The purinergic P2×7 receptor is expressed on monocytes in Behçet's disease and is modulated by TNF-α

The roles of immune cells in Behçet's disease

Behçet's disease (BD) is a systemic vasculitis that can affect multiple systems, including the skin, mucous membranes, joints, eyes, gastrointestinal and nervous. However, the pathogenesis of BD remains unclear, and it is believed that immune-inflammatory reactions play a crucial role in its development. Immune cells are a critical component of this process and contribute to the onset and progression of BD. By regulating the function of these immune cells, effective control over the occurrence and development of BD can be achieved, particularly with regards to monocyte activation and aggregation, macrophage differentiation and polarization, as well as T cell subset differentiation. This review provides a brief overview of immune cells and their role in regulating BD progression, which may serve as a theoretical foundation for preventing and treating this disease.

P2X7-dependent immune pathways in retinal diseases

Adenosine triphosphate (ATP) is a signalling molecule acting as a neurotransmitter but also as a danger signal. The purinergic receptor P2X7 is the main sensor of high concentration of ATP released by damaged cells. In the eye, P2X7 is expressed by resident microglia and immune cells that infiltrate the retina in disease such as age-related macular degeneration (AMD), a degenerative retinal disease, and uveitis, an inflammatory eye disease. Activation of P2X7 is involved in several physiological and pathological processes: phagocytosis, activation of the inflammasome NLRP3, release of pro-inflammatory mediators and cell death. The aim of this review is to discuss the potential involvement of P2X7 in the development of AMD and uveitis.

Physiologic roles of P2 receptors in leukocytes

Since their discovery in the 1970s, purinergic receptors have been shown to play key roles in a wide variety of biologic systems and cell types. In the immune system, purinergic receptors participate in innate immunity and in the modulation of the adaptive immune response. In particular, P2 receptors, which respond to extracellular nucleotides, are widely expressed on leukocytes, causing the release of cytokines and chemokines and the formation of inflammatory mediators, and inducing phagocytosis, degranulation, and cell death. The activity of these receptors is regulated by ectonucleotidases-expressed in these same cell types-which regulate the availability of nucleotides in the extracellular environment. In this article, we review the characteristics of the main purinergic receptor subtypes present in the immune system, focusing on the P2 family. In addition, we describe the physiologic roles of the P2 receptors already identified in leukocytes and how they can positively or negatively modulate the development of infectious diseases, inflammation, and pain.

New insights on multigenic autoinflammatory diseases

Autoinflammatory diseases are disorders of the innate immune system, which can be either monogenic due to a specific genetic mutation or complex multigenic due to the involvement of multiple genes. The aim of this review is to explore and summarize the recent advances in pathogenesis, diagnosis, and management of genetically complex autoinflammatory diseases, such as Schnitzler's syndrome; adult-onset Still's disease; synovitis, acne, pustulosis, hyperostosis, osteitis syndrome/chronic recurrent multifocal osteomyelitis/chronic non-bacterial osteomyelitis; Adamantiades-Behçet's disease; Yao syndrome; and periodic fever with aphthous stomatitis, pharyngitis, and adenitis syndrome. The PubMed database was screened for relevant articles using free text words and specific search strings. The search was limited to English-language articles, reporting the results of studies in humans, published through March 2021. Evidence from literature suggest that these rare multigenic autoinflammatory diseases can present with different clinical features and the diagnosis of these diseases can be challenging due to a combination of nonspecific manifestations that can be seen in a variety of other conditions. Diagnostic delays and disease complications may occur due to low disease awareness and the lack of pathognomonic markers. The pathogeneses of these diseases are complex and in some cases precise pathogenesis is not clearly understood. Conventional treatments are commonly used for the management of these conditions, but biologics have shown promising results. Biologics targeting proinflammatory cytokines including IL-1, IL-6, TNF-α, IL-17A and IL-18 have been shown to ameliorate signs and symptoms of different multigenic autoinflammatory diseases.

