Interleukin-18 and the treatment of rheumatoid arthritis

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

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

Antioxidant, Antiapoptotic and Inflammatory Effects of Interleukin-18 Binding Protein on Kidney Damage Induced by Hepatic Ischemia Reperfusion

OBJECTIVE

Acute kidney injury (AKI) is a serious condition that can be induced by liver transplantation, major hepatic resection or prolonged portal vein occlusion. The AKI can increase the frequency of postoperative complications. In the current study, we aimed to investigate whether interleukin-18 binding protein (IL-18BP) pretreatment has a protective effect against possible kidney injury-mediated liver ischemia-reperfusion (IR) achieved by Pringle maneuver in an experimental rat model.

MATERIALS AND METHODS

A total of 21 Wistar albino rats were included in this study. Animals were equally and randomly separated into 3 groups as follows: Sham (n = 7), IR group (n = 7) and IR + IL-18BP group (n = 7). Serum aspartate transaminase, alanine aminotransaminase and lactate dehydrogenase enzyme activities and serum urea and creatinine levels were determined. Tumor necrosis factor-α, IL-6, IL-1β, interferon gamma, total oxidant status, total antioxidant status and oxidative stress index were measured in kidney tissue homogenate samples. Histopathological examination and immunohistochemical Caspase-3 staining were applied to examine the general morphologic structure and apoptosis.

RESULTS

Renal total oxidant status; oxidative stress index; IL-18 levels; serum aspartate transaminase, alanine aminotransaminase and lactate dehydrogenase activities and creatinine levels were significantly lower in IR + IL-18BP group, when compared with the IR group. Beside this, total antioxidant status levels were remarkably higher in IR + IL-18BP group, when compared with the IR group. The caspase-3 expression degree in IR group was remarkably higher than other groups.

CONCLUSIONS

It has been demonstrated that IL-18BP pretreatment may have inflammatory, antioxidant and antiapoptotic effects against AKI induced by hepatic IR.

The effects of IL-18BP on mRNA expression of inflammatory cytokines and apoptotic genes in renal injury induced by infrarenal aortic occlusion

BACKGROUND

Renal injury is an important complication of infrarenal aortic occlusion (IAO), which is mainly encountered during the postoperative period. Aortic clamping procedure may lead to turbulent blood flow and eventually vasoconstriction at renal arterial level of the abdominal aorta. IL-18BP has well-known antioxidant and anti-inflammatory properties. In this study, we aimed to determine whether IL-18BP has anti-inflammatory, antiapoptotic, antioxidant, and protective effects on acute kidney damage induced by IAO rat model.

MATERIALS AND METHODS

A total of 30 adult male Wistar-Albino rats were equally and randomly separated to three groups as follows: SHAM laparotomy, ischemia-reperfusion (IR), and IR + IL-18BP. We applied 30-min IAO and 2-h reperfusion. Inflammatory cytokine levels (TNF-α, IL-1β, IL-18, IL-6, and IFN-γ) and oxidative stress parameters (TAS, TOS, and OSI) were measured. In addition to this, urea and creatinine levels, histopathology of kidney, mRNA expression levels of inflammatory cytokines, and apoptotic genes were investigated.

RESULTS

Urea and creatinine, tissue and serum levels of TNF-α, IL-6, IL-18, IFN-γ, and TOS, and oxidative stress index (OSI) were found significantly lower in IR + IL-18BP group, when compared to the IR group. Moreover, mRNA expression levels of inflammatory cytokines and apoptotic genes were prominently depressed in IR + IL-18BP pre-treatment group in histopathologic examination, there was a significant difference between the IR and other three groups (P < 0.001). These improvements were demonstrated with a total score of histopathologic damage. In our previous studies, we have demonstrated that IL-18BP has antioxidant, inflammatory, and protective effects on liver and spinal cord IR injury. Data established from the present study suggest that IL-18BP may exert anti-inflammatory, antiapoptotic, antioxidant, and protective effects on IAO-induced acute kidney injury in rats, and this would be the first study to be conducted in this field.

CONCLUSIONS

Data established from the present study suggest that IL-18BP may exert anti-inflammatory, antiapoptotic, antioxidant, and protective effects on IAO-induced acute kidney injury in rats.

