Plasma levels of interleukin-18 and interleukin-18 binding protein are elevated in patients with chronic liver disease

Aberrant cytokine and VCAM-1 expression in patients with viral and non-viral related liver cirrhosis

The study aim was to compare the alterations in the expression levels of proinflammatory and chemotactic cytokines as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-17A and IL-8, the down regulatory cytokine IL-10, in addition to the vascular cell adhesion molecule-1 (VCAM-1) gene in different groups of patients with cirrhosis due to various etiologies. This case-control study included 84 patients suffering from cirrhosis of viral and non-viral etiologies and 20 sex and age-matched healthy controls. All patients were subjected to detailed history taking, clinical examination, and liver function assessment. The expression levels of TNF-α, IL-17A, IL-8, IL-10, and VCAM-1 were assessed in peripheral blood mononuclear cells by real-time PCR. Patients with cirrhosis showed marked changes in the tested gene expression levels relative to the control group. Higher expression levels of all genes except IL-10 were seen in patients of the viral than in the non-viral groups. Most of the significant correlations of liver function parameters were observed with TNF-α in both the viral and non-viral groups, followed by IL-17A. Increased TNF-α and IL-17A presented potential risk factors for disease progression to cirrhosis of Child class C.

Potential biomarkers to predict return to fertility after discontinuation of female contraceptives-looking to the future

Nowadays there are multiple types of contraceptive methods, from reversible to permanent, for those choosing to delay pregnancy. Misconceptions about contraception and infertility are a key factor for discontinuation or the uptake of family planning methods. Regaining fertility (the ability to conceive) after contraceptive discontinuation is therefore pivotal. Technical studies to date have evaluated return to fertility by assessing pregnancy as an outcome, with variable results, or return to ovulation as a surrogate measure by assessing hormone levels (such as progesterone, LH, FSH) with or without transvaginal ultrasound. In general, relying on time to pregnancy as an indicator of return to fertility following contraceptive method discontinuation can be problematic due to variable factors independent of contraceptive effects on fertility, hormone clearance, and fertility recovery. Since the ability to conceive after contraceptive method discontinuation is a critical factor influencing product uptake, it is important to have robust biomarkers that easily and accurately predict the timing of fertility return following contraception and isolate that recovery from extrinsic and circumstantial factors. The main aim of this review is to summarize the current approaches, existing knowledge, and gaps in methods of evaluating return-to-fertility as well as to provide insights into the potential of new biomarkers to more accurately predict fertility restoration after contraceptive discontinuation. Biomarker candidates proposed in this document include those associated with folliculogenesis, cumulus cell expansion, follicular rupture and ovulation, and endometrial transport and receptivity which have been selected and scored on predefined criteria meant to evaluate their probable viability for advancement. The review also describes limitations, regulatory requirements, and a potential path to clinically testing these selected biomarkers. It is important to understand fertility restoration after contraceptive method discontinuation to provide users and health providers with accurate evidence-based information. Predictive biomarkers, if easy and low-cost, have the potential to enable robust evaluation of RTF, and provide potential users the information they desire when selecting a contraceptive method. This could lead to expanded uptake and continuation of modern contraception and inform the development of new contraceptive methods to widen user's family planning choices.

Inflammatory Mediators of Endothelial Dysfunction

Endothelial dysfunction (ED) is characterized by imbalanced vasodilation and vasoconstriction, elevated reactive oxygen species (ROS), and inflammatory factors, as well as deficiency of nitric oxide (NO) bioavailability. It has been reported that the maintenance of endothelial cell integrity serves a significant role in human health and disease due to the involvement of the endothelium in several processes, such as regulation of vascular tone, regulation of hemostasis and thrombosis, cell adhesion, smooth muscle cell proliferation, and vascular inflammation. Inflammatory modulators/biomarkers, such as IL-1α, IL-1β, IL-6, IL-12, IL-15, IL-18, and tumor necrosis factor α, or alternative anti-inflammatory cytokine IL-10, and adhesion molecules (ICAM-1, VCAM-1), involved in atherosclerosis progression have been shown to predict cardiovascular diseases. Furthermore, several signaling pathways, such as NLRP3 inflammasome, that are associated with the inflammatory response and the disrupted H2S bioavailability are postulated to be new indicators for endothelial cell inflammation and its associated endothelial dysfunction. In this review, we summarize the knowledge of a plethora of reviews, research articles, and clinical trials concerning the key inflammatory modulators and signaling pathways in atherosclerosis due to endothelial dysfunction.

Interleukin-18 signaling promotes activation of hepatic stellate cells in mouse liver fibrosis

BACKGROUND AND AIMS

Nucleotide-binding oligomerization domain-like receptor-family pyrin domain-containing 3 (NLRP3) inflammasome activation has been shown to result in liver fibrosis. Mechanisms and downstream signaling remain incompletely understood. Here, we studied the role of IL-18 in hepatic stellate cells (HSCs), and its impact on liver fibrosis.

APPROACH AND RESULTS

We observed significantly increased serum levels of IL-18 (128.4 pg/ml vs. 74.9 pg/ml) and IL-18 binding protein (BP; 46.50 ng/ml vs. 15.35 ng/ml) in patients with liver cirrhosis compared with healthy controls. Single cell RNA sequencing data showed that an immunoregulatory subset of murine HSCs highly expresses Il18 and Il18r1 . Treatment of cultured primary murine HSC with recombinant mouse IL-18 accelerated their transdifferentiation into myofibroblasts. In vivo , IL-18 receptor-deficient mice had reduced liver fibrosis in a model of fibrosis induced by HSC-specific NLRP3 overactivation. Whole liver RNA sequencing analysis from a murine model of severe NASH-induced fibrosis by feeding a choline-deficient, L-amino acid-defined, high fat diet showed that genes related to IL-18 and its downstream signaling were significantly upregulated, and Il18-/- mice receiving this diet for 10 weeks showed protection from fibrotic changes with decreased number of alpha smooth muscle actin-positive cells and collagen deposition. HSC activation triggered by NLRP3 inflammasome activation was abrogated when IL-18 signaling was blocked by its naturally occurring antagonist IL-18BP. Accordingly, we observed that the severe inflammatory phenotype associated with myeloid cell-specific NLRP3 gain-of-function was rescued by IL-18BP.

CONCLUSIONS

Our study highlights the role of IL-18 in the development of liver fibrosis by its direct effect on HSC activation identifying IL-18 as a target to treat liver fibrosis.

Overview of Cellular and Soluble Mediators in Systemic Inflammation Associated with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is currently the most prevalent chronic liver disease in Western countries, affecting approximately 25% of the adult population. This condition encompasses a spectrum of liver diseases characterized by abnormal accumulation of fat in liver tissue (non-alcoholic fatty liver, NAFL) that can progress to non-alcoholic steatohepatitis (NASH), characterized by the presence of liver inflammation and damage. The latter form often coexists with liver fibrosis which, in turn, may progress to a state of cirrhosis and, potentially, hepatocarcinoma, both irreversible processes that often lead to the patient's death and/or the need for liver transplantation. Along with the high associated economic burden, the high mortality rate among NAFLD patients raises interest, not only in the search for novel therapeutic approaches, but also in early diagnosis and prevention to reduce the incidence of NAFLD-related complications. In this line, an exhaustive characterization of the immune status of patients with NAFLD is mandatory. Herein, we attempted to gather and compare the current and relevant scientific evidence on this matter, mainly on human reports. We addressed the current knowledge related to circulating cellular and soluble mediators, particularly platelets, different leukocyte subsets and relevant inflammatory soluble mediators.

