Bradykinin Receptor Antagonist Research Articles

Current treatment options for idiopathic angioedema

BackgroundIdiopathic angioedema is defined as localized swelling of the cutaneous and mucosal tissue that occurs in episodes without a clear etiology. It can be problematic to treat when the underlying pathophysiology is not well understood. ObjectiveTo identify successful treatments of idiopathic angioedema reported in the literature. MethodsA literature search was performed using PubMed. Published case reports and articles discussing treatment of idiopathic angioedema were used in the formulation of this review. In addition, 2 case reports are provided. ResultsAlthough there are no approved treatments for idiopathic angioedema, several medications used for the treatment of hereditary angioedema, such as bradykinin receptor antagonists (icatibant), kallikrein inhibitors (ecallantide), and C1 inhibitors, were successful in 10 patients. Anti-IgE monoclonal antibody (omalizumab) proved successful in 5 patients. The most widely used and successful medication was tranexamic acid (154 patients). ConclusionDespite an unknown etiology, this article highlights viable treatment options for idiopathic angioedema. More clinical trials and better markers identifying the cause of angioedema are needed.

Icatibant in angiotensin-converting enzyme (ACE) inhibitor-associated angioedema.

Angioedema occurs in up to 2% of those taking angiotensin-converting enzyme (ACE) inhibitors. Upper airway angioedema may potentially require endotracheal intubation or cricothyrotomy, and is usually unresponsive to adrenaline. The bradykinin receptor antagonist icatibant is proven to be effective in the treatment of acute attacks of hereditary angioedema, and has also been reported effective in the treatment of angioedema associated with ACE inhibitors. To describe the use of icatibant for ACE inhibitor-associated airway angioedema. We treated 13 consecutive emergency department (ED) patients, who had not improved with adrenaline and/or corticosteroids, with icatibant 30 mg subcutaneously for ACE inhibitor-associated upper respiratory tract angioedema according to an agreed protocol. Four patients were intubated in the ED either before or after receiving icatibant; three of these were extubated within 24 h of treatment. Eight patients received early icatibant and did not require intubation. The time from onset of airway angioedema to ED presentation ranged from 1 h to 3 days (median 4 h); from ED presentation to receiving icatibant, from 30 minutes to 3 days (median 3 h); and to onset of symptom improvement after icatibant, 15 minutes to 7 h (median 2 h). One patient received a second dose of icatibant. All patients improved after receiving icatibant, consistent with its bradykinin receptor blocking mechanism. Icatibant rapidly reversed symptoms, and appeared to avert the need for intubation or expedite extubation. Timely use of icatibant in ACE inhibitor-associated angioedema may avert the need for invasive airway procedures and intensive care unit admission.

Chemotherapy Related Angioedema.

Chemotherapy Related Angioedema.

Tip-enhanced Raman spectroscopy of bradykinin and its B2 receptor antagonists adsorbed onto colloidal suspended Ag nanowires.

The tip-enhanced Raman scattering (TERS) spectra of bradykinin (BK) and its potent B2 BK receptor antagonists, [d-Arg(0),Hyp(3),Thi(5,8),l-Pip(7)]BK and [d-Arg(0),Hyp(3),Thi(5),d-Phe(7),l-Pip(8)]BK, approximately with a size of about 40 nm, adsorbed onto colloidal suspended Ag nanowires with diameter in the range of 350-500 nm and length of 2-50 μm were recorded. The metal surface plasmon resonance and morphology of the Ag nanowires were studied by ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). Briefly, it was shown that two C-terminal amino acids of BK and [d-Arg(0),Hyp(3),Thi(5,8),l-Pip(7)]BK are involved in the interaction with the colloidal suspended Ag nanowire surface, whereas three last amino acids of the [d-Arg(0),Hyp(3),Thi(5),d-Phe(7),l-Pip(8)]BK sequence attached the Ag surface. Thus, BK adsorbs on the colloidal suspended Ag nanowires mainly through the Phe(5/8) ring (tilted orientation) and the one oxygen atom of the carboxylate group and the H2N-C-NH-CH2- fragment of Arg(9). In the case of [d-Arg(0),Hyp(3),Thi(5,8),l-Pip(7)]BK, the Thi(8) ring (through the lone electron pair on the sulfur atom) and the both oxygen atoms of the carboxylate group and the amine group of Arg(9) mainly participated in the interaction with the Ag nanowire surface. For [d-Arg(0),Hyp(3),Thi(5),d-Phe(7),l-Pip(8)]BK, the d-Phe(7) ring, the Pip(8) ring, and the Arg(9) side-chain assisted in the peptide interaction with the Ag surface. The obtained results emphasize the importance of the C-terminal part of these peptides in the adsorption process onto the colloidal suspended Ag nanowires.

