Altering inflammation can impact the recovering heart's structure and function following myocardial infarction (MI). MAP kinase-activated protein kinase 2 (MK2) regulates the stability of several pro-inflammatory cytokines. Hence, this study was to determine if MK2 deficiency impaired the inflammatory phase of post-MI wound repair. Myocardial infarctions were induced by permanent ligation of the left anterior descending coronary artery in 12-week-old male MK2+/+ and MK2-/- mice. Five days post-MI, survival was 100% in MI-MK2-/- (n = 20) and 79% in MI-MK2+/+ mice (n = 29; Mandel-Cox test: p < 0.05). Systolic and diastolic LV diameters were greater in MI-MK2+/+ than MI-MK2-/- mice. Infiltration of neutrophils or monocytes did not differ significantly. Cytokine and chemokine transcripts were quantified in infarcted and non-infarcted LV tissue using qPCR arrays. Three days post-MI, Ifna2 was increased and Il16 was decreased in infarcted tissue from MK2-/- hearts, compared with infarcted MK2+/+ tissue, whereas in the non-infarcted MK2-/- myocardium Il27 increased and Tnfsf11, Ccl3, and Il1rn were decreased. Five days post-MI, Ctf16 and Il10 increased in infarcted MK2-/- tissue whereas in the non-infarcted MK2-/- myocardium Ccl9, Nodal, and Xcl2 increased and Il15 decreased. These findings suggest MK2 deficiency is an advantage during the inflammatory phase of cardiac wound repair post-MI.

Despite significant advancements in therapies, heart failure (HF) remains a major health challenge. Women, who are underrepresented in HF research, are particularly in need of effective treatments. B-vitamins are a promising and cost-effective option for improving cardiac function. Our study aimed to investigate the sex-specific effects of B-vitamin supplementation on HF with reduced ejection fraction in mice. Male and female mice underwent transverse aortic constriction (TAC) to induce pressure overload. Four weeks post-TAC, mice were randomized to receive either a standard or a vitamin B-enriched (VitB) diet. We found that in females, but not in males, VitB 1) extended survival, 2) slowed down the decrease in ejection fraction (EF), and 3) improved left ventricular morphology. The observed benefits in females were associated with evidence of improved cardiac and lung fibrosis and lower inflammation. In contrast, in males, VitB treatment did not reduce cardiac and lung fibrosis, whereas inflammation remained active in the myocardium. Regarding the circulating lipidome, disturbances were normalized in females with a specific enrichment in long-chain and polyunsaturated triglycerides (TGs) in response to VitB. Conversely, in males, lipidomic alterations remained under VitB treatment and were characterized by the accumulation of shorter and saturated TG in the circulation and myocardium. These data reveal a sex-specific response to VitB supplementation in HF in the context of pressure overload and point to a differential lipidomic remodeling that is only favorable in females.NEW & NOTEWORTHY This study explores the sex-specific effects of B-vitamin supplementation on heart failure with reduced ejection fraction in mice subjected to pressure overload. Our study found that B-vitamins improved survival rates, cardiac function, and reduced fibrosis in female mice, with favorable lipidomic remodeling characterized by an increase in polyunsaturated triglycerides. In contrast, male mice exhibited persistent inflammation, fibrosis, and unfavorable lipidome remodeling despite the B-vitamin supplementation. These findings underscore the sex-specific benefits of B-vitamins in heart failure, suggesting their potential therapeutic value for women, who remain underrepresented in cardiovascular research.

