Bradykinin Antagonist Research Articles

Analgesic effect of a bradykinin antagonist – a 1,4-benzodiazepine-2-one derivative

Aim. To study the analgesic effect of a new 1,4-benzodiazepine-2-one derivative (codenamed PAV-0056) in pain models in mice, its anti-inflammatory effect in experimental exudative inflammation in rats, and its potential ulcerogenic effect.Materials and methods. A 1,4-benzodiazepine-2-one derivative (codenamed PAV-0056) was orally administered in polyvinylpyrrolidone (PVP) solution to 192 CD-1 mice weighing 20–25 g and 140 Sprague – Dawley rats weighing 250–300 g. The analgesic effect of the PAV-0056 compound at a dose of 0.01, 0.1, and 1 mg / kg was studied in murine acute thermal pain models (hot plate test, hot water immersion tail-flick test), acute chemogenic pain models (formalin test), and visceral spasticity-related pain models (acetic acid-induced writhing test). The anti-inflammatory effect of PAV-0056 at doses of 0.01, 0.1, and 1 mg / kg was studied in an experimental rat model of inflammation induced by subplantar administration of bradykinin and histamine. The potential ulcerogenic effect was studied in intact rats, who were injected with PAV-0056 at doses of 1 and 50 mg / kg four times. The analgesic effect of the PAV-0056 compound was compared to that of diclofenac sodium at a dose of 10 mg / kg and tramadol at a dose of 20 mg / kg. Its anti-inflammatory and potential ulcerogenic effects were compared to those of diclofenac sodium at a dose of 10 mg / kg.Results. In the hot plate test, the PAV-0056 compound at a dose of 0.1 mg / kg increased response latency in mice by 36%, and at a dose of 1 mg / kg, it increased response latency by 46% (p < 0.05). In the tail-flick test, the PAV-0056 compound at a dose of 1 mg / kg increased response latency to heat stimulation in mice by 46% (p < 0.05). After subplantar administration of formalin, PAV-0056 at doses of 0.01–1 mg / kg had a pronounced analgesic effect, as shown by a decrease in the number of pain responses by 39–55% (p < 0.05). When mice were intraperitoneally injected with an acetic acid solution, the PAV-0056 compound at doses of 0.1 and 1 mg / kg reduced the frequency of writhings by 46 and 57%, respectively; at a dose of 0.1 mg / kg, it delayed the onset of the first writhing by 21% (p < 0.05). In experiments on rats, the PAV-0056 compound prevented the development of exudative inflammation induced by subplantar administration of bradykinin and did not have an anti-inflammatory effect in histamine-induced inflammation. PAV-0056 did not cause formation of gastric ulcers and gastric mucosal bleeding.Conclusion. A 1,4-benzodiazepine-2-one derivative, PAV-0056, has a pronounced analgesic effect in models of thermal, chemogenic, somatic, and visceral pain in a wide range of doses (0.01–1 mg / kg). Its analgesic effects are the same as those of diclofenac sodium at a dose of 10 mg / kg and tramadol at a dose of 20 mg / kg. The analgesic effect of the PAV-0056 compound is selective, depends little on suppression of inflammatory exudation, and is caused by bradykinin antagonism. This substance has low toxicity and does not damage the gastric mucosa.

Report of the first seven agents in the I-SPY COVID trial: a phase 2, open label, adaptive platform randomised controlled trial

