ECMO-associated endothelial dysfunction also affected coronary circulation. Ten-day-old piglets were randomized to undergo either 8 h of veno-arterial ECMO (n = 5) or no treatment (Control, n = 5). Hearts were harvested and coronary arteries were dissected and mounted as 3 mm rings in organ baths for isometric force measurement. Following precontraction with the thromboxane prostanoid (TP) receptor agonist U46619, concentration−response curves to the endothelium-dependent vasodilator bradykinin (BK) and the nitric oxide (NO) donor (endothelium-independent vasodilator) sodium nitroprusside (SNP) were performed. Relaxation to BK was studied in the absence or presence of the NO synthase inhibitor Nω-nitro-L-arginine methyl ester HCl (L-NAME). U46619-induced contraction and SNP-induced relaxation were similar in control and ECMO coronary arteries. However, BK-induced relaxation was significantly impaired in the ECMO group (30.4 ± 2.2% vs. 59.2 ± 2.1%; p < 0.0001). When L-NAME was present, no differences in BK-mediated relaxation were observed between the control and ECMO groups. Taken together, our data suggest that ECMO exposure impairs endothelium-derived NO-mediated coronary relaxation. However, there is a NO-independent component in BK-induced relaxation that remains unaffected by ECMO. In addition, the smooth muscle cell response to exogenous NO is not altered by ECMO exposure.

Hydrogen sulfide donors prevent lipopolysaccharide-induced airway hyperreactivity in an in vitro model of chronic inflammation in mice

We aimed to investigate and compare the effects of rapid (NaHS) and slow (GYY4137 and AP39) hydrogen sulfide (H₂ S) releasing donors on LPS-induced tracheal hyperreactivity and pro-inflammatory cytokine levels in lung tissues of mice. Tissues were isolated from male BALB/c mice and incubated with LPS (10 µg/mL) in tissue culture. The subgroups were incubated with NaHS, GYY4137 and mitochondria-targeted donor AP39. LPS incubation did not alter contraction response to carbachol, but enhanced 5-HT and bradykinin-induced contractions in tracheal rings, and elevated IL-1β, IL-6 and TNF-α levels in lung homogenates. NaHS at 300 µmol/L and 1000 µmol/L, GYY4137 at 30 µmol/L and 100 µmol/L, and AP39 at 30 nmol/L concentrations inhibited the tracheal hyperreactivity to 5-HT, whereas none of these donors affected the enhanced contraction to bradykinin. GYY4137 was also effective to inhibit 5-HT hyperreactivity acutely. In lung tissues, NaHS prevented the elevation of IL-1β level at 1000 μmol/L, and IL-6 and TNF-α levels at 100 μmol/L concentrations. Incubation with GYY4137 (100 µmol/L) and AP39 (30 nmol/L and 300 nmol/L) inhibited the increase in IL-6 and TNF-α levels, but not IL-1β at concentrations that they affected tracheal hyperreactivity. These results indicate that H₂ S donors can decrease inflammation and prevent airway hyperreactivity.

PM2.5 upregulates rat mesenteric arteries 5-HT2A receptor via inflammatory-mediated mitogen-activated protein kinases signaling pathway

Fine particulate matter (PM_2.5 ) is an important environmental risk factor for cardiovascular diseases. However, little is known about the effects of PM_2.5 on arteries. The present study investigated whether PM_2.5 alters 5-hydroxytryptamine (5-HT) receptor expression and inflammatory mediators on rat mesenteric arteries, and examined the underlying mechanisms. Isolated rat mesenteric arteries segments were cultured with PM_2.5 in the presence or absence of ERK1/2, JNK, and p38 pathway inhibitors. Contractile reactivity was monitored by a sensitive myograph. The expression of 5-HT_2A/1B receptors and inflammatory mediators were studied by a real-time polymerase chain reaction and/or by immunohistochemistry. The phosphorylation of mitogen-activated protein kinases (MAPK) pathway was detected by Western blot. Compared with the fresh or culture alone groups, 1.0 μg/mL PM_2.5 cultured for 16 hours significantly enhanced contractile response induced by 5-HT and increased 5-HT_2A receptor mRNA and protein expressions, indicating PM_2.5 upregulates 5-HT_2A receptor. SB203580 (p38 inhibitor) and U0126 (ERK1/2 inhibitor) significantly decreased PM_2.5 -induced elevated contraction and mRNA and protein expression of 5-HT_2A receptor. Cultured with PM_2.5 significantly increased the mRNA expression of inflammatory mediators (NOS2, IL-1β, and TNF-α), while SB203580 decreased mRNA expression level of NOS2, IL-1β, and TNF-α. SP600125 (JNK inhibitor) decreased mRNA expression level of TNF-α and IL-1β. After PM_2.5 exposure, the phosphorylation of p38 and ERK1/2 protein were increased. SB203580 and U0126 inhibited the PM_2.5 caused increased phosphorylation protein of p38 and ERK1/2. In conclusion, PM_2.5 induces inflammatory-mediated MAPK pathway in artery which subsequently results in enhanced vascular contraction responding to 5-HT via the upregulated 5-HT_2A receptors.

Regulation of Airway Smooth Muscle Contraction in Health and Disease

Airway smooth muscle (ASM) extends from the trachea throughout the bronchial tree to the terminal bronchioles. In utero, spontaneous phasic contraction of fetal ASM is critical for normal lung development by regulating intraluminal fluid movement, ASM differentiation, and release of key growth factors. In contrast, phasic contraction appears to be absent in the adult lung, and regulation of tonic contraction and airflow is under neuronal and humoral control. Accumulating evidence suggests that changes in ASM responsiveness contribute to the pathophysiology of lung diseases with lifelong health impacts.Functional assessments of fetal and adult ASM and airways have defined pharmacological responses and signaling pathways that drive airway contraction and relaxation. Studies using precision-cut lung slices, in which contraction of intrapulmonary airways and ASM calcium signaling can be assessed simultaneously in situ, have been particularly informative. These combined approaches have defined the relative importance of calcium entry into ASM and calcium release from intracellular stores as drivers of spontaneous phasic contraction in utero and excitation-contraction coupling.Increased contractility of ASM in asthma contributes to airway hyperresponsiveness. Studies using animal models and human ASM and airways have characterized inflammatory and other mechanisms underlying increased reactivity to contractile agonists and reduced bronchodilator efficacy of β₂-adrenoceptor agonists in severe diseases. Novel bronchodilators and the application of bronchial thermoplasty to ablate increased ASM within asthmatic airways have the potential to overcome limitations of current therapies. These approaches may directly limit excessive airway contraction to improve outcomes for difficult-to-control asthma and other chronic lung diseases.

Cigarette Smoke Particles-Induced Airway Hyperreactivity in Vivo and in Vitro

Cigarette smoke is a well-known strong risk factor for inducing airway hyperreactivity (AHR), but the underlying molecular mechanisms are not fully understood. In the present study, mouse in-vivo and in-vitro models were used to study effects of dimethyl sulfoxide (DMSO)-extracted cigarette smoke particles (DSP) on the airway, and to explore the underlying molecular mechanisms that are involved in DSP-induced AHR. In mouse in-vivo model, DSP (0.75, 1.5 or 3 µL/mL) was administered intranasally daily for 7 d. At the end of this period, lung functions were measured with flexiVent™. The results showed that the mice exhibited AHR in a dose-dependent manner following methacholine inhalation in vivo. In mouse in-vitro organ culture model, exposure of mouse tracheal segments to DSP (0.1 µL/mL) with or without the following pharmacological inhibitors: specific c-Jun-N-terminal kinase (JNK) inhibitor SP600125 (10 µM) or the anti-inflammatory drug dexamethasone (1 µM). DSP-induced bradykinin receptor-mediated airway contraction with increased mRNA and protein expressions for bradykinin B1 and B2 receptors could be significantly reduced by SP600125 or dexamethasone. In conclusion, the present study demonstrates that DSP could induce AHR in vivo and in vitro. In addition to this, the upregulation of bradykinin receptors in airway is most likely one of the underlying molecular mechanisms involved.

