Specialized pro-resolving mediators (SPMs) are key effectors of resolution of inflammation. This is highly relevant for cardiac and vessel remodeling, where the net inflammatory response contributes to determine disease outcome. Herein, we used a mice model of angiotensin (Ang)-II-induced hypertension to study the effect of the SPM Resolvin D2 (RvD2), on hypertension and cardiac remodeling. By using subcutaneous osmotic minipumps, mice were treated with PBS or Ang-II in combination with or without RvD2 for two weeks. Mice receiving RvD2 gained less blood pressure increase compared to Ang-II alone. Surprisingly, however, examination of intracardiac arteries revealed that RvD2 treatment in combination with Ang-II exacerbated Ang-II-induced fibrosis. Measures of vascular smooth muscle cell dedifferentiation correlated with the level of vascular remodeling, indicating that this dedifferentiation, including increased proliferation and migration, is a contributing factor. RNA sequencing of left ventricle cardiac tissue supported these findings as pathways related to cell proliferation and cell differentiation were upregulated in mice treated with Ang-II in combination with RvD2. Additionally, the RNA sequencing also showed upregulation of pathways related to SPM metabolism. In line with this, Mass spectrometry analysis of lipid mediators showed reduced cardiac levels of the arachidonic acid derived metabolite leukotriene E4 in RvD2 treated mice. Our study suggests that continuous infusion through osmotic minipumps should not be the recommended route of RvD2 administration in future studies.

Background: Patients with rheumatoid arthritis face an elevated risk of developing heart failure (HF), but the cardiac prerequisites and disease mechanisms are unknown. Objectives: This study employed experimental models of chronic arthritis and HF to explore the cardiac effects of arthritis-induced chronic inflammation on HF development. Methods: Rheumatoid arthritis-like phenotype was induced by delayed-type hypersensitivity arthritis (DTHA) in male BALB/c mice (n=29). Control mice received vehicle injections (n=29). The DTHA protocol includes 1) immunization towards methylated bovine serum albumin (mBSA) 2) intravenous injection of mixed anti-collagen II antibodies, and finally 3) release of local arthritis by hind-leg subcutaneous mBSA injection. Three days after induction of arthritis, the mice in both the DTHA group and controls were randomized to HF surgery (n=16 in both groups) or sham surgery (n=13 in both groups). HF was induced via thoracotomy and placement of a constricting o-ring around the ascending aorta. Step 2 and 3 of the DTHA protocol were repeated weekly for 8 consecutive weeks to uphold inflammation. Cardiac magnetic resonance imaging (MRI) was performed 12 and 54 days after surgery, with subsequent euthanization and harvesting of blood and tissue. Results: We found evidence of fluctuating, yet sustained local and systemic inflammation after induction of experimental arthritis, and clear development of HF after surgery. Mice with both arthritis and HF exhibited significantly increased mortality compared to the HF group without arthritis (p=0.04). Increased levels of brain natriuretic peptide (BNP) in cardiac tissue (p=0.03), suggests worsening of HF as cause of this observation. However, no significant functional differences were detected on cardiac MRI. Conclusion: Chronic systemic inflammation mediated by limb-restricted arthritis increased mortality in mice with HF induced by aortic constriction. Even though statistically significant increments of BNP were found, the cause of observed increased mortality remains elusive, as no functional differences could be found on MRI. REFERENCES: NIL. Acknowledgements: The authors wish to thank Merete Høyem for expert technical assistance. Disclosure of Interests: None declared.