Monocyte-derived and M1 macrophages from ankylosing spondylitis patients released higher TNF-α and expressed more IL1B in response to BzATP than macrophages from healthy subjects

Macrophages participate in the pathogenesis of ankylosing spondylitis (AS) by producing inflammatory cytokines. Extracellular adenosine triphosphate (eATP), released during cell stress, acts through purinergic receptors (P2XR and P2YR) and induces inflammatory responses. We investigated the effect of 2'(3')-O-(4-benzoyl benzoyl) ATP (BzATP) (a prototypic agonist of P2X7R) on the production of inflammatory cytokines in both monocyte-generated (M2-like) and M1 macrophages from patients and controls. Macrophages were differentiated from isolated periphery-monocytes (n = 14 in each group) by macrophage colony-stimulating factor (M-CSF). Using LPS and IFN-γ, macrophages were skewed toward M1 type and were treated with BzATP. Gene expression and protein release of IL-1β, IL-23, and TNF-α were evaluated by real-time PCR and ELISA methods respectively before and after treatment. BzATP significantly increased the protein release of TNF-α and the expression of TNFA and IL1B in monocyte-generated macrophages. Besides, BzATP treatment significantly upregulated IL1B expression, reduced TNFA and IL23A expression, and TNF-α release in M1 macrophages from both groups. Monocyte-generated and M1 macrophages from AS patients released higher TNF-α and expressed more IL1B in response to the same concentration of BzATP treatment respectively. Based on our results, AS macrophages were more sensitive to BzATP treatment and responded more intensively. Besides, the diverse effects of BzATP on monocyte-derived and M1 macrophages in our study may represent the differed inflammatory properties of these two groups of macrophages in response to eATP in the body.

Safety of systemic treatments for Behçet's syndrome

INTRODUCTION

Treatment of Behçet's syndrome (BS) is aimed at controlling all symptoms of such a complex disorder, ensuring a good quality of life and preventing life-threatening complications. A better understanding of the pathogenic role of different chemokines has improved our knowledge of BS and elicited a more specific use of therapies currently available, minimizing the burden of potential side-effects related to treatment.

AREAS COVERED

This work aims to provide a detailed overview of the safety profile for current therapies available in the treatment of BS, focusing on the main side-effects, toxicity and contraindications.

EXPERT OPINION

The greatest experience in the management of BS has been achieved with the employment of monoclonal anti-tumor necrosis factor antibodies which have been advocated for BS refractory manifestations. Moreover, interleukin-1 inhibitors have proven to be effective as well as safe, despite escalation of their dosage, especially to manage the most severe and difficult-to-treat ocular manifestations. However, general treatment of BS patients remains awkward as protean clinical features may respond differently to the same treatment or even worsen. Therefore, patients' safety for therapies used in BS promotes the implementation of precision medicine, which could help targeting accurately the pathogenetic mechanisms concealed behind specific clinical phenotypes.

The autoinflammatory side of recurrent pericarditis: Enlightening the pathogenesis for a more rational treatment

Recurrent pericarditis (RP) is a troublesome and debilitating complication of acute pericarditis. Although the etiopathogenesis of this condition remains unknown, an intricate overlap of autoimmune and autoinflammatory pathways has been hypothesized to explain its beginning and recurrence over time. The majority of cases are defined as "idiopathic", reflecting our awkwardness to unravel the intimate mechanisms of RP. Given the possible occurrence of anti-nuclear, anti-heart and anti-intercalated disk antibodies as well as the association with peculiar human leukocyte antigen haplotypes, an autoimmune contribution has been claimed to specify the nature of RP. However, the most innovative pathogenic scenario of RP has been conferred to the innate immune system, mainly involving neutrophils and macrophages that produce a large amount of interleukin (IL)-1 via inflammasome activation. The clinical resemblance of RP with autoinflammatory diseases that may be marked by symptomatic serositis, high fevers and strikingly increased inflammatory parameters further suggests a similar inflammasome-mediated pathogenesis. Aspirin or non-steroidal anti-inflammatory drugs (NSAIDs) remain the mainstay of therapy in RP, whereas colchicine is recommended on top of standard anti-inflammatory therapy, due to its role in inhibiting the IL-1 converting enzyme (caspase 1) within the inflammasome as well as the release of additional pro-inflammatory mediators and reactive oxygen species. With regard to treatment of RP refractory to NSAIDs and colchicine, blockade of IL-1 is the most relevant advance achieved in the last decade: the outstanding effect of the short-acting IL-1 receptor antagonist anakinra has been first recognized in the pediatric population, giving a proof of its practical feasibility. Over a more recent time, a growing experience with anakinra deriving from both large and small studies has further confirmed that RP might be regarded as an IL-1-mediated disease. This review aims to provide a contemporary insight into the mechanisms leading to RP as well as into the most recent literature data showing the beneficial approach originating from IL-1 blockade in this intriguing disorder.

