IL-18BPa:Fc cooperates with immunosuppressive drugs in human whole blood

Cutibacterium acnes and Staphylococcus epidermidis: the unmissable modulators of skin inflammatory response

Acne is a multifactorial inflammatory dermatose that affects all age categories from teenagers to adults, resulting in important psychological impacts. Multiple hypotheses currently attempt to decrypt the physiopathology of this disease, and four main actors were identified as highly implicated in it: hyperkeratinization of the pilosebaceous follicle, hyperseborrheae, host factors (innate immunity) and skin microbiota. In this letter, we present results illustrating the impact of skin microbiota on inflammatory skin response, and how far the proper balance between each bacterial community, especially C. acnes and S. epidermidis, is crucial to maintain an appropriate inflammatory response on the skin. The data presented in this study demonstrate that within the skin microbiota, an imbalance between Cutibacterium acnes and Staphylococcus epidermidis, is able to induce the activation of inflammation-related markers such as IL-1ra, IL-6, IL-8, G-CSF and the molecules C5/C5a, soluble CD14 MIP-3beta, Serpin E1, VCAM-1 and beta-defensin-2. Moreover, S. epidermidis appears to have a more important role than C. acnes on the induction of inflammation-related markers, particularly on IL-6. This work is the basis of future in vitro studies to further understand acne physiopathology, inspiring the development of future innovative therapies based on skin microbiota modulation.

IL-18/IL-18BP and IL-22/IL-22BP: Two interrelated couples with therapeutic potential

Interleukin (IL)-18 and IL-22 are key components of cytokine networks that play a decisive role in (pathological) inflammation, host defense, and tissue regeneration. Tight regulation of cytokine-driven signaling, inflammation, and immunoactivation is supposed to enable nullification of a given deleterious trigger without mediating overwhelming collateral tissue damage or even activating a cancerous face of regeneration. In fact, feedback regulation by specific cytokine opponents is regarded as a major means by which the immune system is kept in balance. Herein, we shine a light on the interplay between IL-18 and IL-22 and their opponents IL-18 binding protein (IL-18BP) and IL-22BP in order to provide integrated information on their biology, pathophysiological significance, and prospect as targets and/or instruments of therapeutic intervention.

Reviews of Interleukin-37: Functions, Receptors, and Roles in Diseases

Interleukin-37 (IL-37) is an IL-1 family cytokine discovered in recent years and has 5 different isoforms. As an immunosuppressive factor, IL-37 can suppress excessive immune response. IL-37 plays a role in protecting the body against endotoxin shock, ischemia-reperfusion injury, autoimmune diseases, and cardiovascular diseases. In addition, IL-37 has a potential antitumor effect. IL-37 and its receptors may serve as novel targets for the study, diagnosis, and treatment of immune-related diseases and tumors.

IL-37 requires the receptors IL-18Rα and IL-1R8 (SIGIRR) to carry out its multifaceted anti-inflammatory program upon innate signal transduction

Interleukin 37 (IL-37) and IL-1R8 (SIGIRR or TIR8) are anti-inflammatory orphan members of the IL-1 ligand family and IL-1 receptor family, respectively. Here we demonstrate formation and function of the endogenous ligand-receptor complex IL-37-IL-1R8-IL-18Rα. The tripartite complex assembled rapidly on the surface of peripheral blood mononuclear cells upon stimulation with lipopolysaccharide. Silencing of IL-1R8 or IL-18Rα impaired the anti-inflammatory activity of IL-37. Whereas mice with transgenic expression of IL-37 (IL-37tg mice) with intact IL-1R8 were protected from endotoxemia, IL-1R8-deficient IL-37tg mice were not. Proteomic and transcriptomic investigations revealed that IL-37 used IL-1R8 to harness the anti-inflammatory properties of the signaling molecules Mer, PTEN, STAT3 and p62(dok) and to inhibit the kinases Fyn and TAK1 and the transcription factor NF-κB, as well as mitogen-activated protein kinases. Furthermore, IL-37-IL-1R8 exerted a pseudo-starvational effect on the metabolic checkpoint kinase mTOR. IL-37 thus bound to IL-18Rα and exploited IL-1R8 to activate a multifaceted intracellular anti-inflammatory program.

