Elevated levels of cerebrospinal fluid and plasma interleukin-37 in patients with Guillain-Barré syndrome

Current Biomarker Strategies in Autoimmune Neuromuscular Diseases

Inflammatory neuromuscular disorders encompass a diverse group of immune-mediated diseases with varying clinical manifestations and treatment responses. The identification of specific biomarkers has the potential to provide valuable insights into disease pathogenesis, aid in accurate diagnosis, predict disease course, and monitor treatment efficacy. However, the rarity and heterogeneity of these disorders pose significant challenges in the identification and implementation of reliable biomarkers. Here, we aim to provide a comprehensive review of biomarkers currently established in Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyneuropathy (CIDP), myasthenia gravis (MG), and idiopathic inflammatory myopathy (IIM). It highlights the existing biomarkers in these disorders, including diagnostic, prognostic, predictive and monitoring biomarkers, while emphasizing the unmet need for additional specific biomarkers. The limitations and challenges associated with the current biomarkers are discussed, and the potential implications for disease management and personalized treatment strategies are explored. Collectively, biomarkers have the potential to improve the management of inflammatory neuromuscular disorders. However, novel strategies and further research are needed to establish clinically meaningful biomarkers.

Interleukin-37 ameliorates cigarette smoke-induced lung inflammation in mice

Cigarette smoking (CS) is the leading cause of chronic obstructive pulmonary disease, and its severity is closely related to lung inflammation. Interleukin (IL)-37 is a newly discovered member of the IL-1 family with anti-inflammatory activity. Our study aimed to elucidate the effect of IL-37 on CS-induced lung inflammation in mice. In this study, mice were exposed to six cigarettes for 1 h three times daily (4 h smoke-free intervals) for 10 consecutive days. Mice were treated intranasally with IL-37-expressing lentivirus and empty lentivirus particles 1 day before the first CS or sham exposure. Mice were sacrificed on day 11 to evaluate the effect of IL-37 on CS-induced pulmonary inflammation in mice. Administering IL-37-expressing lentivirus significantly reduced CS-induced weight loss in mice compared to empty lentivirus controls (P < 0.05). Histological analysis showed that IL-37 significantly alleviated inflammatory cell recruitment, alveolar septum enlargement, alveolar wall attenuation, mucus hypersecretion, and goblet cell metaplasia in mouse lungs (P < 0.001). IL-37 expression also significantly inhibited CS-induced increases in inflammatory cells (including lymphocytes, neutrophils, and macrophages) in mouse lungs (P < 0.05), as well as pro-inflammatory cytokines such as IL-1β, IL-6, IL-17, monocyte chemotactic protein-1 and tumor necrosis factor-α production (P < 0.05). IL-37 also significantly reduced myeloperoxidase activity in mouse serum (P < 0.01) and lung tissues (P < 0.001). Therefore, IL-37 can ameliorate CS-induced pulmonary inflammation in mice and IL-37 may be a potential therapeutic strategy for CS-induced lung inflammatory diseases.

Recent Advances in Progresses and Prospects of IL-37 in Central Nervous System Diseases

Interleukin-37 (IL-37) is an effective anti-inflammatory factor and acts through intracellular and extracellular pathways, inhibiting the effects of other inflammatory cytokines, such as IL-1β, IL-6, and tumor necrosis factor-α (TNF-α), thereby exerting powerful anti-inflammatory effects. In numerous recent studies, the anti-inflammatory effects of IL-37 have been described in many autoimmune diseases, colitis, and tumors. However, the current research on IL-37 in the field of the central nervous system (CNS) is not only less, but mainly for clinical research and little discussion of the mechanism. In this review, the role of IL-37 and its associated inflammatory factors in common CNS diseases are summarized, and their therapeutic potential in CNS diseases identified.

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.

Circulating Interleukin-37 Levels in Healthy Adult Humans - Establishing a Reference Range

Interleukin (IL)-37 has an important function in limiting excessive inflammation. Its expression is increased in numerous inflammatory and autoimmune conditions and correlates with disease activity, suggesting it could have potential as a disease biomarker. Nevertheless, a reference range has yet to be determined. Our aim was to establish the first reference range of circulating IL-37 levels in healthy adult humans. PubMed was searched for studies reporting blood IL-37 concentrations in healthy adult subjects as measured by enzyme-linked immunosorbent assay. Nineteen studies were included in the analysis. Mean IL-37 levels were weighted by sample sizes, and weighted mean lower and upper levels ( ± 2SD of means) were calculated to provide a weighted mean and reference range. IL-37 levels were quantified in either serum or plasma from a total of 1035 (647 serum; 388 plasma) healthy subjects. The serum, plasma and combined matrix weighted means (reference ranges) were 72.9 (41.5 – 104.4) pg/mL, 83.9 (41.1 – 126.8) pg/mL, and 77.1 (41.4 – 112.8) pg/mL, respectively. There were no significant differences between serum and plasma means and upper and lower limits. Study means and upper IL-37 levels were significantly higher in Chinese population studies. From our analysis, a preliminary reference range for circulating IL-37 levels in healthy human adults has been established. In order to determine a reliable reference range for clinical application, large, prospective, multi-ethnic, healthy population studies are necessary. In addition, demographics, sample matrix, collection, processing and storage methods potentially affecting IL-37 detection levels should be thoroughly investigated.

