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

Novel Insights into the Kallikrein-Kinin System in Fulminant Myocarditis: Physiological Basis and Potential Therapeutic Advances

Fulminant myocarditis (FM) is characterized by rapid cardiac deterioration often instigated by an inflammatory cytokine storm. The kallikrein-kinin system (KKS) is a metabolic cascade known for releasing vasoactive kinins, such as bradykinin-related peptides, possessing diverse pharmacological activities that include inflammation, regulation of vascular permeability, endothelial barrier dysfunction, and blood pressure modulation. The type 1 and type 2 bradykinin receptors (B1R and B2R), integral components of the KKS system, mediate the primary biological effects of kinin peptides. This review aims to offer a comprehensive overview of the primary mechanisms of the KKS in FM, including an examination of the structural components, regulatory activation, and downstream signaling pathways of the KKS. Furthermore, it explores the involvement of the tissue kallikrein/B1R/inducible nitric oxide synthase (TK/B1R/iNOS) pathway in myocyte dysfunction, modulation of the immune response, and preservation of endothelial barrier integrity. The potential therapeutic advances targeting the inhibition of the KKS in managing FM will be discussed, providing valuable insights for the development of clinical treatment strategies.

Electroacupuncture alleviates diabetes-induced mechanical allodynia and downregulates bradykinin B1 receptor expression in spinal cord dorsal horn

OBJECTIVE

Diabetic neuropathic pain (DNP) is one of the most prevalent symptoms of diabetes. The alteration of proteins in the spinal cord dorsal horn (SCDH) plays a significant role in the genesis and the development of DNP. Our previous study has shown electroacupuncture could effectively relieve DNP. However, the potential mechanism inducing DNP's genesis and development remains unclear and needs further research.

METHODS

This study established DNP model rats by intraperitoneally injecting a single high-dose streptozotocin; 2 Hz electroacupuncture was used to stimulate Zusanli (ST36) and Kunlun (BL60) of DNP rats daily from day 15 to day 21 after streptozotocin injection. Behavioral assay, quantitative PCR, immunofluorescence staining, and western blotting were used to study the analgesic mechanism of electroacupuncture.

RESULTS

The bradykinin B1 receptor (B1R) mRNA, nuclear factor-κB p65 (p65), substance P, and calcitonin gene-related peptide (CGRP) protein expression were significantly enhanced in SCDH of DNP rats. The paw withdrawal threshold was increased while body weight and fasting blood glucose did not change in DNP rats after the electroacupuncture treatment. The expression of B1R, p65, substance P, and CGRP in SCDH of DNP rats was also inhibited after the electroacupuncture treatment.

CONCLUSION

This work suggests that the potential mechanisms inducing the allodynia of DNP rats were possibly related to the increased expression of B1R, p65, substance P, and CGRP in SCDH. Downregulating B1R, p65, substance P, and CGRP expression levels in SCDH may achieve the analgesic effect of 2 Hz electroacupuncture treatment.

Kinin Receptors and Kinin-Related Gene Expression in Astrocytic Brain Tumors

Kinins are a set of peptides present in tissues that are involved in the inflammatory response and cancer progression. However, studies showing the expression of kinin receptors in human glioma samples are still incomplete and contradictory. The aim of the present study was to ascertain the expression of BDKRB1 and BDKRB2 genes, as well as the level of B1R and B2R proteins in human gliomas, depending on the degree of malignancy. Additionally, representative kinin-dependent genes with altered expression were indicated. The expression profile of kinin-dependent genes was determined using oligonucleotide microarray technique. In addition, RT-qPCR was used to assess the expression level of selected differentiating genes. The location of kinin receptors in brain gliomas was assessed using immunohistochemical methods. The oligonucleotide microarray method was used to identify 12 mRNA IDs of kinin-related genes whose expression was upregulated or downregulated in gliomas of different grades. In immunohistochemically stained samples, the concentrations of BR1 and BR2 proteins, measured by optical density, were statistically significantly higher in grade G3 vs. G2 and G4 vs. G3. Increased expression of kinin receptors BDKRB1 and BDKRB2 in brain gliomas, depending on the degree of malignancy, suggests the involvement of kinins and their receptors in the disease's pathogenesis. Quantitative assessment of mRNA BDKRB1, PRKAR1A, MAP2K, and EGFR in patients with brain tumors may hold diagnostic and therapeutic significance.

An overview of kinin mediated events in cancer progression and therapeutic applications

Kinins are bioactive peptides generated in the inflammatory milieu of the tissue microenvironment, which is involved in cancer progression and inflammatory response. Kinins signals through activation of two G-protein coupled receptors; inducible Bradykinin Receptor B1 (B1R) and constitutive receptor B2 (B2R). Activation of kinin receptors and its cross-talk with receptor tyrosine kinases activates multiple signaling pathways, including ERK/MAPK, PI3K, PKC, and p38 pathways regulating cancer hallmarks. Perturbations of the kinin-mediated events are implicated in various aspects of cancer invasion, matrix remodeling, and metastasis. In the tumor microenvironment, kinins initiate fibroblast activation, mesenchymal stem cell interactions, and recruitment of immune cells. Albeit the precise nature of kinin function in the metastasis and tumor microenvironment are not completely clear yet, several kinin receptor antagonists show anti-metastatic potential. Here, we showcase an overview of the complex biology of kinins and their role in cancer pathogenesis and therapeutic aspects.

The family of kallikrein-related peptidases and kinin peptides as modulators of epidermal homeostasis

The epidermis is the outermost skin layer and is part of one of the largest organs in the body; it is supported by the dermis, a network of fibrils, blood vessels, pilosebaceous units, sweat glands, nerves, and cells. The skin as a whole is a protective shield against numerous noxious agents, including microorganisms and chemical and physical factors. These functions rely on the activity of multiple growth factors, peptide hormones, proteases, and specific signaling pathways that are triggered by the activation of distinct types of receptors sited in the cell membranes of the various cell types present in the skin. The human kallikrein family comprises a large group of 15 serine proteases synthesized and secreted by different types of epithelial cells throughout the body, including the skin. At this site, they initiate a proteolytic cascade that generates the active forms of the proteases, some of which regulate skin desquamation, activation of cytokines, and antimicrobial peptides. Kinin peptides are formed by the action of plasma and tissue kallikreins on kininogens, two plasma proteins produced in the liver and other organs. Although kinins are well known for their proinflammatory abilities, in the skin they are also considered important modulators of keratinocyte differentiation. In this review, we summarize the contributions of the kallikreins and kallikrein-related peptidases family and those of kinins and their receptors in skin homeostasis, with special emphasis on their pathophysiological role.

