New aspects on the role of kinins in neurogenic inflammation

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.

Peripheral denervation participates in heterotopic ossification in a spinal cord injury model

We previously reported the development of a new acquired neurogenic HO (NHO) mouse model, combining spinal cord transection (SCI) and chemical muscle injury. Pathological mechanisms responsible for ectopic osteogenesis after central neurological damage are still to be elucidated. In this study, we first hypothesized that peripheral nervous system (PNS) might convey pathological signals from injured spinal cord to muscles in NHO mouse model. Secondly, we sought to determine whether SCI could lead to intramuscular modifications of BMP2 signaling pathways. Twenty one C57Bl6 mice were included in this protocol. Bilateral cardiotoxin (CTX) injection in hamstring muscles was associated with a two-stage surgical procedure, combining thoracic SCI with unilateral peripheral denervation. Volumes of HO (Bone Volume, BV) were measured 28 days after surgery using micro-computed tomography imaging techniques and histological analyses were made to confirm intramuscular osteogenesis. Volume comparisons were conducted between right and left hind limb of each animal, using a Wilcoxon signed rank test. Quantitative polymerase chain reaction (qPCR) was performed to explore intra muscular expression of BMP2, Alk3 and Id1. Nineteen mice survive the complete SCI and peripheral denervation procedure. When CTX injections were done right after surgery (n = 7), bilateral HO were detected in all animals after 28 days. Micro-CT measurements showed significantly increased BV in denervated paws (1.47 mm3 +/- 0.5) compared to contralateral sides (0.56 mm3 +/-0.4), p = 0.03. When peripheral denervation and CTX injections were performed after sham SCI surgery (n = 6), bilateral HO were present in three mice at day 28. Quantitative PCR analyses showed no changes in intra muscular BMP2 expression after SCI as compared to control mice (shamSCI). Peripheral denervation can be reliably added to spinal cord transection in NHO mouse model. This new experimental design confirms that neuro inflammatory mechanisms induced by central or peripheral nervous system injury plays a key role in triggering ectopic osteogenesis.

Neurogenic inflammation after traumatic brain injury and its potentiation of classical inflammation

Background

The neuroinflammatory response following traumatic brain injury (TBI) is known to be a key secondary injury factor that can drive ongoing neuronal injury. Despite this, treatments that have targeted aspects of the inflammatory pathway have not shown significant efficacy in clinical trials.

Main body

We suggest that this may be because classical inflammation only represents part of the story, with activation of neurogenic inflammation potentially one of the key initiating inflammatory events following TBI. Indeed, evidence suggests that the transient receptor potential cation channels (TRP channels), TRPV1 and TRPA1, are polymodal receptors that are activated by a variety of stimuli associated with TBI, including mechanical shear stress, leading to the release of neuropeptides such as substance P (SP). SP augments many aspects of the classical inflammatory response via activation of microglia and astrocytes, degranulation of mast cells, and promoting leukocyte migration. Furthermore, SP may initiate the earliest changes seen in blood-brain barrier (BBB) permeability, namely the increased transcellular transport of plasma proteins via activation of caveolae. This is in line with reports that alterations in transcellular transport are seen first following TBI, prior to decreases in expression of tight-junction proteins such as claudin-5 and occludin. Indeed, the receptor for SP, the tachykinin NK1 receptor, is found in caveolae and its activation following TBI may allow influx of albumin and other plasma proteins which directly augment the inflammatory response by activating astrocytes and microglia.

Conclusions

As such, the neurogenic inflammatory response can exacerbate classical inflammation via a positive feedback loop, with classical inflammatory mediators such as bradykinin and prostaglandins then further stimulating TRP receptors. Accordingly, complete inhibition of neuroinflammation following TBI may require the inhibition of both classical and neurogenic inflammatory pathways.

Improved fracture healing in patients with concomitant traumatic brain injury: proven or not?