IL-37b alleviates endothelial cell apoptosis and inflammation in Kawasaki disease through IL-1R8 pathway

Kawasaki disease (KD) is an acute vasculitis of pediatric populations that may develop coronary artery aneurysms if untreated. It has been regarded as the principal cause of acquired heart disease in children of the developed countries. Interleukin (IL)-37, as one of the IL-1 family members, is a natural suppressor of inflammation that is caused by activation of innate and adaptive immunity. However, detailed roles of IL-37 in KD are largely unclear. Sera from patients with KD displayed that IL-37 level was significantly decreased compared with healthy controls (HCs). QRT-PCR and western blot analyses showed that the expression level of IL-37 variant, IL-37b, was remarkably downregulated in human umbilical vein endothelial cells (HUVECs) exposed to KD sera-treated THP1 cells. Therefore, we researched the role of IL-37b in the context of KD and hypothesized that IL-37b may have a powerful protective effect in KD patients. We first observed and substantiated the protective role of IL-37b in a mouse model of KD induced by Candida albicans cell wall extracts (CAWS). In vitro experiments demonstrated that IL-37b alleviated endothelial cell apoptosis and inflammation via IL-1R8 receptor by inhibiting ERK and NFκB activation, which were also recapitulated in the KD mouse model. Together, our findings suggest that IL-37b play an effective protective role in coronary endothelial damage in KD, providing new evidence that IL-37b is a potential candidate drug to treat KD.

Purinergic Signaling of ATP in COVID-19 Associated Guillain-Barré Syndrome

Declared as a global public health emergency, coronavirus disease 2019 (COVID-19) is presented as a disease of the respiratory tract, although severe cases can affect the entire organism. Several studies have shown neurological symptoms, ranging from dizziness and loss of consciousness to cerebrovascular and neurodegenerative diseases. In this context, Guillain-Barré syndrome, an immune-mediated inflammatory neuropathy, has been closely associated with critical cases of infection with "severe acute respiratory syndrome of coronavirus 2" (SARS-CoV-2), the etiological agent of COVID-19. Its pathophysiology is related to a generalized inflammation that affects the nervous system, but neurotropism was also revealed by the new coronavirus, which may increase the risk of neurological sequel, as well as the mortality of the disease. Thus, considering the comorbidities that SARS-CoV-2 infection can promote, the modulation of purinergic signaling can be applied as a potential therapy. In this perspective, given the role of adenosine triphosphate (ATP) in neural intercommunication, the P2X7 receptor (P2X7R) acts on microglia cells and its inhibition may be able to reduce the inflammatory condition of neurodegenerative diseases. Finally, alternative measures to circumvent the reality of the COVID-19 pandemic need to be considered, given the severity of critical cases and the viral involvement of multiple organs.

Evidence of altered Th17 pathway signatures in the cerebrospinal fluid of patients with Guillain Barré Syndrome

Data indexing the contribution of various immuno-inflammatory components in the cerebrospinal fluid (CSF) towards the pathophysiology of Guillain Barré Syndrome (GBS) are limited. Th17 pathway plays crucial role in many immune mediated disorders of the nervous system. This study was aimed at exploring the role of Th17 pathway related cytokines in the CSF of patients with GBS. Levels of multiple key cytokines of Th17 pathway in CSF of patients with GBS (N = 37) and controls (N = 37) were examined in this prospective study using Bio-plex Pro Human Th17 cytokine assays in a Multiplex Suspension Array platform. The findings were correlated with clinical features and electrophysiological subtypes. Three key cytokines of Th17 pathway (IL-6, IL-17A and IL-22) were significantly elevated in CSF of patients with GBS as compared to controls. There was a positive correlation between the levels of IL-6 and IL-17A as well as between the levels of IL-17A and IL-22 in the CSF of patients with GBS. The CSF levels of IL-6 and IL-22 were negatively correlated with the duration of symptoms of GBS. None of the studied cytokines correlated with functional disability scores at admission to hospital or with the electrophysiological subtypes. Identification of Th17 pathway signatures in CSF sheds more insights into the pathogenic role of Th17 cells in GBS. These findings complement the contemporary knowledge and tender further support towards the involvement of Th17 pathway in GBS.

Insight into interleukin-37: The potential therapeutic target in allergic diseases

Allergic diseases are ubiquitous diseases with detrimental effects on the quality of life of people worldwide. Common allergic diseases include asthma, allergic rhinitis (AR) and allergic dermatitis (AD). Recently, studies have shown that interleukin (IL)-37, a novel cytokine in the IL-1 family, exhibits broad protective properties in various diseases, such as autoimmune diseases and cancer. IL-37 displays its anti-inflammatory effect on diseases by curbing innate and acquired immunity as well as inflammatory reactions. IL-37 functions by forming a complex with IL-18Rα and IL-1R8 extracellularly and can be translocated to the nucleus upon forming a complex with mothers against decapentaplegic homolog 3 (Smad3) intracellularly, thereby affecting gene transcription and signaling pathway activation. In addition, increasing evidence confirms that IL-37 expression is aberrant in asthma, AR and AD, which indicates that IL-37 may also play essential roles in allergic diseases. Furthermore, accumulating data obtained from recombinant IL-37 (rIL-37)-treated mice and from IL-37 transgenic (IL-37tg) mice suggest a protective role for IL-37. This review will detail the role of IL-37 in the occurrence and development of allergic diseases and discuss the potential of IL-37 as a therapeutic target in allergic diseases.

Potential role of IL-37 signaling pathway in feedback regulation of autoimmune Hashimoto thyroiditis

IL-37, the anti-inflammatory cytokine of the IL-1 family, plays several key roles in the regulation of autoimmune diseases. Yet, its role in Hashimoto's thyroiditis (HT) is not clear. In the present study, we found that, in tissues from HT patients, most of the follicular epithelial cells were positive for both IL-37 and single Ig IL-1-related receptor (SIGIRR) by immunohistochemical staining, while the infiltrating lymphocytes and other inflammatory cells hardly expressed any. Meanwhile, mRNA expression levels of IL-37 in peripheral blood mononuclear cells (PBMC) of HT patients were significantly higher than those in normal controls measured by quantitative real-time PCR. Finally, we studied the possible role of IL-37 in IFN-γ-stimulated rat FRTL-5 cells. The results showed that IL-1β, TNF-α, and MCP-1 mRNA levels were significantly decreased, while the expression of IL-4 mRNA was dramatically up-regulated in IFN-γ-stimulated rat thyroid cell line FRTL-5 pre-treated with IL-37. The current study, for the first time, demonstrated that the IL-37 network is involved in Hashimoto's thyroiditis, and IL-37 signaling pathway may ameliorate the excessive autoimmune responses in this chronic lymphocytic thyroiditis.

