Bradykinin-induced Contraction Research Articles

Inhibitory mechanisms of docosahexaenoic acid on carbachol-, angiotensin II-, and bradykinin-induced contractions in guinea pig gastric fundus smooth muscle

We studied the inhibitory actions of docosahexaenoic acid (DHA) on the contractions induced by carbachol (CCh), angiotensin II (Ang II), and bradykinin (BK) in guinea pig (GP) gastric fundus smooth muscle (GFSM), particularly focusing on the possible inhibition of store-operated Ca2+ channels (SOCCs). DHA significantly suppressed the contractions induced by CCh, Ang II, and BK; the inhibition of BK-induced contractions was the strongest. Although all contractions were greatly dependent on external Ca2+, more than 80% of BK-induced contractions remained even in the presence of verapamil, a voltage-dependent Ca2+ channel inhibitor. BK-induced contractions in the presence of verapamil were not suppressed by LOE-908 (a receptor-operated Ca2+ channel (ROCC) inhibitor) but were suppressed by SKF-96365 (an SOCC and ROCC inhibitor). BK-induced contractions in the presence of verapamil plus LOE-908 were strongly inhibited by DHA. Furthermore, DHA inhibited GFSM contractions induced by cyclopiazonic acid (CPA) in the presence of verapamil plus LOE-908 and inhibited the intracellular Ca2+ increase due to Ca2+ addition in CPA-treated 293T cells. These findings indicate that Ca2+ influx through SOCCs plays a crucial role in BK-induced contraction in GP GFSM and that this inhibition by DHA is a new mechanism by which this fatty acid inhibits GFSM contractions.

Vitamin C Deficiency Exacerbates Dysfunction of Atherosclerotic Coronary Arteries in Guinea Pigs Fed a High-Fat Diet.

Vitamin C (vitC) deficiency has been associated with an increased risk of cardiovascular disease; while several putative mechanistic links have been proposed, functional evidence supporting a causal relationship is scarce. In this study, we investigated how vitC deficiency affects coronary artery vasomotor function and the development of coronary atherosclerotic plaques in guinea pigs subjected to chronic dyslipidemia by a high-fat diet regime. Female Hartley guinea pigs were fed either a control (low-fat diet and sufficient vitC) (N = 8) or a high-fat diet with either sufficient (N = 8) or deficient (N = 10) vitC for 32 weeks. Guinea pigs subjected to the high-fat diet developed significant atherosclerotic plaques in their coronary arteries, with no quantitative effect of vitC deficiency. In isolated coronary arteries, vasomotor responses to potassium, carbachol, nitric oxide, or bradykinin were studied in a wire myograph. Carbachol, bradykinin, and nitric oxide mediated relaxation in the coronary arteries of the control group. While vasorelaxation to carbachol and nitric oxide was preserved in the two high-fat diet groups, bradykinin-induced vasorelaxation was abolished. Interestingly, bradykinin induced a significant contraction in coronary arteries from vitC-deficient guinea pigs (p < 0.05). The bradykinin-induced contraction was unaffected by L-NAME but significantly inhibited by both indomethacin and vitC, suggesting that, during vitC deficiency, increased release of arachidonic acid metabolites and vascular oxidative stress are involved in the constrictor effects mediated by bradykinin. In conclusion, the present study shows supporting evidence that poor vitC status negatively affects coronary artery function.

Signaling Pathways Mediating Bradykinin-Induced Contraction in Murine and Human Detrusor Muscle.

