ASC oligomer favors caspase-1CARD domain recruitment after intracellular potassium efflux.

Signaling through the inflammasome is important for the inflammatory response. Low concentrations of intracellular K+ are associated with the specific oligomerization and activation of the NLRP3 inflammasome, a type of inflammasome involved in sterile inflammation. After NLRP3 oligomerization, ASC protein binds and forms oligomeric filaments that culminate in large protein complexes named ASC specks. ASC specks are also initiated from different inflammasome scaffolds, such as AIM2, NLRC4, or Pyrin. ASC oligomers recruit caspase-1 and then induce its activation through interactions between their respective caspase activation and recruitment domains (CARD). So far, ASC oligomerization and caspase-1 activation are K+-independent processes. Here, we found that when there is low intracellular K+, ASC oligomers change their structure independently of NLRP3 and make the ASCCARD domain more accessible for the recruitment of the pro-caspase-1CARD domain. Therefore, conditions that decrease intracellular K+ not only drive NLRP3 responses but also enhance the recruitment of the pro-caspase-1 CARD domain into the ASC specks.

Galvanic current activates the NLRP3 inflammasome to promote Type I collagen production in tendon.

The NLRP3 inflammasome coordinates inflammation in response to different pathogen- and damage-associated molecular patterns, being implicated in different infectious, chronic inflammatory, metabolic and degenerative diseases. In chronic tendinopathic lesions, different non-resolving mechanisms produce a degenerative condition that impairs tissue healing and which therefore complicates their clinical management. Percutaneous needle electrolysis consists of the application of a galvanic current and is an emerging treatment for tendinopathies. In the present study, we found that galvanic current activates the NLRP3 inflammasome and induces an inflammatory response that promotes a collagen-mediated regeneration of the tendon in mice. This study establishes the molecular mechanism of percutaneous electrolysis that can be used to treat chronic lesions and describes the beneficial effects of an induced inflammasome-related response.

Effect of a surgical care bundle on the incidence of surgical site infection in colorectal surgery: a quasi-experimental intervention

Background: Surgical site infections (SSI) have an important impact on morbidity and mortality. Objective: This study, therefore, sought to assess the effect of a surgical care bundle on the incidence of SSI in colorectal surgery. Methods: We conducted a quasi-experimental intervention study with reference to the introduction of a surgical care bundle in 2011. Our study population, made up of patients who underwent colorectal surgery, was divided into the following two periods: 2007-2011 (pre-intervention) and 2012-2017 (post-intervention). The intervention's effect on SSI incidence was analyzed using adjusted odds ratios (OR). Results: A total of 1,727 patients were included in the study. SSI incidence was 13.0% before versus 11.6% after implementation of the care bundle (OR: 0.88, 95% confidence interval: 0.66-1.17, p = 0.37). Multivariate analysis showed that cancer, chronic obstructive pulmonary disease, neutropenia, and emergency surgery were independently associated with SSI. In contrast, laparoscopic surgery proved to be a protective factor against SSI. Conclusions: Care bundles have proven to be very important in reducing SSI incidence since the measures that constitute these protocols are mutually reinforcing. In our study, the implementation of a care bundle reduced SSI incidence from 13% to 11.6%, though the reduction was not statistically significant.

Gasdermins mediate cellular release of mitochondrial DNA during pyroptosis and apoptosis.

Pyroptosis and intrinsic apoptosis are two forms of regulated cell death driven by active caspases where plasma membrane permeabilization is induced by gasdermin pores. Caspase-1 induces gasdermin D pore formation during pyroptosis, whereas caspase-3 promotes gasdermin E pore formation during apoptosis. These two types of cell death are accompanied by mitochondrial outer membrane permeabilization due to BAK/BAX pore formation in the external membrane of mitochondria, and to some extent, this complex also affects the inner mitochondrial membrane facilitating mitochondrial DNA relocalization from the matrix to the cytosol. However, the detailed mechanism responsible for this process has not been investigated. Herein, we reported that gasdermin processing is required to induce mitochondrial DNA release from cells during pyroptosis and apoptosis. Gasdermin targeted at the plasma membrane promotes a fast mitochondrial collapse along with the initial accumulation of mitochondrial DNA in the cytosol and then facilitates the DNA's release from the cell when the plasma membrane ruptures. These findings demonstrate that gasdermin action has a critical effect on the plasma membrane and facilitates the release of mitochondrial DNA as a damage-associated molecular pattern.