Dividing neutrophils in subsets reveals a significant role for activated neutrophils in the development of airway hyperreactivity

BACKGROUND

Previous research has emphasized the importance of eosinophils in allergic asthma, while paying less attention to neutrophils. The known functionality of neutrophils in the inflammatory process has recently changed and knowledge about subsets of neutrophils, as characterized by their expression of CD16 and CD62L, has surfaced. Their specific roles in asthma are still unknown.

OBJECTIVE

To study the functional differences between subsets of neutrophils by characterizing the impact of individual subsets on airway smooth muscle reactivity.

METHODS

The direct effect of neutrophils on airway hyperresponsiveness was assessed by co-culturing different subsets of neutrophils (produced by LPS in vitro stimulation) with human isolated small airways or murine tracheae with subsequent evaluation of smooth muscle reactivity to bradykinin in myographs. Supernatants and tissue were saved for ELISA and immunohistochemistry.

RESULTS

The CD16^high CD62L^dim neutrophils were found to enhance the response to bradykinin in both human isolated small airways and murine tracheae. No such effects were obtained for the other subsets. The response is due to an upregulation of bradykinin receptor 2 through release of TNFα from the neutrophil.

CONCLUSIONS AND CLINICAL RELEVANCE

The present study introduces a new concept regarding the role of neutrophils and defines a novel direct link between a specific activated neutrophil subset and airway smooth muscle, establishing neutrophils as important players in the development of asthmatic airway hyperactivity.

Bradykinin in asthma: Modulation of airway inflammation and remodelling

Bradykinin, a pro-inflammatory molecule, and its related peptides have been studied for their effects on acute reactions in upper and lower airways, where they can be synthesised and metabolized after exposure to different stimuli including allergens and viral infection. Bradykinin B₁ and B₂ receptors are constitutively expressed in the airways on several residential and/or immune cells. Their expression can also be induced by inflammatory mediators, usually associated with eosinophil and neutrophil recruitment, such as IL-4, IL-13, TNF-α, IL-6 and IL-8, via intracellular MAPK and NF-κB signalling. In turn, the latters up-regulate both bradykinin receptors. Bradykinin activates epithelial/endothelial and immune cells, neurons and mesenchymal cells (such as fibroblasts, myofibroblasts and smooth muscle cells), which are implicated in the development of airway chronic inflammation, responsiveness and remodelling (a major feature of severe asthma). This review highlights the role of bradykinin and its receptors in respect to chronic inflammatory response involving eosinophils/neutrophils and to vascular/matrix-related airway remodelling in asthmatic airways. This scenario is especially important for understanding the mechanisms involved in the pathogenesis of eosinophilic and/or neutrophilic asthma and hence their therapeutic approach.

Bradykinin B2 receptor expression in the bronchial mucosa of allergic asthmatics: the role of NF-kB

BACKGROUND

Bradykinin (BK) mediates acute allergic asthma and airway remodelling. Nuclear factor-kappa B (NF-kB) is potentially involved in BK B2 receptor (B2R) regulation.

OBJECTIVE

In this observational cross-sectional study, B2R and NF-kB expression was evaluated in bronchial biopsies from mild asthmatics (after diluent/allergen challenge) and healthy controls, examining the role of NF-kB in B2R expression in primary human fibroblasts from normal and asthmatic subjects (HNBFb and HABFb).

METHODS

B2R and NF-kB (total and nuclear) expression was analysed by immunohistochemistry in biopsies from 10 mild intermittent asthmatics (48 h after diluent/allergen challenge) and 10 controls undergoing bronchoscopy. B2R co-localization in 5B5(+) and αSMA(+) mesenchymal cells was studied by immunofluorescence/confocal microscopy, and B2R expression in HABFb/HNBFb incubated with interleukin (IL)-4/IL-13 with/without BK, and after NF-kB inhibitor, by Western blotting.

RESULTS

Bronchial mucosa B2R and nuclear NF-kB expression was higher in asthmatics after diluent (B2R only) and allergen challenge than in controls (P < 0.05), while B2R and NF-kB (total and nuclear) increased after allergen compared with after diluent (P < 0.05). Allergen exposure increased B2R expression in 5B5(+) and αSMA(+) cells. Constitutive B2R protein expression was higher in HABFb than in HNBFb (P < 0.05) and increased in both cell types after IL-13 or IL-4/IL-13 and BK treatment. This increase was suppressed by a NF-kB inhibitor (P < 0.05).

CONCLUSIONS & CLINICAL RELEVANCE

Bronchial B2R expression is constitutively elevated in allergic asthma and is further increased after allergen exposure together with NF-kB expression. NF-kB inhibitor blocked IL-4/IL-13-induced increase in B2R expression in cultured fibroblasts, suggesting a role as potential anti-asthma drug.

Specific immunotherapy with mugwort pollen allergoid reduce bradykinin release into the nasal fluid

Introduction

A pathomechanism of allergic rhinitis is complex. A neurogenic mechanism seems to play a significant role in this phenomenon.

Aim

The evaluation of influence of specific immunotherapy of mugwort pollen allergic patients on the bradykinin concentration in the nasal lavage fluid.

Material and methods

The study included 22 seasonal allergic rhinitis patients. Thirty persons with monovalent allergy to mugwort pollen, confirmed with skin prick tests and allergen-specific immunoglobulin E, underwent a 3-year-long allergen immunotherapy with the mugwort extract (Allergovit, Allergopharma, Germany). The control group was composed of 9 persons with polyvalent sensitivity to pollen, who were treated with pharmacotherapy. Before the allergen-specific immunotherapy (AIT) and in subsequent years before the pollen seasons, a provocation allergen test with the mugwort extract was performed, together with collection of nasal fluids, where bradykinin concentration was determined according to Proud method.

Results

There were similar levels of bradykinin in both groups at baseline prior to therapy (AIT group: 584.0 ±87.2 vs. controls 606.3 ±106.5 pg/ml) and changes after allergen challenge 1112.4 ±334.8 vs. 1013.3 ±305.9 pg/ml as well. The bradykinin concentration in nasal lavage fluid after mugwort challenge in 1 year was lower in the AIT group (824.1 ±184.2 pg/ml vs. 1000.4 ±411.5 pg/l; p < 005) with a further significant decrease after the 2^nd and 3^rd year of specific immunotherapy. Significant reduction of symptoms and medications use was observed in hyposensitized patients.

Conclusions

A decreased level of bradykinin as a result of AIT suggests that some of the symptomatic benefits of AIT may be related to the reduced release of bradykinin into nasal secretions. These values correlate with clinical improvement within the course of treatment.