Background: Angiopoietin-like 2 (ANGPTL2) is a pro-inflammatory and pro-oxidant circulating protein that predicts and promotes chronic inflammatory diseases such as atherosclerosis in humans. Transgenic murine models demonstrated the deleterious role of ANGPTL2 in vascular diseases, while deletion of ANGPTL2 was protective. The nature of its role in cardiac tissues is, however, less clear. Indeed, in adult mice knocked down (KD) for ANGPTL2, we recently reported a mild left ventricular (LV) dysfunction originating from a congenital aortic valve stenosis, demonstrating that ANGPTL2 is essential to cardiac development and function.Hypothesis: Because we originally demonstrated that the KD of ANGPTL2 protected vascular endothelial function via an upregulation of arterial NOX4, promoting the beneficial production of dilatory H2O2, we tested the hypothesis that increased cardiac NOX4 could negatively affect cardiac redox and remodeling and contribute to LV dysfunction observed in adult Angptl2-KD mice.Methods and results: Cardiac expression and activity of NOX4 were higher in KD mice, promoting higher levels of cardiac H2O2 when compared to wild-type (WT) mice. Immunofluorescence showed that ANGPTL2 and NOX4 were co-expressed in cardiac cells from WT mice and both proteins co-immunoprecipitated in HEK293 cells, suggesting that ANGPTL2 and NOX4 physically interact. Pressure overload induced by transverse aortic constriction surgery (TAC) promoted LV systolic dysfunction in WT mice but did not further exacerbate the dysfunction in KD mice. Importantly, the severity of LV systolic dysfunction in KD mice (TAC and control SHAM) correlated with cardiac Nox4 expression. Injection of an adeno-associated virus (AAV9) delivering shRNA targeting cardiac Nox4 expression fully reversed LV systolic dysfunction in KD-SHAM mice, demonstrating the causal role of NOX4 in cardiac dysfunction in KD mice. Targeting cardiac Nox4 expression in KD mice also induced an antioxidant response characterized by increased expression of NRF2/KEAP1 and catalase.Conclusion: Together, these data reveal that the absence of ANGPTL2 induces an upregulation of cardiac NOX4 that contributes to oxidative stress and LV dysfunction. By interacting and repressing cardiac NOX4, ANGPTL2 could play a new beneficial role in the maintenance of cardiac redox homeostasis and function.

ERK3/MAPK6 activates MAP kinase-activated protein kinase (MK)-5 in selected cell types. Male MK5 haplodeficient mice show reduced hypertrophy and attenuated increase in Col1a1 mRNA in response to increased cardiac afterload. In addition, MK5 deficiency impairs cardiac fibroblast function. This study determined the effect of reduced ERK3 on cardiac hypertrophy following transverse aortic constriction (TAC) and fibroblast biology in male mice. Three weeks post-surgery, ERK3, but not ERK4 or p38 alpha, co-immunoprecipitated with MK5 from both sham and TAC heart lysates. The increase in left ventricular mass and myocyte diameter was lower in TAC-ERK3+/- than TAC-ERK3+/+ hearts, whereas ERK3 haploinsufficiency did not alter systolic or diastolic function. Furthermore, the TAC-induced increase in Col1a1 mRNA abundance was diminished in ERK3+/- hearts. ERK3 immunoreactivity was detected in atrial and ventricular fibroblasts but not myocytes. In both quiescent fibroblasts and "activated" myofibroblasts isolated from adult mouse heart, siRNA-mediated knockdown of ERK3 reduced the TGF-beta-induced increase in Col1a1 mRNA. In addition, intracellular type 1 collagen immunoreactivity was reduced following ERK3 depletion in quiescent fibroblasts but not myofibroblasts. Finally, knocking down ERK3 impaired motility in both atrial and ventricular myofibroblasts. These results suggest that ERK3 plays an important role in multiple aspects of cardiac fibroblast biology.