Effect of a Surgical Care Bundle on the Incidence of Surgical Site Infection in Colorectal Surgery: A Quasi-Experimental Intervention.

BACKGROUND: Surgical site infections (SSI) have an important impact on morbidity and mortality. OBJECTIVE: This study, therefore, sought to assess the effect of a surgical care bundle on the incidence of SSI in colorectal surgery. METHODS: We conducted a quasi-experimental intervention study with reference to the introduction of a surgical care bundle in 2011. Our study population, made up of patients who underwent colorectal surgery, was divided into the following two periods: 2007-2011 (pre-intervention) and 2012-2017 (post-intervention). The intervention's effect on SSI incidence was analyzed using adjusted odds ratios (OR). RESULTS: A total of 1,727 patients were included in the study. SSI incidence was 13.0% before versus 11.6% after implementation of the care bundle (OR: 0.88, 95% confidence interval: 0.66-1.17, p = 0.37). Multivariate analysis showed that cancer, chronic obstructive pulmonary disease, neutropenia, and emergency surgery were independently associated with SSI. In contrast, laparoscopic surgery proved to be a protective factor against SSI. CONCLUSIONS: Care bundles have proven to be very important in reducing SSI incidence since the measures that constitute these protocols are mutually reinforcing. In our study, the implementation of a care bundle reduced SSI incidence from 13% to 11.6%, though the reduction was not statistically significant.

Constraints for Use of Ultraviolet Spectropolarimetry to Detect Chiral Amino Acids from Comets.

Life is pervasive on planet Earth, but whether life is ubiquitous in the Galaxy and sustainable over timescales comparable to stellar evolution is unknown. Evidence suggests that life first appeared on Earth more than 3.77 Gyr ago, during a period of heavy meteoric bombardment. Amino acids, the building blocks of proteins, have been demonstrated to exist in interstellar ice. As such, the contribution of space-generated amino acids to those existing on Earth should be considered. However, detection of space amino acids is challenging. In this study, we used analytical data from several meteorites and in situ measurements of the comet 67P/Churyumov-Gerasimenko collected by the Rosetta probe to evaluate the detectability of alanine by ultraviolet spectropolarimetry. Alanine is the second-most abundant amino acid after glycine and is optically active. This chirality produces a unique signature that enables reliable identification of this amino acid using the imprint of optical rotatory dispersion (ORD) and circular dichroism (CD) in the ultraviolet spectrum (130-230 nm). Here, we show that the ORD signature could be detected in comets by using ultraviolet spectropolarimetric observations conducted at middle size space observatories. These observations can also provide crucial information for the study of sources of enantiomeric imbalance on Earth.

Signaling Through Purinergic Receptor P2Y2 Enhances Macrophage IL-1ß Production.

The release of nucleotides during necrosis or apoptosis has been described to have both proinflammatory and anti-inflammatory effect on the surrounding cells. Here we describe how low concentrations of UTP and ATP applied during macrophage priming enhance IL-1ß production when subsequently the NLRP3 inflammasome is activated in murine resident peritoneal macrophages. Deficiency or pharmacological inhibition of the purinergic receptor P2Y2 reverted the increase of IL-1ß release induced by nucleotides. IL-1ß increase was found dependent on the expression of Il1b gene and probably involving JNK activity. On the contrary, nucleotides decreased the production of a different proinflammatory cytokines such as TNF-α. These results suggest that nucleotides could shape the response of macrophages to obtain a unique proinflammatory signature that might be relevant in unrevealing specific inflammatory conditions.