Role of ERK1/2 activation on itch sensation induced by bradykinin B1 activation in inflamed skin

It has previously been demonstrated that bradykinin receptor B1 (B1R) agonists evoke an itch-related scratching response in inflamed skin via the B1 receptor; however, the mechanisms responsible for this abnormal itch sensation remain unclear. Therefore, the present study utilized a complete Freund's adjuvant (CFA)-induced mouse model of inflammation to elucidate the mechanisms responsible. Over a period of 30 min, scratching behavior was quantified by the number of hind limb scratches of the area surrounding the drug injection site on the neck. Furthermore, western blot analysis was used to investigate the potential role of extracellular signal-regulated kinase (ERK) 1/2 signaling as a mediator of itch in CFA-treated mice. The results demonstrated that CFA-induced inflammation at the back of the neck is associated with sustained enhancement of ERK1/2 activation in the spinal cord. Moreover, B1R agonist treatment resulted in increased expression of phosphorylated ERK1/2 in the spinal cord, which peaked at 45 min. Consistent with these findings, inhibition of either mitogen-activated protein/ERK kinase or ERK1/2, as well as inhibition of ERK1/2 activation following inflammation, attenuated B1 receptor-mediated scratching responses to a greater extent, as compared with control mice. Collectively, the results of the present study indicated that enhanced and persistent ERK1/2 activation in the spinal cord may be required to induce a scratching response to B1R agonists following CFA-induced inflammation.

Involvement of Extracellular Signal-Regulated Kinase 5 in Kinin B1 Receptor Upregulation in Isolated Human Umbilical Veins

The upregulated kinin B1 receptors exert a pivotal role in modulating inflammatory processes. In isolated human umbilical veins (HUVs), kinin B1 receptor is upregulated as a function of in vitro incubation time and proinflammatory stimuli. The aim of this study was to evaluate, using functional and biochemical methods, the involvement of extracellular signal-regulated kinase 5 (ERK5), p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase 1/2 (ERK1/2) on the kinin B1 receptor upregulation process in HUV. Real-time polymerase chain reaction analysis revealed for the first time that kinin B1 receptor mRNA expression closely parallels the functional sensitization to kinin B1 receptor selective agonist des-Arg(10)-kallidin (DAKD) in HUV. Moreover, the selective inhibition of ERK5, p38 MAPK, and JNK, but not ERK1/2, produced a dose-dependent rightward shift of the concentration-response curves to DAKD after 5-hour incubation and a reduction in kinin B1 receptor mRNA expression. Biochemical analyses showed that ERK5, p38 MAPK, and JNK phosphorylation is maximal during the first 2 hours postisolation, followed by a significant reduction in the last 3 hours. None of the treatments modified the responses to serotonin, an unrelated agonist, suggesting a specific effect on kinin B1 receptor upregulation. The present work provides for the first time pharmacologic evidence indicating that ERK5 plays a significant role on kinin B1 receptor upregulation. Furthermore, we confirm the relevance of p38 MAPK and JNK as well as the lack of effect of ERK1/2 in this process. This study may contribute to a better understanding of MAPK involvement in inflammatory and immunologic diseases.

MAPK/NF-κB-dependent upregulation of kinin receptors mediates airway hyperreactivity: a new perspective for the treatment

Airway hyperreactivity (AHR) is a major feature of asthmatic and inflammatory airways. Cigarette smoke exposure, and bacterial and viral infections are well-known environmental risk factors for AHR, but knowledge about the underlying molecular mechanisms on how these risk factors lead to the development of AHR is limited. Activation of intracellular mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) and their related signal pathways including protein kinase C (PKC), phosphoinositide 3-kinase (PI3K) and protein kinase A (PKA) signaling pathways may result in airway kinin receptor upregulation, which is suggested to play an important role in the development of AHR. Environmental risk factors trigger the production of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interleukins (ILs) that activate intracellular MAPK- and NF-κB-dependent inflammatory pathways, which subsequently lead to AHR via kinin receptor upregulation. Blockage of intracellular MAPK/NF-κB signaling prevents kinin B₁ and B₂ receptor expression in the airways, resulting in a decrease in the response to bradykinin (kinin B₂ receptor agonist) and des-Arg⁹-bradykinin (kinin B₁ receptor agonist). This suggests that MAPK- and NF-κB-dependent kinin receptor upregulation can provide a novel option for treatment of AHR in asthmatic as well as in other inflammatory airway diseases.

Bradykinin-induced asthmatic fibroblast/myofibroblast activities via bradykinin B2 receptor and different MAPK pathways

Bradykinin drives normal lung fibroblasts into myofibroblasts, induces fibroblast proliferation and activates mitogen activated protein kinase pathways (MAPK) but its effects on bronchial fibroblasts from asthmatics (HBAFb) have not been yet studied. We studied bradykinin-induced fibroblast proliferation and differentiation and the related intracellular mechanisms in HBAFb compared to normal bronchial fibroblasts (HNBFb). Bradykinin-stimulated HBAFb and HNBFb were used to assess: bradykinin B2 receptor expression by Western blot analysis; cell proliferation by [(3)H] thymidine incorporation; α-smooth muscle actin (SMA) expression/polymerization by Western blot and immunofluorescence; epidermal growth factor (EGF) receptor, extracellular-regulated kinase (ERK) 1/2 and p38 MAPK activation by immunoprecipitation and Western blot, respectively. Constitutive bradykinin B2 receptor and α-SMA expression was higher in HBAFb as compared to HNBFb. Bradykinin increased bradykinin B2 receptor expression in HBAFb. Bradykinin, via bradykinin B2 receptor, significantly increased fibroblast proliferation at lower concentration (10(-11)M) and α-SMA expression/polymerization at higher concentration (10(-6)M) in both cells. Bradykinin increased ERK1/2 and p38 phosphorylation via bradykinin B2 receptor; EGF receptor inhibitor AG1478 and panmetalloproteinase inhibitor GM6001 blocked bradykinin-induced ERK1/2 activation but not p38 phosphorylation. Bradykinin, via bradykinin B2 receptor, induced EGF receptor phosphorylation that was suppressed by AG1478. In HBAFb AG1478, GM6001, the ERK1/2-inhibitor U0126 and the p38 inhibitor SB203580 suppressed bradykinin-induced cell proliferation, but only SB203580 reduced myofibroblast differentiation. These data indicate that bradykinin is actively involved in asthmatic bronchial fibroblast proliferation and differentiation, through MAPK pathways and EGF receptor transactivation, by which bradykinin may contribute to airway remodeling in asthma, opening new horizons for potential therapeutic implications in asthmatic patients.

Infliximab alleviates inflammation and ex vivo airway hyperreactivity in asthmatic E3 rats

Tumor necrosis factor-α (TNF-α) has been implicated in the pathogenesis of asthma, and neutralization of TNF-α is an effective therapy for inflammatory diseases. The present study tested the idea that a TNF-α antibody, infliximab, may be useful in the management of asthma. E3 rats were immunized with ovalbumin (OVA)/alum and received infliximab intra-peritoneally. Two weeks later, OVA-PBS was instilled intranasally daily for 7 days. Bronchoalveolar lavage fluids (BALFs), serum and lung homogenates were collected for analysis of cells and inflammatory mediators. Contractile responses of lobar-bronchus segments to agonists were functionally tested. Pulmonary tissues were investigated using histological examination. The results showed that the sensitized 'model E3 rats' exhibited an increase in the total amount of inflammatory cells, primarily eosinophils, in BALF and pulmonary tissue, as well as epithelial damage. Serum levels of IgE increased and so did the levels of nitric oxide, inducible nitric oxide synthase, TNF-α and IL-4, IL-5 and IL-13 in lung homogenate and serum. Furthermore, the contractile responses in bronchi induced by endothelin-1, sarafotoxin 6c and bradykinin increased and isoprenaline-induced relaxations decreased. All these changes induced by the sensitization procedure were reduced by the infliximab treatment. The results suggest that infliximab prevents the development of local airway inflammation and antagonizes changes of the bronchial smooth muscle receptor phenotype, thereby blocking the development of airway smooth muscle hyperreactivity of asthmatic rats.