Background: Polymorphisms in the adenylate cyclase 9 (ADCY9) gene influence the benefits of the cholesteryl ester transfer protein (CETP) modulator dalcetrapib on cardiovascular events after acute coronary syndrome. We hypothesized that Adcy9 inactivation could improve cardiac function and remodelling following myocardial infarction (MI) in absence of CETP activity. Methods: Wild-type (WT) and Adcy9-inactivated (Adcy9Gt/Gt) male mice, transgenic or not for human CETP (tgCETP+/-), were subjected to MI by permanent left anterior descending coronary artery ligation and studied for 4 weeks. Left ventricular (LV) function was assessed by echocardiography at baseline, 1, and 4 weeks after MI. At sacrifice, blood, spleen and bone marrow cells were collected for flow cytometry analysis, and hearts were harvested for histologic analyses. Results: All mice developed LV hypertrophy, dilation, and systolic dysfunction, but Adcy9Gt/Gt mice exhibited reduced pathologic LV remodelling and better LV function compared with WT mice. There were no differences between tgCETP+/-and Adcy9Gt/Gt tgCETP+/-mice, which both exhibited intermediate responses. Histologic analyses showed smaller cardiomyocyte size, reduced infarct size, and preserved myocardial capillary density in the infarct border zone in Adcy9Gt/Gt vs WT mice. Count of bone marrow T cells and B cells were significantly increased in Adcy9Gt/Gt mice compared with the other genotypes. Conclusions: Adcy9 inactivation reduced infarct size, pathologic remodelling, and cardiac dysfunction. These changes were accompanied by preserved myocardial capillary density and increased adaptive immune response. Most of the benefits of Adcy9 inactivation were only observed in the absence of CETP.

Atrial fibrillation (AF) is the most common type of arrhythmia encountered clinically. AF risk factors include hypertension, respiratory diseases, obesity, or heart failure. Right heart disease (RHD) has also been described among AF risk factors associated with an atrial inflammatory profile leading to AF. Studies focusing on the cardiomyocytes (CM) orchestration of the tri-factorial relation between RHD, inflammation, and AF are rare. This project aims to characterize the proarrhythmogenic remodeling affecting atrial cardiomyocyte in a rat model of RHD induced by permanent pulmonary trunk constriction. Characterize RHD induced electrophysiological and morphological CM remodeling leading to atrial inflammation and fibrosis, responsible for increased AF susceptibility. Pulmonary artery banding (PAB) was performed on Wistar rats weighing 225–275 g to induce right-sided cardiac hypertrophy and dilation. Sham animals did not receive the PAB surgery. Cardiac echography and electrophysiological studies were performed in vivo on all animals before sacrifice, 21 days post-surgery. Optical mapping was performed ex-vivo on Langendorff-perfused hearts. Freshly isolated right ventricular (RV), as well as right and left atrial (RA and LA) CM, underwent contractility recording in vitro. Histological analyses were performed to assess myocardial fibrosis and Connexin-43 levels. Genes and protein levels were obtained by qPCR and Western-blot analyses respectively. PAB animals developed severe ventricular and atrial myocardial hypertrophy and dilation compared to Sham, as assessed by echocardiography. PAB animals were significantly more susceptible to AF compared to Sham. Freshly isolated CM revealed that overall CM size was increased in PAB animals, and contractile activity of CM was increased compared to the Sham rats. Analyses of targeted protein and gene expression levels by immunohistochemistry and qPCR analyses showed enhanced expression of fibrosis and inflammation-related compounds in whole-RA and RA CM from PAB, compared to Sham. RHD induces electro-physiological remodeling influencing the RA CM contractile machinery which in turn, leads to the development of pro-arrhythmogenic substrate including atrial inflammation, fibrosis, and enhanced AF inducibility.

Atrial fibrillation (AF) is the most common type of arrhythmia encountered clinically. AF risk factors include hypertension, diabetes, obesity, or heart failure. Right heart disease (RHD) has also been described among AF risk factors associated with an atrial inflammatory profile leading to AF. The mechanisms relating RHD, inflammation, and AF are poorly described. The main objective of the project is to characterize the proarrhythmogenic cardiomyocyte (CM) remodeling and CM inflammation profile in rat atria affected by RHD.

