Bradykinin Antagonist Research Articles

Impact of Early Pharmacological Treatment on Cognitive and Behavioral Outcome After Traumatic Brain Injury in Adults

Early pharmacological treatment has the potential to reduce some of the disabling cognitive and behavioral problems that result from traumatic brain injury (TBI). Although a large number of treatments have been developed, clinical research has yielded inconsistent findings with respect to the effectiveness of these pharmacological treatments on cognitive and behavioral outcomes. Furthermore, their relative efficacy has not been evaluated, thereby hindering advances in the treatment of TBI. A meta-analysis of research that examined the impact of pharmacological treatments on cognitive and behavioral outcomes in the early stages after TBI between January 1980 and May 2008 was therefore undertaken. The PubMed and PsycINFO databases were searched using 35 terms. All articles were screened using detailed inclusion criteria. Weighted Cohen's d effect sizes, percent overlap statistics, and fail-safe N statistics were calculated for each pharmacological agent. Studies that used different experimental designs were examined separately. Eleven pharmacological treatments were investigated by 22 clinical studies, comprising 6472 TBI patients in the treatment groups and 6460 TBI controls. One dopamine agonist (amantadine) and 1 bradykinin antagonist (CP-0127 [Bradycor]) produced marked treatment benefits (d > or = 0.8) for a single measure of arousal (Glasgow Coma Scale). Notably, drug dosage and the measure chosen to assess outcome influenced the probability of finding a treatment benefit.

Bradykinin receptor antagonists – a review of the patent literature 2005 – 2008

Background: For > 20 years, pharmaceutical companies and academic centers have been developing bradykinin antagonists. The patent literature on these molecules (up to and including 2004) has been analyzed previously in this journal in two review articles. Objective: The aim of this review is to provide an update (from 2005 to early 2009) on the patenting activity in the field of bradykinin antagonists (including patents on their formulation). Where possible, the information from the patents has been supplemented with that from the primary literature, clinical trial databases and company websites in an attempt to give a more complete picture. Conclusions: In the past 4 years, nearly 50 new patents have been filed on bradykinin antagonists – in the case of several filings, only the original source has been considered in this analysis – the vast majority of these (> 93%) on B1 antagonists. However, despite this large amount of work, only one compound, icatibant – a hydrophilic decapeptide selective for the B2 receptor – has reached the market, although it needs to be administered parenterally.

Triggering of proteinase‐activated receptor 4 leads to joint pain and inflammation in mice

To investigate the role of proteinase-activated receptor 4 (PAR-4) in mediating joint inflammation and pain in mice. Knee joint blood flow, edema, and pain sensitivity (as induced by thermal and mechanical stimuli) were assessed in C57BL/6 mice following intraarticular injection of either the selective PAR-4 agonist AYPGKF-NH(2) or the inactive control peptide YAPGKF-NH(2). The mechanism of action of AYPGKF-NH(2) was examined by pretreatment of each mouse with either the PAR-4 antagonist pepducin P4pal-10 or the bradykinin antagonist HOE 140. Finally, the role of PAR-4 in mediating joint inflammation was tested by pretreating mice with acutely inflamed knees with pepducin P4pal-10. PAR-4 activation caused a long-lasting increase in joint blood flow and edema formation, which was not seen following injection of the control peptide. The PAR-4-activating peptide was also found to be pronociceptive in the joint, where it enhanced sensitivity to a noxious thermal stimulus and caused mechanical allodynia and hyperalgesia. The proinflammatory and pronociceptive effects of AYPGKF-NH(2) could be inhibited by pepducin P4pal-10 and HOE 140. Finally, pepducin P4pal-10 ameliorated the clinical and physiologic signs of acute joint inflammation. This study demonstrates that local activation of PAR-4 leads to proinflammatory changes in the knee joint that are dependent on the kallikrein-kinin system. We also show for the first time that PARs are involved in the modulation of joint pain, with PAR-4 being pronociceptive in this tissue. Thus, blockade of articular PAR-4 may be a useful means of controlling joint inflammation and pain.

