Kinins' Contribution to Postoperative Pain in an Experimental Animal Model and Its Implications

Postoperative pain causes discomfort and disability, besides high medical costs. The search for better treatments for this pain is essential to improve recovery and reduce morbidity and risk of chronic postoperative pain. Kinins and their receptors contribute to different painful conditions and are among the main painful inflammatory mediators. We investigated the kinin's role in a postoperative pain model in mice and reviewed data associating kinins with this painful condition. The postoperative pain model was induced by an incision in the mice's paw's skin and fascia with the underlying muscle's elevation. Kinin levels were evaluated by enzyme immunoassays in sham or operated animals. Kinin's role in surgical procedure-associated mechanical allodynia was investigated using systemic or local administration of antagonists of the kinin B₁ receptor (DALBk or SSR240612) or B₂ receptor (Icatibant or FR173657) and a kallikrein inhibitor (aprotinin). Kinin levels increased in mice's serum and plantar tissue after the surgical procedure. All kinin B₁ or B₂ receptor antagonists and aprotinin reduced incision-induced mechanical allodynia. Although controversial, kinins contribute mainly to the initial phase of postoperative pain. The kallikrein-kinin system can be targeted to relieve this pain, but more investigations are necessary, especially associations with other pharmacologic targets.

Function and structure of bradykinin receptor 2 for drug discovery

Type 2 bradykinin receptor (B2R) is an essential G protein-coupled receptor (GPCR) that regulates the cardiovascular system as a vasodepressor. Dysfunction of B2R is also closely related to cancers and hereditary angioedema (HAE). Although several B2R agonists and antagonists have been developed, icatibant is the only B2R antagonist clinically used for treating HAE. The recently determined structures of B2R have provided molecular insights into the functions and regulation of B2R, which shed light on structure-based drug design for the treatment of B2R-related diseases. In this review, we summarize the structure and function of B2R in relation to drug discovery and discuss future research directions to elucidate the remaining unknown functions of B2R dimerization.

Kinins and their B1 and B2 receptors as potential therapeutic targets for pain relief

Kinins are endogenous peptides that belong to the kallikrein-kinin system, which has been extensively studied for over a century. Their essential role in multiple physiological and pathological processes is demonstrated by activating two transmembrane G-protein-coupled receptors, the kinin B₁ and B₂ receptors. The attention is mainly given to the pathological role of kinins in pain transduction mechanisms. In the past years, a wide range of preclinical studies has amounted to the literature reinforcing the need for an updated review about the participation of kinins and their receptors in pain disorders. Here, we performed an extensive literature search since 2004, describing the historical progress and the current understanding of the kinin receptors' participation and its potential therapeutic in several acute and chronic painful conditions. These include inflammatory (mainly arthritis), neuropathic (caused by different aetiologies, such as cancer, multiple sclerosis, antineoplastic toxicity and diabetes) and nociplastic (mainly fibromyalgia) pain. Moreover, we highlighted the pharmacological actions and possible clinical applications of the kinin B₁ and B₂ receptor antagonists, kallikrein inhibitors or kallikrein-kinin system signalling pathways-target molecules in these different painful conditions. Notably, recent findings sought to elucidate mechanisms for guiding new and better drug design targeting kinin B₁ and B₂ receptors to treat a disease diversity. Since the kinin B₂ receptor antagonist, Icatibant, is clinically used and well-tolerated by patients with hereditary angioedema gives us hope kinin receptors antagonists could be more robustly tested for a possible clinical application in the treatment of pathological pains, which present limited pharmacology management.

Targeting Proteinase Activated Receptor-4 Reduces Mechanonociception During the Acute Inflammatory Phase but not the Chronic Neuropathic Phase of Osteoarthritis in Rats

Serine proteases are elevated in arthritic joints where they can cleave protease activated receptors (PARs) to modulate pain and inflammation. Activation of protease-activated receptor 4 (PAR4) has been implicated in inflammatory joint pain. Whether PAR4 is involved in osteoarthritis (OA) pain has not yet been explored. The aim of this study was to compare the role of PAR4 in modulating early versus late stage OA pain using two models of OA viz. monoiodoacetate (MIA) and medial meniscal transection (MMT). G-ratio calculation and electron microscopy analysis revealed saphenous nerve demyelination and structural damage during late stage but not early OA in both models. Using immunohistochemistry, neuronal expression of PAR4 was higher in early versus late OA. Systemic administration of the PAR4 antagonist pepducin P4pal10 reduced both secondary allodynia (von Frey hair algesiometry) and joint nociceptor firing (single unit recordings) in MMT and MIA animals compared to vehicle-treated animals in early OA. The PAR4 antagonist was ineffective at altering pain or joint afferent firing in post-inflammatory OA. During the acute phase of the models, joint inflammation as determined by laser speckle contrast analysis and intravital microscopy could be partially blocked by pepducin P4pal10. Compared to late-stage disease, inflammatory cytokines were elevated in early MIA and MMT rats. These findings suggest that PAR4 may be a viable target to treat the pain of early onset OA or during episodic inflammatory flares.