Bradykinin (BK) has been proposed to modulate urinary bladder functions and implicated in the pathophysiology of detrusor overactivity. The present study aims to elucidate the signaling pathways of BK-induced detrusor muscle contraction, with the goal of better understanding the molecular regulation of micturition and identifying potential novel therapeutic targets of its disorders. Experiments have been carried out on bladders isolated from wild-type or genetically modified [smooth muscle-specific knockout (KO): Gαq/11-KO, Gα12/13-KO and constitutive KO: thromboxane prostanoid (TP) receptor-KO, cyclooxygenase-1 (COX-1)-KO] mice and on human bladder samples. Contractions of detrusor strips were measured by myography. Bradykinin induced concentration-dependent contractions in both murine and human bladders, which were independent of secondary release of acetylcholine, ATP, or prostanoid mediators. B2 receptor antagonist HOE-140 markedly diminished contractile responses in both species, whereas B1 receptor antagonist R-715 did not alter BK's effect. Consistently with these findings, pharmacological stimulation of B2 but not B1 receptors resembled the effect of BK. Interestingly, both Gαq/11- and Gα12/13-KO murine bladders showed reduced response to BK, indicating that simultaneous activation of both pathways is required for the contraction. Furthermore, the Rho-kinase (ROCK) inhibitor Y-27632 markedly decreased contractions in both murine and human bladders. Our results indicate that BK evokes contractions in murine and human bladders, acting primarily on B2 receptors. Gαq/11-coupled and Gα12/13-RhoA-ROCK signaling appear to mediate these contractions simultaneously. Inhibition of ROCK enzyme reduces the contractions in both species, identifying this enzyme, together with B2 receptor, as potential targets for treating voiding disorders.

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 (10µg/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 300µmol/L and 1000µmol/L, GYY4137 at 30µmol/L and 100µmol/L, and AP39 at 30nmol/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 1000μmol/L, and IL-6 and TNF-α levels at 100μmol/L concentrations. Incubation with GYY4137 (100µmol/L) and AP39 (30nmol/L and 300nmol/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.

Pharmacological Effects of a Novel Bradykinin-Related Peptide (RR-18) from the Skin Secretion of the Hejiang Frog (Ordorrana hejiangensis) on Smooth Muscle.

Bradykinin (BK) and bradykinin-related peptides (BRPs), which were identified from a diversity of amphibian skin secretions, exerted contractile and relaxing effects on non-vascular and vascular smooth muscle, respectively. Here, we report a novel bradykinin-related peptide with a molecular mass of 1890.2 Da, RVAGPDKPARISGLSPLR, which was isolated and identified from Ordorrana hejiangensis skin secretions, followed by a C-terminal extension sequence VAPQIV. The biosynthetic precursor-encoding cDNA was cloned by the “shotgun” cloning method, and the novel RR-18 was identified and structurally confirmed by high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). Subsequently, the myotropic activity of the synthetic replicate of RR-18 was investigated on the rat bladder, uterus, tail artery and ileum smooth muscle. The peptide was named RR-18 in accordance (R = N-terminal arginine, R = C-terminal arginine, 18 = number of residues). In this study, the synthetic replicates of RR-18 showed no agonist/antagonism of BK-induced rat bladder and uterus smooth muscle contraction. However, it displayed an antagonism of bradykinin-induced rat ileum contraction and arterial smooth muscle relaxation. The EC50 values of BK for ileum and artery, were 214.7 nM and 18.3 nM, respectively. When the tissue was pretreated with the novel peptide, RR-18, at the maximally effective concentration of bradykinin (1 × 10−6 M), bradykinin-induced contraction of the ileum and relaxation of the arterial smooth muscle was reduced by 50–60% and 30–40%, respectively. In conclusion, RR-18 represents novel bradykinin antagonising peptide from amphibian skin secretions. It may provide new insight into possible treatment options for chronic pain and chronic inflammation.

Effect of 3-substituted 1,4-benzodiazepin-2-ones on maximal normalized rate of bradykinin-induced smooth muscle contraction in the presence of calcium channel blockers

