Interleukin-33 prevents apoptosis and improves survival after experimental myocardial infarction through ST2 signaling

Modulation of IL-33/ST2 system in postinfarction heart failure: correlation with cardiac remodelling markers

BACKGROUND

Interleukin (IL)-33 and sST2 are molecules with an opposite pathophysiologic implications in the myocardial response after acute myocardial infarction (AMI). Both may be a target for therapeutic interventions. The kinetics of IL-33 and sST2 expression in infarcted myocardium and their correlation with the ongoing processes of fibrosis, inflammation and apoptosis remains poorly defined.

MATERIALS AND METHODS

Fifty Wistar rats underwent left anterior descending coronary artery surgical ligation and were sacrificed at 1, 2, 4, 12 or 24 weeks post-AMI. A sham-operated group was also included. The mRNA cardiac expression levels of IL-33, sST2, fibrosis markers, inflammatory markers and apoptosis markers were assessed by RT-PCR. The protein expression of IL-33 was also measured by Western blotting.

RESULTS

The mRNA levels of IL-33 and sST2 were upregulated in the infarcted myocardium during the first week after AMI. However, while IL-33 levels remained elevated during the first 12 weeks post-AMI, sST2 levels showed a marked drop at 4 weeks. IL-33 protein expression showed a similar kinetic than mRNA expression. The expression of sST2 positively correlated with cardiac gene expression of inflammatory and fibrosis markers. However, the IL-33 level did not correlate with these cardiac remodelling markers. No correlation of sST2 with apoptosis markers was observed.

CONCLUSION

After AMI, expression of sST2 is rapidly upregulated during the first 4 weeks and, in contrast to IL-33, its levels correlated with the ongoing processes of fibrosis and inflammation. These findings suggest differential regulation of IL33 and sST2. Therapeutic modulation of early sST2 expression may be of greater importance to prevent adverse remodelling after AMI.

IL-33/ST2 axis promotes mast cell survival via BCLXL

Mast cells (MC) are potent innate immune cells that accumulate in chronically inflamed tissues. MC express the IL-33 receptor IL-1 receptor-related protein ST2 at high level, and this IL-1 family cytokine both activates MC directly and primes them to respond to other proinflammatory signals. Whether IL-33 and ST2 play a role in MC survival remains to be defined. In skin-derived human MC, we found that IL-33 attenuated MC apoptosis without altering proliferation, an effect mediated principally through the antiapoptotic molecule B-cell lymphoma-X large (BCLXL). Murine MC demonstrated a similar mechanism, dependent entirely on ST2. In line with these observations, St2(-/-) mice exhibited reduced numbers of tissue MC in inflamed arthritic joints, in helminth-infected intestine, and in normal peritoneum. To confirm an MC-intrinsic role for ST2 in vivo, we performed peritoneal transfer of WT and St2(-/-) MC. In St2(-/-) hosts treated with IL-33 and in WT hosts subjected to thioglycollate peritonitis, WT MC displayed a clear survival advantage over coengrafted St2(-/-) MC. IL-33 blockade specifically attenuated this survival advantage, confirming IL-33 as the relevant ST2 ligand mediating MC survival in vivo. Together, these data reveal a cell-intrinsic role for the IL-33/ST2 axis in the regulation of apoptosis in MC, identifying thereby a previously unappreciated pathway supporting expansion of the MC population with inflammation.

Aerobic exercise training induces an anti-apoptotic milieu in myocardial tissue

This study evaluated modulators of apoptosis in the myocardium of rats subjected to exercise training. Rats were assigned to non-trained and exercise-trained groups, respectively. The animals ran for 1 h per day, 6 times per week and, for a total of 13 weeks. The left ventricle was processed for analysis of gene and protein anti- (Bcl-2, c-IAP1, c-IAP2, Survivin, ILK, Akt and pAkt) and pro- (Bad) apoptotic expression by real-time PCR (except for Akt and pAkt) and Western blot, respectively. The Bad mRNA (p<0.05), but not the protein expression (p = 0.19), was significantly lower after training. The exercise training significantly increased the gene and protein expression for all anti-apoptotic factors. However, a significant change in the c-IAP2 was seen only for gene expression (p<0.05). The present findings indicate that exercise can create a favorable milieu for the survival of cardiomyocytes when apoptosis is increased.

Unique temporal and spatial expression patterns of IL-33 in ovaries during ovulation and estrous cycle are associated with ovarian tissue homeostasis

Ovaries are among the most active organs. Frequently occurring events such as ovulation and ovarian atresia are accompanied with tissue destruction and repairing. Critical roles of immune cells or molecules in those events have been well recognized. IL-33 is a new member of the IL-1 cytokine gene family. Recent studies suggest its roles beyond immune responses. We systemically examined its expression in ovaries for its potential roles in ovarian functions. During ovulation, a high level of IL-33 was transiently expressed, making it the most significantly upregulated immune gene. During estrous cycle, IL-33 expression levels fluctuated along with numbers of ovarian macrophages and atresia wave. Cells with nuclear form of IL-33 (nIL-33(+) cells) were mostly endothelial cells of veins, either in the inner layer of theca of ovulating follicles during ovulation, or surrounding follicles during estrous cycle. Changes in number of nIL-33(+) cells showed a tendency similar to that in IL-33 mRNA level during estrous cycle. However, the cell number sharply declined before a rapid increase of macrophages and a surge of atresia. The decline in nIL-33(+) cell number was coincident with detection of higher level of the cytokine form of IL-33 by Western blot, suggesting a release of cytokine form of IL-33 before the surge of macrophage migration and atresia. However, IL-33 Ab, either by passive transfer or immunization, showed a limited effect on ovulation or atresia. It raises a possibility of IL-33's role in tissue homeostasis after ovarian events, instead of a direct involvement in ovarian functions.

Soluble ST2 and interleukin-33 levels in coronary artery disease: relation to disease activity and adverse outcome

Objectives

ST2 is a receptor for interleukin (IL)-33. We investigated an association of soluble ST2 (sST2) and IL-33 serum levels with different clinical stages of coronary artery disease. We assessed the predictive value of sST2 and IL-33 in patients with stable angina, non-ST elevation myocardial infarction (NSTEMI) and ST elevation myocardial infarction (STEMI).

Methods

We included 373 patients of whom 178 had stable angina, 97 had NSTEMI, and 98 had STEMI. Patients were followed for a mean of 43 months. The control group consisted of 65 individuals without significant stenosis on coronary angiography. Serum levels of sST2 and IL-33 were measured by ELISAs.

