Long-term endemic situation caused by a linezolid- and meticillin-resistant clone of Staphylococcus epidermidis in a tertiary hospital

BACKGROUND

Linezolid (LZD)-resistant Staphylococcus epidermidis (LRSE) are increasing, and are mainly associated with outbreaks in hospital wards with high LZD consumption.

AIM

To investigate the frequency of LRSE in a tertiary hospital in the context of LZD use.

METHODS

The frequency of LRSE and the data on LZD usage [expressed as defined daily dose (DDD) per 100 patient-days], from 2011 to 2017, were analysed retrospectively. Selected LRSE were typed by pulsed-field gel electrophoresis (PFGE) and screened for transferable LZD resistance genes. Representative isolates were typed by multi-locus sequence typing, and ribosomal mechanisms of LZD resistance were investigated.

FINDINGS

In total, 435 LRSE were detected, with frequencies ranging from 13.56% to 32.93% in the intensive care unit (ICU) where LZD consumption was high (6.34-8.10 DDDs), and from 2.48 to 6.80% in the remaining wards where LZD use was considerably lower (0.63-2.49 DDDs). The first 44 LRSE isolates recovered (June 2013-June 2014) were closely related according to PFGE patterns, and all except one were resistant to meticillin due to mecA production. Selected isolates belonged to ST2, carried SCCmec III, and had the G2576T mutation in the V domain of each of the six copies of the 23S rRNA gene. Five of the 44 isolates (11.36%) were positive for the cfr gene.

CONCLUSION

An ST2 LZD- and meticillin-resistant clone was found in the ICU and also in wards with low consumption of LZD. This highlights the need to implement and maintain infection control measures as well as antimicrobial stewardship programmes in all hospital units in order to preserve the efficacy of LZD.

ST2 and REG3α as Predictive Biomarkers After Haploidentical Stem Cell Transplantation Using Post-transplantation High-Dose Cyclophosphamide

Allogenic hematopoietic stem cell transplantation (allo-HSCT) is a curative procedure for several hematological malignancies. Haploidentical HSCT (haplo-HSCT) using high-dose post-transplantation cyclophosphamide (PTCy) makes transplantation possible for patients with no HLA-matched sibling donor. However, this treatment can cause complications, mainly infection, graft-vs.-host disease (GVHD), and conditioning-related toxicity. In recent years, different biomarkers in the form of tissue-specific proteins have been investigated; these may help us to predict complications of allo-HSCT. In this study we explored two such biomarkers, suppression of tumorigenicity 2 (ST2) and regenerating islet-derived 3α (REG3α), in the largest series reported of T cell–replete haplo-HSCT with PTCy. Plasma samples drawn from 87 patients at days +15 and +30 were analyzed. ST2 and REG3α levels at day +15 were not associated with post-transplant complications. ST2 levels at day +30 were higher in patients with grade II-IV acute GVHD, mainly those who received reduced intensity conditioning (RIC; median 2,503 vs. 1,830 ng/ml; p = 0.04). Of note, patients with higher plasma ST2 levels at day +30 also presented a higher incidence of non-relapse mortality (HR, 7.9; p = 0.004) and lower 2-year overall survival (25 vs. 44 months; p = 0.02) than patients with lower levels. Patients with REG3α levels higher than 1,989 pg/ml at day +30 presented a higher incidence of acute gastrointestinal GVHD in the whole cohort (HR, 8.37; p = 0.003) and in the RIC cohort (HR 6.59; p = 0.01). These data suggest that measurement of ST2 and REG3α might be useful for the prognosis and prediction of complications in patients undergoing haplo-HSCT with PTCy.

The Prognostic Value of Soluble ST2 in Adults with Pulmonary Hypertension

Soluble ST2 (sST2) is upregulated in response to myocardial stress and may serve as biomarker in adults with pulmonary hypertension (PH). This prospective cohort study investigated sST2 levels and its association with echocardiographic and hemodynamic measures, and adverse clinical outcomes in adults with PH of different etiologies. sST2 was measured during the diagnostic right heart catheterization for PH, in adult patients enrolled between May 2012 and October 2016. PH due to left heart failure was excluded. The association between sST2 and a primary endpoint composed of death or lung transplantation and a secondary composite endpoint including death, lung transplantation or heart failure, was investigated using Cox regression with adjustment for NT-proBNP. In total 104 patients were included (median age was 59 years, 66% woman, 51% pulmonary arterial hypertension). Median sST2 was 28 [IQR 20–46] ng/mL. Higher sST2 was associated with worse right ventricular dysfunction and higher mean pulmonary and right atrial pressures. Median follow-up was 3.3 [IQR 2.3–4.6] years. The primary and secondary endpoint occurred in 33 (31.7%) and 43 (41.3%) patients, respectively. sST2 was significantly associated with both endpoints (HR per 2-fold higher value 1.53, 95%CI 1.12–2.07, p = 0.007 and 1.45, 95%CI 1.10–1.90, p = 0.008, respectively). However, after adjustment for NT-proBNP, both associations did not reach statistical significance. In conclusions, higher sST2 levels are associated with more severe PH and right ventricular dysfunction and yields prognostic value in adults with PH, although not independently of NT-proBNP.

Can Biomarkers Provide Right Ventricular-Specific Prognostication in the Perioperative Setting?

Since the introduction of biomarkers in the late 1980s, considerable research has been dedicated to their validation and application. As a result, many biomarkers are now commonly used in clinical practice. However, the role of biomarkers in the prediction of right ventricular failure (RVF) and in the prognostication for patients with RVF remains underexplored. Barriers include a lack of awareness of the importance of right ventricular function, especially in the perioperative setting, as well as a lack of reproducible means to assess right ventricular function in this setting. We provide an overview of biomarkers with right ventricular prognostic capabilities that could be further explored in patients expecting cardiac surgery, who are notoriously susceptible to developing RVF. We discuss biomarkers' mechanistic pathways and highlight their potential strengths and weaknesses in use in research and clinical care.

Interleukin-1/-33 Signaling Pathways as Therapeutic Targets for Endometriosis

Endometriosis is an estrogen-dependent disease with symptoms of dysmenorrhea, chronic pain, and infertility that affects 6–10% of women of reproductive age. Medical or surgical therapy, such as administration of an anti-gonadotropin or ovarian cystectomy, provide effective pain relief. However, neither therapy can be used for patients wishing to become pregnant. Despite the high morbidity, the pathogenesis of endometriosis has not been well-elucidated. Several inflammatory cytokines are reported to participate in the onset of endometriosis. Here, we examined the role of interleukin (IL)-1/IL-33 signaling in the development of endometriosis using a mouse model of endometriosis. Endometriotic lesion volume was significantly reduced in Il33^−/− and Il1r1^−/− mice, and almost completely suppressed in Myd88^−/− mice. Mice intraperitoneally administered with an antibody against IL-1 receptor 1 (IL-1R1) or IL-33 developed limited endometriotic lesions. Oral administration of an inhibitor against IL-1R-associated kinase 4 (IRAK4), a downstream signal molecule of MyD88, also suppressed lesion formation. Furthermore, even after the development of cystic lesions the IRAK4 inhibitor prevented the enlargement of lesions. These treatments all significantly reduced cellular proliferation, shown by decreased Ki-67 expression. These results reveal that IL-1/IL-1R1, IL-33/IL-33R and associated downstream signaling molecules are involved in the pathogenesis of endometriosis, and may provide novel therapeutic targets for endometriosis.

Memory CD8+ T Cell Protection From Viral Reinfection Depends on Interleukin-33 Alarmin Signals

Memory CD8⁺ cytotoxic T lymphocytes (CTLs) can protect against viral reinfection. However, the signals driving rapid memory CTL reactivation have remained ill-defined. Viral infections can trigger the release of the alarmin interleukin-33 (IL-33) from non-hematopoietic cells. IL-33 signals through its unique receptor ST2 to promote primary effector expansion and activation of CTLs. Here, we show that the transcription factor STAT4 regulated the expression of ST2 on CTLs in vitro and in vivo in primary infections with lymphocytic choriomeningitis virus (LCMV). In the primary antiviral response, IL-33 enhanced effector differentiation and antiviral cytokine production in a CTL-intrinsic manner. Further, using sequential adoptive transfers of LCMV-specific CD8⁺ T cells, we deciphered the IL-33 dependence of circulating memory CTLs at various stages of their development. IL-33 was found dispensable for the formation and maintenance of memory CTLs, and its absence during priming did not affect their recall response. However, in line with the CTL-boosting role of IL-33 in primary LCMV infections, circulating memory CTLs required IL-33 for efficient secondary expansion, enhanced effector functions, and virus control upon challenge infection. Thus, beyond their effector-promoting activity in primary immune reactions, innate alarmin signals also drive memory T cell recall responses, which has implications for immunity to recurrent diseases.

Serum levels of interleukin 33 and its receptor ST2 in patients treated with subcutaneous allergen immunotherapy in intermittent allergic rhinitis

Introduction

Interleukin 33 (IL-33) is a pleiotropic cytokine involved in pathological processes in seasonal allergic rhinitis. IL-33 binds to ST2 receptor, which is highly expressed on mast cells and selectively on Th2 cells. Information is lacking on the role of IL-33/ST2 axis in allergen subcutaneous immunotherapy.

