Elevation of plasma interleukin-18 concentration is correlated with disease activity in systemic lupus erythematosus

Leveraging Lymphatic System Targeting in Systemic Lupus Erythematosus for Improved Clinical Outcomes

The role of advanced drug delivery strategies in drug repositioning and minimizing drug attrition rates, when applied early in drug discovery, is poised to increase the translational impact of various therapeutic strategies in disease prevention and treatment. In this context, drug delivery to the lymphatic system is gaining prominence not only to improve the systemic bioavailability of various pharmaceutical drugs but also to target certain specific diseases associated with the lymphatic system. Although the role of the lymphatic system in lupus is known, very little is done to target drugs to yield improved clinical benefits. In this review, we discuss recent advances in drug delivery strategies to treat lupus, the various routes of drug administration leading to improved lymph node bioavailability, and the available technologies applied in other areas that can be adapted to lupus treatment. Moreover, this review also presents some recent findings that demonstrate the promise of lymphatic targeting in a preclinical setting, offering renewed hope for certain pharmaceutical drugs that are limited by efficacy in their conventional dosage forms. These findings underscore the potential and feasibility of such lymphatic drug-targeting approaches to enhance therapeutic efficacy in lupus and minimize off-target effects of the pharmaceutical drugs. SIGNIFICANCE STATEMENT: The World Health Organization estimates that there are currently 5 million humans living with some form of lupus. With limited success in lupus drug discovery, turning to effective delivery strategies with existing drug molecules, as well as those in the early stage of discovery, could lead to better clinical outcomes. After all, effective delivery strategies have been proven to improve treatment outcomes.

Structural basis of human IL-18 sequestration by the decoy receptor IL-18 binding protein (IL-18BP) in inflammation and tumor immunity

Human Interleukin-18 (IL-18) is an omnipresent proinflammatory cytokine of the IL-1 family with central roles in autoimmune and inflammatory diseases and serves as a staple biomarker in the evaluation of inflammation in physiology and disease, including the inflammatory phase of COVID-19. The sequestration of IL-18 by its soluble decoy receptor IL-18-Binding Protein (IL-18BP) is critical to the regulation of IL-18 activity. Since an imbalance in expression and circulating levels of IL-18 is associated with disease, structural insights into how IL-18BP outcompetes binding of IL-18 by its cognate cell-surface receptors are highly desirable; however, the structure of human IL-18BP in complex with IL-18 has been elusive. Here, we elucidate the sequestration mechanism of human IL-18 mediated by IL-18BP based on the crystal structure of the IL-18:IL-18BP complex. These detailed structural snapshots reveal the interaction landscape leading to the ultra-high affinity of IL-18BP toward IL-18 and identify substantial differences with respect to previously characterized complexes of IL-18 with IL-18BP of viral origin. Furthermore, our structure captured a fortuitous higher-order assembly between IL-18 and IL-18BP coordinated by a disulfide-bond distal to the binding surface connecting IL-18 and IL-18BP molecules from different complexes, resulting in a novel tetramer with 2:2 stoichiometry. This tetrapartite assembly was found to restrain IL-18 activity more effectively than the canonical 1:1 complex. Collectively, our findings provide a framework for innovative, structure-driven therapeutic strategies and further functional interrogation of IL-18 in physiology and disease.

Elevated serum free IL-18 in neuropsychiatric systemic lupus erythematosus patients with seizure disorders

BACKGROUND

Since dysregulation of total Interleukin (IL)-18 and IL-18 binding protein (IL-18BP) may participate in systemic lupus erythematosus (SLE) and contribute to the occurrence of non-autoimmune epilepsy, the aim of the current work is to investigate whether the interaction between IL-18 and IL-18BP plays any role in neuropsychiatric systemic lupus erythematosus related seizures.

METHODS

Data from 137 SLE patients and 30 healthy controls (HC) were consecutively collected from 2020 to 2021. Serum levels of total IL-18 and IL-18BP for all patients and HC were measured by ELISA test. Free IL-18 was calculated based on the law of mass action.

RESULTS

Among the 137 SLE patients, 103 had active disease and were classified into NPSLE (n = 50) and Non-NPSLE (n = 53) groups. Among the NPSLE patients, 16 had seizure disorders. Serum free IL-18 levels were increased in NPSLE (277.6 [150.9-428.8]pg/mL) and were correlated with disease activity (r = 0.268, p = 0.002). Moreover, serum free IL-18 levels in NPSLE patients with seizure disorders (350.9 [237.9-455.9]pg/mL) were significantly higher than the levels in those with other neuropsychiatric symptoms (237.7 [124.6-428.8] pg/mL).

CONCLUSIONS

The expression of free IL-18 was increased in neuropsychiatric systemic lupus erythematosus(NPSLE), especially in NPSLE related seizures. Also, serum levels of free IL-18 were significantly increased in active SLE patients. In this regard, free IL-18 may be involved in the pathogenesis of NPSLE related seizures and associated with disease activity.

The Role of Interleukin 18/Interleukin 18-Binding Protein in Adult-Onset Still's Disease and Systemic Juvenile Idiopathic Arthritis

Interleukin 18 (IL-18) is a pro-inflammatory cytokine of the IL-1 family, whose activity is tightly controlled at the level of production, as well as signalization. Notably, it is buffered by its natural inhibitor, IL-18 binding protein (IL-18BP), which is massively present in circulation in normal and in most pathological conditions, thus preventing harmful pro-inflammatory systemic effects of IL-18. IL-18 has long been considered to be involved in the pathophysiology of various inflammatory diseases. However, a first clinical trial using recombinant IL-18BP for the treatment of rheumatoid arthritis and psoriasis gave disappointing results. Direct measurements of unbound, bioactive, free form of circulating IL-18 demonstrated that IL-18 was more specifically involved in adult-onset Still’s disease (AOSD) and systemic juvenile idiopathic arthritis (sJIA) but also in their most severe complication, macrophage activation syndrome (MAS). More importantly, administration of recombinant IL-18BP to patients with AOSD, and sJIA with MAS, showed promising results. This review summarizes available data regarding IL-18 and IL-18BP in AOSD and sJIA in mouse models and humans and shows the importance of IL-18/IL-18BP imbalance in these conditions, leading to the conclusion that IL-18, particularly free IL-18, may be a useful biomarker in these diseases and an interesting therapeutic target.

The Role of Interleukins in the Pathogenesis of Dermatological Immune-Mediated Diseases

Autoimmune inflammatory diseases are primarily characterized by deregulated expression of cytokines, which drive pathogenesis of these diseases. A number of approved and experimental therapies utilize monoclonal antibodies against cytokine proteins. Cytokines can be classified into different families including the interleukins, which are secreted and act on leukocytes, the tumor necrosis factor (TNF) family, as well as chemokine proteins. In this review article, we focus on the interleukin family of cytokines, of which 39 members have been identified to this date. We outline the role of each of these interleukins in the immune system, and various dermatological inflammatory diseases with a focused discussion on the pathogenesis of psoriasis and atopic dermatitis. In addition, we describe the roles of various interleukins in psychiatric, cardiovascular, and gastrointestinal comorbidities. Finally, we review clinical efficacy and safety data from emerging late-phase anti-interleukin therapies under development for psoriasis and atopic dermatitis. Collectively, additional fundamental and clinical research remains necessary to fully elucidate the roles of various interleukin proteins in the pathogenesis of inflammatory dermatologic diseases, and treatment outcomes in patients.