Peripheral Blood and Cerebrospinal Fluid Cytokine Levels in Guillain Barré Syndrome: A Systematic Review and Meta-Analysis

Background: Guillain Barré Syndrome (GBS) is an autoimmune disorder caused by the immune-mediated damage of the peripheral nervous system. Increasing evidence suggests that inflammatory cytokines are important mediators for the onset and progression of GBS. A number of clinical studies have demonstrated elevated levels of T helper-1 (Th1-), Th2-, and Th17-related cytokines in patients with GBS; however, the results were inconsistent across studies.

Methods: We performed a systematic review and a meta-analysis of studies comparing the levels of inflammatory cytokines in the cerebrospinal fluid and peripheral blood between patients with GBS and healthy individuals, using Comprehensive Meta-Analysis Version 2 software. A database search identified 30 studies comprising 1,302 patients with GBS and 1,073 healthy controls.

Results: The random-effects meta-analysis demonstrated that peripheral blood tumor necrosis factor-α (Hedges g, 1.544; 95% confidence interval (CI), 0.923–2.165; p < 0.001), interleukin-1β (IL-1β; Hedges g, 0.678; 95% CI, 0.183–1.172; p = 0.007), IL-6 (Hedges g, 0.630; 95% CI, 0.100–1.160; p = 0.02), IL-4 (Hedges g, 0.822; 95% CI, 0.220–1.423; p = 0.007), IL-17 (Hedges g, 1.452; 95% CI, 0.331–2.573; p = 0.011), interferon-γ (Hedges g, 1.104; 95% CI, 0.490–1.719; p < 0.001), and C-reactive protein (Hedges g, 0.909; 95% CI, 0.453–1.365; p < 0.001) levels were significantly increased in patients with GBS when compared with healthy controls. Contrastingly, the blood IL-10 and transforming growth factor-β levels were not significantly associated with GBS. Furthermore, the meta-analysis found that cerebrospinal fluid IL-17 levels were significantly associated with GBS (Hedges g, 1.882; 95% CI, 0.104–3.661; p = 0.038).

Conclusion: Altogether, our results clarified the circulating inflammatory cytokine profile in patients with GBS, and revealed that Th1-, Th2-, and Th17-related cytokines were highly elevated in the GBS patients, suggesting the potential use of these cytokines as biomarkers for GBS.

IL1F7 Gene Polymorphism Is not Associated with Rheumatoid Arthritis Susceptibility in the Northern Chinese Han Population: A Case-Control Study

Background:

Interleukin (IL)-37, also called IL1F7, is a natural inhibitor of inflammatory and immune responses. It is involved in the pathogenesis of rheumatoid arthritis (RA). This study aimed to investigate the role of IL1F7 gene polymorphism in RA susceptibility in a large cohort of patients.

Methods:

Five selected single-nucleotide polymorphisms in IL1F7 genes (rs2723186, rs3811046, rs4241122, rs4364030, and rs4392270) were genotyped by TaqMan Allelic Discrimination in Northern Chinese Han population. The allele and the genotype were compared between patients with RA and healthy controls. Association analyses were performed on the entire data set and on different RA subsets based on the status of the anti-cyclic citrullinated peptide antibody and the rheumatoid factor by logistic regression, adjusting for age and gender.

Results:

Trend associations were detected between rs2723186, rs4241122, rs4392270, and RA in Stage I (160 patients with RA; 252 healthy controls). Further validation in Stage II comprised 730 unrelated patients with RA (mean age: 54.9 ± 12.6 years; 81.6% females) and 778 unrelated healthy individuals (mean age: 53.5 ± 15.7 years; 79.5% females). No significant differences in the distributions of alleles and genotypes were observed between the case and control groups in both the entire set and the different RA subsets. Disease activity and age of RA onset were also not associated with genotype distributions.

Conclusion:

IL1F7 gene polymorphism does not significantly influence RA susceptibility in the Northern Chinese Han population.

Can we assess severity of Guillain-Barré syndrome using absolute monocyte count?

INTRODUCTION

Guillain-Barré syndrome (GBS) is an inflammatory demyelinating autoimmune disease, associated with blood-nerve barrier breakdown, inflammatory cells infiltration, and cytokine leakage in the peripheral nervous system. Currently, it has been revealed that monocytes play key roles in the inflammatory response. Therefore, we aimed to assess the correlation between monocyte count and GBS in this study.

METHODS

Retrospective study was conducted in 114 patients with GBS and 120 age- and gender-matched individuals.

RESULTS

Absolute monocyte count in patients with GBS was higher than that in healthy controls (0.61 ± 0.24 vs 0.41 ± 0.10; P  < .001). Interestingly, monocyte count had significant positive correlations with CRP, ESR, and disease severity of GBS (r = .244, P = .009; r = .269, P = .004; r = .322, P < .001). A cutoff value of 0.515 for monocyte count was observed in patients with GBS (areas under the curve = 0.808, 95% confidence interval = 0.749-0.868, P  < .001). Meanwhile, absolute monocyte count was independently associated with GBS in logistic regression analysis (odds ratio = 2.291, 95% confidence interval = 3.557-27.493, P < .001).