Background: Altering the onset, intensity, or duration of inflammation can impact the recovering heart’s structure and function following myocardial infarction (MI). Substrates of MAP kinase-activated protein kinase 2 (MK2) include proteins that regulate the stability of AU-rich transcripts, including those of several pro-inflammatory cytokines. This study was to determine if MK2-deficiency impaired the inflammatory phase of post-MI wound repair. Methods and Results: Myocardial infarctions were induced by permanent ligation of the left anterior descending coronary artery in 12-week-old male MK2 +/+ and MK2 -/- littermate mice. Five days post-MI, survival was 100% in MI-MK2 -/- (n = 20) and 79% in MI-MK2 +/+ mice (n = 29; Mandel-Cox test: P < 0.05). Area at risk and infarct size were similar. Echocardiographic imaging revealed that both systolic and diastolic LV diameters were greater in MI-MK2 +/+ than MI-MK2 -/- mice. MK2-deficiency did not affect the increase in wall motion score index. Infiltration of neutrophils or monocytes did not differ significantly. Cytokine and chemokine transcripts were quantified in infarcted and non-infarcted LV tissue using qPCR arrays (QIAGEN). Three days post-MI, Ifna2 was increased and Il16 was decreased in infarcted tissue from MK2 -/- hearts, compared with infarcted MK2 +/+ tissue, whereas in the non-infarcted MK2 -/- myocardium Il27 increased and Tnfsf11 , Ccl3 , and Il1rn were decreased. Five days post-MI, Ctf16 and Il10 increased in infarcted MK2 -/- tissue whereas in the non-infarcted MK2 -/- myocardium Ccl9, Nodal, and Xcl2 increased and Il15 decreased. Conclusions: The findings of this study suggest MK2-deficiency is an advantage during the inflammatory phase of cardiac wound repair post-MI. Clinical Perspective What is new? -The effects of MAP kinase-activated protein kinase 2 (MK2) deficiency on survival, cardiac structure and function, and the inflammatory phase of wound healing following myocardial infarction were assessed using a constitutive, pan MK2-null mouse model. -MK2-deficiency reduced mortality but did not alter area at risk or infarct size post-myocardial infarction. Inflammatory cell infiltration was also unaffected. -MK2-deficiency altered the abundance of several cytokines (increased, decreased) in infarcted and non-infarcted myocardium post-MI. What are the clinical implications? -The initial phase of wound repair post-MI involves inflammation. -The risk of damage to the myocardium and mortality may be reduced by inhibition of MK2 activity during the inflammatory phase of wound healing post-MI.

Among all cardiac arrhythmias, atrial fibrillation (AF) is the most commonly diagnosed. Aging and comorbid pathological conditions such as obesity, sleep apnea or myocardial infarction increase the prevalence and incidence of AF. Clinical and experimental evidence have shown that pulmonary hypertension (PH) can initiate the development of right heart disease (RHD), which is also considered an important AF risk factor. Inflammation emerges as a common denominator between cardiovascular comorbidities and AF susceptibility. The underlying mechanisms linking (a) RHD, (b) atrial inflammation, and (c) the development of AF, remain unclear. We hypothesize that a constriction of the pulmonary artery trunk (PAT) progressively generates atrial inflammation and fibrosis responsible for increasing AF susceptibility. Describe the evolution of atrial inflammation and fibrosis in a rat model of RHD. RHD was induced on anesthetized Wistar rats (225–275 g) by performing a Pulmonary Artery Banding (PAB) which permanently reduced the PAT diameter to 1 mm. Sham animals had a PAB-mimicking surgery without suture. At day 0, 7, 14 and 21 post-surgery echocardiography and electrophysiological studies were performed in vivo on every animal. Optical mapping, histological study using Masson's trichrome, qPCR and immunoblotting were performed to analyze atrial tissues at each timepoint. PAB rats showed myocardial hypertrophy and cavity dilation affecting the right atrium (RA) and right ventricle (RV). Optical mapping performed on the RA showed that the conduction velocity was slower, the effective refractory periods were shorter, and the action potential durations were smaller in PAB rats compared to Sham. These electrical and structural remodeling were associated with significantly increased AF inducibility in PAB rats starting at day 7 until day 21 post-surgery. RA Fibrous area was also significantly higher in PAB rats compared to Sham at day 14 to day 21 post-PAT ligation. Inflammation and fibrosis-related genes such as IL6, TGFβ1 and CO1LA1 were progressively and significantly increased in the RA from PAB rats compared to Sham, from the 7th to 21st day post-PAT constriction. PAB-induced RHD provoked a progressively aggravating right atrial inflammatory and fibrotic profile leading to an increased risk of AF in rats.

