Elizabeth S. Fernandes

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: B1 and B2. Whereas B2 receptors are constitutive entities, B1 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 B1 receptor activation in certain disease models. Furthermore, research on B1 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 B1 receptor antagonists. Likewise, development of kinin B1 receptor knockout mice greatly helped to extend the evidence about the relevance of B1 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 B1 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 B1 receptor antagonists could have a potential relevant therapeutic interest.

Kinin B1 Receptor Up-Regulation after Lipopolysaccharide Administration: Role of Proinflammatory Cytokines and Neutrophil Influx

Several studies have now clearly established the ability of LPS to induce bradykinin B1 receptor up-regulation in vivo and the functional relevance of this up-regulation for the pathophysiological effects of LPS. Using an in vivo system in which LPS is injected locally into the rat paw, we have examined the potential contribution of proinflammatory cytokines, NF-κB activation, and neutrophil influx for the functional and molecular up-regulation of the bradykinin B1 receptor. Treatment with LPS resulted in a rapid and sustained functional up-regulation of B1 receptors in the rat paw that correlated with the increase in B1 receptor mRNA levels. B1 receptor up-regulation is preceded by the rapid activation of the transcription factor NF-κB and the production of proinflammatory cytokines, including TNF-α and IL-1β. More importantly, blockade of NF-κB translocation, TNF-α, or IL-1β prevented the functional and molecular up-regulation of B1 receptors. Injection of LPS also induced the influx of neutrophils that followed the peak of cytokine production and associated with the persistent activation of NF-κB and functional B1 receptor up-regulation. Blockade of neutrophil influx with platelet-activating factor receptor antagonists or cell adhesion molecule blockers prevented B1 receptor up-regulation. Thus, by acting in cooperation and in a coordinated, timely manner, TNF-α, IL-1β, neutrophils, and the transcription factor NF-κB are major and essential players in the ability of LPS to induce B1 receptor expression in vivo.

Relevance of tumour necrosis factor-α for the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw

1 The present study evaluated the participation of tumour necrosis factor‐α (TNF‐α) in the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw. 2 The intraplantar injection of carrageenan (300 μg paw−1) induced a marked and biphasic paw oedema formation (peaks at 6 and 72 h), which was accompanied by a long‐lasting mechanical allodynia (that remained elevated for up to 72 h) and a significant increase of myeloperoxidase (MPO) activity (peak at 6 h) in both Swiss and C57/BL6 mice. 3 The paw oedema, the elevation of MPO activity and to a lesser extent the mechanical allodynia elicited by carrageenan were found to be significantly reduced in TNF‐α p55 receptor knockout mice. 4 Of interest, the systemic administration of an anti‐TNF‐α antibody produced a significant inhibition of paw oedema, mechanical allodynia and MPO activity. A noteworthy decrease in inflammatory and nociceptive responses caused by carrageenan was also observed when mice were previously treated with the preferential inhibitor of TNF‐α synthesis, thalidomide. 5 The present results clearly indicate that the proinflammatory cytokine TNF‐α plays a critical role in the oedema formation, as well as in the mechanical allodynia and the neutrophil migration, following carrageenan administration into the mouse paw. Intraplantar injection of carrageenan in mice could constitute a useful model for assessment of the in vivo effects of potential inhibitors of TNF‐α‐related pathways.

Bradykinin B1 Receptor Expression Induced by Tissue Damage in the Rat Portal Vein A Critical Role for Mitogen-Activated Protein Kinase and Nuclear Factor-κB Signaling Pathways

The bradykinin B1 receptor (B1R) is normally absent under physiological conditions, but is highly inducible during inflammatory conditions or following tissue damage. The present study attempted to determine some of the mechanisms underlying B1R upregulation following tissue injury in rat portal vein. Damage induced by tissue isolation and in vitro incubation caused a significant and time-dependent increase in des-Arg9–bradykinin (des-Arg9–BK) responsiveness that paralleled the B1R mRNA expression, as confirmed by real-time quantitative PCR. In vitro incubation of rat portal vein also induced the activation of some members of the mitogen activated protein kinase (MAPK) family, namely, extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAPK, an effect accompanied by degradation of the inhibitory protein IκB&agr; and translocation of nuclear transcription factor-κB (NF-κB) to the nucleus. The blockade of p38 MAPK, JNK or NF-κB, but not ERK pathways with selective inhibitors, resulted in a significant reduction of the upregulated contractile response caused by the selective B1R agonist des-Arg9–BK, and largely prevented the induction of B1R mRNA expression in the rat portal vein. Together, these results demonstrate that in vitro tissue damage induces activation of several intracellular signaling pathways that have a key role in the control of B1R expression. B1R could exert a pivotal role in the development of the cardiovascular response associated with vascular damage.