A comprehensive review on current understanding of bradykinin in COVID-19 and inflammatory diseases

Bradykinin, a member of the kallikrein–kinin system (KKS), is a potent, short-lived vasoactive peptide that acts as a vasodilator and an inflammatory mediator in a number of signaling mechanisms. Bradykinin induced signaling is mediated through kinin B1 (BDKRB1) and B2 (BDKRB2) transmembrane receptors coupled with different subunits of G proteins (G_αi/G_α0, G_αq and G_β1γ2). The bradykinin-mediated signaling mechanism activates excessive pro-inflammatory cytokines, including IL-6, IL-1β, IL-8 and IL-2. Upregulation of these cytokines has implications in a wide range of clinical conditions such as inflammation leading to fibrosis, cardiovascular diseases, and most recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In SARS-CoV-2 infection, bradykinin is found to be at raised levels and is reported to trigger a diverse array of symptoms. All of this brings bradykinin to the core point as a molecule of immense therapeutic value. Our understanding of its involvement in various pathways has expanded with time. Therefore, there is a need to look at the overall picture that emerges from the developments made by deciphering the bradykinin mediated signaling mechanisms involved in the pathological conditions. It will help devise strategies for developing better treatment modalities in the implicated diseases. This review summarizes the current state of knowledge on bradykinin mediated signaling in the diverse conditions described above, with a marked emphasis on the therapeutic potential of targeting the bradykinin receptor.

Acute kidney injury caused by venomous animals: inflammatory mechanisms

Either bites or stings of venomous animals comprise relevant public health problems in tropical countries. Acute kidney injury (AKI) induced by animal toxins is related to worse prognostic and outcomes. Being one the most important pathways to induce AKI following envenoming due to animal toxins, inflammation is an essential biological response that eliminates pathogenic bacteria and repairs tissue after injury. However, direct nephrotoxicity (i.e. apoptotic and necrotic mechanisms of toxins), pigmenturia (i.e. rhabdomyolysis and hemolysis), anaphylactic reactions, and coagulopathies could contribute to the renal injury. All these mechanisms are closely integrated, but inflammation is a distinct process. Hence, it is important to improve our understanding on inflammation mechanisms of these syndromes to provide a promising outlook to reduce morbidity and mortality. This literature review highlights the main scientific evidence of acute kidney injury induced by bites or stings from venomous animals and their inflammatory mechanisms. It included observational, cross-sectional, case-control and cohort human studies available up to December 2019. Descriptors were used according to Medical Subject Headings (MeSH), namely: “Acute kidney injury” or “Venom” and “Inflammation” on Medline/Pubmed and Google Scholar; “Kidney disease” or “Acute kidney injury” on Lilacs and SciELO. The present review evidenced that, among the described forms of renal inflammation, it can occur either directly or indirectly on renal cells by means of intravascular, systemic and endothelial hemolysis, activation of inflammatory pathway, as well as direct action of venom cytotoxic components on kidney structures.

Blockade of the kinin B1 receptor counteracts the depressive-like behaviour and mechanical allodynia in ovariectomised mice

Menopause is related to a decline in ovarian oestrogen production, affecting the perception of the somatosensory stimuli, changing the immune-inflammatory systems, and triggering depressive symptoms. It has been demonstrated that the inhibition of the kinin B₁ and B₂ receptors (B₁R and B₂R) prevented the depressive-like behaviour and the mechanical allodynia that was induced by immune-inflammatory mediators in mice. However, there is no evidence regarding the role of the kinin receptors in the depressive-like and nociceptive behaviour in female mice that were subjected to bilateral ovariectomy (OVX). This study has shown that the OVX mice developed time-related mechanical allodynia, together with an increased immobility time as indicative of depression. Both of these changes were reduced by the genetic deletion of B₁R, or by the pharmacological blockade of the selective kinin B₁R antagonist R-715 (acute, i.p.). The genetic deletion or the pharmacological inhibition of B₂R (HOE 140, i.p.) did not prevent the OVX-elicited behavioural changes. The data has suggested a particular modulation of kinin B₁R in the nociceptive and depressive-like behaviour in the OVX mice. The selective inhibition of the B₁R receptor may be a new pharmacological target for treating pain and depression symptoms in women during the perimenopause/menopause period.

Kinins and Their Receptors in Infectious Diseases

Kinins and their receptors have been implicated in a series of pathological alterations, representing attractive pharmacological targets for several diseases. The present review article aims to discuss the role of the kinin system in infectious diseases. Literature data provides compelling evidence about the participation of kinins in infections caused by diverse agents, including viral, bacterial, fungal, protozoan, and helminth-related ills. It is tempting to propose that modulation of kinin actions and production might be an adjuvant strategy for management of infection-related complications.

Mechanisms for Reducing Neuropathic Pain

Injury typically results in the development of neuropathic pain, but the pain normally decreases and disappears in paralleled with wound healing. The pain results from cells resident at, and recruited to, the injury site releasing pro-inflammatory cytokines and other mediators leading to the development of pro-inflammatory environment and causing nociceptive neurons to develop chronic ectopic electrical activity, which underlies neuropathic pain. The pain decreases as some of the cells that induce pro-inflammation, changing their phenotype leading to the blocking the release of pro-inflammatory mediators while releasing anti-inflammatory mediators, and blocking nociceptive neuron chronic spontaneous electrical activity. Often, despite apparent wound healing, the neuropathic pain becomes chronic. This raises the question of how chronic pain can be eliminated. While many of the cells and mediators contributing to the development and maintenance of neuropathic pain are known, a better understanding is required of how the injury site environment can be controlled to permanently eliminate the pro-inflammatory environment and silence the chronically electrically active nociceptive neurons. This paper examines how methods that can promote the transition of the pro-inflammatory injury site to an anti-inflammatory state, by changing the composition of local cell types, modifying the activity of pro- and anti-inflammatory receptors, inducing the release of anti-inflammatory mediators, and silencing the chronically electrically active nociceptive neurons. It also examines the hypothesis that factors released from platelet-rich plasma applied to chronic pain sites can permanently eliminate chronic inflammation and its associated chronic pain.

Functional interrelationships between the kallikrein-related peptidases family and the classical kinin system in the human neutrophil

In the human neutrophil, kallikrein-related peptidases (KLKs) have a significant functional relationship with the classical kinin system as a kinin B1 receptor agonist induces secretion of KLK1, KLK6, KLK10, KLK13 and KLK14 into the medium. Secretion of KLK1, the kinin-forming enzyme, may perpetuate formation of kinin in the inflammatory milieu by hydrolyzing extravasated kininogens present in tissue edema. Secretion of KLKs into the inflammatory milieu, induced by kinins or other proinflammatory mediators, provides the human neutrophil with a wide range of molecular interactions to hydrolyze different cellular and extracellular matrix components, which may be of critical relevance in different mechanisms involving inflammation.