Department of Medicine, Diakonhjemmet Hospital, Oslo, Norway Institute for Surgical Research, Oslo University Hospital, Oslo, Norway Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway Research Institute of Internal Medicine, Oslo University Hospital, Oslo, Norway Institute for Experimental Medical Research and KG Jebsen Center for Cardiac Research, Oslo University Hospital and University of Oslo, Oslo, Norway

AIMS:Patients with rheumatoid arthritis (RA) have increased risk of heart failure (HF). The mechanisms and cardiac prerequisites explaining this association remain unresolved. In this study, we sought to determine the potential cardiac impact of an experimental model of RA in mice subjected to HF by constriction of the ascending aorta.METHODS:Aorta was constricted via thoracotomy and placement of o-rings with inner diameter 0.55 mm or 0.66 mm, or sham operated. RA-like phenotype was instigated by delayed-type hypersensitivity arthritis (DTHA) two weeks after surgery and re-iterated after additional 18 days. Cardiac magnetic resonance imaging (MRI) was performed before surgery and at successive time points throughout the study. Six weeks after surgery the mice were euthanized, blood and tissue were collected, organ weights were documented, and expression levels of cardiac foetal genes were analysed. In a supplemental study, DTHA-mice were euthanized throughout 14 days after induction of arthritis, and blood was analysed for important markers and mediators of RA (SAP, TNF-α and IL-6). In order to put the latter findings into clinical context, the same molecules were analysed in serum from untreated RA patients and compared to healthy controls.RESULTS:Significant elevations of inflammatory markers were found in both patient- and murine blood. Furthermore, the DTHA model appeared clinically relevant when compared to the inflammatory responses observed in three prespecified RA severity disease states. Two distinct trajectories of cardiac dysfunction and HF development were found using the two o-ring sizes. These differences were consistent by both MRI, organ weights and cardiac foetal gene expression levels. Still, no difference within the HF groups, nor within the sham groups, could be found when DTHA was induced.CONCLUSION:DTHA mediated systemic inflammation did not cause, nor modify HF caused by aortic constriction. This indicates other prerequisites for RA-induced cardiac dysfunction.

BACKGROUND:Although very rare, cardiac sarcoma is the most common malignant cardiac tumour. Cardiac tumours may present with constitutional symptoms and this can lead to delayed diagnosis.CASE PRESENTATION:A woman in her late twenties was admitted to the acute psychiatric ward with suspected depressive psychosis. Although she presented with insomnia, auditory hallucinosis and paranoid delusions, her main symptoms were dyspnoea, tachycardia and exhaustion. She was discharged after 17 days and admitted directly to the medical ward for further examination. A thorough somatic examination, including diagnostic imaging, revealed a tumour in the left atrium obstructing the mitral ostium in the diastole, resulting in orthopnoea. She had urgent cardiac surgery and the histology was consistent with an intimal sarcoma.INTERPRETATION:This case illustrates a rare disease presenting with atypical symptoms. Her psychiatric symptoms resolved after surgery and oncologic treatment of her cardiac tumour.

BACKGROUND Although very rare, cardiac sarcoma is the most common malignant cardiac tumour. Cardiac tumours may present with constitutional symptoms and this can lead to delayed diagnosis. CASE PRESENTATION A woman in her late twenties was admitted to the acute psychiatric ward with suspected depressive psychosis. Although she presented with insomnia, auditory hallucinosis and paranoid delusions, her main symptoms were dyspnoea, tachycardia and exhaustion. She was discharged after 17 days and admitted directly to the medical ward for further examination. A thorough somatic examination, including diagnostic imaging, revealed a tumour in the left atrium obstructing the mitral ostium in the diastole, resulting in orthopnoea. She had urgent cardiac surgery and the histology was consistent with an intimal sarcoma. INTERPRETATION This case illustrates a rare disease presenting with atypical symptoms. Her psychiatric symptoms resolved after surgery and oncologic treatment of her cardiac tumour.