Interleukin-18 and IL-18BP in inflammatory dermatological diseases

Interleukin (IL)-18, an interferon-γ inducer, belongs to the IL-1 family of pleiotropic pro-inflammatory factors, and IL-18 binding protein (IL-18BP) is a native antagonist of IL-18 in vivo, regulating its activity. Moreover, IL-18 exerts an influential function in host innate and adaptive immunity, and IL-18BP has elevated levels of interferon-γ in diverse cells, suggesting that IL-18BP is a negative feedback inhibitor of IL-18-mediated immunity. Similar to IL-1β, the IL-18 cytokine is produced as an indolent precursor that requires further processing into an active cytokine by caspase-1 and mediating downstream signaling pathways through MyD88. IL-18 has been implicated to play a role in psoriasis, atopic dermatitis, rosacea, and bullous pemphigoid in human inflammatory skin diseases. Currently, IL-18BP is less explored in treating inflammatory skin diseases, while IL-18BP is being tested in clinical trials for other diseases. Thereby, IL-18BP is a prospective therapeutic target.

Revealing immune infiltrate characteristics and potential immune-related genes in hepatic fibrosis: based on bioinformatics, transcriptomics and q-PCR experiments

Background

The occurrence and progression of hepatic fibrosis (HF) is accompanied by inflammatory damage. Immune genes play a pivotal role in fibrogenesis and inflammatory damage in HF by regulating immune cell infiltration. However, the immune mechanisms of HF are inadequately studied. Therefore, this research aims to identify the immune genes and biological pathway which involved in fibrosis formation and inflammatory damage in HF and explore immune target-based therapeutics for HF.

Methods

The expression dataset GSE84044 of HF was downloaded from the GEO database. The crucial module genes for HF were screened according to weighted gene co-expression network analysis (WGCNA). The crucial module genes were mapped to immune-related genes obtained from the ImmPort database to obtain the hepatic fibrosis immune genes (HFIGs). In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses were performed on HFIGs. Then, the protein-protein interaction (PPI) network was conducted on HFIGs and hub genes were identified from the PPI network. Moreover, immune infiltration analysis was performed to identified correlation between hub gene and immune cell infiltration. To verify the reliability of the GSE84044 expression profile data analysis, a rat model of CCl4-induced HF was established, followed by transcriptome sequencing and immunofluorescence analysis and quantitative reverse transcription (q-PCR) experiments were performed in HF rats and normal rat liver tissues. Finally, CMAP platform was used to explore immune target-based therapeutics for HF.

Results

In the bioinformatics analysis of GSE84044 data, 98 HFIGs were screened. These genes were mainly involved in inflammation-related biological pathways such as NOD-like receptor signaling pathway, NF-kappa B signaling pathway, Toll-like receptor signaling pathway and PI3K-Akt signaling pathway. From the PPI network, 10 hub genes were identified, including CXCL8, IL18, CXCL10, CD8A, IL7, PTPRC, CCL5, IL7R, CXCL9 and CCL2. Immune infiltration analysis showed that immune cells like neutrophils, natural killer (NK) cells, macrophages M1 and macrophages M2 were significantly correlated with the hepatic fibrosis process and hub gene expression was significantly correlated with these immune cells. Notably, most of the biological pathways HFIGs riched and all the hub gene expression except CXCL8 were validated in subsequent transcriptome and qRCR experiments. Finally, 15 small molecule compounds with the potential to reverse the high expression of hub genes were screen out as potential therapeutic agents for HF.

Conclusion

The immune genes CXCL8, IL18, CXCL10, CD8A, IL7, PTPRC, CCL5, IL7R, CXCL9 and CCL2 may play an essential role in the fibrosis formation and inflammatory damage in HF. The outcomes of this research provide a basis for the study of the immune mechanisms of HF and contribute to the diagnosis and prevention and treatment of HF in clinical practice.

Interleukin-18 in metabolism: From mice physiology to human diseases

Interleukin-18 (IL-18) is a classical member of the IL-1 superfamily of cytokines. As IL-1β, IL-18 precursor is processed by inflammasome/caspase-1 into a mature and biologically active form. IL-18 binds to its specific receptor composed of two chains (IL-18Rα and IL-18Rβ) to trigger a similar intracellular signaling pathway as IL-1, ultimately leading to activation of NF-κB and inflammatory processes. Independently of this IL-1-like signaling, IL-18 also specifically induces IFN-γ production, driving the Th1 immune response. In circulation, IL-18 binds to the IL-18 binding protein (IL-18BP) with high affinity, letting only a small fraction of free IL-18 able to trigger receptor-mediated signaling. In contrast to other IL-1 family members, IL-18 is produced constitutively by different cell types, suggesting implications in normal physiology. If the roles of IL-18 in inflammatory processes and infectious diseases are well described, recent experimental studies in mice have highlighted the action of IL-18 signaling in the control of energy homeostasis, pancreatic islet immunity and liver integrity during nutritional stress. At the same time, clinical observations implicate IL-18 in various metabolic diseases including obesity, type 1 and 2 diabetes and nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH). In the present review, we summarize and discuss both the physiological actions of IL-18 in metabolism and its potential roles in pathophysiological mechanisms leading to the most common human metabolic disorders, such as obesity, diabetes and NAFLD/NASH.

Functional roles of cytokines in infectious disease associated colorectal carcinogenesis

Infection processes induce various soluble factors that are carcinogens in humans; therefore, research into the soluble factors of chronic disease released from cells that have been infected with parasites is warranted. Parasitic infections in host cells release high levels of IFNγ. Studies have hypothesised that parasitosis-associated carcinogenesis might be analogous to colorectal cancers developed from inflammatory bowel diseases, whereby various cytokines and chemokines are secreted during chronic inflammation. IL-18 and IL-21 are other factors that might be involved in the development of colorectal cancer in schistosomiasis patients and patients with other infections. IL-21 has profound effects on tumour growth and immunosurveillance of colitis-associated tumourigenesis, thereby emphasising its involvement in the pathogenesis of colorectal cancer. The prominent role of IL-21 in antitumour effects greatly depends on the enhanced cytolytic activity of NK cells and the pathogenic role of IL-21, which is often associated with enhanced risks of cancer and chronic inflammatory processes. As IL-15 is also related to chronic disease, it is believed to also play a role in the antitumour effect of colorectal carcinogenesis. IL-15 generates and maintains long-term CD8⁺ T cell immunity against T. gondii to control the infection of intracellular pathogens. The lack of IL-15 in mice contributes to the downregulation of the IFNγ-producing CD4⁺ T cell response against acute T. gondii infection. IL-15 induces hyperplasia and supports the progressive growth of colon cancer via multiple functions. The limited role of IL-15 in the development of NK and CD8⁺ T cells suggests that there may be other cytokines compensating for the loss of the IL-15 gene.

Effects and mechanisms of SGLT2 inhibitors on the NLRP3 inflammasome, with a focus on atherosclerosis

Atherosclerosis is a lipid-driven chronic inflammatory disease that is widespread in the walls of large and medium-sized arteries. Its pathogenesis is not fully understood. The currently known pathogenesis includes activation of pro-inflammatory signaling pathways in the body, increased oxidative stress, and increased expression of cytokines/chemokines. In the innate immune response, inflammatory vesicles are an important component with the ability to promote the expression and maturation of inflammatory factors, release large amounts of inflammatory cytokines, trigger a cascade of inflammatory responses, and clear pathogens and damaged cells. Studies in the last few years have demonstrated that NLRP3 inflammatory vesicles play a crucial role in the development of atherosclerosis as well as its complications. Several studies have shown that NLRP3 binding to ligands promotes inflammasome formation, activates caspase-1, and ultimately promotes its maturation and the maturation and production of IL-1β and IL-18. IL-1β and IL-18 are considered to be the two most prominent inflammatory cytokines in the inflammasome that promote the development of atherosclerosis. SGLT2 inhibitors are novel hypoglycemic agents that also have significant antiatherosclerotic effects. However, their exact mechanism is not yet clear. This article is a review of the literature on the effects and mechanisms of SGLT2 inhibitors on the NLRP3 inflammasome, focusing on their role in antiatherosclerosis.