Results

sST2 levels were significantly increased in patients with STEMI as compared to patients with NSTEMI and stable angina as well as with controls. IL-33 levels did not differ between the four groups. During follow-up, 37 (10%) patients died and the combined endpoint (all cause death, MI and rehospitalisation for cardiac causes) occurred in 66 (17.6%) patients. sST2 serum levels significantly predicted mortality in the total cohort. When patients were stratified according to their clinical presentation, the highest quintile of sST2 significantly predicted mortality in patients with STEMI, but not with NSTEMI or stable coronary artery disease. sST2 was a significant predictor for the combined endpoint in STEMI patients and in patients with stable angina. Serum levels of IL-33 were not associated with clinical outcome in the total cohort, but the highest quintile of IL-33 predicted mortality in patients with STEMI.

Conclusions

Serum levels of sST2 are increased in patients with acute coronary syndromes as compared to levels in patients with stable coronary artery disease and in individuals without coronary artery disease. sST2 and IL-33 were associated with mortality in patients with STEMI but not in patients with NSTEMI or stable angina.

Increased Soluble ST2 Predicts Long-term Mortality in Patients with Stable Coronary Artery Disease: Results from the Ludwigshafen Risk and Cardiovascular Health Study

BACKGROUND

Soluble suppression of tumorigenicity 2 (sST2) has emerged as a strong prognostic biomarker in patients with heart failure and myocardial infarction. The aim of this study was to evaluate the long-term prognostic value of sST2 in patients with stable coronary artery disease (CAD).

METHODS

sST2 plasma concentrations were measured in 1345 patients with stable CAD referred for coronary angiography at a single tertiary care center. The primary endpoint was all-cause mortality.

RESULTS

During a median follow-up time of 9.8 years, 477 (36%) patients died. The median sST2 plasma concentration at baseline was significantly higher among decedents than survivors (21.4 vs 18.5 ng/mL; P &lt; 0.001). In multivariate Cox proportional hazards regression analysis, sST2 was an independent predictor of all-cause mortality (risk ratio 1.16 per 1-SD increase in log-transformed values; 95% CI 1.05–1.29; P = 0.004). In the same multivariate analysis, amino-terminal pro–B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT) were also independent predictors, whereas galectin-3 was not. Patients with sST2 in the highest quartile (&gt;24.6 ng/mL) displayed a 2-fold increased risk of death in univariate analysis, which was attenuated but remained significant in a fully adjusted model (risk ratio 1.39; 95% CI 1.10–1.76; P = 0.006). Further analysis showed that the prognostic impact of sST2 was additive to NT-proBNP and hs-cTnT. Using a multibiomarker approach combining these 3 complementary makers, we demonstrated that patients with all 3 biomarkers in the highest quartiles had the poorest outcome.

CONCLUSIONS

In this cohort of patients with stable CAD, increased sST2 was an independent predictor of long-term all-cause mortality and provided complementary prognostic information to hs-cTnT and NT-proBNP.

Cardiomyocyte-specific transforming growth factor β suppression blocks neutrophil infiltration, augments multiple cytoprotective cascades, and reduces early mortality after myocardial infarction

RATIONALE

Wound healing after myocardial infarction involves a highly regulated inflammatory response that is initiated by the appearance of neutrophils to clear out dead cells and matrix debris. Neutrophil infiltration is controlled by multiple secreted factors, including the master regulator transforming growth factor β (TGFβ). Broad inhibition of TGFβ early postinfarction has worsened post-myocardial infarction remodeling; however, this signaling displays potent cell specificity, and targeted suppression particularly in the myocyte could be beneficial.

OBJECTIVE

Our aims were to test the hypothesis that targeted suppression of myocyte TGFβ signaling ameliorates postinfarct remodeling and inflammatory modulation and to identify mechanisms by which this may be achieved.

METHODS AND RESULTS

Mice with TGFβ receptor-coupled signaling genetically suppressed only in cardiac myocytes (conditional TGFβ receptor 1 or 2 knockout) displayed marked declines in neutrophil recruitment and accompanying metalloproteinase 9 activation after infarction and were protected against early-onset mortality due to wall rupture. This is a cell-specific effect, because broader inhibition of TGFβ signaling led to 100% early mortality due to rupture. Rather than by altering fibrosis or reducing the generation of proinflammatory cytokines/chemokines, myocyte-selective TGFβ inhibition augmented the synthesis of a constellation of highly protective cardiokines. These included thrombospondin 4 with associated endoplasmic reticulum stress responses, interleukin-33, follistatin-like 1, and growth and differentiation factor 15, which is an inhibitor of neutrophil integrin activation and tissue migration.

CONCLUSIONS

These data reveal a novel role of myocyte TGFβ signaling as a potent regulator of protective cardiokine and neutrophil-mediated infarct remodeling.

Cardiac biomarkers in heart failure

BACKGROUND

Heart failure is a syndrome characterized by the inability of the heart to meet the body's circulatory demands. Heart failure is a growing health issue worldwide and the prevalence of heart failure is expected to rise as populations age. Therapies and interventions for a variety of cardiac conditions continue to advance and biomarkers will play an increasing role in patient management.

METHODS

This is a review of the clinical research in blood based biomarkers for diagnosis, prognosis and therapeutic guidance of heart failure. The focus of this review is biomarkers that are currently available for clinical measurement, and their current and potential for applications for managing heart failure patients.

RESULTS

The various biologic pathways and physiologic processes of heart failure biomarkers represent a host of different including inflammation, remodeling, strain, neurohormonal activation, metabolism and cardiac myocyte injury. The clinical characteristics and applications of each heart failure biomarker are discussed.

CONCLUSION

As populations age and effective treatments and interventions for coronary artery disease improve, heart failure will increase in incidence and prevalence. Blood biomarkers will play an increasing role in the early diagnosis, therapeutic monitoring and management of heart failure patients in the future.

Soluble ST2 predicts elevated SBP in the community

BACKGROUND

Soluble ST2 (sST2) is an emerging prognostic biomarker in patients with existing cardiovascular disease. ST2 and its ligand, interleukin-33 (IL-33), are expressed in endothelial cells, and may play an important role in the development of early atherosclerosis and vascular biology. We sought to investigate the association of sST2 and progression of blood pressure (BP), as well as the development of hypertension.

METHODS

Circulating sST2 concentrations were measured in 1834 participants (mean age 56 years, 57% women) of the community-based Framingham Offspring study. Participants were free of hypertension at baseline. Multivariable linear and logistic regression models were used to evaluate the association of sST2 concentrations and subsequent BP outcomes.

RESULTS

Higher sST2 concentrations were associated with incident hypertension over 3 years of follow-up [multivariable-adjusted odds ratio per 1 standard deviation increase in sST2 1.22, 95% confidence interval 1.05-1.42, P=0.01]. Individuals in the upper sST2 quartile had a 2.6 mmHg greater increase in SBP compared with those in the lowest quartile (P for trend across quartiles 0.002) and a 1.8 mmHg greater increase in pulse pressure (P for trend 0.005). In contrast, sST2 concentrations were not associated with changes in DBP (P=0.27).

