Nonlinear relationship between serum uric acid and body mass index: a cross-sectional study of a general population in coastal China

Background

Conflicting evidence exists on the relationship between body mass index (BMI) and serum uric acid (SUA). Therefore, we aimed to evaluate the SUA–BMI relationship in a large-scale epidemiological survey in coastal China.

Methods

This survey was conducted among the general population in the coastal region of China from September 2014 to January 2015. SUA Levels were measured by the automatic Sysmex Chemix-180 biochemical analyzer.

Results

A total of 6098 men (BMI: 24.58 ± 3.74 kg/m²) and 7941 women (24.56 ± 3.64 kg/m²) were included in this study. A stronger positive BMI-SUA association was found for men than women (all P-values < 0.05). The piecewise linear spline models indicated a U-shaped relationship of SUA-BMI association for both men and women; and the lowest turning points were at 19.12 kg/m² for men and 21.3 kg/m² for women. When BMIs were lower than the nadir point, each 1 kg/m² increase in BMI related to a 7.74-fold (95% CI − 14.73, − 0.75) reduction for men and 2.70-fold reduction (− 4.47, − 0.94) for women in SUA levels. Once the BMI was higher than the nadir point, each 1 kg/m² increase in BMI was related to a 5.10-fold (4.44, 5.77) increment for men and 3.93-fold increment (3.42, 4.43) for women in SUA levels. The regression coefficient differences between the two stages were 12.84 (5.66, 20.03) for men and 6.63 (4.65, 8.61) for women.

Conclusions

A U-shaped relationship between BMI and SUA was found for both men and women; the association was stronger for men than women.

MSU Crystals induce sterile IL-1β secretion via P2X7 receptor activation and HMGB1 release

BACKGROUD

The mechanism by which monosodium urate (MSU) crystals induce inflammation is not completely understood. Few studies have shown that MSU is capable of stimulating the release of IL-1β in the absence of LPS treatment. The purinergic P2X7 receptor is involved in the release of IL-1β in inflammatory settings caused by crystals, as is the case in silicosis.

METHODS

We investigated the role of P2X7 receptor in sterile MSU-induced inflammation by evaluating peritonitis and paw edema. In in vitro models, we performed the experiments using peritoneal macrophages and THP-1 cells. We measured inflammatory parameters using ELISA and immunoblotting. We measured cell recruitment using cell phenotypic identification and hemocytometer counts.

RESULTS

Our in vivo data showed that animals without P2X7 receptors generated less paw edema, less cell recruitment, and lower levels of IL-1β release in a peritonitis model. In the in vitro model, we observed that MSU induced dye uptake by the P2X7 receptor. In the absence of the receptor, or when it was blocked, MSU crystals induced less IL-1β release and this effect corresponded to the concentration of extracellular ATP. Moreover, MSU treatment induced HMGB1 release; pre-treatment with P2X7 antagonist reduced the amount of HMGB1 in cell supernatants.

CONCLUSIONS

IL-1β secretion induced by MSU depends on P2X7 receptor activation and involves HMGB1 release.

GENERAL SIGNIFICANCE

We propose that cell activation caused by MSU crystals induces peritoneal macrophages and THP-1 cells to release ATP and HMGB1, causing IL-1β secretion via P2X7 receptor activation.

P2X4 receptor as a modulator in the function of P2X receptor in CD4+ T cells from peripheral blood and adipose tissue

Obesity is characterized by immune cell infiltration and inflammation. Purinergic receptors such as P2X1, 4 and 7 are expressed on immune cells and their activation contributes with an inflammatory response. However, the simultaneous expression of P2X1, 4 and 7 during overweight or obesity have not been described. Therefore, the aim of this study was to determine single and simultaneously expression and function of the P2X1, 4 and 7 receptors in lymphocytes and CD4 + T cells from peripheral blood (PB) and adipose tissue (AT). Our results showed a higher expression of the P2X4 receptor on CD4 + T cells from PB regarding P2X7 and P2X1 receptor expression. In addition, P2X4 receptor expression on CD4 + T cells from PB and AT was increased in individuals with BMI ≥ 25 Kg/m². Moreover, a higher simultaneous expression of the P2X4 and P2X7 receptors on CD4 + T cells from AT compared to CD4 + T cells expressing P2X1 and P2X7 receptors simultaneously. Besides, CD4 + T cells expressing P2X4 and P2X7 receptors from PB and AT were augmented in individuals with BMI ≥ 25 Kg/m². In addition, the percentage of lymphocytes and also CD4 + T cells expressing P2X4 receptor were elevated both in PB and AT compared to cells expressing P2X7 or P2X1. However, CD4 + T cells expressing P2X4 and P2X7 were augmented in AT compared to PB. The function of the receptors showed a lower shedding of CD62 L in adipose tissue mononuclear cells (ATMC) compared with peripheral blood mononuclear cells (PBMC) and a greater participation of P2X4 in the mobilization of intracellular calcium. We concluded that it was possible to determine for the first time the simultaneous expression of purinergic receptors in ATMC, where the P2X4 receptor has a greater participation in the activation of CD4 + T cells possibly modulating the function of the other two receptors.

Research progress of P2X7 receptor in inflammatory bowel disease

Inflammatory bowel disease is a chronic nonspecific inflammatory disease of the intestine. Its pathogenesis is not yet fully understood. It may be related to heredity, environmental triggers, infection, immune dysfunction and other factors. Purinergic receptor (P2X7R) ligand-gated ion channel is closely related to inflammation and widely expressed in intestinal cells. Previous studies have shown that ATP/P2X7R signal is involved in the pathogenesis of intestinal inflammation, but its specific mechanism needs further study. This article reviews the research progress of P2X7 receptor in inflammatory bowel disease.

P2X7 Receptor Expression in Patients With Serositis Related to Systemic Lupus Erythematosus

Introduction: P2X7R is an extracellular ATP-gated receptor involved in inflammatory and autoimmune processes mainly acting through NLPR3-inflammasome activation and IL-1β release, also implicated in lymphocyte proliferation and cellular apoptosis. Several observations from animal models and patients’ studies highlight a possible link between P2X7R-NLRP3 axis and Systemic Lupus Erythematosus (SLE) pathogenesis. The P2X7R-inflammasome axis in addition to the direct production of IL-1β and IL-18, indirectly mediates the release of other cytokines implicated in the pathogenesis of SLE, such as IL-6. The aim of this study was to investigate the role of P2X7R and NLRP3-inflammasome in SLE.