CONCLUSION

Our findings demonstrated that elevated monocyte count is independently associated with GBS patients, and suggested monocyte count is positively associated with disease severity of GBS.

Comprehensive cytokine profiling provides evidence for a multi-lineage Th responses in Guillain Barré Syndrome

Guillain Barré Syndrome (GBS) is one of the commonest acquired immune-mediated neuropathies, often preceded by infections. Although cellular immune responses are shown to substantially account for the pathophysiology of GBS, the precise mechanistic basis of risk and disease course remains enigmatic till date. Cytokines are best known for their abilities to drive cellular immunity and inflammation through their co-ordinated actions. Data obtained from clinical and animal model studies suggest important implications of some of the cytokines in the progression and recovery of GBS. However, these studies were performed on few cytokines and small set of GBS patients, thereby lacking a complete understanding of the patterns of association of cytokines representing Th1, Th2, and Th17 responses with GBS. We studied 65 well-characterized GBS patients and 73 age- and sex-matched healthy controls. A panel of 15 cytokines representing Th1, Th2 and Th17 pathways was assayed using Multiplex Suspension Array platform. Plasma levels of five cytokines were found to be altered in GBS patients compared to healthy control subjects: (i) IL-1β exhibited reduced levels, and (ii) IFN-γ, IL-4, IL-21 and IL-33 were elevated in GBS patients. The most important finding of this study was up-regulated expression of IL-21 and IL-33 in patients with GBS. Given the role of IL-33 as an alarmin, the elevated level of this cytokine provides important indication about a much broader role of cytokines in GBS. This study also provides evidence towards a multi-lineage Th cells (Th1, Th2 and Th17) associated cytokine responses in the pathophysiology of GBS.

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

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

Associations between tumor necrosis factor-α gene polymorphisms and the risk of Guillain-Barré syndrome and its subtypes: A systematic review and meta-analysis

This meta-analysis aimed to assess the relationship between tumor necrosis factor-α (TNF-α) polymorphisms and Guillain-Barré syndrome (GBS) or its subtypes of acute inflammatory demyelinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), and acute motor-sensory axonal neuropathy (AMSAN). A total of six studies with 1013 cases and 1029 controls were included. Our pooled data indicated that TNF-α 308G/A polymorphism was significantly associated with GBS, AMAN, and AMSAN but not with AIDP; TNF-α 857C/T polymorphism was significantly associated with AMAN but not with GBS or AIDP. Besides, no association was found between TNF-α 238G/A and 863C/A polymorphisms and GBS or its subtypes.

Is serum bilirubin associated with the severity of Guillain-Barré syndrome?

OBJECTIVE

Our aim was to assess the correlation between serum bilirubin levels and Guillain-Barré syndrome (GBS).

PATIENTS AND METHODS

One hundred and one newly diagnosed patients with Guillain-Barré syndrome and 111 healthy age- and sex-matched individuals in the First Affiliated Hospital of Guangxi Medical University (Guangxi, China) from June 2012 to May 2017 were included in this study. Clinical characteristics and laboratory parameters of Guillain-Barré syndrome patients and healthy controls were retrospectively analysed.

RESULTS

Serum bilirubin levels in Guillain-Barré syndrome patients were significantly lower as compared with those in healthy controls (p < 0.001); besides, log C-reactive protein and erythrocyte sedimentation rate were significantly higher. We found that there was a negative correlation between GBS disability scale scores and total bilirubin, direct bilirubin, indirect bilirubin (r = -0.541, P < 0.001; r = -0.403, P < 0.001; r = -0.526, P < 0.001), respectively. Among patients with GBS, serum total bilirubin, direct bilirubin, and indirect bilirubin levels were independently associated with Guillain-Barré syndrome disability scale scores in multiple linear regression analysis, respectively.

CONCLUSIONS

We observed that serum bilirubin levels were lower in patients with Guillain-Barré syndrome, and suggested total bilirubin, direct bilirubin, and indirect bilirubin were independently and inversely associated with Guillain-Barré syndrome severity.

Measurement of Elevated IL-37 Levels in Acute Ischemic Brain Injury: A Cross-sectional Pilot Study

Interleukin (IL)-37 is a new member of the IL-1 cytokine family with a defined role as a negative feedback inhibitor of proinflammatory responses. IL-37 has yet to be evaluated in non-immune-mediated neurological diseases, such as ischemic or hemorrhagic strokes. This study aimed to measure urine and serum IL-37 levels in patients with ischemic stroke. Twelve patients consented for our study. Two sets of serum and urine samples were obtained and analyzed, one upon admission to the hospital and the second the next morning. The trends in serum levels of IL- 37 in six stroke patients and the trends in the urine levels of eight stroke patients were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Our pilot study showed IL-37 levels in urine in stroke patients ranging between 210 and 4,534. Serum IL-37 levels were in the range of 44 - 5,235 in patients with ischemic stroke. Three patients who presented within three hours of stroke onset had IL-37 serum levels of 2,655 pg/ml, 3,517 pg/ml, and 5,235 pg/ml, respectively. In all others, it ranged much less than that, with the trend of delayed presentation giving lower IL-37 levels. The study shows a rather stable early elevation of serum IL-37 levels post-ischemic stroke. IL-37 plays a certain role in mediating post-stroke inflammation with a significant increase in serum levels of this novel cytokine observed in ischemic stroke patients. Further large-scale studies need to be done to establish its definite role. A prospective "CRISP" trial is registered with the ClinicalTrials.gov (Identifier: NCT03297827) to determine the role of IL-37 in modulating post-stroke inflammation.