Inflammation-induced airway smooth muscle responsiveness is strain dependent in mice

Different mouse strains display different degrees of inflammation-induced airway hyperresponsiveness in vivo. It is not known whether these variations are attributable to distinct properties of the airway smooth muscle. Therefore, tracheal ring segments from C57BL/6 and BALB/c mice were exposed to three different pro-inflammatory stimuli for 4 days while maintained under tissue-culture conditions: tumour necrosis factor α (100 ng/ml), the Toll-like receptor (TLR) 3 agonist polyI:C (10 μg/ml), and the TLR4 agonist LPS (10 μg/ml). The contractile responses to carbachol, 5-hydroxytryptamine (5-HT) and bradykinin were assessed after culture. In addition, gene expression of TLR1-TLR9, pivotal inflammatory signal transduction proteins (jun-kinase, p38 and p65) and critical negative regulators of inflammation (A20, Itch, Tax1bp1 and RNF11) were studied in tracheal smooth muscle strips, fresh and following treatment for 4 days with LPS, from both strains. No differences between the strains were detected regarding the response of freshly isolated preparations to carbachol, 5-HT and bradykinin. After stimulation with pro-inflammatory mediators, contractions in response to 5-HT and bradykinin, but not to carbachol, were up-regulated. This up-regulation was markedly larger in BALB/c than in C57BL/6 segments and depended on the type of inflammatory stimulus. Expression of the genes investigated did not differ between the two strains. These findings indicate that strain differences in airway hyperresponsiveness can be linked to differences in the responsiveness of airway smooth muscle to pro-inflammatory mediators per se. The differences do not appear to be due to differential expression of TLR or common inflammatory transduction and repressor proteins.

Mechanism of cigarette smoke-induced kinin B(1) receptor expression in rat airways

Pulmonary inflammation is an important pathological feature of tobacco smoke related lung diseases such as chronic obstructive pulmonary disease (COPD). Kinin type 1 and type 2 receptors (B(1)R, B(2)R) are known to be associated with inflammatory responses of the lungs and other organs. In this study, we investigated whether cigarette smoke-induced airway inflammation could up-regulate B(1)R and B(2)R in correlation with IL-1β and TNF-α. Rat lung slices treated with 5 μg/ml total particulate matter (TPM) of cigarette smoke for 24 h showed an enhanced expression of B(1)R and IL-1β by 5-fold and 30-fold, respectively, in comparison to vehicle treatment (dimethyl sulfoxide). However, higher concentrations of TPM failed to induce B(1)R. No significant increase of B(2)R or TNF-α gene induction was observed. IL-1 receptor antagonist (IL-1Ra, 2 ng/ml) significantly blocked B(1)R gene induction by TPM, while 500 μM pentoxifylline, TNF-α inhibitor, reduced it partially. Western blot analysis showed a 2-fold enhanced expression of B(1)R in rat lung slices treated with 5 μg/ml TPM for 24 h and such protein expression was totally blocked by a co-treatment with IL-1Ra but not with pentoxifylline. In addition to the lower airways, rat trachea subchronically exposed to cigarette whole smoke exhibited 11-fold B(1)R gene induction in comparison with those exposed only to air. Our results demonstrate the involvement of B(1)R in cigarette smoke-induced airway inflammation through a mechanism which is mediated by the pro-inflammatory cytokine IL-1β.

Molecular effects of interleukin-1β on dorsal root ganglion neurons: prevention of ligand-induced internalization of the bradykinin 2 receptor and downregulation of G protein-coupled receptor kinase 2

In dorsal root ganglion sections numerous small-to medium-sized neurons were found to exhibit extensive colocalization of the bradykinin receptor 2, the interleukin-1 receptor 1 and G protein-coupled receptor kinase 2. Application of bradykinin to cultured DRG neurons caused substantial internalization of the bradykinin 2 receptor which significantly reduced the responsiveness of DRG neurons to a second application of bradykinin. Such an internalization was not observed in DRG neurons which were exposed to long-term pretreatment with interleukin-1β. The long-term incubation with interleukin-1β on its own did neither change the proportion of neurons which expressed the bradykinin 2 receptor in the cytoplasma nor the proportion of neurons expressing the bradykinin 2 receptor in the membrane but it reduced the proportion of neurons expressing G protein-coupled receptor kinase 2, an enzyme which facilitates the internalization of G protein-coupled receptors. These results show that interleukin-1β maintains the responsiveness of DRG neurons to bradykinin in the long-term range, and they suggest that the downregulation of G protein-coupled receptor kinase 2 could be a cellular mechanism involved in this interleukin-1β effect.

Airway smooth muscle modulation and airway hyper-responsiveness in asthma: new cellular and molecular paradigms

There is growing evidence indicating the existence of a causal relationship between abnormal airway smooth muscle (ASM) function and airway hyper-responsiveness, a poorly understood feature of asthma that can be defined as an excessive bronchospastic response. In recent years, there has been a veritable explosion of articles suggesting that ASM exposed to proasthmatic cytokines can elicit a hyper-responsive state to contractile G-protein-coupled receptor (GPCR) agonists. Aberrant airway responsiveness could result from abnormal calcium signaling, with changes occurring at various levels of GPCR-associated signal transduction. This review presents the latest observations describing novel mechanistic models that could explain the involvement of ASM in airway hyper-responsiveness. This review will discuss the role of ASM in beta(2)-agonist-mediated bronchial hyper-responsiveness and the clinical significance of cell-cell contact between ASM and mast cells recently described to be intimately infiltrated within the ASM tissues in asthmatic patients. The possibility that allergens could trigger airway hyper-responsiveness by directly acting on ASM via activation of immunoglobulin E receptors, FcepsilonRI and FCepsilonRII will also be discussed. These important findings further support the notion that targeting ASM could offer new treatment for many features of asthma, including airway hyper-responsiveness. Future therapeutic intervention includes: the prevention of ASM-inflammatory cell physical and/or functional interaction, the inhibition of Immunoglobulin E receptor-dependent signal transduction, and the abrogation of cytokine-dependent pathways that modulate receptor-associated calcium metabolism.

Transcriptional activity of genes-encoding kinin B1 and B2 receptors and kinin-dependent genes in nasal polyps

PURPOSE

The pro-inflammatory effects of kinins are mediated by two bradykinin receptors: BR1 and BR2. The aim of this study was to evaluate the expression profile of kinin receptor genes by an estimation of mRNA levels in human nasal polyps (NP) and normal mucosa (NM).

MATERIAL AND METHODS

BR1 and BR2-dependent genes differentially transcribed in NP were investigated using oligonucleotide microarray technology. The mRNA copy number of BR1, BR2 and TIMP1 genes was assessed by QRT-PCR. Thirty six eosinophilic (ENP), 17 neutrophilic nasal polyps (NNP) and 28 NM samples were included into the study.

RESULTS

Among 92 genes encoding proteins involved in signal transduction via B1 and B2 kinin receptors TIMP1 was found to be 2,63-fold higher in the NP than in NM. Increased TIMP1 gene expression was proved by QRT-PCR (p=0,003). Moreover two genes: FOS and PTGS1 presented higher (3,82- and 4,27-fold, respectively) expression in NM compared to NP tissues. In QRT-PCR analysis insignificantly higher expression of gene encoding BR1 in ENP [2564 mRNA copies/microg RNA (22-32863)] compared with NM [1426 copies mRNA (15-27995)] was found. mRNA expression for the BR2 in ENP [9872 copies mRNA (19-244832)] was insignificantly higher than in NM [5753 copies (46-199658)]. BR2 mRNA was the predominant transcript in most NP and NM samples followed by BR1 mRNA (p<0,01). There was a positive correlation between the expression of BR1 and BR2 in the ENP (r=0,91; p<0,01) and NNP (r=0,6; p<0,01).