Background: Identification of novel biomarkers could provide prognostic information and improve risk stratification in patients with aortic stenosis (AS). YKL-40 (chitinase-3-like protein 1), a protein involved in atherogenesis, is upregulated in human calcific aortic valves. We hypothesized that circulating YKL-40 would be elevated and associated with the degree of AS severity and outcome in patients with symptomatic AS. Methods: Plasma YKL-40 was analyzed in 2 AS populations, one severe AS (n=572) with outcome measures and one with mixed severity (n=67). YKL-40 expression in calcified valves and in an experimental pressure overload model was assessed. Results: We found (1) patients with AS had upregulated circulating YKL-40 compared with healthy controls (median 109 versus 34 ng/mL, P <0.001), but levels were not related to the degree of AS severity. (2) High YKL-40 levels (quartile 4) were associated with long-term (median follow-up 4.7 years) all-cause mortality (adjusted hazard ratio, 1.93 [95% CI, 1.37–2.73], P <0.001). (3) YKL-40 protein expression in human calcific valves co-localized with its putative receptor IL-13rα2 in close proximity to valve interstitial cells. (4) Myocardial YKL-40 increased in experimental pressure overload (6-fold in decompensated versus sham mice). Conclusions: YKL-40 levels were elevated in AS and associated with mortality but not with other metrics of disease severity including the degree of AS severity. Despite scientific rationale for its role in AS, the clinical utility of circulating YKL-40 as a biomarker is limited. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01794832.

Background: IL-1β is a highly potent pro-inflammatory cytokine and its secretion is tightly regulated. Inactive pro-IL-1β is transcribed in response to innate immune receptors activating NFκB. If tissue damage occurs, danger signals released from necrotic cells, such as ATP, can activate NLRP3-inflammasomes (multiprotein complexes consisting of NLRP3, ASC, and active caspase-1) which cleaves and activates pro-IL-1β. NLRP3 activation also depends on NEK7 and mitochondrial ROS-production. Thus, IL-1β secretion may be regulated at the level of each involved component. We have previously shown that NLRP3-dependent IL-1β release can be induced in cardiac fibroblasts by pro-inflammatory stimuli. However, anti-inflammatory mechanisms targeting IL-1β release in cardiac cells have not been investigated. mTOR is a key regulator of protein metabolism, including autophagy and proteasome activity. In this study we explored whether autophagy or proteasomal degradation are regulators of NLRP3 inflammasome activation and IL-1β release from cardiac fibroblasts. Methods and Results: Serum starvation selectively reduced LPS/ATP-induced IL-1β secretion from cardiac fibroblasts. However, no other inflammasome components, nor mitochondrial mass, were affected. The mTOR inhibitor rapamycin restored pro-IL-1β protein levels as well as LPS/ATP-induced IL-1β release from serum starved cells. However, neither serum starvation nor rapamycin induced autophagy in cardiac fibroblasts. Conversely, chloroquine and bafilomycin A (inhibitors of autophagy) and betulinic acid (a proteasome activator) effectively reduced LPS-induced pro-IL-1β protein levels. Key findings were reinvestigated in human monocyte-derived macrophages. Conclusion: In cardiac fibroblasts, mTOR inhibition selectively favors pro-IL-1β synthesis while proteasomal degradation and not autophagy is the major catabolic anti-inflammatory mechanism for degradation of this cytokine.

BACKGROUND:Depression and anxiety are common in patients with cardiac disease and predict a poorer prognosis, increased mortality and reduced compliance with treatment. National and international guidelines recommend procedures for screening, but there is a lack of studies of such practices in Norwegian hospitals. The objective of this study was to implement a simple screening method for symptoms of depression and anxiety in patients with cardiac disease.MATERIAL AND METHOD:Patients in the Department of Cardiology at Diakonhjemmet Hospital who had valvular heart disease, tachyarrhythmia, myocardial infarction or heart failure were screened for symptoms of depression, anxiety and panic attacks with the aid of five questions from the Patient Health Questionnaire-2 (PHQ-2), Generalized Anxiety Disorder Scale-2 (GAD-2) and Patient Health Questionnaire - Somatic, Anxiety, and Depressive Symptom Scales (PHQ-SADS). The patients were recruited from the outpatient clinic or ward at least one month after acute heart disease.RESULTS:A total of 57 of 232 patients reported symptoms of depression or anxiety when screened. The screening method was easy to implement, but time constraints and uncertainty regarding procedures for follow-up and the effect of following up the patients were reported.INTERPRETATION:Good tools and methods are available for screening for symptoms of depression and anxiety and anxiety in patients with cardiac disease. More studies are needed regarding the benefits of screening, at what stage of the disease it should be performed, and whether it should be performed by the primary and/or the specialist health services.