Formulation and in vitro/in vivo evaluation of chitosan-based film forming gel containing ketoprofen

The film forming gel, adhered to skin surfaces upon application and formed a film, has an advantage onto skin to provide protection and continuous drug release to the application site. This study aimed to prepare a chitosan-based film forming gel containing ketoprofen (CbFG) and to evaluate the CbFG and film from CbFG (CbFG-film). CbFG were prepared with chitosan, lactic acid and various skin permeation enhancers. The physicochemical characteristics were evaluated by texture analysis, viscometry, SEM, DSC, XRD and FT-IR. To identify the mechanism of skin permeation, in vitro skin permeation study was conducted with a Franz diffusion cell and excised SD-rat and hairless mouse dorsal skin. In vivo efficacy assessment in mono-iodoacetate (MIA)-induced rheumatoid arthritis animal model was also conducted. CbFG was successfully prepared and, after applying CbFG to the excised rat dorsal skin, the CbFG-film was also formed well. The physicochemical characteristics of CbFG and CbFG-film could be explained by the grafting of oleic acid onto chitosan in the absence of catalysts. In addition, CbFG containing oleic acid had a higher skin permeation rate in comparison with any other candidate enhancers. The in vivo efficacy study also confirmed significant anti-inflammatory and analgesic effects. Consequently, we report the successful preparation of chitosan-based film forming gel containing ketoprofen with excellent mechanical properties, skin permeation and anti-inflammatory and analgesic effects.

Osteoarthritis model induced by intra-articular monosodium iodoacetate in rats knee

PURPOSE:

To evaluate the usefulness of a knee osteoarthritis model through functional, radiological and microscopic changes of the synovial membrane.

METHODS:

Forty eight rats were divided randomly into two groups. The first received 0.9% saline in the joint and corresponded to the control group. The second was submitted to experimental osteoarthritis of the right knee induced by monosodium iodoacetate and corresponded to the osteoarthritis group. All animals were subjected to comparative tests of forced ambulation and joint movements, inability to articulate and tactile allodynia on day 1 post-experiment by forced ambulation (Roto-rod test), joint assessment of disability (weight bearing test) and assessment of tactile allodynia (Von Frey test). After inflammatory induction they were divided into four sub-groups corresponding to the scheduled death in 7, 14, 21 and 28 days when they were submitted to radiographic examination of the knee, arthrotomy and collection of the synovial membrane.

RESULTS:

The osteoarthritis group showed significant differences compared to control group on days 7 and 14 in Roto-rod, in weight bearing and Von Frey tests in all days, and in radiological evaluation. Microscopic examination of the synovial membrane showed abnormalities of inflammatory character at all stages.

CONCLUSION:

The osteoarthritis induced by intra-articular monosodium iodoacetate in rats knee is a good model to be used in related research, because it provides mensurable changes on joint movements, tactile allodynia, progressive radiological degeneration and microscopic inflammation of the synovial membrane, that represent markers for osteoarthritis evaluation.

Spinal neuropeptide modulation, functional assessment and cartilage lesions in a monosodium iodoacetate rat model of osteoarthritis

BACKGROUND AND AIMS

Characterising the temporal evolution of changes observed in pain functional assessment, spinal neuropeptides and cartilage lesions of the joint after chemical osteoarthritis (OA) induction in rats.

METHODS AND RESULTS

On day (D) 0, OA was induced by an IA injection of monosodium iodoacetate (MIA). Rats receiving 2mg MIA were temporally assessed at D3, D7, D14 and D21 for the total spinal cord concentration of substance P (SP), calcitonin gene related-peptide (CGRP), bradykinin (BK) and somatostatin (STT), and for severity of cartilage lesions. At D21, the same outcomes were compared with the IA 1mg MIA, IA 2mg MIA associated with punctual IA injection of lidocaine at D7, D14 and D21, sham (sterile saline) and naïve groups. Tactile allodynia was sequentially assessed using a von Frey anaesthesiometer. Non-parametric and mixed models were applied for statistical analysis. Tactile allodynia developed in the 2mg MIA group as soon as D3 and was maintained up to D21. Punctual IA treatment with lidocaine counteracted it at D7 and D14. Compared to naïve, [STT], [BK] and [CGRP] reached a maximum as early as D7, which plateaued up to D21. For [SP], the increase was delayed up to D14 and maintained at D21. No difference in levels of neuropeptides was observed between MIA doses, except for higher [STT] in the 2mg MIA group (P=0.029). Neuropeptides SP and BK were responsive to lidocaine treatment. The increase in severity of cartilage lesions was significant only in the 2mg MIA groups (P=0.01).

