Interleukin (IL)-18 Binding Protein Deficiency Disrupts Natural Killer Cell Maturation and Diminishes Circulating IL-18

Natural killer cells promote neutrophil extracellular traps and restrain macular degeneration in mice

Neovascular age-related macular degeneration (nvAMD) is the leading cause of blindness in the elderly population. Although it is known that nvAMD is associated with focal inflammation, understanding of the precise immune components governing this process remains limited. Here, we identified natural killer (NK) cells as a prominent lymphocyte population infiltrating the perivascular space of choroidal neovascularization (CNV) lesions in patients with nvAMD and in mouse models. Olink proteomic analysis and single-cell RNA sequencing combined with knockout studies demonstrated the involvement of C-C chemokine receptor 5 (CCR5) in NK cell recruitment and extravasation at the CNV sites of mice. Depletion of NK cells or inhibition of activating receptor NK group 2, member D (NKG2D) inhibited the formation of neutrophil extracellular traps, increased vascular leakage, and exacerbated pathological angiogenesis, indicating that NK cells restrain pathogenesis in this mouse model. Age is the strongest risk factor for AMD, and we show that NK cells from aged human donors exhibited a less cytotoxic phenotype. NK cells from old mice exhibited compromised protective effects in the CNV mouse model. In addition, interleukin-2 complex-mediated expansion of NK cells improved CNV formation in mice. Collectively, our study highlights NK cells as a potential therapeutic target for patients with nvAMD.

Gastric digestion of the sweet-tasting plant protein thaumatin releases bitter peptides that reduce H. pylori induced pro-inflammatory IL-17A release via the TAS2R16 bitter taste receptor

About half of the world's population is infected with the bacterium Helicobacter pylori. For colonization, the bacterium neutralizes the low gastric pH and recruits immune cells to the stomach. The immune cells secrete cytokines, i.e., the pro-inflammatory IL-17A, which directly or indirectly damage surface epithelial cells. Since (I) dietary proteins are known to be digested into bitter tasting peptides in the gastric lumen, and (II) bitter tasting compounds have been demonstrated to reduce the release of pro-inflammatory cytokines through functional involvement of bitter taste receptors (TAS2Rs), we hypothesized that the sweet-tasting plant protein thaumatin would be cleaved into anti-inflammatory bitter peptides during gastric digestion. Using immortalized human parietal cells (HGT-1 cells), we demonstrated a bitter taste receptor TAS2R16-dependent reduction of a H. pylori-evoked IL-17A release by up to 89.7 ± 21.9% (p ≤ 0.01). Functional involvement of TAS2R16 was demonstrated by the study of specific antagonists and siRNA knock-down experiments.

Acquisition of different transcriptional shear mRNA and biological function of porcine interleukin 18 binding protein in PRRSV infection