Over the last 3 decades, scientific evidence advocates an association between traumatic brain injury (TBI) and accelerated fracture healing. Multiple clinical and preclinical studies have shown an enhanced callus formation and an increased callus volume in patients, respectively, rats with concomitant TBI. Over time, different substances (cytokines, hormones, etc.) were in focus to elucidate the relationship between TBI and fracture healing. Until now, the mechanism behind this relationship is not fully clarified and a consensus on which substance plays the key role could not be attained in the literature. In this review, we will give an overview of current concepts and opinions on this topic published in the last decade and both clinical and pathophysiological theories will be discussed.

Substance P mRNA expression during zebrafish development: influence of mu opioid receptor and cocaine

Zebrafish has emerged as an important vertebrate animal model for the study of human diseases and for developmental studies in mammals. Since there are few studies of the tachykinin 1 gene (TAC1), precursor of substance P (SP), in relation to embryonic development, we aimed to study the expression of SP transcript (mRNA) and determine the influence of cocaine and opioid receptors on the expression of this neuropeptide. In order to analyse the spatial and temporal SP mRNA expression in zebrafish, we cloned - based on human TAC1 sequence - the sequence that originates SP. Phylogenetic analyses of the precursor of SP, revealed an alignment in the fish cluster, with a clear distinction from other species (amphibians, birds and mammals). Real time PCR (qPCR) results showed that SP mRNA was expressed in several stages of embryonic development, where it increased progressively from gastrula-8hpf (hour post-fertilisation) to the end of the embryogenesis-72hpf. SP mRNA was expressed mainly in the spinal cord in embryos at 20-30hpf, whereas at 36, 42 and 48hpf embryos SP mRNA was expressed mainly in the CNS telencephalon, diencephalon, hypothalamus, rhombomeres, epiphysis and in peripheral areas (heart and somites). Exposure of embryos to 1.5μM cocaine altered the SP mRNA expression at 24 (increasing) and 48hpf (decreasing). We also report that knockdown of μ-opioid receptor induced an increase of SP mRNA expression while the knockdown of the two delta opioid receptors did not produce changes in SP mRNA expression. In conclusion, SP mRNA in zebrafish is expressed during embryonic development in the CNS and peripherally, suggesting that SP would play a critical role during embryogenesis. Furthermore, cocaine exposure and the knockdown of μ-opioid receptor affect the SP mRNA expression. These observations can be important in the pain and addiction field where SP is involved.

Mitochondria in traumatic brain injury and mitochondrial-targeted multipotential therapeutic strategies

Traumatic brain injury (TBI) is a major health and socioeconomic problem throughout the world. It is a complicated pathological process that consists of primary insults and a secondary insult characterized by a set of biochemical cascades. The imbalance between a higher energy demand for repair of cell damage and decreased energy production led by mitochondrial dysfunction aggravates cell damage. At the cellular level, the main cause of the secondary deleterious cascades is cell damage that is centred in the mitochondria. Excitotoxicity, Ca(2+) overload, reactive oxygen species (ROS), Bcl-2 family, caspases and apoptosis inducing factor (AIF) are the main participants in mitochondria-centred cell damage following TBI. Some preclinical and clinical results of mitochondria-targeted therapy show promise. Mitochondria- targeted multipotential therapeutic strategies offer new hope for the successful treatment of TBI and other acute brain injuries.

Transient receptor potential ankyrin 1 channel localized to non-neuronal airway cells promotes non-neurogenic inflammation

Background

The transient receptor potential ankyrin 1 (TRPA1) channel, localized to airway sensory nerves, has been proposed to mediate airway inflammation evoked by allergen and cigarette smoke (CS) in rodents, via a neurogenic mechanism. However the limited clinical evidence for the role of neurogenic inflammation in asthma or chronic obstructive pulmonary disease raises an alternative possibility that airway inflammation is promoted by non-neuronal TRPA1.

