Therapeutic Target In Heart Failure Research Articles

Leveraging metabolism for better outcomes in heart failure.

Whilst metabolic inflexibility and substrate constraint have been observed in heart failure for many years, their exact causal role remains controversial. In parallel, many of our fundamental assumptions about cardiac fuel use are now being challenged like never before. For example, the emergence of sodium glucose cotransporter 2 inhibitor (SGLT2i) therapy as one of the four "pillars" of heart failure therapy is causing a revisit of metabolism as a key mechanism and therapeutic target in heart failure. Improvements in the field of cardiac metabolomics will lead to a far more granular understanding of the mechanisms underpinning normal and abnormal human cardiac fuel use, an appreciation of drug action, and novel therapeutic strategies. Technological advances and expanding biorepositories offer exciting opportunities to elucidate the novel aspects of these metabolic mechanisms. Methodologic advances include comprehensive and accurate substrate quantitation such as metabolomics and stable-isotope fluxomics, improved access to arterio-venous blood samples across the heart to determine fuel consumption and energy conversion, high quality cardiac tissue biopsies, biochemical analytics, and informatics. Pairing these technologies with recent discoveries in epigenetic regulation, mitochondrial dynamics, and organ-microbiome metabolic crosstalk will garner critical mechanistic insights in heart failure. In this state-of-the-art review, we focus on new metabolic insights, with an eye on emerging metabolic strategies for heart failure. Our synthesis of the field will be valuable for a diverse audience with an interest in cardiac metabolism.

Proteomics of left ventricular structure in the Multi-Ethnic Study of Atherosclerosis.

Proteomic profiling offers an expansive approach to biomarker discovery and mechanistic hypothesis generation for LV remodelling, a critical component of heart failure (HF). We sought to identify plasma proteins cross-sectionally associated with left ventricular (LV) size and geometry in a diverse population-based cohort without known cardiovascular disease (CVD). Among participants of the Multi-Ethnic Study of Atherosclerosis (MESA), we quantified plasma abundances of 1305 proteins using an aptamer-based platform at exam 1 (2000-2002) and exam 5 (2010-2011) and assessed LV structure by cardiac magnetic resonance (CMR) at the same time points. We used multivariable linear regression with robust variance to assess cross-sectional associations between plasma protein abundances and LV structural characteristics at exam 1, reproduced findings in later-life at exam 5, and explored relationships of associated proteins using annotated enrichment analysis. We studied 763 participants (mean age 60±10years at exam 1; 53% female; 19% Black race; 31% Hispanic ethnicity). Following adjustment for renal function and traditional CVD risk factors, plasma levels of 3 proteins were associated with LV mass index at both time points with the same directionality (FDR<0.05): leptin (LEP), renin (REN), and cathepsin-D (CTSD); 20 with LV end-diastolic volume index: LEP, NT-proBNP, histone-lysine N-methyltransferase (EHMT2), chordin-like protein 1 (CHRDL1), tumour necrosis factor-inducible gene 6 protein (TNFAIP6), NT-3 growth factor receptor (NTRK3), c5a anaphylatoxin (C5), neurogenic locus notch homologue protein 3 (NOTCH3), ephrin-B2 (EFNB2), osteomodulin (OMD), contactin-4 (CNTN4), gelsolin (GSN), stromal cell-derived factor 1 (CXCL12), calcineurin subunit B type 1 (PPP3R1), insulin-like growth factor 1 receptor (IGF1R), bone sialoprotein 2 (IBSP), interleukin-11 (IL-11), follistatin-related protein 1 (FSTL1), periostin (POSTN), and biglycan (BGN); and 4 with LV mass-to-volume ratio: RGM domain family member B (RGMB), transforming growth factor beta receptor type 3 (TGFBR3), ephrin-A2 (EFNA2), and cell adhesion molecule 3 (CADM3). Functional annotation implicated regulation of the PI3K-Akt pathway, bone morphogenic protein signalling, and cGMP-mediated signalling. We report proteomic profiling of LV size and geometry, which identified novel associations and reinforced previous findings on biomarker candidates for LV remodelling and HF. If validated, these proteins may help refine risk prediction and identify novel therapeutic targets for HF.

Mitochondrial Structure and Function in Human Heart Failure.