CONCLUSIONS

We did not document any changes in the expression profile of kinin receptors in the analyzed groups, which may suggest that kinin receptors do not make an important contribution in the etiology of NP.

Nicotine enhances murine airway contractile responses to kinin receptor agonists via activation of JNK- and PDE4-related intracellular pathways

Background

Nicotine plays an important role in cigarette-smoke-associated airway disease. The present study was designed to examine if nicotine could induce airway hyperresponsiveness through kinin receptors, and if so, explore the underlying mechanisms involved.

Methods

Murine tracheal segments were cultured for 1, 2 or 4 days in serum-free DMEM medium in presence of nicotine (1 and 10 μM) or vehicle (DMSO). Contractile responses induced by kinin B₁ receptor agonist, des-Arg⁹-bradykinin, and B₂ receptor agonist, bradykinin, were monitored with myographs. The B₁ and B₂ receptor mRNA expressions were semi-quantified using real-time PCR and their corresponding protein expressions assessed with confocal-microscopy-based immunohistochemistry. Various pharmacological inhibitors were used for studying intracellular signaling pathways.

Results

Four days of organ culture with nicotine concentration-dependently increased kinin B₁ and B₂ receptor-mediated airway contractions, without altering the kinin receptor-mediated relaxations. No such increase was seen at day 1 or day 2. The airway contractile responses to 5-HT, acetylcholine and endothelin receptor agonists remained unaffected by nicotine. Two different neuronal nicotinic receptor antagonists MG624 and hexamethonium blocked the nicotine-induced effects. The enhanced contractile responses were accompanied by increased mRNA and protein expression for both kinin receptors, suggesting the involvement of transcriptional mechanisms. Confocal-microscopy-based immunohistochemistry showed that 4 days of nicotine treatment induced activation (phosphorylation) of c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase 1 and 2 (ERK1/2) and p38. Inhibition of JNK with its specific inhibitor SP600125 abolished the nicotine-induced effects on kinin receptor-mediated contractions and reverted the enhanced receptor mRNA expression. Administration of phosphodiesterase inhibitors (YM976 and theophylline), glucocorticoid (dexamethasone) or adenylcyclase activator (forskolin) suppressed the nicotine-enhanced airway contractile response to des-Arg⁹-bradykinin and bradykinin.

Conclusions

Nicotine induces airway hyperresponsiveness via transcriptional up-regulation of airway kinin B₁ and B₂ receptors, an effect mediated via neuronal nicotinic receptors. The underlying molecular mechanisms involve activation of JNK- and PDE4-mediated intracellular inflammatory signal pathways. Our results might be relevant to active and passive smokers suffering from airway hyperresponsiveness, and suggest new therapeutic targets for the treatment of smoke-associated airway disease.

The Raf-1 inhibitor GW5074 and dexamethasone suppress sidestream smoke-induced airway hyperresponsiveness in mice

BACKGROUND

Sidestream smoke is closely associated with airway inflammation and hyperreactivity. The present study was designed to investigate if the Raf-1 inhibitor GW5074 and the anti-inflammatory drug dexamethasone suppress airway hyperreactivity in a mouse model of sidestream smoke exposure.

METHODS

Mice were repeatedly exposed to smoke from four cigarettes each day for four weeks. After the first week of the smoke exposure, the mice received either dexamethasone intraperitoneally every other day or GW5074 intraperitoneally every day for three weeks. The tone of the tracheal ring segments was recorded with a myograph system and concentration-response curves were obtained by cumulative administration of agonists. Histopathology was examined by light microscopy.

RESULTS

Four weeks of exposure to cigarette smoke significantly increased the mouse airway contractile response to carbachol, endothelin-1 and potassium. Intraperitoneal administration of GW5074 or dexamethasone significantly suppressed the enhanced airway contractile responses, while airway epithelium-dependent relaxation was not affected. In addition, the smoke-induced infiltration of inflammatory cells and mucous gland hypertrophy were attenuated by the administration of GW5074 or dexamethasone.

CONCLUSION

Sidestream smoke induces airway contractile hyperresponsiveness. Inhibition of Raf-1 activity and airway inflammation suppresses smoking-associated airway hyperresponsiveness.

Regulation of kinin B2 receptors by bradykinin in human lung cells

Bradykinin is a potent mediator of inflammation that has been shown to participate in allergic airway inflammation. The biologic effects of bradykinin are mediated by binding and activation of its cognate receptor, the B2receptor (B2R). In the lung fibroblast cell line IMR-90, binding of bradykinin to B2R triggers down-regulation of receptor surface expression, suggesting that bradykinin-induced inflammation is transient and self-limited. Notably, subjects with chronic airway inflammation continue to respond to BK following a first challenge. B2Rs are expressed on many different lung cell types, including airway epithelial cells. We therefore compared IMR-90 cells with the human lung epithelial cell line BEAS2B and found that B2R expression in the two cell types is differently regulated by BK. Whereas BK induces down-regulation of B2R in IMR-90 cells, the same treatment leads to up-regulation of the receptor in BEAS2B cells. These results provide a possible explanation for the potency of bradykinin in inducing ongoing airway inflammation.

Interleukin-1beta up-regulates tumor necrosis factor receptors in the mouse airways

Cytokines like interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha), released during the inflammatory process, play important roles in the development of airway hyperresponsiveness. The effects of these cytokines are mediated by cell surface receptors, specific for each cytokine. The expression of cytokine receptors is a dynamic process, where receptors can be up- or down-regulated in response to changes in the environment. One such environmental factor is the presence of cytokines per se. The present study was designed to evaluate the effects of IL-1beta on the expression of its corresponding receptor IL-1 RI, as well as on the closely related TNFalpha receptors TNF RI and TNF RII in airways using a mouse organ culture assay and intranasal inoculation model. Immunohistochemical staining was used to quantify expressional differences between fresh and cultured tracheal segments. In the fresh, uncultured, segments, IL-1 RI and TNF RI were seen in the epithelial layer and TNF RI in the smooth muscle layer. After 4 days of culture, the expression of TNF RI decreased in the epithelial layer, whereas the corresponding expression of IL-1 RI and TNF RI in the smooth muscle remained unchanged. When culture was performed in the presence of IL-1beta, the expression of IL-1 RI and TNF RI in the epithelial cells and TNF RI in the smooth muscle cells increased. TNF RII was not detected in either fresh or cultured trachea, but after treatment with IL-1beta an expression was found in both the epithelial layer and in the smooth muscle cells. The IL-1beta-induced increased expression, on TNF RI and TNF RII in the smooth muscle ex vivo and in the lung parenchyma after intranasal challenge in vivo, was verified at the mRNA level using real-time RT PCR. To summarize, presence of IL-1beta increases the expression of IL-1 R1 and TNF RI and induces expression of TNF RII in the airway wall. It is not inconceivable that these alterations of the IL-1 and TNF receptors may have important functional implications for the development of hyperresponsiveness in inflammatory airway diseases like asthma.