Aim of the study

To determine if allergen immunotherapy changes the IL-33/ST2l axis in seasonal allergic rhinitis patients.

Material and methods

40 patients with intermittent allergic rhinitis sensitive to grass and/or tree pollen were studied. Among these, 10 patients were longitudinally assessed in the follow-up visit after completing the first course of immunotherapy. Twenty-two healthy subjects were included as controls. Immunotherapy was applied according to a perennial schedule comprising up-building and maintenance phases. Serum levels of ST2/IL-33 R and IL-33 were measured by ELISA (R&D Systems).

Results

Serum levels of IL-33 significantly rose after the first course of immunotherapy and reached the controls levels. Serum levels of ST2 were comparable before the pollen season and after the first course of immunotherapy.

Conclusions

Increase in serum levels of IL-33 after the first course of immunotherapy may suggest it is too short period to prevent the expected raise in serum IL-33 levels in the pollen season, and longer treatment is required to observe significant changes of this cytokine. ST2 serum levels are independent of immunotherapy and pollen season.

ST2 in patients with severe aortic stenosis and heart failure

BACKGROUND

ST2 is a circulating biomarker that is well established for predicting outcome in heart failure (HF). This is the first study to look at ST2 concentrations in optimally treated patients with stable but significant left ventricular systolic dysfunction (LVSD) compared to patients with severe aortic stenosis (AS).

METHODS

Two cohorts were retrospectively studied: 94 patients undergoing transcatheter aortic valve implantation for severe AS (63 with normal ejection fraction [EF] and 31 with reduced EF), and 50 patients with severe LVSD from non-valvular causes. ST2 pre-procedural samples were taken, and repeated again at 3 and 6 months. Patients were followed-up for 2 years. Data was analyzed using SPSS software.

RESULTS

Baseline concentrations of soluble ST2 did not differ significantly between the HF group and AS group with normal EF (EF ≥ 50%). However, in the AS group with a low EF (EF < 50%) ST2 concentrations were significantly higher that the HF group (p = 0.009). New York Heart Association class IV HF, baseline N-terminal pro-B-type natriuretic peptide and gender were all independent predictors of soluble ST2 (sST2) baseline concentrations.

CONCLUSIONS

Raised ST2 concentrations in the context of severe AS may be a marker for subclinical or clinical left ventricular dysfunction. More research is required to assess its use for assessment of prognosis and response to treatment.

Interleukin 1 Receptor-Like 1 (IL1RL1) Promotes Airway Bacterial and Viral Infection and Inflammation

Interleukin 1 receptor-like 1 (IL1RL1), also known as suppression of tumorigenicity 2 (ST2), is the receptor for interleukin 33 (IL-33) and has been increasingly studied in type 2 inflammation. An increase in airway IL-33/ST2 signaling in asthma has been associated with eosinophilic inflammation, but little is known about the role of ST2 in neutrophilic inflammation. Airway Mycoplasma pneumoniae and human rhinovirus (HRV) infections are linked to neutrophilic inflammation during acute exacerbations of asthma. However, whether ST2 contributes to M. pneumoniae- and HRV-mediated airway inflammation is poorly understood. The current study sought to determine the functions of ST2 during airway M. pneumoniae or HRV infection. In cultured normal human primary airway epithelial cells, ST2 overexpression (OE) increased the production of neutrophilic chemoattractant IL-8 in the absence or presence of M. pneumoniae or HRV1B infection. ST2 OE also enhanced HRV1B-induced IP-10, a chemokine involved in asthma exacerbations. In the M. pneumoniae-infected mouse model, ST2 deficiency, in contrast to sufficiency, significantly reduced the levels of neutrophils following acute (≤24 h) infection, while in the HRV1B-infected mouse model, ST2 deficiency significantly reduced the levels of proinflammatory cytokines KC, IP-10, and IL-33 in bronchoalveolar lavage (BAL) fluid. Overall, ST2 overexpression in human epithelial cells and ST2 sufficiency in mice increased the M. pneumoniae and HRV loads in cell supernatants and BAL fluid. After pathogen infection, ST2-deficient mice showed a higher level of the host defense protein lactotransferrin in BAL fluid. Our data suggest that ST2 promotes proinflammatory responses (e.g., neutrophils) to airway bacterial and viral infection and that blocking ST2 signaling may broadly attenuate airway infection and inflammation.

Contribution of tissue transglutaminase to the severity of hepatic fibrosis resulting from Schistosoma japonicum infection through the regulation of IL-33/ST2 expression

Background

Tissue transglutaminase (tTG)-regulating IL-13 plays an important role in the pathogenesis of liver fibrosis resulting from Schistosoma japonicum (Sj) infection. IL-33 and its receptor ST2 are involved in Th2-biased immune responses through the release of IL-5 and IL-13 and subsequent hepatic granuloma pathology induced by Sj infection. However, the relationship between tTG, IL-33/ST2, and liver fibrosis during Schistosoma infection has not been established.

Results

This study investigated the link between tTG and IL-33/ST2 in the induction of liver fibrogenesis during Sj infection in mice. The extent of liver fibrosis coincided with an increase in tTG and IL-33/ST2 expression in the liver of infected mice between five to eight weeks, with a peak of correlation at six weeks after Sj infection. The inhibition of tTG activity through cystamine administration or gene knockout alleviated the level of TLR4, NF-κB pathway molecules, IL-33/ST2, and the severity of liver fibrosis resulting from Sj infection.

Conclusions

These results indicate that during Sj infection tTG may control liver fibrosis at least partially through TLR4, NF-κB pathway activation and then IL-33/ST2. tTG, IL-33 or ST2 might be promising drug targets against liver fibrosis induced by Sj infection.

Biomarkers in Atrial Fibrillation and Heart Failure

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice and an important contributor to cardiovascular morbidity and mortality. Although the exact mechanisms behind AF are not completely elucidated, the underlying pathophysiological changes have been well described. Predisposal factors for AF include the older age, the increased left atrial size, the decreased left atrial function, the presence of heart failure and left ventricular systolic dysfunction and the presence of coronary heart disease or pulmonary or mitral valve disease. In addition to these factors, emerging evidence demonstrate that myocardial strain, fibrosis and inflammation, are associated with AF as well as the pathogenesis of the arrhythmia. The natruretic peptide system including Atrial Natriuretic Peptide (ANP), Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP) is indicative of the level of myocardial strain which may predispose to AF. As a result, the aforementioned peptides are increased in AF patients. The levels of myocardial fibrosis biomarkers, such as ST2 and Galectin-3, are elevated suggesting atrial structural abnormalities, while the increased levels of CRP and Interleukin-6 supplement the inflammatory profile of AF patients. Emerging data for the aforementioned biomarkers are discussed in the present review.

Spinal IL-33/ST2 signaling mediates chronic itch in mice through the astrocytic JAK2-STAT3 cascade

Interleukin-33 (IL-33) and its receptor ST2 contribute to spinal glial activation and chronic pain. A recent study showed that peripheral IL-33 plays a pivotal role in the pathogenesis of chronic itch induced by poison ivy. However, how IL-33/ST2 signaling in the spinal cord potentially mediates chronic itch remains elusive. Here, we determined that St2^-/- substantially reduced scratching behaviors in 2,4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD) as well as acetone and diethylether followed by water-induced dry skin in mice. Intrathecal administration of the neutralizing anti-ST2 or anti-IL-33 antibody remarkably decreased the scratching response in DNFB-induced ACD mice. Expression of spinal IL-33 and ST2 significantly increased in ACD mice, as evidenced by increased mRNA and protein levels. Immunofluorescence and in situ hybridization demonstrated that increased expression of spinal IL-33 was predominant in oligodendrocytes and astrocytes, whereas ST2 was mainly expressed in astrocytes. Further studies showed that in ACD mice, the activation of astrocytes and increased phosphorylation of signal transducer and activator of transcription 3 (STAT3) were markedly attenuated by St2^-/- . Intrathecal injection of Janus Kinase 2 Inhibitor AG490 significantly alleviated scratching behaviors in ACD mice. rIL-33 pretreatment exacerbated gastrin-releasing peptide (GRP)-evoked scratching behaviors. This increased gastrin-releasing peptide receptor (GRPR) expression was abolished by St2^-/- . Tnf-α upregulation was suppressed by St2^-/- . Our results indicate that the spinal IL-33/ST2 signaling pathway contributes to chronic itch via astrocytic JAK2-STAT3 cascade activation, promoting TNF-α release to regulate the GRP/GRPR signaling-related itch response. Thus, these findings provide a potential therapeutic option for treating chronic pruritus.

Biomarkers in the Diagnosis, Management, and Prognostication of Perioperative Right Ventricular Failure in Cardiac Surgery-Are We There Yet?