Suppression of innate inflammation and immunity by interleukin-37

IL-37 is unique in the IL-1 family in that unlike other members of the family, IL-37 broadly suppresses innate immunity. IL-37 can be elevated in humans with inflammatory and autoimmune diseases where it likely functions to limit inflammation. Transgenic mice expressing human IL-37 (IL37-tg) exhibit less severe inflammation in models of endotoxin shock, colitis, myocardial infarction, lung, and spinal cord injury. IL37-tg mice have reduced antigen-specific responses and dendritic cells (DCs) from these mice exhibit characteristics of tolerogenic DCs. Compared to aging wild-type (WT) mice, aging IL37-tg mice are protected against B-cell leukemogenesis and heart failure. Treatment of WT mice with recombinant human IL-37 has been shown to be protective in several models of inflammation and injury. IL-37 binds to the IL-18 receptor but then recruits the orphan IL-1R8 (formerly TIR8 or SIGIRR) in order to function as an inhibitor. Here, we review the discovery of IL-37, its production, release, and mechanisms by which IL-37 reduces inflammation and suppresses immune responses. The data reviewed here suggest a therapeutic potential for IL-37.

Elevated serum interleukin-37 level is a predictive biomarker of poor prognosis in epithelial ovarian cancer patients

PURPOSE

Interleukin-37 (IL-37) has been identified as a novel anti-inflammatory cytokine which is involved in tumor development. This study aimed to evaluate the expression of IL-37 in serum and determine its clinical significance in human epithelial ovarian cancer (EOC).

METHODS

Enzyme-linked immunosorbent assay (ELISA) was performed to examine the serum IL-37 levels in 76 patients with EOC and 76 healthy controls. The association of IL-37 levels with clinical factors and prognosis of EOC patients was analyzed. The diagnostic accuracy of serum IL-37 was performed by receiver operator characteristic (ROC) curve analysis.

RESULTS

Serum IL-37 levels in patients with EOC (187.3 ± 75.57 pg/ml) were significantly higher than those in healthy controls (84.89 ± 28.92 pg/ml, P < 0.001). High serum IL-37 levels were significantly associated with FIGO stage (P < 0.001), tumor size (P = 0.002), lymph node metastasis (P = 0.021), positive recurrence (P = 0.047) and residual tumor size (P < 0.001). The Kaplan-Meier survival analysis demonstrated that high serum IL-37 levels were significantly associated with poor overall survival and the progression-free survival (log-rank, P = 0.026, and P = 0.039, respectively). Univariate and multivariate analysis indicated that serum IL-37 levels (HR = 3.007, 95% CI 2.125-4.842, P = 0.008) were an independent prognostic factor for EOC patients. ROC curve analyses revealed an AUC (the areas under the ROC curve) of 0.881 (95% CI 0.829-0.945; P < 0.001).

CONCLUSIONS

High serum IL-37 levels are associated with an unfavorable prognosis of EOC patients. IL-37 may serve as a promising and useful prognostic biomarker for EOC.

Interleukin 37 expression in mice alters sleep responses to inflammatory agents and influenza virus infection

Multiple interactions between the immune system and sleep are known, including the effects of microbial challenge on sleep or the effects of sleep loss on facets of the immune response. Cytokines regulate, in part, sleep and immune responses. Here we examine the role of an anti-inflammatory cytokine, interleukin-37 (IL-37) on sleep in a mouse strain that expresses human IL-37b (IL37tg mice). Constitutive expression of the IL-37 gene in the brains of these mice under resting conditions is low; however, upon an inflammatory stimulus, expression increases dramatically. We measured sleep in three conditions; (a) under baseline conditions and after 6 h of sleep loss, (b) after bolus intraperitoneal administration of lipopolysaccharide (LPS) or IL-1β and (c) after intranasal influenza virus challenge. Under baseline conditions, the IL37tg mice had 7% more spontaneous non-rapid eye movement sleep (NREMS) during the light period than wild-type (WT) mice. After sleep deprivation both WT mice and IL37tg mice slept an extra 21% and 12%, respectively, during the first 6 h of recovery. NREMS responses after sleep deprivation did not significantly differ between WT mice and IL37tg mice. However, in response to either IL-1β or LPS, the increases in time spent in NREMS were about four-fold greater in the WT mice than in the IL37tg mice. In contrast, in response to a low dose of mouse-adapted H1N1 influenza virus, sleep responses developed slowly over the 6 day recording period. By day 6, NREMS increased by 10% and REMS increased by 18% in the IL37tg mice compared to the WT mice. Further, by day 4 IL37tg mice lost less weight, remained more active, and retained their body temperatures closer to baseline values than WT mice. We conclude that conditions that promote IL-37 expression attenuate morbidity to severe inflammatory challenge.

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Sleep responses to mild acute sleep deprivation are similar in mice transgenic for interleukin-37 (IL37tg) IL37tg and wild type (WT) mice.

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Sleep responses induced by either IL-β or LPS are greatly attenuated in IL37tg mice compared to WT mice.

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After influenza virus challenge, IL37tg mice have reduced morbidities and enhanced sleep responses.

Quantitative proteomics reveals Piccolo as a candidate serological correlate of recovery from Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune-mediated peripheral neuropathy of unknown cause. However, about a quarter of GBS patients have suffered a recent bacterial or viral infection, and axonal forms of the disease are especially common in these patients. Proteomics is a good methodological approach for the discovery of disease biomarkers. Until recently, most proteomics studies of GBS and other neurodegenerative diseases have focused on the analysis of the cerebrospinal fluid (CSF). However, serum represents an attractive alternative to CSF because it is easier to sample and has potential for biomarker discovery. The goal of this research was the identification of serum biomarkers associated with recovery from GBS. To address this objective, a quantitative proteomics approach was used to characterize differences in the serum proteome between a GBS patient and her healthy identical twin in order to lessen variations due to differences in genetic background, and with additional serum samples collected from unrelated GBS (N = 3) and Spinal Cord Injury (SCI) (N = 3) patients with similar medications. Proteomics results were then validated by ELISA using sera from additional GBS patients (N = 5) and healthy individuals (N = 3). All GBS and SCI patients were recovering from the acute phase of the disease. The results showed that Piccolo, a protein that is essential in the maintenance of active zone structure, constitutes a potential serological correlate of recovery from GBS. These results provided the first evidence for the Piccolo´s putative role in GBS, suggesting a candidate target for developing a serological marker of disease recovery.