Crucial role of P2X7 receptor for effector T cell activation in experimental autoimmune uveitis

PURPOSE

To investigate the roles of P2X7 receptors (P2RX7) in the pathogenesis of experimental autoimmune uveoretinitis (EAU).

STUDY DESIGN

Experimental.

METHODS

Either wild-type (P2rx7 ^+/+ ) or P2rx7-deficient (P2rx7 ^-∕- ) mice were immunized with interphotoreceptor retinoid-binding protein (IRBP) peptide 1-20. Severity of EAU was evaluated clinically and histopathologically. The induction of IRBP-specific proliferation and cytokines in draining lymph nodes was assessed by enzyme-linked immunosorbent assays (ELISA). The frequency of activation markers was examined by flow cytometry. Furthermore, inhibitory roles of systemic administration of Brilliant Blue G (BBG), an antagonist for P2RX7, in EAU were also assessed in the wild-type mice.

RESULTS

The severity of EAU in P2rx7 ^-∕- mice was reduced as compared with that in P2rx7 ^+/+ mice, both clinically and histopathologically. IRBP-specific proliferation in P2rx7 ^-∕- on day 16 was slightly decreased compared to that in P2rx7 ^+/+ mice. The induction of IRBP-specific interferon (IFN)-γ and interleukin (IL)-17 in P2rx7 ^-∕- mice on day 16 was lower than that in P2rx7 ^+/+ mice. The up-regulation of surface expression of activation markers such as CD25, CD44, and CD69 in response to TCR stimulation in P2rx7 ^-∕- mice was decreased as compared with that in P2rx7 ^+/+ mice. Furthermore, neutralization of P2RX7 in vivo by BBG suppressed EAU clinically and histopathologically. IRBP-specific IFN-γ and IL-17 induction in BBG-treated mice was significantly lower than that in vehicle-treated mice.

CONCLUSION

The results suggest that P2RX7 is a novel preventative therapeutic target for uveitis as it suppresses the effector functions of both Th1 and Th17 cell responses.

The Potential Role of Trained Immunity in Autoimmune and Autoinflammatory Disorders

During induction of trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward increased activation. Important rewiring of cellular metabolism of the myeloid cells takes place during induction of trained immunity, including a shift toward glycolysis induced through the mTOR pathway, as well as glutaminolysis and cholesterol synthesis. Subsequently, this leads to modulation of the function of epigenetic enzymes, resulting in important changes in chromatin architecture that enables increased gene transcription. However, in addition to the beneficial effects of trained immunity as a host defense mechanism, we hypothesize that trained immunity also plays a deleterious role in the induction and/or maintenance of autoimmune and autoinflammatory diseases if inappropriately activated.