Despite clinical and scientific advancements, heart failure is the major cause of morbidity and mortality worldwide. Both mitochondrial dysfunction and inflammation contribute to the development and progression of heart failure. Although inflammation is crucial to reparative healing following acute cardiomyocyte injury, chronic inflammation damages the heart, impairs function, and decreases cardiac output. Mitochondria, which comprise one third of cardiomyocyte volume, may prove a potential therapeutic target for heart failure. Known primarily for energy production, mitochondria are also involved in other processes including calcium homeostasis and the regulation of cellular apoptosis. Mitochondrial function is closely related to morphology, which alters through mitochondrial dynamics, thus ensuring that the energy needs of the cell are met. However, in heart failure, changes in substrate use lead to mitochondrial dysfunction and impaired myocyte function. This review discusses mitochondrial and cristae dynamics, including the role of the mitochondria contact site and cristae organizing system complex in mitochondrial ultrastructure changes. Additionally, this review covers the role of mitochondria-endoplasmic reticulum contact sites, mitochondrial communication via nanotunnels, and altered metabolite production during heart failure. We highlight these often-neglected factors and promising clinical mitochondrial targets for heart failure.

Focus on emerging cancer drugs, artificial intelligence applied to imaging, and a new therapeutic target in heart failure

Focus on emerging cancer drugs, artificial intelligence applied to imaging, and a new therapeutic target in heart failure

The m7G Methyltransferase Mettl1 Drives Cardiac Hypertrophy by Regulating SRSF9-Mediated Splicing of NFATc4.

Cardiac hypertrophy is a key factor driving heart failure (HF), yet its pathogenesis remains incompletely elucidated. Mettl1-catalyzed RNA N7-methylguanosine (m7G) modification has been implicated in ischemic cardiac injury and fibrosis. This study aims to elucidate the role of Mettl1 and the mechanism underlying non-ischemic cardiac hypertrophy and HF. It is found that Mettl1 is upregulated in human failing hearts and hypertrophic murine hearts following transverse aortic constriction (TAC) and Angiotensin II (Ang II) infusion. YY1 acts as a transcriptional factor for Mettl1 during cardiac hypertrophy. Mettl1 knockout alleviates cardiac hypertrophy and dysfunction upon pressure overload from TAC or Ang II stimulation. Conversely, cardiac-specific overexpression of Mettl1 results in cardiac remodeling. Mechanically, Mettl1 increases SRSF9 expression by inducing m7G modification of SRSF9 mRNA, facilitating alternative splicing and stabilization of NFATc4, thereby promoting cardiac hypertrophy. Moreover, the knockdown of SRSF9 protects against TAC- or Mettl1-induced cardiac hypertrophic phenotypes in vivo and in vitro. The study identifies Mettl1 as a crucial regulator of cardiac hypertrophy, providing a novel therapeutic target for HF.

Using Omics to Identify Novel Therapeutic Targets in Heart Failure.

Omics refers to the measurement and analysis of the totality of molecules or biological processes involved within an organism. Examples of omics data include genomics, transcriptomics, epigenomics, proteomics, metabolomics, and more. In this review, we present the available literature reporting omics data on heart failure that can inform the development of novel treatments or innovative treatment strategies for this disease. This includes polygenic risk scores to improve prediction of genomic data and the potential of multiomics to more efficiently identify potential treatment targets for further study. We also discuss the limitations of omic analyses and the barriers that must be overcome to maximize the utility of these types of studies. Finally, we address the current state of the field and future opportunities for using multiomics to better personalize heart failure treatment strategies.

Cardiomyocyte-specific deletion of the mitochondrial transporter Abcb10 causes cardiac dysfunction via lysosomal-mediated ferroptosis.