Interleukin-18 binding protein (IL-18BP), a natural regulator molecule of the pro-inflammatory cytokine interleukin-18 (IL-18), plays an important role in regulating the expression of the cellular immunity factor interferon-γ (IFN-γ). In a previous RNA-seq analysis of porcine alveolar macrophages (PAM) infected with the TIM and TJ strains of porcine reproductive and respiratory syndrome virus (PRRSV), we unexpectedly found that the mRNA expression of porcine interleukin 18-binding protein (pIL-18BP) in PAM cells infected with the TJM strain was significantly higher than that infected with the TJ strain. Studies have shown that human interleukin-18 binding protein (hIL-18bp) plays an important role in regulating cellular immunity in the course of the disease. However, there is a research gap on pIL-18BP. At the same time, PRRSV infection in pigs triggers weak cellular immune response problems. To explore the expression and the role of pIL-18BP in the cellular immune response induced by PRRSV, we strived to acquire the pIL-18BP gene from PAM or peripheral blood mononuclear cell (PBMC) with RT-PCR and sequencing. Furthermore, pIL-18BP and pIL-18 were both expressed prokaryotically and eukaryotically. The colocalization and interaction based on recombinant pIL-18BP and pIL-18 on cells were confirmed in vitro. Finally, the expression of pIL-18BP, pIL-18, and pIFN-γ was explored in pigs with different PRRSV infection states to interpret the biological function of pIL-18BP in vivo. The results showed there were five shear mutants of pIL-18BP. The mutant with the longest coding region was selected for subsequent functional validation. First, it was demonstrated that TJM-induced pIL-18BP mRNA expression was higher than that of TJ. A direct interaction between pIL-18BP and pIL-18 was confirmed through fluorescence colocalization, bimolecular fluorescent complimentary (BIFC), and co-immunoprecipitation (CO-IP). pIL-18BP also can regulate pIFN-γ mRNA expression. Finally, the expression of pIL-18BP, pIL-18, and pIFN-γ was explored in different PRRSV infection states. Surprisingly, both mRNA and protein expression of pIL-18 were suppressed. These findings fill the gap in understanding the roles played by pIL-18BP in PRRSV infection and provide a foundation for further research.IMPORTANCEPRRSV-infected pigs elicit a weak cellular immune response and the mechanisms of cellular immune regulation induced by PRRSV have not yet been fully elucidated. In this study, we investigated the role of pIL-18BP in PRRSV-induced immune response referring to the regulation of human IL-18BP to human interferon-gamma (hIFN-γ). This is expected to be used as a method to enhance the cellular immune response induced by the PRRSV vaccine. Here, we mined five transcripts of the pIL-18BP gene and demonstrated that it interacts with pIL-18 and regulates pIFN-γ mRNA expression. Surprisingly, we also found that both mRNA and protein expression of pIL-18 were suppressed under different PRRSV strains of infection status. These results have led to a renewed understanding of the roles of pIL-18BP and pIL-18 in cellular immunity induced by PRRSV infection, which has important implications for the prevention and control of PRRS.

Interleukin‑18 binding protein: Biological properties and roles in human and animal immune regulation (Review)

IL-18 binding protein (IL-18BP) is a natural regulatory molecule of the proinflammatory cytokine IL-18. It can regulate activity of IL-18 by high affinity binding. The present review aimed to highlight developments, characteristics and functions of IL-18BP. IL-18BP serves biological and anti-pathological roles in treating disease. In humans, it modulates progression of a number of chronic diseases, such as adult-onset Still's disease. The present review summarizes molecular structure, role of IL-18BP in disease and interaction with other proteins in important pathological processes.

Biological and clinical roles of IL-18 in inflammatory diseases

Several new discoveries have revived interest in the pathogenic potential and possible clinical roles of IL-18. IL-18 is an IL-1 family cytokine with potent ability to induce IFNγ production. However, basic investigations and now clinical observations suggest a more complex picture. Unique aspects of IL-18 biology at the levels of transcription, activation, secretion, neutralization, receptor distribution and signalling help to explain its pleiotropic roles in mucosal and systemic inflammation. Blood biomarker studies reveal a cytokine for which profound elevation, associated with detectable 'free IL-18', defines a group of autoinflammatory diseases in which IL-18 dysregulation can be a primary driving feature, the so-called 'IL-18opathies'. This impressive specificity might accelerate diagnoses and identify patients amenable to therapeutic IL-18 blockade. Pathogenically, human and animal studies identify a preferential activation of CD8+ T cells over other IL-18-responsive lymphocytes. IL-18 agonist treatments that leverage the site of production or subversion of endogenous IL-18 inhibition show promise in augmenting immune responses to cancer. Thus, the unique aspects of IL-18 biology are finally beginning to have clinical impact in precision diagnostics, disease monitoring and targeted treatment of inflammatory and malignant diseases.

Microenvironmental signals shaping NK-cell reactivity in cancer

Since the postulation of the "missing-self" concept, much progress has been made in defining requirements for NK-cell activation. Unlike T lymphocytes that process signals from receptors in a hierarchic manner dominated by the T-cell receptors, NK cells integrate receptor signals more "democratically." Signals originate not only the downstream of cell-surface receptors triggered by membrane-bound ligands or cytokines, but are also mediated by specialized microenvironmental sensors that perceive the cellular surrounding by detecting metabolites or the availability of oxygen. Thus, NK-cell effector functions are driven in an organ and disease-dependent manner. Here, we review the latest findings on how NK-cell reactivity in cancer is determined by the reception and integration of complex signals. Finally, we discuss how this knowledge can be exploited to guide novel combinatorial approaches for NK-cell-based anticancer therapies.

