Immunological and inflammatory functions of the interleukin-1 family

Epithelial-derived IL-33 and its receptor ST2 are dysregulated in ulcerative colitis and in experimental Th1/Th2 driven enteritis

IL-33 is a novel member of the IL-1 family and ligand for the IL-1 receptor-related protein, ST2. Recent evidence suggests that the IL-33/ST2 axis plays a critical role in several autoimmune and inflammatory disorders; however, its role in inflammatory bowel disease (IBD) has not been clearly defined. We characterized IL-33 and ST2 expression and modulation after conventional anti-TNF therapy in Crohn's disease and ulcerative colitis (UC) patients and investigated the role of IL-33 in SAMP1/YitFc (SAMP) mice, a mixed Th1/Th2 model of IBD. Our results showed a specific increase of mucosal IL-33 in active UC, localized primarily to intestinal epithelial cells (IEC) and colonic inflammatory infiltrates. Importantly, increased expression of full-length IL-33, representing the most bioactive form, was detected in UC epithelium, whereas elevated levels of cleaved IL-33 were present in IBD serum. ST2 isoforms were differentially modulated in UC epithelium, and sST2, a soluble decoy receptor with anti-inflammatory properties, was also elevated in IBD serum. Infliximab (anti-TNF) treatment of UC decreased circulating IL-33 and increased sST2, whereas stimulation of HT-29 IEC confirmed IL-33 and sST2 regulation by TNF. Similarly, IL-33 significantly increased and correlated with disease severity, and potently induced IL-5, IL-6, and IL-17 from mucosal immune cells in SAMP mice. Taken together, the IL-33/ST2 system plays an important role in IBD and experimental colitis, is modulated by anti-TNF therapy, and may represent a specific biomarker for active UC.

Targeting TLR/IL-1R signalling in human diseases

The members of Toll-like receptor/Interleukin (IL)-1 receptor (TLR/IL-1R) superfamily play a fundamental role in the immune response. These receptors detect microbial components and trigger complex signalling pathways that result in increased expression of multiple inflammatory genes. On the other hand, an aberrant activation of TLR/IL-1R signalling can promote the onset of inflammatory and autoimmune diseases, raising the interest in the development of therapeutic strategies for the control of their function. In this review, we illustrate the structural and functional features of TLR/IL-1R proteins and discuss some recent advances in the approaches undertaken to develop anti-inflammatory therapeutic drugs. In particular, we will focus on inhibitors, such as decoy peptides and synthetic mimetics, that interfere with protein-protein interactions between signalling molecules of the TLR/IL-1R superfamily. Given their central role in innate and adaptive immune responses, it is foreseen that pharmaceutical modulation of TLR/IL-1R signalling pathways by these drugs might yield clinical benefits in the treatment of inflammatory and autoimmune diseases.

[Interleukin-1 cytokines, inflammasomes, NOD-signalosomes and autoinflammation]

The understanding of the genetic and immunological basis of human periodic fever syndromes, in particular cryopyrin-associated periodic syndromes (CAPS), has led to important new insights into the pathogenesis of monogenic and complex interleukin-1beta-associated autoinflammatory diseases. Currently the focus of attention is on the nucleotide-binding oligomerization domain (NOD)-like receptors (NLR), which take part in the regulation of the synthesis and maturation of cytokines in the IL-1 families, NOD-signalosomes and inflammasomes.

Anti-inflammatory Agents: Present and Future

Inflammation involving the innate and adaptive immune systems is a normal response to infection. However, when allowed to continue unchecked, inflammation may result in autoimmune or autoinflammatory disorders, neurodegenerative disease, or cancer. A variety of safe and effective anti-inflammatory agents are available, including aspirin and other nonsteroidal anti-inflammatories, with many more drugs under development. In particular, the new era of anti-inflammatory agents includes "biologicals" such as anticytokine therapies and small molecules that block the activity of kinases. Other anti-inflammatories currently in use or under development include statins, histone deacetylase inhibitors, PPAR agonists, and small RNAs. This Review discusses the current status of anti-inflammatory drug research and the development of new anti-inflammatory therapeutics.

Monogenic IL-1 mediated autoinflammatory and immunodeficiency syndromes: finding the right balance in response to danger signals

INTRODUCTION

Interleukin-1 was the first cytokine identified and is a powerful inducer of fever and inflammation. The biologically active receptor for IL-1, shares signaling pathways with some pathogen recognition receptors, the Toll-like receptors (TLRs) which early on suggested an important role in innate immune function.

DISCUSSION

The discovery that some intracellular "danger receptors", the NOD like receptors (NLRs) can assemble to form multimolecular platforms, the inflammasomes, that not only sense intracellular danger but also activate IL-1beta, has provided the molecular basis for the integration of IL-1 as an early response mediator in danger recognition. The critical role of balancing IL-1 production and signaling in human disease has recently been demonstrated in rare human monogenic diseases with mutations that affect the meticulous control of IL-1 production, release and signaling by leading to decreased or increased TLR/IL-1 signaling. In diseases of decreased TLR/IL-1 signaling (IRAK-4 and MyD88 deficiencies) patients are at risk for infections with gram positive organisms; and in diseases of increased signaling, patients develop systemic autoinflammatory diseases (cryopyrin-associated periodic syndromes (CAPS), and deficiency of the IL-1 receptor antagonist (DIRA)).

CONCLUSION

Monogenic defects in a number of rare diseases that affect the balance of TLR/IL-1 signaling have provided us with opportunities to study the systemic effects of IL-1 in human diseases. The molecular defects in CAPS and DIRA provided a therapeutic rationale for targeting IL-1 and the impressive clinical results from IL-1 blocking therapies have undoubtedly confirmed the pivotal role of IL-1 in human disease and spurred the exploration of modifying IL-1 signaling in a number of genetically complex common human diseases.

The AIM2 inflammasome is essential for host defense against cytosolic bacteria and DNA viruses

Inflammasomes regulate the activity of capase-1 and maturation of interleukin-1β and interleukin-18. Recently, AIM2 was shown to bind DNA and engage ASC to form a caspase-1 activating inflammasome. Using Aim2-deficient mice, we reveal a central role for AIM2 in regulating caspase-1-dependent maturation of IL-1β and IL-18, as well as pyroptosis in response to synthetic dsDNA. AIM2 is essential for inflammasome activation in response to Fransicella tularensis, vaccinia virus, mouse cytomegalovirus and plays a partial role in sensing Listeria monocytogenes. Moreover, production of IL-18 and NK cell-dependent IFN-γ production, events critical in early control of virus replication were dependent on AIM2 during mCMV infection in vivo. Collectively, these observations reveal the importance of AIM2 in sensing both bacterial and viral pathogens and triggering innate immunity.