3D chitosan scaffolds impair NLRP3 inflammasome response in macrophages.

Chitosan (Ch) is used in different biomedical applications to promote tissue repair. However, tissue injury caused by biomaterial implantation lead to the release of danger signals that engage different inflammatory pathways on the host. Different implanted materials activate the inflammasome leading to the modulation of the immune response. Here we have studied how macroscopic biomaterials, Ch scaffolds with different chemical composition: 4% or 15% degree of acetylation (DA) modulate the activation of the NLRP3 inflammasome in vitro. For that, we assessed the NLRP3 inflammasome in bone marrow derived mouse macrophages (BMDM) and human macrophages cultured within 3D Ch scaffolds. We found that both Ch scaffolds did not trigger the NLRP3 inflammasome activation in macrophages. Furthermore, BMDMs and human macrophages cultured in both Ch scaffolds presented a reduction in the number of apoptosis-associated speck-like protein containing a caspase activating recruitment domain (ASC) specks and in IL-1ß release upon classical NLRP3 inflammasome stimulation. We also found a decrease in proIL-1ß in BMDMs after priming with LPS when cultured in Ch scaffolds with DA 4% DA after priming with LPS when compared to Ch scaffolds with 15% DA or to macrophages cultured in cell-culture plates. Our results shows that 3D Ch scaffolds with different DA impair NLRP3 inflammasome priming and activation. STATEMENT OF SIGNIFICANCE: In this research work we have assessed the role of the NLRP3 inflammasome in the macrophage response to 3D chitosan scaffolds with different degrees of acetylation (DA). To our knowledge this is the first work that demonstrates the modulatory capacity of 3D porous chitosan scaffolds in the NLRP3 inflammasome activation, because our results show that Ch scaffolds impair NLRP3 inflammasome assembly in macrophages. Interestingly, our results are in contrast with studies reported in the literature that indicate that chitosan is a powerful activator of the NLRP3 inflammasome in nanoscale chitosan products. Our studies that were performed in large scale chitosan scaffolds, stress out that the process of phagocytosis is pivotal in inflammasome assembly and activation, are rather important since they clearly illustrate the different role of the inflammasome in the biological response to large scale and nanoscale biomaterials.

Evaluating the pharmacological response in fluorescence microscopy images: The Δm algorithm.

Current drug discovery procedures require fast and effective quantification of the pharmacological response evoked in living cells by agonist compounds. In the case of G-protein coupled receptors (GPCRs), the efficacy of a particular drug to initiate the endocytosis process is related to the formation of endocytic vesicles or endosomes and their subsequent internalisation within intracellular compartments that can be observed with high spatial and temporal resolution by fluorescence microscopy techniques. Recently, an algorithm has been proposed to evaluate the pharmacological response by estimating the number of endosomes per cell on time series of images. However, the algorithm was limited by the dependence on some manually set parameters and in some cases the quality of the image does not allow a reliable detection of the endosomes. Here we propose a simple, fast and automated image analysis method-the Δm algorithm- to quantify a pharmacological response with data obtained from fluorescence microscopy experiments. This algorithm does not require individual object detection and computes the relative increment of the third order moment in fluorescence microscopy images after filtering with the Laplacian of Gaussian function. It was tested on simulations demonstrating its ability to discriminate different experimental situations according to the number and the fluorescence signal intensity of the simulated endosomes. Finally and in order to validate this methodology with real data, the algorithm was applied to several time-course experiments based on the endocytosis of the mu opioid receptor (MOP) initiated by different agonist compounds. Each drug displayed a different Δm sigmoid time-response curve and statistically significant differences were observed among drugs in terms of efficacy and kinetic parameters.

Food poisoning caused by scombroids: A case-control study.

