Combined effect of bradykinin B2 and neurokinin-1 receptor activation on endothelial cell proliferation in acute synovitis

Space microgravity increases expression of genes associated with proliferation and differentiation in human cardiac spheres

Efficient generation of cardiomyocytes from human-induced pluripotent stem cells (hiPSCs) is important for their application in basic and translational studies. Space microgravity can significantly change cell activities and function. Previously, we reported upregulation of genes associated with cardiac proliferation in cardiac progenitors derived from hiPSCs that were exposed to space microgravity for 3 days. Here we investigated the effect of long-term exposure of hiPSC-cardiac progenitors to space microgravity on global gene expression. Cryopreserved 3D hiPSC-cardiac progenitors were sent to the International Space Station (ISS) and cultured for 3 weeks under ISS microgravity and ISS 1 G conditions. RNA-sequencing analyses revealed upregulation of genes associated with cardiac differentiation, proliferation, and cardiac structure/function and downregulation of genes associated with extracellular matrix regulation in the ISS microgravity cultures compared with the ISS 1 G cultures. Gene ontology analysis and Kyoto Encyclopedia of Genes and Genomes mapping identified the upregulation of biological processes, molecular function, cellular components, and pathways associated with cell cycle, cardiac differentiation, and cardiac function. Taking together, these results suggest that space microgravity has a beneficial effect on the differentiation and growth of cardiac progenitors.

Synovial membrane receptors as therapeutic targets: A review of receptor localization, structure, and function

Joint pathology and degeneration is a significant cause of pain. The synovial membrane plays an important role in maintenance of the joint, contributes to the pathology of many arthropathies and may be adversely affected in joint disease. Improving knowledge of the receptors present within the synovium will aid in a better understanding of joint pathology and the development of new treatments for diseases such as osteoarthritis and rheumatoid arthritis. Knowledge of the location and function of synovial membrane receptors (both in healthy and diseased synovium) may provide important targets in the treatment of various arthropathies. Classic pain receptors such as opioid receptors in the synovium are a mainstay in local and systemic management of chronic pain in many species. In addition to these, many other receptors such as bradykinin, neurokinin, transient receptor potential vanilloid, and inflammatory receptors, such as prostanoid and interleukin receptors have been discovered within the synovial membrane. These receptors are important in pain, inflammation, and in maintenance of normal joint function and may serve as targets for pharmacologic intervention in pathologic states. The goal of this review is to outline synovial membrane receptor localization and local therapeutic modulation of these receptors, in order to stimulate further research into pharmacological management of arthropathies at the local level. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1589-1605, 2017.

Differential Expression of Inflammation-Related Genes in Children with Down Syndrome

OBJECTIVE

The aim of the study was to investigate the expression patterns of a specific set of genes involved in the inflammation process in children with Down Syndrome (DS) and children without the syndrome (control group) to identify differences that may be related to the immune abnormalities observed in DS individuals.

METHOD

RNA samples were obtained from peripheral blood, and gene expression was quantified using the TaqMan® Array Plate Human Inflammation Kit, which facilitated the investigation into 92 inflammation-related genes and four reference genes using real-time polymerase chain reaction (qPCR).

RESULTS

Twenty genes showed differential expression in children with DS; 12 were overexpressed (PLA2G2D, CACNA1D, ALOX12, VCAM1, ICAM1, PLCD1, ADRB1, HTR3A, PDE4C, CASP1, PLA2G5, and PLCB4), and eight were underexpressed (LTA4H, BDKRB1, ADRB2, CD40LG, ITGAM, TNFRSF1B, ITGB1, and TBXAS1). After statistically correcting for the false discovery rate, only the genes BDKRB1 and LTA4H showed differential expression, and both were underexpressed within the DS group.

CONCLUSION

DS children showed differential expression of inflammation-related genes that were not located on chromosome 21 compared with children without DS. The BDKRB1 and LTA4H genes may differentiate the case and control groups based on the inflammatory response, which plays an important role in DS pathogenesis.