Treatment of angiotensin-converting enzyme inhibitor related angioedema with icatibant

Background The absolute risk of angiotensin-converting enzyme (ACE) inhibitor angioedema is 0.3% [1]. The mechanism is felt to be accumulation of bradykinin. The current treatment is discontinuation of ACE-I inhibitor, and intubation if necessary. Icatibant is a bradykinin receptor antagonist, useful in treating hereditary angioedema [2]. We present a patient from a Canadian center who had ACE-inhibitor induced angioedema requiring intubation who did not respond to epinephrine or C1 esterase inhibitor concen

Modulation of the kallikrein/kinin system by the angiotensin-converting enzyme inhibitor alleviates experimental autoimmune encephalomyelitis.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Bradykinin is the end-product of the kallikrein/kinin system, which has been recognized as an endogenous target for combating CNS inflammation. Angiotensin-converting enzyme (ACE) inhibitors influence the kallikrein/kinin system and reportedly have immunomodulatory characteristics. The objectives of this study were to determine whether bradykinin is involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and whether bradykinin control by the ACE inhibitor could be a therapeutic target in MS. The ACE inhibitor enalapril (1·0 or 0·2 mg/kg/day) was administered orally to EAE mice and the serum levels of bradykinin and cytokines in EAE mice were analysed. As a result, the administration of enalapril increased serum bradykinin levels, decreased the clinical and pathological severity of EAE and attenuated interleukin-17-positive cell invasion into the CNS. Additionally, bradykinin receptor antagonist administration reduced the favourable effects of enalapril. Our results suggest that bradykinin is involved in the pathomechanism underlying CNS inflammation in EAE, possibly through inhibiting cell migration into CNS. Control of the kallikrein/kinin system using ACE inhibitors could be a potential therapeutic strategy in MS.

B1 but not B2 bradykinin receptor agonists promote DU145 prostate cancer cell proliferation and migration.

The kallikrein-kinin system (KKS) is an endogenous pathway involved in angiogenesis and tumourigenesis, both vital for cancer growth and progression. To investigate the effect of two bradykinin receptor (B1R and B2R) agonists on growth and motility of prostate tumour (DU145) and micro-vascular endothelial cells (dMVECs). Increasing concentrations of selective B1R and B2R agonists were added to cultured cells. Cell proliferation and migration were assessed using the 3-[4,5 dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) and modified Boyden Chamber assays, respectively. Where significant stimulation was found, the influence of an antagonist was also investigated. Neither growth nor motility of endothelial cells was affected by either agonist. In DU145 cells, while the B2R agonist was without any significant effect, the B1R agonist stimulated proliferation and migration at concentrations of 10nM and 50nM respectively. Further, this effect was abrogated when cells were pre-incubated with a B1R antagonist. Unlike the physiologically-active B2R, the pathologically-inducible B1R may be implicated in prostate tumourigenic events. The involvement of the KKS in malignant prostate pathology supports on-going exploration of bradykinin receptor antagonists as target candidates in the development of alternate approaches to cancer therapy.

Pathophysiology of a severe case of Puumala hantavirus infection successfully treated with bradykinin receptor antagonist icatibant

We recently described a patient with very severe Puumala hantavirus infection manifested by capillary leakage syndrome and shock. He was successfully treated with the bradykinin receptor antagonist, icatibant (Antonen et al., 2013). Here we report analysis of the pathophysiology which indicated pronounced complement activation, prolonged leukocytosis, extensive fibrinolysis, circulating histones, and defects in liver function. The patient had an uncommon HLA-phenotype, which may have contributed to the severe course of the disease.

