Christen P. Dahl

Increased systemic and myocardial expression of neutrophil gelatinase-associated lipocalin in clinical and experimental heart failure.

AIMS Neutrophil gelatinase-associated lipocalin (NGAL or lipocalin-2) is a glycoprotein with bacteriostatic properties. Growing evidence suggests that NGAL may also be involved in cell survival, inflammation, and matrix degradation. We therefore aimed to investigate the role of NGAL in heart failure (HF). METHODS AND RESULTS Our main findings were (i) patients with acute post-myocardial infarction (MI) HF (n = 236) and chronic HF (n = 150) had elevated serum levels of NGAL (determined by enzyme immunoassay), significantly correlated with clinical and neurohormonal deterioration, (ii) in patients with HF following acute MI, elevated NGAL levels of at baseline were associated with adverse outcomes (median of 27 months follow-up), (iii) in a rat model of post-MI HF, NGAL/lipocalin-2 gene expression was increased in the non-ischaemic part of the left ventricle primarily located to cardiomyocytes, (iv) strong NGAL immunostaining was found in cardiomyocytes within the failing myocardium both in experimental and clinical HF, (v) interleukin-1beta and agonists for toll-like receptors 2 and 4, representing components of the innate immune system, were potent inducers of NGAL/lipocalin-2 in isolated neonatal cardiomyocytes. CONCLUSION Our demonstration of enhanced systemic and myocardial NGAL expression in clinical and experimental HF further support a role for innate immune responses in the pathogenesis of HF.

The NLRP3 inflammasome is up-regulated in cardiac fibroblasts and mediates myocardial ischaemia–reperfusion injury

AIMS Nucleotide-binding oligomerization domain-Like Receptor with a Pyrin domain 3 (NLRP3) is considered necessary for initiating a profound sterile inflammatory response. NLRP3 forms multi-protein complexes with Apoptosis-associated Speck-like protein containing a Caspase recruitment domain (ASC) and Caspase-1, which activate pro-interleukin-1β (IL-1β) and pro-IL-18. The role of NLRP3 in cardiac cells is not known. Thus, we investigated the expression and function of NLRP3 during myocardial ischaemia. METHODS AND RESULTS Myocardial infarction (MI) was induced in adult C57BL/6 mice and Wistar rats by ligation of the coronary artery. A marked increase in NLRP3, IL-1β, and IL-18 mRNA expression was found in the left ventricle after MI, primarily located to myocardial fibroblasts. In vitro studies in cells from adult mice showed that myocardial fibroblasts released IL-1β and IL-18 when primed with lipopolysaccharide and subsequently exposed to the danger signal adenosine triphosphate, a molecule released after tissue damage during MI. When hearts were isolated from NLRP3-deficient mice, perfused and subjected to global ischaemia and reperfusion, a marked improvement of cardiac function and reduction of hypoxic damage was found compared with wild-type hearts. This was not observed in ASC-deficient hearts, potentially reflecting a protective role of other ASC-dependent inflammasomes or inflammasome-independent effects of NLRP3. CONCLUSION This study shows that the NLRP3 inflammasome is up-regulated in myocardial fibroblasts post-MI, and may be a significant contributor to infarct size development during ischaemia-reperfusion.

Microbiota‐dependent metabolite trimethylamine‐N‐oxide is associated with disease severity and survival of patients with chronic heart failure

Recent metabolomic, experimental and clinical studies have demonstrated that trimethylamine‐N‐oxide (TMAO), a microbiota‐dependent metabolite from dietary phosphatidylcholine and carnitine, is a strong predictor of coronary artery disease (CAD). This finding suggests a link between the gut microbiota and atherosclerosis. The potential impact of TMAO in chronic heart failure (HF) is unknown. We hypothesized that TMAO levels would provide prognostic information about adverse outcomes in chronic HF.

Undercarboxylated matrix Gla protein is associated with indices of heart failure and mortality in symptomatic aortic stenosis.

Abstract.  Ueland T, Gullestad L, Dahl CP, Aukrust P, Aakhus S, Solberg OG, Vermeer C, Schurgers LJ (Research Institute for Internal Medicine, University of Oslo, Oslo; University of Oslo, Oslo, Norway; and VitaK & Cardiovascular Research Institute CARIM (CV, LS), Maastricht University, Maastricht, The Netherlands) Undercarboxylated matrix Gla protein is associated with indices of heart failure and mortality in symptomatic aortic stenosis. J Intern Med 2010; 268: 483–492.

Prognostic importance of renal function 1 year after heart transplantation for all-cause and cardiac mortality and development of allograft vasculopathy.