Elevated Interleukin-18 Receptor Accessory Protein Mediates Enhancement in Reactive Oxygen Species Production in Neutrophils of Systemic Lupus Erythematosus Patients

Interleukin-18 receptor accessory protein (IL18RAP) is an indispensable subunit for the IL-18 receptor (IL-18R) complex's ability to mediate high-affinity IL-18 binding and signalling transduction. Interest in IL-18 in systemic lupus erythematosus (SLE) has been mostly focused on its role as a type 1 T helper cell-driving cytokine. The functional significance of IL18RAP in mediating the IL-18-driven response in myeloid cells in SLE remains largely unexplored. This study aimed to investigate the expression and function significance of IL18RAP in neutrophils of SLE patients. By qRT-PCR and Western blot analyses, elevated expressions of IL18RAP mRNA and protein were observed in neutrophils from SLE patients-particularly those with a history of nephritis. IL18RAP expression correlated negatively with complement 3 level and positively with disease activity, with higher expression in patients exhibiting renal and immunological manifestations. The increased IL18RAP expression in SLE neutrophils could be attributed to elevated type I interferon level in sera. Functionally, neutrophils from SLE patients showed higher IL-18-mediated enhancement in reactive oxygen species (ROS) generation, which showed positive correlation with IL18RAP expression and could be neutralized by anti-IL18RAP blocking antibodies. Taken together, our findings suggest that IL-18 could contribute to SLE pathogenesis through mediation of neutrophil dysfunction via the upregulation of IL18RAP expression.

Predicting lupus flares: epidemiological and disease related risk factors

Introduction: Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder, characterized by a relapsing and remitting pattern of disease activity in majority of the patients. Areas covered: This narrative review provides an overview of flare definition, major flare mimics, and the burden of flares in SLE. The authors highlight epidemiology and disease-related risk factor for flares and discuss strategies to reduce flares in SLE. Articles were selected from Pubmed searches conducted between June 2020 and September 2020. Expert opinion: Prolonged clinical remission is observed in approximately 20% of SLE patients flare over the course of the disease. Studies have shown that low disease activity is a good target in SLE, with similar risk of flares, mortality, and quality of life when compared to patients in remission. Clinical and immunological features have shown inconsistent results to identify patients at risk of flares in different cohorts. Cytokine, in serum and urine, has shown promising results to predict flares. However to be useful in clinical practice, they have to be simple, easy, and cost-effective. Future efforts in this direction will allow a more personalized treatment plan for SLE patients, reducing the burden associated with flares.

Synergistic Signaling of TLR and IFNα/β Facilitates Escape of IL-18 Expression from Endotoxin Tolerance

Rationale: IL-18 is a member of the IL-1 cytokine family, and elevated blood IL-18 concentrations associate with disease activity in macrophage activation syndrome (MAS) and poor clinical outcomes in severe inflammatory and septic conditions.

Objectives: Although recent investigations provide mechanistic evidence for a contribution of IL-18 to inflammation and hyperinflammation in sepsis and MAS, we sought to study regulatory mechanisms underlying human IL-18 expression.

Methods: Samples from in vivo and in vitro endotoxin rechallenge experiments, patients with inflammatory disease, and isolated human monocytes treated with various stimulants and drugs were tested for cytokine gene and protein expression. Serum IL-18 expression with or without JAK/STAT inhibition was analyzed in two MAS mouse models and in a patient with recurrent MAS.

Measurements and Main Results: Peripheral blood and monocytic IL-18 expression escaped LPS-induced immunoparalysis. LPS-stimulated primary human monocytes revealed specific IL-18 expression kinetics controlled by IFNα/β signaling. JAK/STAT inhibition or IFNβ neutralization during LPS stimulation blunted cytokine expression. Similarly, microtubule-destabilizing drugs abrogated LPS-induced IL18 expression, but this effect could be fully reversed by addition of IFNα/β. Ex vivo analysis of inflammatory disease patients’ whole blood revealed strong correlation of type I IFN score and IL18 expression, whereas JAK/STAT inhibition strongly reduced IL-18 serum levels in two MAS mouse models and in a patient with recurrent MAS.

Conclusions: Our data indicate that IL-18 (but not IL-1β) production from human monocytes requires cooperative Toll-like receptor and IFNα/β signaling. Interference with IFNα/β expression or signaling following JAK/STAT inhibition may control catastrophic hyperinflammation in MAS.

Performance of cytokine models in predicting SLE activity

Background

Identification of universal biomarkers to predict systemic lupus erythematosus (SLE) flares is challenging due to the heterogeneity of the disease. Several biomarkers have been reported. However, the data of validated biomarkers to use as a predictor for lupus flares show variation. This study aimed to identify the biomarkers that are sensitive and specific to predict lupus flares.

Methods

One hundred and twenty-four SLE patients enrolled in this study and were prospectively followed up. The evaluation of disease activity achieved by the SLE disease activity index (SLEDAI-2K) and clinical SLEDAI (modified SLEDAI). Patients with active SLE were categorized into renal or non-renal flares. Serum cytokines were measured by multiplex bead-based flow cytometry. The correlation and logistic regression analysis were performed.

Results

Levels of IFN-α, MCP-1, IL-6, IL-8, and IL-18 significantly increased in active SLE and correlated with clinical SLEDAI. Complement C3 showed a weakly negative relationship with IFN-α and IL-18. IL-18 showed the highest positive likelihood ratios for active SLE. Multiple logistic regression analysis showed that IL-6, IL-8, and IL-18 significantly increased odds ratio (OR) for active SLE at baseline while complement C3 and IL-18 increased OR for active SLE at 12 weeks. IL-18 and IL-6 yielded higher sensitivity and specificity than anti-dsDNA and C3 to predict active renal and active non-renal, respectively.

Conclusion

The heterogeneity of SLE pathogenesis leads to different signaling mechanisms and mediates through several cytokines. The monitoring of cytokines increases the sensitivity and specificity to determine SLE disease activity. IL-18 predicts the risk of active renal SLE while IL-6 and IL-8 predict the risk of active non-renal. The sensitivity and specificity of these cytokines are higher than the anti-dsDNA or C3. We propose to use the serum level of IL-18, IL-6, and IL-8 to monitor SLE disease activity in clinical practice.