Background: Termination of acute inflammation is an active process orchestrated by lipid mediators (LM) derived from polyunsaturated fatty acids, referred to as specialized pro-resolving mediators (SPM). These mediators also provide novel therapeutic opportunities for treating inflammatory disease. However, the regulation of these molecules following acute myocardial infarction (MI) remains of interest. Methods: In this prospective observational study we aimed to profile plasma levels of SPMs in ST-elevation MI (STEMI) patients during the first week following MI. Plasma LM concentrations were measured in patients with STEMI (n = 15) at three time points and compared with stable coronary artery disease (CAD; n = 10) and healthy controls (n = 10). Findings: Our main findings were: (i) Immediately after onset of MI and before peak troponin T levels, STEMI patients had markedly increased levels of SPMs as compared with healthy controls and stable CAD patients, with levels of these mediators declining during follow-up. (ii) The increase in SPMs primarily reflected an increase in docosapentaenoic acid- and docosahexaenoic add-derived protectins. (iii) Several individual protectins were correlated with the rapid increase in neutrophil counts, but not with CRP. (iv) A shift in 5-LOX activity from the leukotriene B4 pathway to the pro-resolving RvTs was observed. Interpretation: The temporal regulation of SPMs indicates that resolution mechanisms are activated early during STEMI as part of an endogenous mechanism to initiate repair. Thus strategies to boost the activity and/or efficacy of these endogenous mechanisms may represent novel therapeutic opportunities for treatment of patients with MI.

Aim. Inflammation is important in heart failure (HF). The role of the immune receptor toll-like receptor 9 (TLR9) in HF is not understood and not investigated in diastolic HF. We investigated the role of TLR9 in a murine diastolic HF model caused by cardiomyocyte SERCA2a excision. Methods and Results. We crossed SERCA2a KO and TLR9 KO mice to generate four mouse lines. Tamoxifen-induced cardiomyocyte SERCA2a gene excision was carried out in mice, causing diastolic HF. After 7.6 weeks, cardiac functions and dimensions were analyzed by echocardiography and heart tissues were processed. HF mice depleted of TLR9 demonstrated reduced survival compared to SERC2a KO mice, with a median life expectancy of 58 days compared to 63 days. Both HF groups displayed increased left atrium size, lung weight, fetal gene expressions, monocyte/macrophage infiltration, and fibrosis. However, there were no significant differences between the groups. Conclusion. In mice with SERCA2a KO-induced diastolic HF, the absence of TLR9 reduced median life expectancy. The cause remains elusive, as all investigated HF parameters were unaltered. Still, these findings support a salutary role of TLR9 in some subsets of HF conditions and underline the importance for future studies on the mechanisms of TLR9 in diastolic HF.

Myocardial infarction (MI) triggers a reparative response involving fibroblast proliferation and differentiation driving extracellular matrix modulation necessary to form a stabilizing scar. Recently, it was shown that a genetic variant of the base excision repair enzyme NEIL3 was associated with increased risk of MI in humans. Here, we report elevated myocardial NEIL3 expression in heart failure patients and marked myocardial upregulation of Neil3 after MI in mice, especially in a fibroblast-enriched cell fraction. Neil3-/- mice show increased mortality after MI caused by myocardial rupture. Genome-wide analysis of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) reveals changes in the cardiac epigenome, including in genes related to the post-MI transcriptional response. Differentially methylated genes are enriched in pathways related to proliferation and myofibroblast differentiation. Accordingly, Neil3-/- ruptured hearts show increased proliferation of fibroblasts and myofibroblasts. We propose that NEIL3-dependent modulation of DNA methylation regulates cardiac fibroblast proliferation and thereby affects extracellular matrix modulation after MI.