Genetic predisposition to gastro-oesophageal cancer

Gastro-oesophageal cancers were ranked as the second cause of death from cancer worldwide despite a steady decrease in incidence for squamous cell carcinoma (SCC) of the oesophagus and distal gastric cancers. Adenocarcinoma of the oesophagus (OAC) is the tumour whose incidence has seen the highest increase in the past 30 years. Most of these cancers are strongly associated with environmental and life style risk factors such as smoking and alcohol for SCC, gastro-oesophageal reflux for OAC and Helicobacter pylori for distal gastric cancer. It may therefore be unsurprising that SCC is associated with polymorphisms in ALDH2 and ADH1B1, enzyme involved in alcohol metabolism, and with CYP1A1, involved in xenobiotics detoxification. OAC, whose incidence in absolute terms remains low, has been much less studied and at best the associations identified with risk are weak. Diffuse type gastric cancers while relatively uncommon have a strong genetic association with mutation of the CDH1 gene and prostate specific cancer antigen (PSCA) was demonstrated in a GWAS to be associated with an increased risk of diffuse gastric cancer but not intestinal type gastric cancer. This family of cancer is more associated with polymorphisms at the IL-1beta, IL-1RN loci and MHTFR loci. Specific strains of H pylori containing the virulence factors VacA s1, VacA m1 and cag A together with polymorphism at the IL-1beta and IL-1RN loci have up to a 87-fold increase in risk for developing intestinal type gastric cancer. While progress has been made to identify genetic variants associated with upper-gastrointestinal cancers, the relative small prevalence for some subtypes underlies the need for consortia, especially in view of the large variations in the prevalence of polymorphisms between different populations.

Interleukin-1 family member 9 stimulates chemokine production and neutrophil influx in mouse lungs

Interleukin-1 (IL-1) is a proinflammatory cytokine that signals through the Type I IL-1 receptor (IL-1RI). Novel IL-1-like cytokines were recently identified. Their functions in lung disease remain unclear. Interleukin-1 family member-9 (IL-1F9) is one such IL-1-like cytokine, expressed in the lungs of humans and mice. IL-1F9 signals through IL-1 receptor-related protein 2 (IL-1Rrp2/IL-1RL2), which is distinct from IL-1RI. We sought to determine if IL-1F9 acts as a proinflammatory cytokine in lung disease. IL-1F9 protein was increased in lung homogenates of house dust mite-challenged A/J mice compared with controls, and expression was seen in airway epithelial cells. The intratracheal administration of recombinant mouse IL-1F9 increased airway hyperresponsiveness and induced neutrophil influx and mucus production, but not eosinophilic infiltration in the lungs of mice. In addition, IL-1α protein levels in bronchoalveolar lavage fluid, chemokines, and chemokine-receptor mRNA expression in the lungs were increased after the instillation of intratracheal IL-1F9. Consistent with these changes, NF-κB transcription factor activity was increased in the lungs of mice challenged with IL-1F9 and in a macrophage cell line treated with IL-1F9. These data suggest that IL-1F9 is upregulated during inflammation, and acts as a proinflammatory cytokine in the lungs.

Scorpion venom and the inflammatory response

Scorpion venoms consist of a complex of several toxins that exhibit a wide range of biological properties and actions, as well as chemical compositions, toxicity, and pharmacokinetic and pharmacodynamic characteristics. These venoms are associated with high morbility and mortality, especially among children. Victims of envenoming by a scorpion suffer a variety of pathologies, involving mainly both sympathetic and parasympathetic stimulation as well as central manifestations such as irritability, hyperthermia, vomiting, profuse salivation, tremor, and convulsion. The clinical signs and symptoms observed in humans and experimental animals are related with an excessive systemic host inflammatory response to stings and stings, respectively. Although the pathophysiology of envenomation is complex and not yet fully understood, venom and immune responses are known to trigger the release of inflammatory mediators that are largely mediated by cytokines. In models of severe systemic inflammation produced by injection of high doses of venom or venoms products, the increase in production of proinflammatory cytokines significantly contributes to immunological imbalance, multiple organ dysfunction and death. The cytokines initiate a cascade of events that lead to illness behaviors such as fever, anorexia, and also physiological events in the host such as activation of vasodilatation, hypotension, and increased of vessel permeability.

Identification of the cellular sensor that stimulates the inflammatory response to sterile cell death

Cell death provokes a robust inflammatory response. We have previously shown that this response is dependent on IL-1alpha. In this study, we investigate the cellular mechanism used by a host to sense cell death, produce IL-1alpha and also the role of IL-1beta in this response. In almost all cases examined, the IL-1 that stimulated the death-induced inflammatory response came from the host rather than the cell that was dying. In these situations, host bone marrow-derived cells were the key source of the IL-1alpha that was required for the inflammatory response. Conditional cellular depletion and reconstitution in CD11b promoter-driven diphtheria toxin receptor transgenic mice revealed that host macrophages played an essential role in the generation of the inflammatory response and were the source of the required IL-1alpha. In addition, we found a role for IL-1beta in the death-induced inflammatory response and that this cytokine was generated by both bone marrow-derived and radioresistant host cells. The one exception to these findings was that when dendritic cells were injected into mice, they provided a portion of the IL-1 that stimulated inflammation, and this was observed whether the dendritic cells were live or necrotic. Together, these findings demonstrate that macrophages play a key role as the primary sentinels that are required to sense and report cell death in ways that initiate the inflammatory response. One key way they accomplish this important task is by producing IL-1alpha that is needed to initiate the inflammatory response.

