Plasma soluble ST2 levels correlate with disease severity and predict clinical worsening in patients with pulmonary arterial hypertension

Soluble ST2: A Novel Biomarker for Diagnosis and Prognosis of Cardiovascular Disease

The increasing incidence of cardiovascular disease (CVD) is a significant global health concern, affecting millions of individuals each year. Accurate diagnosis of acute CVD poses a formidable challenge, as misdiagnosis can significantly decrease patient survival rates. Traditional biomarkers have played a vital role in the diagnosis and prognosis of CVDs, but they can be influenced by various factors, such as age, sex, and renal function. Soluble ST2 (sST2) is a novel biomarker that is closely associated with different CVDs. Its low reference change value makes it suitable for continuous measurement, unaffected by age, kidney function, and other confounding factors, facilitating risk stratification of CVDs. Furthermore, the combination of sST2 with other biomarkers can enhance diagnostic accuracy and prognostic value. This review aims to provide a comprehensive overview of sST2, focusing on its diagnostic and prognostic value as a myocardial marker for different types of CVDs and discussing the current limitations of sST2.

Current Trends in Biohumoral Screening for the Risk of Sudden Cardiac Death: A Systematic Review

Background and Objectives: Sudden cardiac death (SCD) represents a challenge to health systems globally and is met with increased frequency in the population. Over time, multiple screening methods have been proposed, including the analysis of various plasma biomarkers. This article aims to analyze for illustrative purposes the specialized literature in terms of current biomarkers and testing trends, in the case of cardiovascular diseases and implicitly sudden cardiac death. Materials and Methods: In this regard, we searched the PubMed database from 2010 to the present time using the keywords "sudden cardiac death" and "biomarkers". The inclusion criteria were clinical trials that analyzed the effectiveness of screening methods in terms of biomarkers used in stratifying the risk of cardiac distress and/or sudden cardiac death. We excluded reviews, meta-analyses, and studies looking at the effectiveness of treatments. Results: An extended approach was found, through studies that brought to the forefront both classical markers analyzed by new, more performant methods, markers for other pathologies that also determined cardiovascular impact, non-specific molecules with effects on the cardiovascular system, and state-of-the-art markers, such as microRNA. Some molecules were analyzed simultaneously in certain groups of patients. Conclusion: The observed current trend revealed the tendency to define the clinical-biological particularities of the person to be screened.

Association of soluble ST2 Level with 6-month Mortality and/or Recurrent Cardiovascular-Related Hospitalization in Pulmonary Embolism

BACKGROUND

The association of soluble suppression of tumorigenesis-2 (sST2) levels with prognosis in pulmonary embolism (PE) is unknown.

OBJECTIVE

This study aimed to investigate the relationship between sST2 levels in patients with acute PE and 6-month mortality and recurrent hospitalizations.

METHODS

This prospective study included 100 patients with acute PE. Patients were classified into two groups according to 6-month mortality and the presence of recurrent Cardiovascular-Related hospitalizations. Two groups were compared. A p-value of 0.05 was considered statistically significant.

RESULTS

Soluble ST2 levels were significantly higher in the group with mortality and recurrent hospitalizations. (138.6 ng/mL (56.7-236.8) vs. 38 ng/mL (26.3-75.4); p<0.001) The best cut-off threshold for sST2 levels in the prediction of a composite outcome of 6-month mortality and/or recurrent Cardiovascular-Related hospitalization was found to be >89.9 with a specificity of 90.6% and a sensitivity of 65.2%, according to the receiver operating characteristic curve (area under the curve = 0.798; 95% CI, 0.705-0.891; p <0.0001). After adjusting for confounding factors that were either statistically significant in the univariate analysis or for the variables correlated with the sST2 levels, sST2 level (OR = 1.019, 95% CI: 1.009-1.028, p 0.001) and C-reactive protein (CRP ) (OR = 1.010, 95% CI: 1.001-1.021, p = 0.046) continued to be significant predictors of 6-month mortality and/or recurrent Cardiovascular-Related hospitalization in the multiple logistic regression model via backward stepwise method.

CONCLUSION

Soluble ST2 level seems to be a biomarker to predict 6-month mortality and/or recurrent Cardiovascular-Related hospitalization in patients with acute PE.

Relationship Between Soluble ST2 Level and Chronic Thromboembolic Pulmonary Hypertension (CTEPH) in Acute Pulmonary Embolism (PE) Patients

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease characterized by right heart failure following recurrent pulmonary embolism (PE). It is important to know the predictors of the development of CTEPH after PE as it is a treatable cause of pulmonary arterial hypertension. Soluble ST2 is a biomarker closely associated with heart failure and the inflammatory process. The aim of this study was to investigate the relationship between sST2 level and the development of CTEPH in patients with PE.

METHODOLOGY

Baseline characteristics, electrocardiographic findings, laboratory findings, transthoracic echocardiography (TTE) findings, location, and extent of involvement in CT pulmonary angiography were recorded in 100 patients with acute PE included in our prospective study. Treatment modalities and treatment durations were followed. Ventilation-perfusion scintigraphy was performed in patients with a systolic pulmonary artery pressure (sPAP) of 35 mmHg or more on TTE and residual thrombus on CT pulmonary angiography after at least three months of anticoagulant use. In the case of findings compatible with CTEPH in these examinations, patients were diagnosed with CTEPH by right heart catheterization. The sST2 levels obtained from all patients at admission were evaluated between the groups of patients with and without CTEPH.