Increased serum concentrations of transforming growth factor-β1 (TGF-β1) in patients with Guillain-Barré syndrome

BACKGROUND

Guillain-Barré syndrome (GBS) is an acquired demyelinating peripheral neuropathy. It has shown that macrophage activation contribute to the pathogenesis of GBS. Therefore macrophage-mediated factors could be the potential markers for disease diagnosis and status of GBS.

METHODS

We measured serum concentrations of 4 macrophage-mediated factors, including interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1), vascular cell adhesion protein 1 (VCAM-1) and vascular endothelial growth factor (VEGF), in 23 chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), 28 GBS, 11 Miller-Fisher syndrome (MFS), 40 multiple sclerosis (MS), and 12 Alzheimer's disease (AD) patients, as well as 15 healthy controls.

RESULTS

Serum TGF-β1 concentration of GBS patients (35.94±2.55ng/ml) was significantly higher compared with CIDP (25.46±1.40ng/ml, P<0.001), MFS (25.32±2.31ng/ml, P=0.010), MS (21.35±0.90ng/ml, P<0.001) and AD patients (22.92±1.82ng/ml, P<0.001), as well as healthy controls (23.12±1.67ng/ml, P<0.001). A positive correlation between serum TGF-β1 concentrations and Hughes' functional grading scales was observed in GBS patients. Serum concentrations of IL-6, VCAM-1 and VEGF were similar between the studied groups.

CONCLUSION

The high serum concentrations of TGF-β1 and the correlation between serum TGF-β1 concentration and disease severity highlight the potential of TGF-β1 as a biomarker of GBS.

Interleukin-37 suppresses tumor growth through inhibition of angiogenesis in non-small cell lung cancer

BACKGROUND

Interleukin-37 (IL-37), a newly identified member of the IL-1 family, has been known to play an immunosuppressive role in a variety of inflammatory disorders, but whether it participates in the regulation of pathogenesis of non-small cell lung cancer (NSCLC) has not been investigated.

METHODS

Real-time polymerase chain reaction (PCR), western blotting, and immunohistochemical staining were employed to detect IL-37 expression in NSCLC tissues and corresponding adjacent tissues. The correlations between IL-37 expression and clinicopathological characteristics, prognosis were analyzed. Stable clone with overexpression of IL-37 was generated in H1299 cell lines. Cell growth, cell cycle and cell apoptosis assays were carried out for detecting proliferation and apoptosis of H1299 cells. The effects of IL-37 on NSCLC progression in vivo was performed in a xenografted lung tumor model in nude mice. The concentrations of IL-37 and VEGF in the s growth medium supernatants were quantified by ELISA. The antiangiogenic effect of IL-37 on HUVEC was measured by tube formation assay.

RESULTS

IL-37 mRNA and protein expressions were significantly decreased in NSCLC tissues, and decreased intratumoral IL-37 expression was significantly associated with tumor state, TNM stage and poor prognosis in NSCLC patients. In addition, intratumoral IL-37 expression was an independent prognostic factors for Overall survival (hazard ratio = 2.047; P = 0.011). Overexpression of IL-37 exerted no direct effect on cell proliferation and apoptosis of H1299 lung cancer cells in vitro, but significantly inhibited tumor growth in a H1299 xenograft model in vivo. Furthermore, there was no significant change in immune cell infiltration in IL-37 over-expressing tumors; instead, we found decreased microvessel density (MVD) and VEGF levels in IL-37-expressing tumors. Additional studies showed IL-37 could directly inhibit HUVEC cells growth and capillary structure formation. Finally, we found that decreased IL-37 expression was associated with high MVD in NSCLC patients.

CONCLUSIONS

Our findings demonstrate a protective role for IL-37 in lung cancer development, possibly through inhibiting tumor angiogenesis. IL-37 could serve as a promising therapeutic target for NSCLC.

IL-37 Is a Novel Proangiogenic Factor of Developmental and Pathological Angiogenesis

OBJECTIVE

Angiogenesis is tightly controlled by growth factors and cytokines in pathophysiological settings. Interleukin 37 (IL-37) is a newly identified cytokine of the IL-1 family, some members of which are important in inflammation and angiogenesis. However, the function of IL-37 in angiogenesis remains unknown. We aimed to explore the regulatory role of IL-37 in pathological and physiological angiogenesis.

APPROACH AND RESULTS

We found that IL-37 was expressed and secreted in endothelial cells and upregulated under hypoxic conditions. IL-37 enhanced endothelial cell proliferation, capillary formation, migration, and vessel sprouting from aortic rings with potency comparable with that of vascular endothelial growth factor. IL-37 activates survival signals including extracellular signal-regulated kinase 1/2 and AKT in endothelial cells. IL-37 promoted vessel growth in implanted Matrigel plug in vivo in a dose-dependent manner with potency comparable with that of basic fibroblast growth factor. In the mouse model of retinal vascular development, neonatal mice administrated with IL-37 displayed increased neovascularization. We demonstrated further that IL-37 promoted pathological angiogenesis in the mouse model of oxygen-induced retinopathy.

CONCLUSIONS

Our findings suggest that IL-37 is a novel and potent proangiogenic cytokine with essential role in pathophy siological settings.