Hepatic encephalopathy and depression in chronic liver disease: is the common link systemic inflammation?

Hepatic encephalopathy and depression share a number of clinical features, such as cognitive impairment and psychomotor retardation, and are highly prevalent in patients with chronic liver disease. Both conditions signify a poor prognosis, carry an increased mortality and are major determinants of reduced health related quality of life. The pathophysiology of hepatic encephalopathy is complex. Whilst cerebral accumulation of ammonia is well-recognised as being central to the development of hepatic encephalopathy, systemic inflammation, which acts in synergy with hyperammonaemia, is emerging as a key driver in its development. The pro-inflammatory state is also widely documented in depression, and peripheral to brain communication occurs resulting in central inflammation, behavioural changes and depressive symptoms. Gut dysbiosis, with a similar reduction in beneficial bacteria, increase in pathogens and decreased bacterial diversity, has been observed in both hepatic encephalopathy and depression, and it may be that the resultant increased bacterial translocation causes their shared inflammatory pathophysiology. Whilst the literature on a positive association between hepatic encephalopathy and depression in cirrhosis remains to be substantiated, there is evolving evidence that treatment with psychobiotics may be of dual benefit, improving cognition and mood in cirrhosis.

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.

The imbalance of peripheral interleukin-18 and transforming growth factor-β1 levels in patients with cirrhosis and esophageal varices

INTRODUCTION

The presence of esophageal varices in liver cirrhosis indicates clinically significant portal hypertension (PH), that results from structural and dynamic changes in the liver and systemic circulation including the activation of several fibrotic and inflammatory pathways. We assessed if interleukin-18 (IL-18) and transforming growth factor-β1 (TGF-β1) serum levels can be used as PH markers and reflect its severity.

MATERIAL AND METHODS

IL-18 and TGF-β1 peripheral blood levels were analyzed in 83 cirrhotic patients with esophageal varices compared to healthy individuals, in relation to MELD and Child-Pugh scores, laboratory and Doppler ultrasound parameters, and non-selective beta-blocker therapy (NSBB).

RESULTS

IL-18 concentration was significantly higher in cirrhotic patients, while TGF-β1 concentration was lower than in controls. MELD score correlated positively with IL-18 levels and negatively with TGF-β1 levels. IL-18 levels correlated positively with bilirubin, INR, ALT and AST levels, and negatively with albumin levels and erythrocyte count. TGF-β1 levels correlated positively with platelet count, leukocyte, and erythrocyte count, and negatively with bilirubin levels and prothrombin time. Moreover, significant correlations were found: between IL and 18 levels and portal, mesenteric superior, and splenic vein velocity, and between TGF-β1 levels and splenic vein diameter and spleen size. In a subgroup of patients, IL-18 levels significantly decreased after NSBB.

CONCLUSION

The observed imbalance of peripheral IL-18 and TGF-β1 levels indicates clinically significant PH associated with the presence of esophageal varices in cirrhosis. The correlation of IL-18 levels with liver failure indicators and decrease with NSBB suggest an important role of IL-18 in disease progression and its potential use as noninvasive test for PH assessment.

Possible involvement of interleukin-18 in the pathology of hepatobiliary adverse effects related to treatment with ceritinib

Background

Ceritinib demonstrated a statistically significant effect on the progression-free survival versus chemotherapy in patients with advanced anaplastic lymphoma kinase (ALK) rearrangement in non-small cell lung cancer (NSCLC) as the first therapy or after previous treatment with crizotinib and one or two prior chemotherapy regimens in global phase 3 studies. However, some serious adverse effects related to ceritinib therapy were reported across these clinical studies. Among them, a grade 3 and 4 increase in hepatobiliary enzymes was one of the common adverse events related to treatment with ceritinib. However, the pathology remains unclear. Previously, increased Interleukin (IL)-18 was observed in both biliary duct disease and liver disease. Therefore, we hypothesized that IL-18 is involved in the pathology of hepatobiliary adverse effects related to treatment with ceritinib and evaluated the serum IL-18.

Case presentation

The patient was a 53-year-old Japanese woman that we previously reported as having severe hepatobiliary adverse effects related to ceritinib therapy. Laboratory data, CT and MRI were obtained at each time point. IL-18 was evaluated by ELISA method at each time point. Immunochemical staining of liver tissue was performed as a standard protocol using antibodies against IL-18. Our records showed that the levels of serum IL-18 increased from the early stage of hepatobiliary adverse effects related to the treatment with ceritinib and were became worse with an increase in hepatobiliary enzymes and the progression of imaging abnormalities in the bile duct. Furthermore, IL-18 positive cells were detected in the inflammatory sites around the interlobular bile duct of the liver tissue.

Conclusion

Our case report shows that the increase of serum IL-18 had a positive correlation with the progression of severe hepatobiliary adverse effects related to treatment with ceritinib and the involvement of IL-18 in the hepatobiliary inflammation by pathological evaluation. These results suggest that IL-18 could be a useful surrogate marker for the hepatobiliary toxicity of ceritinib. However, this is only one case report and further prospective observations will complement our data in the future.

Interleukin-18: Biological properties and role in disease pathogenesis

Initially described as an interferon (IFN)γ‐inducing factor, interleukin (IL)‐18 is indeed involved in Th1 and NK cell activation, but also in Th2, IL‐17‐producing γδ T cells and macrophage activation. IL‐18, a member of the IL‐1 family, is similar to IL‐1β for being processed by caspase 1 to an 18 kDa‐biologically active mature form. IL‐18 binds to its specific receptor (IL‐18Rα, also known as IL‐1R7) forming a low affinity ligand chain. This is followed by recruitment of the IL‐18Rβ chain. IL‐18 then uses the same signaling pathway as IL‐1 to activate NF‐kB and induce inflammatory mediators such as adhesion molecules, chemokines and Fas ligand. IL‐18 also binds to the circulating high affinity IL‐18 binding protein (BP), such as only unbound free IL‐18 is active. IL‐18Rα may also bind IL‐37, another member of the IL‐1 family, but in association with the negative signaling chain termed IL‐1R8, which transduces an anti‐inflammatory signal. IL‐18BP also binds IL‐37 and this acts as a sink for the anti‐inflammatory properties of IL‐37. There is now ample evidence for a role of IL‐18 in various infectious, metabolic or inflammatory diseases such as influenza virus infection, atheroma, myocardial infarction, chronic obstructive pulmonary disease, or Crohn's disease. However, IL‐18 plays a very specific role in the pathogenesis of hemophagocytic syndromes (HS) also termed Macrophage Activation Syndrome. In children affected by NLRC4 gain‐of‐function mutations, IL‐18 circulates in the range of tens of nanograms/mL. HS is treated with the IL‐1 Receptor antagonist (anakinra) but also specifically with IL‐18BP. Systemic juvenile idiopathic arthritis or adult‐onset Still's disease are also characterized by high serum IL‐18 concentrations and are treated by IL‐18BP.

Predictive Role of Interleukin-18 in Liver Steatosis in Obese Children

INTRODUCTION

Interleukin-18 (IL-18) is a proinflammatory cytokine associated with metabolic syndrome (MS). Nonalcoholic fatty liver disease (NAFLD) can be recognized as a feature of MS.

MATERIAL AND METHODS

Serum IL-18 concentration was evaluated in serum of 108 obese children, determined with ELISA, and referred to degree of liver steatosis in USG or total intrahepatic lipid content assessed by magnetic resonance proton spectroscopy (¹HMRS).