The development of modern organic chemistry and molecular modeling technologies simplify the search for potential inhibitors of various receptor systems and biological processes. The one of the directions is the development of analgesics of broad spectrum and low toxicity. It is important to search for inhibitors of the kinin-kallikrein system that regulates many functions: inflammation, pain, carcinogenesis, vascular tone, smooth muscle contraction and other. Derivatives of 3-substituted 1,4-benzodiazepine-2-ones have a unique spatial conformation that allows one to simulate β-structures of bioactive peptides. The functional activity of compounds is determined by properties of their peripheral chemical radicals. We analyzed the effect of 3-substituted 1,4-benzodiazepin-2-ones derivatives on the normalized maximal rate of bradykinin-induced smooth muscle contraction and relaxation of the stomach in the presence of calcium channel blockers: verapamil (1 μM), gadolinium (300 μM) and 2-aminoethyl diphenylborinate (0.1 μM). The levels of bradykinin and 3-arylamino-1,2-dihydro-3H-1,4-benzodiazepine-2-ones in incubation solution were 10–6 M. Data processing on dynamics of contraction was performed according to the method of Burdyha and Kosterin. Compounds MX-1775 and MX-1925 reduced maximal normalized rate (Vn) of bradykinin-induced smooth muscle contraction in the presence of Gd3+ by 21.2% and 31.0% respectively. Compound MX-1925 increased Vn of relaxation by 11.6%. A similar effect is typical for MX-2011, where there is an increase by 34.6%. In the presence of verapamil this compound additionally decreased Vn contraction by 20.5%. Substances MX-1775, MX-2004 and MX-1925 restored maximal normalized rate of relaxation to original values of bradykinin-induced contraction. In the presence of 2-aminoethyldiphenylborinate MX-1775 additionally reduced Vn of contractions by 7.5%. 3-substituted 1,4-benzo­diazepine-2-ones did not change the maximal normalized rate of contraction and relaxation of carbachol- and potential-induced smooth muscle contraction. Based on the results and previous investigations, the MX-1775 is a potential blocker of kinin B2-receptors. Effects obtained for other compounds require additional research.

Chronic Hypoxia uncouples Ca2+ and eNOS in bradykinin‐induced relaxation of Ovine pulmonary arteries

Bradykinin‐induced activation of the pulmonary endothelium triggers a rise in intracellular Ca2+, which activates a nitric oxide (NO)‐dependent signaling pathway. This pathway leads to vasodilation, thereby regulating pulmonary blood flow and 02 uptake. This vasodilation process includes stimulation of endothelial nitric oxide synthase (eNOS) and downstream activation of large‐conductance K+ (Maxi K+) channels. Chronic hypoxia (CH) is known to increase pulmonary pressures and restrict arterial relaxation, and can contribute to the development of pulmonary hypertension. We thus examined the effects of CH on bradykinin‐induced Ca2+ signals, bradykinin‐induced vasorelaxation, and the roles of eNOS and Maxi K+ channels in this relaxation. Wire‐myography and confocal microscopy studies were performed on pulmonary arteries (PA) from nonpregnant ewes that lived in a normoxic state at low altitude or a hypoxic state at high altitude (3,801 m) for >100 days. eNOS was inhibited with 100 μM NG‐nitro‐L‐arginine methyl ester (LNAME), and Maxi K+ channels were blocked with 1mM tetraethylammonium (TEA). The data show CH augmented endothelial Ca2+ signals, but restricted bradykinin relaxation. Further, CH caused bradykinin‐induced contraction. LNAME sensitivity was restricted, which suggests eNOS dysfunction is central to the uncoupling of Ca2+ signals and bradykinin relaxation. CH also abolished TEA‐sensitivity in bradykinin relaxation, suggesting there is loss of Maxi K+ function following CH. Overall, these results suggest that CH causes uncoupling of endothelial Ca2+ signaling and eNOS function and mediates major changes in the mechanisms of membrane hyperpolarization. It follows that CH‐induced Ca2+‐eNOS uncoupling and Maxi K+ channel dysfunction are important mechanisms to examine as future therapeutic avenues for pulmonary hypertension.Support or Funding InformationSupport from NIH, NSF and Loma Linda University School of Medicine

Effect of 3-substituted 1,4-benzodiazepin-2-ones on bradykinin-induced smooth muscle contraction.

Biochemical properties of 3-substituted 1,4-benzodiazepine determined by the characteristics of their chemical structure. Influence of 3-substituted 1,4-benzodiazepin-2-ones on maximal normalized rate and amplitudes of isometric smooth muscle contraction in rats was investigated. Compounds MX-1775 and MX-1828 demonstrated the similar inhibition effect on bradykinin-induced contraction of smooth muscle like competitive inhibitor des-arg9-bradykinin-acetate to bradykinin B2-receptors. MX-1626 demonstrated unidirectional changes of maximal normalized rate and force of smooth muscle that proportionally depended on bradykinin concentration in the range 10-10-10-6 M. MX-1828 has statistically significant decrease of normalized rate of smooth muscle contraction for bradykinin concentrations 10-10 and 10-9 M by 20.7 and 8.6%, respectively, but for agonist concentration 10-6 M, this parameter increased by 10.7% and amplitude was reduced by 29.5%. Compounds MX-2011, MX-1785 and MX-2004 showed no natural effect on bradykinin-induced smooth muscle contraction. Compounds MX-1775, MX-1828, MX-1626 were selected for further research of their influence on kinin-kallikrein system and pain perception.