An urgent need exists to rapidly screen potential therapeutics for severe COVID-19 or other emerging pathogens associated with high morbidity and mortality. Using an adaptive platform design created to rapidly evaluate investigational agents, hospitalised patients with severe COVID-19 requiring ≥6L/min oxygen were randomised to either a backbone regimen of dexamethasone and remdesivir alone (controls) or backbone plus one open-label investigational agent. Patients were enrolled to the arms described between July 30, 2020 and June 11, 2021 in 20 medical centres in the United States. The platform contained up to four potentially available investigational agents and controls available for randomisation during a single time-period. The two primary endpoints were time-to-recovery (<6L/min oxygen for two consecutive days) and mortality. Data were evaluated biweekly in comparison to pre-specified criteria for graduation (i.e., likely efficacy), futility, and safety, with an adaptive sample size of 40-125 individuals per agent and a Bayesian analytical approach. Criteria were designed to achieve rapid screening of agents and to identify large benefit signals. Concurrently enrolled controls were used for all analyses. https://clinicaltrials.gov/ct2/show/NCT04488081. The first 7 agents evaluated were cenicriviroc (CCR2/5 antagonist; n=92), icatibant (bradykinin antagonist; n=96), apremilast (PDE4 inhibitor; n=67), celecoxib/famotidine (COX2/histamine blockade; n=30), IC14 (anti-CD14; n=67), dornase alfa (inhaled DNase; n=39) and razuprotafib (Tie2 agonist; n=22). Razuprotafib was dropped from the trial due to feasibility issues. In the modified intention-to-treat analyses, no agent met pre-specified efficacy/graduation endpoints with posterior probabilities for the hazard ratios [HRs] for recovery ≤1.5 between 0.99 and 1.00. The data monitoring committee stopped Celecoxib/Famotidine for potential harm (median posterior HR for recovery 0.5, 95% credible interval [CrI] 0.28-0.90; median posterior HR for death 1.67, 95% CrI 0.79-3.58). None of the first 7 agents to enter the trial met the prespecified criteria for a large efficacy signal. Celecoxib/Famotidine was stopped early for potential harm. Adaptive platform trials may provide a useful approach to rapidly screen multiple agents during a pandemic. Quantum Leap Healthcare Collaborative is the trial sponsor. Funding for this trial has come from: the COVID R&D Consortium, Allergan, Amgen Inc., Takeda Pharmaceutical Company, Implicit Bioscience, Johnson & Johnson, Pfizer Inc., Roche/Genentech, Apotex Inc., FAST Grant from Emergent Venture George Mason University, The DoD Defense Threat Reduction Agency (DTRA), The Department of Health and Human ServicesBiomedical Advanced Research and Development Authority (BARDA), and The Grove Foundation. Effort sponsored by the U.S. Government under Other Transaction number W15QKN-16-9-1002 between the MCDC, and the Government.

APPROACHING THE STIFF UPPER LIP: A CASE OF PSEUDOANGIOEDEMA DIAGNOSED AS OROFACIAL GRANULOMATOSIS

<h3>Introduction</h3> Angioedema describes transient swelling in the deeper layers of the skin and mucosa, broadly categorized as histaminergic or bradykinin-mediated. Allergists should also be familiar with conditions that mimic angioedema to hasten proper management and avoid negative impact from misdiagnosis. We describe a case of one such condition, Orofacial granulomatosis with pyostomatitis vegetans, involving disfiguring inflammation of the orofacial soft tissue and often associated with comorbid inflammatory bowel disease. <h3>Case Description</h3> A 61-year-old female with a history of dysphagia, COPD, Esophageal stenosis and stroke was referred to Allergy for ten years of recurrent facial and lip swelling. ER visits resulted in multiple rounds of corticosteroids with variable success. Antibiotics for presumed cellulitis, epinephrine, high dose antihistamines and bradykinin antagonists (icatibant) were unsuccessful. Work up included normal complement studies (C3, C4, C1q, C1 esterase quantity/function). After being lost to follow up, the patient re-presented with firm, fixed lip swelling (figure 1), pustules of the buccal mucosa, dysphagia and diarrhea, prompting hospital admission. Buccal biopsy demonstrated pathology suggestive of pyostomatitis vegetans, a rare inflammatory dermatosis strongly associated with IBD. Labs demonstrated high titer positivity for <i>saccharomyces cerevisiae</i> antibody (ASCA) IgG and IgA, with a 95% specificity for IBD, particularly ulcerative colitis. She is currently being trialed on empiric anti-TNF therapy with adalimumab. <h3>Discussion</h3> This is a rare case of pseudoangioedema from Orofacial granulomatosis with pyostomatitis vegetans in the setting of suspected inflammatory bowel disease. The progressive nature and complexity of this disease underscore the importance of Allergists being familiar with disorders that mimic angioedema.