RESULTS

Fatty liver was confirmed in 89 children with USG and in 72 with ¹HMRS. IL-18 concentration demonstrated significantly higher values in patients than in controls. Significant correlations between IL-18 and ALT, GGT, triglycerides, hsCRP, and the degree of liver steatosis were demonstrated. NAFLD children had significantly higher level of IL-18, ALT, GGT, HOMA-IR, waist circumference, and total lipids content in ¹HMRS than other obese children. IL-18 level was also significantly higher in obese children with advanced liver steatosis. Measurement of serum IL-18 showed ability to differentiate children with fatty liver from those without steatosis.

CONCLUSION

Elevated serum IL-18 concentration and its correlation with hepatocyte injury, systemic inflammation, and degree of liver steatosis support role in NAFLD pathomechanism. IL-18 can be considered to play a role in predicting advanced liver steatosis and fatty liver in obese children.

Overview of the IL-1 family in innate inflammation and acquired immunity

The interleukin-1 (IL-1) family of cytokines and receptors is unique in immunology because the IL-1 family and Toll-like receptor (TLR) families share similar functions. More than any other cytokine family, the IL-1 family is primarily associated with innate immunity. More than 95% of living organisms use innate immune mechanisms for survival whereas less than 5% depend on T- and B-cell functions. Innate immunity is manifested by inflammation, which can function as a mechanism of host defense but when uncontrolled is detrimental to survival. Each member of the IL-1 receptor and TLR family contains the cytoplasmic Toll-IL-1-Receptor (TIR) domain. The 50 amino acid TIR domains are highly homologous with the Toll protein in Drosophila. The TIR domain is nearly the same and present in each TLR and each IL-1 receptor family. Whereas IL-1 family cytokine members trigger innate inflammation via IL-1 family of receptors, TLRs trigger inflammation via bacteria, microbial products, viruses, nucleic acids, and damage-associated molecular patterns (DAMPs). In fact, IL-1 family member IL-1a and IL-33 also function as DAMPs. Although the inflammatory properties of the IL-1 family dominate in innate immunity, IL-1 family member can play a role in acquired immunity. This overview is a condensed update of the IL-1 family of cytokines and receptors.

Imbalanced production of IL-18 and its antagonist in human diseases, and its implications for HIV-1 infection

IL-18 is a pleiotropic and multifunctional cytokine that belongs to the IL-1 family. It is produced as a biologically inactive precursor, which is cleaved into its active mature form mainly by caspase-1. The caspase becomes active from its inactive precursor (procaspase-1) upon assembly of an inflammasome. Because of IL-18's potential pro-inflammatory and tissue destructive effects, its biological activities are tightly controlled in the body by its naturally occurring antagonist called IL-18BP. The antagonist is produced in the body both constitutively and in response to an increased production of IL-18 as a negative feedback mechanism. Under physiological conditions, most of IL-18 in the circulation is bound with IL-18BP and is inactive. However, an imbalance in the production of IL-18 and its antagonist (an increase in the production of IL-18 with a decrease, no increase or an insufficient increase in the production of IL-18BP) has been described in many chronic inflammatory diseases in humans. The imbalance results in an increase in the concentrations of free IL-18 (unbound with its antagonist) resulting in increased biological activities of the cytokine that contribute towards pathogenesis of the disease. In this article, we provide an overview of the current biology of IL-18 and its antagonist, discuss how the imbalance occurs in HIV infections and how it contributes towards development of AIDS and other non-AIDS-associated clinical conditions occurring in HIV-infected individuals undergoing combination anti-retroviral therapy (cART). Finally, we discuss challenges facing immunotherapeutic strategies aimed at restoring balance between IL-18 and its antagonist in these patients.

Temporal dynamics of inflammatory cytokines/chemokines during sofosbuvir and ribavirin therapy for genotype 2 and 3 hepatitis C infection

The analysis of inflammatory cytokines and chemokines produced during hepatitis C virus (HCV) infection has advanced our understanding of viral-host interactions and identified predictors of treatment response. Administration of interferons (IFNs) made it difficult to interpret biomarkers of immune activation during treatment. Direct-acting antiviral (DAA) regimens without IFN are now being used to treat HCV with excellent efficacy. To gain insight into HCV-host interactions occurring before, during, and after HCV treatment, we performed a case-control study that measured serial plasma levels of IFN-γ-inducible protein 10 (IP-10), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 1 beta (MIP-1β), and interleukin-18 (IL-18) in 131 patients with chronic HCV treated with sofosbuvir (SOF) plus ribavirin (RBV). A linear regression analysis using baseline factors identified strong positive associations between elevated alanine aminotransferase and pretreatment IP-10 and between the presence of cirrhosis and elevated pretreatment IL-18. Mean IP-10, MCP-1, MIP-1β, and IL-18 levels all decline on therapy, but display different dynamics late in treatment and after cessation of therapy. On treatment, IP-10 and MIP-1β levels were significantly higher in individuals who achieved sustained virological response (SVR). Logistic regression analyses examining treatment response in all patients demonstrated significant associations between higher baseline MIP-1β levels and smaller decreases in MIP-1β early in treatment and SVR. Higher early MIP-1β levels were also significantly associated with SVR in subsets of patients with cirrhosis and individuals with genotype 3 (GT3) infection, two factors associated with decreased responsiveness to treatment.

CONCLUSION

Changes in IP-10 levels mirror HCV RNA, suggesting that IP-10 is an indicator of innate immune viral recognition. MIP-1β levels remain elevated in GT2/3 patients who achieved SVR, suggesting differential immune activation in those who respond to SOF/RBV therapy and a potential role in predicting treatment responses.

Transcriptional analysis identifies key genes involved in metabolism, fibrosis/tissue repair and the immune response against Fasciola hepatica in sheep liver

BACKGROUND

Although fascioliasis has been relatively well studied, little is known about the molecular basis of this disease. This is particularly relevant, considering the very different response that sheep have to Fasciola hepatica relative to cattle. The acute phase of this disease is severe in sheep, whereas chronic fascioliasis is more common in cattle.

METHODS

To begin to explore the host-response to Fasciola in sheep and improve the understanding of the host-pathogen interactions during the parasite's migration through liver parenchyma to the bile duct, we used RNA sequencing (RNA-seq) to investigate livers from sheep infected for eight weeks compared with those from uninfected controls.

RESULTS

This study identified 572 and 42 genes that were up- and down-regulated, respectively, in infected livers relative to uninfected controls. Our molecular findings provide significant new insights into the mechanisms linked to metabolism, fibrosis and tissue-repair in sheep, and highlight the relative importance of specific components of immune response pathways, which appear to be driven toward a suppression of inflammation.

CONCLUSIONS

This study is, to our knowledge, the first detailed investigation of the transcriptomic responses in the liver tissue of any host to F. hepatica infection. It defines the involvement of specific genes associated with the host's metabolism, immune response and tissue repair/regeneration, and highlights an apparent overlapping function of many genes involved in these processes.