The kinin B1 and B2 receptors and TNFR1/p55 axis on neuropathic pain in the mouse brachial plexus

Tumour necrosis factor (TNF) and kinins have been associated with neuropathic pain-like behaviour in numerous animal models. However, the way that they interact to cause neuron sensitisation remains unclear. This study assessed the interaction of kinin receptors and TNF receptor TNFR1/p55 in mechanical hypersensitivity induced by an intraneural (i.n.) injection of rm-TNF into the lower trunk of brachial plexus in mice. The i.n. injection of rm-TNF reduced the mechanical withdrawal threshold of the right forepaw from the 3rd to the 10th day after the injection, indicating that TNF1/p55 displays a critical role in the onset of TNF-elicited neuropathic pain. The connection between TNF1/p55 and kinin B₁ and B₂ receptors (B₁R and B₂R) was confirmed using both knockout mice and mRNAs quantification in the injected nerve, DRG and spinal cord. The treatment with the B₂R antagonist HOE 140 or with B₁R antagonist des-Arg⁹-Leu⁸-BK reduced both BK- and DABK-induced hypersensitivity. The experiments using kinin receptor antagonists and CPM inhibitor (thiorphan) suggest that BK does not only activate B₂R as an orthosteric agonist, but also seems to be converted into DABK that consequently activates B₁R. These results indicate a connection between TNF and the kinin system, suggesting a relevant role for B₁R and B₂R in the process of sensitisation of the central nervous systems by the cross talk between the receptor and CPM after i.n. injection of rm-TNF.

Renal and vascular effects of kallikrein inhibition in a model of Lonomia obliqua venom-induced acute kidney injury

BACKGROUND

Lonomia obliqua venom is nephrotoxic and acute kidney injury (AKI) is the main cause of death among envenomed victims. Mechanism underlying L. obliqua-induced AKI involves renal hypoperfusion, inflammation, tubular necrosis and loss of glomerular filtration and tubular reabsorption capacities. In the present study, we aimed to investigate the contribution of kallikrein to the hemodynamic instability, inflammation and consequent renal and vascular impairment.

METHODOLOGY/PRINCIPAL FINDINGS

Addition of L. obliqua venom to purified prekallikrein and human plasma in vitro or to vascular smooth muscle cells (VSMC) in culture, was able to generate kallikrein in a dose-dependent manner. Injected in rats, the venom induced AKI and increased kallikrein levels in plasma and kidney. Kallikrein inhibition by aprotinin prevented glomerular injury and the decrease in glomerular filtration rate, restoring fluid and electrolyte homeostasis. The mechanism underlying these effects was associated to lowering renal inflammation, with decrease in pro-inflammatory cytokines and matrix metalloproteinase expression, reduced tubular degeneration, and protection against oxidative stress. Supporting the key role of kallikrein, we demonstrated that aprotinin inhibited effects directly associated with vascular injury, such as the generation of intracellular reactive oxygen species (ROS) and migration of VSMC induced by L. obliqua venom or by diluted plasma obtained from envenomed rats. In addition, kallikrein inhibition also ameliorated venom-induced blood incoagulability and decreased kidney tissue factor expression.

CONCLUSIONS/SIGNIFICANCE

These data indicated that kallikrein and consequently kinin release have a key role in kidney injury and vascular remodeling. Thus, blocking kallikrein may be a therapeutic alternative to control the progression of venom-induced AKI and vascular disturbances.

Effect of the bradykinin 1 receptor antagonist SSR240612 after oral administration in Mycobacterium tuberculosis-infected mice

The role, if any, played by the kinin system in tuberculosis infection models, either in vivo or in vitro, was investigated. The effects of Mycobacterium tuberculosis infection on C57BL/6 wild type, B₁R-/-, B₂R-/- and double B₁R/B₂R knockout mice were evaluated. Immunohistochemistry analysis was carried out to assess B₁R and B₂R expression in spleens and lungs of M. tuberculosis-infected mice. In addition, in vitro experiments with M. tuberculosis-infected macrophages were performed. The in vivo effects of HOE-140 and SSR240612 on the mice model of infection were also evaluated. Infected B₂R-/- mice exhibited increased splenomegaly, whereas decreased spleen weight in infected double B₁R/B₂R knockout mice was observed. The bacterial load, determined as colony-forming units, did not differ in the spleens and lungs of the studied mouse strains. Importantly, immunohistochemical analysis revealed that B₁R was upregulated in both spleens and lungs of infected mice. M. tuberculosis-infected macrophages incubated with SSR240612, alone or in combination with des-Arg⁹-BK, for four days, displayed a marked inhibitory effect on CFU counts. However, the pre-incubation of the selective B₁R (des-Arg⁹-BK and SSR240612) and B₂R (BK and HOE-140) agonists and antagonists, respectively, did not significantly affect the bacterial loads. A statistically significant reduction in the CFU of M. tuberculosis in lungs and spleens of animals treated with SSR240612, but not with HOE-140, was observed. Further efforts should be pursued to clarify whether or not SSR240612 might be considered an option for the treatment of tuberculosis.

Exploiting cancer's phenotypic guise against itself: targeting ectopically expressed peptide G-protein coupled receptors for lung cancer therapy

Lung cancer, claiming millions of lives annually, has the highest mortality rate worldwide. This advocates the development of novel cancer therapies that are highly toxic for cancer cells but negligibly toxic for healthy cells. One of the effective treatments is targeting overexpressed surface receptors of cancer cells with receptor-specific drugs. The receptors-in-focus in the current review are the G-protein coupled receptors (GPCRs), which are often overexpressed in various types of tumors. The peptide subfamily of GPCRs is the pivot of the current article owing to the high affinity and specificity to and of their cognate peptide ligands, and the proven efficacy of peptide-based therapeutics. The article summarizes various ectopically expressed peptide GPCRs in lung cancer, namely, Cholecystokinin-B/Gastrin receptor, the Bombesin receptor family, Bradykinin B1 and B2 receptors, Arginine vasopressin receptors 1a, 1b and 2, and the Somatostatin receptor type 2. The autocrine growth and pro-proliferative pathways they mediate, and the distinct tumor-inhibitory effects of somatostatin receptors are then discussed. The next section covers how these pathways may be influenced or 'corrected' through therapeutics (involving agonists and antagonists) targeting the overexpressed peptide GPCRs. The review proceeds on to Nano-scaled delivery platforms, which enclose chemotherapeutic agents and are decorated with peptide ligands on their external surface, as an effective means of targeting cancer cells. We conclude that targeting these overexpressed peptide GPCRs is potentially evolving as a highly promising form of lung cancer therapy.

JA, Zamuner SR. Analgesic Effect of Photobiomodulation on Bothrops Moojeni Venom-Induced Hyperalgesia: A Mechanism Dependent on Neuronal Inhibition, Cytokines and Kinin Receptors Modulation

Background

Envenoming induced by Bothrops snakebites is characterized by drastic local tissue damage that involves an intense inflammatory reaction and local hyperalgesia which are not neutralized by conventional antivenom treatment. Herein, the effectiveness of photobiomodulation to reduce inflammatory hyperalgesia induced by Bothrops moojeni venom (Bmv), as well as the mechanisms involved was investigated.

Methodology/Principal Findings

Bmv (1 μg) was injected through the intraplantar route in the right hind paw of mice. Mechanical hyperalgesia and allodynia were evaluated by von Frey filaments at different time points after venom injection. Low level laser therapy (LLLT) was applied at the site of Bmv injection at wavelength of red 685 nm with energy density of 2.2 J/cm² at 30 min and 3 h after venom inoculation. Neuronal activation in the dorsal horn spinal cord was determined by immunohistochemistry of Fos protein and the mRNA expression of IL-6, TNF-α, IL-10, B1 and B2 kinin receptors were evaluated by Real time-PCR 6 h after venom injection. Photobiomodulation reversed Bmv-induced mechanical hyperalgesia and allodynia and decreased Fos expression, induced by Bmv as well as the mRNA levels of IL-6, TNF-α and B1 and B2 kinin receptors. Finally, an increase on IL-10, was observed following LLLT.