Inflammatory markers in systemic lupus erythematosus

While systemic lupus erythematosus (SLE) is an autoantibody and immune complex disease by nature, most of its organ manifestations are in fact inflammatory. SLE activity scores thus heavily rely on assessing inflammation in the various organs. This focus on clinical items demonstrates that routine laboratory markers of inflammation are still limited in their impact. The erythrocyte sedimentation rate (ESR) is used, but represents a rather crude overall measure. Anemia and diminished serum albumin play a role in estimating inflammatory activity, but both are reflecting more than one mechanism, and the association with inflammation is complex. C-reactive protein (CRP) is a better marker for infections than for SLE activity, where there is only a limited association, and procalcitonin (PCT) is also mainly used for detecting severe bacterial infection. Of the cytokines directly induced by immune complexes, type I interferons, interleukin-18 (IL-18) and tumor necrosis factor (TNF) are correlated with inflammatory disease activity. Still, precise and timely measurement is an issue, which is why they are not currently used for routine purposes. While somewhat more robust in the assays, IL-18 binding protein (IL-18BP) and soluble TNF-receptor 2 (TNF-R2), which are related to the respective cytokines, have not yet made it into clinical routine. The same is true for several chemokines that are increased with activity and relatively easy to measure, but still experimental parameters. In the urine, proteinuria leads and is essential for assessing kidney involvement, but may also result from damage. Similar to the situation in serum and plasma, several cytokines and chemokines perform reasonably well in scientific studies, but are not routine parameters. Cellular elements in the urine are more difficult to assess in the routine laboratory, where sufficient routine is not always available. Therefore, the analysis of urinary T cells may have potential for better monitoring renal inflammation.

Whole blood assay as a model for in vitro evaluation of inflammasome activation and subsequent caspase-mediated interleukin-1 beta release

Processing of pro-interleukin (IL)-1β and IL-18 is regulated by multiprotein complexes, known as inflammasomes. Inflammasome activation results in generation of bioactive IL-1β and IL-18, which can exert potent pro-inflammatory effects. Our aim was to develop a whole blood-based assay to study the inflammasome in vitro and that also can be used as an assay in clinical studies. We show whole blood is a suitable milieu to study inflammasome activation in primary human monocytes. We demonstrated that unprocessed human blood cells can be stimulated to activate the inflammasome by the addition of adenosine 5'-triphosphate (ATP) within a narrow timeframe following lipopolysaccharide (LPS) priming. Stimulation with LPS resulted in IL-1β release; however, addition of ATP is necessary for "full-blown" inflammasome stimulation resulting in high IL-1β and IL-18 release. Intracellular cytokine staining demonstrated monocytes are the major producers of IL-1β in human whole blood cultures, and this was associated with activation of caspase-1/4/5, as detected by a fluorescently labelled caspase-1/4/5 probe. By applying caspase inhibitors, we show that both the canonical inflammasome pathway (via caspase-1) as well as the non-canonical inflammasome pathway (via caspases-4 and 5) can be studied using this whole blood-based model.

Serum IL-18 as biomarker in predicting long-term renal outcome among pediatric-onset systemic lupus erythematosus patients

An urge of biomarker identification is needed to better monitor lupus nephritis (LN) disease activity, guide clinical treatment, and predict patient's long-term outcome. With the proinflammatory effect and its association with inflammasomes, the significance of interleukin-18 (IL-18) among pediatric-onset systemic lupus erythematous (pSLE) patient, especially, its importance in predicting long-term renal outcome was investigated.In a pSLE cohort of 96 patients with an average follow-up period of 10.39 ± 3.31 years, clinical data and laboratory workups including serum IL-18 were collected at time of disease onset and 6 months after treatment despite their initial renal status. Through Cox regression analysis, the parameters at baseline and at 6 months posttreatment were carefully analyzed.Average age of all cases was 12.74 ± 3.01 years old and 65 of them underwent renal biopsy at the time of diagnosis. Nine subjects (9.38%) progressed to end-stage renal disease (ESRD) and 2 cases (2.08%) died during follow-up. Through multivariate analysis, serum IL-18 level 6 months posttreatment was found to be the most unfavorable factor associating poor clinical outcome despite patient's initial renal status. In addition, the presentation of serum IL-18 in its correlation with SLE global disease activity as well as the presence and severity of LN were all significant (P < 0.001, P = 0.03, and P = 0.02, respectively). The histological classification of LN, however, was not associated with the level of IL-18 among the pSLE patients (P = 0.64).The role of serum IL-18 as biomarker representing global disease activity and status of renal flares among pSLE population was shown for the first time. Additionally, we have identified IL-18 at 6 months posttreatment a novel marker for long-term renal outcome prediction.

Deciphering systemic lupus erythematosus-associated serum biomarkers reflecting apoptosis and disease activity

Systemic lupus erythematosus (SLE) is a severe chronic inflammatory autoimmune connective tissue disease. Despite major efforts, SLE remains a poorly understood disease with unpredictable course, unknown etiology and complex pathogenesis. Apoptosis combined with deficiency in clearing apoptotic cells is an important etiopathogenic event in SLE, which could contribute to the increased load of potential autoantigen(s); however, the lack of disease-specific protein signatures deciphering SLE and the underlying biological processes is striking and represents a key limitation. In this retrospective pilot study, we explored the immune system as a specific sensor for disease, in order to advance our understanding of SLE. To this end, we determined multiplexed serum protein expression profiles of crude SLE serum samples, using antibody microarrays. The aim was to identify differential immunoprofiles, or snapshots of the immune response modulated by the disease, reflecting apoptosis, a key process in the etiology of SLE and disease activity. The results showed that multiplexed panels of SLE-associated serum biomarkers could be decoded, in particular reflecting disease activity, but potentially the apoptosis process as well. While the former biomarkers could display a potential future use for prognosis, the latter biomarkers might help shed further light on the apoptosis process taking place in SLE.

Elevated serum levels of free interleukin-18 in adult-onset Still's disease

OBJECTIVE

IL-18 is a pro-inflammatory cytokine of the IL-1 family that is naturally inhibited by IL-18 binding protein (IL-18BP). High levels of IL-18 have been described in the serum of adult-onset Still's disease (AOSD) patients, but only total IL-18 levels (including inactive IL-18 bound to IL-18BP) have been measured. With a specific immunoassay, we aimed to measure free IL-18 serum levels in AOSD patients and other rheumatic diseases.

METHODS

An ELISA was developed to measure free IL-18. Its sensitivity and specificity were tested by spiking recombinant IL-18 or IL-18BP in serum and PBS supplemented with 5% BSA. The binding affinity of IL-18 to IL-18BP was calculated by titration experiments using the ELISA and by Biacore analysis. Sera of 37 AOSD patients and 138 controls (40 healthy controls, 30 RA, 29 SLE, 21 AS and 18 PsA) were assayed for free IL-18, IL-18BP, total IL-18 and other cytokines. Correlations were performed between free IL-18 and markers of disease activity in AOSD patients.

RESULTS

Free IL-18 serum levels were significantly higher in AOSD patients (median 8.89 pg/ml) than in healthy and disease controls (1.37 pg/ml; P < 0.01). Free IL-18 serum levels correlated with AOSD activity. The affinity of IL-18 to IL-18BP was found to be much higher than previously described, with a dissociation constant ranging from 30 to 50 pM.