Palmitate triggers inflammatory responses in several cell types, but its effects on cardiac fibroblasts are at present unknown. The aims of the study were to (1) assess the potential of palmitate to promote inflammatory signaling in cardiac fibroblasts through TLR4 and the NLRP3 inflammasome and (2) characterize the cellular phenotype of cardiac fibroblasts exposed to palmitate. We examined whether palmitate induces inflammatory responses in cardiac fibroblasts from WT, NLRP3-/- and ASC-/-mice (C57BL/6 background). Exposure to palmitate caused production of TNF, IL-6 and CXCL2 via TLR4 activation. NLRP3 inflammasomes are activated in a two-step manner. Whereas palmitate did not prime the NLRP3 inflammasome, it induced activation in LPS-primed cardiac fibroblasts as indicated by IL-1β, IL-18 production and NLRP3-ASC co-localization. Palmitate-induced NLRP3 inflammasome activation in LPS-primed cardiac fibroblasts was associated with reduced AMPK activity, mitochondrial reactive oxygen species production and mitochondrial dysfunction. The cardiac fibroblast phenotype caused by palmitate, in an LPS and NLRP3 independent manner, was characterized by decreased cellular proliferation, contractility, collagen and MMP-2 expression, as well as increased senescence-associated β-galactosidase activity, and consistent with a state of cellular senescence. This study establishes that in vitro palmitate exposure of cardiac fibroblasts provides inflammatory responses via TLR4 and NLRP3 inflammasome activation. Palmitate also modulates cardiac fibroblast functionality, in a NLRP3 independent manner, resulting in a phenotype related to cellular senescence. These effects of palmitate could be of importance for myocardial dysfunction in obese and diabetic patients.

Wnt signaling is dysregulated in heart failure (HF) and may promote cardiac hypertrophy, fibrosis, and inflammation. Blocking the Wnt ligand Wnt5a prevents HF in animal models. However, the role of Wnt5a in human HF and its functions in cardiac cells remain unclear. Here, we investigated Wnt5a regulation in HF patients and its effects on primary mouse and human cardiac fibroblasts. Serum Wnt5a was elevated in HF patients and associated with hemodynamic, neurohormonal, and clinical measures of disease severity. In failing human hearts, Wnt5a protein correlated with interleukin (IL)-6 and tissue inhibitor of metalloproteinase (TIMP)-1. Wnt5a messenger RNA (mRNA) levels were markedly upregulated in failing myocardium and both mRNA and protein levels declined following left ventricular assist device therapy. In primary mouse and human cardiac fibroblasts, recombinant Wnt5a dose-dependently upregulated mRNA and protein release of IL-6 and TIMP-1. Wnt5a did not affect β-catenin levels, but activated extracellular signal-regulated kinase 1/2 (ERK1/2) signaling. Importantly, inhibition of ERK1/2 activation attenuated Wnt5a-induced release of IL-6 and TIMP-1. In conclusion, our results show that Wnt5a is elevated in the serum and myocardium of HF patients and is associated with measures of progressive HF. Wnt5a induces IL-6 and TIMP-1 in cardiac fibroblasts, which might promote myocardial inflammation and fibrosis, and thereby contribute to HF progression. Key messages • Wnt5a is elevated in serum and myocardium of HF patients and is associated with measures of progressive HF. • In cardiac fibroblasts, Wnt5a upregulates interleukin (IL)-6 and tissue inhibitor of metalloproteinase (TIMP)-1 through the ERK pathway. • Wnt5a-mediated effects might promote myocardial inflammation and fibrosis, and thereby contribute to HF progression.

Background: Mitochondrial DNA (mtDNA) and possibly nuclear DNA (nDNA) are released as danger associated molecular patterns during cardiac stress, and may activate several innate immune receptors. The purpose of this study was to investigate the regulation of these danger-associated molecular patterns during human heart failure (HF).Methods and Results: Plasma levels of mtDNA and nDNA from HF patients (n = 84) were analyzed by reverse transcriptase-polymerase chain reaction and compared with controls (n = 72). Increased levels of mtDNA were found in New York Heart Association (NYHA) I-II and NYHA III-IV. There was evidence of increased nDNA in NYHA III-IV compared with controls and NYHA I-II. Kaplan-Meier analysis revealed higher mortality in patients with high nDNA levels, whereas high levels of mtDNA were associated with survival.Conclusions: Plasma levels of mtDNA and nDNA are elevated in human HF associated with increased and decreased mortality, respectively. This study may suggest a rationale for exploring interventions within inflammatory signaling pathways activated by nucleic acids as novel targets in treatment of HF.