Effect of IL-18 binding protein on hepatic ischemia-reperfusion injury induced by infrarenal aortic occlusion

PURPOSE

Severe local and systemic tissue damage called ischemia/reperfusion (IR) injury occurs during the period of reperfusion. Free oxygen radicals and proinflammatory cytokines are responsible for reperfusion injury. IL-18 binding protein (IL-18BP) is a natural inhibitor of IL-18. The balance between IL-18 and IL-18BP has an important role in the inflammatory setting. The present study aimed to investigate whether IL-18BP had a protective role in remote organ hepatic IR injury.

METHODS

Wistar-Albino rats were divided into three groups that contained seven rats. Group I (sham): Laparotomy and infrarenal abdominal aorta (AA) dissection were done but no clamping was done. Group II (I/R): The infrarenal AA was clamped by atraumatic microvascular clamp for 30 minutes and then was exposed to 90 minutes of reperfusion. Group III (IR + IL-18BP): 75 µg/kg of IL-18BP in 0.9% saline (1 mL) was administered 30 minutes before infrarenal AA dissection and clamping; 30 minutes of ischemia was applied and then was exposed to 90 minutes of reperfusion.

RESULTS

Serum AST, ALT, and LDH levels were remarkably higher in IR group and returned to normal levels in treatment group. The proinflammatory cytokine levels had decreased in treatment group, and was statistically significant compared with the IR group. Serum levels of total oxidant status and oxidative stress index decreased and levels of total antioxidant status increased by IL-18BP.

CONCLUSION

This study suggested that IL-18BP has antioxidant, anti-inflammatory and hepatoprotective effects in cases of IR with infrarenal AA induced liver oxidative damage.

Therapeutic targets for rheumatoid arthritis: Progress and promises

Recent therapeutic advancements in understanding of molecular and cellular mechanisms of rheumatoid arthritis (RA) have highlighted the strategies that aim to inhibit the harmful effects of up-regulated cytokines or other inflammatory mediators and to inhibit their associated signaling events. The utility of cytokine as therapeutic targets in RA has been unequivocally demonstrated by the success of tumor necrosis factor (TNF)-α blockade in clinical practice. Partial and non-responses to TNF-α blocking agents, however, together with the increasing clinical drive to remission induction, requires that further therapeutic targets be identified. Numerous proinflammatory mediators with their associated cell signaling events have now been demonstrated in RA, including interleukin (IL)-1 and IL-12 superfamilies. Continued efforts are ongoing to target IL-6, IL-15 and IL-17 in clinical trials with promising data emerging. In the present review, we focus on IL-7, IL-18, IL-32 and IL-10 family of cytokines (IL-19, IL-20 and IL-22) as they are implicated in contributing to the pathogenesis of RA, which could be targeted and offer new therapeutic options for RA therapy. Recent evidences also suggest that multiligand receptor for advanced glycation end products (RAGE), several adipokines and various components of immune system play a critical role in the pathophysiology of RA; therefore we have also highlighted them as therapeutic targets for RA therapy. Components of subcellular pathways, involve in nuclear transcription factor (NF)-κB, mitogen-activated protein kinases (MAPKs) and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway have also been discussed and offer several novel potential therapeutic opportunities for RA.

BIRB 796 has Distinctive Anti-inflammatory Effects on Different Cell Types

The pro-inflammatory cytokines tumor necrosis factor-α (TNFα) and interleukin (IL)-1β are crucial mediators involved in chronic inflammatory diseases. Inflammatory signal pathways regulate inflammatory cytokine expression-mediated by p38 mitogen activated protein kinase (p38MAPK). Therefore, considerable attention has been given to p38MAPK as a target molecule for the development of a novel anti-inflammatory therapeutics. BIRB 796, one of p38MAPK inhibitor, is a candidate of therapeutic drug for chronic inflammatory diseases. In this study, we investigated the effect of BIRB 796 on inflammatory cytokine productions by lipopolysaccharide (LPS) in different immune cell types. BIRB 796 reduced LPS-mediated IL-8 production in THP-1 cells but not in Raw 264.7 cells. Further analysis of signal molecules by western blot revealed that BIRB 796 sufficiently suppressed LPS-mediated phosphorylation of p38MAPK in both cell types whereas it failed to block inhibitor of kappa B (I-κB) degradation in Raw 264.7 cells. Taken together, these results suggest that the anti-inflammatory function of BIRB 796 depends on cell types.