Background. Impaired renal function is associated with increased mortality among heart failure patients. Although a significant proportion of heart transplant (HTx) recipients have reduced renal function at 1 year post-HTx, no previous study has evaluated the associated risk for both all-cause and cardiac mortality. Hence, we assessed the relationship between glomerular filtration rate (GFR) at 1 year post-HTx and all-cause and cardiac mortality and development of cardiac allograft vasculopathy (CAV). Methods. We evaluated 381 patients with a minimum survival of 1 year post-HTx and the Modification of Diet in Renal Disease Study formula was used to calculate estimated GFR. Mortality and angiographic CAV were defined as separate endpoints, and median follow-up was 7.4 and 4.0 years, respectively. Results. During the follow-up period, 122 patients died and 154 patients developed CAV. Reduced GFR pre-HTx was not a risk factor for either endpoint. Overall, 193 (51%) patients had GFR <60 ml/min/1.73 m2 at one year post-HTx and this was an independent predictor of all-cause mortality with an adjusted hazard ratio of 1.7 (P=0.01) for a GFR between 30–60 and 3.2 (P=0.006) for GFR <30 ml/min/1.73 m2. GFR <60 ml/min/1.73 m2 at 1 year post-HTx was also associated with a higher risk of cardiac mortality (HR=1.9; P=0.04) but did not predict the development of CAV. Conclusions. Renal impairment is evident in a majority of HTx recipients at 1 year post-HTx. It is an important risk factor for both all-cause and cardiac mortality but does not predict the development of angiographic CAV.

Osteoprotegerin Predicts Progression of Chronic Heart Failure: Results From CORONA

Background—Osteoprotegerin (OPG) may be implicated in the pathogenesis of heart failure (HF), and circulating levels predict survival in patients with postinfarction HF. Our primary goal was to determine whether OPG provided independent prognostic information in patients with chronic HF, and to examine its potential interactions with statin therapy. Methods and Results—OPG as a risk factor for the primary end point (cardiovascular death, nonfatal myocardial infarction, nonfatal stroke; n=318), all-cause mortality (n=329), and all-cause mortality/hospitalization for worsening of heart failure (WHF; n=475) was investigated in 1464 patients (≥60 years, New York Heart Association class II to IV, ischemic systolic HF, optimal pharmacological therapy) in the Controlled Rosuvastatin Multinational Trial in HF (CORONA) population, randomly assigned to 10 mg rosuvastatin or placebo. In multivariate analyses, OPG (continuous variable) added no significant predictive information for risk estimation of the primary end point (adjusting for left ventricular ejection fraction, New York Heart Association class, age, body mass index, diabetes, sex, intermittent claudication, heart rate, serum creatinine, apoA1, and N-terminal pro-B-type natriuretic peptide). However, OPG added independent predictive information for WHF hospitalization (hazard ratio [HR] 1.10 [1.04 to 1.16], P<0.001) and all-cause mortality/WHF hospitalization (HR 1.06 [1.01 to 1.11]). The HR indicated a reduced risk for all-cause mortality in the rosuvastatin group in those with lowest OPG values (tertile 1, HR=0.66 unadjusted [P=0.025]; HR=0.71 Cox adjusted [P=0.025]; interaction by treatment effect for the tertiles P=0.086). Conclusions—OPG added no predictive information for the primary end point, but independently predicted WHF hospitalization in older patients with advanced chronic systolic HF of ischemic etiology. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00206310.

Noninvasive assessment of myocardial fibrosis in patients with obstructive hypertrophic cardiomyopathy

Objective Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) imaging is the reference standard for non-invasive assessment of fibrosis. In hypertrophic cardiomyopathy (HCM) patients the histological substrate for LGE is still unknown. The aim of this study was to assess the ability of LGE and strain echocardiography to detect type and extent of myocardial fibrosis in obstructive HCM patients undergoing septal myectomy. Methods Thirty-two HCM patients (age 60±10) were included in this cross-sectional study and preoperatively examined by speckle-tracking strain echocardiography and LGE-CMR (n=21). Histological fibrosis was classified as interstitial, replacement and total. Results Histological fibrosis was present in 31 patients. The percentage of total, interstitial and replacement fibrosis was 15(7, 31)%, 11(5, 24)% and 3(1, 6)%, respectively. Reduced longitudinal septal strain correlated with total (r=0.50, p=0.01) and interstitial (r=0.40, p=0.03), but not with replacement fibrosis (r=0.28, p=0.14). Septal LGE was detected in 13/21 (62%), but percentage LGE did not correlate with total fibrosis (r=0.25, p=0.28). Extent of fibrosis did not differ between patients with and without septal LGE (20(9, 58)% versus 14(5, 19)% p=0.41). Patients with ventricular arrhythmias (n=8) had lower septal longitudinal strain and increased extent total and interstitial fibrosis in myectomy specimens, but no differences were demonstrated in LGE. Reduced longitudinal septal strain and increased extent of interstitial fibrosis predicted ventricular arrhythmias independently of age and gender. Conclusions In myectomised HCM patients, reduced longitudinal septal strain correlated better with interstitial and total fibrosis in myectomy specimens, and was a more powerful tool to predict arrhythmias than LGE.

Circulating levels of non-phosphorylated undercarboxylated matrix Gla protein are associated with disease severity in patients with chronic heart failure.