High-level expression and one-step purification of a soluble recombinant human interleukin-37b in Escherichia coli

Interleukin (IL)-37 is a novel member of the IL-1 cytokine family. However, as a result of lacking efficient method to generate relatively large quantity of IL-37, little is known of its functions in man. In the present study, the recombinant human IL-37b containing a C-hexahistidine tag was expressed in Escherichia coli (E. coli). The expression level of IL-37b in E. coli was very high after induction with IPTG. Furthermore, IL-37b protein was largely found in the soluble fraction. The expressed protein was readily purified by one-step immobilized metal-ion affinity chromatography using Ni(2+)-nitrilotriacetic acid agarose. The purified IL-37b appeared as a single band on SDS-PAGE and the purity was more than 97%. The yield was 90mg IL-37b from 1l of bacterial culture. Western blotting and N-terminal sequencing confirmed the identity of the purified protein. The purified IL-37b inhibited significantly the release of tumor necrosis factor-α and IL-1β in lipopolysaccharide-activated THP-1 cells. Thus, this method provides an efficient way to obtain an active IL-37 with high yield and high purity.

The growing spectrum of anti-inflammatory interleukins and their potential roles in the development of sepsis

Sepsis, recognized as a deadly immunological disorder, is one of the major causes of death in intensive care units globally. Traditionally, sepsis was characterized by an excessive systemic proinflammatory response to invasive microbial pathogens. However, failures of highly sophisticated trials directed toward the uncontrolled inflammatory reaction have led to an appeal by experts for reevaluation of the present approach toward sepsis. With accumulated evidence, a principal role for immunosuppression in severe sepsis has been evaluated. Different pathways of negative regulation in the pathophysiological process of sepsis have been investigated. Significant among these regulatory elements are the anti-inflammatory cytokines. In the past few years, several interleukins (ILs) have been identified and characterized, among which IL-35 and IL-37 represent newly identified ones in the spectrum of anti-inflammatory cytokines. In this study, we focus on regulatory cytokines of the IL family (including the old members: IL-4, IL-10, and IL-13, and newly discovered ones: IL-35 and IL-37) to address current knowledge regarding their structural and functional characteristics as well as their roles in the development of sepsis. Although the exact roles for these cytokines are pending further elucidation, the current advances in our understanding of mechanisms that regulate the immune responses during severe sepsis may lead to the identification of new diagnostic or treatment targets.

The role of cytokines in the pathogenesis of systemic lupus erythematosus - from bench to bedside

The pathogenesis of systemic lupus erythematosus (SLE) entails a complex interaction between the different arms of the immune system. While autoantibodies production and immune complex deposition are cornered as hallmark features of SLE, there is growing evidence to propose the pathogenic role of cytokines in this disease. Examples of these cytokines include BLys, interleukin-6, interleukin-17, interleukin-18, type I interferons and tumour necrosis factor alpha. These cytokines all assume pivotal functions to orchestrate the differentiation, maturation and activation of various cell types, which would mediate local inflammatory process and tissue injury. The knowledge on these cytokines not only fosters our understanding of the disease, but also provides insights in devising biomarkers and targeted therapies. In this review, we focus on cytokines which have substantial pathogenic significance and also highlight the possible clinical applications of these cytokines.

New Insights in the Immunobiology of IL-1 Family Members

The interleukin-1 (IL 1) family of ligands is associated with acute and chronic inflammation, and plays an essential role in the non-specific innate response to infection. The biological properties of IL 1 family ligands are typically pro-inflammatory. The IL 1 family has 11 family members and can be categorized into subfamilies according to the length of their precursor and the length of the propiece for each precursor (Figure 1). The IL 1 subfamily consists of IL 1α, IL 1β, and IL 33, with the longest propieces of the IL 1 family. IL 18 and IL 37 belong to the IL 18 subfamily and contain smaller propieces than IL 1 and IL-33. Since IL 37 binds to the IL 18Rα chain it is part of the IL 18 subfamily, however it remains to be elucidated how the propiece of IL 37 is removed. IL 36α, β, and γ as well as IL 36 Ra belong to the IL 36 subfamily. In addition, IL 38 likely belongs to this family since it has the ability to bind to the IL 36R. The IL 36 subfamily has the shortest propiece. The one member of the IL 1 family that cannot be categorized in these subfamilies is IL 1 receptor antagonist (IL 1Ra), which has a signal peptide and is readily secreted. In the present review we will describe the biological functions of the IL-1F members and new insights in their biology.