CONCLUSION

Free IL-18 levels are specifically elevated in AOSD compared with other inflammatory diseases, suggesting that IL-18 represents a potential target for the treatment of AOSD.

Elevation of plasma interleukin-18 concentration is associated with insulin levels in patients with systemic lupus erythematosus

We previously reported that systemic lupus erythematosus (SLE) patients have a higher risk of insulin resistance and abnormal insulin secretion. Recent studies demonstrated that interleukin (IL)-18, a novel pro-inflammatory cytokine, may be involved in triggering the inflammatory processes in SLE and the concentrations of circulating IL-18 in SLE patients were significantly higher than those in healthy subjects. IL-12 has a synergistic effect with IL-18, and both cytokines are inducers of interferon γ. The objective of this study was to identify the effect of fasting insulin levels on circulating concentrations of IL-18, IL-12 and IFN-γ in patients with SLE. Plasma levels of proinflammatory Th-1 cytokines were determined by enzyme-linked immunosorbent assay in a total of 70 female SLE patients and 34 age-matched healthy females. Insulin resistance (IR) and secretion were evaluated by homeostasis model assessment (HOMA). All patients were further classified into subgroups based on the quartiles of fasting insulin levels. SLE patients with fasting insulin levels in the top quartile compared with other quartiles had significantly higher plasma levels of IL-18. The presence of insulin auto-antibodies (IAA) in SLE patients had no influence on plasma levels of IL-18. In addition, fasting insulin levels and HOMA IR were positively correlated with IL-18 in all SLE patients, respectively. In conclusion, elevated circulating IL-18 concentrations corresponded with increases in fasting insulin levels and the status of insulin resistance in patients with SLE.

Elevated Expression and Pro-Inflammatory Activity of IL-36 in Patients with Systemic Lupus Erythematosus

We investigated the expression and proinflammatory activity of interleukin (IL)-36 in patients with systemic lupus erythematosus (SLE). The expression level of IL-36, its putative receptors and the frequency of CD19⁺CD24^highCD27⁺ regulatory B (Breg) lymphocytes of peripheral blood from 43 SLE patients and 16 normal control (NC) subjects were studied using ELISA and flow cytometry. Plasma cytokines/chemokines and ex vivo productions of cytokine/chemokine from peripheral blood mononuclear cells (PBMC) stimulated with recombinant IL-36 were determined by Luminex multiplex assay. Plasma concentrations of IL-36α, IL-36γ and the proportions of circulating IL-36R-positive CD19⁺ B lymphocytes in total B lymphocytes and PBMC were significantly increased in active SLE patients compared with NC (all p < 0.05). Plasma IL-36α and IL-36γ correlated positively with SLE disease activity and elevated plasma IL-10 concentration (all p < 0.05). The frequencies of circulating Breg lymphocytes in total B lymphocytes and PBMC were significantly decreased in both inactive and active SLE patients compared with NC (all p < 0.01). The frequency of Breg lymphocytes in total B lymphocytes correlated negatively with the proportion of IL-36R-positive B lymphocytes (p < 0.05). IL-36α exerted substantial proinflammatory effect in PBMC from SLE patients by inducing the production of IL-6 and CXCL8. Upon stimulation with IL-36α and IL-36γ, ex vivo productions of IL-6 and CXCL8 were significantly increased in SLE patients compared with NC (all p < 0.05). This cross-sectional study demonstrated that over expression of circulating IL-36α may exert a proinflammatory effect as observed in human SLE.

Deletion of IL-18 Expression Ameliorates Spontaneous Kidney Failure in MRLlpr Mice

The role of IL-18 in the pathogenesis of systemic lupus erythematosus is still not definitively solved. In this study, we generated MRL^lpr mice, which develop a disease resembling systemic lupus erythematosus, genetically devoid of IL-18 expression. These mice in comparison to IL-18-competent MRL^lpr mice show reduced signs of renal pathogenesis, while other parameters such as mean survival time, lymphadenopathy, constitutive interferon-γ production, and frequency of CD3⁺B220⁺ abnormal T cells were without differences. We conclude that in the systemic lupus erythematosus syndrom IL-18 is involved specifically in the renal pathogenesis.

Elevation of Interleukin-18 Correlates With Cardiovascular, Cerebrovascular, and Peripheral Vascular Events: A Cohort Study of Hemodialysis Patients

Cardiocerebral vascular events are the major cause of mortality among patients with end-stage renal disease (ESRD). Subclinical inflammation and atherosclerosis have been implicated in the pathophysiology of ESRD. Evidence has shown the crucial role of interleukin-18 (IL-18) in inflammation. Interleukin-18 has been markedly upregulated in ESRD patients. Nevertheless, the ability of the IL-18 level to predict cardiocerebral vascular events and the correlation between IL-18 levels and cardiocerebral vascular events have not been established in hemodialysis patients.To determine whether the serum IL-18 level predicts cardiocerebral vascular events, the authors studied 171 ESRD patients. Samples were collected and patients were followed for 24 months. Demographic data, the duration of hemodialysis, nutrition status, inflammatory parameters, dialysis adequacy, and lipid profiles were analyzed to predict the outcome by using multivariate logistic regression. Cutoff points were calculated by acquiring the highest Youden index. The Kaplan-Meier method was used to scrutinize the cumulative proportion of events.The multivariate logistic regression model revealed that serum creatinine, C-reactive protein, and IL-18 levels were independent predictors for cardiocerebral vascular events. The odds ratio of events for each increase in IL-18 (pg/mL) was 1.008 for cardiocerebral vascular events. The area under the receiver operating characteristic curve of IL-18 was 0.779 ± 0.039, the overall correctness was 73%, and the Youden index was highest at a cutoff of 463 pg/mL. In the Kaplan-Meier model, patients with an IL-18 level higher than 463 pg/mL exhibited the highest probability of experiencing an adverse event during the entire follow-up period.Increased serum IL-18 could be considered as a predictor of cardiocerebral vascular events in dialysis patients. It is noteworthy that various comorbidities might interfere the expression of IL-18; therefore, further validation study is required to incorporate IL-18 in clinical use.

Endotoxin tolerance in monocytes can be mitigated by α2-interferon

Endotoxin tolerance is characterized by diminished expression of inflammatory cytokines after sequential exposure to Toll-like receptor stimuli. Many mechanisms contribute to tolerance; however, chromatin remodeling appears to be the most significant regulator. The type II interferon, IFN-γ, has been recognized as being able to reverse or abrogate the establishment of tolerance. Type I interferons have not been investigated previously, and they bind a distinct receptor. We found that α2-interferon was able to abrogate or diminish tolerance by endotoxin, as defined by measuring mRNA levels at recognized tolerance targets. We also found that α2-interferon treatment during tolerization was associated with increased H3K4me3 and H3K4me2 levels at promoters of tolerance targets in THP1 cells. These marks were normalized after exposure of the cells to α2-interferon. Interferon regulatory factor 1 is a transcription factor activated and induced by types I and II interferons. We found recruitment of this transcription factor paralleled tolerance and inhibition of tolerance at target genes. Therefore, there are at least 2 distinct pathways by which endotoxin tolerance may be mitigated. A type I interferon, in spite of binding to a different receptor, was just as able to inhibit tolerance as the type II interferon and also appeared to act by modifying chromatin at tolerance target genes.