Right ventricular failure (RVF) is a major risk factor for end organ morbidity and mortality following cardiac surgery. Perioperative RVF is difficult to predict and detect, and to date, no convenient, accurate, or reproducible measure of right ventricular (RV) function is available. Few studies have examined the use of biomarkers in RVF, and even fewer have examined their utility in the perioperative setting of patients undergoing cardiac surgery. Of the available classes of biomarkers, this review focuses on biomarkers of (1) inflammation and (2) myocyte injury/stress, due to their superior potential in perioperative RV assessment, including Galectin 3, ST2/sST2, CRP, cTN/hs-cTn, and BNP/NT-proBNP. This review was performed to help highlight the importance of perioperative RV function in patients undergoing cardiac surgery, to review the current modalities of RV assessment, and to provide a review of RV specific biomarkers and their potential utilization in the clinical and perioperative setting in cardiac surgery. Based on current evidence, we suggest the potential utility of ST2, sST2, Gal-3, CRP, hs-cTn, and NT-proBNP in predicting and detecting RVF in cardiac surgery patients, as they encompass the multifaceted nature of perioperative RVF and warrant further investigation to establish their clinical utility.

Role of the IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to Aspergillus fumigatus infection

AIM

To investigate the expression of interleukin (IL)-33 in the cornea and human corneal epithelial cells (HCECs) exposed to Aspergillus fumigatus (A. fumigatus), and to determine the function of IL-33/ST2/p38 signaling pathway in the immune response of corneal epithelial cells to A. fumigatus infection.

METHODS

The mRNA and protein expression of IL-33 in HCECs and mice corneas were examined by quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis, respectively. IL-33 expression was also detected in cornea samples from healthy donors and patients with fungal keratitis with immunohistochemistry. The cultured HCECs were treated with inactive A. fumigatus hyphae at various concentrations with or without recombinant human IL-33 protein, soluble recombinant ST2 protein, specific ST2 neutralizing antibody, or the mitogen-activated protein kinase (MAPK) p38 inhibitor SB203580 for evaluation of the expression and activation of IL-33/ST2/p38 signaling in the regulation of proinflammatory cytokines. The production levels of IL-6 and IL-1β were determined by qRT-PCR and enzyme-linked immunosorbent assay (ELISA). The proliferation of HCECs was determined by a Cell Counting Kit-8 (CCK8) assay and cell count.

RESULTS

IL-33 expression levels increased in the corneal tissues of patients with fungal keratitis and in mice corneas of experimental A. fumigatus infection, as well as in HCECs with infection of A. fumigatus. A. fumigatus strongly stimulated HCECs-generated proinflammatory cytokine (IL-6 and IL-1β) production at both the mRNA and protein levels. This production of pro-inflammatory mediators stimulated by A. fumigatus was further stimulated by IL-33 and was prevented by soluble ST2 protein or ST2 neutralizing antibody. Moreover, IL-33 naturally promoted the p38 phosphorylation induced by A. fumigatus, which was suppressed by soluble ST2 protein. The MAPK p38 inhibitor SB203580 also inhibited the A. fumigatus-induced proinflammatory cytokine production. IL-33 administration for 48h and 72h promoted the proliferation of HCECs, which was attenuated by treatment with soluble recombinant human ST2 protein.

CONCLUSION

A. fumigatus elevates IL-33 expression in human and mice corneas and HCECs. Thus, IL-33/ST2/p38 signaling may play an important role in amplifying the immune response of corneal epithelial cells to A. fumigatus infection. Besides, IL-33 promotes the cell proliferation of HCECs via its receptor ST2. These findings suggest a novel autocrine mechanism of amplification of the fungal-induced inflammatory response in the corneal epithelium, highlighting a potential therapeutic target for fungal keratitis.

Increased serum concentrations of soluble ST2 are associated with pulmonary complications and mortality in polytraumatized patients

BACKGROUND

We sought to evaluate the role of soluble ST2 (suppression of tumorigenicity) serum concentrations in polytraumatized patients and its potential role as biomarker for pulmonary complications.

METHODS

We included severely injured patients (injury severity score≥16) admitted to our level I trauma center and analyzed serum samples obtained on the day of admission and on day 2. Furthermore, patients with isolated thoracic injury and healthy probands were included and served as control groups. Serum samples were analyzed for soluble ST2 concentrations with a commercially available ELISA kit.

RESULTS

A total of 130 patients were included in the present study. Five patients with isolated thoracic injury and eight healthy probands were further included. Serum analyses revealed significantly elevated concentrations of soluble ST2 in polytraumatized patients compared to patients suffering from isolated thoracic trauma and healthy probands. In polytraumatized patients who developed pulmonary complications (acute respiratory distress syndrome and pneumonia) and in patients who died, significantly higher serum concentrations of soluble ST2 were found on day 2 (p<0.001). Serum concentrations of soluble ST2 on day 2 were of prognostic value to predict pulmonary complications in polytraumatized patients (area under the curve=0.720, 95% confidence interval=0.623-0.816). Concomitant thoracic trauma had no further impact on serum concentrations of soluble ST2.

CONCLUSIONS

Serum concentrations of soluble ST2 are upregulated following polytrauma. Increased concentrations were associated with worse outcome.

Tollip Inhibits ST2 Signaling in Airway Epithelial Cells Exposed to Type 2 Cytokines and Rhinovirus

The negative immune regulator Tollip inhibits the proinflammatory response to rhinovirus (RV) infection, a contributor to airway neutrophilic inflammation and asthma exacerbations, but the underlying molecular mechanisms are poorly understood. Tollip may inhibit IRAK1, a signaling molecule downstream of ST2, the receptor of IL-33. This study was carried out to determine whether Tollip downregulates ST2 signaling via inhibition of IRAK1, but promotes soluble ST2 (sST2) production, thereby limiting excessive IL-8 production in human airway epithelial cells during RV infection in a type 2 cytokine milieu (e.g., IL-13 and IL-33 stimulation). Tollip- and IRAK1-deficient primary human tracheobronchial epithelial (HTBE) cells and Tollip knockout (KO) HTBE cells were generated using the shRNA knockdown and CRISPR/Cas9 approaches, respectively. Cells were stimulated with IL-13, IL-33, and/or RV16. sST2, activated IRAK1, and IL-8 were measured. A Tollip KO mouse model was utilized to test if Tollip regulates the airway inflammatory response to RV infection in vivo under IL-13 and IL-33 treatment. Following IL-13, IL-33, and RV treatment, Tollip-deficient (vs. -sufficient) HTBE cells produced excessive IL-8, accompanied by decreased sST2 production but increased IRAK1 activation. IL-8 production following IL-13/IL-33/RV exposure was markedly attenuated in IRAK1-deficient HTBE cells, as well as in Tollip KO HTBE cells treated with an IRAK1 inhibitor or a recombinant sST2 protein. Tollip KO (vs. wild-type) mice developed exaggerated airway neutrophilic responses to RV in the context of IL-13 and IL-33 treatment. Collectively, these data demonstrate that Tollip restricts excessive IL-8 production in type 2 cytokine-exposed human airways during RV infection by promoting sST2 production and inhibiting IRAK1 activation. sST2 and IRAK1 may be therapeutic targets for attenuating excessive neutrophilic airway inflammation in asthma, especially during RV infection.

Pleiotropic Effects of IL-33 on CD4+ T Cell Differentiation and Effector Functions

IL-33, a member of the IL-1 family of cytokines, was originally described in 2005 as a promoter of type 2 immune responses. However, recent evidence reveals a more complex picture. This cytokine is released locally as an alarmin upon cellular damage where innate cell types respond to IL-33 by modulating their differentiation and influencing the polarizing signals they provide to T cells at the time of antigen presentation. Moreover, the prominent expression of the IL-33 receptor, ST2, on GATA3⁺ T helper 2 cells (T_H2) demonstrated that IL-33 could have a direct impact on T cells. Recent observations reveal that T-bet⁺ T_H1 cells and Foxp3⁺ regulatory T (T_REG) cells can also express the ST2 receptor, either transiently or permanently. As such, IL-33 can have a direct effect on the dynamics of T cell populations. As IL-33 release was shown to play both an inflammatory and a suppressive role, understanding the complex effect of this cytokine on T cell homeostasis is paramount. In this review, we will focus on the factors that modulate ST2 expression on T cells, the effect of IL-33 on helper T cell responses and the role of IL-33 on T_REG cell function.

Dysregulation of IL-33/ST2 signaling and myocardial periarteriolar fibrosis

Microvascular dysfunction in the heart and its association with periarteriolar fibrosis may contribute to the diastolic dysfunction seen in heart failure with preserved ejection fraction. Interleukin-33 (IL-33) prevents global myocardial fibrosis in a pressure overloaded left ventricle by acting via its receptor, ST2 (encoded by the gene, Il1rl1); however, whether this cytokine can also modulate periarteriolar fibrosis remains unclear. We utilized two approaches to explore the role of IL-33/ST2 in periarteriolar fibrosis. First, we studied young and old wild type mice to test the hypothesis that IL-33 and ST2 expression change with age. Second, we produced pressure overload in mice deficient in IL-33 or ST2 by transverse aortic constriction (TAC). With age, IL-33 expression increased and ST2 expression decreased. These alterations accompanied increased periarteriolar fibrosis in aged mice. Mice deficient in ST2 but not IL-33 had a significant increase in periarteriolar fibrosis following TAC compared to wild type mice. Thus, loss of ST2 signaling rather than changes in IL-33 expression may contribute to periarteriolar fibrosis during aging or pressure overload, but manipulating this pathway alone may not prevent or reverse fibrosis.