Effects of bradykinin on venous capacitance in health and treated chronic heart failure

In the present study, we investigated the effects of basal and intra-arterial infusion of bradykinin on unstressed forearm vascular volume (a measure of venous tone) and blood flow in healthy volunteers (n=20) and in chronic heart failure patients treated with ACEIs [ACE (angiotensin-converting enzyme) inhibitors] (n=16) and ARBs (angiotensin receptor blockers) (n=14). We used radionuclide plethysmography to examine the effects of bradykinin and of the bradykinin antagonists B9340 [B1 (type 1)/B2 (type 2) receptor antagonist] and HOE140 (B2 antagonist). Bradykinin infusion increased unstressed forearm vascular volume in a similar dose-dependent manner in healthy volunteers and ARB-treated CHF patients (healthy volunteers maximum 12.3±2.1%, P<0.001 compared with baseline; ARB-treated CHF patients maximum 9.3±3.3%, P<0.05 compared with baseline; P=not significant for difference between groups), but the increase in unstressed volume in ACEI-treated CHF patients was higher (maximum 28.8±7.8%, P<0.001 compared with baseline; P<0.05 for the difference between groups). In contrast, while the increase in blood flow in healthy volunteers (maximum 362±9%, P<0.001) and in ACEI-treated CHF patients (maximum 376±12%, P<0.001) was similar (P=not significant for the difference between groups), the increase in ARB-treated CHF patients was less (maximum 335±7%, P<0.001; P<0.05 for the difference between groups). Infusion of each receptor antagonist alone similarly reduced basal unstressed volume and blood flow in ACEI-treated CHF patients, but not in healthy volunteers or ARB-treated CHF patients. In conclusion, bradykinin does not contribute to basal venous tone in health, but in ACEI-treated chronic heart failure it does. In ARB-treated heart failure, venous responses to bradykinin are preserved but arterial responses are reduced compared with healthy controls. Bradykinin-mediated vascular responses in both health and heart failure are mediated by the B2, rather than the B1, receptor.

A fluorescent version of the bradykinin B 2 receptor antagonist B-9430: Pharmacological characterization and use in live cell imaging

B-9430 ( d-Arg-[Hyp 3, Igl 5, D-Igl 7, Oic 8]-bradykinin), where Hyp is trans-4-hydroxyproline, Igl is α-(2-indanyl)glycine and Oic is (3as, 7as)-octahydroindol-2-yl-carbonyl is a high affinity bradykinin B 2 receptor antagonist with effects extended to the B 1 receptors at high concentrations. The N-terminus of B-9430 has been extended with d-biotinyl (B-10330) or 5(6)-carboxyfluorescein-ɛ-aminocaproyl (B-10380) to derive fluorescent receptor probes. The pharmacological profile of B-10380 was similar to that of B-9430 with a minor loss of potency (a competitive antagonist of bradykinin at the B 2 receptors of the human isolated umbilical vein, pA 2 6.83; an insurmountable antagonist at the B 2 receptors in the rabbit jugular vein; a weak competitive antagonist of the B 1 receptors in the rabbit aorta, pA 2 5.95). B-10330 and B-10380 displaced the binding of [ 3H]bradykinin from rabbit B 2 receptors with a potency slightly inferior to that of B-9430 (larger gap at the rat B 2 receptor). Treatment with B-10330 and fluorescent streptavidin did not support imaging of recombinant B 2 receptors. However, the plasma membrane of HEK 293a cells that transiently expressed recombinant rabbit B 2 receptors, but not B 1 receptors, was labeled with 5–50 nM B-10380 (epifluorescence microscopy). B-10380 staining was not observed in nontransfected cells and was abolished by co-treating receptor-expressing cells with a nonpeptide antagonist. The N-terminal extension of a potent peptide antagonist of the bradykinin B 2 receptor with a fluorophore produced a fluorescent probe suitable for live cell imaging and other applications at the expense of a minor loss of affinity.