Imbalance of interleukin-18 and interleukin-18 binding protein in children with Henoch-Schönlein purpura

The balance between interleukin-18 (IL-18) and its endogenous antagonist, IL-18 binding protein (IL-18BP), was evaluated in children with Henoch-Schönlein purpura (HSP). Plasma IL-18 and IL-18BP levels and peripheral blood mononuclear cell IL-18 mRNA expression were significantly higher in patients with active HSP (n = 30) than in healthy controls (n = 20); IL-18BP mRNA expression was similar in active HSP and controls. Plasma levels and mRNA expression of IL-18 and IL-18BP in patients in remission (n = 19) were similar to those in controls. The ratios of IL-18 / IL-18BP plasma levels and IL-18 / IL-18BP mRNA levels in active HSP were significantly higher than in patients in remission and healthy controls. Thus, adequate IL-18BP to block the proinflammatory activity of IL-18 may not be present in active HSP and regulation of the IL-18 / IL-18BP balance might provide a potential therapeutic strategy.

IL-37 is a fundamental inhibitor of innate immunity

The function of interleukin 37 (formerly IL-1 family member 7) remains elusive. Expression of IL-37 in macrophages or epithelial cells imparted near complete suppression of pro-inflammatory cytokines, whereas the abundance of these cytokines increased with silencing of endogenous IL-37 in human blood cells. Anti-inflammatory cytokines remained unchanged under similar conditions. IL-37-transgenic mice were protected from lipopolysaccharide-induced shock, exhibiting markedly improved lung and kidney function and reduced liver damage. IL-37-transgenic mice had less circulating and tissue cytokines (72-95% lower) than wild-type mice and exhibited less dendritic cell activation. IL-37 interacted intracellularly with Smad3 and IL-37-expressing cells and transgenic mice exhibited less cytokine suppression when endogenous Smad3 was depleted. IL-37 thus emerges as a natural suppressor of innate inflammatory and immune responses.

Evidence for a pathogenetic role of interleukin-18 in cutaneous lupus erythematosus

OBJECTIVE

Cutaneous manifestations are the most common clinical features of lupus erythematosus (LE). The aim of this study was to analyze differences in the inflammatory response of keratinocytes from patients with cutaneous LE (CLE) compared with healthy controls.

METHODS

Keratinocytes from LE patients and controls were cultured from epidermal stem cells of the hair follicle of anagen head hairs. Functional responses of keratinocytes to cytokine stimulation were determined by flow cytometry and enzyme-linked immunosorbent assay. Biopsy samples of lesional skin were analyzed by immunohistochemistry.

RESULTS

Keratinocytes from CLE patients expressed higher levels of IL-18 receptor on their cell surface in response to tumor necrosis factor alpha (TNFalpha) or interferon-gamma stimulation. In response to IL-18 stimulation, these cells produced large amounts of TNFalpha. Of note, in the presence of IL-18, CLE keratinocytes failed to express IL-12. IL-12 has previously been shown to protect keratinocytes from ultraviolet irradiation-induced apoptosis. Keratinocytes from LE patients were more prone to die upon exposure to IL-18, and this increased apoptosis was abrogated by blockade of endogenously produced TNFalpha as well as by the addition of exogenous IL-12. IL-18 was highly expressed in biopsy samples of lesional skin from CLE patients.

CONCLUSION

Our results demonstrate an intrinsic difference in the inflammatory response of keratinocytes and indicate an autocrine feedback loop involving TNFalpha, IL-18, and IL-12 family members. Our results suggest that IL-18 may occupy an important position in the cytokine hierarchy in CLE, indicating the potential benefit of a local agent that blocks IL-18 activity in the treatment of the manifestations of CLE.