Human astrocytes express a novel NLRP2 inflammasome

Central nervous system (CNS) trauma involves extensive cellular damage that is due, in part, to an innate inflammatory response induced by extracellular ATP. The innate immune response is regulated by pattern recognition receptors (PRRs), which include NOD-like receptors (NLRs). The PRRs and signaling cascades that regulate innate glial responses to CNS injury remain largely undefined. In this report, we show that human astrocytes express the NLR protein 2 (NLRP2) inflammasome that is activated by the danger associated molecular pattern (DAMP) ATP. The NLRP2 inflammasome is a multiprotein complex that consists of NLRP2, the adaptor protein apoptosis-speck-like protein containing a caspase recruitment domain (ASC) and caspase-1. NLRP2 also interacts with the P2X7 receptor and the pannexin 1 channel. Stimulation of human astrocytes with ATP resulted in activation of the NLRP2 inflammasome leading to the processing of inflammatory caspase-1 and interleukin-1β (IL-1β). ATP-induced activation of the NLRP2 inflammasome was inhibited by the pannexin 1 inhibitor probenecid and by the P2X7 receptor antagonist Brilliant Blue G (BBG). siRNA knockdown of NLRP2 significantly decreased NLRP2 levels and caspase-1 processing in human astrocytes in response to ATP. Our findings suggest that the astrocytic NLRP2 inflammasome is an important component of the CNS inflammatory response and that the NLRP2 inflammasome may be a therapeutic target to inhibit inflammation induced by CNS injury.

Protective effects of exogenous interleukin 18-binding protein in a rat model of acute renal ischemia-reperfusion injury

Ischemia-reperfusion (I/R) renal injury is considered the most common cause of acute kidney injury (AKI). The pathophysiology of I/R AKI involves a complex interplay among tubular epithelial cell injury, microcirculation dysfunction, and inflammation. Interleukin 18-binding protein (IL-18BP) is a natural inhibitor of IL-18 a cytokine that plays an important role in the pathogenesis of AKI. Therefore, we hypothesized that exogenous IL-18BP could protect against renal injuries after kidney I/R. Male Sprague-Dawley rats were divided into three groups: a sham operation group, I/R with vehicle injection, and I/R with IL-18BP injection. Rats underwent bilateral renal pedicle clamping, and IL-18BP or vehicle was administered just before reperfusion. Rats were killed 6, 24, and 72 h after reperfusion. After IL-18BP treatment, renal tubule epithelium showed reduced apoptosis and enhanced proliferation. For peritubular capillary (PTC) endothelium, apoptosis was inhibited, and there was an increase in PTC endothelium density. Macrophage infiltration was inhibited, and inflammatory cytokines were downregulated. Increased expression of vascular endothelial growth factor and decreased expression of thrombospondin 1 were also observed. Exogenous IL-18BP attenuated renal injury caused by I/R via inhibiting inflammation in the renal tissue and protecting tubular epithelium and PTC endothelium.

Soluble IL-18 receptor complex: a new star in the firmament of rheumatoid arthritis diagnosis?

It has long been recognized that laboratory tests are useful in the diagnosis of disease and to monitor treatment outcome. Their performance has become even more demanding with the development of personalized medicine. In patients with rheumatoid arthritis (RA) the standard biochemical tests measure serological markers of disease, such as C-reactive protein, and RA-associated auto-antibodies, such as rheumatoid factor and anti-citrullinated protein antibodies. The information obtained from these markers does not, however, provide a complete picture of the disease and treatment efficacy. New biomarkers based on cytokine receptor complexes are promising for RA theragnostics.

Interleukin-18 binding protein transgenic mice are protected against ischemic acute kidney injury