Neuropathic plasticity in the opioid and non-opioid actions of dynorphin A fragments and their interactions with bradykinin B2 receptors on neuronal activity in the rat spinal cord

Dynorphin A is an endogenous opioid peptide derived from the precursor prodynorphin. The proteolytic fragment dynorphin A (1–17) exhibits inhibitory effects via opioid receptors. Paradoxically, the activity of the dynorphin system increases with chronic pain and neuropathy is associated with the up-regulation of dynorphin biosynthesis. Dynorphin A (1–17) is cleaved in vivo to produce a non-opioid fragment, dynorphin A (2–17). Previously, a mechanism by which the non-opioid fragment promotes pain through agonist action at bradykinin receptors was revealed. Bradykinin receptor expression is up-regulated after nerve injury and both a truncated version of non-opioid fragment dynorphin A (2–17), referred to as ‘Ligand 10’, and novel bradykinin receptor antagonist ‘Ligand 14’, are known to bind to the bradykinin receptor. Here we show that Ligand 10 facilitates the response of wide dynamic range (WDR) neurons to innocuous and noxious mechanical stimuli in neuropathic, but not naïve, animals, while Ligand 14 exhibits inhibitory effects in neuropathic animals only. Furthermore, we reveal an inhibitory effect of Ligand 14 in naïve animals by pre-dosing with either Ligand 10 or a 5-HT3 receptor agonist to reflect activation of descending excitatory drives. Thus remarkably, by mimicking pro-excitatory pharmacological changes that occur after nerve injury in a naïve animal, we induce a state whereby the inhibitory actions of Ligand 14 are now effective. Ultimately our data support an increasing number of studies that suggest that blocking spinal bradykinin receptors may have a therapeutic potential in chronic pain states, here, in particular, in neuropathic pain.

Direct intrawound administration of dimethylsulphoxide relieves acute pain in rats.

Wounds associated with injuries such as burns can produce moderate to severe pain. Besides causing distress to the patient, unrelieved pain could delay healing owing to stress-related problems. Thus, pain needs to be treated as early as possible after injury. It was hypothesised that local treatment of wounds with appropriate analgesic drugs could attenuate pain. HOE 140, a bradykinin receptor antagonist, reduced acute inflammatory pain in rats after intrawound administration. In this study, the analgesic effect of dimethylsulphoxide (DMSO) was investigated in a similar hind-paw incision model in rats. An extremely small quantity (10 µl) of 100% DMSO was administered into the incision site just before closure of the wound. It persistently attenuated guarding behaviour in rats over a period of 3 days without affecting thermal hyperalgesia or allodynia. Accumulated evidence indicates that guarding is equivalent to pain at rest in humans. The possible mechanisms of the analgesic effect could be inhibition of C group of peripheral nerve fibres or even free radical scavenging. Healing of the wound was found to be normal at the end of the study period. In conclusion, DMSO could be useful in the treatment of acute pain resulting from tissue injuries such as burns.

Rare diseases and expensive drugs.

Immunologists/allergists are a physician group that is familiar with caring for patients with rare diseases. Conditions that come under the umbrella of our specialty include various primary immunodeficiency diseases, mast cell disorders, various autoinflammatory and of the complement cascade including Hereditary Angioedema (HAE). A rare or disease is defined by the Europeans as that which occurs in 5 people per 10,000 population. There are 6,000-8,000 known rare with this number growing annually following new discoveries; 5-8% of the population will be affected by a rare disease, 80% of which have a genetic component. While these have a low prevalence, they have a high degree of complexity in either their diagnosis, their management or both. Most are life-threatening or are chronically debilitating. For the individual, these carry special challenges; little is known about them; there is difficulty finding specialists who are knowledgeable; there are very few specific treatments available and when they are, they are very expensive and thus out of reach of the majority of patients. HAE is one rare disease that has received a lot more attention in recent years, mainly because of the registration and marketing of new agents with which to manage the condition. HAE is a rare autosomal dominant disorder with an estimated prevalence of 1:50,000 that has been described in 3 forms; types 1, 2, and 3. Types 1 and 2 result from deficiency in functional C1 inhibitor (C1 INH), either from low absolute levels or production of a dysfunctional protein. In the absence of adequate levels of C1 INH, subcutaneous and submucosal oedema result from the uninhibited action of vasoactive mediators, of which bradykinin is considered the most important. HAE is characterised by recurrent oedema of the limbs, trunk, face, abdomen and sometimes genitals without urticaria, typically taking 24 hours to peak and resolving over 48-72 hours. The most serious manifestation is laryngeal swelling, which was reported in older cohort studies to result in fatal asphyxiation in up to a third of patients. Caring for patients with this condition within Asia Pacific countries poses special challenges. We have no accurate data on patient numbers in individual countries; patients face many obstacles with gaining an accurate diagnosis because of lack of recognition of the condition and, in many countries, lack of access to specific tests. There is stigma attached to the distortion of facial features that occurs with swelling attacks and there is a significant impact on quality of life and physical functioning among those with frequent attacks. A number of treatments for HAE are now available including replacement treatments and pharmacological treatments such as a bradykinin receptor antagonist and kallikrein inhibitor. Drugs for orphan diseases are particularly difficult and expensive to develop and have a high price tag when they eventually come to market as the pharmaceutical companies attempt to regain the costs of their investments. No individual patient is able to bear the cost of indefinite treatment so they will require a governmental approach to funding such treatments. Bearing the costs of expensive treatments for a very small number of individuals is particularly problematic in countries where there remain major public health issues with communicable where the investment of similar amounts of money required for a single patient's treatment would see large scale immunisation programmes completed. However all patients have a legitimate expectation of treatment whether their condition is common or rare. Our societies need to find solutions that allow access to high cost drugs for rare while not impeding funding for the very common communicable and noncommunicable and for public health programmes that benefit much larger numbers of the population. Ideally, pharmaceutical companies who discover and develop treatments for rare need to be part of the solution that allows access to these drugs. Some see development of drugs as part of their research effort and contribution to the greater good; others may enter cost sharing agreements with various governmental funding bodies. With rare diseases, there are only a small number of patients available for clinical trials so by necessity there are significant limitations on the number of studies that are performed. This poses difficulties when attempts are made to register new products. Government agencies can assist by facilitating and simplifying the registration process for drugs. Sharing assessments for marketing authorisation would relieve some of the financial burden pharmaceutical companies face in the registration process. Professional bodies such as the Asia Pacific Association of Allergy, Asthma and Clinical Immunology have a duty to critically evaluate the various guidelines for management and find the most acceptable recommendations for their own constituents. These may vary from what is considered best practice in the United States or Europe but may better meet the needs of our patients while balancing this against the pressures on the health dollar in countries where communicable still extract a huge toll.