Targeting the opioid remifentanil: Protective effects and molecular mechanisms against organ ischemia-reperfusion injury

Opioids are widely used in clinical practice by activating opioid receptors (OPRs), but their clinical application is limited by a series of side effects. Researchers have been making tremendous efforts to promote the development and application of opioids. Fortunately, recent studies have identified the additional effects of opioids in addition to anesthesia and analgesia, particularly in terms of organ protection against ischemia-reperfusion (I/R) injury, with unique advantages. I/R injury in vital organs not only leads to cell dysfunction and structural damage but also induces acute and chronic organ failure, even death. Early prevention and appropriate therapeutic targets for I/R injury are crucial for organ protection. Opioids have shown cardioprotective effects for over 20 years, especially remifentanil, a derivative of fentanyl, which is a new ultra-short-acting opioid analgesic widely used in clinical anesthesia induction and maintenance. In this review, we provide current knowledge about the physiological effects related to OPR-mediated organ protection, focusing on the protective effect and mechanism of remifentanil on I/R injury in the heart and other vital organs. Herein, we also explored the potential application of remifentanil in clinical I/R injury. These findings provide a theoretical basis for the use of remifentanil to inhibit or alleviate organ I/R injury during the perioperative period and provide insights for opioid-induced human organ protection and drug development.

Identification and function of a novel human memory-like NK cell population expressing CD160 in melioidosis

NK cells are endowed with immunological memory to a range of pathogens but the development of NK cell memory in bacterial infections remains elusive. Here, we establish an assay inducing memory-like NK cell response to Burkholderia pseudomallei, the causative agent of the severe bacterial disease called melioidosis, and explore NK cell memory in a melioidosis patient cohort. We show that NK cells require bacteria-primed monocytes to acquire memory-like properties, demonstrated by bacteria-specific responses, features that strongly associate with CD160 expression. Induction of this memory-like NK cell is partly dependent on CD160 and IL-12R. Importantly, CD160 expression identifies memory-like NK cells in a cohort of recovered melioidosis patients with heightened responses maintained at least 3 months post hospital admission and reduced numbers of this cell population independently correlate with recurrent melioidosis. These newly identified memory-like NK cells are a promising target for future vaccine design and for monitoring protection against infection.

Research Progress on the Role and Mechanism of IL-37 in Liver Diseases

Cytokines are important components of the immune system that can predict or influence the development of liver diseases. IL-37, a new member of the IL-1 cytokine family, exerts potent anti-inflammatory and immunosuppressive effects inside and outside cells. IL-37 expression differs before and after liver lesions, suggesting that it is associated with liver disease; however, its mechanism of action remains unclear. This article mainly reviews the biological characteristics of IL-37, which inhibits hepatitis, liver injury, and liver fibrosis by inhibiting inflammation, and inhibits the development of hepatocellular carcinoma (HCC) by regulating the immune microenvironment. Based on additional evidence, combining IL-37 with liver disease markers for diagnosis and treatment can achieve more significant effects, suggesting that IL-37 can be developed into a powerful tool for the clinical adjuvant treatment of liver diseases, especially HCC.

TREM2 macrophages drive NK cell paucity and dysfunction in lung cancer

Natural killer (NK) cells are commonly reduced in human tumors, enabling many to evade surveillance. Here, we sought to identify cues that alter NK cell activity in tumors. We found that, in human lung cancer, the presence of NK cells inversely correlated with that of monocyte-derived macrophages (mo-macs). In a murine model of lung adenocarcinoma, we show that engulfment of tumor debris by mo-macs triggers a pro-tumorigenic program governed by triggering receptor expressed on myeloid cells 2 (TREM2). Genetic deletion of Trem2 rescued NK cell accumulation and enabled an NK cell-mediated regression of lung tumors. TREM2+ mo-macs reduced NK cell activity by modulating interleukin (IL)-18/IL-18BP decoy interactions and IL-15 production. Notably, TREM2 blockade synergized with an NK cell-activating agent to further inhibit tumor growth. Altogether, our findings identify a new axis, in which TREM2+ mo-macs suppress NK cell accumulation and cytolytic activity. Dual targeting of macrophages and NK cells represents a new strategy to boost antitumor immunity.