Caspase-1 independent IL-1beta production is critical for host resistance to mycobacterium tuberculosis and does not require TLR signaling in vivo

To investigate the respective contributions of TLR versus IL-1R mediated signals in MyD88 dependent control of Mycobacterium tuberculosis, we compared the outcome of M. tuberculosis infection in MyD88, TRIF/MyD88, IL-1R1, and IL-1beta-deficient mice. All four strains displayed acute mortality with highly increased pulmonary bacterial burden suggesting a major role for IL-1beta signaling in determining the MyD88 dependent phenotype. Unexpectedly, the infected MyD88 and TRIF/MyD88-deficient mice, rather than being defective in IL-1beta expression, displayed increased cytokine levels relative to wild-type animals. Similarly, infected mice deficient in caspase-1 and ASC, which have critical functions in inflammasome-mediated IL-1beta maturation, showed unimpaired IL-1beta production and importantly, were considerably less susceptible to infection than IL-1beta deficient mice. Together our findings reveal a major role for IL-1beta in host resistance to M. tuberculosis and indicate that during this infection the cytokine can be generated by a mechanism that does not require TLR signaling or caspase-1.

Blockade of interleukin 1 in type 1 diabetes mellitus

Interleukin 1 (IL-1) is a 17 kDa protein highly conserved through evolution and is a key mediator of inflammation, fever and the acute-phase response. IL-1 has important functions in the innate immune defense against microbes, trauma and stress, and is also an effector molecule involved in tissue destruction and fibrosis. The inhibition of IL-1 action has clinical efficacy in many inflammatory diseases, such as hereditary autoinflammatory disorders, familial hereditary fever, gout, rheumatoid arthritis and type 2 diabetes mellitus (T2DM). The latter is a common metabolic condition caused by insulin resistance and pancreatic beta-cell failure, the causes of both of which have inflammatory components. IL-1 signaling has roles in beta-cell dysfunction and destruction via the NFkappaB and mitogen-activated-protein-kinase pathways, leading to endoplasmic reticulum and mitochondrial stress and eventually activating the apoptotic machinery. In addition, IL-1 acts on T-lymphocyte regulation. The modulating effect of IL-1 on the interaction between the innate and adaptive immune systems and the effects of IL-1 on the beta-cell point to this molecule being a potential interventional target in autoimmune diabetes mellitus. Genetic or pharmacological abrogation of IL-1 action reduces disease incidence in animal models of type 1 diabetes mellitus (T1DM) and clinical trials have been started to study the feasibility, safety and efficacy of IL-1 therapy in patients with T1DM. Here, we review the rationale for blocking IL-1 in patients with T1DM.

Staphylococcus aureus stimulates neutrophil targeting chemokine expression in keratinocytes through an autocrine IL-1alpha signaling loop

Staphylococcus aureus is a significant human pathogen that can colonize the skin. Neutrophils are well known to be involved in clearance of the bacterium. This study focused on exploring the role that human keratinocytes have as first responders to bacterial challenges. IL-1alpha and IL-1beta increased mRNA production and protein secretion of the neutrophil chemotactic CXCL1, CXCL2, and IL-8 in keratinocytes. S. aureus and the bacterial cell wall components lipoteichoic acid (LTA) and peptidoglycan (PGN) induced similar expression profiles in a Toll-like receptor (TLR)-2-dependent manner. Interestingly, the S. aureus-induced mRNA levels peaked at later time points than those induced by IL-1. The S. aureus-activated chemokine production was preceded by significant IL-1alpha and IL-1beta secretion. Expression of IL-1alpha was significantly higher than that of IL-1beta. Inhibition of IL-1RI using neutralizing antibodies revealed that S. aureus-derived LTA and PGN-induced chemokine expression requires IL-1RI engagement. Surprisingly, we further found that chemokine secretion is dependent upon endocrine IL-1alpha, but not IL-1beta, signaling. Our data show that the innate immune response of keratinocytes is regulated differently than those of other cell types. This may represent a fail-safe system that protects the host against genetic variation and immune evasion mechanisms developed by pathogens.

Pulsed dye laser-induced inflammatory response and extracellular matrix turnover in rat vocal folds and vocal fold fibroblasts

BACKGROUND AND OBJECTIVES

Disruption of the vocal fold extracellular matrix (ECM) can induce a profound and refractory dysphonia. Pulsed dye laser (PDL) irradiation has shown early promise as a treatment modality for disordered ECM in patients with chronic vocal fold scar; however, there are limited data addressing the mechanism by which this laser energy might induce cellular and extracellular changes in vocal fold tissues. In this study, we examined the inflammatory and ECM modulating effects of PDL irradiation on normal vocal fold tissues and cultured vocal fold fibroblasts (VFFs).

STUDY DESIGN/MATERIALS AND METHODS

We evaluated the effects of 585 nm PDL irradiation on inflammatory cytokine and collagen/collagenase gene transcription in normal rat vocal folds in vivo (3-168 hours following delivery of approximately 39.46 J/cm(2) fluence) and VFFs in vitro (3-72 hours following delivery of 4.82 or 9.64 J/cm(2) fluence). We also examined morphological vocal fold tissue changes 3 hours, 1 week, and 1 month post-irradiation.

RESULTS

PDL irradiation altered inflammatory cytokine and procollagen/collagenase expression at the transcript level, both in vitro and in vivo. Additionally, PDL irradiation induced an inflammatory repair process in vivo that was completed by 1 month with preservation of normal tissue morphology.

CONCLUSIONS

PDL irradiation can modulate ECM turnover in phenotypically normal vocal folds. Additional work is required to determine if these findings extend to disordered ECM, such as is seen in vocal fold scar. Lasers Surg. Med. 41:585-594, 2009. (c) 2009 Wiley-Liss, Inc.

Blockade of T cell contact-activation of human monocytes by high-density lipoproteins reveals a new pattern of cytokine and inflammatory genes

BACKGROUND

Cellular contact with stimulated T cells is a potent inducer of cytokine production in human monocytes and is likely to play a substantial part in chronic/sterile inflammatory diseases. High-density lipoproteins (HDL) specifically inhibit the production of pro-inflammatory cytokines induced by T cell contact.