CONCLUSION

In the MIA OA pain model, neuropeptide modulation appears early, and confirms the central nervous system to be an attractive target for OA pain quantification. The relationship of neuropeptide release with severity of cartilage lesions and functional assessment are promising and need further validation.

Bioactive Turmerosaccharides from Curcuma longa Extract (NR-INF-02): Potential Ameliorating Effect on Osteoarthritis Pain

Background:

Curcuma longa has long history of medicinal use in Ayurveda. A unique product NR-INF-02 was prepared from C. longa that was standardized to contain turmerosaccharides.

Objective:

The present study investigated the effect of turmerosaccharides rich fraction of NR-INF-02 on monosodium iodoacetate (MIA)-induced OA pain animal model that mimics human OA. Further, the analgesic effect of turmerosaccharides rich fraction was compared to turmerosaccharides less fraction of NR-INF-02.

Materials and Methods:

OA pain was chemically induced by intra-articular administration of single dose of 25 μl of 0.9% saline containing 0.3 mg MIA into the right knee of male albino Wistar rat. Turmerosaccharides rich fraction and turmerosaccharides less fraction (at 22.5, 45 and 90 mg/kg rat body weight dose levels) were administered as a single dose orally on day 5 of post-MIA injection. OA pain was measured using hind limb weight-bearing ability at 1, 3, 6, and 24 h post-test substance administration on day 5.

Results:

Oral administration of turmerosaccharides rich fraction and turmerosaccharides less fraction (at 45 and 90 mg/kg) although significantly decreased the OA pain at all the intervals, the effect of turmerosaccharides rich fraction (57%) on OA pain was superior to turmerosaccharides less fraction (35%).

Conclusion:

Bioactive turmerosaccharides from C. longa extract contribute to the observed anti-arthritic effect in rats.

SUMMARY

Osteoarthritic pain was induced by intra-articular injection of MIA into the right knee

Single administration of TRF/TLF on day 5 resulted in dose-dependent significant reduction of OA pain

TRF showed better analgesic activity than TLF

TRF at 45 and 90 mg/kg has similar effects on OA pain as that of tramadol

Turmerosaccharides identified as bioactive constituents of C. longa extract.

Abbreviations used: MIA: Monosodium iodoacetate; i.ar: Intra-articular; OA: Osteoarthritis; TRF: Turmerosaccharides rich fraction; TLF: Turmerosaccharides less fraction; PGE2: Prostaglandin E2; ROS: Reactive oxygen species.

Photobiomodulation therapy in the modulation of inflammatory mediators and bradykinin receptors in an experimental model of acute osteoarthritis

The objective of this study was to evaluate the effects of photobiomodulation therapy (PBMT) on inflammatory indicators, i.e., inflammatory mediators (TNF-α and CINC-1), and pain characterized by hyperalgesia and B1 and B2 receptor activation at 6, 24, and 48 h after papain-induced osteoarthritis (OA) in rats. Fifty-four rats were subjected to hyperalgesia evaluations and then divided randomly into three groups-a control group and two groups OA and OA PBMT group by using laser parameters at wavelength (808 nm), output power (50 mW), energy per point (4 Joules), power density (1.78 W/cm²), laser beam (0.028 cm²), and energy density (144 J/cm²)-the induction of osteoarthritis was then performed with 20-μl injections of a 4 % papain solution dissolved in 10 μl of saline solution, to which 10 μl of cysteine solution (0.03 M). The statistical analysis was performed using two-way ANOVA with Bonferroni's post hoc test for comparisons between the 6, 24, and 48 h and team points within each group, and between the control, injury, and PBMT groups, and p < 0.05 was considered to indicate a significant difference. The hyperalgesia was evaluated at 6, 24, and 48 h after the injury. PBMT at a wavelength of 808 nm and doses of 4 J, administered afterward, promotes increase at the threshold of pressure stimulus at 6, 24, and 48 h after application and promote cytokine attenuation levels (TNF and CINC-1) and bradykinin receptor (B1 and B2) along the experimental period. We conclude that photobiomodulation therapy was able to promote the reduction of proinflammatory cytokines such as TNF-α and CINC-1, to reduce the gene and protein expression of the bradykinin receptor (B1 and B2), as well as increasing the stimulus response threshold of pressure in an experimental model of acute osteoarthritis.

Investigational drugs for the treatment of osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a common joint disease with multiple pathophysiological processes, affecting the whole joint. Current therapeutic options such as NSAIDs can provide a palliative effect on symptoms but have limited effect on disease progression. New drugs targeting OA structures may retard disease progression at an earlier stage and delay the need for joint replacement.

AREAS COVERED

Some drugs have entered into clinical trials and a few, such as strontium ranelate, do have improvements in both pain and structure changes. However, most of them have failed in clinical trials largely due to increased side effects or the failure to identify the right OA phenotype for the right drug in clinical design. This review describes various investigational drugs developed for the treatment of OA covering those at stages from preclinical experiments to early phase clinical trials. They include drugs for slowing cartilage degradation, regulating cartilage metabolism, targeting subchondral bone, controlling inflammation and relieving pain.