IL33/ST2 Axis in Diabetic Kidney Disease: A Literature Review

Interleukin-33 (IL-33) is a cytokine belonging to the IL-1 family, playing a role in inflammatory, infectious and autoimmune diseases and expressed in the cellular nucleus in several tissues. High levels of IL-33 are expressed in epithelial barrier tissues and endothelial barriers. ST2 is a receptor for IL-33, expressed selectively on a subset of Th2 cells, mediating some of their functions. The IL-33/ST2 axis plays an important role in several acute and chronic inflammatory diseases, including asthma and rheumatoid arthritis. Different disorders are related to the activity of IL-33, ST2, or their axis, including cardiovascular disease or renal disturbances. Therefore, in the present work, a literature review was conducted, covering the period from 1 January 2000 to 30 November 2018, in PubMed, ScienceDirect, and Google Scholar database, to assess the involvement of the IL-33/ST2 axis in diabetic kidney disease. 6 articles directly dealing with the argument were identified, highlighting a clear link between IL-33/ST2 axis and diabetic kidney disease or related nephropathy. Overall, the involvement of ST2 seems to be more predictive than IL-33, especially in investigating the deterioration of kidney function; however, both compounds are pivotal in the field of renal diseases. Future studies are required to confirm the scientific evidences on larger and more heterogeneous cohorts.

Deficiency in IL-33/ST2 Axis Reshapes Mitochondrial Metabolism in Lipopolysaccharide-Stimulated Macrophages

The polarization and function of macrophages play essential roles in controlling immune responses. Interleukin (IL)-33 is a member of the IL-1 family that has been shown to influence macrophage activation and polarization, but the underlying mechanisms are not fully understood. Mitochondrial metabolism has been reported to be a central player in shaping macrophage polarization; previous studies have shown that both aerobic glycolysis and oxidative phosphorylation uniquely regulate the functions of M1 and M2 macrophages. Whether IL-33 polarizes macrophages by reshaping mitochondrial metabolism requires further investigation. In this work, we examined the mitochondrial metabolism of bone marrow-derived macrophages (BMDMs) from either wild type (WT), Il33-overexpressing, or IL-33 receptor knockout (St2^−/−) mice challenged with lipopolysaccharide (LPS). We found that after LPS stimulation, compared with WT BMDMs, St2^−/− BMDMs had reduced cytokine production and increased numbers and activity of mitochondria via the metabolism regulator peroxisome proliferator-activated receptor-C coactivator-1 α (PGC1α). This was demonstrated by increased mitochondrial DNA copy number, mitochondria counts, mitochondria fission- and fusion-related gene expression, oxygen consumption rates, and ATP production, and decreased glucose uptake, lactate production, and extracellular acidification rates. For Il33-overexpressing BMDMs, the metabolic reprogramming upon LPS stimulation was similar to WT BMDMs, and was accompanied by increased M1 macrophage activity. Our findings suggested that the pleiotropic IL-33/ST2 pathway may influence the polarization and function of macrophages by regulating mitochondrial metabolism.

IL-33 at the Crossroads of Metabolic Disorders and Immunity

As a cytokine in interleukin-1(IL-1) family, interleukin-33(IL-33) usually exists in the cytoplasm and cell nucleus. When the cells are activated or damaged, IL-33 can be secreted into extracellular and regulate the functions of various immune cells through binding to its specific receptor suppression of tumorigenicity 2 (ST2). Except regulating the function of immune cells including T cells, B cells, dendritic cells (DCs), macrophages, mast cells, and innate lymphoid cells, IL-33 also plays an important role in metabolic diseases and has received an increasing attention. This review summarizes the regulation of IL-33 on different immune cells in lipid metabolism, which will help to understand the pathology of abnormal lipid metabolic diseases, such as atherosclerosis and type 2 diabetes.

Increased Expression of sST2 in Early HIV Infected Patients Attenuated the IL-33 Induced T Cell Responses

T cell responses were less functional and persisted in an exhausted state in chronic HIV infection. Even in early phase of HIV infection, the dysfunction of HIV-specific T cells can be observed in rapid progressors, but the underlying mechanisms are not fully understood. Cytokines play a central role in regulating T cell function. In this study, we sought to elucidate whether IL-33/ST2 axis plays roles in the regulation of T cell function in HIV infection. We found that the level of IL-33 was upregulated in early HIV-infected patients compared with that in healthy controls and has a trend associated with disease progression. In vitro study shows that IL-33 promotes the expression of IFN-γ by Gag stimulated CD4+ and CD8+T cells from HIV-infected patients to a certain extent. However, soluble ST2 (sST2), a decoy receptor of IL-33, was also increased in early HIV infected patients, especially in those with progressive infection. We found that anti-ST2 antibodies attenuated the effect of IL-33 to CD4+ and CD8+T cells. Our data indicates that elevated expression of IL-33 in early HIV infection has the potential to enhance the function of T cells, but the upregulated sST2 weakens the activity of IL-33, which may indirectly contribute to the dysfunction of T cells and rapid disease progression. This data broadens the understanding of HIV pathogenesis and provides critical information for HIV intervention.

Contribution of IL-33 to the Pathogenesis of Colorectal Cancer

The development of colorectal cancer (CRC) is not only determined by transformed cells per se, but also by factors existing in their immune microenvironment. Accumulating scientific evidence has revealed that interleukin (IL)-33, an IL-1 family member, plays an essential role in the regulation of immune response and is relevant in CRC pathogenesis. Data from both human and experimental studies demonstrated that IL-33 inhibits host anti-tumor immunity, remodels tumor stroma and enhances angiogenesis, thereby promoting the development of CRC. These pro-tumor effects of IL-33 are mainly mediated by IL-33 receptor ST2 (also known as IL-1RL1). Based on those findings, it is currently hypothesized that the IL-33/ST2 pathway is a potential biomarker and therapeutic target for colorectal tumorigenesis. Herein, we summarize the recent discoveries in understanding the critical role of the IL-33/ST2 pathway in contributing to the pathogenesis of colorectal tumorigenesis and discuss its potential implications for the future development of effective anti-tumor strategies.

Expression and Function of IL-33/ST2 Axis in the Central Nervous System Under Normal and Diseased Conditions

Interleukin-33 (IL-33) is a well-recognized immunomodulatory cytokine which plays critical roles in tissue function and immune-mediated diseases. The abundant expression of IL-33 in brain and spinal cord prompted many scientists to explore its unique role in the central nervous system (CNS) under physiological and pathological conditions. Indeed emerging evidence from over a decade's research suggests that IL-33 acts as one of the key molecular signaling cues coordinating the network between the immune and CNS systems, particularly during the development of neurological diseases. Here, we highlight the recent advances in our knowledge regarding the distribution and cellular localization of IL-33 and its receptor ST2 in specific CNS regions, and more importantly the key roles IL-33/ST2 signaling pathway play in CNS function under normal and diseased conditions.

Disruption of IL-33 Signaling Limits Early CD8+ T Cell Effector Function Leading to Exhaustion in Murine Hemophagocytic Lymphohistiocytosis

Danger signals mediated through ST2, the interleukin-33 (IL-33) receptor, amplify CD8⁺ T cell-mediated inflammation in the murine model of familial hemophagocytic lymphohistiocytosis type 2 (FHL2), and blockade of ST2 provides a potential therapeutic strategy in this disease. However, the long-term effects of disrupting IL-33/ST2 signaling on the CD8⁺ T cell compartment are unknown. Here, we examined the evolution of the T cell response in murine FHL type 2 in the absence of ST2 signaling and found that CD8⁺ T cells gradually undergo exhaustion, similar to a related nonfatal FHL model. ST2 inhibition indirectly promotes CD8⁺ T cell exhaustion, and in contrast to other forms of FHL, reversal of exhaustion does not affect mortality. Disruption of IL-33 signaling exerts a more significant impact on the CD8⁺ T cell compartment early in the course of disease by intrinsically limiting CD8⁺ T cell proliferative and cytokine production capacity. Our data thus suggest that while ST2 blockade ultimately enables the development of CD8⁺ T cell exhaustion in late-stage murine FHL2, exhaustion is merely an effect, rather than the cause, of extended survival in these mice. The acute impact of ST2 inhibition on both the quantity and quality of the effector CD8⁺ T cell response more likely underlies the protective benefits of this treatment. This study provides evidence that redefines the relationship between CD8⁺ T cell exhaustion and mortality in murine FHL and supports the therapeutic use of ST2 blockade during the acute stage of disease.

Interleukin-33 in Systemic Sclerosis: Expression and Pathogenesis

Interleukin-33 (IL-33), a member of the IL-1 superfamily, functions as a traditional cytokine and nuclear factor. It is proposed to have an “alarmin” role. IL-33 mediates biological effects by interacting with the ST2 receptor and IL-1 receptor accessory protein, particularly in innate immune cells and T helper 2 cells. Recent articles have described IL-33 as an emerging pro-fibrotic cytokine in the immune system as well as a novel potential target for systemic sclerosis. Here, we review the available information and focus on the pleiotropic expression and pathogenesis of IL-33 in systemic sclerosis, as well as the feasibility of using IL-33 in clinical applications.