Heart function is highly dependent on mitochondria, which not only produce energy but also regulate many cellular functions. Therefore, mitochondria are important therapeutic targets in heart failure. Abcb10 is a member of the ABC transporter superfamily located in the inner mitochondrial membrane and plays an important role in haemoglobin synthesis, biliverdin transport, antioxidant stress, and stabilization of the iron transporter mitoferrin-1. However, the mechanisms underlying the impairment of mitochondrial transporters in the heart remain poorly understood. Here, we generated mice with cardiomyocyte-specific loss of Abcb10. The Abcb10 knockouts exhibited progressive worsening of cardiac fibrosis, increased cardiovascular risk markers and mitochondrial structural abnormalities, suggesting that the pathology of heart failure is related to mitochondrial dysfunction. As the mitochondrial dysfunction was observed early but mildly, other factors were considered. We then observed increased Hif1α expression, decreased NAD synthase expression, and reduced NAD+ levels, leading to lysosomal dysfunction. Analysis of ABCB10 knockdown HeLa cells revealed accumulation of Fe2+ and lipid peroxides in lysosomes, leading to ferroptosis. Lipid peroxidation was suppressed by treatment with iron chelators, suggesting that lysosomal iron accumulation is involved in ferroptosis. We also observed that Abcb10 knockout cardiomyocytes exhibited increased ROS production, iron accumulation, and lysosomal hypertrophy. Our findings suggest that Abcb10 is required for the maintenance of cardiac function and reveal a novel pathophysiology of chronic heart failure related to lysosomal function and ferroptosis.

Cardiomyocyte Specific MLK3 Deletion Opposes LV Dysfunction and Cardiac Fetal Gene Re-Expression

Study Objective: To determine the cardiac myocyte (CM) and blood pressure-independent effects of Mixed lineage kinase 3 (MLK3) in the regulation of left ventricular (LV) function at baseline and in response to pathological stress. Background: MLK3 functions as a direct substrate effector of cGMP-dependent protein kinase 1α (PKG1α). Whole-body MLK3 deletion in mice increases cardiac dysfunction and remodeling after pressure overload and prevents the therapeutic effect of cGMP augmentation on LV function. However, MLK3 deletion also causes hypertension, which may confound these findings. Hypothesis: MLK3 opposes LV dysfunction through a blood pressure-independent function in the cardiac myocyte (CM). Methods: We generated mice harboring LoxP sites flanking the MAP3K11 gene encoding MLK3 (MLK3fl/fl) and crossed them with αMHC-Cre transgenic mice, enabling constitutive postnatal cardiac myocyte-specific MLK3 deletion (CMKO). Male and female 3- and 6-month-old MLK3 CMKO and control MLK3 intact (MLK3fl/fl Cre-) littermates were studied in the basal state. We also performed transaortic constriction (TAC) or sham surgery for 4 weeks on 3-month-old male mice. We assessed LV structure and function by organ mass, echocardiography, pressure volume loop analysis, qPCR, and immunoblot. In basal and TAC studies, we used age-matched αMHC-Cre x MLK3+/+ (non-floxed) mice as additional controls. Results: MLK3 gene excision in CMs was confirmed by PCR. By 6 months of age, MLK3 CMKO mice displayed: progressive reduction in LV ejection fraction; increase in LV internal diameter; and LV hypertrophy, indicating LV dysfunction and pathological remodeling, compared with littermate controls or with αMHC-Cre x MLK3+/+ non-floxed mice. This effect was more prominent in females than in males. LV fetal gene expression did not differ between genotypes at 3 months. At 6 months of age, however, the fetal genes nppa, RCAN, and CTGF were significantly upregulated in both male and female MLK3 CMKO mice, compared with MLK3 intact, indicating pathological remodeling. After 4-week TAC, MLK3 CMKO LVs developed more severe reduction in LV systolic function compared with MLK3 intact littermates as assayed by echocardiographic measures of LV ejection fraction; and invasive hemodynamic indices of preload recruitable stroke work, maximum LV pressure and LV developed pressure. The MLK3 CMKO LVs also demonstrated a more eccentric remodeling phenotype in which LV mass/tibia length, LV end diastolic and end systolic diameters increased more severely in CMKO mice, with corresponding reduced LV wall thicknesses. Finally, lung mass/tibia length was elevated in the MLK3 CMKO TAC mice compared to MLK3 intact TAC littermates, indicating overt heart failure. Conclusion: (1) MLK3 functions as a tonic inhibitor of LV dysfunction and pathological remodeling through a role in the CM, possibly through sex-specific mechanisms. (2) Intact MLK3 is required for normal LV compensation and concentric remodeling in response to pressure overload. These findings have important clinical implications, as drugs which activate PKG1 in heart failure improve outcomes but are limited by excess hypotension. As a myocardial PKG1 substrate which opposes pathological LV remodeling through blood pressure-independent mechanisms, MLK3 may represent a candidate therapeutic target for heart failure. NIH 1R01HL162919. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiac Remodeling: Novel Pathophysiological Mechanisms and Therapeutic Strategies.