Effect of 3-arylamino-1,2-dihydro-3H-1,4-benzodiazepine-2-ones on the bradykinin-induced smooth muscle contraction

Damage to tissue, inflammation and disruption of normal functioning of organs are often accompanied by pain. In pain perceptions, the kinin-kallikrein system with bradykinin as mediator is very important. Regulatory activity of the kinin-kallikrein system permits the control of inflammation, pain, vascular tone and other functions. A new group of substances that may used for this purpose are 3-substituted 1,4-benzdiazepinones. We analyzed the effect of 3-aryl amino-1,2-dihydro-3H-1,4-benzodiazepine-2-ones derivatives on the normalized maximal rate of bradykinin-induced smooth muscle contraction of the stomach in the presence of calcium channel blockers verapamil (1 μM) and gadolinium (300 μM). The levels of bradykinin and 3-arylamino-1,2-dihydro-3H-1,4-benzodiazepine-2-ones in the incubation solution were 10–6 M. Data processing on the dynamics of contraction was performed according to the method of T. Burdyha and S. Kosterin. Statistically significant changes were found for MX-1828. This compound reduced the maximal normalized rate of bradykinin-induced smooth muscle contraction in the presence of Gd3+ and verapamil by 19.3% and 32.0%, respectively. Also, MX-1828 demonstrated effects similar to those of the competitive inhibitor bradykinin B2-receptor – des-Arg9-bradykinin-acetate, which is possible evidence of its interaction with the receptor or signal transduction pathways. MX-1828 additionally reduced the maximum normalized rate of relaxation by 6.2% in the presence of Gd3+. This effect was demonstrated for MX-1906 in the presence of verapamil with additional reduction of the maximal normalized rate of relaxation, which was 26.4%. The results suggest the presence of inhibitory interaction between MX-1828 and kinin-kallikrein system receptors or signal transduction pathways. The effects which were found for MX-1906 require further studies to clarify the mechanisms of influence on bradykinin-induced smooth muscle contraction.

COX-2 mediated induction of endothelium-independent contraction to bradykinin in endotoxin-treated porcine coronary artery.

This study examined the vascular effects of bradykinin in health and vascular inflammation comparing responses of isolated pig coronary arteries in the absence and presence of endotoxins. Bradykinin induced contractions in lipopolysaccharide-treated, but not untreated, arterial rings without endothelium. The B2-receptor antagonist HOE140, but not the B1-receptor inhibitor SSR240612, blocked these endothelium-independent contractions in response to bradykinin. The bradykinin-induced contractions were blocked by indomethacin, celecoxib, and terbogrel but not valeryl salicylate, AH6809, AL 8810, or RO1138452. They were attenuated by N-(p-amylcinnamoyl) anthranilic acid, and by diethyldithiocarbamate plus tiron but not by L-NAME. Quantitative reverse-transcription polymerase chain reaction revealed significant upregulations of messenger RNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following lipopolysaccharide incubation but not of B2 receptors or COX-1. The present data demonstrate that bradykinin induces contractions mediated by the COX-2 pathway in endotoxin-treated pig coronary arteries. These results support differential roles of bradykinin in health and disease.

Resveratrol prevents bradykinin-induced contraction of rat urinary bladders by decreasing prostaglandin production and calcium influx