EXPERT OPINION

Treatment options for OA remain limited. However, with the emergence of sensitive tools to detect early disease progression and identification of different OA phenotypes, disease-modifying anti-OA drugs with increased benefit and reduced risks will become available for OA treatment in the near future.

Comparison of piroxicam pharmacokinetics and anti-inflammatory effect in rats after intra-articular and intramuscular administration

This study evaluated the pharmacokinetic profile and therapeutic efficacy of piroxicam (PX), a long acting non-steroidal anti-inflammatory drug for the treatment of arthritis, following intra-articular (IA) injection in comparison to the pharmacokinetic profile and therapeutic efficacy of PX after intramuscular (IM) injection. In the pharmacokinetic study in rats, systemic exposure and pharmacokinetic parameters of PX after a single IA dose were compared with systemic exposure and pharmacokinetic parameters of PX after administration of the same dose IM (0.6 mg/kg). The anti-inflammatory and analgesic effects of IA PX were evaluated simultaneously in a monoiodoacetate-induced osteoarthritis rat model. The plasma PX concentration rapidly rose following IA injection, and it was comparable to the plasma PX concentration following IM injection, suggesting the rapid efflux of the drug molecule from the joint cavity. However, in the efficacy study, the IA PX administration significantly reduced the knee swelling by reducing the level of prostaglandin E₂ in the joint, compared to that following administration of IA vehicle and after administration of the IM PX dose. In addition, we found that the anti-inflammatory and anti-nociceptive efficacies of IA PX were synergistically increased upon co-treatment with hyaluronic acid (HA), a potent agent for the treatment of osteoarthritis, at the weight ratio of 1:1 or 1:2, and these effects were more pronounced than those following administration of HA or PX alone. In conclusion, this study demonstrated the efficacy of the IA use of PX alone and/or in combination with HA in osteoarthritis.

Antagonism of bradykinin B2 receptor prevents inflammatory responses in human endothelial cells by quenching the NF-kB pathway activation

Background

Bradykinin (BK) induces angiogenesis by promoting vessel permeability, growth and remodeling. This study aimed to demonstrate that the B2R antagonist, fasitibant, inhibits the BK pro-angiogenic effects.

Methodology

We assesed the ability of fasibitant to antagonize the BK stimulation of cultured human cells (HUVEC) and circulating pro-angiogenic cells (PACs), in producing cell permeability (paracellular flux), migration and pseocapillary formation. The latter parameter was studied in vitro (matrigel assay) and in vivo in mice (matrigel plug) and in rat model of experimental osteoarthritis (OA). We also evaluated NF-κB activation in cultured cells by measuring its nuclear translocation and its downstream effectors such as the proangiogenic ciclooxygenase-2 (COX-2), prostaglandin E-2 and vascular endothelial growth factor (VEGF).

Principal findings

HUVEC, exposed to BK (1–10 µM), showed increased permeability, disassembly of adherens and tight-junction, increased cell migration, and pseudocapillaries formation. We observed a significant increase of vessel density in the matrigel assay in mice and in rats OA model. Importantly, B2R stimulation elicited, both in HUVEC and PACs, NF-κB activation, leading to COX-2 overexpression, enhanced prostaglandin E-2 production. and VEGF output. The BK/NF-κB axis, and the ensuing amplification of inflammatory/angiogenic responses were fully prevented by fasitibant as well as by IKK VII, an NF-κB. Inhibitor.

Conclusion

This work illustrates the role of the endothelium in the inflammation provoked by the BK/NF-κB axis. It also demonstates that B2R blockade by the antaogonist fasibitant, abolishes both the initial stimulus and its amplification, strongly attenuating the propagation of inflammation.