Introduction: Atrial fibrillation (AF) is the most common form of cardiac arrhythmia. Chlordecone (CLD) is a pesticide known for its carcinogenic effects. Data suggest that CLD may disrupt the activity of myocardial Na + /K + -ATPase, deregulate mitochondrial Mg2+/ATPase in cardiomyocytes (CM), and inhibit CM Ca 2+ /ATPase. Little is known about the link between CLD and AF. Hypothesises: 1. Prolonged exposure to CLD induces arrhythmogenic cardiac remodeling in rats. 2.Cycle of CLD-withdrawal is accompanied by reduction of CLD-induced AF vulnerability. Methods: Male Wistar rats (250g) were exposed to CLD (0.1 μg/L or 1 μg/L) diluted in their daily water for 28 days. Control rats (CTRL) received water without CLD. Starting on day 29, all animals were exposed to CLD-free water. Electrophysiological study (EPS), echocardiography, and cardiac optical mapping (OM) were performed at days 28 and 56 to study cardiac function and atrial conduction. Expression levels of genes and proteins involved in inflammation, fibrosis and senescence were quantified by histology, immunoblot and qPCR. Results: At D28, all CLD-rats developed AF while CTRL rats did not. Compared to CTRL, weight up-take and water consumption were lower in animals exposed to CLD, although their food consumption was higher. Echocardiography revealed that CLD animals showed increased left ventricular contractility and atrial filling compared to CTRL. Acute CLD contamination caused a decrease in atrial conduction velocity and atrial action potential durations determined by cardiac OM ex-vivo . A 28-days CLD-withdrawal cycle was accompanied by weight normalization, and attenuation of AF inducibility, without improving atrial fibrosis and AF duration. CLD also decreased right and left atrial p21 mRNA expression, an effect not reversed by CLD weaning. Conclusion: CLD exposure is associated with increased AF vulnerability. CLD-weaning decreased (without abolishing), cardiac fibrosis and AF susceptibility.

Our pilot study suggests a sexual dimorphism in the response to BVit treatment in experimental HF. Indeed, the benefit of BVit treatment is only shown in females with a delay in the mortality rate associated with improved cardiac function and normalisation of lipid disturbances. To explore and understand the mechanisms underlying this sexual dimorphism, the lipid profile hypothesis appears as a relevant avenue to explore in the future.

Aortic valve (AoV) abnormalities during embryogenesis are a major risk for the development of aortic valve stenosis (AVS) and cardiac events later in life. Here, we identify an unexpected role for Angiopoietin-like 2 (ANGPTL2), a pro-inflammatory protein secreted by senescent cells, in valvulogenesis. At late embryonic stage, mice knocked-down for Angptl2 (Angptl2-KD) exhibit a premature thickening of AoV leaflets associated with a dysregulation of the fine balance between cell apoptosis, senescence and proliferation during AoV remodeling and a decrease in the crucial Notch signalling. These structural and molecular abnormalities lead toward spontaneous AVS with elevated trans-aortic gradient in adult mice of both sexes. Consistently, ANGPTL2 expression is detected in human fetal semilunar valves and associated with pathways involved in cell cycle and senescence. Altogether, these findings suggest that Angptl2 is essential for valvulogenesis, and identify Angptl2-KD mice as an animal model to study spontaneous AVS, a disease with unmet medical need.