Cirrhosis-associated immune dysfunction: distinctive features and clinical relevance

The term cirrhosis-associated immune dysfunction refers to the main syndromic abnormalities of immune function, immunodeficiency and systemic inflammation that are present in cirrhosis. The course of advanced cirrhosis, regardless of its aetiology, is complicated by cirrhosis-associated immune dysfunction and this constitutes the pathophysiological hallmark of an increased susceptibility to bacterial infection, distinctive of the disease. Cirrhosis impairs the homeostatic role of the liver in the systemic immune response. Damage to the reticulo-endothelial system compromises the immune surveillance function of the organ and the reduced hepatic synthesis of proteins, involved in innate immunity and pattern recognition, hinders the bactericidal ability of phagocytic cells. Systemic inflammation, in form of activated circulating immune cells and increased serum levels of pro-inflammatory cytokines, is the result of persistent episodic activation of circulating immune cells from damage-associated molecular patterns, released from necrotic liver cells and, as cirrhosis progresses, from pathogen-associated molecular patterns, released from the leaky gut. Cirrhosis-associated immune dysfunction phenotypes switch from predominantly "pro-inflammatory" to predominantly "immunodeficient" in patients with stable ascitic cirrhosis and in patients with severely decompensated cirrhosis and extra-hepatic organ failure (e.g. acute-on-chronic liver failure), respectively. These cirrhosis-associated immune dysfunction phenotypes represent the extremes of a spectrum of reversible dynamic events that take place during the course of cirrhosis. Systemic inflammation can affect the functions of tissue somatic cells and modify the clinical manifestation of cirrhosis. The best characterized example is the contribution of systemic inflammation to the haemodynamic derangement of cirrhosis, which correlates negatively with prognosis.

Progression of autoimmune hepatitis is mediated by IL-18-producing dendritic cells and hepatic CXCL9 expression in mice

Clinical manifestations of autoimmune hepatitis (AIH) range from mild chronic to acute, sometimes fulminant hepatitis. However, it is unknown how the progression to fatal hepatitis occurs. We developed a mouse model of fatal AIH by inducing a concurrent loss of forkhead box P3(+) regulatory T cells and programmed cell death-1 (PD-1)-mediated signaling. In this model, dysregulated follicular helper T cells in the spleen are responsible for the induction, and the C-C chemokine receptor 6/C-C chemokine ligand 20 axis is crucial for the migration of these T cells into the liver. Using this fatal AIH model, we aimed to clarify key molecules triggering fatal AIH progression. During progression, T-bet together with interferon (IFN)-γ and C-X-C chemokine receptor (CXCR)3 were highly expressed in the inflamed liver, suggesting helper T (Th)1-type inflammation. T cells that dominantly expanded in the spleen and the inflamed liver were CXCR3-expressing CD8(+) T cells; depletion of these CD8(+) T cells suppressed AIH progression. Expression of one CXCR3 ligand, chemokine (C-X-C motif) ligand (CXCL)9, was elevated in the liver. CXCL9-expressing macrophages/Kupffer cells were colocalized with infiltrating T cells, and in vivo administration of anti-CXCL9 suppressed AIH progression. In addition, serum levels of interleukin (IL)-18, but not IL-1β, were elevated during progression, and dendritic cells in the spleen and liver highly produced IL-18. In vivo administration of anti-IL-18R suppressed the increase of splenic CXCR3(+) T cells and the progression to fatal AIH. Moreover, tumor necrosis factor alpha, but not IFN-γ, was involved in up-regulating CXCL9 in the liver and for increased serum levels of IL-18.

CONCLUSION

These data suggest that, in our mouse model, fatal progression of AIH is mediated by IL-18-dependent differentiation of T cells into Th1 cells and effector T cells, respectively, and that CXCR3-CXCL9 axis-dependent migration of those T cells is crucial for fatal progression.

Macrophage activation syndrome and cytokine-directed therapies

Macrophage activation syndrome (MAS) is an episode of overwhelming inflammation that occurs most commonly in children with systemic juvenile idiopathic arthritis (SJIA). It is characterized by expansion and activation of T lymphocytes and hemophagocytic macrophages and bears great similarity to hemophagocytic lymphohistiocytosis (HLH). This disorder has substantial morbidity and mortality, and there is frequently a delay in recognition and initiation of treatment. Here, we will review what is known about the pathogenesis of MAS and, in particular, its similarities to HLH. The development of MAS is characterized by a cytokine storm, with the elaboration of numerous pro-inflammatory cytokines. We will examine the evidence for various cytokines in the initiation and pathogenesis of MAS and discuss how new biologic therapies may alter the risk of MAS. Finally, we will review current treatment options for MAS and examine how cytokine-directed therapy could serve as novel treatment modalities.

Interleukin-18, more than a Th1 cytokine

Together with IL-12 or IL-15, interleukin-18 (IL-18) plays a major role in the production of interferon-γ from T-cells and natural killer cells; thus, IL-18 is considered to have a major role in the Th1 response. However, without IL-12, IL-18 is proinflammatory in an IFNγ independent manner. IL-18 is a member of the IL-1 family of cytokines and similar to IL-1β, the cytokine is synthesized as an inactive precursor requiring processing by caspase-1 into an active cytokine. IL-18 is also present as an integral membrane protein but requires caspase-1 for full activity in order to induce IFNγ. Uniquely, unlike IL-1β, the IL-18 precursor is constitutively present in nearly all cells in healthy humans and animals. The activity of IL-18 is balanced by the presence of a high-affinity, naturally occurring IL-18 binding protein (IL-18BP). In humans, increased disease severity can be associated with an imbalance of IL-18 to IL-18BP such that the levels of free IL-18 are elevated in the circulation. Increasing number of studies have expanded the role of IL-18 in mediating inflammation in animal models of disease using the IL-18BP, IL-18 deficient mice, neutralization of IL-18 or deficiency in the IL-18 receptor alpha chain. A role for IL-18 has been implicated in several autoimmune diseases, myocardial function, emphysema, metabolic syndromes, psoriasis, inflammatory bowel disease, macrophage activation syndrome, sepsis and acute kidney injury, although paradoxically, in some models of disease, IL-18 is protective. The IL-18BP has been used safely in humans and clinical trials of IL-18BP as well as neutralizing anti-IL-18 antibodies are being tested in various diseases.

Interleukin-18 and IL-18 binding protein

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines. Similar to IL-1β, IL-18 is synthesized as an inactive precursor requiring processing by caspase-1 into an active cytokine but unlike IL-1β, the IL-18 precursor is constitutively present in nearly all cells in healthy humans and animals. The activity of IL-18 is balanced by the presence of a high affinity, naturally occurring IL-18 binding protein (IL-18BP). In humans, increased disease severity can be associated with an imbalance of IL-18 to IL-18BP such that the levels of free IL-18 are elevated in the circulation. Increasing number of studies have expanded the role of IL-18 in mediating inflammation in animal models of disease using the IL-18BP, IL-18-deficient mice, neutralization of IL-18, or deficiency in the IL-18 receptor alpha chain. A role for IL-18 has been implicated in several autoimmune diseases, myocardial function, emphysema, metabolic syndromes, psoriasis, inflammatory bowel disease, hemophagocytic syndromes, macrophage activation syndrome, sepsis, and acute kidney injury, although in some models of disease, IL-18 is protective. IL-18 plays a major role in the production of interferon-γ from T-cells and natural killer cells. The IL-18BP has been used safely in humans and clinical trials of IL-18BP as well as neutralizing anti-IL-18 antibodies are in clinical trials. This review updates the biology of IL-18 as well as its role in human disease.

Interleukin-33 overexpression is associated with gamma-glutamyl transferase in biliary atresia

Interleukin-33 (IL-33) plays a crucial role in inflammation. However, it is not clear whether IL-33 levels are of clinical significance for patients with biliary atresia (BA). The purpose of this study was to determine correlations between serum IL-33 levels and the clinicopathologic features of BA. Serum samples were collected from 18 BA infants, 12 nonicteric choledochal cyst (CC) infants with normal liver function, and 10 healthy controls (HCs). Serum IL-33 levels were measured with an enzyme-linked immunosorbent assay (ELISA). Routine liver function tests were performed on the serum samples. qRT-PCR and Western blot analysis were used to detect IL-33 expression in BA liver biopsy tissues. Hepatic lobule localization of IL-33 expression in the hepatic lobule was conducted by immunohistochemistry (IHC). IL-33 levels in serum collected from BA infants were significantly elevated in comparison with CC and HC patients. Furthermore, the elevated serum levels of IL-33 in BA infants were correlated with gamma-glutamyl transferase (GGT) levels. The expression of IL-33 mRNA and protein levels were up-regulated in BA liver biopsy tissues in comparison with CC patients. IHC analysis revealed increased positive immunostaining for IL-33 in BA liver tissues as compared to that in CC tissues. These results suggest that IL-33 may play an important role in the pathogenesis of BA. In addition, the correlation of serum IL-33 levels with GGT levels may provide a novel marker for the diagnosis of BA.