Longitudinal transcriptional analysis of peripheral blood leukocytes in COVID-19 convalescent donors

BACKGROUND

SARS-CoV2 can induce a strong host immune response. Many studies have evaluated antibody response following SARS-CoV2 infections. This study investigated the immune response and T cell receptor diversity in people who had recovered from SARS-CoV2 infection (COVID-19).

METHODS

Using the nCounter platform, we compared transcriptomic profiles of 162 COVID-19 convalescent donors (CCD) and 40 healthy donors (HD). 69 of the 162 CCDs had two or more time points sampled.

RESULTS

After eliminating the effects of demographic factors, we found extensive differential gene expression up to 241 days into the convalescent period. The differentially expressed genes were involved in several pathways, including virus-host interaction, interleukin and JAK-STAT signaling, T-cell co-stimulation, and immune exhaustion. A subset of 21 CCD samples was found to be highly "perturbed," characterized by overexpression of PLAU, IL1B, NFKB1, PLEK, LCP2, IRF3, MTOR, IL18BP, RACK1, TGFB1, and others. In addition, one of the clusters, P1 (n = 8) CCD samples, showed enhanced TCR diversity in 7 VJ pairs (TRAV9.1_TCRVA_014.1, TRBV6.8_TCRVB_016.1, TRAV7_TCRVA_008.1, TRGV9_ENST00000444775.1, TRAV18_TCRVA_026.1, TRGV4_ENST00000390345.1, TRAV11_TCRVA_017.1). Multiplexed cytokine analysis revealed anomalies in SCF, SCGF-b, and MCP-1 expression in this subset.

CONCLUSIONS

Persistent alterations in inflammatory pathways and T-cell activation/exhaustion markers for months after active infection may help shed light on the pathophysiology of a prolonged post-viral syndrome observed following recovery from COVID-19 infection. Future studies may inform the ability to identify druggable targets involving these pathways to mitigate the long-term effects of COVID-19 infection.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT04360278 Registered April 24, 2020.

Inflammatory cytokines and appetite in older hospitalized patients

It has already been confirmed that the decline in appetite during disease is a common issue and the biologic players of inflammation such as cytokines may serve as mediators of this effect. This study aimed to investigate the association of appetite with individual cytokines that could be involved in the inflammation-associated loss of appetite in acutely ill older hospitalized patients. 191 patients (mean age 81.3 ± 6.6 years, 64% women) participated in this prospective observational study. Risk of malnutrition and patient's appetite were evaluated using the Mini Nutritional Assessment Short Form and the Simplified Nutritional Appetite Questionnaire on admission, respectively. Serum C-reactive protein (CRP) and serum cytokines such as Interleukin 1 beta (IL-1β), IL-6, IL-8, IL-10, IL-12p70, IL-17, IL-18, IL-23 and IL-33, interferon alpha-2, interferon gamma, tumor necrosis factor alpha and monocyte chemoattractant protein-1 (MCP-1) were measured. Of total population, 30% had CRP>3.0 (mg/dL), 31% were malnourished and 31% demonstrated poor and very poor appetite. There were significant differences in the mean concentrations of a number of cytokines including IL-1β, MCP-1, IL-6, IL-10, IL-12p70, IL-18 and IL-23 across the appetite scores. In a regression analysis, an increased IL-18 level (P = 0.049) was the most prominent biomarker for poor appetite. No other significant associations between appetite and circulating levels of other cytokines were found in the regression analysis, except for IL-6 and IL-33, which were only significantly associated in the unadjusted model. The association of IL-18 with decreased appetite was independent from the severity of CRP-level and infections. In this study, certain cytokines, in particular IL-18 were associated with poor appetite in acutely diseased patients and should therefore be considered as a potential target of the prevention and treatment of malnutrition.