SUCCESSFUL USE OF ICATIBANT PRE-TREATMENT TO PREVENT SYSTEMIC REACTION DURING LDL APHERESIS

<h3>Introduction</h3> Familial hyperlipidemia(FH) is a hereditary condition characterized by elevated low-density lipoprotein (LDL) levels, treated by medications and possibly apheresis when refractory. There's a rare risk of anaphylactoid reactions in 0.2-0.4%. Current literature reports apheresis reactions could be mediated by complement, bradykinin, or cytokine activation. <h3>Case Description</h3> A 62-year-old man with FH and coronary artery disease, not taking ACE-inhibitors/ARBs, developed recurrent systemic reactions during apheresis after COVID-19 infection 1 month prior. Reactions consisted of headache, facial/tongue swelling, and oral tingling. For 7 years before his COVID-19 infection, he tolerated apheresis with a pre-medication routine of solumedrol and diphenhydramine. After the COVID-19 infection, reactions subsided after stopping the procedure. For his subsequent procedure, prednisone prior was unsuccessful at preventing reactions. For the following infusion, adjunctive prednisone, cetirizine, aspirin, montelukast administered the night prior and morning of the infusion and slowing the infusion rate to the lowest settings were unsuccessful. Complement and tryptase levels were all normal at baseline and following symptomatic treatments (Table 1) suggesting no predisposition to angioedema. Given elevated bradykinin levels are associated with LDL apheresis and these reactions, Icatibant was administered before infusion along with his routine pre-medications, and the apheresis procedure was completed without incident. <h3>Discussion</h3> Limited documented cases of these reactions during LDL apheresis respond to bradykinin antagonists and none of which began after COVID-19 infection. COVID-19 is associated with significant inflammation, but rarely angioedema. Further investigation is needed as to why this FH patient is more sensitive to the effects of bradykinin after COVID-19 infection.

Role of methyle blue in the management of mild, moderate and severe COVID-19 disease.

Role of methyle blue in the management of mild, moderate and severe COVID-19 disease.

In silico drug designing for the identification of promising antagonist hit molecules against bradykinin receptor

The Bradykinin system is concerned in the intervention and infection of the vasoconstrictor renin-angiotensin system and the vasodilators of prostacyclin and blood pressure lowering in humans. Consequently, Bradykinin antagonist’s molecules have long been sought after for therapeutic intervention. This study is designed to predict the potential inhibitory compound against Bradykinin receptor (BKRB1 and BKRB2) by molecular docking and molecular dynamics study. Further the DFT calculations and Binding free Energy also calculated by prime MM-GBSA analysis. As results we found the Life Chemical (227973, 228010 and 228006) Enamine (106442 and 98932) compounds are inhibits a BKRB1 and Life Chemical (60420, 52337, and 217153) and Enamine (110650 and 41276) compounds are having inhibitory action against BKRB2. Therefore, BKRB1 and BKRB2 inhibitory compounds binding energy value range from −78.82 to 51.10 and −71.12, to –33.50 kcal/mol respectively. Furthermore, the experimental validations are essential to confirm the influence of identified compounds against the target.

Exploiting Knowledge on Structure-Activity Relationships for Designing Peptidomimetics of Endogenous Peptides.

Endogenous peptides are important mediators in cell communication, being consequently involved in many physiological processes. Their use as therapeutic agents is limited due to their poor pharmacokinetic profile. To circumvent this drawback, alternative diverse molecules based on the stereochemical features that confer their activity can be synthesized, using them as guidance; from peptide surrogates provided with a better pharmacokinetic profile, to small molecule peptidomimetics, through cyclic peptides. The design process requires a competent use of the structure-activity results available on individual peptides. Specifically, it requires synthesis and analysis of the activity of diverse analogs, biophysical information and computational work. In the present work, we show a general framework of the process and show its application to two specific examples: the design of selective AT1 antagonists of angiotensin and the design of selective B2 antagonists of bradykinin.