Kinin-B1 and B2 receptor activity in proliferation and neural phenotype determination of mouse embryonic stem cells

The kinins bradykinin and des-arg(9) -bradykinin cleaved from kininogen precursors by kallikreins exert their biological actions by stimulating kinin-B2 and B1 receptors, respectively. In vitro models of neural differentiation such as P19 embryonal carcinoma cells and neural progenitor cells have suggested the involvement of B2 receptors in neural differentiation and phenotype determination; however, the involvement of B1 receptors in these processes has not been established. Here, we show that B1 and B2 receptors are differentially expressed in mouse embryonic E14Tg2A stem cells undergoing neural differentiation. Proliferation and differentiation assays, performed in the presence of receptor subtype-selective agonists and antagonists, revealed that B1 receptor activity is required for the proliferation of embryonic and differentiating cells as well as for neuronal maturation at later stages of differentiation, while the B2 receptor acts on neural phenotype choice, promoting neurogenesis over gliogenesis. Besides the elucidation of bradykinin functions in an in vitro model reflecting early embryogenesis and neurogenesis, this study contributes to the understanding of B1 receptor functions in this process.

Peripheral neurokinin-1 receptors contribute to kaolin-induced acute monoarthritis in rats

OBJECTIVE

intra-articular co-injection of kaolin with carrageenan (CGN) in rodents is widely used as an experimental model of arthritis. However, the ability of kaolin to cause arthritis and related immune responses when administered alone is unclear. We evaluated the contribution of prostanoids and sensory C-fibres (and their neuropeptide substance P) to kaolin-induced inflammation in the rat knee.

METHODS

Wistar rats, 8-10 weeks old, received an intra-articular injection of kaolin (1-10 μg/joint) or saline into the knee joint. Knee inflammation, proinflammatory cytokines, pain behaviour and secondary tactile allodynia were assessed over 5 h, when synovial leukocyte counts, histopathological changes and proinflammatory cytokine levels were evaluated.

RESULTS

The intra-articular injection of kaolin caused a dose- and time-dependent knee swelling and impairment of motion that were associated with secondary tactile allodynia, elevated concentrations of IL-1β, IL-6 and TNFα, leukocyte infiltration, and histopathological changes in the ipsilateral hindpaw. The neurokinin-1 (NK1) receptor antagonist SR140333 or neonatal treatment with capsaicin markedly reduced the inflammatory parameters, cytokines and allodynia but failed to significantly inhibit the impaired motion. The cyclo-oxygenase inhibitor indomethacin partially inhibited knee oedema and allodynia but did not affect the leukocyte influx, myeloperoxidase activity or impaired motion in the kaolin-injected rat.

CONCLUSIONS

We show the first evidence that intra-articular injection of kaolin without CGN produced severe acute monoarthritis. This was highly dependent on substance P (released from C-fibres) and NK1 receptor activation, which stimulated local production of proinflammatory cytokines. This model may be of critical importance for mechanistic studies and screening new anti-inflammatory/analgesic drugs.

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.

The kinin-kallikrein system: physiological roles, pathophysiology and its relationship to cancer biomarkers

The kinin-kallikrein system (KKS) is an endogenous multiprotein cascade, the activation of which leads to triggering of the intrinsic coagulation pathway and enzymatic hydrolysis of kininogens with the consequent release of bradykinin-related peptides. This system plays a crucial role in inflammation, vasodilation, smooth muscle contraction, cardioprotection, vascular permeability, blood pressure control, coagulation and pain. In this review, we will outline the physiology and pathophysiology of the KKS and also highlight the association of this system with carcinogenesis and cancer progression.

A role for the sensory neuropeptide calcitonin gene-related peptide in endothelial cell proliferation in vivo

BACKGROUND AND PURPOSE

We have tested the hypothesis that calcitonin gene-related peptide (CGRP) is a mediator of capsaicin-induced angiogenesis in vivo.

EXPERIMENTAL APPROACH

In a series of experiments, the knee joints of rats were injected with CGRP, capsaicin or vehicle control. Groups of animals (n=6) were treated with the CGRP receptor antagonist BIBN4096BS and/or the NK₁ receptor antagonist SR140333. Endothelium, proliferating endothelial cell nuclei and macrophages were identified 24 h later in the synovium by immunohistochemistry and quantified by image analysis. mRNA for the receptors for CGRP and adrenomedullin were sought in normal and inflamed rat and human synovia using RT-PCR.