IL-18 function is neutralized in IL-18 binding protein transgenic (IL-18BP Tg) mice. First, we determined whether IL-18BP Tg mice are protected against ischemic acute kidney injury (AKI). Ischemic AKI was induced by bilateral renal pedicle clamping. IL-18BP Tg mice were functionally and histologically protected against ischemic AKI as determined by blood urea nitrogen, serum creatinine, and acute tubular necrosis score. We have demonstrated that the injurious effect of IL-18 in the kidney is independent of neutrophils and lymphocytes. Thus the effect of IL-18 inhibition on renal macrophage infiltration was determined. The number of macrophages was significantly reduced in IL-18BP Tg compared with wild-type kidneys. To determine the cytokines and chemokines that are dependent on IL-18, we performed flow cytometry based assays. Multiple chemokines/cytokines, IL-3, IL-6, IL-15, IL-18, leukemia inhibitory factor, macrophage colony-stimulating factor, macrophage inflammatory protein-2, granulocyte-macrophage colony-stimulating factor, and monocyte chemotactic protein-1 were significantly increased in AKI vs. sham kidneys. Only CXCL1 (also known as KC or IL-8) was significantly increased in AKI vs. sham kidneys and significantly reduced in IL-18BP Tg AKI vs. wild-type AKI kidneys. To determine whether macrophages are the source of CXCL1 in the kidney, we depleted macrophages with liposomal encapsulated clodronate. CXCL1 was significantly decreased in macrophage-depleted vs. control AKI mice. In summary, in ischemic AKI in mice, 1) IL-18BP Tg mice are functionally and histologically protected, 2) macrophage infiltration in the kidney and CXCL1 are significantly reduced in IL-18BP Tg mice, and 3) macrophage depletion significantly reduces CXCL1 in the kidney. In conclusion, protection against ischemic AKI in IL-18BP Tg mice is associated with less macrophage infiltration and less production of CXCL1 in the kidney.

Biomarkers of acute kidney injury

The diagnosis of acute kidney injury (AKI) is usually based on measurements of blood urea nitrogen (BUN) and serum creatinine. BUN and serum creatinine are not very sensitive or specific for the diagnosis of AKI because they are affected by many renal and nonrenal factors that are independent of kidney injury or kidney function. Biomarkers of AKI that are made predominantly by the injured kidney have been discovered in preclinical studies. In clinical studies of patients with AKI, some of these biomarkers (eg, interleukin-18, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1) have been shown to increase in the urine before the increase in serum creatinine. These early biomarkers of AKI are being tested in different types of AKI and in larger clinical studies. Biomarkers of AKI may also predict long-term kidney outcomes and mortality.

A molecular platform in neurons regulates inflammation after spinal cord injury

Vigorous immune responses are induced in the immune privileged CNS by injury and disease, but the molecular mechanisms regulating innate immunity in the CNS are poorly defined. The inflammatory response initiated by spinal cord injury (SCI) involves activation of interleukin-1beta (IL-1beta) that contributes to secondary cell death. In the peripheral immune response, the inflammasome activates caspase-1 to process proinflammatory cytokines, but the regulation of trauma-induced inflammation in the CNS is not clearly understood. Here we show that a molecular platform [NALP1 (NAcht leucine-rich-repeat protein 1) inflammasome] consisting of caspase-1, caspase-11, ASC (apoptosis-associated speck-like protein containing a caspase-activating recruitment domain), and NALP1 is expressed in neurons of the normal rat spinal cord and forms a protein assembly with the X-linked inhibitor of apoptosis protein (XIAP). Moderate cervical contusive SCI induced processing of IL-1beta, IL-18, activation of caspase-1, cleavage of XIAP, and promoted assembly of the multiprotein complex. Anti-ASC neutralizing antibodies administered to injured rats entered spinal cord neurons via a mechanism that was sensitive to carbenoxolone. Therapeutic neutralization of ASC reduced caspase-1 activation, XIAP cleavage, and interleukin processing, resulting in significant tissue sparing and functional improvement. Thus, rat spinal cord neurons contain a caspase-1, pro-ILbeta, and pro-IL-18 activating complex different from the human NALP1 inflammasome that constitutes an important arm of the innate CNS inflammatory response after SCI.

Novel targets and new potential: developments in the treatment of inflammation in chronic kidney disease

BACKGROUND

Patients with chronic kidney disease (CKD) of all stages experience extremely high mortality, with cardiovascular causes accounting for about half of all their deaths. Traditional risk factors such as hypertension, hypercholesterolemia and diabetes mellitus cannot explain the excessively high cardiovascular mortality in CKD. Chronic inflammation is one of the novel risk factors that appear to contribute to the increased mortality seen in patients with CKD. Therapeutic interventions targeting chronic inflammation in CKD may lead to improved outcomes.

OBJECTIVES

To describe the role of inflammation in CKD and to review anti-inflammatory pharmacologic therapies that could have a role in its therapy.

METHODS

A review of the literature was carried out and expert opinion expressed.

RESULTS/CONCLUSION

Inflammation is a common and significant problem in CKD. There are currently no approved pharmacologic anti-inflammatory therapies in CKD but several agents are being studied in early clinical trials, while others could become viable alternatives in the future.