Methodology/Principal Findings

By using Real-Time PCR and calcium imaging, we found that cultured human airway cells, including fibroblasts, epithelial and smooth muscle cells express functional TRPA1 channels. By using immunohistochemistry, TRPA1 staining was observed in airway epithelial and smooth muscle cells in sections taken from human airways and lung, and from airways and lung of wild-type, but not TRPA1-deficient mice. In cultured human airway epithelial and smooth muscle cells and fibroblasts, acrolein and CS extract evoked IL-8 release, a response selectively reduced by TRPA1 antagonists. Capsaicin, agonist of the transient receptor potential vanilloid 1 (TRPV1), a channel co-expressed with TRPA1 by airway sensory nerves, and acrolein or CS (TRPA1 agonists), or the neuropeptide substance P (SP), which is released from sensory nerve terminals by capsaicin, acrolein or CS), produced neurogenic inflammation in mouse airways. However, only acrolein and CS, but not capsaicin or SP, released the keratinocyte chemoattractant (CXCL-1/KC, IL-8 analogue) in bronchoalveolar lavage (BAL) fluid of wild-type mice. This effect of TRPA1 agonists was attenuated by TRPA1 antagonism or in TRPA1-deficient mice, but not by pharmacological ablation of sensory nerves.

Conclusions

Our results demonstrate that, although either TRPV1 or TRPA1 activation causes airway neurogenic inflammation, solely TRPA1 activation orchestrates an additional inflammatory response which is not neurogenic. This finding suggests that non-neuronal TRPA1 in the airways is functional and potentially capable of contributing to inflammatory airway diseases.

Mechanisms of cerebral edema in traumatic brain injury: therapeutic developments

PURPOSE OF REVIEW

Although a number of factors contribute to the high mortality and morbidity associated with traumatic brain injury (TBI), the development of cerebral edema with brain swelling remains the most significant predictor of outcome. The present review summarizes the most recent advances in the understanding of mechanisms associated with development of posttraumatic cerebral edema, and highlights areas of therapeutic promise.

RECENT FINDINGS

Despite the predominance of cytotoxic (or cellular) edema in the first week after traumatic brain injury, brain swelling can only occur with addition of water to the cranial vault from the vasculature. As such, regulation of blood-brain barrier permeability has become a focus of recent research seeking to manage brain edema. Aquaporins, matrix metalloproteinases and vasoactive inflammatory agents have emerged as potential mediators of cerebral edema following traumatic brain injury. In particular, kinins (bradykinins) and tachykinins (substance P) seem to play an active physiological role in modulating blood-brain barrier permeability after trauma. Substance P neurokinin-1 receptor antagonists show particular promise as novel therapeutic agents.

SUMMARY

Attenuating blood-brain barrier permeability has become a promising approach to managing brain edema and associated swelling given that increases in cranial water content can only be derived from the vasculature. Inflammation, both classical and neurogenic, offers a number of attractive targets.

Substance P antagonists as a therapeutic approach to improving outcome following traumatic brain injury

Although a number of secondary injury factors are known to contribute to the development of morphological injury and functional deficits following traumatic brain injury, accumulating evidence has suggested that neuropeptides, and in particular substance P, may play a critical role. Substance P is released early following acute injury to the CNS as part of a neurogenic inflammatory response. In so doing, it facilitates an increase in the permeability of the blood-brain barrier and the development of vasogenic edema. At the cellular level, substance P has been shown to directly result in neuronal cell death; functionally, substance P has been implicated in learning and memory, mood and anxiety, stress mechanisms, emotion-processing, migraine, emesis, pain, and seizures, all of which may be adversely affected after brain injury. Inhibition of post-traumatic substance P activity, either by preventing release or by antagonism of the neurokinin-1 receptor, has consistently resulted in a profound decrease in development of edema and marked improvements in functional outcome. This review summarizes the current evidence supporting a role for substance P in acute brain injury.

The role of Transient Receptor Potential Vanilloid 1 (TRPV1) channels in pancreatitis

Premature activation of digestive enzymes within the pancreas which leads to autodigestion of the gland is an early step in the pathogenesis of pancreatitis. Pancreatic injury is followed by other manifestations of inflammation including plasma extravasation, edema, and neutrophil infiltration which constitute the features of pancreatitis. Recent studies indicate that neural innervation of the pancreas may play an important role in the initiation and maintenance of the inflammatory response to injury. The pancreas is innervated by vagal, sympathetic and parasympathetic neurons, as well as sensory neurons. Activation of pancreatic primary sensory neurons causes the release of inflammatory neuropeptides both in the spinal cord to signal pain and in the pancreas itself where they produce plasma extravasation and neutrophil infiltration. Recent studies indicate that primary sensory neurons of the pancreas express transient receptor potential V1 (TRPV1) channels whose activation induces pancreatic inflammation. Moreover, blockade of these TRP channels significantly ameliorates experimental pancreatitis. This review describes our current understanding of the role of TRPV1 channels in pancreatitis and illustrates how this mechanism might be used to direct future treatments of pancreatic diseases.