RESULTS

CTEPH was observed in 11 of the 100 patients who participated in the trial, with a median follow-up of 284 ± 60 days. The mean age of the 11 patients with CTEPH was 67 ± 10 years; five were males and six were females. The mean age of 89 patients without CTEPH was 65 ± 18 years, 36 were males and 53 were females. The sST2 values of the group with CTEPH were found to be statistically significantly higher than those of patients without CTEPH [193.7 (184.3-244.7) vs 58.6 (29.5-122.9) p=0.020]. This receiver operating characteristic (ROC) curve shows that the optimal cutoff point of sST2 levels in the prediction of CTEPH was > 157.4 with specificity of 83.7% and sensitivity of 81.8% (area under the curve = 0.783; 95% CI, 1.005-1.027; p < 0.001).

CONCLUSION

In acute PE patients, sST2 levels may be a useful biomarker to predict the development of CTEPH.

The ST2/IL-33 Pathway in Adult and Paediatric Heart Disease and Transplantation

ST2 is a member of interleukin 1 receptor family with soluble sST2 and transmembrane ST2L isoforms. The ligand of ST2 is IL-33, which determines the activation of numerous intracytoplasmic mediators following the binding with ST2L and IL-1RAcP, leading to nuclear signal and cardiovascular effect. Differently, sST2 is released in the blood and works as a decoy receptor, binding IL-33 and blocking IL-33/ST2L interaction. sST2 is mainly involved in maintaining homeostasis and/or alterations of different tissues, as counterbalance/activation of IL-33/ST2L axis is typically involved in the development of fibrosis, tissue damage, inflammation and remodeling. sST2 has been described in different clinical reports as a fundamental prognostic marker in patients with cardiovascular disease, as well as marker for the treatment monitoring of patients with heart failure; however, further studies are needed to better elucidate its role. In this review we reported the current knowledge about its role in coronary artery disease, heart failure, heart transplantation, heart valve disease, pulmonary arterial hypertension, and cardiovascular interventions.

Modulation of IL-33/ST2 signaling as a potential new therapeutic target for cardiovascular diseases

IL-33 belongs to the IL-1 family of cytokines, which function as inducers of Th2 cytokine production by binding with ST2L and IL-1RAcP. This, in turn, activates various signaling pathways, including the mitogen-activated protein kinase (MAPK), the inhibitor of Kappa-B kinase (IKK) pathway, and the phospholipase D-sphingosine kinase pathway. IL-33 has demonstrated protective effects against various cardiovascular diseases (CVDs) by inducing Th2 cytokines and promoting alternative activating M2 polarization. However, the soluble decoy form of ST2 (sST2) mitigates the biological effects of IL-33, exacerbating CVDs. Furthermore, IL-33 also plays a significant role in the development of asthma, arthritis, atopic dermatitis, and anaphylaxis through the activation of Th2 cells and mast cells. In this review, we aim to demonstrate the protective role of IL-33 against CVDs from 2005 to the present and explore the potential of serum soluble ST2 (sST2) as a diagnostic biomarker for CVDs. Therefore, IL-33 holds promise as a potential therapeutic target for the treatment of CVDs.

Assessment and diagnosis of right ventricular failure-retrospection and future directions

The right ventricle (RV) has a critical role in hemodynamics and right ventricular failure (RVF) often leads to poor clinical outcome. Despite the clinical importance of RVF, its definition and recognition currently rely on patients' symptoms and signs, rather than on objective parameters from quantifying RV dimensions and function. A key challenge is the geometrical complexity of the RV, which often makes it difficult to assess RV function accurately. There are several assessment modalities currently utilized in the clinical settings. Each diagnostic investigation has both advantages and limitations according to its characteristics. The purpose of this review is to reflect on the current diagnostic tools, consider the potential technological advancements and propose how to improve the assessment of right ventricular failure. Advanced technique such as automatic evaluation with artificial intelligence and 3-dimensional assessment for the complex RV structure has a potential to improve RV assessment by increasing accuracy and reproducibility of the measurements. Further, noninvasive assessments for RV-pulmonary artery coupling and right and left ventricular interaction are also warranted to overcome the load-related limitations for the accurate evaluation of RV contractile function. Future studies to cross-validate the advanced technologies in various populations are required.

Soluble ST2 as a New Oxidative Stress and Inflammation Marker in Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MS) is a complex and prevalent disorder. Oxidative stress and inflammation might contribute to the progression of MS. Soluble ST2 (sST2) is an attractive and druggable molecule that sits at the interface between inflammation, oxidative stress and fibrosis. This study aims to analyze the relationship among sST2, oxidative stress, inflammation and echocardiographic parameters in MS patients.

METHODS

Fifty-eight patients with MS were recruited and underwent physical, laboratory and transthoracic echocardiography examinations. Commercial ELISA and appropriate colorimetric assays were used to quantify serum levels of oxidative stress and inflammation markers and sST2.

RESULTS

Circulating sST2 was increased in MS patients and was significantly correlated with the oxidative stress markers nitrotyrosine and 8-hydroxy-2'-deoxyguanosine as well as with peroxide levels. The inflammatory parameters interleukin-6, intercellular adhesion molecule-1 and myeloperoxidase were positively correlated with sST2. Noteworthy, sST2 was positively correlated with left ventricular mass, filling pressures and pulmonary arterial pressures.