Solution conformations of bradykinin antagonists modified with CαCα cyclized nonaromatic residues

The conformations of four BK antagonists, [D-Arg 0, Hyp3, Thi5, D-Phe7, Acc8]BK (1), Aaa[D-Arg 0, Hyp3, Thi5, D-Phe7, Acc8]BK (2), [D-Arg 0, Hyp3, Thi5, 8, Apc7]BK (3), and Aaa[D-Arg(0), Hyp(3), Thi(5, 8), Apc7]BK (4) were studied by using 2D NMR spectroscopy and MD simulations with time-averaged (TAV) restraints. According to the results of the NMR measurements, the BK antagonists contain 7-30% of minor conformation resulting from cis/trans isomerization of the peptide bonds preceding either Pro or Hyp residues. The major conformation of each peptide possesses all peptide bonds in trans configuration. Peptides modified with the Apc residue at position 7 (peptides 3 and 4) possess a higher percentage of minor isomer. Peptide 1 exhibits the strongest vasodepressor potency among the analogs studied and as a single one forms the betaII-turn in the 2-5 fragment, which is believed to be crucial for antagonistic activity. This peptide is also the most compact. The radius of gyration (Rg) amounts to 6.9 A and is by ca 1.5 A lower than that of the remaining analogs. With peptide 4, the ST-turn of type I within the Ser6-Thi8 fragment was found.

EFFECTS OF THE BRADYKININ B2 RECEPTOR ANTAGONIST ICATIBANT ON MICROVASCULAR PERMEABILITY AFTER THERMAL INJURY IN SHEEP

Peptide kinins are potent vasoactive agents in the microcirculation that might be released after burn injury. The present study was designed to test the hypothesis that Icatibant (JE 049), a potent, selective peptidomimetic bradykinin-B2 receptor antagonist, would reduce the cardiovascular pathology occurring in sheep exposed to 40% total body surface area (TBSA), third-degree burn. Female sheep were surgically prepared for chronic study. After 5 to 7 days' recovery from the operative procedure, they were randomized to five groups: sham (n = 6, noninjured, nontreated), medicated sham (n = 4, noninjured, treated with 20 microg kg h Icatibant), control (n = 7, 40% TBSA third-degree burn, nontreated), Icatibant-4 (n = 6, 40% TBSA third-degree burn, treated with 4 microg kg h Icatibant [low dose]), Icatibant-20 (n = 8, 40% TBSA third-degree burn, treated with 20 microg kg h Icatibant [high dose]). Prefemoral lymph flow (milliliters per hour) remained constant in the sham and medicated sham groups but increased after injury: control (0 h, 3.9 +/- 0.5; 24 h, 28 +/- 4.2; 48 h, 33.0 +/- 8.1). The increased fluid flux was associated with enhanced protein flux. Both low and high doses of Icatibant significantly reduced the microvascular fluid flux: Icatibant-4 (0 h, 5.3 +/- 0.6; 24 h, 17.5 +/- 3.5; 48 h, 20.3 +/- 3.4); Icatibant-20 (0 h, 5.3 +/- 1.1; 24 h, 15.2 +/- 2; 48 h, 17.6 +/- 4.1). Total prefemoral protein leak was reduced in all treatment groups. The low dose of Icatibant significantly reduced prefemoral lymph flow without adversely affecting the hemodynamic changes observed after burn injury in sheep, suggesting that the bradykinin antagonist would reduce edema formation and improve fluid management of thermally injured patients.

Helokinestatin: A new bradykinin B 2 receptor antagonist decapeptide from lizard venom

Synthetic bradykinin antagonist peptides/peptoids have been powerful tools for delineating the roles of kinins in both normal physiology and in pathological states. Here, we report the identification of a novel, naturally occurring bradykinin B 2 receptor antagonist peptide, helokinestatin, isolated and structurally characterized from the venoms of helodermatid lizards—the Gila monster ( Heloderma suspectum) and the Mexican beaded lizard ( Heloderma horridum). The primary structure of the peptide was established by a combination of microsequencing and mass spectroscopy as Gly-Pro-Pro-Tyr-Gln-Pro-Leu-Val-Pro-Arg ( M r 1122.62). A synthetic replicate of helokinestatin was found to inhibit bradykinin-induced vasorelaxation of phenylephrine pre-constricted rat tail artery smooth muscle, mediated by the B 2 receptor sub-type, in a dose-dependent manner. Natural selection, that generates functional optimization of predatory reptile venom peptides, can potentially provide new insights for drug lead design or for normal physiological or pathophysiological processes.