Conclusion/Significance

These data demonstrate that LLLT interferes with mechanisms involved in nociception and hyperalgesia and modulates Bmv-induced nociceptive signal. The use of photobiomodulation in reducing local pain induced by Bothropic venoms should be considered as a novel therapeutic tool for the treatment of local symptoms induced after bothropic snakebites.

Envenoming caused by Bothrops snakes is characterized by drastic local tissue damage involving hemorrhage, blistering, myonecrosis, prominent inflammatory response and intense pain. The most effective treatment for Bothrops snakebites is antivenom therapy, which is very efficient in reversing systemic effects of envenomation but not the severe local effects. Thus, there exists a need to find novel complementary therapies that may further assist in the prevention or even counteract the severe local effects of bothrops snakebite. Several studies have shown the effectiveness of photobiomodulation in reducing local effects induced by Bothropic venoms, however its mechanisms still remain unknown. In this study, we analyzed the effectiveness of photobiomodulation in reducing BmV-induced mechanical allodynia and hyperalgesia as well as part of the mechanisms involved in such effect. Results demonstrate that photobiomodulation reduces venom-induced mechanical allodynia and hyperalgesia and this effect depends on a decrease of nociceptor activation at the spinal cord level and by a modulation of pro- and anti- inflammatory cytokines as well as kinin receptors at mRNA transcriptional levels. These findings make phtobiomodulation a promising candidate to be associated to antivenom therapy for the treatment of the local response induced by Bothrops venoms.

New insights into the stereochemical requirements of the bradykinin B1 receptor antagonists binding

Bradykinin (BK) is a nonapeptide involved in several pathophysiological conditions including among others, septic and haemorrhagic shock, anaphylaxis, arthritis, rhinitis, asthma, inflammatory bowel disease. Accordingly, BK antagonists have long been sought after for therapeutic intervention. Action of BK is mediated through two different G-protein coupled receptors known as B1 and B2. Although there are several B1 antagonists reported in literature, their pharmacological profile is not yet optimal so that new molecules need to be discovered. In the present work we have constructed an atomistic model of the B1 receptor and docked diverse available non-peptide antagonists in order to get a deeper insight into the structure-activity relationships involving binding to this receptor. The model was constructed by homology modeling using the chemokine CXC4 and bovine rhodopsin receptors as template. The model was further refined using molecular dynamics for 600ns with the protein embedded in a POPC bilayer. From the refinement process we obtained an average structure that was used for docking studies using the Glide software. Antagonists selected for the docking studies include Compound 11, Compound 12, Chroman28, SSR240612, NPV-SAA164 and PS020990. The results of the docking study underline the role of specific receptor residues in ligand binding. The results of this study permitted to define a pharmacophore that describes the stereochemical requirements of antagonist binding, and can be used for the discovery of new compounds.

Sesquiterpenes from Essential Oils and Anti-Inflammatory Activity

This review is aimed at presenting relevant information on the therapeutic potential of essential oil sesquiterpenes with anti-inflammatory activity. The data reviewed provide a basis for seeking new anti-inflammatory drugs from natural products that do not exhibit the undesirable side effects often displayed by anti-inflammatory drugs. In this review the experimental models, possible mechanisms of action, and chemical structures of 12 sesquiterpenes are presented.

Divergence in endothelin-1- and bradykinin-activated store-operated calcium entry in afferent sensory neurons

Endothelin-1 (ET-1) and bradykinin (BK) are endogenous peptides that signal through Gαq/11-protein coupled receptors (GPCRs) to produce nociceptor sensitization and pain. Both peptides activate phospholipase C to stimulate Ca²⁺ accumulation, diacylglycerol production, and protein kinase C activation and are rapidly desensitized via a G-protein receptor kinase 2-dependent mechanism. However, ET-1 produces a greater response and longer lasting nocifensive behavior than BK in multiple models, indicating a potentially divergent signaling mechanism in primary afferent sensory neurons. Using cultured sensory neurons, we demonstrate significant differences in both Ca²⁺ influx and Ca²⁺ release from intracellular stores following ET-1 and BK treatments. As intracellular store depletion may contribute to the regulation of other signaling cascades downstream of GPCRs, we concentrated our investigation on store-operated Ca²⁺ channels. Using pharmacological approaches, we identified transient receptor potential canonical channel 3 (TRPC3) as a dominant contributor to Ca²⁺ influx subsequent to ET-1 treatment. On the other hand, BK treatment stimulated Orai1 activation, with only minor input from TRPC3. Taken together, data presented here suggest that ET-1 signaling targets TRPC3, generating a prolonged Ca²⁺ signal that perpetuates nocifensive responses. In contrast, Orai1 dominates as the downstream target of BK receptor activation and results in transient intracellular Ca²⁺ increases and abridged nocifensive responses.

Antinociceptive and anti-hyperalgesic effects of bis(4-methylbenzoyl) diselenide in mice: evidence for the mechanism of action

CONTEXT

The organoselenium compounds have been described to demonstrate several biological activities, including pain management.

OBJECTIVE

This study investigated the antinociceptive, hyperalgesic, and toxic effects of oral administration of bis(4-methylbenzoyl) diselenide (BMD) in mice.

MATERIALS AND METHODS

The antinociceptive and anti-hyperalgesic effects of BMD (1, 5, 10, 25, and 50 mg/kg, p.o.) were evaluated using models of nociception: formalin, capsaicin, bradykinin (BK), cinnamaldehyde, phorbol myristate acetate (PMA), 8-bromo-cAM, and glutamate-induced nociception; and mechanical hyperalgesia induced by carrageenan (Cg) or complete Freund's adjuvant (CFA). The acute toxicity was evaluated by biochemical markers for hepatic and renal damages.

RESULTS

BMD significantly inhibited the licking time of the injected paw in the early and late phases of a formalin test with ED50 values of 14.2 and 10.8 mg/kg, respectively. This compound reduced nociception produced by capsaicin (ED50 of 32.5 mg/kg), BK (ED50 of 24.6 mg/kg), glutamate (ED50 of 28.7 mg/kg), cinnamaldehyde (ED50 of 18.9 mg/kg), PMA (ED50 of 9.6 mg/kg), and 8-bromo-cAMP (ED50 of 24.8 mg/kg). In the glutamate test, the pretreatment with nitric oxide (NO) precursor, L-arginine, reversed antinociception caused by BMD or N(ω)-nitro-L-arginine (L-NOARG), but the effect of BMD was not abolished by naloxone. Mechanical hyperalgesia induced by Cg and CFA was attenuated by BMD, 70 ± 4% and 65 ± 4%, respectively. Furthermore, a single oral dose of BMD did not change plasma aspartate (AST) and alanine aminotransferase (ALT) activities or urea and creatinine levels.