CONCLUSION

Circulating levels of sST2 are associated with oxidative stress and inflammation burden and may underlie the pathological remodeling and dysfunction of the heart in MS patients. Our results suggest that sST2 elevation precedes diastolic dysfunction, emerging as an attractive biotarget in MS.

Biomarkers in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe medical condition characterized by elevated pulmonary vascular resistance (PVR), right ventricular (RV) failure, and death in the absence of appropriate treatment. The progression and prognosis are strictly related to the etiology, biochemical parameters, and treatment response. The gold-standard test remains right-sided heart catheterization, but dynamic monitoring of systolic pressure in the pulmonary artery is performed using echocardiography. However, simple and easily accessible non-invasive assays are also required in order to monitor this pathology. In addition, research in this area is in continuous development. In recent years, more and more biomarkers have been studied and included in clinical guidelines. These biomarkers can be categorized based on their associations with inflammation, endothelial cell dysfunction, cardiac fibrosis, oxidative stress, and metabolic disorders. Moreover, biomarkers can be easily detected in blood and urine and correlated with disease severity, playing an important role in diagnosis, prognosis, and disease progression.

GDF-15 and soluble ST2 as biomarkers of right ventricular dysfunction in pulmonary hypertension

Background: This study analyzed the utility of soluble ST2 (sST2) and GDF-15 as biomarkers of right ventricular (RV) function in patients with pulmonary hypertension (PH). Methods: GDF-15 and sST2 serum concentrations were measured in patients with PH (n = 628), dilated cardiomyopathy (n = 31) and left ventricular hypertrophy (n = 47), and in healthy controls (n = 61). Results: Median sST2 and GDF-15 levels in patients with left ventricular hypertrophy were higher than in patients with PH and dilated cardiomyopathy. In tertile analysis GDF-15 >1363 pg/ml and sST2 >38 ng/ml were associated with higher N-terminal pro-brain natriuretic peptide, RV systolic dysfunction, RV-pulmonary arterial uncoupling and hemodynamic impairment. Conclusion: GDF-15 and sST2 are potential biomarkers of RV dysfunction in patients with PH.

Interrelationship and Sequencing of Interleukins4, 13, 31, and 33 - An Integrated Systematic Review: Dermatological and Multidisciplinary Perspectives

The interrelations and sequencing of interleukins are complex (inter)actions where each interleukin can stimulate the secretion of its preceding interleukin. In this paper, we attempt to summarize the currently known roles of IL-4, IL-13, IL-31, and IL-33 from a multi-disciplinary perspective. In order to conduct a comprehensive review of the current literature, a search was conducted using PubMed, Google Scholar, Medscape, UpToDate, and Key Elsevier for keywords. The results were compiled from case reports, case series, letters, and literature review papers, and analyzed by a panel of multi-disciplinary specialist physicians for relevance. Based on 173 results, we compiled the following review of interleukin signaling and its clinical significance across a multitude of medical specialties. Interleukins are at the bed rock of a multitude of pathologies across different organ systems and understanding their role will likely lead to novel treatments and better outcomes for our patients. New interleukins are being described, and the role of this inflammatory cascade is still coming to light. We hope this multi-discipline review on the role interleukins play in current pathology assists in this scope.

Soluble ST2 as a Potential Biomarker for Risk Assessment of Pulmonary Hypertension in Patients Undergoing TAVR?

Background: Severe aortic valve stenosis (AS) is associated with pulmonary hypertension (PH) and has been shown to limit patient survival. Soluble suppression of tumorigenicity-2 (sST2) is a cardiovascular biomarker that has proven to be an important prognostic marker for survival in patients undergoing transcatheter aortic valve replacement (TAVR). The aim of this study was to assess the importance of the sST2 biomarker for risk stratification in patients with severe AS in presence or absence of PH. Methods: In 260 patients with severe AS undergoing TAVR procedure, sST2 serum level concentrations were analyzed. Right heart catheter measurements were performed in 152 patients, with no PH detection in 43 patients and with PH detection in 109 patients. Correlation analyses according to Spearman, AUROC analyses and Kaplan–Meier curves were calculated. Results: Patients with severe AS and PH showed significantly higher serum sST2 concentrations (p = 0.006). The sST2 cut-off value for non-PH patients regarding 1-year survival yielded 5521.15 pg/mL, whereas the cut-off value of PH patients was at a considerably higher level of 10,268.78 pg/mL. A cut-off value of 6990.12 pg/mL was related with a significant probability of PH presence. Survival curves showed that patients with severe AS and PH not only had higher 1-year mortality, but also that increased levels of sST2 plasma concentration were associated with earlier death. Conclusion: sST2 definitely has the potential to provide information about the presence of PH in patients with severe AS, in a noninvasive way.