Discovery of a Bradykinin B2 Partial Agonist Profile of Raloxifene in a Drug Repurposing Campaign.

Covid-19 urges a deeper understanding of the underlying molecular mechanisms involved in illness progression to provide a prompt therapeutical response with an adequate use of available drugs, including drug repurposing. Recently, it was suggested that a dysregulated bradykinin signaling can trigger the cytokine storm observed in patients with severe Covid-19. In the scope of a drug repurposing campaign undertaken to identify bradykinin antagonists, raloxifene was identified as prospective compound in a virtual screening process. The pharmacodynamics profile of raloxifene towards bradykinin receptors is reported in the present work, showing a weak selective partial agonist profile at the B2 receptor. In view of this new profile, its possible use as a therapeutical agent for the treatment of severe Covid-19 is discussed.

Molecular Features of Non-Selective Small Molecule Antagonists of the Bradykinin Receptors.

Angiotensin converting enzyme 2 (ACE2) downregulation is a key negative factor for the severity of lung edema and acute lung failure observed in patients infected with SARS-CoV-2. ACE2 downregulation affects the levels of diverse peptide mediators of the renin-agiotensin-aldestosterone and kallikrein-kinin systems, compromising vascular hemostasis. Increasing evidence suggests that the inflammatory response observed in covid-19 patients is initiated by the action of kinins on the bradykinin receptors. Accordingly, the use of bradykinin antagonists should be considered as a strategy for therapeutic intervention against covid-19 illness progression. Presently, icatibant is the only bradykinin antagonist drug approved. In the present report, we investigated the molecular features characterizing non-selective antagonists targeting the bradykinin receptors and carried out a in silico screening of approved drugs, aimed at the identification of compounds with a non-selective bradykinin antagonist profile that can be evaluated for drug repurposing. The study permitted to identify eight compounds as prospective non-selective antagonists of the bradykinin receptors, including raloxifene; sildenafil; cefepime; cefpirome; imatinib; ponatinib; abemaciclib and entrectinib.

Bradykinin 1 Receptor Antagonist BI1026706 Does Not Reduce Central Retinal Thickness in Center-Involved Diabetic Macular Edema.

PurposeThe bradykinin 1 receptor may be important in inflammatory retinal vascular leakage in diabetic macular edema. BI 1026706 is an antagonist of bradykinin 1 receptor that has demonstrated efficacy in preclinical studies. Boehringer Ingelheim trial 1320.22 (NCT02732951) was a randomized, double-blind, placebo-controlled study. The pharmacodynamics, safety, and tolerability of oral BI 1026706 for 12 weeks were evaluated in patients with type 1 or type 2 diabetes mellitus and mild visual impairment owing to center-involved diabetic macular edema.MethodsPatients (n = 105) were randomized to receive either oral BI 1026706 100 mg twice daily (morning and evening) or placebo for 12 weeks. The primary end point of the study was week 12 change from baseline in central subfield foveal thickness (CSFT) by spectral domain optical coherence tomography. Additional end points included absolute CSFT values, safety, and pharmacokinetics.ResultsAfter 12 weeks of treatment, there was no meaningful change from baseline in the adjusted mean CSFT in either treatment group (BI 1026706, 10.3 µm; placebo, –6.2 µm; adjusted mean treatment difference, 16.5 µm [95% confidence interval, –16.2 to 49.1]). There were also no differences in best-corrected visual acuity outcomes between treatment groups. Most reported adverse events were of mild or moderate intensity, and were balanced between treatment groups.ConclusionsBI 1026706 was not superior to placebo in CSFT week-12 change from baseline. Therefore, BI 1026706 does not reduce CSFT, a morphologic sign of diabetic macular edema.Translational RelevanceKinin-kallikrein inhibition effects may not be apparent over 12 weeks for bradykinin 1 receptor inhibition alone.