Metabolic and Molecular Mechanisms of Macrophage Polarisation and Adipose Tissue Insulin Resistance

Inflammation plays a key role in the development and progression of type-2 diabetes (T2D), a disease characterised by peripheral insulin resistance and systemic glucolipotoxicity. Visceral adipose tissue (AT) is the main source of inflammation early in the disease course. Macrophages are innate immune cells that populate all peripheral tissues, including AT. Dysregulated AT macrophage (ATM) responses to microenvironmental changes are at the root of aberrant inflammation and development of insulin resistance, locally and systemically. The inflammatory activation of macrophages is regulated at multiple levels: cell surface receptor stimulation, intracellular signalling, transcriptional and metabolic levels. This review will cover the main mechanisms involved in AT inflammation and insulin resistance in T2D. First, we will describe the physiological and pathological changes in AT that lead to inflammation and insulin resistance. We will next focus on the transcriptional and metabolic mechanisms described that lead to the activation of ATMs. We will discuss more novel metabolic mechanisms that influence macrophage polarisation in other disease or tissue contexts that may be relevant to future work in insulin resistance and T2D.

Production of IL-18 Binding Protein by Radiosensitive and Radioresistant Cells in CpG-Induced Macrophage Activation Syndrome

IL-18 binding protein (IL-18BP) acts as a naturally occurring IL-18 decoy receptor. If the balance between IL-18 and IL-18BP is dysregulated, abnormal levels of free bioactive IL-18 are detected, such as in the sera of Il-18bp knockout (KO) mice with CpG-induced macrophage activation syndrome. To determine the cellular sources of Il-18bp in vivo, we selectively depleted Il-18bp expression in either radiosensitive or radioresistant cells using bone marrow transfer between wild-type (WT) and Il-18bp KO mice. Following repeated CpG injections, Il-18bp KO (donor)→ Il-18bp KO (recipient) chimeric mice exhibited more severe disease, with an enhanced Ifn-γ signature and circulating free Il-18 levels, in comparison with WT→WT chimeras. Interestingly, the phenotype of KO→WT and WT→KO mice did not differ from that of WT→WT mice. Consistent with this finding, serum Il-18bp levels were similar in these three groups of mice. The contribution of radioresistant and radiosensitive cells to Il-18bp production varied markedly according to the organ examined, with a major contribution of radiosensitive cells in the spleen as opposed to a major contribution of radioresistant cells in the lung. Finally, Ifn-γ blockade abrogated the CpG-induced but not the constitutive Il-18bp production. Our results demonstrate that circulating Il-18bp is induced in response to Ifn-γ during CpG-induced macrophage activation syndrome and is present at high levels in the circulation to prevent the deleterious systemic effects of Il-18.

A comprehensive pathway map of IL-18-mediated signalling

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines and was initially described as an IFN-γ-inducing factor derived from anti-CD3-stimulated T-helper (Th)1 cells. IL-18 plays a significant role in the activation of hematopoietic cell types mediating both Th1 and Th2 responses and is the primary inducer of interferon-γ in these cells. The biological activity of IL-18 is mediated through its binding to the IL-18 receptor complex and activation of nuclear factor-κB (NF-κB), culminating in the production and release of several cytokines, chemokines, and cellular adhesion molecules. In certain cell types, IL-18 also activates mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase/ AKT serine/threonine kinase (PI3K/AKT) signaling modules leading to the production and release of proinflammatory cytokines. IL-18-mediated signaling acts as one of the vital components of the immunomodulatory cytokine networks involved in host defense, inflammation, and tissue regeneration. Albeit its biomedical importance, a comprehensive resource of IL-18 mediated signaling pathway is currently lacking. In this study, we report on the development of an integrated pathway map of IL-18/IL-18R signaling. The pathway map was developed through literature mining from published literature based on manual curation guidelines adapted from NetPath and includes information on 16 protein-protein interaction events, 38 enzyme-catalysis events, 12 protein translocation events, 26 activations/inhibition events, transcriptional regulators, 230 gene regulation events and 84 induced protein expression events. The IL-18 signaling pathway can be freely accessed through the WikiPathways database (https://www.wikipathways.org/index.php/Pathway:WP4754).