The kallikrein-kinin system as a regulator of cardiovascular and renal function

Autocrine, paracrine, endocrine, and neuroendocrine hormonal systems help regulate cardio-vascular and renal function. Any change in the balance among these systems may result in hypertension and target organ damage, whether the cause is genetic, environmental or a combination of the two. Endocrine and neuroendocrine vasopressor hormones such as the renin-angiotensin system (RAS), aldosterone, and catecholamines are important for regulation of blood pressure and pathogenesis of hypertension and target organ damage. While the role of vasodepressor autacoids such as kinins is not as well defined, there is increasing evidence that they are not only critical to blood pressure and renal function but may also oppose remodeling of the cardiovascular system. Here we will primarily be concerned with kinins, which are oligopeptides containing the aminoacid sequence of bradykinin. They are generated from precursors known as kininogens by enzymes such as tissue (glandular) and plasma kallikrein. Some of the effects of kinins are mediated via autacoids such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF), and/or tissue plasminogen activator (tPA). Kinins help protect against cardiac ischemia and play an important part in preconditioning as well as the cardiovascular and renal protective effects of angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARB). But the role of kinins in the pathogenesis of hypertension remains controversial. A study of Utah families revealed that a dominant kallikrein gene expressed as high urinary kallikrein excretion was associated with a decreased risk of essential hypertension. Moreover, researchers have identified a restriction fragment length polymorphism (RFLP) that distinguishes the kallikrein gene family found in one strain of spontaneously hypertensive rats (SHR) from a homologous gene in normotensive Brown Norway rats, and in recombinant inbred substrains derived from these SHR and Brown Norway rats this RFLP cosegregated with an increase in blood pressure. However, humans, rats and mice with a deficiency in one or more components of the kallikrein-kinin-system (KKS) or chronic KKS blockade do not have hypertension. In the kidney, kinins are essential for proper regulation of papillary blood flow and water and sodium excretion. B2-KO mice appear to be more sensitive to the hypertensinogenic effect of salt. Kinins are involved in the acute antihypertensive effects of ACE inhibitors but not their chronic effects (save for mineralocorticoid-salt-induced hypertension). Kinins appear to play a role in the pathogenesis of inflammatory diseases such as arthritis and skin inflammation; they act on innate immunity as mediators of inflammation by promoting maturation of dendritic cells, which activate the body's adaptive immune system and thereby stimulate mechanisms that promote inflammation. On the other hand, kinins acting via NO contribute to the vascular protective effect of ACE inhibitors during neointima formation. In myocardial infarction produced by ischemia/reperfusion, kinins help reduce infarct size following preconditioning or treatment with ACE inhibitors. In heart failure secondary to infarction, the therapeutic effects of ACE inhibitors are partially mediated by kinins via release of NO, while drugs that activate the angiotensin type 2 receptor act in part via kinins and NO. Thus kinins play an important role in regulation of cardiovascular and renal function as well as many of the beneficial effects of ACE inhibitors and ARBs on target organ damage in hypertension.

Blockade of nociceptive sensory afferent activity of the rat knee joint by the bradykinin B2 receptor antagonist fasitibant

OBJECTIVE

The aim of this study was to determine in intact and inflamed knee joints of the rat, the effect of the bradykinin (BK) B2 receptor antagonist fasitibant (MEN16132) on nociceptor mechanosensitivity and hyperalgesia.

METHODS

Joint afferent sensory fibers of the medial articular nerve of anesthetized animals were electrophysiologically recorded, measuring nerve impulse activity evoked by passive innocuous and noxious movements of the joint, in intact and kaolin and carrageenan-injected joints. Knee joints of rats were also acutely inflamed by intra-articular injection of carrageenan alone. Long term duration of fasitibant antinociceptive effects were behaviorally evaluated using the incapacitance test.

RESULTS

BK (100 μM) injected into the saphenous artery, induced excitation and sensitization of multi- and single unit recordings. Fasitibant (300 μM) injected prior to BK, reduced its excitatory effects as well as the overall increase of movement-evoked activity resulting from repeated injections of BK. Fasitibant did not affect movement-evoked activity of sensory fibers of intact, non-inflamed knee joints. Intra-articular fasitibant (100 μg/knee) significantly reduced the carrageenan-induced inflammatory hyperalgesia measured with the incapacitance test up to four days after treatment. This antinociceptive effect was not obtained with systemic endovenous injection of the drug.

CONCLUSIONS

Fasitibant prevents B2 receptor-mediated activation and sensitization of peripheral joint afferents and the ensuing inflammatory hyperalgesia, and may be a useful, novel drug for arthritis pain treatment.

Osteoarthritis pain mechanisms: basic studies in animal models

OBJECTIVE

Osteoarthritis (OA) is a complex and painful disease of the whole joint. At present there are no satisfying agents for treating OA. To promote OA research and improved treatment, this review summarizes current preclinical evidence on the development of OA.

METHODS

Preclinical OA research was searched and key findings are summarized and commented.

RESULTS

Mechanisms of OA-associated pain have been studied in rodent knee OA models produced by intra-knee injection of the chondrocyte glycolytic inhibitor mono-iodoacetate (MIA), surgery, or spontaneous development in some species. These models are clinically relevant in terms of histological damage and functional changes, and are used to study mechanisms underlying mechanical, thermal, ambulatory, body weight supporting-evoked, and ongoing OA pain. Recent peripheral, spinal, and supraspinal biochemical and electrophysiological studies in these models suggest that peripheral pro-inflammatory mediators and neuropeptides sensitize knee nociceptors. Spinal cytokines and neuropeptides promote OA pain, and peripheral and spinal cannabinoids inhibit OA pain respectively through cannabinoid-1 (CB1) and CB1/CB2 receptors. TRPV1 and metalloproteinases contribute and supraspinal descending facilitation of 5-hydroxytryptamine (5-HT)/5-HT 3 receptors may also contribute to OA pain. Conditioned place preference tests demonstrate that OA pain induces aversive behaviors, suggesting the involvement of brain. During OA, brain functional connectivity is enhanced, but at present it is unclear how this change is related to OA pain.