Methods: Forty-eight SLE patients, 16 with (SLE-S) and 32 without (SLE-NS) history of serositis, and 20 healthy control (HC) subjects were enrolled. Demographic, clinical, and therapeutic data were collected. IL-1β and IL-6 plasma levels were evaluated by ELISA. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood by Ficoll gradient sedimentation and employed as follows: (1) evaluation of P2X7R and NLRP3 expression by RT-PCR; (2) determination of P2X7R activity as Benzoyl ATP (BzATP)-induced [Ca²⁺]_i increments using Fura-2-AM fluorescent probe; (3) isolation of monocytes/macrophages and assessment of in vitro IL-1β and IL-6 release following stimulation with lipopolysaccharide (LPS) and BzATP, either separately or in combination.

Results: Plasma IL-1β levels were unmodified in SLE respect to HC whereas IL-6 levels were higher in SLE than in HC, resulting significantly increased in SLE-S. Macrophages isolated from SLE patients released lower quantities of IL-1β after stimulation with BzATP, whereas IL-6 release was significantly augmented in SLE-NS respect to both HC and SLE-S after all types of stimulation. The [Ca²⁺]i increase following BzATP stimulation was significantly lower in PBMCs from SLE patients than in PBMCs from HC. RT-PCR showed significantly reduced P2X7R and significantly augmented NLRP3 expression in PBMCs from SLE patients.

Conclusion: Our data indicate reduced P2X7R expression and function in SLE patients compared with HC and, conversely, increased IL-6 signaling. The possible consequences of reduced P2X7R, mainly on cytokines network deregulation and lymphocyte proliferation, will be further investigated as well as the role of IL-6 as a possible therapeutic target especially in lupus serositis.

Serum Uric Acid and Atrial Fibrillation: Meta-analysis

Hyperuricemia has been recently speculated to be associated with the development of atrial fibrillation (AF). A meta-analysis of observational studies was conducted to explore the relationship between serum uric acid (SUA) and AF. We searched the MEDLINE, EMBASE, and CINAHL databases and performed extensive bibliography search to identify studies with mean SUA level for patients with and without AF. Key search terms were "atrial fibrillation" and "uric acid." Under the random-effects model, the pooled standardized difference in means between patients with and without AF was calculated. A total of 24 studies with 30,609 patients were included for quantitative analyzation of the difference in SUA levels between the patients with and without AF. The SUA level of patients with atrial AF was found to be significantly higher compared with those without AF (standardized difference in means = 0.66; 95% confidence interval, 0.43-0.88; P < 0.0001). The mean SUA level of patients with AF significantly is higher than those without AF.

P2X7 receptor in cardiovascular disease: The heart side

The P2X7 receptor is a ligand-gated purinergic receptor activated by extracellular ATP. The receptor is highly expressed in immune cells and in the brain, and, upon activation, the P2X7 receptor allows a cation flux, leading to the distinct activation of intracellular signalling pathways as the secretion of pro-inflammatory cytokines, and modulation of cell survival. Through these molecular mechanisms, P2X7 is known to play important roles in physiology and pathophysiology of a wide spectrum of diseases, including cancer, inflammatory diseases, neurological, respiratory and more recently cardiovascular diseases. Recent studies demonstrated that the P2X7 could modulate the assembly of the NLRP3 inflammasome, leading to the secretion of pro-inflammatory factors and worsen the cardiac disease phenotypes. This review discusses the critical molecular function of P2X7 in the modulation of the onset, progression and resolution of cardiovascular diseases and analyses the putative future use of P2X7-based therapies that modulate the IL-1β secretion arm and direct P2X7 antagonists.

Connexin-43-dependent ATP release mediates macrophage activation during sepsis

Bacterial spillage into a sterile environment following intestinal hollow-organ perforation leads to peritonitis and fulminant sepsis. Outcome of sepsis critically depends on macrophage activation by extracellular ATP-release and associated autocrine signalling via purinergic receptors. ATP-release mechanisms, however, are poorly understood. Here, we show that TLR-2 and −4 agonists trigger ATP-release via Connexin-43 hemichannels in macrophages leading to poor sepsis survival. In humans, Connexin-43 was upregulated on macrophages isolated from the peritoneal cavity in patients with peritonitis but not in healthy controls. Using a murine peritonitis/sepsis model, we identified increased Connexin-43 expression in peritoneal and hepatic macrophages. Conditional Lyz2^cre/creGja1^flox/flox mice were developed to specifically assess Connexin-43 impact in macrophages. Both macrophage-specific Connexin-43 deletion and pharmacological Connexin-43 blockade were associated with reduced cytokine secretion by macrophages in response to LPS and CLP, ultimately resulting in increased survival. In conclusion, inhibition of autocrine Connexin-43-dependent ATP signalling on macrophages improves sepsis outcome.

Ethanol upregulates the P2X7 purinergic receptor in human macrophages

Alcohol consumption is considered to be the third leading cause of death in the United States. In addition to its direct toxicity, ethanol has two contrasting effects on the immune system: the nucleotide oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) inflammasome is inhibited by acute ethanol exposure but activated by chronic ethanol exposure. Purinergic receptors (especially the P2X7 receptor) are able to activate the NLRP3 inflammasome and are involved in many ethanol-related diseases (such as gout, pulmonary fibrosis, alcoholic steatohepatitis, and certain cancers). We hypothesized that ethanol regulates purinergic receptors and thus modulates the NLRP3 inflammasome's activity. In experiments with monocyte-derived macrophages, we found that interleukin (IL)-1β secretion was inhibited after 7 h of exposure (but not 48 h of exposure) to ethanol. The disappearance of ethanol's inhibitory effect on IL-1β secretion after 48 h was not mediated by the upregulated production of IL-1β, IL-1α, IL-6 or the inflammasome components NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase 1. P2X7R expression was upregulated by ethanol, whereas expression of the P2X4 and P2X1 receptors was not. Taken as a whole, our results suggest that ethanol induces NLRP3 inflammasome activation by upregulating the P2X7 receptor. This observation might have revealed a new mechanism for inflammation in ethanol-related diseases.

A central role for P2X7 receptors in human microglia

BACKGROUND

The ATP-gated ionotropic P2X7 receptor (P2X7R) has the unusual ability to function as a small cation channel and a trigger for permeabilization of plasmalemmal membranes. In murine microglia, P2X7R-mediated permeabilization is fundamental to microglial activation, proliferation, and IL-1β release. However, the role of the P2X7R in primary adult human microglia is poorly understood.

METHODS

We used patch-clamp electrophysiology to record ATP-gated current in cultured primary human microglia; confocal microscopy to measure membrane blebbing; fluorescence microscopy to demonstrate membrane permeabilization, caspase-1 activation, phosphatidylserine translocation, and phagocytosis; and kit-based assays to measure cytokine levels.