Increased production of reactive oxygen species plays an essential role in the pathogenesis of several diseases, including cardiac hypertrophy. In our search to identify redox-sensitive targets that contribute to redox signaling, we found that protein tyrosine phosphatase 1B (PTP1B) was reversibly oxidized and inactivated in hearts undergoing hypertrophy. Cardiomyocyte-specific deletion of PTP1B in mice (PTP1B cKO mice) caused a hypertrophic phenotype that was exacerbated by pressure overload. Furthermore, we showed that argonaute 2 (AGO2), a key component of the RNA-induced silencing complex, was a substrate of PTP1B in cardiomyocytes and in the heart. Our results revealed that phosphorylation at Tyr 393 and inactivation of AGO2 in PTP1B cKO mice prevented miR-208b–mediated repression of thyroid hormone receptor–associated protein 1 (THRAP1; also known as MED13) and contributed to thyroid hormone–mediated cardiac hypertrophy. In support of this conclusion, inhibiting the synthesis of triiodothyronine (T3) with propylthiouracil rescued pressure overload–induced hypertrophy and improved myocardial contractility and systolic function in PTP1B cKO mice. Together, our data illustrate that PTP1B activity is cardioprotective and that redox signaling is linked to thyroid hormone responsiveness and microRNA-mediated gene silencing in pathological hypertrophy.

Background and aims:The anti-inflammatory agent colchicine is gaining interest as a treatment for coronary artery disease. However, the effects of colchicine in atherosclerotic animal models are mostly unknown. This study aimed to evaluate colchicine in a rabbit model of atherosclerosis. Methods:Twenty-two rabbits were fed a 0.5% cholesterol-enriched diet for 10 weeks and then randomized to receive either oral saline (n=11) or colchicine (350 μg/kg/day; n=11) for 6 weeks, with 0.2% cholesterol-diet during the treatment period. We performed intravascular ultrasound imaging (at start and end of treatment) and histology analyses of the descending thoracic aorta. Leucocyte activation was assessed in vitro on blood samples obtained during treatment. Results:Colchicine prevented positive aortic vascular remodelling (p=0.029 vs placebo). This effect was even more marked at high plasma cholesterol level (third quartile of plasma cholesterol, p=0.020). At high cholesterol level, both atherosclerotic plaque and media areas on histomorphology were reduced by colchicine compared to placebo (p=0.031 and p=0.039, respectively). Plaque fibrosis and macrophage area were reduced by colchicine (Masson's trichrome stain: p=0.038; RAM-11: p=0.026). The plaque vulnerability index, assessed by histology, was reduced by colchicine (p=0.040). Elastin/type I collagen ratio in media was significantly higher with colchicine compared to placebo (p=0.013). At a high level of plasma cholesterol, in vitro LPS challenge revealed a decrease in monocyte activation following treatment with colchicine (p<0.001) and no change in the placebo group (p=0.353). Conclusions:Colchicine decreases plaque vulnerability with reductions in plaque inflammation, medial fibrosis, outward vascular remodelling and ex vivo monocyte activation.

Pulmonary hypertension (PH) complicating idiopathic pulmonary fibrosis (IPF) is associated to worse outcome. There is a great need for a non-invasive diagnostic modality to detect and evaluate the severity of pulmonary vascular disease (PVD). 99mTc-PulmoBind is a novel imaging agent that binds to the adrenomedullin (AM) receptor on the pulmonary microvascular endothelium. SPECT imaging employing the endothelial cell tracer 99mTc-PulmoBind was used to assess PVD associated with lung fibrosis. Rats with selective right lung bleomycin-induced fibrosis were compared to control rats. SPECT imaging was performed after three weeks with 99mTc-PulmoBind and 99mTc-macroaggregates of albumin (MAA). PH and right ventricular (RV) function were assessed by echocardiography. Lung perfusion was evaluated by fluorescent microangiography. Lung AM receptor expression was measured by qPCR and by immunohistology. Relevance to human IPF was explored by measuring AM receptor expression in lung biopsies from IPF patients and healthy controls. The bleomycin group developed preferential right lung fibrosis with remodeling and reduced perfusion as assessed with fluorescent microangiography. These rats developed PH with RV hypertrophy and dysfunction. 99mTc-PulmoBind uptake was selectively reduced by 50% in the right lung and associated with reduced AM receptor expression, PH and RV hypertrophy. AM receptor was co-expressed with the endothelial cell protein CD31 in alveolar capillaries, and markedly reduced after bleomycin. Quantitative dynamic analysis of 99mTc-PulmoBind uptake in comparison to 99mTc-MAA revealed that the latter distributed only according to flow, with about 60% increased left lung uptake while left lung uptake of 99mTc-PulmoBind was not affected. Lung from human IPF patients showed important reduction in AM receptor expression closely associated with CD31. SPECT imaging with 99mTc-PulmoBind detects PVD and its severity in bleomycin-induced lung fibrosis. Reduced AM receptor expression in human IPF supports further clinical development of this imaging approach.