IL-27 Regulates IL-18 binding protein in skin resident cells

IL-18 is an important mediator involved in chronic inflammatory conditions such as cutaneous lupus erythematosus, psoriasis and chronic eczema. An imbalance between IL-18 and its endogenous antagonist IL-18 binding protein (BP) may account for increased IL-18 activity. IL-27 is a cytokine with dual function displaying pro- and anti-inflammatory properties. Here we provide evidence for a yet not described anti-inflammatory mode of action on skin resident cells. Human keratinocytes and surprisingly also fibroblasts (which do not produce any IL-18) show a robust, dose-dependent and highly inducible mRNA expression and secretion of IL-18BP upon IL-27 stimulation. Other IL-12 family members failed to induce IL-18BP. The production of IL-18BP peaked between 48-72 h after stimulation and was sustained for up to 96 h. Investigation of the signalling pathway showed that IL-27 activates STAT1 in human keratinocytes and that a proximal GAS site at the IL-18BP promoter is of importance for the functional activity of IL-27. The data are in support of a significant anti-inflammatory effect of IL-27 on skin resident cells. An important novel property of IL-27 in skin pathobiology may be to counter-regulate IL-18 activities by acting on keratinocytes and importantly also on dermal fibroblasts.

The role of Kupffer cells in rat liver regeneration revealed by cell-specific microarray analysis

Liver regeneration after partial hepatectomy is a process with various types of cells involved. The role of Kupffer cells (KCs) in liver regeneration is still controversial. In this study we isolated KCs from regenerating liver and conducted cell-specific microarray analysis. The results demonstrated that the controversial role of KCs in liver regeneration could be explained with the expression patterns of TGF-α, IL-6, TNF, and possibly IL-18 during liver regeneration. IL-18 may play an important role in negative regulation of liver regeneration. The functional profiles of gene expression in KCs also indicated that KC signaling might play a negative role in cell proliferation: signaling genes were down regulated before cell division. Immune response genes in KCs were also down regulated during liver regeneration, demonstrating similar expression profiles to that of hepatocytes. The expression patterns of key genes in these functional categories were consistent with the temporal functional profiles.

Relationship between interleukin 18 polymorphisms and susceptibility to chronic hepatitis B virus infection

AIM

To identify the relationship between the tagging single nucleotide polymorphism sites (tagSNPs) of the Interleukin-18 (IL-18) gene and genetic susceptibility to chronic hepatitis B virus infection in Chinese patients.

METHODS

Five hundred and one cases of chronic hepatitis B virus (HBV) infection and 301 HBV natural clearance controls were studied. Two tagSNPs in the IL-18 gene (rs1946518A/C and rs574424C/G) were genotyped by the Multiplex Snapshot technique. The genotype and allele frequencies were calculated and analyzed.

RESULTS

In the genotypes of rs1946518, the AA type was present at a higher frequency in the patients compared to those in the controls. Odds ratio (OR) of the AA genotype for the comparison with that of the AC and the CC genotype was 1.537 (95% confidence intervals (CI): 1.116-2.218, P = 0.009 < 0.025). In phenotypes, the allele C at rs1946518 was of a significantly lower frequency in the patients with chronic hepatitis B than that in the controls (P = 0.017 < 0.025). OR of the allele A for the comparison with that of the allele C was 1.279 (95% CI: 1.045-1.567). As for the rs574424 genotypes, no significant difference in this genotype distribution or in this allele frequency between the patients and the control subjects was observed. No significant difference in the haplotype frequencies between the patients with chronic hepatitis B and HBV natural clearance individuals was displayed.

CONCLUSION

The data suggest that genotype AA and the allele A of the IL-18 at position rs1946518 are closely associated with the resistance to chronic hepatitis B and may be the dangerous gene. However, no statistical association was found between polymorphisms of rs574424 for IL-18 and hepatitis B.

Suppressive effects of interleukin-18 on liver function in rat liver allografts

BACKGROUND

Interleukin-18 (IL-18) is a potent proinflammatory cytokine that augments both innate and acquired immune responses. It is also a crucial regulator of lymphocyte production of interferon-γ (IFN-γ), which can promote acute cellular rejection of transplanted solid organs.

METHODS

To evaluate the role of IL-18 in liver transplantation, we constructed an adenoviral vector encoding IL-18 binding protein (Adex-IL18bp), which specifically suppressed the biologic activity of IL-18, and examined the effect of this suppression on liver allografts by using a high-responder rat model (ACI to Lewis) of orthotopic liver transplantation (OLTx). Donor rats were given one intravenous injection of Adex-IL18bp or Adex-LacZ (control vector) 2 d before OLTx.

RESULTS

Seven days after OLTx, overexpression of IL-18bp resulting from the adenovirus gene transfer was associated with significantly decreased serum alanine aminotransferase levels and less histologic hepatic injury in recipient rats with Adex-IL18bp-pretreated donors compared with Adex-LacZ controls. Adex-IL18bp pretreatment also significantly prolonged rat/allograft survival, inhibited expression of IFN-γ, and reduced levels (versus control values) of both CXCL10 and CX3CL1, which can be induced by IFN-γ.

CONCLUSION

These results suggest that IL-18 has an important role in liver allograft rejection through IFN-γ and chemokines and that specific suppression of IL-18 may improve liver function early after transplantation.

The association between adiponectin (+45T/G) and adiponectin receptor-2 (+795G/A) single nucleotide polymorphisms with cirrhosis in Iranian population

Adiponectin which possesses anti-inflammatory and insulin-sensitizing properties is elevated in blood circulation of liver cirrhosis patients. The genetic variations in the adiponectin gene can affect the circulating adiponectin level and stimulation of adiponectin receptor that may affect the activity of adiponectin. We investigated the effect of adiponectin single nucleotide polymorphisms (SNP) 45 T/G and adiponectin receptor-2 gene SNP 795G/A in cirrhotic Iranian population. A total of 97 cirrhotic patients and 128 healthy controls from Iranian population were genotyped for the adiponectin and adiponectin receptor 2 gene (+45T>G and 795G/A) by polymerase chain reaction-restriction fragment length polymorphism. G frequency was 21.1% versus 12.89% (P = 0.001) for SNP45, and G frequency was 75.8% versus 76.2% (P = 0.526) for SNP795G/A in the patients and control group, respectively. Based on our findings, the expression of the G allele at SNP45 is higher in the patient group compared with healthy subjects, suggesting that it may affect liver injury through changes in the plasma adiponectin level.

The inhibition of apoptosis by glycyrrhizin in hepatic injury induced by injection of lipopolysaccharide / D-galactosamine in mice

The inhibition of apoptosis by glycyrrhizin (GL) in hepatic injury induced by injection of lipopolysaccharide (LPS)/D-galactosamine (D-GalN) was examined in the present study. Morphological and biochemical analyses of LPS/D-GalN-induced mouse liver injury revealed that apoptosis occurred exclusively in injured hepatocytes of the centrilobular area. The degree of hepatic injury was associated with a substantial number of hepatocytes undergoing apoptosis. Transaminase levels were significantly increased at 6 to 8 h after the injection of LPS/D-GalN compared with controls. GL inhibited the elevation of serum transaminase levels when it was given to mice at 30 min before the administration of LPS/D-GalN. Morphological analyses using the TUNEL-method showed GL significantly reduced the number of TUNEL-labeled cells in acute hepatitis induced with LPS/D-GalN-treatment. Cells from the pericentral hepatic injury region were dissected out using a microdissection-method, and the DNA-ladder was clearly documented. Furthermore, results obtained through the TUNEL-method were confirmed with an oligonucleosome-bound DNA ELISA. From the current results, it seems reasonable to conclude that the protective role of GL in LPS/D-GalN-induced liver injury is performed through the inhibition of hepatic apoptosis.