Angiotensin-converting Enzyme Inhibitor-induced Angioedema – A Dangerous New Epidemic

Angioedema is a sudden localised and often asymmetric swelling of the skin or mucous membranes caused by transient increased endothelial permeability causing plasma extravasation. In the last decades the incidence of severe angioedema involving the upper airways and even fatal outcome due to asphyxia has increased. This is mainly due to pharmaceuticals such as angiotensin converting enzyme-inhibitors, which are extensively used worldwide. Some aspects of the pathophysiology have been elucidated and the vasoactive molecule bradykinin is shown to be one of the main causative agents. The diagnosis is often delayed and traditional treatment usually ineffective. Complement C1 inhibitor concentrate and bradykinin receptor antagonists, normally used to treat patients with hereditary angioedema, have shown good results when used in patients with bradykinin-mediated angioedema. This review discusses the disease, prognosis and treatment options.

Interaction of Bradykinin and B2Bradykinin Receptor Antagonists with Colloidal Au Surface Explored by Surface-Enhanced Raman Scattering

Bradykinin (BK), an endogenous peptide hormone, which is involved in a number of physiological and pathophysiological processes, and the potent B2bradykinin receptor antagonists, [D-Arg0,Hyp3,Thi5,8,L-Pip7]BK, Aaa[D-Arg0,Hyp3,Thi5,8,L-Pip7]BK, [D-Arg0,Hyp3,Thi5,D-Phe7,L-Pip8]BK, and Aaa[D-Arg0,Hyp3,Thi5,D-Phe7,L-Pip8]BK, were deposited onto colloidal Au particles of 20 nm size. Interaction of these molecules with colloidal Au surface was explored by surface-enhanced Raman scattering (SERS). Briefly, it was shown that BK adsorbs on the Au surface mainly through the Phe5/Phe8residues. In case of the BK specifically modified analogues mainly the Pip and Thi rings are involved in the interaction process; however, Pip and Thi adopt slightly different orientation with respect to Au for each of the analogues. In addition, the lack of the Aaa vibrations, together with the enhancement of the Thi, Pip, or Phe modes, emphasizes the importance of theC-terminus in the interaction with the Au surface.

Basic and clinical aspects of bradykinin receptor antagonists.

Bradykinin and related kinins may act on two types of receptors designated as B1 and B2. It seems that the B2 receptors are most commonly found in various vascular and non-vascular smooth muscles, whereas B1 receptors are formed in vitro during trauma, and injury, and are found in bone tissues. These bradykinin (BK) receptors are involved in the regulation of various physiological and pathological processes. The mode of kinin actions are based upon the interactions between the kinin and their specific receptors, which can lead to activation of several second-messenger systems. Recently, numerous BK receptor antagonists have been synthesized with prime aim to treat diseases caused by excessive kinin production. These diseases are rheumatoid arthritis (RA), inflammatory diseases of the bowel, asthma, rhinitis and sore throat, allergic reactions, pain, inflammatory skin disorders, endotoxic and anaphylactic shock and coronary heart diseases. On the other hand, BK receptor antagonists could be contraindicated in hypertension, since these drugs may antagonize the antihypertensive therapy and/ or may trigger the hypertensive crisis. It is worth suggesting that the BK receptor agonists might be useful antihypertensive drugs.