RESULTS

We found that ATP-gated inward currents facilitated with repetitive applications of ATP as expected for current through P2X7Rs and that P2X7R antagonists inhibited these currents. P2X7R antagonists also prevented the ATP-induced uptake of large cationic fluorescent dyes whereas drugs that target pannexin-1 channels had no effect. In contrast, ATP did not induce uptake of anionic dyes. The uptake of cationic dyes was blocked by drugs that target Cl^- channels. Finally, we found that ATP activates caspase-1 and inhibits phagocytosis, and these effects are blocked by both P2X7R and Cl^- channel antagonists.

CONCLUSIONS

Our results demonstrate that primary human microglia in culture express functional P2X7Rs that stimulate both ATP-gated cationic currents and uptake of large molecular weight cationic dyes. Importantly, our data demonstrate that hypotheses drawn from work on murine immune cells accurately predict the essential role of P2X7Rs in a number of human innate immune functions such as phagocytosis and caspase-1 activation. Therefore, the P2X7R represents an attractive target for therapeutic intervention in human neuroinflammatory disorders.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Sera from Septic Patients Contain the Inhibiting Activity of the Extracellular ATP-Dependent Inflammasome Pathway

Immunoparalysis is a common cause of death for critical care patients with sepsis, during which comprehensive suppression of innate and adaptive immunity plays a significant pathophysiological role. Although the underlying mechanisms are unknown, damage-associated molecular patterns (DAMPs) from septic tissues might be involved. Therefore, we surveyed sera from septic patients for factors that suppress the innate immune response to DAMPs, including adenosine triphosphate (ATP), monosodium urate, and high mobility group box-1. Macrophages, derived from THP-1 human acute monocytic leukemia cells, were incubated with each DAMP, in the presence or absence of sera that were collected from critically ill patients. Secreted cytokines were then quantified, and cell lysates were assayed for relevant intracellular signaling mediators. Sera from septic patients who ultimately did not survive significantly suppressed IL-1β production only in response to extracellular ATP. This effect was most pronounced with sera collected on day 3, and persisted with sera collected on day 7. However, this effect was not observed when THP-1 cells were treated with sera from survivors of sepsis. Septic sera collected at the time of admission (day 1) also diminished intracellular levels of inositol 1,4,5-triphosphate and cytosolic calcium (P < 0.01), both of which are essential for ATP signaling. Finally, activated caspase-1 was significantly diminished in cells exposed to sera collected on day 7 (P < 0.05). In conclusion, the sera of septic patients contain certain factors that persistently suppress the immune response to extracellular ATP, thereby leading to adverse clinical outcomes.

P2X7, a critical regulator and potential target for bone and joint diseases

Abundant evidence indicted that P2X7 receptor show a essential role in human health and some human diseases including hypertension, atherosclerosis, pulmonary inflammation, tuberculosis infection, psychiatric disorders, and cancer. P2X7 receptor also has an important role in some central nervous system diseases such as neurodegenerative disorders. Recently, more research suggested that P2X7 receptor also plays a crucial role in bone and joint diseases. But the effect of P2X7 receptor on skeletal and joint diseases has not been systematically reviewed. In this article, the role of P2X7 receptor in skeletal and joint diseases is elaborated. The activation of P2X7 receptor can ameliorate osteoporosis by inducing a fine balance between osteoclastic resorption and osteoblastic bone formation. The activation of P2X7 receptor can relieve the stress fracture injury by increasing the response to mechanical loading and inducing osteogenesis. But the activation of P2X7 receptor mediates the cell growth and cell proliferation in bone cancer. In addition, the activation of P2X7 receptor can aggravate the process of some joint diseases such as osteoarthritis, rheumatoid arthritis, and acute gouty arthritis. The inhibition of P2X7 receptor can alleviate the pathological process of joint disease to some extent. In conclusion, P2X7 receptor may be a critical regulator and therapeutic target for bone and joint diseases.

Association between serum uric acid and arterial stiffness in a low-risk, middle-aged, large Korean population: A cross-sectional study

We investigated the association between serum uric acid (SUA) and brachial ankle pulse wave velocity (baPWV) in an apparently healthy population. We performed a cross-sectional study on middle-aged Koreans who completed a yearly health-screening program between January and December 2014. Subjects with coronary artery disease, diabetes, or hypertension were excluded. Linear regression analyses were used to study the relationship between SUA and baPWV. Multiple adjustments were made for variables based on clinical or statistical significance. Of 66,917 study participants (38,170 men and 28,747 women), the mean age was 39.4 ± 6.7 years and the average SUA level was 5.23 ± 1.4 mg/dL. SUA values were higher in men than in women (6.1 ± 1.2 mg/dL vs. 4.1 ± 0.8 mg/dL). SUA was linearly associated with baPWV in women and in men (P < .001, respectively). Multiple regression analyses remained significant for women with a positive association with baPWV across SUA quintiles in a dose-response manner (P < .001) while no longer for men with a J-shaped association between SUA quintiles and baPWV. When SUA modeled continuously, baPWV rose by 12.413 cm/s in women (P < .001) and by 6.588 cm/s in men (P < .001) for each 1 mg/dL increase of SUA. In a low-risk, middle-aged, large Korean population, higher SUA levels could have an unfavorable impact on arterial stiffness as measured by baPWV, and this association was stronger in women than in men.

IL-1β activation in response to Staphylococcus aureus lung infection requires inflammasome-dependent and independent mechanisms

Maintaining balanced levels of IL-1β is extremely important to avoid host tissue damage during infection. Our goal was to understand the mechanisms behind the reduced pathology and decreased bacterial burdens in Ifnlr1^-/- mice during lung infection with Staphylococcus aureus. Intranasal infection of Ifnlr1^-/- mice with S. aureus led to significantly improved bacterial clearance, survival and decrease of proinflammatory cytokines in the airway including IL-1β. Ifnlr1^-/- mice treated with recombinant IL-1β displayed increased bacterial burdens in the airway and lung. IL-1β levels in neutrophils from Ifnlr1^-/- infected mice lungs were decreased when compared to neutrophils from WT mice. Mice lacking NLRP3 and caspase-1 had reduced IL-1β levels 4 h after infection, due to reductions or absence of active caspase-1 respectively, but levels at 24 h were comparable to WT infected mice. Ifnlr1^-/- infected mice had decreases in both active caspase-1 and neutrophil elastase indicating an important role for the neutrophil serine protease in IL-1β processing. By inhibiting neutrophil elastase, we were able to decrease IL-1β levels by 39% in Nlrp3^-/- infected mice when compared to WT mice. These results highlight the crucial role of both proteases in IL-1β processing, via inflammasome-dependent and -independent mechanisms.