Elevated Circulating Levels of Inflammatory Markers in Patients with Acute Coronary Syndrome

Objective. We evaluated inflammatory cytokines and chemokine in peripheral blood mononuclear cells (PBMCs) in patients with either acute coronary syndrome (ACS) or stable coronary artery disease (CAD). Methods. We enrolled 20 ACS patients and 50 stable CAD patients without previous history of ACS who underwent cardiac catheterization. Patients with an estimated glomerular filtration rate of ≤30 mL/min/1.73 m(2) and C-reactive protein of ≥1.0 mg/dL were excluded. Blood samples were collected from the patients just before catheterization, and PBMCs were isolated from the whole blood. The levels of inflammatory cytokines and chemokine were measured by using real-time quantitative polymerase chain reaction and immunoassays. Results. The expression of tumor necrosis factor alpha (TNF-α), interleukin- (IL-) 6, IL-10, IL-23A, IL-27, and IL-37 was significantly higher in the ACS group than in the CAD group (P < 0.05). In contrast, the expression of IL-33 was significantly lower in the ACS group than in the CAD group (P < 0.05). The ACS patients had higher plasma levels of TNF-α, IL-6, and IL-10 in the ACS group than in the CAD group. Conclusion. Circulating levels of pro-/anti-inflammatory cytokines, including IL-23A, IL-27, IL-33, and IL-37, may be associated with the pathogenesis of atherosclerosis in ACS patients.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Biomarkers of Guillain-Barré Syndrome: Some Recent Progress, More Still to Be Explored

Guillain-Barré syndrome (GBS), the axonal subtype of which is mainly triggered by C. jejuni with ganglioside-mimicking lipooligosaccharides (LOS), is an immune-mediated disorder in the peripheral nervous system (PNS) accompanied by the disruption of the blood-nerve barrier (BNB) and the blood-cerebrospinal fluid barrier (B-CSF-B). Biomarkers of GBS have been extensively explored and some of them are proved to assist in the clinical diagnosis and in monitoring disease progression as well as in assessing the efficacy of immunotherapy. Herein, we systemically review the literature on biomarkers of GBS, including infection-/immune-/BNB, B-CSF-B, and PNS damage-associated biomarkers, aiming at providing an overview of GBS biomarkers and guiding further investigations. Furthermore, we point out further directions for studies on GBS biomarkers.

Plasma Interleukin-37 Is Elevated in Patients with Rheumatoid Arthritis: Its Correlation with Disease Activity and Th1/Th2/Th17-Related Cytokines

Interleukin- (IL-) 37 is a novel anti-inflammatory cytokine that suppresses immune response and inflammation. This study was performed to determine whether IL-37 was elevated in patients with rheumatoid arthritis (RA) and investigate the correlation between IL-37 level and disease activity and the concentration of Th1/Th2/Th17-related cytokines. Clinical parameters of disease activity, including the 28-joint disease activity score (DAS28) and C-reactive protein (CRP), were collected in 34 RA patients and 34 age- and sex-matched healthy controls. Plasma IL-37 was measured by ELISA. Plasma levels of TNF-α, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13, IL-17, G-CSF, GM-CSF, IFN-γ, MCP-1, and MIP-1β were analyzed using the Bio-Plex suspension array system. It was found that IL-37 levels were elevated markedly in RA patients and almost undetectable in healthy controls. In addition, IL-37 levels in patients with active RA were significantly enhanced as compared with those in patients of remission. More importantly, IL-37 showed a significant correlation with disease activity (DAS28) and IL-4, IL-7, IL-10, IL-12, and IL-13 concentrations in RA patients. These findings suggest that IL-37 plays an important role in the pathogenesis of RA and may prove to be a potential biomarker of active RA.

Cytokine Dysregulation in MECP2- and CDKL5-Related Rett Syndrome: Relationships with Aberrant Redox Homeostasis, Inflammation, and ω-3 PUFAs

An involvement of the immune system has been suggested in Rett syndrome (RTT), a devastating neurodevelopmental disorder related to oxidative stress, and caused by a mutation in the methyl-CpG binding protein 2 gene (MECP2) or, more rarely, cyclin-dependent kinase-like 5 (CDKL5). To date, it is unclear whether both mutations may have an impact on the circulating cytokine patterns. In the present study, cytokines involved in the Th1-, Th2-, and T regulatory (T-reg) response, as well as chemokines, were investigated in MECP2- (MECP2-RTT) (n = 16) and CDKL5-Rett syndrome (CDKL5-RTT) (n = 8), before and after ω-3 polyunsaturated fatty acids (PUFAs) supplementation. A major cytokine dysregulation was evidenced in untreated RTT patients. In MECP2-RTT, a Th2-shifted balance was evidenced, whereas in CDKL5-RTT both Th1- and Th2-related cytokines (except for IL-4) were upregulated. In MECP2-RTT, decreased levels of IL-22 were observed, whereas increased IL-22 and T-reg cytokine levels were evidenced in CDKL5-RTT. Chemokines were unchanged. The cytokine dysregulation was proportional to clinical severity, inflammatory status, and redox imbalance. Omega-3 PUFAs partially counterbalanced cytokine changes, as well as aberrant redox homeostasis and the inflammatory status. RTT is associated with a subclinical immune dysregulation as the likely consequence of a defective inflammation regulatory signaling system.

Levels of interleukin-37 in gingival crevicular fluid, saliva, or plasma in periodontal disease

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the levels of levels of interleukin-37 (IL-37) in gingival crevicular fluid, saliva and plasma in patients with periodontal disease and patients with healthy periodontium and to correlate these levels with clinical parameters.

