Alexandra Vanessa Finsen

Inflammatory Cytokines in Heart Failure: Mediators and Markers

Evidence from both experimental and clinical trials indicates that inflammatory mediators are of importance in the pathogenesis of chronic heart failure (HF) contributing to cardiac remodeling and peripheral vascular disturbances. Several studies have shown raised levels of inflammatory cytokines such as tumor necrosis factor (TNF)α, interleukin (IL)-1β and IL-6 in HF patients in plasma and circulating leukocytes, as well as in the failing myocardium itself. There is strong evidence that these mediators are involved in processes leading to cardiac remodeling such as hypertrophy, fibrosis and apoptosis. Some of these cytokines can also give useful prognostic information as reliable biomarkers in this disorder. In general, immunomodulating treatments have, with a few exceptions, been neutral or even harmful. However, the negative results of anti-TNF studies, for instance, do not necessarily argue against the ‘cytokine hypothesis’. These studies just underscore the challenges in developing treatment modalities that can modulate the cytokine network in HF patients and result in beneficial net effects. Future studies should identify the crucial actors and their mechanisms of action in the immunopathogenesis of chronic HF and, in particular, clarify the balance between adaptive and maladaptive effects of these molecules. Such studies are a prerequisite for the development of new treatment strategies that target inflammatory and immunopathogenic mechanisms in HF. In this review article, these issues are thoroughly discussed, and we also argue for the possibility of future therapeutic targets such as mediators in innate immunity, chemokines and mediators in matrix remodeling.

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.

Moderate heart dysfunction in mice with inducible cardiomyocyte-specific excision of the Serca2 gene

The sarco(endo)plasmic reticulum calcium ATPase 2 (SERCA2) transports Ca(2+) from cytosol into the sarcoplasmic reticulum (SR) of cardiomyocytes, thereby maintaining the store of releasable Ca(2+) necessary for contraction. Reduced SERCA function has been linked to heart failure, and loss of SERCA2 in the adult mammalian heart would be expected to cause immediate severe myocardial contractile dysfunction and death. We investigated heart function in adult mice with an inducible cardiomyocyte-specific excision of the Atp2a2 (Serca2) gene (SERCA2 KO). Seven weeks after induction of Serca2 gene excision, the mice displayed a substantial reduction in diastolic function with a 5-fold increase in the time constant of isovolumetric pressure decay (tau). However, already at 4 weeks following gene excision less than 5% SERCA2 protein was found in myocardial tissue. Surprisingly, heart function was only moderately impaired at this time point. Tissue Doppler imaging showed slightly reduced peak systolic tissue velocity and a less than 2-fold increase in tau was observed. The SR Ca(2+) content was dramatically reduced in cardiomyocytes from 4-week SERCA2 KO mice, and Ca(2+) transients were predominantly generated by enhanced Ca(2+) flux through L-type Ca(2+) channels and the Na(+)-Ca(2+) exchanger. Moreover, equivalent increases in cytosolic [Ca(2+)] in control and SERCA2 KO myocytes induced greater cell shortening in SERCA2 KO, suggesting enhanced myofilament responsiveness. Our data demonstrate that SR-independent Ca(2+) transport mechanisms temporarily can prevent major cardiac dysfunction despite a major reduction of SERCA2 in cardiomyocytes.

Cytokine expression profiling of the myocardium reveals a role for CX3CL1 (fractalkine) in heart failure.

Several lines of evidence suggest that inflammatory processes mediated by cytokines are involved in the pathogenesis of heart failure (HF). However, the regulation of cytokine expression and the role of cytokines during HF development are not well understood. To address this issue, we have examined alterations in gene expression during HF progression by microarray technology in non-infarcted left ventricular (LV) murine tissue at various time points after myocardial infarction (MI). The highest number of regulated genes was found five days after MI. In total, we identified 14 regulated genes encoding cytokines with no previous association to HF. The strongest up-regulation was found for the chemokine fractalkine (CX3CL1). In human failing hearts we detected a 3-fold increase in CX3CL1 protein production, and both cardiomyocytes and fibrous tissue revealed immunoreactivity for CX3CL1 and its specific receptor CX3CR1. We also found that the circulating level of CX3CL1 was increased in patients with chronic HF in accordance with disease severity (1.6-fold in NYHA II, 2.2-fold in NYHA III and 2.9-fold in NYHA IV). In vitro experiments demonstrated that CX3CL1 production could be induced by inflammatory cytokines known to be highly expressed in HF. CX3CL1 itself induced the expression of markers of cardiac hypertrophy and protein phosphatases in neonatal cardiomyocytes. Given the increased CX3CL1 production in both an experimental HF model and in patients with chronic HF as well as its direct effects on cardiomyocytes, we suggest a role for CX3CL1 and its receptor CX3CR1 in the pathogenesis of HF.