ATP as a Pathophysiologic Mediator of Bacteria-Host Crosstalk in the Gastrointestinal Tract

Extracellular nucleotides, such as adenosine triphosphate (ATP), are released from host cells including nerve termini, immune cells, injured or dead cells, and the commensal bacteria that reside in the gut lumen. Extracellular ATP interacts with the host through purinergic receptors, and promotes intercellular and bacteria-host communication to maintain the tissue homeostasis. However, the release of massive concentrations of ATP into extracellular compartments initiates acute and chronic inflammatory responses through the activation of immunocompetent cells (e.g., T cells, macrophages, and mast cells). In this review, we focus on the functions of ATP as a pathophysiologic mediator that is required for the induction and resolution of inflammation and inter-species communication.

Multiple Membrane Transporters and Some Immune Regulatory Genes are Major Genetic Factors to Gout

Gout is a common form of inflammatory arthritis caused by hyperuricemia and the deposition of Monosodium Urate (MSU) crystals. It is also considered as a complex disorder in which multiple genetic factors have been identified in association with its susceptibility and/or clinical outcomes. Major genes that were associated with gout include URAT1, GLUT9, OAT4, NPT1 (SLC17A1), NPT4 (SLC17A3), NPT5 (SLC17A4), MCT9, ABCG2, ABCC4, KCNQ1, PDZK1, NIPAL1, IL1β, IL-8, IL-12B, IL-23R, TNFA, MCP-1/CCL2, NLRP3, PPARGC1B, TLR4, CD14, CARD8, P2X7R, EGF, A1CF, HNF4G and TRIM46, LRP2, GKRP, ADRB3, ADH1B, ALDH2, COMT, MAOA, PRKG2, WDR1, ALPK1, CARMIL (LRRC16A), RFX3, BCAS3, CNIH-2, FAM35A and MYL2-CUX2. The proteins encoded by these genes mainly function in urate transport, inflammation, innate immunity and metabolism. Understanding the functions of gout-associated genes will provide important insights into future studies to explore the pathogenesis of gout, as well as to develop targeted therapies for gout.

Flavonoids interfere with NLRP3 inflammasome activation

NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) inflammasome is a component of innate immunity, and is responsible for producing mature IL-1β and -18. Several flavonoids were found to affect inflammasome pathway, but the mechanism of action is still obscure. To elucidate the effects on NLRP3 inflammasome pathway and to determine the structure-activity relationships, NLRP3 inflammasome in differentiated THP-1 cells was activated via treatment with monosodium urate (MSU) crystals. Levels of mature IL-1β, NLRP3 inflammasome components and apoptosis-associated speck-like protein containing a CARD (caspase recruitment domain) (ASC) oligomerization were investigated and the mechanisms of action were also elucidated. Among the 56 flavonoids initially tested, only flavone, 2',4'-dihhydroxyflavone, 3',4'-dichloroflavone, 4',5,7-trihydroxyflavone (apigenin), 3,4',5,7-tetrahydroxyflavone (kaempferol) and 3,3',4',5,7-pentahydroxyflavone (quercetin) significantly inhibited IL-1β production at 10 μM. Apigenin, kaempferol and 3',4'-dichloroflavone inhibited ASC oligomerization without affecting the ASC level in cell lysates. Apigenin also inhibited absent in melanoma 2 (AIM2) inflammasome-related pathway, but not NLR family CARD domain-containing protein 4 (NLRC4) inflammasome activation. The action of apigenin on NLRP3 inflammasome activation is mediated partly via inhibition of phosphorylation of spleen tyrosine kinase/protein tyrosine kinase 2 (Syk/Pyk2) pathway. Furthermore, orally administered apigenin (100 mg/kg) strongly reduced the number of neutrophils and monocytes in MSU-induced peritonitis in mice. The present study, for the first time, demonstrated the structure-activity profiles of flavonoids in NLRP3 inflammasome activation and mechanisms of cellular action. Certain flavonoids including apigenin are expected to ameliorate the inflammatory symptoms in autoinflammatory diseases associated with NLRP3 inflammasome activation.

The release of pro-inflammatory cytokines is mediated via mitogen-activated protein kinases rather than by the inflammasome signalling pathway in keratinocytes

Toll-like receptors (TLRs) are expressed in the skin and airway epithelial tissues, which are the most important sites of host-pathogen interactions. TLRs recognize the 3-D structures of pathogen-associated molecules and are therefore useful markers of the innate immune response. Here, we investigated the role of lipopolysaccharides and monosodium urate (MSU) crystals in the activation of the TLR and NOD-like receptor (NLR) pathways in human keratinocytes. Analysis of the inflammasome compounds revealed that NOD-like receptor P3 and TLR4, both of which are components of inflammasome complexes involved in the activation of interleukin (IL)-1β, were not expressed in keratinocytes. Transcriptomic analysis showed that the combination of MSU and lipopolysaccharide priming did not elicit significant results compared to MSU treatment, which induced the expression of TLR2, IL-6 and IL-8/chemokine (C-X-C motif) ligand 8 CXCL8 in the keratinocyte cell line HaCaT. Furthermore, MSU promoted the phosphorylation of extracellular signal-regulated kinase 1/2 and MAPK14/p38α mitogen-activated protein kinases. We concluded that MSU stimulates a pro-inflammatory response in keratinocytes via mitogen-activated protein kinase pathway to induce production of IL-8/CXCL8 chemokine (C-X-C motif) ligand 8 and TLR2.

The level of physical training modulates cytokine levels through P2X7 receptor in healthy subjects

INTRODUCTION

The P2X7 receptor-NLRP3 inflammasome complex (P2X7R-Infl) regulates inflammatory and immune responses. Physical exercise modulates heat-shock proteins (Hsps), influencing cytokine levels and oxidative stress; Hsp72 triggers P2X7R-Infl-dependent responses.

SUBJECTS AND METHODS

We studied the effect of a single bout of maximal exercise on lymphomonocyte expression of P2X7R, NLRP3, caspase-1, NF-kB and Hsp72 and circulating levels of IL-1β, IL-18 and MCP-1, all modulated by P2X7R-Infl, in healthy sedentary (SED), trained (ATH), endurance (END) male individuals.

RESULTS

Baseline P2X7R, NLRP3 and Caspase-1 expression progressively increased from SED to ATH and END; NF-kβ showed the same trend. Hsp72 did not differ among groups. Acute exercise strongly reduced P2X7R in all participants, irrespective of their degree of physical training. Inflammasome responses differed across groups: in SED, NLRP3 and Caspase-1 increased; in ATH, NLRP3 reduced and caspase-1 did not vary; in END, NLRP3 and Caspase-1 declined. Baseline IL-1β, higher in END, was unmodified after exercise; IL-18 decreased; MCP-1 doubled in SED, did not vary in ATH, declined in END. In the whole study population, significant direct relationships emerged between P2X7R expression and IL-1β, IL-18, MCP-1 levels, all P < .001; also Caspase-1 related with these markers. A multivariate analysis showed age, BMI and P2X7R as determinants of postexercise IL-1β levels.