CONCLUSION

Animal studies demonstrate that peripheral and central sensitization contributes to OA pain, involving inflammatory cytokines, neuropeptides, and a variety of chemical mediators. Interestingly, brainstem descending facilitation of 5-HT/5-HT3 receptors plays a role OA pain.

Characterization of a novel proinflammatory effect mediated by BK and the kinin B₂ receptor in human preadipocytes

Obesity and adipose tissue contribute to local and systemic inflammation. However the role of the inflammatory mediator bradykinin (BK) in this context is not known. We therefore evaluated the effect of BK on adipokines secretion in human preadipocytes during the course of differentiation and characterized the receptors involved. Results obtained from antibody array and ELISA experiments showed that several adipokines are released by human preadipocytes under basal conditions while BK specifically stimulated the production of interleukin(IL)-6 and IL-8. The effect of BK diminished with the progression of differentiation, being almost inactive on adipocytes. In preadipocytes, BK also induced a rapid and transient [Ca²⁺](i) mobilization, a rapid and sustained increase in ERK1/2 activation and enhanced forskolin-stimulated cAMP accumulation. BK was without effect on cell proliferation and viability as assessed by bromodeoxyuridine incorporation, WST-1 conversion, or lactate dehydrogenase leakage and was without effect on adipogenesis as measured by triglyceride accumulation, GPDH activity and leptin release. The B₁ receptor agonist, Lys-[des-Arg⁹]-BK, displayed poor activity or was without effect while overall BK effects were prevented by the selective B₂ receptor antagonist, fasitibant chloride, but not by the B₁ selective antagonist, Lys-[Leu⁸][des-Arg⁹]-BK. Immunoblot analysis and immunofluorescence studies showed that the kinin B₂ receptor was essentially expressed at the beginning of the differentiation program. In conclusion, human preadipocytes expressed kinin B₂ receptors linked to multiple signaling pathways, IL-6 and IL-8 production, and BK proinflammatory response in adipose tissue could be prevented by fasitibant chloride.

Fasitibant chloride, a kinin B₂ receptor antagonist, and dexamethasone interact to inhibit carrageenan-induced inflammatory arthritis in rats

BACKGROUND AND PURPOSE

Bradykinin, through the kinin B₂ receptor, is involved in inflammatory processes related to arthropathies. B₂ receptor antagonists inhibited carrageenan-induced arthritis in rats in synergy with anti-inflammatory steroids. The mechanism(s) underlying this drug interaction was investigated.

EXPERIMENTAL APPROACH

Drugs inhibiting inflammatory mediators released by carrageenan were injected, alone or in combination, into the knee joint of pentobarbital anaesthetized rats 30 min before intra-articular administration of carrageenan. Their effects on the carrageenan-induced inflammatory responses (joint pain, oedema and neutrophil recruitment) and release of inflammatory mediators (prostaglandins, IL-1β, IL-6 and the chemokine GRO/CINC-1), were assessed after 6 h.

KEY RESULTS

The combination of fasitibant chloride (MEN16132) and dexamethasone was more effective than each drug administered alone in inhibiting knee joint inflammation and release of inflammatory mediators. Fasitibant chloride, MK571, atenolol, des-Arg⁹-[Leu⁸]-bradykinin (B₂ receptor, leukotriene, catecholamine and B₁ receptor antagonists, respectively) and dexketoprofen (COX inhibitor), reduced joint pain and, except for the latter, also diminished joint oedema. A combination of drugs inhibiting joint pain (fasitibant chloride, des-Arg⁹-[Leu⁸]-bradykinin, dexketoprofen, MK571 and atenolol) and oedema (fasitibant chloride, des-Arg⁹-[Leu⁸]-bradykinin, MK571 and atenolol) abolished the respective inflammatory response, producing inhibition comparable with that achieved with the combination of fasitibant chloride and dexamethasone. MK571 alone was able to block neutrophil recruitment.

CONCLUSIONS AND IMPLICATIONS

Bradykinin-mediated inflammatory responses to intra-articular carrageenan were not controlled by steroids, which were not capable of preventing bradykinin effects either by direct activation of the B₂ receptor, or through the indirect effects mediated by release of eicosanoids and cytokines.