Background: We previously demonstrated that high-density lipoprotein (HDL) infusions may improve left ventricular diastolic dysfunction (LVDD) in an aortic valve stenosis (AVS) model. Whether the benefit was direct or mediated by the observed reduction in AVS severity is not dear. Here, we aimed to test the direct effect of an ApoA-I mimetic on LVDD in the absence of AVS. Methods: Rabbits were exposed to three different protocols to develop LVDD. First, rabbits were exposed to 0.5% cholesterol-rich diet for an average of 17 weeks. Second, rabbits were subjected to surgical ascending aortic constriction (AAC), to mimic the effect of fixed reduced aortic valve area, and studied after 10 weeks. The third model combined both cholesterol-enriched diet (for 12 weeks) and surgical AAC. The control group consisted of agematched rabbits under normal diet. After development of LVDD, rabbits were randomized to receive infusions of saline or apoA-I mimetic (25 mg/kg) 3 times per week for 4 weeks. Detailed cardiac structure and function measurements were assessed at baseline and weekly during treatment period. Histological and molecular analyses were performed on LV samples. Results: In the three models, echocardiographic results showed development of LVDD over time, with preserved LV systolic and aortic valve functions versus controls. ApoA-I mimetic infusions did not significantly improve echocardiographic parameters nor molecular markers of cardiac inflammation, oxidative stress and fibrosis. Conclusion: ApoA-I mimetic therapy did not directly improve LVDD. These results indicate that previously observed changes of LVDD were caused by AVS improvement induced by this treatment. (C) 2021 Elsevier B.V. All rights reserved.

Background Mitogen‐activated protein kinase–activated protein kinase‐2 (MK2) is a protein serine/threonine kinase activated by p38α/β. Herein, we examine the cardiac phenotype of pan MK2‐null (MK2 −/− ) mice. Methods and Results Survival curves for male MK2 +/+ and MK2 −/− mice did not differ (Mantel‐Cox test, P =0.580). At 12 weeks of age, MK2 −/− mice exhibited normal systolic function along with signs of possible early diastolic dysfunction; however, aging was not associated with an abnormal reduction in diastolic function. Both R‐R interval and P‐R segment durations were prolonged in MK2‐deficient mice. However, heart rates normalized when isolated hearts were perfused ex vivo in working mode. Ca 2+ transients evoked by field stimulation or caffeine were similar in ventricular myocytes from MK2 +/+ and MK2 −/− mice. MK2 −/− mice had lower body temperature and an age‐dependent reduction in body weight. mRNA levels of key metabolic genes, including Ppargc1a , Acadm , Lipe , and Ucp3, were increased in hearts from MK2 −/− mice. For equivalent respiration rates, mitochondria from MK2 −/− hearts showed a significant decrease in Ca 2+ sensitivity to mitochondrial permeability transition pore opening. Eight weeks of pressure overload increased left ventricular mass in MK2 +/+ and MK2 −/− mice; however, after 2 weeks the increase was significant in MK2 +/+ but not MK2 −/− mice. Finally, the pressure overload–induced decrease in systolic function was attenuated in MK2 −/− mice 2 weeks, but not 8 weeks, after constriction of the transverse aorta. Conclusions Collectively, these results implicate MK2 in (1) autonomic regulation of heart rate, (2) cardiac mitochondrial function, and (3) the early stages of myocardial remodeling in response to chronic pressure overload.