Modulation of P2X7 Receptor during Inflammation in Multiple Sclerosis

Multiple sclerosis (MS) is characterized by macrophage accumulation and inflammatory infiltrates into the CNS contributing to demyelination. Because purinergic P2X7 receptor (P2X7R) is known to be abundantly expressed on cells of the hematopoietic lineage and of the nervous system, we further investigated its phenotypic expression in MS and experimental autoimmune encephalomyelitis conditions. By quantitative reverse transcription polymerase chain reaction and flow cytometry, we analyzed the P2X7R expression in human mononuclear cells of peripheral blood from stable and acute relapsing-remitting MS phases. Human monocytes were also challenged in vitro with pro-inflammatory stimuli such as the lipopolysaccharide, or the P2X7R preferential agonist 2′(3′)-O-(4 Benzoylbenzoyl)adenosine 5′-triphosphate, before evaluating P2X7R protein expression. Finally, by immunohistochemistry and immunofluorescence confocal analysis, we investigated the P2X7R expression in frontal cortex from secondary progressive MS cases. We demonstrated that P2X7R is present and inhibited on peripheral monocytes isolated from MS donors during the acute phase of the disease, moreover it is down-regulated in human monocytes after pro-inflammatory stimulation in vitro. P2X7R is instead up-regulated on astrocytes in the parenchyma of frontal cortex from secondary progressive MS patients, concomitantly with monocyte chemoattractant protein-1 chemokine, while totally absent from microglia/macrophages or oligodendrocytes, despite the occurrence of inflammatory conditions. Our results suggest that inhibition of P2X7R on monocytes and up-regulation in astrocytes might contribute to sustain inflammatory mechanisms in MS. By acquiring further knowledge about P2X7R dynamics and identifying P2X7R as a potential marker for the disease, we expect to gain insights into the molecular pathways of MS.

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.

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.

SAPHO Syndrome: Current Developments and Approaches to Clinical Treatment

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, and osteitis) is a rare autoimmune disease which, due to its clinical presentation and symptoms, is often misdiagnosed and unrecognized. Its main features are prominent inflammatory cutaneous and articular manifestations. Treatments with immunosuppressive drugs have been used for the management of SAPHO with variable results. To date, the use of anti-TNF-α agents has proved to be an effective alternative to conventional treatment for unresponsive or refractory SAPHO cases. TNF-α is a pro-inflammatory cytokine and pivotal regulator of other cytokines, including IL-1 β, IL-6, and IL-8, involved in inflammation, acute-phase response induction, and chemotaxis. IL-1 inhibition strategies with anakinra have shown efficacy as first and second lines of treatment. In this review, we will describe the main characteristics of biological drugs currently used for SAPHO syndrome. We also describe some of the promising therapeutic effects of ustekinumab, an antibody against the p40 subunit of IL-12 and IL-23, after failure of multiple drugs including anti-TNF-α and anakinra. We discuss the use and impact of the new anti-IL-1 antagonists involved in the IL-17 blockade, in particular for the most difficult-to-treat SAPHO cases.

ROLE OF PURINERGIC RECEPTORS IN IMMUNE RESPONSE

Purine receptors are located on immune and somatic cells of animal and human organisms. Summation of signals from purine and TOLL-like receptors takes place on the level of inflammasome formation and results in summation of the first and second signals of innate immunity. The first signal - from PAMPs (pathogen associated molecular patterns), the second - from DAMPs (danger associated molecular patterns). Adenosine triphosphate (ATP) is the most studied DAMP. ATP connects with purine receptors, which include P2 (P2X7 receptors are the best described), that results in opening of channels of these receptors and transit of ATP into the cell. In parallel exit of K+ from cells and entrance of Ca2+ and Na+ into the cells is observed, that is associated with activation of the immune competent cell. Damaged cells dying via necrosis or apoptosis are the source of extracellular ATP, as well as activated immunocytes. Signals from P2 and TOLL-like receptors are summarized in effectors of immune response, and activation of P2 receptors in lymphocytes makes a contribution into activation of cells, mediated by T-cell receptor. Negative side of purine receptor activation is a stimulating effect on proliferation and metastasis of malignant cells. The practical output of knowledge on functioning of purine receptors for clinical immunology is the application of agonists and antagonists of purine receptors, as well as explanation of effect of immune modulators from the position of launch of K+/Na+-pump, resulting in prolonged activation of immune competent cells.