Morphological and structural remodeling of the heart, including cardiac hypertrophy and fibrosis, has been considered a therapeutic target for heart failure for approximately three decades. Groundbreaking heart failure medications demonstrating reverse remodeling effects have contributed significantly to medical advancements. However, nearly 50% of heart failure patients still exhibit drug resistance, posing a challenge to the healthcare system. Recently, characteristics of heart failure resistant to ARBs and β-blockers have been defined, highlighting preserved systolic function despite impaired diastolic function, leading to the classification of heart failure with preserved ejection fraction (HFpEF). The pathogenesis and etiology of HFpEF may be related to metabolic abnormalities, as evidenced by its mimicry through endothelial dysfunction and excessive intake of high-fat diets. Our recent findings indicate a significant involvement of mitochondrial hyper-fission in the progression of heart failure. This mitochondrial pathological remodeling is associated with redox imbalance, especially hydrogen sulfide accumulation due to abnormal electron leak in myocardium. In this review, we also introduce a novel therapeutic strategy for heart failure from the current perspective of mitochondrial redox-metabolic remodeling.

Visualization analysis of mitochondrial dynamics in heart failure based on bibliometrics: Trends, hotspots, and topics.

This study aimed to conduct a visual analysis of the relevant literature on mitochondrial dynamics in heart failure, explore the research progress, frontier topics, and development trends in this field, and provide references for the study concerning mitochondrial dynamics in the prevention and treatment of heart failure. The Web of Science was searched from inception to October 1, 2023 to identify relevant English literature on mitochondrial dynamics in heart failure. Bibliometric methods were utilized to statistically analyze the eligible literature, and CiteSpace 6.2.R5 software was employed to visualize data such as countries of publication, institutions, authors, and keywords. A total of 1755 Science Citation Index articles were included. The global publication volume showed an increasing trend year by year, with China and the United States having the most publications, and the United States displaying the highest centrality in publications. As revealed by keyword and citation analyses, the research hotspots and frontiers in this field mainly included the pathogenesis of heart failure, mitochondrial dynamics markers, mitochondrial quality control, and potential therapeutic targets for heart failure. Research on mitochondrial dynamics in heart failure is under vigorous development. It is a development trend in this research field to explore the differential gene expression and molecular mechanisms of targeted treatment in the mitochondrial dynamics in heart failure, which will contribute to the formulation of new strategies for the prevention and treatment of heart failure.

Targeting NPM1 Epigenetically Promotes Postinfarction Cardiac Repair by Reprogramming Reparative Macrophage Metabolism.

Reparative macrophages play a crucial role in limiting excessive fibrosis and promoting cardiac repair after myocardial infarction (MI), highlighting the significance of enhancing their reparative phenotype for wound healing. Metabolic adaptation orchestrates the phenotypic transition of macrophages; however, the precise mechanisms governing metabolic reprogramming of cardiac reparative macrophages remain poorly understood. In this study, we investigated the role of NPM1 (nucleophosmin 1) in the metabolic and phenotypic shift of cardiac macrophages in the context of MI and explored the therapeutic effect of targeting NPM1 for ischemic tissue repair. Peripheral blood mononuclear cells were obtained from healthy individuals and patients with MI to explore NPM1 expression and its correlation with prognostic indicators. Through RNA sequencing, metabolite profiling, histology, and phenotype analyses, we investigated the role of NPM1 in postinfarct cardiac repair using macrophage-specific NPM1 knockout mice. Epigenetic experiments were conducted to study the mechanisms underlying metabolic reprogramming and phenotype transition of NPM1-deficient cardiac macrophages. The therapeutic efficacy of antisense oligonucleotide and inhibitor targeting NPM1 was then assessed in wild-type mice with MI. NPM1 expression was upregulated in the peripheral blood mononuclear cells from patients with MI that closely correlated with adverse prognostic indicators of MI. Macrophage-specific NPM1 deletion reduced infarct size, promoted angiogenesis, and suppressed tissue fibrosis, in turn improving cardiac function and protecting against adverse cardiac remodeling after MI. Furthermore, NPM1 deficiency boosted the reparative function of cardiac macrophages by shifting macrophage metabolism from the inflammatory glycolytic system to oxygen-driven mitochondrial energy production. The oligomeric NPM1 recruited histone demethylase KDM5b to the promoter of Tsc1 (TSC complex subunit 1), the mTOR (mechanistic target of rapamycin kinase) complex inhibitor, reduced histone H3K4me3 modification, and inhibited TSC1 expression, which then facilitated mTOR-related inflammatory glycolysis and antagonized the reparative function of cardiac macrophages. The in vivo administration of antisense oligonucleotide targeting NPM1 or oligomerization inhibitor NSC348884 substantially ameliorated tissue injury and enhanced cardiac recovery in mice after MI. Our findings uncover the key role of epigenetic factor NPM1 in impeding postinfarction cardiac repair by remodeling metabolism pattern and impairing the reparative function of cardiac macrophages. NPM1 may serve as a promising prognostic biomarker and a valuable therapeutic target for heart failure after MI.