IL-18 in inflammatory and autoimmune disease

Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.

Association of interleukin-18 (-137G/C) polymorphism with rheumatoid arthritis and systemic lupus erythematosus: a meta-analysis

BACKGROUND

Recent studies have suggested that interleukin (IL)-18 gene (-137G/C) polymorphism is associated with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, other studies did not confirm this correlation.

OBJECTIVE

The objective of this study was to evaluate the relationships of IL-18 -137G/C and RA and SLE using a meta-analysis.

METHODS

Pubmed, Embase and Cochrane library databases were systemically searched. Data were extracted by two independent reviewers and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated.

RESULTS

In RA, the overall ORs and 95% CIs of -137C were 1.03, 0.88-1.22 (p=0.391); 1.22, 0.89-1.68 (p=0.020) and 1.06, 0.93-1.21 (p=0.110) in dominant, recessive, and additive models, respectively. Furthermore, in SLE, the overall ORs and 95% CIs of -137C were 1.10, 0.94-1.29 (p=0.980); 1.21, 0.91-1.60 (p=0.010) and 1.10, 0.97-1.24 (p=0.454) in dominant, recessive, and additive models, respectively. IL-18 -137G/C could increase the risk of RA and SLE. No publication bias was found in this meta-analysis. After population stratification analysis, under recessive model, the pooled ORs and 95% CIs of -137C were 1.14, 0.82-1.60 (p=0.008) and 1.01, 0.66-1.55 (p=0.004) in European RA patients and Asian SLE patients, respectively.

CONCLUSIONS

This meta-analysis showed that IL-18 -137G/C was a risk factor for RA and SLE, especially for RA in Europeans and SLE in Asians.

Polymorphisms in the IL-18 and IL-12B genes and their association with the clinical outcome in Croatian patients with Type 1 diabetes

Genetic variants of IL-18 and IL-12B may be important in immunoregulatory abnormalities, observed in the patients with Type 1 diabetes mellitus (T1DM), that contribute to individual differences in response to a treatment. Therefore, we examined the significance of IL-18-137G/C, IL-18-607C/A, and IL-12B A/C polymorphisms in Croatians (187 patients, 236 controls), not only as factors that contribute to susceptibility to T1DM, but also as determinants of the clinical presentation of disease. The polymorphism screening has been performed using PCR sequence-specific primers (IL-18) or PCR-RFLP (IL-12B) approach. Results were evaluated by GraphPad Prism and Sigma Stat 3.5, Arlequin software and calculator for Hardy-Weinberg equilibrium. The genotype, allele and haplotype distribution were not statistically different between the patients and control subjects. The clinical parameter analysis revealed that patients with minor alleles at each locus, IL-18-137C/-607A, were significantly younger at T1DM onset than carriers of major alleles, IL-18-137G/-607C (20 vs 23.5 years). Moreover, the concomitant presence of minor alleles not only of IL-18 but also of IL-12B, is associated with the risk of disease progression even at younger age. These patients developed diabetes at 16 years of age, what is significantly earlier (p=0.044) compared to 25.5 years of age in patients with common alleles IL-18-137G/-607C/IL-12B A. Furthermore, combined genotype analysis of IL-18 and IL-12B has pointed out that patients with CC/AA/AA genotype have the worst glucose control based on HbA1c (8.7%, range 6.8-13.1%). In conclusion, susceptibility to T1DM in Croatians is not strongly associated with IL-18-137/-607 and IL-12B polymorphisms. These SNPs are associated with the higher risk of earlier disease development and might be implicated in the effectiveness of glycemic control.

Increased serum β2-microglobulin is associated with clinical and immunological markers of disease activity in systemic lupus erythematosus patients

The objective of this study was to explore the relationship between serum levels of β2-microglobulin (β2MG), which some studies suggest reflect disease activity in systemic lupus erythematosus (SLE), and various clinical and immunological markers of disease activity in SLE. Twenty-six SLE patients and 10 healthy controls were included. Disease activity was assessed by: SLEDAI, 24 hr-proteinuria, circulating levels of complement C3, anti-double-stranded DNA (anti-dsDNA), β2MG and various pro-inflammatory and anti-inflammatory cytokines (IL-6, IL-8, IL-10, IL-18) measured with a multiplex assay, IFN-α assessed with a reporter gene assay, and a combined expression score of 12 IFN-α inducible genes in peripheral blood mononuclear cells.

Median serum levels of β2MG were significantly higher in SLE patients vs controls (2.8 mg/L, range: 1.1–21.6 and 1.2 mg/L, range: 0.9–1.7, respectively, p < 0.001). β2MG was correlated with SLEDAI score ( R = 0.68, p < 0.001), 24 hr-proteinuria ( R = 0.64, p < 0.001), and complement C3 ( R = −0.52, p = 0.007). The cytokines were significantly correlated with β2MG: IL-6 ( R = 0.45, p = 0.02), IL-8 ( R = 0.75, p < 0.001), IL-10 ( R = 0.67, p < 0.001) and IL-18 ( R = 0.71, p < 0.001) as were serum IFN-α ( R = 0.45, p = 0.02) and the IFN-α inducible gene-score ( R = 0.51, p = 0.01). The results support that β2MG may serve as a marker of disease activity in SLE. The correlations with the measured cytokines indicate that increased β2MG in SLE reflects immunological activity.

Immunopathological roles of cytokines, chemokines, signaling molecules, and pattern-recognition receptors in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with unknown etiology affecting more than one million individuals each year. It is characterized by B- and T-cell hyperactivity and by defects in the clearance of apoptotic cells and immune complexes. Understanding the complex process involved and the interaction between various cytokines, chemokines, signaling molecules, and pattern-recognition receptors (PRRs) in the immune pathways will provide valuable information on the development of novel therapeutic targets for treating SLE. In this paper, we review the immunopathological roles of novel cytokines, chemokines, signaling molecules, PRRs, and their interactions in immunoregulatory networks and suggest how their disturbances may implicate pathological conditions in SLE.

Recent advances in cytokines in cutaneous and systemic lupus erythematosus

Lupus erythematosus (LE) includes a broad spectrum of diseases from a cutaneous-limited type to a systemic type. Systemic lupus erythematosus (SLE) is a systemic autoimmune disease which affects multiple organs. Cutaneous lupus erythematosus (CLE) includes skin symptoms seen in SLE and cutaneous-limited LE. Although immune abnormalities, as well as heritable, hormonal and environmental factors, are involved in the pathology of LE, the actual pathogenesis is still unclear. Recently, the involvement of various cytokines has been shown in the pathogenesis of LE. Moreover, some trials with biological agents targeted specific cytokines are also ongoing for SLE. In this article, we review the contributions of major cytokines such as interferon, tumor necrosis factor-α and interleukin-18 to LE, especially SLE and CLE.