The aim of this study is to report the epidemiological characteristics of a food poisoning outbreak due to scombroid fish in a hospital. A case-control study (1:4) was conducted. Patients either symptomatic of food poisoning (cases) or asymptomatic (controls) eating at the hospital cafeteria were included. To identify the source of the outbreak, sanitary control factors were assessed. Microbiological studies and the mast cell tryptase test were performed. All cases and controls received a questionnaire enquiring about symptoms and foods consumed. The odds ratios (OR) for all risk factors and their 95% confidence intervals (CI) were assessed. In total, 20 individuals (90% female) were included in the study: four cases and 16 controls. The overall mean age was 43 years (SD: 10.2). The most frequent symptom observed was facial and neck erythaema (100%). Microbiological cultures were negative, the mast cell tryptase test was normal and breakdown of the cold chain did not occur. The most likely source of the outbreak was fried anchovies (OR: 34.7; 95% CI: 1.50-809.6; p=0.02). Methods suitable to the rapid assessment of the outbreak allowed us to establish prompt preventive measures and identify the likely aetiology.

[Efecto de un Plan de Mejora de Calidad y Seguridad Clínica en la incidencia de infección de sitio quirúrgico en apendicectomía. Estudio cuasi-experimental]. / Effect of a Plan for Quality Improvement and Clinical Safety in the incidence of surgical site infections in appendectomy. A quasi-experimental study.

OBJETIVO: Las infecciones de sitio quirúrgico se pueden evitar y los programas de control basados en paquetes de medidas preventivas son eficaces para reducir su incidencia. El objetivo de este estudio fue evaluar el efecto de un Plan de Mejora de Calidad y Seguridad Clínica del paciente intervenido de apendicectomía en la incidencia de infección del sitio quirúrgico. MÉTODO: Se realizó un estudio cuasi-experimental con análisis antes y después de la introducción de un Plan de Calidad y Seguridad Clínica. Se incluyeron pacientes intervenidos de apendicectomía. Se estudió la incidencia de infección del sitio quirúrgico durante los 30 días posteriores a la cirugía (periodo máximo de incubación de infección quirúrgica). Se evaluó el efecto de la intervención con la odds ratio (OR) ajustada con un modelo de regresión logística. RESULTADOS: Se incluyeron 606 pacientes, 267 en el periodo 2009-2010 (antes del plan) y 339 durante 2012-2013 (después del plan). La incidencia de infección del sitio quirúrgico descendió después del plan del 6 al 5.6% (OR: 0.72; intervalo de confianza del 95%: 0.33-1.56; p = 0.839). Hubo mayor cumplimiento de la profilaxis antibiótica, de la preparación prequirúrgica y de la adherencia a la higiene de manos tras la introducción de las medidas. CONCLUSIONES: Aunque la reducción de la incidencia de infección del sitio quirúrgico no presentó diferencias estadísticamente significativas tras las medidas adoptadas, se ha conseguido mejorar la administración de la profilaxis antibiótica, la adherencia a la higiene de manos y la preparación prequirúrgica. OBJECTIVE: Surgical site infections can be prevented. Control programs based on care bundle have proven to be effective in reducing its incidence. The objective of this study was to assess the effectiveness of a Plan for Quality Improvement and Clinical Safety in preventing the incidence of surgical site infection in patients undergoing appendectomy. METHOD: A quasi-experimental study was designed for analysis before and after the introduction of a Plan for Quality and Clinical Safety. Patients undergoing appendectomy were included. The incidence of surgical site infection was studied within 30 days from the time of surgery (maximum incubation period of surgical site infection). The effectiveness of the intervention was evaluated using the odds ratio (OR) adjusted with a logistic regression model. RESULTS: A total of 606 patients were included, of which 267 were operated in the period 2009-2010 (before the plan) and 339 in 2012-2013 (after the plan). The incidence of surgical site ­infection decreased after the plan from 6 to 5.6% (OR: 0.72; 95% confidence interval: 0.33-1.56; p = 0.839). There was greater compliance of antibiotic prophylaxis, preoperative preparation and adherence to hand hygiene after the introduction of the measures. CONCLUSIONS: Although the reduction in the incidence of surgical site infection after the measures adopted did not show statistical significant differences, important progress has been made in the compliance of antibiotic prophylaxis, adherence to hand hygiene and in the preoperative preparation.