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.

CD83+ CCR7+ NK cells induced by interleukin 18 by dendritic cells promote experimental autoimmune uveitis

Natural killer (NK) cells have been reported to play a pathological role in autoimmune uveitis. However, the mechanisms regarding NK cells in uveitis and factors that affect NK-cell activation in this condition remain unclear. Here, we report that the number of CD3- NK1.1+ CD83+ CCR7+ cells is increased in the inflamed eyes within a mouse model of experimental autoimmune uveitis (EAU), and these cells express elevated levels of NKG2D, CD69 and IFN-γ. Adoptively transferring CD83+ CCR7+ NK cells aggravates EAU symptoms and increases the number of CD4+ IFN-γ+ T cells and dendritic cells (DCs) within the eye. These CD83+ CCR7+ NK cells then promote the maturation of DCs and IFN-γ expression within T cells as demonstrated in vitro. Furthermore, IL-18, as primarily secreted by DCs in the eyes, is detected to induce CD83+ CCR7+ NK cells. In EAU mice, anti-IL-18R antibody treatment also decreases retinal tissue damage, as well as the number of infiltrating CD83+ CCR7+ NK cells, T cells and DCs in the inflamed eyes and spleens of EAU mice. These results suggest that CD83+ CCR7+ NK cells, as induced by IL-18 that primarily secreted by DCs, play a critical pathological role in EAU. Anti-IL-18R antibody might serve as a potential therapeutic agent for uveitis through its capacity to inhibit CD83+ CCR7+ NK cells infiltration.

Inoculation of fowlpox viruses coexpressing avian influenza H5 and chicken IL-15 cytokine gene stimulates diverse host immune responses

Fowlpox virus (FWPV) has been used as a recombinant vaccine vector to express antigens from several important avian pathogens. Attempts have been made to improve vaccine strains induced-host immune responses by coexpressing cytokines. This study describes the construction of recombinant FWPV (rFWPV) strain FP9 and immunological responses in specific-pathogen-free (SPF) chickens, co-expressing avian influenza virus (AIV) H5 of A/Chicken/Malaysia/5858/2004, and chicken IL-15 cytokine genes. Expression of H5 (50 kD) was confirmed by western blotting. Anti-H5 antibodies, which were measured by the haemagglutinin inhibition test, were at the highest levels at Week 3 post-inoculation in both rFWPV/H5- and rFWPV/H5/IL-15-vaccinated chickens, but decreased to undetectable levels from Week 5 onwards. CD3+/CD4+ or CD3+/CD8+T cell populations, assessed using flow cytometry, were significantly increased in both WT FP9- and rFWPV/H5-vaccinated chickens and were also higher than in rFWPV/H5/IL-15- vaccinated chickens, at Week 2. Gene expression analysis using real time quantitative polymerase chain reaction (qPCR) demonstrated upregulation of IL-15 expression in all vaccinated groups with rFWPV/H5/IL-15 having the highest fold change, at day 2 (117±51.53). Despite showing upregulation, fold change values of the IL-18 expression were below 1.00 for all vaccinated groups at day 2, 4 and 6. This study shows successful construction of rFWPV/H5 co-expressing IL-15, with modified immunogenicity upon inoculation into SPF chickens.

Interleukin-18 in Health and Disease

Interleukin (IL)-18 was originally discovered as a factor that enhanced IFN-γ production from anti-CD3-stimulated Th1 cells, especially in the presence of IL-12. Upon stimulation with Ag plus IL-12, naïve T cells develop into IL-18 receptor (IL-18R) expressing Th1 cells, which increase IFN-γ production in response to IL-18 stimulation. Therefore, IL-12 is a commitment factor that induces the development of Th1 cells. In contrast, IL-18 is a proinflammatory cytokine that facilitates type 1 responses. However, IL-18 without IL-12 but with IL-2, stimulates NK cells, CD4⁺ NKT cells, and established Th1 cells, to produce IL-3, IL-9, and IL-13. Furthermore, together with IL-3, IL-18 stimulates mast cells and basophils to produce IL-4, IL-13, and chemical mediators such as histamine. Therefore, IL-18 is a cytokine that stimulates various cell types and has pleiotropic functions. IL-18 is a member of the IL-1 family of cytokines. IL-18 demonstrates a unique function by binding to a specific receptor expressed on various types of cells. In this review article, we will focus on the unique features of IL-18 in health and disease in experimental animals and humans.