CONCLUSION

Endurance show higher P2X7R-Infl expression and function vs SED and ATH; however, maximal exercise determines prevailing pro-inflammatory vs anti-inflammatory responses in untrained and trained participants, respectively, highlighting a likely cause-effect relationship between degree of physical activity and P2X7R-Infl-mediated responses.

The P2X7 receptor: A main player in inflammation

Damage associated molecular patterns (DAMPs) are intracellular molecules released from infected or injured cells to activate inflammatory and reparatory responses. One of the most ancient and conserved DAMPs is extracellular ATP that exerts its phlogistic activity mainly through activation of the P2X7 receptor (P2X7R). The P2X7R is an ATP gated ion channel, expressed by most immune cells, including the monocyte-derived cell lineages, T and B lymphocytes and their precursors. Here we give an overview of recent and established literature on the role of P2X7R in septic and sterile inflammation. P2X7R ability in restraining intracellular bacteria and parasite infection by modulation of the immune response are described, with particular focus on Mycobacteria and Plasmodium. Emerging literature on the role of P2X7 in viral infections such as HIV-1 is also briefly covered. Finally, we describe the numerous intracellular pathways related to inflammation and activated by the P2X7R, including the NLRP3 inflammasome, NF-kB, NFAT, GSK3β and VEGF, and discuss the involvement of P2X7R in chronic diseases. The possible therapeutic applications of P2X7R antagonists are also described.

Searching Novel Therapeutic Targets for Scleroderma: P2X7-Receptor Is Up-regulated and Promotes a Fibrogenic Phenotype in Systemic Sclerosis Fibroblasts

Objectives: Systemic sclerosis (SSc) is a connective tissue disorder presenting fibrosis of the skin and internal organs, for which no effective treatments are currently available. Increasing evidence indicates that the P2X7 receptor (P2X7R), a nucleotide-gated ionotropic channel primarily involved in the inflammatory response, may also have a key role in the development of tissue fibrosis in different body districts. This study was aimed at investigating P2X7R expression and function in promoting a fibrogenic phenotype in dermal fibroblasts from SSc patients, also analyzing putative underlying mechanistic pathways. Methods: Fibroblasts were isolated by skin biopsy from 9 SSc patients and 8 healthy controls. P2X7R expression, and function (cytosolic free Ca²⁺ fluxes, α-smooth muscle actin [α-SMA] expression, cell migration, and collagen release) were studied. Moreover, the role of cytokine (interleukin-1β, interleukin-6) and connective tissue growth factor (CTGF) production, and extracellular signal-regulated kinases (ERK) activation in mediating P2X7R-dependent pro-fibrotic effects in SSc fibroblasts was evaluated. Results: P2X7R expression and Ca²⁺ permeability induced by the selective P2X7R agonist 2'-3'-O-(4-benzoylbenzoyl)ATP (BzATP) were markedly higher in SSc than control fibroblasts. Moreover, increased αSMA expression, cell migration, CTGF, and collagen release were observed in lipopolysaccharides-primed SSc fibroblasts after BzATP stimulation. While P2X7-induced cytokine changes did not affect collagen production, it was completely abrogated by inhibition of the ERK pathway. Conclusion: In SSc fibroblasts, P2X7R is overexpressed and its stimulation induces Ca²⁺-signaling activation and a fibrogenic phenotype characterized by increased migration and collagen production. These data point to the P2X7R as a potential, novel therapeutic target for controlling exaggerated collagen deposition and tissue fibrosis in patients with SSc.

P2X7 receptor antagonism modulates IL-1β and MMP9 in human atherosclerotic vessels

In atherosclerosis, matrix metallopeptidases (MMPs) contribute to plaque rupture through weakening of the fibrous cap. Pleiotropic P2X purinoceptor 7 (P2X7), expressed in the carotid plaque (PL), is involved in interleukin 1 beta (IL-1β) release that may influence MMP9 generation, thus their possible modulation through acting on P2X7 was investigated. P2X7-related machinery was characterized and the effects of P2X7 antagonists (A740003, KN62) and MMPs inhibitors (Batimastat, Ro28-2653) were studied in ex-vivo tissue cultures of human PL’s vs. non-atherosclerotic internal mammary artery (IMA) by using molecular biology, immune-biochemical and microscopy methodologies. We highlighted atherosclerosis-related differences between PLs and IMAs molecular patterns, and their responsivity to P2X7 antagonism. High IL-1β tissue content was associated with PLs morphology and instability/vulnerability. We demonstrated that A740003, but not KN62, decreased IL-1β and MMP9 independently from NLR family pyrin domain containing 3, but in relationship with patient’s smoking status. Acting downstream P2X7 by MMPs inhibitors, diminished IL-1β mRNA without transcriptional effect at MMP9, possibly because the assumption of statin by patients. These data firstly demonstrated A740003 suitability as a specific tool to decrease inflammatory status in human vessels and might support the design of studies applying P2X7 antagonists for the local targeting and tailored therapy of atherosclerosis.

The anticancer effect of mebendazole may be due to M1 monocyte/macrophage activation via ERK1/2 and TLR8-dependent inflammasome activation

Mebendazole (MBZ), a drug commonly used for helminitic infections, has recently gained substantial attention as a repositioning candidate for cancer treatment. However, the mechanism of action behind its anticancer activity remains unclear. To address this problem, we took advantage of the curated MBZ-induced gene expression signatures in the LINCS Connectivity Map (CMap) database. The analysis revealed strong negative correlation with MEK/ERK1/2 inhibitors. Moreover, several of the most upregulated genes in response to MBZ exposure were related to monocyte/macrophage activation. The MBZ-induced gene expression signature in the promyeloblastic HL-60 cell line was strongly enriched in genes involved in monocyte/macrophage pro-inflammatory (M1) activation. This was subsequently validated using MBZ-treated THP-1 monocytoid cells that demonstrated gene expression, surface markers and cytokine release characteristic of the M1 phenotype. At high concentrations MBZ substantially induced the release of IL-1β and this was further potentiated by lipopolysaccharide (LPS). At low MBZ concentrations, cotreatment with LPS was required for MBZ-stimulated IL-1β secretion to occur. Furthermore, we show that the activation of protein kinase C, ERK1/2 and NF-kappaB were required for MBZ-induced IL-1β release. MBZ-induced IL-1β release was found to be dependent on NLRP3 inflammasome activation and to involve TLR8 stimulation. Finally, MBZ induced tumor-suppressive effects in a coculture model with differentiated THP-1 macrophages and HT29 colon cancer cells. In summary, we report that MBZ induced a pro-inflammatory (M1) phenotype of monocytoid cells, which may, at least partly, explain MBZ's anticancer activity observed in animal tumor models and in the clinic.