Syndecan-4 Is Essential for Development of Concentric Myocardial Hypertrophy via Stretch-Induced Activation of the Calcineurin-NFAT Pathway

Sustained pressure overload leads to compensatory myocardial hypertrophy and subsequent heart failure, a leading cause of morbidity and mortality. Further unraveling of the cellular processes involved is essential for development of new treatment strategies. We have investigated the hypothesis that the transmembrane Z-disc proteoglycan syndecan-4, a co-receptor for integrins, connecting extracellular matrix proteins to the cytoskeleton, is an important signal transducer in cardiomyocytes during development of concentric myocardial hypertrophy following pressure overload. Echocardiographic, histochemical and cardiomyocyte size measurements showed that syndecan-4−/− mice did not develop concentric myocardial hypertrophy as found in wild-type mice, but rather left ventricular dilatation and dysfunction following pressure overload. Protein and gene expression analyses revealed diminished activation of the central, pro-hypertrophic calcineurin-nuclear factor of activated T-cell (NFAT) signaling pathway. Cardiomyocytes from syndecan-4−/−-NFAT-luciferase reporter mice subjected to cyclic mechanical stretch, a hypertrophic stimulus, showed minimal activation of NFAT (1.6-fold) compared to 5.8-fold increase in NFAT-luciferase control cardiomyocytes. Accordingly, overexpression of syndecan-4 or introducing a cell-permeable membrane-targeted syndecan-4 polypeptide (gain of function) activated NFATc4 in vitro. Pull-down experiments demonstrated a direct intracellular syndecan-4-calcineurin interaction. This interaction and activation of NFAT were increased by dephosphorylation of serine 179 (pS179) in syndecan-4. During pressure overload, phosphorylation of syndecan-4 was decreased, and association between syndecan-4, calcineurin and its co-activator calmodulin increased. Moreover, calcineurin dephosphorylated pS179, indicating that calcineurin regulates its own binding and activation. Finally, patients with hypertrophic myocardium due to aortic stenosis had increased syndecan-4 levels with decreased pS179 which was associated with increased NFAT activation. In conclusion, our data show that syndecan-4 is essential for compensatory hypertrophy in the pressure overloaded heart. Specifically, syndecan-4 regulates stretch-induced activation of the calcineurin-NFAT pathway in cardiomyocytes. Thus, our data suggest that manipulation of syndecan-4 may provide an option for therapeutic modulation of calcineurin-NFAT signaling.

Increased Production of CXCL16 in Experimental and Clinical Heart Failure: A Possible Role in Extracellular Matrix Remodeling

Background—Inflammation has been implicated in the pathogenesis of heart failure (HF), but knowledge about the production and role of inflammatory actors remains incomplete. On the basis of its role in vascular inflammation, vascular proliferation, and matrix degradation, we hypothesized a role for the chemokine CXCL16 in the pathogenesis of myocardial remodeling and development of HF. Methods and Results—Our main findings were (1) patients with chronic HF (n=188) had increased plasma levels of CXCL16, which correlated with disease severity. (2) Left ventricular tissue from patients with end-stage HF (n=8) showed enhanced CXCL16 levels compared with nonfailing left ventricular (n=6) as assessed by Western blotting. (3) In mice with postmyocardial infarction HF, expression of CXCL16, as assessed by real-time RT-PCR, was increased in the infarcted and the noninfarcted areas of left ventricular 3 and 7 days after coronary ligation, indicating early onset of CXCL16 production. Furthermore, mice exposed to aortic banding had enhanced CXCL16 expression in left ventricular, indicating that CXCL16 expression is not related to ischemia alone. (4) In vitro, CXCL16 promoted proliferation and impaired collagen synthesis in myocardial fibroblasts, and in cardiomyocytes and myocardial fibroblasts, CXCL16 increased matrix metalloproteinase activity, primarily reflecting increased matrix metalloproteinase-2 levels. (5) By using specific inhibitors, we showed that the effect of CXCL16 on fibroblasts involved activation of Jun N-terminal kinase. Conclusion—We show enhanced myocardial CXCL16 expression in experimental and clinical HF. The effect of CXCL16 on cardiomyocytes and fibroblasts suggests a role for CXCL16 in matrix remodeling and ultimately in the development of HF.Background— Inflammation has been implicated in the pathogenesis of heart failure (HF), but knowledge about the production and role of inflammatory actors remains incomplete. On the basis of its role in vascular inflammation, vascular proliferation, and matrix degradation, we hypothesized a role for the chemokine CXCL16 in the pathogenesis of myocardial remodeling and development of HF. Methods and Results— Our main findings were (1) patients with chronic HF (n=188) had increased plasma levels of CXCL16, which correlated with disease severity. (2) Left ventricular tissue from patients with end-stage HF (n=8) showed enhanced CXCL16 levels compared with nonfailing left ventricular (n=6) as assessed by Western blotting. (3) In mice with postmyocardial infarction HF, expression of CXCL16, as assessed by real-time RT-PCR, was increased in the infarcted and the noninfarcted areas of left ventricular 3 and 7 days after coronary ligation, indicating early onset of CXCL16 production. Furthermore, mice exposed to aortic banding had enhanced CXCL16 expression in left ventricular, indicating that CXCL16 expression is not related to ischemia alone. (4) In vitro, CXCL16 promoted proliferation and impaired collagen synthesis in myocardial fibroblasts, and in cardiomyocytes and myocardial fibroblasts, CXCL16 increased matrix metalloproteinase activity, primarily reflecting increased matrix metalloproteinase-2 levels. (5) By using specific inhibitors, we showed that the effect of CXCL16 on fibroblasts involved activation of Jun N-terminal kinase. Conclusion— We show enhanced myocardial CXCL16 expression in experimental and clinical HF. The effect of CXCL16 on cardiomyocytes and fibroblasts suggests a role for CXCL16 in matrix remodeling and ultimately in the development of HF. Received September 11, 2008; accepted July 27, 2009.