P2X7 Receptor Induces Tumor Necrosis Factor-α Converting Enzyme Activation and Release to Boost TNF-α Production.

Tumor necrosis factor (TNF)-α is a major pro-inflammatory cytokine produced in response to toll-like receptor stimulation. TNF-α release is controlled by the activity of TNF-α converting enzyme (TACE) that cut membrane-bound TNF-α to shed its ectodomain as a soluble cytokine. The purinergic receptor P2X ligand-gated ion channel 7 (P2X7) is activated in response to elevated concentrations of extracellular ATP and induces different pro-inflammatory pathways in macrophages to establish an inflammatory response. P2X7 receptor promotes the activation of the inflammasome and the release of interleukin-1ß, the production of inflammatory lipids, and the generation of reactive oxygen species. In this study, we analyzed the mechanism of P2X7 receptor responsible of TNF-α release after priming macrophages with LPS doses ≤100 ng/ml. We found that P2X7 receptor increases the extracellular activity of TACE through the release of the mature form of TACE in exosomes. This effect was blocked using P2X7 receptor inhibitors or in macrophages obtained from P2X7 receptor-deficient mice. Elevation of intracellular Ca2+ and p38 mitogen-activated protein kinase after P2X7 receptor activation were involved in the release of TACE, which was able to process TNF-α on nearby expressing cells. Finally, we observed an increase of TNF-α in the peritoneal lavage of mice treated with LPS and ATP. In conclusion, P2X7 receptor induces the release of TACE in exosomes to the extracellular compartment that could amplify the pro-inflammatory signal associated to this receptor. These results are important for the development of therapeutics targeting P2X7 receptor.

Surgical Wound Infection Rates and Risk Factors in Spinal Fusion in a University Teaching Hospital in Madrid, Spain.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: To study risk factors linked to spinal fusion surgical wound infection (SWI) incidence and compare the incidence with rates in Madrid Region, Spain and United States as a whole. SUMMARY OF BACKGROUND DATA: SWI is one of the complications posed by spinal surgery. Indeed, spinal surgery has a higher infection rate than do other orthopedic surgeries such as total hip or knee arthroplasty. The study of risk factors that are susceptible to be modified will enable both the incidence of SWI and, by extension, related morbidity, mortality, and costs to be reduced. METHODS: All patients undergoing spinal fusion at a tertiary hospital from June 2011 to June 2014 were included. Infection rate was calculated, and the association between risk factors and SWI incidence was assessed by reference to odds ratio (OR) with univariate and multivariate analysis. RESULTS: The study population (n = 892) had a SWI rate of 3.9%. The standardized infection ratio of our hospital was 0.58 with respect to the Madrid Region, 0.76 with respect to Spain's national rate and 2.05 with respect to the US NHSN/CDC. The multivariate analysis showed that predictive factors of SWI were diabetes mellitus (OR 2.81, 95% confidence interval, CI: 1.18-6.72, P < 0.05), chronic obstructive pulmonary disease (COPD) (OR 5.16, 95% CI: 2.04-13.08, P < 0.05), duration of surgery higher than the 75th percentile (OR 5.39, 95% CI: 1.77-110.84, P < 0.05) and dirty surgery (OR 14.01, 95% CI: 1.01-28.88, P < 0.05). CONCLUSION: Independent risk factors for SWI in spinal fusion are existence of diabetes mellitus, COPD, duration of surgery higher than the 75th percentile and dirty surgery. Knowing these risk factors enables action to be taken to reduce the SWI rate. LEVEL OF EVIDENCE: 3.

Macrophage activation and polarization modify P2X7 receptor secretome influencing the inflammatory process.