MATERIAL AND METHODS

Samples of gingival crevicular fluid, whole saliva and plasma were collected from systemically healthy, nonsmoker periodontally healthy controls (group 1, n = 20), gingivitis patients (group 2, n = 20) and chronic periodontitis patients (group 3, n = 20). Full-mouth clinical periodontal parameters, including probing depth, plaque index, gingival index and bleeding on probing, were also recorded. IL-37 levels in the biofluid samples were determined by ELISA. Data were tested statistically using the Kruskal-Wallis test followed by the Mann-Whitney U-test.

RESULTS

The concentration of IL-37 in gingival crevicular fluid was significantly lower in group 3 than in groups 1 and 2 (p = 0.001), whereas the total amounts in gingival crevicular fluid samples were similar (p > 0.05). The salivary and plasma concentrations of IL-37 were similar in the study groups (p > 0.05). There were negative correlations between gingival crevicular fluid IL-37 concentrations and gingival crevicular fluid volume in all groups (p < 0.05). There was also a negative correlation between the gingival crevicular fluid IL-37 concentration and gingival index in group 3 (p < 0.05).

CONCLUSIONS

IL-37 was expressed in all biofluids. According to our findings, the total amount of IL-37 in gingival crevicular fluid, or salivary or plasma concentrations of IL-37, may not be useful diagnostic markers to differentiate periodontal disease and the periodontally healthy condition. The difference in gingival crevicular fluid IL-37 concentration between the study groups may be a result of the variation in gingival crevicular fluid volume, as suggested by the negative correlation between gingival crevicular fluid volume and gingival crevicular fluid IL-37 concentration. In the light of our findings, it seems that IL-37 is not involved in periodontal disease. Further comprehensive studies may clarify this issue more clearly.

Immunobiology of IL-37: mechanism of action and clinical perspectives

This article provides an overview of the biological function of a recently discovered cytokine, IL-37, formerly referred to as IL-1F7, and its role in chronic inflammation and autoimmune disease. Much has been discovered about IL-37 in the past decade, including its ability to down-regulate systemic and local inflammation by lowering levels of pro-inflammatory molecules. Here, we critically review the published reports. Future research is necessary to understand the receptor-dependent effects of IL-37, its intracellular and extracellular functions in both normal and diseased states and its potential role as a biomarker and pharmacological target in human disease.

Role of cytokines and Toll-like receptors in the immunopathogenesis of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune disease of the peripheral nervous system, mostly triggered by an aberrant immune response to an infectious pathogen. Although several infections have been implicated in the pathogenesis of GBS, not all such infected individuals develop this disease. Moreover, infection with a single agent might also lead to different subtypes of GBS emphasizing the role of host factors in the development of GBS. The host factors regulate a broad range of inflammatory processes that are involved in the pathogenesis of autoimmune diseases including GBS. Evidences suggest that systemically and locally released cytokines and their involvement in immune-mediated demyelination and axonal damage of peripheral nerves are important in the pathogenesis of GBS. Toll-like receptors (TLRs) link innate and adaptive immunity through transcription of several proinflammatory cytokines. TLR genes may increase susceptibility to microbial infections; an attenuated immune response towards antigen and downregulation of cytokines occurs due to mutation in the gene. Herein, we discuss the crucial role of host factors such as cytokines and TLRs that activate the immune response and are involved in the pathogenesis of the disease.

Anti-inflammatory effect of IL-37b in children with allergic rhinitis

Background. Interleukin-37 (IL-37), a newly described member of IL-1family, functioned as a fundamental inhibitor of innate inflammatory and immune responses, especially its isoform IL-37b. Objective. This study was undertaken to evaluate the expression and regulation of IL-37b in children with allergic rhinitis (AR). Methods. Forty children with AR and twenty-five normal controls were included. The relationship between IL-37b and Th1/2 cytokines production in serum and nasal lavage was examined by enzyme-linked immunosorbent assay (ELISA). Peripheral blood mononuclear cells (PBMCs) were purified for in vitro regulation experiment of IL-37b. Intranasal mometasone furoate was given in AR children and IL-37b change after one-month treatment was detected using ELISA. Results. We observed significantly decreased IL-37b expression levels in both serum and nasal lavage compared to controls. IL-37b was negatively correlated with Th2 cytokines. Our results also showed that IL-37b downregulated Th2 cytokine expressed by PBMCs and this modulation was through mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathway. We also found that intranasal mometasone furoate therapy can promote nasal IL-37b expression. Conclusion. IL-37b may be involved in Th2 cytokine regulation in AR and its expression was related to the efficacy of intranasal steroid therapy.

Elevated plasma IL-37, IL-18, and IL-18BP concentrations in patients with acute coronary syndrome

OBJECTIVE

More recently, evidence showed that the novel anti-inflammatory cytokine interleukin- (IL-) 37 was expressed in the foam-like cells of atherosclerotic coronary and carotid artery plaques, suggesting that IL-37 is involved in atherosclerosis-related diseases. However, the plasma levels of IL-37 in patients with acute coronary syndrome (ACS, including unstable angina pectoris and acute myocardial infarction) have yet to be investigated.

METHODS

Plasma IL-37, IL-18, and IL-18BP levels were measured in 50 patients with stable angina pectoris (SAP), 75 patients with unstable angina pectoris (UAP), 67 patients with acute myocardial infarction (AMI), and 65 control patients.

RESULTS

The plasma IL-37, IL-18, and IL-18BP levels were significantly increased in ACS patients compared to SAP and control patients. A correlation analysis showed that the plasma biomarker levels were positively correlated with each other and with the levels of C-reactive protein (CRP), N-terminal probrain natriuretic peptide (NT-proBNP), and left ventricular end-diastolic dimension (LVEDD) but negatively correlated with left ventricular ejection fraction (LVEF). Furthermore, the plasma IL-37, IL-18, and IL-18BP had no correlation with the severity of the coronary artery stenosis.

CONCLUSIONS

The results indicate that the plasma IL-37 levels are associated with the onset of ACS.