KEY RESULTS

Intra-articular CGRP injection increased the endothelial cell proliferation index, whereas macrophage infiltration and knee joint diameters were similar to saline-injected controls. CGRP-induced endothelial cell proliferation was dose-dependently inhibited by BIBN4096BS. mRNA for adrenomedullin and the CGRP receptor subunits were detected in normal and inflamed human and rat synovia. In capsaicin-induced synovitis, the increased endothelial cell proliferation index was partially blocked by administration of NK₁ or CGRP antagonists individually and was reduced to the level of saline controls by coadministration of both receptor antagonists.

CONCLUSIONS AND IMPLICATIONS

These data support the hypothesis that CGRP stimulates angiogenesis in vivo directly by activating CGRP receptors. Capsaicin-induced endothelial cell proliferation was completely blocked by coadministration of CGRP and NK₁ receptor antagonists, indicating that both CGRP and substance P may contribute to angiogenesis in this model of synovitis.

Mechanisms and targets of angiogenesis and nerve growth in osteoarthritis

During osteoarthritis (OA), angiogenesis is increased in the synovium, osteophytes and menisci and leads to ossification in osteophytes and the deep layers of articular cartilage. Angiogenic and antiangiogenic factors might both be upregulated in the osteoarthritic joint; however, vascular growth predominates, and the articular cartilage loses its resistance to vascularization. In addition, blood vessel growth is increased at--and disrupts--the osteochondral junction. Angiogenesis in this location is dependent on the creation of channels from subchondral bone spaces into noncalcified articular cartilage. Inflammation drives synovial angiogenesis through macrophage activation. Blood vessel and nerve growth are linked by common pathways that involve the release of proangiogenic factors, such as vascular endothelial growth factor, β-nerve growth factor and neuropeptides. Proangiogenic factors might also stimulate nerve growth, and molecules produced by vascular cells could both stimulate and guide nerve growth. As sensory nerves grow along new blood vessels in osteoarthritic joints, they eventually penetrate noncalcified articular cartilage, osteophytes and the inner regions of menisci. Angiogenesis could, therefore, contribute to structural damage and pain in OA and provide potential targets for new treatments.

Pre-treatment with capsaicin in a rat osteoarthritis model reduces the symptoms of pain and bone damage induced by monosodium iodoacetate

A rat model of osteoarthritis was used to investigate the effect of pre-treatment with capsaicin on the symptoms of osteoarthritis induced by the injection of monosodium iodoacetate. This model mimics both histopathology and symptoms associated of human osteoarthritis. Injection of monosodium iodoacetate, an inhibitor of glycolysis, into the femorotibial joints of rodents promotes loss of articular trabecular bone and invokes pain symptoms similar to those noted in human osteoarthritis. Twenty rats were divided in two groups either receiving placebo or monosodium iodoacetate. Each group was subdivided in two groups either receiving pre-treatment with capsaicin two weeks before monosodium iodoacetate injection or not, resulting in four groups of five rats each. The impact of a single intra-articular administration of capsaicin (0.5%) on the generation of evoked mechanical pain (hind limb weight bearing, automated von Frey monofilament and RotaRod tests) and bone lesions (micro-CT scan radiographic analyses of bone structure) following monosodium iodoacetate-induced osteoarthritis in rats was determined. Evoked mechanical pain as monitored over a period of 4 weeks after monosodium iodoacetate injection was abolished in capsaicin pre-treated animals and pain values are comparable to those of capsaicin controls. Chronic joint pathological changes such as bone erosion and trabecular damage were significantly reduced by pre-treatment with a single administration of capsaicin. Decrease of bone volume was considerably ameliorated and trabecular connectivity was substantially better in capsaicin pre-treated animals. Capsaicin, an agonist activator of the vanilloid nociceptors (TRPV1), appears to be effective in protecting bone from arthritic damage. The present results support the hypothesis that capsaicin-sensitive sensory neurons contribute to bone lesions in the monosodium iodoacetate-induced osteoarthritis rat model.