Substance P in traumatic brain injury

Recent evidence has suggested that neuropeptides, and in particular substance P (SP), may play a critical role in the development of morphological injury and functional deficits following acute insults to the brain. Few studies, however, have examined the role of SP, and more generally, neurogenic inflammation, in the pathophysiology of traumatic brain injury and stroke. Those studies that have been reported suggest that SP is released following injury to the CNS and facilitates the increased permeability of the blood brain barrier, the development of vasogenic edema and the subsequent cell death and functional deficits that are associated with these events. Inhibition of the SP activity, either through inhibition of the neuropeptide release or the use of SP receptor antagonists, have consistently resulted in profound decreases in edema formation and marked improvements in functional outcome. The current review summarizes the role of SP in acute brain injury, focussing on its properties as a neurotransmitter and the potential for SP to adversely affect outcome.

Stress and the inflammatory response: a review of neurogenic inflammation

The subject of neuroinflammation is reviewed. In response to psychological stress or certain physical stressors, an inflammatory process may occur by release of neuropeptides, especially Substance P (SP), or other inflammatory mediators, from sensory nerves and the activation of mast cells or other inflammatory cells. Central neuropeptides, particularly corticosteroid releasing factor (CRF), and perhaps SP as well, initiate a systemic stress response by activation of neuroendocrinological pathways such as the sympathetic nervous system, hypothalamic pituitary axis, and the renin angiotensin system, with the release of the stress hormones (i.e., catecholamines, corticosteroids, growth hormone, glucagons, and renin). These, together with cytokines induced by stress, initiate the acute phase response (APR) and the induction of acute phase proteins, essential mediators of inflammation. Central nervous system norepinephrine may also induce the APR perhaps by macrophage activation and cytokine release. The increase in lipids with stress may also be a factor in macrophage activation, as may lipopolysaccharide which, I postulate, induces cytokines from hepatic Kupffer cells, subsequent to an enhanced absorption from the gastrointestinal tract during psychologic stress. The brain may initiate or inhibit the inflammatory process. The inflammatory response is contained within the psychological stress response which evolved later. Moreover, the same neuropeptides (i.e., CRF and possibly SP as well) mediate both stress and inflammation. Cytokines evoked by either a stress or inflammatory response may utilize similar somatosensory pathways to signal the brain. Other instances whereby stress may induce inflammatory changes are reviewed. I postulate that repeated episodes of acute or chronic psychogenic stress may produce chronic inflammatory changes which may result in atherosclerosis in the arteries or chronic inflammatory changes in other organs as well.

Biphenyl derivatives as novel dual NK(1)/NK(2)-receptor antagonists

In a continuation of our efforts to simplify the structure of our neurokinin antagonists, a series of substituted biphenyl derivatives has been prepared. Several compounds exhibit potent affinities for both the NK(1) receptor (<10nM) and for the NK(2) receptor (<50 nM). Details on the design, synthesis, biological activities, SAR and conformational analysis of this new class of dual NK(1)/NK(2) receptor antagonists are presented.

Dual neurokinin NK(1)/NK(2) antagonists: N-[(R,R)-(E)-1-arylmethyl-3-(2-oxo-azepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamides and 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-arylmethyl-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamides

Based on the structure of N-[(R,R)-(E)-1-(4-chlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (1), attempts to improve the NK(2) affinity have resulted in the discovery of N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (9, DNK333) exhibiting a 5-fold improved affinity to the NK(2) receptor in comparison to 1. Simplification of the structure via elimination of a chiral centre led to 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-(3,4-dichlorobenzyl)-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamide (22), a potent and fairly balanced NK(1)/NK(2) antagonist.