CONCLUSION

These findings suggest that sST2 concentrations predict changes in BP physiology typically seen with aging and progressive arterial stiffness. Further studies are needed to elucidate underlying mechanisms by which the ST2/IL-33 pathway may contribute to BP physiology.

Cardiac fibroblasts protect cardiomyocytes against lethal ischemia-reperfusion injury

Roles of cardiac fibroblasts (CFs) in the regulation of myocardial structure and function have been emphasized in the last decade. Their implications in pathophysiological aspects of chronic heart diseases such as myocardial remodeling and fibrosis are now well established; however their contribution to the acute phase of ischemia-reperfusion injury still remains elusive. We hypothesized that CF may contribute to cardiomyocyte (CM) protection against ischemia-reperfusion injuries. Experiments performed on isolated neonatal rat CF and CM demonstrated that the presence of CF in co-cultures increases CM viability (58 ± 2% versus 30 ± 2% in control) against hypoxia-reoxygenation injury, in a paracrine manner. It was confirmed by a similar effect of hypoxic CF secretome alone on CM viability (51 ± 9% versus 31 ± 4% in untreated cells). These findings were corroborated by in vivo experiments in a mice model of myocardial infarction in which a 25% infarct size reduction was observed in CF secretome treated mice compared to control. Tissue inhibitor of metalloproteinases-1 (TIMPs-1) alone, abundantly detected in CF secretome, was able to decrease CM cell death (35%) and experiments with pharmacological inhibitors of PI3K/Akt and ERK1/2 pathways provided more evidence that this paracrine protection is partly mediated by these signaling pathways. In vivo experiments strengthened that TIMP-1 alone was able to decrease infarct size (37%) and were validated by depletion experiments demonstrating that CF secretome cardioprotection was abolished by TIMP-1 depletion. Our data demonstrated for the first time that CFs participate in cardioprotection during the acute phase of ischemia-reperfusion via a paracrine pathway involving TIMP-1.

Soluble ST2 and galectin-3 in heart failure

Circulating biomarkers that directly reflect disease progression, hemodynamics, and ventricular remodeling at a molecular level are critical to risk stratification in heart failure (HF), affording unique insights into pathophysiology not fully captured by traditional risk markers. Despite the wealth of data confirming the importance of natriuretic peptides in HF diagnosis and prognosis, residual clinical risk in HF suggests that additional biomarkers complementary to natriuretic peptides may be useful. In this article, the current literature addressing the role of these biomarkers in the clinical diagnosis and risk stratification in HF is summarized.

Prognostic and diagnostic value of plasma soluble suppression of tumorigenicity-2 concentrations in acute respiratory distress syndrome

OBJECTIVES

Soluble suppression of tumorigenicity-2 is a biomarker of myocardial strain and inflammation. The characteristics of acute respiratory distress syndrome include inflammation and cardiovascular dysfunction. We sought to determine whether plasma soluble suppression of tumorigenicity-2 concentration is associated with outcome and response to conservative fluid management and whether soluble suppression of tumorigenicity-2 concentration discriminates acute respiratory distress syndrome from decompensated heart failure.

DESIGN

A retrospective analysis of the Fluid and Catheter Treatment Trial, a multi-center randomized controlled trial of conservative fluid management in the acute respiratory distress syndrome, as well as of a cohort of patients with decompensated heart failure.

SETTING

Twenty acute care hospitals.

PATIENTS

Eight hundred twenty-six patients with acute respiratory distress syndrome and 209 patients with acutely decompensated heart failure.

MEASUREMENTS AND MAIN RESULTS

Nonsurvivors had higher day 0 (p < 0.0001) and day 3 (p < 0.0001) soluble suppression of tumorigenicity-2 concentrations. After adjustment for severity of illness, higher soluble suppression of tumorigenicity-2 concentration was associated with mortality, with odds ratioadj 1.47 (95% CI, 0.99-2.20; p = 0.06) at day 0, 2.94 (95% CI, 2.00-4.33; p < 0.0001) at day 3, and 3.63 (95% CI, 2.38-5.53; p < 0.0001) if soluble suppression of tumorigenicity-2 increased between days. Cumulative fluid balance was more positive among patients with higher day 0 (median, 5,212 mL [interquartile range, 200-12,284 mL] vs median, 2,020 mL [interquartile range, -2,034 to 7,091 mL]; p < 0.0001) and day 3 soluble suppression of tumorigenicity-2 (median, 7,678 mL [interquartile range, 2,217-14,278 mL] vs median, 1,492 mL [interquartile range, -2,384 to 6,239 mL]; p < 0.0001). Soluble suppression of tumorigenicity-2 showed excellent discriminative ability between the Fluid and Catheter Treatment Trial and heart failure populations (area under receiver-operating characteristic curve = 0.98; p < 0.0001).

CONCLUSIONS

Higher soluble suppression of tumorigenicity-2 concentrations are associated with worse outcome in acute respiratory distress syndrome and may have value for discriminating acute respiratory distress syndrome from heart failure.

A novel cardiac bio-marker: ST2: a review

Cardiovascular diseases (CVD) are the major cause of death worldwide. The identification of markers able to detect the early stages of such diseases and/or their progression is fundamental in order to adopt the best actions in order to reduce the worsening of clinical condition. Brain natriuretic peptide (BNP) and NT-proBNP are the best known markers of heart failure (HF), while troponins ameliorated the diagnosis of acute and chronic coronary artery diseases. Nevertheless, many limitations reduce their accuracy. Physicians have tried to develop further detectable molecules in order to improve the detection of the early moments of CVD and prevent their development. Soluble ST2 (suppression of tumorigenicity 2) is a blood protein confirmed to act as a decoy receptor for interleukin-33. It seems to be markedly induced in mechanically overloaded cardiac myocytes. Thus, HF onset or worsening of a previous chronic HF status, myocardial infarct able to induce scars that make the myocardium unable to stretch well, etc, are all conditions that could be detected by measuring blood levels of soluble ST2. The aim of this review is to explore the possible role of ST2 derived-protein as an early marker of cardiovascular diseases, above all in heart failure and ischemic heart diseases.

IL-33/ST2 pathway and classical cytokines in end-stage heart failure patients submitted to left ventricular assist device support: a paradoxic role for inflammatory mediators?