High circulating levels of interleukin-18 binding protein indicate the severity of glomerular involvement in systemic lupus erythematosus

In systemic lupus erythematosus (SLE), glomerular involvement often progresses with the activity of the disease. Immune complexes and abnormal secretion of cytokines are thought to be involved in the central mechanism of the development of lupus nephritis. We investigated serum levels of interleukin 18 (IL-18), a proinflammatory cytokine, and its natural antagonist IL-18 binding protein (IL-18 BP) in 45 patients with lupus nephritis. IL-18 levels were significantly increased in patients with Class II, Class III, and Class IV lupus nephritis compared with the level in a healthy control group. However, the levels stayed within the non-significant range in Class V. IL-18 BP levels were significantly increased in patients with Class III and Class IV lupus nephritis, in which histological activity and chronicity are severe. However, IL-18 BP levels stayed within the non-significant range in Class II and Class V, in which histological markers are mild. We also compared the levels of IL-18 and IL-18 BP in patients with and without glomerular infiltration of inflammatory cells. IL-18 was increased regardless of glomerular infiltration. However, IL-18 BP was increased only in patients with glomerular infiltration. These data suggest that IL-18 levels indicate the extent of the offending inflammatory response not only in the bloodstream but also in renal tissue, and that high IL-18 BP levels indicate the severity of existing glomerular injury.

Lack of association of interleukin-18 gene promoter -607 A/C polymorphism with susceptibility to autoimmune diseases: a meta-analysis

OBJECTIVE

Published data on the association between interleukin (IL)-18 gene promoter -607 A/C polymorphism and autoimmune diseases risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed.

METHODS

A total of 17 studies, including six studies on type 1 diabetes (T1D), four on rheumatoid arthritis (RA), five on systemic lupus erythematosus (SLE), three on Crohn's Disease (CD) and three on ulcerative colitis (UC), were available for the meta-analysis. Meta-analysis was performed for genotypes A/A (recessive effect), genotypes A/A + A/C (dominant effect), and A allele in fixed or random-effects models.

RESULTS

Overall, no significantly elevated autoimmune diseases risk was found in all genetic models when all studies were pooled into the meta-analysis. The overall odds ratios (ORs) and 95% confidence intervals (CIs) for A-allele were T1D (OR = 0.938, 95% CI = 0.757-1.162), RA (OR = 0.759, 95% CI = 0.540-1.067), SLE (OR = 0.858, 95% CI = 0.609-1.208), CD (OR = 1.159, 95% CI = 0.975-1.379) and UC (OR = 1.170, 95% CI = 0.977-1.402), respectively. In the subgroup analysis by ethnicity, there was still no significant association detected in all genetic models.

CONCLUSIONS

To date, there is still not enough evidence to indicate the association of IL-18 gene promoter -607 A/C polymorphism and the development of autoimmune diseases.

IFN-α production by plasmacytoid dendritic cells stimulated with RNA-containing immune complexes is promoted by NK cells via MIP-1β and LFA-1

Several systemic autoimmune diseases display a prominent IFN signature. This is caused by a continuous IFN-α production by plasmacytoid dendritic cells (pDCs), which are activated by immune complexes (ICs) containing nucleic acid. The IFN-α production by pDCs stimulated with RNA-containing IC (RNA-IC) consisting of anti-RNP autoantibodies and U1 small nuclear ribonucleoprotein particles was recently shown to be inhibited by monocytes, but enhanced by NK cells. The inhibitory effect of monocytes was mediated by TNF-α, PGE(2), and reactive oxygen species, but the mechanisms for the NK cell-mediated increase in IFN-α production remained unclear. In this study, we investigated the mechanisms whereby NK cells increase the RNA-IC-induced IFN-α production by pDCs. Furthermore, NK cells from patients with systemic lupus erythematosus (SLE) were evaluated for their capacity to promote IFN-α production. We found that CD56(dim) NK cells could increase IFN-α production >1000-fold after RNA-IC activation, whereas CD56(bright) NK cells required costimulation by IL-12 and IL-18 to promote IFN-α production. NK cells produced MIP-1α, MIP-1β, RANTES, IFN-γ, and TNF-α via RNA-IC-mediated FcγRIIIA activation. The IFN-α production in pDCs was promoted by NK cells via MIP-1β secretion and LFA-mediated cell-cell contact. Moreover, NK cells from SLE patients displayed a reduced capacity to promote the RNA-IC-induced IFN-α production, which could be restored by exogenous IL-12 and IL-18. Thus, different molecular mechanisms can mediate the NK cell-dependent increase in IFN-α production by RNA-IC-stimulated pDCs, and our study suggests that the possibility to therapeutically target the NK-pDC axis in IFN-α-driven autoimmune diseases such as SLE should be investigated.

Docosahexaenoic acid-enriched fish oil attenuates kidney disease and prolongs median and maximal life span of autoimmune lupus-prone mice

The therapeutic efficacy of individual components of fish oils (FOs) in various human inflammatory diseases still remains unresolved, possibly due to low levels of n-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) or lower ratio of DHA to EPA. Because FO enriched with DHA (FO-DHA) or EPA (FO-EPA) has become available recently, we investigated their efficacy on survival and inflammatory kidney disease in a well-established animal model of human systemic lupus erythematosus. Results show for the first time that FO-DHA dramatically extends both the median (658 d) and maximal (848 d) life span of (NZB x NZW)F1 (B x W) mice. In contrast, FO-EPA fed mice had a median and maximal life span of approximately 384 and 500 d, respectively. Investigations into possible survival mechanisms revealed that FO-DHA (versus FO-EPA) lowers serum anti-dsDNA Abs, IgG deposition in kidneys, and proteinuria. Further, FO-DHA lowered LPS-mediated increases in serum IL-18 levels and caspase-1-dependent cleavage of pro-IL-18 to mature IL-18 in kidneys. Moreover, FO-DHA suppressed LPS-mediated PI3K, Akt, and NF-kappaB activations in kidney. These data indicate that DHA, but not EPA, is the most potent n-3 fatty acid that suppresses glomerulonephritis and extends life span of systemic lupus erythematosus-prone short-lived B x W mice, possibly via inhibition of IL-18 induction and IL-18-dependent signaling.

Activation profile of intracellular mitogen-activated protein kinases in peripheral lymphocytes of patients with systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease associated with aberrant activation of T and B lymphocytes. Abnormal activation of intracellular signaling molecules in lymphocytes by inflammatory cytokines can instigate the inflammation in SLE.