SAPHO Syndrome: Current Developments and Approaches to Clinical Treatment

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, and osteitis) is a rare autoimmune disease which, due to its clinical presentation and symptoms, is often misdiagnosed and unrecognized. Its main features are prominent inflammatory cutaneous and articular manifestations. Treatments with immunosuppressive drugs have been used for the management of SAPHO with variable results. To date, the use of anti-TNF-α agents has proved to be an effective alternative to conventional treatment for unresponsive or refractory SAPHO cases. TNF-α is a pro-inflammatory cytokine and pivotal regulator of other cytokines, including IL-1 β, IL-6, and IL-8, involved in inflammation, acute-phase response induction, and chemotaxis. IL-1 inhibition strategies with anakinra have shown efficacy as first and second lines of treatment. In this review, we will describe the main characteristics of biological drugs currently used for SAPHO syndrome. We also describe some of the promising therapeutic effects of ustekinumab, an antibody against the p40 subunit of IL-12 and IL-23, after failure of multiple drugs including anti-TNF-α and anakinra. We discuss the use and impact of the new anti-IL-1 antagonists involved in the IL-17 blockade, in particular for the most difficult-to-treat SAPHO cases.

Tumor necrosis factor reduces Plasmodium falciparum growth and activates calcium signaling in human malaria parasites

Background

Plasmodium has a complex biology including the ability to interact with host signals modulating their function through cellular machinery. Tumor necrosis factor (TNF) elicits diverse cellular responses including effects in malarial pathology and increased infected erythrocyte cytoadherence. As TNF levels are raised during Plasmodium falciparum infection we have investigated whether it has an effect on the parasite asexual stage.

Methods

Flow cytometry, spectrofluorimetric determinations, confocal microscopy and PCR real time quantifications were employed for characterizing TNF induced effects and membrane integrity verified by wheat germ agglutinin staining.

Results

TNF is able to decrease intracellular parasitemia, involving calcium as a second messenger of the pathway. Parasites incubated for 48 h with TNF showed reduced erythrocyte invasion. Thus, TNF induced rises in intracellular calcium concentration, which were blocked by prior addition of the purinergic receptor agonists KN62 and A438079, or interfering with intra- or extracellular calcium release by thapsigargin or EGTA (ethylene glycol tetraacetic acid). Importantly, expression of PfPCNA1 which encodes the Plasmodium falciparum Proliferating-Cell Nuclear Antigen 1, decreased after P. falciparum treatment of TNF (tumor necrosis factor) or 6-Bnz cAMP (N⁶-benzoyladenosine-3′,5′-cyclic monophosphate sodium salt).

Conclusions

This is potentially interesting data showing the relevance of calcium in downregulating a gene involved in cellular proliferation, triggered by TNF.

General significance

The data show that Plasmodium may subvert the immunological system and use TNF for the control of its proliferation within the vertebrate host.

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TNF is able to decrease parasitemia in P. falciparum‐infected RBCs.

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TNF induced rises in intracellular calcium concentration, which were blocked by the purinergic receptor agonists KN62 and A438079.

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Interfering with intra‐ or extracellular calcium release by thapsigargin or EGTA also block TNF‐induce calcium release in P. falciparum.

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Expression of the P. falciparum Proliferating‐Cell Nuclear Antigen 1 (PfPCNA1) decreased after P. falciparum treatment with TNF or 6‐Bnz cAMP.

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The data show that Plasmodium may subvert the immunological system and use TNF for the control of its proliferation within the vertebrate host.

Innate immune cells in the pathogenesis of primary systemic vasculitis

Innate immune system forms the first line of defense against foreign substances. Neutrophils, eosinophils, erythrocytes, platelets, monocytes, macrophages, dendritic cells, γδ T cells, natural killer and natural killer T cells comprise the innate immune system. Genetic polymorphisms influencing the activation of innate immune cells predispose to development of vasculitis and influence its severity. Abnormally activated innate immune cells cross-talk with other cells of the innate immune system, present antigens more efficiently and activate T and B lymphocytes and cause tissue destruction via cell-mediated cytotoxicity and release of pro-inflammatory cytokines. These secreted cytokines further recruit other cells to the sites of vascular injury. They are involved in both the initiation as well as the perpetuation of vasculitis. Evidences suggest reversal of aberrant activation of immune cells in response to therapy. Understanding the role of innate immune cells in vasculitis helps understand the potential of therapeutic modulation of their activation to treat vasculitis.