Interleukin-18 gene polymorphism, but not interleukin-2 gene polymorphism, is associated with rheumatoid arthritis

To investigate whether polymorphisms of IL-2 and IL-18 genes are associated with rheumatoid arthritis (RA), polymorphisms of IL-2 and IL-18 genes were detected by polymerase-chain-reaction-based restriction analysis in the patients with RA and normal controls. The results for the IL-18 gene revealed a significant difference between the patients and the normal controls (p = 0.000003), but there was no significant difference for the IL-2 gene (p = 0.876). The IL-18 gene 105A allele was associated with RA in Chinese patients. Individuals possessing the 105A allele had a higher incidence of RA. A lack of association of IL-2 gene polymorphism between RA patients and healthy individuals was noted. The results of this study provide genetic evidence that IL-18-105A/C polymorphism may play an effective role in RA.

Restraint stress decreases virus-induced pro-inflammatory cytokine mRNA expression during acute Theiler's virus infection

Stressful life events have been associated with the onset and/or exacerbation of multiple sclerosis (MS). Our previous studies have indicated that restraint stress (RS) reduces inflammation and virus-induced chemokine expression in the Theiler's virus-induced demyelination (TVID) model of MS. Here we report that RS significantly reduced the virus-induced interferon-gamma mRNA levels in the brain. Additionally, mRNA levels of lymphotoxin-beta, tumor necrosis factor-alpha, and interferon-gamma in the brain were negatively correlated with viral titers in the brain. These results indicated an immunosuppressive effect of stress during early TVID causing impaired viral clearance, which may be a potential exacerbating factor for later demyelination.

MyD88 deficiency results in tissue-specific changes in cytokine induction and inflammation in interleukin-18-independent mice infected with Borrelia burgdorferi

Toll-like receptors (TLRs) play an important role in the control of infection with Borrelia burgdorferi. Deficiencies in TLR-2 or the shared TLR adapter molecule MyD88 have been shown to result in greatly increased bacterial burdens in mice. However, although in vitro studies have shown that the activation of TLR pathways by B. burgdorferi results in the release of inflammatory cytokines, studies in deficient mice have shown either no change or increased rather than decreased inflammation in infected animals. In this study, we looked at mechanisms to explain the increase in inflammation in the absence of MyD88. We found that MyD88-deficient mice infected with B. burgdorferi did not show increased inflammation at sites typically associated with Lyme disease (joints and heart). However, there was markedly increased inflammation in the muscles, kidneys, pancreas, and lungs of deficient animals. Muscle inflammation was typically seen perivascularly and perineuronally similar to that seen in infected humans. Chemotactic chemokines and cytokines were greatly increased in the muscle and kidneys of MyD88-deficient animals but not in the joints or heart tissue, suggesting that MyD88-independent pathways for recognizing B. burgdorferi and inducing these chemokines are present in the muscle and kidneys. Interleukin-18 signaling through MyD88 does not appear to play a role in either control of infection or inflammation.

Pharmacokinetics of IL-18 binding protein in healthy volunteers and subjects with rheumatoid arthritis or plaque psoriasis

IL-18 binding protein (BP) neutralizes the activity of IL-18, a cytokine implicated in psoriasis and rheumatoid arthritis (RA). We investigated the pharmacokinetics, pharmacodynamics and safety of recombinant human IL-18 BP (r-hIL-18 BP) in healthy volunteers and subjects with psoriasis or RA in four phase I studies. A) Healthy volunteers (n = 24) were randomised to receive a single subcutaneous (sc) injection of r-hIL-18 BP (20, 70, 210 or 350 mg) or placebo. B) Healthy volunteers (n = 10) were randomised to receive six sc injections of r-hIL-18 BP (35 or 175 mg, 48 h between injections) or placebo. C) Subjects with moderate-to-severe plaque psoriasis (n = 35) were randomised to receive r-hIL-18 BP (20, 160 or 320 mg, sc tiw) or placebo for 6 weeks. D) Subjects with active, moderate-to-severe RA (n = 36) were randomised to receive r-hIL-18 BP (20, 80, 160 mg, sc tiw) or placebo for 6 weeks. Pharmacokinetics, pharmacodynamics and safety were assessed in all four studies. r-hIL-18 BP showed a dose-dependent pharmacokinetic profile, with a peak serum concentration of 6-48 hours. With repeated sc injections tiw, a steady state was achieved in 1-2 weeks among subjects with psoriasis or RA. The majority of adverse events were mild or moderate in severity. Injection site reactions were the most frequently reported event in subjects with psoriasis or RA. r-hIL-18 BP displays dose-dependent pharmacokinetics, has a favourable safety profile and is well-tolerated in healthy volunteers and in subjects with moderate-to-severe plaque psoriasis or active, moderate-to-severe RA.