IL-27 enhances LPS-induced IL-1β in human monocytes and murine macrophages

IL-27 bridges innate and adaptive immunity by modulating cytokine production from myeloid cells and regulating Th cell differentiation. During bacterial infection, TLR4 triggering by LPS induces IL-27 production by monocytes and macrophages. We have previously shown that IL-27 can prime monocytes for LPS responsiveness by enhancing TLR4 expression and intracellular signaling. If unregulated, this could result in damaging inflammation, whereas on the other hand, this may also provide greater responses by inflammatory processes induced in response to bacterial pathogens. A key process in fine-tuning inflammatory responses is activation of the inflammasome, which ultimately results in IL-1β production. Herein, we investigated the molecular mechanisms by which IL-27 modulates LPS-induced IL-1β secretion in monocytes and macrophages. We found that when delivered simultaneously with LPS, IL-27 augments activation of caspase-1 and subsequent release of IL-1β. Furthermore, we determined that IL-27 primes cells for enhanced IL-1β production by up-regulating surface expression of TLR4 and P2X purinoceptor 7 (P2X7) for enhanced LPS and ATP signaling, respectively. These findings provide new evidence that IL-27 plays an important role in the proinflammatory capacity of monocytes and macrophages via enhancing IL-1β secretion levels triggered by dual LPS-ATP stimulation.

Dipeptidyl Vinyl Sulfone as a Novel Chemical Tool to Inhibit HMGB1/NLRP3-Inflammasome and Inflamma-miRs in Aβ-Mediated Microglial Inflammation

Rapid microglial activation and associated inflammatory pathways contribute to immune-defense and tissue repair in the central nervous system (CNS). However, persistent activation of these cells will ultimately result in vast production of pro-inflammatory mediators and other neurotoxic factors, which may induce neuronal damage and contribute to chronic neurodegenerative diseases, as Alzheimer's disease (AD). Therefore, small molecules with immunomodulatory effects on microglia may be considered as potential tools to counteract their proinflammatory phenotype and neuroimmune dysregulation in such disorders. Indeed, reducing amyloid-β (Aβ)-induced microglia activation is believed to be effective in treating AD. In this study, we investigated whether dipeptidyl vinyl sulfone (VS) was able to attenuate Aβ-mediated inflammatory response using a mouse microglial (N9) cell line and a solution containing a mixture of Aβ aggregates. We show that low levels of VS are able to prevent cell death while reducing microglia phagocytosis upon Aβ treatment. VS also suppressed Aβ-induced expression of inflammatory mediators in microglia, such as matrix metalloproteinase (MMP)-2 and MMP-9, as well as high-mobility group box protein-1 (HMGB1), nod-like receptor protein 3 (NLRP3)-inflammasome, and interleukin (IL)-1β. Interestingly, increased expression of the two critical inflammation-related microRNAs (miR)-155 and miR-146a in microglia upon Aβ treatment was also prevented by VS coincubation. Taken together, VS emerges as a potential new therapeutic strategy worthy of further investigation in improved cellular and animal models of AD.

Purinergic receptors: new targets for the treatment of gout and fibrosis

Adenosine triphosphate is involved in many metabolic reactions, but it has also a role as a cellular danger signal transmitted through purinergic receptors (PRs). Indeed, adenosine 5'-triphosphate (ATP) can bind to PRs which are found in the membrane of many cell types, although the relative proportions of the receptor subtypes differ. PRs are classified according to genetic and pharmacological criteria and especially their affinities for agonists and their transduction mechanism (i.e. as metabotropic P2YRs or ionotropic P2XRs). Extracellular ATP release by activated or necrotic cells may activate various PRs and especially P2X7R, the best-characterized PR, on immune cells. P2X7R is known to regulate the activation of the Nod-like receptor (NLR)-family protein, NLRP3 inflammasome, which permit the release of IL-1β, a potent pro-inflammatory cytokine. The P2X7R/NLRP3 pathway is involved in many inflammatory diseases, such as gout, and in fibrosis diseases associated with inflammatory process, liver or lung fibrosis. Some authors imaging also a real promising therapeutic potential of P2X7R blockage. Thus, several pharmaceutical companies have developed P2X7R antagonists as novel anti-inflammatory drug candidates. Clinical trials of the efficacy of these antagonists are now underway. A better understanding of the P2X7R/NLRP3 signalling pathways permits the identification of targets and the development of a new class of drugs able to inhibit the fibrogenesis process and collagen deposition.

Potentiation of hepatic stellate cell activation by extracellular ATP is dependent on P2X7R-mediated NLRP3 inflammasome activation

Purinergic receptor P2x7 (P2x7R) is a key modulator of liver inflammation and fibrosis. The present study aimed to investigate the role of P2x7R in hepatic stellate cells activation. Lipopolysaccharide (LPS) or the conditioned medium (CM) from LPS-stimulated RAW 264.7 mouse macrophages was supplemented to human hepatic stellate cells, LX-2 for 24h and P2x7R selective antagonist A438079 (10μM) was supplemented to LX-2 cells 1h before LPS or CM stimulation. In addition LX-2 cells were primed with LPS for 4h and subsequently stimulated for 30min with 3mM of adenosine 5'-triphosphate (ATP). A438079 was supplemented to LX-2 cells 10min prior to ATP. Directly treated with LPS on LX-2 cells, mRNA expressions of interleukin (IL)-1β, IL-18 and IL-6 were increased, as well as mRNA expressions of P2x7R, caspase-1, apoptosis-associated speck-like protein containing CARD (ASC) and NOD-like receptor family, pyrin domain containing 3 (NLRP3) mRNA. LPS also increased α-smooth muscle actin (α-SMA) and type I collagen mRNA expressions, as well as collagen deposition. Interestingly treatment of LX-2 cells with LPS-activated CM exhibited the greater increase of above factors than those in LX-2 cells directly treated with LPS. Pretreatment of A438079 on LX-2 cells stimulated by LPS or LPS-activated CM both suppressed IL-1β mRNA expression. LPS combined with ATP dramatically increased protein synthesis and cleavage of IL-1β and its mRNA level than those in HSC treated with LPS or ATP alone. Additionally LX-2 cells primed with LPS and subsequently stimulated for 30min with ATP greatly increased mRNA and protein expression of caspase-1, NLRP3 and P2x7R, as well as liver fibrosis markers, α-SMA and type I collagen. These events were remarkably suppressed by A438079 pretreatment. siRNA against P2x7R reduced protein expression of NLRP3 and α-SMA, and suppressed deposition and secretion of type I collagen. The involvement of P2X7R-mediated NLRP3 inflammasome activation in IL-1β production of HSC might contribute to ECM deposition and suggests that blockade of the P2x7R-NLRP3 inflammasome axis represents a potential therapeutic target to liver fibrosis.