Antidepressant-like effects of Trichilia catigua (Catuaba) extract: evidence for dopaminergic-mediated mechanisms.

RationaleCurrently available therapy for depression treatment is often associated with several undesirable side effects, and it is effective only in a certain portion of the population. Therefore, the identification of alternative therapeutic tools for the treatment of depression is still needed.ObjectiveThe present study analyzed the possible antidepressant-like effects of the Brazilian medicinal plant, Trichilia catigua, in rodents. Attempts were also made to investigate some of the possible mechanisms implicated in its actions.MethodsThe antidepressant-like effects of T. catigua extract were assessed in two species of rodents (mice and rats) by means of in vivo (forced swimming test) and in vitro (monoamine reuptake and release in synaptosomal preparations) approaches.ResultsAcute oral treatment with the extract of T. catigua produced antidepressant-like effects in the forced swimming model in both mice and rats. Anti-immobility actions of T. catigua extract in mice were significantly reversed by haloperidol or by chlorpromazine, but not by pimozide, ketanserin, spiroxatrine or p-chlorophenylalanine. In vitro, T. catigua extract concentration-dependently inhibited the uptake and increased the release of serotonin, and especially of dopamine, from rat brain synaptosomal preparations.ConclusionsThe present study provides convincing evidence for a dopamine-mediated antidepressant-like effect of the active principle(s) present in the hydroalcoholic extract of T. catigua in mice and rats when in vivo and in vitro strategies were employed. Therefore, a standardized T. catigua extract or its purified constituents could be of potential interest for the treatment of depressive disorders.

The relevance of kinin B1 receptor upregulation in a mouse model of colitis

Kinins are implicated in many pathophysiological conditions, and recent evidence has suggested their involvement in colitis. This study assessed the role of the kinin B1 receptors in a mouse model of colitis.

Mechanisms underlying the modulatory action of platelet activating factor (PAF) on the upregulation of kinin B1 receptors in the rat paw

The present study evaluated the ability of the administration of platelet activating factor (PAF) to induce the upregulation of B1 receptors in the rat paw. Local treatment with PAF resulted in a time‐dependent increase of oedema formation induced by the B1 receptor agonist des‐Arg9‐BK (des‐Arg9‐bradykinin), but not by the B2 receptor agonist tyrosine8‐bradykinin. Functional upregulation of B1 receptors was accompanied by a prominent increase of B1 receptor mRNA expression in the rat paw. In PAF‐treated paws, des‐Arg9‐BK‐induced oedema formation was significantly inhibited by the B1 receptor antagonists des‐Arg9‐[Leu8]‐BK and R‐715. The effects of PAF pretreatment were receptor operated, as assessed by the effects of the PAF receptor antagonist WEB2086 or by desensitisation of PAF receptors. The protein synthesis inhibitor cycloheximide, the anti‐inflammatory steroid dexamethasone or the nuclear factor (NF‐κB) blockers pyrrolidine‐dithiocarbamate (PDTC) and Nα‐tosyl‐L‐chloromethylketone significantly blocked the functional upregulation of B1 receptors. The selectin inhibitor fucoidin, an anti‐CD18 antibody or an anti‐rat neutrophil antiserum, also significantly prevented des‐Arg9‐BK‐induced paw oedema in rats pretreated with PAF. Intradermal injection of PAF induced a 25‐fold increase of myeloperoxidase activity in the rat paw, a response that was significantly inhibited by fucoidin, anti‐CD‐18, anti‐rat neutrophil antiserum or PDTC. Local treatment with PAF also resulted in a marked increase of NF‐κB activation, an effect largely prevented by PDTC or by the anti‐rat neutrophil antiserum. Collectively, the present results indicate that the induction of B1 receptors following treatment with the chemotatic mediator PAF is dependent on the recruitment of neutrophils, an event that is under the control of adhesion molecules, protein synthesis and NF‐κB activation. These findings provide new insights into the role played by cell migration and chemotatic factors on B1 receptor upregulation in vivo.