Aryl Hydrocarbon Receptor Signaling Cell Intrinsically Inhibits Intestinal Group 2 Innate Lymphoid Cell Function

Innate lymphoid cells (ILCs) are important for mucosal immunity. The intestine harbors all ILC subsets, but how these cells are balanced to achieve immune homeostasis and mount appropriate responses during infection remains elusive. Here, we show that aryl hydrocarbon receptor (Ahr) expression in the gut regulates ILC balance. Among ILCs, Ahr is most highly expressed by gut ILC2s and controls chromatin accessibility at the Ahr locus via positive feedback. Ahr signaling suppresses Gfi1 transcription-factor-mediated expression of the interleukin-33 (IL-33) receptor ST2 in ILC2s and expression of ILC2 effector molecules IL-5, IL-13, and amphiregulin in a cell-intrinsic manner. Ablation of Ahr enhances anti-helminth immunity in the gut, whereas genetic or pharmacological activation of Ahr suppresses ILC2 function but enhances ILC3 maintenance to protect the host from Citrobacter rodentium infection. Thus, the host regulates the gut ILC2-ILC3 balance by engaging the Ahr pathway to mount appropriate immunity against various pathogens.

Interleukin 5-producing ST2+ memory Th2 cells in IgG4-related dacryoadenitis and sialadenitis

Objectives: Immunoglobulin (Ig) G4-related disease (IgG4-RD) is often complicated by allergic disorders. This study was conducted to investigate the mechanism of type 2 helper T-inflammation (Th2-inflammation) in IgG4-related dacryoadenitis and sialadenitis (IgG4-DS). Methods: We separated and analyzed the proportion of growth stimulation expressed gene 2 (ST2)⁺ memory Th2 cells among the peripheral blood mononuclear cells by flow cytometry in cases with IgG4-DS and healthy individuals. Finally, we identified the role of ST2⁺ memory Th2 cells in the involved tissues. Results: The proportion of circulating ST2⁺ memory Th2 cells was much higher in the patients with IgG4-DS than in the healthy controls. Abundant infiltration of ST2⁺ memory Th2 cells was detected in the involved salivary glands and lymph nodes, and these cells produced interleukin-5. Conclusion: We demonstrated that there is an increase of interleukin-5 producing ST2⁺ memory Th2 cells in the involved tissues in IgG4-DS. This subset of cells is considered to be an important player in inducing the inflammatory Th2 environment characteristic of IgG4-DS.

IL-33/ST2 Axis in Organ Fibrosis

Interleukin 33 (IL-33) is highly expressed in barrier sites, acting via the suppression of tumorigenicity 2 receptor (ST2). IL-33/ST2 axis has long been known to play a pivotal role in immunity and cell homeostasis by promoting wound healing and tissue repair. However, it is also involved in the loss of balance between extensive inflammation and tissue regeneration lead to remodeling, the hallmark of fibrosis. The aim of the current review is to critically evaluate the available evidence regarding the role of the IL-33/ST2 axis in organ fibrosis. The role of the axis in tissue remodeling is better understood considering its crucial role reported in organ development and regeneration. Generally, the IL-33/ST2 signaling pathway has mainly anti-inflammatory/anti-proliferative effects; however, chronic tissue injury is responsible for pro-fibrogenetic responses. Regarding pulmonary fibrosis mature IL-33 enhances pro-fibrogenic type 2 cytokine production in an ST2- and macrophage-dependent manner, while full-length IL-33 is also implicated in the pulmonary fibrotic process in an ST2-independent, Th2-independent fashion. In liver fibrosis, evidence indicate that when acute and massive liver damage occurs, the release of IL-33 might act as an activator of tissue-protective mechanisms, while in cases of chronic injury IL-33 plays the role of a hepatic fibrotic factor. IL-33 signaling has also been involved in the pathogenesis of acute and chronic pancreatitis. Moreover, IL-33 could be used as an early marker for ulcer-associated activated fibroblasts and myofibroblast trans-differentiation; thus one cannot rule out its potential role in inflammatory bowel disease-associated fibrosis. Similarly, the upregulation of the IL-33/ST2 axismay contribute to tubular cell injury and fibrosis via epithelial to mesenchymal transition (EMT) of various cell types in the kidneys. Of note, IL-33 exerts a cardioprotective role via ST2 signaling, while soluble ST2 has been demonstrated as a marker of myocardial fibrosis. Finally, IL-33 is a crucial cytokine in skin pathology responsible for abnormal fibroblast proliferation, leukocyte infiltration and morphologic differentiation of human endothelial cells. Overall, emerging data support a novel contribution of the IL-33/ST2 pathway in tissue fibrosis and highlight the significant role of the Th2 pattern of immune response in the pathophysiology of organ fibrosis.

Down-regulated SHARPIN may accelerate the development of atopic dermatitis through activating interleukin-33/ST2 signalling

SHARPIN is an important component of the linear ubiquitin chain assembly complex (LUBAC). Loss of function of SHARPIN results in eosinophilic inflammation in multiple organs including skin with Th₂ -dominant cytokines and dysregulated development of lymphoid tissues in mice. The clinicopathological features are similar to atopic dermatitis (AD) in humans. In order to investigate the potential role of SHARPIN in the pathogenesis of AD, we performed genetic association study of the genotypes and haplotypes as well as SHARPIN's expression between AD cases and controls. We found three mutations (g.480G>A, g.4576A>G and g.5070C>T) in patient group, and significantly decreased expression in AD lesions, suggesting a primary role of SHARPIN during AD development. Lentivirus-mediated in vitro assays identified that knockdown of SHARPIN can induce elevated expression of IL-33 and its orphan receptor ST2, FLG and STAT3 and NF-κB inactivation in HaCaT keratinocytes, which has been widely evidenced in regulating AD development. ST2 expression was highly induced in SHARPIN-silenced HaCaT keratinocytes after the combined stimulation of IL-4 and IL-13. Our in vivo and in vitro findings implicated that SHARPIN may be a novel participant in the pathogenesis and/or new therapeutic target of AD.

IL-33 increases ST2+ Tregs and promotes metastatic tumour growth in the lungs in an amphiregulin-dependent manner

Regulatory T cells (Tregs) facilitate primary and metastatic tumour growth through the suppression of anti-tumour immunity. Emerging evidence suggests a distinct role for Tregs in mediating tissue repair and barrier integrity in the lungs by IL-33 mediated production of the growth factor amphiregulin (AREG). Dependent on the type of cancer and local microenvironment, AREG may induce tumour cell proliferation, invasion, migration or resistance to apoptosis by signaling through the epidermal growth factor receptor (EGFR). We have found that IL-33 is dramatically increased in and around metastatic tumour foci in the lungs of mice bearing orthotopic murine mammary tumours. We observed that Tregs express significantly more of the IL-33 receptor, ST2, relative to conventional T cells, that ST2⁺ Tregs accumulate in the lungs of metastatic tumour-bearing mice, and that ST2⁺ Tregs produce significantly more AREG than ST2^- Tregs. The intranasal administration of recombinant IL-33 increased the proportion of AREG producing ST2⁺ Tregs and enhanced the level of phosphorylated EGFR in the metastatic lungs. While recombinant AREG did not impact mammary tumour cell proliferation in vitro despite inducing a dose-dependent increase in phosphorylated EGFR, intranasal administration of AREG resulted in a ten-fold increase in pulmonary metastatic tumour burden in vivo. Further, the intranasal administration of recombinant IL-33 significantly increased metastatic tumour burden in the lungs in an amphiregulin-dependent manner. These data identify ST2⁺ Tregs as a microenvironmental source of AREG in the lungs of mice with orthotopic metastatic mammary tumours and highlight an important role for AREG in promoting metastatic tumour growth in the lungs.

Innate Immunity Induces the Accumulation of Lung Mast Cells During Influenza Infection

Mast cells release disease-causing mediators and accumulate in the lung of asthmatics. The most common cause of exacerbations of asthma is respiratory virus infections such as influenza. Recently, we demonstrated that influenza infection in mice triggers the recruitment of mast cell progenitors to the lung. This process starts early after infection and leads to the accumulation of mast cells. Previous studies showed that an adaptive immune response was required to trigger the recruitment of mast cell progenitors to the lung in a mouse model of allergic lung inflammation. Therefore, we set out to determine whether an adaptive immune response against the virus is needed to cause the influenza-induced recruitment of mast cell progenitors to the lung. We found that influenza-induced recruitment of mast cell progenitors to the lung was intact in Rag2 ^-/- mice and mice depleted of CD4⁺ cells, implicating the involvement of innate immune signals in this process. Seven weeks after the primary infection, the influenza-exposed mice harbored more lung mast cells than unexposed mice. As innate immunity was implicated in stimulating the recruitment process, several compounds known to trigger innate immune responses were administrated intranasally to test their ability to cause an increase in lung mast cell progenitors. Poly I:C, a synthetic analog of viral dsRNA, induced a TLR3-dependent increase in lung mast cell progenitors. In addition, IL-33 induced an ST2-dependent increase in lung mast cell progenitors. In contrast, the influenza-induced recruitment of mast cell progenitors to the lung occurred independently of either TLR3 or ST2, as demonstrated using Tlr3 ^-/- or Il1rl1 ^-/- mice. Furthermore, neutralization of IL-33 in Tlr3 ^-/- mice could not abrogate the influenza-induced influx of mast cell progenitors to the lung. These results suggest that other innate receptor(s) contribute to mount the influx of mast cell progenitors to the lung upon influenza infection. Our study establishes that mast cell progenitors can be rapidly recruited to the lung by innate immune signals. This indicates that during life various innate stimuli of the respiratory tract trigger increases in the mast cell population within the lung. The expanded mast cell population may contribute to the exacerbations of symptoms which occurs when asthmatics are exposed to respiratory infections.