METHODOLOGY/PRINCIPAL FINDINGS

To further elucidate the pro-inflammatory functions of cellular contact with stimulated T cells and its inhibition by HDL, we carried out multiplex and microarray analyses. Multiplex analysis of monocyte supernatant revealed that 12 out of 27 cytokines were induced upon contact with stimulated T cells, which cytokines included IL-1Ra, G-CSF, GM-CSF, IFNgamma, CCL2, CCL5, TNF, IL-1beta, IL-6, IL-8, CCL3, and CCL4, but only the latter six were inhibited by HDL. Microarray analysis showed that 437 out of 54,675 probe sets were enhanced in monocytes activated by contact with stimulated T cells, 164 probe sets (i.e., 38%) being inhibited by HDL. These results were validated by qPCR. Interestingly, the cytokines induced by T cell contact in monocytes comprised IL-1beta, IL-6 but not IL-12, suggesting that this mechanism might favor Th17 polarization, which emphasizes the relevance of this mechanism to chronic inflammatory diseases and highlights the contrast with acute inflammatory conditions that usually involve lipopolysaccharides (LPS). In addition, the expression of miR-155 and production of prostaglandin E(2)-both involved in inflammatory response-were triggered by T cell contact and inhibited in the presence of HDL.

CONCLUSIONS/SIGNIFICANCE

These results leave no doubt as to the pro-inflammatory nature of T cell contact-activation of human monocytes and the anti-inflammatory functions of HDL.

Variable number of tandem repeat polymorphisms of the interleukin-1 receptor antagonist gene IL-1RN: a novel association with the athlete status

BACKGROUND

The interleukin-1 (IL-1) family of cytokines is involved in the inflammatory and repair reactions of skeletal muscle during and after exercise. Specifically, plasma levels of the IL-1 receptor antagonist (IL-1ra) increase dramatically after intense exercise, and accumulating evidence points to an effect of genetic polymorphisms on athletic phenotypes. Therefore, the IL-1 family cytokine genes are plausible candidate genes for athleticism. We explored whether IL-1 polymorphisms are associated with athlete status in European subjects.

METHODS

Genomic DNA was obtained from 205 (53 professional and 152 competitive non-professional) Italian athletes and 458 non-athlete controls. Two diallelic polymorphisms in the IL-1beta gene (IL-1B) at -511 and +3954 positions, and a variable number tandem repeats (VNTR) in intron 2 of the IL-1ra gene (IL-1RN) were assessed.

RESULTS

We found a 2-fold higher frequency of the IL-1RN 1/2 genotype in athletes compared to non-athlete controls (OR = 1.93, 95% CI = 1.37-2.74, 41.0% vs. 26.4%), and a lower frequency of the 1/1 genotype (OR = 0.55, 95% CI = 0.40-0.77, 43.9% vs. 58.5%). Frequency of the IL-1RN 2/2 genotype did not differ between groups. No significant differences between athletes and controls were found for either -511 or +3954 IL-1B polymorphisms. However, the haplotype (-511)C-(+3954)T-(VNTR)2 was 3-fold more frequent in athletes than in non-athletes (OR = 3.02, 95% CI = 1.16-7.87). Interestingly, the IL-1RN 1/2 genotype was more frequent in professional than in non-professional athletes (OR = 1.92, 95% CI = 1.02-3.61, 52.8% vs. 36.8%).

CONCLUSIONS

Our study found that variants at the IL-1ra gene associate with athletic status. This confirms the crucial role that cytokine IL-1ra plays in human physical exercise. The VNTR IL-1RN polymorphism may have implications for muscle health, performance, and/or recovery capacities. Further studies are needed to assess these specific issues. As VNTR IL-1RN polymorphism is implicated in several disease conditions, athlete status may constitute a confounding variable that will need to be accounted for when examining associations of this polymorphism with disease risk.

Islet inflammation impairs the pancreatic beta-cell in type 2 diabetes

Onset of Type 2 diabetes occurs when the pancreatic beta-cell fails to adapt to the increased insulin demand caused by insulin resistance. Morphological and therapeutic intervention studies have uncovered an inflammatory process in islets of patients with Type 2 diabetes characterized by the presence of cytokines, immune cells, beta-cell apoptosis, amyloid deposits, and fibrosis. This insulitis is due to a pathological activation of the innate immune system by metabolic stress and governed by IL-1 signaling. We propose that this insulitis contributes to the decrease in beta-cell mass and the impaired insulin secretion observed in patients with Type 2 diabetes.

La mala educación of tumor-associated macrophages: Diverse pathways and new players

Inflammation is a key component of the tumor microenvironment. Two reports published in this issue of Cancer Cell, Andreu et al. and Erez et al., shed new light on pathways and players involved in the orchestration of cancer-related inflammation.

IL-1R1/MyD88 signaling is critical for elastase-induced lung inflammation and emphysema

Lung emphysema and fibrosis are severe complications of chronic obstructive pulmonary disease, and uncontrolled protease activation may be involved in the pathogenesis. Using experimental elastase-induced acute inflammation, we demonstrate here that inflammation and development of emphysema is IL-1R1 and Toll/IL-1R signal transduction adaptor MyD88 dependent; however, TLR recognition is dispensable in this model. Elastase induces IL-1beta, TNF-alpha, keratinocyte-derived chemokine, and IL-6 secretion and neutrophil recruitment in the lung, which is drastically reduced in the absence of IL-1R1 or MyD88. Further, tissue destruction with emphysema and fibrosis is attenuated in the lungs of IL-1R1- and MyD88-deficient mice. Specific blockade of IL-1 by IL-1R antagonist diminishes acute inflammation and emphysema. Finally, IL-1beta production and inflammation are reduced in mice deficient for the NALP3 inflammasome component apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and we identified uric acid, which is produced upon elastase-induced lung injury, as an activator of the NALP3/ASC inflammasome. In conclusion, elastase-mediated lung pathology depends on inflammasome activation with IL-1beta production. IL-1beta therefore represents a critical mediator and a possible therapeutic target of lung inflammation leading to emphysema.

Inflammasome-associated nucleotide-binding domain, leucine-rich repeat proteins and inflammatory diseases

The nucleotide-binding domain, leucine-rich repeat (NLR) proteins are a recently discovered family of intracellular pathogen and danger signal sensors. NLRs have emerged as important contributors to innate immunity in animals. The physiological impact of these genes is increasingly evident, underscored by the genetic association of variant family members with an array of inflammatory diseases. The association of mutations in NLR genes with autoinflammatory diseases indicates an important function of these genes in inflammation in vivo. This review summarizes the role of the inflammasome NLR proteins in innate immunity and inflammatory diseases and explores the possible utility of some of these NLRs as pharmacological targets.