Remifentanil upregulates hepatic IL-18 binding protein (IL-18BP) expression through transcriptional control

Interleukin (IL)-18 plays an important role in liver ischemia/reperfusion (I/R) injury. We have previously demonstrated that remifentanil protects against liver I/R injury by upregulating the hepatic expression of IL-18-binding protein (IL-18BP), a natural IL-18 inhibitor. The current study was performed to further clarify the effects of remifentanil on IL-18BP expression in the liver as well as investigate the underlying mechanisms. In Sprague-Dawley (SD) rats, we demonstrated that remifentanil significantly increased the expression of IL-18BP in normal rat liver tissue over a 24-h time period with maximal expression at 24 h after treatment. The upregulation of remifentanil on IL-18BP expression displayed similar trends in in vitro cellular studies, including mouse primary hepatocytes, normal human hepatocyte LO2, and mouse hepatoma cells Hep1-6. In LO2 cells, preexposure of the cells to remifentanil significantly inhibited IL-18-activated p65 NF-κB phosphorylation, and the inhibition was absent when the cells were transfected with IL-18BP siRNA, indicating the functional effects of IL-18BP induced by remifentanil. Pretreatment with actinomycin D abolished remifentanil-induced upregulation of IL-18BP mRNA, suggesting that the induction occurred at the transcriptional level. This was further supported by the luciferase reporter assay, which demonstrated that remifentanil treatment significantly increased transcription of the IL-18BP promoter. Both western blot analysis and ChIP assays showed that STAT1 and C/EBP β were activated by remifentanil. Furthermore, remifentanil failed to upregulate IL-18BP expression after silencing STAT1 or C/EBP β gene expression. These findings demonstrate that remifentanil could upregulate hepatic IL-18BP expression through transcriptional activation of the IL-18BP promoter, and STAT1 and C/EBP β are two key transcriptional factors involved in this process.

Abnormal T Cell Frequencies, Including Cytomegalovirus-Associated Expansions, Distinguish Seroconverted Subjects at Risk for Type 1 Diabetes

We analyzed T cell subsets from cryopreserved PBMC obtained from the TrialNet Pathway to Prevention archives. We compared subjects who had previously seroconverted for one or more autoantibodies with non-seroconverted, autoantibody negative individuals. We observed a reduced frequency of MAIT cells among seroconverted subjects. Seroconverted subjects also possessed decreased frequencies of CCR4-expressing CD4 T cells, including a regulatory-like subset. Interestingly, we found an elevation of CD57+, CD28–, CD127–, CD27– CD8 T cells (SLEC) among seroconverted subjects that was most pronounced among those that progressed to disease. The frequency of these SLEC was strongly correlated with CMV IgG abundance among seroconverted subjects, associated with IA-2 levels, and most elevated among CMV+ seroconverted subjects who progressed to disease. Combined, our data indicate discrete, yet profound T cell alterations are associated with islet autoimmunity among at-risk subjects.

Cisplatin-Induced Rodent Model of Kidney Injury: Characteristics and Challenges

Cisplatin is an antitumor drug used in the treatment of a wide variety of malignancies. However, its primary dose-limiting side effect is kidney injury, which is a major clinical concern. To help understand mechanisms involved in the development of kidney injury, cisplatin rodent model has been developed. Given the complex pathogenesis of kidney injury, which involves both local events in the kidney and interconnected and interdependent systemic effects in the body, cisplatin rodent model is indispensable in the investigation of underlying mechanisms and potential treatment strategies of both acute and chronic kidney injury. Cisplatin rodent model is well appreciated and widely used model due to its simplicity. It has many similarities to human cisplatin nephrotoxicity, which are mentioned in the paper. In spite of its simplicity and wide applicability, there are also traps that need to be taken into account when using cisplatin model. The present paper is aimed at giving a concise insight into the complex characteristics of cisplatin rodent model and heterogeneity of cisplatin dosage regimens as well as outlining factors that can severely influence the outcome of the model and the study. Challenges for future research are also mentioned.