IntroductionAngiopoietin‐like 2 (ANGPTL2) is a pro‐inflammatory and pro‐oxidative glycoprotein that induces vascular endothelial dysfunction in mice and promotes atherosclerosis. Higher circulating levels of ANGPTL2 have been reported in patients with heart failure, but the potentially deleterious effect of ANGPTL2 on cardiac function is ill defined. Our aim was to investigate the cardiac function of adult mice knockdown for angptl2 (KD mice).HypothesisBased on the available data in the literature, we hypothesized that KD for angptl2 would be cardioprotective.MethodsCardiac function was measured by high frequency echocardiography in adult 7‐month old KD and wild‐type (WT) littermates. Gene expression was measured by quantitative RT‐PCR.ResultsIn contrast to our hypothesis, when compared to WT mice (n=32), KD mice (n=31) exhibited a left ventricular (LV) systolic dysfunction, characterized by a reduced fractional shortening (35.8±1.0 vs 32.2±1.2%, p<0.05), a reduced ejection fraction (71.6±1.3 vs 66.4±1.8%, p<0.05), a lower lateral (2.3±0.1 vs 2.1±0.1 cm/s, p<0.05) and septal (2.5±0.1 vs 2.2±0.1 cm/s, p<0.05) contractility. This LV systolic dysfunction observed in KD mice was reproduced in WT mice exposed to a cardiac pressure overload generated by transverse aortic constriction (TAC); in KD mice, TAC did not further alter cardiac function. Interestingly, we observed that cardiac NADPH oxidase Nox4 mRNA expression tended to be higher in KD mice (+13%, p>0.05). NOX4 is known to produce H2O2, a deleterious hypertrophic stimulus in cardiomyocytes. Cardiac Nox4 was strongly and negatively correlated with fractional shortening (r=−0.836, p<0.001) and ejection fraction (r=−0.839, p<0.001) in KD mice only (sham and TAC mice, n=15), i.e. the higher Nox4, the worse LV dysfunction. In contrast, Nox4 expression was not correlated with markers of LV dysfunction in WT mice (sham and TAC, n=12; p>0.05). We then tested the effects of repressing, or not, cardiac expression of Nox4 by a single injection of cardiac specific associated adenovirus AAV9 delivering a NOX4 targeted shRNA (shNOX4) or a scramble shRNA (SCR), in both WT and KD mice. The shNOX4, which significantly reduced cardiac Nox4 mRNA expression (‐34%, p<0.05), fully reversed LV systolic dysfunction in KD mice (Table ). In contrast, in WT mice AAV9‐shNOX4 had no effect (Table ).ConclusionKnockdown of ANGPTL2 promotes LV systolic dysfunction that can be reversed by the decrease of NOX4 expression in the heart of KD mice.Support or Funding InformationThis work was funded by grants from the Canadian Institutes of Health Research (PJT‐162446) and by the Foundation of the Montreal Heart Institute. WT‐SCR (n=5) KD‐SCR (n=7) WT‐shNOX4 (n=8) KD‐shNOX4 (n=5) Fractional shortening (%) 38.6±2.8 27.7±1.7 35.3±1.8 37.4±2.4 Ejection fraction (%) 74.9±3.5 60.1±2.7 71.1±2.2 73.7±3.0 Lateral contractility (cm/s) 2.5±0.1 1.7±0.1 2.4±0.1 2.3±0.1 Septal contractility (cm/s) 2.7±0.1 2.0±0.1 2.6±0.1 2.7±0.1 *p<0.05 WT‐SCR vs KD‐SCR; †p<0.05 KD‐SCR vs KD‐shNOX4 (Two‐way ANOVA Bonferroni’s multiple comparisons test).