Immune checkpoints in cardiac physiology and pathology: therapeutic targets for heart failure.

Immune checkpoint molecules are physiological regulators of the adaptive immune response. Immune checkpoint inhibitors (ICIs), such as monoclonal antibodies targeting programmed cell death protein 1 or cytotoxic T lymphocyte-associated protein 4, have revolutionized cancer treatment and their clinical use is increasing. However, ICIs can cause various immune-related adverse events, including acute and chronic cardiotoxicity. Of these cardiovascular complications, ICI-induced acute fulminant myocarditis is the most studied, although emerging clinical and preclinical data are uncovering the importance of other ICI-related chronic cardiovascular complications, such as accelerated atherosclerosis and non-myocarditis-related heart failure. These complications could be more difficult to diagnose, given that they might only be present alongside other comorbidities. The occurrence of these complications suggests a potential role of immune checkpoint molecules in maintaining cardiovascular homeostasis, and disruption of physiological immune checkpoint signalling might thus lead to cardiac pathologies, including heart failure. Although inflammation is a long-known contributor to the development of heart failure, the therapeutic targeting of pro-inflammatory pathways has not been successful thus far. The increasingly recognized role of immune checkpoint molecules in the failing heart highlights their potential use as immunotherapeutic targets for heart failure. In this Review, we summarize the available data on ICI-induced cardiac dysfunction and heart failure, and discuss how immune checkpoint signalling is altered in the failing heart. Furthermore, we describe how pharmacological targeting of immune checkpoints could be used to treat heart failure.

TAOK1-mediated regulation of the YAP/TEAD pathway as a potential therapeutic target in heart failure.

This study aimed to determine the roles of interleukin (IL)-17, TAO kinase 1 (TAOK1), and NOD-like receptor protein 3 (NLRP3) in cardiomyocyte pyroptosis and proliferation. The IL-17-treated H9C2 cells were used as in vitro heart failure (HF) models. These cells were subjected to TAOK1 overexpression or knockdown and treated with BMS-986299 (NLRP3 inflammasome agonist), MCC950 (NLRP3 inflammasome inhibitor), or verteporfin (Yes-associated protein [YAP] inhibitor). Thereafter, their pyroptosis, proliferative capacity, and gene and protein expression levels were detected. Doxorubicin-induced HF rats were used as in vivo models and subjected to TAOK1 overexpression. Thereafter, their myocardial pathology, NLRP3 inflammasome-mediated pyroptosis, and YAP/TEAD pathway function were evaluated. IL-17 treatment increased the pyroptosis and decreased the proliferative capacity of H9C2 cells. Additionally, IL-17 treatment inducedto the activation of the NLRP3 inflammasomes and inhibition of the YAP/TEAD pathway in the H9C2 cells. Moreover, the IL-17-mediated effects on the H9C2 cells were alleviated by TAOK1 overexpression and augmented by TAOK1 knockdown. Furthermore, treatment with BMS-986299 or verteporfin affected the pyroptosis, proliferative capacity, and NLRP3 inflammasome activation of the H9C2 cells independently of TAOK1 expression. In the doxorubicin-induced HF rat model, TAOK1 overexpression mitigated myocardial injury, suppressed NLRP3 inflammasome pathway activation, and restored the YAP/TEAD pathway activity. TAOK1 played a crucial role in regulating IL-17-mediated increase in the pyroptosis and decrease in the proliferation of cardiomyocytes by regulating the activities of the NLRP3 inflammasomes and the YAP/TEAD pathway.