Intravital imaging of IL-1beta production in skin

IL-1 is a prototypic inflammatory cytokine that has pathogenic roles in various skin disorders. Although Langerhans cells (LCs) have been reported to express IL-1beta mRNA upon application of contact sensitizers, it remains unclear whether other cell types produce IL-1beta in skin. Thus, we sought to directly identify IL-1beta-producing cells in living animals by construction of transgenic mice expressing DsRed fluorescence protein gene under the control of IL-1beta promoter. Little DsRed fluorescence signal was detected in skin under steady-state conditions. Striking increases in DsRed signal were observed after topical application of a contact sensitizer, oxazolone, which also induced markedly elevated IL-1beta mRNA and protein expression. DsRed signal was expressed primarily by CD45(+)/CD11b(+) myeloid leukocytes in both epidermal and dermal compartments and was detected only in small fractions of epidermal LCs. Interestingly, DsRed(+) cells emerged preferentially as clusters around hair follicles. Intravital confocal imaging experiments revealed highly motile potentials of DsRed(+) cells-they constantly crawled around hair follicles via amoeba-like movements with a mean velocity of 1.0+/-0.4 microm min(-1) (epidermis) or 2.7+/-1.4 microm min(-1) (dermis). The newly developed in vivo imaging system represents a useful tool for studying spatial regulation of IL-1beta production in skin.

The IL-1 family: regulators of immunity

Over recent years it has become increasingly clear that innate immune responses can shape the adaptive immune response. Among the most potent molecules of the innate immune system are the interleukin-1 (IL-1) family members. These evolutionarily ancient cytokines are made by and act on innate immune cells to influence their survival and function. In addition, they act directly on lymphocytes to reinforce certain adaptive immune responses. This Review provides an overview of both the long-established and more recently characterized members of the IL-1 family. In addition to their effects on immune cells, their involvement in human disease and disease models is discussed.

A bovine whey protein extract stimulates human neutrophils to generate bioactive IL-1Ra through a NF-kappaB- and MAPK-dependent mechanism

Innate immunity depends on the efficiency of neutrophils to be activated rapidly to restore homeostasis. It can benefit from priming agents that enhance neutrophil capacity to respond more efficiently to a subsequent stimulation. Among natural products, a bovine whey protein extract (WPE) has been shown to prime normal human blood neutrophils by enhancing their chemotaxis, phagocytosis, oxidative burst, and degranulation. These leukocytes are also an important source of cytokines, some of which have antiinflammatory functions. We investigated the role of WPE, as well as its mechanisms of action, on the production of interleukin (IL)-1 receptor antagonist (IL-1Ra) by neutrophils in vitro. WPE dose-dependently stimulated de novo synthesis and release of IL-1Ra by normal human blood neutrophils. Among the major proteins present in WPE, beta-lactoglobulin (beta-LG) and alpha-lactalbumin (alpha-LA) were the only active components. They had additive effects that exactly reproduced those of WPE. Similarly to WPE, they also stimulated the accumulation of IL-1beta, IL-8, IL-6, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and tumor necrosis factor-alpha. However, neutrophils incubated with WPE, beta-LG, and alpha-LA produced IL-1Ra in excess of IL-1beta and the ratio IL-1Ra:IL-1beta increased linearly. The amounts of IL-1Ra stimulated by WPE or beta-LG + alpha-LA significantly reduced the IL-1 activity in EL4 cells. Inhibitors of p38 and extracellular signal-regulated kinases (ERK)1/2 mitogen-activated protein kinase, and nuclear factor-kappaB cascades reduced neutrophil production of IL-1Ra. Our data suggest that WPE, through beta-LG + alpha-LA, has immunomodulatory properties and the potential to increase host defenses.

Modulation of immune responses through direct activation of Toll-like receptors to T cells

Toll-like receptors (TLRs), which are a family of pattern recognition receptors (PRRs), are involved critically in the generation and regulation of innate immunity as well as initiation of subsequent adaptive immune responses. However, recent research results showed that different subsets of T cells express certain types of TLRs during development and activation stages. Importantly, TLRs participate in the direct regulation of adaptive immune response, possibly as co-stimulatory molecules. In this review we summarize recent studies about the novel regulation of TLRs on the homeostasis and immunity of different T cell subtypes including CD4+CD25+T regulatory cells (Treg) and interleukin (IL)-17-producing CD4+T cells (T helper type 17). The direct involvement of TLRs in T cell-mediated immunity prompted us to reconsider the role of TLRs in the occurrence of autoimmune diseases, infectious diseases and graft rejection. The important effects of TLRs in T cell-intrinsic components also prompt us to explore novel vaccine adjuvants for modifying desired immune responses in an efficient way.

Differential release of chromatin-bound IL-1alpha discriminates between necrotic and apoptotic cell death by the ability to induce sterile inflammation

IL-1alpha, like IL-1beta, possesses multiple inflammatory and immune properties. However, unlike IL-1beta, the cytokine is present intracellularly in healthy tissues and is not actively secreted. Rather, IL-1alpha translocates to the nucleus and participates in transcription. Here we show that intracellular IL-1alpha is a chromatin-associated cytokine and highly dynamic in the nucleus of living cells. During apoptosis, IL-1alpha concentrates in dense nuclear foci, which markedly reduces its mobile nature. In apoptotic cells, IL-1alpha is retained within the chromatin fraction and is not released along with the cytoplasmic contents. To simulate the in vivo inflammatory response to cells undergoing different mechanisms of death, lysates of cells were embedded in Matrigel plugs and implanted into mice. Lysates from cells undergoing necrosis recruited cells of the myeloid lineage into the Matrigel, whereas lysates of necrotic cells lacking IL-1alpha failed to recruit an infiltrate. In contrast, lysates of cells undergoing apoptotic death were inactive. Cells infiltrating the Matrigel were due to low concentrations (20-50 pg) of the IL-1alpha precursor containing the receptor interacting C-terminal, whereas the N-terminal propiece containing the nuclear localization site failed to do so. When normal keratinocytes were subjected to hypoxia, the constitutive IL-1alpha precursor was released into the supernatant. Thus, after an ischemic event, the IL-1alpha precursor is released by hypoxic cells and incites an inflammatory response by recruiting myeloid cells into the area. Tissues surrounding the necrotic site also sustain damage from the myeloid cells. Nuclear trafficking and differential release during necrosis vs. apoptosis demonstrate that inflammation by IL-1alpha is tightly controlled.