Interleukin-18: a pro-inflammatory cytokine that plays an important role in acute pancreatitis

A large body of clinical and experimental evidence suggests that cytokines play a key role in the pathogenesis of local and systemic complications of acute pancreatitis. IL-18 is a pro-inflammatory cytokine that plays a key role in many human diseases, including acute pancreatitis. This review focuses on the present understanding in IL-18 and its potential role in acute pancreatitis. IL-18 levels reflect the severity of acute pancreatitis and display a significant negative correlation with the concentrations of antioxidative damage factors, serum selenium and glutathione peroxidases (GPx). The relationship between IL-18 and other pro-inflammatory cytokines shows that IL-18 is one of the key mediators of inflammation in the pathogenesis of acute pancreatitis. Elevation of serum IL-18 levels may mediate acute pancreatitis associated liver injury. The use of IL-18 antagonists as direct routes to block IL-18 activity and P2X7 receptor antagonists and interleukin-1beta-converting enzyme (ICE) inhibitors as indirect routes to block IL-18 activity suggest that specific therapeutic inhibition of IL-18 is a promising therapeutic approach for acute pancreatitis.

IFN-gamma-mediated survival enables human neutrophils to produce MCP-1/CCL2 in response to activation by TLR ligands

TLRs are key elements of the pathogen recognition mechanism used by the host immune system. Neutrophils express almost all TLRs, and activation of TLRs, such as TLR2 and TLR4, has been shown to induce the production of proinflammatory cytokines and chemokines, potentially linking innate and adaptive immunity. In the present study, we investigated whether activation of TLRs induces neutrophil production of MCP-1/CCL2, a key mediator involved in the development of adaptive immunity. Activation of neutrophils with LPS, lipoteichoic acid, or N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-[R]-Cys-[S]-Ser-[S]-Lys did not induce significant MCP-1 production and release; however, the Th1 cytokine IFN-gamma dramatically up-regulated MCP-1 production in cells activated with each TLR ligand. The majority of MCP-1 was released between 24 and 48 h of culture, indicating that this is a late event. The effect of IFN-gamma appeared to be due to its antiapoptotic effect, but not priming effect, revealing a biological consequence of IFN-gamma-induced neutrophil survival. Although IFN-gamma failed to protect neutrophils from cell death at a higher dose of LPS, the p38 MAPK inhibitor SB203580 dramatically increased MCP-1 release and neutrophil survival at this LPS concentration. Thus, p38 MAPK plays a previously uncharacterized role in neutrophil function. Taken together, our results indicate that human neutrophils produce MCP-1 in a Th1 microenvironment and this neutrophil-derived MCP-1 potentially amplifies the development of Th1 adaptive responses.

T-helper type 1/T-helper type 2 balance in malignant pleural effusions compared to tuberculous pleural effusions

STUDY OBJECTIVES

Malignant and tuberculous pleurisies are two major causes of lymphocyte-dominant pleurisy. Several studies have already reported that tuberculous pleurisy is a T-helper type 1(Th1)-dominant disease. In this study, we sought to examine the Th1/T-helper type 2 (Th2) balance, especially focusing on the polarizing status of T-cells to Th1/Th2 in malignant pleural effusions by measuring cytokines in pleural effusions and by evaluating the polarizing status of T-cells on the point of stimulation with interleukin (IL)-12 and/or IL-18. Furthermore, we evaluated inhibitors of interferon (IFN)-gamma production in effusions to rule out the possibility of direct inhibition of T-cell polarization.

PATIENTS

Effusion samples were collected from 19 patients with malignant pleurisy caused by lung cancer and from 7 patients with tuberculous pleurisy.

MEASUREMENTS

Concentrations of pleural fluid IFN-gamma, IL-12, and IL-4 were measured. IFN-gamma production of T-cells enriched from malignant pleural effusions in the presence of IL-12 and/or IL-18 was also examined. We further compared the inhibitory activity of malignant pleural effusions against IFN-gamma production and analyzed the expression of T-cell immunoglobulin mucin, mucin domain (Tim-3), a Th1-specific molecule in pleural fluid T-cells.

RESULTS

Although malignant pleural effusions showed low levels of Th1 and Th2 cytokines and ratios of IFN-gamma and IL-12 to IL-4 were low, isolated T-cells produced a significant level of IFN-gamma in the presence of IL-12 and IL-18. Soluble factors were not found to inhibit IFN-gamma production in malignant pleural effusions. In tuberculous pleural effusion, ratios of IFN-gamma and IL-12 to IL-4 were significantly higher, and T-cells showed the expression of Tim-3 messenger RNA.

