| 1. |
- Ottesen, Anett H., et al.
(författare)
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Secretoneurin Is an Endogenous Calcium/Calmodulin-Dependent Protein Kinase II Inhibitor That Attenuates Ca2+-Dependent Arrhythmia
- 2019
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Ingår i: Circulation. - : Lippincott Williams & Wilkins. - 1941-3149 .- 1941-3084. ; 12:4
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Circulating SN (secretoneurin) concentrations are increased in patients with myocardial dysfunction and predict poor outcome. Because SN inhibits CaMKII delta (Ca2+/calmodulin-dependent protein kinase II delta) activity, we hypothesized that upregulation of SN in patients protects against cardiomyocyte mechanisms of arrhythmia. METHODS: Circulating levels of SN and other biomarkers were assessed in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT; n=8) and in resuscitated patients after ventricular arrhythmia-induced cardiac arrest (n=155). In vivo effects of SN were investigated in CPVT mice (RyR2 [ryanodine receptor 2]-R2474S) using adeno-associated virus-9-induced overexpression. Interactions between SN and CaMKII delta were mapped using pull-down experiments, mutagenesis, ELISA, and structural homology modeling. Ex vivo actions were tested in Langendorff hearts and effects on Ca2+ homeostasis examined by fluorescence (fluo-4) and patchclamp recordings in isolated cardiomyocytes. RESULTS: SN levels were elevated in patients with CPVT and following ventricular arrhythmia-induced cardiac arrest. In contrast to NT-proBNP (N-terminal proB- type natriuretic peptide) and hs-TnT (high-sensitivity troponin T), circulating SN levels declined after resuscitation, as the risk of a new arrhythmia waned. Myocardial pro-SN expression was also increased in CPVT mice, and further adeno-associated virus-9-induced overexpression of SN attenuated arrhythmic induction during stress testing with isoproterenol. Mechanistic studies mapped SN binding to the substrate binding site in the catalytic region of CaMKII delta. Accordingly, SN attenuated isoproterenol induced autophosphorylation of Thr287-CaMKII delta in Langendorff hearts and inhibited CaMKII delta-dependent RyR phosphorylation. In line with CaMKII delta and RyR inhibition, SN treatment decreased Ca2+ spark frequency and dimensions in cardiomyocytes during isoproterenol challenge, and reduced the incidence of Ca2+ waves, delayed afterdepolarizations, and spontaneous action potentials. SN treatment also lowered the incidence of early afterdepolarizations during isoproterenol; an effect paralleled by reduced magnitude of L-type Ca2+ current. CONCLUSIONS: SN production is upregulated in conditions with cardiomyocyte Ca2+ dysregulation and offers compensatory protection against cardiomyocyte mechanisms of arrhythmia, which may underlie its putative use as a biomarker in at-risk patients.
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| 2. |
- Herum, Kate M., et al.
(författare)
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Syndecan-4 Protects the Heart From the Profibrotic Effects of Thrombin-Cleaved Osteopontin
- 2020
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Ingår i: Journal of the American Heart Association. - 2047-9980. ; 9:3, s. 013518-013518
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Tidskriftsartikel (refereegranskat)abstract
- Background: Pressure overload of the heart occurs in patients with hypertension or valvular stenosis and induces cardiac fibrosis because of excessive production of extracellular matrix by activated cardiac fibroblasts. This initially provides essential mechanical support to the heart, but eventually compromises function. Osteopontin is associated with fibrosis; however, the underlying signaling mechanisms are not well understood. Herein, we examine the effect of thrombin-cleaved osteopontin on fibrosis in the heart and explore the role of syndecan-4 in regulating cleavage of osteopontin. Methods and Results: Osteopontin was upregulated and cleaved by thrombin in the pressure-overloaded heart of mice subjected to aortic banding. Cleaved osteopontin was higher in plasma from patients with aortic stenosis receiving crystalloid compared with blood cardioplegia, likely because of less heparin-induced inhibition of thrombin. Cleaved osteopontin and the specific osteopontin peptide sequence RGDSLAYGLR that is exposed after thrombin cleavage both induced collagen production in cardiac fibroblasts. Like osteopontin, the heparan sulfate proteoglycan syndecan-4 was upregulated after aortic banding. Consistent with a heparan sulfate binding domain in the osteopontin cleavage site, syndecan-4 was found to bind to osteopontin in left ventricles and cardiac fibroblasts and protected osteopontin from cleavage by thrombin. Shedding of the extracellular part of syndecan-4 was more prominent at later remodeling phases, at which time levels of cleaved osteopontin were increased. Conclusions: Thrombin-cleaved osteopontin induces collagen production by cardiac fibroblasts. Syndecan-4 protects osteopontin from cleavage by thrombin, but this protection is lost when syndecan-4 is shed in later phases of remodeling, contributing to progression of cardiac fibrosis.
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| 3. |
- Herum, Kate M., et al.