Curcumin Represses NLRP3 Inflammasome Activation via TLR4/MyD88/NF-κB and P2X7R Signaling in PMA-Induced Macrophages

Aims: In the NOD-like receptor (NLR) family, the pyrin domain containing 3 (NLRP3) inflammasome is closely related to the progression of atherosclerosis. This study aimed to assess the effects of curcumin on NLRP3 inflammasome in phorbol 12-myristate 13-acetate (PMA)-induced macrophages and explore its underlying mechanism.

Methods: Human monocytic THP-1 cells were pretreated with curcumin for 1 h and subsequently induced with PMA for 48 h. Total protein was collected for Western blot analysis. Cytokine interleukin (IL)-1β release and nuclear factor kappa B (NF-κB) p65 translocation were detected by ELISA assay and cellular NF-κB translocation kit, respectively.

Results: Curcumin significantly reduced the expression of NLRP3 and cleavage of caspase-1 and IL-1β secretion in PMA-induced macrophages. Moreover, Bay (a NF-κB inhibitor) treatment considerably suppressed the expression of NLRP3 inflammasome in PMA-induced THP-1 cells. Curcumin also markedly inhibited the upregulation of toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), phosphorylation level of IκB-α, and activation of NF-κB in PMA-induced macrophages. In addition, purinergic 2X7 receptor (P2X7R) siRNA was administered, and it significantly decreased NLRP3 inflammasome expression in PMA-induced macrophages. Furthermore, curcumin reversed PMA-stimulated P2X7R activation, which further reduced the expression of NLRP3 and cleavage of caspase-1 and IL-1β secretion. Silencing of P2X7R using siRNA also suppressed the activation of NF-κB pathway in PMA-induced macrophages, but P2X7R-silenced cells did not significantly decrease the expression of TLR4 and MyD88.

Conclusion: Curcumin inhibited NLRP3 inflammasome through suppressing TLR4/MyD88/NF-κB and P2X7R pathways in PMA-induced macrophages.

Opsonisation of nanoparticles prepared from poly(β-hydroxybutyrate) and poly(trimethylene carbonate)-b-poly(malic acid) amphiphilic diblock copolymers: Impact on the in vitro cell uptake by primary human macrophages and HepaRG hepatoma cells

The present work reports the investigation of the biocompatibility, opsonisation and cell uptake by human primary macrophages and HepaRG cells of nanoparticles (NPs) formulated from poly(β-malic acid)-b-poly(β-hydroxybutyrate) (PMLA-b-PHB) and poly(β-malic acid)-b-poly(trimethylene carbonate) (PMLA-b-PTMC) diblock copolymers, namely PMLA₈₀₀-b-PHB₇₃₀₀, PMLA₄₅₀₀-b-PHB₄₄₀₀, PMLA₂₅₀₀-b-PTMC₂₈₀₀ and PMLA₄₃₀₀-b-PTMC₁₄₀₀. NPs derived from PMLA-b-PHB and PMLA-b-PTMC do not trigger lactate dehydrogenase release and do not activate the secretion of pro-inflammatory cytokines demonstrating the excellent biocompatibility of these copolymers derived nano-objects. Using a protein adsorption assay, we demonstrate that the binding of plasma proteins is very low for PMLA-b-PHB-based nano-objects, and higher for those prepared from PMLA-b-PTMC copolymers. Moreover, a more efficient uptake by macrophages and HepaRG cells is observed for NPs formulated from PMLA-b-PHB copolymers compared to that of PMLA-b-PTMC-based NPs. Interestingly, the uptake in HepaRG cells of NPs formulated from PMLA₈₀₀-b-PHB₇₃₀₀ is much higher than that of NPs based on PMLA₄₅₀₀-b-PHB₄₄₀₀. In addition, the cell internalization of PMLA₈₀₀-b-PHB₇₃₀₀ based-NPs, probably through endocytosis, is strongly increased by serum pre-coating in HepaRG cells but not in macrophages. Together, these data strongly suggest that the binding of a specific subset of plasmatic proteins onto the PMLA₈₀₀-b-PHB₇₃₀₀-based NPs favors the HepaRG cell uptake while reducing that of macrophages.

Target deletion of complement component 9 attenuates antibody-mediated hemolysis and lipopolysaccharide (LPS)-induced acute shock in mice

Terminal complement membrane attack complex (MAC) formation is induced initially by C5b, followed by the sequential condensation of the C6, C7, C8. Polymerization of C9 to the C5b-8 complex forms the C5b-9 (or MAC). The C5b-9 forms lytic or non lytic pores in the cell membrane destroys membrane integrity. The biological functionalities of MAC has been previously investigated by using either the mice deficient in C5 and C6, or MAC’s regulator CD59. However, there is no available C9 deficient mice (mC9^−/−) for directly dissecting the role of C5b-9 in the pathogenesis of human diseases. Further, since C5b-7 and C5b-8 complexes form non lytic pore, it may also plays biological functionality. To better understand the role of terminal complement cascades, here we report a successful generation of mC9^−/−. We demonstrated that lack of C9 attenuates anti-erythrocyte antibody-mediated hemolysis or LPS-induced acute shock. Further, the rescuing effect on the acute shock correlates with the less release of IL-1β in mC9^−/−, which is associated with suppression of MAC-mediated inflammasome activation in mC9^−/−. Taken together, these results not only confirm the critical role of C5b-9 in complement-mediated hemolysis and but also highlight the critical role of C5b-9 in inflammasome activation.

Purinergic regulation of the immune system

Cellular stress or apoptosis triggers the release of ATP, ADP and other nucleotides into the extracellular space. Extracellular nucleotides function as autocrine and paracrine signalling molecules by activating cell-surface P2 purinergic receptors that elicit pro-inflammatory immune responses. Over time, extracellular nucleotides are metabolized to adenosine, leading to reduced P2 signalling and increased signalling through anti-inflammatory adenosine (P1 purinergic) receptors. Here, we review how local purinergic signalling changes over time during tissue responses to injury or disease, and we discuss the potential of targeting purinergic signalling pathways for the immunotherapeutic treatment of ischaemia, organ transplantation, autoimmunity or cancer.