Peptide hormone regulation of angiogenesis

It is now apparent that regulation of blood vessel growth contributes to the classical actions of hormones on development, growth, and reproduction. Endothelial cells are ideally positioned to respond to hormones, which act in concert with locally produced chemical mediators to regulate their growth, motility, function, and survival. Hormones affect angiogenesis either directly through actions on endothelial cells or indirectly by regulating proangiogenic factors like vascular endothelial growth factor. Importantly, the local microenvironment of endothelial cells can determine the outcome of hormone action on angiogenesis. Members of the growth hormone/prolactin/placental lactogen, the renin-angiotensin, and the kallikrein-kinin systems that exert stimulatory effects on angiogenesis can acquire antiangiogenic properties after undergoing proteolytic cleavage. In view of the opposing effects of hormonal fragments and precursor molecules, the regulation of the proteases responsible for specific protein cleavage represents an efficient mechanism for balancing angiogenesis. This review presents an overview of the actions on angiogenesis of the above-mentioned peptide hormonal families and addresses how specific proteolysis alters the final outcome of these actions in the context of health and disease.

Angiogenesis in osteoarthritis

PURPOSE OF REVIEW

Much has been documented in recent years on the possible involvement of angiogenesis in osteoarthritis. An understanding of the various regulatory mechanisms controlling blood vessel growth in the joint should lead to novel therapeutics, which selectively inhibit undesirable angiogenesis. Here, we summarize recent findings on the roles of angiogenesis in osteoarthritis and place this evidence in the context of previous literature in order to help explain pain and disease progression.

RECENT FINDINGS

Inflammation and angiogenesis are closely associated in osteoarthritis, modulating functions of chondrocytes, contributing towards abnormal tissue growth and perfusion, ossification and endochondral bone development, leading to radiographic changes observed in the joint. Innervation accompanies vascularization and inflammation, hypoxia and mechanical overload are all thought to contribute in sensitizing these new nerves leading to increased pain. Articular cartilage provides a unique environment in which blood vessel growth is regulated by endogenous angiogenesis inhibitors and matrix constituents, as well as by growth factors produced by chondrocytes, subchondral bone and synovium. MRI and ultrasound enable the in-vivo visualization of abnormal vascularity in synovium and subchondral bone that have not been apparent with conventional radiography. As a result of these new findings, the widely accepted notion that osteoarthritis is primarily a disease of the cartilage is being challenged.

SUMMARY

Molecular mechanisms and consequences of angiogenesis in osteoarthritis are slowly being elucidated. Studies, both in humans and animal models, support the notion that inhibiting angiogenesis will provide effective therapeutic strategies for treating osteoarthritis. Better techniques that can more precisely visualize the vascular changes of the whole joint can further enhance our understanding of osteoarthritis, and can provide proof of concept and early evidence of efficacy in trials of novel therapeutic interventions.

Observations favouring the occurrence of local production and marked effects of bombesin/gastrin-releasing peptide in the synovial tissue of the human knee joint--comparisons with substance P and the NK-1 receptor

We have previously shown that levels of the neuropeptides substance P (SP) and bombesin/gastrin-releasing peptide (BN/GRP) in blood and synovial fluid correlate with levels of pro-inflammatory cytokines in patients with rheumatoid arthritis (RA). It is well-established that SP is present in nerve endings in the synovium whilst the source of BN/GRP in human joints is completely unknown. Nor is it known whether GRP-receptors (GRP-R) are present in human synovial tissue. This study aimed to investigate the expression pattern of SP, BN/GRP and their receptors (NK-1R and GRP-R) in synovial tissue. Synovial tissue specimens from patients with RA or osteoarthritis (OA) were processed for immunohistochemistry, in situ hybridisation and ELISA. The results show the presence of BN/GRP, but not SP, in cells in the synovial tissue at both the protein and mRNA level. We did not find immunoreactive BN/GRP in nerve structures. NK-1R and GRP-R were also expressed at both protein and mRNA levels in cells associated with blood vessels and cells in the interstitial tissue. ELISA analyses revealed both SP and BN/GRP to be present in synovial tissue extracts and that synovial levels of SP were higher in RA patients than those with OA. Our results indicate that BN/GRP is produced by non-neuronal cells in the synovial tissue. Furthermore, both BN/GRP and SP may exert their effects on the synovial tissue through the respective receptors. These results suggest that BN/GRP and SP may modulate inflammation and vascular events, and possibly healing processes in the synovium. Finally, nerves should not be considered as the source of BN/GRP in synovial tissue although this peptide is presumably intimately involved functionally in synovial tissue, a previously unrecognised fact.