Essential role of IFNbeta and CD38 in TNFalpha-induced airway smooth muscle hyper-responsiveness

We recently identified autocrine interferon (IFN)beta as a novel mechanism mediating tumor necrosis factor (TNF)alpha-induced expression of inflammatory genes in airway smooth muscle (ASM) cells, including CD38, known to regulate calcium signaling. Here, we investigated the putative involvement of IFNbeta in regulating TNFalpha-induced airway hyper-responsiveness (AHR), a defining feature of asthma. Using our pharmacodynamic model to assess ex vivo AHR isolated murine tracheal rings, we found that TNFalpha-induced enhanced contractile responses to carbachol and bradykinin was abrogated by neutralizing anti-IFNbeta antibody or in tracheal rings deficient in CD38. In cultured human ASM cells, where CD38 has been involved in TNFalpha-induced enhanced calcium signals to carbachol and bradykinin, we found that neutralizing anti-IFNbeta prevented TNFalpha enhancing action only on carbachol responses but not to that induced by bradykinin. In a well-characterized model of allergic asthma (mice sensitized and challenged with Aspergillus fumigatus (Af)), we found heightened expression of both IFNbeta and CD38 in the airways. Furthermore, allergen-associated AHR to methacholine, assessed by lung resistance and dynamic compliance, was completely suppressed in CD38-deficient mice, despite the preservation of airway inflammation. These data provide the first evidence that ASM-derived IFNbeta and CD38 may play a significant role in the development of TNFalpha-associated AHR.

Targeting TNF-alpha: a novel therapeutic approach for asthma

Approximately 5% to 10% of patients with asthma have severe disease that is refractory or poorly responsive to inhaled corticosteroid therapy. These patients represent an important unmet clinical need because they experience considerable morbidity and mortality and consume a disproportionately large amount of health care resources. TNF-alpha is a proinflammatory cytokine that has been implicated in many aspects of the airway pathology in asthma. Evidence is emerging to suggest that it might play an important role in severe refractory disease. The development of novel TNF-alpha antagonists has allowed us to test the role of this cytokine in vivo. Preliminary studies have demonstrated an improvement in asthma quality of life, lung function, and airway hyperresponsiveness and a reduction in exacerbation frequency in patients treated with anti-TNF-alpha therapy. However, there is marked heterogeneity in response, suggesting that benefit is likely to be reserved to a small subgroup. Importantly, where efficacy is reported, this also needs to be considered in the context of concerns about the safety of anti-TNF-alpha therapies. Therefore the challenge for clinicians is to evaluate the risk/benefit ratio of these therapies in individual patients with asthma.

Salmeterol and cytokines modulate inositol-phosphate signalling in human airway smooth muscle cells via regulation at the receptor locus

Background

Airway hyper-responsiveness (AHR) is a key feature of asthma and a causal relationship between airway inflammation and AHR has been identified. The aim of the current study was to clarify the effect of proinflammatory cytokines and asthma medication on primary human airway smooth muscle (ASM) inositol phosphate (IPx) signalling and define the regulatory loci involved.

Methods

Primary Human ASM cells were isolated from explants of trachealis muscle from individuals with no history of respiratory disease. The effect of cytokine or asthma medication on histamine or bradykinin induced IPx signalling was assessed by [³H] inositol incorporation. Quantitative Real Time PCR was used to measure mRNA levels of receptors and downstream signalling components. Transcriptional mechanisms were explored using a combination of 5'Rapid Amplification of cDNA Ends (5'RACE) and promoter-reporter techniques.

Results

Treatment of Human ASM cells with IL-13, IFNγ or salmeterol for 24 hours lead to a modest augmentation of histamine induced IPx responses (144.3 +/- 9.3, 126.4 +/- 7.5 and 117.7 +/- 5.2%, p < 0.05). Similarly, TNFα, IFNγ or salmeterol treatment augmented bradykinin induced IPx responses (127.4 +/- 8.3, 128.0 +/- 8.4 and 111.7 +/- 5.0%, P < 0.05). No treatment significantly influenced sodium fluoride induced IPx responses suggesting regulation occurs at the receptor locus. Analyses of mRNA expression of components of the IPx pathway i.e. H1 Histamine Receptor (HRH1), B2 Bradykinin Receptor (BDKRB2), Gαq/11 and PLC-β1 identified that a significant induction of receptor mRNA (>2 fold) was a feature of these responses explaining the cytokine and spasmogen specificity. The HRH1 and BDKRB2 promoter regions were mapped in ASM and promoter-reporter analyses identified that salmeterol can induce HRH1 (>2 fold) and BDKRB2 (2–5 fold) transcription. The effect of cytokines on HRH1 and BDKRB2 promoter-reporter expression suggested a more complex regulation of mRNA expression involving additional loci to the core promoter.

Conclusion

Our results indicate that the spasmogen specific receptor locus may be a key site of regulation determining the magnitude of spasmogen mediated ASM IPx responses during airway inflammation or following asthma medication. These data provide further insight into the molecular basis of AHR and extend our understanding of potentially detrimental effects associated with existing therapies used in the treatment of asthma.

Participation of kallikrein-kinin system in different pathologies

The general description of kinins refers to these peptides as molecules involved in vascular tone regulation and inflammation. Nevertheless, in the last years a series of evidences has shown that local hormonal systems, such as the kallikrein-kinin system, may be differently regulated and are of pivotal importance to pathophysiological control. The combined interpretations of many recent studies allow us to conclude that the kallikrein-kinin system plays broader and richer roles than those classically described until recently. In this review, we report findings concerning the participation of the kallikrein-kinin system in inflammation, cancer, and in pathologies related to cardiovascular, renal and central nervous systems.

IL-1beta induces murine airway 5-HT2A receptor hyperresponsiveness via a non-transcriptional MAPK-dependent mechanism

BACKGROUND

Interleukin 1 beta (IL-1beta) is found in bronchoalveolar lavage fluids from asthmatic patients and plays an important role in normal immunoregulatory processes but also in pathophysiological inflammatory responses. The present study was designed to investigate if IL-1beta could be involved in the development of airway hyperresponsiveness and if transcriptional mechanisms, epithelium contractile factors and mitogen-activated protein kinase (MAPK) pathways are involved in IL-1beta effect.

METHODS

The effect of IL-1beta on 5-hydroxytryptamine (5-HT) induced bronchoconstriction was evaluated in an in-vitro model for assessment of long-term effects of inflammatory mediators on the airway smooth muscle. Murine tracheal segments were cultured up to 8 days in the absence or presence of IL-1beta with subsequent evaluation in a myograph system, along with mRNA quantification, focusing on the role of the epithelium, acetylcholine release, transcriptional mechanisms and MAPK activity.

RESULTS

During control conditions, 5-HT induced a relatively weak contraction. Presence of IL-1beta increased this response in a time- and concentration-dependent way. The increased concentration-effect curves could be shifted rightwards in a parallel manner by ketanserin, a selective 5-HT2A receptor antagonist, indicating that the responses are mediated by 5-HT2A receptors. The mRNA levels of 5-HT2A receptors were not changed as a consequence of the IL-1beta treatment and actinomycin D, a general transcriptional inhibitor, failed to affect the contractile response, suggesting a non-transcriptional mechanism behind this phenomenon. Neither the removal of the epithelium nor the addition of atropine affected the IL-1beta induced enhancement of 5-HT2A receptor-mediated contractile response. Application of inhibitors for c-Jun N-terminal kinase (JNK), p38 and extracellular signal-regulated kinase 1 and 2 (ERK1/2) showed that the signaling pathways for JNK and ERK1/2 dominated only in cultured segments (control) whereas JNK and p38 dominated in segments treated with IL-1beta.

CONCLUSION

IL-1beta induces murine airway hyperresponsiveness, via a non-transcriptional up-regulation of 5-HT2A receptor-mediated contractile response. The increase of 5-HT contraction is unrelated to epithelial and cholinergic factors, but is dependent on IL-1beta-induced changes of MAPK pathways. The fact that IL-1beta can alter airway responses to contractile agents such as 5-HT, via alteration of the intracellular MAPK signal transduction pathways, might provide a new concept for future treatment of asthma.