Structural modification of the highly potent peptide bradykinin B1 receptor antagonist B9958

Bradykinin (BK)-related peptides stimulate two major classes of receptors, B1 and B2. The B1 receptor (B1R) plays an important role in various pathophysiological states including chronic inflammation, pain, hypotension, trauma and proliferation of cancer. Therefore, there is interest in the development of highly potent peptide BK B1R antagonists. We previously developed a highly potent and selective BK B1R receptor antagonist, B9958 (Lys-Lys-[Hyp3, CpG5, d-Tic7, CpG8]des-Arg9-BK) (Hyp, trans-4-hydroxyproline; CpG, α-cyclopentylglycine; Tic, tetrahydroisoquinoline-3-carboxylic acid). We now report on new BK B1R antagonist analogs of B9958 with N-terminal basic residues in the d-configuration, or Lys-, Orn- derivatives (NiK, ε-nicotinoyllysine; PzO, 3-pyrazinoylornithine) and/or having hindered unusual amino acids at position 5 (Igl, α-(2-indanyl)glycine). These changes were designed to prevent enzyme degradation while keeping an acceptable affinity. However, these new analogs do not show higher B1R antagonist activity than B9958, but its N-terminal acylated derivative with a bulky and hydrophobic 2,3,4,5,6-pentafluorocinnamic acid (F5c), B10324, retains a B1R antagonist activity close to that of B9958 and, in addition, has high inhibition in vivo against lung cancer (SCLC, 86 %) and moderate inhibition against prostate cancer (PC3, 43%) xenografts. This class of compounds offers hope for the development of new BK antagonist peptide drugs for lung or prostate cancer.

Calotropis procera latex‐induced inflammatory hyperalgesia – effect of bradyzide and morphine

1 The milky white latex of the plant Calotropis procera induces inflammatory response upon accidental exposure and on local administration that could be effectively ameliorated by antihistaminic and standard anti-inflammatory drugs. 2 The aim of the present study was to evaluate the anti-oedematogenic and analgesic effect of the bradykinin antagonist, bradyzide (BDZ) and the opioidergic analgesic, morphine (Mor) against inflammatory hyperalgesia induced by the dried latex (DL) of C. procera in the rat paw oedema model. 3 An aqueous solution of DL (0.1 ml of 1% solution) was injected into the sub-plantar surface of the rat paw and the paw volume was measured at different time intervals. The inhibitory effect of bradyzide and morphine on oedema formation and hyperalgesic response was compared with that of cyproheptadine (CPH), a potent inhibitor of DL-induced oedema formation. 4 The hyperalgesic response was evaluated by the dorsal flexion pain test, compression test and by observing motility, stair-climbing ability, and the grooming behaviour of the rats. 5 The effect of these drugs was also evaluated against DL-induced writhings in the mouse model. 6 Both bradyzide and morphine inhibited DL-induced oedema formation by 30-40% and CPH was more effective in this regard (81% inhibition). The antihyperalgesic effect of both the drugs was more pronounced than that of CPH. Both bradyzide and morphine markedly inhibited the grooming behaviour and the effect of morphine could be reversed by pretreatment with naloxone. 7 Thus, our study shows that DL-induced oedema formation is effectively inhibited by antihistaminic/antiserotonergic drug and associated hyperalgesia by analgesic drugs.

Antihyperalgesic effects of vanilloid-1 and bradykinin-1 receptor antagonists following spinal cord injury in rats

The authors previously discovered that genes for the bradykinin-1 (B1) receptor and the transient receptor potential vanilloid subtype 1 (TRPV1) were overexpressed in animals exhibiting thermal hyperalgesia (TH) following spinal cord injury (SCI). They now report the effect of TRPV1 (AMG9810) and B1 (Lys-[Des-Arg9,Leu8]-bradykinin) antagonists on TH in animals following SCI. The rats were subjected to contusion SCI and then divided into groups in which TH did or did not develop. The animals from both groups were given either AMG9810, Lys-(Des-Arg9,Leu8)-bradykinin, or the drug-specific vehicle (control groups). Animals were tested for TH preinjury and at regular intervals after SCI by using the hindlimb withdrawal latency test. The administration of AMG9810 likely improves TH as a result of a generalized analgesic effect, whereas the effect of Lys-(Des-Arg9,Leu8)-bradykinin appears more specific to the reversal of TH. This information has potential usefulness in the development of treatment strategies for post-SCI neuropathic pain.