Background. Inflammation is a critical process contributing to heart failure (HF). We hypothesized that IL-33/ST2 pathway, a new mechanism regulated during cardiac stress, may be involved in the functional worsening of end-stage HF patients, candidates for left ventricular assist device (LVAD) implantation, and potentially responsible for their outcome. Methods. IL-33, ST2, and conventional cytokines (IL-6, IL-8, and TNF-α) were determined in cardiac biopsies and plasma of 22 patients submitted to LVAD implantation (pre-LVAD) and compared with (1) control stable chronic HF patients on medical therapy at the moment of heart transplantation without prior circulatory support (HT); (2) patients supported by LVAD at the moment of LVAD weaning (post-LVAD). Results. Cardiac expression of ST2/IL-33 and cytokines was lower in the pre-LVAD than in the HT group. LVAD determined an increase of inflammatory mediators comparable to levels of the HT group. Only ST2 correlated with outcome indices after LVAD implantation. Conclusions. IL-33/ST2 and traditional cytokines were involved in decline of cardiac function of ESHF patients as well as in hemodynamic recovery induced by LVAD. IL-33/ST2 pathway was also associated to severity of clinical course. Thus, a better understanding of inflammation is the key to achieving more favorable outcome by new specific therapies.

Soluble ST2 and N-terminal pro-brain natriuretic peptide combination. Useful biomarker for predicting outcome of childhoodpulmonary arterial hypertension

BACKGROUND

Some potential biomarkers have been reported recently in patients with pulmonary arterial hypertension (PAH), but the most clinically useful among these potential biomarkers, especially in childhood PAH, has not been identified. Therefore, this study investigated which biomarker is useful in assessing severity of and patient prognosis in childhood idiopathic PAH (IPAH)/heritable PAH (HPAH).

METHODS AND RESULTS

Fifty-nine patients who were younger than 16 years at onset of IPAH/HPAH were selected. The following 10 biomarker candidates were quantified: high-sensitivity troponin T, human heart fatty acid-binding protein, N-terminal pro-brain natriuretic peptide (NT-proBNP), pentraxin-3, soluble ST2 (sST2), angiopoietin-2 (Ang-2), matrix metalloproteinase 2, tenascin C, endostatin (ES), and thymidine kinase. Functional characteristics and clinical outcomes were analyzed retrospectively. NT-proBNP, sST2, Ang-2, and ES correlated well with New York Heart Association class. On area under the receiver operating characteristic curve analysis, sST2 had a significantly good relationship with prognosis. On Kaplan-Meier curve and univariate Cox regression analyses, elevated sST2 and NT-proBNP level predicted poor outcome of the present patients with childhood IPAH/HPAH. Furthermore, patients with elevated sST2 had significantly worse prognosis among those with high NT-proBNP.

CONCLUSIONS

The sST2 and NT-proBNP combination is a useful biomarker to predict clinical condition and outcome in patients with childhood IPAH/HPAH.  

Association of novel biomarkers of cardiovascular stress with left ventricular hypertrophy and dysfunction: implications for screening

Background

Currently available screening tools for left ventricular (LV) hypertrophy (LVH) and systolic dysfunction (LVSD) are either expensive (echocardiography) or perform suboptimally (B‐type natriuretic peptide [BNP]). It is unknown whether newer biomarkers are associated with LVH and LVSD and can serve as screening tools.

Methods and Results

We studied 2460 Framingham Study participants (mean age 58 years, 57% women) with measurements of biomarkers mirroring cardiac biomechanical stress (soluble ST‐2 [ST2], growth differentiation factor‐15 [GDF‐15] and high‐sensitivity troponin I [hsTnI]) and BNP. We defined LVH as LV mass/height² ≥the sex‐specific 80th percentile and LVSD as mild/greater impairment of LV ejection fraction (LVEF) or a fractional shortening <0.29. Adjusting for standard risk factors in logistic models, BNP, GDF‐15, and hsTnI were associated with the composite echocardiographic outcome (LVH or LVSD), odds ratios (OR) per SD increment in log‐biomarker 1.29, 1.14, and 1.18 (95% CI: 1.15 to 1.44, 1.004 to 1.28, and 1.06 to 1.31), respectively. The C‐statistic for the composite outcome increased from 0.765 with risk factors to 0.770 adding BNP, to 0.774 adding novel biomarkers. The continuous Net Reclassification Improvement was 0.212 (95% CI: 0.119 to 0.305, P<0.0001) after adding the novel biomarkers to risk factors plus BNP. BNP was associated with LVH and LVSD in multivariable models, whereas GDF‐15 was associated with LVSD (OR 1.41, 95% CI: 1.16 to 1.70), and hsTnI with LVH (OR 1.22, 95% CI: 1.09 to 1.36). ST2 was not significantly associated with any outcome.

Conclusions

Our community‐based investigation suggests that cardiac stress biomarkers are associated with LVH and LVSD but may have limited clinical utility as screening tools.

Soluble Concentrations of the Interleukin Receptor Family Member ST2 and β-Blocker Therapy in Chronic Heart Failure

Background—

Concentrations of soluble (s)ST2 predict prognosis in heart failure. We recently found changing doses of β-blocker (BB) may affect sST2 concentrations. It remains unclear whether sST2 concentrations identify benefit of BB therapy, however.

Methods and Results—

A total of 151 subjects with heart failure attributable to left ventricular systolic dysfunction were examined in this post hoc analysis; >96% were taking BB at enrollment. Medication regimen and sST2 values were obtained during 10 months. Cardiovascular events were examined as a function of baseline sST2 status (low ≤35 versus high >35 ng/mL) and final achieved BB dose (high ≥50 versus low <50 mg daily equivalent dose of metoprolol succinate). Patients with low sST2 titrated to high-dose BB had the lowest cardiovascular event rate at 0.53 events ( P =0.001), and lowest cumulative hazard ( P =0.003). Those with low sST2/low-dose BB, or high sST2/high-dose BB had intermediate outcomes (0.92 and 1.19 events). Patients with high sST2 treated with low-dose BB had the highest cardiovascular event rate (2.08 events) and the highest cumulative hazard. Compared with low sST2/high-dose BB, those with high sST2 treated with low-dose BB had an odds ratio of 6.77 ( P <0.001) for a cardiovascular event. Patients with low sST2/low-dose BB or high sST2/high-dose BB had intermediate odds ratios for cardiovascular events ( P =0.18 and 0.02). Similar results were found for heart failure hospitalization and cardiovascular death.

Conclusions—

Although BB therapy exerted dose-related benefits across all study participants, sST2 measurement identifies patients with chronic heart failure who may particularly benefit from higher BB doses.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00351390.

Association of interleukin-33 gene single nucleotide polymorphisms with ischemic stroke in north Chinese population

Background

IL-33, an IL-1-like cytokine, is a ligand for IL1RL1, which is an important effector molecule of type 2 T helper responses. Although IL-33/IL1RL1 interaction has been suggested to be important in the development of atherosclerosis, genetic influences of the polymorphisms of IL33 in human ischemic stroke are unclear. The aim of this study was to examine whether the single nucleotide polymorphisms in IL33 are associated with ischemic stroke in Northern Chinese population.