Circulating Blood-Based Biomarkers in Pulmonary Hypertension

Pulmonary hypertension (PH) is a serious hemodynamic condition, characterized by increased pulmonary vascular resistance (PVR), leading to right heart failure (HF) and death when not properly treated. The prognosis of PH depends on etiology, hemodynamic and biochemical parameters, as well as on response to specific treatment. Biomarkers appear to be useful noninvasive tools, providing information about the disease severity, treatment response, and prognosis. However, given the complexity of PH, it is impossible for a single biomarker to be adequate for the broad assessment of patients with different types of PH. The search for novel emerging biomarkers is still ongoing, resulting in a few potential biomarkers mirroring numerous pathophysiological courses. In this review, markers related to HF, myocardial remodeling, inflammation, hypoxia and tissue damage, and endothelial and pulmonary smooth muscle cell dysfunction are discussed in terms of diagnosis and prognosis. Extracellular vesicles and other markers with complex backgrounds are also reviewed. In conclusion, although many promising biomarkers have been identified and studied in recent years, there are still insufficient data on the application of multimarker strategies for monitoring and risk stratification in PH patients.

Suppression of tumorigenicity 2 after exercise: a systematic review

Exercise is a pivotal physiological activity, associated with benefits. Whilst the importance of physical activity is consensual along different steps of the cardiovascular (CV) continuum, there has been interest in assessing the CV adaptations to vigorous exercise. Indeed, exercise can be associated with increases in cardiac biomarkers, though the scope of this observation remains elusive. Interleukin 1 receptor related protein, Suppression of tumorigenicity 2 (ST2) is a biomarker related to the pathophysiology of fibrosis, having shown promise in the study of heart failure. Knowledge of ST2 kinetics could improve understanding of the mechanistic pathways related to CV adaptations to exercise. To assess the current state-of-the-art concerning ST2 levels after exercise in healthy individuals. A systematic review was carried out on three databases (Pubmed, ISI Web of Science and Scopus), up to October 2020, using the queries "ST2" or "ST-2" + "exercise" or "running". A total of six studies were included in the review, encompassing 349 subjects (73% male gender) in which ST2 was assessed. Most studies reported increases in ST2 levels after exercise. Three studies, encompassing a total of 219 individuals, described a cut-off level of 35 ng/dL for ST2. In these, 92.7% of subjects had ST2 levels above this cut-off after exercise (running in all studies). Most studies report increased levels of ST2 after exercise, with an important number of individuals exceeding the 35 ng/dL threshold. Given the small number of individuals represented and the lack of imaging data and long-term follow-up, further prospective larger studies should target this.

ST2 Is a Biomarker of Pediatric Pulmonary Arterial Hypertension Severity and Clinical Worsening

BACKGROUND

Pediatric pulmonary hypertension is a severe disease defined by sustained elevation of pulmonary artery pressures and pulmonary vascular resistance (PVR). Noninvasive diagnostic and prognostic markers that are more pulmonary vascular specific have been elusive because of disease heterogeneity and patient growth.

RESEARCH QUESTION

Is soluble suppressor of tumorigenicity (ST2) associated with pulmonary hemodynamic and functional changes in pediatric pulmonary hypertension? Does ST2 improve mortality risk models in pediatric pulmonary hypertension?

STUDY DESIGN AND METHODS

Two pediatric cohorts (age < 21 years) were assayed for ST2 and N-terminal prohormone B-natriuretic peptide: a cross-sectional cohort from the National Heart Lung and Blood Institute-funded National Biological Sample and Data Repository for PAH (PAHB) (N = 182), and a second longitudinal cohort from Children's Hospital of Colorado (N = 61). Adjusted linear regression was used for association with clinical variables. Clinical mortality models (the Registry to Evaluate Early and Long-Term PAH Disease Management [REVEAL] score) with and without ST2 were used to predict worsening outcomes and compared. Pulmonary artery endothelial and smooth muscle cell ST2 expression and secretion were assayed in vitro.

RESULTS

In an adjusted (age and sex) analysis in the PAHB, ST2 was significantly associated with shorter 6-min walk distance (P = .03) and increased PVR index (P = .02). In adjusted longitudinal regression in the Children's Hospital of Colorado cohort, ST2 was significantly associated with higher PVR index (P < .001), shorter 6-min walk distance (P = .01), and higher mean pulmonary artery pressure (P < .001). Although the REVEAL Risk Score Calculator 2.0 was predictive of clinical worsening in the PAHB (hazard ratio, 1.88), addition of ST2 significantly improved the model (hazard ratio, 2.05). In cell culture, ST2 was produced and secreted predominately by endothelial cells as opposed to smooth muscle cells (P < .0001).

INTERPRETATION

In two pediatric PAH cohorts, elevated ST2 was associated with unfavorable pulmonary hemodynamics and functional measures, clinical worsening, and significantly improved prediction of clinical worsening. Pulmonary artery endothelial cellular expression of ST2 suggests that ST2 is a more pulmonary vascular-specific marker for pulmonary hypertension.

The Novel Perspectives Opened by ST2 in the Pandemic: A Review of Its Role in the Diagnosis and Prognosis of Patients with Heart Failure and COVID-19

The increasing incidence of coronavirus disease 19 (COVID-19) and its polymorphic clinical manifestations due to local and systemic inflammation represent a high burden for many public health systems. Multiple evidence revealed the interdependence between the presence of cardiovascular comorbidities and a severe course of COVID-19, with heart failure (HF) being incriminated as an independent predictor of mortality. Suppression of tumorigenicity-2 ST2 has emerged as one of the most promising biomarkers in assessing the evolution and prognosis of patients with HF. The uniqueness of ST2 is determined by its structural particularities. Its transmembrane isoform exerts cardioprotective effects, while the soluble isoform (sST2), which is detectable in serum, is associated with myocardial fibrosis and poor outcome in patients with HF. Some recent data also suggested the potential role of sST2 as a marker of inflammation, while other studies highlighted it as a valuable prognostic factor in patients with COVID-19. In this review, we summarized the pathways by which sST2 is related to myocardial injury and its connection to the severity of inflammation in patients with COVID-19. Also, we reviewed possible perspectives of using it as a dual cardio-inflammatory biomarker, for both early diagnosis, risk stratification and prognosis assessment of patients with concomitant HF and COVID-19.