Bradykinin Antagonist Counteracts the Acute Effect of Both Angiotensin-Converting Enzyme Inhibition and of Angiotensin Receptor Blockade on the Lower Limit of Autoregulation of Cerebral Blood Flow

The lower limit of autoregulation of cerebral blood flow (CBF) can be modulated with both angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB). The influence of bradykinin antagonism on ARB-induced changes was the subject of this study. CBF was measured in Sprague-Dawley rats with laser Doppler technique. The blood pressure was lowered by controlled bleeding. Six groups of rats were studied: a control group and five groups given drugs intravenously: an ACE inhibitor (enalaprilat), an ARB (candesartan), a bradykinin-2 receptor antagonist (Hoe 140), a combination of enalaprilat and Hoe 140, and a combination of candesartan and Hoe 140. In the control group, the lower limit of CBF autoregulation was 54±9 mm Hg (mean±s.d.), with enalaprilat it was 46±6, with candesartan 39±8, with Hoe 140 53±6, with enalaprilat/Hoe 140 52±6, and with candesartan/Hoe 140 50±7. Both enalaprilat and candesartan lowered the lower limit of autoregulation of CBF significantly. The bradykinin antagonist abolished not only the effect of the ACE inhibitor but surprisingly also the effect of the ARB on the lower limit of CBF autoregulation, the latter suggesting an effect on intravascular bradykinin.

ACE inhibition enhances bradykinin relaxations through nitric oxide and B1 receptor activation in bovine coronary arteries.

Bradykinin causes vascular relaxations through release of endothelial relaxing factors including prostacyclin, nitric oxide (NO) and epoxyeicosatrienoic acids (EETs). Bradykinin is metabolized by angiotensin converting enzyme (ACE) and ACE inhibition enhances bradykinin relaxations. Our goal was to characterize the role of bradykinin receptors and endothelial factors in ACE inhibitor-enhanced relaxations in bovine coronary arteries. In U46619 preconstricted arteries, bradykinin (10-11-10-8m) caused concentration-dependent relaxations (maximal relaxation ≥100%, log EC50=-9.8±0.1). In the presence of the NO synthase inhibitor, N-nitro-L-arginine (L-NA, 30 μm) and the cyclooxygenase inhibitor, indomethacin (10 μm), relaxations were reduced by an inhibitor of EET synthesis, miconazole (10 μm) (maximal relaxation=55±10%). Bradykinin relaxations were inhibited by the bradykinin 2 (B2) receptor antagonist, D-Arg0-Hyp3-Thi5,8-D-Phe7-bradykinin (1 μm) (log EC50=-8.5±0.1) but not altered by the B1 receptor antagonist, des-Arg9[Leu8]bradykinin (1 μm). Mass spectrometric analysis of bovine coronary artery bradykinin metabolites revealed a time-dependent increase in bradykinin (1-5) and (1-7) suggesting metabolism by ACE. ACE inhibition with captopril (50 μm) enhanced bradykinin relaxations (log EC50=-10.3±0.1). The enhanced relaxations were eliminated by L-NA or the B1 receptor antagonist but not the B2 receptor antagonist. Our results demonstrate that ACE inhibitor-enhanced bradykinin relaxations of bovine coronary arteries occur through endothelial cell B1 receptor activation and NO.

Therapeutic management of hereditary angioedema due to C1 inhibitor deficiency

Hereditary angioedema (HAE) due to C1 inhibitor (C1-INH) deficiency is a rare genetic disease characterized by recurrent swellings of the subcutaneous and submucosal tissues that can manifest as cutaneous edema, abdominal pain and laryngeal edema with airway obstruction. These symptoms have a significant impact on patients’ quality of life. The reduction in C1-INH function leads to uncontrolled activation of the contact system and generation of bradykinin, the mediator of increased vascular permeability and edema formation. In the past, few treatment options were available; however, several new therapies with proven efficacy have recently become available to treat and prevent HAE attacks, such as plasma-derived and recombinant C1-INHs that replace the deficient protein, bradykinin receptor antagonist (icatibant) that blocks bradykinin activity and kallikrein inhibitor (ecallantide) that prevents bradykinin release. Such therapies can improve disease outcome. This article reviews the therapeutic management of HAE, which involves the treatment of acute attacks and prophylaxis.