Methods

We used a nested case–control study involving 90 ischemic stroke patients and 270 age-matched, sex-matched and blood pressure-matched non-ischemic stroke controls from a rural population and determined the genotypes of four polymorphisms (rs1929992, rs10975519, rs4742170, rs16924159) in IL33 by Snapshot SNP genotyping assays to assess any links with ischemic stroke.

Results

Univariate analysis showed two single nucleotide polymorphisms (rs1929992, rs4742170) in IL33 were associated with ischemic stroke in additive, dominant, and recessive model. Binary Logistic Regression shows that rs4742170 variation is the most important factor associated with ischemic stroke (adjusted odds ratio (OR) = 1.880, 95% confidence interval (CI) = 1.316-2.686 in an additive model; OR = 2.091, CI = 1.249-3.498 in a dominant model; OR = 2.623, CI = 1.366-5.036 in a recessive model).

Conclusion

In this sample of patients, genetic variation of rs4742170 in IL33 is significantly associated with the developing of ischemic stroke.

Soluble ST2 in ambulatory patients with heart failure: Association with functional capacity and long-term outcomes

BACKGROUND

ST2 is involved in cardioprotective signaling in the myocardium and has been identified as a potentially promising biomarker in heart failure (HF). We evaluated ST2 levels and their association with functional capacity and long-term clinical outcomes in a cohort of ambulatory patients with HF enrolled in the Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) study-a multicenter, randomized study of exercise training in HF.

METHODS AND RESULTS

HF-ACTION randomized 2331 patients with left ventricular ejection fraction <0.35 and New York Heart Association class II to IV HF to either exercise training or usual care. ST2 was analyzed in a subset of 910 patients with evaluable plasma samples. Correlations and Cox models were used to assess the relationship among ST2, functional capacity, and long-term outcomes. The median baseline ST2 level was 23.7 ng/mL (interquartile range, 18.6-31.8). ST2 was modestly associated with measures of functional capacity. In univariable analysis, ST2 was significantly associated with death or hospitalization (hazard ratio, 1.48; P<0.0001), cardiovascular death or HF hospitalization (hazard ratio, 2.14; P<0.0001), and all-cause mortality (hazard ratio, 2.33; P<0.0001; all hazard ratios for log2 ng/mL). In multivariable models, ST2 remained independently associated with outcomes after adjustment for clinical variables and amino-terminal pro-B-type natriuretic peptide. However, ST2 did not add significantly to reclassification of risk as assessed by changes in the C statistic, net reclassification improvement, and integrated discrimination improvement.

CONCLUSIONS

ST2 was modestly associated with functional capacity and was significantly associated with outcomes in a well-treated cohort of ambulatory patients with HF although it did not significantly affect reclassification of risk.

CLINICAL TRIAL INFORMATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00047437.

Common genetic variation at the IL1RL1 locus regulates IL-33/ST2 signaling

The suppression of tumorigenicity 2/IL-33 (ST2/IL-33) pathway has been implicated in several immune and inflammatory diseases. ST2 is produced as 2 isoforms. The membrane-bound isoform (ST2L) induces an immune response when bound to its ligand, IL-33. The other isoform is a soluble protein (sST2) that is thought to be a decoy receptor for IL-33 signaling. Elevated sST2 levels in serum are associated with an increased risk for cardiovascular disease. We investigated the determinants of sST2 plasma concentrations in 2,991 Framingham Offspring Cohort participants. While clinical and environmental factors explained some variation in sST2 levels, much of the variation in sST2 production was driven by genetic factors. In a genome-wide association study (GWAS), multiple SNPs within IL1RL1 (the gene encoding ST2) demonstrated associations with sST2 concentrations. Five missense variants of IL1RL1 correlated with higher sST2 levels in the GWAS and mapped to the intracellular domain of ST2, which is absent in sST2. In a cell culture model, IL1RL1 missense variants increased sST2 expression by inducing IL-33 expression and enhancing IL-33 responsiveness (via ST2L). Our data suggest that genetic variation in IL1RL1 can result in increased levels of sST2 and alter immune and inflammatory signaling through the ST2/IL-33 pathway.

Soluble ST2 levels are not associated with secondary cardiovascular events and vulnerable plaque phenotype in patients with carotid artery stenosis

OBJECTIVE

Soluble ST2 (sST2), a novel biomarker predictive for heart disease, has recently been shown associated with the progression of atherosclerotic disease in a mouse model. The present study was designed to assess sST2 plasma levels in patients scheduled for carotid endarterectomy and relate it with the occurrence of adverse cardiovascular events during follow-up. In addition, sST2 levels were associated to patient clinical data and atherosclerotic plaque characteristics.

METHODS AND RESULTS

Plasma sST2 levels were measured in 391 patients who underwent carotid endarterectomy and were subsequently followed for 3 years. Primary composite endpoint was the occurrence of an adverse cardiovascular event. At baseline, no differences were observed in sST2 levels between asymptomatic (n = 75) and symptomatic (n = 316) patients (85 [49-122] versus 90 [58-137] pg/ml, p = 0.263). Soluble ST2 plasma levels did not differ between patients who experienced a secondary manifestation of cardiovascular disease and patients who remained free of symptoms (90 [60-129] versus 88 [46-140] pg/ml, p = 0.519). There was no association between sST2 levels and any of the following plaque characteristics: size of a lipid core, degree of calcification, number of macrophages or smooth muscle cells, amount of collagen and number of microvessels.

CONCLUSIONS

Soluble ST2 plasma levels have no predictive value for future cardiovascular events in patients with significant carotid artery stenosis. In addition, we did not observe an association between plasma sST2 levels and the histopathological features of a rupture prone plaque. This study does not provide supportive evidence that sST2 reflects a progressive state of advanced atherosclerotic disease.

Control of inflammatory heart disease by CD4+ T cells

This review focuses on autoimmune myocarditis and its sequela, inflammatory dilated cardiomyopathy (DCMI), and the inflammatory and immune mechanisms underlying the pathogenesis of these diseases. Several mouse models of myocarditis and DCMI have improved our knowledge of the pathogenesis of these diseases, informing more general problems of cardiac remodeling and heart failure. CD4(+) T cells are critical in driving the pathogenesis of myocarditis. We discuss in detail the role of T helper cell subtypes in the pathogenesis of myocarditis, the biology of T cell-derived effector cytokines, and the participation of other leukocytic effectors in mediating disease pathophysiology. We discuss interactions between these subsets in both suppressive and collaborative fashions. These findings indicate that cardiac inflammatory disease, and autoimmunity in general, may be more diverse in divergent effector mechanisms than has previously been appreciated.