Elevation of interleukin-18 in chronic hepatitis C: implications for hepatitis C virus pathogenesis

The outcome of hepatitis C virus (HCV) infection is determined by the interplay between the virus and the host immune response. Interleukin (IL)-18, an interferon-gamma-inducing factor, plays a critical role in the T helper type 1 (Th1) response required for host defence against viruses, and antibodies to IL-18 have been found to prevent liver damage in a murine model. The present study was conducted to investigate the possible role of IL-18 in the pathogenesis and persistence of HCV. IL-18 levels were measured in sera of 50 patients at various stages of HCV infection (resolved, chronic and cirrhosis) and compared with those of normal controls. IL-18 gene expression was studied in peripheral blood mononuclear cells (PBMC) from each group, and in liver biopsy tissue from patients with chronic hepatitis C. The mean levels of IL-18 in sera were markedly elevated in patients with chronic hepatitis and cirrhosis, and were reduced in patients with resolved HCV infection. The serum IL-18 concentrations were related to the Child-Pugh severity of liver disease in cirrhotic patients. There also existed a strong positive correlation of IL-18 levels with histological activity score and necrosis. IL-18 mRNA expression was significantly up-regulated in the PBMC of cirrhotic patients when compared with other groups, while in the liver, higher levels of IL-18 transcripts were expressed in patients with chronic hepatitis C. The results of our study indicate that IL-18 levels reflect the severity and activity of HCV infection, and may contribute to the pathogenesis and progression of liver disease associated with HCV.

Local and systemic interleukin-18 and interleukin-18-binding protein in children with inflammatory bowel disease

BACKGROUND

Interleukin-18 (IL-18) is increased in the inflamed mucosa of patients with Crohn's disease (CD). The balance between this pleiotropic proinflammatory cytokine and its natural inhibitor, IL-18-binding protein (IL-18BP), may contribute to the pathogenesis of inflammatory bowel disease (IBD).

METHODS

Serum and mucosal biopsies were collected from children with IBD, from children with celiac disease, and from controls. Biopsies were maintained in culture for 24 hours, and supernatant was collected. Serum and supernatant IL-18 and IL-18BPa concentrations were measured by immunoassay. Disease activity score (PCDAI) and standard serum inflammatory markers (albumin, platelets, ESR, and CRP) were recorded.

RESULTS

Serum IL-18 was greater in children with CD (537 pg/mL) than in controls (335 pg/mL; P < 0.05) but not in children with ulcerative colitis (UC) or IBD type unclassified (IBDU). Mucosal IL-18 was greater in children with CD and UC/IBDU than in controls (P < 0.01). Serum IL-18BPa was increased in children with CD compared with that in controls (3.9 versus 2.6 ng/mL; P < 0.05), but was not elevated in children with UC/IBDU. Furthermore, calculated free-serum IL-18 was elevated in CD, but not UC/IBDU, compared with that in controls (P = 0.001). Total and free-serum IL-18 were elevated in severe CD relative to in mild/moderate disease.

CONCLUSIONS

IL-18, produced in the colons of children with IBD, may contribute to local inflammatory changes. Systemic IL-18 level may be a useful indicator of gut inflammation. Furthermore, free IL-18 is greatly elevated in children with CD, suggesting that compensatory increases in IL-18BPa are insufficient. Further exploration of the role of this cytokine in the pathogenesis of IBD is now required.

Inhibitory effect of glycyrrhizin on lipopolysaccharide and d-galactosamine-induced mouse liver injury

The effects of glycyrrhizin isolated from licorice root were investigated on acute hepatitis induced by lipopolysaccharide (LPS) and d-galactosamine in mice. Serum alanine aminotransferase (ALT) activity was markedly increased 6 h to 8 h after administration of LPS/d-galactosamine. Levels in serum of cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10 and IL-12 reached a maximum by 2 h, whereas levels of IL-18, as well as of ALT, were maximal at 8 h. Glycyrrhizin (ED(50): 14.3 mg/kg) inhibited the increase in ALT levels when it was given to mice at 30 min before administration of LPS/d-galactosamine. Inflammatory responses, including infiltration of neutrophils and macrophages in the liver injury, were modulated by glycyrrhizin. Increases in ALT levels were reduced by an administration of glycyrrhizin at 10 min and 60 min but not 3 h, even after LPS/d-galactosamine treatment. However, glycyrrhizin had no effect on the production of TNF-alpha, IL-6, IL-10 and IL-12, whereas it significantly inhibited IL-18 production. Exogenous IL-18 further increased the elevation in ALT levels in mice treated with LPS/d-galactosamine. Glycyrrhizin completely suppressed the effect of IL-18 of increasing ALT levels. IL-18 was detected by immunohistochemistry in inflammatory cells such neutrophils and macrophages in liver injury. Glycyrrhizin reduced the responsiveness of cells to IL-18 in the liver injury. These results suggest that glycyrrhizin inhibits the LPS/d-galactosamine-induced liver injury through preventing inflammatory responses and IL-18 production. Furthermore, it seems that glycyrrhizin prevents IL-18-mediated inflammation in liver injury.

The tale of soluble receptors and binding proteins: from bench to bedside

Our approach of isolating proteins from a rich source of human proteins by ligand-affinity-chromatography enabled rapid and efficient isolation of not only soluble receptors corresponding to cell-associated receptors, but also independent binding-proteins and associated enzymes. No other approach would yield the latter. During the early 80's we prepared the tools and the infrastructure that enabled the subsequent 20 years of achievements. Thus we described eight soluble receptors (R) and binding proteins (BP) for various cytokines including the IL-6R, IFN-gammaR, TNFRI, TNFRII, LDLR, IFN-alpha/betaR, IL-18BP and IL-32BP identified as Proteinase 3. The isolation of the soluble IFN-alpha/beta receptor led to the cloning of its long sought cell surface ligand binding counterpart. We have established the concept that soluble receptors and binding proteins are normal constituents of body fluids in healthy individuals and that the levels of these biomarkers are modulated in various pathological situations. Each of these proteins contributed to basic science, one of them serves as a basis for therapy and some others are in various stages of clinical development.

The role of interleukin-18 in renal injury

Interleukin (IL)-18 is a relatively new pro-inflammatory cytokine, formerly known as interferon-gamma-inducing factor, which induces interferon-gamma production in T cells and natural killer cells. It is synthesized as a biologically inactive precursor, which requires cleavage into an active molecule by an intracellular cysteine protease similar to IL-1beta. This review examines the pro-inflammatory role of IL-18 in various types of renal injury (i.e., endotoxemia, cisplatin toxicity, allograft rejection, and ischemia-reperfusion injury) and explores the integral role of IL-12 in IL-18 function and activity.