Background: Adipose tissue has endocrine properties, secreting a wide range of mediators into the circulation, including factors involved in cardiovascular disease. However, little is known about the potential role of adipose tissue in heart failure (HF), and the aim of this study was to investigate epicardial (EAT) and subcutaneous (SAT) adipose tissue in HF patients.Methods and Results: Thirty patients with systolic HF and 30 patients with normal systolic function undergoing thoracic surgery were included in the study. Plasma was sampled and examined with the use of enzyme-linked immunosorbent assays, whereas SAT and EAT biopsies were collected and examined by means of reverse-transcription polymerase chain reaction and gas chromatography. Significantly higher expressions of mRNA encoding interleukin-6, adrenomedullin, peroxisome proliferator activated receptor a, and fatty acid (FA) binding protein 3, as well as higher levels of monounsaturated FA and palmitoleic acid, were seen in the EAT of HF patients, whereas the levels of docosahexaenoic acid were lower. Palmitoleic acid levels in EAT were correlated with 2 parameters of cardiac remodeling: increasing left ventricular end-diastolic diameter and N-terminal pro B-type natriuretic peptide.Conclusions: Our results demonstrate adipose tissue depot specific alterations of synthesis of FA and inflammatory and metabolic mediators in systolic HF patients. EAT may be a source of increased circulatory and myocardial levels of these mediators through endocrine actions.

AIM:Cardiac inflammation is important in the pathogenesis of heart failure. However, the consequence of systemic inflammation on concomitant established heart failure, and in particular diastolic heart failure, is less explored. Here we investigated the impact of systemic inflammation, caused by sustained Toll-like receptor 9 activation, on established diastolic heart failure.METHODS AND RESULTS:Diastolic heart failure was established in 8-10 week old cardiomyocyte specific, inducible SERCA2a knock out (i.e., SERCA2a KO) C57Bl/6J mice. Four weeks after conditional KO, mice were randomized to receive Toll-like receptor 9 agonist (CpG B; 2μg/g body weight) or PBS every third day. After additional four weeks, echocardiography, phase contrast magnetic resonance imaging, histology, flow cytometry, and cardiac RNA analyses were performed. A subgroup was followed, registering morbidity and death. Non-heart failure control groups treated with CpG B or PBS served as controls. Our main findings were: (i) Toll-like receptor 9 activation (CpG B) reduced life expectancy in SERCA2a KO mice compared to PBS treated SERCA2a KO mice. (ii) Diastolic function was lower in SERCA2a KO mice with Toll-like receptor 9 activation. (iii) Toll-like receptor 9 stimulated SERCA2a KO mice also had increased cardiac and systemic inflammation.CONCLUSION:Sustained activation of Toll-like receptor 9 causes cardiac and systemic inflammation, and deterioration of SERCA2a depletion-mediated diastolic heart failure.