Pathophysiological mechanisms of angiogenesis

The growth of new blood vessels may be either beneficial or harmful. The angiogenic process may be measured by a variety of techniques, although it may often be the quality rather than quantity of resulting blood vessels that determines function. Endothelial cells play a key role in the initiation of angiogenesis, and vascular endothelial growth factor (VEGF) may be viewed as a prototypical direct-acting angiogenic factor. VEGF acts through multiple cell surface receptors and signaling pathways to stimulate endothelial cell proliferation, survival, and migration. By inducing other growth factor expression, VEGF stimulates a cascade of angiogenic activity. Different tissues may utilize various angiogenic pathways that are modulated by diverse host tissue responses. Furthermore, a single tissue may progress through a sequence of angiogenic pathways, for example, as acute injury progresses to chronic inflammation. The phenotype of the resulting neovasculature is critically dependent on the context in which it is formed. Biomarkers of angiogenesis are being developed as an aid to assessing human disease. Histological assessment of vascular density and angiogenic factor expression, in vivo imaging, Doppler ultrasound, and biofluid assays each may have clinical utility. Therapeutic targeting of angiogenesis will depend both on the generation of acceptable pharmacological agents and on the identification of patients who may and do gain benefit from such treatments.

Transcription inhibition using oligonucleotide-modified gold nanoparticles

The capture of T7 RNA polymerase using double-stranded promoter DNA on the surface of gold nanoparticles has been demonstrated. The competitive binding and inhibition of T7 RNA polymerase due to specific interactions on the nanoparticle surface represents a transcription factor decoy approach in a model system. The efficiency of inhibition was determined for various nanoparticle sizes, surface coverage, and linker length for double-stranded promoter DNA on gold nanoparticles. The experiments provide a basis for determining the accessibility of binding sites on nanoparticle surfaces for applications involving cell targeting or the use of nanoparticles as binding agents in solution.

Non-peptide antagonists for kinin B1 receptors: new insights into their therapeutic potential for the management of inflammation and pain

Kinin B1 and B2 receptors are central to the aetiology of pain and inflammation. Constitutive B2 receptors are commonly associated with the acute phase of inflammation and nociception, whereas the inducible B1 receptors are mostly linked to the chronic or persistent phase (or both). Therefore, selective, orally active kinin B1 receptor antagonists could be potentially therapeutic. B1 receptor antagonists have long been exclusively peptides, but recently a few non-peptide representatives have been identified. The clinical potential of these non-peptide molecules has not yet been evaluated, but they might have a role in treating persistent inflammation and pain, especially when no satisfactory therapy is available. This review summarizes recent advances in the identification and the potential therapeutic properties of these molecules.

Angiotensin-Converting Enzyme in Systemic Sclerosis: From Endothelial Injury to a Genetic Polymorphism

The main pathologic hallmark of systemic sclerosis (SSc) is endothelial derangement; the pathologic alterations of the vessel wall in SSc are strikingly similar to the modification detected in the atherosclerotic lesions, and it is now evident that SSc is also characterized by accelerated macrovascular disease. Peptides related to angiotensin II, the final product of the renin-angiotensin system (RAS), play a role as regulators of endothelial cell function. Angiotensin-converting enzyme (ACE), the key enzyme in the RAS, is the predominant pathway of angiotensin II formation in blood and tissues. In intron 16 of the gene encoding for ACE an insertion/deletion (I/D) polymorphism, consisting of the presence or absence of a 287-base pair Alu sequence, has been identified. This polymorphism has been related to ACE enzyme levels, and data from experimental studies reported a functional role for this polymorphism in modulating the angiotensin II levels. We previously documented a high ACE D allele frequency in SSc patients and its role in increasing the risk of SSc, thus suggesting that the I/D polymorphism might be a useful genetic marker to identify SSc patients at risk to develop a severe vascular disease, frequently leading to gangrene. Moreover, our preliminary data, besides supporting the role of ACE I/D polymorphism as a predisposing factor to SSc, demonstrated its involvement in accelerated macrovascular disease by increasing the intima media thickness. Therefore, in SSc, not only endothelial dysfunction, but also vascular damage, linked to ACE I/D polymorphism, may significantly contribute to accelerated macrovascular disease, as the ACE D allele, by regulating both the production of angiotensin II and the degradation of bradykinin, contributes to mechanisms involved in the induction and maintenance of vessel wall modification.