The activation of P2X7 receptor (P2X7R) on M1 polarized macrophages induces the assembly of the NLRP3 inflammasome leading to the release of pro-inflammatory cytokines and the establishment of the inflammatory response. However, P2X7R signaling to the NLRP3 inflammasome is uncoupled on M2 macrophages without changes on receptor activation. In this study, we analyzed P2X7R secretome in wild-type and P2X7R-deficient macrophages polarized either to M1 or M2 and proved that proteins released after P2X7R stimulation goes beyond caspase-1 secretome. The characterization of P2X7R-secretome reveals a new function of this receptor through a fine-tuning of protein release. We found that P2X7R stimulation in macrophages is able to release potent anti-inflammatory proteins, such as Annexin A1, independently of their polarization state suggesting for first time a potential role for P2X7R during resolution of the inflammation and not linked to the release of pro-inflammatory cytokines. These results are of prime importance for the development of therapeutics targeting P2X7R.

Apoptosis-associated speck-like protein containing a CARD forms specks but does not activate caspase-1 in the absence of NLRP3 during macrophage swelling.

Apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC) is a key adaptor molecule required for the inflammatory processes. ASC acts by bridging NLRP proteins, such as NLRP3, with procaspase-1 within the inflammasome complex, which subsequently results in the activation of caspase-1 and the secretion of IL-1ß and IL-18. In response to bacterial infection, ASC also forms specks by self-oligomerization to activate caspase-1 and induce pyroptosis. Hitherto, the role of these specks in NLRP3 inflammasome activation in response to danger signals, such as a hypotonic environment, largely has been unexplored. In this article, we report that, under hypotonic conditions and independently of NLRP3, ASC was able to form specks that did not activate caspase-1. These specks were not associated with pyroptosis and were controlled by transient receptor potential vanilloid 2 channel-mediated signaling. However, interaction with NLRP3 enhanced ASC speck formation, leading to fully functional inflammasomes and caspase-1 activation. This study reveals that the ASC speck can present different oligomerization assemblies and represents an essential step in the activation of functional NLRP3 inflammasomes.

Isolation of Particles of Recombinant ASC and NLRP3.

NLRP3 inflammasome is a multiprotein complex responsible for the activation of inflammatory caspase-1, resulting in processing and release of pro-inflammatory cytoquines IL-1ß and IL-18 (Schroder and Tschopp, 2010). This inflammasome is composed of the sensor protein NLRP3 connected to caspase-1 through the adaptor protein ASC (apoptosis-associated speck-like protein with a caspase-recruitment domain) (Schroder and Tschopp, 2010). We and others have reported that upon inflammasome activation functional oligomeric inflammasome particles of NLRP3 and ASC were released from cells, acting as danger signals to amplify inflammation by promoting the activation of caspase-1 extracellularly (Baroja-Mazo et al., 2014; Franklin et al., 2014). Studying the extracellular function of oligomeric ASC and NLRP3 inflammasome particles was possible by purification of recombinant particles of ASC or the constitutively activated NLRP3 mutant associated with cryopyrin-associated periodic syndromes (CAPS, mutation p.D303N), both tagged with the yellow fluorescent protein (YFP) and expressed in HEK293 cells. The purification process was facilitated by the fact that expression of recombinant ASC or mutant NLRP3 in HEK293 cells resulted in their spontaneous aggregation into specks (Baroja-Mazo et al., 2014) and the protocol was originally adapted from Fernandes-Alnemri and Alnemri (2008).

The NLRP3 inflammasome is released as a particulate danger signal that amplifies the inflammatory response.

Assembly of the NLRP3 inflammasome activates caspase-1 and mediates the processing and release of the leaderless cytokine IL-1ß and thereby serves a central role in the inflammatory response and in diverse human diseases. Here we found that upon activation of caspase-1, oligomeric NLRP3 inflammasome particles were released from macrophages. Recombinant oligomeric protein particles composed of the adaptor ASC or the p.D303N mutant form of NLRP3 associated with cryopyrin-associated periodic syndromes (CAPS) stimulated further activation of caspase-1 extracellularly, as well as intracellularly after phagocytosis by surrounding macrophages. We found oligomeric ASC particles in the serum of patients with active CAPS but not in that of patients with other inherited autoinflammatory diseases. Our findings support a model whereby the NLRP3 inflammasome, acting as an extracellular oligomeric complex, amplifies the inflammatory response.