Involvement of matrix metalloproteinases (MMPs) and inflammasome pathway in molecular mechanisms of fibrosis

Fibrosis is a basic connective tissue lesion defined by the increase in the fibrillar extracellular matrix (ECM) components in tissue or organ. Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate the turn-over of ECM and so they are suggested to be important in tissue remodelling observed during fibrogenic process associated with chronic inflammation. Tissue remodelling is the result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components markedly controlled by the MMPs/TIMP imbalance. We previously showed an association of the differences in collagen deposition in the lungs of bleomycin-treated mice with a reduced molar pro-MMP-9/TIMP-1 ratio. Using the carbon tetrachloride (CCl₄) preclinical model of liver fibrosis in mice, we observed a significant increase in collagen deposition with increased expression and release of tissue inhibitors of metalloproteinase (TIMP)-1 both at 24 h and 3 weeks later. This suggests an early altered regulation of matrix turnover involved in the development of fibrosis. We also demonstrated an activation of NLRP3-inflammasome pathway associated with the IL-1R/MyD88 signalling in the development of experimental fibrosis both in lung and liver. This was also associated with an increased expression of purinergic receptors mainly P2X₇. Finally, these observations emphasize those effective therapies for these disorders must be given early in the natural history of the disease, prior to the development of tissue remodelling and fibrosis.

CORM-2 inhibits TXNIP/NLRP3 inflammasome pathway in LPS-induced acute lung injury

OBJECTIVE

Accumulated studies suggest that exogenously administered carbon monoxide is beneficial for the resolution of acute lung inflammation. The present study aimed to examine the effects and the underlying mechanisms of CORM-2 on thioredoxin-interacting protein (TXNIP)/NLRP3 inflammasome pathway in lipopolysaccharide (LPS)-induced acute lung injury (ALI).

METHODS

ALI was intratracheally induced by LPS in C57BL6 mice. CORM-2 or iCORM-2 (30mg/kg i.p.) was administered immediately before LPS instillation. 6 h later, lung bronchoalveolar lavage (BAL) fluids were acquired for IL-18, IL-1β, and cell measurement, and lung issues were collected for histologic examination, wet/dry weight ratio, and determination of TXNIP/NLRP3 inflammasome expression, NLRP3 inflammasome and NF-ΚB activity, and reactive oxygen species (ROS) production.

RESULTS

LPS triggered significant lung edema, lung injury, and leukocyte infiltration, and elevated the levels of IL-1β and IL-18 in lung BAL fluids. CORM-2 pretreatment resulted in a marked amelioration of lung injury and reduced IL-1β and IL-18 secretion in BAL fluids. In lung tissues; CORM-2 down-regulated mRNA and protein level of TXNIP, NLRP3, ASC, and caspase-1. Furthermore, CORM-2 reduced ROS production, inhibited NLRP3 inflammasome and NF-κB activity, and interaction of TXNIP-NLRP3. However, no significant differences were detected between the LPS and iCORM-2 (an inactive variant of CORM-2) group.

CONCLUSION

CORM-2 suppresses TXNIP/NLRP3 inflammasome pathway and protects against LPS-induced lung injury.

Lipopolysaccharide-Mediated Induction of Concurrent IL-1β and IL-23 Expression in THP-1 Cells Exhibits Differential Requirements for Caspase-1 and Cathepsin B Activity

The inflammasome is a multimeric protein complex required for interleukin (IL)-1β production. Upon lipopolysaccharide (LPS) triggering of toll-like receptor (TLR)-4 and subsequent ATP signaling, the NOD-like receptor containing-pyrin domain 3 (NLRP3) inflammasome is activated to cleave pro-caspase-1 into caspase-1, allowing the secretion of IL-1β. IL-1β is known to function with IL-23 in the regulation of IL-17-producing CD4(+) T cells, Th17 cells, in adaptive immunity. Recently, studies have shown that IL-1β and IL-23 together activate IL-17-producing innate lymphoid cells, demonstrating that the pair may exhibit additional effects on cell differentiation. Using an in vitro model of bacterial infection, LPS treatment of human monocytic cells, we investigated the molecular mechanisms involved in the co-expression of IL-1β and IL-23. We found that IL-1β is partially required for optimal LPS-induced IL-23 production. We also found that IL-23 production was partially dependent on ATP signaling via the P2X7 receptor, whereas IL-1β production required this signaling. Furthermore, we identified a novel role for cathepsin B activity in IL-23 production. Taken together, this study identifies differential requirements for the co-expression of IL-1β and IL-23. Due to their similar roles in Th17 differentiation, characterization of the regulatory mechanisms for LPS-induced IL-1β and IL-23 may reveal novel information into the pathology of the inflammatory response particularly during bacterial infection.

[The NLRP3 inflammasome: Physiopathology and therapeutic application]

The innate immune system constitutes the first line of host defense against pathogens. "Nonself", such as exogenous particles or pathogens, triggers an inflammatory response. Inflammasomes are molecular platforms activated upon cellular infection or stress that trigger the maturation of proinflammatory cytokines such as IL-1β. Activation of the NLRP3 inflammasome pathway, the most extensively studied, appears to be the corner stone of many inflammatory diseases, including Crohn's disease, rheumatoid arthritis and gout. Cryopyrine-associated periodic syndromes (CAPS) are NLRP3 inflammasome-associated diseases. Canakinumab (Ilaris(®)) is the only drug approved for CAPS treatment in France. Targeted therapy against NLRP3 inflammasome and IL-1β might be the new anti-inflammatory drugs.

Extracellular ATP and other nucleotides-ubiquitous triggers of intercellular messenger release

Extracellular nucleotides, and ATP in particular, are cellular signal substances involved in the control of numerous (patho)physiological mechanisms. They provoke nucleotide receptor-mediated mechanisms in select target cells. But nucleotides can considerably expand their range of action. They function as primary messengers in intercellular communication by stimulating the release of other extracellular messenger substances. These in turn activate additional cellular mechanisms through their own receptors. While this applies also to other extracellular messengers, its omnipresence in the vertebrate organism is an outstanding feature of nucleotide signaling. Intercellular messenger substances released by nucleotides include neurotransmitters, hormones, growth factors, a considerable variety of other proteins including enzymes, numerous cytokines, lipid mediators, nitric oxide, and reactive oxygen species. Moreover, nucleotides activate or co-activate growth factor receptors. In the case of hormone release, the initially paracrine or autocrine nucleotide-mediated signal spreads through to the entire organism. The examples highlighted in this commentary suggest that acting as ubiquitous triggers of intercellular messenger release is one of the major functional roles of extracellular nucleotides. While initiation of messenger release by nucleotides has been unraveled in many contexts, it may have been overlooked in others. It can be anticipated that additional nucleotide-driven messenger functions will be uncovered with relevance for both understanding physiology and development of therapy.