New Therapeutics in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic disorder characterized predominately by a chronic inflammatory polyarthritis, with frequent progression to joint destruction and disability. Radiographic joint damage develops in as many as 75% of patients within the first 2 years of disease. For this reason, current RA treatment approaches have focused on early intensive therapy with multiple disease-modifying antirheumatic drugs. The approval of new drugs for this indication has expanded the number of therapeutic options that can potentially allow for tight control of the inflammatory process.

Application of plasmid DNA encoding IL-18 diminishes development of herpetic stromal keratitis by antiangiogenic effects

HSV-1 infection of the eye can cause a blinding immunoinflammatory stromal keratitis (SK) lesion. Using the mouse model, we have demonstrated that angiogenesis is an essential step in lesion pathogenesis because its inhibition results in diminished severity. The molecules involved in causing corneal angiogenesis are multiple and include the vascular endothelial growth factor (VEGF) family of proteins. In this report we show that application of plasmid DNA encoding IL-18 to the cornea of mice before HSV-1 ocular infection resulted in reduced angiogenesis and diminished SK immunoinflammatory lesions. The antiangiogenic effects of IL-18 treatment appeared to be mediated by inhibition of VEGF production in the cornea. We also showed that IL-18 controlled VEGF expression in vitro and also decreased CpG oligodeoxynucleotide induced VEGF-dependent neovascularization. In addition the administration of IL-18-binding protein, an IL-18 antagonist, into the inflammatory eye resulted in elevated angiogenesis and increased VEGF expression. Our results indicate that IL-18 is an important endogenous negative regulator of HSV-induced angiogenesis resulting in reduced SK lesion severity. Our results could mean that IL-18 administration may represent a useful approach to manage unwanted angiogenesis.

Caspase-1-processed interleukins in hyperoxia-induced cell death in the developing brain

Infants born prematurely may develop neurocognitive deficits without an obvious cause. Oxygen, which is widely used in neonatal medicine, constitutes one possible contributing neurotoxic factor, because it can trigger neuronal apoptosis in the developing brain of rodents. We hypothesized that two caspase-1-processed cytokines, interleukin (IL)-1beta and IL-18, are involved in oxygen-induced neuronal cell death. Six-day-old Wistar rats or C57/BL6 mice were exposed to 80% oxygen for various time periods (2, 6, 12, 24, and 48 hours). Neuronal cell death in the brain, as assessed by Fluoro-Jade B and silver staining, peaked at 12 to 24 hours and was preceded by a marked increase in mRNA and protein levels of caspase 1, IL-1beta, IL-18, and IL-18 receptor alpha (IL-18Ralpha). Intraperitoneal injection of recombinant human IL-18-binding protein, a specific inhibitor of IL-18, attenuated hyperoxic brain injury. Mice deficient in IL-1 receptor-associated kinase 4 (IRAK-4), which is pivotal for both IL-1beta and IL-18 signal transduction, were protected against oxygen-mediated neurotoxicity. These findings causally link IL-1beta and IL-18 to hyperoxia-induced cell death in the immature brain. These cytokines might serve as useful targets for therapeutic approaches aimed at preserving neuronal function in the immature brain, which is exquisitely sensitive to a variety of iatrogenic measures including oxygen.

Interleukin-18: a therapeutic target in rheumatoid arthritis?

Interleukin 18 (IL-18), a member of the IL-1 superfamily of cytokines has been demonstrated to be an important mediator of both innate and adaptive immune responses. Several reports have implicated its role in the pathogenesis of rheumatoid arthritis (RA). Although biologic therapy is firmly established in the treatment of a number of inflammatory diseases including RA, partial and non-responder patients constitute residual unmet clinical need. The aim of this article is to briefly review the biology of, and experimental approaches to IL-18 neutralisation, together with speculation as to the relative merits of IL-18 as an alternative to existing targets.