Natriuretic peptides as biomarkers and therapeutic target in heart failure

Natriuretic peptides as biomarkers and therapeutic target in heart failure

Identification of diagnostic immune-related gene biomarkers for predicting heart failure after acute myocardial infarction.

Post-myocardial infarction heart failure (HF) is a major public health concern. Previous studies have reported the critical role of immune response in HF pathogenesis. However, limited studies have reported predictive immune-associated biomarkers for HF. So we attempted to identify potential immune-related indicators for HF early diagnosis and therapy guidance. This study identified two potential immune-related hub genes (IRHGs), namely CXCR5 and FOS, using bioinformatic approaches. The expression levels of CXCR5 and FOS and their ability to predict long-term HF were analyzed. Functional enrichment analysis revealed that the hub genes were enriched in immune system processes, including the interleukin-17 and nuclear factor-kappa B signaling pathways, which are involved in the pathogenesis of HF. Quantitative real-time polymerase chain reaction revealed that the Fos mRNA levels, but not the Cxcr5 mRNA levels, were downregulated in the mice of the HF group. This study successfully identified two IRHGs that were significantly and differentially expressed in the HF group and could predict long-term HF, providing novel insights for future studies on HF and developing novel therapeutic targets for HF.

EVs derived from physiologically loaded myocardial slices affect remodelling of overloaded myocardial slices

Abstract Introduction Mechanical load is an important determinant of cardiac output, and excessive mechanical load can lead to heart remodelling, and ultimately failure. Cardiac intercellular communication is partially mediated by extracellular vesicles (EVs), which are 30-200 nm sized nanoparticles acting as shuttles of many bioactive cargoes that modulate cell behaviour, such as microRNAs. Living myocardial slices are an ideal platform to study how mechanical load affect intercellular communication through EVs, as they can be manipulated to obtain different degrees of preload and are an organotypic multicellular platform that retains the electrophysiology and extracellular matrix of the adult myocardial tissue. Purpose The aim of the study is to investigate how EVs derived from physiologically-loaded slices modulate the myocardial remodelling of overloaded slices. Methods 300 µm slices were obtained from the left ventricle of 300-350 g male Sprague Dawley rats. Mechanical load was applied by stretching the slices to either 2.2 or 2.4 µm of their sarcomere length, to recapitulate physiological and overloaded condition, respectively. Following 48-hours of biomimetic culture, force-stretch relationship of the slices was assessed, the tissue collected for RNA and protein extraction and the media of physiological slices was harvested for EVs isolation by size exclusion chromatography. Physiological EVs were then applied onto overloaded slices (1x108 EVs/slice) and cultured for 48-hours to assess force-stretch relationship, and protein and mRNA expression associated with cardiac remodelling. Physiological and overloaded EVs content was analysed through a microRNA array. Results Physiological slices had a significantly higher contractility (P &amp;lt; 0.05), higher blood vessel density (P &amp;lt; 0.0001) and lower apoptosis (P&amp;lt;0.01) compared to overloaded slices. Application of physiological EVs on overloaded slices restored their contractility (P&amp;lt;0.05), attenuated apoptosis by reducing protein PARP-1 expression (P&amp;lt;0.05) and reduced blood vessels density loss (P&amp;lt; 0.01), as shown by Isolectin B4 staining and increased mRNA levels of VEGF. microRNAs analysis showed significant downregulation of miR-346 and miR-16-5p and upregulation of miR-143-3p miR-378a-3p in physiological EVs, compared to overloaded. The upregulation or downregulation of these microRNAs was positively associated with cardiac apoptosis and migration of vascular smooth muscle cells. Conclusions Physiological EVs affect remodelling in overloaded slices. This is likely due to an effect on apoptosis or to an indirect effect on endothelial cells. Further validation and mechanistic studies with miRNAs selected candidates may reveal interesting therapeutic targets for heart failure.