Growth differentiation factor 11 is a circulating factor that reverses age-related cardiac hypertrophy

The most common form of heart failure occurs with normal systolic function and often involves cardiac hypertrophy in the elderly. To clarify the biological mechanisms that drive cardiac hypertrophy in aging, we tested the influence of circulating factors using heterochronic parabiosis, a surgical technique in which joining of animals of different ages leads to a shared circulation. After 4 weeks of exposure to the circulation of young mice, cardiac hypertrophy in old mice dramatically regressed, accompanied by reduced cardiomyocyte size and molecular remodeling. Reversal of age-related hypertrophy was not attributable to hemodynamic or behavioral effects of parabiosis, implicating a blood-borne factor. Using modified aptamer-based proteomics, we identified the TGF-β superfamily member GDF11 as a circulating factor in young mice that declines with age. Treatment of old mice to restore GDF11 to youthful levels recapitulated the effects of parabiosis and reversed age-related hypertrophy, revealing a therapeutic opportunity for cardiac aging.

The Presage(®) ST2 Assay: analytical considerations and clinical applications for a high-sensitivity assay for measurement of soluble ST2

The Presage(®) ST2 Assay (Critical Diagnostics, CA, USA) is an in vitro diagnostic device that quantitatively measures soluble suppression of tumorigenicity 2 (sST2) in serum and plasma by ELISA. This assay is US FDA approved and is indicated to be used in conjunction with clinical evaluation as an aid in assessing the prognosis of patients diagnosed with chronic heart failure. sST2 binds to IL-33 and functions as a 'decoy' receptor for IL-33, thereby attenuating the systemic effects of IL-33. Due to the role of IL-33/transmembrane isoform of suppression of tumorigenicity 2 signaling in cardiac remodeling, sST2 has emerged as a novel cardiovascular biomarker. In recent studies, it was shown that sST2 is a valuable predictor of several end points in heart failure, in acute coronary syndromes and in critically ill patients. In this review, analytical considerations and clinical applications of the Presage ST2 Assay will be discussed, as well as probable future concepts for adoption of sST2 measurements into clinical practice.

Implications for Interleukin-33 in solid organ transplantation

Interleukin(IL)-33 is a member of the IL-1 cytokine family that has been attributed T helper (Th) type 2 immunity-promoting capacity. However, new studies indicate that IL-33 is a multifunctional protein that acts as transcriptional/signaling repressor, functions as an alarmin alerting the immune system to necrosis, as well as serves as a cytokine that targets cells expressing ST2, the IL-33 receptor. Interestingly, IL-33 is also emerging as a pleiotropic cytokine. Depending on the innate or adaptive immune cells targeted by IL-33, it can not only promote type 2, but also IFN-γ dominated type 1 immunity. In addition, IL-33 expands regulatory T cells. In this review, we assimilate the current knowledge of IL-33 immunobiology and discuss how IL-33 may mediate such diverse roles in the immune response to pathogens and development of immune-mediated pathologies. The function of IL-33 in shaping alloimmune responses to transplanted organs is poorly explored, but a particularly beneficial role of IL-33 in experimental heart transplant models is summarized. Finally, given the implication of IL-33 in pathologies of the lung and intestine, we discuss how IL-33 may contribute to the comparatively poor outcomes following transplantation of these two organs.

IL-33 attenuates anoxia/reoxygenation-induced cardiomyocyte apoptosis by inhibition of PKCβ/JNK pathway

BACKGROUND

Interleukin-33 (IL-33) is a new member of the IL-1 cytokine family. The objectives of present study are to assess whether IL-33 can protect cardiomyocytes from anoxia/reoxygenation (A/R)-induced injury and the mechanism involved in the protection.

METHODS

Cardiomyocytes derived from either wild type or JNK1(-/-) mice were challenged with an A/R with or without IL-33. Myocyte apoptosis was assessed by measuring caspase 3 activity, fragmented DNA and TUNEL staining. In addition, cardiomyocyte oxidative stress was assessed by measuring DHR123 oxidation; PKCβII and JNK phosphorylation were assessed with Western blot.

RESULTS

Challenge of cardiomyocytes with an A/R resulted in cardiomyocyte oxidative stress, PKCβII and JNK phosphorylation, and myocyte apoptosis. Treatment of the cardiomyocytes with IL-33 attenuated the A/R-induced myocyte oxidative stress, prevented PKCβII and JNK phosphorylation and attenuated the A/R-induced myocyte apoptosis. The protective effect of the IL-33 did not show in cardiac myocytes with siRNA specific to PKCβII or myocytes deficient in JNK1. Inhibition of PKCβII prevented the A/R-induced JNK phosphorylation, but inhibition of JNK1 showed no effect on A/R-induced PKCβII phosphorylation.

CONCLUSIONS

Our results indicate that IL-33 prevents the A/R-induced myocyte apoptosis through inhibition of PKCβ/JNK pathway.

Temporal changes of soluble ST2 after cardiovascular interventions

BACKGROUND

Soluble ST2 (sST2), a member of the IL-1 receptor family, has been proposed as a novel biomarker with predictive value for heart failure and mortality in patients suffering from cardiovascular diseases. The influence of clinical characteristics on variability of sST2 levels is relatively unexplored. Here, we studied the effect of cardiovascular interventions and clinical characteristics on plasma sST2 expression levels.

MATERIAL AND METHODS

In the current study, sST2 levels were assessed in the plasma of patients scheduled for coronary artery bypass grafting (CABG) (n = 76), percutaneous coronary intervention (PCI) (n = 68) or peripheral vascular surgery (n = 27).

RESULTS

Age was the only classical risk factor significantly correlating with sST2 levels. Soluble ST2 levels were significantly increased 1 h after CABG (48 [33-70] vs. 61 [42-89] pg/mL, P = 0·001) and increased even further after 24 h (1116 [578-13 666] pg/mL, P < 0·001). An average threefold increase in sST2 levels was also observed in patients 24 h after peripheral interventions (30 [21-41] vs. 98 [48-211] pg/mL, P < 0·001). Two months after PCI, we found that sST2 levels were significantly higher compared with baseline levels (41 [29-61] vs. 48 [31-80] pg/mL, P = 0·007, n = 52). In addition, we did not observe an association between sST2 and any inflammatory or cardiac-specific markers that were measured in this study.

CONCLUSIONS

Soluble ST2 increases significantly following cardiovascular interventions. The notion of a recent cardiovascular intervention is a strong determinant of sST2 levels and therefore needs to be taken into account when exploring sST2 as predictor of future cardiovascular events.