New horizons in osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis worldwide and rapidly increasing with ageing populations. It is a major source of pain and disability for individuals and economic burden for health economies. Modern imaging, in particular magnetic resonance imaging (MRI), has helped us to understand that OA is a dynamic remodelling process involving all the structures within the joint. Inflammation is common in OA, with a high prevalence of synovitis seen on imaging, and this has been associated with joint pain. MRI detected changes within the subchondral bone are also common and associated with pain and structural progression. Targeting individual pathologies may offer potential new therapeutic options for OA; this is particularly important given the current treatments are often limited by side effects or lack of efficacy. New approaches to understanding the pathology and pain pathways in OA offer hope of novel analgesic options, for example, monoclonal antibodies against nerve growth factor and centrally acting drugs such as duloxetine, tapentadol and bradykinin receptor antagonists have all recently undergone trials in OA. While treatment for OA has until now relied on symptom management, for the first time, recent trials suggest that structure modification may be possible by treating the subchondral bone.

Bradykinin 2 receptor blockade attenuates the responses of group III afferents to contraction in decerebrate cats

Exercise‐induced stimulation of group III and IV muscle afferents raises blood pressure, heart rate, and ventilation. Bradykinin has been shown to stimulate and sensitize group III and IV afferents, but the effect of bradykinin 2 (B2) receptor blockade on the responses of group III afferents during exercise was unknown. Using decerebrate cats, we examined the effect of carotid arterial injections of the B2 receptor antagonist, HOE‐140 (40 μg/kg) on the responses of group III afferents (conduction velocity range: 2.8 – 26.2 m/s; mean: 16.1 ± 2.3 m/s) to both 45 second intermittent and static contraction. Before HOE‐140, static contraction increased the impulse activity of ten group III afferents from 0.3 ± 0.1 imp/s at rest to 6.7 ± 3.0 imp/s during contraction (p<0.05). After HOE‐140, impulse activity went from 0.7 ± 0.3 imp/s at rest to 2.9 ± 1.2 imp/s during contraction (p>;0.05). There was a similar trend during intermittent contraction. Before HOE‐140, intermittent contraction increased the activity of seven group III afferents from 0.2 ± 0.04 imp/s at rest to 9.1 ± 5.2 imp/s during contraction (p>;0.05). After HOE‐140, impulse activity increased from 0.5 ± 0.2 imp/s at rest to 4.0 ± 2.3 imp/s during contraction (p>;0.05). Our data suggests B2 receptors contribute to group III afferent impulse activity during exercise.

PsT-1: A new tryptophyllin peptide from the skin secretion of Waxy Monkey Leaf Frog, Phyllomedusa sauvagei

The Waxy Monkey Leaf Frog, Phyllomedusa sauvagei, has been extensively-studied for many years, and a broad spectrum of bioactive peptides has been found in its skin secretions. Here we report the discovery of a novel tryptophyllin (TPH) peptide, named PsT-1, from this frog species. Skin secretions from specimens of P. sauvagei were collected by mild electrical stimulation. Peptides were identified and characterized by transcriptome cloning, and the structure was confirmed by MALDI-TOF mass spectrometry and automated Edman degradation. This novel peptide was encoded by a single precursor of 61 amino acid residues, whose primary structure was deduced from cloned skin cDNA. Analysis of different amphibian tryptophyllins revealed that PsT-1 exhibited a high degree of primary structural similarity to its homologs, PdT-1 and PdT-2, from the Mexican giant leaf frog, Pachymedusa dacnicolor. A synthetic replicate of PsT-1 was found to inhibit bradykinin-induced vasorelaxation of phenylephrine pre-constricted rat tail artery smooth muscle. It was also found that PsT-1 had an anti-proliferative effect on three different human prostate cancer cell lines (LNCaP/PC3/DU145), by use of an MTT assay coupled with direct cell counting as measures of cell growth. These data indicate that PsT-1 is a likely bradykinin receptor antagonist and its biological effects are probably mediated through bradykinin receptors. As a BK antagonist, PST-1, with antagonistic effects on BK in artery smooth muscle, inhibition of proliferation in prostate cancer cells and lack of undesirable side effects, may have potential in cardiovascular, inflammatory and anticancer therapy.