Clinical and experimental approaches to the pathophysiology of interleukin-18 in cancer progression

Interleukin-18 (IL-18, interferon [IFN]-gamma-inducing factor) is a proinflammatory cytokine converted to a biologically active molecule by interleukin (IL)-1beta converting enzyme (caspase-1). A wide range of normal and cancer cell types can produce and respond to IL-18 through a specific receptor (IL-18R) belonging to the toll-like receptor family. The activity of IL-18 is regulated by IL-18-binding protein (IL-18bp), a secreted protein possessing the ability to neutralize IL-18 and whose blood level is affected by renal function and is induced by IFNgamma. IL-18 plays a central role in inflammation and immune response, contributing to the pathogenesis and pathophysiology of infectious and inflammatory diseases. Because immune-stimulating effects of IL-18 have antineoplastic properties, IL-18 has been proposed as a novel adjuvant therapy against cancer. However, IL-18 increases in the blood of the majority of cancer patients and has been associated with disease progression and, in some cancer types, with metastatic recurrence risk and poor clinical outcome and survival. Under experimental conditions, cancer cells can also escape immune recognition, increase their adherence to the microvascular wall and even induce production of angiogenic and tumor growth-stimulating factors via IL-18-dependent mechanism. This is particularly visible in melanoma cells. Thus, the role of IL-18 in cancer progression and metastasis remains controversial. This review examines the clinical correlations and biological effects of IL-18 during cancer development and highlights recent experimental insights into prometastatic and proangiogenic effects of IL-18 and the use of IL-18bp against cancer progression.

Increased serum and hepatic tissue levels of interleukin-18 in patients with fulminant hepatic failure

BACKGROUND

Fulminant hepatic failure is a serious clinical condition associated with a high mortality rate. Interleukin (IL)-18 is a pro-inflammatory cytokine that is associated with several inflammatory diseases. The purpose of the present paper was therefore to investigate whether IL-18 is elevated in patients with fulminant hepatic failure.

METHODS

Serum levels of IL-18 were measured in patients with fulminant hepatic failure before and after liver transplantation. Native liver tissue samples were collected and the tissue levels of IL-18 were determined. Liver tissues were stained immunohistochemically with antihuman IL-18 antibody. The serum levels of IL-1beta, IL-6, IL-8, IL-12, interferon-gamma, and tumor necrosis factor-alpha were also determined in patients with fulminant hepatic failure before and after liver transplantation.

RESULTS

Elevated levels of IL-18 in serum and hepatic tissue were observed in patients with fulminant hepatic failure. Native liver tissue samples were immunohistochemically positive for IL-18. Interleukin-18 levels were markedly reduced after liver replacement. No other inflammatory cytokines were substantially elevated in patients with fulminant hepatic failure.

CONCLUSION

The serum levels of IL-18 levels are elevated much more than those of other cytokines in patients with fulminant hepatic failure.

Potential role of interleukin-18 in liver disease associated with insulin resistance

OBJECTIVE

Interleukin (IL)-18 has been associated with obesity and insulin resistance, both risk factors for the development of liver disease, but the role of IL-18 in liver disease associated with insulin resistance is presently unknown. We hypothesized that circulating IL-18 would be related to serum concentrations of liver chemistry tests (LCTs) in apparently healthy subjects and wished to study whether this correlation was dependent on insulin sensitivity (S(I)).

RESEARCH METHODS AND PROCEDURES

One hundred six apparently healthy white men consecutively enrolled in a cross-sectional, population-based study dealing with S(I) in men were studied, and S(I) (minimal model analysis), LCTs (colorimetry), and IL-18 serum concentrations (immunoassay) were assessed.

RESULTS

Compared with subjects in the lowest quartile for serum IL-18, subjects in the highest quartile exhibited increased serum triglycerides and decreased S(I), in addition to higher serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (all p < 0.05). The direct association between both ALT and AST and IL-18 was further confirmed by examining the distribution of serum IL-18 by quartiles of ALT and AST. Subjects in the highest quartile for serum ALT and AST had higher IL-18 concentrations compared with subjects in the lowest quartile for these LCTs (both p = 0.01). In multiple regression analysis, IL-18, but not S(I), was an independent predictor of serum concentrations of ALT and AST, explaining 7% and 4% of their variance, respectively.

DISCUSSION

In summary, IL-18 serum concentrations are associated in apparently healthy humans with plasma concentrations of various LCTs. IL-18 could contribute to the development of liver disease associated with insulin resistance.

Circulating adiponectin reflects severity of liver disease but not insulin sensitivity in liver cirrhosis

BACKGROUND

The adipocytokine adiponectin has been proposed to play important roles in the regulation of energy homeostasis, insulin sensitivity and shows anti-inflammatory properties.

AIM

In this study we investigated the role of circulating adiponectin in different chronic liver diseases, its regulation by systemic anti-tumour necrosis factor (TNF)-alpha treatment and its hepatic metabolism.

PATIENTS AND METHODS

Plasma adiponectin levels were determined in 87 patients with liver cirrhosis of different aetiologies, seven patients with alcoholic steatohepatitis undergoing systemic anti-TNF-alpha treatment, in 11 patients with liver cirrhosis receiving transjugular intrahepatic portosystemic shunt implantation and in 21 healthy controls.

RESULTS

Adiponectin levels were significantly higher in all subjects with liver cirrhosis of different aetiologies when compared with healthy controls and increased dependent on Child-Pugh classification. In subjects with alcoholic steatohepatitis, systemic anti-TNF-alpha treatment caused a significant decrease in circulating adiponectin. Adiponectin concentrations were similar in portal, hepatic and peripheral veins. No correlation between adiponectin levels and insulin resistance was found in any patient group.

CONCLUSIONS

Our data suggest that circulating adiponectin is increased in liver cirrhosis independent of the aetiology of liver disease. We suggest that high adiponectin levels in chronic liver disease might reflect one of the body's anti-inflammatory mechanisms in chronic liver diseases.

Accessory protein-like is essential for IL-18-mediated signaling

IL-18 is an essential cytokine for both innate and adaptive immunity. Signaling by IL-18 requires IL-18Ralpha, which binds specifically to the ligand and contains sequence homology to IL-1R and TLRs. It is well established that IL-1R signaling requires an accessory cell surface protein, AcP. Other accessory proteins also exist with roles in regulating TLR signaling, but some have inhibitory functions. An AcP-like molecule (AcPL) has been identified with the ability to cooperate with IL-18Ralpha in vitro; however, the physiological function of AcPL remains unknown. In this study, we demonstrate that IL-18 signals are abolished in AcPL-deficient mice and cells. Splenocytes from mutant mice fail to respond to IL-18-induced proliferation and IFN-gamma production. In particular, Th1 cells lacking AcPL fail to produce IFN-gamma in response to IL-18. AcPL-deficient neutrophils also fail to respond to IL-18-induced activation and cytokine production. Furthermore, AcPL is required for NK-mediated cytotoxicity induced by in vivo IL-18 stimulation. However, AcPL is dispensable for the activation or inhibition of IL-1R and the various TLR signals that we have examined. These results suggest that AcPL is a critical and specific cell surface receptor that is required for IL-18 signaling.

Pathophysiological roles for IL-18 in inflammatory arthritis

IL-18 is a unique cytokine with prominently wide spectrum biological actions. Among these, its IFN-gamma/TNF-alpha-inducing activity primarily contributes to the development of various inflammatory diseases including inflammatory arthritis. IL-18 levels correlate with the disease activity of rheumatoid arthritis (RA) and osteoarthritis (OA). IL-18 is spontaneously released from RA synovial cells and OA chondrocytes and seems to participate in the development of the inflammatory and destructive alterations of joints via induction of TNF-alpha, a potent effector molecule. TNF-alpha, in turn, increases IL-18 expression in RA synovial cells. Recent clinical trials have revealed the efficacy of TNF-alpha in RA with a reduction in circulatory IL-18 levels. These may implicate the positive circuit between IL-18 and TNF-alpha for development of RA. As IL-18-deficient mice evade collagen-induced arthritis in a mouse RA model, therapeutics targeting IL-18 may be beneficial against RA/OA. Here, the authors review the possible roles of IL-18 in inflammatory arthritis.

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.