BACKGROUND:The innate immune receptor NLRP3 recognizes tissue damage and initiates inflammatory processes through formation multiprotein complexes with the adaptor protein ASC and caspase-1, i.e. NLRP3 inflammasomes, which through cleavage of pro-IL-1β mediates release of bioactive IL-1β. We hypothesized that NLRP3 mediates tissue damage during acute myocardial infarction (MI) and sought to investigate the mechanisms herein in an experimental MI model in mice. METHODS AND RESULTS:The left coronary artery (LCA) of WT, NLRP3(-/-) and ASC(-/-) mice of both genders was ligated for 30 min followed by 3 or 24 h reperfusion. For pre-conditioning studies, the TLR2 agonist Pam3CSK4 or PBS was injected intraperitoneally 60 min prior to LCA ligation. For mechanistic investigations, blood plasmas and left ventricle tissues were collected, and a hypothesis-driven selection of protein or mRNA targets was investigated. Surprisingly, hearts from NLRP3-deficient mice featured larger infarct size than WT mice (p = 0.0048). In general, there were only modest changes with no significant pattern in myocardial infiltration of neutrophils and macrophages and systemic and myocardial cytokine expression between the three genotypes. Preconditioning with the TLR2 agonist Pam3CSK4 induced Akt phosphorylation and reduced infarct size in WT but not NLRP3 -or ASC -deficient hearts. CONCLUSION:Absence of NLRP3 results in increased myocardial infarct size after in vivo ischemia reperfusion, seemingly due to dysfunction of the cardioprotective RISK pathway. Our data imply that NLRP3 contributes to cardio-protection during I/R and do not support a role for NLRP3 or ASC inhibition in the management of acute MI including revascularization therapy.

Accumulation of DNA damage due to impaired base excision repair (BER) may play a role in the pathogenesis of myocardial failure. The DNA glycosylase Neil3 is known to carry out BER during oxidative stress induced DNA damage, but is also thought to have a role in stem cell biology. Based on this, we hypothesized that Neil3 plays a role in myocardial remodeling during heart failure (HF). qPCR showed an increased expression of Neil3 in myocardial biopsies from patients with severe HF, and that the Neil3 expression significantly decreased following improvement of myocardial function following treatment with left ventricular assist device. In a murine model of myocardial infarction (MI) we found a strong upregulation of Neil3 on day 3, 7 and 21 after MI. At day 7, myocardial cell isolation revealed a low Neil3 expression in cardiomyocytes, while a 2.5- and a 4.5-fold increased expression was found in endothelial cells and fibroblasts, respectively, following MI compared to sham. In leukocytes an equally high expression of Neil3 was observed in both sham and MI. Using Neil3 knock-out (KO) mice we found a significantly higher mortality in KO compared to wild type (WT) mice after MI ( 73% vs. 40%), despite smaller infarct sizes in the Neil3 KO, as determined by MRI. The first week post MI, all animals died from cardiac rupture. Zymography on protein extracts from the infarcted tissue revealed significantly increased levels of MMP2 in the Neil3 KO, 3 days after MI. Immunohistochemistry (IHC), at the same time point, showed similar numbers of inflammatory cells measured by the presence of Ly6G+ neutrophils, Mac2+ monocytes/macrophages and CD45+ leukocytes. At day 6 a significantly higher number of Ki67+ proliferating cells were observed in the Neil3 KO infarcted areas. In accordance with this, primary cardiac fibroblasts lacking Neil3 showed a higher proliferation rate, measured both by BrdU and scrape wound assay. Furthermore, we found a significantly higher mRNA expression of both the myofibroblast marker α-SMA, and collagen type III in cardiac fibroblasts isolated from Neil3 KO mice 7 days post MI, indicating increased levels of activated fibroblasts and altered fibroblast function. IHC 6 days post MI showed the same tendency towards more α-SMA-positive fibroblasts and more collagen by Sirius red in the Neil3 KO infarcts, however these differences were not statistically significant. In conclusion, our data suggest that after MI, Neil3 plays a role in regulating fibroblast proliferation and function, affecting wound healing and extracellular matrix composition and quality, altogether reducing mortality.

Purpose: Type 2 diabetes (T2D) is an important risk factor for heart failure. T2D is associated with the metabolic syndrome, encompassing cardiovascular risk factors such as obesity, insulin resistance and dyslipidemia, factors also associated with left ventricular diastolic dysfunction. Patients with T2D have elevated plasma levels of free fatty acids and these are proposed to activate inflammation. Interleukin-1β (IL-1β) is activated by the NLRP3 inflammasome and a central mediator in T2D. Palmitate, the most abundant saturated fatty acid in plasma was recently shown to activate the NLRP3 inflammasome in macrophages. The aim of this study was to investigate if this mechanism operates within myocardial cells.