We recently demonstrated that circulating MGP [matrix Gla (γ-carboxylated glutamate) protein] levels were associated with left ventricular dysfunction and increased mortality in patients with symptomatic aortic stenosis. We hypothesized that patients with chronic HF (heart failure) would have dysregulated MGP levels. We examined plasma dp-cMGP (non-phosphorylated carboxylated MGP) and dp-ucMGP (non-phosphorylated undercarboxylated MGP) in 179 patients with chronic HF and matched healthy controls as well as the relationship between MGP and cardiac dysfunction as assessed by echocardiographic measurements, inflammation [CRP (C-reactive protein)] and neurohormonal activation [NT-proBNP (N-terminal proB-type natriuretic peptide)] and the prognostic value of MGP levels in relation to mortality in these patients. We found markedly enhanced plasma dp-cMGP and, in particular, of dp-ucMGP in chronic HF with increasing levels with disease severity. Elevated MGP species were associated with ischaemic aetiology, increased CRP and NT-proBNP levels, as well as systolic and diastolic dysfunction. Finally, dp-ucMGP was associated with long-term heart transplant-free survival (n=48) in univariate, but not in multivariate, analysis. However, plasma dp-ucMGP was markedly higher in patients who died because of progression of HF (n=12) and gave prognostic information also in multivariate analysis. In conclusion, a dysregulated MGP system could be involved in left ventricular dysfunction in patients with chronic HF.

Lumican is increased in experimental and clinical heart failure, and its production by cardiac fibroblasts is induced by mechanical and proinflammatory stimuli

During progression to heart failure (HF), myocardial extracellular matrix (ECM) alterations and tissue inflammation are central. Lumican is an ECM‐localized proteoglycan associated with inflammatory conditions and known to bind collagens. We hypothesized that lumican plays a role in the dynamic alterations in cardiac ECM during development of HF. Thus, we examined left ventricular cardiac lumican in a mouse model of pressure overload and in HF patients, and investigated expression, regulation and effects of increased lumican in cardiac fibroblasts. After 4 weeks of aortic banding, mice were divided into groups of hypertrophy (AB) and HF (ABHF) based on lung weight and left atrial diameter. Sham‐operated mice were used as controls. Accordingly, cardiac lumican mRNA and protein levels were increased in mice with ABHF. Similarly, cardiac biopsies from patients with end‐stage HF revealed increased lumican mRNA and protein levels compared with control hearts. In vitro, mechanical stretch and the proinflammatory cytokine interleukin‐1β increased lumican mRNA as well as secreted lumican protein from cardiac fibroblasts. Stimulation with recombinant glycosylated lumican increased collagen type I alpha 2, lysyl oxidase and transforming growth factor‐β1 mRNA, which was attenuated by costimulation with an inhibitor of the proinflammatory transcription factor NFκB. Furthermore, lumican increased the levels of the dimeric form of collagen type I, decreased the activity of the collagen‐degrading enzyme matrix metalloproteinase‐9 and increased the phosphorylation of fibrosis‐inducing SMAD3. In conclusion, cardiac lumican is increased in experimental and clinical HF. Inflammation and mechanical stimuli induce lumican production by cardiac fibroblasts and increased lumican altered molecules important for cardiac remodeling and fibrosis in cardiac fibroblasts, indicating a role in HF development.

Innate immune signaling induces expression and shedding of the heparan sulfate proteoglycan syndecan-4 in cardiac fibroblasts and myocytes, affecting inflammation in the pressure-overloaded heart.

Sustained pressure overload induces heart failure, the main cause of mortality in the Western world. Increased understanding of the underlying molecular mechanisms is essential to improve heart failure treatment. Despite important functions in other tissues, cardiac proteoglycans have received little attention. Syndecan‐4, a transmembrane heparan sulfate proteoglycan, is essential for pathological remodeling, and we here investigated its expression and shedding during heart failure. Pressure overload induced by aortic banding for 24 h and 1 week in mice increased syndecan‐4 mRNA, which correlated with mRNA of inflammatory cytokines. In cardiac myocytes and fibroblasts, tumor necrosis factor‐α, interleukin‐1β and lipopolysaccharide through the toll‐like receptor‐4, induced syndecan‐4 mRNA. Bioinformatical and mutational analyses in HEK293 cells identified a functional site for the proinflammatory nuclear factor‐κB transcription factor in the syndecan‐4 promoter, and nuclear factor‐κB regulated syndecan‐4 mRNA in cardiac cells. Interestingly, tumor necrosis factor‐α, interleukin‐1β and lipopolysaccharide induced nuclear factor‐κB‐dependent shedding of the syndecan‐4 ectodomain from cardiac cells. Overexpression of syndecan‐4 with mutated enzyme‐interacting domains suggested enzyme‐dependent heparan sulfate chains to regulate shedding. In cardiac fibroblasts, lipopolysaccharide reduced focal adhesion assembly, shown by immunohistochemistry, suggesting that inflammation‐induced shedding affects function. After aortic banding, a time‐dependent cardiac recruitment of T lymphocytes was observed by measuring CD3, CD4 and CD8 mRNA, which was reduced in syndecan‐4 knockout hearts. Finally, syndecan‐4 mRNA and shedding were upregulated in failing human hearts. Conclusively, our data suggest that syndecan‐4 plays an important role in the immune response of the heart to increased pressure, influencing cardiac remodeling and failure progression.