Soluble ST2 as a Biomarker for Early Complications in Patients with Chronic Thromboembolic Pulmonary Hypertension Treated with Balloon Pulmonary Angioplasty

Background: The aim of the study was to assess soluble ST2 (sST2) concentration and its dynamic changes in the periprocedural period in patients with chronic thromboembolic pulmonary hypertension (CTEPH) treated with balloon pulmonary angioplasty (BPA). Methods: We prospectively analyzed 57 procedures of BPA performed in 37 patients with CTEPH. Biomarkers, such as N-terminal pro B-type natriuretic peptide (NT-proBNP), troponin T (TnT), and sST2 were assessed at four time points: Before the BPA procedure, 24 h and 48 h after the procedure, and at the discharge from hospital. Each postprocedural period was assessed for complications. Results: Before the BPA procedure, median sST2 concentration was 26.56 ng/mL (IQR: 16.66–40.83 ng/mL). sST2 concentration was significantly higher 24 h and 48 h after the BPA compared to the baseline measurements (33.31 ng/mL (IQR: 20.81–62.56), p = 0.000 and 27.45 ng/mL (IQR: 17.66–54.45), p = 0.028, respectively). sST2 level 24 h after the BPA procedure was significantly higher in the group with complications compared to the group without complications in the postprocedural period (97.66 ng/mL (IQR: 53.07–126.18) vs. 26.86 ng/mL (IQR: 19.10–40.12), p = 0.000). Conclusions: sST2 concentration in patients with CTEPH treated with BPA changes significantly in the postprocedural period and is significantly higher in the group with complications in postprocedural period.

Pulmonary hypertension: Proteins in the blood

The plasma proteome is rich in information. It comprises proteins that are secreted or lost from cells as they respond to their local environment. Changes in the constitution of the plasma proteome offer a relatively non-invasive report on the health of tissues. This is particularly true of the lung in pulmonary hypertension, given the large surface area of the pulmonary vasculature in direct communication with blood. So far, this is relatively untapped; we have relied on proteins released from the heart, specifically brain natriuretic peptide and troponin, to inform clinical management. New technology allows the measurement of a larger number of proteins that cover a broad range of molecular pathways in a single small aliquot. The emerging data will yield more than just new biomarkers of pulmonary hypertension for clinical use. Integrated with genomics and with the help of new bioinformatic tools, the plasma proteome can provide insight into the causative drivers of pulmonary vascular disease and guide drug development.

Serum soluble suppression of tumorigenicity-2 level associates with severity of pulmonary hypertension associated with uncorrected atrial septal defect

Uncorrected atrial septal defect undergoes right ventricle chronic volume overload which may lead to pulmonary hypertension and Eisenmenger Syndrome. The soluble suppression of tumorigenicity-2 is a left ventricle strain biomarker; however, its role in right ventricle strain is unclear. This study aimed to investigate the implication of serum soluble suppression of tumorigenicity-2 in adult uncorrected atrial septal defect. This was a cross-sectional study. We enrolled 81 adult uncorrected secundum atrial septal defect patients. Clinical and hemodynamic data were collected. Serum samples were withdrawn from the pulmonary artery during right heart catheterization. Serum soluble suppression of tumorigenicity-2 and NT-proBNP levels were measured. Subjects were divided into three groups based on clinical and hemodynamic severity. The correlation of soluble suppression of tumorigenicity-2 with patients' data and comparison among groups were analyzed. A p value <0.05 was considered statistically significant. Results showed that, there were significant correlations between serum soluble suppression of tumorigenicity-2 and mean pulmonary artery pressure (r = 0.203, p = 0.035) and right ventricle end-diastolic diameter (r = 0.203, p <0.05). Median serum soluble suppression of tumorigenicity-2 level was incrementally increased from group I (atrial septal defect and no-pulmonary hypertension), group II (left-to-right atrial septal defect and pulmonary hypertension), to group III (Eisenmenger Syndrome): (17.4 ng/mL, 21.8 ng/mL, and 29.4 ng/mL, respectively). A post-hoc analysis showed that serum soluble suppression of tumorigenicity-2 level was significantly different between groups I and III (p = 0.01). Serum N terminal pro brain natriuretic peptide (NT-proBNP) level was consistently associated with worse clinical and hemodynamic parameters. No correlation was found between serum soluble suppression of tumorigenicity-2 and NT-proBNP level. In conclusion, serum soluble suppression of tumorigenicity-2 level had significant positive correlation with mean pulmonary artery pressure and right ventricle end-diastolic diameter in uncorrected secundum atrial septal defect patients. Higher serum soluble suppression of tumorigenicity-2 level was associated with the presence of pulmonary hypertension and Eisenmenger Syndrome in uncorrected secundum atrial septal defect patients.