MATERIALS AND METHODS

The activation of extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) in inflammatory cytokine IL-18-activated monocytes, CD4+ T helper (Th) lymphocytes, CD8+ T lymphocytes, and CD19+ B lymphocytes in 22 SLE patients and 20 sex- and age-matched control subjects were measured by flow cytometry.

RESULTS AND DISCUSSION

The basal expressions of phospho-p38 MAPK in CD4+ T lymphocytes, CD8+ T lymphocytes, and B lymphocytes were significantly higher in SLE patients than controls (all p<0.05). The expression of phospho-p38 MAPK in CD4+ T lymphocytes, CD8+ T lymphocytes and B lymphocytes, and phospho-JNK in CD8+ T lymphocytes and B lymphocytes was also significantly elevated in SLE patients upon the activation by IL-18, exhibiting significant correlation with the plasma concentrations of Th1 chemokine CXCL10 (all p<0.05). The expression of phospho-JNK in IL-18 activated CD8+ T lymphocytes and the relative % fold increase of the expression of phospho-JNK upon IL-18 activation in B lymphocytes were significantly correlated with SLE disease activity index (both p<0.05).

CONCLUSION

The inflammation-mediated activation of JNK and p38 MAPK signaling pathways in T and B lymphocytes can be the underlying intracellular mechanisms causing lymphocyte hyperactivity in SLE.

IL-18 activity in systemic lupus erythematosus

Interleukin-18 (IL-18) is an inflammation-related cytokine that plays a central role both in innate defense reactions and in Th1 activation and specific immune responses. Increased levels of IL-18 can be detected in biological fluids and organs of individuals affected by several autoimmune pathologies, as well as in autoimmune animal models. In this review, the role of IL-18 in systemic lupus erythematosus (SLE) is critically examined, including its possible role in the pathogenesis of disease. In SLE, increased levels of IL-18 have been found in serum/plasma of affected persons, which positively correlated with disease severity. The possibility that circulating IL-18 levels are predictive of renal damage has been proposed, suggesting that IL-18 may be a prognostic marker of renal involvement useful to identify patients at risk of renal failure. The evaluation of urinary levels of free active IL-18 indeed suggests a correlation with the degree of renal involvement. The possible pathogenic role of IL-18 in lupus has been studied in a mouse model of progressive disease, which makes possible the identification, at the level of the different affected organs, of IL-18 changes preceding disease development and those appearing after disease onset. It can be concluded that IL-18 has a multifaceted role in autoimmune lupus, being apparently involved both in the effector phases of the late organ damage and, in some organs, in the initial pathogenic events. Therapeutic strategies targeting IL-18 in autoimmunity are under development.

High circulating levels of free interleukin-18 in patients with active SLE in the presence of elevated levels of interleukin-18 binding protein

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies particularly to nuclear antigens and by an abnormal production of proinflammatory cytokines. In the present study, we measured the levels of the proinflammatory cytokine IL-18 and its natural inhibitor, the IL-18 binding protein (IL-18BP), in sera of SLE patients at various stages of the disease. This is the first study to present IL-18BP levels in sera of SLE patients as well as the calculated, biologically active, free IL-18 concentrations that are most probably more relevant to the pathology of SLE. Sera from 48 unselective SLE patients (total of 195 samples) were obtained longitudinally with a mean follow-up period of 11.1 +/- 8.9 years and were compared to sera from 100 healthy volunteers. Circulating levels of IL-18, IL-18BP and free IL-18 in the SLE patients were significantly higher than the levels of healthy controls (5 fold, 6 fold and 3 fold for IL-18, IL-18BP and free IL-18, respectively) and correlated with disease activity as scored by SLEDAI-2K. Furthermore, these levels during active disease (SLEDAI-2K > or = 6) were higher compared to the levels measured in the sera of the same patients during remission or during mild disease (SLEDAI-2K 0-5). The high levels of IL-18 and IL-18BP in sera of active SLE patients suggest their possible role in the pathogenesis and course of the disease. However, despite the elevated levels of IL-18BP during active disease, free IL-18 remained more than 2 fold higher than the levels in healthy controls suggesting a potential benefit of administration of exogenous IL-18BP as a novel therapeutic approach for active SLE.

Increased Spontaneous But Decreased Mitogen-stimulated Expression and Excretion of Interleukin 18 by Mononuclear Cells in Patients with Active Systemic Lupus Erythematosus

Objective.

To measure serum concentration and analyze the expression of interleukin 18 (IL-18) mRNA in mononuclear cells of patients with systemic lupus erythematosus (SLE).

Methods.

IL-18 concentrations in sera and culture supernatants of peripheral blood mononuclear cells (PBMC) from healthy controls and patients with active SLE were measured by ELISA. PBMC and polymorphonuclear leukocytes (PMN) purified from patients with active SLE were stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM), and lipopolysaccharide (LPS). Expression of IL-18 mRNA in cells was analyzed by RT-PCR.

Results.

Serum IL-18 levels were significantly higher in SLE patients than in controls, and correlated with disease activity in SLE patients (r2 = 0.602). Two patients receiving intravenous methylprednisolone therapy (1.0 g/day for 3 days) showed profound decreases in serum IL-18 levels after therapy. The quiescent PBMC from SLE patients (30/30) expressed IL-18 transcript more frequently than control PBMC (20/30). PBMC from SLE patients produced more IL-18 than control PBMC after 72 hours of incubation, by RT-PCR. PHA and PWM inhibited the production of IL-18 in PBMC from both SLE patients and controls. Inhibition by PWM was more pronounced than that by PHA, especially in SLE-PBMC. Control and SLE-PMN with or without LPS stimulation produced negligible IL-18.

Conclusion.

IL-18 is involved in the autoimmune derangement of leukocyte function in patients with active SLE.

Association of interleukin-18 promoter polymorphisms with WHO pathological classes and serum IL-18 levels in Chinese patients with lupus nephritis

Accumulating evidence indicates that interleukin (IL)-18 has a central role in the pathogenesis of lupus nephritis (LN). Although two recent studies showed that IL-18 promoter gene polymorphisms might be associated with systemic lupus erythematosus (SLE), to our knowledge, there have not been any reports concerning their association with LN. The aim of our study was to investigate the association of IL-18 promoter polymorphisms with World Health Organization pathological classes and identify their functional correlations. Sequence-specific primer polymerase chain reaction and the restriction fragment length polymorphism method were used to analyse the genotypes of IL-18 promoter polymorphism at the position −607 in 101 unrelated patients with LN, 64 non-renal patients with SLE and 174 ethnically matched healthy controls. Serum IL-18 levels were determined using enzyme-linked immunosorbent assay during the active phase. Immunohistochemical analysis was performed for IL-18 expression on renal biopsies from 72 patients with LN. Our results showed that patients with non-renal SLE had significantly higher frequencies of SNP−607/AA when compared to patients with LN (37.5% vs 18.8%, P < 0.05). LN patients with the AA genotype had significantly lower levels of serum IL-18 than those with the CA or CC genotype ( P < 0.01) and also had lower levels of glomerular IL-18 expression than those with the CC genotype ( P < 0.05). Significantly, higher frequencies of the SNP−607/AA genotype were observed in LN patients with WHO class III than in those with class IV (34.6% vs 15.6%, P < 0.05). The SNP−607/AA genotype was not observed in patients with LN who progressed to end-stage renal failure that required haemodialysis or renal transplantation. In conclusion, the SNP−607/AA genotype that had lower IL-18 levels might be a genetically protective factor against renal involvement in Chinese patients with SLE and against development of severe nephritis in patients with LN.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Interleukin-18 binding protein in the sera of patients with Wegener's granulomatosis

INTRODUCTION

In the present study, we examined the levels of the pro-inflammatory cytokine IL-18 and its natural inhibitor, the IL-18 binding protein (IL-18BP), in sera of Wegener's granulomatosis (WG) patients at various stages of the disease.