Resveratrol, a polyphenol found in grapes and peanuts, exerts beneficial effects on a number of diseases of cardiovascular and central nervous system. However, effects of resveratrol on the urinary system have not been fully investigated. In the present study, we examined effects of resveratrol on bradykinin-induced contraction and release of prostaglandin E 2 in isolated rat urinary bladders. The effects of resveratrol on contractions induced by several agonists (prostaglandin E 2, prostaglandin F 2α and carbachol) and high K + were also examined. We found that resveratrol concentration-dependently reduced the bradykinin-induced contraction in the rat urinary bladder preparations. The higher concentration of resveratrol (100 μM) abolished the bradykinin-induced prostaglandin E 2 release. Similar results were obtained when the cyclooxygenase inhibitor indomethacin (10 μM) was used instead of resveratrol. Resveratrol also attenuated the prostaglandin E 2-, prostaglandin F 2α-, and to a lesser extent carbachol-induced contractions. Contractile responses to bradykinin, prostaglandin E 2 and carbachol were largely prevented by blockade of Ca 2+ channels with diltiazem. Both resveratrol and diltiazem prevented contractions induced by an addition of Ca 2+ (2.5–10 mM) into Ca 2+-free/50 mM K + solution or by 50 mM K + solution containing normal Ca 2+ (2.5 mM). These results suggest that resveratrol prevents bradykinin-induced contractions by attenuating not only the production of prostaglandins but also actions of them. The effect of resveratrol on contractile actions seems to be in part due to inhibition of Ca 2+ influx. Because bradykinin plays an important role in pathological conditions of urinary bladder function, resveratrol may exert beneficial effects on the urinary bladder diseases.

Indomethacin in low concentration potentiates the actions of some spasmogens on the isolated oestrous rat uterus.

The potentiation of some spasmogens by indomethacin, an inhibitor of prostaglandin synthetase activity, in the isolated rat uterus is reported. Low concentrations of indomethacin were found to potentiate bradykinin-induced contractions in the uterus. Parallel dose-response curves to bradykinin were observed in the presence of increasing amounts of indomethacin. As little as .14 mcM indomethacin potentiated uterine contractions. It is unlikely that the potentiation of spasmogenic activity by low concentrations of indomethacin involved the inhibition of prostaglandin synthesis. The possibility that this effect of indomethacin may involve the reduction of tissue calcium concentrations is being evaluated.

Relaxant Effect of Prostaglandin D2–Receptor DP Agonist on Liver Myofibroblast Contraction

Increased intrahepatic resistance causes portal hypertension in cirrhosis. Liver myofibroblasts (MFs) are now regarded as the principle cells involved in sinusoidal blood flow regulation. Many other prostaglandin-receptor agonists have been reported to regulate liver MF contraction, but the role of the prostaglandin D(2)-receptor DP is unknown. In this study, we investigated the effect of a synthetic agonist of prostanoid DP receptor, BW245C, on contractile properties of primary rat liver MFs. Collagen gel contraction assay revealed that BW245C alone (1 and 10 µM) did not induce contraction but induced cell relaxation. Pretreatment with BW245C (10 µM, 30 min) attenuated bradykinin (100 nM)-induced liver MF contraction. Elevation of [Ca(2+)](i) induced by bradykinin (100 nM) was partially suppressed by BW245C pretreatment (10 µM, 3 min). BW245C (1 and 10 µM) significantly increased intracellular cAMP level in a dose-dependent manner. Pretreatment with forskolin (30 - 300 nM, 30 min) and dibutyryl-cAMP (3 - 30 µM, 30 min) significantly reduced bradykinin-induced contraction. Furthermore, a protein kinase A (PKA) inhibitor KT5720 (10 nM to 1 µM, 30 min) blocked the relaxant effect of BW245C. These results suggest that prostanoid DP receptor agonism inhibits bradykinin-induced [Ca(2+)](i) elevation and contraction through cAMP-PKA signal activation in rat liver MFs.

Effect of Montelukast on bradykinin-induced contraction of isolated tracheal smooth muscle of guinea pig.