(författare)
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Syndecan-4 signaling via NFAT regulates extracellular matrix production and cardiac myofibroblast differentiation in response to mechanical stress
- 2013
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Ingår i: Journal of Molecular and Cellular Cardiology. - : Elsevier BV. - 1095-8584 .- 0022-2828. ; 54, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- Pressure overload activates cardiac fibroblasts leading to excessive production of extracellular matrix which may contribute to compromised heart function. The activated fibroblast acquires smooth muscle-like features such as expression of smooth muscle alpha-actin (SMA) and SM22 and is therefore referred to as myofibroblast. The molecular mechanisms underlying mechanical stress-induced myofibroblast differentiation are poorly defined. The objective of this study was to examine the potential roles of the transmembrane proteoglycan syndecan-4 and the calcineurin-dependent transcription factor nuclear factor of activated T-cells (NFAT) in myofibroblast differentiation. Aortic banding resulted in elevated collagen land III, fibronectin, SMA and SM22 mRNA in the left ventricles of wild-type mice, whereas this response was markedly reduced in syndecan-4(-/-) mice. Myofibroblast differentiation in vitro was associated with increased SMA, collagen I and III expression and NFAT-luciferase activity, all of which were reduced in fibroblasts from syndecan-4(-/-) mice or after treatment with calcineurin/NFAT blockers. Following cyclic stretch, NFATc4 was activated in cardiac fibroblasts in a syndecan-4- and calcineurin-dependent manner. Syndecan-4 and calcineurin co-localized and mechanical stress resulted in dephosphorylation of serine179 of syndecan-4, an intracellular residue critical for calcineurin interaction. Over-expression of NFATc4 up-regulated collagen III, MRTF-A (a transcriptional regulator of SMA) and the NFAT-target regulator of calcineurin 1.4 (RCAN1.4). Our data demonstrate that syndecan-4 is important for the differentiation of cardiac fibroblasts into myofibroblasts in the pressure-overloaded heart and that the calcineurin/NFAT pathway is engaged upon mechanical stress in a syndecan-4-dependent manner, playing an active role in myofibroblast differentiation and extracellular matrix production. This article is part of a Special Issue entitled 'Possible Editorial'. (c) 2012 Elsevier Ltd. All rights reserved.
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| 4. |
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| 5. |
- Ottesen, Anett Hellebø, et al.
(författare)
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Glycosylated Chromogranin A in Heart Failure : Implications for Processing and Cardiomyocyte Calcium Homeostasis
- 2017
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Ingår i: Circulation Heart Failure. - 1941-3289 .- 1941-3297. ; 10:2
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Chromogranin A (CgA) levels have previously been found to predict mortality in heart failure (HF), but currently no information is available regarding CgA processing in HF and whether the CgA fragment catestatin (CST) may directly influence cardiomyocyte function.METHODS AND RESULTS: CgA processing was characterized in postinfarction HF mice and in patients with acute HF, and the functional role of CST was explored in experimental models. Myocardial biopsies from HF, but not sham-operated mice, demonstrated high molecular weight CgA bands. Deglycosylation treatment attenuated high molecular weight bands, induced a mobility shift, and increased shorter CgA fragments. Adjusting for established risk indices and biomarkers, circulating CgA levels were found to be associated with mortality in patients with acute HF, but not in patients with acute exacerbation of chronic obstructive pulmonary disease. Low CgA-to-CST conversion was also associated with increased mortality in acute HF, thus, supporting functional relevance of impaired CgA processing in cardiovascular disease. CST was identified as a direct inhibitor of CaMKIIδ (Ca(2+)/calmodulin-dependent protein kinase IIδ) activity, and CST reduced CaMKIIδ-dependent phosphorylation of phospholamban and the ryanodine receptor 2. In line with CaMKIIδ inhibition, CST reduced Ca(2+) spark and wave frequency, reduced Ca(2+) spark dimensions, increased sarcoplasmic reticulum Ca(2+) content, and augmented the magnitude and kinetics of cardiomyocyte Ca(2+) transients and contractions.CONCLUSIONS: CgA-to-CST conversion in HF is impaired because of hyperglycosylation, which is associated with clinical outcomes in acute HF. The mechanism for increased mortality may be dysregulated cardiomyocyte Ca(2+) handling because of reduced CaMKIIδ inhibition.
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| 6. |
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| 7. |
- Ottesen, Anett Hellebø, et al.
(författare)
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Secretoneurin is a novel prognostic cardiovascular biomarker associated with cardiomyocyte calcium handling.
- 2015
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Ingår i: Journal of the American College of Cardiology. - : Elsevier BV. - 0735-1097 .- 1558-3597. ; 65:4, s. 339-51
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Secretoneurin (SN) levels are increased in patients with heart failure (HF), but whether SN provides prognostic information and influences cardiomyocyte function is unknown.OBJECTIVES: This study sought to evaluate the merit of SN as a cardiovascular biomarker and assess effects of SN on cardiomyocyte Ca(2+) handling.METHODS: We assessed the association between circulating SN levels and mortality in 2 patient cohorts and the functional properties of SN in experimental models.RESULTS: In 143 patients hospitalized for acute HF, SN levels were closely associated with mortality (n = 66) during follow-up (median 776 days; hazard ratio [lnSN]: 4.63; 95% confidence interval: 1.93 to 11.11; p = 0.001 in multivariate analysis). SN reclassified patients to their correct risk strata on top of other predictors of mortality. In 155 patients with ventricular arrhythmia-induced cardiac arrest, SN levels were also associated with short-term mortality (n = 51; hazard ratio [lnSN]: 3.33; 95% confidence interval: 1.83 to 6.05; p < 0.001 in multivariate analysis). Perfusing hearts with SN yielded markedly increased myocardial levels and SN internalized into cardiomyocytes by endocytosis. Intracellularly, SN reduced Ca(2+)/calmodulin (CaM)-dependent protein kinase II δ (CaMKIIδ) activity via direct SN-CaM and SN-CaMKII binding and attenuated CaMKIIδ-dependent phosphorylation of the ryanodine receptor. SN also reduced sarcoplasmic reticulum Ca(2+) leak, augmented sarcoplasmic reticulum Ca(2+) content, increased the magnitude and kinetics of cardiomyocyte Ca(2+) transients and contractions, and attenuated Ca(2+) sparks and waves in HF cardiomyocytes.CONCLUSIONS: SN provided incremental prognostic information to established risk indices in acute HF and ventricular arrhythmia-induced cardiac arrest.
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