The role of potassium in inflammasome activation by bacteria

Many Gram-negative bacteria possess a type III secretion system (TTSS( paragraph sign)) that can activate the NLRC4 inflammasome, process caspase-1 and lead to secretion of mature IL-1beta. This is dependent on the presence of intracellular flagellin. Previous reports have suggested that this activation is independent of extracellular K(+) and not accompanied by leakage of K(+) from the cell, in contrast to activation of the NLRP3 inflammasome. However, non-flagellated strains of Pseudomonas aeruginosa are able to activate NLRC4, suggesting that formation of a pore in the cell membrane by the TTSS apparatus may be sufficient for inflammasome activation. Thus, we set out to determine if extracellular K(+) influenced P. aeruginosa inflammasome activation. We found that raising extracellular K(+) prevented TTSS NLRC4 activation by the non-flagellated P. aeruginosa strain PA103DeltaUDeltaT at concentrations above 90 mm, higher than those reported to inhibit NLRP3 activation. Infection was accompanied by efflux of K(+) from a minority of cells as determined using the K(+)-sensitive fluorophore PBFI, but no formation of a leaky pore. We obtained exactly the same results following infection with Salmonella typhimurium, previously described as independent of extracellular K(+). The inhibitory effect of raised extracellular K(+) on NLRC4 activation thus reflects a requirement for a decrease in intracellular K(+) for this inflammasome component as well as that described for NLRP3.

Anti-inflammatory compounds parthenolide and Bay 11-7082 are direct inhibitors of the inflammasome

Activation of the inflammasome generates the pro-inflammatory cytokines interleukin-1 beta and -18, which are important mediators of inflammation. Abnormal activation of the inflammasome leads to many inflammatory diseases, including gout, silicosis, neurodegeneration, and genetically inherited periodic fever syndromes. Therefore, identification of small molecule inhibitors that target the inflammasome is an important step toward developing effective therapeutics for the treatment of inflammation. Here, we show that the herbal NF-kappaB inhibitory compound parthenolide inhibits the activity of multiple inflammasomes in macrophages by directly inhibiting the protease activity of caspase-1. Additional investigations of other NF-kappaB inhibitors revealed that the synthetic I kappaB kinase-beta inhibitor Bay 11-7082 and structurally related vinyl sulfone compounds selectively inhibit NLRP3 inflammasome activity in macrophages independent of their inhibitory effect on NF-kappaB activity. In vitro assays of the effect of parthenolide and Bay 11-7082 on the ATPase activity of NLRP3 demonstrated that both compounds inhibit the ATPase activity of NLRP3, suggesting that the inhibitory effect of these compounds on inflammasome activity could be mediated in part through their effect on the ATPase activity of NLRP3. Our results thus elucidate the molecular mechanism for the therapeutic anti-inflammatory activity of parthenolide and identify vinyl sulfones as a new class of potential therapeutics that target the NLRP3 inflammasome.

Rilonacept in the management of cryopyrin-associated periodic syndromes (CAPS)

Cryopyrin-associated periodic syndromes (CAPS) are a subgroup of the hereditary periodic fever syndromes, which are rare autoinflammatory and inherited disorders, characterized by recurrent inflammation and varying degrees of severity. CAPS are thought to be driven by excessive production of interleukin-1β (IL-1β), through over-activation of the inflammasome by gain of function mutations in the gene encoding cryopyrin (NLRP3). This conclusion is supported by the remarkable efficacy of IL-1β blockade in these conditions. Rilonacept (Arcalyst^TM; Regeneron) is the first us Food and Drug Administration-approved treatment for familial cold autoinflammatory syndrome and Muckle–Wells syndrome and the first in a new line of drugs designed for longer-acting IL-1 blockade. Rilonacept has been associated with a decrease in disease activity, high-sensitivity C-reactive protein (hsCRP) and serum amyloid A (SAA) in the treatment of CAPS. The clinical safety and efficacy of rilonacept in CAPS and non-CAPS populations will be summarized in this review. Rilonacept is also beneficial for patients who tolerate injections poorly, due to an extended half-life over the unapproved CAPS treatment, anakinra, requiring weekly rather than daily self-administration. Other autoinflammatory disorders may also benefit from rilonacept treatment, with clinical trials in progress for systemic onset juvenile idiopathic arthritis, gout and familial mediterranean fever.

Interleukin-1beta (IL-1beta) processing pathway

The innate immune system senses molecular patterns from invading microorganisms. Once activated, it orchestrates the inflammatory response by secreting proinflammatory cytokines, such as interleukin-1 (IL-1)-type cytokines, in particular IL-1beta. IL-1 mediates the expression of a vast array of genes involved in secondary inflammation. IL-1-responsive genes coordinate all aspects of local inflammation and also attract and activate cells of the adaptive immune system at sites of infection. Moreover, the innate immune system can also sense a wide range of nonmicrobial molecular patterns that represent danger or damage signals. These signals activate the NALP3-inflammasome pathway, which plays a central role in acute and chronic sterile inflammation. Here, we describe the essential components of the NALP3-inflammasome that control processing and release of IL-1beta.

Interleukin-1 (IL-1) pathway

The interleukin-1 (IL-1) family of cytokines comprises 11 proteins (IL-1F1 to IL-1F11) encoded by 11 distinct genes in humans and mice. IL-1-type cytokines are major mediators of innate immune reactions, and blockade of the founding members IL-1alpha or IL-1beta by the interleukin-1 receptor antagonist (IL-1RA) has demonstrated a central role of IL-1 in a number of human autoinflammatory diseases. IL-1alpha or IL-1beta rapidly increase messenger RNA expression of hundreds of genes in multiple different cell types. The potent proinflammatory activities of IL-1alpha and IL-1beta are restricted at three major levels: (i) synthesis and release, (ii) membrane receptors, and (iii) intracellular signal transduction. This pathway summarizes extracellular and intracellular signaling of IL-1alpha or IL-1beta, including positive- and negative-feedback mechanisms that amplify or terminate the IL-1 response. In response to ligand binding of the receptor, a complex sequence of combinatorial phosphorylation and ubiquitination events results in activation of nuclear factor kappaB signaling and the JNK and p38 mitogen-activated protein kinase pathways, which, cooperatively, induce the expression of canonical IL-1 target genes (such as IL-6, IL-8, MCP-1, COX-2, IkappaBalpha, IL-1alpha, IL-1beta, MKP-1) by transcriptional and posttranscriptional mechanisms. Of note, most intracellular components that participate in the cellular response to IL-1 also mediate responses to other cytokines (IL-18 and IL-33), Toll-like-receptors (TLRs), and many forms of cytotoxic stresses.