Hereditary angioedema

Hereditary angioedema (HAE) encompasses aheterogeneous group of diseases with similar phenotypes but different underlying genotypes. Specific clinical signs may point to HAE as opposed to histaminergic angioedema: the typical prolonged development of angioedema over time, positive family history, a lack of response to antihistamines and steroids and response to bradykinin antagonists are typical signs of HAE. The different types of HAE may be associated with asevere clinical course. They are life-long conditions and are still potentially life-threatening. The quality of life of patients with HAE may be considerably impaired. Management plans should be individualized, which is facilitated by the variety of specific medicastions available.

Serum bradykinin levels as a diagnostic marker in cervical cancer with a potential mechanism to promote VEGF expression via BDKRB2.

Bradykinin (BK) is one of the kinin peptides and preferentially binds to bradykinin B2 receptor (BDKRB2). A recent study indicated that BK played an important role in the occurrence and progression of cancer. In this study, we evaluated the serum BK levels in 130 cervical cancer (CC) cases (including 65 cases with pre- and post-surgery paired samples, another 65 cases with only pre-surgery samples), 35 cervical intraepithelial neoplasia (CIN) cases (pre- and post-surgery paired) and 35 control cases. We found that BK was overexpressed in patients with CC compared to patients with CIN and the control group. When combined with squamous cell carcinoma-related antigen (SCCA), the diagnostic efficacy of BK was prominently enhanced. Moreover, we detected the expression level of the BK receptor BDKRB2 in CC, CIN and normal cervical tissues and observed a higher expression in the CC and CIN tissues than in the normal cervix. We then explored the possible mechanisms of action of BK in promoting the progression of CC. When BK was added to the cell culture medium, human umbilical vein endothelial cell (HUVEC) angiogenesis increased and vascular endothelial growth factor (VEGF) expression in CC cell lines was also elevated. The BK antagonist, HOE140, exerted an opposite effect. The knockdown or the overexpression of BDKRB2 in CC cell lines further confirmed its oncogenic role in angiogenesis. Taken together, the findings of this study suggest that BK may be a diagnostic biomarker for CC and may notably improve the diagnostic efficacy when combined with SCCA. BK promotes the progression of CC by upregulating the expression of VEGF via BDKRB2 and subsequently facilitating angiogenesis.

Incidence of orolingual angioedema after intravenous thrombolysis for stroke.

Orolingual angioedema (OA) is a known adverse effect of intravenous (i.v.) alteplase. We analyzed all patients treated with i.v. alteplase for stroke at our hospital since approval of i.v. thrombolysis in Italy in 2004 to assess the incidence of this complication. Four hundred thirty-three patients received alteplase for stroke from April 2004 to May 2017. Two women developed OA (0.4%; 95% confidence interval 0.1 to 1.6%). Angioedema was mild in one case and severe in the other, with massive swelling of the lips, tongue, and oropharyngeal mucosa, and oropharyngeal bleeding, requiring intubation. Neither patient used ACE-inhibitors. The incidence of orolingual angioedema was very low in our series. Although OA is usually mild, anaphylactoid reactions may rarely occur, because of the variable degree of activation of the complement system and kinin cascade caused by alteplase. In such instances, admission to neurointensive care may be required. Specific bradykinin antagonists or drugs that target the kallikrein-kinin system are beginning to be used in the more severe cases. Thus, doctors and nurses caring for acute stroke patients need to be able to recognize and treat this complication.

Pharmacotherapy for Angiotensin-Converting Enzyme Inhibitor-Induced Angioedema: A Systematic Review.