CONCLUSION

BMD demonstrated as a promising compound because of the antinociceptive and anti-hyperalgesic properties in mice.

Calcium-permeable ion channels in pain signaling

The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.

Exacerbation of DSS-induced colitis in mice lacking kinin B(1) receptors through compensatory up-regulation of kinin B(2) receptors: the role of tight junctions and intestinal homeostasis

BACKGROUND AND PURPOSE

Kinins are pro-inflammatory peptides that are released during tissue injury, including that caused by inflammatory bowel disease. Herein, we assessed the role and underlying mechanisms through which the absence of kinin B(1) receptors exacerbates the development of dextran sulfate sodium (DSS)-induced colitis in mice.

EXPERIMENTAL APPROACH

B(1) and B(2) receptor antagonists and B(1) receptor knockout mice (B1(-/-) ) were used to assess the involvement of B(1) and B(2) receptor signalling in a DSS-colitis. B(1) receptor, B(2) receptor, occludin and claudin-4 expression, cytokine levels and cell permeability were evaluated in colon from wild-type (WT) and B1(-/-) mice.

KEY RESULTS

DSS-induced colitis was significantly exacerbated in B1(-/-) compared with WT mice. IL-1β, IFN-γ, keratinocyte-derived chemokine and macrophage inflammatory protein-2 were markedly increased in the colon from DSS-treated B1(-/-) compared with DSS-treated WT mice. Treatment of WT mice with a selective B(1) receptor antagonist, DALBK or SSR240612, had no effect on DSS-induced colitis. Of note, B(2) receptor mRNA expression was significantly up-regulated in colonic tissue from the B1(-/-) mice after DSS administration. Moreover, treatment with a selective B(2) receptor antagonist prevented the exacerbation of colitis in B1(-/-) mice following DSS administration. The water- or DSS-treated B1(-/-) mice showed a decrease in occludin gene expression, which was partially prevented by the B(2) receptor antagonist.

CONCLUSIONS AND IMPLICATIONS

A loss of B(1) receptors markedly exacerbates the severity of DSS-induced colitis in mice. The increased susceptibility of B1(-/-) may be associated with compensatory overexpression of B(2) receptors, which, in turn, modulates tight junction expression.

MAPK/NF-κB-dependent upregulation of kinin receptors mediates airway hyperreactivity: a new perspective for the treatment

Airway hyperreactivity (AHR) is a major feature of asthmatic and inflammatory airways. Cigarette smoke exposure, and bacterial and viral infections are well-known environmental risk factors for AHR, but knowledge about the underlying molecular mechanisms on how these risk factors lead to the development of AHR is limited. Activation of intracellular mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) and their related signal pathways including protein kinase C (PKC), phosphoinositide 3-kinase (PI3K) and protein kinase A (PKA) signaling pathways may result in airway kinin receptor upregulation, which is suggested to play an important role in the development of AHR. Environmental risk factors trigger the production of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interleukins (ILs) that activate intracellular MAPK- and NF-κB-dependent inflammatory pathways, which subsequently lead to AHR via kinin receptor upregulation. Blockage of intracellular MAPK/NF-κB signaling prevents kinin B₁ and B₂ receptor expression in the airways, resulting in a decrease in the response to bradykinin (kinin B₂ receptor agonist) and des-Arg⁹-bradykinin (kinin B₁ receptor agonist). This suggests that MAPK- and NF-κB-dependent kinin receptor upregulation can provide a novel option for treatment of AHR in asthmatic as well as in other inflammatory airway diseases.

The bradykinin B1 receptor regulates Aβ deposition and neuroinflammation in Tg-SwDI mice

The deposition of amyloid-β peptides (Aβ) in the cerebral vasculature, a condition known as cerebral amyloid angiopathy, is increasingly recognized as an important component leading to intracerebral hemorrhage, neuroinflammation, and cognitive impairment in Alzheimer disease (AD) and related disorders. Recent studies demonstrated a role for the bradykinin B1 receptor (B1R) in cognitive deficits induced by Aβ in mice; however, its involvement in AD and cerebral amyloid angiopathy is poorly understood. Herein, we investigated the effect of B1R inhibition on AD-like neuroinflammation and amyloidosis using the transgenic mouse model (Tg-SwDI). B1R expression was found to be up-regulated in brains of Tg-SwDI mice, specifically in the vasculature, neurons, and astrocytes. Notably, administration of the B1R antagonist, R715, to 8-month-old Tg-SwDI mice for 8 weeks resulted in higher Aβ40 levels and increased thioflavin S-positive fibrillar Aβ deposition. Moreover, blockage of B1R inhibited neuroinflammation, as evidenced by the decreased accumulation of activated microglia and reactive astrocytes, diminished NF-κB activation, and reduced cytokine and chemokine levels. Together, our results indicate that B1R activation plays an important role in limiting the accumulation of Aβ in AD-like brain, likely through the regulation of activated glial cell accumulation and release of pro-inflammatory mediators. Therefore, the modulation of the receptor may represent a novel therapeutic approach for AD.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

Functional and molecular characterization of kinin B1 and B 2 receptors in human bladder cancer: implication of the PI3Kγ pathway

Kinins and their receptors have been recently implicated in cancer. Using functional and molecular approaches, we investigated the relevance of kinin B1 and B2 receptors in bladder cancer. Functional studies were conducted using bladder cancer cell lines, and human biopsies were employed for molecular studies. Both B1 des-Arg(9)-BK and B2 BK receptor agonists stimulated the proliferation of grade 3-derived T24 bladder cancer cells. Furthermore, treatment with B1 and B2 receptor antagonists (SSR240612 and HOE140) markedly inhibited the proliferation of T24 cells. Only higher concentrations of BK increased the proliferation of the grade 1 bladder cancer cell line RT4, while des-Arg(9)-BK completely failed to induce its proliferation. Real-time PCR revealed that the mRNA expression of kinin receptors, particularly B1 receptors, was increased in T24 cells relative to RT4 cells. Data from bladder cancer human biopsies revealed that B1 receptor expression was increased in all tumor samples and under conditions of chronic inflammation. We also show novel evidence demonstrating that the pharmacological inhibition of PI3Kγ (phosphatidylinositol 3-kinase) with AS252424, concentration-dependently reduced T24 cell proliferation induced by BK or des-Arg(9)-BK. Finally, the incubation of T24 cells with kinin agonists led to a marked activation of the PI3K/AKT and ERK 1/2 signaling pathways, whereas p38 MAP kinase remained unaffected. Kinin receptors, especially B1 receptors, appear to be implicated in bladder cancer progression. It is tempting to suggest that selective kinin antagonists might represent potential alternative therapies for bladder cancer.