The family of the interleukin-1 receptors

The extracellular forms of the IL-1 cytokines are active through binding to specific receptors on the surface of target cells. IL-1 ligands bind to the extracellular portion of their ligand-binding receptor chain. For signaling to take place, a non-binding accessory chain is recruited into a heterotrimeric complex. The intracellular approximation of the Toll-IL-1-receptor (TIR) domains of the 2 receptor chains is the event that initiates signaling. The family of IL-1 receptors (IL-1R) includes 10 structurally related members, and the distantly related soluble protein IL-18BP that acts as inhibitor of the cytokine IL-18. Over the years the receptors of the IL-1 family have been known with many different names, with significant confusion. Thus, we will use here a recently proposed unifying nomenclature. The family includes several ligand-binding chains (IL-1R1, IL-1R2, IL-1R4, IL-1R5, and IL-1R6), 2 types of accessory chains (IL-1R3, IL-1R7), molecules that act as inhibitors of signaling (IL-1R2, IL-1R8, IL-18BP), and 2 orphan receptors (IL-1R9, IL-1R10). In this review, we will examine how the receptors of the IL-1 family regulate the inflammatory and anti-inflammatory functions of the IL-1 cytokines and are, more at large, involved in modulating defensive and pathological innate immunity and inflammation. Regulation of the IL-1/IL-1R system in the brain will be also described, as an example of the peculiarities of organ-specific modulation of inflammation.

Molecular insight into targeting the NK cell immune response to cancer

Natural Killer (NK) cells have long been considered an important part of the anti-tumor immune response due to their potent cytolytic and cytokine-secreting abilities. To date, a clear demonstration of the role NK cells play in human cancer is lacking, and there are still very few examples of therapies that efficiently exploit or enhance the spontaneous ability of NK cells to destroy the autologous cancer cells. Given the paradigm shift toward cancer immunotherapy over the past decade, there is a renewed push to understand how NK cell homeostasis and function are regulated in order to therapeutically harness these cells to treat cancer. This review will highlight recent advancements in our understanding of how growth factors impact on NK cell development, differentiation, survival and function with an emphasis on how these pathways may influence NK cell activity in the tumor microenvironment and control of cancer metastasis.

Unopposed IL-18 signaling leads to severe TLR9-induced macrophage activation syndrome in mice

The term macrophage activation syndrome (MAS) defines a severe, potentially fatal disorder characterized by overwhelming inflammation and multiorgan involvement. Interleukin-18 (IL-18) is a proinflammatory cytokine belonging to the IL-1 family, the activity of which is regulated by its endogenous inhibitor IL-18 binding protein (IL-18BP). Elevated IL-18 levels have been reported in patients with MAS. Herein, we show that on repeated toll-like receptor 9 (TLR9) stimulation with unmethylated cytosine guanine dinucleotide containing single-stranded DNA (CpG), IL-18BP^-/- mice display severe MAS manifestations, including increased weight loss, splenomegaly, anemia, thrombocytopenia, hyperferritinemia, and bone marrow hemophagocytosis as compared with wild-type mice. Serum-free IL-18 was detected in CpG-treated IL-18BP^-/- mice only. Levels of interferon-γ (IFN-γ) and of IFN-γ signature genes, such as the chemokine Cxcl9 or the transcription factor CIIta, were significantly increased in IL-18BP^-/- mice. Blocking IL-18 receptor signaling attenuated the severity of MAS and IFN-γ responses in IL-18BP^-/- mice. Blocking IFN-γ had comparable effects to IL-18 inhibition on most MAS manifestations. Our data indicate that endogenous IL-18BP exerts a protective role in CpG-induced MAS and that IL-18, which acts upstream of IFN-γ, is involved in the severity of MAS.