Objective Angioedema is a potentially life-threatening complication of angiotensin-converting enzyme inhibitor (ACEI) use, occurring in up to 0.5% of users. Although the pathophysiology of ACEI-induced angioedema is attributable to elevated serum bradykinin, standard management typically includes corticosteroids and antihistamines. We sought to summarize the evidence supporting pharmacotherapy for ACEI-induced angioedema. Data Sources PubMed, MEDLINE, and Embase portals. Methods A systematic literature review was conducted according to the PRISMA guidelines. Databases were queried by 3 independent reviewers for English-language studies published between 1980 and 2017. The initial search screened for all occurrences of "angioedema" and then was further refined to include studies of ACEI-related cases and exclude hereditary angioedema. Results Five articles representing 218 cases were identified, including 3 randomized controlled trials and 2 prospective case series with historical controls. One of 2 studies of icatibant (bradykinin B2 receptor antagonist) found more rapid symptom improvement than that with a control group of corticosteroids and antihistamines. Two studies of ecallantide (plasma kallikrein inhibitor) and 1 study of C1 inhibitor replacement found no significant benefit over control. No studies were identified that compared the efficacy of corticosteroids with antihistamines, of one dose with another, of fresh frozen plasma, or of combination therapy. Conclusion The efficacy of treatment of ACEI-induced angioedema with bradykinin antagonists, kallikrein inhibitor, and C1 inhibitor warrants further study. Although consistent benefit of these medications has not been demonstrated, their use has not caused harm. One study examining off-label use of icatibant has demonstrated efficacy over control. In addition, further study is needed to establish the efficacy and mechanism of action of standard pharmacotherapy such as corticosteroids and antihistamines in treatment of this condition.

Urodilatin reverses the detrimental influence of bradykinin in acute ischemic stroke

Occlusion of cerebral arteries leads to ischemic stroke accompanied by subsequent brain edema. Bradykinin (BK) is involved in the formation of cerebral edema, and natriuretic peptides (NPs) potentially have beneficial effects on brain edema formation via a still unknown mechanism. The aim of this study was clarifying the mechanisms of action of NPs on BK signaling, and their interactive effects after ischemic brain injury. We used a mouse model for stroke, the middle cerebral artery (MCA) occlusion. Brain lesion and edema were measured by microcomputerized tomography volumetric measurements. To determine the effects of NPs on the BK signaling pathway in the MCAs we measured changes in vessel diameter and membrane potentials in endothelial cells. To determine the effects of NPs on BK signaling pathway in isolated astrocytes and neurons, membrane potentials and intercellular Ca2+ concentrations were measured. Urodilatin inhibited and when applied together with BK, reduced the formation of the ischemic lesion via activation of G-Protein–Signaling Protein Type 4 at the cellular (atrocities, neurons) and blood vessel (endothelial cells and isolated MCA) level as well as in in vivo experiments. The results of this study show the existence of a natural antagonist of BK in the brain, and the possible use of NPs in the treatment of stroke.

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.

Role of selective blocking of bradykinin receptor subtypes in attenuating allergic airway inflammation in guinea pigs

The present study was designed to evaluate the potential role of bradykinin antagonists (R-715; bradykinin B1 receptor antagonist and icatibant; bradykinin B2 receptor antagonist) in treatment of allergic airway inflammation in comparison to dexamethasone and montelukast. R-715 as dexamethasone significantly decreased peribronchial leukocyte infiltration, bronchoalveolar lavage fluid (BALF) albumin and interleukin 1β as well as serum OVA-specific IgE level. Also, R-715 like montelukast significantly decreased BALF cell count (total and eosinophils). Icatibant showed negative results. The current findings suggest that selective bradykinin B1 receptor antagonists may have the therapeutic potential for the treatment of allergic airway inflammation.

Alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin.