IkBz is an inhibitor of the serine/threonine kinase and liquid-liquid phase separation that causes transition from adaptive cardiac hypertrophy to heart failure during pressure overload

Abstract Background and Purpose Inflammation contributes to both adaptive cardiac hypertrophy and heart failure. However, how inflammation causes transition from compensatory response to heart failure remains largely unknown. IkBz is a transcriptional modulator that changes gene expression pattern in the NF-kB system. IkBz does not have a DNA-binding domain and is suggested to exert its function through protein-protein interaction. IkBz is upregulated in the murine failing heart. This study was performed to elucidate the roles of IkBz and their mechanisms in the pathogenesis of heart failure. Methods Eight- to 12-week old wild-type (WT) and IκB hetero knockout (HKO) mice were used for animal experiments. Pressure overload was induced by transverse aortic constriction (TAC). Cardiac phenotype was assessed by echocardiographic and histological analyses. Bone marrow transplantation experiment was performed by injecting bone marrow cells isolated from donor femurs and tibias into 8-week-old mice. Neonatal rat ventricular myocytes (NRVMs) were used for in vitro experiments. Transcriptome was assessed in NRVMs treated with IkBz or control siRNA. Immunoprecipitation coupled with mass spectrometry (IP-MS) was performed by using NRVMs overexpressing FLAG-tag-labelled IkBz. Gene and protein expression levels were assessed by quantitative RT-PCR and Western blot. Results Pressure overload induced adaptive cardiac hypertrophy until 14 days after TAC and heart failure at 28 days after TAC in WT mice. TAC induced adaptive cardiac hypertrophy in HKO mice similarly to WT mice, whereas at 28 days after TAC HKO hearts showed preserved systolic function with attenuated left ventricular dilatation compared with WT hearts. Bone marrow transplantation experiment revealed that IkBz expressed in bone marrow-derived cells has little effect on cardiac phenotype after TAC. Transcriptome analysis showed that IkBz knockdown leads to upregulation of genes related to muscle contraction and extracellular matrix organization, which was confirmed by quantitative RT-PCR in heart samples of WT and HKO mice. IP-MS and IP/western blot demonstrated that IkBz binds to the epigenetic modulator and the serine/threonine kinase. IkBz inhibited liquid-liquid phase separation induced by the epigenetic modulator. In WT failing hearts, the serine/threonine kinase protein level was suppressed compared with sham-operated WT hearts, while the protein level of the serine/threonine kinase was higher in HKO hearts at 28 days after TAC compared with WT hearts. Pharmacological inhibition of the serine/threonine kinase in WT mice impaired cardiac compensatory response at 14 days after TAC. Conclusion Our results suggest that IkBz causes transition from adaptive cardiac hypertrophy to heart failure through inhibition of the serine/threonine kinase activity and liquid-liquid phase separation. IkBz might be a novel therapeutic target for heart failure.

Relaxin as a biological marker and therapeutic target in heart failure

An important task of modern cardiology is the search and study of new cardiovascular biological markers that can help in the early diagnosis of heart diseases, serve as a tool to assess the effectiveness of treatment, and act as a prognostic marker and risk stratification criterion. This literature review aimed to consider relaxin (RLN) as a new diagnostic and prognostic cardiovascular biological marker. RLN is a natural peptide hormone with a molecular weight of approximately 6000 daltons. RLN2 is the main circulating form of RLN in the blood. Although human RLN2 was originally discovered as a hormone mainly secreted by the corpus luteum of the ovary, it is also synthesized in various tissues in non-pregnant women and men and is considered one of the most pleiotropic hormones of the human body, which perform various activities beyond reproduction.&#x0D; The availability of serelaxin (a recombinant molecule identical to human RLN2) has made it possible to study the effects of RLN2 on the cardiovascular system, kidneys, liver, and brain and to evaluate it in several randomized placebo-controlled clinical trials. RLN2 exerts many cardioprotective effects on the heart and vessels and has been proposed as a therapeutic target for cardiovascular diseases such as heart failure, atrial fibrillation, coronary heart disease, myocardial infarction, and arterial hypertension. Through the activation of its cognate receptor and subsequent flow of several molecular signaling pathways in the cardiovascular system, RLN2 can induce vasodilation and angiogenesis, increase arterial compliance and cardiac output, reduce vascular resistance, exert antifibrotic effects through regulation and remodeling of extracellular matrix turnover, reduce inflammation and apoptosis, inhibit oxidative stress, induce chronotropic and inotropic effects, and inhibit ventricular and atrial ectopic activity.&#x0D; Further studies are needed to demonstrate the potential use of RLN as an additional laboratory tool for diagnosis, risk stratification, and prediction of cardiovascular events in patients with heart failure. The effects of relaxin on morbidity and mortality in patients with heart failure have yet to be evaluated in more detail.