Collagen isoform shift during the early phase of reverse left ventricular remodelling after relief of pressure overload

AIMS Aortic stenosis induces pressure overload and myocardial remodelling with concentric hypertrophy and alterations in extracellular matrix (ECM). Aortic valve replacement leads to reverse remodelling, a process of which knowledge is scarce. The aims of the present study were to examine alterations in myocardial gene expression and subsequently identify molecular alterations important for the early phase of reverse remodelling. METHODS AND RESULTS After 4 weeks of ascending aortic banding, mice were subjected to a debanding operation (DB) and followed for 3, 7, or 14 days. Cardiac function was assessed by echocardiography/tissue Doppler ultrasonography. Myocardial gene expression was examined using Affymetrix microarray and the topGO software and verified by real-time polymerase chain reaction. Quantitative measurements of collagen subtypes were performed. Aortic banding increased left ventricular mass by 60%, with normalization to sham level 14 days after DB. Extracellular matrix genes were the most regulated after DB. Three days after DB, collagen I was transiently increased, whereas collagens III and VIII increased later at 7 days. CONCLUSION The ECM genes were the most altered during reverse remodelling. There was a change in isoform constitution as collagen type I increased transiently at 3 days followed by a later increase in types III and VIII at 7 days after DB. This might be important for the biomechanical properties of the heart and recovery of cardiac function.

Mice carrying a conditional Serca2flox allele for the generation of Ca2+ handling-deficient mouse models

Sarco(endo)plasmic reticulum calcium ATPases (SERCA) are cellular pumps that transport Ca(2+) into the sarcoplasmic reticulum (SR). Serca2 is the most widely expressed gene family member. The very early embryonic lethality of Serca2(null) mouse embryos has precluded further evaluation of loss of Serca2 function in the context of organ physiology. We have generated mice carrying a conditional Serca2(flox) allele which allows disruption of the Serca2 gene in an organ-specific and/or inducible manner. The model was tested by mating Serca2(flox) mice with MLC-2v(wt/Cre) mice and with alphaMHC-Cre transgenic mice. In heterozygous Serca2(wt/flox)MLC-2v(wt/Cre) mice, the expression of SERCA2a and SERCA2b proteins were reduced in the heart and slow skeletal muscle, in accordance with the expression pattern of the MLC-2v gene. In Serca2(flox/flox) Tg(alphaMHC-Cre) embryos with early homozygous cardiac Serca2 disruption, normal embryonic development and yolk sac circulation was maintained up to at least embryonic stage E10.5. The Serca2(flox) mouse is the first murine conditional gene disruption model for the SERCA family of Ca(2+) ATPases, and should be a powerful tool for investigating specific physiological roles of SERCA2 function in a range of tissues and organs in vivo both in adult and embryonic stages.

Chromogranin B in heart failure: a putative cardiac biomarker expressed in the failing myocardium.