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.

Alteration of the IL-33-sST2 pathway in hypertensive patients and a mouse model

Inflammatory cells play an important role in the occurrence of hypertension. Recent studies have demonstrated that interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) signaling plays a critical role in the pathogenesis of several cardiovascular diseases. We aimed to evaluate the association of IL-33 and its receptor levels with the occurrence of hypertension in angiotensin II (Ang II)-infused mice using microarray analysis and validated our results in human specimens. Male wild-type mice were infused with Ang II (1500 ng/kg/min) for 1, 3 and 7 days. Patients with essential hypertension (EH) (n = 166) and healthy control subjects (n = 306) were enrolled. Levels of IL-33 and ST2 mRNAs in serum and peripheral blood mononuclear cells (PBMCs) were analyzed by Luminex assay or ELISA and qPCR analysis. We found that IL-33 expression was significantly increased in the aortas of mice receiving Ang II infusion compared with that of control mice. In contrast, the levels of IL-33 in serum and PBMCs were not significantly different between hypertensive patients and normal controls. However, the levels of soluble ST2 (sST2) in serum and PBMCs were markedly higher in hypertensive patients than in controls (P < 0.001 and P = 0.014, respectively). In addition, the ST2L level in PBMCs was also significantly decreased in hypertensive patients (P = 0.028). Further, logistic analysis showed that the odds ratios of having hypertension based on sST2 levels in serum and PBMCs were 9.714 and 2.244 (P = 0.013 and P = 0.024, respectively) compared with the control group. Above all, sST2 acted as a risk factor for the occurrence of hypertension and may be a promising novel predictive marker for EH.

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.

Conflicting vascular and metabolic impact of the IL-33/sST2 axis

Interleukin 33 (IL-33), which is expressed by several immune cell types, endothelial and epithelial cells, and fibroblasts, is a cytokine of the IL-1 family that acts both intra- and extracellularly to either enhance or resolve the inflammatory response. Intracellular IL-33 acts in the nucleus as a regulator of transcription. Once released from cells by mechanical stress, inflammatory cytokines, or necrosis, extracellular IL-33 is proteolytically processed to act in an autocrine/paracrine manner as an 'alarmin' on neighbouring or various immune cells expressing the ST2 receptor. Thus, IL-33 may serve an important role in tissue preservation and repair in response to injury; however, the actions of IL-33 are dampened by a soluble form of ST2 (sST2) that acts as a decoy receptor and is produced by endothelial and certain immune cells. Accumulating evidence supports the conclusion that sST2 is a biomarker of vascular health with diagnostic and/or prognostic value in various cardiovascular diseases, including coronary artery disease, myocardial infarction, atherosclerosis, giant-cell arteritis, acute aortic dissection, and ischaemic stroke, as well as obesity and diabetes. Although sST2 levels are positively associated with cardiovascular disease severity, the assumption that IL-33 is always beneficial is naïve. It is increasingly appreciated that the pathophysiological importance of IL-33 is highly dependent on cellular and temporal expression. Although IL-33 is atheroprotective and may prevent obesity and type 2 diabetes by regulating lipid metabolism, IL-33 appears to drive endothelial inflammation. Here, we review the current knowledge of the IL-33/ST2/sST2 signalling network and discuss its pathophysiological and translational implications in cardiovascular diseases.

Right ventricular fibrosis and dysfunction: Actual concepts and common misconceptions

Fibrosis and remodeling of the right ventricle (RV) are associated with RV dysfunction and mortality of patients with pulmonary hypertension (PH) but it is unknown how much RV fibrosis contributes to RV dysfunction and mortality. RV fibrosis manifests as fibroblast accumulation and collagen deposition which may be excessive. Although extracellular matrix deposition leads to elevated ventricular stiffness, it is not known to which extent it affects RV function. Various animal models of pulmonary hypertension have been established to investigate the role of fibrosis in RV dysfunction and failure. However, they do not perfectly resemble the human disease. In the current review we describe the major characteristics of RV fibrosis, molecular mechanisms regulating the fibrotic process, and discuss how therapeutic targeting of fibrosis might affect RV function.

Pulmonary arterial hypertension - progress in understanding the disease and prioritizing strategies for drug development

Pulmonary arterial hypertension (PAH), at one time a largely overlooked disease, is now the subject of intense study in many academic and biotech groups. The availability of new treatments has increased awareness of the condition. This in turn has driven a change in the demographics of PAH, with an increase in the mean age at diagnosis. The diagnosis of PAH in more elderly patients has highlighted the need for careful phenotyping of patients and for further studies to understand how best to manage pulmonary hypertension associated with, for example, left heart disease. The breadth and depth of expertise focused on unravelling the molecular pathology of PAH has yielded novel insights, including the role of growth factors, inflammation and metabolic remodelling. The description of the genetic architecture of PAH is accelerating in parallel, with novel variants, such as those reported in potassium two-pore domain channel subfamily K member 3 (KCNK3), adding to the list of more established mutations in genes associated with bone morphogenetic protein receptor type 2 (BMPR2) signalling. These insights have supported a paradigm shift in treatment strategies away from simply addressing the imbalance of vasoactive mediators observed in PAH towards tackling more directly the structural remodelling of the pulmonary vasculature. Here, we summarize the changing clinical and molecular landscape of PAH. We highlight novel drug therapies that are in various stages of clinical development, targeting for example cell proliferation, metabolic, inflammatory/immune and BMPR2 dysfunction, and the challenges around developing these treatments. We argue that advances in the treatment of PAH will come through deep molecular phenotyping with the integration of clinical, genomic, transcriptomic, proteomic and metabolomic information in large populations of patients through international collaboration. This approach provides the best opportunity for identifying key signalling pathways, both as potential drug targets and as biomarkers for patient selection. The expectation is that together these will enable the prioritization of potential therapies in development and the evolution of personalized medicine for PAH.