Kinin-mediated inflammation in neurodegenerative disorders

The mediatory role of kinins in both acute and chronic inflammation within nervous tissues has been widely described. Bradykinin, the major representative of these bioactive peptides, is one of a few mediators of inflammation that directly stimulates afferent nerves due to the broad expression of specific kinin receptors in cell types in these tissues. Moreover, kinins may be delivered to a site of injury not only after their production at the endothelium surface but also following their local production through the enzymatic degradation of kininogens at the surface of nerve cells. A strong correlation between inflammatory processes and neurodegeneration has been established. The activation of nerve cells, particularly microglia, in response to injury, trauma or infection initiates a number of reactions in the neuronal neighborhood that can lead to cell death after the prolonged action of inflammatory substances. In recent years, there has been a growing interest in the effects of kinins on neuronal destruction. In these studies, the overexpression of proteins involved in kinin generation or of kinin receptors has been observed in several neurologic disorders including neurodegenerative diseases such Alzheimer's disease and multiple sclerosis as well as disorders associated with a deficiency in cell communication such as epilepsy. This review is focused on recent findings that provide reliable evidence of the mediatory role of kinins in the inflammatory responses associated with different neurological disorders. A deeper understanding of the role of kinins in neurodegenerative diseases is likely to promote the future development of new therapeutic strategies for the control of these disorders. An example of this could be the prospective use of kinin receptor antagonists.

Characterization of dual agonists for kinin B1 and B2 receptors and their biased activation of B2 receptors

Kinin B1 and B2 receptors (kB1R and kB2R) play important roles in many physiological and pathological processes. In some cases, kB1R or kB2R activation can have overlapping or complementary beneficial effects, thus an activator of both receptors might be advantageous. We found that replacement of the C-terminal Arg in the natural kB2R activators bradykinin (BK) or kallidin (KD) with Lys (K(9)-BK or K(10)-KD) resulted in agonists that effectively stimulate the downstream signaling of both the kB1R and kB2R as measured by increased inositol turnover, intracellular calcium, ERK1/2 phosphorylation, arachidonic acid release and NO production. However, K(9)-BK and K(10)-KD displayed some characteristics of biased agonism for kB2Rs as indicated by the rapid kinetics of ERK1/2 phosphorylation induced by K(9)-BK or K(10)-KD compared with the prolonged response mediated by BK or KD. In contrast, kinetics of ERK phosphorylation stimulated by K(10)-KD activation of the kB1R was the same as that induced by known kB1R agonist des-Arg(10)-KD. Furthermore, the endocytosis of kB2Rs mediated by K(9)-BK and K(10)-KD was remarkably less than that induced by BK and KD respectively. K(10)-KD stimulated kB1R and kB2R-dependent calcium responses and ERK1/2 phosphorylation in bovine endothelial cells. In cytokine-treated human endothelial cells, K(10)-KD stimulated ERK1/2 phosphorylation and a transient peak of NO production that was primarily kB2R-dependent. K(10)-KD also stimulated prolonged NO production that was both kB1R and kB2R-dependent. These data provide the first examples of dual agonists of kB1R and kB2R, and a biased agonist of kB2R and may provide useful clues for developing dual modulators of kB1Rs and kB2Rs for potential therapeutic use.

Anti-nociceptive effect of kinin B₁ and B₂ receptor antagonists on peripheral neuropathy induced by paclitaxel in mice

BACKGROUND AND PURPOSE

In the current study, we investigated the role of both kinin B₁ and B₂ receptors in peripheral neuropathy induced by the chronic treatment of mice with paclitaxel a widely used chemotherapeutic agent.

EXPERIMENTAL APPROACH

Chemotherapy-evoked hyperalgesia was induced by i.p. injections of paclitaxel (2 mg·kg⁻¹) over 5 consecutive days. Mechanical and thermal hyperalgesia were evaluated between 7 and 21 days after the first paclitaxel treatment.

KEY RESULTS

Treatment with paclitaxel increased both mechanical and thermal hyperalgesia in mice (C57BL/6 and CD1 strains). Kinin receptor deficient mice (B₁, or B₂ receptor knock-out and B₁B₂ receptor, double knock-out) presented a significant reduction in paclitaxel-induced hypernociceptive responses in comparison to wild-type animals. Treatment of CD1 mice with kinin receptor antagonists (DALBK for B₁ or Hoe 140 for B₂ receptors) significantly inhibited both mechanical and thermal hyperalgesia when tested at 7 and 14 days after the first paclitaxel injection. DALBK and Hoe 140 were also effective against paclitaxel-induced peripheral neuropathy when given intrathecally or i.c.v. A marked increase in B₁ receptor mRNA was observed in the mouse thalamus, parietal and pre-frontal cortex from 7 days after the first paclitaxel treatment.

CONCLUSIONS AND IMPLICATIONS

Kinins acting on both B₁ and B₂ receptors, expressed in spinal and supra-spinal sites, played a crucial role in controlling the hypernociceptive state caused by chronic treatment with paclitaxel.

Blockade of kinin B(1) receptor reverses plasma fatty acids composition changes and body and tissue fat gain in a rat model of insulin resistance

AIM

Kinin B(1) receptor (B(1) R) contributes to insulin resistance through a mechanism involving oxidative stress. This study examined the effect of B(1) R blockade on the changes in plasma fatty acids composition, body and tissue fat mass and adipose tissue inflammation that influence insulin resistance.

METHODS

Sprague-Dawley rats were fed with 10% D-glucose or tap water (Control) for 13 weeks and during the last week, rats were administered the B(1) R antagonist SSR240612 (10 mg/kg/day, gavage) or vehicle. The following parameters were assessed: plasma fatty acids (by gas chromatography), body composition (by EchoMRI), metabolic hormone levels (by radioimmunoassay), expression of B(1) R and inflammatory markers in adipose tissue (by Western blot and qRT-PCR).

RESULTS

Glucose feeding significantly increased plasma levels of glucose, insulin, leptin, palmitoleic acid (16:1n-7), oleic acid (18:1n-9), Δ6 and Δ9 desaturases while linoleic acid (18:2n-6), arachidonic acid (20:4n-6) and Δ5 desaturase were decreased. SSR240612 reduced plasma levels of insulin, glucose, the homeostasis model assessment index of insulin resistance, palmitoleic acid and n-7 family. Alterations of Δ5, Δ6 and Δ9 desaturases were normalized by SSR240612. The B(1) R antagonist also reversed the enhancing effect of glucose feeding on whole body and epididymal fat mass and on the expression of macrophage CD68, interleukin-1β, tumour necrosis factor-α and inducible nitric oxide synthase in retroperitoneal adipose tissue. B(1) R protein and mRNA were not detected in retroperitoneal adipose tissue.

CONCLUSION

Insulin resistance in glucose-fed rats is associated with low state inflammation in adipose tissue and plasma fatty acids changes which are reversed by B(1) R blockade. These beneficial effects may contribute to insulin sensitivity improvement and the prevention of obesity.

The role of kinin receptors in preventing neuroinflammation and its clinical severity during experimental autoimmune encephalomyelitis in mice

Background

Multiple sclerosis (MS) is a demyelinating and neuroinflammatory disease of the human central nervous system (CNS). The expression of kinins is increased in MS patients, but the underlying mechanisms by which the kinin receptor regulates MS development have not been elucidated.