Interleukin-33 and ST2 Signaling in Tumor Microenvironment

Interleukin-33 (IL-33) is one of the members of the IL-1 family of cytokines and a ligand of ST2 and IL-1 receptor accessory protein (IL-1RAcP) that is known to affect Th2 inflammatory response with partial effects on Th1 responses. This cytokine is released by epithelial and smooth muscle cells of the airway system during their injury by several environmental stimuli, such as allergens, viruses, helminths, and pollutants. IL-33 is an alarmin that acts as an endogenous danger signal, and it has been known to affect various types of cells, such as mast cells, basophils, eosinophils, T cells, and specific subsets of innate lymphoid cells (ILCs). In recent findings, this cytokine is believed to have a critical role in several types of cancers, such as lung cancer, liver cancer, and head and neck squamous cell cancer. The expression of IL-33/ST2 in cancer tissues shows a close association with tumor growth and tumor progression in several types of cancer, suggesting the IL-33/ST2 pathway as a potential target for therapy.

Regulatory Mechanisms of IL-33-ST2-Mediated Allergic Inflammation

Interleukin-33 (IL-33) plays multiple roles in tissue homeostasis, prevention of parasitic infection, and induction of allergic inflammation. Especially, IL-33-ST2 (IL-1RL1) axis has been regarded as the villain in allergic diseases such as asthma and atopic dermatitis and in autoimmune diseases such as rheumatoid arthritis. Indeed, a number of studies have indicated that IL-33 produced by endothelial cells and epithelial cells plays a critical role in the activation and expansion of group 2 innate lymphoid cells (ILC2s) which cause allergic inflammation by producing large amounts of IL-5 and IL-13. However, mechanisms that antagonize IL-33-ST2-mediated allergic responses remain largely unknown. Recently, several groups including our group have demonstrated cellular and molecular mechanisms that could suppress excessive activation of ILC2s by the IL-33-ST2 axis. In this review, we summarize recent progress in the regulatory mechanisms of IL-33-ST2-mediated allergic responses. Selective targeting of the IL-33-ST2 axis would be a promising strategy in the treatment of allergic diseases.

ST2 elevation in heart failure, predictive of a high early mortality

Background

Soluble suppression of tumorigenicity-2 (sST2) is a novel biomarker shown to be useful for prognostic assessment in heart failure (HF). However, very limited data exists about its prognostic utility in patients with HF in India.

Methods

We studied 150 patients [mean age 67.7 ± 13.3, 93 (62%) males], hospitalized with clinical HF, irrespective of their left ventricular ejection fraction (LVEF). HF was confirmed by N-terminal probrain natriuretic peptide (NT-proBNP) value above 125 ng/L. Primary end point was death or cardiac transplant at 1-year follow-up, with additional telephonic follow-up performed at 2 years. The clinical outcomes were correlated with the sST2 values obtained at the time of initial hospitalization.

Results

HF was ischemic in origin in 82.0% patients. The primary outcome occurred in 9.3% patients at the end of 1-year follow-up and in 16.7% patients at the end of 2 years. The patients who had events had significantly higher NT-proBNP and sST2 values, but there was no difference in the clinical characteristics, cause of HF, baseline LVEF, or serum creatinine. The patients with elevated sST2 levels (>35 ng/mL) had substantially higher event rates than those with normal sST2 levels (13.7% vs 0.0% at 1-year, P = 0.005; 22.5% vs 4.2% at 2-years, P = 0.004). On multivariate analysis, sST2 was the strongest predictor of adverse outcomes at both 1-year and 2-year follow-ups.

Conclusion

In patients hospitalized for HF, elevated sST2 >35 ng/mL at the time of initial hospitalization was associated with significantly high mortality over a 2-year period. The prognostic value of sST2 was incremental to that of NT-proBNP. These findings suggest that a single elevated sST2 value at the time of hospitalization should alert the physicians about the high risk of adverse outcomes and should help facilitate timely intensification of HF treatment.

Interleukin 33 Selectively Augments Rhinovirus-Induced Type 2 Immune Responses in Asthmatic but not Healthy People

Interleukin- 33 (IL-33) is an epithelial-derived cytokine that initiates type 2 immune responses to allergens, though whether IL-33 has the ability to modify responses to respiratory viral infections remains unclear. This study aimed to investigate the effects of IL-33 on rhinovirus (RV)-induced immune responses by circulating leukocytes from people with allergic asthma, and how this response may differ from non-allergic controls. Our experimental approach involved co-exposing peripheral blood mononuclear cells to IL-33 and RV in order to model how the functions of virus-responsive lymphocytes could be modified after recruitment to an airway environment enriched in IL-33. In the current study, IL-33 enhanced RV-induced IL-5 and IL-13 release by cells from people with allergic asthma, but had no effect on IL-5 and IL-13 production by cells from healthy donors. In asthmatic individuals, IL-33 also enhanced mRNA and surface protein expression of ST2 (the IL-33 receptor IL1RL1), while soluble ST2 concentrations were low. In contrast, IL-33 had no effect on mRNA and surface expression of ST2 in healthy individuals. In people with allergic asthma, RV-activated ST2⁺ innate lymphoid cells (ST2⁺ILC) were the predominant source of IL-33 augmented IL-13 release. In contrast, RV-activated natural killer cells (NK cells) were the predominant source of IL-33 augmented IFNγ release in healthy individuals. This suggests that the effects of IL-33 on the cellular immune response to RV differ between asthmatic and healthy individuals. These findings provide a mechanism by which RV infections and IL-33 might interact in asthmatic individuals to exacerbate type 2 immune responses and allergic airway inflammation.

Elevated ST2 levels are associated with antibody-mediated rejection in heart transplant recipients

Soluble ST2 (sST2) is a novel biomarker of inflammation and fibrosis. Elevated sST2 levels (≥35 ng/mL) are associated with worse outcomes in patients with heart failure (HF). There are sparse data regarding the significance of sST2 levels after heart transplantation (HTx). The study aims were to evaluate trends in soluble ST2 levels after the resolution of HF status with HTx and association between post-HTx sST2 levels and outcomes. Plasma sST2 levels were measured at baseline (median [IQR] of 118 days pre-HTx) and 12 months post-HTx in 62 subjects who were stratified into two groups by post-HTx sST2 levels < or ≥35 ng/mL: "Group 1" or "Group 2," respectively. Plasma sST2 levels were elevated in 58% of patients pre-HTx and in 50% of patients post-HTx. There was no association between elevated sST2 levels before and after HTx, and no significant differences in baseline characteristics between Group 1 and Group 2 patients. Group 2 as compared to Group 1 HTx recipients had significantly higher incidence of antibody-mediated rejection (AMR) for the entire post-transplant follow-up period (32% vs 4%, P = 0.006). There was no association between post-HTx sST2 level status and other post-HTx outcomes including survival. In conclusion, elevated plasma sST2 levels after HTx are associated with increased risk for AMR.

ST2/IL-33 signaling promotes malignant development of experimental squamous cell carcinoma by decreasing NK cells cytotoxicity and modulating the intratumoral cell infiltrate

Squamous cell carcinoma (SCC) is the second most common form of skin cancer and the mechanism(s) involved in the progression of this tumor are unknown. Increases in the expression of IL-33/ST2 axis components have been demonstrated to contribute to neoplastic transformation in several tumor models and interleukin-33 is correlated with poor prognosis of patients with squamous cell carcinoma of the tongue. Based on these observations, we sought to determine the role of the IL-33/ST2 pathway during the development of SCC. Our findings show that ST2-deficiency led to a marked decrease in the severity of skin lesions, suggesting that ST2 signaling contributed to tumor development. An analysis of tumor lesions in wild-type and ST2KO mice revealed that a lack of ST2 was associated with specific and significant reductions in the numbers of CD4⁺ T cells, CD8⁺ T cells, dendritic cells, and macrophages. In addition, NK cells that were isolated from ST2KO mice exhibited higher cytotoxic activity than cells isolated from wild-type mice. Notably, ST2 deficiency resulted in lower IFN-γ, TNF-α, IL-10, and IL-17 production in tumor samples. Our findings indicate that the IL-33/ST2 pathway contributes to the development of SCC by affecting leukocyte migration to tumor microenvironment and impairing NK cytotoxic activity.