MSK1 regulates the transcription of IL-1ra in response to TLR activation in macrophages

The activity of the pro-inflammatory cytokine IL (interleukin)-1 is closely regulated in vivo via a variety of mechanisms, including both the control of IL-1 production and secretion as well as naturally occurring inhibitors of IL-1 function, such as IL-1ra (IL-1 receptor antagonist). IL-1ra is homologous with IL-1, and is able to bind but not activate the IL-1 receptor. IL-1ra can be produced by a variety of cell types, and its production is stimulated by inflammatory signals. In the present study, we show that in macrophages the TLR (Toll-like receptor)-mediated induction of IL-1ra from both its proximal and distal promoters involves the p38 and ERK1/2 (extracellular-signal-regulated kinase 1/2) MAPK (mitogen-activated protein kinase) cascades. In addition, we show that MSK1 and 2 (mitogen- and stress-activated kinase 1 and 2), kinases activated by either ERK1/2 or p38 in vivo, are required for the induction of both IL-1ra mRNA and protein. MSKs regulate IL-1ra transcription via both IL-10-dependent and -independent mechanisms in cells. Consistent with this, knockout of MSK in mice was found to result in a decrease in IL-1ra production following LPS (lipopolysaccharide) injection. MSKs therefore act as important negative regulators of inflammation following TLR activation.

Canakinumab

Canakinumab (ACZ885, Ilaris) is a human anti-IL-1beta monoclonal antibody developed by Novartis. Its mode of action is based on the neutralization of IL-1beta signaling, resulting in suppression of inflammation in patients with disorders of autoimmune origin. In June 2009 the drug was approved by the US Food and Drug Administration for the treatment of familial cold auto-inflammatory syndrome and Muckle-Wells syndrome, which are inflammatory diseases related to cryopyrin-associated periodic syndromes. The drug is currently being evaluated for its potential in the treatment of rheumatoid arthritis, systemic-onset juvenile idiopathic arthritis, chronic obstructive pulmonary disease, type 1 and 2 diabetes and ocular diseases. Reports from clinical trials suggest that canakinumab is well-tolerated in most patients, and no serious adverse effects have been reported. The drug provides significant advantages over existing competitive therapies, including bimonthly administration and approved use in children.

Autoinflammation: the prominent role of IL-1 in monogenic autoinflammatory diseases and implications for common illnesses

The discovery of the genetic causes of a rare group of immune-mediated inflammatory conditions that mimic infections and allergic conditions in their clinical presentation and the molecular understanding of the function of the mutated molecules in these diseases has led to a revolution in our understanding of the pathogenesis of systemic and local inflammation. The proteins mutated in a number of these so-called autoinflammatory diseases are part of, or regulate the activity of, intracellular molecular complexes, the inflammasomes, that sense "danger" to the body and coordinate an initial immune response. Our understanding of specific triggers of the inflammasomes, coupled with the recognition that inflammasomes are critical for activation of the proinflammatory cytokine IL-1, has provided a rational and very effective target in the treatment of a number of these rare autoinflammatory diseases. In addition, the ongoing discovery of the role of inflammasomes and IL-1 activation and secretion in a number of genetically complex disorders have fundamentally changed our view of disease pathogenesis in a growing number of disorders that were heretofore not even thought of as "immunologic" diseases.

The inflammasomes: mechanisms of activation and function

In response to injurious or infectious agents caspase-1 activating multiprotein complexes, termed inflammasomes, assemble in the cytoplasm of cells. Activated caspase-1 cleaves the proforms of the interleukin-1 cytokine family members leading to their activation and secretion. The IL-1 family cytokines have multiple proinflammatory activities implicating them in the pathogenesis of many inflammatory diseases. While defined ligands have been identified for the NLRP1, IPAF, and AIM2 inflammasomes, little is known about the activation mechanisms of the NLRP3 inflammasome. Numerous different molecular entities, such as various crystals, pore-forming toxins, or extracellular ATP can trigger the NLRP3 inflammasome. Recent work proposes that NLRP3 is activated indirectly by host factors that are generated in response to NLRP3 triggers.

Immunomodulatory effects of dsRNA and its potential as vaccine adjuvant

dsRNA can be detected by pattern recognition receptors, for example, TLR3, MDA-5, NLRP3 to induce proinflammatory cytokines responsible for innate/adaptive immunity. Recognized by endosomal TLR3 in myeloid DCs (mDCs), dsRNA can activate mDCs into mature antigen presenting cells (mAPCs) which in turn present antigen epitopes with MHC-I molecules to naïve T cells. Coadministration of protein and synthetic dsRNA analogues can elicit an antigen-specific Th1-polarized immune response which stimulates the CD8+ CTL response and possibly dampen Th17 response. Synthetic dsRNA analogues have been tested as vaccine adjuvant against viral infections in animal models. However, a dsRNA receptor, TLR3 can be expressed in tumor cells while other members of TLR family, for example, TLR4 and TLR2 have been shown to promote tumor progression, metastasis, and chemoresistance. Thus, the promising potential of dsRNA analogues as a tumor therapeutic vaccine adjuvant should be evaluated cautiously.

Follicle-stimulating hormone, interleukin-1, and bone density in adult women

Recent studies have indicated that follicle-stimulating hormone (FSH) promotes bone loss. The present study tested the hypothesis that FSH enhances the activity of bone-resorbing cytokines [interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-6], either by inducing their secretion or by altering their receptor expression. Thirty-six women between the ages of 20 and 50 were assessed for bone mineral density (BMD), reproductive hormone, cytokine ligand and soluble receptor concentrations, and surface expression of cytokine receptors on monocytes. In addition, isolated mononuclear cells were incubated in vitro with exogenous FSH. Univariate regression analyses indicated that BMD was inversely related to serum FSH (r = -0.29 to -0.51, P = 0.03-0.001, depending upon the skeletal site). Physical activity and body composition were also identified as significant factors by multiple regressions. Exogenous FSH induced isolated cells to secrete IL-1beta, TNF-alpha, and IL-6 in proportion to the surface expression of FSH receptors on the monocytes. Endogenous (serum) FSH concentrations correlated with the circulating concentrations of these cytokines. None of these individual cytokines was related to BMD, but the IL-1beta to IL-1 receptor antagonist (IL-1Ra) ratio was inversely related to BMD (r = -0.53, P = 0.002) in all but the most physically active women, who had significantly lower expression of IL-1 type I receptors relative to type II (decoy receptors, P = 0.01). Physical activity also correlated positively with secretion of inhibitory soluble IL-1 receptors (r = 0.53, P = 0.003). Moreover, IL-1Ra correlated strongly with percent body fat (r = 0.66, P < 0.0001). These results indicate that BMD is related to FSH concentration, physical activity, and body composition. Although each of these factors likely has direct effects on bone, the present study suggests that each may also influence BMD by modulating the activity of the osteoresorptive cytokine IL-1beta.