Of the 450,000 burn patients each year, 50% have a positive blood alcohol content, and this predisposes them to worsened clinical outcomes. Despite high prevalence and established consequences, the mechanisms responsible for alcohol-mediated complications of postburn remote organ damage are currently unknown. To this end, mice received a single dose of alcohol (1.12 g/kg) or water by oral gavage and were subjected to a 15% total body surface area burn. Animals with a burn alone lost ∼5% of their body weight in 24 h, whereas intoxicated and burned mice lost only 1% body weight (P < 0.05) despite a 17% increase in hematocrit (P < 0.05) and a 57% increase in serum creatinine (P < 0.05) over burn injury alone. This retention of water weight despite increased dehydration suggests that intoxication at the time of a burn causes a shift in fluid compartments that may exacerbate end-organ ischemia and damage as evidenced by a 3-fold increase in intestinal bacterial translocation (P < 0.05), a 30% increase (P < 0.05) in liver weight-to-body weight ratio, and an increase in alveolar wall thickness over a burn alone. Furthermore, administration of the bradykinin antagonist HOE140 30 min after intoxication and burn restored fluid balance and alleviated end-organ damage. These findings suggest that alcohol potentiates postburn remote organ damage through shifts in fluid compartments mediated by bradykinin.

Muscle hyperalgesia induced by peripheral P2X3 receptors is modulated by inflammatory mediators

ATP, via activation of P2X3 receptors, has been highlighted as a key target in inflammatory hyperalgesia. Therefore, the aim of this study was to confirm whether the activation of P2X3 receptors in the gastrocnemius muscle of rats induces mechanical muscle hyperalgesia and, if so, to analyze the involvement of the classical inflammatory mediators (bradykinin, prostaglandins, sympathetic amines, pro-inflammatory cytokines and neutrophil migration) in this response. Intramuscular administration of the non-selective P2X3 receptor agonist α,β-meATP in the gastrocnemius muscle of rats induced mechanical muscle hyperalgesia, which, in turn, was prevented by the selective P2X3 and P2X2/3 receptors antagonist A-317491, the selective bradykinin B1-receptor antagonist Des-Arg9-[Leu8]-BK (DALBK), the cyclooxygenase inhibitor indomethacin, the β1- or β2-adrenoceptor antagonist atenolol and ICI 118,551, respectively. Also, the nonspecific selectin inhibitor fucoidan. α,β-meATP induced increases in the local concentration of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β), which were reduced by bradykinin antagonist. Finally, α,β-meATP also induced neutrophil migration. Together, these findings suggest that α,β-meATP induced mechanical hyperalgesia in the gastrocnemius muscle of rats via activation of peripheral P2X3 receptors, which involves bradykinin, prostaglandins, sympathetic amines, pro-inflammatory cytokines release and neutrophil migration. It is also indicated that bradykinin is the key modulator of the mechanical muscle hyperalgesia induced by P2X3 receptors. Therefore, we suggest that P2X3 receptors are important targets to control muscle inflammatory pain.

Neutrophil elastase causes tissue damage that decreases host tolerance to lung infection with burkholderia species.

Two distinct defense strategies can protect the host from infection: resistance is the ability to destroy the infectious agent, and tolerance is the ability to withstand infection by minimizing the negative impact it has on the host's health without directly affecting pathogen burden. Burkholderia pseudomallei is a Gram-negative bacterium that infects macrophages and causes melioidosis. We have recently shown that inflammasome-triggered pyroptosis and IL-18 are equally important for resistance to B. pseudomallei, whereas IL-1β is deleterious. Here we show that the detrimental role of IL-1β during infection with B. pseudomallei (and closely related B. thailandensis) is due to excessive recruitment of neutrophils to the lung and consequent tissue damage. Mice deficient in the potentially damaging enzyme neutrophil elastase were less susceptible than the wild type C57BL/6J mice to infection, although the bacterial burdens in organs and the extent of inflammation were comparable between C57BL/6J and elastase-deficient mice. In contrast, lung tissue damage and vascular leakage were drastically reduced in elastase-deficient mice compared to controls. Bradykinin levels were higher in C57BL/6 than in elastase-deficient mice; administration of a bradykinin antagonist protected mice from infection, suggesting that increased vascular permeability mediated by bradykinin is one of the mechanisms through which elastase decreases host tolerance to melioidosis. Collectively, these results demonstrate that absence of neutrophil elastase increases host tolerance, rather than resistance, to infection by minimizing host tissue damage.