ST2 regulates bone loss in a site-dependent and estrogen-dependent manner

Interleukin-33 (IL-33) and its receptor, ST2, are implicated in bone remodeling. The lack of estrogen after menopause results in an accelerated bone loss. Here we investigated the role of ST2 in the bone loss induced by estrogen deficiency. ST2-deficient mice (ST2^-/- ) and their littermates (wildtype [WT]) were ovariectomized (OVX), while ovary-intact mice were used as controls. Bone sites were analyzed by microcomputed tomography, histomorphometry, and quantitative real-time polymerase chain reaction (qPCR). Deletion of IL-33 or ST2 resulted in a similar bone loss in the femur and maxilla. Ovariectomy in WT mice caused bone loss in the same areas. The lack of ST2 in OVX mice did not alter bone remodeling in the femur but prevented bone loss in the maxilla. Consistently, ovariectomy increased the IL-33 messenger RNA (mRNA) levels in the maxilla but not in the femur. Under mechanical stimulation, ovariectomy and ST2 deletion independently increased bone remodeling induced by orthodontic tooth movement, which was also associated with a greater number of osteoclasts and a reduced number of osteoblasts in the maxillary bone. ST2^-/- OVX mice, however, displayed twice as many osteoblasts as that of WT OVX mice. Ovariectomy and ST2 deletion differently altered the cytokine mRNA levels in the maxilla. Remarkably, interleukin-10 expression was decreased in both WT OVX and ST2^-/- mice, and this reduction was completely restored in ST2^-/- OVX mice. The results demonstrate that estrogen and IL33/ST2 independently protect against bone loss. However, the ovariectomy-induced bone loss is IL-33/ST2-dependent in the maxilla but not in the femur, indicating a bimodal and site-specific role of ST2 in bone remodeling.

IL-33 receptor (ST2) deficiency downregulates myeloid precursors, inflammatory NK and dendritic cells in early phase of sepsis

BACKGROUND

Sepsis is a life-threatening disease mediated by profound disturbances in systemic inflammatory response to infection. IL-33 is multifunctional regulator of numerous aspects of innate and adaptive immune response. The aim of this article was to further evaluate the role of IL-33 receptor (ST2) in different pathways of innate immunity during early polymicrobial sepsis.

METHODS

Polymicrobial sepsis was induced using cecal ligation and puncture (CLP) model in ST2 deficient (ST2-/-) and wild type BALB/c mice. Peritoneal and spleen cells were isolated for further phenotyping. Apoptosis was determined by immunohistochemistry and flow cytometry.

RESULTS

Deletion of ST2 leads to increased susceptibility to early manifestations of sepsis as evaluated by clinical signs and survival. These are accompanied by decrease in the total number of neutrophils, eosinophils and mast cells in peritoneal cavity 12 h after CLP. In early sepsis there was also low number of precursors of myeloid cells in particular CD11b+Ly6G+Ly6Clow cells in spleen of ST2-/- mice. Although the number of NK cells in the spleen was similar, there were significant differences in the presence of inflammatory IFN-γ and IL-17 producing NK cells. Further, ST2 deletion affects the phenotype and maturation of dendritic cell in sepsis. The total number of dendritic cells in the spleen was lower as well as IL-12 expressing dendritic cells. Finally, there was higher frequency of active caspase-3 positive and early apoptotic cells, in particular CD11c positive cells, in spleen of septic ST2-/- mice.

CONCLUSION

Taken together, our data provide the evidence that ST2 deficiency in early phase of sepsis downregulates myeloid precursors, inflammatory NK and dendritic cells.

Role of Soluble ST2 Levels and Beta-Blockers Dosage on Cardiovascular Events of Patients with Unselected ST-Segment Elevation Myocardial Infarction

Background:

Serum soluble ST2 (sST2) levels are elevated early after acute myocardial infarction and are related to adverse left ventricular (LV) remodeling and cardiovascular outcomes in ST-segment elevation myocardial infarction (STEMI). Beta-blockers (BB) have been shown to improve LV remodeling and survival. However, the relationship between sST2, final therapeutic BB dose, and cardiovascular outcomes in STEMI patients remains unknown.

Methods:

A total of 186 STEMI patients were enrolled at the Wuhan Asia Heart Hospital between January 2015 and June 2015. All patients received standard treatment and were followed up for 1 year. Serum sST2 was measured at baseline. Patients were divided into four groups according to their baseline sST2 values (high >56 ng/ml vs. low ≤56 ng/ml) and final therapeutic BB dose (high ≥47.5 mg/d vs. low <47.5 mg/d). Cox regression analyses were performed to determine whether sST2 and BB were independent risk factors for cardiovascular events in STEMI.

Results:

Baseline sST2 levels were positively correlated with heart rate (r = 0.327, P = 0.002), Killip class (r = 0.408, P = 0.000), lg N-terminal prohormone B-type natriuretic peptide (r = 0.467, P = 0.000), lg troponin I (r = 0.331, P = 0.000), and lg C-reactive protein (r = 0.307, P = 0.000) and negatively correlated to systolic blood pressure (r = −0.243, P = 0.009) and LV ejection fraction (r = −0.402, P = 0.000). Patients with higher baseline sST2 concentrations who were not titrated to high-dose BB therapy (P < 0.0001) had worse outcomes. Baseline high sST2 (hazard ratio [HR]: 2.653; 95% confidence interval [CI]: 1.201–8.929; P = 0.041) and final low BB dosage (HR: 1.904; 95% CI, 1.084–3.053; P = 0.035) were independent predictors of cardiovascular events in STEMI.

Conclusions:

High baseline sST2 levels and final low BB dosage predicted cardiovascular events in STEMI. Hence, sST2 may be a useful biomarker in cardiac pathophysiology.

Integrated Expression Profiles Analysis Reveals Correlations Between the IL-33/ST2 Axis and CD8+ T Cells, Regulatory T Cells, and Myeloid-Derived Suppressor Cells in Soft Tissue Sarcoma

Soft tissue sarcoma (STS) is a rare solid malignant cancer, and there are few effective treatment options for advanced disease. Cancer immunotherapy is a promising new strategy for STS treatment. IL-33 is a candidate cytokine for immunotherapy that can activate T lymphocytes and modulate antitumor immunity in some cancers. However, the expression and biological role of IL-33 in STS are poorly understood. In this study, we found that the expression of IL-33 and its receptor ST2 was decreased in STS using real-time PCR assays. By analyzing sarcoma data from The Cancer Genome Atlas, we found that higher transcriptional levels of IL-33 and ST2 were associated with a favorable outcome. There were positive correlations between the expression levels of ST2 and CD3E, CD4, CD8A, CD45RO, FOXP3, CD11B, CD33, and IFN-γ. Strong positive correlations between the expression of IFN-γ and CD3E and CD8A were also observed. Moreover, the expression levels of both IL-33 and ST2 were positively correlated with those of CD3E, CD8A, and chemokines that recruit CD8⁺ T cells, indicating that the IL-33/ST2 axis may play an important role in recruiting and promoting the immune response of type 1-polarized CD8⁺ T cells in STS. Meanwhile, we also found that the expression of IL-33 was negatively correlated with that of TGF-β1 and chemokines that recruit regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), indicating that the IL-33/ST2 axis may also contribute to antagonizing Tregs, MDSCs, and TGF-β1-mediated immunosuppression in STS. The correlations between the IL-33/ST2 axis and CD8⁺ T cells and IFN-γ, as well as Tregs, MDSCs, and TGF-β1 were validated by additional analyses using three other independent GEO datasets of sarcoma. Our results implicate the possible role of the IL-33/ST2 axis in modulating antitumor immunity in STS. IL-33 may not only serve as a useful prognostic biomarker for STS but also as a potential therapeutic target for STS immunotherapy and worth further investigation.

Association between functional polymorphisms in IL-33/ST2 pathway and risk of osteosarcoma

Interleukin (IL)-33/ST2 pathway plays crucial roles in tumour growth and metastasis. The aim of this study was to investigate the association of two functional polymorphisms (IL-33 rs7025417 and ST2 rs3821204) with osteosarcoma (OS) risk. The rs7025417 and rs3821204 were genotyped by Taqman assay. IL-33mRNA and protein levels were measured by real-time PCR or enzyme-linked immunosorbent assay. The luciferase activity was measured by a dual luciferase reporter gene assay. The allele-specific transcription factor binding for rs7025417 was examined by ChIP-seq. The IL-33 rs7025417 CC genotype was significantly associated with a decreased risk of OS (CC vs TT: OR = 0.59, 95% CI, 0.41-0.85; recessive model: OR = 0.68, 95% CI, 0.49-0.94; C vs T: OR = 0.76, 95% CI, 0.63-0.91). Combined analysis showed that the IL-33 rs7025417CT/CC-ST2 rs3821204CG/CC and the IL-33 rs7025417CT/CC-ST2 rs3821204GG genotypes also had a decreased risk of OS. IL-33mRNA and protein levels in OS patients were significantly higher than controls. Patients with the rs7025417 CC genotype exhibited lower levels of IL-33 (P = .03). The rs7025417 C allele presented a lower transcriptional activity by disrupting the binding site to c-Myb (P < .01). Moreover, the rs3821204 G/C influences the transcriptional activity and ST2mRNA expression by altering the binding site of miR-202-3p. These findings suggest that the rs7025417 and rs3821204 may have a combined effect to protect against the development of OS by decreasing the expression levels of IL-33 or ST2.

The IL-33/ST2 pathway, inflammation and atherosclerosis: Trigger and target?