Neuroprotection in traumatic brain injury: a complex struggle against the biology of nature

Translating the efficacy of neuroprotective agents in experimental traumatic brain injury to clinical benefit has proven an extremely complex and, to date, unsuccessful undertaking. The focus of this review is on neuroprotective agents that have recently been evaluated in clinical trials and are currently under clinical evaluation, as well as on those that appear promising and are likely to undergo clinical evaluation in the near future. Excitatory neurotransmitter blockage and magnesium have recently been evaluated in phase III clinical trials, but showed no neuroprotective efficacy. Cyclosporin A, erythropoietin, progesterone and bradykinin antagonists are currently under clinical investigation, and appear promising. Traumatic brain injury is a complex disease, and development of clinically effective neuroprotective agents is a difficult task. Experimental traumatic brain injury has provided numerous promising compounds, but to date these have not been translated into successful clinical trials. Continued research efforts are required to identify and test new neuroprotective agents, to develop a better understanding of the sequential activity of pathophysiologic mechanisms, and to improve the design and analysis of clinical trials, thereby optimizing chances for showing benefit in future clinical trials.

Functional characterization of the mechanisms underlying bradykinin-induced relaxation in the isolated rat carotid artery

This work aimed to functionally characterize the mechanisms underlying the relaxation induced by bradykinin (BK) in the rat carotid artery. Vascular reactivity experiments, using standard muscle bath procedures, showed that BK (0.1 nmol/L–3 μmol/L) induced relaxation of phenylephrine-pre-contracted rings in a concentration-dependent manner. Endothelial removal strongly attenuated BK-induced relaxation. HOE-140, the selective antagonist of bradykinin B 2 receptors concentration-dependently reduced the relaxation induced by BK. Pre-incubation of endothelium-intact rings with l-NAME (100 µmol/L), a non-selective nitric oxide synthase (NOS) inhibitor, l-NAME (100 µmol/L), a selective inhibitor of the eNOS or 7-nitroindazole (100 µmol/L), the selective inhibitor of nNOS, reduced BK-induced relaxation. Conversely, 1400 W (10 nmol/L), a selective inhibitor of iNOS, did not alter the relaxation induced by BK. Surprisingly, indomethacin (10 µmol/L) a non-selective inhibitor of cyclooxygenase (COX) increased BK-induced relaxation in endothelium-intact but not denuded rings. Neither SQ29548 (3 µmol/L), a competitive antagonist of PGH 2/TXA 2 receptors nor AH6809 (10 µmol/L), an antagonist of PGF 2α receptors significantly altered the relaxation induced by BK in endothelium-intact rings. The combination of SQ29548 and AH6809 increased BK-induced relaxation. The present study shows that the vasorelaxant action displayed by BK in the rat carotid is mediated by endothelial B 2 receptors and the activation of the NO pathway. The major finding of this work is that it demonstrated functionally that endothelial-derived vasoconstrictor prostanoids (probably PGH 2, TXA 2 and PGF 2α) counteract the vasorelaxant action displayed by BK.

Cross-talk between G Protein–Coupled Receptor and Epidermal Growth Factor Receptor Signaling Pathways Contributes to Growth and Invasion of Head and Neck Squamous Cell Carcinoma