The role of P2X7 receptors in tissue fibrosis: a brief review

Many previous studies have demonstrated that P2X(7) receptors (P2X(7)Rs) have a pleiotropic function in different pathological conditions and could represent a novel target for the treatment of a range of diseases. In particular, recent studies have explored the role of P2X(7)R in fibrosis, the pathological outcome of most chronic inflammatory diseases. The aim of this review is to discuss the biological features of P2X(7)R and summarize the current knowledge about the putative role of the P2X(7)R in triggering fibrosis in a wide spectrum of organs such as the lung, kidney, liver, pancreas, and heart.

Interleukin-1 as a common denominator from autoinflammatory to autoimmune disorders: premises, perils, and perspectives

A complex web of dynamic relationships between innate and adaptive immunity is now evident for many autoinflammatory and autoimmune disorders, the first deriving from abnormal activation of innate immune system without any conventional danger triggers and the latter from self-/non-self-discrimination loss of tolerance, and systemic inflammation. Due to clinical and pathophysiologic similarities giving a crucial role to the multifunctional cytokine interleukin-1, the concept of autoinflammation has been expanded to include nonhereditary collagen-like diseases, idiopathic inflammatory diseases, and metabolic diseases. As more patients are reported to have clinical features of autoinflammation and autoimmunity, the boundary between these two pathologic ends is becoming blurred. An overview of monogenic autoinflammatory disorders, PFAPA syndrome, rheumatoid arthritis, type 2 diabetes mellitus, uveitis, pericarditis, Behçet's disease, gout, Sjögren's syndrome, interstitial lung diseases, and Still's disease is presented to highlight the fundamental points that interleukin-1 displays in the cryptic interplay between innate and adaptive immune systems.

Purinergic and calcium signaling in macrophage function and plasticity

In addition to a fundamental role in cellular bioenergetics, the purine nucleotide adenosine triphosphate (ATP) plays a crucial role in the extracellular space as a signaling molecule. ATP and its metabolites serve as ligands for a family of receptors that are collectively referred to as purinergic receptors. These receptors were first described and characterized in the nervous system but it soon became evident that they are expressed ubiquitously. In the immune system, purinergic signals regulate the migration and activation of immune cells and they may also orchestrate the resolution of inflammation (1, 2). The intracellular signal transduction initiated by purinergic receptors is strongly coupled to Ca(2+)-signaling, and co-ordination of these pathways plays a critical role in innate immunity. In this review, we provide an overview of purinergic and Ca(2+)-signaling in the context of macrophage phenotypic polarization and discuss the implications on macrophage function in physiological and pathological conditions.

Effectiveness and tuberculosis-related safety profile of interleukin-1 blocking agents in the management of Behçet's disease

Behçet's disease (BD) is a multi-systemic disorder of unknown etiology characterized by relapsing oral-genital ulcers, uveitis, and involvement of the articular, gastrointestinal, neurologic, and vascular systems. Although the primum movens of this condition remains unknown, a tangled plot combining autoimmune and autoinflammatory pathways has been hypothesized to explain its start and recurrence. In-depth analysis of BD pathogenetic mechanisms, involving dysfunction of multiple proinflammatory molecules, has opened new modalities of treatment: different agents targeting interleukin-1 have been studied in recent years to manage the most difficult and multi-resistant cases of BD. Growing experience with anakinra, canakinumab and gevokizumab is discussed in this review, highlighting the relative efficacy of each drug upon the protean BD clinical manifestations. Safety and tolerability of interleukin-1 antagonists in different doses have been confirmed by numerous observational studies on both large and small cohorts of patients with BD. In particular, the potential for Mycobacterium tuberculosis reactivation and tuberculosis development appears to be significantly lower with interleukin-1 blockers compared to tumor necrosis factor-α inhibitors, thus increasing the beneficial profile of this approach.