The "inflammatory hypothesis" of atherosclerosis postulates that inflammatory cell signalling drives the formation, growth and ultimately the instability of atherosclerotic plaques, setting up the substrate for the thrombotic response that causes myocardial damage or infarction. The recent Canakinumab Antiinflammatory Thrombosis Outcome Study (CANTOS) trial has been hailed as the first demonstration, ex iuvantibus, of the inflammatory hypothesis. Indeed, interleukin (IL)-1β inhibition was found to reduce cardiovascular events in patients with previous myocardial infarction and raised high-sensitivity C-reactive protein, despite no effects on the lipid profile. These results prompt a dissection of inflammatory mechanisms of atherosclerosis in order to search for specific biomarkers with prognostic value and/or therapeutic targets. Under this respect, the IL-33/suppression of tumorigenesis 2 (ST2) pathway deserves consideration. Indeed, its elements are particularly expressed in the endothelium of arterial vessels, and the interaction between IL-33 and the ST2 receptor blunts the immune response characteristic of atherosclerosis. By contrast, soluble ST2 (sST2) acts as a decoy receptor for IL-33, thus blocking its protective effects. Despite a solid theoretical framework, no definite demonstration of an involvement of the IL-33/ST2 pathway in atherosclerosis has been provided. Therefore, further studies are warranted to verify if elements of the IL-33/ST2 pathway may be proposed as markers of plaque burden and predictors of future cardiovascular events, and to explore the potential clinical benefit of enhanced IL-33/ST2 signalling in atherosclerosis.

Interleukin-33 Receptor (ST2) Deficiency Improves the Outcome of Staphylococcus aureus-Induced Septic Arthritis

The ST2 receptor is a member of the Toll/IL-1R superfamily and interleukin-33 (IL-33) is its agonist. Recently, it has been demonstrated that IL-33/ST2 axis plays key roles in inflammation and immune mediated diseases. Here, we investigated the effect of ST2 deficiency in Staphylococcus aureus-induced septic arthritis physiopathology. Synovial fluid samples from septic arthritis and osteoarthritis individuals were assessed regarding IL-33 and soluble (s) ST2 levels. The IL-33 levels in samples from synovial fluid were significantly increased, whereas no sST2 levels were detected in patients with septic arthritis when compared with osteoarthritis individuals. The intra-articular injection of 1 × 10⁷ colony-forming unity/10 μl of S. aureus American Type Culture Collection 6538 in wild-type (WT) mice induced IL-33 and sST2 production with a profile resembling the observation in the synovial fluid of septic arthritis patients. Data using WT, and ST2 deficient (^−/−) and interferon-γ (IFN-γ)^−/− mice showed that ST2 deficiency shifts the immune balance toward a type 1 immune response that contributes to eliminating the infection due to enhanced microbicide effect via NO production by neutrophils and macrophages. In fact, the treatment of ST2^−/− bone marrow-derived macrophage cells with anti-IFN-γ abrogates the beneficial phenotype in the absence of ST2, which confirms that ST2 deficiency leads to IFN-γ expression and boosts the bacterial killing activity of macrophages against S. aureus. In agreement, WT cells achieved similar immune response to ST2 deficiency by IFN-γ treatment. The present results unveil a previously unrecognized beneficial effect of ST2 deficiency in S. aureus-induced septic arthritis.

Interleukin-33 Predicts Poor Prognosis and Promotes Renal Cell Carcinoma Cell Growth Through its Receptor ST2 and the JNK Signaling Pathway

BACKGROUND/AIMS

Renal cell carcinoma (RCC) is currently the ninth most common cancer in men. Interleukin (IL)-33 expression has previously been associated with a number of cancers; however, its biological role in RCC is poorly understood. In this study, we sought to elucidate the role of IL-33 in RCC.

METHODS

Serum IL-33 levels were measured by ELISA. IL-33 expression in clinical RCC samples was examined by immunocytochemistry. The proliferation and apoptosis rate of RCC were determined by CCK8 and flow cytometry. Mcl1 and Bcl-2 expression were measured by quantitative real-time PCR and western blotting. JNK expression were measured by western blotting and flow cytometry. The in vivo role of IL-33 in RCC tumorigenesis was examined by animal models.

RESULTS

We found that increased expression of IL-33 in RCC was associated with tumor-lymph node-metastasis (TNM) stage and inversely correlated with prognosis. IL-33 enhances RCC cell growth in vivo and stimulates RCC cell proliferation and prevents chemotherapy-induced tumor apoptosis in vitro. Furthermore, we demonstrated that IL-33 promotes RCC cell proliferation and chemotherapy resistance via its receptor ST2 and the JNK signaling activation in tumor cells.

CONCLUSION

Our findings suggest that targeting IL-33/ST2 and JNK signaling may have potential value in the treatment of RCC.

Soluble ST2 in Heart Failure

Suppression of tumorigenicity 2 (ST2) is a member of the interleukin (IL)-1 receptor family, whose role was originally established in the context of inflammatory and autoimmune diseases. More recently, testing for ST2 has been used in the setting of cardiovascular disease. The soluble form of ST2 is a decoy receptor that inhibits beneficial cardioprotective effects of IL-33; such inhibition results in cardiac hypertrophy, myocardial fibrosis, and ventricular dysfunction. Measurement of soluble ST2 has utility for assessing heart failure severity and prognosis. In this review, we examine the role of soluble ST2 in both acute and chronic heart failure.

IL-33 and Its Receptor ST2 after Inhaled Allergen Challenge in Allergic Asthmatics

BACKGROUND

Previous murine models have demonstrated interleukin (IL)-33 to be an important mediator of type-2 inflammation and to promote airway hyperresponsiveness in allergic asthma. A number of inflammatory cells produce IL-33 and eosinophils express ST2 mRNA. The relationship between IL-33 and eosinophils in allergic asthma, however, remains unclear.

OBJECTIVE

The aim of this work was to evaluate in vitro the effect of allergen inhalation on IL-33 levels and expression of its receptor (ST2L) on eosinophils in allergic asthmatics, and the effect of IL-33 stimulation on eosinophil activity.

METHODS

Plasma and sputum IL-33, soluble ST2 (sST2) levels, and ST2L expression on eosinophils were measured in 10 healthy controls and 10 allergic asthmatics. Asthmatics underwent allergen and diluent inhalation challenges. Blood and sputum samples were collected to measure IL-33, sST2, and ST2L eosinophil expression before and 24 h after allergen inhalation. Purified blood eosinophils from allergic asthmatics were incubated overnight with IL-33 to assess ST2 and intracellular IL-5 expression.

RESULTS

Baseline levels of IL-33 in sputum and sST2 in plasma and sputum were similar in allergic asthmatics compared to healthy controls. In addition, there was no difference in blood or sputum eosinophil ST2L expression in healthy controls versus allergic asthmatics. Eosinophil ST2L expression was significantly increased 24 h postallergen inhalation in allergic asthmatics. In vitro stimulation of human eosinophils with IL-33 and LPS significantly increased eosinophil ST2L expression and IL-33 stimulation increased intracellular IL-5 expression, which was attenuated by treatment with sST2 and ST2 blockade.

CONCLUSION AND CLINICAL RELEVANCE

In mild asthmatics, there was a significant upregulation of ST2 surface expression on eosinophils from blood and sputum following allergen inhalation challenge. In vitro, IL-33 stimulation of eosinophils increases both ST2 membrane expression and IL-5 production. These results support a role for IL-33 in causing allergen-induced eosinophilia. Blockade of IL-33 and ST2 signaling may present a novel therapeutic avenue for asthma treatment.

Genetic variants in IL-33/ST2 pathway with the susceptibility to hepatocellular carcinoma in a Chinese population

Interleukin (IL)-33/ST2 pathway plays a pivotal role in tumorigenesis through influencing cancer stemness, tumor growth, metastasis, angiogenesis, and accumulation of regulatory T cells in tumor microenvironments. The aim of this study was to investigate the association of IL-33 rs7025417 and ST2 rs3821204 with the risk of hepatocellular carcinoma (HCC). Genotyping of IL-33 rs7025417 and ST2 rs3821204 was carried out using a Taqman assay. IL-33 and ST2 mRNA was examined using real-time PCR and plasma IL-33 and sST2 levels were measured using enzyme-linked immunosorbent assay. The ST2 rs3821204 CC genotype was associated with a significantly increased risk of HCC (CC vs. GG: adjusted OR = 2.29, 95% CI, 1.39-3.78; dominant model: adjusted OR = 1.58, 95% CI, 1.12-2.23; recessive model: adjusted OR = 1.88, 95% CI, 1.21-2.93; C vs. G: adjusted OR = 1.53, 95% CI, 1.20-1.95). Gene-environment interaction analysis showed that the risk effect of rs3821204 CG/CC genotypes was more evident in smokers (adjusted OR = 1.70, 95% CI, 1.13-2.55) and drinkers (adjusted OR = 1.57, 95% CI, 1.04-2.37). The increased risk was also observed in combined analysis. Moreover, HCC patients with ST2 rs3821204 CC genotype had higher levels of mRNA and protein expression (P < 0.05). These findings suggest that ST2 rs3821204 CC genotype may contribute to hepatocarcinogenesis by enhancing ST2 production at the transcriptional and translational level.