Methodology/Principal Findings

Experimental autoimmune encephalomyelitis (EAE) was induced in female C57BL/6 mice by immunization with MOG_35–55 peptide emulsified in complete Freund's adjuvant and injected with pertussis toxin on day 0 and day 2. Here, we report that blockade of the B₁R in the induction phase of EAE markedly suppressed its progression by interfering with the onset of the immune response. Furthermore, B₁R antagonist suppressed the production/expression of antigen-specific T_H1 and T_H17 cytokines and transcription factors, both in the periphery and in the CNS. In the chronic phase of EAE, the blockade of B₁R consistently impaired the clinical progression of EAE. Conversely, administration of the B₁R agonist in the acute phase of EAE suppressed disease progression and inhibited the increase in permeability of the blood-brain barrier (BBB) and any further CNS inflammation. Of note, blockade of the B₂R only showed a moderate impact on all of the studied parameters of EAE progression.

Conclusions/Significance

Our results strongly suggest that kinin receptors, mainly the B₁R subtype, play a dual role in EAE progression depending on the phase of treatment through the lymphocytes and glial cell-dependent pathways.

Antinociceptive and anti-hypernociceptive effects of Se-phenyl thiazolidine-4-carboselenoate in mice

In this study, the antinociceptive, anti-hypernociceptive and toxic effects of orally administered (R)-Se-phenyl thiazolidine-4-carboselenoate (Se-PTC, 1-50 mg/kg) were evaluated in mice. Se-PTC did not change plasma aspartate (AST) and alanine aminotransferase (ALT) activities or urea and creatinine levels. Furthermore, in an open field test, Se-PTC did not alter the number of crossings and rearing. Se-PTC significantly reduced the amount of writhing when assessed by acetic acid-induced visceral nociception and attenuated the licking time of the injected paw in the early and late phases of a formalin test. In addition, Se-PTC reduced nociception produced by intra-plantar (i.pl.) injection of glutamate, capsaicin, cinnalmaldehyde, bradykinin, phorbol myristate acetate and 8-Bromo-cAMP. Se-PTC caused a significant increase in hot plate and tail-immersion response latencies, but the antinociceptive effect of Se-PTC in the tail immersion was not abolished by pretreatment with the non-selective opioid receptor antagonist, naloxone. Se-PTC (25 mg/kg) significantly inhibited nociceptive behavior induced by intrathecal (i.t.) injection of glutamate, N-methyl-D-aspartate (NMDA) and (±)-1-aminocyclopentane-trans-1,3-dicarboxylic acid (trans-ACPD), but failed to affect nociception induced by kainate and α-amino-3-hydroxy-5-mehtyl-4-isoxazolepropionic acid (AMPA). Mechanical hypernociception induced by carrageenan and Complete Freund's Adjuvant was attenuated by Se-PTC administration. These results indicate that Se-PTC produces antinociception in several models of nociception.

Cross-talk between carboxypeptidase M and the kinin B1 receptor mediates a new mode of G protein-coupled receptor signaling

G protein-coupled receptor (GPCR) signaling is affected by formation of GPCR homo- or heterodimers, but GPCR regulation by other cell surface proteins is not well understood. We reported that the kinin B1 receptor (B1R) heterodimerizes with membrane carboxypeptidase M (CPM), facilitating receptor signaling via CPM-mediated conversion of bradykinin or kallidin to des-Arg kinin B1R agonists. Here, we found that a catalytically inactive CPM mutant that still binds substrate (CPM-E264Q) also facilitates efficient B1R signaling by B2 receptor agonists bradykinin or kallidin. This response required co-expression of B1R and CPM-E264Q in the same cell, was disrupted by antibody that dissociates CPM from B1R, and was not found with a CPM-E264Q-B1R fusion protein. An additional mutation that reduced the affinity of CPM for C-terminal Arg and increased the affinity for C-terminal Lys inhibited the B1R response to bradykinin (with C-terminal Arg) but generated a response to Lys(9)-bradykinin. CPM-E264Q-mediated activation of B1Rs by bradykinin resulted in increased intramolecular fluorescence resonance energy transfer (FRET) in a B1R FRET construct, similar to that generated directly by a B1R agonist. In cytokine-treated human lung microvascular endothelial cells, disruption of B1R-CPM heterodimers inhibited B1R-dependent NO production stimulated by bradykinin and blocked the increased endothelial permeability caused by treatment with bradykinin and pyrogallol (a superoxide generator). Thus, CPM and B1Rs on cell membranes form a critical complex that potentiates B1R signaling. Kinin peptide binding to CPM causes a conformational change in the B1R leading to intracellular signaling and reveals a new mode of GPCR activation by a cell surface peptidase.

A novel pathway for receptor-mediated post-translational activation of inducible nitric oxide synthase

Inducible nitric oxide synthase (iNOS) is a major source of nitric oxide during inflammation whose activity is thought to be controlled primarily at the expression level. The B1 kinin receptor (B1R) post-translationally activates iNOS beyond its basal activity via extracellular signal regulated kinase (ERK)-mediated phosphorylation of Ser(745) . Here we identified the signalling pathway causing iNOS activation in cytokine-treated endothelial cells or HEK293 cells transfected with iNOS and B1R. To allow kinetic measurements of nitric oxide release, we used a sensitive porphyrinic microsensor (response time = 10 msec.; 1 nM detection limit). B1Rs signalled through Gαi coupling as ERK and iNOS activation were inhibited by pertussis toxin. Furthermore, transfection of constitutively active mutant Gαi Q204L but not Gαq Q209L resulted in high basal iNOS-derived nitric oxide. G-βγ subunits were also necessary as transfection with the β-adrenergic receptor kinase C-terminus inhibited the response. B1R-dependent iNOS activation was also inhibited by Src family kinase inhibitor PP2 and trans-fection with dominant negative Src. Other ERK-MAP kinase members were involved as the response was inhibited by dominant negative H-Ras, Raf kinase inhibitor, ERK activation inhibitor and MEK inhibitor PD98059. In contrast, PI3 kinase inhibitor LY94002, calcium chelator 1,2-bis-(o-Aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid, tetraacetoxymethyl ester (BAPTA-AM), protein kinase C inhibitor calphostin C and protein kinase C activator PMA had no effect. Angiotensin converting enzyme inhibitor enalaprilat also directly activated B1Rs to generate high output nitric oxide via the same pathway. These studies reveal a new mechanism for generating receptor-regulated high output nitric oxide in inflamed endothelium that may play an important role in the development of vascular inflammation.

Kinin B1 receptors mediate depression-like behavior response in stressed mice treated with systemic E. coli lipopolysaccharide

BACKGROUND

Kinin B1 receptors are inducible molecules up-regulated after inflammatory stimuli. This study evaluated the relevance of kinin B1 receptors in a mouse depression behavior model.

METHODS

Mice were exposed to a 5-min swimming session, and 30 min later they were injected with E. coli lipopolysaccharide (LPS). Depression-like behavior was assessed by determining immobility time in a tail suspension test. Different brain structures were collected for molecular and immunohistochemical studies. Anhedonia was assessed by means of a sucrose intake test.