Prognostic role of soluble suppression of tumorigenicity-2 on cardiovascular mortality in outpatients with heart failure

Objective:

Soluble suppression of tumorigenicity-2 (sST2), a member of the interleukin 1 receptor family, is increased in mechanical stress conditions and is produced by cardiomyocytes and cardiac fibroblasts. Elevated sST2 level is associated with the prognosis of acute coronary syndrome, pulmonary arterial hypertension, and acute and chronic heart failure (HF). In this study, we aimed to investigate the relationship between sST2 levels and cardiovascular mortality in outpatients with HF.

Methods:

This study used a prospective observational cohort design. A total of 130 consecutive outpatients with HF were prospectively evaluated. Clinical characteristics, laboratory results, cardiovascular risk factors, comorbidities, and medication use were recorded. The patients were followed up for a mean period of 12±4 months for the development of cardiovascular death. They were classified into two groups: those who survived and those who died.

Results:

Mean age of patients was 67±11 years (69% males). After follow-up, 23 of 130 patients (18%) experienced cardiovascular death. sST2 levels were higher among those who died compared with among those who survived [51 (21–162) vs. 27 (9–198) ng/mL, p<0.001]. Optimal cut-off sST2 level to predict cardiovascular mortality was found to be >30 ng/mL with a sensitivity of 87% and a specificity of 67% (AUC =0.808, 95% CI=0.730 to 0.872). sST2 levels were negatively correlated with left ventricular ejection fraction and triglyceride, total cholesterol, LDL cholesterol, and hemoglobin levels and were positively correlated with left atrium size and the presence of right ventricular dilatation. In multiple Cox regression analysis, sST2 level of >30 ng/mL (HR=6.756, p=0.002, 95% CI=1.983–23.018), hemoglobin level (HR=0.705, p<0.001, 95% CI=0.587–0.847), age (HR=1.050, p=0.013, 95% CI=1.010–1.091), and HDL cholesterol level (HR=0.936, p=0.010, 95% CI=0.889–0.984) remained to be associated with an increased risk of mortality.

Conclusion:

sST2 measurement could help risk stratification in outpatients with HF. Moreover, this is the first study describing the impact of sST2 protein in Turkish patients with HF.

Association of soluble ST2 with functional capacity in outpatients with heart failure

BACKGROUND

Biomarkers play an important role in the risk stratification of patients with heart failure (HF). Recent studies have shown that soluble suppression of tumorigenicity 2 (sST2), a member of the interleukin 1 receptor family, is associated with disease prognosis in acute and chronic HF. In this study we aimed to investigate the relation between sST2 level and functional capacity in outpatients with systolic HF.

PATIENTS AND METHODS

This study included 120 HF patients with reduced ejection fraction (HFrEF; EF ≤ 40%). The mean age of patients was 66 ± 11 years. Advanced HF (New York Heart Association [NYHA] functional class III-IV) was observed in 35 patients (29%).

RESULTS

sST2 levels were on average higher in patients with NYHA functional classes III and IV than in patients with NYHA functional classes I and II (51 [9-198] vs. 25 ng/ml [9-118], p < 0.001). In a multiple logistic regression model, sST2 level (OR: 1.044, p = 0.004, 95% CI: 1.014-1.075), hemoglobin level (OR: 0.590, p = 0.001, 95% CI: 0.433-0.805), total cholesterol level (OR: 0.977, p = 0.004, 95% CI: 0.962-0.993), and age (OR: 1.066, p = 0.047, 95% CI: 1.001-1.136) were associated with poor functional capacity. In receiver operating characteristic (ROC) curve analysis, the optimal cut-off value of sST2 for predicting poor functional capacity was >42 ng/ml, with 63% sensitivity and 88% specificity (AUC: 0.810, 95% CI: 0.728- 0.875).

CONCLUSION

Higher sST2 levels were strongly associated with poor NYHA functional class, independent of cardiac risk factors, in outpatients with HFrEF.

Soluble ST2 is associated with disease severity in arrhythmogenic right ventricular cardiomyopathy

PURPOSE

Diagnostic and prognostic evaluation remains challenging in arrhythmogenic right ventricular cardiomyopathy (ARVC). We measured plasma concentration of soluble ST2 (sST2) and assessed its association with right ventricular (RV) function and ventricular arrhythmias in patients with ARVC.

METHODS

We included patients with ARVC and genotype positive relatives. Soluble ST2 was determined by ELISA. We assessed myocardial function by echocardiography including strain by speckle tracking technique.