Cytokines and neutrophils as important mediators of platelet-activating factor-induced kinin B1 receptor expression.

PAF injection into the rat paw is accompanied by the concomitant activation of NF‐κB and neutrophil influx, which appears to be relevant to the up‐regulation of kinin B1 receptors. Herein, we analyse the role of TNF‐α and IL‐1β production for PAF‐induced B1 receptor upregulation in the rat paw. Additionally, we evaluate how cytokine production and neutrophil migration fit into the temporal sequence of events leading to PAF‐induced B1 receptor upregulation. In our experiments, treatment with PAF resulted in a marked increase of B1 receptor‐mediated paw oedema and in situ production of TNF‐α at 1 h and IL‐1β at 3 and 6 h later. B1 receptor‐mediated paw oedema was significantly inhibited by anti‐TNF‐α antibody and by interleukin‐1 receptor antagonist (IRA). TNF‐α was necessary for the local PAF‐induced IL‐1β production. NF‐κB blocker PDTC prevented the production of both TNF‐α and IL‐1β, indicating that cytokine production is NF‐κB dependent. Depletion of neutrophils with an anti‐PMN antibody prevented IL‐1β, but not TNF‐α, production. Although both TNF‐α and IL‐1β are relevant to functional B1 receptor upregulation, PAF‐induced increase in B1 receptor mRNA was markedly suppressed by anti‐TNF‐α and, to a lesser extent, by IRA. B1 receptor mRNA expression was also prevented by the anti‐PMN antibody. In conclusion, the activation of the TNF‐α/neutrophil axis by PAF seems to be sufficient for B1 receptor mRNA production. However, the TNF‐α/neutrophil axis is also necessary for IL‐1β production. These two processes might lead to the appearance of functional kinin B1 upregulation receptors in vivo after PAF treatment.

Pharmacological and neurochemical evidence for antidepressant-like effects of the herbal product Catuama

Catuama is a marketed herbal product currently used as a tonic, especially for the management of mental or physical fatigue. In the present study, we have shown pharmacological and neurochemical evidence for antidepressant-like actions of the product Catuama. Acute and chronic oral treatments with Catuama both resulted in a significant reduction of the immobility time in two models of depression in mice, the forced swimming and the tail suspension tests. Conversely, treatment with the same doses of Catuama did not significantly interfere with motor activity according to assessment in the open-field test. The antidepressant-like effects were comparable to those observed for classical antidepressant drugs. When assessed in vitro, Catuama inhibited, in a concentration-dependent manner, the synaptosomal uptake of noradrenaline and principally of serotonin and dopamine, in rat brain. Likewise, in vitro incubation of Catuama also resulted in a marked increase of the release of serotonin and dopamine in rat brain crude preparation of synaptosomal membranes. Finally, Catuama was found to be effective in interfering with the synaptosomal uptake of serotonin and dopamine following long-term oral treatment of rats. The present findings allow us to suggest that the herbal product Catuama might be useful for the clinical management of moderate and mild depressive states, alone or in association with current antidepressant drugs.

Effect of novel selective non-peptide kinin B1 receptor antagonists on mouse pleurisy induced by carrageenan

Two novel selective non-peptide kinin B(1) receptor antagonists, the benzodiazepine antagonist and SSR240612, were evaluated in carrageenan-induced mouse pleurisy. The peptide R-715 (0.5 mg/kg, i.p.) and the non-peptide benzodiazepine (3 mg/kg, i.p.) antagonists significantly decreased cellular migration (predominantly neutrophils), without altering plasma exudation. SSR240612 (1 mg/kg, i.p.) diminished total cells and neutrophils, besides exudation. Oral administration of SSR240612 (10 mg/kg) also reduced total cell and neutrophil counts. Only the benzodiazepine antagonist inhibited the lung myeloperoxidase activity. No tested antagonist significantly altered the lung and pleural TNFalpha and IL-1beta production. We provide interesting evidence on the anti-inflammatory in vivo effects of non-peptide B(1) receptor antagonists.