IL-1beta-induced transcriptional up-regulation of bradykinin B1 and B2 receptors in murine airways

Hyperresponsiveness to bronchoconstrictor stimuli is a major pathophysiologic feature of asthma, but the molecular mechanisms behind this are not fully understood. The release of TNF-alpha and IL-1beta during the inflammatory process is believed to play an important role in airway hyperresponsiveness. We have previously demonstrated, using a murine in vitro model of chronic airway inflammation, that TNF-alpha up-regulated bradykinin B(1) and B(2) receptors in the airway smooth muscle. By using the same model, the present study was designed to investigate the effects of IL-1beta and its interaction with TNF-alpha on the expression of bradykinin B(1) and B(2) receptors in mouse tracheal smooth muscle. IL-1beta up-regulated bradykinin B(1) and B(2) receptor expression and increased contractile response to bradykinin B(1) and B(2) receptor agonists (des-Arg(9)-bradykinin and bradykinin, respectively) in the tracheal smooth muscle. Transcriptional inhibitor actinomycin D, c-Jun N-terminal kinase (JNK) inhibitors SP600125 and TAT-TI-JIP(153-163), but not extracellular signal-regulated kinase 1 and 2 (ERK 1/2) inhibitor PD98059, significantly attenuated this up-regulation, indicating that a transcriptional mechanism and intracellular JNK signal transduction pathway were involved. In addition, IL-1beta did not affect bradykinin B(1) and B(2) receptor mRNA stability. Remicade, an anti-TNF-alpha antibody, markedly suppressed IL-1beta-induced up-regulation of bradykinin B(1) and B(2) receptors, suggesting that TNF-alpha was involved in the up-regulation, which is further supported by the fact that IL-1beta enhanced TNF-alpha mRNA expression in the tracheae. Intracellular JNK pathway and TNF-alpha might provide key links between inflammatory mediators like IL-1beta and airway hyperresponsiveness to bradykinin.

Comparative antagonist pharmacology at the native mouse bradykinin B2 receptor: radioligand binding and smooth muscle contractility studies

BACKGROUND AND PURPOSE

The aim was to characterize the recently discovered non-peptide antagonist MEN16132 at the mouse B2 receptor, relative to other antagonists.

EXPERIMENTAL APPROACH

[3H]-BK binding experiments used mouse lung and ileum tissue membranes and antagonist potency was measured in the isolated ileum contractility assay.

KEY RESULTS

Two BK binding sites resulted from saturation and homologous competition experiments. A role for the B1 receptor was excluded because of the poor affinity of B1 receptor ligands (pIC50<5). MEN16132, and the other reference antagonists, inhibited only one portion of BK specific binding, and the rank order of potency was (pIC50): Icatibant (lung 10.7; ileum 10.2)=MEN11270 (lung 10.4; ileum 9.9)=MEN16132 (lung 10.5; ileum 9.9).>LF16-0687 (lung 8.9; ileum 8.8)>FR173657 (lung 8.6; ileum 8.2). BK homologous curves performed with lung membranes after treatment with the antagonist MEN16132 or Icatibant (10 nM) displayed only the low affinity site. The functional antagonism by MEN16132 (pA2 9.4) and Icatibant (pA2 9.1), towards BK (control EC50 6.1 nM) induced ileum contractions, was concentration-dependent and surmountable, but the Schild plot slope was less than unity.

CONCLUSIONS AND IMPLICATIONS

In mouse tissue, radiolabelled BK recognizes two binding sites and B2 receptor antagonists can compete only for the higher affinity one. The pharmacological profile of the novel non-peptide antagonist MEN16132 indicates that it exhibits subnanomolar affinity and potency for the mouse B2 receptor and is suitable for further characterization in in vivo pathophysiological models.

Bradykinin activates calcium-dependent potassium channels in cultured human airway smooth muscle cells

Bradykinin (BK) is an inflammatory mediator that can cause bronchoconstriction. In this study, we investigated the membrane currents induced by BK in cultured human airway smooth muscle (ASM) cells. Depolarization of the cells induced outward currents, which were inhibited by tetraethylammonium (TEA) in a concentration-dependent manner with an IC50 of 0.33 microM. The currents were increased by elevating intracellular free Ca2+ concentration, suggesting they are calcium-activated potassium channels [I(K(Ca))]. Preexposure to inhibitor of I(K(Ca)) of large conductance (BKCa), iberiotoxin, and small conductance (SKCa), apamin, inhibited the increase of outward current induced by BK. The relative contribution of BKCa was greatest in early passage cells. Both nickel and SKF-96365 (10 microM) inhibited the increase of the I(K(Ca)) induced by BK; however, the l-type Ca2+ channel blocker, nifedipine, had no effect. Activation of the BK-induced current was inhibited by heparin, indicating dependence on intact inositol 1,4,5-triphosphate (IP3)-sensitive intracellular Ca2+ stores. BK also increased inositol phosphate accumulation and induced a transient Ca2+-activated chloride current (CACC) and a sustained nonselective cation current (I(CAT)). In summary, BK activates BKCa, SKCa, CACC, and I(CAT) via IP3-sensitive stores in human ASM.

Effect of novel selective non-peptide kinin B(1) receptor antagonists on mouse pleurisy induced by carrageenan

Two novel selective non-peptide kinin B(1) receptor antagonists, the benzodiazepine antagonist and SSR240612, were evaluated in carrageenan-induced mouse pleurisy. The peptide R-715 (0.5 mg/kg, i.p.) and the non-peptide benzodiazepine (3 mg/kg, i.p.) antagonists significantly decreased cellular migration (predominantly neutrophils), without altering plasma exudation. SSR240612 (1 mg/kg, i.p.) diminished total cells and neutrophils, besides exudation. Oral administration of SSR240612 (10 mg/kg) also reduced total cell and neutrophil counts. Only the benzodiazepine antagonist inhibited the lung myeloperoxidase activity. No tested antagonist significantly altered the lung and pleural TNFalpha and IL-1beta production. We provide interesting evidence on the anti-inflammatory in vivo effects of non-peptide B(1) receptor antagonists.

Airway smooth muscle as a regulator of immune responses and bronchomotor tone

The traditional view of airway smooth muscle (ASM) in asthma, as a purely contractile tissue, seems to be inadequate. Compelling evidence now suggests that ASM plays an important role in regulating bronchomotor tone, in perpetuating airway inflammation, and in remodeling of the airways. This article reviews three distinct functions of ASM cells: the process of excitation-contraction coupling, with a particular focus on the role of cytokines in modulating calcium responses; the processes of smooth muscle cell proliferation and migration; and the synthetic and immunomodulatory function of ASM cells. This article also discusses how altered synthetic function contributes to airway remodeling.

Vascular endothelin ET(B) receptor-mediated contraction requires phosphorylation of ERK1/2 proteins

In cardiovascular diseases, endothelin type B (ET(B)) receptors in arterial smooth muscle cells are upregulated. The present study revealed that organ culture of rat mesenteric artery segments enhanced endothelin ET(B) receptor-mediated contraction paralleled with increase in the receptor mRNA and protein expressions. The endothelin ET(B) receptor-mediated contraction was associated with increase in phosphorylation of extracellular regulation kinase 1 and 2 (ERK1/2) proteins and elevated levels of intracellular calcium. The elevation curve of intracellular calcium consisted of two phases: one rapid and one sustained. Inhibition of ERK1/2 phosphorylation by SB386023 or blockage of calcium channels by nifedipine significantly reduced the endothelin ET(B) receptor-mediated contraction (P<0.05) and decreased the sustained phase of intracellular calcium level, but not the rapid phase. Thus, phosphorylation of ERK1/2 proteins and elevation of intracellular calcium level are required for endothelin ET(B) receptor-mediated contraction in rat mesenteric artery.