G protein-coupled receptors (GPCR) and the epidermal growth factor receptor (EGFR) are often both overexpressed and contribute to the growth of cancers by activating autocrine pathways. GPCR ligands have been reported to trigger EGFR signaling via receptor cross-talk in cancer cells. Here, we show that GPCR ligands prostaglandin E2 (PGE2) and bradykinin (BK) activate EGFR signaling. Inhibition of EGFR using several strategies, including small-molecule inhibitors and an EGFR-specific antibody, resulted in partial attenuation of signaling downstream of EGFR. PGE2 and BK triggered EGFR signaling by increasing selective autocrine release of transforming growth factor-alpha (TGF-alpha). Inhibition of tumor necrosis factor-alpha-converting enzyme abrogated BK- or PGE2-mediated activation of EGFR signaling. Both PGE2 and BK stimulated head and neck squamous cell carcinoma (HNSCC) invasion via EGFR. Treatment of HNSCC cells with the BK antagonist CU201 resulted in growth inhibition. The combination of CU201 with the EGFR small-molecule inhibitor erlotinib resulted in additive inhibitory effects on HNSCC cell growth in vitro. Inhibition of the PGE2 synthesis pathway with sulindac induced HNSCC cytotoxicity at high doses (EC(50), 620 micromol/L). However, combined inhibition of both EGFR with the tyrosine kinase inhibitor erlotinib and GPCR with sulindac at low doses of 6 and 310 micromol/L, respectively, resulted in synergistic killing of HNSCC tumor cells. Combined blockade of both EGFR and GPCRs may be a rational strategy to treat cancers, including HNSCC that shows cross-talk between GPCR and EGFR signaling pathways.

Bradykinin antagonist protects against myocardial ischemic-reperfusion injury in cat

The effect of icatibant, a selective bradykinin receptor (B2) antagonist on myocardial ischemic–reperfusion injury was studied in open-chest barbiturate anaesthetized cats. Left anterior descending coronary artery was occluded for 15 min, followed by 60 min of reperfusion. Saline or icatibant (200 μg/kg) was administered intravenously slowly over 2 min, 5 min before reperfusion. In the saline-treated group, myocardial ischemic reperfusion injury was evidenced by depressed mean arterial pressure (MAP), peak positive and negative dP/dt and elevated left ventricular end-diastolic pressure and enhanced oxidant stress [elevated TBARS (thiobarbituric acid reactive substances; a marker for lipid peroxidation), depressed GSH (glutathione), SOD (superoxide dismutase), catalase] and depletion of ATP.

Bradykinin Does Not Contribute to Peripheral Vascular Tone in Patients With Cirrhosis and Ascites

Bradykinin is an endothelium-dependent vasodilator and inflammatory mediator. The aim of the present study was to examine the effects of bradykinin on peripheral vascular tone in patients with cirrhosis and ascites. Forearm blood flow was measured using venous occlusion plethysmography in 8 patients with biopsy-proven alcohol-induced cirrhosis, ascites, and portal hypertension, and 8 age- and sex-matched healthy controls. On 1 occasion, subjects received an intrabrachial infusion of the selective bradykinin antagonist B9340 (1.5-13.5 nmol/min) followed by a control vasoconstrictor norepinephrine (60-540 pmol/min), and on another occasion bradykinin (100-900 pmol/min) followed by the endothelium-independent vasodilator, sodium nitroprusside (SNP, 2-8 microg/min). Bradykinin and SNP caused a dose-dependent vasodilatation (P < 0.001 for both) that did not differ between the 2 groups. Although norepinephrine caused a similar dose-dependent vasoconstriction in both groups (P < 0.001), B9340 had no effect on forearm blood flow in either group (at 13.5 nmol/min in patients; -5%, 95% CI -13-3). Bradykinin does not provide a major contribution to the maintenance of peripheral vascular tone in patients with cirrhosis and ascites. Our findings also suggest that, in contrast to cardiovascular disease, patients with liver cirrhosis do not have marked endothelial dysfunction.

Bradykinin antagonists modified with dipeptide mimetic β-turn inducers

Bradykinin (BK) is involved in a wide variety of pathophysiological processes. Potent BK peptide antagonists can be developed introducing constrained unnatural amino acids, necessary to force the secondary structure of the molecule. In this paper, we report a structure–activity relationship study of two peptide analogues of the potent B2 antagonist HOE 140 by replacing the D-Tic-Oic dipeptide with conformationally constrained dipeptide mimetic β-turn inducers.