Constitutively active inflammasome in human melanoma cells mediating autoinflammation via caspase-1 processing and secretion of interleukin-1beta

Interleukin-1beta (IL-1beta) is a pleiotropic cytokine promoting inflammation, angiogenesis, and tissue remodeling as well as regulation of immune responses. Although IL-1beta contributes to growth and metastatic spread in experimental and human cancers, the molecular mechanisms regulating the conversion of the inactive IL-1beta precursor to a secreted and active cytokine remains unclear. Here we demonstrate that NALP3 inflammasome is constitutively assembled and activated with cleavage of caspase-1 in human melanoma cells. Late stage human melanoma cells spontaneously secrete active IL-1beta via constitutive activation of the NALP3 inflammasome and IL-1 receptor signaling, exhibiting a feature of autoinflammatory diseases. Unlike human blood monocytes, these melanoma cells require no exogenous stimulation. In contrast, NALP3 functionality in intermediate stage melanoma cells requires activation of the IL-1 receptor to secrete active IL-1beta; cells from an early stage of melanoma require stimulation of the IL-1 receptor plus the co-stimulant muramyl dipeptide. The spontaneous secretion of IL-1beta from melanoma cells was reduced by inhibition of caspase-1 or the use of small interfering RNA directed against ASC. Supernatants from melanoma cell cultures enhanced macrophage chemotaxis and promoted in vitro angiogenesis, both prevented by pretreating melanoma cells with inhibitors of caspases-1 and -5 or IL-1 receptor blockade. These findings implicate IL-1-mediated autoinflammation as contributing to the development and progression of human melanoma and suggest that inhibiting the inflammasome pathway or reducing IL-1 activity can be a therapeutic option for melanoma patients.

Free fatty acids induce a proinflammatory response in islets via the abundantly expressed interleukin-1 receptor I

Islets of patients with type 2 diabetes mellitus (T2DM) display features of an inflammatory process including elevated levels of the cytokine IL-1beta, various chemokines, and macrophages. IL-1beta is a master regulator of inflammation, and IL-1 receptor type I (IL-1RI) blockage improves glycemia and insulin secretion in humans with T2DM and in high-fat-fed mice pointing to a pivotal role of IL-1RI activity in intra-islet inflammation. Given the association of dyslipidemia and T2DM, we tested whether free fatty acids (FFA) promote the expression of proinflammatory factors in human and mouse islets and investigated a role for the IL-1RI in this response. A comparison of 22 mouse tissues revealed the highest IL-1RI expression levels in islets and MIN6 beta-cells. FFA induced IL-1beta, IL-6, and IL-8 in human islets and IL-1beta and KC in mouse islets. Elevated glucose concentrations enhanced FFA-induced proinflammatory factors in human islets. Blocking the IL-1RI with the IL-1R antagonist (IL-1Ra) strongly inhibited FFA-mediated expression of proinflammatory factors in human and mouse islets. Antibody inhibition of IL-1beta revealed that FFA stimulated IL-1RI activity via the induction of the receptor ligand. FFA-induced IL-1beta and KC expression in mouse islets was completely dependent on the IL-1R/Toll-like receptor (TLR) docking protein Myd88 and partly dependent on TLR2 and -4. Activation of TLR2 in purified human beta-cells and islets stimulated the expression of proinflammatory factors, and IL-1RI activity increased the TLR2 response in human islets. We conclude that FFA and TLR stimulation induce proinflammatory factors in islets and that IL-1RI engagement results in signal amplification.

Caspase 1-independent activation of interleukin-1beta in neutrophil-predominant inflammation

OBJECTIVE

Interleukin-1beta (IL-1beta) is a key cytokine linked to the pathogenesis of acute arthritis. Caspase 1, neutrophil elastase, and chymase all process proIL-1beta to its biologically active form. This study was undertaken to examine the potential contributions of each of these proteases in experimental models of inflammatory arthritis.

METHODS

Caspase 1-deficient (Casp1-/-) and wild-type (WT) mice were tested for their response to arthritogenic K/BxN serum transfer for induction of arthritis or injection of monosodium urate monohydrate (MSU) crystals for induction of peritonitis. All mice were prophylactically treated with inhibitors of neutrophil elastase or chymase. Arthritic paws were tested for the presence of IL-1beta protein by enzyme-linked immunosorbent assay and Western blotting. Neutrophils and mast cells from WT and mutant mice were tested for their ability to secrete IL-1beta after in vitro stimulation, in the presence of protease inhibitors.

RESULTS

Casp1-/- and WT mice developed paw swelling to the same extent in the K/BxN serum transfer-induced arthritis model. MSU crystal injection into Casp1-/- mice also resulted in neutrophil influx and production of measurable peritoneal IL-1beta protein. Both of these responses were attenuated with neutrophil elastase inhibitors. K/BxN serum transfer-induced arthritis was also reduced by treatment with a chymase inhibitor. Casp1-/- neutrophils and mast cells, when exposed to MSU crystals, secreted similar amounts of IL-1beta protein upon in vitro stimulation with lipopolysaccharide, albeit at lower levels than that secreted by WT cells. Elastase and chymase inhibitors reduced the amount of IL-1beta released by these cells.

CONCLUSION

The production of IL-1beta by neutrophils and mast cells is not exclusively dependent on caspase 1, and other proteases can compensate for the loss of caspase 1 in vivo. These pathways might therefore compromise the caspase 1-targeted therapies in neutrophil-predominant arthritis.