High plasma levels of soluble ST2 but not its ligand IL-33 is associated with severe forms of pediatric dengue

Identification of early determinants of dengue disease progression, which could potentially enable individualized patient care are needed at present times. Soluble ST2 (sST2) has been recently reported to be elevated in the serum of children older than 2 years old and adults with dengue infection and it was correlated with secondary infections as well as with severe presentations of the disease. The mechanism by which secreted ST2 is linked to severe dengue and plasma leakage remains unclear. One possibility is that IL-33 ligand may be elevated, contributing to membrane bound ST2 as part of the immune activation in dengue infection. We determined plasma levels of sST2 and the ligand IL-33 in 66 children with acute secondary dengue infections clinically classified using the guidelines of the World Health Organization, 2009. Dengue infection showed significant increases in cytokines IL-12p70, IL-10, IL-8, IL-6, IL-1β and TNFα measured by flow cytometry based assay compared to uninfected individuals. In contrast, IL-33 levels remained unchanged between infected and uninfected individuals. The levels of sST2 positively correlated with values of IL-6 and IL-8 and inversely correlated with number of median value of platelet levels. In addition to circulating cytokine positive correlations we found that sST2 and isoenzyme creatine kinase-MB (CK-MB), a marker of myocardial muscle damage present in severe dengue cases were associated. Our pediatric study concluded that in dengue infections sST2 elevation does not involve concomitant changes of IL-33 ligand. We propose a study to assess its value as a predictor factor of disease severity.

Soluble ST2 is regulated by p75 neurotrophin receptor and predicts mortality in diabetic patients with critical limb ischemia

OBJECTIVE

The p75 neurotrophin receptor (p75(NTR)) contributes to diabetes mellitus-induced defective postischemic neovascularization. The interleukin-33 receptor ST2 is expressed as transmembrane (ST2L) and soluble (sST2) isoforms. Here, we studied the following: (1) the impact of p75(NTR) in the healing of ischemic and diabetic calf wounds; (2) the link between p75(NTR) and ST2; and (3) circulating sST2 levels in critical limb ischemia (CLI) patients.

METHODS AND RESULTS

Diabetes mellitus was induced in p75(NTR) knockout (p75KO) mice and wild-type (WT) littermates by streptozotocin. Diabetic and nondiabetic p75KO and WT mice received left limb ischemia induction and a full-thickness wound on the ipsilateral calf. Diabetes mellitus impaired wound closure and angiogenesis and increased ST2 expression in WT, but not in p75KO wounds. In cultured endothelial cells, p75(NTR) promoted ST2 (both isoforms) expression through p38(MAPK)/activating transcription factor 2 pathway activation. Next, sST2 was measured in the serum of patients with CLI undergoing either revascularization or limb amputation and in the 2 nondiabetic groups (with CLI or nonischemic individuals). Serum sST2 increased in diabetic patients with CLI and was directly associated with higher mortality at 1 year from revascularization.

CONCLUSIONS

p75(NTR) inhibits the healing of ischemic lower limb wounds in diabetes mellitus and promotes ST2 expression. Circulating sST2 predicts mortality in diabetic CLI patients.

Cross talk between cardiac myocytes and fibroblasts: from multiscale investigative approaches to mechanisms and functional consequences

The heart is comprised of a syncytium of cardiac myocytes (CM) and surrounding nonmyocytes, the majority of which are cardiac fibroblasts (CF). CM and CF are highly interspersed in the myocardium with one CM being surrounded by one or more CF. Bidirectional cross talk between CM and CF plays important roles in determining cardiac mechanical and electrical function in both normal and diseased hearts. Genetically engineered animal models and in vitro studies have provided evidence that CM and CF can regulate each other's function. Their cross talk contributes to structural and electrical remodeling in both atria and ventricles and appears to be involved in the pathogenesis of various heart diseases that lead to heart failure and arrhythmia disorders. Mechanisms of CM-CF cross talk, which are not yet fully understood, include release of paracrine factors, direct cell-cell interactions via gap junctions and potentially adherens junctions and nanotubes, and cell interactions with the extracellular matrix. In this article, we provide an overview of the existing multiscale experimental and computational approaches for the investigation of cross talk between CM and CF and review recent progress in our understanding of the functional consequences and underlying mechanisms. Targeting cross talk between CM and CF could potentially be used therapeutically for the modulation of the cardiac remodeling response in the diseased heart and may lead to new strategies for the treatment of heart failure or rhythm disturbances.

Distribution and clinical correlates of the interleukin receptor family member soluble ST2 in the Framingham Heart Study

BACKGROUND

Soluble ST2 (sST2) is a cardiac biomarker whose concentration rises in response to myocardial strain. Increased sST2 concentrations may predict adverse outcomes in patients with heart failure and myocardial infarction. Because sST2 was largely undetectable with first-generation assays in ambulatory individuals, there are few data regarding its distribution and correlates in community-based populations.

METHODS

We measured sST2 using a highly sensitive ELISA in 3450 Framingham Heart Study participants who attended a routine examination. We used multivariable linear regression models to identify covariates associated with sST2 in the general sample. We obtained a reference sample (n = 1136) by excluding individuals with prevalent coronary disease, heart failure, atrial fibrillation, diabetes, hypertension, obesity, valvular disease, left ventricular systolic dysfunction, and pulmonary and renal dysfunction. We used empiric and quantile regression techniques to estimate the 2.5th, 50th, 97.5th, and 99th quantiles.

RESULTS

In the general sample (mean age 59 years, 55% women), systolic blood pressure (P = 0.006), antihypertensive medication use (P = 0.03), and diabetes (P < 0.001) were associated with sST2 concentrations. In the reference sample (mean age 55, 59% women), male sex (P < 0.0001) and older age (P = 0.004) were predictive of higher sST2 concentrations. Quantile and empirical methods were used to define the reference intervals. Using the empirical approach, upper 99% percentile values in different age groups ranged from 46.6 to 64.4 μg/L in men and 36.7 to 53.0 μg/L in women.

CONCLUSIONS

In a well-characterized, community-based cohort, values for sST2 differ between men and women, increase with age, and are associated with diabetes and hypertension.

IL-1 family cytokines trigger sterile inflammatory disease

Inflammation plays vital roles in protective responses against pathogens and tissue repair, however, improper resolution of inflammatory networks is centrally involved in the pathogenesis of many acute and chronic diseases. Extensive advances have been made in recent years to define the inflammatory processes that are required for pathogen clearance, however, in comparison, less is known about the regulation of inflammation in sterile settings. Over the past decade non-communicable chronic diseases that are potentiated by sterile inflammation have replaced infectious diseases as the major threat to global human health. Thus, improved understanding of the sterile inflammatory process has emerged as one of the most important areas of biomedical investigation during our time. In this review we highlight the central role that interleukin-1 family cytokines play in sterile inflammatory diseases.

Prognostic utility of novel biomarkers of cardiovascular stress: the Framingham Heart Study

BACKGROUND

Biomarkers for predicting cardiovascular events in community-based populations have not consistently added information to standard risk factors. A limitation of many previously studied biomarkers is their lack of cardiovascular specificity.