Disparities in HIV screening among pregnant women--El Salvador, 2011.

OBJECTIVES: To provide an accurate estimate of antenatal HIV screening and its determinants among pregnant women in El Salvador and help local authorities make informed decisions for targeted interventions around mother-to-child transmission (MTCT). METHODS: A total sample of 4,730 women aged 15-49 years were interviewed from a random sample of 3,625 households. We collected data on antenatal care services, including HIV screening, during last pregnancy through a pre-established questionnaire. We used a backward elimination multivariate logistic regression model to examine the association between HIV screening and sociodemographic and health care-related factors. RESULTS: A total of 2,929 women were included in this analysis. About 98% of participants reported receiving antenatal care, but only 83% of these reported being screened for HIV. Screening was lower in geographic areas with higher HIV incidence and ranged from 69.1% among women who were not seen by a physician during antenatal care, to 93.7% among those who attended or completed college. Odds for screening varied also by age, employment status, household economic expenditure, possession of health care coverage, health care settings, and number of antenatal care visits. CONCLUSIONS: We found disparities in HIV screening during antenatal care at the environmental, social, demographic, and structural levels despite a high uptake of antenatal care in El Salvador. Our findings should urge health authorities to tailor and enhance current strategies implemented to eliminate MTCT and reduce inequities and HIV morbidity among women in El Salvador.

Cell volume regulation modulates NLRP3 inflammasome activation.

Cell volume regulation is a primitive response to alterations in environmental osmolarity. The NLRP3 inflammasome is a multiprotein complex that senses pathogen- and danger-associated signals. Here, we report that, from fish to mammals, the basic mechanisms of cell swelling and regulatory volume decrease (RVD) are sensed via the NLRP3 inflammasome. We found that a decrease in extracellular osmolarity induced a K(+)-dependent conformational change of the preassembled NLRP3-inactive inflammasome during cell swelling, followed by activation of the NLRP3 inflammasome and caspase-1, which was controlled by transient receptor potential channels during RVD. Both mechanisms were necessary for interleukin-1ß processing. Increased extracellular osmolarity prevented caspase-1 activation by different known NLRP3 activators. Collectively, our data identify cell volume regulation as a basic conserved homeostatic mechanism associated with the formation of the NLRP3 inflammasome and reveal a mechanism for NLRP3 inflammasome activation.

P2X7 receptor-stimulation causes fever via PGE2 and IL-1ß release.

Prostaglandins (PGs) are important lipid mediators involved in the development of inflammatory associated pain and fever. PGE2 is a well-established endogenous pyrogen activated by proinflammatory cytokine interleukin (IL)-1ß. P2X7 receptors (P2X7Rs) expressed by inflammatory cells are stimulated by the danger signal extracellular ATP to activate the inflammasome and release IL-1ß. Here we show that P2X7R activation is required for the release of PGE2 and other autacoids independent of inflammasome activation, with an ATP EC(50) for PGE2 and IL-1ß release of 1.58 and 1.23 mM, respectively. Furthermore, lack of P2X7R or specific antagonism of P2X7R decreased the febrile response in mice triggered after intraperitoneal LPS or IL-1ß inoculation. Accordingly, LPS inoculation caused intraperitoneal ATP accumulation. Therefore, P2X7R antagonists emerge as novel therapeutics for the treatment for acute inflammation, pain and fever, with wider anti-inflammatory activity than currently used cyclooxygenase inhibitors.-Barberà-Cremades, M., Baroja-Mazo, A., Gomez, A. I., Machado, F., Di Virgilio, F., Pelegrín, P. P2X7 receptor-stimulation causes fever via PGE2 and IL-1ß release.