Aim:To explore the effect of montelukast on bradykinin-induced tracheal smooth muscle contraction of isolated guinea pig trachea.Study Design:To study the effect of bradykinin in the absence and in the presence of montelukast on the isolated tracheal smooth muscle of a guinea pig pretreated with indomethacin (10-6M), phentolamine (10-5M), and propranalol (10-6M), to eliminate the effect of endogenous prostaglandins and catecholamines. The trachealis smooth muscle activity was recorded through the Isometric Force Displacement Transducer on a Four Channel Oscillograph. A cumulative dose-response relationship was demonstrated by adding successive doses of bradykinin on the tracheal strips, starting with 11 μg to 77 μg of 10-4 concentration. A similar procedure was repeated in the presence of montelukast 0.5 μg/ml, which, was equal to approximate Cmax achieved in vivo with a 10 mg oral dose of montelukast, and in the presence of 1 μg/ml of montelukast.Statistical Analysis:Data was expressed as mean ± standard error (SEM), and was analyzed using the SPSS version 15. A P value of less than 0.05 was considered significant.Results:Bradykinin produced a dose-dependent, reversible contraction of isolated tracheal smooth muscle. Montelukast significantly reduced the bradykinin-induced tracheal smooth muscle reactivity and shifted the bradykinin curve to the right and downwards, in the presence of both concentrations of montelukast. The mean magnitude of response achieved with 77 μg of bradykinin in the absence of montelukast was 39 mm ± 6.26, in the presence of 0.5 μg/ml of montelukast it was 24.17 mm ± 4.11, and in the presence of 1 μg/ml of montelukast it was 13 mm ± 2.6.Conclusion:It is concluded that montelukast significantly inhibits, in a dose-dependent manner, the bradykinin-induced contraction of the guinea pig tracheal smooth muscle, and alludes to an interaction between the bradykinin and leukotriene mediators.

Depletion of calcium stores contributes to progesterone-induced attenuation of calcium signaling of G protein-coupled receptors.

Progesterone non-genomically attenuates the calcium signaling of the human oxytocin receptor and several other Galpha(q) protein-coupled receptors. High progesterone concentrations are found in the endometrium during pregnancy opposing the responsiveness of the underlying myometrium to labor-inducing hormones. Here, we demonstrate that within minutes, progesterone inhibits oxytocin- and bradykinin-induced contractions of rat uteri, calcium responses induced by platelet-activating factor in the human endometrial cell line MFE-280, and oxytocin-induced calcium signals in PHM1-31 immortalized pregnant human myometrial cells. Using human embryonic kidney (HEK293) cells as model system, we analyzed the molecular mechanisms underlying these effects. Our data indicate that progesterone rapidly depletes intracellular calcium stores. The resulting desensitization of the cells might contribute to the quiescence of the uterus during pregnancy.

Mechanisms of bradykinin-induced contraction in human fetal lung fibroblasts

Bradykinin (BK) induces fibroblast contraction but the structural changes and intracellular mechanisms involved have not been completely explored. We stimulated HFL-1 fibroblasts with BK to assess: 1) fibroblast contractility; 2) the role of α-smooth muscle actin (SMA) in contraction by small interfering RNA (siRNA); 3) α-SMA protein expression; 4) α-SMA and F-actin structure; 5) intracellular calcium concentration ([Ca(2+)](i)); and 6) phosphorylated myosin light-chain (pMLC) and MLC kinase (MLCK) expression. BK triggered concentration- and time-dependent fibroblast gel contraction in conjunction with α-SMA over expression, but not in α-SMA-siRNA-treated cells. BK also increased α-SMA(+) and F-actin(+) cell number and stress fibre polymerisation (detectable at 5-60 min). These BK-induced changes were associated with an increase in [Ca(2+)](i), which peaked within 15 s, and activation of pMLC, which was detectable at 5-60 min. No MLCK content modification was observed. The different manifestations of the BK-induced fibroblast activation were downregulated at different levels (25-100%) by HOE140, a specific BK B2 receptor (B2R) antagonist and by the Ca(2+) chelator, EGTA. Thus, BK-induced fibroblast contraction, associated with differentiation into α-SMA(+) myofibroblasts, is mediated through the activation of the B2R and involves the Ca(2+)/calmodulin pMLC-dependent pathway.

Women’s health—what’s new worldwide

Women’s health—what’s new worldwide

In vitro antibradykinin activity of Aloe barbadensis gel

When bradykinin-induced contraction of the isolated rat ileum was tested in the presence of Aloe barbadensis Mill. (Liliaceae) gel (fraction F-1) and with the fraction obtained by precipitation of the F-1 with 55% ammonium sulfate (F-55), the maximal responses to bradykinin were reduced by 10 and 22%, respectively. Furthermore, purification of the F-55 by filtration through a column of Sephacryl (S-500-HR) yielded the F-SH fraction, which inhibited the bradykinin effect by 60%. Purification of the F-SH fraction, by filtration through a column of Sephadex G-100, brought about four new fractions: F-GA, F-GB, F-GC, and F-GD. F-GB was the only one that showed the bradykinin inhibition effect (67%). Clearly, Aloe barbadensis gel contains a material that inhibits the bradykinin effect, which might explain the anti-inflammatory properties of Aloe barbadensis.