CONCLUSIONS

We confirmed that T-cells in the malignant pleural effusions are mainly naïve or not definitely polarized to Th1. Moreover, malignant tumor does not actively distort the cytokine condition through production of soluble inhibitors within effusions. The present study indicates that antitumor immunity may be enhanced by restored IFN-gamma activity through combination of IL-12 and IL-18, and that it will lead to new therapies for malignant effusion.

Interleukin-18 bioactivity: a novel target for immunopharmacological anti-inflammatory intervention

Interleukin-18 is a member of the interleukin-1 family of cytokines with pro-inflammatory and tumor-suppressive properties. Its ability to potently enhance the production of interferon-gamma indicates in particular the crucial function of interleukin-18 as an immunomodulatory molecule. In fact, high levels of interleukin-18 are detected in human diseases associated with immunoactivation including viral or bacterial infections and chronic inflammation. Animal models suggest suppression of interleukin-18 bioactivity as a novel therapeutic concept specifically for the treatment of chronic inflammatory diseases such as rheumatoid arthritis, Crohn's disease, and psoriasis. Here we introduce into the biology of interleukin-18 and review immunopharmacological strategies that aim at reducing interleukin-18 bioactivity in human disease.

Inhibition of lipopolysaccharide/ATP-induced release of interleukin-18 by KN-62 and glyburide

Monocytes release interleukin-18 after activation by lipopolysaccharide/ATP. Since inflammatory conditions such as sepsis are characterized by augmented interleukin-18 in sera of patients, we sought to modulate lipopolysaccharide/ATP-induced interleukin-18 release by pharmacological means. Here we report that 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), an inhibitor of ATP-mediated cellular activation by the purinoreceptor subtype P(2x7), potently suppresses interleukin-18 release from peripheral blood mononuclear cells. Interleukin-18 liberation was likewise inhibited by glyburide, a modulator of ion transport and inhibitor of ATP-binding cassette transporter 1. The data presented herein indicate that by pharmacologically interfering with the process of cytokine secretion agents such as KN-62 or glyburide have the potential to curb overproduction of interleukin-18 in septic patients.

Induction of genes mediating interferon-dependent extracellular trap formation during neutrophil differentiation

Interferons (IFNs) are cytokines that possess potent anti-viral and immunoregulatory activities. In contrast, their potential role(s) in anti-bacterial defense and neutrophil activation mechanisms is less well explored. By comparing gene expression patterns between immature and mature human neutrophils, we obtained evidence that intracellular proteases and other anti-bacterial proteins are produced at earlier stages of maturation, whereas the genes for receptors and signaling molecules required for the release of these effector molecules are preferentially induced during terminal differentiation. For instance, mature neutrophils strongly expressed genes that increase their responses to type I and type II IFNs. Interestingly, granulocyte/macrophage colony-stimulating factor was identified as a repressor of IFN signaling components and consequently of IFN-responsive genes. Both IFN-alpha and IFN-gamma induced strong tyrosine phosphorylation of STAT1 in mature but not in immature neutrophils. Functional in vitro studies suggested that IFNs act as priming factors on mature neutrophils, allowing the formation of extracellular traps upon subsequent stimulation with complement factor 5a (C5a). In contrast, both IFN-alpha and IFN-gamma had only little capacity to prime immature cells in this system. Moreover, both IFNs did not have significant anti-proliferative effects on immature neutrophils. These data contribute to our understanding regarding changes of gene expression during neutrophil differentiation and IFN-mediated anti-bacterial defense mechanisms.

Anti-inflammatory properties of pro-inflammatory interferon-gamma

Production of interferon-gamma (IFNgamma) in response to infection is a hallmark of innate and adaptive immunity. In addition to the pivotal role of IFNgamma in host defense, its excessive release has been associated with the pathogenesis of chronic inflammatory and autoimmune diseases. In fact, knockout models reveal that IFNgamma plays a key role in mediating a number of pathological processes related to chronic immune activation. On the other hand, evidence has been accumulated in recent years that supports the concept of a dual role of IFNgamma in inflammation. Here, we review anti-inflammatory aspects of IFNgamma in the regulatory network of cytokine biology. These include induction of anti-inflammatory molecules such as interleukin (IL)-1 receptor antagonist (IL-1Ra) and IL-18 binding protein (IL-18BP), modulation of pro-inflammatory cytokine production, activation of apoptosis, and interference with the signal transduction machinery by induction of suppressors of cytokine signaling (SOCS).