Background—Chromogranin B (CgB) is a member of the granin protein family. Because CgB is often colocalized with chromogranin A (CgA), a recently discovered cardiac biomarker, we hypothesized that CgB is regulated during heart failure (HF) development. Methods and Results—CgB regulation was investigated in patients with chronic HF and in a post–myocardial infarction HF mouse model. Animals were phenotypically characterized by echocardiography and euthanized 1 week after myocardial infarction. CgB mRNA levels were 5.2-fold increased in the noninfarcted part of the left ventricle of HF animals compared with sham-operated animals (P<0.001). CgB mRNA level in HF animals correlated closely with animal lung weight (r=0.74, P=0.04) but not with CgA mRNA levels (r=0.20, P=0.61). CgB protein levels were markedly increased in both the noninfarcted (110%) and the infarcted part of the left ventricle (70%) but unaltered in other tissues investigated. Myocardial CgB immunoreactivity was confined to cardiomyocytes. Norepinephrine, angiotensin II, and transforming growth factor-&bgr; increased CgB gene expression in cardiomyocytes. Circulating CgB levels were increased in HF animals (median levels in HF animals versus sham, 1.23 [interquartile range, 1.03 to 1.93] versus 0.98 [0.90 to 1.04] nmol/L; P=0.003) and in HF patients (HF patients versus control, 1.66 [1.48 to 1.85] versus 1.47 [1.39 to 1.58] nmol/L; P=0.007), with levels increasing in proportion to New York Heart Association functional class (P=0.03 for trend). Circulating CgB levels were only modestly correlated with CgA (r=0.31, P=0.009) and B-type natriuretic peptide levels (r=0.27, P=0.014). Conclusions—CgB production is increased and regulated in proportion to disease severity in the left ventricle and circulation during HF development.Background— Chromogranin B (CgB) is a member of the granin protein family. Because CgB is often colocalized with chromogranin A (CgA), a recently discovered cardiac biomarker, we hypothesized that CgB is regulated during heart failure (HF) development. Methods and Results— CgB regulation was investigated in patients with chronic HF and in a post–myocardial infarction HF mouse model. Animals were phenotypically characterized by echocardiography and euthanized 1 week after myocardial infarction. CgB mRNA levels were 5.2-fold increased in the noninfarcted part of the left ventricle of HF animals compared with sham-operated animals ( P <0.001). CgB mRNA level in HF animals correlated closely with animal lung weight ( r =0.74, P =0.04) but not with CgA mRNA levels ( r =0.20, P =0.61). CgB protein levels were markedly increased in both the noninfarcted (110%) and the infarcted part of the left ventricle (70%) but unaltered in other tissues investigated. Myocardial CgB immunoreactivity was confined to cardiomyocytes. Norepinephrine, angiotensin II, and transforming growth factor-β increased CgB gene expression in cardiomyocytes. Circulating CgB levels were increased in HF animals (median levels in HF animals versus sham, 1.23 [interquartile range, 1.03 to 1.93] versus 0.98 [0.90 to 1.04] nmol/L; P =0.003) and in HF patients (HF patients versus control, 1.66 [1.48 to 1.85] versus 1.47 [1.39 to 1.58] nmol/L; P =0.007), with levels increasing in proportion to New York Heart Association functional class ( P =0.03 for trend). Circulating CgB levels were only modestly correlated with CgA ( r =0.31, P =0.009) and B-type natriuretic peptide levels ( r =0.27, P =0.014). Conclusions— CgB production is increased and regulated in proportion to disease severity in the left ventricle and circulation during HF development.

The Homeostatic Chemokine CCL21 Predicts Mortality and May Play a Pathogenic Role in Heart Failure

Background CCL19 and CCL21, acting through CCR7, are termed homeostatic chemokines. Based on their role in concerting immunological responses and their proposed involvement in tissue remodeling, we hypothesized that these chemokines could play a pathogenic role in heart failure (HF). Methodology/Principal Findings Our main findings were: (i) Serum levels of CCL19 and particularly CCL21 were markedly raised in patients with chronic HF (n = 150) as compared with healthy controls (n = 20). A CCL21 level above median was independently associated with all-cause mortality. (ii) In patients with HF following acute myocardial infarction (MI; n = 232), high versus low CCL21 levels 1 month post-MI were associated with cardiovascular mortality, even after adjustment for established risk factors. (iii). Explanted failing human LV tissue (n = 29) had markedly increased expression of CCL21 as compared with non-failing myocardium (n = 5). (iv) Our studies in CCR7−/− mice showed improved survival and attenuated increase in markers of myocardial dysfunction and wall stress in post-MI HF after 1 week, accompanied by increased myocardial expression of markers of regulatory T cells. (v) Six weeks post-MI, there was an increase in markers of myocardial dysfunction and wall stress in CCR7 deficient mice. Conclusions/Significance High serum levels of CCL21 are independently associated with mortality in chronic and acute post-MI HF. Our findings in CCR7 deficient mice may suggest that CCL21 is not only a marker, but also a mediator of myocardial failure. However, while short term inhibition of CCR7 may be beneficial following MI, a total lack of CCR7 during long-term follow-up could be harmful.