Abstract 16593: The DEAD-Box RNA Helicase Ddx41 Contributes to Adverse Cardiac Remodeling During Pressure Overload Through Modulation of RNA Metabolism

Introduction: RNA metabolism represents an essential biochemical process that governs protein biosynthesis, an operation that is modulated by RNA-binding proteins. Although shifts in RNA metabolism have been implicated in the pathogenesis of heart failure, the role of RNA-binding proteins in the heart remains largely unknown. Methods: Whole-genome CRISPRi screening was performed in HL-1 cardiomyocyte cell line transduced with dCAS9-KRAB. Phenylephrine, cobalt chloride and hydrogen peroxide were used as pathological stressors. Neonatal rat ventricular myocytes (NRVMs) were used for further in vitro experiments. DNA damage and mitochondrial function were assessed by phospho-H2AX detection and mitochondrial membrane potential assay, respectively. Transcriptome was assessed in NRVMs treated with Ddx41 or control siRNA. RNA Immunoprecipitation sequencing (RIP-seq) was performed by using NRVMs overexpressing FLAG-tag-labelled Ddx41. 8- to 12-week old wild-type and transgenic mice with cardiomyocyte-specific overexpression of Ddx41 were used for animal experiments. Pressure overload was induced by transverse aortic constriction (TAC). Cardiac phenotype was assessed by echocardiographic and histological analyses. Results: CRISPRi screening and validation experiment identified Ddx41, a DEAD-box RNA helicase, as one of molecules whose inhibition protects HL-1 cardiomyocytes against various pathological stressors. Knockdown of Ddx41 showed protective effect in NRVMs against doxorubicin stress with improvement of DNA damage, whereas overexpression of Ddx41 induced mitochondrial dysfunction. Transcriptome analysis using NRVMs demonstrated that Ddx41 knockdown alters expression levels of genes related to cardiac hypertrophy, energy metabolism, extracellular matrix formation and wound healing. RIP-seq analysis revealed that Ddx41 binds to mRNAs of genes related to inflammatory responses. Ddx41-Tg mice showed higher mortality and exacerbated adverse cardiac remodeling after TAC, compared with wild-type mice. Conclusions: Our results suggest that Ddx41 contributes to adverse cardiac remodeling during pressure overload through modulation of RNA metabolism. Ddx41 might be a novel therapeutic target for heart failure.

Abstract 16374: Perm1 Regulates Mitochondrial Energetics Through O-Glcnacylation in Cardiomyocytes

O-GlcNAcylation is a post-translational modification of proteins that plays an important role in cellular homeostasis and stress responses. Two enzymes regulate O-GlcNAcylation: O-GlcNAc transferase (OGT) that adds O-GlcNAc to proteins; O-GlcNAcase (OGA) that removes O-GlcNAc from proteins. While O-GlcNAcylation is necessary to respond to ischemia/reperfusion injury, chronic activation of O-GlcNAcylation in the heart has adverse effects, and excessive O-GlcNAcylation leads to the development of heart failure. However, there is currently no therapy for heart failure that targets O-GlcNAcylation. Perm1 is a striated muscle-specific regulator of mitochondrial bioenergetics. We previously demonstrated that Perm1-knockout mice exhibit reduced cardiac function and myocardial energy reserve, in association with excessive O-GlcNAcylation and upregulation of OGT. Here, we hypothesized that Perm1 maintains mitochondrial energetics by suppressing O-GlcNAcylation. We found that adenovirus-mediated overexpression of Perm1 in cardiomyocytes significantly decreased O-GlcNAcylation (Figure 1A-B) and increased the basal and maximal respiration and ATP production rates as compared with control in Cell Mito Stress Test using a Seahorse 96x flux analyzer (orange vs. green, Figure 1C-D). Furthermore, the increased levels of O-GlcNAcylated proteins (215% of control, p&lt;0.05) via silencing OGA (si-OGA) in cardiomyocytes significantly decreased the basal and maximal respiration capacity and ATP production rates as compared with control (green vs. purple, Figure 1C-D), all which were completely rescued by Perm1 overexpression (blue, Figure 1C-D). These results suggest that Perm1 positively regulates mitochondrial energetics, in part, via suppressing O-GlcNAcylation and that Perm1 might be a new therapeutic target of heart failure that maintains mitochondrial function through preventing excessive O-GlcNAcylation under pathological stress.