Icatibant , the bradykinin B2 receptor antagonist with target to the interconnected kinin systems

INTRODUCTION

HOE-140/ Icatibant is a selective, competitive antagonist to bradykinin (BK) against its binding to the kinin B2 receptor. Substitution of five non-proteogeneic amino acid analogues makes icatibant resistant to degradation by metalloproteases of kinin catabolism. Icatibant has clinical applications in inflammatory and vascular leakage conditions caused by an acute (non-controlled) production of kinins and their accumulation at the endothelium B2 receptor. The clinical manifestation of vascular leakage, called angioedema (AE), is characterized by edematous attacks of subcutaneous and submucosal tissues, which can cause painful intestinal consequences, and life-threatening complications if affecting the larynx. Icatibant is registered for the treatment of acute attacks of the hereditary BK-mediated AE, i.e., AE due to C1 inhibitor deficiency.

AREAS COVERED

This review discusses emerging knowledge on the kinin system: kinin pharmacological properties, biochemical characteristics of the contact phase and kinin catabolism proteases. It underlines the responsibility of the kinins in AE initiation and the potency of icatibant to inhibit AE formation by kinin-receptor interactions.

EXPERT OPINION

Icatibant antagonist properties protect BK-mediated AE patients against severe attacks, and could be developed for use in inflammatory conditions. More studies are required to confirm whether or not prolonged and frequent applications of icatibant could result in the impairment of the cardioprotective effect of BK.

Fasitibant prevents the bradykinin and interleukin 1β synergism on prostaglandin E₂ release and cyclooxygenase 2 expression in human fibroblast-like synoviocytes

This study investigates the effect of the selective and potent B(2) receptor antagonist fasitibant (MEN16132) on the proinflammatory effect of bradykinin (BK) and its interaction with interleukin 1β (IL-1β) in human synoviocytes. PGE(2) content was detected in the surnatants and COX-2 and COX-1 gene and protein expression determined in the cells. Radioligand binding ([(3) H]BK) and BK-induced inositolphosphate experiments were performed. Incubation of synoviocytes with BK induced a sustained production of PGE(2) and transient COX-2 gene expression that were prevented by pretreatment with fasitibant (1 μM, 30 min preincubation). IL-1β increased PGE(2) release and COX-2 expression more than BK alone. The combined treatment of cells with BK and IL-1β induced an even increase of released PGE(2) and COX-2 gene and protein expression indicating a synergistic rather than an additive effect, not related to an increase of B(2) receptors density or its coupling. These potentiating effects of BK on PGE(2) production and increased COX-2 expression produced by IL-1β were B(2)-receptor-mediated as fasitibant could prevent them. None of the treatments induced changes in the COX-1 expression. The synergistic PGE(2) production was abolished by the specific NF-kappaB inhibitor (BAY-117085), whereas specific inhibitors for the p38 (SB203580), JNK (SP600125), and ERK1/2 (PD98059) mitogen-activated protein kinases could prevent the prostanoid release. BK can potentiate the COX-2 gene expression and consequent prostanoid production induced by IL-1β. The prevention of this synergism by fasitibant indicates BK B(2) receptor blockade as an alternative symptomatic therapy for osteoarthritis.

Skullcapflavone II inhibits ovalbumin-induced airway inflammation in a mouse model of asthma

Skullcapflavone II is a flavonoid derived from Scutellaria baicalensis, a widely used herbal medicine in anti-inflammatory and anticancer therapy in Korea. Skullcapflavone II antagonized the bradykinin receptor more potently than any of the other flavonoids derived from this plant. Here, we were investigated its therapeutic effects in a mouse model of ovalbumin (OVA)-induced allergic asthma. Administration of skullcapflavone II significantly reduced airway hyperresponsiveness (AHR), airway eosinophilia, Th2 cytokine production, and increased transforming growth factor-β1 (TGF-β1) levels in bronchoalveolarlavage (BAL) fluids and lungs from OVA-sensitized and -challenged mice. Skullcapflavone II administration also significantly suppressed subepithelial collagen deposition and goblet cell hyperplasia, elevated Smad7 expression and suppressed pSmad2/3 levels. Collectively, these findings indicate that skullcapflavone II, a potential bradykinin antagonist, reduced the major pathophysiological features of allergic asthma, at least in part by acting on TGF-β1/Smad signaling pathways. Thus, skullcapflavone II may have therapeutic potential for the treatment of allergic asthma.

Comparison of the molecular interactions of two antagonists, MEN16132 or icatibant, at the human kinin B₂ receptor

BACKGROUND AND PURPOSE

Icatibant is a well-known kinin B₂ receptor antagonist currently used for angiooedema attacks. MEN16132 is a non-peptide B₂ receptor antagonist, more potent and long lasting than icatibant in different models. Here we studied the reasons for these differences between the two antagonists.

EXPERIMENTAL APPROACH

Rate of reversibility (over about 3 h) of the functional receptor blockade exerted by the antagonists was compared (inositol phosphates accumulation assay) in CHO cells expressing the human B₂ receptor and in human synovial cells. Antagonist pretreated cells were washed with medium and the time taken to restore bradykinin (BK) response measured. Antagonist affinity was measured by radioligand binding to wild type and mutated B₂ receptors.