RESULTS

Our protocol elicited an increase in depression-like behavior in CF1 mice, as assessed by the tail-suspension test, at 24 h. This behavior was significantly reduced by treatment with the selective B1 receptor antagonists R-715 and SSR240612. Administration of SSR240612 also prevented an increase in number of activated microglial cells in mouse hippocampus, but did not affect a reduction in expression of mRNA for brain-derived neurotrophic factor. The increased immobility time following LPS treatment was preceded by an enhancement of hippocampal and cortical B1 receptor mRNA expression (which were maximal at 1 h), and a marked production of TNFα in serum, brain and cerebrospinal fluid (between 1 and 6 h). The depression-like behavior was virtually abolished in TNFα p55 receptor-knockout mice, and increased B1 receptor mRNA expression was completely absent in this mouse strain. Furthermore, treatment with SSR240612 was also effective in preventing anhedonia in LPS-treated mice, as assessed using a sucrose preference test.

CONCLUSION

Our data show, for the first time, involvement of kinin B1 receptors in depressive behavioral responses, in a process likely associated with microglial activation and TNFα production. Thus, selective and orally active B1 receptor antagonists might well represent promising pharmacological tools for depression therapy.

Kinin B1 receptor enhances the oxidative stress in a rat model of insulin resistance: outcome in hypertension, allodynia and metabolic complications

Background

Kinin B₁ receptor (B₁R) is induced by the oxidative stress in models of diabetes mellitus. This study aims at determining whether B₁R activation could perpetuate the oxidative stress which leads to diabetic complications.

Methods and Findings

Young Sprague-Dawley rats were fed with 10% D-Glucose or tap water (controls) for 8–12 weeks. A selective B₁R antagonist (SSR240612) was administered acutely (3–30 mg/kg) or daily for a period of 7 days (10 mg/kg) and the impact was measured on systolic blood pressure, allodynia, protein and/or mRNA B₁R expression, aortic superoxide anion (O₂^•−) production and expression of superoxide dismutase (MnSOD) and catalase. SSR240612 reduced dose-dependently (3–30 mg/kg) high blood pressure in 12-week glucose-fed rats, but had no effect in controls. Eight-week glucose-fed rats exhibited insulin resistance (HOMA index), hypertension, tactile and cold allodynia and significant increases of plasma levels of glucose and insulin. This was associated with higher aortic levels of O₂^•−, NADPH oxidase activity, MnSOD and catalase expression. All these abnormalities including B₁R overexpression (spinal cord, aorta, liver and gastrocnemius muscle) were normalized by the prolonged treatment with SSR240612. The production of O₂^•− in the aorta of glucose-fed rats was also measured in the presence and absence of inhibitors (10–100 µM) of NADPH oxidase (apocynin), xanthine oxidase (allopurinol) or nitric oxide synthase (L-NAME) with and without Sar[D-Phe⁸]des-Arg⁹-BK (20 µM; B₁R agonist). Data show that the greater aortic O₂^•− production induced by the B₁R agonist was blocked only by apocynin.

Conclusions

Activation of kinin B₁R increased O₂^•− through the activation of NADPH oxidase in the vasculature. Prolonged blockade of B₁R restored cardiovascular, sensory and metabolic abnormalities by reducing oxidative stress and B₁R gene expression in this model.

Blockade of the kinin B1 receptor ameloriates glomerulonephritis

Severe inflammation characterizes rapidly progressive glomerulonephritides, and expression of the kinin B1 receptor (B1R) associates with inflammation. Delayed B1R blockade reduces renal inflammation in a model of unilateral ureteral obstruction, but whether B1R modulates the pathophysiology of glomerulonephritides is unknown. Here, we observed an association of B1R protein expression and inflammation, in both glomeruli and the renal interstitium, in biopsies of patients with glomerulonephritides, Henoch-Schönlein purpura nephropathy, and ANCA-associated vasculitis. In the nephrotoxic serum-induced glomerulonephritis model, we observed upregulation of the B1R receptor; treatment with a B1R antagonist beginning 2 weeks after the onset of disease reduced both glomerular and tubular lesions and improved renal function. B1R blockade reduced renal chemokine expression and macrophage accumulation. Collectively, our data demonstrate that blockade of the kinin B1R has significant potential for the treatment of glomerulonephritis.

Distribution and expression of B2-kinin receptor on human leukocyte subsets in young adults and elderly using flow cytometry

The kallikrein-kinin system has been investigated in many experimental models. Dysregulations of the KKS are likely to be involved in pathologies such as inflammation, cancer and cardiovascular diseases. Previous works on the human KKS mostly rely on gene polymorphism and mRNA expression. In order to assess the KKS in human at the protein level, we have developed an approach based on flow cytometric analysis of leukocytes. Whole blood samples were collected and erythrocytes were lysed. Permeabilised leukocytes were incubated with anti-B2R (IgG2b), anti-IgG2b-PE, anti-CD3-PerCP (lymphocytes) and anti-CD14-APC (monocytes) antibodies. FACScalibur analyzed fluorescence intensities. Results were expressed as per cent of B2R-positive cells in each leukocyte subset and as B2R fluorescence intensity per positive cell. Detection of the B2R protein by this methodology was validated by (i) correlation with Western blotting using two different B2R antibodies, (ii) BK-induced Erk activation, (iii) B2R mRNA expression. The methodology was then applied to evaluate variations of B2R expression in a population including young healthy, elderly healthy, and elderly treated hypertensive men and women. In the young healthy subjects, B2R distribution was: monocytes>polymorphonuclear neutrophils (PMN)>lymphocytes and no difference with gender was observed. Moreover, no difference was observed on PMN B2R expression. B2R expression remained unchanged in the elderly healthy or hypertensive men. By contrast, monocytes and lymphocytes B2R expressions were decreased in the elderly healthy women. Finally, FACS analysis of B2R expression on leukocytes subsets provides single cell quantification of B2R expression allowing comparison of cellular sub-populations. This approach provides a new efficient tool to investigate B2R profiling of immune system in pathological states.

Differential regulation of inducible and endothelial nitric oxide synthase by kinin B1 and B2 receptors

Kinins are vasoactive peptides that play important roles in cardiovascular homeostasis, pain and inflammation. After release from their precursor kininogens, kinins or their C-terminal des-Arg metabolites activate two distinct G protein-coupled receptors (GPCR), called B2 (B2R) or B1 (B1R). The B2R is expressed constitutively with a wide tissue distribution. In contrast, the B1R is not expressed under normal conditions but is upregulated by tissue insult or inflammatory mediators. The B2R is considered to mediate many of the acute effects of kinins while the B1R is more responsible for chronic responses in inflammation. Both receptors can couple to Galphai and Galphaq families of G proteins to release mediators such as nitric oxide (NO), arachidonic acid, prostaglandins, leukotrienes and endothelium-derived hyperpolarizing factor and can induce the release of other inflammatory agents. The focus of this review is on the different transduction events that take place upon B2R and B1R activation in human endothelial cells that leads to generation of NO via activation of different NOS isoforms. Importantly, B2R-mediated eNOS activation leads to a transient ( approximately 5min) output of NO in control endothelial cells whereas in cytokine-treated endothelial cells, B1R activation leads to very high and prolonged ( approximately 90min) NO production that is mediated by a novel signal transduction pathway leading to post-translational activation of iNOS.