Role of bradykinin and tachykinins in the potentiation by enalapril of coughing induced by citric acid in pigs

Angiotensin-converting enzyme (ACE) inhibitors are among the first-choice drugs for treating hypertension and congestive heart disease. It has been reported, however, that these drugs could induce chronic cough and airway hyperresponsiveness. The aim of this work was to assess in pigs the effects of bradykinin and tachykinins on citric-acid-induced coughing after ACE inhibitor pretreatment. Coughing was induced by challenging pigs with an aerosol of 0.8 M citric acid over 15 min. Coughs were counted by a trained observer for 30 min. The animals underwent two cough induction tests two days apart (days 1 and 3), the first being taken as a control. All drugs were injected intravenously 30 min before the second challenge. In the control group, no difference was observed between days 1 and 3. The ACE inhibitor enalapril (7.5 and 15 microg/kg) caused the cough frequency to increase significantly. In contrast, a dose-related decrease was observed with Hoe140 (icatibant), a bradykinin B2 receptor antagonist (0.5 and 1 mg/kg). When both drugs were administered simultaneously (15 microg/kg for enalapril and 1 mg/kg for Hoe140), a significant increase was observed as compared with the control value obtained on day 1. When enalapril was combined with the three tachykinin receptor antagonists SR 140333 (NK1 receptor antagonist), SR 48968 (NK2 receptor antagonist) and SR 142801 (NK3 receptor antagonist), a significant decrease was observed as compared with control value obtained on day 1; the percentage of variation was also significantly different as compared with those observed in enalapril groups at both doses. These data suggest that ACE-inhibitor-induced enhancement of the cough reflex is mainly due to tachykinins and not to bradykinin in our pig model. Bradykinin, however, plays a major role in coughing induced by citric acid alone.

Neurokinin mediation of edema and inflammation

The aim of this article is to furnish a brief review of the role played by neurokinins in the inflammatory process. Further attention is given to the mechanisms, as well as to the receptor subtypes involved in neurokinin-mediated inflammation, in an attempt to clarify the participation of neurokinins in different models of acute and chronic inflammation. The involvement of SP, NKA and NKB is also examined in relation to the major signs of inflammation, including edema formation, protein plasma extravasation and vasodilatation. Finally, we provide a general overview on the potential clinical applications of neurokinin antagonists, along with the involvement of neurokinins in human diseases.

Analysis of the inflammatory response induced by substance P in the mouse pleural cavity

This study analyzes both cell migration and exudation responses elicited by substance P (SP) in the mouse pleural cavity. SP caused, 4 h after its administration into the mouse pleural cavity, a dose-related recruitment of leukocytes (ED50 = 14.2 nmol), mainly due to mononuclears. Leukocytes peaked between 2 and 4 h, being followed by a slight decay that remained elevated for up to 24 h. Exudation, although small, was significantly elevated from 2 to 96 h after. NK1 (FK 888) or NK3 (SR 142801), but not NK2 (SR 48968) tachykinin receptor antagonists, significantly inhibited cell migration. HOE 140 and NPC 17731, bradykinin B2 receptor antagonists, caused graded inhibition of cell influx (ID50s of 0.03 and 0.04 pmol), but des-Arg9-Leu8-BK, B1 receptor antagonist, had no effect. The nitric oxide inhibitors L-NOARG and L-NAME, but not D-NAME, significantly inhibited SP-induced pleurisy. Pretreatment of the animals with indomethacin, dexamethasone, terfenadine, theophylline or salbutamol produced significant inhibition of the inflammatory parameters, whereas cromolyn only inhibited exudation. These results indicate that intrapleural injection of SP in mice elicit a long-lasting inflammatory reaction that is characterized by the participation of nitric oxide, kinins, cyclooxygenase metabolites and histamine. Antiasthmatic drugs such as theophylline, salbutamol, dexamethasone, and, to a lesser extent cromolyn, also markedly inhibit this inflammatory reaction. These results provide clear evidence supporting the role played by SP in neurogenic inflammation.