Two faces of high-molecular-weight kininogen (HK) in angiogenesis: bradykinin turns it on and cleaved HK (HKa) turns it off

High-molecular-weight kininogen (HK) is a plasma protein that possesses multiple physiological functions. Originally identified as a precursor of bradykinin, a bioactive peptide that regulates many cardiovascular processes, it is now recognized that HK plays important roles in fibrinolysis, thrombosis, and inflammation. HK binds to endothelial cells where it can be cleaved by plasma kallikrein to release bradykinin (BK). The remaining portion of the molecule, cleaved HK, is designated cleaved high-molecular-weight kininogen or HKa. While BK has been intensively studied, the physiological implication of the generation of HKa is not clear. Recent studies have revealed that HKa inhibits angiogenesis while BK promotes angiogenesis. These findings represent novel functions of the kallikrein-kinin system that have not yet been fully appreciated. In this review, we will briefly discuss the recent progress in the studies of the molecular mechanisms that mediate the antiangiogenic effect of HKa and the proangiogenic activity of BK.

Levels of gastrin-releasing peptide and substance P in synovial fluid and serum correlate with levels of cytokines in rheumatoid arthritis

It is well known that cytokines are highly involved in the disease process of rheumatoid arthritis (RA). Recently, targeting of neuropeptides has been suggested to have potential therapeutic effects in RA. The aim of this study was to investigate possible interrelations between five neuropeptides (bombesin/gastrin-releasing peptide (BN/GRP), substance P (SP), vasoactive intestinal peptide, calcitonin-gene-related peptide, and neuropeptide Y) and the three cytokines tumour necrosis factor (TNF)-α, IL-6, and monocyte chemoattractant protein-1 in synovial fluid of patients with RA. We also investigated possible interrelations between these neuropeptides and soluble TNF receptor 1 in serum from RA patients. Synovial fluid and sera were collected and assayed with ELISA or RIA. The most interesting findings were correlations between BN/GRP and SP and the cytokines. Thus, in synovial fluid, the concentrations of BN/GRP and SP grouped together with IL-6, and SP also grouped together with TNF-α and monocyte chemoattractant protein-1. BN/GRP and SP concentrations in synovial fluid also grouped together with the erythrocyte sedimentation rate. In the sera, BN/GRP concentrations and soluble TNF receptor 1 concentrations were correlated. These results are of interest because blocking of SP effects has long been discussed in relation to RA treatment and because BN/GRP is known to have trophic and growth-promoting effects and to play a role in inflammation and wound healing. Furthermore, the observations strengthen a suggestion that combination treatment with agents interfering with neuropeptides and cytokines would be efficacious in the treatment of RA. In conclusion, BN/GRP and SP are involved together with cytokines in the neuroimmunomodulation that occurs in the arthritic joint.

Kinin B1 receptors: key G-protein-coupled receptors and their role in inflammatory and painful processes

Kinins are a family of peptides implicated in several pathophysiological events. Most of their effects are likely mediated by the activation of two G-protein-coupled receptors: B(1) and B(2). Whereas B(2) receptors are constitutive entities, B(1) receptors behave as key inducible molecules that may be upregulated under some special circumstances. In this context, several recent reports have investigated the importance of B(1) receptor activation in certain disease models. Furthermore, research on B(1) receptors in the last years has been mainly focused in determining the mechanisms and pathways involved in the process of induction. This was essentially favoured by the advances obtained in molecular biology studies, as well as in the design of selective and stable peptide and nonpeptide kinin B(1) receptor antagonists. Likewise, development of kinin B(1) receptor knockout mice greatly helped to extend the evidence about the relevance of B(1) receptors during pathological states. In the present review, we attempted to remark the main advances achieved in the last 5 years about the participation of kinin B(1) receptors in painful and inflammatory disorders. We have also aimed to point out some groups of chronic diseases, such as diabetes, arthritis, cancer or neuropathic pain, in which the strategic development of nonpeptidic oral-available and selective B(1) receptor antagonists could have a potential relevant therapeutic interest.