Pharmacologic Targets and Prototype Therapeutics in the Kallikrein-Kinin System: Bradykinin Receptor Agonists or Antagonists

The kallikrein-kinin system (KKS) is a complex system produced in various organs. This system includes kininogen (precursor for kinin), kallikreins, and pharmacologically active bradykinin (BK), which is considered to be proinflammatory and/or cardioprotective. It is a proinflammatory polypeptide that is involved in many pathological conditions and can cause pain, inflammation, increased vascular permeability, vasodilation, contraction of various smooth muscles, as well as cell proliferation. On the other hand, it has been shown that BK has cardioprotective effects, as all components of KKS are located in the cardiac muscles. Numerous observations have indicated that decreased activity of this system may lead to cardiovascular diseases, such as hypertension, cardiac failure, and myocardial infarction. BK acts on two receptors, B1 and B2, which are linked physiologically through their natural stimuli and their common participation in a variety of inflammatory responses. Recently, numerous BK antagonists have been developed in order to treat several diseases that are due to excessive BK formation. Although BK has many beneficial effects, it has been recognized to have some undesirable effects that can be reversed with BK antagonists. In addition, products of this system have multiple interactions with other important metabolic pathways, such as the renin-angiotensin system.

Analgesic Efficacy of Bradykinin B 1 Antagonists in a Murine Bone Cancer Pain Model

Cancer pain is a significant clinical problem because it is the first symptom of disease in 20% to 50% of all cancer patients, and 75% to 90% of patients with advanced or terminal cancer must cope with chronic pain syndromes related to failed treatment and/or tumor progression. One of the most difficult to treat cancer pains is metastatic invasion of the skeleton that can generate ongoing and bone breakthrough pain, which represents one of the most debilitating cancer-related events. Because bradykinin has been shown to be released in response to tissue injury and plays a significant role in driving acute and chronic inflammatory pain, we focused on bradykinin antagonists in a model of bone cancer pain. In our model of bone cancer, which involves the injection and confinement of 2472 sarcoma cells to the mouse femur, pharmacologic blockade of the bradykinin B 1 receptor is effective in reducing pain-related behaviors at both early and advanced stages of bone cancer. Perspective Bone cancer pain can be severe and difficult to control fully. With a mouse model of bone cancer pain we demonstrate that pharmacologic blockade of the bradykinin B 1 receptor is effective in reducing bone cancer pain–related behaviors, suggesting that B 1 antagonists might be useful in attenuating bone cancer pain in humans.

Conformational Studies of Two Bradykinin Antagonists by Using Two-dimensional NMR Techniques and Molecular Dynamics Simulations

The solution conformations of two potent antagonists of bradykinin (Arg1-Pro2-Pro3-Gly4- Phe5-Ser6-Pro7-Phe8-Arg9), [Aca-1, DArg0, Hyp3, Thi5, DPhe7,(N-Bzl)Gly8]BK (1) and [Aaa- 1, DArg0, Hyp3, Thi5,(2-DNal)7, Thi8]BK (2), were studied by using 2D NMR spectroscopy in DMSO-dg and molecular dynamics simulations. The NMR spectra of peptide 1 reveals the existence of at least two isomers arising from isomerization across the DPhe7-(N-Bzl)Gly8peptide bond. The more populated isomer possesses the cis peptide bond at this position. The ratio of cis/trans isomers amounted to 7:3. With both antagonists, the NMR data indicate a β-turn structure for the Hyp3-Gly4 residues. In addition, for peptide 2, position 2,3 is likely to be occupied by turn-like structures. The cis peptide bond between DPhe7 and (N- Bzl)Gly8 in analogue 1 suggests type VI β-turn at position 7,8. The molecular dynamics runs were performed on both peptides in DMSO solution. The results indicate that the structure of peptide 1 is characterized by type VIb β-turn comprising residues Ser-Arg9 and the βI or βII-turn involving the Pro2-Thi5 fragment, whereas peptide 2 shows the tendency towards the formation of type I β-turn at position 2,3. The structures of both antagonists are stabilized by a salt bridge between the guanidine moiety of Arg1 and the carboxyl group of Arg9. Moreover, the side chain of DArg0 is apart of the rest of molecule and is not involved in structural elements except for a few calculated structures.