KEY RESULTS

Recovery of BK-induced responses was slower in cells pretreated with MEN16132 than in those treated with icatibant. The affinity of icatibant (for the [³H]-BK or the B₂ receptor antagonist [³H]-MEN11270 binding site) was compared to that of MEN16132 using a panel of point-mutated receptors with mutations located at the transmembrane regions of the B₂ receptor, previously shown to decrease MEN16132 high affinity interaction. No consistent decrease of icatibant affinity was observed. From the different affinity of MEN16132 derivatives at wild type and W86A (transmembrane 2 region) receptors, and by evaluating its antagonist profile at the D266A/D284A double mutant receptor, a model of the MEN16132-B₂ receptor complex is proposed.

CONCLUSIONS AND IMPLICATIONS

MEN16132 dissociated from the B₂ receptor compartment more slowly than icatibant and interacted at a deeper level in transmembrane regions of the receptor.

Bradykinin and B₂ receptor antagonism in rat and human articular chondrocytes

BACKGROUND AND PURPOSE

In osteoarthritis (OA), bradykinin (BK) is known to contribute to pain and synovitis, but not to cartilage degradation. Here, we investigated effects of BK and its antagonists on chondrocytes, cells involved in cartilage homeostasis.

EXPERIMENTAL APPROACH

BK receptor density and affinities of BK, its analogues and antagonists were measured in cultured human and rat chondrocytes by radioligand binding. Effects of BK were assessed by accumulation of inositol phosphates (IP) and release of interleukin (IL)-6 and IL-8.

KEY RESULTS

Density of [³H]-BK binding sites was higher (13-30-fold) and BK evoked a greater (48-fold) IP production, in human than in rat chondrocytes. The BK B₂ receptor antagonists MEN16132 and icatibant displayed similar binding affinity. MEN16132 was 40-fold more potent than icatibant in the IP assay. In human chondrocytes, BK increased release (over 24 h) of IL-6 and IL-8, effects blocked by MEN16132 but not by the B₁ receptor antagonist Lys-[Leu⁸][desArg⁹]BK. BK-induced release of IL-6, but not of IL-8, was partially inhibited by indomethacin (10 µM) and nordihydroguaiaretic acid (10 µM). Antagonists for the prostanoid EP receptors (AH6809 10 µM; L-798,196, 200 nM; L-161,982, 1 µM) were ineffective. Dexamethasone (100 nM) partially inhibited release of both IL-6 and IL-8. Inhibitors of intracellular downstream signalling pathways (SB203580 10 µM; PD98059, 30 µM; SP600125, 30 µM; BAY-117085, 5 µM) indicated the involvement of p38 MAPK and the activation of NF-κB.

CONCLUSION AND IMPLICATIONS

BK mediated inflammatory changes and cartilage degradation and B₂ receptor blockade would, therefore, be a potential treatment for OA.

Anti-inflammatory synergy of MEN16132, a kinin B(2) receptor antagonist, and dexamethasone in carrageenan-induced knee joint arthritis in rats

BACKGROUND AND PURPOSE

Bradykinin, through its B(2) receptor, is involved in inflammatory processes related to arthropathies. In carrageenan and lipopolysaccharide (LPS)-induced arthritis in rat, the anti-inflammatory activity of MEN16132, a potent and selective kinin B(2) receptor antagonist, was compared with that of steroidal and nonsteroidal anti-inflammatory drugs. The interaction between MEN16132 and dexamethasone was also investigated.

EXPERIMENTAL APPROACH

Drugs, alone or in combination, were injected into the knee joint 30min before intra-articular administration of carrageenan or LPS, in pentobarbital anaesthetized rats. Effects on incapacitation, oedema, neutrophil recruitment and kallikrein system activation, in the knee joint, were assessed.

KEY RESULTS

MEN16132 and dexamethasone (10-300µg per knee) dose-dependently reduced carrageenan-induced joint pain, oedema and neutrophil infiltration, reaching a maximal inhibition of about 50%. Dexketoprofen exerted a similar analgesic activity, whereas it did not affect the other inflammatory responses. MEN16132 showed a partial inhibition of LPS-induced joint pain, whereas dexamethasone produced a full analgesic effect. Combination of MEN16132 and dexamethasone showed a strong synergistic interaction in inhibiting both carrageenan and LPS-induced knee joint inflammation. Dexamethasone did not prevent the contact activation of prekallikrein by carrageenan and the subsequent release of kallikreins and bradykinin in the synovium.

CONCLUSIONS AND IMPLICATIONS

Steroids and kinin B(2) receptor antagonists appear to relieve arthritic symptoms induced by carrageenan or LPS and act synergistically to inhibit joint inflammation. This could have interesting therapeutic implications, possibly opening the way for combination therapies in the control of inflammatory arthropathies.