PATIENTS AND METHODS

Sera from eight consecutive biopsy-proven systemic WG patients (four men and four women; age at diagnosis 58.4 +/- 13.8 years) were obtained longitudinally with a follow-up period of 55.2 +/- 30 months. Sera obtained from 50 healthy subjects were used as controls.

RESULTS AND DISCUSSION

Serum levels of IL-18, IL-18BP, and free IL-18 obtained during an active phase of the disease (Birmingham Vasculitis Activity Score, BVAS > 10) were more than twofold higher than levels in the same patients during inactive disease stages (BVAS < 5; P < 0.002; P < 0.006, and P < 0.03 for IL-18, IL-18BP, and free IL-18, respectively). During inactive stages, the levels of these markers were comparable to those of healthy controls. The elevated levels of IL-18 and IL-18BP in sera during active stages of disease suggest a possible role in the pathogenesis and course of the WG.

CONCLUSION

Despite the elevated IL-18BP levels during active disease, free IL-18 remained higher than in the inactive disease stages, suggesting a potential benefit of administration of exogenous IL-18BP as a novel therapeutic approach for active WG.

A/C polymorphism in the interleukin-18 coding region among Taiwanese systemic lupus erythematosus patients

Interleukin-18 (IL-18) is associated with chronic inflammation, autoimmune diseases and various cancers and infectious diseases. An IL-18 genetic A/C polymorphism at coding position 105 (rs549908) has been linked with asthma and rheumatoid arthritis. We tested a hypothesis that the IL-18 genetic polymorphism confers systemic lupus erythematosus (SLE) susceptibility. Study participants were Taiwanese SLE patients and a healthy control group. Our results indicate (1) a significantly higher A allele frequency in SLE patients (P = 0.003; OR = 1.97; 95% CI = 1.26-3.08) and (2) a significantly higher A allele frequency in SLE patients with a central nervous system disorder (P = 0.027; OR = 7.18; 95% CI = 0.95-54.28). Our results suggest that the A/C polymorphism contributes to SLE pathogenesis.

Hyperproduction of IL-23 and IL-17 in patients with systemic lupus erythematosus: implications for Th17-mediated inflammation in auto-immunity

IL-23-dependent IL-17-producing T helper (Th) lymphocytes are associated with autoimmunity. We investigated the immunopathological mechanisms for activation of Th17 cells of patients with systemic lupus erythematosus (SLE). Concentration of cytokines/chemokine in plasma and culture supernatant from SLE patients and healthy controls were measured by ELISA or flow cytometry. Plasma IL-12, IL-17, IL-23 and CXCL10 concentrations and the number of Th17 cells were significantly elevated in SLE patients than control subjects (both p<0.05). Elevated IL-12, IL-17 and CXCL10 concentrations correlated positively and significantly with SLEDAI (all p<0.05). Plasma IL-12 and IL-17 showed significant and positive correlation with plasma Th1 chemokine CXCL10 concentration in SLE patients (all p<0.05). Ex vivo inductions of IL-17 by IL-23 or IL-18 from co-stimulated lymphocytes were significantly higher in SLE patients than controls (all p<0.05). The activated IL-23/IL-17 axis is important for the inflammatory immunity in SLE.

The Synthetic Tellurium Compound, AS101, Is a Novel Inhibitor of IL-1βConverting Enzyme

The organotellurium compound, trichloro(dioxoethylene-O,O') tellurate (AS101) has been shown previously to exert diverse biologic activities both in vitro and in vivo. This compound was recently found to react with thiols and to catalyze their oxidation. This property of AS101 raises the possibility that it may serve as a cysteine protease inhibitor. In the present study, using a substrate-specific enzymatic assay, we show that treatment of caspase-1 (interleukin-1beta [IL-1beta] converting enzyme [ICE]) with AS101 inhibits its enzymatic activity in a dose-dependent manner. Moreover, the results show that AS101 treatment causes a significant reduction in the active form of IL-18 and IL-1beta in peripheral blood mononuclear cells (PBMC) and in human HaCat keratinocytes. We further demonstrate that the inhibitory effect of AS101 does not involve nitric oxide (NO) or interferon-gamma (IFN-gamma), two possible regulators of IL-18 production, and does not occur at the mRNA level, suggesting a posttranscriptional mechanism of action. More importantly, AS101 downregulates IL-18 and IL-1beta serum levels in a mouse model of lipopolysaccharide (LPS)-induced sepsis, resulting in increased survival. Recent studies emphasize the pathophysiologic role of IL-18 and IL-1beta in a variety of inflammatory diseases. Thus, their blockage by the nontoxic compound, AS101, currently used in clinical studies, may provide clinical advantage in the treatment of these diseases.

Induction of serum IL-18 withPropionibacterium acnesand lipopolysaccharide in phagocytic macrophage-inactivated mice

IL-18, an important regulator of immune responses, is expressed in activated macrophages and also in nonimmune cells, such as keratinocytes and epithelial cells. Increased levels of serum IL-18 are reported in patients with a wide variety of diseases, but it is unclear which type of cell is the major source of serum IL-18. Here, we showed that the administration of liposomes encapsulating clodronate (Clo-lip) in mice selectively depleted F4/80(+) phagocytic macrophages in the liver and spleen. Serum levels of mature IL-18 with 18 kDa were increased markedly in mice treated with Propionibacterium acnes and LPS, whereas administration of Clo-lip and gadolinium chloride, another widely used macrophage inactivator, showed no obvious effect on serum IL-18 levels, which were marginal in the liver, lung, and spleen and more pronounced in the intestines, especially in the duodenum. Treatment with P. acnes alone induced IL-18 more than twofold in each organ, and P. acnes and LPS induced a marked increase in IL-18 levels in the liver and spleen but decreased in the intestines. The administration of Clo-lip showed only a marginal effect on the IL-18 levels in these organs. Furthermore, serum levels of liver enzymes and TNF-alpha and liver injury (necrotic change and granuloma formation) induced by P. acnes and LPS were reduced moderately by Clo-lip. These results suggest that phagocytic macrophages do not actively contribute to the induction of serum IL-18 and liver injury in mice treated with P. acnes and LPS.