Bradykinin augments EGF-induced airway smooth muscle proliferation by activation of conventional protein kinase C isoenzymes

This study aims to investigate the effects of bradykinin, alone and in combination with growth factors on proliferation of cultured bovine tracheal smooth muscle cells. Bradykinin did not induce mitogenic responses by itself, but concentration-dependently augmented growth factor-induced [3H]thymidine incorporation and cell proliferation. The bradykinin effect was mediated by bradykinin B2 receptors, and not dependent on cyclo-oxygenase. Bradykinin-induced synergism with epidermal growth factor (EGF) could be suppressed by the protein kinase C (PKC) inhibitors GF 109203X (Bisindolylmaleimide I; specific for conventional and novel PKCs) and Gö 6976 (12-(2-Cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole; specific for conventional PKCs). In addition, sole activation of PKC using Phorbol 12-myristate 13-acetate (PMA) was sufficient for a synergistic interaction with EGF. In contrast to bradykinin however, PMA was mitogenic by itself which was not at all affected by Gö 6976, but abolished by GF 109203X. Bradykinin transiently activated the p42/p44 MAP kinase pathway, whereas PMA-induced activation of p42/p44 mitogen activated protein (MAP) kinase was sustained. Neither the combination of bradykinin and EGF nor that of PMA and EGF induced synergistic activation of p42/p44 MAP kinase, however. These results show that bradykinin B2 receptor-stimulation augments growth factor-induced mitogenic responses of airway smooth muscle cells through activation of conventional PKC isozymes. In addition, the results show that PKC isozyme-specificity underlies stimulus-specific differences in mitogenic capacity for bradykinin and PMA.

Glucocorticoids suppress transcriptional up-regulation of bradykinin receptors in a murine in vitro model of chronic airway inflammation

BACKGROUND

Glucocorticoids are effective drugs for controlling symptoms and airway inflammation in respiratory diseases such as asthma and chronic obstructive pulmonary disease. However, the mechanisms behind their effects are not fully understood. We have recently demonstrated that prolonged exposure to the pro-inflammatory mediator tumour necrosis factor-alpha (TNF-alpha) markedly enhanced contractile responses to des-Arg9-bradykinin (selective bradykinin B1 receptor agonist) and bradykinin (selective bradykinin B2 receptor agonist) in murine airways. This increase was paralleled with elevated mRNA levels for bradykinin B1 and B2 receptors, a process involving intracellular mitogen-activated protein kinase pathways.

OBJECTIVE

To investigate the effects of glucocorticoids on the TNF-alpha up-regulated bradykinin B1 and B2 receptor response.

METHODS

Tracheal segments from BALB/c J mice were cultured with and without TNF-alpha, in the absence and presence of the transcriptional inhibitor actinomycin D or the glucocorticoid, dexamethasone. The contractile response induced by des-Arg9-bradykinin and bradykinin was subsequently assessed in a myograph system and mRNA for bradykinin B1 and B2 receptors was quantified using real-time polymerase chain reaction.

RESULTS

Actinomycin D abolished and dexamethasone concentration-dependently suppressed the TNF-alpha-induced enhancement of the des-Arg9-bradykinin and bradykinin responses. This was paralleled by a reduction of the mRNA expression for the bradykinin B1 and B2 receptors.

CONCLUSION

The presented data suggests the involvement of transcriptional mechanisms in the up-regulation of bradykinin B1 and B2 receptors during asthmatic airway inflammation, as well as in their down-regulation following glucocorticoid treatment.

TGF-beta potentiates airway smooth muscle responsiveness to bradykinin

The molecular mechanisms by which bradykinin induces excessive airway obstruction in asthmatics remain unknown. Transforming growth factor (TGF)-beta has been involved in regulating airway inflammation and remodeling in asthma, although it is unknown whether TGF-beta can modulate bradykinin-associated bronchial hyperresponsiveness. To test whether TGF-beta directly modulates airway smooth muscle (ASM) responsiveness to bradykinin, isolated murine tracheal rings were used to assess whether TGF-beta alters ASM contractile responsiveness to bradykinin. Interestingly, we found TGF-beta-treated murine rings (12.5 ng/ml, 18 h) exhibited increased expression of bradykinin 2 (B(2)) receptors and became hyperreactive to bradykinin, as shown by increases in maximal contractile responses and receptor distribution. We investigated the effect of TGF-beta on bradykinin-evoked calcium signals since calcium is a key molecule regulating ASM excitation-contraction coupling. We reported that TGF-beta, in a dose- (0.5-10 ng/ml) and time- (2-24 h) dependent manner, increased mRNA and protein expression of the B(2) receptor in cultured human ASM cells. Maximal B(2) receptor protein expression that colocalized with CD44, a marker of membrane cell surface, occurred after 18 h of TGF-beta treatment and was further confirmed using fluorescence microscopy. TGF-beta (2.5 ng/ml, 18 h) also increased bradykinin-induced intracellular calcium mobilization in fura-2-loaded ASM cells. TGF-beta-mediated enhancement of calcium mobilization was not attenuated with indomethacin, a cyclooxygenase inhibitor. These data demonstrate for the first time that TGF-beta may play a role in mediating airway hyperresponsiveness to bradykinin seen in asthmatics by enhancing ASM contractile responsiveness to bradykinin, possibly as a result of increased B(2) receptor expression and signaling.

Enhanced reactivity to vasopressin in rat basilar arteries during vasospasm after subarachnoid hemorrhage

Subarachnoid hemorrhage increases the plasma level of vasopressin, a well-known vasoconstrictor. We examined the sensitivity to vasopressin in rat basilar artery after subarachnoid hemorrhage using a rat subarachnoid hemorrhage model. Vasospasm was observed 1-2 days after subarachnoid hemorrhage induction, and the contractile response to vasopressin in rat basilar arteries was assessed. The concentration-response curve for vasopressin in subarachnoid hemorrhage (1 day) rats shifted leftward compared with that of control rats. The concentration-response curve for vasopressin V(1) receptor agonist also shifted leftward and upward compared with that of control rats. The concentration-response curve for vasopressin was inhibited not by vasopressin V(2) receptor antagonist but by vasopressin V(1) receptor antagonist. Thus, it was demonstrated that the vasoconstricting effect of vasopressin was significantly enhanced in the vasospasm phase after subarachnoid hemorrhage.

Kinin B1 receptors: key G-protein-coupled receptors and their role in inflammatory and painful processes

Kinins are a family of peptides implicated in several pathophysiological events. Most of their effects are likely mediated by the activation of two G-protein-coupled receptors: B(1) and B(2). Whereas B(2) receptors are constitutive entities, B(1) receptors behave as key inducible molecules that may be upregulated under some special circumstances. In this context, several recent reports have investigated the importance of B(1) receptor activation in certain disease models. Furthermore, research on B(1) receptors in the last years has been mainly focused in determining the mechanisms and pathways involved in the process of induction. This was essentially favoured by the advances obtained in molecular biology studies, as well as in the design of selective and stable peptide and nonpeptide kinin B(1) receptor antagonists. Likewise, development of kinin B(1) receptor knockout mice greatly helped to extend the evidence about the relevance of B(1) receptors during pathological states. In the present review, we attempted to remark the main advances achieved in the last 5 years about the participation of kinin B(1) receptors in painful and inflammatory disorders. We have also aimed to point out some groups of chronic diseases, such as diabetes, arthritis, cancer or neuropathic pain, in which the strategic development of nonpeptidic oral-available and selective B(1) receptor antagonists could have a potential relevant therapeutic interest.