RESULTS

We included 44 subjects (age 41 ± 15 years, 21 (48%) female). Soluble ST2 was associated with RV global strain (r = 0.44; p = 0.008), as well as with left ventricular (LV) function. Plasma levels of sST2 were higher in patients with ventricular arrhythmias than in patients without ventricular arrhythmias (35 ± 13 ng/mL vs. 26 ± 7 ng/mL, p = 0.009). The association between sST2 and ventricular arrhythmias remained significant even after adjusting for RV function (Wald = 5.2; p = 0.02).

CONCLUSIONS

Soluble ST2 is associated with RV and LV function in patients with ARVC. Soluble ST2 may aid in the determination of disease severity in ARVC.

Cardio-Pulmonary-Renal Interactions: A Multidisciplinary Approach

Over the past decade, science has greatly advanced our understanding of interdependent feedback mechanisms involving the heart, lung, and kidney. Organ injury is the consequence of maladaptive neurohormonal activation, oxidative stress, abnormal immune cell signaling, and a host of other mechanisms that precipitate adverse functional and structural changes. The presentation of interorgan crosstalk may include an acute, chronic, or acute on chronic timeframe. We review the current, state-of-the-art understanding of cardio-pulmonary-renal interactions and their related pathophysiology, perpetuating nature, and cycles of increased susceptibility and reciprocal progression. To this end, we present a multidisciplinary approach to frame the diverse spectrum of published observations on the topic. Assessment of organ functional reserve and use of biomarkers are valuable clinical strategies to screen and detect disease, assist in diagnosis, assess prognosis, and predict recovery or progression to chronic disease.

Novel serum biomarkers in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) remains a difficult-to-treat condition with high mortality. Biomarkers are utilized to aid with diagnosis, prognostication and response to treatment. A clinically useful and PAH-specific single biomarker that is easy to measure remains elusive. This is in part due to the heterogeneity of PAH and its complex etiology. Brain natriuretic peptide and its N-terminal fragment are currently the most widely used serum markers; however, several novel serum biomarkers have been investigated recently. Taken individually, the evidence for each of these seems provisionally promising though currently weak overall. It is likely that a multibiomarker panel will be recommended in the future, with the optimal combination yet to be determined.

NGAL and ST2 levels in ambulatory patients with chronic heart failure. Clinical and echocardiographic correlates

AIM

Neutrophil gelatinase-associated lipocalin (NGAL) and ST2 receptor, a member of the interleukin-1 receptor family, are novel biomarkers with a potential role in the diagnosis and risk stratification of patients with chronic heart failure (CHF). There is however scarce data on their relation with clinical characteristics and cardiac function in patients with CHF.

METHODS

Consecutive ambulatory patients with CHF were studied. All patients underwent clinical and echocardiographic assessment, and blood samples were collected for the estimation of ST2 and NGAL serum levels during the same assessment.

RESULTS

A total of 76 patients (79% male, mean age: 63 ± 14 years), with CHF and left ventricular ejection fraction of 28 ± 7% were included. Median NGAL was 0.16 (0.09-0.275) mg/L and median ST2 was 0.0125 (0.0071-0.0176) mg/L. No association between NGAL and ST2 was observed. Multivariate analysis revealed tissue Doppler-derived right ventricular systolic velocity as an independent predictor of ST2, and the duration of HF and serum creatinine levels as independent predictors of NGAL.

CONCLUSIONS

NGAL levels depend on the renal function and the duration of HF, while ST2 levels are affected by the right but not the left ventricular function and show no association with clinical indices of HF.

Soluble ST2 in Ventricular Dysfunction

Heart failure is a commonly encountered condition associated with increased morbidity, mortality, and healthcare cost. For years, its management has been strongly influenced by the use of B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide biomarkers. In some cases, this approach does not always identify patients with heart failure accurately and may not provide the best prognostic assessment, particularly in the presence of comorbidities. Biomarkers that help refine diagnosis and risk stratification are needed. Soluble ST2, a peptide belonging to the interleukin-1 receptor family, is secreted when cardiomyocytes and cardiac fibroblasts are subjected to mechanical strain. Although preliminary results on this novel biomarker are encouraging, additional and more comprehensive studies are clearly needed to establish its role in the management of patients with heart failure. The purpose of this chapter is to provide an overview of data currently available.

Various forms of tissue damage and danger signals following hematopoietic stem-cell transplantation

Hematopoietic stem-cell transplantation (HSCT) is the most potent curative therapy for many malignant and non-malignant disorders. Unfortunately, a major complication of HSCT is graft-versus-host disease (GVHD), which is mediated by tissue damage resulting from the conditioning regimens before the transplantation and the alloreaction of dual immune components (activated donor T-cells and recipient’s antigen-presenting cells). This tissue damage leads to the release of alarmins and the triggering of pathogen-recognition receptors that activate the innate immune system and subsequently the adaptive immune system. Alarmins, which are of endogenous origin, together with the exogenous pathogen-associated molecular patterns (PAMPs) elicit similar responses of danger signals and represent the group of damage-associated molecular patterns (DAMPs). Effector cells of innate and adaptive immunity that are activated by PAMPs or alarmins can secrete other alarmins and amplify the immune responses. These complex interactions and loops between alarmins and PAMPs are particularly potent at inducing and then aggravating the GVHD reaction. In this review, we highlight the role of these tissue damaging molecules and their signaling pathways. Interestingly, some DAMPs and PAMPs are organ specific and GVHD-induced and have been shown to be interesting biomarkers. Some of these molecules may represent potential targets for novel therapeutic approaches.