Pro-inflammatory effects induced by bradykinin in a murine model of pleurisy

Bradykinin caused a dose-related increase in cell influx 4 h after its administration into the mouse pleural cavity (ED50 = 3.2 nmol/cav., 95% confidence limits = 0.6-15.5). Cell influx peaked at 4 h and remained elevated for up to 72 h, whereas exudation was detected between 2 and 6 h after bradykinin administration. Both HOE 140 (D-Arg-[Hyp3,Thi5,D-Tic7, Oic8]bradykinin) and NPC 17731 (D-Arg0-[Hyp3 D-HypE(transpropyl7)Oic8]bradykinin) inhibited bradykinin-induced cell influx (ID50 0.028 (0.05-0.16) and 0.4 (0.3-0.7) pmol/cav., respectively). Des-Arg9-[Leu8]bradykinin (0.1 and 3.0 nmol/cav., 30 min before) did not inhibit the effects of bradykinin. Pre-treatment of animals with either indomethacin, terfenadine, dexamethasone, N(omega)-nitro-L-arginine benzyl ester, cromolyn, theophylline, salbutamol, FK 888 (N2-[(4R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl-L-propyl]N-met hyl-N-phenyl-methyl-3-(2-naphthyl)-L-alaninamide) or SR 142801 ((N)-(1-[3-[1-benzoyl-3-(3,4-dichloro-phenyl)-piperidin-3-yl]pr opy l]-4-phenyl-piperidin-4-yl)-N-methyl-acetamide) significantly inhibited cell migration (P < 0.01). These results indicate that bradykinin had a significant pro-inflammatory effect on the pleural cavity of the mice. This effect seems to be primarily mediated via activation bradykinin B2 receptors which trigger the release of other mediators.

Effects of FR173657, a non-peptide B2 antagonist, on kinin-induced hypotension, visceral and peripheral oedema formation and bronchoconstriction

1. Kinins are believed to play a key role in many inflammatory conditions. Therefore, bradykinin antagonists are being developed for potential therapeutic applications. In the present investigation we describe the pharmacology, in vivo, of (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[2-methyl-8-quinoliny l) oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide (FR173657), a novel, non-peptide bradykinin antagonist. 2. The hypotensive effects of i.v. injections of bradykinin (50 pmol) in captopril-pre-treated anaesthetized rats were significantly inhibited by 100 nmol kg-1 FR173657 s.c., and completely abolished by 300 nmol kg-1. The full inhibitory effect developed within 60 min and remained unchanged for at least 4 h. However, the effect was reversible, since 24 h after an injection of 300 nmol kg-1 FR173657 no inhibitory effect could be observed. 3. The plasma protein extravasation into the pancreas and duodenum induced by an i.v. infusion of bradykinin (11 nmol kg-1 within 20 min) in captopril-treated anaesthetized rats was completely abolished by FR173657 at doses of 30 nmol kg-1 s.c. and above, given 60 min before bradykinin. FR173657 3 nmol kg-1 was ineffective, while a dose of 10 nmol kg-1 produced an intermediate effect. 4. The paw oedema induced by the subplantar injection of bradykinin (30 nmol) in anaesthetized rats was inhibited slightly by s.c. injection of FR173657 0.3 mumol kg-1, whereas 1 and 3 mumol kg-1 produced significant inhibition of the bradykinin-induced oedema. The maximum inhibition amounted to about 50% and could not be increased even when the dose of FR173657 was increased to 30 mumol kg-1. FR173657 did not effect the oedema caused by histamine or 5-hydroxytryptamine. 5. Bradykinin (20 nmol kg-1, i.v.) caused increases in pulmonary inflation pressure by 300-600 Pa in anaesthetized, respirated guinea-pigs. The effect was reduced to 58 +/- 9% of the initial value 60 min after the s.c. injection of FR173657 1 mumol kg-1, whereas only 9 +/- 7% remained after 10 mumol kg-1. The bronchoconstrictor actions of histamine remained unaffected by FR173657. 6. In summary, FR173657 is a highly potent and selective bradykinin antagonist. The inhibitory action in vivo lasts for longer than 4 h but is fully reversible. FR173657, or similar compounds, will be a useful tool for the pharmacological investigation of pathophysiological states and may possess a therapeutic potential in diseases involving the endogenous release of kinins.