METHODS AND RESULTS

To determine the prognostic value of 3 novel biomarkers induced by cardiovascular stress, we measured soluble ST2, growth differentiation factor-15, and high-sensitivity troponin I in 3428 participants (mean age, 59 years; 53% women) in the Framingham Heart Study. We performed multivariable-adjusted proportional hazards models to assess the individual and combined ability of the biomarkers to predict adverse outcomes. We also constructed a "multimarker" score composed of the 3 biomarkers in addition to B-type natriuretic peptide and high-sensitivity C-reactive protein. During a mean follow-up of 11.3 years, there were 488 deaths, 336 major cardiovascular events, 162 heart failure events, and 142 coronary events. In multivariable-adjusted models, the 3 new biomarkers were associated with each end point (P<0.001) except coronary events. Individuals with multimarker scores in the highest quartile had a 3-fold risk of death (adjusted hazard ratio, 3.2; 95% confidence interval, 2.2-4.7; P<0.001), 6-fold risk of heart failure (6.2; 95% confidence interval, 2.6-14.8; P<0.001), and 2-fold risk of cardiovascular events (1.9; 95% confidence interval, 1.3-2.7; P=0.001). Addition of the multimarker score to clinical variables led to significant increases in the c statistic (P=0.005 or lower) and net reclassification improvement (P=0.001 or lower).

CONCLUSION

Multiple biomarkers of cardiovascular stress are detectable in ambulatory individuals and add prognostic value to standard risk factors for predicting death, overall cardiovascular events, and heart failure.

Altered serum levels of IL-33 in patients with advanced systolic chronic heart failure: correlation with oxidative stress

Background

Interleukin-33 (IL-33) has been linked to chronic heart failure (CHF) in animal studies, but data on serum IL-33 levels in human CHF are not available. We analyzed levels of IL-33 in serum, and investigated the possible role of IL-33 in oxidative stress.

Methods

A total of 191 subjects with advanced systolic CHF (CHF group), 175 patients with pre-existing cardiac diseases but no CHF (non-CHF group), and 177 healthy controls (HC group) were enrolled. Serum levels of IL-33, soluble ST2 (sST2) and N-terminal-pro-brain natriuretic peptide (NT-proBNP), malondialdehyde (MDA) content, erythrocyte superoxide dismutase (eSOD) activity, as well as left ventricular ejection fraction (LVEF), were determined. The exact form of IL-33 in serum was identified. Effects of IL-33 and sST2 on MDA content and SOD activity in angiotensin (Ang II)-stimulated AC16 cells were assessed.

Results

Serum levels of IL-33 and sST2 were elevated in CHF patients, whereas IL-33/sST2 ratios were decreased. In CHF patients, pre-existing cardiac diseases and medications used upon hospital admission did not affect IL-33 concentrations or the IL-33/sST2 ratio. Full-length IL-33, which could not be detected in serum from HC and barely detected in non-CHF patients, was significantly up-regulated in CHF patients. IL-33 levels were positively correlated with markers of CHF severity. IL-33/sST2 ratios were slightly and negatively related to MDA concentrations. IL-33 directly reduced MDA and enhanced SOD activity in Ang II-stimulated AC16 cells, which were greatly attenuated by sST2.

Conclusions

Serum levels of IL-33, especially the full-length form, were elevated in CHF patients whereas IL-33 bioactivity was reduced. In advanced CHF, IL-33 may exert anti-oxidation effects, which may be overwhelmed by concurrently elevated levels of sST2.

Interleukin-33 and the function of innate lymphoid cells

Interleukin (IL)-33 is a member of the IL-1 cytokine family that has been shown to play an important role in the induction and effector phases of type 2 immune responses. Both innate and adaptive immunity are regulated by IL-33, and many studies have shown disease-associated functions for this cytokine. Recently, IL-33 has been implicated in the function of novel innate lymphocyte populations that regulate both protective responses in parasitic infections and allergic airway inflammation. Here, we discuss recent data highlighting the dual roles of IL-33 in protective and deleterious immune responses.

IL-33 independently induces eosinophilic pericarditis and cardiac dilation: ST2 improves cardiac function

BACKGROUND

IL-33 through its receptor ST2 protects the heart from myocardial infarct and hypertrophy in animal models but, paradoxically, increases autoimmune disease. In this study, we examined the effect of IL-33 or ST2 administration on autoimmune heart disease.

METHODS AND RESULTS

We used pressure-volume relationships and isoproterenol challenge to assess the effect of recombinant (r) IL-33 or rST2 (eg, soluble ST2) administration on the development of autoimmune coxsackievirus B3 myocarditis and dilated cardiomyopathy in male BALB/c mice. The rIL-33 treatment significantly increased acute perimyocarditis (P=0.006) and eosinophilia (P=1.3×10(-5)), impaired cardiac function (maximum ventricular power, P=0.0002), and increased ventricular dilation (end-diastolic volume, P=0.01). The rST2 treatment prevented eosinophilia and improved heart function compared with rIL-33 treatment (ejection fraction, P=0.009). Neither treatment altered viral replication. The rIL-33 treatment increased IL-4, IL-33, IL-1β, and IL-6 levels in the heart during acute myocarditis. To determine whether IL-33 altered cardiac function on its own, we administered rIL-33 to undiseased mice and found that rIL-33 induced eosinophilic pericarditis and adversely affected heart function. We used cytokine knockout mice to determine that this effect was due to IL-33-mediated signaling but not to IL-1β or IL-6.

CONCLUSIONS

We show for the first time to our knowledge that IL-33 induces eosinophilic pericarditis, whereas soluble ST2 prevents eosinophilia and improves systolic function, and that IL-33 independently adversely affects heart function through the IL-33 receptor.

Novel biomarkers in chronic heart failure

Understanding of chronic heart failure (HF) has progressed from a syndrome of disordered hemodynamics caused by alterations in the structure of the heart to one that involves intertwined molecular pathways in disarray. Accordingly, the assessment and treatment of patients with chronic HF has shifted from a focus on hemodynamics to modification of maladaptive molecular processes. Accumulating evidence shows that molecular biomarkers of disease could provide a unique window into the pathophysiology of chronic HF, potentially improving our ability to predict adverse outcomes, provide novel drug targets, and even help gauge therapeutic efficacy. The more 'traditional' biomarkers such as cardiac troponin, natriuretic peptides, and C-reactive protein have been studied in large cohorts of patients with chronic HF and have relatively established clinical applications. In this Review, we summarize the properties, clinical data, and potential applications of some emerging biomarkers that could uniquely indicate the level of biomechanical stretch, inflammation, ventricular remodeling, myocardial injury, and renal dysfunction that occurs in chronic HF. We will also discuss the potential role for these biomarkers within a multimarker-based strategy that could, in the future, lead to better care for these patients.