Toll-like receptor stimulation induces airway hyper-responsiveness to bradykinin, an effect mediated by JNK and NF-kappa B signaling pathways.

Airway infections induce hyper-responsiveness in asthmatic patients. Toll-like receptors (TLR) mediate inflammatory responses to microbes. Occurrence and effects of TLR2, TLR3 and TLR4 were examined in a mouse organ culture model of asthma focusing on the smooth muscle responses to bradykinin. TLR2, TLR3 and TLR4 mRNA, and TLR2 and TLR4 immunoreactivity were detected in the tracheal muscle layer. Tracheal organ culture for 1 or 4 days with lipopolysaccharide (LPS; TLR2/4 agonist) or polyinosinic polycytidylic acid (poly-I-C; TLR3 agonist) enhanced bradykinin- and [des-Arg(9)]-bradykinin-induced contractions. Simultaneous LPS and poly-I-C treatment resulted in synergistic enhancement of bradykinin-induced contraction. In carbachol-pre-contracted segments TLR stimulation induced less potent relaxations to bradykinin and [des-Arg(9)]-bradykinin. The LPS and poly-I-C enhancement of bradykinin-induced contraction was inhibited by the transcriptional inhibitor actinomycin-D, dexamethasone, the proteasome inhibitor MG-132 and the c-Jun N-terminal kinase (JNK) inhibitor SP600125. LPS and poly-I-C induced translocation of NF-kappa B p65 to the nucleus and up-regulation of kinin B(1) and B(2) receptor mRNA. In summary, TLR2, TLR3 and TLR4 are expressed in the mouse tracheal smooth muscle. Costimulation of these receptors results in NF-kappa B- and JNK-mediated transcription of B(1) and B(2) receptor, inducing hyper-responsiveness to bradykinin.

BK2 but not BK1 receptors mediating contractile response in human umbilical arteries: Role of thromboxane A2

Bradykinin receptors have been divided into B1 and B2 subtypes. The aim of this study on human umbilical arteries was: i) to compare the recognition properties of the mediating contractions of bradykinin receptors; and ii) to assess the possible role of thromboxane A2 in a bradykinin-induced contraction of smooth muscle. Umbilical arteries were dissected and mounted in organ baths for isometric measurement of force. Our results showed that the B1 agonist [Sar1dPhe8desArg9]-bradykinin had no effect on the concentration-response 10(-9)-3 x 10(-5) mM. Cumulative additions of bradykinin (10(-9)-3 x 10(-5) mM) and of the B2 agonist [Hyp3TyrMe8]-bradykinin (10(-9)-3 x 10(-5) mM) produced dose-dependent contractions. Dose response curves to bradykinin (10(-9)-3 x 10(-5) mM) were not significantly altered by the presence of B1 selective antagonist [des-Arg9, Leu8]-bradykinin (10(-5) mM), or by the selective B2 antagonist [Thi(5,8), D-Phe7]-bradykinin (10(-5) mM). However, Hoe 140 D-Arg-[Hyp3, Thi5,D-Tic7, Oic8]-bradykinin, an antagonist of B2 responses, significantly inhibited bradykinin-induced contraction. The responses to bradykinin were unaffected by indomethacin (10(-4) mM), dazoxiben (10(-5) mM) or even by nordihydroguaiaretic acid (10(-5) mM). However, bradykinin contractions were antagonized in a noncompetitive manner by quinacrine (10(-5) mM). These results showed that bradykinin contracts human umbilical arteries essentially through B2 receptors. Moreover, the responses to bradykinin are unlikely to be mediated by the cyclooxygenase/lipooxygenase pathway. The inhibitory effects of quinacrine may be due to a specific or nonspecific effect at a cellular level on smooth muscle contractility, or due to a direct action to block Ca2+ influx at membrane level.